Sample records for analytical ultracentrifugation gel

  1. Characterization of Polymeric Nanomaterials Using Analytical Ultracentrifugation.

    PubMed

    Diaz, Leosveys; Peyrot, Caroline; Wilkinson, Kevin J

    2015-06-16

    The characterization of nanomaterials represents a complex analytical challenge due to their dynamic nature (small size, high reactivity, and instability) and the low concentrations in the environment, often below typical analytical detection limits. Analytical ultracentrifugation (AUC) is especially useful for the characterization of small nanoparticles (1-10 nm), which are often the most problematic for the commonly used techniques such as electron microscopy or dynamic light scattering. In this study, small polymeric nanomaterials (allospheres) that are used commercially to facilitate the distribution of pesticides in agricultural fields were characterized under a number of environmentally relevant conditions. Under most of the studied conditions, the allospheres were shown to have a constant hydrodynamic diameter (dH) of about 7.0 nm. Only small increases in diameter were observed, either at low pH or very high ionic strength or hardness, demonstrating their high physicochemical stability (and thus high mobility in soils). Furthermore, natural organic matter had little effect on the hydrodynamic diameters of the allospheres. The concentration of the nanoparticles was an important parameter influencing their agglomeration-results obtained using dynamic light scattering at high particle concentrations showed large agglomerate sizes and significant particle losses through sedimentation, clearly indicating the importance of characterizing the nanomaterials under environmentally relevant conditions. PMID:25988704

  2. Current Methods in Sedimentation Velocity and Sedimentation Equilibrium Analytical Ultracentrifugation

    PubMed Central

    Zhao, Huaying; Brautigam, Chad A.; Ghirlando, Rodolfo; Schuck, Peter

    2013-01-01

    Significant progress in the interpretation of analytical ultracentrifugation (AUC) data in the last decade has led to profound changes in the practice of AUC, both for sedimentation velocity (SV) and sedimentation equilibrium (SE). Modern computational strategies have allowed for the direct modeling of the sedimentation process of heterogeneous mixtures, resulting in SV size-distribution analyses with significantly improved detection limits and strongly enhanced resolution. These advances have transformed the practice of SV, rendering it the primary method of choice for most existing applications of AUC, such as the study of protein self- and hetero-association, the study of membrane proteins, and applications in biotechnology. New global multi-signal modeling and mass conservation approaches in SV and SE, in conjunction with the effective-particle framework for interpreting the sedimentation boundary structure of interacting systems, as well as tools for explicit modeling of the reaction/diffusion/sedimentation equations to experimental data, have led to more robust and more powerful strategies for the study of reversible protein interactions and multi-protein complexes. Furthermore, modern mathematical modeling capabilities have allowed for a detailed description of many experimental aspects of the acquired data, thus enabling novel experimental opportunities, with important implications for both sample preparation and data acquisition. The goal of the current commentary is to supplement previous AUC protocols, Current Protocols in Protein Science 20.3 (1999) and 20.7 (2003), and 7.12 (2008), and provide an update describing the current tools for the study of soluble proteins, detergent-solubilized membrane proteins and their interactions by SV and SE. PMID:23377850

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

    Microsoft Academic Search

    K. L. Planken

    2008-01-01

    Several case studies of the sedimentation velocity of non-interacting, attractive and repulsive colloids are discussed. After a brief introduction that highlights historical facts, basic analytical ultracentrifugation theory, some instrument issues and experiments are reviewed. The existence of discrete single molecular molybdenum Keplerate-type clusters in aqueous solution is demonstrated. Starting from a discrete spherical molybdenum cluster the formation of an 'open'

  4. Sedimentation analysis of von Willebrand and factor VIIIC protein using partition cells in the analytical ultracentrifuge.

    PubMed

    Barlow, G H; Martin, S E; Marder, V J

    1984-04-01

    Sedimentation analysis of factor VIII complex was performed in the analytical ultracentrifuge using partition cells. This method allowed for the calculation of three different sedimentation coefficients from each run: one based on ristocetin agglutination activity for von Willebrand protein, SWF; one based on coagulant activity for factor VIIIC, SVIIIC; and one based on the schlieren or adsorption data for protein concentration, Sconc. In most cases, there was no agreement between the three values calculated from the same run, indicating a heterogeneous system. The calculated functional sedimentation coefficients give values that require the molecules to be highly asymmetric to be consistent with a glycoprotein of high molecular weight, which is in agreement with results observed in electron microscope studies. The dissociation of VIIIC into a smaller form can be demonstrated by this method. Determination of the three sedimentation coefficients in a series of fractions from gel filtration indicates a uniform size for the VIIIC activity but not for the WF activity. These observations are in agreement with the concept of a copolymer between WF and VIIIC and also with the concept of separate polymers for the two activities. PMID:6423013

  5. Human liver alkaline phosphatase purified by affinity chromatography, ultracentrifugation and polyacrylamide-gel electrophoresis.

    PubMed Central

    Latner, A L; Hodson, A W

    1976-01-01

    A method is presented for the preparation of human liver alkaline phosphatase (orthophosphoric monoester phosphohydrolase, EC 3.1.3.1). The method gives a purification factor of 12.5 X 10(3) over the initial aq. butan-1-ol extract, a recovery of 6.0% and a specific activity for the preparation of 1450-1550 units/mg of protein, 1 unit being defined as the amount of enzyme catalysing the hydrolysis of 1mumol of p-nitrophenyl phosphate/min at 35 degrees C in 0.1 M-2-amino-2-methylpropan-1-ol/HCl buffer, pH 10.5, containing 10mM-p-nitrophenyl phosphate. Homogeneity was studied by ultracentrifugation, by immunoelectrophoresis and by polyacrylamide-gel electrophoresis. A single contaminating protein was present which was less than 5% of the total. Ultracentrifugation and equilibrium-gradient-pore electrophoresis techniques indicated a mol.wt. of 156000 and 160000 respectively. Equilibrium-gradient-pore electrophoresis indicated that the alkaline phosphatase molecule is possibly a dimer, comprising two subunits of about 80000 mol.wt. Amino acid analysis proved remarkably similar to that for alkaline phosphatase from other sources, regardless of species. Images PLATE 1 PMID:1008827

  6. A critical review of analytical ultracentrifugation and field flow fractionation methods for measuring protein aggregation.

    PubMed

    Liu, Jun; Andya, James D; Shire, Steven J

    2006-01-01

    Analytical ultracentrifugation (AUC) and field flow fractionation (FFF) are 2 important biophysical methods for measuring protein aggregates. Both methods can separate protein monomer from its aggregate forms under a broad range of solution conditions. Recent advances in instrumentation and data analysis, particularly in the field of analytical ultracentrifugation technology, have significantly improved the capability and sensitivity of these biophysical methods for detecting protein aggregates. These advances have resulted in an increased use of these methods in the biopharmaceutical industry for characterization of therapeutic proteins. However, despite their many advantages over conventional methods, the difficulty in the use of the instrumentation and the complexity of data analysis process, have often hampered the widespread use and proper interpretation of data. This article reviews the recent progress in both technologies, and a few case studies are also presented to discuss their advantages and limitations. PMID:17025276

  7. Hydrodynamic characterization of surfactant encapsulated carbon nanotubes using an analytical ultracentrifuge.

    PubMed

    Arnold, Michael S; Suntivich, Jin; Stupp, Samuel I; Hersam, Mark C

    2008-11-25

    The hydrodynamic properties of surfactant encapsulated single-walled carbon nanotubes (SWNTs) have been characterized by optically measuring their spatial and temporal redistribution in situ in an analytical ultracentrifuge. The measured redistribution profiles are fit to the Lamm equation, thus determining the sedimentation, diffusion, and hydrodynamic frictional coefficients of the surfactant encapsulated SWNTs. For sodium cholate encapsulated SWNTs, we demonstrate that the technique of analytical ultracentrifugation can be utilized to determine the linear packing density of surfactant molecules along the length of the SWNTs, 3.6 +/- 0.8 nm(-1), and the anhydrous molar volume of the surfactant molecules on the SWNT surfaces, 270 +/- 20 cm(3) mol(-1). Additionally, analytical ultracentrifugation is used to measure and compare the sedimentation rates of bundled and isolated carbon nanotubes. This study should serve as a guide for designing centrifuge-based processing procedures for preparing samples of SWNTs for a wide variety of applications and studies. Additionally, the results obtained here should aid in understanding the hydrodynamic properties of SWNTs and the interactions between SWNTs and surfactants in aqueous solution. PMID:19206395

  8. A new adaptive grid-size algorithm for the simulation of sedimentation velocity profiles in analytical ultracentrifugation

    NASA Astrophysics Data System (ADS)

    Brown, Patrick H.; Schuck, Peter

    2008-01-01

    Analytical ultracentrifugation allows one to measure in real-time the concentration gradients arising from the application of a centrifugal force to macromolecular mixtures in solution. In the last decade, the ability to efficiently solve the partial differential equation governing the ultracentrifugal sedimentation and diffusion process, the Lamm equation, has spawned significant progress in the application of sedimentation velocity analytical ultracentrifugation for the study of biological macromolecules, for example, the characterization of protein oligomeric states and the study of multi-protein complexes in solution. The present work describes a numerical algorithm that can provide an improvement in accuracy or efficiency over existing algorithms by more than one order of magnitude, and thereby greatly facilitate the practical application of sedimentation velocity analysis, in particular, for the study of multi-component macromolecular mixtures. It is implemented in the public domain software SEDFIT for the analysis of experimental data.

  9. Histidine-tag-directed chromophores for tracer analyses in the analytical ultracentrifuge

    PubMed Central

    Hellman, Lance M.; Zhao, Chunxia; Melikishvili, Manana; Tao, Xiaorong; Hopper, James E.; Whiteheart, Sidney W.; Fried, Michael G.

    2011-01-01

    Many recombinant proteins carry an oligohistidine (HisX)-tag that allows their purification by immobilized metal affinity chromatography (IMAC). This tag can be exploited for the site-specific attachment of chromophores and fluorophores, using the same metal ion–nitrilotriacetic acid (NTA) coordination chemistry that forms the basis of popular versions of IMAC. Labeling proteins in this way can allow their detection at wavelengths outside of the absorption envelopes of un-modified proteins and nucleic acids. Here we describe use of this technology in tracer sedimentation experiments that can be performed in a standard analytical ultracentrifuge equipped with absorbance or fluorescence optics. Examples include sedimentation velocity in the presence of low molecular weight chromophoric solutes, sedimentation equilibrium in the presence of high concentrations of background protein and selective labeling to simplify the assignment of species in a complex interacting mixture. PMID:21187151

  10. Determination of nanoparticle size distribution together with density or molecular weight by 2D analytical ultracentrifugation

    PubMed Central

    Carney, Randy P.; Kim, Jin Young; Qian, Huifeng; Jin, Rongchao; Mehenni, Hakim; Stellacci, Francesco; Bakr, Osman M.

    2011-01-01

    Nanoparticles are finding many research and industrial applications, yet their characterization remains a challenge. Their cores are often polydisperse and coated by a stabilizing shell that varies in size and composition. No single technique can characterize both the size distribution and the nature of the shell. Advances in analytical ultracentrifugation allow for the extraction of the sedimentation (s) and diffusion coefficients (D). Here we report an approach to transform the s and D distributions of nanoparticles in solution into precise molecular weight (M), density (?P) and particle diameter (dp) distributions. M for mixtures of discrete nanocrystals is found within 4% of the known quantities. The accuracy and the density information we achieve on nanoparticles are unparalleled. A single experimental run is sufficient for full nanoparticle characterization, without the need for standards or other auxiliary measurements. We believe that our method is of general applicability and we discuss its limitations. PMID:21654635

  11. Combined Analysis of Polycation/ODN Polyplexes by Analytical Ultracentrifugation and Dynamic Light Scattering Reveals their Size,

    E-print Network

    Buschmann, Michael

    Combined Analysis of Polycation/ODN Polyplexes by Analytical Ultracentrifugation and Dynamic Light polyplexes formed with 10 kDa chitosan or 10 kDa PEI and oligodeoxynucleotides (ODN). Combined analysis diameters were of 46 and 55 nm for chitosan/ODN and PEI/ODN complexes, respectively. Transformation

  12. Dynamics of single polyelectrolyte chains in salt-free dilute solutions investigated by analytical ultracentrifugation.

    PubMed

    Cao, Zhonglin; Wu, Sha; Zhang, Guangzhao

    2015-06-28

    The dynamics of polyelectrolytes in salt-free solution is an unsolved problem. We have investigated the sedimentation and diffusion of xanthan and poly(N-methyl 4-vinyl pyridine iodide) (P4VPI) in salt-free dilute solutions by analytical ultracentrifugation (AUC) using sedimentation velocity (SV) as a function of polyelectrolyte concentration (Cp). Our study reveals two concentration regimes distinguished in either polyanion (xanthan) or polycation (P4VPI) dilute aqueous solution. When Cp is below the Debye concentration (Cd) at which the chain separation (d) is close to the debye length (lD), the interchain electrostatic repulsion is negligible, and the reciprocal apparent sedimentation coefficient (1/s), apparent diffusion coefficient (D) or reciprocal apparent molecular weight (1/Mw) is linearly related to Cp. In the range Cp > Cd with d < lD, the interchain electrostatic repulsion is present, and the dynamics of polyelectrolytes becomes complex. The real sedimentation coefficient (s0), the diffusion coefficient (D0) and the molecular weight (Mw,0) of the single polyelectrolyte chain in salt-free dilute solution can be obtained by extrapolating the concentration to zero. The present study reveals that the complex dynamics of polyelectrolytes in salt-free dilute solutions arises due to the interchain electrostatic repulsion. PMID:26018174

  13. Overview of current methods in sedimentation velocity and sedimentation equilibrium analytical ultracentrifugation.

    PubMed

    Zhao, Huaying; Brautigam, Chad A; Ghirlando, Rodolfo; Schuck, Peter

    2013-02-01

    Modern computational strategies have allowed for the direct modeling of the sedimentation process of heterogeneous mixtures, resulting in sedimentation velocity (SV) size-distribution analyses with significantly improved detection limits and strongly enhanced resolution. These advances have transformed the practice of SV, rendering it the primary method of choice for most existing applications of analytical ultracentrifugation (AUC), such as the study of protein self- and hetero-association, the study of membrane proteins, and applications in biotechnology. New global multisignal modeling and mass conservation approaches in SV and sedimentation equilibrium (SE), in conjunction with the effective-particle framework for interpreting the sedimentation boundary structure of interacting systems, as well as tools for explicit modeling of the reaction/diffusion/sedimentation equations to experimental data, have led to more robust and more powerful strategies for the study of reversible protein interactions and multiprotein complexes. Furthermore, modern mathematical modeling capabilities have allowed for a detailed description of many experimental aspects of the acquired data, thus enabling novel experimental opportunities, with important implications for both sample preparation and data acquisition. The goal of the current unit is to describe the current tools for the study of soluble proteins, detergent-solubilized membrane proteins and their interactions by SV and SE. PMID:23377850

  14. Simultaneous analysis of hydrodynamic and optical properties using analytical ultracentrifugation equipped with multiwavelength detection.

    PubMed

    Walter, Johannes; Sherwood, Peter J; Lin, Wei; Segets, Doris; Stafford, Walter F; Peukert, Wolfgang

    2015-03-17

    Analytical ultracentrifugation (AUC) has proven to be a powerful tool for the study of particle size distributions, particle shapes, and interactions with high accuracy and unrevealed resolution. In this work we show how the analysis of sedimentation velocity data from the AUC equipped with a multiwavelength detector (MWL) can be used to gain an even deeper understanding of colloidal and macromolecular mixtures. New data evaluation routines have been integrated in the software SEDANAL to allow for the handling of MWL data. This opens up a variety of new possibilities because spectroscopic information becomes available for individual components in mixtures at the same time using MWL-AUC. For systems of known optical properties information on the hydrodynamic properties of the individual components in a mixture becomes accessible. For the first time, the determination of individual extinction spectra of components in mixtures is demonstrated via MWL evaluation of sedimentation velocity data. In our paper we first provide the informational background for the data analysis and expose the accessible parameters of our methodology. We further demonstrate the data evaluation by means of simulated data. Finally, we give two examples which are highly relevant in the field of nanotechnology using colored silica and gold nanoparticles of different size and extinction properties. PMID:25679871

  15. Recent Advances in the Analysis of Macromolecular Interactions Using the Matrix-Free Method of Sedimentation in the Analytical Ultracentrifuge

    PubMed Central

    Harding, Stephen E.; Gillis, Richard B.; Almutairi, Fahad; Erten, Tayyibe; Kök, M. ?amil; Adams, Gary G.

    2015-01-01

    Sedimentation in the analytical ultracentrifuge is a matrix free solution technique with no immobilisation, columns, or membranes required and can be used to study self-association and complex or “hetero”-interactions, stoichiometry, reversibility and interaction strength of a wide variety of macromolecular types and across a very large dynamic range (dissociation constants from 10?12 M to 10?1 M). We extend an earlier review specifically highlighting advances in sedimentation velocity and sedimentation equilibrium in the analytical ultracentrifuge applied to protein interactions and mucoadhesion and to review recent applications in protein self-association (tetanus toxoid, agrin), protein-like carbohydrate association (aminocelluloses), carbohydrate-protein interactions (polysaccharide-gliadin), nucleic-acid protein (G-duplexes), nucleic acid-carbohydrate (DNA-chitosan) and finally carbohydrate-carbohydrate (xanthan-chitosan and a ternary polysaccharide complex) interactions. PMID:25756246

  16. Recent advances in the analysis of macromolecular interactions using the matrix-free method of sedimentation in the analytical ultracentrifuge.

    PubMed

    Harding, Stephen E; Gillis, Richard B; Almutairi, Fahad; Erten, Tayyibe; Kök, M ?amil; Adams, Gary G

    2015-01-01

    Sedimentation in the analytical ultracentrifuge is a matrix free solution technique with no immobilisation, columns, or membranes required and can be used to study self-association and complex or "hetero"-interactions, stoichiometry, reversibility and interaction strength of a wide variety of macromolecular types and across a very large dynamic range (dissociation constants from 10-12 M to 10-1 M). We extend an earlier review specifically highlighting advances in sedimentation velocity and sedimentation equilibrium in the analytical ultracentrifuge applied to protein interactions and mucoadhesion and to review recent applications in protein self-association (tetanus toxoid, agrin), protein-like carbohydrate association (aminocelluloses), carbohydrate-protein interactions (polysaccharide-gliadin), nucleic-acid protein (G-duplexes), nucleic acid-carbohydrate (DNA-chitosan) and finally carbohydrate-carbohydrate (xanthan-chitosan and a ternary polysaccharide complex) interactions. PMID:25756246

  17. A multilaboratory comparison of calibration accuracy and the performance of external references in analytical ultracentrifugation.

    PubMed

    Zhao, Huaying; Ghirlando, Rodolfo; Alfonso, Carlos; Arisaka, Fumio; Attali, Ilan; Bain, David L; Bakhtina, Marina M; Becker, Donald F; Bedwell, Gregory J; Bekdemir, Ahmet; Besong, Tabot M D; Birck, Catherine; Brautigam, Chad A; Brennerman, William; Byron, Olwyn; Bzowska, Agnieszka; Chaires, Jonathan B; Chaton, Catherine T; Cölfen, Helmut; Connaghan, Keith D; Crowley, Kimberly A; Curth, Ute; Daviter, Tina; Dean, William L; Díez, Ana I; Ebel, Christine; Eckert, Debra M; Eisele, Leslie E; Eisenstein, Edward; England, Patrick; Escalante, Carlos; Fagan, Jeffrey A; Fairman, Robert; Finn, Ron M; Fischle, Wolfgang; de la Torre, José García; Gor, Jayesh; Gustafsson, Henning; Hall, Damien; Harding, Stephen E; Cifre, José G Hernández; Herr, Andrew B; Howell, Elizabeth E; Isaac, Richard S; Jao, Shu-Chuan; Jose, Davis; Kim, Soon-Jong; Kokona, Bashkim; Kornblatt, Jack A; Kosek, Dalibor; Krayukhina, Elena; Krzizike, Daniel; Kusznir, Eric A; Kwon, Hyewon; Larson, Adam; Laue, Thomas M; Le Roy, Aline; Leech, Andrew P; Lilie, Hauke; Luger, Karolin; Luque-Ortega, Juan R; Ma, Jia; May, Carrie A; Maynard, Ernest L; Modrak-Wojcik, Anna; Mok, Yee-Foong; Mücke, Norbert; Nagel-Steger, Luitgard; Narlikar, Geeta J; Noda, Masanori; Nourse, Amanda; Obsil, Tomas; Park, Chad K; Park, Jin-Ku; Pawelek, Peter D; Perdue, Erby E; Perkins, Stephen J; Perugini, Matthew A; Peterson, Craig L; Peverelli, Martin G; Piszczek, Grzegorz; Prag, Gali; Prevelige, Peter E; Raynal, Bertrand D E; Rezabkova, Lenka; Richter, Klaus; Ringel, Alison E; Rosenberg, Rose; Rowe, Arthur J; Rufer, Arne C; Scott, David J; Seravalli, Javier G; Solovyova, Alexandra S; Song, Renjie; Staunton, David; Stoddard, Caitlin; Stott, Katherine; Strauss, Holger M; Streicher, Werner W; Sumida, John P; Swygert, Sarah G; Szczepanowski, Roman H; Tessmer, Ingrid; Toth, Ronald T; Tripathy, Ashutosh; Uchiyama, Susumu; Uebel, Stephan F W; Unzai, Satoru; Gruber, Anna Vitlin; von Hippel, Peter H; Wandrey, Christine; Wang, Szu-Huan; Weitzel, Steven E; Wielgus-Kutrowska, Beata; Wolberger, Cynthia; Wolff, Martin; Wright, Edward; Wu, Yu-Sung; Wubben, Jacinta M; Schuck, Peter

    2015-01-01

    Analytical ultracentrifugation (AUC) is a first principles based method to determine absolute sedimentation coefficients and buoyant molar masses of macromolecules and their complexes, reporting on their size and shape in free solution. The purpose of this multi-laboratory study was to establish the precision and accuracy of basic data dimensions in AUC and validate previously proposed calibration techniques. Three kits of AUC cell assemblies containing radial and temperature calibration tools and a bovine serum albumin (BSA) reference sample were shared among 67 laboratories, generating 129 comprehensive data sets. These allowed for an assessment of many parameters of instrument performance, including accuracy of the reported scan time after the start of centrifugation, the accuracy of the temperature calibration, and the accuracy of the radial magnification. The range of sedimentation coefficients obtained for BSA monomer in different instruments and using different optical systems was from 3.655 S to 4.949 S, with a mean and standard deviation of (4.304 ± 0.188) S (4.4%). After the combined application of correction factors derived from the external calibration references for elapsed time, scan velocity, temperature, and radial magnification, the range of s-values was reduced 7-fold with a mean of 4.325 S and a 6-fold reduced standard deviation of ± 0.030 S (0.7%). In addition, the large data set provided an opportunity to determine the instrument-to-instrument variation of the absolute radial positions reported in the scan files, the precision of photometric or refractometric signal magnitudes, and the precision of the calculated apparent molar mass of BSA monomer and the fraction of BSA dimers. These results highlight the necessity and effectiveness of independent calibration of basic AUC data dimensions for reliable quantitative studies. PMID:25997164

  18. Investigation of pH-induced conformational change and hydration of poly(methacrylic acid) by analytical ultracentrifugation.

    PubMed

    Wang, Xiaoyan; Ye, Xiaodong; Zhang, Guangzhao

    2015-07-14

    Analytical ultracentrifugation was performed on poly(methacrylic acid) (PMAA) with a series of weight average molar masses (Mw) in aqueous solutions as a function of pH. The scales of the sedimentation coefficient (s) and the diffusion coefficient (D) to Mw at infinite dilutions were obtained at different pH values, indicating that PMAA chains adopt a collapsed structure at low pH values, and stretch at pH higher than 5.2. Our results show that the sedimentation coefficient exhibits a minimum at pH ? 6.0, presumably due to the effect of the conformational change and the hydration state of PMAA chains. When pH increases from 6.0 to 8.5, PMAA chains with high molar mass shrink a little bit, presumably because the sodium ions act as a bridging agent between nonadjacent carboxylate groups. Furthermore, the weight average molar mass of PMAA at pH 8.5 increases by one fold than that at pH 4.0, indicating the condensation of sodium ions and the increase in the number of hydration water molecules around carboxylate groups at high pH values. PMID:26059391

  19. Analyzing surfactant structures on length and chirality resolved (6,5) single-wall carbon nanotubes by analytical ultracentrifugation.

    PubMed

    Fagan, Jeffrey A; Zheng, Ming; Rastogi, Vinayak; Simpson, Jeffrey R; Khripin, Constantine Y; Silvera Batista, Carlos A; Hight Walker, Angela R

    2013-04-23

    The structure and density of the bound interfacial surfactant layer and associated hydration shell were investigated using analytical ultracentrifugation for length and chirality purified (6,5) single-wall carbon nanotubes (SWCNTs) in three different bile salt surfactant solutions. The differences in the chemical structures of the surfactants significantly affect the size and density of the bound surfactant layers. As probed by exchange of a common parent nanotube population into sodium deoxycholate, sodium cholate, or sodium taurodeoxycholate solutions, the anhydrous density of the nanotubes was least for the sodium taurodeoxycholate surfactant, and the absolute sedimentation velocities greatest for the sodium cholate and sodium taurodeoxycholate surfactants. These results suggest that the thickest interfacial layer is formed by the deoxycholate, and that the taurodeoxycholate packs more densely than either sodium cholate or deoxycholate. These structural differences correlate well to an observed 25% increase in fluorescence intensity relative to the cholate surfactant for deoxycholate and taurodeoxycholate dispersed SWCNTs displaying equivalent absorbance spectra. Separate sedimentation velocity experiments including the density modifying agent iodixanol were used to establish the buoyant density of the (6,5) SWCNT in each of the bile salt surfactants; from the difference in the buoyant and anhydrous densities, the largest hydrated diameter is observed for sodium deoxycholate. Understanding the effects of dispersant choice and the methodology for measurement of the interfacial density and hydrated diameter is critical for rationally advancing separation strategies and applications of nanotubes. PMID:23530719

  20. Aggregation analysis of pharmaceutical human immunoglobulin preparations using size-exclusion chromatography and analytical ultracentrifugation sedimentation velocity.

    PubMed

    Krayukhina, Elena; Uchiyama, Susumu; Nojima, Kiyoko; Okada, Yoshiaki; Hamaguchi, Isao; Fukui, Kiichi

    2013-01-01

    In the pharmaceutical industry, analysis of soluble aggregates in pharmaceutical formulations is most commonly performed using size-exclusion chromatography (SEC). However, owing to concerns that aggregates can be overlooked by SEC analysis, it has been suggested that its results should be confirmed with orthogonal methods. One of the main alternative methods for SEC is analytical ultracentrifugation sedimentation velocity (AUC-SV), which has been indicated as an important tool for the measurement of protein aggregation. The present study aimed to show that AUC-SV can be effectively applied for the characterization of marketed immunoglobulin pharmaceutical preparations to support the results obtained by SEC. In addition, the present research aimed to assess the appropriateness of two integration approaches for the quantitative analysis of the SEC results. Thus, the aggregates were measured in seven different preparations of human immunoglobulins by AUC-SV and SEC, and the acquired chromatographic data were processed by using either the vertical drop method or the Gaussian skim approach, implemented in the Empower II chromatography data software (Waters, Tokyo, Japan). The results of aggregation measurements performed using AUC-SV were in good agreement with those obtained using SEC. As expected, the Gaussian skim integration approach inherently provided lower estimates of aggregation content than the results of the vertical drop method. The finding of this study confirmed the complementary nature of AUC-SV to SEC for aggregate composition analysis and underscored the important role that the different integration methods can play in the quantitative interpretation of chromatographic results. PMID:22925901

  1. Comparison of scanning electron microscopy, dynamic light scattering and analytical ultracentrifugation for the sizing of poly(butyl cyanoacrylate) nanoparticles.

    PubMed

    Bootz, Alexander; Vogel, Vitali; Schubert, Dieter; Kreuter, Jörg

    2004-03-01

    Nanoparticles represent promising carriers for controlled drug delivery. This work focuses on the size and molecular mass characterization of polyalkylcyanoacrylate nanoparticles formed by anionic emulsion polymerization of butylcyanoacrylate in the presence of poloxamer 188 as a stabilizer. Three different methods were used to determine the size and size distribution of the particle populations: scanning electron microscopy (SEM), dynamic light scattering (DLS), and analytical ultracentrifugation (ANUC). SEM on freeze-dried and Au-shadowed samples showed a relatively narrow distribution of virtually spherical particles with a mean diameter of 167 nm. DLS yielded a monomodal distribution with hydrodynamic diameters around 199 nm (in the absence of additional stabilizer) or 184 nm (in the presence of 1% poloxamer 188). The size distribution determined by ANUC using sedimentation velocity analysis was somewhat more complex, the size of the most abundant particles being around 184 nm. Molar particle mass distributions centered around 2.3x10(9) g/mol. The advantages and disadvantages of the three sizing techniques are discussed. PMID:15018998

  2. Resolving the challenge of measuring ligand binding to membrane proteins by combining analytical ultracentrifugation and light scattering photometry.

    PubMed

    Doran, J D; Mohanty, A K; Fox, T

    2012-01-01

    Membrane proteins are attractive therapeutic targets, however the presence of detergents complicates biophysical binding measurements. Difficulties in determining quantitative dissociation constants for problematic membrane proteins were addressed by combining analytical ultracentrifugation and classical light scattering techniques. Validation of the algorithm used to calculate dissociation constants from sedimentation equilibrium experiments was demonstrated by analyzing binding data of the inhibitor Y-27632 to rho-kinase (ROCK). Kd's of 1.3 ± 0.7 and 52 ± 27 µM were calculated for ROCK constructs (S6-R415) and (M71-E379) respectively, consistent with previously published Ki's of 1.4 ± 0.1 and > 30 µM. Extension of the algorithm to membrane proteins required the collection of light scattering data to determine the partial specific volume, ?, for the membrane protein-detergent complex. Vitamin B12 binding to the bacterial protein btuB in octyl ?-D-glucopyranoside (?-OG) illustrates the applicability of the method. A ? of 0.781 ml/g was determined for the btuB-?-OG complex. Incorporating this value into the algorithm generated a Kd of 7.0 ± 1.5 µM for the vitamin B12-btuB affinity. A Kd of 9.7 ± 2.7 µM was determined by equilibrium dialysis under similar experimental conditions. Successfully applying AUC to quantifying small-molecule ligand affinities to membrane proteins represents a significant advance to the field. PMID:21922461

  3. Analytical Ultracentrifugation Sedimentation Velocity for the Characterization of Detergent-Solubilized Membrane Proteins Ca++-ATPase and ExbB

    PubMed Central

    Salvay, Andrés G.; Santamaria, Monica; le Maire, Marc

    2008-01-01

    We have investigated the potential of new methods of analysis of sedimentation velocity (SV) analytical ultracentrifugation (AUC) for the characterization of detergent-solubilized membrane proteins. We analyze the membrane proteins Ca++-ATPase and ExbB solubilized with DDM (dodecyl-?-d-maltoside). SV is extremely well suited for characterizing sample heterogeneity. DDM micelles (s20w?=?3.1 S) and complexes (Ca++-ATPase: s20w?=?7.3 S; ExbB: s20w?=?4 S) are easily distinguished. Using different detergent and protein concentrations, SV does not detect any evidence of self-association for the two proteins. An estimate of bound detergent of 0.9 g/g for Ca++-ATPase and 1.5 g/g for ExbB is obtained from the combined analysis of SV profiles obtained using absorbance and interference optics. Combining s20w with values of the hydrodynamic radius, Rs?=?5.5 nm for Ca++-ATPase or Rs?=?3.4 nm for ExbB, allows the determination of buoyant molar masses, Mb. In view of their Mb and composition, Ca++-ATPase and ExbB are monomers in our experimental conditions. We conclude that one of the main advantages of SV versus other techniques is the possibility to ascertain the homogeneity of the samples and to focus on a given complex even in the presence of other impurities or aggregates. The relative rapidity of SV measurements also allows experiments on unstable samples. PMID:19669527

  4. Measuring agglomerate size distribution and dependence of localized surface plasmon resonance absorbance on gold nanoparticle agglomerate size using analytical ultracentrifugation.

    PubMed

    Zook, Justin M; Rastogi, Vinayak; Maccuspie, Robert I; Keene, Athena M; Fagan, Jeffrey

    2011-10-25

    Agglomeration of nanoparticles during measurements in relevant biological and environmental media is a frequent problem in nanomaterial property characterization. The primary problem is typically that any changes to the size distribution can dramatically affect the potential nanotoxicity or other size-determined properties, such as the absorbance signal in a biosensor measurement. Herein we demonstrate analytical ultracentrifugation (AUC) as a powerful method for measuring two critical characteristics of nanoparticle (NP) agglomerates in situ in biological media: the NP agglomerate size distribution, and the localized surface plasmon resonance (LSPR) absorbance spectrum of precise sizes of gold NP agglomerates. To characterize the size distribution, we present a theoretical framework for calculating the hydrodynamic diameter distribution of NP agglomerates from their sedimentation coefficient distribution. We measure sedimentation rates for monomers, dimers, and trimers, as well as for larger agglomerates with up to 600 NPs. The AUC size distributions were found generally to be broader than the size distributions estimated from dynamic light scattering and diffusion-limited colloidal aggregation theory, an alternative bulk measurement method that relies on several assumptions. In addition, the measured sedimentation coefficients can be used in nanotoxicity studies to predict how quickly the agglomerates sediment out of solution under normal gravitational forces, such as in the environment. We also calculate the absorbance spectra for monomer, dimer, trimer, and larger gold NP agglomerates up to 600 NPs, to enable a better understanding of LSPR biosensors. Finally, we validate a new method that uses these spectra to deconvolute the net absorbance spectrum of an unknown bulk sample and approximate the proportions of monomers, dimers, and trimers in a polydisperse sample of small agglomerates, so that every sample does not need to be measured by AUC. These results demonstrate the potential utility of AUC to characterize NP agglomeration and sedimentation for nanotoxicity and biosensor studies, as well as to characterize NP agglomerate size and absorbance to improve LSPR and surface-enhanced Raman spectroscopy based biosensors. PMID:21888410

  5. Self-association and active enzyme forms of Naja naja naja and Crotalus atrox phospholipase A2 studied by analytical ultracentrifugation.

    PubMed

    Bukowski, T; Teller, D C

    1986-12-01

    The dimerization of phospholipase A2 (PLPA2) from Naja naja naja (Pakistani cobra) and Crotalus atrox (Western Diamondback rattlesnake) has been studied from pH 2.5 to 11 at 20 degrees C in 1 mM CaCl2, 0.21 M ionic strength. For the C. atrox enzyme, it was found necessary to use a combination of sedimentation equilibrium and fluorescence yield data to analyze the association. Sedimentation equilibrium in the analytical ultracentrifuge sufficed for the study of the N. naja PLPA2. In the region of enzymatic activity at pH 8, the dimerization association constants found were k2 = 2.8 X 10(6) L/mol and k2 = 6.9 X 10(4) L/mol for the C. atrox and N. naja enzymes, respectively. Analytical linked functions are presented which describe the data. Because the associations are linked to Ca2+ as well as the hydrogen ion, no attempt was made to interpret the ionization of residues in terms of the molecular structure. Active-enzyme sedimentation velocity experiments have been used to study the relation between enzymatic activity and association for both the C. atrox and N. naja enzymes. The substrate 1,2-dibutyryl-sn-glycero-3-phosphocholine (diC4PC) did not dissociate the C. atrox PLPA2. The substrate 1,2-dihexanoyl-sn-glycero-3-phosphocholine (diC6PC) at 7.5 mM dissociated the C. atrox PLPA2 when monitored either as the active enzyme or as the Sr2+-inhibited enzyme. At low enzyme concentrations, 40 mM diC4PC had no effect on N. naja PLPA2 dimerization. However, the sedimentation coefficients observed at enzyme concentrations above 0.2 mg/mL in active-enzyme sedimentation velocity experiments were larger than the values predicted from the thermodynamic studies. Sedimentation coefficients observed for the N. naja PLPA2 acting on diC6PC were larger than those of the monomeric protein, which was the form layered on this substrate. The dissociation of the C. atrox PLPA2 effected by diC6PC was analyzed by the thermodynamics of association and the kinetic Michaelis constant. The analysis suffices to account for the observed sedimentation coefficient. The sedimentation behavior of the N. naja PLPA2 acting on diC6PC substrate was analyzed in terms of a protein-lipid complex. With this model, 68 +/- 16 phospholipid molecules per protein monomer were determined. It is proposed that this enzyme has two micelle nucleation sites per monomer. These putative sites promote micelle formation of the substrate on the enzyme below the critical micelle concentration of the lipid alone. PMID:3801457

  6. The implementation of SOMO (SOlution MOdeller) in the UltraScan analytical ultracentrifugation data analysis suite: enhanced capabilities allow the reliable hydrodynamic modeling of virtually any kind of biomacromolecule.

    PubMed

    Brookes, Emre; Demeler, Borries; Rosano, Camillo; Rocco, Mattia

    2010-02-01

    The interpretation of solution hydrodynamic data in terms of macromolecular structural parameters is not a straightforward task. Over the years, several approaches have been developed to cope with this problem, the most widely used being bead modeling in various flavors. We report here the implementation of the SOMO (SOlution MOdeller; Rai et al. in Structure 13:723-734, 2005) bead modeling suite within one of the most widely used analytical ultracentrifugation data analysis software packages, UltraScan (Demeler in Modern analytical ultracentrifugation: techniques and methods, Royal Society of Chemistry, UK, 2005). The US-SOMO version is now under complete graphical interface control, and has been freed from several constraints present in the original implementation. In the direct beads-per-atoms method, virtually any kind of residue as defined in the Protein Data Bank (e.g., proteins, nucleic acids, carbohydrates, prosthetic groups, detergents, etc.) can be now represented with beads whose number, size and position are all defined in user-editable tables. For large structures, a cubic grid method based on the original AtoB program (Byron in Biophys J 72:408-415, 1997) can be applied either directly on the atomic structure, or on a previously generated bead model. The hydrodynamic parameters are then computed in the rigid-body approximation. An extensive set of tests was conducted to further validate the method, and the results are presented here. Owing to its accuracy, speed, and versatility, US-SOMO should allow to fully take advantage of the potential of solution hydrodynamics as a complement to higher resolution techniques in biomacromolecular modeling. PMID:19234696

  7. Improved optics for an ultracentrifuge

    NASA Technical Reports Server (NTRS)

    Miller, C. G.; Stephens, J. B.

    1980-01-01

    Ultracentrifuge is important tool in study of polymers, biomolecules, and cell structures. In typical ultracentrifuge rotor supports pair of optically matched vials; one contains sample mixed in solvent, and other is reference that contains only solvent. Doubleslit optical system, transverse to rotor, creates interference pattern on photographic plate each time vials pass through optics. Medium in sample vial displaces interference maximums such that shift gives measurement of density distribution along length of sample.

  8. Evaluation of Gel Permeation Chromatography as an analytical tool for aspect cement testing 

    E-print Network

    Holmgreen, Richard J

    1985-01-01

    EVALUATION OF GEL PERMEATION CHROMATOGRAPHY AS AN ANALYTICAL TOOL FOR ASPHALT CEMENT TESTING A Thesis by RICHARD JOHN HOLMGREEN, JR. Submitted to the Graduate College of Texas A8, M University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE May 1985 Ma]or Subgect: Civil Engineering EVALUATION OF GEL PERMEATION CHROMATOGRAPHY AS AN ANALYTICAL TOOL FOR ASPHALT CEMENT TESTING A Thesis by RICHARD JOHN HOLMGREEN, JR. Approved as to style and content by...

  9. Analytical Ultracentrifugation for Characterizing Nanocrystals and Their

    E-print Network

    , and Vicki L. Colvin* The Department of Biochemistry and Cell Biology and The Department of Chemistry, Rice from red to blue as DNA hybridization induces cross-linking between nanocrystals.2,17 Alternatively

  10. Bovine papillomavirus isolation by ultracentrifugation.

    PubMed

    Araldi, R P; Giovanni, D N S; Melo, T C; Diniz, N; Mazzuchelli-de-Souza, J; Sant'Ana, T A; Carvalho, R F; Beçak, W; Stocco, R C

    2014-11-01

    The bovine papillomavirus (BPV) is the etiological agent of bovine papillomatosis, which causes significant economic losses to livestock, characterized by the presence of papillomas that regress spontaneously or persist and progress to malignancy. Currently, there are 13 types of BPVs described in the literature as well as 32 putative new types. This study aimed to isolate viral particles of BPV from skin papillomas, using a novel viral isolation method. The virus types were previously identified with new primers designed. 77 cutaneous papilloma samples of 27 animals, Simmental breed, were surgically removed. The DNA was extracted and subjected to PCR using Delta-Epsilon and Xi primers. The bands were purified and sequenced. The sequences were analyzed using software and compared to the GenBank database, by BLAST tool. The viral typing showed a prevalence of BPV-2 in 81.81% of samples. It was also detected the presence of the putative new virus type BR/UEL2 in one sample. Virus isolation was performed by ultracentrifugation in a single density of cesium chloride. The method of virus isolation is less laborious than those previously described, allowing the isolation of complete virus particles of BPV-2. PMID:25102429

  11. The effect of silica gel sampling tube design on the analytical recovery of fluorine ions / by Daniel Howard Anna

    E-print Network

    Anna, Daniel Howard

    1991-01-01

    THE EFFECT OF SILICA GEL SAMPLING TUBE DESIGN ON THE ANALYTICAL RECOVERY OF FLUORINE IONS A Thesis by DANIEL HOWARD ANNA Submitted to the Office of Graduate Studies of Texas ARM University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE August 1991 Major Subject: Industrial Hygiene THE EFFECI' OF SILICA GEL SAMPLING TUBE DESIGN ON THE ANALYTICAL RECOVERY OF FLUORINE IONS A Thesis by DANIEL HOWARD ANNA Approved as to style and content by: Ri rd B. n...

  12. Dual analyte flow injection fluorescence immunoassays using thiophilic gel reactors and synchronous scanning detection.

    PubMed

    Guo, J C; Miller, J N; Evans, M; Palmer, D A

    2000-10-01

    Heterogeneous fluorescence immunoassays have been automated using flow injection manifolds incorporating thiophilic gel solid phase reactors to separate antibody-bound and unbound analyte molecules. Antibody elution is achieved by changes in ionic strength, thus allowing the use of pH sensitive fluorescent labels. This facilitates the development of dual analyte systems, in which two competitive immunoassays with separate labels are monitored in parallel. Detection of the fluorophores by high speed synchronous fluorescence scanning while the flow is briefly stopped utilises either one synchronous interval which detects both fluorophores, or two separate scans at different wavelength intervals, one for each fluorophore. Simultaneous analyses of serum albumin and transferrin exemplify these novel approaches. Spectroscopic interferences are very small, analyte recoveries are close to 100%, with a relative standard deviation of 5-6% and a sampling rate of 20 h-1. PMID:11070537

  13. Size-Distribution Analysis of Macromolecules by Sedimentation Velocity Ultracentrifugation and Lamm Equation Modeling

    Microsoft Academic Search

    Peter Schuck

    2000-01-01

    A new method for the size-distribution analysis of polymers by sedimentation velocity analytical ultracentrifugation is described. It exploits the ability of Lamm equation modeling to discriminate between the spreading of the sedimentation boundary arising from sample heterogeneity and from diffusion. Finite element solutions of the Lamm equation for a large number of discrete noninteracting species are combined with maximum entropy

  14. A Sedimentation Experiment Using a Preparative Ultracentrifuge

    ERIC Educational Resources Information Center

    Boudreau, Raymond E.; And Others

    1975-01-01

    Describes an experiment that illustrates the use of the preparative ultracentrifuge in isolating and purifying bacterial ribosomes, determines the sedimentation coefficients of the ribonucleoprotein particles, and demonstrates the subunit structure of the 70-S ribosome and the role of the magnesium ion in the association of subunits. (Author/GS)

  15. Pathways, Scaling Laws and Analytical Solutions for Crease Formations in a Gel Layer

    E-print Network

    Xiaoyi Chen; Hui-Hui Dai

    2014-10-30

    An analytical study on crease formations in a swelling gel layer is conducted. By exploring the smallness of the layer thickness and using a method of coupled series-asymptotic expansions, the original nonlinear eigenvalue problem of partial differential equations is reduced to one of ordinary differential equations. The latter problem is then solved analytically to obtain closed-form solutions for all the post-bifurcation branches. With the available analytical results, a number of deep insights on crease formations are provided, including the unveiling of three pathways to crease (depending on the layer thickness), determination of the bifurcation type, establishment of a lower bound for mode numbers and two scaling laws. Also, a number of experimental results are captured, which are then nicely interpreted based on the analytical solutions. In particular, it is shown that some critical physical quantities are invariant with respect to the thickness at the moment of crease formation. It appears that the present work offers a comprehensive understanding on crease formation, a widely-spread phenomenon.

  16. Separation of the principal HDL subclasses by iodixanol ultracentrifugation

    PubMed Central

    Harman, Nicola L.; Griffin, Bruce A.; Davies, Ian G.

    2013-01-01

    HDL subclasses detection, in cardiovascular risk, has been limited due to the time-consuming nature of current techniques. We have developed a time-saving and reliable separation of the principal HDL subclasses employing iodixanol density gradient ultracentrifugation (IxDGUC) combined with digital photography. HDL subclasses were separated in 2.5 h from prestained plasma on a three-step iodixanol gradient. HDL subclass profiles were generated by digital photography and gel scan software. Plasma samples (n = 46) were used to optimize the gradient for the resolution of HDL heterogeneity and to compare profiles generated by IxDGUC with gradient gel electrophoresis (GGE); further characterization from participants (n = 548) with a range of lipid profiles was also performed. HDL subclass profiles generated by IxDGUC were comparable to those separated by GGE as indicated by a significant association between areas under the curve for both HDL2 and HDL3 (HDL2, r = 0.896, P < 0.01; HDL3, r = 0.894, P < 0.01). The method was highly reproducible, with intra- and interassay coefficient of variation percentage < 5 for percentage area under the curve HDL2 and HDL3, and < 1% for peak Rf and peak density. The method provides time-saving and cost-effective detection and preparation of the principal HDL subclasses. PMID:23690506

  17. Gram-scale fractionation of nanodiamonds by density gradient ultracentrifugation

    NASA Astrophysics Data System (ADS)

    Peng, Wei; Mahfouz, Remi; Pan, Jun; Hou, Yuanfang; Beaujuge, Pierre M.; Bakr, Osman M.

    2013-05-01

    Size is a defining characteristic of nanoparticles; it influences their optical and electronic properties as well as their interactions with molecules and macromolecules. Producing nanoparticles with narrow size distributions remains one of the main challenges to their utilization. At this time, the number of practical approaches to optimize the size distribution of nanoparticles in many interesting materials systems, including diamond nanocrystals, remains limited. Diamond nanocrystals synthesized by detonation protocols - so-called detonation nanodiamonds (DNDs) - are promising systems for drug delivery, photonics, and composites. DNDs are composed of primary particles with diameters mainly <10 nm and their aggregates (ca. 10-500 nm). Here, we introduce a large-scale approach to rate-zonal density gradient ultracentrifugation to obtain monodispersed fractions of nanoparticles in high yields. We use this method to fractionate a highly concentrated and stable aqueous solution of DNDs and to investigate the size distribution of various fractions by dynamic light scattering, analytical ultracentrifugation, transmission electron microscopy and powder X-ray diffraction. This fractionation method enabled us to separate gram-scale amounts of DNDs into several size ranges within a relatively short period of time. In addition, the high product yields obtained for each fraction allowed us to apply the fractionation method iteratively to a particular size range of particles and to collect various fractions of highly monodispersed primary particles. Our method paves the way for in-depth studies of the physical and optical properties, growth, and aggregation mechanism of DNDs. Applications requiring DNDs with specific particle or aggregate sizes are now within reach.Size is a defining characteristic of nanoparticles; it influences their optical and electronic properties as well as their interactions with molecules and macromolecules. Producing nanoparticles with narrow size distributions remains one of the main challenges to their utilization. At this time, the number of practical approaches to optimize the size distribution of nanoparticles in many interesting materials systems, including diamond nanocrystals, remains limited. Diamond nanocrystals synthesized by detonation protocols - so-called detonation nanodiamonds (DNDs) - are promising systems for drug delivery, photonics, and composites. DNDs are composed of primary particles with diameters mainly <10 nm and their aggregates (ca. 10-500 nm). Here, we introduce a large-scale approach to rate-zonal density gradient ultracentrifugation to obtain monodispersed fractions of nanoparticles in high yields. We use this method to fractionate a highly concentrated and stable aqueous solution of DNDs and to investigate the size distribution of various fractions by dynamic light scattering, analytical ultracentrifugation, transmission electron microscopy and powder X-ray diffraction. This fractionation method enabled us to separate gram-scale amounts of DNDs into several size ranges within a relatively short period of time. In addition, the high product yields obtained for each fraction allowed us to apply the fractionation method iteratively to a particular size range of particles and to collect various fractions of highly monodispersed primary particles. Our method paves the way for in-depth studies of the physical and optical properties, growth, and aggregation mechanism of DNDs. Applications requiring DNDs with specific particle or aggregate sizes are now within reach. Electronic supplementary information (ESI) available: Discussion of the influence of sample solution concentrations on DLS measurements, comparisons of the size distributions of our raw milled particles and NanoAmando particles, a detailed description of the RZDGU procedure, discussion of the influences of the gradients and centrifugation times on fractionation, TEM images, zeta potentials, AUC analysis and determination of mpDND density. See DOI: 10.1039/c3nr00990d

  18. Comparative proteomic analysis of casein and whey as prepared by chymosin-induced separation, isoelectric precipitation or ultracentrifugation.

    PubMed

    Jensen, Hanne B; Poulsen, Nina A; Møller, Hanne S; Stensballe, Allan; Larsen, Lotte B

    2012-11-01

    Fractionation of bovine milk was performed using chymosin-induced separation, isoelectric precipitation or ultracentrifugation as separation techniques prior to gel-based proteomic analysis. This approach allowed for comparative display and identification of proteins partitioned into casein and whey, respectively. Initially, three different staining methods (silver staining, colloidal Coomassie Blue G-250 or fluorescent Flamingo Pink staining) for two-dimensional gel electrophoresis (2-DGE) analysis were compared for their suitability as staining agent, especially in relation to their suitability to reveal differences in the casein fractions. Fluorescent staining proved to be the most appropriate for this purpose, giving a high sensitivity, and using this staining method, characteristic 2-DGE fingerprints were obtained for each casein and whey fraction from each separation method. A number of protein spots in both casein and whey fractions varied with separation method and these spots were subsequently identified using tandem mass spectrometry (MS). In rennet casein, proteolytic fragmentation of caseins (?(s1)-, ?(s2),-, ?- and ?-) was identified as a result of chymosin hydrolysis, whereas the 2-DGE profile of acid and ultracentrifuged casein was dominated by the presence of multiple isoforms of ?-caseins. Furthermore, casein remnants were identified in milk serum after ultracentrifugation. This study shows that gel-based proteomic analysis is suitable for characterisation of subtle variations in protein composition of milk fractions that occur as a consequence of different milk fractionation strategies. PMID:22998726

  19. On polymer loop in a gel under external fields: analytical approach using white noise analysis

    NASA Astrophysics Data System (ADS)

    Gemao, B.; Bornales, J.; Loquero, M.

    2015-06-01

    This paper presents derivation of the probability distribution for the area enclosed by a polymer loop in a gel and under different external fields using white noise analysis. In this context, the polymer loop is represented by Brownian paths and its immersion in a gel constraints it to occupy a constant area[1]. The external fields considered are electric field, and crossed electric-magnetic fields.

  20. Immobilization of Biomolecules in Sol–Gels: Biological and Analytical Applications

    Microsoft Academic Search

    Vivek Babu Kandimalla; Vijay Shyam Tripathi; Huangxian Ju

    2006-01-01

    The encapsulation or generation of new surfaces that can fix biomolecules firmly without altering their original conformations and activities is still challenging for the utilization of biochemical functions of active biomolecules. Presently, sol–gel chemistry offers new and interesting possibilities for the promising encapsulation of heat-sensitive and fragile biomolecules (enzyme, protein, antibody and whole cells of plant, animal and microbes); mainly,

  1. THE DEVELOPMENT OF SHORT BOWL ULTRACENTRIFUGES. Progress Report

    Microsoft Academic Search

    Zippe

    1959-01-01

    Progress in uranium isotope separation by the ultracentrifuge method is ; reported. Construction and life time testing of centrifuge mechanical protctypes ; are described including operation of two such prototypes for a year. High speed ; spin tests are also described and materials which yield at 402 plus or minus ; 0.3 meters\\/sec were tested. Development of molecular pumps for

  2. Sedimentation Velocity Ultracentrifugation Analysis for Hydrodynamic Characterization of G-Quadruplex Structures

    PubMed Central

    Garbett, Nichola C.; Mekmaysy, Chongkham S.; Chaires, Jonathan B.

    2010-01-01

    Summary Analytical ultracentrifugation (AUC) is a powerful technique for the characterization of hydrodynamic and thermodynamic properties. The intent of this article is to demonstrate the utility of sedimentation velocity (SV) studies to obtain hydrodynamic information for G-quadruplex systems and to provide insights into one part of this process, namely, data analysis of existing SV data. An array of data analysis software is available, mostly written and continually developed by established researchers in the AUC field, with particularly rapid advances in the analysis of SV data. Each program has its own learning curve and this article is intended as a resource in the data analysis process for beginning researchers in the field. We discuss the application of three of the most commonly used data analysis programs, DCDT+, Sedfit and SedAnal, to the interpretation of SV data obtained in our laboratory on two G-quadruplex systems. PMID:20012418

  3. Sol–gel immobilized short-chain poly(ethylene glycol) coating for capillary microextraction of underivatized polar analytes

    Microsoft Academic Search

    Sameer Kulkarni; Anne M. Shearrow; Abdul Malik

    2007-01-01

    Sol–gel coating with covalently bonded low-molecular-weight (MW<300Da) poly(ethylene glycol) (PEG) chains was developed for capillary microextraction (CME). The sol–gel chemistry proved effective in the immobilization of low-molecular-weight PEGs thanks to the formation of chemical bonds between the organic–inorganic hybrid sol–gel PEG coating and the fused silica capillary inner surface. This chemical anchorage provided excellent thermal and solvent stability to the

  4. SEDFIT-MSTAR: Molecular weight and molecular weight distribution analysis of polymers by sedimentation equilibrium in the ultracentrifuge

    PubMed Central

    Schuck, Peter; Gillis, Richard B.; Besong, Tabot M.D.; Almutairi, Fahad; Adams, Gary G.; Rowe, Arthur J.; Harding, Stephen E.

