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Sample records for analytical ultracentrifugation gel

  1. Analytical Ultracentrifuge User Guide Volume 1: Hardware

    E-print Network

    Nicholson, Bruce J.

    , but high speed ultracentrifugation became a reality in the 1920's. The ultracentrifuge was initially . . . . . . . . . . . . . . . . . . . . . . . . . 11 4 Rotors 13 5 Counterbalance 14 6 AUC Cells 16 6.1 General Remarks.6 Cell Disassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 7 Cell and Rotor

  2. Analytical Ultracentrifugation: Sedimentation Velocity and Sedimentation Equilibrium

    PubMed Central

    Cole, James L.; Lary, Jeffrey W.; Moody, Thomas; Laue, Thomas M.

    2009-01-01

    Analytical ultracentrifugation (AUC) is a versatile and powerful method for the quantitative analysis of macromolecules in solution. AUC has broad applications for the study of biomacromolecules in a wide range of solvents and over a wide range of solute concentrations. Three optical systems are available for the analytical ultracentrifuge (absorbance, interference and fluorescence) that permit precise and selective observation of sedimentation in real time. In particular, the fluorescence system provides a new way to extend the scope of AUC to probe the behavior of biological molecules in complex mixtures and at high solute concentrations. In sedimentation velocity, the movement of solutes in high centrifugal fields is interpreted using hydrodynamic theory to define the size, shape and interactions of macromolecules. Sedimentation equilibrium is a thermodynamic method where equilibrium concentration gradients at lower centrifugal fields are analyzed to define molecule mass, assembly stoichiometry, association constants and solution nonideality. Using specialized sample cells and modern analysis software, researchers can use sedimentation velocity to determine the homogeneity of a sample and define whether it undergoes concentration-dependent association reactions. Subsequently, more thorough model-dependent analysis of velocity and equilibrium experiments can provide a detailed picture of the nature of the species present in solution and their interactions. PMID:17964931

  3. Probing metal nanoparticles and assemblies with analytical ultracentrifugation

    E-print Network

    Carney, Randy (Randy Patrick)

    2010-01-01

    Analytical Ultracentrifugation (AUC) is a powerful tool to obtain statistically relevant size and shape measurements for macromolecular systems. Metal nanoparticles coated by a ligand shell of thiolated molecules provide ...

  4. Characterization of Intrinsically Disordered Proteins by Analytical Ultracentrifugation.

    PubMed

    Scott, David J; Winzor, Donald J

    2015-01-01

    Intrinsically disordered proteins have traditionally been largely neglected by structural biologists because a lack of rigid structure precludes their study by X-ray crystallography. Structural information must therefore be inferred from physicochemical studies of their solution behavior. Analytical ultracentrifugation yields important information about the gross conformation of an intrinsically disordered protein. Sedimentation velocity studies provide estimates of the weight-average sedimentation and diffusion coefficients of a given macromolecular state of the protein. PMID:26412654

  5. Improved Measurement of the Rotor Temperature in Analytical Ultracentrifugation

    PubMed Central

    Zhao, Huaying; Balbo, Andrea; Metger, Howard; Clary, Robert; Ghirlando, Rodolfo; Schuck, Peter

    2014-01-01

    Sedimentation velocity is a classical method for measuring the hydrodynamic, translational friction coefficient of biological macromolecules. In a recent study, comparing various analytical ultracentrifuges, we have shown that external calibration of the scan time, radial magnification, and temperature are critically important for accurate measurements (Anal. Biochem., 2013, doi: 10.1016/j.ab.2013.05.011). To achieve accurate temperature calibration, we have introduced the use of an autonomous miniature temperature logging integrated circuit (Maxim Thermochron iButton ™) that can be inserted in an ultracentrifugation cell assembly and spun at low rotor speeds. In the present work, we developed an improved holder for the temperature sensor located in the rotor handle. This has the advantage of not reducing the rotor capacity and allows for a direct temperature measurement of the spinning rotor during high-speed sedimentation velocity experiments up to 60,000 rpm. We demonstrate the sensitivity of this approach by monitoring the adiabatic cooling due to rotor stretching during rotor acceleration, and the reverse process upon rotor deceleration. Based on this, we developed a procedure to approximate isothermal rotor acceleration for better temperature control. PMID:24530285

  6. Improved measurement of the rotor temperature in analytical ultracentrifugation.

    PubMed

    Zhao, Huaying; Balbo, Andrea; Metger, Howard; Clary, Robert; Ghirlando, Rodolfo; Schuck, Peter

    2014-04-15

    Sedimentation velocity is a classical method for measuring the hydrodynamic, translational friction coefficient of biological macromolecules. In a recent study comparing various analytical ultracentrifuges, we showed that external calibration of the scan time, radial magnification, and temperature is critically important for accurate measurements (Anal. Biochem. 440 (2013) 81-95). To achieve accurate temperature calibration, we introduced the use of an autonomous miniature temperature logging integrated circuit (Maxim Thermochron iButton) that can be inserted into an ultracentrifugation cell assembly and spun at low rotor speeds. In the current work, we developed an improved holder for the temperature sensor located in the rotor handle. This has the advantage of not reducing the rotor capacity and allowing for a direct temperature measurement of the spinning rotor during high-speed sedimentation velocity experiments up to 60,000rpm. We demonstrated the sensitivity of this approach by monitoring the adiabatic cooling due to rotor stretching during rotor acceleration and the reverse process on rotor deceleration. Based on this, we developed a procedure to approximate isothermal rotor acceleration for better temperature control. PMID:24530285

  7. 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

  8. Assembly, loading, and alignment of an analytical ultracentrifuge sample cell.

    PubMed

    Balbo, Andrea; Zhao, Huaying; Brown, Patrick H; Schuck, Peter

    2009-01-01

    The analytical ultracentrifuge (AUC) is a powerful biophysical tool that allows us to record macromolecular sedimentation profiles during high speed centrifugation. When properly planned and executed, an AUC sedimentation velocity or sedimentation equilibrium experiment can reveal a great deal about a protein in regards to size and shape, sample purity, sedimentation coefficient, oligomerization states and protein-protein interactions. This technique, however, requires a rigorous level of technical attention. Sample cells hold a sectored center piece sandwiched between two window assemblies. They are sealed with a torque pressure of around 120-140 in/lbs. Reference buffer and sample are loaded into the centerpiece sectors and then after sealing, the cells are precisely aligned into a titanium rotor so that the optical detection systems scan both sample and reference buffer in the same radial path midline through each centerpiece sector while rotating at speeds of up to 60, 000 rpm and under very high vacuum Not only is proper sample cell assembly critical, sample cell components are very expensive and must be properly cared for to ensure they are in optimum working condition in order to avoid leaks and breakage during experiments. Handle windows carefully, for even the slightest crack or scratch can lead to breakage in the centrifuge. The contact between centerpiece and windows must be as tight as possible; i.e. no Newton s rings should be visible after torque pressure is applied. Dust, lint, scratches and oils on either the windows or the centerpiece all compromise this contact and can very easily lead to leaking of solutions from one sector to another or leaking out of the centerpiece all together. Not only are precious samples lost, leaking of solutions during an experiment will cause an imbalance of pressure in the cell that often leads to broken windows and centerpieces. In addition, plug gaskets and housing plugs must be securely in place to avoid solutions being pulled out of the centerpiece sector through the loading holes by the high vacuum in the centrifuge chamber. Window liners and gaskets must be free of breaks and cracks that could cause movement resulting in broken windows. This video will demonstrate our procedures of sample cell assembly, torque, loading and rotor alignment to help minimize component damage, solution leaking and breakage during the perfect AUC experiment. PMID:19893484

  9. Probing the Oligomeric Assemblies of Pea Porphobilinogen Synthase by Analytical Ultracentrifugation

    E-print Network

    Fairman, Robert

    Probing the Oligomeric Assemblies of Pea Porphobilinogen Synthase by Analytical Ultracentrifugation. Biol. 10, 757-763]. Herein, we establish that the distribution of pea PBGS quaternary structures also of tetrapy- rroles including heme, chlorophyll, vitamin B12, and cofactor F430 (1). The pea (Pisum sati

  10. Faster, safer, and better DNA purification by ultracentrifugation using GelRed stain and development of mismatch oligo DNA for genome walking.

    PubMed

    Kasajima, Ichiro; Ohtsubo, Norihiro; Sasaki, Katsutomo

    2014-01-01

    Purification of plant DNA involves lengthy ultracentrifugation using ethidium bromide. Here, ultracentrifugation method is improved by staining with GelRed. The resulting method is faster, safer and of higher sensitivity. Purified DNA quality was confirmed by treatment with restriction enzymes and isolation of gene promoters. New type of long adaptor with mismatch sequence was also developed for promoter isolation. PMID:25081591

  11. Measurement of the Temperature of the Resting Rotor in Analytical Ultracentrifugation

    PubMed Central

    Ghirlando, Rodolfo; Zhao, Huaying; Balbo, Andrea; Piszczek, Grzegorz; Curth, Ute; Brautigam, Chad A.; Schuck, Peter

    2014-01-01

    Accurate measurements of rotor temperature are critical for the interpretation of hydro dynamic parameters in analytical ultracentrifugation. We have recently developed methods for a more accurate determination of the temperature of a spinning rotor utilizing iButton® temperature loggers. Here we report that the temperature measured with the iButton on the counterbalance of a resting rotor, following thermal equilibration under high vacuum, closely corresponded to the temperature of the spinning rotor with a precision better than 0.2 °C. This strategy offers an inexpensive and straightforward approach to monitor the accuracy of the temperature calibration and determine corrective temperature offsets. PMID:24799348

  12. Multidimensional analysis of nanoparticles with highly disperse properties using multiwavelength analytical ultracentrifugation.

    PubMed

    Walter, Johannes; Löhr, Konrad; Karabudak, Engin; Reis, Wieland; Mikhael, Jules; Peukert, Wolfgang; Wohlleben, Wendel; Cölfen, Helmut

    2014-09-23

    The worldwide trend in nanoparticle technology toward increasing complexity must be directly linked to more advanced characterization methods of size, shape and related properties, applicable to many different particle systems in science and technology. Available techniques for nanoparticle characterization are predominantly focused on size characterization. However, simultaneous size and shape characterization is still an unresolved major challenge. We demonstrate that analytical ultracentrifugation with a multiwavelength detector is a powerful technique to address multidimensional nanoparticle analysis. Using a high performance optical setup and data acquisition software, information on size, shape anisotropy and optical properties were accessible in one single experiment with unmatched accuracy and resolution. A dynamic rotor speed gradient allowed us to investigate broad distributions on a short time scale and differentiate between gold nanorod species including the precise evaluation of aggregate formation. We report how to distinguish between different species of single-wall carbon nanotubes in just one experiment using the wavelength-dependent sedimentation coefficient distribution without the necessity of time-consuming purification methods. Furthermore, CdTe nanoparticles of different size and optical properties were investigated in a single experiment providing important information on structure-property relations. Thus, multidimensional information on size, density, shape and optical properties of nanoparticulate systems becomes accessible by means of analytical ultracentrifugation equipped with multiwavelength detection. PMID:25130765

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

    PubMed Central

    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 reversible 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. PMID:18196178

  14. Analytic ultracentrifuge calibration and determination of lipoprotein-specific refractive increments

    SciTech Connect

    Talwinder, S.K.; Adamson, G.L.; Glines, L.A.; Lindgren, F.T.; Laskaris, M.A.; Shore, V.G.

