WorldWideScience

Sample records for colloidal magnetic fluids

  1. Application of mixed colloidal magnetic fluid of single domain Fe3O4 and NiFe2O4 ferrite nanoparticles in audio speaker

    Directory of Open Access Journals (Sweden)

    S. D. Kemkar

    2017-01-01

    Full Text Available Ferrofluids are stable suspensions of colloidal ferrimagnetic particles in suitable non – magnetic carrier liquids. They have attracted a lot of attention from scientists and engineers due to their many interesting properties and applications in various branches of engineering. The present work reports the performance of colloidal fluid of single domain nanoparticles of NiFe2O4 and Fe3O4. The thermal properties and its dynamics on magnetization as well as its effect on thermal conductivity on the colloidal fluid are studied here. Advantages of the increased thermal conductivity and optimization of magnetization of mixed colloidal fluid is used to extract the heat from voice coil. Nanoparticles of 21 nm of Fe3O4 and 12 nm of NiFe2O4 are used for mixed colloidal fluid. The suspension of particles is achieved by coating the nanoparticles with mono-corboxylic group on both the types of particles. The higher size (21 nm of Fe3O4 and 12 nm of NiFe2O4 particles are taken for synthesizing colloidal fluid, to have magnetic property of mixed colloidal liquid at elevated temperature of voice coil of speaker (Higher sized particles gives better magnetization. Oil is used as a carrier. Mixed magnetic colloidal fluid is used as a medium for damping so that noise is reduced at higher temperature of voice coil.

  2. 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...

  3. Colloidal Thermal Fluids

    Science.gov (United States)

    Lotzadeh, Saba

    In this dissertation, a reversible system with a well controlled degree of particle aggregation was developed. By surface modification of colloidal silica with aminosilanes, interactions among the particles were tuned in a controlled way to produce stable sized clusters at different pH values ranges from well-disposed to a colloidal gel. N-[3-(trimethoxysilyl)propyl]ethylenediamine (TMPE) monolayer on particle surface not only removes all the reactive sites to prevent chemical aggregation, also provides steric stabilization in the absence of any repulsion. After surface modification, electrokinetic behavior of silica particles were changed to that of amino groups, positive in acidic pH and neutral at basic pH values. By tuning the pH, the balance between electrostatic repulsion and hydrophobic interactions was reversibly controlled. As a result, clusters with different sizes were developed. The effect of clustering on the thermal conductivity of colloidal dispersions was quantified using silane-treated silica, a system engineered to exhibit reversible clustering under well-controlled conditions. Thermal conductivity of this system was measured by transient hot wire, the standard method of thermal conductivity measurements in liquids. We show that the thermal conductivity increases monotonically with cluster size and spans the entire range between the two limits of Maxwell's theory. The results, corroborated by numerical simulation, demonstrate that large increases of the thermal conductivity of colloidal dispersions are possible, yet fully within the predictions of classical theory. Numerical calculations were performed to evaluate the importance of structural properties of particles/aggregates on thermal conduction in colloidal particles. Thermal conductivity of non-spherical particles including hollow particles, cubic particles and rods was studied using a Monte Carlo algorithm. We show that anisotropic shapes, increase conductivity above that of isotropic

  4. Magnetic Assisted Colloidal Pattern Formation

    Science.gov (United States)

    Yang, Ye

    phase transitions in condensed matter systems that can be tracked with single particle resolution. Compared with other research on colloidal crystal formation, my research has focused on multi-component colloidal systems of magnetic and non-magnetic colloids immersed in a ferrofluid. Initially, I studied the types of patterns that form as a function of the concentrations of the different particles and ferrofluid, and I discovered a wide variety of chains, rings and crystals forming in bi-component and tri-component systems. Based on these results, I narrowed my focus to one specific crystal structure (checkerboard lattice) as a model of phase transformations in alloy. Liquid/solid phase transitions were studied by slowly adjusting the magnetic field strength, which serves to control particle-particle interactions in a manner similar to controlling the physical temperature of the fluid. These studies were used to determine the optimal conditions for forming large single crystal structures, and paved the way for my later work on solid/solid phase transitions when the angle of the external field was shifted away from the normal direction. The magnetostriction coefficient of these crystals was measured in low tilt angle of the applied field. At high tilt angles, I observed a variety of martensitic transformations, which followed different pathways depending on the crystal direction relative to the in-plane field. In the last part of my doctoral studies, I investigated colloidal patterns formed in a superimposed acoustic and magnetic field. In this approach, the magnetic field mimics "temperature", while the acoustic field mimics "pressure". The ability to simultaneously tune both temperature and pressure allows for more efficient exploration of phase space. With this technique I demonstrated a large class of particle structures ranging from discrete molecule-like clusters to well ordered crystal phases. Additionally, I demonstrated a crosslinking strategy based on

  5. 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

  6. Self-Assembly of Magnetic Colloids in Soft Confinement

    NARCIS (Netherlands)

    Liu, P.

    2016-01-01

    The central theme in this thesis is the effect of the soft confinements consisting of molecular microtubes and fluid interfaces, on the self-assembly of colloids. We have specially focused on the synthesis of magnetic colloids and the magnetic responses of self-assembled structures including

  7. Ultrasonic wave interactions with magnetic colloids

    CERN Document Server

    Chapman, J R

    2001-01-01

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

  8. Colloidal Stability and Magnetic Field-Induced Ordering of Magnetorheological Fluids Studied with a Quartz Crystal Microbalance

    Directory of Open Access Journals (Sweden)

    Jaime Rodriguez-López

    2015-12-01

    Full Text Available This work proposes the use of quartz crystal microbalances (QCMs as a method to analyze and characterize magnetorheological (MR fluids. QCM devices are sensitive to changes in mass, surface interactions, and viscoelastic properties of the medium contacting its surface. These features make the QCM suitable to study MR fluids and their response to variable environmental conditions. MR fluids change their structure and viscoelastic properties under the action of an external magnetic field, this change being determined by the particle volume fraction, the magnetic field strength, and the presence of thixotropic agents among other factors. In this work, the measurement of the resonance parameters (resonance frequency and dissipation factor of a QCM are used to analyze the behavior of MR fluids in static conditions (that is, in the absence of external mechanical stresses. The influence of sedimentation under gravity and the application of magnetic fields on the shifts of resonance frequency and dissipation factor were measured and discussed in the frame of the coupled resonance produced by particles touching the QCM surface. Furthermore, the MR-fluid/QCM system has a great potential for the study of high-frequency contact mechanics because the translational and rotational stiffness of the link between the surface and the particles can be tuned by the magnetic field.

  9. 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.

  10. 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.

  11. 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...

  12. 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

  13. Synthesis and Analytical Centrifugation of Magnetic Model Colloids

    NARCIS (Netherlands)

    Luigjes, B.

    2012-01-01

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

  14. MOLECULAR DESIGN OF COLLOIDS IN SUPERCRITICAL FLUIDS

    Energy Technology Data Exchange (ETDEWEB)

    Keith P. Johnston

    2009-04-06

    The environmentally benign, non-toxic, non-flammable fluids water and carbon dioxide (CO2) are the two most abundant and inexpensive solvents on earth. Emulsions of these fluids are of interest in many industrial processes, as well as CO2 sequestration and enhanced oil recovery. Until recently, formation of these emulsions required stabilization with fluorinated surfactants, which are expensive and often not environmentally friendly. In this work we overcame this severe limitation by developing a fundamental understanding of the properties of surfactants the CO2-water interface and using this knowledge to design and characterize emulsions stabilized with either hydrocarbon-based surfactants or nanoparticle stabilizers. We also discovered a new concept of electrostatic stabilization for CO2-based emulsions and colloids. Finally, we were able to translate our earlier work on the synthesis of silicon and germanium nanocrystals and nanowires from high temperatures and pressures to lower temperatures and ambient pressure to make the chemistry much more accessible.

  15. Self-replication with magnetic dipolar colloids.

    Science.gov (United States)

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

    2015-10-01

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

  16. Mechanics of magnetic fluid column in strong magnetic fields

    Science.gov (United States)

    Polunin, V. M.; Ryapolov, P. A.; Platonov, V. B.

    2017-06-01

    Elastic-and magnetic properties of magnetic fluid confined by ponderomotive force in a tube fixed in horizontal position are considered. The system is placed in a strong magnetic field under the influence of external static and dynamic perturbations. An experimental setup has been developed. A theoretical basis of the processes of magnetic colloid elastic deformation has been proposed. The values of the static ponderomotive elasticity coefficient and the elasticity coefficient under dynamic action are experimentally determined. The calculations of the saturation magnetization for two magnetic fluid samples, carried out according to the equation containing the dynamic elasticity coefficient, are in good agreement with the experimental magnetization curve. The described method is of interest when studying magnetophoresis and aggregation of nanoparticles in magnetic colloids.

  17. 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.

  18. Magnetic hyperthermia in solid magnetic colloids

    Science.gov (United States)

    Zubarev, A. Yu.; Iskakova, L. Yu.; Abu-Bakr, A. F.

    2017-02-01

    We present results of theoretical study of magnetic hyperthermia in systems of single-domain ferromagnetic particles homogeneously distributed in a solid matrix. The heat effect is induced by linearly polarized alternating magnetic field. The effect of magnetic interaction between the particles as well as influence of orientation of the particles magnetic axes are in a focus of our consideration. Analysis shows that the interparticle interaction increases intensity of the heat production. The thermal effect in the systems with parallel orientation of the particles axes of easy magnetization is significantly higher than that in the case of random orientation of these axes.

  19. Diffusion of colloidal fluids in random porous media.

    Science.gov (United States)

    Chávez-Rojo, M A; Juárez-Maldonado, R; Medina-Noyola, M

    2008-04-01

    The diffusive relaxation of a colloidal fluid adsorbed in a porous medium depends on many factors, including the concentration and composition of the adsorbed colloidal fluid, the average structure of the porous matrix, and the nature of the colloid-colloid and colloid-substrate interactions. A simple manner to describe these effects is to model the porous medium as a set of spherical particles fixed in space at random positions with prescribed statistical structural properties. Within this model one may describe the relaxation of concentration fluctuations of the adsorbed fluid by simply setting to zero the short-time mobility of one species (the porous matrix) in a theory of the dynamics of equilibrium colloidal mixtures, or by extending such dynamic theory to explicitly consider the porous matrix as a random external field, as recently done in the framework of mode coupling theory [V. Krakoviack, Phys. Rev. Lett. 94, 065703 (2005)]. Here we consider the first approach and employ the self-consistent generalized Langevin equation (SCGLE) theory of the dynamics of equilibrium colloidal mixtures, to describe the dynamics of the mobile component. We focus on the short- and intermediate-time regimes, which we compare with Brownian dynamics simulations involving a binary mixture with screened Coulomb interactions for two models of the average static structure of the matrix: a porous matrix constructed by quenching configurations of an equilibrium mixture in which both species were first equilibrated together, and a preexisting matrix with prescribed average structure, in which we later add the mobile species. We conclude that in both cases, if the correct static structure factors are provided as input, the SCGLE theory correctly predicts the main features of the dynamics of the permeating fluid.

  20. Dynamic Elasticity of a Magnetic Fluid Column in a Strong Magnetic Field

    Science.gov (United States)

    Polunin, V. M.; Ryapolov, P. A.; Shel'deshova, E. V.; Kuz'ko, A. E.; Aref'ev, I. M.

    2017-07-01

    The elastomagnetic parameters of a magnetic fluid kept by magnetic levitation in a tube placed horizontally in a strong magnetic field are measured, including the oscillation frequency, the ponderomotive and dynamic elasticity coefficients, the magnetization curve, and the magnetic field strength and its gradient. Results of calculations for the model of ponderomotive elasticity for the examined sample of the magnetic fluid corrected for the resistance of the moving viscous fluid are in good agreement with the experimental magnetization curve. The described method is of interest for a study of magnetophoresis, nanoparticle aggregations, viscosity, and their time dependences in magnetic colloids.

  1. The Colloidal Stability of Magnetic Nanoparticles in Ionic Liquids

    Science.gov (United States)

    2015-08-03

    Final 3. DATES COVERED (From - To) 14 May 2014 – 13 May 2015 4. TITLE AND SUBTITLE The Colloidal Stability of Magnetic Nanoparticles in...Rev. 8-98) Prescribed by ANSI Std Z39-18 Final Report for AOARD Grant 144062 “The Colloidal Stability of Magnetic Nanoparticles in Ionic Liquids...sterically stabilized magnetic nanoparticles : Magnetic nanoparticles with an average core diameter of 25 nm used in this work were obtained from

  2. Magnetic fluid readily controlled in zero gravity environment

    Science.gov (United States)

    Papell, S. S.

    1965-01-01

    Colloid composed of finely ground iron oxide in a fluid such as heptane, is controlled and directed magnetically in a zero gravity environment. It will not separate on standing for long periods or after exposure to magnetic or centrifugal forces. Because of its low density and low viscosity, it is easily pumped.

  3. Phase behavior of mixtures of magnetic colloids and non-adsorbing polymer

    NARCIS (Netherlands)

    Ewijk, G.A. van

    2001-01-01

    In this thesis, we have studied the thermodynamic stability of magnetic fluids, also called ferrofluids. These consist of spherical colloids of typically 10 nm, coated with a monolayer of oleic acid and dispersed in cyclohexane. The core material, Fe3O4, is ferrimagnetic and because of its small siz

  4. Phase behavior of mixtures of magnetic colloids and non-adsorbing polymer

    NARCIS (Netherlands)

    Ewijk, G.A. van

    2001-01-01

    In this thesis, we have studied the thermodynamic stability of magnetic fluids, also called ferrofluids. These consist of spherical colloids of typically 10 nm, coated with a monolayer of oleic acid and dispersed in cyclohexane. The core material, Fe3O4, is ferrimagnetic and because of its small

  5. 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.

  6. Colloids versus crystalloids for fluid resuscitation in critically ill patients.

    Science.gov (United States)

    Perel, Pablo; Roberts, Ian; Ker, Katharine

    2013-02-28

    Colloid solutions are widely used in fluid resuscitation of critically ill patients. There are several choices of colloid, and there is ongoing debate about the relative effectiveness of colloids compared to crystalloid fluids. To assess the effects of colloids compared to crystalloids for fluid resuscitation in critically ill patients. We searched the Cochrane Injuries Group Specialised Register (17 October 2012), the Cochrane Central Register of Controlled Trials (The Cochrane Library) (Issue 10, 2012), MEDLINE (Ovid) 1946 to October 2012, EMBASE (Ovid) 1980 to October 2012, ISI Web of Science: Science Citation Index Expanded (1970 to October 2012), ISI Web of Science: Conference Proceedings Citation Index-Science (1990 to October 2012), PubMed (October 2012), www.clinical trials.gov and www.controlled-trials.com. We also searched the bibliographies of relevant studies and review articles. Randomised controlled trials (RCTs) of colloids compared to crystalloids, in patients requiring volume replacement. We excluded cross-over trials and trials involving pregnant women and neonates. Two review authors independently extracted data and rated quality of allocation concealment. We analysed trials with a 'double-intervention', such as those comparing colloid in hypertonic crystalloid to isotonic crystalloid, separately. We stratified the analysis according to colloid type and quality of allocation concealment. We identified 78 eligible trials; 70 of these presented mortality data.COLLOIDS COMPARED TO CRYSTALLOIDS: Albumin or plasma protein fraction - 24 trials reported data on mortality, including a total of 9920 patients. The pooled risk ratio (RR) from these trials was 1.01 (95% confidence interval (CI) 0.93 to 1.10). When we excluded the trial with poor-quality allocation concealment, pooled RR was 1.00 (95% CI 0.92 to 1.09). Hydroxyethyl starch - 25 trials compared hydroxyethyl starch with crystalloids and included 9147 patients. The pooled RR was 1.10 (95% CI 1

  7. 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.

  8. 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.

  9. Magnetic Fluids: Biomedical Applications and Magnetic Fractionation

    OpenAIRE

    Rheinländer, Thomas; Kötitz, Róman; Weitschies, Werner; Semmler, Wolfhard

    2000-01-01

    In addition to engineering applications, magnetic fluids containing magnetic nanoparticles are being increasingly applied to biomedical purposes. Besides the well established use of magnetic particles for biological separation or as contrast agents for magnetic resonance imaging, magnetic particles are also being tested for the inductive heat treatment of tumors or as markers for the quantification of biologically active substances. The properties of magnetic nanoparticles usually exhibit a b...

  10. Tuning of Heat Transfer Rate of Cobalt Manganese Ferrite Based Magnetic Fluids in Varying Magnetic Field

    Directory of Open Access Journals (Sweden)

    Margabandhu MARIMUTHU

    2017-08-01

    Full Text Available Magnetic fluids are the colloidal solutions containing suspended magnetic nanoparticles in carrier fluids. The present work analyzed the heat transfer characteristics of de-ionized water and transformer oil (base fluids based cobalt manganese ferrite (Co1-xMnxFe2O4 coated with oleic acid synthesized via co-precipitation technique magnetic fluids in  varying magnetic field. Experimental investigations were carried out to analyze the heat transfer property of synthesized magnetic fluids (MNF in varying magnetic field applied in perpendicular direction to the thermal gradient of magnetic fluids. The experimental results indicate that the magnetic fluids show enhancement in heat transfer rate than carrier fluids in absence of magnetic field and it shows decrement in heat transfer rate in presence of varying magnetic field. Thus, the results reveal that the heat transfer characteristics of cobalt manganese ferrite based magnetic fluids was tunable by controlling the direction and influence of magnetic field strength. This tunable heat transfer property of cobalt manganese ferrite based magnetic fluids could be applicable in heat transport phenomena of transformers and in microelectronic devices.DOI: http://dx.doi.org/10.5755/j01.ms.23.3.16662

  11. Magnetic manipulation of self-assembled colloidal asters.

    Energy Technology Data Exchange (ETDEWEB)

    Snezhko, A.; Aranson, I. S. (Materials Science Division)

    2011-09-01

    Self-assembled materials must actively consume energy and remain out of equilibrium to support structural complexity and functional diversity. Here we show that a magnetic colloidal suspension confined at the interface between two immiscible liquids and energized by an alternating magnetic field dynamically self-assembles into localized asters and arrays of asters, which exhibit locomotion and shape change. By controlling a small external magnetic field applied parallel to the interface, we show that asters can capture, transport, and position target microparticles. The ability to manipulate colloidal structures is crucial for the further development of self-assembled microrobots

  12. Degenerate Rayleigh-Plateau instability in a magnetically annealed colloidal dispersion

    CERN Document Server

    Swan, James W; First, Eric M

    2013-01-01

    This fluid dynamics video depicts the evolution of a suspension of paramagnetic colloids un- der the influence of a uniform, pulsed magnetic field. At low pulse frequencies, the suspension condenses into columns which decompose via a Rayleigh-Plateau instability. At high pulse fre- quencies, the suspension forms a kinetically arrested, system spanning network. We demonstrate the degeneration of the Rayleigh-Plateau instability with increasing pulse frequency.

  13. 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.

  14. Immobilization of Colloidal Monolayers at Fluid–Fluid Interfaces

    Directory of Open Access Journals (Sweden)

    Peter T. Bähler

    2016-07-01

    Full Text Available Monolayers of colloidal particles trapped at an interface between two immiscible fluids play a pivotal role in many applications and act as essential models in fundamental studies. One of the main advantages of these systems is that non-close packed monolayers with tunable inter-particle spacing can be formed, as required, for instance, in surface patterning and sensing applications. At the same time, the immobilization of particles locked into desired structures to be transferred to solid substrates remains challenging. Here, we describe three different strategies to immobilize monolayers of polystyrene microparticles at water–decane interfaces. The first route is based on the leaking of polystyrene oligomers from the particles themselves, which leads to the formation of a rigid interfacial film. The other two rely on in situ interfacial polymerization routes that embed the particles into a polymer membrane. By tracking the motion of the colloids at the interface, we can follow in real-time the formation of the polymer membranes and we interestingly find that the onset of the polymerization reaction is accompanied by an increase in particle mobility determined by Marangoni flows at the interface. These results pave the way for future developments in the realization of thin tailored composite polymer-particle membranes.

  15. The Effect of Electrolyte Concentration for Colloid Adsorption toward a Fluid-Fluid Interface

    Energy Technology Data Exchange (ETDEWEB)

    Park, Bum Jun [Kyung Hee University, Youngin (Korea, Republic of)

    2013-08-15

    I present the behavior of colloidal adsorption to an oil-water interface in the presence of electrolyte in an aqueous subphase. The optical laser tweezers and the piezo controller are used to trap an individual polystyrene microsphere in water and forcibly transfer it to the interface in the vertical direction. Addition of an electrolyte (i.e., NaCl) in the aqueous subphase enables the particle to attach to the interface, whereas the particle escapes from the trap without the adsorption in the absence of the electrolyte. Based on the analytical calculations of the optical trapping force and the electrostatic disjoining pressure between the particle and the oil-water interface, it is found that a critical energy barrier between them should exist. This study will provide a fundamental understanding for applications of colloidal particles as solid surfactants that can stabilize the immiscible fluid-fluid interfaces, such as emulsions (i.e., Pickering emulsions) and foams.

  16. Dissolution of a Colloidal Particle in an Oscillatory Fluid Medium

    Science.gov (United States)

    Ye, Dezhuang; Li, Ji-Qin; Bogner, Robin; Fan, Tai-Hsi

    Understanding dissolution kinetics of a colloidal particle in an aqueous solution is of great importance in many pharmaceutical and biochemical applications. We present theoretical analysis of low Reynolds number transient dynamics and mass transfer of a dissolving spherical particle in a unidirectional oscillatory flow. The coupling of fluid flow and passive motion of the particle are resolved analytically, and the transient mass transfer associated with the oscillation of the particle is numerically computed. The flow patterns, diffusive and convective transport phenomena, and the dissolution kinetics under various saturation concentrations and flow conditions are characterized by the frequency parameter, Schmidt number, and Peclet number. The result severs as a basic case in determining the efficiency of drug dissolution or reconstitution that depends on various shaking methods.

  17. The structure and dynamics of self-assembling colloidal monolayers in oscillating magnetic fields

    CERN Document Server

    Koser, Alison E; Arratia, Paulo E

    2013-01-01

    Many fascinating phenomena such as large-scale collective flows, enhanced fluid mixing and pattern formation have been observed in so-called active fluids, which are composed of particles that can absorb energy and dissipate it into the fluid medium. For active particles immersed in liquids, fluid-mediated viscous stresses can play an important role on the emergence of collective behavior. Here, we experimentally investigate their role in the dynamics of self-assembling magnetically-driven colloidal particles which can rapidly form organized hexagonal structures. We find that viscous stresses reduce hexagonal ordering, generate smaller clusters, and significantly decrease the rate of cluster formation, all while holding the system at constant number density. Furthermore, we show that time and length scales of cluster formation depend on the Mason number (Mn), or ratio of viscous to magnetic forces, scaling as t / Mn and L / Mn^(1/2). Our results suggest that viscous stresses hinder collective behavior in a se...

  18. TO EVALUATION TEST OF QUALITY OF MAGNETIC FLUIDS FOR MAGNETOFLUID DEVICES

    Directory of Open Access Journals (Sweden)

    V. G. Bashtovoi

    2016-01-01

    Full Text Available Magnetic fluid is a colloid of magnetic nanoparticles. Using of magnetic fluids in technical devices demands applying of strong non-uniform magnetic fields for a long time. One of the most widespread magnetic fluid devices are magnetic fluid seals of mobile shafts, magnetic fluid supports, bearings, acceleration and angle of inclination gauges, devices for information input in the computer and etc. These devices demand high quality of used fluids. Processes of magnetophoresis and Brownian diffusion in magnetic fluid lead to concentration of magnetic particles in the areas with higher intensity of magnetic field and increase of fluid magnetization in these areas. A local change of particles concentration in the fluid leads to variation of its physical properties. Formation of aggregates from the particles and the further stratification of magnetic fluid, up to its destruction, may be the most serious consequence of redistribution of concentration of magnetic particles. These factors lead to variation of parameters of magnetic fluid devices; cause disturbance of their normal operation and even failure. Therefore, the consistent, high quality magnetic fluids which are not subject to fast stratification in a non-uniform magnetic field are necessary for effective work of the devices. The procedure of evaluation test of quality of magnetic fluids is proposed in this paper. The test is based on studying of influence of processes of magnetophoresis and Brownian diffusion of magnetic particles in magnetic fluid on the forces acting on the volume of fluid in an external non-uniform magnetic field. The procedure is developed on the basis of analysis of magnetic force variation in time under the action of non-uniform field of permanent magnets. Methods of determination of stability of magnetic fluid, known at present, demand rather complicated equipment and laborious and complex investigations. Proposed procedure can be used as an express method for

  19. Magnetoresponsive conductive colloidal suspensions with magnetized carbon nanotubes

    Science.gov (United States)

    Abdalla, Ahmed M.; Abdel Fattah, Abdel Rahman; Ghosh, Suvojit; Puri, Ishwar K.

    2017-01-01

    We synthesize a novel and hitherto unreported class of colloidal suspensions for which the dispersed phase, which consists of multiwall carbon nanotubes (MWNTs) decorated with magnetic nanoparticles (MNPs), is both magnetoresponsive and electrically conductive. Synthesis of the dispersed phase merges processes for producing ferrofluids and magnetic MWNTs (mMWNTs). We explore means to tune the properties of these magnetic conductive colloids (MCCs) by varying the (1) MNP material composition, and (2) MNP:MWNT (w/w) magnetization weight ratio (γ). The mMWNTs are examined using XRD, TEM, EDX and SQUID and MCCs are by measuring their zeta potential and electric conductivity. Magnetite (Fe3O4) MNPs, which possess a high Curie temperature, produce mMWNTs with high saturation magnetization that respond relatively weakly to temperature variations. Mn0.2Cu0.2Zn0.6Fe2O4 and Cu0.4Zn0.6Fe2O4 MNPs with lower Curie temperatures are more sensitive to changing temperature. Increasing the MNP Cu content improves the electric conductivity of the corresponding MCC while increasing γ enhances its magnetic response. After γ is raised above a threshold value, mMWNT decoration on the CNT surface becomes nonuniform since the MNPs now agglomerate perpendicular to the nanotube surface. These colloidal suspensions are a promising new class of material that can be manipulated with a magnetic field to tune their electrical conductivity.

  20. Magnetically responsive dry fluids

    Science.gov (United States)

    Sousa, Filipa L.; Bustamante, Rodney; Millán, Angel; Palacio, Fernando; Trindade, Tito; Silva, Nuno J. O.

    2013-07-01

    Ferrofluids and dry magnetic particles are two separate classes of magnetic materials with specific niche applications, mainly due to their distinct viscosity and interparticle distances. For practical applications, the stability of these two properties is highly desirable but hard to achieve. Conceptually, a possible solution to this problem would be encapsulating the magnetic particles but keeping them free to rotate inside a capsule with constant interparticle distances and thus shielded from changes in the viscosity of the surrounding media. Here we present an example of such materials by the encapsulation of magnetic ferrofluids into highly hydrophobic silica, leading to the formation of dry ferrofluids, i.e., a material behaving macroscopically as a dry powder but locally as a ferrofluid where magnetic nanoparticles are free to rotate in the liquid.Ferrofluids and dry magnetic particles are two separate classes of magnetic materials with specific niche applications, mainly due to their distinct viscosity and interparticle distances. For practical applications, the stability of these two properties is highly desirable but hard to achieve. Conceptually, a possible solution to this problem would be encapsulating the magnetic particles but keeping them free to rotate inside a capsule with constant interparticle distances and thus shielded from changes in the viscosity of the surrounding media. Here we present an example of such materials by the encapsulation of magnetic ferrofluids into highly hydrophobic silica, leading to the formation of dry ferrofluids, i.e., a material behaving macroscopically as a dry powder but locally as a ferrofluid where magnetic nanoparticles are free to rotate in the liquid. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr01784b

  1. Dynamical density functional theory for molecular and colloidal fluids: a microscopic approach to fluid mechanics.

    Science.gov (United States)

    Archer, A J

    2009-01-07

    In recent years, a number of dynamical density functional theories (DDFTs) have been developed for describing the dynamics of the one-body density of both colloidal and atomic fluids. In the colloidal case, the particles are assumed to have stochastic equations of motion and theories exist for both the case when the particle motion is overdamped and also in the regime where inertial effects are relevant. In this paper, we extend the theory and explore the connections between the microscopic DDFT and the equations of motion from continuum fluid mechanics. In particular, starting from the Kramers equation, which governs the dynamics of the phase space probability distribution function for the system, we show that one may obtain an approximate DDFT that is a generalization of the Euler equation. This DDFT is capable of describing the dynamics of the fluid density profile down to the scale of the individual particles. As with previous DDFTs, the dynamical equations require as input the Helmholtz free energy functional from equilibrium density functional theory (DFT). For an equilibrium system, the theory predicts the same fluid one-body density profile as one would obtain from DFT. Making further approximations, we show that the theory may be used to obtain the mode coupling theory that is widely used for describing the transition from a liquid to a glassy state.

  2. Electrical Properties of Nanostructured Magnetic Colloid and Influence of Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    PU Sheng-Li; CHEN Xian-Feng; DI Zi-Yun; GENG Tao; XIA Yu-Xing

    2007-01-01

    We investigate the electrical properties of the nanostructured magnetic colloid without and with magnetic Held. The competition between the directional motion of the charged magnetic nanoparticles and other minor nonmagnetic impurities (also small amount of ions) under applied voltage and their random orientation due to thermal activation is implemented to elaborate the electrically conduction mechanism under zero magnetic Geld. Two equivalent electric circuits are employed for explaining the charging and discharging processes. The tunnelling conduction mechanism upon application of externally magnetic field may exist in the nanostructured magnetic colloid. The alternation of the two conduction mechanisms accounts for the current spikes when the magnetic field is switched on or off. This work presents the peculiar electrical phenomena of the magnetically colloidal system.

  3. Motion of a colloidal sphere with interfacial self-electrochemical reactions induced by a magnetic field.

    Science.gov (United States)

    Hsieh, Tzu H; Keh, Huan J

    2012-05-07

    The motion of a spherical colloidal particle with spontaneous electrochemical reactions occurring on its surface in an ionic solution subjected to an applied magnetic field is analyzed for an arbitrary zeta potential distribution. The thickness of the electric double layer adjacent to the particle surface is assumed to be much less than the particle radius. The solutions of the Laplace equations governing the magnetic scalar potential and electric potential, respectively, lead to the magnetic flux and electric current density distributions in the particle and fluid phases of arbitrary magnetic permeabilities and electric conductivities. The Stokes equations modified with the Lorentz force contribution for the fluid motion are dealt by using a generalized reciprocal theorem, and closed-form formulas for the translational and angular velocities of the colloidal sphere induced by the magnetohydrodynamic effect are obtained. The dipole and quadrupole moments of the zeta potential distribution over the particle surface cause the particle translation and rotation, respectively. The induced velocities of the particle are unexpectedly significant, and their dependence on the characteristics of the particle-fluid system is physically different from that for electromagnetophoretic particles or phoretic swimmers.

  4. Dielectrophoresis-magnetophoresis force driven magnetic nanoparticle movement in transformer oil based magnetic fluids.

    Science.gov (United States)

    Lee, Jong-Chul; Lee, Sangyoup

    2013-09-01

    Magnetic fluid is a stable colloidal mixture contained magnetic nanoparticles coated with a surfactant. Recently, it was found that the fluid has properties to increase heat transfer and dielectric characteristics due to the added magnetic nanoparticles in transformer oils. The magnetic nanoparticles in the fluid experience an electrical force directed toward the place of maximum electric field strength when the electric field is applied. And when the external magnetic field is applied, the magnetic nanoparticles form long chains oriented along the direction of the field. The behaviors of magnetic nanoparticles in both the fields must play an important role in changing the heat transfer and dielectric characteristics of the fluids. In this study, we visualized the movement of magnetic nanoparticles influenced by both the fields applied in-situ. It was found that the magnetic nanoparticles travel in the region near the electrode by the electric field and form long chains along the field direction by the magnetic field. It can be inferred that the movement of magnetic nanoparticles appears by both the fields, and the breakdown voltage of transformer oil based magnetic fluids might be influenced according to the dispersion of magnetic nanoparticles.

  5. Self-assembling paramagnetic colloids in oscillating magnetic fields

    CERN Document Server

    Koser, Alison E; Arratia, Paulo E

    2013-01-01

    Many fascinating phenomena such as large-scale collective flows, enhanced fluid mixing and pattern formation have been observed in so-called active fluids, which are composed of particles that can absorb energy and dissipate it into the fluid medium. In order to investigate the role of hydrodynamic interactions in the collective behavior of an active fluid, we choose a model system: paramagnetic particles submerged in water and activated by an oscillating magnetic field. The magnetic field induces magnetic attractions among the paramagnetic particles, activating the particles, and injecting energy into the fluid. Over many cycles, the particles aggregate together and form clusters. In order to form clusters, however, the particles must overcome viscous drag. We investigate the relative roles of viscosity and magnetism. When the role of viscosity is important, the particles cannot form large clusters. But when the role of magnetism is important, the particles rapidly form organized, large clusters. Our results...

  6. Preparation and electrical properties of oil-based magnetic fluids

    Science.gov (United States)

    Sartoratto, P. P. C.; Neto, A. V. S.; Lima, E. C. D.; Rodrigues de Sá, A. L. C.; Morais, P. C.

    2005-05-01

    This paper describes an improvement in the preparation of magnetic fluids for electrical transformers. The samples are based on surface-coated maghemite nanoparticles dispersed in transformer insulating oil. Colloidal stability at 90°C was higher for oleate-grafted maghemite-based magnetic fluid, whereas decanoate and dodecanoate-grafted samples were very unstable. Electrical properties were evaluated for samples containing 0.80%-0.0040% maghemite volume fractions. Relative permittivity varied from 8.8 to 2.1 and the minimum value of the loss factor was 12% for the most diluted sample. The resistivity falls in the range of 0.7-2.5×1010Ωm, whereas the ac dielectric strength varied from 70to79kV. These physical characteristics reveal remarkable step forward in the properties of the magnetic fluid samples and may result in better operation of electrical transformers.

  7. Colloidal self assembly of non-magnetic particles in magnetic nanofluid

    Science.gov (United States)

    Jadav, Mudra; Patel, Rajesh

    2015-06-01

    Here we present a technique using magnetic nanofluid to induce bidispersed suspension of nonmagnetic particles to assemble into colloidal chain, triangle, rectangle, ring-flower configurations. By changing the amplitude and direction of the magnetic field, we could tune the structure of nonmagnetic particles in magnetic nanofluid. The structures are assembled using magneto static interactions between effectively nonmagnetic particles dispersed in magnetizable magnetic nanofluid. The assembly of complex structures out of simple colloidal building blocks is of practical interest in photonic crystals and DNA biosensors.

  8. Colloidal self assembly of non-magnetic particles in magnetic nanofluid

    Energy Technology Data Exchange (ETDEWEB)

    Jadav, Mudra; Patel, Rajesh, E-mail: rjp@mkbhavuni.edu.in, E-mail: rpat7@yahoo.co [Department of Physics, Maharaja Krishnakumarsinhji Bhavnagar University, Bhavnagar-364002 (India)

    2015-06-24

    Here we present a technique using magnetic nanofluid to induce bidispersed suspension of nonmagnetic particles to assemble into colloidal chain, triangle, rectangle, ring-flower configurations. By changing the amplitude and direction of the magnetic field, we could tune the structure of nonmagnetic particles in magnetic nanofluid. The structures are assembled using magneto static interactions between effectively nonmagnetic particles dispersed in magnetizable magnetic nanofluid. The assembly of complex structures out of simple colloidal building blocks is of practical interest in photonic crystals and DNA biosensors.

  9. Magnetic properties of colloidal cobalt nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Torchio, R; Meneghini, C; Mobilio, S; Capellini, G [Dipartimento di Fisica ' E. Amaldi' , Universita di Roma Tre, via della Vasca Navale 84, I-00146 Roma (Italy); Prieto, A Garcia; Alonso, J; Fdez-Gubieda, M L [Departamento de Electricidad y Electronica y Fisica Aplicada I, Universidad del PaIs Vasco (Spain); Liveri, V Turco; Ruggirello, A M [Dipartimento di Chimica Fisica ' F. Accascina' , Universita di Palermo, Viale delle Scienze, Parco d' Orleans II, Edificio 17, 90128 Palermo (Italy); Longo, A [ISMN, Istituto per lo Studio dei Materiali Nanostrutturati, CNR, Via U. La Malfa 153, 90146 Palermo (Italy); Neisius, T, E-mail: torchio@fis.uniroma3.i [Universite Paul CEZANNE, Faculte des Sciences et Techniques, Marseille (France)

    2010-01-01

    Co nanoclusters were synthesized by an inverse-micelle chemical route. The magnetic and microstructural properties of the nanoparticles have been analyzed as a function of the surfactant (AOT and DEHP) and the drying method. Microstructural analysis has been performed by TEM and XANES; magnetic properties have been studied by hysteresis loops and zero-field cooling - field cooling (ZFC-FC) curves. TEM images show 2 to 4 nm sized particles spherical in shape. XANES measurements point out a significant presence of Co{sub 3}O{sub 4}with metallic Co and some Co{sup 2+} bound to the surfactant. The presence of antiferromagnetic Co{sub 3}O{sub 4} explains the magnetic transition observed at low T in both ZFC-FC measurements and hysteresis loops. Finally, the presence of magnetic interactions explains the bigger effective cluster size obtained from hysteresis loops fits (6-10 nm) compared to the sizes observed by TEM (2-4 nm).

  10. Magnetically Remanent Hydrogels with Colloidal Crosslinkers

    NARCIS (Netherlands)

    van Berkum, S.

    2014-01-01

    Hydrogels are widely used in biomedical applications such as drug delivery and tissue engineering. In this research, the feasibility of a hydrogel with embedded magnetic nanoparticles, also called a ferrogel, for biosensor applications was tested. A pH sensitive poly(acrylic acid) hydrogel was used

  11. Magnetically Remanent Hydrogels with Colloidal Crosslinkers

    NARCIS (Netherlands)

    van Berkum, S.

    2014-01-01

    Hydrogels are widely used in biomedical applications such as drug delivery and tissue engineering. In this research, the feasibility of a hydrogel with embedded magnetic nanoparticles, also called a ferrogel, for biosensor applications was tested. A pH sensitive poly(acrylic acid) hydrogel was used

  12. Features of the Rotational Kinetic of Magnetic Fluid Nanoparticles

    Directory of Open Access Journals (Sweden)

    A.M. Storozhenko

    2014-07-01

    Full Text Available The results of theoretical and experimental studies of the effect of the perturbation of magnetization of magnetic fluid in the initial part of magnetization curve, caused by thermal oscillations in the adiabatic sound wave are considered. The measurements were carried out on the magnetic colloid samples with different viscosity of the dispersion medium within the frequency band of 20-60 kHz. In this frequency band, studied samples are characterized by the absence of thermal relaxation of the magnetization. The comparison of the conclusions of the model of thermal relaxation of magnetization and the experimental results makes it possible to obtain information about the features of the rheology for the nearest molecular environment of a particle − nanorheology.

  13. Magnetic fluids - suspensions of magnetic dipoles and their magnetic control

    CERN Document Server

    Odenbach, S

    2003-01-01

    Suspensions of magnetic nanoparticles exhibit normal liquid behaviour coupled with superparamagnetic properties. This leads to the possibility to control the properties and the flow of these liquids with moderate magnetic fields. The magnetic control enables various experiments in fluid mechanics and gives rise to the development of numerous technical and medical applications. Ferrofluids and their general properties will be introduced and, as examples for the magnetic control of their flow and properties, thermomagnetic convection and magnetoviscous effects will be discussed in some detail.

  14. Multidirectional colloidal assembly in concurrent electric and magnetic fields.

    Science.gov (United States)

    Bharti, Bhuvnesh; Kogler, Florian; Hall, Carol K; Klapp, Sabine H L; Velev, Orlin D

    2016-10-07

    Dipolar interactions between nano- and micron sized colloids lead to their assembly into domains with well-defined local order. The particles with a single dipole induced by an external field assemble into linear chains and clusters. However, to achieve the formation of multidirectionally organized nano- or microassemblies with tunable physical characteristics, more sophisticated interaction tools are needed. Here we demonstrate that such complex interactions can be introduced in the form of two independent, non-interacting dipoles (double-dipoles) within a microparticle. We show how this can be achieved by the simultaneous application of alternating current (AC)-electric field and uniform magnetic field to dispersions of superparamagnetic microspheres. Depending on their timing and intensity, concurrent electric and magnetic fields lead to the formation of bidirectional particle chains, colloidal networks, and discrete crystals. We investigate the mechanistic details of the assembly process, and identify and classify the non-equilibrium states formed. The morphologies of different experimental states are in excellent correlation with our theoretical predictions based on Brownian dynamics simulations combined with a structural analysis based on local energy parameters. This novel methodology of introducing and interpreting double-dipolar particle interactions may assist in the assembly of colloidal coatings, dynamically reconfigurable particle networks, and bidirectional active structures.

  15. 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.

  16. Single crystal growth and anisotropic crystal-fluid interface tension in soft colloidal systems

    NARCIS (Netherlands)

    Nguyen, V.D.; Hu, Z.; Schall, P.

    2011-01-01

    We measure the anisotropy of the crystal-fluid interfacial free energy in soft colloidal systems. A temperature gradient is used to direct crystal nucleation and control the growth of large single crystals in order to achieve well-equilibrated crystal-fluid interfaces. Confocal microscopy is used to

  17. Magnetic fields for fluid motion.

    Science.gov (United States)

    Weston, Melissa C; Gerner, Matthew D; Fritsch, Ingrid

    2010-05-01

    Three forces induced by magnetic fields offer unique control of fluid motion and new opportunities in microfluidics. This article describes magnetoconvective phenomena in terms of the theory and controversy, tuning by redox processes at electrodes, early-stage applications in analytical chemistry, mature applications in disciplines far afield, and future directions for micro total analysis systems. (To listen to a podcast about this article, please go to the Analytical Chemistry multimedia page at pubs.acs.org/page/ancham/audio/index.html .).

  18. Size-sorted anionic iron oxide nanomagnets as colloidal mediators for magnetic hyperthermia.

    Science.gov (United States)

    Fortin, Jean-Paul; Wilhelm, Claire; Servais, Jacques; Ménager, Christine; Bacri, Jean-Claude; Gazeau, Florence

    2007-03-07

    Iron oxide colloidal nanomagnets generate heat when subjected to an alternating magnetic field. Their heating power, governed by the mechanisms of magnetic energy dissipation for single-domain particles (Brown and Néel relaxations), is highly sensitive to the crystal size, the material, and the solvent properties. This study was designed to distinguish between the contributions of Néel and Brownian mechanisms to heat generation. Anionic nanocrystals of maghemite and cobalt ferrite, differing by their magnetic anisotropy, were chemically synthesized and dispersed in an aqueous suspension by electrostatic stabilization. The particles were size-sorted by successive electrostatic phase separation steps. Parameters governing the efficiency of nanomagnets as heat mediators were varied independently; these comprised the particle size (from 5 to 16.5 nm), the solvent viscosity, magnetic anisotropy, and the magnetic field frequency and amplitude. The measured specific loss powers (SLPs) were in quantitative agreement with the results of a predictive model taking into account both Néel and Brown loss processes and the whole particle size distribution. By varying the carrier fluid viscosity, we found that Brownian friction within the carrier fluid was the main contributor to the heating power of cobalt ferrite particles. In contrast, Néel internal rotation of the magnetic moment accounted for most of the loss power of maghemite particles. Specific loss powers were varied by 3 orders of magnitude with increasing maghemite crystal size (from 4 to 1650 W/g at 700 kHz and 24.8 kA/m). This comprehensive parametric study provides the groundwork for the use of anionic colloidal nanocrystals to generate magnetically induced hyperthermia in various media, including complex systems and biological materials.

  19. "Smart" Magnetic Fluids Experiment Operated on the International Space Station

    Science.gov (United States)

    Agui, Juan H.; Lekan, Jack F.

    2004-01-01

    InSPACE is a microgravity fluid physics experiment that was operated on the International Space Station (ISS) in the Microgravity Science Glovebox from late March 2003 through early July 2003. (InSPACE is an acronym for Investigating the Structure of Paramagnetic Aggregates From Colloidal Emulsions.) The purpose of the experiment is to obtain fundamental data of the complex properties of an exciting class of smart materials termed magnetorheological (MR) fluids. MR fluids are suspensions, or colloids, comprised of small (micrometer-sized) superparamagnetic particles in a nonmagnetic medium. Colloids are suspensions of very small particles suspended in a liquid. (Examples of other colloids are blood, milk, and paint.) These controllable fluids can quickly transition into a nearly solid state when exposed to a magnetic field and return to their original liquid state when the magnetic field is removed. Controlling the strength of the magnetic field can control the relative stiffness of these fluids. MR fluids can be used to improve or develop new seat suspensions, robotics, clutches, airplane landing gear, and vibration damping systems. The principal investigator for InSPACE is Professor Alice P. Gast of the Massachusetts Institute of Technology (MIT). The InSPACE hardware was developed at the NASA Glenn Research Center. The InSPACE samples were delivered to the ISS in November 2002, on the Space Shuttle Endeavour, on Space Station Utilization Flight UF-2/STS113. Operations began on March 31, 2003, with the processing of three different particle size samples at multiple test parameters. This investigation focused on determining the structural organization of MR colloidal aggregates when exposed to a pulsing magnetic field. On Earth, the aggregates take the shape of footballs with spiky tips. This characteristic shape may be influenced by the pull of gravity, which causes most particles initially suspended in the fluid to sediment, (i.e., settle and collect at the

  20. Random porous media and magnetic separation of magnetic colloids

    NARCIS (Netherlands)

    Baars, R.J.

    2016-01-01

    The separation of magnetic nanoparticles from a stable dispersion is a challenging task because of the nanoparticles' thermal motion and relatively small magnetic moments. Strong magnetic gradients are required to capture such particles, which can be achieved in a high-gradient magnetic separator. I

  1. Enhanced shear separation for chiral magnetic colloidal aggregates.

    Science.gov (United States)

    Mendoza, C I; Marques, C M; Thalmann, F

    2010-12-01

    We study the designing principles of the simplest colloidal propeller, an architecture built from four identical spheres that can couple translation with rotation to produce controlled drift motion. By considering superparamagnetic beads, we show that the simultaneous action of a magnetic field and a shear flow leads to the migration of the cluster in the vorticity direction. We investigate the dependence of the migration velocity on the geometrical parameters of the cluster and find that significant cluster separation can be achieved under the typical operation conditions of microfluidic devices.

  2. Numerical Analysis of Magnetic Fluid Sealing Performance

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The sealing performance of magnetic fluid is related to the magnetic fluid itself. Many factors can influence the magnetic field and the seal pressure differences of magnetic fluid seals, such as the sealing gap, the shaft eccentricity, the shaft diameter, the volume of the magnetic fluid and the centrifugal force. These factors are analyzed by numerical computation . When the seal material and structure are the same, the seal pressure difference is directly proportional to the magnetic field intensity and the saturation magnetization of the magnetic fluid. The sealing performance of the magnetic fluid will reduce with the increase of the sealing gap and shaft eccentricity. The sealing performance will increase with the volume of the magnetic fluid and decrease with the increase of the shaft diameter taking gravity into account. The increase of the shaft diameter is the same as the reduction of the volume of the magnetic fluid. The magnetic fluid cross-section can change because of the centrifugal force. Some improvements can reduce the influence of the centrifugal force. The centrifugal force can be utilized to improve the sealing performance.

  3. Anisotropic thermal conductivity of magnetic fluids

    Institute of Scientific and Technical Information of China (English)

    Xiaopeng Fang; Yimin Xuan; Qiang Li

    2009-01-01

    Considering the forces acting on the particles and the motion of the particles, this study uses a numerical simulation to investigate the three-dimensional microstructure of the magnetic fluids in the presence of an external magnetic field. A method is proposed for predicting the anisotropic thermal conductivity of magnetic fluids. By introducing an anisotropic structure parameter which characterizes the non-uniform distribution of particles suspended in the magnetic fluids, the traditional Maxwell formula is modified and extended to calculate anisotropic thermal conductivity of the magnetic fluids. The results show that in the presence of an external magnetic field the magnetic nanoparticles form chainlike clusters along the direction of the external magnetic field, which leads to the fact that the thermal conduc-tivity of the magnetic fluid along the chain direction is bigger than that along other directions. The thermal conductivity of the magnetic fluids presents an anisotropic feature. With the increase of the magnetic field strength the chainlike clusters in the magnetic fluid appear to be more obvious, so that the anisotropic feature of heat conduction in the fluids becomes more evident.

  4. Magnetic-fluid microelectromechanical light modulator

    Institute of Scientific and Technical Information of China (English)

    SEO Jong-wook; WANG Xi-jun

    2005-01-01

    A new microfluidic microelectromechanical light modulator using a magnetic fluid is introduced. The optical reflection from the device is modulated by applying an electric current into an electrode, which is enclosed by ferromagnetic thin films as in an inductive head for a magnetic data storage device. The magnetic field produced by the current exerts a magnetic force on the magnetic fluid and drives the fluid to cover the cell surface. The surface tension of the fluid provides a restoring force when the field is reduced. The actuation of the fluid is completed in about 12 ms for both thin-to-thick and thick-to-thin fluid film switchings by magnetic forces and surface tension forces, respectively. It was observed that the switching speed was almost independent of the driving current, and no considerable thermal effect were observed when driven by a current up to 100 mA.

  5. Alignment and segregation of bidisperse colloids in a shear-thinning viscoelastic fluid under shear flow

    NARCIS (Netherlands)

    Santos de Oliveira, I.S.; Otter, den W.K.; Briels, W.J.

    2013-01-01

    Computer simulations are presented of colloids, bidisperse in size, suspended in a shear-thinning viscoelastic fluid with the flow characteristics of a surfactant solution. The worm-like micelles are modeled in Responsive Particle Dynamics (RaPiD) as single soft particles obeying a generalized Brown

  6. Interface deformations affect the orientation transition of magnetic ellipsoidal particles adsorbed at fluid–fluid interfaces

    NARCIS (Netherlands)

    Davies, G.; Kruger, T.; Coveney, P.V.; Harting, J.D.R.; Bresme, F.

    2014-01-01

    Manufacturing new soft materials with specific optical, mechanical and magnetic properties is a significant challenge. Assembling and manipulating colloidal particles at fluid interfaces is a promising way to make such materials. We use lattice-Boltzmann simulations to investigate the response of ma

  7. Interface deformations affect the orientation transition of magnetic ellipsoidal particles adsorbed at fluid–fluid interfaces

    NARCIS (Netherlands)

    Davies, G.; Kruger, T.; Coveney, P.V.; Harting, Jens Dieter Rolf; Bresme, F.

    2014-01-01

    Manufacturing new soft materials with specific optical, mechanical and magnetic properties is a significant challenge. Assembling and manipulating colloidal particles at fluid interfaces is a promising way to make such materials. We use lattice-Boltzmann simulations to investigate the response of

  8. Paramagnetic colloidal ribbons in a precessing magnetic field

    Science.gov (United States)

    Alvarez-Nodarse, R.; Quintero, N. R.; Mertens, F. G.; Casic, N.; Fischer, Th. M.

    2015-03-01

    We investigate the dynamics of a kink in a damped parametrically driven nonlinear Klein-Gordon equation. We show by using a method of averaging that, in the high-frequency limit, the kink moves in an effective potential and is driven by an effective constant force. We demonstrate that the shape of the solitary wave can be controlled via the frequency and the eccentricity of the modulation. This is in accordance with the experimental results reported in a recent paper [Casic et al., Phys. Rev. Lett. 110, 168302 (2013), 10.1103/PhysRevLett.110.168302], where the dynamic self-assembly and propulsion of a ribbon formed from paramagnetic colloids in a time-dependent magnetic field has been studied.

  9. Paramagnetic colloidal ribbons in a precessing magnetic field.

    Science.gov (United States)

    Alvarez-Nodarse, R; Quintero, N R; Mertens, F G; Casic, N; Fischer, Th M

    2015-03-01

    We investigate the dynamics of a kink in a damped parametrically driven nonlinear Klein-Gordon equation. We show by using a method of averaging that, in the high-frequency limit, the kink moves in an effective potential and is driven by an effective constant force. We demonstrate that the shape of the solitary wave can be controlled via the frequency and the eccentricity of the modulation. This is in accordance with the experimental results reported in a recent paper [Casic et al., Phys. Rev. Lett. 110, 168302 (2013)], where the dynamic self-assembly and propulsion of a ribbon formed from paramagnetic colloids in a time-dependent magnetic field has been studied.

  10. Relaxation time diagram for identifying heat generation mechanisms in magnetic fluid hyperthermia

    Energy Technology Data Exchange (ETDEWEB)

    Lima, Enio, E-mail: lima@cab.cnea.gov.ar; De Biasi, Emilio; Zysler, Roberto D.; Vasquez Mansilla, Marcelo; Mojica-Pisciotti, Mary L. [Centro Atómico Bariloche/CONICET (Argentina); Torres, Teobaldo E.; Calatayud, M. Pilar; Marquina, C.; Ricardo Ibarra, M.; Goya, Gerardo F. [Universidad de Zaragoza, Instituto de Nanociencia de Aragón INA (Spain)

    2014-12-15

    We present a versatile diagram to envisage the dominant relaxation mechanism of single-domain magnetic nanoparticles (MNPs) under alternating magnetic fields, as those used in magnetic fluid hyperthermia (MFH). The diagram allows estimating the heating efficiency, measured by the Specific Power Absorption (SPA), originated in the magnetic and viscous relaxation times of single-domain MNPs for a given frequency of the ac magnetic field (AFM). The diagram has been successfully applied to different colloids, covering a wide variety of MNPs with different magnetic anisotropy and particle size, and dispersed in different viscous liquid carriers. From the general diagram, we derived a specific chart based on the Linear Response Theory in order to easily estimate the experimental condition for the optimal SPA values of most colloids currently used in MFH.

  11. Fluid-fluid coexistence in an athermal colloid-polymer mixture: thermodynamic perturbation theory and continuum molecular-dynamics simulation

    Science.gov (United States)

    Jover, Julio; Galindo, Amparo; Jackson, George; Müller, Erich A.; Haslam, Andrew J.

    2015-09-01

    Using both theory and continuum simulation, we examine a system comprising a mixture of polymer chains formed from 100 hard-sphere (HS) segments and HS colloids with a diameter which is 20 times that of the polymer segments. According to Wertheim's first-order thermodynamic perturbation theory (TPT1) this athermal system is expected to phase separate into a colloid-rich and a polymer-rich phase. Using a previously developed continuous pseudo-HS potential [J. F. Jover, A. J. Haslam, A. Galindo, G. Jackson, and E. A. Muller, J. Chem. Phys. 137, 144505 (2012)], we simulate the system at a phase point indicated by the theory to be well within the two-phase binodal region. Molecular-dynamics simulations are performed from starting configurations corresponding to completely phase-separated and completely pre-mixed colloids and polymers. Clear evidence is seen of the stabilisation of two coexisting fluid phases in both cases. An analysis of the interfacial tension of the phase-separated regions is made; ultra-low tensions are observed in line with previous values determined with square-gradient theory and experiment for colloid-polymer systems. Further simulations are carried out to examine the nature of these coexisting phases, taking as input the densities and compositions calculated using TPT1 (and corresponding to the peaks in the probability distribution of the density profiles obtained in the simulations). The polymer chains are seen to be fully penetrable by other polymers. By contrast, from the point of view of the colloids, the polymers behave (on average) as almost-impenetrable spheres. It is demonstrated that, while the average interaction between the polymer molecules in the polymer-rich phase is (as expected) soft-repulsive in nature, the corresponding interaction in the colloid-rich phase is of an entirely different form, characterised by a region of effective intermolecular attraction.

  12. Protein-stabilized magnetic fluids

    Science.gov (United States)

    Soenen, S. J. H.; Hodenius, M.; Schmitz-Rode, T.; De Cuyper, M.

    The adsorption of bovine serum albumin (BSA) and egg yolk phosvitin on magnetic fluid particles was investigated. Incubation mixtures were prepared by mixing an alkaline suspension of tetramethylammonium-coated magnetite cores with protein solutions at various protein/Fe 3O 4 ratios, followed by dialysis against a 5 mM TES buffer (pH 7.0), after which separation of bound and non-bound protein by high-gradient magnetophoresis was executed. Both the kinetic profiles as well as the isotherms of adsorption strongly differed for both proteins. In case of the spherical BSA, initially, abundant adsorption occurred, then it decreased and—at high protein concentrations—it slowly raised again. In contrast, with the highly phosphorylated phosvitin, binding slowly started and the extent of protein adsorption remained unchanged both as a function of time and phosvitin concentration. Competition binding studies, using binary protein mixtures composed of equal weight amounts of BSA and phosvitin, showed that binding of the latter protein is 'unrealistically' high. Based on the geometry of the two proteins, putative pictures on their orientation on the particle's surface in the various experimental conditions were deduced.

  13. Sterically stabilized water based magnetic fluids: Synthesis, structure and properties

    Science.gov (United States)

    Bica, Doina; Vékás, Ladislau; Avdeev, Mikhail V.; Marinică, Oana; Socoliuc, Vlad; Bălăsoiu, Maria; Garamus, Vasil M.

    2007-04-01

    Magnetic fluids (MFs), prepared by chemical co-precipitation followed by double layer steric and electrostatic (combined) stabilization of magnetite nanoparticles dispersed in water, are presented. Several combinations of surfactants with different chain lengths (lauric acid (LA), myristic acid (MA), oleic acid (OA) and dodecyl-benzene-sulphonic acid (DBS)) were used, such as LA+LA, MA+MA, LA+DBS, MA+DBS, OA+DBS, OA+OA and DBS+DBS. Static light scattering, transmission electron microscopy, small angle neutron scattering, magnetic and magneto-rheological measurements revealed that MFs with MA+MA or LA+LA biocompatible double layer covered magnetite nanoparticles are the most stable colloidal systems among the investigated samples, and thus suitable for biomedical applications.

  14. Sterically stabilized water based magnetic fluids: Synthesis, structure and properties

    Energy Technology Data Exchange (ETDEWEB)

    Bica, Doina [Laboratory of Magnetic Fluids, Center for Fundamental and Advanced Technical Research, Romanian Academy, Timisoara Division, Bd. Mihai Viteazul 24, 300223 Timisoara (Romania); Vekas, Ladislau [Laboratory of Magnetic Fluids, Center for Fundamental and Advanced Technical Research, Romanian Academy, Timisoara Division, Bd. Mihai Viteazul 24, 300223 Timisoara (Romania) and National Centre for Engineering of Systems with Complex Fluids, University Politehnica Timisoara, Bd. Mihai Viteazul 1, 300222 Timisoara (Romania)]. E-mail: vekas@acad-tim.tm.edu.ro; Avdeev, Mikhail V. [Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna (Russian Federation); Marinica, Oana [National Centre for Engineering of Systems with Complex Fluids, University Politehnica Timisoara, Bd. Mihai Viteazul 1, 300222 Timisoara (Romania); Socoliuc, Vlad [National Institute R and D for Electrochemistry and Condensed Matter, Str. Diaconu Coressi 144, 300588 Timisoara (Romania); Balasoiu, Maria [Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna (Russian Federation); Garamus, Vasil M. [GKSS Research Centre, Geesthacht (Germany)

    2007-04-15

    Magnetic fluids (MFs), prepared by chemical co-precipitation followed by double layer steric and electrostatic (combined) stabilization of magnetite nanoparticles dispersed in water, are presented. Several combinations of surfactants with different chain lengths (lauric acid (LA), myristic acid (MA), oleic acid (OA) and dodecyl-benzene-sulphonic acid (DBS)) were used, such as LA+LA, MA+MA, LA+DBS, MA+DBS, OA+DBS, OA+OA and DBS+DBS. Static light scattering, transmission electron microscopy, small angle neutron scattering, magnetic and magneto-rheological measurements revealed that MFs with MA+MA or LA+LA biocompatible double layer covered magnetite nanoparticles are the most stable colloidal systems among the investigated samples, and thus suitable for biomedical applications.

  15. Magnetic colloid by PLA: Optical, magnetic and thermal transport properties

    Science.gov (United States)

    Pandey, B. K.; Shahi, A. K.; Gopal, Ram

    2015-08-01

    Ferrofluids of cobalt and cobalt oxide nanoparticles (NPs) have been successfully synthesized using liquid phase-pulse laser ablation (LP-PLA) in ethanol and double distilled water, respectively. The mechanism of laser ablation in liquid media and formation process for Co target in double distilled water (DDW) and ethanol are speculated based on the reactions between laser generated highly nascent cobalt species and vaporized solvent media in a confined high temperature and pressure at the plume-surrounding liquid interface region. Optical absorption, emission, vibrational and rotational properties have been investigated using UV-vis absorption, photoluminescence (PL) and Fourier transform-infra red (FT-IR) spectroscopy, respectively. In this study optical band gap of cobalt oxide ferrofluids has been engineered using different pulse energy of Nd:YAG laser in the range of (2.80-3.60 eV). Vibrating sample magnetometer (VSM) is employed to determine the magnetic properties of ferrofluids of cobalt and cobalt oxide NPs while their thermal conductivities are examined using rotating disc method. Ferrofluids have gained enormous curiosity due to many technological applications, i.e. drug delivery, coolant and heating purposes.

  16. Structural deformations in liquid crystals with dispersed magnetic nano-colloids

    Directory of Open Access Journals (Sweden)

    S Shoarinejad

    2012-06-01

    Full Text Available  The stable colloidal dispersions of magnetic nano-particles in nematic liquid crystals are called ferronematics. Their behaviour in magnetic fields depends on various parameters such as anchoring energy, magnetic anisotropy, and shape and volume fraction of the particles. In the present paper, the threshold field is obtained for these colloidal nematics. Then, the influence of magnetic anisotropy, cell thickness, magnetic moment, and volume fraction of the particles are discussed . It is found that due to the influence of some effective parameters, the threshold field changes when compared to pure nematic liquid crystals. The obtained results are consistent with the reported experimental results.

  17. Fluid Replacement in Treatment of Hypovolemia and Shock: Crystalloids and Colloids

    Directory of Open Access Journals (Sweden)

    Fatih Yildiz

    2013-06-01

    Full Text Available Shock is a pathologic state with high mortality rate and characterized by a reduction of systemic tissue perfusion and decresead oxygen delivery. Absolute or relative hypovolemia is a common pathology of most shock types. Correction of hypovolemia might reverse the disturbance and increase the tissue perfusion. Fluid resuscitation with crystalloid and colloid solutions can carry the risk of increasing morbidity and mortality if not used properly. Although crystalloid and colloid solutions are considered to have equal efficacy and safety profile, recent studies showed that this assumption may not be correct. Early and effective management of hypovolemia is the cornerstone of shock resuscitation. Initial management of patients with septic shock and hypovolemia should be done with 30ml/kg of crystalloids. Proper fluid replacement and resuscitation algoritms might increase the survival rate. [Archives Medical Review Journal 2013; 22(3.000: 347-361

  18. New Applications of Magnetic Separation Using Superconducting Magnets and Colloid Chemical Processes

    Science.gov (United States)

    Takeda, S.; Yu, S.-J.; Nakahira, A.; Izumi, Y.; Nishijima, S.; Watanabe, T.

    2005-07-01

    High gradient magnetic separation (HGMS) can be a promising new environmental purification technique as it produces no contaminants, such as flocculants, and could possibly treat large amounts of waste water within a short time frame. A colloid chemical process for magnetic seeding can allow us to rapidly recover a large quantity of adsorbate and to strongly magnetize individual particles in order to improve the recovery efficiency of magnetic separation. In this paper, we will report on the fundamental study of the magnetic seeding process and purification processes using HGMS, and also on studies of applications of the water treatment system for actual factories. Emphasized is a report on a system constructed for water treatment from a paper-manufacturing factory.

