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Sample records for prepared colloids experience

  1. Advanced Colloids Experiment (ACE-H-2)

    Science.gov (United States)

    Meyer, William V.; Sicker, Ron; Chmiel, Alan J.; Eustace, John; LaBarbera, Melissa

    2015-01-01

    Increment 43 - 44 Science Symposium presentation of Advanced Colloids Experiment (ACE-H-2) 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.

  2. 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.

  3. Preparation of (non-)aqueous dispersins of colloidal boehmite needles

    NARCIS (Netherlands)

    Buining, P.A.; Pathmamanoharan, C.; Philipse, A.P.; Lekkerkerker, H.N.W.

    1993-01-01

    A novel hydrothermal alkoxide method is presented for the preparation of stable, aqueousdispersions of fairly monodisperse, charged colloidal boehmite needles. A polymer coating procedure for the needles is described which leads to sterically stabilized dispersions in organic solvents.

  4. Preparation of colloidal Sb2O5 and its stability

    Institute of Scientific and Technical Information of China (English)

    陈文汩; 张利; 龚竹青

    2004-01-01

    Colloidal antimony pentoxide was prepared by oxidation of antimony trioxide with hydrogen peroxide as oxidant and phosphoric acid as stabilizer. Effects of stabilizer, oxidant amount and reaction temperature on the diameter of colloidal particles and their size distribution were discussed. And static electricity effects on colloidal stability were studied by measurement of Zeta potential. Results show that Zeta potential of colloidal Sb2 O5 moves from -30mV to -56.8 mV with the addition of H3 PO4 as the stabilizer, zero point of charge of colloidal H3 PO4-Sb2 O5 moves from pH= 1.85 to more acidic regions, and colloidal H3 PO4-Sb2 O5 is stable in wider pH range. The stable time of colloidal H3 PO4-Sb2 O5 particles without coagulation is more than six months. The size of colloidal particles is smaller and their distribution is narrower by adding H3 PO4 as the stabilizer and decreasing reaction temperature, and the average diameter of H3 PO4-Sb2 O5 particles prepared is 30 nm.

  5. 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; hide

    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

  6. Preparation of colloidal graphene in quantity by electrochemical exfoliation.

    Science.gov (United States)

    Chen, Kunfeng; Xue, Dongfeng

    2014-12-15

    We reported the preparation of colloidal graphene in quantity via the anodic exfoliation of graphite in (NH4)2SO4 aqueous solution. In the currently designed electrochemical exfoliation route, mass high-quality graphene was produced within short reaction time, around 1h. The proposed electrochemical exfoliation mechanism showed that SO4(2-) and H2O can be intercalated into those graphite sheets, monolayer and few-layer graphene were obtained by the formation of gaseous SO2 and O2 within graphite sheets. Stability evaluation showed that our exfoliated colloidal graphene can be perfectly stabilized in DMF solvent more than 1 week. The colloidal graphene can be used to construct various simple and complex patterns by writing it on A4 paper, which can be applied to flexible printed electronic devices. Furthermore, colloidal graphene can show promising applications in the fabrication of binder- and additive-free electrodes for supercapacitors and lithium-ion batteries. Our present method shows huge potential for industrial-scale synthesis of high-quality graphene and further commercialization of graphene colloid for numerous advanced applications in flexible printed electronics and energy storage devices.

  7. A SURFACTANT-ASSISTED APPROACH FOR PREPARING COLLOIDAL AZO POLYMER SPHERES WITH NARROW SIZE DISTRIBUTION

    Institute of Scientific and Technical Information of China (English)

    Xiao-lan Tong; Yao-bang Li; Ya-ning He; Xiao-gong Wang

    2006-01-01

    A surfactant-assisted method for preparing colloidal spheres with narrow size distribution from a polydispersed azo polymer has been developed in this work. The colloidal spheres were formed through gradual hydrophobic aggregation of the polymeric chains in THF-H2O dispersion media, which was induced by a steady increase in the water content. Results showed that the addition of a small amount of surfactant (SDBS) could significantly narrow the size distribution of the colloidal spheres. The size distribution of the colloidal spheres was determined by the concentrations of azo polymer and the amount of surfactant in the systems. When the concentrations of polymer and surfactant amount were in a proper range,colloidal spheres with narrow size distribution could be obtained. The colloidal spheres formed by this method could be elongated along the polarization direction of the laser beams upon Ar+ laser irradiation. The colloidal spheres are considered to be a new type of the colloid-based functional materials.

  8. Colloidal Metal Nanoparticles Prepared by Laser Ablation and their Applications.

    Science.gov (United States)

    Zhang, Jianming; Claverie, Jerome; Chaker, Mohamed; Ma, Dongling

    2017-05-05

    This review article highlights the recent advances of the synthesis and application of metal nanoparticles (NPs) fabricated via pulsed laser ablation in liquid (PLAL) phase and also introduces relevant NP formation mechanisms. Although wet-chemical approaches have been well established to synthesize colloidal metal NPs with various components and structures, some inherent drawbacks, such as reaction residuals and/or contaminations, largely limit some of their applications. The PLAL method has recently been developed as an alternative approach and received increasing attention for colloidal NP preparation, without involving complicated chemical reactions. In certain cases, by using PLAL, ligand-free and surface-clean NPs can be obtained and well dispersed in liquid, leading to the formation of a "surface-clean" NP dispersion. This unique feature renders PLAL-synthesised metal NPs attractive candidates for many interesting applications in catalysis, biology, sensing, and clean energy generation and storage. We conclude this review by proposing several interesting research directions and future challenges, from PLAL fabrication to applications. We hope this review can serve as a good reference and help with the further development of PLAL-NPs and their diverse applications. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Preparation of colloidal gold immunochromatography strip for detection of methamidophos residue

    Institute of Scientific and Technical Information of China (English)

    SHI Chenggang; ZHAO Suqing; ZHANG Kun; HONG Guobao; ZHU Zhenyu

    2008-01-01

    Methamidophos (Met) is a broad spectrum organophosphorus insecticide and acaricide. Even a trace of its residue is harmful to humans and many animals. In this study, the synthesis and identification of colloidal gold particles and antibody-colloidal gold conjugates were performed, and the preparation of colloidal gold immunochromatography strip was conducted for detection of Met residue. The size of colloidal gold particles was checked using a transmission electron microscope (TEM). The formation of antibody-colloidal gold conjugates was monitored by UV/Vis spectroscopy. The preparation of colloidal gold immunochromatography strips,analysis of Met standard solutions, and other four pesticides and vegetable samples were operated with common methods and principals.The TEM images showed the average diameter of colloidal gold particles was almost the same size: approximately 40.0 nm in diameter.For the conjugation of colloidal gold and monoclonal antibody (MAb), 0.03 mg/ml of MAb was confirmed to be the minimum amount for stabilization of colloidal gold. With the prepared colloidal gold immunochromatography test strip to determine the standard Met solution, the results demonstrated a detection limit of approximately 1.0 μg/ml. Cross-reaction indicated that the strip had a high specificity to Met. The results of 10 green vegetable sample tests confirmed that one sample was positive by HPLC analysis. There was evidence to suggest that colloidal gold particles and antibody-colloidal gold conjugates were synthesized successfully. The prepared colloidal gold immunochromatography strip was applicable for preliminary screening of Met residue.

  10. Advanced Colloids Experiment (Microscopy) - ACE-M2R

    Science.gov (United States)

    Weitz, David; Meyer, William V.; Sicker, Ronald J.; Bailey, Kelly Ann; Eustace, John G.

    2017-01-01

    Increment 53 - 54 Science Symposium presentation of Advanced Colloids Experiment (ACE-H-2) 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.

  11. Advanced Colloids Experiment (Temperature Controlled) - ACE-T6

    Science.gov (United States)

    Meyer, William V.; Sicker, Ronald J.; Bailey, Kelly; Eustace, John; Lynch, Matthew

    2017-01-01

    Increment 53 - 54 Science Symposium presentation of Advanced Colloids Experiment (ACE-T6) 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.

  12. Advanced Colloids Experiment (Temperature Controlled) - ACE-T9

    Science.gov (United States)

    Marr, David W. M.; Meyer, William V.; Sicker, Ronald; Bailey, Kelly; Eustace, John G.

    2017-01-01

    Increment 53 - 54 Science Symposium presentation of Advanced Colloids Experiment (ACE-T9) 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.

  13. Preparation of polystyrene spheres in different particle sizes and assembly of the PS colloidal crystals

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Monodisperse polystyrene (PS) colloidal spheres were successfully prepared through emulsifier-free emulsion polymerization by controlling the polymerization reaction time, ionic strength of the system, concentration of the ionic copolymer (sodium p-styrenesulfonate) and other factors. The PS colloidal spheres were assembled into colloidal crystals whose structures were mainly face-centered cubic (fcc) close-packed. Then FDTD method was used to calculate the color-rendering characteristics of the colloidal crystals surface. The calculated results were consistent with the experimental results.

  14. Preparation and Characterization of Colloidal Silica Particles under Mild Conditions

    Science.gov (United States)

    Neville, Frances; Zin, Azrinawati Mohd.; Jameson, Graeme J.; Wanless, Erica J.

    2012-01-01

    A microscale laboratory experiment for the preparation and characterization of silica particles at neutral pH and ambient temperature conditions is described. Students first employ experimental fabrication methods to make spherical submicrometer silica particles via the condensation of an alkoxysilane and polyethyleneimine, which act to catalyze…

  15. Preparation of Nanoelectrode Ensembles by Assembly of Nano- Silver Colloid on Gold Surface

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A novel method for preparing silver nanoelectrode ensembles (SNEEs) and gold nanoelectrode ensembles (GNEEs) has been developed. Silver colloid particles were first absorbed to the gold electrode surface to form a monolayer silver colloid. N-hexadecyl mercaptan was then assembled on the electrode to form a thiol monolayer on which hydrophilic ions cannot be transfered. The SNEEs was prepared by removing thiol from silver colloid surface through applying an AC voltage with increasing frequency at 0.20 V (vs. SCE). Finally, GNEEs was obtained by immersing a SNEEs into 6 mol/L HNO3 to remove the silver colloid particles. By comparison with other methods such as template method etc., this method enjoys some advantages of lower resistance, same diameter, easy preparation, controllable size and density.

  16. Preparation of Nanoelectrode Ensembles by Assembly of Nano—Silver Colloid on Gold Surface

    Institute of Scientific and Technical Information of China (English)

    GangXIA; XiaoYaHU; 等

    2002-01-01

    A novel method for preparing silver nanoelectrode ensembles(SNEEs) and gold nanoelectrode ensembles (GNEEs) has been developed. Silver colloid particles were first absorbed to the gold electrode surface to form a monolayer silver colloid. N-hexadecyl nercaptan was then assembled on the electrode to form a thoil monolayer on which hydrophilic ions cannot be transfered. The SNEEs was prepared by removing thiol from silver colloid surface through applying and AC voltage with increasing frequency at 0.20V(vs.SCE). Finally,GNEEs was obtained by immersing a SNEEs into 6 mol/L HNO3 to remove the silver colloid particles. By comparison with other methods such as template method ect., this method enjoys some advantages of lower resistance, same diameter,easy preparation,controllable size and density.

  17. Incorporation of ovalbumin into ISCOMs and related colloidal particles prepared by the lipid film hydration method.

    Science.gov (United States)

    Demana, Patrick H; Davies, Nigel M; Berger, Bianca; Rades, Thomas

    2004-07-08

    The aim of this study was to investigate the incorporation of a model antigen, fluorescently labelled ovalbumin (FITC-OVA), into various colloidal particles including immune stimulating complexes (ISCOMs), liposomes, ring and worm-like micelles, lamellae and lipidic/layered structures that are formed from various combinations of the triterpene saponin Quil A, cholesterol and phosphatidylethanolamine (PE) following hydration of PE/cholesterol lipid films with aqueous solutions of Quil A. Colloidal dispersions of these three components were also prepared by the dialysis method for comparison. FITC-OVA was conjugated with palmitic acid (P) and PE to produce P-FITC-OVA and PE-FITC-OVA, respectively. Both P-FITC-OVA and PE-FITC-OVA could be incorporated in all colloidal structures whereas FITC-OVA was incorporated only into liposomes. The incorporation of PE-FITC-OVA into all colloidal structures was significantly higher than P-FITC-OVA (P < 0.05). The degree of incorporation of protein was in the order: ring and worm-like micelles < liposomes and lipidic/layered structures < ISCOMs and lamellae. The incorporation of protein into the various particles prepared by the lipid film hydration method was similar to those for colloidal particles prepared by the dialysis method (provided both methods lead to the formation of the same colloidal structures). In the case of different colloidal structures arising due to the preparation method, differences in encapsulation efficiency were found (P < 0.05) for formulations with the same polar lipid composition. This study demonstrates that the various colloidal particles formed as a result of hydrating PE/cholesterol lipid films with different amounts of Quil A are capable of incorporating antigen, provided it is amphipathic. Some of these colloidal particles may be used as effective vaccine delivery systems.

  18. Effect of weightlessness on colloidal particle transport and segregation in self-organising microtubule preparations.

    Science.gov (United States)

    Tabony, James; Rigotti, Nathalie; Glade, Nicolas; Cortès, Sandra

    2007-05-01

    Weightlessness is known to effect cellular functions by as yet undetermined processes. Many experiments indicate a role of the cytoskeleton and microtubules. Under appropriate conditions in vitro microtubule preparations behave as a complex system that self-organises by a combination of reaction and diffusion. This process also results in the collective transport and organisation of any colloidal particles present. In large centimetre-sized samples, self-organisation does not occur when samples are exposed to a brief early period of weightlessness. Here, we report both space-flight and ground-based (clinorotation) experiments on the effect of weightlessness on the transport and segregation of colloidal particles and chromosomes. In centimetre-sized containers, both methods show that a brief initial period of weightlessness strongly inhibits particle transport. In miniature cell-sized containers under normal gravity conditions, the particle transport that self-organisation causes results in their accumulation into segregated regions of high and low particle density. The gravity dependence of this behaviour is strongly shape dependent. In square wells, neither self-organisation nor particle transport and segregation occur under conditions of weightlessness. On the contrary, in rectangular canals, both phenomena are largely unaffected by weightlessness. These observations suggest, depending on factors such as cell and embryo shape, that major biological functions associated with microtubule driven particle transport and organisation might be strongly perturbed by weightlessness.

  19. Results From the Physics of Colloids Experiment on ISS

    Science.gov (United States)

    Weitz, David; Bailey, Arthur; Manley, Suliana; Prasad, Vikram; Christianson, Rebecca; Sankaran, Subramanian; Doherty, Michael; Jankovsky, Amy; Lorik, Tibor; Shiley, William

    2002-12-01

    The Physics of Colloids in Space (PCS) experiment was accommodated within International Space Station (ISS) EXpedite the PRocessing of Experiments to Space Station (EXPRESS) Rack 2 and was remotely operated from early June 2001 until February 2002 from NASA Glenn Research Center's Telescience Support Center (TSC) in Cleveland, Ohio, and from the remote site at Harvard University in Cambridge, Massachusetts. PCS was launched on 4/19/2001 on Space Shuttle STS-100. The experiment was activated on 5/31/2001. The entire experimental setup performed remarkably well, and accomplished 2400 hours of science operations on-orbit. The sophisticated instrumentation in PCS is capable of dynamic and static light scattering from 11 to 169 degrees, Bragg scattering over the range from 10 to 60 degrees, dynamic and static light scattering at low angles from 0.3 to 6.0 degrees, and color imaging. The long duration microgravity environment on the ISS facilitated extended studies on the growth and coarsening characteristics of binary crystals. The de-mixing of the colloid-polymer critical-point sample was also studied as it phase-separated into two phases. Further, aging studies on a col-pol gel, gelation rate studies in extremely low concentration fractal gels over several days, and studies on a glass sample, all provided valuable information. Several exciting and unique aspects of these results are discussed here.

  20. Bright and multicolor luminescent colloidal Si nanocrystals prepared by pulsed laser irradiation in liquid

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, Toshihiro, E-mail: nakamura@el.gunma-u.ac.jp; Watanabe, Kanta; Adachi, Sadao [Graduate School of Science and Technology, Gunma University, Kiryu, Gunma 376-8515 (Japan); Yuan, Ze [Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan)

    2016-01-11

    We reported the preparation of bright and multicolor luminescent colloidal Si nanocrystal (Si-nc) by pulsed UV laser irradiation to porous Si (PSi) in an organic solvent. The different-luminescence-color (different-sized) colloidal Si-nc was produced by the pulsed laser-induced fragmentation of different-sized porous nanostructures. The colloidal Si-nc samples were found to have higher photoluminescence quantum efficiencies (20%–23%) than the PSi samples (1%–3%). The brighter emission of the colloidal Si-nc was attributed to an enhanced radiative band-to-band transition rate due to the presence of a surface organic layer formed by UV laser-induced hydrosilylation.

  1. Physics of Hard Sphere Experiment: Scattering, Rheology and Microscopy Study of Colloidal Particles

    Science.gov (United States)

    Cheng, Z.-D.; Zhu, J.; Phan, S.-E.; Russel, W. B.; Chaikin, P. M.; Meyer, W. V.

    2002-01-01

    The Physics of Hard Sphere Experiment has two incarnations: the first as a scattering and rheology experiment on STS-83 and STS-94 and the second as a microscopy experiment to be performed in the future on LMM on the space station. Here we describe some of the quantitative and qualitative results from previous flights on the dynamics of crystallization in microgravity and especially the observed interaction of growing crystallites in the coexistance regime. To clarify rheological measurements we also present ground based experiments on the low shear rate viscosity and diffusion coefficient of several hard sphere experiments at high volume fraction. We also show how these experiments will be performed with confocal microscopy and laser tweezers in our lab and as preparation for the phAse II experiments on LMM. One of the main aims of the microscopy study will be the control of colloidal samples using an array of applied fields with an eye toward colloidal architectures. Temperature gradients, electric field gradients, laser tweezers and a variety of switchable imposed surface patterns are used toward this control.

  2. Colloidal Clusters by Using Emulsions and Dumbbell-Shaped Particles: Experiments and Simulations

    NARCIS (Netherlands)

    Peng, B.; Smallenburg, F.; Imhof, A.; Dijkstra, M.; van Blaaderen, A.

    2013-01-01

    With (dumb)bells on: A variety of colloidal stereoisomers (all the same materials) have been prepared through evaporation of emulsions by using symmetric and asymmetric dumbbell-shaped particles (see figure). The colloid configurations are in good agreement with the results of computer simulations.

  3. Preparation and characterization of silver colloids with different morphologies under ultrasonic field

    Institute of Scientific and Technical Information of China (English)

    Cheng Jingquan; Yao Suwei; Zhang Weiguo; Zou Yi

    2006-01-01

    In the ultrasonic field,stable silver colloids were produced by the reduction of AgNO3 with the protection of PVP using KBH4 or N2H4.H2O as reductant.The main factors affecting the morphology of silver nanoparticles,such as distribution of the ultrasonic field,ultrasonic time,ultrasonic power,and the species of reductant,were studied.The silver colloids were identified by TEM and spectrophotometry.The results indicate that the factors such as distribution of the ultrasonic field,ultrasonic time,ultrasonic power,and the species of reductant have a great impact on the morphology of the silver nanoparticles.The size of the silver nanoparticles decreases with the ultrasonic power and ultrasonic time increasing.Ag nanoparticles prepared in standing wave field preferentially grow in a certain direction,which is propitious for forming hexagonal- and spherical-like silver nanoparticles.Monodispersed spherical silver nanoparticles are easily synthesized in the diffusion field.The stability of silver colloid becomes improved by ultrasonic treatment.For example,precipitate is not found after several weeks for the silver colloid prepared with an ultrasonic treatment time of 180 min.The silver nanoparticles prepared without ultrasonic treatment are large spherical-like and hexagonal.Well-dispersed spherical silver particles with a mean size of about 20 nm have been prepared under ultrasonic treatment.Spherical,spherical-like,and hexagonal silver nanoparticles can be obtained by changing the reductants..

  4. A novel colloid probe preparation method based on chemical etching technique

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Several fundamental problems in hydrophobic force measurements using atomic force microscope (AFM) are discussed in this paper. A novel method for colloid probe preparation based on chemical etching technology is proposed, which is specially fit for the unique demands of hydrophobic force measurements by AFM. The features of three different approaches for determining spring constants of rectangular cantilevers, including geometric dimension, Cleveland and Sader methods are compared. The influences of the sizes of the colloids on the measurements of the hydrophobic force curves are investigated. Our experimental results showed that by selecting colloid probe with proper spring constant and tip size, the hydrophobic force and the complete hydrophobic interaction force curve can be measured by using AFM.

  5. Preparation of colloidal gold immunochromatographic strip for detection of Paragonimiasis skrjabini.

    Directory of Open Access Journals (Sweden)

    Ying Wang

    Full Text Available BACKGROUND: Paragonimiasis is a food-borne trematodiasis, a serious public health issue and a neglected tropical disease. Paragonimus skrjabini is a unique species found in China. Unlike paragonimiasis westermani, it is nearly impossible to make a definitive diagnosis for paragonimiasis skrjabini by finding eggs in sputum or feces. Immunodiagnosis is the best choice to detect paragonimiasis skrjabini. There is an urgent need to develop a novel, rapid and simple immunoassay for large-scale screening patients in endemic areas. METHODOLOGY/PRINCIPAL FINDINGS: To develop a rapid, simple immunodiagnostic assay for paragonimiasis, rabbit anti-human IgG was conjugated to colloidal gold particles and used to detect antibodies in the sera of paragonimiasis patients. The synthesis and identification of colloidal gold particles and antibody-colloidal gold conjugates were performed. The size of colloidal gold particles was examined using a transmission electron microscope (TEM. The average diameter of colloidal gold particles was 17.46 nm with a range of 14.32-21.80 nm according to the TEM images. The formation of antibody-colloidal gold conjugates was monitored by UV/Vis spectroscopy. Excretory-secretory (ES antigen of Paragonimus skrjabini was coated on nitrocellulose membrane as the capture line. Recombinant Staphylococcus protein A was used to prepare the control line. This rapid gold immunochromatographic strip was assembled in regular sequence through different accessories sticked on PVC board. The relative sensitivity and specificity of the strip was 94.4% (51/54 and 94.1% (32/34 respectively using ELISA as the standard method. Its stability and reproducibility were quite excellent after storage of the strip at 4°C for 6 months. CONCLUSIONS/SIGNIFICANCE: Immunochromatographic strip prepared in this study can be used in a rapid one-step immunochromatographic assay, which is instantaneous and convenient.

  6. 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.

  7. Experiments in which oil, water and colloidal particles meet

    NARCIS (Netherlands)

    Elbers, N.A.

    2015-01-01

    In this thesis, the results are reported of experimental studies in which oil, water and colloidal particles meet. Colloidal particles are particles that have at least one characteristic length scale in the range between a few nanometers (nm) and several micrometers (μm). Mixtures of oil and water,

  8. Observation platform for colloid science experiments using the ISS Light Microscopy Module

    Science.gov (United States)

    Kurk, Michael Andy; Todd, Paul; Vellinger, John C.

    2012-07-01

    The role of gravity in colloid self-assembly is a long-standing subject of inquiry. The International Space Station Light Microscopy Module (LMM) is a potentially powerful tool for implementing the observation of colloids in a high-quality low-gravity environment. The main requirements for making observations of colloid self-assembly include a small-volume, thermally stabilized environment, the addition and removal of small volumes of fluids (colloidal suspensions or reagents), and on-demand access to electrokinetic and/or magnetophoretic body forces. A modular device has been designed in which a custom electronics module is designed to mate with the existing LMM cold plate and LMM controlling power. All control features, electrical power, microscope illuminator, fluid pumps and valves are components of this module. This module lies under, mates with and serves an experiment module which houses the fluid containers that fit under the LMM objective lenses and fluid transfer tubing. Four versions of the experiment module have been designed: a hollow-slide stopped flow cell, a multiwell quiescent module, a magnetization module and an electrokinetic module. Interfaces can be established in the viewing field using the stopped-flow cell, which is also applicable to living systems such as microbial cultures, suspended blood cells, nematodes, etc. Multi-well modules can be equipped with in-line static mixers that allow the investigator to combine pairs of fluids or to re-homogenize settled samples. The maximum dimension of all modules is 16 cm, so the modules can be transported in large numbers on cargo or manned spacecraft to the ISS. A doubly-contained transfer tool can be used to transfer fluids in and out of the experiment module, which is equipped with a fluid coupling that mates to the transfer tool. Experiment-specific versions of these modules can be prepared for approved experimenters within a 1-year period. The research for these devices is supported by NASA

  9. PREPARATION OF POLYMER MICROSPHERES WITH PYRIDYL GROUP AND THEIR STABILIZED GOLD METALLIC COLLOIDS

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Narrow disperse poly(ethyleneglycol dimethacrylate-co-4-vinylpyridine) (poly(EGDMA-co-4-VPy)) microspheres were prepared by distillation-precipitation copolymerization of ethyleneglycol dimethacrylate (EGDMA) and 4-vinylpyridine (4-VPy) with 2,2'-azobisisobutyronitrile (AIBN) as initiator in neat acetonitrile. The polymer microspheres containing pyridyl group were then utilized as stabilizer for gold metallic colloids with the diameter around 7 nm, which were prepared by the in situ reduction of gold chloride trihydrate with sodium borohydride through the coordination of the pyridyl group on the gel layer and surface of the microsphere with the gold metallic nano-particles. The catalytic properties of the pyridyl-functionalized microsphere-stabilized gold metallic colloids and the behavior of the stabilized-catalyst for the recycling were investigated with reduction of 4-nitrophenol to 4-aminophenol as a model reaction.

  10. Preparation of Three-Dimensional Photonic Crystals of Zirconia by Electrodeposition in a Colloidal Crystals Template

    Directory of Open Access Journals (Sweden)

    Lei Pan

    2016-07-01

    Full Text Available Three-dimensional photonic crystals of zirconia were prepared by electrodeposition in a colloidal crystals template following calcination at 500 °C. Scanning electron microscopy, thermogravimetric analysis, X-ray diffraction, and reflectance spectroscopy were employed to characterize the photonic crystals of zirconia. It was found that hydrated zirconium ions could penetrate the colloidal crystals template and reach the substrate easily by electrodeposition, which resulted in stronger bonding between the substrate and the as-deposited membrane. Moreover, the electrodeposited membrane had low water content, leading to a low amount of shrinkage during calcination. Both these properties could suppress detachment from the substrate upon removal of the colloidal crystals template. Therefore, the three-dimensional photonic crystals of zirconia synthesized in this study exhibited very good preservation of the ordered structures of the colloidal crystals template with a high density. A peak of reflection higher than 70% was formed in the reflectance spectrum because of the strong diffraction of the ordered structures.

  11. Nonlinear-Optical and Fluorescent Properties of Ag Aqueous Colloid Prepared by Silver Nitrate Reduction

    Directory of Open Access Journals (Sweden)

    Xiaoqiang Zhang

    2010-01-01

    Full Text Available The nonlinear-optical properties of metal Ag colloidal solutions, which were prepared by the reduction of silver nitrate, were investigated using Z-scan method. Under picosecond 532 nm excitation, the Ag colloidal solution exhibited negative nonlinear refractive index (n2=−5.17×10−4 cm2/W and reverse saturable absorption coefficient (β=4.32 cm/GW. The data fitting result of optical limiting (OL response of metal Ag colloidal solution indicated that the nonlinear absorption was attributed to two-photon absorption effect at 532 nm. Moreover, the fluorescence emission spectra of Ag colloidal solution were recorded under excitations at both 280 nm and 350 nm. Two fluorescence peaks, 336 nm and 543 nm for 280 nm excitation, while 544 nm and 694 nm for 350 nm excitation, were observed.

  12. Column experiments to investigate transport of colloidal humic acid through porous media during managed aquifer recharge

    Science.gov (United States)

    Liu, Dan; Zhou, Jingjing; Zhang, Wenjing; Huan, Ying; Yu, Xipeng; Li, Fulin; Chen, Xuequn

    2016-09-01

    Colloids act as vectors for pollutants in groundwater, thereby creating a series of environmental problems. While managed aquifer recharge plays an important role in protecting groundwater resources and controlling land subsidence, it has a significant effect on the transport of colloids. In this study, particle size and zeta potential of colloidal humic acid (HA) have been measured to determine the effects of different hydrochemistry conditions. Column experiments were conducted to examine the effects on the transport of colloidal HA under varying conditions of pH (5, 7, 9), ionic strength (<0.0005, 0.02, 0.05 M), cation valence (Na+, Ca2+) and flow rate (0.1, 0.2, 0.4 ml/min) through collectors (glass beads) to model the properties and quality of artificial recharge water and changes in the hydrodynamic field. Breakthrough curves showed that the behavior of colloidal HA being transported varied depending on the conditions. Colloid transport was strongly influenced by hydrochemical and hydrodynamic conditions. With decreasing pH or increasing ionic strength, a decrease in the peak effluent concentration of colloidal HA and increase in deposition could be clearly seen. Comparison of different cation valence tests indicated that changes in transport and deposition were more pronounced with divalent Ca2+ than with monovalent Na+. Changes in hydrodynamic field (flow rate) also had an impact on transportation of colloidal HA. The results of this study highlight the need for further research in this area.

  13. Third-order nonlinear optical response of colloidal gold nanoparticles prepared by sputtering deposition

    Energy Technology Data Exchange (ETDEWEB)

    Castro, Hemerson P. S.; Alencar, Márcio A. R. C.; Hickmann, Jandir M. [Optics and Materials Group–OPTMA, Universidade Federal de Alagoas, CAIXA POSTAL 2051, 57061-970 Maceió (Brazil); Wender, Heberton [Brazilian Synchrotron National Laboratory (LNLS), CNPEM, Rua Giuseppe Máximo Scolfaro 10.000, 13083-970 Campinas (Brazil); Department of Physics, Universidade Federal do Mato Grosso do Sul, 79070-900, Campo Grande (Brazil); Teixeira, Sergio R. [Institute of Physics, Universidade Federal do Rio Grande do Sul, 91501-970, Porto Alegre (Brazil); Dupont, Jairton [Laboratory of Molecular Catalysis, Institute of Chemistry, Universidade Federal do Rio Grande do Sul, 91501-970, Porto Alegre (Brazil)

    2013-11-14

    The nonlinear optical responses of gold nanoparticles dispersed in castor oil produced by sputtering deposition were investigated, using the thermally managed Z-scan technique. Particles with spherical shape and 2.6 nm of average diameter were obtained and characterized by transmission electron microscopy and small angle X-ray scattering. This colloid was highly stable, without the presence of chemical impurities, neither stabilizers. It was observed that this system presents a large refractive third-order nonlinear response and a negligible nonlinear absorption. Moreover, the evaluation of the all-optical switching figures of merit demonstrated that the colloidal nanoparticles prepared by sputtering deposition have a good potential for the development of ultrafast photonic devices.

  14. Testing Record Dynamics in Experiments on Jammed Colloids

    DEFF Research Database (Denmark)

    Robe, Dominic M.; Boettcher, Stefan; Sibani, Paolo;

    2016-01-01

    When quenched rapidly beyond their glass transition, colloidal suspensions fall out of equilibrium. The pace of their dynamics then slows down with the system age, i.e., with the time elapsed after the quench. This breaking of time translational invariance is associated with dynamical observables...

  15. Size- and concentration-dependent deposition of fluorescent silica colloids in saturated sand columns: transport experiments and modeling.

    Science.gov (United States)

    Vitorge, Elsa; Szenknect, Stéphanie; Martins, Jean M F; Gaudet, Jean-Paul

    2013-08-01

    This study investigates the size and concentration effects on the transport of silica colloids in columns of sandy aquifer material. Colloid transport experiments were performed with specifically developed fluorescent labeled silica colloids in columns of a repacked natural porous medium under hydro-geochemical conditions representative of sandy aquifers. Breakthrough curves and vertical deposition profiles of colloids were measured for various colloid concentrations and sizes. The results showed that for a given colloid concentration injected, deposition increased when increasing the size of the colloids. For a given colloid size, retention was also shown to be highly concentration-dependent with a non-monotonous pattern presenting low and high concentration specificities. Deposition increases when increasing both size and injected concentration, until a threshold concentration is reached, above which retention decreases, thus increasing colloid mobility. Results observed above the threshold concentration agree with a classical blocking mechanism typical of a high concentration regime. Results observed at lower colloid concentrations were not modeled with a classical blocking model and a depth- and time-dependent model with a second order kinetic law was necessary to correctly fit the experimental data in the entire range of colloid concentrations with a single set of parameters for each colloidal size. The colloid deposition mechanisms occuring at low concentrations were investigated through a pore structure analysis carried out with Mercury Intrusion Porosimetry and image analysis. The determined pore size distribution permitted estimation of the maximal retention capacity of the natural sand as well as some low flow zones. Altogether, these results stress the key role of the pore space geometry of the sand in controlling silica colloids deposition under hydro-geochemical conditions typical of sandy aquifers. Our results also showed originally that colloid

  16. Preparation of nifedipine immune colloidal gold probe%硝苯地平免疫胶体金探针的制备

    Institute of Scientific and Technical Information of China (English)

    宋翔; 王云贵; 黄登宇

    2016-01-01

    Objective To optimize the preparation conditions of immune colloidal gold probe for detection of nifedipine drugs. Methods Colloidal gold solution was prepared by sodium citrate reduction method, and the absorbance of colloidal gold was determined by ultraviolet spectroscopy (UV) at 400~700 nm, so as to observe the size of colloidal gold. By adjustment of the pH value of labeled colloidal gold solution, the amount of antibody protein and the reconstituted solution to determine the optimal conditions for preparing immune colloidal gold probes, test strip was tested and spiked experiment was verified. Results The size of prepared gold particles was 20~40 nm. The best preparation conditions for immune colloidal gold probe were as follows:the pH value of labeled monoclonal antibodies was 9.0, the labeled amount of monoclonal antibodies was 5.0 µg/mL, and complex solution was 0.5 mol/LTris (pH 9.0, containing 0.5% Tween20). After verification of standard addition recovery experiment, the sensitivity of the test strip could meet the design requirements. Conclusion The optimization of preparation conditions of immune colloidal gold probe for detection of nifedipine can provide technical preparation for making high quality immune colloidal gold strip, which can be applied for rapid detection of nifedipine illegally added in food.%目的:优化硝苯地平药物的免疫胶体金探针的制备条件。方法采用柠檬酸三钠还原法制备胶体金溶液,采用紫外分光光度法在400~700 nm处测定胶体金溶液吸光度,判断胶体金颗粒大小。调整标记胶体金溶液pH、抗体蛋白量以及复溶液等因素,试制试纸条并进行加标验证实验,确定制备免疫胶体金探针的最优条件。结果实验制备胶体金颗粒大小在20~40 nm;最佳制备条件为:单抗标记pH为9.0,单抗标记量为5.0μL,复溶液为0.5 mol/L Tris(pH 9.0,含0.5%Tween20)。经加标实验验证,试纸条的检测灵敏度可以达到设计要求

  17. The impact of the salting-out technique on the preparation of colloidal particulate systems for pharmaceutical applications.

    Science.gov (United States)

    Mendoza-Muñoz, Néstor; Quintanar-Guerrero, David; Allémann, Eric

    2012-12-01

    The recent advances in nanotechnology and its application in medicine have merged into a new concept called nanomedicine. Colloidal drug delivery systems and specifically polymeric nanoparticles are one of the most promising novel drug carriers due to their capacity for passive or active targeting for therapeutic and diagnostic applications. The introduction of novel therapeutic nanoscaled agents requires simple, efficient and feasible industrial-scale production methods. Biodegradable polymeric nanoparticles are usually prepared from preformed polymers by five techniques: emulsification- solvent evaporation, solvent displacement, salting-out, emulsification-solvent diffusion and double emulsion solvent evaporation. This review discusses the use of the salting-out technique for the preparation of nanoparticles in the development of systems for drug delivery and other pharmaceutical applications. The relevant applications, formulations and release characteristics of novel colloidal drug delivery preparations from research literature and patents are summarized. This review is intended as a tool for the rational development of polymeric colloidal systems for pharmaceutical use.

  18. Preparation of modified SiO2 colloidal spheres with succinic acid and the assembly of colloidal crystals

    Institute of Scientific and Technical Information of China (English)

    FANG Jun; WANG XiuFeng; WANG LieSong; CHENG Bing; WU YuanTing; ZHU WanLin

    2007-01-01

    SiO2 colloidal spheres were synthesized by St(o)ber method. In order to enhance surface charge of the SiO2 spheres, they were modified with succinic acid. Scanning electron microscope (SEM) shows that the average size of modified SiO2 spheres is 473 nm, and its distribution standard deviation is less than 5%; Fourier-transform infrared spectra (FT-IR) and X-ray photoelectron spectrometer (XPS) results indicate that one end of succinic acid is chemically bonded to the SiO2 spheres through esterification; Zeta potential of the modified SiO2 spheres in water solution is improved from -53.72 to -67.46 mV, and surface charge density of the modified SiO2 spheres is enhanced from 0.19 to 0.94 μC/cm2. SiO2 colloidal crystal was fabricated from aqueous colloidal solution by the vertical deposition method at 40℃ and 60% relative humidity. SEM images show that the sample of SiO2 colloidal crystal is face-centered cubic (fcc) structure with its (111) planes parallel to the substrate. Transmission measurement shows the existence of photonic band gap at 1047 nm.

  19. Preparation and characterization of zirconium based colloidal suspensions; Preparacao e caracterizacao de suspensoes coloidais a base de zirconio

    Energy Technology Data Exchange (ETDEWEB)

    Chiavacci, Leila Aparecida; Pulcinelli, Sandra Helena; Santilli, Celso Valentim [UNESP, Araraquara, SP (Brazil). Inst. de Quimica

    1995-12-31

    Attention has been paid to zirconia based ceramic materials due to its technological applications, like catalysts, ionic changers, sensors, etc. Colloidal suspensions based on zirconium, containing different cation/anion molar ratio, have been prepared aiming the improvement of its extrinsical properties. The systems have been characterized by turbidimetry and the xerogels have been analysed by scanning electronic microscopy, infrared spectroscopy and x-ray diffraction. Results make evident the viability of preparation of transparent colloidal suspensions, gel and powders, in which the particles size and morphology could be controlled. (author) 3 figs.

  20. Pickering Emulsion Gels Prepared by Hydrogen-Bonded Zein/Tannic Acid Complex Colloidal Particles.

    Science.gov (United States)

    Zou, Yuan; Guo, Jian; Yin, Shou-Wei; Wang, Jin-Mei; Yang, Xiao-Quan

    2015-08-26

    Food-grade colloidal particles and complexes, which are formed via modulation of the noncovalent interactions between macromolecules and natural small molecules, can be developed as novel functional ingredients in a safe and sustainable way. For this study was prepared a novel zein/tannic acid (TA) complex colloidal particle (ZTP) based on the hydrogen-bonding interaction between zein and TA in aqueous ethanol solution by using a simple antisolvent approach. Pickering emulsion gels with high oil volume fraction (φ(oil) > 50%) were successfully fabricated via one-step homogenization. Circular dichroism (CD) and small-angle X-ray scattering (SAXS) measurements, which were used to characterize the structure of zein/TA complexes in ethanol solution, clearly showed that TA binding generated a conformational change of zein without altering their supramolecular structure at pH 5.0 and intermediate TA concentrations. Consequently, the resultant ZTP had tuned near neutral wettability (θ(ow) ∼ 86°) and enhanced interfacial reactivity, but without significantly decreased surface charge. These allowed the ZTP to stabilize the oil droplets and further triggered cross-linking to form a continuous network among and around the oil droplets and protein particles, leading to the formation of stable Pickering emulsion gels. Layer-by-layer (LbL) interfacial architecture on the oil-water surface of the droplets was observed, which implied a possibility to fabricate hierarchical interface microstructure via modulation of the noncovalent interaction between hydrophobic protein and natural polyphenol.

  1. Colloidal polypyrrole

    Science.gov (United States)

    Armes, Steven P.; Aldissi, Mahmoud

    1990-01-01

    Processable electrically conductive latex polymer compositions including colloidal particles of an oxidized, polymerized aromatic heterocyclic monomer, a stabilizing effective amount of a vinyl pyridine-containing polymer and dopant anions and a method of preparing such polymer compositions are disclosed.

  2. Peroxidase-like catalytic activity of Ag3PO4 nanocrystals prepared by a colloidal route.

    Directory of Open Access Journals (Sweden)

    Yuanjun Liu

    Full Text Available Nearly monodispersed Ag3PO4 nanocrystals with size of 10 nm were prepared through a colloidal chemical route. It was proven that the synthesized Ag3PO4 nanoparticles have intrinsic peroxidase-like catalytic activity. They can quickly catalyze oxidation of the peroxidase substrate 3, 3, 5, 5-tetramethylbenzidine (TMB in the presence of H2O2, producing a blue color. The catalysis reaction follows Michaelis-Menten kinetics. The calculated kinetic parameters indicate a high catalytic activity and the strong affinity of Ag3PO4 nanocrystals to the substrate (TMB. These results suggest the potential applications of Ag3PO4 nanocrystals in fields such as biotechnology, environmental chemistry, and medicine.

  3. Characteristics of colloidal aluminum nanoparticles prepared by nanosecond pulsed laser ablation in deionized water in presence of parallel external electric field

    Science.gov (United States)

    Mahdieh, Mohammad Hossein; Mozaffari, Hossein

    2017-10-01

    In this paper, we investigate experimentally the effect of electric field on the size, optical properties and crystal structure of colloidal nanoparticles (NPs) of aluminum prepared by nanosecond Pulsed Laser Ablation (PLA) in deionized water. The experiments were conducted for two different conditions, with and without the electric field parallel to the laser beam path and the results were compared. To study the influence of electric field, two polished parallel aluminum metals plates perpendicular to laser beam path were used as the electrodes. The NPs were synthesized for target in negative, positive and neutral polarities. The colloidal nanoparticles were characterized using the scanning electron microscopy (SEM), UV-vis absorption spectroscopy and X-ray Diffraction (XRD). The results indicate that initial charge on the target has strong effect on the size properties and concentration of the synthesized nanoparticles. The XRD patterns show that the structure of produced NPs with and without presence of electric field is Boehmite (AlOOH).

  4. Physics of Colloids in Space: Microgravity Experiment Launched, Installed, and Activated on the International Space Station

    Science.gov (United States)

    Doherty, Michael P.

    2002-01-01

    The Physics of Colloids in Space (PCS) experiment is a Microgravity Fluids Physics investigation that is presently located in an Expedite the Process of Experiments to Space Station (EXPRESS) Rack on the International Space Station. PCS was launched to the International Space Station on April 19, 2001, activated on May 31, 2001, and will continue to operate about 90 hr per week through May 2002.

  5. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Avramenko, Valentin [Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159 ave 100-letiya Vladivostoka, Vladivostok 690022 (Russian Federation); Bratskaya, Svetlana, E-mail: sbratska@ich.dvo.ru [Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159 ave 100-letiya Vladivostoka, Vladivostok 690022 (Russian Federation); Zheleznov, Veniamin; Sheveleva, Irina [Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159 ave 100-letiya Vladivostoka, Vladivostok 690022 (Russian Federation); Voitenko, Oleg [Far Eastern Federal University, Laboratory of Electron Microscopy and Image Processing, 27, Oktyabr' skaya Street, Vladivostok 690950 (Russian Federation); Sergienko, Valentin [Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159 ave 100-letiya Vladivostoka, Vladivostok 690022 (Russian Federation)

    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.

  7. Effect of sodium citrate on preparation of nano-sized cobalt particles by organic colloidal process

    Institute of Scientific and Technical Information of China (English)

    Huaping ZHU; Hao LI; Huiyu SONG; Shijun LIAO

    2009-01-01

    Nano-sized cobalt particles with the diameter of 2 nm were prepared via an organic colloidal process with sodium formate, ethylene glycol and sodium citrate as the reducing agent, the solvent and the complexing agent, respectively. The effects of sodium citrate on the yield, crystal structure, particle size and size distribution of the prepared nano-sized cobalt particles were then investigated. The results show that the average particle diameter decreases from 200 nm to 2 nm when the molar ratio of sodium citrate to cobalt chloride changes from 0 to 6. Furthermore, sodium citrate plays a crucial role in the controlling of size distribution of the nano-sized particles. The size distribution of the particle without sodium citrate addition is in range from tens of nanometers to 300 or 400 nm, while that with sodium citrate addition is limited in the range of (2±0.25) nm. Moreover, it is found that the addition of sodium citrate as a complex agent could decrease the yield of the nano-sized cobalt particle.

  8. Effect of gravity on colloid transport through water-saturated columns packed with glass beads: modeling and experiments.

    Science.gov (United States)

    Chrysikopoulos, Constantinos V; Syngouna, Vasiliki I

    2014-06-17

    The role of gravitational force on colloid transport in water-saturated columns packed with glass beads was investigated. Transport experiments were performed with colloids (clays: kaolinite KGa-1b, montmorillonite STx-1b). The packed columns were placed in various orientations (horizontal, vertical, and diagonal) and a steady flow rate of Q = 1.5 mL/min was applied in both up-flow and down-flow modes. All experiments were conducted under electrostatically unfavorable conditions. The experimental data were fitted with a newly developed, analytical, one-dimensional, colloid transport model. The effect of gravity is incorporated in the mathematical model by combining the interstitial velocity (advection) with the settling velocity (gravity effect). The results revealed that flow direction influences colloid transport in porous media. The rate of particle deposition was shown to be greater for up-flow than for down-flow direction, suggesting that gravity was a significant driving force for colloid deposition.

  9. Preparation of Ultrafine Fe-Pt Alloy and Au Nanoparticle Colloids by KrF Excimer Laser Solution Photolysis.

    Science.gov (United States)

    Watanabe, Masato; Takamura, Hitoshi; Sugai, Hiroshi

    2009-03-10

    We prepared ultrafine Fe-Pt alloy nanoparticle colloids by UV laser solution photolysis (KrF excimer laser of 248 nm wavelength) using precursors of methanol solutions into which iron and platinum complexes were dissolved together with PVP dispersant to prevent aggregations. From TEM observations, the Fe-Pt nanoparticles were found to be composed of disordered FCC A1 phase with average diameters of 0.5-3 nm regardless of the preparation conditions. Higher iron compositions of nanoparticles require irradiations of higher laser pulse energies typically more than 350 mJ, which is considered to be due to the difficulty in dissociation of Fe(III) acetylacetonate compared with Pt(II) acetylacetonate. Au colloid preparation by the same method was also attempted, resulting in Au nanoparticle colloids with over 10 times larger diameters than the Fe-Pt nanoparticles and UV-visible absorption peaks around 530 nm that originate from the surface plasmon resonance. Differences between the Fe-Pt and Au nanoparticles prepared by the KrF excimer laser solution photolysis are also discussed.

  10. Preparation of Ultrafine Fe–Pt Alloy and Au Nanoparticle Colloids by KrF Excimer Laser Solution Photolysis

    Directory of Open Access Journals (Sweden)

    Sugai Hiroshi

    2009-01-01

    Full Text Available Abstract We prepared ultrafine Fe–Pt alloy nanoparticle colloids by UV laser solution photolysis (KrF excimer laser of 248 nm wavelength using precursors of methanol solutions into which iron and platinum complexes were dissolved together with PVP dispersant to prevent aggregations. From TEM observations, the Fe–Pt nanoparticles were found to be composed of disordered FCC A1 phase with average diameters of 0.5–3 nm regardless of the preparation conditions. Higher iron compositions of nanoparticles require irradiations of higher laser pulse energies typically more than 350 mJ, which is considered to be due to the difficulty in dissociation of Fe(III acetylacetonate compared with Pt(II acetylacetonate. Au colloid preparation by the same method was also attempted, resulting in Au nanoparticle colloids with over 10 times larger diameters than the Fe–Pt nanoparticles and UV–visible absorption peaks around 530 nm that originate from the surface plasmon resonance. Differences between the Fe–Pt and Au nanoparticles prepared by the KrF excimer laser solution photolysis are also discussed.

  11. Colloid Facilitated Transport of Radioactive Cations in the Vadose Zone: Field Experiments Oak Ridge

    Energy Technology Data Exchange (ETDEWEB)

    James E. Saiers

    2012-09-20

    The overarching goal of this study was to improve understanding of colloid-facilitated transport of radioactive cations through unsaturated soils and sediments. We conducted a suite of laboratory experiments and field experiments on the vadose-zone transport of colloids, organic matter, and associated contaminants of interest to the U.S. Department of Energy (DOE). The laboratory and field experiments, together with transport modeling, were designed to accomplish the following detailed objectives: 1. Evaluation of the relative importance of inorganic colloids and organic matter to the facilitation of radioactive cation transport in the vadose zone; 2. Assessment of the role of adsorption and desorption kinetics in the facilitated transport of radioactive cations in the vadose zone; 3. Examination of the effects of rainfall and infiltration dynamics and in the facilitated transport of radioactive cations through the vadose zone; 4. Exploration of the role of soil heterogeneity and preferential flow paths (e.g., macropores) on the facilitated transport of radioactive cations in the vadose zone; 5. Development of a mathematical model of facilitated transport of contaminants in the vadose zone that accurately incorporates pore-scale and column-scale processes with the practicality of predicting transport with readily available parameters.

  12. Preparation for your Foreign Learning Experience

    NARCIS (Netherlands)

    Jos Walenkamp; Manuela Hernandez

    2012-01-01

    It is a well-known fact that a good preparation in the pre-departure stage can maximize the chances of a succesful foreign experience. But what is meant by a good preparation? And what are the expected results of such a preparation? This course focuses in internship and study abroad (pre-departure)

  13. Preparation for your Foreign Learning Experience

    NARCIS (Netherlands)

    Manuela Hernandez; Jos Walenkamp

    2015-01-01

    It is a well-known fact that a good preparation in the pre-departure stage can maximize the chances of a succesful foreign experience. But what is meant by a good preparation? And what are the expected results of such a preparation? This course focuses in internship and study abroad (pre-departure)

  14. Physics of Colloids in Space (PCS): Microgravity Experiment Completed Operations on the International Space Station

    Science.gov (United States)

    Doherty, Michael P.; Sankaran, Subramanian

    2003-01-01

    Immediately after mixing, the two-phase-like colloid-polymer critical point sample begins to phase separate, or de-mix, into two phases-one that resembles a gas and one that resembles a liquid, except that the particles are colloids and not atoms. The colloid-poor black regions (colloidal gas) grow bigger, and the colloid-rich white regions (colloidal liquid) become whiter as the domains further coarsen. Finally, complete phase separation is achieved, that is, just one region of each colloid-rich (white) and colloid-poor (black) phase. This process was studied over four decades of length scale, from 1 micrometer to 1 centimeter.

  15. Colloidal silicon quantum dots: from preparation to the modification of self-assembled monolayers (SAMs) for bio-applications.

    Science.gov (United States)

    Cheng, Xiaoyu; Lowe, Stuart B; Reece, Peter J; Gooding, J Justin

    2014-04-21

    Concerns over possible toxicities of conventional metal-containing quantum dots have inspired growing research interests in colloidal silicon nanocrystals (SiNCs), or silicon quantum dots (SiQDs). This is related to their potential applications in a number of fields such as solar cells, optoelectronic devices and fluorescent bio-labelling agents. The past decade has seen significant progress in the understanding of fundamental physics and surface properties of silicon nanocrystals. Such understanding is based on the advances in the preparation and characterization of surface passivated colloidal silicon nanocrystals. In this critical review, we summarize recent advances in the methods of preparing high quality silicon nanocrystals and strategies for forming self-assembled monolayers (SAMs), with a focus on their bio-applications. We highlight some of the major challenges that remain, as well as lessons learnt when working with silicon nanocrystals (239 references).

  16. CHARACTERISTIC OF SENSITIVITY OF STAPHYLOCOCCUS AUREUS AND CANDIDA ALBICANS TO ANTIBACTERIAL PREPARATIONS AND COLLOIDAL SILVER

    Directory of Open Access Journals (Sweden)

    I. A. Afonina

    2011-01-01

    Full Text Available Abstract. Constant use of antibiotics leads to reliable increasing of resistance among microorganisms. Using non-toxic concentrations of colloidal silver in combination with antimicrobial agents can reduce using concentrations of antibiotics, kept necessary antimicrobial effect. In case of Staphylococcus aureus bactericidal activity of the complex of colloidal silver with unit concentration of neomycin is bigger than the bactericidal effect of double concentration of the antibiotic. Fungicidal effect of combination of antifungal agents with a solution of the colloidal silver on Candida albicans is equal to fungicidal effect of double concentration of antifungal drugs.

  17. Preparation of high dispersion and high performance PtRu/CNTs catalyst by an organic colloid method

    Institute of Scientific and Technical Information of China (English)

    王宁卡特; 刘军民; 廖世军; V.Birss

    2006-01-01

    A high dispersion and high performance PtRu catalyst supported on carbon nanotubes was prepared by an organic colloid method. The particle size of the active components could be as small as 1.0 nm,the active surface area was about 466 m2/g(Pt). The catalytic activity toward anodic oxidation of methanol was about 3 ~ 4 times higher than that of Johnson Matthey PtRu/XC-72R catalyst. The single testing showed that the performance of the prepared catalyst was higher than that of the commercial one.

  18. CHARACTERISTIC OF SENSITIVITY OF STAPHYLOCOCCUS AUREUS AND CANDIDA ALBICANS TO ANTIBACTERIAL PREPARATIONS AND COLLOIDAL SILVER

    OpenAIRE

    Afonina, I A; L. A. Kraeva; G. Y. Tseneva

    2011-01-01

    Abstract. Constant use of antibiotics leads to reliable increasing of resistance among microorganisms. Using non-toxic concentrations of colloidal silver in combination with antimicrobial agents can reduce using concentrations of antibiotics, kept necessary antimicrobial effect. In case of Staphylococcus aureus bactericidal activity of the complex of colloidal silver with unit concentration of neomycin is bigger than the bactericidal effect of double concentration of the antibiotic. Fungicida...

  19. A Study of Functional Polymer Colloids Prepared Using Thiol-Ene/Yne Click Chemistry

    Science.gov (United States)

    Durham, Olivia Z.

    -ene chemistry was also employed toward the synthesis of degradable polyanhydride polymer particles. Unlike the aforementioned studies, the approach to particle synthesis was conducted by using a premade thiol-ene polymer. Various linear thiol-ene polyanhydrides were emulsified in water or buffered solutions via sonication. Polymer latex was obtained upon solvent evaporation of the dichloromethane (DCM) solvent used to solubilize the polymer. In this work, variation of polymer composition as well as degradation was examined. Additional experiments included a study of the release of Rhodamine B dye, functionalization of the linear polymers, and studies involving the delay of degradation through the incorporation of crosslinking in the polymer particles. The projects presented herein provide an innovative approach to the synthesis of polymer colloids using thiol-ene and thiol-yne 'click' chemistry in both heterogeneous polymerizations as well as through solvent evaporation of premade polymer solutions. Polymer colloids prove to be an area of great interest for numerous applications that encompass various areas involving biomedical and industrial technologies including paints and coatings, cosmetics, diagnostics, and drug delivery. Improvements in methods of chemical synthesis as well as advances in the tailoring of material properties are of utmost importance for the ever increasing demands of new technologies and educational enlightenment.

  20. Effect of inter-pulse delay time on production and size properties of colloidal nanoparticles prepared by collinear double-pulse laser ablation in liquid

    Science.gov (United States)

    Fattahi, Behzad; Mahdieh, Mohammah Hossein

    2016-08-01

    The influence of inter-pulse delay times (0-20 ns) between two collinear sequential nanosecond pulses on the production and size properties (mean size and size distribution) of colloidal nanoparticles prepared by pulsed laser ablation of a silver target in a distilled water medium has been studied. Various laser fluences at different inter-pulse delay times between two collinear pulses were used. Furthermore, for a better understanding of the effect of the double-pulse and single-pulse mode, experiments were performed. The characterization of the synthesized colloidal nanoparticles was investigated using scanning electron microscopy (SEM) and UV-vis absorption spectroscopy. Our results showed that 5 ns time-delayed double-pulse laser ablation results in the production of nanoparticles with the highest concentration among the other time-delayed ablation experiments and even more than single-pulse-mode experiments. It also found that using a double-pulse approach with inter-pulse delay times in the range of 0-20 ns leads to the production of nanoparticles with smaller mean sizes and narrower size distributions in comparison to single-pulse-mode laser ablation. The effect of time overlapping between two pulses in the case of double-pulse ablation was analyzed.

  1. Preparation of poly(N-vinylpyrrolidone-stabilized ZnO colloid nanoparticles

    Directory of Open Access Journals (Sweden)

    Tatyana Gutul

    2014-04-01

    Full Text Available We propose a method for the synthesis of a colloidal ZnO solution with poly(N-vinylpyrrolidone (PVP as stabilizer. Stable colloidal solutions with good luminescence properties are obtained by using PVP as stabilizer in the synthesis of ZnO nanoparticles by a sol–gel method assisted by ultrasound. Nanoparticles with sizes of 30–40 nm in a PVP matrix are produced as a solid product. The colloidal ZnO/PVP/methanol solution, apart from the most intense PL band at 356 nm coming from the PVP, exhibits a strong PL band at 376 nm (3.30 eV which corresponds to the emission of the free exciton recombination in ZnO nanoparticles.

  2. Preparation of Ce-doped colloidal SiO{sub 2} composite abrasives and their chemical mechanical polishing behavior on sapphire substrates

    Energy Technology Data Exchange (ETDEWEB)

    Lei, Hong, E-mail: hong_lei2005@aliyun.com [School of Materials Science and Engineering, Shanghai Institute of Technology, Shanghai 201418 (China); Research Center of Nano-science and Nano-technology, Shanghai University, Shanghai 200444 (China); Tong, Kaiyu; Wang, Zhanyong [School of Materials Science and Engineering, Shanghai Institute of Technology, Shanghai 201418 (China)

    2016-04-01

    Chemical mechanical polishing (CMP) has become a widely accepted global planarization technology. Abrasive is one of key elements during CMP process. In order to enhance removal rate and improve surface quality of sapphire substrate, a series of novel Ce-doped colloidal SiO{sub 2} composite abrasives were prepared by chemical co-precipitation method. The CMP performances of the Ce-doped colloidal SiO{sub 2} composite abrasives on sapphire substrate were investigated by using UNIPOL-1502 polishing equipment. The analyses on the surface of polished sapphire substrate indicate that slurries containing the Ce-doped colloidal SiO{sub 2} composite abrasives exhibit lower surface roughness, higher material removal rate than that of pure colloidal SiO{sub 2} abrasive under the same testing conditions. Furthermore, the acting mechanism of the Ce-doped colloidal silica in sapphire CMP was investigated. X-ray photoelectron spectroscopy analysis shows that solid-state chemical reactions between Ce-doped silica abrasives and sapphire surface occur during CMP process, which can promote the chemical effect in CMP and lead to the improvement of material removing rate. - Highlights: • Novel Ce-doped colloidal SiO{sub 2} composite abrasives were prepared. • The chemical mechanical polishing (CMP) performances of the composite abrasives on sapphire substrate were investigated. • Novel composite abrasives show excellent polishing characteristics comparison with pure colloidal SiO{sub 2} abrasive. • We explore and report the acting mechanism of composite abrasives to sapphire CMP.

  3. 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

  4. Self-assembly of "Mickey Mouse" shaped colloids into tube-like structures: experiments and simulations.

    Science.gov (United States)

    Wolters, Joost R; Avvisati, Guido; Hagemans, Fabian; Vissers, Teun; Kraft, Daniela J; Dijkstra, Marjolein; Kegel, Willem K

    2015-02-14

    The self-assembly of anisotropic patchy particles with a triangular shape was studied by experiments and computer simulations. The colloidal particles were synthesized in a two-step seeded emulsion polymerization process, and consist of a central smooth lobe connected to two rough lobes at an angle of ∼90°, resembling the shape of a "Mickey Mouse" head. Due to the difference in overlap volume, adding an appropriate depletant induces an attractive interaction between the smooth lobes of the colloids only, while the two rough lobes act as steric constraints. The essentially planar geometry of the Mickey Mouse particles is a first geometric deviation of dumbbell shaped patchy particles. This new geometry enables the formation of one-dimensional tube-like structures rather than spherical, essentially zero-dimensional micelles. At sufficiently strong attractions, we indeed find tube-like structures with the sticky lobes at the core and the non-sticky lobes pointing out as steric constraints that limit the growth to one direction, providing the tubes with a well-defined diameter but variable length both in experiments and simulations. In the simulations, we found that the internal structure of the tubular fragments could either be straight or twisted into so-called Bernal spirals.