    1984-01-01

    Accurate quantification of the major classes and subfractions of human serum lipoproteins is an important analytical need in the characterization and evaluation of therapy of lipid and lipoprotein abnormalities. For calibrating the analytic ultracentrifuge (AnUC), the authors routinely use a Beckman calibration wedge cell with parallel scribed lines 1 cm apart. Such a cell give a rectangular pattern in the schlieren diagram, which determines magnification and also provides an area corresponding to an invariant refractive increment. Complete calibration for AnUC analysis of lipoproteins also requires accurate determination of the specific refractive increments (SRI) of the major lipoprotein classes, namely low density lipoprotein (LDL) and high density lipoprotein (HDL). These are measured in the density in which they are analyzed, i.e., 1.061 g/ml for LDL and 1.200 g/ml for HDL. Five fresh serum samples were fractionated for total LDL and total HDL and their SRI determined. Total lipoprotein mass was determined using precise CHN elemental analysis and compositional analyses. The results yielded corrected SRI of 0.00142 and 0.00135 ..delta..n/g/100 ml for LDL and HDL. Thus, their current values using 0.00154 and 0.00149 ..delta..n/g/100 ml underestimate LDL and HDL by 9% and 11%. Corrections of all previous LDL and HDL AnUC data can be made using appropriate factors of 1.087 and 1.106.

  15. 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

  16. A trimeric, alpha-helical, coiled coil peptide: association stoichiometry and interaction strength by analytical ultracentrifugation.

    PubMed

    Thomas, R M; Zampieri, A; Jumel, K; Harding, S E

    1997-01-01

    Alpha-helical coiled coils are proving to be almost ideal systems for the modelling of peptide and protein self-association processes. Stable oligomeric systems, in which the stoichiometry is well defined, can be produced by the careful selection of the appropriate amino acid sequence, although the principles behind this are still not fully understood. Here we report on a 35 residue peptide, FZ, synthesized by the solid phase method, which was originally designed to form a dimer, but which, in fact, associates to the trimeric state. A detailed characterization of the associative properties of the peptide has been performed by circular dichroism spectroscopy and, in particular, by sedimentation equilibrium in the analytical ultracentrifuge. The presence of the trimeric state, which is stable even at low peptide concentrations, has been confirmed by various independent methods of analysis for molar mass. The effects of both temperature and of guanidinium chloride on the peptide have been investigated and both found to be peptide-concentration dependent. The unfolding induced by the denaturant cannot be adequately described by a simple, two state monomer-trimer equilibrium. PMID:9213557

  17. Next-Generation AUC Adds a Spectral Dimension: Development of Multiwavelength Detectors for the Analytical Ultracentrifuge.

    PubMed

    Pearson, Joseph Z; Krause, Frank; Haffke, Dirk; Demeler, Borries; Schilling, Kristian; Cölfen, Helmut

    2015-01-01

    We describe important advances in analytical ultracentrifugation (AUC) hardware, which add new information to the hydrodynamic information observed in traditional AUC instruments. In contrast to the Beckman-Coulter XLA UV/visible detector, multiwavelength (MWL) detection is able to collect sedimentation data not just for one wavelength, but for a large wavelength range in a single experiment. The additional dimension increases the data density by orders of magnitude, significantly improving the statistics of the measurement and adding important information to the experiment since an additional dimension of spectral characterization is now available to complement the hydrodynamic information. The new detector avoids tedious repeats of experiments at different wavelengths and opens up new avenues for the solution-based investigation of complex mixtures. In this chapter, we describe the capabilities, characteristics, and applications of the new detector design with biopolymers as the focus of study. We show data from two different MWL detectors and discuss strengths and weaknesses of differences in the hardware and different data acquisition modes. Also, difficulties with fiber optic applications in the UV are discussed. Data quality is compared across platforms. PMID:26412645

  18. 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

  19. Variable-Field Analytical Ultracentrifugation: I. Time-Optimized Sedimentation Equilibrium.

    PubMed

    Ma, Jia; Metrick, Michael; Ghirlando, Rodolfo; Zhao, Huaying; Schuck, Peter

    2015-08-18

    Sedimentation equilibrium (SE) analytical ultracentrifugation (AUC) is a gold standard for the rigorous determination of macromolecular buoyant molar masses and the thermodynamic study of reversible interactions in solution. A significant experimental drawback is the long time required to attain SE, which is usually on the order of days. We have developed a method for time-optimized SE (toSE) with defined time-varying centrifugal fields that allow SE to be attained in a significantly (up to 10-fold) shorter time than is usually required. To achieve this, numerical Lamm equation solutions for sedimentation in time-varying fields are computed based on initial estimates of macromolecular transport properties. A parameterized rotor-speed schedule is optimized with the goal of achieving a minimal time to equilibrium while limiting transient sample preconcentration at the base of the solution column. The resulting rotor-speed schedule may include multiple over- and underspeeding phases, balancing the formation of gradients from strong sedimentation fluxes with periods of high diffusional transport. The computation is carried out in a new software program called TOSE, which also facilitates convenient experimental implementation. Further, we extend AUC data analysis to sedimentation processes in such time-varying centrifugal fields. Due to the initially high centrifugal fields in toSE and the resulting strong migration, it is possible to extract sedimentation coefficient distributions from the early data. This can provide better estimates of the size of macromolecular complexes and report on sample homogeneity early on, which may be used to further refine the prediction of the rotor-speed schedule. In this manner, the toSE experiment can be adapted in real time to the system under study, maximizing both the information content and the time efficiency of SE experiments. PMID:26287634

  20. 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

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

    PubMed Central

    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

  2. Effects of rotational speed on the hydrodynamic properties of pharmaceutical antibodies measured by analytical ultracentrifugation sedimentation velocity.

    PubMed

    Krayukhina, Elena; Uchiyama, Susumu; Fukui, Kiichi

    2012-09-29

    Analytical ultracentrifugation sedimentation velocity (AUC-SV) has recently become one of the most important tools for the measurement of hydrodynamic properties of proteins. Although a number of studies using AUC-SV as applied to pharmaceutical antibodies have been conducted, the effect of rotational speed on molecular properties has not been systematically examined. The present study aimed to elucidate the influence of rotational speed on the hydrodynamic parameters of pharmaceutical antibodies. A monoclonal and a polyclonal antibody were studied by using AUC-SV at 5 different rotor speeds, and the acquired data were analyzed either by using the computer programs SEDFIT or UltraScan. The frictional ratio of the studied antibodies decreased at high rotor speeds, resulting in underestimation of molecular weight. The frictional ratio value of the monoclonal antibody measured at the low rotor speed was consistent with that of human immunoglobulin G1 computed from its three-dimensional structure. The best agreement between the measured molecular weight and the value calculated from the antibody sequence was achieved at the lower rotor speed. Similar to the results obtained using antibodies, AUC-SV analysis of human serum albumin revealed that the frictional ratio and apparent molecular weight behave in a speed-dependent manner. We deduced that the findings were mainly attributable to the hydrostatic pressure in the analytical ultracentrifuge. The current study implies that rotor speed should be carefully considered in antibody studies using AUC-SV. PMID:22728396

  3. 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

  4. Characterization of Protein Detergent Complexes by NMR, Light Scattering, and Analytical Ultracentrifugation

    PubMed Central

    Maslennikov, Innokentiy; Krupa, Martin; Dickson, Christopher; Esquivies, Luis; Blain, Katherine; Kefala, Georgia; Choe, Senyon; Kwiatkowski, Witek

    2009-01-01

    Bottlenecks in expression, solubilization, purification and crystallization hamper the structural study of integral membrane proteins (IMPs). Successful crystallization is critically dependent on the purity, stability and oligomeric homogeneity of an IMP sample. These characteristics are in turn strongly influenced by the type and concentration of the detergents used in IMP preparation. By utilizing the techniques and analytical tools we earlier developed for the characterization of protein-detergent complexes (PDCs) (Maslennikov et al., 2007), we demonstrate that for successful protein extraction from E. coli membrane fractions, the solubilizing detergent associates preferentially to IMPs rather than to membrane lipids. Notably, this result is contrary to the generally accepted mechanism of detergent-mediated IMP solubilization. We find that for one particular member of the family of proteins studied (E. coli receptor kinases, which is purified in mixed multimeric states and oligomerizes through its transmembrane region), the protein oligomeric composition is largely unaffected by a 10-fold increase in protein concentration, by alteration of micelle properties through addition of other detergents to the PDC sample, or by a 20-fold variation in the detergent concentration used for solubilization of the IMP from the membrane. We observed that the conditions used for expression of the IMP, which impact protein density in the membrane, has the greatest influence on the IMP oligomeric structure. Finally, we argue that for concentrating PDCs smaller than 30 kDa, stirred concentration cells are less prone to over-concentration of detergent and are therefore more effective than centrifugal ultrafiltration devices. PMID:19214777

  5. Critical velocities of ultracentrifuges

    NASA Technical Reports Server (NTRS)

    Sokolov, V I

    1951-01-01

    The Euler equations for the rotation of a solid body are applied to the problem of the motion of ultracentrifuges. Particular attention is paid to the problem of the passage of an ultracentrifuge rotor through the critical velocity. The factors that affect the passage of rotors through the critical point are stressed.

  6. Sol-gel matrices for direct colorimetric detection of analytes

    DOEpatents

    Charych, Deborah H. (Albany, CA); Sasaki, Darryl (Albuquerque, NM); Yamanaka, Stacey (Dallas, TX)

    2000-01-01

    The present invention relates to methods and compositions for the direct detection of analytes using color changes that occur in immobilized biopolymeric material in response to selective binding of analytes to their surface. In particular, the present invention provides methods and compositions related to the encapsulation of biopolymeric material into metal oxide glass using the sol-gel method.

  7. Sol-Gel Matrices For Direct Colorimetric Detection Of Analytes

    DOEpatents

    Charych, Deborah H. (Albany, CA); Sasaki, Darryl (Albuquerque, NM); Yamanaka, Stacey (Dallas, TX)

    2002-11-26

    The present invention relates to methods and compositions for the direct detection of analytes using color changes that occur in immobilized biopolymeric material in response to selective binding of analytes to their surface. In particular, the present invention provides methods and compositions related to the encapsulation of biopolymeric material into metal oxide glass using the sol-gel method.

  8. 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 Central

    Brookes, Emre; Demeler, Borries; Rosano, Camillo

    2010-01-01

    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

  9. ANALYTICAL BIOCHEMISTRY 196,427-432 (19%) Denaturing Gradient Gel Method for Mapping Single

    E-print Network

    Ernst, Susan G.

