Semiflexible polymer dynamics with a bead-spring model

NASA Astrophysics Data System (ADS)

Barkema, Gerard T.; Panja, Debabrata; van Leeuwen, J. M. J.

2014-11-01

We study the dynamical properties of semiflexible polymers with a recently introduced bead-spring model. We focus on double-stranded DNA (dsDNA). The two parameters of the model, T* and ν, are chosen to match its experimental force-extension curve. In comparison to its groundstate value, the bead-spring Hamiltonian is approximated in the first order by the Hessian that is quadratic in the bead positions. The eigenmodes of the Hessian provide the longitudinal (stretching) and transverse (bending) eigenmodes of the polymer, and the corresponding eigenvalues match well with the established phenomenology of semiflexible polymers. At the Hessian approximation of the Hamiltonian, the polymer dynamics is linear. Using the longitudinal and transverse eigenmodes, for the linearized problem, we obtain analytical expressions of (i) the autocorrelation function of the end-to-end vector, (ii) the autocorrelation function of a bond (i.e. a spring, or a tangent) vector at the middle of the chain, and (iii) the mean-square displacement of a tagged bead in the middle of the chain, as the sum over the contributions from the modes—the so-called ‘mode sums’. We also perform simulations with the full dynamics of the model. The simulations yield numerical values of the correlations functions (i-iii) that agree very well with the analytical expressions for the linearized dynamics. This does not however mean that the nonlinearities are not present. In fact, we also study the mean-square displacement of the longitudinal component of the end-to-end vector that showcases strong nonlinear effects in the polymer dynamics, and we identify at least an effective t7/8 power-law regime in its time-dependence. Nevertheless, in comparison to the full mean-square displacement of the end-to-end vector the nonlinear effects remain small at all times—it is in this sense we state that our results demonstrate that the linearized dynamics suffices for dsDNA fragments that are shorter than or comparable to the persistence length. Our results are consistent with those of the wormlike chain (WLC) model, the commonly used descriptive tool of semiflexible polymers.

Bead-bead interaction parameters in dissipative particle dynamics: Relation to bead-size, solubility parameter, and surface tension

NASA Astrophysics Data System (ADS)

Maiti, Amitesh; McGrother, Simon

2004-01-01

Dissipative particle dynamics (DPD) is a mesoscale modeling method for simulating equilibrium and dynamical properties of polymers in solution. The basic idea has been around for several decades in the form of bead-spring models. A few years ago, Groot and Warren [J. Chem. Phys. 107, 4423 (1997)] established an important link between DPD and the Flory-Huggins χ-parameter theory for polymer solutions. We revisit the Groot-Warren theory and investigate the DPD interaction parameters as a function of bead size. In particular, we show a consistent scheme of computing the interfacial tension in a segregated binary mixture. Results for three systems chosen for illustration are in excellent agreement with experimental results. This opens the door for determining DPD interactions using interfacial tension as a fitting parameter.

Microfabricated magnetic traps for single molecule manipulation and measurement

NASA Astrophysics Data System (ADS)

Mirowski, Elizabeth; Moreland, John; Russek, Stephen; Donahue, Michael

2003-03-01

We have microfabricated patterned magnetic thin film traps for capturing superparamagnetic beads in microfluidic cells. The traps are based on a novel concept of using a magnetic force microsope cantilever for transporting magnetic beads from one trap to another along the surface of a thin silicon nitride membrane. We specifically address the optimal design criteria for the traps. In addition, we present measurements of the forces on a bead (attached to a functionalized cantilever tip) as a function of its position near the trap. Equivalent spring constants of various trap geometries are extrapolated from the force measurements. The force measurements will be compared to micromagnetic modelling of the system as well as the Brownian motion of the bead in the trap.

Impact-based piezoelectric energy harvester for multidimensional, low-level, broadband, and low-frequency vibrations

NASA Astrophysics Data System (ADS)

Zhang, Hongjiang; Jiang, Senlin; He, Xuefeng

2017-05-01

This letter proposes an impact-based piezoelectric energy harvester that uses a rolling bead contained in a bracket that is supported by a spring. Under either translational or rotational base excitation, the bead moves within the bracket and collides with piezoelectric cantilevers that are located around the bracket; these collisions cause the piezoelectric beams to vibrate and thus produce electrical outputs. The low rolling friction and the motion amplification effect of the spring make the resulting device suitable for collection of low-level vibration energy. Experiments show that the proposed harvester is promising for use in scavenging of energy from the multidimensional, low-level, broadband, and low-frequency vibrations that occur in natural environments.

Lattice Boltzmann simulations of the bead-spring microswimmer with a responsive stroke—from an individual to swarms

NASA Astrophysics Data System (ADS)

Pickl, Kristina; Pande, Jayant; Köstler, Harald; Rüde, Ulrich; Smith, Ana-Sunčana

2017-03-01

Propulsion at low Reynolds numbers is often studied by defining artificial microswimmers which exhibit a particular stroke. The disadvantage of such an approach is that the stroke does not adjust to the environment, in particular the fluid flow, which can diminish the effect of hydrodynamic interactions. To overcome this limitation, we simulate a microswimmer consisting of three beads connected by springs and dampers, using the self-developed waLBerla and pe framework based on the lattice Boltzmann method and the discrete element method. In our approach, the swimming stroke of a swimmer emerges as a balance of the drag, the driving and the elastic internal forces. We validate the simulations by comparing the obtained swimming velocity to the velocity found analytically using a perturbative method where the bead oscillations are taken to be small. Including higher-order terms in the hydrodynamic interactions between the beads improves the agreement to the simulations in parts of the parameter space. Encouraged by the agreement between the theory and the simulations and aided by the massively parallel capabilities of the waLBerla-pe framework, we simulate more than ten thousand such swimmers together, thus presenting the first fully resolved simulations of large swarms with active responsive components.

Fabrication of electron beam deposited tip for atomic-scale atomic force microscopy in liquid.

PubMed

Miyazawa, K; Izumi, H; Watanabe-Nakayama, T; Asakawa, H; Fukuma, T

2015-03-13

Recently, possibilities of improving operation speed and force sensitivity in atomic-scale atomic force microscopy (AFM) in liquid using a small cantilever with an electron beam deposited (EBD) tip have been intensively explored. However, the structure and properties of an EBD tip suitable for such an application have not been well-understood and hence its fabrication process has not been established. In this study, we perform atomic-scale AFM measurements with a small cantilever and clarify two major problems: contaminations from a cantilever and tip surface, and insufficient mechanical strength of an EBD tip having a high aspect ratio. To solve these problems, here we propose a fabrication process of an EBD tip, where we attach a 2 μm silica bead at the cantilever end and fabricate a 500-700 nm EBD tip on the bead. The bead height ensures sufficient cantilever-sample distance and enables to suppress long-range interaction between them even with a short EBD tip having high mechanical strength. After the tip fabrication, we coat the whole cantilever and tip surface with Si (30 nm) to prevent the generation of contamination. We perform atomic-scale AFM imaging and hydration force measurements at a mica-water interface using the fabricated tip and demonstrate its applicability to such an atomic-scale application. With a repeated use of the proposed process, we can reuse a small cantilever for atomic-scale measurements for several times. Therefore, the proposed method solves the two major problems and enables the practical use of a small cantilever in atomic-scale studies on various solid-liquid interfacial phenomena.

Big Atoms for Small Children: Building Atomic Models from Common Materials to Better Visualize and Conceptualize Atomic Structure

ERIC Educational Resources Information Center

Cipolla, Laura; Ferrari, Lia A.

2016-01-01

A hands-on approach to introduce the chemical elements and the atomic structure to elementary/middle school students is described. The proposed classroom activity presents Bohr models of atoms using common and inexpensive materials, such as nested plastic balls, colored modeling clay, and small-sized pasta (or small plastic beads).

The glass transition temperature of thin films: A molecular dynamics study for a bead-spring model.

PubMed

Stevenson, Craig S; Curro, John G; McCoy, John D

2017-05-28

Molecular dynamics simulations were carried out on free-standing liquid films of different thicknesses h using a bead-spring model of 10 beads per chain. The glass transition temperatures, T g , of the various films were determined from plots of the internal energy versus temperature. We used these simulations to test the validity of our earlier conjecture that the glass transition of a confined liquid could be approximated by pre-averaging over the non-uniform density profile of the film. Using the density profiles from our simulations, we computed the average density of the free-standing films as a function of temperature. In all our film simulations we found, within the error of the simulation, that T g of the film occurred at the same density (or packing fraction) as the bulk system at the bulk glass transition temperature T g B . By equating these densities at their respective glass transition temperatures, as suggested by the simulations, we deduced that T g /T g B is proportional to h 0 /h. This is consistent with previous simulations and experimental data. Moreover, the parameter h 0 is determinable in our model from the density profile of the films.

Thin film atomic hydrogen detectors

NASA Technical Reports Server (NTRS)

Gruber, C. L.

1977-01-01

Thin film and bead thermistor atomic surface recombination hydrogen detectors were investigated both experimentally and theoretically. Devices were constructed on a thin Mylar film substrate. Using suitable Wheatstone bridge techniques sensitivities of 80 microvolts/2x10 to the 13th power atoms/sec are attainable with response time constants on the order of 5 seconds.

Preparation of hydrophilic polymer-grafted polystyrene beads for hydrophilic interaction chromatography via surface-initiated atom transfer radical polymerization.

PubMed

Dai, Xiaojun; He, Yuan; Wei, Yinmao; Gong, Bolin

2011-11-01

A one-step procedure based on surface-initiated atom transfer radical polymerization (SI-ATRP) to hydrophilize monodisperse poly(chloromethylstyrene-co-divinylbenzene) beads has been presented in this work, using 2-hydroxyl-3-[4-(hydroxymethyl)-1H-1,2,3-triazol-1-yl]propyl 2-methylacrylate (HTMA) as a monomer. The chain length of the grafted poly(HTMA) was controlled via varying the ratio of HTMA to initiator on the surface of the beads. When using the grafted beads as a stationary phase in hydrophilic interaction chromatography (HILIC), good resolution for nucleobases/nucleosides was obtained with acetonitrile aqueous solution as an eluent; while for phenolic acids and glycosides, they could be eluted and separated in the presence of TFA. The retention time of the solutes increased with the amount of the grafted HTMA. The retention mechanisms of solutes were investigated by the effects of mobile phase composition and buffer pH on the retention of solutes. The results illustrated that the retention behaviors of the tested solutes were dominated by hydrogen bonding interaction and electrostatic interaction. From the chemical structure of the ligands, the modified beads could not only be used as a stationary phase in HILIC, but also act as a useful building block to develop new stationary phases for other chromatographic modes such as affinity media. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

TMFF-A Two-Bead Multipole Force Field for Coarse-Grained Molecular Dynamics Simulation of Protein.

PubMed

Li, Min; Liu, Fengjiao; Zhang, John Z H

2016-12-13

Coarse-grained (CG) models are desirable for studying large and complex biological systems. In this paper, we propose a new two-bead multipole force field (TMFF) in which electric multipoles up to the quadrupole are included in the CG force field. The inclusion of electric multipoles in the proposed CG force field enables a more realistic description of the anisotropic electrostatic interactions in the protein system and, thus, provides an improvement over the standard isotropic two-bead CG models. In order to test the accuracy of the new CG force field model, extensive molecular dynamics simulations were carried out for a series of benchmark protein systems. These simulation studies showed that the TMFF model can realistically reproduce the structural and dynamical properties of proteins, as demonstrated by the close agreement of the CG results with those from the corresponding all-atom simulations in terms of root-mean-square deviations (RMSDs) and root-mean-square fluctuations (RMSFs) of the protein backbones. The current two-bead model is highly coarse-grained and is 50-fold more efficient than all-atom method in MD simulation of proteins in explicit water.

Two-bead polarizable water models combined with a two-bead multipole force field (TMFF) for coarse-grained simulation of proteins.

PubMed

Li, Min; Zhang, John Z H

2017-03-08

The development of polarizable water models at coarse-grained (CG) levels is of much importance to CG molecular dynamics simulations of large biomolecular systems. In this work, we combined the newly developed two-bead multipole force field (TMFF) for proteins with the two-bead polarizable water models to carry out CG molecular dynamics simulations for benchmark proteins. In our simulations, two different two-bead polarizable water models are employed, the RTPW model representing five water molecules by Riniker et al. and the LTPW model representing four water molecules. The LTPW model is developed in this study based on the Martini three-bead polarizable water model. Our simulation results showed that the combination of TMFF with the LTPW model significantly stabilizes the protein's native structure in CG simulations, while the use of the RTPW model gives better agreement with all-atom simulations in predicting the residue-level fluctuation dynamics. Overall, the TMFF coupled with the two-bead polarizable water models enables one to perform an efficient and reliable CG dynamics study of the structural and functional properties of large biomolecules.

Analysis of removal of cadmium by action of immobilized Chlorella sp. micro-algae in alginate beads

PubMed Central

Valdez, Christian; Perengüez, Yomaira; Mátyás, Bence; Guevara, María Fernanda

2018-01-01

Cadmium (Cd) is a metal that can negatively interfere with the metabolic systems of living beings. The objective of this work was to evaluate the capacity for cadmium removal in aqueous solutions by immobilized Chlorella sp. in calcium alginate beads. Beads without Chlorella sp. were used as a control. All the treatments were established in triplicate for 80 min, at four concentrations of cadmium (0, 20, 100 and 200 ppm), taking samples of aqueous solution every 10 min, to be read using atomic absorption equipment. The study determined that the treatment of alginate beads with immobilized Chlorella sp. removed 59.67% of cadmium at an initial concentration of 20 ppm, this being the best removal result. PMID:29399326

Mesoporous zirconium titanium oxides. Part 2: Synthesis, porosity, and adsorption properties of beads.

PubMed

Sizgek, G Devlet; Sizgek, Erden; Griffith, Christopher S; Luca, Vittorio

2008-11-04

Mesoporous zirconium titanium mixed-oxide beads having disordered wormhole textures and mole fractions of Zr (x) ranging from x=0.25 to 0.67 have been prepared. The bead preparation method combined the forced hydrolysis of mixtures of zirconium-titanium alkoxides in the presence of long-chain carboxylates with external gelation. Uniformly sized beads could be produced in the size range 0.5-1.1 mm by varying the droplet size and viscosity of the mixed-oxide sol, thus making them suitable for large-scale column chromatographic applications. The beads exhibited narrow pore size distributions with similar mean pore diameters of around 3.7 nm. The specific surface areas of the beads were linked to the Zr mole fraction in the precursor solution and were generally greater than 350 m2/g for x=0.5. A combination of scanning transmission electron microscopy and X-ray absorption fine structure analysis indicated that the pore walls of the beads were composed of atomically dispersed Zr and Ti to form a continuous network of Zr-O-Ti bonds. Mass transport in the beads was evaluated by monitoring the kinetics of vanadate and vanadyl adsorption at pH 10.5 and 0.87, respectively.

Enhanced quality factors and force sensitivity by attaching magnetic beads to cantilevers for atomic force microscopy in liquid

NASA Astrophysics Data System (ADS)

Hoof, Sebastian; Nand Gosvami, Nitya; Hoogenboom, Bart W.

2012-12-01

Dynamic-mode atomic force microscopy (AFM) in liquid remains complicated due to the strong viscous damping of the cantilever resonance. Here, we show that a high-quality resonance (Q >20) can be achieved in aqueous solution by attaching a microgram-bead at the end of the nanogram-cantilever. The resulting increase in cantilever mass causes the resonance frequency to drop significantly. However, the force sensitivity—as expressed via the minimum detectable force gradient—is hardly affected, because of the enhanced quality factor. Through the enhancement of the quality factor, the attached bead also reduces the relative importance of noise in the deflection detector. It can thus yield an improved signal-to-noise ratio when this detector noise is significant. We describe and analyze these effects for a set-up that includes magnetic actuation of the cantilevers and that can be easily implemented in any AFM system that is compatible with an inverted optical microscope.

Constructing Molecular Models with Low-Cost Toy Beads

ERIC Educational Resources Information Center

Ng, Pun-hon; Wong, Siu-ling; Mak, Se-yuen

2012-01-01

In teaching the science of the nano world, ball-and-stick molecular models are frequently used as 3D representations of molecules. Unlike a chemical formula, a molecular model allows us to visualise the 3D shape of the molecule and the relative positions of its atoms, the bonds between atoms and why a pair of mirror isomers with the same atoms,…

Improving proton conduction pathways in di- and triblock copolymer membranes: Branched versus linear side chains

NASA Astrophysics Data System (ADS)

Dorenbos, G.

2017-06-01

Phase separation within a series of polymer membranes in the presence of water is studied by dissipative particle dynamics. Each polymer contains hydrophobic A beads and hydrophilic C beads. Three parent architectures are constructed from a backbone composed of connected hydrophobic A beads to which short ([C]), long ([A3C]), or symmetrically branched A5[AC][AC] side chains spring off. Three di-block copolymer derivatives are constructed by covalently bonding an A30 block to each parent architecture. Also three tri-blocks with A15 blocks attached to both ends of each parent architecture are modeled. Monte Carlo tracer diffusion calculations through the water containing pores for 1226 morphologies reveal that water diffusion for parent architectures is slowest and diffusion through the di-blocks is fastest. Furthermore, diffusion increases with side chain length and is highest for branched side chains. This is explained by the increase of water pore size with , which is the average number of bonds that A beads are separated from a nearest C bead. Optimization of within the amphiphilic parent architecture is expected to be essential in improving proton conduction in polymer electrolyte membranes.

Westinghouse Modular Grinding Process - Enhancement of Volume Reduction for Hot Resin Supercompaction - 13491

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fehrmann, Henning; Aign, Joerg

2013-07-01

In nuclear power plants (NPP) ion exchange (IX) resins are used in several systems for water treatment. Spent resins can contain a significant amount of contaminates which makes treatment for disposal of spent resins mandatory. Several treatment processes are available such as direct immobilization with technologies like cementation, bitumisation, polymer solidification or usage of a high integrity container (HIC). These technologies usually come with a significant increase in final waste volume. The Hot Resin Supercompaction (HRSC) is a thermal treatment process which reduces the resin waste volume significantly. For a mixture of powdered and bead resins the HRSC process hasmore » demonstrated a volume reduction of up to 75 % [1]. For bead resins only the HRSC process is challenging because the bead resins compaction properties are unfavorable. The bead resin material does not form a solid block after compaction and shows a high spring back effect. The volume reduction of bead resins is not as good as for the mixture described in [1]. The compaction properties of bead resin waste can be significantly improved by grinding the beads to powder. The grinding also eliminates the need for a powder additive.Westinghouse has developed a modular grinding process to grind the bead resin to powder. The developed process requires no circulation of resins and enables a selective adjustment of particle size and distribution to achieve optimal results in the HRSC or in any other following process. A special grinding tool setup is use to minimize maintenance and radiation exposure to personnel. (authors)« less

Active elastic dimers: cells moving on rigid tracks.

PubMed

Lopez, J H; Das, Moumita; Schwarz, J M

2014-09-01

Experiments suggest that the migration of some cells in the three-dimensional extracellular matrix bears strong resemblance to one-dimensional cell migration. Motivated by this observation, we construct and study a minimal one-dimensional model cell made of two beads and an active spring moving along a rigid track. The active spring models the stress fibers with their myosin-driven contractility and α-actinin-driven extendability, while the friction coefficients of the two beads describe the catch and slip-bond behaviors of the integrins in focal adhesions. In the absence of active noise, net motion arises from an interplay between active contractility (and passive extendability) of the stress fibers and an asymmetry between the front and back of the cell due to catch-bond behavior of integrins at the front of the cell and slip-bond behavior of integrins at the back. We obtain reasonable cell speeds with independently estimated parameters. We also study the effects of hysteresis in the active spring, due to catch-bond behavior and the dynamics of cross linking, and the addition of active noise on the motion of the cell. Our model highlights the role of α-actinin in three-dimensional cell motility and does not require Arp2/3 actin filament nucleation for net motion.

Fracture Simulation of Highly Crosslinked Polymer Networks: Triglyceride-Based Adhesives

NASA Astrophysics Data System (ADS)

Lorenz, Christian; Stevens, Mark; Wool, Richard

2003-03-01

The ACRES program at the U. of Delaware has shown that triglyceride oils derived from plants are a favorable alternative to the traditional adhesives. The triglyceride networks are formed from an initial mixture of styrene monomers, free-radical initiators and triglycerides. We have performed simulations to study the effect of physical composition and physical characteristics of the triglyceride network on the strength of triglyceride network. A coarse-grained, bead-spring model of the triglyceride system is used. The average triglyceride consists of 6 beads per chain, the styrenes are represented as a single bead and the initiators are two bead chains. The polymer network is formed using an off-lattice 3D Monte Carlo simulation, in which the initiators activate the styrene and triglyceride reactive sites and then bonds are randomly formed between the styrene and active triglyceride monomers producing a highly crosslinked polymer network. Molecular dynamics simulations of the network under tensile and shear strains were performed to determine the strength as a function of the network composition. The relationship between the network structure and its strength will also be discussed.

Construction of hydrodynamic bead models from high-resolution X-ray crystallographic or nuclear magnetic resonance data.

PubMed Central

Byron, O

1997-01-01

Computer software such as HYDRO, based upon a comprehensive body of theoretical work, permits the hydrodynamic modeling of macromolecules in solution, which are represented to the computer interface as an assembly of spheres. The uniqueness of any satisfactory resultant model is optimized by incorporating into the modeling procedure the maximal possible number of criteria to which the bead model must conform. An algorithm (AtoB, for atoms to beads) that permits the direct construction of bead models from high resolution x-ray crystallographic or nuclear magnetic resonance data has now been formulated and tested. Models so generated then act as informed starting estimates for the subsequent iterative modeling procedure, thereby hastening the convergence to reasonable representations of solution conformation. Successful application of this algorithm to several proteins shows that predictions of hydrodynamic parameters, including those concerning solvation, can be confirmed. PMID:8994627

Chemically Layered Porous Solids

NASA Technical Reports Server (NTRS)

Koontz, Steve

1991-01-01

Aerogels and other porous solids in which surfaces of pores have chemical properties varying with depth below macroscopic surfaces prepared by sequences of chemical treatments. Porous glass or silica bead treated to make two depth zones having different chemical properties. Beads dropped along tube filled with flowing gas containing atomic oxygen, generated in microwave discharge. General class of materials treatable include oxides of aluminum, silicon, zirconium, tin, titanium, and nickel, and mixtures of these oxides. Potential uses of treated materials include chromatographic separations, membrane separations, controlled releases of chemicals, and catalysis.

Local dynamics of glass-forming polystyrene thin films from atomistic simulation

NASA Astrophysics Data System (ADS)

Zhou, Yuxing; Milner, Scott

Despite a wide technological application ranging from protective coatings to organic solar cells, there still no consensus on the mechanism for the glass transition in polymer thin films a manifestation of the infamous glass problem under confinement. Many experimental and computational studies have observed a large deviation of nanoscale dynamical properties in thin films from the corresponding properties in bulk. In this work, we perform extensive united-atom simulations on atactic polystyrene free-standing thin films near the glass transition temperature and focus on the effect of free surface on the local dynamics. We study the segmental dynamics as a function of distance from the surface for different temperatures, from which relaxation time and thereby local Tg is obtained for each layer. We find the dynamics near free surface is not only enhanced but becomes less strongly temperature dependent as Tg is approached compared to the bulk. We find an increasing length scale associated with mobility propagation from the free surface as temperature decreases, but no correlation between local structure and enhanced relaxation rates near the surface, consistent with studies on bead-spring chains.

Normalization of mass cytometry data with bead standards

PubMed Central

Finck, Rachel; Simonds, Erin F.; Jager, Astraea; Krishnaswamy, Smita; Sachs, Karen; Fantl, Wendy; Pe’er, Dana; Nolan, Garry P.; Bendall, Sean C.

2013-01-01

Mass cytometry uses atomic mass spectrometry combined with isotopically pure reporter elements to currently measure as many as 40 parameters per single cell. As with any quantitative technology, there is a fundamental need for quality assurance and normalization protocols. In the case of mass cytometry, the signal variation over time due to changes in instrument performance combined with intervals between scheduled maintenance must be accounted for and then normalized. Here, samples were mixed with polystyrene beads embedded with metal lanthanides, allowing monitoring of mass cytometry instrument performance over multiple days of data acquisition. The protocol described here includes simultaneous measurements of beads and cells on the mass cytometer, subsequent extraction of the bead-based signature, and the application of an algorithm enabling correction of both short- and long-term signal fluctuations. The variation in the intensity of the beads that remains after normalization may also be used to determine data quality. Application of the algorithm to a one-month longitudinal analysis of a human peripheral blood sample reduced the range of median signal fluctuation from 4.9-fold to 1.3-fold. PMID:23512433

Optical tweezers based force measurement system for quantitating binding interactions: system design and application for the study of bacterial adhesion.

PubMed

Fällman, Erik; Schedin, Staffan; Jass, Jana; Andersson, Magnus; Uhlin, Bernt Eric; Axner, Ove

2004-06-15

An optical force measurement system for quantitating forces in the pN range between micrometer-sized objects has been developed. The system was based upon optical tweezers in combination with a sensitive position detection system and constructed around an inverted microscope. A trapped particle in the focus of the high numerical aperture microscope-objective behaves like an omnidirectional mechanical spring in response to an external force. The particle's displacement from the equilibrium position is therefore a direct measure of the exerted force. A weak probe laser beam, focused directly below the trapping focus, was used for position detection of the trapped particle (a polystyrene bead). The bead and the condenser focus the light to a distinct spot in the far field, monitored by a position sensitive detector. Various calibration procedures were implemented in order to provide absolute force measurements. The system has been used to measure the binding forces between Escherichia coli bacterial adhesins and galabiose-functionalized beads.

Size, shape, and diffusivity of a single Debye-Hückel polyelectrolyte chain in solution.

PubMed

Soysa, W Chamath; Dünweg, B; Prakash, J Ravi

2015-08-14

Brownian dynamics simulations of a coarse-grained bead-spring chain model, with Debye-Hückel electrostatic interactions between the beads, are used to determine the root-mean-square end-to-end vector, the radius of gyration, and various shape functions (defined in terms of eigenvalues of the radius of gyration tensor) of a weakly charged polyelectrolyte chain in solution, in the limit of low polymer concentration. The long-time diffusivity is calculated from the mean square displacement of the centre of mass of the chain, with hydrodynamic interactions taken into account through the incorporation of the Rotne-Prager-Yamakawa tensor. Simulation results are interpreted in the light of the Odjik, Skolnick, Fixman, Khokhlov, and Khachaturian blob scaling theory (Everaers et al., Eur. Phys. J. E 8, 3 (2002)) which predicts that all solution properties are determined by just two scaling variables-the number of electrostatic blobs X and the reduced Debye screening length, Y. We identify three broad regimes, the ideal chain regime at small values of Y, the blob-pole regime at large values of Y, and the crossover regime at intermediate values of Y, within which the mean size, shape, and diffusivity exhibit characteristic behaviours. In particular, when simulation results are recast in terms of blob scaling variables, universal behaviour independent of the choice of bead-spring chain parameters, and the number of blobs X, is observed in the ideal chain regime and in much of the crossover regime, while the existence of logarithmic corrections to scaling in the blob-pole regime leads to non-universal behaviour.

Note: Spring constant calibration of nanosurface-engineered atomic force microscopy cantilevers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ergincan, O., E-mail: orcunergincan@gmail.com; Palasantzas, G.; Kooi, B. J.

2014-02-15

The determination of the dynamic spring constant (k{sub d}) of atomic force microscopy cantilevers is of crucial importance for converting cantilever deflection to accurate force data. Indeed, the non-destructive, fast, and accurate measurement method of the cantilever dynamic spring constant by Sader et al. [Rev. Sci. Instrum. 83, 103705 (2012)] is confirmed here for plane geometry but surface modified cantilevers. It is found that the measured spring constants (k{sub eff}, the dynamic one k{sub d}), and the calculated (k{sub d,1}) are in good agreement within less than 10% error.

Determination of iridium in mafic rocks by atomic absorption

USGS Publications Warehouse

Grimaldi, F.S.; Schnepfe, M.M.

1970-01-01

Iridium is determined in mineralized mafic rocks by atomic absorption after fire-assay concentration into a gold bead. Interelement interferences in the atomic-absorption determination are removed and Ir sensitivity is increased by buffering the solutions with a mixture of copper and sodium sulphates. Substantial amounts of Ag, Al, Au, Bi, Ca, Cd, Co, Cr, Fe, Ho, Hg, K, La, Mg, Mn, Mo, Ni, Pb, Te, Ti, V, Y, Zn and platinum metals can be tolerated in the atomic-absorption determination. The sensitivity and detection limits are 3.2 and 0.25 ppm of Ir, respectively. ?? 1970.

Hydrodynamic and elastic interactions of sedimenting flexible fibers

NASA Astrophysics Data System (ADS)

Ekiel-Jezewska, Maria L.; Bukowicki, Marek

2017-11-01

Dynamics of flexible micro and nano filaments in fluids is intensively investigated in many laboratories, with a perspective of numerous applications in biology, medicine or modern technology. In the literature, different theoretical models of elastic interactions between flexible fiber segments are applied. The task of this work is to examine the impact of a chosen elastic model on the dynamics of fibers settling in a viscous fluid under low Reynolds number. To this goal, we construct two trumbbells, each made of three beads connected by springs and with a bending resistance, and we describe hydrodynamic interactions of the beads in terms of the Rotne-Prager mobility tensors. Using the harmonic bending potential, and coupling it to the spring potential by the Young's modulus, we find simple benchmark solutions: stable stationary configurations of a single elastic trumbbell and a fast horizontal attraction of two elastic trumbbells towards a periodic long-lasting orbit. We show that for sufficiently large bending angles, other models of bending interactions can lead to qualitatively and quantitatively different spurious effects. We also demonstrate examples of essential differences between the dynamics of elastic dumbbells and trumbbells. This work was supported in part by Narodowe Centrum Nauki under Grant No. 2014/15/B/ST8/04359.

Discretized modeling of beads-on-a-string morphology from electrically driven, conducting, and viscoelastic polymer jets

NASA Astrophysics Data System (ADS)

Divvela, Mounica Jyothi; Joo, Yong Lak

2017-04-01

In this paper, we provide a theoretical investigation of axisymmetric instabilities observed during electrospinning, which lead to beads-on-a-string morphology. We used a discretized method to model the instability phenomena observed in the jet. We considered the fluid to be analogous to a bead-spring model. The motion of these beads is governed by the electrical, viscoelastic, surface tension, aerodynamic drag, and gravitational forces. The bead is perturbed at the nozzle, and the growth of the instability is observed over time, and along the length of the jet. We considered both lower electrical conducting polyisobutylene (PIB)-based Boger fluids and highly electrical conducting, polyethylene oxide (PEO)/water systems. In PIB fluids, the onset of the axisymmetric instability is predominantly based on the capillary mode, and the growth rate of the instability is decreased with the viscoelasticity of the jet. However, in the PEO/water system, the instability is electrically driven, and a significant increase in the growth rate of the instability is observed with the increase in the voltage. Our predictions from the discretized model are in good agreement with the previous linear stability analysis and experimental results. Our results also revealed the non-stationary behavior of the disturbance, where the amplitude of the perturbation is observed to be oscillating. Furthermore, we showed that the discretized model is also used to observe the non-axisymmetric behavior of the jet, which can be further used to study the bending instability in electrospinning.

Determination of palladium and platinum by atomic absorption

USGS Publications Warehouse

Schnepfe, M.M.; Grimaldi, F.S.

1969-01-01

Palladium and platinum are determined by atomic absorption after fire-assay concentration into a gold bead. The limit of determination is ~0??06 ppm in a 20-g sample. Serious depressive interelement interferences are removed by buffering the solutions with a mixture of cadmium and copper sulphates with cadmium and copper concentrations each at 0??5%. Substantial amounts of Ag, Al, Au, Bi, Ca, Co, Cr, Fe, Hg, K, La, Mg, Mn, Mo, Na, Ni, Pb, Te, Ti, V, Y, Zn, and the platinum metals do not interfere in the atomic-absorption determination. ?? 1969.

Cultivation of human dermal fibroblasts and epidermal keratinocytes on keratin-coated silica bead substrates.

PubMed

Tan, Bee Yi; Nguyen, Luong T H; Kim, Hyo-Sop; Kim, Jae-Ho; Ng, Kee Woei

2017-10-01

Human hair keratin is promising as a bioactive material platform for various biomedical applications. To explore its versatility further, human hair keratin was coated onto monolayers of silica beads to produce film-like substrates. This combination was hypothesized to provide a synergistic effect in improving the biochemical properties of the resultant composite. Atomic force microscopy analysis showed uniform coatings of keratin on the silica beads with a slight increase in the resulting surface roughness. Keratin-coated silica beads had higher surface energy and relatively lower negative charge than those of bare silica beads. To investigate cell response, human dermal fibroblasts (HDFs), and human epidermal keratinocytes (HEKs) were cultured on the substrates over 4 days. Results showed that keratin coatings significantly enhanced the metabolic activity of HDFs and encouraged cell spreading but did not exert any significant effects on HEKs. HDF expression of collagen I was significantly more intense on the keratin-coated compared to the bare silica substrates. Furthermore, HDF secretion of various cytokines suggested that keratin coatings triggered active cell responses related to wound healing. Collectively, our study demonstrated that human hair keratin-coated silica bead monolayers have the potential to modulate HDF behavior in culture and may be exploited further. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2789-2798, 2017. © 2017 Wiley Periodicals, Inc.

Determination of gold in geologic materials by solvent extraction and atomic-absorption spectrometry

USGS Publications Warehouse

Huffman, Claude; Mensik, J.D.; Riley, L.B.

1967-01-01

The two methods presented for the determination of traces of gold in geologic materials are the cyanide atomic-absorption method and the fire-assay atomic-absorption method. In the cyanide method gold is leached with a sodium-cyanide solution. The monovalent gold is then oxidized to the trivalent state and concentrated by extracting into methyl isobutyl ketone prior to estimation by atomic absorption. In the fire-assay atomic-absorption method, the gold-silver bead obtained from fire assay is dissolved in nitric and hydrochloric acids. Gold is then concentrated by extracting into methyl isobutyl ketone prior to determination by atomic absorption. By either method concentrations as low as 50 parts per billion of gold can be determined in a 15-gram sample.

Computational model for noncontact atomic force microscopy: energy dissipation of cantilever.

PubMed

Senda, Yasuhiro; Blomqvist, Janne; Nieminen, Risto M

2016-09-21

We propose a computational model for noncontact atomic force microscopy (AFM) in which the atomic force between the cantilever tip and the surface is calculated using a molecular dynamics method, and the macroscopic motion of the cantilever is modeled by an oscillating spring. The movement of atoms in the tip and surface is connected with the oscillating spring using a recently developed coupling method. In this computational model, the oscillation energy is dissipated, as observed in AFM experiments. We attribute this dissipation to the hysteresis and nonconservative properties of the interatomic force that acts between the atoms in the tip and sample surface. The dissipation rate strongly depends on the parameters used in the computational model.

Unified description of the slip phenomena in sheared polymer films: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Priezjev, Nikolai

2010-03-01

The dynamic behavior of the slip length in shear flow of polymer melts past atomically smooth surfaces is investigated using MD simulations. The polymer melt was modeled as a collection of FENE-LJ bead-spring chains. We consider shear flow conditions at low pressures and weak wall-fluid interaction energy so that fluid velocity profiles are linear throughout the channel at all shear rates examined. In agreement with earlier studies we confirm that for shear- thinning fluids the slip length passes through a local minimum at low shear rates and then increases rapidly at higher shear rates. We found that the rate dependence of the slip length depends on the lattice orientation at high shear rates. The MD results show that the ratio of slip length to viscosity follows a master curve when plotted as a function of a single variable that depends on the structure factor, contact density and temperature of the first fluid layer near the solid wall. The universal dependence of the slip length holds for a number of parameters of the interface: fluid density and structure (chain length), wall-fluid interaction energy, wall density, lattice orientation, thermal or solid walls.

Removal of toxic metals from leachates from hazardous solid wastes and reduction of toxicity to microtox by the use of calcium alginate beads containing humic acid.

PubMed

Pandey, Ashok K; Pandey, Shri Dhar; Misra, Virendra

2002-06-01

Improper disposal of hazardous wastes can lead to release of potentially harmful substances through leaching such as heavy metals, which ultimately contaminate soil, sediment surface water, and groundwater through runoff. To remove these toxic metals and avoid any adverse effect on the ecosystem, a novel approach involving calcium alginate (CA) beads containing humic acid (HA) was used. For this, 10% leachates of the waste obtained from two major industrial units with electroplating processess were prepared at neutral pH and analyzed by atomic absorption spectrophotometry (AAS). Both leachates contained Cd, Cu, Cr, Ni, Mn, Fe, and Zn. The concentrations of Ni, Mn, Fe, and Zn in the waste were found to be significant. The leachates analyzed were passed through columns packed with calcium alginate beads with or without humic acid. The concentrations of various metals in beads and in different fractions collected after adsorption were measured. Data recorded indicate that calcium alginate beads containing humic acids are more efficient in removal of all metals in substantial amounts from the two leachates. Along with removal of metals, this process led to considerable detoxification of the leachates as tested by Microtox assay, indicated by earlier protection and higher EC(50). The significance of the results in relation to removal of toxic metals by beads containing humic acid is discussed. (c) 2002 Elsevier Science (USA).

Brownian dynamics of wall tethered polymers in shear flow

NASA Astrophysics Data System (ADS)

Lin, Tiras Y.; Saadat, Amir; Kushwaha, Amit; Shaqfeh, Eric S. G.

2017-11-01

The dynamics of a wall tethered polymer in shear flow is studied using Brownian dynamics. Simulations are performed with bead-spring chains, and the effect of hydrodynamic interactions (HI) is incorporated through Blake's tensor with a finite size bead correction. We characterize the configuration of the polymer as a function of the Weissenberg number by investigating the regions the polymer explores in both the flow-gradient and flow-vorticity planes. The fractional extension in the flow direction, the width in the vorticity direction, and the thickness in the gradient direction are reported as well, and these quantities are found to compare favorably with the experimental data of the literature. The cyclic motion of the polymer is demonstrated through analysis of the mean velocity field of the end bead. We characterize the collision process of each bead with the wall as a Poisson process and extract an average wall collision rate, which in general varies along the backbone of the chain. The inclusion of HI with the wall for a tethered polymer is found to reduce the average wall collision rate. We anticipate that results from this work will be directly applicable to, e.g., the design of polymer brushes or the use of DNA for making nanowires in molecular electronics. T.Y.L. is supported by the Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program.

Solid Solutions of Rare Earth Cations in Mesoporous Anatase Beads and Their Performances in Dye-Sensitized Solar Cells

PubMed Central

Cavallo, Carmen; Salleo, Alberto; Gozzi, Daniele; Di Pascasio, Francesco; Quaranta, Simone; Panetta, Riccardo; Latini, Alessandro

2015-01-01

Solid solutions of the rare earth (RE) cations Pr3+, Nd3+, Sm3+, Gd3+, Er3+ and Yb3+ in anatase TiO2 have been synthesized as mesoporous beads in the concentration range 0.1–0.3% of metal atoms. The solid solutions were have been characterized by XRD, SEM, diffuse reflectance UV-Vis spectroscopy, BET and BJH surface analysis. All the solid solutions possess high specific surface areas, up to more than 100 m2/g. The amount of adsorbed dye in each photoanode has been determined spectrophotometrically. All the samples were tested as photoanodes in dye-sensitized solar cells (DSSCs) using N719 as dye and a nonvolatile, benzonitrile based electrolyte. All the cells were have been tested by conversion efficiency (J–V), quantum efficiency (IPCE), electrochemical impedance spectroscopy (EIS) and dark current measurements. While lighter RE cations (Pr3+, Nd3+) limit the performance of DSSCs compared to pure anatase mesoporous beads, cations from Sm3+ onwards enhance the performance of the devices. A maximum conversion efficiency of 8.7% for Er3+ at a concentration of 0.2% has been achieved. This is a remarkable efficiency value for a DSSC employing N719 dye without co-adsorbents and a nonvolatile electrolyte. For each RE cation the maximum performances are obtained for a concentration of 0.2% metal atoms. PMID:26577287

Dynamics of a fluctuating semi-flexible membrane

NASA Astrophysics Data System (ADS)

Tukdarian, Nathaniel; Huang, Aiqun; Adhikari, Ramesh; Bhattacharya, Aniket

2015-03-01

We report our preliminary studies of conformations and dynamics of a fluctuating semi-flexible membrane. Our model of membrane with linear dimension L consists of N2 (L = Nbl) excluded volume beads connected by anharmonic springs. The stiffness of the membrane is controlled by adjusting the strength κb of the bending potential Ubend =κb(1-n̂i .n̂j) between adjacent elementary plaquettes consisting of three beads at the corners connected by bonds and characterized by normal unit vectors n̂i and n̂j. We study the conformations and dynamic fluctuations of the membrane using Brownian dynamics simulation. We show how the radius of gyration scales with N and κb, and study characteristics of the transverse fluctuations, the root-mean-square displacement of the center of mass, and the dynamics of the end monomers at each corner.

Experimental and numerical studies of tethered DNA dynamics in shear flow

NASA Astrophysics Data System (ADS)

Lueth, Christopher A.

Polymer physics has a rich tradition spanning nearly two centuries. In the 1830s, Henri Braconnot and coworkers were perhaps the first to work on what is today known as polymer science when they derived semi-synthetic materials from naturally occurring cellulose. However, the true nature of polymers, as long chain molecules, had not been proposed until 1910 by Pickles. It was not until the 1950's when polymer models were developed using statistical mechanics. Recently, the field has been revitalized by the ability to study individual polymer molecules for the first time. The development of DNA single molecule fluorescence microscopy coupled with ever increasing computational power has opened the door to molecular level understanding of polymer physics, resolving old disputes and uncovering new interesting phenomena. In this work, we use a combination of theoretical predictions and lambda-phage DNA single molecule fluorescence microscopy to study the behavior of polymers tethered to surfaces. Brownian dynamics simulations of a number of coarse-grained polymer models---dynamic and equilibrium Kratky-Porod chains as well as bead-spring chains---were completed and compared with analytical and experimental results. First, an expression is developed for the entropic exclusion force experienced by a tethered polymer chain. We propose that, for a freely jointed chain, a modification to the free entropic force of kBT/y is needed in the direction normal to the surface. Analogously, we propose that for a wormlike chain, a modification of 2kBT/y is needed, due to the finite curvature of the model. Then, the reliability of discretized bead spring simulations containing this modified entropic force are analyzed using Kratky-Porod simulations and are found to reproduce most statistics, except for those very near the surface, such as end-wall contact. Next, experiments of tethered lambda-phage DNA in shear flow are presented for the first time in the flow-gradient plane. The tethering surface chemistry proved to be arduous work, but with the aide of contact angle and ellipsometry measurements, success was achieved. Extension behavior was shown to agree well with bead spring simulations, but deviations were discovered for weak flows in the extensional fluctuations, mean distance from the wall, and orientation angle. Cyclic dynamics---where the polymer continuously diffuses away from the wall, subsequently undergoes stretch in the flow direction, is then "entropically pulled back" towards the wall, and finally recoils---was observed and quantified through correlation and power spectral densities. Again, quantitative agreement was observed between experiments and bead spring simulations. The onset of cyclic dynamics was found to occur at Wi ≈ 3 and was found to decline with increasing Wi up to ≈ 200. Finally, a reliable procedure was developed utilizing Dip Pen Nanolithography to controllably tether DNA to gold surfaces. Preliminary experiments were performed and successful tethering was achieved, an important first step toward creating DNA scaffolds for molecular wires. However, further research is needed to fully develop the process and successfully double tether DNA molecules between gold electrodes.

Brownian dynamics simulations of polyelectrolyte adsorption in shear flow with hydrodynamic interaction

NASA Astrophysics Data System (ADS)

Hoda, Nazish; Kumar, Satish

2007-12-01

The adsorption of single polyelectrolyte molecules in shear flow is studied using Brownian dynamics simulations with hydrodynamic interaction (HI). Simulations are performed with bead-rod and bead-spring chains, and electrostatic interactions are incorporated through a screened Coulombic potential with excluded volume accounted for by the repulsive part of a Lennard-Jones potential. A correction to the Rotne-Prager-Yamakawa tensor is derived that accounts for the presence of a planar wall. The simulations show that migration away from an uncharged wall, which is due to bead-wall HI, is enhanced by increases in the strength of flow and intrachain electrostatic repulsion, consistent with kinetic theory predictions. When the wall and polyelectrolyte are oppositely charged, chain behavior depends on the strength of electrostatic screening. For strong screening, chains get depleted from a region close to the wall and the thickness of this depletion layer scales as N1/3Wi2/3 at high Wi, where N is the chain length and Wi is the Weissenberg number. At intermediate screening, bead-wall electrostatic attraction competes with bead-wall HI, and it is found that there is a critical Weissenberg number for desorption which scales as N-1/2κ-3(lB∣σq∣)3/2, where κ is the inverse screening length, lB is the Bjerrum length, σ is the surface charge density, and q is the bead charge. When the screening is weak, adsorbed chains are observed to align in the vorticity direction at low shear rates due to the effects of repulsive intramolecular interactions. At higher shear rates, the chains align in the flow direction. The simulation method and results of this work are expected to be useful for a number of applications in biophysics and materials science in which polyelectrolyte adsorption plays a key role.

Atomic-absorption determination of rhodium in chromite concentrates

USGS Publications Warehouse

Schnepfe, M.M.; Grimaldi, F.S.

1969-01-01

Rhodium is determined in chromite concentrates by atomic absorption after concentration either by co-precipitation with tellurium formed by the reduction of tellurite with tin(II) chloride or by fire assay into a gold bead. Interelement interferences in the atomic-absorption determination are removed by buffering the solutions with lanthanum sulphate (lanthanum concentration 1%). Substantial amounts of Ag, Al, Au, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ho, Hg, K, La, Mg, Mn, Mo, Na, Ni, Pb, Te, Ti, V, Y, Zn and platinum metals can be tolerated. A lower limit of approximately 0.07 ppm Rh can be determined in a 3-g sample. ?? 1969.

Glass transition temperature of polymer nano-composites with polymer and filler interactions

NASA Astrophysics Data System (ADS)

Hagita, Katsumi; Takano, Hiroshi; Doi, Masao; Morita, Hiroshi

2012-02-01

We systematically studied versatile coarse-grained model (bead spring model) to describe filled polymer nano-composites for coarse-grained (Kremer-Grest model) molecular dynamics simulations. This model consists of long polymers, crosslink, and fillers. We used the hollow structure as the filler to describe rigid spherical fillers with small computing costs. Our filler model consists of surface particles of icosahedra fullerene structure C320 and a repulsive force from the center of the filler is applied to the surface particles in order to make a sphere and rigid. The filler's diameter is 12 times of beads of the polymers. As the first test of our model, we study temperature dependence of volumes of periodic boundary conditions under constant pressures through NPT constant Andersen algorithm. It is found that Glass transition temperature (Tg) decrease with increasing filler's volume fraction for the case of repulsive interaction between polymer and fillers and Tg weakly increase for attractive interaction.

Low-Reynolds-number predator.

PubMed

Ebrahimian, Mehran; Yekehzare, Mohammad; Ejtehadi, Mohammad Reza

2015-12-01

To generalize simple bead-linker model of swimmers to higher dimensions and to demonstrate the chemotaxis ability of such swimmers, here we introduce a low-Reynolds predator, using a two-dimensional triangular bead-spring model. Two-state linkers as mechanochemical enzymes expand as a result of interaction with particular activator substances in the environment, causing the whole body to translate and rotate. The concentration of the chemical stimulator controls expansion versus the contraction rate of each arm and so affects the ability of the body for diffusive movements; also the variation of activator substance's concentration in the environment breaks the symmetry of linkers' preferred state, resulting in the drift of the random walker along the gradient of the density of activators. External food or danger sources may attract or repel the body by producing or consuming the chemical activators of the organism's enzymes, inducing chemotaxis behavior. Generalization of the model to three dimensions is straightforward.

Low-Reynolds-number predator

NASA Astrophysics Data System (ADS)

Ebrahimian, Mehran; Yekehzare, Mohammad; Ejtehadi, Mohammad Reza

2015-12-01

To generalize simple bead-linker model of swimmers to higher dimensions and to demonstrate the chemotaxis ability of such swimmers, here we introduce a low-Reynolds predator, using a two-dimensional triangular bead-spring model. Two-state linkers as mechanochemical enzymes expand as a result of interaction with particular activator substances in the environment, causing the whole body to translate and rotate. The concentration of the chemical stimulator controls expansion versus the contraction rate of each arm and so affects the ability of the body for diffusive movements; also the variation of activator substance's concentration in the environment breaks the symmetry of linkers' preferred state, resulting in the drift of the random walker along the gradient of the density of activators. External food or danger sources may attract or repel the body by producing or consuming the chemical activators of the organism's enzymes, inducing chemotaxis behavior. Generalization of the model to three dimensions is straightforward.

Tube Visualization and Properties from Isoconfigurational Averaging

NASA Astrophysics Data System (ADS)

Qin, Jian; Bisbee, Windsor; Milner, Scott

2012-02-01

We introduce a simulation method to visualize the confining tube in polymer melts and measure its properties. We studied bead-spring ring polymers, which conveniently suppresses constraint release and contour length fluctuations. We allow molecules to cross and reach topologically equilibrated states by invoking various molecular rebridging moves in Monte Carlo simulations. To reveal the confining tube, we start with a well equilibrated configuration, turn off rebridging moves, and run molecular dynamics simulation multiple times, each with different initial velocities. The resulting set of ``movies'' of molecular trajectories defines an isoconfigurational ensemble, with the bead positions at different times and in different ``movies'' giving rise to a cloud. The cloud shows the shape, range and strength of the tube confinement, which enables us to study the statistical properties of tube. Using this approach, we studied the effects of free surface, and found that the tube diameter near the surface is greater than the bulk value by about 25%.

Coaxial atomic force microscope probes for dielectrophoresis of DNA under different buffer conditions

NASA Astrophysics Data System (ADS)

Tao, Yinglei; Kumar Wickramasinghe, H.

2017-02-01

We demonstrate a coaxial AFM nanoprobe device for dielectrophoretic (DEP) trapping of DNA molecules in Tris-EDTA (TE) and phosphate-buffered saline (PBS) buffers. The DEP properties of 20 nm polystyrene beads were studied with coaxial probes in media with different conductivities. Due to the special geometry of our DEP probe device, sufficiently high electric fields were generated at the probe end to focus DNA molecules with positive DEP. DEP trapping for both polystyrene beads and DNA molecules was quantitatively analyzed over the frequency range from 100 kHz to 50 MHz and compared with the Clausius-Mossotti theory. Finally, we discussed the negative effect of medium salinity during DEP trapping.

Growth of arrays of oriented epitaxial platinum nanoparticles with controlled size and shape by natural colloidal lithography

DOE PAGES

Komanicky, Vladimir; Barbour, Andi; Lackova, Miroslava; ...

2014-07-05

Here, we developed a method for production of arrays of platinum nanocrystals of controlled size and shape using templates from ordered silica bead monolayers. Silica beads with nominal sizes of 150 and 450 nm were self-assembl into monolayers over strontium titanate single crystal substrates. The monolayers were used as shadow masks for platinum metal deposition on the substrate using the three-step evaporation technique. Produced arrays of epitaxial platinum islands were transformed into nanocrystals by annealing in a quartz tube in nitrogen flow. The shape of particles is determined by the substrate crystallography, while the size of the particles and theirmore » spacing are controlled by the size of the silica beads in the mono- layer mask. As a proof of concept, arrays of platinum nanocrystals of cubooctahedral shape were prepared on (100) strontium titanate substrates. We also characterized the nanocrystal arrays by atomic force microscopy, scanning electron microscopy, and synchrotron X-ray diffraction techniques.« less

A Generic Force Field for Protein Coarse-Grained Molecular Dynamics Simulation

PubMed Central

Gu, Junfeng; Bai, Fang; Li, Honglin; Wang, Xicheng

2012-01-01

Coarse-grained (CG) force fields have become promising tools for studies of protein behavior, but the balance of speed and accuracy is still a challenge in the research of protein coarse graining methodology. In this work, 20 CG beads have been designed based on the structures of amino acid residues, with which an amino acid can be represented by one or two beads, and a CG solvent model with five water molecules was adopted to ensure the consistence with the protein CG beads. The internal interactions in protein were classified according to the types of the interacting CG beads, and adequate potential functions were chosen and systematically parameterized to fit the energy distributions. The proposed CG force field has been tested on eight proteins, and each protein was simulated for 1000 ns. Even without any extra structure knowledge of the simulated proteins, the Cα root mean square deviations (RMSDs) with respect to their experimental structures are close to those of relatively short time all atom molecular dynamics simulations. However, our coarse grained force field will require further refinement to improve agreement with and persistence of native-like structures. In addition, the root mean square fluctuations (RMSFs) relative to the average structures derived from the simulations show that the conformational fluctuations of the proteins can be sampled. PMID:23203075

Discrete-to-continuum simulation approach to polymer chain systems: Subdiffusion, segregation, and chain folding

NASA Astrophysics Data System (ADS)

Foo, Grace M.; Pandey, R. B.

1998-05-01

A discrete-to-continuum approach is introduced to study the static and dynamic properties of polymer chain systems with a bead-spring chain model in two dimensions. A finitely extensible nonlinear elastic potential is used for the bond between the consecutive beads with the Lennard-Jones (LJ) potential with smaller (Rc=21/6σ=0.95) and larger (Rc=2.5σ=2.1) values of the upper cutoff for the nonbonding interaction among the neighboring beads. We find that chains segregate at temperature T=1.0 with Rc=2.1 and remain desegregated with Rc=0.95. At low temperature (T=0.2), chains become folded, in a ribbonlike conformation, unlike random and self-avoiding walk conformations at T=1.0. The power-law dependence of the rms displacements of the center of mass (Rc.m.) of the chains and their center node (Rcn) with time are nonuniversal, with the range of exponents ν1~=0.45-0.25 and ν2~=0.30-0.10, respectively. Both radius of gyration (Rg) and average bond length () decrease on increasing the range of interaction (Rc), consistent with the extended state in good solvent to collapsed state in poor solvent description of the polymer chains. Analysis of the radial distribution function supports these observations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bürger, Stefan; Riciputi, Lee R; Bostick, Debra A

A ThermoFisher 'Triton' multi-collector thermal ionization mass spectrometer (MC-TIMS) was evaluated for trace and ultra-trace level isotoperatioanalysis of actinides (uranium, plutonium, and americium), fission products and geolocators (strontium, cesium, and neodymium). Total efficiencies (atoms loaded to ions detected) of up to 0.5-2% for U, Pu, and Am, and 1-30% for Sr, Cs, and Nd can be reported employing resin bead load techniques onto flat ribbon Re filaments or resin beads loaded into a millimeter-sized cavity drilled into a Re rod. This results in detection limits of <0.1 fg (10{sup 4} atoms to 10{sup 5} atoms) for {sup 239-242+244}Pu, {sup 233+236}U,more » {sup 241-243}Am, {sup 89,90}Sr, and {sup 134,135,137}Cs, and {le} 1 pg for natural Nd isotopes (limited by the chemical processing blank) using a secondary electron multiplier (SEM) or multiple-ion counters (MICs). Relative standard deviations (RSD) as small as 0.1% and abundance sensitivities of 1 x 10{sup 6} or better using a SEM are reported here. Precisions of RSD {approx} 0.01-0.001% using a multi-collector Faraday cup array can be achieved at sub-nanogram concentrations for strontium and neodymium and are suitable to gain crucial geolocation information. The analytical protocols reported herein are of particular value for nuclear forensic and nuclear safeguard applications.« less

Atomic force microscopy for cellular level manipulation: imaging intracellular structures and DNA delivery through a membrane hole.

PubMed

Afrin, Rehana; Zohora, Umme Salma; Uehara, Hironori; Watanabe-Nakayama, Takahiro; Ikai, Atsushi

2009-01-01

The atomic force microscope (AFM) is a versatile tool for imaging, force measurement and manipulation of proteins, DNA, and living cells basically at the single molecular level. In the cellular level manipulation, extraction, and identification of mRNA's from defined loci of a cell, insertion of plasmid DNA and pulling of membrane proteins, for example, have been reported. In this study, AFM was used to create holes at defined loci on the cell membrane for the investigation of viability of the cells after hole creation, visualization of intracellular structure through the hole and for targeted gene delivery into living cells. To create large holes with an approximate diameter of 5-10 microm, a phospholipase A(2) coated bead was added to the AFM cantilever and the bead was allowed to touch the cell surface for approximately 5-10 min. The evidence of hole creation was obtained mainly from fluorescent image of Vybrant DiO labeled cell before and after the contact with the bead and the AFM imaging of the contact area. In parallel, cells with a hole were imaged by AFM to reveal intracellular structures such as filamentous structures presumably actin fibers and mitochondria which were identified with fluorescent labeling with rhodamine 123. Targeted gene delivery was also attempted by inserting an AFM probe that was coated with the Monster Green Fluorescent Protein phMGFP Vector for transfection of the cell. Following targeted transfection, the gene expression of green fluorescent protein (GFP) was observed and confirmed by the fluorescence microscope. Copyright (c) 2009 John Wiley & Sons, Ltd.

Viscoelastic Properties Measurement of Human Lymphocytes by Atomic Force Microscopy Based on Magnetic Beads Cell Isolation.

PubMed

Mi Li; Lianqing Liu; Xiubin Xiao; Ning Xi; Yuechao Wang

2016-07-01

Cell mechanics has been proved to be an effective biomarker for indicating cellular states. The advent of atomic force microscopy (AFM) provides an exciting instrument for measuring the mechanical properties of single cells. However, current AFM single-cell mechanical measurements are commonly performed on cell lines cultured in vitro which are quite different from the primary cells in the human body. Investigating the mechanical properties of primary cells from clinical environments can help us to better understand cell behaviors. Here, by combining AFM with magnetic beads cell isolation, the viscoelastic properties of human primary B lymphocytes were quantitatively measured. B lymphocytes were isolated from the peripheral blood of healthy volunteers by density gradient centrifugation and CD19 magnetic beads cell isolation. The activity and specificity of the isolated cells were confirmed by fluorescence microscopy. AFM imaging revealed the surface topography and geometric parameters of B lymphocytes. The instantaneous modulus and relaxation time of living B lymphocytes were measured by AFM indenting technique, showing that the instantaneous modulus of human normal B lymphocytes was 2-3 kPa and the relaxation times were 0.03-0.06 s and 0.35-0.55 s. The differences in cellular visocoelastic properties between primary B lymphocytes and cell lines cultured in vitro were analyzed. The study proves the capability of AFM in quantifying the viscoelastic properties of individual specific primary cells from the blood sample of clinical patients, which will improve our understanding of the behaviors of cells in the human body.

Optical tweezers for the measurement of binding forces: system description and application for the study of E. coli adhesion

NASA Astrophysics Data System (ADS)

Fallman, Erik G.; Schedin, Staffan; Andersson, Magnus J.; Jass, Jana; Axner, Ove

2003-06-01

Optical tweezers together with a position sensitive detection system allows measurements of forces in the pN range between micro-sized biological objects. A prototype force measurement system has been constructed around in inverted microscope with an argon-ion pumped Ti:sapphire laser as light source for optical trapping. A trapped particle in the focus of the high numerical aperture microscope-objective behaves like an omni-directional mechanical spring if an external force displaces it. The displacement from the equilibrium position is a measure of the exerted force. For position detection of the trapped particle (polystyrene beads), a He-Ne laser beam is focused a small distance below the trapping focus. An image of the bead appears as a distinct spot in the far field, monitored by a photosensitive detector. The position data is converted to a force measurement by a calibration procedure. The system has been used for measuring the binding forces between E-coli bacterial adhesin and their receptor sugars.

An analytic model for accurate spring constant calibration of rectangular atomic force microscope cantilevers.

PubMed

Li, Rui; Ye, Hongfei; Zhang, Weisheng; Ma, Guojun; Su, Yewang

2015-10-29

Spring constant calibration of the atomic force microscope (AFM) cantilever is of fundamental importance for quantifying the force between the AFM cantilever tip and the sample. The calibration within the framework of thin plate theory undoubtedly has a higher accuracy and broader scope than that within the well-established beam theory. However, thin plate theory-based accurate analytic determination of the constant has been perceived as an extremely difficult issue. In this paper, we implement the thin plate theory-based analytic modeling for the static behavior of rectangular AFM cantilevers, which reveals that the three-dimensional effect and Poisson effect play important roles in accurate determination of the spring constants. A quantitative scaling law is found that the normalized spring constant depends only on the Poisson's ratio, normalized dimension and normalized load coordinate. Both the literature and our refined finite element model validate the present results. The developed model is expected to serve as the benchmark for accurate calibration of rectangular AFM cantilevers.

Using Beads and Divided Containers to Study Kinetic and Equilibrium Isotope Effects in the Laboratory and in the Classroom

ERIC Educational Resources Information Center

Campbell, Dean J.; Brewer, Emily R.; Martinez, Keri A.; Fitzjarrald, Tamara J.

2017-01-01

The purpose of this laboratory experiment is to study fundamental concepts of kinetics and equilibria and the isotope effects associated with both of these concepts. The concepts of isotopes in introductory and general chemistry courses are typically used within the contexts of atomic weights and radioactivity. Kinetic and equilibrium isotope…

ME8373 Spring 2015 ICME Proposal ICME Analysis of Fatigue Crack Growth Through a Weld in SA-516 Grade 70 Plate

NASA Technical Reports Server (NTRS)

Woods, Jody L.

2015-01-01

This paper describes work accomplished to predict the service life of a flexure joint design which is a component of a diffuser duct in the A3 Test Stand, an altitude simulation rocket engine test facility at NASA's Stennis Space Center. The duct has two pressure shells separated by cooling water passages and connected by stiffening ribs and flexure joints. Rocket exhaust flows within the duct and heats the inner pressure shell while the outer pressure shell remains at ambient temperature. The flexure joints allow for differential thermal expansion of the inner and outer pressure shells and are subject to in-service loading by this thermal expansion along with water pressure in the cooling water passage, atmospheric pressure outside the duct, near vacuum conditions within the duct, and vibrational loads from operation of the facility and rocket engine. Figure 1 shows a schematic axisymmetric cross section of the diffuser pressure shells and flexure joints with a zoomed in view of the flexure joint. The flexure joints are expected to eventually fail by fatigue cracking leading to leaks from the cooling water passages to the outside. The zoomed in view in Figure 1 indicates where cracking is expected to occur, namely through a weld bead between two plates of SA-516 Grade 70 steel. This weld bead acts as the fulcrum of the flexure joint and it is clear from inspection of the geometry and loading represented in the zoomed in portion of Figure 1 that inherent in the design there is a severe notch formed between the flexure plate, weld bead, and stiffening ring that will be the site of crack initiation and location from which the crack grows to the outer surface of the weld bead.

Seasonal arsenic accumulation in stream sediments at a groundwater discharge zone.

PubMed

MacKay, Allison A; Gan, Ping; Yu, Ran; Smets, Barth F

2014-01-21

Seasonal changes in arsenic and iron accumulation rates were examined in the sediments of a brook that receives groundwater discharges of arsenic and reduced iron. Clean glass bead columns were deployed in sediments for known periods over the annual hydrologic cycle to monitor changes in arsenic and iron concentrations in bead coatings. The highest accumulation rates occurred during the dry summer period (July-October) when groundwater discharges were likely greatest at the sample locations. The intermediate flow period (October-March), with higher surface water levels, was associated with losses of arsenic and iron from bead column coatings at depths below 2-6 cm. Batch incubations indicated iron releases from solids to be induced by biological reduction of iron (oxy)hydroxide solids. Congruent arsenic releases during incubation were limited by the high arsenic sorption capacity (0.536 mg(As)/mg(Fe)) of unreacted iron oxide solids. The flooded spring (March-June) with high surface water flows showed the lowest arsenic and iron accumulation rates in the sediments. Comparisons of accumulation rates across a shoreline transect were consistent with greater rates at regions exposed above surface water levels for longer times and greater losses at locations submerged below surface water. Iron (oxy)hydroxide solids in the shallowest sediments likely serve as a passive barrier to sorb arsenic released to pore water at depth by biological iron reduction.

Mesoscopic model of actin-based propulsion.

PubMed

Zhu, Jie; Mogilner, Alex

2012-01-01

Two theoretical models dominate current understanding of actin-based propulsion: microscopic polymerization ratchet model predicts that growing and writhing actin filaments generate forces and movements, while macroscopic elastic propulsion model suggests that deformation and stress of growing actin gel are responsible for the propulsion. We examine both experimentally and computationally the 2D movement of ellipsoidal beads propelled by actin tails and show that neither of the two models can explain the observed bistability of the orientation of the beads. To explain the data, we develop a 2D hybrid mesoscopic model by reconciling these two models such that individual actin filaments undergoing nucleation, elongation, attachment, detachment and capping are embedded into the boundary of a node-spring viscoelastic network representing the macroscopic actin gel. Stochastic simulations of this 'in silico' actin network show that the combined effects of the macroscopic elastic deformation and microscopic ratchets can explain the observed bistable orientation of the actin-propelled ellipsoidal beads. To test the theory further, we analyze observed distribution of the curvatures of the trajectories and show that the hybrid model's predictions fit the data. Finally, we demonstrate that the model can explain both concave-up and concave-down force-velocity relations for growing actin networks depending on the characteristic time scale and network recoil. To summarize, we propose that both microscopic polymerization ratchets and macroscopic stresses of the deformable actin network are responsible for the force and movement generation.

Development of a new passive sampler based on diffusive milligel beads for copper analysis in water.

PubMed

Perez, M; Reynaud, S; Lespes, G; Potin-Gautier, M; Mignard, E; Chéry, P; Schaumlöffel, D; Grassl, B

2015-08-26

A new passive sampler was designed and characterized for the determination of free copper ion (Cu(2+)) concentration in aqueous solution. Each sampling device was composed of a set of about 30 diffusive milligel (DMG) beads. Milligel beads with incorporated cation exchange resin (Chelex) particles were synthetized using an adapted droplet-based millifluidic process. Beads were assumed to be prolate spheroids, with a diameter of 1.6 mm and an anisotropic factor of 1.4. The milligel was controlled in chemical composition of hydrogel (monomer, cross-linker, initiator and Chelex concentration) and characterized in pore size. Two types of sampling devices were developed containing 7.5% and 15% of Chelex, respectively, and 6 nm pore size. The kinetic curves obtained demonstrated the accumulation of copper in the DMG according to the process described in the literature as absorption (and/or adsorption) and release following the Fick's first law of diffusion. For their use in water monitoring, the typical physico-chemical characteristics of the samplers, i.e. the mass-transfer coefficient (k0) and the sampler-water partition coefficient (Ksw), were determined based on a static exposure design. In order to determine the copper concentration in the samplers after their exposure, a method using DMG bead digestion combined to Inductively Coupled Plasma - Atomic Emission Spectrometry (ICP-AES) analysis was developed and optimized. The DMG devices proved to be capable to absorb free copper ions from an aqueous solution, which could be accurately quantified with a mean recovery of 99% and a repeatability of 7% (mean relative uncertainty). Copyright © 2015 Elsevier B.V. All rights reserved.

Precise and direct method for the measurement of the torsion spring constant of the atomic force microscopy cantilevers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jarząbek, D. M., E-mail: djarz@ippt.pan.pl

2015-01-15

A direct method for the evaluation of the torsional spring constants of the atomic force microscope cantilevers is presented in this paper. The method uses a nanoindenter to apply forces at the long axis of the cantilever and in the certain distance from it. The torque vs torsion relation is then evaluated by the comparison of the results of the indentations experiments at different positions on the cantilever. Next, this relation is used for the precise determination of the torsional spring constant of the cantilever. The statistical analysis shows that the standard deviation of the calibration measurements is equal tomore » approximately 1%. Furthermore, a simple method for calibration of the photodetector’s lateral response is proposed. The overall procedure of the lateral calibration constant determination has the accuracy approximately equal to 10%.« less

Coarse-grained protein-protein stiffnesses and dynamics from all-atom simulations

NASA Astrophysics Data System (ADS)

Hicks, Stephen D.; Henley, C. L.

2010-03-01

Large protein assemblies, such as virus capsids, may be coarse-grained as a set of rigid units linked by generalized (rotational and stretching) harmonic springs. We present an ab initio method to obtain the elastic parameters and overdamped dynamics for these springs from all-atom molecular-dynamics simulations of one pair of units at a time. The computed relaxation times of this pair give a consistency check for the simulation, and we can also find the corrective force needed to null systematic drifts. As a first application we predict the stiffness of an HIV capsid layer and the relaxation time for its breathing mode.

Coarse graining of atactic polystyrene and its derivatives

NASA Astrophysics Data System (ADS)

Agrawal, Anupriya; Perahia, Dvora; Grest, Gary S.

2014-03-01

Capturing large length scales in polymers and soft matter while retaining atomistic properties is imperative to computational studies of dynamic systems. Here we present a new methodology developing coarse-grain model based on atomistic simulation of atactic polystyrene (PS). Similar to previous work by Fritz et al., each monomer is described by two coarse grained beads. In contrast to this earlier work where intramolecular potentials were based on Monte Carlo simulation of both isotactic and syndiotactic single PS molecule to capture stereochemistry, we obtained intramolecular interactions from a single molecular dynamics simulation of an all-atom atactic PS melts. The non-bonded interactions are obtained using the iterative Boltzmann inversion (IBI) scheme. This methodology has been extended to coarse graining of poly-(t-butyl-styrene) (PtBS). An additional coarse-grained bead is used to describe the t-butyl group. Similar to the process for PS, the intramolecular interactions are obtained from a single all atom atactic melt simulation. Starting from the non-bonded interactions for PS, we show that the IBI method for the non-bonded interactions of PtBS converges relatively fast. A generalized scheme for substituted PS is currently in development. We would like to acknowledge Prof. Kurt Kremer for helpful discussions during this work.

Fabrication and optical characterization of imaging fiber-based nanoarrays.

PubMed

Tam, Jenny M; Song, Linan; Walt, David R

2005-09-15

In this paper, we present a technique for fabricating arrays containing a density at least 90 times higher than previously published. Specifically, we discuss the fabrication of two imaging fiber-based nanoarrays, one with 700nm features, another with 300nm features. With arrays containing up to 4.5x10(6) array elements/mm(2), these nanoarrays have an ultra-high packing density. A straightforward etching protocol is used to create nanowells into which beads can be deposited. These beads comprise the sensing elements of the nanoarray. Deposition of the nanobeads into the nanowells using two techniques is described. The surface characteristics of the etched arrays are examined with atomic force microscopy and scanning electron microscopy. Fluorescence microscopy was used to observe the arrays. The 300nm array features and the 500nm center-to-center distance approach the minimum feature sizes viewable using conventional light microscopy.

A rapid method for determining tin and molybdenum in geological samples by flame atomic-absorption spectroscopy

USGS Publications Warehouse

Welsch, E.P.

1985-01-01

The proposed method uses a lithium metaborate fusion, dissolution of the fusion bead in 15% v v hydrochloric acid, extraction into a 4% solution of trioctylphosphine oxide in methyl isobutyl ketone, and aspiration into a nitrous oxide-acetylene flame. The limits of detection for tin and molybdenum are 1.0 and 0.5 ppm, respectively. Approximately 50 samples can be analysed per day. ?? 1985.

Demonstration of Double EIT Using Coupled Harmonic Oscillators and RLC Circuits

ERIC Educational Resources Information Center

Harden, Joshua; Joshi, Amitabh; Serna, Juan D.

2011-01-01

Single and double electromagnetically induced transparencies (EIT) in a medium, consisting of four-level atoms in the inverted-Y configuration, are discussed using mechanical and electrical analogies. A three-coupled spring-mass system subject to damping and driven by an external force is used to represent the four-level atom mechanically. The…

Driven translocation of Polymer through a nanopore: effect of heterogeneous flexibility

NASA Astrophysics Data System (ADS)

Adhikari, Ramesh; Bhattacharya, Aniket

2014-03-01

We have studied translocation of a model bead-spring polymer through a nanopore whose building blocks consist of alternate stiff and flexible segments and variable elastic bond potentials. For the case of uniform spring potential translocation of a symmetric periodic stiff-flexible chain of contour length N and segment length m (mod(N,2m)=0), we find that the end-to-end distance and the mean first passage time (MFPT) have weak dependence on the length m. The characteristic periodic pattern of the waiting time distribution captures the stiff and flexible segments of the chain with stiff segments taking longer time to translocate. But when we vary both the elastic bond energy, and the bending energy, as well as the length of stiff/flexible segments, we discover novel patterns in the waiting time distribution which brings out structural information of the building blocks of the translocating chain. Partially supported by UCF Office of Research and Commercialization & College of Science SEED grant.

Development of New Transferable Coarse-Grained Models of Hydrocarbons.

PubMed

An, Yaxin; Bejagam, Karteek K; Deshmukh, Sanket A

2018-06-21

We have utilized an approach that integrates molecular dynamics (MD) simulations with particle swarm optimization (PSO) to accelerate the development of coarse-grained (CG) models of hydrocarbons. Specifically, we have developed new transferable CG beads, which can be used to model the hydrocarbons (C5 to C17) and reproduce their experimental properties with good accuracy. Firstly, the PSO method was used to develop the CG beads of the decane model represented with 2:1 (2-2-2-2-2) mapping scheme. This was followed by the development of the nonane model described with hybrid 2-2-3-2, and 3:1 (3-3-3) mapping schemes. The force-field (FF) parameters for these three CG models were optimized to reproduce four experimentally observed properties including density, enthalpy of vaporization, surface tension, and self-diffusion coefficient at 300 K. The CG MD simulations conducted with these new CG models of decane and nonane, at different timesteps, for various system sizes, and at a range of different temperatures, were able to predict their density, enthalpy of vaporization, surface tension, self-diffusion coefficient, expansibility, and isothermal compressibility with a good accuracy. Moreover, comparison of structural features obtained from the CG MD simulations and the CG beads of mapped all-atom (AA) trajectories of decane and nonane showed very good agreement. To test the chemical transferability of these models, we have constructed the models for hydrocarbons ranging from pentane to heptadecane, by using different combination of the CG beads of decane and nonane. The properties of pentane to heptadecane predicted by these new CG models showed an excellent agreement with the experimental data.