  5. Laser-induced particle size tuning and structural transformations in germanium nanoparticles prepared by stain etching and colloidal synthesis route

    Energy Technology Data Exchange (ETDEWEB)

    Karatutlu, Ali, E-mail: a.karatutlu@qmul.ac.uk, E-mail: ali.karatutlu@bou.edu.tr [Centre for Condensed Matter and Materials Physics, School of Physics and Astronomy, Queen Mary, University of London, London E1 4NS (United Kingdom); Electrical and Electronics Engineering, Bursa Orhangazi University, 16310 Yıldırım/Bursa (Turkey); Little, William; Ersoy, Osman; Zhang, Yuanpeng; Sapelkin, Andrei [Centre for Condensed Matter and Materials Physics, School of Physics and Astronomy, Queen Mary, University of London, London E1 4NS (United Kingdom); Seker, Isa [Bio-Nanotechnology Research and Development Centre, Fatih University, 34500 Buyukcekmece, Istanbul (Turkey)

    2015-12-28

    In this study, with the aid of Raman measurements, we have observed transformations in small (∼3 nm and ∼10 nm) free-standing Ge nanoparticles under laser light exposure. The nanoparticles were obtained by the chemical stain etching of a monocrystalline Ge wafer and of Ge powder and by colloidal synthesis route. We found that the transformation path depends on laser power and exposure time. At relatively low values of the laser power (2 mW) over a period of 100 min, the Raman signal indicates transformation of the sample from a nanocrystaline to bulk-like state, followed by partial oxidation and finally a conversion of the entire sample into alpha-quartz type GeO{sub 2}. However, when the laser power is set at 60 mW, we observed a heat release during an explosive crystallization of the nanocrystalline material into bulk Ge without noticeable signs of oxidation. Together with the transmission electron microscopy measurements, these results suggest that the chemical stain etching method for the preparation of porous Ge may not be a top-down process as has been widely considered, but a bottom up one. Systematic studies of the laser exposure on Ge nanoparticles prepared by colloidal synthesis results in the fact that the explosive crystallisation is common for H-terminated and partially disordered Ge nanoparticles regardless of its particle size. We suggest possible bio-medical applications for the observed phenomena.

  6. 生物法制备纳米银溶胶的稳定性%Stability of Colloidal Silver Nanoparticles Prepared by Bioreduction

    Institute of Scientific and Technical Information of China (English)

    孙道华; 李清彪; 何宁; 黄加乐; 王惠璇

    2011-01-01

    利用生物还原法制备纳米银溶胶,借助于UV-Vis表征技术对其热稳定性和化学稳定性进行考察.结果表明:生物法制备的纳米银溶胶在100℃下加热6 h,UV-Vis谱图未发生明显变化;H+和具有高价阳离子的电解质对其稳定性的影响明显;OH-对银溶胶的稳定性影响相对较弱.生物法制备的纳米银溶胶在热稳定性、化学稳定性方面均略优于柠檬酸三钠法制得的银溶胶.%The thermal and chemical statoilities of the colloid silver nanoparticles prepared by bioreduction were investigated in virtue of UV-Vis spectrometer.The results indicate that UV-Vis spectra of silver colloid prepared by bioreduction have not significant change after heat treatment at 100 ℃ for 6 h.Hydrogen ion and the electrolyte with multivalent cation markedly influence stabilities of the silver colloid, while hydroxide anion has a weak influence on its stability.Thermal and chemical stabilities of the silver colloid prepared by bioreduction are superior to that of the silver colloid prepared by the sodium citrate reduction method.

  7. The study of the antimicrobial activity of colloidal solutions of silver nanoparticles prepared using food stabilizers.

    Science.gov (United States)

    Balandin, G V; Suvorov, O A; Shaburova, L N; Podkopaev, D O; Frolova, Yu V; Ermolaeva, G A

    2015-06-01

    The bactericidal effect of colloidal solutions of silver nanoparticles based on food stabilizers, gum arabic and chitosan, against bacterial cultures of microorganisms in food production is described. The antibacterial activity of nanotechnology products containing different amounts of stabilizing additives when applied to solid pH-neutral substrates is studied. For its evaluation a method making it possible to take into account the capability of nanoparticles to diffuse in solid media was applied. Minimal inhibitory concentrations of nanoparticles used against Erwinia herbicola, Pseudomonas fluorescens, Bacillus subtilis, Sarcina flava were found. A suggestion was made concerning the influence of the spatial structure of bacteria on the antibacterial activity of colloidal solutions of silver nanoparticles. The data concerning the antibacterial activity and minimal inhibiting concentrations of nanoparticles may be used for development of products suppressing activity of microorganisms hazardous for food production.

  8. COLLOID MOBILIZATION AND TRANSPORT IN CONTAMINANT PLUMES: FIELD EXPERIMENTS, LABORATORY EXPERIMENTS, AND MODELING (EPA/600/S-99/001)

    Science.gov (United States)

    The major hypothesis driving this research, that the transport of colloids in a contaminant plume is limited by the advance of the chemical agent causing colloid mobilization, was tested by (1) examining the dependence of colloid transport and mobilization on chemical perturbatio...

  9. Selective hydrogenation of maleic anhydride over Pd/Al2O3 catalysts prepared via colloid deposition

    Indian Academy of Sciences (India)

    Hongjing Yuan; Chunlei Zhang; Weitao Huo; Chunli Ning; Yong Tang; Yi Zhang; Dequan Cong; Wenxiang Zhang; Jiahuan Luo; Su Li; Zhenlu Wang

    2014-01-01

    Pd/Al2O3 catalysts were prepared via colloid deposition and the performance of the catalysts was examined in the selective hydrogenation of maleic anhydride to succinic anhydride. When the reaction was carried on in a batch system with 1,4-dioxane as the solvent (353K and 1.0MPa), high conversion of maleic anhydride (>98%) and high selectivity (>99%) for succinic anhydride were observed after 5 h. The as-prepared Pd/Al2O3 catalyst also showed excellent performance in solvent-free system and fixed-bed systems. The maleic anhydride (MA) conversion was greater than 98%, and high selectivity (>99%) for succinic anhydride was obtained after 1600 h in a fixed bed reacter. The results showed that the activity of the Pd/Al2O3 catalysts was excellent due to its high active surface area.

  10. Hierarchical opal grating films prepared by slide coating of colloidal dispersions in binary liquid media.

    Science.gov (United States)

    Lee, Wonmok; Kim, Seulgi; Kim, Seulki; Kim, Jin-Ho; Lee, Hyunjung

    2015-02-15

    There are active researches on well ordered opal films due to their possible applications to various photonic devices. A recently developed slide coating method is capable of rapid fabrication of large area opal films from aqueous colloidal dispersion. In the current study, the slide coating of polystyrene colloidal dispersions in water/i-propanol (IPA) binary media is investigated. Under high IPA content in a dispersing medium, resulting opal film showed a deterioration of long range order, as well as a decreased film thickness due to dilution effect. From the binary liquid, the dried opal films exhibited the unprecedented topological groove patterns with varying periodic distances as a function of alcohol contents in the media. The groove patterns were consisted of the hierarchical structures of the terraced opal layers with periodic thickness variations. The origin of the groove patterns was attributed to a shear-induced periodic instability of colloidal concentration within a thin channel during the coating process which was directly converted to a groove patterns in a resulting opal film due to rapid evaporation of liquid. The groove periods of opal films were in the range of 50-500 μm, and the thickness differences between peak and valley of the groove were significantly large enough to be optically distinguishable, such that the coated films can be utilized as the optical grating film to disperse infra-red light. Utilizing a lowered hydrophilicity of water/IPA dispersant, an opal film could be successfully coated on a flexible Mylar film without significant dewetting problem.

  11. Synthesis of vinyl polymer-silica colloidal nanocomposites prepared using commercial alcoholic silica sols.

    Science.gov (United States)

    Percy, M J; Amalvy, J I; Randall, D P; Armes, S P; Greaves, S J; Watts, J F

    2004-03-16

    The surfactant-free synthesis of vinyl polymer-silica nanocomposite particles has been achieved in aqueous alcoholic media at ambient temperature in the absence of auxiliary comonomers. Styrene, methyl methacrylate, methyl acrylate, n-butyl acrylate, and 2-hydroxypropyl methacrylate were homopolymerized in turn in the presence of three commercially available ultrafine alcoholic silica sols. Stable colloidal dispersions with reasonably narrow size distributions were obtained, with silica contents of up to 58% by mass indicated by thermogravimetric analysis. Particle size distributions were assessed using both dynamic light scattering and disk centrifuge photosedimentometry. The former technique indicated that the particle size increased for the first 1-2 h at 25 degrees C and thereafter remained constant. Particle morphologies were studied using electron microscopy. Most of the colloidal nanocomposites comprised approximately spherical particles with relatively narrow size distributions, but in some cases more polydisperse or nonspherical particles were obtained. Selected acrylate-based nanocomposites were examined in terms of their film formation behavior. Scanning electron microscopy studies indicated relatively smooth films were obtained on drying at 20 degrees C, with complete loss of the original particle morphology. The optical clarity of solution-cast 10 microm nanocomposite films was assessed using visible absorption spectrophotometry, with 93-98% transmission being obtained from 400 to 800 nm; the effect of long-term immersion of such films in aqueous solutions was also examined. X-ray photoelectron spectroscopy studies indicated that the surface compositions of these nanocomposite particles are invariably silica-rich, which is consistent with their long-term colloidal stability and also with aqueous electrophoresis measurements. FT-IR studies suggested that in the case of the poly(methyl methacrylate)-silica nanocomposite particles, the carbonyl ester

  12. Largescale Preparation of Organic-Dispersible Lanthanide Fluorides Nanocrystals via Colloid-Extraction Route

    Institute of Scientific and Technical Information of China (English)

    Zhao Weiwan; Zhang Shengmao; He Benfang; Wu Zhishen; Zhang Zhijun

    2007-01-01

    Organic-dispersible lanthanide fluorides nanocrystals were synthesized at a large Scale using colloid-extraction method, in the presence of dialkyl-dithiophosphinic acid (DDPA) as the extraction agent. The products were characterized by means of X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier transformation infrared (FTIR) spectroscopy. It was found that the synthesized lanthanide fluorides nanoparticles had high purity and crystallinity, and could be well dispersed in organic solvents such as chloroform, toluene etc., which could be closely related to the surface-capping of the nanocrystals by the DDPA molecules. Moreover, the nanocrystals before and after extraction by DDPA showed few differences in the microscopic morphologies. It was implied that DDPA as the extraction agent had good protection to the nanocrystals as well, which could be essential to the commercial application of the titled rare earth nanocrystals as novel multifunctional additives in the fields of lubrication.

  13. Using data from colloid transport experiments to parameterize filtration model parameters for favorable conditions

    Science.gov (United States)

    Kamai, Tamir; Nassar, Mohamed K.; Nelson, Kirk E.; Ginn, Timothy R.

    2017-04-01

    Colloid filtration in porous media spans across many disciplines and includes scenarios such as in-situ bioremediation, colloid-facilitated transport, water treatment of suspended particles and pathogenic bacteria, and transport of natural and engineered nanoparticles in the environment. Transport and deposition of colloid particles in porous media are determined by a combination of complex processes and forces. Given the convoluted physical, chemical, and biological processes involved, and the complexity of porous media in natural settings, it should not come as surprise that colloid filtration theory does not always sufficiently predict colloidal transport, and that there is still a pressing need for improved predictive capabilities. Here, instead of developing the macroscopic equation from pore-scale models, we parametrize the different terms in the macroscopic collection equation through fitting it to experimental data, by optimizing the parameters in the different terms of the equation. This way we combine a mechanistically-based filtration-equation with empirical evidence. The impact of different properties of colloids and porous media are studied by comparing experimental properties with different terms of the correlation equation. This comparison enables insight about different processes that occur during colloid transport and retention under in porous media under favorable conditions, and provides directions for future theoretical developments.

  14. Endoscopic management of third ventricular colloid cysts: Eight years′ institutional experience and description of a new technique

    Directory of Open Access Journals (Sweden)

    Mishra Shashwat

    2010-01-01

    Full Text Available Background : The operative approaches for colloid cyst excision are varied with open microsurgical excision still being considered as the "gold standard". Endoscopic removal of these cysts is gaining in popularity. Aims : To document the efficacy and safety of the endoscope for colloid cyst excision. Materials and Methods : Retrospective study of all the patients who underwent endoscopic colloid cyst excision between January 2000 and March 2009. Patient records, radiological images and operative notes were assessed. Follow-up data including clinical and radiological details were retrieved. Results : Fifty-nine cases underwent endoscopic surgery during the study period. Gross total excision of cyst (with small residual nubbin could be achieved in 46 (78% patients. Others patients underwent: near-total excision (seven; partial excision (five; and cyst aspiration (one. A two-port technique for achieving excision was used in 18 patients. There was one death due to fulminant meningitis. No patients had recurrence, follow-up till 99 months. Two patients required ventriculo peritonealshunt for persistent hydrocephalus. Conclusions : Endoscopic excision is a safe and effective, minimally invasive method for colloid cyst removal. Even a subtotal excision of these slow-growing cysts may be acceptable when experience with the endoscope is limited.

  15. Dynamic self-organization of side-propelling colloidal rods: experiments and simulations.

    Science.gov (United States)

    Vutukuri, Hanumantha Rao; Preisler, Zdeněk; Besseling, Thijs H; van Blaaderen, Alfons; Dijkstra, Marjolein; Huck, Wilhelm T S

    2016-12-06

    In recent years, there is a growing interest in designing artificial analogues of living systems, fueled not only by potential applications as 'smart micro-machines', but also by the demand for simple models that can be used to study the behavior of their more complex natural counterparts. Here, we present a facile, internally driven, experimental system comprised of fluorescently labeled colloidal silica rods of which the self-propulsion is powered by the decomposition of H2O2 catalyzed by a length-wise half Pt coating of the particles in order to study how shape anisotropy and swimming direction affect the collective behavior. We investigated the emerging structures and their time evolution for various particle concentrations in (quasi-)two dimensional systems for three aspect ratios of the rods on a single particle level using a combination of experiments and simulations. We found that the dynamic self-organization relied on a competition between self-propulsion and phoretic attractions induced by phoresis of the rods. We observed that the particle clustering behavior depends on the concentration as well as the aspect ratio of the rods. Our findings provide a more detailed understanding of dynamic self-organization of anisotropic particles and the role the propulsion direction plays in internally driven systems.

  16. Preparation of SMART wound dressings based on colloidal microgels and textile fibres

    Science.gov (United States)

    Cornelius, Victoria J.; Majcen, Natasa; Snowden, Martin J.; Mitchell, John C.; Voncina, Bojana

    2007-01-01

    Wound dressings and other types of wound healing technologies are experiencing fast-paced development and rapid growth. As the population ages, demand will continue to rise for advanced dressings used to treat chronic wounds, such as pressure ulcers, venous stasis ulcers, and diabetic ulcers. Moist wound dressings, which facilitate natural wound healing in a cost-effective manner, will be increasingly important. In commercially available hydrogel / gauze wound dressings the gel swells to adsorb wound excreta and provide an efficient non adhesive particle barrier. An alternative to hydrogels are microgels. Essentially discrete colloidal gel particles, as a result of their very high surface area to volume ratio compared to bulk gels, they have a much faster response to external stimuli such as temperature or pH. In response to either an increase or decrease in solvent quality these porous networks shrink and swell reversibly. When swollen the interstitial regions within the polymer matrix are available for further chemistry; such as the incorporation of small molecules. The reversible shrinking and swelling as a function of external stimuli provides a novel drug release system. As the environmental conditions of a wound change over its lifetime, tending to increase in pH if there is an infection combining these discrete polymeric particles with a substrate such as cotton, results in a smart wound dressing.

  17. A new method to prepare colloids of size-controlled clusters from a matrix assembly cluster source

    Science.gov (United States)

    Cai, Rongsheng; Jian, Nan; Murphy, Shane; Bauer, Karl; Palmer, Richard E.

    2017-05-01

    A new method for the production of colloidal suspensions of physically deposited clusters is demonstrated. A cluster source has been used to deposit size-controlled clusters onto water-soluble polymer films, which are then dissolved to produce colloidal suspensions of clusters encapsulated with polymer molecules. This process has been demonstrated using different cluster materials (Au and Ag) and polymers (polyvinylpyrrolidone, polyvinyl alcohol, and polyethylene glycol). Scanning transmission electron microscopy of the clusters before and after colloidal dispersion confirms that the polymers act as stabilizing agents. We propose that this method is suitable for the production of biocompatible colloids of ultraprecise clusters.

  18. Influence of HCl on the NPs-CdSe synthesis prepared by the colloidal method

    Directory of Open Access Journals (Sweden)

    J. Sarmiento Arellano

    2016-08-01

    Full Text Available Cadmium selenide nanoparticles (NPs-CdSe were synthesized by colloidal route at room temperature and atmospheric pressure using cadmium chloride (CdCl2·2.5 hydrate and elemental selenium (Se as precursors. Sodium borohydride (NaBH4 was used as reducing agent to obtain Se2− ions and an aqueous solution with a NaOH and Penta sodium tripolyphosphate (STPP was used to protect Cd2+ ions. To remove the by-products generated during the chemical reaction and to promote the precipitation of NPs-CdSe, a cleaning process with an aqueous solution of HCl was performed. The HCl volume was varied from 0.2 to 1.2 ml during the cleaning process to study its effects on CdSe synthesis. The crystalline structure was analyzed by inspection of the high-resolution transmission electron microscope (HR-TEM and X-ray diffraction (XRD. This analysis showed that crystals of CdSe exhibit a face-centered cubic structure (FCC. The calculated crystallite size is 3.5 nm and increases to 4.5 nm as the HCl volume increases. The morphologies of the products were observed by SEM and TEM techniques. HRTEM images showed that NPs-CdSe synthetized to 0.8 ml are composed of a great number of homogeneous and smooth nanospheres which are not appreciable in SEM but are observable in TEM. By contrast, 0.2 and 1.2 ml HCl samples are comprised of a great deal of rods of compounds of Se mixed with CdSe spheres nanostructures. This work, which did not require the use of surfactants complexes or specials environment, is considered to have advantages over other works.

  19. [Toxicological evaluation of nanosized colloidal silver, stabilized with polyvinylpyrrolidone, in 92-day experiment on rats. II. Internal organs morphology].

    Science.gov (United States)

    Zaytseva, N V; Zemlyanova, M A; Zvezdin, V N; Dovbysh, A A; Gmoshinsky, I V; Khotimchenko, S A; Akafieva, T I

    2016-01-01

    The aim of the study was to evaluate the safe doses of commercially available nanosized colloidal silver (NCS), stabilized with polyvinilpirrolidone (PVP, food additive E1201) when administered in gastrointestinal tract of rats in the 92-day experiment in terms of the morphological changes in the internals of animals. The sample studied contained non-aggregated nanoparticles (NPs) of silver belonging to size fractions with a diameter of less than 5 nm, 10-20 nm or 50-80 nm. 80% of NPs were inside the range of hydrodynamic diameters 10.6-61.8 nm. The preparation of NCS was administered to growing male Wistar rats. (initial body weight 80 ± 10 g) for 1 month by intragastric gavage and then consumed with food at doses of 0.1, 1.0 and 10 mg/kg of body weight based on silver. The control animals received water or vehicle of nanomaterial--water solution of PVP. After withdrawal of animals from the experiment by exsanguination under ether anesthesia organs (liver, spleen, kidney, ileum) were isolated and their slides were prepared by standard methods following 'by staining with hematoxylin-eosin. Analysis was performed in light optical microscope equipped with a digital camera at a magnification from 1 x 100 to 1 x 1000. It was shown that the experimental animals treated with the NCS developed series of morphological changes in the tissues of the internal organs (liver, spleen and kidney) with the elevation of the range and severity of structural changes with increasing doses of silver. The most sensitive target of NCS action was apparently liver, which has already shown at a dose of 0.1 mg of silver NP/kg of body weight marked eosinophilic infiltration of portal tracts, which was accompanied at doses of 1.0 and 10.0 mg/kg by the emergence of medium and large-drop fat vacuoles in the cytoplasm of hepatocytes, swelling and lympho-macrophage. infiltration of the portal tracts. Detectable changes can be regarded as symptoms of inflammation of hepatocytes, at least, at a

  20. Synthesis of soft shell poly(styrene) colloids for filtration experiments

    DEFF Research Database (Denmark)

    Hinge, Mogens

    Separating a solid from a liquid is an important unit operation in many different industries e.g. mining, chemical, pharmaceutical and food industries. Solid liquid separation can roughly be divided into three groups. 1) Separation by gravity forces e.g. sedimentation, centrifugation, 2) Separation...... of the core-shell colloids on the filtration dewatering behavior. The third and final series has been chosen to investigate the effect from a non-ionic water swollen material. The model colloids from series one and two were synthesized by a free-radicale surfactant-free emulsion co-polymerization process...... of acrylic acid monomer added to the synthesis. Further it was shown that it is possible to increase the PS core diameter by increasing the ionic strength of the synthesis solution. The model colloids from series three were synthesized by a two step free-radical surfactant-free emulsion polymerization (SFEP...

  1. Colloid-Facilitated Transport of 137Cs in Fracture-Fill Material. Experiments and Modeling

    Energy Technology Data Exchange (ETDEWEB)

    Dittrich, Timothy M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Reimus, Paul William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-10-29

    In this study, we demonstrate how a combination of batch sorption/desorption experiments and column transport experiments were used to effectively parameterize a model describing the colloid-facilitated transport of Cs in the Grimsel granodiorite/FFM system. Cs partition coefficient estimates onto both the colloids and the stationary media obtained from the batch experiments were used as initial estimates of partition coefficients in the column experiments, and then the column experiment results were used to obtain refined estimates of the number of different sorption sites and the adsorption and desorption rate constants of the sites. The desorption portion of the column breakthrough curves highlighted the importance of accounting for adsorption-desorption hysteresis (or a very nonlinear adsorption isotherm) of the Cs on the FFM in the model, and this portion of the breakthrough curves also dictated that there be at least two different types of sorption sites on the FFM. In the end, the two-site model parameters estimated from the column experiments provided excellent matches to the batch adsorption/desorption data, which provided a measure of assurance in the validity of the model.

  2. 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

  3. Control of Colloid Surface Chemistry through Matrix Confinement: Facile Preparation of Stable Antibody Functionalized Silver Nanoparticles

    Science.gov (United States)

    Skewis, Lynell R.; Reinhard, Björn M.

    2010-01-01

    Here we describe a simple yet efficient gel matrix assisted preparation method which improves synthetic control over the interface between inorganic nanomaterials and biopolymers and yields stable biofunctionalized silver nanoparticles. Covalent functionalization of the noble metal surface is aided by the confinement of polyethylene glycol acetate functionalized silver nanoparticles in thin slabs of a 1% agarose gel. The gel confined nanoparticles can be transferred between reaction and washing media simply by immersing the gel slab in the solution of interest. The agarose matrix retains nanoparticles but is swiftly penetrated by the antibodies of interest. The antibodies are covalently anchored to the nanoparticles using conventional crosslinking strategies, and the resulting antibody functionalized nanoparticles are recovered from the gel through electroelution. We demonstrate the efficacy of this nanoparticle functionalization approach by labeling specific receptors on cellular surfaces with functionalized silver nanoparticles that are stable under physiological conditions. PMID:20161660

  4. Colloidally stable surface-modified iron oxide nanoparticles: Preparation, characterization and anti-tumor activity

    Energy Technology Data Exchange (ETDEWEB)

    Macková, Hana [Institute of Macromolecular Chemistry, AS CR, Heyrovsky Sq. 2, 162 06 Prague 6 (Czech Republic); Horák, Daniel, E-mail: horak@imc.cas.cz [Institute of Macromolecular Chemistry, AS CR, Heyrovsky Sq. 2, 162 06 Prague 6 (Czech Republic); Donchenko, Georgiy Viktorovich; Andriyaka, Vadim Ivanovich; Palyvoda, Olga Mikhailovna; Chernishov, Vladimir Ivanovich [Palladin Institute of Biochemistry, NASU, 9 Leontovich St., 01601 Kiev (Ukraine); Chekhun, Vasyl Fedorovich; Todor, Igor Nikolaevich [R. E. Kavetsky Institute of Experimental Pathology, Oncology and Radiobiology, NASU, 45 Vasylkivska St., 03022 Kiev (Ukraine); Kuzmenko, Oleksandr Ivanovich [Palladin Institute of Biochemistry, NASU, 9 Leontovich St., 01601 Kiev (Ukraine)

    2015-04-15

    Maghemite (γ-Fe{sub 2}O{sub 3}) nanoparticles were obtained by co-precipitation of Fe(II) and Fe(III) chlorides and subsequent oxidation with sodium hypochlorite and coated with poly(N,N-dimethylacrylamide-co-acrylic acid) [P(DMAAm-AA)]. They were characterized by a range of methods including transmission electron microscopy (TEM), elemental analysis, dynamic light scattering (DLS) and zeta potential measurements. The effect of superparamagnetic P(DMAAm-AA)-γ-Fe{sub 2}O{sub 3} nanoparticles on oxidation of blood lipids, glutathione and proteins in blood serum was detected using 2-thiobarbituric acid and the ThioGlo fluorophore. Finally, mice received magnetic nanoparticles administered per os and the antitumor activity of the particles was tested on Lewis lung carcinoma (LLC) in male mice line C57BL/6 as an experimental in vivo metastatic tumor model; the tumor size was measured and the number of metastases in lungs was determined. Surface-modified γ-Fe{sub 2}O{sub 3} nanoparticles showed higher antitumor and antimetastatic activities than commercial CuFe{sub 2}O{sub 4} particles and the conventional antitumor agent cisplatin. - Highlights: • Maghemite nanoparticles were prepared and characterized. • Poly(N,N-dimethylacrylamide-co-acrylic acid) coating was synthetized. • Blood lipid, glutathione and protein peroxidation/oxidation was determined. • Antitumor effect of coated particles on Lewis lung carcinoma in mice was observed.

  5. Synthesis and Analytical Centrifugation of Magnetic Model Colloids

    OpenAIRE

    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 specially adapted centrifuge for measuring heavy and strongly light absorbing colloids. Magnetic composite colloids can be prepared from thermodynamically stable Pickering emulsions of 3-methacrylox...

  6. Transparent NaGdF4:Nd3+ colloid prepared by femtosecond laser ablation as a liquid laser medium

    Science.gov (United States)

    Dai, Jiangyun; Feng, Guoying; Wang, Shutong; Zhang, Hong; Dai, Shengyu; Zhou, Shouhuan

    2017-07-01

    By using femtosecond-pulsed laser to ablate the larger nanosized target in liquid, stable transparent NaGdF4:Nd3+ colloid has been successfully fabricated. The X-ray diffraction (XRD) spectra reveal that the colloidal nanoparticles remain the hexagonal phase crystal structure of NaGdF4 powder target. SEM and TEM images results indicate that the size of these colloidal nanoparticles decreases sharply. FT-IR results indicate that the number of O-H and C-H groups on the surface is decreased. The emission properties of the colloid have been investigated using 794 nm pulsed wave laser radiation, and it is found that the colloid exhibits near-infrared luminescent emissions in the spectral range of 850-1400 nm, and the decay time for 4F3/2→4I11/2 (1058 nm) Nd3+ ion transitions is lengthened than that of powder target, these results are probably due to the reduced nonradiative relaxation assisted by high energy oscillators. The observed near-infrared emission of the stable transparent colloid makes it a good candidate for application in liquid laser.

  7. Thermal vitrification in suspensions of soft colloids: molecular dynamics simulations and comparison with experiments.

    Science.gov (United States)

    Rissanou, A N; Vlassopoulos, D; Bitsanis, I A

    2005-01-01

    Dense suspensions of multiarm star polymers are known to develop liquidlike microstructure, which has been attributed to the similarities between high functionality stars and colloidal particles interacting via soft, long ranged potentials. Recent experimental studies reported a counterintuitive solidification of suspensions with f=128 , upon increase of the temperature in marginal solvents. We present our results from molecular dynamics simulations of dense suspensions of multiarm star polymers. Star polymers are modeled as "soft spheres" interacting via a theoretically developed potential of mean field. Our results show a transition towards a "glassy" state at a temperature very close to the one reported experimentally. The features of the transition are consistent with those of ideal glass transitions, as described by ideal mode coupling theory. Furthermore, our findings illustrate the road to vitrification for these soft-colloidal suspensions. Higher temperatures result in arm expansion that causes jamming and more than compensates for faster short time, temperature induced kinetics.

  8. Old relief printing applied to the current preparation of multi-color and high resolution colloidal photonic crystal patterns.

    Science.gov (United States)

    Yang, Dongpeng; Ye, Siyun; Ge, Jianping

    2015-12-11

    Monodisperse SiO2 colloids are assembled into colloidal crystals in the mixture of monomer and solvent, which is transformed into a mechanochromic photonic crystal paper by polymerization. Following the relief printing strategy, the printing plates are pressed onto the paper to generate letters or images due to the contrast of structural color between the deformed and the undeformed paper, and the images can be permanently retained through UV curing. The wide tunable range of structural color for the current paper under deformation helps to realize multi-color printing. The localized deformation among or even inside the colloidal microcrystals renders the paper with a precise mechanochromic response to the printing plates and leads to the production of high resolution photonic crystal patterns.

  9. Shear-induced breaking of cages in colloidal glasses: Scattering experiments and mode coupling theory

    Energy Technology Data Exchange (ETDEWEB)

    Amann, Christian P., E-mail: Christian.2.Amann@uni-konstanz.de; Fuchs, Matthias, E-mail: Matthias.Fuchs@uni-konstanz.de [Fachbereich Physik, Universität Konstanz, 78457 Konstanz (Germany); Denisov, Dmitry; Dang, Minh Triet; Schall, Peter [Van der Waals-Zeeman Institute, University of Amsterdam, Amsterdam (Netherlands); Struth, Bernd [Deutsches Elektronen-Synchrotron, Hamburg (Germany)

    2015-07-21

    We employ x-ray scattering on sheared colloidal suspensions and mode coupling theory to study structure factor distortions of glass-forming systems under shear. We find a transition from quadrupolar elastic distortion at small strains to quadrupolar and hexadecupolar modes in the stationary state. The latter are interpreted as signatures of plastic rearrangements in homogeneous, thermalized systems. From their transient evolution with strain, we identify characteristic strain and length-scale values where these plastic rearrangements dominate. This characteristic strain coincides with the maximum of the shear stress versus strain curve, indicating the proliferation of plastic flow. The hexadecupolar modes dominate at the wavevector of the principal peak of the equilibrium structure factor that is related to the cage-effect in mode coupling theory. We hence identify the structural signature of plastic flow of glasses.

  10. 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

  11. 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. Copyright

  12. Colloid facilitated transport of humic substances in soil: laboratory experiment and modeling calculation.

    Science.gov (United States)

    Dinu, Marina; Moiseenko, Tatyana

    2016-04-01

    An understanding of ability to predict the fate and transport of colloids in soil systems are of great importance in many environmental and industrial applications. Especially, in the case study sizes and zeta potentials of lignin and humus components (as a parameter reflecting the mobility and tread of organic substances). The objects of investigation were water extracts of gleepodzolic soil of European territory of Russia and Western Siberia, as well as humus substances extracted from this soil. In this study, evaluation of size, molecular weight distribution and zeta potential were used to predict the mobility of the organic component fractions of the soil. Fractionation was performed using multistage filtration plant (100 Da) and measuring physic-chemical parameters measured with the Malvern Zetasizer Nano ZSP. Significant differences in the distribution of organic matter on the molecular weight, charge (sign) of the zeta potential and the size of the sample of European Russia in comparison with samples of Western Siberia have been found. Also, laboratory studies have demonstrated of any differences in physicochemical parameters as infrared spectra, ultraviolet spectra, complexing ability of samples of the same soil type but different areas of Russia. The results can be used in the prediction of the migration ability of fractions humus substances and their stability at change physic-chemical conditions (the coefficient of mobility of the organic components by calculated in MathCad). This work was supported by the grant № 14-17-00460 RSF from 07.11.2014

  13. EDITORIAL: Colloidal suspensions Colloidal suspensions

    Science.gov (United States)

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

    2011-05-01

    fluid-fluid interface [2]. Together with Remco Tuinier, Henk has recently completed a book in this area which is to appear later this year. A major theme in Henk's research is that of phase transitions in lyotropic liquid crystals. Henk, together with Daan Frenkel and Alain Stroobants, realized in the 1980s that a smectic phase in dispersions of rod-like particles can be stable without the presence of attractive interactions, similar to nematic ordering as predicted earlier by Onsager [3]. Together with Gert-Jan Vroege he wrote a seminal review in this area [4]. Henk once said that 'one can only truly develop one colloidal model system in one's career' and in his case this must be that of gibbsite platelets. Initially Henk's group pursued another polymorph of aluminium hydroxide, boehmite, which forms rod-like particles [5], which already displayed nematic liquid crystal phases. The real breakthrough came when the same precursors treated the produced gibbsite platelets slightly differently. These reliably form a discotic nematic phase [6] and, despite the polydispersity in their diameter, a columnar phase [7]. A theme encompassing a wide range of soft matter systems is that of colloidal dynamics and phase transition kinetics. Many colloidal systems have a tendency to get stuck in metastable states, such as gels or glasses. This is a nuisance if one wishes to study phase transitions, but it is of great practical significance. Such issues feature in many of Henk's publications, and with Valerie Anderson he wrote a highly cited review in this area [8]. Henk Lekkerkerker has also invested significant effort into the promotion of synchrotron radiation studies of colloidal suspensions. He was one of the great supporters of the Dutch-Belgian beamline 'DUBBLE' project at the ESRF [9]. He attended one of the very first experiments in Grenoble in 1999, which led to a Nature publication [7]. He was strongly involved in many other experiments which followed and also has been a

  14. 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.

  15. 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

  16. 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

  17. [Compared with colloidal silica and porous silica as baicalin solid dispersion carrier].

    Science.gov (United States)

    Yan, Hong-Mei; Ding, Dong-Mei; Wang, Jing; Sun, E; Jia, Xiao-Bin; Zhang, Zhen-Hai

    2014-07-01

    To compare the dissolution characteristics of colloidal silica and porous silica as the solid dispersion carrier, with baicalin as the model drug. The baicalin solid dispersion was prepared by the solvent method, with colloidal silica and porous silica as the carriers. In the in vitro dissolution experiment, the solid dispersion was identified by scanning electron microscopy, differential scanning and X-ray diffraction. The solid dispersion carriers prepared with both colloidal silica and porous silica could achieve the purpose of rapid release. Along with the increase in the proportion of the carriers, the dissolution rate is accelerated to more than 80% within 60 min. Baicalin existed in the solid dispersion carriers in the non-crystalline form. The release behaviors of the baicalin solid dispersion prepared with two types of carrier were different. Among the two solid dispersion carriers, porous silica dissolved slowly than colloidal silica within 60 min, and they showed similar dissolutions after 60 min.

  18. Intercultural Preparation for Future Mobile Students: A Pedagogical Experience

    Science.gov (United States)

    Beaven, Ana; Golubeva, Irina

    2016-01-01

    Higher education (HE) student mobility offers the opportunity to acquire, among other things, intercultural experience. Nevertheless, it is crucial to prepare students and give them the tools to reflect on their experiences before, during and after study abroad. In this pedagogical paper, we present and discuss "Perceptions of self and…

  19. 稳定分散的纳米银溶胶的制备及其表征%Preparation and Characterization of Stable Dispersive Colloidal Silver Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    王悦辉; 周济; 王婷

    2007-01-01

    Stable aqueous dispersive colloidal Ag nanoparticles were prepared by reducing silver nitrate with sodium borohydride in the presence of 3-mercaptopropionic acid. The formation process of the Ag nanoparticles was investigated by UV-Visible spectroscopy and transmission electron microscopy. The results show that the spherical and rodlike particles and aggregates are formed in the initial stage of the reaction, then the rodlike particles and aggregates are gradually decomposed into small Spherical particles, and the final obtained Ag nanoparticles with an average size of 8 nm are in uniform shapes and narrow size distribution, and the colloid remains stable for more than one month, which makes it convenient for use in practice. The presence of capping agent plays an extra role over nanoparticles stabilization and morphology.The presence of capping agent on the surface of Ag nanoparticle is confirmed by the X-ray photoelectron spectroscopy. It is found that Ag nanoparticles are negatively charged in alkaline condition, whereas they are positively charged in acid condition. Electrosteric effect is responsible for their long-term stability.

  20. Encapsulation of biomaterials in porous glass-like matrices prepared via an aqueous colloidal sol-gel process

    Science.gov (United States)

    Liu, Dean-Mo; Chen, I-Wei

    2001-01-01

    The present invention provides a process for the encapsulation of biologically important proteins into transparent, porous silica matrices by an alcohol-free, aqueous, colloidal sol-gel process, and to the biological materials encapsulated thereby. The process is exemplified by studies involving encapsulated cytochrome c, catalase, myoglobin, and hemoglobin, although non-proteinaceous biomaterials, such as active DNA or RNA fragments, cells or even tissues, may also be encapsulated in accordance with the present methods. Conformation, and hence activity of the biomaterial, is successfully retained after encapsulation as demonstrated by optical characterization of the molecules, even after long-term storage. The retained conformation of the biomaterial is strongly correlated to both the rate of gelation and the subsequent drying speed of the encapsulatng matrix. Moreover, in accordance with this process, gelation is accelerated by the use of a higher colloidal solid concentration and a lower synthesis pH than conventional methods, thereby enhancing structural stability and retained conformation of the biomaterials. Thus, the invention also provides a remarkable improvement in retaining the biological activity of the encapsulated biomaterial, as compared with those involved in conventional alkoxide-based processes. It further provides new methods for the quantitative and qualitative detection of test substances that are reactive to, or catalyzed by, the active, encapsulated biological materials.

  1. Preparation of SnS2 colloidal quantum dots and their application in organic/inorganic hybrid solar cells

    Science.gov (United States)

    Tan, Furui; Qu, Shengchun; Wu, Ju; Liu, Kong; Zhou, Shuyun; Wang, Zhanguo

    2011-12-01

    Dispersive SnS2 colloidal quantum dots have been synthesized via hot-injection method. Hybrid photovoltaic devices based on blends of a conjugated polymer poly[2-methoxy-5-(3",7"dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) as electron donor and crystalline SnS2 quantum dots as electron acceptor have been studied. Photoluminescence measurement has been performed to study the surfactant effect on the excitons splitting process. The photocurrent of solar cells with the hybrid depends greatly on the ligands exchange as well as the device heat treatment. AFM characterization has demonstrated morphology changes happening upon surfactant replacement and annealing, which can explain the performance variation of hybrid solar cells.

  2. 超声场下银胶体的制备%Preparation of Well-Dispersed Silver Colloids in the Ultrasonic Field

    Institute of Scientific and Technical Information of China (English)

    程敬泉; 姚素薇

    2005-01-01

    Well-dispersed Silver colloids are prepared from AgNO3 and KBH4 under the protection of polyvinylpyrrolidone (PVP) in the ultrasonic field. The main factors influencing on stability of silver colloids, such as the concentration of PVP and KBH4, ultrasonic time and power, are discussed. The silver colloids are characterized by TEM, SAED and Spectrophotometer.The result indicates that the stable silver nanoparticles are prepared with PVP/AgNO3 mass ratio of 1:1. Selected area electron diffraction pattern reveals that the silver nanoparticle is of face-centered cubic structure. Spherical-like silver nanoparticles with about 20 nm size are synthesized with AgNO3/KBH4 molar ratio of 1:2. The dispersion and stability of the silver colloid will be improved after ultrasonic wave treatment. The diameters of silver nanoparticles decrease and the particle size distribution becomes narrow with the ultrasonic power increase. Silver particles with 10~20 nm size and spherical shape have been prepared after 50 min of ultrasonic wave treatment.%在超声场作用下,以聚乙烯吡咯烷酮为保护剂,硝酸银为前驱物,经硼氢化钾还原制备了稳定的银胶体.研究了保护剂和还原剂用量、超声时间和超声功率等因素对银胶体稳定性的影响,利用透射电镜、选区电子衍射和分光光度等技术对制备的银胶体进行了表征.结果表明:银纳米粒子为面心立方(fcc)结构;PVP与AgNO3质量比为1:1时,PVP可有效保护银粒子,获得了球形颗粒;AgNO3与KBH4摩尔比为1:2时,可制得分散较好的直径约为20 nm的类球形银纳米颗粒;在超声场作用下,银胶体的分散性和稳定性增强.随着超声功率的增大,银纳米粒子直径变小,粒径分布变窄.超声50 min制得的银胶体主要以球形纳米颗粒形式存在,粒径在10 nm~20 nm范围内,稳定性好.

  3. High pressure organic colloid method for the preparation of high performance carbon nanotube-supported Pt and PtRu catalysts for fuel cell applications

    Institute of Scientific and Technical Information of China (English)

    WANG; KateNing; Viola; BIRSS

    2010-01-01

    Highly dispersed,high performance Pt and PtRu catalysts,supported on multiwalled carbon nanotubes(CNTs),were prepared by a high pressure organic colloid method.The particle sizes of the active components were as small as 1.2 nm for Pt and 1.1 nm for PtRu,and the active Pt surface areas were 295 and 395 m2/g,respectively.The catalysts showed very high activities toward the anodic oxidation of methanol,evaluated by cyclic voltammetry,being up to 4 times higher than that of commercial Johnson Matthey Hispec 2000 Pt/XC-72R and 5 times better than Hispec 5000 PtRu/XC-72R catalysts.In a full air/hydrogen fuel cell,a membrane-electrode assembly prepared using our Pt/CNT and PtRu/CNT catalysts showed 50% and 100% higher performances than those prepared with commercial Johnson Matthey Pt/XC-72R and PtRu/XC-72R catalysts for the same Pt loading and operating conditions.

  4. Microstructure and magnetic properties of MFe{sub 2}O{sub 4} (M = Co, Ni, and Mn) ferrite nanocrystals prepared using colloid mill and hydrothermal method

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Wei, E-mail: wangwei@mail.buct.edu.cn; Ding, Zui; Zhao, Xiruo [State Key Laboratory of Chemical Resource Engineering and School of Science, Beijing University of Chemical Technology, Beijing 100029 (China); Beijing Key Laboratory of Environmentally Harmful Chemical Analysis, Beijing University of Chemical Technology, Beijing 100029 (China); Wu, Sizhu [State Key Laboratory of Organic–Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029 (China); Li, Feng [State Key Laboratory of Chemical Resource Engineering and School of Science, Beijing University of Chemical Technology, Beijing 100029 (China); Yue, Ming [College of Materials Science and Engineering, Beijing University of Technology, Beijing 100022 (China); Liu, J. Ping [Department of Physics, University of Texas at Arlington, Arlington, Texas 76019 (United States)

    2015-05-07

    Three kinds of spinel ferrite nanocrystals, MFe{sub 2}O{sub 4} (M = Co, Ni, and Mn), are synthesized using colloid mill and hydrothermal method. During the synthesis process, a rapid mixing and reduction of cations with sodium borohydride (NaBH{sub 4}) take place in a colloid mill then through a hydrothermal reaction, a slow oxidation and structural transformation of the spinel ferrite nanocrystals occur. The phase purity and crystal lattice parameters are estimated by X-ray diffraction studies. Scanning electron microscopy and transmission electron microscopy images show the morphology and particle size of the as-synthesized ferrite nanocrystals. Raman spectrum reveals active phonon modes at room temperature, and a shifting of the modes implies cation redistribution in the tetrahedral and octahedral sites. Magnetic measurements show that all the obtained samples exhibit higher saturation magnetization (M{sub s}). Meanwhile, experiments demonstrate that the hydrothermal reaction time has significant effects on microstructure, morphologies, and magnetic properties of the as-synthesized ferrite nanocrystals.

  5. Spherical colloidal photonic crystals.

    Science.gov (United States)

    Zhao, Yuanjin; Shang, Luoran; Cheng, Yao; Gu, Zhongze

    2014-12-16

    generated by evaporation-induced nanoparticle crystallization or polymerization of ordered nanoparticle crystallization arrays. In particular, because microfluidics was used for the generation of the droplet templates, the development of spherical colloidal PhCs has progressed significantly. These new strategies not only ensure monodispersity, but also increase the structural and functional diversity of the PhC beads, paving the way for the development of advanced optoelectronic devices. In this Account, we present the research progress on spherical colloidal PhCs, including their design, preparation, and potential applications. We outline various types of spherical colloidal PhCs, such as close-packed, non-close-packed, inverse opal, biphasic or multiphasic Janus structured, and core-shell structured geometries. Based on their unique optical properties, applications of the spherical colloidal PhCs for displays, sensors, barcodes, and cell culture microcarriers are presented. Future developments of the spherical colloidal PhC materials are also envisioned.

  6. Preoperative mechanical preparation of the colon: the patient's experience

    Directory of Open Access Journals (Sweden)

    Arodell Malin

    2007-05-01

    Full Text Available Abstract Background Preoperative mechanical bowel preparation can be questioned as standard procedure in colon surgery, based on the result from several randomised trials. Methods As part of a large multicenter trial, 105 patients planned for elective colon surgery for cancer, adenoma, or diverticulitis in three hospitals were asked to complete a questionnaire regarding perceived health including experience with bowel preparation. There were 39 questions, each having 3 – 10 answer alternatives, dealing with food intake, pain, discomfort, nausea/vomiting, gas distension, anxiety, tiredness, need of assistance with bowel preparation, and willingness to undergo the procedure again if necessary. Results 60 patients received mechanical bowel preparation (MBP and 45 patients did not (No-MBP. In the MBP group 52% needed assistance with bowel preparation and 30% would consider undergoing the same preoperative procedure again. In the No-MBP group 65 % of the patients were positive to no bowel preparation. There was no significant difference between the two groups with respect to postoperative pain and nausea. On Day 4 (but not on Days 1 and 7 postoperatively patients in the No-MBP group perceived more discomfort than patients in the MBP group, p = 0.02. Time to intake of fluid and solid food did not differ between the two groups. Bowel emptying occurred significantly earlier in the No-MBP group than in the MBP group, p = 0.03. Conclusion Mechanical bowel preparation is distressing for the patient and associated with a prolonged time to first bowel emptying.

  7. Preparation and Characterization of Polymeric Nanoparticles: An Interdisciplinary Experiment

    Science.gov (United States)

    Ramalho, Maria J.; Pereira, M. Carmo

    2016-01-01

    In this work, a laboratory experiment to introduce graduate students to nanotechnology is described. Students prepared poly(lactic-"co"-glycolic acid) (PLGA) nanoparticles using two different synthesis procedures, a single and a double emulsion-solvent evaporation method. The students also performed a physicochemical characterization of…

  8. Synthesis of soft shell poly(styrene) colloids for filtration experiments

    DEFF Research Database (Denmark)

    Hinge, Mogens

    (e.g. titanium oxide, clay, bentonite). It is often possible to apply these model in predicting and scaling up the filtration dewatering process for inorganic materials based on fundamental material parameters (e.g. particle size, density) and/or based on laboratory experiments. It has, however, been...

  9. Preparation, characterization and mechanical properties of microarc oxidation coating formed on titanium in Al(OH)3 colloidal solution

    Science.gov (United States)

    Li, Y.; Yao, B.; Long, B. Y.; Tian, H. W.; Wang, B.

    2012-04-01

    A ceramic coating with thickness of 20-70 μm was grown on titanium plate in Al(OH)3 colloidal solution by microarc oxidation (MAO) in constant current mode. It is found that the as-grown coating consists of rutile TiO2 phase together with a thin layer of Ai2TiO5 phase near the surface of the coating. After removing the Ai2TiO5 layer by polishing, a single phase of rutile TiO2 coating is achieved, which is different from results reported previously, where the coating is usually composed of two phases of rutile and anatase TiO2. It is suggested that the formation of the coating with single phase of rutile TiO2 is related to the existence of Al(OH)3 in the solution. The growth rate of the coating increases with increasing current density in the range of 17-23 A/dm2, but it increases little in the range of 23-30 A/dm2. The rutile TiO2 coating looks compactness and solidity in the coating grown in the density range of 17-23 A/dm2 but looseness and insubstantiality in the range of 23-30 A/dm2. The hardness and elastic modulus of the rutile TiO2 decreases with the density increasing. The mechanism of formation of the coating is discussed in the present work.

  10. Study of Pd-Sn/Al{sub 2}O{sub 3} catalysts prepared by an oxide colloidal route; Etude de catalyseurs Pd-Sn/Al{sub 2}O{sub 3} prepares par voie colloidale oxyde

    Energy Technology Data Exchange (ETDEWEB)

    Verdier, St.

    2001-09-01

    The oxide colloidal route, developed in the laboratory for mono-metallic catalysts, consists in preparing a metallic oxide hydro-sol which leads to the supported catalyst after deposition onto a support and an activation stage. In this work, this method has been adapted to the preparation of alumina supported bimetallic Pd-Sn catalysts to determine its interest for the control of the properties of the bimetallic phase (size, composition and structure). In the preliminary study concerning tin oxide sols, SnO{sub 2} (size=2,3 nm) and Sn{sub 6}O{sub 4}(OH){sub 4} (size = 25 nm) nano-particles were synthesized by neutralization respectively for tin(IV) and tin(H). The control through the pH of the aggregation of the PdO and SnO{sub 2} particles revealed that increasing oxide solubility promotes integral re-dispersion of the oxide particles. To synthesize oxide bimetallic sols, three strategies were defined. Copolymerization (formation of a mixed oxide nano-sol by cross condensation of both metals) does not lead to a mixed oxide Pd-Sn phase. Surface precipitation (neutralization of the second metal in the presence of the first oxide sol) yields nano-particles of both oxides in close interaction. Adsorption (adsorption of the second metal onto the first oxide sol) significantly occurs when contacting tin with a basic PdO sol (hydrolytic adsorption). The characterization and the assessment of the catalytic properties (selective hydrogenation of buta-1,3-diene) of the catalysts prepared by deposition of oxide bimetallic sols showed that the oxide colloidal route allows the control of the properties of the supported bimetallic phase. Moreover, our results display that both Pd-Sn alloy formation and,aggregation of the metallic particles contribute to increase the selectivity for this reaction. (author)

  11. 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.

  12. Correlated two-particle diffusion in dense colloidal suspensions at early times: Theory and comparison to experiment.

    Science.gov (United States)

    Dell, Zachary E; Tsang, Boyce; Jiang, Lingxiang; Granick, Steve; Schweizer, Kenneth S

    2015-11-01

    The spatially resolved diffusive dynamic cross correlations of a pair of colloids in dense quasi-two-dimensional monolayers of identical particles are studied experimentally and theoretically at early times where motion is Fickian. In very dense systems where strong oscillatory equilibrium packing correlations are present, we find an exponential decay of the dynamic cross correlations on small and intermediate length scales. At large separations where structure becomes random, an apparent power law decay with an exponent of approximately -2.2 is observed. For a moderately dense suspension where local structural correlations are essentially absent, this same apparent power law decay is observed over all probed interparticle separations. A microscopic nonhydrodynamic theory is constructed for the dynamic cross correlations which is based on interparticle frictional effects and effective structural forces. Hydrodynamics enters only via setting the very short-time single-particle self-diffusion constant. No-adjustable-parameter quantitative predictions of the theory for the dynamic cross correlations are in good agreement with experiment over all length scales. The origin of the long-range apparent power law is the influence of the constraint of fixed interparticle separation on the amplitude of the mean square force exerted on the two tagged particles by the surrounding fluid. The theory is extended to study high-packing-fraction 3D hard sphere fluids. The same pattern of an oscillatory exponential form of the dynamic cross correlation function is predicted in the structural regime, but the long-range tail decays faster than in monolayers with an exponent of -3.

  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. 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

  15. Fabrication of size-controllable hexagonal non-close-packed colloidal crystals and binary colloidal crystals by pyrolysis combined with plasma-electron coirradiation of polystyrene colloidal monolayer.

    Science.gov (United States)

    Kim, Jae Joon; Li, Yue; Lee, Eun Je; Cho, Sung Oh

    2011-03-15

    We present an unprecedented and systematic route to controllably fabricate hexagonal non-close-packed (hncp) monolayer colloidal crystals and binary colloidal crystals (BCCs) based on plasma-electron coirradiation of polystyrene colloidal monolayers followed by thermal decomposition. Hncp colloidal crystals with tunable particle sizes and periods could be fabricated by changing the pristine colloidal particle size and the thermal decomposition time. In addition, BCCs and trimodal colloidal crystals that are composed of different-sized colloidal particles can also be fabricated by adding small particles on the prepared hncp colloidal crystals. Both the particle size ratio and the volume fraction of the BCCs can be widely tuned. These hncp colloidal crystals and BCCs have various potential applications as optical and photonic materials as well as in catalysis and sensors.

  16. Efficacy of some colloidal silver preparations and silver salts against Proteus bacteria, one possible cause of rheumatoid arthritis.

    Science.gov (United States)

    Disaanayake, D M B T; Faoagali, Joan; Laroo, Hans; Hancock, Gerald; Whitehouse, Michael

    2014-04-01

    There has been increased interest in the role of anti-Proteus antibodies in the aetiology of rheumatoid arthritis (RA) and whether chemotherapeutic agents active against Proteus species might reduce the risk and/or exacerbations of RA. We examined the in vitro antibacterial effects of ten different silver preparations which were either ionic silver [Ag(I)] solutions or nanoparticulate silver (NPS) (Ag(0)) suspensions against ATCC and two wild (clinical) strains of Proteus. The data establish the low minimum inhibitory concentration and minimum bactericidal concentration of all the silver formulations tested against these four Proteus strains. In a pilot study, a potent NPS preparation ex vivo showed long-lasting anti-Proteus activity in a normal human volunteer.

  17. 胶体模板法制备三维锗光子晶体%THREE-DIMENSIONAL GERMANIUM PHOTONIC CRYSTALS PREPARED BY COLLOIDAL TEMPLATE METHOD

    Institute of Scientific and Technical Information of China (English)

    张良静; 许静; 龙永福; 谢凯

    2006-01-01

    采用胶体模板法并通过简单可控的化学填充工艺制备了三维锗光子晶体:以单分散二氧化硅小球的蛋白石结构为模板,由氯化亚锗与丙烯酸化合制备得到3-三氯锗丙酸(Cl3GeCH2CH2COOH)白色粉末,以三氯锗丙酸的乙醇溶液作为锗源先驱体,低温水解得到β-羧乙基锗倍半氧化物,在600~660℃经H2还原后形成锗,由2%HF化学浸蚀消除模板,对终产物进行X射线衍射分析.结果表明:产物为多晶锗.通过扫描电子显微镜对终产物的形貌进行观察的结果表明:包裹有空气的锗壳球有序阵列已经形成.将先驱体浓度为0.6 mol/L的溶液填入模板空隙后,壳层表面可以获得较为光滑致密的锗壳.%Three-dimensional photonic crystals (PCs) were prepared by colloidal template method through a simple controllable chemical filling technique. The synthetic opal made from monodisperse silica colloidal spheres was used as a template, and a white powder of 3-trichlorogermanium propanoic acid (Cl3 GeCH2 CH2 COOH )was synthesized by combination reaction between germanium( Ⅱ )chloride and crylic acid. The Cl3 GeCH2 CH2 COOH solution in ethanol as the germanium precursor was infiltrated into the opal template voids, which was hydrolyzed to form carboxyethyl germanium sesquioxide and reduced by H2 at600 660℃ to form germanium, and then the template was removed chemically by being etched in 2% HF solution. The X-ray diffraction result shows that the final product is the polycrystalline germanium phase. The surface morphology of the final product observed by scanning electron microscopy (SEM) shows that an ordered array composed of air spheres coated with germanium shells was formed. The SEM photographs of the shell surfaces indicate that a smooth and compact shell can be formed when the concentration of the precursor is 0.6 mol/L.

  18. Study on Preparation and Characterization of Silver Nanoparticle Colloid Solution%纳米银的制备与表征

    Institute of Scientific and Technical Information of China (English)

    马守栋; 李明春; 叶勇; 曹恩惠; 赵丽艳

    2011-01-01

    目的 制备粒径小、性质稳定、抗菌活性强的纳米银.方法 化学合成法制备纳米银,以超滤法将反应体系中的杂质除去得高纯度的纳米银.以紫外分光光度计、透射电子显微镜、激光纳米粒度测定仪对其进行理化表征.结果 制备出的纳米银平均粒径为18.29nm,分布窄;表面带负电荷,平均表面Zeta电位为-36.5 mV;性质稳定,抗菌活性强.结论 实验结果表明,本方法可以制备出优良的纳米银.%OBJECTIVE To prepare silver nanoparticles with small particle diameter, good stability and high antimicrobial activity. METHODS The silver nanoparticles were prepared by chemical synthesis using silver nitrate,maltose and ammonia water as the reactants. The main physical properties of silver nanoparticles were characterized by UV spectrophotometer, transmission electron microscope and laser nanoparticle detecter. The bacteriostasis activity was determined by tube dilution method,using silver sulphadia-zine as the positive control. RESULTS The mean diameter of the silver nanoparticles was 18. 29 nm,and the Zeta potential was -36. 5 mV. The silver nanoparticles were steady and had higher bacteriostatic activity than silver sulphadiazine. CONCLUSION Hie chemical synthesis method can be used to prepare desired silver nanoparticles.

  19. PHOTOCHEMICAL PREPARATION OF GREEN SILVER AND YELLOW SILVER COLLOID AND THEIR RESONANCE SCATTERING SPECTROSCOPIC STUDY%绿色和黄色银胶的光化学制备及其共振散射光谱研究

    Institute of Scientific and Technical Information of China (English)

    钟福新; 蒋治良; 李廷盛; 李芳; 梁宏

    2001-01-01

    The green silver colloid and yellow silver colloid were prepared by two-step photochemical procedure and UV photochemical procedure respectively.Their sizes measured by TEM are 100 nm and 40 nm respectively.The green silver solloid exhibits two absorption peaks at 393.9 nm and 713.3 nm,The absorption peak of yellow silver colloid is at 419.3 nm.They have a maxium resonance scattering peak at 470 nm,and the green silver colloid has other two resonance scattering peaks at 340 nm and 680nm.%研究了不同光源、光照时间、反应物浓度等对绿色银胶形成的影响,分别制备了绿色银胶和黄色银胶.透射电镜显示,它们的平均粒径分别为100 nm和40 nm.绿色银胶在393.9 nm和713.3 nm处有两个吸收峰;黄色银胶在419.3 nm处有一较宽的吸收峰.它们的最强共振散射峰位于470 nm处;绿色银胶在340 nm和680 nm还有两个小共振峰.

  20. Preparation of Nanogold Colloid Using Triphenylphosphine as Protective Agent%以三苯基膦为保护剂制备纳米金溶胶

    Institute of Scientific and Technical Information of China (English)

    邵霞; 索掌怀

    2015-01-01

    以三苯基膦( PPh3)为保护剂,采用水相化学还原法制备了纳米金溶胶.利用紫外可见分光光度计和透射电子显微镜对纳米金颗粒的尺寸及形貌进行表征.讨论了还原剂种类与用量、保护剂用量与加入方式、金粒子浓度、溶液pH值等因素对纳米金颗粒粒径、形貌和分散性的影响.结果表明:采用硼氢化钠为还原剂时,PPh3与金质量比为0.02∶1,溶液pH值为7,制得纳米金粒子平均粒径为4~5 nm.采用柠檬酸钠为还原剂时,PPh3与金质量比为0.04∶1,柠檬酸钠与金质量比为10∶1,溶液pH=3~4,制得金粒子平均粒径为13~15 nm.采用草酸为还原剂时,PPh3与金质量比为0.08∶1,草酸与金质量比为3∶1,金前驱液pH值为6,制得金粒子平均粒径为23~25 nm.加入保护剂后,粒子的分散性增强,形状不规则粒子增多.%Nanogold colloid is synthesized by chemical reduction using triphenylphosphine ( PPh3 ) solution as pro-tective agent. UV-Vis spectroscopy and transmission electron microscopy ( TEM) are used to characterize the pre-pared Au nanoparticles. Some factors such as the type and the amount of reducing agent, the adding way and the a-mount of protective agent, the concentration and pH value of Au solution, which affects the particle size, morpholo-gy and dispersion of Au nanoparticles, are discussed. The results show that the optimized processing parameters for preparing gold nanoparticles using NaBH4 with an average diameter from 4 to 5 nm are:mPPh3∶mAu=0. 02∶1, pH=7. The optimal conditions obtained for making gold nanoparticles using Na3 C6 H5 O7 with particle size from 13 to 15 nm are:mPPh3∶mAu =0. 04∶1, mNa3C6H5O7∶mAu =10∶1, pH =3 -4. The size of Au nanoparticles prepared with H2 C2 O4 is within the range of 23~25 nm. The optimal conditions are mPPh3∶mAu=0. 08∶1, mH2C2O4∶mAu=3∶1, pH=6. After adding a certain amount of PPh3 , colloidal gold nanoparticles show higher dispersion and more

  1. The FASES instrument development and experiment preparation for the ISS

    Science.gov (United States)

    Picker, Gerold; Gollinger, Klaus; Greger, Ralf; Dettmann, Jan; Winter, Josef; Dewandre, Thierry; Castiglione, Luigi; Vincent-Bonnieu, Sebastien; Liggieri, Libero; Clausse, Daniele; Antoni, Mickael

    The FASES experiments target the investigation of the stability of emulsions. The main objec-tives are the study of the surfactant adsorption at the liquid / liquid interfaces, the interaction of the droplets as well as the behaviour of the liquid film between nearby drops. Particular focus is given to the dynamic droplet evolution during emulsion destabilisation. The results of the experiments shall support development of methods for the modelling of droplet size distri-butions, which are important to many industries using stable emulsions like food production, cosmetics and pharmaceutics or unstable emulsions as required for applications in waste water treatment or crude oil recovery. The development of the experimental instrumentation was initiated in 2002. The flight instru-ment hardware development was started in 2004 and finally the flight unit was completed in 2009. Currently the final flight preparation is proceeding targeting a launch to the International Space Station (ISS) with Progress 39P in September 2010. The experiment setup of the instrument is accommodated in a box type insert called Experiment Container (EC), which will be installed in the Fluid Science Laboratory part of the European Columbus module of the ISS. The EC is composed of two diagnostics instruments for the investigation of transparent and opaque liquid emulsion. The transparent emulsions will be subject to the experiment called "Investigations on drop/drop interactions in Transparent Emulsions" (ITEM). The opaque emulsion samples will be studied in the experiment called "Investigations on concentrated or opaque Emulsions and on Phase Inversions" (EMPI). The thermal conditioning unit (TCU) allows performing homogeneous thermalization, tem-perature sweeps, emulsion preparation by stirrer, and optical diagnostics with a scanning mi-croscope. The objective of the instrument is the 3D reconstruction of the emulsion droplet distribution in the liquid matrix in terms of the droplet sizes

  2. Preparation of nano-nickel colloid and its application to activation of electroless plating of fabrics%纳米镍胶体的制备及其在织物化学镀活化中的应用

    Institute of Scientific and Technical Information of China (English)

    赖冬志; 陈文兴

    2012-01-01

    为制备可在织物化学镀铜上使用的经济实惠的胶体镍活化液,在酸性条件下,以聚乙烯吡咯烷酮为稳定剂,采用硼氢化钠还原硫酸镍制备的镍微粒为催化剂,催化次亚磷酸钠液相还原硫酸镍,制备出纳米镍胶体.将该胶体应用于织物化学镀铜的活化工序,实验结果表明该胶体镍具有良好的催化活性.用透射电镜、扫描电镜及X射线衍射仪对该胶体及活化前后织物进行了表征,结果表明:所得纳米镍胶体成分纯净,粒径分布均匀;浸渍了该胶体镍的织物可以在以甲醛为还原剂的化学镀铜液中顺利起镀.%For preparation of nano-nickel colloid which is suitable for the activation of electroless-plating of fabrics with copper economically, under acidic conditions, the nano-nickel colloid was prepared with nickel particles as catalyst and polyvinylpyrrollidone ( PVP) as stabilizer. The nickel particles were prepared by reduction of nickel sulfate with sodium borohydride in the presence of sodium hypophosphite solution. Then the nano-nickel colloid was used in the activation process of electroless plating of fabrics with copper. Transmission electron microscopy (TEM) , scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the nickel colloid and fabrics before and after activation treatment. The results showed that the nano-nickel colloid has pure composition, uniform particle size distribution, and good catalytic activity, and fabrics dipped with this nickel colloid can be successfully electroless plated with copper using formaldehyde as reducing agent.