    ANALYTICAL BIOCHEMISTRY 196,427-432 (19%) Denaturing Gradient Gel Method for Mapping Single Base, Massachusetts 02155 Received February 26,199l A denaturing gradient gel electrophoresis (DGGE) method the appli- cation of a denaturing gradient gel electrophoresis (DGGE) method (described first by Gray et al

  10. Analytical Ultracentrifugation for Characterizing Nanocrystals and Their

    E-print Network

    Natelson, Douglas

    or physical means to an active biomolecule. Historically, gold nano- crystal/antibody conjugates have found circumstances, however. Single-stranded DNA-gold nano- crystal conjugate systems, for instance, change color from red to blue as DNA hybridization induces cross-linking between nanocrystals.2,17 Alternatively

  11. HORMONE STUDIES WITH THE ULTRACENTRIFUGE

    PubMed Central

    Chiles, James A.; Severinghaus, Aura E.

    1938-01-01

    1. An ultracentrifuge is described in which the rotor is driven by a compressed air turbine, and is spun in an evacuated chamber to minimize friction and heating. The rotating parts are supported by a cushion of air in an air bearing. 2. The centrifuge rotor holds 10 test tubes inclined at 45° to the axis, and has a capacity of 55 cc. It is operated at a maximum speed of 51,000 R.P.M., which develops at the top of the fluid column in the test tubes a centrifugal field of over 100,000 times gravity, and at the bottom of the fluid column a field of over 200,000 times gravity. 3. By means of a reverse turbine, the rotor can be brought to a stop from full speed in a relatively short time. 4. A precession damping device is described, which effectively damps the precession and wobbling of the rotor that usually occurs at certain speeds in machines of this type. 5. A relatively long section of shaft is used between the centrifuge rotor and lower bearings. This prevents vibrations from being appreciably transmitted through the shaft to the lower bearings and driving mechanism, and results in a negligible wear on the bearings. 6. The driving mechanism is designed so that the positions of its parts are adjustable, and so that the driving mechanism may be dismantled without disturbing these adjustments. PMID:19870769

  12. Analysis of Endoscopic Pancreatic Function Test (ePFT)-Collected Pancreatic Fluid Proteins Precipitated Via Ultracentrifugation

    PubMed Central

    Paulo, Joao A; Kadiyala, Vivek; Gaun, Aleksandr; Sauld, John FK; Ghoulidi, Ali; Banks, Peter A; Steen, Hanno; Conwell, Darwin L

    2015-01-01

    Context We have shown previously that trichloroacetic acid precipitation is an effective method of protein extraction from pancreatic fluid for downstream biomarker discovery, compared to other common extraction methods tested. Objective We aim to assess the utility of ultracentrifugation as an alternative method of protein extraction from pancreatic fluid. Design Proteins extracted from trichloroacetic acid- and ultracentrifugation-precipitated pancreatic fluid were identified using mass spectrometry techniques (in-gel tryptic digestion followed by liquid chromatography-tandem mass spectrometry; GeLC-MS/MS). Data were analyzed using Proteome Discoverer and Scaffold 3. Setting This is a proteomic analysis experiment of endoscopically collected fluid in an academic center. Patients The study population included adult patients referred to the Center for Pancreatic Disease at Brigham and Women’s Hospital, Boston, MA, USA for the evaluation of abdominal pain and gastrointestinal symptoms. Interventions Secretin-stimulated pancreatic fluid was collected as standard of care for the evaluation of abdominal pain and gastrointestinal symptoms. Main outcome measures We compared proteins identified via standard trichloroacetic acid precipitation and this alternative ultracentrifugation strategy. Results A subset of pancreatic fluid proteins was identified via the ultracentrifugation method. Of these proteins, similar numbers were obtained from fully tryptic or semi-tryptic database searching. Proteins identified in the ultracentrifugation-precipitated samples included previously identified biomarker candidates of chronic pancreatitis. Conclusions This alternative ultracentrifugation strategy requires less time and fewer handling procedures than standard trichloroacetic acid precipitation, at the expense of higher sample volume. As such, this method is well suited for targeted assays (i.e., dot blotting or targeted mass spectrometry) if the protein of interest is among those readily identified by ultracentrifugation-promoted precipitation. PMID:23474565

  13. 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)

  14. 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

  15. 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

  16. AN AIR-DRIVEN ULTRACENTRIFUGE FOR MOLECULAR SEDIMENTATION

    PubMed Central

    Biscoe, J.; Pickels, E. G.; Wyckoff, Ralph W. G.

    1936-01-01

    Details of construction are given for an air-driven ultracentrifuge for molecular sedimentation. This instrument, like the standard oil-driven machine of Svedberg, uses rotors giving a 6.50 cm. radius of rotation and has cameras of great depth of focus. PMID:19870521

  17. Analytical QbD: development of a native gel electrophoresis method for measurement of monoclonal antibody aggregates.

    PubMed

    Pathak, Mili; Dutta, Debayon; Rathore, Anurag

    2014-08-01

    This paper presents a quality by design (QbD) based development of a novel native PAGE (N-PAGE) method as a low-cost analytical tool for analysis of aggregates of monoclonal antibodies. Comparability to the present gold standard of SEC has been established. The motivation is the fact that SEC requires relatively expensive equipment and consumables, thus making N-PAGE relevant to those academicians and other small companies involved in early-stage development of biotherapeutics that do not have access to SEC, especially in developing countries. Furthermore, SEC suffers from certain disadvantages including the possibility of secondary interactions between the stationary phase and analyte resulting in higher elution time and therefore underestimation of the analyte size. The proposed N-PAGE method can also serve as an orthogonal analytical method for aggregate analysis. A QbD-based approach has been used for development and optimization of the protocol. First, initial screening studies were carried out with parameters including the running buffer pH, running buffer molarity, gel buffer pH, loading dye, sample concentration, and running voltage. Next, optimization of operating parameters was performed using principles of design of experiments. The final optimized protocol was compared to the traditional SEC method and the results were found to be comparable. While N-PAGE has been in use for protein analysis for several decades, use of N-PAGE for analysis of mAb aggregates with data comparable to SEC such as the case presented here is novel. PMID:24643784

  18. Separation of colloidal two dimensional materials by density gradient ultracentrifugation

    NASA Astrophysics Data System (ADS)

    Kuang, Yun; Song, Sha; Huang, Jinyang; Sun, Xiaoming

    2015-04-01

    Two-dimensional (2D) materials have been made through various approaches but obtaining monodispersed simply by synthesis optimization gained little success, which highlighted the need for introducing nanoseparation methods. Density gradient ultracentrifugation method has emerged as a versatile and scalable method for sorting colloidal 2D nanomaterials. Isopycnic separation was applied on thickness-dependent separation of graphene nanosheets. And rate-zonal separation, as a more versatile separation method, demonstrated its capability in sorting nanosheets of chemically modified single layered graphene, layered double hydroxide, and even metallic Ag. Establishing such density gradient ultracentrifugation method not only achieves monodispersed nanosheets and provides new opportunities for investigation on size dependent properties of 2D materials, but also makes the surface modification possible by introducing "reaction zones" during sedimentation of the colloids.

  19. Improving Blood Plasma Glycoproteome Coverage by Coupling Ultracentrifugation Fractionation to Electrostatic Repulsion-Hydrophilic Interaction Chromatography Enrichment.

    PubMed

    Adav, Sunil S; Hwa, Ho Hee; de Kleijn, Dominique; Sze, Siu Kwan

    2015-07-01

    Blood plasma is considered to be an excellent source of disease biomarkers because it contains proteins, lipids, metabolites, cell, and cell-derived extracellular vesicles from different cellular origins including diseased tissues. Most secretory and membranous proteins that can be found in plasma are glycoproteins; therefore, the plasma glycoproteome is one of the major subproteomes that is highly enriched with disease biomarkers. As a result, the glycoproteome has attracted much attention in clinical proteomic research. The modification of proteins with glycans regulates a wide range of functions in biology, but profiling plasma glycoproteins on a global scale has been hampered by the presence of low stoichiometry of glycoproteins in a complex high abundance plasma proteome background and lack of effective analytical technique. This study aims to improve plasma glycoproteome coverage using pig plasma as a model sample with a two-step strategy. The first step involves fractionation of the plasma proteins using ultracentrifugation into supernatant and pellet that is believed to contain low abundant glycoproteins. In the second step, further enrichment of glycopeptides was achieved in both fractions by adopting electrostatic repulsion hydrophilic interaction chromatography (ERLIC) coupled to tandem mass spectrometry (LC-MS/MS) analysis. The coverage of enriched glycoproteins in supernatant, pellet, and whole plasma sample as control was compared. Using this simple sample fractionation approach by ultracentrifugation and further ERLIC enrichment technique, sample complexity was reduced and glycoproteome coverage was significantly enhanced in supernatant and pellet fractions (by >50%) compared with whole plasma sample. This study showed that when ultracentrifugation is coupled to ERLIC glycopeptides enrichment and glycoproteome identification are significantly improved. This study demonstrates the combination of ultracentrifugation and ERLIC as a useful method for discovering plasma glycoprotein disease biomarkers. PMID:26044363

  20. 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

  1. On the general concept of buoyancy in sedimentation and ultracentrifugation.

    PubMed

    Piazza, Roberto; Buzzaccaro, Stefano; Secchi, Eleonora; Parola, Alberto

    2013-08-01

    Gravity or ultracentrifuge settling of colloidal particles and macromolecules usually involves several disperse species, either because natural and industrial colloids display a large size polydispersity, or because additives are put in on purpose to allow for density-based fractionation of the suspension. Such 'macromolecular crowding', however, may have surprising effects on sedimentation, for it strongly affects the buoyant force felt by a settling particle. Here we show that, as a matter of fact, the standard Archimedes' principle is just a limiting law, valid only for mesoscopic particles settling in a molecular fluid, and we obtain a fully general expression for the actual buoyancy force providing a microscopic basis to the general thermodynamic analysis of sedimentation in multi-component mixtures. The effective buoyancy also depends on the particle shape, being much more pronounced for thin rods and discs. Our model is successfully tested on simple colloidal mixtures, and used to predict rather unexpected effects, such as denser particles floating on top of a lighter fluid, which we actually observe in targeted experiments. This 'generalized Archimedes principle' may provide a tool to devise novel separation methods sensitive to particle size and shape. PMID:23913160

  2. HORMONE STUDIES WITH THE ULTRACENTRIFUGE : I. AN IMPROVED AIR-DRIVEN VACUUM ULTRACENTRIFUGE SUITABLE FOR CONCENTRATION WORK IN BIOLOGICAL EXPERIMENTS.