    2014-01-01

    Sedimentation equilibrium (analytical ultracentrifugation) is one of the most inherently suitable methods for the determination of average molecular weights and molecular weight distributions of polymers, because of its absolute basis (no conformation assumptions) and inherent fractionation ability (without the need for columns or membranes and associated assumptions over inertness). With modern instrumentation it is also possible to run up to 21 samples simultaneously in a single run. Its application has been severely hampered because of difficulties in terms of baseline determination (incorporating estimation of the concentration at the air/solution meniscus) and complexity of the analysis procedures. We describe a new method for baseline determination based on a smart-smoothing principle and built into the highly popular platform SEDFIT for the analysis of the sedimentation behavior of natural and synthetic polymer materials. The SEDFIT-MSTAR procedure – which takes only a few minutes to perform - is tested with four synthetic data sets (including a significantly non-ideal system) a naturally occurring protein (human IgG1) and two naturally occurring carbohydrate polymers (pullulan and ?–carrageenan) in terms of (i) weight average molecular weight for the whole distribution of species in the sample (ii) the variation in “point” average molecular weight with local concentration in the ultracentrifuge cell and (iii) molecular weight distribution. PMID:24244936

  5. ULTRACENTRIFUGATION STUDIES ON THE ELEMENTARY BODIES OF VACCINE VIRUS

    PubMed Central

    Smadel, Joseph E.; Pickels, Edward G.; Shedlovsky, Theodore

    1938-01-01

    Ultracentrifugal studies of the CL dermal strain of vaccine virus warrant the following conclusions: 1. When suspended in increasing concentrations of sucrose, glycerol, or urea solutions, elementary bodies of vaccinia show variations in sedimentation rate which indicate changes in the density or size of the particles. For a given change in the density of the medium these changes are smallest with sucrose and most marked with urea. The normal rate of sedimentation of Paschen bodies may be restored by resuspending them in dilute buffer solution. 2. The density of elementary bodies of vaccinia suspended in dilute buffer solutions is estimated to be 1.16 gm. per cc. Higher values for the density are found if the particles are suspended in solutions containing sucrose, glycerol, or urea. In 53 per cent sucrose, for example, the density is 1.25 gm. per cc. 3. Paschen bodies appear to be quite permeable to water and urea, less so to glycerol, and only slightly, if at all, to sucrose. 4. The increased density of the elementary bodies of vaccinia in sucrose solutions may be accounted for by an osmotic extraction of water from the particles. On this basis the water which can be thus extracted corresponds to at least a third of the original volume of the particles. PMID:19870806

  6. ULTRACENTRIFUGATION STUDIES ON THE ELEMENTARY BODIES OF VACCINE VIRUS

    PubMed Central

    Pickels, Edward G.; Smadel, Joseph E.

    1938-01-01

    Ultracentrifugal studies on the CL dermal strain of vaccine virus indicate the following characteristics of the elementary bodies:— 1. A stable suspension of Paschen bodies in a dilute buffer solution of pH 6.2 to 8 sediments with the formation of a characteristic primary boundary which consistently shows a spread of approximately 14 per cent. 2. The principal sedimentation boundary is accompanied frequently by one or several more rapidly moving boundaries which probably are produced by groups of agglutinated elementary bodies consisting of two or more particles. 3. Occasionally the principal boundary may exhibit an irregular or peculiar behavior, a fact which necessitates a careful selection of material and the performance of many experiments for accurate interpretation of results. 4. The sedimentation constant of the slowest moving particles forming the principal boundary is computed to be 49.1 x 10–11 cm./sec./dyne. On the basis of this sedimentation rate, the average diameter of the smallest virus particles in appreciable amounts is estimated at 236 mµ. If the boundary spread is due principally to slight differences in particle size, then the largest single elementary bodies are approximately 252 mµ in diameter. PMID:19870805

  7. Enrichment of calcifying extracellular vesicles using density-based ultracentrifugation protocol

    PubMed Central

    Hutcheson, Joshua D.; Goettsch, Claudia; Pham, Tan; Iwashita, Masaya; Aikawa, Masanori; Singh, Sasha A.; Aikawa, Elena

    2014-01-01

    Calcifying extracellular vesicles (EVs) released from cells within atherosclerotic plaques have received increased attention for their role in mediating vascular calcification, a major predictor of cardiovascular morbidity and mortality. However, little is known about the difference between this pathologic vesicle population and other EVs that contribute to physiological cellular processes. One major challenge that hinders research into these differences is the inability to selectively isolate calcifying EVs from other vesicle populations. In this study, we hypothesized that the formation of mineral within calcifying EVs would increase the density of the vesicles such that they would pellet at a faster rate during ultracentrifugation. We show that after 10 min of ultracentrifugation at 100,000×g, calcifying EVs are depleted from the conditioned media of calcifying coronary artery smooth muscle cells and are enriched in the pelleted portion. We utilized mass spectrometry to establish functional proteomic differences between the calcifying EVs enriched in the 10 min ultracentrifugation compared to other vesicle populations preferentially pelleted by longer ultracentrifugation times. The procedures established in this study will allow us to enrich the vesicle population of interest and perform advanced proteomic analyses to find subtle differences between calcifying EVs and other vesicle populations that may be translated into therapeutic targets for vascular calcification. Finally, we will show that the differences in ultracentrifugation times required to pellet the vesicle populations can also be used to estimate physical differences between the vesicles. PMID:25491249

  8. A Multilaboratory Comparison of Calibration Accuracy and the Performance of External References in Analytical Ultracentrifugation

    E-print Network

    Zhao, Huaying; Ghirlando, Rodolfo; Alfonso, Carlos; Arisaka, Fumio; Attali, Ilan; Bain, David L.; Bakhtina, Marina M.; Becker, Donald F.; Bedwell, Gregory J.; Bekdemir, Ahmet; Besong, Tabot M. D.; Birck, Catherine; Brautigam, Chad A.; Brennerman, William; Byron, Owlyn; Bzowska, Agnieszka; Chaires, Johnathan B.; Chaton, Catherine T.; Coelfen, Helmut; Connaghan, Keith D.; Crowley, Kimberly A.; Curth, Ute; Daviter, Tina; Dean, William L.; Diez, Ana I.; Ebel, Christine; Eckert, Debra M.; Eisele, Leslie E.; Eisenstein, Edward; England, Patrick; Escalante, Carlos; Fagan, Jeffery A.; Fairman, Robert; Finn, Ron M.; Fischle, Wolfgang; de la Torre, Jose Garcia; Gor, Jayesh; Gustafsson, Henning; Hall, Damien; Harding, Stephen E.; Cifre, Jose G. Hernadez; Herr, Andrew B.; Howell, Elizebeth E.; Isaac, Richard S.; Jao, Shu-Chuan; Jose, Davis; Kim, Soon-Jong; Kokona, Bashkim; Kornblatt, Jack A.; Kosek, Dalibor; Krayukhina, Elena; Krzizike, Daniel; Kusznir, Eric A.; Kwon, Hyewon; Larson, Adam; Laue, Thomas M.; Le Roy, Aline; Leech, Andrew P.; Lilie, Hauke; Luger, Karolin; Luque-Ortega, Juan R.; Ma, Jia; May, Carrie A.; Maynard, Ernest L.; Modrak-Wojcik, Anna; Mok, Yee-Foong; Muecke, Norbert; Nagel-Steger, Luitgard; Narlikar, Geeta J.; Noda, Masanori; Nourse, Amanda; Obsil, Tomas; Park, Chad K.; Park, Jin-Ku; Pawelek, Peter D.; Perdue, Erby E.; Perkins, Stephen J.; Perugini, Matthew A.; Peterson, Craig L.; Peverelli, Martin G.; Piszczek, Grzegorz; Prag, Gali; Prevelige, Peter E.; Raynal, Bertrand D. E.; Rezabkova, Lenka; Richter, Klaus; Ringel, Alison E.; Rosenberg, Rose; Rowe, Arthur J.; Rufer, Arne C.; Scott, David J.; Seravalli, Javier G.; Solovyova, Alexandra S.; Song, Renjie; Staunton, David; Stoddard, Caitlin; Stott, Katherine; Strauss, Holger M.; Streicher, Werner W.; Sumida, John P.; Swygert, Sarah G.; Szczepanowski, Roman H.; Tessmer, Ingrid; Toth IV, Ronald T.; Tripathy, Ashutosh; Uchiyama, Susumu; Uebel, Stephan F. W.; Unazi, Satoru; Gruben, Anna Vitlin; von Hippel, Peter H.; Wandrey, Christine; Wang, Szu-Huan; Weitzel, Steven E.; Wielgu-Kutrowska, Beata; Wolberger, Cynthia; Wolff, Martin; Wright, Edward; Yu-Sung, Wu; Wubben, Jacinta M.; Schuck, Peter

    2015-05-21

    system of the data acquisition computer [27,31]; the rotor temperature can be logged in various configu- rations using miniature integrated circuits [27,33,34]; the radial magnification was measured with a precision mask installed in a cell assembly... States of America, 10 Supramolecular Nanomaterials and Interfaces Laboratory, Institute of Materials, École Polytechnique Fédérale de Lausanne, Lausanne, CH-1015, Switzerland, 11 National Centre for Macromolecular Hydrodynamics, University of Nottingham...

  9. Size-distribution analysis of proteins by analytical ultracentrifugation: strategies and application to model systems.

    PubMed

    Schuck, Peter; Perugini, Matthew A; Gonzales, Noreen R; Howlett, Geoffrey J; Schubert, Dieter

    2002-02-01

    Strategies for the deconvolution of diffusion in the determination of size-distributions from sedimentation velocity experiments were examined and developed. On the basis of four different model systems, we studied the differential apparent sedimentation coefficient distributions by the time-derivative method, g(s*), and by least-squares direct boundary modeling, ls-g*(s), the integral sedimentation coefficient distribution by the van Holde-Weischet method, G(s), and the previously introduced differential distribution of Lamm equation solutions, c(s). It is shown that the least-squares approach ls-g*(s) can be extrapolated to infinite time by considering area divisions analogous to boundary divisions in the van Holde-Weischet method, thus allowing the transformation of interference optical data into an integral sedimentation coefficient distribution G(s). However, despite the model-free approach of G(s), for the systems considered, the direct boundary modeling with a distribution of Lamm equation solutions c(s) exhibited the highest resolution and sensitivity. The c(s) approach requires an estimate for the size-dependent diffusion coefficients D(s), which is usually incorporated in the form of a weight-average frictional ratio of all species, or in the form of prior knowledge of the molar mass of the main species. We studied the influence of the weight-average frictional ratio on the quality of the fit, and found that it is well-determined by the data. As a direct boundary model, the calculated c(s) distribution can be combined with a nonlinear regression to optimize distribution parameters, such as the exact meniscus position, and the weight-average frictional ratio. Although c(s) is computationally the most complex, it has the potential for the highest resolution and sensitivity of the methods described. PMID:11806949

  10. Chemistry and processability of crude oil asphaltenes as studied by ultracentrifugation

    SciTech Connect

    Weeks, R.W. Jr.; McBride, W.L.

    1980-01-01

    From the number of crudes of this study, there appears to be a positive correlation between the total quantity of crude oil hetero atoms (S, N, Ni, and V) which are precipitated under conditions of ultracentrifugation and the degree of that particular crude's difficulty of hydroprocessing. Because of its powerful ability to separate colloidal material from suspensions and because of the known colloidal nature of asphaltenes, the ultracentrifuge was employed to effect the separation of crude oil constituents, and to thus provide information relating to the hydrocracking of resids. Asphaltenes vary greatly in their response to hydrocracking with some being remarkably refractive while others are readily destroyed. By studying the chemical nature of the asphaltene/colloid fractions, a correlation between this chemical constitution and processability was observed. The observation of Liesegang band-like phenomena is also reported along with chemical analyses of these bands.

  11. Advanced sorting of single-walled carbon nanotubes by nonlinear density-gradient ultracentrifugation

    NASA Astrophysics Data System (ADS)

    Ghosh, Saunab; Bachilo, Sergei M.; Weisman, R. Bruce

    2010-06-01

    Existing methods for growing single-walled carbon nanotubes produce samples with a range of structures and electronic properties, but many potential applications require pure nanotube samples. Density-gradient ultracentrifugation has recently emerged as a technique for sorting as-grown mixtures of single-walled nanotubes into their distinct (n,m) structural forms, but to date this approach has been limited to samples containing only a small number of nanotube structures, and has often required repeated density-gradient ultracentrifugation processing. Here, we report that the use of tailored nonlinear density gradients can significantly improve density-gradient ultracentrifugation separations. We show that highly polydisperse samples of single-walled nanotubes grown by the HiPco method are readily sorted in a single step to give fractions enriched in any of ten different (n,m) species. Furthermore, minor variants of the method allow separation of the mirror-image isomers (enantiomers) of seven (n,m) species. Optimization of this approach was aided by the development of instrumentation that spectroscopically maps nanotube contents inside undisturbed centrifuge tubes.

  12. Advanced sorting of single-walled carbon nanotubes by nonlinear density-gradient ultracentrifugation.

    PubMed

    Ghosh, Saunab; Bachilo, Sergei M; Weisman, R Bruce

    2010-06-01

    Existing methods for growing single-walled carbon nanotubes produce samples with a range of structures and electronic properties, but many potential applications require pure nanotube samples. Density-gradient ultracentrifugation has recently emerged as a technique for sorting as-grown mixtures of single-walled nanotubes into their distinct (n,m) structural forms, but to date this approach has been limited to samples containing only a small number of nanotube structures, and has often required repeated density-gradient ultracentrifugation processing. Here, we report that the use of tailored nonlinear density gradients can significantly improve density-gradient ultracentrifugation separations. We show that highly polydisperse samples of single-walled nanotubes grown by the HiPco method are readily sorted in a single step to give fractions enriched in any of ten different (n,m) species. Furthermore, minor variants of the method allow separation of the mirror-image isomers (enantiomers) of seven (n,m) species. Optimization of this approach was aided by the development of instrumentation that spectroscopically maps nanotube contents inside undisturbed centrifuge tubes. PMID:20453856

  13. Estimation oftheConcentration of Low-Density Lipoprotein Cholesterol inPlasma, Without UseofthePreparative Ultracentrifuge

    Microsoft Academic Search

    William T. Friedewald; Robert I. Levy; Donald S. Fredrickson

    1972-01-01

    A method for estimating the cholesterol content of the serum low-density lipoprotein fraction (Sf- 0.20)is presented. The method involves measure- ments of fasting plasma total cholesterol, tri- glyceride, and high-density lipoprotein cholesterol concentrations, none of which requires the use of the preparative ultracentrifuge. Cornparison of this suggested procedure with the more direct procedure, in which the ultracentrifuge is used, yielded

  14. A technique for isolation of rubella virus-like particles by sucrose gradient ultracentrifugation using Coomassie brilliant blue G crystals

    Microsoft Academic Search

    Andreas Giessauf; Manuel Flaim; Manfred P Dierich; Reinhard Würzner

    2002-01-01

    An improved method for the isolation of rubella virus-like particles (RVLP) from cell culture supernatant of transfected Chinese hamster ovary (CHO24S) cells is described. It employs a combination of membrane filtration with sucrose gradient ultracentrifugation. It was found that staining the RVLP band with Coomassie brilliant blue G (CBB) resulted in the CBB crystals adsorbing RVLP. After ultracentrifugation (25,000rpm, 3h,

  15. Combining ultracentrifugation and peptide termini group-specific immunoprecipitation for multiplex plasma protein analysis.

    PubMed

    Volk, Sonja; Schreiber, Thomas D; Eisen, David; Wiese, Calvin; Planatscher, Hannes; Pynn, Christopher J; Stoll, Dieter; Templin, Markus F; Joos, Thomas O; Pötz, Oliver

    2012-07-01

    Blood plasma is a valuable source of potential biomarkers. However, its complexity and the huge dynamic concentration range of its constituents complicate its analysis. To tackle this problem, an immunoprecipitation strategy was employed using antibodies directed against short terminal epitope tags (triple X proteomics antibodies), which allow the enrichment of groups of signature peptides derived from trypsin-digested plasma. Isolated signature peptides are subsequently detected using MALDI-TOF/TOF mass spectrometry. Sensitivity of the immunoaffinity approach was, however, compromised by the presence of contaminant peaks derived from the peptides of nontargeted high abundant proteins. A closer analysis of the enrichment strategy revealed nonspecific peptide binding to the solid phase affinity matrix as the major source of the contaminating peptides. We therefore implemented a sucrose density gradient ultracentrifugation separation step into the procedure. This yielded a 99% depletion of contaminating peptides from a sucrose fraction containing 70% of the peptide-antibody complexes and enabled the detection of the previously undetected low abundance protein filamin-A. Assessment of this novel approach using 15 different triple X proteomics antibodies demonstrated a more consistent detection of a greater number of targeted peptides and a significant reduction in the intensity of nonspecific peptides. Ultracentrifugation coupled with immunoaffinity MS approaches presents a powerful tool for multiplexed plasma protein analysis without the requirement for demanding liquid chromatography separation techniques. PMID:22527512

  16. Gel Electrophoresis

    NSDL National Science Digital Library

    2011-08-20

    In this activity, learners simulate the process of DNA fingerprinting by using electricity to separate colored dyes. Learners use simple materials to assemble a comb (electrophoresis chamber) to hold the samples, make a 0.2% sodium bicarbonate buffer and 1% gel solution, connect a high voltage power supply, and prepare 5 different samples. Then learners test their model and observe each sample.

  17. Simultaneous determination of residual saturation and capillary pressure curves utilizing the ultracentrifuge

    SciTech Connect

    King, M.J.; Falzone, A.J.; Cook, W.R.; Jennings, J.W. Jr.; Mills, W.H.

    1986-01-01

    Residual saturation and capillary pressure curves are important for modelling reservoir and laboratory processes. Knowledge of the residual saturation curve is necessary to determine the ultimate production from a tertiary recovery process. Capillary pressure is required to interpret laboratory core floods and to describe multi-phase reservoir fluid flow. The ultracentrifuge provides a rapid means of determining capillary pressure and residual saturation relationships. It is non-destructive, uses small samples, and is capable of attaining both high capillary pressures and extremely low residual saturations. The effects of variation in residual saturation with Bond number are not included in the traditional Hassier-Brunner analysis for capillary pressure. Such desaturation effects can explain the anomalous experimental saturation distributions reported at high rotation rates. The current work generalizes the Hassler-Brunner analysis to include desaturation and also to include the variation in centripeta acceleration through the core. The analysis also provides for the determination of residual saturation as a function of Bond number (k..delta..rhog/sigma.

  18. Thickness sorting of two-dimensional transition metal dichalcogenides via copolymer-assisted density gradient ultracentrifugation

    NASA Astrophysics Data System (ADS)

    Kang, Joohoon; Seo, Jung-Woo T.; Alducin, Diego; Ponce, Arturo; Yacaman, Miguel Jose; Hersam, Mark C.

    2014-11-01

    Two-dimensional transition metal dichalcogenides have emerged as leading successors to graphene due to their diverse properties, which depend sensitively on sample thickness. Although solution-based exfoliation methods hold promise for scalable production of these materials, existing techniques introduce irreversible structural defects and/or lack sufficient control over the sample thickness. In contrast, previous work on carbon nanotubes and graphene has shown that isopycnic density gradient ultracentrifugation can produce structurally and electronically monodisperse nanomaterial populations. However, this approach cannot be directly applied to transition metal dichalcogenides due to their high intrinsic buoyant densities when encapsulated with ionic small molecule surfactants. Here, we overcome this limitation and thus demonstrate thickness sorting of pristine molybdenum disulfide (MoS2) by employing a block copolymer dispersant composed of a central hydrophobic unit flanked by hydrophilic chains that effectively reduces the overall buoyant density in aqueous solution. The resulting solution-processed monolayer MoS2 samples exhibit strong photoluminescence without further chemical treatment.

  19. Thickness sorting of two-dimensional transition metal dichalcogenides via copolymer-assisted density gradient ultracentrifugation.

    PubMed

    Kang, Joohoon; Seo, Jung-Woo T; Alducin, Diego; Ponce, Arturo; Yacaman, Miguel Jose; Hersam, Mark C

    2014-01-01

    Two-dimensional transition metal dichalcogenides have emerged as leading successors to graphene due to their diverse properties, which depend sensitively on sample thickness. Although solution-based exfoliation methods hold promise for scalable production of these materials, existing techniques introduce irreversible structural defects and/or lack sufficient control over the sample thickness. In contrast, previous work on carbon nanotubes and graphene has shown that isopycnic density gradient ultracentrifugation can produce structurally and electronically monodisperse nanomaterial populations. However, this approach cannot be directly applied to transition metal dichalcogenides due to their high intrinsic buoyant densities when encapsulated with ionic small molecule surfactants. Here, we overcome this limitation and thus demonstrate thickness sorting of pristine molybdenum disulfide (MoS2) by employing a block copolymer dispersant composed of a central hydrophobic unit flanked by hydrophilic chains that effectively reduces the overall buoyant density in aqueous solution. The resulting solution-processed monolayer MoS2 samples exhibit strong photoluminescence without further chemical treatment. PMID:25391315

  20. Modeling Analytical Ultracentrifugation Experiments with an Adaptive Space-Time Finite Element Solution for Multicomponent Reacting Systems

    PubMed Central

    Cao, Weiming; Demeler, Borries

    2008-01-01

    We describe an extension of the adaptive space-time finite element method (ASTFEM) used in the solution of the Lamm equation to the case of multicomponent reacting systems. We use an operator splitting technique to decouple the sedimentation-diffusion process from the reaction process. The former is solved with an ASTFEM approach based on the Petrov-Galerkin method and on adaptive moving grids, and the latter is solved with the implicit midpoint Euler's method. Our solution can effectively eliminate the sedimentation errors for each component or species involved in the reaction, and it is free from oscillation near the cell bottom. It offers second-order accuracy, and guarantees conservation of mass without any additional postprocessing, and it permits modeling of multicomponent, equilibrating systems where the reaction rate can be kinetically controlled between an instantaneous reaction and a noninteracting mixture. The proposed ASTFEM solution provides improved efficiency and accuracy compared to classical approaches, especially when medium-sized and large molecules are modeled. PMID:18390609

  1. Analytical ultracentrifugation and preliminary X-ray studies of the chloroplast envelope quinone oxidoreductase homologue from Arabidopsis thaliana.

    PubMed

    Mas y mas, Sarah; Giustini, Cécile; Ferrer, Jean Luc; Rolland, Norbert; Curien, Gilles; Cobessi, David

    2015-04-01

    Quinone oxidoreductases reduce a broad range of quinones and are widely distributed among living organisms. The chloroplast envelope quinone oxidoreductase homologue (ceQORH) from Arabidopsis thaliana binds NADPH, lacks a classical N-terminal and cleavable chloroplast transit peptide, and is transported through the chloroplast envelope membrane by an unknown alternative pathway without cleavage of its internal chloroplast targeting sequence. To unravel the fold of this targeting sequence and its substrate specificity, ceQORH from A. thaliana was overexpressed in Escherichia coli, purified and crystallized. Crystals of apo ceQORH were obtained and a complete data set was collected at 2.34?Å resolution. The crystals belonged to space group C222?, with two molecules in the asymmetric unit. PMID:25849509

  2. Comparison of scanning electron microscopy, dynamic light scattering and analytical ultracentrifugation for the sizing of poly(butyl cyanoacrylate) nanoparticles

    Microsoft Academic Search

    Alexander Bootz; Vitali Vogel; Dieter Schubert; Jörg Kreuter

    2004-01-01

    Nanoparticles represent promising carriers for controlled drug delivery. This work focuses on the size and molecular mass characterization of polyalkylcyanoacrylate nanoparticles formed by anionic emulsion polymerization of butylcyanoacrylate in the presence of poloxamer 188 as a stabilizer. Three different methods were used to determine the size and size distribution of the particle populations: scanning electron microscopy (SEM), dynamic light scattering

  3. Aerosol gels

    NASA Technical Reports Server (NTRS)

    Sorensen, Christopher M. (Inventor); Chakrabarti, Amitabha (Inventor); Dhaubhadel, Rajan (Inventor); Gerving, Corey (Inventor)

    2010-01-01

    An improved process for the production of ultralow density, high specific surface area gel products is provided which comprises providing, in an enclosed chamber, a mixture made up of small particles of material suspended in gas; the particles are then caused to aggregate in the chamber to form ramified fractal aggregate gels. The particles should have a radius (a) of up to about 50 nm and the aerosol should have a volume fraction (f.sub.v) of at least 10.sup.-4. In preferred practice, the mixture is created by a spark-induced explosion of a precursor material (e.g., a hydrocarbon) and oxygen within the chamber. New compositions of matter are disclosed having densities below 3.0 mg/cc.

  4. AN IMPROVED AIR-DRIVEN TYPE OF ULTRACENTRIFUGE FOR MOLECULAR SEDIMENTATION

    PubMed Central

    Bauer, Johannes H.; Pickels, Edward G.

    1937-01-01

    1. A description is given of the construction details and operation characteristics of an improved type of air-driven ultracentrifuge operating in vacuum and suitable for the determination of sedimentation constants of protein molecules. 2. The rotor of the centrifuge is made of a forged aluminum alloy; it is oval in shape, measures 185 mm. at its greatest diameter, and weighs 3,430 gm. It carries a transparent cell located at a distance of 65 mm. from the axis of rotation and designed to accommodate a fluid column 15 mm. high. 3. The rotor has been run repeatedly over long periods at a speed of 60,000 R.P.M., which corresponds to a centrifugal force of 260,000 times gravity in the center of the cell. At this speed no deformation of the rotor nor leakage of the cell has been observed. 4. The sharp definition of sedimentation photographs taken at high speed serves to indicate the absence of detectable vibrations in the centrifuge. 5. When a vacuum of less than 1 micron of mercury is maintained in the centrifuge chamber, the rise in the rotor temperature amounts to only 1 or 2°C. after several hours' run at high speed. 6. There has been no evidence of convection currents interfering with normal sedimentation of protein molecules in the centrifugal field. 7. A driving air pressure of about 18 pounds per square inch is sufficient to maintain the centrifuge at a steady speed of 60,000 R.P.M. With a driving pressure of 80 pounds per square inch, it can be accelerated to this speed in less than 20 minutes, and also brought to rest in about the same length of time by the application of the braking system. 8. The adaptation of Svedberg's optical systems to this centrifuge for photographically recording the movement of sedimentation boundaries is described. PMID:19870619

  5. The statistical estimation of molecular weights from normal and difference ultracentrifuge boundaries.

    PubMed

    McCallum, M A; Spragg, S P

    1972-06-01

    1. To determine molecular weights from boundary data taken from a sedimentation velocity experiment in an ultracentrifuge, the parameter s/D must be estimated. This can be obtained by using non-linear statistical methods to fit a mathematical model [the Fujita & MacCosham (1959) equation] to the results. 2. The statistical method chosen was the simplex method of Nelder & Mead (1965), which was found to be ideal for this problem. Internal errors were calculated at the end of the search for the minimum in the residuals, but in general these errors were found to not represent the overall true error of the experiment. 3. Calculations of molecular weights of myoglobin showed that instabilities at low concentrations of protein (less than 0.8mg/ml) disturbed the calculation of s/D. If 1% (w/v) sucrose was included in the solvent, these instabilities were decreased, and extrapolating to infinite time the linear function of s versus 1/(time) gave an acceptable value for s with an error of +/-4.8%. The estimates of the molecular weights were less well-defined and the mean value was low by 8%, with an estimated error of the mean of +/-3%. The conclusion was that vibration was responsible for the instabilities without sucrose. 4. The Fujita-MacCosham equation can be extended to make it possible to estimate ratios of sedimentation and molecular weights for difference boundaries. Tests using two solutions of orosomucoid in which a 2% decrease in velocity of one boundary was achieved by adding a calculated quantity of sucrose showed that the analysis gave realistic values for the two ratios, and the error for the ratio of sedimentation coefficients was +/-10%. The error was larger for the estimated ratio of the molecular weights, but the analysis gave the expected value for the ratio. PMID:5084797

  6. Fractionation of subcellular membrane vesicles of epithelial and non-epithelial cells by OptiPrep™ density gradient ultracentrifugation.

    PubMed

    Li, Xuhang; Donowitz, Mark

    2014-01-01

    Density gradient ultracentrifugation (DGUC) is widely used for physical isolation (enrichment rather than purification) of subcellular membrane vesicles. It has been a valuable tool to study specific subcellular localization and dynamic trafficking of proteins. While sucrose has been the main component of density gradients, several years ago, synthetic OptiPrep™ (iodixanol) began being used for separation of organelles due to its iso-osmotic property. Here, we describe a detailed protocol for density gradient fractionation of various mammalian subcellular vesicles, including endoplasmic reticulum (ER), Golgi apparatus, endosomes, and lipid rafts, as well as apical and basolateral membranes of polarized epithelial cells. PMID:24947376

  7. Fractionation of subcellular membrane vesicles of epithelial and nonepithelial cells by OptiPrep density gradient ultracentrifugation.

    PubMed

    Li, Xuhang; Donowitz, Mark

    2008-01-01

    Density gradient ultracentrifugation (DGUC) is widely used for physical isolation (enrichment rather than purification) of subcellular membrane vesicles. It has been a valuable tool to study specific subcellular localization and dynamic trafficking of proteins. While sucrose has been the main component of density gradients, a few years ago synthetic OptiPrep (iodixanol) began being used for separation of organelles because of its iso-osmotic property. Here, we describe a detailed protocol for density gradient fractionation of various mammalian subcellular vesicles, including endoplasmic reticulum (ER), Golgi apparatus, endosomes, and lipid rafts, as well as apical and basolateral membranes of polarized epithelial cells. PMID:18369940

  8. Disease proteomics of high-molecular-mass proteins by two-dimensional gel electrophoresis with agarose gels in the first dimension (Agarose 2-DE).

    PubMed

    Oh-Ishi, Masamichi; Maeda, Tadakazu

    2007-04-15

    Agarose gel is the preferred electrophoretic medium currently used for separating high molecular mass (HMM) proteins (MW>100 kDa). Agarose gels are widely used for both SDS-agarose gel electrophoresis and agarose isoelectric focusing (IEF). A two-dimensional gel electrophoresis method employing agarose gels in the first dimension (agarose 2-DE) that is sufficiently good at separating up to 1.5mg of HMM proteins with molecular masses as large as 500 kDa has been used to separate proteins from various diseased tissues and cells. Although resolution of the agarose 2-DE pattern always depends on the tissue being analyzed, sample preparation procedures including (i) protein extraction with an SDS sample buffer; (ii) ultracentrifugation of a tissue homogenate; and (iii) 1% SDS in both stacking and separation gels of the second-dimension SDS-PAGE gel, are generally effective for HMM protein detection. In a comprehensive prostate cancer proteome study using agarose 2-DE, the HMM region of the gel was rich in proteins of particular gene/protein expression groups (39.1% of the HMM proteins but only 28.4% of the LMM ones were classified as transcription/translation-related proteins). Examples include transcription factors, DNA or RNA binding proteins, and ribosomal proteins. To understand oxidative stress-induced cellular damage at the protein level, a novel proteomic method, in which protein carbonyls were derivatized with biotin hydrazide followed by agarose 2-DE, was useful for detecting HMM protein carbonyls in tissues of both a diabetes model Ostuka Long-Evans Tokushima Fatty (OLETF) rat and a control Long-Evans Tokushima Otsuka (LETO) rat. In this paper, we review the use of agarose gels for separation of HMM proteins and disease proteomics of HMM proteins in general, with particular attention paid to our proteome analyzes based on the use of agarose 2-DE for protein separation followed by the use of mass spectrometry for protein identification. PMID:17141588

  9. Physical and chemical properties of gels. Application to protein nucleation control in the gel acupuncture technique

    NASA Astrophysics Data System (ADS)

    Moreno, Abel; Juárez-Martínez, Gabriela; Hernández-Pérez, Tomás; Batina, Nikola; Mundo, Manuel; McPherson, Alexander

    1999-09-01

    In this work, we present a new approach using analytical and optical techniques in order to determine the physical and chemical properties of silica gel, as well as the measurement of the pore size in the network of the gel by scanning electron microscopy. The gel acupuncture technique developed by Garc?´a-Ruiz et al. (Mater. Res. Bull 28 (1993) 541) Garc?´a-Ruiz and Moreno (Acta Crystallogr. D 50 (1994) 484) was used throughout the history of crystal growth. Several experiments were done in order to evaluate the nucleation control of model proteins (thaumatin I from Thaumatococcus daniellii, lysozyme from hen egg white and catalase from bovine liver) by the porous network of the gel. Finally, it is shown how the number and the size of the crystals obtained inside X-ray capillaries is controlled by the size of the porous structure of the gel.

  10. Unified Theory for Gel Electrophoresis and Gel Filtration

    Microsoft Academic Search

    David Rodbard; Andreas Chrambach

    1970-01-01

    Unified theory for gel electrophoresis and gel filtration: The behavior of macromolecules in gel filtration and gel electrophoresis may be predicted from Ogston's model for a random meshwork of fibers. This model has been generalized to apply to nonspherical molecules and to several gel types. The model provides equations for inter-relationships between mobility, partition coefficient, gel concentration, and molecular radius;

  11. Gel chemical transistor

    NASA Astrophysics Data System (ADS)

    Arai, Masanori; Gong, Jin; Makino, Masato; Kabir, M. Hasnat; Furukawa, Hidemitsu

    2015-04-01

    Shape Memory Gel (SMG) is one of the most interesting unique soft and wet materials. The elastic modulus of the SMG is changed by the kinds of solvent ( S-switch SMG). Here we have an idea that these properties are possibly applied to develop a novel gel-switch chemical semiconductor, named "Gel-con(ductor)". The Gel-con will be made from the combination of the different kinds of the S-switch gel membranes and is used to rectify the flux of the solvent in chemical circuits, where the solvent molecules behave as electron and hole.

  12. Sol-Gel Glasses

    NASA Technical Reports Server (NTRS)

    Mukherjee, S. P.

    1985-01-01

    Multicomponent homogeneous, ultrapure noncrystalline gels/gel derived glasses are promising batch materials for the containerless glass melting experiments in microgravity. Hence, ultrapure, homogeneous gel precursors could be used to: (1) investigate the effect of the container induced nucleation on the glass forming ability of marginally glass forming compositions; and (2) investigate the influence of gravity on the phase separation and coarsening behavior of gel derived glasses in the liquid-liquid immiscibility zone of the nonsilicate systems having a high density phase. The structure and crystallization behavior of gels in the SiO2-GeO2 as a function of gel chemistry and thermal treatment were investigated. As are the chemical principles involved in the distribution of a second network former in silica gel matrix being investigated. The procedures for synthesizing noncrystalline gels/gel-monoliths in the SiO2-GeO2, GeO2-PbO systems were developed. Preliminary investigations on the levitation and thermal treatment of germania silicate gel-monoliths in the Pressure Facility Acoustic Levitator were done.

  13. CONFORMANCE IMPROVEMENT USING GELS

    SciTech Connect

    Randall S. Seright

    2004-09-30

    This report describes work performed during the third and final year of the project, ''Conformance Improvement Using Gels.'' Corefloods revealed throughput dependencies of permeability reduction by polymers and gels that were much more prolonged during oil flow than water flow. This behavior was explained using simple mobility ratio arguments. A model was developed that quantitatively fits the results and predicts ''clean up'' times for oil productivity when production wells are returned to service after application of a polymer or gel treatment. X-ray computed microtomography studies of gels in strongly water-wet Berea sandstone and strongly oil-wet porous polyethylene suggested that oil penetration through gel-filled pores occurs by a gel-dehydration mechanism, rather than gel-ripping or gel-displacement mechanisms. In contrast, analysis of data from the University of Kansas suggests that the gel-ripping or displacement mechanisms are more important in more permeable, strongly water-wet sandpacks. These findings help to explain why aqueous gels can reduce permeability to water more than to oil under different conditions. Since cement is the most commonly used material for water shutoff, we considered when gels are preferred over cements. Our analysis and experimental results indicated that cement cannot be expected to completely fill (top to bottom) a vertical fracture of any width, except near the wellbore. For vertical fractures with apertures less than 4 mm, the cement slurry will simply not penetrate very far into the fracture. For vertical fractures with apertures greater than 4 mm, the slurry may penetrate a substantial distance into the bottom part of the fracture. However, except near the wellbore, the upper part of the fracture will remain open due to gravity segregation. We compared various approaches to plugging fractures using gels, including (1) varying polymer content, (2) varying placement (extrusion) rate, (3) using partially formed gels, (4) using combinations of high and low molecular weight (Mw) polymers, (5) using secondary crosslinking reactions, (6) injecting un-hydrated polymer particles, and (7) incorporating particulates. All of these methods showed promise in some aspects, but required performance improvements in other aspects. All materials investigated to date showed significant performance variations with fracture width. High pressure gradients and limited distance of penetration are common problems in tight fractures. Gravity segregation and low resistance to breaching are common problems in wide fractures. These will be key issues to address in future work. Although gels can exhibit disproportionate permeability reduction in fractures, the levels of permeability reduction for oil flow are too high to allow practical exploitation in most circumstances. In contrast, disproportionate permeability reduction provided by gels that form in porous rock (adjacent to the fractures) has considerable potential in fractured systems.

  14. Characterization of physical properties of tissue factor–containing microvesicles and a comparison of ultracentrifuge-based recovery procedures

    PubMed Central

    Ettelaie, Camille; Collier, Mary E. W.; Maraveyas, Anthony; Ettelaie, Rammile

    2014-01-01

    Microvesicles were isolated from the conditioned media of 3 cell lines (MDA-MB-231, AsPC-1 and A375) by ultracentrifugation at a range of relative centrifugal forces, and the tissue factor (TF) protein and activity, microvesicle number, size distribution and relative density compared. Also, by expressing TF-tGFP in cells and isolating the microvesicles, the relative density of TF-containing microvesicles was established. Nanoparticle tracking analysis (NTA) indicated that the larger-diameter microvesicles (>200 nm) were primarily sedimented at 100,000g and possessed TF-dependent thrombin and factor Xa generation potential, while in the absence of factor VII, all microvesicles possessed some thrombin generation capacity. Immuno-precipitation of TF-containing microvesicles followed by NTA also indicated the range of these microvesicles to be 200–400 nm. Analysis of the microvesicles by gradient density centrifugation showed that lower-density (<1.1 g/ml) microvesicles were mainly present in the samples recovered at 100,000g and were associated with TF antigen and activity. Analysis of these fractions by NTA confirmed that these fractions were principally composed of the larger-diameter microvesicles. Similar analysis of microvesicles from healthy or patient plasma supported those obtained from conditioned media indicating that TF activity was mainly associated with lower-density microvesicles. Furthermore, centrifugation of healthy plasma, supplemented with TF-tGFP-containing microvesicles, resulted in 67% retrieval of the fluorescent microvesicles at 100,000g, but only 26% could be recovered at 20,000g. Pre-centrifugation of conditioned media or plasma at 10,000g improved the speed and yield of recovered TF-containing microvesicles by subsequent centrifugation at either 20,000g or 100,000g. In conclusion, TF appears to be associated with low-density (1.03–1.08 g/ml), larger-diameter (200–350 nm) microvesicles. PMID:25206957

  15. CONFORMANCE IMPROVEMENT USING GELS

    SciTech Connect

    Randall S. Seright

    2004-03-01

    This technical progress report describes work performed from September 1, 2003, through February 29, 2004, for the project, ''Conformance Improvement Using Gels.'' We examined the properties of several ''partially formed'' gels that were formulated with a combination of high and low molecular weight HPAM polymers. After placement in 4-mm-wide fractures, these gels required about 25 psi/ft for brine to breach the gel (the best performance to date in fractures this wide). After this breach, stabilized residual resistance factors decreased significantly with increased flow rate. Also, residual resistance factors were up to 9 times greater for water than for oil. Nevertheless, permeability reduction factors were substantial for both water and oil flow. Gel with 2.5% chopped fiberglass effectively plugged 4-mm-wide fractures if a 0.5-mm-wide constriction was present. The ability to screen-out at a constriction appears crucial for particulate incorporation to be useful in plugging fractures. In addition to fiberglass, we examined incorporation of polypropylene fibers into gels. Once dispersed in brine or gelant, the polypropylene fibers exhibited the least gravity segregation of any particulate that we have tested to date. In fractures with widths of at least 2 mm, 24-hr-old gels (0.5% high molecular weight HPAM) with 0.5% fiber did not exhibit progressive plugging during placement and showed extrusion pressure gradients similar to those of gels without the fiber. The presence of the fiber roughly doubled the gel's resistance to first breach by brine flow. The breaching pressure gradients were not as large as for gels made with high and low molecular weight polymers (mentioned above). However, their material requirements and costs (i.e., polymer and/or particulate concentrations) were substantially lower than for those gels. A partially formed gel made with 0.5% HPAM did not enter a 0.052-mm-wide fracture when applying a pressure gradient of 65 psi/ft. This result suggests a lower limit of fracture width for entry of formed or partially formed gels (when reasonable pressure gradients are applied). In unfractured porous rock, we investigated the time dependence of oil and water permeabilities during various cycles of oil and water injection after placement of a Cr(III)-acetate-HPAM gel. Permeability to water stabilized rapidly (within 1 pore volume, PV), while permeability to oil stabilized gradually over the course of 100 PV. The behavior was surprisingly insensitive to core material (strongly water-wet Berea sandstone and strongly oil-wet porous polyethylene), core permeability (740 to 10,000 md), and applied pressure gradient (10 to 100 psi/ft).

  16. Modeling chemoresponsive polymer gels.

    PubMed

    Kuksenok, Olga; Deb, Debabrata; Dayal, Pratyush; Balazs, Anna C

    2014-01-01

    Stimuli-responsive gels are vital components in the next generation of smart devices, which can sense and dynamically respond to changes in the local environment and thereby exhibit more autonomous functionality. We describe recently developed computational methods for simulating the properties of such stimuli-responsive gels in the presence of optical, chemical, and thermal gradients. Using these models, we determine how to harness light to drive shape changes and directed motion in spirobenzopyran-containing gels. Focusing on oscillating gels undergoing the Belousov-Zhabotinksy reaction, we demonstrate that these materials can spontaneously form self-rotating assemblies, or pinwheels. Finally, we model temperature-sensitive gels that encompass chemically reactive filaments to optimize the performance of this system as a homeostatic device for regulating temperature. These studies could facilitate the development of soft robots that autonomously interconvert chemical and mechanical energy and thus perform vital functions without the continuous need of external power sources. PMID:24498954

  17. Toward sol-gel-based sensors

    SciTech Connect

    Jordan, J.D.; Ingersoll, C.M.; Dunbar, R.A. [State Univ. of New York, Buffalo, NY (United States)] [and others

    1995-12-31

    Advances in biotechnology have produced a variety of antibodies and other biomolecules that possess selective recognition capabilities. Current techniques for the immobilization of these biomolecules typically involve multistep derivatization of a primary substrate, which is labor intensive and often requires large volumes of costly reagents. Further, these immobilization chemistries often adversely affect the characteristic properties of the protein (e.g., the binding affinity). As a result, the need for fast, accurate, inexpensive, and simple to operate diagnostic assays escalates. Because of their room temperature processing, transparency, inertness, and tunable pore structure, sol-gel-derived composites represent promising chemical and biosensing platforms. To date, many researchers have entrapped proteins and enzymes in sol-gel monoliths, and found that they retain some of their native properties. Our group first reported on the affinity of a sol-gel entrapped antibody. However, although these biogel monoliths were promising, analyte diffusion through the monolith matrix is slow, resulting in long response times. Thus, it is clear that the next level of sol-gel-derived biosensor must depend on thin film technology. In the current work, the affinity of fluorescein entrapped within a sol-gel derived thin film for the anti fluorescent hapten, 5- (and 6-)-carboxy 4{prime}, 5{prime}-dimethylfluorescein, is investigated. A novel film preparation technique will be introduced, and the response and response times of these films as a function of processing and storage conditions will be discussed.

  18. DNA DAMAGE QUANTITATION BY ALKALINE GEL ELECTROPHORESIS.

    SciTech Connect

    SUTHERLAND,B.M.; BENNETT,P.V.; SUTHERLAND, J.C.

    2004-03-24

    Physical and chemical agents in the environment, those used in clinical applications, or encountered during recreational exposures to sunlight, induce damages in DNA. Understanding the biological impact of these agents requires quantitation of the levels of such damages in laboratory test systems as well as in field or clinical samples. Alkaline gel electrophoresis provides a sensitive (down to {approx} a few lesions/5Mb), rapid method of direct quantitation of a wide variety of DNA damages in nanogram quantities of non-radioactive DNAs from laboratory, field, or clinical specimens, including higher plants and animals. This method stems from velocity sedimentation studies of DNA populations, and from the simple methods of agarose gel electrophoresis. Our laboratories have developed quantitative agarose gel methods, analytical descriptions of DNA migration during electrophoresis on agarose gels (1-6), and electronic imaging for accurate determinations of DNA mass (7-9). Although all these components improve sensitivity and throughput of large numbers of samples (7,8,10), a simple version using only standard molecular biology equipment allows routine analysis of DNA damages at moderate frequencies. We present here a description of the methods, as well as a brief description of the underlying principles, required for a simplified approach to quantitation of DNA damages by alkaline gel electrophoresis.

  19. Protocol for analytical ultracentrifugation sample preparation: 1. Provide partial specific volume (v-bar) of the proteins. If v-bar is not available, send

    E-print Network

    Chan, Hue Sun

    Silver nitrate Sodium acetate Sodium bicarbonate Sodium bromide Sodium carbonate Sodium chloride Sodium Phosphoric acid Potassium bicarbonate Potassiuim biphthalate Potassium bromide Potassium carbonate Potassium citrate Sodium diatrizoate Sodium dichromate Sodium ferrocyanide Sodium hydroxide Sodium molybdate Sodium

  20. Periodic mesoporous silica gels

    SciTech Connect

    Anderson, M.T.; Martin, J.E.; Odinek, J.G. [and others

    1996-06-01

    We have synthesized monolithic particulate gels of periodic mesoporous silica by adding tetramethoxysilane to a homogeneous alkaline micellar precursor solution. The gels exhibit 5 characteristic length scales over 4 orders of magnitude: fractal domains larger than the particle size (>500 nm), particles that are {approximately}150 to 500 nm in diameter, interparticle pores that are on the order of the particle size, a feature in the gas adsorption measurements that indicates pores {approximately}10-50 nm, and periodic hexagonal arrays of {approximately}3 nm channels within each particle. The wet gel monoliths exhibit calculated densities as low as {approximately}0.02 g/cc; the dried and calcined gels have bulk densities that range from {approximately}0.3-0.5 g/cc. The materials possess large interparticle ({approximately}1.0-2.3 cc/g) and intraparticle ({approximately}0.6 cc/g) porosities.

  1. Microfluidics with Gel Emulsions

    NASA Astrophysics Data System (ADS)

    Priest, Craig; Surenjav, Enkhtuul; Herminghaus, Stephan; Seemann, Ralf

    2006-03-01

    Microfluidic processing is usually achieved using single phase liquids. Instead, we use monodisperse emulsions to compartment liquids within microchannel geometries. At low continuous phase volume fractions, droplets self-organize to form well-defined arrangements, analogous to foam. While it is well-known that confined geometries can induce rearrangement of foam compartments at the millimeter-scale, similar dynamics are also expected for gel emulsions. We have studied online generation, organization and manipulation of gel emulsions using a variety of microchannel geometries. ``Passive'' reorganization, based on fixed channel geometries, can be supplemented by ``active'' manipulation by incorporating a ferrofluid phase. A ferromagnetic phase facilitates reorganization of liquid compartments on demand using an electromagnetic trigger. Moreover, coalescence between adjacent compartments within a gel emulsion can be induced using electrical potential. Microfluidics using gel emulsions will be well-suited for combinatorial chemistry, DNA sequencing, drug screening and protein crystallizations.

  2. Crystallization from Gels

    NASA Astrophysics Data System (ADS)

    Narayana Kalkura, S.; Natarajan, Subramanian

    Among the various crystallization techniques, crystallization in gels has found wide applications in the fields of biomineralization and macromolecular crystallization in addition to crystallizing materials having nonlinear optical, ferroelectric, ferromagnetic, and other properties. Furthermore, by using this method it is possible to grow single crystals with very high perfection that are difficult to grow by other techniques. The gel method of crystallization provides an ideal technique to study crystal deposition diseases, which could lead to better understanding of their etiology. This chapter focuses on crystallization in gels of compounds that are responsible for crystal deposition diseases. The introduction is followed by a description of the various gels used, the mechanism of gelling, and the fascinating phenomenon of Liesegang ring formation, along with various gel growth techniques. The importance and scope of study on crystal deposition diseases and the need for crystal growth experiments using gel media are stressed. The various crystal deposition diseases, viz. (1) urolithiasis, (2) gout or arthritis, (3) cholelithiasis and atherosclerosis, and (4) pancreatitis and details regarding the constituents of the crystal deposits responsible for the pathological mineralization are discussed. Brief accounts of the theories of the formation of urinary stones and gallstones and the role of trace elements in urinary stone formation are also given. The crystallization in gels of (1) the urinary stone constituents, viz. calcium oxalate, calcium phosphates, uric acid, cystine, etc., (2) the constituents of the gallstones, viz. cholesterol, calcium carbonate, etc., (3) the major constituent of the pancreatic calculi, viz., calcium carbonate, and (4) cholic acid, a steroidal hormone are presented. The effect of various organic and inorganic ions, trace elements, and extracts from cereals, herbs, and fruits on the crystallization of major urinary stone and gallstone constituents are described. In addition, tables of gel-grown organic and inorganic crystals are provided.

  3. Fluorescent staining of gels.

    PubMed

    Buxbaum, Engelbert

    2012-01-01

    Certain transition metal complexes show intensive fluorescence when bound to proteins. They can be used to stain gels after electrophoresis with a sensitivity approaching that of silver staining, but in a much simpler and more reproducible procedure. Stains can be prepared easily and at a fraction of the cost of commercially available reagents.Hydrophobic dyes can be used to stain gels without fixing; they do not interfere with later blotting or electro-elution. PMID:22585519

  4. Electrically controlled polymeric gel actuators

    Microsoft Academic Search

    Douglas B. Adolf; Mohsen Shahinpoor; Daniel J. Segalman; Walter R. Witkowski

    1993-01-01

    Electrically controlled polymeric gel actuators or synthetic muscles capable of undergoing substantial expansion and contraction when subjected to changing pH environments, temperature, or solvent. The actuators employ compliant containers for the gels and their solvents. The gels employed may be cylindrical electromechanical gel fibers such as polyacrylamide fibers or a mixture of poly vinyl alcohol-polyacrylic acid arranged in a parallel

  5. Electrically controlled polymeric gel actuators

    Microsoft Academic Search

    D. B. Adolf; M. Shahinpoor; D. J. Segalman; W. R. Witkowski

    1993-01-01

    Electrically controlled polymeric gel actuators or synthetic muscles are described capable of undergoing substantial expansion and contraction when subjected to changing pH environments, temperature, or solvent. The actuators employ compliant containers for the gels and their solvents. The gels employed may be cylindrical electromechanical gel fibers such as polyacrylamide fibers or a mixture of poly vinyl alcohol-polyacrylic acid arranged in

  6. Analytical Sciences

    NSDL National Science Digital Library

    From the Japan Society for Analytical Chemistry, Analytical Sciences is a completely free journal covering topics related to "the theory and practice of analytical sciences, including fundamental and applied, inorganic and organic, wet chemical and instrumental methods." Full-text content is available beginning 1998 (Vol 14); Table of Contents begins December, 1992 (Vol 8).

  7. Gel Electrophoresis of Dyes

    NSDL National Science Digital Library

    Janice Stephens

    2011-01-01

    In this experiment related to plant biotechnology, learners discover how to prepare and load an electrophoresis gel. They will then run the gels in an electrophoresis system to separate several dyes that are of different molecular sizes and carry different charges. This technique is fundamental to many of the procedures used in biotechnology. This lesson guide includes background information for the educator, safety precautions, and questions with answers for learners. For safety reasons, adult supervision is recommended. Modifications for use with younger learners are described in a related PDF (see related resource).

  8. Rheology of Active Gels

    NASA Astrophysics Data System (ADS)

    Chen, Daniel

    2015-03-01

    Active networks drive a diverse range of critical processes ranging from motility to division in living cells, yet a full picture of their rheological capabilities in non-cellular contexts is still emerging, e.g., How does the rheological response of a network capable of remodeling under internally-generated stresses differ from that of a passive biopolymer network? In order to address this and other basic questions, we have engineered an active gel composed of microtubules, bidirectional kinesin motors, and molecular depletant that self-organizes into a highly dynamic network of active bundles. The network continually remodels itself under ATP-tunable cycles of extension, buckling, fracturing, and self-healing. Using confocal rheometry we have simultaneously characterized the network's linear and non-linear rheological responses to shear deformation along with its dynamic morphology. We find several surprising and unique material properties for these active gels; most notably, rheological cloaking, the ability of the active gel to drive large-scale fluid mixing over several orders of flow magnitude while maintaining an invariant, solid-like rheological profile and spontaneous flow under confinement, the ability to exert micro-Newton forces to drive persistent directed motion of the rheometer tool. Taken together, these results and others to be discussed highlight the rich stress-structure-dynamics relationships in this class of biologically-derived active gels.

  9. Pouring an Agarose Gel

    NSDL National Science Digital Library

    Hinkley, Craig

    This video from CUNY Kingsborough Community College shows how to pour an Agarose Gel. The video describes the process step by step and would be easy to replicate in a laboratory setting. Running time for the video is 2:13.

  10. Running an Agarose Gel

    NSDL National Science Digital Library

    Hinkley, Craig

    This video from CUNY Kingsborough Community College shows the process of running an agarose gel. The video describes the process step by step and would be easy to replicate in a laboratory setting. Running time for the video is 2:52.

  11. Swelling-induced and controlled curving in layered gel beams.

    PubMed

    Lucantonio, A; Nardinocchi, P; Pezzulla, M

    2014-11-01

    We describe swelling-driven curving in originally straight and non-homogeneous beams. We present and verify a structural model of swollen beams, based on a new point of view adopted to describe swelling-induced deformation processes in bilayered gel beams, that is based on the split of the swelling-induced deformation of the beam at equilibrium into two components, both depending on the elastic properties of the gel. The method allows us to: (i) determine beam stretching and curving, once assigned the characteristics of the solvent bath and of the non-homogeneous beam, and (ii) estimate the characteristics of non-homogeneous flat gel beams in such a way as to obtain, under free-swelling conditions, three-dimensional shapes. The study was pursued by means of analytical, semi-analytical and numerical tools; excellent agreement of the outcomes of the different techniques was found, thus confirming the strength of the method. PMID:25383031

  12. MAGIC Gel Dosimetry

    NASA Astrophysics Data System (ADS)

    Mifflin, Rachel; Shahnazi, Kambiz; Jesseph, Rick

    2008-10-01

    Proton therapy has proven a very successful tool in treating certain tumors, but a three dimensional view of this fact has not yet been clearly demonstrated. In this experiment we have used MAGIC (Methacrylic and Ascorbic Acid in Gelatin Initiated by Copper) gel to represent brain tissue and gone through normal treatment planning for an Acoustic Neuroma to show the three dimensional dose distributions associated with such a tumor.

  13. Liquid-gel partitioning using Lipidex in the determination of polychlorinated biohenyls, napthalenes, dibenzo- p-dioxins and dibenzofurans in blood plasma

    Microsoft Academic Search

    Cecilia Weistrand; Eva Jakobsson; Koidu Norén

    1995-01-01

    A method was developed for the transfer of fat, polychlorinated biphenyls (PCBs), naphthalenes (PCNs), dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) from blood plasma into the lipophilic gel Lipidex 5000. Subsequent elution of the gel separated about 70% of the fat from the analytes. Different adsorbents and activated charcoal were applied for further purification of the sample and separation of analytes. Identification

  14. Prescribed pattern transformation in swelling gel tubes by elastic instability

    E-print Network

    Howon Lee; Jiaping Zhang; Hanqing Jiang; Nicholas X. Fang

    2012-04-12

    We present a study on swelling-induced circumferential buckling of tubular shaped gels. Inhomogeneous stress develops as gel swells under mechanical constraints, which gives rise to spontaneous buckling instability without external force. Full control over the post-buckling pattern is experimentally demonstrated. A simple analytical model is developed using elastic energy to predict stability and post-buckling patterns upon swelling. Analysis reveals that height to diameter ratio is the most critical design parameter to determine buckling pattern, which agrees well with experimental and numerical results.