  3. USMP-4 experiments are prepared for flight in the SSPF

    Science.gov (United States)

    1997-01-01

    United States Microgravity Payload-4 (USMP-4) experiments are prepared to be flown on Space Shuttle mission STS-87 in the Space Station Processing Facility at Kennedy Space Center (KSC). nThe vertical tube in the center of the photo is the Advanced Automated Directional Solidification Furnace (AADSF), which will be used by researchers to study the solidification of semiconductor materials in microgravity. Scientists will be able to better understand how microgravity influences the solidification process of these materials and develop better methods for controlling that process during future Space flights and Earth-based production. To its left is MEPHISTO, the French acronym for a cooperative American-French investigation of the fundamentals of crystal growth. All STS-87 experiments are scheduled for launch on Nov. 19 from KSC.

  4. 水牛伊氏锥虫病免疫胶体金试纸条的研制及初步应用%Preparation and Primary Application of Immunity Colloidal Gold Test Strip for Water Buffalo Trypanosomiasis

    Institute of Scientific and Technical Information of China (English)

    孟盟; 曹池; 陈汉忠; 刘明如; 王华俊; 奉彬; 陈国宝

    2011-01-01

    为建立一种快速、简便、适应现场应用的水牛伊氏锥虫病诊断方法,采用柠檬酸三钠还原法制备胶体金颗粒,标记纯化的抗伊氏锥虫VSG抗原的OB6单克隆抗体,在硝酸纤维素膜上包被纯化的抗伊氏锥虫VSG抗原的TB7单克隆抗体和兔抗小鼠IgG,作为检测带和质控带,然后优化条件,研制成检测伊氏锥虫病的免疫胶体金试纸条.通过交叉试验表明该试纸条与衣原体、弓形虫、旋毛虫、巴贝斯焦虫和大片吸虫无交叉反应.该试纸条最低可以检出1∶3 200倍稀释的伊氏锥虫VSG抗原(浓度为3.11 mg·mL-1).应用该试纸条对230份水牛血清样本进行初步检测,同时用ELISA做平行试验,阳性符合率为88.2%.结果证明该试纸条是一种快速、灵敏、特异的水牛伊氏锥虫病的检测方法,为水牛伊氏锥虫病的现场检测诊断和预控提供了有效的方法.%To establish a rapid, simple, sensitive and adapting field application assay for water buffalo Trypanosoma evansi diseases, the colloidal gold particles was prepared by the sodium citrate reduction method. Purified OB6 monoclonal antibodies of anti-Trypanosoma evansi VSG antigen was labelled with the colloidal gold particles. The detection zone and quality control zone of the nitrocellulose membrane was made by appending purified anti-Trypanosoma evansi VSG antigen TB7, monoclonal antibody and rabbit anti-mouse IgG. The immune colloidal gold test strip was developed by optimizing the experiment conditions. The crossing test showed that the strip can't cross react with Chlamydia, Toxoplasma gondii, Trichina, Babesia coke worms and Fas-ciola gigantic a. The sensitivity test showed that the strip can detected in the lowest dilution of 1: 3 200 Trypanosoma evansi VSG antigen (concentration 3. 11 mg·mL-1). 230 clinic serum samples of water buffalo were detected by using the test strip, while a parallel experiment were conducted using ELISA, and the positive

  5. Laboratory investigation of the role of desorption kinetics on americium transport associated with bentonite colloids.

    Science.gov (United States)

    Dittrich, Timothy Mark; Boukhalfa, Hakim; Ware, Stuart Douglas; Reimus, Paul William

    2015-10-01

    Understanding the parameters that control colloid-mediated transport of radionuclides is important for the safe disposal of used nuclear fuel. We report an experimental and reactive transport modeling examination of americium transport in a groundwater-bentonite-fracture fill material system. A series of batch sorption and column transport experiments were conducted to determine the role of desorption kinetics from bentonite colloids in the transport of americium through fracture materials. We used fracture fill material from a shear zone in altered granodiorite collected from the Grimsel Test Site (GTS) in Switzerland and colloidal suspensions generated from FEBEX bentonite, a potential repository backfill material. The colloidal suspension (100 mg L(-1)) was prepared in synthetic groundwater that matched the natural water chemistry at GTS and was spiked with 5.5 × 10(-10) M (241)Am. Batch characterizations indicated that 97% of the americium in the stock suspension was adsorbed to the colloids. Breakthrough experiments conducted by injecting the americium colloidal suspension through three identical columns in series, each with mean residence times of 6 h, show that more than 95% of the bentonite colloids were transported through each of the columns, with modeled colloid filtration rates (k(f)) of 0.01-0.02 h(-1). Am recoveries in each column were 55-60%, and Am desorption rate constants from the colloids, determined from 1-D transport modeling, were 0.96, 0.98, and 0.91 h(-1) in the three columns, respectively. The consistency in Am recoveries and desorption rate constants in each column indicates that the Am was not associated with binding sites of widely-varying strengths on the colloids, as one binding site with fast kinetics represented the system accurately for all three sequential columns. Our data suggest that colloid-mediated transport of Am in a bentonite-fracture fill material system is unlikely to result in transport over long distance scales because

  6. Colloid facilitated transport of lanthanides through discrete fractures in chalk

    Science.gov (United States)

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

    2015-04-01

    Geological disposal of high-level radioactive waste is the internationally agreed-upon, long term solution for the disposal of long lived radionuclides and spent fuel. Eventually, corrosion of the waste canisters may lead to leakage of their hazardous contents, and the radionuclides can ultimately make their way into groundwater and pose a threat to the biosphere. Engineered bentonite barriers placed around nuclear waste repositories are generally considered sufficient to impede the transport of radionuclides from their storage location to the groundwater. However, colloidal-sized mobile bentonite particles eroding from these barriers have come under investigation as a potential transport vector for radionuclides sorbed to them. In addition, the presence of organic matter in groundwater has been shown to additionally facilitate the uptake of radionuclides by the clay colloids. This study aims to evaluate the transport behaviors of radionuclides in colloid-facilitated transport through a fractured chalk matrix and under geochemical conditions representative of the Negev desert, Israel. Lanthanides are considered an acceptable substitute to actinides for research on radionuclide transportation due to their similar chemical behavior. In this study, the migration of Ce both with and without colloidal particles was explored and compared to the migration of a conservative tracer (bromide). Tracer solutions containing known concentrations of Ce, bentonite colloids, humic acid and bromide were prepared in a matrix solution containing salt concentrations representative of that of the average rain water found in the Negev. These solutions were then injected into a flow system constructed around a naturally fractured chalk core. Samples were analyzed for Ce and Br using ICP-MS, and colloid concentrations were determined using spectrophotographic analysis. Breakthrough curves comparing the rates of transportation of each tracer were obtained, allowing for comparison of

  7. Sweet Nanochemistry: A Fast, Reliable Alternative Synthesis of Yellow Colloidal Silver Nanoparticles Using Benign Reagents

    Science.gov (United States)

    Cooke, Jason; Hebert, Dominique; Kelly, Joel A.

    2015-01-01

    This work describes a convenient and reliable laboratory experiment in nanochemistry that is flexible and adaptable to a wide range of educational settings. The rapid preparation of yellow colloidal silver nanoparticles is achieved by glucose reduction of silver nitrate in the presence of starch and sodium citrate in gently boiling water, using…

  8. Sweet Nanochemistry: A Fast, Reliable Alternative Synthesis of Yellow Colloidal Silver Nanoparticles Using Benign Reagents

    Science.gov (United States)

    Cooke, Jason; Hebert, Dominique; Kelly, Joel A.

    2015-01-01

    This work describes a convenient and reliable laboratory experiment in nanochemistry that is flexible and adaptable to a wide range of educational settings. The rapid preparation of yellow colloidal silver nanoparticles is achieved by glucose reduction of silver nitrate in the presence of starch and sodium citrate in gently boiling water, using…

  9. Soil colloidal behavior

    Science.gov (United States)

    Recent understanding that organic and inorganic contaminants are often transported via colloidal particles has increased interest in colloid science. The primary importance of colloids in soil science stems from their surface reactivity and charge characteristics. Characterizations of size, shape,...

  10. Preparation of colloid photonic crystal structural color glaze%胶体光子晶体结构色釉的制备

    Institute of Scientific and Technical Information of China (English)

    王芬; 安凯妮; 朱建锋; 董龙龙; 盖言成; 李伟东; 李强

    2014-01-01

    Structural color glazes were assembled by a variety of different size of monodisperse silica colloidal microspheres prepared by sol-gel on porcelain body with vertical deposition method .T he influences of particle size on structural color and the control methods of particle size were researched .SEM analysis shows that the size of the silica microspheres become large as increasing amount of ammonia and TEOS in the preparation process ,but will decrea-ses as the increase of reaction temperature .The size of the microspheres will increase to the maximum and then decrease with the rise of water concentration .And it is found that the films with good three-dimensional orderly close packing structure could have red-shift of the color by increasing the particle size ,by this way ,we have made various structural colors g laze .%采用溶胶凝胶法制备了多种不同粒径的单分散二氧化硅胶体微球,并利用制备的微球以垂直沉积自组装法在瓷胎表面制备了颜色艳丽的结构色釉.研究了微球粒径的工艺控制方法及微球尺寸对结构色的影响.SEM 分析表明:在二氧化硅微球制备过程中,随着反应液中氨水和正硅酸乙酯浓度的增大,微球粒径逐渐增大;水解、缩聚反应温度升高,微球尺寸会逐渐减小;体系水浓度增大,二氧化硅微球尺寸先增大后减小,存在一个峰值.薄膜分析表明,具有良好三维有序密堆积结构的薄膜,其颜色随着自组装用微球粒径的增大发生红移,色调发生变化,从而能够生成多种结构色釉.

  11. 化学还原法制备小粒径金纳米粒子%Preparation of Small Size Au Colloid by Chemical Reduction

    Institute of Scientific and Technical Information of China (English)

    丰荣娟; 李敏; 刘家祥

    2013-01-01

    The colloidal gold nanoparticles were prepared by reducing chloroauric acid with NaBH4 in the presence of polyvinyl pyrrolidone (PVP).The influences of the amount of NaBH4 and PVP,reaction temperature and the order of adding NaBH4 on the morphology,particle size and dispersion of the synthesized gold nanoparticles are discussed.The gold nanoparticles' morphology and particle size distribution were characterized by transmission electron microscopy and UV-Vis spectroscopy.The results show that the optimized processing parameters for preparing gold nanoparticles with an average diameter of 4.3nm were worked out,the molar ratio of NaBH4 to chloroauric acid is 3.75∶1; the mass ratio of PVP to chloroauric acid is 1∶1; the reaction temperature is 100℃ ; the NaBH4 is added after chloroauric acid.The ways of influencing factors were explained and the reasons were analyzed.%以聚乙烯吡咯烷酮(PVP)为保护剂,用硼氢化钠还原氯金酸制备出金纳米颗粒,研究了还原剂和保护剂用量、反应温度及试剂加入顺序对金纳米颗粒粒径、形貌、分散性的影响.利用透射电子显微镜和紫外分光光度计对纳米金颗粒的形貌、分散性及尺寸进行表征.结果表明:采用硼氢化钠为还原剂时,硼氢化钠与氯金酸的摩尔比为3.75∶1,PVP与氯金酸的质量比为1∶1,反应温度为100℃并且在氯金酸和PVP的混合溶液中迅速加入硼氢化钠制备的金纳米颗粒均一、平均粒径在4.3nm、分散性好.同时研究了各个影响因素的作用方式并分析了原因.

  12. Direct visualization of colloidal liquids

    Science.gov (United States)

    Durand, Richard Vernon

    We have investigated various colloidal systems consisting of aqueous suspensions of micron sized polystyrene particles. These systems are appealing because they provide a fertile testing ground for theories of both the liquid and solid states, as well as for theories describing hydrodynamic interactions. Our first study of colloidal systems was motivated by some interesting observations we made while looking at a suspension under a light microscope. We, as well as other workers, noticed that particles undergoing Brownian motion can appear to linger around each other for long periods of time. The question arose as to whether this lingering was a product of interparticle interactions, or was an artifact due to random thermal motion and projection onto a two dimensional image plane. We found that the latter was true, which drove home the idea that we must be wary of our own biases when making scientific observations. During the course of the research on this lingering behavior, we developed a mathematical technique for generating successively more accurate approximate analytical solutions to initial value linear partial differential equations which are first order in time and have no mixing of spatial and time derivatives. This formalism is especially useful for diffusion problems, since the analytical approximation conserves probability at each order of approximation. Our next experimental effort involved colloidal systems in which the suspending medium was carefully prepared to promote long ranged electrostatic interactions between the particles. The interaction potential in such a suspension has been the topic of much research recently. Using digital video microscopy, as well as techniques we developed allowing the proper analysis of two dimensional data, we found that the interaction length in our samples was surprisingly short ranged compared to what we expected based on our water purification experiments. The problems with projection effects associated with two

  13. The gangue preparation coagulant (PFASS) experiment research and application

    Institute of Scientific and Technical Information of China (English)

    ZHENG Jing-hua; LIU Zhi-bin; LUO Ke-Jie

    2007-01-01

    In order to design a new technological process system to take the polymeric ferric aluminum silicate sulfate(PFASS) and to apply it in wastewater processing, the chemical composition analysis was carried on to the Fuxin gangue, adopted the orthogonal experiment method to obtain optimum response condition of with the acid pickling taking the aluminum in the gangue and with alkali extracting taking the silicon in the gangue,The experiments indicate that the sample chemistry content which tests elect completely conform to the preparation inorganic polymer water treatment coagulant request standard.Used the polymeric ferric aluminum silicate sulfate results in which with the system take as the coagulant of treatment wastewater, used the mercerizing degree, the wastewater pH value, the coagulation time, the coagulant throws increment factors and so on to test and verify its influence on the waste water processing. The result indicates that by using this craft production PFASS in waste water processing, after the processed waste water achieves the emission standard, the processing effect is good.

  14. Colloidal Thermal Fluids

    Science.gov (United States)

    Lotzadeh, Saba

    particles where Maxwell's theory is reliable. This method also provides an accurate tool for evaluation of conductivity in colloidal suspensions between Maxwell's limits where theory is inadequate and experiments are limited due to colloidal difficulties. The effect of cluster configuration and degree of aggregation was investigated and showed that clusters of about the same size, but with different structures increases conductivity by different degree. We also showed that even small structural details such as the size of the neck that particles form during aggregation, can change the enhancement significantly. Colloidal clusters conduct heat more efficiently compared to fully dispersed particles at the same volume fraction. We present a predictive model to calculate the thermal conductivity of clusters by extending Maxwell's theory to non-spherical particles. We treat the clusters as spheres with effective thermal conductivity kc and volume fraction φc. We calculate conductivity of the cluster from the upper bound of Maxwell's theory, and the conductivity of a dispersion of such clusters from the lower limit of the theory. We show that structural effects can be represented by a single parameter and a method was provided to obtain this parameter from numerical simulations. We test the theory against simulations as well as dispersions of colloidal cluster and find it to be in very good agreement with both. The results suggest that the variability of literature data and the unusually high values of thermal conductivity that have been reported in the literature can be fully accounted by the presence of clusters. (Abstract shortened by ProQuest.).

  15. Preparation of highly permeable BPPO microfiltration membrane with binary porous structures on a colloidal crystal substrate by the breath figure method.

    Science.gov (United States)

    Yuan, Hua; Yu, Bing; Cong, Hailin; Peng, Qiaohong; Yang, Zhen; Luo, Yongli; Chi, Ming

    2016-01-01

    A highly permeable brominated poly(phenylene oxide) (BPPO) microfiltration membrane with binary porous structures was fabricated by combination of the breath figure and colloidal crystal template methods. The pore size in the bottom layer of the membrane was adjusted by the diameter of SiO2 microspheres in the colloidal crystal template, while the pore size in the top layer of the membrane was adjusted by varying the BPPO concentration in the casting solution. The permeability of the membrane cast on the colloidal crystal substrate was much higher than that of the membrane cast on a bare silicon wafer. The binary porous BPPO membrane with high permeability and antifouling property was used for microfiltration applications.

  16. 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

  17. Flocking ferromagnetic colloids

    Science.gov (United States)

    Kaiser, Andreas; Snezhko, Alexey; Aranson, Igor S.

    2017-01-01

    Assemblages of microscopic colloidal particles exhibit fascinating collective motion when energized by electric or magnetic fields. The behaviors range from coherent vortical motion to phase separation and dynamic self-assembly. Although colloidal systems are relatively simple, understanding their collective response, especially under out-of-equilibrium conditions, remains elusive. We report on the emergence of flocking and global rotation in the system of rolling ferromagnetic microparticles energized by a vertical alternating magnetic field. By combing experiments and discrete particle simulations, we have identified primary physical mechanisms, leading to the emergence of large-scale collective motion: spontaneous symmetry breaking of the clockwise/counterclockwise particle rotation, collisional alignment of particle velocities, and random particle reorientations due to shape imperfections. We have also shown that hydrodynamic interactions between the particles do not have a qualitative effect on the collective dynamics. Our findings shed light on the onset of spatial and temporal coherence in a large class of active systems, both synthetic (colloids, swarms of robots, and biopolymers) and living (suspensions of bacteria, cell colonies, and bird flocks). PMID:28246633

  18. Synthesis and characterization of organic–inorganic hybrid materials prepared by sol–gel and containing Zn{sub x}Cd{sub 1−x}S nanoparticles prepared by a colloidal method

    Energy Technology Data Exchange (ETDEWEB)

    Gonçalves, Luis F.F.F., E-mail: luisf@quimica.uminho.pt [Centro de Química, Departamento de Química, Universidade do Minho, 4710-057 Braga (Portugal); Centro de Física, Departamento de Física, Universidade do Minho, 4710-057 Braga (Portugal); Silva, Carlos J.R. [Centro de Química, Departamento de Química, Universidade do Minho, 4710-057 Braga (Portugal); Kanodarwala, Fehmida K.; Stride, John A. [School of Chemistry, University of New South Wales, Sydney 2052 (Australia); Pereira, Mário R.; Gomes, Maria J.M. [Centro de Física, Departamento de Física, Universidade do Minho, 4710-057 Braga (Portugal)

    2013-12-15

    Nanocomposite materials based on a hybrid organic–inorganic ureasilicate matrix doped with Zn{sub x}Cd{sub 1−x}S nanoparticles were prepared. Zn{sub x}Cd{sub 1−x}S nanoparticles with different compositions (Zn/Cd mole ratio) were prepared through a colloidal method using reverse micelles. Previously to dispersion within the matrix precursors used to prepare the hybrid gel composite, the nanoparticles surface was modified in order to improve compatibility and stability with the matrix and to assure the preservation of the original optical properties of the nanoparticles. The matrix was obtained by the reaction between a silicon alkoxide modified by an isocyanate group and a di-amine functionalized oligopolyoxyethylene (Jeffamine ED-600), which by subsequent hydrolysis and condensation reactions formed a mechanically stable and highly transparent solid network containing the Zn{sub x}Cd{sub 1−x}S nanoparticles. The materials were characterized by absorption, steady-state and time-resolved photoluminescence spectroscopy and by HRTEM. The obtained nanocomposites show a high transparency in the visible range accounting for the good dispersion of the nanoparticles within the matrix. The results obtained confirmed the preservation of the original optical properties of the nanoparticles after their incorporation into the ureasilicate matrix, showing that the developed method is suitable for the production of materials with potential applications in which it is necessary to take advantage of the optical properties of the nanoparticles incorporated. The HRTEM analysis confirmed that the dispersed nanoparticles show a high level of crystallinization. -- Highlights: • Synthesis of a hybrid ureasilicate matrix doped with Zn{sub x}Cd{sub 1−x}S nanoparticles. • The influence of the composition of the nanoparticles plays an important role in the optical properties of the nanocomposites. • Preservation of the optical properties of the nanoparticles associated with

  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. Toxicological evaluation of nano-sized colloidal silver in experiments on mice. behavioral reactions, morphology of internals

    Directory of Open Access Journals (Sweden)

    N.V. Zaitseva

    2015-06-01

    Full Text Available The results of toxicity studies of nano-sized colloidal silver (NCC, the most widely used in medicine, food and life, are given. When evaluating safe doses of silver NP (using commercially available NCC solution stabilized with polyvinylpyrrolidone (PVP, with the size of silver NP at the range of 5-80 nm when orally administered to male mice, BALB/c mice at doses of 0.1; 1.0 and 10 mg/kg of body weight per silver different effects from the motor and orienting-exploratory activity were revealed, for the part of them the dependence on the dose of the NCC was typical. The following peculiarities were found: reduction in motor activity to reduce the frequency of activities requiring physical effort, reduction of the execution time of these actions; increasing anxiety in terms of frequency and duration of attacks of orienting-investigative activity and animals washing. Morphological examination revealed a series of tissue changes of internal organs (especially liver and spleen, to a lesser extent – kidney, heart and colon with increase of the spectrum and severity of structural changes with increasing doses of the NCC. From the combination of the data the conclusion was made that maximal ineffective dose (NOAEL of this nanomaterial at subacute oral administration is no more than 0.1 mg/kg body weight.

  1. Interactions between radioactively labeled colloids and natural particles: Evidence for colloidal pumping

    Science.gov (United States)

    Wen, Liang-Saw; Santschi, Peter H.; Tang, Degui

    1997-07-01

    It has been hypothesized that colloidal forms of trace metals can be reactive intermediaries in the scavenging processes leading to the removal of their particulate forms. A series of radiotracer experiments using natural colloidal organic matter from Galveston Bay, USA were carried out in order to test this hypothesis. Suspended particle uptake of originally colloidally bound trace metals occurred in a matter of hours to days in estuarine waters. After ten days, the majority (>50%) of the colloidal trace metals had been transferred into the particulate phase (≥0.45 μm), except for 65Zn. Two distinctively different temporal regions of removal of colloidal trace metals were identified: a faster reaction during the first four hours, followed by a slower reaction after approximately one day. In a separate river water-seawater mixing experiment, the solid/solution partitioning of the radiotracers was investigated in the absence of suspended matter. About 30% of most of the elements, except Ag and Fe (˜60%), were associated with a newly formed particulate phase after eight days. There were two major trends: (1) the particulate fraction of 59Fe and 110Ag increased while the colloidal fraction decreased, suggesting a colloidal pumping mechanism. (2) The particulate fraction of 54Mn, 133Ba, 65Zn, 109Cd, 113Sn, and 60CO increased while the LMW (≤ 1 kDa) fraction decreased, suggesting a direct uptake into the particulate fraction with less involvement of a transitory colloidal phase. The values of the particle-water ( Kd) and colloid-water partitioning ( Kc) coefficients for most trace metals were similar to those observed in Galveston Bay waters, suggesting complementary results to field studies. The results from these experiments suggested two different pathways for colloidal tracer uptake by particles: (1) colloidal pumping of a major component (e.g., biopolymer) of the colloidal pool and (2) coagulation of trace components (e.g., phytochelatins) with varying

  2. Preparation and coloring of magnetic colloidal crystals%磁性胶体晶体的制备与呈色特性

    Institute of Scientific and Technical Information of China (English)

    胡光强; 陈永利; 朱欢; 李龙成; 刘文霞

    2016-01-01

    通过化学合成的方法制备出被表面活性剂聚丙烯酸(PAA)修饰的Fe3O4纳米粒子,并应用透射电子显微镜、X射线衍射、磁强计及傅里叶红外光谱仪对产物进行表征,同时利用FDTD solutions光学软件对产物的呈现性能进行建模仿真。最后通过分析得到制备的胶体产物具有超顺磁性能,粒径均一,在水中具有良好的分散性,粒子分散在水中形成的胶体在外在磁场的作用下能够自组装成液态光子晶体,不同磁场大小的调节下能够呈现不同的结构色,磁场越小,颜色越向着波长大的方向偏移,同时,用软件对胶体粒子仿真得到的呈色特性与实验结果一致。这种光子晶体在结构色印刷、传感器、防伪等各个领域有广泛的应用。%Fe3O4nanoparticles modified by surfactant polyacrylic acid (PAA) were synthesized through chemical method.The products were characterized by transmission electron microscopy(TEM),X-ray diffraction,vibrating sample magnetometers(VSM) and Fourier transform infrared spectroscopy(FTIR Spectrometer),respectively.The modeling and simulation of the chromatic performance of products are realized by optical software FDTD solutions. Product was prepared with superparamagnetism,uniform particle size,good dispersion and high water solubility in aqueous solution. These particles dispersed in water can form colloidal solution which can self-assemble into liquid photonic crystal under magnetic field.The different types of structural color will be showed under the regulations of different intensities of magnetic field. The peak of wave will shift towards the direction of the larger wavelength with decreasing magnetic field. In the meantime,there are the same results in the chromatic performance of products between simulation and experimental method. This kind of photonic crystal has many applications in all kinds of fields,such as structural color printing,sensor and anti-counterfeiting.

  3. The colloid investigations conducted at the Aespoe Hard Rock Laboratory during 2000-2004

    Energy Technology Data Exchange (ETDEWEB)

    Laaksoharju, Marcus [Geopoint AB, Stockholm (Sweden); Wold, Susanna [Royal Inst. of Tech., Stockholm (Sweden). School of Chemical Science and Engineering, Nuclear Chemistry] (eds.)

    2005-12-15

    In 2000, SKB decided to initiate an international colloid project at the Aespoe Hard Rock Laboratory in Sweden. The objectives of the colloid project are to: (i) study the role of bentonite as a colloid source, (ii) verify the background colloid concentration at Aespoe HRL and, (iii) investigate the potential for colloid formation/transport in natural groundwater concentrations. The experimental concepts for the colloid project are: laboratory experiments with bentonite, background field measurements of natural colloids, borehole specific bentonite colloid stability experiments and a fracture specific transport experiment. The activities concerning the laboratory experiments and background field measurements are described in this work; the other activities are ongoing or planned. The following conclusions were made: The bentonite colloid stability is strongly dependent on the groundwater ionic strength. Natural colloids are organic degradation products such as humic and fulvic acids, inorganic colloids (clay, calcite, iron hydroxide) and microbes. Microbes form few but large particles and their concentration increase with increasing organic carbon concentrations. The small organic colloids are present in very low concentrations in deep granitic groundwater. The concentrations can be rather high in shallow waters. The colloid concentration decreases with depth and salinity, since colloids are less stable in saline waters. The colloid content at Aespoe is less than 300 ppb. The colloid content at repository level is less than 50 ppb. The groundwater variability obtained in the boreholes reflects well the natural groundwater variability along the whole HRL tunnel.

  4. Hot spot(s) of the lung in technetium-99m albumin colloid liver-spleen scintigraphy: case report

    Energy Technology Data Exchange (ETDEWEB)

    Shih, W.J.; Brandenburg, S.; Coupal, J.J.; Sullivan, J.D.; Beeler, J.A.; Magoun, S.; Ryo, U.Y.

    1988-06-01

    The authors replaced /sup 99m/Tc albumin colloid for /sup 99m/Tc sulfur colloid as a radiopharmaceutical for liver-spleen imaging and found two instances of hot spot(s) in the lung. The preparation procedure of albumin colloid is easier and more convenient as compared to that of sulfur colloid. Whereas replacement of /sup 99m/Tc sulfur colloid by /sup 99m/Tc albumin colloid is inevitable, it should be emphasized that one should avoid blood withdrawal in the syringe containing albumin colloid to prevent formation of clot(s) during the venous puncture for /sup 99m/Tc albumin colloid.

  5. Preparing meals under time stress. The experience of working mothers.

    Science.gov (United States)

    Beshara, Monica; Hutchinson, Amanda; Wilson, Carlene

    2010-12-01

    The present study quantitatively explored the effects of mothers' perceived time pressure, as well as meal-related variables including mothers' convenience orientation and meal preparation confidence, on the healthiness of evening meals served to school-aged children (5-18 years old) over a 7-day period. A sample of 120 employed mothers, who identified themselves as the chief meal-preparers in their households, completed a brief, self-report, meal-related questionnaire. Results revealed that mothers' perceived time pressure did not significantly predict meal healthiness. Mothers' confidence in their ability to prepare a healthy meal was the only unique, significant predictor of a healthy evening meal. Mothers who were more confident in their ability to prepare a healthy meal served healthier evening meals than those who were less confident. In addition, mothers' perceived time pressure and convenience orientation were negatively related to healthy meal preparation confidence. Results suggest that mothers' perceived time pressure and convenience orientation, may indirectly compromise meal healthiness, by decreasing mothers' meal preparation confidence. Practical and theoretical implications of the study's findings are discussed.

  6. 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...... 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...... 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...

  7. Fabrication of size-controllable hexagonal non-close-packed colloidal crystals and binary colloidal crystals by pyrolysis combined with plasma-electron co-irradiation of polystyrene colloidal monolaye

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jae Joon

    2011-02-15

    We present an unprecedented and systematic route to controllably fabricate hexagonal non-close-packed (HNCP) monolayer colloidal crystals and binary colloidal crystals (BCCs) based on plasma-electron co-irradiation of polystyrene colloidal monolayers followed by thermal decomposition. HNCP colloidal crystals with tunable particle sizes and periods could be fabricated by changing the pristine colloidal particle size and the thermal decomposition time. In addition, BCCs and trimodal colloidal crystals that are composed of different-sized colloidal particles can also be fabricated by adding small particles on the prepared HNCP colloidal crystals. Both the particle size ratio and the volume fraction of the BCCs can be widely tuned. These HNCP colloidal crystals and BCCs have various potential applications as optical and photonic materials as well as in catalysis and sensors.

  8. Transport and Deposition of Variably Charged Soil Colloids in Saturated Porous Media

    DEFF Research Database (Denmark)

    Sharma, Anu; Kawamoto, Ken; Møldrup, Per

    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 colloids) and a red-yellow soil from...... Okinawa (RYS colloids) in Japan. The VAS colloids exhibited a negative surface charge with a high pH dependency, whereas the RYS colloids exhibited a negative surface charge with less pH dependency. The soil colloids were applied as colloidal suspensions to 10-cm-long saturated sand columns packed....... Breakthrough curves and deposition profiles for soil colloids were strong functions of the hydrodynamics, solution pH, and surface charge of the colloids and sand grains. Greater deposition was typical for lower flow rates and lower pH. The deposition of VAS colloids in both sands under low-pH conditions...

  9. Study on preparation of nano-silver colloids and its antibacterial properties of some common foods%纳米银胶的制备及对食品的抗菌性能研究

    Institute of Scientific and Technical Information of China (English)

    曹雪玲; 陈静; 李艳薇; 张革

    2012-01-01

    Silver nitrate and sodium citrate as reactants with boiling water bath heating method used to prepare the nano-silver colloids.The nano silver particles were characterized by using transmission electron microscopy(TEM) and UV-Vis absorption spectroscopy.Respectively to choose the response of 20,40,60 minutes the nano-silver as anti-bacterial reagents,choose milk,bread and watermelon as anti-bacterial targets were studied in this paper,to study the anti-bacterial properties of silver nano-particles of colloid.According to visual observations,microbial culture and electron microscopy found that three nano-silver colloids had a certain degree of antibacterial activity of deterioration for these substances produced by micro-organisms,the response of 20 minutes the nano-silver had the best antimicrobial activity.%用硝酸银和柠檬酸钠作为反应物,采用沸水浴加热法,制备了纳米银胶,并用紫外可见光及透射电镜对其进行了表征。分别选择反应20、40、60min的纳米银胶作为抗菌试剂,牛奶、馒头和西瓜作为抗菌对象,研究了本文所制备的纳米银胶的抗菌性能。根据直观观察法、微生物培养法和电子显微镜,发现制备的纳米银胶对于这三种物质变坏后所产生的微生物都具有一定的抗菌作用,其中反应20min的纳米银胶抗菌作用最好。

  10. 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.

  11. Molecular dynamics on nonequilibrium motion of a colloidal particle driven by an external torque

    Science.gov (United States)

    Yoo, Donghwan; Jung, Youngkyun; Kwon, Chulan

    2017-03-01

    We investigate the motion of a colloidal particle driven out of equilibrium by an external torque. We use molecular dynamics simulation as an alternative to the Langevin dynamics. We prepare a heat bath composed of thousands of particles interacting with each other through the Lennard–Jones potential and impose the Langevin thermostat to maintain the heat bath in equilibrium. We consider a single colloidal particle interacting with with the particles of the heat bath also by the Lennard–Jones potential, without applying any types of dissipative or fluctuating forces used in Langevin dynamics. We set up simulation protocol fit for the overdamped limit as in real experiments, by increasing the size and mass of the colloidal particle. We study nonequilibrium fluctuations for work and heat produced incessantly in time and compare the results with those obtained from the previous studies via the overdamped Langevin dynamics. We confirm the Gallavotti–Cohen symmetry and the fluctuation theorem.

  12. Interactions between radioactively labeled colloids and natural particles: Evidence for colloidal pumping

    Energy Technology Data Exchange (ETDEWEB)

    Wen, L.S.; Santschi, P.H.; Tang, D. [Texas A & M Univ., Galveston, TX (United States)

    1997-07-01

    It has been hypothesized that colloidal forms of trace metals can be reactive intermediaries in the scavenging processes leading to the removal of their particulate forms. A series of radiotracer experiments using natural colloidal organic matter from Galveston Bay, USA were carried out in order to test this hypothesis. Suspended particle uptake of originally colloidally bound trace metals occurred in a matter of hours to days in estuarine waters. After ten days, the majority ( >50%) of the colloidal trace metals had been transferred into the particulate phase ({ge} 0.45{mu}m), except for {sup 65}Zn. Two distinctively different temporal regions of removal of colloidal trace metals were identified: a faster reaction during the first four hours, followed by a slower reaction after approximately one day. In a separate river water-seawater mixing experiment, the solid/solution partitioning of the radiotracers was investigated in the absence of suspended matter. About 30% of most of the elements, except Ag and Fe ({approximately}60%), were associated with a newly formed particulate phase after eight days. There were two major trends: (1) the particulate fraction of {sup 59}Fe and {sup 110}Ag increased while the colloidal fraction decreased, suggesting a colloidal pumping mechanism. (2) The particulate fraction of {sup 54}Mn, {sup 133}Ba, {sup 65}Zn, {sup 109}Cd, {sup 113}Sn, and {sup 60}Co increased while the LMW({le}1 kDa) fraction decreased, suggesting a direct uptake into the particulate fraction with less involvement of a transitory colloidal phase. The results from these experiments suggested two different pathways for colloidal tracer uptake by particles: (1) colloidal pumping of a major component (e.g., biopolymer) of the colloidal pool and (2) coagulation of trace components (e.g., phytochelatins) with varying affinities for different trace metals. 39 refs., 8 figs., 3 tabs.

  13. [Bactericidal activity of colloidal silver against grampositive and gramnegative bacteria].

    Science.gov (United States)

    Afonina, I A; Kraeva, L A; Tseneva, G Ia

    2010-01-01

    It was shown that colloidal silver solution prepared in cooperation with the A. F. Ioffe Physical Technical Institute of the Russian Academy of Sciences, had significant bactericidal activity. Stable bactericidal effect on gramnegative microorganisms was observed after their 2-hour exposition in the solution of colloidal silver at a concentration of 10 ppm. Grampositive capsule-forming microorganisms were less susceptible to the colloidal silver solution: their death was observed after the 4-hour exposition in the solution.

  14. 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.

  15. 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.

  16. 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

  17. Facile preparation of ZIF-8@Pd-CSS sandwich-type microspheres via in situ growth of ZIF-8 shells over Pd-loaded colloidal carbon spheres with aggregation-resistant and leach-proof properties for the Pd nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Tong; Lin, Lu [State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian, 116024 (China); Zhang, Xiongfu, E-mail: xfzhang@dlut.edu.cn [State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian, 116024 (China); Liu, Haiou; Yan, Xinjuan [State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian, 116024 (China); Liu, Zhang; Yeung, King Lun [Department of Chemical and Biomolecular Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR (China)

    2015-10-01

    Graphical abstract: - Highlights: • Uniform-sized colloidal carbon spheres were synthesized from low-cost glucose. • Pd nanoparticles were loaded onto the carbon spheres via self-reduction method. • A layer of ZIF-8 shell was in situ grown over the Pd-loaded carbon spheres. • The ZIF-8@Pd-CCS showed leach-proof and aggregation-resistant properties of Pd. - Abstract: Aiming to enhance the stability of noble metal nanoparticles that are anchored on the surface of colloidal carbon spheres (CCSs), we designed and prepared a new kind of sandwich-structured ZIF-8@Pd-CCS microsphere. Typically, uniform CCSs were first synthesized by the aromatization and carbonization of glucose under hydrothermal conditions. Subsequently, noble metal nanoparticles, herein Pd nanoparticles, were attached to the surface of CCSs via self-reduction route, followed by in situ assembly of a thin layer of ZIF-8 over the Pd nanoparticles to form the sandwich-type ZIF-8@Pd-CCS microspheres. X-ray diffraction (XRD) patterns and Fourier transform infrared spectroscopy (FTIR) spectra confirmed the presence of crystalline ZIF-8, while TEM analysis revealed that the ZIF-8 shells were closely bound to the Pd-loaded CCSs. The shell thickness could be tuned by varying the ZIF-8 assembly cycles. Further, liquid-phase hydrogenation of 1-hexene as the probe reaction was carried out over the ZIF-8@Pd-CCS microspheres and results showed that the prepared microspheres exhibited excellent agglomeration-resistant and leach-proof properties for the Pd nanoparticles, thus leading to the good reusability of the ZIF-8@Pd-CCS microspheres.

  18. Preparation and Current Situation of Proton-ICCHIBAN-2 Experiment

    Science.gov (United States)

    Uchihori, Yukio; Yasuda, Nakahiro; Kitamura, H.; Kodaira, S.; Benton, Eric; Hajek, Michael; Berger, Thomas; Jadrnickova, Iva; Ploc, Ondrej

    The ICCHIBAN (Inter Comparison for Cosmicrays with Heavy Ion Beams at NIRS) working group has organized and performed various ICCHIBAN runs for active and passive radiation detectors at HIMAC, NIRS, Japan, Loma Linda and Brookhaven, USA and CERN, Switzer-land since the start of the ICCHIBAN project in the year 2002. One of the main focus points of this project is to understand the response of the applied detector systems (either active or passive) for personal and area dosimetry in space environment to a simulated sub-set of the space radiation environment, focusing on the heavy ion response. This is of special importance for the further intercomparison of space radiation data gathered by various international in-stitutes and universities for space radiation experiments as MATROSHKA, DOSIS, DOBIES, BRADOS, MATROSHKA-R etc. The ICCHIBAN experiments have created a big database of response data, especially for all the different passive radiation detectors and detector materials (Thermoluminescence (TLD) and Optical Luminescence (OSL)) over the last 7 years, resulting in a better understanding of how and why we still have differences in the measurement results from common space experiments -as the Space ICCHIBAN 2 experiment. One of the reasons why for the differences in the TLD/OSL results is the lack of intercomparison and response data for low LET particles up to around 10 keV/m, especially protons. Due to the fact, that the main contribution to absorbed dose in low earth orbit is due to protons, the ICCHIBAN working group has started the set-up of a Proton ICCHIBAN intercomparison experiment at NIRS. The Proton ICCHIBAN run has been performed at the cyclotron at NIRS, Chiba in February 2010. 15 institutes from 12 countries sent or brought their dosimeters and exposed them to 40 and 70 MeV proton beams with the same doses and exposure conditions. In this paper, the experiment procedures and current situation of the intercomparision experiments will be shown.

  19. Anisotropic oxygen plasma etching of colloidal particles in electrospun fibers.

    Science.gov (United States)

    Ding, Tao; Tian, Ye; Liang, Kui; Clays, Koen; Song, Kai; Yang, Guoqiang; Tung, Chen-Ho

    2011-02-28

    Oxygen plasma etching of electrospun polymer fibers containing spherical colloids is presented as a new approach towards anisotropic colloidal nanoparticles. The detailed morphology of the resulting nanoparticles can be precisely controlled in a continuous way. The same approach is also amenable to prepare inorganic nanoparticles with double-sided patches.

  20. 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

  1. An analysis of a didactical experience in science teacher preparation

    Directory of Open Access Journals (Sweden)

    Alberto Villani

    1998-05-01

    Full Text Available What follows is the description of a didactical experience whose results were considered more successful than expected. Future biology teachers not only became involved in the course and learned scientific and pedagogical knowledge, but also changed their relationship with it, assuming the responsability to solve a problem with all they creativity. The experience will be analized and interpreted by means of “quasi-psychoanalytical” categories which consider the changes in the relation between student, teacher and knowledge and the instruments the teacher used to foster them.

  2. Comparision of {sup 188}Rhenuim-tin colloid and {sup 188}Rhenium-sulfur colloid as a radiation synovectomy agent

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Y. J.; Jung, J. M.; Kim, Y. J.; Jang, Y. S.; Lee, D. S.; Jung, J. K.; Song, Y. W.; Lee, M. C. [KAERI, Taejon (Korea, Republic of)

    1999-10-01

    Beta-emitting radiocolloids have been used for the treatment of rheumatoid arthritis. As a generator produced beta-emitting radionuclide, the importance of Re-188 for radionuclide therapy is increasing rapidly. We compared the radiochemistry of two {sup 188}Re labeled radiocolloids: {sup 188}Re-tin colloid and {sup 188}Re-sulfur colloid. {sup 188}Re-tin colloid was obtained by reacting 10 mg SnCl{sub 2}{center_dot}H{sub 2}O and {sup 188}Re perrhenate. {sup 188}Re-sulfur colloid was labeled by boiling 40 mg sodium thiosulfate, 0.8 mg Na{sub 2}{center_dot}EDTA, and 0.8 mg potassium perrhenate with {sup 188}Re perrhenate. Radiochemical purity was checked by ITLC-SG/ saline. Labeling efficiencies reached >98% for tin colloid at 2 hr and 89{approx}94% for sulfur colloid at 3 hr. All the preparations were stable for 72 hr in water, serum, and synovial fluid. If labeled at higher temperature, particle size of tin colloid increased. Remained radioactivity of {sup 188}Re-sulfur colloid in disposable polypropylene syringe after injecting to mice was high (62.0{+-}7.0%) due to its hydrophobic nature, although, tin colloid did not show high remained radioactivity (2.9{+-}1.6%). Biodistribution in Antigen induced arthratitis model rabbit after synovial space injection showed that {sup 188}Re-tin colloid was well retained in synovial space for 48 hr. Although, both {sup 188}Re-tin colloid and {sup 188}Re-sulfur colloid might be useful for radionuclide therapy, we concluded that {sup 188}Re-tin colloid is more adventageous over {sup 188}Re-sulfur colloid, due to higher labeling efficency, size-controllable property, and lower residual activity in syringe.

  3. Designing Online Resources in Preparation for Authentic Laboratory Experiences.

    Science.gov (United States)

    Boulay, Rachel; Parisky, Alex; Leong, Peter

    2013-01-01

    Professional development for science teachers can be benefited through active learning in science laboratories. However, how online training materials can be used to complement traditional laboratory training is less understood. This paper explores the design of online training modules to teach molecular biology and user perception of those modules that were part of an intensive molecular biology "boot camp" targeting high school biology teachers in the State of Hawaii. The John A. Burns School of Medicine at the University of Hawaii had an opportunity to design and develop professional development that prepares science teachers with an introduction of skills, techniques, and applications for their students to conduct medical research in a laboratory setting. A group of 29 experienced teachers shared their opinions of the online materials and reported on how they used the online materials in their learning process or teaching.

  4. 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.

  5. Aqueous Colloidal Stability of Graphene Oxide and Chemically Converted Graphene

    Directory of Open Access Journals (Sweden)

    Swarnima Kashyap

    2014-01-01

    Full Text Available Graphene oxide (GO was prepared by modified Hummer’s method, and chemically converted graphene (CCG was prepared by further reduction of the aqueous GO colloid. The effect of pH on particle size, particle charge, and light absorption of the aqueous colloids of GO and CCG was studied with titration against HCl or NaOH, to find the ideal characteristics for a stable dispersion. The GO colloid was stable in the pH range of 4–11, whereas the CCG colloid gained stability at a relatively narrower pH range of 7–10. Poor stability of the colloids was observed for both GO and CCG colloids at both extremes of the pH scale. Both of the colloids exhibited average size of ~1 micron in the low pH range, whereas for higher pH the size ranged between 300 and 500 nm. The UV-Vis spectra showed absorption peak at 230 nm for GO colloids that shifted to 260 nm for the CCG colloid. Such shift can be ascribed to restoring of electronic conjugation of the C=C bonds in CCG.

  6. Hospital preparations for viral hemorrhagic fever patients and experience gained from admission of an Ebola patient

    NARCIS (Netherlands)

    Haverkort, J. J Mark; Minderhoud, A.L.C (Ben); Wind, Jelte D D; Leenen, Luke P H; Hoepelman, Andy I M; Ellerbroek, Pauline M.

    2016-01-01

    The Major Incident Hospital of the University Medical Centre of Utrecht has a longstanding history of preparing for the management of highly pathogenic and infectious organisms. An assessment of the hospital’s preparations for an outbreak of viral hemorrhagic fever and its experience during admissio

  7. Teaching Assistants' Preparation for, Attitudes towards, and Experiences with Academic Dishonesty: Lessons Learned

    Science.gov (United States)

    Seals, Michael; Hammons, James O.; Mamiseishvili, Ketevan

    2014-01-01

    This study examined teaching assistants' (TAs) preparation for, attitudes towards, and experiences with academic dishonesty at a public research university. Of 470 TAs, 184 (39%) completed the survey instrument. The major findings of the study were: (a) TAs were more satisfied with their informal than their formal preparation for dealing with…

  8. Hospital preparations for viral hemorrhagic fever patients and experience gained from admission of an Ebola patient

    NARCIS (Netherlands)

    Haverkort, J. J Mark; Minderhoud, A.L.C (Ben); Wind, Jelte D D; Leenen, Luke P H; Hoepelman, Andy I M; Ellerbroek, Pauline M.

    2016-01-01

    The Major Incident Hospital of the University Medical Centre of Utrecht has a longstanding history of preparing for the management of highly pathogenic and infectious organisms. An assessment of the hospital’s preparations for an outbreak of viral hemorrhagic fever and its experience during

  9. Research on Preparation and UV-vis Absorption Spectrum of Au Colloids under the Ultrasonic Field%超声场下金胶体的制备及其紫外-可见吸收光谱研究

    Institute of Scientific and Technical Information of China (English)

    程敬泉; 姚素薇

    2012-01-01

    Well-dispersed Au colloids were prepared from A11CI3 and KBH4 under the protection of polyvinylpyrrolidone (PVP) in the ultrasonic field. The Au colloids were characterized by means of transmission electron microscope (TEM), X-ray diffraction (XRD) and spectrophotometer. The results indicate that Au nanoparticles are spherical or axiolitic and the grain diameter is about 25 nm. The reductant dosage has a great effect on the UV-vis absorption spectrum of Au colloids. When the dosage of KBH4 is lower than 1 mL, the maximum absorption peak is in 530 nm and the peak is low and broad. When the dosage of KBH4 is over 2 mL, the maximum absorption peak has a large blue shift to 512 -514 nm. The peak is strong and broad. When the dosage of KBH4 is over 5 mL, the absorbency graphs are alike. When the dosage of KBH4 is over 8 mL the maximum absorption peaks are in 510 nm around. The peak is strong, sharp and narrow, so the Au colloids are well-dispersed. The ultrasonic field distribution, power and temperature have a great effect on the absorbency graphs of Au colloids. The peaks are weak and the maximum peaks are in 510 nm around.%在超声场作用下,以氯金酸为前驱物,PVP为保护剂,经KBH4还原,制备了分散均匀的金胶体.利用X射线衍射、透射电子显微镜和分光光度技术等对制备的金胶体进行了表征.结果表明:金纳米粒子为25 nm左右的球形或椭球形.还原剂用量对金胶体的最大吸收峰位影响较大,当KBH4用量小于1 mL时,最大吸收波长为530 nm,吸收峰较低而宽;KBH4加入量超过2 mL时,最大吸收峰明显蓝移,在512~514 nm,最大吸收峰增强,但峰变宽.继续增加KBH4用量超过5 mL,吸光度曲线基本不变,KBH4用量超过8 mL后最大吸收峰在510 nm左右,但吸光度较高,且峰形尖而窄,单分散性好.超声场分布、超声功率和温度使金胶体的最大吸收峰变小,最大吸收峰位在510 nm左右.

  10. Colloidal Fouling of Nanofiltration Membranes: Development of a Standard Operating Procedure

    Science.gov (United States)

    Al Mamun, Md Abdullaha; Bhattacharjee, Subir; Pernitsky, David; Sadrzadeh, Mohtada

    2017-01-01

    Fouling of nanofiltration (NF) membranes is the most significant obstacle to the development of a sustainable and energy-efficient NF process. Colloidal fouling and performance decline in NF processes is complex due to the combination of cake formation and salt concentration polarization effects, which are influenced by the properties of the colloids and the membrane, the operating conditions of the test, and the solution chemistry. Although numerous studies have been conducted to investigate the influence of these parameters on the performance of the NF process, the importance of membrane preconditioning (e.g., compaction and equilibrating with salt water), as well as the determination of key parameters (e.g., critical flux and trans-membrane osmotic pressure) before the fouling experiment have not been reported in detail. The aim of this paper is to present a standard experimental and data analysis protocol for NF colloidal fouling experiments. The developed methodology covers preparation and characterization of water samples and colloidal particles, pre-test membrane compaction and critical flux determination, measurement of experimental data during the fouling test, and the analysis of that data to determine the relative importance of various fouling mechanisms. The standard protocol is illustrated with data from a series of flat sheet, bench-scale experiments. PMID:28106775

  11. UZ Colloid Transport Model

    Energy Technology Data Exchange (ETDEWEB)

    M. McGraw

    2000-04-13

    The UZ Colloid Transport model development plan states that the objective of this Analysis/Model Report (AMR) is to document the development of a model for simulating unsaturated colloid transport. This objective includes the following: (1) use of a process level model to evaluate the potential mechanisms for colloid transport at Yucca Mountain; (2) Provide ranges of parameters for significant colloid transport processes to Performance Assessment (PA) for the unsaturated zone (UZ); (3) Provide a basis for development of an abstracted model for use in PA calculations.

  12. 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.

  13. Colloid Transport and Retention

    DEFF Research Database (Denmark)

    Yuan, Hao; Shapiro, Alexander

    2012-01-01

    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......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...

  14. Colloidal Gelation-2 and Colloidal Disorder-Order Transition-2 Investigations Conducted on STS-95

    Science.gov (United States)

    Hoffmann, Monica T.

    2000-01-01

    The Colloidal Gelation-2 (CGEL 2) and Colloidal Disorder-Order Transition-2 (CDOT 2) investigations flew on Space Shuttle Discovery mission STS-95 (also known as the John Glenn Mission). These investigations were part of a series of colloid experiments designed to help scientists answer fundamental science questions and reduce the trial and error involved in developing new and better materials. Industries dealing with semiconductors, electro-optics, ceramics, and composites are just a few that may benefit from this knowledge. The goal of the CGEL 2 investigation was to study the fundamental properties of colloids to help scientists better understand their nature and make them more useful for technology. Colloids consist of very small (submicron) particles suspended in a fluid. They play a critical role in the technology of this country, finding uses in materials ranging from paints and coatings to drugs, cosmetics, food, and drink. Although these products are routinely produced and used, there are still many aspects of their behavior about which scientists know little. Understanding their structures may allow scientists to manipulate the physical properties of colloids (a process called "colloidal engineering") to produce new materials and products. Colloid research may even improve the processing of known products to enhance their desirable properties.

  15. 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…

  16. 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…

  17. Colloidal oatmeal: history, chemistry and clinical properties.

    Science.gov (United States)

    Kurtz, Ellen S; Wallo, Warren

    2007-02-01

    Oatmeal has been used for centuries as a soothing agent to relieve itch and irritation associated with various xerotic dermatoses. In 1945, a ready to use colloidal oatmeal, produced by finely grinding the oat and boiling it to extract the colloidal material, became available. Today, colloidal oatmeal is available in various dosage forms from powders for the bath to shampoos, shaving gels, and moisturizing creams. Currently, the use of colloidal oatmeal as a skin protectant is regulated by the U.S. Food and Drug Administration (FDA) according to the Over-The-Counter Final Monograph for Skin Protectant Drug Products issued in June 2003. Its preparation is also standardized by the United States Pharmacopeia. The many clinical properties of colloidal oatmeal derive from its chemical polymorphism. The high concentration in starches and beta-glucan is responsible for the protective and water-holding functions of oat. The presence of different types of phenols confers antioxidant and anti-inflammatory activity. Some of the oat phenols are also strong ultraviolet absorbers. The cleansing activity of oat is mostly due to saponins. Its many functional properties make colloidal oatmeal a cleanser, moisturizer, buffer, as well as a soothing and protective anti-inflammatory agent.

  18. The use of objects and methods of colloid chemistry in nanochemistry

    Science.gov (United States)

    Summ, Boris D.; Ivanova, Nina I.

    2000-11-01

    Experimental methods and theoretical concepts of colloid chemistry regarding their possible use in nanochemistry and nanotechnology are considered. The main types of disperse systems which can be regarded as nanosystems are distinguished. Some methods for the preparation of colloidal nanosystems are described. Conditions for extrapolation of phenomenological laws of colloid chemistry to nanosize objects are considered. Examples of self-organised colloidal structures are given. The bibliography includes 205 references.

  19. Kinetic control of the coverage of oil droplets by DNA-functionalized colloids

    OpenAIRE

    Joshi, Darshana; Bargteil, Dylan; Caciagli, Alessio; Burelbach, Jerome; Xing, Zhongyang; Nunes, André S.; Pinto, Diogo E. P.; Araújo, Nuno A. M.; Brujic, Jasna; Eiser, Erika

    2016-01-01

    We report a study of reversible adsorption of DNA-coated colloids on complementary functionalized oil droplets. We show that it is possible to control the surface coverage of oil droplets by colloidal particles, by exploiting the fact that during slow adsorption, compositional arrest takes place well before structural arrest occurs. As a consequence, we can prepare colloid-coated oil droplets with a `frozen' degree of loading, but with fully ergodic colloidal dynamics on the droplets. We illu...

  20. Preparing normal tissue cells for space flight experiments.

    Science.gov (United States)

    Koch, Claudia; Kohn, Florian P M; Bauer, Johann

    2016-01-01

    Deterioration of health is a problem in modern space flight business. In order to develop countermeasures, research has been done on human bodies and also on single cells. Relevant experiments on human cells in vitro are feasible when microgravity is simulated by devices such as the Random Positioning Machine or generated for a short time during parabolic flights. However, they become difficult in regard to performance and interpretation when long-term experiments are designed that need a prolonged stay on the International Space Station (ISS). One huge problem is the transport of living cells from a laboratory on Earth to the ISS. For this reason, mainly rapidly growing, rather robust human cells such as cancer cells, embryonic cells, or progenitor cells have been investigated on the ISS up to now. Moreover, better knowledge on the behavior of normal mature cells, which mimic the in vivo situation, is strongly desirable. One solution to the problem could be the use of redifferentiable cells, which grow rapidly and behave like cancer cells in plain medium, but are reprogrammed to normal cells when substances like retinoic acid are added. A list of cells capable of redifferentiation is provided, together with names of suitable drugs, in this review.

  1. 不同粒径单分散SiO2粒子的制备与表面改性%Preparation and Surface Modification of Monodispersed Silica Colloid Particles with Different Dimensions

    Institute of Scientific and Technical Information of China (English)

    刘文军; 罗鲲; 喻亮

    2012-01-01

    TEOS was employed to prepare SiO2 colloid particles in diameters of 290nm, 960nm, 1.3μm and 1.9 μm, respectively,by sol-gel and seed-mediated growth methods. The effect of KH570 treatment on the surface hydro-phobicity of the S1O2 colloid particles was investigated. The SiO2 colloid particles were characterized by particle size analysis, SEM and XRD, which indicate that the products are monodispersed spherical SiO2 particles. Measurements of contact angle, hydroxyl group number and lipophilic degree were also carried out to investigate the modification process, which reveal that the concentration of KH570 and modification time exert a significant effect on the hydro-phobicity of the as^modified S\\Ch colloid particles, where the addition of acetone into the KH570 ethanol solution is more beneficial than water for the surface modification, An ethanol solution containing 1% KH570 with addition of acetone and 6-hour reflux were determined as the optimized condition for the modification of SiO2 particles. The introduction of KH570 into the sol-gel process was able to prepare hydrophobic monodispersed SiO2 particles with a diameter of 1.9μm in one step.%以正硅酸乙酯为原料,采用溶胶-凝胶法及种子生长法制备出不同粒径(290nm、960nm、1.3μm和1.9μm)的SiO2胶体颗粒,并研究了KH570对SiO2胶体颗粒表面疏水性的影响.粒度分析、扫描电镜及X射线衍射分析结果表明,产物均为球形单分散SiO2胶体颗粒;而接触角、表面羟基数和亲油化度等测试结果显示,KH570浓度和改性时间对SiO2胶体表面性质影响显著,且丙酮作为助剂改性效果比水更好,最佳条件是以丙酮为助剂,使用1%KH570回流处理6h.此外,在存在KH570时进行溶胶-凝胶过程可一步制备出直径为1.9μm的单分散SiO2疏水颗粒.

  2. Failing to prepare, preparing to fail? : Home country alliance experience as an antecedent to international expansion

    NARCIS (Netherlands)

    Rademaker, Linda

    2016-01-01

    This thesis consists of three empirical chapters on the effect of domestic collaborations with foreign multinational enterprises (MNEs) on the internationalization of emerging market firms. The first chapter studies the effect of domestic joint venture experience with foreign MNEs on the internation

  3. Morphology of colloidal metal pyrophosphate salts

    NARCIS (Netherlands)

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

    2012-01-01

    We report the preparation and characterization of colloidal particles of several pyrophosphate metal salts, including, for the first time, salts containing multiple metals. These materials are compared in order to determine the influence of the composition and experimental conditions on particle

  4. Manipulation of colloidal crystallization

    NARCIS (Netherlands)

    Vermolen, E.C.M.