  19. Magnetic resonance of magnetic fluid and magnetoliposome preparations

    Energy Technology Data Exchange (ETDEWEB)

    Morais, Paulo C. [Universidade de Brasilia, Instituto de Fisica, Nucleo de Fisica Aplicada, 70919-970 Brasilia-DF (Brazil)]. E-mail: pcmor@unb.br; Santos, Judes G. [Universidade de Brasilia, Instituto de Fisica, Nucleo de Fisica Aplicada, 70919-970 Brasilia-DF (Brazil); Skeff Neto, K. [Universidade de Brasilia, Instituto de Fisica, Nucleo de Fisica Aplicada, 70919-970 Brasilia-DF (Brazil); Pelegrini, Fernando [Universidade Federal de Goias, Instituto de Fisica, 74001-970 Goiania-GO (Brazil); Cuyper, Marcel de [Katholieke Universiteit Leuven, Campus Kortrijk, Interdisciplinary Research Centre, B-8500 Kortrijk (Belgium)

    2005-05-15

    In this study, magnetic resonance was used to investigate lauric acid-coated magnetite-based magnetic fluid particles and particles which are surrounded by a double layer of phospholipid molecules (magnetoliposomes). The data reveal the presence of monomers and dimers in both samples. Whereas evidence for a thermally induced disruption of dimers is found in the magnetic fluid, apparently, the bilayer phospholipid envelop prevents the dissociation in the magnetoliposome samples.

  20. In vitro hyperthermia with improved colloidal stability and enhanced SAR of magnetic core/shell nanostructures.

    Science.gov (United States)

    Patil, R M; Thorat, N D; Shete, P B; Otari, S V; Tiwale, B M; Pawar, S H

    2016-02-01

    Magnetic core/shell nanostructures of Fe3O4 nanoparticles coated with oleic acid and betaine-HCl were studied for their possible use in magnetic fluid hyperthermia (MFH). Their colloidal stability and heat induction ability were studied in different media viz. phosphate buffer solution (PBS), saline solution and glucose solution with different physiological conditions and in human serum. The results showed enhanced colloidal stability in these media owing to their high zeta potential values. Heat induction studies showed that specific absorption rates (SAR) of core/shells were 82-94W/g at different pH of PBS and concentrations of NaCl and glucose. Interestingly, core/shells showed 78.45±3.90W/g SAR in human serum. The cytotoxicity of core/shells done on L929 and HeLa cell lines using 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyl tetrazolium bromide and trypan blue dye exclusion assays showed >89% and >80% cell viability for 24 and 48h respectively. Core/shell structures were also found to be very efficient for in vitro MFH on cancer cell line. About 95% cell death was occurred in 90min after hyperthermia treatment. The mechanism of cell death was found to be elevated ROS generation in cells after exposure to core/shells in external magnetic field. This study showed that these core/shells have a great potential to be used in in vivo MFH. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Designing magnetic composite materials using aqueous magnetic fluids

    CERN Document Server

    Galicia, J A; Cousin, F; Guemghar, D; Menager, C; Cabuil, V

    2003-01-01

    In this paper, we report on how to take advantage of good knowledge of both the chemistry and the stability of an aqueous magnetic colloidal suspension to realize different magnetic composites. The osmotic pressure of the magnetic nanoparticles is set prior to the realization of the composite to a given value specially designed for the purpose for each hybrid material: magnetic particles in polymer networks, particles as probes for studying the structure of clay suspensions and shape modification of giant liposomes. First, we show that the introduction of magnetic particles in polyacrylamide gels enhances their Young modulus and reduces the swelling caused by water. The particles cause both a mechanical and an osmotic effect. The latter is strongly dependent on the ionic strength and is attributed to an attraction between particles and the polymeric matrix. In the second part, we determine the microscopic structure of suspensions of laponite as a function of concentration, by combining SANS and magneto-optica...

  2. Electrocapillary instability of magnetic fluid peak

    CERN Document Server

    Mkrtchyan, Levon; Dikansky, Yuri

    2013-01-01

    The paper presents an experimental study of the capillary electrostatic instability occurring under effect of a constant electric field on a magnetic fluid individual peak. The peaks under study occur at disintegration of a magnetic fluid layer applied on a flat electrode surface under effect of a perpendicular magnetic field. The electrocapillary instability shows itself as an emission of charged drops jets from the peak point in direction of the opposing electrode. The charged drops emission repeats periodically and results in the peak shape pulsations. It is shown that a magnetic field affects the electrocapillary instability occurrence regularities and can stimulate its development. The critical electric and magnetic field strengths at which the instability occurs have been measured; their dependence on the peak size is shown. The hysteresis in the system has been studied; it consists in that the charged drops emission stops at a lesser electric (or magnetic) field strength than that of the initial occurr...

  3. Dissipative charged fluid in a magnetic field

    Directory of Open Access Journals (Sweden)

    Navid Abbasi

    2016-05-01

    Full Text Available We study the collective excitations in a dissipative charged fluid at zero chemical potential when an external magnetic field is present. While in the absence of magnetic field, four collective excitations appear in the fluid, we find five hydrodynamic modes here. This implies that the magnetic field splits the degeneracy between the transverse shear modes. Using linear response theory, we then compute the retarded response functions. In particular, it turns out that the correlation between charge and the energy fluctuations will no longer vanish, even at zero chemical potential. By use of the response functions, we also derive the relevant Kubo formulas for the transport coefficients.

  4. Measurement of the zero-field magnetic dipole moment of magnetizable colloidal silica spheres

    Energy Technology Data Exchange (ETDEWEB)

    Claesson, E M; Erne, B H; Bakelaar, I A; Kuipers, B W M; Philipse, A P [Van' t Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute, Utrecht University, Padualaan 8, 3584 CH Utrecht (Netherlands)

    2007-01-24

    The magnetic properties of dispersions of magnetic silica microspheres have been investigated by measuring the magnetization curves and the complex magnetic susceptibility as a function of frequency and field amplitude. The silica spheres appear to have a net permanent magnetic dipole moment, even in zero field, which is increased significantly after a temporary exposure of the silica colloids to a saturating magnetic field. The magnetic properties of the microparticles in zero field are discussed in terms of the number and the orientations of the embedded nanoparticle dipoles along an easy axis of magnetization in the absence of an external field.

  5. Intra-operative colloid administration increases the clearance of a post-operative fluid load

    DEFF Research Database (Denmark)

    Borup, Tine; Hahn, Robert; Holte, K;

    2009-01-01

    BACKGROUND: It is unknown whether an intra-operative colloid infusion alters the dynamics of a crystalloid load administered post-operatively. METHODS: Ten patients received 12.5 ml/kg of Ringer's lactate over 30 min 1-3 days before and 4 h after laparoscopic cholecystectomy, during which 10 ml....../kg of a colloid solution, hydroxyethylstarch (HES 130/0.4), was infused. The total body clearance of the pre- and post-operative test infusions was taken as the ratio between the urinary excretion and the Hb-derived dilution of venous plasma over 150 min. The plasma clearance of the infused fluid was calculated...... using volume kinetics based on the plasma dilution alone. The pre-operative plasma clearance was compared with the post-operative plasma clearance and patients served as their own control. RESULTS: The urinary excretion averaged 350 ml for the pre-operative infusion and 612 ml post-operatively, which...

  6. Bulk fluid phase behaviour of colloidal platelet-sphere and platelet-polymer mixtures.

    Science.gov (United States)

    de las Heras, Daniel; Schmidt, Matthias

    2013-04-13

    Using a geometry-based fundamental measure density functional theory, we calculate bulk fluid phase diagrams of colloidal mixtures of vanishingly thin hard circular platelets and hard spheres. We find isotropic-nematic phase separation, with strong broadening of the biphasic region, upon increasing the pressure. In mixtures with large size ratio of platelet and sphere diameters, there is also demixing between two nematic phases with differing platelet concentrations. We formulate a fundamental measure density functional for mixtures of colloidal platelets and freely overlapping spheres, which represent ideal polymers, and use it to obtain phase diagrams. We find that, for low platelet-polymer size ratio, in addition to isotropic-nematic and nematic-nematic phase coexistence, platelet-polymer mixtures also display isotropic-isotropic demixing. By contrast, we do not find isotropic-isotropic demixing in hard-core platelet-sphere mixtures for the size ratios considered.

  7. Phase Behavior and Percolation Properties of the Patchy Colloidal Fluids in the Random Porous Media.

    Science.gov (United States)

    Kalyuzhnyi, Y V; Holovko, M; Patsahan, T; Cummings, P T

    2014-12-18

    The lack of a simple analytical description of the hard-sphere fluid in a matrix with hard-core obstacles is limiting progress in the development of thermodynamic perturbation theories for the fluid in random porous media. We propose a simple and highly accurate analytical scheme, which allows us to calculate thermodynamic and percolation properties of a network-forming fluid confined in the random porous media, represented by the hard-sphere fluid and overlapping hard-sphere matrices, respectively. Our scheme is based on the combination of scaled-particle theory, Wertheim's thermodynamic perturbation theory for associating fluids and extension of the Flory-Stockmayer theory for percolation. The liquid-gas phase diagram and percolation threshold line for several versions of the patchy colloidal fluid model confined in a random porous media are calculated and discussed. The method presented enables calculation of the thermodynamic and percolation properties of a large variety of polymerizing and network-forming fluids confined in random porous media.

  8. Tuning the Colloidal Crystal Structure of Magnetic Particles by External Field

    NARCIS (Netherlands)

    Pal, Antara; Malik, Vikash; He, Le; Erne, Ben H.; Yin, Yadong; Kegel, Willem K.; Petukhov, A. V.

    2015-01-01

    Manipulation of the self-assembly of magnetic colloidal particles by an externally applied magnetic field paves a way toward developing novel stimuli responsive photonic structures. Using microradian X-ray scattering technique we have investigated the different crystal structures exhibited by self-a

  9. Designing magnetic composite materials using aqueous magnetic fluids

    Energy Technology Data Exchange (ETDEWEB)

    Galicia, Jose Alberto [Laboratoire Liquides Ioniques et Interfaces Chargees - Equipe Colloides Inorganiques, UMR 7612 CNRS/Universite Pierre et Marie Curie (Paris 6), 4 place Jussieu, case 63 - 75252 Paris Cedex 05 (France); Sandre, Olivier [Laboratoire Liquides Ioniques et Interfaces Chargees - Equipe Colloides Inorganiques, UMR 7612 CNRS/Universite Pierre et Marie Curie (Paris 6), 4 place Jussieu, case 63 - 75252 Paris Cedex 05 (France); Cousin, Fabrice [Laboratoire Leon Brillouin, UMR 12 CNRS/CEA CEA-Saclay - 91191, Gif-sur-Yvette (France); Guemghar, Dihya [Laboratoire Liquides Ioniques et Interfaces Chargees - Equipe Colloides Inorganiques, UMR 7612 CNRS/Universite Pierre et Marie Curie (Paris 6), 4 place Jussieu, case 63 - 75252 Paris Cedex 05 (France); Menager, Christine [Laboratoire Liquides Ioniques et Interfaces Chargees - Equipe Colloides Inorganiques, UMR 7612 CNRS/Universite Pierre et Marie Curie (Paris 6), 4 place Jussieu, case 63 - 75252 Paris Cedex 05 (France); Cabuil, Valerie [Laboratoire Liquides Ioniques et Interfaces Chargees - Equipe Colloides Inorganiques, UMR 7612 CNRS/Universite Pierre et Marie Curie (Paris 6), 4 place Jussieu, case 63 - 75252 Paris Cedex 05 (France)

    2003-04-23

    In this paper, we report on how to take advantage of good knowledge of both the chemistry and the stability of an aqueous magnetic colloidal suspension to realize different magnetic composites. The osmotic pressure of the magnetic nanoparticles is set prior to the realization of the composite to a given value specially designed for the purpose for each hybrid material: magnetic particles in polymer networks, particles as probes for studying the structure of clay suspensions and shape modification of giant liposomes. First, we show that the introduction of magnetic particles in polyacrylamide gels enhances their Young modulus and reduces the swelling caused by water. The particles cause both a mechanical and an osmotic effect. The latter is strongly dependent on the ionic strength and is attributed to an attraction between particles and the polymeric matrix. In the second part, we determine the microscopic structure of suspensions of laponite as a function of concentration, by combining SANS and magneto-optical experiments with the probes. This study requires conditions suitable for including the magnetic particles as probes without disturbing the clay suspensions. The third part presents giant magnetoliposomes, which encapsulate magnetic nanoparticles. Shape transitions are obtained with either a magnetic field or an osmotic stress.

  10. Comparison of Theories of Anisotropy in Transformer Oil-Based Magnetic Fluids

    Directory of Open Access Journals (Sweden)

    Jozef Kudelcik

    2013-01-01

    Full Text Available The external magnetic field in transformer oil-based magnetic fluids leads to the aggregation of magnetic nanoparticles and formation of clusters. These aggregations are the result of the interaction between the external magnetic field and the magnetic moments of the nanoparticles occurs. However, the temperature of magnetic fluids has also very important influence on the structural changes because the mechanism of thermal motion acts against the cluster creation. The acoustic spectroscopy was used to study the anisotropy of transformer oil-based magnetic fluids upon the effect of an external magnetic field and temperature. In present the anisotropy of the magnetic fluids can be described by two theories. Taketomi theory assumes the existence of spherical clusters. These clusters form long chains, aligned in a magnetic field direction. Shliomis in his theory supposed that only nanoparticles formed chains. A comparison of the experimental results with the predictions of the Taketomi theory allowed a determination of the cluster radius and the number density of the colloidal particles. The proportions of the acoustic wave energy used for excitation of the translational and rotational motion were determined.

  11. Magnetic movement of biological fluid droplets

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Antonio A. [Harrington Department of Bioengineering, Arizona State University, Tempe, AZ 85287 (United States)]. E-mail: tony.garcia@asu.edu; Egatz-Gomez, Ana [Harrington Department of Bioengineering, Arizona State University, Tempe, AZ 85287 (United States); Lindsay, Solitaire A. [Harrington Department of Bioengineering, Arizona State University, Tempe, AZ 85287 (United States); Dominguez-Garcia, P. [Departamento de Fisica Fundamental, UNED, Senda del Rey 9, Madrid 28040 (Spain); Melle, Sonia [Harrington Department of Bioengineering, Arizona State University, Tempe, AZ 85287 (United States); Departamento de Optica, Universidad Complutense de Madrid, Arcos de Jalon s/n, Madrid 28037 (Spain); Marquez, Manuel [Harrington Department of Bioengineering, Arizona State University, Tempe, AZ 85287 (United States); Research Center, Philip Morris USA, Richmond, VA 23234 (United States); Rubio, Miguel A. [Departamento de Fisica Fundamental, UNED, Senda del Rey 9, Madrid 28040 (Spain); Picraux, S.T. [Department of Chemical and Materials Engineering, Arizona State University, Tempe, AZ 85287 (United States); Los Alamos National Laboratory, MST-CINT, Los Alamos, NM 87545 (United States); Yang, Dongqing [Department of Chemical and Materials Engineering, Arizona State University, Tempe, AZ 85287 (United States); Aella, P. [Department of Chemical and Materials Engineering, Arizona State University, Tempe, AZ 85287 (United States); Hayes, Mark A. [Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 8528 (United States); Gust, Devens [Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 8528 (United States); Loyprasert, Suchera [Biodesign Institute, Arizona State University, Tempe, AZ 85287 (United States); Vazquez-Alvarez, Terannie [Biodesign Institute, Arizona State University, Tempe, AZ 85287 (United States); Wang, Joseph [Biodesign Institute, Arizona State University, Tempe, AZ 85287 (United States)

    2007-04-15

    Magnetic fields can be used to control the movement of aqueous drops on non-patterned, silicon nanowire superhydrophobic surfaces. Drops of aqueous and biological fluids are controlled by introducing magnetizable carbonyl iron microparticles into the liquid. Key elements of operations such as movement, coalescence, and splitting of water and biological fluid drops, as well as electrochemical measurement of an analyte are demonstrated. Superhydrophobic surfaces were prepared using vapor-liquid-solid (VLS) growth systems followed by coating with a perfluorinated hydrocarbon molecule. Drops were made from aqueous and biological fluid suspensions with magnetizable microparticle concentrations ranging from 0.1 to 10 wt%.

  12. Magnetic method for stimulating transport in fluids

    Science.gov (United States)

    Martin, James E.; Solis, Kyle J.

    2016-10-18

    A method for producing mass and heat transport in fluids, wherein the method does not rely on conventional convection, that is, it does not require gravity, a thermal gradient, or a magnetic field gradient. This method gives rise to a unique class of vigorous, field-controllable flow patterns termed advection lattices. The advection lattices can be used to transport heat and/or mass in any desired direction using only magnetic fields.

  13. Influence of constant magnetic field on aggregation processes in magnetite colloids

    Science.gov (United States)

    Gareev, K. G.; Kononova, I. E.; Levitckii, V. S.; Moshnikov, V. A.; Nalimova, S. S.

    2014-12-01

    Colloids of Fe3O4/SiO2 nanoparticles derived by a two-stage technique on the base of tetraetoxisilane soles were studied. Phase composition of the particles was analyzed by X-ray diffraction and Raman spectroscopy. It was found that phase transition of Fe3O4 into α-Fe2O3 occurs at a laser power exceeding a threshold value. The aggregation of the particles to linear structures in a constant magnetic field was studied by atomic force microscopy. The data on the change in resistance of Fe3O4/SiO2 colloids under an applied magnetic field were obtained.

  14. Experimental investigation on a colloidal damper rendered controllable under the variable magnetic field generated by moving permanent magnets

    Science.gov (United States)

    Suciu, B.

    2016-09-01

    In this work, a colloidal damper rendered controllable under variable magnetic fields is proposed and its controllability is experimentally evaluated. This absorber employs a water- based ferrofluid (FERROTEC MSGW10) in association with a liquid-repellent nanoporous solid matrix, consisted of particles of gamma alumina or/and silica gel. Control of the dynamic characteristics is obtained by moving permanent neodymium annular magnets, which are placed either on the piston head (axial magnetic field) or on the external surface of the cylinder (radial magnetic field). In order to properly select these magnets, flow visualizations inside of a transparent model damper were performed, and the quantity of the displaced liquid by the magnets through the damper's filter and through the nanoporous solid matrix was determined. Experimental data concerning variation of the magnetic flux density at the magnet surface versus the height of the magnet, and versus the target distance was collected. Based on such data, the suitable magnet geometry was decided. Then, the 3D structural model of the trial colloidal damper obtained by using Solidworks, and the excitation test rig are presented. From excitation tests on a ball-screw shaker, one confirmed larger damping abilities of the proposed absorber relative to the traditional colloidal damper, and also the possibility to adjust the damping coefficient according to the excitation type.

  15. Biocompatible Colloidal Suspensions Based on Magnetic Iron Oxide Nanoparticles: Synthesis, Characterization and Toxicological Profile

    Science.gov (United States)

    Coricovac, Dorina-Elena; Moacă, Elena-Alina; Pinzaru, Iulia; Cîtu, Cosmin; Soica, Codruta; Mihali, Ciprian-Valentin; Păcurariu, Cornelia; Tutelyan, Victor A.; Tsatsakis, Aristidis; Dehelean, Cristina-Adriana

    2017-01-01

    The use of magnetic iron oxide nanoparticles in biomedicine has evolved intensely in the recent years due to the multiple applications of these nanomaterials, mainly in domains like cancer. The aim of the present study was: (i) to develop biocompatible colloidal suspensions based on magnetic iron oxide nanoparticles as future theranostic tools for skin pathology and (ii) to test their effects in vitro on human keratinocytes (HaCat cells) and in vivo by employing an animal model of acute dermal toxicity. Biocompatible colloidal suspensions were obtained by coating the magnetic iron oxide nanoparticles resulted during the solution combustion synthesis with a double layer of oleic acid, as innovative procedure in increasing bioavailability. The colloidal suspensions were characterized in terms of dynamic light scattering (DLS) and transmission electron microscopy (TEM). The in vitro effects of these suspensions were tested by means of Alamar blue assay and the noxious effects at skin level were measured using non-invasive methods. The in vitro results indicated a lack of toxicity on normal human cells induced by the iron oxide nanoparticles colloidal suspensions after an exposure of 24 h to different concentrations (5, 10, and 25 μg·mL−1). The dermal acute toxicity test showed that the topical applications of the colloidal suspensions on female and male SKH-1 hairless mice were not associated with significant changes in the quality of barrier skin function.

  16. Quasi-static magnetic measurements to predict specific absorption rates in magnetic fluid hyperthermia experiments

    OpenAIRE

    Coral, DF; Zelis, PM; de Sousa, ME; Muraca, D.; Lassalle, V.; Nicolas, P.; Ferreira,ML.; van Raap, MBF

    2014-01-01

    In this work, the issue on whether dynamic magnetic properties of polydispersed magnetic colloids modeled using physical magnitudes derived from quasi-static magnetic measurement can be extrapolated to analyze specific absorption rate data acquired at high amplitudes and frequencies of excitation fields is addressed. To this end, we have analyzed two colloids of magnetite nanoparticles coated with oleic acid and chitosan in water displaying, under a radiofrequency field, high and low specific...

  17. Crystalloids versus colloids for goal-directed fluid therapy in major surgery

    Science.gov (United States)

    Hiltebrand, Luzius B; Kimberger, Oliver; Arnberger, Michael; Brandt, Sebastian; Kurz, Andrea; Sigurdsson, Gisli H

    2009-01-01

    Introduction Perioperative hypovolemia arises frequently and contributes to intestinal hypoperfusion and subsequent postoperative complications. Goal-directed fluid therapy might reduce these complications. The aim of this study was to compare the effects of goal-directed administration of crystalloids and colloids on the distribution of systemic, hepatosplanchnic, and microcirculatory (small intestine) blood flow after major abdominal surgery in a clinically relevant pig model. Methods Twenty-seven pigs were anesthetized and mechanically ventilated and underwent open laparotomy. They were randomly assigned to one of three treatment groups: the restricted Ringer lactate (R-RL) group (n = 9) received 3 mL/kg per hour of RL, the goal-directed RL (GD-RL) group (n = 9) received 3 mL/kg per hour of RL and intermittent boluses of 250 mL of RL, and the goal-directed colloid (GD-C) group (n = 9) received 3 mL/kg per hour of RL and boluses of 250 mL of 6% hydroxyethyl starch (130/0.4). The latter two groups received a bolus infusion when mixed venous oxygen saturation was below 60% ('lockout' time of 30 minutes). Regional blood flow was measured in the superior mesenteric artery and the celiac trunk. In the small bowel, microcirculatory blood flow was measured using laser Doppler flowmetry. Intestinal tissue oxygen tension was measured with intramural Clark-type electrodes. Results After 4 hours of treatment, arterial blood pressure, cardiac output, mesenteric artery flow, and mixed oxygen saturation were significantly higher in the GD-C and GD-RL groups than in the R-RL group. Microcirculatory flow in the intestinal mucosa increased by 50% in the GD-C group but remained unchanged in the other two groups. Likewise, tissue oxygen tension in the intestine increased by 30% in the GD-C group but remained unchanged in the GD-RL group and decreased by 18% in the R-RL group. Mesenteric venous glucose concentrations were higher and lactate levels were lower in the GD-C group

  18. Fluid mechanics aspects of magnetic drug targeting.

    Science.gov (United States)

    Odenbach, Stefan

    2015-10-01

    Experiments and numerical simulations using a flow phantom for magnetic drug targeting have been undertaken. The flow phantom is a half y-branched tube configuration where the main tube represents an artery from which a tumour-supplying artery, which is simulated by the side branch of the flow phantom, branches off. In the experiments a quantification of the amount of magnetic particles targeted towards the branch by a magnetic field applied via a permanent magnet is achieved by impedance measurement using sensor coils. Measuring the targeting efficiency, i.e. the relative amount of particles targeted to the side branch, for different field configurations one obtains targeting maps which combine the targeting efficiency with the magnetic force densities in characteristic points in the flow phantom. It could be shown that targeting efficiency depends strongly on the magnetic field configuration. A corresponding numerical model has been set up, which allows the simulation of targeting efficiency for variable field configuration. With this simulation good agreement of targeting efficiency with experimental data has been found. Thus, the basis has been laid for future calculations of optimal field configurations in clinical applications of magnetic drug targeting. Moreover, the numerical model allows the variation of additional parameters of the drug targeting process and thus an estimation of the influence, e.g. of the fluid properties on the targeting efficiency. Corresponding calculations have shown that the non-Newtonian behaviour of the fluid will significantly influence the targeting process, an aspect which has to be taken into account, especially recalling the fact that the viscosity of magnetic suspensions depends strongly on the magnetic field strength and the mechanical load.

  19. A colloidal assembly approach to synthesize magnetic porous composite nanoclusters for efficient protein adsorption

    Science.gov (United States)

    Yang, Qi; Lan, Fang; Yi, Qiangying; Wu, Yao; Gu, Zhongwei

    2015-10-01

    A combination strategy of the inverse emulsion crosslinking approach and the colloidal assembly technique is first proposed to synthesize Fe3O4/histidine composite nanoclusters as new-type magnetic porous nanomaterials. The nanoclusters possess uniform morphology, high magnetic content and excellent protein adsorption capacity, exhibiting their great potential for bio-separation.A combination strategy of the inverse emulsion crosslinking approach and the colloidal assembly technique is first proposed to synthesize Fe3O4/histidine composite nanoclusters as new-type magnetic porous nanomaterials. The nanoclusters possess uniform morphology, high magnetic content and excellent protein adsorption capacity, exhibiting their great potential for bio-separation. Electronic supplementary information (ESI) available: Experimental details. See DOI: 10.1039/c5nr05800g

  20. Dynamical density functional theory for arbitrary-shape colloidal fluids including inertia and hydrodynamic interactions

    Science.gov (United States)

    Duran-Olivencia, Miguel A.; Goddard, Ben; Kalliadasis, Serafim

    2015-11-01

    Over the last few decades the classical density-functional theory (DFT) and its dynamic extensions (DDFTs) have become a remarkably powerful tool in the study of colloidal fluids. Recently there has been extensive research to generalise all previous DDFTs finally yielding a general DDFT equation (for spherical particles) which takes into account both inertia and hydrodynamic interactions (HI) which strongly influence non-equilibrium properties. The present work will be devoted to a further generalisation of such a framework to systems of anisotropic particles. To this end, the kinetic equation for the Brownian particle distribution function is derived starting from the Liouville equation and making use of Zwanzig's projection-operator techniques. By averaging over all but one particle, a DDFT equation is finally obtained with some similarities to that for spherical colloids. However, there is now an inevitable translational-rotational coupling which affects the diffusivity of asymmetric particles. Lastly, in the overdamped (high friction) limit the theory is notably simplified leading to a DDFT equation which agrees with previous derivations. We acknowledge financial support from European Research Council via Advanced Grant No. 247031.

  1. Synthesis and real-time magnetic manipulation of a biaxial superparamagnetic colloid.

    Science.gov (United States)

    Kim, Jin Young; Osterloh, Frank E; Hiramatsu, Hiroki; Dumas, R K; Liu, Kai

    2005-06-09

    Superparamagnetic colloidal plates were synthesized from tetrabutylammonium stabilized Ca(2)Nb(3)O(10) nanosheets and oleic acid-stabilized Fe(3)O(4) nanoparticles. Modification with 3-aminopropyltrimethoxysilane produces amine-terminated Ca(2)Nb(3)O(10) with an amine concentration of 0.43 +/- 0.06 groups per Ca(2)Nb(3)O(10) unit as follows from spectroscopic quantification with trinitrobenzenesulfonic acid as a dye. Treatment of the modified sheets in THF/ethanol with 5.3 nm oleic acid-stabilized magnetite nanoparticles yields pseudo-2D assemblies that consist of 2 nm thick nanosheets decorated on both sides with a dense collection (9.3 +/- 0.5 x 10(3) particles per square micrometer per side) of magnetite particles. In noncoordinating or weakly coordinating solvents, these composite particles further aggregate into stacked aggregates with a mean edge length of 1.6 +/- 0.7 microm and a thickness of 79 +/- 30 nm. The colloidal plates were characterized by elemental analysis, X-ray powder diffraction, and infrared and UV/vis spectroscopy. SQUID measurements show that films of the aligned particles are superparamagnetic at room temperature. The magnetic hysteresis that is observed at 5 K reveals that the plates have a magnetic anisotropy with the easy axis in the plane of the plates and the hard axis perpendicular to it. Calculations show that the magnetic anisotropy is a direct consequence of the two-dimensional distribution of the magnetic nanoparticles on the sheets. Optical microscopy reveals that when suspended in ethanol or THF, the colloidal plates can be rotated in real time with a variable external magnetic field (200 Oe). Magnetic alignment of the particles in suspensions also produces asymmetric light scattering patterns and magnetic birefringence. These effects and the observed magneto-orientational properties make the biaxial colloids interesting as components in displays and as magnetic actuators.

  2. Rotating convection in a viscoelastic magnetic fluid

    Energy Technology Data Exchange (ETDEWEB)

    Pérez, L.M. [Departamento de Fíisica y Matemática Aplicada, Universidad de Navarra, 31080 Pamplona (Spain); Laroze, D., E-mail: dlarozen@uta.cl [Instituto de Alta Investigación, Universidad de Tarapacá, Casilla 7D, Arica (Chile); Díaz, P. [Departamento de Ciencias Físicas, Universidad de La Frontera, Casilla 54 D, Temuco (Chile); Martinez-Mardones, J. [Instituto de Física, Pontificia Universidad Católica de Valparaíso, Casilla 4059, Valparaíso (Chile); Mancini, H.L. [Departamento de Fíisica y Matemática Aplicada, Universidad de Navarra, 31080 Pamplona (Spain)

    2014-09-01

    We report theoretical and numerical results on convection for a magnetic fluid in a viscoelastic carrier liquid under rotation. The viscoelastic properties are given by the Oldroyd model. We obtain explicit expressions for the convective thresholds in terms of the parameters of the system in the case of idealized boundary conditions. We also calculate numerically the convective thresholds for the case of realistic boundary conditions. The effects of the rheology and of the rotation rate on the instability thresholds for a diluted magnetic suspension are emphasized. - Highlights: • Ferrofluids. • Thermal convection. • Viscoelastic model. • Realistic boundary conditions.

  3. Electro-Optic Effects in Colloidal Dispersion of Metal Nano-Rods in Dielectric Fluid

    Directory of Open Access Journals (Sweden)

    Oleg D. Lavrentovich

    2011-02-01

    Full Text Available In modern transformation optics, one explores metamaterials with properties that vary from point to point in space and time, suitable for application in devices such as an “optical invisibility cloak” and an “optical black hole”. We propose an approach to construct spatially varying and switchable metamaterials that are based on colloidal dispersions of metal nano-rods (NRs in dielectric fluids, in which dielectrophoretic forces, originating in the electric field gradients, create spatially varying configurations of aligned NRs. The electric field controls orientation and concentration of NRs and thus modulates the optical properties of the medium. Using gold (Au NRs dispersed in toluene, we demonstrate electrically induced change in refractive index on the order of 0.1.

  4. Electro-Optic Effects in Colloidal Dispersion of Metal Nano-Rods in Dielectric Fluid

    Science.gov (United States)

    Golovin, Andrii B.; Xiang, Jie; Park, Heung-Shik; Tortora, Luana; Nastishin, Yuriy A.; Shiyanovskii, Sergij V.; Lavrentovich, Oleg D.

    2011-01-01

    In modern transformation optics, one explores metamaterials with properties that vary from point to point in space and time, suitable for application in devices such as an “optical invisibility cloak” and an “optical black hole”. We propose an approach to construct spatially varying and switchable metamaterials that are based on colloidal dispersions of metal nano-rods (NRs) in dielectric fluids, in which dielectrophoretic forces, originating in the electric field gradients, create spatially varying configurations of aligned NRs. The electric field controls orientation and concentration of NRs and thus modulates the optical properties of the medium. Using gold (Au) NRs dispersed in toluene, we demonstrate electrically induced change in refractive index on the order of 0.1. PMID:28879997

  5. Second virial coefficient at the critical point in a fluid of colloidal spheres plus depletants.

    Science.gov (United States)

    Tuinier, Remco; Feenstra, Maartje S

    2014-11-11

    Vliegenthart-Lekkerkerker (VL) criterion B2 = -6vc for second virial coefficient B2 at the critical (colloidal) gas-liquid point is considered for a mixture of spheres with volume vc plus depletants. For the onset of fluid-phase instability, the VL criterion holds for a wide range of shapes of direct attractive forces between hard-core spheres (Vliegenthart, G. A.; Lekkerkerker, H. N. W. J. Chem. Phys. 2000, 112, 5364). In the case of long-ranged attractions imposed indirectly via depletants, it is found that the VL relation fails. Instead, B2/vc at the critical point depends strongly on the sphere/depletant size ratio. By making the hard spheres sticky, we find that B2 moves gradually toward the VL criterion upon increasing the stickiness.

  6. Local order in a supercooled colloidal fluid observed by confocal microscopy

    CERN Document Server

    Gasser, U; Weitz, D A

    2003-01-01

    The local order in a supercooled monodisperse colloidal fluid is studied by direct imaging of the particles with a laser scanning confocal microscope. The local structure is analysed with a bond order parameter method, which allows one to discern simple structures that are relevant in this system. As expected for samples that crystallize eventually, a large fraction of the particles are found to sit in surroundings with dominant face-centred cubic or hexagonally close-packed character. Evidence for local structures that contain fragments of icosahedra is found, and, moreover, the icosahedral character increases with volume fraction phi, which indicates that it might play an important role at volume fractions near the glass transition.

  7. Local order in a supercooled colloidal fluid observed by confocal microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gasser, U [Department of Physics and Division of Engineering and Applied Sciences, Harvard University, Cambridge, MA (United States); Schofield, Andrew [Department of Physics and Astronomy, University of Edinburgh, Edinburgh (United Kingdom); Weitz, D A [Department of Physics and Division of Engineering and Applied Sciences, Harvard University, Cambridge, MA (United States)

    2003-01-15

    The local order in a supercooled monodisperse colloidal fluid is studied by direct imaging of the particles with a laser scanning confocal microscope. The local structure is analysed with a bond order parameter method, which allows one to discern simple structures that are relevant in this system. As expected for samples that crystallize eventually, a large fraction of the particles are found to sit in surroundings with dominant face-centred cubic or hexagonally close-packed character. Evidence for local structures that contain fragments of icosahedra is found, and, moreover, the icosahedral character increases with volume fraction {phi}, which indicates that it might play an important role at volume fractions near the glass transition.

  8. Novel optical devices based on the tunable refractive index of magnetic fluid and their characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Yong, E-mail: zhaoyong@ise.neu.edu.cn [College of Information Science and Engineering, Northeastern University, Shenyang 110819 (China); Zhang Yuyan [College of Information Science and Engineering, Northeastern University, Shenyang 110819 (China); Shenyang Institute of Engineering, Shenyang 110136 (China); Lv Riqing; Wang Qi [College of Information Science and Engineering, Northeastern University, Shenyang 110819 (China)

    2011-12-15

    As a new type of functional material, magnetic fluid (MF) is a stable colloid of magnetic nanoparticles, dressed with surfactant and dispersed in the carrier liquid uniformly. The MF has many unique optical properties, and the most important one is its tunable refractive index property. This paper summarizes the properties of the MF refractive index and the related optical devices. The refractive index can be easily controlled by external magnetic field, temperature, and so on. But the tunable refractive index of MF has a relaxation effect. As a result, the response time is more than milliseconds and the MF is only suitable for low speed environment. Compared with the traditional optical devices, the magnetic fluid based optical devices have the tuning ability. Compared with the tunable optical devices (the electro-optic devices (LiNbO{sub 3}) of more than 10 GHz modulation speed, acoustic-optic devices (Ge) of more than 20 MHz modulation speed), the speed of the magnetic fluid based optical devices is low. Now there are many applications of magnetic fluid based on the refractive index in the field of optical information communication and sensing technology, such as tunable beam splitter, optical-fiber modulator, tunable optical gratings, tunable optical filter, optical logic device, tunable interferometer, and electromagnetic sensor. With the development of the research and application of magnetic fluid,a new method, structure and material to improve the response time can be found, which will play an important role in the fields of optical information communication and sensing technology. - Highlights: > Magnetic fluid is a new type of functional material, which has many unique optical properties. > We summarize the tunable refractive index property and the related optical devices. > Refractive index can be easily controlled by external magnetic field, temperature and so on. > There are many applications in the field of optical communication and sensing technology

  9. Optical, magnetic and thermal properties of colloidal suspension of ferrofluids synthesized by laser ablation

    Science.gov (United States)

    Pandey, B. K.; Shahi, A. K.; Shah, Jyoti; Kotnala, R. K.; Gopal, Ram

    2017-07-01

    A high power Nd: YAG laser has been employed to produce magnetic colloids (ferrofluids) of iron oxide nanoparticles (NPs) in double distilled water. It is found that FeO (Wüstite) phase of iron oxide has been produced as an initial product; after oxidation and agglomeration it appears as Fe2O3 a stable composition of iron oxide. UV-visible absorption spectroscopy has been employed to distinguish both phases of iron oxide NPs. Absorption band gap of as synthesized ferrofluids at different pulse energies (30, 40, 50, 60 mJ) has been calculated. The absorption band gap of as synthesized FeO magnetic colloids is found in the range of (2.91-3.13 eV) and (3.37-3.91 eV) respectively which arises due to pair excitation and charge transfer. Absorption band gaps of Fe2O3 are found in the range of (2.16-2.28 eV) and (2.68-3.10 eV) respectively again due to pair excitation and charge transfer. Magnetic measurement was performed using VSM which confirms antiferromagnetic nature of FeO NPs with coercivity 47 Oe and magnetic domain size 73.50 Å at 300 K. Zero field cooled and field cooled magnetization confirms blocking and Néel temperature 245  ±  2 K and 181  ±  2 K respectively. Highlight for review 1. As synthesized colloidal suspension of iron oxide NPs can be used as efficient cooling agent. 2. FeO composition of iron oxide has been synthesized using PLA 3. Optical band gap of colloidal suspension of iron oxide NPs is calculated at different laser energy. 4. Magnetic properties of iron oxide NPs have been studied.

  10. Waves in Radial Gravity Using Magnetic Fluid

    Science.gov (United States)

    Ohlsen, D. R.; Hart, J. E.; Weidman, P. D.

    1999-01-01

    Terrestrial laboratory experiments studying various fluid dynamical processes are constrained, by being in an Earth laboratory, to have a gravitational body force which is uniform and unidirectional. Therefore fluid free-surfaces are horizontal and flat. Such free surfaces must have a vertical solid boundary to keep the fluid from spreading horizontally along a gravitational potential surface. In atmospheric, oceanic, or stellar fluid flows that have a horizontal scale of about one-tenth the body radius or larger, sphericity is important in the dynamics. Further, fluids in spherical geometry can cover an entire domain without any sidewall effects, i.e. have truly periodic boundary conditions. We describe spherical body-force laboratory experiments using ferrofluid. Ferrofluids are dilute suspensions of magnetic dipoles, for example magnetite particles of order 10 nm diameter, suspended in a carrier fluid. Ferrofluids are subject to an additional body force in the presence of an applied magnetic field gradient. We use this body force to conduct laboratory experiments in spherical geometry. The present study is a laboratory technique improvement. The apparatus is cylindrically axisymmetric. A cylindrical ceramic magnet is embedded in a smooth, solid, spherical PVC ball. The geopotential field and its gradient, the body force, were made nearly spherical by careful choice of magnet height-to-diameter ratio and magnet size relative to the PVC ball size. Terrestrial gravity is eliminated from the dynamics by immersing the "planet" and its ferrofluid "ocean" in an immiscible silicone oil/freon mixture of the same density. Thus the earth gravity is removed from the dynamics of the ferrofluid/oil interface and the only dynamically active force there is the radial magnetic gravity. The entire apparatus can rotate, and waves are forced on the ferrofluid surface by exterior magnets. The biggest improvement in technique is in the wave visualization. Fluorescing dye is added to

  11. Statics of Magnetic Fluid Drop with Compound Magnetic Core in a Wedge-Shaped Channel

    Directory of Open Access Journals (Sweden)

    V. Bashtovoi

    2013-12-01

    Full Text Available A behavior of magnetic fluid drop with compound magnetic core in a wedge-shaped channel was studied experimentally. The study examines influence of magnetic fluid properties, its volume and magnetic field on statics of the system compound magnetmagnetic fluid drop in wedge-shaped channel. The possibility to change the static conditions of such system by altering magnetic field of the core was observed

  12. EXPERIMENTAL APPARATUS FOR EXAMINATION OF MAGNETIC FLUID LUBRICATED THURST BEARING

    Directory of Open Access Journals (Sweden)

    Józef SALWIŃSKI

    2014-06-01

    Full Text Available In recent years, there has been development of the structure of thrust bearing with magnetic fluids . The essence of this type of bearing is to maintain a liquid lubricant in a very narrow gap with magnetic fluid by a magnetic field. Such systems can act as the bearing lubrication and sealing. This paper presents description of the experimental apparatus for examination magnetic fluid lubricated thrust bearing. Description of the construction and characteristics of the measuring possibilities ware presented.

  13. Magnetization of polydisperse colloidal ferrofluids: effect of magnetostriction.

    Science.gov (United States)

    Huang, J P; Holm, C

    2004-12-01

    We exploit magnetostriction in polydisperse ferrofluids in order to generate nonlinear responses and apply a thermodynamical method to derive the desired nonlinear magnetic susceptibility. For an ideal gas, this method has been demonstrated to be in excellent agreement with a statistical method. In the presence of a sinusoidal ac magnetic field, the magnetization of the polydisperse ferrofluid contains higher-order harmonics, which can be extracted analytically by using a perturbation approach. We find that the harmonics are sensitive to the particle distribution and the degree of field-induced anisotropy of the system. In addition, we find that the magnetization is higher in the polydisperse system than in the monodisperse one, as also found by a recent Monte Carlo simulation. Thus, it seems possible to detect the size distribution in a polydisperse ferrofluid by measuring the harmonics of the magnetization under the influence of magnetostriction.

  14. Microstructure and magnetic properties of colloidal cobalt nano-clusters

    Energy Technology Data Exchange (ETDEWEB)

    Torchio, R. [Dipartimento di Fisica ' E. Amaldi' , Universita di Roma Tre, via della Vasca Navale 84, I-00146 Roma (Italy); CNR-TASC c/o GILDA-ESRF Grenoble (France); European Synchrotron Radiation Facility, 6 Rue Jules Horowitz, BP220, 38043 Grenoble Cedex (France); Meneghini, C., E-mail: meneghini@fis.uniroma3.i [Dipartimento di Fisica ' E. Amaldi' , Universita di Roma Tre, via della Vasca Navale 84, I-00146 Roma (Italy); CNR-TASC c/o GILDA-ESRF Grenoble (France); Mobilio, S. [Dipartimento di Fisica ' E. Amaldi' , Universita di Roma Tre, via della Vasca Navale 84, I-00146 Roma (Italy); CNR-TASC c/o GILDA-ESRF Grenoble (France); Laboratori Nazionali di Frascati INFN, via E. Fermi 40, I-00044 Frascati, Roma (Italy); Capellini, G. [Dipartimento di Fisica ' E. Amaldi' , Universita di Roma Tre, via della Vasca Navale 84, I-00146 Roma (Italy); Garcia Prieto, A. [Departamento de Fisica Aplicada I, Universidad del Pais Vasco (Spain); Alonso, J.; Fdez-Gubieda, M.L. [Departamento de Electricidad y Electronica, Universidad del Pais Vasco (Spain); Turco Liveri, V. [Dipartimento di Chimica Fisica ' F. Accascina' , Universita di Palermo, Viale delle Scienze, Parco d' Orleans II, Edificio 17, 90128 Palermo (Italy); Longo, A. [ISMN, Istituto per lo Studio dei Materiali Nanostrutturati, CNR, Via U. La Malfa 153, 90146 Palermo (Italy); Ruggirello, A.M. [Dipartimento di Chimica Fisica ' F. Accascina' , Universita di Palermo, Viale delle Scienze, Parco d' Orleans II, Edificio 17, 90128 Palermo (Italy); Neisius, T. [Federation des Sciences Chimiques de Marseille, Universite Paul Cezanne, Faculte des Sciences et Techniques Campus de Saint Jerome av. Escadrille Normandie Niemen 13397 Marseille Cedex (France)

    2010-11-15

    The magnetic response of nanometer sized Co nanoparticles (NP) prepared using reverse micelle solutions are presented. The use of complementary structural and morphological probes (like transmission electron microscopy, high resolution electron microscopy, X-ray absorption spectroscopy) allowed to relate the magnetic properties to the size, morphology, composition and atomic structure of the nanoparticles. All data agree on the presence of a core-shell structure of NPs made of a metallic Co core surrounded by a thin Co-oxide layer. The core-shell microstructure of NPs affects its magnetic response mainly raising the anisotropy constant.

  15. Pattern formation and coarse-graining in two-dimensional colloids driven by multiaxial magnetic fields.

    Science.gov (United States)

    Müller, Kathrin; Osterman, Natan; Babič, Dušan; Likos, Christos N; Dobnikar, Jure; Nikoubashman, Arash

    2014-05-13

    We study the pattern formation in a two-dimensional system of superparamagnetic colloids interacting via spatially coherent induced interactions driven by an external precessing magnetic field. On the pair level, upon changing the opening angle of the external field, the interactions smoothly vary from purely repulsive (opening angle equal to zero) to purely attractive (time-averaged pair interactions at an opening angle of 90°). In the experiments, we observed ordered hexagonal crystals at the repulsive end and coarsening frothlike structures for purely attractive interactions. In both of these limiting cases, the dense colloidal systems can be sufficiently accurately described by assuming pairwise additivity of the interaction potentials. However, for a range of intermediate angles, pronounced many-body depolarization effects compete with the direct induced interactions, resulting in inherently anisotropic effective interactions. Under such conditions, we observed the decay of hexagonal order with the concomitant formation of short chains and percolated networks of chains coexisting with free colloids. In order to describe and investigate these systems theoretically, we developed a coarse-grained model of a binary mixture of patchy and nonpatchy particles with the ratio of patchy and nonpatchy colloids as the order parameter. Combining genetic algorithms with Monte Carlo simulations, we optimized the model parameters and quantitatively reproduced the experimentally observed sequence of colloidal structures. The results offer new insight into the anisotropy induced by the many-body effects. At the same time, they allow for a very efficient description of the system by means of a pairwise-additive Hamiltonian, whereupon the original, one-component system features a two-component mixture of isotropic and patchy colloids.

  16. Synthesis and magnetic properties of Co-Zn magnetic fluid

    Energy Technology Data Exchange (ETDEWEB)

    Vaidyanathan, G. [Department of Physics, Pondicherry Engineering College, Pondicherry 605014 (India)], E-mail: gvn_pec@yahoo.com; Sendhilnathan, S. [Department of Physics, Sri Manakula Vinayagar Engineering College, Pondicherry 605107 (India)], E-mail: sendhil29@yahoo.co.in

    2008-03-15

    Co{sub 1-x}Zn{sub x}Fe{sub 2}O{sub 4} (with x varying from 0 to 0.7) nanoparticles to be used for ferrofluid preparation were prepared by chemical co-precipitation method. The fine particles were suitably dispersed in transformer oil using oleic acid as the surfactant. The magnetization (M{sub s}) and the size of the particles were measured at room temperature. The magnetization (M{sub s}) was found to decrease with the increase in zinc substitution. The magnetic particle size (D{sub m}) of the fluid was found to vary from 11.19 to 4.25 nm decreasing with the increase in zinc substitution.

  17. The friction control of magnetic fluid in the Couette flow

    Science.gov (United States)

    Labkovich, O. N.; Reks, A. G.; Chernobai, V. A.

    2017-06-01

    In the work characteristic areas of magnetic fluid flow are experimentally determined in the gap between the cylinders: the area of strong dipole-dipole interaction between magnetite particles 041,2. For areas with high flow losses in viscous friction is shown the possibility of reducing the introduction of magnetic fluid of carbon nanotubes and creating a rotating magnetic field.

  18. Simulation and control scheme of microstructure in magnetic fluids

    Institute of Scientific and Technical Information of China (English)

    LI Qiang; XUAN YiMin; LI Bin

    2007-01-01

    By accounting for the external and internal force acting on the suspended magnetic nanoparticles and motion characteristics of the suspended magnetic nanoparticles in the magnetic fluids, the three-dimensional microstructure of magnetic fluids is investigated by means of the molecular dynamics simulation method. The distribution of suspended magnetic nanoparticles and microstructure of the magnetic fluid are simulated in both absence and presence of an external magnetic field. The effecta of the nanoparticles volume fraction, the dipole-dipole interaction potential and the particle-field interaction potential on the microstructures of the magnetic fluids are discussed. The main results obtained here are summarized as follows.The suspended magnetic nanoparticles tend to aggregate and make the irregular distribution structure in the absence of an external magnetic field. When the magnetic fluid is exposed to a magnetic field, the magnetic nanoparticles suspended in the carrier fluid tend to remain chained-alignment in the direction of the external magnetic field. The tendency of chain-alignment morphology of the suspended magnetic nanoparticles is enhanced with the nanoparticles volume fraction, the dipole-dipole interaction potential and the particle-field interaction potential.

  19. Simulation and control scheme of microstructure in magnetic fluids

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    By accounting for the external and internal force acting on the suspended magnetic nanoparticles and motion characteristics of the suspended magnetic nanoparticles in the magnetic fluids,the three-dimensional microstructure of magnetic fluids is investigated by means of the molecular dynamics simulation method. The distribu-tion of suspended magnetic nanoparticles and microstructure of the magnetic fluid are simulated in both absence and presence of an external magnetic field. The ef-fects of the nanoparticles volume fraction,the dipole-dipole interaction potential and the particle-field interaction potential on the microstructures of the magnetic fluids are discussed. The main results obtained here are summarized as follows. The suspended magnetic nanoparticles tend to aggregate and make the irregular distribution structure in the absence of an external magnetic field. When the mag-netic fluid is exposed to a magnetic field,the magnetic nanoparticles suspended in the carrier fluid tend to remain chained-alignment in the direction of the external magnetic field. The tendency of chain-alignment morphology of the suspended magnetic nanoparticles is enhanced with the nanoparticles volume fraction,the dipole-dipole interaction potential and the particle-field interaction potential.

  20. Assembly and photonic properties of superparamagnetic colloids in complex magnetic fields.

    Science.gov (United States)

    He, Le; Hu, Yongxing; Han, Xiaogang; Lu, Yu; Lu, Zhenda; Yin, Yadong

    2011-11-15

    Interparticle magnetic dipole force has been found to drive the formation of dynamic superparamagnetic colloidal particle chains that can lead to the creation of photonic nanostructures with rapidly and reversibly tunable structural colors in the visible and near-infrared spectrum. Although most studies on magnetic assembly utilize simple permanent magnets or electromagnets, magnetic fields, in principle, can be more complex, allowing the localized modulation of assembly and subsequent creation of complex superstructures. To explore the potential applications of a magnetically tunable photonic system, we study the assembly of magnetic colloidal particles in the complex magnetic field produced by a nonideal linear Halbach array. We demonstrate that a horizontal magnetic field sandwiched between two vertical fields would allow one to change the orientation of the particle chains, producing a high contrast in color patterns. A phase transition of Fe(3)O(4)@SiO(2) particles from linear particle chains to three-dimensional crystals is found to be determined by the interplay of the magnetic dipole force and packing force, as well as the strong electrostatic force. While a color pattern with tunable structures and diffractions can be instantly created when the particles are assembled in the form of linear chains in the regions with vertical fields, the large field gradient in the horizontal orientation may destabilize the chain structures and produces a pattern of 3D crystals that compliments that of initial chain assemblies. Our study not only demonstrates the great potential of magnetically responsive photonic structures in the visual graphic applications such as signage and security documents but also points out the potential challenge in pattern stability when the particle assemblies are subjected to complex magnetic fields that often involve large field gradients.

  1. Use of the photoacoustic spectroscopy for characterization of magnetic fluid based on mamona oil

    Energy Technology Data Exchange (ETDEWEB)

    Silveira, L B; Webler, G D; Santos, J G [Departamento de Fisica, Universidade Federal de Rondonia/NCT/UNIR, BR 364, Km 9.5. Porto Velho - RO. CEP 78.900-000 (Brazil); Oliveira, A C; Garg, V K; Morais, P C, E-mail: lbatistadasilveira@gmail.co [Instituto de Fisica, Nucleo de Fisica Aplicada, Universidade de Brasilia BrasIlia-DF CEP 70919-970 (Brazil)

    2010-03-01

    In this study the photoacoustic spectroscopy was used to investigate the interaction between colloidal suspended nanosized maghemite particles and molecules present in mamona oil (ricinus communis L.). Maghemite nanoparticles were used to produce a magnetic fluid sample dispersed in mamona oil (MF-Mamona oil). In the L-band region (600 to 900 nm) of the photoacoustic spectra we found the photoacustic signal of sample MF-Mamona oil enhanced with respect to the signal of the purified mamona oil. This finding is claimed to be the signature of the strong interaction between the mamona oil's molecules and the solid surface provided by the suspended nanosized maghemite particles.

  2. Use of the photoacoustic spectroscopy for characterization of magnetic fluid based on mamona oil

    Science.gov (United States)

    Silveira, L. B.; Webler, G. D.; Oliveira, A. C.; Garg, V. K.; Santos, J. G.; Morais, P. C.

    2010-03-01

    In this study the photoacoustic spectroscopy was used to investigate the interaction between colloidal suspended nanosized maghemite particles and molecules present in mamona oil (ricinus communis L.). Maghemite nanoparticles were used to produce a magnetic fluid sample dispersed in mamona oil (MF-Mamona oil). In the L-band region (600 to 900 nm) of the photoacoustic spectra we found the photoacustic signal of sample MF-Mamona oil enhanced with respect to the signal of the purified mamona oil. This finding is claimed to be the signature of the strong interaction between the mamona oil's molecules and the solid surface provided by the suspended nanosized maghemite particles.

  3. Colloidal complexed silver and silver nanoparticles in extrapallial fluid of Mytilus edulis.

    Science.gov (United States)

    Zuykov, Michael; Pelletier, Emilien; Demers, Serge

    2011-02-01

    Metal transport in mollusk extrapallial fluid (EPF) that acts as a "bridge" between soft tissues and shell has surprisingly received little attention until now. Using ultrafiltration and radiotracer techniques we determined silver concentrations and speciation in the EPF of the blue mussel Mytilus edulis after short-term uptake and depuration laboratory experiments. Radiolabelled silver ((¹¹⁰m)Ag) was used in dissolved or nanoparticulate phases (AgNPs silver nanoparticles were transported to the EPF of blue mussels at a level similar to the Ag ionic form. Bulk activity of radiolabelled silver in the EPF represented only up to 7% of the bulk activity measured in the whole mussels. The EPF extracted from mussels exposed to both treatments exhibited an Ag colloidal complexed form based on EPF ultrafiltration through a 3 kDa filter. This original study brings new insights to internal circulation of nanoparticles in living organisms and contributes to the international effort in studying the potential impacts of engineered nanomaterials on marine bivalves which play an essential role in coastal ecosystems, and are important contributors to human food supply from the sea.

  4. Autowaves in near-surface layer of magnetic fluid

    Energy Technology Data Exchange (ETDEWEB)

    Chekanov, V.V. [Stavropol State University, 1 Pushkin st., Stavropol 355009 (Russian Federation)]. E-mail: fmf@stavsu.ru; Iljuch, P.M. [Stavropol Branch of Moskow Apparatus Bilding and Informatics Academy, 25 Kulakova st., Stavropol 355000 (Russian Federation); Kandaurova, N.V. [Stavropol Branch of Moskow Apparatus Bilding and Informatics Academy, 25 Kulakova st., Stavropol 355000 (Russian Federation); Bondarenko, E.A. [Stavropol State University, 1 Pushkin st., Stavropol 355009 (Russian Federation)

    2005-03-15

    Autowaves processes in a magnetic fluids in an electric and magnetic fields has been investigated. Different type of autowaves in near-surface region of electrochemical cell has been found. Equation of autowave process has been described.

  5. Non-equilibrium magnetic colloidal dispersions at liquid-air interfaces: dynamic patterns, magnetic order and self-assembled swimmers.

    Science.gov (United States)

    Snezhko, Alexey

    2011-04-20

    Colloidal dispersions of interacting particles subjected to an external periodic forcing often develop nontrivial self-assembled patterns and complex collective behavior. A fundamental issue is how collective ordering in such non-equilibrium systems arises from the dynamics of discrete interacting components. In addition, from a practical viewpoint, by working in regimes far from equilibrium new self-organized structures which are generally not available through equilibrium thermodynamics can be created. In this review spontaneous self-assembly phenomena in magnetic colloidal dispersions suspended at liquid-air interfaces and driven out of equilibrium by an alternating magnetic field are presented. Experiments reveal a new type of nontrivially ordered self-assembled structures emerging in such systems in a certain range of excitation parameters. These dynamic structures emerge as a result of the competition between magnetic and hydrodynamic forces and have complex unconventional magnetic ordering. Nontrivial self-induced hydrodynamic fields accompany each out-of-equilibrium pattern. Spontaneous symmetry breaking of the self-induced surface flows leading to a formation of self-propelled microstructures has been discovered. Some features of the self-localized structures can be understood in the framework of the amplitude equation (Ginzburg-Landau type equation) for parametric waves coupled to the conservation law equation describing the evolution of the magnetic particle density and the Navier-Stokes equation for hydrodynamic flows. To understand the fundamental microscopic mechanisms governing self-assembly processes in magnetic colloidal dispersions at liquid-air interfaces a first-principle model for a non-equilibrium self-assembly is presented. The latter model allows us to capture in detail the entire process of out-of-equilibrium self-assembly in the system and reproduces most of the observed phenomenology.

  6. Synthesis of colloidal silver iron oxide nanoparticles--study of their optical and magnetic behavior.

    Science.gov (United States)

    Kumar, Anil; Singhal, Aditi

    2009-07-22

    Silver iron oxide nanoparticles of fairly small size (average diameter approximately 1 nm) with narrow size distribution have been synthesized by the interaction of colloidal beta- Fe2O3 and silver nanoparticles. The surface morphology and size of these particles have been analyzed by using atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Their structural analysis has been carried out by employing x-ray diffraction (XRD), selected-area electron diffraction (SAED), optical and infrared (IR) spectroscopic techniques. The ageing of these particles exhibits the formation of self-assembly, possibly involving weak supramolecular interactions between Ag(I)O4 and Fe(III)O4 species. These particles display the onset of absorption in the near-infrared region and have higher absorption coefficient in the visible range compared to that of its precursors. Magnetic measurements reveal an interesting transition in their magnetic behavior from diamagnetic to superparamagnetic. The magnetic moment of these particles attains a limiting value of about 0.19 emu cm(-2), which is more than two times higher than that of colloidal beta- Fe2O3. With enhanced optical and magnetic properties, this system is suggested to have possible applications in optoelectronic and magnetic devices.

  7. Tunable magneto-optic modulation based on magnetically responsive nanostructured magnetic fluid

    Institute of Scientific and Technical Information of China (English)

    Bai Xue-Kun; Pu Sheng-Li; Wang Lun-Wei; Wang Xiang; Yu Guo-Jun; Ji Hong-Zhu

    2011-01-01

    Magnetic fluid is a kind of functional composite material with nanosized structure and unique optical properties.The tunable magneto-optic modulation of magnetic fluid under external magnetic field,achieved by adjusting the polarization direction of incident light,is investigated theoretically and experimentally in this work.The corresponding modulation depth and response time are obtained.The accompanying mechanisms are clarified by using the theory of dichroism of magnetic fluid and the aggregation/disintegration processes of magnetic particles within magnetic fluid when the external magnetic field turns on/off.

  8. Faraday effect in magnetic fluids at a frequency 10 GHz

    Energy Technology Data Exchange (ETDEWEB)

    Maiorov, M.M. E-mail: maiorov@tesla.sal.1v

    2002-11-01

    This work presents some results of observed Faraday effect in magnetic fluids in the centimetric region of the electromagnetic spectrum. The effect is observed when a transversal electric wave of mode H{sub 11} propagates in the circular waveguide with a magnetic fluid. The constant magnetic field was applied along the waveguide. Magnetic fluids with different concentrations of magnetite core nanoparticles suspended in tetradecane (C{sub 14}H{sub 30}) are used in the magnetic fields from 0 to 1500 Oe. A 160 deg. rotation of wave polarization is obtained for a 200 mm sample.

  9. Synthesis of silicone magnetic fluid for use in eye surgery

    Science.gov (United States)

    Dailey, J. P.; Phillips, J. P.; Li, C.; Riffle, J. S.

    1999-04-01

    Retinal detachment is repaired by external and internal tamponade. There is as yet no direct internal tamponade which provides 360° coverage to the retina. With a magnetized encircling scleral buckle, magnetic fluids would provide 360° encircling internal tamponade. Our magnetic fluid is a dispersion of ultrafine (4-10 nm) magnetic particles in silicone secured with triblock copolymer steric stabilizers. Triblock copolymers are good steric stabilizers for suspensions of γ-Fe 2O 3 powder in octamethylcyclotetrasiloxane (D 4).

  10. Magnetic nanoparticles in fluid environment: combining molecular dynamics and Lattice-Boltzmann

    Science.gov (United States)

    Melenev, Petr

    2017-06-01

    Hydrodynamic interactions between magnetic nanoparticles suspended in the Newtonian liquid are accounted for using a combination of the lattice Boltzmann method and molecular dynamics simulations. Nanoparticle is modelled by the system of molecular dynamics material points (which form structure resembles raspberry) coupled to the lattice Boltzmann fluid. The hydrodynamic coupling between the colloids is studied by simulations of the thermo-induced rotational diffusion of two raspberry objects. It was found that for the considered range of model parameters the approaching of the raspberries leads to slight retard of the relaxation process. The presence of the weak magnetic dipolar interaction between the objects leads to modest decrease of the relaxation time and the extent of the acceleration of the diffusion is intensified along with magnetic forces.

  11. Colloidal domain lithography for regularly arranged artificial magnetic out-of-plane monodomains in Au/Co/Au layers.

    Science.gov (United States)

    Kuświk, Piotr; Ehresmann, Arno; Tekielak, Maria; Szymański, Bogdan; Sveklo, Iosif; Mazalski, Piotr; Engel, Dieter; Kisielewski, Jan; Lengemann, Daniel; Urbaniak, Maciej; Schmidt, Christoph; Maziewski, Andrzej; Stobiecki, Feliks

    2011-03-04

    Regularly arranged magnetic out-of-plane patterns in continuous and flat films are promising for applications in data storage technology (bit patterned media) or transport of individual magnetic particles. Whereas topographic magnetic structures are fabricated by standard lithographical techniques, the fabrication of regularly arranged artificial domains in topographically flat films is difficult, since the free energy minimization determines the existence, shape, and regularity of domains. Here we show that keV He(+) ion bombardment of Au/Co/Au layer systems through a colloidal mask of hexagonally arranged spherical polystyrene beads enables magnetic patterning of regularly arranged cylindrical magnetic monodomains with out-of-plane magnetization embedded in a ferromagnetic matrix with easy-plane anisotropy. This colloidal domain lithography creates artificial domains via periodic lateral anisotropy variations induced by periodic defect density modulations. Magnetization reversal of the layer system observed by magnetic force microscopy shows individual disc switching indicating monodomain states.

  12. Long term stability and reproducibility of magnetic colloids are key issues for steady values of Specific Power Absorption through time

    CERN Document Server

    Sanz, B; Cassinelli, N; Ibarra, M R; Goya, G F

    2016-01-01

    Virtually all clinical applications of magnetic nanoparticles (MNPs) require the formulation of biocompatible, water-based magnetic colloids. For magnetic hyperthermia, the requirements also include a high colloidal stability against precipitation and agglomeration of the constituent MNPs, in order to keep the heating efficiency of the ferrofluid in the long term. The specific power absorption (SPA) of single-domain MNPs depends critically on the average particle size and size distribution width, therefore first-rate reproducibility among different batches regarding these parameters are also needed. We have studied the evolution of the SPA of highly reproducible and stable water-based colloid composed of polymer coated $Fe_{3}O_{4}$ magnetic nanoparticles. By measuring the specific power absorption (SPA) values along one year as a function of field amplitude and frequencies ($H \\leq 24 kA/m$; $260 \\leq f \\leq 830 kHz$), we demonstrated that SPA in these samples can be made reproducible between successive synt...

  13. Surface-modified magnetic colloids for affinity adsorption of immunoglobulins

    Science.gov (United States)

    Martins, Fernanda; Pinho, Samantha C.; Zollner, Terezinha C. A.; Zollner, Ricardo L.; de Cuyper, Marcel; Santana, Maria Helena A.