  15. Hydrodynamics of active permeating gels

    NASA Astrophysics Data System (ADS)

    Callan-Jones, A. C.; Jülicher, F.

    2011-09-01

    We develop a hydrodynamic theory of active permeating gels with viscoelasticity in which a polymer network is embedded in a background fluid. This situation is motivated by active processes in the cell cytoskeleton in which motor molecules generate elastic stresses in the network, which can drive permeation flows of the cytosol. Our approach differs from earlier ones by considering the elastic strain in the polymer network as a slowly relaxing dynamical variable. We first present the general ideas for the case of a passive, isotropic gel and then extend this description to a polar, active gel. We discuss two specific cases to illustrate the role of permeation in active gels: self-propulsion of a thin slab of gel relative to a substrate driven by filament polymerization and depolymerization; and non-equilibrium deswelling of a gel driven by molecular motors.

  16. Polyoxometalate-based Supramolecular Gel

    NASA Astrophysics Data System (ADS)

    He, Peilei; Xu, Biao; Liu, Huiling; He, Su; Saleem, Faisal; Wang, Xun

    2013-05-01

    Self-assemblyings of surfactant-encapsulated Wells-Dawson polyoxometalates (SEPs) nanobuilding blocks in butanone and esters yielded supramolecular gels showing thermo and photo responsive properties. The gels can be further polymerized if unsaturated esters were used and subsequently electrospinned into nanowires and non-woven mats. The as-prepared non-woven mats have a Young's modulus as high as 542.55 MPa. It is believed that this supramolecular gel is a good platform for polyoxometalates processing.

  17. Supramolecular gels: functions and uses.

    PubMed

    Sangeetha, Neralagatta M; Maitra, Uday

    2005-10-01

    In recent years there has been immense interest in studying gels derived from low molecular mass gelators (supramolecular, or simply molecular gels). The motivation for this is not only to understand the fundamental aggregate structures in the gels at different length scales, but also to explore their potential for futuristic technological applications. Gels have been made sensitive to external stimuli like light and chemical entities by incorporating a spectroscopically active or a receptor unit as part of the gelator molecule. This makes them suitable for applications such as sensing and actuating. The diversity of gel structural architectures has allowed them to be utilized as templates to prepare novel inorganic superstructures for possible applications in catalysis and separation. Gels derived from liquid crystals (anisotropy gels) that can act as dynamically functional materials have been prepared, for example, for (re-writable) information recording. Supramolecular gels can be important in controlled release applications, in oil recovery, for gelling cryogenic fuels etc. They can also serve as media for a range of applications. This tutorial review highlights some of the instructive work done by various groups to develop smart and functional gels, and covers a wide spectrum of scientific interest ranging from medicine to materials science. PMID:16172672

  18. Electrically controlled polymeric gel actuators

    DOEpatents

    Adolf, Douglas B. (Albuquerque, NM); Shahinpoor, Mohsen (Albuquerque, NM); Segalman, Daniel J. (Albuquerque, NM); Witkowski, Walter R. (Albuquerque, NM)

    1993-01-01

    Electrically controlled polymeric gel actuators or synthetic muscles capable of undergoing substantial expansion and contraction when subjected to changing pH environments, temperature, or solvent. The actuators employ compliant containers for the gels and their solvents. The gels employed may be cylindrical electromechanical gel fibers such as polyacrylamide fibers or a mixture of poly vinyl alcohol-polyacrylic acid arranged in a parallel aggregate and contained in an electrolytic solvent bath such as salt water. The invention includes smart, electrically activated devices exploiting this phenomenon. These devices are capable of being manipulated via active computer control as large displacement actuators for use in adaptive structure such as robots.

  19. Electrically controlled polymeric gel actuators

    DOEpatents

    Adolf, D.B.; Shahinpoor, M.; Segalman, D.J.; Witkowski, W.R.

    1993-10-05

    Electrically controlled polymeric gel actuators or synthetic muscles are described capable of undergoing substantial expansion and contraction when subjected to changing pH environments, temperature, or solvent. The actuators employ compliant containers for the gels and their solvents. The gels employed may be cylindrical electromechanical gel fibers such as polyacrylamide fibers or a mixture of poly vinyl alcohol-polyacrylic acid arranged in a parallel aggregate and contained in an electrolytic solvent bath such as salt water. The invention includes smart, electrically activated devices exploiting this phenomenon. These devices are capable of being manipulated via active computer control as large displacement actuators for use in adaptive structure such as robots. 11 figures.

  20. Analytical Microscopy

    SciTech Connect

    Not Available

    2006-06-01

    In the Analytical Microscopy group, within the National Center for Photovoltaic's Measurements and Characterization Division, we combine two complementary areas of analytical microscopy--electron microscopy and proximal-probe techniques--and use a variety of state-of-the-art imaging and analytical tools. We also design and build custom instrumentation and develop novel techniques that provide unique capabilities for studying materials and devices. In our work, we collaborate with you to solve materials- and device-related R&D problems. This sheet summarizes the uses and features of four major tools: transmission electron microscopy, scanning electron microscopy, the dual-beam focused-ion-beam workstation, and scanning probe microscopy.

  1. Analytical toxicology.

    PubMed

    Maurer, Hans H

    2010-01-01

    This paper reviews procedures for screening, identification and quantification of drugs, poisons and their metabolites in biosamples, and the corresponding work-up procedures. Gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry are mostly used today in analytical toxicology. Selection of the most appropriate biosample, e.g., ante/postmortem blood, urine, or tissues or alternative matrices like hair, sweat and oral fluid, nails or meconium, is discussed. The importance of quality control and possibilities and limitations of interpretation of the analytical result are also discussed. PMID:20358688

  2. Gel Permeation Chromatography: Gel Preparation and Packing Technique

    Microsoft Academic Search

    F. W. Peaker; C. R. Tweedale

    1967-01-01

    SINCE the original publication by Moore1, gel permeation chromatography has been widely recognized as a rapid means of assessing the molecular weight distributions of polymeric materials soluble in organic solvents. While the use of this technique, principally based on the reliable commercial instrument2, is well established, reference in published work to the preparation of the cross-linked polystyrene gel, and its

  3. Rheology and structure of milk protein gels

    Microsoft Academic Search

    Ton van Vliet; Catriona M. M. Lakemond; Ronald W. Visschers

    2004-01-01

    Recent studies on gel formation and rheology of milk gels are reviewed. A distinction is made between gels formed by aggregated casein, gels of ‘pure’ whey proteins and gels in which both casein and whey proteins contribute to their properties. For casein–whey protein mixtures, it has been shown that both the fraction whey protein aggregated with the casein particles and

  4. Homogeneity of gels and gel-derived glasses

    NASA Technical Reports Server (NTRS)

    Mukherjee, S. P.

    1984-01-01

    The significance and implications of gel preparation procedures in controlling the homogeneity of multicomponent oxide gels are discussed. The role of physicochemical factors such as the structure and chemical reactivities of alkoxides, the formation of double-metal alkoxides, and the nature of solvent(s) are critically analyzed in the context of homogeneity of gels during gelation. Three procedures for preparing gels in the SiO2-B2O3-Na2O system are examined in the context of cation distribution. Light scattering results for glasses in the SiO2-B2O3-Na2O system prepared by both the gel technique and the conventional technique are examined.

  5. Native agarose gel electrophoresis and electroelution: A fast and cost-effective method to separate the small and large hepatitis B capsids.

    PubMed

    Yoon, Kam Yee; Tan, Wen Siang; Tey, Beng Ti; Lee, Khai Wooi; Ho, Kok Lian

    2013-01-01

    Hepatitis B core antigen (HBcAg) expressed in Escherichia coli is able to self-assemble into large and small capsids comprising 240 (triangulation number T = 4) and 180 (triangulation number T = 3) subunits, respectively. Conventionally, sucrose density gradient ultracentrifugation and SEC have been used to separate these capsids. However, good separation of the large and small particles with these methods is never achieved. In the present study, we employed a simple, fast, and cost-effective method to separate the T = 3 and T = 4 HBcAg capsids by using native agarose gel electrophoresis followed by an electroelution method (NAGE-EE). This is a direct, fast, and economic method for isolating the large and small HBcAg particles homogenously based on the hydrodynamic radius of the spherical particles. Dynamic light scattering analysis demonstrated that the T = 3 and T = 4 HBcAg capsids prepared using the NAGE-EE method are monodisperse with polydispersity values of ?15% and ?13%, respectively. ELISA proved that the antigenicity of the capsids was not affected in the purification process. Overall, NAGE-EE produced T = 3 and T = 4 capsids with a purity above 90%, and the recovery was 34% and 50%, respectively (total recovery of HBcAg is ?84%), and the operation time is 15 and 4 times lesser than that of the sucrose density gradient ultracentrifugation and SEC, respectively. PMID:23161478

  6. Analytical Chemistry

    NSDL National Science Digital Library

    Hardy, James K.

    This site features lecture notes for first and second level courses in analytical chemistry. Topics include titrations, gravimetry, kinetics and electrochemistry (redox). Potentiometry, coulometry, voltammetry, spectroscopic and separation methods are presented as well, and are illustrated with QuickTime animations.

  7. Purification, separation and extraction of inner tubes from double-walled carbon nanotubes by tailoring density gradient ultracentrifugation using optical probes

    PubMed Central

    Rohringer, Philip; Shi, Lei; Liu, Xianjie; Yanagi, Kazuhiro; Pichler, Thomas

    2014-01-01

    We studied the effect of varying sonication and centrifugation parameters on double-walled carbon nanotubes (DWCNT) by measuring optical absorption and photoluminescence (PL) of the samples. We found that by using a low sonication intensity before applying density gradient ultracentrifugation (DGU), only inner tube species with a diameter ?0.8 nm can be identified in absorption measurements. This is in stark contrast to the result after sonicating at higher intensities, where also bigger inner tubes can be found. Furthermore, by comparing PL properties of samples centrifugated either with or without a gradient medium, we found that applying DGU greatly enhances the PL intensity, whereas centrifugation at even higher speeds but without a gradient medium results in lower intensities. This can be explained by extraction of inner tubes from their host outer tubes in a two-stage process: the different shearing forces from the sonication treatments result in some DWCNT to be opened, whereas others stay uncut. A subsequent application of DGU leads to the extraction of the inner tubes or not if the host nanotube stayed uncut or no gradient medium was used. This work shows a pathway to avoid this phenomenon to unravel the intrinsic PL from inner tubes of DWCNT. PMID:25843961

  8. ANALYTICAL CHEMISTRY: Analytes Ante Portas

    NSDL National Science Digital Library

    Norbert Hampp (University of Marburg; Institute of Physical Chemistry)

    2002-11-22

    Access to the article is free, however registration and sign-in are required. From genomics to proteomics, analytical tools for high-throughput screening are in increasing demand. In his Perspective, Hampp highlights the report by Das et al., who have developed a simple and flexible analytical tool based on synthetic membrane pores. The method is based on differential binding of the substrate and product of an enzymatic reaction to the pore and should be particularly useful for high-throughout screening in proteomics.

  9. Crystallization of steroids in gels

    NASA Astrophysics Data System (ADS)

    Kalkura, S. Narayana; Devanarayanan, S.

    1991-03-01

    The crystal growth and characterization of certain steriods, viz., cholesterol, cholesteryl acetate, ?-sitosterol, progesterone and testosterone, in a silica gel medium is discussed. The present study shows that the single test tube diffusion method can be used to grow crystals of steroids in a silica gel medium by the reduction of steroid solubility.

  10. Foam and gel decontamination techniques

    Microsoft Academic Search

    J. F. McGlynn; W. N. Rankin

    1989-01-01

    The Savannah River Site is investigating decontamination technology to improve current decontamination techniques, and thereby reduce radiation exposure to plant personnel, reduce uptake of radioactive material, and improve safety during decontamination and decommissioning activities. When decontamination chemicals are applied as foam and gels, the contact time and cleaning ability of the chemical increases. Foam and gel applicators apply foam or

  11. SYPRO Ruby Protein Gel Stain Advanced staining technology for 2-D gels and proteomics

    E-print Network

    Lebendiker, Mario

    SYPRO Ruby Protein Gel Stain Advanced staining technology for 2-D gels and proteomics ® Detection steps Broad linear quantitation range and consistent gel-to-gel staining allow for accurate protein especially for the analysis of proteins in 2-D polyacrylamide gels, SYPRO Ruby protein gel stain is ideal

  12. Living bacteria in silica gels

    NASA Astrophysics Data System (ADS)

    Nassif, Nadine; Bouvet, Odile; Noelle Rager, Marie; Roux, Cécile; Coradin, Thibaud; Livage, Jacques

    2002-09-01

    The encapsulation of enzymes within silica gels has been extensively studied during the past decade for the design of biosensors and bioreactors. Yeast spores and bacteria have also been recently immobilized within silica gels where they retain their enzymatic activity, but the problem of the long-term viability of whole cells in an inorganic matrix has never been fully addressed. It is a real challenge for the development of sol-gel processes. Generic tests have been performed to check the viability of Escherichia coli bacteria in silica gels. Surprisingly, more bacteria remain culturable in the gel than in an aqueous suspension. The metabolic activity of the bacteria towards glycolysis decreases slowly, but half of the bacteria are still viable after one month. When confined within a mineral environment, bacteria do not form colonies. The exchange of chemical signals between isolated bacteria rather than aggregates can then be studied, a point that could be very important for 'quorum sensing'.

  13. Methylthymol blue in Fricke gels

    NASA Astrophysics Data System (ADS)

    Penev, K. I.; Mequanint, K.

    2015-01-01

    The initial trial of methylthymol blue (MTB) as a chelator for ferric iron in Fricke gel dosimeters, used for three-dimensional (3D) dosimetry in cancer radiotherapy, is reported. MTB is a structural analogue of the conventionally used xylenol orange (XO); however, the absorbance spectrum of the ferric-MTB complex is shifted to higher wavelengths, which should allow for lower amount of light scattering during gel scanning. In this study, two gelatin substrates, two sources of XO and one source of MTB have been compared. The MTB- containing gels exhibited similar dose response and diffusion coefficient to the XO-containing gels at their wavelengths of maximum absorption (620 and 585 nm, respectively). In addition, the MTB gels gave an excellent dose response at 633 nm, which is an important wavelength that is already used with other 3D dosimeters.

  14. Analytical sedimentology

    SciTech Connect

    Lewis, D.W. (Univ. of Canterbury, Christchurch (New Zealand). Dept. of Geology); McConchie, D.M. (Southern Cross Univ., New South Wales (Australia). Centre for Coastal Management)

    1994-01-01

    Both a self instruction manual and a cookbook'' guide to field and laboratory analytical procedures, this book provides an essential reference for non-specialists. With a minimum of mathematics and virtually no theory, it introduces practitioners to easy, inexpensive options for sample collection and preparation, data acquisition, analytic protocols, result interpretation and verification techniques. This step-by-step guide considers the advantages and limitations of different procedures, discusses safety and troubleshooting, and explains support skills like mapping, photography and report writing. It also offers managers, off-site engineers and others using sediments data a quick course in commissioning studies and making the most of the reports. This manual will answer the growing needs of practitioners in the field, either alone or accompanied by Practical Sedimentology, which surveys the science of sedimentology and provides a basic overview of the principles behind the applications.

  15. Gel electrophoresis of linear and star-branched DNA.

    PubMed

    Lau, Henry W; Archer, Lynden A

    2011-12-01

    The electrophoretic mobility of double-stranded DNA in polyacrylamide gel is investigated using an activated hopping model for the transport of a charged object within a heterogeneous medium. The model is premised upon a representation of the DNA path through the gel matrix as a series of traps with alternating large and small cross sections. Calculations of the trap dimensions from gel data show that the path imposes varying degrees of confinement upon migrating analytes, which retard their forward motion in a size-dependent manner. An expression derived for DNA mobility is shown to provide accurate predictions for the dynamics of linear DNA (67-622 bp) in gels of multiple concentrations. For star-branched DNA, the incorporation within the model of a length scale previously proposed to account for analyte architecture [Yuan et al., Anal. Chem. 78, 6179 (2006)] leads to mobility predictions that compare well with experimental results for a wide range of DNA shapes and molecular weights. PMID:22304125

  16. Detection of nitroaromatic explosives with fluorescent molecular assemblies and ?-gels.

    PubMed

    Kartha, Kalathil K; Sandeep, Anjamkudy; Praveen, Vakayil K; Ajayaghosh, Ayyappanpillai

    2015-02-01

    Molecular assemblies and gels made up of fluorescent ?-systems through noncovalent interactions are fascinating materials with a wide range of properties and applications. Fluorescence is an extremely sensitive property, which gets perturbed upon molecular self-assembly and gelation. Further manipulation of fluorescence in such materials is possible with external stimuli, such as stress, temperature, or with different analytes. Explosives are a class of analytes that respond to certain fluorescent molecular systems; thus allowing their sensing in a required environment. In recent times, this research has become a topic of great demand, resulting in a large number of publications, due to their relevance in safety and security issues. In this account, we record some of the major developments in the field of explosive sensing with fluorescent molecular assemblies and gels. PMID:25351991

  17. Lignin Gels: SOL-GEL NANOPOROUS CARBONS & COMPOSITES

    E-print Network

    Cao, Guozhong

    synthesis of phenolic resins (a renewable source) followed by freeze drying and subsequent pyrolysis matter) + amine catalyst in an organic Processing: · gel + aging time: 7days at 80ºC · Freeze drying

  18. Hydrodynamics of Active Permeating Gels

    NASA Astrophysics Data System (ADS)

    Callan-Jones, Andrew; Jülicher, Frank

    2012-02-01

    We present a hydrodynamic theory of active viscoelastic gels in which a polymer network is embedded in a background fluid. This work is motivated by active processes in the cell cytoskeleton in which motor molecules generate elastic stresses in the network which can drive permeation flows of the cytosol. Our approach differs from earlier ones by considering the elastic strain in the polymer network as a slowly relaxing dynamical variable. We discuss a specific case that illustrates the role of permeation in active gels: the self-propulsion of a thin slab of gel relative to a substrate driven by filament polymerization and depolymerization.

  19. Adhesive, elastomeric gel impregnating composition

    DOEpatents

    Shaw, David Glenn (Tucson, AZ); Pollard, John Randolph (Tucson, AZ); Brooks, Robert Aubrey (Tijeras, NM)

    2002-01-01

    An improved capacitor roll with alternating film and foil layers is impregnated with an adhesive, elastomeric gel composition. The gel composition is a blend of a plasticizer, a polyol, a maleic anhydride that reacts with the polyol to form a polyester, and a catalyst for the reaction. The impregnant composition is introduced to the film and foil layers while still in a liquid form and then pressure is applied to aid with impregnation. The impregnant composition is cured to form the adhesive, elastomeric gel. Pressure is maintained during curing.

  20. Gel-based immunoassay for non-instrumental detection of pyrene in water samples

    Microsoft Academic Search

    Irina Yu. Goryacheva; Natalia V. Beloglazova; Sergei A. Eremin; Dmitry A. Mikhirev; Reinhard Niessner; Dietmar Knopp

    2008-01-01

    A new qualitative immunologically based tube test for non-instrumental detection of pyrene (PYR) in water samples was developed. The method combines the pre-concentration of analyte by immunoextraction and its detection by immunoassay using Sepharose 4B-immobilized IgG-fraction of a polyclonal anti-PYR antiserum (immunoaffinity gel) and 1-pyrenebutyric acid-horseradish peroxidase conjugate (PYR-BA-HRP). The immunoaffinity gel was placed in a standard 1-ml SPE column

  1. Tuning colloidal gels by shear.

    PubMed

    Koumakis, Nick; Moghimi, Esmaeel; Besseling, Rut; Poon, Wilson C K; Brady, John F; Petekidis, George

    2015-06-01

    Using a powerful combination of experiments and simulations we demonstrate how the microstructure and its time evolution are linked with mechanical properties in a frustrated, out-of-equilibrium, particle gel under shear. An intermediate volume fraction colloid-polymer gel is used as a model system, allowing quantification of the interplay between interparticle attractions and shear forces. Rheometry, confocal microscopy and Brownian dynamics reveal that high shear rates, fully breaking the structure, lead after shear cessation to more homogeneous and stronger gels, whereas preshear at low rates creates largely heterogeneous weaker gels with reduced elasticity. We find that in comparison, thermal quenching cannot produce structural inhomogeneities under shear. We argue that external shear has strong implications on routes towards metastable equilibrium, and therefore gelation scenarios. Moreover, these results have strong implications for material design and industrial applications, such as mixing, processing and transport protocols coupled to the properties of the final material. PMID:25962849

  2. Nanodosemeters based on gel scintillators.

    PubMed

    Grau Carles, A

    2006-01-01

    The feasibility of a nanodosemeter based on a liquid scintillator cocktail of four components (ethoxylated nonylphenol, pseudocumene, water and a lipophilic mixture) is studied. The dosemeter can work in distinct gel phases, for which the radioactive substance can be confined inside aqueous nanoscale structures of different size. For water volumes ranging 0-15%, it results in a gel with micelles of 4 nm radius. For water volumes ranging 30-50%, the resulting liquid-crystal gel contains nanostructures of approximately 20 nm radius. The low-energy electron emission arising from the decay of (3)H and (55)Fe is counted in a commercial liquid-scintillation counting spectrometer for both homogeneous and gel samples. The counting efficiency gap between the two phases is used to compute the average energy deposited inside the micelle. PMID:17213221

  3. Pre-Cast Gel Electrophoresis Guide

    E-print Network

    Kirschner, Marc W.

    Novex® Pre-Cast Gel Electrophoresis Guide Version B January 27, 2003 IM-1002 Novex® Pre-Cast Gel Electrophoresis Guide General information and protocols for using Novex® pre-cast gels www.invitrogen.com tech.....................................................................................................................1 Novex® Pre-Cast Gels

  4. Thermoreversible konjac glucomannan gel crosslinked by borax

    Microsoft Academic Search

    Shanjun Gao; Jinming Guo; Katsuyoshi Nishinari

    2008-01-01

    Dynamic viscoelastic measurements were carried out for novel konjac glucomannan\\/borax gels. Gel networks were formed through the crosslinking reaction between borate ions dissociated from borax and the cis-diol sites on the polysaccharide chains. At lower oscillation frequencies, the complex gels behave like a liquid, whereas at higher frequency they relax like true gel materials with a predominant elastic relaxation response.

  5. Thixotropic gel for vadose zone remediation

    DOEpatents

    Rhia, Brian D. (Augusta, GA)

    2011-03-01

    A thixotropic gel suitable for use in subsurface bioremediation is provided along with a process of using the gel. The thixotropic gel provides a non-migrating injectable substrate that can provide below ground barrier properties. In addition, the gel components provide for a favorable environment in which certain contaminants are preferentially sequestered in the gel and subsequently remediated by either indigenous or introduced microorganisms.

  6. Thixotropic gel for vadose zone remediation

    DOEpatents

    Riha, Brian D.

    2012-07-03

    A thixotropic gel suitable for use in subsurface bioremediation is provided along with a process of using the gel. The thixotropic gel provides a non-migrating injectable substrate that can provide below ground barrier properties. In addition, the gel components provide for a favorable environment in which certain contaminants are preferentially sequestered in the gel and subsequently remediated by either indigenous or introduced microorganisms.

  7. Optical Sensors for Biomolecules Using Nanoporous Sol-Gel Materials

    NASA Technical Reports Server (NTRS)

    Fang, Jonathan; Zhou, Jing C.; Lan, Esther H.; Dunn, Bruce; Gillman, Patricia L.; Smith, Scott M.

    2004-01-01

    An important consideration for space missions to Mars is the ability to detect biosignatures. Solid-state sensing elements for optical detection of biological entities are possible using sol-gel based biologically active materials. We have used these materials as optical sensing elements in a variety of bioassays, including immunoassays and enzyme assays. By immobilizing an appropriate biomolecule in the sol-gel sensing element, we have successfully detected analytes such as amino acids and hormones. In the case of the amino acid glutamate, the enzyme glutamate dehydrogenase was the immobilized molecule, whereas in the case of the hormone cortisol, an anti-cortisol antibody was immobilized in the sensing element. In this previous work with immobilized enzymes and antibodies, excellent sensitivity and specificity were demonstrated in a variety of formats including bulk materials, thin films and fibers. We believe that the sol-gel approach is an attractive platform for bioastronautics sensing applications because of the ability to detect a wide range of entities such as amino acids, fatty acids, hopanes, porphyrins, etc. The sol-gel approach produces an optically transparent 3D silica matrix that forms around the biomolecule of interest, thus stabilizing its structure and functionality while allowing for optical detection. This encapsulation process protects the biomolecule and leads to a more "rugged" sensor. The nanoporous structure of the sol-gel matrix allows diffusion of small target molecules but keeps larger, biomolecules immobilized in the pores. We are currently developing these biologically active sol-gel materials into small portable devices for on-orbit cortisol detection

  8. Gel placement in fractured systems

    SciTech Connect

    Seright, R.S. [New Mexico Petroleum Recovery Research Center, Socorro, NM (United States)

    1995-11-01

    This paper examines several factors that can have an important effect on gel placement in fractured systems, including gelant viscosity, degree of gelation, and gravity. For an effective gel treatment, the conductivity of the fracture must be reduced and a viable flow path must remain open between the wellbore and mobile oil in the reservoir. During placement, the gelant that``leaks off`` from the fracture into the rock plays an important role in determining how well a gel treatment will reduce channeling. For a given volume of gelant injected the distance of gelant leakoff is greater for a viscous gelant than for a low-viscosity gelant. In one method to minimize gelant leakoff, sufficient gelation is designed to occur before the gelant leaves the wellbore. The authors investigated this approach in numerous experiments with both fractured and unfractured cores. They studied Cr(III)/acetate/hydrolyzed polyacrylamide (HPAM), resorcinol/formaldehyde, Cr(III)/xanthan, aluminum/citrate/HPAM, and other gelants and gels with various delay times between gelant preparation and injection. Their results suggest both hope and caution concerning the injection of gels into fractured systems.

  9. Capillary fracture of soft gels

    NASA Astrophysics Data System (ADS)

    Bostwick, Joshua B.; Daniels, Karen E.

    2013-10-01

    A liquid droplet resting on a soft gel substrate can deform that substrate to the point of material failure, whereby fractures develop on the gel surface that propagate outwards from the contact line in a starburst pattern. In this paper, we characterize (i) the initiation process, in which the number of arms in the starburst is controlled by the ratio of the surface tension contrast to the gel's elastic modulus, and (ii) the propagation dynamics showing that once fractures are initiated they propagate with a universal power law L?t3/4. We develop a model for crack initiation by treating the gel as a linear elastic solid and computing the deformations within the substrate from the liquid-solid wetting forces. The elastic solution shows that both the location and the magnitude of the wetting forces are critical in providing a quantitative prediction for the number of fractures and, hence, an interpretation of the initiation of capillary fractures. This solution also reveals that the depth of the gel is an important factor in the fracture process, as it can help mitigate large surface tractions; this finding is confirmed with experiments. We then develop a model for crack propagation by considering the transport of an inviscid fluid into the fracture tip of an incompressible material and find that a simple energy-conservation argument can explain the observed material-independent power law. We compare predictions for both linear elastic and neo-Hookean solids, finding that the latter better explains the observed exponent.

  10. Copolymers For Capillary Gel Electrophoresis

    DOEpatents

    Liu, Changsheng (State College, PA); Li, Qingbo (State College, PA)

    2005-08-09

    This invention relates to an electrophoresis separation medium having a gel matrix of at least one random, linear copolymer comprising a primary comonomer and at least one secondary comonomer, wherein the comonomers are randomly distributed along the copolymer chain. The primary comonomer is an acrylamide or an acrylamide derivative that provides the primary physical, chemical, and sieving properties of the gel matrix. The at least one secondary comonomer imparts an inherent physical, chemical, or sieving property to the copolymer chain. The primary and secondary comonomers are present in a ratio sufficient to induce desired properties that optimize electrophoresis performance. The invention also relates to a method of separating a mixture of biological molecules using this gel matrix, a method of preparing the novel electrophoresis separation medium, and a capillary tube filled with the electrophoresis separation medium.

  11. Sol-gel derived sorbents

    DOEpatents

    Sigman, Michael E.; Dindal, Amy B.

    2003-11-11

    Described is a method for producing copolymerized sol-gel derived sorbent particles for the production of copolymerized sol-gel derived sorbent material. The method for producing copolymerized sol-gel derived sorbent particles comprises adding a basic solution to an aqueous metal alkoxide mixture for a pH.ltoreq.8 to hydrolyze the metal alkoxides. Then, allowing the mixture to react at room temperature for a precalculated period of time for the mixture to undergo an increased in viscosity to obtain a desired pore size and surface area. The copolymerized mixture is then added to an immiscible, nonpolar solvent that has been heated to a sufficient temperature wherein the copolymerized mixture forms a solid upon the addition. The solid is recovered from the mixture, and is ready for use in an active sampling trap or activated for use in a passive sampling trap.

  12. Tracer diffusion in colloidal gels

    E-print Network

    Sujin Babu; Jean Christophe Gimel; Taco Nicolai

    2007-05-09

    Computer simulations were done of the mean square displacement (MSD) of tracer particles in colloidal gels formed by diffusion or reaction limited aggregation of hard spheres. The diffusion coefficient was found to be determined by the volume fraction accessible to the spherical tracers ($\\phi_a$) independent of the gel structure or the tracer size. In all cases, critical slowing down was observed at $\\phi_a\\approx 0.03$ and was characterized by the same scaling laws reported earlier for tracer diffusion in a Lorentz gas. Strong heterogeneity of the MSD was observed at small $\\phi_a$ and was related to the size distribution of pores.

  13. Subcritical drying of silica gels

    Microsoft Academic Search

    Siv Hæreid; Elin Nilsen; Mari-Ann Einarsrud

    1995-01-01

    Silica aerogel is a sol-gel prepared material characterized by high porosity and large inner surface area. Aerogels can be prepared with a high transparency and low thermal conductivity, giving a material excellent for application as transparent thermal insulator. The traditional route to prepare silica aerogels is by formation of an alcogel by hydrolysis and condensation of silicon alkoxides followed by

  14. Commercial applications of block copolymer photonic gels

    E-print Network

    Lou, Sally S

    2008-01-01

    Block copolymer photonic gels are a simple and easily processed material which responds rapidly to environmental stimuli through a color change. The diblock copolymer that forms the gel self-assembles into a lamellar ...

  15. Regenerative medicine: Noodle gels for cells

    NASA Astrophysics Data System (ADS)

    Deming, Timothy J.

    2010-07-01

    Heating and cooling of peptide amphiphile suspensions converts disorganized nanofibres into liquid-crystalline nanofibre bundles that gel on addition of salts. The noodle-shaped strings of gel can entrap and align cells.

  16. Business Intelligence & Analytics

    E-print Network

    Yang, Eui-Hyeok

    with "deep analytical skills," as well as another 1.5 million "managers and analysts to analyze big data Statistics BIA 652 Multivariate Data Analytics BIA 654 Experimental Design Data Mining and Machine Learning 656 Statistical Learning & Analytics BIA 652 Multivariate Data Analytics BIA 660 Web Analytics BIA 658

  17. Electric-field-induced response of a droplet embedded in a polyelectrolyte gel

    NASA Astrophysics Data System (ADS)

    Mohammadi, Aliasghar

    2013-08-01

    The electric-field induced response of a droplet embedded in a quenched polyelectrolyte gel is calculated theoretically. The response comprises the droplet translation and the electric-field induced flow fields within the droplet. The gel is modeled as a soft, and electrically charged porous solid saturated with a salted Newtonian fluid. The droplet is considered an incompressible Newtonian fluid with no free charge. An analytical solution, using the perturbation methodology and linear superposition, is obtained for the leading-order steady response to a DC electric-field. The fluid within the droplet is driven due to hydrodynamic coupling with the electroosmotic flow. The fluid velocity within the droplet is linearly proportional to the electroosmotic flow. Moreover, the microrheological response function of a droplet within a polyelectrolyte gel is also provided, highlighting the importance of boundary conditions at the droplet-gel interface on microrheological measurements.

  18. Capillary fracture of soft gels.

    PubMed

    Bostwick, Joshua B; Daniels, Karen E

    2013-10-01

    A liquid droplet resting on a soft gel substrate can deform that substrate to the point of material failure, whereby fractures develop on the gel surface that propagate outwards from the contact line in a starburst pattern. In this paper, we characterize (i) the initiation process, in which the number of arms in the starburst is controlled by the ratio of the surface tension contrast to the gel's elastic modulus, and (ii) the propagation dynamics showing that once fractures are initiated they propagate with a universal power law L[proportional]t(3/4). We develop a model for crack initiation by treating the gel as a linear elastic solid and computing the deformations within the substrate from the liquid-solid wetting forces. The elastic solution shows that both the location and the magnitude of the wetting forces are critical in providing a quantitative prediction for the number of fractures and, hence, an interpretation of the initiation of capillary fractures. This solution also reveals that the depth of the gel is an important factor in the fracture process, as it can help mitigate large surface tractions; this finding is confirmed with experiments. We then develop a model for crack propagation by considering the transport of an inviscid fluid into the fracture tip of an incompressible material and find that a simple energy-conservation argument can explain the observed material-independent power law. We compare predictions for both linear elastic and neo-Hookean solids, finding that the latter better explains the observed exponent. PMID:24229192

  19. An Alternate Sampling and Analytical Method for 2Butanone

    Microsoft Academic Search

    CARL J. ELSKAMP; GERALD R. SCHULTZ

    1983-01-01

    2-Butanone air samples were found to be unstable after collection on widely used coconut shell charcoal. An alternate sampling and analytical method has been developed where samples are stable and recovery is high. Samples are collected on standard size silica gel tubes, desorbed with dimethylsulfoxide, and analyzed by gas chromatography with a flame ionization detector. Recovery was not affected by

  20. Diffusion coefficients of humic substances in agarose gel and in water.

    PubMed

    Lead, J R; Starchev, K; Wilkinson, K J

    2003-02-01

    Measurements of the diffusion coefficients of five different humic substances (HS) have been performed in water and in agarose hydrogels at several pH values (in the range of 3-10) and gel concentrations (in the range of 0.7-3% w/w). Fluorescence correlation spectroscopy (FCS) and classical diffusion cells were used in parallel to probe diffusion over both microscopic and mesoscopic distance scales. In general, agreement between the techniques was reasonable, which indicated that local nonhomogenities in the gel did not play an important role. Diffusion coefficients (D) in the gel were generally in the range of 0.9-2.5 x 10(-10) m2 s(-1) but were generally only 10-20% lower than in solution. At low pH values, one of the studied humic substances (a peat humic acid, PPHA) formed large aggregates that could not penetrate into the gel and therefore could not be defined by a single D value. The observed decreases of D in the gel for other HS were too large to be explained by the tortuousity and obstructive effects of the gel alone. D decreased slightly with increasing gel concentration and increased slightly with pH. Because modifications of D due to pH were similar in both the gel and the free solution, it is unlikely that complexation with the gel was greatly influenced by the pH. Rather, the main effect that appeared to decrease the diffusive flux in gels was likely small increases in the hydrodynamic radii of the humic macromolecules. An anomalous diffusion model was used to describe the FCS data in the gel. The characteristic exponent determined by fitting the autocorrelation functions with this model decreased only slightly (from 0.96 to 0.90) with increasing gel concentration providing support that HS complexation with the gel fibers was not very important. The results have important implications for our understanding of the fate and behavior of the HS and their associated pollutants and for interpreting metal speciation data obtained using gel-covered analytical sensors. PMID:12630462

  1. Protein/arabinoxylans gels: effect of mass ratio on the rheological, microstructural and diffusional characteristics.

    PubMed

    Berlanga-Reyes, Claudia M; Carvajal-Millan, Elizabeth; Hicks, Kevin B; Yadav, Madhav P; Rascón-Chu, Agustín; Lizardi-Mendoza, Jaime; Toledo-Guillén, Alma R; Islas-Rubio, Alma R

    2014-01-01

    Wheat bran arabinoxylan (WBAX) gels entrapping standard model proteins at different mass ratios were formed. The entrapment of protein affected the gel elasticity and viscosity values, which decreased from 177 to 138 Pa. The presence of protein did not modify the covalent cross-links content of the gel. The distribution of protein through the network was investigated by confocal laser scanning microscopy. In mixed gels, protein aggregates forming clusters were detected at protein/polysaccharide ratios higher than 0.25. These clusters were not homogeneously distributed, suggesting that WBAX and protein are located in two different phases. The apparent diffusion coefficient (Dm) of proteins during release from mixed gels was investigated for mass ratios of 0.06 and 0.12. For insulin, Dm increased significantly from 2.64 × 10-7 to 3.20 × 10-7 cm2/s as the mass ratio augmented from 0.06 to 0.12. No significant difference was found for Dm values of ovalbumin and bovine serum albumin released from the mixed gels. The results indicate that homogeneous protein/WBAX gels can be formed at low mass ratios, allowing the estimation of Dm by using an analytical solution of the second Fick's law. PMID:25338049

  2. Protein/Arabinoxylans Gels: Effect of Mass Ratio on the Rheological, Microstructural and Diffusional Characteristics

    PubMed Central

    Berlanga-Reyes, Claudia M.; Carvajal-Millan, Elizabeth; Hicks, Kevin B.; Yadav, Madhav P.; Rascón-Chu, Agustín; Lizardi-Mendoza, Jaime; Toledo-Guillén, Alma R.; Islas-Rubio, Alma R.

    2014-01-01

    Wheat bran arabinoxylan (WBAX) gels entrapping standard model proteins at different mass ratios were formed. The entrapment of protein affected the gel elasticity and viscosity values, which decreased from 177 to 138 Pa. The presence of protein did not modify the covalent cross-links content of the gel. The distribution of protein through the network was investigated by confocal laser scanning microscopy. In mixed gels, protein aggregates forming clusters were detected at protein/polysaccharide ratios higher than 0.25. These clusters were not homogeneously distributed, suggesting that WBAX and protein are located in two different phases. The apparent diffusion coefficient (Dm) of proteins during release from mixed gels was investigated for mass ratios of 0.06 and 0.12. For insulin, Dm increased significantly from 2.64 × 10?7 to 3.20 × 10?7 cm2/s as the mass ratio augmented from 0.06 to 0.12. No significant difference was found for Dm values of ovalbumin and bovine serum albumin released from the mixed gels. The results indicate that homogeneous protein/WBAX gels can be formed at low mass ratios, allowing the estimation of Dm by using an analytical solution of the second Fick’s law. PMID:25338049

  3. Spring-loaded polymeric gel actuators

    DOEpatents

    Shahinpoor, Mohsen (Albuquerque, NM)

    1995-01-01

    Spring-loaded electrically controllable polymeric gel actuators are disclosed. The polymeric gels can be polyvinyl alcohol, polyacrylic acid, or polyacrylamide, and are contained in an electrolytic solvent bath such as water plus acetone. The action of the gel is mechanically biased, allowing the expansive and contractile forces to be optimized for specific applications.

  4. Spring-loaded polymeric gel actuators

    DOEpatents

    Shahinpoor, M.

    1995-02-14

    Spring-loaded electrically controllable polymeric gel actuators are disclosed. The polymeric gels can be polyvinyl alcohol, polyacrylic acid, or polyacrylamide, and are contained in an electrolytic solvent bath such as water plus acetone. The action of the gel is mechanically biased, allowing the expansive and contractile forces to be optimized for specific applications. 5 figs.

  5. Advanced gel propulsion controls for kill vehicles

    Microsoft Academic Search

    W. K. Yasuhara; A. Olson; S. Finato

    1993-01-01

    A gel propulsion control concept for tactical applications is reviewed, and the status of the individual component technologies currently under development at the Aerojet Propulsion Division is discussed. It is concluded that a gel propellant Divert and Attitude Control Subsystem (DACS) provides a safe, insensitive munitions compliant alternative to current liquid Theater Missile Defense (TMD) DACS approaches. The gel kill

  6. Pro-Q Diamond Phosphoprotein Gel Stain

    E-print Network

    Lebendiker, Mario

    Pro-Q Diamond Phosphoprotein Gel Stain In-gel Detection Technology for Protein Phosphorylation and phosphoproteomics, the Pro-Q Diamond phos- phoprotein gel stain is a breakthrough technology that provides a simple phosphoproteins, the Pro-Q Diamond signal is linear over three orders of magnitude and the strength of the signal

  7. Characteristics of platelet gels combined with silk

    PubMed Central

    Pallotta, Isabella; Kluge, Jonathan A.; Moreau, Jodie; Calabrese, Rossella

    2014-01-01

    Platelet gel, a fibrin network containing activated platelets, is widely used in regenerative medicine due the capacity of platelet-derived growth factors to accelerate and direct healing processes. However, limitations to this approach include poor mechanical properties, relatively rapid degradation, and the lack of control of release of growth factors at the site of injection. These issues compromise the ability of platelet gels for sustained function in regenerative medicine. In the present study, a combination of platelet gels with silk fibroin gel was studied to address the above limitations. Mixing sonicated silk gels with platelet gels extended the release of growth factors without inhibiting gel forming ability. The released growth factors were biologically active and their delivery was modified further by manipulation of the charge of the silk protein. Moreover, the silk gel augmented both the rheological properties and compressive stiffness of the platelet gel, tuned by the silk concentration and/or silk/platelet gel ratio. Silk-platelet gel injections in nude rats supported enhanced cell infiltration and blood vessel formation representing a step towards new platelet gel formulations with enhanced therapeutic impact. PMID:24480538

  8. Food Gels: Gelling Process and New Applications

    Microsoft Academic Search

    Soumya Banerjee; Suvendu Bhattacharya

    2012-01-01

    Food gels are viscoelastic substances and several gelled products are manufactured throughout the world. The gelling agents in foods are usually polysaccharides and proteins. In food gels, the polymer molecules are not cross-linked by covalent bonds with the exception of disulphide bonds in some protein gels. Instead, the molecules are held together by a combination of weak inter-molecular forces like

  9. Food gels: Gelling process and new applications

    Microsoft Academic Search

    SOUMYA BANERJEE; SUVENDU BHATTACHARYA

    2011-01-01

    Food gels are viscoelastic substances and several gelled products are manufactured throughout the world. The gelling agents in foods are usually polysaccharides and proteins. In food gels, the polymer molecules are not cross-linked by covalent bonds with the exception of disulphide bonds in some protein gels. Instead, the molecules are held together by a combination of weak inter-molecular forces like

  10. Inertness of Bonded Silica Gel Packings

    Microsoft Academic Search

    M. Ohhira; F. Ohmura; T. Hanai

    1989-01-01

    Stability and inertness of bonded silica gel packings were examined from the retention behavior of acidic and basic compounds, and also metal sensitive compounds. Bonded silica gels made from pure silica gel were stable in acidic and basic solutions, and did not interfere with chromatography of chelate reagents in reversed-phase liquid chromatography.

  11. Evaluation of an ambient air sampling system for tritium (as tritiated water vapor) using silica gel adsorbent columns

    SciTech Connect

    Patton, G.W.; Cooper, A.T.; Tinker, M.R.

    1995-08-01

    Ambient air samples for tritium analysis (as the tritiated water vapor [HTO] content of atmospheric moisture) are collected for the Hanford Site Surface Environmental Surveillance Project (SESP) using the solid adsorbent silica gel. The silica gel has a moisture sensitive indicator which allows for visual observation of moisture movement through a column. Despite using an established method, some silica gel columns showed a complete change in the color indicator for summertime samples suggesting that breakthrough had occurred; thus a series of tests was conducted on the sampling system in an environmental chamber. The purpose of this study was to determine the maximum practical sampling volume and overall collection efficiency for water vapor collected on silica gel columns. Another purpose was to demonstrate the use of an impinger-based system to load water vapor onto silica gel columns to provide realistic analytical spikes and blanks for the Hanford Site SESP. Breakthrough volumes (V{sub b}) were measured and the chromatographic efficiency (expressed as the number of theoretical plates [N]) was calculated for a range of environmental conditions. Tests involved visual observations of the change in the silica gel`s color indicator as a moist air stream was drawn through the column, measurement of the amount of a tritium tracer retained and then recovered from the silica gel, and gravimetric analysis for silica gel columns exposed in the environmental chamber.

  12. Characterization of a sol-gel-entrapped artificial receptor

    NASA Astrophysics Data System (ADS)

    Dunbar, Richard A.; Narang, Upvan; Prasad, Paras N.; Bright, Frank V.

    1993-04-01

    We report on the development, characterization, and photophysics of a new fiber-optic-based sensor which uses a sol-gel entrapped recognition element. The recognition element is modified (beta) -cyclodextrin to which we have added a short tether (glycine) and a fluorophore (dansyl). This recognition element forms an intramolecular complex, and the dansyl group can include within the cyclodextrin cavity. Non-fluorescent analytes, that bind to the cyclodextrin cavity, can effectively displace the included dansyl group and result in a measurable change in signal. We report on the detection limits, dynamic range, and photophysics (i.e., transduction mechanism) of this new sensor.

  13. Fluctuations in strained polymer gels

    SciTech Connect

    Rabin, Y.; Pekarski, P. [Bar-Ilan Univ., Ramat-Gan (Israel); Bruinsma, R. [Univ. of California, Los Angeles, CA (United States)

    1993-12-31

    Following the recent observations of butterfly-like isointensity patterns in neutron scattering from stretched gels, swollen rubbers and mixtures of molten polymers. The authors represent a Landau-de Gennes theory of coupled strain and concentration fluctuations in such systems. This paper shows that while {open_quotes}anomalous{close_quotes} patterns with fluctuations enhanced along the deformation axis appear in systems that exhibit linear elasticity at strains or order unity. {open_quotes}Normal{close_quotes} patterns result when nonlinear effects are important. The magnitude of the asymmetry is proportional to the strength of the coupling between concentration and strain and to the concentration dependence of the elastic moduli. These effects also play an important role in understanding the swelling of polymer gels.

  14. Selective gel system for permeability profile control

    SciTech Connect

    Shu, P.

    1990-02-27

    This patent describes a process for closing pores in a more permeable zone of a formation. It comprises: placing into an aqueous solution a first composition sufficient to form ex-situ a size selective, shear thinning first gel which comprises a xanthan biopolymer, and a transitional metal ion; placing into the aqueous solution a second composition sufficient to form thermally a second in-situ gel which is substantially more resistant to formation conditions than the first gel. The composition comprises an aldehyde, and a phenolic compound; allowing the aqueous solution sufficient time to form the ex-situ gel; and injecting the aqueous solution containing the gel into the permeable zone where it reheals, is heated by the formation and thereafter forms a solid gel substantially more resistant to formation conditions than the first gel.

  15. Mechanical characterization of active polymer gels

    NASA Astrophysics Data System (ADS)

    Marra, Steven P.; Ramesh, Kaliat T.; Douglas, Andrew S.

    2000-06-01

    Ionic polymer gels shrink and swell in response to certain environmental stimuli, such as the application of an electric field or a change in the pH level of the surroundings. This ability to achieve large, reversible deformations with no external mechanical loading has generated much interest in the use of these gels as actuators and artificial muscles. This work focuses on developing a means of characterizing the mechanical properties of such ionic gels and describing how these properties evolve as the gel actuates. A thermodynamically consistent finite elastic constitutive model of an active polymer gel is developed to describe this behavior. The mechanical properties of the gel are characterized by a strain-energy function and the model utilizes an evolving internal variable to describe the actuation state. Applications of the mode to poly(vinyl alcohol)-poly (acrylic acid) gels are presented.

  16. Multiscale modeling of polyelectrolyte gels

    NASA Astrophysics Data System (ADS)

    Wallmersperger, Thomas; Wittel, Falk K.; Kröplin, Bernd H.

    2006-03-01

    Electrolyte polymer gels are a very attractive class of actuation materials with remarkable electronic and mechanical properties having a great similarity to biological contractile tissues. They consist of a polymer network with ionizable groups and a liquid phase with mobile ions. Absorption and delivery of solvent lead to a considerably large change of volume. Due to this capability, they can be used as actuators for technical applications, where large swelling and shrinkage is desired. In the present work chemically and electrically stimulated polymer gels in a solution bath are investigated. To describe the different complicated phenomena occurring in these gels adequately, the modeling can be conducted on different scales. Therefore, models based on the statistical theory and porous media theory, as well as a multi-field model and a discrete element formulation are derived. A refinement of the different theories from global macroscopic to microscopic are presented in this paper: The statistical theory is a macroscopic theory capable to describe the global swelling or bending e.g. of a gel film, while the general theory of porous media (TPM) is a macroscopic continuum theory which is based on the theory of mixtures extended by the concept of volume fractions. The TPM is a homogenized model, i.e. all geometrical and physical quantities can be seen as statistical averages of the real quantities. The presented chemo-electro-mechanical multi-field formulation is a mesoscopic theory. It is capable of giving the concentrations and the electric potential in the whole domain. Finally the (micromechanical) discrete element (DE) theory is employed. In this case, the continuum is represented by distributed particles with local interaction relations combined with balance equations for the chemical field. This method is predestined for problems involving large displacements, strains and discontinuities. The presented formulations are compared and conclusions on their applicability in engineering practice are finally drawn.

  17. "Gray Areas": Silica gels, amorphous silica and cryptocrystalline silica on fault surfaces

    NASA Astrophysics Data System (ADS)

    Rowe, C. D.; Kirkpatrick, J. D.; White, J. C.; Faber, C.; Caine, J. S.

    2012-12-01

    Silica gels, in the form of their solid-phase equivalents, are widely found in brittle fault zones and are commonly associated with mineral deposits. High- to moderate-velocity rotary friction experiments have produced silica gels on sliding surfaces coeval with dramatic slip weakening. In light of the latter, silica gel formation has been proposed as a potential mechanism of slip weakening during earthquakes in the shallow crust. However, low velocity sliding experiments have also produced significant amounts of amorphous material distributed throughout slipping layers, and dramatic weakening is not observed. Comparison of the products of laboratory experiments to geological examples is complicated by the diagenesis and lithification of silica gels. They may form hydrous and amorphous solids, hydrous crystalline solids, or dehydrate to quartz. In addition, the abundance and style of occurrence of these products in faults suggest that there are multiple origins for silica gels in faults. We review the mechanisms by which silica gels may form in fault zones and describe the solidification, crystallization and dehydration evolution of the silica. Analytical transmission electron microscope (TEM) observations of slip-surface silica deposits from the Corona Fault, San Francisco, the Dixie Valley Fault, Nevada, and the Olive Fault, Namibia typify the nano- to micro-structural evolution of the fault surface silica layers. We suggest criteria for identifying these materials in natural fault rocks. Some of these gels may form by comminution and hydrolization of silica-rich wall rocks, as has been observed in high-velocity experiments (Corona Fault). Others may form by depressurization and boiling of aqueous fluids, probably during fault valving (Olive Fault). Silica saturated hydrothermal fluids released during faulting may contribute in some cases (Dixie Valley Fault). Regardless of the mechanism of gel formation, the dramatic rheological weakening observed in friction experiments may be important if a continuous layer of gel is formed during earthquake slip.

  18. Analytical chemistry instrumentation

    SciTech Connect

    Laing, W.R.

    1986-01-01

    In nine sections, 48 chapters cover 1) analytical chemistry and the environment 2) environmental radiochemistry 3) automated instrumentation 4) advances in analytical mass spectrometry 5) fourier transform spectroscopy 6) analytical chemistry of plutonium 7) nuclear analytical chemistry 8) chemometrics and 9) nuclear fuel technology.

  19. Analytical chemistry instrumentation

    SciTech Connect

    Laing, W.R. (ed.)

    1986-01-01

    Separate abstracts were prepared for 48 papers in these conference proceedings. The topics covered include: analytical chemistry and the environment; environmental radiochemistry; automated instrumentation; advances in analytical mass spectrometry; Fourier transform spectroscopy; analytical chemistry of plutonium; nuclear analytical chemistry; chemometrics; and nuclear fuel technology. (LEW)

  20. Smart Polymeric Gels: Redefining the Limits of Biomedical Devices

    PubMed Central

    Chaterji, Somali; Kwon, Il Keun; Park, Kinam

    2007-01-01

    This review describes recent progresses in the development and applications of smart polymeric gels, especially in the context of biomedical devices. The review has been organized into three separate sections: defining the basis of smart properties in polymeric gels; describing representative stimuli to which these gels respond; and illustrating a sample application area, namely, microfluidics. One of the major limitations in the use of hydrogels in stimuli–responsive applications is the diffusion rate limited transduction of signals. This can be obviated by engineering interconnected pores in the polymer structure to form capillary networks in the matrix and by downscaling the size of hydrogels to significantly decrease diffusion paths. Reducing the lag time in the induction of smart responses can be highly useful in biomedical devices, such as sensors and actuators. This review also describes molecular imprinting techniques to fabricate hydrogels for specific molecular recognition of target analytes. Additionally, it describes the significant advances in bottom–up nanofabrication strategies, involving supramolecular chemistry. Learning to assemble supramolecular structures from nature has led to the rapid prototyping of functional supramolecular devices. In essence, the barriers in the current performance potential of biomedical devices can be lowered or removed by the rapid convergence of interdisciplinary technologies. PMID:18670584

  1. Molecular thermodynamics for swelling of a mesoscopic ionomer gel in 1 : 1 salt solutions.

    PubMed

    Victorov, A; Radke, C; Prausnitz, J

    2006-01-14

    For a microphase-separated diblock copolymer ionic gel swollen in salt solution, a molecular-thermodynamic model is based on the self-consistent field theory in the limit of strongly segregated copolymer subchains. The geometry of microdomains is described using the Milner generic wedge construction neglecting the packing frustration. A geometry-dependent generalized analytical solution for the linearized Poisson-Boltzmann equation is obtained. This generalized solution not only reduces to those known previously for planar, cylindrical and spherical geometries, but is also applicable to saddle-like structures. Thermodynamic functions are expressed analytically for gels of lamellar, bicontinuous, cylindrical and spherical morphologies. Molecules are characterized by chain composition, length, rigidity, degree of ionization, and by effective polymer-polymer and polymer-solvent interaction parameters. The model predicts equilibrium solvent uptakes and the equilibrium microdomain spacing for gels swollen in salt solutions. Results are given for details of the gel structure: distribution of mobile ions and polymer segments, and the electric potential across microdomains. Apart from effects obtained by coupling the classical Flory-Rehner theory with Donnan equilibria, viz. increased swelling with polyelectrolyte charge and shrinking of gel upon addition of salt, the model predicts the effects of microphase morphology on swelling. PMID:16482269

  2. Generative force of self-oscillating gel.

    PubMed

    Hara, Yusuke; Mayama, Hiroyuki; Morishima, Keisuke

    2014-03-01

    We succeeded in measuring the generative force of a self-oscillating polymer gel in an aqueous solution comprising the three substrates of the Belousov-Zhabotinsky (BZ) reaction (malonic acid, sodium bromate, and nitric acid) under constant temperature. In this study, we developed an apparatus with a microforce sensor for measuring the generative force of small-sized gels (1 mm(3)). The self-oscillating polymer gel directly converts the chemical energy of the BZ reaction into mechanical work. It was determined that the generative force of the self-oscillating gel was 972 Pa, and the period of self-oscillation was 480 s at 18 °C. We demonstrated that the generative force of the gel was about a hundredth the generative force of a muscle in the body. We analyzed the time dependence of the color change in the self-oscillating polymer gel. The color of the gel changed periodically owing to the cyclic change in the redox state of the Ru moiety, induced by the BZ reaction. The peaks of the waveforms of the generative force and color change were almost identical. This result showed that the generative force was synchronized with the periodical change in the oxidation number of the Ru catalytic moiety in the gel. To understand a theoretical basis for the generative force of a self-oscillating gel, we considered a general theory that is based on the volume phase transition of gel and the two-parameter Oregonator model of the BZ reaction. PMID:24524539

  3. Bacterial cellulose gels with high mechanical strength.

    PubMed

    Numata, Yukari; Sakata, Tadanori; Furukawa, Hidemitsu; Tajima, Kenji

    2015-02-01

    A composite structure was formed between polyethylene glycol diacrylate (PEGDA) and bacterial cellulose (BC) gels swollen in polyethylene glycol (PEG) as a solvent (BC/PEG gel) to improve the mechanical strength of the gels. The mechanical strength under compression and the rheostatic properties of the gels were evaluated. The compression test results indicated that the mechanical strength of the gels depended on the weight percent of cross-linked PEGDA in the gel, the chain length between the cross-linking points, and the cross-linking density of PEGDA polymers. The PEGDA polymers around the cellulose fibers were resistant to pressure; thus, the BC/PEG-PEGDA gel was stronger than the BC/PEG gel under compression. The results of transmittance measurements and thermomechanical analysis showed that the rheostatic properties of the gels were retained even after composite structure formation. BC/PEG-PEGDA gels, which are expected to be biocompatible, may be useful for clinical applications as a soft material. PMID:25492172

  4. Tailoring the properties of supramolecular gels

    NASA Astrophysics Data System (ADS)

    Buerkle, Lauren

    Supramolecular gels created from low molecular weight species (gelators) have gathered wide attention over the past few decades on account of their highly ordered assembly and ability to respond to external stimuli. These properties make such gels highly promising candidates for a diverse range of applications including biomaterials, viscosity modifiers, sensors, and liquid crystalline materials. We have focused on the design and tailoring of guanosine (the ribonucleoside of the nucleobase guanine) hydrogels. It is well known that in an aqueous environment, guanosine forms circular hydrogen-bonded quartets around a monovalent metal ion, most commonly potassium. These quartets then stack to form high-aspect ratio fibers that entangle and branch to form gels. Despite facile gel formation, crystallization of the guanosine molecules out of the gel is a common occurrence that leads to gel collapse within hours of fabrication. In addition, guanosine and related gelators often require a high potassium concentration or acidic pH to gel, which presents limited practical use in our target application of tissue engineering. We have focused on the modification and analysis of guanosine gels via an additive and/or a change in chemical structure to inhibit crystallization and promote gelation at physiological salt concentrations. Additionally, initial cell culture experiments suggest that these gel materials show great potential as an easily accessible and inexpensive tissue engineering scaffold. We also examined the potential for supramolecular gels for use in personal care formulations as electrolyte-resistant rheology modifiers for aqueous systems. Sugar-based gels fit the necessary criteria; however, many of these molecules also crystallize from the gel over time. We achieved lifetime stabilization again via a mixing approach and examined the resulting properties of the stabilized gels.