    2008-01-01

    Colloidal particles (approximately a micrometer in diameter) that are dispersed in a fluid, behave thermodynamically similar to atoms and molecules: at low concentrations they form a fluid, while at high concentrations they can crystallize into a colloidal crystal to gain entropy. The analogy with m

  5. Transport of barrel and spherical shaped colloids in unsaturated porous media.

    Science.gov (United States)

    Knappenberger, Thorsten; Aramrak, Surachet; Flury, Markus

    2015-09-01

    Model colloids are usually spherical, but natural colloids have irregular geometries. Transport experiments of spherical colloids may not reflect the transport characteristics of natural colloids in porous media. We investigated saturated and unsaturated transport of colloids with spherical and angular shapes under steady-state, flow conditions. A pulse of negatively-charged colloids was introduced into a silica sand column at three different effective water saturations (Se = 0.31, 0.45, and 1.0). Colloids were introduced under high ionic strength of [106]mM to cause attachment to the secondary energy minimum and later released by changing the pore water to low ionic strength. After the experiment, sand was sampled from different depths (0, -4, and -11 cm) for scanning electron microscopy (SEM) analysis and colloid extraction. Water saturation affected colloid transport with more retention under low than under high saturation. Colloids were retained and released from a secondary energy minimum with more angular-shaped colloids being retained and released. Colloids extracted from the sand revealed highest colloid deposition in the top layer and decreasing deposition with depth. Pore straining and grain-grain wedging dominated colloid retention. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Fabrication of Phase-Change Polymer Colloidal Photonic Crystals

    Directory of Open Access Journals (Sweden)

    Tianyi Zhao

    2014-01-01

    Full Text Available This paper presents the preparation of phase-change polymer colloidal photonic crystals (PCs by assembling hollow latex spheres encapsulated with dodecanol for the first time. The monodispersed hollow latex spheres were obtained by phase reversion of monodispersed core-shell latex spheres in the n-hexane, which dissolves the PS core and retains the PMMA/PAA shell. The as-prepared phase-change colloidal PCs show stable phase-change behavior. This fabrication of phase-change colloidal PCs would be significant for PC’s applications in functional coatings and various optic devices.

  7. Rapid Preparation of Monodisperse Nano-Silver Colloids Using Microwave Irradiation%微波法快速制备单分散纳米银溶胶

    Institute of Scientific and Technical Information of China (English)

    徐光年; 乔学亮; 邱小林; 陈建国

    2012-01-01

    不添加任何还原剂,在PVP保护下通过微波辐射[Ag(NH3)2]OH络合物水溶液激发自由电子还原Ag+形成纳米银溶胶.UV-Vis吸收光谱测试表明,胶态纳米银粒子的吸光度随微波辐射时间的延长而增加,但最大吸收波长基本不变.当Ag+/PVP质量比为1:8,微波辐射时间为5 min时,吸光度趋于稳定.TEM观测和图像分析结果表明,纳米银粒子的形貌为球形、单分散、平均粒径1.36 nm、标准偏差0.54 nm.%The Ag+ were reduced to elemental silver by free-electron from microwave radiation [Ag(NH3)2]OH complex aqueous solution without any reducing agent, and the nano-silver sol was formed under the protection of PVP. UV-Vis absorption spectra show that the absorbance of the colloidal silver nanoparticles increases with the radiation time, but the maximal absorption wavelength does not change. The absorbance keeps stable when the microwave radiation time is up to 5 min at the mass ratio of Ag7PVP=l:8. TEM observation and image analysis results show that the morphology of nano-silver particles are spherical and monodisperse, with an average diameter of 1.36 nm and the standard deviation of 0.54 nm.

  8. A Facile Method to Prepare Quickly Colloidal Silver Nanoparticles%快速制备胶态银纳米粒子

    Institute of Scientific and Technical Information of China (English)

    徐光年; 乔学亮; 邱小林; 陈建国

    2010-01-01

    通过紫外光与热激发协同作用于[Ag(N-H3)2]+络合离子与聚乙烯吡咯烷酮水溶液,制备高浓度、粒径分布均匀的胶态银纳米粒子,并用紫外-可见吸收光谱对银纳米粒子的形核与增长过程进行监控.结果表明:所制得银纳米粒子的等离子共振吸收峰对应的波长大约为419 mm.TEM结果显示,大多数银纳米粒子为球形,其平均粒径约为1.32nm,标准偏差只有0.53 nm.所得产物的pH值几乎是中性,这使得该银胶有着更广泛的应用.%A high-concentration silver colloidal nanoparticles with a narrow size distribution were obtained using [Ag(NH3)2]+-PVP(poly (N-vinyl-2-pyrrolidone)) solution via the synergistic action of UV and heat excitation. The nucleation and growth of the silver nanoparticles were monitored by UV-vis. Absorption spectroscopy. The results show surface plasma resonance peaks of silver nanoparticles are located at about 419 nm. Transmission electron microscopy (TEM) reveals that most of the particles possess spherical shape with an average size of about 1.32 nm and standard deviation 0.53 nm. Moreover, the pH value of the obtained samples is nearly neutral, which will lead to a more extensive application.

  9. CT colonography with limited bowel preparation: prospective assessment of patient experience and preference in comparison to optical colonoscopy with cathartic bowel preparation

    NARCIS (Netherlands)

    S. Jensch; S. Bipat; J. Peringa; A.H. de Vries; A. Heutinck; E. Dekker; L.C. Baak; A.D. Montauban van Swijndregt; J. Stoker

    2010-01-01

    The purpose of this study was to prospectively compare participant experience and preference of limited preparation computed tomography colonography (CTC) with full-preparation colonoscopy in a consecutive series of patients at increased risk of colorectal cancer. CTC preparation comprised 180 ml di

  10. 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

    2015-01-01

    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 pH7 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. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Tuning Colloid-Interface Interactions by Salt Partitioning

    Science.gov (United States)

    Everts, J. C.; Samin, S.; van Roij, R.

    2016-08-01

    We show that the interaction of an oil-dispersed colloidal particle with an oil-water interface is highly tunable from attractive to repulsive, either by varying the sign of the colloidal charge via charge regulation or by varying the difference in hydrophilicity between the dissolved cations and anions. In addition, we investigate the yet unexplored interplay between the self-regulated colloidal surface charge distribution with the planar double layer across the oil-water interface and the spherical one around the colloid. Our findings explain recent experiments and have direct relevance for tunable Pickering emulsions.

  12. Magnetic Assisted Colloidal Pattern Formation

    Science.gov (United States)

    Yang, Ye

    Pattern formation is a mysterious phenomenon occurring at all scales in nature. The beauty of the resulting structures and myriad of resulting properties occurring in naturally forming patterns have attracted great interest from scientists and engineers. One of the most convenient experimental models for studying pattern formation are colloidal particle suspensions, which can be used both to explore condensed matter phenomena and as a powerful fabrication technique for forming advanced materials. In my thesis, I have focused on the study of colloidal patterns, which can be conveniently tracked in an optical microscope yet can also be thermally equilibrated on experimentally relevant time scales, allowing for ground states and transitions between them to be studied with optical tracking algorithms. In particular, I have focused on systems that spontaneously organize due to particle-surface and particle-particle interactions, paying close attention to systems that can be dynamically adjusted with an externally applied magnetic or acoustic field. In the early stages of my doctoral studies, I developed a magnetic field manipulation technique to quantify the adhesion force between particles and surfaces. This manipulation technique is based on the magnetic dipolar interactions between colloidal particles and their "image dipoles" that appear within planar substrate. Since the particles interact with their own images, this system enables massively parallel surface force measurements (>100 measurements) in a single experiment, and allows statistical properties of particle-surface adhesion energies to be extracted as a function of loading rate. With this approach, I was able to probe sub-picoNewton surface interactions between colloidal particles and several substrates at the lowest force loading rates ever achieved. In the later stages of my doctoral studies, I focused on studying patterns formed from particle-particle interaction, which serve as an experimental model of

  13. 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

  14. Colloid-Mediated Transport of Pharmaceutical and Personal Care Products through Porous Media

    Science.gov (United States)

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

    2016-10-01

    Pharmaceutical and personal care products (PPCPs) enter soils through reclaimed water irrigation and biosolid land applications. Colloids, such as clays, that are present in soil may interact with PPCPs and thus affect their fate and transport in the subsurface environment. This study addresses the influence of soil colloids on the sorption and transport behaviors of PPCPs through laboratory column experiments. Results show that the affinities of PPCPs for colloids vary with their molecular chemistry and solution ionic strength. The presence of colloids promotes the breakthrough of ciprofloxacin (over 90% sorbed on colloids) from ~4% to 30–40%, and the colloid-facilitated effect was larger at lower ionic strength (e.g., 2 mM). In comparison, the net effect of colloids on the transport of tetracycline (~50% sorbed on colloids) could be facilitation or inhibition, depending on solution chemistry. This dual effect of colloids is primarily due to the opposite response of migration of dissolved and colloid-bound tetracycline to the change in solution ionic strength. Colloids could also facilitate the transport of ibuprofen (~10% sorbed on colloids) by ~50% due likely to exclusion of dispersion pathways by colloid straining. This study suggests that colloids are significant carriers or transport promoters of some PPCPs in the subsurface environment and could affect their off-site environmental risks.

  15. 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.

  16. Three-dimensional Ordered Silica Colloidal Film Self-assembly Deposited on a Vertical Substrate

    Institute of Scientific and Technical Information of China (English)

    刘丽霞; 董鹏; 王晓冬; 程丙英

    2003-01-01

    A method for preparation of particle crystal film constructed trom monodisperse silica colloidal partices in diameter of about 300 nm is reported. The films were prepared from an ethanol suspension by vertical deposition that relies on capillary forces to assemble colloidal crystal particles on a vertical substrate. The 3D ordered films were characterized by transmission spectra and scanning electric microscope (SEM). The effect of evaporation temperature, particle concentration and sintered temperature on the quality of colloidal particle crystal film was investigated.

  17. CT colonography with limited bowel preparation: prospective assessment of patient experience and preference in comparison to optical colonoscopy with cathartic bowel preparation

    Energy Technology Data Exchange (ETDEWEB)

    Jensch, Sebastiaan [University of Amsterdam, Department of Radiology, Amsterdam (Netherlands); Onze Lieve Vrouwe Gasthuis, Department of Radiology, Amsterdam (Netherlands); Academic Medical Center, Department of Radiology, Amsterdam (Netherlands); Bipat, Shandra; Vries, Ayso H. de; Heutinck, Anneke; Stoker, Jaap [University of Amsterdam, Department of Radiology, Amsterdam (Netherlands); Peringa, Jan; Montauban van Swijndregt, Alexander D. [Onze Lieve Vrouwe Gasthuis, Department of Radiology, Amsterdam (Netherlands); Dekker, Evelien [University of Amsterdam, Department of Gastroenterology and Hepatology, Amsterdam (Netherlands); Baak, Lubbertus C. [Onze Lieve Vrouwe Gasthuis, Department of Gastroenterology, Amsterdam (Netherlands)

    2010-01-15

    The purpose of this study was to prospectively compare participant experience and preference of limited preparation computed tomography colonography (CTC) with full-preparation colonoscopy in a consecutive series of patients at increased risk of colorectal cancer. CTC preparation comprised 180 ml diatrizoate meglumine, 80 ml barium and 30 mg bisacodyl. For the colonoscopy preparation 4 l of polyethylene glycol solution was used. Participants' experience and preference were compared using the Wilcoxon signed rank test and the chi-squared test, respectively. Associations between preference and experience parameters for the 173 participants were determined by logistic regression. Diarrhoea occurred in 94% of participants during CTC preparation. This side effect was perceived as severely or extremely burdensome by 29%. Nonetheless, the total burden was significantly lower for the CTC preparation than for colonoscopy (9% rated the CTC preparation as severely or extremely burdensome compared with 59% for colonoscopy; p<0.001). Participants experienced significantly more pain, discomfort and total burden with the colonoscopy procedure than with CTC (p<0.001). After 5 weeks, 69% preferred CTC, 8% were indifferent and 23% preferred colonoscopy (p<0.001). A burdensome colonoscopy preparation and pain at colonoscopy were associated with CTC preference (p<0.04). In conclusion, participants' experience and preference were rated in favour of CTC with limited bowel preparation compared with full-preparation colonoscopy. (orig.)

  18. Liquid crystal colloids

    CERN Document Server

    Muševič, Igor

    2017-01-01

    This book brings together the many concepts and discoveries in liquid crystal colloids contributed over the last twenty years and scattered across numerous articles and book chapters. It provides both a historical overview of the development of the field and a clear perspective on the future applications in photonics. The book covers all phenomena observed in liquid crystal colloids with an emphasis on experimental tools and applications of topology in condensed matter, as well as practical micro-photonics applications. It includes a number of spectacular manifestations of new topological phenomena not found or difficult to observe in other systems. Starting from the early works on nematic colloids, it explains the basics of topological defects in ordered media, charge and winding, and the elastic forces between colloidal particles in nematics. Following a detailed description of experimental methods, such as optical tweezing and particle tracking, the book eases the reader into the theoretical part, which de...

  19. Confocal microscopy of colloids

    Energy Technology Data Exchange (ETDEWEB)

    Prasad, V; Semwogerere, D; Weeks, Eric R [Department of Physics, Emory University, Atlanta, GA 30322 (United States)

    2007-03-21

    Colloids have increasingly been used to characterize or mimic many aspects of atomic and molecular systems. With confocal microscopy these colloidal particles can be tracked spatially in three dimensions with great precision over large time scales. This review discusses equilibrium phases such as crystals and liquids, and non-equilibrium phases such as glasses and gels. The phases that form depend strongly on the type of particle interaction that dominates. Hard-sphere-like colloids are the simplest, and interactions such as the attractive depletion force and electrostatic repulsion result in more non-trivial phases which can better model molecular materials. Furthermore, shearing or otherwise externally forcing these colloids while under microscopic observation helps connect the microscopic particle dynamics to the macroscopic flow behaviour. Finally, directions of future research in this field are discussed. (topical review)

  20. Preparation

    Directory of Open Access Journals (Sweden)

    M.M. Dardir

    2014-03-01

    Full Text Available Some hexanamide-mono and di-linoleniate esters were prepared by the reaction of linolenic acid and hexanamide (derived from the reaction of hexanoic acid and diethanolamine. The chemical structure for the newly prepared hexanamide-mono and di-linoleniate esters were elucidated using elemental analysis, (FTIR, H 1NMR and chemical ionization mass spectra (CI/Ms spectroscopic techniques. The results of the spectroscopic analysis indicated that they were prepared through the right method and they have high purity. The new prepared esters have high biodegradability and lower toxicity (environmentally friendly so they were evaluated as a synthetic-based mud (ester-based mud for oil-well drilling fluids. The evaluation included study of the rheological properties, filtration and thermal properties of the ester based-muds formulated with the newly prepared esters compared to the reference commercial synthetic-based mud.

  1. Molecular Recognition in the Colloidal World.

    Science.gov (United States)

    Elacqua, Elizabeth; Zheng, Xiaolong; Shillingford, Cicely; Liu, Mingzhu; Weck, Marcus

    2017-10-06

    ) and can engage in tunable high-fidelity interactions. Examples include metal coordination and host-guest interactions as well as hydrogen bonding and DNA hybridization. On the colloidal scale, these interactions can be used to drive the reversible formation of open structures. Key to the design is the ability to covalently conjugate supramolecular motifs onto the particle surface and/or noncovalently associate with small molecules that can mediate and direct assembly. Efforts exploiting the binding strength inherent to DNA hybridization for the preparation of reversible open-packed structures are then detailed. We describe strategies that led to the introduction of dual-responsive DNA-mediated orthogonal assembly as well as colloidal clusters that afford distinct DNA-ligated close-packed lattices. Further focus is placed on two essential and related efforts: the engineering of complex superstructures that undergo phase transitions and colloidal crystals featuring a high density of functional anchors that aid in crystallization. The design principles discussed in this Account highlight the synergy stemming from coupling well-established noncovalent interactions common on the molecular and polymeric length scales with colloidal platforms to engineer reconfigurable functional architectures by design. Directional strategies and methods such as those illustrated herein feature molecular control and dynamic assembly that afford both open-packed 1D and 2D lattices and are amenable to 3D colloidal frameworks. Multiple methods to direct colloidal assembly have been reported, yet few are capable of crystallizing 2D and 3D architectures of interest for optical data storage, electronics, and photonics. Indeed, early implications are that [supra]molecular control over colloidal assembly can fabricate rationally structured designer materials from simple fundamental building blocks.

  2. Preparation and modification of SiO2 colloidal spheres and it' s self - assembly%二氧化硅胶体球的制备、改性及其胶体晶体的组装

    Institute of Scientific and Technical Information of China (English)

    伍媛婷; 王秀峰

    2011-01-01

    Monodisperse SiO2 particles were synthesized by StOber method. The SiO2 particles were moddied by butanedioic acid. And SiO2 colloidal crystal was fabricated by the vertical deposition method.The crystal formation, micromorphology and electrical properties were characterized by X -ray diffraction (XRD), Scanning electron microscope (SEM) and Zeta potential instrument. The results show that the SiO2 particles are monodisperse non - crystalline solid particles with the particle size in 150 ~ 360nm. Zeta potential instrument indicates that the zeta potentials of the SiO2 specimens with different particle sizes reach the maximum values when the modified amount of butanedioic acid is 1.5g in the 50mL acetonitrile solvents. And the colloidal crystal prepared by modified SiO2 microspheres has more ordered structure.%采用改进的St(O)ber法制备了单分散性较好、表面光滑的SiO2球形颗粒,将丁二酸化学键合于SiO2胶体球表面以提高其Zeta电势,再采用垂直沉积法在水溶液中制备出SiO2胶体晶体.通过X射线衍射仪、场发射扫描电子显微镜(SEM)和Zeta电位粒度仪对颗粒和胶体晶体的晶型、显微形貌、电学性能进行测试分析.结果表明:所得SiO2颗粒为无定形态,SiO2颗粒均为完整的球形颗粒,粒径在150~360nm范围内;不同粒径SiO2颗粒经丁二酸改性后Zeta电势均出现极大值,且改性后的SiO2微球组装的胶体晶体排列紧密有序,呈现密堆垛结构.

  3. 41-D crewmembers Resnik and Walker prepare experiments in training for flight

    Science.gov (United States)

    1984-01-01

    Astronaut Judith A. Resnik, mission specialist, and Charles D. Walker, payload specialist for 41-D, prepare for some scheduled intravehicular activity involving the continuous flow electrophoresis systems (CFES) experiment. In the background are stowage lockers and a CFES trainer - part of the shuttle one-G trainer at JSC (35755,35757); Resnik works with a sample connected to the CFE experiment during training session (35756,35758).

  4. Physical factors affecting the transport and fate of colloids in saturated porous media

    Science.gov (United States)

    Bradford, Scott A.; Yates, Scott R.; Bettahar, Mehdi; Simunek, Jirka

    2002-12-01

    Saturated soil column experiments were conducted to explore the influence of colloid size and soil grain size distribution characteristics on the transport and fate of colloid particles in saturated porous media. Stable monodispersed colloids and porous media that are negatively charged were employed in these studies. Effluent colloid concentration curves and the final spatial distribution of retained colloids by the porous media were found to be highly dependent on the colloid size and soil grain size distribution. Relative peak effluent concentrations decreased and surface mass removal by the soil increased when the colloid size increased and the soil median grain size decreased. These observations were attributed to increased straining of the colloids; i.e., blocked pores act as dead ends for the colloids. When the colloid size is small relative to the soil pore sizes, straining becomes a less significant mechanism of colloid removal and attachment becomes more important. Mathematical modeling of the colloid transport experiments using traditional colloid attachment theory was conducted to highlight differences in colloid attachment and straining behavior and to identify parameter ranges that are applicable for attachment models. Simulated colloid effluent curves using fitted first-order attachment and detachment parameters were able to describe much of the effluent concentration data. The model was, however, less adequate at describing systems which exhibited a gradual approach to the peak effluent concentration and the spatial distribution of colloids when significant mass was retained in the soil. Current colloid filtration theory did not adequately predict the fitted first-order attachment coefficients, presumably due to straining in these systems.

  5. Novel Routes to Model Colloids: ellipsoids, latices and stable meso-emulsions

    NARCIS (Netherlands)

    Sacanna, S.

    2007-01-01

    The research described in this thesis focuses on novel synthetic strategies for the preparation of well-defined model colloids. The preparation routes, involving self-assembly, emulsions and colloidal templating, are meant to facilitate design and fabrication of complex multi-shell composite

  6. Crisis in the Curriculum? New Counselors' Crisis Preparation, Experiences, and Self-Efficacy

    Science.gov (United States)

    Morris, Carrie A. Wachter; Minton, Casey A. Barrio

    2012-01-01

    Professional counselors are responsible for providing crisis assessment, referral, and intervention (Council for Accreditation of Counseling and Related Educational Programs, 2009); however, little is known about their preparation and experiences in these areas. This study examined new professional counselors' (N= 193) crisis intervention…

  7. Experiments of Applying the Rare-Earth Modifying Agents in New Dental Materials Preparation

    Institute of Scientific and Technical Information of China (English)

    Chen Xiaohu; Wang Hua; Wang Qin; Li Xiaodi; Ma Rui

    2007-01-01

    Harmless rare-earth modifying agents were prepared by orthogonal experiments. A new resin material was synthesized with the qualities such as rigidity, rubbing abrasion, aging, luster and plasticity better than the dental resin materials in common used. It could be used as the substitutes for the applied resin teeth materials.

  8. Preparation, spectroscopic and acidity properties of two hydrazones: an organic lab experiment

    Energy Technology Data Exchange (ETDEWEB)

    Rezende, Marcos Caroli; Pizarro, Claudia; Millan, Daniela [Universidad de Santiago, Santiago (Chile). Facultad de Quimica y Biologia]. E-mail: mcaroli@lauca.usach.cl

    2007-01-15

    An undergraduate organic lab experiment is described based on the preparation of two readily accessible hydrazones. The UVvisible spectra of these N-H acids and of their conjugate bases are employed to illustrate the importance of through-conjugation in determining their acid strength and their internal charge-transfer-band transitions. (auth0008.

  9. Using the Learning Activities Survey to Examine Transformative Learning Experiences in Two Graduate Teacher Preparation Courses

    Science.gov (United States)

    Caruana, Vicki; Woodrow, Kelli; Pérez, Luis

    2015-01-01

    The Learning Activities Survey (LAS) detected whether, and to what extent, a perspective transformation occurred during two graduate courses in teacher preparation. The LAS examined the types of learning identified as contributing to their transformative experiences. This study examined pre-service teachers' critical reflection of the course…

  10. Imperial scientists lead the way in preparation for the biggest experiment on earth

    CERN Multimedia

    Reeves, Danielle

    2006-01-01

    "An international team of over 2'000 scientist, led by Professor Tejinder Virdee from Imperial College London's Departement of Physics is stepping up preparations for the world's largest ever physics experiment, starting next year at CERN near Geneva, Switzerland." (1 page)

  11. Postglobal Teacher Preparation: Border Thinking along the Global South through International Cross-Cultural Experiences

    Science.gov (United States)

    Rahatzad, Jubin; Sasser, Hannah L.; Phillion, JoAnn; Karimi, Nastaran; Deng, Yuwen; Akiyama, Reiko; Sharma, Suniti

    2013-01-01

    Preservice teachers' international cross-cultural experiences can provide opportunities for the exploration of epistemic frontiers. In this article we suggest that postglobal teacher preparation take a critically reflective approach that engages preservice teachers in border thinking, which allows for other ways of knowing while studying abroad.…

  12. Experience, Knowledge and Attitudes: Are Paramedic Students Prepared to Care for Older Patients?

    Science.gov (United States)

    Ross, Linda; Jennings, Paul; Williams, Brett

    2016-01-01

    As the population ages, so does the number of older patients encountered by paramedics. It is vital that paramedics are adequately prepared to meet the unique and growing needs of these patients. Experience and education play key roles in the formation of attitudes that impact behavior, and ultimately patient care. The aim of this study was to…

  13. Internationalising the Student Experience: Preparing Instructors to Embed Intercultural Skills in the Curriculum

    Science.gov (United States)

    Mak, Anita S.; Kennedy, Monica

    2012-01-01

    The Internationalising the Student Experience Project was devised and piloted as a teaching innovation to improve the intercultural awareness of instructors and, subsequently, that of their domestic and international students. In this article we claim that instructor preparation in the use of the Alliance Building and Cultural Mapping tools of the…

  14. Preparation, spectroscopic and acidity properties of two hydrazones: an organic lab experiment

    Directory of Open Access Journals (Sweden)

    Marcos Caroli Rezende

    2007-02-01

    Full Text Available An undergraduate organic lab experiment is described based on the preparation of two readily accessible hydrazones. The UV-visible spectra of these N-H acids and of their conjugate bases are employed to illustrate the importance of through-conjugation in determining their acid strength and their internal charge-transfer-band transitions.

  15. SUPERFUND TREATABILITY CLEARINGHOUSE: CERCLA BDAT SARM PREPARATION AND RESULTS OF PHYSICAL SOILS WASHING EXPERIMENTS (FINAL REPORT)

    Science.gov (United States)

    This study reports on the results of work preparing 30,000 Ibs of SARM or synthetic analytical reference matrix, a surrogate Superfund soil containing a vide range of contaminants. It also reports the results ©f bench scale treatability experiments designed to simulate the EP...

  16. Crisis in the Curriculum? New Counselors' Crisis Preparation, Experiences, and Self-Efficacy

    Science.gov (United States)

    Morris, Carrie A. Wachter; Minton, Casey A. Barrio

    2012-01-01

    Professional counselors are responsible for providing crisis assessment, referral, and intervention (Council for Accreditation of Counseling and Related Educational Programs, 2009); however, little is known about their preparation and experiences in these areas. This study examined new professional counselors' (N= 193) crisis intervention…

  17. Sustainable low temperature preparation of Mn{sub 3−x}Co{sub x}O{sub 4} (0 ≤ x < 3) spinel oxide colloidal dispersions used for solar absorber thin films

    Energy Technology Data Exchange (ETDEWEB)

    Salek, G.; Dufour, P.; Guillemet-Fritsch, S.; Tenailleau, C., E-mail: tenailleau@chimie.ups-tlse.fr

    2015-07-15

    of oxide nanoparticles. • Stabilization of colloidal dispersions free of organic precursors or surfactants. • Influence of hydrodynamic parameters and physicochemical properties. • Thin films preparation by the dip-coating method and their optical properties. • Promising method for enhanced efficiency in the preparation and use of nanomaterials.

  18. Controllable fabrication of 2D colloidal-crystal films with polystyrene nanospheres of various diameters by spin-coating

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jian; Dong, Peitao [College of Mechatronics Engineering and Automation, National University of Defense Technology, Changsha, Hunan, 410073 (China); State Key Laboratory of Transducer Technology, Chinese Academy of Science (China); Di, Di; Wang, Chaoguang; Wang, Haoxu; Wang, Junfeng [College of Mechatronics Engineering and Automation, National University of Defense Technology, Changsha, Hunan, 410073 (China); Wu, Xuezhong, E-mail: xzwu@nudt.edu.cn [College of Mechatronics Engineering and Automation, National University of Defense Technology, Changsha, Hunan, 410073 (China)

    2013-04-01

    Monolayer and bilayer colloidal-crystal films are used as physical mask in nanosphere lithography (NSL). So far, spin-coating experiments have mainly been designed to form nanosphere monolayer with one given size or obtain small areas of polystyrene (PS) nanosphere monolayer which limited the application of these films used as physical masks. The development of NSL required more study focused on the preparation of colloidal-crystal films with large-scale, high ordering degree and nanospheres of different diameters. In this study, PS nanospheres were self-assembled to form monolayer and bilayer colloidal-crystal films by employing spin-coating technology. Based on our experiments, we have built an experiment system of PS nanospheres of certain size ranging from 200 nm to 1300 nm. To give an instance, we have chosen PS nanospheres of four diameters (223 nm, 347 nm, 509 nm, 1300 nm) to fabricate colloidal-crystal films by adjusting the spin speed and acceleration, and we have investigated the relationship between the monolayer coverage areas and spin parameters by designing different spin speed and acceleration for 509 nm nanosphere. Results revealed that monolayer and bilayer films of PS nanospheres with four different diameters were prepared successfully and the single structure where PS nanospheres were in hexagonal close-packed (HCP) order dominated the surface morphologies of both monolayer and bilayer colloidal-crystal films. For 509 nm PS nanosphere, as the spin speed and acceleration increasing, the monolayer coverage areas increase firstly then decrease and at spin speed 1750 rpm and acceleration 600 rpm/s, the areas reaches the biggest.

  19. ROLE OF EXPERIMENT IN PROFESSIONAL PREPARATION OF FUTURE SPECIALISTS IN THE SYSTEM «COLLEGE-UNIVERSITY»

    Directory of Open Access Journals (Sweden)

    Mariia T. Levochko

    2010-08-01

    Full Text Available In the article a value and role of experiment in professional preparation of future specialists opens up in the system “college-university”. An experiment plays a considerable role during realization of pedagogical, educational reforms, enables to check up the professional competence of specialists, professional abilities and skills, theoretical purchased knowledgе which are inculcated in practical activity in practicе. During research, by carrying out the experiments, the basic criteria of learning efficiency with use of test tasks and questioning for formation of professional competence and professional skills of the future specialists of economic branch in the system "college-university" have been offered.

  20. Stable colloidal Co-Pd nanocatalysts for carbon nanotube growth

    Energy Technology Data Exchange (ETDEWEB)

    Berenguer, A.; Golovko, V.B.; Johnson, B.F.G.; Robertson, John [Department of Chemistry, University of Cambridge (United Kingdom); Cantoro, M.; Hofmann, S.; Wirth, C.T. [Department of Engineering, University of Cambridge (United Kingdom)

    2009-12-15

    The standard preparation method for catalysts for surface-bound growth of carbon nanotubes (CNT) is to sputter or evaporate the metal catalyst (Fe, Co, and Ni) onto the surface. A lower cost method for large areas is to use liquid delivery. Colloids have the advantage of containing the catalyst in nanocluster form. Our previously developed colloidal catalysts were successful for growth but had limited shelf-life due to oxidation and coagulation. Here, we develop an air-stable colloidal catalyst with long shelf-life of many months to years. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  1. 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.

  2. Hydrophobicity of soil colloids and heavy metal mobilization: effects of drying.

    Science.gov (United States)

    Klitzke, Sondra; Lang, Friederike

    2007-01-01

    Drying of soil may increase the hydrophobicity of soil and affect the mobilization of colloids after re-wetting. Results of previous research suggest that colloid hydrophobicity is an important parameter in controlling the retention of colloids and colloid-associated substances in soils. We tested the hypothesis that air-drying of soil samples increases the hydrophobicity of water-dispersible colloids and whether air-drying affects the mobilization of colloid-associated heavy metals. We performed batch experiments with field-moist and air-dried (25 degrees C) soils from a former sewage farm (sandy loam), a municipal park (loamy sand), and a shooting range site (loamy sand with 25% C(org)). The filtered suspensions (<1.2 microm) were analyzed for concentrations of dissolved and colloidal organic C and heavy metals (Cu, Cd, Pb, Zn), average colloid size, zeta potential, and turbidity. The hydrophobicity of colloids was determined by their partitioning between a hydrophobic solid and a hydrophilic aqueous phase. Drying increased hydrophobicity of the solid phase but did not affect the hydrophobicity of the dispersed colloids. Drying decreased the amount of mobilized mineral and (organo-)mineral colloids in the sewage farm soils but increased the mobilization of organic colloids in the C-rich shooting range soil. Dried samples released less colloid-bound Cd and Zn than field-moist samples. Drying-induced mobilization of dissolved organic C caused a redistribution of Cu from the colloidal to the dissolved phase. We conclude that drying-induced colloid mobilization is not caused by a change in the physicochemical properties of the colloids. Therefore, it is likely that the mobilization of colloids in the field is caused by increasing shear forces or the disintegration of aggregates.

  3. Colloids with continuously tunable surface charge.

    Science.gov (United States)

    van Ravensteijn, Bas G P; Kegel, Willem K

    2014-09-09

    In this paper, we present a robust way to tune the surface potential of polystyrene colloids without changing the pH, ionic strength, etc. The colloids are composed of a cross-linked polystyrene core and a cross-linked vinylbenzyl chloride layer. Besides the chlorine groups, the particle surface contains sulfate/sulfonate groups (arising from the polymerization initiators) that provide a negative surface potential. Performing a Menschutkin reaction on the surface chlorine groups with tertiary amines allows us to introduce quaternary, positively charged amines. The overall charge on the particles is then determined by the ratio between the sulfate/sulfonate moieties and the quaternary amines. Using this process, we were able to invert the charge in a continuous manner without losing colloidal stability upon passing the isoelectric point. The straightforward reaction mechanism together with the fact that the reaction could be quenched rapidly resulted in a colloidal system in which the ζ potential can be tuned between -80 and 45 mV. As proof of principle, the positively charged particles were used in heterocoagulation experiments with nanometer- and micrometer-sized negatively charged silica particles to create geometrically well-defined colloidal (nano) clusters.

  4. Sterically Stabilized Poly(3,4-ethylenedioxythiophene) Colloidal Dispersions Doped with Different Sulfonic Acids

    Institute of Scientific and Technical Information of China (English)

    Tie Jun WANG; Ping CHEN; Xiu Jie HU; Shu Yun ZHOU

    2006-01-01

    The preparation of sterically stabilized poly(3, 4-ethylenedioxythiophene)(PEDOT)colloidal dispersions doped with different sulfonic acids is described. Three different sulfonic acids, i.e., p-toluenesulfonic acid, β-naphthalenesuffonic acid and D-camphor-10-sulfonic acid are used, facilitating the preparation of sterically stable PEDOT colloidal particles. The influences of the dopants and concentration of polymeric stabilizer on the yields, morphologies and electrical properties of the resultant colloidal particles were investigated. The colloidal particles with the size ranging from 172 to 334 nm have been obtained in good yields. The compressed pellet conductivity was as high as 4.5 Scm-1.

  5. Targeted delivery of colloids by swimming bacteria

    Science.gov (United States)

    Koumakis, N.; Lepore, A.; Maggi, C.; Di Leonardo, R.

    2013-01-01

    The possibility of exploiting motile microorganisms as tiny propellers represents a fascinating strategy for the transport of colloidal cargoes. However, delivery on target sites usually requires external control fields to steer propellers and trigger cargo release. The need for a constant feedback mechanism prevents the design of compact devices where biopropellers could perform their tasks autonomously. Here we show that properly designed three-dimensional (3D) microstructures can define accumulation areas where bacteria spontaneously and efficiently store colloidal beads. The process is stochastic in nature and results from the rectifying action of an asymmetric energy landscape over the fluctuating forces arising from collisions with swimming bacteria. As a result, the concentration of colloids over target areas can be strongly increased or depleted according to the topography of the underlying structures. Besides the significance to technological applications, our experiments pose some important questions regarding the structure of stationary probability distributions in non-equilibrium systems. PMID:24100868

  6. Dynamic Assembly of Magnetic Colloidal Vortices

    Energy Technology Data Exchange (ETDEWEB)

    Mohorič, Tomaž; Kokot, Gašper; Osterman, Natan; Snezhko, Alexey; Vilfan, Andrej; Babič, Dušan; Dobnikar, Jure

    2016-04-29

    Magnetic colloids in external time-dependent fields are subject to complex induced many-body interactions governing their self-assembly into a variety of equilibrium and out-of-equilibrium structures such as chains, networks, suspended membranes, and colloidal foams. Here, we report experiments, simulations, and theory probing the dynamic assembly of superparamagnetic colloids in precessing external magnetic fields. Within a range of field frequencies, we observe dynamic large-scale structures such as ordered phases composed of precessing chains, ribbons, and rotating fluidic vortices. We show that the structure formation is inherently coupled to the buildup of torque, which originates from internal relaxation of induced dipoles and from transient correlations among the particles as a result of short-lived chain formation. We discuss in detail the physical properties of the vortex phase and demonstrate its potential in particle-coating applications.

  7. Fast microbial reduction of ferrihydrite colloids from a soil effluent

    Science.gov (United States)

    Fritzsche, Andreas; Bosch, Julian; Rennert, Thilo; Heister, Katja; Braunschweig, Juliane; Meckenstock, Rainer U.; Totsche, Kai U.

    2012-01-01

    Recent studies on the microbial reduction of synthetic iron oxide colloids showed their superior electron accepting property in comparison to bulk iron oxides. However, natural colloidal iron oxides differ in composition from their synthetic counterparts. Besides a potential effect of colloid size, microbial iron reduction may be accelerated by electron-shuttling dissolved organic matter (DOM) as well as slowed down by inhibitors such as arsenic. We examined the microbial reduction of OM- and arsenic-containing ferrihydrite colloids. Four effluent fractions were collected from a soil column experiment run under water-saturated conditions. Ferrihydrite colloids precipitated from the soil effluent and exhibited stable hydrodynamic diameters ranging from 281 (±146) nm in the effluent fraction that was collected first and 100 (±43) nm in a subsequently obtained effluent fraction. Aliquots of these oxic effluent fractions were added to anoxic low salt medium containing diluted suspensions of Geobacter sulfurreducens. Independent of the initial colloid size, the soil effluent ferrihydrite colloids were quickly and completely reduced. The rates of Fe2+ formation ranged between 1.9 and 3.3 fmol h-1 cell-1, and are in the range of or slightly exceeding previously reported rates of synthetic ferrihydrite colloids (1.3 fmol h-1 cell-1), but greatly exceeding previously known rates of macroaggregate-ferrihydrite reduction (0.07 fmol h-1 cell-1). The inhibition of microbial Fe(III) reduction by arsenic is unlikely or overridden by the concurrent enhancement induced by soil effluent DOM. These organic species may have increased the already high intrinsic reducibility of colloidal ferrihydrite owing to quinone-mediated electron shuttling. Additionally, OM, which is structurally associated with the soil effluent ferrihydrite colloids, may also contribute to the higher reactivity due to increasing solubility and specific surface area of ferrihydrite. In conclusion, ferrihydrite

  8. The Gelation of Polyvinyl Alcohol with Borax: A Novel Class Participation Experiment Involving the Preparation and Properties of a "Slime."

    Science.gov (United States)

    Casassa, E. Z.; And Others

    1986-01-01

    Background information, procedures used, and typical results obtained are provided for an experiment in which students prepare and study the characteristics of a "slime." A list of general, inorganic, and polymer chemistry concepts fostered in the experiment is included. (JN)

  9. Anisotropic Model Colloids

    Science.gov (United States)

    van Kats, C. M.

    2008-10-01

    The driving forces for fundamental research in colloid science are the ability to manage the material properties of colloids and to unravel the forces that play a role between colloids to be able to control and understand the processes where colloids play an important role. Therefore we are searching for colloidal materials with specific physical properties to better understand our surrounding world.Until recently research in colloid science was mainly focused on spherical (isotropic) particles. Monodisperse spherical colloids serve as a model system as they exhibit similar phase behaviour as molecular and atomic systems. Nevertheless, in many cases the spherical shape is not sufficient to reach the desired research goals. Recently the more complex synthesis methods of anisotropic model colloids has strongly developed. This thesis should be regarded as a contribution to this research area. Anisotropic colloids can be used as a building block for complex structures and are expected not only to lead to the construction of full photonic band gap materials. They will also serve as new, more realistic, models systems for their molecular analogues. Therefore the term ‘molecular colloids” is sometimes used to qualify these anisotropic colloidal particles. In the introduction of this thesis, we give an overview of the main synthesis techniques for anisotropic colloids. Chapter 2 describes the method of etching silicon wafers to construct monodisperse silicon rods. They subsequently were oxidized and labeled (coated) with a fluorescent silica layer. The first explorative phase behaviour of these silica rods was studied. The particles showed a nematic ordering in charge stabilized suspensions. Chapter 3 describes the synthesis of colloidal gold rods and the (mesoporous) silica coating of gold rods. Chapter 4 describes the physical and optical properties of these particles when thermal energy is added. This is compared to the case where the particles are irradiated with

  10. Application of colloidal chemistry in aqueous phase to the preparation of supported metallic catalysts: particles size and aggregation control; Application de la chimie colloidale en phase aqueuse a la preparation de catalyseurs metalliques supportes: controle de la taille et de l`etat d`agregation des particules

    Energy Technology Data Exchange (ETDEWEB)

    Pages, T.

    1998-09-16

    This work is an application of colloidal chemistry in aqueous phase on supported metal catalyst preparation. The objective is the control of particle size and aggregation. The preparation of the materials was achieved in two steps: - the synthesis of PdO hydrosols was obtained by two ways: neutralisation of the solution containing metallic salt by adding alkaline solution or by thermo-hydrolysis; the sols were then deposited on carriers (Al{sub 2}O{sub 3}, SIO{sub 2}). The use of partial charge model allowed us to determine the complexes that were able to generate PdO. The preparation of PdO from Pd(H{sub 2}O){sub 4}{sup 2+} was studied and a mechanism of oxide formation was elaborated. The neutralisation of Pd(H{sub 2}O){sub 4}{sup 2+} obtained by adding alkaline solution led to particles with an average size of 1.8 nm and a narrow particle size distribution. Only the thermo-hydrolysis of Pd(H{sub 2}O){sub 4}{sup 2+} led to particles which size is higher than 3.0 nm. In the last case, particle size is controlled by the precursor concentration (Pd(H{sub 2}O){sub 2}(OH){sub 2}) generated in the medium. We have demonstrated that particle aggregation in the sol depends on the Ph and the way of preparation. It can be controlled by adding complexing anions (Cl{sup -}, NO{sub 2}{sup -}). Concerning the deposition of sols on carriers, it led to isolated or aggregated particles according to experimental conditions. Particle size was not modified during the deposition. Moreover, in our experimental conditions, reduction of particles did not modify particle size and aggregation. An application of this original way of preparation on catalysis allowed us to demonstrate the interest of controlling particle size and aggregation. (author) 186 refs.

  11. 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.

  12. Teachers' literacy-related knowledge and self-perceptions in relation to preparation and experience.

    Science.gov (United States)

    Spear-Swerling, Louise; Brucker, Pamela Owen; Alfano, Michael P

    2005-12-01

    After rating their own literacy-related knowledge in three areas (knowledge about reading/reading development, phonemic awareness/phonics, and morpheme awareness/structural analysis), graduate teacher-education students completed five tasks intended to measure their actual disciplinary knowledge in these areas. Teachers with high levels of prior background (i.e., course preparation and experience) rated themselves as significantly more knowledgeable than did low-background teachers in all areas; high-background participants also significantly outperformed low-background participants on all tasks. However, even high-background teachers scored well below ceiling on the tasks. Regression analyses indicated that teachers' self-perceptions and knowledge were positively influenced by both level of preparation and teaching experience, although the influences on teachers' knowledge differed by task. Teachers had some accurate perceptions of their own knowledge, especially in the area of phonics. Results suggest that differentiating levels of preparation may be useful in studying teacher knowledge, and also support the notion of a substantial gap between research on reading and teacher preparation in reading.

  13. Colloidal pen lithography.

    Science.gov (United States)

    Xue, Mianqi; Cai, Xiaojing; Chen, Ghenfu

    2015-02-04

    Colloidal pen lithography, a low-cost, high-throughput scanning probe contact printing method, has been developed, which is based on self-assembled colloidal arrays embedded in a soft elastomeric stamp. Patterned protein arrays are demonstrated using this method, with a feature size ranging from 100 nm to several micrometers. A brief study into the specificity reorganization of protein gives evidence for the feasibility of this method for writing protein chips. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Formation of gold colloids using thioether derivatives as stabilizing ligands

    NARCIS (Netherlands)

    Li, X.; de Jong, M.R.; Inoue, K.; Huskens, Jurriaan; Shinkai, Seiji; Reinhoudt, David

    2001-01-01

    Thioethers were used as adsorbates for preparing gold nanoparticles. Different thioether derivatives having from 1 to 4 thioether functionalities were synthesized. Colloids were prepared in a two-phase system, and characterized by 1H NMR and transmission electron microscopy (TEM). The stability of

  15. Structural color from colloidal glasses

    Science.gov (United States)

    Magkiriadou, Sofia

    When a material has inhomogeneities at a lengthscale comparable to the wavelength of light, interference can give rise to structural colors: colors that originate from the interaction of the material's microstructure with light and do not require absorbing dyes. In this thesis we study a class of these materials, called photonic glasses, where the inhomogeneities form a dense and random arrangement. Photonic glasses have angle-independent structural colors that look like those of conventional dyes. However, when this work started, there was only a handful of colors accessible with photonic glasses, mostly hues of blue. We use various types of colloidal particles to make photonic glasses, and we study, both theoretically and experimentally, how the optical properties of these glasses relate to their structure and constituent particles. Based on our observations from glasses of conventional particles, we construct a theoretical model that explains the scarcity of yellow, orange, and red photonic glasses. Guided by this model, we develop novel colloidal systems that allow a higher degree of control over structural color. We assemble glasses of soft, core-shell particles with scattering cores and transparent shells, where the resonant wavelength can be tuned independently of the reflectivity. We then encapsulate glasses of these core-shell particles into emulsion droplets of tunable size; in this system, we observe, for the first time, angle-independent structural colors that cover the entire visible spectrum. To enhance color saturation, we begin experimenting with inverse glasses, where the refractive index of the particles is lower than the refractive index of the medium, with promising results. Finally, based on our theoretical model for scattering from colloidal glasses, we begin an exploration of the color gamut that could be achieved with this technique, and we find that photonic glasses are a promising approach to a new type of long-lasting, non-toxic, and

  16. Developing Research-Ready Skills: Preparing Early Academic Students for Participation in Research Experiences

    Science.gov (United States)

    Charlevoix, D. J.; Morris, A. R.

    2015-12-01

    Engaging lower-division undergraduates in research experiences is a key but challenging aspect of guiding talented students into the geoscience research pipeline. UNAVCO conducted a summer internship program to prepare first and second year college students for participation in authentic, scientific research. Many students in their first two years of academic studies do not have the science content knowledge or sufficient math skills to conduct independent research. Students from groups historically underrepresented in the geosciences may face additional challenges in that they often have a less robust support structure to help them navigate the university environment and may be less aware of professional opportunities in the geosciences.UNAVCO, manager of NSF's geodetic facility, hosted four students during summer 2015 internship experience aimed to help them develop skills that will prepare them for research internships and skills that will help them advance professionally. Students spent eight weeks working with UNAVCO technical staff learning how to use equipment, prepare instrumentation for field campaigns, among other technical skills. Interns also participated in a suite of professional development activities including communications workshops, skills seminars, career circles, geology-focused field trips, and informal interactions with research interns and graduate student interns at UNAVCO. This presentation will outline the successes and challenges of engaging students early in their academic careers and outline the unique role such experiences can have in students' academic careers.

  17. Designing Zirconium Coated Polystyrene Colloids and Application

    Directory of Open Access Journals (Sweden)

    Diana Chira

    2009-01-01

    Full Text Available A simple technique has been developed to prepare core colloids that are modified using zirconium oxychloride, based on heating a solution of core colloid composites, consisting of poly (ethylenimine (PEI and zirconium oxychloride. The interaction of zirconium oxychloride with the polystyrene (PS core colloids has been investigated using Fourier transform-infrared spectroscopy (FT-IR, energy dispersive X-ray spectroscopy (EDX, and scanning electron microscopy (SEM data. FT-IR studies confirm the occurrence of amine groups present in PEI which are oxidized to carboxyl groups after the reaction. The EDX data and the SEM images confirm the presence of zirconium particles immobilized on the polystyrene surfaces. Demeton, a highly toxic nerve agent, was used due to its ability to easily bind through its organophosphate group illustrating a practical application of the PS-PEI-Zr particles. Attenuated Total Reflection (ATR Spectroscopy was used to assess the interactions between the toxic nerve agent demeton-S and the PS-PEI-Zr particles. The results show that the presented technique for coating polystyrene core colloids with zirconium was successfully accomplished, and the newly formed particles easily bond with demeton agents through the P=O functional group.

  18. Synthesis of Cone-Shaped Colloids from Rod-Like Silica Colloids with a Gradient in the Etching Rate.

    Science.gov (United States)

    Hagemans, Fabian; van der Wee, Ernest B; van Blaaderen, Alfons; Imhof, Arnout

    2016-04-26

    We present the synthesis of monodisperse cone-shaped silica colloids and their fluorescent labeling. Rod-like silica colloids prepared by ammonia-catalyzed hydrolysis and condensation of tetraethyl orthosilicate in water droplets containing polyvinylpyrrolidone cross-linked by citrate ions in pentanol were found to transform into cone-shaped particles upon mild etching by NaOH in water. The diameter and length of the resulting particles were determined by those of the initial rod-like silica colloids. The mechanism responsible for the cone-shape involves silica etching taking place with a varying rate along the length of the particle. Our experiments thus also lead to new insights into the variation of the local particle structure and composition. These are found to vary gradually along the length of the rod, as a result of the way the rod grows out of a water droplet that keeps itself attached to the flat end of the bullet-shaped particles. Subtle differences in composition and structure could also be resolved by high-resolution stimulated emission depletion confocal microscopy on fluorescently labeled particles. The incorporation of a fluorescent dye chemically attached to an amine-based silane coupling agent resulted in a distribution of fluorophores mainly on the outside of the rod-shaped particles. In contrast, incorporation of the silane coupling agent alone resulted in a homogeneous distribution. Additionally, we show that etching rods, where a silane coupling agent alone was incorporated and subsequently coupled to a fluorescent dye, resulted in fluorescent silica cones, the orientation of which can be discerned using super-resolution confocal microscopy.

  19. USING COLLOIDAL LAYERED DOUBLE HYDROXIDES AS CATIONIC MICROPARTICULATE COMPONENT

    Institute of Scientific and Technical Information of China (English)

    Songlin Wang; Wenxia Liu

    2004-01-01

    Layered double hydroxides consisting of layers with cationic charges may be potential candidates of cationic microparticles forming synergetic retention effect with anionic polyacrylamide. In this work, the layered double hydroxides with various molar ratios of Mg/Al were synthesized by co-precipitation of magnesium chloride and aluminum chloride and peptized by intense washing with water. The chemical formula, particle size, Zeta potential of the layered double hydroxide were analyzed. It was found that positively charged magnesium aluminum hydroxide with particle diameter in nanoparticle size could be prepared. The Zeta potential and particle size vary with the feed molar ratio of Mg/Al and the peptizing process, respectively. The Zeta potential is also pH dependent. The retention experiments carried out on DDJ show that when used together with anionic polyacrylamide, the positively charged colloidal double hydroxide greatly improves the retention of reed pulps. The chemical formula, particle size and Zeta potential of the colloidal double hydroxide all affect its retention behavior.

  20. Dispersion stability and electrokinetic properties of intrinsic plutonium colloids: implications for subsurface transport.

    Science.gov (United States)

    Abdel-Fattah, Amr I; Zhou, Dongxu; Boukhalfa, Hakim; Tarimala, Sowmitri; Ware, S Doug; Keller, Arturo A

    2013-06-04

    Subsurface transport of plutonium (Pu) may be facilitated by the formation of intrinsic Pu colloids. While this colloid-facilitated transport is largely governed by the electrokinetic properties and dispersion stability (resistance to aggregation) of the colloids, reported experimental data is scarce. Here, we quantify the dependence of ζ-potential of intrinsic Pu(IV) colloids on pH and their aggregation rate on ionic strength. Results indicate an isoelectric point of pH 8.6 and a critical coagulation concentration of 0.1 M of 1:1 electrolyte at pH 11.4. The ζ-potential/pH dependence of the Pu(IV) colloids is similar to that of goethite and hematite colloids. Colloid interaction energy calculations using these values reveal an effective Hamaker constant of the intrinsic Pu(IV) colloids in water of 1.85 × 10(-19) J, corresponding to a relative permittivity of 6.21 and refractive index of 2.33, in agreement with first principles calculations. This relatively high Hamaker constant combined with the positive charge of Pu(IV) colloids under typical groundwater aquifer conditions led to two contradicting hypotheses: (a) the Pu(IV) colloids will exhibit significant aggregation and deposition, leading to a negligible subsurface transport or (b) the Pu(IV) colloids will associate with the relatively stable native groundwater colloids, leading to a considerable subsurface transport. Packed column transport experiments supported the second hypothesis.

  1. Medical applications of colloids

    CERN Document Server

    Matijevic, Egon

    2008-01-01

    The first book of its type on the medical and biomedical applications of colloids, although there are some related titles on different topicsDiscusses the effects of uniform particles in drug formulations and releaseEvaluates particle transport and deposition in the human body.

  2. Liquid crystal colloids

    Directory of Open Access Journals (Sweden)

    2010-01-01

    Full Text Available This special issue of "Condensed Matter Physics" focuses on the most recent developments in the study of a fascinating soft matter system, representing colloidal particles in a liquid crystalline environment. Furthermore, some articles address pioneering steps in the discovery of liquid crystals going back to 1861 paper by Julius Planer.

  3. Nucleation in food colloids

    Science.gov (United States)

    Povey, Malcolm J. W.

    2016-12-01

    Nucleation in food colloids has been studied in detail using ultrasound spectroscopy. Our data show that classical nucleation theory (CNT) remains a sound basis from which to understand nucleation in food colloids and analogous model systems using n-alkanes. Various interpretations and modifications of CNT are discussed with regard to their relevance to food colloids. Much of the evidence presented is based on the ultrasound velocity spectrometry measurements which has many advantages for the study of nucleating systems compared to light scattering and NMR due to its sensitivity at low solid contents and its ability to measure true solid contents in the nucleation and early crystal growth stages. Ultrasound attenuation spectroscopy also responds to critical fluctuations in the induction region. We show, however, that a periodic pressure fluctuation such as a quasi-continuous (as opposed to a pulse comprising only a few pressure cycles) ultrasound field can alter the nucleation process, even at very low acoustic intensity. Thus care must be taken when using ultrasound techniques that the measurements do not alter the studied processes. Quasi-continuous ultrasound fields may enhance or suppress nucleation and the criteria to determine such effects are derived. The conclusions of this paper are relevant to colloidal systems in foods, pharmaceuticals, agro-chemicals, cosmetics, and personal products.

  4. Binary colloidal crystals

    NARCIS (Netherlands)

    Christova-Zdravkova, C.G.

    2005-01-01

    Binary crystals are crystals composed of two types of particles having different properties like size, mass density, charge etc. In this thesis several new approaches to make binary crystals of colloidal particles that differ in size, material and charge are reported We found a variety of crystal st

  5. Electrodynamics of colloids.

    NARCIS (Netherlands)

    Minor, M.

    1998-01-01

    The goal of the present study is to deepen the insight into the non-equilibrium properties of the electric double layer of colloidal systems. Of basic interest are the ionic mobilities in the different regions of the electric double layer as well as the potential at the plane of shear, i.e., the ele

  6. Gel trapping of dense colloids.

    Science.gov (United States)

    Laxton, Peter B; Berg, John C

    2005-05-01

    Phase density differences in sols, foams, or emulsions often lead to sedimentation or creaming, causing problems for materials where spatial uniformity over extended periods of time is essential. The problem may be addressed through the use of rheology modifiers in the continuous phase. Weak polymer gels have found use for this purpose in the food industry where they appear to be capable of trapping dispersoid particles in a three-dimensional matrix while displaying water-like viscosities at low shear. Attempts to predict sedimentation stability in terms of particle properties (size, shape, density difference) and gel yield stress have led to qualitative success for suspensions of large particles. The effect of particle size, however, in particular the case in which colloidal dimensions are approached, has not been investigated. The present work seeks to determine useful stability criteria for colloidal dispersions in terms of readily accessible viscoelastic descriptors. Results are reported for systems consisting of 12 microm poly(methyl methacrylate) (PMMA) spheres dispersed in aqueous gellan gum. Monovalent salt concentration is varied to control rheological properties, and sedimentation/centrifugation experiments are performed to determine dispersion stability. Necessary conditions for stability consist of a minimum yield stress together with a value of tan delta less than unity.

  7. Experimental Studies to Evaluate the Role of Colloids on the Radionuclide Migration in a Crystalline Medium

    Energy Technology Data Exchange (ETDEWEB)

    Albarran, Nairoby; Missana, Tiziana; Alonso, Ursula; Garcia-Gutierrez, Miguel; Mingarro, Manuel; Lopez, Trinidad [CIEMAT, Departamento de Medioambiente, Avenida Complutense, 22 28040 Madrid (Spain)

    2008-07-01

    In a deep geological repository (DGR) of high level radioactive waste, all the possible phenomena affecting radionuclide migration have to be studied to assess its security over time. Colloids can play an important role for contaminant transport if the following conditions are fulfilled: colloids exist in a non negligible concentration, they are mobile and stable in the environment of interest, and they are able to adsorb radionuclides irreversibly. In this study, different transport experiments where performed to improve the knowledge on the main mechanisms affecting the radionuclide migration in the presence of colloids in a crystalline medium. Firstly, colloid stability was analysed and then transport experiments in an artificial granite longitudinal fracture were carried out. Synthetic colloids of different size and bentonite clay colloids were used to evaluate the effects of colloid size, charge, and water flow rate on their mobility. Results showed that both major importance of the water flow rate on the mobility of colloids and their recovery and a higher interaction of smaller particles with the surface. Finally, the migration behaviour of Sr, and Sr adsorbed onto bentonite colloids was compared. The elution curves of Sr adsorbed onto colloid were significantly different from the ones of Sr alone, pointing out that sorption/desorption mechanisms must be taken into account to understand the radionuclide migration in the fracture in the presence of colloids. (authors)

  8. An elective pharmaceutical care course to prepare students for an advanced pharmacy practice experience in Kenya.

    Science.gov (United States)

    Schellhase, Ellen M; Miller, Monica L; Ogallo, William; Pastakia, Sonak D

    2013-04-12

    OBJECTIVE. To develop a prerequisite elective course to prepare students for an advanced pharmacy practice experience (APPE) in Kenya. DESIGN. The course addressed Kenyan culture, travel preparation, patient care, and disease-state management. Instructional formats used were small-group discussions and lectures, including some Web-based presentations by Kenyan pharmacists on disease states commonly treated in Kenya. Cultural activities include instruction in conversational and medical Kiswahili and reading of a novel related to global health programs. ASSESSMENT. Student performance was assessed using written care plans, quizzes, reflection papers, a formulary management exercise, and pre- and post-course assessments. Student feedback on course evaluations indicated that the course was well received and students felt prepared for the APPE. CONCLUSION. This course offered a unique opportunity for students to learn about pharmacy practice in global health and to apply previously acquired skills in a resource-constrained international setting. It prepares students to actively participate in clinical care activities during an international APPE.

  9. CVD Method for Carbon Nanotubes Preparation Based on Orthogonal Experiment Using C3H6

    Institute of Scientific and Technical Information of China (English)

    SU Xunwen; JIANG Fang

    2015-01-01

    Carbon nanotubes (CNTs) have potential applications in many fields, chemical vapor deposition (CVD) is an effective method for CNTs preparation. By CVD, the catalytic pyrolysis temperature, pyrolysis time and the size of the raw gas lfow have a great inlfuence on yield rate of CNTs and their form. In this paper, the orthogonal experiment analysis method is used for studying the inlfuence factors of yield rate of CNTs. Research results show that, in the suitable temperature range of preparing CNTs, there is relatively more CNTs with excellent morphology, otherwise, if the temperature is too low, the growth of CNTs will not be sufifcient; if the temperature is too high, then CNTs will be generated with excessive defects; with longer growth time of suitable pyrolysis of CNTs, higher yield of CNTs will be obtained; CNTs morphology with reaction time is not proportional; too low or too high raw gas lfow rate is not conducive to the growth of CNTs. We have found the optimum conditions for the CNTs preparation: pyrolysis temperature 680℃, pyrolysis time 35 min, propylene lfow rate of 180 mL/min. The results have a reference value for the preparation of CNTS and their composites.

  10. Fabrication of anisotropic multifunctional colloidal carriers

    Science.gov (United States)

    Jerri, Huda A.

    , lithographed patches have been designed to serve as nanoparticle launching pads to illustrate the behavior of released fluorescent tracer nanoparticles. Finally, experience with electrostatics and nanoparticle coatings was translated to real-world applications by quickly developing and testing naturally-functionalized antimicrobial sand for water clarification. This dissertation comprises many research areas including: colloidal assembly; site-specific functionalizations; polymer and metal particle syntheses and growth; mammalian cell and microbial culture; multilayered functionalizations with nanoparticles, fluorophores, polyelectrolytes, ionic initiators, biomolecules, proteins and bacteria.

  11. Hospital Preparations for Viral Hemorrhagic Fever Patients and Experience Gained from Admission of an Ebola Patient.

    Science.gov (United States)

    Haverkort, J J Mark; Minderhoud, A L C Ben; Wind, Jelte D D; Leenen, Luke P H; Hoepelman, Andy I M; Ellerbroek, Pauline M

    2016-02-01

    The Major Incident Hospital of the University Medical Centre of Utrecht has a longstanding history of preparing for the management of highly pathogenic and infectious organisms. An assessment of the hospital's preparations for an outbreak of viral hemorrhagic fever and its experience during admission of a patient with Ebola virus disease showed that the use of the buddy system, frequent training, and information sessions for staff and their relatives greatly increased the sense of safety and motivation among staff. Differing procedures among ambulance services limited the number of services used for transporting patients. Waste management was the greatest concern, and destruction of waste had to be outsourced. The admission of an Ebola patient proceeded without incident but led to considerable demands on staff. The maximum time allowed for wearing personal protective equipment was 45 minutes to ensure safety, and an additional 20 minutes was needed for recovery.