    This work describes the preparation, characterization and in vitro adsorption tests of surface-modified magnetoliposomes for affinity binding of (i) anticardiolipin (isotype G) antibodies and (ii) specific isotype E antibodies generated by hypersensitivity reactions in humans with respiratory allergy. In the first case, cardiolipin embedded in the bilayer of magnetoliposomes was used as specific ligand. In the second case, antigenic proteins present in an extract of Dermatophagoids pteronyssinus and Blomia tropicalis mites were covalently coupled on the surface of magnetoliposomes via a diglycolic spacer arm, and used as specific ligands for IgE. Antibody adsorption was performed in a high-gradient magnetophoresis system, using either sera of healthy individuals or a pool of sera from autoimmune or allergic patients. The selectivity and capacity of the system were quantified by a frontal analysis in a capillary column, and by constructing breakthrough curves. The results show that the highest yield and selectivity were obtained if the ligand was extended into the aqueous layer surrounding the magnetoliposome surface. A 100% selectivity was obtained for adsorption of specific IgE, and 8% for IgG. These results demonstrate the potentialities of both types of surface-modified magnetic biocolloids in the field of in vitro diagnosis tests for allergic or autoimmune conditions.

  14. Surface-modified magnetic colloids for affinity adsorption of immunoglobulins

    Energy Technology Data Exchange (ETDEWEB)

    Martins, Fernanda [School of Chemical Engineering, State University of Campinas, C.P. 6066, 13083-970 Campinas-SP (Brazil); Pinho, Samantha C. [School of Chemical Engineering, State University of Campinas, C.P. 6066, 13083-970 Campinas-SP (Brazil)], E-mail: samantha@usp.br; Zollner, Terezinha C.A. [School of Chemical Engineering, State University of Campinas, C.P. 6066, 13083-970 Campinas-SP (Brazil); Zollner, Ricardo L. [School of Medical Sciences, State University of Campinas, Campinas-SP (Brazil)], E-mail: zollner@unicamp.br; Cuyper, Marcel de [Interdisciplinary Research Centre, Katholieke Universiteit Leuven-Campus Kortrijk, B-8500 Kortrijk (Belgium)], E-mail: Marcel.DeCuyper@kulak.ac.be; Santana, Maria Helena A. [School of Chemical Engineering, State University of Campinas, C.P. 6066, 13083-970 Campinas-SP (Brazil)], E-mail: lena@feq.unicamp.br

    2008-07-15

    This work describes the preparation, characterization and in vitro adsorption tests of surface-modified magnetoliposomes for affinity binding of (i) anticardiolipin (isotype G) antibodies and (ii) specific isotype E antibodies generated by hypersensitivity reactions in humans with respiratory allergy. In the first case, cardiolipin embedded in the bilayer of magnetoliposomes was used as specific ligand. In the second case, antigenic proteins present in an extract of Dermatophagoids pteronyssinus and Blomia tropicalis mites were covalently coupled on the surface of magnetoliposomes via a diglycolic spacer arm, and used as specific ligands for IgE. Antibody adsorption was performed in a high-gradient magnetophoresis system, using either sera of healthy individuals or a pool of sera from autoimmune or allergic patients. The selectivity and capacity of the system were quantified by a frontal analysis in a capillary column, and by constructing breakthrough curves. The results show that the highest yield and selectivity were obtained if the ligand was extended into the aqueous layer surrounding the magnetoliposome surface. A 100% selectivity was obtained for adsorption of specific IgE, and 8% for IgG. These results demonstrate the potentialities of both types of surface-modified magnetic biocolloids in the field of in vitro diagnosis tests for allergic or autoimmune conditions.

  15. Low-temperature dynamics of magnetic colloids studied by time-resolved small-angle neutron scattering

    NARCIS (Netherlands)

    Wiedenmann, A.; Keiderling, U.; Meissner, M.; Wallacher, D.; Gähler, R.; May, R.P.; Prévost, S.; Klokkenburg, M.; Erne, B.H.; Kohlbrecher, J.

    2008-01-01

    The dynamics of ordering and relaxation processes in magnetic colloids has been studied by means of stroboscopic small angle neutron scattering techniques in an oscillating magnetic field. Surfactant stabilized ferrofluids (FFs) of Fe3O4 and Co nanoparticles have been investigated as a function of t

  16. Novel colloidal system: Magnetite-polymer particles/lyotropic liquid crystal under magnetic field

    Science.gov (United States)

    Mănăilă-Maximean, D.; Cîrtoaje, C.; Dănilă, O.; Donescu, D.

    2017-09-01

    We obtained a new highly ordered colloidal composite using specially manufactured magnetite-polymer nanoparticles and lyotropic liquid crystal. A good compatibility between the components was ensured by the functionalization of the particles during their synthesis. We studied the laser light transmission for the mixtures filled in sandwich-glass cells with homeotropic and planar treatment of the surfaces under external magnetic field. The Fréedericksz transition critical field was estimated, and its' behavior was compared to our new theoretical model based on the Brochard-de Gennes one.

  17. Optical transmission versus ac magnetization measurements for monitoring colloidal Ni nanorod rotational dynamics

    Science.gov (United States)

    Gratz, M.; Tschöpe, A.

    2017-01-01

    Ni nanorods with an average length transmission of nanorod colloidal dispersions in alternating magnetic fields were measured and analyzed with the objective of comparing the intrinsic Brownian relaxation times obtained with the two methods. The different physical origin of the measured signal, related to different moments of the orientation distribution function, and the non-linear effects expected for the large magnetic moments of the Ni nanorods at common field amplitudes required a comprehensive modelling. The time-dependent magnetization and optical transmission in ac magnetic fields was derived by numerical solution of the Fokker-Planck equation. The simulated time-dependent magnetization and optical transmission at a given frequency and field amplitude were analyzed analogous to experimental data to determine characteristic relaxation frequencies. Empirical relationships were derived which enabled extraction of the intrinsic Brownian relaxation time from the characteristic frequencies measured in the non-linear regime. Despite large differences in the characteristic frequencies obtained from magnetization and optical transmission measurements, the retrieved intrinsic Brownian relaxation times were found to agree well. The potential of ac magnetic field-dependent optical transmission for biosensing applications was demonstrated by monitoring the adsorption of the protein gelatine on the nanorod labels.

  18. Preparation of Rare-Earth Composite Ferrite Magnetic Fluid

    Institute of Scientific and Technical Information of China (English)

    蒋荣立; 刘永超; 刘守坤; 鞠明礼

    2004-01-01

    Water-based rare-earth ferrite (RexFe3-xO4)magnetic fluids were prepared by chemical co-precipitation method. The result shows that saturation magnetic intensity of ferrite magnetic fluids can be improved by adding Dy3+ and the saturation magnetic intensity will reach the highest if n(Fe)∶n(Dy3+)=30∶1. The modification and formation mechanism of RexFe3-xO4 particles is discussed in detail. The physicochemical properties are investigated by the Gouy magnetic balance, IR, TEM, XRD, and EDX, etc.

  19. Critical Pressures of the Thrust Bearing Using a Magnetic Fluid

    OpenAIRE

    長屋, 幸助; 武田, 定彦; 佐藤, 淳; 井開, 重男; 関口, 肇; 斉藤, 登

    1990-01-01

    This paper proposes a thrust bearing lubricated by a magnetic fluid under a magnetic field. The critical pressures of the bearing versus the magnitude of the magnetic flux densities have been investigated experimentally. It is clarified that the critical pressures of the proposed bearing are larger than those of the normal lubricant bearing under high speeds.

  20. Magnetocaloric effect in temperature-sensitive magnetic fluids

    Indian Academy of Sciences (India)

    Kinnari Parekh; R V Upadhyay; R V Mehta

    2000-04-01

    The magnetocaloric properties of three different temperature-sensitive magnetic fluids were studied. The pyromagnetic coefficient for all the materials were obtained and it was found that this property depends on physical and magnetic properties like size, magnetization and Curie temperature. A theoretical model was developed to explain the behaviour of change in entropy with temperature.

  1. Colloidal Magnetic Heterostructured Nanocrystals with Asymmetric Topologies: Seeded-Growth Synthetic Routes and Formation Mechanisms

    Directory of Open Access Journals (Sweden)

    Riccardo Scarfiello

    2016-12-01

    Full Text Available Colloidal inorganic nanocrystals, free-standing crystalline nanostructures generated and processed in solution phase, represent an important class of advanced nanoscale materials owing to the flexibility with which their physical–chemical properties can be controlled through synthetic tailoring of their compositional, structural and geometric features and the versatility with which they can be integrated in technological fields as diverse as optoelectronics, energy storage/ conversion/production, catalysis and biomedicine. In recent years, building upon mechanistic knowledge acquired on the thermodynamic and kinetic processes that underlie nanocrystal evolution in liquid media, synthetic nanochemistry research has made impressive advances, opening new possibilities for the design, creation and mastering of increasingly complex colloidal molecules, in which nanocrystal modules of different materials are clustered together via solid-state bonding interfaces into free-standing, easily processable multifunctional nanocomposite systems. This Review will provide a glimpse into this fast-growing research field by illustrating progress achieved in the wet-chemical development of last-generation breeds of all-inorganic heterostructured nanocrystals (HNCs in asymmetric non-onionlike geometries, inorganic analogues of polyfunctional organic molecules, in which distinct nanoscale crystalline modules are interconnected in hetero-dimer, hetero-oligomer and anisotropic multidomain architectures via epitaxial heterointerfaces of limited extension. The focus will be on modular HNCs entailing at least one magnetic material component combined with semiconductors and/or metals, which hold potential for generating enhanced or unconventional magnetic properties, while offering diversified or even new chemical-physical properties and functional capabilities. The available toolkit of synthetic strategies, all based on the manipulation of seeded-growth techniques

  2. Periodically microstructured composite films made by electric- and magnetic-directed colloidal assembly

    Science.gov (United States)

    Demirörs, Ahmet Faik; Courty, Diana; Libanori, Rafael; Studart, André R.

    2016-01-01

    Living organisms often combine soft and hard anisotropic building blocks to fabricate composite materials with complex microstructures and outstanding mechanical properties. An optimum design and assembly of the anisotropic components reinforces the material in specific directions and sites to best accommodate multidirectional external loads. Here, we fabricate composite films with periodic modulation of the soft–hard microstructure by simultaneously using electric and magnetic fields. We exploit forefront directed-assembly approaches to realize highly demanded material microstructural designs and showcase a unique example of how one can bridge colloidal sciences and composite technology to fabricate next-generation advanced structural materials. In the proof-of-concept experiments, electric fields are used to dictate the position of the anisotropic particles through dielectrophoresis, whereas a rotating magnetic field is used to control the orientation of the particles. By using such unprecedented control over the colloidal assembly process, we managed to fabricate ordered composite microstructures with up to 2.3-fold enhancement in wear resistance and unusual site-specific hardness that can be locally modulated by a factor of up to 2.5. PMID:27071113

  3. β-Cyclodextrin polymer brushes decorated magnetic colloidal nanocrystal clusters for the release of hydrophobic drugs

    Science.gov (United States)

    Lv, Shaonan; Zhao, Meiqin; Cheng, Changjing; Zhao, Zhigang

    2014-05-01

    β-Cyclodextrin (β-CD) polymer brushes decorated magnetic Fe3O4 colloidal nanocrystal clusters (Fe3O4@PG-CD) were fabricated by a combination of surface-initiated atom transfer radical polymerization on the surface of Br-anchored Fe3O4 colloidal nanocrystal clusters (Fe3O4-Br) and ring-opening reaction of epoxy groups. The resulted Fe3O4@PG-CD hybrid nanoparticles were characterized by several methods including Fourier transform infrared, transmission electron microscope, dynamic light scattering instrument, X-ray diffraction, thermogravimetric analysis, and vibrating sample magnetometer. Moreover, the potential of as-synthesized Fe3O4@PG-CD as a carrier of hydrophobic anticancer drug 5-fluorouracil (5-FU) was also investigated. The results showed that the prepared Fe3O4@PG-CD have core/shell structure and high saturated magnetism. 5-FU could be loaded into the Fe3O4@PG-CD via the formation of β-CD/5-FU inclusion complex. Furthermore, the Fe3O4@PG-CD displayed a high loading capacity and pH-dependent release behavior for 5-FU. The release behavior demonstrated a simple Fickian diffusion in the acidic environment (pH 2.0 and 4.0) but neither non-Fickian nor anomalous when neutral. The results reveal that this nanosystem seems to be a very promising vehicle for the hydrophobic drugs for pH-dependent controlled release.

  4. Periodically microstructured composite films made by electric- and magnetic-directed colloidal assembly.

    Science.gov (United States)

    Demirörs, Ahmet Faik; Courty, Diana; Libanori, Rafael; Studart, André R

    2016-04-26

    Living organisms often combine soft and hard anisotropic building blocks to fabricate composite materials with complex microstructures and outstanding mechanical properties. An optimum design and assembly of the anisotropic components reinforces the material in specific directions and sites to best accommodate multidirectional external loads. Here, we fabricate composite films with periodic modulation of the soft-hard microstructure by simultaneously using electric and magnetic fields. We exploit forefront directed-assembly approaches to realize highly demanded material microstructural designs and showcase a unique example of how one can bridge colloidal sciences and composite technology to fabricate next-generation advanced structural materials. In the proof-of-concept experiments, electric fields are used to dictate the position of the anisotropic particles through dielectrophoresis, whereas a rotating magnetic field is used to control the orientation of the particles. By using such unprecedented control over the colloidal assembly process, we managed to fabricate ordered composite microstructures with up to 2.3-fold enhancement in wear resistance and unusual site-specific hardness that can be locally modulated by a factor of up to 2.5.

  5. Effect of temperature on rotational viscosity in magnetic nano fluids.

    Science.gov (United States)

    Patel, R

    2012-10-01

    Flow behavior of magnetic nano fluids with simultaneous effect of magnetic field and temperature is important for its application for cooling devices such as transformer, loud speakers, electronic cooling and for its efficiency in targeted drug delivery and hyperthermia treatment. Using a specially designed horizontal capillary viscometer, temperature-sensitive and non-temperature-sensitive magnetic nano fluids are studied. In both these case the temperature-dependent rotational viscosity decreases, but follows a quite different mechanism. For temperature-sensitive magnetic nano fluids, the reduction in rotational viscosity is due to the temperature dependence of magnetization. Curie temperature ((T)(c)) and pyromagnetic coefficient are extracted from the study. A fluid with low T(c) and high pyromagnetic coefficient is useful for thermo-sensitive cooling devices and magnetic hyperthermia. For non-temperature-sensitive magnetic nano fluids, reduction in rotational viscosity is due to removal of physisorbed secondary surfactant on the particle because of thermal and frictional effects. This can be a good analogy for removal of drug from the magnetic particles in the case of targeted drug delivery.

  6. Synthesis of Fe 3O 4 magnetic fluid used for magnetic resonance imaging and hyperthermia

    Science.gov (United States)

    Wang, Y. M.; Cao, X.; Liu, G. H.; Hong, R. Y.; Chen, Y. M.; Chen, X. F.; Li, H. Z.; Xu, B.; Wei, D. G.

    2011-12-01

    Fe3O4 magnetic nanoparticles were prepared by co-precipitation from FeSO4·7H2O and FeCl3·6H2O aqueous solutions using NaOH as precipitating reagent. The nanoparticles have an average size of 12 nm and exhibit superparamagnetism at room temperature. The nanoparticles were used to prepare a water-based magnetic fluid using oleic acid and Tween 80 as surfactants. The stability and magnetic properties of the magnetic fluid were characterized by Gouy magnetic balance. The experimental results imply that the hydrophilic block of Tween 80 can make the Fe3O4 nanoparticles suspending in water stable even after dilution and autoclaving. The magnetic fluid demonstrates excellent stability and fast magneto-temperature response, which can be used both in magnetic resonance imaging and magnetic fluid hyperthermia.

  7. PVA and PEG functionalised LSMO nanoparticles for magnetic fluid hyperthermia application

    Energy Technology Data Exchange (ETDEWEB)

    Jadhav, S.V.; Nikam, D.S.; Khot, V.M. [Center for Interdisciplinary Research, D. Y. Patil University, Kolhapur 416006, MS India (India); Mali, S.S.; Hong, C.K. [Polymer Energy Materials Laboratory, Chonnam National University, Gwangju (Korea, Republic of); Pawar, S.H., E-mail: pawar_s_h@yahoo.com [Center for Interdisciplinary Research, D. Y. Patil University, Kolhapur 416006, MS India (India)

    2015-04-15

    La{sub 0.7}Sr{sub 0.3}MnO{sub 3} magnetic nanoparticles are synthesized by a solution combustion method and functionalised with polyvinyl alcohol and polyethylene glycol. The induction heating characteristics of coated magnetic nanoparticles (42 °C) were observed at a reasonably low concentration (5 mg/mL). Remarkably, coated magnetic nanoparticles exhibited a promisingly high specific absorption rate with varying magnetic field and constant frequency. The surface analysis is carried out by X-ray photoelectron spectroscopy. A reduction in the agglomeration of the particles was observed when the magnetic nanoparticles were functionalised with polyvinyl alcohol or polyethylene glycol and can be confirmed by transmission electron microscopy and dynamic light scattering studies. Vibrating sample magnetometer measurements indicate superparamagnetic behaviour at room temperature before and after coating. Colloidal stability revealed a considerably higher zeta potential value for coated system. In vitro cytotoxicity test of the magnetic nanoparticles indicates that coated nanoparticles have no significant effect on cell viability within the tested concentrations (1–5 mg mL{sup -1}) as compared to uncoated La{sub 0.7}Sr{sub 0.3}MnO{sub 3}. All these findings explore the potentiality of La{sub 0.7}Sr{sub 0.3}MnO{sub 3} nanoparticles for magnetic fluid hyperthermia. - Highlights: • Surface functionalization of LSMO nanoparticles — first time with PVA • Surface functionalization of LSMO nanoparticles — first time with PEG • BSA protein — first time used as dispersion medium for stability of LSMO nanoparticles • The heating ability observed at low concentration • Improved efficiency of magnetic fluid hyperthermia treatment with surfactants.

  8. Fluid-magnetic helicity in axisymmetric stationary relativistic magnetohydrodynamics

    Science.gov (United States)

    Prasad, G.

    2017-10-01

    The present work is intended to gain a fruitful insight into the understanding of the formations of magneto-vortex configurations and their role in the physical processes of mutual exchange of energies associated with fluid's motion and the magnetic fields in an axisymmetric stationary hydromagnetic system subject to strong gravitational field (e.g., neutron star/magnetar). It is found that the vorticity flux vector field associated with vorticity 2-form is a linear combination of fluid's vorticity vector and of magnetic vorticity vector. The vorticity flux vector obeys Helmholtz's flux conservation. The energy equation associated with the vorticity flux vector field is deduced. It is shown that the mechanical rotation of vorticity flux surfaces contributes to the formation of vorticity flux vector field. The dynamo action for the generation of toroidal components of vorticity flux vector field is described in the presence of meridional circulations. It is shown that the stretching of twisting magnetic lines due to differential rotation leads to the breakdown of gravitational isorotation in the absence of meridional circulations. An explicit expression consists of rotation of vorticity flux surface, energy and angular momentum per baryon for the fluid-magnetic helicity current vector is obtained. The conservation of fluid-magnetic helicity is demonstrated. It is found that the fluid-magnetic helicity displays the energy spectrum arising due to the interaction between the mechanical rotation of vorticity flux surfaces and the fluid's motion obeying Euler's equations. The dissipation of a linear combination of modified fluid helicity and magnetic twist is shown to occur due to coupled effect of frame dragging and meridional circulation. It is found that the growing twist of magnetic lines causes the dissipation of modified fluid helicity in the absence of meridional circulations.

  9. The cylindrical magnetic Rayleigh-Taylor instability for viscous fluids

    Energy Technology Data Exchange (ETDEWEB)

    Chambers, K.; Forbes, L. K. [School of Mathematics and Physics, University of Tasmania, Private Bag 37-Hobart, Tasmania 7005 (Australia)

    2012-10-15

    This paper considers a cylindrical Rayleigh-Taylor instability, in which a heavy fluid surrounds a light fluid, and gravity is directed radially inwards. A massive object is located at the centre of the light fluid, and it behaves like a line dipole both for fluid flow and magnetic field strength. The initially circular interface between the two conducting fluids evolves into plumes, dependent on the magnetic and fluid dipole strengths and the nature of the initial disturbance to the interface. A spectral method is presented to solve the time-dependent interface shapes, and results are presented and discussed. Bipolar solutions are possible, and these are of particular relevance to astrophysics. The solutions obtained resemble structures of some HII regions and nebulae.

  10. Effect of viscosity on harmonic signals from magnetic fluid

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, Takashi, E-mail: t_yoshi@ees.kyushu-u.ac.jp; Bai, Shi; Hirokawa, Aiki; Tanabe, Kazuhiro; Enpuku, Keiji

    2015-04-15

    We explored the effect of viscosity on harmonic signals from a magnetic fluid. Using a numerical simulation that accounts for both the Brownian and Néel processes, we clarified how the magnetization mechanism is affected by viscosity. When the excitation field varies much slower than the Brownian relaxation time, magnetization can be described by the Langevin function. On the other hand, for the case when the excitation field varies much faster than the Brownian relaxation time, but much slower than the Néel relaxation time, the easy axes of the magnetic nanoparticles (MNPs) turn to some extent toward the direction of the excitation field in an equilibrium state. This alignment of the easy axes of MNPs caused by the AC field becomes more significant with the increase of the AC field strength. Consequently, the magnetization is different from the Langevin function even though Néel relaxation time is faster than time period of the external frequency. It is necessary to consider these results when we use harmonic signals from a magnetic fluid in a high-viscosity medium. - Highlights: • We explore the effect of viscosity on harmonic signals from a magnetic fluid. • We clarify how the magnetization mechanism is affected by the viscosity of the fluid. • The magnetization in a high-viscosity medium is different from a Langevin function. • We empirically express the alignment of easy axes of the MNPs caused by an AC field.

  11. On the Fulfillment of Curie's Law in Magnetic Fluids

    Science.gov (United States)

    Zhernovoi, A. I.; Dyachenko, S. V.

    2015-05-01

    A fulfillment of Curie's law in magnetic fluids provides an option of their thermometric applications to measure thermodynamic temperature. On the other hand, it was shown elsewhere that the initial magnetic susceptibility χ of magnetic fluids follows Curie-Weiss's law rather than Curie's law. To obtain its values, use was made of the formula χ = M/N0, where M is magnetization, and N0 is the external magnetic field strength without any specimen. This work deals with investigations of the dependence of magnetic susceptibility of magnetic fluid on temperature for the cases where its values are found via the following formulas: 1) χ = M/N0, and 2) χ = Mμ0/M, where M is the magnetic field induction inside the specimen. It is found that in the first case the temperature dependence of χ obeys Curie-Weiss's law while in the second case - Curie's law. The reason for this results from the fact that induction M acting on the particles of magnetic fluid is noticeably higher than that of the external field, M0.

  12. Analysis of the static magnetic field-dependent optical transmission of Ni nanorod colloidal suspensions

    Science.gov (United States)

    Krämer, Florian; Gratz, Micha; Tschöpe, Andreas

    2016-07-01

    The magnetic field-dependent optical transmission of dilute Ni nanorod aqueous suspensions was investigated. A series of four samples of nanorods were synthesized using the AAO template method and processed to stable colloids. The distributions of their length and diameter were characterized by analysis of TEM images and revealed average diameters of ˜25 nm and different lengths in the range of 60 nm-1100 nm. The collinear magnetic and optical anisotropy was studied by static field-dependent transmission measurements of linearly polarized light parallel and perpendicular to the magnetic field direction. The experimental results were modelled assuming the field-dependent orientation distribution function of a superparamagnetic ensemble for the uniaxial ferromagnetic nanorods in liquid dispersion and extinction cross sections for longitudinal and transversal optical polarization derived from different approaches, including the electrostatic approximation and the separation of variables method, both applied to spheroidal particles, as well as finite element method simulations of spheroids and capped cylindrical particles. The extinction cross sections were compared to reveal the differences associated with the approximations of homogeneous polarization and/or particle shape. The consequences of these approximations for the quantitative analysis of magnetic field-dependent optical transmission measurements were investigated and a reliable protocol derived. Furthermore, the changes in optical cross sections induced by electromagnetic interaction between two nanorods in parallel end-to-end and side-by-side configuration as a function of their separation were studied.

  13. Magnetic-field-driven crack formation in an evaporated anisotropic colloidal assembly

    Science.gov (United States)

    Lama, Hisay; Dugyala, Venkateshwar Rao; Basavaraj, Madivala G.; Satapathy, Dillip K.

    2016-07-01

    We report the effect of applied magnetic field on the morphology of cracks formed after evaporation of a colloidal suspension consisting of shape-anisotropic ellipsoidal particles on a glass substrate. The evaporation experiments are performed in sessile drop configuration, which usually leads to accumulation of particles at the drop boundaries, commonly known as the "coffee-ring effect." The coffee-ring-like deposits that accompany cracks are formed in the presence as well as in the absence of magnetic field. However, the crack patterns formed in both cases are found to differ markedly. The direction of cracks in the presence of the magnetic field is found to be governed by the orientation of particles and not solely by the magnetic field direction. Our experimental results show that at the vicinity of cracks the particles are ordered and oriented with their long-axis parallel to crack direction. In addition, we observe that the crack spacing in general increases with the height of the particulate film.

  14. Electrohydrodynamical instability of microdrops shapes in a magnetic fluid

    Energy Technology Data Exchange (ETDEWEB)

    Dikansky, Yury I. [Stavropol State University, 1 Pushkin street, Stavropol 355009 (Russian Federation)]. E-mail: genphys@pm.stavsu.ru; Nechaeva, Oksana A. [Stavropol State University, 1 Pushkin street, Stavropol 355009 (Russian Federation)

    2005-03-15

    The investigation results of peculiarities of microdrop aggregate shapes stability in a magnetic fluid in alternate electric field and upon joint actions of electric and magnetic fields have been described. The behavior of microdrop aggregates under these conditions has been observed.

  15. Mesoscopic simulation for the structures of magnetic fluids

    Science.gov (United States)

    Li, Wuming; Li, Qiang

    2017-02-01

    The microstructures of magnetic fluids are simulated using a dissipative particle dynamics (DPD)-based method and are fundamentally important for controlling the macroscopic properties of magnetic fluids and understanding the corresponding rheological behaviors in diverse engineering applications. The cubic polynomial spline function often used as smoothing function in smoothed particle hydrodynamics (SPH) is employed as the conservative force potential function, which can provide a stronger conservative force weight function than the conventional weight function by choosing properly the cutoff radius between the dissipative particles. By employing the above method, the desired results are obtained for both stronger and weaker magnetic particle-particle interaction under the condition of varying the mass of the dissipative particles. In addition, the influences of the magnetic particle-particle interaction and of the magnetic particle area fraction on the microstructure of magnetic fluids are also investigated, respectively, and the obtained results agree qualitatively well with those in the literature obtained by other numerical approaches and experiments. The numerical solutions of the mean equilibrium velocities of the magnetic and dissipative particles are also calculated and approximate the corresponding theoretical values very well. Therefore the employed DPD-based method is highly effective in the simulation of the microstructure of magnetic fluids.

  16. Magnetic fluid equipment for sorting of secondary polyolefins from waste

    NARCIS (Netherlands)

    Rem, P.C.; Di Maio, F.; Hu, B.; Houzeaux, G...; Baltes, L.; Tierean, M.

    2012-01-01

    The paper presents the researches made on the FP7 project „Magnetic Sorting and Ultrasound Sensor Technologies for Production of High Purity Secondary Polyolefins from Waste” in order to develop a magnetic fluid equipment for sorting of polypropylene (PP) and polyethylene (PE) from polymers mixed

  17. Magnetic fluid equipment for sorting of secondary polyolefins from waste

    NARCIS (Netherlands)

    Rem, P.C.; Di Maio, F.; Hu, B.; Houzeaux, G...; Baltes, L.; Tierean, M.

    2012-01-01

    The paper presents the researches made on the FP7 project „Magnetic Sorting and Ultrasound Sensor Technologies for Production of High Purity Secondary Polyolefins from Waste” in order to develop a magnetic fluid equipment for sorting of polypropylene (PP) and polyethylene (PE) from polymers mixed wa

  18. Thin-Film Magnetic-Field-Response Fluid-Level Sensor for Non-Viscous Fluids

    Science.gov (United States)

    Woodard, Stanley E.; Shams, Qamar A.; Fox, Robert L.; Taylor, Bryant D.

    2008-01-01

    An innovative method has been developed for acquiring fluid-level measurements. This method eliminates the need for the fluid-level sensor to have a physical connection to a power source or to data acquisition equipment. The complete system consists of a lightweight, thin-film magnetic-field-response fluid-level sensor (see Figure 1) and a magnetic field response recorder that was described in Magnetic-Field-Response Measurement-Acquisition System (LAR-16908-1), NASA Tech Briefs, Vol. 30, No. 6 (June 2006), page 28. The sensor circuit is a capacitor connected to an inductor. The response recorder powers the sensor using a series of oscillating magnetic fields. Once electrically active, the sensor responds with its own harmonic magnetic field. The sensor will oscillate at its resonant electrical frequency, which is dependent upon the capacitance and inductance values of the circuit.

  19. Vortexlike topological defects in nematic colloids: chiral colloidal dimers and 2D crystals.

    Science.gov (United States)

    Tkalec, U; Ravnik, M; Zumer, S; Musevic, I

    2009-09-18

    We show that chiral ordering of the underlying complex fluid strongly influences defect formation and colloidal interactions. Nonsingular defect loops with a topological charge -2 are observed, with a cross section identical to hyperbolic vortices in magnetic systems. These loops are binding spontaneously formed pairs of colloidal particles and dimers, which are chiral objects. Chiral dimer-dimer interaction weakly depends on the chirality of dimers and leads to the assembly of 2D nematic colloidal crystals of pure or "mixed" chirality, intercalated with a lattice of nonsingular vortexlike defects.

  20. Dysprosium Modification of Cobalt Ferrite Ionic Magnetic Fluids

    Institute of Scientific and Technical Information of China (English)

    JIANG Rong-li; LIU Yong-chao; GENG Quan-rong; ZHAO Wen-tao

    2005-01-01

    Dysprosium composite cobalt ferrite ionic magnetic fluids were prepared by precipitation in the presence of Tri-sodium citrate. Influence of dysprosium modification on magnetic property is studied. The result shows that magnetic response toward exterior magnetic field can be improved by adding Dy3+. Studies also show that the increase of reaction temperature may improve the modification effect of dysprosium. By adding dysprosium ions, the average diameter of the magnetic nanoparticles will be decreased evidently. It is clear that the particles appear as balls, Cobalt ferrite with sizes of 12-15 nm, rare earth composite cobalt ferrite with sizes of 6-8 nm.

  1. Characterization of magnetically actuated resonant cantilevers in viscous fluids

    Science.gov (United States)

    Vančura, Cyril; Lichtenberg, Jan; Hierlemann, Andreas; Josse, Fabien

    2005-10-01

    The vibration behavior of magnetically actuated resonant microcantilevers immersed in viscous fluids has been studied. A dependence of the resonance frequency and the quality factor (Q factor) on the fluid properties, such as density and viscosity and on the cantilever geometry is described. Various cantilever geometries are analyzed in pure water and glycerol solutions, and the results are explained in terms of the added displaced fluid mass and the fluid damping force for both the resonance frequency and the quality factor. An in-depth knowledge and understanding of such systems is necessary when analyzing resonant cantilevers as biochemical sensors in liquid environments.

  2. Magnetic resonance imaging of cerebrospinal fluid flow in pediatrics

    Energy Technology Data Exchange (ETDEWEB)

    Heroux, R. [Children' s Hospital of Eastern Ontario, Magnetic Resonance Imaging Dept., Ottawa, Ontario (Canada)

    2000-06-30

    Magnetic Resonance Imaging of flowing protons in cerebrospinal fluid is useful for demonstrating areas of obstruction or stenosis of the ventricular system causing hydrocephalus. This is used in pediatric patients to assess the circulation of the cerebrospinal fluid. This article discusses two studies. In the first, the cerebrospinal fluid flow study helped the neurosurgeon assess the patency after a third ventriculocisternostomy. The second study evaluated the cerebrospinal fluid flowing through the foramen magnum in a patient with cerebellar tonsilar descent (Chiari malformation) and a syringomyelia. Different techniques to evaluate the flow studies are also discussed. (author)

  3. Bio-inactivation of human malignant cells through highly responsive diluted colloidal suspension of functionalized magnetic iron oxide nanoparticles

    Science.gov (United States)

    Ferreira, Roberta V.; Silva-Caldeira, Priscila P.; Pereira-Maia, Elene C.; Fabris, José D.; Cavalcante, Luis Carlos D.; Ardisson, José D.; Domingues, Rosana Z.

    2016-04-01

    Magnetic fluids, more specifically aqueous colloidal suspensions containing certain magnetic nanoparticles (MNPs), have recently been gaining special interest due to their potential use in clinical treatments of cancerous formations in mammalians. The technological application arises mainly from their hyperthermic behavior, which means that the nanoparticles dissipate heat upon being exposed to an alternating magnetic field (AMF). If the temperature is raised to slightly above 43 °C, cancer cells are functionally inactivated or killed; however, normal cells tend to survive under those same conditions, entirely maintaining their bioactivity. Recent in vitro studies have revealed that under simultaneous exposure to an AMF and magnetic nanoparticles, certain lines of cancer cells are bio-inactivated even without experiencing a significant temperature increase. This non-thermal effect is cell specific, indicating that MNPs, under alternating magnetic fields, may effectively kill cancer cells under conditions that were previously thought to be implausible, considering that the temperature does not increase more than 5 °C, which is also true in cases for which the concentration of MNPs is too low. To experimentally test for this effect, this study focused on the feasibility of inducing K562 cell death using an AMF and aqueous suspensions containing very low concentrations of MNPs. The assay was designed for a ferrofluid containing magnetite nanoparticles, which were obtained through the co-precipitation method and were functionalized with citric acid; the particles had an average diameter of 10 ± 2 nm and a mean hydrodynamic diameter of approximately 40 nm. Experiments were first performed to test for the ability of the ferrofluid to release heat under an AMF. The results show that for concentrations ranging from 2.5 to 1.0 × 103 mg L-1, the maximum temperature increase was actually less than 2 °C. However, the in vitro test results from K562 cells and suspensions

  4. Magnetization of High Density Hadronic Fluid

    DEFF Research Database (Denmark)

    Bohr, Henrik; Providencia, Constanca; da Providencia, João

    2012-01-01

    of the magnetization is derived by first considering and solving the Dirac equation of a fermion in interaction with a magnetic field and with a chiral sigma-pion pair. The solution provides the energies of single-particle states. The energy of the system is found by summing up contributions from all particles...

  5. A magnetic tunnel to shelter hyperpolarized fluids

    Energy Technology Data Exchange (ETDEWEB)

    Milani, Jonas, E-mail: jonas.milani@epfl.ch; Vuichoud, Basile; Bornet, Aurélien; Miéville, Pascal; Mottier, Roger [Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), Batochime, CH-1015 Lausanne (Switzerland); Jannin, Sami [Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), Batochime, CH-1015 Lausanne (Switzerland); Bruker BioSpin AG, Industriestrasse 26, CH-8117 Fällanden (Switzerland); Bodenhausen, Geoffrey [Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), Batochime, CH-1015 Lausanne (Switzerland); Département de Chimie, École Normale Supérieure-PSL Research University, 24 rue Lhomond, F-75005 Paris (France); Sorbonne Universités, UPMC Univ Paris 06, LBM, 4 place Jussieu, F-75005 Paris (France); CNRS, UMR 7203 LBM, F-75005 Paris (France)

    2015-02-15

    To shield solutions carrying hyperpolarized nuclear magnetization from rapid relaxation during transfer through low fields, the transfer duct can be threaded through an array of permanent magnets. The advantages are illustrated for solutions containing hyperpolarized {sup 1}H and {sup 13}C nuclei in a variety of molecules.

  6. Fluorescent magnetic Fe3 O4 /rare Earth colloidal nanoparticles for dual-modality imaging.

    Science.gov (United States)

    Zhu, Haie; Shang, Yalei; Wang, Wenhao; Zhou, Yingjie; Li, Penghui; Yan, Kai; Wu, Shuilin; Yeung, Kelvin W K; Xu, Zushun; Xu, Haibo; Chu, Paul K

    2013-09-09

    Fluorescent magnetic colloidal nanoparticles (FMCNPs) are produced by a two-step, seed emulsifier-free emulsion polymerization in the presence of oleic acid and sodium undecylenate-modified Fe3 O4 nanoparticles (NPs). The Fe3 O4 /poly(St-co-GMA) nanoparticles are first synthesized as the seed and Eu(AA)3 Phen is copolymerized with the remaining St and GMA to form the fluorescent polymer shell in the second step. The uniform core-shell structured FMCNPs with a mean diameter of 120 nm exhibit superparamagnetism with saturation magnetization of 1.92 emu/g. Red luminescence from the FMCNPs is confirmed by the salient fluorescence emission peaks of europium ions at 594 and 619 nm as well as 2-photon confocal scanning laser microscopy. The in vitro cytotoxicity test conducted using the MTT assay shows good cytocompatibility and the T2 relaxivity of the FMCNPs is 353.86 mM(-1) S(-1) suggesting its potential in magnetic resonance imaging (MRI). In vivo MRI studies based on a rat model show significantly enhanced T2 -weighted images of the liver after administration and prussian blue staining of the liver tissue slice reveals accumulation of FMCNPs in the organ. The cytocompatibility, superparamagnetism, and excellent fluorescent properties of FMCNPs make them suitable for biological imaging probes in MRI and optical imaging.

  7. Detection of the change of a magnetic field in the environment by magnetic fluid

    Science.gov (United States)

    Zyatkov, D.; Yurchenko, A.; Yurchenko, V.

    2017-08-01

    The experimental results of the magnetic field sensor based on various materials are presented. In article the possibility of use of magnetic fluid as a sensitive element of the magnetic field sensor is considered. The importance of current tasks deals with the search of the perspective magnetic substances susceptible to weak magnetic field. The operation principle of the sensor is based on change in the capacity of the condenser with magnetic active medium caused by the magnetic field. The complex organization of magnetic particles into chain aggregates was considered. The principle of measuring the condenser capacity is described. The experimental results are promising for future application.

  8. Controlled capillary assembly of magnetic Janus particles at fluid-fluid interfaces.

    Science.gov (United States)

    Xie, Qingguang; Davies, Gary B; Harting, Jens

    2016-08-21

    Capillary interactions can be used to direct assembly of particles adsorbed at fluid-fluid interfaces. Precisely controlling the magnitude and direction of capillary interactions to assemble particles into favoured structures for materials science purposes is desirable but challenging. In this paper, we investigate capillary interactions between magnetic Janus particles adsorbed at fluid-fluid interfaces. We develop a pair-interaction model that predicts that these particles should arrange into a side-side configuration, and carry out simulations that confirm the predictions of our model. Finally, we investigate the monolayer structures that form when many magnetic Janus particles adsorb at the interface. We find that the particles arrange into long, straight chains exhibiting little curvature, in contrast with capillary interactions between ellipsoidal particles. We further find a regime in which highly ordered, lattice-like monolayer structures form, which can be tuned dynamically using an external magnetic field.

  9. Magnetic investigation of zero-field-cooled dextran-coated magnetite-based magnetic fluid

    Energy Technology Data Exchange (ETDEWEB)

    Morais, P.C. [Universidade de Brasilia, Instituto de Fisica, Fisica Aplicada, C.P. 004455, Campus Universitario, Brasilia-DF 70919 970 (Brazil)]. E-mail: pcmor@unb.br; Santos, J.G. [Universidade de Brasilia, Instituto de Fisica, Fisica Aplicada, C.P. 004455, Campus Universitario, Brasilia-DF 70919 970 (Brazil); Silveira, L.B. [Universidade de Brasilia, Instituto de Fisica, Fisica Aplicada, C.P. 004455, Campus Universitario, Brasilia-DF 70919 970 (Brazil); Nunes, W.C. [Universidade Federal doRio de Janeiro, Instituto de Fisica, 21945-970, Rio de Janeiro-RJ (Brazil); Sinnecker, J.P. [Universidade Federal doRio de Janeiro, Instituto de Fisica, 21945-970, Rio de Janeiro-RJ (Brazil); Novak, M.A. [Universidade Federal doRio de Janeiro, Instituto de Fisica, 21945-970, Rio de Janeiro-RJ (Brazil)

    2005-03-15

    In this study, we investigate the temperature dependence of the zero-field-cooled magnetization of a quasi-monodisperse dextran-coated magnetite-based magnetic fluid. The well-defined maximum in the magnetization versus temperature curve and its downshift with the applied external field is explained by a simple model considering thermally activated dynamics of the nanoparticles magnetic moment and the temperature dependence of the saturation magnetization.

  10. A hyperosmolar-colloidal additive to the CPB-priming solution reduces fluid load and fluid extravasation during tepid CPB.

    Science.gov (United States)

    Kvalheim, V; Farstad, M; Haugen, O; Brekke, H; Mongstad, A; Nygreen, E; Husby, P

    2008-01-01

    Cardiopulmonary bypass(CPB) is associated with fluid overload. We hypothesized that fluid gain during CPB could be reduced by substituting parts of a crystalloid prime with 7.2% hypertonic saline and 6% poly (O-2-hydroxyethyl) starch solution (HyperHaes). 14 animals were randomized to a control group (Group C) or to Group H. CPB-prime in Group C was Ringer's solution. In group H, 4 ml/kg of Ringer's solution was replaced by the hypertonic saline/hydroxyethyl starch solution. After 60 min stabilization, CPB was initiated and continued for 120 min. All animals were allowed drifting of normal temperature (39.0 degrees C) to about 35.0 degrees C. Fluid was added to the CPB circuit as needed to maintain a 300-ml level in the venous reservoir. Blood chemistry, hemodynamic parameters, fluid balance, plasma volume, fluid extravasation rate (FER), tissue water content and acid-base parameters were measured/calculated. Total fluid need during 120 min CPB was reduced by 60% when hypertonic saline/hydroxyethyl starch solution was added to the CPB prime (p CPB, with 0.6 (0.43) (Group H) compared with 1.5 (0.40) ml/kg/min (Group C) (p CPB prime reduces fluid needs and FER during tepid CPB.

  11. Dynamics of magnetic nano-flake vortices in Newtonian fluids

    Science.gov (United States)

    Bazazzadeh, Nasim; Mohseni, Seyed Majid; Khavasi, Amin; Zibaii, Mohammad Ismail; Movahed, S. M. S.; Jafari, G. R.

    2016-12-01

    We study the rotational motion of nano-flake ferromagnetic disks suspended in a Newtonian fluid, as a potential material owing the vortex-like magnetic configuration. Using analytical expressions for hydrodynamic, magnetic and Brownian torques, the stochastic angular momentum equation is determined in the dilute limit conditions under applied magnetic field. Results are compared against experimental ones and excellent agreement is observed. We also estimate the uncertainty in the orientation of the disks due to the Brownian torque when an external magnetic field aligns them. Interestingly, this uncertainty is roughly proportional to the ratio of thermal energy of fluid to the magnetic energy stored in the disks. Our approach can be implemented in many practical applications including biotechnology and multi-functional fluidics.

  12. Differentiating benign from malignant bone tumors using fluid-fluid level features on magnetic resonance imaging

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Hong; Cui, Jian Ling; Cui, Sheng Jie; Sun, Ying Cal; Cui, Feng Zhen [Dept. of Radiology, The Third Hospital of Hebei Medical University, Hebei Province Biomechanical Key Laborary of Orthopedics, Shijiazhuang, Hebei (China)

    2014-12-15

    To analyze different fluid-fluid level features between benign and malignant bone tumors on magnetic resonance imaging (MRI). This study was approved by the hospital ethics committee. We retrospectively analyzed 47 patients diagnosed with benign (n = 29) or malignant (n = 18) bone tumors demonstrated by biopsy/surgical resection and who showed the intratumoral fluid-fluid level on pre-surgical MRI. The maximum length of the largest fluid-fluid level and the ratio of the maximum length of the largest fluid-fluid level to the maximum length of a bone tumor in the sagittal plane were investigated for use in distinguishing benign from malignant tumors using the Mann-Whitney U-test and a receiver operating characteristic (ROC) analysis. Fluid-fluid level was categorized by quantity (multiple vs. single fluid-fluid level) and by T1-weighted image signal pattern (high/low, low/high, and undifferentiated), and the findings were compared between the benign and malignant groups using the chi2 test. The ratio of the maximum length of the largest fluid-fluid level to the maximum length of bone tumors in the sagittal plane that allowed statistically significant differentiation between benign and malignant bone tumors had an area under the ROC curve of 0.758 (95% confidence interval, 0.616-0.899). A cutoff value of 41.5% (higher value suggests a benign tumor) had sensitivity of 73% and specificity of 83%. The ratio of the maximum length of the largest fluid-fluid level to the maximum length of a bone tumor in the sagittal plane may be useful to differentiate benign from malignant bone tumors.

  13. Particle size dependent rheological property in magnetic fluid

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Jie; Pei, Lei; Xuan, Shouhu, E-mail: xuansh@ustc.edu.cn; Yan, Qifan; Gong, Xinglong, E-mail: gongxl@ustc.edu.cn

    2016-06-15

    The influence of the particle size on the rheological property of magnetic fluid was studied both by the experimental and computer simulation methods. Firstly, the magnetic fluids were prepared by dispersing Fe{sub 3}O{sub 4} nanospheres with size varied from 40 nm to 100 nm and 200 nm in the solution. Then, the rheological properties were investigated and it was found that the relative magnetorheological effects increased with increasing the particle size. Finally, the molecular dynamic simulation was used to analyze the mechanical characteristics of the magnetic fluid and the chain-like model agreed well with the experimental result. The authentic chain-like structure observed by a microscope agreed with the simulation results. The three particles composed of the similar cluster nanostructure, thus they exhibited similar magnetic property. To this end, the unique assembling microstructures was the origination of the mechanical difference. And it was found that the higher MR (magnetorheological) effects of the large particle based magnetic fluid was originated from the stronger assembling microstructure under the applying magnetic field. - Highlights: • 40 nm, 100 nm and 200 nm Fe{sub 3}O{sub 4} nanospheres were dispersed in water. • The magnetorheological effect increased with increasing the particle sizes. • Molecular dynamic simulation was used in this article.

  14. Waves on the surface of a magnetic fluid layer in a traveling magnetic field[75.50.Mm; 43.35.Pt; Magnetic fluid film; Surface waves; Traveling magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Zimmermann, K.; Zeidis, I.; Naletova, V.A. E-mail: naletova@imec.msu.ru; Turkov, V.A

    2004-01-01

    The plane flow of a layer of incompressible viscous magnetic fluid with constant magnetic permeability under the action of a traveling magnetic field is analyzed. The strength of the magnetic field producing a sinusoidal traveling small-amplitude wave on the surface of a magnetic fluid is found. This flow can be used in designing mobile robots.

  15. 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

  16. Application study of magnetic fluid seal in hydraulic turbine

    Science.gov (United States)

    Yu, Z. Y.; Zhang, W.

    2012-11-01

    The waterpower resources of our country are abundant, and the hydroelectric power is developed, but at present the main shaft sealing device of hydraulic turbine is easy to wear and tear and the leakage is great. The magnetic fluid seal has the advantages of no contact, no wear, self-healing, long life and so on. In this paper, the magnetic fluid seal would be used in the main shaft of hydraulic turbine, the sealing structure was built the model, meshed the geometry, applied loads and solved by using MULTIPHYSICS in ANSYS software, the influence of the various sealing structural parameters such as tooth width, height, slot width, sealing gap on the sealing property were analyzed, the magnetic fluid sealing device suitable for large-diameter shaft and sealing water was designed, the sealing problem of the hydraulic turbine main shaft was solved effectively which will bring huge economic benefits.

  17. Application of hydrophilic magnetic fluid to oil seal

    Science.gov (United States)

    Kim, Y. S.; Nakatsuka, K.; Fujita, T.; Atarashi, T.

    1999-07-01

    Bearing and gear are important components in machines. Lubricant for bearing or gear is usually confined in working space by rubber retainer or mechanical seal, and its lifetime which is determined by the friction wear of sealing material is important. In this report, the basic characteristics of magnetic fluid seal applied to lubricant retainer is studied. The fluid used for this purpose is ethyleneglycol-based magnetic fluid in which silica-coated iron particles are dispersed. The lubricant oil seal set consisting of six stages of pole piece and Nd-permanent magnets (4.0 Wb/m 2) in seal housing showed an excellent pressure resistance of 618 kPa under a rotating speed of 1800 rpm.

  18. Stimuli-Responsive Polymers and Colloids under Electric and Magnetic Fields

    Directory of Open Access Journals (Sweden)

    Wen Ling Zhang

    2014-11-01

    Full Text Available Electrorheological (ER and magnetorheological (MR suspensions undergo a reverse phase transition from a liquid-like to solid-like state in response to an external electric or magnetic field, respectively. This paper briefly reviews various types of electro- or magneto-responsive materials from either polymeric or inorganic and hybrid composite materials. The fabrication strategies for ER/MR candidates and their ER/MR characteristics (particularly for ER fluids are also included.

  19. Low-temperature heat capacity of magnetic fluids

    Science.gov (United States)

    Lebedev, A. V.

    2008-12-01

    This paper continues the previous investigation into a recently discovered phenomenon of magnetic fluid solidification at temperatures essentially exceeding the freezing point of the base fluid. Physically, this phenomenon is related to the fact that at decreasing temperatures the magnetic fluid loses fluidity (with its viscosity tending to infinity) at a temperature higher than the freezing point of the base fluid. The main factor determining the freezing point is the type of the surface-active substance covering the particles. A group of different surfactants is examined with the aim of finding the lowest possible solidification temperature. The best result is obtained for linoleic acid (-100°C). In order to gain a deeper insight into the mechanisms of fluid solidification, a series of thermophysical measurements has been done. Heat capacity measurements made for an isooctane-based magnetic fluid stabilized by oleic acid at a temperature ranging from -130°C to 0 did not reveal any noticeable heat capacity anomalies in the vicinity of the solidification temperature. This suggests that the solidification of the magnetic fluid proceeds without phase transition. The highest peak of the heat flux is observed at the freezing point of isooctane. The position of the maximum slightly changes with the concentration of magnetic particles. With an increase of the concentration the temperature of the heat flux maximum decreases. In the presence of free oleic acid in isooctane a low peak is observed at a temperature of about -15°C. The peak position is independent of the oleic acid concentration. Tables 1, Figs 7, Refs 1.

  20. Magnetic fields of Uranus and Neptune: Metallic fluid hydrogen

    Science.gov (United States)

    Nellis, W. J.

    2017-01-01

    Based on a substantial database measured over several decades for representative planetary fluids at representative dynamic pressures and temperatures up to 200 GPa and a few 1000 K, the complex magnetic fields of Uranus and Neptune (U/N) are (i) made primarily by degenerate metallic fluid H (MFH) at or near crossovers from H-He envelopes to "Ice" cores at 100 GPa (Mbar) pressures and 90% the radii of U/N; (ii) electrical conductivity of MFH is a factor of 100 larger than conductivity of "Ices" thought previously to make the magnetic fields of U/N; (iii) because those magnetic fields are made close to outer surfaces, non-dipolar magnetic fields can be expected as observed; (iv) the "Ice" cores are a heterogeneous fluid mixture of nebular Ice and Rock that accreted, sank below the H-He envelopes into the cores in which nebular materials decomposed at high pressures and temperatures and re-reacted to form new chemical species; (v) those magnetic fields are probably non-axisymmetric because rotational motions of U/N are weakly coupled to convective motions that make their magnetic fields by dynamos. For U/N "polar wander" is probably a better descriptor for variations of magnetic field over time than "polar reversal" as for Earth. Ironically, there probably is little "Ice" in the Ice Giants.

  1. On a static charged fluid around a magnetized mass

    CERN Document Server

    Cabrera-Munguia, I

    2008-01-01

    We show that any magnetostatic axially symmetric solution of the Einstein-Maxwell equations can be endowed with a specific charged fluid source of the Polanco et al type via a simple procedure requiring the knowledge of exclusively the magnetostatic seed spacetime. Using this procedure we construct yet another exact solution for a massive magnetic dipole surrounded by a static charged fluid which is different from the Polanco et al metric.

  2. Magnetic separation of micro-spheres from viscous biological fluids.

    Science.gov (United States)

    Chen, Haitao; Kaminski, Michael D; Caviness, Patricia L; Liu, Xianqiao; Dhar, Promila; Torno, Michael; Rosengart, Axel J

    2007-02-21

    A magnetically based detoxification system is being developed as a therapeutic tool for selective and rapid removal of biohazards, i.e. chemicals and radioactive substances, from human blood. One of the key components of this system is a portable magnetic separator capable of separating polymer-based magnetic nano/micro-spheres from arterial blood flow in an ex vivo unit. The magnetic separator consists of an array of alternating and parallel capillary tubing and magnetizable wires, which is exposed to an applied magnetic field created by two parallel permanent magnets such that the magnetic field is perpendicular to both the wires and the fluid flow. In this paper, the performance of this separator was evaluated via preliminary in vitro flow experiments using a separator unit consisting of single capillary glass tubing and two metal wires. Pure water, ethylene glycol-water solution (v:v=39:61 and v:v=49:51) and human whole blood were used as the fluids. The results showed that when the viscosity increased from 1.0 cp to 3.0 cp, the capture efficiency (CE) decreased from 90% to 56%. However, it is still feasible to obtain >90% CE in blood flow if the separator design is optimized to create higher magnetic gradients and magnetic fields in the separation area.

  3. LHC II system sensitivity to magnetic fluids

    CERN Document Server

    Cotae, Vlad

    2005-01-01

    Experiments have been designed to reveal the influences of ferrofluid treatment and static magnetic field exposure on the photosynthetic system II, where the light harvesting complex (LHC II) controls the ratio chlorophyll a/ chlorophyll b (revealing, indirectly, the photosynthesis rate). Spectrophotometric measurement of chlorophyll content revealed different influences for relatively low ferrofluid concentrations (10-30 mul/l) in comparison to higher concentrations (70-100 mul/l). The overlapped effect of the static magnetic field shaped better the stimulatory ferrofluid action on LHC II system in young poppy plantlets.

  4. Fluid–fluid coexistence in colloidal systems with short-ranged strongly directional attraction

    NARCIS (Netherlands)

    Kern, N.; Frenkel, D.

    2003-01-01

    We present a systematic numerical study of the phase behavior of square-well fluids with a "patchy" short-ranged attraction. In particular, we study the effect of the size and number of attractive patches on the fluid–fluid coexistence. The model that we use is a generalization of the hard sphere

  5. The contribution of combined crystalloid and colloid osmosis to fluid and sodium management in peritoneal dialysis.

    Science.gov (United States)

    Freida, P; Wilkie, M; Jenkins, S; Dallas, F; Issad, B

    2008-04-01

    The achievement of euvolemia is essential to the successful management of peritoneal dialysis patients. However, the concern that hypertonic glucose exchanges may have a role in long-term changes to the peritoneal membrane has lead to an alternative strategy to enhance ultrafiltration (UF) over the long dwell by combining crystalloid and colloid osmosis. This review summarizes the experience of mixing glucose or amino acids with polyglucose (icodextrin), with particular focus given to data from studies using glucose/icodextrin in combinations of 1.36%/7.5% and 2.61%/6.8%. Both combinations demonstrate a significant increment of UF volume and sodium removal compared with the component osmotic agents used individually over long dwells, with the 2.61%/6.8% mixture having an effect over dwells extending to 15 h. Hypothetically, the mechanism of the enhanced UF is the attenuation by the colloid osmotic force of the backflow of water through small pores from dialysate to the peritoneal capillary circulation once the crystalloid osmotic force has dissipated. This experience provides promising data that deserves further examination in longer term clinical studies.

  6. Chromosomal aberrations in plants under magnetic fluid influence

    Energy Technology Data Exchange (ETDEWEB)

    Pavel, Angela [University of Medicine and Pharmacy Gr.T. Popa, Fac. of Pharmacy, Iasi (Romania)]. E-mail: angelapavel04@yahoo.com; Creanga, Dorina-Emilia [Faculty of Physics, University of Al. I. Cuza, Bd. Copou 11A, Iasi (Romania)]. E-mail: dorinacreanga@yahoo.com

    2005-03-15

    The study was focussed on the influence of a petroleum magnetic fluid upon the cell proliferation in young plants of agricultural interest. Zea mays plants, in their early ontogenetic stages were treated with magnetic fluid in relatively low concentrations (up to 100{mu}l/l) and root meristem was investigated by cytogenetical methods. The cell proliferation rate was found significantly enhanced as well as the percentage of chromosomal aberrations. Micronuclei, bridges, chromosome fragments and three-polar anaphases were the main types of chromosomal aberrations.

  7. Fabrication and manipulation of polymeric magnetic particles with magnetorheological fluid

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-Lopez, Jaime [Centro de Acustica Aplicada y Evaluacion No Destructivos (CAEND), CSIC-UPM, C/Serrano 144, 28006, Madrid (Spain); Shum, Ho Cheung, E-mail: ashum@hku.hk [Department of Mechanical Engineering, University of Hong Kong, 7/F Haking Wong Building, Pokfulam Road (Hong Kong); Elvira, Luis; Montero de Espinosa, Francisco [Centro de Acustica Aplicada y Evaluacion No Destructivos (CAEND), CSIC-UPM, C/Serrano 144, 28006, Madrid (Spain); Weitz, David A., E-mail: weitz@seas.harvard.edu [Department of Physics and School of Engineering and Applied Sciences, Harvard University, 9 and 15 Oxford Street, Cambridge, MA 02138 (United States)

    2013-01-15

    Polymeric magnetic microparticles have been created using a microfluidic device via ultraviolet (UV) polymerization of double emulsions, resulting in cores of magnetorheological (MR) fluids surrounded by polymeric shells. We demonstrate that the resultant particles can be manipulated magnetically to achieve triggered rupture of the capsules. This illustrates the great potential of our capsules for triggered release of active ingredients encapsulated in the polymeric magnetic microparticles. - Highlights: Black-Right-Pointing-Pointer Polymeric microparticles encapsulating MR fluids have been fabricated. Black-Right-Pointing-Pointer A double-emulsion-templated approach using microfluidic techniques has been used. Black-Right-Pointing-Pointer The monodisperse microparticles obtained are easily manipulated under magnetic field. Black-Right-Pointing-Pointer These microparticles have great potential for encapsulation-and-release applications.

  8. MAGNETIC FLUID BEARINGS OF MINING EQUIPMENT

    Directory of Open Access Journals (Sweden)

    I. Gorlov

    2012-01-01

    Full Text Available The paper considers a problem pertaining to selection friction pair materials for plain bearings of mining equipment which are lubricated with  nano-dispersed magnetic oil. Methodology for equipment tests, technology for obtaining new anti-friction materials (polymer, ceramic, amorphous and investigation results are presented in the paper.

  9. Static charged fluid around a massive magnetic dipole

    CERN Document Server

    Polanco, Jose D; Ujevic, Maximiliano

    2008-01-01

    An analytical solution of Einstein-Maxwell equations with a static fluid as a source is presented. The spacetime is represented by the axially symmetric Weyl metric and the energy-momentum tensor describes a coupling of a fluid with an electromagnetic field. When appropriate limits are performed we recover the well-known solutions of Gutsunaev-Manko and Schwarzschild. Also, using Eckart's thermodynamics, we calculated the temperature, the mechanical pressure, the charge density and the energy density of the system. The analysis of thermodynamic quantities suggests that the solution can be used to represent a magnetized compact stellar object surrounded by a charged fluid.

  10. Magnetic interaction of Janus magnetic particles suspended in a viscous fluid.

    Science.gov (United States)

    Seong, Yujin; Kang, Tae Gon; Hulsen, Martien A; den Toonder, Jaap M J; Anderson, Patrick D

    2016-02-01

    We studied the magnetic interaction between circular Janus magnetic particles suspended in a Newtonian fluid under the influence of an externally applied uniform magnetic field. The particles are equally compartmentalized into paramagnetic and nonmagnetic sides. A direct numerical scheme is employed to solve the magnetic particulate flow in the Stokes flow regime. Upon applying the magnetic field, contrary to isotropic paramagnetic particles, a single Janus particle can rotate due to the magnetic torque created by the magnetic anisotropy of the particle. In a two-particle problem, the orientation of each particle is found to be an additional factor that affects the critical angle separating the nature of magnetic interaction. Using multiparticle problems, we show that the orientation of the particles has a significant influence on the dynamics of the particles, the fluid flow induced by the actuated particles, and the final conformation of the particles. Straight and staggered chain structures observed experimentally can be reproduced numerically in a multiple particle problem.

  11. Temperature dependence of magnetic moments of nanoparticles and their dipole interaction in magnetic fluids

    Energy Technology Data Exchange (ETDEWEB)

    Lebedev, A.V.

    2015-01-15

    Magnetic susceptibility measurements were carried out for magnetite-based fluids over a wide temperature range. The fluids were stabilized with commonly used surfactants (fatty acids) and new surfactants (polypropylene glycol and tallow acids). The coefficients of temperature dependence of the particle magnetic moments were determined by fitting of the measured and calculated values of magnetic susceptibility. The influence of the inter-particle dipole–dipole interaction on the susceptibility was taken into account in the framework of A.O. Ivanov's model. The corrections for thermal expansion were determined by density measurements of the carrier fluid. The obtained values of temperature coefficients correlate to the solidification temperature of the fluid samples. For fluids with a low solidification temperature the value of the temperature coefficient of particle magnetization coincides with its value for bulk magnetite. - Highlights: • Susceptibility measurements made for magnetic fluids over a wide temperature range. • Temperature coefficients of particle magnetization found from susceptibility data. • The value of coefficients correlates to the solidification temperature of the fluid. • For the lowest solidification temperature the coefficient corresponds to that of bulk magnetite.

  12. Measurement of the magnetic field-dependent refractive index of magnetic fluids in bulk

    Institute of Scientific and Technical Information of China (English)

    Ting Liu; Xianfeng Chen; Ziyun Di; Junfeng Zhang; Xinwan Li; Jianping Chen

    2008-01-01

    An optical alignment-free and highly accurate method is employed to measure the magnetic field-dependent refractive index of magnetic fluid(MF) in bulk.The measured refractive index decreases significantly with the increasing magnetic strength and then tends to saturate in the high intensity range.By applying a tunable magnetic field ranging between 0 and 1661 Oe,the maximum shift of the refractive index of MF in bulk iS found to be 0.0231.

  13. Dynamics of magnetic nano-flake vortices in Newtonian fluids

    Energy Technology Data Exchange (ETDEWEB)

    Bazazzadeh, Nasim, E-mail: n.bazazzadeh@gmail.com [Department of Physics, Shahid Beheshti University, G.C., Evin, Tehran 19839 (Iran, Islamic Republic of); Mohseni, Seyed Majid, E-mail: m-mohseni@sbu.ac.ir [Department of Physics, Shahid Beheshti University, G.C., Evin, Tehran 19839 (Iran, Islamic Republic of); Khavasi, Amin, E-mail: khavasi@sharif.edu [Department of Electrical Engineering, Sharif University of Technology, Tehran 11555-4363 (Iran, Islamic Republic of); Zibaii, Mohammad Ismail, E-mail: mizibaye@gmail.com [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Evin, Tehran 19839 (Iran, Islamic Republic of); Movahed, S.M.S., E-mail: m_movahed@sbu.ac.ir [Department of Physics, Shahid Beheshti University, G.C., Evin, Tehran 19839 (Iran, Islamic Republic of); Jafari, G.R., E-mail: gjafari@gmail.com [Department of Physics, Shahid Beheshti University, G.C., Evin, Tehran 19839 (Iran, Islamic Republic of)

    2016-12-01

    We study the rotational motion of nano-flake ferromagnetic disks suspended in a Newtonian fluid, as a potential material owing the vortex-like magnetic configuration. Using analytical expressions for hydrodynamic, magnetic and Brownian torques, the stochastic angular momentum equation is determined in the dilute limit conditions under applied magnetic field. Results are compared against experimental ones and excellent agreement is observed. We also estimate the uncertainty in the orientation of the disks due to the Brownian torque when an external magnetic field aligns them. Interestingly, this uncertainty is roughly proportional to the ratio of thermal energy of fluid to the magnetic energy stored in the disks. Our approach can be implemented in many practical applications including biotechnology and multi-functional fluidics. - Highlights: • The rotational motion of magnetic-vortex microdiscs in a Newtonian fluid is studied. • Results are compared against experimental ones and excellent agreement is observed. • The uncertainty in the orientation of the microdiscs is analytically derived.