Eukaryotic membrane tethers revisited using magnetic tweezers.

PubMed

Hosu, Basarab G; Sun, Mingzhai; Marga, Françoise; Grandbois, Michel; Forgacs, Gabor

2007-04-19

Membrane nanotubes, under physiological conditions, typically form en masse. We employed magnetic tweezers (MTW) to extract tethers from human brain tumor cells and compared their biophysical properties with tethers extracted after disruption of the cytoskeleton and from a strongly differing cell type, Chinese hamster ovary cells. In this method, the constant force produced with the MTW is transduced to cells through super-paramagnetic beads attached to the cell membrane. Multiple sudden jumps in bead velocity were manifest in the recorded bead displacement-time profiles. These discrete events were interpreted as successive ruptures of individual tethers. Observation with scanning electron microscopy supported the simultaneous existence of multiple tethers. The physical characteristics, in particular, the number and viscoelastic properties of the extracted tethers were determined from the analytic fit to bead trajectories, provided by a standard model of viscoelasticity. Comparison of tethers formed with MTW and atomic force microscopy (AFM), a technique where the cantilever-force transducer is moved at constant velocity, revealed significant differences in the two methods of tether formation. Our findings imply that extreme care must be used to interpret the outcome of tether pulling experiments performed with single molecular techniques (MTW, AFM, optical tweezers, etc). First, the different methods may be testing distinct membrane structures with distinct properties. Second, as soon as a true cell membrane (as opposed to that of a vesicle) can attach to a substrate, upon pulling on it, multiple nonspecific membrane tethers may be generated. Therefore, under physiological conditions, distinguishing between tethers formed through specific and nonspecific interactions is highly nontrivial if at all possible.

Eukaryotic membrane tethers revisited using magnetic tweezers

NASA Astrophysics Data System (ADS)

Hosu, Basarab G.; Sun, Mingzhai; Marga, Françoise; Grandbois, Michel; Forgacs, Gabor

2007-06-01

Membrane nanotubes, under physiological conditions, typically form en masse. We employed magnetic tweezers (MTW) to extract tethers from human brain tumor cells and compared their biophysical properties with tethers extracted after disruption of the cytoskeleton and from a strongly differing cell type, Chinese hamster ovary cells. In this method, the constant force produced with the MTW is transduced to cells through super-paramagnetic beads attached to the cell membrane. Multiple sudden jumps in bead velocity were manifest in the recorded bead displacement-time profiles. These discrete events were interpreted as successive ruptures of individual tethers. Observation with scanning electron microscopy supported the simultaneous existence of multiple tethers. The physical characteristics, in particular, the number and viscoelastic properties of the extracted tethers were determined from the analytic fit to bead trajectories, provided by a standard model of viscoelasticity. Comparison of tethers formed with MTW and atomic force microscopy (AFM), a technique where the cantilever-force transducer is moved at constant velocity, revealed significant differences in the two methods of tether formation. Our findings imply that extreme care must be used to interpret the outcome of tether pulling experiments performed with single molecular techniques (MTW, AFM, optical tweezers, etc). First, the different methods may be testing distinct membrane structures with distinct properties. Second, as soon as a true cell membrane (as opposed to that of a vesicle) can attach to a substrate, upon pulling on it, multiple nonspecific membrane tethers may be generated. Therefore, under physiological conditions, distinguishing between tethers formed through specific and nonspecific interactions is highly nontrivial if at all possible.

Jet atomization and cavitation induced by interactions between focused ultrasound and a water surfacea)

NASA Astrophysics Data System (ADS)

Tomita, Y.

2014-09-01

Atomization of a jet produced by the interaction of 1 MHz focused ultrasound with a water surface was investigated using high-speed photography. Viewing various aspects of jet behavior, threshold conditions were obtained necessary for water surface elevation and jet breakup, including drop separation and spray formation. In addition, the position of drop atomization, where a single drop separates from the tip of a jet without spraying, showed good correlation with the jet Weber number. For a set of specified conditions, multiple beaded water masses were formed, moving upwards to produce a vigorous jet. Cavitation phenomena occurred near the center of the primary drop-shaped water mass produced at the leading part of the jet; this was accompanied by fine droplets at the neck between the primary and secondary drop-shaped water masses, due to the collapse of capillary waves.

Advanced Structural Analyses by Third Generation Synchrotron Radiation Powder Diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sakata, M.; Aoyagi, S.; Ogura, T.

2007-01-19

Since the advent of the 3rd generation Synchrotron Radiation (SR) sources, such as SPring-8, the capabilities of SR powder diffraction increased greatly not only in an accurate structure refinement but also ab initio structure determination. In this study, advanced structural analyses by 3rd generation SR powder diffraction based on the Large Debye-Scherrer camera installed at BL02B2, SPring-8 is described. Because of high angular resolution and high counting statistics powder data collected at BL02B2, SPring-8, ab initio structure determination can cope with a molecular crystals with 65 atoms including H atoms. For the structure refinements, it is found that a kindmore » of Maximum Entropy Method in which several atoms are omitted in phase calculation become very important to refine structural details of fairy large molecule in a crystal. It should be emphasized that until the unknown structure is refined very precisely, the obtained structure by Genetic Algorithm (GA) or some other ab initio structure determination method using real space structural knowledge, it is not possible to tell whether the structure obtained by the method is correct or not. In order to determine and/or refine crystal structure of rather complicated molecules, we cannot overemphasize the importance of the 3rd generation SR sources.« less

Arsenic and antimony in geothermal waters of Yellowstone National Park, Wyoming, USA

USGS Publications Warehouse

Stauffer, R.E.; Thompson, J.M.

1984-01-01

A total of 268 thermal spring samples were analyzed for total soluble As using reduced molybdenum-blue; 27 of these samples were also analyzed for total Sb using flame atomic absorption spectrometry. At Yellowstone the Cl As atomic ratio is nearly constant among neutral-alkaline springs with Cl > 100 mg L-1, and within restricted geographic areas, indicating no differential effects of adiabatic vs. conductive cooling on arsenic. The Cl As ratio increases with silica and decreases with decreasing Cl ??CO3; the latter relationship is best exemplified for springs along the extensively sampled SE-NW trend within the Lone Star-Upper-Midway Basin region. The relationship between Cl As and Cl ??CO3 at Yellowstone suggests a possible rock leaching rather than magmatic origin for much of the Park's total As flux. Condensed vapor springs are low in both As and Cl. Very high Cl As ratios ( > 1000) are associated exclusively with highly diluted (Cl < 100 mg L-1) mixed springs in the Norris and Shoshone Basins and in the Upper White Creek and Firehole Lake areas of Lower Basin. The high ratios are associated with acidity and/or oxygen and iron; they indicate precipitation of As following massive dilution of the Asbearing high-Cl parent water. Yellowstone Sb ranged from 0.009 at Mammoth to 0.166 mg L-1 at Joseph's Coat Spring. Within basins, the Cl Sb ratio increases as the Cl ??CO3 ratio decreases, in marked contrast to As. Mixed springs also have elevated Cl Sb ratios. White (1967) and Weissberg (1969) previously reported stibnite (Sb2S3), but not orpiment (As2S3), precipitating in the near surface zone of alkaline geothermal systems. ?? 1984.

Insights into the factors responsible for curative effects of Aab-E-Shifa Spring Hasan Abdal (Pakistan)

NASA Astrophysics Data System (ADS)

ur Rahman, Sami; Bilal, Salma

2017-07-01

Springs are the gifts of nature on the earth as they contribute about eighty essential nutrients that are involved in more than 7000 enzymatic processes in the human body. European balneologists have recommended spring mineral waters for different therapeutic applications. In the present investigation, Aab- e- Shifa (Punjab Pakistan) spring water was analyzed due to its therapeutic behavior in the healing of various skin diseases via atomic absorption spectroscopy (AAS). It was found that besides other important minerals (Ca, Mg, K, and Na), the spring water contains the most significant antioxidant, i.e., Zn which is probably one of the major features of the curative behavior of Aab- e- Shifa. Other trace elements (Cr, Cd, Ni, Mn, Fe, and Cu) were also found to be present in the spring water under the permissible limits of various national and international organizations.

Rheology of wormlike micellar fluids from Brownian and molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Padding, J. T.; Boek, E. S.; Briels, W. J.

2005-11-01

There is a great need for understanding the link between the detailed chemistry of surfactants, forming wormlike micelles, and their macroscopic rheological properties. In this paper we show how this link may be explored through particle simulations. First we review an existing bead-spring model. We find that shear flow enhances the formation of rings at the expense of linear chains. The shear viscosity of this model is dominated by solvent contributions, however, and the link with the chemistry of the surfactants is missing. We introduce a more realistic Brownian dynamics model, the parameters of which are measured from atomistic molecular dynamics simulations.

Modeling and Control of State-Affine Probabilistic Systems for Atomic-Scale Dynamics

DTIC Science & Technology

2007-06-01

Analysis for Nonlinear Systems. New York: Spring -Verlag, 1987. [5] M. Itoh, "Atomic-scale homoepitaxial growth simulations of reconstructed III-V surfaces...Ridge, NJ; 1995. -- SSC function of the Node 182 [2] M. K. Weldon , K. T. Queeney, J. Eng Jr., K. Raghavachari, and Y. J. Chabal, "The surface science

Effects of Blank Curvature and Tool Conditions on the Spring Back of Thin Sheet Panel Formed through Local Embossing and Edge L-Bending

NASA Astrophysics Data System (ADS)

Park, Keecheol; Park, Jongyoun; Nam, Jaebok

2011-08-01

Due to the application of thinner sheet steels, the stamped panels in the forming process, generally, are severely distorted. The wavy shape of embossed panel finally converted to residual stress embedded in the panel at final forming (edge L-bending) and it is known as the cause of twisting and oil canning of spring backed panel. Another important source of stamped shape deviation is the curvature of blank. The effects of blank curvature on the shape defects (panel curvature and twisting) after stamping were investigated from defective panel analysis, model experiment and stamping simulation. And the effect of tool conditions (BHF and bead height change) on spring backed shape of real TV bottom chassis were studied. The initial curvature of blank was remained in the flat area of stamped panels as width directional curvature. It converted from length direction curvature of blank. The curvature of initial blank reduced the wavy shape after local emboss forming, but twisting after edge L-bending was increased at large blank curvature cases. The effects of emboss forming conditions, the forming heights and blank holding force were studied and it was found that the wavy shape of stamped sheet was rapidly changed although the forming conditions altered very small amount.

Computational Modeling of Hydroxypropyl-Methylcellulose Acetate Succinate (HPMCAS) and Phenytoin Interactions: A Systematic Coarse-Graining Approach.

PubMed

Huang, Wenjun; Mandal, Taraknath; Larson, Ronald G

2017-03-06

We present coarse-grained (CG) force fields for hydroxypropyl-methylcellulose acetate succinate (HPMCAS) polymers and the drug molecule phenytoin using a bead/stiff spring model, with each bead representing a HPMCAS monomer or monomer side group (hydroxypropyl acetyl, acetyl, or succinyl) or a single phenytoin ring. We obtain the bonded and nonbonded interaction parameters in our CG model using the RDFs from atomistic simulations of short HPMCAS model oligomers (20-mer) and atomistic simulations of phenytoin molecules. The nonbonded interactions are modeled using a LJ 12-6 potential, with separate parameters for each monomer substitution type, which allows heterogeneous polymer chains to be modeled. The cross interaction terms between the polymer and phenytoin CG beads are obtained explicitly from atomistic level polymer-phenytoin simulations, rather than from mixing rules. We study the solvation behavior of 50-mer and 100-mer polymer chains and find chain-length-dependent aggregation. We also compare the phenytoin CG force field developed in this work with that in Mandal et al. (Soft Matter, 2016, 12, 8246-8255) and conclude both are suitable for studying the interaction between polymer and drug in solvated solid dispersion formulation, in the absence of drug crystallization. Finally, we present simulations of heterogeneous HPMCAS model polymer chains and phenytoin molecules. Polymer and drug form a complex in a short period of simulation time due to strong intermolecular interactions. Moreover, the protonated polymer chains are more effective than deprotonated ones in inhibiting the drug aggregation in the polymer-drug complex.

COLLABORATIVE RESEARCH AND DEVELOPMENT (CR&D) Delivery Order 0034: Aircraft Coatings Modeling and Simulation

DTIC Science & Technology

2008-03-01

bonded potentials used. The interactions between the beads were described using 6-12 Lennard - Jones (LJ) potential (Equation (1)) with a 2.5 d cutoff...in Lennard - Jones potential for the non-bonded interactions is at 1.12 d in line with the second peak. The remainder of the g(r)chain-chain has...Simulator). 40 Lennard - Jones and Coulombic interactions for pairs of organic atoms were computed using a switching function with inner and outer cutoffs of

An Investigation of G-Quadruplex Structural Polymorphism in the Human Telomere Using a Combined Approach of Hydrodynamic Bead Modeling and Molecular Dynamics Simulation

PubMed Central

2015-01-01

Guanine-rich oligonucleotides can adopt noncanonical tertiary structures known as G-quadruplexes, which can exist in different forms depending on experimental conditions. High-resolution structural methods, such as X-ray crystallography and NMR spectroscopy, have been of limited usefulness in resolving the inherent structural polymorphism associated with G-quadruplex formation. The lack of, or the ambiguous nature of, currently available high-resolution structural data, in turn, has severely hindered investigations into the nature of these structures and their interactions with small-molecule inhibitors. We have used molecular dynamics in conjunction with hydrodynamic bead modeling to study the structures of the human telomeric G-quadruplex-forming sequences at the atomic level. We demonstrated that molecular dynamics can reproduce experimental hydrodynamic measurements and thus can be a powerful tool in the structural study of existing G-quadruplex sequences or in the prediction of new G-quadruplex structures. PMID:24779348

Electrostatic Levitation Technique for Investigations of Physical Properties of Liquid States

NASA Astrophysics Data System (ADS)

Okada, Junpei; Ishikawa, Takehiko; Paradis, Paul-Francois; Yoda, Shinichi

Electrostatic levitator (ESL) levitates a charged sample in a high vacuum using computer con-trolled electrostatic fields [1]. It can levitate materials such as metals, semiconductors, and some insulators. Sample temperature can be varied over a wide range, and samples can be deeply undercooled. We have been engaged in the research and development of the electro-static levitation technique with the aim of performing levitation dissolution experiments in the International Space Station (ISS). Our device for the electrostatic levitation dissolution test has been developed for experiments on the ISS. To this end, the system is designed to be compact and portable so that it can be launched by rocket and used for experiments in the limited space on the ISS. Accordingly, the device can be installed not just on the ISS or our research laboratory, but also in various external sites. We devised a plan to install the electrostatic levitation system in a site other than the ISS to study atomic structure and electron structure of ultra-high-temperature liquids. We mounted our system on third generation synchrotron radiation facility "SPring-8" in Japan, to investigate the atomic and electron structures of high-temperature liquids. The SPring-8 is an experimental facility that allows use of the most powerful X-rays in the world. We conducted a variety of experiments on ultra-high-temperature liquids using SPring-8. The X-ray is ideal for exploring atomic structure and electron structure. Since the X-ray is an electromagnetic wave, it interacts with electrons. In addition, most electrons gather around the atomic nucleus. By close analysis of the scattered x-rays, we can determine its atomic structure and electron structure in detail. In this talk, we introduce an x-ray Compton scattering and x-ray Raman scattering measurements on liquid aluminum and silicon. [1] W. -K. Rhim, et al, Rev. Sci. Instrum. (1985) 56 307.

Entropy gives rise to topologically associating domains

PubMed Central

Vasquez, Paula A.; Hult, Caitlin; Adalsteinsson, David; Lawrimore, Josh; Forest, Mark G.; Bloom, Kerry

2016-01-01

We investigate chromosome organization within the nucleus using polymer models whose formulation is closely guided by experiments in live yeast cells. We employ bead-spring chromosome models together with loop formation within the chains and the presence of nuclear bodies to quantify the extent to which these mechanisms shape the topological landscape in the interphase nucleus. By investigating the genome as a dynamical system, we show that domains of high chromosomal interactions can arise solely from the polymeric nature of the chromosome arms due to entropic interactions and nuclear confinement. In this view, the role of bio-chemical related processes is to modulate and extend the duration of the interacting domains. PMID:27257057

Relaxation processes and glass transition of confined polymer melts: A molecular dynamics simulation of 1,4-polybutadiene between graphite walls.

PubMed

Solar, M; Binder, K; Paul, W

2017-05-28

Molecular dynamics simulations of a chemically realistic model for 1,4-polybutadiene in a thin film geometry confined by two graphite walls are presented. Previous work on melts in the bulk has shown that the model faithfully reproduces static and dynamic properties of the real material over a wide temperature range. The present work studies how these properties change due to nano-confinement. The focus is on orientational correlations observable in nuclear magnetic resonance experiments and on the local intermediate incoherent neutron scattering function, F s (q z , z, t), for distances z from the graphite walls in the range of a few nanometers. Temperatures from about 2T g down to about 1.15T g , where T g is the glass transition temperature in the bulk, are studied. It is shown that weakly attractive forces between the wall atoms and the monomers suffice to effectively bind a polymer coil that is near the wall. For a wide regime of temperatures, the Arrhenius-like adsorption/desorption kinetics of the monomers is the slowest process, while very close to T g the Vogel-Fulcher-Tammann-like α-relaxation takes over. The α-process is modified only for z≤1.2 nm due to the density changes near the walls, less than expected from studies of coarse-grained (bead-spring-type) models. The weakness of the surface effects on the glass transition in this case is attributed to the interplay of density changes near the wall with the torsional potential. A brief discussion of pertinent experiments is given.

A biophysical study of clathrin utilizing light scattering, neutron scattering and structure based computer modeling

NASA Astrophysics Data System (ADS)

Ferguson, Matthew Lee

A principal component in the protein coats of certain post-golgi and endocytic vesicles is clathrin, which appears as a three-legged heteropolymer (known as a triskelion) that assembles into polyhedral baskets principally made up of pentagonal and hexagonal faces. In vitro, this assembly depends on the pH, with baskets forming more readily at low pH and less readily at high pH. We have developed procedures, based on static and dynamic light scattering, to determine the radius of gyration, Rg, and hydrodynamic radius, RH, of isolated triskelia under conditions where basket assembly occurs. Calculations based on rigid molecular bead models of a triskelion show that the measured values can be accounted for by bending of the legs and a puckering at the vertex. We also show that the values of Rg and R H measured for clathrin triskelia in solution are qualitatively consistent with the conformation of an individual triskelion that is part of a "D6 barrel" basket assembly measured by cryo-EM tomography. We extended this study by performing small angle neutron scattering (SANS) experiments on isolated triskelia in solution under conditions where baskets do not assemble. SANS experiments were consistent with previous static light scattering experiments but showed a shoulder in the scattering function at intermediate q-values just beyond the central diffraction peak (the Guinier regime). Theoretical calculations based on rigid bead models of a triskelion showed well-defined features in this region different from the experiment. A flexible bead-spring model of a triskelion and Brownian dynamics simulations were used to generate a time averaged scattering function. This model adequately described the experimental data for flexibilities close to previous estimates from the analysis of electron micrographs.

Structure of flexible and semiflexible polyelectrolyte chains in confined spaces of slit micro/nanochannels.

PubMed

Jeon, Jonggu; Chun, Myung-Suk

2007-04-21

Understanding the behavior of a polyelectrolyte in confined spaces has direct relevance in design and manipulation of microfluidic devices, as well as transport in living organisms. In this paper, a coarse-grained model of anionic semiflexible polyelectrolyte is applied, and its structure and dynamics are fully examined with Brownian dynamics (BD) simulations both in bulk solution and under confinement between two negatively charged parallel plates. The modeling is based on the nonlinear bead-spring discretization of a continuous chain with additional long-range electrostatic, Lennard-Jones, and hydrodynamic interactions between pairs of beads. The authors also consider the steric and electrostatic interactions between the bead and the confining wall. Relevant model parameters are determined from experimental rheology data on the anionic polysaccharide xanthan reported previously. For comparison, both flexible and semiflexible models are developed accompanying zero and finite intrinsic persistence lengths, respectively. The conformational changes of the polyelectrolyte chain induced by confinements and their dependence on the screening effect of the electrolyte solution are faithfully characterized with BD simulations. Depending on the intrinsic rigidity and the medium ionic strength, the polyelectrolyte can be classified as flexible, semiflexible, or rigid. Confined flexible and semiflexible chains exhibit a nonmonotonic variation in size, as measured by the radius of gyration and end-to-end distance, with changing slit width. For the semiflexible chain, this is coupled to the variations in long-range bond vector correlation. The rigid chain, realized at low ionic strength, does not have minima in size but exhibits a sigmoidal transition. The size of confined semiflexible and rigid polyelectrolytes can be well described by the wormlike chain model once the electrostatic effects are taken into account by the persistence length measured at long length scale.

High Speed Video Measurements of a Magneto-optical Trap

NASA Astrophysics Data System (ADS)

Horstman, Luke; Graber, Curtis; Erickson, Seth; Slattery, Anna; Hoyt, Chad

2016-05-01

We present a video method to observe the mechanical properties of a lithium magneto-optical trap. A sinusoidally amplitude-modulated laser beam perturbed a collection of trapped ce7 Li atoms and the oscillatory response was recorded with a NAC Memrecam GX-8 high speed camera at 10,000 frames per second. We characterized the trap by modeling the oscillating cold atoms as a damped, driven, harmonic oscillator. Matlab scripts tracked the atomic cloud movement and relative phase directly from the captured high speed video frames. The trap spring constant, with magnetic field gradient bz = 36 G/cm, was measured to be 4 . 5 +/- . 5 ×10-19 N/m, which implies a trap resonant frequency of 988 +/- 55 Hz. Additionally, at bz = 27 G/cm the spring constant was measured to be 2 . 3 +/- . 2 ×10-19 N/m, which corresponds to a resonant frequency of 707 +/- 30 Hz. These properties at bz = 18 G/cm were found to be 8 . 8 +/- . 5 ×10-20 N/m, and 438 +/- 13 Hz. NSF #1245573.

A Novel Inherently Radiopaque Bead for Transarterial Embolization to Treat Liver Cancer - A Pre-clinical Study.

PubMed

Duran, Rafael; Sharma, Karun; Dreher, Matthew R; Ashrafi, Koorosh; Mirpour, Sahar; Lin, MingDe; Schernthaner, Ruediger E; Schlachter, Todd R; Tacher, Vania; Lewis, Andrew L; Willis, Sean; den Hartog, Mark; Radaelli, Alessandro; Negussie, Ayele H; Wood, Bradford J; Geschwind, Jean-François H

2016-01-01

Embolotherapy using microshperes is currently performed with soluble contrast to aid in visualization. However, administered payload visibility dimishes soon after delivery due to soluble contrast washout, leaving the radiolucent bead's location unknown. The objective of our study was to characterize inherently radiopaque beads (RO Beads) in terms of physicomechanical properties, deliverability and imaging visibility in a rabbit VX2 liver tumor model. RO Beads, which are based on LC Bead® platform, were compared to LC Bead. Bead size (light microscopy), equilibrium water content (EWC), density, X-ray attenuation and iodine distribution (micro-CT), suspension (settling times), deliverability and in vitro penetration were investigated. Fifteen rabbits were embolized with either LC Bead or RO Beads + soluble contrast (iodixanol-320), or RO Beads+dextrose. Appearance was evaluated with fluoroscopy, X-ray single shot, cone-beam CT (CBCT). Both bead types had a similar size distribution. RO Beads had lower EWC (60-72%) and higher density (1.21-1.36 g/cc) with a homogeneous iodine distribution within the bead's interior. RO Beads suspension time was shorter than LC Bead, with durable suspension (>5 min) in 100% iodixanol. RO Beads ≤300 µm were deliverable through a 2.3-Fr microcatheter. Both bead types showed similar penetration. Soluble contrast could identify target and non-target embolization on fluoroscopy during administration. However, the imaging appearance vanished quickly for LC Bead as contrast washed-out. RO Beads+contrast significantly increased visibility on X-ray single shot compared to LC Bead+contrast in target and non-target arteries (P=0.0043). Similarly, RO beads demonstrated better visibility on CBCT in target arteries (P=0.0238) with a trend in non-target arteries (P=0.0519). RO Beads+dextrose were not sufficiently visible to monitor embolization using fluoroscopy. RO Beads provide better conspicuity to determine target and non-target embolization compared to LC Bead which may improve intra-procedural monitoring and post-procedural evaluation of transarterial embolization.

Coarse-grained Brownian dynamics simulations of protein translocation through nanopores

NASA Astrophysics Data System (ADS)

Lee, Po-Hsien; Helms, Volkhard; Geyer, Tihamér

2012-10-01

A crucial process in biological cells is the translocation of newly synthesized proteins across cell membranes via integral membrane protein pores termed translocons. Recent improved techniques now allow producing artificial membranes with pores of similar dimensions of a few nm as the translocon system. For the translocon system, the protein has to be unfolded, whereas the artificial pores are wide enough so that small proteins can pass through even when folded. To study how proteins permeate through such membrane pores, we used coarse-grained Brownian dynamics simulations where the proteins were modeled as single beads or bead-spring polymers for both folded and unfolded states. The pores were modeled as cylindrical holes through the membrane with various radii and lengths. Diffusion was driven by a concentration gradient created across the porous membrane. Our results for both folded and unfolded configurations show the expected reciprocal relation between the flow rate and the pore length in agreement with an analytical solution derived by Brunn et al. [Q. J. Mech. Appl. Math. 37, 311 (1984)], 10.1093/qjmam/37.2.311. Furthermore, we find that the geometric constriction by the narrow pore leads to an accumulation of proteins at the pore entrance, which in turn compensates for the reduced diffusivity of the proteins inside the pore.

Characterization of solid particle erosion resistance of ductile metals based on their properties

NASA Technical Reports Server (NTRS)

Rao, P. V.; Buckley, D. H.

1985-01-01

This paper presents experimental results pertaining to spherical glass bead and angular crushed glass particle impingement. A concept of energy absorption to explain the failure of material is proposed and is correlated with the erosion characteristics of several pure metals. Analyses of extensive erosion data indicate that the properties - surface energy, specific melting energy, strain energy, melting point, bulk modulus, hardness, atomic volume - and the product of the parameters - linear coefficient of thermal expansion x bulk modulus x temperature rise required for melting, and ultimate resilience x hardness - exhibit the best correlations. The properties of surface energy and atomic volume are suggested for the first time for correlation purposes and are found to correlate well with erosion rates at different angles of impingement. It further appears that both energy and thermal properties contribute to the total erosion.

Note: Improved calibration of atomic force microscope cantilevers using multiple reference cantilevers.

PubMed

Sader, John E; Friend, James R

2015-05-01

Overall precision of the simplified calibration method in J. E. Sader et al., Rev. Sci. Instrum. 83, 103705 (2012), Sec. III D, is dominated by the spring constant of the reference cantilever. The question arises: How does one take measurements from multiple reference cantilevers, and combine these results, to improve uncertainty of the reference cantilever's spring constant and hence the overall precision of the method? This question is addressed in this note. Its answer enables manufacturers to specify of a single set of data for the spring constant, resonant frequency, and quality factor, from measurements on multiple reference cantilevers. With this data set, users can trivially calibrate cantilevers of the same type.

Effect of cantilever geometry on the optical lever sensitivities and thermal noise method of the atomic force microscope.

PubMed

Sader, John E; Lu, Jianing; Mulvaney, Paul

2014-11-01

Calibration of the optical lever sensitivities of atomic force microscope (AFM) cantilevers is especially important for determining the force in AFM measurements. These sensitivities depend critically on the cantilever mode used and are known to differ for static and dynamic measurements. Here, we calculate the ratio of the dynamic and static sensitivities for several common AFM cantilevers, whose shapes vary considerably, and experimentally verify these results. The dynamic-to-static optical lever sensitivity ratio is found to range from 1.09 to 1.41 for the cantilevers studied - in stark contrast to the constant value of 1.09 used widely in current calibration studies. This analysis shows that accuracy of the thermal noise method for the static spring constant is strongly dependent on cantilever geometry - neglect of these dynamic-to-static factors can induce errors exceeding 100%. We also discuss a simple experimental approach to non-invasively and simultaneously determine the dynamic and static spring constants and optical lever sensitivities of cantilevers of arbitrary shape, which is applicable to all AFM platforms that have the thermal noise method for spring constant calibration.

Analytical Model of the Nonlinear Dynamics of Cantilever Tip-Sample Surface Interactions for Various Acoustic-Atomic Force Microscopies

NASA Technical Reports Server (NTRS)

Cantrell, John H., Jr.; Cantrell, Sean A.

2008-01-01

A comprehensive analytical model of the interaction of the cantilever tip of the atomic force microscope (AFM) with the sample surface is developed that accounts for the nonlinearity of the tip-surface interaction force. The interaction is modeled as a nonlinear spring coupled at opposite ends to linear springs representing cantilever and sample surface oscillators. The model leads to a pair of coupled nonlinear differential equations that are solved analytically using a standard iteration procedure. Solutions are obtained for the phase and amplitude signals generated by various acoustic-atomic force microscope (A-AFM) techniques including force modulation microscopy, atomic force acoustic microscopy, ultrasonic force microscopy, heterodyne force microscopy, resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM), and the commonly used intermittent contact mode (TappingMode) generally available on AFMs. The solutions are used to obtain a quantitative measure of image contrast resulting from variations in the Young modulus of the sample for the amplitude and phase images generated by the A-AFM techniques. Application of the model to RDF-AFUM and intermittent soft contact phase images of LaRC-cp2 polyimide polymer is discussed. The model predicts variations in the Young modulus of the material of 24 percent from the RDF-AFUM image and 18 percent from the intermittent soft contact image. Both predictions are in good agreement with the literature value of 21 percent obtained from independent, macroscopic measurements of sheet polymer material.

A simple, efficient polarizable coarse-grained water model for molecular dynamics simulations.

PubMed

Riniker, Sereina; van Gunsteren, Wilfred F

2011-02-28

The development of coarse-grained (CG) models that correctly represent the important features of compounds is essential to overcome the limitations in time scale and system size currently encountered in atomistic molecular dynamics simulations. Most approaches reported in the literature model one or several molecules into a single uncharged CG bead. For water, this implicit treatment of the electrostatic interactions, however, fails to mimic important properties, e.g., the dielectric screening. Therefore, a coarse-grained model for water is proposed which treats the electrostatic interactions between clusters of water molecules explicitly. Five water molecules are embedded in a spherical CG bead consisting of two oppositely charged particles which represent a dipole. The bond connecting the two particles in a bead is unconstrained, which makes the model polarizable. Experimental and all-atom simulated data of liquid water at room temperature are used for parametrization of the model. The experimental density and the relative static dielectric permittivity were chosen as primary target properties. The model properties are compared with those obtained from experiment, from clusters of simple-point-charge water molecules of appropriate size in the liquid phase, and for other CG water models if available. The comparison shows that not all atomistic properties can be reproduced by a CG model, so properties of key importance have to be selected when coarse graining is applied. Yet, the CG model reproduces the key characteristics of liquid water while being computationally 1-2 orders of magnitude more efficient than standard fine-grained atomistic water models.

Natural fluoride levels in some springs and streams from the late Maastrichtian Ajali formation in Ohafia-Arochukwu area of south eastern Nigeria.

PubMed

Ibe, K K; Adlegbembo, A O; Mafeni, J O; Danfillo, I S

1999-09-01

The aim of this study was to provide baseline data on the fluoride levels in waters associated with the late Maastrichtian Ajali formation in Ohafia-Arochukwu area of South Eastern Nigeria. Water samples from 14 artesian, perched springs and eight streams from the formation were collected with plastic containers. Fluoride analysis was carried out with inductively coupled plasma Atomic Emission Spectrometry (ICP-AES) equipment at the laboratories of the Department of Earth Science, University of Leeds, United Kingdom. The results showed that fluoride occurred in only one of the 14 spring water samples. Fluoride level in the sample was 0.03 ppm. The spring water, which contained some fluoride, was possibly associated with another rock formation: namely, the limestone bearing Nsukka formation, which overlies the Ajali formation. No fluoride was observed in all the stream water samples. This study reported the absence of fluoride in spring and stream waters associated with the late Maastrichtian formations in Nigeria.

Confocal nanoscanning, bead picking (CONA): PickoScreen microscopes for automated and quantitative screening of one-bead one-compound libraries.

PubMed

Hintersteiner, Martin; Buehler, Christof; Uhl, Volker; Schmied, Mario; Müller, Jürgen; Kottig, Karsten; Auer, Manfred

2009-01-01

Solid phase combinatorial chemistry provides fast and cost-effective access to large bead based libraries with compound numbers easily exceeding tens of thousands of compounds. Incubating one-bead one-compound library beads with fluorescently labeled target proteins and identifying and isolating the beads which contain a bound target protein, potentially represents one of the most powerful generic primary high throughput screening formats. On-bead screening (OBS) based on this detection principle can be carried out with limited automation. Often hit bead detection, i.e. recognizing beads with a fluorescently labeled protein bound to the compound on the bead, relies on eye-inspection under a wide-field microscope. Using low resolution detection techniques, the identification of hit beads and their ranking is limited by a low fluorescence signal intensity and varying levels of the library beads' autofluorescence. To exploit the full potential of an OBS process, reliable methods for both automated quantitative detection of hit beads and their subsequent isolation are needed. In a joint collaborative effort with Evotec Technologies (now Perkin-Elmer Cellular Technologies Germany GmbH), we have built two confocal bead scanner and picker platforms PS02 and a high-speed variant PS04 dedicated to automated high resolution OBS. The PS0X instruments combine fully automated confocal large area scanning of a bead monolayer at the bottom of standard MTP plates with semiautomated isolation of individual hit beads via hydraulic-driven picker capillaries. The quantification of fluorescence intensities with high spatial resolution in the equatorial plane of each bead allows for a reliable discrimination between entirely bright autofluorescent beads and real hit beads which exhibit an increased fluorescence signal at the outer few micrometers of the bead. The achieved screening speed of up to 200,000 bead assayed in less than 7 h and the picking time of approximately 1 bead/min allow exploitation of one-bead one-compound libraries with high sensitivity, accuracy, and speed.

Ordered quasi-two-dimensional structure of nanoparticles in semiflexible ring polymer brushes under compression

NASA Astrophysics Data System (ADS)

Hua, Yunfeng; Deng, Zhenyu; Jiang, Yangwei; Zhang, Linxi

2017-06-01

Molecular dynamics simulations of a coarse-grained bead-spring model of ring polymer brushes under compression are presented. Flexible polymer brushes are always disordered during compression, whereas semiflexible polymer brushes tend to be ordered under sufficiently strong compression. Further, the polymer monomer density of the semiflexible polymer brush is very high near the brush surface, inducing a peak value of the free energy near the surface. Therefore, when nanoparticles are compressed in semiflexible ring polymer brushes, they tend to exhibit a closely packed single-layer structure between the brush surface and the impenetrable wall, and a quasi-two-dimensional ordered structure near the brush surface is formed under strong compression. These findings provide a new approach to designing responsive applications.

Predicting Flory-Huggins χ from Simulations

NASA Astrophysics Data System (ADS)

Zhang, Wenlin; Gomez, Enrique D.; Milner, Scott T.

2017-07-01

We introduce a method, based on a novel thermodynamic integration scheme, to extract the Flory-Huggins χ parameter as small as 10-3k T for polymer blends from molecular dynamics (MD) simulations. We obtain χ for the archetypical coarse-grained model of nonpolar polymer blends: flexible bead-spring chains with different Lennard-Jones interactions between A and B monomers. Using these χ values and a lattice version of self-consistent field theory (SCFT), we predict the shape of planar interfaces for phase-separated binary blends. Our SCFT results agree with MD simulations, validating both the predicted χ values and our thermodynamic integration method. Combined with atomistic simulations, our method can be applied to predict χ for new polymers from their chemical structures.

Noninvasive determination of optical lever sensitivity in atomic force microscopy

NASA Astrophysics Data System (ADS)

Higgins, M. J.; Proksch, R.; Sader, J. E.; Polcik, M.; Mc Endoo, S.; Cleveland, J. P.; Jarvis, S. P.

2006-01-01

Atomic force microscopes typically require knowledge of the cantilever spring constant and optical lever sensitivity in order to accurately determine the force from the cantilever deflection. In this study, we investigate a technique to calibrate the optical lever sensitivity of rectangular cantilevers that does not require contact to be made with a surface. This noncontact approach utilizes the method of Sader et al. [Rev. Sci. Instrum. 70, 3967 (1999)] to calibrate the spring constant of the cantilever in combination with the equipartition theorem [J. L. Hutter and J. Bechhoefer, Rev. Sci. Instrum. 64, 1868 (1993)] to determine the optical lever sensitivity. A comparison is presented between sensitivity values obtained from conventional static mode force curves and those derived using this noncontact approach for a range of different cantilevers in air and liquid. These measurements indicate that the method offers a quick, alternative approach for the calibration of the optical lever sensitivity.

Designing pinhole vacancies in graphene towards functionalization: Effects on critical buckling load

NASA Astrophysics Data System (ADS)

Georgantzinos, S. K.; Markolefas, S.; Giannopoulos, G. I.; Katsareas, D. E.; Anifantis, N. K.

2017-03-01

The effect of size and placement of pinhole-type atom vacancies on Euler's critical load on free-standing, monolayer graphene, is investigated. The graphene is modeled by a structural spring-based finite element approach, in which every interatomic interaction is approached as a linear spring. The geometry of graphene and the pinhole size lead to the assembly of the stiffness matrix of the nanostructure. Definition of the boundary conditions of the problem leads to the solution of the eigenvalue problem and consequently to the critical buckling load. Comparison to results found in the literature illustrates the validity and accuracy of the proposed method. Parametric analysis regarding the placement and size of the pinhole-type vacancy, as well as the graphene geometry, depicts the effects on critical buckling load. Non-linear regression analysis leads to empirical-analytical equations for predicting the buckling behavior of graphene, with engineered pinhole-type atom vacancies.

Protein simulation using coarse-grained two-bead multipole force field with polarizable water models.

PubMed

Li, Min; Zhang, John Z H

2017-02-14

A recently developed two-bead multipole force field (TMFF) is employed in coarse-grained (CG) molecular dynamics (MD) simulation of proteins in combination with polarizable CG water models, the Martini polarizable water model, and modified big multipole water model. Significant improvement in simulated structures and dynamics of proteins is observed in terms of both the root-mean-square deviations (RMSDs) of the structures and residue root-mean-square fluctuations (RMSFs) from the native ones in the present simulation compared with the simulation result with Martini's non-polarizable water model. Our result shows that TMFF simulation using CG water models gives much stable secondary structures of proteins without the need for adding extra interaction potentials to constrain the secondary structures. Our result also shows that by increasing the MD time step from 2 fs to 6 fs, the RMSD and RMSF results are still in excellent agreement with those from all-atom simulations. The current study demonstrated clearly that the application of TMFF together with a polarizable CG water model significantly improves the accuracy and efficiency for CG simulation of proteins.

Protein simulation using coarse-grained two-bead multipole force field with polarizable water models

NASA Astrophysics Data System (ADS)

Li, Min; Zhang, John Z. H.

2017-02-01

A recently developed two-bead multipole force field (TMFF) is employed in coarse-grained (CG) molecular dynamics (MD) simulation of proteins in combination with polarizable CG water models, the Martini polarizable water model, and modified big multipole water model. Significant improvement in simulated structures and dynamics of proteins is observed in terms of both the root-mean-square deviations (RMSDs) of the structures and residue root-mean-square fluctuations (RMSFs) from the native ones in the present simulation compared with the simulation result with Martini's non-polarizable water model. Our result shows that TMFF simulation using CG water models gives much stable secondary structures of proteins without the need for adding extra interaction potentials to constrain the secondary structures. Our result also shows that by increasing the MD time step from 2 fs to 6 fs, the RMSD and RMSF results are still in excellent agreement with those from all-atom simulations. The current study demonstrated clearly that the application of TMFF together with a polarizable CG water model significantly improves the accuracy and efficiency for CG simulation of proteins.

Effect of pH on film structure and electrical property of PMMA-Au composite particles prepared by redox transmetalation

NASA Astrophysics Data System (ADS)

Wu, Hong-Mao; Lin, Kuan-Ju; Yu, Yi-Hsiuan; Ho, Chan-Yuan; Wei, Ming-Hsiung; Lu, Fu-Hsing; Tseng, Wenjea J.

2014-01-01

Surface-selective deposition of gold (Au) on electroless plated poly(methyl methacrylate)-nickel (PMMA-Ni) beads was prepared chemically by a facile redox-transmetalation route in which the Ni atoms on the PMMA surface were reacted with Au precursors, i.e., chloroauric acid (HAuCl4), in water to form predominately core-shell PMMA-Au composite particles without the need of reducing agent. The Ni layer acted as a sacrificial template to facilitate the selective transmetalation deposition of a metallic Au film. When pH of the precursor solution was adjusted from 6 to 9, morphology of the Au film changed from a uniform particulate film consisting of assemblies of Au nanoparticles, to densely packed, continuous film with platelet Au crystals, and finally to isolated Au islands on the PMMA surface with a raspberry-like core-shell morphology. Uniformly dense Au coating with a thickness of about 200 nm was formed on the PMMA beads at pH of 7 to 8, which gave rise to an electrical resistivity as low as 3 × 10-2 Ω cm.

Coarse Graining to Investigate Membrane Induced Peptide Folding of Anticancer Peptides

NASA Astrophysics Data System (ADS)

Ganesan, Sai; Xu, Hongcheng; Matysiak, Silvina

Information about membrane induced peptide folding mechanisms using all-atom molecular dynamics simulations is a challenge due to time and length scale issues.We recently developed a low resolution Water Explicit Polarizable PROtein coarse-grained Model by adding oppositely charged dummy particles inside protein backbone beads.These two dummy particles represent a fluctuating dipole,thus introducing structural polarization into the coarse-grained model.With this model,we were able to achieve significant α- β secondary structure content de novo,without any added bias.We extended the model to zwitterionic and anionic lipids,by adding oppositely charged dummy particles inside polar beads, to capture the ability of the head group region to form hydrogen bonds.We use zwitterionic POPC and anionic POPS as our model lipids, and a cationic anticancer peptide,SVS1,as our model peptide.We have characterized the driving forces for SVS1 folding on lipid bilayers with varying anionic and zwitterionic lipid compositions.Based on our results, dipolar interactions between peptide backbone and lipid head groups contribute to stabilize folded conformations.Cooperativity in folding is induced by both intra peptide and membrane-peptide interaction.

Detection of cancerous cervical cells using physical adhesion of fluorescent silica particles and centripetal force

PubMed Central

Gaikwad, Ravi M.; Dokukin, Maxim E.; Iyer, K. Swaminathan; Woodworth, Craig D.; Volkov, Dmytro O.; Sokolov, Igor

2012-01-01

Here we describe a non-traditional method to identify cancerous human cervical epithelial cells in a culture dish based on physical interaction between silica beads and cells. It is a simple optical fluorescence-based technique which detects the relative difference in the amount of fluorescent silica beads physically adherent to surfaces of cancerous and normal cervical cells. The method utilizes the centripetal force gradient that occurs in a rotating culture dish. Due to the variation in the balance between adhesion and centripetal forces, cancerous and normal cells demonstrate clearly distinctive distributions of the fluorescent particles adherent to the cell surface over the culture dish. The method demonstrates higher adhesion of silica particles to normal cells compared to cancerous cells. The difference in adhesion was initially observed by atomic force microscopy (AFM). The AFM data were used to design the parameters of the rotational dish experiment. The optical method that we describe is much faster and technically simpler than AFM. This work provides proof of the concept that physical interactions can be used to accurately discriminate normal and cancer cells. PMID:21305062

Water-Chemistry Data for Selected Springs, Geysers, and Streams in Yellowstone National Park, Wyoming, 2003-2005

USGS Publications Warehouse

Ball, James W.; McCleskey, R. Blaine; Nordstrom, D. Kirk; Holloway, JoAnn M.

2008-01-01

Water analyses are reported for 157 samples collected from numerous hot springs, their overflow drainages, and Lemonade Creek in Yellowstone National Park (YNP) during 2003-2005. Water samples were collected and analyzed for major and trace constituents from ten areas of YNP including Terrace and Beryl Springs in the Gibbon Canyon area, Norris Geyser Basin, the West Nymph Creek thermal area, the area near Nymph Lake, Hazle Lake, and Frying Pan Spring, Lower Geyser Basin, Washburn Hot Springs, Mammoth Hot Springs, Potts Hot Spring Basin, the Sulphur Caldron area, and Lemonade Creek near the Solfatara Trail. These water samples were collected and analyzed as part of research investigations in YNP on arsenic, antimony, and sulfur redox distribution in hot springs and overflow drainages, and the occurrence and distribution of dissolved mercury. Most samples were analyzed for major cations and anions, trace metals, redox species of antimony, arsenic, iron, nitrogen, and sulfur, and isotopes of hydrogen and oxygen. Analyses were performed at the sampling site, in an on-site mobile laboratory vehicle, or later in a U.S. Geological Survey laboratory, depending on stability of the constituent and whether it could be preserved effectively. Water samples were filtered and preserved onsite. Water temperature, specific conductance, pH, Eh (redox potential relative to the Standard Hydrogen Electrode), and dissolved hydrogen sulfide were measured onsite at the time of sampling. Acidity was determined by titration, usually within a few days of sample collection. Alkalinity was determined by titration within 1 to 2 weeks of sample collection. Concentrations of thiosulfate and polythionate were determined as soon as possible (generally minutes to hours after sample collection) by ion chromatography in an on-site mobile laboratory vehicle. Total dissolved-iron and ferrous-iron concentrations often were measured onsite in the mobile laboratory vehicle. Concentrations of dissolved aluminum, arsenic, boron, barium, beryllium, calcium, cadmium, cobalt, chromium, copper, iron, potassium, lithium, magnesium, manganese, molybdenum, sodium, nickel, lead, selenium, silica, strontium, vanadium, and zinc were determined by inductively-coupled plasma-optical emission spectrometry. Trace concentrations of dissolved antimony, cadmium, cobalt, chromium, copper, lead, and selenium were determined by Zeeman-corrected graphite-furnace atomic-absorption spectrometry. Dissolved concentrations of total arsenic, arsenite, total antimony, and antimonite were determined by hydride-generation atomic-absorption spectrometry using a flow-injection analysis system. Dissolved concentrations of total mercury and methyl mercury were determined by cold-vapor atomic-fluorescence spectrometry. Concentrations of dissolved chloride, fluoride, nitrate, bromide, and sulfate were determined by ion chromatography. Concentrations of dissolved ferrous and total iron were determined by the FerroZine colorimetric method. Concentrations of dissolved nitrite were determined by colorimetry or chemiluminescence. Concentrations of dissolved ammonium were determined by ion chromatography, with reanalysis by colorimetry when separation of sodium and ammonia peaks was poor. Dissolved organic carbon concentrations were determined by the wet persulfate oxidation method. Hydrogen and oxygen isotope ratios were determined using the hydrogen and CO2 equilibration techniques, respectively.

76 FR 14058 - Notice of Inventory Completion: Fremont County Coroner, Riverton, WY

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-15

... associated funerary objects are 2 fragments of freshwater clam shells, 32 dentalia shell beads, 2 bird bone beads, 8 chokecherry seed beads, 162 bone heishi-style beads, 158 lignite heishi-style beads, 5 fragmentary bone heishi-style beads, 1 shell bead, and 3 chert microflakes. The Sinks Canyon site is located...

Bottom-up derivation of conservative and dissipative interactions for coarse-grained molecular liquids with the conditional reversible work method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deichmann, Gregor; Marcon, Valentina; Vegt, Nico F. A. van der, E-mail: vandervegt@csi.tu-darmstadt.de

Molecular simulations of soft matter systems have been performed in recent years using a variety of systematically coarse-grained models. With these models, structural or thermodynamic properties can be quite accurately represented while the prediction of dynamic properties remains difficult, especially for multi-component systems. In this work, we use constraint molecular dynamics simulations for calculating dissipative pair forces which are used together with conditional reversible work (CRW) conservative forces in dissipative particle dynamics (DPD) simulations. The combined CRW-DPD approach aims to extend the representability of CRW models to dynamic properties and uses a bottom-up approach. Dissipative pair forces are derived frommore » fluctuations of the direct atomistic forces between mapped groups. The conservative CRW potential is obtained from a similar series of constraint dynamics simulations and represents the reversible work performed to couple the direct atomistic interactions between the mapped atom groups. Neopentane, tetrachloromethane, cyclohexane, and n-hexane have been considered as model systems. These molecular liquids are simulated with atomistic molecular dynamics, coarse-grained molecular dynamics, and DPD. We find that the CRW-DPD models reproduce the liquid structure and diffusive dynamics of the liquid systems in reasonable agreement with the atomistic models when using single-site mapping schemes with beads containing five or six heavy atoms. For a two-site representation of n-hexane (3 carbons per bead), time scale separation can no longer be assumed and the DPD approach consequently fails to reproduce the atomistic dynamics.« less

Cantilever spring constant calibration using laser Doppler vibrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ohler, Benjamin

2007-06-15

Uncertainty in cantilever spring constants is a critical issue in atomic force microscopy (AFM) force measurements. Though numerous methods exist for calibrating cantilever spring constants, the accuracy of these methods can be limited by both the physical models themselves as well as uncertainties in their experimental implementation. Here we report the results from two of the most common calibration methods, the thermal tune method and the Sader method. These were implemented on a standard AFM system as well as using laser Doppler vibrometry (LDV). Using LDV eliminates some uncertainties associated with optical lever detection on an AFM. It also offersmore » considerably higher signal to noise deflection measurements. We find that AFM and LDV result in similar uncertainty in the calibrated spring constants, about 5%, using either the thermal tune or Sader methods provided that certain limitations of the methods and instrumentation are observed.« less

Deterministic bead-in-droplet ejection utilizing an integrated plug-in bead dispenser for single bead-based applications

NASA Astrophysics Data System (ADS)

Kim, Hojin; Choi, In Ho; Lee, Sanghyun; Won, Dong-Joon; Oh, Yong Suk; Kwon, Donghoon; Sung, Hyung Jin; Jeon, Sangmin; Kim, Joonwon

2017-04-01

This paper presents a deterministic bead-in-droplet ejection (BIDE) technique that regulates the precise distribution of microbeads in an ejected droplet. The deterministic BIDE was realized through the effective integration of a microfluidic single-particle handling technique with a liquid dispensing system. The integrated bead dispenser facilitates the transfer of the desired number of beads into a dispensing volume and the on-demand ejection of bead-encapsulated droplets. Single bead-encapsulated droplets were ejected every 3 s without any failure. Multiple-bead dispensing with deterministic control of the number of beads was demonstrated to emphasize the originality and quality of the proposed dispensing technique. The dispenser was mounted using a plug-socket type connection, and the dispensing process was completely automated using a programmed sequence without any microscopic observation. To demonstrate a potential application of the technique, bead-based streptavidin-biotin binding assay in an evaporating droplet was conducted using ultralow numbers of beads. The results evidenced the number of beads in the droplet crucially influences the reliability of the assay. Therefore, the proposed deterministic bead-in-droplet technology can be utilized to deliver desired beads onto a reaction site, particularly to reliably and efficiently enrich and detect target biomolecules.

Deterministic bead-in-droplet ejection utilizing an integrated plug-in bead dispenser for single bead-based applications.

PubMed

Kim, Hojin; Choi, In Ho; Lee, Sanghyun; Won, Dong-Joon; Oh, Yong Suk; Kwon, Donghoon; Sung, Hyung Jin; Jeon, Sangmin; Kim, Joonwon

2017-04-10

This paper presents a deterministic bead-in-droplet ejection (BIDE) technique that regulates the precise distribution of microbeads in an ejected droplet. The deterministic BIDE was realized through the effective integration of a microfluidic single-particle handling technique with a liquid dispensing system. The integrated bead dispenser facilitates the transfer of the desired number of beads into a dispensing volume and the on-demand ejection of bead-encapsulated droplets. Single bead-encapsulated droplets were ejected every 3 s without any failure. Multiple-bead dispensing with deterministic control of the number of beads was demonstrated to emphasize the originality and quality of the proposed dispensing technique. The dispenser was mounted using a plug-socket type connection, and the dispensing process was completely automated using a programmed sequence without any microscopic observation. To demonstrate a potential application of the technique, bead-based streptavidin-biotin binding assay in an evaporating droplet was conducted using ultralow numbers of beads. The results evidenced the number of beads in the droplet crucially influences the reliability of the assay. Therefore, the proposed deterministic bead-in-droplet technology can be utilized to deliver desired beads onto a reaction site, particularly to reliably and efficiently enrich and detect target biomolecules.

Heterogeneous immunoassays using magnetic beads on a digital microfluidic platform.

PubMed

Sista, Ramakrishna S; Eckhardt, Allen E; Srinivasan, Vijay; Pollack, Michael G; Palanki, Srinivas; Pamula, Vamsee K

2008-12-01

A digital microfluidic platform for performing heterogeneous sandwich immunoassays based on efficient handling of magnetic beads is presented in this paper. This approach is based on manipulation of discrete droplets of samples and reagents using electrowetting without the need for channels where the droplets are free to move laterally. Droplet-based manipulation of magnetic beads therefore does not suffer from clogging of channels. Immunoassays on a digital microfluidic platform require the following basic operations: bead attraction, bead washing, bead retention, and bead resuspension. Several parameters such as magnetic field strength, pull force, position, and buffer composition were studied for effective bead operations. Dilution-based washing of magnetic beads was demonstrated by immobilizing the magnetic beads using a permanent magnet and splitting the excess supernatant using electrowetting. Almost 100% bead retention was achieved after 7776-fold dilution-based washing of the supernatant. Efficient resuspension of magnetic beads was achieved by transporting a droplet with magnetic beads across five electrodes on the platform and exploiting the flow patterns within the droplet to resuspend the beads. All the magnetic-bead droplet operations were integrated together to generate standard curves for sandwich heterogeneous immunoassays on human insulin and interleukin-6 (IL-6) with a total time to result of 7 min for each assay.

Heterogeneous Immunoassays Using Magnetic beads On a Digital Microfluidic Platform

PubMed Central

Sista, Ramakrishna S.; Eckhardt, Allen E.; Srinivasan, Vijay; Pollack, Michael G.; Palanki, Srinivas; Pamula, Vamsee K.

2009-01-01

A digital microfluidic platform for performing heterogeneous sandwich immunoassays based on efficient handling of magnetic beads is presented in this paper. This approach is based on manipulation of discrete droplets of samples and reagents using electrowetting without the need for channels where the droplets are free to move laterally. Droplet-based manipulation of magnetic beads therefore does not suffer from clogging of channels. Immunoassays on a digital microfluidic platform require the following basic operations: bead attraction, bead washing, bead retention, and bead resuspension. Several parameters such as magnetic field strength, pull force, position, and buffer composition were studied for effective bead operations. Dilution-based washing of magnetic beads was demonstrated by immobilizing the magnetic beads using a permanent magnet and splitting the excess supernatant using electrowetting. Almost 100% bead retention was achieved after 7776 fold dilution-based washing of the supernatant. Efficient resuspension of magnetic beads was achieved by transporting a droplet with magnetic beads across five electrodes on the platform and exploiting the flow patterns within the droplet to resuspend the beads. All the magnetic-bead droplet operations were integrated together to generate standard curves for sandwich heterogeneous immunoassays on Human Insulin and Interleukin-6 (IL-6) with a total time to result of seven minutes for each assay. PMID:19023486

Note: Improved calibration of atomic force microscope cantilevers using multiple reference cantilevers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sader, John E., E-mail: jsader@unimelb.edu.au; Friend, James R.

2015-05-15

Overall precision of the simplified calibration method in J. E. Sader et al., Rev. Sci. Instrum. 83, 103705 (2012), Sec. III D, is dominated by the spring constant of the reference cantilever. The question arises: How does one take measurements from multiple reference cantilevers, and combine these results, to improve uncertainty of the reference cantilever’s spring constant and hence the overall precision of the method? This question is addressed in this note. Its answer enables manufacturers to specify of a single set of data for the spring constant, resonant frequency, and quality factor, from measurements on multiple reference cantilevers. Withmore » this data set, users can trivially calibrate cantilevers of the same type.« less

Cooperative geochemical investigation of geothermal resources in the Imperial Valley and Yuma areas. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coplen, T.B.

1973-10-01

Preliminary studies indicate that the Imperial Valley has a large geothermal potential. In order to delineate additional geothermal systems a chemical and isotopic investigation of samples from water wells, springs, and geothermal wells in the Imperial Valley and Yuma areas was conducted. Na, K, and Ca concentrations of nearly 200 well water, spring water, hot spring, and geothermal fluid samples from the Imperial Valley area were measured by atomic absorption spectrophotometry. Fournier and Truesdell's function was determined for each water sample. Suspected geothermal areas are identified. Hydrogen and oxygen isotope abundances were determined in order to determine and to identifymore » the source of the water in the Mesa geothermal system. (JGB)« less

NIST/ISAC standardization study: variability in assignment of intensity values to fluorescence standard beads and in cross calibration of standard beads to hard dyed beads.

PubMed

Hoffman, Robert A; Wang, Lili; Bigos, Martin; Nolan, John P

2012-09-01

Results from a standardization study cosponsored by the International Society for Advancement of Cytometry (ISAC) and the US National Institute of Standards and Technology (NIST) are reported. The study evaluated the variability of assigning intensity values to fluorophore standard beads by bead manufacturers and the variability of cross calibrating the standard beads to stained polymer beads (hard-dyed beads) using different flow cytometers. Hard dyed beads are generally not spectrally matched to the fluorophores used to stain cells, and spectral response varies among flow cytometers. Thus if hard dyed beads are used as fluorescence calibrators, one expects calibration for specific fluorophores (e.g., FITC or PE) to vary among different instruments. Using standard beads surface-stained with specific fluorophores (FITC, PE, APC, and Pacific Blue™), the study compared the measured intensity of fluorophore standard beads to that of hard dyed beads through cross calibration on 133 different flow cytometers. Using robust CV as a measure of variability, the variation of cross calibrated values was typically 20% or more for a particular hard dyed bead in a specific detection channel. The variation across different instrument models was often greater than the variation within a particular instrument model. As a separate part of the study, NIST and four bead manufacturers used a NIST supplied protocol and calibrated fluorophore solution standards to assign intensity values to the fluorophore beads. Values assigned to the reference beads by different groups varied by orders of magnitude in most cases, reflecting differences in instrumentation used to perform the calibration. The study concluded that the use of any spectrally unmatched hard dyed bead as a general fluorescence calibrator must be verified and characterized for every particular instrument model. Close interaction between bead manufacturers and NIST is recommended to have reliable and uniformly assigned fluorescence standard beads. Copyright © 2012 International Society for Advancement of Cytometry.

Influence of Immobilized Biomolecules on Magnetic Bead Plug Formation and Retention in Capillary Electrophoresis

PubMed Central

Henken, Rachel L.; Chantiwas, Rattikan; Gilman, S. Douglass

2012-01-01

Significant changes in the formation and retention of magnetic bead plugs in a capillary during electrophoresis were studied, and it was demonstrated that these effects were due to the type of biological molecule immobilized on the surface of these beads. Three biological molecules, an antibody, an oligonucleotide and alkaline phosphatase, were attached to otherwise identical streptavidin-coated magnetic beads through biotin-avidin binding in order to isolate differences in bead immobilization in a magnetic field resulting from the type of biological molecule immobilized on the bead surface. Alkaline phosphatase also was attached to the magnetic beads using epoxy groups on the bead surfaces (instead of avidin-biotin binding) to study the impact of immobilization chemistry. The formation and retention of magnetic bead plugs were studied quantitatively using light scattering detection of magnetic particles eluting from the bead plugs and qualitatively using microscopy. Both the type of biomolecule immobilized on the magnetic bead surface and the chemistry used to link the biomolecule to the magnetic bead impacted the formation and retention of the bead plugs. PMID:22437880

Nanoengineered analytical immobilized metal affinity chromatography stationary phase by atom transfer radical polymerization: Separation of synthetic prion peptides

PubMed Central

McCarthy, P.; Chattopadhyay, M.; Millhauser, G.L.; Tsarevsky, N.V.; Bombalski, L.; Matyjaszewski, K.; Shimmin, D.; Avdalovic, N.; Pohl, C.

2010-01-01

Atom transfer radical polymerization (ATRP) was employed to create isolated, metal-containing nanoparticles on the surface of non-porous polymeric beads with the goal of developing a new immobilized metal affnity chromatography (IMAC) stationary phase for separating prion peptides and proteins. Transmission electron microscopy was used to visualize nanoparticles on the substrate surface. Individual ferritin molecules were also visualized as ferritin–nanoparticle complexes. The column's resolving power was tested by synthesizing peptide analogs to the copper binding region of prion protein and injecting mixtures of these analogs onto the column. As expected, the column was capable of separating prion-related peptides differing in number of octapeptide repeat units (PHGGGWGQ), (PHGGGWGQ)2, and (PHGGGWGQ)4. Unexpectedly, the column could also resolve peptides containing the same number of repeats but differing only in the presence of a hydrophilic tail, Q → A substitution, or amide nitrogen methylation. PMID:17481564

Direct comparison of linear and macrocyclic compound libraries as a source of protein ligands.

PubMed

Gao, Yu; Kodadek, Thomas

2015-03-09

There has been much discussion of the potential desirability of macrocyclic molecules for the development of tool compounds and drug leads. But there is little experimental data comparing otherwise equivalent macrocyclic and linear compound libraries as a source of protein ligands. In this Letter, we probe this point in the context of peptoid libraries. Bead-displayed libraries of macrocyclic and linear peptoids containing four variable positions and 0-2 fixed residues, to vary the ring size, were screened against streptavidin and the affinity of every hit for the target was measured. The data show that macrocyclization is advantageous, but only when the ring contains 17 atoms, not 20 or 23 atoms. This technology will be useful for conducting direct comparisons between many different types of chemical libraries to determine their relative utility as a source of protein ligands.

Solvated dissipative electro-elastic network model of hydrated proteins

NASA Astrophysics Data System (ADS)

Martin, Daniel

2013-03-01

Elastic network models coarse grain proteins into a network of residue beads connected by springs. We add dissipative dynamics to this mechanical system by applying overdamped Langevin equations of motion to normal-mode vibrations of the network. In addition, the network is made heterogeneous and softened at the protein surface by accounting for hydration of the ionized residues. Solvation changes the network Hessian in two ways. Diagonal solvation terms soften the spring constants and off-diagonal dipole-dipole terms correlate displacements of the ionized residues. The model is used to formulate the response functions of the electrostatic potential and electric field appearing in theories of redox reactions and spectroscopy. We also formulate the dielectric response of the protein and find that solvation of the surface ionized residues leads to a slow relaxation peak in the dielectric loss spectrum, about two orders of magnitude slower than the main peak of protein relaxation. Finally, the solvated network is used to formulate the allosteric response of the protein to ion binding. The global thermodynamics of ion binding is not strongly affected by the network solvation, but it dramatically enhances conformational changes in response to placing a charge at the a the active site.

Solvated dissipative electro-elastic network model of hydrated proteins

NASA Astrophysics Data System (ADS)

Martin, Daniel R.; Matyushov, Dmitry V.

2012-10-01

Elastic network models coarse grain proteins into a network of residue beads connected by springs. We add dissipative dynamics to this mechanical system by applying overdamped Langevin equations of motion to normal-mode vibrations of the network. In addition, the network is made heterogeneous and softened at the protein surface by accounting for hydration of the ionized residues. Solvation changes the network Hessian in two ways. Diagonal solvation terms soften the spring constants and off-diagonal dipole-dipole terms correlate displacements of the ionized residues. The model is used to formulate the response functions of the electrostatic potential and electric field appearing in theories of redox reactions and spectroscopy. We also formulate the dielectric response of the protein and find that solvation of the surface ionized residues leads to a slow relaxation peak in the dielectric loss spectrum, about two orders of magnitude slower than the main peak of protein relaxation. Finally, the solvated network is used to formulate the allosteric response of the protein to ion binding. The global thermodynamics of ion binding is not strongly affected by the network solvation, but it dramatically enhances conformational changes in response to placing a charge at the active site of the protein.

NOVA[R] Spring 2002 Teacher's Guide.

ERIC Educational Resources Information Center

Armstrong, Peter; Ransick, Kristi; Rosene, Dale; Sammons, James

The guide presents lesson plans from "NOVA" which targets middle school and junior high school students and meet the National Science Education Standards. Lessons include: (1) "Neanderthals on Trial"; (2) "Fireworks"; (3) "Secrets, Lies and Atomic Spies"; (4) "Bioterror"; (5) "The Missing…

Regular oscillations and random motion of glass microspheres levitated by a single optical beam in air

DOE PAGES

Moore, Jeremy; Martin, Leopoldo L.; Maayani, Shai; ...

2016-02-03

We experimentally reporton optical binding of many glass particles in air that levitate in a single optical beam. A diversity of particle sizes and shapes interact at long range in a single Gaussian beam. Our system dynamics span from oscillatory to random and dimensionality ranges from 1 to 3D. In conclusion, the low loss for the center of mass motion of the beads could allow this system to serve as a standard many body testbed, similar to what is done today with atoms, but at the mesoscopic scale.

The time variation of atomic oxygen emission around Io during a volcanic event observed with Hisaki/EXCEED

NASA Astrophysics Data System (ADS)

Koga, Ryoichi; Tsuchiya, Fuminori; Kagitani, Masato; Sakanoi, Takeshi; Yoneda, Mizuki; Yoshioka, Kazuo; Kimura, Tomoki; Murakami, Go; Yamazaki, Atsushi; Yoshikawa, Ichiro; Smith, H. Todd

2018-01-01

Io has an atmosphere produced by volcanism and sublimation of frosts deposited around active volcanoes. However, the time variation of atomic oxygen escaping Io's atmosphere is not well known. In this paper, we show a significant increase in atomic oxygen around Io during a volcanic event. Brightening of Io's extended sodium nebula was observed in the spring of 2015. We used the Hisaki satellite to investigate the time variation of atomic oxygen emission around Io during the same period. This investigation reveals that the duration of atomic oxygen brightness increases from a volcanically quiet level to a maximum level during the same approximate time period of 30 days as the observed sodium brightness. On the other hand, the recovery of the atomic oxygen brightness from the maximum to the quiet level (60 days) was longer than that of the sodium nebula decreasing (40 days). Additionally, a dawn-dusk asymmetry of the atomic oxygen emission is observed.

A highly efficient bead extraction technique with low bead number for digital microfluidic immunoassay

PubMed Central

Tsai, Po-Yen; Lee, I-Chin; Hsu, Hsin-Yun; Huang, Hong-Yuan; Fan, Shih-Kang; Liu, Cheng-Hsien

2016-01-01

Here, we describe a technique to manipulate a low number of beads to achieve high washing efficiency with zero bead loss in the washing process of a digital microfluidic (DMF) immunoassay. Previously, two magnetic bead extraction methods were reported in the DMF platform: (1) single-side electrowetting method and (2) double-side electrowetting method. The first approach could provide high washing efficiency, but it required a large number of beads. The second approach could reduce the required number of beads, but it was inefficient where multiple washes were required. More importantly, bead loss during the washing process was unavoidable in both methods. Here, an improved double-side electrowetting method is proposed for bead extraction by utilizing a series of unequal electrodes. It is shown that, with proper electrode size ratio, only one wash step is required to achieve 98% washing rate without any bead loss at bead number less than 100 in a droplet. It allows using only about 25 magnetic beads in DMF immunoassay to increase the number of captured analytes on each bead effectively. In our human soluble tumor necrosis factor receptor I (sTNF-RI) model immunoassay, the experimental results show that, comparing to our previous results without using the proposed bead extraction technique, the immunoassay with low bead number significantly enhances the fluorescence signal to provide a better limit of detection (3.14 pg/ml) with smaller reagent volumes (200 nl) and shorter analysis time (<1 h). This improved bead extraction technique not only can be used in the DMF immunoassay but also has great potential to be used in any other bead-based DMF systems for different applications. PMID:26858807

Seeds used for Bodhi beads in China

PubMed Central

2014-01-01

Background Bodhi beads are a Buddhist prayer item made from seeds. Bodhi beads have a large and emerging market in China, and demand for the beads has particularly increased in Buddhism regions, especially Tibet. Many people have started to focus on and collect Bodhi beads and to develop a Bodhi bead culture. But no research has examined the source plants of Bodhi beads. Therefore, ethnobotanical surveys were conducted in six provinces of China to investigate and document Bodhi bead plants. Reasons for the development of Bodhi bead culture were also discussed. Methods Six provinces of China were selected for market surveys. Information was collected using semi-structured interviews, key informant interviews, and participatory observation with traders, tourists, and local residents. Barkhor Street in Lhasa was focused on during market surveys because it is one of the most popular streets in China. Results Forty-seven species (including 2 varieties) in 19 families and 39 genera represented 52 types of Bodhi beads that were collected. The most popular Bodhi bead plants have a long history and religious significance. Most Bodhi bead plants can be used as medicine or food, and their seeds or fruits are the main elements in these uses. ‘Bodhi seeds’ have been historically used in other countries for making ornaments, especially seeds of the legume family. Many factors helped form Bodhi bead culture in China, but its foundation was in Indian Buddhist culture. Conclusions As one of the earliest adornment materials, seeds played an important role for human production and life. Complex sources of Bodhi beads have different cultural and historical significance. People bought and collected Bodhi beads to reflect their love and admiration for the plants. Thus, the documentation of Bodhi bead plants can serve as a basis for future investigation of Bodhi bead culture and modern Buddhist culture. PMID:24479788

Seeds used for Bodhi beads in China.

PubMed

Li, Feifei; Li, Jianqin; Liu, Bo; Zhuo, Jingxian; Long, Chunlin

2014-01-30

Bodhi beads are a Buddhist prayer item made from seeds. Bodhi beads have a large and emerging market in China, and demand for the beads has particularly increased in Buddhism regions, especially Tibet. Many people have started to focus on and collect Bodhi beads and to develop a Bodhi bead culture. But no research has examined the source plants of Bodhi beads. Therefore, ethnobotanical surveys were conducted in six provinces of China to investigate and document Bodhi bead plants. Reasons for the development of Bodhi bead culture were also discussed. Six provinces of China were selected for market surveys. Information was collected using semi-structured interviews, key informant interviews, and participatory observation with traders, tourists, and local residents. Barkhor Street in Lhasa was focused on during market surveys because it is one of the most popular streets in China. Forty-seven species (including 2 varieties) in 19 families and 39 genera represented 52 types of Bodhi beads that were collected. The most popular Bodhi bead plants have a long history and religious significance. Most Bodhi bead plants can be used as medicine or food, and their seeds or fruits are the main elements in these uses. 'Bodhi seeds' have been historically used in other countries for making ornaments, especially seeds of the legume family. Many factors helped form Bodhi bead culture in China, but its foundation was in Indian Buddhist culture. As one of the earliest adornment materials, seeds played an important role for human production and life. Complex sources of Bodhi beads have different cultural and historical significance. People bought and collected Bodhi beads to reflect their love and admiration for the plants. Thus, the documentation of Bodhi bead plants can serve as a basis for future investigation of Bodhi bead culture and modern Buddhist culture.

Metal-Containing Polystyrene Beads as Standards for Mass Cytometry

PubMed Central

Abdelrahman, Ahmed I.; Ornatsky, Olga; Bandura, Dmitry; Kinach, Robert; Dai, Sheng; Thickett, Stuart C.; Tanner, Scott

2010-01-01

We examine the suitability of metal-containing polystyrene beads for the calibration of a mass cytometer instrument, a single particle analyser based on an inductively coupled plasma ion source and a time of flight mass spectrometer. These metal-containing beads are also verified for their use as internal standards for this instrument. These beads were synthesized by multiple-stage dispersion polymerization with acrylic acid as a comonomer. Acrylic acid acts as a ligand to anchor the metal ions within the interior of the beads. Mass cytometry enabled the bead-by-bead measurement of the metal-content and determination of the metal-content distribution. Beads synthesized by dispersion polymerization that involved three stages were shown to have narrower bead-to-bead variation in their lanthanide content than beads synthesized by 2-stage dispersion polymerization. The beads exhibited insignificant release of their lanthanide content to aqueous solutions of different pHs over a period of six months. When mixed with KG1a or U937 cell lines, metal-containing polymer beads were shown not to affect the mass cytometry response to the metal content of element-tagged antibodies specifically attached to these cells. PMID:20390041

Metal-Containing Polystyrene Beads as Standards for Mass Cytometry.

PubMed

Abdelrahman, Ahmed I; Ornatsky, Olga; Bandura, Dmitry; Baranov, Vladimir; Kinach, Robert; Dai, Sheng; Thickett, Stuart C; Tanner, Scott; Winnik, Mitchell A

2010-01-01

We examine the suitability of metal-containing polystyrene beads for the calibration of a mass cytometer instrument, a single particle analyser based on an inductively coupled plasma ion source and a time of flight mass spectrometer. These metal-containing beads are also verified for their use as internal standards for this instrument. These beads were synthesized by multiple-stage dispersion polymerization with acrylic acid as a comonomer. Acrylic acid acts as a ligand to anchor the metal ions within the interior of the beads. Mass cytometry enabled the bead-by-bead measurement of the metal-content and determination of the metal-content distribution. Beads synthesized by dispersion polymerization that involved three stages were shown to have narrower bead-to-bead variation in their lanthanide content than beads synthesized by 2-stage dispersion polymerization. The beads exhibited insignificant release of their lanthanide content to aqueous solutions of different pHs over a period of six months. When mixed with KG1a or U937 cell lines, metal-containing polymer beads were shown not to affect the mass cytometry response to the metal content of element-tagged antibodies specifically attached to these cells.