  12. Preparation and characterisation of magnetic nanostructured samples for inelastic neutron scattering experiments

    Energy Technology Data Exchange (ETDEWEB)

    Kreuzpaintner, Wolfgang

    2010-06-22

    Recent advances in thin-film structuring techniques have generated significant interest in the dynamics of spin waves in magnetic nanostructures and the possible use of inelastic neutron scattering (INS) for their investigation. This thesis describes the design and implementation, at GKSS Research Centre, of equipment for preparation of large and laterally submicron and nanometre structured magnetic samples for such future INS experiments. After a brief resume on spin waves in nanostructures, the development work on new purpose-designed equipment, including high vacuum (HV) argon ion beam milling and ultra high vacuum (UHV) e-beam evaporation setups, is described. Ni nanodot as well as Ni and novel Gd nanowire samples were prepared using combinations of sputter deposition, laser interference lithography, argon ion beam milling, e-beam evaporation and self organisation techniques. With reference to sample preparation, epitaxial growth studies for Ni on Si(100) substrate were performed, resulting in the development of a new deposition process, which by thermal tuning allows for the direct epitaxial growth of Ni on Si with unprecedented crystalline quality. The results of various characterisation experiments on the prepared nanostructured samples, including Scanning Electron Microscopy (SEM), microprobe analysis, Atomic and Magnetic Force Microscopy (AFM/MFM), Vibrating Sample Magnetometry (VSM), X-ray Diffraction (XRD) and Reflectivity (XRR), unpolarised and Polarised Neutron Scattering (PNR) and off-specular scattering by X-rays and neutrons using rocking scans and Time-Of-Flight Grazing Incidence Small Angle Neutron Scattering (TOF-GISANS), together with various analysis procedures such as Distorted-Wave Born Approximation (DWBA), are reported. The analysis of a Gd nanowire sample by TOF-GISANS led to a novel evaluation technique which in comparison with single wavelength methods allows portions of reciprocal space to be scanned without changing the angle of

  13. Colloids and Nucleation

    Science.gov (United States)

    Ackerson, Bruce

    1997-01-01

    The objectives of the work funded under this grant were to develop a microphotographic technique and use it to monitor the nucleation and growth of crystals of hard colloidal spheres. Special attention is given to the possible need for microgravity studies in future experiments. A number of persons have been involved in this work. A masters student, Keith Davis, began the project and developed a sheet illumination apparatus and an image processing system for detection and analysis. His work on a segmentation program for image processing was sufficient for his master's research and has been published. A post doctoral student Bernie Olivier and a graduate student Yueming He, who originally suggested the sheet illumination, were funded by another source but along with Keith made photographic series of several samples (that had been made by Keith Davis). Data extraction has been done by Keith, Bernie, Yueming and two undergraduates employed on the grant. Results are published in Langmuir. These results describe the sheet lighting technique as one which illuminates not only the Bragg scattering crystal, but all the crystals. Thus, accurate crystal counts can be made for nucleation rate measurements. The strange crystal length scale reduction, observed in small angle light scattering (SALS) studies, following the initial nucleation and growth period, has been observed directly. The Bragg scattering (and dark) crystal size decreases in the crossover region. This could be an effect due to gravitational forces or due to over- compression of the crystal during growth. Direct observations indicate a complex morphology for the resulting hard sphere crystals. The crystal edges are fairly sharp but the crystals have a large degree of internal structure. This structure is a result of (unstable) growth and not aggregation. As yet unpublished work compares growth exponents data with data obtained by SALS. The nucleation rate density is determined over a broad volume fraction range

  14. 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

  15. 辅助微波法制备纳米银胶及对几种常见食品的抗菌性能%Preparation and anti-bacterial effect on nano-silver colloids by microwave-assisted synthesis method

    Institute of Scientific and Technical Information of China (English)

    曹雪玲; 谢莹; 刘发现

    2012-01-01

    利用简单而快捷的试验方法制备纳米银胶,并对几种常见的食品进行抗茵研究;采用微波加热法,硝酸银和柠檬酸三钠作为反应物制备纳米银胶,并选择反应时间为8、15、20min的纳米银胶作为抗茵试剂,豆浆、馒头、西瓜作为抗菌对象,研究所制备纳米银胶的抗茵性能。根据肉眼和电子显微镜的观察结果发现,制备的纳米银胶对于这3种物质变坏后所产生的微生物都具有一定的抗茵作用。几种常见食品的抗茵结果,为纳米银胶应用于食物保鲜、抗菌提供了一定理论基础。%Simple and quick method to the preparation of nano-silver colloids, and several common food antibacterial research. Silver nitrate and sodium citrate as reactants with Microwave-assisted synthesis method used to prepare the nano-silver colloids respectively to choose the response of 8, 15, 20 minutes the nano-silver as anti-bacterial reagents, choose soyabean milk, bread and watermelon as anti-bacterial targets studied in this paper, to study the anti-bacterial properties of nano-silver colloids. According to visual observations and electron microscopy found that these three nano-silver colloid have a certain degree of antibacterial activity of deterioration for these substances produced by micro-organisms. The antibacterial results of several common foods, nano-silver colloids used in food preservation and antibacterial provides some theoretical basis.

  16. Preparing for practice: Nursing intern and faculty perceptions on clinical experiences.

    Science.gov (United States)

    AlThiga, Hanan; Mohidin, Sharifah; Park, Yoon Soo; Tekian, Ara

    2017-04-01

    Clinical experience and exposure to real patients are required elements of nursing education. Trainees in nursing are expected to be prepared adequately for the hard-working environment, increasing patient complexity, and higher-level competencies. This study investigates differences between nursing interns and clinical faculty on actual and perceived importance of educational preparation and development of clinical competencies, focusing on the nursing curriculum and transition to practice. A convenient sampling technique with a mixed-methods design was used to collect quantitative and qualitative data, by surveying and interviewing nursing interns and faculty members from King Abdul-Aziz University in Saudi Arabia; data collection occurred in December 2015. The survey (23 items) and focused interviews measured perceptions of clinical instruction and experience. Descriptive statistics and t-tests were used to analyze differences in mean ratings between actual and perceived importance. Themes collected from narrative interview data were summarized. Significant differences were found between nursing interns (n = 46) and faculty (n = 29) perceptions of actual clinical teaching and experiences and its importance including the clinical teaching and the development of clinical competence, p interns rated actual experiences of knowledge base and skills significantly lower than faculty perceptions, p = .001. Narrative data provided in-depth information on factors contributing and hindering the learning and teaching environment. Findings from this study call for clinical instruction and experiences to take a step further to meet current practice standards and to improve patient safety in the health professions education of nurses.

  17. ANTIOXIDANT AND ANTIMICROBIAL PROPERTIES OF STEVIA LEAVES EXTRACTS AND SILVER NANOPARTICLES COLLOIDS

    Directory of Open Access Journals (Sweden)

    Iryna Laguta

    2016-12-01

    Full Text Available Three extracts of Stevia rebaudiana (Bertoni were prepared using various types of raw materials: leaves of plants grown ex situ, leaves of plants grown in vitro, callus culture formed on damaged leaves. Composition of the extracts, their activity in the synthesis of silver nanoparticles colloids, as well as antioxidant and antimicrobial properties of the extracts and the colloids were investigated.

  18. Colloidal quantum dots as optoelectronic elements

    Science.gov (United States)

    Vasudev, Milana; Yamanaka, Takayuki; Sun, Ke; Li, Yang; Yang, Jianyong; Ramadurai, Dinakar; Stroscio, Michael A.; Dutta, Mitra

    2007-02-01

    Novel optoelectronic systems based on ensembles of semiconductor nanocrystals are addressed in this paper. Colloidal semiconductor quantum dots and related quantum-wire structures have been characterized optically; these optical measurements include those made on self-assembled monolayers of DNA molecules terminated on one end with a common substrate and on the other end with TiO II quantum dots. The electronic properties of these structures are modeled and compared with experiment. The characterization and application of ensembles of colloidal quantum dots with molecular interconnects are considered. The chemically-directed assembly of ensembles of colloidal quantum dots with biomolecular interconnects is demonstrated with quantum dot densities in excess of 10 +17 cm -3. A number of novel photodetectors have been designed based on the combined use of double-barrier quantum-well injectors, colloidal quantum dots, and conductive polymers. Optoelectronic devices including photodetectors and solar cells based on threedimensional ensembles of quantum dots are considered along with underlying phenomena such as miniband formation and the robustness of minibands to displacements of quantum dots in the ensemble.

  19. Micro-rheology on (polymer-grafted) colloids using optical tweezers

    Energy Technology Data Exchange (ETDEWEB)

    Gutsche, C; Elmahdy, M M; Kegler, K; Semenov, I; Stangner, T; Otto, O; Ueberschaer, O; Kremer, F [Institute of Experimental Physics I, Leipzig University, Linnestrasse 5, D-04103, Leipzig (Germany); Keyser, U F [Cavendish Laboratory, University of Cambridge, Cambridge, CB3 OHE (United Kingdom); Krueger, M; Rauscher, M [Max-Planck-Institut fuer Metallforschung, Heisenbergstrasse 3, D-70569 Stuttgart (Germany); Weeber, R; Harting, J [Institut fuer Computerphysik, Universitaet Stuttgart, Pfaffenwaldring 27, D-70569 Stuttgart (Germany); Kim, Y W [School of Physics, Korea Institute for Advanced Study, Seoul 130-722 (Korea, Republic of); Lobaskin, V [Physics Department, Technical University Munich, D-85748 Garching (Germany); Netz, R R, E-mail: kremer@physik.uni-leipzig.de [Materials Research Laboratory, University of California at Santa Barbara, Santa Barbara, CA 93106 (United States)

    2011-05-11

    Optical tweezers are experimental tools with extraordinary resolution in positioning ({+-} 1 nm) a micron-sized colloid and in the measurement of forces ({+-} 50 fN) acting on it-without any mechanical contact. This enables one to carry out a multitude of novel experiments in nano- and microfluidics, of which the following will be presented in this review: (i) forces within single pairs of colloids in media of varying concentration and valency of the surrounding ionic solution, (ii) measurements of the electrophoretic mobility of single colloids in different solvents (concentration, valency of the ionic solution and pH), (iii) similar experiments as in (i) with DNA-grafted colloids, (iv) the nonlinear response of single DNA-grafted colloids in shear flow and (v) the drag force on single colloids pulled through a polymer solution. The experiments will be described in detail and their analysis discussed.

  20. Design and synthesis of model transparent aqueous colloids with optimal scattering properties.

    Science.gov (United States)

    Perro, Adeline; Meng, Guangnan; Fung, Jerome; Manoharan, Vinothan N

    2009-10-06

    We demonstrate the synthesis and self-assembly of colloidal particles with independently controlled diameter and scattering cross section. We show that it is possible to prepare bulk colloidal suspensions that are nearly transparent in water, while the particles themselves can be individually resolved using optical microscopy. These particles may be ideal model colloids for real-space studies of self-assembly in aqueous media. Moreover, they illustrate the degree to which the optical properties of colloids can be engineered through straightforward chemistry.

  1. Fractal nematic colloids

    Science.gov (United States)

    Hashemi, S. M.; Jagodič, U.; Mozaffari, M. R.; Ejtehadi, M. R.; Muševič, I.; Ravnik, M.

    2017-01-01

    Fractals are remarkable examples of self-similarity where a structure or dynamic pattern is repeated over multiple spatial or time scales. However, little is known about how fractal stimuli such as fractal surfaces interact with their local environment if it exhibits order. Here we show geometry-induced formation of fractal defect states in Koch nematic colloids, exhibiting fractal self-similarity better than 90% over three orders of magnitude in the length scales, from micrometers to nanometres. We produce polymer Koch-shaped hollow colloidal prisms of three successive fractal iterations by direct laser writing, and characterize their coupling with the nematic by polarization microscopy and numerical modelling. Explicit generation of topological defect pairs is found, with the number of defects following exponential-law dependence and reaching few 100 already at fractal iteration four. This work demonstrates a route for generation of fractal topological defect states in responsive soft matter. PMID:28117325

  2. Fractal nematic colloids

    Science.gov (United States)

    Hashemi, S. M.; Jagodič, U.; Mozaffari, M. R.; Ejtehadi, M. R.; Muševič, I.; Ravnik, M.

    2017-01-01

    Fractals are remarkable examples of self-similarity where a structure or dynamic pattern is repeated over multiple spatial or time scales. However, little is known about how fractal stimuli such as fractal surfaces interact with their local environment if it exhibits order. Here we show geometry-induced formation of fractal defect states in Koch nematic colloids, exhibiting fractal self-similarity better than 90% over three orders of magnitude in the length scales, from micrometers to nanometres. We produce polymer Koch-shaped hollow colloidal prisms of three successive fractal iterations by direct laser writing, and characterize their coupling with the nematic by polarization microscopy and numerical modelling. Explicit generation of topological defect pairs is found, with the number of defects following exponential-law dependence and reaching few 100 already at fractal iteration four. This work demonstrates a route for generation of fractal topological defect states in responsive soft matter.

  3. Experimental evidence for ternary colloid-facilitated transport of Th(IV) with hematite (α-Fe2O3) colloids and Suwannee River fulvic acid.

    Science.gov (United States)

    Emerson, Hilary P; Hickok, Katherine A; Powell, Brian A

    2016-12-01

    Previous field experiments have suggested colloid-facilitated transport via inorganic and organic colloids as the primary mechanism of enhanced actinide transport in the subsurface at former nuclear weapons facilities. In this work, research was guided by the hypothesis that humic substances can enhance tetravalent actinide (An(IV)) migration by coating and mobilizing natural colloids in environmental systems and increasing An(IV) sorption to colloids. This mechanism is expected to occur under relatively acidic conditions where organic matter can sorb and coat colloid surfaces and facilitate formation of ternary colloid-ligand-actinide complexes. The objective of this work was to examine Th transport through packed columns in the presence of hematite colloids and/or Suwannee River fulvic acid (SRFA). In the presence of SRFA, with or without hematite colloids, significant transport (>60% recovery within the effluent) of thorium occurred through quartz columns. It is notable that the SRFA contributed to increased transport of both Th and hematite colloids, while insignificant transport occurred in the absence of fulvic acid. Further, in the presence of a natural sandy sediment (as opposed to pure quartz), transport is negligible in the presence of SRFA due to interactions with natural, clay-sized sediment coatings. Moreover, this data shows that the transport of Th through quartz columns is enhanced in ternary Th-colloid-SRFA and binary Th-SRFA systems as compared to a system containing only Th. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Single Molecule Raman Detection of Enkephalin on Silver Colloidal Particles

    DEFF Research Database (Denmark)

    Kneipp, Katrin; Kneipp, Holger; Abdali, Salim;

    2004-01-01

    the Raman signal the enkephalin molecules have been attached to silver colloidal cluster structures. The experiments demonstrate that the SERS signal of the strongly enhanced ring breathing vibration of phenylalanine at 1000 cm-1 can be used as “intrinsic marker” for detecting a single enkephalin molecule...... and for monitoring its diffusion on the surface of the silver colloidal cluster without using a specific label molecule....

  5. Colloidal Covalent Organic Frameworks

    Science.gov (United States)

    2017-01-01

    Covalent organic frameworks (COFs) are two- or three-dimensional (2D or 3D) polymer networks with designed topology and chemical functionality, permanent porosity, and high surface areas. These features are potentially useful for a broad range of applications, including catalysis, optoelectronics, and energy storage devices. But current COF syntheses offer poor control over the material’s morphology and final form, generally providing insoluble and unprocessable microcrystalline powder aggregates. COF polymerizations are often performed under conditions in which the monomers are only partially soluble in the reaction solvent, and this heterogeneity has hindered understanding of their polymerization or crystallization processes. Here we report homogeneous polymerization conditions for boronate ester-linked, 2D COFs that inhibit crystallite precipitation, resulting in stable colloidal suspensions of 2D COF nanoparticles. The hexagonal, layered structures of the colloids are confirmed by small-angle and wide-angle X-ray scattering, and kinetic characterization provides insight into the growth process. The colloid size is modulated by solvent conditions, and the technique is demonstrated for four 2D boronate ester-linked COFs. The diameter of individual COF nanoparticles in solution is monitored and quantified during COF growth and stabilization at elevated temperature using in situ variable-temperature liquid cell transmission electron microscopy imaging, a new characterization technique that complements conventional bulk scattering techniques. Solution casting of the colloids yields a free-standing transparent COF film with retained crystallinity and porosity, as well as preferential crystallite orientation. Collectively this structural control provides new opportunities for understanding COF formation and designing morphologies for device applications. PMID:28149954

  6. Colloidal Covalent Organic Frameworks.

    Science.gov (United States)

    Smith, Brian J; Parent, Lucas R; Overholts, Anna C; Beaucage, Peter A; Bisbey, Ryan P; Chavez, Anton D; Hwang, Nicky; Park, Chiwoo; Evans, Austin M; Gianneschi, Nathan C; Dichtel, William R

    2017-01-25

    Covalent organic frameworks (COFs) are two- or three-dimensional (2D or 3D) polymer networks with designed topology and chemical functionality, permanent porosity, and high surface areas. These features are potentially useful for a broad range of applications, including catalysis, optoelectronics, and energy storage devices. But current COF syntheses offer poor control over the material's morphology and final form, generally providing insoluble and unprocessable microcrystalline powder aggregates. COF polymerizations are often performed under conditions in which the monomers are only partially soluble in the reaction solvent, and this heterogeneity has hindered understanding of their polymerization or crystallization processes. Here we report homogeneous polymerization conditions for boronate ester-linked, 2D COFs that inhibit crystallite precipitation, resulting in stable colloidal suspensions of 2D COF nanoparticles. The hexagonal, layered structures of the colloids are confirmed by small-angle and wide-angle X-ray scattering, and kinetic characterization provides insight into the growth process. The colloid size is modulated by solvent conditions, and the technique is demonstrated for four 2D boronate ester-linked COFs. The diameter of individual COF nanoparticles in solution is monitored and quantified during COF growth and stabilization at elevated temperature using in situ variable-temperature liquid cell transmission electron microscopy imaging, a new characterization technique that complements conventional bulk scattering techniques. Solution casting of the colloids yields a free-standing transparent COF film with retained crystallinity and porosity, as well as preferential crystallite orientation. Collectively this structural control provides new opportunities for understanding COF formation and designing morphologies for device applications.

  7. Colloid Facilitated Transport of Plutonium in Fractured Volcanic Tuff

    Science.gov (United States)

    Kersting, A. B.; Zhao, P.; Walensky, J. R.; Roberts, S. K.; Johnson, M. R.; Zavarin, M.; Ramon, E. C.

    2004-12-01

    The transport of low-solubility radionuclides in a colloidal- or colloidal bound state is frequently suspected or observed. Groundwater contaminated with radionuclides associated with underground nuclear tests was collected from several different well locations at the Nevada Test Site (NTS). In each case, the low-levels of plutonium detected in the groundwater were overwhelmingly (>95percent) associated with the colloidal and not the dissolved fraction of the groundwater. The colloidal fractions consisted of secondary minerals such as clays and zeolites. To better understand the mechanisms controlling the potential colloidal transport of plutonium, colloid-facilitated fracture flow laboratory experiments are being conducted. Pseudocolloids consisting of Pu(IV) sorbed to clinoptilolite were combined with a radionuclide solution cocktail consisting of Np, U, Cs, Sr, Sm and 3H and Re (analog to Tc) tracers in NTS-type synthetic groundwater (4.5mM NaHCO3-). The cocktail was injected into a smooth fracture in a volcanic tuff rock core from the NTS and the effluent analyzed. Autoradiography and secondary ion mass spectrometry will be used to understand the mineral -colloid-radionuclide interactions in the fracture volcanic tuff.

  8. Ground-based activities in preparation of SELENE ISS experiment on self-rewetting fluids

    Science.gov (United States)

    Savino, R.; Abe, Y.; Castagnolo, D.; Celata, G. P.; Kabov, O.; Kawaji, M.; Sato, M.; Tanaka, K.; Thome, J. R.; Van Vaerenbergh, S.

    2011-12-01

    SELENE (SELf rewetting fluids for thermal ENErgy management) is a microgravity experiment proposed to the European Space Agency (ESA) in response to the Announcement of Opportunities for Physical Sciences. Main objectives of the microgravity research onboard ISS include the quantitative investigation of heat transfer performances of "self-rewetting fluids" and "nano self-rewetting fluids" in model heat pipes and validation of adequate theoretical and numerical modelling able to predict their behaviour in microgravity conditions. This article summarizes the results of ground-based research activities in preparation of the microgravity experiments. They include: 1) thermophysical properties measurements; 2) study of thermo-soluto-capillary effects in micro-channels; 3) numerical modelling; 4) thermal and concentration distribution measurements with optical (e.g. interferometric) and intrusive techniques; 5) surface tension-driven effects and thermal performances test on different capillary structures and heat pipes; 6) breadboards development and support to definition of scientific requirements.

  9. Increasing entropy for colloidal stabilization

    Science.gov (United States)

    Mo, Songping; Shao, Xuefeng; Chen, Ying; Cheng, Zhengdong

    2016-11-01

    Stability is of paramount importance in colloidal applications. Attraction between colloidal particles is believed to lead to particle aggregation and phase separation; hence, stability improvement can be achieved through either increasing repulsion or reducing attraction by modifying the fluid medium or by using additives. Two traditional mechanisms for colloidal stability are electrostatic stabilization and steric stabilization. However, stability improvement by mixing attractive and unstable particles has rarely been considered. Here, we emphasize the function of mixing entropy in colloidal stabilization. Dispersion stability improvement is demonstrated by mixing suspensions of attractive nanosized titania spheres and platelets. A three-dimensional phase diagram is proposed to illustrate the collaborative effects of particle mixing and particle attraction on colloidal stability. This discovery provides a novel method for enhancing colloidal stability and opens a novel opportunity for engineering applications.

  10. Kinetic control of the coverage of oil droplets by DNA-functionalized colloids.

    Science.gov (United States)

    Joshi, Darshana; Bargteil, Dylan; Caciagli, Alessio; Burelbach, Jerome; Xing, Zhongyang; Nunes, André S; Pinto, Diogo E P; Araújo, Nuno A M; Brujic, Jasna; Eiser, Erika

    2016-08-01

    We report a study of reversible adsorption of DNA-coated colloids on complementary functionalized oil droplets. We show that it is possible to control the surface coverage of oil droplets using colloidal particles by exploiting the fact that, during slow adsorption, compositional arrest takes place well before structural arrest occurs. As a consequence, we can prepare colloid-coated oil droplets with a "frozen" degree of loading but with fully ergodic colloidal dynamics on the droplets. We illustrate the equilibrium nature of the adsorbed colloidal phase by exploring the quasi-two-dimensional phase behavior of the adsorbed colloids under the influence of depletion interactions and present simulations of a simple model that illustrates the nature of the compositional arrest and the structural ergodicity.

  11. Colloid-Facilitated Plutonium Transport in Fractured Tuffaceous Rock.

    Science.gov (United States)

    Wolfsberg, Andrew; Dai, Zhenxue; Zhu, Lin; Reimus, Paul; Xiao, Ting; Ware, Doug

    2017-05-16

    Colloids have the potential to enhance the mobility of strongly sorbing radionuclide contaminants in groundwater at underground nuclear test sites. This study presents an experimental and numerical investigation of colloid-facilitated plutonium transport in fractured porous media to identify plutonium reactive transport processes. The transport parameters for dispersion, diffusion, sorption, and filtration are estimated with inverse modeling by minimizing the least-squares objective function of multicomponent concentration data from multiple transport experiments with the shuffled complex evolution metropolis algorithm. Capitalizing on an unplanned experimental artifact that led to colloid formation, we adopt a stepwise strategy to first interpret the data from each experiment separately and then to incorporate multiple experiments simultaneously to identify a suite of plutonium-colloid transport processes. Nonequilibrium or kinetic attachment and detachment of plutonium-colloid in fractures were clearly demonstrated and captured in the inverted modeling parameters along with estimates of the source plutonium fraction that formed plutonium-colloids. The results from this study provide valuable insights for understanding the transport mechanisms and environmental impacts of plutonium in groundwater aquifers.

  12. Surface functionalized LSMO nanoparticles with improved colloidal stability for hyperthermia applications

    Science.gov (United States)

    Thorat, N. D.; Khot, V. M.; Salunkhe, A. B.; Prasad, A. I.; Ningthoujam, R. S.; Pawar, S. H.

    2013-03-01

    LSMO (La0.7Sr0.3MnO3) magnetic nanoparticles (MNPs) coated with double layer oleic acid (OA) surfactant are prepared to make a water based magnetic nanofluid for hyperthermia application. Various experimental techniques are used for bilayer coating analysis. The effect of the bilayer coating on magnetic properties is studied by superconducting quantum interface device (SQUID). Colloidal behaviour of coated MNPs in aqueous medium is studied by the zeta potential and dynamic light scattering. The effects of pH and ionic strength on the colloidal stability of the MNPs are studied in detail. For the bilayer-coated LSMO MNPs aggregation is not observed even in high ionic strength and at physiological pH (7.4). For making the nanofluid of the bilayer-coated MNPs the colloidal stability is studied in physiological media like phosphate buffer solution. Under induction heating experiment, hyperthermia temperature (42-43 °C) could be achieved by the bilayer-coated sample at a magnetic field of 168-335 Oe and frequency of 267 kHz. The bilayer OA coating can hinder the agglomeration of MNPs significantly and produce stable suspension with improved hyperthermia properties. The bilayer OA coating also improves the specific absorption rate (SAR) of LSMO MNPs from 25 to 40 W g-1.

  13. Observed Dependence of Colloid Detachment on the Concentration of Initially Attached Colloids and Collector Surface Heterogeneity in Porous Media.

    Science.gov (United States)

    Li, Tiantian; Jin, Yan; Huang, Yuanfang; Li, Baoguo; Shen, Chongyang

    2017-03-07

    Sand column experiments were conducted to examine the effects of the concentration of attached colloids (CAC) on their subsequent detachment upon decreasing solution ionic strength (IS). Different pore volumes of latex microparticle suspensions were injected into the columns to allow different amounts of colloids to attach at ISs of 0.001, 0.01, and 0.2 M. Then, deionized water was introduced to release the attached colloids. Results show that the fraction of attachments that were reversible to reduction of IS (FRA) increased with increasing CAC at a given IS if the sand was extensively treated using acids to reduce surface charge heterogeneity. This indicates that colloids were preferentially immobilized in sites favoring irreversible attachment and then gradually occupied reversible sites. In contrast, the FRA decreased with increasing CAC at 0.001 M in sand without the acid treatment, illustrating the opposite attachment sequence. Scanning electron microscope examinations reveal that the concave regions favored irreversible colloid attachment. Reversible attachment is likely due to immobilization on flat surfaces with charge heterogeneities, retention in stagnation point regions via secondary minimum association, ripening in the acid-treated sand, and capture of colloids by protruding asperities with charge heterogeneity in the untreated sand. At ISs of 0.01 and 0.2 M, the FRA was essentially independent of CAC in the untreated sand because the colloids were randomly attached on the sand surfaces over time.

  14. Colloids in the mortar backfill of a cementitious repository for radioactive waste.

    Science.gov (United States)

    Wieland, E; Spieler, P

    2001-01-01

    Colloids are present in groundwater aquifers and water-permeable engineered barrier systems and may facilitate the migration of radionuclides. A highly permeable mortar is foreseen to be used as backfill for the engineered barrier of the Swiss repository for low- and intermediate-level waste. The backfill is considered to be a chemical environment with some potential for colloid generation and, due to its high porosity, for colloid mobility. Colloid concentration measurements were carried out using an in-situ liquid particle counting system. The in-house developed counting system with three commercially available sensors allowed the detection of single particles and colloids at low concentrations in the size range 50-5000 nm. The counting system was tested using suspensions prepared from certified size standards. The concentrations of colloids with size range 50-1000 nm were measured in cement pore water, which was collected from a column filled with a highly permeable backfill mortar. The chemical composition of the pore water corresponded to a Ca(OH)2-controlled cement system. Colloid concentrations in the backfill pore water were found to be typically lower than approximately 0.1 ppm. The specific (geometric) surface areas of the colloid populations were in the range 240 m2 g(-1) to 770 m2 g(-1). The low colloid inventories observed in this study can be explained by the high ionic strength and Ca concentrations of the cement pore water. These conditions are favourable for colloid-colloid and colloid-backfill interactions and unfavourable for colloid-enhanced nuclide transport.

  15. Colloids and Radionuclide Transport: A Field, Experimental and Modeling Effort

    Science.gov (United States)

    Zhao, P.; Zavarin, M.; Sylwester, E. E.; Allen, P. G.; Williams, R. W.; Kersting, A. B.

    2002-05-01

    Natural inorganic colloids (clinoptilolite, colloids particle size 171 ñ 25 nm) were conducted in synthetic groundwater (similar to J-13, Yucca Mountain standard) with a pH range from 4 to 10 and initial plutonium concentration of 10-9 M. The results show that Pu(IV) sorption takes place within an hour, while the rates of Pu(V) sorption onto the colloids is much slower and mineral dependent. The kinetic results from the batch sorption/desorption experiments, coupled with redox kinetics of plutonium in solution will be used in geochemical modeling of Pu surface complexation to colloids and reactive transport. (This work was performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.)

  16. Assembly of Colloidal Materials Using Bioadhesive Interactions

    Science.gov (United States)

    Hammer, Daniel A.; Hiddessen, Amy L.; Tohver, Valeria; Crocker, John C.; Weitz, David A.

    2002-01-01

    these different crosslinking molecules, we have assembled colloidal materials from different-sized colloidal particles, A and B. In the first sets of experiment, we used high densities of adhesion molecules, and 0.96 micron (A) and 5.5 micron (B) diameter particles. The high density of adhesion molecules means that the structures are kinetically trapped in nonequilibrium configurations. The structure of the suspension can be varied by changing the number ratio of the two types of colloidal particles, NA and NB, where A is the smaller particle. With carbohydrate-selectin or avidin-biotin interactions, large NA/NB leads to the formation of colloidal micelles, with the large center B particle surrounded by many smaller A particles. As the ratio NA/NB decreases, the structures become more extended, approaching the formation of macro-Rouse polymers - extended linear chains where A beads are connected with intervening small B linkers.

  17. Chancellor Water Colloids: Characterization and Radionuclide Associated Transport

    Energy Technology Data Exchange (ETDEWEB)

    Reimus, Paul William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Boukhalfa, Hakim [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-09-26

    Column transport experiments were conducted in which water from the Chancellor nuclear test cavity was transported through crushed volcanic tuff from Pahute Mesa. In one experiment, the cavity water was spiked with solute 137Cs, and in another it was spiked with 239/240Pu(IV) nanocolloids. A third column experiment was conducted with no radionuclide spike at all, although the 137Cs concentrations in the water were still high enough to quantify in the column effluent. The radionuclides strongly partitioned to natural colloids present in the water, which were characterized for size distribution, mass concentration, zeta potential/surface charge, critical coagulation concentration, and qualitative mineralogy. In the spiked water experiments, the unanalyzed portion of the high-concentration column effluent samples were combined and re-injected into the respective columns as a second pulse. This procedure was repeated again for a third injection. Measurable filtration of the colloids was observed after each initial injection of the Chancellor water into the columns, but the subsequent injections (spiked water experiments only) exhibited no apparent filtration, suggesting that the colloids that remained mobile after relatively short transport distances were more resistant to filtration than the initial population of colloids. It was also observed that while significant desorption of 137Cs from the colloids occurred after the first injection in both the spiked and unspiked waters, subsequent injections of the spiked water exhibited much less 137Cs desorption (much greater 137Cs colloid-associated transport). This result suggests that the 137Cs that remained associated with colloids during the first injection represented a fraction that was more strongly adsorbed to the mobile colloids than the initial 137Cs associated with the colloids. A greater amount of the 239/240

  18. Colloidal forming of metal/ceramic composites

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Herencia, A.J.; Gutierrez, C.A.; Millan, A.J.; Nieto, M.I.; Moreno, R. [Inst. de Ceramica y Vidrio, Madrid (Spain)

    2002-07-01

    Metal/Ceramic composites have very attractive properties as either structural or electronic materials. For certain applications, complex microstructures and shapes are required. Colloidal processing of ceramics has proved to provide better properties and allows to obtain near net complex shaped parts. However colloidal processing has not received a similar attention in powder metallurgy. This work deals with the colloidal approach to the forming of metallic and metal/ceramic composites in an aqueous medium. Rheological behavior of concentrated pure nickel, nickel/alumina and nickel/zirconia suspensions is studied and optimized for obtaining flat surfaces or near net shaped parts by tape casting and gel casting respectively. In each case the influence of the processing additives (acrylic binders for tape casting and carrageenans for gel casting) on the rheological behavior of the slurries is determined. Pure nickel and nickel/ceramic composites with different compositions have been prepared. Static and dynamic sintering studies were performed at different conditions in order to control the porosity and microstructure of the final bodies, which were characterized by optical microscopy. (orig.)

  19. 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.

  20. Doping for speed: colloidal nanoparticles for thin-film optoelectronics.

    Science.gov (United States)

    Noone, Kevin M; Ginger, David S

    2009-02-24

    Solution-processable semiconductor materials ranging from conjugated polymers and small organic molecules to colloidal inorganic nanoparticles are being studied for applications in both low-cost solar cells and photodetectors. High-quality thin films of many inorganic semiconductors can be prepared by techniques such as chemical vapor deposition, molecular beam epitaxy, and atomic layer deposition. In contrast, preparing device-quality films of inorganic materials from colloidal solutions can be more difficult due to the challenge of achieving well-defined doping, controlled trap densities, and reproducible surface chemistry. Nevertheless, solution deposition using colloidal precursors is an attractive goal because of the potential for low-cost, large-area processing. In recent years, a great deal of effort has focused on the colloidal synthesis of wide-band-gap metal oxides such as TiO(2), visible-absorbing II-VI compounds such as CdSe, and small-band-gap materials such as PbSe. Much of the work on visible- and IR-absorbing photodetectors has been done on materials containing metals such as Cd and Pb. A new paper in this issue demonstrates photoconductive detectors made from Cu-containing In(2)S(3) nanoplates. The incorporation of Cu into the In(2)S(3) nanoplates leads to a significant decrease in the lifetime of the photoexcited carriers, resulting in significantly faster response times for the photodetectors processed from colloidal solution.

  1. Causes and implications of colloid and microorganism retention hysteresis

    Science.gov (United States)

    Bradford, Scott A.; Kim, Hyunjung

    2012-09-01

    Experiments were designed to better understand the causes and implications of colloid and microorganism retention hysteresis with transients in solution ionic strength (IS). Saturated packed column experiments were conducted using two sizes of carboxyl modified latex (CML) microspheres (0.1 and 1.1 μm) and microorganisms (coliphage φX174 and E. coli D21g) under various transient solution chemistry conditions, and 360 μm Ottawa sand that was subject to different levels of cleaning, namely, a salt cleaning procedure that removed clay particles, and a salt + acid cleaning procedure that removed clay and reduced microscopic heterogeneities due to metal oxides and surface roughness. Comparison of results from the salt and salt + acid treated sand indicated that microscopic heterogeneity was a major contributor to colloid retention hysteresis. The influence of this heterogeneity increased with IS and decreasing colloid/microbe size on salt treated sand. These trends were not consistent with calculated mean interaction energies (the secondary minima), but could be explained by the size of the electrostatic zone of influence (ZOI) near microscopic heterogeneities. In particular, the depth of local minima in the interaction energy has been predicted to increase with a decrease in the ZOI when the colloid size and/or the Debye length decreased (IS increased). The adhesive interaction was therefore largely irreversible for smaller sized 0.1 μm CML colloids, whereas it was reversible for larger 1.1 μm CML colloids. Similarly, the larger E. coli D21g exhibited greater reversibility in retention than φX174. However, direct comparison of CML colloids and microbes was not possible due to differences in size, shape, and surface properties. Retention and release behavior of CML colloids on salt + acid treated sand was much more consistent with mean interaction energies due to reduction in microscopic heterogeneities.

  2. 亲和胶质气体泡沫的制备及其对胰蛋白酶的吸附分离特性%PREPARATION OF AFFINITY-BASED COLLOIDAL GAS APHRONS FOR SELECTIVE ADSORPTION AND SEPARATION OF TRYPSIN

    Institute of Scientific and Technical Information of China (English)

    何彬; 刘杨; 孙彦

    2004-01-01

    Triton X-114, an non-ionic surfactant, was modified with the affinity ligand of trypsin, paminobenzamidine (PAB) and the affinity surfactant (PAB-TX) was synthesized. Then, the affinity surfactant was used to prepare affinity-based colloidal gas aphrons (CGA). The stability of the affinity CGA was investigated at different temperatures and compared with that of the CGA prepared from Triton X-114. Compared with the CGA from Triton X-114, the affinity CGA showed high selective adsorption property for trypsin. In the separation of a protein mixture, recovery yield higher than 74% were achieved for trypsin and the separation factor reached over 1.5. The results showed that the affinity CGA possessed promising selectivity for separating trypsin from a protein mixture.

  3. [Evaluation of the treatment effectiveness of domestic G-SCF preparations in experiments on irradiated dogs].

    Science.gov (United States)

    Rozhdestvenskiĭ, L M; Shliakova, T G; Shchegoleva, R A; Lisina, N I; Zorin, V V

    2013-01-01

    We have evaluated the treatment effectiveness of Leucostim and Neupomax in dogs exposed to radiation at lethal doses of 3 and 3.5 Gy, correspondingly, by testing the dynamics of the blood cell number, first of all, leucocytes and neutrophiles, and the 45-day survival. Supportive therapy for all the dogs, including the control ones, consisted in antibiotic treatment during the acute period of 7-24 days. It was shown that both pre-parations administered consecutively for about 17-21 days after irradiation positively influenced the dynamics of all blood cells but predominantly impacted the neutrophile number dynamics. The latter ones manifested a higher nadir level and an earlier onset of restoration in the G-SCF treated dogs in comparison with the control ones. The tendency to a positive influence on the survival has been shown in Neupomax-treated dogs exposed to 3.5 Gy of radiation (plus about 40%). The results of the experiments were in good accordance with the data by foreign authors who used Neupogen. This allows a conclusion that home-produced G-SCF preparations can replace their foreign analogues.

  4. Tuning particle geometry of chemically anisotropic dumbbell-shaped colloids

    NARCIS (Netherlands)

    van Ravensteijn, Bas G P; Kegel, Willem K

    2017-01-01

    Chemically anisotropic dumbbell-shaped colloids are prepared starting from cross-linked polymer seed particles coated with a chlorinated outer layer. These chlorinated seeds are swollen with monomer. Subsequently, a liquid protrusion is formed on the surface of the seed particle by phase separation

  5. Preparing culturally and linguistically diverse preservice Early Childhood teachers for field experience

    Directory of Open Access Journals (Sweden)

    Melinda Miller

    2016-07-01

    Full Text Available This article reports on an action research project focussed on preparing culturally and linguistically diverse (CALD preservice early childhood teachers for field experience. A series of targeted workshops delivered over one semester was designed to support the students to develop intercultural competence in relation to knowledge, attitude, skills and behaviours that contribute to success on field placement. Findings indicate that short-term initiatives targeted specifically to students’ identified needs and strengths can help to build intercultural competence for both students and teacher educators. For the participants, access to communication strategies, opportunities for rehearsal of teaching practice, and peer and academic support contributed to shifts in attitude, and the development of skills and new knowledge. New learnings for the teacher educators included challenging assumptions about CALD students’ sense of community and belonging in the university context.

  6. Governmental entities accounting: domestic standards and foreign experience of preparation and presentation

    Directory of Open Access Journals (Sweden)

    Ambarchian V.S.

    2015-12-01

    Full Text Available The purpose of research refers to comparison of Ukrainian and the USA standards of preparation and presentation of governmental entities financial reports with the aim of implementation of foreign experience regarding financial data disclosure of a governmental entity activity in domestic reporting system of budgetary resources disposers. In order to achieve the aim the author applied the following general methods of cognition: induction, deduction, analogy, comparison, and historical one. Special economic methods include grouping, tabular, graphical, information and logical analysis. The research resulted in detailed analysis of the standards of the USA governmental entities financial reports presentation and comparison of their statements with domestic governmental accounting standards. As a result of performed research, the key differences in the Ukrainian and the USA rules of presentation of governmental entities financial reports are considered. The author determined the dependence of structure and a public level of the financial reports on the character of the state political and economic systems.

  7. [The first experience in using the stabilized hyaluronic acid preparation to correct lagophthalmos].

    Science.gov (United States)

    Grusha, Ia O; Ismailova, D S; Ivanchenko, Iu F; Agafonova, E I

    2010-01-01

    The authors report the results of the first experience in using the stabilized hyaluronic acid preparation in patients with lagopthalmos in the presence of facial nerve palsy and thyroid eye disease and resultant keratopathy of varying degrees. The study included 21 patients, including 15 patients with facial nerve palsy and 6 with endocrine ophthalmopathy. The gel was injected externally to the levator aponeurosis and/or intramuscular, and/or under the pretarsal portion of the orbicularis oculi muscle, and/or subcutaneously. The use of this method led to a significant reduction of lagophthalmos and to a considerable corneal improvement. That of this procedure permitted avoidance of surgical intervention in some patients. The mean follow-up period after injection was 11.2 months (range 6-24 months).

  8. The Mirror Program: Preparing Women for the Postoperative Mastectomy Mirror-Viewing Experience.

    Science.gov (United States)

    Freysteinson, Wyona M; Deutsch, Amy S; Davin, Karen; Lewis, Carol; Sisk, Angela; Sweeney, Lilian; Wuest, Linda; Cesario, Sandra K

    2015-01-01

    Preparing women for the experiences they will endure during the breast cancer trajectory improves psychological outcomes and quality of life. Women have found that it may be difficult to view themselves in a mirror after having a mastectomy. Supporting women who have had a mastectomy in mirror-viewing and body image is a relatively new yet important intervention in oncology nursing. The feasibility of a preoperative mirror program given by oncology nurse navigators to women who were scheduled for a mastectomy was examined in this randomized control study. Pre- and postoperative data on anxiety, body image, depression, emotional well-being, and mirror use were collected from intervention participants (n = 10) and control subjects (n = 9). This article illustrates the development of the mirror program and the results of the feasibility trial, and provides a discussion with implications for future research. © 2014 Wiley Periodicals, Inc.

  9. Experiments and Modeling of the Preparation of Ultrafine Calcium Carbonate in Spouted Beds with Inert Particles

    Institute of Scientific and Technical Information of China (English)

    林诚; 朱涛; 朱跃姿; 张济宇

    2003-01-01

    A novel reaction-drying process was carried out in a spouted bed reactor with inert particles and used to prepare ultrafine CaCO3 particles. Effects of concentrations of CO2 and Ca(OH)2, and reaction temperature on Ca(OH)2 conversion were experimentally investigated. The particle sizes and composition of CaCO3 produced were characterized with transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results indicated that ultrafine CaCO3 particles with mean size of 80 nm could be obtained with this novel process.By modifying the Arrhenius Equation and considering the Ca(OH)2 state, a kinetic model was established to describe the process in the spouted bed. The model parameters estimated from the reaction-drying experiments were found to fit well the experimental data, indicating the applicability of the proposed kinetic model.

  10. Before Student Teaching: How Undergraduate Students in Early Childhood Teacher Preparation Programs Describe Their Early Classroom-Based Experience

    Science.gov (United States)

    Maynard, Christine; La Paro, Karen M.; Johnson, Amy V.

    2014-01-01

    Classroom-based experiences, alternatively known as practica, are an integral component of undergraduate teacher preparation programs, which provide students essential opportunities to apply knowledge in practice. Though much is known about student teaching, much less is known about students' earlier classroom-based experiences. This…

  11. 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.

  12. Colloid Release From Differently Managed Loess Soil

    DEFF Research Database (Denmark)

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

    2012-01-01

    of the total clay not associated with organic matter. No significant difference in release rate was found for air-dry aggregates. The low-carbon soils initially had a higher content of WSA but were more susceptible to disaggregation than the high-carbon soils. Furthermore, the application of NPK fertilizer had......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 Lauchsta¨dt longterm static fertilizer experiment with different management histories were investigated to relate basic soil properties to the content of WDC, the content of water-stable aggregates (WSA...

  13. Organized Assemblies of Colloids Formed at the Poles of Micrometer-Sized Droplets of Liquid Crystal

    Science.gov (United States)

    Wang, Xiaoguang; Miller, Daniel S.; de Pablo, Juan J.

    2014-01-01

    We report on the formation of organized assemblies of 1 μm-in-diameter colloids (polystyrene (PS)) at the poles of water-dispersed droplets (diameters 7 - 20 μm) of nematic liquid crystal (LC). For 4-cyano-4′-pentylbiphenyl droplets decorated with two to five PS colloids, we found 32 distinct arrangements of the colloids to form at the boojums of bipolar droplet configurations. Significantly, all but one of these configurations (a ring comprised of five PS colloids) could be mapped onto a local (non-close packed) hexagonal lattice. To provide insight into the origin of the hexagonal lattice, we investigated planar aqueous—LC interfaces, and found that organized assemblies of PS colloids did not form at these interfaces. Experiments involving the addition of salts revealed that a repulsive interaction of electrostatic origin prevented formation of assemblies at planar interfaces, and that regions of high splay near the poles of the LC droplets generated cohesive interactions between colloids that could overcome the repulsion. Support for this interpretation was obtained from a model that included (i) a long-range attraction between adsorbed colloids and the boojum due to the increasing rate of strain (splay) of LC near the boojum (splay attraction), (ii) an attractive inter-colloid interaction that reflects the quadrupolar symmetry of the strain in the LC around the colloids, and (iii) electrostatic repulsion between colloids. The model predicts that electrostatic repulsion between colloids can lead to a ∼1,000 kBT energy barrier at planar interfaces of LC films, and that the repulsive interaction can be overcome by splay attraction of the colloids to the boojums of the LC droplets. Overall, the results reported in this paper advance our understanding of the directed assembly of colloids at interfaces of LC droplets. PMID:25284139

  14. Synthesis of nanosized silver colloids by microwave dielectric heating

    Indian Academy of Sciences (India)

    Kirti Patel; Sudhir Kapoor; D P Dave; Tulsi Mukherjee

    2005-01-01

    Silver nanosized crystallites have been synthesized in aqueous and polyols viz., ethylene glycol and glycerol, using a microwave technique. Dispersions of colloidal silver have been prepared by the reduction of silver nitrate both in the presence and absence of stabilizer poly(vinylpyrolidone) (PVP). It was observed that PVP is capable of complexing and stabilizing Ag nanoparticles formed through the reduction of Ag+ ions in water and ethylene glycol. In the case of ethylene glycol, it has been shown that the use of PVP leads to particles with a high degree of stability. The colloids are stable in glycerol for months even in the absence of stabilizer.

  15. Influences of Natural Colloid in Seawater on the Growth of a Microalga

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Colloid concentrates were obtained by employing a cross-flow filtration system to ultrafiltrate seawater(which was pre-filtrated by 0.45 μm acetate cellulose membrane) sucessively with three membranes.The retentions (colloid concentrates) and control sample(in which colloid was removed)were then inoculated with a microalga and cultivated in vitro.After continuously monitoring cell content during cultivation,it was found that colloid had an obvious beneficial effect on the growth of microalga.Although colloids with different sizes influenced microalga's growth in different extent and ways,a brief conclusion could be draw from experiments that colloid might be a potential nutrition source for microalga's growth.

  16. Synthesis of zirconia colloidal dispersions by forced hydrolysis

    Directory of Open Access Journals (Sweden)

    JELENA P. MARKOVIC

    2006-06-01

    Full Text Available Different zirconia colloidal dispersions (sols were prepared from zirconyl oxynitrate and zirconyl oxychloride solutions by forced hydrolysis. Vigorously stirred acidic solutions of these salts were refluxed at 102 oC for 24 h. Characterization of the obtained sols (pH, solid phase content, crystal structure was performed by potentiometric, XRD, TGA/DTA and SEM measurements. The prepared sols contained almost spherical monoclinic hydrated zirconia particles 7–10 nm in diameter.

  17. Nanosized Iron Oxide Colloids Strongly Enhance Microbial Iron Reduction▿ †

    Science.gov (United States)

    Bosch, Julian; Heister, Katja; Hofmann, Thilo; Meckenstock, Rainer U.

    2010-01-01

    Microbial iron reduction is considered to be a significant subsurface process. The rate-limiting bioavailability of the insoluble iron oxyhydroxides, however, is a topic for debate. Surface area and mineral structure are recognized as crucial parameters for microbial reduction rates of bulk, macroaggregate iron minerals. However, a significant fraction of iron oxide minerals in the subsurface is supposed to be present as nanosized colloids. We therefore studied the role of colloidal iron oxides in microbial iron reduction. In batch growth experiments with Geobacter sulfurreducens, colloids of ferrihydrite (hydrodynamic diameter, 336 nm), hematite (123 nm), goethite (157 nm), and akaganeite (64 nm) were added as electron acceptors. The colloidal iron oxides were reduced up to 2 orders of magnitude more rapidly (up to 1,255 pmol h−1 cell−1) than bulk macroaggregates of the same iron phases (6 to 70 pmol h−1 cell−1). The increased reactivity was not only due to the large surface areas of the colloidal aggregates but also was due to a higher reactivity per unit surface. We hypothesize that this can be attributed to the high bioavailability of the nanosized aggregates and their colloidal suspension. Furthermore, a strong enhancement of reduction rates of bulk ferrihydrite was observed when nanosized ferrihydrite aggregates were added. PMID:19915036

  18. Assembly of colloidal strings in a simple fluid flow

    Science.gov (United States)

    Abe, Yu; Francis, Lorraine; Cheng, Xiang

    Colloidal particles self-assemble into ordered structures ranging from face- and body-centered cubic crystals to binary ionic crystals and to kagome lattices. Such diverse micron-scale structures are of practical importance for creating photonic materials and also of fundamental interest for probing equilibrium and non-equilibrium statistical mechanics. As a particularly interesting example, 1D colloidal strings provide a unique system for investigating non-equilibrium dynamics of crystal lattices. Here, we report a simple experimental method for constructing 1D colloidal crystals, where colloidal particles self-assemble into flow-aligned string structures near solid boundary under unidirectional flows. Using fast confocal microscopy, we explore the degree of particle alignment as functions of flow rate, particle concentrations, wetting properties of solid boundary and ionic strength of solvent. Through our systematic experiments, we show that these colloidal strings arise from hydrodynamic coupling, facilitated by electrostatic attractions between particles and the boundary. Compared with previous methods, our work provides a much simpler experimental procedure for assembling a large number of colloidal strings.

  19. Clinical Experiences and Mediational Activities in Urban Teacher Preparation: Learning and Critical Consciousness

    Directory of Open Access Journals (Sweden)

    Craig Willey

    2016-11-01

    Full Text Available In a longitudinal design experiment conducted within an urban teacher preparation program, we employed ethnographic and auto-ethnographic methods to investigate the following questions: 1 In what ways do clinical experiences (CEs support prospective teachers’ (PTs development of knowledge, skills, and dispositions necessary for urban teaching? 2 How is it determined that adjustments need to be made to the design and facilitation of CEs, and what did these adjustments yield in terms of student learning outcomes? The program centers and leverages CEs in order for PTs to connect theory and practice, particularly an awareness of, and skills associated with, equitable teaching practices. In our two-year field-based program, CEs included community explorations, one-on-one and small group work with children, two student teaching practicums, and various school-community events. We describe the process undertaken to maximize the benefits yielded from CEs. After working with three cohorts of PTs for their entire professional training, we found that: 1 focusing attention on the intentional design and assessment of the mediational activities coupled with CEs leads to more nuanced understandings and enactments of culturally relevant teaching among PTs; and 2 CEs afford PTs abundant opportunities to shape complex identities as urban teachers. Specifically, we found that clinical experiences and corresponding mediational activities support PTs’ understanding of families of color, allow them to recognize and address problematic schooling practices, and strengthen PTs’ otherwise fragile critical consciousness. We conclude that strategic interventions can provide clarity for PTs around what has been learned, and what is left to be developed

  20. Clinical Experiences and Mediational Activities in Urban Teacher Preparation: Learning and Critical Consciousness

    Directory of Open Access Journals (Sweden)

    Craig Willey

    2016-11-01

    Full Text Available In a longitudinal design experiment conducted within an urban teacher preparation program, we employed ethnographic and auto-ethnographic methods to investigate the following research questions: 1 In what ways do clinical experiences (CEs support prospective teachers’ (PTs development of knowledge, skills, and dispositions necessary for urban teaching? 2 How is it determined that adjustments need to be made to the design and facilitation of CEs, and what did these adjustments yield in terms of student learning outcomes? The program centers and leverages CEs in order for PTs to connect theory and practice, particularly an awareness of, and skills associated with, equitable teaching practices. In our two-year field-based program, CEs include community explorations, one-on-one and small group work with children, two student teaching practicums, and various school-community events. We describe the iterative design process undertaken to maximize the benefits yielded from CEs. After working with three cohorts of PTs for their entire professional training, we found that: 1 focusing attention on the intentional design and assessment of the mediational activities coupled with CEs leads to more nuanced understandings and enactments of culturally relevant teaching among PTs; and 2 CEs afford PTs abundant opportunities to shape complex identities as urban teachers. Specifically, we found that clinical experiences and corresponding mediational activities support PTs’ understanding of families of color, allow them to recognize and address problematic schooling practices, and strengthen PTs’ otherwise fragile critical consciousness. We conclude that strategic interventions can provide clarity for PTs around what has, indeed, been learned at particular intervals in the program, and what is left to be developed in the final practicum and beyond.

  1. Causes and implications of colloid and microorganism retention hysteresis

    Science.gov (United States)

    Experiments were designed to better understand the causes and implications of colloid and microorganism retention hysteresis with transients in solution ionic strength (IS). Saturated packed column experiments were conducted using two sizes of carboxyl modified latex (CML) microspheres (0.1 and 1.1...

  2. Light-structured colloidal assemblies

    Science.gov (United States)

    Aubret, Antoine; Mena, Youssef; Ramananarivo, Sophie; Sacanna, Stefano; Palacci, Jeremie; Palacci lab Team; Sacanna lab Team

    2016-11-01

    Self-propelled particles (SPP) are a key tool since they are of relative simplicity as compared to biological micro-entities and provide a higher level of control. They can convert an energy source into motion and work, and exhibit surprising non-equilibrium behavior. In our work, we focus on the manipulation of colloids using light. We exploit osmotic and phoretic effects to act on single and ensemble of colloids. The key mechanism relies on the photocatalytic decomposition of hydrogen peroxide using hematite, which triggers the motion of colloids around it when illuminated. We use hematite particles and particles with photocatalytic inclusions (i.e. SPP). We first show that the interactions between hematite and colloidal tracers can be tuned by adjusting the chemical environment. Furthermore, we report a phototaxic behavior (migration in light gradient) of the particles. From this, we explore the effect of spatio-temporal modulation of the light to control the motion of colloids at the single particle level, and to generate self-assembled colloidal structures through time and space. The so-formed structures are maintained by phoretic and hydrodynamic forces resulting from the motion of each particles. Ultimately, a dynamic light modulation may be a route for the creation of active colloidal motion on a collective scale through the synchronization of the individual motions of SPP. This work is supported by NSF CAREER DMR 1554724.

  3. Colloidal microcapsules: Surface engineering of nanoparticles for interfacial assembly

    Science.gov (United States)

    Patra, Debabrata

    2011-12-01

    Colloidal Microcapsules (MCs), i.e. capsules stabilized by nano-/microparticle shells are highly modular inherently multi-scale constructs with applications in many areas of material and biological sciences e.g. drug delivery, encapsulation and microreactors. These MCs are fabricated by stabilizing emulsions via self-assembly of colloidal micro/nanoparticles at liquid-liquid interface. In these systems, colloidal particles serve as modular building blocks, allowing incorporation of the particle properties into the functional capabilities of the MCs. As an example, nanoparticles (NPs) can serve as appropriate antennae to induce response by external triggers (e.g. magnetic fields or laser) for controlled release of encapsulated materials. Additionally, the dynamic nature of the colloidal assembly at liquid-liquid interfaces result defects free organized nanostructures with unique electronic, magnetic and optical properties which can be tuned by their dimension and cooperative interactions. The physical properties of colloidal microcapsules such as permeability, mechanical strength, and biocompatibility can be precisely controlled through the proper choice of colloids and preparation conditions for their. This thesis illustrates the fabrication of stable and robust MCs through via chemical crosslinking of the surface engineered NPs at oil-water interface. The chemical crosslinking assists NPs to form a stable 2-D network structure at the emulsion interface, imparting robustness to the emulsions. In brief, we developed the strategies for altering the nature of chemical interaction between NPs at the emulsion interface and investigated their role during the self-assembly process. Recently, we have fabricated stable colloidal microcapsule (MCs) using covalent, dative as well as non-covalent interactions and demonstrated their potential applications including encapsulation, size selective release, functional devices and biocatalysts.

  4. Colloids in Acute Burn Resuscitation.

    Science.gov (United States)

    Cartotto, Robert; Greenhalgh, David

    2016-10-01

    Colloids have been used in varying capacities throughout the history of formula-based burn resuscitation. There is sound experimental evidence that demonstrates colloids' ability to improve intravascular colloid osmotic pressure, expand intravascular volume, reduce resuscitation requirements, and limit edema in unburned tissue following a major burn. Fresh frozen plasma appears to be a useful and effective immediate burn resuscitation fluid but its benefits must be weighed against its costs, and risks of viral transmission and acute lung injury. Albumin, in contrast, is less expensive and safer and has demonstrated ability to reduce resuscitation requirements and possibly limit edema-related morbidity. Copyright © 2016 Elsevier Inc. All rights reserved.

  5. Microfluidic Control Using Colloidal Devices

    Science.gov (United States)

    Terray, Alex; Oakey, John; Marr, David W. M.

    2002-06-01

    By manipulating colloidal microspheres within customized channels, we have created micrometer-scale fluid pumps and particulate valves. We describe two positive-displacement designs, a gear and a peristaltic pump, both of which are about the size of a human red blood cell. Two colloidal valve designs are also demonstrated, one actuated and one passive, for the direction of cells or small particles. The use of colloids as both valves and pumps will allow device integration at a density far beyond what is currently achievable by other approaches and may provide a link between fluid manipulation at the macro- and nanoscale.

  6. In situ growth of gold colloids within alginate films

    Energy Technology Data Exchange (ETDEWEB)

    Jaouen, Vincent; Lantiat, David; Steunou, Nathalie; Coradin, Thibaud [UPMC Univ Paris 06, CNRS, Laboratoire de Chimie de la Matiere Condensee de Paris (LCMCP), College de France, 11 place Marcellin Berthelot, F-75005 Paris (France); Brayner, Roberta, E-mail: thibaud.coradin@upmc.fr [Interfaces, Traitements, Organisation et Dynamique des Systemes (ITODYS), Universite Paris Diderot, UMR-CNRS 7086, F-75205 Paris (France)

    2010-05-07

    Gold-alginate bionanocomposite films were prepared by impregnation of alginate films with HAuCl{sub 4} followed by reduction with glucose. The mannuronate over guluronate ratio (M/G) of the polymer as well as the initial polymer concentration were shown to influence the film thickness, the amount of trapped Au{sup 3+} ions, and the volume fraction of Au(0) nanoparticles but not the size of these colloids (about 4 nm). The homogeneity of the gold colloid dispersion within the alginate gels was studied by transmission electron microscopy (TEM) and confirmed by simulation of the surface plasmon resonance (SPR) spectra using the Maxwell-Garnett model. The calculated spectra also provided fruitful information about the gold colloid/alginate interface. Overall, the whole process is controlled by the balance between the M/G ratio, defining the polymer affinity for Au(III) species, and the solution viscosity, controlling the diffusion phenomena.

  7. Phase diagrams of binary mixtures of oppositely charged colloids.

    Science.gov (United States)

    Bier, Markus; van Roij, René; Dijkstra, Marjolein

    2010-09-28

    Phase diagrams of binary mixtures of oppositely charged colloids are calculated theoretically. The proposed mean-field-like formalism interpolates between the limits of a hard-sphere system at high temperatures and the colloidal crystals which minimize Madelung-like energy sums at low temperatures. Comparison with computer simulations of an equimolar mixture of oppositely charged, equally sized spheres indicate semiquantitative accuracy of the proposed formalism. We calculate global phase diagrams of binary mixtures of equally sized spheres with opposite charges and equal charge magnitude in terms of temperature, pressure, and composition. The influence of the screening of the Coulomb interaction upon the topology of the phase diagram is discussed. Insight into the topology of the global phase diagram as a function of the system parameters leads to predictions on the preparation conditions for specific binary colloidal crystals.

  8. The use of colloid-SEM method for domain observation in CoCrfilms

    NARCIS (Netherlands)

    Simšová, J.; Gemperle, R.; Lodder, J.C.

    1991-01-01

    The aim of this paper is to describe in detail our experience with the colloid-SEM method, especially as far as the colloids are concerned, to summarize the results which we obtained on CoCr films using this method, and to show some advantages and disadvantages of this method in comparison with the

  9. Phase behaviour of colloids suspended in a near-critical solvent : A mean-field approach

    NARCIS (Netherlands)

    Edison, John R.; Belli, Simone; Evans, Robert; Van Roij, René; Dijkstra, Marjolein

    2015-01-01

    Colloids suspended in a binary solvent may, under suitable thermodynamic conditions, experience a wide variety of solvent-mediated interactions that can lead to colloidal phase transitions and aggregation phenomena. We present a simple mean-field theory, based on free-volume arguments, that describe

  10. Transport of reactive colloids and contaminants in groundwater: effect of nonlinear kinetic interactions.

    NARCIS (Netherlands)

    Weerd, van de H.; Leijnse, A.; Riemsdijk, van W.H.