  5. The streptococcal flavoprotein NADH peroxidase: Purification, analysis of structural and redox properties, and identification of the active-site cysteinyl derivate

    Microsoft Academic Search

    Poole

    1988-01-01

    The NADH peroxidase of Streptococcus faecalis 10C1, purified to homogeneity, was studied using a variety of structural and spectroscopic techniques. The cofactor content of the enzyme was established using standard techniques, including atomic absorption analyses for the metal content. The native and subunit molecular weights of the protein were obtained through a combination of analytical ultracentrifugation, sodium dodecyl sulfate-polyacrylamide gel

  6. How do helix-helix interactions help determine the folds of membrane proteins? Perspectives from the study of homo-oligomeric helical bundles

    Microsoft Academic Search

    WILLIAM F. DEGRADO; HOLLY GRATKOWSKI; JAMES D. LEAR

    2007-01-01

    The final, structure-determining step in the folding of membrane proteins involves the coalescence of preformed transmembrane helices to form the native tertiary structure. Here, we review recent studies on small peptide and protein systems that are providing quantitative data on the interactions that drive this process. Gel electrophoresis, analytical ultracentrifugation, and fluorescence resonance energy transfer (FRET) are useful methods for

  7. Division of Analytical Sciences ANALYTICAL SCIENCES DOCTORAL REQUIREMENTS

    E-print Network

    Sheridan, Jennifer

    Division of Analytical Sciences ANALYTICAL SCIENCES DOCTORAL REQUIREMENTS The doctoral with permission of the Analytical Division faculty. I. Coursework Each Ph.D. student in Analytical Sciences from the Analytical Division Coordinator. In the written document, the student will develop

  8. ANALYTIC CELL DECOMPOSITION AND ANALYTIC MOTIVIC ...

    E-print Network

    2005-03-30

    5. 3. Rational analytic functions in one variable. 12. 4. A-analytic languages and quantifier ... 1 The author has been supported as a postdoctoral fellow by the Fund for .... |fK(x)||dx|, and one would like to understand the dependence on K in a ...

  9. Active Gel Model of Amoeboid Cell Motility

    E-print Network

    A. C. Callan-Jones; R. Voituriez

    2013-02-01

    We develop a model of amoeboid cell motility based on active gel theory. Modeling the motile apparatus of a eukaryotic cell as a confined layer of finite length of poroelastic active gel permeated by a solvent, we first show that, due to active stress and gel turnover, an initially static and homogeneous layer can undergo a contractile-type instability to a polarized moving state in which the rear is enriched in gel polymer. This agrees qualitatively with motile cells containing an actomyosin-rich uropod at their rear. We find that the gel layer settles into a steadily moving, inhomogeneous state at long times, sustained by a balance between contractility and filament turnover. In addition, our model predicts an optimal value of the gel-susbstrate adhesion leading to maximum layer speed, in agreement with cell motility assays. The model may be relevant to motility of cells translocating in complex, confining environments that can be mimicked experimentally by cell migration through microchannels.

  10. Selective gel system for permeability profile control

    SciTech Connect

    Shu, P.

    1990-10-16

    This patent describes a selective gel for closing pores in a more permeable zone of a formation. It comprises: an aqueous solution of a first composition sufficient to form ex-situ a size selective, shear thinning first gel which comprises a xanthan biopolymer, and a transitional metal ion; and an aqueous solution of a second composition sufficient to form thermally a second in-situ gel that which comprises and aldehyde, and a phenolic compound which solutions are combined and allowed to form a shearable, rehealable ex-situ gel which can be injected into the permeable zone where it reheals when heated by the formation and thereafter forms a solid gel substantially more resistant to formation conditions than the first gel.

  11. A polymer gel with electrically driven motility

    NASA Astrophysics Data System (ADS)

    Osada, Yoshihito; Okuzaki, Hidenori; Hori, Hirofumi

    1992-01-01

    A SYSTEM capable of converting chemical energy to mechanical energy could serve as an actuator or an 'artificial muscle' in several applications. Here we describe a chemomechanical system of this sort based on a synthetic polymer gel. The gel network is anionic, and positively charged surfactant molecules can therefore bind to its surface, inducing local shrinkage by decreasing the difference in osmotic pressure between the gel interior and the solution outside. By using an electric field to direct surfactant binding selectively to one side of the gel, we can induce contraction and curvature of a strip of gel. Reversing the direction of the field causes contraction of the opposite side, and when the gel is suspended in solution from a ratchet mechanism, it can thereby be made to move with a worm-like motion at a velocity of up to 25 cm min-1.

  12. Motility initiation in active gels

    E-print Network

    Recho, Pierre; Truskinovsky, Lev

    2015-01-01

    Motility initiation in crawling cells requires a symmetry breaking mechanism which transforms a symmetric state into a polarized state. Experiments on keratocytes suggest that polarization is triggered by increased contractility of motor proteins. In this paper we argue that contraction can be responsible not only for the symmetry breaking transition but also for the incipient translocation of the segment of an active gel mimicking the crawling cell. Our model suggests that when the contractility increases sufficiently far beyond the motility initiation threshold, the cell can stop and re-symmetrizes. The proposed theory reproduces the motility initiation pattern in fish keratocytes and the behavior of keratocytes prior to cell division.

  13. Population Dynamics of Chesapeake Bay Virioplankton: Total-Community Analysis by Pulsed-Field Gel Electrophoresis†

    PubMed Central

    Wommack, K. Eric; Ravel, Jacques; Hill, Russell T.; Chun, Jongsik; Colwell, Rita R.

    1999-01-01

    Recognition of viruses as the most abundant component of aquatic microbial communities has stimulated investigations of the impact of viruses on bacterio- and phytoplankton host communities. From results of field studies to date, it is concluded that in most aquatic environments, a reduction in the number of bacteria on a daily basis is caused by viral infection. However, the modest amount of in situ virus-mediated mortality may be less significant than viral infection serving to maintain clonal diversity in the host communities directly, through gene transmission (i.e., transduction), and indirectly, by elimination of numerically dominant host species. If the latter mechanism for controlling community diversity prevails, then the overall structure of aquatic viral communities would be expected to change as well over short seasonal and spatial scales. To determine whether this occurs, pulsed-field gel electrophoresis (PFGE) was used to monitor the population dynamics of Chesapeake Bay virioplankton for an annual cycle (1 year). Virioplankton in water samples collected at six stations along a transect running the length of the bay were concentrated 100-fold by ultrafiltration. Viruses were further concentrated by ultracentrifugation, and the concentrated samples were embedded in agarose. PFGE analysis of virus DNA in the agarose plugs yielded several distinct bands, ranging from 50 to 300 kb. Principal-component and cluster analyses of the virus PFGE fingerprints indicated that changes in virioplankton community structure were correlated with time, geographical location, and extent of water column stratification. From the results of this study, it is concluded that, based on the dynamic nature of the Chesapeake Bay virioplankton community structure, the clonal diversity of bacterio- and phytoplankton host communities is an important component of the virus community. PMID:9872784

  14. Spectrophotometric analysis of molecular transport in gels

    Microsoft Academic Search

    Erik N. Dunmire; Audra M. Plenys; David F. Katz

    1999-01-01

    An automated spectrophotometric method has been developed for analyzing molecular transport out from and into gels. A Beckman DU7500 diode-array UV-visible spectrophotometer with gel scanner was modified to accept and longitudinally scan a quartz diffusion cell, 0.3×10×40 mm. Molecules of interest are identified and concentrations quantitated via analysis of spectrophotometric absorbance peaks relative to background absorbance of the gel. Thus,

  15. Morphology of starch in surimi gels

    Microsoft Academic Search

    Isabel Couso; Cristina Alvarez; M. Teresa Solas; Carlos Barba; M. Tejada

    1998-01-01

    The purpose of this work was to study the changes undergone by starch during heat-induced surimi gel preparation either with\\u000a or without added egg white, and their effects on the structure of gels using light and scanning electron microscopy. Gels\\u000a were made from SA-grade Alaska pollack (Theragra chalcogramma) surimi with: (1) salt (3%, w\\/w); (2) salt and waxy corn starch

  16. Gel-Based Microchips: History and Prospects

    Microsoft Academic Search

    A. M. Kolchinsky; D. A. Gryadunov; Yu. P. Lysov; V. M. Mikhailovich; T. V. Nasedkina; A. Yu. Turygin; A. Yu. Rubina; V. E. Barsky; A. S. Zasedatelev

    2004-01-01

    The review describes the history of formation and development of the microchip technology and its role in the human genome project in Russia. The main accent was done on the three-dimensional gel-based microchips developed at the Center of Biological Microchips headed by A.D. Mirzabekov since 1988. The gel-based chips of the last generation, IMAGE chips (Immobilized Micro Array of Gel

  17. 21 CFR 866.4900 - Support gel.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents § 866.4900 Support gel. (a)...

  18. Conducting Polymer Electrodes for Gel Electrophoresis

    PubMed Central

    Bengtsson, Katarina; Nilsson, Sara; Robinson, Nathaniel D.

    2014-01-01

    In nearly all cases, electrophoresis in gels is driven via the electrolysis of water at the electrodes, where the process consumes water and produces electrochemical by-products. We have previously demonstrated that ?-conjugated polymers such as poly(3,4-ethylenedioxythiophene) (PEDOT) can be placed between traditional metal electrodes and an electrolyte to mitigate electrolysis in liquid (capillary electroosmosis/electrophoresis) systems. In this report, we extend our previous result to gel electrophoresis, and show that electrodes containing PEDOT can be used with a commercial polyacrylamide gel electrophoresis system with minimal impact to the resulting gel image or the ionic transport measured during a separation. PMID:24586761

  19. Static Inhomogeneities in Thermoreversible Physical Gels

    NASA Astrophysics Data System (ADS)

    Ikkai, Fumiyoshi; Shibayama, Mitsuhiro

    1999-06-01

    Thermoreversible gels of poly(vinyl alcohol)/Congo red in aqueous solutions have been studied by dynamic light scattering. Below Tgel \\(~ 43 °C\\), a speckle pattern appeared, while it disappeared for T>Tgel. This indicates that nonergodicity observed in chemically cross-linked gels also exists in thermoreversible physical gels. Analogous to the ? and ? relaxations of glasses, the intensity correlation function showed a power-law behavior for T<=Tgel and a stretched exponential behavior for T>=Tgel, respectively, while the thermal fluctuations characteristic of polymer gels were present independent of Tgel.

  20. Determination of diclazuril, toltrazuril and its two metabolites in poultry tissues and eggs by gel permeation chromatography–liquid chromatography–tandem mass spectrometry

    Microsoft Academic Search

    Lianfeng Ai; Hanwen Sun; Fengchi Wang; Ruichun Chen; Chunhai Guo

    2011-01-01

    A new procedure has been described for the extraction of diclazuril (DIZ), toltrazuril (TOZ) and its two main metabolites toltrazuril sulphoxide (TZSO) and toltrazuril sulphone (TZS) from poultry tissues and eggs, using gel permeation chromatography (GPC). The analytes and the deuterated internal standard were extracted from the samples with ethyl acetate. The analytes were measured by LC coupled to an

  1. Principles of Gel Permeation Chromatography

    NSDL National Science Digital Library

    Principles of Gel Permeation Chromatography presents the principles of gel permeation chromatography (GPC) for students in introductory undergraduate courses of chemistry and biochemistry. These principles are presented in four sections: Introduction, Real Lab, Virtual Lab, and Microscopic Model. The Introduction and Real Lab sections present a brief view of the basic experimental apparatus typically used in laboratory GPC in order to provide a concrete connection of the real process of separation. The basic elements of column chromatography, emphasizing the stationary and mobile phases, are presented in the Introduction, followed by a sequence of pictures and texts describing major steps in GPC analysis in the Real Lab section. The Virtual Lab section is a simulator. Three samples are available for a virtual GPC experiment: sample 1, containing hemoglobin; sample 2, containing methylene blue; and sample 3, containing both methylene blue and hemoglobin. Each sample undergoes a virtual separation run, which is dynamically represented in three ways in the software: a virtual column, the collected fractions, and a virtual chromatogram. This threefold representation allows the simultaneous view of key aspects of the process to demonstrate the correlation between the experimental procedure and the resulting chromatogram.

  2. Effect of gel structure on the gastric digestion of whey protein emulsion gels.

    PubMed

    Guo, Qing; Ye, Aiqian; Lad, Mita; Dalgleish, Douglas; Singh, Harjinder

    2014-02-28

    This study aimed to characterize and determine the disintegration of emulsion gels in a human gastric simulator (HGS) and the physicochemical characteristics of gastric digesta. Using thermal treatment at 90 °C, whey protein emulsion gels with different structures and gel strengths were formed by varying the ionic strength. Simulated boluses of soft (containing 10 mM NaCl) and hard (200 mM NaCl) gels, which had similar particle sizes to those of human subjects, were created for gastric digestion. Soft gels disintegrated faster than hard gels in the HGS. The boluses of both gels gradually disintegrated into particles of size ?10 ?m. With further digestion, the protein matrix of the soft gel particles dissolved, the proteins were disrupted mainly by proteolysis and large quantities of oil droplets were released. In contrast, for the hard gel particles, although all proteins were hydrolysed after 240 min the breakdown of the particles was slow and no oil droplets were released after 300 min. The differences in the breakdown of soft and hard gels in the HGS were attributed to the structures of the emulsion gel, which may result in different sets of peptides in the digestion. In addition, coalescence of the oil droplets was observed only for the soft gel. PMID:24652237

  3. Applications of SYPRO Orange and SYPRO Red Protein Gel Stains

    Microsoft Academic Search

    Thomas H. Steinberg; Richard P. Haugland; Victoria L. Singer

    1996-01-01

    We have further characterized the sensitivity and specificity of SYPRO Orange protein gel stain and SYPRO Red protein gel stain with native and 2-dimensional polyacrylamide gels and for staining gels prior to Western blot analysis. We found that nucleic acids are not stained by the SYPRO protein gel stains, in contrast to results obtained with commonly used silver staining techniques.

  4. Evaluation of the dosimetric performance of BANG3? polymer gel

    Microsoft Academic Search

    N D MacDougall; M E Miquel; D J Wilson; S F Keevil; M A Smith

    2005-01-01

    New radiotherapy techniques call for three-dimensional dosimetric methods with high spatial resolution. Radiation sensitive gels read out using MRI T2 mapping provide an extremely promising option, and commercially available BANG polymer gels provide a convenient route into gel dosimetry. Gel dosimetry is dependent on the ability to calibrate gel response against radiation dose. This in turn is dependent on the

  5. Evaluation of the dosimetric performance of BANG3® polymer gel

    Microsoft Academic Search

    N. D. MacDougall; M. E. Miquel; D. J. Wilson; S. F. Keevil; M. A. Smith

    2005-01-01

    New radiotherapy techniques call for three-dimensional dosimetric methods with high spatial resolution. Radiation sensitive gels read out using MRI T2 mapping provide an extremely promising option, and commercially available BANG® polymer gels provide a convenient route into gel dosimetry. Gel dosimetry is dependent on the ability to calibrate gel response against radiation dose. This in turn is dependent on the

  6. Multimedia Analysis plus Visual Analytics = Multimedia Analytics

    SciTech Connect

    Chinchor, Nancy; Thomas, James J.; Wong, Pak C.; Christel, Michael; Ribarsky, Martin W.

    2010-10-01

    Multimedia analysis has focused on images, video, and to some extent audio and has made progress in single channels excluding text. Visual analytics has focused on the user interaction with data during the analytic process plus the fundamental mathematics and has continued to treat text as did its precursor, information visualization. The general problem we address in this tutorial is the combining of multimedia analysis and visual analytics to deal with multimedia information gathered from different sources, with different goals or objectives, and containing all media types and combinations in common usage.

  7. Analytical Sciences Digital Library

    NSDL National Science Digital Library

    The Analytical Sciences Digital Library (ASDL) provides a collection of peer-reviewed web-based educational resources related to technical resources in the analytical sciences. Materials include articles, labware, educational practices, and more.

  8. CHARLOTTE: BIG DATA & ANALYTICS

    E-print Network

    Raja, Anita

    CHARLOTTE: BIG DATA & ANALYTICS #12;Charlotte: Big Data & Analytics charlottechamber.com2 ManyFab, Inc. UGL Services Weyco Group #12;charlottechamber.com Charlotte: Big Data & Analytics 3 12/13 330 S and cltecondev facebook.com/charlottechamber charlottechamber Table of Contents Charlotte: Embracing Big Data

  9. STUDY OF THE EFFECTS OF CONCENTRATION, BLOOM DEGREES AND pH ON THE GEL POINT OF GELATIN GELS

    Microsoft Academic Search

    F. A. Osorio; E. R. Bilbao; F. A. Alvarez

    Gelatin gels are applied to increase viscosity and to form aqueous gels in the food industry. Gel strength, viscosity, melting and gelling point are the most important properties which characterize a gel. These properties are affected by concentration, temperature, pH and Bloom degrees. The objective of this work was to study the effect of concentration, gel strength and pH on

  10. Contaminant containment using polymer gel barriers

    Microsoft Academic Search

    M. I. M. Darwish; R. K. Rowe; L. Pel; HP Huinink; P. L. J. Zitha

    2004-01-01

    Polymer gels are well known in the oil industry, but their potential for use as barriers to contaminant trans- port has not previously received significant study. As a first step, this paper examines the potential for a polyelectrolyte gel to serve as a barrier to the migration of sodium chloride. Two series of tests are reported. These involve the use

  11. Viscosity of Weak Whey Protein Gels

    Microsoft Academic Search

    George S. Georgiev; Veselka S. Pashava; Ventsislava T. Toncheva

    Viscosity behaviour of the membrane separated whey protein concentrates and the weak whey protein gels, produced by the chemically induced whey protein aggregation, are compared . Viscosityand the thixotropic loop width for the latter are greater than those for the former . The critical non-Newtonian protein concentration for membrane concentrates is 2 .3 times that for gels, whilst the k,

  12. Image analysis of particulate whey protein gels

    Microsoft Academic Search

    Maud Langton; Anne-Marie Hermansson

    1996-01-01

    Two different methods of image analysis have been used to characterize particulate gel networks quantitatively. The methods have been used to analyse the effect of different preparation conditions on the microstructure of whey protein gels. The microstructure has been characterized at different structural levels by light microscopy, transmission electron microscopy and scanning electron microscopy. The structural parameters have been quantified

  13. Mechanical Properties of Gel Propellants with Nanoparticles

    Microsoft Academic Search

    U. TEIPEL; U. FOERTER-BARTH

    2004-01-01

    Gel propellants provide rocket propulsion systems of high specific impulse, low sensitivity, and low vulnerability in combination with the capability to control the thrust, that is, variation of thrust and thrust cutoff. The characterization of the mechanical properties is essential for the development of gel propellant formulations and for the design of an applicable propulsion system. In this contribution the

  14. A Simple Vertical Slab Gel Electrophoresis Apparatus.

    ERIC Educational Resources Information Center

    Carter, J. B.; And Others

    1983-01-01

    Describes an inexpensive, easily constructed, and safe vertical slab gel kit used routinely for sodium dodecyl sulphate-polyacrylamide gel electrophoresis research and student experiments. Five kits are run from a single transformer. Because toxic solutions are used, students are given plastic gloves and closely supervised during laboratory…

  15. Moisture transport in silica gel particle beds

    Microsoft Academic Search

    1983-01-01

    A theoretical and experimental study of the performance of silica gel packed particle beds is described. A bench-scale test rig was used to obtain data for parameter values pertinent to solar air-conditioning applications. Both adsorption and desorption experiments were performed for Regular Density (RD) silica gel for a wide range of particle size. Adsorption data were also obtained for Intermediate

  16. Photoswitchable gel assembly based on molecular recognition

    PubMed Central

    Yamaguchi, Hiroyasu; Kobayashi, Yuichiro; Kobayashi, Ryosuke; Takashima, Yoshinori; Hashidzume, Akihito; Harada, Akira

    2012-01-01

    The formation of effective and precise linkages in bottom-up or top-down processes is important for the development of self-assembled materials. Self-assembly through molecular recognition events is a powerful tool for producing functionalized materials. Photoresponsive molecular recognition systems can permit the creation of photoregulated self-assembled macroscopic objects. Here we demonstrate that macroscopic gel assembly can be highly regulated through photoisomerization of an azobenzene moiety that interacts differently with two host molecules. A photoregulated gel assembly system is developed using polyacrylamide-based hydrogels functionalized with azobenzene (guest) or cyclodextrin (host) moieties. Reversible adhesion and dissociation of the host gel from the guest gel may be controlled by photoirradiation. The differential affinities of ?-cyclodextrin or ?-cyclodextrin for the trans-azobenzene and cis-azobenzene are employed in the construction of a photoswitchable gel assembly system. PMID:22215078

  17. Surfactant-driven fracture of gels: Initiation

    NASA Astrophysics Data System (ADS)

    Bostwick, Joshua; Schillaci, Mark; Daniels, Karen

    2012-11-01

    A droplet of surfactant spreading on a gel substrate can produce fractures on the gel surface, which originate at the contact-line and propagate outwards in a star-burst pattern. Experiments show that the number of arms is controlled by the ratio of surface tension contrast to the gel's shear modulus. To further understand the mechanism behind crack initiation, we model the gel as a linear elastic solid and compute the state of stress that develops within the substrate from the uncompensated contact-line forces. The elastic solution yields an effective metric to predict the number of fractures. We also show that the depth of the gel is critical parameter in the fracture process, as it can help mitigate large surface tractions. This observation is confirmed in experiments.

  18. Nonlinear Elasticity in Biological Gels

    E-print Network

    Cornelis Storm; Jennifer J. Pastore; Fred C. MacKintosh; Tom C. Lubensky; Paul A. Janmey

    2004-06-01

    Unlike most synthetic materials, biological materials often stiffen as they are deformed. This nonlinear elastic response, critical for the physiological function of some tissues, has been documented since at least the 19th century, but the molecular structure and the design principles responsible for it are unknown. Current models for this response require geometrically complex ordered structures unique to each material. In this Article we show that a much simpler molecular theory accounts for strain stiffening in a wide range of molecularly distinct biopolymer gels formed from purified cytoskeletal and extracellular proteins. This theory shows that systems of semi-flexible chains such as filamentous proteins arranged in an open crosslinked meshwork invariably stiffen at low strains without the need for a specific architecture or multiple elements with different intrinsic stiffnesses.

  19. Moisture Transport in Silica Gel Particle Beds: I. Theoretical Study

    SciTech Connect

    Pesaran, A. A.; Mills, A. F.

    1986-08-01

    Diffusion mechanisms of moisture within silica gel particles are investigated. It is found that for microporous silica gel surface diffusion is the dominant mechanism of moisture transport, while for macroporous silica gel both Knudsen and surface diffusion are important.

  20. Dewatering fine coal slurries by gel extraction

    SciTech Connect

    Gehrke, S.H.; Lyu, Lii-Hurng.

    1990-01-01

    A new technology called gel extraction has been evaluated to determine its economic viability in dewatering the fine and ultrafine coal slurries generated upon separation of sulfur and ash from clean coal during the physical coal cleaning process. Water must be removed from such slurries prior to transportation and combustion but the dewatering costs are substantial, especially for the fine particles below 28 mesh (0.6 mm). Gel extraction is a potential breakthrough in slurry dewatering technology. The goal of this project was to acquire the qualitative and quantitative data needed to estimate the potential of gel extraction for dewatering coal slurries. The specific objectives were to determine the maximum extents of dewatering (minimum surface moisture in the coal product), the clarity of the water removed (minimum solids content), the speed of the dewatering cycles, the service lifetime of the gels, and the factors which influence all of these. With the results obtained, an economic analysis of Ohio coal cleaning plant dewatering technologies was carried out. The polymer gel at the heart of this project, poly (N-isopropylacrylamide) (PNIPA), can swell several times its shrunken weight at 32[degrees]C by absorbing water at 25[degrees]C. In gel extraction, a shrunken NIPA gel is contacted with a slurry at ambient temperature or cooler; the gel swells by absorbing water from the slurry. The gel is then removed from the dewatered slurry and warmed above its critical temperature of 33[degrees]C, which returns it to the shrunken state by releasing the absorbed water. The facts that the gel is reusable and the process is simple and driven by low-grade energy (warm temperatures), and not inherently limited by particle size, made the process an attractive possible alternative to centrifugation, screening, filtration, etc. for slurry dewatering.

  1. Radiological properties of normoxic polymer gel dosimeters

    SciTech Connect

    Venning, A.J.; Nitschke, K.N.; Keall, P.J.; Baldock, C. [School of Physical and Chemical Sciences, Queensland University of Technology, GPO Box 2434, Brisbane, Qld 4001 (Australia); Medical Physics Section, Biomedical Engineering Services, Canberra Hospital, P.O. Box 11, Woden, ACT 2606 (Australia); Institute of Medical Physics, School of Physics, University of Sydney, Sydney, NSW 2006 (Australia); School of Physical and Chemical Sciences, Queensland University of Technology, GPO Box 2434, Brisbane, Qld 4001 (Australia); Southern Zone Radiation Oncology Service-Mater Centre, Raymond Terrace, South Brisbane, Qld 4101 (Australia); Medical Physics Division, Department of Radiation Oncology, Massey Cancer Centre, Virginia Commonwealth University, P.O. Box 980058, Richmond, VA 23298 (United States); Institute of Medical Physics, School of Physics, University of Sydney, Sydney, NSW 2006 (Australia)

    2005-04-01

    The radiological properties of the normoxic polymer gel dosimeters MAGIC, MAGAS, and MAGAT [methacrylic and ascorbic acid in gelatin initiated by copper; methacrylic acid gelatine gel with ascorbic acid; and methacrylic acid gelatine and tetrakis (hydroxymethyl) phosphonium chloride, respectively] have been investigated. The radiological water equivalence was determined by comparing the polymer gel macroscopic photon and electron interaction cross sections over the energy range from 10 keV to 20 MeV and by Monte Carlo modeling of depth doses. Normoxic polymer gel dosimeters have a high gelatine and monomer concentration and therefore mass density (kg m{sup -3}) up to 3.8% higher than water. This results in differences between the cross-section ratios of the normoxic polymer gels and water of up to 3% for the attenuation, energy absorption, and collision stopping power coefficient ratios through the Compton dominant energy range. The mass cross-section ratios were within 2% of water except for the mass attenuation and energy absorption coefficients ratios, which showed differences with water of up to 6% for energies less than 100 keV. Monte Carlo modeling was undertaken for the polymer gel dosimeters to model the electron and photon transport resulting from a 6 MV photon beam. The absolute percentage differences between gel and water were within 1% and the relative percentage differences were within 3.5%. The results show that the MAGAT gel formulation is the most radiological water equivalent of the normoxic polymer gel dosimeters investigated due to its lower mass density measurement compared with MAGAS and MAGIC gels.

  2. Some Thoughts on The Definition of a Gel

    NASA Astrophysics Data System (ADS)

    Nishinari, Katsuyoshi

    To avoid the confusion of the concept of a gel frequently encountered in daily markets of food, cosmetics, and other industrial products, the definition of a gel is revisited. Recent proposals of the definition of a gel are overviewed, and classifications of various gels from different points of view are described. Discussion is mainly focused on the gel-sol transition and the difference between the structured liquid and the gel, and the classification of gels by temperature dependence of elastic modulus. Finally, the definition of a gel is proposed as a working hypothesis from rheological and structural view points.

  3. Development and Validation of HPTLC Method for Determination of Glycyrrhizin in Herbal Extract and in Herbal Gel

    Microsoft Academic Search

    Varsha M. Jadhav; Uttam S. Kedar; Sachin B. Gholve; Vilasrao J. Kadam

    A new, simple, sensitive, selective, precise and robust high-performance thin-layer chromatographic (HPTLC) method for analysis of glycyrrhizin has been developed and validated for the determination of glycyrrhizin in herbal extracts and in herbal gel. The analyte was extracted with ethanol and applied on TLC aluminium plates along with standard using Linomat 5 spray on sample applicator (CAMAG). Analysis of glycyrrhizin

  4. New procedure of silica gel surface modification preparation of gaseous standard mixtures for calibration purposes.

    PubMed

    Switaj-Zawadka, A; Konieczka, P; Szczygelska-Tao, J; Biernat, J F; Namie?nik, J

    2004-04-01

    The new type of silica gel surface modification with using the trimethylamine as a reagent is described. The samples of chemically modified silica gel have been used for generation of gaseous standard mixtures (methyl chloride as a measurand) using the technique of thermal decomposition of the surface compound. The main aim of the research was to check the suitability of the new type of silica gel surface modification for obtaining methyl chloride as a measurand of gaseous standard mixture. The gaseous standard mixture obtained with using this technique was used for calibration of a thermal desorber-gas chromatography-flame ionization detector (TD-GC-FID) system. The homogeneity of coverage of silica gel surface with the immobilized compound has been evaluated. The full uncertainty budget of determination of liberated amount of methyl chloride has been calculated. The average amount of methyl chloride liberated from the unit sample of chemically modified silica gel is 3.59 +/- 0.13 mg g(-1). The influence of the modification way on the amount of liberated analyte has also been determined. PMID:15072299

  5. Evaluation of radiochromic gel dosimetry and polymer gel dosimetry in a clinical dose verification.

    PubMed

    Vandecasteele, Jan; De Deene, Yves

    2013-09-21

    A quantitative comparison of two full three-dimensional (3D) gel dosimetry techniques was assessed in a clinical setting: radiochromic gel dosimetry with an in-house developed optical laser CT scanner and polymer gel dosimetry with magnetic resonance imaging (MRI). To benchmark both gel dosimeters, they were exposed to a 6 MV photon beam and the depth dose was compared against a diamond detector measurement that served as golden standard. Both gel dosimeters were found accurate within 4% accuracy. In the 3D dose matrix of the radiochromic gel, hotspot dose deviations up to 8% were observed which are attributed to the fabrication procedure. The polymer gel readout was shown to be sensitive to B0 field and B1 field non-uniformities as well as temperature variations during scanning. The performance of the two gel dosimeters was also evaluated for a brain tumour IMRT treatment. Both gel measured dose distributions were compared against treatment planning system predicted dose maps which were validated independently with ion chamber measurements and portal dosimetry. In the radiochromic gel measurement, two sources of deviations could be identified. Firstly, the dose in a cluster of voxels near the edge of the phantom deviated from the planned dose. Secondly, the presence of dose hotspots in the order of 10% related to inhomogeneities in the gel limit the clinical acceptance of this dosimetry technique. Based on the results of the micelle gel dosimeter prototype presented here, chemical optimization will be subject of future work. Polymer gel dosimetry is capable of measuring the absolute dose in the whole 3D volume within 5% accuracy. A temperature stabilization technique is incorporated to increase the accuracy during short measurements, however keeping the temperature stable during long measurement times in both calibration phantoms and the volumetric phantom is more challenging. The sensitivity of MRI readout to minimal temperature fluctuations is demonstrated which proves the need for adequate compensation strategies. PMID:23965800

  6. Evaluation of radiochromic gel dosimetry and polymer gel dosimetry in a clinical dose verification

    NASA Astrophysics Data System (ADS)

    Vandecasteele, Jan; De Deene, Yves

    2013-09-01

    A quantitative comparison of two full three-dimensional (3D) gel dosimetry techniques was assessed in a clinical setting: radiochromic gel dosimetry with an in-house developed optical laser CT scanner and polymer gel dosimetry with magnetic resonance imaging (MRI). To benchmark both gel dosimeters, they were exposed to a 6 MV photon beam and the depth dose was compared against a diamond detector measurement that served as golden standard. Both gel dosimeters were found accurate within 4% accuracy. In the 3D dose matrix of the radiochromic gel, hotspot dose deviations up to 8% were observed which are attributed to the fabrication procedure. The polymer gel readout was shown to be sensitive to B0 field and B1 field non-uniformities as well as temperature variations during scanning. The performance of the two gel dosimeters was also evaluated for a brain tumour IMRT treatment. Both gel measured dose distributions were compared against treatment planning system predicted dose maps which were validated independently with ion chamber measurements and portal dosimetry. In the radiochromic gel measurement, two sources of deviations could be identified. Firstly, the dose in a cluster of voxels near the edge of the phantom deviated from the planned dose. Secondly, the presence of dose hotspots in the order of 10% related to inhomogeneities in the gel limit the clinical acceptance of this dosimetry technique. Based on the results of the micelle gel dosimeter prototype presented here, chemical optimization will be subject of future work. Polymer gel dosimetry is capable of measuring the absolute dose in the whole 3D volume within 5% accuracy. A temperature stabilization technique is incorporated to increase the accuracy during short measurements, however keeping the temperature stable during long measurement times in both calibration phantoms and the volumetric phantom is more challenging. The sensitivity of MRI readout to minimal temperature fluctuations is demonstrated which proves the need for adequate compensation strategies.

  7. Spectrophotometric analysis of molecular transport in gels.

    PubMed

    Dunmire, E N; Plenys, A M; Katz, D F

    1999-02-01

    An automated spectrophotometric method has been developed for analyzing molecular transport out from and into gels. A Beckman DU7500 diode-array UV-visible spectrophotometer with gel scanner was modified to accept and longitudinally scan a quartz diffusion cell, 0.3x10x40 mm. Molecules of interest are identified and concentrations quantitated via analysis of spectrophotometric absorbance peaks relative to background absorbance of the gel. Thus, concentration profiles are obtained as functions of both position and time. Test data are fitted to a diffusion model via nonlinear least-squares regression. Precision and accuracy of the method were assessed via analysis of several test molecules and gels: (1) 30 mg/ml nonoxynol-9 (N9), contained in 1% sodium alginate gel cross-linked with 2.5 mM calcium chloride, permeating standardized, reconstituted bovine cervical mucus (BCM); (2) 2.5 mg/ml sodium fluorescein, contained in and permeating 10 mg/ml and 100 mg/ml gelatin gels; and (3) 1.0 mg/ml sodium ganciclovir, contained in and permeating 10 mg/ml sodium hyaluronate gel. Diffusion coefficients for (1) and (3) were 3.8x10-7 and 54.1x10-7 cm2/s, respectively. All measurements of diffusion coefficients, partition coefficients, and solute loads obtained in this study were highly repeatable (most C.V.'s<8%). The mean diffusion coefficient for (2) was within 3% of values predicted from theory for the 100 mg/ml gel; the mean partition coefficient for (3) was within 2% of the expected value. This new technique is simpler than many traditional ones in that it does not require labeling of test molecules nor changes in refractive index of target materials. It is particularly well-suited to situations in which the target material is a gel, because no stirring of the target is necessary. PMID:9971891

  8. Composite sol-gel ceramics

    NASA Astrophysics Data System (ADS)

    Yang, Quanzu

    1999-11-01

    The fundamental goal of the present study was to develop an understanding of the mechanisms of dispersion, gelation, drying, interfacial bonding and densification of composite sol-gel (CSG) ceramics. The general applied objective was to fabricate high performance CSG ceramics and to produce novel, non-permeable, adherent CSG coatings on stainless steel substrates for high temperature corrosion and wear protection. The properties of the alumina sols and CSG were studied by measuring viscosity, conductivity, ionic strength, and pH of the sol. The dispersion and stability of ceramic particles in alumina sols were investigated by measuring particle size distributions, measuring zeta potentials, and calculating the interaction energy according to DLVO theory. The CSG technology has been developed to fabricate high performance engineering composite ceramics and coatings through dispersing ceramic fillers (alumina, zirconia, SiC) into alumina sols, gelcasting, drying, and pressureless sintering. A sintering model for CSG was developed and validated by experiment results. The model was then used successfully to predict sinterability and to optimize the processing technologies of CSG. The research results indicate that hydrated alumina sols can be used as a sintering and dispersion additive for alumina-based ceramics. The sol-gel matrix provides fast diffusion paths for mass transport during sintering CSG. Dispersion of alumina and SiC particles is substantially improved in alumina sols, as compared to pure water of similar acidity, e.g. the average agglomerate size is decreased by at least 50%. For alumina/alumina CSG ceramics sintered at 1400°C, the microhardness is 20 GPa and porosity is less than 1 vol%. The CSG composite with composition of 50vol%SiC-50vol%Al2O 3 has been sintered successfully to full densification and microhardness of 22.9 GPa. A novel process for ceramic coatings on the metallic substrates has been developed successfully by combining chemical bonding and CSG technologies. Non-permeable, crack-free, thick ceramic coatings (2--600 mum) on the substrates were fabricated by spraying and dipping, followed by low temperature (500--600°C) sintering. The correlations between the processing methods, microstructure, and mechanical properties of CSG coatings were investigated by varying the preparation methods, studying morphology, and measuring mechanical properties of the ceramics. The chemically bonded CSG coatings have the best performance. The bonding strength between the substrates and coatings is about 42 MPa, and the surface microhardness of the coatings is about 6.5 GPa.

  9. Electromechanical coupling in polyelectrolyte gels

    NASA Astrophysics Data System (ADS)

    Prudnikova, Katsiaryna I.

    This work concerns the systematic characterization of the electromechanical coupling in polyelectrolyte gels (PGs) in correlation with their structure and physical properties in view of their potential application as pressure sensors. PGs are electroactive polymers that respond with an electrical potential difference to gradients in mechanical stress and vice versa. So far, these materials have mainly been studied as electrical actuators, but they can also be used as mechanical sensors. Polyelectrolyte gels are biocompatible, and could form the basis for incorporating tactile sensitivity into artificial skin systems. However, how PGs respond to mechanical stimuli in relation to their structure and electrochemical properties has not been studied systematically in a quantitative manner. In this work, the physical-electrochemical properties of copolymers of acrylamide and acrylic acid of varying compositions were characterized in terms of their equilibrium swelling degree, elastic modulus and Donnan potential. Experimental results were tested against the theory of large deformation and electrochemistry of PGs recently developed by Hong et al. Systematic characterization of the electromechanical coupling in PGs was carried out using a new quantitative test based on the indentation of a flat polymer sample with a spherical indenter, while the potential was monitored with an array of planar electrodes. The experimental results suggest that electromechanical coupling in soft PGs directly subjected to a pressure gradient can be understood as a pressure modulation of the Donnan potential. The idea of the potential application of PGs as pressure transducers was illustrated by showing the prototype of the PG spatially resolved sensor capable of distinguishing between sharp and blunt loads and the prototype of the PG pressure sensor in a microfluidic chip. Spatial resolution of both prototypes was solely given by the resolution of the patterned electrodes. The design framework of the potential application of PGs as sensing layers was discussed with a view to the limitations imposed by the increased electrical impedance and reduced signal-to-noise ratio of the voltage measurements on small-length scales. These limitations were experimentally verified by quantifying the electromechanical response with an array of planar electrodes of systematically varying size.

  10. Western Blot Protocol 1. Cast Gel

    E-print Network

    Ye, Jianping

    resolution gel (recipe) and mix Make stacking gel (recipe) à diwater--acrylamide/bis Add 7.5ml of res gel 200ul 100ul 40% Acrylamide/Bis 12.5ml 5.1ml 2.5ml TEMED 50ul 20ul 10ul 10% APS(Fresh) 250ulml 2.5ml 1.25ml 10% SDS 200ul 100ul 50ul 40% Acrylamide/Bis 1.95ml 1000ul 600ul TEMED 40

  11. Frictional properties of gel engineering materials with laser surface texturing

    NASA Astrophysics Data System (ADS)

    Yamada, Naoya; Gong, Jin; Kabir, M. Hasnat; Makino, Masato; Maekawa, Keisuke; Wada, Masato; Furukawa, Hidemitsu

    2014-03-01

    Several synthesis methods have been devised to improve the mechanical strength of gels extraordinarily after 2001. It was a trigger to use gels as a new industrial materials, since gels had been considered difficult for industrial materials because of their weakness. In a recent study, we had designed transparency shape memory gels for the first time. Shape memory gels are one of the gels with characteristic networks, and have a shape memory function by copolymerizing an acrylic monomer with a hydrophobic long alkyl side group. It is well known that the mechanical properties such as Young's modulus and friction coefficient of shape memory gels depend on temperature. In this study, we tried to change the frictional properties of shape memory gels by laser surface texturing. Two types of processed surface were prepared. The hexagonal close packed pattern and the square close packed pattern of dimples were formed on the surface of gel sheets with CO2 laser. The intensity of laser was optimized to avoid cutting gels. The friction coefficients of unprocessed gels and two types of processed gels were measured by ball-on-disk method. Measurement partner material was sodalime glass ball. The measurement results of processed gels showed clear differences from unprocessed gels. The friction coefficients of processed gels were larger than unprocessed gels. However, these results specifically showed the velocity dependence. It indicates that surface texturing enable to control the friction coefficient of polymer gels by surface pattern and velocity.

  12. Science Update: Analytical Chemistry.

    ERIC Educational Resources Information Center

    Worthy, Ward

    1980-01-01

    Briefly discusses new instrumentation in the field of analytical chemistry. Advances in liquid chromatography, photoacoustic spectroscopy, the use of lasers, and mass spectrometry are also discussed. (CS)

  13. Procedure to prepare transparent silica gels

    NASA Technical Reports Server (NTRS)

    Barber, Patrick G. (inventor); Simpson, Norman R. (inventor)

    1987-01-01

    This invention relates to the production of silica gels and in particular to a process for the preparation of silica gels which can be used as a crystal growth medium that simulates the convectionless environment of space to produce structurally perfect crystals. Modern utilizations of substances in electronics, such as radio transmitters and high frequency microphones, often require single crystals with controlled purity and structural perfection. The near convectionless environment of silica gel suppresses nucleation, thereby reducing the competitive nature of crystal growth. This competition limits the size and perfection of the crystal; and it is obviously desirable to suppress nucleation until, ideally, only one crystal grows in a predetermined location. A silica gel is not a completely convectionless environment like outer space, but is the closest known environment to that of outer space that can be created on Earth.

  14. Sol-gel deposited electrochromic coatings

    SciTech Connect

    Ozer, N.; Lampert, C.M.

    1995-06-01

    Electrochromic devices have increasing application in display devices, switchable mirrors and smart windows. A variety of vacuum deposition technologies have been used to make electrochromic devices. The sol- gel process offers an alternative approach to the synthesis of optical quality and low cost electrochromic device layers. This study summarizes the developments in sol-gel deposited electrochromic films. The sol-gel process involves the formation of oxide networks upon hydrolysis-condensation of alkoxide precursors. In this study we cover the sol-gel deposited oxides of WO[sub 3], V[sub 2]O[sub 5], TiO[sub 2], Nb[sub 2]O[sub 5], and NiO[sub x].

  15. Sol-gel antireflective coating on plastics

    DOEpatents

    Ashley, Carol S. (Albuquerque, NM); Reed, Scott T. (Albuquerque, NM)

    1990-01-01

    An antireflection film made from a reliquified sol-gel hydrolyzation, condensation polymeric reaction product of a silicon, alkoxides and/or metal alkoxides, or mixtures thereof. The film is particularly useful for coating plastics.

  16. Turbidimetric studies of Limulus coagulin gel formation.

    PubMed Central

    Moody, T P; Donovan, M A; Laue, T M

    1996-01-01

    The turbidity during trypsin-induced coagulin gel formation was studied over a range of wavelengths. The range of wavelengths used (686-326 nm) also made it possible to investigate the dependence of turbidity on wavelength (the wavelength exponent). Using the results from that work, and structural information on coagulin and the coagulin gel from other studies, a model gel-forming system was designed that consists of species for which the turbidity can be calculated relatively simply. These species include small particles (small in all dimensions relative to the wavelength of incident light); long rods and long random coils (particles that are large in just one dimension relative to the wavelength of incident light); and reflective regions (aggregated material that is large in more than one dimension relative to the wavelength of incident light). The turbidimetric characteristics of the real coagulin gel-forming system are compared with those of the model system. PMID:8889175

  17. Sample collection system for gel electrophoresis

    DOEpatents

    Olivares, Jose A.; Stark, Peter C.; Dunbar, John M.; Hill, Karen K.; Kuske, Cheryl R.; Roybal, Gustavo

    2004-09-21

    An automatic sample collection system for use with an electrophoretic slab gel system is presented. The collection system can be used with a slab gel have one or more lanes. A detector is used to detect particle bands on the slab gel within a detection zone. Such detectors may use a laser to excite fluorescently labeled particles. The fluorescent light emitted from the excited particles is transmitted to low-level light detection electronics. Upon the detection of a particle of interest within the detection zone, a syringe pump is activated, sending a stream of buffer solution across the lane of the slab gel. The buffer solution collects the sample of interest and carries it through a collection port into a sample collection vial.

  18. 21 CFR 866.4900 - Support gel.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents § 866.4900 Support gel. (a) Identification....

  19. Formation of Anisotropic Block Copolymer Gels

    NASA Astrophysics Data System (ADS)

    Liaw, Chya Yan; Shull, Kenneth; Henderson, Kevin; Joester, Derk

    2011-03-01

    Anisotropic, fibrillar gels are important in a variety of processes. Biomineralization is one example, where the mineralization process often occurs within a matrix of collagen or chitin fibers that trap the mineral precursors and direct the mineralization process. We wish to replicate this type of behavior within block copolymer gels. Particularly, we are interested in employing gels composed of cylindrical micelles, which are anisotropic and closely mimic biological fibers. Micelle geometry is controlled in our system by manipulating the ratio of molecular weights of the two blocks and by controlling the detailed thermal processing history of the copolymer solutions. Small-Angle X-ray Scattering and Dynamic Light Scattering are used to determine the temperature dependence of the gel formation process. Initial experiments are based on a thermally-reversible alcohol-soluble system, that can be subsequently converted to a water soluble system by hydrolysis of a poly(t-butyl methacrylate) block to a poly (methacrylic acid) block. MRSEC.

  20. Sol-gel antireflective coating on plastics

    DOEpatents

    Ashley, C.S.; Reed, S.T.

    1988-01-26

    An antireflection film made from reliquified sol-gel hydrolyzation, condensation polymeric reaction product of a silicon, alkoxides and/or metal alkoxides, or mixtures thereof. The film is particularly useful for coating plastics.

  1. [Formulation of benzethonium chloride into gels].

    PubMed

    Cižmárik, Jozef; Vitková, Zuzana; Herdová, Petra; Kodadová, Alexandra; Vími, Daniel

    2014-06-01

    This study is focused on the preparation of gels with antimicrobial effects. A quaternary ammonium salt, benzethonium chloride, in a concentration of 0.01-0.5% (w/w) was employed as the drug. The humectant employed was propylene glycol in concentrations of 5% and 10% (w/w). Two types of polymers, chitosan and hydroxyethyl cellulose, in the same concentrations of 2.5% (w/w), were used for gel preparation. Finally the flow properties, rheological parameters and pH values of the gels were evaluated. Based on the obtained results, the samples of the gels prepared on the basis of chitosan and hydroxyethyl cellulose, which have the following optimum composition shown below, were found: 2,5% (w/w) CHIT + 0,5% (w/w) BZCl + 10% (w/w) PG; 2,5% (w/w) HEC + 0,5% (w/w) BZCl + 5% (w/w) PG. PMID:25115665

  2. Sol-gel-based poliovirus-1 detector.

    PubMed

    Zolkov, Chen; Avnir, David; Armon, Robert

    2009-02-01

    Hybrid sol-gel films were used to grow Buffalo Green Monkey kidney cell tissues, which were used for poliovirus-1 detection. It is shown that the sol-gel approach allows cutting the standard EPA procedure from 48 to 24h of detection time; that better visualization of the plaques is obtained; that a variety of stains, including fluorescence, can be used; and that the shelf life of the resulting plaques system is well over a year. PMID:18996413

  3. Gel displays based on the transparent to cloudy transition in polymer gels

    NASA Astrophysics Data System (ADS)

    Zheng, Yindong; Wang, Changjie; Hu, Zhibing

    1998-10-01

    Gel displays based on transparent to cloudy transition in polymer gels have been synthesized. The central idea is to precisely control the local properties of the one gel surface by incorporating different materials onto the given areas selected with a mask. Specifically, a N-isopropylacylamide gel has been deposited on the surface of an acrylamide gel. The acrylamide gel has no transparent to cloudy transition in the range from room temperature to 50 ^0C, while the NIPA gel has such a transition at 34 ^0C. As a result, the pattern of the NIPA deposited area can be either visible or invisible by simply switching temperature above or below the low critical solution temperature (LCST) of the NIPA gel. Preliminary results of electric-current-controlled transparent to cloudy transition in the NIPA gel will be also presented. set of curly braces; then put the associated URL in the set. The command may go anywhere in the abstract. the text in the first curly braces will show the printed version.

  4. Viscoelastic Properties of Carbopol 940 Gels and Their Relationships to Piroxicam Diffusion Coefficients in Gel Bases

    Microsoft Academic Search

    Rathapon A-sasutjarit; Anuvat Sirivat; Panida Vayumhasuwan

    2005-01-01

    \\u000a Purpose  This study was conducted to determine the effect of formula compositions on viscoelastic properties of piroxicam gels using\\u000a Carbopol 940 as a gelling agent and to determine the relationships between viscoelastic properties of Carbopol 940 gel bases\\u000a and diffusion coefficients of piroxicam in gel bases.\\u000a \\u000a \\u000a \\u000a Methods  Piroxicam gels (1.0% w\\/w) were prepared by using Carbopol 940 as a gelling agent and

  5. Signals: Applying Academic Analytics

    ERIC Educational Resources Information Center

    Arnold, Kimberly E.

    2010-01-01

    Academic analytics helps address the public's desire for institutional accountability with regard to student success, given the widespread concern over the cost of higher education and the difficult economic and budgetary conditions prevailing worldwide. Purdue University's Signals project applies the principles of analytics widely used in…

  6. Extreme Scale Visual Analytics

    SciTech Connect

    Wong, Pak C.; Shen, Han-Wei; Pascucci, Valerio

    2012-05-08

    Extreme-scale visual analytics (VA) is about applying VA to extreme-scale data. The articles in this special issue examine advances related to extreme-scale VA problems, their analytical and computational challenges, and their real-world applications.

  7. ?-function for analytic curves

    Microsoft Academic Search

    I. K. Kostov; I. Krichever; M. Mineev-Weinstein; P. B. Wiegmann; A. Zabrodin

    We review the concept of ?-function for simple analytic curves. The ?-function gives a formal solution to the 2D inverse potential problem and appears as the ?-function of the integrable hierarchy which describes conformal maps of simply- connected domains bounded by analytic curves to the unit disk. The ?-function also emerges in the context of topological gravity and enjoys an

  8. Learning Analytics Considered Harmful

    ERIC Educational Resources Information Center

    Dringus, Laurie P.

    2012-01-01

    This essay is written to present a prospective stance on how learning analytics, as a core evaluative approach, must help instructors uncover the important trends and evidence of quality learner data in the online course. A critique is presented of strategic and tactical issues of learning analytics. The approach to the critique is taken through…

  9. Analytical mass spectrometry. Abstracts

    SciTech Connect

    Not Available

    1990-12-31

    This 43rd Annual Summer Symposium on Analytical Chemistry was held July 24--27, 1990 at Oak Ridge, TN and contained sessions on the following topics: Fundamentals of Analytical Mass Spectrometry (MS), MS in the National Laboratories, Lasers and Fourier Transform Methods, Future of MS, New Ionization and LC/MS Methods, and an extra session. (WET)

  10. Analytical mass spectrometry

    SciTech Connect

    Not Available

    1990-01-01

    This 43rd Annual Summer Symposium on Analytical Chemistry was held July 24--27, 1990 at Oak Ridge, TN and contained sessions on the following topics: Fundamentals of Analytical Mass Spectrometry (MS), MS in the National Laboratories, Lasers and Fourier Transform Methods, Future of MS, New Ionization and LC/MS Methods, and an extra session. (WET)

  11. Power Law Behavior of Structural Properties of Protein Gels

    Microsoft Academic Search

    Marleen Verheul; Sebastianus P. F. M. Roefs; Jorrit Mellema; Kees G. de Kruif

    1998-01-01

    Whey proteins are globular, heat-sensitive proteins. The gel structure, the formation of this structure, and the rheological properties of particulate whey protein isolate (WPI) gels have been investigated. On increasing the NaCl concentration, the permeability of the WPI gels increased, indicating a coarsening of the gel structure, confirmed by confocal scanning laser microscopy pictures. Only a part of the total

  12. Actuator device utilizing a conductive polymer gel

    DOEpatents

    Chinn, Douglas A.; Irvin, David J.

    2004-02-03

    A valve actuator based on a conductive polymer gel is disclosed. A nonconductive housing is provided having two separate chambers separated by a porous frit. The conductive polymer is held in one chamber and an electrolyte solution, used as a source of charged ions, is held in the second chamber. The ends of the housing a sealed with a flexible elastomer. The polymer gel is further provide with electrodes with which to apply an electrical potential across the gel in order to initiate an oxidation reaction which in turn drives anions across the porous frit and into the polymer gel, swelling the volume of the gel and simultaneously contracting the volume of the electrolyte solution. Because the two end chambers are sealed the flexible elastomer expands or contracts with the chamber volume change. By manipulating the potential across the gel the motion of the elastomer can be controlled to act as a "gate" to open or close a fluid channel and thereby control flow through that channel.