    PubMed

    Chiles, J A; Severinghaus, A E

    1938-06-30

    1. An ultracentrifuge is described in which the rotor is driven by a compressed air turbine, and is spun in an evacuated chamber to minimize friction and heating. The rotating parts are supported by a cushion of air in an air bearing. 2. The centrifuge rotor holds 10 test tubes inclined at 45 degrees to the axis, and has a capacity of 55 cc. It is operated at a maximum speed of 51,000 R.P.M., which develops at the top of the fluid column in the test tubes a centrifugal field of over 100,000 times gravity, and at the bottom of the fluid column a field of over 200,000 times gravity. 3. By means of a reverse turbine, the rotor can be brought to a stop from full speed in a relatively short time. 4. A precession damping device is described, which effectively damps the precession and wobbling of the rotor that usually occurs at certain speeds in machines of this type. 5. A relatively long section of shaft is used between the centrifuge rotor and lower bearings. This prevents vibrations from being appreciably transmitted through the shaft to the lower bearings and driving mechanism, and results in a negligible wear on the bearings. 6. The driving mechanism is designed so that the positions of its parts are adjustable, and so that the driving mechanism may be dismantled without disturbing these adjustments. PMID:19870769

  3. Analytical and micropreparative peptide mapping by high performance liquid chromatography/electrospray mass spectrometry of proteins purified by gel electrophoresis.

    PubMed Central

    Hess, D.; Covey, T. C.; Winz, R.; Brownsey, R. W.; Aebersold, R.

    1993-01-01

    We report the use of microbore reverse-phase high performance liquid chromatography connected on-line to an electrospray mass spectrometer for the separation/detection of peptides derived by proteolytic digestion of proteins separated by polyacrylamide gel electrophoresis. A small fraction (typically 10% of the total) of the peptides eluting from the column was diverted through a flow-splitting device into the ion source of the mass spectrometer, whereas the majority of the peptide samples was collected for further analyses. We demonstrate the feasibility of obtaining reproducible peptide maps from submicrogram amounts of protein applied to the gel and good correlation of the signal detected by the mass spectrometer with peptide detection by UV absorbance. Furthermore, independently verifiable peptide masses were determined from subpicomole amounts of peptides directed into the mass spectrometer. The method was used to analyze the 265-kDa and the 280-kDa isoforms of the enzyme acetyl-CoA carboxylase isolated from rat liver. The results provide compelling evidence that the two enzyme isoforms are translation products of different genes and suggest that these approaches may be of general utility in the definitive comparison of protein isoforms. We furthermore illustrate that knowledge of peptide masses as determined by this technique provides a major advantage for error-free data interpretation in chemical high-sensitivity peptide sequence analysis. PMID:8104612

  4. 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

  5. ESR studies of spin-labeled membranes aligned by isopotential spin-dry ultracentrifugation: lipid-protein interactions.

    PubMed Central

    Ge, M; Budil, D E; Freed, J H

    1994-01-01

    Electron spin resonance (ESR) studies have been performed on spin-labeled model membranes aligned using the isopotential spin-dry ultracentrifugation (ISDU) method of Clark and Rothschild. This method relies on sedimentation of the membrane fragments onto a gravitational isopotential surface with simultaneous evaporation of the solvent in a vacuum ultracentrifuge to promote alignment. The degree of alignment obtainable using ISDU, as monitored by ESR measurements of molecular ordering for both lipid (16-PC) and cholestane spin labels (CSL), in dipalmitoylphosphatidylcholine (DPPC) model membranes compares favorably with that obtainable by pressure-annealing. The much gentler conditions under which membranes may be aligned by ISDU greatly extends the range of macroscopically aligned membrane samples that may be investigated by ESR. We report the first ESR study of an integral membrane protein, bacteriorhodopsin (BR) in well-aligned multilayers. We have also examined ISDU-aligned DPPC multilayers incorporating a short peptide gramicidin A' (GA), with higher water content than previously studied. 0.24 mol% BR/DPPC membranes with CSL probe show two distinct components, primarily in the gel phase, which can be attributed to bulk and boundary regions of the bilayer. The boundary regions show sharply decreased molecular ordering and spectral effects comparable to those observed from 2 mol% GA/DPPC membranes. The boundary regions for both BR and GA also exhibit increased fluidity as monitored by the rotational diffusion rates. The high water content of the GA/DPPC membranes reduces the disordering effect as evidenced by the reduced populations of the disordered components. The ESR spectra obtained slightly below the main phase transition of DPPC from both the peptide- and protein-containing membranes reveals a new component with increased ordering of the lipids associated with the peptide or protein. This increase coincides with a broad endothermic peak in the DSC, suggesting a disaggregation of both the peptide and the protein before the main phase transition of the lipid. Detailed simulations of the multicomponent ESR spectra have been performed by the latest nonlinear least-squares methods, which have helped to clarify the spectral interpretations. It is found that the simulations of ESR spectra from CSL in the gel phase for all the lipid membranes studied could be significantly improved by utilizing a model with CSL molecules existing as both hydrogen-bonded to the bilayer interface and non-hydrogen-bonded within the bilayer. Images FIGURE 1 PMID:7535112

  6. 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

  7. Improving the thermal, radial, and temporal accuracy of the analytical ultracentrifuge through external references.

    PubMed

    Ghirlando, Rodolfo; Balbo, Andrea; Piszczek, Grzegorz; Brown, Patrick H; Lewis, Marc S; Brautigam, Chad A; Schuck, Peter; Zhao, Huaying

    2013-09-01

    Sedimentation velocity (SV) is a method based on first principles that provides a precise hydrodynamic characterization of macromolecules in solution. Due to recent improvements in data analysis, the accuracy of experimental SV data emerges as a limiting factor in its interpretation. Our goal was to unravel the sources of experimental error and develop improved calibration procedures. We implemented the use of a Thermochron iButton temperature logger to directly measure the temperature of a spinning rotor and detected deviations that can translate into an error of as much as 10% in the sedimentation coefficient. We further designed a precision mask with equidistant markers to correct for instrumental errors in the radial calibration that were observed to span a range of 8.6%. The need for an independent time calibration emerged with use of the current data acquisition software (Zhao et al., Anal. Biochem., 437 (2013) 104-108), and we now show that smaller but significant time errors of up to 2% also occur with earlier versions. After application of these calibration corrections, the sedimentation coefficients obtained from 11 instruments displayed a significantly reduced standard deviation of approximately 0.7%. This study demonstrates the need for external calibration procedures and regular control experiments with a sedimentation coefficient standard. PMID:23711724

  8. Improving the Thermal, Radial and Temporal Accuracy of the Analytical Ultracentrifuge through External References

    PubMed Central

    Ghirlando, Rodolfo; Balbo, Andrea; Piszczek, Grzegorz; Brown, Patrick H.; Lewis, Marc S.; Brautigam, Chad A.; Schuck, Peter; Zhao, Huaying

    2013-01-01

    Sedimentation velocity (SV) is a method based on first-principles that provides a precise hydrodynamic characterization of macromolecules in solution. Due to recent improvements in data analysis, the accuracy of experimental SV data emerges as a limiting factor in its interpretation. Our goal was to unravel the sources of experimental error and develop improved calibration procedures. We implemented the use of a Thermochron iButton® temperature logger to directly measure the temperature of a spinning rotor, and detected deviations that can translate into an error of as much as 10% in the sedimentation coefficient. We further designed a precision mask with equidistant markers to correct for instrumental errors in the radial calibration, which were observed to span a range of 8.6%. The need for an independent time calibration emerged with use of the current data acquisition software (Zhao et al., doi 10.1016/j.ab.2013.02.011) and we now show that smaller but significant time errors of up to 2% also occur with earlier versions. After application of these calibration corrections, the sedimentation coefficients obtained from eleven instruments displayed a significantly reduced standard deviation of ? 0.7 %. This study demonstrates the need for external calibration procedures and regular control experiments with a sedimentation coefficient standard. PMID:23711724

  9. 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

    -Ortega3, Jia Ma1, Carrie A. May51, Ernest L. Maynard54, Anna Modrak-Wojcik16, Yee-Foong Mok55, Norbert Mücke56, Luitgard Nagel-Steger57, Geeta J. Narlikar39, Masanori Noda47¤c, Amanda Nourse58, Tomas Obsil46, Chad K. Park59, Jin-Ku Park60, Peter D. Pawelek..., Baltimore, Maryland, 21205, United States of America, 67 Research Complex at Harwell, Rutherford Appleton Laboratory, Oxfordshire, OX11 0FA, United Kingdom, 68 Proteome and Protein Analysis, University of Newcastle, Newcastle upon Tyne, NE1 7RU, United...

  10. Ultracentrifugation and inductively coupled plasma mass spectrometry for metal-protein equilibrium studies

    NASA Astrophysics Data System (ADS)

    Arnquist, Isaac J.; Holcombe, James A.

    2012-10-01

    The coupling of separation by preparative ultracentrifugation and metal detection by inductively coupled plasma mass spectrometry (ICP-MS) has been explored for metal-protein equilibrium determinations. This study characterizes the stoichiometry as well as apparent (Kapp) and intrinsic (Kint) binding affinities of the metal-protein association for a model protein. In particular, the affinity of Cu2 + for the high affinity binding site in bovine serum albumin (BSA) is determined. Once equilibrium is established between Cu2 + and BSA, preparative ultracentrifugation moves the metalloprotein away from the meniscus, leaving unbound equilibrium copper in the protein free solution. Since the initial (total) concentrations of purified BSA and Cu2 + can be determined, the free copper concentration at equilibrium can also be determined by taking a small aliquot above the sedimenting boundary for analysis using ICP-MS. This analysis allows for the determination of free Cu2 + ion, which is identical to the equilibrium concentration prior to ultracentrifugation. From these data Kapp and Kint were determined at two different conditions, 100 mM Tris(hydroxymethyl)aminomethane (Tris) at pH 9.53 and pH 7.93. log Kapp values of 17.6 and 14.6 were determined at pH 9.53 and pH 7.93, respectively. Furthermore, pH-independent log Kint values of - 1.43 and - 1.04 were determined at pH 9.53 and 7.93, respectively. While the log Kint at pH 9.53 was in good agreement with literature values obtained from alternative methods, Kint at pH 7.93 was about 2.5 × larger than previously reported. BSA undergoes a structural rearrangement between pH 7-9, and the generally accepted pH-dependency of protein tertiary structure may be responsible for the variations in the "intrinsic" binding constant. The Cu-BSA binding affinity was also monitored in 100 mM Tris 0.1% sodium dodecyl sulfate (SDS) solution at pH 7.93 in order to determine the effect of a denaturant on metal binding. Results for both log Kapp and log Kint were similar to those obtained in the absence of 0.1% SDS at pH 7.93. Overall, this study validates and shows the efficacy of combining preparative ultracentrifugation with ICP-MS detection for interrogating metal-protein associations while causing minimal equilibrium perturbations as a result of the separation and measurement processes. Advantages and disadvantages of this methodology are discussed as it relates to alternative methods for metal-protein studies.