    1998-01-01

    Transport of reactive colloids in groundwater may enhance the transport of contaminants in groundwater. Often, the interpretation of results of transport experiments is not a simple task as both reactions of colloids with the solid matrix and reactions of contaminants with the solid matrix and

  11. Order-to-Disorder Transition in Ring-Shaped Colloidal Stains

    NARCIS (Netherlands)

    Marin, Alvaro G.; Gelderblom, Hanneke; Lohse, Detlef; Snoeijer, Jacco H.

    2011-01-01

    A colloidal dispersion droplet evaporating from a surface, such as a drying coffee drop, leaves a distinct ring-shaped stain. Although this mechanism is frequently used for particle self-assembly, the conditions for crystallization have remained unclear. Our experiments with monodisperse colloidal p

  12. Preparation of colloid solution of compound radix pulsatillae extract and its in vitro pharmacodynamics effect on resistant trichomonas vaginalis%复方白头翁胶体制剂的研制及体外抗阴道毛滴虫耐药株的实验研究

    Institute of Scientific and Technical Information of China (English)

    刘波; 王璐; 郑华

    2013-01-01

    Objective:To develop the new kind of drug-releasing system containing colloid solution of compound Radix Pulsatillae extract (CRPE) on trichomonas vaginalis and explore the inhibitory molecular mechanism of anti-trichomonas vaginalis.Methods:The colloid solution agent containing total alkaloids of Radix Pulsatillae,bombyxmoril's compound amino acids and minerals including Cu2 (OH)and borax were prepared,the death rate was determined on resistant strain with broth dilution assay.Results:The colloid solution of 1.0 g/ml and 0.1g/ml on resistant Trichomonas vaginalis were higher than negative controlrespectively.Compared with the negative groups,there was statistic meaning between the two groups (P <0.01).Conclusion:The colloid solution had a significant inhibitory effects in vitro on resistant trichomonas vaginalis.%目的:探讨复方白头翁胶体制剂对阴道毛滴虫耐药株的抑制作用,开发出适合女性泌尿生殖道阴道毛滴虫感染的新型药物释放系统.方法:白头翁提取物与蚕蛹复合氨基酸及铜绿等矿物质络合成胶体溶液制剂,以肉汤稀释法测定不同浓度的制剂对阴道毛滴虫耐药株的灭活效应.结果:复方白头翁提取物胶体制剂含量为1.0g/ml、0.1 g/ml时,两组的滴虫死亡率均高于空白对照组(P<0.01),滴虫的死亡率随着药物浓度的增加而增加,同一药物浓度随着作用时间的延长滴虫死亡率也增高.药物作用24 h后,滴虫全部死亡.结论:复方白头翁胶体制剂可明显抑制阴道毛滴虫耐药株,具有高活性抗阴道毛滴虫耐药株生长的药效学作用.

  13. 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.

  14. Are All Colloids Same? How to Select the Right Colloid?

    Directory of Open Access Journals (Sweden)

    Sukanya Mitra

    2009-01-01

    Full Text Available The administration of intravenous fluids is one of the most common and universal interventions in medicine. Colloids are an alternative to the frequently used crystalloids, with highly variable use depending on a myriad of clinical variables. A colloid is defined as a high molecular weight (MW substance that largely remains in the intravas-eular compartment, thereby generating an oncotic pressure. Colloids are considered to have a greater intravaseular persistence when compared to crystalloids. All colloids, however, are clearly not the same. Differences in the physi-cochemical properties, pharmacokinetics and safety profile exist amongst various colloids. This review explores the different types of colloids, with their properties and usefulness as well as adverse effects. While all the available colloids are reviewed briefly (e.g., albumin, gelatin, dextran with respect to their pharmacology, indications, advan-tages and disadvantages, particular emphasis is laid on the hydroxyethyl starches (HES because of their rising prominence. It is shown that HES differ widely in their physicochemical and pharmacokinetic properties, composition, usefulness, and especially in their adverse effect profiles. The third generation HES (tetrastarches, in particular, seem to offer a unique combination of safety and efficacy. Several issues related to this are discussed in detail. This review of the available clinical data demonstrates that HES should not be regarded as one homogenous group, and data for one product should not be automatically extrapolated to another. Thus, among the synthetic colloids, the tetrastarches appear to offer the best currently available compromise between efficacy, safety profile, and cost. They also appear to be the best suited for use in the intensive care setting. Finally, balanced (rather than saline-based HES solutions appear promising as a plasma-adapted volume replacement strategy and may further refine the ongoing quest of

  15. Laser Synthesis and Processing of Colloids: Fundamentals and Applications.

    Science.gov (United States)

    Zhang, Dongshi; Gökce, Bilal; Barcikowski, Stephan

    2017-03-08

    Driven by functionality and purity demand for applications of inorganic nanoparticle colloids in optics, biology, and energy, their surface chemistry has become a topic of intensive research interest. Consequently, ligand-free colloids are ideal reference materials for evaluating the effects of surface adsorbates from the initial state for application-oriented nanointegration purposes. After two decades of development, laser synthesis and processing of colloids (LSPC) has emerged as a convenient and scalable technique for the synthesis of ligand-free nanomaterials in sealed environments. In addition to the high-purity surface of LSPC-generated nanoparticles, other strengths of LSPC include its high throughput, convenience for preparing alloys or series of doped nanomaterials, and its continuous operation mode, suitable for downstream processing. Unscreened surface charge of LSPC-synthesized colloids is the key to achieving colloidal stability and high affinity to biomolecules as well as support materials, thereby enabling the fabrication of bioconjugates and heterogeneous catalysts. Accurate size control of LSPC-synthesized materials ranging from quantum dots to submicrometer spheres and recent upscaling advancement toward the multiple-gram scale are helpful for extending the applicability of LSPC-synthesized nanomaterials to various fields. By discussing key reports on both the fundamentals and the applications related to laser ablation, fragmentation, and melting in liquids, this Article presents a timely and critical review of this emerging topic.

  16. Integration of colloids into a semi-flexible network of fibrin.

    Science.gov (United States)

    Bharadwaj, N Ashwin K; Kang, Jin Gu; Hatzell, Marta C; Schweizer, Kenneth S; Braun, Paul V; Ewoldt, Randy H

    2017-02-15

    Typical colloid-polymer composites have particle diameters much larger than the polymer mesh size, but successful integration of smaller colloids into a large-mesh network could allow for the realization of new colloidal states of spatial organization and faster colloid motion which can allow the possibility of switchable re-configuration of colloids or more dramatic stimuli-responsive property changes. Experimental realization of such composites requires solving non-trivial materials selection and fabrication challenges; key questions include composition regime maps of successful composites, the resulting structure and colloidal contact network, and the mechanical properties, in particular the ability to form a network and retain strain stiffening in the presence of colloids. Here, we study these fundamental questions by formulating composites with fluorescent (though not stimuli-responsive) carboxylate modified polystyrene/latex (CML) colloidal particles (diameters 200 nm and 1000 nm) in bovine fibrin networks (a semi-flexible biopolymer network with mesh size 1-5 μm). We describe and characterize two methods of composite preparation: adding colloids before fibrinogen polymerization (Method I), and electrophoretically driving colloids into a network already formed by fibrinogen polymerization (Method II). We directly image the morphology of colloidal and fibrous components with two-color fluorescent confocal microscopy under wet conditions and SEM of fixed dry samples. Mechanical properties are studied with shear and extensional rheology. Both fabrication methods are successful, though with trade-offs. Method I retains the nonlinear strain-stiffening and extensibility of the native fibrin network, but some colloid clustering is observed and fibrin network integrity is lost above a critical colloid concentration that depends on fibrinogen and thrombin concentration. Larger colloids can be included at higher volume fractions before massive aggregation occurs

  17. Results of Numerical Modeling and Experimental Activities in Preparation of the Maxus-5 Experiment

    Science.gov (United States)

    Bassano, Edmondo; Castagnolo, Dario; Albano, Floriana; Fortezza, Raimondo

    2002-01-01

    The present paper describes numerical and experimental research activities carried out at MARS center for the preparation of an experiment on the Marangoni migration of a dissolving drop, composed by a liquid binary mixture having a miscibility gap. The paper integrates the results already presented in the previous congress, the emphasis is set on the determination of the parameters to be used for the MAXUS 5 sounding rocket mission, which is scheduled for spring 2003. Level set technique has been used for the calculation of the non-steady thermo-solutal capillary flow evolution in a bounded medium.Migration velocities and volume variation are calculated for different Marangoni numbers. The results of the numerical simulations provide the determination of drop radii and temperature gradients to be used during 12 minutes of low gravity, as provided by a MAXUS rocket. Experimental results provide accurate information on the refraction index gradient variation, due to the improvement of the interpretation of the fringe pattern. These results have allowed us to determine the optical parameters that optimize the Wollaston interferometer features. Comparison between numerical and experimental results shows a good agreement.

  18. Colloidal gels: Clay goes patchy

    Science.gov (United States)

    Kegel, Willem K.; Lekkerkerker, Henk N. W.

    2011-01-01

    Empty liquids and equilibrium gels have so far been only theoretical possibilities, predicted for colloids with patchy interactions. But evidence of both has now been found in Laponite, a widely studied clay.

  19. 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...

  20. Bentonite as a colloid source in groundwaters at Olkiluoto

    Energy Technology Data Exchange (ETDEWEB)

    Vuorinen, U. [VTT Processes, Espoo (Finland); Hirvonen, H.

    2005-02-15

    addition to the ultrafiltrations some Nuclepore filter membranes with different cut-off values (0.4 {mu}m, 0.2 {mu}m, 0.1 {mu}m and 0.05 {mu}m) were prepared for SEM/EDS examination. The results of the groundwater samples collected before interaction with bentonite indicated that iron and aluminium were also associated with colloidal species, for example with SiO{sub 2}, clay mineral or/and calcite colloids. The estimated size range of the colloids was from 50nm up to 400nm in PVA1 and in the more saline PVA3 up to 300nm (SEM). The estimate of Fe-associated colloids in PVA1 was 0.8mg/L and Alassociated colloids 0.004mg/L, whereas, in PVA3 the corresponding concentrations were clearly lower, 0.07mg/L and 0.001mg/L, respectively. After bentonite interaction bentonite colloids were detected (EDS) only in PVA1 groundwater. The size of the colloids varied from about 50nm up to about 200nm (SEM). However, the upper size limit was difficult to estimate due to large aggregates. No clear indication of bentonite colloids was obtained in PVA3 samples, but the element composition (EDS) indicated that minor amounts could be present. In PVA1 the estimated amount of Fe-associated colloids was 0.4mg/L and the amount of Al associated colloids was 0.001mg/L, whereas, in PVA3 the contents were 0.06mg/L and 0.001mg/L, respectively. Overall, the estimated concentrations of colloids in the studied size range (<0.45 {mu}m) were small in both groundwaters and interaction with bentonite somewhat decreased the amount of Fe- and Al-associated colloids. However, the decrease in the colloid amount was more prominent in the case of the fresh PVA1 groundwater, which contained a little more to begin with. The salinity of groundwater affected the amount of colloids; more saline - less colloids. Bentonite colloids released from the bentonite source were detected only in the fresh PVA1 groundwater, but the amount was too small for obtaining an assessment of the concentration. (orig.)

  1. Mechanical Failure in Colloidal Gels

    Science.gov (United States)

    Kodger, Thomas Edward

    When colloidal particles in a dispersion are made attractive, they aggregate into fractal clusters which grow to form a space-spanning network, or gel, even at low volume fractions. These gels are crucial to the rheological behavior of many personal care, food products and dispersion-based paints. The mechanical stability of these products relies on the stability of the colloidal gel network which acts as a scaffold to provide these products with desired mechanical properties and to prevent gravitational sedimentation of the dispersed components. Understanding the mechanical stability of such colloidal gels is thus of crucial importance to predict and control the properties of many soft solids. Once a colloidal gel forms, the heterogeneous structure bonded through weak physical interactions, is immediately subject to body forces, such as gravity, surface forces, such as adhesion to a container walls and shear forces; the interplay of these forces acting on the gel determines its stability. Even in the absence of external stresses, colloidal gels undergo internal rearrangements within the network that may cause the network structure to evolve gradually, in processes known as aging or coarsening or fail catastrophically, in a mechanical instability known as syneresis. Studying gel stability in the laboratory requires model colloidal system which may be tuned to eliminate these body or endogenous forces systematically. Using existing chemistry, I developed several systems to study delayed yielding by eliminating gravitational stresses through density matching and cyclic heating to induce attraction; and to study syneresis by eliminating adhesion to the container walls, altering the contact forces between colloids, and again, inducing gelation through heating. These results elucidate the varied yet concomitant mechanisms by which colloidal gels may locally or globally yield, but then reform due to the nature of the physical, or non-covalent, interactions which form

  2. Nonequilibrium Equation of State in Suspensions of Active Colloids

    Science.gov (United States)

    Ginot, Félix; Theurkauff, Isaac; Levis, Demian; Ybert, Christophe; Bocquet, Lydéric; Berthier, Ludovic; Cottin-Bizonne, Cécile

    2015-01-01

    Active colloids constitute a novel class of materials composed of colloidal-scale particles locally converting chemical energy into motility, mimicking micro-organisms. Evolving far from equilibrium, these systems display structural organizations and dynamical properties distinct from thermalized colloidal assemblies. Harvesting the potential of this new class of systems requires the development of a conceptual framework to describe these intrinsically nonequilibrium systems. We use sedimentation experiments to probe the nonequilibrium equation of state of a bidimensional assembly of active Janus microspheres and conduct computer simulations of a model of self-propelled hard disks. Self-propulsion profoundly affects the equation of state, but these changes can be rationalized using equilibrium concepts. We show that active colloids behave, in the dilute limit, as an ideal gas with an activity-dependent effective temperature. At finite density, increasing the activity is similar to increasing adhesion between equilibrium particles. We quantify this effective adhesion and obtain a unique scaling law relating activity and effective adhesion in both experiments and simulations. Our results provide a new and efficient way to understand the emergence of novel phases of matter in active colloidal suspensions.

  3. Nonequilibrium Equation of State in Suspensions of Active Colloids

    Directory of Open Access Journals (Sweden)

    Félix Ginot

    2015-01-01

    Full Text Available Active colloids constitute a novel class of materials composed of colloidal-scale particles locally converting chemical energy into motility, mimicking micro-organisms. Evolving far from equilibrium, these systems display structural organizations and dynamical properties distinct from thermalized colloidal assemblies. Harvesting the potential of this new class of systems requires the development of a conceptual framework to describe these intrinsically nonequilibrium systems. We use sedimentation experiments to probe the nonequilibrium equation of state of a bidimensional assembly of active Janus microspheres and conduct computer simulations of a model of self-propelled hard disks. Self-propulsion profoundly affects the equation of state, but these changes can be rationalized using equilibrium concepts. We show that active colloids behave, in the dilute limit, as an ideal gas with an activity-dependent effective temperature. At finite density, increasing the activity is similar to increasing adhesion between equilibrium particles. We quantify this effective adhesion and obtain a unique scaling law relating activity and effective adhesion in both experiments and simulations. Our results provide a new and efficient way to understand the emergence of novel phases of matter in active colloidal suspensions.

  4. [Our experience with the application of collagen-based preparations in reconstructive surgery of the middle ear].

    Science.gov (United States)

    Kulakova, L A; Eremeeva, K V; Triakina, E G; Lopatin, A S; Ovchinnikov, Iu M

    2012-01-01

    This paper summarizes our experience with the application of collagen-based preparations for reconstructive surgery of the middle ear. The best morphological results (88.46%) were obtained by the closure of extensive defects with the Oblecolum membrane as a temporary supporting structure and the outer atraumatic dressing for the tympanic transplant (in 30 patients) or by the use of the compact-porous explants from the "Sanguicol" preparation as an overlay on the transplant (in 22 patients). Twenty seven patients presenting with the so-called "operated ear disease" underwent mastoidoplasty with the use of the compact-porous preparation "Stimul-oss" as a supporting structure to induce the ingrowth of the bone tissue and the subsequent substitution of the defect. This treatment ensured the reduction of the volume of the bony trepanation cavity. In addition, we have obtained preliminary encouraging results of the application of collagene preparations for the surgical intervention on the stirrup in the patients suffering otosclerosis.

  5. In vitro cell tests of pancreatic malignant tumor cells by photothermotherapy based on DMSO porous silicon colloids.

    Science.gov (United States)

    Hong, Chanseok; Lee, Chongmu

    2014-01-01

    Dimethyl sulfoxide porous silicon (DMSO-PSi) colloid in which DMSO was used as a surfactant suitable for inhibiting the agglomeration of PSi nanoparticles was prepared for use in cancer photothermotherapy. The photothermal effect of the DMSO-PSi colloid was found to be high enough to destroy cancer cells (T = ∼52 °C). The mean particle size of the PSi nanoparticles in the DMSO-PSi colloid was 67 nm, which is low enough to flow through blood vessels without causing a blockage. The DMSO-PSi colloid in combination with an NIR laser resulted in a cell viability of 5.70%, which is a sufficiently high cytotoxic effect.

  6. Exam Preparation: The Influence of Action Control, Procrastination and Examination Experience on Students' Goal Intention and Implementation Intention

    Science.gov (United States)

    Sommer, Lutz

    2013-01-01

    Introduction: In the framework of the intention-behavior-gap analysis in relation to exam preparation I examined whether intention--subdivided into goal and implementation intention--is influenced directly by the determinants action control, procrastination and examination experience which is consistent with the Theory of Planned Behavior and…

  7. Using Undergraduate Facilitators for Active Learning in Organic Chemistry: A Preparation Course and Outcomes of the Experience

    Science.gov (United States)

    Jardine, Hannah E.; Friedman, Lee A.

    2017-01-01

    In this study, we describe a course to educate and prepare undergraduate "facilitators" for small group problem solving sessions in a large, first semester, introductory undergraduate organic chemistry course. We then explore the outcomes of the facilitator experience for one cohort of facilitators through qualitative analysis of written…

  8. Exam Preparation: The Influence of Action Control, Procrastination and Examination Experience on Students' Goal Intention and Implementation Intention

    Science.gov (United States)

    Sommer, Lutz

    2013-01-01

    Introduction: In the framework of the intention-behavior-gap analysis in relation to exam preparation I examined whether intention--subdivided into goal and implementation intention--is influenced directly by the determinants action control, procrastination and examination experience which is consistent with the Theory of Planned Behavior and…

  9. Experience, Intersubjectivity, and Reflection: A Human Science Perspective on Preparation of Future Professionals in Adaptive Physical Activity

    Science.gov (United States)

    Standal, Øyvind F.; Rugseth, Gro

    2016-01-01

    The aim of this article is to show that and how philosophy and philosophical thinking can be of relevance for the preparation of future professionals in adaptive physical activity. To this end we utilize philosophical insights from the human science perspective on two central issues, namely experience and intersubjectivity, which are weaved…

  10. 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.

  11. 3-D Distribution of Retained Colloids in Unsaturated Porous Media

    Science.gov (United States)

    Morales, V. L.; Perez-Reche, F. J.; Holzner, M.; Kinzelbach, W. K.; Otten, W.

    2013-12-01

    It is well accepted that colloid transport processes in porous media differ substantially between water saturated and unsaturated conditions. Differences are frequently ascribed to colloid immobilization by association with interfaces with the gas, as well as to restrictions of the liquid medium through which colloids are transported. Such factors depend on interfacial conditions provided by the water saturation of the porous medium. Yet, the current understanding of the importance of colloid retention at gas interfaces is based on observations of single pores or two-dimensional pore network representations, leaving open the question of their statistical significance when all pores in the medium are considered. In order to address this question, column experiments were performed using a model porous medium of glass beads through which colloidal silver particles were transported for conditions of varying water content. X-ray microtomography was subsequently employed as a non-destructive imaging technique to obtain pore-scale information of the entire column regarding: i) the presence and distribution of the four main locations where colloids can become retained (interfaces with the liquid-solid, gas-liquid and gas-solid, and the bulk liquid), ii) deposition profiles of colloids along the column classified by the available retention location, iii) morphological characteristics of the deposited colloidal aggregates, and iv) channel widths of 3-dimensional pore-water network representations. The results presented provide, for the first time, a direct statistical evaluation on the significance of colloid retention by attachment to the liquid-solid, gas-liquid, gas-solid interfaces, and by straining in the bulk liquid. Additionally, an effective-pore structure characteristic is proposed to improve predictions of mass removal by straining under various water saturations. A) Unsaturated conditions. B) Saturated conditions. Left: Tomograph slice illustrating with false

  12. Temperature control of colloidal phases by Critical Casimir forces -- a simulation study

    Science.gov (United States)

    Triet Dang, Minh; Nguyen, Van Duc; Vila Verde, Ana; Bolhuis, Peter; Schall, Peter

    2012-02-01

    Critical Casimir forces arising from the confinement of critical solvent fluctuations between the surfaces of colloidal particles have recently been shown a promising route to control colloidal assembly. Such forces are strongly temperature dependent, and thus allow for direct temperature control of colloidal interactions. However, colloidal phase transitions controlled by this highly temperature-dependent potential are still poorly understood. Here, we report Monte Carlo simulations of critical Casimir-driven colloidal phase behavior using input potentials directly measured in experiments. We map the gas-liquid coexistence region using Gibbs ensemble simulations and the solid-fluid coexistence boundaries using Gibbs-Duhem integration, and determine the gas-liquid critical point by applying scaling theory. The constructed gas-liquid-solid phase diagram agrees quantitatively with that observed in experiments. Remarkably, the simulated gas-liquid coexistence curve exhibits 3D Ising scaling despite the strong temperature dependence of the pair potentials.

  13. Snapshots of Authentic Scientific Inquiry and Teacher Preparation: Undergraduate STEM Courses, Preservice and Inservice Teachers' Experiences

    Science.gov (United States)

    French, Debbie Ann

    In this dissertation, the researcher describes authentic scientific inquiry (ASI) within three stages of teacher preparation and development: a1) undergraduate STEM courses, b2) preservice secondary science education methods courses, and c3) inservice teacher professional development (PD). Incorporating (ASI)-- pedagogy closely modeling the research practices of scientists--is at the forefront of national science, technology, engineering, and mathematics (STEM) initiatives and the Next Generation Science Standards (NGSS). In the first of three research articles, 42 students participated in an introductory astronomy course which employed inquiry-based pedagogy. The researcher administered the Test Of Astronomy STandards (TOAST) pre/post instruction. In the second article, 56 preservice secondary science teachers completed ideal lesson plan scenarios before and after 80 hours of methods instruction. The researcher scored the scenarios using a rubrirubric developedc according to the NGSS Science and Engineering Practices, and analyzed the components from the scenarios. The third article surveyed 63 inservice STEM teachers with prior research and industry experience. The researcher highlights teacher ASI perspectives. Overall, teachers incorporated opportunities for K-20 students to use scientific instrumentation and technology to collect and analyze data, work collaboratively, and develop evidence-based conclusions. Few teachers provided opportunities for students to ask scientific questions or disseminate results, suggesting the need that teachers (at all levels) need scaffolded instruction in these areas. The researcher argues that while ASI and STEM PDs are effective for teachers, developing similar interest, on-going communities of practice may provide support for teacher to implement the ASI practices in their classrooms.

  14. Learning Leadership Matters: The Influence of Innovative School Leadership Preparation on Teachers' Experiences and Outcomes

    Science.gov (United States)

    Orphanos, Stelios; Orr, Margaret Terry

    2014-01-01

    School leadership has been shown to exert a positive but mostly indirect influence on school and student outcomes. Currently, there is great interest in how quality leadership preparation is related to leadership practice and improved teacher outcomes. The purpose of the study was to understand the moderating influence of leadership preparation on…

  15. Learning Leadership Matters: The Influence of Innovative School Leadership Preparation on Teachers' Experiences and Outcomes

    Science.gov (United States)

    Orphanos, Stelios; Orr, Margaret Terry

    2014-01-01

    School leadership has been shown to exert a positive but mostly indirect influence on school and student outcomes. Currently, there is great interest in how quality leadership preparation is related to leadership practice and improved teacher outcomes. The purpose of the study was to understand the moderating influence of leadership preparation on…

  16. Preparation of 3D Colloidal Crystal Film and Gold-Infiltrated Silica Artificial Opals%3D胶状晶体膜及其渗透金的氧化硅人工蛋白石的制备

    Institute of Scientific and Technical Information of China (English)

    李文江; 谢飞

    2007-01-01

    A free-standing 3D colloidal crystal film (opal) was fabricated at a water-air interface using purified monodispersed SiO2 colloids. The gold/silica opal was obtained through the infiltration of gold nanoparticles by electroplating. The transmission and reflection spectra of the gold/silica composite opal show a red shift with increasing electroplating time.SEM images show that gold nanoparticles can be directly deposited on the surface of silica spheres in the opaline structure. Gold/silica composite opal film could provide a simple way to tune opal properties through controlling the amount of gold in the silica opal.%用纯的单分散氧化硅胶体微球作为基质,在水-空气界面构筑无载体三维有序胶质晶体膜.该高度有序三维周期性结构具有明显的光学衍射现象.利用电沉积的方法将纳米金渗透到这种人工蛋白石的空隙中,构成gold/silica复合蛋白石材料.详细研究了该复合蛋白石的透射光谱和反射光谱,用扫描电镜观察了复合蛋白石结构的形貌特征,并对渗透金后蛋白石的光谱移动进行了分析.

  17. Strain-responsive structural colored elastomers by fixing colloidal crystal assembly.

    Science.gov (United States)

    Ito, Tatsunori; Katsura, Chihiro; Sugimoto, Hideki; Nakanishi, Eiji; Inomata, Katsuhiro

    2013-11-12

    Colloidal crystal assembly film was prepared by using monodispersed colloidal particles of cross-linked random copolymer of methyl methacrylate and ethyl acrylate prepared by soap-free emulsion polymerization. The colloidal crystal film exhibited structural color when swollen with ethyl acrylate monomer. The structural color was maintained even after polymerization of the swelling monomer and cross-linker, suggesting the colloidal crystalline order was successfully fixed and embedded in the matrix of poly(ethyl acrylate) elastomer. Stretching deformation of the structural colored elastomer induced a sensitive change to shorter wavelength color. Peak wavelength of the UV-vis absorption spectrum of the stretched elastomer revealed an excellent proportional relationship with film thickness. In the swollen colloidal crystal film, ethyl acrylate was absorbed in the colloidal particle; therefore, poly(ethyl acrylate) chain should be penetrating into the colloidal particle after the polymerization of the matrix elastomer. This interpenetrated polymer network structure was considered to be effective for the rubber-like elasticity and sensitive strain-responsive color-changing phenomena of the structural colored elastomer.

  18. Chemical factors influencing colloid-facilitated transport of contaminants in porous media

    Science.gov (United States)

    Roy, Sujoy B.; Dzombak, David A.

    1997-01-01

    The effects of colloids on the transport of two strongly sorbing solutesa hydrophobic organic compound, phenanthrene, and a metal ion, Ni2+were studied in sand-packed laboratory columns under different pH and ionic strength conditions. Two types of column experiments were performed as follows:  (i) sorption/mobilization experiments where the contaminant was first sorbed in the column under conditions where no colloids were released and mobilized under conditions where colloids were released as a result of ionic strength reduction in the influent; and (ii) transport experiments where the contaminant, dissolved or sorbed on colloids, was injected into columns packed with a strongly sorbing porous medium. In the first type of experiment, contaminant mobilization was significant only when all releasable colloids were flushed from the column. In all other cases, although high colloid particle concentrations were encountered, there was no marked effect on total contaminant concentrations. In the second type of experiment, colloid deposition efficiencies were shown to control the enhancement of transport. The deposition efficiency was a function of the pH (for a high organic content sand) and of the contaminant concentration (for a charged species such as Ni2+).

  19. SYNTHESIS OF POLYMER-STABILIZED RUTHENIUM COLLOIDS BY LOW BOILING POINT ALCOHOL REDUCTION

    Institute of Scientific and Technical Information of China (English)

    Ya-li Su; Xiu-ru Li; Yue-jin Tong; Yue-sheng Li

    2003-01-01

    Stable and well-dispersed poly(N-vinyl-2-pyrrolidone) (PVP)-stabilized ruthenium colloidal clusters were prepared via the reduction of ruthenium(Ⅲ) chloride by refluxing with low boiling point alcohols. Investigation of the size of Ru colloids by transmission electron microscopy (TEM) indicated that the average diameters could be controlled in the range of 1.2-1.6 nm with relative standard deviations of less than 0.33 by changing the molar ratio of PVP to Ru. The X-ray photoelectron spectroscopy (XPS) characterization verified the formation of elemental ruthenium colloids.

  20. Association of calcium with colloidal particles and speciation of calcium in the Kalix and Amazon rivers

    Science.gov (United States)

    Dahlqvist, Ralf; Benedetti, Marc F.; Andersson, Karen; Turner, David; Larsson, Tobias; Stolpe, Björn; Ingri, Johan

    2004-10-01

    A considerable amount of colloidally bound Ca has been detected in water samples from Amazonian rivers and the Kalix River, a sub-arctic boreal river. Fractionation experiments using several analytical techniques and processing tools were conducted in order to elucidate the matter. Results show that on average 84% of the total Ca concentration is present as free Ca. Particulate, colloidal and complexed Ca constitute the remaining 16%, of which the colloidal fraction is significant. Ultrafiltration experiments show that the colloidal fraction in the sampled Amazonian rivers and the Kalix River range between 1% and 25%. In both the Amazonian and the Kalix rivers the technique of cross-flow ultrafiltration was used to isolate particles and colloids. The difference in concentration measured with ICP-AES and a Ca ion-selective electrode in identical samples was used to define the free Ca concentration and thus indirectly the magnitude of the particulate, colloidal and complexed fractions. Results from the Kalix and Amazonian rivers are in excellent agreement. Furthermore, the results show that the colloidal concentrations of Ca can be greatly overestimated (up to 227%) when conventional analysis and calculation of ultrafiltration data is used due to retention of free Ca ions during the ultrafiltration process. Calculation methods for colloidal matter are presented in this work, using complementary data from ISE analysis. In the Kalix River temporal changes in the fractionation of Ca were studied before, during and after a spring-flood event. Changes in the size distribution of colloidally associated Ca was studied using FlFFF (Flow Field-Flow Fractionation) coupled on-line to a HR ICP-MS. The FlFFF-HR ICP-MS fractograms clearly show the colloidal component of Ca, supporting the ultrafiltration findings. During winter conditions the size distribution of colloidally associated Ca has a concentration maximum at ˜5 to 10 nm in diameter, shifting to smaller sizes (<5 nm

  1. Control over colloidal crystallization by shear and electric fields

    NARCIS (Netherlands)

    Wu, Y.L.

    2007-01-01

    We used shear flow and an electric field to control colloidal crystallization. The structures were examined in situ with confocal microscopy. For experiments under shear, a new parallel plate shear cell was designed. It had a zero-velocity plane that was stationary with respect to the microscope. Th

  2. Critical Casimir Interactions: New fluctuation forces in colloidal science

    Science.gov (United States)

    Schall, Peter

    2012-02-01

    Casimir forces arise from the confinement of fluctuations between two walls. Critical Casimir forces provide thermodynamic analogues of quantum-mechanical Casimir forces and arise from the confinement of concentration fluctuations of a critical solvent. These forces act also between colloidal particles that are suspended in this solvent, giving rise to temperature-dependent attractive interactions between the particles. We use these temperature-dependent forces to control colloidal phase transitions. In this talk, I will present a new index and density-matched model system that allows direct observation of these phase transitions with confocal microscopy. In three dimensions and real time, we follow how a colloidal gas freezes into a colloidal liquid, and the colloidal liquid freezes into a solid, all driven by critical Casimir forces. We measure the critical Casimir particle pair potential directly from the pair correlation function, and use Monte Carlo simulations to map the complete gas-liquid-solid phase diagram. Excellent agreement with the experimental observations is obtained. Our measurements include microgravity experiments on board the International Space Station (ISS) to elucidate non-equilibrium assembly of the particles achieved by controlled temperature quench.

  3. Opto-thermophoretic assembly of colloidal matter.

    Science.gov (United States)

    Lin, Linhan; Zhang, Jianli; Peng, Xiaolei; Wu, Zilong; Coughlan, Anna C H; Mao, Zhangming; Bevan, Michael A; Zheng, Yuebing

    2017-09-01

    Colloidal matter exhibits unique collective behaviors beyond what occurs at single-nanoparticle and atomic scales. Treating colloidal particles as building blocks, researchers are exploiting new strategies to rationally organize colloidal particles into complex structures for new functions and devices. Despite tremendous progress in directed assembly and self-assembly, a truly versatile assembly technique without specific functionalization of the colloidal particles remains elusive. We develop a new strategy to assemble colloidal matter under a light-controlled temperature field, which can solve challenges in the existing assembly techniques. By adding an anionic surfactant (that is, cetyltrimethylammonium chloride), which serves as a surface charge source, a macro ion, and a micellar depletant, we generate a light-controlled thermoelectric field to manipulate colloidal atoms and a depletion attraction force to assemble the colloidal atoms into two-dimensional (2D) colloidal matter. The general applicability of this opto-thermophoretic assembly (OTA) strategy allows us to build colloidal matter of diverse colloidal sizes (from subwavelength scale to micrometer scale) and materials (polymeric, dielectric, and metallic colloids) with versatile configurations and tunable bonding strengths and lengths. We further demonstrate that the incorporation of the thermoelectric field into the optical radiation force can achieve 3D reconfiguration of the colloidal matter. The OTA strategy releases the rigorous design rules required in the existing assembly techniques and enriches the structural complexity in colloidal matter, which will open a new window of opportunities for basic research on matter organization, advanced material design, and applications.

  4. A comparative study of solid carbon acid catalysts for the esterification of free fatty acids for biodiesel production. Evidence for the leaching of colloidal carbon.

    Science.gov (United States)

    Deshmane, Chinmay A; Wright, Marcus W; Lachgar, Abdessadek; Rohlfing, Matthew; Liu, Zhening; Le, James; Hanson, Brian E

    2013-11-01

    The preparation of a variety of sulfonated carbons and their use in the esterification of oleic acid is reported. All sulfonated materials show some loss in activity associated with the leaching of active sites. Exhaustive leaching shows that a finite amount of activity is lost from the carbons in the form of colloids. Fully leached catalysts show no loss in activity upon recycling. The best catalysts; 1, 3, and 6; show initial TOFs of 0.07 s(-1), 0.05 s(-1), and 0.14 s(-1), respectively. These compare favorably with literature values. Significantly, the leachate solutions obtained from catalysts 1, 3, and 6, also show excellent esterification activity. The results of TEM and catalyst poisoning experiments on the leachate solutions associate the catalytic activity of these solutions with carbon colloids. This mechanism for leaching active sites from sulfonated carbons is previously unrecognized.

  5. Size dependence of tracer diffusion in a laponite colloidal gel.

    Science.gov (United States)

    Petit, Laure; Barentin, Catherine; Colombani, Jean; Ybert, Christophe; Bocquet, Lydéric

    2009-10-20

    Using a fluorescence recovery after photobleaching (FRAP) technique, we present measurements of probe diffusion in a colloidal glass-a Laponite suspension. By varying the probe size over 2 orders of magnitude, as well as the concentration of the colloidal glass, we evidence and quantify the deviations of the probe diffusivity from the bulk Stokes-Einstein expectations. These experiments suggest that the probe diffusion in the dynamically arrested Laponite structure is mainly controlled by the ratio between the probe size and the typical clay platelets interdistance. Comparing with a simple hindered diffusion mechanism, the reduction of tracer diffusion is discussed in terms of the hydrodynamic interaction of the probe with the Laponite structure. Finally, these results can be interpreted in terms of a scale dependent viscosity of the colloidal glass.

  6. Transformations and Reconstructions of DNA-directed colloidal crystals

    Science.gov (United States)

    Crocker, John; Wang, Yifan; Jenkins, Ian; Sinno, Talid

    DNA is a versatile tool for directing the equilibrium self-assembly of nanoscopic and microscopic objects, but also for subsequently transforming them into new structures. In experiment, at high densities of long grafted DNA strands, and temperatures where the binding is reversible, these systems readily form colloidal crystals and colloidal clusters having a range of symmetries. For interactions that favor alloying between two differently-sized colloidal species, our experimental observations compare favorably to a simulation framework that predicts the equilibrium phase behavior, growth kinetics and solid-solid transitions. Overall, we find that this system recapitulates both ionic crystals and noble-metal alloys. We will discuss the crystallography of the alloy structures formed as well as the interesting Martensitic-type transformations and super-lattice reconstructions they undergo.

  7. Colloidal stability of polymeric nanoparticles in biological fluids

    Energy Technology Data Exchange (ETDEWEB)

    Lazzari, Stefano [ETH Zurich, Department of Chemistry and Applied Biosciences, Institute for Chemical and Bioengineering (Switzerland); Moscatelli, Davide, E-mail: davide.moscatelli@polimi.it [Materiali e Ingegneria Chimica ' Giulio Natta' , Politecnico di Milano, Dipartimento di Chimica (Italy); Codari, Fabio [ETH Zurich, Department of Chemistry and Applied Biosciences, Institute for Chemical and Bioengineering (Switzerland); Salmona, Mario [Istituto di Ricerche Farmacologiche ' Mario Negri' , Department of Molecular Biochemistry and Pharmacology (Italy); Morbidelli, Massimo [ETH Zurich, Department of Chemistry and Applied Biosciences, Institute for Chemical and Bioengineering (Switzerland); Diomede, Luisa [Istituto di Ricerche Farmacologiche ' Mario Negri' , Department of Molecular Biochemistry and Pharmacology (Italy)

    2012-06-15

    Estimating the colloidal stability of polymeric nanoparticles (NPs) in biological environments is critical for designing optimal preparations and to clarify the fate of these devices after administration. To characterize and quantify the physical stability of nanodevices suitable for biomedical applications, spherical NPs composed of poly-lactic acid (PLA) and poly-methyl-methacrylate (PMMA), in the range 100-200 nm, were prepared. Their stability in salt solutions, biological fluids, serum and tissue homogenates was analyzed by dynamic light scattering (DLS). The PMMA NPs remained stable in all fluids, while PLA NPs aggregated in gastric juice and spleen homogenate. The proposed stability test is therefore useful to see in advance whether NPs might aggregate when administered in vivo. To assess colloidal stability ex vivo as well, spectrophotofluorimetric analysis was employed, giving comparable results to DLS.

  8. Directed Assembly of Soft Anisotropic Nanoparticles by Colloid Electrospinning.

    Science.gov (United States)

    Jiang, Shuai; Mable, Charlotte J; Armes, Steven P; Crespy, Daniel

    2016-10-01

    Directed assembly of triblock copolymer worms to produce nanostructured fibers is achieved via colloid electrospinning. These copolymer worms are conveniently prepared by polymerization-induced self-assembly in concentrated aqueous dispersion. Addition of a second water-soluble component, poly(vinyl alcohol), is found to be critical for the production of well-defined fibers: trial experiments performed using the worms alone produce only spherical microparticles. Transmission electron microscopy studies confirm that the worm morphology survives electrospinning and the worms become orientated parallel to the main axis of the fibers during their generation. The average deviant angle (θdev ) between the worm orientation and fiber axis decreases from 17° to 9° as the worm/PVA mass ratio increases from 1.15:1 to 5:1, indicating a greater degree of worm alignment within fibers with higher worm contents and smaller fiber diameters. Thus triblock copolymer fibers of ≈300 ± 120 nm diameter can be readily produced that comprise aligned worms on the nanoscale.

  9. Adsorption of polar, nonpolar, and substituted aromatics to colloidal graphene oxide nanoparticles

    NARCIS (Netherlands)

    Wang, Fang; Haftka, Joris J H; Sinnige, Theo L.; Hermens, Joop L M; Chen, Wei

    2014-01-01

    We conducted batch adsorption experiments to understand the adsorptive properties of colloidal graphene oxide nanoparticles (GONPs) for a range of environmentally relevant aromatics and substituted aromatics, including model nonpolar compounds (pyrene, phenanthrene, naphthalene, and 1,3-dichlorobenz

  10. Analytical Ultracentrifugation of Inorganic Colloids; Sedimentation Velocity of Interacting and Non-Interacting Particles

    NARCIS (Netherlands)

    Planken, K.L.|info:eu-repo/dai/nl/304841099

    2008-01-01

    Several case studies of the sedimentation velocity of non-interacting, attractive and repulsive colloids are discussed. After a brief introduction that highlights historical facts, basic analytical ultracentrifugation theory, some instrument issues and experiments are reviewed. The existence of disc

  11. 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......, using laser diffraction, by agitating the samples using a wet-dispersion unit. This approach eliminated the need for long sedimentation times required by the more classical end-over-end shaking approach and provided information about the time-dependent release of WDC. The total clay content of the soils...... ranged from 0.1 to 0.44 kg kg−1. The WDC content was measured on air-dry and moist 1- to 2-mm aggregates. The WDC content at a reference time was highly correlated to the total clay content (r > 0.91, P soils. Only for two sites was the WDC content correlated to the content of clay...

  12. Quantitative Evaluation of the Total Magnetic Moments of Colloidal Magnetic Nanoparticles: A Kinetics-based Method.

    Science.gov (United States)

    Liu, Haiyi; Sun, Jianfei; Wang, Haoyao; Wang, Peng; Song, Lina; Li, Yang; Chen, Bo; Zhang, Yu; Gu, Ning

    2015-06-08

    A kinetics-based method is proposed to quantitatively characterize the collective magnetization of colloidal magnetic nanoparticles. The method is based on the relationship between the magnetic force on a colloidal droplet and the movement of the droplet under a gradient magnetic field. Through computational analysis of the kinetic parameters, such as displacement, velocity, and acceleration, the magnetization of colloidal magnetic nanoparticles can be calculated. In our experiments, the values measured by using our method exhibited a better linear correlation with magnetothermal heating, than those obtained by using a vibrating sample magnetometer and magnetic balance. This finding indicates that this method may be more suitable to evaluate the collective magnetism of colloidal magnetic nanoparticles under low magnetic fields than the commonly used methods. Accurate evaluation of the magnetic properties of colloidal nanoparticles is of great importance for the standardization of magnetic nanomaterials and for their practical application in biomedicine.

  13. COLLOID RELEASE FROM DIFFERENT SOIL DEPTH

    Directory of Open Access Journals (Sweden)

    Gang Chen

    2013-01-01

    Full Text Available Naturally occurring clay colloidal particles are heavily involved in sediment processes in the subsurface soil. Due to the import ance of these processes in the subsurface environment, the transport of clay colloidal particles has been studied in several disciplines, including soil sciences, petr ology, hydrology, etc. Specifically, in environmental engineering, clay colloid re lease and transport in the sediments have been extensively investigated, which are motiv ated by environmental concerns such as colloid-facilitated contaminant transport in groundwater and the subsurface soil. Clay colloid release is resulted from physical alteration of subsurface sediments. Despite the potential importance of clay colloid activiti es, the detailed mechanisms of release and transport of clay colloidal particles with in natural sediments are poorly understood. Pore medium structure, properties and flow dynamics, etc. are factors that affect clay colloid generation, mobilization, and subse quent transport. Possible mechanisms of clay colloid generation in the sediments in clude precipitation, erosion and mobilization by changes in pore water chemistry and clay colloid release depends on a balance of applied hydrodynamic and resisting adhesive torques and forces. The coupled role of pore water chemistry and fluid hydrodynamics thus play key roles in controlling clay colloid release and transport in the sediment s. This paper investigated clay colloidal particle release and transport, especially th e colloidal particle release mechanisms as well as the process modeling in the sediments. In this research, colloidal particle release from intact sediment columns with variable length was examined and colloidal particle release curves were simulated using an im plicit, finite-difference scheme. Colloidal particle release rate coefficient was found to be an exponential function of the sediment depth. The simulated results demonstrated that transport parameters were

  14. Tuning the localized surface plasmon resonance of silver nanoplatelet colloids

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Asha; Jayabalan, J; Chari, Rama [Laser Physics Applications Division, Raja Ramanna Centre for Advanced Technology, Indore (India); Srivastava, Himanshu [Indus Synchrotrons Utilization Division, Raja Ramanna Centre for Advanced Technology, Indore (India); Oak, S M, E-mail: jjaya@rrcat.gov.i [Solid State Laser Division, Raja Ramanna Centre for Advanced Technology, Indore (India)

    2010-08-25

    The effect of femtosecond laser irradiation on silver nanoplatelet colloids is described. It is shown that irradiation with a femtosecond laser of appropriate fluence can be used to tune the localized surface plasmon resonances of triangular silver nanoplatelets by a few tens of nanometres. This peak shift is shown to be caused by the structural modifications of the particle tips. We have also shown that post-preparation addition of poly-vinyl pyrrolidone to the nanocolloid arrests the peak shift.

  15. Extraordinary Hall-effect in colloidal magnetic nanoparticle films

    Science.gov (United States)

    Ben Gur, Leah; Tirosh, Einat; Segal, Amir; Markovich, Gil; Gerber, Alexander

    2017-03-01

    Colloidal nickel nanoparticles (NPs) coated with polyvinylpyrrolidone (PVP) were synthesized. The nanoparticle dispersions were deposited on substrates and dried under mild heating to form conductive films. The films exhibited very small coercivity, nearly metallic conductivity, and a significant extraordinary Hall effect signal. This method could be useful for preparing simple, printed magnetic field sensors with the advantage of relatively high sensitivity around zero magnetic field, in contrast to magnetoresistive sensors, which have maximal field sensitivity away from zero magnetic field.

  16. Changing the way that I am: students experience of educational preparation for advanced nursing roles in the community.

    Science.gov (United States)

    Illingworth, Andrea; Aranda, Kay F; De Goeas, Sharon M; Lindley, Penny J

    2013-09-01

    The redesign of the healthcare workforce in the United Kingdom (UK) has resulted in the rapid introduction of more 'advanced' community nursing roles. This presents varying challenges for universities seeking to prepare practitioners for these roles. This paper reports on a qualitative study conducted at one university in England which sought to explore the educational experiences of students preparing for and engaging in advanced nursing roles. Data was collected through focus groups and semi-structured interviews. This study found that educational preparation for advanced nursing roles in the community is varied and complex and involved a number of claims, concerns and issues, captured in three themes: 1. Re-inventing roles; 2. Re-creating selves; and 3. Re-engaging with learning. The findings reveal how those in advanced roles work across occupational boundaries and manage conflicts, using differentiated and complex sources and forms of knowledge and skills. Learning occurs in non-linear ways and is a good example of expansive or sideways learning. There is a need for further research on the type of curriculum and methods to best support students preparing for these roles and further study on the impact on patient experience and outcomes.

  17. THE LIME PURIFICATION OF SUGAR –CONTAINING SOLUTION USING HIGH VISCOSITY COLLOIDAL SOLUTIONS

    Directory of Open Access Journals (Sweden)

    K. V.

    2015-12-01

    Full Text Available Aim of the work was to determine the efficiency of combined application of lime and high-viscous suspensions, containing the aluminium nanoparticles as a precursor in treatment of sugar-containing solutions. At the first stage the aluminium nanopowder, encapsulated into a salt matrix, was produced by the combined precipitation from a gas phase of metal and halogenide of alkali metal (NaCl. For the long-term stabilization of aluminum nanoparticles the method, developed by the authors, for dispersing these powders in the composition of polyethylene glycols was used, providing the colloidal solution of high viscosity (gel. At the second stage, as an object of investigation a juice of sugar beet, produced in the laboratory conditions by water extracting from the beet chips, was applied. In the produced juice the main characteristics of its quality were determined: the content of solids, sucrose, its purity was calculated (ratio of sucrose to solids content, in%. The content of protein and pectin components was also determined (as the main components of the colloidal fraction of the diffusion juice. Conventionally, as a basic reagent for the process of a lime pretreatment a lime milk of 1.18 g/cm3 density, prepared by liming the burned lime using hot water, was used. During the experiments the effectiveness of reagents, containing aluminum in nanoform, on the degree of removal of the colloidal dispersion substances in the process of juice purification in sugar beet production and improvement of its quality, is shown. However, the obtained results show that, depending on the method of producing, the additional reagents with aluminium nanoparticles have different effect on change of diffusion juice purity in the process of its treatment by the lime milk.

  18. EDITORIAL: Colloidal dispersions in external fields Colloidal dispersions in external fields

    Science.gov (United States)

    Löwen, Hartmut

    2012-11-01

    third conference in a series that began in 2004 [2] and was continued in 2008 [3]. The CODEF meeting series is held in conjunction with the German Dutch Transregional Collaborative Research Centre SFB TR6 with the title Physics of Colloidal Dispersions in External Fields. Papers from scientists working within this network as well as those from further invited contributors are summarized in this issue. They are organized according to the type of field applied, namely: shear flow electric field laser-optical and magnetic field confinement other fields and active particles To summarize the highlights of this special issue as regards shear fields, the response of depletion-induced colloidal clusters to shear is explored in [4]. Soft particles deform under shear and their structural and dynamical behaviour is studied both by experiment [5] and theory [6]. Transient dynamics after switching on shear is described by a joint venture of theory, simulation and experiment in [7]. Colloids provide the fascinating possibility to drag single particles through the suspension, which gives access to microrheology (as opposed to macrorheology, where macroscopic boundaries are moved). Several theoretical aspects of microrheology are discussed in this issue [8-10]. Moreover, a microscopic theory for shear viscosity is presented [11]. Various aspects of colloids in electric fields are also included in this issue. Electrokinetic phenomena for charged suspensions couple flow and electric phenomena in an intricate way and are intensely discussed both by experiment and simulation in contributions [12-14]. Dielectric phenomena are also influenced by electric fields [15]. Electric fields can induce effective dipolar forces between colloids leading to string formation [16]. Finally, binary mixtures in an electric driving field exhibit laning [17]. Simulation [18] and theoretical [19] studies of this nonequilibrium phenomenon are also discussed in this issue. Laser-optical fields can be used to

  19. Synthesis and Characterization of Supramolecular Colloids.

    Science.gov (United States)

    Vilanova, Neus; De Feijter, Isja; Voets, Ilja K

    2016-04-22

    Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical properties for applications in photonics, drug delivery and coating technology. Here we present a new family of colloidal building blocks, coined supramolecular colloids, whose self-assembly is controlled through surface-functionalization with a benzene-1,3,5-tricarboxamide (BTA) derived supramolecular moiety. Such BTAs interact via directional, strong, yet reversible hydrogen-bonds with other identical BTAs. Herein, a protocol is presented that describes how to couple these BTAs to colloids and how to quantify the number of coupling sites, which determines the multivalency of the supramolecular colloids. Light scattering measurements show that the refractive index of the colloids is almost matched with that of the solvent, which strongly reduces the van der Waals forces between the colloids. Before photo-activation, the colloids remain well dispersed, as the BTAs are equipped with a photo-labile group that blocks the formation of hydrogen-bonds. Controlled deprotection with UV-light activates the short-range hydrogen-bonds between the BTAs, which triggers the colloidal self-assembly. The evolution from the dispersed state to the clustered state is monitored by confocal microscopy. These results are further quantified by image analysis with simple routines using ImageJ and Matlab. This merger of supramolecular chemistry and colloidal science offers a direct route towards light- and thermo-responsive colloidal assembly encoded in the surface-grafted monolayer.

  20. Colloidal gelation of oppositely charged particles

    NARCIS (Netherlands)

    Russel, E.; Sprakel, J.H.B.; Kodger, T.E.; Weitz, D.A.

    2012-01-01

    Colloidal gelation has been extensively studied for the case of purely attractive systems, but little is understood about how colloidal gelation is affected by the presence of repulsive interactions. Here we demonstrate the gelation of a binary system of oppositely charged colloids, in which repulsi

  1. Preparation of a N-Heterocyclic Carbene Nickel(II) Complex: Synthetic Experiments in Current Organic and Organometallic Chemistry

    Science.gov (United States)

    Ritleng, Vincent; Brenner, Eric; Chetcuti, Michael J.

    2008-01-01

    A four-part experiment that leads to the synthesis of a cyclopentadienyl chloro-nickel(II) complex bearing a N-heterocyclic carbene (NHC) ligand is presented. In the first part, the preparation of 1,3-bis-(2,4,6-trimethylphenyl)imidazolium chloride (IMes[middle dot]HCl) in a one-pot procedure by reaction of 2,4,6-trimethylaniline with…

  2. Plutonium partitioning in three-phase systems with water, granite grains, and different colloids.

    Science.gov (United States)

    Xie, Jinchuan; Lin, Jianfeng; Zhou, Xiaohua; Li, Mei; Zhou, Guoqing

    2014-01-01

    Low-solubility contaminants with high affinity for colloid surfaces may form colloid-associated species. The mobile characteristics of this species are, however, ignored by the traditional sorption/distribution experiments in which colloidal species contributed to the immobile fraction of the contaminants retained on the solids as a result of centrifugation or ultrafiltration procedures. The mobility of the contaminants in subsurface environments might be underestimated accordingly. Our results show that colloidal species of (239)Pu in three-phase systems remained the highest percentages in comparison to both the dissolved species and the immobile species retained on the granite grains (solid phase), although the relative fraction of these three species depended on the colloid types. The real solid/liquid distribution coefficients (K s/d) experimentally determined were generally smaller than the traditional K s/d (i.e., the K s+c/d in this study) by ~1,000 mL/g for the three-phase systems with the mineral colloids (granite particle, soil colloid, or kaolinite colloid). For the humic acid system, the traditional K s/d was 140 mL/g, whereas the real K s/d was approximately zero. The deviations from the real solid/liquid K s/d were caused by the artificially increased immobile fraction of Pu. One has to be cautious in using K s/d-based transport models to predict the fate and transport of Pu in the environment.

  3. Strong collective attraction in colloidal clusters on a liquid-air interface.

    Science.gov (United States)

    Pergamenshchik, V M

    2009-01-01

    It is shown that in a cluster of many colloids, trapped at a liquid-air interface, the well-known vertical-force-induced pairwise logarithmic attraction changes to a strongly enhanced power-law attraction. In large two-dimensional clusters, the attraction energy scales as the inverse square of the distance between colloids. The enhancement is given by the ratio eta = (square of the capillary length) / (interface surface area per colloid) and can be as large as 10;{5} . This explains why a very small vertical force on colloids, which is too weak to bring two of them together, can stabilize many-body structures on a liquid-air interface. The profile of a cluster is shown to consist of a large slow collective envelope modulated by a fast low-amplitude perturbation due to individual colloids. A closed equation for the slow envelope, which incorporates an arbitrary power-law repulsion between colloids, is derived. For example, this equation is solved for a large circular cluster with the hard-core colloid repulsion. It is suggested that the predicted effect is responsible for mysterious stabilization of colloidal structures observed in experiments on a surface of isotropic liquid and nematic liquid crystal.

  4. Multimodal Plasmonics in Fused Colloidal Networks

    CERN Document Server

    Teulle, Alexandre; Girard, C; Gurunatha, Kargal L; Li, Mei; Mann, Stephen; Dujardin, Erik

    2014-01-01

    Harnessing the optical properties of noble metals down to the nanometer-scale is a key step towards fast and low-dissipative information processing. At the 10-nm length scale, metal crystallinity and patterning as well as probing of surface plasmon (SP) properties must be controlled with a challenging high level of precision. Here, we demonstrate that ultimate lateral confinement and delocalization of SP modes are simultaneously achieved in extended self-assembled networks comprising linear chains of partially fused gold nanoparticles. The spectral and spatial distributions of the SP modes associated with the colloidal superstructures are evidenced by performing monochromated electron energy loss spectroscopy with a nanometer-sized electron probe. We prepare the metallic bead strings by electron beam-induced interparticle fusion of nanoparticle networks. The fused superstructures retain the native morphology and crystallinity but develop very low energy SP modes that are capable of supporting long range and s...

  5. Bonding assembled colloids without loss of colloidal stability

    NARCIS (Netherlands)

    Vutukuri, H.R.; Stiefelhagen, J.C.P.; Vissers, T; Imhof, A.; van Blaaderen, A.

    2012-01-01

    In recent years the diversity of self-assembled colloidal structures has strongly increased, as it is fueled by a wide range of applications in materials science and also in soft condensed-matter physics.[1–4] Some potential applications include photonic bandgap (PBG) crystals, materials for plasmon

  6. Influence of Intrinsic Colloid Formation on Migration of Cerium through Fractured Carbonate Rock.

    Science.gov (United States)

    Tran, Emily L; Klein-BenDavid, Ofra; Teutsch, Nadya; Weisbrod, Noam

    2015-11-17

    Migration of colloids may facilitate the transport of radionuclides leaked from near surface waste sites and geological repositories. Intrinsic colloids are favorably formed by precipitation with carbonates in bicarbonate-rich environments, and their migration may be enhanced through fractured bedrock. The mobility of Ce(III) as an intrinsic colloid was studied in an artificial rainwater solution through a natural discrete chalk fracture. The results indicate that at variable injection concentrations (between 1 and 30 mg/L), nearly all of the recovered Ce takes the form of an intrinsic colloid of >0.45 μm diameter, including in those experiments in which the inlet solution was first filtered via 0.45 μm. In all experiments, these intrinsic colloids reached their maximum relative concentrations prior to that of the Br conservative tracer. Total Ce recovery from experiments using 0.45 μm filtered inlet solutions was only about 0.1%, and colloids of >0.45 μm constituted the majority of recovered Ce. About 1% of Ce was recovered when colloids of >0.45 μm were injected, indicating the enhanced mobility and recovery of Ce in the presence of bicarbonate.

  7. Reading in Preparation for Writing a PhD Thesis: Case Studies of Experiences

    Science.gov (United States)

    Kwan, Becky S. C.

    2009-01-01

    The paper presents stories of how a group of doctoral students chose the key disciplinary literature that they read in preparation for their thesis-undertaking (RT). The stories were analyzed in light of current understanding of literature reviewing as a situated practice and theory of doctoral education as socio-cognitive apprenticeship. As the…

  8. Field Experience as the Centerpiece of an Integrated Model for STEM Teacher Preparation

    Science.gov (United States)

    van den Kieboom, Leigh A.; McNew-Birren, Jill C.; Eckman, Ellen W.; Silver-Thorn, M. Barbara

    2013-01-01

    The purpose of this study was to provide a descriptive account of one pathway for preparing high-quality STEM (science, technology, engineering, and mathematics) teachers for work in high-need urban schools. In this account, we discuss the supports that STEM majors need in learning how to think about the content that they know well, through an…

  9. Reading in Preparation for Writing a PhD Thesis: Case Studies of Experiences

    Science.gov (United States)

    Kwan, Becky S. C.

    2009-01-01

    The paper presents stories of how a group of doctoral students chose the key disciplinary literature that they read in preparation for their thesis-undertaking (RT). The stories were analyzed in light of current understanding of literature reviewing as a situated practice and theory of doctoral education as socio-cognitive apprenticeship. As the…

  10. Educational Leadership and Technology Integration: An Investigation into Preparation, Experiences, and Roles

    Science.gov (United States)

    Schrum, Lynne; Galizio, Lyndsie M.; Ledesma, Patrick

    2011-01-01

    This research, looking through the lens of Fullan (1991) regarding the complexity of implementing school wide change, sought to explore preparation and requirements of new administrators with respect to the integration of technology by first gathering data regarding licensure and course requirements from state departments of education and…

  11. Preparing FCS Professionals for a Multilingual Society: Building Community through the Experiences of Multilingual Families

    Science.gov (United States)

    Duncan, Janine; Duncan, Daniel

    2014-01-01

    As demographics in the United States shift, family and consumer sciences (FCS) professionals must be prepared to foster healthy communities that embrace multilingual families. Because hegemonic language ideologies challenge multilingual families, FCS professionals need to know how to inclusively reframe communities to honor multilingual families.…

  12. Educational Leadership and Technology Integration: An Investigation into Preparation, Experiences, and Roles

    Science.gov (United States)

    Schrum, Lynne; Galizio, Lyndsie M.; Ledesma, Patrick

    2011-01-01

    This research, looking through the lens of Fullan (1991) regarding the complexity of implementing school wide change, sought to explore preparation and requirements of new administrators with respect to the integration of technology by first gathering data regarding licensure and course requirements from state departments of education and…

  13. Preparation for Full Time Employment: A Capstone Experience for Students in Leadership Programs

    Science.gov (United States)

    Gifford, Gregory T.; Cannon, Karen J.; Stedman, Nicole L.; Telg, Ricky W.