Modeling of weld bead geometry for rapid manufacturing by robotic GMAW

NASA Astrophysics Data System (ADS)

Yang, Tao; Xiong, Jun; Chen, Hui; Chen, Yong

2015-03-01

Weld-based rapid prototyping (RP) has shown great promises for fabricating 3D complex parts. During the layered deposition of forming metallic parts with robotic gas metal arc welding, the geometry of a single weld bead has an important influence on surface finish quality, layer thickness and dimensional accuracy of the deposited layer. In order to obtain accurate, predictable and controllable bead geometry, it is essential to understand the relationships between the process variables with the bead geometry (bead width, bead height and ratio of bead width to bead height). This paper highlights an experimental study carried out to develop mathematical models to predict deposited bead geometry through the quadratic general rotary unitized design. The adequacy and significance of the models were verified via the analysis of variance. Complicated cause-effect relationships between the process parameters and the bead geometry were revealed. Results show that the developed models can be applied to predict the desired bead geometry with great accuracy in layered deposition with accordance to the slicing process of RP.

Formulation and characterization of a compacted multiparticulate system for modified release of water-soluble drugs--part 1--acetaminophen.

PubMed

Cantor, Stuart L; Hoag, Stephen W; Augsburger, Larry L

2009-03-01

The aim of this study was to characterize and evaluate a modified release, multiparticulate tablet formulation consisting of placebo beads and drug-loaded beads. Acetaminophen (APAP) bead formulations containing ethylcellulose (EC) from 40-60% and placebo beads containing 30% calcium silicate and prepared using 0-20% alcohol were developed using extrusion-spheronization and studied using a central composite experimental design. Particle size and true density of beads were measured. Segregation testing was performed using the novel ASTM D6940-04 method on a 50:50 blend of uncoated APAP beads (60%EC) : calcium silicate placebo beads (10% alcohol). Tablets were prepared using an instrumented Stokes-B2 rotary tablet press and evaluated for crushing strength and dissolution rate. Compared with drug beads (60%EC), placebo beads (10% alcohol) were smaller but had higher true densities: 864.8 mum and 1.27 g/cm(3), and 787.1 mum and 1.73 g/cm(3), respectively. Segregation testing revealed that there was approximately a 20% difference in drug content (as measured by the coefficient of variation) between initial and final blend samples. Although calcium silicate-based placebo beads were shown to be ineffective cushioning agents in blends with Surelease(R)-coated APAP beads, they were found to be very compactibile when used alone and gave tablet crushing strength values between 14 and 17 kP. The EC in the APAP bead matrix minimally suppressed the drug release from uncoated beads (t(100%) = 2 h). However, while tablets containing placebo beads reformulated with glycerol monostearate (GMS) showed a slower release rate (t(60%)= 5 h) compared with calcium silicate-based placebos, some coating damage ( approximately 30%) still occurred on compression as release was faster than coated APAP beads alone. While tablets containing coated drug beads can be produced with practical crushing strengths (>8 kP) and low compression pressures (10-35 MPa), dissolution studies revealed that calcium silicate-based placebos are ineffective as cushioning agents. Blend segregation was likely observed due to the particle size and the density differences between APAP beads and calcium silicate-based placebo beads; placebo bead percolation can perhaps be minimized by increasing their size during the extrusion-spheronization process. The GMS- based placebos offer greater promise as cushioning agents for compacted, coated drug beads; however, this requires an optimized compression pressure range and drug bead : placebo bead ratio (i.e., 50:50).

Deterministic bead-in-droplet ejection utilizing an integrated plug-in bead dispenser for single bead–based applications

PubMed Central

Kim, Hojin; Choi, In Ho; Lee, Sanghyun; Won, Dong-Joon; Oh, Yong Suk; Kwon, Donghoon; Sung, Hyung Jin; Jeon, Sangmin; Kim, Joonwon

2017-01-01

This paper presents a deterministic bead-in-droplet ejection (BIDE) technique that regulates the precise distribution of microbeads in an ejected droplet. The deterministic BIDE was realized through the effective integration of a microfluidic single-particle handling technique with a liquid dispensing system. The integrated bead dispenser facilitates the transfer of the desired number of beads into a dispensing volume and the on-demand ejection of bead-encapsulated droplets. Single bead–encapsulated droplets were ejected every 3 s without any failure. Multiple-bead dispensing with deterministic control of the number of beads was demonstrated to emphasize the originality and quality of the proposed dispensing technique. The dispenser was mounted using a plug-socket type connection, and the dispensing process was completely automated using a programmed sequence without any microscopic observation. To demonstrate a potential application of the technique, bead-based streptavidin–biotin binding assay in an evaporating droplet was conducted using ultralow numbers of beads. The results evidenced the number of beads in the droplet crucially influences the reliability of the assay. Therefore, the proposed deterministic bead-in-droplet technology can be utilized to deliver desired beads onto a reaction site, particularly to reliably and efficiently enrich and detect target biomolecules. PMID:28393911

Microscopic Examination of Chitosan Polyphosphate Beads with Entrapped Spores of the Biocontrol Agent, Streptomyces melanosporofaciens EF-76

NASA Astrophysics Data System (ADS)

Jobin, Guy; Grondin, Gilles; Couture, Geneviève; Beaulieu, Carole

2005-04-01

Spores of the biocontrol agent, Streptomyces melanosporofaciens EF-76, were entrapped by complex coacervation in beads composed of a macromolecular complex (MC) of chitosan and polyphosphate. A proportion of spores entrapped in beads survived the entrapment procedure as shown by treating spores from chitosan beads with a dye allowing the differentiation of live and dead cells. The spore-loaded chitosan beads could be digested by a chitosanase, suggesting that, once introduced in soil, the beads would be degraded to release the biocontrol agent. Spore-loaded beads were examined by optical and scanning electron microscopy because the release of the biological agent depends on the spore distribution in the chitosan beads. The microscopic examination revealed that the beads had a porous surface and contained a network of inner microfibrils. Spores were entrapped in both the chitosan microfibrils and the bead lacuna.

DC bead: in vitro characterization of a drug-delivery device for transarterial chemoembolization.

PubMed

Lewis, Andrew L; Gonzalez, M Victoria; Lloyd, Andrew W; Hall, Brenda; Tang, Yiqing; Willis, Sean L; Leppard, Simon W; Wolfenden, Laura C; Palmer, Rosemary R; Stratford, Peter W

2006-02-01

The purpose of this investigation is to present the in vitro characterization and detailed drug-loading procedure for DC Bead, a microsphere product that can be loaded with chemotherapeutic agents for embolization. DC Bead is an embolic microsphere product that is capable of being loaded with anthracycline drugs such as doxorubicin just before administration in a transarterial chemoembolization (TACE) procedure. Beads can be loaded from solutions prepared from doxorubicin powder or the doxorubicin HCl formulation. In this evaluation, bead sizes were measured by optical microscopy with video imaging. Gravimetric analysis demonstrated the effect of drug loading on bead water content, and its consequent impact on bead compressibility was determined. The subsequent deliverability of the beads was assessed by mixing the beads with contrast medium and saline solution and passing the beads through an appropriately sized microcatheter. A T-cell apparatus was used to monitor the in vitro elution of the drug from the beads over a period of 24 hours in various elution media. DC Bead spheres could be easily loaded with doxorubicin to a recommended level of 25 mg/mL of hydrated beads by immersion of the beads in the drug solution for 10-120 minutes depending on microsphere size. Other commercial embolic microspheres were shown not to load doxorubicin to the same extent or release it in the same fashion and were considered unsuitable for local drug delivery. Maximum theoretic capacity for DC Bead was approximately 45 mg/mL. Increase in doxorubicin loading resulted in a concomitant decrease in water content and consequential increase in bead resistance to compression force. Drug loading also resulted in a decrease in the average size of the beads, which was dependent on bead size and drug dose. This did not impact bead delivery at any drug loading level to a maximum of 37.5 mg/mL. Beads 100-700 microm in size could be delivered through 2.7-F microcatheters, whereas the 700-900-microm range required 3-F catheters. Modeling of the kinetics of drug elution from the beads in vitro at a loading dose of 25 mg/mL yielded calculated half-lives of 150 hours for the 100-300-microm range to a maximum of 1,730 hours for the 700-900-microm size range, which was dependent on the ionic strength of the elution medium. For comparison, there was a rapid loss of drug from an unstable Lipiodol emulsion with a half-life of approximately 1 hour. DC Bead can be loaded with doxorubicin to provide an accurate dosage of drug per unit volume of beads. Drug elution is dependent on ion exchange with the surrounding environment and is controlled and sustained, unlike the rapid separation of the drug from Lipiodol. Drug loading has no impact on the handling and deliverability of the beads, making them suitable for superselective TACE.

Recent advances in the UltraScan SOlution MOdeller (US-SOMO) hydrodynamic and small-angle scattering data analysis and simulation suite.

PubMed

Brookes, Emre; Rocco, Mattia

2018-03-28

The UltraScan SOlution MOdeller (US-SOMO) is a comprehensive, public domain, open-source suite of computer programs centred on hydrodynamic modelling and small-angle scattering (SAS) data analysis and simulation. We describe here the advances that have been implemented since its last official release (#3087, 2017), which are available from release #3141 for Windows, Linux and Mac operating systems. A major effort has been the transition from the legacy Qt3 cross platform software development and user interface library to the modern Qt5 release. Apart from improved graphical support, this has allowed the direct implementation of the newest, almost two-orders of magnitude faster version of the ZENO hydrodynamic computation algorithm for all operating systems. Coupled with the SoMo-generated bead models with overlaps, ZENO provides the most accurate translational friction computations from atomic-level structures available (Rocco and Byron Eur Biophys J 44:417-431, 2015a), with computational times comparable with or faster than those of other methods. In addition, it has allowed us to introduce the direct representation of each atom in a structure as a (hydrated) bead, opening interesting new modelling possibilities. In the small-angle scattering (SAS) part of the suite, an indirect Fourier transform Bayesian algorithm has been implemented for the computation of the pairwise distance distribution function from SAS data. Finally, the SAS HPLC module, recently upgraded with improved baseline correction and Gaussian decomposition of not baseline-resolved peaks and with advanced statistical evaluation tools (Brookes et al. J Appl Cryst 49:1827-1841, 2016), now allows automatic top-peak frame selection and averaging.

First Atomic Force Microscope Image from Mars

NASA Technical Reports Server (NTRS)

2008-01-01

This calibration image presents three-dimensional data from the atomic force microscope on NASA's Phoenix Mars Lander, showing surface details of a substrate on the microscope station's sample wheel. It will be used as an aid for interpreting later images that will show shapes of minuscule Martian soil particles.

The area imaged by the microscope is 40 microns by 40 microns, small enough to fit on an eyelash. The grooves in this substrate are 14 microns (0.00055 inch) apart, from center to center. The vertical dimension is exaggerated in the image to make surface details more visible. The grooves are 300 nanometers (0.00001 inch) deep.

This is the first atomic force microscope image recorded on another planet. It was taken on July 9, 2008, during the 44th Martian day, or sol, of the Phoenix mission since landing.

Phoenix's Swiss-made atomic force microscope builds an image of the surface shape of a particle by sensing it with a sharp tip at the end of a spring, all microfabricated out of a silicon wafer. A strain gauge records how far the spring flexes to follow the contour of the surface. It can provide details of soil-particle shapes smaller than one-hundredth the width of a human hair. This is about 20 times smaller than what can be resolved with Phoenix's optical microscope, which has provided much higher-magnification imaging than anything seen on Mars previously. Both microscopes are part of Phoenix's Microscopy, Electrochemistry and Conductivity Analyzer.

A Molecular Dynamic Modeling of Hemoglobin-Hemoglobin Interactions

NASA Astrophysics Data System (ADS)

Wu, Tao; Yang, Ye; Sheldon Wang, X.; Cohen, Barry; Ge, Hongya

2010-05-01

In this paper, we present a study of hemoglobin-hemoglobin interaction with model reduction methods. We begin with a simple spring-mass system with given parameters (mass and stiffness). With this known system, we compare the mode superposition method with Singular Value Decomposition (SVD) based Principal Component Analysis (PCA). Through PCA we are able to recover the principal direction of this system, namely the model direction. This model direction will be matched with the eigenvector derived from mode superposition analysis. The same technique will be implemented in a much more complicated hemoglobin-hemoglobin molecule interaction model, in which thousands of atoms in hemoglobin molecules are coupled with tens of thousands of T3 water molecule models. In this model, complex inter-atomic and inter-molecular potentials are replaced by nonlinear springs. We employ the same method to get the most significant modes and their frequencies of this complex dynamical system. More complex physical phenomena can then be further studied by these coarse grained models.

Dual stimuli-responsive smart beads that allow "on-off" manipulation of cancer cells.

PubMed

Kim, Young-Jin; Kim, Soo Hyeon; Fujii, Teruo; Matsunaga, Yukiko T

2016-06-24

Temperature- and electric field-responsive polymer-conjugated polystyrene beads, termed smart beads, are designed to isolate cancer cells. In smart beads, the reversible "on-off" antigen-antibody reaction and dielectrophoresis force on an electrode are accomplished to realize "on-off" remote manipulation of smart beads and cancer cells. Both the zeta-potential and the hydrodynamic diameter of the smart beads are sensitive to temperature, allowing "on-off" reversible capture and release of cancer cells. Cancer cell-captured smart beads are then localized on electrodes by applying an electrical signal.

An Attempt to Shorten Loading Time of Epirubicin into DC Beads® Using Vibration and a Sieve.

PubMed

Sonoda, Akinaga; Nitta, Norihisa; Yamamoto, Takefumi; Tomozawa, Yuki; Ohta, Shinichi; Watanabe, Shobu; Murata, Kiyoshi

2017-04-01

We investigated the possibility of shortening the time required for loading epirubicin into calibrated polyvinyl alcohol-based hydrogel beads (DC Beads ® ) to be used for transarterial chemoembolization. After separating the beads suspended in phosphate-buffered saline (PBS) solution by the use of a sieve (clearance 75 µm), epirubicin hydrochloride (EH) was loaded for 20, 30, or 60 s under vibration into DC beads. The EH loading rate into conventionally prepared (control) beads, i.e., beads loaded for 30 min without vibration, and vibration-loaded beads were calculated from the residual EH concentration in the bead-depleted EH solution. The amount of EH eluted from conventionally and vibration-loaded samples into a PBS solution (pH 7.0) was measured at 15 and 30 min and 1, 2, 6, 12, and 24 h. We also recorded the inhibitory effect of the PBS solution on the loading time. Using frozen sections, the EH load in the beads was evaluated visually under a fluorescence microscope. Spectrophotometry (495 nm) showed that the loading rate was 98.98 ± 0.34, 99.02 ± 0.32, and 99.50 ± 0.11 % with 20-, 30-, and 60-s vibration, respectively. The eluted rate was statistically similar between vibration- and statically loaded (control) beads. The PBS solution hampered EH loading into the beads. Visually, the distribution of EH in conventionally and vibration-loaded DC beads was similar. The use of vibration and the removal of PBS solution when epirubicin hydrochloride was loaded into DC beads dramatically shortened the loading time of epirubicin hydrochloride into DC beads.

Coupled thermomechanical behavior of graphene using the spring-based finite element approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Georgantzinos, S. K., E-mail: sgeor@mech.upatras.gr; Anifantis, N. K., E-mail: nanif@mech.upatras.gr; Giannopoulos, G. I., E-mail: ggiannopoulos@teiwest.gr

The prediction of the thermomechanical behavior of graphene using a new coupled thermomechanical spring-based finite element approach is the aim of this work. Graphene sheets are modeled in nanoscale according to their atomistic structure. Based on molecular theory, the potential energy is defined as a function of temperature, describing the interatomic interactions in different temperature environments. The force field is approached by suitable straight spring finite elements. Springs simulate the interatomic interactions and interconnect nodes located at the atomic positions. Their stiffness matrix is expressed as a function of temperature. By using appropriate boundary conditions, various different graphene configurations aremore » analyzed and their thermo-mechanical response is approached using conventional finite element procedures. A complete parametric study with respect to the geometric characteristics of graphene is performed, and the temperature dependency of the elastic material properties is finally predicted. Comparisons with available published works found in the literature demonstrate the accuracy of the proposed method.« less

Rare Earth Adsorption and Desorption with PEGDA Beads

DOE Data Explorer

Jiao, Yongqin; Brewer, Aaron; Park, Dan

2017-03-01

We synthesized PEGDA polymer hydrogel beads for cell embedding and compared REE biosorption with these beads via a gravity-driven flow through setup. One way to set up a flow through system is by cell encapsulation into polymer beads with a column setup similar to that used in the chromatography industry. To achieve this, we tested PEGDA for cell encapsulation, and tested REE biosorption under both batch mode and a follow through setup based on gravity . For making the cell embedded polymer beads, we used a fluidic device by which homogenous spherical particles of 0.5 to1 mm in diameter were synthesized. The beads are made relatively quickly, and the size of the beads can be controlled. PEGDA beads were polymerized by UV. Tb adsorption experiment was performed with beads with or without cells embedded.

Scaling, clustering and avalanches for steel beads in an external magnetic field

NASA Astrophysics Data System (ADS)

Marquinez, Alyse; Thvedt, Ingrid; Lehman, S. Y.; Jacobs, D. T.

2011-03-01

We investigated avalanches using uniform 3mm steel spheres (``beads'') dropped onto a conical bead pile within a uniform magnetic field. The bead pile is built by pouring beads onto a circular base where the bottom layer of beads had been glued randomly. Beads are then individually dropped from a fixed height after which the pile is massed. This process is repeated for thousands of bead drops. By measuring the number of avalanches of a given size that occurred during the experiment, the resulting avalanche size distribution was compared to a power law description as predicted by self-organized criticality. As the magnetic field intensity increased, the beads clustered to give a larger angle of repose and we measured the change in the avalanche size distribution. The moments of the distribution give a sensitive test of mean-field theory as the universality class for these bead piles. We acknowledge support from Research Corporation and NSF-REU grant DMR 0649112.

Preparation of ionic-crosslinked chitosan-based gel beads and effect of reaction conditions on drug release behaviors.

PubMed

Chen, Shilan; Liu, Mingzhu; Jin, Shuping; Wang, Bin

2008-02-12

Drug-loaded chitosan (CS) beads were prepared under simple and mild condition using trisodium citrate as ionic crosslinker. The beads were further coated with poly(methacrylic acid) (PMAA) by dipping the beads in PMAA aqueous solution. The surface and cross-section morphology of these beads were observed by scanning electron microscopy and the observation showed that the coating beads had core-shell structure. In vitro release of model drug from these beads obtained under different reaction conditions was investigated in buffer medium (pH 1.8). The results showed that the rapid drug release was restrained by PMAA coating and the optimum conditions for preparing CS-based drug-loaded beads were decided through the effect of reaction conditions on the drug release behaviors. In addition, the drug release mechanism of CS-based drug-loaded beads was analyzed by Peppa's potential equation. According to this study, the ionic-crosslinked CS beads coated by PMAA could serve as suitable candidate for drug site-specific carrier in stomach.

Charging of multiple interacting particles by contact electrification.

PubMed

Soh, Siowling; Liu, Helena; Cademartiri, Rebecca; Yoon, Hyo Jae; Whitesides, George M

2014-09-24

Many processes involve the movement of a disordered collection of small particles (e.g., powders, grain, dust, and granular foods). These particles move chaotically, interact randomly among themselves, and gain electrical charge by contact electrification. Understanding the mechanisms of contact electrification of multiple interacting particles has been challenging, in part due to the complex movement and interactions of the particles. To examine the processes contributing to contact electrification at the level of single particles, a system was constructed in which an array of millimeter-sized polymeric beads of different materials were agitated on a dish. The dish was filled almost completely with beads, such that beads did not exchange positions. At the same time, during agitation, there was sufficient space for collisions with neighboring beads. The charge of the beads was measured individually after agitation. Results of systematic variations in the organization and composition of the interacting beads showed that three mechanisms determined the steady-state charge of the beads: (i) contact electrification (charging of beads of different materials), (ii) contact de-electrification (discharging of beads of the same charge polarity to the atmosphere), and (iii) a long-range influence across beads not in contact with one another (occurring, plausibly, by diffusion of charge from a bead with a higher charge to a bead with a lower charge of the same polarity).

Integration of Magnetic Bead-Based Cell Selection into Complex Isolations

PubMed Central

2018-01-01

Magnetic bead-based analyte capture has emerged as a ubiquitous method in cell isolation, enabling the highly specific capture of target populations through simple magnetic manipulation. To date, no “one-size fits all” magnetic bead has been widely adopted leading to an overwhelming number of commercial beads. Ultimately, the ideal bead is one that not only facilitates cell isolation but also proves compatible with the widest range of downstream applications and analytic endpoints. Despite the diverse offering of sizes, coatings, and conjugation chemistries, few studies exist to benchmark the performance characteristics of different commercially available beads; importantly, these bead characteristics ultimately determine the ability of a bead to integrate into the user’s assay. In this report, we evaluate bead-based cell isolation considerations, approaches, and results across a subset of commercially available magnetic beads (Dynabeads FlowComps, Dynabeads CELLection, GE Healthcare Sera-Mag SpeedBeads streptavidin-blocked magnetic particles, Dynabeads M-270s, Dynabeads M-280s) to compare and contrast both capture-specific traits (i.e., purity, capture efficacy, and contaminant isolations) and endpoint compatibility (i.e., protein localization, fluorescence imaging, and nucleic acid extraction). We identify specific advantages and contexts of use in which distinct bead products may facilitate experimental goals and integrate into downstream applications. PMID:29732449

Controlling the size of alginate gel beads by use of a high electrostatic potential.

PubMed

Klokk, T I; Melvik, J E

2002-01-01

The effect of several parameters on the size of alginate beads produced by use of an electrostatic potential bead generator was examined. Parameters studied included needle diameter, electrostatic potential, alginate solution flow rate, gelling ion concentration and alginate concentration and viscosity, as well as alginate composition. Bead size was found to decrease with increasing electrostatic potential, but only down to a certain level. Minimum bead size was reached at between 2-4 kV/cm for the needles tested. The smallest alginate beads produced (using a needle with inner diameter 0.18 mm) had a mean diameter of approximately 300 microm. Bead size was also found to be dependent upon the flow rate of the fed alginate solution. Increasing the gelling ion concentration resulted in a moderate decrease in bead size. The concentration and viscosity of the alginate solution also had an effect on bead size as demonstrated by an increased bead diameter when the concentration or viscosity was increased. This effect was primarily an effect of the viscosity properties of the solution, which led to changes in the rate of droplet formation in the bead generator. Lowering the flow rate of the alginate solution could partly compensate for the increase in bead size with increased viscosity. For a constant droplet size, alginates with a low G block content (F(GG) approximately 0.20) resulted in approximately 30% smaller beads than alginates with a high G block content (F(GG) approximately 0.60). This is explained as a result of differences in the shrinking properties of the beads.

Elution of Clindamycin and Enrofloxacin From Calcium Sulfate Hemihydrate Beads In Vitro.

PubMed

Phillips, Heidi; Boothe, Dawn M; Bennett, R Avery

2015-11-01

To compare the in vitro elution characteristics of clindamycin and enrofloxacin from calcium sulfate hemihydrate beads containing a single antibiotic, both antibiotics, and each antibiotic incubated in the same eluent well. Experimental in vitro study. Calcium sulfate hemihydrate beads were formed by mixing with clindamycin and/or enrofloxacin to create 4 study groups: (1) 160 mg clindamycin/10 beads; (2) 160 mg enrofloxacin/10 beads; (3) 160 mg clindamycin + 160 mg enrofloxacin/10 beads; and (4) 160 mg clindamycin/5 beads and 160 mg enrofloxacin/5 beads. Chains of beads were formed in triplicate and placed in 5 mL phosphate buffered saline (PBS; pH 7.4 and room temperature) with constant agitation. Antibiotic-conditioned PBS was sampled at 14 time points from 1 hour to 30 days. Clindamycin and enrofloxacin concentrations in PBS were determined using high-performance liquid chromatography. Eluent concentrations from clindamycin-impregnated beads failed to remain sufficiently above minimum inhibitory concentration (MIC) for common infecting bacteria over the study period. Enrofloxacin eluent concentrations remained sufficiently above MIC for common wound pathogens of dogs and cats and demonstrated an atypical biphasic release pattern. No significant differences in elution occurred as a result of copolymerization of the antibiotics into a single bead or from individual beads co-eluting in the same eluent well. Clindamycin-impregnated beads cannot be recommended for treatment of infection at the studied doses; however, use of enrofloxacin-impregnated beads may be justified when susceptible bacteria are cultured. © Copyright 2015 by The American College of Veterinary Surgeons.

Digital microfluidics-enabled single-molecule detection by printing and sealing single magnetic beads in femtoliter droplets.

PubMed

Witters, Daan; Knez, Karel; Ceyssens, Frederik; Puers, Robert; Lammertyn, Jeroen

2013-06-07

Digital microfluidics is introduced as a novel platform with unique advantages for performing single-molecule detection. We demonstrate how superparamagnetic beads, used for capturing single protein molecules, can be printed with unprecedentedly high loading efficiency and single bead resolution on an electrowetting-on-dielectric-based digital microfluidic chip by micropatterning the Teflon-AF surface of the device. By transporting droplets containing suspended superparamagnetic beads over a hydrophilic-in-hydrophobic micropatterned Teflon-AF surface, single beads are trapped inside the hydrophilic microwells due to their selective wettability and tailored dimensions. Digital microfluidics presents the following advantages for printing and sealing magnetic beads for single-molecule detection: (i) droplets containing suspended beads can be transported back and forth over the array of hydrophilic microwells to obtain high loading efficiencies of microwells with single beads, (ii) the use of hydrophilic-in-hydrophobic patterns permits the use of a magnet to speed up the bead transfer process to the wells, while the receding droplet meniscus removes excess beads off the chip surface and thereby shortens the bead patterning time, and (iii) reagents can be transported over the printed beads multiple times, while capillary forces and a magnet hold the printed beads in place. High loading efficiencies (98% with a CV of 0.9%) of single beads in microwells were obtained by transporting droplets of suspended beads over the array 10 times in less than 1 min, which is much higher than previously reported methods (40-60%), while the total surface area needed for performing single-molecule detection can be decreased. The performance of the device was demonstrated by fluorescent detection of the presence of the biotinylated enzyme β-galactosidase on streptavidin-coated beads with a linear dynamic range of 4 orders of magnitude ranging from 10 aM to 90 fM.

Functionalisation of Detonation Nanodiamond for Monodispersed, Soluble DNA-Nanodiamond Conjugates Using Mixed Silane Bead-Assisted Sonication Disintegration

DOE PAGES

Edgington, Robert; Spillane, Katelyn M.; Papageorgiou, George; ...

2018-01-15

Here, nanodiamonds have many attractive properties that make them suitable for a range of biological applications, but their practical use has been limited because nanodiamond conjugates tend to aggregate in solution during or after functionalisation. Here we demonstrate the production of DNA-detonation nanodiamond (DNA-DND) conjugates with high dispersion and solubility using an ultrasonic, mixed-silanization chemistry protocol based on the in situ Bead-Assisted Sonication Disintegration (BASD) silanization method. We use two silanes to achieve these properties: (1) 3-(trihydroxysilyl)propyl methylphosphonate (THPMP); a negatively charged silane that imparts high zeta potential and solubility in solution; and (2) (3-aminopropyl)triethoxysilane (APTES); a commonly used functionalmore » silane that contributes an amino group for subsequent bioconjugation. We target these amino groups for covalent conjugation to thiolated, single-stranded DNA oligomers using the heterobifunctional crosslinker sulfosuccinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate (Sulfo-SMCC). The resulting DNA-DND conjugates are the smallest reported to date, as determined by Dynamic Light Scattering (DLS) and Atomic Force Microscopy (AFM). The functionalisation method we describe is versatile and can be used to produce a wide variety of soluble DND-biomolecule conjugates.« less

Functionalisation of Detonation Nanodiamond for Monodispersed, Soluble DNA-Nanodiamond Conjugates Using Mixed Silane Bead-Assisted Sonication Disintegration.

PubMed

Edgington, Robert; Spillane, Katelyn M; Papageorgiou, George; Wray, William; Ishiwata, Hitoshi; Labarca, Mariana; Leal-Ortiz, Sergio; Reid, Gordon; Webb, Martin; Foord, John; Melosh, Nicholas; Schaefer, Andreas T

2018-01-15

Nanodiamonds have many attractive properties that make them suitable for a range of biological applications, but their practical use has been limited because nanodiamond conjugates tend to aggregate in solution during or after functionalisation. Here we demonstrate the production of DNA-detonation nanodiamond (DNA-DND) conjugates with high dispersion and solubility using an ultrasonic, mixed-silanization chemistry protocol based on the in situ Bead-Assisted Sonication Disintegration (BASD) silanization method. We use two silanes to achieve these properties: (1) 3-(trihydroxysilyl)propyl methylphosphonate (THPMP); a negatively charged silane that imparts high zeta potential and solubility in solution; and (2) (3-aminopropyl)triethoxysilane (APTES); a commonly used functional silane that contributes an amino group for subsequent bioconjugation. We target these amino groups for covalent conjugation to thiolated, single-stranded DNA oligomers using the heterobifunctional crosslinker sulfosuccinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate (Sulfo-SMCC). The resulting DNA-DND conjugates are the smallest reported to date, as determined by Dynamic Light Scattering (DLS) and Atomic Force Microscopy (AFM). The functionalisation method we describe is versatile and can be used to produce a wide variety of soluble DND-biomolecule conjugates.

Direct torsional actuation of microcantilevers using magnetic excitation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gosvami, Nitya Nand; Nalam, Prathima C.; Tam, Qizhan

2014-09-01

Torsional mode dynamic force microscopy can be used for a wide range of studies including mapping lateral contact stiffness, torsional frequency or amplitude modulation imaging, and dynamic friction measurements of various materials. Piezo-actuation of the cantilever is commonly used, but it introduces spurious resonances, limiting the frequency range that can be sampled, and rendering the technique particularly difficult to apply in liquid medium where the cantilever oscillations are significantly damped. Here, we demonstrate a method that enables direct torsional actuation of cantilevers with high uniformity over wide frequency ranges by attaching a micrometer-scale magnetic bead on the back side ofmore » the cantilever. We show that when beads are magnetized along the width of the cantilever, efficient torsional actuation of the cantilevers can be achieved using a magnetic field produced from a solenoid placed underneath the sample. We demonstrate the capability of this technique by imaging atomic steps on graphite surfaces in tapping mode near the first torsional resonance of the cantilever in dodecane. The technique is also applied to map the variations in the lateral contact stiffness on the surface of graphite and polydiacetylene monolayers.« less

Functionalisation of Detonation Nanodiamond for Monodispersed, Soluble DNA-Nanodiamond Conjugates Using Mixed Silane Bead-Assisted Sonication Disintegration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Edgington, Robert; Spillane, Katelyn M.; Papageorgiou, George

Here, nanodiamonds have many attractive properties that make them suitable for a range of biological applications, but their practical use has been limited because nanodiamond conjugates tend to aggregate in solution during or after functionalisation. Here we demonstrate the production of DNA-detonation nanodiamond (DNA-DND) conjugates with high dispersion and solubility using an ultrasonic, mixed-silanization chemistry protocol based on the in situ Bead-Assisted Sonication Disintegration (BASD) silanization method. We use two silanes to achieve these properties: (1) 3-(trihydroxysilyl)propyl methylphosphonate (THPMP); a negatively charged silane that imparts high zeta potential and solubility in solution; and (2) (3-aminopropyl)triethoxysilane (APTES); a commonly used functionalmore » silane that contributes an amino group for subsequent bioconjugation. We target these amino groups for covalent conjugation to thiolated, single-stranded DNA oligomers using the heterobifunctional crosslinker sulfosuccinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate (Sulfo-SMCC). The resulting DNA-DND conjugates are the smallest reported to date, as determined by Dynamic Light Scattering (DLS) and Atomic Force Microscopy (AFM). The functionalisation method we describe is versatile and can be used to produce a wide variety of soluble DND-biomolecule conjugates.« less

Detection of cancerous cervical cells using physical adhesion of fluorescent silica particles and centripetal force.

PubMed

Gaikwad, Ravi M; Dokukin, Maxim E; Iyer, K Swaminathan; Woodworth, Craig D; Volkov, Dmytro O; Sokolov, Igor

2011-04-07

Here we describe a non-traditional method to identify cancerous human cervical epithelial cells in a culture dish based on physical adhesion between silica beads and cells. It is a simple optical fluorescence-based technique which detects the relative difference in the amount of fluorescent silica beads physically adherent to surfaces of cancerous and normal cervical cells. The method utilizes the centripetal force gradient that occurs in a rotating culture dish. Due to the variation in the balance between adhesion and centripetal forces, cancerous and normal cells demonstrate clearly distinctive distributions of the fluorescent particles adherent to the cell surface over the culture dish. The method demonstrates higher adhesion of silica particles to normal cells compared to cancerous cells. The difference in adhesion was initially observed by atomic force microscopy (AFM). The AFM data were used to design the parameters of the rotational dish experiment. The optical method that we describe is much faster and technically simpler than AFM. This work provides proof of the concept that physical interactions can be used to accurately discriminate normal and cancer cells. © The Royal Society of Chemistry 2011

Method of synthesizing bulk transition metal carbide, nitride and phosphide catalysts

DOEpatents

Choi, Jae Soon; Armstrong, Beth L; Schwartz, Viviane

2015-04-21

A method for synthesizing catalyst beads of bulk transmission metal carbides, nitrides and phosphides is provided. The method includes providing an aqueous suspension of transition metal oxide particles in a gel forming base, dropping the suspension into an aqueous solution to form a gel bead matrix, heating the bead to remove the binder, and carburizing, nitriding or phosphiding the bead to form a transition metal carbide, nitride, or phosphide catalyst bead. The method can be tuned for control of porosity, mechanical strength, and dopant content of the beads. The produced catalyst beads are catalytically active, mechanically robust, and suitable for packed-bed reactor applications. The produced catalyst beads are suitable for biomass conversion, petrochemistry, petroleum refining, electrocatalysis, and other applications.

Optimization and Prediction of Angular Distortion and Weldment Characteristics of TIG Square Butt Joints

NASA Astrophysics Data System (ADS)

Narang, H. K.; Mahapatra, M. M.; Jha, P. K.; Biswas, P.

2014-05-01

Autogenous arc welds with minimum upper weld bead depression and lower weld bead bulging are desired as such welds do not require a second welding pass for filling up the upper bead depressions (UBDs) and characterized with minimum angular distortion. The present paper describes optimization and prediction of angular distortion and weldment characteristics such as upper weld bead depression and lower weld bead bulging of TIG-welded structural steel square butt joints. Full factorial design of experiment was utilized for selecting the combinations of welding process parameter to produce the square butts. A mathematical model was developed to establish the relationship between TIG welding process parameters and responses such as upper bead width, lower bead width, UBD, lower bead height (bulging), weld cross-sectional area, and angular distortions. The optimal welding condition to minimize UBD and lower bead bulging of the TIG butt joints was identified.

A Wide-Field Fluorescence Microscope Extension for Ultrafast Screening of One-Bead One-Compound Libraries Using a Spectral Image Subtraction Approach.

PubMed

Heusermann, Wolf; Ludin, Beat; Pham, Nhan T; Auer, Manfred; Weidemann, Thomas; Hintersteiner, Martin

2016-05-09

The increasing involvement of academic institutions and biotech companies in drug discovery calls for cost-effective methods to identify new bioactive molecules. Affinity-based on-bead screening of combinatorial one-bead one-compound libraries combines a split-mix synthesis design with a simple protein binding assay operating directly at the bead matrix. However, one bottleneck for academic scale on-bead screening is the unavailability of a cheap, automated, and robust screening platform that still provides a quantitative signal related to the amount of target protein binding to individual beads for hit bead ranking. Wide-field fluorescence microscopy has long been considered unsuitable due to significant broad spectrum autofluorescence of the library beads in conjunction with low detection sensitivity. Herein, we demonstrate how such a standard microscope equipped with LED-based excitation and a modern CMOS camera can be successfully used for selecting hit beads. We show that the autofluorescence issue can be overcome by an optical image subtraction approach that yields excellent signal-to-noise ratios for the detection of bead-associated target proteins. A polymer capillary attached to a semiautomated bead-picking device allows the operator to efficiently isolate individual hit beads in less than 20 s. The system can be used for ultrafast screening of >200,000 bead-bound compounds in 1.5 h, thereby making high-throughput screening accessible to a wider group within the scientific community.

Effect of Surface Preparation and Gas Flow on Nitrogen Atom Surface Recombination

NASA Technical Reports Server (NTRS)

Prok, George M.

1961-01-01

The effects of surface preparation and gas flow on the recombination of nitrogen atoms at copper and platinum surfaces were determined. Atoms were generated by an electrodeless 2450-megacycle-per-second discharge, and their concentration was measured by gas-phase titration with nitric oxide. Test surfaces were either vacuum-evaporated films or spheres machined from bulk metal and cemented around small glass-bead thermistors. Heat released by recombination was measured as the difference in electrical energy required to maintain a given thermistor temperature with and without a catalytic surface exposed. Recombination coefficients measured at flow velocities of 1120, 1790, 2250, and 3460 centimeters per second and at pressures of 0.42 and 0.59 millimeter of mercury showed that flow conditions had no effect. The results were also independent of atom concentration. A rough indication of the temperature dependence was obtained; it was greater for copper than for platinum. Platinum films deposited on platinum or on glass had the same activity - about 3 percent of the atoms impinging recombined. With copper, however, the glass substrate greatly reduced the percent of atoms recombining over that of a bulk copper substrate where 4 percent of the impinging atoms recombined. This effect could be overcome by depositing a second film on top of the first. Bulk metal samples were subjected to various surface treatments including polishing, degreasing with a chlorinated hydrocarbon, washing with nitric acid, and rinsing with water. Polished, degreased platinum had low activity compared to an evaporated film, but nitric acid treatment made it equivalent. Polished, degreased copper was only slightly less active than a copper film; nitric acid etching decreased the activity still further, probably by preferentially exposing facets of low catalytic efficiency.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sonoda, Akinaga, E-mail: akinagasonoda@yahoo.co.jp; Nitta, Norihisa; Yamamoto, Takefumi

PurposeWe investigated the possibility of shortening the time required for loading epirubicin into calibrated polyvinyl alcohol-based hydrogel beads (DC Beads{sup ®}) to be used for transarterial chemoembolization.MethodAfter separating the beads suspended in phosphate-buffered saline (PBS) solution by the use of a sieve (clearance 75 µm), epirubicin hydrochloride (EH) was loaded for 20, 30, or 60 s under vibration into DC beads. The EH loading rate into conventionally prepared (control) beads, i.e., beads loaded for 30 min without vibration, and vibration-loaded beads were calculated from the residual EH concentration in the bead-depleted EH solution. The amount of EH eluted from conventionally and vibration-loadedmore » samples into a PBS solution (pH 7.0) was measured at 15 and 30 min and 1, 2, 6, 12, and 24 h. We also recorded the inhibitory effect of the PBS solution on the loading time. Using frozen sections, the EH load in the beads was evaluated visually under a fluorescence microscope.ResultsSpectrophotometry (495 nm) showed that the loading rate was 98.98 ± 0.34, 99.02 ± 0.32, and 99.50 ± 0.11 % with 20-, 30-, and 60-s vibration, respectively. The eluted rate was statistically similar between vibration- and statically loaded (control) beads. The PBS solution hampered EH loading into the beads. Visually, the distribution of EH in conventionally and vibration-loaded DC beads was similar.DiscussionThe use of vibration and the removal of PBS solution when epirubicin hydrochloride was loaded into DC beads dramatically shortened the loading time of epirubicin hydrochloride into DC beads.« less

Stimulation of wound healing by positively charged dextran beads depends upon clustering of beads and cells in close proximity to the wound.

PubMed

Tawil, N J; Connors, D; Gies, D; Bennett, S; Gruskin, E; Mustoe, T

1999-01-01

We have previously shown that positively charged dextran (DEAE A25) increases wound breaking strength in linear incisions in rats and nonhuman primates at days 10-14 postwounding. In this article, we examined the cellular responses to different types of charged dextran beads (DEAE A50 and Cytodex-1) in culture studies and in rat incisional wounds. We show that Cytodex 1 and DEAE A50 beads also increased wound breaking strength in a rat linear incisional model. However, the increase was approximately 30-40% less than that observed in wounds treated with DEAE A25 beads. The main distinction between the three types of beads was the presence of bead clusters observed in tissue sections. Wounds treated with DEAE A25 beads formed distinct clusters while both Cytodex 1 and DEAE A50 beads clustered to a lesser extent or failed to cluster at all. We propose that the different types of charged dextran beads improve healing by promoting cell adhesion and encouraging proliferation in close proximity to the wound. We also hypothesize that the 30-40% improvement in wound breaking strength seen with DEAE A25 beads compared to other types of charged dextran beads (DEAE A50 and Cytodex-1) originates from the unique characteristic of DEAE A25 beads in forming cell-bead aggregates adjacent to the wounded area. This clustering, in turn, affects the distribution of cells infiltrating the wounded area (such as macrophages) during the healing process and, as a consequence, alters the distribution of matrix molecules and growth factors secreted by these cells.

Surface adsorption and hopping cause probe-size-dependent microrheology of actin networks

NASA Astrophysics Data System (ADS)

He, Jun; Tang, Jay X.

2011-04-01

A network of filaments formed primarily by the abundant cytoskeletal protein actin gives animal cells their shape and elasticity. The rheological properties of reconstituted actin networks have been studied by tracking micron-sized probe beads embedded within the networks. We investigate how microrheology depends on surface properties of probe particles by varying the stickiness of their surface. For this purpose, we chose carboxylate polystyrene (PS) beads, silica beads, bovine serum albumin (BSA) -coated PS beads, and polyethylene glycol (PEG) -grafted PS beads, which show descending stickiness to actin filaments, characterized by confocal imaging and microrheology. Probe size dependence of microrheology is observed for all four types of beads. For the slippery PEG beads, particle-tracking microrheology detects weaker networks using smaller beads, which tend to diffuse through the network by hopping from one confinement “cage” to another. This trend is reversed for the other three types of beads, for which microrheology measures stiffer networks for smaller beads due to physisorption of nearby filaments to the bead surface. We explain the probe size dependence with two simple models. We also evaluate depletion effect near nonadsorption bead surface using quantitative image analysis and discuss the possible impact of depletion on microrheology. Analysis of these effects is necessary in order to accurately define the actin network rheology both in vitro and in vivo.

An Integrated Microfluidic Processor for DNA-Encoded Combinatorial Library Functional Screening

PubMed Central

2017-01-01

DNA-encoded synthesis is rekindling interest in combinatorial compound libraries for drug discovery and in technology for automated and quantitative library screening. Here, we disclose a microfluidic circuit that enables functional screens of DNA-encoded compound beads. The device carries out library bead distribution into picoliter-scale assay reagent droplets, photochemical cleavage of compound from the bead, assay incubation, laser-induced fluorescence-based assay detection, and fluorescence-activated droplet sorting to isolate hits. DNA-encoded compound beads (10-μm diameter) displaying a photocleavable positive control inhibitor pepstatin A were mixed (1920 beads, 729 encoding sequences) with negative control beads (58 000 beads, 1728 encoding sequences) and screened for cathepsin D inhibition using a biochemical enzyme activity assay. The circuit sorted 1518 hit droplets for collection following 18 min incubation over a 240 min analysis. Visual inspection of a subset of droplets (1188 droplets) yielded a 24% false discovery rate (1166 pepstatin A beads; 366 negative control beads). Using template barcoding strategies, it was possible to count hit collection beads (1863) using next-generation sequencing data. Bead-specific barcodes enabled replicate counting, and the false discovery rate was reduced to 2.6% by only considering hit-encoding sequences that were observed on >2 beads. This work represents a complete distributable small molecule discovery platform, from microfluidic miniaturized automation to ultrahigh-throughput hit deconvolution by sequencing. PMID:28199790

An Integrated Microfluidic Processor for DNA-Encoded Combinatorial Library Functional Screening.

PubMed

MacConnell, Andrew B; Price, Alexander K; Paegel, Brian M

2017-03-13

DNA-encoded synthesis is rekindling interest in combinatorial compound libraries for drug discovery and in technology for automated and quantitative library screening. Here, we disclose a microfluidic circuit that enables functional screens of DNA-encoded compound beads. The device carries out library bead distribution into picoliter-scale assay reagent droplets, photochemical cleavage of compound from the bead, assay incubation, laser-induced fluorescence-based assay detection, and fluorescence-activated droplet sorting to isolate hits. DNA-encoded compound beads (10-μm diameter) displaying a photocleavable positive control inhibitor pepstatin A were mixed (1920 beads, 729 encoding sequences) with negative control beads (58 000 beads, 1728 encoding sequences) and screened for cathepsin D inhibition using a biochemical enzyme activity assay. The circuit sorted 1518 hit droplets for collection following 18 min incubation over a 240 min analysis. Visual inspection of a subset of droplets (1188 droplets) yielded a 24% false discovery rate (1166 pepstatin A beads; 366 negative control beads). Using template barcoding strategies, it was possible to count hit collection beads (1863) using next-generation sequencing data. Bead-specific barcodes enabled replicate counting, and the false discovery rate was reduced to 2.6% by only considering hit-encoding sequences that were observed on >2 beads. This work represents a complete distributable small molecule discovery platform, from microfluidic miniaturized automation to ultrahigh-throughput hit deconvolution by sequencing.

Atomic and electronic structure of Pd40Ni40P20 bulk metallic glass from ab initio simulations

NASA Astrophysics Data System (ADS)

Kumar, Vijay; Fujita, T.; Konno, K.; Matsuura, M.; Chen, M. W.; Inoue, A.; Kawazoe, Y.

2011-10-01

The atomic structure of Pd40Ni40P20 bulk metallic glass has been simulated using an ab initio molecular dynamics method with projector-augmented wave pseudopotentials for electron-ion interaction and generalized gradient approximation for exchange-correlation energy. The calculated extended x-ray absorption fine structure (EXAFS) spectra of Pd-K and Ni-K edges, the mass density, and the electronic structure agree remarkably well with the available experimental data and the EXAFS spectra measured at the SPring-8 synchrotron radiation facility. Our results show that the atomic structure can be described in terms of P-centered polyhedra. There are no two P atoms that are nearest neighbors at this composition, and this could be a reason for the observed optimal P concentration of about 20 at.%. The neighboring polyhedra share metal (M) atoms and form a polar covalently bonded random network of P-M-P favoring certain angles. The remaining M atoms act as metallic glue with a tendency of nanoscale clustering of Pd-Pd and Ni-Ni atoms.

Dynamics of periodic spring-mass chain coupled with an electric transmission line

NASA Astrophysics Data System (ADS)

Belloni, Edoardo; Cenedese, Mattia; Braghin, Francesco

2017-04-01

Periodic structures have received large interest due to their peculiar behavior: they have band gaps, that is portions of the frequency response along with any wave incoming in the structure is reflected. Numerous are the applications, like metamaterials and locally resonant structures. Nowadays, new possibilities could come from mechanical periodic structures that are connected to an electrical transmission line, periodic in turn. Starting from this idea, this paper analyses ideal a mono-atomic spring-mass chain, considering the springs connected to a periodic electric network, composed by inductances (and resistors): these simple examples will show how the frequency response is affected. In particular, the mutual influence between the electric and mechanical domain is highlighted, and the contribution of parameters on band gap positioning and design is explored. Details are provided about vibration modes and wave transmission.

Flow injection analysis-flame atomic absorption spectrometry system for indirect determination of sulfite after on-line reduction of solid-phase manganese (IV) dioxide reactor.

PubMed

Zare-Dorabei, Rouholah; Boroun, Shokoufeh; Noroozifar, Meissam

2018-02-01

A new and simple flow injection method followed by atomic absorption spectrometry was developed for indirect determination of sulfite. The proposed method is based on the oxidation of sulfite to sulphate ion using solid-phase manganese dioxide (30% W/W suspended on silica gel beads) reactor. MnO 2 will be reduced to Mn(II) by sample injection in to the column under acidic carrier stream of HNO 3 (pH 2) with flow rate of 3.5mLmin -1 at room temperature. Absorption measurement of Mn(II) which is proportional to the concentration of sulfite in the sample was carried out by atomic absorption spectrometry. The calibration curve was linear up to 25mgL -1 with a detection limit (DL) of 0.08mgL -1 for 400µL injection sample volume. The presented method is efficient toward sulfite determination in sugar and water samples with a relative standard deviation (RSD) less than 1.2% and a sampling rate of about 60h -1 . Copyright © 2017 Elsevier B.V. All rights reserved.

A novel magnet focusing plate for matrix-assisted laser desorption/ionization analysis of magnetic bead-bound analytes.

PubMed

Gode, David; Volmer, Dietrich A

2013-05-15

Magnetic beads are often used for serum profiling of peptide and protein biomarkers. In these assays, the bead-bound analytes are eluted from the beads prior to mass spectrometric analysis. This study describes a novel matrix-assisted laser desorption/ionization (MALDI) technique for direct application and focusing of magnetic beads to MALDI plates by means of dedicated micro-magnets as sample spots. Custom-made MALDI plates with magnetic focusing spots were made using small nickel-coated neodymium micro-magnets integrated into a stainless steel plate in a 16 × 24 (384) pattern. For demonstrating the proof-of-concept, commercial C-18 magnetic beads were used for the extraction of a test compound (reserpine) from aqueous solution. Experiments were conducted to study focusing abilities, the required laser energies, the influence of a matrix compound, dispensing techniques, solvent choice and the amount of magnetic beads. Dispensing the magnetic beads onto the micro-magnet sample spots resulted in immediate and strong binding to the magnetic surface. Light microscope images illustrated the homogeneous distribution of beads across the surfaces of the magnets, when the entire sample volume containing the beads was pipetted onto the surface. Subsequent MALDI analysis of the bead-bound analyte demonstrated excellent and reproducible ionization yields. The surface-assisted laser desorption/ionization (SALDI) properties of the strongly light-absorbing γ-Fe2O3-based beads resulted in similar ionization efficiencies to those obtained from experiments with an additional MALDI matrix compound. This feasibility study successfully demonstrated the magnetic focusing abilities for magnetic bead-bound analytes on a novel MALDI plate containing small micro-magnets as sample spots. One of the key advantages of this integrated approach is that no elution steps from magnetic beads were required during analyses compared with conventional bead experiments. Copyright © 2013 John Wiley & Sons, Ltd.

Molecular diagnostics using magnetic nanobeads

NASA Astrophysics Data System (ADS)

Zardán Gómez de la Torre, Teresa; Strömberg, Mattias; Göransson, Jenny; Gunnarsson, Klas; Nilsson, Mats; Svedlindh, Peter; Strømme, Maria

2010-01-01

In this paper, we investigate the volume-amplified magnetic nanobead detection assay with respect to bead size, bead concentration and bead oligonucleotide surface coverage in order to improve the understanding of the underlying microscopic mechanisms. It has been shown that: (i) the immobilization efficiency of the beads depends on the surface coverage of oligonucleotides, (ii) by using lower amounts of probe-tagged beads, detection sensitivity can be improved and (iii) using small enough beads enables both turn-off and turn-on detection. Finally, biplex detection was demonstrated.

The energy of naturally curved elastic rods with an application to the stretching and contraction of a free helical spring as a model for DNA

NASA Astrophysics Data System (ADS)

Manning, Gerald S.

2015-09-01

We give a contemporary and direct derivation of a classical, but insufficiently familiar, result in the theory of linear elasticity—a representation for the energy of a stressed elastic rod with central axis that intrinsically takes the shape of a general space curve. We show that the geometric torsion of the space curve, while playing a crucial role in the bending energy, is physically unrelated to the elastic twist. We prove that the twist energy vanishes in the lowest-energy states of a rod subject to constraints that do not restrict the twist. The stretching and contraction energies of a free helical spring are computed. There are local high-energy minima. We show the possibility of using the spring to model the chirality of DNA. We then compare our results with an available atomic level energy simulation that was performed on DNA unconstrained in the same sense as the free spring. We find some possible reflections of springlike behavior in the mechanics of DNA, but, unsurprisingly, the base pairs lend a material substance to the core of DNA that a spring does not capture.

The energy of naturally curved elastic rods with an application to the stretching and contraction of a free helical spring as a model for DNA.

PubMed

Manning, Gerald S

2015-09-14

We give a contemporary and direct derivation of a classical, but insufficiently familiar, result in the theory of linear elasticity-a representation for the energy of a stressed elastic rod with central axis that intrinsically takes the shape of a general space curve. We show that the geometric torsion of the space curve, while playing a crucial role in the bending energy, is physically unrelated to the elastic twist. We prove that the twist energy vanishes in the lowest-energy states of a rod subject to constraints that do not restrict the twist. The stretching and contraction energies of a free helical spring are computed. There are local high-energy minima. We show the possibility of using the spring to model the chirality of DNA. We then compare our results with an available atomic level energy simulation that was performed on DNA unconstrained in the same sense as the free spring. We find some possible reflections of springlike behavior in the mechanics of DNA, but, unsurprisingly, the base pairs lend a material substance to the core of DNA that a spring does not capture.

Accurate calibration and uncertainty estimation of the normal spring constant of various AFM cantilevers.

PubMed

Song, Yunpeng; Wu, Sen; Xu, Linyan; Fu, Xing

2015-03-10

Measurement of force on a micro- or nano-Newton scale is important when exploring the mechanical properties of materials in the biophysics and nanomechanical fields. The atomic force microscope (AFM) is widely used in microforce measurement. The cantilever probe works as an AFM force sensor, and the spring constant of the cantilever is of great significance to the accuracy of the measurement results. This paper presents a normal spring constant calibration method with the combined use of an electromagnetic balance and a homemade AFM head. When the cantilever presses the balance, its deflection is detected through an optical lever integrated in the AFM head. Meanwhile, the corresponding bending force is recorded by the balance. Then the spring constant can be simply calculated using Hooke's law. During the calibration, a feedback loop is applied to control the deflection of the cantilever. Errors that may affect the stability of the cantilever could be compensated rapidly. Five types of commercial cantilevers with different shapes, stiffness, and operating modes were chosen to evaluate the performance of our system. Based on the uncertainty analysis, the expanded relative standard uncertainties of the normal spring constant of most measured cantilevers are believed to be better than 2%.

The energy of naturally curved elastic rods with an application to the stretching and contraction of a free helical spring as a model for DNA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manning, Gerald S., E-mail: jerrymanning@rcn.com

We give a contemporary and direct derivation of a classical, but insufficiently familiar, result in the theory of linear elasticity—a representation for the energy of a stressed elastic rod with central axis that intrinsically takes the shape of a general space curve. We show that the geometric torsion of the space curve, while playing a crucial role in the bending energy, is physically unrelated to the elastic twist. We prove that the twist energy vanishes in the lowest-energy states of a rod subject to constraints that do not restrict the twist. The stretching and contraction energies of a free helicalmore » spring are computed. There are local high-energy minima. We show the possibility of using the spring to model the chirality of DNA. We then compare our results with an available atomic level energy simulation that was performed on DNA unconstrained in the same sense as the free spring. We find some possible reflections of springlike behavior in the mechanics of DNA, but, unsurprisingly, the base pairs lend a material substance to the core of DNA that a spring does not capture.« less

A microhydrodynamic rationale for selection of bead size in preparation of drug nanosuspensions via wet stirred media milling.

PubMed

Li, Meng; Alvarez, Paulina; Bilgili, Ecevit

2017-05-30

Although wet stirred media milling has proven to be a robust process for producing nanoparticle suspensions of poorly water-soluble drugs and thereby enhancing their bioavailability, selection of bead size has been largely empirical, lacking fundamental rationale. This study aims to establish such rationale by investigating the impact of bead size at various stirrer speeds on the drug breakage kinetics via a microhydrodynamic model. To this end, stable suspensions of griseofulvin, a model BCS Class II drug, were prepared using hydroxypropyl cellulose and sodium dodecyl sulfate. The suspensions were milled at four different stirrer speeds (1000-4000rpm) using various sizes (50-1500μm) of zirconia beads. Laser diffraction, SEM, and XRPD were used for characterization. Our results suggest that there is an optimal bead size that achieves fastest breakage at each stirrer speed and that it shifts to a smaller size at higher speed. Calculated microhydrodynamic parameters reveal two counteracting effects of bead size: more bead-bead collisions with less energy/force upon a decrease in bead size. The optimal bead size exhibits a negative power-law correlation with either specific energy consumption or the microhydrodynamic parameters. Overall, this study rationalizes the use of smaller beads for more energetic wet media milling. Copyright © 2017 Elsevier B.V. All rights reserved.

Characterisation of physico-mechanical properties and degradation potential of calcium alginate beads for use in embolisation.

PubMed

Forster, Richard E J; Thürmer, Frank; Wallrapp, Christine; Lloyd, Andrew W; Macfarlane, Wendy; Phillips, Gary J; Boutrand, Jean-Pierre; Lewis, Andrew L

2010-07-01

High molecular weight alginate beads with 59% mannuronic acid content or 68% guluronic acid were prepared using a droplet generator and crosslinked in calcium chloride. The alginate beads were compared to current embolisation microspheres for compressibility and monitored over 12 weeks for size and weight change at 37 degrees C in low volumes of ringers solutions. A sheep uterine model was used to analyse bead degradation and inflammatory response over 12 weeks. Both the in vitro and in vivo data show good delivery, with a compressibility similar to current embolic beads. In vitro, swelling was noted almost immediately and after 12 weeks the first signs of degradation were noted. No difference was noted in vivo. This study has shown that high molecular weight alginate gel beads were well tolerated by the body, but beads associated with induced thrombi were susceptible to inflammatory cell infiltration. The beads were shown to be easy to handle and were still observable after 3 months in vivo. The beads were robust enough to be delivered through a 2.7 Fr microcatheter. This study has demonstrated that high molecular weight, high purity alginate bead can be considered as semi-permanent embolisation beads, with the potential to bioresorb over time.

Highly sensitive bacteria quantification using immunomagnetic separation and electrochemical detection of guanine-labeled secondary beads.

PubMed

Jayamohan, Harikrishnan; Gale, Bruce K; Minson, Bj; Lambert, Christopher J; Gordon, Neil; Sant, Himanshu J

2015-05-22

In this paper, we report the ultra-sensitive indirect electrochemical detection of E. coli O157:H7 using antibody functionalized primary (magnetic) beads for capture and polyguanine (polyG) oligonucleotide functionalized secondary (polystyrene) beads as an electrochemical tag. Vacuum filtration in combination with E. coli O157:H7 specific antibody modified magnetic beads were used for extraction of E. coli O157:H7 from 100 mL samples. The magnetic bead conjugated E. coli O157:H7 cells were then attached to polyG functionalized secondary beads to form a sandwich complex (magnetic bead/E. coli secondary bead). While the use of magnetic beads for immuno-based capture is well characterized, the use of oligonucleotide functionalized secondary beads helps combine amplification and potential multiplexing into the system. The antibody functionalized secondary beads can be easily modified with a different antibody to detect other pathogens from the same sample and enable potential multiplexing. The polyGs on the secondary beads enable signal amplification up to 10⁸ guanine tags per secondary bead (7.5 x 10⁶ biotin-FITC per secondary bead, 20 guanines per oligonucleotide) bound to the target (E. coli). A single-stranded DNA probe functionalized reduced graphene oxide modified glassy carbon electrode was used to bind the polyGs on the secondary beads. Fluorescent imaging was performed to confirm the hybridization of the complex to the electrode surface. Differential pulse voltammetry (DPV) was used to quantify the amount of polyG involved in the hybridization event with tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)3(2+)) as the mediator. The amount of polyG signal can be correlated to the amount of E. coli O157:H7 in the sample. The method was able to detect concentrations of E. coli O157:H7 down to 3 CFU/100 mL, which is 67 times lower than the most sensitive technique reported in literature. The signal to noise ratio for this work was 3. We also demonstrate the use of the protocol for detection of E. coli O157:H7 seeded in waste water effluent samples.

Hands-on Force Spectroscopy: Weird Springs and Protein Folding

ERIC Educational Resources Information Center

Euler, Manfred

2008-01-01

A force spectroscopy model experiment is presented using a low-cost tensile apparatus described earlier. Force-extension measurements of twisted rubber bands are obtained. They exhibit a complex nonlinear elastic behaviour that resembles atomic force spectroscopy investigations of molecules of titin, a muscle protein. The model experiments open up…

Plasmodium falciparum-induced CD36 clustering rapidly strengthens cytoadherence via p130CAS-mediated actin cytoskeletal rearrangement

PubMed Central

Davis, Shevaun P.; Amrein, Matthias; Gillrie, Mark R.; Lee, Kristine; Muruve, Daniel A.; Ho, May

2012-01-01

The adhesion of infected red blood cells (IRBCs) to microvascular endothelium is critical in the pathogenesis of severe malaria. Here we used atomic force and confocal microscopy to examine the adhesive forces between IRBCs and human dermal microvascular endothelial cells. Initial contact of the cells generated a mean ± sd adhesion force of 167 ± 208 pN from the formation of single or multiple bonds with CD36. The strength of adhesion increased by 5- to 6-fold within minutes of contact through a signaling pathway initiated by CD36 ligation by live IRBCs, or polystyrene beads coated with anti-CD36 or PpMC-179, a recombinant peptide representing the minimal binding domain of the parasite ligand PfEMP1 to CD36. Engagement of CD36 led to localized phosphorylation of Src family kinases and the adaptor protein p130CAS, resulting in actin recruitment and CD36 clustering by 50–60% of adherent beads. Uninfected red blood cells or IgG-coated beads had no effect. Inhibition of the increase in adhesive strength by the Src family kinase inhibitor PP1 or gene silencing of p130CAS decreased adhesion by 39 ± 12 and 48 ± 20%, respectively, at 10 dyn/cm2 in a flow chamber assay. Modulation of adhesive strength at PfEMP1-CD36-actin cytoskeleton synapses could be a novel target for antiadhesive therapy.—Davis, S. P., Amrein, M., Gillrie, M. R., Lee, K., Muruve, D. A., Ho, M. Plasmodium falciparum-induced CD36 clustering rapidly strengthens cytoadherence via p130CAS-mediated actin cytoskeletal rearrangement. PMID:22106368

Functionalized AFM probes for force spectroscopy: eigenmode shapes and stiffness calibration through thermal noise measurements.

PubMed

Laurent, Justine; Steinberger, Audrey; Bellon, Ludovic

2013-06-07

The functionalization of an atomic force microscope (AFM) cantilever with a colloidal bead is a widely used technique when the geometry between the probe and the sample must be controlled, particularly in force spectroscopy. But some questions remain: how does a bead glued at the end of a cantilever influence its mechanical response? And more importantly for quantitative measurements, can we still determine the stiffness of the AFM probe with traditional techniques?In this paper, the influence of the colloidal mass loading on the eigenmode shape and resonant frequency is investigated by measuring the thermal noise on rectangular AFM microcantilevers with and without beads attached at their extremities. The experiments are performed with a home-made ultra-sensitive AFM, based on differential interferometry. The focused beam from the interferometer probes the cantilever at different positions and the spatial shapes of the modes are determined up to the fifth resonance, without external excitation. The results clearly demonstrate that the first eigenmode is almost unchanged by mass loading. However the oscillation behavior of higher resonances presents a marked difference: with a particle glued at its extremity, the nodes of the modes are displaced towards the free end of the cantilever. These results are compared to an analytical model taking into account the mass and inertial moment of the load in an Euler-Bernoulli framework, where the normalization of the eigenmodes is explicitly worked out in order to allow a quantitative prediction of the thermal noise amplitude of each mode. A good agreement between the experimental results and the analytical model is demonstrated, allowing a clean calibration of the probe stiffness.

Effect of molecular topology on the transport properties of dendrimers in dilute solution at Θ temperature: A Brownian dynamics study

NASA Astrophysics Data System (ADS)

Bosko, Jaroslaw T.; Ravi Prakash, J.

2008-01-01

Structure and transport properties of dendrimers in dilute solution are studied with the aid of Brownian dynamics simulations. To investigate the effect of molecular topology on the properties, linear chain, star, and dendrimer molecules of comparable molecular weights are studied. A bead-spring chain model with finitely extensible springs and fluctuating hydrodynamic interactions is used to represent polymer molecules under Θ conditions. Structural properties as well as the diffusivity and zero-shear-rate intrinsic viscosity of polymers with varied degrees of branching are analyzed. Results for the free-draining case are compared to and found in very good agreement with the Rouse model predictions. Translational diffusivity is evaluated and the difference between the short-time and long-time behavior due to dynamic correlations is observed. Incorporation of hydrodynamic interactions is found to be sufficient to reproduce the maximum in the intrinsic viscosity versus molecular weight observed experimentally for dendrimers. Results of the nonequilibrium Brownian dynamics simulations of dendrimers and linear chain polymers subjected to a planar shear flow in a wide range of strain rates are also reported. The flow-induced molecular deformation of molecules is found to decrease hydrodynamic interactions and lead to the appearance of shear thickening. Further, branching is found to suppress flow-induced molecular alignment and deformation.

From particle condensation to polymer aggregation

NASA Astrophysics Data System (ADS)

Janke, Wolfhard; Zierenberg, Johannes

2018-01-01

We draw an analogy between droplet formation in dilute particle and polymer systems. Our arguments are based on finite-size scaling results from studies of a two-dimensional lattice gas to three-dimensional bead-spring polymers. To set the results in perspective, we compare with in part rigorous theoretical scaling laws for canonical condensation in a supersaturated gas at fixed temperature, and derive corresponding scaling predictions for an undercooled gas at fixed density. The latter allows one to efficiently employ parallel multicanonical simulations and to reach previously not accessible scaling regimes. While the asymptotic scaling can not be observed for the comparably small polymer system sizes, they demonstrate an intermediate scaling regime also observable for particle condensation. Altogether, our extensive results from computer simulations provide clear evidence for the close analogy between particle condensation and polymer aggregation in dilute systems.

Van der Waals model for phase transitions in thermoresponsive surface films.

PubMed

McCoy, John D; Curro, John G

2009-05-21

Phase transitions in polymeric surface films are studied with a simple model based on the van der Waals equation of state. Each chain is modeled by a single bead attached to the surface by an entropic-Hooke's law spring. The surface coverage is controlled by adjusting the chemical potential, and the equilibrium density profile is calculated with density functional theory. The interesting feature of this model is the multivalued nature of the density profile seen at low temperature. This van der Waals loop behavior is resolved with a Maxwell construction between a high-density phase near the wall and a low-density phase in a "vertical" phase transition. Signatures of the phase transition in experimentally measurable quantities are then found. Numerical calculations are presented for isotherms of surface pressure, for the Poisson ratio, and for the swelling ratio.

Floating dosage forms to prolong gastro-retention--the characterisation of calcium alginate beads.

PubMed

Stops, Frances; Fell, John T; Collett, John H; Martini, Luigi G

2008-02-28

Floating calcium alginate beads, designed to improve drug bioavailability from oral preparations compared with that from many commercially available and modified release products, have been investigated as a possible gastro-retentive dosage form. A model drug, riboflavin, was also incorporated into the formula. The aims of the current work were (a) to obtain information regarding the structure, floating ability and changes that occurred when the dosage form was placed in aqueous media, (b) to investigate riboflavin release from the calcium alginate beads in physiologically relevant media prior to in vivo investigations. Physical properties of the calcium alginate beads were investigated. Using SEM and ESEM, externally the calcium alginate beads were spherical in shape, and internally, air filled cavities were present thereby enabling floatation of the beads. The calcium alginate beads remained buoyant for times in excess of 13h, and the density of the calcium alginate beads was <1.000gcm(-3). Riboflavin release from the calcium alginate beads showed that riboflavin release was slow in acidic media, whilst in more alkali media, riboflavin release was more rapid. The characterisation studies showed that the calcium alginate beads could be considered as a potential gastro-retentive dosage form.

Controlled drug release properties of ionically cross-linked chitosan beads: the influence of anion structure.

PubMed

Shu, X Z; Zhu, K J

2002-02-21

By adopting a novel chitosan cross-linked method, i.e. chitosan/gelatin droplet coagulated at low temperature and then cross-linked by anions (sulfate, citrate and tripolyphosphate (TPP)), the chitosan beads were prepared. Scanning electron microscopy (SEM) observation showed that sulfate/chitosan and citrate/chitosan beads usually had a spherical shape, smooth surface morphology and integral inside structure. Cross-sectional analysis indicated that the cross-linking process of sulfate and citrate to chitosan was much faster than that of TPP due to their smaller molecular size. But, once completely cross-linked, TPP/chitosan beads possessed much better mechanical strength and the force to break the beads was approximately ten times higher than that of sulfate/chitosan or citrate/chitosan beads. Release media pH and ionic strength seriously influenced the controlled drug release properties of the beads, which related to the strength of electrostatic interaction between anions and chitosan. Sulfate and citrate cross-linked chitosan beads swelled and even dissociated in simulated gastric fluid (SGF) and hence, model drug (riboflavin) released completely in 5 h; while in simulated intestinal fluid (SIF), beads remained in a shrinkage state and drug released slowly (release % usually <70% in 24 h). However, swelling and drug release of TPP/chitosan bead was usually insensitive to media pH. Chitosan beads, cross-linked by a combination of TPP and citrate (or sulfate) together, not only had a good shape, but also improved pH-responsive drug release properties. Salt weakened the interaction of citrate, especially sulfate with chitosan and accelerated beads swelling and hence drug release rate, but it was insensitive to that of TPP/chitosan. These results indicate that ionically cross-linked chitosan beads may be useful in stomach specific drug delivery.

Elution of platinum from carboplatin-impregnated calcium sulfate hemihydrate beads in vitro.

PubMed

Tulipan, Rachel J; Phillips, Heidi; Garrett, Laura D; Dirikolu, Levent; Mitchell, Mark A

2016-11-01

OBJECTIVE To characterize the elution of platinum from carboplatin-impregnated calcium sulfate hemihydrate (CSH) beads in vitro. SAMPLE 60 carboplatin-impregnated CSH beads and 9 CSH beads without added carboplatin (controls). PROCEDURES Carboplatin-impregnated CSH beads (each containing 4.6 mg of carboplatin [2.4 mg of platinum]) were placed into separate 10-mL plastic tubes containing 5 mL of PBSS in groups of 1, 3, 6, or 10; 3 control beads were placed into a single tube of PBSS at the same volume. Experiments were conducted in triplicate at 37°C and a pH of 7.4 with constant agitation. Eluent samples were collected at 1, 2, 3, 6, 12, 24, and 72 hours. Samples were analyzed for platinum content by inductively coupled plasma-mass spectrometry. RESULTS The mean concentration of platinum released per carboplatin-impregnated bead over 72 hours was 445.3 mg/L. Cumulative concentrations of platinum eluted increased as the number of beads per tube increased. There was a significant difference in platinum concentrations over time, with values increasing over the first 12 hours and then declining for all tubes. There was also a significant difference in percentage of total incorporated platinum released into tubes with different numbers of beads: the percentage of eluted platinum was higher in tubes containing 1 or 3 beads than in those containing 6 or 10 beads. CONCLUSIONS AND CLINICAL RELEVANCE Carboplatin-impregnated CSH beads eluted platinum over 72 hours. Further studies are needed to determine whether implantation of carboplatin-impregnated CSH beads results in detectable levels of platinum systemically and whether the platinum concentrations eluted locally are toxic to tumor cells.

Analysis of platinum content in biodegradable carboplatin-impregnated beads and retrospective assessment of tolerability for intralesional use of the beads in dogs following excision of subcutaneous sarcomas: 29 cases (2011-2014).

PubMed

Hess, Theresa A; Drinkhouse, Macy E; Prey, Joshua D; Miller, Jonathan M; Fettig, Arthur A; Carberry, Carol A; Brenn, Stephen H; Bailey, Dennis B

2018-02-15

OBJECTIVE To evaluate platinum content in biodegradable carboplatin-impregnated beads and retrospectively assess tolerability and outcome data for dogs treated by intralesional placement of such beads following surgical excision of subcutaneous sarcomas. DESIGN Evaluation study and retrospective case series. SAMPLE 9 carboplatin-impregnated beads and 29 client-owned dogs. PROCEDURES Platinum content in 9 carboplatin-impregnated beads from 3 lots was measured by spectrophotometry, and calculated carboplatin content was compared with the labeled content. Medical records were searched to identify dogs with subcutaneous sarcomas for which treatment included placement of carboplatin-impregnated beads between 2011 and 2014. Signalment, tumor characteristics, surgical and histologic data, adverse events, and local recurrences were recorded. Associations between variables of interest and adverse events or local disease-free interval were analyzed. RESULTS In vitro analysis identified a mean ± SD platinum content of 5.38 ± 0.97 mg/bead. Calculated carboplatin content (10.24 ± 1.84 mg/bead) was significantly greater than the labeled amount (4.6 mg/bead). Bead weight and total platinum content differed significantly among lots, but platinum content per bead weight did not. Mild-to-moderate local adverse events were reported for 11 of 29 tumors; all resolved without additional surgery. No dogs had signs of systemic toxicosis. Overall local disease-free rates 1, 2, and 3 years after surgery were 70%, 70%, and 58%, respectively, as determined by Kaplan-Meier analysis. CONCLUSIONS AND CLINICAL RELEVANCE Carboplatin-impregnated beads were well tolerated; however, results of in vitro tests indicated that caution is needed because of manufacturing inconsistencies.

Probing the stiffness of isolated nucleoli by atomic force microscopy.