  14. Numerical simulation and experimental verification of silicone oil flow over magnetic fluid under applied magnetic field

    Institute of Scientific and Technical Information of China (English)

    Ruoyu Hong; Zhiqiang Ren; Shizhong Zhang; Jianmin Ding; Hongzhong Li

    2007-01-01

    Two-layer flow of magnetic fluid and non-magnetic silicone oil was simulated numerically. The continuity equation, momentum equations,kinematic equation, and magnetic potential equation were solved in two-dimensional Cartesian coordinate. PLIC (piecewise linear integration calculation) VOF (volume of fluid) scheme was employed to track the free interface. Surface tension was treated via a continuous surface force(CSF) model that ensures robustness and accuracy. The influences of applied magnetic field, inlet velocity profile, initial surface disturbance of interface and surface tension were analyzed. The computed interface shapes at different conditions were compared with experimental observation.

  15. Internalization of silica nanoparticles into fluid liposomes: formation of interesting hybrid colloids.

    Science.gov (United States)

    Michel, Raphael; Kesselman, Ellina; Plostica, Tobias; Danino, Dganit; Gradzielski, Michael

    2014-11-10

    The formation of hybrid materials consisting of membrane-coated silica nanoparticles (SiNPs) concentrated within small unilamellar vesicles (SUVs) of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) is described. They are formed by a simple self-assembly process resulting from invagination of the SiNPs into the SUVs and subsequent vesicle fusion, thereby retaining an almost constant size. This process was followed under conditions where it proceeds slowly and could be analyzed in structural detail. The finally formed well-defined SiNP-filled vesicles are long-time stable hybrid colloids and their structure is conveniently controlled by the initial mixing ratio of SiNPs and vesicles. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Dynamics of colloidal systems of magnetic nanoparticles under influence of magnetic fields investigated by XPCS

    Energy Technology Data Exchange (ETDEWEB)

    Schavkan, Alexander

    2017-05-15

    This thesis investigates structural properties and the underlying microscopic dynamics of suspensions of α-FeOOH goethite platelets in water under the influence of magnetic fields. Goethite particles show unusual physical properties and a rich phase diagram, which makes their suspensions an object of high interest for research in the area of ''smart nanoparticles''. Five nanoparticle concentrations were chosen such that different liquid crystal phases could be studied. The suspensions of platelets of these chosen concentrations were exposed to magnetic fields of varying strength. Small angle X-ray scattering and X-ray photon correlation spectroscopy data were taken and evaluated. The appearing phases and phase transitions were studied as a function of concentration and applied magnetic field. For this purpose, order parameters, ellipticity, radial and azimuthal peak positions and widths of scattering features were investigated to clarify the structural properties in detail. For the analysis of the underlying dynamics, the relaxation rates and the shape of measured time correlation functions were evaluated. The results show that with increasing magnetic field a partial realignment of the platelets occurs. This realignment is connected to the magnetic properties of the particles. The dynamics of the corresponding phases revealed a dependence on the concentration of nanoparticles in the suspension. At a concentration of c=20 vol% the transition from the nematic to the anti-nematic phase traverses a mixed state. The nematic and anti-nematic phases show ballistic motion and very similar properties, even though a realignment of the particles from an orientation with the long axis parallel to the applied magnetic field in the nematic phase to an orientation with the long axis perpendicular to the magnetic field in the anti-nematic phase occurs. The mixed state of 20 vol%-suspension exhibits a diffusive motion of the particles and different

  17. A hybrid transducer to magnetically and ultrasonically evaluate magnetic fluids.

    Science.gov (United States)

    Bruno, Alexandre Colello; Pavan, Théo Z; Baffa, Oswaldo; Carneiro, Antonio Adilton Oliveira

    2013-09-01

    Ultrasound, magnetic fields, and optical techniques have been explored for clinical diagnosis and therapy. However, these techniques have limitations. In this study, we constructed and characterized a transducer to magnetically and ultrasonically investigate samples labeled with magnetic particles. The transducer is a hybrid system consisting of an ac biosusceptometer (ACB) and an ultrasonic transducer. The basic operation principle consisted of measuring the magnetization and microvibrations of ferromagnetic particles (37 and 70 μm) mixed in yogurt and excited by an external alternating magnetic field generated by the ACB's excitation coils. The vibration of the ferromagnetic particles was measured in phantoms using a Doppler ultrasonic transducer; we verified the sensitivity to detecting the vibrations at low concentrations of ferromagnetic material (~1%). The responses of the susceptometer and Doppler ultrasound linearly depended on the voltage level applied to the magnetizing coils at low ferromagnetic particle concentrations (⩽ 5%). We also conducted a repeatability test on the prototype, which indicated a deviation of 0.94% and 0.25% in the Doppler and susceptometric measurements, respectively. We can conclude that the hybrid transducer technique has potential clinical applications.

  18. Visualization of the equilibrium position of colloidal particles at fluid-water interfaces by deposition of nanoparticles.

    Science.gov (United States)

    Sabapathy, Manigandan; Kollabattula, Viswas; Basavaraj, Madivala G; Mani, Ethayaraja

    2015-09-07

    We present a general yet simple method to measure the contact angle of colloidal particles at fluid-water interfaces. In this method, the particles are spread at the required fluid-water interface as a monolayer. In the water phase a chemical reaction involving reduction of a metal salt such as aurochloric acid is initiated. The metal grows as a thin film or islands of nanoparticles on the particle surface exposed to the water side of the interface. Analyzing the images of particles by high resolution scanning microscopy (HRSEM), we trace the three phase contact line up to which deposition of the metal film occurs. From geometrical relations, the three phase contact angle is then calculated. We report the measurements of the contact angle of silica and polystyrene (PS) particles at different interfaces such as air-water, decane-water and octanol-water. We have also applied this method to measure the contact angle of surfactant treated polystyrene particles at the air-water interface, and we find a non-monotonic change of the contact angle with the concentration of the surfactant. Our results are compared with the well-known gel trapping technique and we find good comparison with previous measurements.

  19. All-fiber magnetic-field sensor based on microfiber knot resonator and magnetic fluid.

    Science.gov (United States)

    Li, Xianli; Ding, Hui

    2012-12-15

    All-fiber magnetic-field sensor based on a device consisting of a microfiber knot resonator and magnetic fluid is proposed for the first time in this Letter. Sensor principles and package technology are introduced in detail. Experimental results show that the resonance wavelength of the proposed sensor regularly varies with changes to the applied magnetic field. When the magnetic field is increased to 600 Oe, the wavelength shift reaches nearly 100 pm. Moreover, the sensor responding to the 50 Hz alternating magnetic field is also experimentally investigated, and a minimal detectable magnetic-field strength of 10 Oe is successfully achieved.

  20. The wavelength dependence of Faraday rotation in magnetic fluids

    Science.gov (United States)

    Yusuf, Nihad A.; Rousan, Akram A.; El-Ghanem, Hassan M.

    1988-09-01

    Measurements of Faraday rotation over the wavelength range 450-633 nm in a dilute Fe3O4 particle magnetic fluid are reported. The results, in agreement with the theory, show an enhancement of Faraday rotation near the wavelength λ≊500 nm.

  1. Design of Magnetic Gelatine/Silica Nanocomposites by Nanoemulsification: Encapsulation versus in Situ Growth of Iron Oxide Colloids

    Directory of Open Access Journals (Sweden)

    Joachim Allouche

    2014-07-01

    Full Text Available The design of magnetic nanoparticles by incorporation of iron oxide colloids within gelatine/silica hybrid nanoparticles has been performed for the first time through a nanoemulsion route using the encapsulation of pre-formed magnetite nanocrystals and the in situ precipitation of ferrous/ferric ions. The first method leads to bi-continuous hybrid nanocomposites containing a limited amount of well-dispersed magnetite colloids. In contrast, the second approach allows the formation of gelatine-silica core-shell nanostructures incorporating larger amounts of agglomerated iron oxide colloids. Both magnetic nanocomposites exhibit similar superparamagnetic behaviors. Whereas nanocomposites obtained via an in situ approach show a strong tendency to aggregate in solution, the encapsulation route allows further surface modification of the magnetic nanocomposites, leading to quaternary gold/iron oxide/silica/gelatine nanoparticles. Hence, such a first-time rational combination of nano-emulsion, nanocrystallization and sol-gel chemistry allows the elaboration of multi-component functional nanomaterials. This constitutes a step forward in the design of more complex bio-nanoplatforms.

  2. EDITORIAL: Colloidal suspensions Colloidal suspensions

    Science.gov (United States)

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

    2011-05-01

    Special issue in honour of Henk Lekkerkerker's 65th birthday Professor Henk N W Lekkerkerker is a world-leading authority in the field of experimental and theoretical soft condensed matter. On the occasion of his 65th birthday in the summer of 2011, this special issue celebrates his many contributions to science. Henk Lekkerkerker obtained his undergraduate degree in chemistry at the University of Utrecht (1968) and moved to Calgary where he received his PhD in 1971. He moved to Brussels as a NATO fellow at the Université Libre de Bruxelles and was appointed to an assistant professorship (1974), an associate professorship (1977) and a full professorship (1980) in physical chemistry at the Vrije Universiteit Brussel. In 1985 he returned to The Netherlands to take up a professorship at the Van 't Hoff Laboratory, where he has been ever since. He has received a series of awards during his career, including the Onsager Medal (1999) of the University of Trondheim, the Bakhuys Roozeboom Gold Medal (2003) of the Royal Dutch Academy of Arts and Sciences (KNAW), the ECIS-Rhodia European Colloid and Interface Prize (2003), and the Liquid Matter Prize of the European Physical Society (2008). He was elected a member of KNAW in 1996, was awarded an Academy Chair position in 2005, and has held several visiting lectureships. Henk's work focuses on phase transitions in soft condensed matter, and he has made seminal contributions to both the theoretical and experimental aspects of this field. Here we highlight three major themes running through his work, and a few selected publications. So-called depletion interactions may lead to phase separation in colloid-polymer mixtures, and Henk realised that the partitioning of polymer needs to be taken into account to describe the phase behaviour correctly [1]. Colloidal suspensions can be used as model fluids, with the time- and length-scales involved leading to novel opportunities, notably the direct observation of capillary waves at a

  3. Active fluid mixing with magnetic microactuators for capture of salmonella

    Science.gov (United States)

    Hanasoge, S.; Owen, D.; Ballard, M.; Mills, Z.; Xu, J.; Erickson, M.; Hesketh, P. J.; Alexeev, A.

    2016-05-01

    Detection of low concentrations of bacteria in food samples is a challenging process. Key to this process is the separation of the target from the food matrix. We demonstrate magnetic beads and magnetic micro-cilia based microfluidic mixing and capture, which are particularly useful for pre-concentrating the target. The first method we demonstrate makes use of magnetic microbeads held on to NiFe discs on the surface of the substrate. These beads are rotated around the magnetic discs by rotating the external magnetic field. The second method we demonstrate shows the use of cilia which extends into the fluid and is manipulated by a rotating external field. Magnetic micro-features were fabricated by evaporating NiFe alloy at room temperature, on to patterned photoresist. The high magnetic permeability of NiFe allows for maximum magnetic force on the features. The magnetic features were actuated using an external rotating magnet up to frequencies of 50Hz. We demonstrate active mixing produced by the microbeads and the cilia in a microchannel. Also, we demonstrate the capture of target species in a sample using microbeads.

  4. Temporal stability of superposed magnetic fluids in porous media

    Energy Technology Data Exchange (ETDEWEB)

    Zakaria, Kadry; Sirwah, Magdy A; Alkharashi, Sameh [Mathematics Department, Faculty of Science, Tanta University, Tanta (Egypt)

    2008-02-15

    The present work deals with the stability properties of time periodically streaming superposed magnetic fluids through porous media under the influence of an oblique alternating magnetic field. The system is composed of a middle fluid sheet of finite thickness embedded between two other bounded layers. The fluids are assumed to be incompressible and there are no volume charges in the layers of the fluids. Such configurations are of relevance in a variety of astrophysical and space configurations. The solutions of the linearized equations of motion and boundary conditions lead to deriving two more general simultaneous Mathieu equations of damping terms with complex coefficients. The method of multiple time scales is used to obtain approximate solutions and analyze the stability criteria for both the non-resonant and resonant cases and hence transition curves are obtained for such cases. The stability criteria are examined theoretically and numerically from which stability diagrams are obtained. It is found that the fluid sheet thickness plays a destabilizing role in the presence of a constant field and velocity, while the damping role is observed for the resonant cases. Dual roles are observed for the fluid velocity and the porosity in the stability criteria.

  5. Magnetic particle translation as a surrogate measure for synovial fluid mechanics.

    Science.gov (United States)

    Shah, Yash Y; Maldonado-Camargo, Lorena; Patel, Neal S; Biedrzycki, Adam H; Yarmola, Elena G; Dobson, Jon; Rinaldi, Carlos; Allen, Kyle D

    2017-07-26

    The mechanics of synovial fluid vary with disease progression, but are difficult to quantify quickly in a clinical setting due to small sample volumes. In this study, a novel technique to measure synovial fluid mechanics using magnetic nanoparticles is introduced. Briefly, microspheres embedded with superparamagnetic iron oxide nanoparticles, termed magnetic particles, are distributed through a 100μL synovial fluid sample. Then, a permanent magnet inside a protective sheath is inserted into the synovial fluid sample. Magnetic particles translate toward the permanent magnet and the percentage of magnetic particles collected by the magnet in a given time can be related to synovial fluid viscosity. To validate this relationship, magnetic particle translation was demonstrated in three phases. First, magnetic particle translation was assessed in glycerol solutions with known viscosities, demonstrating that as fluid viscosity increased, magnetic particle translation decreased. Next, the relationship between magnetic particle translation and synovial fluid viscosity was assessed using bovine synovial fluid that was progressively degenerated via ultrasonication. Here, particle collection in a given amount of time increased as fluid degenerated, demonstrating that the relationship between particle collection and fluid mechanics holds in non-Newtonian synovial fluid. Finally, magnetic particle translation was used to assess differences between healthy and OA affected joints in equine synovial fluid. Here, particle collection in a given time was higher in OA joints relative to healthy horses (pmagnetic particle translation in a clinical setting to evaluate synovial fluid mechanics in limited volumes of synovial fluid sample. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. Inventions Utilizing Microfluidics and Colloidal Particles

    Science.gov (United States)

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

    2009-01-01

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

  7. Characterization of the physical parameters in a process of magnetic separation and pressure-driven flow of a magnetic fluid

    Science.gov (United States)

    Cunha, F. R.; Sobral, Y. D.

    2004-11-01

    The equations governing the motion of a magnetic fluid are presented. These equations are non-linear and give rise to non-Newtonian effects attributable to the magnetization of the fluid. The equations are made dimensionless and the physical parameters of the coupled hydrodynamic-magnetic problem identified. The study is first applied to describe the motion of a magnetic droplet freely suspended in a viscous fluid undergoing a permanent magnetic field. A first-order theory is developed for the regime of small drop deformation in which viscous forces dominate inertial hydrodynamic force. At this regime, it is shown that the drift velocity of a magnetic drop scales with the square of the applied magnetic field and the deformation of the drop scales linearly with the applied field. Experiments are carried out and the range of validity of the small deformation analysis determined. The pressure-driven flow of a magnetic fluid is solved by a regular asymptotic expansion for two cases: a Poiseuille flow of a single magnetic fluid and a core pipe flow with a magnetic fluid adjacent to the tube wall. The theory is used to predict the volume rate of a viscous magnetic fluid separated from a non-magnetic viscous fluid by the action of a magnetic field. The apparent viscosity of a magnetic fluid as a function of magnetic parameters is also examined from our theory. A possible application of the present theoretical studies is on the remediation technology addressed to oil spills in natural environments.

  8. A New Design of Magnetic Fluid Seal for Liquids

    Institute of Scientific and Technical Information of China (English)

    LIU Tong-gang; YANG Zhi-yi

    2005-01-01

    Direct contract between the sealed liquid and the magnetic fluid in a dynamic system under magnetic field may lead to an unstable interface, consequently, break down the seal. Aiming at this problem, a new magnetic fluid seal (MFS) was developed. In this new MFS, a soft iron bushing with high permeability was introduced on the shaft and nonferrous shields were installed beside the bushing and the pole pieces. The parameters of the bushing and the shields were optimized in a seal simulation facility. The results show that the bushing with a thickness of 7 mm and shields with a width of 8 mm are best for sealing a shaft 20 mm in diameter. The MFS designed based on the optimum parameters shows good performance and long life span for sealing lubricating oil.

  9. A Magnetic Field Sensor Based on a Magnetic Fluid-Filled FP-FBG Structure

    Directory of Open Access Journals (Sweden)

    Ji Xia

    2016-04-01

    Full Text Available Based on the characteristic magnetic-controlled refractive index property, in this paper, a magnetic fluid is used as a sensitive medium to detect the magnetic field in the fiber optic Fabry-Perot (FP cavity. The temperature compensation in fiber Fabry-Perot magnetic sensor is demonstrated and achieved. The refractive index of the magnetic fluid varies with the applied magnetic field and external temperature, and a cross-sensitivity effect of the temperature and magnetic field occurs in the Fabry-Perot magnetic sensor and the accuracy of magnetic field measurements is affected by the thermal effect. In order to overcome this problem, we propose a modified sensor structure. With a fiber Bragg grating (FBG written in the insert fiber end of the Fabry-Perot cavity, the FBG acts as a temperature compensation unit for the magnetic field measurement and it provides an effective solution to the cross-sensitivity effect. The experimental results show that the sensitivity of magnetic field detection improves from 0.23 nm/mT to 0.53 nm/mT, and the magnetic field measurement resolution finally reaches 37.7 T. The temperature-compensated FP-FBG magnetic sensor has obvious advantages of small volume and high sensitivity, and it has a good prospect in applications in the power industry and national defense technology areas.

  10. A Magnetic Field Sensor Based on a Magnetic Fluid-Filled FP-FBG Structure.

    Science.gov (United States)

    Xia, Ji; Wang, Fuyin; Luo, Hong; Wang, Qi; Xiong, Shuidong

    2016-04-29

    Based on the characteristic magnetic-controlled refractive index property, in this paper, a magnetic fluid is used as a sensitive medium to detect the magnetic field in the fiber optic Fabry-Perot (FP) cavity. The temperature compensation in fiber Fabry-Perot magnetic sensor is demonstrated and achieved. The refractive index of the magnetic fluid varies with the applied magnetic field and external temperature, and a cross-sensitivity effect of the temperature and magnetic field occurs in the Fabry-Perot magnetic sensor and the accuracy of magnetic field measurements is affected by the thermal effect. In order to overcome this problem, we propose a modified sensor structure. With a fiber Bragg grating (FBG) written in the insert fiber end of the Fabry-Perot cavity, the FBG acts as a temperature compensation unit for the magnetic field measurement and it provides an effective solution to the cross-sensitivity effect. The experimental results show that the sensitivity of magnetic field detection improves from 0.23 nm/mT to 0.53 nm/mT, and the magnetic field measurement resolution finally reaches 37.7 T. The temperature-compensated FP-FBG magnetic sensor has obvious advantages of small volume and high sensitivity, and it has a good prospect in applications in the power industry and national defense technology areas.

  11. Influence of Brownian Diffusion on Levitation of Bodies in Magnetic Fluid

    Directory of Open Access Journals (Sweden)

    V. Bashtovoi

    2013-12-01

    Full Text Available The present work deals with experimental investigation of the levitation of magnetic and non-magnetic bodies in a magnetic fluid when essentially influenced by Brownian diffusion of magnetic particles in it. It is established that the point of levitation of bodies in a magnetic fluid varies with time.

  12. Some applications of magnetic resonance imaging in fluid mechanics: Complex flows and complex fluids

    NARCIS (Netherlands)

    Bonn, D.; Rodts, S.; Groenink, M.; Rafaï, S.; Shahidzadeh-Bonn, N.; Coussot, P.

    2008-01-01

    The review deals with applications of magnetic resonance imaging (MRI) techniques to study flow. We first briefly discuss the principles of flow measurement by MRI and give examples of some applications, such as multiphase flows, the MRI rheology of complex fluid flows, and blood flows in the human

  13. Effect of perioperative crystalloid or colloid fluid therapy on hemorrhage, coagulation competence, and outcome

    DEFF Research Database (Denmark)

    Rasmussen, Kirsten C; Secher, Niels H; Pedersen, Tom

    2016-01-01

    for fluid administration during major elective surgery. Surgery was restricted to cardiovascular and noncardiovascular surgery, and HESs were stratified to HES 130/0.4 and HES 200/0.5. METHODS: We searched Cochrane Central Register of Controlled Trials, MEDLINE, ISI Web of Science, EMBASE, conference...

  14. Open channel flows of magnetic fluid induced by traveling magnetic field

    Science.gov (United States)

    Kuwahara, Takuya; Okubo, Masaaki; Yamane, Ryuichiro

    A theoretical analysis is made on laminar open channel flows of magnetic fluid induced by a non uniform traveling magnetic field which is applied with a stator of a single-sided linear induction motor. The induced flows are mainly in the direction opposite to the traveling direction of the magnetic field and in proportion to the phase velocity of the magnetic field. The velocity profiles are greatly affected by dimensionless wave number of the magnetic field. Near the bottom of the channel, the theoretical velocity distributions agree well with experimental ones which are measured with a laser optical fiber velocity sensor. However, the experimental velocity distributions become larger near the free surface.

  15. Response of self-assembly for magnetite nanocrystal in magnetic fluid under an applied magnetic field

    Institute of Scientific and Technical Information of China (English)

    Yun Zou; Yiyou Nie; Ziyun Di; Dongchen Zhang; Minghuang Sang; Xianfeng Chen

    2008-01-01

    @@ The response time and transmittivity of the magnetic fluid (MF) for different concentrations at room temperature were investigated in this letter. The volume fraction of the investigated sample ranged from 0.44% to 6.47%. It was found that the transmittivity decreased with increasing concentration under a given magnetic field, and the evolution time was changed with different concentrations. Moreover, the light intensity decreased rapidly at the beginning and then became stable when the magnetic field was applied.

  16. Multifractality in dilute magnetorheological fluids under an oscillating magnetic field.

    Science.gov (United States)

    Moctezuma, R E; Arauz-Lara, J L; Donado, F

    2014-12-01

    A study of the multifractal characteristics of the structure formed by magnetic particles in a dilute magnetorheological fluid is presented. A quasi-two-dimensional magnetorheological fluid sample is simultaneously subjected to a static magnetic field and a sinusoidal magnetic field transverse to each other. We analyzed the singularity spectrum f(α) and the generalized dimension D(q) of the whole structure to characterize the distribution of the aggregates under several conditions of particle concentration, magnetic field intensities, and liquid viscosity. We also obtained the fractal dimension D(g), calculated from the radius of gyration of the chains, to describe the internal distribution of the particles. We present a thermodynamic interpretation of the multifractal analysis, and based on this, we discussed the characteristics of the structure formed by the particles and its relation with previous studies of the average chain length. We have found that this method is useful to quantitatively describe the structure of magnetorheological fluids, especially in systems with high particle concentration where the aggregates are more complex than simple chains or columns.

  17. Three-dimensional global fluid simulations of cylindrical magnetized plasmas

    DEFF Research Database (Denmark)

    Naulin, Volker; Windisch, T.; Grulke, O.

    2008-01-01

    . Thus, it is possible to assess the reproductive and predictive capabilities of plasma simulations in unprecedented detail. Here, three-dimensional global fluid simulations of a cylindrical magnetized plasma are presented. This plasma is characterized by the existence of spatially localized sources...... and sinks. The traditional scale separation paradigm is not applied in the simulation model to account for the important evolution of the background profiles due to the dynamics of turbulent fluctuations. Furthermore, the fluid modeling of sheath boundary conditions, which determine the plasma conditions...

  18. Interfacial deformation and jetting of a magnetic fluid

    CERN Document Server

    Afkhami, Shahriar; Griffiths, Ian M

    2015-01-01

    An attractive technique for forming and collecting aggregates of magnetic material at a liquid--air interface by an applied magnetic field gradient was recently addressed theoretically and experimentally [Soft Matter, (9) 2013, 8600-8608]: when the magnetic field is weak, the deflection of the liquid--air interface has a steady shape, while for sufficiently strong fields, the interface destabilizes and forms a jet that extracts magnetic material. Motivated by this work, we develop a numerical model for the closely related problem of solving two-phase Navier--Stokes equations coupled with the static Maxwell equations. We computationally model the forces generated by a magnetic field gradient produced by a permanent magnet and so determine the interfacial deflection of a magnetic fluid (a pure ferrofluid system) and the transition into a jet. We analyze the shape of the liquid--air interface during the deformation stage and the critical magnet distance for which the static interface transitions into a jet. We d...

  19. Influence of the aggregation, concentration, and viscosity on the nanomagnetism of iron oxide nanoparticle colloids for magnetic hyperthermia

    Energy Technology Data Exchange (ETDEWEB)

    Cabrera, David; Camarero, Julio; Ortega, Daniel; Teran, Francisco J., E-mail: francisco.teran@imdea.org [Ciudad Universitaria de Cantoblanco, IMDEA Nanociencia (Spain)

    2015-03-15

    Iron oxide nanoparticles have become ubiquitous in many biomedical applications, acting as core elements in an increasing number of therapeutic and diagnostic modalities. These applications mainly rely on their static and dynamic magnetic properties, through which they can be remotely actuated. However, little attention has been paid to understand the variation of the magnetic response of nanoparticles inside cells or tissues, despite of the remarkable changes reported to date. In this article, we provide some hints to analyze the influence of the biological matrix on the magnetism of iron oxide nanoparticles. To this aim, we propose the assessment of the heating efficiency of magnetic colloids against nanoparticle aggregation, concentration, and viscosity in order to mimic the fate of nanoparticles upon cell internalization.

  20. Experimental measurements of ultrasonic propagation velocity and attenuation in a magnetic fluid.

    Science.gov (United States)

    Motozawa, M; Iizuka, Y; Sawada, T

    2008-05-21

    The ultrasonic propagation velocity and attenuation in a magnetic fluid subjected to magnetic field are measured precisely. Various characteristic properties of ultrasonic propagation in magnetic fluid such as hysteresis and anisotropy are observed. These results show that the ultrasonic propagation velocity and attenuation are dependent upon the intensity and the length of time for which the magnetic field is applied. When the magnetic field is applied, some of the magnetic particles in the magnetic fluid form clustering structures that influence ultrasonic propagation in a magnetic fluid. Our results indicate that the inner structure of a magnetic fluid can be analysed experimentally and we discuss the application of this non-contact inspection of the clustering structures in a magnetic fluid by ultrasonic techniques.

  1. Investigation of magneto-induced linear dichroism of magnetic fluid.

    Science.gov (United States)

    Du, Bobo; Yang, Dexing; Bai, Yang; Yuan, Yuan; Mao, Dong; Zhang, Wending; She, Xiaoyang

    2017-01-20

    A fiber-optic component is fabricated with etched fiber coated by magnetic fluid (MF) for its evanescent field to be modulated by the MF. The magneto-induced linear dichroism of the MF is investigated under different temperatures with the component. The experimental results show that the MF possesses weak linear dichroism (maximum of 2.37% at 25°C) caused by its sparse magneto-induced chains. Considering the relationships between the linear dichroisms and temperature, there is a transition point of magnetic field at ∼4  mT. Up to ∼4  mT, the linear dichroisms decrease with the temperature; however, for higher magnetic field strengths, the linear dichroisms increase with the temperature. Interestingly, a small initial linear dichroism (up to 0.255% at 5°C) without magnetic field is also observed.

  2. Temperature dependent small-angle neutron scattering of CTABr-magnetic fluid emulsion

    Indian Academy of Sciences (India)

    V K Aswal; J V Joshi; P S Goyal; Rajesh Patel; R V Upadhyay; R V Mehta

    2004-08-01

    Small-angle neutron scattering studies have been carried out to check the structural integrity of citryltrimethylammonium bromide (CTABr) micelles in a magnetic fluid for different magnetic fluid concentrations at two different temperatures 303 and 333 K. It is found that the CTABr micelles grow with increasing magnetic fluid concentration and there is a decrease in the micellar size with increase in temperature.

  3. Energy transport in cooling device by magnetic fluid

    Science.gov (United States)

    Yamaguchi, Hiroshi; Iwamoto, Yuhiro

    2017-06-01

    Temperature sensitive magnetic fluid has a great potential with high performance heat transport ability as well as long distance energy (heat) transporting. In the present study experimental set-up was newly designed and constructed in order to measure basic heat transport characteristics under various magnetic field conditions. Angular dependence for the device (heat transfer section) was also taken into consideration for a sake of practical applications. The energy transfer characteristic (heat transport capability) in the magnetically-driven heat transport (cooling) device using the binary TSMF was fully investigated with the set-up. The obtained results indicate that boiling of the organic mixture (before the magnetic fluid itself reaching boiling point) effectively enhances the heat transfer as well as boosting the flow to circulate in the closed loop by itself. A long-distance heat transport of 5 m is experimentally confirmed, transferring the thermal energy of 35.8 W, even when the device (circulation loop) is horizontally placed. The highlighted results reveal that the proposed cooling device is innovative in a sense of transporting substantial amount of thermal energy (heat) as well as a long distance heat transport. The development of the magnetically-driven heat transport device has a great potential to be replaced for the conventional heat pipe in application of thermal engineering.

  4. Reflective all-fiber current sensor based on magnetic fluids

    Science.gov (United States)

    Li, Lin; Han, Qun; Liu, Tiegen; Chen, Yaofei; Zhang, Rongxiang

    2014-08-01

    A reflective all-fiber current sensor based on magnetic fluid (MF) is reported. The MF is used as the cladding of a piece of no-core fiber which is spliced between two sections of singlemode fiber to form a singlemode-multimode-singlemode structure. An intensity based interrogation scheme with a superluminescent diode as the light source and the dual-balanced detection method is used in the sensing system. The influence of the direction of the magnetic field on the sensitivity of the sensor is also experimentally investigated and analyzed.

  5. Particle contact angles at fluid interfaces: pushing the boundary beyond hard uniform spherical colloids

    Science.gov (United States)

    Zanini, Michele; Isa, Lucio

    2016-08-01

    Micro and nanoparticles at fluid interfaces have been attracting increasing interest in the last few decades as building blocks for materials, as mechanical and structural probes for complex interfaces and as models for two-dimensional systems. The three-phase contact angle enters practically all aspects of the particle behavior at the interface: its thermodynamics (binding energy to the interface), dynamics (motion and drag at the interface) and interactions with the interface (adsorption and wetting). Moreover, many interactions among particles at the interface also strongly depend on the contact angle. These concepts have been extensively discussed for non-deformable, homogeneous and mostly spherical particles, but recent progress in particle synthesis and fabrication has instead moved in the direction of producing more complex micro and nanoscale objects, which can be responsive, deformable, heterogenous and/or anisotropic in shape, surface chemistry and material properties. These new particles have a much greater potential for applications and new science, and the study of their behavior at interfaces has only very recently started. In this paper, we critically review the current state of the art of the experimental methods available to measure the contact angle of micro and nanoparticles at fluid interfaces, indicating their strengths and limitations. We then comment on new particle systems that are currently attracting increasing interest in relation to their adsorption and assembly at fluid interfaces and discuss if and which ones of the current techniques are suited to investigate their properties at interfaces. Based on this discussion, we will finally try to indicate a direction in which new experimental methods should develop in the future to tackle the new challenges posed by the novel types of particles that more and more often are used at interfaces.

  6. Hemodynamic recovery after hypovolemic shock with lactated Ringer's and keratin resuscitation fluid (KRF), a novel colloid.

    Science.gov (United States)

    Nunez, Fiesky A; Callahan, Michael F; Trach, Simon; Burnett, Luke R; Kislukhin, Victor; Smith, Thomas L; Van Dyke, Mark

    2013-10-01

    Death after severe hemorrhage remains an important cause of mortality in people under 50 years of age. Keratin resuscitation fluid (KRF) is a novel resuscitation solution made from keratin protein that may restore cardiovascular stability. This postulate was tested in rats that were exsanguinated to 40% of their blood volume. Test groups received either low or high volume resuscitation with either KRF or lactated Ringer's solution. KRF low volume was more effective than LR in recovering cardiac function, blood pressure and blood chemistry. Furthermore, in contrast to LR-treated rats, KRF-treated rats exhibited vital signs that resembled normal controls at 1-week.

  7. Quantifying Chiral Magnetic Effect from Anomalous-Viscous Fluid Dynamics

    CERN Document Server

    Jiang, Yin; Yin, Yi; Liao, Jinfeng

    2016-01-01

    Chiral Magnetic Effect (CME) is the macroscopic manifestation of the fundamental chiral anomaly in a many-body system of chiral fermions, and emerges as anomalous transport current in the fluid dynamics framework. Experimental observation of CME is of great interest and has been reported in Dirac and Weyl semimetals. Significant efforts have also been made to search for CME in heavy ion collisions. Encouraging evidence of CME-induced charge separation in those collisions has been reported, albeit with ambiguity due to background contamination. Crucial for addressing such issue, is the need of quantitative predictions for CME signal with sophisticated modelings. In this paper we develop such a tool, the Anomalous Viscous Fluid Dynamics (AVFD) framework, which simulates the evolution of fermion currents in QGP on top of the data-validated VISHNU bulk hydrodynamic flow. With realistic initial conditions and magnetic field lifetime, the AVFD-predicted CME signal could be quantitatively consistent with measured ch...

  8. Magnetoviscosity in magnetic fluids: Testing different models of the magnetization equation

    Directory of Open Access Journals (Sweden)

    Huei Chu Weng

    2013-09-01

    Full Text Available Despite a long research history, theoretical predictions for the material properties as well as the flow fields and characteristics of magnetic fluids were not well consistent with the experimental data. The lack of a universally accepted magnetization equation for accurately modeling hydrodynamics of magnetic fluids/nanofluids is particularly a major issue. In this paper, we give an overview on the continuum theory and test the six well-known models via comparisons with magnetoviscosity measurements to make clear the magnetization relaxation due to the rotation of magnetic particles and see how well they make predictions on the basis of numerical calculations. Results reveal that the ML model leads to unexplainable behavior. Moreover, the WC model with a ‘relaxation rate’ modification is found to reproduce the predictions of the MRSh model, which agree well with experimental data. The revised WC model (WCC should therefore be preferred.

  9. Failure of Magnetic Fluid Seals Operating in Water: Preliminary Conclusions

    Directory of Open Access Journals (Sweden)

    Matuszewski Leszek

    2017-06-01

    Full Text Available The article analyses properties of magnetic fluid seals installed in rotary sealing nodes which operate in the utility water environment. Seals of this type have been examined as a possible solution to the problem with ship manoeuvring propulsion sealing. The present analysis bases on laboratory durability tests of magnetic fluid seals exposed to longterm utility water loads, at different water pressures and shaft revolutions. The basic seal durability criterion was the number of revolutions made by the sealing node shaft until the appearance of water tightness loss (leakage. It was found that the main factor leading to the wear of the seal is the relative speed of the magnetic fluid with respect to that of the utility water, and this process is heavily affected by the pressure acting on the seal. The reported test results are presented in the form of diagrams showing the seal durability (time until water tightness loss as a function of rotational speed. The curves shown in the diagrams are regular, with two different rotational speed ranges: the highspeed range, when the tightness loss is relatively fast, and the low-speed range, with a clear tendency to prolong the seal lifetime. These diagrams were given the name of durability curves of the MF seal operating in water. The results of the performed tests suggest formal similarity between the experimental data distribution concerning tightness loss processes occurring in magnetic fluid seals operating in water environment and metal fatigue processes. The article proposes a preliminary simplified durability model to describe the examined phenomenon.

  10. Motion of compressible magnetic fluids in T^3

    Directory of Open Access Journals (Sweden)

    Weiping Yan

    2013-10-01

    Full Text Available This article shows the existence of weak time-periodic motion of a three-dimensional system of compressible magnetic fluid driven by time-dependent external forces in a torus T^3. The model consists of the mass conservation equation, the linear momentum equation, the angular momentum equation, the Bloch-Torrey type equation and the magnetostatic equation. This analysis is based on the Faedo-Galerkin method and weak compactness techniques.

  11. Combination of crystalloid (glucose) and colloid (icodextrin) osmotic agents markedly enhances peritoneal fluid and solute transport during the long PD dwell.

    Science.gov (United States)

    Freida, Philippe; Galach, Magda; Divino Filho, Jose C; Werynski, Andrzej; Lindholm, Bengt

    2007-01-01

    Fluid and sodium removal is often inadequate in peritoneal dialysis patients with high peritoneal solute transport rate, especially when residual renal function is declining. We studied the effects of using simultaneous crystalloid (glucose) and colloid (icodextrin) osmotic agents on the peritoneal transport of fluid, sodium, and other solutes during 15-hour single-dwell exchanges using 3.86% glucose, 7.5% icodextrin, and a combination fluid with 2.61% glucose and 6.8% icodextrin in 7 prevalent peritoneal dialysis patients with fast peritoneal solute transport rate. The combination fluid enhanced net ultrafiltration (mean 990 mL) and sodium removal (mean 158 mmol) compared with 7.5% icodextrin (mean net ultrafiltration 462 mL, mean net sodium removal 49 mmol). In contrast, the 3.86% glucose-based solution yielded negligible ultrafiltration (mean -85 mL) and sodium removal (mean 16 mmol). The combination solution resulted in significantly improved urea (+41%) and creatinine (+26%) clearances compared with 7.5% icodextrin. A solution containing both crystalloid (glucose 2.61%) and colloid (icodextrin 6.8%) osmotic agents enhanced fluid removal by twofold and sodium removal by threefold compared with 7.5% icodextrin solution during a dwell of 15 hours, indicating that such a combination solution could represent a new treatment option for anuric peritoneal dialysis patients with high peritoneal solute transport rate.

  12. An investigation of critical and noncritical correlations in model colloidal fluids

    Energy Technology Data Exchange (ETDEWEB)

    Pini, D; Reatto, L [Dipartimento di Fisica, Universita di Milano, Via Celoria 16, 20133 Milano (Italy); Parola, A [Dipartimento di Scienze Fisiche, Universita dell' Insubria, Via Valleggio 11, 22100 Como (Italy); Lo Verso, F [Chimie Analytique et Biophysico-chimie de l' Environnement (CABE), Universite de Geneve, Sciences II, 30 quai Ernest Ansermet, CH-1211 Geneve 4 (Switzerland); Tau, M [Dipartimento di Fisica, Universita di Parma, Parco Area delle Scienze 7/A, 43100 Parma (Italy)], E-mail: davide.pini@mi.infm.it

    2008-12-10

    We present a study of the correlation length {xi} of a hard-core fluid with three different tail interactions, namely, the Asakura-Oosawa potential, an attractive Yukawa tail, and a double Yukawa tail which is attractive at short distance and repulsive at long distance. The correlation length is obtained along the critical isochore in the whole range of supercritical temperatures by determining the leading pole of the structure factor S(k) in the complex plane, where S(k) is obtained from the hierarchical reference theory. We focus on how {xi} changes from its Ornstein-Zernike form in the critical region to its high-temperature limit, and find instances of both the Fisher-Widom and Kirkwood scenarios for the monotonic to oscillatory crossover of the decay of correlations at long distance.

  13. Effects of fluid resuscitation with colloids vs crystalloids on mortality in critically ill patients presenting with hypovolemic shock: the CRISTAL randomized trial.

    Science.gov (United States)

    Annane, Djillali; Siami, Shidasp; Jaber, Samir; Martin, Claude; Elatrous, Souheil; Declère, Adrien Descorps; Preiser, Jean Charles; Outin, Hervé; Troché, Gilles; Charpentier, Claire; Trouillet, Jean Louis; Kimmoun, Antoine; Forceville, Xavier; Darmon, Michael; Lesur, Olivier; Reignier, Jean; Régnier, Jean; Abroug, Fékri; Berger, Philippe; Clec'h, Christophe; Cle'h, Christophe; Cousson, Joël; Thibault, Laure; Chevret, Sylvie

    2013-11-06

    Evidence supporting the choice of intravenous colloid vs crystalloid solutions for management of hypovolemic shock remains unclear. To test whether use of colloids compared with crystalloids for fluid resuscitation alters mortality in patients admitted to the intensive care unit (ICU) with hypovolemic shock. A multicenter, randomized clinical trial stratified by case mix (sepsis, trauma, or hypovolemic shock without sepsis or trauma). Therapy in the Colloids Versus Crystalloids for the Resuscitation of the Critically Ill (CRISTAL) trial was open label but outcome assessment was blinded to treatment assignment. Recruitment began in February 2003 and ended in August 2012 of 2857 sequential ICU patients treated at 57 ICUs in France, Belgium, North Africa, and Canada; follow-up ended in November 2012. Colloids (n = 1414; gelatins, dextrans, hydroxyethyl starches, or 4% or 20% of albumin) or crystalloids (n = 1443; isotonic or hypertonic saline or Ringer lactate solution) for all fluid interventions other than fluid maintenance throughout the ICU stay. The primary outcome was death within 28 days. Secondary outcomes included 90-day mortality; and days alive and not receiving renal replacement therapy, mechanical ventilation, or vasopressor therapy. Within 28 days, there were 359 deaths (25.4%) in colloids group vs 390 deaths (27.0%) in crystalloids group (relative risk [RR], 0.96 [95% CI, 0.88 to 1.04]; P = .26). Within 90 days, there were 434 deaths (30.7%) in colloids group vs 493 deaths (34.2%) in crystalloids group (RR, 0.92 [95% CI, 0.86 to 0.99]; P = .03). Renal replacement therapy was used in 156 (11.0%) in colloids group vs 181 (12.5%) in crystalloids group (RR, 0.93 [95% CI, 0.83 to 1.03]; P = .19). There were more days alive without mechanical ventilation in the colloids group vs the crystalloids group by 7 days (mean: 2.1 vs 1.8 days, respectively; mean difference, 0.30 [95% CI, 0.09 to 0.48] days; P = .01) and by 28 days (mean: 14

  14. Magnetic field sensor based on cascaded microfiber coupler with magnetic fluid

    Energy Technology Data Exchange (ETDEWEB)

    Mao, Lianmin; Su, Delong; Wang, Zhaofang [College of Science, University of Shanghai for Science and Technology, Shanghai 200093 (China); Pu, Shengli, E-mail: shlpu@usst.edu.cn [College of Science, University of Shanghai for Science and Technology, Shanghai 200093 (China); Shanghai Key Laboratory of Modern Optical System, University of Shanghai for Science and Technology, Shanghai 200093 (China); Zeng, Xianglong [The Key Lab of Specialty Fiber Optics and Optical Access Network, Shanghai University, Shanghai 200072 (China); Lahoubi, Mahieddine [Laboratory L.P.S., Department of Physics, Faculty of Sciences, Badji-Mokhtar Annaba University, Annaba 23000 (Algeria)

    2016-09-07

    A kind of magnetic field sensor based on cascaded microfiber coupler with magnetic fluid is proposed and experimentally demonstrated. The magnetic fluid is utilized as the cladding of the fused regions of the cascaded microfiber coupler. As the interference valley wavelength of the sensing structure is sensitive to the ambient variation, considering the magnetic-field-dependent refractive index of magnetic fluid, the proposed structure is employed for magnetic field sensing. The effective coupling length for each coupling region of the as-fabricated cascaded microfiber coupler is 6031 μm. The achieved sensitivity is 125 pm/Oe, which is about three times larger than that of the previously similar structure based on the single microfiber coupler. Experimental results indicate that the sensing sensitivity can be easily improved by increasing the effective coupling length or cascading more microfiber couplers. The proposed magnetic field sensor is attractive due to its low cost, immunity to electromagnetic interference, as well as high sensitivity, which also has the potentials in other tunable all-fiber photonic devices, such as filter.

  15. Hyperchaotic Intermittent Convection in a Magnetized Viscous Fluid

    CERN Document Server

    Macek, Wieslaw M

    2014-01-01

    We consider a low-dimensional model of convection in a horizontally magnetized layer of a viscous fluid heated from below. We analyze in detail the stability of hydromagnetic convection for a wide range of two control parameters. Namely, when changing the initially applied temperature difference or magnetic field strength, one can see transitions from regular to irregular long-term behavior of the system, switching between chaotic, periodic, and equilibrium asymptotic solutions. It is worth noting that owing to the induced magnetic field a transition to hyperchaotic dynamics is possible for some parameters of the model. We also reveal new features of the generalized Lorenz model, including both type I and III intermittency.

  16. Rotating magnetic particle microrheometry in biopolymer fluid dynamics: mucus microrheology.

    Science.gov (United States)

    Besseris, George J; Yeates, Donovan B

    2007-09-14

    The polymer properties of canine mucus were investigated through the method of rotating magnetic particle microrheometry. Mucus is visualized as a physically entangled biopolymer of low polydispersity in a water-based solution. Mucus was modeled according to the constitutive law of a Doi-Edwards fluid. The magnetic-particle equation of rotational motion is analytically solved in the linear viscoelastic limit rendering theoretical flow profiles which are used to fit the experimental trace signals of the particle remanent-magnetic-field decay. The zero-shear-rate viscosity was found to be 18,000 P and the relaxation time at about 42 s. The molecular weight between entanglements for mucins was estimated at 1.7 MDa rendering an estimation of about seven physical cross-links per molecule. Rheological investigations were extended also to diluted and concentrated rations of the normal mucus simulating the conditions found in more physiological extremes.

  17. Viscosity behavior of magnetic suspensions in fluid-assisted finishing

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Magnetic fluid-assisted finishing has been verified both theoretically and experimentally as an effective fabrication technology for optical mirrors and lenses. The purpose of this paper is to introduce a novel design of polishing tool and demonstrate the possible applications of this technology. The work includes studying the viscosity of the magnetic suspensions of micrometer-sized Carbonyl iron particles under the influence of a magnetic field. Both the cases of magnetizable suspension with and without abrasive cerium oxide particles are studied for their ensuing polishing effectiveness. Determination of material removal function is conducted using a Wyko Nat1100 interferometer. Experiments to reduce surface roughness with the proposed tool are also performed using a K9 mirror as the work-piece. Results show that the surface accuracy is improved over three times to less than 0.5 nm after two cycles of polishing.

  18. Improved magnetic induction heating of nanoferrites for hyperthermia applications: Correlation with colloidal stability and magneto-structural properties

    Energy Technology Data Exchange (ETDEWEB)

    Khot, V.M., E-mail: wish_khot@yahoo.co.in [Center for Interdisciplinary Research, D. Y. Patil University, Kolhapur 416006 (India); Salunkhe, A.B. [Advanced Materials Laboratory, Department of Physics, Savitribai Phule University of Pune (India); Ruso, J.M. [Soft Matter and Molecular Biophysics Group, Applied Physics Department, University of Santiago de Compostela, Santiago de Compostela (Spain); Pawar, S.H. [Center for Interdisciplinary Research, D. Y. Patil University, Kolhapur 416006 (India)

    2015-06-15

    Nanoferrites with compositions Mn{sub 0.4}Zn{sub 0.6}Fe{sub 2}O{sub 4}, Co{sub 0.4}Zn{sub 0.6}Fe{sub 2}O{sub 4}, Ni{sub 0.4}Zn{sub 0.6}Fe{sub 2}O{sub 4} (MZF, CZF and NZF respectively) coated with polyethylene glycol (PEG) were prepared in a single step. These nanoparticles are highly water dispersible with zeta potential values between 14 and 21 mV. Magnetic induction heating characteristics of these NPs have been studied as a function of magnetic field amplitude from 6.7 to 26.7 kA m{sup −1} (at fixed frequency 265 kHz) and concentration of nanoparticles. Notable enhancement in specific absorption rate (334.5 W g{sup −1}) by CZF nanoparticles has been observed. This enhanced induction heating properties have been studied and correlated with colloidal stability and magnetostructural properties such as tuned magnetic anisotropy arising from zinc substitution. Cytotoxicity of synthesized mixed ferrites has been evaluated in vitro on HeLa cell lines using MTT assay to explore their use as heating agents in magnetic hyperthermia. - Highlights: • Magnetic nanoferrites (sizes 8–12 nm) with improved specific absorption rate (334.5 W g{sup −1}) at lowest particle concentration have been prepared • The results have been explained by correlating colloidal stability and magnetostructural properties such as magnetocrystalline anisotropy. • It has been shown that substitution of zinc tunes anisotropy of cobalt iron oxide within the value optimized previously in achieving high throughput in magnetic induction heating. • In vitro cytotoxicity proves nanoparticles are non-toxic suggesting their use as a potential heating agent in hyperthermia therapy.

  19. Theory of activated penetrant diffusion in viscous fluids and colloidal suspensions.

    Science.gov (United States)

    Zhang, Rui; Schweizer, Kenneth S

    2015-10-14

    We heuristically formulate a microscopic, force level, self-consistent nonlinear Langevin equation theory for activated barrier hopping and non-hydrodynamic diffusion of a hard sphere penetrant in very dense hard sphere fluid matrices. Penetrant dynamics is controlled by a rich competition between force relaxation due to penetrant self-motion and collective matrix structural (alpha) relaxation. In the absence of penetrant-matrix attraction, three activated dynamical regimes are predicted as a function of penetrant-matrix size ratio which are physically distinguished by penetrant jump distance and the nature of matrix motion required to facilitate its hopping. The penetrant diffusion constant decreases the fastest with size ratio for relatively small penetrants where the matrix effectively acts as a vibrating amorphous solid. Increasing penetrant-matrix attraction strength reduces penetrant diffusivity due to physical bonding. For size ratios approaching unity, a distinct dynamical regime emerges associated with strong slaving of penetrant hopping to matrix structural relaxation. A crossover regime at intermediate penetrant-matrix size ratio connects the two limiting behaviors for hard penetrants, but essentially disappears if there are strong attractions with the matrix. Activated penetrant diffusivity decreases strongly with matrix volume fraction in a manner that intensifies as the size ratio increases. We propose and implement a quasi-universal approach for activated diffusion of a rigid atomic/molecular penetrant in a supercooled liquid based on a mapping between the hard sphere system and thermal liquids. Calculations for specific systems agree reasonably well with experiments over a wide range of temperature, covering more than 10 orders of magnitude of variation of the penetrant diffusion constant.

  20. Theory of activated penetrant diffusion in viscous fluids and colloidal suspensions

    Science.gov (United States)

    Zhang, Rui; Schweizer, Kenneth S.

    2015-10-01

    We heuristically formulate a microscopic, force level, self-consistent nonlinear Langevin equation theory for activated barrier hopping and non-hydrodynamic diffusion of a hard sphere penetrant in very dense hard sphere fluid matrices. Penetrant dynamics is controlled by a rich competition between force relaxation due to penetrant self-motion and collective matrix structural (alpha) relaxation. In the absence of penetrant-matrix attraction, three activated dynamical regimes are predicted as a function of penetrant-matrix size ratio which are physically distinguished by penetrant jump distance and the nature of matrix motion required to facilitate its hopping. The penetrant diffusion constant decreases the fastest with size ratio for relatively small penetrants where the matrix effectively acts as a vibrating amorphous solid. Increasing penetrant-matrix attraction strength reduces penetrant diffusivity due to physical bonding. For size ratios approaching unity, a distinct dynamical regime emerges associated with strong slaving of penetrant hopping to matrix structural relaxation. A crossover regime at intermediate penetrant-matrix size ratio connects the two limiting behaviors for hard penetrants, but essentially disappears if there are strong attractions with the matrix. Activated penetrant diffusivity decreases strongly with matrix volume fraction in a manner that intensifies as the size ratio increases. We propose and implement a quasi-universal approach for activated diffusion of a rigid atomic/molecular penetrant in a supercooled liquid based on a mapping between the hard sphere system and thermal liquids. Calculations for specific systems agree reasonably well with experiments over a wide range of temperature, covering more than 10 orders of magnitude of variation of the penetrant diffusion constant.

  1. Theory of activated penetrant diffusion in viscous fluids and colloidal suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Rui; Schweizer, Kenneth S., E-mail: kschweiz@illinois.edu [Department of Materials Science and Frederick Seitz Materials Research Laboratory, University of Illinois, 1304 West Green Street, Urbana, Illinois 61801 (United States)

    2015-10-14

    We heuristically formulate a microscopic, force level, self-consistent nonlinear Langevin equation theory for activated barrier hopping and non-hydrodynamic diffusion of a hard sphere penetrant in very dense hard sphere fluid matrices. Penetrant dynamics is controlled by a rich competition between force relaxation due to penetrant self-motion and collective matrix structural (alpha) relaxation. In the absence of penetrant-matrix attraction, three activated dynamical regimes are predicted as a function of penetrant-matrix size ratio which are physically distinguished by penetrant jump distance and the nature of matrix motion required to facilitate its hopping. The penetrant diffusion constant decreases the fastest with size ratio for relatively small penetrants where the matrix effectively acts as a vibrating amorphous solid. Increasing penetrant-matrix attraction strength reduces penetrant diffusivity due to physical bonding. For size ratios approaching unity, a distinct dynamical regime emerges associated with strong slaving of penetrant hopping to matrix structural relaxation. A crossover regime at intermediate penetrant-matrix size ratio connects the two limiting behaviors for hard penetrants, but essentially disappears if there are strong attractions with the matrix. Activated penetrant diffusivity decreases strongly with matrix volume fraction in a manner that intensifies as the size ratio increases. We propose and implement a quasi-universal approach for activated diffusion of a rigid atomic/molecular penetrant in a supercooled liquid based on a mapping between the hard sphere system and thermal liquids. Calculations for specific systems agree reasonably well with experiments over a wide range of temperature, covering more than 10 orders of magnitude of variation of the penetrant diffusion constant.

  2. Colloids versus crystalloids in objective-guided fluid therapy, systematic review and meta-analysis. Too early or too late to draw conclusions.

    Science.gov (United States)

    Ripollés, Javier; Espinosa, Ángel; Casans, Rubén; Tirado, Ana; Abad, Alfredo; Fernández, Cristina; Calvo, José

    2015-01-01

    Several clinical trials on Goal directed fluid therapy (GDFT) were carried out, many of those using colloids in order to optimize the preload. After the decision of European Medicines Agency, there is such controversy regarding its use, benefits, and possible contribution to renal failure. The objective of this systematic review and meta-analysis is to compare the use of last-generation colloids, derived from corn, with crystalloids in GDFT to determine associated complications and mortality. A bibliographic research was carried out in MEDLINE PubMed, EMBASE and Cochrane Library, corroborating randomized clinical trials where crystalloids are compared to colloids in GDFT for major non-cardiac surgery in adults. One hundred thirty references were found and among those 38 were selected and 29 analyzed; of these, six were included for systematic review and meta-analysis, including 390 patients. It was observed that the use of colloids is not associated with the increase of complications, but rather with a tendency to a higher mortality (RR [95% CI] 3.87 [1.121-13.38]; I(2)=0.0%; p=0.635). Because of the limitations of this meta-analysis due to the small number of randomized clinical trials and patients included, the results should be taken cautiously, and the performance of new randomized clinical trials is proposed, with enough statistical power, comparing balanced and unbalanced colloids to balanced and unbalanced crystalloids, following the protocols of GDFT, considering current guidelines and suggestions made by groups of experts. Copyright © 2014 Sociedade Brasileira de Anestesiologia. Published by Elsevier Editora Ltda. All rights reserved.

  3. Colloids versus crystalloids in objective-guided fluid therapy, systematic review and meta-analysis. Too early or too late to draw conclusions

    Directory of Open Access Journals (Sweden)

    Javier Ripollés

    2015-08-01

    Full Text Available INTRODUCTION: Several clinical trials on Goal directed fluid therapy (GDFT were carried out, many of those using colloids in order to optimize the preload. After the decision of European Medicines Agency, there is such controversy regarding its use, benefits, and possible contribution to renal failure. The objective of this systematic review and meta-analysis is to compare the use of last-generation colloids, derived from corn, with crystalloids in GDFT to determine associated complications and mortality.METHODS: A bibliographic research was carried out in MEDLINE PubMed, EMBASE and Cochrane Library, corroborating randomized clinical trials where crystalloids are compared to colloids in GDFT for major non-cardiac surgery in adults.RESULTS: One hundred thirty references were found and among those 38 were selected and 29 analyzed; of these, six were included for systematic review and meta-analysis, including 390 patients. It was observed that the use of colloids is not associated with the increase of complications, but rather with a tendency to a higher mortality (RR [95% CI] 3.87 [1.121-13.38]; I2 = 0.0%; p = 0.635.CONCLUSIONS: Because of the limitations of this meta-analysis due to the small number of randomized clinical trials and patients included, the results should be taken cautiously, and the performance of new randomized clinical trials is proposed, with enough statistical power, comparing balanced and unbalanced colloids to balanced and unbalanced crystalloids, following the protocols of GDFT, considering current guidelines and suggestions made by groups of experts.

  4. [Colloids versus crystalloids in objective-guided fluid therapy, systematic review and meta-analysis. Too early or too late to draw conclusions].

    Science.gov (United States)

    Ripollés, Javier; Espinosa, Ángel; Casans, Rubén; Tirado, Ana; Abad, Alfredo; Fernández, Cristina; Calvo, José

    2015-01-01

    Several clinical trials on Goal directed fluid therapy (GDFT) were carried out, many of those using colloids in order to optimize the preload. After the decision of European Medicines Agency, there is such controversy regarding its use, benefits, and possible contribution to kidney failure. The objective of this systematic review and meta-analysis is to compare the use of last-generation colloids, derived from corn, with crystalloids, in GDFT, to determine complications and mortality associated associated. A bibliographic research was carried out in Medline, Pubmed, Embase and Cochrane Library, corroborating randomized clinical trials in those crystalloids are compared to colloids in GDFT for mayor non-cardiac surgery in adults. One hundred thirty references were found, among those 38 were selected, and 29 analyzed; of these, 6 were included for systematic review and meta-analysis, including 390 patients. It was perceived that the use of colloids it not associated with the increase of complications, but rather with a tendency to a higher mortality (RR [95% IC] 3.87 [1.121, 13, 38]); I(2)=0.0%; p=0.635). Due to this meta-analysis' limitations for small number of randomized clinical trials and patients included, the results should be taken cautiously, and it is proposed to carry out new randomized clinical trials, with enough statistical power, comparing balanced and non-balanced colloids to balanced and non-balanced crystalloids, following the protocols of GDFT, respecting current guidelines and suggestions made by groups of experts. Copyright © 2014 Sociedade Brasileira de Anestesiologia. Publicado por Elsevier Editora Ltda. All rights reserved.

  5. An experimental and numerical investigation of flat panel display cell using magnetic fluid

    CERN Document Server

    Seo, J W; Park, S J; Lee, H S

    2002-01-01

    Optical and fluid dynamical properties of magnetic fluid have been studied experimentally and numerically using a test device with a water-base magnetite magnetic fluid. It has been found that the 3.5 mu m thick fluid film absorbs most of the incoming visible light and can be actuated fast enough to realize display devices. The computational simulation shows that the surface tension of the liquid plays the most dominant roles for the test device, and a device that can actuate the magnetic fluid magnetically is proposed.

  6. Influence of electric field upon the formation of particles cluster in magnetic fluid

    Energy Technology Data Exchange (ETDEWEB)

    Yerin, C.V. [Stavropol State University, 1 Pushkin st., Stavropol 355009 (Russian Federation)]. E-mail: exiton@inbox.ru; Padalka, V.V. [Stavropol State University, 1 Pushkin st., Stavropol 355009 (Russian Federation)

    2005-03-15

    Aggregation process in magnetic fluid has been investigated by optical methods. Phase exfoliation in magnetic fluid and large aggregate formation in an electric field have been found. The size of aggregates has been measured by the dynamic light scattering method. After switching off the electric field 'mist' formation and sharp turbidity of fluids have been found.

  7. Nonlocal vibration of Y-shaped CNT conveying nano-magnetic viscous fluid under magnetic field

    Directory of Open Access Journals (Sweden)

    A. Ghorbanpour Arani

    2015-06-01

    Full Text Available This study deals with the vibration and stability analysis of a Y-shaped single-walled carbon nanotube (SWCNT embedded in visco-Pasternak foundation and conveying nano-magnetic viscous fluid (NMF based on nonlocal elasticity theory and Euler–Bernoulli beam model. The fluid is two-phases due to the existence of magnetic nanoparticles which its volume fraction is much little in comparison with the base fluid where the influence of 2D magnetic field is taken into account. Also, Knudsen number is used to correct the velocity profile of fluid. The Galerkin method is applied to solve the equation of motion which is obtained by employing Hamilton’s principle. The detail parametric study is conducted, focusing on the combined effects of carbon nanotube and Y-shaped junction fitted at the downstream end, fluid velocity, Knudsen number and elastic medium. The results indicate that increasing the angle between centerline of the CNT and the downstream elbows decreases stability of system.

  8. Magnetic resonance of field-frozen and zero-field-frozen magnetic fluids

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, A.R. E-mail: anarita@fis.ufg.br; Pelegrini, F.; Neto, K. Skeff; Buske, N.; Morais, P.C. E-mail: pcmor@unb.br

    2004-05-01

    In this study magnetic resonance was used to investigate magnetic fluid samples frozen under zero and non-zero (15 kG) external fields. The magnetite-based sample containing 2x10{sup 17} particle/cm{sup 3} was investigated from 100 to 400 K. Analysis of the temperature dependence of the resonance field revealed bigger magnetic structures in the frozen state than in the liquid phase. Also, differences in the mesoscopic organization in the frozen state may explain the data obtained from samples frozen under zero and non-zero fields.

  9. Position feedback control of a nonmagnetic body levitated in magnetic fluid

    Energy Technology Data Exchange (ETDEWEB)

    Lee, J H; Nam, Y J; Park, M K [Graduate School, Pusan National University, Busan 609-735 (Korea, Republic of); Yamane, R [Kokushikan University, Tokyo 154-8515 (Japan)], E-mail: magooro@pusan.ac.kr

    2009-02-01

    This paper is concerned with the position feedback control of a magnetic fluid actuator which is characterized by the passive levitation of a nonmagnetic body immersed in a magnetic fluid under magnetic fields. First of all, the magnetic fluid actuator is designed based on the ferrohydrostatic relation. After manufacturing the actuator, its static and dynamic characteristics are investigated experimentally. With the aid of the dynamic governing relation obtained experimentally and the proportional-derivative controller, the position tracking control of the actuator is carried out both theoretically and experimentally. As a result, the applicability of the proposed magnetic fluid actuator to various engineering devices is verified.

  10. Magnetoviscous effect of ferrite-based magnetic fluid for EOR application

    Science.gov (United States)

    Latiff, Noor Rasyada Ahmad; Soleimani, Hassan; Zaid, Hasnah Mohd; Adil, Muhammad

    2016-11-01

    Magnetic fluid is proposed as a substitute for the application of polymer solution as a means to recover the residual oil left in the bypassed region in oil reservoirs. When subjected to magnetic field, the viscosity of magnetic fluids increases and enable flow control. In this study, the response of magnetic nanofluid with the applied magnetic field was observed as a function of shear rate. Two types of samples, namely magnetite and cobalt ferrite of 0.1% w/v of different polydispersity index, saturation magnetization and mean hydrodynamic particle size were used. The strength of the applied magnetic field was also varied to investigate the effect of magnetic field strength on the viscosity enhancement of magnetic fluid. Shear dependence response of the magnetic fluid exhibit non-Newtonian behavior when magnetic field of 20 to 40 mT was applied. Viscosity of the magnetic fluid reduced with increasing shear rates, showing shear thinning behavior. At a particular shear rate, viscosity remains constant when the strength of magnetic field increases indicating saturation in chain length even at low field. Magnetoviscous effect (MVE) is calculated as an indicator for a viscosity gain magnitude when magnetic field is applied. Cobalt ferrite sample shows larger MVE compared to magnetite that may be attributed to the higher polydispersity index. In conclusion, particle size distribution is the most dominant factor affecting MVE of the dilute magnetic fluid when magnetic field is applied.