  11. Size reduction of 3D-polymer-coated single-walled carbon nanotubes by ultracentrifugation.

    PubMed

    Tsutsumi, Yusuke; Fujigaya, Tsuyohiko; Nakashima, Naotoshi

    2015-12-14

    We describe a novel single-walled carbon nanotube (SWNT) cutting method without introducing any structural defects on the tubes; namely, the finding that simple ultracentrifugation at 600?000g for the SWNTs coated with a cross-linked polymer formed by poly(N-isopropylacrylamide) (PNIPAM) or the polyethylene glycol-carrying PNIPAM copolymer provides shortened (<200 nm) SWNTs, which was revealed by dynamic light scattering (DLS) and atomic force microscopy (AFM) measurements. The Raman and absorption measurements of the obtained SWNTs indicated that the graphitic structure and optical properties, such as characteristic absorption and photoluminescence in the near-IR region of the SWNTs, were almost unchanged even after the cutting. The obtained shortened SWNTs were individually solubilized in water and buffer solution due to the remaining cross-linked polymer structures on the SWNTs. The present method is very simple (only ultracentrifugation) and the yield is very high, which are the advantages in the preparation of many shortened isolated SWNTs with specific properties and functions that are applicable in many fields including bioapplications in vivo, such as imaging, NIR-hyperthermic treatment, photodynamic therapy, etc. PMID:26538202

  12. Polyelectrolyte gels

    SciTech Connect

    Segalman, D.J.; Witkowski, W.R.

    1995-06-01

    Polyelectrolyte (PE) gels are swollen polymer/solvent networks that undergo a reversible volume collapse/expansion through various types of stimulation. Applications that could exploit this large deformation and solvent expulsion/absorption characteristics include robotic {open_quotes}fingers{close_quotes} and drug delivery systems. The goals of the research were to first explore the feasibility of using the PE gels as {open_quotes}smart materials{close_quotes} - materials whose response can be controlled by an external stimulus through a feedback mechanism. Then develop a predictive capability to simulate the dynamic behavior of these gels. This involved experimentally characterizing the response of well-characterized gels to an applied electric field and other stimuli to develop an understanding of the underlying mechanisms which cause the volume collapse. Lastly, the numerical analysis tool was used to simulate various potential engineering devices based on PE gels. This report discusses the pursuit of those goals through experimental and computational means.

  13. Density-gradient ultracentrifugation ... ... can be used to separate empty (end-capped) and water-filled (open) carbon

    E-print Network

    Wenseleers, Wim

    . Density-gradient ultracentrifugation ... ... can be used to separate empty (end-capped) and water in their Communication on page 2764 ff., each nanotube chirality can be observed at two different densities, which Separation and Diameter-Sorting of Empty (End-Capped) and Water-Filled (Open) Carbon Nanotubes by Density

  14. What buoyancy really is. A Generalized Archimedes Principle for sedimentation and ultracentrifugation

    E-print Network

    Roberto Piazza; Stefano Buzzaccaro; Eleonora Secchi; Alberto Parola

    2012-05-28

    Particle settling is a pervasive process in nature, and centrifugation is a much versatile separation technique. Yet, the results of settling and ultracentrifugation experiments often appear to contradict the very law on which they are based: Archimedes Principle - arguably, the oldest Physical Law. The purpose of this paper is delving at the very roots of the concept of buoyancy by means of a combined experimental-theoretical study on sedimentation profiles in colloidal mixtures. Our analysis shows that the standard Archimedes' principle is only a limiting approximation, valid for mesoscopic particles settling in a molecular fluid, and we provide a general expression for the actual buoyancy force. This "Generalized Archimedes Principle" accounts for unexpected effects, such as denser particles floating on top of a lighter fluid, which in fact we observe in our experiments.

  15. Fluorescence detection for gel and capillary electrophoresis

    SciTech Connect

    Hogan, B.

    1992-07-21

    First, an indirect fluorescence detection system for the separation of proteins via gel electrophoresis. Quantities as low as 50 nanograms of bovine serum albumin and soybean trypsin inhibitor are separated and detected visually without the need for staining of the analytes. This is very similar to levels of protein commonly separated with gel electrophoresis.

  16. An optimized method for high-titer lentivirus preparations without ultracentrifugation

    PubMed Central

    Jiang, Wei; Hua, Rui; Wei, Mengping; Li, Chenhong; Qiu, Zilong; Yang, Xiaofei; Zhang, Chen

    2015-01-01

    Lentiviral technology has proven to be a powerful tool to express exogenous genes in dividing and non-dividing cells. Currently, most protocols for generating high-titer lentivirus require ultracentrifugation, which can be an instrumental barrier for routine operations in a laboratory. In this study, the effect of relative centrifugal force (RCF) on the concentration efficiency of the lentivirus was systematically explored, and it was found that sucrose gradient centrifugation with a relatively low speed (?10,000?g) robustly produces a high-titer virus (up to 2?×?108?TU/ml). The optimal sucrose concentration is 10%, and the recovery rate of the functional virus is greater than 80%. The infection efficiency of both concentrated and un-concentrated lentivirus decreases rapidly when the viruses are stored at 4?°C (????1.3 days) or subjected to multiple freeze-thaw cycles (??=?1.1 rounds). In summary, we describe an efficient and easy-to-handle protocol for high-titer lentivirus purification. PMID:26348152

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

    E-print Network

    Buschmann, Michael

    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 weight of 19 and 29 MDa for chitosan and PEI polyplexes, respectively. Data from AUC also allowed

  18. Characterization of Homogeneous, Cooperative Protein-DNA Clusters by Sedimentation Equilibrium Analytical Ultracentrifugation and Atomic Force Microscopy.

    PubMed

    Tessmer, Ingrid; Fried, Michael G

    2015-01-01

    Strong, positively cooperative binding can lead to the clustering of proteins on DNA. Here, we describe one approach to the analysis of such clusters. Our example is based on recent studies of the interactions of O(6)-alkylguanine DNA alkyltransferase (AGT) with high-molecular-weight DNAs (Adams et al., 2009; Tessmer, Melikishvili, & Fried, 2012). Cooperative cluster size distributions are predicted using the simplest homogeneous binding and cooperativity (HBC) model, together with data obtained by sedimentation equilibrium analysis. These predictions are tested using atomic force microscopy imaging; for AGT, measured cluster sizes are found to be significantly smaller than those predicted by the HBC model. A mechanism that may account for cluster size limitation is briefly discussed. PMID:26412659

  19. 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.

  20. 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

  1. DMBC: Analytics Google Analytics

    E-print Network

    Stowell, Michael

    Dashboard: Audience · Overview · Demographics · Interests · Geo · Behavior · Technology · Mobile · Users Flow Analytics Dashboard: Real-Time · Overview · Locations · Traffic Sources · Content Analytics Dashboard: Acquisitions · Overview #12;Assignment: Google Analytics Integration Deliverables: · Create

  2. Characterization and comparative performance of lentiviral vector preparations concentrated by either one-step ultrafiltration or ultracentrifugation.

    PubMed

    Papanikolaou, Eleni; Kontostathi, Georgia; Drakopoulou, Ekati; Georgomanoli, Maria; Stamateris, Evangelos; Vougas, Kostas; Vlahou, Antonia; Maloy, Andrew; Ware, Mark; Anagnou, Nicholas P

    2013-07-01

    Gene therapy utilizing lentiviral vectors (LVs) constitutes a real therapeutic alternative for many inherited monogenic diseases. Therefore, the generation of functional vectors using fast, non-laborious and cost-effective strategies is imperative. Among the available concentration methods for VSV-G pseudotyped lentiviruses to achieve high therapeutic titers, ultracentrifugation represents the most common approach. However, the procedure requires special handling and access to special instrumentation, it is time-consuming, and most importantly, it is cost-ineffective due to the high maintenance expenses and consumables of the ultracentrifuge apparatus. Here we describe an improved protocol in which vector stocks are prepared by transient transfection using standard cell culture media and are then concentrated by ultrafiltration, resulting in functional vector titers of up to 6×10(9) transducing units per millilitre (TU/ml) without the involvement of any purification step. Although ultrafiltration per se for concentrating viruses is not a new procedure, our work displays one major novelty; we characterized the nature and the constituents of the viral batches produced by ultrafiltration using peptide mass fingerprint analysis. We also determined the viral functional titer by employing flow cytometry and evaluated the actual viral particle size and concentration in real time by using laser-based nanoparticle tracking analysis based on Brownian motion. Vectors generated by this production method are contained in intact virions and when tested to transduce in vitro either murine total bone marrow or human CD34(+) hematopoietic stem cells, resulted in equal transduction efficiency and reduced toxicity, compared to lentiviral vectors produced using standard ultracentrifugation-based methods. The data from this study can eventually lead to the improvement of protocols and technical modifications for the clinical trials for gene therapy. PMID:23583684

  3. 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.

  4. Effects of ultracentrifugation on plasma biochemical values of prefledged wild peregrine falcons (Falco peregrinus) in northeastern Illinois.

    PubMed

    Pond, Joel; Thompson, Steve; Hennen, Mary; Pauley, John; Gamble, Kathryn C

    2012-09-01

    Centrifugation is performed on whole blood samples to obtain serum or plasma for biochemical analysis. Although blood samples centrifuged in a microhematocrit tube may maximize recovery of plasma from small-volume samples, plasma biochemical values from such samples have been implicated as causing erroneous results. To compare blood biochemical values obtained by microhematocrit centrifugation and centrifugation with a commercial tilt-rotor machine, blood samples were collected from peregrine falcon (Falco peregrinus) eyases aged 32-40 days (n=51). The samples were separated into 2 equal aliquots with 1 aliquot centrifuged in a tilt-rotor machine and the other aliquot ultracentrifuged in microhematocrit tubes. Separated plasma from both processes was sent to a commercial veterinary reference laboratory for routine clinical biochemical analysis. No significant differences were found in the biochemical results of the paired samples by the 2 centrifugation methods. These results show that the centrifugation method has no effect on the plasma quality for biochemical analysis in young peregrine falcons. PMID:23156975

  5. 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.