  13. Phase separation in calcium alginate gels.

    PubMed

    Straatmann, A; Borchard, W

    2003-08-01

    Alginates are polysaccharides consisting of beta-D-mannuronate and alpha-L-guluronate units. In the presence of bivalent cations like calcium the guluronate blocks form physically cross-linked gels. The gelation properties of alginates play an important role in the stability of extracellular polymer substances and in the food industry. When stock solutions of Ca2+ ions and alginate are mixed, the gelation starts before the Ca2+ ions are evenly distributed, which leads to non-uniform gels. In this contribution, Ca alginate gels were prepared by in situ gelation using glucono-delta-lactone and CaCO3. In this way, uniform gels could be prepared directly in the measuring cell. Below a critical concentration, highly viscous solutions were obtained, which were below the critical point of gel formation. In these solutions at low rotational speeds a Schlieren peak arose, which became smaller and steeper with increasing time until a new meniscus could be detected. This behaviour is in contrast to the peak broadening due to diffusion after a synthetic boundary was formed. Evaluation of the data leads to negative diffusion coefficients. It has been shown by others that the mutual diffusion coefficient must be negative in the spinodal region. This phenomena is known as uphill diffusion and leads to phase separation of a binary system. The formation of the gel phase in this case is therefore discussed as uphill diffusion. PMID:12692695

  14. The Microrheology of Sickle Hemoglobin Gels

    PubMed Central

    Zakharov, Mikhail N.; Aprelev, Alexey; Turner, Matthew S.; Ferrone, Frank A.

    2010-01-01

    Sickle cell disease is a rheological disease, yet no quantitative rheological data exist on microscopic samples at physiological concentrations. We have developed a novel method for measuring the microrheology of sickle hemoglobin gels, based on magnetically driven compression of 5- to 8-?m-thick emulsions containing hemoglobin droplets ?80 ?m in diameter. Using our method, by observing the expansion of the droplet area as the emulsion is compressed, we were able to resolve changes in thickness of a few nanometers with temporal resolution of milliseconds. Gels were formed at various initial concentrations and temperatures and with different internal domain structure. All behaved as Hookean springs with Young's modulus from 300 to 1500 kPa for gels with polymerized hemoglobin concentration from 6 g/dl to 12 g/dl. For uniform, multidomain gels, Young's modulus mainly depended on the terminal concentration of the gel rather than the conditions of formation. A simple model reproduced the quadratic dependence of the Young's modulus on the concentration of polymerized hemoglobin. Partially desaturated samples also displayed quadratic concentration dependence but with a smaller proportionality coefficient, as did samples that were desaturated in steps; such samples were significantly less rigid than gels formed all at once. The magnitude of the Young's modulus provides quantitative support for the dominant models of sickle pathophysiology. PMID:20712998

  15. Binary diamondoid building blocks for molecular gels.

    PubMed

    Zhang, Mengwen; Zukoski, Charles F

    2014-07-01

    Adamantane is a type of diamondoid molecules that has a cage or globular shape with a diameter of 6.34 ± 0.04 Å.8 Anisotropic interactions between these truly nanoscopic particles can be induced through the derivatization of the diamondoid cage. Here we explore the gelation of paired systems of adamantane where attractions are introduced through van der Waals forces and hydrogen bonding. Gels are produced through the mixing of 1-adamantanecarboxylic acid (A1C) and 1-adamantylamine (A1N). Upon mixing dimethyl sulfoxide solutions of these molecules at vanishing concentrations, these diamondoid molecules rapidly precipitate. A space-filling gel of the resulting aggregates is observed at approximately 3% by weight. These resulting gels have elastic moduli of 10(2)-10(4) Pa in the 3-7 wt % concentration range. At a 1:1 mol ratio of 1-adamantanecarboxylic acid (A1C) and 1-adamantylamine (A1N), the gel's elastic modulus and yield stress increase as volume fractions ?(x) and ?(y) with x ? 4.2 and y ? 3.5. The dependencies of moduli and yield stress on the volume fraction display characteristics of colloidal gels. Transmission electron microscope (TEM) images indicate that the gels are formed from a network of interwoven and branched fibers which are composed of ?30 nm crystallites that have undergone oriented aggregation to form fibers. PMID:24902001

  16. Gel electrolyte for lithium-ion batteries.

    SciTech Connect

    Chen, Z.; Zhang, L. Z.; West, R.; Amine, K.; Chemical Sciences and Engineering Division; Univ. of Wisconsin-Madison

    2008-03-10

    The electrochemical performance of gel electrolytes based on crosslinked poly[ethyleneoxide-co-2-(2-methoxyethyoxy)ethyl glycidyl ether-co-allyl glycidyl ether] was investigated using graphite/Li{sub 1.1}[Ni{sub 1/3}Mn{sub 1/3}Co{sub 1/3}]{sub 0.9}O{sub 2} lithium-ion cells. It was found that the conductivity of the crosslinked gel electrolytes was as high as 5.9 mS/cm at room temperature, which is very similar to that of the conventional organic carbonate liquid electrolytes. Moreover, the capacity retention of lithium-ion cells comprising gel electrolytes was also similar to that of cells with conventional electrolytes. Despite of the high conductivity of the gel electrolytes, the rate capability of lithium-ion cells comprising gel electrolytes is inferior to that of the conventional cells. The difference was believed to be caused by the poor wettability of gel electrolytes on the electrode surfaces.

  17. Swelling/deswelling of anionic copolymer gels.

    PubMed

    Khare, A R; Peppas, N A

    1995-05-01

    Studies of dynamic and equilibrium swelling of ionic gels are important in understanding the diffusion of physiologically important fluids in materials for site-specific controlled drug delivery applications. The dynamic and equilibrium swelling properties of dry glassy poly(2-hydroxyethyl methacrylate-co-methacrylic acid) and poly(2-hydroxyethyl methacrylate-co-acrylic acid) polymeric networks were studied as a function of pH, ionic strength, nature of the counterion and buffer composition. The mechanism of water diffusion in these gels became more anomalous as the pH of the swelling medium increased and as the ionic strength decreased at a constant pH > or = pKa,gel. The mechanism of water diffusion was Fickian in all unbuffered swelling media at pH 4.0, which is lower than the pKa,gel. The pKa,gel of these gels was between 5.5 and 6. At pH 4.0, the diffusion mechanism was independent of ionic strength. This swelling behaviour is explained in terms of the concept of ion osmotic swelling pressure and ion exchange kinetics. PMID:7492721

  18. Structural evolution of colloidal silica gels to glass

    SciTech Connect

    Ying, J.Y.; Benziger, J.B. (Princeton Univ., NJ (United States). Dept. of Chemical Engineering); Navrotsky, A. (Princeton Univ., NJ (United States). Dept. of Geological and Geophysical Sciences)

    1993-10-01

    The gel-to-ceramic evolution of colloidal-derived silica gels was examined by thermal analysis, infrared photoacoustic spectroscopy, physical characteristic, and high-temperature calorimetry. Oxygen in the firing atmosphere promoted sintering of colloidal gels relative to firing in a nitrogen or argon atmosphere. Water vapor in the atmosphere promoted consolidation and crystallization to cristobalite. Addition of PVA to the colloidal gel resulted in consolidation and crystallization of the gel at 1000 C, [approximately]150 C less than gels without the PVA binder. The enthalpy of consolidation of the gels to fused silica glass was approximately [minus]10kJ/mol, primarily due to reduction of surface area.

  19. Combined microscopic and dynamic rheological methods for studying the structural breakdown properties of whey protein gels and emulsion filled gels

    Microsoft Academic Search

    Aniket R. Abhyankar; Daniel M. Mulvihill; Mark A. E. Auty

    2011-01-01

    The microstructural and large deformation rheological properties of model food gels were studied by performing notch propagation tensile testing on the gels using a tensile stage and observing changes in the microstructure of the gels during tensile testing using confocal laser scanning microscopy (CLSM). Heat-set whey protein (WP) gels containing either added sodium caseinate (NaCN) or sunflower oil droplets emulsified

  20. Gel growth of lysozyme crystals studied by small angle neutron scattering: case of silica gel, a nucleation inhibitor

    Microsoft Academic Search

    O. Vidal; M. C. Robert; F. Boué

    1998-01-01

    Silica gels were used as a media for crystal growth of hen egg white lysozyme crystals. Using small angle neutron scattering, gel-free solutions have been compared to gelled samples in the pre-nucleation period and in the growth period. Characterisation of the protein solution trapped in the gel network shows an adsorption of protein on the gel surface through electrostatic and

  1. Ocular contact time of a carbomer gel (GelTears) in humans

    Microsoft Academic Search

    Clive G Wilson; Ya Ping Zhu; Malcolm Frier; L S Rao; Peter Gilchrist; Alan C Perkins

    1998-01-01

    BACKGROUND\\/AIMSCarbomers are widely used in products for the treatment of dry eye; however, the polymer gel thins on addition of probes (for example, fluorescein salt) confounding the comparison of products by objective clinical tests such as spectrophotofluorimetry or scintigraphy. A novel method of radiolabelling carbomer gels, with minimum change to their rheology, has permitted the non-invasive evaluation of precorneal residence

  2. The gel edge electric field gradients in denaturing polyacrylamide gel electrophoresis.

    PubMed

    Desruisseaux, C; Slater, G W; Drouin, G

    1998-05-01

    It has previously been shown that zones of higher electric field form close to the loading end of the gel during denaturing polyacrylamide gel electrophoresis. Here we show that the field can reach up to three times its normal mean value a few cm in front of the loading wells when 44.5 mM Tris-44.5 mM boric acid-1 mM EDTA is used as the gel buffer. We also demonstrate that this electric field gradient is mostly due to the difference in ion transference numbers at the gel/buffer interface caused by the high viscosity of the urea solution contained in the gel. This field gradient leads to increased band widths and forces us to redefine both the electrophoretic mobility and the mean field intensity. We discuss some methods that can be used to minimize the effects of this gradient. PMID:9629888

  3. Visual Analytics: Why Now?

    SciTech Connect

    Thomas, James J.

    2007-04-01

    Commentary: An emerging field of study, visual analytics, is briefly described with its motivations and partnerships to bring the best talents and technologies to missions such as homeland security and human health.

  4. Enzymes in Analytical Chemistry.

    ERIC Educational Resources Information Center

    Fishman, Myer M.

    1980-01-01

    Presents tabular information concerning recent research in the field of enzymes in analytic chemistry, with methods, substrate or reaction catalyzed, assay, comments and references listed. The table refers to 128 references. Also listed are 13 general citations. (CS)

  5. Reprogramming cellular phenotype by soft collagen gels.

    PubMed

    Ali, M Yakut; Chuang, Chih-Yuan; Saif, M Taher A

    2014-11-28

    A variety of cell types exhibit phenotype changes in response to the mechanical stiffness of the substrate. Many cells excluding neurons display an increase in the spread area, actin stress fiber formation and larger focal adhesion complexes as substrate stiffness increases in a sparsely populated culture. Cell proliferation is also known to directly correlate with these phenotype changes/changes in substrate stiffness. Augmented spreading and proliferation on stiffer substrates require nuclear transcriptional regulator YAP (Yes associated protein) localization in the cell nucleus and is tightly coupled to larger traction force generation. In this study, we show that different types of fibroblasts can exhibit spread morphology, well defined actin stress fibers, and larger focal adhesions even on very soft collagen gels (modulus in hundreds of Pascals) as if they are on hard glass substrates (modulus in GPa, several orders of magnitude higher). Strikingly, we show, for the first time, that augmented spreading and other hard substrate cytoskeleton architectures on soft collagen gels are not correlated with the cell proliferation pattern and do not require YAP localization in the cell nucleus. Finally, we examine the response of human colon carcinoma (HCT-8) cells on soft collagen gels. Recent studies show that human colon carcinoma (HCT-8) cells form multicellular clusters by 2-3 days when cultured on soft polyacrylamide (PA) gels with a wide range of stiffness (0.5-50 kPa) and coated with an extracellular matrix, ECM (collagen monomer/fibronectin). These clusters show limited spreading/wetting on PA gels, form 3D structures at the edges, and eventually display a remarkable, dissociative metastasis like phenotype (MLP), i.e., epithelial to rounded morphological transition after a week of culture on PA gels only, but not on collagen monomer coated stiff polystyrene/glass where they exhibit enhanced wetting and form confluent monolayers. Here, we show that HCT-8 cell clusters also show augmented spreading/wetting on soft collagen gels and eventually form confluent monolayers as on rigid glass substrates and MLP is completely inhibited on soft collagen gels. Overall, these results suggest that cell-material interactions (soft collagen gels in this case) can induce cellular phenotype and cytoskeleton organization in a remarkably distinct manner compared to a classical synthetic polyacrylamide (PA) hydrogel cell culture model and may contribute in designing new functional biomaterials. PMID:25284029

  6. A meta-analytic approach to an integrated summary of efficacy

    Microsoft Academic Search

    Barbara H. Perry; Allan R. Sampson; Barry H. Schwab; M. Rezaul Karim; Janice M. Smiell

    2002-01-01

    This paper presents a case study involving a meta-analytic approach for an integrated summary of efficacy based upon four phase II and III clinical trials that comprised the basis for a Biologics License Application to the U.S. Food and Drug Administration for approval of becaplermin gel. There were substantial variations in observed response rates across the four studies that were

  7. Extreme Scale Visual Analytics

    SciTech Connect

    Steed, Chad A [ORNL] [ORNL; Potok, Thomas E [ORNL] [ORNL; Pullum, Laura L [ORNL] [ORNL; Ramanathan, Arvind [ORNL] [ORNL; Shipman, Galen M [ORNL] [ORNL; Thornton, Peter E [ORNL] [ORNL

    2013-01-01

    Given the scale and complexity of today s data, visual analytics is rapidly becoming a necessity rather than an option for comprehensive exploratory analysis. In this paper, we provide an overview of three applications of visual analytics for addressing the challenges of analyzing climate, text streams, and biosurveilance data. These systems feature varying levels of interaction and high performance computing technology integration to permit exploratory analysis of large and complex data of global significance.

  8. Mucosal effects of tenofovir 1% gel.

    PubMed

    Hladik, Florian; Burgener, Adam; Ballweber, Lamar; Gottardo, Raphael; Vojtech, Lucia; Fourati, Slim; Dai, James Y; Cameron, Mark J; Strobl, Johanna; Hughes, Sean M; Hoesley, Craig; Andrew, Philip; Johnson, Sherri; Piper, Jeanna; Friend, David R; Ball, T Blake; Cranston, Ross D; Mayer, Kenneth H; McElrath, M Juliana; McGowan, Ian

    2015-01-01

    Tenofovir gel is being evaluated for vaginal and rectal pre-exposure prophylaxis against HIV transmission. Because this is a new prevention strategy, we broadly assessed its effects on the mucosa. In MTN-007, a phase-1, randomized, double-blinded rectal microbicide trial, we used systems genomics/proteomics to determine the effect of tenofovir 1% gel, nonoxynol-9 2% gel, placebo gel or no treatment on rectal biopsies (15 subjects/arm). We also treated primary vaginal epithelial cells from four healthy women with tenofovir in vitro. After seven days of administration, tenofovir 1% gel had broad-ranging effects on the rectal mucosa, which were more pronounced than, but different from, those of the detergent nonoxynol-9. Tenofovir suppressed anti-inflammatory mediators, increased T cell densities, caused mitochondrial dysfunction, altered regulatory pathways of cell differentiation and survival, and stimulated epithelial cell proliferation. The breadth of mucosal changes induced by tenofovir indicates that its safety over longer-term topical use should be carefully monitored. PMID:25647729

  9. Sol-gel growth of vanadium dioxide

    SciTech Connect

    Speck, K.R.

    1990-01-01

    This thesis examines the chemical reactivity of vanadium (IV) tetrakis(t-butoxide) as a precursor for the sol-gel synthesis of vanadium dioxide. Hydrolysis and condensation of the alkoxide was studied by FTIR spectroscopy. Chemical modification of the vanadium tetraalkoxide by alcohol interchange was studied using {sup 51}V NMR and FTIR. Vanadium dioxide thin films and powders were made from vanadium tetrakis(t-butoxide) by standard sol-gel techniques. Post-deposition heating under nitrogen was necessary to transform amorphous gels into vanadium dioxide. Crystallization of films and powders was studied by FTIR, DSC, TGA, and XRD. Gel-derived vanadium dioxide films undergo a reversible semiconductor-to-metal phase transition near 68C, exhibiting characteristic resistive and spectral changes. The electrical resistance decreased by two to three orders of magnitude and the infrared transmission sharply dropped as the material was cycled through this thermally induced phase transition. The sol-gel method was also used to make doped vanadium dioxide films. Films were doped with tungsten and molybdenum ions to effectively lower the temperature at which the transition occurs.

  10. Sampling and Sensing Systems for High Priority Analytes

    SciTech Connect

    Brinker, C.Jeffrey; Frye-Mason, Gregory C.; Kottenstette, Richard J.; Lewis, Patrick R.; Sasaki, Darryl Y.; Sellinger, Alan

    1999-04-01

    This reports summarizes the results from a Laboratory Directed Research and Development effort to develop selective coastings for detecting high priority analytes (HPAs), such as chemical warfare (CW) agents and their precursors, in the presence of common interferents. Accomplishments during this project included synthesis and testing of new derivatized sol-gel coatings for surface acoustic wave sensors (SAWs). Surfactant modified and fluoroalcohol derivatized sol-gel oxides were coated onto SAW devices and tested with volatile organic compounds (VOCs). Theses modified sol-gel coatings improved SAW sensitivity to DMMP by over three orders of magnitude when compared to standard polymeric oatings such as polyisobutylene and by over two orders of magnitude compared with polymers tailor made for enhanced sensitivity to phosphonates. SAW sensors coated with these materials exhibit highly sensitive reversible behavior at elevated temperatures (>90 degree C), possibly leading to low detection levels for semivolatile analytes while remaining insensitive to volatile organic interferants. Additionally, we have investigated the use of reactive polymers for detection of volatile and reactive CW agent precursors (Chemical Weapons Convention Schedule 3 Agents) such as phosphouous oxychloride (POCl(3)). The results obtained in this study find that sensitive and selective responses can be obtained for Schedule 3 agents using commercially available polymers and chemical guidelines from solution phase chemistry.

  11. Reduction of gas and water permeabilities using gels

    SciTech Connect

    Seright, R.S. [New Mexico Petroleum Recovery Research Center, Socorro, NM (United States)

    1995-05-01

    The authors investigated how different types of gels reduce permeability to water and gases in porous rock. Five types of gels were studied, including (1) a ``weak`` resorcinol-formaldehyde gel, (2) a ``strong`` resorcinol-formaldehyde gel, (3) a Cr(III)-xanthan gel, (4) a Cr(III)-acetate-HPAM gel, and (5) a colloidal-silica gel. For all gels, extensive coreflood experiments were performed to assess the permeability-reduction characteristics and the stability to repeated water-alternating-gas (WAG) cycles. Studies were performed at pressures up to 1,500 psi using either nitrogen or carbon dioxide as the compressed gas. They developed a coreflood apparatus with an inline high-pressure spectrophotometer that allowed tracer studies to be performed without depressurizing the core. They noted several analogies between the results reported here and those observed during a parallel study of the effects of gel on oil and water permeabilities.

  12. Agarose gel shift assay reveals that calreticulin favors substrates with a quaternary structure in solution.

    PubMed

    Boelt, Sanne Grundvad; Houen, Gunnar; Højrup, Peter

    2015-07-15

    Here we present an agarose gel shift assay that, in contrast to other electrophoresis approaches, is loaded in the center of the gel. This allows proteins to migrate in either direction according to their isoelectric points. Therefore, the presented assay enables a direct visualization, separation, and prefractionation of protein interactions in solution independent of isoelectric point. We demonstrate that this assay is compatible with immunochemical methods and mass spectrometry. The assay was used to investigate interactions with several potential substrates for calreticulin, a chaperone that is involved in different biological aspects through interaction with other proteins. The current analytical assays used to investigate these interactions are mainly spectroscopic aggregation assays or solid phase assays that do not provide a direct visualization of the stable protein complex but rather provide an indirect measure of interactions. Therefore, no interaction studies between calreticulin and substrates in solution have been investigated previously. The results presented here indicate that calreticulin has a preference for substrates with a quaternary structure and primarily ?-sheets in their secondary structure. It is also demonstrated that the agarose gel shift assay is useful in the study of other protein interactions and can be used as an alternative method to native polyacrylamide gel electrophoresis. PMID:25908558

  13. Complex Analytic and Differential Geometry

    E-print Network

    Demailly, Jean-Pierre

    Complex Analytic and Differential Geometry Jean-Pierre Demailly Universit´e de Grenoble I Institut. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .60 Chapter II. Coherent Sheaves and Analytic Spaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 2. The Local Ring of Germs of Analytic Functions

  14. Gel-sol synthesis of rutile nanoparticles.

    PubMed

    Verhovšek, Dejan; Lešnik, Maja; Veronovski, Nika; Samardžija, Zoran; Žagar, Kristina; ?eh, Miran

    2014-01-01

    Titanium dioxide (TiO(2)) rutile nanoparticles were synthesized at temperatures below 100 °C using a gel-sol process that provides control of the final particles' characteristics, such as the nanoparticle size, morphology, crystal structure and crystallinity. The synthesized rutile nanoparticles were analyzed using X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that the gel-sol process allows control over the final nanoparticle characteristics with the proper choice of reaction parameters. The most profound influence on the nanoparticles' properties is achieved by the type and concentration of the acid used in the reaction mixture. The gel-sol synthesis resulted in anisotropic rutile nanoparticles that are 60-160 nm long, depending on the reaction parameters, and have an aspect ratio of about 5. A reaction mechanism is presented, explaining the influence of various reaction parameters on the characteristics of the TiO(2) nanoparticles. PMID:25286202

  15. Ten years of silica gels from TEOS

    SciTech Connect

    Klein, L.C.; Woodman, R.H. [Rutgers-the State Univ. of New Jersey, Piscataway, NJ (United States)

    1995-12-31

    After more than ten years of making silica gels from tetraethylorthosilicate (TEOS), it would seem that the sol-gel process should be more scientific than empirical. The relationships between processing and microstructure, at least, should be possible to predict, or better yet, explain. Ideally, the success rate for a given composition -- preparation, forming and drying without defects -- should approach 100%. Why is it that only a handful of compositions have emerged that work all the time, and a few others seem to work some of the time? An attempt is made to draw a map on the gel time vs pH scale (pH = 0-8) that delineates compositions according to their behavior.

  16. Process ceramic fibers by Sol-Gel

    SciTech Connect

    Fernandez de, M.E.P.; Kang, Cheolho; Mangonon, P.L.

    1993-09-01

    The Sol-Gel process may transform the materials of construction chemical engineers make and use--thin films, fibers, and powders. The advantage of the Sol-Gel technology is the ability to produce high purity products at low temperatures. For example, silica film is used to passivate integrated circuits. To achieve this, the native silicon substrate now is oxidized at about 1,000C for a short period of time. At this temperature, diffusion of the dopant atoms may be induced to alter the electronic properties of the chip. In contrast, the film application using Sol-Gel may be done at 400-600C. Another example is the interest in ceramic fibers to incorporate in fiber-reinforced ceramic matrix composite materials. The latter is considered an enabling technology for the 21st Century high-speed civil transport plane (NASA) and the National Aerospace plane (X-30). Glass and ceramic fibers have been prepared conventionally by drawing or blowing a high temperature melt through an orifice. The traditional process requires the conversion of the raw materials into a homogeneous, high temperature melt, which makes producing fibers based on materials having high melting points or materials that are immiscible in the liquid state difficult. The Sol-Gel process applied to the production of fibers offers an advantage over the conventional method, since the fibers are drawn from the Gel at low temperatures and then are converted to glass or ceramics by heating the fibers at high temperatures, T[lt]600C. Also by using this technique there is the potential to produce glasses of new compositions with high purity and homogeneity. This article will briefly discuss the polymerization aspect of the Sol-Gel process. The chemical, physical, and rheological aspects of the process to produce the desired product will be discussed.

  17. Dynamic Light Scattering From Colloidal Gels

    NASA Technical Reports Server (NTRS)

    Krall, A. H.; Weitz, David A.

    1996-01-01

    We present a brief, preliminary account of the interpretation of dynamic light scattering from fractal colloidal gels. For small scattering angles, and for high initial colloid particle volume fractions, the correlation functions exhibit arrested decay, reflecting the non-ergodic nature of these systems and allowing us to directly determine the elastic modulus of the gels. For smaller initial volume fractions, the correlation functions decay completely. In all cases, the initial decay is not exponential, but is instead described by a stretched exponential. We summarize the principles of a model that accounts for these data and discuss the scaling behavior of the measured parameters.

  18. Adsorbed gels versus brushes: Viscoelastic differences

    PubMed Central

    Dutta, Amit K.; Belfort, Georges

    2014-01-01

    It is of fundamental import to be able to easily distinguish between the viscoelastic properties of a molecular gel (non-covalent cross-linked three dimensional polymer structure) and a brush (polymer structure that emanates from a surface in three-dimensions sans cross-linking). This has relevance in biology and in designing surfaces with desired chemical and viscoelastic properties for nano- and genomic-technology applications. Agarose and thiol tagged poly(ethylene glycol) were chosen model systems as they are known, on adsorption, to behave like a molecular gel and brush, respectively. Here, we focus on their viscoelastic differences using a quartz crystal microbalance with dissipation monitoring (QCM-D). Changes in resonance frequency and dissipation for three overtones using QCM-D were fitted with the Voigt viscoelastic model to calculate the shear viscosity and shear modulus for the adsorbed agarose gel and the PEG brush. At a surface coverage of 500 ng/cm2, the shear viscosities and shear moduli were 0.0025 ± 0.0002 Pa-s and 2.0 ± 0.17 × 105 Pa and 0.0010 ± 0.0001 Pa-s and 5.0 ± 0.3 × 104 Pa for the gel and brush, respectively. Thus, the adsorbed agarose gel layer was far more rigid than that of covalently bound PEG brush due to its cross-linked network. Also, the diffusivity of agarose and PEG in solution was compared during adsorption onto a bare gold surface. The estimated value for the effective diffusivity of the PEG (without a thiol tag) and of the agarose gel was of the order of 10?11 and 10?15 m2/s, respectively. This low diffusivity for agarose supports the contention that it exists as a molecular gel with a H-bonded cross-linked network in aqueous solution. With the methods used here, it is relatively easy to distinguish the differences in viscoelastic properties between an adsorbed gel and brush. PMID:17286418

  19. Hybrid sol-gel optical materials

    DOEpatents

    Zeigler, John M. (Albuquerque, NM)

    1993-01-01

    Hybrid sol-gel materials comprise silicate sols cross-linked with linear polysilane, polygermane, or poly(silane-germane). The sol-gel materials are useful as optical identifiers in tagging and verification applications and, in a different aspect, as stable, visible light transparent non-linear optical materials. Methyl or phenyl silicones, polyaryl sulfides, polyaryl ethers, and rubbery polysilanes may be used in addition to the linear polysilane. The linear polymers cross-link with the sol to form a matrix having high optical transparency, resistance to thermooxidative aging, adherence to a variety of substrates, brittleness, and a resistance to cracking during thermal cycling.

  20. Hybrid sol-gel optical materials

    DOEpatents

    Zeigler, J.M.

    1993-04-20

    Hybrid sol-gel materials comprise silicate sols cross-linked with linear polysilane, polygermane, or poly(silane-germane). The sol-gel materials are useful as optical identifiers in tagging and verification applications and, in a different aspect, as stable, visible light transparent non-linear optical materials. Methyl or phenyl silicones, polyaryl sulfides, polyaryl ethers, and rubbery polysilanes may be used in addition to the linear polysilane. The linear polymers cross-link with the sol to form a matrix having high optical transparency, resistance to thermooxidative aging, adherence to a variety of substrates, brittleness, and a resistance to cracking during thermal cycling.

  1. Hybrid sol-gel optical materials

    DOEpatents

    Zeigler, John M. (Albuquerque, NM)

    1992-01-01

    Hybrid sol-gel materials comprise silicate sols cross-linked with linear polysilane, polygermane, or poly(silane-germane). The sol-gel materials are useful as optical identifiers in tagging and verification applications and, in a different aspect, as stable, visible light transparent non-linear optical materials. Methyl or phenyl silicones, polyaryl sulfides, polyaryl ethers, and rubbery polysilanes may be used in addition to the linear polysilane. The linear polymers cross-link with the sol to form a matrix having high optical transparency, resistance to thermooxidative aging, adherence to a variety of substrates, brittleness, and a resistance to cracking during thermal cycling.

  2. Neutron detector using sol-gel absorber

    DOEpatents

    Hiller, John M. (Oak Ridge, TN); Wallace, Steven A. (Oak Ridge, TN); Dai, Sheng (Knoxville, TN)

    1999-01-01

    An neutron detector composed of fissionable material having ions of lithium, uranium, thorium, plutonium, or neptunium, contained within a glass film fabricated using a sol-gel method combined with a particle detector is disclosed. When the glass film is bombarded with neutrons, the fissionable material emits fission particles and electrons. Prompt emitting activated elements yielding a high energy electron contained within a sol-gel glass film in combination with a particle detector is also disclosed. The emissions resulting from neutron bombardment can then be detected using standard UV and particle detection methods well known in the art, such as microchannel plates, channeltrons, and silicon avalanche photodiodes.

  3. Characterization of gels prepared from silicon ethoxide

    E-print Network

    Yun, Su-Jin

    1990-01-01

    CHAPTER I INTRODUCTION CHAPTER II LITERATURE REVIEW 2, 1. Sol-gel process 2. 1. 1. Raw materials 2. 1. 2. Geladon process 2. 1. 3. Effect of operating conditions 2. 2. Drying 2. 2. 1. Crack development 2. 2. 2. Drying techniques 2. 2. 3... 33 35 37 45 45 53 57 60 69 77 C~V CONCLUSIONS 84 REFEIKNCES APPENDIX A APPENDIX B Polymorphic forms of silica 87 91 92 96 LIST OF FIGURES Figure 1. Pardculate growth of a) Sol to b) Gel 2. a Bond formation between silica...

  4. Alignment and nonlinear elasticity in biopolymer gels

    NASA Astrophysics Data System (ADS)

    Feng, Jingchen; Levine, Herbert; Mao, Xiaoming; Sander, Leonard M.

    2015-04-01

    We present a Landau-type theory for the nonlinear elasticity of biopolymer gels with a part of the order parameter describing induced nematic order of fibers in the gel. We attribute the nonlinear elastic behavior of these materials to fiber alignment induced by strain. We suggest an application to contact guidance of cell motility in tissue. We compare our theory to simulation of a disordered lattice model for biopolymers. We treat homogeneous deformations such as simple shear, hydrostatic expansion, and simple extension, and obtain good agreement between theory and simulation. We also consider a localized perturbation which is a simple model for a contracting cell in a medium.

  5. Alignment and Nonlinear Elasticity in Biopolymer Gels

    E-print Network

    Jingchen Feng; Herbert Levine; Xiaoming Mao; Leonard M. Sander

    2014-10-14

    We present a Landau type theory for the non-linear elasticity of biopolymer gels with a part of the order parameter describing induced nematic order of fibers in the gel. We attribute the non-linear elastic behavior of these materials to fiber alignment induced by strain. We suggest an application to contact guidance of cell motility in tissue. We compare our theory to simulation of a disordered lattice model for biopolymers. We treat homogeneous deformations such as simple shear, hydrostatic expansion, and simple extension, and obtain good agreement between theory and simulation. We also consider a localized perturbation which is a simple model for a contracting cell in a medium.

  6. Electroactive polymer gels based on epoxy resin

    NASA Astrophysics Data System (ADS)

    Samui, A. B.; Jayakumar, S.; Jayalakshmi, C. G.; Pandey, K.; Sivaraman, P.

    2007-04-01

    Five types of epoxy gels have been synthesized from common epoxy resins and hardeners. Fumed silica and nanoclay, respectively, were used as fillers and butyl methacrylate/acrylamide were used as monomer(s) for making interpenetrating polymer networks (IPNs) in three compositions. Swelling study, tensile property evaluation, dynamic mechanical thermal analysis, thermo-gravimetric analysis, scanning electron microscopy and electroactive property evaluation were done. The gels have sufficient mechanical strength and the time taken for bending to 20° was found to be 22 min for forward bias whereas it was just 12 min for reverse bias.

  7. Biomonitoring of infant exposure to phenolic endocrine disruptors using urine expressed from disposable gel diapers.

    PubMed

    Liu, Liangpo; Xia, Tongwei; Zhang, Xueqin; Barr, Dana Boyd; Alamdar, Ambreen; Zhang, Jie; Tian, Meiping; Huang, Qingyu; Shen, Heqing

    2014-08-01

    Infant exposure to endocrine disruptors (EDs) may cause adverse health effects because of their fast growth and development during this life stage. However, collecting urine from infants for exposure assessment using biological monitoring is not an easy task. For this purpose, we evaluated the feasibility of using urine expressed from disposable gel absorbent diapers (GADs) as a matrix for biomonitoring selected phenolic EDs. GADs urine was expressed with the assistance of CaCl(2) and was collected using a device fabricated in our laboratory. The analytes were extracted and concentrated using a liquid-liquid method and their hydroxyl groups were modified by dansyl chloride to enhance their chromatography and detection. Finally, the analytes were measured by high-performance liquid chromatography (HPLC) coupled with electrospray ionization (ESI) tandem mass spectrometry (MS/MS). The target chemicals were bisphenol A, triclosan, 17 ?-ethynylestradiol, the natural hormone estrone, and 17 ?-estradiol. The ratio of the CaCl(2) to the urine-wetted gel absorbent, variation of the inter-urination volume, and analyte deposition bias in the diaper were assessed. Analyte blank values in the diapers, the sample storage stabilities, and recoveries of the analytes were also evaluated. The results showed that 70-80 % of the urine could be expressed from the diaper with the assistance of CaCl(2) and 70.5-124 % of the spiked analytes can be recovered in the expressed urine. The limits of detections (LODs) were 0.02-0.27 ng/mL, well within the range for detection in human populations. Our pilot data suggest that infants are widely exposed to the selected EDs. PMID:24924209

  8. An x-ray CT polymer gel dosimetry prototype: II. Gel characterization and clinical application

    NASA Astrophysics Data System (ADS)

    Johnston, H.; Hilts, M.; Carrick, J.; Jirasek, A.

    2012-05-01

    This article reports on the dosimetric properties of a new N-isopropylacrylamide, high %T, polymer gel formulation (19.5%T, 23%C), optimized for x-ray computed tomography (CT) polymer gel dosimetry (PGD). In addition, a new gel calibration technique is introduced together with an intensity-modulated radiation therapy (IMRT) treatment validation as an example of a clinical application of the new gel dosimeter. The dosimetric properties investigated include the temporal stability, spatial stability, batch reproducibility and dose rate dependence. The polymerization reaction is found to stabilize after 15 h post-irradiation. Spatial stability investigations reveal a small overshoot in response for gels imaged later than 36 h post-irradiation. Based on these findings, it is recommended that the new gel formulation be imaged between 15-36 h after irradiation. Intra- and inter-batch reproducibility are found to be excellent over the entire range of doses studied (0-28 Gy). A significant dose rate dependence is found for gels irradiated between 100-600 MU?min-1. Overall, the new gel is shown to have promising characteristics for CT PGD, however the implication of the observed dose rate dependence for some clinical applications remains to be determined. The new gel calibration method, based on pixel-by-pixel matching of dose and measured CT numbers, is found to be robust and to agree with the previously used region of interest technique. Pixel-by-pixel calibration is the new recommended standard for CT PGD. The dose resolution for the system was excellent, ranging from 0.2-0.5 Gy for doses between 0-20 Gy and 0.3-0.6 Gy for doses beyond 20 Gy. Comparison of the IMRT irradiation with planned doses yields excellent results: gamma pass rate (3%, 3 mm) of 99.3% at the isocentre slice and 93.4% over the entire treated volume.

  9. 3D gel printing for soft-matter systems innovation

    NASA Astrophysics Data System (ADS)

    Furukawa, Hidemitsu; Kawakami, Masaru; Gong, Jin; Makino, Masato; Kabir, M. Hasnat; Saito, Azusa

    2015-04-01

    In the past decade, several high-strength gels have been developed, especially from Japan. These gels are expected to use as a kind of new engineering materials in the fields of industry and medical as substitutes to polyester fibers, which are materials of artificial blood vessels. We consider if various gel materials including such high-strength gels are 3D-printable, many new soft and wet systems will be developed since the most intricate shape gels can be printed regardless of the quite softness and brittleness of gels. Recently we have tried to develop an optical 3D gel printer to realize the free-form formation of gel materials. We named this apparatus Easy Realizer of Soft and Wet Industrial Materials (SWIM-ER). The SWIM-ER will be applied to print bespoke artificial organs, including artificial blood vessels, which will be possibly used for both surgery trainings and actual surgery. The SWIM-ER can print one of the world strongest gels, called Double-Network (DN) gels, by using UV irradiation through an optical fiber. Now we also are developing another type of 3D gel printer for foods, named E-Chef. We believe these new 3D gel printers will broaden the applications of soft-matter gels.

  10. COMPLEX ANALYTIC GEOMETRY AND ANALYTIC-GEOMETRIC CATEGORIES

    E-print Network

    Peterzil, Ya'acov

    COMPLEX ANALYTIC GEOMETRY AND ANALYTIC-GEOMETRIC CATEGORIES YA'ACOV PETERZIL AND SERGEI STARCHENKO, and complex analytic geometry. The questions are of the following nature: We start with a subset Abstract. The notion of a analytic-geometric category was introduced by v.d. Dries and Miller in [4

  11. Advances in analytical chemistry

    NASA Technical Reports Server (NTRS)

    Arendale, W. F.; Congo, Richard T.; Nielsen, Bruce J.

    1991-01-01

    Implementation of computer programs based on multivariate statistical algorithms makes possible obtaining reliable information from long data vectors that contain large amounts of extraneous information, for example, noise and/or analytes that we do not wish to control. Three examples are described. Each of these applications requires the use of techniques characteristic of modern analytical chemistry. The first example, using a quantitative or analytical model, describes the determination of the acid dissociation constant for 2,2'-pyridyl thiophene using archived data. The second example describes an investigation to determine the active biocidal species of iodine in aqueous solutions. The third example is taken from a research program directed toward advanced fiber-optic chemical sensors. The second and third examples require heuristic or empirical models.

  12. Transaxillary Endoscopic Silicone Gel Breast Augmentation

    Microsoft Academic Search

    Louis L. Strock

    2010-01-01

    Following the return of silicone gel breast implants to the US market in 2006, augmentation with these implants has become increasingly popular. Surgeons have an array of refined techniques from which to choose when performing these procedures, many of which offer the advantage of reduced or less-obvious postoperative scarring. For obvious reasons, many patients are requesting placement of the implants

  13. Driven Polymer Translocation into a Crosslinked Gel

    NASA Astrophysics Data System (ADS)

    Sean, David; Slater, Gary

    2015-03-01

    In a typical polymer translocation setup, a thin membrane is used to separate two chambers and a polyelectrolyte is driven by an electric field to translocate from one side of the membrane to the other via a small nanopore. However, the high translocation rate that results from the forces required to drive this process makes optical and/or electrical analysis of the translocating polymer challenging. Using coarse-grained Langevin Dynamics simulations we investigate how the translocation process can be slowed down by placing a crosslinked gel on the trans-side of the membrane. Since the driving electric field is localized in the neighborhood of the nanopore, electrophoretic migration is only achieved by a ``pushing'' action from the polymer segment residing in the nanopore. For the case of a flexible polymer we find that the polymer fills the gel pores via multiple ``herniation'' processes, whereas for a semi-flexible chain in a tight gel there are no hernias and the polymer follows a smooth curvilinear path. Moreover, for the case of a semi-flexible polymer the gel makes the translocation process more uniform by reducing the acceleration at the end of the process.

  14. Rheology and sensory texture of biopolymer gels

    Microsoft Academic Search

    E. Allen Foegeding

    2007-01-01

    Sensory texture perception is based on food structure and the mastication process. Real-time observations of crack growth and rheological measurements have shown different patterns of microstructural fracture. This has allowed for a reductive approach in consolidating a range of gels into characteristic microstructures and fracture patterns that can be linked to sensory texture.

  15. Mechanical stability of sol-gel films

    Microsoft Academic Search

    A. Atkinson; R. M. Guppy

    1991-01-01

    The relationship between film cracking and film thickness has been studied experimentally for films of ceria gel deposited by spinning on to stainless steel substrates from an aqueous ceria sol. A critical film thickness below which films were crack-free was observed at about 0.6 µm. For films thicker than the critical thickness the crack spacing was approximately ten times the

  16. Gel Filtration Chromatography: A Laboratory Experiment.

    ERIC Educational Resources Information Center

    Hurlbut, Jeffrey A.; Schonbeck, Niels D.

    1984-01-01

    Describes a rapid, visual demonstration of protein separation by gel filtration chromatography. The procedure separates two highly colored proteins of different molecular weights on a Sephadex G-75 in 45 minutes. This time includes packing the column as well. Background information, reagents needed, procedures used, and results obtained are…

  17. Sol-Gel Synthesis Of Aluminoborosilicate Powders

    NASA Technical Reports Server (NTRS)

    Bull, Jeffrey; Leiser, Daniel; Selvaduray, Guna

    1992-01-01

    Application of sol-gel process to synthesis of aluminoborosilicate powders shows potential for control of microstructures of materials. Development of materials having enhanced processing characteristics prove advantageous in extending high-temperature endurance of fibrous refractory composite insulation made from ceramic fibers.

  18. Sol-Gel Derived Hafnia Coatings

    NASA Technical Reports Server (NTRS)

    Feldman, Jay D.; Stackpoole, Mairead; Blum, Yigal; Sacks, Michael; Ellerby, Don; Johnson, Sylvia M.; Venkatapathy, Ethiras (Technical Monitor)

    2002-01-01

    Sol-gel derived hafnia coatings are being developed to provide an oxidation protection layer on ultra-high temperature ceramics for potential use in turbine engines (ultra-efficient engine technology being developed by NASA). Coatings using hafnia sol hafnia filler particles will be discussed along with sol synthesis and characterization.

  19. Electrophoretic Porosimetry of Sol-Gels

    NASA Technical Reports Server (NTRS)

    Snow, L. A.; Smith, D. D.; Sibille, L.; Hunt, A. J.; Ng, J.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    It has been hypothesized that gravity has an effect on the formation and resulting microstructure of sol-gels. In order to more clearly resolve the effect of gravity, pores may be non-destructively analyzed in the wet gel, circumventing the shrinkage and coarsening associated with the drying procedure. We discuss the development of an electrophoretic technique, analogous to affinity chromatography, for the determination of pore size distribution and its application to silica gels. Specifically a monodisperse charged dye is monitored by an optical densitometer as it moves through the wet gel under the influence of an electric field. The transmittance data (output) represents the convolution of the dye concentration profile at the beginning of the run (input) with the pore size distribution (transfer function), i.e. linear systems theory applies. Because of the practical difficulty in producing a delta function input dye profile we prefer instead to use a step function. Average pore size is then related to the velocity of this dye front, while the pore size distribution is related to the spreading of the front. Preliminary results of this electrophoretic porosimetry and its application to ground and space-grown samples will be discussed.

  20. Rheology of ?-carrageenan and ?-lactoglobulin mixed gels

    Microsoft Academic Search

    M. M. Ould Eleya; S. L. Turgeon

    2000-01-01

    Gel formation and the melting of ?-carrageenan in the presence of ?-lactoglobulin were investigated using dynamic rheological techniques as well as a sequence of experimental sweeps of time–temperature, frequency, and strain. The blends, initially prepared at 45°C, show homogeneous mixtures, which then lead to the formation of a gelled ?-carrageenan network containing inclusions of native ?-lactoglobulin during the controlled cooling

  1. Bioactive nanocrystalline sol-gel hydroxyapatite coatings.

    PubMed

    Chai, C S; Ben-Nissan, B

    1999-08-01

    Sol-gel technology offers an alternative technique for producing bioactive surfaces for improved bone attachment. Previous work indicated that monophasic hydroxyapatite coatings were difficult to produce. In the present work hydroxyapatite was synthesized using the sol-gel technique with alkoxide precursors and the solution was allowed to age up to seven days prior to coating. It was found that, similar to the wet-chemical method of hydroxyapatite powder synthesis, an aging time is required to produce a pure hydroxyapatite phase. A methodology that has been successfully used to produce nanocrystalline hydroxyapatite thin film coatings via the sol-gel route on various substrates including alumina, Vycor glass, partially stabilized zirconia, Ti-6Al-4V alloy and single crystal MgO is described. Coatings produced on MgO substrates were characterized by X-ray diffraction and atomic force microscopy, while the analogous gels were examined with thermogravimetric and differential thermal analyses. The coatings were crack free and the surface was covered with small grains, of approximately 200 nm in size for samples fired to 1000 degrees C. Coating thickness varied between 70 and 1000 nm depending on the number of applied layers. PMID:15348113

  2. Electrochemical Growth Of Crystals In Gels

    NASA Technical Reports Server (NTRS)

    Barber, Patrick G.; Coleman, James

    1988-01-01

    Nucleation and growth rates readily controlled. Technique developed to grow crystals by controlling rate of transfer of one component into crystallization volume. Method involves electrochemically controlled generation of one of precipitation species, coupled with diffusion barrier. New procedure, developed in connection with formation of lead tin telluride by reaction in gels of metal ions with telluride ions.

  3. Xanthan gel system effective for profile modification

    SciTech Connect

    Burkholder, L.

    1985-04-15

    To cope with the problem of optimizing reservoir sweep efficiency, many companies today are utilizing a technique known as profile modification. This technique is based on the premise that a gelled polymer formulation can be injected into the reservoir some distance beyond the well bore where it creates a flow diversion. The successful application of profile modification techniques has resulted in significant increases in incremental oil recovery. The injectant is a xanthan-gum solution precross-linked with a chromium complex to form a gel. The polymer/chromium combination reduces permeability in the thief zones and diverts a higher percentage of the displacing fluids into previously unswept, oil-saturated portions of the reservoir. Although reservoir characteristics and brine composition are key considerations, xanthan/chrome gels can be tailored to meet almost any conditions. Fractures will require strong gels while tight formations, or formations with low parting pressures, will require thinner gels. Slug volume is designed to treat the ''thief'' interval and must be carefully sized to improve sweep efficiency within economical limits.

  4. Denaturing Urea Polyacrylamide Gel Electrophoresis (Urea PAGE)

    PubMed Central

    Summer, Heike; Grämer, René; Dröge, Peter

    2009-01-01

    Urea PAGE or denaturing urea polyacrylamide gel electrophoresis employs 6-8 M urea, which denatures secondary DNA or RNA structures and is used for their separation in a polyacrylamide gel matrix based on the molecular weight. Fragments between 2 to 500 bases, with length differences as small as a single nucleotide, can be separated using this method1. The migration of the sample is dependent on the chosen acrylamide concentration. A higher percentage of polyacrylamide resolves lower molecular weight fragments. The combination of urea and temperatures of 45-55 °C during the gel run allows for the separation of unstructured DNA or RNA molecules. In general this method is required to analyze or purify single stranded DNA or RNA fragments, such as synthesized or labeled oligonucleotides or products from enzymatic cleavage reactions. In this video article we show how to prepare and run the denaturing urea polyacrylamide gels. Technical tips are included, in addition to the original protocol 1,2. PMID:19865070

  5. The Genetic Science Learning Center: Gel Electrophoresis

    NSDL National Science Digital Library

    Gel Electrophoresis, designed and run by the University of Utah, is an interactive program that allows the student to learn and practice basic techniques that molecular biologists use every day. This program is an interactive animated procedure that allows the user to "see" DNA strands and instructs the student or user on the basics of DNA.

  6. Egg yolk protein gels and emulsions

    Microsoft Academic Search

    V Kiosseoglou

    2003-01-01

    Egg yolk remains a key ingredient of a number of food products. Yet, its main functional properties, e.g. emulsifying ability and gel structure formation, upon heating, have not attracted the attention of too many researchers specializing in the area of food colloids. It is not surprising then that there have been only very few major advances in the field over

  7. Gel bead composition for metal adsorption

    DOEpatents

    Scott, Charles D. (Oak Ridge, TN); Woodward, Charlene A. (Oak Ridge, TN); Byers, Charles H. (Oak Ridge, TN)

    1990-01-01

    The invention is a gel bead comprising propylene glycol alginate and bone gelatin and is capable of removing metals such as Sr and Cs from solution without adding other adsorbents. The invention could have application to the nuclear industry's waste removal activities.

  8. Gel bead composition for metal adsorption

    DOEpatents

    Scott, Charles D. (Oak Ridge, TN); Woodward, Charlene A. (Oak Ridge, TN); Byers, Charles H. (Oak Ridge, TN)

    1991-01-01

    The invention is a gel bead comprising propylene glycol alginate and bone gelatin and is capable of removing metals such as Sr and Cs from solution without adding other adsorbents. The invention could have application to the nuclear industry's waste removal activities.

  9. Simple cloud chambers using gel ice packs

    Microsoft Academic Search

    Masahiro Kamata; Miki Kubota

    2012-01-01

    Although cloud chambers are highly regarded as teaching aids for radiation education, school teachers have difficulty in using cloud chambers because they have to prepare dry ice or liquid nitrogen before the experiment. We developed a very simple and inexpensive cloud chamber that uses the contents of gel ice packs which can substitute for dry ice or liquid nitrogen. The

  10. Gel injection successfully shuts off excess water

    SciTech Connect

    NONE

    1995-11-01

    Unocal applied a high-temperature organic polymer gel in Feather field Well H-43 in the UK North Sea to reduce water production in them more-permeable upper perforated section of the Brent Sand. The operation and technical details of the polymer system developed by Unocal, and how it was applied, are described in paper SPE 30426, ``Water shut off in the North Sea; Testing a new polymer system in the Heather field, UKCS Block 2/5.`` The authors concluded that the new gel system successfully isolated the Upper Brent water production, increasing oil production and decreasing water production. Lower perforations were successfully isolated using sized calcium carbonate suspended in an HEC polymer--a technique difficult to monitor in the deviated well. Batch mixing provided ``excellent`` quality gel, closely matching lab measured performance. And the gel required no pre-cooling in the near-wellbore area. Some 1,100 bbl were injected without excessive wellhead pressure, at 1 bpm. A summary of the paper`s highlights is presented here.

  11. Staining and Imaging an Agarose Gel

    NSDL National Science Digital Library

    Hinkley, Craig

    This video from CUNY Kingsborough Community College shows the process of staining and imaging an agarose gel. The video describes the process step by step and would be easy to replicate in a laboratory setting. Running time for the video is 3:18.

  12. Gel bead composition for metal adsorption

    SciTech Connect

    Scott, C.D.; Woodward, C.A.; Byers, C.H.

    1989-04-04

    The invention is a gel bead comprising propylene glycol alginate and bone gelatin and is capable of removing metals such as Sr and Cs from solution without adding other adsorbents. The invention could have application to the nuclear industry's waste removal activities. 4 tabs.

  13. Simple Cloud Chambers Using Gel Ice Packs

    ERIC Educational Resources Information Center

    Kamata, Masahiro; Kubota, Miki

    2012-01-01

    Although cloud chambers are highly regarded as teaching aids for radiation education, school teachers have difficulty in using cloud chambers because they have to prepare dry ice or liquid nitrogen before the experiment. We developed a very simple and inexpensive cloud chamber that uses the contents of gel ice packs which can substitute for dry…

  14. Preparation for Pouring an Agarose Gel

    NSDL National Science Digital Library

    Hinkley, Craig

    This video from CUNY Kingsborough Community College describes the technique of preparing to pour an Agarose Gel. The video describes the process step by step and would be easy to replicate in a laboratory setting. Running time for the video is 3:22.

  15. Prescribed Pattern Transformation in Swelling Gel Tubes by Elastic Instability

    E-print Network

    Lee, Howon

    We present a study on swelling-induced circumferential buckling of tubular shaped gels. Inhomogeneous stress develops as the gel swells under mechanical constraints, which gives rise to spontaneous buckling instability ...

  16. Practice guidelines for the application of nonsilicone or silicone gels and gel sheets after burn injury.

    PubMed

    Nedelec, Bernadette; Carter, Alissa; Forbes, Lisa; Hsu, Shu-Chuan Chen; McMahon, Margaret; Parry, Ingrid; Ryan, Colleen M; Serghiou, Michael A; Schneider, Jeffrey C; Sharp, Patricia A; de Oliveira, Ana; Boruff, Jill

    2015-01-01

    The objective of this review was to systematically evaluate available clinical evidence for the application of nonsilicone or silicone gels and gel sheets on hypertrophic scars and keloids after a burn injury so that practice guidelines could be proposed. This review provides evidence based recommendations, specifically for the rehabilitation interventions required for the treatment of aberrant wound healing after burn injury with gels or gel sheets. These guidelines are designed to assist all healthcare providers who are responsible for initiating and supporting scar management interventions prescribed for burn survivors. Summary recommendations were made after the literature, retrieved by systematic review, was critically appraised and the level of evidence determined according to Oxford Centre for Evidence-based Medicine criteria. PMID:25094007

  17. Synthetic and Biopolymer Gels - Similarities and Difference.

    NASA Astrophysics Data System (ADS)

    Horkay, Ferenc

    2006-03-01

    Ion exchange plays a central role in a variety of physiological processes, such as nerve excitation, muscle contraction and cell locomotion. Hydrogels can be used as model systems for identifying fundamental chemical and physical interactions that govern structure formation, phase transition, etc. in biopolymer systems. Polyelectrolyte gels are particularly well-suited to study ion-polymer interactions because their structure and physical-chemical properties (charge density, crosslink density, etc) can be carefully controlled. They are sensitive to different external stimuli such as temperature, ionic composition and pH. Surprisingly few investigations have been made on polyelectrolyte gels in salt solutions containing both monovalent and multivalent cations. We have developed an experimental approach that combines small angle neutron scattering and osmotic swelling pressure measurements. The osmotic pressure exerted on a macroscopic scale is a consequence of changes occurring at a molecular level. The intensity of the neutron scattering signal, which provides structural information as a function of spatial resolution, is directly related to the osmotic pressure. We have found a striking similarity in the scattering and osmotic behavior of polyacrylic acid gels and DNA gels swollen in nearly physiological salt solutions. Addition of calcium ions to both systems causes a sudden volume change. This volume transition, which occurs when the majority of the sodium counterions are replaced by calcium ions, is reversible. Such reversibility implies that the calcium ions are not strongly bound by the polyanion, but are free to move along the polymer chain, which allows these ions to form temporary bridges between negative charges on adjacent chains. Mechanical measurements reveal that the elastic modulus is practically unchanged in the calcium-containing gels, i.e., ion bridging is qualitatively different from covalent crosslinks.

  18. Structural evolution of colloidal silica gels to glass

    Microsoft Academic Search

    Jackie Y. Ying; Jay B. Benziger; Alexandra Navrotsky

    1993-01-01

    The gel-to-ceramic evolution of colloidal-derived silica gels was examined by thermal analysis, infrared photoacoustic spectroscopy, physical characteristic, and high-temperature calorimetry. Oxygen in the firing atmosphere promoted sintering of colloidal gels relative to firing in a nitrogen or argon atmosphere. Water vapor in the atmosphere promoted consolidation and crystallization to cristobalite. Addition of PVA to the colloidal gel resulted in consolidation

  19. DC Electrical Field Effects on Plant Tissues and Gels

    Microsoft Academic Search

    Amos Nussinovitch; Ronit Zvitov

    \\u000a Gels (intermediate between a solid and a liquid) have similarities to both animal and vegetative materials. Most food products\\u000a are solids composed of 50–90% water, and they can be regarded in many ways as multicomponent gels. Moreover, the cellular\\u000a structure of fruits and vegetables can be considered a “foam” with a closed-cell geometry, filled with gel. Gels are omnipresent,\\u000a and

  20. Influence of Environmental Conditions on Whey Protein Gels Properties and Gels Microstructure

    Microsoft Academic Search

    CUI Xu-hai; KONG Bao-hua

    Objective)The effects of ionic variety, ionic strength, heating temperature, pH value and protein concentration on texture properties,water-holding capacity and microstructure of whey protein gels were investigated. (Method)The influence of different concentrations of NaCl and CaCl2 on gels hardness, springiness and cohesiveness was studied by using TA-XT plus instrument, and the microstructure was observed with scanning electron microscopy (SEM). (Result) The

  1. Statistics for Analytical Chemistry

    NSDL National Science Digital Library

    Van Bramer, Scott E.