PubMed

Louvet, Emilie; Yoshida, Aiko; Kumeta, Masahiro; Takeyasu, Kunio

2014-04-01

In eukaryotic cells, ribosome biogenesis occurs in the nucleolus, a membraneless nuclear compartment. Noticeably, the nucleolus is also involved in several nuclear functions, such as cell cycle regulation, non-ribosomal ribonucleoprotein complex assembly, aggresome formation and some virus assembly. The most intriguing question about the nucleolus is how such dynamics processes can occur in such a compact compartment. We hypothesized that its structure may be rather flexible. To investigate this, we used atomic force microscopy (AFM) on isolated nucleoli. Surface topography imaging revealed the beaded structure of the nucleolar surface. With the AFM's ability to measure forces, we were able to determine the stiffness of isolated nucleoli. We could establish that the nucleolar stiffness varies upon drastic morphological changes induced by transcription and proteasome inhibition. Furthermore, upon ribosomal proteins and LaminB1 knockdowns, the nucleolar stiffness was increased. This led us to propose a model where the nucleolus has steady-state stiffness dependent on ribosome biogenesis activity and requires LaminB1 for its flexibility.

From the one-bead-one-compound concept to one-bead-one-reactor.

PubMed

Marani, Mariela M; Paradís-Bas, Marta; Tulla-Puche, Judit; Côté, Simón; Camperi, Silvia A; Cascone, Osvaldo; Albericio, Fernando

2007-01-01

The one-bead-one-compound method gives access to millions of compounds that can be screened directly on the bead. Although characterization techniques are increasingly potent and reliable, problems can still be encountered in deciphering the sequence of the active compound because of sensitiveness or manipulation of the bead. ChemMatrix, a totally PEG-based resin, has resolved the synthesis of peptides of outstanding difficulty. Like other PEG-based resins, it permits on-bead screening because of its compatibility in aqueous media and has the further advantage of having a high loading, comparable to polystyrene resins. ChemMatrix beads previously swelled in water can be nicely divided into four parts that can be characterized using different analytical techniques or just stored for safety or for further testing. The four bead parts show high homogeneity and can thus be considered to be replicas.

Synthesis and characterization of nanoporous silica aerogel beads using cheap industrial grade sodium silacte precursor

NASA Astrophysics Data System (ADS)

Khan, Tasneem M. A.; Khan, Asiya; Sarawade, Pradip B.

2018-05-01

We report a method to synthesize low-density transparent mesoporous silica aerogel beads by ambient pressure drying (APD). The beads were prepared by acid-base sol-gel polymerization of sodium silicate in via the ball dropping method (BDM). To minimize shrinkage during drying, wet silica beads were initially prepared; their surfaces were then modified using trimethylchlorosilane (TMCS) via simultaneous solvent exchange and surface modification. The specific surface area and cumulative pore volume of the silica aerogel beads increased with an increase in the %V of TMCS. Silica aerogel beads with low packing bed density, high surface area, and large cumulative pore volume was obtained when TMCS was used. Properties of the final product were examined by BET, and TG-DT analyses. The hydrophobic silica aerogel beads were thermally stable up to 350°C. We discuss our results and compare our findings for modified versus unmodified silica beads.

Role of special cross-links in structure formation of bacterial DNA polymer

NASA Astrophysics Data System (ADS)

Agarwal, Tejal; Manjunath, G. P.; Habib, Farhat; Lakshmi Vaddavalli, Pavana; Chatterji, Apratim

2018-01-01

Using data from contact maps of the DNA-polymer of Escherichia coli (E. Coli) (at kilobase pair resolution) as an input to our model, we introduce cross-links between monomers in a bead-spring model of a ring polymer at very specific points along the chain. Via suitable Monte Carlo simulations, we show that the presence of these cross-links leads to a particular organization of the chain at large (micron) length scales of the DNA. We also investigate the structure of a ring polymer with an equal number of cross-links at random positions along the chain. We find that though the polymer does get organized at the large length scales, the nature of the organization is quite different from the organization observed with cross-links at specific biologically determined positions. We used the contact map of E. Coli bacteria which has around 4.6 million base pairs in a single circular chromosome. In our coarse-grained flexible ring polymer model, we used 4642 monomer beads and observed that around 80 cross-links are enough to induce the large-scale organization of the molecule accounting for statistical fluctuations caused by thermal energy. The length of a DNA chain even of a simple bacterial cell such as E. Coli is much longer than typical proteins, hence we avoided methods used to tackle protein folding problems. We define new suitable quantities to identify the large scale structure of a polymer chain with a few cross-links.

Bead mediated separation of microparticles in droplets.

PubMed

Wang, Sida; Sung, Ki-Joo; Lin, Xiaoxia Nina; Burns, Mark A

2017-01-01

Exchange of components such as particles and cells in droplets is important and highly desired in droplet microfluidic assays, and many current technologies use electrical or magnetic fields to accomplish this process. Bead-based microfluidic techniques offer an alternative approach that uses the bead's solid surface to immobilize targets like particles or biological material. In this paper, we demonstrate a bead-based technique for exchanging droplet content by separating fluorescent microparticles in a microfluidic device. The device uses posts to filter surface-functionalized beads from a droplet and re-capture the filtered beads in a new droplet. With post spacing of 7 μm, beads above 10 μm had 100% capture efficiency. We demonstrate the efficacy of this system using targeted particles that bind onto the functionalized beads and are, therefore, transferred from one solution to another in the device. Binding capacity tests performed in the bulk phase showed an average binding capacity of 5 particles to each bead. The microfluidic device successfully separated the targeted particles from the non-targeted particles with up to 98% purity and 100% yield.

Method for preparing spherical ferrite beads and use thereof

DOEpatents

Lauf, Robert J.; Anderson, Kimberly K.; Montgomery, Frederick C.; Collins, Jack L.

2002-01-01

The invention allows the fabrication of small, dense, highly polished spherical beads of hexagonal ferrites with selected compositions for use in nonreciprocal microwave and mm-wave devices as well as in microwave absorbent or reflective coatings, composites, and the like. A porous, generally spherical bead of hydrous iron oxide is made by a sol-gel process to form a substantially rigid bead having a generally fine crystallite size and correspondingly finely distributed internal porosity. The resulting gel bead is washed and hydrothermally reacted with a soluble alkaline earth salt (typically Ba or Sr) under conditions of elevated temperature and pressure to convert the bead into a mixed hydrous iron-alkaline earth oxide while retaining the generally spherical shape. This mixed oxide bead is then washed, dried, and calcined to produce the desired (BaFe.sub.12 O.sub.19 or SrFe.sub.12 O.sub.19) crystal structure. The calcined bead is then sintered to form a dense bead of the BaFe.sub.12 O.sub.19 and SrFe.sub.12 O.sub.19 phase suitable for polishing and incorporation into various microwave devices and components.

Congo red adsorption from aqueous solutions by using chitosan hydrogel beads impregnated with nonionic or anionic surfactant.

PubMed

Chatterjee, Sudipta; Lee, Dae S; Lee, Min W; Woo, Seung H

2009-09-01

The adsorption performance of CS beads impregnated with triton X-100 (TX-100) as a nonionic surfactant and sodium dodecyl sulfate (SDS) as an anionic surfactant was investigated for the removal of anionic dye (congo red) from aqueous solution. While the adsorption capacity of CS/TX-100 beads was enhanced at all concentrations of TX-100 (0.005-0.1%), the increase in the concentration of SDS above 0.01% in the CS/SDS beads gradually reduced the adsorption capacity of the beads. Equilibrium adsorption isotherm data indicated a good fit to the Sips isotherm model and a heterogeneous adsorption process. The Sips maximum adsorption capacity in dry weight of the CS/TX-100 beads was 378.79 mg/g and 318.47 mg/g for the CS/SDS beads, higher than the 223.25mg/g of the CS beads. Modification of CS beads by impregnation with nonionic surfactant, or even anionic surfactant, at low concentrations is a possible way to enhance adsorption of anionic dye.

Optical Manipulation of Single Magnetic Beads in a Microwell Array on a Digital Microfluidic Chip.

PubMed

Decrop, Deborah; Brans, Toon; Gijsenbergh, Pieter; Lu, Jiadi; Spasic, Dragana; Kokalj, Tadej; Beunis, Filip; Goos, Peter; Puers, Robert; Lammertyn, Jeroen

2016-09-06

The detection of single molecules in magnetic microbead microwell array formats revolutionized the development of digital bioassays. However, retrieval of individual magnetic beads from these arrays has not been realized until now despite having great potential for studying captured targets at the individual level. In this paper, optical tweezers were implemented on a digital microfluidic platform for accurate manipulation of single magnetic beads seeded in a microwell array. Successful optical trapping of magnetic beads was found to be dependent on Brownian motion of the beads, suggesting a 99% chance of trapping a vibrating bead. A tailor-made experimental design was used to screen the effect of bead type, ionic buffer strength, surfactant type, and concentration on the Brownian activity of beads in microwells. With the optimal conditions, the manipulation of magnetic beads was demonstrated by their trapping, retrieving, transporting, and repositioning to a desired microwell on the array. The presented platform combines the strengths of digital microfluidics, digital bioassays, and optical tweezers, resulting in a powerful dynamic microwell array system for single molecule and single cell studies.

Engineered elastomeric proteins with dual elasticity can be controlled by a molecular regulator.

PubMed

Cao, Yi; Li, Hongbin

2008-08-01

Elastomeric proteins are molecular springs that confer excellent mechanical properties to many biological tissues and biomaterials. Depending on the role performed by the tissue or biomaterial, elastomeric proteins can behave as molecular springs or shock absorbers. Here we combine single-molecule atomic force microscopy and protein engineering techniques to create elastomeric proteins that can switch between two distinct types of mechanical behaviour in response to the binding of a molecular regulator. The proteins are mechanically labile by design and behave as entropic springs with an elasticity that is governed by their configurational entropy. However, when a molecular regulator binds to the protein, it switches into a mechanically stable state and can act as a shock absorber. These engineered proteins effectively mimic and combine the two extreme forms of elastic behaviour found in natural elastomeric proteins, and thus represent a new type of smart nanomaterial that will find potential applications in nanomechanics and material sciences.

Absolute marine gravimetry with matter-wave interferometry.

PubMed

Bidel, Y; Zahzam, N; Blanchard, C; Bonnin, A; Cadoret, M; Bresson, A; Rouxel, D; Lequentrec-Lalancette, M F

2018-02-12

Measuring gravity from an aircraft or a ship is essential in geodesy, geophysics, mineral and hydrocarbon exploration, and navigation. Today, only relative sensors are available for onboard gravimetry. This is a major drawback because of the calibration and drift estimation procedures which lead to important operational constraints. Atom interferometry is a promising technology to obtain onboard absolute gravimeter. But, despite high performances obtained in static condition, no precise measurements were reported in dynamic. Here, we present absolute gravity measurements from a ship with a sensor based on atom interferometry. Despite rough sea conditions, we obtained precision below 10 -5  m s -2 . The atom gravimeter was also compared with a commercial spring gravimeter and showed better performances. This demonstration opens the way to the next generation of inertial sensors (accelerometer, gyroscope) based on atom interferometry which should provide high-precision absolute measurements from a moving platform.

Parametric Cooling of Ultracold Atoms

NASA Astrophysics Data System (ADS)

Boguslawski, Matthew; Bharath, H. M.; Barrios, Maryrose; Chapman, Michael

2017-04-01

An oscillator is characterized by a restoring force which determines the natural frequency at which oscillations occur. The amplitude and phase-noise of these oscillations can be amplified or squeezed by modulating the magnitude of this force (e.g. the stiffness of the spring) at twice the natural frequency. This is parametric excitation; a long-studied phenomena in both the classical and quantum regimes. Parametric cooling, or the parametric squeezing of thermo-mechanical noise in oscillators has been studied in micro-mechanical oscillators and trapped ions. We study parametric cooling in ultracold atoms. This method shows a modest reduction of the variance of atomic momenta, and can be easily employed with pre-existing controls in many experiments. Parametric cooling is comparable to delta-kicked cooling, sharing similar limitations. We expect this cooling to find utility in microgravity experiments where the experiment duration is limited by atomic free expansion.

Chemical bond imaging using higher eigenmodes of tuning fork sensors in atomic force microscopy

NASA Astrophysics Data System (ADS)

Ebeling, Daniel; Zhong, Qigang; Ahles, Sebastian; Chi, Lifeng; Wegner, Hermann A.; Schirmeisen, André

2017-05-01

We demonstrate the ability of resolving the chemical structure of single organic molecules using non-contact atomic force microscopy with higher normal eigenmodes of quartz tuning fork sensors. In order to achieve submolecular resolution, CO-functionalized tips at low temperatures are used. The tuning fork sensors are operated in ultrahigh vacuum in the frequency modulation mode by exciting either their first or second eigenmode. Despite the high effective spring constant of the second eigenmode (on the order of several tens of kN/m), the force sensitivity is sufficiently high to achieve atomic resolution above the organic molecules. This is observed for two different tuning fork sensors with different tip geometries (small tip vs. large tip). These results represent an important step towards resolving the chemical structure of single molecules with multifrequency atomic force microscopy techniques where two or more eigenmodes are driven simultaneously.

77 FR 32986 - Notice of Inventory Completion: The University of Alabama Museums, Tuscaloosa, AL

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-04

... than 2,032 glass beads, 1 lot of more than 17 shell beads, 1 unidentified bead, 1 gun lock, 1 gun butt plate, 1 gun stock, 2 gun barrels, 1 brass ramrod support, 8 musket balls, 2 iron buckles, 1 iron handle... fragments, 1 unidentified bead, 2 glass beads, 1 gun flint, 1 iron knife blade, 1 iron nail, 1 musket ball...

Magnetic bead detection using nano-transformers.

PubMed

Kim, Hyung Kwon; Hwang, Jong Seung; Hwang, Sung Woo; Ahn, Doyeol

2010-11-19

A novel scheme to detect magnetic beads using a nano-scale transformer with a femtoweber resolution is reported. We have performed a Faraday's induction experiment with the nano-transformer at room temperature. The transformer shows the linear output voltage responses to the sinusoidal input current. When magnetic beads are placed on the transformer, the output responses are increased by an amount corresponding to the added magnetic flux from the beads when compared with the case of no beads on the transformer. In this way, we could determine whether magnetic beads are on top of the transformer in a single particle level.

Phosphate uptake studies of cross-linked chitosan bead materials.

PubMed

Mahaninia, Mohammad H; Wilson, Lee D

2017-01-01

A systematic experimental study is reported that provides a molecular based understanding of cross-linked chitosan beads and their adsorption properties in aqueous solution containing phosphate dianion (HPO 4 2- ) species. Synthetically modified chitosan using epichlorohydrin and glutaraldehyde cross-linkers result in surface modified beads with variable hydrophile-lipophile character and tunable HPO 4 2- uptake properties. The kinetic and thermodynamic adsorption properties of cross-linked chitosan beads with HPO 4 2- species were studied in aqueous solution. Complementary structure and physicochemical characterization of chitosan beads via potentiometry, Raman spectroscopy, DSC, and dye adsorption measurements was carried out to establish structure-property relationships. The maximum uptake (Q m ) of bead systems with HPO 4 2- at equilibrium was 52.1mgg -1 ; whereas, kinetic uptake results for chitosan bead/phosphate systems are relatively rapid (0.111-0.113min -1 ) with an intraparticle diffusion rate-limiting step. The adsorption process follows a multi-step pathway involving inner- and outer-sphere complexes with significant changes in hydration. Phosphate uptake strongly depends on the composition and type of cross-linker used for preparation of chitosan beads. The adsorption isotherms and structural characterization of bead systems illustrate the role of surface charge, hydrophile-lipophile balance, adsorption site accessibility, and hydration properties of the chitosan bead surface. Copyright © 2016 Elsevier Inc. All rights reserved.

Determining the unique refractive index properties of solid polystyrene aerosol using broadband Mie scattering from optically trapped beads.

PubMed

Jones, Stephanie H; King, Martin D; Ward, Andrew D

2013-12-21

A method is described to measure the refractive index dispersion with wavelength of optically trapped solid particles in air. Knowledge of the refraction properties of solid particles is critical for the study of aerosol; both in the laboratory and in the atmosphere for climate studies. Single micron-sized polystyrene beads were optically trapped in air using a vertically aligned counter-propagating configuration of focussed laser beams. Each bead was illuminated using white light from a broadband light emitting diode (LED) and elastic scattering within the bead was collected onto a spectrograph. The resulting Mie spectra were analysed to accurately determine polystyrene bead radii to ±0.4 nm and values of the refractive index to ±0.0005 over a wavelength range of 480-700 nm. We demonstrate that optical trapping combined with elastic scattering can be used to both accurately size polystyrene beads suspended in air and determine their wavelength dependent refractive index. The refractive index dispersions are in close agreement with reported values for polystyrene beads in aqueous dispersion. Our results also demonstrate a variation in the refractive index of polystyrene, from bead to bead, in a commercial sample. The measured variation highlights that care must be taken when using polystyrene beads as a calibration aerosol.

Carryover effects associated with the single-trial passive avoidance learning task in the young chick.

PubMed

Crowe, Simon F; Hale, Matthew W

2002-09-01

The single-trial passive avoidance task is a useful procedure for examining learning and memory in the young chick. However, it has recently been suggested that discrepant results reported by different laboratories are due to differences in training procedure. The present study investigated a number of parameters surrounding the passive avoidance task, using day-old White Leghorn, Black Australorp cockerels. The results suggested that presentation of a water-dipped bead immediately after the aversive bead significantly altered retention levels. In addition, when the water-dipped bead was presented after the aversive bead, chicks failed to discriminate between beads for a period of 10 min following exposure to the aversant experience. A novel variant of the passive avoidance procedure, involving pretraining with a water-dipped red bead, training with an aversant-coated red bead, and testing with a dry red bead, was evaluated. A measure of avoidance was calculated using all three trials. It is suggested that the use of a single bead, measured both before and after the training experience and using both aversant- and water-trained controls, results in the most concise characterization of memory-related phenomena in the chick which is not contaminated by a carryover effect from the aversive training experience to the nonaversive bead.

The Water Production Rate of Recent Comets (2013-2014) by SOHO/SWAN: 2P/Encke (2013), C/2013 R1 (Lovejoy), and C/2013 A1 (Siding Spring)

NASA Astrophysics Data System (ADS)

Combi, Michael R.; Mäkinen, J. T.; Bertaux, J. L.; Quémerais, Eric; Ferron, Stéphane

2014-11-01

The all-sky hydrogen Lyman-alpha camera, SWAN (Solar Wind Anisotropies), on the SOlar and Heliospheric Observatory (SOHO) satellite makes observations of the hydrogen comae of comets. Most water vapor produced by the comet is ultimately photodissociated into two H atoms and one O atom producing a huge atomic hydrogen coma that is routinely observed in the daily full-sky SWAN images in comets of sufficient brightness. Water production rates are calculated using our time-resolved model (Mäkinen & Combi, 2005, Icarus 177, 217), typically yielding about 1 observation every 2 days on the average. Here we describe the progress in analysis of observations of comets observed during 2013-2014 and those selected from the archive for analysis. These include comets 2P/Encke (2013), 45P/Honda Mrkos-Pajdusakova (2011), C/2013 R1 (Lovejoy), as well as C/2013 A1 (Siding Spring), for which results are expected. A status report on the entire SOHO/SWAN archive of water production rates in comets will be given. SOHO is an international cooperative mission between ESA and NASA. Support from grants NNX11AH50G from the NASA Planetary Astronomy Program and NNX13AQ66G from the NASA Planetary Mission Data Analysis Program are gratefully acknowledged.

Echicetin Coated Polystyrene Beads: A Novel Tool to Investigate GPIb-Specific Platelet Activation and Aggregation

PubMed Central

Petunin, Alexey; Clemetson, Kenneth J.; Gambaryan, Stepan; Walter, Ulrich

2014-01-01

von Willebrand factor/ristocetin (vWF/R) induces GPIb-dependent platelet agglutination and activation of αIIbβ3 integrin, which also binds vWF. These conditions make it difficult to investigate GPIb-specific signaling pathways in washed platelets. Here, we investigated the specific mechanisms of GPIb signaling using echicetin-coated polystyrene beads, which specifically activate GPIb. We compared platelet activation induced by echicetin beads to vWF/R. Human platelets were stimulated with polystyrene beads coated with increasing amounts of echicetin and platelet activation by echicetin beads was then investigated to reveal GPIb specific signaling. Echicetin beads induced αIIbβ3-dependent aggregation of washed platelets, while under the same conditions vWF/R treatment led only to αIIbβ3-independent platelet agglutination. The average distance between the echicetin molecules on the polystyrene beads must be less than 7 nm for full platelet activation, while the total amount of echicetin used for activation is not critical. Echicetin beads induced strong phosphorylation of several proteins including p38, ERK and PKB. Synergistic signaling via P2Y12 and thromboxane receptor through secreted ADP and TxA2, respectively, were important for echicetin bead triggered platelet activation. Activation of PKG by the NO/sGC/cGMP pathway inhibited echicetin bead-induced platelet aggregation. Echicetin-coated beads are powerful and reliable tools to study signaling in human platelets activated solely via GPIb and GPIb-triggered pathways. PMID:24705415

Basket design as a factor in retention and release of calculi in vitro.

PubMed

Zeltser, Ilia S; Bagley, Demetrius H

2007-03-01

To compare stone retrieval and release from seven basket designs in vitro. We tested two tipped and one tipless NCompass models, three other tipless Nitinol designs (NCircle, Sur-Catch, and Dimension), and the Segura Hemisphere for their ability to retrieve and release single beads 8, 6, 5.6, and 5 mm diameter and multiple beads 3.6 mm diameter in both a ureteral and a caliceal model in three separate attempts. In the ureteral model, all baskets were successful in retrieving all sizes of single beads. With multiple 3.6-mm beads, only the NCompass and Dimension designs were able to retrieve at least two of three beads in all attempts. With the exception of the Segura Hemisphere, all designs were successful in releasing all bead sizes. In the caliceal model, only the NCircle, Dimension, and tipless NCompass models were able to retrieve all bead sizes in 100% of the trials. The tipped NCompass and Hemisphere designs were unable to retrieve any beads in this model. The Sur-Catch basket was successful in the retrieval of large beads only. The Dimension articulating design was the only basket able to release all bead sizes in all attempts. The tipless NCompass basket did not release any of the beads once engaged. Nitinol basket designs show excellent retrieval and release capabilities in the in-vitro ureteral model. The articulating Nitinol basket has the best stone-releasing capability of all baskets tested.

Rhenium-coated glass beads for intracolonic administration attenuate TNBS-induced colitis in mice: Proof-of-Concept Study.

PubMed

Siczek, Krzysztof; Zatorski, Hubert; Pawlak, Wojciech; Fichna, Jakub

2015-01-01

In search for novel effective treatments in inflammatory bowel diseases, a new strategy employing glass beads coated with rhenium nanolayer has been developed and validated in the mouse model of 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis. Briefly, mice were randomly divided into 5 experimental groups: control (vehicle alone, Group 1); control treated with rhenium-coated glass beads (Group 2); TNBS (Group 3); TNBS treated with rhenium-coated glass beads (Group 4); and TNBS treated with uncoated glass beads (Group 5). Mice from Group 2, 4 and 5 were treated with respective beads (once daily, 5 beads / animal, i.c.) between D3-D6 post-TNBS/vehicle and evaluation of colonic damage was performed on D7, based on macroscopic scoring and clinical parameters. Severe colonic inflammation developed in post-TNBS mice (Group 3) [P <0.001 vs. control (Group 1) for macroscopic score], which was significantly attenuated by treatment with rhenium-coated glass beads (Group 4) [P <0.01 vs. TNBS (Group 3), for macroscopic score]. Neither rhenium-coated glass beads had any effect in control animals (Group 2), nor uncoated glass beads influenced TNBS-induced colitis (Group 5). In conclusion, a novel and attractive strategy for the treatment of colonic inflammation has been proposed; therapy with rhenium-coated glass beads already proved effective in the mouse model of TNBS-induced colitis, now requires further characterization in clinical conditions.

Air and Space Power Journal. Volume 20, Number 1, Spring 2006

DTIC Science & Technology

2006-01-01

to Farquhar, inadequate strategic reconnaissance dictated that emergency war plans, such as Pincher, Broiler , and Offtackle, include atomic bombing...would do well to read this book, digest its essays, and do what they can to make the most out of the next 30 years of our all-volunteer force

Exchange spring in A1/L1{sub 0} FePt composite and its application in magnetic force microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Guoqing, E-mail: gqli@swu.edu.cn; Zhu, Yanyan, E-mail: zhubai@swu.edu.cn; Zhang, Yong

2015-02-23

This paper reported fabrication of Fe{sub x}Pt{sub 100-x} films with (001) epitaxy on MgO(100) substrates. The atomic percentage of Fe was changed within the range of x = 10–85 in order to search the optimal atomic ratio for achieving both high and isotropic-like coercivity. It was found that the Fe{sub 60}Pt{sub 40} film exhibited large coercivities exceeding 5 kOe along both in-plane and out-of-plane directions due to the formation of A1/L1{sub 0} FePt composite. A penta-domain model for hard/soft/hard exchange spring system was proposed to interpret the anomalous magnetization behaviors observed in Fe{sub 60}Pt{sub 40} sample. By using Fe{sub 60}Pt{sub 40} asmore » the magnetic coating layer on a probe of magnetic force microscope, the flux changes at a linear density of 1000 kfci could be readily observed at a resolution of ∼13 nm.« less

Zero and root loci of disturbed spring–mass systems

PubMed Central

Lecomte, Christophe

2014-01-01

Models consisting of chains of particles that are coupled to their neighbours appear in many applications in physics or engineering, such as in the study of dynamics of mono-atomic and multi-atomic lattices, the resonances of crystals with impurities and the response of damaged bladed discs. Analytical properties of the dynamic responses of such disturbed chains of identical springs and masses are presented, including when damping is present. Several remarkable properties in the location of the resonances (poles) and anti-resonances (zeros) of the displacements in the frequency domain are presented and proved. In particular, it is shown that there exists an elliptical region in the frequency–disturbance magnitude plane from which zeros are excluded and the discrete values of the frequency and disturbance at which double poles occur are identified. A particular focus is on a local disturbance, such as when a spring or damper is modified at or between the first and last masses. It is demonstrated how, notably through normalization, the techniques and results of the paper apply to a broad category of more complex systems in physics, chemistry and engineering. PMID:24711724

Structurally stable gel bead containing entrapped enzyme and method for manufacture thereof

DOEpatents

Woodward, J.

1998-12-08

This research provides a structurally stable gel bead containing an entrapped enzyme and a method for its manufacture. The enzyme is covalently cross-linked to gelatin in the presence of glutaraldehyde prior to the formation of the gel bead, to prevent leakage of the enzyme. Propylene glycol alginate is then added to the mixture. Once the gel beads are formed, they are then soaked in glutaraldehyde, which imparts structural stability to the gel beads. This method can be used with many types of enzymes, such as proteases, carbohydrases, proteases, ligases, isomerases, oxidoreductases, and specialty enzymes. These and other enzymes can be immobilized in the gel beads and utilized in a number of enzymatic processes. Exogenously added ions are not required to maintain the structural stability of these gel beads. 7 figs.

Structurally stable gel bead containing entrapped enzyme and method for manufacture thereof

DOEpatents

Woodward, Jonathan

1998-01-01

A structurally stable gel bead containing an entrapped enzyme and a method for its manufacture. The enzyme is covalently cross-linked to gelatin in the presence of glutaraldehyde prior to the formation of the gel bead, to prevent leakage of the enzyme. Propylene glycol alginate is then added to the mixture. Once the gel beads are formed, they are then soaked in glutaraldehyde, which imparts structural stability to the gel beads. This method can be used with many types of enzymes, such as proteases, carbohydrases, proteases, ligases, isomerases, oxidoreductases, and specialty enzymes. These and other enzymes can be immobilized in the gel beads and utilized in a number of enzymatic processes. Exogenously added ions are not required to maintain the structural stability of these gel beads.

Development of electrospun beaded fibers from Thai silk fibroin and gelatin for controlled release application.

PubMed

Somvipart, Siraporn; Kanokpanont, Sorada; Rangkupan, Rattapol; Ratanavaraporn, Juthamas; Damrongsakkul, Siriporn

2013-04-01

Thai silk fibroin and gelatin are attractive biomaterials for tissue engineering and controlled release applications due to their biocompatibility, biodegradability, and bioactive properties. The development of electrospun fiber mats from silk fibroin and gelatin were reported previously. However, burst drug release from such fiber mats remained the problem. In this study, the formation of beads on the fibers aiming to be used for the sustained release of drug was of our interest. The beaded fiber mats were fabricated using electrospinning technique by controlling the solution concentration, weight blending ratio of Thai silk fibroin/gelatin blend, and applied voltage. It was found that the optimal conditions including the solution concentration and the weight blending ratio of Thai silk fibroin/gelatin at 8-10% (w/v) and 70/30, respectively, with the applied voltage at 18 kV provided the fibers with homogeneous formation of beads. Then, the beaded fiber mats obtained were crosslinked by the reaction of carbodiimide hydrochloride (EDC)/N-hydroxysuccinimide (NHS). Methylene blue as a model active compound was loaded on the fiber mats. The release test of methylene blue from the beaded fiber mats was carried out in comparison to that of the smooth fiber mats without beads. It was found that the beaded fiber mats could prolong the release of methylene blue, comparing to the smooth fiber mats without beads. This was possibly due to the beaded fiber mats that would absorb and retain higher amount of methylene blue than the fiber mats without beads. Thai silk fibroin/gelatin beaded fiber mats were established as an effective carrier for the controlled release applications. Copyright © 2013 Elsevier B.V. All rights reserved.

Formulation and characterization of a compacted multiparticulate system for modified release of water-soluble drugs--Part II theophylline and cimetidine.

PubMed

Cantor, Stuart L; Hoag, Stephen W; Augsburger, Larry L

2009-05-01

The purpose was to investigate the effectiveness of an ethylcellulose (EC) bead matrix and different film-coating polymers in delaying drug release from compacted multiparticulate systems. Formulations containing theophylline or cimetidine granulated with Eudragit RS 30D were developed and beads were produced by extrusion-spheronization. Drug beads were coated using 15% wt/wt Surelease or Eudragit NE 30D and were evaluated for true density, particle size, and sphericity. Lipid-based placebo beads and drug beads were blended together and compacted on an instrumented Stokes B2 rotary tablet press. Although placebo beads were significantly less spherical, their true density of 1.21 g/cm(3) and size of 855 mum were quite close to Surelease-coated drug beads. Curing improved the crushing strength and friability values for theophylline tablets containing Surelease-coated beads; 5.7 +/- 1.0 kP and 0.26 +/- 0.07%, respectively. Dissolution profiles showed that the EC matrix only provided 3 h of drug release. Although tablets containing Surelease-coated theophylline beads released drug fastest overall (t(44.2%) = 8 h), profiles showed that coating damage was still minimal. Size and density differences indicated a minimal segregation potential during tableting for blends containing Surelease-coated drug beads. Although modified release profiles >8 h were achievable in tablets for both drugs using either coating polymer, Surelease-coated theophylline beads released drug fastest overall. This is likely because of the increased solubility of theophylline and the intrinsic properties of the Surelease films. Furthermore, the lipid-based placebos served as effective cushioning agents by protecting coating integrity of drug beads under a number of different conditions while tableting.

Guar gum succinate-sodium alginate beads as a pH-sensitive carrier for colon-specific drug delivery.

PubMed

Seeli, D Sathya; Dhivya, S; Selvamurugan, N; Prabaharan, M

2016-10-01

Guar gum succinate - sodium alginate (GGS-SA) beads cross-linked with barium ions were prepared and characterized as a pH sensitive carrier for colon-specific drug delivery. The structure of GGS-SA beads was confirmed by FT-IR spectroscopy. Scanning Electron Microscope (SEM) studies revealed that the drug loaded GGS-SA beads prepared using 2:2 (w/v) weight percent of GGS and SA had a diameter about 1.4mm and roughly spherical in shape. X-ray diffraction (XRD) studies showed that the peaks corresponding to GGS and SA at 13.5°, 17.5°, 20.2° and 13.5°, 22°, 24.1°, respectively were destroyed in GGS-SA beads which show that these beads are more amorphous in nature. Swelling studies demonstrated the pH-dependent swelling behavior of GGS-SA beads. The beads showed higher swelling degrees in pH 7.4 than that in pH 1.2 due to the existence of anionic groups in the polymer chains. The drug release study showed that the amount of model drug, ibuprofen, released from the GGS-SA beads was higher in pH 7.4 than that in pH 1.2 due to the pH-dependent swelling behavior of the beads. MTT assay revealed that GGS-SA beads at a concentration range of 0-30μg/ml had no cytotoxic effect on the cultured mouse mesenchymal stem cells (C3H10T1/2). These results suggest that GGS-SA beads can be used as effective colon-specific drug delivery system with pH-dependent drug release ability. Copyright © 2016 Elsevier B.V. All rights reserved.

Steady-state force-velocity relation in the ATP-dependent sliding movement of myosin-coated beads on actin cables in vitro studied with a centrifuge microscope.

PubMed Central

Oiwa, K; Chaen, S; Kamitsubo, E; Shimmen, T; Sugi, H

1990-01-01

To eliminate the gap between the biochemistry of actomyosin in solution and the physiology of contracting muscle, we developed an in vitro force-movement assay system in which the steady-state force-velocity relation in the actin-myosin interaction can be studied. The assay system consists of the internodal cells of an alga, Nitellopsis obtusa, containing well-organized actin filament arrays (actin cables); tosyl-activated polystyrene beads (diameter, 2.8 microns; specific gravity, 1.3) coated with skeletal muscle myosin; and a centrifuge microscope equipped with a stroboscopic light source and a video system. The internodal cell preparation was mounted on the rotor of the centrifuge microscope, so that centrifugal forces were applied to the myosin-coated beads moving along the actin cables in the presence of ATP. Under constant centrifugal forces directed opposite to the bead movement ("positive" loads), the beads continued to move with constant velocities, which decreased with increasing centrifugal forces. The steady-state force-velocity curve thus obtained was analogous to the double-hyperbolic force-velocity curve of single muscle fibers. The unloaded velocity of bead movement was 1.6-3.6 microns/s (20-23 degrees C), while the maximum "isometric" force generated by the myosin molecules on the bead was 1.9-39 pN. If, on the other hand, the beads were subjected to constant centrifugal forces in the direction of bead movement ("negative" loads), the bead also moved with constant velocities. Unexpectedly, the velocity of bead movement did not increase with increasing negative loads but first decreased by 20-60% and then increased towards the initial unloaded velocity until the beads were eventually detached from the actin cables. Images PMID:2236007

Steady-state force-velocity relation in the ATP-dependent sliding movement of myosin-coated beads on actin cables in vitro studied with a centrifuge microscope.

PubMed

Oiwa, K; Chaen, S; Kamitsubo, E; Shimmen, T; Sugi, H

1990-10-01

To eliminate the gap between the biochemistry of actomyosin in solution and the physiology of contracting muscle, we developed an in vitro force-movement assay system in which the steady-state force-velocity relation in the actin-myosin interaction can be studied. The assay system consists of the internodal cells of an alga, Nitellopsis obtusa, containing well-organized actin filament arrays (actin cables); tosyl-activated polystyrene beads (diameter, 2.8 microns; specific gravity, 1.3) coated with skeletal muscle myosin; and a centrifuge microscope equipped with a stroboscopic light source and a video system. The internodal cell preparation was mounted on the rotor of the centrifuge microscope, so that centrifugal forces were applied to the myosin-coated beads moving along the actin cables in the presence of ATP. Under constant centrifugal forces directed opposite to the bead movement ("positive" loads), the beads continued to move with constant velocities, which decreased with increasing centrifugal forces. The steady-state force-velocity curve thus obtained was analogous to the double-hyperbolic force-velocity curve of single muscle fibers. The unloaded velocity of bead movement was 1.6-3.6 microns/s (20-23 degrees C), while the maximum "isometric" force generated by the myosin molecules on the bead was 1.9-39 pN. If, on the other hand, the beads were subjected to constant centrifugal forces in the direction of bead movement ("negative" loads), the bead also moved with constant velocities. Unexpectedly, the velocity of bead movement did not increase with increasing negative loads but first decreased by 20-60% and then increased towards the initial unloaded velocity until the beads were eventually detached from the actin cables.

Force measurements of a magnetic micro actuator proposed for a microvalve array

NASA Astrophysics Data System (ADS)

Chang, Pauline J.; Chang, Frank W.; Yuen, Michelle C.; Otillar, Robert; Horsley, David A.

2014-03-01

Low-cost, easily-fabricated and power-efficient microvalves are necessary for many microfluidic lab-on-a-chip applications. In this study, we present a simple, low-power, scalable, CMOS-compatible magnetic actuator for microvalve applications composed of a paramagnetic bead as the ball valve over a picoliter reaction well etched into a silicon substrate. The paramagnetic bead, composed of either pure FeSi or magnetite in a SiO2 matrix, is actuated by the local magnetic field gradient generated by a microcoil in an aqueous environment, and the reaction well is situated at the microcoil center. A permanent magnet beneath the microvalve device provides an external magnetic biasing field that magnetizes the bead, enabling bidirectional actuation and reducing the current required to actuate the bead to a level below 10 mA. The vertical and radial magnetic forces exerted on the bead by the microcoil were measured for both pure FeSi and composite beads and agree well with the predictions of 2D axisymmetric finite element method models. Vertical forces were within a range of 13-80 nN, and radial forces were 11-60 nN depending on the bead type. The threshold current required to initiate bead actuation was measured as a function of bead diameter and is found to scale inversely with volume for small beads, as expected based on the magnetic force model. To provide an estimate of the stiction force acting between the bead and the passivation layer on the substrate, repeated actuation trials were used to study the bead throw distance for substrates coated with silicon dioxide, Parylene-C, and photoresist. The stiction observed was lowest for a photoresist-coated substrate, while silicon dioxide and Parylene-C coated substrates exhibited similar levels of stiction.

Method for preparing dielectric composite materials

DOEpatents

Lauf, Robert J.; Anderson, Kimberly K.; Montgomery, Frederick C.; Collins, Jack L.; Felten, John J.

2004-11-23

The invention allows the fabrication of small, dense beads of dielectric materials with selected compositions, which are incorporated into a polymeric matrix for use in capacitors, filters, and the like. A porous, generally spherical bead of hydrous metal oxide containing titanium or zirconium is made by a sol-gel process to form a substantially rigid bead having a generally fine crystallite size and correspondingly finely distributed internal porosity. The resulting gel bead may be washed and hydrothermally reacted with a soluble alkaline earth salt (typically Ba or Sr) at elevated temperature and pressure to convert the bead into a mixed hydrous titanium- or zirconium-alkaline earth oxide while retaining the generally spherical shape. Alternatively, the gel bead may be made by coprecipitation. This mixed oxide bead is then washed, dried and calcined to produce the desired (BaTiO.sub.3, PbTiO.sub.3, SrZrO.sub.3) structure. The sintered beads are incorporated into a selected polymer matrix. The resulting dielectric composite material may be electrically "poled" if desired.

Dielectric composite materials and method for preparing

DOEpatents

Lauf, Robert J.; Anderson, Kimberly K.; Montgomery, Frederick C.; Collins, Jack L.; Felten, John J.

2003-07-29

The invention allows the fabrication of small, dense beads of dielectric materials with selected compositions, which are incorporated into a polymeric matrix for use in capacitors, filters, and the like. A porous, generally spherical bead of hydrous metal oxide containing titanium or zirconium is made by a sol-gel process to form a substantially rigid bead having a generally fine crystallite size and correspondingly finely distributed internal porosity. The resulting gel bead may be washed and hydrothermally reacted with a soluble alkaline earth salt (typically Ba or Sr) at elevated temperature and pressure to convert the bead into a mixed hydrous titanium- or zirconium-alkaline earth oxide while retaining the generally spherical shape. Alternatively, the gel bead may be made by coprecipitation. This mixed oxide bead is then washed, dried and calcined to produce the desired (BaTiO.sub.3, PbTiO.sub.3, SrZrO.sub.3) structure. The sintered beads are incorporated into a selected polymer matrix. The resulting dielectric composite material may be electrically "poled" if desired.

Superparamagnetic poly(methyl methacrylate) beads for nattokinase purification from fermentation broth.

PubMed

Yang, Chengli; Xing, Jianmin; Guan, Yueping; Liu, Huizhou

2006-09-01

An effective method for purification of nattokinase from fermentation broth using magnetic poly(methyl methacrylate) (PMMA) beads immobilized with p-aminobenzamidine was proposed in this study. Firstly, magnetic PMMA beads with a narrow size distribution were prepared by spraying suspension polymerization. Then, they were highly functionalized via transesterification reaction with polyethylene glycol. The surface hydroxyl-modified magnetic beads obtained were further modified with chloroethylamine to transfer the surface amino-modified magnetic functional beads. The morphology and surface functionality of the magnetic beads were examined by scanning electron microscopy and Fourier transform infrared. An affinity ligand, p-aminobenzamidine was covalently immobilized to the amino-modified magnetic beads by the glutaraldehyde method for nattokinase purification directly from the fermentation broth. The purification factor and the recovery of the enzyme activity were found to be 8.7 and 85%, respectively. The purification of nattokinase from fermentation broth by magnetic beads only took 40 min, which shows a very fast purification of nattokinase compared to traditional purification methods.

Stability optimization of microbial surface-enhanced Raman spectroscopy detection with immunomagnetic separation beads

NASA Astrophysics Data System (ADS)

Uusitalo, Sanna; Kögler, Martin; Välimaa, Anna-Liisa; Petäjä, Jarno; Kontturi, Ville; Siitonen, Samuli; Laitinen, Riitta; Kinnunen, Matti; Viitala, Tapani; Hiltunen, Jussi

2017-03-01

Immunomagnetic separation (IMS) beads with antibody coating are an interesting option for biosensing applications for the identification of biomolecules and biological cells, such as bacteria. The paramagnetic properties of the beads can be utilized with optical sensing by migrating and accumulating the beads and the bound analytes toward the focus depth of the detection system by an external magnetic field. The stability of microbial detection with IMS beads was studied by combining a flexible, inexpensive, and mass producible surface-enhanced Raman spectroscopy (SERS) platform with gold nanoparticle detection and antibody recognition by the IMS beads. Listeria innocua ATCC 33090 was used as a model sample and the effect of the IMS beads on the detected Raman signal was studied. The IMS beads were deposited into a hydrophobic sample well and accumulated toward the detection plane by a neodymium magnet. For the first time, it was shown that the spatial stability of the detection could be improved up to 35% by using IMS bead capture and sample well placing. The effect of a neodymium magnet under the SERS chip improved the temporal detection and significantly reduced the necessary time for sample stabilization for advanced laboratory testing.

Facile fabrication and characterization of a novel oral pH-sensitive drug delivery system based on CMC hydrogel and HNT-AT nanohybrid.

PubMed

Hossieni-Aghdam, Seyed Jamal; Foroughi-Nia, Behrouz; Zare-Akbari, Zhila; Mojarad-Jabali, Solmaz; Motasadizadeh, Hamidreza; Farhadnejad, Hassan

2018-02-01

The main aim of the present study was to design pH-sensitive bionanocomposite hydrogel beads based on CMC and HNT-AT nanohybrid and evaluate whether prepared bionanocomposite beads have the potential to be used in drug delivery applications. Atenolol (AT), as a model drug, was incorporated into the lumen of HA nanotubes via the co-precipitation technique. HNT/AT nanohybrid and CMC/HNT-AT beads were characterized via XRD, SEM, TGA, and FT-IR techniques. Drug loading and encapsulation efficiency was found to be high for CMC/HNT3 beads. Moreover, the swelling and drug release properties of the prepared CMC/HA-AT beads were investigated, and showed a pH sensitive swelling behavior with maximum its content at pH 6.8. Also, it was found that the swelling ratio of CMC/HNT beads was lower than that of pristine CMC beads. Drug release behavior of CMC/HNT-AT bionanocomposite hydrogel beads were investigated. A more sustained and controlled drug releases were observed for CMC/HNT-AT beads. Copyright © 2017 Elsevier B.V. All rights reserved.

The elution of colistimethate sodium from polymethylmethacrylate and calcium phosphate cement beads.

PubMed

Waterman, Paige; Barber, Melissa; Weintrob, Amy C; VanBrakle, Regina; Howard, Robin; Kozar, Michael P; Andersen, Romney; Wortmann, Glenn

2012-06-01

Gram-negative bacilli resistance to all antibiotics, except for colistimethate sodium (CMS), is an emerging healthcare concern. Incorporating CMS into orthopedic cement to treat bone and soft-tissue infections due to these bacteria is attractive, but the data regarding the elution of CMS from cement are conflicting. The in vitro analysis of the elution of CMS from polymethylmethacrylate (PMMA) and calcium phosphate (CP) cement beads is reported. PMMA and CP beads containing CMS were incubated in phosphate-buffered saline and the eluate sampled at sequential time points. The inhibition of the growth of a strain of Acinetobacter baumannii complex by the eluate was measured by disk diffusion and microbroth dilution assays, and the presence of CMS in the eluate was measured by mass spectroscopy. Bacterial growth was inhibited by the eluate from both PMMA and CP beads. Mass spectroscopy demonstrated greater elution of CMS from CP beads than PMMA beads. The dose of CMS in PMMA beads was limited by failure of bead integrity. CMS elutes from both CP and PMMA beads in amounts sufficient to inhibit bacterial growth in vitro. The clinical implications of these findings require further study.

Alginate Beads as Synthetic Inoculant Carriers for Slow Release of Bacteria That Affect Plant Growth †‡

PubMed Central

Bashan, Yoav

1986-01-01

Uniform synthetic beads were developed as carriers for the bacterial inoculation of plants. The beads are made of sodium alginate and skim milk and contain a large reservoir of bacterial culture which releases the bacteria at a slow and constant rate. The beads are biodegradable and produce no environmental pollution. The strength of the beads, the rate of bacterial release, and the time of their survival in the soil can be controlled by several hardening treatments. The final product, lyophilized beads, is simple to use and is applied to the seeds concomitantly with sowing. The released bacteria are available for root colonization immediately at seed germination. Dry beads containing bacteria can be stored at ambient temperature over a long period without loss of bacterial content; storage requires a limited space, and the quality control of a number of bacteria in the bead is simple. The level of plant inoculation with beads was similar to that with previously used peat inoculants, but the former method yielded more consistent results, as the frequency of inoculated plants was much higher. The former method provides a different approach for inoculation of plants with beneficial rhizosphere bacteria. Images PMID:16347055

A new efficient method of generating photoaffinity beads for drug target identification.

PubMed

Nishiya, Yoichi; Hamada, Tomoko; Abe, Masayuki; Takashima, Michio; Tsutsumi, Kyoko; Okawa, Katsuya

2017-02-15

Affinity purification is one of the most prevalent methods for the target identification of small molecules. Preparation of an appropriate chemical for immobilization, however, is a tedious and time-consuming process. A decade ago, a photoreaction method for generating affinity beads was reported, where compounds are mixed with agarose beads carrying a photoreactive group (aryldiazirine) and then irradiated with ultraviolet light under dry conditions to form covalent attachment. Although the method has proven useful for identifying drug targets, the beads suffer from inefficient ligand incorporation and tend to shrink and aggregate, which can cause nonspecific binding and low reproducibility. We therefore decided to craft affinity beads free from these shortcomings without compromising the ease of preparation. We herein report a modified method; first, a compound of interest is mixed with a crosslinker having an activated ester and a photoreactive moiety on each end. This mixture is then dried in a glass tube and irradiated with ultraviolet light. Finally, the conjugates are dissolved and reacted with agarose beads with a primary amine. This protocol enabled us to immobilize compounds more efficiently (approximately 500-fold per bead compared to the original method) and generated beads without physical deterioration. We herein demonstrated that the new FK506-immobilized beads specifically isolated more FKBP12 than the original beads, thereby proving our method to be applicable to target identification experiments. Copyright © 2017 Elsevier Ltd. All rights reserved.

The profile of adsorbed plasma and serum proteins on methacrylic acid copolymer beads: Effect on complement activation.

PubMed

Wells, Laura A; Guo, Hongbo; Emili, Andrew; Sefton, Michael V

2017-02-01

Polymer beads made of 45% methacrylic acid co methyl methacrylate (MAA beads) promote vascular regenerative responses in contrast to control materials without methacrylic acid (here polymethyl methacrylate beads, PMMA). In vitro and in vivo studies suggest that MAA copolymers induce differences in macrophage phenotype and polarization and inflammatory responses, presumably due to protein adsorption differences between the beads. To explore differences in protein adsorption in an unbiased manner, we used high resolution shotgun mass spectrometry to identify and compare proteins that adsorb from human plasma or serum onto MAA and PMMA beads. From plasma, MAA beads adsorbed many complement proteins, such as C1q, C4-related proteins and the complement inhibitor factor H, while PMMA adsorbed proteins, such as albumin, C3 and apolipoproteins. Because of the differences in complement protein adsorption, follow-up studies focused on using ELISA to assess complement activation. When incubated in serum, MAA beads generated significantly lower levels of soluble C5b9 and C3a/C3a desarg in comparison to PMMA beads, indicating a decrease in complement activation with MAA beads. The differences in adsorbed protein on the two materials likely alter subsequent cell-material interactions that ultimately result in different host responses and local vascularization. Copyright © 2016 Elsevier Ltd. All rights reserved.

Preparation of porous 2,3-dialdehyde cellulose beads crosslinked with chitosan and their application in adsorption of Congo red dye.

PubMed

Ruan, Chang-Qing; Strømme, Maria; Lindh, Jonas

2018-02-01

Micrometer sized 2,3-dialdehyde cellulose (DAC) beads were produced via a recently developed method relying on periodate oxidation of Cladophora nanocellulose. The produced dialdehyde groups and pristine hydroxyl groups provided the DAC beads with a vast potential for further functionalization. The sensitivity of the DAC beads to alkaline conditions, however, limits their possible functionalization and applications. Hence, alkaline-stable and porous cellulose beads were prepared via a reductive amination crosslinking reaction between 2,3-dialdehyde cellulose beads and chitosan. The produced materials were thoroughly characterized with different methods. The reaction conditions, including the amount of chitosan used, conditions for reductive amination, reaction temperature and time, were investigated and the maintained morphology of the beads after exposure to 1M NaOH (aq.) was verified with SEM. Different washing and drying procedures were used and the results were studied by SEM and BET analysis. Furthermore, FTIR, TGA, EDX, XPS, DLS and elemental analysis were performed to characterize the properties of the prepared beads. Finally, the alkaline-stable porous chitosan cross-linked 2,3-dialdehyde cellulose beads were applied as adsorbent for the dye Congo red. The crosslinked beads displayed fast and high adsorption capacity at pH 2 and good desorption properties at pH 12, providing a promising sorption material. Copyright © 2017 Elsevier Ltd. All rights reserved.

Dispersion of fine phosphor particles by newly developed beads mill

NASA Astrophysics Data System (ADS)

Joni, I. Made; Panatarani, C.; Maulana, Dwindra W.

2016-02-01

Fine phosphor Y2O3:Eu3+ particles has advanced properties compare to conventional particles applied for compact fluorescent lamp (CFL) as three band phosphor. However, suspension of fine particles easily agglomerated during preparation of spray coating of the CFL tube. Therefore, it is introduced newly developed beads mill system to disperse fine phosphor. The beads mill consist of glass beads, dispersing chamber (impellers), separator chamber, slurry pump and motors. The first important performance of beads mill is the performance of the designed on separating the beads with the suspended fine particles. We report the development of beads mill and its separation performance vary in flow rate and separator rotation speeds. The 27 kg of glass beads with 30 µm in size was poured into dispersing chamber and then water was pumped continuously through the slurry pump. The samples for the separation test was obtained every 1 hours vary in rotation speed and slurry flow rate. The results shows that the separation performance was 99.99 % obtained for the rotation speed of >1000 rpm and flow rate of 8 L/minute. The performances of the system was verified by dispersing fine phosphor Y2O3:Eu3+ particles with concentration 1 wt.%. From the observed size distribution of particles after beads mill, it is concluded that the current design of bead mill effectively dispersed fine phosphor Y2O3:Eu3+.

Characterization of product capture resin during microbial cultivations.

PubMed

Frykman, Scott; Tsuruta, Hiroko; Galazzo, Jorge; Licari, Peter

2006-06-01

Various bioactive small molecules produced by microbial cultivation are degraded in the culture broth or may repress the formation of additional product. The inclusion of hydrophobic adsorber resin beads to capture these products in situ and remove them from the culture broth can reduce or prevent this degradation and repression. These product capture beads are often subjected to a dynamic and stressful microenvironment for a long cultivation time, affecting their physical structure and performance. Impact and collision forces can result in the fracturing of these beads into smaller pieces, which are difficult to recover at the end of a cultivation run. Various contaminating compounds may also bind in a non-specific manner to these beads, reducing the binding capacity of the resin for the product of interest (fouling). This study characterizes resin bead binding capacity (to monitor bead fouling), and resin bead volume distributions (to monitor bead fracture) for an XAD-16 adsorber resin used to capture epothilone produced during myxobacterial cultivations. Resin fouling was found to reduce the product binding capacity of the adsorber resin by 25-50%. Additionally, the degree of resin bead fracture was found to be dependent on the cultivation length and the impeller rotation rate. Microbial cultivations and harvesting processes should be designed in such a way to minimize bead fragmentation and fouling during cultivation to maximize the amount of resin and associated product harvested at the end of a run.

Magnetic Beads Enhance Adhesion of NIH 3T3 Fibroblasts: A Proof-of-Principle In Vitro Study for Implant-Mediated Long-Term Drug Delivery to the Inner Ear

PubMed Central

Aliuos, Pooyan; Schulze, Jennifer; Schomaker, Markus; Reuter, Günter; Stolle, Stefan R. O.; Werner, Darja; Ripken, Tammo; Lenarz, Thomas; Warnecke, Athanasia

2016-01-01

Introduction Long-term drug delivery to the inner ear may be achieved by functionalizing cochlear implant (CI) electrodes with cells providing neuroprotective factors. However, effective strategies in order to coat implant surfaces with cells need to be developed. Our vision is to make benefit of electromagnetic field attracting forces generated by CI electrodes to bind BDNF-secreting cells that are labelled with magnetic beads (MB) onto the electrode surfaces. Thus, the effect of MB-labelling on cell viability and BDNF production were investigated. Materials and Methods Murine NIH 3T3 fibroblasts—genetically modified to produce BDNF—were labelled with MB. Results Atomic force and bright field microscopy illustrated the internalization of MB by fibroblasts after 24 h of cultivation. Labelling cells with MB did not expose cytotoxic effects on fibroblasts and allowed adhesion on magnetic surfaces with sufficient BDNF release. Discussion Our data demonstrate a novel approach for mediating enhanced long-term adhesion of BDNF-secreting fibroblasts on model electrode surfaces for cell-based drug delivery applications in vitro and in vivo. This therapeutic strategy, once transferred to cells suitable for clinical application, may allow the biological modifications of CI surfaces with cells releasing neurotrophic or other factors of interest. PMID:26918945

Inertial-ordering-assisted droplet microfluidics for high-throughput single-cell RNA-sequencing.

PubMed

Moon, Hui-Sung; Je, Kwanghwi; Min, Jae-Woong; Park, Donghyun; Han, Kyung-Yeon; Shin, Seung-Ho; Park, Woong-Yang; Yoo, Chang Eun; Kim, Shin-Hyun

2018-02-27

Single-cell RNA-seq reveals the cellular heterogeneity inherent in the population of cells, which is very important in many clinical and research applications. Recent advances in droplet microfluidics have achieved the automatic isolation, lysis, and labeling of single cells in droplet compartments without complex instrumentation. However, barcoding errors occurring in the cell encapsulation process because of the multiple-beads-in-droplet and insufficient throughput because of the low concentration of beads for avoiding multiple-beads-in-a-droplet remain important challenges for precise and efficient expression profiling of single cells. In this study, we developed a new droplet-based microfluidic platform that significantly improved the throughput while reducing barcoding errors through deterministic encapsulation of inertially ordered beads. Highly concentrated beads containing oligonucleotide barcodes were spontaneously ordered in a spiral channel by an inertial effect, which were in turn encapsulated in droplets one-by-one, while cells were simultaneously encapsulated in the droplets. The deterministic encapsulation of beads resulted in a high fraction of single-bead-in-a-droplet and rare multiple-beads-in-a-droplet although the bead concentration increased to 1000 μl -1 , which diminished barcoding errors and enabled accurate high-throughput barcoding. We successfully validated our device with single-cell RNA-seq. In addition, we found that multiple-beads-in-a-droplet, generated using a normal Drop-Seq device with a high concentration of beads, underestimated transcript numbers and overestimated cell numbers. This accurate high-throughput platform can expand the capability and practicality of Drop-Seq in single-cell analysis.

Development of hydrogel TentaGel shell-core beads for ultrahigh throughput solution-phase screening of encoded OBOC combinatorial small molecule libraries.

PubMed

Baek, Hyoung Gee; Liu, Ruiwu; Lam, Kit S

2009-01-01

The one-bead one-compound (OBOC) combinatorial library method enables the rapid generation and screening of millions of discrete chemical compounds on beads. Most of the OBOC screening methods require the library compounds to remain tethered to the bead during screening process. Methods have also been developed to release library compounds from immobilized beads for in situ solution phase or "lawn" assays. However, this latter approach, while extremely powerful, is severely limited by the lack of suitable solid supports for such assays. Here, we report on the development of a novel hydrogel TentaGel shell-core (HTSC) bead in which hydrogel is grafted onto the polystyrene-based TentaGel (TG) bead as an outer shell (5-80 mum thick) via free radical surface-initiated polymerization. This novel shell-core bilayer resin enables the preparation of encoded OBOC combinatorial small molecule libraries, such that the library compounds reside on the highly hydrophilic outer layer and the coding tags reside in the polystyrene-based TG core. Using fluorescein as a model small molecule compound, we have demonstrated that fluorescein molecules that have been linked covalently to the hydrogel shell via a disulfide bond could readily diffuse out of the hydrogel layer into the bead surrounding after reduction with dithiothreitol. In contrast, under identical condition, the released fluorescein molecules remained bound to unmodified TG bead. We have prepared an encoded OBOC small molecule library on the novel shell-core beads and demonstrated that the beads can be readily decoded.

Immobilized OBOC combinatorial bead array to facilitate multiplicative screening.

PubMed

Xiao, Wenwu; Bononi, Fernanda C; Townsend, Jared; Li, Yuanpei; Liu, Ruiwu; Lam, Kit S

2013-07-01

One-bead-one-compound (OBOC) combinatorial library screening has been broadly utilized for the last two decades to identify small molecules, peptides or peptidomimetics targeting variable screening probes such as cell surface receptors, bacteria, protein kinases, phosphatases, proteases etc. In previous screening methods, library beads were suspended in solution and screened against one single probe. Only the positive beads were tracked and isolated for additional screens and finally selected for chemical decoding. During this process, the remaining negative beads were not tracked and discarded. Here we report a novel bead immobilization method such that a bead library array can be conveniently prepared and screened in its entirety, sequentially many times with a series of distinct probes. This method not only allows us to increase the screening efficiency but also permits us to determine the binding profile of each and every library bead against a large number of target receptors. As proof of concept, we serially screened a random OBOC disulfide containing cyclic heptapeptide library with three water soluble dyes as model probes: malachite green, bromocresol purple and indigo carmine. This multiplicative screening approach resulted in a rapid determination of the binding profile of each and every bead respective to each of the three dyes. Beads that interacted with malachite green only, bromocresol purple only, or both indigo carmine and bromocresol purple were isolated, and their peptide sequences were determined with microsequencer. Ultimately, the novel OBOC multiplicative screening approach could play a key role in the enhancement of existing on-bead assays such as whole cell binding, bacteria binding, protein binding, posttranslational modifications etc. with increased efficiency, capacity, and specificity.

Fused Bead Analysis of Diogenite Meteorites

NASA Technical Reports Server (NTRS)

Mittlefehldt, D.W.; Beck, B.W.; McSween, H.Y.; Lee, C.T. A.

2009-01-01

Bulk rock chemistry is an essential dataset in meteoritics and planetary science [1]. A common method used to obtain the bulk chemistry of meteorites is ICP-MS. While the accuracy, precision and low detection limits of this process are advantageous [2], the sample size used for analysis (approx.70 mg) can be a problem in a field where small and finite samples are the norm. Fused bead analysis is another bulk rock analytical technique that has been used in meteoritics [3]. This technique involves forming a glass bead from 10 mg of sample and measuring its chemistry using a defocused beam on a microprobe. Though the ICP-MS has lower detection limits than the microprobe, the fused bead method destroys a much smaller sample of the meteorite. Fused bead analysis was initially designed for samples with near-eutectic compositions and low viscosities. Melts generated of this type homogenize at relatively low temperatures and produce primary melts near the sample s bulk composition [3]. The application of fused bead analysis to samples with noneutectic melt compositions has not been validated. The purpose of this study is to test if fused bead analysis can accurately determine the bulk rock chemistry of non-eutectic melt composition meteorites. To determine this, we conduct two examinations of the fused bead. First, we compare ICP-MS and fused bead results of the same samples using statistical analysis. Secondly, we inspect the beads for the presence of crystals and chemical heterogeneity. The presence of either of these would indicate incomplete melting and quenching of the bead.

Accurate Calibration and Uncertainty Estimation of the Normal Spring Constant of Various AFM Cantilevers

PubMed Central

Song, Yunpeng; Wu, Sen; Xu, Linyan; Fu, Xing

2015-01-01

Measurement of force on a micro- or nano-Newton scale is important when exploring the mechanical properties of materials in the biophysics and nanomechanical fields. The atomic force microscope (AFM) is widely used in microforce measurement. The cantilever probe works as an AFM force sensor, and the spring constant of the cantilever is of great significance to the accuracy of the measurement results. This paper presents a normal spring constant calibration method with the combined use of an electromagnetic balance and a homemade AFM head. When the cantilever presses the balance, its deflection is detected through an optical lever integrated in the AFM head. Meanwhile, the corresponding bending force is recorded by the balance. Then the spring constant can be simply calculated using Hooke’s law. During the calibration, a feedback loop is applied to control the deflection of the cantilever. Errors that may affect the stability of the cantilever could be compensated rapidly. Five types of commercial cantilevers with different shapes, stiffness, and operating modes were chosen to evaluate the performance of our system. Based on the uncertainty analysis, the expanded relative standard uncertainties of the normal spring constant of most measured cantilevers are believed to be better than 2%. PMID:25763650

Wetting behavior on hexagonally close-packed polystyrene bead arrays with different topographies.

PubMed

Park, Yi-Seul; Yoon, Seo Young; Lee, Jin Seok

2016-01-21

Herein, we investigated the wetting behavior of hexagonally close-packed polystyrene bead arrays with different bead diameters and surface flatness. The contact angle was found to be influenced by the surface roughness as well as the contact area of the polystyrene bead array with a water droplet.

49 CFR 173.221 - Polymeric beads, expandable and Plastic molding compound.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 2 2011-10-01 2011-10-01 false Polymeric beads, expandable and Plastic molding... Than Class 1 and Class 7 § 173.221 Polymeric beads, expandable and Plastic molding compound. (a) Non-bulk shipments of Polymeric beads (or granules), expandable, evolving flammable vapor and Plastic...

49 CFR 173.221 - Polymeric beads, expandable and Plastic molding compound.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Polymeric beads, expandable and Plastic molding... Than Class 1 and Class 7 § 173.221 Polymeric beads, expandable and Plastic molding compound. (a) Non-bulk shipments of Polymeric beads (or granules), expandable, evolving flammable vapor and Plastic...

49 CFR 173.221 - Polymeric beads, expandable and Plastic molding compound.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 2 2012-10-01 2012-10-01 false Polymeric beads, expandable and Plastic molding... Than Class 1 and Class 7 § 173.221 Polymeric beads, expandable and Plastic molding compound. (a) Non-bulk shipments of Polymeric beads (or granules), expandable, evolving flammable vapor and Plastic...

49 CFR 173.221 - Polymeric beads, expandable and Plastic molding compound.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 2 2014-10-01 2014-10-01 false Polymeric beads, expandable and Plastic molding... Than Class 1 and Class 7 § 173.221 Polymeric beads, expandable and Plastic molding compound. (a) Non-bulk shipments of Polymeric beads (or granules), expandable evolving flammable vapor and Plastic...

49 CFR 173.221 - Polymeric beads, expandable and Plastic molding compound.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 2 2013-10-01 2013-10-01 false Polymeric beads, expandable and Plastic molding... Than Class 1 and Class 7 § 173.221 Polymeric beads, expandable and Plastic molding compound. (a) Non-bulk shipments of Polymeric beads (or granules), expandable evolving flammable vapor and Plastic...

Three-dimensional structure of porcine pancreatic carboxypeptidase B with an acetate ion and two zinc atoms in the active site

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akparov, V. Kh., E-mail: valery@akparov.ru; Timofeev, V. I., E-mail: tostars@mail.ru; Maghsoudi, N. N., E-mail: maghsudi@yahoo.com

2017-03-15

Crystals of porcine pancreatic carboxypeptidase B (CPB) were grown by the capillary counter-diffusion method in the presence of polyethylene glycol and zinc acetate. The three-dimensional structure of CPB was determined at 1.40 Å resolution using the X-ray diffraction data set collected from the crystals of the enzyme at the SPring 8 synchrotron facility and was refined to R{sub fact} = 17.19%, R{sub free} = 19.78%. The structure contains five zinc atoms, two of which are present in the active site of the enzyme, and an acetate ion. The arrangement of an additional zinc atom in the active site and themore » acetate ion is different from that reported by Yoshimoto et al.« less

Coarse-grained model of conformation-dependent electrophoretic mobility and its influence on DNA dynamics

NASA Astrophysics Data System (ADS)

Pandey, Harsh; Underhill, Patrick T.

2015-11-01

The electrophoretic mobility of molecules such as λ -DNA depends on the conformation of the molecule. It has been shown that electrohydrodynamic interactions between parts of the molecule lead to a mobility that depends on conformation and can explain some experimental observations. We have developed a new coarse-grained model that incorporates these changes of mobility into a bead-spring chain model. Brownian dynamics simulations have been performed using this model. The model reproduces the cross-stream migration that occurs in capillary electrophoresis when pressure-driven flow is applied parallel or antiparallel to the electric field. The model also reproduces the change of mobility when the molecule is stretched significantly in an extensional field. We find that the conformation-dependent mobility can lead to a new type of unraveling of the molecule in strong fields. This occurs when different parts of the molecule have different mobilities and the electric field is large.

Computational model of polarized actin cables and cytokinetic actin ring formation in budding yeast

PubMed Central

Tang, Haosu; Bidone, Tamara C.

2015-01-01

The budding yeast actin cables and contractile ring are important for polarized growth and division, revealing basic aspects of cytoskeletal function. To study these formin-nucleated structures, we built a 3D computational model with actin filaments represented as beads connected by springs. Polymerization by formins at the bud tip and bud neck, crosslinking, severing, and myosin pulling, are included. Parameter values were estimated from prior experiments. The model generates actin cable structures and dynamics similar to those of wild type and formin deletion mutant cells. Simulations with increased polymerization rate result in long, wavy cables. Simulated pulling by type V myosin stretches actin cables. Increasing the affinity of actin filaments for the bud neck together with reduced myosin V pulling promotes the formation of a bundle of antiparallel filaments at the bud neck, which we suggest as a model for the assembly of actin filaments to the contractile ring. PMID:26538307

Engineering single-polymer micelle shape using nonuniform spontaneous surface curvature

NASA Astrophysics Data System (ADS)

Moths, Brian; Witten, T. A.

2018-03-01

Conventional micelles, composed of simple amphiphiles, exhibit only a few standard morphologies, each characterized by its mean surface curvature set by the amphiphiles. Here we demonstrate a rational design scheme to construct micelles of more general shape from polymeric amphiphiles. We replace the many amphiphiles of a conventional micelle by a single flexible, linear, block copolymer chain containing two incompatible species arranged in multiple alternating segments. With suitable segment lengths, the chain exhibits a condensed spherical configuration in solution, similar to conventional micelles. Our design scheme posits that further shapes are attained by altering the segment lengths. As a first study of the power of this scheme, we demonstrate the capacity to produce long-lived micelles of horseshoe form using conventional bead-spring simulations in two dimensions. Modest changes in the segment lengths produce smooth changes in the micelle's shape and stability.

Induced movement of the magnetic beads and DNA-based dumbbell in a micro fluidic channel

NASA Astrophysics Data System (ADS)

Babić, B.; Ghai, R.; Dimitrov, K.

2007-12-01

We have explored controlled movement of magnetic beads and a dumbbell structure composed of DNA, a magnetic and a non-magnetic bead in a micro fluidic channel. Movement of the beads and dumbbells is simulated assuming that a net force is described as a superposition between the magnetic and hydrodynamic drag forces. Trajectories of beads and dumbbells are observed with optical light microscopy. The experimentally measured data show a good agreement with the simulations. This dynamical approach offers the prospect to stretch the DNA within the dumbbell and investigate its conformational changes. Further on, we demonstrate that short sonication can reduce multiple attachments of DNA to the beads.

Formation Mechanisms of the Spring-Autumn Asymmetry of the Midlatitudinal NmF2 under Daytime Quiet Geomagnetic Conditions at Low Solar Activity

NASA Astrophysics Data System (ADS)

Pavlov, A. V.; Pavlova, N. M.

2018-05-01

Formation mechanism of the spring-autumn asymmetry of the F2-layer peak electron number density of the midlatitudinal ionosphere, NmF2, under daytime quiet geomagnetic conditions at low solar activity are studied. We used the ionospheric parameters measured by the ionosonde and incoherent scatter radar at Millstone Hill on March 3, 2007, March 29, 2007, September 12, 2007, and September 18, 1984. The altitudinal profiles of the electron density and temperature were calculated for the studied conditions using a one-dimensional, nonstationary, ionosphere-plasmasphere theoretical model for middle geomagnetic latitudes. The study has shown that there are two main factors contributing to the formation of the observed spring-autumn asymmetry of NmF2: first, the spring-autumn variations of the plasma drift along the geomagnetic field due to the corresponding variations in the components of the neutral wind velocity, and, second, the difference between the composition of the neutral atmosphere under the spring and autumn conditions at the same values of the universal time and the ionospheric F2-layer peak altitude. The seasonal variations of the rate of O+(4S) ion production, which are associated with chemical reactions with the participation of the electronically excited ions of atomic oxygen, does not significantly affect the studied NmF2 asymmetry. The difference in the degree of influence of O+(4S) ion reactions with vibrationally excited N2 and O2 on NmF2 under spring and autumn conditions does not significantly change the spring-autumn asymmetry of NmF2.

A Controlled Drug-Delivery Experiment Using Alginate Beads

ERIC Educational Resources Information Center

Farrell, Stephanie; Vernengo, Jennifer

2012-01-01

This paper describes a simple, cost-effective experiment which introduces students to drug delivery and modeling using alginate beads. Students produce calcium alginate beads loaded with drug and measure the rate of release from the beads for systems having different stir rates, geometries, extents of cross-linking, and drug molecular weight.…

Prediction of purification of biopharmeceuticals with molecular dynamics

NASA Astrophysics Data System (ADS)

Ustach, Vincent; Faller, Roland

Purification of biopharmeceuticals remains the most expensive part of protein-based drug production. In ion exchange chromatography (IEX), prediction of the elution ionic strength of host cell and target proteins has the potential to reduce the parameter space for scale-up of protein production. The complex shape and charge distribution of proteins and pores complicates predictions of the interactions in these systems. All-atom molecular dynamics methods are beyond the scope of computational limits for mass transport regimes. We present a coarse-grained model for proteins for prediction of elution pH and ionic strength. By extending the raspberry model for colloid particles to surface shapes and charge distributions of proteins, we can reproduce the behavior of proteins in IEX. The average charge states of titratatable amino acid residues at relevant pH values are determined by extrapolation from all-atom molecular dynamics at pH 7. The pH specific all-atom electrostatic field is then mapped onto the coarse-grained surface beads of the raspberry particle. The hydrodynamics are reproduced with the lattice-Boltzmann scheme. This combination of methods allows very long simulation times. The model is being validated for known elution procedures by comparing the data with experiments. Defense Threat Reduction Agency (Grant Number HDTRA1-15-1-0054).

Degradation of synthetic pollutants in real wastewater using laccase encapsulated in core-shell magnetic copper alginate beads.

PubMed

Le, Thao Thanh; Murugesan, Kumarasamy; Lee, Chung-Seop; Vu, Chi Huong; Chang, Yoon-Seok; Jeon, Jong-Rok

2016-09-01

Immobilization of laccase has been highlighted to enhance their stability and reusability in bioremediation. In this study, we provide a novel immobilization technique that is very suitable to real wastewater treatment. A perfect core-shell system composing copper alginate for the immobilization of laccase (Lac-beads) was produced. Additionally, nFe2O3 was incorporated for the bead recycling through magnetic force. The beads were proven to immobilize 85.5% of total laccase treated and also to be structurally stable in water, acetate buffer, and real wastewater. To test the Lac-beads reactivity, triclosan (TCS) and Remazol Brilliant Blue R (RBBR) were employed. The Lac-beads showed a high percentage of TCS removal (89.6%) after 8h and RBBR decolonization at a range from 54.2% to 75.8% after 4h. Remarkably, the pollutants removal efficacy of the Lac-beads was significantly maintained in real wastewater with the bead recyclability, whereas that of the corresponding free laccase was severely deteriorated. Copyright © 2016 Elsevier Ltd. All rights reserved.

Microfluidic Bead Suspension Hopper

PubMed Central

2014-01-01

Many high-throughput analytical platforms, from next-generation DNA sequencing to drug discovery, rely on beads as carriers of molecular diversity. Microfluidic systems are ideally suited to handle and analyze such bead libraries with high precision and at minute volume scales; however, the challenge of introducing bead suspensions into devices before they sediment usually confounds microfluidic handling and analysis. We developed a bead suspension hopper that exploits sedimentation to load beads into a microfluidic droplet generator. A suspension hopper continuously delivered synthesis resin beads (17 μm diameter, 112,000 over 2.67 h) functionalized with a photolabile linker and pepstatin A into picoliter-scale droplets of an HIV-1 protease activity assay to model ultraminiaturized compound screening. Likewise, trypsinogen template DNA-coated magnetic beads (2.8 μm diameter, 176,000 over 5.5 h) were loaded into droplets of an in vitro transcription/translation system to model a protein evolution experiment. The suspension hopper should effectively remove any barriers to using suspensions as sample inputs, paving the way for microfluidic automation to replace robotic library distribution. PMID:24761972

Bead mediated separation of microparticles in droplets

PubMed Central

Sung, Ki-Joo; Lin, Xiaoxia Nina; Burns, Mark A.