  6. Pulse Field Gel Electrophoresis.

    PubMed

    Sharma-Kuinkel, Batu K; Rude, Thomas H; Fowler, Vance G

    2016-01-01

    Pulse Field Gel Electrophoresis (PFGE) is a powerful genotyping technique used for the separation of large DNA molecules (entire genomic DNA) after digesting it with unique restriction enzymes and applying to a gel matrix under the electric field that periodically changes direction. PFGE is a variation of agarose gel electrophoresis that permits analysis of bacterial DNA fragments over an order of magnitude larger than that with conventional restriction enzyme analysis. It provides a good representation of the entire bacterial chromosome in a single gel with a highly reproducible restriction profile, providing clearly distinct and well-resolved DNA fragments. PMID:25682374

  7. CONFORMANCE IMPROVEMENT USING GELS

    SciTech Connect

    Randall S. Seright

    2003-09-01

    This report describes work performed during the second year of the project, ''Conformance Improvement Using Gels.'' The project has two objectives. The first objective is to identify gel compositions and conditions that substantially reduce flow through fractures that allow direct channeling between wells, while leaving secondary fractures open so that high fluid injection and production rates can be maintained. The second objective is to optimize treatments in fractured production wells, where the gel must reduce permeability to water much more than that to oil. Pore-level images from X-ray computed microtomography were re-examined for Berea sandstone and porous polyethylene. This analysis suggests that oil penetration through gel-filled pores occurs by a gel-dehydration mechanism, rather than a gel-ripping mechanism. This finding helps to explain why aqueous gels can reduce permeability to water more than to oil. We analyzed a Cr(III)-acetate-HPAM gel treatment in a production well in the Arbuckle formation. The availability of accurate pressure data before, during, and after the treatment was critical for the analysis. After the gel treatment, water productivity was fairly constant at about 20% of the pre-treatment value. However, oil productivity was stimulated by a factor of 18 immediately after the treatment. During the six months after the treatment, oil productivity gradually decreased to approach the pre-treatment value. To explain this behavior, we proposed that the fracture area open to oil flow was increased substantially by the gel treatment, followed by a gradual closing of the fractures during subsequent production. For a conventional Cr(III)-acetate-HPAM gel, the delay between gelant preparation and injection into a fracture impacts the placement, leakoff, and permeability reduction behavior. Formulations placed as partially formed gels showed relatively low pressure gradients during placement, and yet substantially reduced the flow capacity of fractures (with widths from 1 to 4 mm) during brine and oil flow after placement. Regardless of gel age before placement, very little gel washed out from the fractures during brine or oil flow. However, increased brine or oil flow rate and cyclic injection of oil and water significantly decreased the level of permeability reduction. A particular need exists for gels that can plug large apertures (e.g., wide fractures and vugs). Improved mechanical strength and stability were demonstrated (in 1- to 4-mm-wide fractures) for a gel that contained a combination of high- and low-molecular weight polymers. This gel reduced the flow capacity of 2- and 4-mm-wide fractures by 260,000. In a 1-mm-wide fracture, it withstood 26 psi/ft without allowing any brine flow through the fracture. Cr(III)-acetate-HPAM gels exhibited disproportionate permeability reduction in fractures. The effect was most pronounced when the gel was placed as gelant or partially formed gels. The effect occurred to a modest extent with concentrated gels and with gels that were ''fully formed'' when placed. The effect was not evident in tubes. We explored swelling polymers for plugging fractures. Polymer suspensions were quickly prepared and injected. In concept, the partially dissolved polymer would lodge and swell to plug the fracture. For three types of swelling polymers, behavior was promising. However, additional development is needed before their performance will be superior to that of conventional gels.

  8. 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

  9. Isolation of Exosomes from Blood Plasma: Qualitative and Quantitative Comparison of Ultracentrifugation and Size Exclusion Chromatography Methods

    PubMed Central

    Baranyai, Tamás; Herczeg, Kata; Onódi, Zsófia; Voszka, István; Módos, Károly; Marton, Nikolett; Nagy, György; Mäger, Imre; Wood, Matthew J.; El Andaloussi, Samir; Pálinkás, Zoltán; Kumar, Vikas; Nagy, Péter; Kittel, Ágnes; Buzás, Edit Irén; Ferdinandy, Péter; Giricz, Zoltán

    2015-01-01

    Background Exosomes are emerging targets for biomedical research. However, suitable methods for the isolation of blood plasma-derived exosomes without impurities have not yet been described. Aim Therefore, we investigated the efficiency and purity of exosomes isolated with potentially suitable methods; differential ultracentrifugation (UC) and size exclusion chromatography (SEC). Methods and Results Exosomes were isolated from rat and human blood plasma by various UC and SEC conditions. Efficiency was investigated at serial UC of the supernatant, while in case of SEC by comparing the content of exosomal markers of various fractions. Purity was assessed based on the presence of albumin. We found that the diameter of the majority of isolated particles fell into the size range of exosomes, however, albumin was also present in the preparations, when 1h UC at 4°C was applied. Furthermore, with this method only a minor fraction of total exosomes could be isolated from blood as deduced from the constant amount of exosomal markers CD63 and TSG101 detected after serial UC of rat blood plasma samples. By using UC for longer time or with shorter sedimentation distance at 4°C, or UC performed at 37°C, exosomal yield increased, but albumin impurity was still observed in the isolates, as assessed by transmission electron microscopy, dynamic light scattering and immunoblotting against CD63, TSG101 and albumin. Efficiency and purity were not different in case of using further diluted samples. By using SEC with different columns, we have found that although a minor fraction of exosomes can be isolated without significant albumin content on Sepharose CL-4B or Sephacryl S-400 columns, but not on Sepharose 2B columns, the majority of exosomes co-eluted with albumin. Conclusion Here we show that it is feasible to isolate exosomes from blood plasma by SEC without significant albumin contamination albeit with low vesicle yield. PMID:26690353

  10. 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.

  11. Control of flow through porous media using polymer gels

    NASA Astrophysics Data System (ADS)

    Zitha, Pacelli L. J.; Botermans, C. Wouter; Hoek, Jeroen v. d.; Vermolen, Fred J.

    2002-07-01

    We examine the effect of a dynamic stress on the reduction of flow in porous media using polymer gels formed in situ. To develop the theory for the response of the gel, we consider three dominant factors: (a) compressive (elastic) deformation of the gel and porous medium, (b) microscopic flow in this system, and (c) gel displacement. The latter occurs when the stress p is larger than a certain critical value pc, satisfying pcR2=constant (R=effective pore radius), where the constant is an increasing function of elastic modulus of the gel and its cross-linking energy. The expulsion of the gel above pc is reminiscent of growing Saffman-Taylor instabilities. To derive analytic expressions for the macroscopic saturation profiles we use the formalism for fully miscible two-phase flow. The equation of evolution of the pressure, established by mass balance arguments, was solved analytically. For pc, the pressure obeys an exponential saturation function while for pc, it first increases, reaches a maximum value, and then decreases towards an asymptotic value. These theoretical predictions are supported by our experiments consisting of injecting (salt) water at a constant flow rate in porous samples containing a organically cross-linked polymer gel (co-polymer of acrylamide and t-butyl-acrylate cross-linked using poly-ethylene-imine). The data confirms further that the product pcR2 is constant and prove that both pc and the maximum pressures increase with intrinsic gel strength.

  12. 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.

  13. Swelling and instability of a gel annulus

    NASA Astrophysics Data System (ADS)

    Chen, Xiaoyi; Dai, Hui-Hui

    2015-10-01

    We study the swelling of a gel annulus attached to a rigid core when it is immersed in a solvent. For equilibrium states, the free-energy function of the gel can be converted into a strain energy function, and as a result the gel can be treated as a compressible hyperelastic material. Asymptotic methods are used to study the inhomogeneous swelling in order to obtain the leading-order solution. Some analytical insights are then deduced. Because of the compressive hoop stress in this state, at some stage instability can occur, leading to wrinkles in the gel. An incremental deformation theory in nonlinear elasticity is used to conduct a linear bifurcation analysis for understanding such instability. More specifically, the critical loading for the onset of a wrinkled state is obtained. Detailed discussions on the behaviors of various physical quantities in this critical state are given. It is found that the critical mode number, while insensitive to the material parameters, is greatly influenced by the ratio of the inner and outer radii of the gel. Also, an interesting finding is that the critical swelling ratio is an increasing function of this geometrical parameter, which implies that a thin annulus is more likely to be unstable than a thick one.

  14. Toward sol-gel-based sensors

    SciTech Connect

    Jordan, J.D.; Ingersoll, C.M.; Dunbar, R.A.

    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.

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

    E-print Network

    Chan, Hue Sun

    hydrochloride Propylene glycol Silver nitrate Sodium acetate Sodium bicarbonate Sodium bromide Sodium carbonate Nitric acid Oxalic acid Phosphoric acid Potassium bicarbonate Potassiuim biphthalate Potassium bromide Sodium chloride Sodium citrate Sodium diatrizoate Sodium dichromate Sodium ferrocyanide Sodium hydroxide

  16. Periodic mesoporous silica gels

    SciTech Connect

    Anderson, M.T.; Martin, J.E.; Odinek, J.G.

    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.

  17. 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.

  18. 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.

  19. Conformance Improvement Using Gels

    SciTech Connect

    Seright, Randall S.; Schrader, Richard; II Hagstrom, John; Wang, Ying; Al-Dahfeeri, Abdullah; Gary, Raven; Marin; Amaury; Lindquist, Brent

    2002-09-26

    This research project had two objectives. The first objective was to identify gel compositions and conditions that substantially reduce flow through fractures that allow direct channeling between wells, while leaving secondary fractures open so that high fluid injection and production rates can be maintained. The second objective was to optimize treatments in fractured production wells, where the gel must reduce permeability to water much more than that to oil.

  20. Chirality-dependent densities of carbon nanotubes by in situ 2D fluorescence-excitation and Raman characterisation in a density gradient after ultracentrifugation.

    PubMed

    Cambré, Sofie; Muyshondt, Pieter; Federicci, Remi; Wenseleers, Wim

    2015-12-21

    Density gradient ultracentrifugation (DGU) becomes increasingly important for the sorting of nanomaterials according to the particles' density, hence structure and dimensions, which determine their unique properties, but the further development of this separation technique is hindered by the limited precision with which the densities could be characterized. In this work, we determine these densities by position-dependent 2D wavelength-dependent IR fluorescence-excitation and resonant Raman spectroscopy measured directly in the density gradient after ultracentrifugation. We apply this method to study the diameter and chirality-dependent sorting of empty and water-filled single-walled carbon nanotubes coated with two different surfactants, sodium cholate (SC) and sodium deoxycholate (DOC). The results elucidate the long standing contradiction that SC would provide better diameter sorting, while DOC is the most efficient surfactant to solubilise the nanotubes. A more predictable separation is obtained for empty DOC-coated nanotubes since their density is found to vary very smoothly with diameter. The accurate and chirality-dependent densities furthermore provide information on the surfactant coating, which is also important for other separation techniques, and allow to determine the mass percentage of water encapsulated inside the nanotubes. PMID:26565985

  1. CONFORMANCE IMPROVEMENT USING GELS

    SciTech Connect

    Randall S. Seright

    2002-02-28

    This technical progress report describes work performed from June 20 through December 19, 2001, for the project, ''Conformance Improvement Using Gels''. Interest has increased in some new polymeric products that purport to substantially reduce permeability to water while causing minimum permeability reduction to oil. In view of this interest, we are currently studying BJ's Aqua Con. Results from six corefloods revealed that the Aqua Con gelant consistently reduced permeability to water more than that to oil. However, the magnitude of the disproportionate permeability reduction varied significantly for the various experiments. Thus, as with most materials tested to date, the issue of reproducibility and control of the disproportionate permeability remains to be resolved. Concern exists about the ability of gels to resist washout after placement in fractures. We examined whether a width constriction in the middle of a fracture would cause different gel washout behavior upstream versus downstream of the constriction. Tests were performed using a formed Cr(III)-acetate-HPAM gel in a 48-in.-long fracture with three sections of equal length, but with widths of 0.08-, 0.02-, and 0.08-in., respectively. The pressure gradients during gel extrusion (i.e., placement) were similar in the two 0.08-in.-wide fracture sections, even though they were separated by a 0.02-in.-wide fracture section. The constriction associated with the middle fracture section may have inhibited gel washout during the first pulse of brine injection after gel placement. However, during subsequent phases of brine injection, the constriction did not inhibit washout in the upstream fracture section any more than in the downstream section.