    This site provides a brief reference on statistics that both analytical faculty and students will find useful. The site includes a series of problem sets and supporting MathCAD spreadsheets. Materials available on the website can be downloaded as a pdf file.

  2. Nuclear analytical chemistry

    Microsoft Academic Search

    D. Brune; B. Forkman; B. Persson

    1984-01-01

    This book covers the general theories and techniques of nuclear chemical analysis, directed at applications in analytical chemistry, nuclear medicine, radiophysics, agriculture, environmental sciences, geological exploration, industrial process control, etc. The main principles of nuclear physics and nuclear detection on which the analysis is based are briefly outlined. An attempt is made to emphasise the fundamentals of activation analysis, detection

  3. Spectrum of analytic continuation

    E-print Network

    David V. Ingerman

    2008-06-03

    I will show that operator of analytic (harmonic) continuation on a lattice graph has a positive spectrum. I use a theorem about positivity of eigenvalues of totally positive matrices. I conjecture that by approximation the similar result holds in continuous case on a plane.

  4. FIELD ANALYTICAL METHODS GUIDANCE

    EPA Science Inventory

    The guidance outlines a strategy for dynamic work planning and on-site decision making so that EPA project managers can minimize the number of mobilizations that are involved in reaching site decisions. As part of this process, it describes how field-based analytical methods can...

  5. Flavonoids as Analytical Reagents

    Microsoft Academic Search

    Krystyna Pyrzynska; Anna P?kal

    2011-01-01

    Compounds from the flavonoid family, while exhibiting a wide range of biological effects, are interesting reagents for analytical purposes as well. They form complexes with several p-, d-, and f-electron metals, which could be employed in the determination of these metal ions in different kinds of samples by various techniques. This article presents and discusses the application of flavonoid compounds

  6. Correlation of Analytical Facilities

    Microsoft Academic Search

    Benjamin A. Moore

    1983-01-01

    New and emerging technologies such as VHSIC\\/VLSI and the expanded use of hybrids have presented a new series of problems in correlating analytical laboratory mass spectrometric moisture measurements. Standards and techniques, designed and tested for application in the more benign environment of smaller scale monolithic packaging, may not be directly applicable to new adsorption\\/desorption conditions and relatively large ( ¿lcc)

  7. Biosensors: Future Analytical Tools

    Microsoft Academic Search

    C S Pundir

    2007-01-01

    Biosensors offer considerable promises for attaining the analytic information in a faster, simpler and cheaper manner compared to conventional assays. Biosensing approach is rapidly advancing and applications ranging from metabolite, biological\\/ chemical warfare agent, food pathogens and adulterant detection to genetic screening and programmed drug delivery have been demonstrated. Innovative efforts, coupling micromachining and nanofabrication may lead to even more

  8. An analytical cache model

    Microsoft Academic Search

    Anant Agarwal; J. Hennessy; M. Horowitz

    1989-01-01

    Trace-driven simulation and hardware measurement are the techniques most often used to obtain accurate performance figures for caches. The former requires a large amount of simulation time to evaluate each cache configuration while the latter is restricted to measurements of existing caches. An analytical cache model that uses parameters extracted from address traces of programs can efficiently provide estimates of

  9. Analytics: Changing the Conversation

    ERIC Educational Resources Information Center

    Oblinger, Diana G.

    2013-01-01

    In this third and concluding discussion on analytics, the author notes that we live in an information culture. We are accustomed to having information instantly available and accessible, along with feedback and recommendations. We want to know what people think and like (or dislike). We want to know how we compare with "others like me."…

  10. HYBRID REGISTRATION FOR TWO-DIMENSIONAL GEL PROTEIN XIUYING WANG

    E-print Network

    Wong, Limsoon

    HYBRID REGISTRATION FOR TWO-DIMENSIONAL GEL PROTEIN IMAGES XIUYING WANG Biomedical and Multimedia of protein sequence data. But due to the elastic deformations of two-dimensional gel protein eletrophoresis images, their registration still remains a challenge. In this paper, a hybrid 2D gel protein image

  11. Formulation and method for preparing gels comprising hydrous aluminum oxide

    SciTech Connect

    Collins, Jack L.

    2014-06-17

    Formulations useful for preparing hydrous aluminum oxide gels contain a metal salt including aluminum, an organic base, and a complexing agent. Methods for preparing gels containing hydrous aluminum oxide include heating a formulation to a temperature sufficient to induce gel formation, where the formulation contains a metal salt including aluminum, an organic base, and a complexing agent.

  12. Formulation and method for preparing gels comprising hydrous hafnium oxide

    SciTech Connect

    Collins, Jack L; Hunt, Rodney D; Montgomery, Frederick C

    2013-08-06

    Formulations useful for preparing hydrous hafnium oxide gels contain a metal salt including hafnium, an acid, an organic base, and a complexing agent. Methods for preparing gels containing hydrous hafnium oxide include heating a formulation to a temperature sufficient to induce gel formation, where the formulation contains a metal salt including hafnium, an acid, an organic base, and a complexing agent.

  13. Formulation and method for preparing gels comprising hydrous cerium oxide

    DOEpatents

    Collins, Jack L; Chi, Anthony

    2013-05-07

    Formulations useful for preparing hydrous cerium oxide gels contain a metal salt including cerium, an organic base, and a complexing agent. Methods for preparing gels containing hydrous cerium oxide include heating a formulation to a temperature sufficient to induce gel formation, where the formulation contains a metal salt including cerium, an organic base, and a complexing agent.

  14. MECHANICAL PROPERTY CHARACTERIZATION OF SOL-GEL DERIVED NANOMATERIALS

    E-print Network

    Brinker, C. Jeffrey

    MECHANICAL PROPERTY CHARACTERIZATION OF SOL-GEL DERIVED NANOMATERIALS USING AN ACOUSTIC WAVE;#12;For my Terra........ iii #12;MECHANICAL PROPERTY CHARACTERIZATION OF SOL-GEL DERIVED NANOMATERIALS, New Mexico November 2006 #12;Mechanical Property Characterization of Sol-gel Derived Nanomaterials

  15. Mathematical modeling of swelling in high moisture whey protein gels

    Microsoft Academic Search

    Mecit H. Oztop; Kathryn L. McCarthy

    2011-01-01

    Gels prepared from whey proteins can be used for controlled release of nutrients or active ingredients in food systems. The objective of this study was to characterize the water uptake by these hydrophilic gels to aid in the design of release systems. Whey protein isolate (WPI) gels (17% w\\/w protein) of different aspect ratios were submersed in aqueous solution at

  16. Citric acid effect on aqueous sol–gel cordierite synthesis

    Microsoft Academic Search

    Celso A Bertran; Nidinalva T da Silva; Gilmar P Thim

    2000-01-01

    Cordierite was synthesized by a simple aqueous sol–gel route. Citric acid action as a chelant for the Al3+ ion, and for controlling phase segregation during the drying and initial thermal treatment of the gel, results in an amorphous precursor that crystallizes to ?-cordierite and spinel. The changes in the ratios of the crystalline phases, formed during dry gel calcination at

  17. Smart polymeric gels: Redefining the limits of biomedical devices

    Microsoft Academic Search

    Somali Chaterji; Il Keun Kwon

    2007-01-01

    This review describes recent progresses in the development and applications of smart polymeric gels, especially in the context of biomedical devices. The review has been organized into three separate sections: defining the basis of smart properties in polymeric gels; describing representative stimuli to which these gels respond; and illustrating a sample application area, namely, microfluidics. One of the major limitations

  18. A basic study of some normoxic polymer gel dosimeters

    Microsoft Academic Search

    Y. DeDeene; C. Hurley; A. Venning; K. Vergote; M. Mather; B. J. Healy; C. Baldock

    2002-01-01

    Polymer gel dosimeters offer a wide range of potential applications in the three-dimensional verification of complex dose distribution such as in intensity-modulated radiotherapy (IMRT). Until now, however, polymer gel dosimeters have not been widely used in the clinic. One of the reasons is that they are difficult to manufacture. As the polymerization in polymer gels is inhibited by oxygen, all

  19. Antimicrobial efficacy of alcohol-based hand gels.

    PubMed

    Guilhermetti, M; Marques Wiirzler, L A; Castanheira Facio, B; da Silva Furlan, M; Campo Meschial, W; Bronharo Tognim, M C; Botelho Garcia, L; Luiz Cardoso, C

    2010-03-01

    In recent years, several commercial alcohol-based hand gels have appeared on the market to improve the hand-cleansing compliance of healthcare workers. Although the antimicrobial efficacy of these products has been reported in different countries, few studies have investigated this subject in Brazil. In this study, we assessed the antimicrobial efficacy of 12 alcohol-based hand gels produced in Brazil, containing 70% w/w or v/v ethyl alcohol as the active ingredient, according to the European Standard EN 1500 (EN 1500). The following alcohol gels were tested: Hand Gel, Voga Gel, Solumax Solugel, Doctor Clean, Rio Gel, Clear Gel, Sevengel, Hand CHC, Gel Bac, WBL-50 Gel, Sanigel and Soft Care Gel. In addition, 70% w/w ethyl alcohol and three alcohol-based hand rubs (Sterillium, Sterillium Gel, and Spitaderm), commonly used in Europe and effective according to EN 1500, were also tested. All the products tested, except for two, were approved by the EN 1500 test protocol with a 60s application. The results confirmed the antimicrobial efficacy of the majority of the alcohol gels produced in Brazil for hand hygiene of healthcare workers. PMID:20061060

  20. Electrically Adjustable Thermotropic Windows Based on Polymer Gels

    Microsoft Academic Search

    Tamas Gyenes; Andras Szilagyi; Tunde Lohonyai; Miklos Zrõ ´ nyi

    Several attempts have been made recently in order to develop ''Smart'' windows, which can moderate light and heat intensities. Based upon the phase transitions of polymer gels, a novel electrically adjustable window, which includes a gel layer, has been developed in our laboratory. Unlike other electrically controlled struc- tures, the optical properties of the gel layer are abruptly modified by

  1. The Biochemistry and Mechanics of Gastropod Adhesive Gels

    Microsoft Academic Search

    Andrew M. Smith

    A wide variety of organisms attach to surfaces using gels as glues, but the mechanism by which a gel can form a strong attachment has only recently been studied in depth. The adhesive gels used by animals are unusual biomaterials. Their structure and properties are strikingly different from common commercial glues. Commercial glues are generally solids; they may be applied

  2. Split-face comparison of adapalene 0.1% gel and tretinoin 0.025% gel in acne patients

    Microsoft Academic Search

    Danièle Caron; Valérie Sorba; Nabil Kerrouche; Alan Clucas

    1997-01-01

    Background: Adapalene is a new naphthoic acid derivative developed for the topical treatment of acne vulgaris.Objective: We compared the skin tolerance of adapalene 0.1% gel with tretinoin 0.025% gel in subjects with acne.Methods: Fifteen acne patient volunteers were enrolled in this investigator-masked, left-right comparison, randomized, controlled, intraindividual study. Adapalene 0.1% gel and tretinoin 0.025% gel were applied once a day

  3. Evaluation of Gel Permeation Chromatography as an analytical tool for aspect cement testing

    E-print Network

    Holmgreen, Richard J

    1985-01-01

    both before and after service. Chromatograms of the asphalts after 4, 6 and 24 months of service were compared. The results showed that. differences in chemica I composition as reflected by GPC could be observed. The report noted the need for a test... effects and construction philosophies. The location of the three sections are shown in Figure 1 and described in Table 1. 4 Dumas 4 Dickens Lufkin Figure 1. Location of Aspha1t Cement Test Sections. Table l. Asphalts Used at the Various Field...

  4. Analysis and simulation of a model of polyelectrolyte gel in one spatial dimension

    NASA Astrophysics Data System (ADS)

    Chen, Haoran; Calderer, Maria-Carme; Mori, Yoichiro

    2014-06-01

    We analyse a model of polyelectrolyte gels that was proposed by the authors in previous work. We first demonstrate that the model can be derived using Onsager's variational principle, a general procedure for obtaining equations in soft condensed matter physics. The model is shown to have a unique steady state under the assumption that a suitably defined mechanical energy density satisfies a convexity condition. We then perform a detailed study of the stability of the steady state in the spatially one-dimensional case, obtaining bounds on the relaxation rate. Numerical simulations for the spatially one-dimensional problem are presented, confirming the analytical calculations on stability.

  5. Requirements for Predictive Analytics

    SciTech Connect

    Troy Hiltbrand

    2012-03-01

    It is important to have a clear understanding of how traditional Business Intelligence (BI) and analytics are different and how they fit together in optimizing organizational decision making. With tradition BI, activities are focused primarily on providing context to enhance a known set of information through aggregation, data cleansing and delivery mechanisms. As these organizations mature their BI ecosystems, they achieve a clearer picture of the key performance indicators signaling the relative health of their operations. Organizations that embark on activities surrounding predictive analytics and data mining go beyond simply presenting the data in a manner that will allow decisions makers to have a complete context around the information. These organizations generate models based on known information and then apply other organizational data against these models to reveal unknown information.

  6. Field Analytic Technologies Encyclopedia

    NSDL National Science Digital Library

    The US Environmental Protection Agency maintains the Field Analytic Technologies Encyclopedia Web site. The online encyclopedia is \\"intended to provide information about technologies that can be used in the field to characterize contaminated soil and groundwater, monitor progress of remedial efforts, and in some cases, for confirmation sampling and analysis for site close-out.\\" The technologies link contains information on analytics such as gas chromatography, mass spectrometry, and test kits; geophysics such as ground penetrating radar; and delivery systems including direct-push platforms, groundwater samplers, and soil-gas samplers. Other links include resources, references, and online training modules for field-based technologies. The site is a great informational resource and training aide for hazardous waste professionals working directly in the field.

  7. Avatars in Analytical Gaming

    SciTech Connect

    Cowell, Andrew J.; Cowell, Amanda K.

    2009-08-29

    This paper discusses the design and use of anthropomorphic computer characters as nonplayer characters (NPC’s) within analytical games. These new environments allow avatars to play a central role in supporting training and education goals instead of planning the supporting cast role. This new ‘science’ of gaming, driven by high-powered but inexpensive computers, dedicated graphics processors and realistic game engines, enables game developers to create learning and training opportunities on par with expensive real-world training scenarios. However, there needs to be care and attention placed on how avatars are represented and thus perceived. A taxonomy of non-verbal behavior is presented and its application to analytical gaming discussed.

  8. Comparison of the cumulative irritation potential of adapalene gel and cream with that of erythromycin\\/tretinoin solution and gel and erythromycin\\/isotretinoin gel

    Microsoft Academic Search

    Catherine Queille-Roussel; Michel Poncet; Stephane Mesaros; Alan Clucas; Michael Baker; Andrew-Marc Soloff

    2001-01-01

    Background: Adapalene is a naphthoic acid derivative with retinoid activity that is effective in the treatment of mild to moderate acne vulgaris.Objective: This study assessed the cumulative irritation potential of adapalene gel (0.1%) and adapalene cream (0.1%) compared with that of erythromycin (4%)\\/tretinoin (0.025%) solution, erythromycin (4%)\\/tretinoin (0.025%) gel, erythromycin (2%)\\/isotretinoin (0.05%) gel, and white petrolatum (negative control).Methods: This was

  9. Fabrication, modeling and optimization of an ionic polymer gel actuator

    NASA Astrophysics Data System (ADS)

    Jo, Choonghee; Naguib, Hani E.; Kwon, Roy H.

    2011-04-01

    The modeling of the electro-active behavior of ionic polymer gel is studied and the optimum conditions that maximize the deflection of the gel are investigated. The bending deformation of polymer gel under an electric field is formulated by using chemo-electro-mechanical parameters. In the modeling, swelling and shrinking phenomena due to the differences in ion concentration at the boundary between the gel and solution are considered prior to the application of an electric field, and then bending actuation is applied. As the driving force of swelling, shrinking and bending deformation, differential osmotic pressure at the boundary of the gel and solution is considered. From this behavior, the strain or deflection of the gel is calculated. To find the optimum design parameter settings (electric voltage, thickness of gel, concentration of polyion in the gel, ion concentration in the solution, and degree of cross-linking in the gel) for bending deformation, a nonlinear constrained optimization model is formulated. In the optimization model, a bending deflection equation of the gel is used as an objective function, and a range of decision variables and their relationships are used as constraint equations. Also, actuation experiments are conducted using poly(2-acrylamido-2-methylpropane sulfonic acid) (PAMPS) gel and the optimum conditions predicted by the proposed model have been verified by the experiments.

  10. Modelling of the inhomogeneous interior of polymer gels

    NASA Astrophysics Data System (ADS)

    Shew, Chwen-Yang; Iwaki, Takafumi

    2006-04-01

    A simple model has been investigated to elucidate the mean squared displacement (MSD) of probe molecules in cross-linked polymer gels. In the model, we assume that numerous cavities distribute in the inhomogeneous interior of a gel, and probe molecules are confined within these cavities. The individual probe molecules trapped in a gel are treated as Brownian particles confined to a spherical harmonic potential. The harmonic potential is chosen to model the effective potential experienced by the probe particle in the cavity of a gel. Each field strength is corresponding to the characteristic of one type of effective cavity. Since the statistical distribution of different effective cavity sizes is unknown, several distribution functions are examined. Meanwhile, the calculated averaged MSDs are compared to the experimental data by Nisato et al (2000 Phys. Rev. E 61 2879). We find that the theoretical results of the MSD are sensitive to the shape of the distribution function. For low cross-linked gels, the best fit is obtained when the interior cavities of a gel follow a bimodal distribution. Such a result may be attributed to the presence of at least two distinct classes of cavity in gels. For high cross-linked gels, the cavities in the gel can be depicted by a single-modal uniform distribution function, suggesting that the range of cavity sizes becomes smaller. These results manifest the voids inside a gel, and the shape of distribution functions may provide the insight into the inhomogeneous interior of a gel.

  11. Gel Encapsulation of Glucose Nanosensors for Prolonged In Vivo Lifetime

    PubMed Central

    Balaconis, Mary K.; Clark, Heather A.

    2013-01-01

    Background Fluorescent glucose-sensitive nanosensors have previously been used in vivo to track glucose concentration changes in interstitial fluid. However, this technology was limited because of loss of fluorescence intensity due to particle diffusion from the injection site. In this study, we encapsulated the nanosensors into injectable gels to mitigate nanosensor migration in vivo. Methods Glucose-sensitive nanosensors were encapsulated in two different commercially available gelling agents: gel 1 and gel 2. Multiple formulations of each gel were assessed in vitro for their nanosensor encapsulation efficiency, permeability to glucose, and nanosensor retention over time. The optimal formulation for each gel, as determined from the in vitro assessment, was then tested in mice, and the lifetime of the encapsulated nanosensors was compared with controls of nanosensors without gel. Results Five gel formulations had encapsulation efficiencies of the nanosensors greater than 90%. Additionally, they retained up to 20% and 40% of the nanosensors over 24 h for gel 1 and gel 2, respectively. In vivo, both gels prevented diffusion of glucose nanosensors at least three times greater than the controls. Conclusions Encapsulating glucose nanosensors in two injectable gels prolonged nanosensor lifetime in vivo; however, the lifetime must still be increased further to be applicable for diabetes monitoring. PMID:23439160

  12. Transaxillary endoscopic silicone gel breast augmentation.

    PubMed

    Strock, Louis L

    2010-09-01

    Following the return of silicone gel breast implants to the US market in 2006, augmentation with these implants has become increasingly popular. Surgeons have an array of refined techniques from which to choose when performing these procedures, many of which offer the advantage of reduced or less-obvious postoperative scarring. For obvious reasons, many patients are requesting placement of the implants through incisions that are removed from the breast area (and thereby hidden). The challenge of these approaches is to provide a level of technical control that matches what is afforded with the traditional inframammary approach. The addition of endoscopic assistance has provided a level of tissue visualization and technical control not previously possible with the transaxillary approach, with results that rival those of an inframammary procedure. In this article, the author presents his current operative technique, which has allowed for the routine placement of silicone gel breast implants through a transaxillary incision using endoscopic assistance. PMID:20884907

  13. Intermittent Dynamics in Aging Colloidal Gels

    NASA Astrophysics Data System (ADS)

    Bissig, Hugo; Cipelletti, Luca; Trappe, Veronique; Schurtenberger, Peter

    2003-03-01

    We present a study on the slow dynamics of strongly aggregated particle gels, which is investigated by means of Diffusing Wave Spectroscopy (DWS) using a Charge Coupled Device (CCD) camera as a multispeckle detector. Two different techniques are applied, the multispeckle method and a novel correlation scheme, Time Resolved Correlation (TRC). The latter scheme is introduced to obtain time-resolved information on the degree of correlation of the particle positions. We find that the intensity autocorrelation function measured by multispeckle DWS exhibits an ultraslow relaxation, whose characteristic time strongly depends on the age of the gel. An analysis of the TCR data reveals that the dynamics is intermittent. We propose that the intermittency is due to rare disruptions or formations of bonds affecting the elastic backbone of the network, which lead to sudden long range rearrangements of the particle position and thus to a sudden change of the speckle pattern.

  14. Structural Hierarchy Governs Fibrin Gel Mechanics

    PubMed Central

    Piechocka, Izabela K.; Bacabac, Rommel G.; Potters, Max; MacKintosh, Fred C.; Koenderink, Gijsje H.

    2010-01-01

    Abstract Fibrin gels are responsible for the mechanical strength of blood clots, which are among the most resilient protein materials in nature. Here we investigate the physical origin of this mechanical behavior by performing rheology measurements on reconstituted fibrin gels. We find that increasing levels of shear strain induce a succession of distinct elastic responses that reflect stretching processes on different length scales. We present a theoretical model that explains these observations in terms of the unique hierarchical architecture of the fibers. The fibers are bundles of semiflexible protofibrils that are loosely connected by flexible linker chains. This architecture makes the fibers 100-fold more flexible to bending than anticipated based on their large diameter. Moreover, in contrast with other biopolymers, fibrin fibers intrinsically stiffen when stretched. The resulting hierarchy of elastic regimes explains the incredible resilience of fibrin clots against large deformations. PMID:20483337

  15. Switching friction with thermal- responsive gels.

    PubMed

    Wu, Yang; Cai, Meirong; Pei, Xiaowei; Liang, Yongmin; Zhou, Feng

    2013-11-01

    The thermosensitive graphene oxide (GO)/poly(N-isopropyl acrylamide) (pNIPAM) composite hydrogels are prepared, and their tribological properties in response to external stimuli are evaluated. The frictional coefficient of the hydrogels is closely related to the gel composition and ambient temperature. When the gel is in swelling state below the low critical solution temperature (LCST), it shows ultra-low friction and exhibits high friction at a shrunk state above the LCST. The huge difference of frictional coefficient under two states can be reversibly switched many times by altering the temperature. The incorporation of a nonthermal sensitive monomer into pNIPAM could change the LCST and thus the transformation point of frictional coefficient can be altered. These reversible and tunable frictional hydrogels have potential application in the design of intelligent control equipment. PMID:24249089

  16. Competing on talent analytics.

    PubMed

    Davenport, Thomas H; Harris, Jeanne; Shapiro, Jeremy

    2010-10-01

    Do investments in your employees actually affect workforce performance? Who are your top performers? How can you empower and motivate other employees to excel? Leading-edge companies such as Google, Best Buy, Procter & Gamble, and Sysco use sophisticated data-collection technology and analysis to answer these questions, leveraging a range of analytics to improve the way they attract and retain talent, connect their employee data to business performance, differentiate themselves from competitors, and more. The authors present the six key ways in which companies track, analyze, and use data about their people-ranging from a simple baseline of metrics to monitor the organization's overall health to custom modeling for predicting future head count depending on various "what if" scenarios. They go on to show that companies competing on talent analytics manage data and technology at an enterprise level, support what analytical leaders do, choose realistic targets for analysis, and hire analysts with strong interpersonal skills as well as broad expertise. PMID:20929194

  17. MSc in Analytical Science Analytical Science: Methods and

    E-print Network

    Davies, Christopher

    underpin research and development in Materials, Environmental, Biological, Biomedical, and Pharmaceutical such as the life sciences (including pharmaceutical and environmental science), and materials science, and weAS:MIT MSc in Analytical Science Analytical Science: Methods and Instrumental Techniques Warwick

  18. Anion-switchable supramolecular gels for controlling pharmaceutical crystal growth

    NASA Astrophysics Data System (ADS)

    Foster, Jonathan A.; Piepenbrock, Marc-Oliver M.; Lloyd, Gareth O.; Clarke, Nigel; Howard, Judith A. K.; Steed, Jonathan W.

    2010-12-01

    We describe the use of low-molecular-weight supramolecular gels as media for the growth of molecular crystals. Growth of a range of crystals of organic compounds, including pharmaceuticals, was achieved in bis(urea) gels. Low-molecular-weight supramolecular gelators allow access to an unlimited range of solvent systems, in contrast to conventional aqueous gels such as gelatin and agarose. A detailed study of carbamazepine crystal growth in four different bis(urea) gelators, including a metallogelator, is reported. The crystallization of a range of other drug substances, namely sparfloxacin, piroxicam, theophylline, caffeine, ibuprofen, acetaminophen (paracetamol), sulindac and indomethacin, was also achieved in supramolecular gel media without co-crystal formation. In many cases, crystals can be conveniently recovered from the gels by using supramolecular anion-triggered gel dissolution; however, crystals of substances that themselves bind to anions are dissolved by them. Overall, supramolecular gel-phase crystallization offers an extremely versatile new tool in pharmaceutical polymorph screening.

  19. Ultrasensitive fluorescence detection of DNA sequencing gels

    SciTech Connect

    Mathies, R.A.

    1991-01-01

    During the three years of this grant we have: (1) Developed and applied a new theory for optimizing high-sensitivity fluorescence detection. (2) Developed and patented a new high-sensitivity confocal-fluorescence laser-excited gel-scanner. (3) Applied this scanner to the development of a new class of versatile and sensitive fluorescent dyes for DNA detection. (4) Developed methods for the detection of single fluorescent molecules by fluorescence burst detection. 11 refs., 10 figs.

  20. The gel route to transition metal oxides

    Microsoft Academic Search

    J. Livage

    1986-01-01

    The so-called ``sol-gel'' process offers new approaches to the synthesis of transition metal oxides. Based on inorganic polymerization from molecular precursors, it leads to highly condensed species or colloids. These colloids are actually two-phase systems in which small oxide particles are dispersed in a liquid medium. A very large interface separates both phases and interfacial phenomena, at the oxide-water interface,

  1. Sol-Gel Growth of Vanadium Dioxide

    Microsoft Academic Search

    Kenneth Richard Speck

    1990-01-01

    This thesis examines the chemical reactivity of vanadium (IV) tetrakis(t-butoxide) as a precursor for the sol-gel synthesis of vanadium dioxide. Hydrolysis and condensation of the alkoxide was studied by FTIR spectroscopy. Chemical modification of the vanadium tetraalkoxide by alcohol interchange was studied using ^{51}V NMR and FTIR. Vanadium dioxide thin films and powders were made from vanadium tetrakis(t-butoxide) by standard

  2. Electron Conducting and Magneto-Sensitive Gels

    Microsoft Academic Search

    Frédéric Fages

    Clearly, many applications of molecular gels from low molecular-mass organic gelators as electronic or magnetosensitive materials\\u000a can be envisioned. Yet, their potential has not been exploited thus far; the few examples are described in this chapter. Given\\u000a the recent advances in the systematic synthesis of organogelators, and relying on the creative imagination of chemists, it\\u000a seems highly probable that the

  3. Characterization of sol–gel-prepared nanoferrites

    Microsoft Academic Search

    M. K. Shobana; S. Sankar

    2009-01-01

    Spinel Co1?xMnxFe2O4 nanoparticles were prepared by the sol–gel combustion technique. X-ray diffraction (XRD), atomic force microscopy (AFM) and vibration sample magnetometer (VSM) studies have been carried out in order to understand the temperature dependence of their properties. It is observed that the high concentration of Mn2+ substituted into CoFe2O4 tends to reduce the particle size. Furthermore, the influence of Mn

  4. Hydrocolloid Gel Particles: Formation, Characterization, and Application

    Microsoft Academic Search

    P. Burey; B. R. Bhandari; T. Howes; M. J. Gidley

    2008-01-01

    Hydrocolloid gel particles of micron and sub-micron size are particularly attractive for use in many applications in the food, agricultural, pharmaceutical, and chemical industries, due to their biocompatibility, perception as “natural” materials, and soft-solid texture. Industrial applications for such particles include uses as texturizers in confectionery and cosmetic products, slow-release encapsulation agents for flavors, nutrients, and pharmaceutical products, and thickeners

  5. Gel structures in leached alkali silicate glass

    Microsoft Academic Search

    B. C. Bunker; T. J. Headley; S. C. Douglas

    1984-01-01

    Transmission electron microscopy of leached NaâO.3SiOâ and KâO.3SiOâ glasses showed that the hydrated glass surface is a silica rich gel which phase separates during leaching. Phase separation is initiated when pockets of an aqueous phase nucleate and grow in the hydrated silica matrix. The aqueous pockets eventually become a network of interconnected pores with a pore diameter of approx. 30

  6. Diffusion of polyelectrolytes in polyelectrolyte gels

    NASA Astrophysics Data System (ADS)

    Rahalkar, Anand; Muthukumar, Murugappan

    2015-03-01

    Using dynamic light scattering, we have investigated the diffusion coefficient of sodium poly(styrene sulfonate) in a matrix of poly(acrylamide-co-acrylate) gels. The diffusion coefficient of the probe polyelectrolyte exhibits a crossover behavior from a particle-diffusion to entropic-barrier dominated diffusion, as the molecular weight is increased. The effect of electrostatics, by varying the charge density of the matrix, on probe diffusion constant will be presented.

  7. [Intermediate moisture foods: polysaccharide and protein gels].

    PubMed

    Cheftel, C; Bousquet-Ricard, M; Quayle, G; Guilbert, S; Elguezabal, L; Masset, R

    1978-01-01

    The aim of this study was to prepare concentrated foods (20-40 p. 100 water), edible as such, chemically and microbiologically stable, nutritionally balanced, and which could be used as meal substitutes (travel, camping, snacks, etc.). With high methoxyl pectins, it was possible to obtain a pectic gel (pH 3,5), similar to a fruit jelly, but containing 20 p. 100 d.w. protein, and less sucrose. Water activity (Aw) was 0,75-0,78, for a 25 p. 100 water content, as a result of adding glucose syrup and sorbitol. After 4 months storage at 20 or 38 degrees C in aluminium pouches, no mold growth was detected (even following prior inoculation) nor practically any change in flavor, texture of Aw. With low methoxyl pectins, gel foods richer in water (35 p. 100), softer, less acid (pH 4,3) and containing even less sugars have been prepared (26 p. 100 d.w. protein, 35 p. 100 carbohydrates, 15 p. 100 lipids). Aw was lowered to 0,84 by adding humectants (sucrose, glycerol, sorbitol, citric acid, sodium citrate and chloride). Starch gels (40 p. 100 starch/d.w.), of pH less than 4,5, containing proteins and lipids, were flavored with vegetale powders. For 30 p. 100 water and with humectants, Aw was 0,84-0,88. The texture changes more or less favorably with time according to the nature of the starch used. Using the technology of processed cheeses, protein gels were made with either of the following characteristics: 1. A reduced Aw (0,86, for 38 p. 100 water) by adding humectants, but with a soft texture similar to that of a processed swiss cheese; 2. The same reduced Aw, with a starch content of 26 p. 100/d.w., and a harder texture, comparable to that of Emmenthal cheese. PMID:707935

  8. Tribological Behavior of Grafted Polymer Gel Nanocoatings

    Microsoft Academic Search

    D. Julthongpiput; Hyo-Sok Ahn; Doo-In Kim; V. V. Tsukruk

    2002-01-01

    A robust molecular lubrication layer on a silicon surface has been fabricated from a grafted polymer gel with thickness below 10 nm. A functionalized rubber-glassy block-copolymer was chemically grafted to a silicon oxide surface and its tribological performance was enhanced by vapor saturation with a minute amount of alkyl-based paraffinic oil. A combination of tribological measurements and Auger electron spectroscopy

  9. Polymer networks and gels: Simulation and theory

    Microsoft Academic Search

    Nirupama Ramamurthy Kenkare

    1998-01-01

    The purpose of this research is to understand the molecular origins of the dynamic and swelling properties of polymer networks and gels. Our approach has been to apply computer simulations techniques to off-lattice, near-perfect, trifunctional and tetrafunctional network models. The networks are constructed by endlinking freely-jointed, tangent-hard-sphere chains. Equilibrium discontinuous molecular dynamics techniques are employed to simulate the relaxation of

  10. Complex analytic geometry and analytic-geometric categories

    Microsoft Academic Search

    Ya'acov Peterzil; Sergei Starchenko

    2009-01-01

    The notion of a analytic-geometric category was introduced by v.d. Dries and Miller in (4). It is a category of subsets of real analytic manifolds which extends the category of subanalytic sets. This paper discusses connec- tions between the subanalytic category, or more generally analytic-geometric categories, and complex analytic geometry. The questions are of the following nature: We start with

  11. Bucky gel actuators optimization towards haptic applications

    NASA Astrophysics Data System (ADS)

    Bubak, Grzegorz; Ansaldo, Alberto; Ceseracciu, Luca; Hata, Kenji; Ricci, Davide

    2014-03-01

    An ideal plastic actuator for haptic applications should generate a relatively large displacement (minimum 0.2-0.6 mm, force (~50 mN/cm2) and a fast actuation response to the applied voltage. Although many different types of flexible, plastic actuators based on electroactive polymers (EAP) are currently under investigation, the ionic EAPs are the only ones that can be operated at low voltage. This property makes them suitable for applications that require inherently safe actuators. Among the ionic EAPs, bucky gel based actuators are very promising. Bucky gel is a physical gel made by grounding imidazolium ionic liquids with carbon nanotubes, which can then be incorporated in a polymeric composite matrix to prepare the active electrode layers of linear and bending actuators. Anyhow, many conflicting factors have to be balanced to obtain required performance. In order to produce high force a large stiffness is preferable but this limits the displacement. Moreover, the bigger the active electrode the larger the force. However the thicker an actuator is, the slower the charging process becomes (it is diffusion limited). In order to increase the charging speed a thin electrolyte would be desirable, but this increases the probability of pinholes and device failure. In this paper we will present how different approaches in electrolyte and electrode preparation influence actuator performance and properties taking particularly into account the device ionic conductivity (which influences the charging speed) and the electrode surface resistance (which influences both the recruitment of the whole actuator length and its speed).

  12. State of water in gelatin Gels

    SciTech Connect

    Naryshkina, E.P.; Izmailova, V.N.; Polinnyi, A.I.

    1986-03-01

    It has been shown on the basis of the variation of the linewidth of water with time in high-resolution NMR spectra of gelatin gels in D/sub 2/O that there is a decrease in the mobility of the water molecules during the formation of the collagen-like helix in the initial stages of gelation. As the concentration of the protein is increased, the linewidth of the water signal ..delta.. increases, and the spin-spin (T/sub 2/) and spin-lattice (T/sub 1/) relaxation times and the self-diffusion coefficient of the water molecules D /SUB S/ in the fully formed gels of gelatin in H/sub 2/O decreases as a result of the immobilization of water by the gelatin macromolecules and the presence of a three-dimensional gel network. The aforementioned parameters vary as a function of the gelatin concentration in parallel with the value of the Flory-Huggins parameter /CHI/.

  13. Highly-correlated charges in polyelectrolyte gels

    NASA Astrophysics Data System (ADS)

    Sing, Charles; Zwanikken, Johannes; Olvera de La Cruz, Monica

    2013-03-01

    Polyelectrolyte gels are ubiquitous in polymer physics due to their attractive combination of structural and chemical features that permit the realization of ``environmentally responsive'' systems. The conventional conceptual picture of the volume response of these systems is based on a competition between osmotic and elastic effects. We elaborate on this fundamental understanding by including ion correlations through the use of liquid-state integral equation theory. This allows for a statistical mechanical representation of the state of the system that not only surpasses traditional Poisson-Boltzmann theories but also renders structural features in a highly accurate fashion. In particular, the local ion structure is elucidated, allowing for detailed articulation of charge inversion and condensation effects in the context of gel swelling. The inclusion of correlations has a number of ramifications that become apparent, with enhanced gel collapse and excluded volume competitions that give rise to novel and ion-dependent reentrant swelling effects. We expect this rigorous theory to prove instructive in understanding any number of gelated structures, such as chromosomes or designed synthetic materials for drug delivery.

  14. Scaling anomalies in the sol–gel transition

    NASA Astrophysics Data System (ADS)

    Leyvraz, F.; Lushnikov, A. A.

    2015-05-01

    Coagulating systems are characterized by the fact that aggregates of masses g and l react irreversibly to form a larger aggregate of mass g+l. The reaction rates K(g,l) for this process are assumed to depend only on the particle masses. This model is described by the corresponding kinetic equations. If the K(g,l) are assumed to grow fast enough, it happens that, at some finite time tc, a fraction of the mass goes into a cluster of infinite size. Near and at the gel time, the mass spectrum cg(t) can be described in scaling terms, that is, there exists a divergent typical mass in terms of which the spectrum can be expressed, as well as two exponents describing the g-dependence of the mass spectrum. These exponents have been extensively studied, both numerically and in terms of the case in which K(g,l)=gl, which is exactly solvable. So far, the exact model strongly suggested the validity of certain general expressions for these exponents in terms of the homogeneity degree of the K(g,l). These, however, were not confirmed numerically. In the following, we study the exact model in the case in which the initial conditions display an algebraic tail, and show that, in this case, the scaling exponents can be calculated analytically and do not conform to the expressions initially suggested.

  15. Responsive Gel-Gel Phase Transitions in Artificially Engineered Protein Hydrogels

    NASA Astrophysics Data System (ADS)

    Olsen, B. D.

    2012-02-01

    Artificially engineered protein hydrogels provide an attractive platform for biomedical materials due to their similarity to components of the native extracellular matrix. Engineering responsive transitions between shear-thinning and tough gel phases in these materials could potentially enable gels that are both shear-thinning and tough to be produced as novel injectable biomaterials. To engineer a gel with such transitions, a triblock copolymer with thermoresponsive polymer endblocks and an artificially engineered protein gel midblock is designed. Temperature is used to trigger a transition from a single network protein hydrogel phase to a double network phase with both protein and block copolymer networks present at different length scales. The thermodynamics of network formation and resulting structural changes are established using small-angle scattering, birefringence, and dynamic scanning calorimetry. The formation of the second network is shown to produce a large, nonlinear increase in the elastic modulus as well as enhancements in creep compliance and toughness. Although the gels show yielding behavior in both the single and double network regimes, a qualitative change in the deformation mechanism is observed due to the structural changes.

  16. Time-dependent gel to gel transformation of a peptide based supramolecular gelator.

    PubMed

    Baral, Abhishek; Basak, Shibaji; Basu, Kingshuk; Dehsorkhi, Ashkan; Hamley, Ian W; Banerjee, Arindam

    2015-06-28

    A dipeptide with a long fatty acid chain at its N-terminus gives hydrogels in phosphate buffer in the pH range 7.0-8.5. The hydrogel with a gelator concentration of 0.45% (w/v) at pH 7.46 (physiological pH) provides a very good platform to study dynamic changes within a supramolecular framework as it exhibits remarkable change in its appearance with time. Interestingly, the first formed transparent hydrogel gradually transforms into a turbid gel within 2 days. These two forms of the hydrogel have been thoroughly investigated by using small angle X-ray scattering (SAXS), powder X-ray diffraction (PXRD), field emission scanning electron microscopic (FE-SEM) and high-resolution transmission electron microscopic (HR-TEM) imaging, FT-IR and rheometric analyses. The SAXS and low angle PXRD studies substantiate different packing arrangements for the gelator molecules for these two different gel states (the freshly prepared and the aged hydrogel). Moreover, rheological studies of these two gels reveal that the aged gel is stiffer than the freshly prepared gel. PMID:26016677

  17. Vanguard-rearguard analytical strategies

    Microsoft Academic Search

    M. Valcárcel; S. Cárdenas

    2005-01-01

    The increasing demands for (bio)chemical information to contribute to solving environmental, health, food, industrial problems will promote important changes in analytical laboratories that should be supported by analytical research and development, and innovation (R&D&I). In this paper, we propose a new strategy: the sequential use of rapid, low-cost vanguard analytical systems and more accurate, rearguard analytical systems, including off-line, on-line

  18. Isoelectric focusing of human von Willebrand factor in urea-agarose gels

    SciTech Connect

    Fulcher, C.A.; Ruggeri, Z.M.; Zimmerman, T.S.

    1983-02-01

    An analytical technique has been developed for the isoelectric focusing (IEF) of plasma von Willebrand factor (vWF) in agarose gels containing urea. Under these conditions, vWF freely enters the gel and focuses without artifact. The focused vWF is visualized by staining fixed gels with /sup 125/I-labeled affinity-purified heterologous antibody. Utilizing a pH gradient of 5.0-6.5, normal vWF in plasma or purified preparations focuses into at least three bands with apparent isoelectric points (pI) between pH 5.7 and 5.9. A reproducible difference in the IEF pattern of vWF has been established between normal plasmas and those of individuals with variant von Willebrand's disease (vWd) type IIA and type IIB. In type IIA, vWF has a distinctly lower pI than normal. This difference may be related to the presence of smaller vWF multimers in IIA plasma because forms of vWF of corresponding size contained in normal cryoprecipitate supernatant have a similar pI. Type IIB von Willebrand factor has a pI intermediate between normal and IIA. Neuraminidase treatment of plasma samples before IEF results in an increase in pI in normal, type IIA, and type IIB vWF. The data suggest that none of the 16 type IIA and 9 IIB plasmas studied here contain significantly decreased amounts of sialic acid.

  19. Mechanical characterization of soft viscoelastic gels via indentation and optimization-based inverse finite element analysis.

    PubMed

    Liu, Kaifeng; VanLandingham, Mark R; Ovaert, Timothy C

    2009-08-01

    Polymer gels are widely accepted as candidate materials for tissue engineering, drug delivery, and orthopedic load-bearing applications. In addition, their mechanical and physical properties can be tailored to meet a wide range of design requirements. For soft gels whose elastic modulus is in the kPa range, mechanical characterization by bulk mechanical testing methods presents challenges, for example, in sample preparation, fixture design, gripping, and/or load measurement accuracy. Nanoindentation, however, has advantages when characterizing the mechanical properties of soft materials. This study was aimed at investigating the application of an inverse finite element analysis technique to identify material parameters of polymer gels via nanoindentation creep testing, optimization, and finite element simulation. Nanoindentation experiments were conducted using a rigid circular flat punch, and then simulated using the commercial software ABAQUS. The optimization (error minimization) procedure was integrated in the parameter determination process using a Matlab shell program, which makes this approach readily adaptable to other test geometries and material models. The finite element results compare well with a derived analytical viscoelastic solution for a rigid circular flat punch on a Kelvin-Voigt half-space. PMID:19627842

  20. Chiral separation of FITC-labeled amino acids with gel electrochromatography using a polydimethylsiloxane microfluidic device.

    PubMed

    Zeng, Hu-Lie; Li, Haifang; Wang, Xu; Lin, Jin-Ming

    2007-01-01

    A chiral separation model of gel electrochromatography in a polydimethylsiloxane (PDMS) microfluidic device for amino acids (AAs) is presented. Six pairs of fluorescein isothiocyanate (FITC)-labeled dansyl amino acids (Dns-AAs) were separated in a 36-mm effectual separation channel in less than 120 sec, with resolutions all above 0.96. This highly efficient PDMS chiral microfluidic chip was prepared by inserting the mixture solution of monomers, crosslinkers, and radical initiation into the microchannel via syringe. Specifically, allyl-gamma-cyclodextrin (CD) as a chiral selector and crosslinker was bonded in gamma-CD-bonded polyacrylamide (PAA) gel, which was the separation media, and was immobilized in a PDMS microchannel through the stable linkage of 3-(trimethoxysilyl)-propyl methacrylate (Bind-Silane, Sigma, St. Louis, MO, U.S.A.). The preparation not only permitted the prompt chiral separation of AAs, but also extended application of the PDMS microfluidic device by restraining its hydrophobicity through the PAA gel monolithic column. Furthermore, the longevity of the PDMS microfluidic device was prolonged significantly. This can also be a powerful way to develop a rapid and efficient bioanalysis method and portable analytical apparatus. PMID:17685238

  1. Dispersion functions and factors that determine resolution for DNA sequencing by gel electrophoresis

    SciTech Connect

    Sutherland, J.C.; Reynolds, K.J.; Fisk, D.J.

    1996-04-01

    The number of bases that can be read in a single run by a DNA sequencing instrument that detects fluorophore labeled DNA arriving at a ``finish-line`` located a fixed distance from the starting wells is influenced by numerous parameters. Strategies for improving the length-of-read of a DNA sequencer can be based on quantitative models of the separation of DNA by gel electrophoresis. The dispersion function of the electrophoretic system--the relationship between molecular contour length and time of arrival at the detector--is useful in characterizing the performance of a DNA sequencer. We adapted analytical representations of dispersion functions, originally developed for snapshot imaging of DNA gels, (samples electrophoresed for constant time), to finish-line imaging, and demonstrated that a logistic-type function with non-integral exponent is required to describe the experimental data. We use this dispersion function to determine the resolution length and resolving power of a LI-COR DNA sequencing system and a custom built capillary gel electrophoresis system, and discuss the factors that presently limit the number of bases that can be determined reliably in a single sequencing run.

  2. New possibilities of accurate particle characterisation by applying direct boundary models to analytical centrifugation.

    PubMed

    Walter, Johannes; Thajudeen, Thaseem; Süss, Sebastian; Segets, Doris; Peukert, Wolfgang

    2015-04-21

    Analytical centrifugation (AC) is a powerful technique for the characterisation of nanoparticles in colloidal systems. As a direct and absolute technique it requires no calibration or measurements of standards. Moreover, it offers simple experimental design and handling, high sample throughput as well as moderate investment costs. However, the full potential of AC for nanoparticle size analysis requires the development of powerful data analysis techniques. In this study we show how the application of direct boundary models to AC data opens up new possibilities in particle characterisation. An accurate analysis method, successfully applied to sedimentation data obtained by analytical ultracentrifugation (AUC) in the past, was used for the first time in analysing AC data. Unlike traditional data evaluation routines for AC using a designated number of radial positions or scans, direct boundary models consider the complete sedimentation boundary, which results in significantly better statistics. We demonstrate that meniscus fitting, as well as the correction of radius and time invariant noise significantly improves the signal-to-noise ratio and prevents the occurrence of false positives due to optical artefacts. Moreover, hydrodynamic non-ideality can be assessed by the residuals obtained from the analysis. The sedimentation coefficient distributions obtained by AC are in excellent agreement with the results from AUC. Brownian dynamics simulations were used to generate numerical sedimentation data to study the influence of diffusion on the obtained distributions. Our approach is further validated using polystyrene and silica nanoparticles. In particular, we demonstrate the strength of AC for analysing multimodal distributions by means of gold nanoparticles. PMID:25789666

  3. Dosimetry in HDR brachytherapy with Fricke-gel layers and Fricke-gel catheters

    NASA Astrophysics Data System (ADS)

    Gambarini, G.; Carrara, M.; Negri, A.; Invernizzi, M.; Tenconi, C.; Scotti, A.; Pirola, L.; Borroni, M.; Tomatis, S.; Fallai, C.

    2010-11-01

    Fricke-gel layer dosimeters (FGLD) and Fricke gel dosimetric catheters (FGDC) have been designed and tested with the aim of enquiring their suitability for HDR 192Ir brachytherapy source control and for in-vivo dose verification during treatment. Anisotropy function measurements have been carried out with FGLDs in which a thin plastic tube has been placed in for the 192Ir source insertion. FGDCs are constituted by plastic tubes (3 mm of external diameter and 13 cm of length) filled with the dosimeter-gel. Absorbed dose images and profiles were attained by means of optical analysis. Dedicated software has been developed both for achieving anisotropy function values and for obtaining reliable results in visible light absorbance measurements across the thin cylindrical dosimeters. Preparation and analysis procedures have been optimised. The results confirm that the proposed methods are very promising for HDR brachytherapy dosimetry.

  4. Quality Indicators for Learning Analytics

    ERIC Educational Resources Information Center

    Scheffel, Maren; Drachsler, Hendrik; Stoyanov, Slavi; Specht, Marcus

    2014-01-01

    This article proposes a framework of quality indicators for learning analytics that aims to standardise the evaluation of learning analytics tools and to provide a mean to capture evidence for the impact of learning analytics on educational practices in a standardised manner. The criteria of the framework and its quality indicators are based on…

  5. Self-oscillating surface of gel for autonomous mass transport.

    PubMed

    Yoshida, Ryo; Murase, Yoko

    2012-11-01

    As a novel biomimetic gels deffering from conventonal stimuli-responsive polymer gels, we have developed a "self-oscillating" gel that swells and deswells periodically under constant condition without on-off switching of external stimuli. The gel is composed of poly(N-isopropylacrylamide) to which the catalyst of the oscillating chemical reaction, called Belousov-Zhabotinsky reaction, is covalently immobilized. The chemical oscillation is converted to the mechanical oscillation of the gel through the change in hydrophilicity of polymer chains with the redox changes of the immobilized catalyst. By utilizing the self-oscillating gel, several kinds of functional material systems such as biomimetic actuators, etc. are expected. Here we review a potential application to functional surface to realize autonomous mass-transport by utilizing the peristaltic motion of the gel. With the propagation of the chemical wave, the loaded cargo is autonomously transported on the surface. In order to fabricate the self-driven gel conveyer for a wider use including biomedical applications, the interactions between the self-oscillating gel and the loaded gel cargo were investigated and their influence on the transport phenomena were evaluated. PMID:22019050

  6. Vaginal deployment and tenofovir delivery by microbicide gels.

    PubMed

    Gao, Y; Yuan, A; Chuchuen, O; Ham, A; Yang, K H; Katz, D F

    2015-06-01

    Gels are one of the soft material platforms being evaluated to deliver topically acting anti-HIV drugs (microbicides) to the vaginal environment. For each drug, its loaded concentration, gel properties and applied volume, and frequency of dosing can be designed to optimize PK and, thence, PD. These factors also impact user sensory perceptions and acceptability. Deterministic compartmental modeling of vaginal deployment and drug delivery achieved by test gels can help delineate how multiple parameters characterizing drug, vehicle, vaginal environment, and dosing govern details of PK and PD and also gel leakage from the canal. Such microbicide delivery is a transport process combining convection, e.g., from gel spreading along the vaginal canal, with drug diffusion in multiple compartments, including gel, mucosal epithelium, and stroma. The present work builds upon prior models of gel coating flows and drug diffusion (without convection) in the vaginal environment. It combines and extends these initial approaches in several key ways, including: (1) linking convective drug transport due to gel spreading with drug diffusion and (2) accounting for natural variations in dimensions of the canal and the site of gel placement therein. Results are obtained for a leading microbicide drug, tenofovir, delivered by three prototype microbicide gels, with a range of rheological properties. The model includes phosphorylation of tenofovir to tenofovir diphosphate (which manifests reverse transcriptase activity in host cells), the stromal concentration distributions of which are related to reference prophylactic values against HIV. This yields a computed summary measure related to gel protection ("percent protected"). Analyses illustrate tradeoffs amongst gel properties, drug loading, volume and site of placement, and vaginal dimensions, in the time and space history of gel distribution and tenofovir transport to sites of its anti-HIV action and concentrations and potential prophylactic actions of tenofovir diphosphate therein. PMID:25874971

  7. A mathematical characterization of the gel point in sol-gel transition

    NASA Astrophysics Data System (ADS)

    Bilge, A. H.; Pekcan, O.

    2015-01-01

    We model the sol-gel transition in terms of Susceptible-Infected-Removed (SIR) and Susceptible-Exposed-Infected-Removed (SEIR) models and compare with experimental results. We show, numerically, that the "gel point" described as the onset of the gelation phenomena and measured experimentally, corresponds to an accumulation point of the extreme values of the derivatives of the gelation curve. We define the "critical point of a sigmoidal curve" as the limit of the points where the derivatives reach their extreme values, provided that this limit exists.

  8. Nonlinear elasticity and cavitation of a triblock copolymer gel.

    PubMed

    Hashemnejad, Seyed Meysam; Kundu, Santanu

    2015-05-20

    Polymer gels are subjected to large-strain deformation during their applications. The gel deformation at large-strain is non-linear and can often lead to failure of the material. Here, we report the large-strain deformation behavior of a physically cross-linked, swollen triblock copolymer gel, which displays unique strain-stiffening response at large-strain. Investigations were performed using large amplitude oscillatory shear (LAOS) and custom developed cavitation rheology techniques. The Gent constitutive equation, which considers finite extensibility of midblock, was fitted with the LAOS data, thereby, linking the estimated parameters from LAOS analysis to the structure of the gel. The pressure responses obtained from the cavitation experiments were modeled using neo-Hookean and Gent constitutive equations. Our results capture the failure behavior of a gel with finite chain extensibility, initiated from a defect within the gel. PMID:25915797

  9. Hybrid slab-microchannel gel electrophoresis system

    DOEpatents

    Balch, Joseph W. (Livermore, CA); Carrano, Anthony V. (Livermore, CA); Davidson, James C. (Livermore, CA); Koo, Jackson C. (San Ramon, CA)

    1998-01-01

    A hybrid slab-microchannel gel electrophoresis system. The hybrid system permits the fabrication of isolated microchannels for biomolecule separations without imposing the constraint of a totally sealed system. The hybrid system is reusable and ultimately much simpler and less costly to manufacture than a closed channel plate system. The hybrid system incorporates a microslab portion of the separation medium above the microchannels, thus at least substantially reducing the possibility of non-uniform field distribution and breakdown due to uncontrollable leakage. A microslab of the sieving matrix is built into the system by using plastic spacer materials and is used to uniformly couple the top plate with the bottom microchannel plate.