    2011-01-01

    This practice paper describes the development and implementation of a senior capstone course for communication and leadership development for undergraduate students. The resulting course is a unique combination of experiential skill development and career preparation. The success of this course provides students with an important and meaningful…

  14. Colloidal Oatmeal (Avena Sativa) Improves Skin Barrier Through Multi-Therapy Activity.

    Science.gov (United States)

    Ilnytska, Olha; Kaur, Simarna; Chon, Suhyoun; Reynertson, Kurt A; Nebus, Judith; Garay, Michelle; Mahmood, Khalid; Southall, Michael D

    2016-06-01

    Oats (Avena sativa) are a centuries-old topical treatment for a variety of skin barrier conditions, including dry skin, skin rashes, and eczema; however, few studies have investigated the actual mechanism of action for the skin barrier strengthening activity of colloidal oatmeal. Four extracts of colloidal oatmeal were prepared with various solvents and tested in vitro for skin barrier related gene expression and activity. Extracts of colloidal oatmeal were found to induce the expression of genes related to epidermal differentiation, tight junctions and lipid regulation in skin, and provide pH-buffering capacity. Colloidal oatmeal boosted the expression of multiple target genes related to skin barrier, and resulted in recovery of barrier damage in an in vitro model of atopic dermatitis. In addition, an investigator-blinded study was performed with 50 healthy female subjects who exhibited bilateral moderate to severe dry skin on their lower legs. Subjects were treated with a colloidal oatmeal skin protectant lotion. Clinically, the colloidal oatmeal lotion showed significant clinical improvements in skin dryness, moisturization, and barrier. Taken together, these results demonstrate that colloidal oatmeal can provide clinically effective benefits for dry and compromised skin by strengthening skin barrier. J Drugs Dermatol. 2016;15(6):684-690.

  15. Rheology, microstructure and migration in brownian colloidal suspensions.

    Science.gov (United States)

    Pan, Wenxiao; Caswell, Bruce; Karniadakis, George Em

    2010-01-05

    We demonstrate that suspended spherical colloidal particles can be effectively modeled as single dissipative particle dynamics (DPD) particles provided that the conservative repulsive force is appropriately chosen. The suspension model is further improved with a new formulation, which augments standard DPD with noncentral dissipative shear forces between particles while preserving angular momentum. Using the new DPD formulation we investigate the rheology, microstructure and shear-induced migration of a monodisperse suspension of colloidal particles in plane shear flows (Couette and Poiseuille). Specifically, to achieve a well-dispersed suspension we employ exponential conservative forces for the colloid-colloid and colloid-solvent interactions but keep the conventional linear force for the solvent-solvent interactions. Our simulations yield relative viscosity versus volume fraction predictions in good agreement with both experimental data and empirical correlations. We also compute the shear-dependent viscosity and the first and second normal-stress differences and coefficients in both Couette and Poiseuille flow. Simulations near the close packingvolume-fraction (64%) at low shear rates demonstrate a transition to flow-induced string-like structures of colloidal particles simultaneously with a transition to a nonlinear Couette velocity profile in agreement with experimental observations. After a sufficient increase ofthe shear rate the ordered structure melts into disorder with restoration of the linear velocity profile. Migration effects simulated in Poiseuille flow compare well with experiments and model predictions. The important role of angular momentum and torque in nondilute suspensions is also demonstrated when compared with simulations by the standard DPD, which omits the angular degrees of freedom. Overall, the new method agrees very well with the Stokesian Dynamics method but it seems to have lower computational complexity and is applicable to general

  16. Colloid facilitated transport in fractured rocks : parameter estimation and comparison with experimental data.

    Energy Technology Data Exchange (ETDEWEB)

    Viswanathan, H. S. (Hari Selvi); Wolfsberg, A. V. (Andrew V.); Reimus, P. W. (Paul William); Ware, S. D. (Stuart D.); Lu, G. (Guoping)

    2003-01-01

    Colloid-facilitated migration of plutonium in fractured rock has been implicated in both field and laboratory studies . Other reactive radionuclides may also experience enhanced mobility due to groundwater colloids. Model prediction of this process is necessary for assessment of contaminant boundaries in systems for which radionuclides are already in the groundwater and for performance assessment of potential repositories for radioactive waste. Therefore, a reactive transport model is developed and parameterized using results from controlled laboratory fracture column experiments. Silica, montmorillonite and clinoptilolite colloids are used in the experiments along with plutonium and Tritium . . The goal of the numerical model is to identify and parameterize the physical and chemical processes that affect the colloid-facilitated transport of plutonium in the fractures. The parameters used in this model are similar in form to those that might be used in a field-scale transport model.

  17. Colloid-Facilitated Transport of Cations in an Unsaturated Fractured Soil Under Transient Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Ryan, Joseph [Univ. of Colorado, Boulder, CO (United States)

    2015-01-31

    Rainfall experiments were conducted using intact soil cores and an instrumented soil pedon to examine the effect of physical heterogeneity and rainfall characteristics on the mobilization of colloids, organic matter, cesium, and strontium in a fractured soil. To measure the spatial variability of infiltration of colloids and contaminants, samples were collected through a 19-port grid placed below the soil core in laboratory study and in 27 samplers at multiple depths in the soil pedon in the field study. Cesium and strontium were applied to the soil cores and the soil pedon prior to mobilization experiments. Rainwater solutions of multiple ionic strengths and organic matter concentrations were applied to the soil cores and soil pedon to mobilize in situ colloids, cesium, and strontium. The mobilization of colloids and metal cations occurred through preferential flow paths in the soil cores. Compared to steady rainfall, greater amounts of colloids were mobilized during rainfall interrupted by pauses, which indicates that the supply of colloids to be mobilized was replenished during the pauses. A maximum in the amount of mobilized colloids were mobilized during a rainfall following a pause of 2.5 d. Pauses of shorter or longer duration resulted in less colloid mobilization. Freeze-thaw cycles, a transient condition in winter, enhanced colloid mobilization and colloid-facilitated transport of cesium and strontium in the soil cores. The exchange of solutes between the soil matrix and macropores caused a hysteretic mobilization of colloids, cesium, and strontium during changes in ionic strength. Colloid-facilitated mobilization of cesium and strontium was important at low ionic strength in fractures where slow flow allowed greater exchange of flow between the fractures and the surrounding matrix. The release of cesium and strontium by cation exchange occurred at high ionic strength in fractures where there is a little exchange of pore water with the surrounding matrix

  18. Colloid-Facilitated Transport of Low-Solubility Radionuclides: A Field, Experimental, and Modeling Investigation

    Energy Technology Data Exchange (ETDEWEB)

    Kersting, A B; Reimus, P W; Abdel-Fattah, A; Allen, P G; Anghel, I; Benedict, F C; Esser, B K; Lu, N; Kung, K S; Nelson, J; Neu, M P; Reilly, S D; Smith, D K; Sylwester, E R; Wang, L; Ware, S D; Warren, RG; Williams, R W; Zavarin, M; Zhao, P

    2003-02-01

    rate of Pu transport. Currently, the role of colloids in facilitating the transport of low-solubility radionuclides is not understood well enough to effectively model contaminant transport. A fundamental understanding of the role that colloids may or may not play in the transport of low-solubility radionuclides is needed in order to predict contaminant transport, design remediation strategies and provide risk assessments. Ryan and Elimelech (1996) have argued that in order to evaluate the potential for colloids to transport radionuclides, several criteria must be met: (1) colloids must exist and be stable, (2) radionuclides must have a high sorption affinity for the colloids, and (3) colloids must be transported. Only then can we understand the conditions where colloids can and will facilitate transport of radionuclides. In this report we compile the results from a series of field, laboratory and modeling studies funded by the UGTA program in order to evaluate the potential for colloids to transport low-solubility radionuclides at the NTS. The studies presented in this report fall under three general areas of investigation: Characterization of natural colloids in groundwater at NTS, Pu sorption/desorption experiments on colloid minerals identified in NTS groundwater, and Transport of Pu-doped colloids through fractured rock core. Chapter 1 is a background review of our current understanding of colloids and their role in facilitating contaminant transport. Chapters 2, and 3 are field studies that focused on characterizing natural colloids at different hydrologic environments at the NTS and address Ryan and Elimelech's (1996) first criteria regarding the existence and stability of colloids. Chapters 4, 5 and 6 are laboratory experimental studies that investigate the sorption/desorption behavior of Pu and other low-solubility radionuclides on colloid minerals observed in NTS groundwater. These studies evaluate Ryan and Elimelech's (1996) second criteria that the

  19. Supramolecular perspectives in colloid science

    NARCIS (Netherlands)

    Cohen Stuart, M.A.

    2008-01-01

    Supramolecular chemistry puts emphasis on molecular assemblies held together by non-covalent bonds. As such, it is very close in spirit to colloid science which also focuses on objects which are small, but beyond the molecular scale, and for which other forces than covalent bonds are crucial. We dis

  20. Colloidal aspects of texture perception

    NARCIS (Netherlands)

    Vliet, van T.

    2010-01-01

    The perception of complex textures in food is strongly related to the way food is processed during eating, and is modulated by other basic characteristics, such as taste and aroma. An understanding at the colloidal level of the basic processes in the mouth is essential in order to link the compositi

  1. Colloidal quantum dot solar cells

    Science.gov (United States)

    Sargent, Edward H.

    2012-03-01

    Solar cells based on solution-processed semiconductor nanoparticles -- colloidal quantum dots -- have seen rapid advances in recent years. By offering full-spectrum solar harvesting, these cells are poised to address the urgent need for low-cost, high-efficiency photovoltaics.

  2. 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

  3. Polydispersity and gelation in concentrated colloids with competing interactions.

    Science.gov (United States)

    Zhang, Tian Hui; Kuipers, Bonny W M; Tian, Wen-de; Groenewold, Jan; Kegel, Willem K

    2015-01-14

    In colloids with competing short-range attractions and long-range repulsions, microcrystalline gels are experimentally formed under conditions where computer simulations point to a lamellar phase as the ground state. Here, upon applying a low-frequency alternating electric field, we bring the system from an initial gel state to a columnar-like state. While molecular dynamics simulations on monodisperse colloids reveal that a columnar structure spontaneously evolves towards a lamellar phase, the columnar-like state in experiments relaxes back to the initial disordered gel state once the electric field is switched off. Similarly, a columnar phase in molecular dynamics simulations decomposes into finite-size crystalline clusters as the relative polydispersity of the colloids is around 1.0%. We conclude that the experimentally observed melting of the columnar structure is driven by polydispersity. Moreover, further simulations reveal that the critical polydispersity required to destabilize a long-range ordered structure increases with the attraction range, pointing to the possibility of observing periodic structures in experiments if the attraction range is sufficiently long compared to the polydispersity of the colloids.

  4. Enhanced colloidal stability of hydroxyapatite

    Science.gov (United States)

    Borum, La Rhonda Terese

    Hydroxyapatite, Ca10(PO4)6(OH) 2 is the most thermodynamically stable calcium phosphate in physiological environments. Hence, it is the main inorganic mineral found in bone and teeth. Its colloidal stability, however, is poor because hydroxyapatite (HAp) particles exhibit sediment formation upon standing at short time periods, where agglomerates form and lead to non-homogeneous suspensions. Surface modification is a promising method to tailor the colloidal stability of hydroxyapatite for biomaterial applications. Three techniques to modify the HAp surface and enhance the colloidal stability of HAp were investigated. Modified particles were characterized by methods sensitive to surface chemistry changes, such as sedimentation studies, diffuse reflectance Fourier transform infrared spectroscopy (DRIFT), Brunauer-Emmett-Teller (BET) surface area, and electrophoresis. Sedimentation studies demonstrated how effective each technique was in improving the colloidal stability of hydroxyapatite particles. Electrophoresis provided information on electrostatic interactions within each system. The first technique entailed an esterification reaction of the HAp surface with dodecyl alcohol at elevated temperatures. DRIFT results showed that dodecyl groups from the alcohol replaced acidic hydroxyl and phosphate sites on the HAp surface, giving rise to enhanced colloidal stability through steric interactions in ethanol suspensions. TGA curves gave insight to the degree of esterification for the esterified particles. Higher reaction temperatures give rise to a higher degree of esterification resulting in better colloidal stability. The second technique applied a silica coating on the HAp surface by the hydrolysis of tetraethyl orthosilicate in ethanol. Silica was coated onto the HAp surface at 5--75 wt% loading amounts. A combination of acid dissolution and x-ray diffraction (XRD), along with BET showed that the silica coating is complete at 50 wt% silica loading. The silica coating

  5. Life at ultralow interfacial tension: Wetting, waves and droplets in demixed colloid-polymer mixtures

    NARCIS (Netherlands)

    Lekkerkerker, H.N.W.; de Villeneuve, V.W.A.; de Folter, J.W.J.; Schmidt, M.; Hennequin, Y.; Bonn, D.; Indekeu, J.O.; Aarts, D.G.A.L.

    2008-01-01

    Mixtures of colloids and polymers display a rich phase behavior, involving colloidal gas (rich in polymer, poor in colloid), colloidal liquid (poor in polymer, rich in colloid) and colloidal crystal phases (poor in polymer, highly ordered colloids). Recently, the colloidal gas-colloidal liquid inter

  6. Life at ultralow interfacial tension: wetting, waves and droplets in demixed colloid-polymer mixtures

    NARCIS (Netherlands)

    Lekkerkerker, H.N.W.; de Villeneuve, V.W.A.; de Folter, J.W.J.; Schmidt, M.; Hennequin, Y.; Bonn, D.; Indekeu, J.O.; Aarts, D.G.A.L.

    2008-01-01

    Mixtures of colloids and polymers display a rich phase behavior, involving colloidal gas (rich in polymer, poor in colloid), colloidal liquid (poor in polymer, rich in colloid) and colloidal crystal phases (poor in polymer, highly ordered colloids). Recently, the colloidal gas-colloidal liquid inter

  7. An approach to optimize sample preparation for MALDI imaging MS of FFPE sections using fractional factorial design of experiments.

    Science.gov (United States)

    Oetjen, Janina; Lachmund, Delf; Palmer, Andrew; Alexandrov, Theodore; Becker, Michael; Boskamp, Tobias; Maass, Peter

    2016-09-01

    A standardized workflow for matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI imaging MS) is a prerequisite for the routine use of this promising technology in clinical applications. We present an approach to develop standard operating procedures for MALDI imaging MS sample preparation of formalin-fixed and paraffin-embedded (FFPE) tissue sections based on a novel quantitative measure of dataset quality. To cover many parts of the complex workflow and simultaneously test several parameters, experiments were planned according to a fractional factorial design of experiments (DoE). The effect of ten different experiment parameters was investigated in two distinct DoE sets, each consisting of eight experiments. FFPE rat brain sections were used as standard material because of low biological variance. The mean peak intensity and a recently proposed spatial complexity measure were calculated for a list of 26 predefined peptides obtained by in silico digestion of five different proteins and served as quality criteria. A five-way analysis of variance (ANOVA) was applied on the final scores to retrieve a ranking of experiment parameters with increasing impact on data variance. Graphical abstract MALDI imaging experiments were planned according to fractional factorial design of experiments for the parameters under study. Selected peptide images were evaluated by the chosen quality metric (structure and intensity for a given peak list), and the calculated values were used as an input for the ANOVA. The parameters with the highest impact on the quality were deduced and SOPs recommended.

  8. Colloidal Nanomolybdenum Influence upon the Antioxidative Reaction of Chickpea Plants ( Cicer arietinum L.)

    Science.gov (United States)

    Taran, Nataliya; Batsmanova, Ludmila; Kosyk, Oksana; Smirnov, Oleksandr; Kovalenko, Mariia; Honchar, Liubov; Okanenko, Alexander

    2016-10-01

    The use of colloidal solutions of metals as micronutrients enhances plant resistance to unfavorable environmental conditions and ensures high yields of food crops. The purpose of the study was a comparative evaluation of presowing treatment with nanomolybdenum and microbiological preparation impact upon the development of adaptive responses in chickpea plants. Oxidative processes did not develop in all variants of the experiment but in variants treated with microbial preparation, and joint action of microbial and nanopreparations even declined, as evidenced by the reduction of thiobarbituric acid reactive substances in photosynthetic tissues by 15 %. The activity of superoxide dismutase increased (by 15 %) in variant "nanomolybdenum" and joint action "microbial + nanomolybdenum," but it decreased by 20 % in variants with microbial preparation treatment. The same dependence was observed in changes of catalase activity. Antioxidant status factor, which takes into account the ratio of antioxidant to pro-oxidant, was the highest in variants with joint action of microbial preparation and nanomolybdenum (0.7), the lowest in variants with microbial treatment only (0.1). Thus, the results show that the action of nanoparticles of molybdenum activated antioxidant enzymes and decreased oxidative processes, thus promoting adaptation of plants.

  9. Flow of colloidal suspensions and gels

    Science.gov (United States)

    Zia, Roseanna

    Our recent studies of yield of colloidal gels under shear show that yield in such gels occurs in distinct stages. Under fixed stress, yield follows a finite delay period of slow solid-like creep. Post yield, the gel fluidizes and may undergo long-time viscous flow or, in some cases, may re-solidify. Under imposed strain rate, the transition from equilibrium to long-time flow is characterized by one or more stress overshoots, signifying a yield process here as well. These rheological changes are accompanied by evolution in morphology and dynamics of the gel network. Similar regimes have been observed in gels subjected to gravitational forcing; the gel initially supports its own weight, or perhaps undergoes slow, weak compaction. This may be followed by a sudden transition to rapid compaction or sedimentation. Various models have been put forth to explain these behaviors based on structural evolution, but this detail is difficult to observe in experiment. Here we examine the detailed microstructural evolution and rheology of reversible colloidal gels as they deform under gravity, identifying the critical buoyant force at which yield occurs, the role played by ongoing gel coarsening, and similarities and differences compared to yield under shear. We gratefully acknowledge the support of the NSF XSEDE Computational Resource, the NSF Early CAREER Program, and the Office of Naval Research Young Investigator Program.

  10. Experience and Explanation: Using Videogames to Prepare Students for Formal Instruction in Statistics

    Science.gov (United States)

    Arena, Dylan A.; Schwartz, Daniel L.

    2014-01-01

    Well-designed digital games can deliver powerful experiences that are difficult to provide through traditional instruction, while traditional instruction can deliver formal explanations that are not a natural fit for gameplay. Combined, they can accomplish more than either can alone. An experiment tested this claim using the topic of statistics,…

  11. Experience and Explanation: Using Videogames to Prepare Students for Formal Instruction in Statistics

    Science.gov (United States)

    Arena, Dylan A.; Schwartz, Daniel L.

    2014-01-01

    Well-designed digital games can deliver powerful experiences that are difficult to provide through traditional instruction, while traditional instruction can deliver formal explanations that are not a natural fit for gameplay. Combined, they can accomplish more than either can alone. An experiment tested this claim using the topic of statistics,…

  12. Clinical Boot Camp: An Innovative Simulation Experience to Prepare Nursing Students for Obstetric and Pediatric Clinicals.

    Science.gov (United States)

    Hogewood, Connie; Smith, Tedra; Etheridge, Sherita; Britt, Sylvia

    2015-01-01

    Obstetric and pediatric patients require unique specialized care not included in traditional adult health education. To prepare nursing students for clinical rotations beginning the second week of class, faculty developed an innovative one-day simulation seminar, the OB/PEDS Boot Camp, in which groups of students rotated through six stations of obstetric and pediatric simulation exercises. This article provides insight on the development and implementation of the OB/PEDS Boot Camp.

  13. Evaluating the impact of a pre-rotation workshop on student preparation for clinical advanced pharmacy practice experiences

    Directory of Open Access Journals (Sweden)

    Medina MS

    2008-12-01

    Full Text Available Objectives: This pilot study was designed to evaluate the impact of a pre-rotation workshop (PRW on pharmacy students’ clinical skills and preparation for clinical Advanced Pharmacy Practice Experiences (APPE involving direct patient care. Methods: Randomized controlled trial of an educational intervention with Institutional Review Board approval. PRW activities designed to simulate rotation activities around five competencies, patient charts, medication histories, SOAP notes, patient presentations, and professionalism. Endpoints were evaluated using clinical rotation preceptors’ evaluation of performance and students’ performance on objective structured clinical exams (OSCE.Results: Eight fourth-year students and eight GPA matched controls (20% of the total class were selected to voluntarily participate. The PRW demonstrated a positive impact on students’ clinical skills and preparation for rotations by improving OSCE performance. However, no significant differences were found between groups when comparing preceptor evaluations of skills on rotations. These results are limited by the small sample size, potential OSCE “test-wiseness” effects, lack of OSCE evaluator blinding to study groups, potential case specificity effects due to the limited number of cases used on the OSCE and possible lack of sensitivity of the rotation evaluation tool to capture true differences among the experimental and control group participants.Conclusion: The PRW was successful at advancing students’ clinical skills and preparation for rotations and may be considered as a tool to help bridge didactic to clinical experiences in the Pharm.D. curriculum.

  14. Near-infrared surface-enhanced Raman spectroscopy of chemisorbed compounds on gold colloids

    Science.gov (United States)

    Xu, Hong; Tseng, Ching-Hui; Vickers, Thomas J.; Mann, Charles K.; Schlenoff, Joseph B.

    1994-05-01

    Near-infrared surface-enhanced Raman scattering (SERS) spectra have been measured for strongly chemisorbed compounds, such as 4-mercaptopyridine and thiophenol, on gold colloids in mixed solvents of ethanol and water using a diode laser as an excitation source. From UV-vis spectroscopy, the aggregated gold colloids show a broad absorbance band through the visible to the near-infrared after adding chemisorbing compounds. The absorption maximum is located in the range 750-850 nm, permitting the use of a near-IR source (826 nm) for the first time in SERS of gold colloid systems. The estimated enhancement is on the order of 10 5. Transmission electron microscopy of aggregated gold particles revealed a cluster morphology. The aggregated mixed-solvent colloids were more stable than those prepared in water, and were useful in dissolving compounds with poor water solubility.

  15. Undergraduate surgical nursing preparation and guided operating room experience: A quantitative analysis.

    Science.gov (United States)

    Foran, Paula

    2016-01-01

    The aim of this research was to determine if guided operating theatre experience in the undergraduate nursing curricula enhanced surgical knowledge and understanding of nursing care provided outside this specialist area in the pre- and post-operative surgical wards. Using quantitative analyses, undergraduate nurses were knowledge tested on areas of pre- and post-operative surgical nursing in their final semester of study. As much learning occurs in nurses' first year of practice, participants were re-tested again after their Graduate Nurse Program/Preceptorship year. Participants' results were compared to the model of operating room education they had participated in to determine if there was a relationship between the type of theatre education they experienced (if any) and their knowledge of surgical ward nursing. Findings revealed undergraduates nurses receiving guided operating theatre experience had a 76% pass rate compared to 56% with non-guided or no experience (p < 0.001). Graduates with guided operating theatre experience as undergraduates or graduate nurses achieved a 100% pass rate compared to 53% with non-guided or no experience (p < 0.001). The research informs us that undergraduate nurses achieve greater learning about surgical ward nursing via guided operating room experience as opposed to surgical ward nursing experience alone.

  16. 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.

  17. Potential importance of transition metals in the induction of DNA damage by sperm preparation media.

    Science.gov (United States)

    Aitken, R J; Finnie, J M; Muscio, L; Whiting, S; Connaughton, H S; Kuczera, L; Rothkirch, T B; De Iuliis, G N

    2014-10-10

    What are the mechanisms by which the preparation of spermatozoa on discontinuous density gradients leads to an increase in oxidative DNA damage? The colloidal silicon solutions that are commonly used to prepare human spermatozoa for assisted reproduction technology (ART) purposes contain metals in concentrations that promote free radical-mediated DNA damage. Sporadic reports have already appeared indicating that the use of colloidal silicon-based discontinuous density gradients for sperm preparation is occasionally associated with the induction of oxidative DNA damage. The cause of this damage is however unknown. This study comprised a series of experiments designed to: (i) confirm the induction of oxidative DNA damage in spermatozoa prepared on commercially available colloidal silicon gradients, (ii) compare the levels of damage observed with alterative sperm preparation techniques including an electrophoretic approach and (iii) determine the cause of the oxidative DNA damage and develop strategies for its prevention. The semen samples employed for this analysis involved a cohort of >50 unselected donors and at least three independent samples were used for each component of the analysis. The setting was a University biomedical science laboratory. The major techniques employed were: (i) flow cytometry to study reactive oxygen species generation, lipid peroxidation and DNA damage, (ii) computer-aided sperm analysis to measure sperm movement and (iii) inductively coupled mass spectrometry to determine the elemental composition of sperm preparation media. Oxidative DNA damage is induced in spermatozoa prepared on PureSperm(®) discontinuous colloidal silicon gradients (P media revealed that metal contamination is a relatively constant feature of such products. While the presence of metals, particularly transition metals, may exacerbate the levels of oxidative DNA damage seen in human spermatozoa, the significance of such damage has not yet been tested in suitably

  18. Direct monitoring of molecular recognition processes using fluorescence enhancement at colloid-coated microplates.

    Science.gov (United States)

    Lobmaier, C; Hawa, G; Götzinger, M; Wirth, M; Pittner, F; Gabor, F

    2001-01-01

    Direct monitoring of recognition processes at the molecular level is a valuable tool for studying reaction kinetics to assess affinity constants (e.g. drugs to receptors) and for designing rapid single step immunoassays. Methods currently used to gain information about binding processes predominantly depend on surface plasmon resonance. These systems use excitation with coherent light in attenuated total reflection geometry to obtain discrimination between surface-bound and free molecules in solution. Therefore labeling of the compounds is not necessary, but due to the complexity of the measuring setup the method is rather costly. In this contribution we present a simple method for performing kinetic single step biorecognition assays with fluorophore labeled compounds using the fluorescence enhancement properties of surface bound silver colloids. Silver colloids are bound to standard microplates via silanization of the plastic surface. Fluorophores close to this colloid coated surface show a significant gain in fluorescence compared to fluorophores farther away in the bulk solution. Therefore discrimination between surface bound and free fluorophores is possible and the binding of, for example, fluorophore labeled antibodies to antigens immobilized on the colloid surface results in increasing fluorescence intensity. Utilization of standard microplates makes this method fully compatible with conventional microplate processing and reading devices. Neither excitation with coherent laser light nor ATR geometry is required, the measurement is performed in a standard fluorescence microplate reader in front face geometry with a xenon flash lamp as excitation source. Methods for the preparation of colloid-coated microplates and fluorescence-enhanced biorecognition assays are presented. Additionally the dependence of the system performance on the structure and properties of the metal colloid coated surface is described. A two-component biorecognition model system shows a

  19. Experi mental Study on Preparation of Decellularized Artery Vascular Graftand Transplantation of Carotid Artery Allografts

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    1 IntroductionRemoval of cells may decrease the antigenicity of artery allografts and xenografts~([1~3]). This study was to set up a new process to prepare the decellularized artery grafts. And the feasibility of small diameter decellularized artery allografts in vivo was evaluate. 2 Materials and Methods2.1 Set up a new processA four-step process, including hypotonic, hypertonic solutions and combining with 1% t-octyl-phenoxypolyethoxyethanol (Triton X-100) and 1% sodium dodecyl sulfate (SDS) detergents, w...

  20. Chemistry of the Colloidal Group II-VI Nanocrystal Synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Haitao [Univ. of California, Berkeley, CA (United States)

    2007-05-17

    In the last two decades, the field of nanoscience andnanotechnology has witnessed tremendous advancement in the synthesis andapplication of group II-VI colloidal nanocrystals. The synthesis based onhigh temperature decomposition of organometallic precursors has becomeone of the most successful methods of making group II-VI colloidalnanocrystals. This methodis first demonstrated by Bawendi and coworkersin 1993 to prepare cadmium chalcogenide colloidal quantum dots and laterextended by others to prepare other group II-VI quantum dots as well asanisotropic shaped colloidal nanocrystals, such as nanorod and tetrapod.This dissertation focuses on the chemistry of this type of nanocrystalsynthesis. The synthesis of group II-VI nanocrystals was studied bycharacterizing the molecular structures of the precursors and productsand following their time evolution in the synthesis. Based on theseresults, a mechanism was proposed to account for the 2 reaction betweenthe precursors that presumably produces monomer for the growth ofnanocrystals. Theoretical study based on density functional theorycalculations revealed the detailed free energy landscape of the precursordecomposition and monomerformation pathway. Based on the proposedreaction mechanism, a new synthetic method was designed that uses wateras a novel reagent to control the diameter and the aspect ratio of CdSeand CdS nanorods.

  1. Stable colloids in molten inorganic salts.

    Science.gov (United States)

    Zhang, Hao; Dasbiswas, Kinjal; Ludwig, Nicholas B; Han, Gang; Lee, Byeongdu; Vaikuntanathan, Suri; Talapin, Dmitri V

    2017-02-15

    A colloidal solution is a homogeneous dispersion of particles or droplets of one phase (solute) in a second, typically liquid, phase (solvent). Colloids are ubiquitous in biological, chemical and technological processes, homogenizing highly dissimilar constituents. To stabilize a colloidal system against coalescence and aggregation, the surface of each solute particle is engineered to impose repulsive forces strong enough to overpower van der Waals attraction and keep the particles separated from each other. Electrostatic stabilization of charged solutes works well in solvents with high dielectric constants, such as water (dielectric constant of 80). In contrast, colloidal stabilization in solvents with low polarity, such as hexane (dielectric constant of about 2), can be achieved by decorating the surface of each particle of the solute with molecules (surfactants) containing flexible, brush-like chains. Here we report a class of colloidal systems in which solute particles (including metals, semiconductors and magnetic materials) form stable colloids in various molten inorganic salts. The stability of such colloids cannot be explained by traditional electrostatic and steric mechanisms. Screening of many solute-solvent combinations shows that colloidal stability can be traced to the strength of chemical bonding at the solute-solvent interface. Theoretical analysis and molecular dynamics modelling suggest that a layer of surface-bound solvent ions produces long-ranged charge-density oscillations in the molten salt around solute particles, preventing their aggregation. Colloids composed of inorganic particles in inorganic melts offer opportunities for introducing colloidal techniques to solid-state science and engineering applications.

  2. Stable colloids in molten inorganic salts

    Science.gov (United States)

    Zhang, Hao; Dasbiswas, Kinjal; Ludwig, Nicholas B.; Han, Gang; Lee, Byeongdu; Vaikuntanathan, Suri; Talapin, Dmitri V.

    2017-02-01

    A colloidal solution is a homogeneous dispersion of particles or droplets of one phase (solute) in a second, typically liquid, phase (solvent). Colloids are ubiquitous in biological, chemical and technological processes, homogenizing highly dissimilar constituents. To stabilize a colloidal system against coalescence and aggregation, the surface of each solute particle is engineered to impose repulsive forces strong enough to overpower van der Waals attraction and keep the particles separated from each other. Electrostatic stabilization of charged solutes works well in solvents with high dielectric constants, such as water (dielectric constant of 80). In contrast, colloidal stabilization in solvents with low polarity, such as hexane (dielectric constant of about 2), can be achieved by decorating the surface of each particle of the solute with molecules (surfactants) containing flexible, brush-like chains. Here we report a class of colloidal systems in which solute particles (including metals, semiconductors and magnetic materials) form stable colloids in various molten inorganic salts. The stability of such colloids cannot be explained by traditional electrostatic and steric mechanisms. Screening of many solute–solvent combinations shows that colloidal stability can be traced to the strength of chemical bonding at the solute–solvent interface. Theoretical analysis and molecular dynamics modelling suggest that a layer of surface-bound solvent ions produces long-ranged charge-density oscillations in the molten salt around solute particles, preventing their aggregation. Colloids composed of inorganic particles in inorganic melts offer opportunities for introducing colloidal techniques to solid-state science and engineering applications.

  3. 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).

  4. Chancellor Water Colloids: Characterization and Radionuclide Association

    Energy Technology Data Exchange (ETDEWEB)

    Abdel-Fattah, Amr I. [Los Alamos National Laboratory

    2012-06-18

    Concluding remarks about this paper are: (1) Gravitational settling, zeta potential, and ultrafiltration data indicate the existence of a colloidal phase of both the alpha and beta emitters in the Chancellor water; (2) The low activity combined with high dispersion homogeneity of the Chancellor water indicate that both alpha and beta emitters are not intrinsic colloids; (3) Radionuclides in the Chancellor water, particularly Pu, coexist as dissolved aqueous and sorbed phases - in other words the radionuclides are partitioned between the aqueous phase and the colloidal phase; (4) The presence of Pu as a dissolved species in the aqueous phase, suggests the possibility of Pu in the (V) oxidation state - this conclusion is supported by the similarity of the k{sub d} value of Pu determined in the current study to that determined for Pu(V) sorbed onto smectite colloids, and the similar electrokinetic behavior of the Chancellor water colloids to smectite colloids; (5) About 50% of the Pu(V) is in the aqueous phase and 50% is sorbed on colloids (mass concentration of colloids in the Chancellor water is 0.12 g/L); (6) The k{sub d} of the Pu and the beta emitters (fission products) between aqueous and colloidal phases in the Chancellor water is {approx}8.0 x 10{sup 3} mL/g using two different activity measurement techniques (LSC and alpha spectroscopy); (7) The gravitational settling and size distributions of the association colloids indicate that the properties (at least the physical ones) of the colloids to which the alpha emitters are associated with seem to be different that the properties of the colloids to which the beta emitters are associated with - the beta emitters are associated with very small particles ({approx}50 - 120 nm), while the alpha emitters are associated with relatively larger particles; and (8) The Chancellor water colloids are extremely stable under the natural pH and ionic strength conditions, indicating high potential for transport in the

  5. Synthesis and optical properties of colloidal gold nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen Ngoc Long; Le Van Vu; Chu Dinh Kiem; Sai Cong Doanh; Cao Thi Nguyet; Pham Thi Hang; Nguyen Duy Thien; Luu Manh Quynh [Faculty of Physics, Hanoi University of Science, 334 Nguyen Trai, Thanh Xuan, Hanoi (Viet Nam)], E-mail: longnn@vnu.edu.vn

    2009-09-01

    Colloidal gold nanoparticles (spheres) have been prepared from HAuCl{sub 4} containing aqueous solution by using X-ray irradiation and by chemical reduction method. Gold nanorods were synthesized according to the seed-mediated growth method. The colloidal gold nanoparticles were characterized by using transmission electron microscopy, X-ray diffraction, and UV-VIS absorption spectroscopy. It was found that the concentration of the precursors affects the size of the nanoparticles. In the chemical reduction approach the size of nanoparticles can be controlled by varying amount of trisodium citrate, but in the photochemical method the size of nanoparticles can been controlled by varying the ratio of HAuCl{sub 4} to TX-100 and X-ray irradiation duration. Gold nanorods have been synthesized according to the seed-mediated growth method with two steps. The effect of silver acetate and CTAB on formation of gold nanorods has been studied.

  6. Surface-modified silica colloidal crystals: nanoporous films and membranes with controlled ionic and molecular transport.

    Science.gov (United States)

    Zharov, Ilya; Khabibullin, Amir

    2014-02-18

    Nanoporous membranes are important for the study of the transport of small molecules and macromolecules through confined spaces and in applications ranging from separation of biomacromolecules and pharmaceuticals to sensing and controlled release of drugs. For many of these applications, chemists need to gate the ionic and molecular flux through the nanopores, which in turn depends on the ability to control the nanopore geometry and surface chemistry. Most commonly used nanoporous membrane materials are based on polymers. However, the nanostructure of polymeric membranes is not well-defined, and their surface is hard to modify. Inorganic nanoporous materials are attractive alternatives for polymers in the preparation of nanoporous membranes. In this Account, we describe the preparation and surface modification of inorganic nanoporous films and membranes self-assembled from silica colloidal spheres. These spheres form colloidal crystals with close-packed face centered cubic lattices upon vertical deposition from colloidal solutions. Silica colloidal crystals contain ordered arrays of interconnected three dimensional voids, which function as nanopores. We can prepare silica colloidal crystals as supported thin films on various flat solid surfaces or obtain free-standing silica colloidal membranes by sintering the colloidal crystals above 1000 °C. Unmodified silica colloidal membranes are capable of size-selective separation of macromolecules, and we can surface-modify them in a well-defined and controlled manner with small molecules and polymers. For the surface modification with small molecules, we use silanol chemistry. We grow polymer brushes with narrow molecular weight distribution and controlled length on the colloidal nanopore surface using atom transfer radical polymerization or ring-opening polymerization. We can control the flux in the resulting surface-modified nanoporous films and membranes by pH and ionic strength, temperature, light, and small molecule

  7. Design and Preparation of a Particle Dynamics Space Flight Experiment, SHIVA

    Science.gov (United States)

    Trolinger, James; L'Esperance, Drew; Rangel, Roger; Coimbra, Carlos; Wiltherow, William

    2003-01-01

    ABSTRACT This paper describes the flight experiment, supporting ground science, and the design rationale for project SHIVA (Spaceflight Holography Investigation in a Virtual Apparatus). SHIVA is a fundamental study of particle dynamics in fluids in microgravity. Gravity often dominates the equations of motion of a particle in a fluid, so microgravity provides an ideal environment to study the other forces, such as the pressure and viscous drag and especially the Basset history force. We have developed diagnostic recording methods using holography to save all of the particle field optical characteristics, essentially allowing the experiment to be transferred from space back to earth in what we call the "virtual apparatus" for on-earth microgravity experimentation. We can quantify precisely the three-dimensional motion of sets of particles, allowing us to test and apply new analytical solutions developed by members of the team as reported in the 2001 Conference (Banff, Canada). In addition to employing microgravity to augment the fundamental study of these forces, the resulting data will allow us to quantify and understand the ISS environment with great accuracy. This paper shows how we used both experiment and theory to identify and resolve critical issues and produce an optimal the study. We examined the response of particles of specific gravity from 0.1 to 20, with radii from 0.2 to 2mm. to fluid oscillation at frequencies up to 80 Hz with amplitudes up to 200 microns. To observe some of the interesting effects predicted by the new solutions requires the precise location of the position of a particle in three dimensions. To this end we have developed digital holography algorithms that enable particle position location to a small fraction of a pixel in a CCD array. The spaceflight system will record holograms both on film and electronically. The electronic holograms can be downlinked providing real time data, essentially acting like a remote window into the ISS

  8. Kossel diffraction and conformation investigation of colloidal crystals

    Science.gov (United States)

    Yang, Hao; Wang, Chao; Sun, Zhibin; Cao, Song; Zhai, Guangjie; Li, Ming

    2010-10-01

    Kossel-line diffraction method is an important way to measure the structure of crystals. Colloidal crystal is one of the hotspots on the condensed physics research. The paper investigates the kinetics process of crystallization on several hundreds nanometer particles in aqueous. In order to obtain the diffraction image, a 473nm wavelength laser is used to irradiate samples, and then the Kossel-line image of sample is projected onto the translucent screen and recorded by IEEE 1394 charge coupled device (CCD) cameras. Especially, gravity convection effects can be eliminated under microgravity environment, therefore the research of growth mechanism of colloidal crystals in the space has great scientific significance. The crystallization processes of three kinds of colloidal solution are investigated in the temperature field and electric field by means of the shear-flow assisted. Finally, laser diffraction images and white conformation images can be analyzed for exploring the phase-change rule of colloidal crystals. Besides, parameters can be adjusted online by remote control function in order to improve the flexibility of experiments.

  9. Intermittent filtration of bacteria and colloids in porous media

    Science.gov (United States)

    Auset, Maria; Keller, Arturo A.; Brissaud, François; Lazarova, Valentina

    2005-09-01

    Intermittent filtration through porous media used for water and wastewater treatment can achieve high pathogen and colloid removal efficiencies. To predict the removal of bacteria, the effects of cyclic infiltration and draining events (transient unsaturated flow) were investigated. Using physical micromodels, we visualized the intermittent transport of bacteria and other colloids in unsaturated porous media. Column experiments provided quantitative measurements of the phenomena observed at the pore scale. Tagged Escherichia coli and a conservative tracer (NaI) were introduced in an initial pulse into a 1.5 m sand column. Subsequent hydraulic flushes without tagged bacteria or tracer were repeated every 4 hours for the next 4 days, during which outflow concentrations were monitored. Breakthrough behavior between colloids and dissolved tracer differed significantly, reflecting the differences in transport processes. Advancement of the wetting front remobilized bacteria which were held in thin water films, attached to the air-water interface (AWI), or entrapped in stagnant pore water between gas bubbles. In contrast, the tracer was only remobilized by diffusion from immobile to mobile water. Remobilization led to successive concentration peaks of bacteria and tracer in the effluent but with significant temporal differences. Observations at the pore-scale indicated that the colloids were essentially irreversibly attached to the solid-water interface, which explained to some extent the high removal efficiency of microbes in the porous media. Straining, cluster filtration, cell lysis, protozoa grazing, and bacteriophage parasitism could also contribute to the removal efficiency of bacteria.

  10. Research Progress of Preparation of Mn2+-dopedⅡ- DilutedⅥMagnetic Semiconductor Nanocrystals by Colloidal Method%胶体法制备Mn2掺杂Ⅱ-Ⅵ族稀磁性半导体纳米晶体材料的研究进展

    Institute of Scientific and Technical Information of China (English)

    李瑞; 钟海政; 张泽朋; 杨春和; 李永舫

    2007-01-01

      近年来兴起的稀磁性半导体纳米晶体(DMSNC)是一种新型的半导体材料,由于其优异的光电磁性能得到了国内外研究人员的重视,并取得了快速发展,有望在多个领域得到应用。本文对以胶体法制备的Mn2+掺杂的ZnS、ZnSe、CdS、CdSe 等为代表的Ⅱ-Ⅵ族 DMSNC 的主要进展和掺杂原理进行了综述,指出了现阶段所存在的问题,并对其未来发展进行了展望。%  Diluted magnetic semiconductor nanocrystal (DMSNC) is a new type of semiconductor materials. Because of their special optical, electrical and magnetic properties as well as their promising applications in various aspects, DMSNCs have drawn great attentions and the research on the DMSNCs has developed quickly in recent years. In this article, the main research progress and doping mechanism of the Mn2+dopedⅡ- ZnS,ⅥZnSe, CdS and CdSe DMSNCs prepared by colloidal method we reviewed. In addition, the problems existing at present and the future development of the DMSNCs were also discussed.

  11. Diverse Field Experiences as a Catalyst for Preparing High Quality Early Childhood Teachers

    Science.gov (United States)

    Recchia, Susan L.; Beck, Lisa; Esposito, Ann; Tarrant, Kate

    2009-01-01

    This paper explores the process through which a group of preservice early childhood/early childhood special education students examined their own beliefs about quality teaching and learning within the context of multiple practicum experiences in diverse settings. Students' reflections and actions are illuminated through a careful individual and…

  12. Preparing Ohio's Youth through Occupational Work Adjustment and Occupational Work Experience Programs: Prospects for the Future.

    Science.gov (United States)

    Miller, Aaron J.; Bragg, Debra D.

    A study undertaken to aid administrators in considering program alternatives for administering Occupational Work Adjustment (OWA) and Occupational Work Experience (OWE) programs in Ohio examined the Ohio Department of Education's certification of OWA and OWE teachers in light of the state's new minimum standards for elementary and secondary…

  13. Colloidal nanoparticles trapped by liquid-crystal defect lines: A lattice Monte Carlo simulation

    Science.gov (United States)

    Jose, Regina; Skačej, Gregor; Sastry, V. S. S.; Žumer, Slobodan

    2014-09-01

    Lattice-based Monte Carlo simulations are performed to study a confined liquid crystal system with a topological disclination line entangling a colloidal nanoparticle. In our microscopic study the disclination line is stretched by moving the colloid, as in laser tweezing experiments, which results in a restoring force attempting to minimize the disclination length. From constant-force simulations we extract the corresponding disclination line tension, estimated as ˜50 pN, and observe its decrease with increasing temperature.

  14. Water evaporation in silica colloidal deposits.

    Science.gov (United States)

    Peixinho, Jorge; Lefèvre, Grégory; Coudert, François-Xavier; Hurisse, Olivier

    2013-10-15

    The results of an experimental study on the evaporation and boiling of water confined in the pores of deposits made of mono-dispersed silica colloidal micro-spheres are reported. The deposits are studied using scanning electron microscopy, adsorption of nitrogen, and adsorption of water through attenuated total reflection-infrared spectroscopy. The evaporation is characterized using differential scanning calorimetry and thermal gravimetric analysis. Optical microscopy is used to observe the patterns on the deposits after evaporation. When heating at a constant rate and above boiling temperature, the release of water out of the deposits is a two step process. The first step is due to the evaporation and boiling of the surrounding and bulk water and the second is due to the desorption of water from the pores. Additional experiments on the evaporation of water from membranes having cylindrical pores and of heptane from silica deposits suggest that the second step is due to the morphology of the deposits.

  15. Dynamics of evaporative colloidal patterning

    OpenAIRE

    Kaplan, Cihan Nadir; Wu, Ning; Mandre, Shreyas; Aizenberg, Joanna; Mahadevan, Lakshminarayanan

    2014-01-01

    Drying suspensions often leave behind complex patterns of particulates, as might be seen in the coffee stains on a table. Here, we consider the dynamics of periodic band or uniform solid film formation on a vertical plate suspended partially in a drying colloidal solution. Direct observations allow us to visualize the dynamics of band and film deposition, where both are made of multiple layers of close packed particles. We further see that there is a transition between banding and filming whe...

  16. Thermophoresis of charged colloidal particles.

    Science.gov (United States)

    Fayolle, Sébastien; Bickel, Thomas; Würger, Alois

    2008-04-01

    Thermally induced particle flow in a charged colloidal suspension is studied in a fluid-mechanical approach. The force density acting on the charged boundary layer is derived in detail. From Stokes' equation with no-slip boundary conditions at the particle surface, we obtain the particle drift velocity and the thermophoretic transport coefficients. The results are discussed in view of previous work and available experimental data.

  17. Thermophoresis of charged colloidal particles

    OpenAIRE

    Fayolle, Sébastien; Bickel, Thomas; Würger, Alois

    2008-01-01

    International audience; Thermally induced particle flow in a charged colloidal suspension is studied in a fluid-mechanical approach. The force density acting on the charged boundary layer is derived in detail. From Stokes' equation with no-slip boundary conditions at the particle surface, we obtain the particle drift velocity and the thermophoretic transport coefficients. The results are discussed in view of previous work and available experimental data.

  18. Influence of Humic Acid on the Transport and Deposition of Colloidal Silica under Different Hydrogeochemical Conditions

    Directory of Open Access Journals (Sweden)

    Jingjing Zhou

    2016-12-01

    Full Text Available The transport and deposition of colloids in aquifers plays an important role in managed aquifer recharge (MAR schemes. Here, the processes of colloidal silica transport and deposition were studied by displacing groundwater with recharge water. The results showed that significant amounts of colloidal silica transport occurred when native groundwater was displaced by HA solution. Solution contains varying conditions of ionic strength and ion valence. The presence of humic acid could affect the zeta potential and size of the colloidal silica, which led to obvious colloidal silica aggregation in the divalent ion solution. Humic acid increased colloidal silica transport by formation of non-adsorbing aqueous phase silica–HA complexes. The experimental and modeling results showed good agreement, indicating that the essential physics were accurately captured by the model. The deposition rates were less than 10−8 s−1 in deionized water and monovalent ion solution. Moreover, the addition of Ca2+ and increase of IS resulted in the deposition rates increasing by five orders of magnitude to 10−4 s−1. In all experiments, the deposition rates decreased in the presence of humic acid. Overall, the promotion of humic acid in colloidal silica was strongly associated with changes in water quality, indicating that they should receive greater attention during MAR.

  19. Critical Casimir interactions and colloidal self-assembly in near-critical solvents

    Science.gov (United States)

    Tasios, Nikos; Edison, John R.; van Roij, René; Evans, Robert; Dijkstra, Marjolein

    2016-08-01

    A binary solvent mixture close to critical demixing experiences fluctuations whose correlation length, ξ, diverges as the critical point is approached. The solvent-mediated (SM) interaction that arises between a pair of colloids immersed in such a near-critical solvent can be long-ranged and this so-called critical Casimir interaction is well-studied. How a (dense) suspension of colloids will self-assemble under these conditions is poorly understood. Using a two-dimensional lattice model for the solvent and hard disks to represent the colloids, we perform extensive Monte Carlo simulations to investigate the phase behaviour of this model colloidal suspension as a function of colloid size and wettability under conditions where the solvent reservoir is supercritical. Unlike most other approaches, where the solvent is modelled as an implicit background, our model employs an explicit solvent and treats the suspension as a ternary mixture. This enables us to capture important features, including the pronounced fractionation of the solvent in the coexisting colloidal phases, of this complex system. We also present results for the partial structure factors; these shed light on the critical behaviour in the ternary mixture. The degree to which an effective two-body pair potential description can describe the phase behaviour and structure of the colloidal suspension is discussed briefly.

  20. Surface roughness directed self-assembly of patchy particles into colloidal micelles.

    Science.gov (United States)

    Kraft, Daniela J; Ni, Ran; Smallenburg, Frank; Hermes, Michiel; Yoon, Kisun; Weitz, David A; van Blaaderen, Alfons; Groenewold, Jan; Dijkstra, Marjolein; Kegel, Willem K

    2012-07-03

    Colloidal particles with site-specific directional interactions, so called "patchy particles", are promising candidates for bottom-up assembly routes towards complex structures with rationally designed properties. Here we present an experimental realization of patchy colloidal particles based on material independent depletion interaction and surface roughness. Curved, smooth patches on rough colloids are shown to be exclusively attractive due to their different overlap volumes. We discuss in detail the case of colloids with one patch that serves as a model for molecular surfactants both with respect to their geometry and their interactions. These one-patch particles assemble into clusters that resemble surfactant micelles with the smooth and attractive sides of the colloids located at the interior. We term these clusters "colloidal micelles". Direct Monte Carlo simulations starting from a homogeneous state give rise to cluster size distributions that are in good agreement with those found in experiments. Important differences with surfactant micelles originate from the colloidal character of our model system and are investigated by simulations and addressed theoretically. Our new "patchy" model system opens up the possibility for self-assembly studies into finite-sized superstructures as well as crystals with as of yet inaccessible structures.

  1. 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.

  2. Three-dimensional colloidal lithography.

    Science.gov (United States)

    Nagai, Hironori; Poteet, Austen; Zhang, Xu A; Chang, Chih-Hao

    2017-03-24

    Light interactions with colloidal particles can generate a variety of complex three-dimensional (3D) intensity patterns, which can be utilized for nanolithography. The study of particle-light interactions can add more types of intensity patterns by manipulating key factors. Here we investigate a novel 3D nanolithography technique using colloidal particles under two-beam coherent illuminations. The fabricated 3D nanostructures are hollow, nested within periodic structures, and possess multiple chamber geometry. The effects of incident angles and particle size on the fabricated nanostructures were examined. The relative phase shift between particle position and interference pattern is identified as another significant parameter influencing the resultant nanostructures. A numerical model has been developed to show the evolution of nanostructure geometry with phase shifts, and experimental studies confirm the simulation results. Through the introduction of single colloidal particles, the fabrication capability of Lloyd's mirror interference can now be extended to fabrication of 3D nanostructure with complex shell geometry. The fabricated hollow nanostructures with grating background could find potential applications in the area of photonics, drug delivery, and nanofluidics.

  3. Three-dimensional colloidal lithography

    Science.gov (United States)

    Nagai, Hironori; Poteet, Austen; Zhang, Xu A.; Chang, Chih-Hao

    2017-03-01

    Light interactions with colloidal particles can generate a variety of complex three-dimensional (3D) intensity patterns, which can be utilized for nanolithography. The study of particle–light interactions can add more types of intensity patterns by manipulating key factors. Here we investigate a novel 3D nanolithography technique using colloidal particles under two-beam coherent illuminations. The fabricated 3D nanostructures are hollow, nested within periodic structures, and possess multiple chamber geometry. The effects of incident angles and particle size on the fabricated nanostructures were examined. The relative phase shift between particle position and interference pattern is identified as another significant parameter influencing the resultant nanostructures. A numerical model has been developed to show the evolution of nanostructure geometry with phase shifts, and experimental studies confirm the simulation results. Through the introduction of single colloidal particles, the fabrication capability of Lloyd’s mirror interference can now be extended to fabrication of 3D nanostructure with complex shell geometry. The fabricated hollow nanostructures with grating background could find potential applications in the area of photonics, drug delivery, and nanofluidics.

  4. Sensitivity analyses of a colloid-facilitated contaminant transport model for unsaturated heterogeneous soil conditions.

    Science.gov (United States)

    Périard, Yann; José Gumiere, Silvio; Rousseau, Alain N.; Caron, Jean

    2013-04-01

    effects and the one-at-a-time approach (O.A.T); and (ii), we applied Sobol's global sensitivity analysis method which is based on variance decompositions. Results illustrate that ψm (maximum sorption rate of mobile colloids), kdmc (solute desorption rate from mobile colloids), and Ks (saturated hydraulic conductivity) are the most sensitive parameters with respect to the contaminant travel time. The analyses indicate that this new module is able to simulate the colloid-facilitated contaminant transport. However, validations under laboratory conditions are needed to confirm the occurrence of the colloid transport phenomenon and to understand model prediction under non-saturated soil conditions. Future work will involve monitoring of the colloidal transport phenomenon through soil column experiments. The anticipated outcome will provide valuable information on the understanding of the dominant mechanisms responsible for colloidal transports, colloid-facilitated contaminant transport and, also, the colloid detachment/deposition processes impacts on soil hydraulic properties. References: Šimůnek, J., C. He, L. Pang, & S. A. Bradford, Colloid-Facilitated Solute Transport in Variably Saturated Porous Media: Numerical Model and Experimental Verification, Vadose Zone Journal, 2006, 5, 1035-1047 Šimůnek, J., M. Šejna, & M. Th. van Genuchten, The C-Ride Module for HYDRUS (2D/3D) Simulating Two-Dimensional Colloid-Facilitated Solute Transport in Variably-Saturated Porous Media, Version 1.0, PC Progress, Prague, Czech Republic, 45 pp., 2012.

  5. Experimental studies on the inventory of cement-derived colloids in the pore water of a cementitious backfill material

    Energy Technology Data Exchange (ETDEWEB)

    Wieland, E

    2001-06-01

    The potential role of near-field colloids for the colloid-facilitated migration of radionuclides has stimulated investigations concerning the generation and presence of colloids in the near-field of a repository for low- and intermediate level waste (L/ILW). The highly gas permeable mortar (Nagra designation: mortar M1) is currently favoured as backfill material for the engineered barrier of the planned Swiss L/ILW repository. The cementitious backfill is considered to be a chemical environment with some potential for colloid generation. In a series of batch-style laboratory experiments the physico-chemical processes controlling the inventory of colloids in cement pore water of the backfill were assessed for chemical conditions prevailing in the initial stage of the cement degradation. In these experiments, backfill mortar M1 or quartz, respectively, which may be used as aggregate material for the backfill, were immersed in artificial cement pore water (a NaOH/KOH rich cement fluid). Colloid concentrations in the cement pore water were recorded as a function of time for different experimental settings. The results indicate that a colloid-colloid interaction process (coagulation) controlled the colloid inventory. The mass concentration of dispersed colloids was found to be typically lower than 0.02 ppm in undisturbed batch systems. An upper-bound value was estimated to be 0.1 ppm taking into account uncertainties on the measurements. To assess the potential for colloid generation in a dynamic system, colloid concentrations were determined in the pore water of a column filled with backfill mortar. The chemical conditions established in the mortar column corresponded to conditions observed in the second stage of the cement degradation (a Ca(OH){sub 2{sup -}} controlled cement system). In this dynamic system, the upper-bound value for the colloid mass concentration was estimated to be 0.1 ppm. Implications for radionuclide mobility were deduced taking into account the

  6. Crystallization of DNA-coated colloids.

    Science.gov (United States)

    Wang, Yu; Wang, Yufeng; Zheng, Xiaolong; Ducrot, Étienne; Yodh, Jeremy S; Weck, Marcus; Pine, David J

    2015-06-16

    DNA-coated colloids hold great promise for self-assembly of programmed heterogeneous microstructures, provided they not only bind when cooled below their melting temperature, but also rearrange so that aggregated particles can anneal into the structure that minimizes the free energy. Unfortunately, DNA-coated colloids generally collide and stick forming kinetically arrested random aggregates when the thickness of the DNA coating is much smaller than the particles. Here we report DNA-coated colloids that can rearrange and anneal, thus enabling the growth of large colloidal crystals from a wide range of micrometre-sized DNA-coated colloids for the first time. The kinetics of aggregation, crystallization and defect formation are followed in real time. The crystallization rate exhibits the familiar maximum for intermediate temperature quenches observed in metallic alloys, but over a temperature range smaller by two orders of magnitude, owing to the highly temperature-sensitive diffusion between aggregated DNA-coated colloids.

  7. 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.

  8. Influence of Arousal, Previous Experience, and Age on Surgery Preparation of Same Day of Surgery and In-Hospital Pediatric Patients.

    Science.gov (United States)

    Faust, Jan; Melamed, Barbara G.

    1984-01-01

    Studied two pediatric surgery populations (N=66) to determine differences in retention of preparatory information. Results showed that children exposed to a hospital-relevant film retained more information than those children not prepared regardless of age, IQ, previous experience, sex, and time of film preparation. (LLL)

  9. Preparation and characterization of single crystal samples for high-pressure experiments

    Energy Technology Data Exchange (ETDEWEB)

    Farber, D; Antonangeli, D; Aracne, C; Benterou, J

    2005-10-26

    To date, most research utilizing the diamond anvil cell (DAC) has been conducted with polycrystalline samples, thus the results are limited to addressing average bulk properties. However, experiments on single crystals can yield data on a range of orientation dependent properties such as thermal and electrical conductivity, magnetic susceptibility, elasticity and plasticity. Here we report new procedures to produce extremely high-quality metallic single crystal samples of size compatible with DAC experiments in the Mbar range. So far, we have produced samples of zinc, Al{sub 2}O{sub 3}, cobalt, molybdenum and cerium, and have evaluated the quality of the finished samples with white-light interferometry, synchrotron x-ray diffraction and inelastic x-ray scattering.

  10. Preparing Students for Research: Synthesis of Substituted Chalcones as a Comprehensive Guided-Inquiry Experience

    Science.gov (United States)

    Vyvyan, James R.; Pavia, Donald L.; Lampman, Gary M.; Kriz, George S., Jr.

    2002-09-01

    A guided inquiry experiment involving the synthesis and characterization of substituted benzalacetophenones (chalcones) is described. The chalcones are produced in the aldol condensation of substituted benzaldehydes with substituted acetophenones. Each student is assigned a different target chalcone and conducts online and printed literature searches on the target. After completing the synthesis and purification of their product, the students compare their data with those found in the literature.

  11. Energetic Particle Physics In Fusion Research In Preparation For Burning Plasma Experiments

    Energy Technology Data Exchange (ETDEWEB)

    Gorelenkov, Nikolai N [PPPL

    2013-06-01

    The area of energetic particle (EP) physics of fusion research has been actively and extensively researched in recent decades. The progress achieved in advancing and understanding EP physics has been substantial since the last comprehensive review on this topic by W.W. Heidbrink and G.J. Sadler [1]. That review coincided with the start of deuterium-tritium (DT) experiments on Tokamak Fusion Test reactor (TFTR) and full scale fusion alphas physics studies. Fusion research in recent years has been influenced by EP physics in many ways including the limitations imposed by the "sea" of Alfven eigenmodes (AE) in particular by the toroidicityinduced AEs (TAE) modes and reversed shear Alfven (RSAE). In present paper we attempt a broad review of EP physics progress in tokamaks and spherical tori since the first DT experiments on TFTR and JET (Joint European Torus) including helical/stellarator devices. Introductory discussions on basic ingredients of EP physics, i.e. particle orbits in STs, fundamental diagnostic techniques of EPs and instabilities, wave particle resonances and others are given to help understanding the advanced topics of EP physics. At the end we cover important and interesting physics issues toward the burning plasma experiments such as ITER (International Thermonuclear Experimental Reactor).

  12. Strategies for helping families prepare for birth: experiences from eastern central Uganda

    Directory of Open Access Journals (Sweden)

    Līga Timša

    2015-03-01

    Full Text Available Background: Promotion of birth preparedness and raising awareness of potential complications is one of the main strategies to enhance the timely utilisation of skilled care at birth and overcome barriers to accessing care during emergencies. Objective: This study aimed to investigate factors associated with birth preparedness in three districts of eastern central Uganda. Design: This was a cross-sectional baseline study involving 2,010 women from Iganga [community health worker (CHW strategy], Buyende (vouchers for transport and services, and Luuka (standard care districts who had delivered within the past 12 months. ‘Birth prepared’ was defined as women who had taken all of the following three key actions at least 1 week prior to the delivery: 1 chosen where to deliver from; 2 saved money for transport and hospital costs; and 3 bought key birth materials (a clean instrument to cut the cord, a clean thread to tie the cord, cover sheet, and gloves. Logistical regression was performed to assess the association of various independent variables with birth preparedness. Results: Only about 25% of respondents took all three actions relating to preparing for childbirth, but discrete actions (e.g. financial savings and identification of place to deliver were taken by 75% of respondents. Variables associated with being prepared for birth were: having four antenatal care (ANC visits [adjusted odds ratio (ORA=1.42; 95% confidence interval (CI 1.10–1.83], attendance of ANC during the first (ORA=1.94; 95% CI 1.09–3.44 or second trimester (ORA=1.87; 95% CI 1.09–3.22, and counselling on danger signs during pregnancy or on place of referral (ORA=2.07; 95% CI 1.57–2.74. Other associated variables included being accompanied by one's husband to the place of delivery (ORA=1.47; 95% CI 1.15–1.89, higher socio-economic status (ORA=2.04; 95% CI 1.38–3.01, and having a regular income (ORA=1.83; 95% CI 1.20–2.79. Women from Luuka and Buyende were less

  13. COLLOID RELEASE FROM DIFFERENT SOIL DEPTH

    OpenAIRE

    Gang Chen; Yue Niu; Boya Wang; Kamal Tawfiq

    2013-01-01

    Naturally occurring clay colloidal particles are heavily involved in sediment processes in the subsurface soil. Due to the import ance of these processes in the subsurface environment, the transport of clay colloidal particles has been studied in several disciplines, including soil sciences, petr ology, hydrology, etc. Specifically, in environmental engineering, clay colloid re lease and transport in the sediments have been extensively investigated, which are motiv ated by environmental conce...