  11. A thermo-fluid analysis in magnetic hyperthermia

    Science.gov (United States)

    Iordana, Astefanoaei; Ioan, Dumitru; Alexandra, Stancu; Horia, Chiriac

    2014-04-01

    In the last years, hyperthermia induced by the heating of magnetic nanoparticles (MNPs) in an alternating magnetic field received considerable attention in cancer therapy. The thermal effects could be automatically controlled by using MNPs with selective magnetic absorption properties. In this paper, we analyze the temperature field determined by the heating of MNPs, injected in a malignant tissue, subjected to an alternating magnetic field. The main parameters which have a strong influence on temperature field are analyzed. The temperature evolution within healthy and tumor tissues are analyzed by finite element method (FEM) simulations in a thermo-fluid model. The cooling effect produced by blood flow in blood vessels from the tumor is considered. A thermal analysis is conducted under different distributions of MNP injection sites. The interdependence between the optimum dose of the nanoparticles and various types of tumors is investigated in order to understand their thermal effect on hyperthermia therapy. The control of the temperature field in the tumor and healthy tissues is an important step in the healing treatment.

  12. Measurement of the zero-field magnetic dipole moment of magnetizable colloidal silica spheres

    NARCIS (Netherlands)

    Claesson, E.M.; Erne, B.H.; Bakelaar, I.A.; Kuipers, B.W.M.; Philipse, A.P.

    2007-01-01

    The magnetic properties of dispersions of magnetic silica microspheres have been investigated by measuring the magnetization curves and the complex magnetic susceptibility as a function of frequency and field amplitude. The silica spheres appear to have a net permanent magnetic dipole moment, even i

  13. Synthesis of Fe{sub 3}O{sub 4} magnetic fluid used for magnetic resonance imaging and hyperthermia

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Y.M.; Cao, X. [College of Chemistry, Chemical Engineering and Materials Science, Key Laboratory of Organic Synthesis of Jiangsu Province, Soochow University, SIP, Suzhou 215123 (China); Liu, G.H. [Resparation Department, the Affiliated Suzhou Municipal Hospital(East-section) of Nanjing Medical University, Suzhou 215001 (China); Hong, R.Y., E-mail: rhong@suda.edu.cn [College of Chemistry, Chemical Engineering and Materials Science, Key Laboratory of Organic Synthesis of Jiangsu Province, Soochow University, SIP, Suzhou 215123 (China); State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100080 (China); Chen, Y.M. [Resparation Department, the Affiliated Suzhou Municipal Hospital(East-section) of Nanjing Medical University, Suzhou 215001 (China); Chen, X.F. [College of Chemistry, Chemical Engineering and Materials Science, Key Laboratory of Organic Synthesis of Jiangsu Province, Soochow University, SIP, Suzhou 215123 (China); Chemical Engineering Department, Chien-shiung Institute of Technology, Suzhou 215411 (China); Li, H.Z. [State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100080 (China); Xu, B. [Suzhou Nanotec Inc., Suzhou 215123 (China); Wei, D.G., E-mail: dougwei@deas.harvard.edu [Center for Nanoscale Systems, School of Engineering and Applied Sciences, Harvard University, 11 Oxford Street, Cambridge, MA 02139 (United States)

    2011-12-15

    Fe{sub 3}O{sub 4} magnetic nanoparticles were prepared by co-precipitation from FeSO{sub 4}.7H{sub 2}O and FeCl{sub 3}.6H{sub 2}O aqueous solutions using NaOH as precipitating reagent. The nanoparticles have an average size of 12 nm and exhibit superparamagnetism at room temperature. The nanoparticles were used to prepare a water-based magnetic fluid using oleic acid and Tween 80 as surfactants. The stability and magnetic properties of the magnetic fluid were characterized by Gouy magnetic balance. The experimental results imply that the hydrophilic block of Tween 80 can make the Fe{sub 3}O{sub 4} nanoparticles suspending in water stable even after dilution and autoclaving. The magnetic fluid demonstrates excellent stability and fast magneto-temperature response, which can be used both in magnetic resonance imaging and magnetic fluid hyperthermia. - Highlights: > Fe{sub 3}O{sub 4} magnetic fluid (MF) was prepared by co-precipitation without protection gas and using NaOH as co-precipitation agent. > Tween 80 was employed as the second layer surfactant. > Hydrophilic ends of Tween 80 were exposed outside making the Fe{sub 3}O{sub 4} MNPs suspending in water stably. > Prepared MF can be used both in magnetic resonance imaging (MRI) and magnetic fluid hyperthermia (MFH).

  14. The Magnetic Nanoparticle Movement in Magnetic Fluid Characterized by the Laser Dynamic Speckle Interferometry

    Directory of Open Access Journals (Sweden)

    Xijun Wang

    2014-01-01

    Full Text Available A dual scanning laser speckle interferometry experiment was designed to observe the dynamic behavior of the magnetic fluid actuated by a magnetic field. In order to improve the spatial resolution of the dynamic speckle measurement, the phase delay scanning was used to compensate the additional phase variation which was caused by the transverse scanning. The correlation coefficients corresponding to the temporal dynamic speckle patterns within the same time interval scattering from the nanoparticles were calculated in the experiment on nanoscale magnetic clusters. In the experiment, the speckle of the magnetic nanoparticle fluid movement has been recorded by the lens unmounted CCD within the interferometry strips, although the speckle led to the distinguished annihilation of the light coherence. The results have showed that the nanoparticle fluid dynamic properties appeared synergistically in the fringe speckles. The analyses of the nanoparticle's relative speed and the speckle pattern moving amount in the fringes have proved the nanoparticle’s movement in a laminar flow in the experiment.

  15. Measurement of interaction force between small distances sandwiched with magnetic fluid under magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Miyazaki, T.; Shibayama, A.; Sato, T.; Fujita, T. E-mail: fujita@ipc.akita-u.ac.jp

    2002-11-01

    In this contribution, the interactive force measurement between 10 nm distance under magnetic field is carried out. Previous measurement of the interactive force is reported by Israelachivili et al. However, its measurement under magnetic field has not been performed. The methodology described in this paper is easier as the distance between two surfaces is not measured optically but dynamically. Therefore, it is different from the previous reported studies. Based on the results of the measurement of the interactive force, the diameter of the particle suspended in a solution under magnetic field is also estimated. Moreover, it may be predictable how the clusters have been formed. The method described will be very useful for new productions based on magnetic fluid.

  16. Chiral magnetic wave in an expanding QCD fluid

    Science.gov (United States)

    Taghavi, Seyed Farid; Wiedemann, Urs Achim

    2015-02-01

    As a consequence of the chiral anomaly, the hydrodynamics of hot quantum chromodynamics (QCD) matter coupled to quantum electrodynamics allows for a long-wavelength mode of chiral charge density, the chiral magnetic wave (CMW), that provides for a mechanism of electric charge separation along the direction of an external magnetic field. Here, we investigate the efficiency of this mechanism for values of the time-dependent magnetic field and of the energy density attained in the hot QCD matter of ultrarelativistic heavy-ion collisions. To this end, we derive the CMW equations of motion for expanding systems by treating the CMW as a charge perturbation on top of an expanding Bjorken-type background field in the limit μ /T ≪1 . Both, approximate analytical and full numerical solutions to these equations of motion, indicate that for the lifetime and thermodynamic conditions of ultrarelativistic heavy-ion collisions, the efficiency of CMW-induced electric charge separation decreases with increasing center-of-mass energy and that the effect is numerically very small. We note, however, that if sizable oriented asymmetries in the axial charge distribution (that are not induced by the CMW) are present in the early fluid dynamic evolution, then the mechanism of CMW-induced electric charge separation can be much more efficient.

  17. Enhancing cancer therapeutics using size-optimized magnetic fluid hyperthermia.

    Science.gov (United States)

    Khandhar, Amit P; Ferguson, R Matthew; Simon, Julian A; Krishnan, Kannan M

    2012-04-01

    Magnetic fluid hyperthermia (MFH) employs heat dissipation from magnetic nanoparticles to elicit a therapeutic outcome in tumor sites, which results in either cell death (>42 °C) or damage (<42 °C) depending on the localized rise in temperature. We investigated the therapeutic effect of MFH in immortalized T lymphocyte (Jurkat) cells using monodisperse magnetite (Fe(3)O(4)) nanoparticles (MNPs) synthesized in organic solvents and subsequently transferred to aqueous phase using a biocompatible amphiphilic polymer. Monodisperse MNPs, ∼16 nm diameter, show maximum heating efficiency, or specific loss power (watts/g Fe(3)O(4)) in a 373 kHz alternating magnetic field. Our in vitro results, for 15 min of heating, show that only 40% of cells survive for a relatively low dose (490 μg Fe/ml) of these size-optimized MNPs, compared to 80% and 90% survival fraction for 12 and 13 nm MNPs at 600 μg Fe/ml. The significant decrease in cell viability due to MNP-induced hyperthermia from only size-optimized nanoparticles demonstrates the central idea of tailoring size for a specific frequency in order to intrinsically improve the therapeutic potency of MFH by optimizing both dose and time of application.

  18. Preclinical dosimetry of magnetic fluid hyperthermia for bladder cancer

    Science.gov (United States)

    Oliveira, Tiago R.; Stauffer, Paul R.; Lee, Chen-Ting; Landon, Chelsea; Etienne, Wiguins; Maccarini, Paolo F.; Inman, Brant; Dewhirst, Mark W.

    2013-02-01

    Background Despite positive efficacy, thermotherapy is not widely used in clinical oncology. Difficulties associated with field penetration and controlling power deposition patterns in heterogeneous tissue have limited its use for heating deep in the body. Heat generation using iron-oxide super-paramagnetic nanoparticles excited with magnetic fields has been demonstrated to overcome some of these limitations. The objective of this preclinical study is to investigate the feasibility of treating bladder cancer with magnetic fluid hyperthermia (MFH) by analyzing the thermal dosimetry of nanoparticle heating in a rat bladder model. Methods The bladders of 25 female rats were injected with 0.4 ml of Actium Biosystems magnetite-based nanoparticles (Actium Biosystems, Boulder CO) via catheters inserted in the urethra. To assess the distribution of nanoparticles in the rat after injection we used the 7 T small animal MRI system (Bruker ClinScan, Bruker BioSpin MRI GmbH, Ettlingen, Germany). Heat treatments were performed with a small animal magnetic field applicator (Actium Biosystems, Boulder CO) with a goal of raising bladder temperature to 42°C in 1°C/min to a steady-state of 42°C. Conclusion Our data demonstrate that a MFH system provides well-localized heating of rat bladder with effective control of temperature in the bladder and minimal heating of surrounding tissues.

  19. Analysis of the distribution of magnetic fluid inside tumors by a giant magnetoresistance probe

    KAUST Repository

    Gooneratne, Chinthaka P.

    2013-11-29

    Magnetic fluid hyperthermia (MFH) therapy uses the magnetic component of electromagnetic fields in the radiofrequency spectrum to couple energy to magnetic nanoparticles inside tumors. In MFH therapy, magnetic fluid is injected into tumors and an alternating current (AC) magnetic flux is applied to heat the magnetic fluid- filled tumor. If the temperature can be maintained at the therapeutic threshold of 42C for 30 minutes or more, the tumor cells can be destroyed. Analyzing the distribution of the magnetic fluid injected into tumors prior to the heating step in MFH therapy is an essential criterion for homogenous heating of tumors, since a decision can then be taken on the strength and localization of the applied external AC magnetic flux density needed to destroy the tumor without affecting healthy cells. This paper proposes a methodology for analyzing the distribution of magnetic fluid in a tumor by a specifically designed giant magnetoresistance (GMR) probe prior to MFH heat treatment. Experimental results analyzing the distribution of magnetic fluid suggest that different magnetic fluid weight densities could be estimated inside a single tumor by the GMR probe. 2013 Gooneratne et al.

  20. Analysis of the distribution of magnetic fluid inside tumors by a giant magnetoresistance probe.

    Directory of Open Access Journals (Sweden)

    Chinthaka P Gooneratne

    Full Text Available Magnetic fluid hyperthermia (MFH therapy uses the magnetic component of electromagnetic fields in the radiofrequency spectrum to couple energy to magnetic nanoparticles inside tumors. In MFH therapy, magnetic fluid is injected into tumors and an alternating current (AC magnetic flux is applied to heat the magnetic fluid- filled tumor. If the temperature can be maintained at the therapeutic threshold of 42 °C for 30 minutes or more, the tumor cells can be destroyed. Analyzing the distribution of the magnetic fluid injected into tumors prior to the heating step in MFH therapy is an essential criterion for homogenous heating of tumors, since a decision can then be taken on the strength and localization of the applied external AC magnetic flux density needed to destroy the tumor without affecting healthy cells. This paper proposes a methodology for analyzing the distribution of magnetic fluid in a tumor by a specifically designed giant magnetoresistance (GMR probe prior to MFH heat treatment. Experimental results analyzing the distribution of magnetic fluid suggest that different magnetic fluid weight densities could be estimated inside a single tumor by the GMR probe.

  1. The mechanical response in a fluid of synthetic antiferromagnetic and ferrimagnetic microdiscs with perpendicular magnetic anisotropy

    Science.gov (United States)

    Vemulkar, T.; Welbourne, E. N.; Petit, D. C. M. C.; Cowburn, R. P.

    2017-01-01

    In this article, we demonstrate the magneto-mechanic behavior in a fluid environment of perpendicularly magnetized microdiscs with antiferromagnetic interlayer coupling. When suspended in a fluid and under the influence of a simple uniaxial applied magnetic field sequence, the microdiscs mechanically rotate to access the magnetic saturation processes that are either that of the easy axis, hard axis, or in-between the two, in order to lower their energy. Further, these transitions enable the magnetic particles to form reconfigurable magnetic chains, and transduce torque from uniaxial applied fields. These microdiscs offer an attractive platform for the fabrication of fluid based micro- and nanodevices, and dynamically self assembled complex architectures. PMID:28190886

  2. The mechanical response in a fluid of synthetic antiferromagnetic and ferrimagnetic microdiscs with perpendicular magnetic anisotropy

    Science.gov (United States)

    Vemulkar, T.; Welbourne, E. N.; Mansell, R.; Petit, D. C. M. C.; Cowburn, R. P.

    2017-01-01

    In this article, we demonstrate the magneto-mechanic behavior in a fluid environment of perpendicularly magnetized microdiscs with antiferromagnetic interlayer coupling. When suspended in a fluid and under the influence of a simple uniaxial applied magnetic field sequence, the microdiscs mechanically rotate to access the magnetic saturation processes that are either that of the easy axis, hard axis, or in-between the two, in order to lower their energy. Further, these transitions enable the magnetic particles to form reconfigurable magnetic chains, and transduce torque from uniaxial applied fields. These microdiscs offer an attractive platform for the fabrication of fluid based micro- and nanodevices, and dynamically self assembled complex architectures.

  3. Effects of magnetic-fluid flow on structural instability of a carbon nanotube conveying nanoflow under a longitudinal magnetic field

    Science.gov (United States)

    Sadeghi-Goughari, Moslem; Jeon, Soo; Kwon, Hyock-Ju

    2017-09-01

    In drug delivery systems, carbon nanotubes (CNTs) can be used to deliver anticancer drugs into target site to kill metastatic cancer cells under the magnetic field guidance. Deep understanding of dynamic behavior of CNTs in drug delivery systems may enable more efficient use of the drugs while reducing systemic side effects. In this paper, we study the effect of magnetic-fluid flow on the structural instability of a CNT conveying nanoflow under a longitudinal magnetic field. The Navier-Stokes equation of magnetic-fluid flow is coupled with Euler-Bernoulli beam theory for modeling fluid structure interaction (FSI). Size effects of the magnetic fluid and the CNT are addressed through small-scale parameters including the Knudsen number (Kn) and the nonlocal parameter. Results show the positive role of magnetic properties of fluid flow on the structural stability of CNT. Specifically, magnetic force applied to the fluid flow has an effect of decreasing the structural stiffness of system while increasing the critical flow velocity. Furthermore, we discover that the nanoscale effects of CNT and fluid flow tend to amplify the influence of magnetic field on the vibrational behavior of the system.

  4. Regulating wave front dynamics from the strongly discrete to the continuum limit in magnetically driven colloidal systems.

    Science.gov (United States)

    Martinez-Pedrero, Fernando; Tierno, Pietro; Johansen, Tom H; Straube, Arthur V

    2016-02-03

    The emergence of wave fronts in dissipative driven systems is a fascinating phenomenon which can be found in a broad range of physical and biological disciplines. Here we report the direct experimental observation of discrete fronts propagating along chains of paramagnetic colloidal particles, the latter propelled above a traveling wave potential generated by a structured magnetic substrate. We develop a rigorously reduced theoretical framework and describe the dynamics of the system in terms of a generalized one-dimensional dissipative Frenkel-Kontorova model. The front dynamics is explored in a wide range of field parameters close to and far from depinning, where the discrete and continuum limits apply. We show how symmetry breaking and finite size of chains are used to control the direction of front propagation, a universal feature relevant to different systems and important for real applications.

  5. Propagation of electro-kinetic waves in magnetized GaN semiconductor with nano-sized ion colloids

    Energy Technology Data Exchange (ETDEWEB)

    Saxena, Ajay [Government College, Garoth, Dist. Mandsaur (M P) (India); Sharma, Giriraj, E-mail: grsharma@gmail.com [SRJ Government Girls’ College, Neemuch (M P) (India); Jat, K. L. [Swami Vivekanand Government P G College, Neemuch (M P) (India); Rishi, M. P. [Shahid Bhagat Singh Government P G College, Jaora, Dist Ratlam (M P) (India)

    2015-07-31

    Based on hydrodynamic model of multi-component plasma, an analytical study on propagation of longitudinal electro-kinetic (LEK) waves in wurtzite and zincblende structures of GaN is carried out. Nano-sized ion colloids (NICs) are embedded in the sample by the technique of ion-implantation. The implanted NICs are considered massive by an order as compared to the host lattice points and do not participate in Based LEK perturbations. Though, the NICs are continuously bombarded by the electrons as well as the holes yet, the former acquires a net negative charge owing to relatively higher mobility of electrons and consequently results into depletion of electron density in the medium. It i s found that the presence of charged NICs significantly modifies the dispersion and amplification characteristics of LEK waves in magnetized GaN semiconductor plasma and their role becomes increasingly effective as the fraction of charge on them increases.

  6. Incrusting structure of nanosized Fe3O4 particles in magnetic fluids

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Jinsheng(张金升); YIN; Yansheng; (尹衍升); Lü; Yinong; (吕忆农); ZHANG; Yinyan; (张银燕); MA; Laipeng; (马来鹏); ZHANG; Shuqing; (张淑卿)

    2003-01-01

    High-performance nanosized Fe3O4 magnetic fluids are prepared by chemical co-pre- cipitate method. The microstructure of magnetic fluids is characterized using a transmission electron microscope (TEM) and high-resolution electron microscope (HREM). The results are satisfactory. The nanosized magnetic particles have diameter of 8-10 nm and the minimum diameter is 4 nm, belonging to super-paramagnetic material. The nanosized magnetic particles crystallized completely and have clear crystal boundary. The surfactant used in the test coats the magnetic particles homogeneously and forms a uniform and complete elastic spherical shell of amorphous phase around the magnetic particles. The study proves that the incrusting layer of surfactant has the protective effect and stable effect on the magnetic particles. These effects can enhance and maintain the magnetic properties of the magnetic fluids effectively.

  7. A Photonic Crystal Magnetic Field Sensor Using a Shoulder-Coupled Resonant Cavity Infiltrated with Magnetic Fluid.

    Science.gov (United States)

    Su, Delong; Pu, Shengli; Mao, Lianmin; Wang, Zhaofang; Qian, Kai

    2016-12-16

    A kind of photonic crystal magnetic field sensor is proposed and investigated numerically. The shoulder-coupled resonant cavity is introduced in the photonic crystal, which is infiltrated with magnetic fluid. Through monitoring the shift of resonant wavelength, the magnetic field sensing is realized. According to the designed infiltration schemes, both the magnetic field sensitivity and full width at half maximum increase with the number of infiltrated air holes. The figure of merit of the structure is defined to evaluate the sensing performance comprehensively. The best structure corresponding to the optimal infiltration scheme with eight air holes infiltrated with magnetic fluid is obtained.

  8. Dynamics of cluster formation in driven magnetic colloids dispersed on a monolayer.

    Science.gov (United States)

    Jäger, Sebastian; Stark, Holger; Klapp, Sabine H L

    2013-05-15

    We report computer simulation results on the cluster formation of dipolar colloidal particles driven by a rotating external field in a quasi-two-dimensional setup. We focus on the interplay between permanent dipolar and hydrodynamic interactions and its influence on the dynamic behavior of the particles. This includes their individual as well as their collective motion. To investigate these characteristics, we employ Brownian dynamics simulations of a finite system with and without hydrodynamic interactions. Our results indicate that hydrodynamic interactions have a profound impact on the dynamic behavior of the clusters and the dynamics of the clustering process.

  9. Preparation of magnetite aqueous dispersion for magnetic fluid hyperthermia

    Energy Technology Data Exchange (ETDEWEB)

    Kikuchi, Teppei; Kasuya, Ryo [Graduate School of Environmental Studies, Tohoku University, 6-6-20, Aramaki, Aoba, Aoba-ku, Sendai 980-8579 (Japan); Endo, Shota; Nakamura, Akira; Takai, Toshiyuki [Institute of Development, Aging and Cancer, Tohoku University, 4-1 Seiryo-cho, Aramaki-Aoba, Aoba-ku, Sendai 980-8575 (Japan); Metzler-Nolte, Nils [Faculty of Chemistry and Biochemistry, Ruhr-University Bochum, Universitaetstrasse 150, D-44801 Bochum (Germany); Tohji, Kazuyuki [Graduate School of Environmental Studies, Tohoku University, 6-6-20, Aramaki, Aoba, Aoba-ku, Sendai 980-8579 (Japan); Balachandran, Jeyadevan, E-mail: jeyadevan.b@mat.usp.ac.j [Department of Material Science, School of Engineering, University of Shiga Prefecture, 2500, Hassaka-cho, Hikone-City, Shiga 522-8533 (Japan)

    2011-05-15

    An aqueous magnetic suspension was prepared by dispersing amphiphilic co-polymer-coated monodispersed magnetite nanoparticles synthesized through thermal decomposition of iron acetylacetonate (Fe(acac){sub 3}) in a mixture of oleic acid and oleylamine. The average diameter of narrow-size-distributed magnetite nanoparticles varied between 5 and 12 nm depending on the experimental parameters such as reaction temperature, metal salt concentration and oleic acid/oleylamine ratio. Though the as-synthesized particles were coated with oleate and were dispersible in organic solvent, their surfaces were modified using amphiphilic co-polymers composed of poly(maleic anhydride-alt-1-octadecene) and polyethylene glycol-methyl ether and made dispersible in water. Infrared spectra of the sample indicated the existence of -COOH groups on the surface for further conjugation with biomolecules for targeted cancer therapy. - Research Highlights: Preparation of magnetite nanoparticles suitable for in vivo magnetic fluid hyperthermia. Thermal decomposition of Fe(acac){sub 3} in a mixture of oleic acid and oleylamine. Monodispersed magnetite particles with average sizes varying between 5 and 12 nm. Modification of the hydrophobic particle surface with amphiphilic co-polymers. These surface modified particles have carboxyl groups and polyethylene glycol.

  10. Specific heating power of fatty acid and phospholipid stabilized magnetic fluids in an alternating magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Cuyper, M de; Soenen, S J H [Interdisciplinary Research Centre, Katholieke Universiteit Leuven-Campus Kortrijk, B-8500 Kortrijk (Belgium); Hodenius, M; Ivanova, G; Baumann, M; Paciok, E; Schmitz-Rode, T [Applied Medical Engineering, Helmholtz-Institute, Rheinisch-Westfaelische Technische Hochschule Aachen, Pauwelsstrasse 20, D-52074 Aachen (Germany); Eckert, T [Department of Physical Chemistry, RWTH Aachen, Landoltweg 2, D-52074 Aachen (Germany)], E-mail: hodenius@hia.rwth-aachen.de

    2008-05-21

    Magnetic fluids (MFs) with a similar narrow size distribution of the iron oxide core were stabilized with lauric acid (MF 1), oleate (MF 2) or, after dialysis in the presence of liposomes, with phospholipid molecules (MF 3 and MF 4, respectively). The hydrodynamic sizes of the MF 1 and MF 3 were half those found for MF 2 and MF 4. The MFs were exposed to inductive heating in an alternating magnetic field at a frequency of 200 kHz and a maximum magnetic field strength of 3.8 kA m{sup -1}. Specific absorption rates (SAR) of 294 {+-} 42 (MF 1), 214 {+-} 16 (MF 2), 297 {+-} 13 (MF 3) and 213 {+-} 6 W g{sup -1} Fe (MF 4) were obtained. The data for MF 2 and MF 4 were identical to those found for the commercially available ferucarbotran. The biomedical relevance of the phospholipid-coated MFs is briefly discussed.

  11. Specific heating power of fatty acid and phospholipid stabilized magnetic fluids in an alternating magnetic field

    Science.gov (United States)

    DeCuyper, M.; Hodenius, M.; Ivanova, G.; Baumann, M.; Paciok, E.; Eckert, T.; Soenen, S. J. H.; Schmitz-Rode, T.

    2008-05-01

    Magnetic fluids (MFs) with a similar narrow size distribution of the iron oxide core were stabilized with lauric acid (MF 1), oleate (MF 2) or, after dialysis in the presence of liposomes, with phospholipid molecules (MF 3 and MF 4, respectively). The hydrodynamic sizes of the MF 1 and MF 3 were half those found for MF 2 and MF 4. The MFs were exposed to inductive heating in an alternating magnetic field at a frequency of 200 kHz and a maximum magnetic field strength of 3.8 kA m-1. Specific absorption rates (SAR) of 294 ± 42 (MF 1), 214 ± 16 (MF 2), 297 ± 13 (MF 3) and 213 ± 6 W g-1 Fe (MF 4) were obtained. The data for MF 2 and MF 4 were identical to those found for the commercially available ferucarbotran. The biomedical relevance of the phospholipid-coated MFs is briefly discussed.

  12. Nanoparticle kinetic effects experimentally observed in a magnetic fluid under a quasi-homogeneous magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Stelina, J., E-mail: julius.stelina@fel.uniza.sk [Department of Physics, University of Zilina, Univerzitna 1, 010 26 Zilina (Slovakia); Musil, C. [Department of Physics, University of Zilina, Univerzitna 1, 010 26 Zilina (Slovakia)

    2012-05-15

    The effect of a quasi-homogeneous external magnetic field on a created and decaying space nanoparticle structure and its distribution in a sample of a magnetic fluid was studied. This space structure was created as a grating by applying an interference field of two crossed Ar laser beams. The magnetic field was formed using two electromagnets and was applied in three main directions of the created nanoparticle grating. The magnetic field oriented parallel to the strips of the grating or perpendicular to the grating plain does not significantly change the shape of it. The magnetic field oriented in the perpendicular direction to the grating plain causes redistribution of the nanoparticles and as a consequence a perpendicular nanoparticle 'quasi-grating' arises. - Highlights: Black-Right-Pointing-Pointer External magnetic field creates a new nanoparticle quasi-grating. Black-Right-Pointing-Pointer We find that the new grating is perpendicular to the original one. Black-Right-Pointing-Pointer We observe a planar grating in the transitional phase of about 15 s. Black-Right-Pointing-Pointer We speculate that the new grating is related to structuralization of particles.

  13. 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

  14. Ultrasonic velocity and amplitude characterization of magnetorheological fluids under magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-Lopez, J., E-mail: jaimerl@caend.upm-csic.es [Centro de Acustica Aplicada y Ensayos No Destructivos, UPM-CSIC, 28006 Madrid (Spain); Elvira Segura, L.; Montero de Espinosa Freijo, F. [Centro de Acustica Aplicada y Ensayos No Destructivos, UPM-CSIC, 28006 Madrid (Spain)

    2012-01-15

    Variations in velocity of sound and amplitude of the signal of a commercial magnetorheological fluid under different magnetic fields are studied experimentally. Different factors such as orientation, uniformity, geometry and intensity of the magnetic field are investigated. An increase in the change of MR fluid acoustical properties is obtained when the magnetic field intensity is risen. In addition, these properties show an opposite behavior when a magnetic field is applied parallel or perpendicular to the ultrasound propagation. Experiments using an electromagnet and permanent magnets as the source of magnetic field are also compared. Properties such as anisotropy in sound velocity and amplitude make these materials interesting regarding applications. - Highlights: > First sound attenuation measurements as function of the magnetic field in MR fluids. > Sound velocity and attenuation anisotropy due to the microstructure is detected. > Geometry, intensity and uniformity of the magnetic field affect sound propagation.

  15. Design optimization of seal structure for sealing liquid by magnetic fluids

    Science.gov (United States)

    Liu, Tonggang; Cheng, Yusheng; Yang, Zhiyi

    2005-03-01

    The durability of the magnetic fluid seal clearly decreases when sealing another liquid because of the interface instability caused by the applied magnetic field and the velocity difference of the two liquids. With an intention to establish a stable interface during sealing liquid, a new magnetic fluid seal was developed in this paper. The parameters of the structure were optimized by a simulation apparatus. And the magnetic fluid seal designed based on the optimum parameters shows good performance and long life for sealing lubricating oil.

  16. Magnetorheology of hybrid colloids obtained by spin-coating and classical rheometry

    Science.gov (United States)

    Aslam, Raheema; Shahrivar, Keshvad; de Vicente, Juan; González-Viñas, Wenceslao

    2016-07-01

    Hybrid colloids composed of micron-sized ferromagnetic (carbonyl iron) and diamagnetic (silica) particles suspended in cyclohexanone, behave as, non-Newtonian, magnetorheological fluids. We measure and compare the magnetic field-dependent viscosity of hybrid diluted colloids using spin-coating and conventional magnetorheometry. We extend a previously developed model for simple colloids to this kind of hybrid colloids. As in the previous model, the viscosity of the colloidal suspension under applied fields can be derived from the surface coverage of the dry spin-coated deposits for each type of particles, and from the viscosity of the colloid at zero field. Also, our results allow us to obtain the evaporation rate of the solvent as a function of the rotation speed. Finally, we also measure the viscosity of the same suspension with a torsional parallel plate magnetorheometer under uniaxial DC magnetic fields aligned in the velocity gradient direction of a steady shearing flow. The experimental results under different conditions and the effect of each component on the magnetorheological properties of the resulting colloid are discussed. Standard spin-coating technique can be used both to characterize smart materials—complex fluids as well as to fabricate films with arbitrary solvents by tuning their viscosity by means of external fields.

  17. Local hyperthermia for esophageal cancer in a rabbit tumor model: Magnetic stent hyperthermia versus magnetic fluid hyperthermia

    OpenAIRE

    LIU, Jiayi; Li, Ning; Li, Li; LI, DANYE; Liu, Kai; Zhao, Lingyun; TANG, JINTIAN; Li, Liya

    2013-01-01

    Magnetic-mediated hyperthermia (MMH) is a promising local thermotherapy approach for cancer treatment. The present study investigated the feasibility and effectiveness of MMH in esophageal cancer using a rabbit tumor model. The therapeutic effect of two hyperthermia approaches, magnetic stent hyperthermia (MSH), in which heat is induced by the clinical stent that is placed inside the esophagus, and magnetic fluid hyperthermia (MFH), where magnetic nanoparticles are applied as the agent, was s...

  18. Influence of external magnetic field on laser breakdown plasma in aqueous Au nanoparticles colloidal solutions

    CERN Document Server

    Serkov, A A; Simakin, A V; Kuzmin, P G; Mikhailova, G N; Antonova, L Kh; Troitskii, A V; Kuzmin, G P; Shafeev, G A

    2016-01-01

    Influence of permanent magnetic field up to 7.5 T on plasma emission and laser-assisted Au nanoparticles fragmentation in water is experimentally studied. It is found that presence of magnetic field causes the breakdown plasma emission to start earlier regarding to laser pulse. Field presence also accelerates the fragmentation of nanoparticles down to a few nanometers. Dependence of Au NPs fragmentation rate in water on magnetic field intensity is investigated. The results are discussed on the basis of laser-induced plasma interaction with magnetic field.

  19. The effect of magnetic field induced aggregates on ultrasound propagation in aqueous magnetic fluid

    Science.gov (United States)

    Parekh, Kinnari; Upadhyay, R. V.

    2017-06-01

    Ultrasonic wave propagation in the aqueous magnetic fluid is investigated for different particle concentrations. The sound velocity decreases while acoustic impedance increases with increasing concentrations. The velocity anisotropy is observed upon application of magnetic field. The velocity anisotropy fits with Tarapov's theory suggests the presence of aggregates in the system. We report that these aggregates are thermodynamically unstable and the length of aggregate changes continuously with increasing concentration and, or magnetic field and resulted in a decrease in effective magnetic moment. The Taketomi's theory fits well with the experimental data suggesting that the particle clusters are aligned in the direction of the magnetic field. The radius of cluster found to increase with increasing concentration, and then decreases whereas the elastic force constant increases and then becomes constant. The increase in cluster radius indicates elongation of aggregate length due to tip-to-tip interaction of aggregates whereas for higher concentration, the lateral alignment is more favorable than tip-to-tip alignment of aggregates which reduces the cluster radius making elastic force constant to raise. Optical images show that the chains are fluctuating and confirming the lateral alignment of chains at higher fields.

  20. Electron microscopy observations of surface morphologies and particle arrangement behaviors of magnetic fluids

    Institute of Scientific and Technical Information of China (English)

    沈辉; 徐雪青; 王伟

    2003-01-01

    The surface morphology of quasi-periodic stripe-shaped patterns of magnetite fluids was observed in applied perpendicular magnetic fields by means of scanning electron microscopy. The nanoparticles of the magnetite fluids are arranged in oriental quasilinear chains in applied perpendicular magnetic fields as observed using transmission electron microscopy. This arrangement results from particle-particle interactions and particle-carrier liquids interactions, which are eventually controlled by the magnetic fields distribution.

  1. The Effect Of A Magnetic Field Dependent Viscosity On The Thermal Convection In A Ferromagnetic Fluid In A Porous Medium

    National Research Council Canada - National Science Library

    Sunil; Pavan Kumar Bharti; Divya Sharma; R. C. Sharma

    2004-01-01

    The effect of the magnetic field dependent (MFD) viscosity on the thermal convection in a ferromagnetic fluid in the presence of a uniform vertical magnetic field is considered for a fluid layer in a porous medium, heated from below...

  2. Separation of Microcystin-LR by Cyclodextrin-Functionalized Magnetic Composite of Colloidal Graphene and Porous Silica.

    Science.gov (United States)

    Sinha, Arjyabaran; Jana, Nikhil R

    2015-05-13

    Microcystin-LR belongs to the family of microcystins produced by cyanobacteria and known to be the most toxic of this family. Existence of cyanobacteria in water bodies leads to the contamination of drinking water with microcystin-LR and thus their separation is essential for an advanced water purification system. Here we report functional nanocomposite-based selective separation of microcystin-LR from contaminated water. We have synthesized cyclodextrin-functionalized magnetic composite of colloidal graphene and porous silica where the cyclodextrin component offers host-guest interaction with microcystin-LR and the magnetic component offers easier separation of microcystin-LR from water. High surface area and large extent of chemical functional groups offer high loading (up to 18 wt %) of cyclodextrin with these nanocomposites, and the dispersible form of the nanocomposite offers easier accessibility of cyclodextrin to microcystin-LR. We have shown that microcystin-LR separation efficiency is significantly enhanced after functionalization with cyclodextrin, and among all the tested cyclodextrins, γ-cyclodextrin offers the best performance. We have also found that graphene-based nanocomposite offers better performance over porous silica-based nanocomposite due to better accessibility of cyclodextrins for interaction with microcystin-LR. The proposed graphene-based functional nanocomposite is environment friendly, reusable, and applicable for advanced water purification.

  3. Preliminary analysis of the MER magnetic properties experiment using a computational fluid dynamics model

    DEFF Research Database (Denmark)

    Kinch, K.M.; Merrison, J.P.; Gunnlaugsson, H.P.;

    2006-01-01

    Motivated by questions raised by the magnetic properties experiments on the NASA Mars Pathfinder and Mars Exploration Rover (MER) missions, we have studied in detail the capture of airborne magnetic dust by permanent magnets using a computational fluid dynamics (CFD) model supported by laboratory...

  4. Synthesis of crystallographically oriented olivine aggregates using colloidal processing in a strong magnetic field

    Science.gov (United States)

    Koizumi, Sanae; Suzuki, Tohru S.; Sakka, Yoshio; Yabe, Kosuke; Hiraga, Takehiko

    2016-11-01

    This study develops a fabrication technique to obtain Fe-free and Fe-bearing (Fe:Mg = 1:9) olivine aggregates not only with high density and fine grain size but with crystallographic preferred orientation (CPO). A magnetic field (≤12 T) is applied to synthetic, fine-grained ( 120 nm), olivine particles dispersed in solvent. The alignment of certain crystallographic axes of the particles with respect to a magnetic direction is anticipated due to magnetic anisotropy of olivine. The dispersed particles are gradually consolidated on a porous alumina mold covered with a solid-liquid separation filter during drainage of the solvent. The resultant aligned consolidated aggregate is then isostatically pressed and vacuum sintered. We find that (1) preparation of fully reacted olivine particles, with less propensity to coalesce; (2) preparation of a suspension with highly dispersed particles; and (3) application of a certain strength of the magnetic field are essential to obtain well-sintered and well-aligned aggregates. High density (i.e., olivine aggregates were successfully synthesized with uniaxially aligned a- and c-axes, respectively. Attempts to uniaxially align the magnetization hard axis and to triaxially align Fe-bearing olivine by rotating the suspension in the magnetic field succeeded in obtaining weakly developed CPO aggregates.

  5. Convective stability of a vertical layer of magnetizable fluid in a uniform magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Bashtovoy, V.G.; Pavlinov, M.I.

    1978-01-01

    An infinitely large plane vertical layer of magnetizable fluid is considered, this layer being heated from below and bounded on both lateral surfaces by ferromagnetic half-spaces. The fluid and the ferromagnetic material on both sides have the same pyromagnetic coefficient. The possibility of overcoming a convective instability of such a fluid layer in a uniform magnetic field is demonstrated by a solution of the equilibrium equation. The result indicates that such a magnetic field raises the stability threshold to full stabilization of the fluid layer, with the instability range in terms of the Rayleigh number now having both a lower and an upper limit. 3 references.

  6. Theory of nonlinear elasticity, stress-induced relaxation, and dynamic yielding in dense fluids of hard nonspherical colloids.

    Science.gov (United States)

    Zhang, Rui; Schweizer, Kenneth S

    2012-04-21

    We generalize the microscopic naïve mode coupling and nonlinear Langevin equation theories of the coupled translation-rotation dynamics of dense suspensions of uniaxial colloids to treat the effect of applied stress on shear elasticity, cooperative cage escape, structural relaxation, and dynamic and static yielding. The key concept is a stress-dependent dynamic free energy surface that quantifies the center-of-mass force and torque on a moving colloid. The consequences of variable particle aspect ratio and volume fraction, and the role of plastic versus double glasses, are established in the context of dense, glass-forming suspensions of hard-core dicolloids. For low aspect ratios, the theory provides a microscopic basis for the recently observed phenomenon of double yielding as a consequence of stress-driven sequential unlocking of caging constraints via reduction of the distinct entropic barriers associated with the rotational and translational degrees of freedom. The existence, and breadth in volume fraction, of the double yielding phenomena is predicted to generally depend on both the degree of particle anisotropy and experimental probing frequency, and as a consequence typically occurs only over a window of (high) volume fractions where there is strong decoupling of rotational and translational activated relaxation. At high enough concentrations, a return to single yielding is predicted. For large aspect ratio dicolloids, rotation and translation are always strongly coupled in the activated barrier hopping event, and hence for all stresses only a single yielding process is predicted.

  7. Absorption and Magnetic Circular Dichroism Analyses of Giant Zeeman Splittings in Diffusion-Doped Colloidal Cd(1-x)Mn(x)Se Quantum Dots.

    Science.gov (United States)

    Barrows, Charles J; Vlaskin, Vladimir A; Gamelin, Daniel R

    2015-08-06

    Impurity ions can transform the electronic, magnetic, or optical properties of colloidal quantum dots. Magnetic impurities introduce strong dopant-carrier exchange coupling that generates giant Zeeman splittings (ΔEZ) of excitonic excited states. To date, ΔEZ in colloidal doped quantum dots has primarily been quantified by analysis of magnetic circular dichroism (MCD) intensities and absorption line widths (σ). Here, we report ΔEZ values detected directly by absorption spectroscopy for the first time in such materials, using colloidal Cd(1-x)Mn(x)Se quantum dots prepared by diffusion doping. A convenient method for decomposing MCD and absorption data into circularly polarized absorption spectra is presented. These data confirm the widely applied MCD analysis in the low-field, high-temperature regime, but also reveal a breakdown at low temperatures and high fields when ΔEZ/σ approaches unity, a situation not previously encountered in doped quantum dots. This breakdown is apparent for the first time here because of the extraordinarily large ΔEZ and small σ achieved by nanocrystal diffusion doping.

  8. Thermal and magnetic properties of iron oxide colloids: influence of surfactants

    Science.gov (United States)

    Soares, Paula I. P.; Lochte, Frederik; Echeverria, Coro; Pereira, Laura C. J.; Coutinho, Joana T.; Ferreira, Isabel M. M.; Novo, Carlos M. M.; Borges, João P. M. R.

    2015-10-01

    Iron oxide nanoparticles (NPs) have been extensively studied in the last few decades for several biomedical applications such as magnetic resonance imaging, magnetic drug delivery and hyperthermia. Hyperthermia is a technique used for cancer treatment which consists in inducing a temperature of about 41-45 °C in cancerous cells through magnetic NPs and an external magnetic field. Chemical precipitation was used to produce iron oxide NPs 9 nm in size coated with oleic acid and trisodium citrate. The influence of both stabilizers on the heating ability and in vitro cytotoxicity of the produced iron oxide NPs was assessed. Physicochemical characterization of the samples confirmed that the used surfactants do not change the particles’ average size and that the presence of the surfactants has a strong effect on both the magnetic properties and the heating ability. The heating ability of Fe3O4 NPs shows a proportional increase with the increase of iron concentration, although when coated with trisodium citrate or oleic acid the heating ability decreases. Cytotoxicity assays demonstrated that both pristine and trisodium citrate Fe3O4 samples do not reduce cell viability. However, oleic acid Fe3O4 strongly reduces cell viability, more drastically in the SaOs-2 cell line. The produced iron oxide NPs are suitable for cancer hyperthermia treatment and the use of a surfactant brings great advantages concerning the dispersion of NPs, also allowing better control of the hyperthermia temperature.

  9. Triggered self-assembly of magnetic nanoparticles

    Science.gov (United States)

    Ye, L.; Pearson, T.; Cordeau, Y.; Mefford, O. T.; Crawford, T. M.

    2016-03-01

    Colloidal magnetic nanoparticles are candidates for application in biology, medicine and nanomanufac-turing. Understanding how these particles interact collectively in fluids, especially how they assemble and aggregate under external magnetic fields, is critical for high quality, safe, and reliable deployment of these particles. Here, by applying magnetic forces that vary strongly over the same length scale as the colloidal stabilizing force and then varying this colloidal repulsion, we can trigger self-assembly of these nanoparticles into parallel line patterns on the surface of a disk drive medium. Localized within nanometers of the medium surface, this effect is strongly dependent on the ionic properties of the colloidal fluid but at a level too small to cause bulk colloidal aggregation. We use real-time optical diffraction to monitor the dynamics of self-assembly, detecting local colloidal changes with greatly enhanced sensitivity compared with conventional light scattering. Simulations predict the triggering but not the dynamics, especially at short measurement times. Beyond using spatially-varying magnetic forces to balance interactions and drive assembly in magnetic nanoparticles, future measurements leveraging the sensitivity of this approach could identify novel colloidal effects that impact real-world applications of these nanoparticles.

  10. Novel phase behaviour of a confined fluid or Ising magnet

    Science.gov (United States)

    Parry, A. O.; Evans, R.

    1992-02-01

    The phase behaviour of a simple fluid or Ising magnet (at temperatures above its roughening transition) confined between parallel walls that exert opposing surface fields h2 = - h1 is found to be markedly different from that which arises for h2 = h1. Whereas critical wetting plays little role for confinement by identical walls, it is of crucial importance for opposing surface fields. Analysis of a Landau functional and other mean-field treatments show that if h1 is such that critical wetting occurs at a single wall ( L = ∞) at a transition temperature Tw, then phase coexistence, for finite wall separation L, is restricted to temperatures T T > Tw there is a single soft mode phase that is characterized, for zero bulk field and large L, by a +- interface located at the centre of the slit, a transverse correlation length ξ∼≈ eL and a solvation force that is repulsive. For large h1, Tw can lie arbitrarily far below the bulk critical temperature Tc, b. Scaling arguments, whose validity we have confirmed in two dimensions by comparison with exact solutions for interfacial Hamiltonians, predict that such behaviour persists beyond mean-field for systems with short-ranged forces. They also predict similar phase behaviour for long-ranged forces, but with ξ ξ ∼ increasing algebraically with L in the soft mode phase. The solvation force t˜f s changes from repulsive to attractive (at large L) as the temperature is reduced below Tw, i.e. the sign of t˜f s reflects wetting characteristics.

  11. Magnetic Partitioning Nanofluid for Rare Earth Extraction from Geothermal Fluids

    Energy Technology Data Exchange (ETDEWEB)

    McGrail, Bernard P. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Thallapally, Praveen K. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Liu, Jian [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Nune, Satish K. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2017-08-21

    Rare earth metals are critical materials in a wide variety of applications in generating and storing renewable energy and in designing more energy efficient devices. Extracting rare earth metals from geothermal brines is a very challenging problem due to the low concentrations of these elements and engineering challenges with traditional chemical separations methods involving packed sorbent beds or membranes that would impede large volumetric flow rates of geothermal fluids transitioning through the plant. We are demonstrating a simple and highly cost-effective nanofluid-based method for extracting rare earth metals from geothermal brines. Core-shell composite nanoparticles are produced that contain a magnetic iron oxide core surrounded by a shell made of silica or metal-organic framework (MOF) sorbent functionalized with chelating ligands selective for the rare earth elements. By introducing the nanoparticles at low concentration (≈0.05 wt%) into the geothermal brine after it passes through the plant heat exchanger, the brine is exposed to a very high concentration of chelating sites on the nanoparticles without need to pass through a large and costly traditional packed bed or membrane system where pressure drop and parasitic pumping power losses are significant issues. Instead, after a short residence time flowing with the brine, the particles are effectively separated out with an electromagnet and standard extraction methods are then applied to strip the rare earth metals from the nanoparticles, which are then recycled back to the geothermal plant. Recovery efficiency for the rare earths at ppm level has now been measured for both silica and MOF sorbents functionalized with a variety of chelating ligands. A detailed preliminary techno-economic performance analysis of extraction systems using both sorbents showed potential to generate a promising internal rate of return (IRR) up to 20%.

  12. 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.

  13. Influence of a strong magnetic field on paramagnetic fluid's flow in cubical enclosure

    Science.gov (United States)

    Kraszewska, A.; Pyrda, L.; Donizak, J.

    2016-10-01

    The fluid behaviour in thermo-magnetic convection of paramagnetic fluid in a strong magnetic field was studied. The fluid was 50% volume aqueous solution of glycerol with an addition of gadolinium nitrate hexahydrate (Gd(NO3)3-6H2O). Experimental enclosure - a vessel with aspect ratio (AR=height/width) equal to 1.0 - was heated from the bottom, and cooled from the top. Temperature difference between top and bottom walls was kept constant at ΔT = 5 and 11 [°C]. The magnetic induction was increased stepwise from 1 to 10 [T] and thermocouples placed inside the enclosures measured temperature changes of the fluid. On the basis of temperature measurements, analysis of the fluid flow was performed.

  14. Collisional transport across the magnetic field in drift-fluid models

    CERN Document Server

    Madsen, Jens; Nielsen, Anders Henry; Rasmussen, Jens Juul

    2015-01-01

    Drift ordered fluid models are widely applied in studies of low-frequency turbulence in the edge and scrape-off layer regions of magnetically confined plasmas. Here, we show how collisional transport across the magnetic field is self-consistently incorporated into drift-fluid models without altering the drift-fluid energy integral. We demonstrate that the inclusion of collisional transport in drift-fluid models gives rise to diffusion of particle density, momentum and pressures in drift-fluid turbulence models and thereby obviate the customary use of artificial diffusion in turbulence simulations. We further derive a computationally efficient, two-dimensional model which can be time integrated for several turbulence de-correlation times using only limited computational resources. The model describes interchange turbulence in a two-dimensional plane perpendicular to the magnetic field located at the outboard midplane of a tokamak. The model domain has two regions modeling open and closed field lines. The model...

  15. Collisional transport across the magnetic field in drift-fluid models

    DEFF Research Database (Denmark)

    Madsen, Jens; Naulin, Volker; Nielsen, Anders Henry

    2016-01-01

    Drift ordered fluid models are widely applied in studies of low-frequency turbulence in the edge and scrape-off layer regions of magnetically confined plasmas. Here, we show how collisional transport across the magnetic field is self-consistently incorporated into drift-fluid models without...... altering the drift-fluid energy integral. We demonstrate that the inclusion of collisional transport in drift-fluid models gives rise to diffusion of particle density, momentum, and pressures in drift-fluid turbulence models and, thereby, obviates the customary use of artificial diffusion in turbulence...... simulations. We further derive a computationally efficient, two-dimensional model, which can be time integrated for several turbulence de-correlation times using only limited computational resources. The model describes interchange turbulence in a two-dimensional plane perpendicular to the magnetic field...

  16. Faraday rotation and magneto-optical figure of merit for the magnetite magnetic fluids

    Directory of Open Access Journals (Sweden)

    Kalandadze L.

    2011-05-01

    Full Text Available In the present paper, using magnetite magnetic fluids as examples, we consider the optical and magneto-optical properties of magnetic fluids based on particles of magnetic oxides, for the optical constants of the material of which, n and k , the relation k2 ≺≺ n2 holds. In this work the Faraday rotation is represented within the theoretical Maxwell-Garnett model. A theoretical analysis has shown that Faraday rotation for magnetic fluids is related to the Faraday rotation on the material of particles by the simple relation. According to this result  in specific experimental conditions the values of the Faraday rotation prorate to q , which is the occupancy of the volume of the magnetic fluid with magnetic particles and spectral dependences of effect in magnetic fluid and in the proper bulk magnetic are similar. We also show that the values of the magneto-optical figure of merit for ultrafine medium and for the bulk material are equal.

  17. Use of a magnetic fluid for particle size analysis by a sedimentation method

    Energy Technology Data Exchange (ETDEWEB)

    Dikansky, Yury [Department of Physics, Stavropol State University, 1 Pushkin Street, Stavropol 355009 (Russian Federation)], E-mail: dikansky@mail.ru; Zakinyan, Arthur; Bedganian, Marita [Department of Physics, Stavropol State University, 1 Pushkin Street, Stavropol 355009 (Russian Federation)

    2009-05-15

    A new method of particle size analysis of micrometer-sized particles is discussed. The improved method of sedimentation analysis with magnetic fluids has the potential and versatility to characterize polydisperse systems.

  18. Characteristics of a magnetic fluid seal and its motion in an axial variable seal gap

    Institute of Scientific and Technical Information of China (English)

    QIAN Ji-guo; YANG Zhi-yi

    2008-01-01

    With suitable assumptions a hydrodynamic model for the magnetic fluid motion in an axial variable gap seal was constructed, and the solution to the equations of the model was deduced. The characteristics of a magnetic fluid seal and its motion,including the speed and pressure distribution, and the seal capacity of a magnetic fluid rotating seal were systematically described.The factors affecting seal capacity and ways to improve seal capacity based on the hydrodynamic model are discussed. The basic condition for dynamic seal availability is presented. The rotating speed and radius of the shafts should be decreased. The work can provide proof of a seal design or suggest ways to improve the seal capacity of magnetic fluid seals.

  19. Mixed Finite Element Formulation for Magnetic Fluid Oil Flow in Electromagnetic Field

    Directory of Open Access Journals (Sweden)

    Tan Phey Hoon

    2017-01-01

    Full Text Available Pressure depletion and high viscosity of crude oil in oil reservoir are the main challenges in oil recovery process. A potential solution is to employ electromagnetic heating coupled with magnetic fluid injection. The present work delivers a fundamental study on the interaction between magnetic fluid flow with electromagnetic field. The two-dimensional, incompressible flow is solved numerically using mixed finite element method. The velocity fields, temperature and pressure are the variables of interest, to be obtained by solving mass, momentum and energy equations coupled with Maxwell’ equations. The fluid stress arises simultaneously with the external magnetic force which mobilises and increases the temperature of the oil flow. Verification is made against available data obtained from different numerical method reported in literature. The results justify feasibility of the mixed finite element formulation as an alternative for the modelling of the magnetic fluid flow.

  20. Viscosity of colloidal suspensions

    Energy Technology Data Exchange (ETDEWEB)

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

    1995-12-31

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

  1. 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.

  2. Aggregation process of paramagnetic particles in fluid in the magnetic field.

    Science.gov (United States)

    Pei, Ning; Cheng, Xiaoye; Huang, Zheyong; Wang, Xiang; Yang, Kai; Wang, Ye; Gong, Yongyong

    2016-07-01

    Magnetic targeting is a promising therapeutic strategy for localizing systemically delivered magnetic responsive drugs or cells to target tissue, but excessive aggregation of magnetic particles could result in vascular embolization. To analyze the reason for embolization, the attractive process of magnetic particles in magnetic field (MF) was studied in this paper by analyzing the form of the aggregated paramagnetic particles while the particle suspension flowed through a tube, which served as a model of blood vessels. The effects of magnetic flux density and fluid velocity on the formation of aggregated paramagnetic particles were investigated. The number of large aggregated clusters dramatically increased with increment in the magnetic flux density and decreased with increment in the fluid velocity. The analysis of accumulative process demonstrates the MF around initially attracted particles was focused, which induced the formation of clusters and increased the possibility of embolism. Bioelectromagnetics. 37:323-330, 2016. © 2016 Wiley Periodicals, Inc.

  3. Demonstration of anisotropic fluid closure capturing the kinetic structure of magnetic reconnection.

    Science.gov (United States)

    Ohia, O; Egedal, J; Lukin, V S; Daughton, W; Le, A

    2012-09-14

    Collisionless magnetic reconnection in high-temperature plasmas has been widely studied through fluid-based models. Here, we present results of fluid simulation implementing new equations of state for guide-field reconnection. The new fluid closure accurately accounts for the anisotropic electron pressure that builds in the reconnection region due to electric and magnetic trapping of electrons. In contrast to previous fluid models, our fluid simulation reproduces the detailed reconnection region as observed in fully kinetic simulations. We hereby demonstrate that the new fluid closure self-consistently captures all the physics relevant to the structure of the reconnection region, providing a gateway to a renewed and deeper theoretical understanding of reconnection in weakly collisional regimes.

  4. Thermodynamics of mixtures of patchy and spherical colloids of different sizes: A multi-body association theory with complete reference fluid information.

    Science.gov (United States)

    Bansal, Artee; Valiya Parambathu, Arjun; Asthagiri, D; Cox, Kenneth R; Chapman, Walter G

    2017-04-28

    We present a theory to predict the structure and thermodynamics of mixtures of colloids of different diameters, building on our earlier work [A. Bansal et al., J. Chem. Phys. 145, 074904 (2016)] that considered mixtures with all particles constrained to have the same size. The patchy, solvent particles have short-range directional interactions, while the solute particles have short-range isotropic interactions. The hard-sphere mixture without any association site forms the reference fluid. An important ingredient within the multi-body association theory is the description of clustering of the reference solvent around the reference solute. Here we account for the physical, multi-body clusters of the reference solvent around the reference solute in terms of occupancy statistics in a defined observation volume. These occupancy probabilities are obtained from enhanced sampling simulations, but we also present statistical mechanical models to estimate these probabilities with limited simulation data. Relative to an approach that describes only up to three-body correlations in the reference, incorporating the complete reference information better predicts the bonding state and thermodynamics of the physical solute for a wide range of system conditions. Importantly, analysis of the residual chemical potential of the infinitely dilute solute from molecular simulation and theory shows that whereas the chemical potential is somewhat insensitive to the description of the structure of the reference fluid, the energetic and entropic contributions are not, with the results from the complete reference approach being in better agreement with particle simulations.

  5. Thermodynamics of mixtures of patchy and spherical colloids of different sizes: A multi-body association theory with complete reference fluid information

    Science.gov (United States)

    Bansal, Artee; Valiya Parambathu, Arjun; Asthagiri, D.; Cox, Kenneth R.; Chapman, Walter G.

    2017-04-01

    We present a theory to predict the structure and thermodynamics of mixtures of colloids of different diameters, building on our earlier work [A. Bansal et al., J. Chem. Phys. 145, 074904 (2016)] that considered mixtures with all particles constrained to have the same size. The patchy, solvent particles have short-range directional interactions, while the solute particles have short-range isotropic interactions. The hard-sphere mixture without any association site forms the reference fluid. An important ingredient within the multi-body association theory is the description of clustering of the reference solvent around the reference solute. Here we account for the physical, multi-body clusters of the reference solvent around the reference solute in terms of occupancy statistics in a defined observation volume. These occupancy probabilities are obtained from enhanced sampling simulations, but we also present statistical mechanical models to estimate these probabilities with limited simulation data. Relative to an approach that describes only up to three-body correlations in the reference, incorporating the complete reference information better predicts the bonding state and thermodynamics of the physical solute for a wide range of system conditions. Importantly, analysis of the residual chemical potential of the infinitely dilute solute from molecular simulation and theory shows that whereas the chemical potential is somewhat insensitive to the description of the structure of the reference fluid, the energetic and entropic contributions are not, with the results from the complete reference approach being in better agreement with particle simulations.

  6. Multifunctional Fluorescent-Magnetic Polymeric Colloidal Particles: Preparations and Bioanalytical Applications.

    Science.gov (United States)

    Kaewsaneha, Chariya; Tangboriboonrat, Pramuan; Polpanich, Duangporn; Elaissari, Abdelhamid

    2015-10-28

    Fluorescent-magnetic particles (FMPs) play important roles in modern materials, especially as nanoscale devices in the biomedical field. The interesting features of FMPs are attributed to their dual detection ability, i.e., fluorescent and magnetic modes. Functionalization of FMPs can be performed using several types of polymers, allowing their use in various applications. The synergistic potentials for unique multifunctional, multilevel targeting nanoscale devices as well as combination therapies make them particularly attractive for biomedical applications. However, the synthesis of FMPs is challenging and must be further developed. In this review article, we summarized the most recent representative works on polymer-based FMP systems that have been applied particularly in the bioanalytical field.

  7. Particle image velocimetry for an automatic cooling device using temperature-sensitive magnetic fluid

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    An automatic cooling device has been developed by using a temperature-sensitive magnetic fluid as the coolant. A particle image velocimetry (PIV) system was used to measure the flow velocity of the fluid inside the loop. The efficiency of the device under varying conditions such as the heat load and the power of cooling were ex- perimentally investigated. The effect of cooperation between external magnetic field and thermal field on the performance of the device was studied. As expected, a continuous flow induced by the thermal and magnetic field was observed in the loop, where heat was transferred by the circulating magnetic fluid. The synergic effect between the magnetic field and the temperature gradient has impact on the performance of the device.

  8. Effect of induced magnetic field on peristaltic flow of a micropolar fluid in an asymmetric channel

    CERN Document Server

    Shit, G C; Ng, E Y K; 10.1002/cnm.1397

    2010-01-01

    Of concern in this paper is an investigation of peristaltic transport of a physiological fluid in an asymmetric channel under long wave length and low-Reynolds number assumptions. The flow is assumed to be incompressible, viscous, electrically conducting micropolar fluid and the effect of induced magnetic field is taken into account. Exact analytical solutions obtained for the axial velocity, microrotation component, stream line pattern, magnetic force function, axial-induced magnetic field as well as the current density distribution across the channel. The flow phenomena for the pumping characteristics, trapping and reflux are also investigated. The results presented reveal that the velocity decreases with the increase of magnetic field as well as the coupling parameter. Moreover, the trapping fluid can be eliminated by the application of an external magnetic field. Thus, the study bears the promise of important applications in physiological systems.

  9. Magnetite-cobalt ferrite nanoparticles for kerosene-based magnetic fluids

    Energy Technology Data Exchange (ETDEWEB)

    Ayala-Valenzuela, O. [Centro de Investigacion en Materiales Avanzados, Miguel de Cervantes Saavedra No. 120, Complejo Industrial Chihuahua, Chihuahua, Chih. (Mexico) and Centro de Investigacion en Quimica Aplicada, Blvd. Enrique Reyna Hermosillo No. 140 CP 25000 Saltillo, Coahuila (Mexico)]. E-mail: oscar.ayala@cimav.edu.mx; Matutes-Aquino, J. [Centro de Investigacion en Materiales Avanzados, Miguel de Cervantes Saavedra No. 120, Complejo Industrial Chihuahua, Chihuahua, Chih. (Mexico); Betancourt-Galindo, R. [Centro de Investigacion en Quimica Aplicada, Blvd. Enrique Reyna Hermosillo No. 140 CP 25000 Saltillo, Coahuila (Mexico); Garcia-Cerda, L.A. [Centro de Investigacion en Quimica Aplicada, Blvd. Enrique Reyna Hermosillo No. 140 CP 25000 Saltillo, Coahuila (Mexico); Rodriguez Fernandez, O. [Centro de Investigacion en Quimica Aplicada, Blvd. Enrique Reyna Hermosillo No. 140 CP 25000 Saltillo, Coahuila (Mexico); Fannin, P.C. [Department of Electronic and Electrical Engineering, Trinity College, Dublin 2 (Ireland); Giannitsis, A.T. [Department of Electronic and Electrical Engineering, Trinity College, Dublin 2 (Ireland)

    2005-07-15

    Due to the magnetic anisotropy introduced by the Co{sup 2+} ion in octahedral sites of cubic spinel ferrites, it is possible to tailor the magnetic properties by changing the cobalt content. Magnetic fluids with magnetite-cobalt ferrite nanoparticles given by the formula Co{sub (} {sub x} {sub )}Fe{sub (3-} {sub x} {sub )}O{sub 4} with x=0, 0.2 and 0.4 were prepared. Kerosene and oleic acid were used as liquid carrier and surfactant, respectively. Spherical magnetic nanoparticles were obtained by coprecipitation from metal salts and ammonium hydroxide; afterwards the magnetic fluids were obtained by a peptization process. Powder properties were characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption isotherma (BET), vibrating sample magnetometry (VSM) and fluids by transmission electron microscopy (TEM), thermogravimetric analyzer (TGA), VSM and the short-circuited transmission line technique.

  10. Particle image velocimetry for an automatic cooling device using temperature-sensitive magnetic fluid

    Institute of Scientific and Technical Information of China (English)

    LIAN WenLei; LI Qiang; XUAN YiMin

    2008-01-01

    An automatic cooling device has been developed by using a temperature-sensitive magnetic fluid as the coolant. A particle image velocimetry (PIV) system was used to measure the flow velocity of the fluid inside the loop. The efficiency of the device under varying conditions such as the heat load and the power of cooling were ex-perimentally investigated. The effect of cooperation between external magnetic field and thermal field on the performance of the device was studied. As expected, a continuous flow induced by the thermal and magnetic field was observed in the loop, where heat was transferred by the circulating magnetic fluid. The synergic effect between the magnetic field and the temperature gradient has impact on the performance of the device.

  11. Magnetically Induced "Dry" Water Like Structure of Charged Fluid at the Core of a Magnetar

    CERN Document Server

    Ghosh, S; Ghosh, Sutapa; Chakrabarty, Somenath

    2001-01-01

    It is shown that charged fluid, e.g., electron gas or proton matter at the core of a magnetar exhibit super-fluid (frictionless) like property if the magnetic field strength is high enough to populate only the zeroth Landau levels.