2017-01-01

Exchange of components such as particles and cells in droplets is important and highly desired in droplet microfluidic assays, and many current technologies use electrical or magnetic fields to accomplish this process. Bead-based microfluidic techniques offer an alternative approach that uses the bead’s solid surface to immobilize targets like particles or biological material. In this paper, we demonstrate a bead-based technique for exchanging droplet content by separating fluorescent microparticles in a microfluidic device. The device uses posts to filter surface-functionalized beads from a droplet and re-capture the filtered beads in a new droplet. With post spacing of 7 μm, beads above 10 μm had 100% capture efficiency. We demonstrate the efficacy of this system using targeted particles that bind onto the functionalized beads and are, therefore, transferred from one solution to another in the device. Binding capacity tests performed in the bulk phase showed an average binding capacity of 5 particles to each bead. The microfluidic device successfully separated the targeted particles from the non-targeted particles with up to 98% purity and 100% yield. PMID:28282412

Growth and morphology of thermophilic dairy starters in alginate beads.

PubMed

Lamboley, Laurence; St-Gelais, Daniel; Champagne, Claude P; Lamoureux, Maryse

2003-06-01

The aim of this research was to produce concentrated biomasses of thermophilic lactic starters using immobilized cell technology (ICT). Fermentations were carried out in milk using pH control with cells microentrapped in alginate beads. In the ICT fermentations, beads represented 17% of the weight. Some assays were carried out with free cells without pH control, in order to compare the ICT populations with those of classical starters. With Streptococcus thermophilus, overall populations in the fermentor were similar, but maximum bead population for (8.2 x 10(9) cfu/g beads) was 13 times higher than that obtained in a traditional starter (4.9 x 10(8) cfu/ml). For both Lactobacillus helveticus strains studied, immobilized-cell populations were about 3 x 10(9) cfu/g beads. Production of immobilized Lb. bulgaricus 210R strain was not possible, since no increases in viable counts occurred in beads. Therefore, production of concentrated cell suspension in alginate beads was more effective for S. thermophilus. Photomicrographs of cells in alginate beads demonstrated that, while the morphology of S. thermophilus remained unchanged during the ICT fermentation, immobilized cells of Lb. helveticus appeared wider. In addition, cells of Lb. bulgaricus were curved and elongated. These morphological changes would also impair the growth of immobilized lactobacilli.

In vivo cleansing efficacy of biodegradable exfoliating beads assessed by skin bioengineering techniques.

PubMed

Kitsongsermthon, J; Duangweang, K; Kreepoke, J; Tansirikongkol, A

2017-11-01

The plastic microbeads, used in many cleansers, will be banned in cosmetic and personal care products within 2017 since they are non-degradable and can disturb the living organisms in water reservoirs. Various choices of biodegradable beads are commercially available, but their efficacy has not been proven yet. This study aimed to compare the cleansing efficacy in dirt and sebum removal aspects of three types of exfoliating beads. The gel scrubs with polyethylene (PE) beads, mannan beads or wax beads, were formulated and evaluated for their stability. The in vivo evaluation was done in 38 healthy volunteers and the skin irritation, efficacy for dirt and sebum removal were measured by Mexameter ® , Colorimeter ® , and Sebumeter ® , respectively. The selected gel scrubs did not cause an irritation in any volunteers. The differences in dirt residues between before and after scrubbing were not statistically significant among three gel scrubs and the similar result was also reported in the sebum removal study. All gel scrubs demonstrated the comparable cleansing efficacy in term of dirt and sebum removal. Thus, mannan beads and wax beads may be replaced non-biodegradable PE beads to achieve the similar cleansing effect. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Development of bioactive porous α-TCP/HAp beads for bone tissue engineering.

PubMed

Asaoka, Teruo; Ohtake, Shoji; Furukawa, Katsuko S; Tamura, Akito; Ushida, Takashi

2013-11-01

Porous beads of bioactive ceramics such as hydroxyapatite (HAp) and tribasic calcium phosphate (TCP) are considered a promising scaffold for cultivating bone cells. To realize this, α-TCP/HAp functionally graded porous beads are fabricated with two main purposes: to maintain the function of the scaffold with sufficient strength up to the growth of new bone, and is absorbed completely after the growth. HAp is a bioactive material that has both high strength and strong tissue-adhesive properties, but is not readily absorbed by the human body. On the contrary, α-TCP is highly bioabsorbable, resulting in a scaffold that is absorbed before it is completely replaced by bone. In this study, we produced porous, bead-shaped carriers as scaffolds for osteoblast culture. To control the solubility in vivo, the fabricated beads contained α-TCP at the center and HAp at the surface. Cell adaptability of these beads for bone tissue engineering was confirmed in vitro. It was found that α-TCP/HAp bead carriers exhibit low toxicity in the initial stages of cell seeding and cell adhesion. The presence of HAp in the composite bead form effectively increased ALP activity. In conclusion, it is suggested that these newly developed α-TCP/HAp beads are a promising tool for bone tissue engineering. Copyright © 2013 Wiley Periodicals, Inc.

Lipase in biphasic alginate beads as a biocatalyst for esterification of butyric acid and butanol in aqueous media.

PubMed

Ng, Choong Hey; Yang, Kun-Lin

2016-01-01

Esterification of organic acids and alcohols in aqueous media is very inefficient due to thermodynamic constraints. However, fermentation processes used to produce organic acids and alcohols are often conducted in aqueous media. To produce esters in aqueous media, biphasic alginate beads with immobilized lipase are developed for in situ esterification of butanol and butyric acid. The biphasic beads contain a solid matrix of calcium alginate and hexadecane together with 5 mg/mL of lipase as the biocatalyst. Hexadecane in the biphasic beads serves as an organic phase to facilitate the esterification reaction. Under optimized conditions, the beads are able to catalyze the production of 0.16 mmol of butyl butyrate from 0.5 mmol of butyric acid and 1.5 mmol of butanol. In contrast, when monophasic beads (without hexadecane) are used, only trace amount of butyl butyrate is produced. One main application of biphasic beads is in simultaneous fermentation and esterification (SFE) because the organic phase inside the beads is very stable and does not leach out into the culture medium. SFE is successfully conducted with an esterification yield of 6.32% using biphasic beads containing iso-octane even though the solvent is proven toxic to the butanol-producing Clostridium spp. Copyright © 2015 Elsevier Inc. All rights reserved.

Microfabricated Renewable Beads-Trapping/Releasing Flow Cell for Rapid Antigen-Antibody Reaction in Chemiluminescent Immunoassay

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fu, Zhifeng; Shao, Guocheng; Wang, Jun

2011-04-01

A filter pillar-array microstructure was coupled with a pneumatic micro-valve to fabricate a reusable miniaturized beads-trapping/releasing flow cell, in which trapping and releasing beads can be conveniently realized by switching the micro-valve. This miniaturized device was suitable to construct automatic fluidic system for “renewable surface analysis”. The renewable surface strategy based on pneumatic micro-valve enabled capture of beads in beads chamber prior to each assay, and release of the used beads after the assay. Chemiluminescent competitive immunoassay of 3,5,6-trichloropyridinol (TCP) was performed as a model to demonstrate the application potential of this reusable miniaturized flow cell. The whole fluidic assaymore » process including beads trapping, immuno-binding, beads washing, beads releasing and signal collection could be completed in 10 min. Immunoassay of TCP using this miniaturized device showed a linear range of 0.20-70 ng/mL with a limit of detection of 0.080 ng/mL. The device had been successfully used for detection of TCP spiked in rat serum with average recovery of 97%. This investigation provides a rapid, sensitive, reusable, low-cost and automatic miniaturized device for solid-phase biochemical analysis for various purposes.« less

Orbeez: the magic water absorbing bead--risk of pediatric bowel obstruction?

PubMed

Darracq, Michael A; Cullen, Jennifer; Rentmeester, Landen; Cantrell, F Lee; Ly, Binh T

2015-06-01

In December 2012, the U.S. Consumer Product Safety Commission recalled the water-absorbing toy WaterBalz after reports of small intestine obstruction after ingestion by children. Orbeez, another water-absorbing bead, remains available and is marketed as a children's toy. We sought to determine the extent to which Orbeez enlarge in various liquid media and the potential risk for bowel obstruction. Three Orbeez beads were added to 210 mL of the following liquid media: room temperature tap water, whole milk, simulated gastric fluid, GoLytely (polyethelyelene glycol, 3350 and electrolytes), and vodka (40% ethanol by volume). Diameters before exposure to media were measured using a caliper to the nearest 0.1 mm and again at 1, 2, 4, 6, 12, and 24 hours. Ten beads were then added to the beads already immersed in simulated gastric fluid and water and observed for an additional 72 hours (96 hours total) for clumping or increase in diameter. Clumping was defined as two or more beads remaining persistently adherent to one another despite gentle circular movement (swirling) of the liquid. Growth in each of the media was observed. Growth in simulated gastric fluid was minimal, whereas the beads were observed to be the largest after 24 hours in vodka. Clumping of the beads was not observed to occur. Orbeez beads enlarge to a different extent in different liquid media. It is unlikely that Orbeez beads would expand to sizes or demonstrate clumping that would be concerning for intestinal obstruction.

Capturing and concentrating adenovirus using magnetic anionic nanobeads

PubMed Central

Sakudo, Akikazu; Baba, Koichi; Ikuta, Kazuyoshi

2016-01-01

We recently demonstrated how various enveloped viruses can be efficiently concentrated using magnetic beads coated with an anionic polymer, poly(methyl vinyl ether-maleic anhydrate). However, the exact mechanism of interaction between the virus particles and anionic beads remains unclear. To further investigate whether these magnetic anionic beads specifically bind to the viral envelope, we examined their potential interaction with a nonenveloped virus (adenovirus). The beads were incubated with either adenovirus-infected cell culture medium or nasal aspirates from adenovirus-infected individuals and then separated from the supernatant by applying a magnetic field. After thoroughly washing the beads, adsorption of adenovirus was confirmed by a variety of techniques, including immunochromatography, polymerase chain reaction, Western blotting, and cell culture infection assays. These detection methods positively identified the hexon and penton capsid proteins of adenovirus along with the viral genome on the magnetic beads. Furthermore, various types of adenovirus including Types 5, 6, 11, 19, and 41 were captured using the magnetic bead procedure. Our bead capture method was also found to increase the sensitivity of viral detection. Adenovirus below the detectable limit for immunochromatography was efficiently concentrated using the magnetic bead procedure, allowing the virus to be successfully detected using this methodology. Moreover, these findings clearly demonstrate that a viral envelope is not required for binding to the anionic magnetic beads. Taken together, our results show that this capture procedure increases the sensitivity of detection of adenovirus and would, therefore, be a valuable tool for analyzing both clinical and experimental samples. PMID:27274228

A calibration method for the higher modes of a micro-mechanical cantilever

NASA Astrophysics Data System (ADS)

Shatil, N. R.; Homer, M. E.; Picco, L.; Martin, P. G.; Payton, O. D.

2017-05-01

Micro-mechanical cantilevers are increasingly being used as a characterisation tool in both material and biological sciences. New non-destructive applications are being developed that rely on the information encoded within the cantilever's higher oscillatory modes, such as atomic force microscopy techniques that measure the non-topographic properties of a sample. However, these methods require the spring constants of the cantilever at higher modes to be known in order to quantify their results. Here, we show how to calibrate the micro-mechanical cantilever and find the effective spring constant of any mode. The method is uncomplicated to implement, using only the properties of the cantilever and the fundamental mode that are straightforward to measure.

Pooling of Immunomagnetic Separation Beads Does Not Affect Detection Sensitivity of Six Major Serogroups of Shiga Toxin-Producing Escherichia coli in Cattle Feces.

PubMed

Noll, Lance W; Baumgartner, William C; Shridhar, Pragathi B; Cull, Charley A; Dewsbury, Diana M; Shi, Xiaorong; Cernicchiaro, Natalia; Renter, David G; Nagaraja, T G

2016-01-01

Shiga toxin-producing Escherichia coli (STEC) of the serogroups O26, O45, O103, O111, O121, and O145, often called non-O157 STEC, are foodborne pathogens. Cattle are asymptomatic reservoirs for STEC; the organisms reside in the hindgut and are shed in the feces, which serve as the source of food product contaminations. Culture-based detection of non-O157 STEC involves an immunomagnetic separation (IMS) step to capture the specific serogroups in complex matrices, such as feces. The IMS procedure is time consuming and labor intensive because of the need to subject each fecal sample to six individual beads. Therefore, our objective was to evaluate whether pooling of IMS beads affects sensitivity of non-O157 STEC detection compared with using individual IMS beads. The evaluation was done by comparing detection of serogroups in feces spiked with pure cultures (experiments 1 and 2) and from feces (n = 384) of naturally shedding cattle (experiment 3). In spiked fecal samples, detection with pools of three, four, six, or seven beads was similar to, or at times higher than, detection with individual IMS beads. In experiment 3, the proportions of fecal samples that tested positive for the six serogroups as detected by individual or pooled beads were similar. Based on noninferiority tests, detection with pooled beads was not substantially inferior to detection with individual beads (P > 0.05). In conclusion, the pooling of IMS beads is a better option for detection of STEC serogroups in fecal samples compared with individual beads because the procedure saves time and labor and has the prospect of a higher throughput.

Effect of Heat Input on Geometry of Austenitic Stainless Steel Weld Bead on Low Carbon Steel

NASA Astrophysics Data System (ADS)

Saha, Manas Kumar; Hazra, Ritesh; Mondal, Ajit; Das, Santanu

2018-05-01

Among different weld cladding processes, gas metal arc welding (GMAW) cladding becomes a cost effective, user friendly, versatile method for protecting the surface of relatively lower grade structural steels from corrosion and/or erosion wear by depositing high grade stainless steels onto them. The quality of cladding largely depends upon the bead geometry of the weldment deposited. Weld bead geometry parameters, like bead width, reinforcement height, depth of penetration, and ratios like reinforcement form factor (RFF) and penetration shape factor (PSF) determine the quality of the weld bead geometry. Various process parameters of gas metal arc welding like heat input, current, voltage, arc travel speed, mode of metal transfer, etc. influence formation of bead geometry. In the current experimental investigation, austenite stainless steel (316) weld beads are formed on low alloy structural steel (E350) by GMAW using 100% CO2 as the shielding gas. Different combinations of current, voltage and arc travel speed are chosen so that heat input increases from 0.35 to 0.75 kJ/mm. Nine number of weld beads are deposited and replicated twice. The observations show that weld bead width increases linearly with increase in heat input, whereas reinforcement height and depth of penetration do not increase with increase in heat input. Regression analysis is done to establish the relationship between heat input and different geometrical parameters of weld bead. The regression models developed agrees well with the experimental data. Within the domain of the present experiment, it is observed that at higher heat input, the weld bead gets wider having little change in penetration and reinforcement; therefore, higher heat input may be recommended for austenitic stainless steel cladding on low alloy steel.

Small Versus Large-Sized Drug-Eluting Beads (DEBIRI) for the Treatment of Hepatic Colorectal Metastases: A Propensity Score Matching Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akinwande, Olaguoke K., E-mail: gokeakin@gmail.com; Philips, Prejesh, E-mail: prejesh.philips@louisville.edu; Duras, Petr, E-mail: durasp@seznam.cz

2015-04-15

PurposeTo compare the feasibility, safety, and efficacy with small and large irinotecan drug-eluting beads (DEBIRI) for treating hepatic colorectal metastases.MethodsUsing our prospectively maintained, multi-center, intra-arterial therapy registry, we identified 196 patients treated with a combination of large beads (100–300 to 500–700 μm) and patients treated with a combination of small beads (70–150 to 100–300 μm). To minimize selection bias, a propensity score analysis was performed to compare both groups.ResultsUnadjusted analysis consisted of 196 and 30 patients treated with large and small beads, respectively. The adjusted analysis consisted of 19 patients each. Unadjusted analysis showed decreased all-grade (p = <0.001) and high-grade adverse effects (p = 0.02)more » in the small bead group, with a persisting trend toward decreased overall side effects in the adjusted analysis favoring small beads (p = 0.09) The adjusted analysis showed the percentage dose delivered (delivered dose/intended dose) was significantly greater in the small bead group compared to the large bead group (96 vs 79 %; p = 0.005). There were also a lower percentage of treatments terminating in complete stasis in the adjusted analysis (0.0035). Adjusted analysis also showed increased objective response rate (ORR) at 12 months (p = 0.04), with a corresponding trend also seen in the unadjusted analysis (0.09).ConclusionSmaller beads result in increased dose delivery probably due to less propensity to reach complete stasis. It may also lead to more durable long-term efficacy. Smaller beads also demonstrate similarly low toxicity compared to large-sized beads with a trend toward less toxicity.« less

Jeffamine derivatized TentaGel beads and poly(dimethylsiloxane) microbead cassettes for ultrahigh-throughput in situ releasable solution-phase cell-based screening of one-bead-one-compound combinatorial small molecule libraries.

PubMed

Townsend, Jared B; Shaheen, Farzana; Liu, Ruiwu; Lam, Kit S

2010-09-13

A method to efficiently immobilize and partition large quantities of microbeads in an array format in microfabricated poly(dimethylsiloxane) (PDMS) cassette for ultrahigh-throughput in situ releasable solution-phase cell-based screening of one-bead-one-compound (OBOC) combinatorial libraries is described. Commercially available Jeffamine triamine T-403 (∼440 Da) was derivatized such that two of its amino groups were protected by Fmoc and the remaining amino group capped with succinic anhydride to generate a carboxyl group. This resulting trifunctional hydrophilic polymer was then sequentially coupled two times to the outer layer of topologically segregated bilayer TentaGel (TG) beads with solid phase peptide synthesis chemistry resulting in beads with increased loading capacity, hydrophilicity, and porosity at the outer layer. We have found that such bead configuration can facilitate ultrahigh-throughput in situ releasable solution-phase screening of OBOC libraries. An encoded releasable OBOC small molecule library was constructed on Jeffamine derivatized TG beads with library compounds tethered to the outer layer via a disulfide linker and coding tags in the interior of the beads. Compound-beads could be efficiently loaded (5-10 min) into a 5 cm diameter Petri dish containing a 10,000-well PDMS microbead cassette, such that over 90% of the microwells were each filled with only one compound-bead. Jurkat T-lymphoid cancer cells suspended in Matrigel were then layered over the microbead cassette to immobilize the compound-beads. After 24 h of incubation at 37 °C, dithiothreitol was added to trigger the release of library compounds. Forty-eight hours later, MTT reporter assay was used to identify regions of reduced cell viability surrounding each positive bead. From a total of about 20,000 beads screened, 3 positive beads were detected and physically isolated for decoding. A strong consensus motif was identified for these three positive compounds. These compounds were resynthesized and found to be cytotoxic (IC(50) 50-150 μM) against two T-lymphoma cell lines and less so against the MDA-MB 231 breast cancer cell line. This novel ultrahigh-throughput OBOC releasable method can potentially be adapted to many existing 96- or 384-well solution-phase cell-based or biochemical assays.

Incorporation of beads into oral films for buccal and oral delivery of bioactive molecules.

PubMed

Castro, Pedro M; Sousa, Flávia; Magalhães, Rui; Ruiz-Henestrosa, Victor Manuel Pizones; Pilosof, Ana M R; Madureira, Ana Raquel; Sarmento, Bruno; Pintado, Manuela E

2018-08-15

The association of alginate beads and guar-gum films in a single delivery system was idealized to promote a more effective buccal and oral delivery of bioactive molecules. A response surface method (experimental design approach) was performed to obtain optimal formulations of alginate beads to be incorporated into guar gum oral films as combined buccal and oral delivery systems for caffeine delivery. The combined formulation was further characterized regarding physicochemical properties, drug release, cell viability and buccal permeability. Beads average size, determined by dynamic light scattering (DLS), was of 3.37 ± 6.36 μm. Film thickness was set to 62 μm. Scanning electron microscopy micrographs revealed that beads were evenly distributed onto the film matrix and beads size was in accordance to data obtained from DLS analysis. Evaluation of Fourier-transform infrared spectra did not indicate the formation of new covalent bonds between the matrix of guar-gum films, alginate beads and caffeine. In vitro release assays by dialysis membrane allowed understanding that the combination of guar-gum films and alginate beads assure a slower release of caffeine when compared with the delivery profile of free caffeine from alginate beads or guar-gum films alone. MTT assay, performed on human buccal carcinoma TR146 cell line, allowed concluding that neither guar-gum film, alginate beads nor guar-gum film incorporated into alginate beads significantly compromised cell viability after 12 h of exposure. As demonstrated by in vitro permeability assay using TR146 human buccal carcinoma cell lines, combination of guar-gum films and alginate beads also promoted a slower release and, thus, lower apparent permeability (1.15E-05 ± 3.50E-06) than for caffeine solution (2.68E-05 ± 7.30E-06), guar-gum film (3.12E-05 ± 4.70E-06) or alginate beads (2.01E-05 ± 3.90E-06). The conjugation of alginate beads within an orodispersible film matrix represents an effective oral/buccal delivery system that induces a controlled release along with an enhanced intimate contact with cell layers that may promote higher in vivo bioavailability of carried drugs. Copyright © 2018. Published by Elsevier Ltd.

Bead-based microfluidic immunoassay for diagnosis of Johne's disease

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wadhwa, Ashutosh; Foote, Robert; Shaw, Robert W

2012-01-01

Microfluidics technology offers a platform for development of point-of-care diagnostic devices for various infectious diseases. In this study, we examined whether serodiagnosis of Johne s disease (JD) can be conducted in a bead-based microfluidic assay system. Magnetic micro-beads were coated with antigens of the causative agent of JD, Mycobacterium avium subsp. paratuberculosis. The antigen-coated beads were incubated with serum samples of JD-positive or negative serum samples and then with a fluorescently-labeled secondary antibody (SAB). To confirm binding of serum antibodies to the antigen, the beads were subjected to flow cytometric analysis. Different conditions (dilutions of serum and SAB, types ofmore » SAB, and types of magnetic beads) were optimized for a great degree of differentiation between the JD-negative and JD-positive samples. Using the optimized conditions, we tested a well-classified set of 155 serum samples from JD negative and JD-positive cattle by using the bead-based flow cytometric assay. Of 105 JD-positive samples, 63 samples (60%) showed higher antibody binding levels than a cut-off value determined by using antibody binding levels of JD-negative samples. In contrast, only 43-49 JD-positive samples showed higher antibody binding levels than the cut-off value when the samples were tested by commercially-available immunoassays. Microfluidic assays were performed by magnetically immobilizing a number of beads within a microchannel of a glass microchip and detecting antibody on the collected beads by laser-induced fluorescence. Antigen-coated magnetic beads treated with bovine serum sample and fluorescently-labeled SAB were loaded into a microchannel to measure the fluorescence (reflecting level of antibody binding) on the beads in the microfluidic system. When the results of five bovine serum samples obtained with the system were compared to those obtained with the flow cytometer, a high level of correlation (linear regression, r2 = 0.994) was observed. In a further experiment, we magnetically immobilized antigen-coated beads in a microchannel, reacted the beads with serum and SAB in the channel, and detected antibody binding to the beads in the microfluidic system. A strong antibody binding in JD-positive serum was detected, whereas there was only negligible binding in negative control experiments. Our data suggest that the bead-based microfluidic system may form a basis for development of an on-site serodiagnosis of JD. Key Words: Mycobacterium avium ssp. paratuberculosis, Johne s disease, microfluidics, lab-on-a-chip.« less

75 FR 68377 - Notice of Inventory Completion: Anthropological Studies Center, Archaeological Collections...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-11-05

... basalt tool, 317 non-human bone fragments, 1 abalone shell fragment, 2 ash/soil samples, 1 groundstone, 1 quartz chunk, 3 abalone pendants and 4 olivella beads. One of the burials identified was associated with... groundstones, 2 steatite beads, 1 abalone pendant, 2 clamshell disk beads, 23 olivella beads and 2 steatite...

COMPARATIVE EVALUATION OF R3f GARNET BEAD FILTRATION AND MULTIMEDIA FILTRATION SYSTEMS; FINAL REPORT

EPA Science Inventory

This report summarizes the results of tests conducted to date at the EPA T&E Facility on the R3f filtration system utilizing fine beads (such as garnet beads or glass beads) and a conventional multimedia filtration system. Both systems have been designed and built by Enprotec, a...

Computer-aided diagnostic detection system of venous beading in retinal images

NASA Astrophysics Data System (ADS)

Yang, Ching-Wen; Ma, DyeJyun; Chao, ShuennChing; Wang, ChuinMu; Wen, Chia-Hsien; Lo, ChienShun; Chung, Pau-Choo; Chang, Chein-I.

2000-05-01

The detection of venous beading in retinal images provides an early sign of diabetic retinopathy and plays an important role as a preprocessing step in diagnosing ocular diseases. We present a computer-aided diagnostic system to automatically detect venous beading of blood vessels. It comprises of two modules, referred to as the blood vessel extraction module and the venus beading detection module. The former uses a bell-shaped Gaussian kernel with 12 azimuths to extract blood vessels while the latter applies a neural network-based shape cognitron to detect venous beading among the extracted blood vessels for diagnosis. Both modules are fully computer-automated. To evaluate the proposed system, 61 retinal images (32 beaded and 29 normal images) are used for performance evaluation.

Cooperative effects between color centers in diamond: applications to optical tweezers and optomechanics

NASA Astrophysics Data System (ADS)

Bradac, Carlo; Prasanna Venkatesh, B.; Besga, Benjamin; Johnsson, Mattias; Brennen, Gavin; Molina-Terriza, Gabriel; Volz, Thomas; Juan, Mathieu L.

2017-08-01

Since the early work by Ashkin in 1970,1 optical trapping has become one of the most powerful tools for manipulating small particles, such as micron sized beads2 or single atoms.3 Interestingly, both an atom and a lump of dielectric material can be manipulated through the same mechanism: the interaction energy of a dipole and the electric field of the laser light. In the case of atom trapping, the dominant contribution typically comes from the allowed optical transition closest to the laser wavelength while it is given by the bulk polarisability for mesoscopic particles. This difference lead to two very different contexts of applications: one being the trapping of small objects mainly in biological settings,4 the other one being dipole traps for individual neutral atoms5 in the field of quantum optics. In this context, solid state artificial atoms present the interesting opportunity to combine these two aspects of optical manipulation. We are particularly interested in nanodiamonds as they constitute a bulk dielectric object by themselves, but also contain artificial atoms such as nitrogen-vacancy (NV) or silicon-vacancy (SiV) colour centers. With this system, both regimes of optical trapping can be observed at the same time even at room temperature. In this work, we demonstrate that the resonant force from the optical transition of NV centres at 637 nm can be measured in a nanodiamond trapped in water. This additional contribution to the total force is significant, reaching up to 10%. In addition, due to the very large density of NV centres in a sub-wavelength crystal, collective effects between centres have an important effect on the magnitude of the resonant force.6 The possibility to observe such cooperatively enhanced optical force at room temperature is also theoretically confirmed.7 This approach may enable the study of cooperativity in various nanoscale solid-state systems and the use of atomic physics techniques in the field of nano-manipulation and opto-mechanics.

A molecular fragment cheminformatics roadmap for mesoscopic simulation.

PubMed

Truszkowski, Andreas; Daniel, Mirco; Kuhn, Hubert; Neumann, Stefan; Steinbeck, Christoph; Zielesny, Achim; Epple, Matthias

2014-12-01

Mesoscopic simulation studies the structure, dynamics and properties of large molecular ensembles with millions of atoms: Its basic interacting units (beads) are no longer the nuclei and electrons of quantum chemical ab-initio calculations or the atom types of molecular mechanics but molecular fragments, molecules or even larger molecular entities. For its simulation setup and output a mesoscopic simulation kernel software uses abstract matrix (array) representations for bead topology and connectivity. Therefore a pure kernel-based mesoscopic simulation task is a tedious, time-consuming and error-prone venture that limits its practical use and application. A consequent cheminformatics approach tackles these problems and provides solutions for a considerably enhanced accessibility. This study aims at outlining a complete cheminformatics roadmap that frames a mesoscopic Molecular Fragment Dynamics (MFD) simulation kernel to allow its efficient use and practical application. The molecular fragment cheminformatics roadmap consists of four consecutive building blocks: An adequate fragment structure representation (1), defined operations on these fragment structures (2), the description of compartments with defined compositions and structural alignments (3), and the graphical setup and analysis of a whole simulation box (4). The basis of the cheminformatics approach (i.e. building block 1) is a SMILES-like line notation (denoted f SMILES) with connected molecular fragments to represent a molecular structure. The f SMILES notation and the following concepts and methods for building blocks 2-4 are outlined with examples and practical usage scenarios. It is shown that the requirements of the roadmap may be partly covered by already existing open-source cheminformatics software. Mesoscopic simulation techniques like MFD may be considerably alleviated and broadened for practical use with a consequent cheminformatics layer that successfully tackles its setup subtleties and conceptual usage hurdles. Molecular Fragment Cheminformatics may be regarded as a crucial accelerator to propagate MFD and similar mesoscopic simulation techniques in the molecular sciences. Graphical abstractA molecular fragment cheminformatics roadmap for mesoscopic simulation.

Modeling the Flexural Rigidity of Rod Photoreceptors

PubMed Central

Haeri, Mohammad; Knox, Barry E.; Ahmadi, Aphrodite

2013-01-01

In vertebrate eyes, the rod photoreceptor has a modified cilium with an extended cylindrical structure specialized for phototransduction called the outer segment (OS). The OS has numerous stacked membrane disks and can bend or break when subjected to mechanical forces. The OS exhibits axial structural variation, with extended bands composed of a few hundred membrane disks whose thickness is diurnally modulated. Using high-resolution confocal microscopy, we have observed OS flexing and disruption in live transgenic Xenopus rods. Based on the experimental observations, we introduce a coarse-grained model of OS mechanical rigidity using elasticity theory, representing the axial OS banding explicitly via a spring-bead model. We calculate a bending stiffness of ∼105 nN⋅μm2, which is seven orders-of-magnitude larger than that of typical cilia and flagella. This bending stiffness has a quadratic relation to OS radius, so that thinner OS have lower fragility. Furthermore, we find that increasing the spatial frequency of axial OS banding decreases OS rigidity, reducing its fragility. Moreover, the model predicts a tendency for OS to break in bands with higher spring number density, analogous to the experimental observation that transgenic rods tended to break preferentially in bands of high fluorescence. We discuss how pathological alterations of disk membrane properties by mutant proteins may lead to increased OS rigidity and thus increased breakage, ultimately contributing to retinal degeneration. PMID:23442852

An Intensified Vibratory Milling Process for Enhancing the Breakage Kinetics during the Preparation of Drug Nanosuspensions.

PubMed

Li, Meng; Zhang, Lu; Davé, Rajesh N; Bilgili, Ecevit

2016-04-01

As a drug-sparing approach in early development, vibratory milling has been used for the preparation of nanosuspensions of poorly water-soluble drugs. The aim of this study was to intensify this process through a systematic increase in vibration intensity and bead loading with the optimal bead size for faster production. Griseofulvin, a poorly water-soluble drug, was wet-milled using yttrium-stabilized zirconia beads with sizes ranging from 50 to 1500 μm at low power density (0.87 W/g). Then, this process was intensified with the optimal bead size by sequentially increasing vibration intensity and bead loading. Additional experiments with several bead sizes were performed at high power density (16 W/g), and the results were compared to those from wet stirred media milling. Laser diffraction, scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, and dissolution tests were used for characterization. Results for the low power density indicated 800 μm as the optimal bead size which led to a median size of 545 nm with more than 10% of the drug particles greater than 1.8 μm albeit the fastest breakage. An increase in either vibration intensity or bead loading resulted in faster breakage. The most intensified process led to 90% of the particles being smaller than 300 nm. At the high power intensity, 400 μm beads were optimal, which enhanced griseofulvin dissolution significantly and signified the importance of bead size in view of the power density. Only the optimally intensified vibratory milling led to a comparable nanosuspension to that prepared by the stirred media milling.

Use of Antibiotic Impregnated Resorbable Beads Reduces Pressure Ulcer Recurrence: A Retrospective Analysis.

PubMed

Khansa, Ibrahim; Barker, Jenny C; Ghatak, Piya Das; Sen, Chandan K; Gordillo, Gayle M

2018-05-17

Recurrence of pressure ulcers remains common. We have employed resorbable antibiotic beads as a therapeutic strategy to deliver high local antibiotic concentrations to the debridement site. Our objective was to determine whether the use of resorbable antibiotic- beads would reduce pressure ulcer recurrence. We reviewed all stage IV pressure ulcers treated with excision, partial ostectomy and flap coverage over 16 years. Baseline patient factors (location of ulcer, presence of osteomyelitis, preoperative prealbumin), surgical factors (type of flap, use of antibiotic beads, bone culture results) and postoperative outcomes (ulcer recurrence at 1 year, dehiscence, seroma, cellulitis) were collected. Outcomes of patients who received antibiotic-impregnated beads were compared to those who did not. 86 patients with 120 stage IV pressure ulcers underwent excision and flap coverage. This included 16 ulcers where antibiotic beads were used, and 104 where they were not. The overall ulcer recurrence rate at 12 months was 35.8%. The recurrence rate in the group treated with antibiotic beads was significantly lower than the group without beads (12.5% vs. 39.4%, p=0.03). Overall, complication rates between the two groups were similar (43.8% vs. 51.9%, p=0.54). No systemic or local toxicity from antibiotic beads occurred. Scanning electron microscopy images of sacral bone from one case showed bacterial biofilm even after debridement. Pressure ulcer recurrence at 1 year after excision and flap coverage decreased significantly with the use of resorbable antibiotic beads. This article is protected by copyright. All rights reserved. © 2018 by the Wound Healing Society.

Development of a novel colorimetric sensor based on alginate beads for monitoring rainbow trout spoilage.

PubMed

Majdinasab, Marjan; Hosseini, Seyed Mohammad Hashem; Sepidname, Marziyeh; Negahdarifar, Manizheh; Li, Peiwu

2018-05-01

Alginate is a non-toxic, renewable, and linear copolymer obtained from the brown algae Laminaria digitata that can be easily shaped into beads. Its good gel forming properties have made it useful for entrapping food and pharmaceutical ingredients. In this study, alginate beads were used in a novel application as a colorimetric sensor in food intelligent packaging. Colorimetric sensor was developed through entrapping red cabbage extract as a pH indicator in alginate beads. The pH indicator beads were used in rainbow trout packaging for monitoring fillets spoilage. Color change of beads during fish storage was measured using the CIELab method. The alginate bead colorimetric sensor is validated by measuring total volatile basic nitrogen (TVB-N) levels and microbial populations in fish samples. Moreover, peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) were evaluated during storage. Results indicated that increasing the bacterial population during storage and production of proteolytic enzymes resulted in protein degradation, accumulation of volatile amine compounds, increase in the pH and finally color change of alginate beads. The values of TVB-N, pH, PV and TBARS increased with time of storage. The results of TVB-N and microbial growth were in accordance with color change of beads and CIELab data. Therefore, the proposed system enjoys a high sensitivity to pH variations and is capable of monitoring the spoilage of fish or other protein-rich products through its wide range of color changes. The alginate beads containing the red cabbage extract can, thus, be used as a low-cost colorimetric sensor for intelligent packaging applications.

Semiflexible macromolecules in quasi-one-dimensional confinement: Discrete versus continuous bond angles.

PubMed

Huang, Aiqun; Hsu, Hsiao-Ping; Bhattacharya, Aniket; Binder, Kurt

2015-12-28

The conformations of semiflexible polymers in two dimensions confined in a strip of width D are studied by computer simulations, investigating two different models for the mechanism by which chain stiffness is realized. One model (studied by molecular dynamics) is a bead-spring model in the continuum, where stiffness is controlled by a bond angle potential allowing for arbitrary bond angles. The other model (studied by Monte Carlo) is a self-avoiding walk chain on the square lattice, where only discrete bond angles (0° and ±90°) are possible, and the bond angle potential then controls the density of kinks along the chain contour. The first model is a crude description of DNA-like biopolymers, while the second model (roughly) describes synthetic polymers like alkane chains. It is first demonstrated that in the bulk the crossover from rods to self-avoiding walks for both models is very similar, when one studies average chain linear dimensions, transverse fluctuations, etc., despite their differences in local conformations. However, in quasi-one-dimensional confinement two significant differences between both models occur: (i) The persistence length (extracted from the average cosine of the bond angle) gets renormalized for the lattice model when D gets less than the bulk persistence length, while in the continuum model it stays unchanged. (ii) The monomer density near the repulsive walls for semiflexible polymers is compatible with a power law predicted for the Kratky-Porod model in the case of the bead-spring model, while for the lattice case it tends to a nonzero constant across the strip. However, for the density of chain ends, such a constant behavior seems to occur for both models, unlike the power law observed for flexible polymers. In the regime where the bulk persistence length ℓp is comparable to D, hairpin conformations are detected, and the chain linear dimensions are discussed in terms of a crossover from the Daoud/De Gennes "string of blobs"-picture to the flexible rod picture when D decreases and/or the chain stiffness increases. Introducing a suitable further coarse-graining of the chain contours of the continuum model, direct estimates for the deflection length and its distribution could be obtained.

Electronic conductance of a poly(p-phenylene)-like nanowire in the presence of thermal atomic vibrations

NASA Astrophysics Data System (ADS)

Shariati, Ashrafalsadat; Rabani, Hassan; Mardaani, Mohammad

2017-10-01

We present a theoretical method based on Green’s function technique and tight-binding approach as well as harmonic approximation in order to calculate the coherent electronic conductance of an extended poly(p-phenylene) oligomer in the presence of thermal atomic vibrations. We study two proposed mass-spring models for atomic vibrations: one, including rigid benzene rings connected to each other by vibrating bonds; and in another, the bonds along the oligomer vibrate even in the benzene rings. The electron-phonon (e-ph) interaction influences the electron hopping energies linearly with respect to atomic displacements. The model shows that the conductance spectra exhibit some new energy gaps in the presence of e-ph interaction even at zero temperature. The conductance is more affected by e-ph interaction when the atomic vibrations are supposed to be present in the benzene rings. At the edges of the band energy and central gap, the phonon-assisted phenomena can be observed. Generally, the increasing e-ph interaction strength as well as temperature destroys the electronic conductance especially in the resonance region.

Nanofibrous polymeric beads from aramid fibers for efficient bilirubin removal.

PubMed

Peng, Zihang; Yang, Ye; Luo, Jiyue; Nie, Chuanxiong; Ma, Lang; Cheng, Chong; Zhao, Changsheng

2016-08-16

Polymer based hemoperfusion has been developed as an effective therapy to remove the extra bilirubin from patients. However, the currently applied materials suffer from either low removal efficiency or poor blood compatibility. In this study, we report the development of a new class of nanofibrous absorbent that exhibited high bilirubin removal efficiency and good blood compatibility. The Kevlar nanofiber was prepared by dissolving micron-sized Kevlar fiber in proper solvent, and the beads were prepared by dropping Kevlar nanofiber solutions into ethanol. Owing to the nanofiborous structure of the Kevlar nanofiber, the beads displayed porous structures and large specific areas, which would facilitate the adsorption of toxins. In the adsorption test, it was noticed that the beads possessed an adsorption capacity higher than 40 mg g(-1) towards bilirubin. In plasma mimetic solutions, the beads still showed high bilirubin removal efficiency. Furthermore, after incorporating with carbon nanotubes, the beads were found to have increased adsorption capacity for human degradation waste. Moreover, the beads showed excellent blood compatibility in terms of a low hemolysis ratio, prolonged clotting times, suppressed coagulant activation, limited platelet activation, and inhibited blood related inflammatory activation. Additionally, the beads showed good compatibility with endothelial cells. In general, the Kevlar nanofiber beads, which integrated with high adsorption capacity, good blood compatibility and low cytotoxicity, may have great potential for hemoperfusion and some other applications in biomedical fields.

Simultaneous detection of Escherichia coli O157:H7 and Salmonella Typhimurium: The use of magnetic beads conjugated with multiple capture antibodies

USDA-ARS?s Scientific Manuscript database

Streptavidin-coated magnetic beads were conjugated with biotinylated capture antibodies to both Escherichia coli O157:H7 and Samonella Typhimurium to form multi-pathogen capture immunomagnetic beads (IMB-M). The efficacy of these beads was investigated and compared to the use of a mixture of IMB ag...

The Beads of Translation: Using Beads to Translate mRNA into a Polypeptide Bracelet

ERIC Educational Resources Information Center

Dunlap, Dacey; Patrick, Patricia

2012-01-01

During this activity, by making beaded bracelets that represent the steps of translation, students simulate the creation of an amino acid chain. They are given an mRNA sequence that they translate into a corresponding polypeptide chain (beads). This activity focuses on the events and sites of translation. The activity provides students with a…

Wax-incorporated emulsion gel beads of calcium pectinate for intragastric floating drug delivery.

PubMed

Sriamornsak, Pornsak; Asavapichayont, Panida; Nunthanid, Jurairat; Luangtana-Anan, Manee; Limmatvapirat, Sontaya; Piriyaprasarth, Suchada

2008-01-01

The purpose of this study was to prepare wax-incorporated pectin-based emulsion gel beads using a modified emulsion-gelation method. The waxes in pectin-olive oil mixtures containing a model drug, metronidazole, were hot-melted, homogenized and then extruded into calcium chloride solution. The beads formed were separated, washed with distilled water and dried for 12 h. The influence of various types and amounts of wax on floating and drug release behavior of emulsion gel beads of calcium pectinate was investigated. The drug-loaded gel beads were found to float on simulated gastric fluid if the sufficient amount of oil was used. Incorporation of wax into the emulsion gel beads affected the drug release. Water-soluble wax (i.e. polyethylene glycol) increased the drug release while other water-insoluble waxes (i.e. glyceryl monostearate, stearyl alcohol, carnauba wax, spermaceti wax and white wax) significantly retarded the drug release. Different waxes had a slight effect on the drug release. However, the increased amount of incorporated wax in the formulations significantly sustained the drug release while the beads remained floating. The results suggest that wax-incorporated emulsion gel beads could be used as a carrier for intragastric floating drug delivery.

Analysis of surface properties of fixed and live cells using derivatized agarose beads.

PubMed

Navarro, Vanessa M; Walker, Sherri L; Badali, Oliver; Abundis, Maria I; Ngo, Lylla L; Weerasinghe, Gayani; Barajas, Marcela; Zem, Gregory; Oppenheimer, Steven B

2002-01-01

A novel assay has been developed for the histochemical characterization of surface properties of cells based on their adhesion to agarose beads derivatized with more than 100 types of molecules, including sugars, lectins and other proteins, and amino acids. The assay simply involves mixing small quantities of washed cells and beads in droplets on glass microscope slides and determining to which beads various cell types adhere. Distilled water was found to be the best medium for this assay because added ions or molecules in other media inhibit adhesion in some cases. Many cells, however, cannot tolerate distilled water. Here we show that cells fixed with either of two fixatives (1% formaldehyde or Prefer fixative) displayed similar bead-binding properties as did live cells. Specificity of cell-bead binding was tested by including specific free molecules in the test suspensions in hapten-type inhibition experiments. If a hapten compound inhibited live-cell adhesion to a specific bead, it also inhibited fixed-cell adhesion to a specific bead. The results of these experiments suggest that fixed cells display authentic surface properties, opening the door for the use of this assay with many cell types that cannot tolerate distilled water.

Effect of matrix composition and process conditions on casein-gelatin beads floating properties.

PubMed

Bulgarelli, E; Forni, F; Bernabei, M T

2000-04-05

Casein-gelatin beads have been prepared by emulsification extraction method and cross-linked with D,L-glyceraldehyde in an acetone-water mixture 3:1 (v/v). Casein emulsifying properties cause air bubble incorporation and the formation of large holes in the beads. The high porosity of the matrix influences the bead properties such as drug loading, drug release and floatation. These effects have been stressed by comparison with low porous beads, artificially prepared without cavities. The percentage of casein in the matrix increases the drug loading of both low and high porous matrices, although the loading of high porous matrices is lower than that of low porous matrices. As a matter of fact, the drug should be more easily removed during washing and recovery because of the higher superficial pore area of the beads. This can explain the drug release rate increase, observed in high porous matrix, in comparison with beads without cavities. This is due to the rapid diffusion of the drug through water filled pores. The study shows that cavities act as an air reservoir and enable beads to float. Therefore, casein seems to be a material suitable to the inexpensive formation of an air reservoir for floating systems.

Sorption kinetics of zinc and nickel on modified chitosan.

PubMed

Tripathi, Nimisha; Choppala, Girish; Singh, Raj S; Srivastava, Prashant; Seshadri, Balaji

2016-09-01

This study was conducted to evaluate the effect of equilibration time on adsorption of zinc [Zn(II)] and nickel [Ni(II)] on pure and modified chitosan beads. The initial adsorption of Zn(II) was high on molybdenum (Mo)-impregnated chitosan beads (MoCB) during the initial 60 min. However, after 240 min, Zn(II) adsorption occurred more on single super phosphate chitosan beads (SSPCB), followed by monocalcium phosphate chitosan beads (MCPCB), untreated pure chitosan beads (UCB), and MoCB. Similarly, Ni(II) adsorption was greatest on MoCB during the initial 60 min. At the conclusion of the experiment (at 240 min), the greatest adsorption was occurred on MCPCB, followed by MoCB, UCB, and SSPCB. Chemical sorption and intra-particle diffusion were probably the dominant processes responsible for Zn(II) and Ni(II) sorption onto chitosan beads. The results demonstrated that modified chitosan beads were effective in adsorbing Zn and Ni and hence, could be used for the removal of these toxic metals from soil.

Ionic liquid as a potential solvent for preparation of collagen-alginate-hydroxyapatite beads as bone filler.

PubMed

Iqbal, Bushra; Sarfaraz, Zenab; Muhammad, Nawshad; Ahmad, Pervaiz; Iqbal, Jibran; Khan, Zia Ul Haq; Gonfa, Girma; Iqbal, Farasat; Jamal, Arshad; Rahim, Abdur

2018-07-01

In this study, collagen/alginate/hydroxyapatite beads having different proportions were prepared as bone fillers for the restoration of osteological defects. Ionic liquid was used to dissolve the collagen and subsequently the solution was mixed with sodium alginate solution. Hydroxyapatite was added in different proportions, with the rationale to enhance mechanical as well as biological properties. The prepared solutions were given characteristic bead shapes by dropwise addition into calcium chloride solution. The prepared beads were characterized using FTIR, XRD, TGA and SEM analysis. Microhardness testing was used to evaluate the mechanical properties. The prepared beads were investigated for water adsorption behavior to ascertain its ability for body fluid uptake and adjusted accordingly to the bone cavity. Drug loading and subsequently the antibacterial activity was investigated for the prepared beads. The biocompatibility was assessed using the hemolysis testing and cell proliferation assay. The prepared collagen-alginate-HA beads, having biocompatibility and good mechanical properties, have showed an option of promising biologically active bone fillers for bone regeneration.

Energy efficient bead milling of microalgae: Effect of bead size on disintegration and release of proteins and carbohydrates.

PubMed

Postma, P R; Suarez-Garcia, E; Safi, C; Yonathan, K; Olivieri, G; Barbosa, M J; Wijffels, R H; Eppink, M H M

2017-01-01

The disintegration of three industry relevant algae (Chlorella vulgaris, Neochloris oleoabundans and Tetraselmis suecica) was studied in a lab scale bead mill at different bead sizes (0.3-1mm). Cell disintegration, proteins and carbohydrates released into the water phase followed a first order kinetics. The process is selective towards proteins over carbohydrates during early stages of milling. In general, smaller beads led to higher kinetic rates, with a minimum specific energy consumption of ⩽0.47kWhkg DW -1 for 0.3mm beads. After analysis of the stress parameters (stress number and stress intensity), it appears that optimal disintegration and energy usage for all strains occurs in the 0.3-0.4mm range. During the course of bead milling, the native structure of the marker protein Rubisco was retained, confirming the mildness of the disruption process. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Using a laser source to measure the refractive index of glass beads and Debye theory analysis.

PubMed

Li, Shui-Yan; Qin, Shuang; Li, Da-Hai; Wang, Qiong-Hua

2015-11-20

Using a monochromatic laser beam to illuminate a homogeneous glass bead, some rainbows will appear around it. This paper concentrates on the study of the scattering intensity distribution and the method of measuring the refractive index for glass beads based on the Debye theory. It is found that the first rainbow due to the scattering superposition of backward light of the low-refractive-index glass beads can be explained approximately with the diffraction, the external reflection plus the one internal reflection, while the second rainbow of high-refractive-index glass beads is due to the contribution from the diffraction, the external reflection, the direct transmission, and the two internal reflections. The scattering intensity distribution is affected by the refractive index, the radius of the glass bead, and the incident beam width. The effects of the refractive index and the glass bead size on the first and second minimum deviation angle position are analyzed in this paper. The results of the measurements agree very well with the specifications.

Pulsed laser manipulation of an optically trapped bead: averaging thermal noise and measuring the pulsed force amplitude.

PubMed

Lindballe, Thue B; Kristensen, Martin V G; Berg-Sørensen, Kirstine; Keiding, Søren R; Stapelfeldt, Henrik

2013-01-28

An experimental strategy for post-eliminating thermal noise on position measurements of optically trapped particles is presented. Using a nanosecond pulsed laser, synchronized to the detection system, to exert a periodic driving force on an optically trapped 10 μm polystyrene bead, the laser pulse-bead interaction is repeated hundreds of times. Traces with the bead position following the prompt displacement from equilibrium, induced by each laser pulse, are averaged and reveal the underlying deterministic motion of the bead, which is not visible in a single trace due to thermal noise. The motion of the bead is analyzed from the direct time-dependent position measurements and from the power spectrum. The results show that the bead is on average displaced 208 nm from the trap center and exposed to a force amplitude of 71 nanoNewton, more than five orders of magnitude larger than the trapping forces. Our experimental method may have implications for microrheology.

Accuracy of semen counting chambers as determined by the use of latex beads.

PubMed

Seaman, E K; Goluboff, E; BarChama, N; Fisch, H

1996-10-01

To assess the accuracy of the Hemacytometer (Hausser Scientific, Horsham, PA), Makler (Sefi-Medical Instrument, Haifa, Israel), Cell-VU (Millennium Sciences Inc., New York, NY), and Micro-Cell chambers (Conception Technologies, San Diego, CA) counting chambers. A solution containing a known concentration of latex beads was used as the standard to perform counts on the four different counting chambers. Bead counts for the four different chambers were compared with the bead counts of the standard solution. Variability within chambers also was determined. Mean bead concentrations for both the Cell-VU and Micro-Cell chambers were consistently similar to the bead concentration of the standard solution. Both the hemacytometer and the Makler chambers overestimated the actual bead concentration of the standard solution by as much as 50% and revealed significant interchamber variability. Our data revealed marked differences in the accuracy and reliability of the different counting chambers tested and emphasized the need for standardization and quality control of laboratory procedures.

Equalizer technology--Equal rights for disparate beads.

PubMed

Keidel, Eva-Maria; Ribitsch, Doris; Lottspeich, Friedrich

2010-06-01

One major limitation in proteomics is the detection and analysis of low-abundant proteins, i.e. in plasma. Several years ago, a technique to selectively enrich the relative concentration of low-abundant proteins was introduced by Boschetti and co-workers. It is based on a specific and saturable interaction of proteins to a high diversity of binding sites, realized by a hexapeptide library coupled to beads. This technology was commercialized as Equalizer beads or ProteoMiner. However, during application of ProteoMiner beads to plasma samples unexpected results questioned the proposed mode of action. Therefore, ProteoMiner beads were compared with chromatographic beads exhibiting completely different surface chemistry. Sepabeads FP-OD400 octadecyl, FP-DA400 diethylamine, FP-BU400 butyl, FP-HG400 hydroxyl and EXE056 epoxy were used. The results show that ProteoMiner or the different Sepabeads behave surprisingly similarly in the separation of complex protein mixtures. ProteoMiner beads interact with protein mixtures according to a general hydrophobic binding mechanism, where diversity in surface ligands plays only a negligible role.

Blends of jackfruit seed starch-pectin in the development of mucoadhesive beads containing metformin HCl.

PubMed

Nayak, Amit Kumar; Pal, Dilipkumar

2013-11-01

In this work, calcium pectinate-jackfruit (Artocarpus heterophyllus Lam.) seed starch (JFSS) mucoadhesive beads containing metformin HCl were developed through ionotropic-gelation. Effects of pectin and JFSS amounts on drug encapsulation efficiency (DEE), and cumulative drug release after 10 h (R10 h) were optimized using 3(2) factorial design. The optimized calcium pectinate-JFSS beads containing metformin HCl showed DEE of 94.11 ± 3.92%, R10 h of 48.88 ± 2.02%, and mean diameter of 2.06 ± 0.20 mm. The in vitro drug release from these beads was followed controlled-release (zero-order) pattern with super case-II transport mechanism. The beads were also characterized by SEM and FTIR. The pH of test mediums was found critical for swelling and mucoadhesion of these beads. The optimized calcium pectinate-JFSS beads also exhibited good mucoadhesivity and significant hypoglycemic effect in alloxan-induced diabetic rats over prolonged period after oral administration. Copyright © 2013 Elsevier B.V. All rights reserved.

Silver nanoparticle-alginate composite beads for point-of-use drinking water disinfection.

PubMed

Lin, Shihong; Huang, Rixiang; Cheng, Yingwen; Liu, Jie; Lau, Boris L T; Wiesner, Mark R

2013-08-01

Silver nanoparticles (AgNPs)-alginate composite beads were synthesized using three different approaches as filler materials of packed columns for simultaneous filtration-disinfection as an alternative portable water treatment process. The prepared composite beads were packed into a column through which Escherichia coli containing water was filtered to evaluate the disinfection efficacy. Excellent disinfection performance (no detectable viable colony) was achieved with a hydraulic retention time (HRT) as short as 1 min (the shortest tested) with the SGR (Simultaneous-Gelation-Reduction) and AR (Adsorption-Reduction) beads that were prepared using in situ reduction of Ag(+). Comparatively, the SGR beads released significantly less Ag(+)/AgNPs than the AR beads did within the same HRT. From the results of this study it was identified that SGR may be the best choice among all three different synthesis approaches in that the SGR beads can achieve satisfactory bactericidal performance with a relatively low material consumption rate. Copyright © 2012 Elsevier Ltd. All rights reserved.

Polymerase chain reaction system using magnetic beads for analyzing a sample that includes nucleic acid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nasarabadi, Shanavaz

2011-01-11

A polymerase chain reaction system for analyzing a sample containing nucleic acid includes providing magnetic beads; providing a flow channel having a polymerase chain reaction chamber, a pre polymerase chain reaction magnet position adjacent the polymerase chain reaction chamber, and a post pre polymerase magnet position adjacent the polymerase chain reaction chamber. The nucleic acid is bound to the magnetic beads. The magnetic beads with the nucleic acid flow to the pre polymerase chain reaction magnet position in the flow channel. The magnetic beads and the nucleic acid are washed with ethanol. The nucleic acid in the polymerase chain reactionmore » chamber is amplified. The magnetic beads and the nucleic acid are separated into a waste stream containing the magnetic beads and a post polymerase chain reaction mix containing the nucleic acid. The reaction mix containing the nucleic acid flows to an analysis unit in the channel for analysis.« less

Topics in the mechanics of self-organizing systems

NASA Astrophysics Data System (ADS)

Tambe, Dhananjay

Self-organization, in one of its accepted definitions, is the appearance of non-random structures in a system without explicit constraints from forces outside the system. In this thesis two self-organizing systems are studied from the viewpoint of mechanics. In the first system---semiconductor crystal surfaces---the internal constraints that lead to self-assembly of nanoscale structures on silicon-germanium (SiGe) films are studied. In the second system---actin cytoskeleton---a consequence of dynamic self-organization of actin filaments in the form of motion of micron-sized beads through a cytoplasmic medium is studied. When Ge film is deposited on Si(001) substrate, nanoscale features form on the surface and self-organize by minimizing energy contributions from the surface and the strain resulting from difference in lattice constants of the film and the substrate. Clean Si(001) and Ge(001) surfaces are very similar, but experiments to date have shown that atomic scale defects such as dimer-vacancies self-organize into vacancy lines only on Si(001). Through atomic simulations, we show that the observed difference originate from the magnitude of compressive surface strain which reduces formation energy of the dimer-vacancies. During initial stages of the film deposition, the surface is composed of steps and vacancy lines organized in periodic patterns. Using theory of elasticity and atomic simulations we show that these line defects self-organize due to monopolar nature of steps and dipolar nature of the vacancy lines. This self-organized pattern further develops to form pyramidal islands bounded with (105) facets and high Ge content. Mismatch strain of the island is then reduced by incorporation of Si from the substrate surrounding the island leaving behind trenches whose depth is proportional to the basewidth of the island. Using finite element simulations we show that such a relationship is an outcome of competition between elastic energy and surface energy. Some experimental studies also report observation of steeper (103) and (104) facets on pyramidal islands. Using numerical simulations we derive a phase diagram which shows that the steeper facets are stabilized because they provide better relaxation of mismatch strain with only slight increase in surface energy. In the second system, the actin cytoskeleton is a key structural and propulsion element of eukaryotic cells. Micron-sized "cargoes", which under pathological conditions include bacteria, are propelled by dynamic self-organization of the actin filaments. Recently it is shown that the trajectories of a bacterium, Listeria monocytogenes, propelled by actin filaments are periodic; implying that the organization of actin filaments impart an effective force that spins about the axis of the bacterium. We show that the motion of spherical beads is also non-random; the effective force has an additional degree of freedom due to the spherical symmetry of the bead. Agreement of the theoretical trajectories with experimental observations suggest that the actin-based motility can be generally described using deterministic equations. We also propose microscopic basis for the effective force model which can guide development of microscopic theory to predict the long term trajectories of actin propelled objects.

In Silico Reconstitution of Actin-Based Symmetry Breaking and Motility

PubMed Central

Dayel, Mark J.; Akin, Orkun; Landeryou, Mark; Risca, Viviana; Mogilner, Alex; Mullins, R. Dyche

2009-01-01

Eukaryotic cells assemble viscoelastic networks of crosslinked actin filaments to control their shape, mechanical properties, and motility. One important class of actin network is nucleated by the Arp2/3 complex and drives both membrane protrusion at the leading edge of motile cells and intracellular motility of pathogens such as Listeria monocytogenes. These networks can be reconstituted in vitro from purified components to drive the motility of spherical micron-sized beads. An Elastic Gel model has been successful in explaining how these networks break symmetry, but how they produce directed motile force has been less clear. We have combined numerical simulations with in vitro experiments to reconstitute the behavior of these motile actin networks in silico using an Accumulative Particle-Spring (APS) model that builds on the Elastic Gel model, and demonstrates simple intuitive mechanisms for both symmetry breaking and sustained motility. The APS model explains observed transitions between smooth and pulsatile motion as well as subtle variations in network architecture caused by differences in geometry and conditions. Our findings also explain sideways symmetry breaking and motility of elongated beads, and show that elastic recoil, though important for symmetry breaking and pulsatile motion, is not necessary for smooth directional motility. The APS model demonstrates how a small number of viscoelastic network parameters and construction rules suffice to recapture the complex behavior of motile actin networks. The fact that the model not only mirrors our in vitro observations, but also makes novel predictions that we confirm by experiment, suggests that the model captures much of the essence of actin-based motility in this system. PMID:19771152

Self-organizing magnetic beads for biomedical applications

NASA Astrophysics Data System (ADS)

Gusenbauer, Markus; Kovacs, Alexander; Reichel, Franz; Exl, Lukas; Bance, Simon; Özelt, Harald; Schrefl, Thomas

2012-03-01

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 developed a simulation tool that combines micromagnetics and discrete particle dynamics, in order to design micropost arrays made of interacting beads. The simulation takes into account the viscous drag of the blood flow, magnetostatic interactions between the magnetic beads and gradient forces from external aligned magnets. We developed a particle-particle particle-mesh method for effective computation of the magnetic force and torque acting on the particles.

A facile method for the preparation of monodisperse beads with uniform pore sizes for cell culture.

PubMed

Moon, Seung-Kwan; Oh, Myeong-Jin; Paik, Dong-Hyun; Ryu, Tae-Kyung; Park, Kyeongsoon; Kim, Sung-Eun; Park, Jong-Hoon; Kim, Jung-Hyun; Choi, Sung-Wook

2013-03-12

This paper describes a facile method for the preparation of porous gelatin beads with uniform pore sizes using a simple fluidic device and their application as supporting materials for cell culture. An aqueous gelatin droplet containing many uniform toluene droplets, produced in the fluidic device, is dropped into liquid nitrogen for instant freezing and the small toluene droplets evolve into pores in the gelatin beads after removal of toluene and then freeze-drying. The porous gelatin beads exhibit a uniform pore size and monodisperse diameter as well as large open pores at the surface. Fluorescence microscopy images of fibroblast-loaded gelatin beads confirm the attachment and proliferation of the cells throughout the porous gelatin beads. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Montmorillonite-Alginate Composites as a Drug delivery System: Intercalation and In vitro Release of Diclofenac sodium

PubMed Central

Kevadiya, B. D.; Patel, H. A.; Joshi, G. V.; Abdi, S. H. R.; Bajaj, H. C.

2010-01-01

Diclofenac sodium and alginate was intercalated into montmorillonite to form uniform sized beads by gelation method. The structure and surface morphology of the synthesized composite beads were characterized by powdered X-ray diffraction, Fourier transform infrared spectroscopy, thermo gravimetric analysis and scanning electron microscopy. Diclofenac release kinetics of the composite in simulated intestinal fluid medium (pH 7.4) and effect of montmorillonite content on the in vitro release of diclofenac from diclofenac-montmorillonite-alginate composites bead was investigated by UV/Vis spectrophotometer. Diclofenac encapsulation efficiency in the montmorillonite-alginate composites bead increases with an increase in the montmorillonite content. The control release of diclofenac from diclofenac-montmorillonite-alginate composites beads was observed to be better as compared to diclofenac-alginate beads. PMID:21969745

The Use of Index-Matched Beads in Optical Particle Counters

PubMed Central

Hu, Zhishang; Ripple, Dean C

2014-01-01

In this paper, we demonstrate the use of 2-pyridinemethanol (2P) aqueous solutions as a refractive index matching liquid. The high refractive index and low viscosity of 2P-water mixtures enables refractive index matching of beads that cannot be index matched with glycerol-water or sucrose-water solutions, such as silica beads that have the refractive index of bulk fused silica or of polymethylmethacrylate beads. Suspensions of beads in a nearly index-matching liquid are a useful tool to understand the response of particle counting instruments to particles of low optical contrast, such as aggregated protein particles. Data from flow imaging and light obscuration instruments are presented for bead diameters ranging from 6 µm to 69 µm, in a matrix liquid spanning the point of matched refractive index. PMID:26601049

Micro-Raman spectroscopy and μ-XRF in the investigation of ancient glass beads from the archaeological sites, eastern Taiwan

NASA Astrophysics Data System (ADS)

San Liou, Ying; Liu, Yi Chang

2017-04-01

Ancient glass beads with different colors, shapes, and stylistics unearthed from the archaeological sites of eastern Taiwan, dating back to approximately 1850-310 BP, have been investigated. It is generally known that glass bead is alien to invade into Taiwan along with metal ware, glass, agate, etc. since the Metal Age of Taiwan. Nevertheless, souring provenance and trade routes still remain controversial. Micro-Raman spectroscopy and μ-XRF have been applied on fifty-six ancient glass beads to reveal the mineralogical and chemical compositions and to help decipher the raw materials used and souring provenance. Micro-Raman measurements indicate the presence of hematite, zincite, siderite, sphalerite, lead tin yellow type II, quartz, feldspar, anatase, rutite, ankerite, graphite, calcite, etc. Among them, hematite, zincite, siderite, sphalerite, lead tin yellow type II, and rutile were found to be colorants/opacifiers. Moreover, crystalline phases such as lead tin yellow type II (PbSn1-xSixO3), zincite (ZnO), tricalcium diphosphate (Ca2(PO4)2), sphalerite ((Zn, Fe)S) and ankerite (Ca(Fe, Mg, Mn)(CO3)2) were detected in ancient glass beads unearthed from Taiwan for the first time. The chemical results obtained by μXRF show SiO2, Al2O3, Na2O, K2O, MgO, CaO, and PbO as the most abundant oxides. Na2O, K2O, Al2O3, MgO, and PbO could be the main/minor fluxes and colorants. In general, results of mineralogical and chemical analyses are compatible. According to chemical results, ancient glass beads can be classified as mineral soda alumina glass (m-Na-Al glass), soda plant ash glass (v-Na-Ca glass), lead silicate glass, and some less well known types. Mineral soda alumina and soda plant ash glass beads, as well as lead silicate glass beads are generally believed to be the distinct phases of production and exchange in Southeast Asia and China, respectively. In terms of chronology of glass bead, beads excavated from sites of 1850-930 BP are mineral soda alumina glass (m-Na-Al glass) and soda plant ash glass (v-Na-Ca glass). On the other hand, beads from sites of <930 BP are belonging to lead silicate glass. It is indicated that the souring provenance of ancient beads of eastern Taiwan is probably a multiple sources, i.e., in earlier time, glass beads were brought into Taiwan through the maritime exchange and/or trade activities between Taiwan and Southeast Asia; at the later period, lead silicate glass beads were imported from China. However, some mineral soda alumina and soda plant ash glass beads were found in a later period, it might be attributed to glass beads reuse or trade route between Taiwan and Southeast Asia is successive since ca. 1850 BP.

Water-chemistry data for selected springs, geysers, and streams in Yellowstone National Park, Wyoming, 2006-2008

USGS Publications Warehouse

Ball, James W.; McMleskey, R. Blaine; Nordstrom, D. Kirk

2010-01-01

Water analyses are reported for 104 samples collected from numerous thermal and non-thermal features in Yellowstone National Park (YNP) during 2006-2008. Water samples were collected and analyzed for major and trace constituents from 10 areas of YNP including Apollinaris Spring and Nymphy Creek along the Norris-Mammoth corridor, Beryl Spring in Gibbon Canyon, Norris Geyser Basin, Lower Geyser Basin, Crater Hills, the Geyser Springs Group, Nez Perce Creek, Rabbit Creek, the Mud Volcano area, and Washburn Hot Springs. These water samples were collected and analyzed as part of research investigations in YNP on arsenic, antimony, iron, nitrogen, and sulfur redox species in hot springs and overflow drainages, and the occurrence and distribution of dissolved mercury. Most samples were analyzed for major cations and anions, trace metals, redox species of antimony, arsenic, iron, nitrogen, and sulfur, and isotopes of hydrogen and oxygen. Analyses were performed at the sampling site, in an on-site mobile laboratory vehicle, or later in a U.S. Geological Survey laboratory, depending on stability of the constituent and whether it could be preserved effectively. Water samples were filtered and preserved on-site. Water temperature, specific conductance, pH, emf (electromotive force or electrical potential), and dissolved hydrogen sulfide were measured on-site at the time of sampling. Dissolved hydrogen sulfide was measured a few to several hours after sample collection by ion-specific electrode on samples preserved on-site. Acidity was determined by titration, usually within a few days of sample collection. Alkalinity was determined by titration within 1 to 2 weeks of sample collection. Concentrations of thiosulfate and polythionate were determined as soon as possible (generally a few to several hours after sample collection) by ion chromatography in an on-site mobile laboratory vehicle. Total dissolved iron and ferrous iron concentrations often were measured on-site in the mobile laboratory vehicle. Concentrations of dissolved aluminum, arsenic, boron, barium, beryllium, calcium, cadmium, cobalt, chromium, copper, iron, potassium, lithium, magnesium, manganese, molybdenum, sodium, nickel, lead, selenium, silica, strontium, vanadium, and zinc were determined by inductively coupled plasma-optical emission spectrometry. Trace concentrations of dissolved antimony, cadmium, cobalt, chromium, copper, lead, and selenium were determined by Zeeman-corrected graphite-furnace atomic-absorption spectrometry. Dissolved concentrations of total arsenic, arsenite, total antimony, and antimonite were determined by hydride generation atomic-absorption spectrometry using a flow-injection analysis system. Dissolved concentrations of total mercury and methylmercury were determined by cold-vapor atomic fluorescence spectrometry. Concentrations of dissolved chloride, fluoride, nitrate, bromide, and sulfate were determined by ion chromatography. For many samples, concentrations of dissolved fluoride also were determined by ion-specific electrode. Concentrations of dissolved ferrous and total iron were determined by the FerroZine colorimetric method. Concentrations of dissolved ammonium were determined by ion chromatography, with reanalysis by colorimetry when separation of sodium and ammonia peaks was poor. Dissolved organic carbon concentrations were determined by the wet persulfate oxidation method. Hydrogen and oxygen isotope ratios were determined using the hydrogen and CO2 equilibration techniques, respectively.

Folding 19 proteins to their native state and stability of large proteins from a coarse-grained model.

PubMed

Kapoor, Abhijeet; Travesset, Alex

2014-03-01

We develop an intermediate resolution model, where the backbone is modeled with atomic resolution but the side chain with a single bead, by extending our previous model (Proteins (2013) DOI: 10.1002/prot.24269) to properly include proline, preproline residues and backbone rigidity. Starting from random configurations, the model properly folds 19 proteins (including a mutant 2A3D sequence) into native states containing β sheet, α helix, and mixed α/β. As a further test, the stability of H-RAS (a 169 residue protein, critical in many signaling pathways) is investigated: The protein is stable, with excellent agreement with experimental B-factors. Despite that proteins containing only α helices fold to their native state at lower backbone rigidity, and other limitations, which we discuss thoroughly, the model provides a reliable description of the dynamics as compared with all atom simulations, but does not constrain secondary structures as it is typically the case in more coarse-grained models. Further implications are described. Copyright © 2013 Wiley Periodicals, Inc.

Jeffamine Derivatized TentaGel Beads and PDMS Microbead Cassettes for Ultra-high Throughput in situ Releasable Solution-Phase Cell-based Screening of OBOC Combinatorial Small Molecule Libraries

PubMed Central

Townsend, Jared B.; Shaheen, Farzana; Liu, Ruiwu; Lam, Kit S.

2011-01-01

A method to efficiently immobilize and partition large quantities of microbeads in an array format in microfabricated polydimethylsiloxane (PDMS) cassette for high-throughput in situ releasable solution-phase cell-based screening of one-bead-one-compound (OBOC) combinatorial libraries is described. Commercially available Jeffamine triamine T-403 (∼440 Da) was derivatized such that two of its amino groups were protected by Fmoc and the remaining amino group capped with succinic anhydride to generate a carboxyl group. This resulting tri-functional hydrophilic polymer was then sequentially coupled two times to the outer layer of topologically segregated bilayer TentaGel (TG) beads with solid phase peptide synthesis chemistry, resulting in beads with increased loading capacity, hydrophilicity and porosity at the outer layer. We have found that such bead configuration can facilitate ultra high-throughput in situ releasable solution-phase screening of OBOC libraries. An encoded releasable OBOC small molecule library was constructed on Jeffamine derivatized TG beads with library compounds tethered to the outer layer via a disulfide linker and coding tags in the interior of the beads. Compound-beads could be efficiently loaded (5-10 minutes) into a 5 cm diameter Petri dish containing a 10,000-well PDMS microbead cassette, such that over 90% of the microwells were each filled with only one compound-bead. Jurkat T-lymphoid cancer cells suspended in Matrigel® were then layered over the microbead cassette to immobilize the compound-beads. After 24 hours of incubation at 37°C, dithiothreitol was added to trigger the release of library compounds. Forty-eight hours later, MTT reporter assay was used to identify regions of reduced cell viability surrounding each positive bead. From a total of about 20,000 beads screened, 3 positive beads were detected and physically isolated for decoding. A strong consensus motif was identified for these three positive compounds. These compounds were re-synthesized and found to be cytotoxic (IC50 50-150 μM) against two T-lymphoma cell lines and less so against the MDA-MB 231 breast cancer cell line. This novel ultra high-throughput OBOC releasable method can potentially be adapted to many existing 96- or 384-well solution-phase cell-based or biochemical assays. PMID:20593859

Chloride Cotransporters as a Molecular Mechanism underlying Spreading Depolarization-Induced Dendritic Beading.

PubMed

Steffensen, Annette B; Sword, Jeremy; Croom, Deborah; Kirov, Sergei A; MacAulay, Nanna

2015-09-02

Spreading depolarizations (SDs) are waves of sustained neuronal and glial depolarization that propagate massive disruptions of ion gradients through the brain. SD is associated with migraine aura and recently recognized as a novel mechanism of injury in stroke and brain trauma patients. SD leads to neuronal swelling as assessed in real time with two-photon laser scanning microscopy (2PLSM). Pyramidal neurons do not express aquaporins and thus display low inherent water permeability, yet SD rapidly induces focal swelling (beading) along the dendritic shaft by unidentified molecular mechanisms. To address this issue, we induced SD in murine hippocampal slices by focal KCl microinjection and visualized the ensuing beading of dendrites expressing EGFP by 2PLSM. We confirmed that dendritic beading failed to arise during large (100 mOsm) hyposmotic challenges, underscoring that neuronal swelling does not occur as a simple osmotic event. SD-induced dendritic beading was not prevented by pharmacological interference with the cytoskeleton, supporting the notion that dendritic beading may result entirely from excessive water influx. Dendritic beading was strictly dependent on the presence of Cl(-), and, accordingly, combined blockade of Cl(-)-coupled transporters led to a significant reduction in dendritic beading without interfering with SD. Furthermore, our in vivo data showed a strong inhibition of dendritic beading during pharmacological blockage of these cotransporters. We propose that SD-induced dendritic beading takes place as a consequence of the altered driving forces and thus activity for these cotransporters, which by transport of water during their translocation mechanism may generate dendritic beading independently of osmotic forces. Spreading depolarization occurs during pathological conditions such as stroke, brain injury, and migraine and is characterized as a wave of massive ion translocation between intracellular and extracellular space in association with recurrent transient focal swelling (beading) of dendrites. Numerous ion channels have been demonstrated to be involved in generation and propagation of spreading depolarization, but the molecular machinery responsible for the dendritic beading has remained elusive. Using real-time in vitro and in vivo two-photon laser scanning microscopy, we have identified the transport mechanisms involved in the detrimental focal swelling of dendrites. These findings have clear clinical significance because they may point to a new class of pharmacological targets for prevention of neuronal swelling that consequently will serve as neuroprotective agents. Copyright © 2015 the authors 0270-6474/15/3512172-16$15.00/0.