  14. Thermophoresis of colloids by mesoscale simulations.

    Science.gov (United States)

    Lüsebrink, Daniel; Yang, Mingcheng; Ripoll, Marisol

    2012-07-18

    The motion of a colloid induced by a temperature gradient is simulated by means of multiparticle collision dynamics, a mesoscale simulation technique. Two algorithms to quantify the thermophoretic behavior are employed and contrasted. The validity of the methods is verified as a function of the temperature gradient, system size, and algorithm parameters. The variation of the solvent-colloid interaction from attractive to purely repulsive interestingly results in the change of the colloid behavior from thermophobic to thermophilic.

  15. Colloidal quantum dots: synthesis, properties and applications

    Science.gov (United States)

    Brichkin, S. B.; Razumov, V. F.

    2016-12-01

    Key recent results obtained in studies of a new class of luminophores, colloidal quantum dots, are analyzed. Modern methods for the synthesis and post-synthetic treatment of colloidal quantum dots that make it possible to achieve record high quantum yield of luminescence and to modify their characteristics for specific applications are considered. Currently important avenues of research on colloidal quantum dots and the problems in and prospects for their practical applications in various fields are discussed. The bibliography includes 272 references.

  16. 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.

  17. 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.

  18. 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.

  19. Cytosolic delivery of materials with endosome-disrupting colloids

    Science.gov (United States)

    Helms, Brett A.; Bayles, Andrea R.

    2016-03-15

    A facile procedure to deliver nanocrystals to the cytosol of live cells that is both rapid and general. The technique employs a unique cationic core-shell polymer colloid that directs nanocrystals to the cytosol of living cells within a few hours of incubation. The present methods and compositions enable a host of advanced applications arising from efficient cytosolic delivery of nanocrystal imaging probes: from single particle tracking experiments to monitoring protein-protein interactions in live cells for extended periods.

  20. Piezoelectric Coatings on Implants : Sample preparation and construction of test-equipment for in vitro experiments

    OpenAIRE

    Olsson, Annakarin

    2005-01-01

    Implants are commonly used for orthopaedic and dental applications. There is however a problem with implants; they have a tendency to get loose after 10-15 years of usage. Bone that is not used will get weaker; this can be concluded from studies of people being immobilised or in microgravity. When an implant is put into bone, the surrounding bone does not experience any deformation and it will resorb. This is called stress shielding. Finally the implant will get loose. To avoid this problem w...

  1. Formation of colloids of the tetravalent uranium under influence of silicate in neutral and low alkaline aqueous systems; Bildung von Kolloiden des tetravalenten Urans unter Einfluss von Silikat in neutralen und schwachalkalischen waessrigen Systemen

    Energy Technology Data Exchange (ETDEWEB)

    Ulbricht, Isabell

    2016-03-30

    This work includes the preparation and characterization of new uranium(IV) colloids which are formed and stabilized in the near neutral pH range and under environmentally relevant conditions. Conclusions on stability behavior and particle size distributions were drawn based on results obtained by dynamic light scattering, zeta potential measurements, as well as ultrafiltration and ultracentrifugation in combination with element analyzes. Spectroscopic methodes confirmed the tetravalent state of uranium in the experiments. Unlike empirical data, it is possible to generate long-term stable uranium(IV) colloids at higher concentrations. By addition of geochemical components such as carbonate and silicate, they are stable and resistant in the near neutral pH range over a long period. It was found that dissolved silica plays an essential role in the preparation of colloids. Colloid-borne uranium(IV) up to a concentration of 10{sup -3} mol/L, corresponding to 0,238 g/L, is stabilized in solutions. This concentration is about three orders of magnitude higher than so far known silicate-free aqueous uranium(IV) colloids. Through the use of different analytical methods (invasive and non-invasive) it could be shown that the resulting uranium(IV) colloids are in the nanoscalar range. A high mobility can be assumed in aquatic systems. Evidence is provided by photon correlation spectroscopy, ultrafiltration, and ultracentrifugation that uranium(IV) can form silicate-containing colloids of a size lower than 20 nm. The particles are generated in near neutral to slightly alkaline solutions containing geochemical relevant components (carbonate, silicate, sodium ions). They remain stable in aqueous suspension over years. Electrostatic repulsion due to a negative zeta potential in the near-neutral to alkaline pH range caused by the silicate stabilizes the uranium(IV) colloids. The isoelectric point of the nanoparticles is shifted towards lower pH values by the silicate. The higher the

  2. Preparation for MoNA/LISA VANDLE ^56Ni(d,n) Experiment at the NSCL

    Science.gov (United States)

    Bergstrom, Z. J.; Kozub, R. L.; Peters, W. A.; Cizewski, J. A.; Howard, M. E.; Bardayan, D. W.; Ikeyama, R.; Paulauskas, S. V.; Madurga, M.; Grzywacz, R.; Deyoung, P. A.; Baumann, T.; Smith, J.; Thoennessen, M.

    2012-10-01

    The rp-process is the explosive nucleosynthesis process in novae by which ions rapidly capture hydrogen nuclei, forming heavy, proton-rich nuclei. Most of the rp-process reactions are believed to pass through the ^56Ni(p,γ)^57Cu reaction which cannot presently be measured directly. An experiment to be performed at the NSCL employs the method of (d,n) proton transfer reactions in inverse kinematics to determine pertinent properties of this reaction via ^56Ni(d,n)^57Cu at 30 MeV/nucleon. The experiment will be carried out using two neutron detector arrays of plastic scintillator bars. The Versatile Array of Neutron Detectors at Low Energy (VANDLE) is able to detect neutrons in the 100 keV to 20 MeV range; however, when used in conjunction with MONA/LISA and the Sweeper detectors at the NSCL, the combined arrays allow for the detection of a wider range of neutron energies. Recently, the trigger logic was tested for the VANDLE-Sweeper coincidences and for the left-right coincidence trigger for MoNA/LISA. Results from these tests will be presented along with details of the approved (d,n) experimental setup.

  3. Optimizing Patient Preparation and Surgical Experience Using eHealth Technology.

    Science.gov (United States)

    Waller, Amy; Forshaw, Kristy; Carey, Mariko; Robinson, Sancha; Kerridge, Ross; Proietto, Anthony; Sanson-Fisher, Rob

    2015-09-01

    With population growth and aging, it is expected that the demand for surgical services will increase. However, increased complexity of procedures, time pressures on staff, and the demand for a patient-centered approach continue to challenge a system characterized by finite health care resources. Suboptimal care is reported in each phase of surgical care, from the time of consent to discharge and long-term follow-up. Novel strategies are thus needed to address these challenges to produce effective and sustainable improvements in surgical care across the care pathway. The eHealth programs represent a potential strategy for improving the quality of care delivered across various phases of care, thereby improving patient outcomes. This discussion paper describes (1) the key functions of eHealth programs including information gathering, transfer, and exchange; (2) examples of eHealth programs in overcoming challenges to optimal surgical care across the care pathway; and (3) the potential challenges and future directions for implementing eHealth programs in this setting. The eHealth programs are a promising alternative for collecting patient-reported outcome data, providing access to credible health information and strategies to enable patients to take an active role in their own health care, and promote efficient communication between patients and health care providers. However, additional rigorous intervention studies examining the needs of potential role of eHealth programs in augmenting patients' preparation and recovery from surgery, and subsequent impact on patient outcomes and processes of care are needed to advance the field. Furthermore, evidence for the benefits of eHealth programs in supporting carers and strategies to maximize engagement from end users are needed.

  4. Analytical pyrolysis experiments of Titan aerosol analogues in preparation for the Cassini Huygens mission

    Science.gov (United States)

    Ehrenfreund, P.; Boon, J. J.; Commandeur, J.; Sagan, C.; Thompson, W. R.; Khare, B.

    1995-01-01

    Comparative pyrolysis mass spectrometric data of Titan aerosol analogs, called 'tholins', are presented. The Titan tholins were produced in the laboratory at Cornell by irradiation of simulated Titan atmospheres with high energy electrons in plasma discharge. Mass-spectrometry measurements were performed at FOM of the solid phase of various tholins by Curie-point pyrolysis Gas-Chromatography/Mass-Spectrometry (GCMS) and by temperature resolved in-source Pyrolysis Mass-Spectrometry to reveal the composition and evolution temperature of the dissociation products. The results presented here are used to further define the ACP (Aerosol Collector Pyrolyser)-GCMS experiment and provide a basis for modelling of aerosol composition on Titan and for the iterpretation of Titan atmosphere data from the Huygens probe in the future.

  5. Mobilization and transport of soil colloids as influenced by texture, organic matter, and structure

    DEFF Research Database (Denmark)

    Vendelboe, Anders Lindblad

    , but via colloid-facilitated transport they may bypass the purification stage and be leached to the groundwater reservoir and via tile drains to surface waters. The main focus of the work presented in this thesis as part of the SOIL-IT-IS project was to increase knowledge about the processes controlling...... mobilization and transport of colloids. This was done using a series of state-of-the-art methods, including end-over-end dispersion measurements of soil aggregates and undisturbed soil cores, and irrigation experiments using undisturbed soil cores. In addition, a novel laser diffraction method was used...... in combination with a wet-dispersion unit proved to be an accurate and highly efficient method for measuring colloid dispersion from aggregates. The method gave highly detailed temporal data, enabling more detailed studies of dispersion kinetics. The contents of water-dispersible colloids measured...

  6. Natural history of colloid cysts of the third ventricle.

    Science.gov (United States)

    Beaumont, Thomas L; Limbrick, David D; Rich, Keith M; Wippold, Franz J; Dacey, Ralph G

    2016-12-01

    outcome variables and defined third ventricle risk zones where colloid cysts can cause obstructive hydrocephalus. No patient with a lesion outside these risk zones presented with obstructive hydrocephalus. The CCRS had significant predictive capacity for symptomatic clinical status (area under the curve [AUC] 0.917) and obstructive hydrocephalus (AUC 0.845). A CCRS ≥ 4 was significantly associated with obstructive hydrocephalus (p < 0.0001, RR 19.4). CONCLUSIONS Patients with incidentally discovered colloid cysts can experience both lesion enlargement and symptom progression or less commonly, contraction and symptom regression. Incidental lesions rarely cause acute obstructive hydrocephalus or sudden neurological deterioration in the absence of antecedent trauma. Nearly one-half of patients with symptomatic colloid cysts present with obstructive hydrocephalus, which has an associated 3.1% risk of death. The CCRS is a simple 5-point clinical tool that can be used to identify symptomatic lesions and stratify the risk of obstructive hydrocephalus. External validation of the CCRS will be necessary before objective surgical indications can be established. Surgical intervention should be considered for all patients with CCRS ≥ 4, as they represent the high-risk subgroup.

  7. Restructuring of colloidal cakes during dewatering.

    Science.gov (United States)

    Madeline, J B; Meireles, M; Bourgerette, C; Botet, R; Schweins, R; Cabane, B

    2007-02-13

    Aqueous suspensions of aggregated silica particles have been dewatered to the point where the colloidal aggregates connect to each other and build a macroscopic network. These wet cakes have been compressed through the application of osmotic pressure. Some cakes offer a strong resistance to osmotic pressure and remain at a low volume fraction of solids; other cakes yield at low applied pressures, achieving nearly complete solid/liquid separation. We used small angle neutron scattering and transmission electron microscopy to determine the processes by which the particles move and reorganize during cake collapse. We found that these restructuring processes follow a general course composed of three stages: (1) at all scales, voids are compressed, with large voids compressed more extensively than smaller ones; the local order remains unchanged; (2) all voids with diameters in the range of 2-20 particle diameters collapse, and a few dense regions (lumps) are formed; and (3) the dense lumps build a rigid skeleton that resists further compression. Depending on the nature of interparticle bonds, some cakes jump spontaneously into stage 3 while others remain stuck in stage 1. To elucidate the relation between bond strength and compression resistance, we have constructed a numerical model of the colloidal network. In this model, particles interact through noncentral forces that are produced by springs attached to their surfaces. Networks made of bonds that break upon stretching evolve through a plastic deformation that reproduces the three stages of restructuring evidenced by the experiments. Networks made of bonds that are fragile jump into stage 3. Networks made of bonds that can be stretched without breaking evolve through elastic compression and restructure only according to stage 1.

  8. On the thermal conductivity of gold nanoparticle colloids.

    Science.gov (United States)

    Shalkevich, Natallia; Escher, Werner; Bürgi, Thomas; Michel, Bruno; Si-Ahmed, Lynda; Poulikakos, Dimos

    2010-01-19

    Nanofluids (colloidal suspensions of nanoparticles) have been reported to display significantly enhanced thermal conductivities relative to those of conventional heat transfer fluids, also at low concentrations well below 1% per volume (Putnam, S. A., et at. J. Appl. Phys. 2006, 99, 084308; Liu, M.-S. L., et al. Int. J. Heat Mass Transfer. 2006, 49; Patel, H. E., et al. Appl. Phys. Lett. 2003, 83, 2931-2933). The purpose of this paper is to evaluate the effect of the particle size, concentration, stabilization method and particle clustering on the thermal conductivity of gold nanofluids. We synthesized spherical gold nanoparticles of different size (from 2 to 45 nm) and prepared stable gold colloids in the range of volume fraction of 0.00025-1%. The colloids were inspected by UV-visible spectroscopy, transmission electron microscope (TEM) and dynamic light scattering (DLS). The thermal conductivity has been measured by the transient hot-wire method (THW) and the steady state parallel plate method (GAP method). Despite a significant search in parameter space no significant anomalous enhancement of thermal conductivity was observed. The highest enhancement in thermal conductivity is 1.4% for 40 nm sized gold particles stabilized by EGMUDE (triethyleneglycolmono-11-mercaptoundecylether) and suspended in water with a particle-concentration of 0.11 vol%.

  9. Recovery and Reutilization of Waste Matter from Coffee Preparation. An Experiment for Environmental Science Courses

    Science.gov (United States)

    Orecchio, Santino

    2001-12-01

    This work is designed as an experience for organic and analytical chemistry laboratories in environmental science courses. Coffee grounds were chosen because they are easily available, they are a fine example of a waste product, and the students are familiar with them. The coffee bean is a source of a number of by-products. By comparing the physicochemical characteristics of coffee oil (from the grounds) with those of common oils, it is found that coffee oil shows similarity to palm oil. We hydrolysed the coffee oil and obtained a soap that had good detergent and foaming properties similar to olive oil soap or commercial products. Another beneficial aspect of the coffee bean results from the high content in organic matter (C = 48.9%) of the degreased coffee grounds, which allows their utilization to improve the fertility of soils. The total nitrogen content of the residue is higher than that of many composts and is similar to the nitrogen content of some commercial products employed for house plants. The economical, technical, and environmental advantages that frequently can derive from the recovery of some by-products of foods and beverages, such as the coffee grounds in this example, are evident.

  10. Preparing beginning reading teachers: An experimental comparison of initial early literacy field experiences.

    Science.gov (United States)

    Al Otaiba, Stephanie; Lake, Vickie E; Greulich, Luana; Folsom, Jessica S; Guidry, Lisa

    2012-01-01

    This randomized-control trial examined the learning of preservice teachers taking an initial Early Literacy course in an early childhood education program and of the kindergarten or first grade students they tutored in their field experience. Preservice teachers were randomly assigned to one of two tutoring programs: Book Buddies and Tutor Assisted Intensive Learning Strategies (TAILS), which provided identical meaning-focused instruction (shared book reading), but differed in the presentation of code-focused skills. TAILS used explicit, scripted lessons, and the Book Buddies required that code-focused instruction take place during shared book reading. Our research goal was to understand which tutoring program would be most effective in improving knowledge about reading, lead to broad and deep language and preparedness of the novice preservice teachers, and yield the most successful student reading outcomes. Findings indicate that all pre-service teachers demonstrated similar gains in knowledge, but preservice teachers in the TAILS program demonstrated broader and deeper application of knowledge and higher self-ratings of preparedness to teach reading. Students in both conditions made similar comprehension gains, but students tutored with TAILS showed significantly stronger decoding gains.

  11. The hydrodynamics of colloidal gelation.

    Science.gov (United States)

    Varga, Zsigmond; Wang, Gang; Swan, James

    2015-12-14

    Colloidal gels are formed during arrested phase separation. Sub-micron, mutually attractive particles aggregate to form a system spanning network with high interfacial area, far from equilibrium. Models for microstructural evolution during colloidal gelation have often struggled to match experimental results with long standing questions regarding the role of hydrodynamic interactions. In nearly all models, these interactions are neglected entirely. In the present work, we report simulations of gelation with and without hydrodynamic interactions between the suspended particles executed in HOOMD-blue. The disparities between these simulations are striking and mirror the experimental-theoretical mismatch in the literature. The hydrodynamic simulations agree with experimental observations, however. We explore a simple model of the competing transport processes in gelation that anticipates these disparities, and conclude that hydrodynamic forces are essential. Near the gel boundary, there exists a competition between compaction of individual aggregates which suppresses gelation and coagulation of aggregates which enhances it. The time scale for compaction is mildly slowed by hydrodynamic interactions, while the time scale for coagulation is greatly accelerated. This enhancement to coagulation leads to a shift in the gel boundary to lower strengths of attraction and lower particle concentrations when compared to models that neglect hydrodynamic interactions. Away from the gel boundary, differences in the nearest neighbor distribution and fractal dimension persist within gels produced by both simulation methods. This result necessitates a fundamental rethinking of how dynamic, discrete element models for gelation kinetics are developed as well as how collective hydrodynamic interactions influence the arrest of attractive colloidal dispersions.

  12. 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

  13. 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.

  14. [Relative bioavailability of glucosamine after oral, intramuscular and transdermal administration of hondroxid maximum preparation in experiment].

    Science.gov (United States)

    Yasso, B; Li, Y; Alexander, A; Mel'nikova, N B; Mukhina, I V

    2014-01-01

    A comparison of the relative bioavailability and intensity of penetration of glucosamine sulfate in oral, injection and topical administration of the dosage form Hondroxid Maximum as a cream containing micellar system for transdermal delivery of glucosamine in the experiment by Sprague-Dawley rats was carried out. On the base on the pharmacokinetic profiles data of glucosamine in rat blood plasma with daily administration in 3 times a day for 1 week by cream Hondroxid Maximum 400 mg/kg and the single injection solution of 4% Glucosamine sulfate 400 mg/kg was found that the relative bioavailability was 61.6%. Calculated penetration rate of glucosamine in the plasma through the rats skin in 4 hours, equal to 26.9 μg/cm2 x h, and the penetration of glucosamine through the skin into the plasma after a single dose of cream in 4 hours was 4.12%. Comparative analysis of literature and experimental data and calculations based on them suggest that medicine Hondroxid Maximum, cream with transdermal glucosamine complex in the treatment in accordance with the instructions can provide an average concentration of glucosamine in the synovial fluid of an inflamed joint in the range (0.7 - 1.5) μg/ml, much higher than the concentration of endogenous glucosamine human synovial joint fluid (0.02 - 0.07 μg/ml). By theoretical calculations taking into account experimental data it is shown that the medicine Hondroxid Maximum can reach the bioavailability level of the modern injection forms and exceed the bioavailability level of modern oral forms of glucosamine up to 2 times.

  15. Thermodynamic perturbation theory for self assembling mixtures of multi - patch colloids and colloids with spherically symmetric attractions

    OpenAIRE

    Marshall, B. D.; Chapman, W. G.

    2013-01-01

    In this paper we extend our previous theory [B. D. Marshall and W.G. Chapman, J. Chem. Phys. 139, 104904 (2013)] for mixtures of single patch colloids (p colloids) and colloids with spherically symmetric attractions (s colloids) to the case that the p colloids can have multiple patches. The theory is then applied to the case of a binary mixture of bi-functional p colloids which have an A and B type patch and s colloids which are not attracted to other s colloids and are attracted to only patc...

  16. Thermodynamic perturbation theory for self assembling mixtures of multi - patch colloids and colloids with spherically symmetric attractions

    OpenAIRE

    Marshall, B. D.; Chapman, W G

    2013-01-01

    In this paper we extend our previous theory [B. D. Marshall and W.G. Chapman, J. Chem. Phys. 139, 104904 (2013)] for mixtures of single patch colloids (p colloids) and colloids with spherically symmetric attractions (s colloids) to the case that the p colloids can have multiple patches. The theory is then applied to the case of a binary mixture of bi-functional p colloids which have an A and B type patch and s colloids which are not attracted to other s colloids and are attracted to only patc...

  17. Tethered polymer chains : surface chemistry and their impact on colloidal and surface properties

    NARCIS (Netherlands)

    Currie, EPK; Norde, W; Stuart, Martien A. Cohen

    2003-01-01

    In this review the grafting of polymer chains to solid supports or interfaces and the subsequent impact on colloidal properties is examined. We start by examining theoretical models for densely grafted polymers (brushes), experimental techniques for their preparation and the properties of the ensuin

  18. Tethered polymer chains: surface chemistry and their impact on colloidal and surface properties

    NARCIS (Netherlands)

    Currie, E.P.K.; Norde, W.; Cohen Stuart, M.A.

    2003-01-01

    In this review the grafting of polymer chains to solid supports or interfaces and the subsequent impact on colloidal properties is examined. We start by examining theoretical models for densely grafted polymers (brushes), experimental techniques for their preparation and the properties of the ensuin

  19. Highly luminescent CdTe/CdSe colloidal heteronanocrystals with temperature-dependent emission color

    NARCIS (Netherlands)

    Chin, P.T.K.; de Mello Donega, C.; van Bavel, S.S.; Meskers, S.C.J.; Sommerdijk, N.A.J.M.; Jansen, R.A.J.

    2007-01-01

    In this work we present the preparation of highly luminescent anisotropic CdTe/CdSe colloidal heteronanocrystals. The reaction conditions used (low temperature, slow precursor addition, and surfactant composition) resulted in a tunable shape from prolate to branched CdTe/CdSe nanocrystals. Upon CdSe

  20. Experimental evidence of colloids and nanoparticles presence from 25 waste leachates

    Energy Technology Data Exchange (ETDEWEB)

    Hennebert, Pierre, E-mail: pierre.hennebert@ineris.fr [INERIS – Institut National de l’Environnement Industriel et des Risques, Domaine du Petit Arbois BP33, F-13545 Aix-en-Provence (France); Avellan, Astrid; Yan, Junfang [INERIS – Institut National de l’Environnement Industriel et des Risques, Domaine du Petit Arbois BP33, F-13545 Aix-en-Provence (France); Aguerre-Chariol, Olivier [INERIS, Parc Technologique ALATA, BP No. 2, 60550 Verneuil en Halatte (France)

    2013-09-15

    Highlights: • This work is the first assessment of colloids in waste leachates. • Analytical methods are proposed and discussed. • All the waste have at least one element in colloidal form, and some elements are always colloidal. • Man-made nanoparticles are observed. • It can change the interpretation of leachate elemental concentration. - Abstract: The potential colloids release from a large panel of 25 solid industrial and municipal waste leachates, contaminated soil, contaminated sediments and landfill leachates was studied. Standardized leaching, cascade filtrations and measurement of element concentrations in the microfiltrate (MF) and ultrafiltrate (UF) fraction were used to easily detect colloids potentially released by waste. Precautions against CO{sub 2} capture by alkaline leachates, or bacterial re-growth in leachates from wastes containing organic matter should be taken. Most of the colloidal particles were visible by transmission electron microscopy with energy dispersion spectrometry (TEM–EDS) if their elemental MF concentration is greater than 200 μg l{sup −1}. If the samples are dried during the preparation for microscopy, neoformation of particles can occur from the soluble part of the element. Size distribution analysis measured by photon correlation spectroscopy (PCS) were frequently unvalid, particularly due to polydispersity and/or too low concentrations in the leachates. A low sensitivity device is required, and further improvement is desirable in that field. For some waste leachates, particles had a zeta potential strong enough to remain in suspension. Mn, As, Co, Pb, Sn, Zn had always a colloidal form (MF concentration/UF concentration > 1.5) and total organic carbon (TOC), Fe, P, Ba, Cr, Cu, Ni are partly colloidal for more than half of the samples). Nearly all the micro-pollutants (As, Ba, Co, Cr, Cu, Mo, Ni, Pb, Sb, Sn, V and Zn) were found at least once in colloidal form greater than 100 μg l{sup −1}. In particular

  1. Colloid transport in dual-permeability media

    Science.gov (United States)

    It has been widely reported that colloids can travel faster and over longer distances in natural structured porous media than in uniform structureless media used in laboratory studies. The presence of preferential pathways for colloids in the subsurface environment is of concern because of the incre...

  2. Colloidal iron(III) pyrophosphate particles

    NARCIS (Netherlands)

    Rossi, L.; Velikov, K. P.; Philipse, A.P.

    2014-01-01

    Ferric pyrophosphate is a widely used material in the area of mineral fortification but its synthesis and properties in colloidal form are largely unknown. In this article, we report on the synthesis and characterisation of colloidal iron(III) pyrophosphate particles with potential for application a

  3. From the Great State to the Great Beyond: A Case Study of How the Study Abroad Experience Prepares Accounting Students to Work in a Global Economy

    Science.gov (United States)

    Pernsteiner, Aimee

    2013-01-01

    The purpose of this study was to understand the study abroad experience, as it relates to employment, from multiple perspectives in order to gain insight into how the study abroad experience prepares accounting students to work in a global economy. Studying abroad has been recognized at the national level as an important component to…

  4. From the Great State to the Great Beyond: A Case Study of How the Study Abroad Experience Prepares Accounting Students to Work in a Global Economy

    Science.gov (United States)

    Pernsteiner, Aimee

    2013-01-01

    The purpose of this study was to understand the study abroad experience, as it relates to employment, from multiple perspectives in order to gain insight into how the study abroad experience prepares accounting students to work in a global economy. Studying abroad has been recognized at the national level as an important component to…

  5. Interaction of chiral rafts in self-assembled colloidal membranes

    Science.gov (United States)

    Xie, Sheng; Hagan, Michael F.; Pelcovits, Robert A.

    2016-03-01

    Colloidal membranes are monolayer assemblies of rodlike particles that capture the long-wavelength properties of lipid bilayer membranes on the colloidal scale. Recent experiments on colloidal membranes formed by chiral rodlike viruses showed that introducing a second species of virus with different length and opposite chirality leads to the formation of rafts—micron-sized domains of one virus species floating in a background of the other viruses [Sharma et al., Nature (London) 513, 77 (2014), 10.1038/nature13694]. In this article we study the interaction of such rafts using liquid crystal elasticity theory. By numerically minimizing the director elastic free energy, we predict the tilt angle profile for both a single raft and two rafts in a background membrane, and the interaction between two rafts as a function of their separation. We find that the chiral penetration depth in the background membrane sets the scale for the range of the interaction. We compare our results with the experimental data and find good agreement for the strength and range of the interaction. Unlike the experiments, however, we do not observe a complete collapse of the data when rescaled by the tilt angle at the raft edge.

  6. Structural transitions in condensed colloidal virus phases

    Science.gov (United States)

    Schmidt, Nathan; Barr, Steve; Udit, Andrew; Gutierrez, Leonardo; Nguyen, Thanh; Finn, M. G.; Luijten, Erik; Wong, Gerard

    2010-03-01

    Analogous to monatomic systems colloidal phase behavior is entirely determined by the interaction potential between particles. This potential can be tuned using solutes such as multivalent salts and polymers with varying affinity for the colloids to create a hierarchy of attractions. Bacteriophage viruses are a naturally occurring type of colloidal particle with characteristics difficult to achieve by laboratory synthesis. They are monodisperse, nanometers in size, and have heterogeneous surface charge distributions. We use the MS2 and Qbeta bacteriophages (diameters 27-28nm) to understand the interplay between different attraction mechanisms on nanometer-sized colloids. Small Angle X-ray Scattering (SAXS) is used to characterize the inter-particle interaction between colloidal viruses using several polymer species and different salt types.

  7. Self-assembly of DNA-functionalized colloids

    Directory of Open Access Journals (Sweden)

    P.E. Theodorakis

    2015-06-01

    Full Text Available Colloidal particles grafted with single-stranded DNA (ssDNA chains can self-assemble into a number of different crystalline structures, where hybridization of the ssDNA chains creates links between colloids stabilizing their structure. Depending on the geometry and the size of the particles, the grafting density of the ssDNA chains, and the length and choice of DNA sequences, a number of different crystalline structures can be fabricated. However, understanding how these factors contribute synergistically to the self-assembly process of DNA-functionalized nano- or micro-sized particles remains an intensive field of research. Moreover, the fabrication of long-range structures due to kinetic bottlenecks in the self-assembly are additional challenges. Here, we discuss the most recent advances from theory and experiment with particular focus put on recent simulation studies.

  8. Nonequilibrium condensation and coarsening of field-driven dipolar colloids.

    Science.gov (United States)

    Jäger, Sebastian; Schmidle, Heiko; Klapp, Sabine H L

    2012-07-01

    In colloidal suspensions, self-organization processes can be easily fueled by external fields. Here we consider monolayers of particles with permanent dipole moments that are driven by rotating external fields. In recent experiments, it has been shown that the particles in such systems self-organize into two-dimensional clusters. Here we report results from a computer simulation study of these pattern forming systems. Specifically, we employ Langevin dynamics simulations, Brownian dynamics simulations that include hydrodynamic interactions, and Wang-Landau Monte Carlo simulations of soft spheres interacting via dipolar potentials. We investigate at which field strengths and frequencies clusters form and explore the influence of hydrodynamic interactions. We also examine the phase behavior of the equilibrium system resulting from a time average of the colloidal interactions in the rotating field. In this way we demonstrate that the clustering described in the driven system arises from a first-order phase transition between a vapor and a condensed phase.

  9. Controlled Levitation of Colloids through Direct Current Electric Fields.

    Science.gov (United States)

    Silvera Batista, Carlos A; Rezvantalab, Hossein; Larson, Ronald G; Solomon, Michael J

    2017-07-07

    We report the controlled levitation of surface-modified colloids in direct current (dc) electric fields at distances as far as 75 μm from an electrode surface. Instead of experiencing electrophoretic deposition, colloids modified through metallic deposition or the covalent bonding of poly(ethylene glycol) (PEG) undergo migration and focusing that results in levitation at these large distances. The levitation is a sensitive function of the surface chemistry and magnitude of the field, thus providing the means to achieve control over the levitation height. Experiments with particles of different surface charge show that levitation occurs only when the absolute zeta potential is below a threshold value. An electrodiffusiophoretic mechanism is proposed to explain the observed large-scale levitation.

  10. Glassy Spin Dynamics in Geometrically Frustrated Buckled Colloidal Crystals

    Science.gov (United States)

    Zhou, Di; Wang, Feng; Li, Bo; Lou, Xiaojie; Han, Yilong

    2017-04-01

    Geometrical frustration arises when the lattice geometry prevents local interaction energies from minimizing simultaneously. Whether and how geometrically frustrated spins or charges in clean crystals exhibit glassy dynamics remain elusive due to the lack of measurements on microscopic dynamics. Here, we employ buckled monolayer colloidal crystals to mimic frustrated antiferromagnetic Ising spins on triangular lattices and measure single-spin dynamics using video microscopy. Both attractive and repulsive colloidal crystals buckled into zigzag stripes with glassy dynamics at low effective temperatures in experiment and simulation. The simple local spin configurations enable uncovering correlations among structure, dynamics, and soft vibrational modes. Machine learning analysis further reveals facilitated dynamics to be an important mechanism of structural relaxation. Moreover, our simulation reveals a similar structure and dynamics in lattice Coulomb liquids. Hence, spin-lattice coupling and long-range interaction can similarly lift degeneracy, induce a rugged landscape, and, thus, produce glassy dynamics.

  11. Relating Brownian motion to diffusion with superparamagnetic colloids

    Science.gov (United States)

    Darras, A.; Fiscina, J.; Vandewalle, N.; Lumay, G.

    2017-04-01

    An original experiment is introduced that allows students to relate the Brownian motion of a set of superparamagnetic colloidal particles to their macroscopic diffusion. An external and constant magnetic field is first applied to the colloidal suspension so that the particles self-organize into chains. When the magnetic field is removed, the particles then freely diffuse from their positions in the chain, starting from the same coordinate on the axis perpendicular to the initial chain. This configuration thus enables an observer to study the one dimensional diffusion process, while also observing the underlying Brownian motion of the microscopic particles. Moreover, by studying the evolution of the particle distribution, a measurement of the diffusion coefficient can be obtained. In addition, by repeating this measurement with fluids of various viscosities, the Stokes-Einstein relation may be illustrated.

  12. USING COLLOIDAL LAYERED DOUBLE HYDROXIDES AS CATIONICMICROPARTICULATE COMPONENT

    Institute of Scientific and Technical Information of China (English)

    SonglinWang; WenxiaLiu

    2004-01-01

    Layered double hydroxides consisting of layers withcationic charges may be potential candidates ofcationic microparticles forming synergetic retentioneffect with anionic polyacrylamide. In this work, thelayered double hydroxides with various molar ratiosof Mg/AI were synthesized by co-precipitation ofmagnesium chloride and aluminum chloride and pep-tized by intense washing with water. The chemicalformula, particle size, Zeta potential of the layereddouble hydroxide were analyzed. It was found thatpositively charged magnesium aluminum hydroxidewith particle diameter in nanoparticle size could beprepared. The Zeta potential and particle size varywith the feed molar ratio of Mg/A1 and the peptizingprocess, respectively. The Zeta potential is also pHdependent. The retention experiments carried out onDDJ show that when used together with anionic poly-acrylamide, the positively charged colloidal doublehydroxide greatly improves the retention of reedpulps. The chemical formula, particle size and Zetapotential of the colloidal double hydroxide all affectits retention behavior.

  13. Diffusion of organic colloids in compacted bentonite. The influence of ionic strength on molecular size and transport capacity of the colloids

    Energy Technology Data Exchange (ETDEWEB)

    Wold, S.; Eriksen, Trygve E. [Royal Inst. of Tech., Stockholm (Sweden)

    2000-09-01

    Diffusion of radionuclides in compacted bentonite can be affected by inorganic and organic colloids if the radionuclides form complexes with the colloids. Formation and mobility of the colloid-radionuclide complexes will be governed by the properties of the colloids as well as the competition between complexation and sorption of the radionuclides on bentonite. This report presents the results of experiments with organic colloids humic acid (HA) and lignosulfonate (LS). The aim of the experiments has been to describe the HA and LS properties: size distribution, acidity, sorption on bentonite, diffusivity in compacted bentonite, complexation with strontium, and diffusion of strontium in bentonite in the presence of HA. This study indicates that the diffusion of cationic radionuclides like Sr{sup 2+} is not affected by the presence of HA in high ionic strength solution. In 0.1 M NaClO{sub 4} solution, HA is most probably not available for complexation due to coiling and shielding of the negative sites.

  14. Stable colloids in molten inorganic salts

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hao; Dasbiswas, Kinjal; Ludwig, Nicholas B.; Han, Gang; Lee, Byeongdu; Vaikuntanathan, Suri; Talapin, Dimitri V.

    2017-02-16

    A colloidal solution is a homogeneous dispersion of particles or droplets of one phase (solute) in a second, typically liquid, phase (solvent). Colloids are ubiquitous in biological, chemical and technological processes1, 2, homogenizing highly dissimilar constituents. To stabilize a colloidal system against coalescence and aggregation, the surface of each solute particle is engineered to impose repulsive forces strong enough to overpower van der Waals attraction and keep the particles separated from each other2. Electrostatic stabilization3, 4 of charged solutes works well in solvents with high dielectric constants, such as water (dielectric constant of 80). In contrast, colloidal stabilization in solvents with low polarity, such as hexane (dielectric constant of about 2), can be achieved by decorating the surface of each particle of the solute with molecules (surfactants) containing flexible, brush-like chains2, 5. Here we report a class of colloidal systems in which solute particles (including metals, semiconductors and magnetic materials) form stable colloids in various molten inorganic salts. The stability of such colloids cannot be explained by traditional electrostatic and steric mechanisms. Screening of many solute–solvent combinations shows that colloidal stability can be traced to the strength of chemical bonding at the solute–solvent interface. Theoretical analysis and molecular dynamics modelling suggest that a layer of surface-bound solvent ions produces long-ranged charge-density oscillations in the molten salt around solute particles, preventing their aggregation. Colloids composed of inorganic particles in inorganic melts offer opportunities for introducing colloidal techniques to solid-state science and engineering applications.

  15. Colloid-Associated Radionuclide Concentration Limits: ANL

    Energy Technology Data Exchange (ETDEWEB)

    C. Mertz

    2000-12-21

    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&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.

  16. Diffusion in active magnetic colloids

    Energy Technology Data Exchange (ETDEWEB)

    Taukulis, R.; Cebers, A., E-mail: aceb@tesla.sal.lv

    2014-11-15

    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.

  17. Quil A-lipid powder formulations releasing ISCOMs and related colloidal structures upon hydration.

    Science.gov (United States)

    Demana, Patrick H; Davies, Nigel M; Hook, Sarah; Rades, Thomas

    2005-03-02

    The aim of the present study was to prepare solid Quil A-cholesterol-phospholipid formulations (as powder mixtures or compressed to pellets) by physical mixing or by freeze-drying of aqueous dispersions of these components in ratios that allow spontaneous formation of ISCOMs and other colloidal structures upon hydration. The effect of addition of excess cholesterol to the lipid mixtures on the release of a model antigen (PE-FITC-OVA) from the pellets was also investigated. Physical properties were evaluated by X-ray powder diffractometry (XPRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and polarized light microscopy (PLM). Characterization of aqueous colloidal dispersions was performed by negative staining transmission electron microscopy (TEM). Physically mixed powders (with or without PE-FITC-OVA) and pellets prepared from the same powders did not spontaneously form ISCOM matrices and related colloidal structures such as worm-like micelles, ring-like micelles, lipidic/layered structures and lamellae (hexagonal array of ring-like micelles) upon hydration as expected from the pseudo-ternary diagram for aqueous mixtures of Quil A, cholesterol and phospholipid. In contrast, spontaneous formation of the expected colloids was demonstrated for the freeze-dried lipid mixtures. Pellets prepared by compression of freeze-dried powders released PE-FITC-OVA slower than those prepared from physically mixed powders. TEM investigations revealed that the antigen was released in the form of colloidal particles (ISCOMs) from pellets prepared by compression of freeze-dried powders. The addition of excess cholesterol slowed down the release of antigen. The findings obtained in this study are important for the formulation of solid Quil A-containing lipid articles as controlled particulate adjuvant containing antigen delivery systems.

  18. Fluid-fluid demixing curves for colloid-polymer mixtures in a random colloidal matrix

    Science.gov (United States)

    Annunziata, Mario Alberto; Pelissetto, Andrea

    2011-12-01

    We study fluid-fluid phase separation in a colloid-polymer mixture adsorbed in a colloidal porous matrix close to the θ point. For this purpose we consider the Asakura-Oosawa model in the presence of a quenched matrix of colloidal hard spheres. We study the dependence of the demixing curve on the parameters that characterize the quenched matrix, fixing the polymer-to-colloid size ratio to 0.8. We find that, to a large extent, demixing curves depend only on a single parameter f, which represents the volume fraction which is unavailable to the colloids. We perform Monte Carlo simulations for volume fractions f equal to 40% and 70%, finding that the binodal curves in the polymer and colloid packing-fraction plane have a small dependence on disorder. The critical point instead changes significantly: for instance, the colloid packing fraction at criticality increases with increasing f. Finally, we observe for some values of the parameters capillary condensation of the colloids: a bulk colloid-poor phase is in chemical equilibrium with a colloid-rich phase in the matrix.

  19. Aqueous colloids of graphene oxide nanosheets by exfoliation of graphite oxide without ultrasonication

    Indian Academy of Sciences (India)

    Tian-You Zhang; Dong Zhang

    2011-02-01

    Aqueous colloids of graphene oxide nanosheets were produced from exfoliation of graphite oxide using a magnetic stirrer and heat treatment in the absence of ultrasonication. Laser particle measurements showed that the particle size distribution of graphite oxide dispersed in de-ionized water was significantly influenced by treatment time indicating an increasing exfoliation level of graphite oxide. Atomic force microscopy (AFM) confirmed that single-layer graphene oxide nanosheets with a thickness of ∼1 nm were obtained after 72 h of magnetic stirring and heat treatment. These findings provide a new methodology for preparation of single-layer graphene oxide nanosheet colloids.

  20. Porous nickel coatings on steel tubes formed by aqueous colloidal processing

    Energy Technology Data Exchange (ETDEWEB)

    Ferrari, B.; Sanchez-Herencia, A.J.; Moreno, R. [Instituto de Ceramica y Vidrio, CSIC, Carretera de Valencia Km. 24,300, Arganda del Rey, E-28500 Madrid (Spain)

    2002-09-01

    A main goal in the manufacture of composite materials is the possibility of applying the colloidal approach to powder metallurgy. Here porous nickel coatings have been prepared in the inner walls of steel tubes by a simple, low-cost colloidal process. Coatings treated at 650 C show good adhesion to the steel surface and a higher porosity that bulk bodies, as desired for manufacturing inner linings on long steel tubes such as those used for heat-exchange applications. (Abstract Copyright [2002], Wiley Periodicals, Inc.)

  1. Adsorption and colloidal behaviour of traces of tellurium(IV) and aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Maruyama, Y.; Yamaashi, Y.

    1985-08-01

    Various NaCl solutions containing traces of tellurium(IV) were prepared. The effects of tellurium(IV) concentration and pH on the adsorption of tellurium(IV) on filter paper were studied by filtration method. The effects of NaCl concentration, tellurium(IV) concentration and pH on the formation of a colloid were also studied by ultracentrifugation and ultrafiltration methods. It was found that tellurium(IV) at concentrations below about 10sup(-10)M in neutral NaCl solutions is adsorbed on filter paper and shows colloidal behaviour. (author). 4 refs.; 7 figs.

  2. Sorption Behavior of Strontium-85 Onto Colloids of Silica and Smectite

    Energy Technology Data Exchange (ETDEWEB)

    Lu, N.; Triay, I.R.; Mason, C.F.V.; Longmire, P.A.

    1998-11-10

    Strontium-90 is one of the sizable radioactive contaminants found in DP Canyon at Los Alamos, New Mexico. Radioactive surveys found the {sup 90}Sr is present in surface and groundwater in DP Canyon and Los Alamos Canyon. Colloids may influence the transport of this radionuclide in surface water and groundwater environments in both canyons. In this study, we investigated the sorption/desorption behavior of Sr on colloids of smectite and silica. Laboratory batch sorption experiments were conducted using {sup 85}Sr as a surrogate to {sup 90}Sr. Groundwater, collected from DP Canyon and from Well J-13 at Yucca Mountain, Nevada, and deionized water were used in this study. Our results show that 92% to 100% of {sup 85}Sr was rapidly adsorbed onto smectite colloids in all three waters. The concentrations of Ca{sup 2+} significantly influence the adsorption of {sup 85}Sr onto silica colloids. Desorption of {sup 85}Sr from smectite colloids is much slower than the sorption process. Desorption of {sup 85}Sr from silica colloids was rapid in DP groundwater and slow using J-13 groundwater and deionized water.

  3. Simulation of the self-assembly of colloidal droplets in a micro-channel

    Science.gov (United States)

    Ge, Zhouyang; Brandt, Luca

    2016-11-01

    In colloidal sciences, much progress has been made on the synthesis of complex building blocks mimicking molecular structures to elaborate innovative materials. The basic elements of such colloidal molecules are particles or droplets less than one millimeter in size. Their self-assembly relies on either lengthy brownian motion or careful microfludic designs, on top of typical colloidal interactions, e.g. depletion attraction. Regardless of the approach, however, questions remain why the colloids undergo certain path to organize themselves and how such process can be optimized. Here, we perform direct numerical simulations using a Navier-Stokes solver at low Reynolds number, combined with either the immersed boundary method (IBM) or a newly-proposed level set (LS) method for interface description. In the IBM simulations, the colloids are treated as rigid, spherical particles under a Lennard-Jones-like potential, reproducing attractive depletion force. Results show that, for four particles, a planar diamond is formed under a weak potential while a 3D tetrahedron is formed under a strong potential, which agree qualitatively with experiments. In the next step, LS simulation of colloidal droplets will be performed to investigate the roles of surface tension in the self-assembly. This project has received funding from the European Union's Horizon 2020 research and innovation programme under Grant agreement No 664823.

  4. Sorption Behavior of Strontium-85 Onto Colloids of Silica and Smectite

    Energy Technology Data Exchange (ETDEWEB)

    Lu, N.; Triay, I.R.; Mason, C.F.V.; Longmire, P.A.

    1998-11-10

    Strontium-90 is one of the sizable radioactive contaminants found in DP Canyon at Los Alamos, New Mexico. Radioactive surveys found the {sup 90}Sr is present in surface and groundwater in DP Canyon and Los Alamos Canyon. Colloids may influence the transport of this radionuclide in surface water and groundwater environments in both canyons. In this study, we investigated the sorption/desorption behavior of Sr on colloids of smectite and silica. Laboratory batch sorption experiments were conducted using {sup 85}Sr as a surrogate to {sup 90}Sr. Groundwater, collected from DP Canyon and from Well J-13 at Yucca Mountain, Nevada, and deionized water were used in this study. Our results show that 92% to 100% of {sup 85}Sr was rapidly adsorbed onto smectite colloids in all three waters. The concentrations of Ca{sup 2+} significantly influence the adsorption of {sup 85}Sr onto silica colloids. Desorption of {sup 85}Sr from smectite colloids is much slower than the sorption process. Desorption of {sup 85}Sr from silica colloids was rapid in DP groundwater and slow using J-13 groundwater and deionized water.

  5. Phase diagram of aggregation of oppositely charged colloids in salty water.

    Science.gov (United States)

    Zhang, R; Shklovskii, B I

    2004-02-01

    Aggregation of two oppositely charged colloids in salty water is studied. We focus on the role of Coulomb interaction in strongly asymmetric systems in which the charge and size of one colloid is much larger than the other one. In the solution, each large colloid (macroion) attracts a certain number of oppositely charged small colloids (Z-ion) to form a complex. If the concentration ratio of the two colloids is such that complexes are not strongly charged, they condense in a macroscopic aggregate. As a result, the phase diagram in a plane of concentrations of two colloids consists of an aggregation domain sandwiched between two domains of stable solutions of complexes. The aggregation domain has a central part of total aggregation and two wings corresponding to partial aggregation. A quantitative theory of the phase diagram in the presence of monovalent salt is developed. It is shown that as the Debye-Hückel screening radius r(s) decreases, the aggregation domain grows, but the relative size of the partial aggregation domains becomes much smaller. As an important application of the theory, we consider solutions of long double-helix DNA with strongly charged positive spheres (artificial chromatin). We also consider implications of our theory for in vitro experiments with the natural chromatin. Finally, the effect of different shapes of macroions on the phase diagram is discussed.

  6. Adsorption of Cadmium by Soil Colloids and Minerals in Presence of Rhizobia

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Experiments were conducted to study the adsorption of Cd on two soil colloids (red soil and yellowbrown soil) and three variable-charge minerals (goethite, noncrystalline Fe oxide and kaolin) in the absence and presence of rhizobia. The tested strain Rhizobium fredii C6, tolerant to 0.8 mmol L-1 Cd, was selected from 30 rhizobial strains. Results showed that the isotherms for the adsorption of Cd by examined soil colloids and minerals in the presence of rhizobia could be described by Langmuir equation. Within the range of the numbers of rhizobial cells studied, the amount of Cd adsorbed by each system increased with increasing rhizobial cells. Greater increases for the adsorption of Cd were found in red soil and kaolin systems.Rhizobia influence on the adsorption of Cd by examined soil colloids and minerals was different from that on the adsorption of Cu. The presence of rhizobia increased the adsorption af~nity of soil colloids and minerals for Cd, particularly for the goethite and kaolin systems. The discrepancies in the influence of rhizobia on the adsorbability and affinity of selected soil colloids and minerals for Cd suggested the different interactions of rhizobia with various soil components. It is assumed that bacterial biomass plays an important role in controlling the mobility and bioavailability of Cd in soils with kaolinite and goethite as the major colloidal components, such as in variable-charge soil.

  7. Photochemical manipulation of colloidal structures in liquid-crystal colloids

    Science.gov (United States)

    Yamamoto, T.; Tabe, Y.; Yokoyama, H.

    2007-05-01

    We investigated photochemical manipulation of physical properties and colloidal structures in liquid-crystal (LC) colloids containing azobenzene compounds. In a LC suspension where polymeric particles were dispersed in a host LC, we achieved photochemical control of light-scattering properties of the suspension. In a nematic phase, when the suspension was sandwiched with two glass plates, the film became opaque. This would be attributable to an appearance of both multidomain structures of LC alignment and mismatches of refractive indices between the materials. The opaque state turned into a transparent one when a nematic-to-isotropic phase transition was induced by the trans-to-cis photoisomerization of the azo-dye. This will result from a disappearance of both the multidomain structures and the refractive-index mismatches in the isotropic phase. The transparent film went back into the initial opaque film when the nematic phase was obtained by the cis-to-trans photoisomerization. In a LC emulsion in which glycerol or water droplets were dispersed in liquid crystals, we examined photochemical change of defect structures and inter-droplet distances by the photochemical manner. At the initial state, Saturn ring and hedgehog defects were formed around the droplets. For the glycerol droplets, we observed structural transformations between Saturn ring and boojums on irradiation with ultra-violet and visible light. For the water droplets, the inter-droplet distances varied by changing defect size on the irradiation. These phenomena would result from modulation of anchoring conditions of the droplets by the photoisomerization of the azo-dyes.

  8. Phosphate binding by natural iron-rich colloids in streams

    NARCIS (Netherlands)

    Baken, S.; Moens, C.; Griffioen, J.J.; Smolders, E.

    2016-01-01

    Phosphorus (P) in natural waters may be bound to iron (Fe) bearing colloids. However, the natural variation in composition and P binding strength of these colloids remain unclear. We related the composition of "coarse colloids" (colloids in the 0.1-1.2 μm size range) in 47 Belgian streams to the

  9. Phosphate binding by natural iron-rich colloids in streams

    NARCIS (Netherlands)

    Baken, S.; Moens, C.; Griffioen, J.J.; Smolders, E.

    2016-01-01

    Phosphorus (P) in natural waters may be bound to iron (Fe) bearing colloids. However, the natural variation in composition and P binding strength of these colloids remain unclear. We related the composition of "coarse colloids" (colloids in the 0.1-1.2 μm size range) in 47 Belgian streams to the che

  10. 胶溶法制备具有自清洁与抗菌性能的TiO2薄膜%Preparation of TiO2 Thin Films with Self-cleaning and Antibacterial Properties by Colloidal Chemical Method

    Institute of Scientific and Technical Information of China (English)

    樊新民; 洪洋; 汪洋

    2013-01-01

    The anatase sol was synthesized by colloidal chemical method and the nanocrystalline TiO2 films were then prepared on glass substrates by the dip-coating method from the anatase sol. XRD,TEM, SEM, AFM and water contact angle were used to characterize the microstructure of TiO2 sol and films. The results showed that the TiO2 sol was anatase with high crystallinity. The TiO2 crystals were needle like and average crystallite size was about 8 nm. The surface of TiO2 flims were smooth and diameter of particles was 86 nm in average. The thickness of three-layer film is approximately ISO nm. Moreover, coating layers had little influence on morphology. The degradation of methylene blue reached 93. 6% when the films prepared at ambient temperature were irradiated by UV light for 80 min, and the photocatalytic activity increased as heat treatment temperature raised. The TiO2 films possessed self-cleaning and antibacterial properties, as well as super hydrophilicity.%采用胶溶法合成了纳米晶锐钛矿溶胶,在玻璃基底上用提拉法制备出TiO2纳米薄膜.使用XRD、TEM、SEM和AFM和接触角等方法对TiO2溶胶和薄膜的结构进行了表征.结果表明,胶溶法合成的TiO2溶胶为锐钛矿型且结晶度较高,TiO2晶粒为针状,平均粒径约为8 nm;TiO2薄膜表面光滑,颗粒平均粒径约为86 nm.3层薄膜的厚度约为150 nm,涂膜层数对膜表面结构形貌影响有限.常温制备出的薄膜经紫外光照80 min,对亚甲基蓝的降解率达到93.6%,其活性随着热处理温度升高而提高.薄膜具备超亲水性,自清洁和抗菌性能.

  11. The effect of colloidal solution of molybdenum nanoparticles on the microbial composition in rhizosphere of Cicer arietinum L.

    Science.gov (United States)

    Taran, Natalia Yu; Gonchar, Olena M.; Lopatko, Kostyantyn G.; Batsmanova, Lyudmila M.; Patyka, Mykola V.; Volkogon, Mykola V.

    2014-06-01

    The use of colloidal solutions of metals as micronutrients enhances plant resistance to unfavorable environmental conditions and ensures high yields of food crops due to the active penetration of nanoelements into the plant cells. Microbiological examination of rhizosphere soil have revealed that combined use of colloidal solution of nanoparticles of molybdenum (CSNM, 8 mg/l), and microbial preparation for pre-sowing inoculation of chickpea seeds stimulates the development of `agronomically valuable' microflora. It was shown that combined seed treatment with colloidal solution of Mo nanoparticles with microbial preparation have stimulated nodule formation per plant by four times compared to controls. Single treatment with CSNM increased the number of nodules by two times, while the treatment of microbial preparation have not significantly affected the number of nodules per plant.

  12. Protective colloids and polylactic acid co-affecting the polymorphic crystal forms and crystallinity of indomethacin encapsulated in microspheres.

    Science.gov (United States)

    Lin, S Y; Chen, K S; Teng, H H

    1999-01-01

    The co-effect of protective colloids and polylactic acid (PLA) on the polymorphic crystal forms and crystallinity of indomethacin (IMC) in IMC-loaded PLA microspheres was investigated with differential scanning calorimetry, infrared spectroscopy and x-ray diffractometry, to evaluate the polymorphic crystal forms and crystallinity of IMC encapsulated in PLA microspheres. The surfactant, sodium dodecyl sulphate (SDS), was also used as a dispersing agent. The results indicate that the polymorphism and crystallinity of IMC encapsulated in IMC-loaded PLA microspheres was dependent on the type of protective colloid and PLA used. The amorphous state and alpha-form of IMC were found in the IMC-loaded PLA microspheres prepared using polysaccharide (pectin or beta-cyclodextrin) as a protective colloid or SDS as a dispersing agent. However, the amorphous and methylene chloride solvate of IMC seemed to exist in the IMC-loaded PLA microspheres prepared with the proteins (gelatin or albumin), synthetic cellulose derivative (methyl cellulose or hydroxylpropyl methylcellulose) or the synthetic nonionic polymer (polyvinyl alcohol, polyvinyl pyrrolidone or biosoluble polymer) as a protective colloid. PLA was found to express a certain crystallinity in microspheres and not be affected by the protective colloids, but it played a more important role in influencing the crystallization of IMC during microencapsulation than the protective colloids. No interaction occurred in the physical mixture of IMC and PLA, nor in the IMC-loaded PLA microspheres.

  13. Direct visualization of the interfacial position of colloidal particles and their assemblies

    Science.gov (United States)

    Vogel, N.; Ally, J.; Bley, K.; Kappl, M.; Landfester, K.; Weiss, C. K.

    2014-05-01

    this method to investigate the formation of complex, binary assembly structures directly at the interface, to visualize soft, nanoscale hydrogel colloids in the swollen state, and to visualize and quantify the equilibrium position of individual micro- and nanoscale colloids at the air-water interface depending of the amount of charge present on the particle surface. We find that the degree of deprotonation of the carboxyl group shifts the air-water contact angle, which is further confirmed by colloidal probe atomic force microscopy. Remarkably, the contact angles determined for individual colloidal particles feature a significant distribution that greatly exceeds errors attributable to the size distribution of the colloids. This finding underlines the importance of accessing soft matter on an individual particle level. Electronic supplementary information (ESI) available: Detailed description of the experiments, additional micrographs and a sketch illustrating the calculation of the contact angles. See DOI: 10.1039/c4nr00401a

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

    DEFF Research Database (Denmark)

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

    2009-01-01

    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......-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 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...

  15. Oxyhydroxy Silicate Colloids: A New Type of Waterborne Actinide(IV) Colloids

    Science.gov (United States)

    Weiss, Stephan; Hennig, Christoph; Brendler, Vinzenz; Ikeda‐Ohno, Atsushi

    2016-01-01

    Abstract At the near‐neutral and reducing aquatic conditions expected in undisturbed ore deposits or in closed nuclear waste repositories, the actinides Th, U, Np, and Pu are primarily tetravalent. These tetravalent actinides (AnIV) are sparingly soluble in aquatic systems and, hence, are often assumed to be immobile. However, AnIV could become mobile if they occur as colloids. This review focuses on a new type of AnIV colloids, oxyhydroxy silicate colloids. We herein discuss the chemical characteristics of these colloids and the potential implication for their environmental behavior. The binary oxyhydroxy silicate colloids of AnIV could be potentially more mobile as a waterborne species than the well‐known mono‐component oxyhydroxide colloids. PMID:27957406

  16. Static and dynamic friction in sliding colloidal monolayers

    Science.gov (United States)

    Vanossi, Andrea; Manini, Nicola; Tosatti, Erio

    2013-03-01

    In a recent experimental breakthrough, the controlled sliding of 2D colloidal crystals over perfectly regular, laser generated periodic or quasi-periodic `corrugation` potentials has been realized in Bechinger's group. Based on realistic MD simulations which reproduce the main experimentally observed features, we explore the potential impact of colloid monolayer sliding in nanotribology. The free motion of edge-spawned kinks and antikinks in smooth incommensurate sliding is contrasted with the kink-antikink pair nucleation at the large static friction threshold in the commensurate case. The Aubry pinning/depinning transition is also demonstrated, e.g., as a function of the corrugation amplitude. Simulated sliding data allow the extraction of frictional work directly from particles coordinates and velocities as a function of classic friction parameters, primarily speed, and corrugation strength. Analogies with sliding charge-density waves, driven Josephson systems, sliding of rare gas islands, and other novel features suggest further experiments and insights, which promote colloid sliding to a novel friction study instrument. Research partly sponsored by Sinergia Project CRSII2 136287/1.

  17. Polarized and asymmetric emission of single colloidal nanoplatelets (Conference Presentation)

    Science.gov (United States)

    Feng, Fu; N'Guyen, Thu Loan; Nasilowski, Michel; Lethiec, Clotilde M.; Dubertret, Benoit; Coolen, Laurent; Maître, Agnès.

    2017-02-01

    Efficient coupling of nanoemitters to photonic or plasmonic structures requires the control of the orientation of the emitting dipoles. Nevertheless controlling the dipole orientation remains an experimental challenge. Many experiments rely on the realization of numerous samples, in order to be able to statistically get a well aligned dipole to realize an efficient coupling to a nanostructure. In order to avoid these statistical trials, the knowledge of the nature of the emitter and its orientation is crucial for a deterministical approach. We developed a method [1],[2] relying on the combination of polarimetric measurement and emission diagram which gives fine information both on the emitting dipolar transition involved and on the dipolar orientation We analyse by this method square and rectangle single colloidal CdSe/CdS nanoplatetelets. We demonstrate that their emission can be described by just by two orthogonal dipoles lying in the plane of the platelets. More surprisingly the emission of the square nanoplatelets is not polarised whereas the rectangle one is. We demonstrate that this polarized emission is due to the rectangular shape anisotropy by a dielectric effect. [1] C. Lethiec, et al, Three-dimensional orientation measurement of a single fluorescent nanoemitter by polarization analysis, Phys. Rev. X 4, 021037 (2014), [2] C. Lethiec et al, Polarimetry-based analysis of dipolar transitions of single colloidal CdSe/CdS dot-inrods, New Journal of Physics 16, 093014 (2014) [3] S. Ithurria et al, colloidal nanoplatelets with 2 dimensional electronic structure, Nature Materials 10, 936 (2011)

  18. The Ongoing Controversy: Crystalloids Versus Colloids.

    Science.gov (United States)

    Pierce, Janet D; Shen, Qiuhua; Thimmesch, Amanda

    2016-01-01

    There is still much debate over the optimal fluid to use for resuscitation. Different studies have indicated either crystalloid or colloid is the ideal intravenous solution to administer, based on mortality or various physiological parameters. Older studies found differences between crystalloids and colloids. However, with the evolving science of fluid administration, more recent studies have shown no differences in patient outcomes. This review article will provide an overview of these substances and discuss the advantages, disadvantages, and implications for giving crystalloids and colloids in clinical practice.

  19. 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

  20. 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.