  10. Polymethacrylate Microparticles Gel for Topical Drug Delivery

    Microsoft Academic Search

    Hagar Ibrahim Labouta; Labiba K. El-Khordagui

    2010-01-01

    Purpose  Evaluating the potentials of particulate delivery systems in topical drug delivery.\\u000a \\u000a \\u000a \\u000a Methods  Polymethacrylate microparticles (MPs) incorporating verapamil hydrochloride (VRP) as a model hydrophilic drug with potential\\u000a topical clinical uses, using Eudragit RS100 and Eudragit L100 were prepared for the formulation of a composite topical gel.\\u000a The effect of initial drug loading, polymer composition, particularly the proportion of Eudragit L100 as an

  11. Lavender fragrance cleansing gel effects on relaxation.

    PubMed

    Field, Tiffany; Diego, Miguel; Hernandez-Reif, Maria; Cisneros, Wendy; Feijo, Larissa; Vera, Yanexy; Gil, Karla; Grina, Diana; Claire He, Qing

    2005-02-01

    Alertness, mood, and math computations were assessed in 11 healthy adults who sniffed a cosmetic cleansing gel with lavender floral blend aroma, developed to be relaxing using Mood Mapping. EEG patterns and heart rate were also recorded before, during, and after the aroma session. The lavender fragrance blend had a significant transient effect of improving mood, making people feel more relaxed, and performing the math computation faster. The self-report and physiological data are consistent with relaxation profiles during other sensory stimuli such as massage and music, as reported in the literature. The data suggest that a specific cosmetic fragrance can have a significant role in enhancing relaxation. PMID:15764002

  12. Klutts 4/2004 Coomassie Staining of Protein Gels

    E-print Network

    Doering, Tamara

    Klutts 4/2004 1 Coomassie Staining of Protein Gels Overview: The laboratory typically uses the Bio if you are staining a gel with a lot of protein, as it is not quite as sensitive on re-use. 3. You canRad catalog number 161-0786. Bio-Safe Coomassie: 1. Wash your gel for 10 minutes in water to remove SDS

  13. Investigation of chemo-mechanical actuation in polymer gels

    Microsoft Academic Search

    Salvador Enrique Lobato Larios

    2009-01-01

    The objective of this thesis is to investigate chemically – driven gel actuators and their usefulness to perform mechanical work. The thesis work has mainly concentrated on chitosan as the gel actuator material. Chitosan is a widely used biopolymer that shows a large volume transition through changing pH. \\u0009 The pH induced actuation behaviour of polymer gels makes these materials analogous

  14. Performance of electric double layer capacitors with polymer gel electrolytes

    Microsoft Academic Search

    Masashi Ishikawa; Takahiro Kishino; Naoji Katada; Masayuki Morita

    2000-01-01

    Polymer gel electrolytes consisting of poly(vinylidene fluoride) (PVdF), tetraethylammonium tetrafluoroborate (TEABF), and propylene carbonate (PC) as a plasticizer have been investigated for electric double layer capacitors. The PVdF gel electrolytes showed high ionic conductivity (ca. 6 mS\\/cm at 298 K). To assemble model capacitors with the PVdF gel electrolytes and activated carbon fiber cloth electrodes, a pair of the fixed

  15. Anion-switchable supramolecular gels for controlling pharmaceutical crystal growth

    Microsoft Academic Search

    Jonathan A. Foster; Marc-Oliver M. Piepenbrock; Gareth O. Lloyd; Nigel Clarke; Judith A. K. Howard; Jonathan W. Steed

    2010-01-01

    We describe the use of low-molecular-weight supramolecular gels as media for the growth of molecular crystals. Growth of a range of crystals of organic compounds, including pharmaceuticals, was achieved in bis(urea) gels. Low-molecular-weight supramolecular gelators allow access to an unlimited range of solvent systems, in contrast to conventional aqueous gels such as gelatin and agarose. A detailed study of carbamazepine

  16. Augmentation of glans penis using injectable hyaluronic acid gel

    Microsoft Academic Search

    DG Moon; TI Kwak; HY Cho; JH Bae; JJ Kim

    2003-01-01

    Recently, injectable hyaluronic acid gel has been widely used in soft-tissue augmentation. We performed this study to identify the feasibility of hyaluronic acid gel for the augmentation of the glans penis. In experiment I, 0.2 cm3 of hyaluronic acid gel (HA) was injected into the dermis of the glans penis of 25 New Zealand white rabbits via a 30 G

  17. Whey protein concentrate gels with honey and wheat flour

    Microsoft Academic Search

    Diego K. Yamul; Cecilia E. Lupano

    2005-01-01

    Structural and functional properties of whey protein concentrate (WPC) gels with different honey and wheat flour contents, prepared at pHs 3.75, 4.2 and 7.0, were analysed. Gel structure was observed by scanning electron microscopy. The apparent transition temperatures for protein denaturation and starch gelatinization were determined by differential scanning calorimetry. Gels were characterised through solubility assays in different extraction solutions

  18. Swelling and dissolution in cleaning of whey protein gels

    Microsoft Academic Search

    P. Saikhwan; R. Mercadé-Prieto; Y. M. J. Chew; S. Gunasekaran; W. R. Paterson; D. I. Wilson

    2010-01-01

    Fluid dynamic gauging was used to study swelling and dissolution, under alkaline conditions, of heat-induced gels prepared from solutions of ?-lactoglobulin (?Lg), a whey protein isolate and whey protein concentrate. Recent developments in the understanding of the cleaning behaviour of proteinaceous dairy foulant, obtained using heat-induced ?Lg gels, are summarised. The thickness-time profiles for ?Lg gels exhibited Fickian behaviour, whilst

  19. Cold-Set Whey Protein Gels with Addition of Polysaccharides

    Microsoft Academic Search

    Ângelo Luiz Fazani Cavallieri; Rosiane Lopes Cunha

    2009-01-01

    Cold-set whey protein (WP) gels with addition of xanthan or guar were evaluated by mechanical properties and scanning electron\\u000a microscopy. Gels were formed after the addition of different amounts of glucono-?-lactone to thermally denatured WP solutions,\\u000a leading to different acidification rates and final pH values. At lower acidification rates and higher final pH, gels showed\\u000a more discontinuous structure and weaker

  20. Dielectric breakdown strength of silicone gel under various environmental conditions

    Microsoft Academic Search

    G. Finis; A. Claudi; G. Malin

    2005-01-01

    Silicone gel belongs to the group of RTV-2 silicone rubbers, which are room-temperature-vulcanizable materials consisting of two components. The material combines the advantages of the electrical and chemical properties of silicones with the unique mechanical properties of gels. The attempt to use silicone gel as insulation material in long-term stable and reliable medium voltage applications, e.g. as insulation material for

  1. Recent advances in gel-based proteome profiling techniques

    Microsoft Academic Search

    Yi Hu; Xuan Huang; Grace Y. J. Chen; Shao Q. Yao

    2004-01-01

    This review focuses on recent developments in gel-based proteomics techniques. By combining traditional sodium dodecyl sulfate-polyacrylamide\\u000a gel electrophoresis (SDS-PAGE) and two-dimensional gel electrophoretic techniques with recent advances in protein labeling\\u000a using different classes of molecules (i.e., fluorescent dyes, chemical probes, radioisotopes), new technologies have been\\u000a developed that allow for high-throughput studies of proteins at the whole-proteome scale.

  2. Lithium borate gel films prepared from aqueous solution

    Microsoft Academic Search

    J. D. Hemry; M. C. Weinberg; D. R. Uhlmann

    1998-01-01

    Transparent, durable films of lithium diborate gel can easily be prepared on a variety of substrates from supersaturated aqueous solutions of lithium hydroxide monohydrate and boric acid by spin-coating. The gel to dried gel to glass to crystalline lithium tetraborate (Li2B4O7) transformation has been studied by infrared spectroscopy of thin films cast on potassium bromide windows. Examination by scanning electron

  3. Gel synthesis and crystallization of lithium-germanate glass powders

    Microsoft Academic Search

    A. Marotta; P. Pernice; A. Aronne; M. Catauro

    1994-01-01

    Lithium germanate gels, whose compositions are expressed by the general formula Li2O·xGeO2 with x=3; 4; 7, were synthesized by hydrolytic polycondensation of germanium ethoxide with lithium methoxide (x=3 and 7) or lithium hydroxide monohydrate (x=4) in alcoholic medium. The values of glass transition temperature of the gels exhibit a maximum at x=4. Crystallization behaviour of the gels, examined by differential

  4. Synthesis of silica glass using solventless sol-gel process

    Microsoft Academic Search

    Kun-Hong Lee; Yung-Pyo Koh; Jae-Gon Lim

    1994-01-01

    Silica glass was synthesized form TEOS and deionized water using sol-gel process. To introduce the physicochemical effects of ultrasonic waves, an ultrasonic homogenizer was used to mix reactants instead of adding cosolvents. 2-step method was chosen to separate hydrolysis reaction and condensation reaction, and thus to control the microstructure of wet gels. Wet gels were dried in 5–8 hours without

  5. Beating polymer gels coupled with a nonlinear chemical reaction

    Microsoft Academic Search

    Ryo Yoshida; Etsuo Kokufuta; Tomohiko Yamaguchi

    1999-01-01

    We report on a beating polymer gel that exhibits periodical volume changes (swelling and deswelling) in a closed solution without external stimuli, like autonomous heartbeat. The mechanical oscillation is driven by the chemical energy of the oscillatory Belousov-Zhabotinsky (BZ) reaction. The gel is a copolymer gel of N-isopropylacrylamide (NIPAAm) in which ruthenium tris(2,2'-bipyridine) [Ru(bpy)3], known as a catalyst of the

  6. Effects of lecithin on thermally induced whey protein isolate gels

    Microsoft Academic Search

    S Ikeda; E. A Foegeding

    1999-01-01

    The effect of lecithin on fundamental fracture properties (true shear stress and true shear strain at fracture) and water holding capacity of heat-induced whey protein isolate (WPI) gels were investigated. Adding egg yolk lecithin to WPI gels substantially increased the fracture stress of gels containing ?50mmol\\/dm3 NaCl but slightly decreased the fracture modulus at concentrations >100mmol\\/dm3. The fracture strain and

  7. Analytical sensor redundancy assessment

    NASA Technical Reports Server (NTRS)

    Mulcare, D. B.; Downing, L. E.; Smith, M. K.

    1988-01-01

    The rationale and mechanization of sensor fault tolerance based on analytical redundancy principles are described. The concept involves the substitution of software procedures, such as an observer algorithm, to supplant additional hardware components. The observer synthesizes values of sensor states in lieu of their direct measurement. Such information can then be used, for example, to determine which of two disagreeing sensors is more correct, thus enhancing sensor fault survivability. Here a stability augmentation system is used as an example application, with required modifications being made to a quadruplex digital flight control system. The impact on software structure and the resultant revalidation effort are illustrated as well. Also, the use of an observer algorithm for wind gust filtering of the angle-of-attack sensor signal is presented.

  8. Fingering to fracturing transition in a transient gel

    E-print Network

    Guillaume Foyart; Laurence Ramos; Serge Mora; Christian Ligoure

    2013-06-21

    Fracture processes are ubiquitous in soft materials, even in complex fluids, subjected to stresses. To investigate these processes in a simple geometry, we use a model self-assembled transient gel and study the instability patterns obtained in a radial Hele-Shaw cell when a low viscosity oil pushes the more viscous transient gel. Thanks to an analysis of the morphology of the patterns, we find a discontinuous transition between the standard Saffman-Taylor fingering instability and a fracturing instability as the oil injection rate increases. Our data suggest that the flow properties of the gel ahead of the finger tip controls the transition towards fracturing. By analyzing the displacement field of the gel in the vicinity of the fingers and cracks, we show that in the fingering regime, the oil gently pushes the gel, whereas in the fracturing regime, the crack tears apart the gel, resulting in a strong drop of the gel velocity ahead of the crack tip as compared to the tip velocity. We find a unique behavior for the whole displacement field of a gel around a crack, which is drastically different from that around a finger, and reveals the solid-like behavior of the gel at short time. Our experiments and analysis provide quantitative yet simple tools to unambiguously discriminate a finger from a crack in a visco-elastic material.

  9. Effect of bloom strength on radiochromic gel dosimeters

    NASA Astrophysics Data System (ADS)

    Ebenezer Suman Babu, S.; Ravindran, B. Paul

    2015-01-01

    The Fricke gel dosimeter has been the widely used dosimeter among the gel dosimeters because of its dose response characteristics and easy preparation. The ferrous to ferric conversion that happens in this gel dosimeter on irradiation, corresponds to the absorbed dose of radiation. Gel dosimetry in India is not moving forward because of the import restrictions on the commercially available high bloom strength gelatin (imported 300 bloom). The feasibility of using Fricke gel dosimeter prepared with the locally available gelatin of 240 bloom and 200 bloom were compared with the 300 bloom gelatin taken as standard. The gel samples were prepared with 5% gelatin by weight and irradiated with 60Co gamma radiation for a dose range from 0-3 Gy used clinically. The optical absorption of gel samples were analyzed using spectrophotometer at 585 nm and dose response curves were generated. The results indicate that Fricke gels prepared with 240 bloom have linear dose response and comparable with those prepared with 300 bloom but the use of gels prepared with 200 bloom was found to be limited because of its poor optical transmittance.

  10. Mechanical properties characterization and modeling of active polymer gels

    NASA Astrophysics Data System (ADS)

    Marra, Steven Paul

    Active polymer gels expand and contract in response to certain environmental stimuli, such as the application of an electric field or a change in the pH level of the surroundings. This ability to achieve large, reversible deformations with no external mechanical loading has generated much interest in the use of these gels as actuators and "artificial muscles." While much work has been done to study the behavior and properties of these gels, little information is available regarding the full constitutive description of the mechanical and actuation properties. This work focuses on developing a means of characterizing the mechanical properties of active polymer gels and describing how these properties evolve as the gel actuates. Poly(vinyl alcohol)-poly(acrylic acid) (PVA-PAA) gel was chosen as the model material for this work because it is relatively simple and safe to both fabricate and actuate. PVA-PAA gels are fabricated on-site using a solvent-casting technique. These gels expand when moved from acidic to basic solutions, and contract when moved from basic to acidic solutions. Citric acid and sodium bicarbonate were used as the testing solutions for this work. The mechanical properties of the gel were characterized by conducting uniaxial and biaxial tests on thin PVA-PAA gel films. A biaxial testing system has been developed which can measure stresses and deformations of these films in a variety of liquid environments. The experimental results on PVA-PAA gels show these materials to be relatively compliant, and slightly viscoelastic and compressible. These gels are also capable of large recoverable deformations in both acidic and basic environments. A thermodynamically consistent finite-elastic constitutive model was developed to describe the mechanical and actuation behaviors of active polymer gels. The mechanical properties of the gel are characterized by a free-energy function, and the model utilizes an evolving internal variable to describe the actuation state. The form and parameters of the free-energy function for the PVA-PAA gel are determined from the uniaxial and biaxial testing results. The evolution law for the internal variable is determined from free actuation experiments. The application of this model to bending gel actuators is also presented.

  11. Gel growth of lysozyme crystals studied by small angle neutron scattering: case of silica gel, a nucleation inhibitor

    NASA Astrophysics Data System (ADS)

    Vidal, O.; Robert, M. C.; Boué, F.

    1998-08-01

    Silica gels were used as a media for crystal growth of hen egg white lysozyme crystals. Using small angle neutron scattering, gel-free solutions have been compared to gelled samples in the pre-nucleation period and in the growth period. Characterisation of the protein solution trapped in the gel network shows an adsorption of protein on the gel surface through electrostatic and most probably through hydrogen bonding interactions. The consecutive decrease of concentration is consistent with the decrease of the nucleation rate with respect to gel-free solutions. By modification of the gel surface, we succeeded in increasing the number of nuclei. Growth occurs by incorporation of free molecules and in a second stage, by incorporation of molecules which are progressively desorbed. This provides a relatively constant concentration of the free molecules.

  12. Catanionic gels based on cholic acid derivatives.

    PubMed

    di Gregorio, M Chiara; Pavel, N Viorel; Miragaya, Javier; Jover, Aida; Meijide, Francisco; Vázquez Tato, José; Tellini, Victor H Soto; Galantini, Luciano

    2013-10-01

    In this paper, the preparation and characterization of an anionic and a cationic surfactant obtained by chemical modifications of a natural bile acid (cholic acid) are reported. The bile acid was modified by introducing a diamine or a dicarboxylic aromatic residue on the lateral chain. The pure cationic surfactant self-assembles in a network of fibers with a cross-section gyration radius of about 15.1 Å, providing hydrogels with a pH-dependent compactness. On the other hand, the anionic molecule gives rise to prolate ellipsoid micelles. Homogeneous catanionic mixtures have also been obtained, with molar fraction of each surfactant ranging from 0.125 to 0.875. At total surfactant concentration of 0.05% (w/v), the mixtures form gels of fibrils partially arranged in secondary twisted superstructures. Comparison of this concentration with the minimum gelation concentration of the pure cationic derivative (0.16% w/v) suggests that, in the mixtures, the presence of the electrostatic component in self-assembly of the molecules allows the formation of gels starting from more dilute samples. In view of these achievements, this work suggests that catanionic mixtures can be exploited to enhance the efficiency of gelators. PMID:24063307

  13. Active biopolymer gels: from cells to tissues

    NASA Astrophysics Data System (ADS)

    Koenderink, Gijsje

    2009-03-01

    Living cells are active soft materials that are far out of thermodynamic equilibrium. They continuously use up chemical energy in order to generate forces that drive processes such as cell migration and division. Moreover, cells actively remodel their surrounding extracellular matrix (primarily collagen), so whole tissues can also be regarded as active soft materials. The aim of our research is to understand the physical mechanisms underlying the self-organization and mechanics of cells and tissues. To this end we use an experimental approach and study simplified model systems for the cytoskeleton (purified actin, tubulin, and accessory proteins) and for tissues (fibroblast-populated collagen and fibrin gels). We use microscopy and rheology to investigate the structure and mechanics on different length scales, from the single protein up to macroscopic level. I will discuss two examples of active mechanical behavior, namely in purified actin-myosin networks, and in purified fibrin matrices with embedded contractile fibroblasts. In both cases we observe active contraction and active stiffening. We quantify the active forces and examine how the structure and mechanics of the active gels depend on motor/cell density.

  14. Sol-gel powders and supported sol-gel polymers for immobilization of lipase in ester synthesis

    Microsoft Academic Search

    Jyh-Ping Chen; Wei-Shin Lin

    2003-01-01

    Candida rugosa lipase was entrapped in hybrid organic–inorganic sol-gel powder prepared by acid-catalyzed polymerization of tetramethoxysilane (TMOS) and alkyltrimethoxysilanes, and used in catalyzing esterification reactions between ethanol and butyric acid in hexane. Optimum preparation conditions were studied, which are gels made from propyltrimethoxysilane (PTMS)\\/TMOS molar ratio=4:1, hydrolysis time of silane precursor=30min, water\\/silane molar ratio=24, enzyme loading=6.25% (w\\/w) of gel, and

  15. Physical properties of nanoparticle silica gel doped with CdS prepared by sol-gel technique

    Microsoft Academic Search

    I. K. Battisha

    2002-01-01

    CdS\\/silica xerogel glasses were prepared via silica gels containing mixture solution of 0.2 M (CdCl2 and thiourea) with molar ratio 1:1. Doping the gels with this mixture solution and its heat treatment gave transparent yellow silica-gel glasses doped with CdS crystals. X-ray diffraction and transmission electron microscope make it possible to evaluate the nanoparticle size of the prepared samples. The

  16. ON THE NON-ANALYTICITY LOCUS OF AN ARC-ANALYTIC KRZYSZTOF KURDYKA AND ADAM PARUSINSKI

    E-print Network

    Paris-Sud XI, Université de

    analytic geometry there are many examples of arc-analytic functions that are not real analytic. ArcON THE NON-ANALYTICITY LOCUS OF AN ARC-ANALYTIC FUNCTION KRZYSZTOF KURDYKA AND ADAM PARUSI´NSKI Abstract. A function is called arc-analytic if it is real analytic on each real analytic arc. In real

  17. Apparatus for the production of gel beads containing a biocatalyst

    DOEpatents

    Scott, C.D.; Scott, T.C.; Davison, B.H.

    1998-03-19

    An apparatus is described for the large-scale and continuous production of gel beads containing a biocatalyst. The apparatus is a columnar system based on the chemical cross-linking of hydrocolloidal gels that contain and immobilize a biocatalyst, the biocatalyst being a microorganism or an enzyme. Hydrocolloidal gels, such as alginate, carrageenan, and a mixture of bone gelatin and modified alginate, provide immobilization matrices that can be used to entrap and retain the biocatalyst while allowing effective contact with substrates and release of products. Such immobilized biocatalysts are generally formulated into small spheres or beads that have high concentrations of the biocatalyst within the gel matrix. The columnar system includes a gel dispersion nozzle submerged in a heated non-interacting liquid, typically an organic liquid, that is immiscible with water to allow efficient formation of spherical gel droplets, the non-interacting liquid having a specific gravity that is less than water so that the gel droplets will fall through the liquid by the force of gravity. The heated non-interacting liquid is in direct contact with a chilled upflowing non-interacting liquid that will provide sufficient residence time for the gel droplets as they fall through the liquid so that they will be cooled below the gelling temperature and form solid spheres. The upflowing non-interacting liquid is in direct contact with an upflowing temperature-controlled aqueous solution containing the necessary chemicals for cross-linking or fixing of the gel beads to add the necessary stability. The flow rates of the two liquid streams can be varied to control the proper residence time in each liquid section to accommodate the production of gel beads of differing settling velocities. A valve is provided for continuous removal of the stabilized gel beads from the bottom of the column. 1 fig.

  18. Apparatus for the production of gel beads containing a biocatalyst

    DOEpatents

    Scott, Charles D. (Oak Ridge, TN); Scott, Timothy C. (Knoxville, TN); Davison, Brian H. (Knoxville, TN)

    1998-01-01

    An apparatus for the large-scale and continuous production of gel beads containing a biocatalyst. The apparatus is a columnar system based on the chemical cross-linking of hydrocolloidal gels that contain and immobilize a biocatalyst, the biocatalyst being a microorganism or an enzyme. Hydrocolloidal gels, such as alginate, carrageenan, and a mixture of bone gelatin and modified alginate, provide immobilization matrices that can be used to entrap and retain the biocatalyst while allowing effective contact with substrates and release of products. Such immobilized biocatalysts are generally formulated into small spheres or beads that have high concentrations of the biocatalyst within the gel matrix. The columnar system includes a gel dispersion nozzle submerged in a heated non-interacting liquid, typically an organic liquid, that is immiscible with water to allow efficient formation of spherical gel droplets, the non-interacting liquid having a specific gravity that is less than water so that the gel droplets will fall through the liquid by the force of gravity. The heated non-interacting liquid is in direct contact with a chilled upflowing non-interacting liquid that will provide sufficient residence time for the gel droplets as they fall through the liquid so that they will be cooled below the gelling temperature and form solid spheres. The upflowing non-interacting liquid is in direct contact with an upflowing temperature-controlled aqueous solution containing the necessary chemicals for cross-linking or fixing of the gel beads to add the necessary stability. The flow rates of the two liquid streams can be varied to control the proper residence time in each liquid section to accommodate the production of gel beads of differing settling velocities. A valve is provided for continuous removal of the stabilized gel beads from the bottom of the column.

  19. Analytic clustered halftone dots

    NASA Astrophysics Data System (ADS)

    Curry, Douglas N.

    1997-04-01

    An analytic method of constructing high fidelity clustered halftone dots is presented.A phase addressable cell space is created which provides numerically precise 2D edge position information. Exposures are produced with variable intensity modulation to phase shift process direction dot edges, and fine granularity timing is used to adjust fast scan direction edges. This allows symmetrically thresholded halftone dots instead of sequentially thresholded dots. Advantages of this technique are more binary halftone gray levels, reduced labor content, spline based tone correction, device independence, and arbitrary screen angle and frequency. An equation which provides the desired shape and tone response over the intensity range is developed and analyzed. Shape information is extracted which is independent of the target printer characteristics. Highly accurate tone information is obtained by integrating the continuous shape function. A printer-dependent, gray enabled modulator drive function is utilized, and step wedge prints are mae with a nominal tone reproduction curve (TRC). Data from densitometer measurements are converted to spline format, and used to correct the nominal TRC with high relative accuracy. Resulting contourless tone corrected prints show very good linearity and shape definition over the entire intensity range.

  20. Perils of analytic continuation

    NASA Astrophysics Data System (ADS)

    Miao, S. P.; Mora, P. J.; Tsamis, N. C.; Woodard, R. P.

    2014-05-01

    A nice paper by Morrison [arXiv:1302.1860] demonstrates the recent convergence of opinion that has taken place concerning the graviton propagator on de Sitter background. We here discuss the few points which remain under dispute. First, the inevitable decay of tachyonic scalars really does result in their 2-point functions breaking de Sitter invariance. This is obscured by analytic continuation techniques which produce formal solutions to the propagator equation that are not propagators. Second, Morrison's de Sitter invariant solution for the spin two sector of the graviton propagator involves derivatives of the scalar propagator at M2=0, where it is not meromorphic unless de Sitter breaking is permitted. Third, de Sitter breaking does not require zero modes. Fourth, the ambiguity Morrison claims in the equation for the spin two structure function is fixed by requiring it to derive from a mode sum. Fifth, Morrison's spin two sector is not "physically equivalent" to ours because their coincidence limits differ. Finally, it is only the noninvariant propagator that gets the time independence and scale invariance of the tensor power spectrum correctly.

  1. Effect of enzymatic deamidation on the heat-induced conformational changes in whey protein isolate and its relation to gel properties.

    PubMed

    Miwa, Noriko; Yokoyama, Keiichi; Nio, Noriki; Sonomoto, Kenji

    2013-03-01

    The effect of protein-glutaminase (PG) on the heat-induced conformational changes in whey protein isolate (WPI) and its relation to gel properties was investigated. The structural properties of WPI treated with PG were examined by several analytical methods. The analysis of the fluorescence spectrum and the binding capacity of a fluorescent probe demonstrated that deamidation prevented the increase in the fluorescence intensity caused by subsequent heat treatment. Measurements of the molecular weight distribution of WPI showed that PG-treated WPI was not likely to polymerize even after heating. This is thought to be due to an increase in electrostatic repulsion between carboxylic acid groups and a decrease in the formation of disulfide bonds, which results in the decrease in heat-induced aggregation. The properties of heat-induced WPI gels were modified by deamidation. PG-treated WPI gels had a soft texture and a high water-holding capacity in the presence of salts. PMID:23379844

  2. Western Protocol 1. Run protein gel (for Int this is usually a 4-12% TG gel at 125V for 2 hours)

    E-print Network

    Segall, Anca

    Western Protocol 1. Run protein gel (for Int this is usually a 4-12% TG gel at 125V for 2 hours) 2 with nano-pure water 3. Soak gel and all required apparatus for a few minutes in transfer buffer (assembly: negative plate (larger one), 2 blotting pads, filter paper, gel, nitrocellulose, filter paper, 3 blotting

  3. New gel phantoms simulating optical properties of biological tissue 

    E-print Network

    Lee, Mija

    1997-01-01

    Gel phantoms made of polyacrylamide gel, India ink, and TiO2 were prepared to simulate biological tissues in optical properties. India ink and TiO2were used to imitate the absorption and scattering properties, respectively, of biological tissues...

  4. Creating Reconfigurable Materials Using ``Colonies'' of Oscillating Polymer Gels

    NASA Astrophysics Data System (ADS)

    Deb, Debabrata; Dayal, Pratyush; Kuksenok, Olga; Balazs, Anna

    2013-03-01

    Species ranging from single-cell organisms to social insects can undergo auto-chemotaxis, where the entities move towards a chemo-attractant that they themselves emit. This mode of signaling allows the organisms to form large-scale structures. Using computational modeling, we show that millimeter-sized polymer gels can display similar auto-chemotaxis. In particular, we demonstrate that gels undergoing the self-oscillating Belousov-Zhabotinsky (BZ) reaction not only respond to a chemical signal from the surrounding solution, but also emit this signal and thus, multiple gel pieces can spontaneously self-aggregate. We focus on the collective behavior of ``colonies'' of BZ gels and show that communication between the individual pieces critically depends on all the neighboring gels. We isolate the conditions at which the BZ gels can undergo a type of self-recombining: if a larger gel is cut into distinct pieces that are moved relatively far apart, then their auto-chemotactic behavior drives them to move and autonomously recombine into a structure resembling the original, uncut sample. These findings reveal that the BZ gels can be used as autonomously moving building blocks to construct multiple structures and thus, provide a new route for creating dynamically reconfigurable materials.

  5. Sense and nonsense of scar creams and gels

    Microsoft Academic Search

    Cees J. M. van den Helder; J. Joris Hage

    1994-01-01

    The wish to prevent or improve scars, whether they are of surgical or traumatic origin, has led to the development of scar creams and gels that are said to influence the aesthetic appearance of a scar. In this article the literature on results of the topical application of various scar creams and gels is reviewed. It is concluded that no

  6. Weibull analysis of the mechanical strength of silica gels

    Microsoft Academic Search

    L. Duffours; F. Pernot; T. Woignier; A. Alaoui; J. Phalippou

    1994-01-01

    Since gels are typically brittle materials, reliable analyses are essential to determine the strength distribution. The mechanical strength of silica gels has been measured by the three point bending technique. Based on the Weibull function, the statistical analysis allows determination of the Weibull modulus (m), which characterizes the strength distribution and the flaw size effect.

  7. Application of MAGAT polymer gel dosimetry in breast balloon

    NASA Astrophysics Data System (ADS)

    Govi, N.; Gueye, P.; Avery, S.

    2013-06-01

    The purpose of this study is to characterize the response of MAGAT normoxic polymer gel for breast brachytherapy applications using two balloon applicators (MammoSite® and Contoura®) and verify the dose distribution with a commercial treatment planning system (BrachyVision® version 8.9.15). We present the fabrication, irradiation and readout of the gel used for the work described herein.

  8. Microfluidic formation of ionically cross-linked polyamine gels.

    PubMed

    Kini, Gautam C; Lai, Justin; Wong, Michael S; Biswal, Sibani Lisa

    2010-05-01

    In this article, we discuss in situ polymer gelation in microfluidic channels from electrostatically mediated interactions when reactant streams of a linear cationic polymer (poly(allylamine hydrochloride, PAH) and a multivalent anion (sodium citrate) are subjected to shear flow. We find that the polyamine exhibits shear-thickening behavior as it is ionically cross-linked by citrate ions to form viscoelastic gel phases. These gels form at room temperature and remain stable and intact after the cessation of flow. Gelation is found to occur in the polymer stream and not the citrate stream because of an appreciably higher diffusivity of citrate ions when compared to the gel and PAH and because of laminar flow conditions in the microfluidic environment. Gel formation occurred when the pH of the PAH stream was below the PAH pK(a) value of 8.38 and when citrate was either in a disodium or trisodium state. The formation of aggregates, gels, and droplets was found to depend strongly on the charge ratio and flow conditions. The gelation of PAH begins with the formation of colloidal aggregates of PAH and citrate, which then combine under shear flow to form noncontinuous or continuous gels. Droplets of citrate can form within regions of continuous gels as excess citrate anions diffuse into the gel stream. PMID:20078130

  9. Improvement and modification of whey protein gel texture using polysaccharides

    Microsoft Academic Search

    Sylvie L Turgeon; Martin Beaulieu

    2001-01-01

    Whey proteins (WP) and polysaccharides are two gelling biopolymers used in the food industry for their wide range of rheological and textural properties. Mixed gels containing more than one gelling agent are usually classified into three types: interpenetrating, coupled, and phase-separated networks. Large deformation behavior of whey protein gels mixed with polysaccharides is presented. pH, and the concentration and nature

  10. Rheological properties and structure of inulin–whey protein gels

    Microsoft Academic Search

    Pawel Glibowski

    2009-01-01

    The rheological properties, structure and synergistic interactions of whey proteins (1–7%) and inulin (20% and 35%) were studied. Gelation of whey proteins was induced with Na+. Inulin was dissolved in preheated whey protein solutions (80 °C, 30 min). Inulin gel formation was strongly affected by whey proteins. The presence of whey proteins at a level allowing for protein gel network formation (7%)

  11. Gel spinning of PVA\\/SWNT composite fiber

    Microsoft Academic Search

    Xiefei Zhang; Tao Liu; T. V. Sreekumar; Satish Kumar; Xiaodong Hu; Ken Smith

    2004-01-01

    Single wall carbon nanotubes (SWNT), polyvinyl alcohol (PVA), dimethyl sulfoxide (DMSO) and water, homogeneous dispersion has been prepared by stirring and sonication. This dispersion was extruded into fiber via gel spinning. The modulus of the PVA\\/SWNT (3wt%) composite fiber was 40% higher than that of the control PVA gel spun fiber. Fiber structure and properties have been studied. The PVA

  12. Tactile measurement with a GelSight sensor

    E-print Network

    Yuan, Wenzhen, S.M. Massachusetts Institute of Technology

    2014-01-01

    This thesis introduces a method of measuring contact force with GelSight. GelSight is an optical-based tactile sensor that uses a piece of coated elastomer as the contact medium. A camera records the distortion of the ...

  13. Biocatalysis with Sol-Gel Encapsulated Acid Phosphatase

    ERIC Educational Resources Information Center

    Kulkarni, Suhasini; Tran, Vu; Ho, Maggie K.-M.; Phan, Chieu; Chin, Elizabeth; Wemmer, Zeke; Sommerhalter, Monika

    2010-01-01

    This experiment was performed in an upper-level undergraduate biochemistry laboratory course. Students learned how to immobilize an enzyme in a sol-gel matrix and how to perform and evaluate enzyme-activity measurements. The enzyme acid phosphatase (APase) from wheat germ was encapsulated in sol-gel beads that were prepared from the precursor…

  14. Inexpensive and Safe DNA Gel Electrophoresis Using Household Materials

    ERIC Educational Resources Information Center

    Ens, S.; Olson, A. B.; Dudley, C.; Ross, N. D., III; Siddiqi, A. A.; Umoh, K. M.; Schneegurt, M. A.

    2012-01-01

    Gel electrophoresis is the single most important molecular biology technique and it is central to life sciences research, but it is often too expensive for the secondary science classroom or homeschoolers. A simple safe low-cost procedure is described here that uses household materials to construct and run DNA gel electrophoresis. Plastic…

  15. Silica Sol-Gel Coatings on Metals Produced by EPD

    Microsoft Academic Search

    Y. Castro; B. Ferrari; R. Moreno; A. Durán

    2003-01-01

    The objective of this work has been to combine the sol-gel method and the electrophoretic deposition (EPD) process to prepare thick coatings onto metallic substrates. Two different routes were used for preparing the sol-gel silica suspensions. On one hand, silica particulate sols were obtained by basic catalysis of alkoxides and alkylalkoxides. On the other, silica suspensions were prepared by adding

  16. INSTRUCTIONS GelCode E-ZincTM

    E-print Network

    Lebendiker, Mario

    become identifiable when placed against a black background. The negative stain can then be removed, stop the gel development by replacing the Developer with DI Water and rinse for 1 minute. Pour off the water and refill with fresh DI water. The gel may be kept in DI water for up to two weeks

  17. Maintenance of Bacterial Cultures on Anhydrous Silica Gel

    ERIC Educational Resources Information Center

    Lennox, John E.

    1977-01-01

    Suspensions of 20 different cultures were grown on appropriate media, then pipetted into sterile anhydrous silica gel. Silica gel cultures after incubation and refrigerated storage were tested for viability. Results showed little mutation, low replication, low contamination, minimal expenses, and survival up to two years. (CS)

  18. Raman study of lower toxicity polymer gel for radiotherapy dosimetry

    NASA Astrophysics Data System (ADS)

    Adenan, M. Z.; Ahmad, M.; Mohd Noor, N.; Deyhimihaghighi, N.; Saion, E.

    2014-11-01

    N-isopropyl acrylamide (NIPAM) monomer and N, N' – methylene-bis-acrylamide (BIS) crosslinker were used to synthesize polymer gel dosimeters for a reason that the monomer is lower toxicity which gives a significant advantage over the other polymer gel compositions. The gels were irradiated with Co-60 gamma rays at doses up to 21 Gy and the irradiated NIPAM polymer gels were used to investigate the dose response characteristics based on Raman spectroscopy analysis on the formation of the polymer gels and the consumptions of NIPAM and BIS co-monomers. From the findings, the polymerization was referred to an increment in Raman intensity at 815 cm?1, assigned for C-C stretching mode of NIPAM polymer gel, as the dose increased. The consumptions of the co-monomers were referred to a decrement in Raman intensities at 1025 cm?1 2353 cm?1 for C=C stretching modes of NIPAM and BIS respectively as the dose increased. The increment and decrement in Raman intensities of polymer and co-monomers respectively with increase of dose indicate that there is occurrence of polymerization of NIPAM polymer gels which could be applied in 3D dose distributions for radiotherapy treatment planning. The correlation factor kBIS is greater than kNIPAM showing that the reaction of BIS crosslinker is more efficient than NIPAM monomer to generate 37% of the NIPAM polymer gel.

  19. Performance of 18 polymers in aluminum citrate colloidal dispersion gels

    SciTech Connect

    Smith, J.E.

    1995-11-01

    Colloidal dispersion gels are made up of low concentrations of polymer and aluminum citrate in water. These gels, which are mixed as a homogeneous solution at the surface, provide a valuable tool for in-depth blockage of high permeability regions of rock in heterogeneous reservoirs. Performance of colloidal dispersion gels depends strongly on the type and quality of polymer used. This paper provides an overview of the performance of 18 different polymers in colloidal dispersion gels. 14 of the polymers were partially hydrolyzed polyacrylamides or AMPS polymers in dry crystalline form with varying degrees of hydrolysis and molecular weight. The group also includes one cationic polyacrylamide, one carboxymethyl cellulose, one partially hydrolyzed polyacrylamide in emulsion form and one polysaccharide in dry form. Gels were mixed with the polymers at two polymer concentrations, three polymer:aluminum ratios and in different concentrations of potassium chloride. The gels were quantitatively tested at 1, 7, 14 and 28 days after crosslinking using the transition pressure test, which is a screen flow resistance test. Of the six polymer types tested, only the dry partially hydrolyzed polyacrylamides and AMPS polymers formed colloidal dispersion gels. Gel strength generally increased with increasing anionic charge and molecular weight; however, the manner in which the polymer is manufactured and the impurities present in the polymer also play roles which are more significant than originally expected.

  20. Gel Electrophoresis--The Easy Way for Students

    ERIC Educational Resources Information Center

    VanRooy, Wilhelmina; Sultana, Khalida

    2010-01-01

    This article describes a simple, inexpensive, easy to conduct gel-electrophoresis activity using food dyes. It is an alternative to the more expensive counterparts which require agarose gel, DNA samples, purchased chamber and Tris-borate-EDTA buffer. We suggest some learning activities for senior biology students along with comments on several…

  1. Supramolecular gel-assisted formation of fullerene nanorods.

    PubMed

    Zhang, Chun; Wang, Jing; Wang, Jing-Jing; Li, Min; Yang, Xiang-Liang; Xu, Hui-Bi

    2012-11-19

    Gel it like it is: Fullerene nanorods (see figure) with a length of several micrometers, can be easily synthesized by a supramolecular gel-assisted self-assembly method (SGAS). The results presented here may be useful for the design and construction of new organic nanomaterials by SGAS. PMID:23112082

  2. AFM examination of sol-gel matrices doped with photosensitizers

    Microsoft Academic Search

    KATARZYNA WYSOCKA; AGNIESZKA ULATOWSKA-JAR?A; JOANNA BAUER; BOGDAN SAVU; GEORGE STANCIU; HALINA PODBIELSKA

    Various compounds may be entrapped into the sol-gel materials, including the photosensitive agents. The nanostructure of the final material depends on the matrix itself, as well as on the structural properties of doped compound. In this work, sol-gel matrices were produced from silica based precursor tetraethoxysilan (TEOS) in the form of single layers deposited on microscopic glasses. Materials were produced

  3. Improvement of protein gel by physical and enzymatic treatment

    Microsoft Academic Search

    Naofumi Kitabatake; Etsushiro Doi

    1993-01-01

    To improve the functional properties of food protein, physical and enzymatic treatments are effective and attractive. As an example of physical treatment, heat treatment of egg protein under various conditions is shown. Egg albumin and egg white usually give turbid (white) gel on heating. However, we have learned that a transparent gel can be prepared by regulating conditions of the

  4. Application of gel growth to hanging drop technique

    NASA Astrophysics Data System (ADS)

    Provost, Karine; Robert, Marie-Claire

    1991-03-01

    Convection effects can be prevented by gelling the hanging drops used in protein crystal growth. An exploratory study has been made on a model material, hen egg white lysozyme, growing in agarose gel. In that case, it is observed that using gel promotes nucleation.

  5. Stable, concentrated solutions of polyaniline using amines as gel inhibitors

    Microsoft Academic Search

    Hsing-Lin Wang; Benjamin R. Mattes

    2002-01-01

    Stable, concentrated solutions of high-molecular weight polyaniline using amines as gel inhibitors. Certain amine compounds (gel inhibitors) are used to form highly concentrated, stable solutions of the emeraldine base form of polyaniline in numerous organic solvents from which coatings, films and fibers are readily prepared without problems associated with rapid gelation which occurs when concentrated solutions are attempted without the

  6. Moisture transport in silica gel particle beds. [DESSICANT

    Microsoft Academic Search

    1983-01-01

    A theoretical and experimental study of the performance of silica gel packed particle beds is described. A bench-state test rig was used to obtain data for parameter values pertinent to solar air-conditioning applications. Both adsorption and desorption experiments were performed for Regular Density (RD) silica gel for a wide range of particle size. Adsorption data was also obtained for Intermediate

  7. Protein Electrophoresis in the Biology Classroom Using "Safe" Gels.

    ERIC Educational Resources Information Center

    Atkins, Thomas

    1991-01-01

    Describes the use of electrophoresis in the high school utilizing two new gels that are easy to pour, do not require degassing, can be used on a horizontal gel electrophoresis, and are not neurotoxic or carcinogenic health hazards. Large diagrams and written instructions are used to present the protocol of setting up the electrophoresis. (PR)

  8. DEWATERING OF DILUTE AQUEOUS HAZARDOUS WASTES USING REVERSIBLE GEL ABSORPTION

    EPA Science Inventory

    The feasiability of using crosslinked gels in a reversible process for extracting pure water from aqueous waste solutions has been investigated. It has potential for concentrating waste streams that contain hazardous chemicals. Near critical gels have been developed which swell a...

  9. Slow Release Of Reagent Chemicals From Gel Matrices

    NASA Technical Reports Server (NTRS)

    Debnam, William J.; Barber, Patrick G.; Coleman, James

    1988-01-01

    Procedure developed for slow release of reagent chemicals into solutions. Simple and inexpensive and not subject to failure of equipment. Use of toothpaste-type tube or pump dispenser conceivably provides more controlled technique for storage and dispensation of gel matrix. Possible uses include controlled, slow release of reagents in chemical reactions, crystal growth, space-flight experiments, and preformed gel medications from packets.

  10. Microelectromechanics of ionic polymeric gels as synthetic robotic muscles

    NASA Astrophysics Data System (ADS)

    Shahinpoor, Mohsen

    1994-05-01

    An ionic polymeric gel is defined as a 3-D charged network of a cross-linked macromolecular polyelectrolyte capable of collapsing or swelling in an acidic or alkaline environment, respectively, purely due to pH changes. Fixed electrical charges reside at all cross-links in such macromolecular networks in the presence of wandering mobile charges that tend to change their spatial distribution within the gel network. In the presence of an electric field, the mobile ions redistribute themselves in the gel network and thus cause the network to deform accordingly. A microelectro-mechanical model is presented that takes into account such internal electric charge redistribution of fixed and mobile ions due to the presence of an electric field. Direct computer control of large expansions and contractions of ionic polymeric gels by means of a voltage gradient appears to be possible. A mechanism is presented for the reversible nonhomogeneous large deformations and in particular bending of strips of ionic polymeric gels in the presence of an electric field. Exact expressions are given relating the deformation characteristics of the gel to the electric field strength or voltage gradient, gel dimensions and other physical parameters. It is concluded that direct voltage control of such nonhomogeneous large deformations in ionic polymeric gels is possible.

  11. Ion exchange selectivities of calcium alginate gels for heavy metals.

    PubMed

    Jodra, Y; Mijangos, F

    2001-01-01

    An equilibrium model has been proposed and verified, based on the conditions in the gel phase and Donnan equilibrium theory, for the analysis of the experimental data on the recovery of lead, copper, cadmium, cobalt, nickel and zinc from synthetic, nonmetallic aqueous solutions on calcium alginate gels. This equilibrium model considers that the system behaves as an ion-exchange process between the calcium in the gels and the divalent metals in solution, and that the metallic portion enclosed in gel fluid is supposed an important quantitative contribution to the total amount of metal uptake by gels. According to the equilibrium constants calculated, it is deduced that the selectivity order is: Pb > Cu > Cd > Ni > Zn > Co. PMID:11380185

  12. The Applications of Shape Memory Gel as a Smart Material

    NASA Astrophysics Data System (ADS)

    Hasnat Kabir, M.; Gong, Jin; Watanabe, Yosuke; Makino, Masato; Furukawa, Hidemitsu

    The research to find a suitable future new material is a big challenge nowadays. The material for biocompatible or biodegradable is an important issue in human life. The environment friendly materials or in other words green materials are required for future applications. The gels are soft and wet material having several unique properties such as high water absorbent, extremely low friction, softness, shape memory, high ductility and so on. The gel consists with a large amount of solvent and a small amount of cross-linker. Due to the high water content, for instants, more than 90%, this material becomes as an environment friendly green material. The shape memory gel (SMG) is one kind of soft materials among them which bears some interesting characteristics. This gel, a smart material, can be used as lens, eyeball, artificial muscle or artificial blood vessel, smart button and so on. In this paper, we have briefly discussed the different applications of the shape memory gel.

  13. Microscopic Picture of Cooperative Processes in Restructuring Gel Networks

    E-print Network

    Jader Colombo; Asaph Widmer-Cooper; Emanuela Del Gado

    2014-06-16

    Colloidal gel networks are disordered elastic solids that can form even in extremely dilute particle suspensions. With interaction strengths comparable to the thermal energy, their stress-bearing network can locally restructure via breaking and reforming interparticle bonds. This allows for yielding, self-healing, and adaptive mechanics under deformation. Designing such features requires controlling stress transmission through the complex structure of the gel and this is challenging because the link between local restructuring and overall response of the network is still missing. Here, we use a space resolved analysis of dynamical processes and numerical simulations of a model gel to gain insight into this link. We show that consequences of local bond breaking propagate along the gel network over distances larger than the average mesh size. This provides the missing microscopic explanation for why nonlocal constitutive relations are necessary to rationalize the nontrivial mechanical response of colloidal gels.

  14. Volume phase transitions of cholesteric liquid crystalline gels

    NASA Astrophysics Data System (ADS)

    Matsuyama, Akihiko

    2015-05-01

    We present a mean field theory to describe anisotropic deformations of a cholesteric elastomer without solvent molecules and a cholesteric liquid crystalline gel immersed in isotropic solvents at a thermal equilibrium state. Based on the neoclassical rubber theory of nematic elastomers, we derive an elastic energy and a twist distortion energy, which are important to determine the shape of a cholesteric elastomer (or gel). We demonstrate that when the elastic energy dominates in the free energy, the cholesteric elastomer causes a spontaneous compression in the pitch axis and elongates along the director on the plane perpendicular to the pitch axis. Our theory can qualitatively describe the experimental results of a cholesteric elastomer. We also predict the first-order volume phase transitions and anisotropic deformations of a gel at the cholesteric-isotropic phase transition temperature. Depending on a chirality of a gel, we find a prolate or oblate shape of cholesteric gels.

  15. Method for preparing hydrous zirconium oxide gels and spherules

    DOEpatents

    Collins, Jack L.

    2003-08-05

    Methods for preparing hydrous zirconium oxide spherules, hydrous zirconium oxide gels such as gel slabs, films, capillary and electrophoresis gels, zirconium monohydrogen phosphate spherules, hydrous zirconium oxide spherules having suspendable particles homogeneously embedded within to form a composite sorbent, zirconium monohydrogen phosphate spherules having suspendable particles of at least one different sorbent homogeneously embedded within to form a composite sorbent having a desired crystallinity, zirconium oxide spherules having suspendable particles homogeneously embedded within to form a composite, hydrous zirconium oxide fiber materials, zirconium oxide fiber materials, hydrous zirconium oxide fiber materials having suspendable particles homogeneously embedded within to form a composite, zirconium oxide fiber materials having suspendable particles homogeneously embedded within to form a composite and spherules of barium zirconate. The hydrous zirconium oxide spherules and gel forms prepared by the gel-sphere, internal gelation process are useful as inorganic ion exchangers, catalysts, getters and ceramics.

  16. Fabrication and characterization of ionic polymer gel actuators

    NASA Astrophysics Data System (ADS)

    Jo, Choonghee; In, Eunji; Naguib, Hani E.

    2010-04-01

    Poly-AMPS (PAMPS) gel was fabricated and its electroactive behavior was studied. A weakly cross-linked anionic PAMPS gel was produced by radical polymerization using 2-acrylamido-2-methylpropane sulfonic acid (AMPS) monomers, where N,N'-methlenebisacrylamide (MBAA) and ? -ketoglutaric acid were used as a cross-linking agent and a radical initiator, respectively. The polymerization was carried out at 55°C for at least 24 hours. Density and the degree of swelling of gel samples were investigated as physical properties. Also, swelling experiments were conducted in a surfactant solution using 1-dodecylpyridinium chloride hydrate. The chemo-mechanical properties of PAMPS gel were studied in a dilute surfactant solution under the electric field. The effect of material parameters on the bending deformation was investigated. As design parameters, sample thickness, current density, ion concentration of the surfactant solution, and cross-linking degree of gel were chosen, and the effect of these parameters on the actuation was studied.

  17. Buckling transition of nematic gels in confined geometry

    E-print Network

    Guangnan Meng; Robert B. Meyer

    2009-10-17

    A spontaneous buckling transition in thin layers of monodomain nematic liquid crystalline gel was observed by polarized light microscopy. The coupling between the orientational ordering of liquid crystalline solvent and the translational ordering of crosslinked polymer backbones inside the nematic gel contributes to such buckling transition. As the nematic mesogens become more ordered when the gel is cooled down from a higher gelation temperature, the polymeric backbones tend to elongate along the direction parallel to the nematic director, which is perpendicular to the rigid glass surfaces in the experimental setup. The shape change of such confined gel sample lead to the spontaneous buckling of polymeric network and the spatial modulation of nematic liquid crystalline director, which is observed as the stripe patterns. The instability analysis was used to explain such transitions, and the relationship between the critical field, stripe's wavelength and temperature can be explained qualitatively by the rubber elasticity theory for liquid crystalline gels.

  18. Observing and quantifying fibroblast-mediated fibrin gel compaction.

    PubMed

    De Jesús, Aribet M; Sander, Edward A

    2014-01-01

    Cells embedded in collagen and fibrin gels attach and exert traction forces on the fibers of the gel. These forces can lead to local and global reorganization and realignment of the gel microstructure. This process proceeds in a complex manner that is dependent in part on the interplay between the location of the cells, the geometry of the gel, and the mechanical constraints on the gel. To better understand how these variables produce global fiber alignment patterns, we use time-lapse differential interference contrast (DIC) microscopy coupled with an environmentally controlled bioreactor to observe the compaction process between geometrically spaced explants (clusters of fibroblasts). The images are then analyzed with a custom image processing algorithm to obtain maps of the strain. The information obtained from this technique can be used to probe the mechanobiology of various cell-matrix interactions, which has important implications for understanding processes in wound healing, disease development, and tissue engineering applications. PMID:24458198

  19. Development of tretinoin gels for enhanced transdermal delivery.

    PubMed

    Shin, Sang-Chul; Kim, Hee-Jung; Oh, In-Joon; Cho, Cheong-Weon; Yang, Kyu-Ho

    2005-05-01

    To develop the new gel formulations that show sustained release for a period of time, the bioadhesive carbopol gels containing tretinoin were prepared. The release characteristics of drug from the carbopol gel were studied according to temperature, receptor medium and drug concentration. For the enhancement of its percutaneous absorption, some kinds of penetration enhancer were used. As the concentration of drug increased, the release of drug from the gel increased, showing concentration dependency. The increase of temperature showed the increased drug release, depending on the activation energy of permeation. Among the enhancers used such as the glycols and the non-ionic surfactants, polyoxyethylene 2-oleyl ether showed the best enhancing effect. The carbopol gels of tretinoin containing an enhancer could be developed for the enhanced transdermal delivery of drug. PMID:15848058

  20. Keggin-type polyoxometalate-based ionic liquid gels.

    PubMed

    Huang, Tianpei; Tian, Naiqin; Wu, Qingyin; Yan, Wenfu

    2015-05-27

    A series of reversible phase transformation ammonium- and phosphonium-based polyoxometalate ionic liquid (POM-IL) gels were synthesized and studied with a focus on the correlation between their physicochemical properties and their chemical structure. The products were successfully characterized by IR, UV, XRD and TG-DTA, and their ionic conductivities were measured. The Keggin-type heteropolyanion clusters decorated with long alkyl chains demonstrated a tendency to exhibit a gel state at room temperature, while all the gels transformed into liquids after heating and then recovered after cooling. With a decrease in the alkyl chain length, a significant improvement in the thermal stability and conductivity of the ammonium-based POM-IL gels can be achieved. Moreover, compared with the corresponding ammonium compound, phosphonium-based POM-IL gel was found to be more stable at high temperature and exhibited better conductivity. PMID:25947074

  1. Tunable dynamics of microtubule based active isotropic gels

    E-print Network

    Gil Henkin; Stephen J. DeCamp; Daniel TN Chen; Tim Sanchez; Zvonimir Dogic

    2014-09-26

    We investigate the dynamics of an active gel of bundled microtubules that is driven by clusters of kinesin molecular motors. Upon the addition of ATP, the coordinated action of thousands of molecular motors drives the gel to a highly dynamical turbulent-like state that persists for hours and is only limited by the stability of constituent proteins and the availability of the chemical fuel. We characterize how enhanced transport and emergent macroscopic flows of active gels depend on relevant molecular parameters, including ATP, kinesin motor, and depletant concentrations, microtubule volume fraction, as well as the stoichiometry of the constituent motor clusters. Our results show that the dynamical and structural properties of microtubule based active gels are highly tunable. They also indicate existence of an optimal concentration of molecular motors that maximize far-from-equilibrium activity of active isotropic MT gels.

  2. Microscopic picture of cooperative processes in restructuring gel networks.

    PubMed

    Colombo, Jader; Widmer-Cooper, Asaph; Del Gado, Emanuela

    2013-05-10

    Colloidal gel networks are disordered elastic solids that can form even in extremely dilute particle suspensions. With interaction strengths comparable to the thermal energy, their stress-bearing network can locally restructure via breaking and reforming interparticle bonds. This allows for yielding, self-healing, and adaptive mechanics under deformation. Designing such features requires controlling stress transmission through the complex structure of the gel and this is challenging because the link between local restructuring and overall response of the network is still missing. Here, we use a space resolved analysis of dynamical processes and numerical simulations of a model gel to gain insight into this link. We show that consequences of local bond breaking propagate along the gel network over distances larger than the average mesh size. This provides the missing microscopic explanation for why nonlocal constitutive relations are necessary to rationalize the nontrivial mechanical response of colloidal gels. PMID:23705744

  3. Novel Printing------Using Polymeric Gel as Ink

    NASA Astrophysics Data System (ADS)

    Toyama, Noboru; Fukumoto, Hiroshi; Tanioka, Hiroshi; Arahara, Kohzoh; Koizumi, Norihiko; Yuasa, Toshiya; Kobayashi, Motokazu; Kan, Fumitaka

    1989-07-01

    Novel printing ink has been developed based on polymeric gel having the nature of gel to sol transition caused by application of electric voltage. The polymeric gel ink consisted of polyvinyl alcohol) (PVA) partially crosslinked with borax, carbon black as a pigment, and water. Printing facilities was also designed. Polymeric gel ink with electric conductivity 4.0 x 10-3 ?-1cm-1 was used. It could offer resolution of more than 200 dots per inch (dpi). Image density was fully controlled from 0.05 to 1.5 as optical density by application of electric voltage of 3 - 12 V. An advantage of this printing system was that polymeric gel ink not only acted as ink but also as the support.