Retro-reflection of glass beads for traffic road stripe paints

NASA Astrophysics Data System (ADS)

Grosges, T.

2008-06-01

The retro-reflection of light by glass beads injected in road stripes is studied experimentally and theoretically. The complete contribution of the retro-reflected intensity is modelled by taking into account the glass beads and the paint stripes. The efficiency of such a technique is evaluated for various compositions and densities of glass beads injected in paints, including the paint meniscus contributions.

The role of silica colloids on facilitated cesium transport through glass bead columns and modeling

NASA Astrophysics Data System (ADS)

Noell, Alan L.; Thompson, Joseph L.; Corapcioglu, M. Yavuz; Triay, Inés R.

1998-05-01

Groundwater colloids can act as a vector which enhances the migration of contaminants. While sorbed to mobile colloids, contaminants can be held in the aqueous phase which prevents them from interacting with immobile aquifer surfaces. In this study, an idealized laboratory set-up was used to examine the influence of amorphous silica colloids on the transport of cesium. Synthetic groundwater and saturated glass bead columns were used to minimize the presence of natural colloidal material. The columns were assembled in replicate, some packed with 150-210 μm glass bead and others packed with 355-420 μm glass beads. The colloids used in these experiments were 100 nm amorphous silica colloids from Nissan Chemical Company. In the absence of these colloids, the retardation factor for cesium was 8.0 in the 150-210 μm glass bead columns and 3.6 in the 355-420 μm glass bead columns. The influence of anthropogenic colloids was tested by injecting 0.09 pore volume slugs of an equilibrated suspension of cesium and colloids into the colloid-free columns. Although there was little noticeable facilitation in the smaller glass bead columns, there was a slight reduction in the retardation of cesium in the larger glass bead columns. This was attributed to cesium having less of a retention time in the larger glass bead columns. When cesium was injected into columns with a constant flux of colloids, the retardation of cesium was reduced by 14-32% in the 150-210 μm glass bead columns and by 38-51% in the 355-420 μm glass bead columns. A model based on Corapcioglu and Jiang (1993) [Corapcioglu, M.Y., Jiang, S., 1993. Colloid-facilitated groundwater contaminant transport, Water Resour. Res., 29 (7) 2215-2226] was compared with the experimental elution data. When equilibrium sorption expressions were used and the flux of colloids through the glass bead columns was constant, the colloid facilitated transport of cesium was able to be described using an effective retardation coefficient. Fully kinetic simulations, however, more accurately described the colloid facilitated transport of cesium.

Self-assembly of suspended graphene wrinkles with high pre-tension and elastic property

NASA Astrophysics Data System (ADS)

Yang, Liusi; Niu, Tianxiao; Zhang, Hui; Xu, Wenjing; Zou, Mingchu; Xu, Lu; Cao, Guoxin; Cao, Anyuan

2017-12-01

Wrinkles exist universally in graphene-based structures, yet their controlled fabrication remains challenging; most graphene wrinkles have been produced either in attachment to elastic substrates or limited in small single sheets. Here, we utilize the phenomenon of gel-cracking to generate uniaxial strains locally on solution-precipitated graphene oxide (GO) sheets, thus creating suspended and aligned wrinkles over the trenches between cracked TiO2 islands. In particular, those GO wrinkles are subjected to a high pre-tension, which is important for making stable suspended configuration, as confirmed by theoretical calculations based on the wrinkle geometry and measured spring constants, respectively. As a result, in situ atomic force microscope indentation reveals elastic deformation with tunable spring constants depending on the gap width. We further obtain chemically reduced GO wrinkles with enhanced spring constants and reversible behavior after 1000 indentation cycles. Our suspended and aligned graphene wrinkles have potential applications in many areas such as sensors, actuators, and micro/nano electromechanical systems.

A Simple Experiment for Determining the Elastic Constant of a Fine Wire

ERIC Educational Resources Information Center

Freeman, W. Larry; Freda, Ronald F.

2007-01-01

Many general physics laboratories involve the use of springs to demonstrate Hooke's law, and much ado is made about how this can be used as a model for describing the elastic characteristics of materials at the molecular or atomic level. In recent years, the proliferation of computers, and appropriate sensors, have made it possible to demonstrate…

Arsenic and fluoride removal from contaminated drinking water with Haix-Fe-Zr and Haix-Zr resin beads.

PubMed

Phillips, Debra H; Sen Gupta, Bhaskar; Mukhopadhyay, Soumyadeep; Sen Gupta, Arup K

2018-06-01

The objective of the study was to carry-out batch tests to examine the effectiveness of Haix-Fe-Zr and Haix-Zr resin beads in the removal of As(III), As(V) and F - from groundwater with a similar geochemistry to a site where a community-based drinking water plant has been installed in West Bengal, India. The groundwater was spiked separately with ∼200 μg/L As(III) and As(V) and 5 mg/L F - . Haix-Zr resin beads were more effective than Haix-Fe-Zr resin beads in removing As(III) and As(V). Haix-Zr resin beads showed higher removal of As(V) compared to As(III). Haix-Zr resin beads removed As(V) below the WHO (10 μg/L) drinking water standards at 8.79 μg/L after 4 h of shaking, while As(III) was reduced to 7.72 μg/L after 8 h of shaking. Haix-Fe-Zr resin beads were more effective in removing F - from the spiked groundwater compared to Haix-Zr resin beads. Concentrations of F - decreased from 6.27 mg/L to 1.26 mg/L, which is below the WHO drinking water standards (1.5 mg/L) for F - , after 15 min of shaking with Haix-Fe-Zr resin beads. After 20 min of shaking in groundwater treated with Haix-Zr resin beads, F - concentrations decreased from 6.27 mg/L to 1.43 mg/L. In the removal of As(III), As(V), and F - from the groundwater, Haix-Fe-Zr and Haix-Zr resin beads fit the parabolic diffusion equation (PDE) suggesting that adsorption of these contaminants was consistent with inter-particle diffusion. Copyright © 2018 Elsevier Ltd. All rights reserved.

Bacterial polyester inclusions engineered to display vaccine candidate antigens for use as a novel class of safe and efficient vaccine delivery agents.

PubMed

Parlane, Natalie A; Wedlock, D Neil; Buddle, Bryce M; Rehm, Bernd H A

2009-12-01

Bioengineered bacterial polyester inclusions have the potential to be used as a vaccine delivery system. The biopolyester beads were engineered to display a fusion protein of the polyester synthase PhaC and the two key antigens involved in immune response to the infectious agent that causes tuberculosis, Mycobacterium tuberculosis, notably antigen 85A (Ag85A) and the 6-kDa early secreted antigenic target (ESAT-6) from Mycobacterium tuberculosis. Polyester beads displaying the respective fusion protein at a high density were successfully produced (henceforth called Ag85A-ESAT-6 beads) by recombinant Escherichia coli. The ability of the Ag85A-ESAT-6 beads to enhance mouse immunity to the displayed antigens was investigated. The beads were not toxic to the animals, as determined by weight gain and absence of lesions at the inoculation site in immunized animals. In vivo injection of the Ag85A-ESAT-6 beads in mice induced significant humoral and cell-mediated immune responses to both Ag85A and ESAT-6. Vaccination with Ag85A-ESAT-6 beads was efficient at stimulating immunity on their own, and this ability was enhanced by administration of the beads in an oil-in-water emulsion. In addition, vaccination with the Ag85A-ESAT-6 beads induced significantly stronger humoral and cell-mediated immune responses than vaccination with an equivalent dose of the fusion protein Ag85A-ESAT-6 alone. The immune response induced by the beads was of a mixed Th1/Th2 nature, as assessed from the induction of the cytokine gamma interferon (Th1 immune response) and increased levels of immunoglobulin G1 (Th2 immune response). Hence, engineered biopolyester beads displaying foreign antigens represent a new class of versatile, safe, and biocompatible vaccines.

Controlled release of D-glucose from starch granules containing 29% free D-glucose and Eudragit L100-55 as a binding and coating agent.

PubMed

Kim, Yeon-Kye; Mukerjea, Rupendra; Robyt, John F

2010-05-27

Waxy maize starch (100% amylopectin) granules were modified by reaction of the granules with glucoamylase in a minimum amount of water to give 29% (w/w) D-glucose inside the granules [Kim, Y.-K.; Robyt, J. F. Carbohydr. Res.1999, 318, 129-134]. These granules were made into beads by dropping an ethanol slurry of starch and different amounts of Eudragit L100-55 in a constant ratio of 100:1 from a pipette onto Whatman 3MM filter paper. The starch beads were air dried and then repeatedly sprayed 0-12 times with 2.0% (w/v) Eudragit L100-55 in ethanol, with drying between each spraying, to coat the surface of the starch beads, giving different amounts of Eudragit L100-55 coating. Seven different kinds of beads, with different amounts of Eudragit L100-55 binding and coating agent, were obtained. The rates of release of D-glucose into water from the seven kinds of beads were inversely proportional to the amount of binding and coating agent. Bead type I, which was without any binding and coating gave a fast 100% release of D-glucose in 30 min. Beads II and III also gave a fast 100% release in 60 min and 90 min, respectively. Bead IV gave a near linear release of 97% D-glucose in 150 min; Bead V gave a 50% release in 120 min followed by the remaining 50% in 60 min; and Beads VI and VII gave a slow release of 10% and 4%, respectively, from 0 to 120 min, followed by a rapid 100% release from 120 to 180 min. (c) 2010 Elsevier Ltd. All rights reserved.

A novel alginate-encapsulated system to study biological response to critical-sized wear particles of UHMWPE loaded with alendronate sodium.

PubMed

Liu, Yumei; Shi, Feng; Bo, Lin; Zhi, Wei; Weng, Jie; Qu, Shuxin

2017-10-01

The aim of this study was to develop a novel alginate-encapsulated system (Alg beads) to investigate the cell response to critical-sized wear particles of ultra-high molecular weight polyethylene loaded with alendronate sodium (UHMWPE-ALN), one of the most effective drugs to treat bone resorption in clinic. The extrusion method was used to prepare Alg beads encapsulating rat calvarial osteoblasts (RCOs) and critical-sized UHMWPE-ALN wear particles with spherical morphology and uniform size. The morphology, permeability and stability of Alg beads were characterized. The proliferation, ALP activity, cell apoptosis and distribution of live/dead RCOs co-cultured with wear particles in Alg beads were evaluated. RCOs and critical-sized UHMWPE-ALN wear particles distributed evenly and contacted efficiently in Alg beads. Alg beads were both permeable to trypsin and BSA, while the smaller the molecular was, the larger the diffuse was. The proliferation of RCOs in Alg beads increased with time, which indicated that Alg beads provided suitable conditions for cell culture. The long-term stability of Alg beads indicated the possibility for the longer time of co-cultured cells with wear particles. Critical-sized UHMWPE-ALN and UHMWPE wear particles both inhibited the proliferation and differentiation of RCOs, and induced the apoptosis of RCOs encapsulated in Alg beads. However, these effects could be significantly alleviated by the ALN released from the critical-sized UHMWPE-ALN wear particles. The present results suggested that this novel-developed co-culture system was feasible to evaluate the cell response to critical-sized UHMWPE-ALN wear particles for a longer time. Copyright © 2017 Elsevier B.V. All rights reserved.

Operational parameters and their influence on particle-side mass transfer resistance in a packed bed bioreactor.

PubMed

Hussain, Amir; Kangwa, Martin; Yumnam, Nivedita; Fernandez-Lahore, Marcelo

2015-12-01

The influence of internal mass transfer on productivity as well as the performance of packed bed bioreactor was determined by varying a number of parameters; chitosan coating, flow rate, glucose concentration and particle size. Saccharomyces cerevisiae cells were immobilized in chitosan and non-chitosan coated alginate beads to demonstrate the effect on particle side mass transfer on substrate consumption time, lag phase and ethanol production. The results indicate that chitosan coating, beads size, glucose concentration and flow rate have a significant effect on lag phase duration. The duration of lag phase for different size of beads (0.8, 2 and 4 mm) decreases by increasing flow rate and by decreasing the size of beads. Moreover, longer lag phase were found at higher glucose medium concentration and also with chitosan coated beads. It was observed that by increasing flow rates; lag phase and glucose consumption time decreased. The reason is due to the reduction of external (fluid side) mass transfer as a result of increase in flow rate as glucose is easily transported to the surface of the beads. Varying the size of beads is an additional factor: as it reduces the internal (particle side) mass transfer by reducing the size of beads. The reason behind this is the distance for reactants to reach active site of catalyst (cells) and the thickness of fluid created layer around alginate beads is reduced. The optimum combination of parameters consisting of smaller beads size (0.8 mm), higher flow rate of 90 ml/min and glucose concentration of 10 g/l were found to be the maximum condition for ethanol production.

Flow-orthogonal bead oscillation in a microfluidic chip with a magnetic anisotropic flux-guide array.

PubMed

van Pelt, Stijn; Derks, Roy; Matteucci, Marco; Hansen, Mikkel Fougt; Dietzel, Andreas

2011-04-01

A new concept for the manipulation of superparamagnetic beads inside a microfluidic chip is presented in this paper. The concept allows for bead actuation orthogonal to the flow direction inside a microchannel. Basic manipulation functionalities were studied by means of finite element simulations and results were oval-shaped steady state oscillations with bead velocities up to 500 μm/s. The width of the trajectory could be controlled by prescribing external field rotation. Successful verification experiments were performed on a prototype chip fabricated with excimer laser ablation in polycarbonate and electroforming of nickel flux-guides. Bead velocities up to 450 μm/s were measured in a 75 μm wide channel. By prescribing the currents in the external quadrupole magnet, the shape of the bead trajectory could be controlled.

Oxytetracycline removal from water by novel microbial embedding gel beads

NASA Astrophysics Data System (ADS)

Wu, Nan; Pan, Peng; Zeng, Ming; Wang, Wei; Xu, Chenshan; Zhang, Zongpeng; Liu, Xinyuan; Wang, Yichao

2018-01-01

As a common antibiotic in aquatic environment, excessive oxytetracycline (OTC) is urgent to be removed due to its great biological toxicity. Compared with the traditional activated sludge, microbial embedding can enhance the treating efficiency. In this study, novel microbial embedding gel beads were produced with the additional agent of cyclodextrin (CD). Results show that CD could increase the mass transfer of OTC into gel beads, possibly because of its strong affinity for organic matters. In terms of OTC biodegradation, gel beads with CD were comparable to gel beads without CD, while the former’s sucrose removal efficiency was higher than the latter. The biodegradation of OTC only occurred in the presence of sucrose. The respiration test also confirmed these findings. Overall, the produced novel gel beads modified with CD could improve the removal performance of OTC.

Functional analysis of alpha5beta1 integrin and lipid rafts in invasion of epithelial cells by Porphyromonas gingivalis using fluorescent beads coated with bacterial membrane vesicles.

PubMed

Tsuda, Kayoko; Furuta, Nobumichi; Inaba, Hiroaki; Kawai, Shinji; Hanada, Kentaro; Yoshimori, Tamotsu; Amano, Atsuo

2008-01-01

Porphyromonas gingivalis, a periodontal pathogen, was previously suggested to exploit alpha5beta1 integrin and lipid rafts to invade host cells. However, it is unknown if the functional roles of these host components are distinct from one another during bacterial invasion. In the present study, we analyzed the mechanisms underlying P. gingivalis invasion, using fluorescent beads coated with bacterial membrane vesicles (MV beads). Cholesterol depletion reagents including methyl-beta-cyclodextrin (MbetaCD) drastically inhibited the entry of MV beads into epithelial cells, while they were less effective on bead adhesion to the cells. Bead entry was also abolished in CHO cells deficient in sphingolipids, components of lipid rafts, whereas adhesion was negligibly influenced. Following MbetaCD treatment, downstream events leading to actin polymerization were abolished; however, alpha5beta1 integrin was recruited to beads attached to the cell surface. Dominant-negative Rho GTPase Rac1 abolished cellular engulfment of the beads, whereas dominant-negative Cdc42 did not. Following cellular interaction with the beads, Rac1 was found to be translocated to the lipid rafts fraction, which was inhibited by MbetaCD. These results suggest that alpha5beta1 integrin, independent of lipid rafts, promotes P. gingivalis adhesion to epithelial cells, while the subsequent uptake process requires lipid raft components for actin organization, with Rho GTPase Rac1.

Removal of phthalate esters from aqueous solutions by chitosan bead.

PubMed

Chen, Chih-Yu; Chung, Ying-Chien

2006-01-01

Removal of phthalate esters (PAEs) by chitosan bead in aqueous solution was studied. The adsorption isotherms of PAEs by chitosan bead were well described by Freundlich isotherm equations. Results of kinetic experiments indicated that diheptyl phthalate (DHpP) had the highest adsorption capacity (1.52 mg/g) among six PAEs in our research. PAE adsorption efficiency by chitosan bead was examined in both batch and continuous systems, and DHpP attained 74.9% recovery efficiency from chitosan bead by shaking with an equal volume mixture of methanol and water. The recovered chitosan bead was reusable as an adsorbent. The influences of temperature, pH, Ca+2, and NaCl on PAE adsorption were also evaluated to determine performance in different water environments (e.g., groundwater, surface water, and sea water). The results showed that PAE adsorption decreased as temperature increased. From pH experiments it appeared that pH 8.0 was optimal for adsorption. The effect of Ca+2 showed that adsorption efficiency did not change by increasing the concentrations of Ca+2 until 400 mg/L. NaCl coexistence showed an insignificant effect on PAE adsorption. Furthermore, the chitosan bead was also applied to treating the discharge of a plastics plant, and the treatment results resembled those of a laboratory continuous system. This is the first report to use chitosan bead as an adsorbent to adsorb phthalate esters from aqueous solution. These results indicate that the application of chitosan bead is feasible in the aqueous environments of Taiwan.

Osteogenic differentiation of human mesenchymal stem cells in mineralized alginate matrices.

PubMed

Westhrin, Marita; Xie, Minli; Olderøy, Magnus Ø; Sikorski, Pawel; Strand, Berit L; Standal, Therese

2015-01-01

Mineralized biomaterials are promising for use in bone tissue engineering. Culturing osteogenic cells in such materials will potentially generate biological bone grafts that may even further augment bone healing. Here, we studied osteogenic differentiation of human mesenchymal stem cells (MSC) in an alginate hydrogel system where the cells were co-immobilized with alkaline phosphatase (ALP) for gradual mineralization of the microenvironment. MSC were embedded in unmodified alginate beads and alginate beads mineralized with ALP to generate a polymer/hydroxyapatite scaffold mimicking the composition of bone. The initial scaffold mineralization induced further mineralization of the beads with nanosized particles, and scanning electron micrographs demonstrated presence of collagen in the mineralized and unmineralized alginate beads cultured in osteogenic medium. Cells in both types of beads sustained high viability and metabolic activity for the duration of the study (21 days) as evaluated by live/dead staining and alamar blue assay. MSC in beads induced to differentiate in osteogenic direction expressed higher mRNA levels of osteoblast-specific genes (RUNX2, COL1AI, SP7, BGLAP) than MSC in traditional cell cultures. Furthermore, cells differentiated in beads expressed both sclerostin (SOST) and dental matrix protein-1 (DMP1), markers for late osteoblasts/osteocytes. In conclusion, Both ALP-modified and unmodified alginate beads provide an environment that enhance osteogenic differentiation compared with traditional 2D culture. Also, the ALP-modified alginate beads showed profound mineralization and thus have the potential to serve as a bone substitute in tissue engineering.

In vitro evaluation of antibiotic diffusion from antibiotic-impregnated biodegradable beads and polymethylmethacrylate beads.

PubMed Central

Mader, J T; Calhoun, J; Cobos, J

1997-01-01

Antibiotic-impregnated beads are used in the dead bone space following debridement surgery to deliver local, high concentrations of antibiotics. Polymethylmethacrylate (PMMA), 2,000-molecular-weight (MW) polylactic acid (PLA), Poly(DL-lactide)-coglycolide (PL:CG; 90:10, 80:20, and 70:30), and the combination 2,000-MW PLA-70:20 PL:CG were individually mixed with clindamycin, tobramycin, or vancomycin. Beads were placed in 1 ml of phosphate-buffered saline (PBS) and incubated at 37 degrees C. The PBS was changed daily, and the removed PBS samples were stored at -70 degrees C until the antibiotic in each sample was determined by microbiological disk diffusion assay. Nondissolving PMMA beads with tobramycin and clindamycin had concentrations well above breakpoint sensitivity concentrations (i.e., the antibiotic concentrations at the transition point between bacterial killing and resistance to the antibiotic) for more than 90 days, but vancomycin concentrations dropped by day 12. ALl PLA, PL:CG, and the 2,000-MW PLA-70:30 PL:CG biodegradable beads release high concentrations of all the antibiotics in vitro for the period of time needed to treat bone infections (i.e., 4 to 8 weeks). Antibiotic-loaded PLA and PL:CG beads have the advantage of better antibiotic elution and the ability to biodegradable (thereby averting the need for secondary surgery for bead removal) compared to the PMMA beads presently used in the clinical setting. PMID:9021200

Digital analysis of the expression levels of multiple colorectal cancer-related genes by multiplexed digital-PCR coupled with hydrogel bead-array.

PubMed

Qi, Zongtai; Ma, Yinjiao; Deng, Lili; Wu, Haiping; Zhou, Guohua; Kajiyama, Tomoharu; Kambara, Hideki

2011-06-07

To digitally analyze expression levels of multiple genes in one reaction, we proposed a method termed as 'MDHB' (Multiplexed Digital-PCR coupled with Hydrogel Bead-array). The template for bead-based emulsion PCR (emPCR) was prepared by reverse transcription using sequence-tagged primers. The beads recovered from emPCR were immobilized with hydrogel to form a single-bead layer on a chip, and then decoded by gene-specific probe hybridization and Cy3-dUTP based primer extension reaction. The specificity of probe hybridization was improved by using electrophoresis to remove mismatched probes on the bead's surface. The number of positive beads reflects the abundance of expressed genes; the expression levels of target genes were normalized to a housekeeping gene and expressed as the number ratio of green beads to red beads. The discrimination limit of MDHB is 0.1% (i.e., one target molecule from 1000 background molecules), and the sensitivity of the method is below 100 cells when using the β-actin gene as the detection target. We have successfully employed MDHB to detect the relative expression levels of four colorectal cancer (CRC)-related genes (c-myc, COX-2, MMP7, and DPEP1) in 8 tissue samples and 9 stool samples from CRC patients, giving the detection rates of 100% and 77%, respectively. The results suggest that MDHB could be a potential tool for early non-invasive diagnosis of CRC.

Digital detection of multiple minority mutants and expression levels of multiple colorectal cancer-related genes using digital-PCR coupled with bead-array.

PubMed

Huang, Huan; Li, Shuo; Sun, Lizhou; Zhou, Guohua

2015-01-01

To simultaneously analyze mutations and expression levels of multiple genes on one detection platform, we proposed a method termed "multiplex ligation-dependent probe amplification-digital amplification coupled with hydrogel bead-array" (MLPA-DABA) and applied it to diagnose colorectal cancer (CRC). CRC cells and tissues were sampled to extract nucleic acid, perform MLPA with sequence-tagged probes, perform digital emulsion polymerase chain reaction (PCR), and produce a hydrogel bead-array to immobilize beads and form a single bead layer on the array. After hybridization with fluorescent probes, the number of colored beads, which reflects the abundance of expressed genes and the mutation rate, was counted for diagnosis. Only red or green beads occurred on the chips in the mixed samples, indicating the success of single-molecule PCR. When a one-source sample was analyzed using mixed MLPA probes, beads of only one color occurred, suggesting the high specificity of the method in analyzing CRC mutation and gene expression. In gene expression analysis of a CRC tissue from one CRC patient, the mutant percentage was 3.1%, and the expression levels of CRC-related genes were much higher than those of normal tissue. The highly sensitive MLPA-DABA succeeds in the relative quantification of mutations and gene expressions of exfoliated cells in stool samples of CRC patients on the same chip platform. MLPA-DABA coupled with hydrogel bead-array is a promising method in the non-invasive diagnosis of CRC.

Osteogenic Differentiation of Human Mesenchymal Stem Cells in Mineralized Alginate Matrices

PubMed Central

Westhrin, Marita; Xie, Minli; Olderøy, Magnus Ø.; Sikorski, Pawel

2015-01-01

Mineralized biomaterials are promising for use in bone tissue engineering. Culturing osteogenic cells in such materials will potentially generate biological bone grafts that may even further augment bone healing. Here, we studied osteogenic differentiation of human mesenchymal stem cells (MSC) in an alginate hydrogel system where the cells were co-immobilized with alkaline phosphatase (ALP) for gradual mineralization of the microenvironment. MSC were embedded in unmodified alginate beads and alginate beads mineralized with ALP to generate a polymer/hydroxyapatite scaffold mimicking the composition of bone. The initial scaffold mineralization induced further mineralization of the beads with nanosized particles, and scanning electron micrographs demonstrated presence of collagen in the mineralized and unmineralized alginate beads cultured in osteogenic medium. Cells in both types of beads sustained high viability and metabolic activity for the duration of the study (21 days) as evaluated by live/dead staining and alamar blue assay. MSC in beads induced to differentiate in osteogenic direction expressed higher mRNA levels of osteoblast-specific genes (RUNX2, COL1AI, SP7, BGLAP) than MSC in traditional cell cultures. Furthermore, cells differentiated in beads expressed both sclerostin (SOST) and dental matrix protein-1 (DMP1), markers for late osteoblasts/osteocytes. In conclusion, Both ALP-modified and unmodified alginate beads provide an environment that enhance osteogenic differentiation compared with traditional 2D culture. Also, the ALP-modified alginate beads showed profound mineralization and thus have the potential to serve as a bone substitute in tissue engineering. PMID:25769043

Chitosan Enriched Three-Dimensional Matrix Reduces Inflammatory and Catabolic Mediators Production by Human Chondrocytes

PubMed Central

Oprenyeszk, Frederic; Sanchez, Christelle; Dubuc, Jean-Emile; Maquet, Véronique; Henrist, Catherine; Compère, Philippe; Henrotin, Yves

2015-01-01

This in vitro study investigated the metabolism of human osteoarthritic (OA) chondrocytes encapsulated in a spherical matrix enriched of chitosan. Human OA chondrocytes were encapsulated and cultured for 28 days either in chitosan-alginate beads or in alginate beads. The beads were formed by slowly passing dropwise either the chitosan 0.6%–alginate 1.2% or the alginate 1.2% solution through a syringe into a 102 mM CaCl2 solution. Beads were analyzed histologically after 28 days. Interleukin (IL)-6 and -8, prostaglandin (PG) E2, matrix metalloproteinases (MMPs), hyaluronan and aggrecan were quantified directly in the culture supernatant by specific ELISA and nitric oxide (NO) by using a colorimetric method based on the Griess reaction. Hematoxylin and eosin staining showed that chitosan was homogeneously distributed through the matrix and was in direct contact with chondrocytes. The production of IL-6, IL-8 and MMP-3 by chondrocytes significantly decreased in chitosan-alginate beads compared to alginate beads. PGE2 and NO decreased also significantly but only during the first three days of culture. Hyaluronan and aggrecan production tended to increase in chitosan-alginate beads after 28 days of culture. Chitosan-alginate beads reduced the production of inflammatory and catabolic mediators by OA chondrocytes and tended to stimulate the synthesis of cartilage matrix components. These particular effects indicate that chitosan-alginate beads are an interesting scaffold for chondrocytes encapsulation before transplantation to repair cartilage defects. PMID:26020773

Optical diamagnetic biosensor for immunocomplexes on beads

NASA Astrophysics Data System (ADS)

Norina, Svetlana B.

2000-12-01

In the present work, diamagnetic separation parameters for the porous beads are studied using optical video recording microscopy. The possible direct amount determination of single or double macromolecular layers immobilized in the meshes of the porous beads is demonstrated for the concentrations' range used in heterogenic immunotest and the affinity chromatography, where the direct rapid detection of ligands within sorbent particles is known to be the actual task. A gradient diamagnetic biosensor is described as suitable for rapid quantitative detection of single or double macromolecular layers in porous nonmagnetic beads. Measurements of capture traveling time or accumulation radius in gradient magnetic field have shown that it is possible to determine 0.20 mg/ml of macromolecular amount within several seconds. The portative devices were made on the base of the fabre optic technique to detect accumulation radius of collected beads in two gradient magnetic positions: diamagnetic and paramagnetic zones of magnetized wire with 55 μm in diameter and to registrate with a lot of fabre wires having 30 μm in diameters. The successive procedures of the present method can be described by: the obtaining of agarose immuno-beads, the incubation of beads with the ligand sample or the injection of sample through affinity mini-column, the submerging of the loaded beads into the glass cell containing Ni-wire or the narrow gap of magnetic poles; the computational obtaining of immuno- parameters; binding constants, accumulation radius. Several biotechnological applications of the biosensor are presented on sorbent beads, human lymphocytes.

Preparation of Silk Sericin/Lignin Blend Beads for the Removal of Hexavalent Chromium Ions.

PubMed

Kwak, Hyo Won; Shin, Munju; Yun, Haesung; Lee, Ki Hoon

2016-09-02

In the present study, novel adsorbents having high adsorption capability and reusability were prepared using agricultural by-products: silk sericin and lignin. Silk sericin and lignin blend beads were successfully prepared using simple coagulation methods for the removal of hexavalent chromium (Cr(VI)) from aqueous solution. A 1 M lithium chloride (LiCl)/dimethyl sulfoxide (DMSO) solvent system successfully dissolved both sericin and lignin and had sufficient viscosity for bead preparation. Compared to the conventional sericin bead adsorbent, sericin/lignin blend beads showed higher Cr(VI) adsorption capacity. The amount of lignin added to the adsorbent greatly affected the adsorption capacity of the beads, and a 50:50 sericin/lignin blend ratio was optimal. Adsorption behavior followed the Freundlich isotherm, which means the adsorption of Cr(VI) occurred on the heterogeneous surface. Cr(VI) adsorption capability increased with temperature because of thermodynamic-kinetic effects. In addition, over 90% of Cr(VI) ions were recovered from the Cr(VI) adsorbed sericin/lignin beads in a 1 M NaOH solution. The adsorption-desorption recycling process was stable for more than seven cycles, and the recycling efficiency was 82%. It is expected that the sericin/lignin beads could be successfully applied in wastewater remediation especially for hazardous Cr(VI) ions in industrial wastewater.

Preparation of Silk Sericin/Lignin Blend Beads for the Removal of Hexavalent Chromium Ions

PubMed Central

Kwak, Hyo Won; Shin, Munju; Yun, Haesung; Lee, Ki Hoon

2016-01-01

In the present study, novel adsorbents having high adsorption capability and reusability were prepared using agricultural by-products: silk sericin and lignin. Silk sericin and lignin blend beads were successfully prepared using simple coagulation methods for the removal of hexavalent chromium (Cr(VI)) from aqueous solution. A 1 M lithium chloride (LiCl)/dimethyl sulfoxide (DMSO) solvent system successfully dissolved both sericin and lignin and had sufficient viscosity for bead preparation. Compared to the conventional sericin bead adsorbent, sericin/lignin blend beads showed higher Cr(VI) adsorption capacity. The amount of lignin added to the adsorbent greatly affected the adsorption capacity of the beads, and a 50:50 sericin/lignin blend ratio was optimal. Adsorption behavior followed the Freundlich isotherm, which means the adsorption of Cr(VI) occurred on the heterogeneous surface. Cr(VI) adsorption capability increased with temperature because of thermodynamic-kinetic effects. In addition, over 90% of Cr(VI) ions were recovered from the Cr(VI) adsorbed sericin/lignin beads in a 1 M NaOH solution. The adsorption-desorption recycling process was stable for more than seven cycles, and the recycling efficiency was 82%. It is expected that the sericin/lignin beads could be successfully applied in wastewater remediation especially for hazardous Cr(VI) ions in industrial wastewater. PMID:27598142

Transfer of Fas (CD95) protein from the cell surface to the surface of polystyrene beads coated with anti-Fas antibody clone CH-11

PubMed Central

Sawai, H.; Domae, N.

2010-01-01

Mouse monoclonal anti-Fas (CD95) antibody clone CH-11 has been widely used in research on apoptosis. CH-11 has the ability to bind to Fas protein on cell surface and induce apoptosis. Here, we used polystyrene beads coated with CH-11 to investigate the role of lipid rafts in Fas-mediated apoptosis in SKW6.4 cells. Unexpectedly, by treatment of the cells with CH-11-coated beads Fas protein was detached from cell surface and transferred to the surface of CH-11-coated beads. Western blot analysis showed that Fas protein containing both extracellular and intracellular domains was attached to the beads. Fas protein was not transferred from the cells to the surface of the beads coated with other anti-Fas antibodies or Fas ligand. Similar phenomenon was observed in Jurkat T cells. Furthermore, CH-11-induced apoptosis was suppressed by pretreatment with CH-11-coated beads in Jurkat cells. These results suggest that CH-11 might possess distinct properties on Fas protein compared with other anti-Fas antibodies or Fas ligand, and also suggest that caution should be needed to use polystyrene beads coated with antibodies such as CH-11. PMID:20353915

Quality assurance for sperm concentration using latex beads.

PubMed

Peters, A J; Zaneveld, L J; Jeyendran, R S

1993-10-01

To provide a simple, universally applicable method of quality assurance for sperm counting, thereby reducing intercounting chamber variation. By using a known concentration of latex beads, the sperm:bead ratio can be used to calculate the actual sperm count. The mean sperm and bead counts were determined in both a Spot-lite hemocytometer (Baxter Diagnostics, McGaw Park, IL) and a Makler chamber (Polymedco Inc., Yorktown, NY) from 21 different ejaculates mixed with a known concentration of beads. The hemocytometer chamber was used as the standard counting chamber because it consistently yielded a low variation in sperm count. The adjusted sperm concentration of the Makler chamber was calculated using the following formula [hemocytometer beads]/[Makler beads] x [Makler sperm]. Observed mean +/- SD sperm counts were significantly different between the hemocytometer chamber (110.6 +/- 66.2 x 10(6)/mL) and Makler chamber (173.3 +/- 103.5 x 10(6)/mL). However, calculated Makler chamber sperm counts (118.1 +/- 76.1 x 10(6)/mL) was not statistically different from observed hemocytometer sperm counts. This novel approach to sperm counting using a known concentration of latex beads as a reference material can be used to reduce variation in sperm counting between observers, counting chambers, and possibly computerized sperm analyzers.

Formulation and optimization of zinc-pectinate beads for the controlled delivery of resveratrol.

PubMed

Das, Surajit; Ng, Ka-Yun; Ho, Paul C

2010-06-01

Preventive and therapeutic efficacies of resveratrol on several lower gastrointestinal (GI) diseases (e.g., colorectal cancer, colitis) are well documented. To overcome the problems due to its rapid absorption and metabolism at the upper GI tract, a delayed release formulation of resveratrol was designed to treat these lower GI diseases. The current study aimed to develop a delayed release formulation of resveratrol as multiparticulate pectinate beads by varying different formulation parameters. Zinc-pectinate (Zn-pectinate) beads exhibited better delayed drug release pattern than calcium-pectinate (Ca-pectinate) beads. The effects of the formulation parameters were investigated on shape, size, Zn content, moisture content, drug encapsulation efficiency, swelling-erosion, and resveratrol retention pattern of the formulated beads. Upon optimization of the formulation parameters in relative to the drug release profiles, the optimized beads were further subjected to morphological, chemical interaction, enzymatic degradation, and stability studies. Almost all prepared beads were spherical with approximately 1 mm diameter and efficiently encapsulated resveratrol. The formulation parameters revealed great influence on resveratrol retention and swelling-erosion behavior. In most of the cases, the drug release data more appropriately fitted with zero-order equation. This study demonstrates that the optimized Zn-pectinate beads can encapsulate very high amount of resveratrol and can be used as delayed release formulation of resveratrol.

Impact of Microplastic Beads and Fibers on Waterflea (Ceriodaphnia dubia) Survival, Growth, and Reproduction: Implications of Single and Mixture Exposures.

PubMed

Ziajahromi, Shima; Kumar, Anupama; Neale, Peta A; Leusch, Frederic D L

2017-11-21

There is limited knowledge regarding the adverse effects of wastewater-derived microplastics, particularly fibers, on aquatic biota. In this study, we examined the acute (48 h) and chronic (8 d) effects of microplastic polyester fibers and polyethylene (PE) beads on freshwater zooplankton Ceriodaphnia dubia. We also assessed the acute response of C. dubia to a binary mixture of microplastic beads and fibers for the first time. Acute exposure to fibers and PE beads both showed a dose-dependent effect on survival. An equitoxic binary mixture of beads and fibers resulted in a toxic unit of 1.85 indicating less than additive effects. Chronic exposure to lower concentrations did not significantly affect survival of C. dubia, but a dose-dependent effect on growth and reproduction was observed. Fibers showed greater adverse effects than PE beads. While ingestion of fibers was not observed, scanning electron microscopy showed carapace and antenna deformities after exposure to fibers, with no deformities observed after exposure to PE beads. While much of the current research has focused on microplastic beads, our study shows that microplastic fibers pose a greater risk to C. dubia, with reduced reproductive output observed at concentrations within an order of magnitude of reported environmental levels.

Alginate and Algal-Based Beads for the Sorption of Metal Cations: Cu(II) and Pb(II)

PubMed Central

Wang, Shengye; Vincent, Thierry; Faur, Catherine; Guibal, Eric

2016-01-01

Alginate and algal-biomass (Laminaria digitata) beads were prepared by homogeneous Ca ionotropic gelation. In addition, glutaraldehyde-crosslinked poly (ethyleneimine) (PEI) was incorporated into algal beads. The three sorbents were characterized by scanning electron microscopy (SEM) coupled with energy dispersive X-ray analysis (EDX): the sorption occurs in the whole mass of the sorbents. Sorption experiments were conducted to evaluate the impact of pH, sorption isotherms, and uptake kinetics. A special attention was paid to the effect of drying (air-drying vs. freeze-drying) on the mass transfer properties. For alginate, freeze drying is required for maintaining the porosity of the hydrogel, while for algal-based sorbents the swelling of the material minimizes the impact of the drying procedure. The maximum sorption capacities observed from experiments were 415, 296 and 218 mg Pb g−1 and 112, 77 and 67 mg Cu g−1 for alginate, algal and algal/PEI beads respectively. Though the sorption capacities of algal-beads decreased slightly (compared to alginate beads), the greener and cheaper one-pot synthesis of algal beads makes this sorbent more competitive for environmental applications. PEI in algal beads decreases the sorption properties in the case of the sorption of metal cations under selected experimental conditions. PMID:27598128

On-bead antibody-small molecule conjugation using high-capacity magnetic beads.

PubMed

Nath, Nidhi; Godat, Becky; Benink, Hélène; Urh, Marjeta

2015-11-01

Antibodies labeled with small molecules such as fluorophore, biotin or drugs play an important role in various areas of biological research, drug discovery and diagnostics. However, the majority of current methods for labeling antibodies is solution-based and has several limitations including the need for purified antibodies at high concentrations and multiple buffer exchange steps. In this study, a method (on-bead conjugation) is described that addresses these limitations by combining antibody purification and conjugation in a single workflow. This method uses high capacity-magnetic Protein A or Protein G beads to capture antibodies directly from cell media followed by conjugation with small molecules and elution of conjugated antibodies from the beads. High-capacity magnetic antibody capture beads are key to this method and were developed by combining porous and hydrophilic cellulose beads with oriented immobilization of Protein A and Protein G using HaloTag technology. With a variety of fluorophores it is shown that the on-bead conjugation method is compatible with both thiol- and amine-based chemistry. This method enables simple and rapid processing of multiple samples in parallel with high-efficiency antibody recovery. It is further shown that recovered antibodies are functional and compatible with downstream applications. Copyright © 2015. Published by Elsevier B.V.

Nanoparticle flotation collectors: mechanisms behind a new technology.

PubMed

Yang, Songtao; Pelton, Robert; Raegen, Adam; Montgomery, Miles; Dalnoki-Veress, Kari

2011-09-06

This is the first report describing a new technology where hydrophobic nanoparticles adsorb onto much larger, hydrophilic mineral particle surfaces to facilitate attachment to air bubbles in flotation. The adsorption of 46 nm cationic polystyrene nanoparticles onto 43 μm diameter glass beads, a mineral model, facilitates virtually complete removal of the beads by flotation. As little as 5% coverage of the bead surfaces with nanoparticles promotes high flotation efficiencies. The maximum force required to pull a glass bead from an air bubble interface into the aqueous phase was measured by micromechanics. The pull-off force was 1.9 μN for glass beads coated with nanoparticles, compared to 0.0086 μN for clean beads. The pull-off forces were modeled using Scheludko's classical expression. We propose that the bubble/bead contact area may not be dry (completely dewetted). Instead, for hydrophobic nanoparticles sitting on a hydrophilic surface, it is possible that only the nanoparticles penetrate the air/water interface to form a three-phase contact line. We present a new model for pull-off forces for such a wet contact patch between the bead and the air bubble. Contact angle measurements of both nanoparticle coated glass and smooth films from dissolved nanoparticles were performed to support the modeling. © 2011 American Chemical Society

BeadArray Expression Analysis Using Bioconductor

PubMed Central

Ritchie, Matthew E.; Dunning, Mark J.; Smith, Mike L.; Shi, Wei; Lynch, Andy G.

2011-01-01

Illumina whole-genome expression BeadArrays are a popular choice in gene profiling studies. Aside from the vendor-provided software tools for analyzing BeadArray expression data (GenomeStudio/BeadStudio), there exists a comprehensive set of open-source analysis tools in the Bioconductor project, many of which have been tailored to exploit the unique properties of this platform. In this article, we explore a number of these software packages and demonstrate how to perform a complete analysis of BeadArray data in various formats. The key steps of importing data, performing quality assessments, preprocessing, and annotation in the common setting of assessing differential expression in designed experiments will be covered. PMID:22144879

Development and evaluation of spherical molecularly imprinted polymer beads.

PubMed

Kempe, Henrik; Kempe, Maria

2006-06-01

The majority of studies on molecularly imprinted polymers has until now been carried out on irregularly shaped particles prepared by grinding of polymer monoliths. The preparation procedures are time- and labor-consuming and produce particles of wide size distributions. To answer the need for fast and straightforward routes to spherical molecularly imprinted polymer beads, we have developed a method comprising the formation of droplets of pre-polymerization solution directly in mineral oil by vigorous mixing followed by transformation of the droplets into solid spherical beads by photoinduced free-radical polymerization. No detergents or stabilizers were required for the droplet formation. Factors influencing the bead synthesis have been investigated and are detailed here. The beads were evaluated in parallel with corresponding irregularly shaped particles prepared from polymer monoliths. Conditions for the synthesis of propranolol-imprinted poly(methacrylic acid-co-trimethylolpropane trimethacrylate) beads in the size range of 1-100 microm in almost quantitative yield are described. The beads were applied as the recognition element in a 96-well plate format radioligand assay of propranolol in human serum.

Insights on novel particulate self-assembled drug delivery beads based on partial inclusion complexes between triglycerides and cyclodextrins.

PubMed

Aburahma, Mona Hassan

2016-09-01

Most of the newly designed drug molecules are lipophilic in nature and often encounter erratic absorption and low bioavailability after oral administration. Finding ways to enhance the absorption and bioavailability of these lipophilic drugs is one of the major challenges that face pharmaceutical industry nowadays. In view of that, the purpose of this review is to shed some light on a novel particulate self-assembling system named "beads" than can act as a safe carrier for delivering lipophilic drugs. The beads are prepared simply by mixing oils with cyclodextrin (CD) aqueous solution in mild conditions. A unique interaction between oil components and CD molecules occurs to form in situ surface-active complexes which are prerequisites for beads formation. This review mainly focuses on the fundamentals of beads preparation through reviewing present, yet scarce, literature. The key methods used for beads characterization are discussed in details. Also, the potential mechanisms by which beads increase the bioavailability of lipophilic drugs are illustrated. Finally, the related research areas that needs to be addressed in future for optimizing this promising delivery system are briefly outlined.

Formulation optimization and evaluation of jackfruit seed starch-alginate mucoadhesive beads of metformin HCl.

PubMed

Nayak, Amit Kumar; Pal, Dilipkumar

2013-08-01

The present study deals with the formulation optimization of jackfruit (Artocarpus heterophyllus Lam., family: Moraceae) seed starch (JFSS)-alginate mucoadhesive beads containing metformin HCl through ionotropic gelation using 3(2) factorial design. The effect of sodium alginate to JFSS ratio and CaCl2 concentration on the drug encapsulation efficiency (DEE, %), and cumulative drug release at 10h (R10h, %) was optimized. The optimized beads containing metformin HCl showed DEE of 97.48±3.92%, R10h of 65.70±2.22%, and mean diameter of 1.16±0.11mm. The in vitro drug release from these beads was followed controlled-release (zero-order) pattern with super case-II transport mechanism. The beads were also characterized by SEM and FTIR. The swelling and degradation of these beads were influenced by pH of the test medium. The optimized beads also exhibited good mucoadhesivity and significant hypoglycemic effect in alloxan-induced diabetic rats over prolonged period after oral administration. Copyright © 2013 Elsevier B.V. All rights reserved.

Dynamic trajectory analysis of superparamagnetic beads driven by on-chip micromagnets

PubMed Central

Abedini-Nassab, Roozbeh; Lim, Byeonghwa; Yang, Ye; Howdyshell, Marci; Sooryakumar, Ratnasingham; Yellen, Benjamin B.

2015-01-01

We investigate the non-linear dynamics of superparamagnetic beads moving around the periphery of patterned magnetic disks in the presence of an in-plane rotating magnetic field. Three different dynamical regimes are observed in experiments, including (1) phase-locked motion at low driving frequencies, (2) phase-slipping motion above the first critical frequency fc1, and (3) phase-insulated motion above the second critical frequency fc2. Experiments with Janus particles were used to confirm that the beads move by sliding rather than rolling. The rest of the experiments were conducted on spherical, isotropic magnetic beads, in which automated particle position tracking algorithms were used to analyze the bead dynamics. Experimental results in the phase-locked and phase-slipping regimes correlate well with numerical simulations. Additional assumptions are required to predict the onset of the phase-insulated regime, in which the beads are trapped in closed orbits; however, the origin of the phase-insulated state appears to result from local magnetization defects. These results indicate that these three dynamical states are universal properties of bead motion in non-uniform oscillators. PMID:26648596

The Investigation Of Carbon Contamination And Sputtering Effects Of Xenon Ion Thrusters

NASA Technical Reports Server (NTRS)

Prak, Moline K.

2004-01-01

The Electro-Physics Branch of the NASA Glenn Research Center investigates the effect of atomic oxygen, environmental durability of high performance power materials and surfaces, and low earth orbit. One of its current projects involves the analysis of ion thrusters. Ion thrusters are devices that initiate a beam of ions to a target area. The type of ion thruster that I have been working with this Summer of 2004 emits positively charged Xenon (Xe(+)) atoms through two grids, the screen grid and the accelerator grid, after it enters an ionization chamber. Insulators are used to mechanically hold and separate these two grids. A propellant isolator, an instrument that closely resembles insulators, is placed in front of the ionization chamber. Both the insulator and isolator are made with a ceramic compound and filled with insulating beads. The main difference between the two devices is that the propellant isolator allows gas to flow through, in this case, the gas is Xe(+) and the insulators do not. In order to avoid carbon deposits and other contaminating chemicals to settle on the insulators and propellant isolator, a metal shadow shield is placed around them. These shadow shields function as a protectant and can be shaped in numerous configurations. Part of my job responsibility this summer is to investigate the effectiveness of different shadow shields that are utilized on three different ion engines: the NSTAR (NASA Solar Electric Propulsion Technology Application Readiness), JIMO (Jupiter Icy Moons Orbiter), and NEXIS (Nuclear Electric Xenon Ion System). Using calculus and other mathematical tactics, I was asked to find the total flux of carbon contamination that was able to pass the protectant shadow shield. I familiarized myself with the software program, MathCad2004, to help perform some mathematical computations such as complex integration. Another method of studying the probability of contamination is by experimental simulation. After attaining the precise parameters of the actual shadow shields, I created replicas of three types of shadow shielding to be used to undergo testing. It will be placed in a machine that produces carbon atoms at a high temperature of 200 C. or beam is aimed at a targeted material. As a result of this collision, atoms and other particles are ejected out of the target surface. Another part of my internship consisted of research on sputter ejection, or the angle distribution of sputtered material. This research entailed finding the past results of sputter ejection investigation as well as creating another type of mock simulation. Other minor projects include calculating the path of Xe(+) gas through the insulating beads of the isolators and assisting my mentor in collecting data for his paper for the Joint Propulsion Conference & Exhibit to be held July 11-14,2004 in Fort Lauderdale, Florida.

Calibration beads containing luminescent lanthanide ion complexes

EPA Science Inventory

The reliability of lanthanide luminescence measurements, by both flow cytometry and digital microscopy, will be enhanced by the availability of narrow-band emitting lanthanide calibration beads. These beads can also be used to characterize spectrographic instruments, including mi...

Observation and Kinematic Description of Long Actin Tracks Induced by Spherical Beads

PubMed Central

Kang, Hyeran; Perlmutter, David S.; Shenoy, Vivek B.; Tang, Jay X.

2010-01-01

We report an in vitro study comparing the growth of long actin tails induced by spherical beads coated with the verprolin central acidic domain of the polymerization enzyme N-WASP to that induced by Listeria monocytogenes in similar cellular extracts. The tracks behind the beads show characteristic differences in shape and curvature from those left by the bacteria, which have an elongated shape and a similar polymerization-inducing enzyme distributed only on the rear surface of the cell. The experimental tracks are simulated using a generalized kinematic model, which incorporates three modes of bead rotation with respect to the tail. The results show that the trajectories of spherical beads are mechanically deterministic rather than random, as suggested by stochastic models. Assessment of the bead rotation and its mechanistic basis offers insights into the biological function of actin-based motility. PMID:21044576

Hollow polydimethylsiloxane beads with a porous structure for cell encapsulation.

PubMed

Oh, Myeong-Jin; Ryu, Tae-Kyoung; Choi, S-W

2013-11-01

Based on a water-in-oil-in-water emulsion system, porous and hollow polydimethylsiloxane (PDMS) beads containing cells using a simple fluidic device with three flow channels are fabricated. Poly(ethylene glycol) (PEG) in the PDMS oil phase is served as a porogen for pore development. The feasibility of the porous PDMS beads prepared with different PEG concentrations (10, 20, and 30 wt%) for cell encapsulation in terms of pore size, protein diffusion, and cell proliferation inside the PDMS beads is evaluated. The PDMS beads prepared with PEG 30 wt% are exhibited a highly porous structure and facilitated fast diffusion of protein from the core domain to the outer phase, eventually leading to enhanced cell proliferation. The results clearly indicate that hollow PDMS beads with a porous structure could provide a favorable microenvironment for cell survival due to the large porous structure. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microinjection - a tool to study gravitropism

NASA Astrophysics Data System (ADS)

Scherp, P.; Hasenstein, K. H.

2003-05-01

Despite extensive studies on plant gravitropism this phenomenon is still poorly understood. The separation of gravity sensing, signal transduction and response is a common concept but especially the mechanism of gravisensing remains unclear. This paper focuses on microinjection as powerful tool to investigate gravisensing in plants. We describe the microinjection of magnetic beads in rhizoids of the green alga Chara and related subsequent manipulation of the gravisensing system. After injection, an external magnet can control the movement of the magnetic beads. We demonstrate successful injection of magnetic beads into rhizoids and describe a multitude of experiments that can be carried out to investigate gravitropism in Chara rhizoids. In addition to examining mechanical properties, bead microinjection is also useful for probing the function of the cytoskeleton by coating beads with drugs that interfere with the cytoskeleton. The injection of fluorescently labeled beads or probes may reveal the involvement of the cytoskeleton during gravistimulation and response in living cells.

Increased Growth of the Microalga Chlorella vulgaris when Coimmobilized and Cocultured in Alginate Beads with the Plant-Growth-Promoting Bacterium Azospirillum brasilense†

PubMed Central

Gonzalez, Luz E.; Bashan, Yoav

2000-01-01

Coimmobilization of the freshwater microalga Chlorella vulgaris and the plant-growth-promoting bacterium Azospirillum brasilense in small alginate beads resulted in a significantly increased growth of the microalga. Dry and fresh weight, total number of cells, size of the microalgal clusters (colonies) within the bead, number of microalgal cells per cluster, and the levels of microalgal pigments significantly increased. Light microscopy revealed that both microorganisms colonized the same cavities inside the beads, though the microalgae tended to concentrate in the more aerated periphery while the bacteria colonized the entire bead. The effect of indole-3-acetic acid addition to microalgal culture prior to immobilization of microorganisms in alginate beads partially imitated the effect of A. brasilense. We propose that coimmobilization of microalgae and plant-growth-promoting bacteria is an effective means of increasing microalgal populations within confined environments. PMID:10742237

An integrated microfluidic cell for detection, manipulation, and sorting of single micron-sized magnetic beads

NASA Astrophysics Data System (ADS)

Jiang, Z.; Llandro, J.; Mitrelias, T.; Bland, J. A. C.

2006-04-01

A lab-on-a-chip integrated microfluidic cell has been developed for magnetic biosensing, which is comprised of anisotropic magnetoresistance (AMR) sensors optimized for the detection of single magnetic beads and electrodes to manipulate and sort the beads, integrated into a microfluidic channel. The device is designed to read out the real-time signal from 9 μm diameter magnetic beads moving over AMR sensors patterned into 18×4.5 μm rectangles and 10 μm diameter rings and arranged in Wheatstone bridges. The beads are moved over the sensors along a 75×75 μm wide channel patterned in SU8. Beads of different magnetic moments can be sorted through a magnetostatic sorting gate into different branches of the microfluidic channel using a magnetic field gradient applied by lithographically defined 120 nm thick Cu striplines carrying 0.2 A current.

Accelerating ab initio path integral molecular dynamics with multilevel sampling of potential surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Geng, Hua Y., E-mail: huay.geng@gmail.com; Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, Ithaca, NY 14853

A multilevel approach to sample the potential energy surface in a path integral formalism is proposed. The purpose is to reduce the required number of ab initio evaluations of energy and forces in ab initio path integral molecular dynamics (AI-PIMD) simulation, without compromising the overall accuracy. To validate the method, the internal energy and free energy of an Einstein crystal are calculated and compared with the analytical solutions. As a preliminary application, we assess the performance of the method in a realistic model—the FCC phase of dense atomic hydrogen, in which the calculated result shows that the acceleration rate ismore » about 3 to 4-fold for a two-level implementation, and can be increased up to 10 times if extrapolation is used. With only 16 beads used for the ab initio potential sampling, this method gives a well converged internal energy. The residual error in pressure is just about 3 GPa, whereas it is about 20 GPa for a plain AI-PIMD calculation with the same number of beads. The vibrational free energy of the FCC phase of dense hydrogen at 300 K is also calculated with an AI-PIMD thermodynamic integration method, which gives a result of about 0.51 eV/proton at a density of r{sub s}=0.912.« less

Treating inertia in passive microbead rheology.

PubMed

Indei, Tsutomu; Schieber, Jay D; Córdoba, Andrés; Pilyugina, Ekaterina

2012-02-01

The dynamic modulus G(*) of a viscoelastic medium is often measured by following the trajectory of a small bead subject to Brownian motion in a method called "passive microbead rheology." This equivalence between the positional autocorrelation function of the tracer bead and G(*) is assumed via the generalized Stokes-Einstein relation (GSER). However, inertia of both bead and medium are neglected in the GSER so that the analysis based on the GSER is not valid at high frequency where inertia is important. In this paper we show how to treat both contributions to inertia properly in one-bead passive microrheological analysis. A Maxwell fluid is studied as the simplest example of a viscoelastic fluid to resolve some apparent paradoxes of eliminating inertia. In the original GSER, the mean-square displacement (MSD) of the tracer bead does not satisfy the correct initial condition. If bead inertia is considered, the proper initial condition is realized, thereby indicating an importance of including inertia, but the MSD oscillates at a time regime smaller than the relaxation time of the fluid. This behavior is rather different from the original result of the GSER and what is observed. What is more, the discrepancy from the GSER result becomes worse with decreasing bead mass, and there is an anomalous gap between the MSD derived by naïvely taking the zero-mass limit in the equation of motion and the MSD for finite bead mass as indicated by McKinley et al. [J. Rheol. 53, 1487 (2009)]. In this paper we show what is necessary to take the zero-mass limit of the bead safely and correctly without causing either the inertial oscillation or the anomalous gap, while obtaining the proper initial condition. The presence of a very small purely viscous element can be used to eliminate bead inertia safely once included in the GSER. We also show that if the medium contains relaxation times outside the window where the single-mode Maxwell behavior is observed, the oscillation can be attenuated inside the window. This attenuation is realized even in the absence of a purely viscous element. Finally, fluid inertia also affects the bead autocorrelation through the Basset force and the fluid dragged around with the bead. We show that the Basset force plays the same role as the purely viscous element in high-frequency regime, and the oscillation of MSD is suppressed if fluid density and bead density are comparable. © 2012 American Physical Society

Microcinematographic analysis of tethered Leptospira illini.

PubMed Central

Charon, N W; Daughtry, G R; McCuskey, R S; Franz, G N

1984-01-01

A model of Leptospira motility was recently proposed. One element of the model states that in translating cells the anterior spiral-shaped end gyrates counterclockwise and the posterior hook-shaped end gyrates clockwise. We tested these predictions by analyzing cells tethered to a glass surface. Leptospira illini was incubated with antibody-coated latex beads (Ab-beads). These beads adhered to the cells, and subsequently some cells became attached to either the slide or the cover glass via the Ab-beads. As previously reported, these cells rapidly moved back and forth across the surface of the beads. In addition, a general trend was observed: cells tethered to the cover glass rotated clockwise around the Ab-bead; cells tethered to the slide rotated counterclockwise around the Ab-bead. A computer-aided microcinematographic analysis of tethered cells indicated that the direction of rotation of cells around the Ab-bead was a function of both the surface of attachment and the shape of the cell ends. The results can best be explained by assuming that the gyrating ends interact with the glass surface to cause rotation around the Ab-beads. The analysis obtained indicates that the hook- and spiral-shaped ends rotate in the directions predicted by the model. In addition, the tethered cell assay permitted detection of rapid, coordinated reversals of the cell ends, e.g., cells rapidly switched from a hook-spiral configuration to a spiral-hook configuration. These results suggest the existance of a mechanism which coordinates the shape of the cell ends of L. illini. Images PMID:6501226

Development of the rectal dosage form with silver-coated glass beads for local-action applications in lower sections of the gastrointestinal tract.

PubMed

Siczek, Krzysztof; Fichna, Jakub; Zatorski, Hubert; Karolewicz, Bożena; Klimek, Leszek; Owczarek, Artur

2018-03-01

Recent findings indicating the anti-inflammatory action of silver preparations through modulation of the gut microbiota and apoptosis of inflammatory cells predestine silver use in inflammatory bowel disease (IBD). The aim of our study was to validate the possibility of effective silver release from silver-coated glass beads for anti-inflammatory local application in the lower sections of the gastrointestinal (GI) tract. Silver-coated glass beads were prepared using magnetron method. Release of silver from the silver-coated glass bead surface was carried out in BIO-DIS reciprocating cylinder apparatus. Erosion of silver coating and indirect estimation of the silver release dynamics was assessed using scanning electron microscope. Rectal suppositories containing silver-coated glass beads were prepared using five different methods (M1-M5) and X-ray scanned for their composition. The XR microanalysis and the chemical composition analysis evidenced for a rapid (within 30 min) release of nearly 50% of silver from the coating of the glass beads, which remained stable up to 24 h of incubation. The most homogeneous distribution of beads in the entire volume of the suppository was obtained for formulation M5, where the molten base was poured into mold placed in an ice bath, and the beads were added after 10 s. Our study is the first to present the concept of enclosing silver-coated glass beads in the lipophilic suppository base to attenuate inflammation in the lower GI tract and promises efficient treatment with reduced side effects.

Sorption Properties of Aerogel in Liquid Nitrogen

NASA Technical Reports Server (NTRS)

Johnson, Wesley L.

2006-01-01

Aerogel products are now available as insulation materials of the future. The Cryogenics Test Laboratory at the NASA Kennedy Space Center is developing aerogel-based thermal insulation systems for space launch applications. Aerogel beads (Cabot Nanogel ) and aerogel blankets (Aspen Aerogels Spaceloft ) have outstanding ambient pressure thermal performance that makes them useful for applications where sealing is not possible. Aerogel beads are open-celled silicone dioxide and have tiny pores that run throughout the body of the bead. It has also recently been discovered that aerogel beads can be used as a filtering device for aqueous compounds at room temperature. With their hydrophobic covering, the beads absorb any non-polar substance and they can be chemically altered to absorb hot gases. The combination of the absorption and cryogenic insulating properties of aerogel beads have never been studied together. For future cryogenic insulation applications, it is crucial to know how the beads react while immersed in cryogenic liquids, most notably liquid nitrogen. Aerogel beads in loose-fill situation and aerogel blankets with composite fiber structure have been tested for absorption properties. Depending on the type of aerogel used and the preparation, preliminary results show the material can absorb up to seven times its own weight of liquid nitrogen, corresponding to a volumetric ratio of 0.70 (unit volume nitrogen per unit volume aerogel). These tests allow for an estimate on how much insulation is needed in certain situations. The theory behind the different processes of sorption is necessary for a better understanding of the preparation of the beads before they are used in an insulation system.

Digital Detection of Multiple Minority Mutants and Expression Levels of Multiple Colorectal Cancer-Related Genes Using Digital-PCR Coupled with Bead-Array

PubMed Central

Huang, Huan; Li, Shuo; Sun, Lizhou; Zhou, Guohua

2015-01-01

To simultaneously analyze mutations and expression levels of multiple genes on one detection platform, we proposed a method termed “multiplex ligation-dependent probe amplification–digital amplification coupled with hydrogel bead-array” (MLPA–DABA) and applied it to diagnose colorectal cancer (CRC). CRC cells and tissues were sampled to extract nucleic acid, perform MLPA with sequence-tagged probes, perform digital emulsion polymerase chain reaction (PCR), and produce a hydrogel bead-array to immobilize beads and form a single bead layer on the array. After hybridization with fluorescent probes, the number of colored beads, which reflects the abundance of expressed genes and the mutation rate, was counted for diagnosis. Only red or green beads occurred on the chips in the mixed samples, indicating the success of single-molecule PCR. When a one-source sample was analyzed using mixed MLPA probes, beads of only one color occurred, suggesting the high specificity of the method in analyzing CRC mutation and gene expression. In gene expression analysis of a CRC tissue from one CRC patient, the mutant percentage was 3.1%, and the expression levels of CRC-related genes were much higher than those of normal tissue. The highly sensitive MLPA–DABA succeeds in the relative quantification of mutations and gene expressions of exfoliated cells in stool samples of CRC patients on the same chip platform. MLPA–DABA coupled with hydrogel bead-array is a promising method in the non-invasive diagnosis of CRC. PMID:25880764

Fabrication of a microfluidic device for studying the in situ drug-loading/release behavior of graphene oxide-encapsulated hydrogel beads.

PubMed

Veerla, Sarath Chandra; Kim, Da Reum; Yang, Sung Yun

2018-01-01

Controlled drug delivery system is highly important for not only prolonged the efficacy of drug but also cellular development for tissue engineering. A number of biopolymer composites and nanostructured carriers behave been used for the controlled drug delivery of therapeutics. Recently, in vitro microfluidic devices that mimic the human body have been developed for drug-delivery applications. A microfluidic channel was fabricated via a two-step process: (i) polydimethyl siloxane (PDMS) and curing agent were poured with a 10:2 mass ratio onto an acrylic mold with two steel pipes, and (ii) calcium alginate beads were synthesized using sodium alginate and calcium chloride solutions. Different amounts (10, 25, 50 μg) of graphene oxide (GO) were then added by Hummers method, and studies on the encapsulation and release of the model drug, risedronate (Ris), were performed using control hydrogel beads (pH 6.3), GO-containing beads (10GO, 25GO and 50GO), and different pH conditions. MC3T3 osteoblastic cells were cultured in a microchannel with Ris-loaded GO-hydrogel beads, and their proliferation, viability, attachment and spreading were assessed for a week. The spongy and textured morphology of pristine hydrogel beads was converted to flowery and rod-shaped structures in drug-loaded hydrogel beads at reduced pH (6.3) and at a lower concentration (10 μg) of GO. These latter 10GO drug-loaded beads rapidly released their cargo owing to the calcium phosphate deposited on the surface. Notably, beads containing a higher amount of GO (50GO) exhibited an extended drug-release profile. We further found that MC3T3 cells proliferated continuously in vitro in the microfluidic channel containing the GO-hydrogel system. MTT and live/dead assays showed similar proliferative potential of MC3T3 cells. Therefore, a microfluidic device with microchannels containing hydrogel beads formulated with different amounts of GO and tested under various pH conditions could be a promising system for controlled drug release. The GO and drug (risedronate, Rig) were directed loaded into a hydrogel placed in a microchannel. Through interactions such as hydrogen bonding between Go and the Rig-loaded GO-hydrogel beads, the bead-loaded microfluidic device supported MC3T3 proliferation and development as osteoblast without additional osteogenic differentiation supplements.

Study of The Effect of Draw-bead Geometry on Stretch Flange Formability

NASA Astrophysics Data System (ADS)

Orlov, O. S.; Winkler, S. L.; Worswick, M. J.; Lloyd, D. J.; Finn, M. J.

2004-06-01

A fully instrumented stretch flange press equipped with a back-up punch and draw-beads near the specimen cutout area is simulated. The utilization of different draw-bead geometries is examined numerically to determine the restraining forces, strains and amount of damage generated in stretch flanges during forming. Simulations of the forming process are conducted for 1mm AA5182 sheets with circular cutouts. The damage evolution with the deformed specimens is investigated using the explicit dynamic finite element code, LS-DYNA, with a modified Gurson-based material model. It was found that double draw-beads can provide the same amount of restraining force as single draw-beads, but at reduced levels of damage.

Aurora Australis, Spiked and Sinuous Red and Green Airglow

NASA Image and Video Library

1991-05-06

STS039-342-026 (28 April-6 May 1991) --- This view of the Aurora Australis, or Southern Lights, shows a band of airglow above the limb of Earth. Photo experts at NASA studying the mission photography identify the airglow as being in the 80-120 kilometer altitude region and attribute its existence to atomic oxygen (wavelength of 5,577 Angstroms), although other atoms can also contribute. The atomic oxygen airglow is usually most intense at altitudes around 65 degrees north and south latitude, and is most intense in the spring and fall of the year. The aurora phenomena is due to atmospheric oxygen and nitrogen being excited by the particles from the Van Allen Radiation belts which extend between the two geomagnetic poles. The red and green rays appear to extend upward to 200-300 kilometers, much higher than the usual upper limits of about 110 kilometers.

Local Antibiotic Delivery by a Bioabsorbable Gel Is Superior to PMMA Bead Depot in Reducing Infection in an Open Fracture Model

DTIC Science & Technology

2014-06-01

be achieved in the wound while avoiding the side effects and cost of systemic administration. Beads molded from polymethylmethacrylate cement are... polymethylmethacrylate antibiotic beads is less effective because this method has to rely on diffusion of the antibiotic from the high concentration close...antibiotics in clinical use is polymethylmethacrylate (PMMA) blended with antibiotics and molded into beads.6–8 There are, however, disadvantages

Continuous microwave regeneration apparatus for absorption media

DOEpatents

Smith, Douglas D.

1999-01-01

A method and apparatus for continuously drying and regenerating ceramic beads for use in process gas moisture drying operations such as glove boxes. A microwave energy source is coupled to a process chamber to internally heat the ceramic beads and vaporize moisture contained therein. In a preferred embodiment, the moisture laden ceramic beads are conveyed toward the microwave source by a screw mechanism. The regenerated beads flow down outside of the screw mechanism and are available to absorb additional moisture.

Pharmaceutical acrylic beads obtained by suspension polymerization containing cellulose nanowhiskers as excipient for drug delivery.

PubMed

Villanova, J C O; Ayres, E; Carvalho, S M; Patrício, P S; Pereira, F V; Oréfice, R L

2011-03-18

Direct compression is one of the most popular techniques to prepare tablets but only a few commercial excipients are well adapted for this process into controlled release formulations. In the last years, the introduction of new materials for drug delivery matrix tablets has become more important. This paper evaluated the physicochemical and flow properties of new polymeric excipient of ethyl acrylate, methyl methacrylate and butyl metacrylate, synthesized by suspension polymerization using cellulose nanowhiskers as co-stabilizer, to be used as direct compression for modified release tablets. Infrared spectroscopy (FTIR) confirmed the success of the copolymerization reaction. Scanning electron microscopy (SEM) showed that excipient was obtained how spherical beads. Thermal properties of the beads were characterized by thermogravimetric (TG) analysis. Particle size analysis of the beads with cellulose nanowhiskers (CNWB) indicated that the presence of the nanowhiskers led to a reduction of particle size and to a narrower size distribution. In vitro test showed that the nanowhiskers and beads produced are nontoxic. Parameters such as Hausner ratio, Carr's index and cotangent of angle α were employed to characterize the flow properties of CNWB beads. Furthermore, the beads are used to produce tablets by direct compression contained propranolol hydrochloride as model drug. Dissolution tests performed suggested that beads could be used as excipient in matrix tablets with a potential use in drug controlled release. Copyright © 2011 Elsevier B.V. All rights reserved.

Hot Forging of a Cladded Component by Automated GMAW Process

NASA Astrophysics Data System (ADS)

Rafiq, Muhammad; Langlois, Laurent; Bigot, Régis

2011-01-01

Weld cladding is employed to improve the service life of engineering components by increasing corrosion and wear resistance and reducing the cost. The acceptable multi-bead cladding layer depends on single bead geometry. Hence, in first step, the relationship between input process parameters and the single bead geometry is studied and in second step a comprehensive study on multi bead clad layer deposition is carried out. This paper highlights an experimental study carried out to get single layer cladding deposited by automated Gas Metal Arc Welding (GMAW) process and to find the possibility of hot forming of the cladded work piece to get the final hot formed improved structure. GMAW is an arc welding process that uses an arc between a consumable electrode and the welding pool with an external shielding gas and the cladding is done by alongside deposition of weld beads. The experiments for single bead were conducted by varying the three main process parameters wire feed rate, arc voltage and welding speed while keeping other parameters like nozzle to work distance, shielding gas and its flow rate and torch angle constant. The effect of bead spacing and torch orientation on the cladding quality of single layer from the results of single bead deposition was studied. Effect of the dilution rate and nominal energy on the cladded layer hot bending quality was also performed at different temperatures.

Fabrication and characterization of superporous cellulose bead for high-speed protein chromatography.

PubMed

Wang, Dong-Mei; Hao, Gang; Shi, Qing-Hong; Sun, Yan

2007-03-30

Novel superporous cellulose (SC) matrix has been fabricated by water-in-oil emulsification-thermal regeneration using granules of calcium carbonate as porogenic agents. As a control, microporous cellulose (MC) bead was fabricated in the absence of calcium carbonate. Simultaneously, double cross-linking was applied to enhance the mechanical strength of the particles. The photographs by scanning electron microscopy of the SC bead illustrated that there were more "craters" of several microns scattering on the surface of the beads. It led to a higher water content and effective porosity of the SC medium. The two beads were then modified with diethylaminoethyl (DEAE) group to prepare anion exchangers. The dynamic uptake results of bovine serum albumin (BSA) exhibited that the pore diffusivity of BSA in the DEAE-SC bead was two to three times larger than that in the DEAE-MC bead. In addition, the column packed with the DEAE-SC showed lower backpressure, higher column efficiency and dynamic binding capacity than the column packed with the DEAE-MC at a flow rate range of 150-900cm/h. Moreover, the column efficiency of the DEAE-SC column was independent of flow velocity up to a flow rate of 1200cm/h. All the results exhibited the superior characteristics of the SC bead as a potential medium for high-speed protein chromatography.

Ecohydraulics of Strings and Beads in Bedrock Rivers

NASA Astrophysics Data System (ADS)

Wohl, E.

2016-12-01

Twenty years ago, Jack Stanford and others described rivers in bedrock canyons as resembling beads on a string when viewed in planform. The beads are relatively wide, low gradient river segments with floodplains, whereas the strings are the intervening steep, narrow river segments with minimal floodplain development. This pattern of longitudinal variations in channel and valley morphology along bedrock canyon rivers is very common, from small channels to major rivers such as the Colorado. Basic understanding of river ecosystems, as well as limited studies, indicates that the beads are more retentive and biologically productive. Although both strings and beads can provide habitat for diverse organisms, strings are more likely to serve as migration corridors, whereas beads provide spawning and nursery habitat, facilitate lateral (channel-floodplain) and vertical (channel-hyporheic) exchanges and associated habitat diversity, and retain dissolved and particulate organic matter. Recognition of the different characteristics and functions of strings and beads can be used to identify their spatial distribution along a river or within a river network and the hydraulically driven processes that sustain channel form, water quality, and biota within strings and beads. Diverse modeling approaches can then be used to quantify the fluxes of water and sediment needed to maintain these hydraulically driven processes. This conceptual framework is illustrated using examples from mountain streams in the Southern Rockies and canyon rivers in the southwestern United States.