  12. Coefficients of viscosity for a fluid in a magnetic field or in a rotating system

    NARCIS (Netherlands)

    Hooyman, G.J.; Mazur, P.; Groot, S.R. de

    1954-01-01

    The linear equations between the elements of the viscous pressure tensor and the rates of deformation are investigated for the case of an isotropic fluid in an external magnetic field or for the equivalent case of a rotating fluid. Since these equations can be incorporated within the thermodynamics

  13. Cyclodextrin conjugated magnetic colloidal nanoparticles as a nanocarrier for targeted anticancer drug delivery

    Science.gov (United States)

    Banerjee, Shashwat S.; Chen, Dong-Hwang

    2008-07-01

    A novel magnetic nanocarrier (CD-GAMNPs) was fabricated for targeted anticancer drug delivery by grafting cyclodextrin (CD) onto gum arabic modified magnetic nanoparticles (GAMNPs) using hexamethylene diisocyanate (HMDI) as a linker. Analyses by transmission electron microscopy (TEM) and dynamic light scattering (DLS) revealed that the product had a mean diameter of 17.1 nm and a mean hydrodynamic diameter of 44.1 nm. The CD grafting was confirmed by Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA) indicated that the amount of CD grafted on the GAMNPs was 16.8 mg g-1. The study on the loading of anticancer drug all-trans-retinoic acid (retinoic acid) revealed that the newly fabricated magnetic nanocarrier possessed a considerably higher adsorption capability as compared to GAMNPs due to the special hydrophobic cavity structure of CD, which could act as a host-guest complex with retinoic acid. Furthermore, it was found that the complexation of CD-GAMNPs with retinoic acid was exothermic and the presence of a surfactant (sodium dodecyl sulfate) led to the decrease in the inclusion of retinoic acid because the linear structure of sodium dodecyl sulfate made it easier to enter the cavity of CD as compared to less linear retinoic acid. In addition, the in vitro release profile of retinoic acid from CD-GAMNPs was characterized by an initial fast release followed by a delayed release phase.

  14. Cyclodextrin conjugated magnetic colloidal nanoparticles as a nanocarrier for targeted anticancer drug delivery

    Energy Technology Data Exchange (ETDEWEB)

    Banerjee, Shashwat S; Chen, D.-H. [Department of Chemical Engineering, National Cheng Kung University, Tainan 701, Taiwan (China)], E-mail: chendh@mail.ncku.edu.tw

    2008-07-02

    A novel magnetic nanocarrier (CD-GAMNPs) was fabricated for targeted anticancer drug delivery by grafting cyclodextrin (CD) onto gum arabic modified magnetic nanoparticles (GAMNPs) using hexamethylene diisocyanate (HMDI) as a linker. Analyses by transmission electron microscopy (TEM) and dynamic light scattering (DLS) revealed that the product had a mean diameter of 17.1 nm and a mean hydrodynamic diameter of 44.1 nm. The CD grafting was confirmed by Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA) indicated that the amount of CD grafted on the GAMNPs was 16.8 mg g{sup -1}. The study on the loading of anticancer drug all-trans-retinoic acid (retinoic acid) revealed that the newly fabricated magnetic nanocarrier possessed a considerably higher adsorption capability as compared to GAMNPs due to the special hydrophobic cavity structure of CD, which could act as a host-guest complex with retinoic acid. Furthermore, it was found that the complexation of CD-GAMNPs with retinoic acid was exothermic and the presence of a surfactant (sodium dodecyl sulfate) led to the decrease in the inclusion of retinoic acid because the linear structure of sodium dodecyl sulfate made it easier to enter the cavity of CD as compared to less linear retinoic acid. In addition, the in vitro release profile of retinoic acid from CD-GAMNPs was characterized by an initial fast release followed by a delayed release phase.

  15. Generation of zonal flows in rotating fluids and magnetized plasmas

    DEFF Research Database (Denmark)

    Juul Rasmussen, J.; Garcia, O.E.; Naulin, V.

    2006-01-01

    contribution the generation of zonal flows will be illustrated in a simple fluid experiment performed in a rotating container with radial symmetric bottom topography. An effective mixing that homogenizes the potential vorticity in the fluid layer will lead to the replacement of the high-potential vorticity...

  16. Magnetically Actuated Artificial Cilia : The Effect of Fluid Inertia

    NARCIS (Netherlands)

    Khaderi, S. N.; den Toonder, J.M.J.; Onck, P. R.

    2012-01-01

    Natural cilia are hairlike microtubule-based structures that are able to move fluid on the micrometer scale using asymmetric motion. In this article, we follow a biomimetic approach to design artificial cilia lining the inner surfaces of microfluidic channels with the goal of propelling fluid. The

  17. R-T instability model of magnetic fluid and its numerical simulations

    Institute of Scientific and Technical Information of China (English)

    郑秋云; 李明军; 舒适

    2008-01-01

    The Rayleigh-Taylor(R-T) instability of ferrofluid has been the subject of recent research,because of its implications on the stability of stellar.By neglecting the viscosity and rotation of magnetic fluid,and assuming that the magnetic particles are irrotational and temperature insensitive,we obtain a simplified R-T instability model of magnetic fluid.For the interface tracing,we use five-order weighted essentially non-oscillatory(WENO) scheme to spatial direction and three-order TVD R-K method to time direction on the uniform mesh,respectively.If the direction of the external magnetic field is the same as that of gravity,the velocities of the interface will be increased.But if the direction of the external magnetic field is in opposition to the direction of gravity,the velocities of the interface will be decreased.When the direction of the external magnetic field is perpendicular to the direction of gravity,the symmetry of the interface will be destroyed.Because of the action which is produced by perpendicular external magnetic field,there are other bubbles at the boudaries which parallel the direction of gravity.When we increase the magnetic susceptibility of the magnetic fluids,the effects of external magnetic fields will be more distinct for the interface tracing.

  18. Optical Properties of Fe3O4 Magnetic Fluid from Iron Sand

    Science.gov (United States)

    Puspitaningrum, A.; Taufiq, A.; Hidayat, A.; Sunaryono; Hidayat, N.; Samian

    2017-05-01

    Nowadays, a high sensitive sensor for the magnetic field has become an essential tool that vastly desired in several fields, especially in biomedical application. Therefore, the development of preparing material for the magnetic sensor becomes crucial to be conducted. In this experimnet, we propose the use of Fe3O4 magnetic fluid prepared from a local iron sand in Indonesia as a material for a magnetic sensor. In this work, optical activities of the Fe3O4 magnetic fluid as the effect of magneto-optics were performed under varying external magnetic field. The polarization direction change of the laser was detected as a function of the external magnetic field with the exponential function. Moreover, the intensity collected by a photodetector exhibited a linear correlation with the external magnetic field. These phenomena become strong evidence that the prepared Fe3O4 magnetic fluid opens potential to be applicated further as sensors, especially as a high sensitive optics-based sensor for the magnetic field.

  19. Zero-field birefringence of biocompatible magnetic fluids: A concentration dependence investigation

    Energy Technology Data Exchange (ETDEWEB)

    Eloi, Marcos T.A. [Universidade de Brasilia, Instituto de Fisica, Nucleo de Fisica Aplicada, 70919-970, Brasilia - DF (Brazil); Azevedo, Ricardo B. [Departamento de Genetica e Morfologia, Universidade de Brasilia, Instituto de Ciencias Biologicas, 70910-900, Brasilia - DF (Brazil); Lima, Emilia C.D. [Universidade Federal de Goias, Instituto de Quimica, 74001-970, Goiania - GO (Brazil); Pimenta, Angela C.M. [Universidade Federal de Goias, Instituto de Quimica, 74001-970, Goiania - GO (Brazil); Morais, Paulo C. [Universidade de Brasilia, Instituto de Fisica, Nucleo de Fisica Aplicada, 70919-970, Brasilia - DF (Brazil)]. E-mail: pcmor@unb.br

    2005-05-15

    Zero-field birefringence was used to investigate maghemite-based biocompatible magnetic fluids surface-coated with citrate. The model used to analyze the birefringence signal considers the dipolar magnetic interaction among dimers and the onset of a nematic phase near the sample holder surface. The data show that zero-field birefringence grows with sample dilution.

  20. The dynamics of the Soret effect in thin film of magnetic fluid

    NARCIS (Netherlands)

    Kopcansky, P; Tomco, L; Timko, M; Koneracka, M; Turek, F; Stelina, J; Musil, C; Ocelik, Vaclav

    2000-01-01

    The Soret effect in interference field of two intensive laser beams in the thin film of magnetic fluid was used to create a periodical structure of density of magnetic particles. The structures obtained were indicated using the self-diffraction of the optical beam creating the structures. The relaxa

  1. A new miniaturized engine based on thermomagnetic effect of magnetic fluids

    Institute of Scientific and Technical Information of China (English)

    Lujun ZHOU; Yimin XUAN; Qiang LI; Wenlei LIAN

    2009-01-01

    A new engine system, essentially consisting of a permanent NdFeB magnet, a kerosene-based magnetic fluid and a rotor, is proposed based on the thermomagnetic effect of a temperature-sensitive magnetic fluid. The rotor was driven by the thermal convection of the magnetic fluid in the presence of a homogeneous external magnetic field. A digital camera was used to record the rotation speed of the rotor to investigate the performance of the engine system under varying conditions such as heat load, heat sink temperature, and magnetic field distribution. The peak angle velocity obtained for the rotor was about 2.1 rad/min. The results illustrate that the rotation speed of the rotor increases as the input heat load increases, or as the heat sink temperature decreases. The performance of the motor is considerably influenced by the magnetic field imposed. Therefore, the performance of such an engine can be controlled conveniently by changing the external magnetic field and/or the temperature distribution in the fluid.

  2. The dynamics of the Soret effect in thin film of magnetic fluid

    NARCIS (Netherlands)

    Kopcansky, P; Tomco, L; Timko, M; Koneracka, M; Turek, F; Stelina, J; Musil, C; Ocelik, Vaclav

    The Soret effect in interference field of two intensive laser beams in the thin film of magnetic fluid was used to create a periodical structure of density of magnetic particles. The structures obtained were indicated using the self-diffraction of the optical beam creating the structures. The

  3. Monitoring of magnetic EOR fluids in reservoir under production by using the electromagnetic method

    Science.gov (United States)

    KIM, S.; Min, D. J.; Moon, S.; Kim, W. K.; Shin, Y.

    2014-12-01

    To increase the amount of oil and gas extracted during production, some techniques like EOR (Enhanced Oil Recovery) are applied by injecting some materials such as water and CO2. Recently, there are some researches for injecting magnetic nanoparticles with fluids during EOR. The size of particle is nano-scale, which can prevent particles from adhering to the pores of reservoir. The main purpose of injecting magnetic nanoparticles is to monitor movement or distribution of EOR fluids. To monitor the injected magnetic EOR fluids in the reservoir, CSEM (controlled source electromagnetic method) can be the most optimized geophysical method among various geophysical monitoring methods. Depending on the reservoir circumstances, we can control the electric or magnetic sources to monitor reservoir during oil or gas production. In this study, we perform numerical simulation of CSEM for 3D horizontal-layered models assuming a reservoir under production. We suppose that there are two wells: one is for the controlled source; the other is for the receiver. By changing the distribution, movement and magnetization of EOR fluids, we compare the electric or magnetic fields recorded at the receiver. Maxwell's equations are the governing equation of CSEM and are approximated by using the edge-based finite-element method. Direct solver is applied to solve the linear equations. Because injected magnetic nanoparticle changes the conductivity of EOR fluid, there is high contrast of conductivity of reservoir. This high contrast of conductivity induces secondary electric or magnetic fields that are recorded at the receiver well. We compare these recorded secondary fields generated by various movement or distribution of magnetic EOR fluid. Acknowledgements This work was supported by the "Development of Technology for CO2 Marine Geological Storage" grant funded by the Ministry of Oceans and Fisheries of Korea, by the "Civil Military Technology Cooperation Center", and by the International

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

    NARCIS (Netherlands)

    de Folter, J.W.J.

    2013-01-01

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

  5. Magnetic fluid based squeeze film between porous circular disks with sealed boundary

    Institute of Scientific and Technical Information of China (English)

    R.M.PATEL; G.M.DEHERI

    2001-01-01

    Efforts have been made to study the effect of the magnetic fluid lubricant and the seal-ing of the boundary for the squeeze film between two circular disks when the upper disk having aporous facing with its boundary sealed, approaches the non-porous lower disk normally. The modi-fied Reynolds equations for the fluid region and the governing Laplacian equation for the pressurein porous region are solved with appropriate boundary conditions. Expressions are obtained forpressure, load carrying capacity and the response time. The results are presented graphically. Thecombined effect of the magnetic fluid lubricant and sealing of the boundary increases the load car-rying capacity significantly and hence the performance of the bearing can be enhanced considera-bly by sealing the boundary and taking a magnetic fluid as lubricant.

  6. INVERSE CASCADE OF NONHELICAL MAGNETIC TURBULENCE IN A RELATIVISTIC FLUID

    Energy Technology Data Exchange (ETDEWEB)

    Zrake, Jonathan [Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Menlo Park, CA 94025 (United States)

    2014-10-20

    The free decay of nonhelical relativistic magnetohydrodynamic turbulence is studied numerically, and found to exhibit cascading of magnetic energy toward large scales. Evolution of the magnetic energy spectrum P{sub M} (k, t) is self-similar in time and well modeled by a broken power law with subinertial and inertial range indices very close to 7/2 and –2, respectively. The magnetic coherence scale is found to grow in time as t {sup 2/5}, much too slow to account for optical polarization of gamma-ray burst afterglow emission if magnetic energy is to be supplied only at microphysical length scales. No bursty or explosive energy loss is observed in relativistic MHD turbulence having modest magnetization, which constrains magnetic reconnection models for rapid time variability of GRB prompt emission, blazars, and the Crab nebula.

  7. Bianchi Type-Ⅰ Massive String Magnetized Barotropic Perfect Fluid Cosmological Model in General Relativity

    Institute of Scientific and Technical Information of China (English)

    BALI Raj; PAREEK Umesh Kumar; PRADHAN Anirudh

    2007-01-01

    @@ Bianchi type-Ⅰ massive string cosmological model with magnetic field of barotropic perfect fluid distribution through the techniques used by Latelier and Stachel is investigated. To obtain the deterministic model of the universe, it is assumed that the universe is filled with barotropic perfect fluid distribution. The magnetic field is due to electric current produced along the x-axis with infinite electrical condúctivity. The behaviour of the model in the presence and absence of magnetic field together with other physical aspects is further discussed.

  8. Effects of magnetic fluids on crystallization characterizations in a multi-component and multiphase system

    Institute of Scientific and Technical Information of China (English)

    SHU BiFen; SHEN Hui; CHEN MeiYuan; XIA JianHan; WANG Xiang; SUN JianWei

    2008-01-01

    In this study, experiments are carried out on the effects of magnetic fluids on the crystallization char- acterizations in a multi-component and multiphase system, which contains the liquid and the vapor of HCFC141b, water, water vapor, and gas hydrates. The mass transfer phenomena between the phase interfaces of water-HCFC141b and water-vapor are also researched. The experimental results show that in the presence of a rotary magnetic field, magnetic fluids can remarkably enhance the heat and mass transfer between phase interfaces and, therefore, improve the performance of crystallization, especially in improving the formation temperature and velocity.

  9. Augmentation of chain formation in a magnetic fluid by the addition of halloysite nanotubes

    Science.gov (United States)

    Desai, Rucha; Upadhyay, R. V.; Mehta, R. V.

    2014-04-01

    The study aims to investigate the effect of the addition of nanotubes of halloysite on the augmentation of chains observed in an aqueous magnetic fluid consisting of co-precipitated magnetite particles stabilized with lauric acid. Three samples of the mixture containing 0.5%, 1% and 2% of halloysite nanotubes (HNTs) and a pure magnetic fluid are used for this study. A room temperature magnetization study shows that for 0.5% and 1% of HNT, the magnetization of the mixture significantly increases, while for the higher concentration (2%) it decreases. Such concentration dependent behaviour on the addition of a nonmagnetic system to a magnetic fluid has not previously been observed. The increase in the magnetization is attributed to smaller sized (<5-6 nm) magnetite attached to the HNT, forming a magnetite-HNT composite. Additionally, field-induced chaining is augmented by the addition of HNT in the magnetic fluid. The augmentation of chain formation is confirmed by optical microscopy, field-induced transmission changes and field-dependent diffraction effects. The augmentation will be useful in enhancing other properties of the composite, such as the viscosity and thermal conductivity of nanofluids.

  10. Recent advances in nanosized Mn-Zn ferrite magnetic fluid hyperthermia for cancer treatment.

    Science.gov (United States)

    Lin, Mei; Huang, Junxing; Sha, Min

    2014-01-01

    This paper reviews the recent research and development of nanosized manganese zinc (Mn-Zn) ferrite magnetic fluid hyperthermia (MFH) for cancer treatment. Mn-Zn ferrite MFH, which has a targeted positioning function that only the temperature of tumor tissue with magnetic nanoparticles can rise, while normal tissue without magnetic nanoparticles is not subject to thermal damage, is a promising therapy for cancer. We introduce briefly the composition and properties of magnetic fluid, the concept of MFH, and features of Mn-Zn ferrite magnetic nanoparticles for MFH such as thermal bystander effect, universality, high specific absorption rate, the targeting effect of small size, uniformity of hyperthermia temperature, and automatic temperature control and constant temperature effect. Next, preparation methods of Mn-Zn ferrite magnetic fluid are discussed, and biocompatibility and biosecurity of Mn-Zn ferrite magnetic fluid are analyzed. Then the applications of nanosized Mn-Zn ferrite MFH in cancer are highlighted, including nanosized Mn-Zn ferrite MFH alone, nanosized Mn-Zn ferrite MFH combined with As2O3 chemotherapy, and nanosized Mn-Zn ferrite MFH combined with radiotherapy. Finally, the combination application of nanosized Mn-Zn ferrite MFH and gene-therapy is conceived, and the challenges and perspectives for the future of nanosized Mn-Zn ferrite MFH for oncotherapy are discussed.

  11. Two-Fluid Theory for Spin Superfluidity in Magnetic Insulators

    NARCIS (Netherlands)

    Flebus, B.; Bender, S. A.; Tserkovnyak, Y.; Duine, R. A.

    2016-01-01

    We investigate coupled spin and heat transport in easy-plane magnetic insulators. These materials display a continuous phase transition between normal and condensate states that is controlled by an external magnetic field. Using hydrodynamic equations supplemented by Gross-Pitaevski phenomenology an

  12. Periodical structure in a magnetic fluid under the action of an electric field and with a shear flow

    Energy Technology Data Exchange (ETDEWEB)

    Veguera, Janna G. [Stavropol State University, 1 Pushkin st., Stavropol 355009 (Russian Federation)]. E-mail: veguera@yandex.ru; Dikansky, Yury I. [Stavropol State University, 1 Pushkin st., Stavropol 355009 (Russian Federation)

    2005-03-15

    The results of ordering structural formation in a flowing magnetic fluid under the action of an electric field are described. The influence of structural formation process on a viscosity and conductivity of this fluids has been considered.

  13. Thermal chiral vortical and magnetic waves: new excitation modes in chiral fluids

    CERN Document Server

    Kalaydzhyan, Tigran

    2016-01-01

    In certain circumstances, chiral (parity-violating) medium can be described hydrodynamically as a chiral fluid with microscopic quantum anomalies. Possible examples of such systems include strongly coupled quark-gluon plasma, liquid helium 3He-A, neutron stars and the Early Universe. We study first-order hydrodynamics of a chiral fluid on a vortex background and in a external magnetic field. We show that there are two previously undiscovered modes describing heat waves propagating along the vortex and magnetic field. We call them the Thermal Chiral Vortical Wave and Thermal Chiral Magnetic Wave. We also identify known gapless excitations of density, the chiral vortical and chiral magnetic waves. We demonstrate that the velocity of the chiral vortical wave is zero, when the full hydrodynamic framework is applied, and hence the excitation reduces to a charge diffusion mode or is completely absent. We also correct the dispersion relation for the chiral magnetic wave.

  14. 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.

  15. The Application of Carbon Nanotubes in Magnetic Fluid Hyperthermia

    Directory of Open Access Journals (Sweden)

    Grzegorz Raniszewski

    2015-01-01

    Full Text Available The aim of this paper is to present the results of the investigation into the applications of carbon nanotubes with ferromagnetic nanoparticles as nanoheaters for targeted thermal ablation of cancer cells. Relevant nanoparticles’ characteristics were exploited in terms of their functionality for biomedical applications and their magnetic properties were examined to determine heat generation efficiency induced by the exposure of the particles to an alternating magnetic field. The influence of the electromagnetic field on the human body tissues was assessed, providing quantitative measures of the interaction. The behavior of a liquid containing magnetic particles, during the exposure to the alternating magnetic field, was verified. As for the application for the ferromagnetic carbon nanotubes, the authors investigated temperature distribution in human liver tumor together with Arrhenius tissue damage model and the thermal dose concept.

  16. Colloidal interactions in two-dimensional nematic emulsions

    Indian Academy of Sciences (India)

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

    2005-06-01

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

  17. Magnetic properties and concurrence for fluid {sup 3}He on kagome lattice

    Energy Technology Data Exchange (ETDEWEB)

    Ananikian, N. S., E-mail: ananik@yerphi.am; Ananikian, L. N. [A.I. Alikhanyan National Science Laboratory (Armenia); Lazaryan, H. A. [Yerevan State University (Armenia)

    2012-10-15

    We present the results of magnetic properties and entanglement for kagome lattice using Heisenberg model with two- and three-site exchange interactions in strong magnetic field. Kagome lattice correspond to the third layer of fluid {sup 3}He absorbed on the surface of graphite. The magnetic properties and concurrence as a measure of pairwise thermal entanglement are studied by means of variational mean-field like treatment based on Gibbs-Bogoliubov inequality. The system exhibits different magnetic behaviors depending on the values of the exchange parameters (J{sub 2}, J{sub 3}). We have obtained the magnetization plateaus at low temperatures. The central theme of the paper is comparing the entanglement and magnetic behavior for kagome lattice. We have found that in the antiferromagnetic region behavior of the concurrence coincides with the magnetic susceptibility one.

  18. Magnetic field effect on blood flow of Casson fluid in axisymmetric cylindrical tube: A fractional model

    Science.gov (United States)

    Ali, Farhad; Sheikh, Nadeem Ahmad; Khan, Ilyas; Saqib, Muhammad

    2017-02-01

    The effects of magnetohydrodynamics on the blood flow when blood is represented as a Casson fluid, along with magnetic particles in a horizontal cylinder is studied. The flow is due to an oscillating pressure gradient. The Laplace and finite Hankel transforms are used to obtain the closed form solutions of the fractional partial differential equations. Effects of various parameters on the flow of both blood and magnetic particles are shown graphically. The analysis shows that, the model with fractional order derivatives bring a remarkable changes as compared to the ordinary model. The study highlights that applied magnetic field reduces the velocities of both the blood and magnetic particles.

  19. Interface profile evolution between binary immiscible fluids induced by high magnetic field gradients

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A mechanical analysis is done to find the evolution of the interface profile between binary immiscible fluids induced by a three-dimensional orthogonal magnetic field gradient.In the experiments,the changes of the interface profile between four groups of binary immiscible fluids are investigated under the same horizontal magnetic field gradients.The binary immiscible fluids are made of benzene and other liquids,like CuSO4,Fecl3,FeSO4 or Cucl2 aqueous solutions.In addition,the interface profile between the benzene and CuSO4 aqueous solution is examined under different horizontal magnetic field gradients.The experimental results are consistent with the theoretical analysis.This study explains the enhanced Moses effect from a mechanics standpoint.Furthermore,a new method for susceptibility measurement is proposed based on this enhanced Moses effect.

  20. 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.

  1. 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.

  2. On heteroclinic separators of magnetic fields in electrically conducting fluids

    CERN Document Server

    Grines, V; Pochinka, O; Zhuzhoma, E

    2014-01-01

    In this paper we partly solve the problem of existence of separators of a magnetic field in plasma. We single out in plasma a 3-body with a boundary in which the movement of plasma is of special kind which we call an (a-d)-motion. We prove that if the body is the 3-annulus or the "fat" orientable surface with two holes the magnetic field necessarily have a heteroclinic separator. The statement of the problem and the suggested method for its solution lead to some theoretical problems from Dynamical Systems Theory which are of interest of their own.

  3. Analytical modeling of magnetic Rayleigh-Taylor instabilities in compressible fluids

    Science.gov (United States)

    Liberatore, Stéphane; Bouquet, Serge

    2008-11-01

    The magnetic Rayleigh-Taylor instability (MRTI) is investigated in the case of compressible plasmas. The goal of this work is highlighting the influence of both the magnetic field and the compressibility of the material on the growth rate of the Rayleigh-Taylor instability, compared to the classical growth rate derived for incompressible fluids. Our analytical linear models are derived in the framework of the ideal magnetohydrodynamics theory. Three general dispersion relations are obtained: (1) Two for stratified fluids, including compressible (denoted CS∥ when the wave vector k is parallel to the equilibrium magnetic field B0 and CS⊥ when k ⊥B0) and incompressible (denoted IS∥ and IS⊥) and (2) one for incompressible uniform density fluids, including finite mass (denoted Ifm) and infinite (denoted IU). For k ⊥B0, Ifm, IU, and IS⊥ are unmagnetized cases. Comparisons of those various configurations are performed and several differences are pointed out. The main results are as follows: Stratification weakens the MRTI while compressibility has a destabilizing effect. The magnetic field enhances these phenomena. The CS∥ and IU configurations have an identical cutoff wave number. The upper fluid (also called heavy fluid) is more sensitive to compressibility than the light one when k ∥B0. Finally, the CS∥ case is more sensitive than the CS⊥ one to physical variations.

  4. Metabolite profile of cerebrospinal fluid in patients with spina bifida: a proton magnetic resonance spectroscopy study.

    Science.gov (United States)

    Pal, Kamalesh; Sharma, Uma; Gupta, D K; Pratap, Akshay; Jagannathan, N R

    2005-02-01

    The present study was carried out to assess the metabolic differences between cerebrospinal fluid samples of patients with spina bifida and age-matched control individuals. To study the metabolite profile of cerebrospinal fluid of patients with spina bifida using proton magnetic resonance spectroscopy, compare the levels of metabolites with controls, establish correlation of underlying neuronal dysfunction with metabolic changes in patients with spina bifida, and evaluate the potential use of this technique as an additional tool for diagnostic assessment. Combination of embryopathy, stretching, ischemia, compression, and trauma is responsible for cord dysfunction in spina bifida. Changes in neuronal metabolism leads to changes in the local milieu of cerebrospinal fluid in the cord. Change in metabolite profile of cerebrospinal fluid in spina bifida in terms of increase in products of anaerobic metabolism, nerve membrane integrity, and nerve ischemia has not yet been studied. Cerebrospinal fluid obtained from patients and control individuals were characterized using various one- and two-dimensional proton magnetic resonance spectroscopy techniques. Concentration of various metabolites was calculated using the area under the nuclear magnetic resonance peak. Statistically significantly higher levels of lactate, choline, glycerophosphocholine, acetate, and alanine in the cerebrospinal fluid of patients with spina bifida was observed compared with control individuals. Significantly higher levels of metabolites were observed in patients with spina bifida, representing a state of nerve ischemia, anaerobic metabolism, and disruption of neuronal membrane.

  5. Instabilities in two-fluid magnetized media with inter-component drift

    CERN Document Server

    Tytarenko, P V; Falle, S A

    2002-01-01

    We analyse the stability of a magnetized medium consisting of a neutral fluid and a fluid of charged particles, coupled to each other through a drag force and exposed to differential body forces (for example, as the result of radiation forces on one phase). We consider a uniform equilibrium and simple model input physics, but do not arbitrarily restrict the relative orientations of the magnetic field, slip velocity and wave vector of the disturbance. We find several instabilities and classify these in terms of wave resonances. We briefly apply our results to the structure of SiO maser regions appearing in the winds from late-type stars.

  6. Nuclear magnetic resonance as a method of fluid mobility detection in porous media

    Science.gov (United States)

    Zhakov, Sergey; Loskutov, Valentin

    2016-04-01

    The nuclear magnetic resonance (NMR) method is widely used for studying the structure of porous media and processes taking place in such media. This method permits to determine porosity and pore-size distributions, which have direct practical application in various areas. The problem of porous media permeability determination is connected directly with extraction of hydrocarbons from pays and water from aquiferous layers. But it is impossible to measure directly amount of fluid past through the fixes cross section for determination of bed permeability. So various indirect approaches are used to find correlation of permeability value with porosity and pore size distribution which can be determined directly using NMR relaxometry. In contrast to porosity, permeability is dynamic characteristic of porous media so it may be measured correctly only in conditions of moving fluid. Natural porous medium has branched pore structure, so a chaotic component of fluid velocity will occur even for constant mean filtration fluid velocity. In the presence of magnetic field gradient this chaotic fluid velocity will produce additional spin dephasing and decrease of relaxation time [1]. Direct detecting of fluid movement in porous core samples through the Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence has been demonstrated and theoretical model and analysis was given. Experiments were made on a set of sandstone samples (Berea, Bentheimer, Castle Gate, Leopard) and with synthetic high-perm samples made of abrasive material. The experiments show that the NMR spin echo measurements permit to fix mean fluid velocity mm/sec. The experiments and the theoretical model show that for low fluid velocities the mean relaxation rate is proportional to fluid velocity . The results may serve as the basis for determination of mobility of liquids in porous media and permeability. 1. P.T.Callaghan. Principles of Nuclear Magnetic Resonance Microscopy. 1991, Oxford University Press.

  7. Investigation of change in surface morphology of heated surfaces upon pool boiling of magnetic fluids under magnetic actuation

    Science.gov (United States)

    Shojaeian, Mostafa; Yildizhan, Melike-Mercan; Coşkun, Ömer; Ozkalay, Ebrar; Tekşen, Yiğit; Gulgun, Mehmet Ali; Funda Yagci Acar, Havva; Koşar, Ali

    2016-09-01

    Nanofluids are becoming a significant candidate for new generation coolants to be used in industrial applications. In order to reduce clustering and sedimentation of nanoparticles and improve the heat transfer performance simultaneously, magnetic fluids prepared with magnetic Fe3O4 nanoparticles dispersed in water, which were placed in a pool and were exposed to varying magnetic fields to actuate nanoparticles in the system. The effect of magnetic actuation on boiling heat transfer characteristics and on the surface morphology of the pool was examined. An average enhancement of 29% in boiling heat transfer was achieved via magnetic actuation with rather low magnetic field (magnetic flux densities up to 11 mT) densities. Furthermore, it was observed that magnetic actuation significantly prevented the deposition and sedimentation of the nanoparticles in the pool. Otherwise, significant destabilization of nanoparticles causing aggregation and heavy sedimentation was present as a result of the performed surface analysis. Even though magnetic actuation reduced the sedimentation on the macroscale, the deposition of a thick and porous film occurred onto the pool floor, increasing the surface roughness.

  8. Enhanced viscoelastic property of iron oxide nanoparticle decorated organoclay fluid under magnetic field

    Science.gov (United States)

    Son, You-Hwan; Jung, Youngsoo; Roh, Heesuk; Lee, Jung-Kun

    2017-08-01

    Stable hydrophobic nanocomposites of magnetic nanoparticles and clay are prepared by the self-assembly of magnetite (Fe3O4) nanoparticles on surfaces of exfoliated clay platelets. Due to the attractive interaction between hydrophobic groups, oleic acid coated nanoparticles are strongly attached to the surface of cetyl trimethylammonium cation coated clay platelets in organic media. Crystal structure and magnetic property of composite particles are examined using electron microscopy, x-ray diffractometer and vibration sample magnetometer. In addition, composite particles are dispersed in mineral oil and rheological properties of composite particle suspensions are characterized using steady-state and oscillatory measurements. Magnetite nanoparticle decorated organoclay forms a tunable network in mineral oil. When a magnetic field is applied, the composite particle fluid exhibits higher storage modulus and maintains a solid-like property at larger strain. Our results show that the viscoelastic property of the magnetite nanoparticle decorated organoclay fluid is controlled by applying external magnetic field.

  9. A Fluid Dynamics Approach for the Computation of Non-linear Force-Free Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    Jing-Qun Li; Jing-Xiu Wang; Feng-Si Wei

    2003-01-01

    Inspired by the analogy between the magnetic field and velocity fieldof incompressible fluid flow, we propose a fluid dynamics approach for comput-ing nonlinear force-free magnetic fields. This method has the advantage that thedivergence-free condition is automatically satisfied, which is a sticky issue for manyother algorithms, and we can take advantage of modern high resolution algorithmsto process the force-free magnetic field. Several tests have been made based on thewell-known analytic solution proposed by Low & Lou. The numerical results arein satisfactory agreement with the analytic ones. It is suggested that the newlyproposed method is promising in extrapolating the active region or the whole sunmagnetic fields in the solar atmosphere based on the observed vector magnetic fieldon the photosphere.

  10. Complex windmill transformation producing new purely magnetic fluids

    NARCIS (Netherlands)

    Lozanovski, L.; Wylleman, L.

    2011-01-01

    Minimal complex windmill transformations of G2IB(ii) spacetimes (admitting a two-dimensional Abelian group of motions of the so-called Wainwright B(ii) class) are defined and the compatibility with a purely magnetic Weyl tensor is investigated. It is shown that the transformed spacetimes cannot be p

  11. Estimating the contribution of Brownian and Néel relaxation in a magnetic fluid through dynamic magnetic susceptibility measurements

    Energy Technology Data Exchange (ETDEWEB)

    Maldonado-Camargo, L. [Department of Chemical Engineering, University of Florida, Gainesville, FL 32611 (United States); Torres-Díaz, I. [J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL 32611 (United States); Chiu-Lam, A. [Department of Chemical Engineering, University of Florida, Gainesville, FL 32611 (United States); Hernández, M. [J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL 32611 (United States); Rinaldi, C., E-mail: carlos.rinaldi@bme.ufl.edu [Department of Chemical Engineering, University of Florida, Gainesville, FL 32611 (United States); J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL 32611 (United States)

    2016-08-15

    We demonstrate how dynamic magnetic susceptibility measurements (DMS) can be used to estimate the relative contributions of Brownian and Néel relaxation to the dynamic magnetic response of a magnetic fluid, a suspension of magnetic nanoparticles. The method applies to suspensions with particles that respond through Brownian or Néel relaxation and for which the characteristic Brownian and Néel relaxation times are widely separated. First, we illustrate this using magnetic fluids consisting of mixtures of particles that relax solely by the Brownian or Néel mechanisms. Then, it is shown how the same approach can be applied to estimate the relative contributions of Brownian and Néel relaxation in a suspension consisting of particles obtained from a single synthesis and whose size distribution straddles the transition from Néel to Brownian relaxation. - Highlights: • Method to estimate the contributions of the relaxation mechanism to the magnetic response. • Method applies to cases where the Brownian and Néel peaks do not overlap. • The method applies for ferrofluids prepared with as–synthesized particles.

  12. Immune Response Augmentation in Metastasized Breast Cancer by Localized Therapy Utilizing Biocompatible Magnetic Fluids. Addendum

    Science.gov (United States)

    2009-08-01

    research is to assess the efficacy of augmenting immune responses to breast cancer through the use of magneto-rheological fluid (MRF), suspensions of...poly(NIPAAm) onto silica nanoparticles using ATRP has been investigated by [5, 6]. In the present work, MRFs were synthesized from suspensions of...of Iron-Based Nanofluids ”, International Journal of Modern Physics B, Vol. 21, pp. 4774 – 4781, 2007 18. J. P. Jakubovics, “Magnetism and Magnetic

  13. Bianchi Type-I bulk viscous fluid string dust magnetized cosmological model in general relativity

    Indian Academy of Sciences (India)

    Raj Bali; Anjali

    2004-09-01

    Bianchi Type-I magnetized bulk viscous fluid string dust cosmological model is investigated. To get a determinate model, we have assumed the conditions and = constant where is the shear, the expansion in the model and the coefficient of bulk viscosity. The behaviour of the model in the presence and absence of magnetic field together with physical and geometrical aspects of the model are also discussed.

  14. 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

  15. 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.

  16. The chiral magnetic wave in an expanding QCD fluid

    CERN Document Server

    Taghavi, Seyed Farid

    2015-01-01

    As a consequence of the chiral anomaly, the hydrodynamics of hot QCD matter coupled to QED allows for a long-wavelength mode of chiral charge density, the chiral magnetic wave (CMW), that provides for a mechanism of electric charge separation along the direction of an external magnetic field. Here, we investigate the efficiency of this mechanism for values of the time-dependent magnetic field and of the energy density attained in the hot QCD matter of ultra-relativistic heavy ion collisions. To this end, we derive the CMW equations of motion for expanding systems by treating the CMW as a charge perturbation on top of an expanding Bjorken-type background field in the limit of small chemical potential. Both, approximate analytical and full numerical solutions to these equations of motion indicate that for the lifetime and thermodynamic conditions of ultra-relativistic heavy ion collisions, the efficiency of CMW-induced electric charge separation decreases with increasing center of mass energy and that the effec...

  17. Tunable flat band slow light in reconfigurable photonic crystal waveguides based on magnetic fluids

    DEFF Research Database (Denmark)

    Pu, Shengli; Wang, Haotian; Wang, Ning;

    2013-01-01

    A kind of two-dimensional photonic crystal line-defect waveguide with 45 -rotated square lattice is proposed to present slow light phenomena. Infiltrating the photonic crystal waveguide with appropriate magnetic fluids can generate very wide flat bands of guided modes, which give rise...

  18. Coupled fluid-flow and magnetic-field simulation of the Riga dynamo experiment

    NARCIS (Netherlands)

    Kenjereš, S.; Hanjalić, K.; Renaudier, S.; Stefani, F.; Gerbeth, G.; Gailitis, A.

    2006-01-01

    Magnetic fields of planets, stars, and galaxies result from self-excitation in moving electroconducting fluids, also known as the dynamo effect. This phenomenon was recently experimentally confirmed in the Riga dynamo experiment [ A. Gailitis et al., Phys. Rev. Lett. 84, 4365 (2000) ; A. Gailitis et

  19. A Noninvasive Method to Study Regulation of Extracellular Fluid Volume in Rats Using Nuclear Magnetic Resonance

    Science.gov (United States)

    Time-domain nuclear magnetic resonance (TD-NMR)-based measurement of body composition of rodents is an effective method to quickly and repeatedly measure proportions of fat, lean, and fluid without anesthesia. TD-NMR provides a measure of free water in a living animal, termed % f...

  20. On the possibility of using short chain length mono-carboxylic acids for stabilization of magnetic fluids

    Energy Technology Data Exchange (ETDEWEB)

    Avdeev, Mikhail V. [Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna Moscow Region (Russian Federation)]. E-mail: avd@nf.jinr.ru; Bica, Doina [Laboratory of Magnetic Fluids, CFATR, Romanian Academy, Timisoara Division, Timisoara (Romania); Vekas, Ladislau [National Center for Engineering of Systems with Complex Fluids, University Politehnica, Timisoara (NC ESCF-UPT) (Romania); Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest-Magurele (Romania); Marinica, Oana [National Center for Engineering of Systems with Complex Fluids, University Politehnica, Timisoara (NC ESCF-UPT) (Romania); Balasoiu, Maria [Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna Moscow Region (Russian Federation); Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, Budapest (Hungary); Aksenov, Victor L. [Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna Moscow Region (Russian Federation); Rosta, Laszlo [Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest-Magurele (Romania); Garamus, Vasil M. [GKSS Research Centre, Geesthacht (Germany); Schreyer, Andreas [GKSS Research Centre, Geesthacht (Germany)

    2007-04-15

    Short chain length mono-carboxylic acids (lauric and myristic acids) are used to coat magnetite nanoparticles in non-polar organic liquids, which results in highly stable magnetic fluids. The new fluids are compared with classical organic fluids stabilized by oleic acid (OA). Magnetic granulometry and small-angle neutron scattering (polarized mode) reveal a great difference in the particle size distribution function for the studied magnetic fluids, particularly a decrease in the characteristic particle radius of magnetite when lauric and myristic acids are used instead of OA.

  1. On the possibility of using short chain length mono-carboxylic acids for stabilization of magnetic fluids

    Science.gov (United States)

    Avdeev, Mikhail V.; Bica, Doina; Vékás, Ladislau; Marinica, Oana; Balasoiu, Maria; Aksenov, Victor L.; Rosta, László; Garamus, Vasil M.; Schreyer, Andreas

    2007-04-01

    Short chain length mono-carboxylic acids (lauric and myristic acids) are used to coat magnetite nanoparticles in non-polar organic liquids, which results in highly stable magnetic fluids. The new fluids are compared with classical organic fluids stabilized by oleic acid (OA). Magnetic granulometry and small-angle neutron scattering (polarized mode) reveal a great difference in the particle size distribution function for the studied magnetic fluids, particularly a decrease in the characteristic particle radius of magnetite when lauric and myristic acids are used instead of OA.

  2. Slow shocks and conduction fronts from Petschek reconnection of skewed magnetic fields: two-fluid effects

    CERN Document Server

    Longcope, D W

    2010-01-01

    In models of fast magnetic reconnection, flux transfer occurs within a small portion of a current sheet triggering stored magnetic energy to be thermalized by shocks. When the initial current sheet separates magnetic fields which are not perfectly anti-parallel, i.e. they are skewed, magnetic energy is first converted to bulk kinetic energy and then thermalized in slow magnetosonic shocks. We show that the latter resemble parallel shocks or hydrodynamic shocks for all skew angles except those very near the anti-parallel limit. As for parallel shocks, the structures of reconnection-driven slow shocks are best studied using two-fluid equations in which ions and electrons have independent temperature. Time-dependent solutions of these equations can be used to predict and understand the shocks from reconnection of skewed magnetic fields. The results differ from those found using a single-fluid model such as magnetohydrodynamics. In the two-fluid model electrons are heated indirectly and thus carry a heat flux alw...

  3. An SV-GMR Needle Sensor-Based Estimation of Volume Density of Magnetic Fluid inside Human Body

    Directory of Open Access Journals (Sweden)

    C. P. Gooneratne

    2008-01-01

    Full Text Available A spin-valve giant magneto-resistive (SV-GMR sensor of needle-type configuration is reported to estimate the volume density of magnetic fluid inside human body. The magnetic fluid is usually injected into human body to kill cancerous cell using hyperthermia-based treatment. To control the heat treatment, a good knowledge of temperature is very much essential. The SV-GMR-based needle-type sensor is used to measure the magnetic flux density of the magnetic fluid inside the human body from which the temperature is estimated. The needle-type sensor provides a semi-invasive approach of temperature determination.

  4. Aptamer conjugated paclitaxel and magnetic fluid loaded fluorescently tagged PLGA nanoparticles for targeted cancer therapy

    Energy Technology Data Exchange (ETDEWEB)

    Aravind, Athulya; Nair, Remya; Raveendran, Sreejith; Veeranarayanan, Srivani; Nagaoka, Yutaka; Fukuda, Takahiro; Hasumura, Takahashi; Morimoto, Hisao; Yoshida, Yasuhiko; Maekawa, Toru; Sakthi Kumar, D., E-mail: sakthi@toyo.jp

    2013-10-15

    Controlled and targeted drug delivery is an essential criterion in cancer therapy to reduce the side effects caused by non-specific drug release and toxicity. Targeted chemotherapy, sustained drug release and optical imaging have been achieved using a multifunctional nanocarrier constructed from poly (D, L-lactide-co-glycolide) nanoparticles (PLGA NPs), an anticancer drug paclitaxel (PTX), a fluorescent dye Nile red (NR), magnetic fluid (MF) and aptamers (Apt, AS1411, anti-nucleolin aptamer). The magnetic fluid and paclitaxel loaded fluorescently labeled PLGA NPs (MF-PTX-NR-PLGA NPs) were synthesized by a single-emulsion technique/solvent evaporation method using a chemical cross linker bis (sulfosuccinimidyl) suberate (BS3) to enable binding of aptamer on to the surface of the nanoparticles. Targeting aptamers were then introduced to the particles through the reaction with the cross linker to target the nucleolin receptors over expressed on the cancer cell surface. Specific binding and uptake of the aptamer conjugated magnetic fluid loaded fluorescently tagged PLGA NPs (Apt-MF-NR-PLGA NPs) to the target cancer cells induced by aptamers was observed using confocal microscopy. Cytotoxicity assay conducted in two cell lines (L929 and MCF-7) confirmed that targeted MCF-7 cancer cells were killed while control cells were unharmed. In addition, aptamer mediated delivery resulting in enhanced binding and uptake to the target cancer cells exhibited increased therapeutic effect of the drug. Moreover, these aptamer conjugated magnetic polymer vehicles apart from actively transporting drugs into specifically targeted tumor regions can also be used to induce hyperthermia or for facilitating magnetic guiding of particles to the tumor regions. - Highlights: • Aptamer escorted, theranostic biodegradable PLGA carriers were developed. • Can target cancer cells, control drug release, image and magnetically guide. • Highly specific to the targeted cancer cells thus delivering

  5. Spatial variation of the magnetic field inside laminar flows of a perfect conductive fluid

    Science.gov (United States)

    Duka, Bejo; Boçi, Sonila

    2017-01-01

    The steady state of a perfect conductive fluid in laminar flow resulting from the ‘Hall effect’ is studied. Using the Maxwell equations, the spatial variation of the magnetic field in the steady state is calculated for three cases of different fluid flow geometries: flow between two infinite parallel planes, flow between two coaxial infinite-long cylinders and flow between two concentric spheres. According to our calculation of the three cases, the spatial variation of the magnetic field depends on the flow velocity. The magnetic field is strengthened in layers where the velocity is greater, but this dependency is negligible for non relativistic flows. Our approach in this study provides an example of how to receive interesting results using only basic knowledge of physics and mathematics.

  6. Two-dimensional convection and interchange motions in fluids and magnetized plasmas

    DEFF Research Database (Denmark)

    Garcia, O.E.; Bian, N.H.; Naulin, V.

    2006-01-01

    In this contribution some recent investigations of two- dimensional thermal convection relevant to ordinary fluids as well as magnetized plasmas are reviewed. An introductory discussion is given of the physical mechanism for baroclinic vorticity generation and convective motions in stratified...... fluids, emphasizing its relation to interchange motions of non- uniformly magnetized plasmas. This is followed by a review of the theories for the onset of convection and quasi-linear saturation in driven-dissipative systems. Non-linear numerical simulations which result in stationary convective states....... The global bursting is interpreted in terms of a predator-prey regulation from the point of view of energetics. Finally, a discussion is given of the relevance of these phenomena to a variety of magnetized plasma experiments....

  7. Collisional transport across the magnetic field in drift-fluid models

    DEFF Research Database (Denmark)

    Madsen, Jens; Naulin, Volker; Nielsen, Anders Henry;

    2016-01-01

    Drift ordered fluid models are widely applied in studies of low-frequency turbulence in the edge and scrape-off layer regions of magnetically confined plasmas. Here, we show how collisional transport across the magnetic field is self-consistently incorporated into drift-fluid models without...... simulations. We further derive a computationally efficient, two-dimensional model, which can be time integrated for several turbulence de-correlation times using only limited computational resources. The model describes interchange turbulence in a two-dimensional plane perpendicular to the magnetic field...... located at the outboard midplane of a tokamak. The model domain has two regions modeling open and closed field lines. The model employs a computational expedient model for collisional transport. Numerical simulations show good agreement between the full and the simplified model for collisional transport....

  8. Beta-cyclodextrins conjugated magnetic Fe{sub 3}O{sub 4} colloidal nanoclusters for the loading and release of hydrophobic molecule

    Energy Technology Data Exchange (ETDEWEB)

    Lv, Shaonan; Song, Yubei; Song, Yaya; Zhao, Zhigang; Cheng, Changjing, E-mail: changjing_cheng@163.com

    2014-06-01

    Herein, we report a facile method to prepare beta-cyclodextrin (β-CD)-conjugated magnetic Fe{sub 3}O{sub 4} colloidal nanocrystal clusters (Fe{sub 3}O{sub 4}@GLY-CD) using (3-glycidyloxypropyl) trimethoxysilane (GLY) as the intermediate linker. The resulting Fe{sub 3}O{sub 4}@GLY-CD was characterized by several methods including Fourier transform infrared (FT-IR) spectroscopy, field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and vibrating sample magnetometer (VSM). In addition, the loading and release properties of the synthesized Fe{sub 3}O{sub 4}@GLY-CD for the hydrophobic molecule 8-anilino-1-naphthalenesulfonic acid ammonium salt (ANS) were also investigated. The results show that the Fe{sub 3}O{sub 4}@GLY-CD has a spherical structure with an average diameter of 186 nm and high saturated magnetism of 51.2 emu/g. The grafting of β-CD onto Fe{sub 3}O{sub 4} colloidal nanocrystal clusters can markedly increase the loading capacity of ANS because of β-CD/ANS inclusion complex formation. The in vitro delivery profile shows that the release of ANS from the Fe{sub 3}O{sub 4}@GLY-CD nanosystem exhibits an initial burst followed by a slow and steady release. Moreover, Fe{sub 3}O{sub 4}@GLY-CD also demonstrates a temperature-dependent release behavior for ANS owing to the effect of temperature on the association constants of β-CD/ANS inclusion complexes. The developed magnetic hybrid nanomaterial is expected to find potential applications in several fields including separation science and biomedicine.

  9. Fluid Simulation of the Ion Temperature Effects on a Collisional Magnetized Sheath of a Dusty Plasma

    Directory of Open Access Journals (Sweden)

    I Driouch

    2013-01-01

    Full Text Available The properties of magnetized dusty plasma sheath with finite ion temperature are studied using a fluid model. Hot electrons, fluid ions, neutral particles and cold fluid dust grains are taken into account in this system. Considering the cross section for collisions between the dust and neutrals has a power law dependence on the dust flow velocity, the fluid model is then solved numerically to obtain detailed sheath information under different ion temperatures. A significant change is observed in the quantities characterizing the sheath with respect to the cold ion assumption. In addition, the result reveals that the effect of ion temperature is more obvious on the dust dynamics in collisional sheath with constant cross section.

  10. 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

  11. Simulating magnetic nanoparticle behavior in low-field MRI under transverse rotating fields and imposed fluid flow

    Science.gov (United States)

    Cantillon-Murphy, P.; Wald, L. L.; Adalsteinsson, E.; Zahn, M.

    2010-09-01

    In the presence of alternating-sinusoidal or rotating magnetic fields, magnetic nanoparticles will act to realign their magnetic moment with the applied magnetic field. The realignment is characterized by the nanoparticle's time constant, τ. As the magnetic field frequency is increased, the nanoparticle's magnetic moment lags the applied magnetic field at a constant angle for a given frequency, Ω, in rad s -1. Associated with this misalignment is a power dissipation that increases the bulk magnetic fluid's temperature which has been utilized as a method of magnetic nanoparticle hyperthermia, particularly suited for cancer in low-perfusion tissue (e.g., breast) where temperature increases of between 4 and 7 °C above the ambient in vivo temperature cause tumor hyperthermia. This work examines the rise in the magnetic fluid's temperature in the MRI environment which is characterized by a large DC field, B0. Theoretical analysis and simulation is used to predict the effect of both alternating-sinusoidal and rotating magnetic fields transverse to B0. Results are presented for the expected temperature increase in small tumors ( ˜1 cm radius) over an appropriate range of magnetic fluid concentrations (0.002-0.01 solid volume fraction) and nanoparticle radii (1-10 nm). The results indicate that significant heating can take place, even in low-field MRI systems where magnetic fluid saturation is not significant, with careful the goal of this work is to examine, by means of analysis and simulation, the concept of interactive fluid magnetization using the dynamic behavior of superparamagnetic iron oxide nanoparticle suspensions in the MRI environment. In addition to the usual magnetic fields associated with MRI, a rotating magnetic field is applied transverse to the main B0 field of the MRI. Additional or modified magnetic fields have been previously proposed for hyperthermia and targeted drug delivery within MRI. Analytical predictions and numerical simulations of the

  12. High-resolution proton nuclear magnetic resonance spectroscopy of ovarian cyst fluid.

    Science.gov (United States)

    Boss, E A; Moolenaar, S H; Massuger, L F; Boonstra, H; Engelke, U F; de Jong, J G; Wevers, R A

    2000-08-01

    Most ovarian tumors are cystic structures containing variable amounts of fluid. Several studies of ovarian cyst fluid focus on one specific metabolite using conventional assay systems. We examined the potential of (1)H-nuclear magnetic resonance spectroscopy in evaluation of the overall metabolic composition of cyst fluid from different ovarian tumors. Ovarian cyst fluid samples obtained from 40 patients with a primary ovarian tumor (12 malignant and 28 benign) were examined. After deproteinization and pD standardization, we performed (1)H-NMR spectroscopy on a 600 MHz instrument. With (1)H-NMR spectroscopy we found detectable concentrations of 36 metabolites with high intersample variation. A number of unassigned resonances as well as unexpected metabolites were found. We introduce an overall inventory of the low-molecular-weight metabolites in ovarian cyst fluid with corresponding resonances. Significant differences in concentration (p overview of low-molecular-weight proton-containing metabolities present in ovarian cyst fluid samples. The metabolic composition of cyst fluid differs significantly between benign and malignant ovarian tumors. Furthermore, differences between benign subgroups possibly related to histopathological behaviour can be detected. The presence of N-acetyl aspartic acid and 5-oxoproline exclusively in serous cystadenoma samples is remarkable. Future studies will concentrate on these findings and explore the possibilities of extrapolating information from the in vitro studies to in vivo practice, in which metabolic differences between malignant and benign subtypes can be of great importance in a pre-operative phase.

  13. PREPARATION OF Fe3O4/PSt MAGNETIC PARTICLES IN THE PRESENCE OF MAGNETIC FLUID IN ETHANOL/WATER MIXTURE

    Institute of Scientific and Technical Information of China (English)

    Xiao-bin Ding; Zong-hua Sun; Guo-xiang Wan; Ying-yan Jiang

    1999-01-01

    Fe3O4/Polystyrene(PSt) magnetic particles with core/shell structure have been prepared in the presence of Fe3O4 magnetic fluid in ethanol/water medium by dispersion polymerization of styrene. A Fe3O4particle formation mechanism was proposed. According to this mechanism, the size of particle nuclei is determined by the extent of aggregation of Fe3O4/oligomer. Magnetic particles with diameter ranging from 5to 200μm were prepared under different reaction conditions. Some polymerization parameters such as the concentration of monomer, stabilizer, initiator, and ethanol which affect particle size and size distribution are discussed and their effect on particle formation are explained by the proposed mechanism.

  14. Transient response of sheared magnetic powder excited by a stepwise magnetic field and its comparison with ER and MR fluids

    Science.gov (United States)

    Chen, KaiKai; Tian, Yu; Shan, Lei; Jiang, Jile

    2013-09-01

    The transient shear behavior of magnetic powder (MP) excited by a stepwise magnetic field in a rotational magnetic powder clutch (MPC) was experimentally studied. The experiment showed that the stable shear stress was approximately proportional to the applied magnetic flux density. The characteristic rising time of the shear stress was independent of the strength of the magnetic field and was affected by the shear rate. It took less than 0.1 s for the shear stress to rise to 63% (1 - e-1) of the stable value. The transient shear stress rising process consisted of two subprocesses: the chain forming process which was less than 100 ms, and the chain coarsening process lasting for dozens of seconds. Upon switching the field off, the shear stress fell rapidly to zero in 0.1 s. Control methods to improve the transient response time of the MPC were discussed and experimentally verified: applying a low voltage in advance; applying a high level voltage for the torque to rise to the target torque and then a desired voltage. These transient characteristics of MP were compared with those of electrorheological (ER) and magneto-rheological (MR) fluids and actuators. The study provides a better understanding of MP excited by a magnetic field and the implications for application.

  15. Sustained Turbulence in Differentially Rotating Magnetized Fluids at Low Magnetic Prandtl Number

    CERN Document Server

    Nauman, Farrukh

    2016-01-01

    We show for the first time that sustained turbulence is possible at low magnetic Prandtl number for Keplerian flows with no mean magnetic flux. Our results indicate that increasing the vertical domain size is equivalent to increasing the dynamical range between the energy injection scale and the dissipative scale. This has important implications for a large variety of differentially rotating systems with low magnetic Prandtl number such as protostellar disks and laboratory experiments.

  16. Sustained Turbulence in Differentially Rotating Magnetized Fluids at Low Magnetic Prandtl Number

    DEFF Research Database (Denmark)

    Nauman, Farrukh; Pessah, Martin E.

    2016-01-01

    We show for the first time that sustained turbulence is possible at low magnetic Prandtl number for Keplerian flows with no mean magnetic flux. Our results indicate that increasing the vertical domain size is equivalent to increasing the dynamical range between the energy injection scale...... and the dissipative scale. This has important implications for a large variety of differentially rotating systems with low magnetic Prandtl number such as protostellar disks and laboratory experiments....

  17. 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.

  18. Comparative structure analysis of magnetic fluids at interface with silicon by neutron reflectometry

    Energy Technology Data Exchange (ETDEWEB)

    Avdeev, M.V. [Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna (Russian Federation); Petrenko, V.I., E-mail: vip@nf.jinr.ru [Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna (Russian Federation); Kyiv Taras Shevchenko National University, Kyiv (Ukraine); Gapon, I.V. [Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna (Russian Federation); Kyiv Taras Shevchenko National University, Kyiv (Ukraine); Bulavin, L.A. [Kyiv Taras Shevchenko National University, Kyiv (Ukraine); Vorobiev, A.A. [Department of Physics and Astronomy, Uppsala University (Sweden); Soltwedel, O. [Max-Planck-Institut for Solid State Research, Outstation at MLZ, Garching (Germany); Balasoiu, M. [Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna (Russian Federation); National Institute of Physics and Nuclear Engineering, Bucharest (Romania); Vekas, L. [Center for Fundamental and Advanced Technical Research, Romanian Academy-Timisoara Branch, Timisoara (Romania); Zavisova, V.; Kopcansky, P. [Institute of Experimental Physics, SAS, Kosice (Slovakia)

    2015-10-15

    Graphical abstract: - Highlights: • Nanoparticles adsorption is studied by neutron reflectometry. • Non-polar and aqueous ferrofluids at interface are considered and compared. • Just one well-defined adsorption layer of nanoparticles is observed. • Preferable adsorption of non-aggregated particles from bulk is concluded. - Abstract: The adsorption of surfactant coated magnetic nanoparticles from highly stable magnetic fluids on crystalline functionalized silicon is studied by neutron reflectometry. Two types of magnetic fluids based on nanomagnetite dispersed and stabilized in non-polar organic solvent (deuterated benzene) and strongly polar solvent (heavy water) are considered. In both cases the interface shows the formation of just one well-defined adsorption layer of nanoparticles, which is insensitive to the effect of the external magnetic field. Still, the particle concentration in the benzene-based fluid is higher in the vicinity to the silicon surface as compared to the bulk distribution. Despite the presence of an aggregate fraction in the water-based system the width of the adsorption layer is consistent with the size of separated particles, thus showing the preferable adsorption of non-aggregated particles.

  19. The Analysis of the Structural Parameters of Magnetic Fluids with SAXS and MGA Techniques

    Directory of Open Access Journals (Sweden)

    P.A. Ryapolov

    2015-12-01

    Full Text Available Purpose – to study the structural parameters of the magnetite particles surrounded by the surfactant in the various carrier liquids using SAXS and based on the magnetization curve obtained applying ballistic method. The samples of the magnetite magnetic fluid based on water, engine oil and kerosene were investigated in this paper. Methodology – three samples of magnetic fluid were chosen for studying. Samples No 1 and No 2 were obtained at the UNESCO department of “Energy Conservation and Renewable Energy Sources”, Belarusian National Technical University. Sample No 3 was obtained in the Fundamental Scientific Research Laboratory of Applied Ferrohydrodynamics of Ivanovo State Power Engineering University. SAXS experiment was conducted using Anton Paar SAXSess mc2 analyzer at the Regional Centre of Nanotechnology of Southwest State University. Originality / value – The value of this work is to obtain new data on the physical parameters of the magnetic fluid samples. Findings – the derived surfactant shell width, which for the samples No 2, 3 was 1,8-1,9 nm, for the sample No 1 surfactant shell width was 3.5 nm, the excess of the calculated width of the surfactant layer can be explained due to the presence of a double layer of stabilizer.

  20. Conductivity maximum in a charged colloidal suspension

    Energy Technology Data Exchange (ETDEWEB)

    Bastea, S

    2009-01-27

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

  1. Dynamics of magnetic nanoparticles in a viscous fluid driven by rotating magnetic fields

    Science.gov (United States)

    Usadel, Klaus D.

    2017-03-01

    The rotational dynamics of magnetic nanoparticles in rotating magnetic fields in the presence of thermal noise is studied both theoretically and by performing numerical calculations. Equations for the dynamics of particles with uniaxial magnetic anisotropy are studied and the phase lag between the rotating magnetic moment and the driving field is obtained. It is shown that for large enough anisotropy energy the magnetic moment is locked to the anisotropy axis so that the particle behaves like a rotating magnetic dipole. The corresponding rigid dipole model is analyzed both numerically by solving the appropriate Fokker-Planck equation and analytically by applying an effective field method. In the special case of a rotating magnetic field applied analytic results are obtained in perfect agreement with numerical results based on the Fokker-Planck equation. The analytic formulas derived are not restricted to small magnetic fields or low frequencies and are therefore important for applications. The illustrative numerical calculations presented are performed for magnetic parameters typical for iron oxide.

  2. Kelvin-Helmholtz discontinuity in two superposed viscous conducting fluids in a horizontal magnetic field

    Directory of Open Access Journals (Sweden)

    Khan Aiyub

    2008-01-01

    Full Text Available The Kelvin-Helmholtz discontinuity in two superposed viscous conducting fluids has been investigated in the taking account of effects of surface tension, when the whole system is immersed in a uniform horizontal magnetic field. The streaming motion is assumed to be two-dimensional. The stability analysis has been carried out for two highly viscous fluid of uniform densities. The dispersion relation has been derived and solved numerically. It is found that the effect of viscosity, porosity and surface tension have stabilizing influence on the growth rate of the unstable mode, while streaming velocity has a destabilizing influence on the system.

  3. Nonequilibrium Brownian dynamics analysis of negative viscosity induced in a magnetic fluid subjected to both ac magnetic and shear flow fields.

    Science.gov (United States)

    Morimoto, Hisao; Maekawa, Toru; Matsumoto, Yoichiro

    2002-06-01

    We study the rheological and magnetic characteristics of a magnetic fluid. The system, which we investigate, is as follows. Ferromagnetic particles are dispersed in a solvent, which is subjected to both ac magnetic and shear flow fields. The translational and rotational motions of particles are calculated by the Brownian dynamics method based on Langevin equations and the rheological and magnetic characteristics of the magnetic fluid system are estimated. First, we investigate the rheological and magnetic characteristics of the system in a dc magnetic field and then we analyze the effect of an ac magnetic field on those characteristics. We find that the negative viscosity effect is induced at a certain frequency range of the ac magnetic field. We also find that there are two main mechanisms responsible for the occurrence of negative viscosity. (1) Resonance between the rotational motions of the dipoles of particles and the fluctuation of ac magnetic fields occurs when applied magnetic fields are weak compared to the shear rate, in which case particles can still rotate in magnetic fields. Beyond this resonance frequency, negative viscosity appears. (2) The magnetic dipole moments of particles are forced to stay in the direction of the magnetic field when strong magnetic fields are applied in relatively low shear flow fields. However, negative viscosity occurs when the frequency of external magnetic fields exceeds a critical value, in which case the dipoles rotate continuously in a shear flow without stopping. In both cases, the mean angular velocity of the particles becomes higher than that of the solvent.

  4. Simulating Magnetic Reconnection Experiment (MRX) with a Guide Field using Fluid Code, HiFi

    Science.gov (United States)

    Budner, Tamas; Chen, Yangao; Meier, Eric; Ji, Hantao; MRX Team

    2015-11-01

    Magnetic reconnection is a phenomenon that occurs in plasmas when magnetic field lines effectively ``break'' and reconnect resulting in a different topological configuration. In this process, energy that was once stored in the magnetic field is transfered into the thermal velocity of the particles, effectively heating the plasma. MRX at the Princeton Plasma Physics Laboratory creates the conditions under which reconnection can occur by initially ramping the current in two adjacent coils and then rapidly decreasing with and without a guide magnetic field along the reconnecting current. We simulate this experiment using a fluid code called HiFi, an implicit and adaptive high order spectral element modeling framework, and compare our results to experimental data from MRX. The purpose is to identify physics behind the observed reconnection process for the field line break and the resultant plasma heating.