  4. Sol-gel synthesis of protoenstatite

    SciTech Connect

    Jones, S.A.; Burlitch, J.M. [Cornell Univ., Ithaca, NY (United States). Dept. of Chemistry

    1994-12-31

    Protoenstatite, a high-temperature polymorph of enstatite (MgSiO{sub 3}), is generally not stable at room temperature, and is difficult to synthesize. Using a recently developed, hydrogen peroxide assisted, sol-gel synthesis, protoenstatite was synthesized in a form that was stable at room temperature. Its crystallization was strongly dependent on processing conditions, particularly on the manner in which the xerogel was formed and fired. Xerogels prepared by evaporation, spray-drying and freeze-drying were compared by XRD, HTXRD, BET, TG/DTA, and {sup 29}Si NMR methods. When samples were prepared by evaporation or spray-drying, the result was a mixture of polymorphs. Only the freeze-dried precursor yielded protoenstatite at a lower temperature and within a shorter time than any previously reported.

  5. Sol-gel processing of energetic materials

    SciTech Connect

    Tillotson, T.M.; Hrubesh, L.H.; Fox, G.L.; Simpson, R.L.; Lee, R.W.; Swansiger, R.W.; Simpson, L.R.

    1997-08-18

    As part of a new materials effort, we are exploring the use of sol- gel chemistry to manufacture energetic materials. Traditional manufacturing of energetic materials involves processing of granular solids. One application is the production of detonators where powders of energetic material and a binder are typically mixed and compacted at high pressure to make pellets. Performance properties are strongly dependent on particle size distribution, surface area of its constituents, homogeneity of the mix, and void volume. The goal is to produce detonators with fast energy release rate the are insensitive to unintended initiation. In this paper, we report results of our early work in this field of research, including the preparation of detonators from xerogel molding powders and aerogels, comparing the material properties with present state-of-the-art technology.

  6. Well completion process using a polymer gel

    SciTech Connect

    Sydansk, R.D.; Ibele, L.C.

    1988-02-02

    This patent describes a wellbore completion process for sealing an uncased face of a wellbore in fluid communication with a subterranean hydrocarbon-bearing formation below an earthen surface, comprising: (a) admixing a gelation solution at the surface consisting essentially of a water-soluble carboxylate-containing polymer, a complex capable of crosslinking the polymer and formed of at least one chromic species and at least one acetate species, and a solvent for the polymer and the complex; (b) injecting the gelation solution into the wellbore; (c) placing the gelation solution at the wellbore; and (d) crosslinking the gelation solution to substantial completion at the wellbore face to form a non-flowing cross-linked polymer gel which substantially seals the wellbore from fluid intrusion across the face while allowing fluid to flow through the wellbore.

  7. Hybrid slab-microchannel gel electrophoresis system

    DOEpatents

    Balch, J.W.; Carrano, A.V.; Davidson, J.C.; Koo, J.C.

    1998-05-05

    A hybrid slab-microchannel gel electrophoresis system is described. The hybrid system permits the fabrication of isolated microchannels for biomolecule separations without imposing the constraint of a totally sealed system. The hybrid system is reusable and ultimately much simpler and less costly to manufacture than a closed channel plate system. The hybrid system incorporates a microslab portion of the separation medium above the microchannels, thus at least substantially reducing the possibility of non-uniform field distribution and breakdown due to uncontrollable leakage. A microslab of the sieving matrix is built into the system by using plastic spacer materials and is used to uniformly couple the top plate with the bottom microchannel plate. 4 figs.

  8. Gel structures in leached alkali silicate glass

    SciTech Connect

    Bunker, B.C.; Headley, T.J.; Douglas, S.C.

    1984-01-01

    Transmission electron microscopy of leached Na/sub 2/O.3SiO/sub 2/ and K/sub 2/O.3SiO/sub 2/ glasses showed that the hydrated glass surface is a silica rich gel which phase separates during leaching. Phase separation is initiated when pockets of an aqueous phase nucleate and grow in the hydrated silica matrix. The aqueous pockets eventually become a network of interconnected pores with a pore diameter of approx. 30 nm. In advanced stages of leaching, the remaining interconnected silica rich phase resembles an aggregation of colloidal silica particles. The observed phase separation is consistent with literature models concerning the chemistry of silica in aqueous solutions and in leached glass.

  9. Sol-gel synthesis of manganese oxides

    NASA Astrophysics Data System (ADS)

    Bach, S.; Henry, M.; Baffier, N.; Livage, J.

    1990-10-01

    Transparent and stable manganese dioxide gels are obtained upon reduction of permanganate aqueous solutions AMnO 4 [ A = Li, Na, K, NH 4, N(CH 3) 4] by fumaric acid. All xerogels are amorphous when dried at room temperature. Their thermal behavior however depends on the nature of the counter cation A+. Ammonium permanganates lead to the formation of ?- or ?-Mn 2O 3 while AMnO 2 mixed oxides are obtained at high temperature when A = Li, Na, K. Other crystalline phases such as LiMn 2O 4 or Na 0.7MnO 2 are also formed at lower temperature around 500°C. Oxidation of these mixed oxides into sulfuric acid lead to the formation of ?- or ?-MnO 2 while A+ and Mn 2+ ions are released into the solution. Such manganese dioxides could be good candidates for making reversible cathodes in nonaqueous lithium batteries.

  10. Nanostructured GGG powders via gel combustion

    NASA Astrophysics Data System (ADS)

    Li, Xianxue; Hu, Zhang-Gui; Li, Jiangtao

    2007-03-01

    Polycrystalline nano-sized gadolinium gallium garnet (Gd3Ga5O12, GGG) powders were synthesized via a gel combustion method from a mixed solution of Ga(NO3)3, Gd(NO3)3 and citric acid. The evolution of phase composition and micro-structure of the powders were characterized by X-ray powder diffraction, thermogravimetry/differential thermal analysis and scanning electron microscopy. Well-crystallized, single phase GGG nano-sized powders could be obtained at the calcining temperature as low as 750 °C for 2 h. No any intermediate phases formed during the calcining process. The resulting powders were well dispersed and had a relatively narrow size distribution with an average particle size of approximately 30-50 nm.

  11. KINETICS OF PITTING CORROSION IN GELS.

    SciTech Connect

    ISAACS, H.S.; ADZIC, G.

    2000-10-22

    An investigation has been carried out on stainless steel to determine the important parameters that related the changes in pH around pits to the current coming from the pits. Potentiodynamic measurements at 1 mV/s were made on Type 302 stainless steel in agar containing 1M NaCl and a wide range pH indicator. Many pits suddenly appeared at the pitting potential, as indicated by the red, low pH region around the pits. Simulations of the changes in pH were based on diffusion from a point current source. The results also were considered in terms of the effects of a minimum detectable thickness of pH change within the gel.

  12. Sol-gel coatings for optoelectronic devices

    NASA Astrophysics Data System (ADS)

    Avellaneda, Cesar O.; Macedo, Marcelo A.; Florentino, Aariovaldo O.; Aegerter, Michel A.

    1994-09-01

    Nb2O5 prepared by a sol-gel process in form of coatings and aerogels are new materials which present interesting properties: (a) the coatings present electrochromic properties and exhibit a blue coloration under Li+ insertion with 100% reversible variation of the optical transmission in the visible and near infrared range between 80% and 20% and have a high chemical stability (tested up to 2000 cycles), (b) they are semiconductor and present a photoelectric effect when illuminating in the UV region ((lambda) < 360 nm). These films are therefore very promising to be used in electrochromic devices, as electrodes for photoelectrochemical purpose and the development of nanocrystalline solar cell, and (c) when prepared in aerogel form, the high BET surface area of the powders is a promising asset to use these new materials for catalytic purposes.

  13. 40 CFR 721.9680 - Alkaline titania silica gel (generic name).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...2011-07-01 2011-07-01 false Alkaline titania silica gel (generic name...Chemical Substances § 721.9680 Alkaline titania silica gel (generic name...substance identified generically as an alkaline titania silica gel (PMN...

  14. 40 CFR 721.9680 - Alkaline titania silica gel (generic name).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...2010-07-01 2010-07-01 false Alkaline titania silica gel (generic name...Chemical Substances § 721.9680 Alkaline titania silica gel (generic name...substance identified generically as an alkaline titania silica gel (PMN...

  15. Phyllosilicates and Amorphous Gel in the Nakhlites

    NASA Astrophysics Data System (ADS)

    Hicks, L. J.; Bridges, J. C.; Gurman, S. J.

    2013-09-01

    Previous studies of the nakhlite martian meteorites have revealed hydrothermal minerals present within the fractures of the olivine minerals and the mesostasis. The olivine fractures of the Lafayette nakhlite reveal variations with initial deposits of siderite on the fracture walls, followed by crystalline phyllosilicates (smectite), and finishing with a rapidly cooled amorphous silicate gel within the central regions of the fractures. The mesostasis fractures of Lafayette also contain a crystalline phyllosilicate (serpentine). The amorphous gel is the most abundant secondary phase within the fractures of the other nakhlites [1, 2]. By studying nine nakhlite samples, including Lafayette, Governador Valadares, Nakhla, Y-000593, Y-000749, Miller-Range 03346, NWA 817, NWA 998, and NWA 5790, our aim is to constrain the identity of the phyllosilicate secondary phase minerals found throughout the nakhlite martian meteorites. This is achieved using methods including Electron Probe Micro-analysis (EPMA); X-ray Absorption Near-Edge Structure (Fe-K XANES) spectroscopy measured using Beamline I-18 at the Diamond Light Source synchrotron; and the use of Transmission Electron Microscopy (TEM) at the University of Leicester for High-Resolution (HR) imaging and Selected Area Electron Diffraction (SAED). BF studying nine nakhlite samples, including Lafayette, Governador Valadares, Nakhla, Y-000593, Y-000749, Miller-Range 03346, NWA 817, NWA 998, and NWA 5790, our aim is to constrain the identity of the phyllosilicate secondary phase minerals found throughout the nakhlite martian meteorites. This is achieved using methods including Electron Probe Micro-analysis (EPMA); X-ray Absorption Near-Edge Structure (Fe-K XANES) spectroscopy measured using Beamline I-18 at the Diamond Light Source synchrotron; and the use of Transmission Electron Microscopy (TEM) at the University of Leicester for High-Resolution (HR) imaging and Selected Area Electron Diffraction (SAED).

  16. Analytical Techniques for Furosemide Determination

    Microsoft Academic Search

    Alain Berthod

    2006-01-01

    Due to the clinical importance of furosemide, a large number of analytical procedures to detect the presence of this drug in pharmaceutical and physiological samples has been developed. In this manuscript, a review of the most frequent analytical techniques described to determine furosemide is presented. Special attention has been paid to spectrophotometric and chromatographic techniques, but also to relevant methods

  17. Quaternionic analytic torsion Kai Kohler

    E-print Network

    Köhler, Kai

    Quaternionic analytic torsion Kai K¨ohler Gregor Weingart April 10, 2001 Abstract We define an (equivariant) quaternionic analytic torsion for anti- selfdual vector bundles on quaternionic K¨ahler manifolds, using ideas by Leung and Yi. We compute this torsion for vector bundles on quaternionic homogeneous

  18. The Case for Assessment Analytics

    ERIC Educational Resources Information Center

    Ellis, Cath

    2013-01-01

    Learning analytics is a relatively new field of inquiry and its precise meaning is both contested and fluid (Johnson, Smith, Willis, Levine & Haywood, 2011; LAK, n.d.). Ferguson (2012) suggests that the best working definition is that offered by the first Learning Analytics and Knowledge (LAK) conference: "the measurement, collection,…

  19. Personal Analytical Calendar Sanaz Tavakkol

    E-print Network

    Tory, Melanie

    i Personal Analytical Calendar by Sanaz Tavakkol Bachelor of Science, Shahid Beheshti University of the author. #12;ii Supervisory Committee Personal Analytical Calendar by Sanaz Tavakkol Bachelor of Science digital calendars as a platform to integrate productivity related information as they provide beneficial

  20. Visual Analytics Law Enforcement Toolkit

    Microsoft Academic Search

    Abish Malik; Ross Maciejewski; Timothy F. Collins; David S. Ebert

    2010-01-01

    We present VALET, a Visual Analytics Law Enforcement Toolkit for analyzing spatiotemporal law enforcement data. VALET provides users with a suite of analytical tools coupled with an interactive visual interface for data exploration and analysis. This system includes linked views and interactive displays that spatiotemporally model criminal, traffic and civil (CTC) incidents and allows officials to observe patterns and quickly

  1. Analytic Geometry, A Tentative Guide.

    ERIC Educational Resources Information Center

    Helwig, G. Alfred; And Others

    This teacher's guide for a semester course in analytic geometry is based on the text "Analytic Geometry" by W. K. Morrill. Included is a daily schedule of suggested topics and homework assignments. Specific teaching hints are also given. The content of the course includes point and plane vectors, straight lines, point and space vectors, planes,…

  2. How deeply cells feel: methods for thin gels

    PubMed Central

    Buxboim, Amnon; Rajagopal, Karthikan; Brown, Andre’ E.X.; Discher, Dennis E.

    2010-01-01

    Tissue cells lack the ability to see or hear but have evolved mechanisms to feel into their surroundings and sense a collective stiffness. A cell can even sense the effective stiffness of rigid objects that are not in direct cellular contact – like the proverbial princess who feels a pea placed beneath soft mattresses. How deeply a cell feels into a matrix can be measured by assessing cell responses on a controlled series of thin and elastic gels that are affixed to a rigid substrate. Gel elasticity E is readily varied with polymer concentrations of now-standard polyacrylamide hydrogels, but to eliminate wrinkling and detachment of thin gels from an underlying glass coverslip, vinyl groups are bonded to the glass before polymerization. Gel thickness is nominally specified using micron-scale beads that act as spacers, but gels swell after polymerization as measured by z-section, confocal microscopy of fluorescent gels. Atomic force microscopy (AFM) is used to measure E at gel surfaces, employing stresses and strains that are typically generated by cells and yielding values for E that span a broad range of tissue microenvironments. To illustrate cell sensitivities to a series of thin-to-thick gels, the adhesive spreading of mesenchymal stem cells was measured on gel mimics of a very soft tissue (eg. brain, E ~ 1 kPa). Initial results show that cells increasingly respond to the rigidity of an underlying ‘hidden’ surface starting at about 10–20 µm gel thickness with a characteristic tactile length of less than about 5 µm. PMID:20454525

  3. Dewatering fine coal slurries by gel extraction. Final report

    SciTech Connect

    Gehrke, S.H.; Lyu, Lii-Hurng

    1990-12-31

    A new technology called gel extraction has been evaluated to determine its economic viability in dewatering the fine and ultrafine coal slurries generated upon separation of sulfur and ash from clean coal during the physical coal cleaning process. Water must be removed from such slurries prior to transportation and combustion but the dewatering costs are substantial, especially for the fine particles below 28 mesh (0.6 mm). Gel extraction is a potential breakthrough in slurry dewatering technology. The goal of this project was to acquire the qualitative and quantitative data needed to estimate the potential of gel extraction for dewatering coal slurries. The specific objectives were to determine the maximum extents of dewatering (minimum surface moisture in the coal product), the clarity of the water removed (minimum solids content), the speed of the dewatering cycles, the service lifetime of the gels, and the factors which influence all of these. With the results obtained, an economic analysis of Ohio coal cleaning plant dewatering technologies was carried out. The polymer gel at the heart of this project, poly (N-isopropylacrylamide) (PNIPA), can swell several times its shrunken weight at 32{degrees}C by absorbing water at 25{degrees}C. In gel extraction, a shrunken NIPA gel is contacted with a slurry at ambient temperature or cooler; the gel swells by absorbing water from the slurry. The gel is then removed from the dewatered slurry and warmed above its critical temperature of 33{degrees}C, which returns it to the shrunken state by releasing the absorbed water. The facts that the gel is reusable and the process is simple and driven by low-grade energy (warm temperatures), and not inherently limited by particle size, made the process an attractive possible alternative to centrifugation, screening, filtration, etc. for slurry dewatering.

  4. Gel formation of lignin and biodegradation of the lignin gels by microorganisms

    Microsoft Academic Search

    Hiroyuki Yamamoto; Masato Amaike; Hideki Saitoh; Yoshiyasu Sano

    2000-01-01

    The multifunctional, polyphenolic nature of isolated lignins invites practical applications in which lignin serves as the principal component of cross-linked network polymers. Unmodified kraft lignin was first condensated with phenols and then further condensated with resorcinol under alkaline conditions, to give lignin–phenol–resorcinol resin (LPR resin). Lignin gels were prepared from the methanol-diluted LPR resin with the use of organic cross-linking

  5. In vivo distribution of a vaginal gel: MRI evaluation of the effects of gel volume, time and simulated intercourse

    Microsoft Academic Search

    Kurt Thomas Barnhart; E. Scott Pretorius; Kelly Timbers; David Shera; Mayadah Shabbout; Daniel Malamud

    2004-01-01

    A microbicide is designed to coat the vaginal epithelium and prevent transmission of HIV. Complete coverage is desired for optimal protection. In vivo factors affecting coverage have not yet been studied. This randomized crossover trial evaluates the effect of gel volume and patient activity upon vaginal epithelial coating. Gynol II gel was mixed with a magnetic resonance imaging (MRI) contrast

  6. Gel growth of lysozyme crystals studied by small angle neutron scattering: case of agarose gel, a nucleation promotor

    NASA Astrophysics Data System (ADS)

    Vidal, O.; Robert, M. C.; Boué, F.

    1998-08-01

    In order to understand why hen egg white lysozyme crystals nucleate more easily in agarose gel than in gel-free solutions, we have made a small angle neutron scattering study of gelled and gel-free lysozyme solutions for different supersaturation conditions by varying the temperature, protein and salt (NaCl) concentrations. For higher supersaturations, some kinetics experiments have been done. We have analysed the SANS signal as resulting from two contributions. A first contribution is due to free protein monomers. It shows that concentration and interactions are identical in gel and gel-free media. In this respect, the gel is neutral and supersaturation is not changed. A second contribution is attributed to lysozyme clusters of several tens to several hundreds of nanometers. This contribution increases by increasing supersaturation and, for a given supersaturation, is noticeably stronger in gel than in solution. This effect being not observed when the gel is not set (agarose sol), it has been related to the mechanical properties of the medium. These considerations lead us to propose a link between clustering and nucleation, namely, nucleation would be built out of some of these clusters.

  7. HeM-Induced Milk Gels. Vl. Effect of Temperature on Firmness in Comparison with Some Common Food Gels 1

    Microsoft Academic Search

    MILOSLAV KALAB; PETER W. VOISEW; V. R. HARWALKAR; J. A. G. LAROSE

    Gels were made by heating 50g sus- pensions of skim milk powder in a 100 C water bath for 10 min. Firmness of gels as measured at 60 C was 70% softer com- pared to that at 20 C. Various additives affected firmness at 20 C but did not affect the general softening pattern at higher temperature. Repeated heating to

  8. Comparative evaluation of subgingivally delivered xanthan-based chlorhexidine gel and herbal extract gel in the treatment of chronic periodontitis

    PubMed Central

    Phogat, Megha; Rana, Tarun; Prasad, Narayan; Baiju, C. S.

    2014-01-01

    Background: Local drug delivery agents can effectively deliver the antimicrobial drugs in bactericidal concentration, and have shown improved clinical outcomes when used as an adjunct to mechanical therapy. The aim of this study was to evaluate the efficacy of a xanthan-based chlorhexidine gel versus herbal extracts’ gel as an adjunct to periodontal therapy in the treatment of chronic periodontitis. Materials and Methods: A total of 150 sites, age group of 30-50 years, periodontal pockets measuring 5-8 mm and diagnosed with chronic periodontitis were selected for the study. The selected sites were randomized in five groups: Scaling and root planing (SRP) alone (Group A), SRP + Chlosite gel (Group B), SRP + Herbal gel (Group C), Chlosite gel alone (Group D) and Herbal gel alone (Group E). Clinical parameters such as Plaque Index, Gingival Index, probing pocket depth and clinical attachment level were recorded at baseline and 1- and 3-month intervals. Results: After 3 months, there were statistically significant reductions in all the clinical parameters for Groups B and C compared with Group A. There was no significant reduction in all clinical parameters between Group D and E where no mechanical therapy was performed. Conclusion: The results indicate that the local application of herbal gel can be comparably used as chlorhexidine gel in the treatment of chronic periodontitis as an adjunct to mechanical periodontal therapy. PMID:24872624

  9. Analytic Patterns for Chaotic Equations

    NASA Astrophysics Data System (ADS)

    Conte, R.

    Chaotic evolution equations sometimes display regular patterns (fronts, kinks, holes), which often correspond to closed form analytic solutions. In the dissipative-dispersive Kuramoto and Sivashinsky travelling wave reduction u(x - ct), ?u? + bu? + ?u? + u2/2 + A = 0, ? ? 0, with (?,b,?,A) constants, such analytic solutions are known for heteroclinic solutions, but one has also observed (Toh, 1987) homoclinic solutions without corresponding analytic solutions yet. We review the search for the most general analytic solution admissible by this chaotic differential equation. Several investigations, both analytic by the Painlevé test (Thual and Frisch, 1986) and numerical by Padé approximants (Yee, Conte, Musette, 2003) indicate its quite probable single valuedness for any (?,b,?,A). Moreover, Nevanlinna theory on the growth of solutions near infinity rules out (Eremenko, 2005) the possibility for the singularities of this unknown closed form single valued expression to be only poles. We propose a qualitative closed form involving a deformed elliptic function.

  10. Separation and determination of some stereoisomers by capillary gel electrophoresis with cyclodextrin incorporated in polyacrylamide gel.

    PubMed

    Lin, J M; Nakagama, T; Okazawa, H; Wu, X Z; Hobo, T

    1996-02-01

    Capillary gel electrophoresis (CGE) was successfully applied to the separation of optically active isomers and position isomers by incorporating a suitable cyclodextrin chiral selector in polyacrylamide gel. A commercially available ss-cyclodextrin (ss-CD) was used for enantioselectivity towards o-, m- and p-nitrobenzoic acid, o-, m- and p-hydroxybenzoic acid, o-, m- and p-toluic acid and the optical isomers of dansyl-D,L-leucine and R,S-1,1'-binaphthyl-2,2-dihydrogenphosphate. Especially the effect of organic solvents, such as acetonitrile, methanol, dimethylsulphoxide and others were examined in detail. The resolution varied to some extent with the addition of the organic solvent to the polyacrylamide gel and the running buffer solution. The possible mechanism has also been discussed. In addition, quantitative aspects of the separation of stereoisomers using CGE have been studied, showing that both the resolution and accuracy of the determinations were affected by the ratio of the enantiomers. PMID:15048432

  11. Gel-Based and Gel-Free Quantitative Proteomics Approaches at a Glance

    PubMed Central

    Abdallah, Cosette; Dumas-Gaudot, Eliane; Renaut, Jenny; Sergeant, Kjell

    2012-01-01

    Two-dimensional gel electrophoresis (2-DE) is widely applied and remains the method of choice in proteomics; however, pervasive 2-DE-related concerns undermine its prospects as a dominant separation technique in proteome research. Consequently, the state-of-the-art shotgun techniques are slowly taking over and utilising the rapid expansion and advancement of mass spectrometry (MS) to provide a new toolbox of gel-free quantitative techniques. When coupled to MS, the shotgun proteomic pipeline can fuel new routes in sensitive and high-throughput profiling of proteins, leading to a high accuracy in quantification. Although label-based approaches, either chemical or metabolic, gained popularity in quantitative proteomics because of the multiplexing capacity, these approaches are not without drawbacks. The burgeoning label-free methods are tag independent and suitable for all kinds of samples. The challenges in quantitative proteomics are more prominent in plants due to difficulties in protein extraction, some protein abundance in green tissue, and the absence of well-annotated and completed genome sequences. The goal of this perspective assay is to present the balance between the strengths and weaknesses of the available gel-based and -free methods and their application to plants. The latest trends in peptide fractionation amenable to MS analysis are as well discussed. PMID:23213324

  12. Viscoelastic and fragmentation characters of model bolus from polysaccharide gels after instrumental mastication

    Microsoft Academic Search

    Sayaka Ishihara; Makoto Nakauma; Takahiro Funami; Sachiko Odake; Katsuyoshi Nishinari

    2011-01-01

    Model bolus from polysaccharide gels was investigated by the stress-relaxation tests and particulate size analyses. Using two gelling agents, gellan gum and a composite of gellan\\/psyllium seed gums, gels with different physical properties (i.e., elastic gellan single gels and plastic composite gels) and gel hardness were prepared. Gels were masticated instrumentally in the presence or absence of artificial saliva to

  13. Agarose gel electrophoresis for the separation of DNA fragments.

    PubMed

    Lee, Pei Yun; Costumbrado, John; Hsu, Chih-Yuan; Kim, Yong Hoon

    2012-01-01

    Agarose gel electrophoresis is the most effective way of separating DNA fragments of varying sizes ranging from 100 bp to 25 kb(1). Agarose is isolated from the seaweed genera Gelidium and Gracilaria, and consists of repeated agarobiose (L- and D-galactose) subunits(2). During gelation, agarose polymers associate non-covalently and form a network of bundles whose pore sizes determine a gel's molecular sieving properties. The use of agarose gel electrophoresis revolutionized the separation of DNA. Prior to the adoption of agarose gels, DNA was primarily separated using sucrose density gradient centrifugation, which only provided an approximation of size. To separate DNA using agarose gel electrophoresis, the DNA is loaded into pre-cast wells in the gel and a current applied. The phosphate backbone of the DNA (and RNA) molecule is negatively charged, therefore when placed in an electric field, DNA fragments will migrate to the positively charged anode. Because DNA has a uniform mass/charge ratio, DNA molecules are separated by size within an agarose gel in a pattern such that the distance traveled is inversely proportional to the log of its molecular weight(3). The leading model for DNA movement through an agarose gel is "biased reptation", whereby the leading edge moves forward and pulls the rest of the molecule along(4). The rate of migration of a DNA molecule through a gel is determined by the following: 1) size of DNA molecule; 2) agarose concentration; 3) DNA conformation(5); 4) voltage applied, 5) presence of ethidium bromide, 6) type of agarose and 7) electrophoresis buffer. After separation, the DNA molecules can be visualized under uv light after staining with an appropriate dye. By following this protocol, students should be able to: Understand the mechanism by which DNA fragments are separated within a gel matrix Understand how conformation of the DNA molecule will determine its mobility through a gel matrix Identify an agarose solution of appropriate concentration for their needs Prepare an agarose gel for electrophoresis of DNA samples Set up the gel electrophoresis apparatus and power supply Select an appropriate voltage for the separation of DNA fragments Understand the mechanism by which ethidium bromide allows for the visualization of DNA bands Determine the sizes of separated DNA fragments. PMID:22546956

  14. Redox-responsive macroscopic gel assembly based on discrete dual interactions.

    PubMed

    Nakahata, Masaki; Takashima, Yoshinori; Harada, Akira

    2014-04-01

    The macroscopic self-assembly of polymeric hydrogels modified with ?-cyclodextrin (?CD gel), ferrocene (Fc gel), and styrenesulfonic acid sodium salt (SSNa gel) was investigated. Under reductive conditions, the Fc gel selectively adhered to the ?CD gel through a host-guest interaction. On the other hand, the oxidized ferrocenium (Fc(+)) gel selectively adhered to the SSNa gel through an ionic interaction under oxidative conditions. The adhesion strength was estimated by a tensile test. We finally succeeded in forming an ABC-type macroscopic assembly of all three gels through two discrete noncovalent interactions. PMID:24596338

  15. Analytical Method for Measuring Cosmogenic (35)S in Natural Waters.

    PubMed

    Urióstegui, Stephanie H; Bibby, Richard K; Esser, Bradley K; Clark, Jordan F

    2015-06-16

    Cosmogenic sulfur-35 in water as dissolved sulfate ((35)SO4) has successfully been used as an intrinsic hydrologic tracer in low-SO4, high-elevation basins. Its application in environmental waters containing high SO4 concentrations has been limited because only small amounts of SO4 can be analyzed using current liquid scintillation counting (LSC) techniques. We present a new analytical method for analyzing large amounts of BaSO4 for (35)S. We quantify efficiency gains when suspending BaSO4 precipitate in Inta-Gel Plus cocktail, purify BaSO4 precipitate to remove dissolved organic matter, mitigate interference of radium-226 and its daughter products by selection of high purity barium chloride, and optimize LSC counting parameters for (35)S determination in larger masses of BaSO4. Using this improved procedure, we achieved counting efficiencies that are comparable to published LSC techniques despite a 10-fold increase in the SO4 sample load. (35)SO4 was successfully measured in high SO4 surface waters and groundwaters containing low ratios of (35)S activity to SO4 mass demonstrating that this new analytical method expands the analytical range of (35)SO4 and broadens the utility of (35)SO4 as an intrinsic tracer in hydrologic settings. PMID:25981756

  16. Influence of colloidal silicon dioxide on gel strength, robustness, and adhesive properties of diclofenac gel formulation for topical application.

    PubMed

    Lu, Zheng; Fassihi, Reza

    2015-06-01

    The objective of this study is to identify the extent of stiffness, adhesiveness, and thixotropic character of a three-dimensional gel network of a 1% diclofenac sodium topical gel formulation in the presence and absence of colloidal silicon dioxide (CSD) and assess its ease of application and adhesiveness using both objective and subjective analysis. The 1% diclofenac gel was mixed with different amounts of CSD (e.g., 0.5, 1, 2, 3, and 5% w/w) and allowed to equilibrate prior to testing. The texture analyzer in combination with a cone-cap assembly was used to objectively investigate the changes in spreadability and adhesiveness of the gel system before and after addition of CSD. Results indicate that an increase in pliability and adhesiveness at levels ?2 to ?5% w/w of CSD dispersed in the gel ensues. For subjective analysis, gels with (2% w/w) CSD and in the absence of CSD were uniformly applied to a 20-cm(2) (5 cm?×?4 cm) surface area on the forearms of healthy volunteers and vehicle preferences by the volunteers regarding ease of application, durability on the skin, compliance, and feelings concerning its textural properties were assessed. It appears that changes in the gel formulation with the addition of CSD enhance gel viscosity and bonding to the skin. Results further show that changes in physical and rheological characteristics of gel containing 2% w/w CSD did not significantly change subject preferences for the gel preparations. These findings may help formulators to have additional options to develop more robust and cost-effective formulations. PMID:25501873

  17. Simultaneous analysis of select pharmaceuticals and personal care products in fish tissue using pressurized liquid extraction combined with silica gel cleanup.

    PubMed

    Subedi, Bikram; Mottaleb, Mohammad A; Chambliss, C Kevin; Usenko, Sascha

    2011-09-16

    Analytical improvements were developed and validated for measuring select personal care products (PCPs) and two pharmaceuticals in fish tissue. The method was validated using fortified fillet tissue for twelve PCPs including fragrance materials, alkylphenols, photo initiators, and triclosan as well as two pharmaceuticals including carbamazepine (anti-seizure) and diazepam (anti-convulsant). The analytical method utilized pressurized liquid extraction (PLE) combined with silica gel cleanup, gel permeation chromatography, and gas chromatography ion-trap tandem mass spectrometry. Silica gel cleanup was combined with the PLE to produce one automated extraction/cleanup technique. This analytical improvement served to reduce the incurred cost, time, and loss of potential target analytes associated with independent cleanup steps. The combined extraction/cleanup technique resulted in an average increase of 10% in analyte recoveries. Average triplicate recoveries and relative standard deviations for the entire method, using 2.5 g of fish fillet tissue, were 92 ± 9% (recoveries ranged from 64 to 131%). The sensitivity of the analytical methods was improved by optimizing the resonant collision induced dissociation energy to the hundredths place (0.01 V). Improvements in ion production range from 24 to 122% for six of the 12 PCPs. Statistically derived method detection limits (MDLs) were also lowered on average by a factor of 8 and ranged from 1.2 to 38 ng/g wet weight. MDLs for carbamazepine and diazepam were 18 and 3.7 ng/g wet weight, respectively. Galaxolide and tonalide were measured in an environmental sample at concentrations of 81 and 5.5 ng/g wet weight, respectively. PMID:21820663

  18. Development of mucoadhesive sprayable gellan gum fluid gels.

    PubMed

    Mahdi, Mohammed H; Conway, Barbara R; Smith, Alan M

    2015-07-01

    The nasal mucosa provides a potentially good route for local and systemic drug delivery. However, the protective feature of the nasal cavity make intranasal delivery challenging. The application of mucoadhesive polymers in nasal drug delivery systems enhances the retention of the dosage form in the nasal cavity. Several groups have investigated using low acyl gellan as a drug delivery vehicle but only limited research however, has been performed on high acyl gellan for this purpose, despite its properties being more conducive to mucoadhesion. High acyl gellan produces highly elastic gels below 60°C which make it difficult to spray using a mechanical spray device. Therefore, in this study we have tried to address this problem by making fluid gels by introducing a shear force during gelation of the gellan polymer. These fluid gel systems contain gelled micro-particles suspended in a solution of un-gelled polymer. These systems can therefore behave as pourable viscoelastic fluids. In this study we have investigated the rheological behavior and mucoadhesion of fluid gels of two different types of gellan (high and low acyl) and fluid gels prepared from blends of high and low acyl gellan at a 50:50 ratio. The results demonstrated that by preparing fluid gels of high acyl gellan, the rheological properties were sufficient to spray through a standard nasal spray device. Moreover fluid gels also significantly enhance both high acyl and low acyl gellan mucoadhesion properties. PMID:25863119

  19. Fibril formation from pea protein and subsequent gel formation.

    PubMed

    Munialo, Claire Darizu; Martin, Anneke H; van der Linden, Erik; de Jongh, Harmen H J

    2014-03-19

    The objective of this study was to characterize fibrillar aggregates made using pea proteins, to assemble formed fibrils into protein-based gels, and to study the rheological behavior of these gels. Micrometer-long fibrillar aggregates were observed after pea protein solutions had been heated for 20 h at pH 2.0. Following heating of pea proteins, it was observed that all of the proteins were hydrolyzed into peptides and that 50% of these peptides were assembled into fibrils. Changes on a structural level in pea proteins were studied using circular dichroism, transmission electron microscopy, and particle size analysis. During the fibril assembly process, an increase in aggregate size was observed, which coincided with an increase in thioflavin T binding, indicating the presence of ?-sheet aggregates. Fibrils made using pea proteins were more branched and curly. Gel formation of preformed fibrils was induced by slow acidification from pH 7.0 to a final pH of around pH 5.0. The ability of pea protein-based fibrillar gels to fracture during an amplitude sweep was comparable to those of soy protein and whey protein-based fibrillar gels, although gels prepared from fibrils made using pea protein and soy protein were weaker than those of whey protein. The findings show that fibrils can be prepared from pea protein, which can be incorporated into protein-based fibrillar gels. PMID:24564788

  20. Gels composed of sodium-aluminum silicate, Lake Magadi, Kenya

    USGS Publications Warehouse

    Eugster, H.P.; Jones, B.F.

    1968-01-01

    Sodium-aluminum silicate gels are found in surftcial deposits as thick as 5 centimeters in the Magadi area of Kenya. Chemical data indicate they are formed by the interaction of hot alkaline springwaters (67?? to 82??C; pH, about 9) with alkali trachyte flows and their detritus, rather than by direct precipitation. In the process, Na2O is added from and silica is released to the saline waters of the springs. Algal mats protect the gels from erosion and act as thermal insulators. The gels are probably yearly accumulates that are washed into the lakes during floods. Crystallization of these gels in the laboratory yields analcite; this fact suggests that some analcite beds in lacustrine deposits may have formed from gels. Textural evidence indicates that cherts of rocks of the Pleistocene chert series in the Magadi area may have formed from soft sodium silicate gels. Similar gels may have acted as substrates for the accumulation and preservation of prebiological organic matter during the Precambrian.

  1. Chemotaxis of active, self-oscillating polymer gels in solution

    NASA Astrophysics Data System (ADS)

    Dayal, Pratyush; Bhattacharya, Amitabh; Kuksenok, Olga; Balazs, Anna C.

    2012-02-01

    Fighting, fleeing and feeding are hallmarks of all living things; all these activities require some degree of mobility. Herein, we undertake the first computational study of self-oscillating polymer gels and show that this system can ``communicate'' to undergo a biomimetic, collective response to small-scale chemical changes. In this study we harness unique properties of polymer gels that undergo oscillatory Belousov-Zhabotinsky (BZ) reaction. The activator for the reaction is generated within these BZ cilia and diffuses between the neighboring gels. In order to simulate the dynamics of the BZ gels in surrounding fluid we have developed a nonlinear hybrid 3D model which captures the elasto-dynamics of polymer gel and diffusive exchange of BZ reagents between the gel and the fluid. We illustrate that multiple BZ gels in solution exhibit a distinct form of chemotaxis, moving towards the highest activator concentration in the solution. Similar ability to sense and move in response to chemical gradients constitutes a vital function in simple organisms, enabling them to find food and flee from poisons.

  2. Chemically responsive gels prepared from microspheres dispersed in liquid crystals.

    PubMed

    Pal, Santanu Kumar; Agarwal, Ankit; Abbott, Nicholas L

    2009-11-01

    Liquid-crystalline materials are a promising class of stimuli-responsive materials that have been demonstrated to undergo surface-induced orientational ordering transitions that can be highly sensitive and specific to chemical species. However, past studies demonstrating surface-induced transitions in liquid crystals (LCs) have employed thin films of low-molecular-weight LCs that are difficult to stabilize (due to dewetting of the LC on a surface). Here, it is reported that it is possible to prepare liquid-crystalline gels using a mixture of polystyrene microspheres and nematic LCs that undergo changes in orientational order, and thus optical appearance, in response to exposure to specific chemical compounds. These colloid-in-liquid-crystal (CLC) gels are mechanically stable and can be molded on chemically functionalized surfaces into thin films containing micrometer-sized LC-rich domains that span the two interfaces of the gels. In contrast to other reports of LC gels, where the presence of a polymeric or self-assembled small-molecule gelator network within a nematic LC frustrates ordering transitions from propagating through the gels over distances, it is demonstrated that thin films of CLC gels, when supported on chemically functionalized surfaces, do undergo easily visualized ordering transitions upon exposure to organophosphonate compounds. Because these optically responsive CLC gels are mechanically robust and can be molded, this class of composite LC material may be broadly useful for the design of chemically responsive LC devices. PMID:19777464

  3. Current issues in sol-gel reaction kinetics

    SciTech Connect

    Assink, R.A.; Kay, B.D.

    1990-01-01

    This paper surveys a few of the current issues in sol-gel reaction kinetics. Many times seemingly modest changes in reactants or reaction conditions can lead to substantial differences in the overall reaction rates and pathways. For example, qualitative features of the reaction kinetics can depend on catalyst concentration. At very high acid-catalyst concentrations, reverse are significant for TMOS sol-gels, while for moderate acid-catalyst concentrations, reverse reactions are substantially reduced. The reaction kinetics are substantially reduced. The reaction kinetics of two similar tetraalkoxysilanes: tetramethoxysilane (TMOS) and tetraethoxysilane (TEOS), can be markedly different under identical reaction conditions. Under acid-catalyzed reaction conditions, a TMOS sol-gel undergoes both water-and alcohol-producing condensation reactions while a TEOS sol-gel undergoes only water-producing condensation. The early time hydrolysis and condensation reactions of a TMOS sol-gel are statistical in nature and can be quantitatively described by a few simple reaction rate constants while the reaction behavior of a TEOS sol-gel is markedly nonstatistical. A comprehensive theory of sol-gel kinetics must address diverse experimental findings. 9 refs., 3 figs., 1 tab.

  4. Alcohol hand gel--a potential fire hazard.

    PubMed

    O'Leary, Fionnuala M; Price, Gareth J

    2011-01-01

    Alcohol hand gel and wipes are the common method of disinfecting the hands of healthcare workers and working surfaces in clinical settings. We present a case of a 40-year-old health care support worker who was referred acutely to our burns unit following flame burns in association with alcohol gel use. Fortunately she was able to extinguish the flames without sustaining a significant thermal injury however this case highlights the potential danger associated with alcohol gel use, especially with smokers. With the ever increasing use of alcohol hand gel, not only in healthcare settings but also in the general population there needs to be clearer warnings regarding the potential for ignition after use. Alcohol hand gel and wipes are the common method of disinfecting the hands of healthcare workers and working surfaces in clinical settings. Most trusts have strict policies regarding mandatory sanitisation of hands before and after patient contact. This is most easily achieved by the use of alcohol gel due to its ease of use and quick drying properties. As a result alcohol hand disinfectant is available is a variety of formats including foam, gel and wipes. It is also now widely available for use to the general public. PMID:20493792

  5. Human platelet gel supernatant inactivates opportunistic wound pathogens on skin.

    PubMed

    Edelblute, Chelsea M; Donate, Amy L; Hargrave, Barbara Y; Heller, Loree C

    2015-01-01

    Activation of human platelets produces a gel-like substance referred to as platelet rich plasma or platelet gel. Platelet gel is used clinically to promote wound healing; it also exhibits antimicrobial properties that may aid in the healing of infected wounds. The purpose of this study was to quantify the efficacy of human platelet gel against the opportunistic bacterial wound pathogens Acinetobacter baumannii, Pseudomonas aeruginosa, and Staphylococcus aureus on skin. These opportunistic pathogens may exhibit extensive antibiotic resistance, necessitating the development of alternative treatment options. The antimicrobial efficacy of platelet gel supernatants was quantified using an in vitro broth dilution assay, an ex vivo inoculated skin assay, and in an in vivo skin decontamination assay. Human platelet gel supernatants were highly bactericidal against A. baumannii and moderately but significantly bactericidal against S. aureus in vitro and in the ex vivo skin model. P. aeruginosa was not inactivated in vitro; a low but significant inactivation level was observed ex vivo. These supernatants were quite effective at inactivating a model organism on skin in vivo. These results suggest application of platelet gel has potential clinical applicability, not only in the acceleration of wound healing, but also against relevant bacteria causing wound infections. PMID:24433255

  6. Western Blot of Stained Proteins from Dried Polyacrylamide Gels

    NASA Technical Reports Server (NTRS)

    Gruber, Claudia; Stan-Lotter, Helga

    1996-01-01

    Western blotting of proteins is customarily performed following their separation on polyacrylamide gels, either prior to staining (1) or, as recently reported, following staining (2). We describe here Western blotting with stained gels, which had been dried and some of which had been stored for years. This procedure permits immunological analysis of proteins, to which antisera may have become available only later, or where the application of newly developed sensitive detection methods is desired. Once rehydration of the gels is achieved, proteins can be-transferred to blotting membranes by any appropriate protocol. Proteins stained with Coomassie Blue have to be detected with a non-chromogenic method, such as the film-based enhanced chemiluminescence (ECL)2) procedure (3). Silver stained proteins, which transfer in the colorless form, may be visualized by any detection method, although, because of the usually very low amounts of proteins, detection by ECL is preferable. Blotting of stained proteins from rehydrated gels is as rapid and as quantitative as from freshly prepared gels, in contrast to blotting from wet stained gels, which requires extensive washing and results in low transfer efficiency (2). Together with a photographic record of the gel pattern, unambiguous identification of immunoreactive proteins from complex mixtures is possible. Some further applications of this work are discussed.

  7. Electrically Induced Volume Modification of Ionic Porous Gels

    NASA Astrophysics Data System (ADS)

    El-Lessy, Hussein N.; Chen, Yuanye; Wang, Changjie; Hu, Zhibing; Li, Yong

    1997-10-01

    Volume alterations of conventional gels such as N-isopropylacrylamides (NIPA) have been widely tested via several mediums. However, mediums such as temperature and pH are often dependent variables difficult to control in some environments such as the human body. It is for this reason that this team has developed an ionic-porous-gel (IPG) capable of responding to an operatively induced electrical stimuli much rapidly than conventional gels. The volume transition of the IPG is tested for maximum shrinkage and expansion in de-ionized water. Results indicate that the gel has ionization and de-ionization properties similar to that of biological muscle, in that it will re-expand to near original size upon termination of electric field. The volume change is effected by the induced electro-osmolosis through the matrix of the gel. The permeability of IPG permits the transition of ions in and out of the gel, subsequently allowing for the active movement of water through the matrix, hence, affecting volume transitions. This experiment has shown the practicality of an operatively controlled polymer gel and its reactivity to numerous impulses. It is thus easy to discern the potential for further research application such as in the field of synthetic muscle development.

  8. Sol-Gel Synthesis and Thermal Evaluation of Cordierite–Zirconia Composites (Ce–ZrO 2 , Y–Ce–ZrO 2 )

    Microsoft Academic Search

    G. Senguttuvan; T. Settu; P. Kuppusamy; V. Kamaraj

    1999-01-01

    Cordierite and cordierite–zirconia composites (ceria- and yttria–ceria-stabilized zirconia) were prepared by sol-gel processing for different compositions. The precursor powders of these composites were studied using analytical techniques such as thermogravimetric analysis, differential thermal analysis, X-ray diffraction, and infrared spectroscopy for different temperatures to investigate the crystallization behavior of the material. It was observed that the cordierite–zirconia composite powders are crystallized

  9. Ionic liquid mediated sol–gel sorbents for hollow fiber solid-phase microextraction of pesticide residues in water and hair samples

    Microsoft Academic Search

    Mahmoud Ebrahimi; Zarrin Es‘haghi; Fatemeh Samadi; Mohammad-Saeid Hosseini

    2011-01-01

    An ionic liquid mediated sol–gel sorbents for hollow fiber solid-phase microextraction (HF-SPME) was developed for extraction of the pesticides: diazinon, fenitrothion, malathion, fenvalerate, phosalone and tridemorph from human hair and water samples. The analytes were subsequently analyzed with high performance liquid chromatography and diode array detection (HPLC–DAD). Preliminary experiments were carried out in order to study experimental conditions for pesticides’

  10. Aging of foamed gel used for subsurface permeability reduction

    SciTech Connect

    Miller, M.J.; Khilar, K.; Fogler, H.S. [Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Chemical Engineering] [Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Chemical Engineering

    1995-10-01

    Foamed gel is a dispersion of gas encapsulated in a continuous cross-linked external phase that may be a plastic, a water-soluble polymer gel, or a colloidal silica gel. Foamed gel has recently been used to plug porous media for the purpose of physically controlling the movement of subsurface fluids. The performance of foamed gel barriers is directly related to the pore level configuration of the foamed gel, specifically, the number and location of gelled lenses that plug flow paths. The pore level configuration of foamed gel changes because of gas diffusion from small bubbles to large bubbles during the shut-in period for gelation that follows foam generation. The evolution of a foamed gel`s texture in porous media has been studied using etched glass micromodels to determine what factors influence the final number and location of gelled lenses. Because the foam disproportionation was so rapid, gelation reactions that restrict gas diffusion must occur within approximately 20 min in order to maintain the initial distribution. Because the walls of the pore body prevent bubbles from exceeding the diameter of the pore body, any multiple pore spanning bubbles formed will coexist indefinitely. It was found that the number of pre spanning bubbles increases as the pore body aspect ratio (pore length/pore width) increases. Applications include plugging high conductivity streaks to modify the injection profile of oil wells, shut-off water in production wells, the stabilization of earthen formations, and the formation of impermeable barriers to divert groundwater flow away from contaminant plumes.

  11. Azelaic acid (15% gel) in the treatment of acne rosacea.

    PubMed

    Gupta, Aditya K; Gover, Melissa D

    2007-05-01

    In December of 2002, the FDA approved azelaic acid 15% gel for the topical treatment of inflammatory papules and pustules of mild to moderate rosacea. Azelaic acid is a saturated dicarboxylic acid, which is naturally occurring and has been used in the treatment of rosacea, acne, and melasma. The 15% gel has a high efficacy and is generally well tolerated, with the local irritation (burning, stinging, itching, and scaling) being typically mild and transient. Azelaic acid 15% gel is considered effective and safe as a therapy for inflammatory papulo-pustular rosacea and is suitable for use on all skin types. PMID:17472690

  12. Purification of radiolabeled RNA products using denaturing gel electrophoresis

    PubMed Central

    Adachi, Hironori; Yu, Yi-Tao

    2014-01-01

    This unit discusses a basic method for purification of radiolabeled RNAs using denaturing polyacrylamide gel electrophoresis. The method consists of a number of experimental procedures, including total RNA preparation from yeast cells, isolation of a specific RNA from total yeast RNA, RNA 3' terminal labeling using nucleotide (5’[32P]pCp) addition (via ligation), denaturing (8 M urea) polyacrylamide gel electrophoresis, and RNA extraction from the gel slice. Key points for achieving good electrophoretic separation of RNA are also discussed. PMID:24510465

  13. pH-Induced In Situ Gel for Periodontal Anesthesia

    PubMed Central

    Gupta, H.; Singh, R. M.; Singh, G. N.; Kaushik, D.; Sharma, A.

    2008-01-01

    A pH mediated in situ gelling system was developed using prilocaine hydrochloride for periodontal anesthesia using combination of chitosan and hydroxypropylmethylcellulose. The gel so developed can be used as anaesthetic in lengthy dental surgery. The gel was evaluated for many parameters like gelation pH, viscosity, physicochemical properties, in vitro release, sterility and stability. Gel with chitosan (0.25% w/v) and hydroxypropylmethylcellulose (0.25% w/v) was found to have good gelation near pH 7.4 (pH of mucous) with prolonged action. PMID:21369439

  14. Sol-gel synthesis of phosphate ceramic composites II

    SciTech Connect

    Cao, Z.; Lee, B.I. [Department of Ceramic and Materials Engineering, Clemson University, Clemson, South Carolina 29634-0907 (United States); Samuels, W.D.; Wang, L.; Exarhos, G.J. [Battelle Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352 (United States)

    1998-06-01

    Phosphate ceramics were synthesized using the sol-gel technique of direct reaction of P{sub 2}O{sub 5} with tetraethoxy silane (TEOS) or titanium tetraethoxide (Ti(OEt){sub 4}). The reaction mechanism of P{sub 2}O{sub 5} and TEOS was deduced using liquid and solid-state NMR. Hexacoordinated silicon in phosphosilicate gels was observed. A specially structured titanium phosphate-layered Ti(HPO{sub 4}){sub 2}{center_dot}2H{sub 2}O was synthesized for the first time through the sol-gel method. The gelation process and sintering properties were investigated. {copyright} {ital 1998 Materials Research Society.}

  15. C60: the first one-component gel?

    E-print Network

    C. Patrick Royall; Stephen R. Williams

    2011-02-15

    Until now, gels have been formed of multicomponent soft matter systems, consisting of a solvent and one or more macromolecular or colloidal species. Here we show that, for sufficient quench rates, the Girifalco model of C60 can form gels which we identify by their slow dynamics and long-lived network structure. These gels are stable at room temperature, at least on the simulation timescale up to 100 ns. At moderate temperatures around 1000 K, below the bulk glass transition temperature, C60 exhibits crystallisation and phase separation proceeds without the dynamical arrest associated with gelation, in contrast to many colloidal systems.

  16. Determination of diclazuril, toltrazuril and its two metabolites in poultry tissues and eggs by gel permeation chromatography-liquid chromatography-tandem mass spectrometry.

    PubMed

    Ai, Lianfeng; Sun, Hanwen; Wang, Fengchi; Chen, Ruichun; Guo, Chunhai

    2011-06-15

    A new procedure has been described for the extraction of diclazuril (DIZ), toltrazuril (TOZ) and its two main metabolites toltrazuril sulphoxide (TZSO) and toltrazuril sulphone (TZS) from poultry tissues and eggs, using gel permeation chromatography (GPC). The analytes and the deuterated internal standard were extracted from the samples with ethyl acetate. The analytes were measured by LC coupled to an electrospray ionization tandem mass spectrometer operating in the negative ion mode. Excellent linear dynamic range was observed from 1 to 500 ?g/L with the correlation coefficients (R(2)) better than 0.99 for all analytes. The method LOQ of the four analytes in real samples was 1.2 ?g/kg for DIZ and TOZ, and 1.8 ?g/kg for TZSO and TZS. These values are far lower than the maximum residue limits (MRLs) established by several control authorities. The developed method was accurate with overall recoveries in four matrices. PMID:21565565

  17. Structural studies on the yttrium-doped cobalt ferrite powders synthesized by sol-gel combustion method

    NASA Astrophysics Data System (ADS)

    Shobana, M. K.; Kwon, Hoon; Choe, Heeman

    2012-07-01

    Y0.2CoFe1.8O4 nanopowders were prepared using a sol-gel combustion method. Metal nitrates, such as yttrium nitrate, cobalt nitrate and ferric nitrate, were used as the source materials. Citric acid and polyvinyl alcohol were used as the burning agent and agglomeration reducing agent, respectively. The pH of the precursor was maintained at 7. The mean crystallite size of the prepared ferrite was in the range of ?20-70 nm. The inverse spinel structure, cubic morphology, and the identification of functional groups of the yttrium-doped cobalt ferrite were analyzed systematically using several analytical tools.

  18. [Comparison of intestinal bacteria composition identified by various analytical methods].

    PubMed

    Fujisawa, Tomohiko

    2014-01-01

    Many different kinds of bacteria are normally found in the intestines of healthy humans and animals. To study the ecology and function of these intestinal bacteria, the culture method was fundamental until recent years, and suitable agar plates such as non-selective agar plates and several selective agar plates have been developed. Furthermore, the roll-tube, glove box, and plate-in-bottle methods have also been developed for the cultivation of fastidious anaerobes that predominantly colonize the intestine. Until recently, the evaluation of functional foods such as pre- and probiotics was mainly done using culture methods, and many valuable data were produced. On the other hand, genomic analysis such as the fluorescence in situ hybridization (FISH), quantitative PCR (qPCR), clone-library, denaturing gradient gel electrophoresis (DGGE), temperature gradient gel electrophoresis (TGGE), terminal-restriction fragment length polymorphism (T-RFLP) methods, and metagenome analysis have been used for the investigation of intestinal microbiota in recent years. The identification of bacteria is done by investigation of the phenotypic characteristics in culture methods, while rRNA genes are used as targets in genomic analysis. Here, I compare the fecal bacteria identified by various analytical methods. PMID:24681991

  19. Gels and gel-derived glasses in the system Na2O-B2O3-SiO2

    NASA Technical Reports Server (NTRS)

    Mukherjee, S. P.

    1983-01-01

    The containerless melting of high-purity multicomponent homogeneous gels and gel monoliths offers a unique approach to making ultrapure multicomponent optical glasses in the reduced gravity environment of space. Procedures for preparing and characterizing gels and gel-derived glasses in the system Na2O-B2O3-SiO2 are described. Preparation is based on the polymerization reactions of alkoxysilane with trimethyl borate or boric acid and a suitable sodium compound. The chemistry of the gelling process is discussed in terms of process parameters and the gel compositions. The physicochemical nature of gels prepared by three different procedures was found to be significantly different. Infrared absorption spectra indicate finite differences in the molecular structures of the different gels. The melting of the gel powders and the transformation of porous gel monoliths to transparent 'glass' without melting are described.

  20. Gels and gel-derived glasses in the Na2O-B2O3-SiO2 system. [containerless melting in space

    NASA Technical Reports Server (NTRS)

    Mukherjee, S. P.

    1982-01-01

    The containerless melting of high-purity multicomponent homogeneous gels and gel-monoliths offers a unique approach to making ultrapure multicomponent optical glasses in the reduced gravity environment of space. Procedures for preparing and characterizing gels and gel-derived glasses in the Na2O-B2O3-SiO2 system are described. Preparation is based on the polymerization reactions of alkoxysilane with trimethyl borate or boric acid and a suitable sodium compound. The chemistry of the gelling process is discussed in terms of process parameters and the gel compositions. The physicochemical nature of gels prepared by three different procedures were found to be significantly different. IR absorption spectra indicate finite differences in the molecular structures of the different gels. The melting of the gel powders and the transformation of porous gel-monoliths to transparent 'glass' without melting are described.