  2. Polymer gel dosimetry technique

    SciTech Connect

    Maryanski, M.J.

    1995-12-31

    Recent advances in radiation therapy techniques, including non-coplanar beams, dynamic wedge, multi-leaf collimator, sterotactic radiosurgery, high-dose-rate brachytherapy using remote afterloading and shielded applicators, and heavy-particle beams such as protons, have created a need for three-dimensional, tissue-equivalent dosimeters, capable of recording time-integrated dose distributions with high spatial resolution and accuracy, and independent of energy and dose rate. All these requirements are met by the recently developed polymer gel dosimetry technique, based on radiation induced formation of polymer microparticles in a tissue-equivalent gel. A permanent image of the dose distribution is encoded in the gel as the distribution of its optical turbidity and of the NMR relaxation rates of the water protons in the gel. Three dimensional dose distributions can be measured using magnetic resonance imaging or optical transmission tomography. The prototype gel, called BANG{trademark}, is now being tested at several hospital sites throughout the U.S. and Europe.

  3. Spatially resolved multicomponent gels

    NASA Astrophysics Data System (ADS)

    Draper, Emily R.; Eden, Edward G. B.; McDonald, Tom O.; Adams, Dave J.

    2015-10-01

    Multicomponent supramolecular systems could be used to prepare exciting new functional materials, but it is often challenging to control the assembly across multiple length scales. Here we report a simple approach to forming patterned, spatially resolved multicomponent supramolecular hydrogels. A multicomponent gel is first formed from two low-molecular-weight gelators and consists of two types of fibre, each formed by only one gelator. One type of fibre in this ‘self-sorted network’ is then removed selectively by a light-triggered gel-to-sol transition. We show that the remaining network has the same mechanical properties as it would have done if it initially formed alone. The selective irradiation of sections of the gel through a mask leads to the formation of patterned multicomponent networks, in which either one or two networks can be present at a particular position with a high degree of spatial control.

  4. Spatially resolved multicomponent gels.

    PubMed

    Draper, Emily R; Eden, Edward G B; McDonald, Tom O; Adams, Dave J

    2015-10-01

    Multicomponent supramolecular systems could be used to prepare exciting new functional materials, but it is often challenging to control the assembly across multiple length scales. Here we report a simple approach to forming patterned, spatially resolved multicomponent supramolecular hydrogels. A multicomponent gel is first formed from two low-molecular-weight gelators and consists of two types of fibre, each formed by only one gelator. One type of fibre in this 'self-sorted network' is then removed selectively by a light-triggered gel-to-sol transition. We show that the remaining network has the same mechanical properties as it would have done if it initially formed alone. The selective irradiation of sections of the gel through a mask leads to the formation of patterned multicomponent networks, in which either one or two networks can be present at a particular position with a high degree of spatial control. PMID:26391086

  5. Modeling mechanochromatic lamellar gels

    NASA Astrophysics Data System (ADS)

    Hong, Wei; Wang, Xiao

    2012-03-01

    Consisting of alternating swelling and nonswelling polymeric layers (SLs and NLs), lamellar gels are one-dimensional photonic crystals with mechanically tunable optical properties. The lamellar structure induces a constraint between the SLs and the NLs, resulting in a highly anisotropic swelling behavior that is coupled with deformation. The coupling gives rise to the mechanochromatic effect, i.e., the color change in the material in response to mechanical deformations. A quantitative understanding of the coupling behavior is the key to many applications. This paper formulates a nonlinear continuum model for lamellar gels by considering the constrained swelling and anisotropic deformation in both layers. A finite-element method is further developed to simulate the mechanochromatic response of a lamellar gel undergoing a nonuniform field.

  6. Polymer gel dosimetry

    NASA Astrophysics Data System (ADS)

    Schreiner, L. J.; Olding, T.; McAuley, K. B.

    2010-11-01

    Polymer gels are chemical dosimeters based on dose dependent radiation-induced polymerization and cross-linking of monomers in an irradiated volume. The changes are spatially localized in the volume by incorporating the initial monomers in an aqueous gel matrix in the dosimeter and can be probed by various imaging techniques such as magnetic resonance imaging (MRI), x-ray computed tomography (CT), and optical CT. As they are chemical dosimeters, polymer gels are sensitive to preparation conditions. The three dimensional dose readout is sensitive to the imaging modality and also to the technical conditions in use during specific scans. This brief article is intended to present an introduction to these points which need to be taken into account as one attempts to establish this dosimetry in the clinic.

  7. Novel detection schemes and automated image analysis algorithms for planar chromatography and gel electrophoresis

    SciTech Connect

    Koutney, L.B.

    1992-09-09

    After a discussion of charge coupled devices and personal computer capabilities, examples of their applications involving novel analytical techniques are presented: laser-based indirect fluorometric detection in thin-layer chromatography; on-line detection of DNA and proteins in gel electrophoresis by uv absorption; automated image analysis for distortion compensation in sequencing gel electrophoresis; and expert systems for data acquisition to achieve constant signal-to-noise, with application to DNA sequencing slab gels.

  8. Electroblotting from Polyacrylamide Gels.

    PubMed

    Goldman, Aaron; Ursitti, Jeanine A; Mozdzanowski, Jacek; Speicher, David W

    2015-01-01

    Transferring proteins from polyacrylamide gels onto retentive membranes is now primarily used for immunoblotting. A second application that was quite common up to about a decade ago was electroblotting of proteins for N-terminal and internal sequencing using Edman chemistry. This unit contains procedures for electroblotting proteins from polyacrylamide gels onto a variety of membranes, including polyvinylidene difluoride (PVDF) and nitrocellulose. In addition to the commonly used tank or wet transfer system, protocols are provided for electroblotting using semidry and dry systems. This unit also describes procedures for eluting proteins from membranes using detergents or acidic extraction with organic solvents for specialized applications. © 2015 by John Wiley & Sons, Inc. PMID:26521711

  9. 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.

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

    PubMed Central

    Lucantonio, A.; Nardinocchi, P.; Pezzulla, M.

    2014-01-01

    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

  11. Polyacrylamide gels synthesized in the presence of surfactants

    NASA Astrophysics Data System (ADS)

    Chakrapani, Mukundan

    The polymerization of acrylamide monomers in the presence of surfactant self-assemblies produces gels with variable pore architecture. Polyacrylamide gels were formed by polymerizing acrylamide plus a cross-linker in the presence of surfactants, which were then removed by soaking in distilled water. Gels formed in the presence of over 28% surfactant (by weight) formed clear, but became opaque upon removal of the surfactants. Other gels formed and remained clear. Several analytical techniques such as X-ray Scattering, Dynamic Rheology measurements, Optical Polarized Microscopy, and Atomic Force Microscopy (AFM) have been used to characterize the formation and the resulting gel structure. The surface morphology as imaged by AFM was studied by numerical scaling analysis. The surface morphology of the gels was studied by several one- and two-dimensional numerical scaling methods. The structure of the final gels were highly dependent on the amount of surfactant present during the formation of gels. At low surfactant concentrations (<25% by weight), the surfactant micelles are randomly distributed throughout the gel matrix. The average spacing between individual micelles is about 10 nm as indicated by X-ray scattering experiments. When the TTAB concentration is increased to moderate levels (25--28%), though the surfactant micelles are randomly distributed, a few surfactant-rich regions may form in the gel matrix. At high TTAB concentrations, phase separation of TTAB from the polymer leads to the formation of many surfactant-rich domains. A model for the gel structure based on symmetry and packing considerations for lattices of spheres of different concentrations was developed. This model was successfully used to interpret the physical observations, the experimental results, and the results from the scaling analysis. Highly porous gel networks with a high degree of mechanical strength have thus been synthesized. The controlled modification of gel structure provides new opportunities in the development of novel materials. A few areas of application include enzyme fixation for building biosensors, controlled release systems for drug delivery, support matrices for bio-molecule separation. The process of gel formation in the presence of unreactive surfactants can also be extended to alter the structure of other polymer materials.

  12. TSK-GEL SEC Columns TOSOH BIOSCIENCE

    E-print Network

    Lebendiker, Mario

    TSK-GEL SEC Columns TOSOH BIOSCIENCE Separations Business Unit Get the most from Size Exclusion. Column Selection Guide SEC II. TSK-GEL SEC Columns Overview III. TSK-GEL SW Columns IV. TSK-GEL PW V. TSK-GEL Alpha/SuperAW VI. Optimizing SEC TSK-GEL SEC Columns TSK-GEL SEC Brochure #12;TSK-GEL Column Selection

  13. Analytical testing

    NASA Technical Reports Server (NTRS)

    Flannelly, W. G.; Fabunmi, J. A.; Nagy, E. J.

    1981-01-01

    Analytical methods for combining flight acceleration and strain data with shake test mobility data to predict the effects of structural changes on flight vibrations and strains are presented. This integration of structural dynamic analysis with flight performance is referred to as analytical testing. The objective of this methodology is to analytically estimate the results of flight testing contemplated structural changes with minimum flying and change trials. The category of changes to the aircraft includes mass, stiffness, absorbers, isolators, and active suppressors. Examples of applying the analytical testing methodology using flight test and shake test data measured on an AH-1G helicopter are included. The techniques and procedures for vibration testing and modal analysis are also described.

  14. 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.

  15. Dynamical hysteresis in a self-oscillating polymer gel

    NASA Astrophysics Data System (ADS)

    Das, Debojyoti; Das, Moupriya; Ray, Deb Shankar

    2012-08-01

    An ionic polymer gel may undergo rhythmical swelling-deswelling kinetics induced by chemical oscillation. We demonstrate that the gel admits of dynamical hysteresis, which is manifested in the non-vanishing area of the response function—concentration (of reaction substrate) hysteresis loop, the response function being the integrated probability of residence of the polymer in any one of the swelled or deswelled states. The loop area depends on temperature and exhibits a turnover as a function of the strength of thermal noise—a phenomenon reminiscent of stochastic resonance. The numerical simulations agree well with our proposed analytical scheme.

  16. Polyacrylamide Gel Electrophoresis for Purification of Large Amounts of RNA.

    PubMed

    Meyer, Mélanie; Masquida, Benoît

    2016-01-01

    Polyacrylamide gel electrophoresis (PAGE) constitutes a powerful technique for the efficient purification of RNA molecules dedicated to applications that require high purity levels. PAGE allows for the fractionation of RNA obtained from cell extracts, chemical or enzymatic synthesis, or modification experiments. Native or denaturing conditions can be chosen for analytical or preparative-scale separations and the nucleotide resolution can be tuned by changing the percentage and reticulation of the gel material. In this protocol, we focus on the preparation of milligram-scale amounts of ~200 nucleotides (nt) RNA molecules that were used in subsequent crystallization experiments. PMID:26227037

  17. 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.