  5. Chromospheric magnetic reconnection: Two-fluid simulations of coalescing current loops

    CERN Document Server

    Smith, P D

    2008-01-01

    Aims: To investigate magnetic reconnection rates during the coalescence of two current loops in the solar chromosphere, by altering the neutral-hydrogen to proton density ratio, ioniziation/recombination coefficients, collision frequency and relative helicity of the loops. Methods: 2.5D numerical simulations of the chromosphere were conducted using a newly developed two-fluid (ion-neutral) numerical code. Developed from the Artificial Wind scheme, the numerical code includes the effects of ion-neutral collisions, ionization/recombination, thermal/resistive diffusivity and collisional/resistive heating. Results: It was found that the rates of magnetic reconnection strongly depend on the neutral-hydrogen to proton density ratio; increasing the density ratio by a thousand-fold decreased the rate of magnetic reconnection by twenty-fold. This result implies that magnetic reconnection proceeds significantly faster in the upper chromosphere, where the density of ions (protons) and neutral-hydrogen is comparable, tha...

  6. Nano-micro composite magnetic fluids: Magnetic and magnetorheological evaluation for rotating seal and vibration damper applications

    Science.gov (United States)

    Marinică, Oana; Susan-Resiga, Daniela; Bălănean, Florica; Vizman, Daniel; Socoliuc, Vlad; Vékás, Ladislau

    2016-05-01

    In this paper, static magnetic properties and magnetorheological behavior of a set of 12 nano-micro composite magnetic fluids (CMFs) were studied. The samples with a ferromagnetic particle volume fraction ranging in a large interval φFe = (1 ÷ 44) % were prepared by adding carbonyl iron powder in a highly concentrated transformer oil-based ferrofluid (FF). The ferrofluid has the magnetite volume fraction of φFe3O4 = 22.90 % and saturation magnetization of Ms = 74 kA / m (930 Gs). No further additives were used in order to prevent sedimentation. It was noticed an increase of the static yield stress, of about 3 orders of magnitude, with the increase of the total solid volume fraction of samples and with the increase of the magnetic field, which varied between 0 kA/m and 950 kA/m. The dynamic yield stress (Herschel-Bulkley model) τHB of the samples strongly increases with the magnetic field and shows a slight tendency of saturation for higher intensities of the magnetic field. There is a less pronounced increase of τHB, about an order of magnitude with the increasing volume fraction of the iron particles. The relative viscosity increase induced by the magnetic field reaches a maximum for both considered shear rates: γ ṡ = 7.85s-1 and γ ṡ = 88.41s-1 and it was revealed an optimal volume fraction of Fe particles, φFe = 20 % , corresponding to a total volume fraction of φtot ≈ 38 % , at which the magnetoviscous effect has its maximum value. The magnetic properties and also the magnetorheological and the magnetoviscous behavior of highly concentrated ferrofluid-based CMFs can be controlled by the addition of iron microparticles in order to attain the optimal concentration for the envisaged engineering applications, rotating seals and magnetorheological vibration dampers.

  7. Monitoring fluid evolution in an Engineered Barrier System using NEO-magnets

    Science.gov (United States)

    Rigonat, N.; Butler, I. B.

    2015-12-01

    Long-term monitoring of the evolution of the engineered barrier system (EBS) of a Geological Disposal Facility (GDF) is important for establishing the safety case for deep disposal of the UK inventory of high level radioactive waste. With a view to developing techniques for remote fluid monitoring using magnetic properties, we have examined the correlation between the corrosion properties of NEO-magnets and related changes in the magnetic properties of the alloy with fluid chemistry and crystal-chemical changes of the Na-bentonite matrix. Batch experiments comprised fragments of NEO-magnets with deionised water, saline and alkaline solution both in the presence and absence of MX-80 bentonite, and were performed in sealed vessels for durations of up to 5 months at 70°C. This study combined PXRD, thermomagnetic and hysteresis analysis to demonstrate how progressive hydrogenation of the main magnetic phase led to a maximum loss of remanence and coercitivity and increasing Curie temperature in the samples reacted with deionised water with the samples reacted in saline and alkaline solutions showing smaller changes. Semi-quantitative analysis allowed comparison of the Curie temperatures with crystal-chemical parameters. This reveals a clear positive correlation of increasing lattice parameters a and c (and cell volume) with mean hydrogens per unit formula and the Curie temperature of the product NdFeB hydrides. Precipitation of Nd and Fe hydrides/oxyhydroxides is also demonstated by the PXRD data. A crucial role is played by the transformations occurring to the smectite matrix, in particular by the cation exchange in the interlayer, which causes precipitation of highly charged K- and Ca-smectites. This study demonstrates how NEO-magnets are capable of detecting water saturation in the EBS, and that the NdFeB corrosion properties are strongly controlled by the initial fluid composition and presence / absence of the bentonite matrix.

  8. Shale characteristics impact on Nuclear Magnetic Resonance (NMR fluid typing methods and correlations

    Directory of Open Access Journals (Sweden)

    Mohamed Mehana

    2016-06-01

    Full Text Available The development of shale reservoirs has brought a paradigm shift in the worldwide energy equation. This entails developing robust techniques to properly evaluate and unlock the potential of those reservoirs. The application of Nuclear Magnetic Resonance techniques in fluid typing and properties estimation is well-developed in conventional reservoirs. However, Shale reservoirs characteristics like pore size, organic matter, clay content, wettability, adsorption, and mineralogy would limit the applicability of the used interpretation methods and correlation. Some of these limitations include the inapplicability of the controlling equations that were derived assuming fast relaxation regime, the overlap of different fluids peaks and the lack of robust correlation to estimate fluid properties in shale. This study presents a state-of-the-art review of the main contributions presented on fluid typing methods and correlations in both experimental and theoretical side. The study involves Dual Tw, Dual Te, and doping agent's application, T1-T2, D-T2 and T2sec vs. T1/T2 methods. In addition, fluid properties estimation such as density, viscosity and the gas-oil ratio is discussed. This study investigates the applicability of these methods along with a study of the current fluid properties correlations and their limitations. Moreover, it recommends the appropriate method and correlation which are capable of tackling shale heterogeneity.

  9. Stationary instability of an axiosymmetric fluid flow in a rotating magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Kapusta, A.B.; Zibol' d, A.F.

    1977-07-01

    A study is made in a noninduction approximation of the effect that the profile deformation of a primary velocity and the interactions between secondary flows and a primary magnetic field have on the stationary instability of an axiosymmetric fluid flow in a rotating magnetic field. The critical state was shown to be determined by two or three independent criteria. Two regions of absolute primary flow stability were identified, and the critical values for the Reynolds number for these regions were calculated. Profiles of velocity perturbances and secondary flow lines were constructed for various sets of values. 6 references, 3 figures, 2 tables.

  10. 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

  11. Fluid-enabled significant enhancement and active tuning of magnetic resonances in free-standing plasmonic metamaterials.

    Science.gov (United States)

    Leong, Eunice Sok Ping; Liu, Yan Jun; Deng, Jie; Fong, Yih Ting; Zhang, Nan; Wu, Si Ji; Teng, Jing Hua

    2014-10-07

    We report significantly enhanced magnetic resonance by fluid infiltration in a free-standing metamaterial that consists of metal-dielectric-metal films on an ultrathin Si3N4 membrane patterned with etched through nanohole arrays. When different fluids are drop-casted on the structure, the magnetic resonance has high sensitivities of 282 nm per RIU in peak shift and 12% per RIU in peak intensity change, whereas the electric resonance has nearly no changes. This work shows a promising way of using fluids to actively tune the magnetic resonance of metamaterial structures by combining with micro/nano-fluidic technologies.

  12. Colloidal Nanocrystals of Wurtzite Zn 1-xCox0 (0 ≤ x ≥ 1) Models of Spinodal Decomposition in an Oxide Diluted Magnetic Semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    White, Michael A.; Ochsenbein, Stefan T.; Gamelin, Daniel R.

    2008-11-25

    Magnetic-ion-rich nanoscale inclusions formed by spinodal decomposition have been observed in many diluted magnetic semiconductors and have recently been implicated in the ferromagnetic ordering observed in some of these materials. In this study, colloidal nanocrystals of the ternary alloy wurtzite Zn1-xCoxO, with x ranging from 0.0 (w-ZnO) to 1.0 (w-CoO), have been synthesized as model systems for the proposed spinodal decomposition nanostrucures of ferromagnetic Zn1-xCoxO thin films and powders. As freestanding nanocrystals, these phases do not show any signs of ferromagnetism or superparamagnetism at any value of x. Changes in the electronic absorption and magnetic circular dichroism (MCD) spectra with x are described that should allow optical identification of spinodal decomposition in other Zn1-xCoxO samples. Optical and magneto-optical spectroscopic results are presented for the end member of this series (w-CoO), apparently for the first time, and show this binary oxide to be an indirect gap chargetransfer insulator with Eg ≈ 2.3 eV.

  13. Colloidal Nanocrystals of Wurtzite Zn1-xCoxO (0 ≤ x ≤ 1): Models of Spinodal Decomposition in an Oxide Diluted Magnetic Semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    White, Michael A.; Ochsenbein, Stefan T.; Gamelin, Daniel R.

    2008-11-25

    Magnetic-ion-rich nanoscale inclusions formed by spinodal decomposition have been observed in many diluted magnetic semiconductors and have recently been implicated in the ferromagnetic ordering observed in some of these materials. In this study, colloidal nanocrystals of the ternary alloy wurtzite Zn1-xCoxO, with x ranging from 0.0 (w-ZnO) to 1.0 (w-CoO), have been synthesized as model systems for the proposed spinodal decomposition nanostrucures of ferromagnetic Zn1-xCoxO thin films and powders. As freestanding nanocrystals, these phases do not show any signs of ferromagnetism or superparamagnetism at any value of x. Changes in the electronic absorption and magnetic circular dichroism (MCD) spectra with x are described that should allow optical identification of spinodal decomposition in other Zn1-xCoxO samples. Optical and magneto-optical spectroscopic results are presented for the end member of this series (w-CoO), apparently for the first time, and show this binary oxide to be an indirect gap chargetransfer insulator with Eg ≈ 2.3 eV.

  14. Facile and efficient one-pot solvothermal and microwave-assisted synthesis of stable colloidal solutions of MFe{sub 2}O{sub 4} spinel magnetic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Solano, Eduardo; Perez-Mirabet, Leonardo [Universitat Autonoma de Barcelona, Departament de Quimica (Spain); Martinez-Julian, Fernando; Guzman, Roger; Arbiol, Jordi; Puig, Teresa; Obradors, Xavier [Institut de Ciencia de Materials de Barcelona, ICMAB-CSIC (Spain); Yanez, Ramon [Universitat Autonoma de Barcelona, Departament de Quimica (Spain); Pomar, Alberto; Ricart, Susagna, E-mail: ricart@icmab.es [Institut de Ciencia de Materials de Barcelona, ICMAB-CSIC (Spain); Ros, Josep [Universitat Autonoma de Barcelona, Departament de Quimica (Spain)

    2012-08-15

    Well-defined synthesis conditions of high quality MFe{sub 2}O{sub 4} (M = Mn, Fe, Co, Ni, Zn, and Cu) spinel ferrite magnetic nanoparticles, with diameters below 10 nm, have been described based on facile and efficient one-pot solvothermal or microwave-assisted heating procedures. Both methods are reproducible and scalable and allow forming concentrated stable colloidal solutions in polar solvents, but microwave-assisted heating allows reducing 15 times the required annealing time and leads to an enhanced monodispersity of the nanoparticles. Non-agglomerated nanoparticles dispersions have been achieved using a simple one-pot approach where a single compound, triethyleneglycol, behaves at the same time as solvent and capping ligand. A narrow nanoparticle size distribution and high quality crystallinity have been achieved through selected nucleation and growth conditions. High resolution transmission electron microscopy images and electron energy loss spectroscopy analysis confirm the expected structure and composition and show that similar crystal faceting has been formed in both synthetic approaches. The spinel nanoparticles behave as ferrimagnets with a high saturation magnetization and are superparamagnetic at room temperature. The influence of synthesis route on phase purity and unconventional magnetic properties is discussed in some particular cases such as CuFe{sub 2}O{sub 4}, CoFe{sub 2}O{sub 4}, and ZnFe{sub 2}O{sub 4}.

  15. A tunable cancer cell filter using magnetic beads: cellular and fluid dynamic simulations

    CERN Document Server

    Gusenbauer, Markus; Bance, Simon; Exl, Lukas; Reichel, Franz; Oezelt, Harald; Schrefl, Thomas

    2011-01-01

    In the field of biomedicine magnetic beads are used for drug delivery and to treat hyperthermia. Here we propose to use self-organized bead structures to isolate circulating tumor cells using lab-on-chip technologies. Typically blood flows past microposts functionalized with antibodies for circulating tumor cells. Creating these microposts with interacting magnetic beads makes it possible to tune the geometry in size, position and shape. We develop a simulation tool that combines micromagnetics, discrete particle dynamics and fluid dynamics, in order to design micropost arrays made of interacting beads. For the simulation of blood flow we use the Lattice-Boltzmann method with immersed elastic blood cell models. Parallelization distributes large fluid and particle dynamic simulations over available resources to reduce overall calculation time.

  16. Simulation of fluid flow induced by opposing ac magnetic fields in a continuous casting mold

    Energy Technology Data Exchange (ETDEWEB)

    Chang, F.C.; Hull, J.R. [Argonne National Lab., IL (United States); Beitelman, L. [J. Mulcahy Enterprises, Whitby, ON (Canada)

    1995-07-01

    A numerical simulation was performed for a novel electromagnetic stirring system employing two rotating magnetic fields. The system controls stirring flow in the meniscus region of a continuous casting mold independently from the stirring induced within the remaining volume of the mold by a main electromagnetic stirrer (M-EMS). This control is achieved by applying to the meniscus region an auxiliary electromagnetic field whose direction of rotation is opposite to that of the main magnetic field produced by the M-EMS. The model computes values and spatial distributions of electromagnetic parameters and fluid flow in the stirred pools of mercury in cylindrical and square geometries. Also predicted are the relationships between electromagnetics and fluid flows pertinent to a dynamic equilibrium of the opposing stirring swirls in the meniscus region. Results of the numerical simulation compared well with measurements obtained from experiments with mercury pools.

  17. Modeling and Control of Magnetic Fluid Deformable Mirrors for Adaptive Optics Systems

    CERN Document Server

    Wu, Zhizheng; Ben Amara, Foued

    2013-01-01

    Modeling and Control of Magnetic Fluid Deformable Mirrors for Adaptive Optics Systems presents a novel design of wavefront correctors based on magnetic fluid deformable mirrors (MFDM) as well as corresponding control algorithms. The presented wavefront correctors are characterized by their linear, dynamic response. Various mirror surface shape control algorithms are presented along with experimental evaluations of the performance of the resulting adaptive optics systems. Adaptive optics (AO) systems are used in various fields of application to enhance the performance of optical systems, such as imaging, laser, free space optical communication systems, etc. This book is intended for undergraduate and graduate students, professors, engineers, scientists and researchers working on the design of adaptive optics systems and their various emerging fields of application. Zhizheng Wu is an associate professor at Shanghai University, China. Azhar Iqbal is a research associate at the University of Toronto, Canada. Foue...

  18. 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

  19. 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.

  20. Phase autowaves in the near-electrode layer in the electrochemical cell with a magnetic fluid

    Science.gov (United States)

    Chekanov, V. V.; Kandaurova, N. V.; Chekanov, V. S.

    2017-06-01

    A change in color of the thin pellicle when light is reflected from the surface of the magnetic fluid at the interface with the transparent electrode in the electric field was observed. The formation of variable thickness near-electrode layer leads to a change in the spectrum of the reflected light depending on the applied voltage. Autowaves, that were observed in the layer are a unique object for the study of self-organization process.

  1. Vlasov fluid stability of a 2-D plasma with a linear magnetic field null

    Energy Technology Data Exchange (ETDEWEB)

    Kim, J.S.

    1984-01-01

    Vlasov fluid stability of a 2-dimensional plasma near an O type magnetic null is investigated. Specifically, an elongated Z-pinch is considered, and applied to Field Reversed Configurations at Los Alamos National Laboratory by making a cylindrical approximation of the compact torus. The orbits near an elliptical O type null are found to be very complicated; the orbits are large and some are stochastic. The kinetic corrections to magnetohydrodynamics (MHD) are investigated by evaluating the expectation values of the growth rates of a Vlasov fluid dispersion functional by using set of trial functions based on ideal MHD. The dispersion functional involves fluid parts and orbit dependent parts. The latter involves phase integral of two time correlations. The phase integral is replaced by the time integral both for the regular and for the stochastic orbits. Two trial functions are used; one has a large displacement near the null and the other away from the null.

  2. Impact of inclined magnetic field on micropolar Casson fluid using Keller box algorithm

    Science.gov (United States)

    Iqbal, Z.; Mehmood, R.; Azhar, Ehtsham; Mehmood, Zaffar

    2017-04-01

    The present study examines the influence of an inclined magnetic field on a micropolar Casson fluid flow over a stretching sheet. Viscous dissipation effects are also taken into consideration. The governing physical problem is presented using the traditional Navier-Stokes theory. By means of the scaling group of transformation, a consequential system of equations is transformed into a set of nonlinear ordinary differential equations which are then solved using the implicit finite-difference approximation (Keller box method). The working fluid is examined for several sundry parameters graphically and in tabular form. It is observed that with an increase in inclination angle, the velocity profile decreases while temperature enhances. The Eckert number enhances flow velocity and temperature, whereas it decreases shear stress at the wall and heat transfer rate. The rheological fluid parameter contributes to the decline of velocity and temperature for weak as well as strong concentrations of micro elements.

  3. Vlasov Fluid stability of a 2-D plasma with a linear magnetic field null

    Energy Technology Data Exchange (ETDEWEB)

    Kim, J.S.

    1984-01-01

    Vlasov Fluid stability of a 2-dimensional plasma near an O type magnetic null is investigated. Specifically, an elongated Z-pinch is considered, and applied to Field Reversed Configurations at Los Alamos National Laboratory by making a cylindrical approximation of the compact torus. The orbits near an elliptical O type null are found to be very complicated; the orbits are large and some are stochastic. The kinetic corrections to magnetohydrodynamics (MHD) are investigated by evaluating the expectation values of the growth rates of a Vlasov Fluid dispersion functional by using a set of trial functions based on ideal MHD. The dispersion functional involves fluid parts and orbit dependent parts. The latter involves phase integral of two time correlations. The phase integral is replaced by the time integral both for the regular and for the stochastic orbits. Two trial functions are used; one has a large displacement near the null and the other away from the null.

  4. Parametric investigation of heating due to magnetic fluid hyperthermia in a tumor with blood perfusion

    Energy Technology Data Exchange (ETDEWEB)

    Liangruksa, Monrudee [Department of Engineering Science and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 (United States); Ganguly, Ranjan [Department of Power Engineering, Jadavpur University, Kolkata 700098 (India); Puri, Ishwar K., E-mail: ikpuri@vt.ed [Department of Engineering Science and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 (United States)

    2011-03-15

    Magnetic fluid hyperthermia (MFH) is a cancer treatment that can selectively elevate the tumor temperature without significantly damaging the surrounding healthy tissue. Optimal MFH design requires a fundamental parametric investigation of the heating of soft materials by magnetic fluids. We model the problem of a spherical tumor and its surrounding healthy tissue that are heated by exciting a homogeneous dispersion of magnetic nanoparticles infused only into the tumor with an external AC magnetic field. The key dimensionless parameters influencing thermotherapy are the Peclet, Fourier, and Joule numbers. Analytical solutions for transient and steady hyperthermia provide correlations between these parameters and the portions of tumor and healthy tissue that are subjected to a threshold temperature beyond which they are damaged. Increasing the ratio of the Fourier and Joule numbers also increases the tumor temperature, but doing so can damage the healthy tissue. Higher magnetic heating is required for larger Peclet numbers due to the larger convection heat loss that occurs through blood perfusion. A comparison of the model predictions with previous experimental data for MFH applied to rabbit tumors shows good agreement. The optimal MFH conditions are identified based on two indices, the fraction I{sub T} of the tumor volume in which the local temperature is above a threshold temperature and the ratio I{sub N} of the damaged normal tissue volume to the tumor tissue volume that also lies above it. The spatial variation in the nanoparticle concentration is also considered. A Gaussian distribution provides efficacy while minimizing the possibility of generating a tumor hot spot. Varying the thermal properties of tumor and normal tissue alters I{sub T}and I{sub N} but the nature of the temperature distribution remains unchanged. - Research highlights: > Analytical model of magnetic fluid hyperthermia of tumor tissue perfused with magnetic nanoparticles that is surrounded

  5. Stability of plane Poiseuille flow of viscoelastic fluids in the presence of a transverse magnetic field

    Directory of Open Access Journals (Sweden)

    Hifdi Ahmed

    2012-07-01

    Full Text Available The linear stability of plan Poiseuille flow of an electrically conducting viscoelastic fluid in the presence of a transverse magnetic field is investigated numerically. The fourth-order Sommerfeld equation governing the stability analysis is solved by spectral method with expansions in lagrange’s polynomials, based on collocation points of Gauss-Lobatto. The critical values of Reynolds number, wave number and wave speed are computed. The results are shown through the neutral curve. The main purpose of this work is to check the combined effect of magnetic field and fluid’s elasticity on the stability of the plane Poiseuille flow. Based on the results obtained in this work, the magnetic field is predicted to have a stabilizing effect on the Poiseuille flow of viscoelastic fluids. Hence, it will be shown that for second-order fluids (K 0 is that the critical Reynolds numbers Rec increase when the Hartman number M increases for certain value of elasticity number K and decrease for others. The latter result is in contrast to previous studies.

  6. Effect of a seed magnetic field on two-fluid plasma Richtmyer-Meshkov instability

    Science.gov (United States)

    Bond, Daryl; Wheatley, Vincent; Samtaney, Ravi; Pullin, Dale

    2016-11-01

    We investigate the effect of a uniform seed magnetic field on the plasma Richtmyer-Meshkov instability (RMI) using two-fluid simulations. These couple sets of conservation equations for the ions and electrons to the full Maxwell's equations. We consider cases where the seed magnetic field is normal to the interface and where the reference Debye length and Larmor radius range from a tenth to a thousandth of the interface perturbation wavelength. In ideal magnetohydrodynamics (MHD), it has been shown that in the presence of such a seed magnetic field, the growth of the RMI is suppressed by the transport of vorticity from the interface by MHD shocks. Our two-fluid plasma simulations reveal that while the RMI is suppressed in the presence of the seed field, the suppression mechanism varies depending on the plasma length-scales. Two-fluid plasma RMI simulations also reveal a secondary, high-wavenumber, electron-driven interface instability. This is not suppressed by the presence of the seed field. This work was partially supported by the KAUST Office of Sponsored Research under Award URF/1/2162-01.

  7. Development of a Hybrid Piezo Natural Rubber Piezoelectricity and Piezoresistivity Sensor with Magnetic Clusters Made by Electric and Magnetic Field Assistance and Filling with Magnetic Compound Fluid

    Directory of Open Access Journals (Sweden)

    Kunio Shimada

    2017-02-01

    Full Text Available Piezoelements used in robotics require large elasticity and extensibility to be installed in an artificial robot skin. However, the piezoelements used until recently are vulnerable to large forces because of the thin solid materials employed. To resolve this issue, we utilized a natural rubber and applied our proposed new method of aiding with magnetic and electric fields as well as filling with magnetic compound fluid (MCF and doping. We have verified the piezoproperties of the resulting MCF rubber. The effect of the created magnetic clusters is featured in a new two types of multilayered structures of the piezoelement. By measuring the piezoelectricity response to pressure, the synergetic effects of the magnetic clusters, the doping and the electric polymerization on the piezoelectric effect were clarified. In addition, by examining the relation between the piezoelectricity and the piezoresistivity created in the MCF piezo element, we propose a hybrid piezoelement.

  8. Development of a Hybrid Piezo Natural Rubber Piezoelectricity and Piezoresistivity Sensor with Magnetic Clusters Made by Electric and Magnetic Field Assistance and Filling with Magnetic Compound Fluid.

    Science.gov (United States)

    Shimada, Kunio; Saga, Norihiko

    2017-02-10

    Piezoelements used in robotics require large elasticity and extensibility to be installed in an artificial robot skin. However, the piezoelements used until recently are vulnerable to large forces because of the thin solid materials employed. To resolve this issue, we utilized a natural rubber and applied our proposed new method of aiding with magnetic and electric fields as well as filling with magnetic compound fluid (MCF) and doping. We have verified the piezoproperties of the resulting MCF rubber. The effect of the created magnetic clusters is featured in a new two types of multilayered structures of the piezoelement. By measuring the piezoelectricity response to pressure, the synergetic effects of the magnetic clusters, the doping and the electric polymerization on the piezoelectric effect were clarified. In addition, by examining the relation between the piezoelectricity and the piezoresistivity created in the MCF piezo element, we propose a hybrid piezoelement.

  9. Development of a Hybrid Piezo Natural Rubber Piezoelectricity and Piezoresistivity Sensor with Magnetic Clusters Made by Electric and Magnetic Field Assistance and Filling with Magnetic Compound Fluid

    Science.gov (United States)

    Shimada, Kunio; Saga, Norihiko

    2017-01-01

    Piezoelements used in robotics require large elasticity and extensibility to be installed in an artificial robot skin. However, the piezoelements used until recently are vulnerable to large forces because of the thin solid materials employed. To resolve this issue, we utilized a natural rubber and applied our proposed new method of aiding with magnetic and electric fields as well as filling with magnetic compound fluid (MCF) and doping. We have verified the piezoproperties of the resulting MCF rubber. The effect of the created magnetic clusters is featured in a new two types of multilayered structures of the piezoelement. By measuring the piezoelectricity response to pressure, the synergetic effects of the magnetic clusters, the doping and the electric polymerization on the piezoelectric effect were clarified. In addition, by examining the relation between the piezoelectricity and the piezoresistivity created in the MCF piezo element, we propose a hybrid piezoelement. PMID:28208625

  10. Aptamer conjugated paclitaxel and magnetic fluid loaded fluorescently tagged PLGA nanoparticles for targeted cancer therapy

    Science.gov (United States)

    Aravind, Athulya; Nair, Remya; Raveendran, Sreejith; Veeranarayanan, Srivani; Nagaoka, Yutaka; Fukuda, Takahiro; Hasumura, Takahashi; Morimoto, Hisao; Yoshida, Yasuhiko; Maekawa, Toru; Sakthi Kumar, D.

    2013-10-01

    Controlled and targeted drug delivery is an essential criterion in cancer therapy to reduce the side effects caused by non-specific drug release and toxicity. Targeted chemotherapy, sustained drug release and optical imaging have been achieved using a multifunctional nanocarrier constructed from poly (D, L-lactide-co-glycolide) nanoparticles (PLGA NPs), an anticancer drug paclitaxel (PTX), a fluorescent dye Nile red (NR), magnetic fluid (MF) and aptamers (Apt, AS1411, anti-nucleolin aptamer). The magnetic fluid and paclitaxel loaded fluorescently labeled PLGA NPs (MF-PTX-NR-PLGA NPs) were synthesized by a single-emulsion technique/solvent evaporation method using a chemical cross linker bis (sulfosuccinimidyl) suberate (BS3) to enable binding of aptamer on to the surface of the nanoparticles. Targeting aptamers were then introduced to the particles through the reaction with the cross linker to target the nucleolin receptors over expressed on the cancer cell surface. Specific binding and uptake of the aptamer conjugated magnetic fluid loaded fluorescently tagged PLGA NPs (Apt-MF-NR-PLGA NPs) to the target cancer cells induced by aptamers was observed using confocal microscopy. Cytotoxicity assay conducted in two cell lines (L929 and MCF-7) confirmed that targeted MCF-7 cancer cells were killed while control cells were unharmed. In addition, aptamer mediated delivery resulting in enhanced binding and uptake to the target cancer cells exhibited increased therapeutic effect of the drug. Moreover, these aptamer conjugated magnetic polymer vehicles apart from actively transporting drugs into specifically targeted tumor regions can also be used to induce hyperthermia or for facilitating magnetic guiding of particles to the tumor regions.

  11. Structural and magnetic properties of size-controlled Mn0.5Zn0.5Fe2O4 nanoparticles and magnetic fluids

    Indian Academy of Sciences (India)

    Rucha Desai; Vipul Davariya; Kinnari Parekh; Ramesh V Upadhyay

    2009-10-01

    Mn0.5Zn0.5Fe2O4 ferrite nanoparticles with tunable Curie temperature and saturation magnetization are synthesized using hydrothermal co-precipitation method. Particle size is controlled in the range of 54 to 135 Å by pH and incubation time of the reaction. All the particles exhibit super-paramagnetic behaviour at room temperature. Langevin’s theory incorporating the interparticle interaction was used to fit the virgin curve of particle magnetization. The low-temperature magnetization follows Bloch spin wave theory. Curie temperature derived from magnetic thermogravimetric analysis shows that Curie temperature increases with increasing particle size. Using these particles magnetic fluid is synthesized and magnetic characterization is reported. The monolayer coating of surfactant on particle surface is confirmed using thermogravimetric measurement. The same technique can be extended to study the magnetic phase transition. The Curie temperature derived using this measurement complies with the low-temperature magnetic measurement. The room-temperature and high-temperature magnetization measurements are also studied for magnetic fluid systems. The magnetic parameters derived for fluid are in good agreement with those obtained for the particle system

  12. Hyperthermia with rotating magnetic nanowires inducing heat into tumor by fluid friction

    Science.gov (United States)

    Egolf, Peter W.; Shamsudhin, Naveen; Pané, Salvador; Vuarnoz, Didier; Pokki, Juho; Pawlowski, Anne-Gabrielle; Tsague, Paulin; de Marco, Bastien; Bovy, William; Tucev, Sinisa; Ansari, M. H. D.; Nelson, Bradley J.

    2016-08-01

    A magnetic hyperthermia cancer treatment strategy that does not operate by means of conventional heating mechanisms is presented. The proposed approach consists of injecting a gel with homogeneously distributed magnetic nanowires into a tumor. Upon the application of a low-frequency rotating or circularly polarized magnetic field, nanowires spin around their center of viscous drag due to torque generated by shape anisotropy. As a result of external rotational forcing and fluid friction in the nanoparticle's boundary layer, heating occurs. The nanowire dynamics is theoretically and experimentally investigated, and different feasibility proofs of the principle by physical modeling, which adhere to medical guidelines, are presented. The magnetic nanorotors exhibit rotations and oscillations with quite a steady center of gravity, which proves an immobile behavior and guarantees a time-independent homogeneity of the spatial particle distribution in the tumor. Furthermore, a fluid dynamic and thermodynamic heating model is briefly introduced. This model is a generalization of Penne's model that for this method reveals theoretic heating rates that are sufficiently high, and fits well into medical limits defined by present standards.

  13. Viriato: A Fourier-Hermite spectral code for strongly magnetized fluid-kinetic plasma dynamics

    Science.gov (United States)

    Loureiro, N. F.; Dorland, W.; Fazendeiro, L.; Kanekar, A.; Mallet, A.; Vilelas, M. S.; Zocco, A.

    2016-09-01

    We report on the algorithms and numerical methods used in Viriato, a novel fluid-kinetic code that solves two distinct sets of equations: (i) the Kinetic Reduced Electron Heating Model (KREHM) equations (Zocco and Schekochihin, 2011) (which reduce to the standard Reduced-MHD equations in the appropriate limit) and (ii) the kinetic reduced MHD (KRMHD) equations (Schekochihin et al., 2009). Two main applications of these equations are magnetized (Alfvénic) plasma turbulence and magnetic reconnection. Viriato uses operator splitting (Strang or Godunov) to separate the dynamics parallel and perpendicular to the ambient magnetic field (assumed strong). Along the magnetic field, Viriato allows for either a second-order accurate MacCormack method or, for higher accuracy, a spectral-like scheme composed of the combination of a total variation diminishing (TVD) third order Runge-Kutta method for the time derivative with a 7th order upwind scheme for the fluxes. Perpendicular to the field Viriato is pseudo-spectral, and the time integration is performed by means of an iterative predictor-corrector scheme. In addition, a distinctive feature of Viriato is its spectral representation of the parallel velocity-space dependence, achieved by means of a Hermite representation of the perturbed distribution function. A series of linear and nonlinear benchmarks and tests are presented, including a detailed analysis of 2D and 3D Orszag-Tang-type decaying turbulence, both in fluid and kinetic regimes.

  14. Parallel Simulation of HGMS of Weakly Magnetic Nanoparticles in Irrotational Flow of Inviscid Fluid

    Directory of Open Access Journals (Sweden)

    Kanok Hournkumnuard

    2014-01-01

    Full Text Available The process of high gradient magnetic separation (HGMS using a microferromagnetic wire for capturing weakly magnetic nanoparticles in the irrotational flow of inviscid fluid is simulated by using parallel algorithm developed based on openMP. The two-dimensional problem of particle transport under the influences of magnetic force and fluid flow is considered in an annular domain surrounding the wire with inner radius equal to that of the wire and outer radius equal to various multiples of wire radius. The differential equations governing particle transport are solved numerically as an initial and boundary values problem by using the finite-difference method. Concentration distribution of the particles around the wire is investigated and compared with some previously reported results and shows the good agreement between them. The results show the feasibility of accumulating weakly magnetic nanoparticles in specific regions on the wire surface which is useful for applications in biomedical and environmental works. The speedup of parallel simulation ranges from 1.8 to 21 depending on the number of threads and the domain problem size as well as the number of iterations. With the nature of computing in the application and current multicore technology, it is observed that 4–8 threads are sufficient to obtain the optimized speedup.

  15. Magnetorheological fluid based on submicrometric silica-coated magnetite particles under an oscillatory magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Agustín-Serrano, R. [Facultad de Ciencias Físico Matemáticas, Universidad Autónoma de Puebla, Puebla 72570, México (Mexico); Donado, F., E-mail: fernando@uaeh.edu.mx [Instituto de Ciencias Básicas e Ingeniería de la Universidad Autónoma del Estado de Hidalgo-AAMF, Pachuca 42184, México (Mexico); Rubio-Rosas, E. [Centro Universitario de Vinculación, Universidad Autónoma de Puebla, Puebla 72570, México (Mexico)

    2013-06-15

    An experimental study conducted on the rheological properties of a magnetorheological fluid based on submicrometric silica-coated magnetite particles dispersed in silicone oil is presented. We investigated the rheological behaviour when the system is simultaneously exposed to a static field and a sinusoidal field used as a perturbation. The results show that the perturbation modifies the rheological behaviour of the system and can be used to control its physical properties; however, the changes that are induced are smaller than expected from previous results for the aggregation of particles under magnetic perturbations. We discussed this difference in terms of the ratio between the magnetic energy and the thermal energy. We observed that a threshold magnetic field exists; below it, the yield stress is practically zero, whereas above it, the yield stress grows quickly. We discuss this result in terms of a model based on chain length distribution. - Highlights: ► We study a magnetorheological fluid under an oscillatory magnetic field. ► The exponential chain length distribution depends on the average chain length. ► A simple yield stress model based on the chain length distribution is proposed.

  16. Hyperthermia with rotating magnetic nanowires inducing heat into tumor by fluid friction

    Energy Technology Data Exchange (ETDEWEB)

    Egolf, Peter W.; Pawlowski, Anne-Gabrielle; Tsague, Paulin; Marco, Bastien de; Bovy, William; Tucev, Sinisa [Institute of Thermal Sciences and Engineering, University of Applied Sciences of Western Switzerland, CH 1401 Yverdon-les-Bains (Switzerland); Shamsudhin, Naveen, E-mail: snaveen@ethz.ch; Pané, Salvador; Pokki, Juho; Ansari, M. H. D.; Nelson, Bradley J. [Multi-Scale Robotics Lab, Institute of Robotics and Intelligent Systems, ETH Zurich, CH 8092 Zurich (Switzerland); Vuarnoz, Didier [Ecole Polytechnique Fédérale de Lausanne (EPFL), EPFL Fribourg, CH 1701 Fribourg (Switzerland)

    2016-08-14

    A magnetic hyperthermia cancer treatment strategy that does not operate by means of conventional heating mechanisms is presented. The proposed approach consists of injecting a gel with homogeneously distributed magnetic nanowires into a tumor. Upon the application of a low-frequency rotating or circularly polarized magnetic field, nanowires spin around their center of viscous drag due to torque generated by shape anisotropy. As a result of external rotational forcing and fluid friction in the nanoparticle's boundary layer, heating occurs. The nanowire dynamics is theoretically and experimentally investigated, and different feasibility proofs of the principle by physical modeling, which adhere to medical guidelines, are presented. The magnetic nanorotors exhibit rotations and oscillations with quite a steady center of gravity, which proves an immobile behavior and guarantees a time-independent homogeneity of the spatial particle distribution in the tumor. Furthermore, a fluid dynamic and thermodynamic heating model is briefly introduced. This model is a generalization of Penne's model that for this method reveals theoretic heating rates that are sufficiently high, and fits well into medical limits defined by present standards.

  17. Thermal chiral vortical and magnetic waves: New excitation modes in chiral fluids

    Energy Technology Data Exchange (ETDEWEB)

    Kalaydzhyan, Tigran, E-mail: tigran@caltech.edu [Department of Physics, University of Illinois, 845 W Taylor Street, Chicago, IL 60607 (United States); Jet Propulsion Laboratory, 4800 Oak Grove Dr, M/S 298, Pasadena, CA 91109 (United States); Murchikova, Elena [TAPIR, California Institute of Technology, MC 350-17, Pasadena, CA 91125 (United States)

    2017-06-15

    In certain circumstances, chiral (parity-violating) medium can be described hydrodynamically as a chiral fluid with microscopic quantum anomalies. Possible examples of such systems include strongly coupled quark–gluon plasma, liquid helium {sup 3}He-A, neutron stars and the Early Universe. We study first-order hydrodynamics of a chiral fluid on a vortex background and in an external magnetic field. We show that there are two previously undiscovered modes describing heat waves propagating along the vortex and magnetic field. We call them the Thermal Chiral Vortical Wave and Thermal Chiral Magnetic Wave. We also identify known gapless excitations of density (chiral vortical and chiral magnetic waves) and transverse velocity (chiral Alfvén wave). We demonstrate that the velocity of the chiral vortical wave is zero, when the full hydrodynamic framework is applied, and hence the wave is absent and the excitation reduces to the charge diffusion mode. We also comment on the frame-dependent contributions to the obtained propagation velocities.

  18. 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.

  19. 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.

  20. Durability test device for MR fluids with permanent magnet and V-shaped groove

    Science.gov (United States)

    Abe, Isao; Kikuchi, Takehito; Noma, Junichi

    2017-05-01

    Magnetorheological fluids (MRFs) are functional fluids whose viscosity changes when magnetic fields are applied. Therefore, these fluids are used in force and torque controllable devices. However, particle sedimentation is one of the drawbacks of conventional MRFs. To solve this problem, Kurimoto Co. Ltd developed a new fluid with sub-micron order Fe particles and a silicone-based solvent known as NanoMRF. The particle distributions of this material are stable over several months. However, its durability has not yet been fully discussed. Therefore, we developed new equipment to test endurance and examined the durability of the magnetorheological effect of the NanoMRF as well as a commercially available MRF. Our results show that the durability of the fluids was affected by the stability of the solvent. In particular, the durability is drastically improved when the solvent is supplemented by the peripheral sealing oil. The oxidation of particles is remarkably varied by the kind of solvent as well as the stability of the oxidation film on the surface of the particles. The energy of the collapse and reproduction of the particles was used not only to generate friction among the particles but also to decompose the solvent molecules.

  1. A hyperbolic-equation system approach for magnetized electron fluids in quasi-neutral plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Kawashima, Rei, E-mail: kawashima@al.t.u-tokyo.ac.jp [Department of Aeronautics and Astronautics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Komurasaki, Kimiya, E-mail: komurasaki@k.u-tokyo.ac.jp [Department of Advanced Energy, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan); Schönherr, Tony, E-mail: schoenherr@al.u-tokyo.ac.jp [Department of Aeronautics and Astronautics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2015-03-01

    A new approach using a hyperbolic-equation system (HES) is proposed to solve for the electron fluids in quasi-neutral plasmas. The HES approach avoids treatments of cross-diffusion terms which cause numerical instabilities in conventional approaches using an elliptic equation (EE). A test calculation reveals that the HES approach can robustly solve problems of strong magnetic confinement by using an upwind method. The computation time of the HES approach is compared with that of the EE approach in terms of the size of the problem and the strength of magnetic confinement. The results indicate that the HES approach can be used to solve problems in a simple structured mesh without increasing computational time compared to the EE approach and that it features fast convergence in conditions of strong magnetic confinement.

  2. On the viscosity of magnetic fluid with low and moderate solid fraction

    Institute of Scientific and Technical Information of China (English)

    Zhiqiang Ren; Yanping Han; Ruoyu Hong; Jianmin Ding; Hongzhong Li

    2008-01-01

    The design of a pressurized capillary rheometer operating at prescribed temperature is described to measure the viscosity of magnetic fluids (MFs) containing Fe3O4 magnetic nanoparticles (MNPs). The equipment constant of the rheometer was obtained using liquids with predetermined viscosities. Experimentally measured viscosities were used to evaluate different equations for suspension viscosities. Deviation of measured suspension viscosities from the Einstein equation was found to be basically due to the influence of spatial distribution and aggregation of Fe3O4 MNPs. By taking account of the coating layer on MNPs and the aggregation of MNPs in MFs, a modified Einstein equation was proposed to fit the experimental data. Moreover, the influence of external magnetic field on viscosity was also taken into account. Viscosities thus predicted are in good agreement with experimental data. Temperature effect on suspension viscosity was shown experimentally to be due to the shear-thinning behavior of the MFs.

  3. Water dispersible superparamagnetic Cobalt iron oxide nanoparticles for magnetic fluid hyperthermia

    Science.gov (United States)

    Salunkhe, Ashwini B.; Khot, Vishwajeet M.; Ruso, Juan M.; Patil, S. I.

    2016-12-01

    Superparamagnetic nanoparticles of Cobalt iron oxide (CoFe2O4) are synthesized chemically, and dispersed in an aqueous suspension for hyperthermia therapy application. Different parameters such as magnetic field intensity, particle concentration which regulates the competence of CoFe2O4 nanoparticle as a heating agents in hyperthermia are investigated. Specific absorption rate (SAR) decreases with increase in the particle concentration and increases with increase in applied magnetic field intensity. Highest value of SAR is found to be 91.84 W g-1 for 5 mg. mL-1 concentration. Oleic acid conjugated polyethylene glycol (OA-PEG) coated CoFe2O4 nanoparticles have shown superior cyto-compatibility over uncoated nanoparticles to L929 mice fibroblast cell lines for concentrations below 2 mg. mL-1. Present work provides the underpinning for the use of CoFe2O4 nanoparticles as a potential heating mediator for magnetic fluid hyperthermia.

  4. Fast Responsive and Controllable Liquid Transport on a Magnetic Fluid/Nanoarray Composite Interface.

    Science.gov (United States)

    Tian, Dongliang; Zhang, Na; Zheng, Xi; Hou, Guanglei; Tian, Ye; Du, Yi; Jiang, Lei; Dou, Shi Xue

    2016-06-28

    Controllable liquid transport on surface is expected to occur by manipulating the gradient of surface tension/Laplace pressure and external stimuli, which has been intensively studied on solid or liquid interface. However, it still faces challenges of slow response rate, and uncontrollable transport speed and direction. Here, we demonstrate fast responsive and controllable liquid transport on a smart magnetic fluid/nanoarray interface, i.e., a composite interface, via modulation of an external magnetic field. The wettability of the composite interface to water instantaneously responds to gradient magnetic field due to the magnetically driven composite interface gradient roughness transition that takes place within a millisecond, which is at least 1 order of magnitude faster than that of other responsive surfaces. A water droplet can follow the motion of the gradient composite interface structure as it responds to the gradient magnetic field motion. Moreover, the water droplet transport direction can be controlled by modulating the motion direction of the gradient magnetic field. The composite interface can be used as a pump for the transport of immiscible liquids and other objects in the microchannel, which suggests a way to design smart interface materials and microfluidic devices.

  5. Aging investigation of cobalt ferrite nanoparticles in low pH magnetic fluid.

    Science.gov (United States)

    Soler, Maria A G; Lima, Emilia C D; da Silva, Sebastião W; Melo, Tiago F O; Pimenta, Angela C M; Sinnecker, João P; Azevedo, Ricardo B; Garg, Vijayendra K; Oliveira, Aderbal C; Novak, Miguel A; Morais, Paulo C

    2007-09-11

    In this study, we report on how surface-passivated and nonpassivated cobalt ferrite nanoparticles (8 nm diameter), suspended as ionic magnetic fluids and aged under low pH conditions, revealed different behavior as far as the time evolution of the iron/cobalt cation distribution, crystal quality, coercivity, and saturation magnetization are concerned. Different techniques were used to perform a detailed study regarding the chemical stability, structural stability, and surface and magnetic properties of the suspended nanoparticles as a function of the aging time. Properties of surface-passivated and nonpassivated nanoparticles were investigated by transmission electron microscopy, X-ray diffraction, atomic absorption spectrometry, magnetic measurements, Raman spectroscopy, and Mössbauer spectroscopy. Our data showed that the employed nanoparticle surface passivation process, besides the formation of an iron-rich surface layer, modifies the nanoparticle core as well, improving the crystal quality while modifying the Fe/Co cation distribution and the nanoparticle dissolution rate profile. Magnetic data showed that the saturation magnetization increases for surface-passivated nanoparticles in comparison to the nonpassivated ones, though coercivity decreases after passivation. These two observations were associated to changes in the cation distribution among the available tetrahedral and octahedral sites.

  6. Damping Force Modeling and Suppression of Self-Excited Vibration due to Magnetic Fluids Applied in the Torque Motor of a Hydraulic Servovalve

    Directory of Open Access Journals (Sweden)

    Wei Zhang

    2017-05-01

    Full Text Available As a key component of hydraulic control systems, hydraulic servovalves influence their performance significantly. Unpredictable self-excited noise inside hydraulic servovalves may cause instability and even failure. Being functional, with higher saturation magnetization and increased viscosity when exposed to a magnetic field, magnetic fluids (MFs have been widely used in dampers, sealing, and biomedical treatment. In this paper, magnetic fluids are applied in the torque motor of a hydraulic servovalve to exert damping and resistance for vibration and noise suppression. Construction of the torque motor armature with magnetic fluids is introduced and the forces due to magnetic fluids on the torque motor armature are studied. Based on a bi-viscosity-constituted relationship, a mathematical model of the damping force from magnetic fluids is built when magnetic fluids are filled in the working gaps of the torque motor. Measurements of the properties of an Fe3O4 composite magnetic fluid are carried out to calculate the parameters of this mathematical model and to investigate the influence of magnetic fluids on the vibration characteristics of the armature assembly. The simulated and tested harmonic responses of the armature with and without magnetic fluids show the good suppression effects of magnetic fluids on the self-excited noise inside the servovalve.

  7. Local hyperthermia for esophageal cancer in a rabbit tumor model: Magnetic stent hyperthermia versus magnetic fluid hyperthermia.

    Science.gov (United States)

    Liu, Jiayi; Li, Ning; Li, Li; Li, Danye; Liu, Kai; Zhao, Lingyun; Tang, Jintian; Li, Liya

    2013-12-01

    Magnetic-mediated hyperthermia (MMH) is a promising local thermotherapy approach for cancer treatment. The present study investigated the feasibility and effectiveness of MMH in esophageal cancer using a rabbit tumor model. The therapeutic effect of two hyperthermia approaches, magnetic stent hyperthermia (MSH), in which heat is induced by the clinical stent that is placed inside the esophagus, and magnetic fluid hyperthermia (MFH), where magnetic nanoparticles are applied as the agent, was systematically evaluated. A rabbit esophageal tumor model was established by injecting VX2 carcinoma cells into the esophageal submucosa. The esophageal stent was deployed perorally into the tumor segment of the esophagus. For the MFH, magnetic nanoparticles (MNPs) were administered to the rabbits by intratumoral injection. The rabbits were exposed under a benchtop applicator using an alternative magnetic field (AMF) with 300 kHz frequency for the hyperthermia treatment. The results demonstrated that esophageal stents and MNPs had ideal inductive heating properties upon exposure under an AMF of 300 kHz. MSH, using a thermal dose of 46°C with a 10-min treatment time, demonstrated antitumor effects on the rabbit esophageal cancer. However, the rabbit esophageal wall is not heat-resistant. Therefore, a higher temperature or longer treatment time may lead to necrosis of the rabbit esophagus. MFH has a significant antitumor effect by confining the heat within the tumor site without damaging the adjacent normal tissues. The present study indicates that the two hyperthermia procedures have therapeutic effects on esophageal cancer, and that MFH may be more specific than MSH in terms of temperature control during the treatment.

  8. Magnetic particle mixing with magnetic micro-convection for microfluidics

    Science.gov (United States)

    Kitenbergs, Guntars; E¯rglis, Kaspars; Perzynski, Régine; Cěbers, Andrejs

    2015-04-01

    In this paper we discuss the magnetic micro-convection phenomenon as a tool for mixing enhancement in microfluidics systems in cases when one of the miscible fluids is a magnetic particle colloid. A system of a water-based magnetic fluid and water is investigated experimentally under homogeneous magnetic field in a Hele-Shaw cell. Subsequent image analysis both qualitatively and quantitatively reveals the high enhancement of mixing efficiency provided by this method. The mixing efficiency dependence on the magnetic field and the physical limits is discussed. A suitable model for a continuous-flow microfluidics setup for mixing with magnetic micro-convection is also proposed and justified with an experiment. In addition, possible applications in improving the speed of ferrohydrodynamic sorting and magnetic label or selected tracer mixing in lab on a chip systems are noted.

  9. Preparation of Fe3O4 magnetic fluid by one-step method with a microemulsion reactor

    Institute of Scientific and Technical Information of China (English)

    Zhang Wenjun; Zhang Huifang; Li Dezhong

    2006-01-01

    A W/O microemulsion was prepared with Span80-PS (petroleum sulfonate) as complex emulsifier,isopropanol as cosurfactant and kerosene as oil phase.The optimal constituents of microemulsion were found from pseudoternary phase diagrams:the mass ratio of Span80 to PS was 4:1 and complex surfactant to cosurfactant was 1:1.The Fe3O4 magnetic fluid was obtained by one-step method with the W/O microemulsion as mieroreactor to synthesize magnetic nanoparticles (reaction temperature was 30℃ and reaction time was 5 h) and kerosene as carder liquid.The magnetic fluid was investigated by TEM,XRD and fluorescence microscope.The magnetism was determined by Gouy magnetic balance,The average particle size of Fe3O4 was 7.4 nm,and magnetic particles were well-dispersed.The stable Fe3O4 magnetic fluid with good magnetism may be produced by one-step method in the W/O microemulsion.Accordingly,the traditional preparation method of magnetic fluid can be simplified greatly.

  10. Relationships between fluid vorticity, kinetic helicity and magnetic field at the small-scale (quiet-network) on the Sun

    CERN Document Server

    Sangeetha, C R

    2016-01-01

    We derive horizontal fluid motions on the solar surface over large areas covering the quiet-Sun magnetic network from local correlation tracking of convective granules imaged in continuum intensity and Doppler velocity by the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). From these we calculate horizontal divergence, vertical component of vorticity, and kinetic helicity of fluid motions. We study the correlations between fluid divergence and vorticity, and that between vorticity (kinetic helicity) and magnetic field. We find that the vorticity (kinetic helicity) around small-scale fields exhibits a hemispherical pattern (in sign) similar to that followed by the magnetic helicity of large-scale active regions (containing sunspots). We identify this pattern to be a result of the Coriolis force acting on supergranular-scale flows (both the outflows and inflows), and is consistent with earlier studies using local helioseismology. Further, we show that the magnetic fields cau...

  11. Vibrations of fluid-conveying inclined single-walled carbon nanotubes acted upon by a longitudinal magnetic field

    Science.gov (United States)

    Kiani, Keivan

    2016-12-01

    This work deals with the influence of the longitudinal magnetic field on vibrations of inclined single-walled carbon nanotubes (SWCNTs) subjected to an inside fluid flow. Using an equivalent continuum structure model for the SWCNT and a plug-like model for the moving inside fluid flow, the nonlocal longitudinal and transverse equations of motion of magnetically affected SWCNTs are obtained in the context of small deformations. By application of the assumed-mode methodology, the displacements are discretized in terms of vibration mode shapes, and by exploiting generalized Newmark-β scheme, their corresponding time-dependent parameters are determined at each time. In the presence of the longitudinal magnetic field, the effects of the small-scale parameter, fluid flow velocity, and inclination angle on both longitudinal and transverse vibrations of SWCNTs are addressed. The obtained results reveal that the longitudinal magnetic field has fairly no effect on the longitudinal dynamic behavior of the nanostructure. However, maximum values of both transverse displacement and nonlocal bending moment of the fluid-conveying SWCNT would reduce as the strength of the magnetic field grows. Such a fact becomes more highlighted for high levels of the fluid flow velocity. The obtained results indicate that the longitudinal magnetic field can be exploited as an efficient way to control transverse vibrations of SWCNTs conveying fluids.

  12. Fast and highly-efficient removal of methylene blue from aqueous solution by poly(styrenesulfonic acid-co-maleic acid)-sodium-modified magnetic colloidal nanocrystal clusters

    Science.gov (United States)

    Song, Yu-Bei; Lv, Shao-Nan; Cheng, Chang-Jing; Ni, Guo-Li; Xie, Xiao-Wa; Huang, Wei; Zhao, Zhi-Gang

    2015-01-01

    Magnetic colloidal nanocrystal clusters (MCNCs) modified with different amounts of poly(4-styrenesulfonic acid-co-maleic acid) sodium (PSSMA) have been prepared through simple one-step solvothermal method for removal of methylene blue (MB) from aqueous solution. The prepared MCNCs are characterized by Fourier transform infrared (FT-IR) spectra, scanning electron microscope (SEM), transmission electron microscope (TEM), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), X-ray diffraction (XRD), nitrogen adsorption-desorption technique and dynamic light scattering (DLS). Moreover, effects of the solution pH, contact time, adsorbent dosage, ionic strength and initial dye concentration on MB adsorption onto the MCNCs are systematically investigated. The PSSMA-modified MCNCs show fast and highly-efficient MB removal capacity, which dramatically depends on the immobilization amounts of PSSMA, solution pH and adsorbent dosage. Their adsorption kinetics and isotherms exhibit that the kinetics and equilibrium adsorptions can be well-described by pseudo-second-order kinetic and Langmuir model, respectively. These magnetic nanocomposites, with high separation efficiency, low production cost and recyclable property, are promising as functional adsorbents for efficient removal of cationic organic pollutants from aqueous solution.

  13. Degradation of Phosphate Ester Hydraulic Fluid in Power Station Turbines Investigated by a Three-Magnet Unilateral Magnet Array

    Directory of Open Access Journals (Sweden)

    Pan Guo

    2014-04-01

    Full Text Available A three-magnet array unilateral NMR sensor with a homogeneous sensitive spot was employed for assessing aging of the turbine oils used in two different power stations. The Carr-Purcell-Meiboom-Gill (CPMG sequence and Inversion Recovery-prepared CPMG were employed for measuring the 1H-NMR transverse and longitudinal relaxation times of turbine oils with different service status. Two signal components with different lifetimes were obtained by processing the transverse relaxation curves with a numeric program based on the Inverse Laplace Transformation. The long lifetime components of the transverse relaxation time T2eff and longitudinal relaxation time T1 were chosen to monitor the hydraulic fluid aging. The results demonstrate that an increase of the service time of the turbine oils clearly results in a decrease of T2eff,long and T1,long. This indicates that the T2eff,long and T1,long relaxation times, obtained from the unilateral magnetic resonance measurements, can be applied as indices for degradation of the hydraulic fluid in power station turbines.

  14. 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,...

  15. Study of Fluid Flow Control in Protein Crystallization using Strong Magnetic Fields

    Science.gov (United States)

    Ramachandran, Narayanan; Leslie, Fred; Ciszak, Ewa

    2002-01-01

    An important component in biotechnology, particularly in the area of protein engineering and rational drug design is the knowledge of the precise three-dimensional molecular structure of proteins. The quality of structural information obtained from X-ray diffraction methods is directly dependent on the degree of perfection of the protein crystals. As a consequence, the growth of high quality macromolecular crystals for diffraction analyses has been the central focus for biochemists, biologists, and bioengineers. Macromolecular crystals are obtained from solutions that contain the crystallizing species in equilibrium with higher aggregates, ions, precipitants, other possible phases of the protein, foreign particles, the walls of the container, and a likely host of other impurities. By changing transport modes in general, i.e., reduction of convection and sedimentation, as is achieved in "microgravity", researchers have been able to dramatically affect the movement and distribution of macromolecules in the fluid, and thus their transport, formation of crystal nuclei, and adsorption to the crystal surface. While a limited number of high quality crystals from space flights have been obtained, as the recent National Research Council (NRC) review of the NASA microgravity crystallization program pointed out, the scientific approach and research in crystallization of proteins has been mainly empirical yielding inconclusive results. We postulate that we can reduce convection in ground-based experiments and we can understand the different aspects of convection control through the use of strong magnetic fields and field gradients. Whether this limited convection in a magnetic field will provide the environment for the growth of high quality crystals is still a matter of conjecture that our research will address. The approach exploits the variation of fluid magnetic susceptibility with concentration for this purpose and the convective damping is realized by appropriately

  16. Investigation of structure and magnetic properties of nanocrystalline iron oxide powders for use in magnetic fluids

    Energy Technology Data Exchange (ETDEWEB)

    Lukashova, N.V.; Savchenko, A.G. [National University of Science and Technology ’’MISIS’’, 4, Leninsky pr., Moscow (Russian Federation); Yagodkin, Yu.D., E-mail: yag52@mail.ru [National University of Science and Technology ’’MISIS’’, 4, Leninsky pr., Moscow (Russian Federation); Muradova, A.G.; Yurtov, E.V. [Mendeleev University of Chemical Technology, Miusskaya sq., 9, Moscow (Russian Federation)

    2014-02-15

    Highlights: • The iron oxide nanopowders were obtained by chemical methods. • The particles of the nanopowders had different size. • The structure and magnetic behavior of the powders depend on nanoparticle size. -- Abstract: Iron oxide nanopowders with particles of different size, obtained by co-precipitation and sonochemical methods, were studied by X-ray diffraction, transmission electron microscopy and Mössbauer spectroscopy. The average size of nanoparticles obtained by a co-precipitation method, was about 10 nm. The main phase component of such nanoparticles was maghemite phase γ-Fe{sub 2}O{sub 3}. It was shown, that these nanoparticles were superparamagnetic. In contrast, the nanoparticles obtained by sonochemical method, consisted of larger particles with an average size of around 25 nm. Their main phase component was magnetite Fe{sub 3}O{sub 4}. This powder clearly showed hard magnetic properties.

  17. Three-dimensional simulations of thin ferro-fluid films and drops in magnetic fields

    Science.gov (United States)

    Conroy, Devin; Wray, Alex; Matar, Omar

    2016-11-01

    We consider the interfacial dynamics of a thin, ferrofluidic film flowing down an inclined substrate, under the action of a magnetic field, bounded above by an inviscid gas. The fluid is assumed to be weakly-conducting. Its dynamics are governed by a coupled system of the steady Maxwell's, the Navier-Stokes, and continuity equations. The magnetisation of the film is a function of the magnetic field, and is prescribed by a Langevin function. We make use of a long-wave reduction in order to solve for the dynamics of the pressure, velocity, and magnetic fields inside the film. The potential in the gas phase is solved with the use of Fourier Transforms. Imposition of appropriate interfacial conditions allows for the construction of an evolution equation for the interfacial shape, via use of the kinematic condition, and the magnetic field. We consider the three-dimensional evolution of the film to spawise perturbations by solving the non-linear equations numerically. The constant flux configuration is considered, which corresponds to a thin film and drop flowing down an incline, and a parametric study is performed to understand the effect of a magnetic field on the stability and structure of the formed drops. EPSRC UK platform Grant MACIPh (EP/L020564/1) and programme Grant MEMPHIS (EP/K003976/1).

  18. Fabrication of ferromagnetic rolled-up microtubes for magnetic sensors on fluids

    Energy Technology Data Exchange (ETDEWEB)

    Bermudez Urena, Esteban; Mei Yongfeng; Coric, Emica; Schmidt, Oliver G [Institute for Integrative Nanosciences, IFW Dresden, Helmholtzstrasse 20, D-01069 Dresden (Germany); Makarov, Denys [Department of Physics, University of Konstanz, Universitaetstrasse 10, D-78457 Konstanz (Germany); Albrecht, Manfred, E-mail: ebermudez85@gmail.co [Chemnitz University of Technology, Institute of Physics, Reichenhainer Str. 70, D-09107 Chemnitz (Germany)

    2009-03-07

    Ferromagnetic microtubes are fabricated by the deterministic release of thin magnetic films from a photoresist sacrificial layer. Crucial steps towards the fabrication of well positioned and uniform single rolled-up tubes are presented, where the final and main approach consists of releasing angled deposited magnetic films by dissolving an underlying patterned photoresist layer. Microtubes from soft magnetic Ni{sub 80}Fe{sub 20} films and Co/Pt multilayer stacks with perpendicular magnetic anisotropy are obtained with predefined lengths and diameters down to 1.5 {mu}m. The nonlinear rotational dynamics of the tubes in viscous fluids is investigated. Sensitivities to viscosity variations for tubes with different lengths are observed and suggest their potential application as single sensing probes in a wide range of viscosities. Moreover, the variation in the characteristic critical frequency of the rotational motion for chains of magnetically coupled microtubes agrees with the expected changes in the theoretical shape factor of cylindrical particles. Evidence of tube remagnetization during the rotation opens the way to investigate properties such as the switching fields of individual tubes.

  19. Pressure distribution in an electrical conducting fluid in spherical form in the presence of crossed electrical and magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Shchelukhin, E.M.; Tsarevskaya, I.I.; Bruskii, V.P.

    1977-01-01

    An examination is made of electromagnetic forces in an isotropic fluid having a spherical form with non-conducting walls in the presence of crossed electrical and magnetic fields. The problem was solved on the assumption that the fluid is in a quiescent state but that the magnetic field is uniform. Computations were made of static pressure distribution and the scalar potential of an electromagnetic field in a fluid. Experimental data are presented on the measurement of static pressure distributions which agree well with the theoretical calculations. The obtained results may be used for engineering estimates of pressure in technological MHD apparatus.

  20. Relationships between Fluid Vorticity, Kinetic Helicity, and Magnetic Field on Small-scales (Quiet-Network) on the Sun

    Science.gov (United States)

    Sangeetha, C. R.; Rajaguru, S. P.

    2016-06-01

    We derive horizontal fluid motions on the solar surface over large areas covering the quiet-Sun magnetic network from local correlation tracking of convective granules imaged in continuum intensity and Doppler velocity by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory. From these we calculate the horizontal divergence, the vertical component of vorticity, and the kinetic helicity of fluid motions. We study the correlations between fluid divergence and vorticity, and between vorticity (kinetic helicity) and the magnetic field. We find that the vorticity (kinetic helicity) around small-scale fields exhibits a hemispherical pattern (in sign) similar to that followed by the magnetic helicity of large-scale active regions (containing sunspots). We identify this pattern to be a result of the Coriolis force acting on supergranular-scale flows (both the outflows and inflows), consistent with earlier studies using local helioseismology. Furthermore, we show that the magnetic fields cause transfer of vorticity from supergranular inflow regions to outflow regions, and that they tend to suppress the vortical motions around them when magnetic flux densities exceed about 300 G (from HMI). We also show that such an action of the magnetic fields leads to marked changes in the correlations between fluid divergence and vorticity. These results are speculated to be of importance to local dynamo action (if present) and to the dynamical evolution of magnetic helicity at the small-scale.

  1. Development of Small-sized Fluid Control Valve with Self-holding Function Using Permanent Magnet

    Science.gov (United States)

    Akagi, Tetsuya; Dohta, Shujiro; Ueda, Hirofumi

    Recently, force feedback devices in virtual reality and power assisted nursing care systems have received much attention and active research. In such a control system, an actuator and a driving device such as a control valve are mounted on the human body. In this condition, the size and weight of the control valve become serious problems. At the same time, the valve should be operated with lower energy consumption because of using a limited electrical power. The typical electro magnetic solenoid valve drives its spool using a larger solenoid to open the valve. The complex construction of the valve for sealing makes its miniaturization and the fabrication of a low cost valve more difficult. In addition, the solenoid in the valve consumes more electrical power while the valve is kept opening. The purpose of our study is to develop a small-sized, lightweight, lower energy consumption and flexible control valve that can be safe enough to mount on the human body at a lower cost. In our pervious study, we proposed and tested the control valve that can open using a vibration motor. In this study, we propose and test a new type of fluid control valve with a self-holding function. The new valve uses a permanent magnet ball. It has a cylindrical magnet and two solenoids. The self-holding function of the valve is done as follows. When one side of the solenoid is stimulated by the current momentarily, the solenoid gives a repulsive force to the cylindrical magnet. The magnet moves toward the opposite side of the solenoid and is attracted to the iron core. Then, the magnet ball moves toward the cylindrical magnet and opens the orifice. The valve can keep open without electrical energy. As a result, the valve with the extremely lower energy consumption can be developed.