Micromagnet arrays for on-chip focusing, switching, and separation of superparamagnetic beads and single cells.

PubMed

Rampini, S; Kilinc, D; Li, P; Monteil, C; Gandhi, D; Lee, G U

2015-08-21

Nonlinear magnetophoresis (NLM) is a novel approach for on-chip transport and separation of superparamagnetic (SPM) beads, based on a travelling magnetic field wave generated by the combination of a micromagnet array (MMA) and an applied rotating magnetic field. Here, we present two novel MMA designs that allow SPM beads to be focused, sorted, and separated on-chip. Converging MMAs were used to rapidly collect the SPM beads from a large region of the chip and focus them into synchronised lines. We characterise the collection efficiency of the devices and demonstrate that they can facilitate on-chip analysis of populations of SPM beads using a single-point optical detector. The diverging MMAs were used to control the transport of the beads and to separate them based on their size. The separation efficiency of these devices was determined by the orientation of the magnetisation of the micromagnets relative to the external magnetic field and the size of the beads and relative to that of micromagnets. By controlling these parameters and the rotation of the external magnetic field we demonstrated the controlled transport of SPM bead-labelled single MDA-MB-231 cells. The use of these novel MMAs promises to allow magnetically-labelled cells to be efficiently isolated and then manipulated on-chip for analysis with high-resolution chemical and physical techniques.

Geochemical features of glass beads excavated from the Iron Age archaeological sites, Eastern Taiwan

NASA Astrophysics Data System (ADS)

Yang, H.

2016-12-01

The uses of metallic artifacts began 2500-2000 years ago in Taiwan; in the meanwhile glass beads have also been as a common ornament by the prehistoric people. Glass, as the earliest artificial ornament, is made by a mixture of quartz sands and flux which were heated to more than one thousand Celsius degrees. Therefore, the production processes, raw material provenance and exchange systems could be revealed by the chemical compositions of glass artifacts. The chemical composition of glass beads studies from four archaeological sites (PL, PN, CHL and TL sites) in early Iron Age are reported in this study. By the producing in drawn method and limited ranges of colors with various hue, all the studied glass beads here should be classified as Indo-Pacific glass beads. As these ancient glass beads are unique and precious, a non-destructive analytical method is always considered at the initial stage. Therefore, we use the best known and most widely-used of the surface analytical techniques SEM/EDX to get the surface and quantitative elemental information of glass beads. According to the analytical results, the PL and PN glass beads all belong to potassium silica glass and those coexisting with so-called Kueishan sherds excavated from CHL and TL sites should be classified as sodium-calcium glass which is the most general composition of Indo-Pacific glass beads. Not only the different flux using between potassium and sodium glass, the variation in the aluminum contents between potassium and sodium glass also exhibits different provenances of glass-making raw materials. As lack of glass-making remains in Taiwan, these ancient glass beads were considered as a precious and trading artifact to Taiwan from overseas and introduced into prehistoric societies via various sources and paths. Although the trading/exchange routes of ancient glass beads are still debatable, we find that compositional analyses can help answer such questions as what types of glass were used for their manufacture and with separate traditions and hope the results can give us some insight into the potential beadmaking sites and in addition to establish the exchange networks of prehistoric people.

Water-chemistry and on-site sulfur-speciation data for selected springs in Yellowstone National Park, Wyoming, 1994-1995

USGS Publications Warehouse

Ball, James W.; Nordstrom, D. Kirk; Cunningham, Kirk M.; Schoonen, Martin A.; Xu, Yong; DeMonge, Jennifer M.

1998-01-01

Forty-two water analyses are reported for samples collected at 8 hot springs and their overflow drainages, two geysers, and two ambient-temperature acid streams in Yellowstone National Park during 1994-95. These water samples were collected and analyzed as part of the initial research investigations on sulfur redox speciation in the hot springs of Yellowstone and to document chemical changes in overflows that affect major ions, redox species, and trace elements. The sulfur redox speciation research is a collaboration between the State University of New York (SUNY) at Stony Brook and the U.S. Geological Survey (USGS). Four hot springs, Ojo Caliente, Azure, Frying Pan, and Angel Terrace, were studied in detail. Analyses were performed adjacent to the sampling site or in an on-site mobile lab truck constructed by the USGS, or later in a USGS laboratory. Water temperature, specific conductance, pH, Eh, D.O., and dissolved H2S were determined adjacent to the sample source at the time of sampling. Alkalinity and F- were determined on-site on the day of sample collection. Thiosulfate and polythionates were determined as soon as possible (minutes to hours later) by ion chromatography (IC). Other major anions (Cl-, SO4 2-, Br-) also were determined on-site by IC within two days of sample collection. Ammonium, Fe(II), and Fe(total) were determined on-site by ultraviolet/visible spectrophotometry within two days of sample collection. Later in the USGS laboratory, densities were determined. Concentrations of Ca, Mg, Li, Na, and K were determined by flame atomic absorption and emission (Na, K) spectrometry. Concentrations of Al, As, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe(total), K, Mg, Mn, Na, Ni, Pb, Si, Sr, V, and Zn were determined by inductively-coupled plasma optical emission spectrometry. Trace concentrations of Al and Mg were determined by Zeeman-corrected graphite furnace atomic absorption spectrometry. Three important conclusions from the sampling and analyses are: (1) variability in H2S concentrations can be caused as much by sampling and preservation artifacts as by actual variations in water composition over time, (2) historical determinations of S2O3 2- were subject to overestimation, most likely because of inadequate preservation leading to H2S oxidation, and (3) S2O3 2- is a common constituent of hot spring waters.

Optimization of Enzyme Co-Immobilization with Sodium Alginate and Glutaraldehyde-Activated Chitosan Beads.

PubMed

Gür, Sinem Diken; İdil, Neslihan; Aksöz, Nilüfer

2018-02-01

In this study, two different materials-alginate and glutaraldehyde-activated chitosan beads-were used for the co-immobilization of α-amylase, protease, and pectinase. Firstly, optimization of multienzyme immobilization with Na alginate beads was carried out. Optimum Na alginate and CaCl 2 concentration were found to be 2.5% and 0.1 M, respectively, and optimal enzyme loading ratio was determined as 2:1:0.02 for pectinase, protease, and α-amylase, respectively. Next, the immobilization of multiple enzymes on glutaraldehyde-activated chitosan beads was optimized (3% chitosan concentration, 0.25% glutaraldehyde with 3 h of activation and 3 h of coupling time). While co-immobilization was successfully performed with both materials, the specific activities of enzymes were found to be higher for the enzymes co-immobilized with glutaraldehyde-activated chitosan beads. In this process, glutaraldehyde was acting as a spacer arm. SEM and FTIR were used for the characterization of activated chitosan beads. Moreover, pectinase and α-amylase enzymes immobilized with chitosan beads were also found to have higher activity than their free forms. Three different enzymes were co-immobilized with these two materials for the first time in this study.

OBT analysis method using polyethylene beads for limited quantities of animal tissue.

PubMed

Kim, S B; Stuart, M

2015-08-01

This study presents a polyethylene beads method for OBT determination in animal tissues and animal products for cases where the amount of water recovered by combustion is limited by sample size or quantity. In the method, the amount of water recovered after combustion is enhanced by adding tritium-free polyethylene beads to the sample prior to combustion in an oxygen bomb. The method reduces process time by allowing the combustion water to be easily collected with a pipette. Sufficient water recovery was achieved using the polyethylene beads method when 2 g of dry animal tissue or animal product were combusted with 2 g of polyethylene beads. Correction factors, which account for the dilution due to the combustion water of the beads, are provided for beef, chicken, pork, fish and clams, as well as egg, milk and cheese. The method was tested by comparing its OBT results with those of the conventional method using animal samples collected on the Chalk River Laboratories (CRL) site. The results determined that the polyethylene beads method added no more than 25% uncertainty when appropriate correction factors are used. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

Wearable glass beads for in vivo dosimetry of total skin electron irradiation treatments

NASA Astrophysics Data System (ADS)

Nabankema, S. K.; Jafari, S. M.; Peet, S. C.; Binny, D.; Sylvander, S. R.; Crowe, S. B.

2017-11-01

Glass beads have recently been proposed for use as radiation therapy dosimeters. Glass beads have a number of characteristics that make them suitable for in vivo skin dose measurements, including an ability to be worn on a string, and therefore avoid possible patient discomfort that may result from the use of adhesives. In this study, their use for in vivo dose measurements in total skin electron irradiation treatments has been tested. First, the dosimetric properties of cylindrical beads with a 3 mm diameter were characterised using electron fields produced by a linear accelerator. The mean individual bead reproducibility was demonstrated to be within 3%; and a batch variation of 7% was observed. The beads were shown to have a linear dose response, and both dose rate and beam energy independence, within the measurement uncertainty. Phantom measurements were then performed for a total skin electron irradiation beam arrangement, and results compared against optically stimulated luminescent dosimeters at five anatomical sites. For a majority of measurement locations, agreement within 3% was observed between the two dosimetry techniques, demonstrating the feasibility of glass beads as in vivo dosimeters for total skin electron irradiation; though further investigation may be needed to minimise uncertainty in results.

Facile preparation and characterization of pH sensitive Mt/CMC nanocomposite hydrogel beads for propranolol controlled release.

PubMed

Farhadnejad, Hassan; Mortazavi, Seyed Alireza; Erfan, Mohammad; Darbasizadeh, Behzad; Motasadizadeh, Hamidreza; Fatahi, Yousef

2018-05-01

The main aim of the present study was to design pH-sensitive nanocomposite hydrogel beads, based on carboxymethyl cellulose (CMC) and montmorillonite (Mt)-propranolol (PPN) nanohybrid, and evaluate whether the prepared nanocomposite beads could potentially be used as oral drug delivery systems. PPN-as a model drug-was intercalated into the interlayer space of Mt clay mineral via the ion exchange procedure. The resultant nanohybrid (Mt-PPN) was applied to fabricate nanocomposite hydrogel beads by association with carboxymethyl cellulose. The characterization of test samples was performed using different techniques: X-Ray Diffraction (XRD), IR spectroscopy (FT-IR), thermal gravity analysis (TGA), and scanning electron microscopy (SEM). The drug encapsulation efficiency was evaluated by UV-vis spectroscopy, and was found to be high for Mt/CMC beads. In vitro drug release test was performed in the simulated gastrointestinal conditions to evaluate the efficiency of Mt-PPN/CMC nanocomposite beads as a controlled-release drug carrier. The drug release profiles indicated that the Mt-PPN/CMC nanocomposite beads had high stability against stomach acid and a sustained- and controlled-release profile for PPN under the simulated intestinal conditions. Copyright © 2018 Elsevier B.V. All rights reserved.

Hydrodynamic Torques and Rotations of Superparamagnetic Bead Dimers

NASA Astrophysics Data System (ADS)

Pease, Christopher; Etheridge, J.; Wijesinghe, H. S.; Pierce, C. J.; Prikockis, M. V.; Sooryakumar, R.

Chains of micro-magnetic particles are often rotated with external magnetic fields for many lab-on-a-chip technologies such as transporting beads or mixing fluids. These applications benefit from faster responses of the actuated particles. In a rotating magnetic field, the magnetization of superparamagnetic beads, created from embedded magnetic nano-particles within a polymer matrix, is largely characterized by induced dipoles mip along the direction of the field. In addition there is often a weak dipole mop that orients out-of-phase with the external rotating field. On a two-bead dimer, the simplest chain of beads, mop contributes a torque Γm in addition to the torque from mip. For dimers with beads unbound to each other, mop rotates individual beads which generate an additional hydrodynamic torque on the dimer. Whereas, mop directly torques bound dimers. Our results show that Γm significantly alters the average frequency-dependent dimer rotation rate for both bound and unbound monomers and, when mop exceeds a critical value, increases the maximum dimer rotation frequency. Models that include magnetic and hydrodynamics torques provide good agreement with the experimental findings over a range of field frequencies.

Use of micrometric latex beads to improve the porosity of hydroxyapatite obtained by chemical coprecipitation method

NASA Astrophysics Data System (ADS)

Webler, G. D.; Rodrigues, W. C.; Silva, A. E. S.; Silva, A. O. S.; Fonseca, E. J. S.; Degenhardt, M. F. S.; Oliveira, C. L. P.; Otubo, L.; Barros Filho, D. A.

2018-04-01

Hydroxyapatite is one of the most important biomaterials whose application mainly extends to implants and drug delivery. This work will discuss the changes in the pore size distribution of hydroxyapatite when there are latex beads present during the synthesis. These changes were monitored using different techniques: small angle X-ray scattering, X-ray diffraction, thermal gravimetrical analysis, N2 adsorption, scanning and transmission electron microscopy. Latex beads and hydroxyapatite form a single nanocomposite with well-distinguished inorganic and organic phases. Latex bead removal in the temperature range of 300-600 °C did not modify the original crystalline structure of hydroxyapatite. However, the latex beads favored an increase in the adsorption capacity of mesopores at temperatures higher than their glassy transition (Tg). The main result of this research work consists on the increase of surface area and pore size distribution obtained after the removal of latex beads template. Latex beads have been used in a different approach changing the porosity of hydroxyapatite scaffolds not only introducing new routes for cell integration but also broadening the pore size distribution which can result in a more high efficiency for drug release in living cells.

Artocarpus heterophyllus L. seed starch-blended gellan gum mucoadhesive beads of metformin HCl.

PubMed

Nayak, Amit Kumar; Pal, Dilipkumar; Santra, Kousik

2014-04-01

Jackfruit (Artocarpus heterophyllus Lam., family: Moraceae) seed starch (JFSS)-gellan gum (GG) mucoadhesive beads containing metformin HCl were developed through ionotropic gelation technique. The effect of GG to JFSS ratio and CaCl2 concentration on the drug encapsulation efficiency (DEE, %) and cumulative drug release at 10h (R10h, %) was optimized and analyzed using response surface methodology based on 3(2) factorial design. The optimized JFSS-GG beads containing metformin HCl showed DEE of 92.67±4.46%, R10h of 61.30±2.37%, and mean diameter of 1.67±0.27 mm. The optimized beads showed pH-dependent swelling and mucoadhesivity with the goat intestinal mucosa. The in vitro drug release from all these JFSS-GG beads containing metformin HCl was followed zero-order pattern (R(2)=0.9907-0.9975) with super case-II transport mechanism over a period of 10 h. The beads were also characterized by SEM and FTIR. The optimized JFSS-GG beads containing metformin HCl exhibited significant hypoglycemic effect in alloxan-induced diabetic rats over prolonged period after oral administration. Copyright © 2014 Elsevier B.V. All rights reserved.

Crosslinked, porous, polyacrylate beads

NASA Technical Reports Server (NTRS)

Rembaum, Alan (Inventor); Yen, Shiao-Ping Siao (Inventor); Dreyer, William J. (Inventor)

1976-01-01

Uniformly-shaped, porous, round beads are prepared by the co-polymerization of an acrylic monomer and a cross-linking agent in the presence of 0.05 to 5% by weight of an aqueous soluble polymer such as polyethylene oxide. Cross-linking proceeds at high temperature above about 50.degree.C or at a lower temperature with irradiation. Beads of even shape and even size distribution of less than 2 micron diameter are formed. The beads will find use as adsorbents in chromatography and as markers for studies of cell surface receptors.

Crosslinked, porous, polyacrylate beads

NASA Technical Reports Server (NTRS)

Rembaum, Alan (Inventor); Yen, Shiao-Ping S. (Inventor); Dreyer, William J. (Inventor)

1977-01-01

Uniformly-shaped, porous, round beads are prepared by the co-polymerization of an acrylic monomer and a cross-linking agent in the presence of 0.05 to 5% by weight of an aqueous soluble polymer such as polyethylene oxide. Cross-linking proceeds at high temperature above about 50.degree. C or at a lower temperature with irradiation. Beads of even shape and even size distribution of less than 2 micron diameter are formed. The beads will find use as adsorbents in chromatography and as markers for studies of cell surface receptors.

Measurement of retroreflection by glass beads for road marking

NASA Astrophysics Data System (ADS)

Ivanov, L. A.; Kiesewetter, D. V.; Kiselev, N. N.; Malyugin, V. I.; Slugin, V. A.

2006-04-01

The parameters of retroreflection of the monolayer of glass beads of the different size and quality in paint for road marking are measured. The new method of simultaneous measurement of the size and coefficient of retroreflection of separate beads is offered. The system of the statistical characteristics of optical quality is introduced. The measurements for different dimensional fractions are carried out. The capability of estimation of influencing of defects of glass beads on retro reflecting properties of the materials is shown.

Small, porous polyacrylate beads

NASA Technical Reports Server (NTRS)

Yen, Shiao-Ping Siao (Inventor); Rembaum, Alan (Inventor); Dreyer, William J. (Inventor)

1976-01-01

Uniformly-shaped, porous, round beads are prepared by the co-polymerization of an acrylic monomer and a cross-linking agent in the presence of 0.05 to 5% by weight of an aqueous soluble polymer such as polyethylene oxide. Cross-linking proceeds at high temperature above about 50.degree.C or at a lower temperature with irradiation. Beads of even shape and even size distribution of less than 2 micron diameter are formed. The beads will find use as adsorbents in chromatography and as markers for studies of cell surface receptors.

Polymeric Beads for Organic Coatings

DTIC Science & Technology

1982-10-31

Clear Solid Polymeric Beads A solid polymeric bead is comprised of a sol id mass of polymerized unsaturated polyester/styrene resin mixture . 2. lear...than the current unsaturated polyester resin . For example, a bead male from acrylic resin could be more trans- - parent, more durable and provide more...0.44 Isopropyl Alcohol I 11.26 I 1 .73 60% Wt. Alkyd Resin - Volume I 251.26 i 30.52 " Sol ids 51% 1 I Anti.-Skinning Agent I 0.90 I 0.12 Mineral

Evaluation of in vitro serial antibiotic elution from meropenem-impregnated polymethylmethacrylate beads after ethylene oxide gas and autoclave sterilization.

PubMed

Báez, L A; Langston, C; Givaruangsawat, S; McLaughlin, R

2011-01-01

To determine the elution properties of meropenem and to compare the elutions of meropenem-impregnated polymethylmethacrylate (PMMA) beads without sterilization (P-M-C) to those sterilized with steam (P-M-A) and ethylene oxide gas (P-M-EO). A commercial bead mould was used to produce four groups of beads: one group without antibiotic (negative control), and three groups of meropenem-impregnated beads: P-M-C, P-M-A, and P-M-EO. The beads were placed in a phosphate buffered solution and eluent samples were collected. Concentrations of the antibiotic in eluent samples from the two sterilized groups and the control beads were determined using a microbiological assay at 1, 3, 6 and 12 hours and at 1, 2, 3, 6, 9, 12, 15, 18, 22, 26, and 30 days. The microbiological assay resulted in no zone of inhibition at all time periods for the P-M-A samples and the samples of PMMA without antimicrobial. The meropenem concentration on the eluent remained above 4 mcg/ml for 15 days in the P-M-C group and until day 18 for P-M-EO group. There was no statistical difference in AUC0-∞ (p<0.318), however significance did occur for MRT (p<0.005) when comparing P-M-C and P-M-EO with the later being higher. The meropenem incorporated in the PMMA beads eluted effectively and gradually decreased after the 24 hour peak, but remained above the concentration level of 4 mcg/ml for 15 days in the P-M-C group and until day 18 for P-M-EO group. Ethylene oxide does not adversely affect meropenem's elution from PMMA beads.

Plasma membrane isolation using immobilized concanavalin A magnetic beads.

PubMed

Lee, Yu-Chen; Srajer Gajdosik, Martina; Josic, Djuro; Lin, Sue-Hwa

2012-01-01

Isolation of highly purified plasma membranes is the key step in constructing the plasma membrane proteome. Traditional plasma membrane isolation method takes advantage of the differential density of organelles. While differential centrifugation methods are sufficient to enrich for plasma membranes, the procedure is lengthy and results in low recovery of the membrane fraction. Importantly, there is significant contamination of the plasma membranes with other organelles. The traditional agarose affinity matrix is suitable for isolating proteins but has limitation in separating organelles due to the density of agarose. Immobilization of affinity ligands to magnetic beads allows separation of affinity matrix from organelles through magnets and could be developed for the isolation of organelles. We have developed a simple method for isolating plasma membranes using lectin concanavalin A (ConA) magnetic beads. ConA is immobilized onto magnetic beads by binding biotinylated ConA to streptavidin magnetic beads. The ConA magnetic beads are used to bind glycosylated proteins present in the membranes. The bound membranes are solubilized from the magnetic beads with a detergent containing the competing sugar alpha methyl mannoside. In this study, we describe the procedure of isolating rat liver plasma membranes using sucrose density gradient centrifugation as described by Neville. We then further purify the membrane fraction by using ConA magnetic beads. After this purification step, main liver plasma membrane proteins, especially the highly glycosylated ones and proteins containing transmembrane domains could be identified by LC-ESI-MS/MS. While not described here, the magnetic bead method can also be used to isolate plasma membranes from cell lysates. This membrane purification method should expedite the cataloging of plasma membrane proteome.

Feasibility of using glass-bead thermoluminescent dosimeters for radiotherapy treatment plan verification.

PubMed

Jafari, Shakardokht M; Jordan, Tom J; Distefano, Gail; Bradley, David A; Spyrou, Nicholas M; Nisbet, Andrew; Clark, Catharine H

2015-01-01

To investigate the feasibility of using glass beads as novel thermoluminescent dosemeters (TLDs) for radiotherapy treatment plan verification. Commercially available glass beads with a size of 1-mm thickness and 2-mm diameter were characterized as TLDs. Five clinical treatment plans including a conventional larynx, a conformal prostate, an intensity-modulated radiotherapy (IMRT) prostate and two stereotactic body radiation therapy (SBRT) lung plans were transferred onto a CT scan of a water-equivalent phantom (Solid Water(®), Gammex, Middleton, WI) and the dose distribution recalculated. The number of monitor units was maintained from the clinical plan and delivered accordingly. The doses determined by the glass beads were compared with those measured by a graphite-walled ionization chamber, and the respective expected doses were determined by the treatment-planning system (TPS) calculation. The mean percentage difference between measured dose with the glass beads and TPS was found to be 0.3%, -0.1%, 0.4%, 1.8% and 1.7% for the conventional larynx, conformal prostate, IMRT prostate and each of the SBRT delivery techniques, respectively. The percentage difference between measured dose with the ionization chamber and glass bead was found to be -1.2%, -1.4%, -0.1%, -0.9% and 2.4% for the above-mentioned plans, respectively. The results of measured doses with the glass beads and ionization chamber in comparison with expected doses from the TPS were analysed using a two-sided paired t-test, and there was no significant difference at p < 0.05. It is feasible to use glass-bead TLDs as dosemeters in a range of clinical plan verifications. Commercial glass beads are utilized as low-cost novel TLDs for treatment-plan verification.

Effect of pH and polypropylene beads in hybrid water treatment process of alumina ceramic microfiltration and PP beads with air back-flushing and UV irradiation.

PubMed

Park, Jin Yong; Song, Seunghwa

2017-07-07

For advanced water treatment, effects of pH and pure polypropylene (PP) beads packing concentration on membrane fouling and treatment efficiency were observed in a hybrid process of alumina ceramic microfiltration (MF; pore size 0.1 μm) and pure PP beads. Instead of natural organic matters and fine inorganic particles in natural water source, a quantity of humic acid (HA) and kaolin was dissolved in distilled water. The synthetic feed flowed inside the MF membrane, and the permeated water contacted the PP beads fluidized in the gap of the membrane and the acryl module case with outside UV irradiation. Periodic air back-flushing was performed to control membrane fouling during 10 s per 10 min. The membrane fouling resistance (R f ) was the maximum at 30 g/L of PP bead concentration. Finally, the maximum total permeated volume (V T ) was acquired at 5 g/L of PP beads, because flux maintained higher all through the operation. The treatment efficiency of turbidity was almost constant, independent of PP bead concentration; however, that of dissolved organic materials (DOM) showed the maximal at 50 g/L of PP beads. The R f increased as increasing feed pH from 5 to 9; however, the maximum V T was acquired at pH 6. It means that the membrane fouling could be inhibited at low acid condition. The treatment efficiency of turbidity increased a little, and that of DOM increased from 73.6 to 75.7% as increasing pH from 5 to 9.

Metal Oxide Assisted Preparation of Core-Shell Beads with Dense Metal-Organic Framework Coatings for the Enhanced Extraction of Organic Pollutants.

PubMed

Del Rio, Mateo; Palomino Cabello, Carlos; Gonzalez, Veronica; Maya, Fernando; Parra, Jose B; Cerdà, Victor; Turnes Palomino, Gemma

2016-08-08

Dense and homogeneous metal-organic framework (MOF) coatings on functional bead surfaces are easily prepared by using intermediate sacrificial metal oxide coatings containing the metal precursor of the MOF. Polystyrene (PS) beads are coated with a ZnO layer to give ZnO@PS core-shell beads. The ZnO@PS beads are reactive in the presence of 2-methylimidazole to transform part of the ZnO coating into a porous zeolitic imidazolate framework-8 (ZIF-8) external shell positioned above the internal ZnO precursor shell. The obtained ZIF-8@ZnO@PS beads can be easily packed in column format for flow-through applications, such as the solid-phase extraction of trace priority-listed environmental pollutants. The prepared material shows an excellent permeance to flow when packed as a column to give high enrichment factors, facile regeneration, and excellent reusability for the extraction of the pollutant bisphenol A. It also shows an outstanding performance for the simultaneous enrichment of mixtures of endocrine disrupting chemicals (bisphenol A, 4-tert-octylphenol and 4-n-nonylphenol), facilitating their analysis when present at very low levels (<1 μg L(-1) ) in drinking waters. For the extraction of the pollutant bisphenol A, the prepared ZIF-8@ZnO@PS beads also show a superior extraction and preconcentration capacity to that of the PS beads used as precursors and the composite materials obtained by the direct growth of ZIF-8 on the surface of the PS beads in the absence of metal oxide intermediate coatings. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization of long-term elution of platinum from carboplatin-impregnated calcium sulfate hemihydrate beads in vitro by two distinct sample collection methods.

PubMed

Tulipan, Rachel J; Phillips, Heidi; Garrett, Laura D; Dirikolu, Levent; Mitchell, Mark A

2017-05-01

OBJECTIVE To characterize long-term elution of platinum from carboplatin-impregnated calcium sulfate hemihydrate (CI-CSH) beads in vitro by comparing 2 distinct sample collection methods designed to mimic 2 in vivo environments. SAMPLES 162 CI-CSH beads containing 4.6 mg of carboplatin (2.4 mg of platinum/bead). PROCEDURES For method 1, which mimicked an in vivo environment with rapid and complete fluid exchange, each of 3 plastic 10-mL conical tubes contained 3 CI-CSH beads and 5 mL of PBS solution. Eluent samples were obtained by evacuation of all fluid at 1, 2, 3, 6, 9, and 12 hours and 1, 2, 3, 6, 9, 12, 15, 18, 22, 26, and 30 days. Five milliliters of fresh PBS solution was then added to each tube. For method 2, which mimicked an in vivo environment with no fluid exchange, each of 51 tubes (ie, 3 tubes/17 sample collection times) contained 3 CI-CSH beads and 5 mL of PBS solution. Eluent samples were obtained from the assigned tubes for each time point. All samples were analyzed for platinum content by inductively coupled plasma-mass spectrometry. RESULTS Platinum was released from CI-CSH beads for 22 to 30 days. Significant differences were found in platinum concentration and percentage of platinum eluted from CI-CSH beads over time for each method. Platinum concentrations and elution percentages in method 2 samples were significantly higher than those of method 1 samples, except for the first hour measurements. CONCLUSIONS AND CLINICAL RELEVANCE Sample collection methods 1 and 2 may provide estimates of the minimum and maximum platinum release, respectively, from CI-CSH beads in vivo.

Design criteria for developing low-resource magnetic bead assays using surface tension valves

PubMed Central

Adams, Nicholas M.; Creecy, Amy E.; Majors, Catherine E.; Wariso, Bathsheba A.; Short, Philip A.; Wright, David W.; Haselton, Frederick R.

2013-01-01

Many assays for biological sample processing and diagnostics are not suitable for use in settings that lack laboratory resources. We have recently described a simple, self-contained format based on magnetic beads for extracting infectious disease biomarkers from complex biological samples, which significantly reduces the time, expertise, and infrastructure required. This self-contained format has the potential to facilitate the application of other laboratory-based sample processing assays in low-resource settings. The technology is enabled by immiscible fluid barriers, or surface tension valves, which stably separate adjacent processing solutions within millimeter-diameter tubing and simultaneously permit the transit of magnetic beads across the interfaces. In this report, we identify the physical parameters of the materials that maximize fluid stability and bead transport and minimize solution carryover. We found that fluid stability is maximized with ≤0.8 mm i.d. tubing, valve fluids of similar density to the adjacent solutions, and tubing with ≤20 dyn/cm surface energy. Maximizing bead transport was achieved using ≥2.4 mm i.d. tubing, mineral oil valve fluid, and a mass of 1-3 mg beads. The amount of solution carryover across a surface tension valve was minimized using ≤0.2 mg of beads, tubing with ≤20 dyn/cm surface energy, and air separators. The most favorable parameter space for valve stability and bead transport was identified by combining our experimental results into a single plot using two dimensionless numbers. A strategy is presented for developing additional self-contained assays based on magnetic beads and surface tension valves for low-resource diagnostic applications. PMID:24403996

Long-term biocompatibility, imaging appearance and tissue effects associated with delivery of a novel radiopaque embolization bead for image-guided therapy.

PubMed

Sharma, Karun V; Bascal, Zainab; Kilpatrick, Hugh; Ashrafi, Koorosh; Willis, Sean L; Dreher, Matthew R; Lewis, Andrew L

2016-10-01

The objective of this study was to undertake a comprehensive long-term biocompatibility and imaging assessment of a new intrinsically radiopaque bead (LC Bead LUMI™) for use in transarterial embolization. The sterilized device and its extracts were subjected to the raft of ISO10993 biocompatibility tests that demonstrated safety with respect to cytotoxicity, mutagenicity, blood contact, irritation, sensitization, systemic toxicity and tissue reaction. Intra-arterial administration was performed in a swine model of hepatic arterial embolization in which 0.22-1 mL of sedimented bead volume was administered to the targeted lobe(s) of the liver. The beads could be visualized during the embolization procedure with fluoroscopy, DSA and single X-ray snapshot imaging modalities. CT imaging was performed before and 1 h after embolization and then again at 7, 14, 30 and 90 days. LC Bead LUMI™ could be clearly visualized in the hepatic arteries with or without administration of IV contrast and appeared more dense than soluble contrast agent. The CT density of the beads did not deteriorate during the 90 day evaluation period. The beads embolized predictably and effectively, resulting in areas devoid of contrast enhancement on CT imaging suggesting ischaemia-induced necrosis nearby the sites of occlusion. Instances of off target embolization were easily detected on imaging and confirmed pathologically. Histopathology revealed a classic foreign body response at 14 days, which resolved over time leading to fibrosis and eventual integration of the beads into the tissue, demonstrating excellent long-term tissue compatibility. Copyright © 2016 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Evaluation of local toxic effects and outcomes for dogs undergoing marginal tumor excision with intralesional cisplatin-impregnated bead placement for treatment of soft tissue sarcomas: 62 cases (2009-2012).

PubMed

Bergman, Noelle S; Urie, Bridget K; Pardo, Anthony D; Newman, Rebecca G

2016-05-15

OBJECTIVE To evaluate outcomes for dogs following marginal tumor excision and intralesional placement of cisplatin-impregnated beads for the treatment of cutaneous or subcutaneous soft tissue sarcomas (STSs) and assess local toxic effects of cisplatin-impregnated beads in these patients. DESIGN Retrospective case series. ANIMALS 62 client-owned dogs. PROCEDURES Medical records were reviewed to identify dogs with STSs treated with marginal excision and intralesional placement of cisplatin-impregnated beads. Patient signalment; tumor location, type, and grade; dates of tumor resection and bead placement; number of beads placed; and concurrent treatments were recorded. Data regarding toxicosis at the bead site (up to the time of suture removal) and tumor recurrence were collected; variables of interest were evaluated for associations with these outcomes, and systemic adverse effects (if any) were recorded. RESULTS 24 of 51 (47%) evaluated dogs had toxicosis at bead placement sites (classified as mild [n = 12] or moderate [10] in most). Fifteen of 51 (29%) tumors recurred. Median disease-free interval was not reached for dogs with grade 1 and 2 STSs, whereas that for dogs with grade 3 STSs was 148 days. Disease-free survival rates of dogs with grade 1 and 2 tumors at 1, 2, and 3 years were 88%, 75%, and 64%, respectively. One dog was treated for presumptive systemic toxicosis but recovered with medical treatment. CONCLUSIONS AND CLINICAL RELEVANCE Cisplatin-impregnated beads were generally well tolerated; good results were achieved for dogs with grade 1 or 2 STSs. Prospective, controlled studies are needed to determine efficacy of this treatment for preventing recurrence of marginally excised STSs in dogs.

Parental experiences with a hospital-based bead programme for children with congenital heart disease.

PubMed

Wilson, Valerie; Chando, Shingisai

2015-02-01

To present survey findings on parental experiences with a hospital-based bead programme for children with congenital heart disease. The Heart Beads programme commenced at a paediatric hospital in Australia in 2008. Children enrolled in the programme are awarded a distinctive bead for every procedure/treatment they have while in hospital. A previous evaluation study on the programme revealed that the beads are therapeutic for the child and parents; however, due to a small sample size, the results were representative of the experiences of a small number of families who participated in the programme. This was an evaluation study which employed a nonexperimental descriptive design. Surveys were mailed to all eligible families who enrolled in the programme. Data collection occurred between July-December 2012. Questions on parental experiences with the Heart Beads programme were divided into three categories: understanding, acknowledgement and quality. Descriptive statistics were obtained and analysed. One hundred and sixty-two mothers and 136 fathers responded to the survey. Heart Beads assisted mothers (83%) and fathers (80%) with understanding their child's condition and helped them with communication (mothers 80%, fathers 58%). The majority of fathers felt that their experience was acknowledged by nursing staff (64%) and medical staff (62%), while mothers indicated a higher response from nurses (76%) compared to medical staff (67%). Overall, parents rated the programme positively; however, there was some concern that children at times missed out on beads. Understanding how mothers and fathers experience the programme differently can guide staff in their communication with parents and inform future initiatives. The Heart Beads help nurses understand how parents are experiencing care and ways in which they can provide support and acknowledgement of the parent's experience. © 2014 John Wiley & Sons Ltd.

Negative dielectrophoresis spectroscopy for rare analyte quantification in biological samples

NASA Astrophysics Data System (ADS)

Kirmani, Syed Abdul Mannan; Gudagunti, Fleming Dackson; Velmanickam, Logeeshan; Nawarathna, Dharmakeerthi; Lima, Ivan T., Jr.

2017-03-01

We propose the use of negative dielectrophoresis (DEP) spectroscopy as a technique to improve the detection limit of rare analytes in biological samples. We observe a significant dependence of the negative DEP force on functionalized polystyrene beads at the edges of interdigitated electrodes with respect to the frequency of the electric field. We measured this velocity of repulsion for 0% and 0.8% conjugation of avidin with biotin functionalized polystyrene beads with our automated software through real-time image processing that monitors the Rayleigh scattering from the beads. A significant difference in the velocity of the beads was observed in the presence of as little as 80 molecules of avidin per biotin functionalized bead. This technology can be applied in the detection and quantification of rare analytes that can be useful in the diagnosis and the treatment of diseases, such as cancer and myocardial infarction, with the use of polystyrene beads functionalized with antibodies for the target biomarkers.

Microinjection--a tool to study gravitropism.

PubMed

Scherp, P; Hasenstein, K H

2003-01-01

Despite extensive studies on plant gravitropism this phenomenon is still poorly understood. The separation of gravity sensing, signal transduction and response is a common concept but especially the mechanism of gravisensing remains unclear. This paper focuses on microinjection as powerful tool to investigate gravisensing in plants. We describe the microinjection of magnetic beads in rhizoids of the green alga Chara and related subsequent manipulation of the gravisensing system. After injection, an external magnet can control the movement of the magnetic beads. We demonstrate successful injection of magnetic beads into rhizoids and describe a multitude of experiments that can be carried out to investigate gravitropism in Chara rhizoids. In addition to examining mechanical properties, bead microinjection is also useful for probing the function of the cytoskeleton by coating beads with drugs that interfere with the cytoskeleton. The injection of fluorescently labeled beads or probes may reveal the involvement of the cytoskeleton during gravistimulation and response in living cells. c2003 COSPAR. Published by Elsevier Ltd. All rights reserved.

Static antibiotic spacers augmented by calcium sulphate impregnated beads in revision TKA: Surgical technique and review of literature.

PubMed

Risitano, Salvatore; Sabatini, Luigi; Atzori, Francesco; Massè, Alessandro; Indelli, Pier Francesco

2018-06-01

Periprosthetic joint infection (PJI) is a serious complication in total knee arthroplasty (TKA) and represents one of the most common causes of revision. The challenge for surgeons treating an infected TKA is to quickly obtain an infection-free joint in order to re-implant, when possible, a new TKA. Recent literature confirms the role of local antibiotic-loaded beads as a strong bactericidal, allowing higher antibiotic elution when compared with antibiotic loaded spacers only. Unfortunately, classical Polymethylmethacrylate (PMMA) beads might allow bacteria adhesion, secondary development of antibiotic resistance and eventually surgical removal once antibiotics have eluted. This article describes a novel surgical technique using static, custom-made antibiotic loaded spacers augmented by calcium sulphate antibiotic-impregnated beads to improve the success rate of revision TKA in a setting of PJI. The use of calcium sulphate beads has several potential benefits, including a longer sustained local antibiotic release when compared with classical PMMA beads and, being resorbable, not requiring accessory surgical interventions.

Effect of lecithin and starch on alginate-encapsulated probiotic bacteria.

PubMed

Donthidi, A R; Tester, R F; Aidoo, K E

2010-01-01

The effect of lecithin and starch on viability of alginate encapsulated probiotics was determined at different temperatures. Probiotic organisms (1% v/v>10Log CFU ml(-1)) were encapsulated using alginate (2% w/v), gelatinized starches (2% w/v) and lecithin (0-4% w/v) and stored in sealed containers at 4, 23 and 37 degrees C (to simulate shelf storage conditions). Incorporation of lecithin improved the entrapment efficiency (p < 0.05) and the viability of encapsulated bacteria (p = 0.02). Encapsulated Lactobacillus, Bifidobacterium species and Lactococcus lactis in lecithin containing freeze-dried beads had good survival stability (above 6Log CFU ml(-1)) at 23 degrees C for 12 weeks. The bacteria in the beads showed 6Log survival by the end of 2 weeks at 37 degrees C. Encapsulated L. casei in the alginate beads containing lecithin were also more stable in the yoghurt than the beads without lecithin. SEM analysis of the beads showed an irregular surface for the beads without lecithin.

Microporous novolac-derived carbon beads/sulfur hybrid cathode for lithium-sulfur batteries

NASA Astrophysics Data System (ADS)

Choudhury, Soumyadip; Krüner, Benjamin; Massuti-Ballester, Pau; Tolosa, Aura; Prehal, Christian; Grobelsek, Ingrid; Paris, Oskar; Borchardt, Lars; Presser, Volker

2017-07-01

Novolac-derived nanoporous carbon beads were used as conductive matrix for lithium-sulfur battery cathodes. We employed a facile self-emulsifying synthesis to obtain sub-micrometer novolac-derived carbon beads with nanopores. After pyrolysis, the carbon beads showed already a specific surface area of 640 m2 g-1 which was increased to 2080 m2 g-1 after physical activation. The non-activated and the activated carbon beads represent nanoporous carbon with a medium and a high surface area, respectively. This allows us to assess the influence of the porosity on the electrochemical performance of lithium-sulfur battery cathodes. The carbon/sulfur hybrids were obtained from two different approaches of sulfur infiltration: melt-infusion of sulfur (annealing) and in situ formation of sulfur from sodium thiosulfate. The best performance (∼880 mAh gsulfur-1 at low charge rate; 5th cycle) and high performance stability (>600 mAh gsulfur-1 after 100 cycles) were found for the activated carbon beads when using melt infusion of sulfur.

Selective accumulation of harmful compounds by the DNA-inorganic hybrid-immobilized glass bead.

PubMed

Yamada, Masanori; Hamai, Akari

2009-08-11

Previously, we reported the DNA-inorganic hybrid material including double-stranded DNA by mixing the aqueous DNA solution and silane coupling reagents. Here, we immobilized the DNA-inorganic hybrid material onto the glass bead and prepared the DNA-immobilized glass bead column. The DNA-immobilized glass beads were stable in water and the amount of eluted DNA from the DNA-glass beads did not change for more than 1 week. Additionally, this DNA-immobilized column selectively accumulated the harmful compounds with the planar structure, such as dioxin- and polychlorinated biphenyl (PCB)-derivatives, and these accumulation percentages were 50-70%. Furthermore, the DNA-immobilized glass bead was recycled nine times by the application of ethanol solution and the accumulative ratio was maintained at more than 60% and did not appear to be decreasing. Therefore, these DNA-columns might have a potential for the selective removal and separation of DNA-intercalating molecules and harmful compounds with the planar structure from experimental or industrial drainages.

Skin permeation and retention of topical bead formulation containing tranexamic acid.

PubMed

Vijayakumar, Ajay; Baskaran, Rengarajan; Yoo, Bong Kyu

2017-02-01

The objective of this study is to develop a topical bead formulation of tranexamic acid (TA) which can be used concomitantly with laser treatment. The bead formulation of TA (TAB) was successfully prepared by fluidized bed drying method. Physicochemical properties of the TAB were evaluated in terms of chemical stability of TA and differential scanning calorimetry. TA in the bead was stable up to six months at 25°C and existed as amorphous state. In vitro skin permeation and in vivo skin retention of TA in the beads were significantly higher compared to a commercial product. When the bead was dissolved into distilled water and applied concomitantly with laser treatment, the amount of TA retained in the skin in the in vivo study was inversely proportional to the energy levels of laser treatment, indicating absorption into subcutaneous tissue and drainage to systemic circulation. Therefore, when laser treatment is used concomitantly with TAB, energy level should be very carefully monitored to avoid possible adverse events associated with systemic side effects of TA.

Calcium gluconate as cross-linker improves survival and shelf life of encapsulated and dried Metarhizium brunneum and Saccharomyces cerevisiae for the application as biological control agents.

PubMed

Humbert, Pascal; Przyklenk, Michael; Vemmer, Marina; Patel, Anant V

2017-02-01

Calcium chloride (CC) is the most common cross-linker for the encapsulation of biocontrol microorganisms in alginate beads. The aim of this study was to evaluate if calcium gluconate (CG) can replace CC as cross-linker and at the same time improve viability after drying and rehydration, hygroscopic properties, shelf life and nutrient supply. Hence, the biocontrol fungi Metarhizium brunneum and Saccharomyces cerevisiae were encapsulated in Ca-alginate beads supplemented with starch. Beads were dried and maximum survival was found in beads cross-linked with CG. Beads prepared with CG showed lower hygroscopic properties, but a higher shelf life for encapsulated fungi. Moreover, we demonstrated that gluconate has a nutritive effect on encapsulated fungi, leading to increased mycelium growth of M. brunneum and to enhanced CO 2 release from beads containing Saccharomyces cerevisiae. The application of CG as cross-linker will pave the way towards increasing drying survival and shelf life of various, especially drying-sensitive microbes.

Characterisation of bare and tannase-loaded calcium alginate beads by microscopic, thermogravimetric, FTIR and XRD analyses.

PubMed

Larosa, Claudio; Salerno, Marco; de Lima, Juliana Silva; Merijs Meri, Remo; da Silva, Milena Fernandes; de Carvalho, Luiz Bezerra; Converti, Attilio

2018-08-01

Incorporating enzymes into calcium alginate beads is an effective method to immobilise them and to preserve, at the same time, their catalytic activity. Sodium alginate was mixed with Aspergillus ficuum tannase in aqueous solution, and tannase-loaded calcium alginate beads were prepared using a simple droplet-based microfluidic system. Extensive experimental analysis was carried out to characterise the samples. Microscopic imaging revealed morphological differences between the surfaces of bare alginate matrix and tannase-loaded alginate beads. Thermal analysis allowed assessing the hydration contents of alginate and revealed the presence of tannase entrapped in the loaded beads, which was confirmed by vibrational spectroscopy. X-ray diffraction allowed us to conclude that alginate of tannase-loaded beads is not crystalline, which would make them suitable as carriers for possible controlled release. Moreover, they could be used in food applications to improve tea quality or clarify juices. Copyright © 2018 Elsevier B.V. All rights reserved.

Microinjection--a tool to study gravitropism

NASA Technical Reports Server (NTRS)

Scherp, P.; Hasenstein, K. H.

2003-01-01

Despite extensive studies on plant gravitropism this phenomenon is still poorly understood. The separation of gravity sensing, signal transduction and response is a common concept but especially the mechanism of gravisensing remains unclear. This paper focuses on microinjection as powerful tool to investigate gravisensing in plants. We describe the microinjection of magnetic beads in rhizoids of the green alga Chara and related subsequent manipulation of the gravisensing system. After injection, an external magnet can control the movement of the magnetic beads. We demonstrate successful injection of magnetic beads into rhizoids and describe a multitude of experiments that can be carried out to investigate gravitropism in Chara rhizoids. In addition to examining mechanical properties, bead microinjection is also useful for probing the function of the cytoskeleton by coating beads with drugs that interfere with the cytoskeleton. The injection of fluorescently labeled beads or probes may reveal the involvement of the cytoskeleton during gravistimulation and response in living cells. c2003 COSPAR. Published by Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wahyuni, Wulan Tri, E-mail: wulantriws@gmail.com; Department of Chemistry, FMIPA, Universitas Indonesia, Kampus UI Depok; Ivandini, Tribidasari A.

Biomolecule modified magnetic beads has been widely used in separation and sensing process. This study used streptavidin modified magnetic beads to immobilize biotin modified zanamivir. Biotin-streptavidin affinity facilitates immobilization of zanamivir on magnetic beads. Then interaction of zanamivir and neuraminidase was adopted as basic for enzyme detection. Detection of neuraminidase was performed at gold modified BDD using cyclic voltammetry technique. The measurement was carried out based on alteration of electrochemical signals of working electrode as neuraminidase response. The result showed that zanamivir was successfully immobilized on magnetic beads. The optimum amount of magnetic beads for zanamivir immobilization was 120 ug.more » Linear responses of neuraminidase were detected in concentration range of 0-15 mU. Detection limit (LOD) of measurement was 2.32 mU (R2 = 0.959) with precision as % RSD of 1.41%. Measurement of neuraminidase on magnetic beads could be also performed in the presence of mucin matrix. The linearity range was 0-8 mU with LOD of 0.64 mU (R2 = 0.950) and % RSD of 7.25%.« less

Viscosity of dilute suspensions of rigid bead arrays at low shear: accounting for the variation in hydrodynamic stress over the bead surfaces.

PubMed

Allison, Stuart A; Pei, Hongxia

2009-06-11

In this work, we examine the viscosity of a dilute suspension of irregularly shaped particles at low shear. A particle is modeled as a rigid array of nonoverlapping beads of variable size and geometry. Starting from a boundary element formalism, approximate account is taken of the variation in hydrodynamic stress over the surface of the individual beads. For a touching dimer of two identical beads, the predicted viscosity is lower than the exact value by 5.2%. The methodology is then applied to several other model systems including tetramers of variable conformation and linear strings of touching beads. An analysis is also carried out of the viscosity and translational diffusion of several dilute amino acids and diglycine in water. It is concluded that continuum hydrodynamic modeling with stick boundary conditions is unable to account for the experimental viscosity and diffusion data simultaneously. A model intermediate between "stick" and "slip" could possibly reconcile theory and experiment.

Disintegration of Nannochloropsis sp. cells in an improved turbine bead mill.

PubMed

Pan, Zhidong; Huang, Ying; Wang, Yanmin; Wu, Zhiwei

2017-12-01

The Nannochloropsis sp. cells in aqueous solution were disintegrated in an improved bead mill with turbine agitator. The disintegration rates of cell samples disrupted under various operating parameters (i.e., circumferential speed, bead size, disintegration time, and cell concentration) were analyzed. An experimental strategy to optimize the parameters affecting the cell disintegration process was proposed. The results show that Nannochloropsis sp. cells can be effectively disintegrated in the turbine stirred bead mill under the optimum condition (i.e., circumferential speed of 2.3m/s, concentration of 15vol.%, disintegration time of 40min and bead size of 0.3-0.4mm). The disintegration mechanism was discussed via the selection and breakage functions from population balance modelling. It is revealed that the impact and compression effects of stirring beads are more effective for the disruption of coarser fraction of cells, and the shear effect dominates the production of finer fractions of disintegrated cells. Copyright © 2017 Elsevier Ltd. All rights reserved.

Spot Surface Labeling of Magnetic Microbeads and Application in Biological Force Measurements

NASA Astrophysics Data System (ADS)

Estes, Ashley; O'Brien, E. Tim; Hill, David; Superfine, Richard

2006-11-01

Biological force measurements on single molecules and macromolecular structures often use microbeads for the application of force. These techniques are often complicated by multiple attachments and nonspecific binding. In one set of experiments, we are applying a magnetic force microscope that allows us to pull on magnetic beads attached to ciliated human bronchial epithelial cells. These experiments provide a means to measure the stall force of cilia and understand how cilia propel fluids. However, because we are using beads with diameters of one and 2.8 microns, and the diameter of human airway cilia is approximately 200 nm, we cannot be assured that the bead is bound to a single cilium. To address this, we have developed a sputter coating technique to block the biotin binding capability of the streptavidin labeled bead over its entire surface except for a small spot. These beads may also have applications in other biological experiments such as DNA force experiments in which binding of a single target to an individual bead is critical.

Serial femtosecond crystallography at the SACLA: breakthrough to dynamic structural biology.

PubMed

Mizohata, Eiichi; Nakane, Takanori; Fukuda, Yohta; Nango, Eriko; Iwata, So

2018-04-01

X-ray crystallography visualizes the world at the atomic level. It has been used as the most powerful technique for observing the three-dimensional structures of biological macromolecules and has pioneered structural biology. To determine a crystal structure with high resolution, it was traditionally required to prepare large crystals (> 200 μm). Later, synchrotron radiation facilities, such as SPring-8, that produce powerful X-rays were built. They enabled users to obtain good quality X-ray diffraction images even with smaller crystals (ca. 200-50 μm). In recent years, one of the most important technological innovations in structural biology has been the development of X-ray free electron lasers (XFELs). The SPring-8 Angstrom Compact free electron LAser (SACLA) in Japan generates the XFEL beam by accelerating electrons to relativistic speeds and directing them through in-vacuum, short-period undulators. Since user operation started in 2012, we have been involved in the development of serial femtosecond crystallography (SFX) measurement systems using XFEL at the SACLA. The SACLA generates X-rays a billion times brighter than SPring-8. The extremely bright XFEL pulses enable data collection with microcrystals (ca. 50-1 μm). Although many molecular analysis techniques exist, SFX is the only technique that can visualize radiation-damage-free structures of biological macromolecules at room temperature in atomic resolution and fast time resolution. Here, we review the achievements of the SACLA-SFX Project in the past 5 years. In particular, we focus on: (1) the measurement system for SFX; (2) experimental phasing by SFX; (3) enzyme chemistry based on damage-free room-temperature structures; and (4) molecular movie taken by time-resolved SFX.

GROMOS polarizable charge-on-spring models for liquid urea: COS/U and COS/U2

NASA Astrophysics Data System (ADS)

Lin, Zhixiong; Bachmann, Stephan J.; van Gunsteren, Wilfred F.

2015-03-01

Two one-site polarizable urea models, COS/U and COS/U2, based on the charge-on-spring model are proposed. The models are parametrized against thermodynamic properties of urea-water mixtures in combination with the polarizable COS/G2 and COS/D2 models for liquid water, respectively, and have the same functional form of the inter-atomic interaction function and are based on the same parameter calibration procedure and type of experimental data as used to develop the GROMOS biomolecular force field. Thermodynamic, dielectric, and dynamic properties of urea-water mixtures simulated using the polarizable models are closer to experimental data than using the non-polarizable models. The COS/U and COS/U2 models may be used in biomolecular simulations of protein denaturation.

Sodium bicarbonate-gelled chitosan beads as mechanically stable carriers for the covalent immobilization of enzymes.

PubMed

Wahba, Marwa I

2018-03-01

The poor mechanical stability of chitosan has long impeded its industrial utilization as an immobilization carrier. In this study, the mechanical properties of chitosan beads were greatly improved through utilizing the slow rate of the sodium bicarbonate-induced chitosan gelation and combining it with the chemical cross-linking action of glutaraldehyde (GA). The GA-treated sodium bicarbonate-gelled chitosan beads exhibited much better mechanical properties and up to 2.45-fold higher observed activity of the immobilized enzyme (β-D-galactosidase (β-gal)) when compared to the GA-treated sodium tripolyphosphate (TPP)-gelled chitosan beads. The differences between the sodium bicarbonate-gelled and the TPP-gelled chitosan beads were proven visually and also via scanning electron microscopy, elemental analysis, and differential scanning calorimetry. Moreover, the optimum pH, the optimum temperature, the apparent K m , and the apparent V max of the β-gals immobilized onto the two aforementioned types of chitosan beads were determined and compared. A reusability study was also performed. This study proved the superiority of the sodium bicarbonate-gelled chitosan beads as they retained 72.22 ± 4.57% of their initial observed activity during the 13 th reusability cycle whereas the TPP-gelled beads lost their activity during the first four reusability cycles, owing to their fragmentation. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:347-361, 2018. © 2017 American Institute of Chemical Engineers.

A prototype of injector to control and to detect the release of magnetic beads within the constraints of multibifurcation magnetic resonance navigation procedures.

PubMed

Bigot, Alexandre; Soulez, Gilles; Martel, Sylvain

2017-01-01

An injector equipped with a bead capture and a bead detection system is presented. In the context of magnetic resonance navigation (MRN), in which MRI gradients are used to steer intravascular therapeutic carriers, fast and reliable injection is essential. In this paper, we present a prototype of injector to control and to detect the release of magnetic beads. The injector relies on two distinct subsystems: (1) the capture subsystem, which creates local magnetic force to stop the flow of magnetic beads; and (2) the detection subsystem, which detects flowing beads and generates a trigger signal to start MRI gradient pulses. Both systems rely on small microcoils wound on the tubing. Five-turn microcoils show the best compromise between size and performance. Less than 5 mW of power is required to capture 0.8-mm beads moving in a flow above 5 mL min -1 or when a gradient above 200 mT m -1 is applied. The detection system is not sensitive to noise and detects every 0.8-mm bead in flow rates up to 14 mL m -1 . The prototype of injector shows performance above the requirements inherent to magnetic resonance navigation. This system is a step toward in vivo multibifurcation MRN. Magn Reson Med 77:444-452, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Microfluidic magnetic bead conveyor belt.

PubMed

van Pelt, Stijn; Frijns, Arjan; den Toonder, Jaap

2017-11-07

Magnetic beads play an important role in the miniaturization of clinical diagnostics systems. In lab-on-chip platforms, beads can be made to link to a target species and can then be used for the manipulation and detection of this species. Current bead actuation systems utilize complex on-chip coil systems that offer low field strengths and little versatility. We demonstrate a novel system based on an external rotating magnetic field and on-chip soft-magnetic structures to focus the field locally. These structures were designed and optimized using finite element simulations in order to create a number of local flux density maxima. These maxima, to which the magnetic beads are attracted, move over the chip surface in a continuous way together with the rotation of the external field, resulting in a mechanism similar to that of a conveyor belt. A prototype was fabricated using PDMS molding techniques mixed with iron powder for the magnetic structures. In the subsequent experiments, a quadrupole electromagnet was used to create the rotating external field. We observed that beads formed agglomerates that rolled over the chip surface, just above the magnetic structures. Field rotation frequencies between 0.1-50 Hz were tested resulting in magnetic bead speeds of over 1 mm s -1 for the highest frequency. With this, we have shown that our novel concept works, combining a simple design and simple operation with a powerful and versatile method for bead actuation. This makes it a promising method for further research and utilization in lab-on-chip systems.

A direct comparison of the performance of ground, beaded and silica-grafted MIPs in HPLC and turbulent flow chromatography applications.

PubMed

Fairhurst, Robert E; Chassaing, Christophe; Venn, Richard F; Mayes, Andrew G

2004-12-15

Spherical molecularly imprinted polymers (MIPs) specific to the beta-blocker propranolol have been synthesised using two different approaches and compared to traditional ground monolithic MIPs in HPLC and TFC applications. TFC is a LC technique used for rapid extraction of compounds directly from complex matrices. It can be easily coupled to HPLC and MS for automation of an extraction/analysis procedure. Spherical MIP beads were produced using a suspension polymerisation technique and silica/MIP composite beads by grafting MIP to spherical silica particles using a surface-bound initiator species. Synthesis of both beaded and silica-grafted MIPs was more practical than using the traditional grinding method and yields of spherical particles of the required size between 80 and 100% were routinely achieved. Under HPLC conditions, beaded and ground MIP materials showed a degree of chiral separation for all of the nine beta-blockers tested. The beaded MIP, however, showed much better flow properties and peak shape than the ground material. Silica-grafted MIP showed some separation in five of the drugs and a large improvement in peak shape and analysis times compared with both ground and beaded MIPs. The materials prepared were also used in extraction columns for Turbulent Flow Chromatography (TFC). Although no imprinting effect was observed under typical TFC conditions, beaded polymer materials showed promise for use as TFC extraction columns due to the good flow properties and clean extracts obtained.

Perfect count: a novel approach for the single platform enumeration of absolute CD4+ T-lymphocytes.

PubMed

Storie, Ian; Sawle, Alex; Goodfellow, Karen; Whitby, Liam; Granger, Vivian; Ward, Rosalie Y; Peel, Janet; Smart, Theresa; Reilly, John T; Barnett, David

2004-01-01

The derivation of reliable CD4(+) T lymphocyte counts is vital for the monitoring of disease progression and therapeutic effectiveness in HIV(+) individuals. Flow cytometry has emerged as the method of choice for CD4(+) T lymphocyte enumeration, with single-platform technology, coupled with reference counting beads, fast becoming the "gold standard." However, although single-platform, bead-based, sample acquisition requires the ratio of beads to cells to remain unchanged, there is no available method, until recently, to monitor this. Perfect Count beads have been developed to address this issue and to incorporate two bead populations, with different densities, to allow the detection of inadequate mixing. Comparison of the relative proportions of both beads with the manufacture's defined limits enables an internal QC check during sample acquisition. In this study, we have compared CD4(+) T lymphocyte counts, obtained from 104 HIV(+) patients, using TruCount beads with MultiSet software (defined as the predicated method) and the new Perfect Count beads, incorporating an in house sequential gating strategy. We have demonstrated an excellent degree of correlation between the predicate method and the Perfect Count system (r(2) = 0.9955; Bland Altman bias +27 CD4(+) T lymphocytes/microl). The Perfect Count system is a robust method for performing single platform absolute counts and has the added advantage of having internal QC checks. Such an approach enables the operator to identify potential problems during sample preparation, acquisition and analysis. Copyright 2003 Wiley-Liss, Inc.

Opportunities for bead-based multiplex assays in veterinary diagnostic laboratories

USDA-ARS?s Scientific Manuscript database

Bead based multiplex assays (BBMA) also referred to as Luminex, MultiAnalyte Profiling or cytometric bead array (CBA) assays, are applicable for high throughput, simultaneous detection of multiple analytes in solution (from several, up to 50-500 analytes within a single, small sample volume). Curren...

Evaluation of the Seismic Characterision of Select Engineered Nanoparticles in Saturated Glass Beads

EPA Science Inventory

A laboratory testing apparatus was developed for the study of seismic body wave propagation through nanoparticles dispersed in pore fluid that is essentially saturating glass beads. First, the responses of water-saturated glass bead specimens were studied to establish baseline si...

Freeforming objects with low-binder slurry

DOEpatents

Cesarano, III, Joseph; Calvert, Paul D.

2000-01-01

In a rapid prototyping system, a part is formed by depositing a bead of slurry that has a sufficient high concentration of particles to be pseudoplastic and almost no organic binders. After deposition the bead is heated to drive off sufficient liquid to cause the bead to become dilatant.

A numerical study of a long flexible fiber in shear flow: dynamics and rheology

NASA Astrophysics Data System (ADS)

Zuk, Pawel; Perazzo, Antonio; Nunes, Janine; Stone, Howard

2017-11-01

Long slender particles can span the whole spectrum of stiffness: from very flexible particles such as globular proteins to extremely rigid particles, e.g. carbon nanotubes or β-amyloid fibers. The behavior of rigid particles is well understood, however there are only few recent experimental reports about long fibers of moderate flexibility. We present a numerical study of a single long flexible fiber in a shear flow. The fiber is simulated as a bead-spring model including hydrodynamic interactions in the Rotne-Prager-Yamakawa approximation. We analyze fiber shape, motion and stress induced in the fluid under the shear flow. We find that all of these properties appear to be related to the characteristic length scale of the kinks formed in the fibers. We present a scaling law for the kink size as a function of shear rate and the fiber parameters and justify it using elastic theory. The study suggests that local properties of a single fiber may condition the behavior of concentrated suspensions.

Temperature dependent micro-rheology of a glass-forming polymer melt studied by molecular dynamics simulation.

PubMed

Kuhnhold, A; Paul, W

2014-09-28

We present a Molecular Dynamics simulation study of a micro-rheological probing of the glass transition in a polymer melt. Our model system consists of short bead-spring chains and the temperature ranges from well above the glass transition temperature to about 10% above it. The nano-particle clearly couples to the slowing down of the polymer segments and the calculated storage and loss moduli reveal the approach to the glass transition. At temperatures close to the mode coupling Tc of the polymer melt, the micro-rheological moduli measure the local viscoelastic response of the cage of monomers surrounding the nano-particle and no longer reveal the true melt moduli. The incoherent scattering function of the nano-particle exhibits a stretched exponential decay, typical for the α-process in glass forming systems. We find no indication of a strong superdiffusive regime as has been deduced from a recent experiment in the same temperature range but for smaller momentum transfers.

Local variation of fragility and glass transition temperature of ultra-thin supported polymer films.

PubMed

Hanakata, Paul Z; Douglas, Jack F; Starr, Francis W

2012-12-28

Despite extensive efforts, a definitive picture of the glass transition of ultra-thin polymer films has yet to emerge. The effect of film thickness h on the glass transition temperature T(g) has been widely examined, but this characterization does not account for the fragility of glass-formation, which quantifies how rapidly relaxation times vary with temperature T. Accordingly, we simulate supported polymer films of a bead-spring model and determine both T(g) and fragility, both as a function of h and film depth. We contrast changes in the relaxation dynamics with density ρ and demonstrate the limitations of the commonly invoked free-volume layer model. As opposed to bulk polymer materials, we find that the fragility and T(g) do not generally vary proportionately. Consequently, the determination of the fragility profile--both locally and for the film as a whole--is essential for the characterization of changes in film dynamics with confinement.

Setting the pace of microswimmers: when increasing viscosity speeds up self-propulsion

NASA Astrophysics Data System (ADS)

Pande, Jayant; Merchant, Laura; Krüger, Timm; Harting, Jens; Smith, Ana-Sunčana

2017-05-01

It has long been known that some microswimmers seem to swim counter-intuitively faster when the viscosity of the surrounding fluid is increased, whereas others slow down. This conflicting dependence of the swimming velocity on the viscosity is poorly understood theoretically. Here we explain that any mechanical microswimmer with an elastic degree of freedom in a simple Newtonian fluid can exhibit both kinds of response to an increase in the fluid viscosity for different viscosity ranges, if the driving is weak. The velocity response is controlled by a single parameter Γ, the ratio of the relaxation time of the elastic component of the swimmer in the viscous fluid and the swimming stroke period. This defines two velocity-viscosity regimes, which we characterize using the bead-spring microswimmer model and analyzing the different forces acting on the parts of this swimmer. The analytical calculations are supported by lattice-Boltzmann simulations, which accurately reproduce the two velocity regimes for the predicted values of Γ.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chremos, Alexandros, E-mail: achremos@imperial.ac.uk; Nikoubashman, Arash, E-mail: arashn@princeton.edu; Panagiotopoulos, Athanassios Z.

In this contribution, we develop a coarse-graining methodology for mapping specific block copolymer systems to bead-spring particle-based models. We map the constituent Kuhn segments to Lennard-Jones particles, and establish a semi-empirical correlation between the experimentally determined Flory-Huggins parameter χ and the interaction of the model potential. For these purposes, we have performed an extensive set of isobaric–isothermal Monte Carlo simulations of binary mixtures of Lennard-Jones particles with the same size but with asymmetric energetic parameters. The phase behavior of these monomeric mixtures is then extended to chains with finite sizes through theoretical considerations. Such a top-down coarse-graining approach is importantmore » from a computational point of view, since many characteristic features of block copolymer systems are on time and length scales which are still inaccessible through fully atomistic simulations. We demonstrate the applicability of our method for generating parameters by reproducing the morphology diagram of a specific diblock copolymer, namely, poly(styrene-b-methyl methacrylate), which has been extensively studied in experiments.« less

Inertial and viscoelastic forces on rigid colloids in microfluidic channels.

PubMed

Howard, Michael P; Panagiotopoulos, Athanassios Z; Nikoubashman, Arash

2015-06-14

We perform hybrid molecular dynamics simulations to study the flow behavior of rigid colloids dispersed in a dilute polymer solution. The underlying Newtonian solvent and the ensuing hydrodynamic interactions are incorporated through multiparticle collision dynamics, while the constituent polymers are modeled as bead-spring chains, maintaining a description consistent with the colloidal nature of our system. We study the cross-stream migration of the solute particles in slit-like channels for various polymer lengths and colloid sizes and find a distinct focusing onto the channel center under specific solvent and flow conditions. To better understand this phenomenon, we systematically measure the effective forces exerted on the colloids. We find that the migration originates from a competition between viscoelastic forces from the polymer solution and hydrodynamically induced inertial forces. Our simulations reveal a significantly stronger fluctuation of the lateral colloid position than expected from thermal motion alone, which originates from the complex interplay between the colloid and polymer chains.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Helfferich, Julian; Lyubimov, Ivan; Reid, Daniel

Glasses produced via physical vapor deposition can display greater kinetic stability and lower enthalpy than glasses prepared by liquid cooling. While the reduced enthalpy has often been used as a measure of the stability, it is not obvious whether dynamic measures of stability provide the same view. Here, we study dynamics in vapor-deposited and liquid-cooled glass films using molecular simulations of a bead-spring polymer model as well as a Lennard-Jones binary mixture in two and three dimensions. We confirm that the dynamics in vapor-deposited glasses is indeed slower than in ordinary glasses. We further show that the inherent structure energymore » is a good reporter of local dynamics, and that aged systems and glasses prepared by cooling at progressively slower rates exhibit the same behavior as vapor-deposited materials when they both have the same inherent structure energy. These findings suggest that the stability inferred from measurements of the energy is also manifested in dynamic observables, and they strengthen the view that vapor deposition processes provide an effective strategy for creation of stable glasses.« less

Topological analysis of polymeric melts: chain-length effects and fast-converging estimators for entanglement length.

PubMed

Hoy, Robert S; Foteinopoulou, Katerina; Kröger, Martin

2009-09-01

Primitive path analyses of entanglements are performed over a wide range of chain lengths for both bead spring and atomistic polyethylene polymer melts. Estimators for the entanglement length N_{e} which operate on results for a single chain length N are shown to produce systematic O(1/N) errors. The mathematical roots of these errors are identified as (a) treating chain ends as entanglements and (b) neglecting non-Gaussian corrections to chain and primitive path dimensions. The prefactors for the O(1/N) errors may be large; in general their magnitude depends both on the polymer model and the method used to obtain primitive paths. We propose, derive, and test new estimators which eliminate these systematic errors using information obtainable from the variation in entanglement characteristics with chain length. The new estimators produce accurate results for N_{e} from marginally entangled systems. Formulas based on direct enumeration of entanglements appear to converge faster and are simpler to apply.

Dynamic Contact Angle at the Nanoscale: A Unified View.

PubMed

Lukyanov, Alex V; Likhtman, Alexei E

2016-06-28

Generation of a dynamic contact angle in the course of wetting is a fundamental phenomenon of nature. Dynamic wetting processes have a direct impact on flows at the nanoscale, and therefore, understanding them is exceptionally important to emerging technologies. Here, we reveal the microscopic mechanism of dynamic contact angle generation. It has been demonstrated using large-scale molecular dynamics simulations of bead-spring model fluids that the main cause of local contact angle variations is the distribution of microscopic force acting at the contact line region. We were able to retrieve this elusive force with high accuracy. It has been directly established that the force distribution can be solely predicted on the basis of a general friction law for liquid flow at solid surfaces by Thompson and Troian. The relationship with the friction law provides both an explanation of the phenomenon of dynamic contact angle and a methodology for future predictions. The mechanism is intrinsically microscopic, universal, and irreducible and is applicable to a wide range of problems associated with wetting phenomena.

Enrichment of dynamic chromosomal crosslinks drive phase separation of the nucleolus

PubMed Central

Hult, Caitlin; Adalsteinsson, David; Vasquez, Paula A.; Lawrimore, Josh; Bennett, Maggie; York, Alyssa; Cook, Diana; Yeh, Elaine; Forest, Mark Gregory

2017-01-01

Abstract Regions of highly repetitive DNA, such as those found in the nucleolus, show a self-organization that is marked by spatial segregation and frequent self-interaction. The mechanisms that underlie the sequestration of these sub-domains are largely unknown. Using a stochastic, bead-spring representation of chromatin in budding yeast, we find enrichment of protein-mediated, dynamic chromosomal cross-links recapitulates the segregation, morphology and self-interaction of the nucleolus. Rates and enrichment of dynamic crosslinking have profound consequences on domain morphology. Our model demonstrates the nucleolus is phase separated from other chromatin in the nucleus and predicts that multiple rDNA loci will form a single nucleolus independent of their location within the genome. Fluorescent labeling of budding yeast nucleoli with CDC14-GFP revealed that a split rDNA locus indeed forms a single nucleolus. We propose that nuclear sub-domains, such as the nucleolus, result from phase separations within the nucleus, which are driven by the enrichment of protein-mediated, dynamic chromosomal crosslinks. PMID:28977453

Shear-induced desorption of isolated polymer molecules from a planar wall

NASA Astrophysics Data System (ADS)

Dutta, Sarit; Dorfman, Kevin; Kumar, Satish

2014-03-01

Shear-induced desorption of isolated polymer molecules is studied using Brownian dynamics simulations. The polymer molecules are modeled as freely jointed bead-spring chains interacting with a planar wall via a short-range potential. The simulations include both intrachain and chain-wall hydrodynamic interactions. Shear flow is found to cause chain flattening, resulting at low shear rates in an increased fraction of chain segments bound to the wall. However, above a critical shear rate the chains desorb completely. The desorption process is nucleated by random protrusions in the shear gradient direction which evolve under the combined effect of drag, hydrodynamic interaction, and vorticity-induced rotation, and subsequently lead to recapture. Above the critical shear rate, these protrusions grow in length until the entire chain is peeled off the wall. For free-draining chains, the protrusions are not sustained and no desorption is observed even at shear rates much higher than the critical value. These simulations can help in interpreting experiments on shear-induced desorption of polymer films and brushes.

Atomic Scattering Factor of the ASTRO-H (Hitomi) SXT Reflector Around the Gold's L Edges

NASA Technical Reports Server (NTRS)

Kikuchi, Naomichi; Kurashima, Sho; Ishida, Manabu; Iizuka, Ryo; Maeda, Yoshitomo; Hayashi, Takayuki; Okajima, Takashi; Matsumoto, Hironori; Mitsubishi, Ikuyuki; Saji, Shigetaka

2016-01-01

The atomic scattering factor in the energy range of 11.2 - 15.4 keV for the ASTRO-H Soft X-ray Telescope (SXT) is reported. The large effective area of the SXT makes use of photon spectra above 10 keV viable, unlike most other X-ray satellites with total-reflection mirror optics. Presence of gold's L-edges in the energy band is a major issue, as it complicates the function of the effective area. In order to model the area, the reflectivity measurements in the 11.2 - 15.4 keV band with the energy pitch of 0.4 - 0.7 eV were made in the synchrotron beam-line Spring-8 BL01B1. We obtained atomic scattering factors f1 and f2 by the curve fitting to the reflectivities of our witness sample. The edges associated with the L-I, II, and III transitions are identified, of which the depths are found to be roughly 60 shallower than those expected from the Henkes atomic scattering factor.

Harnessing the damping properties of materials for high-speed atomic force microscopy.

PubMed

Adams, Jonathan D; Erickson, Blake W; Grossenbacher, Jonas; Brugger, Juergen; Nievergelt, Adrian; Fantner, Georg E

2016-02-01

The success of high-speed atomic force microscopy in imaging molecular motors, enzymes and microbes in liquid environments suggests that the technique could be of significant value in a variety of areas of nanotechnology. However, the majority of atomic force microscopy experiments are performed in air, and the tapping-mode detection speed of current high-speed cantilevers is an order of magnitude lower in air than in liquids. Traditional approaches to increasing the imaging rate of atomic force microscopy have involved reducing the size of the cantilever, but further reductions in size will require a fundamental change in the detection method of the microscope. Here, we show that high-speed imaging in air can instead be achieved by changing the cantilever material. We use cantilevers fabricated from polymers, which can mimic the high damping environment of liquids. With this approach, SU-8 polymer cantilevers are developed that have an imaging-in-air detection bandwidth that is 19 times faster than those of conventional cantilevers of similar size, resonance frequency and spring constant.