  2. Second-order-like cluster-monomer transition within magnetic fluids and its impact upon the magnetic susceptibility.

    Science.gov (United States)

    Zhong, Jing; Xiang, Qing; Massa, Letícia O; Qu, Fanyao; Morais, Paulo C; Liu, Wenzhong

    2012-03-05

    The low-field (below 5 Oe) ac and dc magnetic response of a magnetic fluid [MF] sample in the range of 305 to 360 K and 410 to 455 K was experimentally and theoretically investigated. We found a systematic deviation of Curie's law, which predicts a linear temperature dependence of inverse initial susceptibility in the range of our investigation. This finding, as we hypothesized, is due to the onset of a second-order-like cluster-to-monomer transition with a critical exponent which is equal to 0.50. The susceptibility data were well fitted by a modified Langevin function, in which cluster dissociation into monomers, at the critical temperature [T*], was included. In the ac experiments, we found that T* was reducing from 381.8 to 380.4 K as the frequency of the applied field increases from 123 to 173 Hz. In addition, our ac experiments confirm that only monomers respond for the magnetic behavior of the MF sample above T*. Furthermore, our Monte Carlo simulation and analytical results support the hypothesis of a thermal-assisted dissociation of chain-like structures.PACS: 75.75.-C; 75.30.Kz; 75.30.Cr.

  3. Uncalibrated Visual Servo Control of Magnetically Actuated Microrobots in a Fluid Environment

    Directory of Open Access Journals (Sweden)

    Jenelle Armstrong Piepmeier

    2014-09-01

    Full Text Available Microrobots have a number of potential applications for micromanipulation and assembly, but also offer challenges in power and control. This paper describes an uncalibrated vision-based control system for magnetically actuated microrobots operating untethered at the interface between two immiscible fluids. The microrobots are 20 μm thick and approximately 100–200 μm in lateral dimension. Several different robot shapes are investigated. The robots and fluid are in a 20 × 20 × 15 mm vial placed at the center of four electromagnets. Pulse width modulation of the electromagnet currents is used to control robot speed and direction. Given a desired position, a controller based on recursive least square estimation drives the microrobot to the goal without a priori knowledge of system parameters such as drag coefficients or intrinsic and extrinsic camera parameters. Results are verified experimentally using a variety of microrobot shapes and system configurations.

  4. Measurement of Fluid Flow in Pipe and Porous Media by High-Resolution Magnetic Resonance Imaging

    Institute of Scientific and Technical Information of China (English)

    JIANG Lan-lan; SONG Yong-chen; LIU Yu; DOU Bin-lin; ZHU Ning-jun; ZHAO Jia-fei; BULITI Abudula

    2012-01-01

    The objective of this study is to understand the process of fluid flow in pipe and porous media with different pore structures.High-resolution Magnetic Resonance Imaging (MRI) technique was used to visualize the pore structure and measure fluid flow.The porous media was formed by packed bed of glass beads.Flow measurement was carried out by a modified spin echo sequence.The results show that the velocity distribution in pipe is annular and the linear relation between MRI velocity and actual velocity is found in pipe flow measurement.The flow distribution in porous media is rather heterogeneous,and it is consistent with heterogeneous pore structure.The flow through pores with the high volume flow rate is determined largely by geometrical effects such as pore size and cross-sectional area.

  5. Stability Of Superposed Fluids Through Magnetic Field With Suspended Particles Of Different Permeability Saturated Through Porous Layer

    Directory of Open Access Journals (Sweden)

    Singh M.

    2015-12-01

    Full Text Available The instability of plane interface between two superposed Rivlin-Ericksen elastico-viscous fluids saturated through a porous medium has been studied to include the suspended (dust particles effect. Following the linearized stability theory and normal mode analysis the dispersion relation is obtained. For stationary convection, the Rivlin-Ericksen elastico-viscous fluid behaves like Newtonian fluids. It found that for a potentially stable arrangement the Rivlin-Ericksen elastico-viscous fluid of different permeabilities in the presence of suspended particles in a porous medium is stable, whereas in a potentially unstable case instability of the system occurs. In the presence of a magnetic field for a potentially stable arrangement the system is always stable and for the potentially unstable arrangement, the magnetic field succeeds in stabilizing certain wave-number band which was unstable in the absence of the magnetic field.

  6. Deformation of the free surface of a conducting fluid in the magnetic field of current-carrying linear conductors

    Science.gov (United States)

    Zubarev, N. M.; Zubareva, O. V.

    2017-06-01

    The magnetic shaping problem is studied for the situation where a cylindrical column of a perfectly conducting fluid is deformed by the magnetic field of a system of linear current-carrying conductors. Equilibrium is achieved due to the balance of capillary and magnetic pressures. Two two-parametric families of exact solutions of the problem are obtained with the help of conformal mapping technique. In accordance with them, the column essentially deforms in the cross section up to its disintegration.

  7. Infrared thermography based magnetic hyperthermia study in Fe3O4 based magnetic fluids

    Science.gov (United States)

    Lahiri, B. B.; Ranoo, Surojit; Philip, John

    2016-09-01

    Owing to the immense clinical benefits, magnetic hyperthermia is likely to emerge as an alternate cancer therapeutic procedure in the near future. Presently, radio frequency immune fiber optic based sensors are being used to monitor temperature changes during magnetic hyperthermia measurements, which have inherent limitations due to the requirement of physical contact of the sensor with the sample, contamination and temperature monitoring at a single point. Here, we investigate the field induced heating of oil based oleic acid coated Fe3O4 nanofluid, synthesized using co-precipitation method, using infrared thermal imaging (IRT) camera and compare the results with those of fiber optic temperature sensor. Experiments were performed on nanofluid samples of four different concentrations and under five different external field amplitudes. The specific absorption rate (SAR) of the samples were determined from the initial rate of temperature rise measured using both the techniques. The SAR values determined from both the techniques were in very good agreement with each other, with in an accuracy of 5%, after incorporating convection loss correction on the infrared thermal imaging data. The consecutive thermal cycling on the samples showed good thermal stability and thermal recovery. The maximum SAR obtained was 95.9 W/gFe for a sample concentration and field amplitude of 23 wt.% and 57.3 kA m-1, respectively. This study showed the efficacy and accuracy of temperature measurement using IRT during field induced heating of magnetic nanofluid and its advantages over conventional point measurements techniques for real-time, non-contact and wide area temperature mapping without sample contamination.

  8. Aggregation dynamics and magnetic properties of magnetic micrometer-sized particles dispersed in a fluid under the action of rotating magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Llera, María [Instituto de Ciencias, Universidad Nacional de General Sarmiento, Buenos Aires (Argentina); Codnia, Jorge [Instituto de Ciencias, Universidad Nacional de General Sarmiento, Buenos Aires (Argentina); Centro de Investigaciones en Láseres y Aplicaciones, CITEDEF-CONICET, Buenos Aires (Argentina); Jorge, Guillermo A., E-mail: gjorge@ungs.edu.ar [Instituto de Ciencias, Universidad Nacional de General Sarmiento, Buenos Aires (Argentina)

    2015-06-15

    We present a dynamic study of soft magnetic, commercial Fe and Ni micrometer-sized particles dispersed in oleic acid and subjected to a variable (rotating) magnetic field in the horizontal plane. A very complex structure is formed after the particles decant towards the bottom liquid–solid interface and the magnetic field is applied for several minutes. The dynamics of structure formation was studied by means of the registration and analysis of microscopic video images, through a Matlab image analysis script. Several parameters, such as the number of clusters, the perimeter-based fractal dimension and circularity, were calculated as a function of time. The time evolution of the number of clusters was found to follow a power-law behavior, with an exponent consistent with that found in other studies for magnetic systems, whereas the typical formation time depends on the particle diameter and field configuration. Complementarily, the magnetic properties of the formed structure were studied, reproducing the experiment with liquid paraffin as the containing fluid, and then letting it solidify. The sample obtained was studied by vibrating sample magnetometry. The magnetization curves show that the material obtained is a planar magnetically anisotropic material, which could eventually be used as an anisotropic magnetic sensor or actuator. - Highlights: • Dynamic study of Fe and Ni particles in oleic acid under rotating fields. • A very complex system of interconnected clusters was observed. • Larger particles had a smaller aggregation time. • A power law behavior of the number of clusters vs. time. • A Fe-paraffin sample with planar anisotropy characterized.

  9. A Hydrostatic Bearing Test System for Measuring Bearing Load Using Magnetic-Fluid Lubricants.

    Science.gov (United States)

    Weng, Huei Chu; Chen, Lu-Yu

    2016-05-01

    This paper conducts a study on the design of a hydrostatic bearing test system. It involves the determination of viscous properties of magnetic-fluid lubricants. The load of a hydrostatic thrust bearing using a water-based magnetite nanofluid of varying volume flow rate is measured under an applied external induction field via the test system. Results reveal that the presence of nanoparticles in a carrier liquid would cause an enhanced bearing load. Such an effect could be further magnified by increasing the lubricant volume flow rate or the external induction field strength.

  10. Effects of Magnetic Field and Nonlinear Temperature Profile on Marangoni Convection in Micropolar Fluid

    Directory of Open Access Journals (Sweden)

    M. N. Mahmud

    2009-01-01

    Full Text Available The combined effects of a uniform vertical magnetic field and a nonuniform basic temperature profile on the onset of steady Marangoni convection in a horizontal layer of micropolar fluid are studied. The closed-form expression for the Marangoni number M for the onset of convection, valid for polynomial-type basic temperature profiles upto a third order, is obtained by the use of the single-term Galerkin technique. The critical conditions for the onset of convection have been presented graphically.

  11. Effect of inclined magnetic field in flow of third grade fluid with variable thermal conductivity

    Directory of Open Access Journals (Sweden)

    T. Hayat

    2015-08-01

    Full Text Available This paper examines effects of inclined magnetic field and heat transfer in the flow of a third-grade fluid by an exponentially stretching surface. Formulation and analysis are given with heat source and sink. Thermal conductivity is taken temperature dependent. The governing boundary layer equations and boundary conditions are simplified through appropriate transformations. Resulting equations are solved for the approximate solutions. Convergence of governed problems is explicitly discussed. Influences of various dimensionless parameters such as on the flow and thermal fields are discussed. Local skin friction coefficient and the local Nusselt number are analyzed through tabulated values.

  12. Inspiration of induced magnetic field on nano hyperbolic tangent fluid in a curved channel

    Science.gov (United States)

    Nadeem, S.; Shahzadi, Iqra

    2016-01-01

    In this research, peristaltic flow of nano hyperbolic tangent fluid is investigated in a curved channel. The model used for the nanofluid includes the effects of thermophoresis and Brownian motion. The resulting equations are assembled in wave frame of reference under the effects of curvature. Influence of induced magnetic field is studied. Long wavelength and low Reynolds number supposition are treated. The travelling wave front of peristaltic flow is chosen sinusoidal (extension /reduction). Analytical solutions are computed by homotopy perturbation method. Results of substantial quantities are explained with particular attention to rheological aspects.

  13. Inspiration of induced magnetic field on nano hyperbolic tangent fluid in a curved channel

    Directory of Open Access Journals (Sweden)

    S. Nadeem

    2016-01-01

    Full Text Available In this research, peristaltic flow of nano hyperbolic tangent fluid is investigated in a curved channel. The model used for the nanofluid includes the effects of thermophoresis and Brownian motion. The resulting equations are assembled in wave frame of reference under the effects of curvature. Influence of induced magnetic field is studied. Long wavelength and low Reynolds number supposition are treated. The travelling wave front of peristaltic flow is chosen sinusoidal (extension /reduction. Analytical solutions are computed by homotopy perturbation method. Results of substantial quantities are explained with particular attention to rheological aspects.

  14. Differentiation in vitro of inflammatory from non inflammatory synovial fluid by nuclear magnetic relaxation

    Energy Technology Data Exchange (ETDEWEB)

    Teyssier, R.; Teyssier, M.; Colson, F.

    1987-01-01

    The differentiation between inflammatory and non inflammatory states has been performed using Nuclear Magnetic Resonance (NMR) in vitro by measuring relaxation times T/sub 1/ and T/sub 2/ in 84 synovials fluids obtained from various rheumatologic diseases. The results show that the T/sub 1//T/sub 2/ ratio is more sensitive to distinguish these two situations rather than the isolated T/sub 1/ or T/sub /2 values. In particular, high values of T/sub 1//T/sub 2/ ratio are found in septic arthritis.

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

    Science.gov (United States)

    Löwen, Hartmut

    2012-11-01

    tailor a random substrate potential for colloids [20] or to bind colloids optically [21]. External magnetic fields are typically used to create dipolar repulsions of colloids pending at an air-water interface. This provides an avenue to two-dimensional systems, where the freezing transition [22] and various transport phenomena through channels are the focus of recent research [23, 24]. Confinement typically leads to interfaces. The classical problem of the Tolman length for a fluid-fluid interface is reviewed in detail in [25]. In fact, colloid-polymer mixtures constitute ideal model systems for liquid-gas interfaces in various geometries [26] and are also suitable for measuring the Tolman length experimentally. Crystalline phases in confinement [27] and crystal-fluid interfaces [28] are even more complex due to the inhomogeneity of the solid phase. Also in the confined fluid phase, there are still open issues in slit-pore geometry. These include how to scale the interparticle distance [29] and how to measure hydrodynamic interactions between colloidal particles [30]. Other external fields which can be applied to colloids are gravity [31] and temperature [32]. An important field of recently emerging research is active colloidal particles (so-called microswimmers) which possess fascinating nonequilibrium properties; for recent reviews see [33-35]. Two examples are also included in this issue: an active deformable particle [36] moving in gravity and the collective turbulent swarming behaviour of dense self-propelled colloidal rod suspensions [37]. References [1]Löwen H 2001 J. Phys. Condens. Matter 13 R415 [2]Löwen H and Likos C N (ed) 2004 J. Phys. Condens. Matter 16 (special issue) [3]Löwen H 1976 J. Phys. Condens. Matter 20 404201 [4]Guu D, Dhont J K G, Vliegenthart G A and Lettinga M P 2012 J. Phys. Condens. Matter 24 464101 [5]Gupta S, Kundu S, Stellbrink J, Willner L, Allgaier J and Richter D 2012 J. Phys. Condens. Matter 24 464102 [6]Singh S P, Fedosov D A

  16. Numerical and analytical treatment on peristaltic flow of Williamson fluid in the occurrence of induced magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Akram, Safia, E-mail: safia_akram@yahoomail.com [Department of Basic Sciences, Military College of Signals, National University of Sciences and Technology (Pakistan); Nadeem, S. [Department of Mathematics, Quaid-i-Azam University 45320, Islamabad 44000 (Pakistan); Hanif, M. [Department of Basic Sciences, Military College of Signals, National University of Sciences and Technology (Pakistan)

    2013-11-15

    In this paper the effects of induced magnetic field on the peristaltic transport of a Williamson fluid model in an asymmetric channel has been investigated. The problem is simplified by using long wave length and low Reynolds number approximations. The perturbation and numerical solutions have been presented. The expressions for pressure rise, pressure gradient, stream function, magnetic force function, current density distribution have been computed. The results of pertinent parameters have been discussed graphically. The trapping phenomena for different wave forms have been also discussed. - highlights: • The main motivation of this work is that we want to see the behavior of peristaltic flow of Williamson fluid in the occurrence of induced magnetic field. In literature no attempt is taken to discuss the lateral Numerical and analytical treatment on peristaltic flow of Williamson fluid in the occurrence of induced magnetic field. • We do not want to fill the gap in literature after studying this.

  17. The glass transition of hard spherical colloids

    Energy Technology Data Exchange (ETDEWEB)

    Pusey, P.N. (Royal Signals and Radar Establishment, Malvern (UK)); Van Megen, W. (Royal Melbourne Inst. of Tech. (Australia). Dept. of Applied Physics)

    1990-03-01

    When suspended in a liquid, hard spherical colloidal particles can show fluid, crystalline and glassy phases. A light scattering study of the dynamics of the metastable fluid and glassy phases is reported. Comparison is made with the predictions of mode-coupling theories applied to the glass transition of simple atomic systems. (orig.).

  18. Weakly Nonlinear Stability Analysis of a Thin Magnetic Fluid during Spin Coating

    Directory of Open Access Journals (Sweden)

    Cha'o-Kuang Chen

    2010-01-01

    Full Text Available This paper investigates the stability of a thin electrically conductive fluid under an applied uniform magnetic filed during spin coating. A generalized nonlinear kinematic model is derived by the long-wave perturbation method to represent the physical system. After linearizing the nonlinear evolution equation, the method of normal mode is applied to study the linear stability. Weakly nonlinear dynamics of film flow is studied by the multiple scales method. The Ginzburg-Landau equation is determined to discuss the necessary conditions of the various critical flow states, namely, subcritical stability, subcritical instability, supercritical stability, and supercritical explosion. The study reveals that the rotation number and the radius of the rotating circular disk generate similar destabilizing effects but the Hartmann number gives a stabilizing effect. Moreover, the optimum conditions can be found to alter stability of the film flow by controlling the applied magnetic field.

  19. The effect of magnetization and electric polarization on the anomalous transport coefficients of a chiral fluid

    Science.gov (United States)

    Sadooghi, N.; Tabatabaee, S. M. A.

    2017-05-01

    The effects of finite magnetization and electric polarization on dissipative and non-dissipative (anomalous) transport coefficients of a chiral fluid are studied. First, using the second law of thermodynamics as well as Onsager’s time-reversal symmetry principle, the complete set of dissipative transport coefficients of this medium is derived. It is shown that the properties of the resulting shear and bulk viscosities are mainly affected by the anisotropy induced by external electric and magnetic fields. Then, using the fact that the anomaly induced currents do not contribute to entropy production, the corresponding algebro-differential equations to non-dissipative anomalous transport coefficients are derived in a certain derivative expansion. The solutions of these equations show that, within this approximation, anomalous transport coefficients are, in particular, given in terms of the electric susceptibility of the medium.

  20. Materials Characterization of Feraheme/Ferumoxytol and Preliminary Evaluation of Its Potential for Magnetic Fluid Hyperthermia

    Directory of Open Access Journals (Sweden)

    Jon Dobson

    2013-08-01

    Full Text Available Feraheme, is a recently FDA-cleared superparamagnetic iron oxide nanoparticle (SPION-based MRI contrast agent that is also employed in the treatment of iron deficiency anemia. Feraheme nanoparticles have a hydrodynamic diameter of 30 nm and consist of iron oxide crystallites complexed with a low molecular weight, semi-synthetic carbohydrate. These features are attractive for other potential biomedical applications such as magnetic fluid hyperthermia (MFH, since the carboxylated polymer coating affords functionalization of the particle surface and the size allows for accumulation in highly vascularized tumors via the enhanced permeability and retention effect. This work presents morphological and magnetic characterization of Feraheme by transmission electron microscopy (TEM, Energy dispersive X-ray spectroscopy (EDX, and superconducting quantum interference device (SQUID magnetometry. Additionally, the results of an initial evaluation of the suitability of Feraheme for MFH applications are described, and the data indicate the particles possess promising properties for this application.

  1. Velocity statistics in holographic fluids: magnetized quark-gluon plasma and superfluid flow

    Energy Technology Data Exchange (ETDEWEB)

    Areán, Daniel [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut),Föhringer Ring 6, D-80805, Munich (Germany); Zayas, Leopoldo A. Pando [The Abdus Salam International Centre for Theoretical Physics,Strada Costiera 11, 34014 Trieste (Italy); Michigan Center for Theoretical Physics, Department of Physics, University of Michigan,450 Church Street, Ann Arbor, MI 48109 (United States); Patiño, Leonardo; Villasante, Mario [Departamento de Física, Facultad de Ciencias, Universidad Nacional Autónoma de México,A.P. 70-542, México D.F. 04510 (Mexico)

    2016-10-28

    We study the velocity statistics distribution of an external heavy particle in holographic fluids. We argue that when the dual supergravity background has a finite temperature horizon the velocity statistics goes generically as 1/v, compatible with the jet-quenching intuition from the quark-gluon plasma. A careful analysis of the behavior of the classical string whose apparent world sheet horizon deviates from the background horizon reveals that other regimes are possible. We numerically discuss two cases: the magnetized quark-gluon plasma and a model of superfluid flow. We explore a range of parameters in these top-down supergravity solutions including, respectively, the magnetic field and the superfluid velocity. We determine that the velocity statistics goes largely as 1/v, however, as we leave the non-relativistic regime we observe some deviations.

  2. Surface chemistry of nanoscale Fe3O4 dispersed in magnetic fluids

    Institute of Scientific and Technical Information of China (English)

    XIA; JianHan

    2007-01-01

    The interaction between stabilizers and nanoparticles is one of the important factors to prepare stable magnetic fluids. The magnetic nano-size Fe3O4 core with single domain and the average grain size around 8-12 nm were prepared by chemical precipitation method. The O/Fe molar ratio of the particle surface was measured by X-ray photoelectron spectroscopy (XPS). The heat effects of stabilizers adsorption on nanoparticles were measured by solution calorimetry. The excess amount of oxygen was possibly the result of the hydroxygen formed on the surface of the nanoparticles. The heat effects showed that compounds containing carboxyl groups can be adsorbed chemically on magnetite by forming chemical bonds. The other stabilizers involving NH-groups, such as polyethylene-imine, can be adsorbed physically. The exothermic value is about half of the former case.

  3. Laminar flow of a conducting fluid between coaxial cylinders in a traveling magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Kamiyama, S.; Kavai, Ya.

    1977-07-01

    An analysis is made of the laminar flow of a conducting fluid between two coaxial cylinders in a traveling magnetic field. A study was made of the characteristics of coaxial induction MHD apparatus as well as the effect of the velocity profile on the efficiency of an ideal machine. The internal cylinder was presumed to consist of a nonconducting material with a magnetic permeability of ..mu../sub 1/ = ..mu../sub 0/ or ..mu../sub 1/ = infinity. The velocity profiles were obtained in the form of functions of the ratios of the external and internal cylinder radii and the radius of the external cylinder to the pole pitch. The heterogeneity of the velocity profile was found to have a significant influence on the energy conversion efficiency of ideal induction MHD machines. 6 references, 4 figures.

  4. Two-dimensional nonstationary flow of a conducting fluid, induced by a rotating magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Kapusta, A.B.

    1977-07-01

    An examination is made of a full induction problem on the planar movement of a conducting fluid in a rotating magnetic field. The solution to this problem is sought by the method of degradation into Fourier series by harmonics of the rotating field. The initial system of partial differential equations is reduced to the system 2+1 of normal differential equations that bind the amplitudes of function harmonics and electrical vector potential. A solution to the problem for small anti ..omega.. was found with an accuracy up to the second approximation. The unsteadiness of flow was found to be manifested in a form of induced cross-sectional waves, traveling along the stream tubes of this flow at a speed that is equal to the phase velocity of the magnetic field. The appearance of wave effects is explained by considerations of symmetry. 5 references, 1 figure.

  5. All-fiber optical modulator based on no-core fiber and magnetic fluid as cladding

    Science.gov (United States)

    Chen, Yao-Fei; Han, Qun; Liu, Tie-Gen

    2015-01-01

    An all-fiber optical modulator, which is composed of a piece of no-core fiber spliced between two sections of single-mode fibers and uses magnetic fluid (MF) as the cladding of the no-core fiber section, is proposed and investigated experimentally. Due to the tunable refractive index and absorption coefficient of MF, the output intensity can be modulated by controlling an applied magnetic field. The dependences of the modulator’s temporal response on the working wavelength, the magnetic field strength (H), and the MF’s concentration are investigated experimentally. The results are explained qualitatively by the dynamic response process of MF under the action of a magnetic field. The findings are helpful for optimizing this kind of modulator. Project supported by the Natural Science Foundation of Tianjin City, China (Grant No. 13JCYBJC16100), the National Natural Science Foundation of China (Grant No. 61107035), the National Key Scientific Instrument and Equipment Development Project of China (Grant No. 2013YQ03091502), and the National Basic Research Program of China (Grant Nos. 2010CB327802 and 2010CB327806).

  6. Multidimensional microstructured photonic device based on all-solid waveguide array fiber and magnetic fluid

    Directory of Open Access Journals (Sweden)

    Miao Yinping

    2016-11-01

    Full Text Available An all-solid waveguide array fiber (WAF is one kind of special microstructured optical fiber in which the higher-index rods are periodically distributed in a low-index silica host to form the transverse two-dimensional photonic crystal. In this paper, one kind of multidimensional microstructured optical fiber photonic device is proposed by using electric arc discharge method to fabricate periodic tapers along the fiber axis. By tuning the applied magnetic field intensity, the propagation characteristics of the all-solid WAF integrated with magnetic fluid are periodically modulated in both radial and axial directions. Experimental results show that the wavelength changes little while the transmission loss increases for an applied magnetic field intensity range from 0 to 500 Oe. The magnetic field sensitivity is 0.055 dB/Oe within the linear range from 50 to 300 Oe. Meanwhile, the all-solid WAF has very similar thermal expansion coefficient for both high- and low-refractive index glasses, and thermal drifts have a little effect on the mode profile. The results show that the temperature-induced transmission loss is <0.3 dB from 26°C to 44°C. Further tuning coherent coupling of waveguides and controlling light propagation, the all-solid WAF would be found great potential applications to develop new micro-nano photonic devices for optical communications and optical sensing applications.

  7. Magnetic fluid hyperthermia probed by both calorimetric and dynamic hysteresis measurements

    Science.gov (United States)

    Guibert, Clément; Fresnais, Jérôme; Peyre, Véronique; Dupuis, Vincent

    2017-01-01

    In this paper, we report an investigation of magnetic fluid hyperthermia (MFH) using combined calorimetric and newly implemented dynamic hysteresis measurements for two sets of well characterized size-sorted maghemite nanoparticles (with diameters of about 10 nm and 20 nm) dispersed in water and in glycerol. Our primary goal was to assess the influence of viscosity on the heating efficiency of magnetic nanoparticles described in terms of specific loss power (SLP or specific absorption rate, SAR) and dynamic hysteresis. In particular, we aimed to investigate how this SLP depends on the transition from Néelian to Brownian behavior of nanoparticles expected to occur between 10 nm and 20 nm (for maghemite) and dependent on the viscosity. While we observed a good agreement between calorimetric and dynamic hysteresis measurements, we found that the SLP measured for the different systems do not depend noticeably on the viscosity of solvent. Calculations performed according to Rosensweig's linear model [1] allow us to quantitatively reproduce our results at low field intensities, provided we use a value for the magnetic anisotropy constant much smaller than the one commonly used in the literature. This raises the question of the temperature dependance of the magnetic anisotropy constant and its relevance for a quantitative description of MFH.

  8. Multidimensional microstructured photonic device based on all-solid waveguide array fiber and magnetic fluid

    Science.gov (United States)

    Miao, Yinping; Ma, Xixi; He, Yong; Zhang, Hongmin; Yang, Xiaoping; Yao, Jianquan

    2017-01-01

    An all-solid waveguide array fiber (WAF) is one kind of special microstructured optical fiber in which the higher-index rods are periodically distributed in a low-index silica host to form the transverse two-dimensional photonic crystal. In this paper, one kind of multidimensional microstructured optical fiber photonic device is proposed by using electric arc discharge method to fabricate periodic tapers along the fiber axis. By tuning the applied magnetic field intensity, the propagation characteristics of the all-solid WAF integrated with magnetic fluid are periodically modulated in both radial and axial directions. Experimental results show that the wavelength changes little while the transmission loss increases for an applied magnetic field intensity range from 0 to 500 Oe. The magnetic field sensitivity is 0.055 dB/Oe within the linear range from 50 to 300 Oe. Meanwhile, the all-solid WAF has very similar thermal expansion coefficient for both high- and low-refractive index glasses, and thermal drifts have a little effect on the mode profile. The results show that the temperature-induced transmission loss is <0.3 dB from 26°C to 44°C. Further tuning coherent coupling of waveguides and controlling light propagation, the all-solid WAF would be found great potential applications to develop new micro-nano photonic devices for optical communications and optical sensing applications.

  9. Pulsatile cerebrospinal fluid flow measurement using phase-contrast magnetic resonance imaging in patients with cervical myelopathy.

    Science.gov (United States)

    Shibuya, Ryoichi; Yonenobu, Kazuo; Koizumi, Toshiaki; Kato, Yasuji; Mitta, Motoharu; Yoshikawa, Hideki

    2002-05-15

    A technical report is presented. To investigate the relation between the severity of myelopathy and the degree of cerebrospinal fluid flow disturbance by using magnetic resonance imaging to measure the velocity of the cerebrospinal fluid flow in patients with cervical spondylotic myelopathy. Analyses of pulsatile cerebrospinal fluid flow measured by phase-contrast magnetic resonance imaging in healthy subjects and patients with Arnold-Chiari syndrome have been reported. Few studies have evaluated the change of pulsatile cerebrospinal fluid flow velocity and the waveform of the plotted velocity in patients with cervical spondylotic myelopathy. Study 1: Pulsatile cerebrospinal fluid flow was measured at C7, positioned with cervical spine flexion and extension, to investigate the influence of cervical alignment on the pulsatile cerebrospinal fluid flow in five patients with cervical spondylotic myelopathy. Study 2: In 31 patients with cervical spondylotic myelopathy, pulsatile cerebrospinal fluid flow was measured at C3 and C7, with the neck set centrally. The relevance of cerebrospinal fluid flow disturbance and the severity of myelopathy evaluated by the Japanese Orthopedic Association scoring system also were studied. Study 1: The waveform of plotted pulsatile cerebrospinal fluid flow velocity showed no change resulting from the position of the cervical spine. Study 2: A high correlation between the Japanese Orthopedic Association score and the cerebrospinal fluid pulsatile flow amplitude at C7 was demonstrated (r = 0.75; P < 0.0001). The average Japanese Orthopedic Association score of 14 patients whose cerebrospinal fluid flow velocity waveforms were absent was significantly lower (P < 0.0001) than that of 17 patients whose waveforms were present. The disturbance of pulsatile cerebrospinal fluid flow demonstrated high correlation with the severity of myelopathy. Measurement of cerebrospinal fluid flow disturbance can quantify the degree of dural sac and spinal

  10. An experimental study on the effects of temperature and magnetic field strength on the magnetorheological fluid stability and MR effect.

    Science.gov (United States)

    Rabbani, Yahya; Ashtiani, Mahshid; Hashemabadi, Seyed Hassan

    2015-06-14

    In this study, the stability and rheological properties of a suspension of carbonyl iron microparticles (CIMs) in silicone oil were investigated within a temperature range of 10 to 85 °C. The effect of adding two hydrophobic (stearic and palmitic) acids on the stability and magnetorheological effect of a suspension of CIMs in silicone oil was studied. According to the results, for preparing a stable and efficient magnetorheological (MR) fluid, additives should be utilized. Therefore, 3 wt% of stearic acid was added to the MR fluid which led to an enhancement of the fluid stability over 92% at 25 °C. By investigating shear stress variation due to the changes in the shear rate for acid-based MR fluids, the maximum yield stress was obtained by fitting the Bingham plastic rheological model at high shear rates. Based on the existing correlations of yield stress and either temperature or magnetic field strength, a new model was fitted to the experimental data to monitor the simultaneous effect of magnetic field strength and temperature on the maximum yield stress. The results demonstrated that as the magnetic field intensified or the temperature decreased, the maximum yield stress increased dramatically. In addition, when the MR fluid reached its magnetic saturation, the viscosity of fluid depended only on the shear rate.

  11. Directed Fluid Flow Produced by Arrays of Magnetically Actuated Core-Shell Biomimetic Cilia

    Science.gov (United States)

    Fiser, B. L.; Shields, A. R.; Evans, B. A.; Superfine, R.

    2010-03-01

    We have developed a novel core-shell microstructure that we use to fabricate arrays of flexible, magnetically actuated biomimetic cilia. Our biomimetic cilia mimic the size and beat shape of biological cilia in order to replicate the transport of fluid driven by cilia in many biological systems including the determination of left-right asymmetry in the vertebrate embryonic nodal plate and mucociliary clearance in the lung. Our core-shell structures consist of a flexible poly(dimethylsiloxane) (PDMS) core surrounded by a shell of nickel approximately forty nanometers thick; by using a core-shell structure, we can tune the mechanical and magnetic properties independently. We present the fabrication process and the long-range transport that occurs above the beating biomimetic cilia tips and will report on progress toward biomimetic cilia induced flow in viscoelastic fluids similar to mucus in the human airway. These flows may have applications in photonics and microfluidics, and our structures may be further useful as sensors or actuators in microelectromechanical systems.

  12. 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

  13. Reduced models accounting for parallel magnetic perturbations: gyrofluid and finite Larmor radius-Landau fluid approaches

    Science.gov (United States)

    Tassi, E.; Sulem, P. L.; Passot, T.

    2016-12-01

    Reduced models are derived for a strongly magnetized collisionless plasma at scales which are large relative to the electron thermal gyroradius and in two asymptotic regimes. One corresponds to cold ions and the other to far sub-ion scales. By including the electron pressure dynamics, these models improve the Hall reduced magnetohydrodynamics (MHD) and the kinetic Alfvén wave model of Boldyrev et al. (2013 Astrophys. J., vol. 777, 2013, p. 41), respectively. We show that the two models can be obtained either within the gyrofluid formalism of Brizard (Phys. Fluids, vol. 4, 1992, pp. 1213-1228) or as suitable weakly nonlinear limits of the finite Larmor radius (FLR)-Landau fluid model of Sulem and Passot (J. Plasma Phys., vol 81, 2015, 325810103) which extends anisotropic Hall MHD by retaining low-frequency kinetic effects. It is noticeable that, at the far sub-ion scales, the simplifications originating from the gyroaveraging operators in the gyrofluid formalism and leading to subdominant ion velocity and temperature fluctuations, correspond, at the level of the FLR-Landau fluid, to cancellation between hydrodynamic contributions and ion finite Larmor radius corrections. Energy conservation properties of the models are discussed and an explicit example of a closure relation leading to a model with a Hamiltonian structure is provided.

  14. Magnetic hyperthermia study in water based magnetic fluids containing TMAOH coated Fe3O4 using infrared thermography

    Science.gov (United States)

    Lahiri, B. B.; Ranoo, Surojit; Philip, John

    2017-01-01

    We study the alternating magnetic field induced heating of a water based ferrofluid containing tetramethyl ammonium hydroxide coated iron oxide nanoparticles using infrared thermography and compare the results obtained from the conventional fiber optic temperature sensor. Experiments are performed on ferrofluid samples of five different concentrations and under four different external field amplitudes at a fixed frequency. The temperature rise curves measured using both the infrared thermography and fiber optic sensor are found to be very similar up to a certain time interval, above which deviations are observed, which are attributed to the internal and external convection phenomena. A correction methodology is developed to account for the convection losses. The convection corrected specific absorption rate is found to be in good agreement with the values obtained from the conventional fiber optic temperature sensor, within a maximum error of ±3.4%. The highest specific absorption rate obtained in the present study is 135.98 (±4.6) W/gFe for a sample concentration of 3 wt.%, at an external field amplitude and a frequency of 63.0 kA m-1 and 126 kHz, respectively. The specific absorption rate is found to decrease with increasing sample concentration, due to the enhancement of dipolar interaction with increasing sample concentration due to agglomeration. This study validates the efficacy and universal applicability of IRT as an alternate, real time, non-contact and wide area temperature measurement methodology for magnetic fluid hyperthermia experiments without any sample contamination.

  15. Study of Fluid Flow Control in Protein Crystallization using Strong Magnetic Fields

    Science.gov (United States)

    Ramachandran, Narayanan; Leslie, Fred; Ciszak, Ewa

    2002-11-01

    An important component in biotechnology, particularly in the area of protein engineering and rational drug design is the knowledge of the precise three-dimensional molecular structure of proteins. The quality of structural information obtained from X-ray diffraction methods is directly dependent on the degree of perfection of the protein crystals. As a consequence, the growth of high quality macromolecular crystals for diffraction analyses has been the central focus for biochemists, biologists, and bioengineers. Macromolecular crystals are obtained from solutions that contain the crystallizing species in equilibrium with higher aggregates, ions, precipitants, other possible phases of the protein, foreign particles, the walls of the container, and a likely host of other impurities. By changing transport modes in general, i.e., reduction of convection and sedimentation, as is achieved in "microgravity", researchers have been able to dramatically affect the movement and distribution of macromolecules in the fluid, and thus their transport, formation of crystal nuclei, and adsorption to the crystal surface. While a limited number of high quality crystals from space flights have been obtained, as the recent National Research Council (NRC) review of the NASA microgravity crystallization program pointed out, the scientific approach and research in crystallization of proteins has been mainly empirical yielding inconclusive results. We postulate that we can reduce convection in ground-based experiments and we can understand the different aspects of convection control through the use of strong magnetic fields and field gradients. Whether this limited convection in a magnetic field will provide the environment for the growth of high quality crystals is still a matter of conjecture that our research will address. The approach exploits the variation of fluid magnetic susceptibility with concentration for this purpose and the convective damping is realized by appropriately

  16. Structure and thermodynamics of a mixture of patchy and spherical colloids: A multi-body association theory with complete reference fluid information.

    Science.gov (United States)

    Bansal, Artee; Asthagiri, D; Cox, Kenneth R; Chapman, Walter G

    2016-08-21

    A mixture of solvent particles with short-range, directional interactions and solute particles with short-range, isotropic interactions that can bond multiple times is of fundamental interest in understanding liquids and colloidal mixtures. Because of multi-body correlations, predicting the structure and thermodynamics of such systems remains a challenge. Earlier Marshall and Chapman [J. Chem. Phys. 139, 104904 (2013)] developed a theory wherein association effects due to interactions multiply the partition function for clustering of particles in a reference hard-sphere system. The multi-body effects are incorporated in the clustering process, which in their work was obtained in the absence of the bulk medium. The bulk solvent effects were then modeled approximately within a second order perturbation approach. However, their approach is inadequate at high densities and for large association strengths. Based on the idea that the clustering of solvent in a defined coordination volume around the solute is related to occupancy statistics in that defined coordination volume, we develop an approach to incorporate the complete information about hard-sphere clustering in a bulk solvent at the density of interest. The occupancy probabilities are obtained from enhanced sampling simulations but we also develop a concise parametric form to model these probabilities using the quasichemical theory of solutions. We show that incorporating the complete reference information results in an approach that can predict the bonding state and thermodynamics of the colloidal solute for a wide range of system conditions.

  17. Structure and thermodynamics of a mixture of patchy and spherical colloids: A multi-body association theory with complete reference fluid information

    Science.gov (United States)

    Bansal, Artee; Asthagiri, D.; Cox, Kenneth R.; Chapman, Walter G.

    2016-08-01

    A mixture of solvent particles with short-range, directional interactions and solute particles with short-range, isotropic interactions that can bond multiple times is of fundamental interest in understanding liquids and colloidal mixtures. Because of multi-body correlations, predicting the structure and thermodynamics of such systems remains a challenge. Earlier Marshall and Chapman [J. Chem. Phys. 139, 104904 (2013)] developed a theory wherein association effects due to interactions multiply the partition function for clustering of particles in a reference hard-sphere system. The multi-body effects are incorporated in the clustering process, which in their work was obtained in the absence of the bulk medium. The bulk solvent effects were then modeled approximately within a second order perturbation approach. However, their approach is inadequate at high densities and for large association strengths. Based on the idea that the clustering of solvent in a defined coordination volume around the solute is related to occupancy statistics in that defined coordination volume, we develop an approach to incorporate the complete information about hard-sphere clustering in a bulk solvent at the density of interest. The occupancy probabilities are obtained from enhanced sampling simulations but we also develop a concise parametric form to model these probabilities using the quasichemical theory of solutions. We show that incorporating the complete reference information results in an approach that can predict the bonding state and thermodynamics of the colloidal solute for a wide range of system conditions.

  18. 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.

  19. 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.

  20. Modeling and analysis of controllable output property of cantilever-beam inertial sensors based on magnetic fluid

    Institute of Scientific and Technical Information of China (English)

    Guixiong LIU; Peiqiang ZHANG; Chen XU

    2009-01-01

    Magnetic fluid is first introduced into thetraditional cantileverbeam senor. Based on the property of the cantilever-beam and the novel controllable mag-viscosity of magnetic fluid, the output of cantilever-beam sensors is under control so that the controllable output of the sensors can be realized. The mathematical model of the sensors is established and analyzed. The dynamic control function and the following educational results, which include the two curves of the displacement ratio and phase function with the different damping ratio and frequency ratio, are obtained based on the model. The result shows that it is valid to realize the controllable output of the sensors by controlling the viscosity of the magnetic fluid,and finally the expanded measurement range can be realized.

  1. Self-pinning by colloids confined at a contact line

    Science.gov (United States)

    Weon, Byung; Je, Jung

    2013-03-01

    Colloidal particles suspended in a fluid usually inhibit complete wetting of the fluid on a solid surface and cause pinning of the contact line, known as self-pinning. We show differences in spreading and drying behaviors of pure and colloidal droplets using optical and confocal imaging methods. These differences come from spreading inhibition by colloids confined at a contact line. We propose a self-pinning mechanism based on spreading inhibition by colloids. We find a good agreement between the mechanism and the experimental result taken by directly tracking individual colloids near the contact lines of evaporating colloidal droplets. This research was supported by the Creative Research Initiatives (Functional X-ray Imaging) of MEST/NRF.

  2. Monodispersed magnetite nanoparticles optimized for magnetic fluid hyperthermia: Implications in biological systems

    Science.gov (United States)

    Khandhar, Amit P.; Ferguson, R. Matthew; Krishnan, Kannan M.

    2011-04-01

    Magnetite (Fe3O4) nanoparticles (MNPs) are suitable materials for Magnetic Fluid Hyperthermia (MFH), provided their size is carefully tailored to the applied alternating magnetic field (AMF) frequency. Since aqueous synthesis routes produce polydisperse MNPs that are not tailored for any specific AMF frequency, we have developed a comprehensive protocol for synthesizing highly monodispersed MNPs in organic solvents, specifically tailored for our field conditions (f = 376 kHz, H0 = 13.4 kA/m) and subsequently transferred them to water using a biocompatible amphiphilic polymer. These MNPs (σavg. = 0.175) show truly size-dependent heating rates, indicated by a sharp peak in the specific loss power (SLP, W/g Fe3O4) for 16 nm (diameter) particles. For broader size distributions (σavg. = 0.266), we observe a 30% drop in overall SLP. Furthermore, heating measurements in biological medium [Dulbecco's modified Eagle medium (DMEM) + 10% fetal bovine serum] show a significant drop for SLP (˜30% reduction in 16 nm MNPs). Dynamic Light Scattering (DLS) measurements show particle hydrodynamic size increases over time once dispersed in DMEM, indicating particle agglomeration. Since the effective magnetic relaxation time of MNPs is determined by fractional contribution of the Neel (independent of hydrodynamic size) and Brownian (dependent on hydrodynamic size) components, we conclude that agglomeration in biological medium modifies the Brownian contribution and thus the net heating capacity of MNPs.

  3. Water dispersible superparamagnetic Cobalt iron oxide nanoparticles for magnetic fluid hyperthermia

    Energy Technology Data Exchange (ETDEWEB)

    Salunkhe, Ashwini B. [Centre for advanced materials research, Department of Physics, Savitribai Phule Pune University, Pune 411007 (India); Soft matter and molecular biophysics group, Department of Applied Physics, University of Santiago de Compostela, Santiago de Compostela (Spain); Khot, Vishwajeet M. [Department of Physics and Astronomy, University College London (United Kingdom); Ruso, Juan M. [Soft matter and molecular biophysics group, Department of Applied Physics, University of Santiago de Compostela, Santiago de Compostela (Spain); Patil, S.I., E-mail: patil@physics.unipune.ac.in [Centre for advanced materials research, Department of Physics, Savitribai Phule Pune University, Pune 411007 (India)

    2016-12-01

    Superparamagnetic nanoparticles of Cobalt iron oxide (CoFe{sub 2}O{sub 4}) are synthesized chemically, and dispersed in an aqueous suspension for hyperthermia therapy application. Different parameters such as magnetic field intensity, particle concentration which regulates the competence of CoFe{sub 2}O{sub 4} nanoparticle as a heating agents in hyperthermia are investigated. Specific absorption rate (SAR) decreases with increase in the particle concentration and increases with increase in applied magnetic field intensity. Highest value of SAR is found to be 91.84 W g{sup −1} for 5 mg. mL{sup −1} concentration. Oleic acid conjugated polyethylene glycol (OA-PEG) coated CoFe{sub 2}O{sub 4} nanoparticles have shown superior cyto-compatibility over uncoated nanoparticles to L929 mice fibroblast cell lines for concentrations below 2 mg. mL{sup −1}. Present work provides the underpinning for the use of CoFe{sub 2}O{sub 4} nanoparticles as a potential heating mediator for magnetic fluid hyperthermia. - Highlights: • Superparamagnetic, water dispersible CoFe{sub 2}O{sub 4} NPs were synthesized by simple and cost effective Co precipitation route. • Effect of coating on various physical and chemical properties of CoFe{sub 2}O{sub 4} NPs were studied. • The effect of coating on induction heating as well as biocompatibility of NPs were studied.

  4. A Comparison of Porous Structures on the Performance of a Magnetic Fluid Based Rough Short Bearing

    Directory of Open Access Journals (Sweden)

    J.R. Patel

    2013-09-01

    Full Text Available Efforts have been made ​​to study and analyze the comparison of variousporous structures on the performance of a magnetic fluid basedtransversely rough short bearing. The globular sphere model of Kozeny - Carman and Irmay's model of capillary fissures have been subjected to investigations. The transverse surface roughness of the bearing surfaces has been characterized by a stochastic random variable with non zero mean, variance and skewness. The stochastically averaged Reynolds type equation has been solved under suitable boundary conditions to obtain The pressure distribution in turn Which gives the expression for the load carrying capacity. It is found that the magnetization affects the bearing system positively while the bearing suffers owing to transverse roughness. This adverse effect is relatively less in the case of Kozeny - Carman model. The negatively skewed roughness induces an increase in Which load carrying capacity can be channelized to compensate the adverse effect of porosity , at least in the case of Kozeny - Carman model. This compensation in the case of Irmay's model is relatively less. The effect of magnetization responds more in the case of Kozeny - Carman model as compared to Irmay's model.

  5. Effect of magnetic field in power-law fluid with mass transfer

    Science.gov (United States)

    Talib, Amira Husni; Abdullah, Ilyani; Sabri, Izzati

    2017-08-01

    Study of non-Newtonian blood flow under the influence of magnetic field through a stenosed artery is carried out. Blood stream is modelled by power-law fluid since the rate of shear stress for blood and shear strain is not linear. Mass transfer refers to the movement of low-density lipoprotein (LDL) between the blood flow and arterial wall. The process of LDL movement brings up to localization of stenosis in the arterial segment. Magnetic field is applied to decrease blood velocity and reduce the risk of stenosis ruptures. The governing equations of blood flow are coupled with convection-diffusion equation of mass transfer. Marker and Cell (MAC) method is used in solving the problem in order to obtain the quantities of the axial velocity (w), radial velocity (u), mass concentration (C) and pressure (p) are calculated at different locations. The results are presented in the graph and discussed in details. The application of magnetic field decreases the axial velocity and mass concentration profiles.

  6. Effects of rotation and initial stress on peristaltic transport of fourth grade fluid with heat transfer and induced magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Abd-Alla, A.M., E-mail: mohmrr@yahoo.com [Mathematics Department, Faculty of Science, Taif University (Saudi Arabia); Mathematics Department, Faculty of Science, Sohag (Egypt); Abo-Dahab, S.M., E-mail: sdahb@yahoo.com [Mathematics Department, Faculty of Science, Taif University (Saudi Arabia); Mathematics Department, Faculty of Science, SVU, Qena 83523 (Egypt); El-Shahrany, H.D. [Mathematics Department, Faculty of Science, Taif University (Saudi Arabia)

    2014-01-15

    This paper investigates the effect of rotation and initial stress on the peristaltic flow of an incompressible fourth grade fluid in asymmetric channel with magnetic field and heat transfer. Constitutive equations obeying the fourth grade fluid model are employed. Assumptions of long wavelength and low Reynolds number are used in deriving solution for the flow. Closed form expressions for the stream function, pressure gradient, temperature, magnetic force function, induced magnetic field and current density are developed. Pressure rise per wavelength and frictional forces on the channel walls have been computed numerically. Effects of rotation, initial stress and inclination of magnetic field on the axial velocity and pressure gradient are discussed in detail and shown graphically. Several limiting results can be obtained as the special cases of the problem under consideration. Numerical illustrations that show the physical effects and the pertinent features are investigated at the end of the paper. - Highlights: • Effect of rotation, magnetic field, heat transfer and initial stress on the peristaltic flow of an incompressible fourth grade fluid. • Assumptions of long wavelength and low Reynolds number are used in deriving solution for the flow. • Closed form expressions for the stream function, pressure gradient, temperature, magnetic force function, induced magnetic field and current density.

  7. Magnetic targeting in the impermeable microvessel with two-phase fluid model--non-Newtonian characteristics of blood.

    Science.gov (United States)

    Shaw, Sachin; Murthy, P V S N

    2010-09-01

    The present investigation deals with finding the trajectories of the drug dosed magnetic carrier particle in a microvessel with two-phase fluid model which is subjected to the external magnetic field. The radius of the microvessel is divided into the endothelial glycocalyx layer in which the blood is assumed to obey Newtonian character and a core and plug regions where the blood obeys the non-Newtonian Herschel-Bulkley character which is suitable for the microvessel of radius 50 microm. The carrier particles, bound with nanoparticles and drug molecules are injected into the vascular system upstream from malignant tissue, and captured at the tumor site using a local applied magnetic field. The applied magnetic field is produced by a cylindrical magnet positioned outside the body and near the tumor position. The expressions for the fluidic force for the carrier particle traversing in the two-phase fluid in the microvessel and the magnetic force due to the external magnetic field are obtained. Several factors that influence the magnetic targeting of the carrier particles in the microvasculature, such as the size of the carrier particle, the volume fraction of embedded magnetic nanoparticles, and the distance of separation of the magnet from the axis of the microvessel are considered in the present problem. An algorithm is given to solve the system of coupled equations for trajectories of the carrier particle in the invasive case. The trajectories of the carrier particle are found for both invasive and noninvasive targeting systems. A comparison is made between the trajectories in these cases. Also, the present results are compared with the data available for the impermeable microvessel with single-phase fluid flow. Also, a prediction of the capture of therapeutic magnetic nanoparticle in the impermeable microvasculature is made for different radii, distances and volume fractions in both the invasive and noninvasive cases.

  8. Convection of Paramagnetic Fluid in a Cube Heated and Cooled from Side Walls and Placed below a Superconducting Magnet

    Science.gov (United States)

    Bednarz, Tomasz; Fornalik, Elzbieta; Tagawa, Toshio; Ozoe, Hiroyuki; Szmyd, Janusz S.

    The magnetic convection of paramagnetic fluid is studied in a strong magnetic field. The fluid in a cubic enclosure is heated from one vertical wall and cooled from the opposite one. The fluid is the 80% mass aqueous solution of glycerol with 0.8 mol/kg concentration of gadolinium nitrate hexahydrate to make the working fluid paramagnetic. The small amount of liquid crystal slurry is added to the fluid in order to visualize the temperature profiles in a vertical cross-section. This system is placed directly below the solenoid of the superconducting magnet which is oriented vertically. The temperature of cold wall is constantly controlled by the water flowing from a thermostating bath. On the other hand, the hot wall is heated by a nichrome wire from a DC power supply. In the numerical computations, the configuration of the system is modeled to be as close as possible to the real system. The physical properties of the working fluid are used to compute dimensionless parameters in the numerical model and the computations are carried out for corresponding cases. Later, the numerical and experimental results are compared with each other.

  9. Effect of magnetic field on unsteady natural convective flow of a micropolar fluid between two vertical walls

    Directory of Open Access Journals (Sweden)

    Hari R. Kataria

    2017-03-01

    Full Text Available We study theoretically the boundary layer flow of an incompressible micropolar fluid under uniform magnetic field and motion takes place due to the buoyancy force between vertical walls. The governing unsteady boundary layer momentum, angular momentum and energy equations of micropolar fluid are nondimensionalized and solved numerically. Analytic result for steady state case is also discussed. The effects of magnetic parameter (M, vortex viscosity parameter (R, Prandtl number (Pr and material parameter (b on velocity, micro-rotation and Temperature profiles are discussed through several figures.

  10. Structure and thermodynamics of a mixture of patchy and spherical colloids: a multi-body association theory with complete reference fluid information

    CERN Document Server

    Bansal, Artee; Cox, Kenneth R; Chapman, Walter G

    2016-01-01

    A mixture of solvent particles with short-range, directional interactions and solute particles with short-range, isotropic interactions that can bond multiple times is of fundamental interest in understanding liquids and colloidal mixtures. Because of multi-body correlations predicting the structure and thermodynamics of such systems remains a challenge. Earlier Marshall and Chapman developed a theory wherein association effects due to interactions multiply the partition function for clustering of particles in a reference hard-sphere system. The multi-body effects are incorporated in the clustering process, which in their work was obtained in the absence of the bulk medium. The bulk solvent effects were then modeled approximately within a second order perturbation approach. However, their approach is inadequate at high densities and for large association strengths. Based on the idea that the clustering of solvent in a defined coordination volume around the solute is related to occupancy statistics in that def...

  11. Effects of rotation and initial stress on peristaltic transport of fourth grade fluid with heat transfer and induced magnetic field

    Science.gov (United States)

    Abd-Alla, A. M.; Abo-Dahab, S. M.; El-Shahrany, H. D.

    2014-01-01

    This paper investigates the effect of rotation and initial stress on the peristaltic flow of an incompressible fourth grade fluid in asymmetric channel with magnetic field and heat transfer. Constitutive equations obeying the fourth grade fluid model are employed. Assumptions of long wavelength and low Reynolds number are used in deriving solution for the flow. Closed form expressions for the stream function, pressure gradient, temperature, magnetic force function, induced magnetic field and current density are developed. Pressure rise per wavelength and frictional forces on the channel walls have been computed numerically. Effects of rotation, initial stress and inclination of magnetic field on the axial velocity and pressure gradient are discussed in detail and shown graphically. Several limiting results can be obtained as the special cases of the problem under consideration. Numerical illustrations that show the physical effects and the pertinent features are investigated at the end of the paper.

  12. Effect of interleukin-2 treatment combined with magnetic fluid hyperthermia on Lewis lung cancer-bearing mice.

    Science.gov (United States)

    Hu, Runlei; Ma, Shenglin; Ke, Xianfu; Jiang, Hong; Wei, Dongshan; Wang, Wei

    2016-01-01

    The present study aimed to investigate the therapeutic effect of interleukin-2 (IL-2) treatment combined with magnetic fluid hyperthermia (MFH) on Lewis lung cancer-bearing mice. Magnetic fluids were prepared in vitro and directly injected into the tumors in the mice, which were subjected to an alternating magnetic field. The temperature in the tumor reached 43°C and was maintained by controlling the strength of magnetic field for 30 min. Twenty-four hours later, IL-2 was injected directly into the tumors. Mice were divided into four groups: Group I (control), II (MFH), III (IL-2) and IV (IL-2+MFH). The tumor grew gradually in groups II and IV (both Pbearing mice.

  13. Computational studies of suppression of microwave gas breakdown by crossed dc magnetic field using electron fluid model

    Science.gov (United States)

    Zhao, Pengcheng; Guo, Lixin; Shu, Panpan

    2016-08-01

    The gas breakdown induced by a square microwave pulse with a crossed dc magnetic field is investigated using the electron fluid model, in which the accurate electron energy distribution functions are adopted. Simulation results show that at low gas pressures the dc magnetic field of a few tenths of a tesla can prolong the breakdown formation time by reducing the mean electron energy. With the gas pressure increasing, the higher dc magnetic field is required to suppress the microwave breakdown. The electric field along the microwave propagation direction generated due to the motion of electrons obviously increases with the dc magnetic field, but it is much less than the incident electric field. The breakdown predictions of the electron fluid model agree very well with the particle-in-cell-Monte Carlo collision simulations as well as the scaling law for the microwave gas breakdown.

  14. Magnetic, fluorescent, and thermo-responsive Fe(3)O(4)/rare earth incorporated poly(St-NIPAM) core-shell colloidal nanoparticles in multimodal optical/magnetic resonance imaging probes.

    Science.gov (United States)

    Zhu, Haie; Tao, Juan; Wang, Wenhao; Zhou, Yingjie; Li, Penghui; Li, Zheng; Yan, Kai; Wu, Shuilin; Yeung, Kelvin W K; Xu, Zushun; Xu, Haibo; Chu, Paul K

    2013-03-01

    Multifunctional colloidal nanoparticles which exhibit fluorescence, superparamagnetism, and thermosensitivity are produced by two step seed emulsifier-free emulsion polymerization in the presence of oleic acid (OA) and sodium undecylenate (NaUA) modified Fe(3)O(4) nanoparticles. In the first step, St and NIPAM polymerize the NaUA on the surface of Fe(3)O(4) nanoparticles to form Fe(3)O(4)/poly(St-NIPAM) nanoparticles which act as seeds for the polymerization of Eu(AA)(3)Phen with the remaining St and NIPAM in the second step to form an outer fluorescent layer. The core-shell composite nanoparticles show reversible dimensional changes in response to external temperature stimuli. Fluorescence spectra acquired from the composites exhibit characteristic emission peaks of Eu(3+) at 594 and 619 nm and vivid red luminescence can be observed by 2-photon confocal scanning laser microscopy (CLSM). In vitro cytotoxicity tests based on the MTT assay demonstrate good cytocompatibility and the composites also possess paramagnetic properties with a maximum saturation magnetization of 6.45 emu/g and high transverse relaxivity rates (r(2)) of 411.78 mM(-1) s(-1). In vivo magnetic resonance imaging (MRI) studies show significant liver and spleen contrast with relative signal intensity reduction of about 86% 10 min after intravenous injection of the composites. These intriguing properties suggest that these nanocarriers have large clinical potential as multimodal optical/MRI probes. Copyright © 2012 Elsevier Ltd. All rights reserved.

  15. Electrochemical synthesis of nanostructured porous materials using liquid crystal and colloidal templates and their magnetic and optical properties

    CERN Document Server

    Ghanem, M A M

    2002-01-01

    material, and that these magnetic properties vary systematically with the diameter of the spherical pores within the films. A new oscillation effect has been observed for the coercivity of macroporous Ni sub 8 sub 0 Fe sub 2 sub 0 film with different pore layer thickness. sphere templates, the resulting films show well-formed, regular, two- and three-dimensional macroporous networks consisting of spherical pores arranged in a highly ordered face centred cubic (fee) structure. The spherical voids are interconnected by a series of smaller windows that form an open porous structure embedded in the material framework. The diameter of the spherical pores can be precisely changed over the range from 200 to 1000 nm by changing the diameter of the latex spheres used to form the templates. The resulting macroporous material structures are robust, self-supported, dense, polycrystalline, uniform and free from filling defects and contamination or problems caused by shrinkage during processing. The nanostructured macropor...

  16. Computational Fluid Dynamics Simulation of a Quadrupole Magnetic Sorter Flow Channel: Effect of Splitter Position on Nonspecific Crossover.

    Science.gov (United States)

    Sajja, V S K; Kennedy, David J; Todd, Paul W; Hanley, Thomas R

    2011-10-01

    In the Quadrupole Magnetic Sorter (QMS) magnetic particles enter a vertical flow annulus and are separated from non-magnetic particles by radial deflection into an outer annulus where the purified magnetic particles are collected via a flow splitter. The purity of magnetically isolated particles in QMS is affected by the migration of nonmagnetic particles across transport lamina in the annular flow channel. Computational Fluid Dynamics (CFD) simulations were used to predict the flow patterns, pressure drop and nonspecific crossover in QMS flow channel for the isolation of pancreatic islets of Langerhans. Simulation results were compared with the experimental results to validate the CFD model. Results of the simulations were used to show that one design gives up to 10% less nonspecific crossover than another and this model can be used to optimise the flow channel design to achieve maximum purity of magnetic particles.

  17. Magnetic Field and Gravity Effects on Peristaltic Transport of a Jeffrey Fluid in an Asymmetric Channel

    Directory of Open Access Journals (Sweden)

    A. M. Abd-Alla

    2014-01-01

    Full Text Available In this paper, the peristaltic flow of a Jeffrey fluid in an asymmetric channel has been investigated. Mathematical modeling is carried out by utilizing long wavelength and low Reynolds number assumptions. Closed form expressions for the pressure gradient, pressure rise, stream function, axial velocity, and shear stress on the channel walls have been computed numerically. Effects of the Hartmann number, the ratio of relaxation to retardation times, time-mean flow, the phase angle and the gravity field on the pressure gradient, pressure rise, streamline, axial velocity, and shear stress are discussed in detail and shown graphically. The results indicate that the effect of Hartmann number, ratio of relaxation to retardation times, time-mean flow, phase angle, and gravity field are very pronounced in the peristaltic transport phenomena. Comparison was made with the results obtained in the presence and absence of magnetic field and gravity field.

  18. Hemodynamic analysis of intracranial aneurysms using phase-contrast magnetic resonance imaging and computational fluid dynamics

    Science.gov (United States)

    Zhao, Xuemei; Li, Rui; Chen, Yu; Sia, Sheau Fung; Li, Donghai; Zhang, Yu; Liu, Aihua

    2017-03-01

    Additional hemodynamic parameters are highly desirable in the clinical management of intracranial aneurysm rupture as static medical images cannot demonstrate the blood flow within aneurysms. There are two ways of obtaining the hemodynamic information—by phase-contrast magnetic resonance imaging (PCMRI) and computational fluid dynamics (CFD). In this paper, we compared PCMRI and CFD in the analysis of a stable patient's specific aneurysm. The results showed that PCMRI and CFD are in good agreement with each other. An additional CFD study of two stable and two ruptured aneurysms revealed that ruptured aneurysms have a higher statistical average blood velocity, wall shear stress, and oscillatory shear index (OSI) within the aneurysm sac compared to those of stable aneurysms. Furthermore, for ruptured aneurysms, the OSI divides the positive and negative wall shear stress divergence at the aneurysm sac.

  19. Heat transfer in micropolar fluid flow under the influence of magnetic field

    Directory of Open Access Journals (Sweden)

    Kocić Miloš M.

    2016-01-01

    Full Text Available In this paper, the steady flow and heat transfer of an incompressible electrically conducting micropolar fluid through a parallel plate channel is investigated. The upper and lower plates have been kept at the two constant different temperatures and the plates are electrically insulated. Applied magnetic field is perpendicular to the flow, while the Reynolds number is significantly lower than one i.e. considered problem is in induction-less approximation. The general equations that describe the discussed problem under the adopted assumptions are reduced to ordinary differential equations and three closed-form solutions are obtained. The velocity, micro-rotation and temperature fields in function of Hartmann number, the coupling parameter and the spin-gradient viscosity parameter are graphically shown and discussed.

  20. Static and dynamic properties of magnetic nanowires in nematic fluids (invited)

    Science.gov (United States)

    Lapointe, C.; Cappallo, N.; Reich, D. H.; Leheny, R. L.

    2005-05-01

    Microscopy experiments are employed to characterize the elastic interactions of magnetic nickel nanowires suspended in a nematic liquid crystal. The nematic imposes a torque on an isolated wire that increases linearly with the angle between the wire and the nematic director in a manner quantitatively consistent with predictions based on an analogy between the nematic elasticity and electrostatics. An extension of this analogy also explains a measured orientation-dependent repulsive force between a wire and a wall. The angular relaxation of a wire in response to the elastic torque displays a nonexponential time dependence from which effective viscosities for the fluid are determined. The behavior of a wire in a twisted nematic cell further demonstrates how spatial variations in the director can convert the torque to a controlled translational force that levitates a wire to a specified height.