Rattler behavior in As skutterudites and oxy-skutterudites

NASA Astrophysics Data System (ADS)

Bridges, Frank; Car, Brad; Hoffman-Stapleton, Mikaela; Keiber, Trevor; Sutton, Logan; Maple, M. Brian

2014-03-01

We report EXAFS measurements for the series CeX4As12 (X = Fe, Ru, Os) and NdCu3Ru4O12 as a function of temperature for most elements in the structure. In each case the rare earth atom is a ``rattler'' atom, with a low Einstein temperature while the skutterudite cage structure is relatively stiff. From temperature dependencies of the correlated Debye model for the cage atoms, one can estimate the effective spring constant for various atom pairs. We also find for the oxy-skutterudites that the planar CuO4 sub-structure is very stiff, and likely vibrates as a rigid unit. We compare the behavior of the As-skutterudites with other skutterudites and with the oxy-skutterudites, and discuss in terms of the rigid cage model. The second neighbor pair Ce-X for the As-skutterudites is softer than expected while for the oxy-skutterudites the second neighbor Nd-Ru pair is stiffer than the nearest neighbor Nd-O pair. Models are need to explore this behavior. Support: NSF DMR1005568.

Solid impingement erosion mechanisms and characterization of erosion resistance of ductile metals

NASA Technical Reports Server (NTRS)

Rao, V. P.; Buckley, D. H.

1982-01-01

Experimental results pertaining to spherical glass bead and angular crushed glass particle impingement are presented. A concept of energy adsorption to explain the failure of material is proposed. The erosion characteristics of several pure metals were correlated with the proposed energy parameters and with other properties. Correlations of erosion and material properties were also carried out with these materials to study the effect of the angle of impingement. Analyses of extensive erosion data indicate that surface energy, strain energy, melting point, bulk modulus, hardness, ultimate resilience, atomic volume and product of linear coefficient of thermal expansion, bulk modulus, and temperature rise required for melting, and ultimate resilience, and hardness exhibit the best correlations. It appears that both energy and thermal properties contribute to the total erosion.

Subatomic electronic feature from dynamic motion of Si dimer defects in Bi nanolines on Si(001)

NASA Astrophysics Data System (ADS)

Kirkham, C. J.; Longobardi, M.; Köster, S. A.; Renner, Ch.; Bowler, D. R.

2017-08-01

Scanning tunneling microscopy (STM) reveals unusual sharp features in otherwise defect-free Bi nanolines self-assembled on Si(001). They appear as subatomic thin lines perpendicular to the Bi nanoline at positive biases and as atomic size beads at negative biases. Density functional theory (DFT) simulations show that these features can be attributed to buckled Si dimers substituting for Bi dimers in the nanoline, where the sharp feature is the counterintuitive signature of these dimers flipping during scanning. The perfect correspondence between the STM data and the DFT simulation demonstrated in this paper highlights the detailed understanding we have of the complex Bi-Si(001) Haiku system. This discovery has applications in the patterning of Si dangling bonds for nanoscale electronics.

75 FR 73159 - Continental Tire North America, Inc., Receipt of Petition for Decision of Inconsequential...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-11-29

... is located in an area that is not more than one-fourth of the distance from the bead to the shoulder... the bead and a point one-half the distance from the bead to the shoulder of the tire, on at least one...

EMP Design Guidelines for Naval Ship Systems

DTIC Science & Technology

1975-08-22

le xc Ci .ube irret i Type FXC it LA 38 Beads 4 * 1 svj- I * 1 1 \\ Measured 3( )0 Beads V i i V 30 Bead 1 s...ATTN: R. W. Rostrom RCA Corporation Government & Commercial Systems Astro Electronics Division P. 0. Box 800 Princeton, New Jersey 08540 ATTN

Method for freeforming objects with low-binder slurry

DOEpatents

Cesarano, III, Joseph; Calvert, Paul D.

2002-01-01

In a rapid prototyping system, a part is formed by depositing a bead of slurry that has a sufficient high concentration of particles to be pseudoplastic and almost no organic binders. After deposition the bead is heated to drive off sufficient liquid to cause the bead to become dilatant.

Nutrient requirements and other factors involved in the culture of human kidney cells on microcarrier beads

NASA Technical Reports Server (NTRS)

Lewis, Marian L.; Morrison, Dennis R.

1987-01-01

The culture of human kidney cells on microcarrier beads in the Bioprocessing Laboratory at the Johnson Space Center is described. These were the first series of studies performed before and during 1983 to determine optimum conditions, including medium type, bead type and density. The composition of several medium types and the molecular weights of some common culture medium supplements and cellular proteins are included. The microgravity cell-to-bead attachment experiment performed on Space Transportation System Flight 8 is described.

Metallic Bead Detection by Using Eddy-Current Probe with SV-GMR Sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yamada, S.; Chomsuwan, K.; Hagino, T.

2005-04-09

The progress of the ECT probe with micro magnetic sensor becomes possible to apply to various applications. The detection of micro metallic bead used for electric packaging has been reported in this paper. We proposed micro ECT probes with meander coil as exciter and spin-valve giant magneto-resistance (SV-GMR) as receiver. Micro metallic bead(solder ball) with the diameter of 0.25 to 0.76 mm is used as a measuring object. We discuss the detection and alignment of metallic bead by using ECT technique.

Note: A quartz cell with Pt single crystal bead electrode for electrochemical scanning tunneling microscope measurements.

PubMed

Xia, Zhigang; Wang, Jihao; Hou, Yubin; Lu, Qingyou

2014-09-01

In this paper, we provide and demonstrate a design of a unique cell with Pt single crystal bead electrode for electrochemical scanning tunneling microscope (ECSTM) measurements. The active metal Pt electrode can be protected from air contamination during the preparation process. The transparency of the cell allows the tip and bead to be aligned by direct observation. Based on this, a new and effective alignment method is introduced. The high-quality bead preparations through this new cell have been confirmed by the ECSTM images of Pt (111).

Single molecule actuation and detection on a lab-on-a-chip magnetoresistive platform

NASA Astrophysics Data System (ADS)

Chaves, R. C.; Bensimon, D.; Freitas, P. P.

2011-03-01

On-chip magnetic tweezers based on current loops were integrated with magnetoresistive sensors. Magnetic forces up to 1.0±0.3pN are produced to actuate on DNA anchored to the surface of a flow cell and labeled with micrometer-sized magnetic beads. The levitation of the beads stretches the immobilized DNA. The relative position of the magnetic beads is monitored using spin-valve sensors. A bead vertical displacement resolution of 60nm is derived for DNA molecular motor activity in a tweezer steady current regime.

Single Cell Detection with Driven Magnetic Beads

NASA Astrophysics Data System (ADS)

McNaughton, B. H.; Agayan, R. R.; Stoica, V. A.; Clarke, R.; Kopelman, R.

Shifts in the nonlinear rotational frequency of magnetic beads (microspheres) offer a new and dynamic approach for the detection of single cells. We present the first demonstration of this capability by measuring the changes in the nonlinear rotational frequency of magnetic beads driven by an external magnetic field. The presence of an Escherichia coli bacterium on the surface of a 2.0 μm magnetic bead affects the drag of the system, thus changing the nonlinear rotation rate. Measurement of this rotational frequency is straight-forward utilizing standard microscopy techniques.

“Nanofiltration” Enabled by Super-Absorbent Polymer Beads for Concentrating Microorganisms in Water Samples

NASA Astrophysics Data System (ADS)

Xie, Xing; Bahnemann, Janina; Wang, Siwen; Yang, Yang; Hoffmann, Michael R.

2016-02-01

Detection and quantification of pathogens in water is critical for the protection of human health and for drinking water safety and security. When the pathogen concentrations are low, large sample volumes (several liters) are needed to achieve reliable quantitative results. However, most microbial identification methods utilize relatively small sample volumes. As a consequence, a concentration step is often required to detect pathogens in natural waters. Herein, we introduce a novel water sample concentration method based on superabsorbent polymer (SAP) beads. When SAP beads swell with water, small molecules can be sorbed within the beads, but larger particles are excluded and, thus, concentrated in the residual non-sorbed water. To illustrate this approach, millimeter-sized poly(acrylamide-co-itaconic acid) (P(AM-co-IA)) beads are synthesized and successfully applied to concentrate water samples containing two model microorganisms: Escherichia coli and bacteriophage MS2. Experimental results indicate that the size of the water channel within water swollen P(AM-co-IA) hydrogel beads is on the order of several nanometers. The millimeter size coupled with a negative surface charge of the beads are shown to be critical in order to achieve high levels of concentration. This new concentration procedure is very fast, effective, scalable, and low-cost with no need for complex instrumentation.

Raman signatures of the modern pigment (Zn,Cd)S1-xSex and glass matrix of a red bead from Magoro Hill, an archaeological site in Limpopo Province, South Africa, recalibrate the settlement chronology

NASA Astrophysics Data System (ADS)

Prinsloo, Linda C.; Boeyens, Jan C. A.; van der Ryst, Maria M.; Webb, Geoffrey

2012-09-01

Two glass trade beads, one red and one yellow, retrieved from a secure archaeological context on Magoro Hill, an erstwhile Venda stronghold in South Africa's Limpopo Province, were analyzed with Raman and photoluminescence spectroscopy. Raman spectroscopy identified the pigment coloring the yellow bead as lead tin yellow Type II and the glass as a typical soda-lime-silica glass. Both pigments and glass type were in use over a long time span and therefore the bead cannot be used as a temporal marker. The pigment coloring the red bead, on the other hand, was identified as nano-(Zn,Cd)S1-xSex mixed crystals, a pigment that was only widely used in the early 20th century. This date casts doubt on local oral tradition that associates the brick-built structure from which the beads were recovered with Manzinzinzi, a Venda chief who, according to contemporary documentary accounts, had already passed away in the 1880s. The more recent date for the red bead resolves the apparent discord between the oral and written records, suggesting that the building was probably erected and/or occupied by one of Manzinzinzi's successors.

PHOS-Select Iron Affinity beads enrich peptides for detection of organophosphorus adducts on albumin

PubMed Central

Jiang, Wei; Dubrovskii, Yaroslav A; Podolskaya, Ekaterina P; Murashko, Ekaterina A; Babakov, Vladimir; Nachon, Florian; Masson, Patrick; Schopfer, Lawrence M; Lockridge, Oksana

2013-01-01

Albumin is covalently modified by organophosphorus toxicants (OP) on tyrosine 411, but less than 1% of albumin is modified in humans by lethal OP doses that inhibit 95% of plasma butyrylcholinesterase. A method that enriches OP-modified albumin peptides could aid analysis of low dose exposures. Soman or chlorpyrifos oxon treated human plasma was digested with pepsin. Albumin peptides were enriched by binding to Fe3+ beads at pH 11 and eluted with pH 2.6 buffer. Similarly, mouse and guinea pig albumin modified by chlorpyrifos oxon were digested with pepsin and enriched by binding to Fe3+ beads. Peptides were identified by MALDI-TOF/TOF mass spectrometry. PHOS-select Iron Affinity beads specifically enriched albumin peptides VRY411TKKVPQVST and LVRY411TKKVPQVST in a pepsin digest of human plasma. The unmodified as well as OP-modified peptides bound to the beads. The binding capacity of 500 μl beads was the pepsin digest of 2.1 μL human plasma. The limit of detection was 0.2% of OP-modified albumin peptide in 0.43 μL plasma. Enrichment of OP-modified albumin peptides by binding to Fe3+ beads is a method with potential application to diagnosis of OP pesticide and nerve agent exposure in humans, mice, and guinea pigs. PMID:24187955

Rapid Detection of Enterobacter Sakazakii in milk Powder using amino modified chitosan immunomagnetic beads.

PubMed

Zhu, Yinglian; Wang, Dongfeng

2016-12-01

Chitosan immunomagnetic beads (CIBs) were first prepared through converting hydroxyl groups of natural polymer material-chitosan into amino groups using epichlorohydrin and ethylenediamine as modification agent and then coupling with polyclonal antibodies of Enterobacter sakazakii using glutaraldehyde as cross-linking agent. The beads before coupling with antibodies were characterized by magnetic property measurement, FTIR, SEM and XRD technologies. In the assay a natural polysaccharide-chitosan, which has good biological and chemical properties such as non-toxicity, biocompatibility and high chemical reactivity was first used for synthesis of immunomagnetic beads. The detection method first established in this paper that combined the beads with chromogenic medium together to rapid detect E. sakazakii in milk powder could greatly improve the detection specificity and working efficiency. The beads exhibited a maximum capturing capacity of 1×10 6 cfu/g with the detection sensitivity of 4cfu/g. The results demonstrate that the assay is a straightforward, specific and sensitive alternative for rapid detection of E.sakazakii in food matrix. The total analysis time was as little as about 25h, which greatly shorten the detection time. The method can provides new ideas not only to preparation technique of immunomagnetic beads but to imunne detection technique in food safety. Copyright © 2016 Elsevier B.V. All rights reserved.

Multiple pathogen biomarker detection using an encoded bead array in droplet PCR.

PubMed

Periyannan Rajeswari, Prem Kumar; Soderberg, Lovisa M; Yacoub, Alia; Leijon, Mikael; Andersson Svahn, Helene; Joensson, Haakan N

2017-08-01

We present a droplet PCR workflow for detection of multiple pathogen DNA biomarkers using fluorescent color-coded Luminex® beads. This strategy enables encoding of multiple singleplex droplet PCRs using a commercially available bead set of several hundred distinguishable fluorescence codes. This workflow provides scalability beyond the limited number offered by fluorescent detection probes such as TaqMan probes, commonly used in current multiplex droplet PCRs. The workflow was validated for three different Luminex bead sets coupled to target specific capture oligos to detect hybridization of three microorganisms infecting poultry: avian influenza, infectious laryngotracheitis virus and Campylobacter jejuni. In this assay, the target DNA was amplified with fluorescently labeled primers by PCR in parallel in monodisperse picoliter droplets, to avoid amplification bias. The color codes of the Luminex detection beads allowed concurrent and accurate classification of the different bead sets used in this assay. The hybridization assay detected target DNA of all three microorganisms with high specificity, from samples with average target concentration of a single DNA template molecule per droplet. This workflow demonstrates the possibility of increasing the droplet PCR assay detection panel to detect large numbers of targets in parallel, utilizing the scalability offered by the color-coded Luminex detection beads. Copyright © 2017. Published by Elsevier B.V.

Microparticle sampling by electrowetting-actuated droplet sweeping.

PubMed

Zhao, Yuejun; Cho, Sung Kwon

2006-01-01

This paper describes a new microparticle sampler where particles can be efficiently swept from a solid surface and sampled into a liquid medium using moving droplets actuated by the electrowetting principle. We successfully demonstrate that super hydrophilic (2 microm and 7.9 microm diameter glass beads of about 14 degrees contact angle), intermediate hydrophilic (7.5 microm diameter polystyrene beads of about 70 degrees contact angle), and super hydrophobic (7.9 microm diameter Teflon-coated glass beads and 3 microm size PTFE particles of over 110 degrees contact angles) particles on a solid surface are picked up by electrowetting-actuated moving droplets. For the glass beads as well as the polystyrene beads, the sampling efficiencies are over 93%, in particular over 98% for the 7.9 microm glass beads. For the PTFE particles, however, the sampling efficiency is measured at around 70%, relatively lower than that of the glass and polystyrene beads. This is due mainly to the non-uniformity in particle size and the particle hydrophobicity. In this case, the collected particles staying (adsorbing) on the air-to-water interface hinder the droplet from advancing. This particle sampler requires an extremely small amount of liquid volume (about 500 nanoliters) and will thus be highly compatible and easily integrated with lab-on-a-chip systems for follow-up biological/chemical analyses.

Sulindac loaded alginate beads for a mucoprotective and controlled drug release.

PubMed

Yegin, Betül Arica; Moulari, Brice; Durlu-Kandilci, N Tugba; Korkusuz, Petek; Pellequer, Yann; Lamprecht, Alf

2007-06-01

Ionotropic gelation was used to entrap sulindac into calcium alginate beads as a potential drug carrier for the oral delivery of this anti-inflammatory drug. Beads were investigated in vitro for a possible sustained drug release and their use in vivo as a gastroprotective system for sulindac. Process parameters such as the polymer concentration, polymer/drug ratio, and different needle diameter were analysed for their influences on the bead properties. Size augmented with increasing needle diameter (0.9 mm needle: 1.28 to 1.44 mm; 0.45 mm needle: 1.04 to 1.07 mm) due to changes in droplet size as well as droplet viscosity. Yields varied between 87% and 98% while sulindac encapsulation efficiencies of about 88% and 94% were slightly increasing with higher alginate concentrations. Drug release profiles exhibited a complete release for all formulations within 4 hours with a faster release for smaller beads. Sulindac loaded alginate beads led to a significant reduction of macroscopic histological damage in the stomach and duodenum in mice. Similarly, microscopic analyses of the mucosal damage demonstrated a significant mucoprotective effect of all bead formulation compared to the free drug. The present alginate formulations exhibit promising properties of a controlled release form for sulindac; meanwhile they provide a distinct tissue protection in the stomach and duodenum.

Organization of microbeads in Leidenfrost drops.

PubMed

Maquet, Laurent; Colinet, Pierre; Dorbolo, Stéphane

2014-06-21

We investigated the organization of micrometric hydrophilic beads (glass or basalt) immersed in Leidenfrost drops. Starting from a large volume of water compared to the volume of the beads, while the liquid evaporates, we observed that the grains are eventually trapped at the interface of the droplet and accumulate. At a moment, the grains entirely cover the droplet. We measured the surface area at this moment as a function of the total mass of particles inserted in the droplet. We concluded that the grains form a monolayer around the droplet assuming (i) that the packing of the beads at the surface is a random close packing and (ii) that the initial surface of the drop is larger than the maximum surface that the beads can cover. Regarding the evaporation dynamics, the beads are found to reduce the evaporation rate of the drop. The slowdown of the evaporation is interpreted as being the consequence of the dewetting of the particles located at the droplet interface which makes the effective surface of evaporation smaller. As a matter of fact, contact angles of the beads with the water deduced from the evaporation rates are consistent with contact angles of beads directly measured at a flat air-water interface of water in a container.

Preparation and testing of a tetra-amine copper(II) chitosan bead system for enhanced phosphate remediation.

PubMed

Kumar, Ilango Aswin; Viswanathan, Natrayasamy

2018-03-01

A tetra-amine copper(II) chitosan bead system (TAC@CS composite beads) was developed by grafting tetra-amine copper(II) (TAC) with chitosan (CS) and utilized for phosphate removal. The prepared TAC@CS composite beads possess enhanced phosphate sorption capacity (SC) of 41.42 ± 0.071 mg/g than copper grafted chitosan (Cu@CS) composite, TAC and chitosan which were found to be 37.01 ± 0.803, 33.20 ± 0.650 and 7.24 ± 0.059 mg/g respectively. In batch mode, various adsorption influencing parameters like contact time, initial phosphate concentration, solution pH, co-anions and temperature were optimized for maximum phosphate sorption. The prepared adsorbents were characterized by FTIR, XRD, UV-Visible, SEM and EDAX analysis. The adsorption isotherms and thermodynamic parameters of the adsorbent were studied. The feasible phosphate uptake mechanism of TAC@CS biocomposite beads was reported. The reusability studies of TAC@CS composite beads were carried out using NaOH as elutant. The suitability of TAC@CS composite beads at field conditions was tested with phosphate contaminated field water samples collected from nearby areas of Dindigul district. Copyright © 2017 Elsevier Ltd. All rights reserved.

"Nanofiltration" Enabled by Super-Absorbent Polymer Beads for Concentrating Microorganisms in Water Samples.

PubMed

Xie, Xing; Bahnemann, Janina; Wang, Siwen; Yang, Yang; Hoffmann, Michael R

2016-02-15

Detection and quantification of pathogens in water is critical for the protection of human health and for drinking water safety and security. When the pathogen concentrations are low, large sample volumes (several liters) are needed to achieve reliable quantitative results. However, most microbial identification methods utilize relatively small sample volumes. As a consequence, a concentration step is often required to detect pathogens in natural waters. Herein, we introduce a novel water sample concentration method based on superabsorbent polymer (SAP) beads. When SAP beads swell with water, small molecules can be sorbed within the beads, but larger particles are excluded and, thus, concentrated in the residual non-sorbed water. To illustrate this approach, millimeter-sized poly(acrylamide-co-itaconic acid) (P(AM-co-IA)) beads are synthesized and successfully applied to concentrate water samples containing two model microorganisms: Escherichia coli and bacteriophage MS2. Experimental results indicate that the size of the water channel within water swollen P(AM-co-IA) hydrogel beads is on the order of several nanometers. The millimeter size coupled with a negative surface charge of the beads are shown to be critical in order to achieve high levels of concentration. This new concentration procedure is very fast, effective, scalable, and low-cost with no need for complex instrumentation.

Structuring and calorie control of bakery products by templating batter with ultra melt-resistant food-grade hydrogel beads.

PubMed

Thompson, Benjamin R; Horozov, Tommy S; Stoyanov, Simeon D; Paunov, Vesselin N

2017-08-01

We report the use of a temperature insensitive, food-grade hydrogel to reduce the caloric density of pancakes that were prepared at temperatures much higher than the boiling point of water. This cheap, facile method utilises a mixed agar-methylcellulose hydrogel, which was blended to produce a slurry of hydrogel microbeads. The pancake batter was mixed with a controlled volume percentage of slurry of hydrogel beads and cooked. From bomb calorimetry experiments, the composites were found to have a reduced caloric density that reflects the volume percentage of hydrogel beads mixed with the batter. Using this procedure, we were able to reduce the caloric density of pancakes by up to 23 ± 3% when the volume percentage of hydrogel beads initially used was 25%. The method is not limited to pancakes and could potentially be applied to various other food products. The structure and morphology of the freeze-dried pancakes and pancake-hydrogel composites were investigated and pores of a similar size to the hydrogel beads were found, confirming that the gel beads maintained their structure during the cooking process. There is scope for further development of this method by the encapsulation of nutritionally beneficial or flavour enhancing ingredients within the hydrogel beads.

Graphene oxide/alginate beads as adsorbents: Influence of the load and the drying method on their physicochemical-mechanical properties and adsorptive performance.

PubMed

Platero, Emiliano; Fernandez, Maria Emilia; Bonelli, Pablo Ricardo; Cukierman, Ana Lea

2017-04-01

Graphene oxide/alginate beads were prepared from lab-synthesized graphene oxide, varying its content within the beads (0.05, 0.125, and 0.25wt.%). Ethanol-drying and lyophilization were compared as drying methods to obtain suitable adsorbents which were later tested to the removal of a model organic molecule (methylene blue). The morphological and textural properties of all the beads were characterized by scanning electron microscopy and N 2 adsorption/desorption isotherms at -196°C, respectively. Limited porosity was obtained for all cases (S BET <60m 2 /g). Uniaxial compression tests were performed to assess the mechanical properties of the beads. Ethanol-dried ones exhibited higher Young's elasticity modulus (E=192kPa) than the lyophilized samples (twice at 0.25wt.% graphene oxide loading), which disclosed breakage points at lower deformation percentages. Adsorption experiments were conducted and dye adsorption isotherms were obtained for the beads with the best removal performance. The experimental data were better fitted by the Langmuir model. The highest maximum adsorption capacity (4.25mmol/g) was obtained for the lyophilized beads with the highest graphene oxide content. Mechanical properties were found to be affected also by the dye adsorption. Copyright © 2016 Elsevier Inc. All rights reserved.

Blood Compatibility of Sulfonated Cladophora Nanocellulose Beads.

PubMed

Rocha, Igor; Lindh, Jonas; Hong, Jaan; Strømme, Maria; Mihranyan, Albert; Ferraz, Natalia

2018-03-07

Sulfonated cellulose beads were prepared by oxidation of Cladophora nanocellulose to 2,3-dialdehyde cellulose followed by sulfonation using bisulfite. The physicochemical properties of the sulfonated beads, i.e., high surface area, high degree of oxidation, spherical shape, and the possibility of tailoring the porosity, make them interesting candidates for the development of immunosorbent platforms, including their application in extracorporeal blood treatments. A desired property for materials used in such applications is blood compatibility; therefore in the present work, we investigate the hemocompatibility of the sulfonated cellulose beads using an in vitro whole blood model. Complement system activation (C3a and sC5b-9 levels), coagulation activation (thrombin-antithrombin (TAT) levels) and hemolysis were evaluated after whole blood contact with the sulfonated beads and the results were compared with the values obtained with the unmodified Cladophora nanocellulose. Results showed that neither of the cellulosic materials presented hemolytic activity. A marked decrease in TAT levels was observed after blood contact with the sulfonated beads, compared with Cladophora nanocellulose. However, the chemical modification did not promote an improvement in Cladophora nanocellulose hemocompatibility in terms of complement system activation. Even though the sulfonated beads presented a significant reduction in pro-coagulant activity compared with the unmodified material, further modification strategies need to be investigated to control the complement activation by the cellulosic materials.

Adsorption of ochratoxin A from grape juice by yeast cells immobilised in calcium alginate beads.

PubMed

Farbo, Maria Grazia; Urgeghe, Pietro Paolo; Fiori, Stefano; Marceddu, Salvatore; Jaoua, Samir; Migheli, Quirico

2016-01-18

Grape juice can be easily contaminated with ochratoxin A (OTA), one of the known mycotoxins with the greatest public health significance. Among the different approaches to decontaminate juice from this mycotoxin, microbiological methods proved efficient, inexpensive and safe, particularly the use of yeast or yeast products. To ascertain whether immobilisation of the yeast biomass would lead to successful decontamination, alginate beads encapsulating Candida intermedia yeast cells were used in our experiments to evaluate their OTA-biosorption efficacy. Magnetic calcium alginate beads were also prepared by adding magnetite in the formulation to allow fast removal from the aqueous solution with a magnet. Calcium alginate beads were added to commercial grape juice spiked with 20 μg/kg OTA and after 48 h of incubation a significant reduction (>80%), of the total OTA content was achieved, while in the subsequent phases (72-120 h) OTA was slowly released into the grape juice by alginate beads. Biosorption properties of alginate-yeast beads were tested in a prototype bioreactor consisting in a glass chromatography column packed with beads, where juice amended with OTA was slowly flowed downstream. The adoption of an interconnected scaled-up bioreactor as an efficient and safe tool to remove traces of OTA from liquid matrices is discussed. Copyright © 2015 Elsevier B.V. All rights reserved.

“Nanofiltration” Enabled by Super-Absorbent Polymer Beads for Concentrating Microorganisms in Water Samples

PubMed Central

Xie, Xing; Bahnemann, Janina; Wang, Siwen; Yang, Yang; Hoffmann, Michael R.

2016-01-01

Detection and quantification of pathogens in water is critical for the protection of human health and for drinking water safety and security. When the pathogen concentrations are low, large sample volumes (several liters) are needed to achieve reliable quantitative results. However, most microbial identification methods utilize relatively small sample volumes. As a consequence, a concentration step is often required to detect pathogens in natural waters. Herein, we introduce a novel water sample concentration method based on superabsorbent polymer (SAP) beads. When SAP beads swell with water, small molecules can be sorbed within the beads, but larger particles are excluded and, thus, concentrated in the residual non-sorbed water. To illustrate this approach, millimeter-sized poly(acrylamide-co-itaconic acid) (P(AM-co-IA)) beads are synthesized and successfully applied to concentrate water samples containing two model microorganisms: Escherichia coli and bacteriophage MS2. Experimental results indicate that the size of the water channel within water swollen P(AM-co-IA) hydrogel beads is on the order of several nanometers. The millimeter size coupled with a negative surface charge of the beads are shown to be critical in order to achieve high levels of concentration. This new concentration procedure is very fast, effective, scalable, and low-cost with no need for complex instrumentation. PMID:26876979

Alginate-caseinate composites: Molecular interactions and characterization of cross-linked beads for the delivery of anticandidals.

PubMed

Khlibsuwan, Rapee; Khunkitti, Watcharee; Pongjanyakul, Thaned

2018-04-19

Polysaccharide-protein composites offer potential utility for the delivery of drugs. The objectives of this work were to investigate the molecular interactions between sodium alginate (SA) and sodium caseinate (SC) in dispersions and films and to characterize calcium alginate (CA) beads mixed with SC for the delivery of fluconazole (FZ) and clotrimazole (CZ). The results demonstrated that SA could interact with SC, which caused a viscosity synergism in the dispersions. Hydrogen bonding between the carboxyl or hydroxyl groups of SA and the amide groups of SC led to the formation of soluble complexes that could reinforce the CA beads prepared by calcium cross-linking. The SC-CA beads provided higher drug entrapment efficiency, lower water uptake and erosion, and slower drug release than for the CA beads. The loaded FZ was an amorphous form, but CZ crystals were embedded in the bead matrix due to the low water solubility of this drug. However, SC micellization could enhance the water solubility and efficacy of CZ against Candida albicans. This finding indicates that SA can interact with SC via hydrogen bonding to form complexes and that the anticandidal-loaded SC-CA beads can be used as drug delivery systems and drug reservoirs in tablets for oral candidiasis. Copyright © 2018 Elsevier B.V. All rights reserved.

A new dimension in retrograde flow: centripetal movement of engulfed particles.

PubMed Central

Caspi, A; Yeger, O; Grosheva, I; Bershadsky, A D; Elbaum, M

2001-01-01

Centripetal motion of surface-adherent particles is a classic experimental system for studying surface dynamics on a eukaryotic cell. To investigate bead migration over the entire cell surface, we have developed an experimental assay using multinuclear giant fibroblasts, which provide expanded length scales and an unambiguous frame of reference. Beads coated by adhesion ligands concanavalin A or fibronectin are placed in specific locations on the cell using optical tweezers, and their subsequent motion is tracked over time. The adhesion, as well as velocity and directionality of their movement, expose distinct regions of the cytoplasm and membrane. Beads placed on the peripheral lamella initiate centripetal motion, whereas beads placed on the central part of the cell attach to a stationary cortex and do not move. Careful examination by complementary three-dimensional methods shows that the motion of a bead placed on the cell periphery takes place after engulfment into the cytoplasm, whereas stationary beads, placed near the cell center, are not engulfed. These results demonstrate that centripetal motion of adhering particles may occur inside as well as outside the cell. Inhibition of actomyosin activity is used to explore requirements for engulfment and aspects of the bead movement. Centripetal movement of adherent particles seems to depend on mechanisms distinct from those driving overall cell contractility. PMID:11566772

Size dependent nanomechanics of coil spring shaped polymer nanowires

NASA Astrophysics Data System (ADS)

Ushiba, Shota; Masui, Kyoko; Taguchi, Natsuo; Hamano, Tomoki; Kawata, Satoshi; Shoji, Satoru

2015-11-01

Direct laser writing (DLW) via two-photon polymerization (TPP) has been established as a powerful technique for fabrication and integration of nanoscale components, as it enables the production of three dimensional (3D) micro/nano objects. This technique has indeed led to numerous applications, including micro- and nanoelectromechanical systems (MEMS/NEMS), metamaterials, mechanical metamaterials, and photonic crystals. However, as the feature sizes decrease, an urgent demand has emerged to uncover the mechanics of nanosized polymer materials. Here, we fabricate coil spring shaped polymer nanowires using DLW via two-photon polymerization. We find that even the nanocoil springs follow a linear-response against applied forces, following Hooke’s law, as revealed by compression tests using an atomic force microscope. Further, the elasticity of the polymer material is found to become significantly greater as the wire radius is decreased from 550 to 350 nm. Polarized Raman spectroscopy measurements show that polymer chains are aligned in nanowires along the axis, which may be responsible for the size dependence. Our findings provide insight into the nanomechanics of polymer materials fabricated by DLW, which leads to further applications based on nanosized polymer materials.

Size dependent nanomechanics of coil spring shaped polymer nanowires.

PubMed

Ushiba, Shota; Masui, Kyoko; Taguchi, Natsuo; Hamano, Tomoki; Kawata, Satoshi; Shoji, Satoru

2015-11-27

Direct laser writing (DLW) via two-photon polymerization (TPP) has been established as a powerful technique for fabrication and integration of nanoscale components, as it enables the production of three dimensional (3D) micro/nano objects. This technique has indeed led to numerous applications, including micro- and nanoelectromechanical systems (MEMS/NEMS), metamaterials, mechanical metamaterials, and photonic crystals. However, as the feature sizes decrease, an urgent demand has emerged to uncover the mechanics of nanosized polymer materials. Here, we fabricate coil spring shaped polymer nanowires using DLW via two-photon polymerization. We find that even the nanocoil springs follow a linear-response against applied forces, following Hooke's law, as revealed by compression tests using an atomic force microscope. Further, the elasticity of the polymer material is found to become significantly greater as the wire radius is decreased from 550 to 350 nm. Polarized Raman spectroscopy measurements show that polymer chains are aligned in nanowires along the axis, which may be responsible for the size dependence. Our findings provide insight into the nanomechanics of polymer materials fabricated by DLW, which leads to further applications based on nanosized polymer materials.

Distribution and biophysical processes of beaded streams in Arctic permafrost landscapes

NASA Astrophysics Data System (ADS)

Arp, C. D.; Whitman, M. S.; Jones, B. M.; Grosse, G.; Gaglioti, B. V.; Heim, K. C.

2015-01-01

Beaded streams are widespread in permafrost regions and are considered a common thermokarst landform. However, little is known about their distribution, how and under what conditions they form, and how their intriguing morphology translates to ecosystem functions and habitat. Here we report on a circum-Arctic survey of beaded streams and a watershed-scale analysis in northern Alaska using remote sensing and field studies. We mapped over 400 channel networks with beaded morphology throughout the continuous permafrost zone of northern Alaska, Canada, and Russia and found the highest abundance associated with medium to high ground-ice content permafrost in moderately sloping terrain. In one Arctic coastal plain watershed, beaded streams accounted for half of the drainage density, occurring primarily as low-order channels initiating from lakes and drained lake basins. Beaded streams predictably transition to alluvial channels with increasing drainage area and decreasing channel slope, although this transition is modified by local controls on water and sediment delivery. The comparisons of one beaded channel using repeat photography between 1948 and 2013 indicate a relatively stable landform, and 14C dating of basal sediments suggest channel formation may be as early as the Pleistocene-Holocene transition. Contemporary processes, such as deep snow accumulation in riparian zones, effectively insulate channel ice and allows for perennial liquid water below most beaded stream pools. Because of this, mean annual temperatures in pool beds are greater than 2 °C, leading to the development of perennial thaw bulbs or taliks underlying these thermokarst features that range from 0.7 to 1.6 m. In the summer, some pools thermally stratify, which reduces permafrost thaw and maintains cold-water habitats. Snowmelt-generated peak flows decrease rapidly by two or more orders of magnitude to summer low flows with slow reach-scale velocity distributions ranging from 0.01 to 0.1 m s-1, yet channel runs still move water rapidly between pools. The repeating spatial pattern associated with beaded stream morphology and hydrological dynamics may provide abundant and optimal foraging habitat for fish. Beaded streams may create important ecosystem functions and habitat in many permafrost landscapes and their distribution and dynamics are only beginning to be recognized in Arctic research.

Beaded streams of Arctic permafrost landscapes

NASA Astrophysics Data System (ADS)

Arp, C. D.; Whitman, M. S.; Jones, B. M.; Grosse, G.; Gaglioti, B. V.; Heim, K. C.

2014-07-01

Beaded streams are widespread in permafrost regions and are considered a common thermokarst landform. However, little is known about their distribution, how and under what conditions they form, and how their intriguing morphology translates to ecosystem functions and habitat. Here we report on a Circum-Arctic inventory of beaded streams and a watershed-scale analysis in northern Alaska using remote sensing and field studies. We mapped over 400 channel networks with beaded morphology throughout the continuous permafrost zone of northern Alaska, Canada, and Russia and found the highest abundance associated with medium- to high-ice content permafrost in moderately sloping terrain. In the Fish Creek watershed, beaded streams accounted for half of the drainage density, occurring primarily as low-order channels initiating from lakes and drained lake basins. Beaded streams predictably transition to alluvial channels with increasing drainage area and decreasing channel slope, although this transition is modified by local controls on water and sediment delivery. Comparison of one beaded channel using repeat photography between 1948 and 2013 indicate relatively stable form and 14C dating of basal sediments suggest channel formation may be as early as the Pleistocene-Holocene transition. Contemporary processes, such as deep snow accumulation in stream gulches effectively insulates river ice and allows for perennial liquid water below most beaded stream pools. Because of this, mean annual temperatures in pool beds are greater than 2 °C, leading to the development of perennial thaw bulbs or taliks underlying these thermokarst features. In the summer, some pools stratify thermally, which reduces permafrost thaw and maintains coldwater habitats. Snowmelt generated peak-flows decrease rapidly by two or more orders of magnitude to summer low flows with slow reach-scale velocity distributions ranging from 0.1 to 0.01 m s-1, yet channel runs still move water rapidly between pools. This repeating spatial pattern associated with beaded stream morphology and hydrological dynamics may provide abundant and optimal foraging habitat for fish. Thus, beaded streams may create important ecosystem functions and habitat in many permafrost landscapes and their distribution and dynamics are only beginning to be recognized in Arctic research.

Processes Leading to Beaded Channels Formation in Central Yakutia

NASA Astrophysics Data System (ADS)

Tarbeeva, A. M.; Lebedeva, L.; Efremov, V. S.; Krylenko, I. V.; Surkov, V. V.

2017-12-01

Beaded channels, consisting of deepened and widened pools and connecting narrow runs, are common fluvial forms in permafrost regions. Recent studies have shown that beaded channels are very important for connecting alluvial rivers with headwater lakes allowing fish passage and foraging habitats, as well as regulating river runoff. Beaded channels are known as typical thermokarst landforms; however, there is no evidence of their origin and formative processes. Geomorphological analyzes of beaded channels have been completed in several permafrost regions including field observations of Shestakovka River in Central Yakutia. The study aims to recognize the modern exogenic processes and formative mechanisms of beaded river channels. We show that beaded channel of Shestakovka River form in the perennially frozen sand with low ice content, leading us to hypothesize that thermokarst is not the main process of formation. Due to the significant volume of water, the pools don't freeze over entirely during winters, even under harsh climatic conditions. As a result, lenses of pressurized water remain under surface ice underlain by perennially thawed sediments. The presence of thawed sediments under the pools and frozen sediments under the runs leads to uneven thermoerosion of the riverbed during floods, providing the beaded form of the channel. In addition, freezing of pools during winter leads to pressure increasing under ice cover and formation of ice mounds, which crack several times during winter leading to disturbance of riverbanks. Many 1st to 3rd order streams have a specific transitional meandering-to-beaded form resembling the shape of unconfined meandering rivers, but consisting of pools and runs. However, such channels exhibit no evidences of present-day erosion of concave banks and sediment accumulation at the convex banks as typically being observed in normally meandering rivers. Such forms of channels indicates that their formation occurred by the greater channel-forming flow discharges in the past. Transition to the beaded channel planform took place only later, presumably as a result of climate changes. Reduction of water runoff and freezing over of taliks leaded to activation of cryogenic processes (thermokarst, uneven thermoerosion, disturbance of riverbanks during the cracking of ice mounds).

Distribution and biophysical processes of beaded streams in Arctic permafrost landscapes

USGS Publications Warehouse

Arp, Christopher D.; Whitman, Matthew S.; Jones, Benjamin M.; Grosse, Guido; Gaglioti, Benjamin V.; Heim, Kurt C.

2015-01-01

Beaded streams are widespread in permafrost regions and are considered a common thermokarst landform. However, little is known about their distribution, how and under what conditions they form, and how their intriguing morphology translates to ecosystem functions and habitat. Here we report on a Circum-Arctic survey of beaded streams and a watershed-scale analysis in northern Alaska using remote sensing and field studies. We mapped over 400 channel networks with beaded morphology throughout the continuous permafrost zone of northern Alaska, Canada, and Russia and found the highest abundance associated with medium- to high- ground ice content permafrost in moderately sloping terrain. In the Fish Creek watershed, beaded streams accounted for half of the drainage density, occurring primarily as low-order channels initiating from lakes and drained lake basins. Beaded streams predictably transition to alluvial channels with increasing drainage area and decreasing channel slope, although this transition is modified by local controls on water and sediment delivery. Comparison of one beaded channel using repeat photography between 1948 and 2013 indicate a relatively stable landform and 14C dating of basal sediments suggest channel formation may be as early as the Pleistocene-Holocene transition. Contemporary processes, such as deep snow accumulation in riparian zones effectively insulates channel ice and allows for perennial liquid water below most beaded stream pools. Because of this, mean annual temperatures in pool beds are greater than 2°C, leading to the development of perennial thaw bulbs or taliks underlying these thermokarst features. In the summer, some pools thermally stratify, which reduces permafrost thaw and maintains coldwater habitats. Snowmelt generated peak-flows decrease rapidly by two or more orders of magnitude to summer low flows with slow reach-scale velocity distributions ranging from 0.1 to 0.01 m/s, yet channel runs still move water rapidly between pools. The repeating spatial pattern associated with beaded stream morphology and hydrological dynamics may provide abundant and optimal foraging habitat for fish. Thus, beaded streams may create important ecosystem functions and habitat in many permafrost landscapes and their distribution and dynamics are only beginning to be recognized in Arctic research.

Automated electrotransformation of Escherichia coli on a digital microfluidic platform using bioactivated magnetic beads.

PubMed

Moore, J A; Nemat-Gorgani, M; Madison, A C; Sandahl, M A; Punnamaraju, S; Eckhardt, A E; Pollack, M G; Vigneault, F; Church, G M; Fair, R B; Horowitz, M A; Griffin, P B

2017-01-01

This paper reports on the use of a digital microfluidic platform to perform multiplex automated genetic engineering (MAGE) cycles on droplets containing Escherichia coli cells. Bioactivated magnetic beads were employed for cell binding, washing, and media exchange in the preparation of electrocompetent cells in the electrowetting-on-dieletric (EWoD) platform. On-cartridge electroporation was used to deliver oligonucleotides into the cells. In addition to the optimization of a magnetic bead-based benchtop protocol for generating and transforming electrocompetent E. coli cells, we report on the implementation of this protocol in a fully automated digital microfluidic platform. Bead-based media exchange and electroporation pulse conditions were optimized on benchtop for transformation frequency to provide initial parameters for microfluidic device trials. Benchtop experiments comparing electrotransformation of free and bead-bound cells are presented. Our results suggest that dielectric shielding intrinsic to bead-bound cells significantly reduces electroporation field exposure efficiency. However, high transformation frequency can be maintained in the presence of magnetic beads through the application of more intense electroporation pulses. As a proof of concept, MAGE cycles were successfully performed on a commercial EWoD cartridge using variations of the optimal magnetic bead-based preparation procedure and pulse conditions determined by the benchtop results. Transformation frequencies up to 22% were achieved on benchtop; this frequency was matched within 1% (21%) by MAGE cycles on the microfluidic device. However, typical frequencies on the device remain lower, averaging 9% with a standard deviation of 9%. The presented results demonstrate the potential of digital microfluidics to perform complex and automated genetic engineering protocols.

Automated electrotransformation of Escherichia coli on a digital microfluidic platform using bioactivated magnetic beads

PubMed Central

Moore, J. A.; Nemat-Gorgani, M.; Madison, A. C.; Punnamaraju, S.; Eckhardt, A. E.; Pollack, M. G.; Church, G. M.; Fair, R. B.; Horowitz, M. A.; Griffin, P. B.

2017-01-01

This paper reports on the use of a digital microfluidic platform to perform multiplex automated genetic engineering (MAGE) cycles on droplets containing Escherichia coli cells. Bioactivated magnetic beads were employed for cell binding, washing, and media exchange in the preparation of electrocompetent cells in the electrowetting-on-dieletric (EWoD) platform. On-cartridge electroporation was used to deliver oligonucleotides into the cells. In addition to the optimization of a magnetic bead-based benchtop protocol for generating and transforming electrocompetent E. coli cells, we report on the implementation of this protocol in a fully automated digital microfluidic platform. Bead-based media exchange and electroporation pulse conditions were optimized on benchtop for transformation frequency to provide initial parameters for microfluidic device trials. Benchtop experiments comparing electrotransformation of free and bead-bound cells are presented. Our results suggest that dielectric shielding intrinsic to bead-bound cells significantly reduces electroporation field exposure efficiency. However, high transformation frequency can be maintained in the presence of magnetic beads through the application of more intense electroporation pulses. As a proof of concept, MAGE cycles were successfully performed on a commercial EWoD cartridge using variations of the optimal magnetic bead-based preparation procedure and pulse conditions determined by the benchtop results. Transformation frequencies up to 22% were achieved on benchtop; this frequency was matched within 1% (21%) by MAGE cycles on the microfluidic device. However, typical frequencies on the device remain lower, averaging 9% with a standard deviation of 9%. The presented results demonstrate the potential of digital microfluidics to perform complex and automated genetic engineering protocols. PMID:28191268

Elemental analysis of bead samples using a laser-induced plasma at low pressure

NASA Astrophysics Data System (ADS)

Lie, Tjung Jie; Kurniawan, Koo Hendrik; Kurniawan, Davy P.; Pardede, Marincan; Suliyanti, Maria Margaretha; Khumaeni, Ali; Natiq, Shouny A.; Abdulmadjid, Syahrun Nur; Lee, Yong Inn; Kagawa, Kiichiro; Idris, Nasrullah; Tjia, May On

2006-01-01

An Nd:YAG laser (1064 nm, 8 ns, 30 mJ) was focused on various types of fresh, fossilized white coral and giant shell samples, including samples of imitation shell and marble. Such samples are extremely important as material for preparing prayer beads that are extensively used in the Buddhist faith. The aim of this research was to develop a non-destructive method to distinguish original beads from their imitations by means of spectral measurements of the carbon, hydrogen, sodium and magnesium emission intensities and by measuring the hardness of the sample using the ratio between Ca (II) 396.8 nm and Ca (I) 422.6 nm. Based on these measurements, original fresh coral beads can be distinguished from any imitation made from hard wood. The same technique was also effective in distinguishing beads made of shell from its imitation. A spectral analysis of bead was also performed on a fossilized white coral sample and the result can be used to distinguish to some extent the fossilized white coral beads from any imitation made from marble. It was also found that the plasma plume should be generated at low ambient pressure to significantly improve the hydrogen and carbon emission intensity and also to avoid energy loss inside the crater during laser irradiation at atmospheric pressure. The results of this study confirm that operating the laser-induced plasma spectroscopy at reduced ambient pressure offers distinct advantage for bead analysis over the conventional laser-induced breakdown spectroscopy (LIBS) technique operated at atmospheric pressure.

Use of antibiotic beads to salvage infected breast implants.

PubMed

Sherif, Rami D; Ingargiola, Michael; Sanati-Mehrizy, Paymon; Torina, Philip J; Harmaty, Marco A

2017-10-01

When an implant becomes infected, implant salvage is often performed where the implant is removed, capsulectomy is performed, and a new implant is inserted. The patient is discharged with a PICC line and 6-8 weeks of intravenous (IV) antibiotics. This method has variable success and subjects the patient to long-term systemic antibiotics. In the 1960s, the use of antibiotic-impregnated beads for the treatment of chronic osteomyelitis was described. These beads deliver antibiotic directly to the site of the infection, thereby eliminating the complications of systemic IV antibiotics. This study aimed to present a case series illustrating the use of STIMULAN calcium sulfate beads loaded with vancomycin and tobramycin to increase the rate of salvage of the infected implant and forgo IV antibiotics. A retrospective analysis was performed of patients who were treated at Mount Sinai Hospital for implant infection with salvage and antibiotic beads. Twelve patients were identified, 10 of whom had breast cancer. Comorbidities included hypertension, smoking, and immunocompromised status. Infections were noted anywhere from 5 days to 8 years postoperatively. Salvage was successful in 9 out of the 12 infected implants using antibiotic bead therapy without home IV antibiotics. The use of antibiotic beads is promising for salvaging infected breast implants without IV antibiotics. Seventy-five percent of the implants were successfully salvaged. Of the three patients who had unsalvageable implants, one was infected with antibiotic-resistant Rhodococcus that was refractory to bead therapy and one was noncompliant with postoperative instructions. Copyright © 2017 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.

Results from the (U-Th)/He dating systems in Japan Atomic Energy Agency

NASA Astrophysics Data System (ADS)

Yamada, K.; Hanamuro, T.; Tagami, T.; Yamada, R.; Umeda, K.

2007-12-01

Japan Atomic Energy Agency (JAEA) has jointly set up the lab of the (U-Th)/He dating in cooperation with Kyoto University and National Research Institute for Earth Science and Disaster Prevention. We use the MM5400 rare gas mass spectrometer and the SPQ9000 ICP quadrupole mass spectrometer, belonging to JAEA, and built a new vacuum heater using infrared laser to extract helium. HF decomposes zircon after the alkali-fusion method using XRF bead sampler and LiBO3 in the preparation of ICP solution. Helium is quantified using sensitivity method. Uranium and thorium are using standard addition method. Quantifications of uranium-238 and thorium-232 are only need for parent isotopes to date samples because they are expected that the state of secular equilibrium becomes established and samarium does not compose the samples. At the present stage, we calibrate our systems by dating some standards, such as zircon from the Fish Canyon Tuff and apatite from the Durango, those are the international age standard, and apatite and zircon from the Tanzawa Tonalite Complex, that was dated in Yamada's PhD thesis, as a working standard. We report the results and detailed views of the dating systems.

Structural, Morphological, Optical and Photocatalytic Properties of Y, N-Doped and Codoped TiO2 Thin Films

PubMed Central

Hamden, Zeineb; Conceição, David; Boufi, Sami; Vieira Ferreira, Luís Filipe; Bouattour, Soraa

2017-01-01

Pure TiO2, Y-N single-doped and codoped TiO2 powders and thin films deposited on glass beads were successfully prepared using dip-coating and sol-gel methods. The samples were analyzed using grazing angle X-ray diffraction (GXRD), Raman spectroscopy, time resolved luminescence, ground state diffuse reflectance absorption and scanning electron microscopy (SEM). According to the GXRD patterns and micro-Raman spectra, only the anatase form of TiO2 was made evident. Ground state diffuse reflectance absorption studies showed that doping with N or codoping with N and Y led to an increase of the band gap. Laser induced luminescence analysis revealed a decrease in the recombination rate of the photogenerated holes and electrons. The photocatalytic activity of supported catalysts, toward the degradation of toluidine, revealed a meaningful enhancement upon codoping samples at a level of 2% (atomic ratio). The photocatalytic activity of the material and its reactivity can be attributed to a reduced, but significant, direct photoexcitation of the semiconductor by the halogen lamp, together with a charge-transfer-complex mechanism, or with the formation of surface oxygen vacancies by the N dopant atoms. PMID:28772962

Structural, Morphological, Optical and Photocatalytic Properties of Y, N-Doped and Codoped TiO₂ Thin Films.

PubMed

Hamden, Zeineb; Conceição, David; Boufi, Sami; Vieira Ferreira, Luís Filipe; Bouattour, Soraa

2017-05-31

Pure TiO₂, Y-N single-doped and codoped TiO₂ powders and thin films deposited on glass beads were successfully prepared using dip-coating and sol-gel methods. The samples were analyzed using grazing angle X-ray diffraction (GXRD), Raman spectroscopy, time resolved luminescence, ground state diffuse reflectance absorption and scanning electron microscopy (SEM). According to the GXRD patterns and micro-Raman spectra, only the anatase form of TiO₂ was made evident. Ground state diffuse reflectance absorption studies showed that doping with N or codoping with N and Y led to an increase of the band gap. Laser induced luminescence analysis revealed a decrease in the recombination rate of the photogenerated holes and electrons. The photocatalytic activity of supported catalysts, toward the degradation of toluidine, revealed a meaningful enhancement upon codoping samples at a level of 2% (atomic ratio). The photocatalytic activity of the material and its reactivity can be attributed to a reduced, but significant, direct photoexcitation of the semiconductor by the halogen lamp, together with a charge-transfer-complex mechanism, or with the formation of surface oxygen vacancies by the N dopant atoms.

Comparison of different immobilized systems in the removal of peanut allergens from peanut extracts.

USDA-ARS?s Scientific Manuscript database

The objective of this study was to determine which of the magnetic-bead systems (Ca2+, Fe3+, caffeic acid, hydrophobic) would bind and separate peanut allergens from other proteins in a peanut extract more efficiently. Commercial Ca2+ and hydrophobic magnetic beads, and caffeic-beads (prepared by at...

Sulfur geochemistry of hydrothermal waters in Yellowstone National Park: I. The origin of thiosulfate in hot spring waters

USGS Publications Warehouse

Xu, Y.; Schoonen, M.A.A.; Nordstrom, D. Kirk; Cunningham, K.M.; Ball, J.W.

1998-01-01

Thiosulfate (S2O2-3), polythionate (SxO2-6), dissolved sulfide (H2S), and sulfate (SO2-4) concentrations in thirty-nine alkaline and acidic springs in Yellowstone National Park (YNP) were determined. The analyses were conducted on site, using ion chromatography for thiosulfate, polythionate, and sulfate, and using colorimetry for dissolved sulfide. Thiosulfate was detected at concentrations typically less than 2 ??mol/L in neutral and alkaline chloride springs with low sulfate concentrations (C1-/SO2-4 > 25). The thiosulfate concentration levels are about one to two orders of magnitude lower than the concentration of dissolved sulfide in these springs. In most acid sulfate and acid sulfate-chloride springs (Cl-/SO2-4 < 10), thiosulfate concentrations were also typically lower than 2 ??mol/L. However, in some chloride springs enriched with sulfate (Cl-/SO2-4 between 10 to 25), thiosulfate was found at concentrations ranging from 9 to 95 ??mol/L, higher than the concentrations of dissolved sulfide in these waters. Polythionate was detected only in Cinder Pool, Norris Geyser basin, at concentrations up to 8 ??mol/L, with an average S-chain-length from 4.1 to 4.9 sulfur atoms. The results indicate that no thiosulfate occurs in the deeper parts of the hydrothermal system. Thiosulfate may form, however, from (1) hydrolysis of native sulfur by hydrothermal solutions in the shallower parts (<50 m) of the system, (2) oxidation of dissolved sulfide upon mixing of a deep hydrothermal water with aerated shallow groundwater, and (3) the oxidation of dissolved sulfide by dissolved oxygen upon discharge of the hot spring. Upon discharge of a sulfide-containing hydrothermal water, oxidation proceeds rapidly as atmospheric oxygen enters the water. The transfer of oxygen is particularly effective if the hydrothermal discharge is turbulent and has a large surface area.

Synthesis, characterization and applications of maghemite beads functionalized with rabbit antibodies.

PubMed

Rodriguez, A F R; Rocha, C O; Piazza, R D; Dos Santos, C C; Morales, M A; Faria, F S E D V; Iqbal, M Zubair; Barbosa, L; Chaves, Y O; Mariuba, L A; Jafelicci, M; Marques, R F C

2018-06-12

Magnetic nanoparticles (NPs) have attracted great attention owing to their applications in the biomedical field. In the present work, maghemite (γFe 2 O 3 ) NPs of 6.5 nm were prepared using a sonochemical method and used to prepare magnetic beads through silanization with 3-aminopropyltrimethoxysilane (APTS). Subsequently, amino groups in the resulting APTS-γFe 2 O 3 beads were converted to carboxylic acid (CARB-γFe 2 O 3 ) through the succinic anhydride reaction, as confirmed by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy and dynamic light scattering (DLS) measurements. The size of these beads was measured as 12 nm and their hydrodynamic diameter as 490 nm, using TEM analysis and DLS, respectively. The CARB-γFe 2 O 3 beads were further functionalized by immobilizing rabbit antibodies on their surfaces; the immobilization was confirmed by flow cytometry and ionic strength. The samples were further characterized by Mössbauer spectroscopy and DC magnetization measurements. Studies on magnetic relaxivities showed that magnetic beads present great potential for application in MR imaging.

Application of a rotating impeller anode in a bioelectrochemical anaerobic digestion reactor for methane production from high-strength food waste.

PubMed

Park, Jungyu; Lee, Beom; Shin, Wonbeom; Jo, Sangyeol; Jun, Hangbae

2018-07-01

In this study, a practical bioelectrochemical anaerobic digestion (BEAD) reactor equipped with a rotating STS304 impeller was tested to verify its methane production performance. Methane production in the BEAD reactor was possible without accumulation of volatile fatty acids (VFAs) and decreases in pH at high organic loading rates (OLRs) up to 6 kg-COD/m 3 ·d (COD: chemical oxygen demand). Methane production in a BEAD-O (open circuit) reactor was inhibited at OLRs above 4 kg-COD/m 3 ·d; however, the performance could be recovered bioelectrochemically by supplying voltage. The population density of hydrogenotrophic methanogens increased to 73.3% in the BEAD-C (closed circuit) reactor, even at high OLRs, through the removal of VFAs and conversion of hydrogen to methane. The energy efficiency in the BEAD-C reactor was 85.6%, indicating that the commercialization of BEAD reactors equipped with rotating STS304 impeller electrodes is possible. Copyright © 2018 Elsevier Ltd. All rights reserved.

In-situ preparation of NaA zeolite/chitosan porous hybrid beads for removal of ammonium from aqueous solution.

PubMed

Yang, Kai; Zhang, Xiang; Chao, Cong; Zhang, Bing; Liu, Jindun

2014-07-17

Inorganic/organic hybrid materials play important roles in removal of contaminants from wastewater. Herein, we used the natural materials of halloysite and chitosan to prepare a new adsorbent of NaA zeolite/chitosan porous hybrid beads by in-situ hydrothermal synthesis method. SEM indicated that the porous hybrid beads were composed of 6-8 μm sized cubic NaA zeolite particles congregated together with chitosan. The adsorption behavior of NH4(+) from aqueous solution onto hybrid beads was investigated at different conditions. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms. A maximum adsorption capacity of 47.62 mg/g at 298 K was achieved according to Langmuir model. The regenerated or reused experiments indicated that the adsorption capacity of the hybrid beads could maintain in 90% above after 10 successive adsorption-desorption cycles. The high adsorption and reusable ability implied potential application of the hybrid beads for removing NH4(+) pollutants from wastewater. Copyright © 2014 Elsevier Ltd. All rights reserved.

Multi-parameter analysis using photovoltaic cell-based optofluidic cytometer

PubMed Central

Yan, Chien-Shun; Wang, Yao-Nan

2016-01-01

A multi-parameter optofluidic cytometer based on two low-cost commercial photovoltaic cells and an avalanche photodetector is proposed. The optofluidic cytometer is fabricated on a polydimethylsiloxane (PDMS) substrate and is capable of detecting side scattered (SSC), extinction (EXT) and fluorescence (FL) signals simultaneously using a free-space light transmission technique without the need for on-chip optical waveguides. The feasibility of the proposed device is demonstrated by detecting fluorescent-labeled polystyrene beads with sizes of 3 μm, 5 μm and 10 μm, respectively, and label-free beads with a size of 7.26 μm. The detection experiments are performed using both single-bead population samples and mixed-bead population samples. The detection results obtained using the SSC/EXT, EXT/FL and SSC/FL signals are compared with those obtained using a commercial flow cytometer. It is shown that the optofluidic cytometer achieves a high detection accuracy for both single-bead population samples and mixed-bead population samples. Consequently, the proposed device provides a versatile, straightforward and low-cost solution for a wide variety of point-of-care (PoC) cytometry applications. PMID:27699122

A Phos-tag-based magnetic-bead method for rapid and selective separation of phosphorylated biomolecules.

PubMed

Tsunehiro, Masaya; Meki, Yuma; Matsuoka, Kanako; Kinoshita-Kikuta, Emiko; Kinoshita, Eiji; Koike, Tohru

2013-04-15

A simple and efficient method based on magnetic-bead technology has been developed for the separation of phosphorylated and nonphosphorylated low-molecular-weight biomolecules, such as nucleotides, phosphorylated amino acids, or phosphopeptides. The phosphate-binding site on the bead is an alkoxide-bridged dinuclear zinc(II) complex with 1,3-bis(pyridin-2-ylmethylamino)propan-2-olate (Phos-tag), which is linked to a hydrophilic cross-linked agarose coating on a magnetic core particle. All steps for the phosphate-affinity separation are conducted in buffers of neutral pH with 50 μL of the magnetic beads in a 1.5-mL microtube. The entire separation protocol for phosphomonoester-type compounds, from addition to elution, requires less than 12 min per sample if the buffers and the zinc(II)-bound Phos-tag magnetic beads have been prepared in advance. The phosphate-affinity magnetic beads are reusable at least 15 times without a decrease in their phosphate-binding ability and they are stable for three months in propan-2-ol. Copyright © 2013 Elsevier B.V. All rights reserved.

Facile preparation of antibacterial chitosan/graphene oxide-Ag bio-nanocomposite hydrogel beads for controlled release of doxorubicin.

PubMed

Rasoulzadehzali, Monireh; Namazi, Hassan

2018-04-27

The present project describes the facile preparation of novel pH-sensitive bio-nanocomposite hydrogel beads based on chitosan (CH) and GO-Ag nanohybrid particles for controlled release of anti-cancer drugs such as doxorubicin (DOX). The loading efficiency of doxorubicin into test beads was measured via UV-vis spectroscopy analysis and was found to be high. The formation of silver nanoparticles on the GO sheets and structural characteristics were evaluated via FT-IR, TEM, XRD, and SEM techniques. In addition, the antibacterial activity, swelling and drug release profiles of prepared nanocomposite beads were evaluated. Also, in vitro drug release test was performed in order to investigate the efficiency of CH/GO-Ag nanocomposite hydrogel beads as a drug carrier for controlled release of anti-cancer drugs such as doxorubicin (DOX). A more sustained and controlled drug release profile was observed for CH/GO-Ag nanocomposite hydrogel beads that enhanced by increasing the GO-Ag nanohybrid particles content. Copyright © 2018 Elsevier B.V. All rights reserved.

Quantum dots encoded Au coated polystyrene bead arranged micro-channel for multiplex arrays.

PubMed

Cao, Yuan-Cheng; Wang, Zhan; Yang, Runyu; Zou, Linling; Zhou, Zhen; Mi, Tie; Shi, Hong

2016-01-01

This paper describes a promising micro-channel multiplex immunoassay method based on the quantum dots encoded beads which requires micro-volume sample. Briefly, Au nanoparticles coated polystyrene (PS) beads were prepared and Quantum dots (QDs) were employed to encode 4 types of the PS beads by different emission wavelength QDs and various intensities. Different coding types of the beads were immobilized with different antibodies on the surface and BSA was used to block the unsatisfied sites. The antibody linked beads were then arranged in the 150 µm diameter optical capillary where the specific reactions took place before the detections. Results showed that the antibody on the Au coated surface maintains the bioactivity for the immunoreactions. Using this system, the fluorescent intensity was linear with analyte concentration in the range of 1×10(-7)-1×10(-5) mg/mL (RSD<5%, 4 repeats) and the lower detection limit reached 5×10(-8) mg/mL. It was proved to be a promising approach for the future miniaturization analytical devices. Copyright © 2015 Elsevier B.V. All rights reserved.

Novel mesalamine-loaded beads in tablets for delayed release of drug to the colon.

PubMed

Nguyen, Chien; Christensen, J Mark; Ayres, James W

2012-01-01

Novel 'beads-in-a-tablet' formulations (total weight ∼740-780 mg) have been prepared that meet USP 31 requirements for Delayed Release of mesalamine. Several methods are presented that overcome breakage of beads during tablet compaction were explored. Bead formulations comprise a combination of extrusion and spheronization to produce a relatively high drug load (80%), followed by coating (25%) with a colonic-targeted drug release polymer (polymethacrylates, Eudragit(®) S100), overcoated (3%) with hydroxypropyl methylcellulose (Opadry(®)) to improve bead binding and compactability, and using 20% coat of lactose/sodium starch glycolate (Explotab(®)) as binder/disintegrant/cushioning agent, thus allowing a sufficiently thick coating to be uniform and without being broken during tablet compaction. Then, the aforementioned beads were compressed into tablets at 1500 pounds of pressure containing 400 mg of mesalamine, and finally coating the compressed tablets with Surelease(®) (ethylcellulose):Opadry(®) = 1:0.5 ranging from 1.5-2.5% weight gain; the resulting tablets met USP 31 dissolution requirements for delayed release tablets.

Surface imprinted beads for the recognition of human serum albumin.

PubMed

Bonini, Francesca; Piletsky, Sergey; Turner, Anthony P F; Speghini, Adolfo; Bossi, Alessandra

2007-04-15

The synthesis of poly-aminophenylboronic acid (ABPA) imprinted beads for the recognition of the protein human serum albumin (HSA) is reported. In order to create homogeneous recognition sites, covalent immobilisation of the template HSA was exploited. The resulting imprinted beads were selective for HSA. The indirect imprinting factor (IF) calculated from supernatant was 1.6 and the direct IF, evaluated from the protein recovered from the beads, was 1.9. The binding capacity was 1.4 mg/g, which is comparable to commercially available affinity materials. The specificity of the HSA recognition was evaluated with competitive experiments, indicating a molar ratio 4.5/1 of competitor was necessary to displace half of the bound HSA. The recognition and binding of the imprinted beads was also tested with a complex sample, human serum and targeted removal of HSA without a loss of the other protein components was demonstrated. The easy preparation protocol of derivatised beads and a good protein recognition properties make the approach an attractive solution to analytical and bio-analytical problems in the field of biotechnology.

Anionic polymer, poly(methyl vinyl ether-maleic anhydride)-coated beads-based capture of human influenza A and B virus.

PubMed

Sakudo, Akikazu; Baba, Koichi; Tsukamoto, Megumi; Sugimoto, Atsuko; Okada, Takashi; Kobayashi, Takanori; Kawashita, Norihito; Takagi, Tatsuya; Ikuta, Kazuyoshi

2009-01-15

An anionic magnetic beads-based method was developed for the capture of human influenza A and B viruses from nasal aspirates, allantoic fluid and culture medium. A polymer, poly(methyl vinyl ether-maleic anhydride) [poly(MVE-MA)], was used to endow magnetic beads with a negative charge and bioadhesive properties. After incubation with samples containing human influenza virus, the beads were separated from supernatants by applying a magnetic field. The adsorption [corrected] of the virus by the beads was confirmed by hemagglutinin assay, immunochromatography, Western blotting, egg infection, and cell infection. Successful capture was proved using 5 H1N1 influenza A viruses, 10 H3N2 influenza A viruses, and 6 influenza B viruses. Furthermore, the infectivity in chicken embryonated eggs and Madin-Darby canine kidney (MDCK) cells of the captured human influenza virus was similar to that of the total viral quantity of starting materials. Therefore, this method of capture using magnetic beads coated with poly(MVE-MA) can be broadly used for the recovery of infectious human influenza viruses.

Surveying colloid sedimentation by coplanar waveguides

NASA Astrophysics Data System (ADS)

Duţu, C. A.; Vlad, A.; Roda-Neve, C.; Avram, I.; Sandu, G.; Raskin, J.-P.; Melinte, S.

2016-06-01

By using coplanar waveguides, direct access to the dielectric properties of aqueous solutions of polystyrene beads with different diameters from 330 nm to 10 μm is provided. The relative variation of the transmission parameter with respect to water is monitored, ranging from ˜ {3}% obtained for a 9.5% solution with 330 nm diameter beads to ˜22% for 10 μm diameter particles at the same concentration. To highlight its applicability in biosensing, the technique was further employed to survey the clustering between biotin and streptavidin-coated beads. The transmission parameter displays a ˜50% increase for mixtures containing nine volumes of biotin and one volume of streptavidin-modified beads (4.5 ng μl-1 of streptavidin) and reaches ˜400% higher values when equal volumes of biotin and streptavidin-coated beads (22.5 ng μl-1 of streptavidin) were mixed.

Drug particle size influence on enteric beads produced by a droplet extrusion/precipitation method.

PubMed

Cerdeira, A M; Gouveia, L F; Goucha, P; Almeida, A J

2000-01-01

The influence of drug particle size on the production of enteric beads by a polymer precipitation technique was investigated. Drug particle dimensions are known to play an important role in most microencapsulation techniques. Bead morphology was greatly influenced by drug particle size, and spherical shaped beads could only be obtained after size reduction of nimesulide crystals. This is confirmed by the angle of repose measurements, which show a significant decrease in theta values when beads are formulated with smaller drug particles. Furthermore, results show that drug encapsulation efficiency and in vitro drug release rates are also greatly dependent on both drug particle size and drug/polymer ratio in the initial suspension. Preparations containing 10.2 microm drug particles show a two-fold increase in the release rates when compared to those prepared with 40 microm particles.

Two-phase mixed media dielectric with macro dielectric beads for enhancing resistivity and breakdown strength

DOEpatents

Falabella, Steven; Meyer, Glenn A; Tang, Vincent; Guethlein, Gary

2014-06-10

A two-phase mixed media insulator having a dielectric fluid filling the interstices between macro-sized dielectric beads packed into a confined volume, so that the packed dielectric beads inhibit electro-hydrodynamically driven current flows of the dielectric liquid and thereby increase the resistivity and breakdown strength of the two-phase insulator over the dielectric liquid alone. In addition, an electrical apparatus incorporates the two-phase mixed media insulator to insulate between electrical components of different electrical potentials. And a method of electrically insulating between electrical components of different electrical potentials fills a confined volume between the electrical components with the two-phase dielectric composite, so that the macro dielectric beads are packed in the confined volume and interstices formed between the macro dielectric beads are filled with the dielectric liquid.

Hot spot formation from shock reflections

NASA Astrophysics Data System (ADS)

Menikoff, R.

2011-04-01

Heterogeneities sensitize an explosive to shock initiation. This is due to hot-spot formation and the sensitivity of chemical reaction rates to temperature. Here, we describe a numerical experiment aimed at elucidating a mechanism for hot-spot formation that occurs when a shock wave passes over a high-density impurity. The simulation performed is motivated by a physical experiment in which glass beads are added to liquid nitromethane. The impedance mismatch between the beads and the nitromethane results in shock reflections. These, in turn, give rise to transverse waves along the lead shock front. Hot spots arise on local portions of the lead front with a higher shock strength, rather than on the reflected shocks behind the beads. Moreover, the interactions generated by reflected waves from neighboring beads can significantly increase the peak hot-spot temperature when the beads are suitably spaced.

Glass bead cultivation of fungi: combining the best of liquid and agar media.

PubMed

Droce, Aida; Sørensen, Jens Laurids; Giese, Henriette; Sondergaard, Teis Esben

2013-09-01

Production of bioactive compounds and enzymes from filamentous fungi is highly dependent on cultivation conditions. Here we present an easy way to cultivate filamentous fungi on glass beads that allow complete control of nutrient supply. Secondary metabolite production in Fusarium graminearum and Fusarium solani cultivated on agar plates, in shaking liquid culture or on glass beads was compared. Agar plate culture and glass bead cultivation yielded comparable results while liquid culture had lower production of secondary metabolites. RNA extraction from glass beads and liquid cultures was easier than from agar plates and the quality was superior. The system allows simple control of nutrient availability throughout fungal cultivation. This combined with the ease of extraction of nucleic acids and metabolites makes the system highly suitable for the study of gene regulation in response to specific nutrient factors. © 2013.

Holographic optical tweezers for object manipulations at an air-liquid surface.

PubMed

Jesacher, Alexander; Fürhapter, Severin; Maurer, Christian; Bernet, Stefan; Ritsch-Marte, Monika

2006-06-26

We investigate holographic optical tweezers manipulating micro-beads at a suspended air-liquid interface. Axial confinement of the particles in the two-dimensional interface is maintained by the interplay between surface tension and gravity. Therefore, optical trapping of the micro-beads is possible even with a long distance air objective. Efficient micro-circulation of the liquid can be induced by fast rotating beads, driven by the orbital angular momentum transfer of incident Laguerre-Gaussian (doughnut) laser modes. Our setup allows various ways of creating a tailored dynamic flow of particles and liquid within the surface. We demonstrate examples of surface manipulations like efficient vortex pumps and mixers, interactive particle flow steering by arrays of vortex pumps, the feasibility of achieving a "clocked" traffic of micro beads, and size-selective guiding of beads along optical "conveyor belts".

Chromium (VI) ion adsorption by grafted cross-linked chitosan beads in aqueous solution - a mathematical and statistical modeling study.

PubMed

Igberase, E; Osifo, P; Ofomaja, A

2017-12-01

Chitosan outstanding qualities and efficient way of binding metal ions even to near zero concentration is the major reason for special attention. Modification of chitosan allows the polymer to be applied in numerous field of research. Depending on the modification techniques, chitosan possesses increased adsorption capacity. In this study chitosan beads (CS) were formulated from chitosan flakes, the beads were cross-linked with glutaraldehyde and thereafter grafted with ethyldiaminetetraacetic acid. The stability and amine concentration of the beads were determined. The chemical functionalities of the beads were obtained by Fourier transform infrared spectroscopy, X-ray diffraction and thermogravimetric analysis (TGA). However, in the adsorption studies with Cr(VI), the number of runs in the experiment was obtained by response surface methodology (RSM), and the maximum adsorption capacity (Q m ) from each run was determined from the Langmuir model. The results of the experiment showed that the non-modified beads were soluble at pH 1-4 and insoluble at pH 5, while the modified beads were insoluble at pH 1-6. The amine concentration of CS, CCS and grafted cross-linked chitosan beads (GCCS) were 4.4, 3.8 and 5.0 mmol/g, respectively. The point of zero charge (pH PZC ) of GCCS was found to be 4.4. The quadratic model was significant and adequate in describing the experimental data. The difference between experimental and predicted Q m was negligible. From the design matrix and results, increased Q m was achieved at pH 5, contact time 70 min, temperature 45°C, adsorbent dosage 5 g and initial concentration 70 mg/l. The desorption of the beads loaded with Cr(VI) was successful with 0.5 M HCl eluant and contact time of 180 min, leading to cost minimization.