  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. Gel polymer electrolytes for batteries

    DOEpatents

    Balsara, Nitash Pervez; Eitouni, Hany Basam; Gur, Ilan; Singh, Mohit; Hudson, William

    2014-11-18

    Nanostructured gel polymer electrolytes that have both high ionic conductivity and high mechanical strength are disclosed. The electrolytes have at least two domains--one domain contains an ionically-conductive gel polymer and the other domain contains a rigid polymer that provides structure for the electrolyte. The domains are formed by block copolymers. The first block provides a polymer matrix that may or may not be conductive on by itself, but that can soak up a liquid electrolyte, thereby making a gel. An exemplary nanostructured gel polymer electrolyte has an ionic conductivity of at least 1.times.10.sup.-4 S cm.sup.-1 at 25.degree. C.

  20. Non-Brownian particle gel

    NASA Astrophysics Data System (ADS)

    Yuan, Chia-Nan; Sheng, Yu-Jane; Tsao, Heng-Kwong

    2009-12-01

    Particle gels are usually formed by density matching or Brownian motion against gravity. However, the suspended state of non-Brownian particles is essential in applications, such as Si-wafer wire sawing. By the addition of alkyl amine, micron-sized SiC suspensions are shown to form particle gel in ethylene glycol. The ratio of storage to loss modulus is about 3, indicating a weak gel. The structure by particle-particle attraction is demonstrated through existing yield stress. With increasing surfactant concentration, the gel forms easier, the sediment layer swells more significantly, and the yield stress is greater accordingly. A gelling mechanism has been proposed and examined.

  1. Colloidal thermoresponsive gel forming hybrids.

    PubMed

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

    2010-09-15

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

  2. Deformation and fracture of cross-linked polymer gels

    NASA Astrophysics Data System (ADS)

    Lin, Wei-Chun

    Because soft materials, particularly polymer gels, are playing a greater role in industrial and biotechnological applications today, the exploration of their mechanical behavior over a range of deformations is becoming more relevant in our daily lives. Understanding these properties is therefore necessary as a means to predict their response for specific applications. To address these concerns, this dissertation presents a set of analytic tools based on flat punch probe indentation tests to predict the response of polymer gels from a mechanical perspective over a large range of stresses and at failure. At small strains, a novel technique is developed to determine the transport properties of gels based on their measured mechanical behavior. Assuming that a polymer gel behaves in a similar manner as a porous structure, the differentiation of solvent flow from viscoelasticity of a gel network is shown to be possible utilizing a flat, circular punch and a flat, rectangular punch under oscillatory conditions. Use of the technique is demonstrated with a poly(N-isopropyl acrylamide) (pNIPAM) hydrogel. Our results indicate that solvent flow is inhibited at temperatures above the critical solution temperature of 35°C. At high stresses and fracture, the flat probe punch indentation geometry is used to understand how the structure and geometry of silicone based gels affect their mechanical properties. A delayed failure response of the gels is observed and the modes of failure are found to be dependent on the geometry of the system. The addition of a sol fraction in these gels was found to toughen the network and play an important role at these large deformations. Potential mechanisms of fracture resistance are discussed, as is the effect of geometric confinement as it relates to large scale deformation and fracture. These results lay the groundwork for understanding the mechanical response of other highly, deformable material systems utilizing this particular geometry.

  3. 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.

  4. 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.

  5. Nanocrystal/sol-gel nanocomposites

    DOEpatents

    Petruska, Melissa A. (Los Alamos, NM); Klimov, Victor L. (Los Alamos, NM)

    2012-06-12

    The present invention is directed to solid composites including colloidal nanocrystals within a sol-gel host or matrix and to processes of forming such solid composites. The present invention is further directed to alcohol soluble colloidal nanocrystals useful in formation of sol-gel based solid composites

  6. Nanocrystal/sol-gel nanocomposites

    DOEpatents

    Petruska, Melissa A. (Los Alamos, NM); Klimov, Victor L. (Los Alamos, NM)

    2007-06-05

    The present invention is directed to solid composites including colloidal nanocrystals within a sol-gel host or matrix and to processes of forming such solid composites. The present invention is further directed to alcohol soluble colloidal nanocrystals useful in formation of sol-gel based solid composites.

  7. 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.

  8. Symmetry breaking in actin gels - Implications for cellular motility

    NASA Astrophysics Data System (ADS)

    John, Karin; Peyla, Philippe; Misbah, Chaouqi

    2007-03-01

    The physical origin of cell motility is not fully understood. Recently minimal model systems have shown, that polymerizing actin itself can produce a motile force, without the help of motor proteins. Pathogens like Shigella or Listeria use actin to propel themselves forward in their host cell. The same process can be mimicked with polystyrene beads covered with the activating protein ActA, which reside in a solution containing actin monomers. ActA induces the growth of an actin gel at the bead surface. Initially the gel grows symmetrically around the bead until a critical size is reached. Subsequently one observes a symmetry breaking and the gel starts to grow asymmetrically around the bead developing a tail of actin at one side. This symmetry breaking is accompanied by a directed movement of the bead, with the actin tail trailing behind the bead. Force generation relies on the combination of two properties: growth and elasticity of the actin gel. We study this phenomenon theoretically within the framework of a linear elasticity theory and linear flux-force relationships for the evolution of an elastic gel around a hard sphere. Conditions for a parity symmetry breaking are identified analytically and illustrated numerically with the help of a phasefield model.

  9. Molecular simulation of polymeric networks and gels: phase behavior and swelling

    NASA Astrophysics Data System (ADS)

    Escobedo, Fernando A.; de Pablo, Juan J.

    1999-09-01

    Polymer gels are commonly used in industrial, analytical, and domestic applications; their uses are likely to continue expanding as gels with novel chemical and structural characteristics are developed. These applications often rely on the precise control of the adsorption behavior of a gel. Development of useful gels, however, has been hampered by a lack of molecular-level understanding of the physics underlying phase transitions in such materials. In this report, we review recent molecular simulation work related to the study of fundamental aspects of network elasticity and of phase transitions in polymeric gels. In particular, simulations of simplified (coarse-grained) molecular models are described which provide insights into the general behavior of gels, as opposed to studies concerned with the properties of specific materials. Methodological aspects unique to the simulation of different properties of polymeric gels are emphasized. We also pay special attention to the role of entropic factors (such as network topology, backbone stiffness, chain length asymmetry), over that of energetic interactions (such as hydrofobic interactions or ionic forces) on the onset and characteristics of phase transitions in gels. In spite of the important advances made over the last years in methodology and computer hardware, many challenges remain if phase transitions for more realistic gel models are to be simulated.

  10. Microchannel gel electrophoretic separation systems and methods for preparing and using

    DOEpatents

    Herr, Amy; Singh, Anup K; Throckmorton, Daniel J

    2013-09-03

    A micro-analytical platform for performing electrophoresis-based immunoassays was developed by integrating photopolymerized cross-linked polyacrylamide gels within a microfluidic device. The microfluidic immunoassays are performed by gel electrophoretic separation and quantifying analyte concentration based upon conventional polyacrylamide gel electrophoresis (PAGE). To retain biological activity of proteins and maintain intact immune complexes, native PAGE conditions were employed. Both direct (non-competitive) and competitive immunoassay formats are demonstrated in microchips for detecting toxins and biomarkers (cytokines, c-reactive protein) in bodily fluids (serum, saliva, oral fluids). Further, a description of gradient gels fabrication is included, in an effort to describe methods we have developed for further optimization of on-chip PAGE immunoassays. The described chip-based PAGE immunoassay method enables immunoassays that are fast (minutes) and require very small amounts of sample (less than a few microliters). Use of microfabricated chips as a platform enables integration, parallel assays, automation and development of portable devices.

  11. Microchannel gel electrophoretic separation systems and methods for preparing and using

    DOEpatents

    Herr, Amy E; Singh, Anup K; Throckmorton, Daniel J

    2015-02-24

    A micro-analytical platform for performing electrophoresis-based immunoassays was developed by integrating photopolymerized cross-linked polyacrylamide gels within a microfluidic device. The microfluidic immunoassays are performed by gel electrophoretic separation and quantifying analyte concentration based upon conventional polyacrylamide gel electrophoresis (PAGE). To retain biological activity of proteins and maintain intact immune complexes, native PAGE conditions were employed. Both direct (non-competitive) and competitive immunoassay formats are demonstrated in microchips for detecting toxins and biomarkers (cytokines, c-reactive protein) in bodily fluids (serum, saliva, oral fluids). Further, a description of gradient gels fabrication is included, in an effort to describe methods we have developed for further optimization of on-chip PAGE immunoassays. The described chip-based PAGE immunoassay method enables immunoassays that are fast (minutes) and require very small amounts of sample (less than a few microliters). Use of microfabricated chips as a platform enables integration, parallel assays, automation and development of portable devices.

  12. Mechanical Failure in Colloidal Gels

    NASA Astrophysics Data System (ADS)

    Kodger, Thomas Edward

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

  13. 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

  14. 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.

  15. One-step casting of Laemmli discontinued sodium dodecyl sulfate-polyacrylamide gel electrophoresis gel.

    PubMed

    Wu, Xiaoqiang; Koiwa, Hisashi

    2012-02-01

    A modified Laemmli sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) protocol is described. The new method saves 30 min for gel casting without loss of the resolution power of Laemmli gel. In this method, both the upper and lower gels can be cast at the same time because the lower gel contains 10% glycerol, which generates higher density in the lower gel than in the upper gel. PMID:22037291

  16. Fabrication and Characterization of Polysaccharide Ion Gels with Ionic Liquids and Their Further Conversion into Value-Added Sustainable Materials

    PubMed Central

    Takada, Akihiko; Kadokawa, Jun-ichi

    2015-01-01

    A review of the fabrication of polysaccharide ion gels with ionic liquids is presented. From various polysaccharides, the corresponding ion gels were fabricated through the dissolution with ionic liquids. As ionic liquids, in the most cases, 1-butyl-3-methylimidazolium chloride has been used, whereas 1-allyl-3methylimidazolium acetate was specifically used for chitin. The resulting ion gels have been characterized by suitable analytical measurements. Characterization of a pregel state by viscoelastic measurement provided the molecular weight information. Furthermore, the polysaccharide ion gels have been converted into value-added sustainable materials by appropriate procedures, such as exchange with other disperse media and regeneration. PMID:25793912

  17. A conjugated polymer plastic gel

    E-print Network

    Alcazar Jorba, Daniel

    2008-01-01

    We present a gel route to process highly oriented conjugated polymer films and fibers. The incorporation of hexafluoroisopropanol, a strong and stable dipolar group, to the polythiophene backbone enhances the solubility ...

  18. Alternative imaging modalities for polymer gel dosimetry

    NASA Astrophysics Data System (ADS)

    Jirasek, Andrew

    2010-11-01

    This review summarizes recent work in the area of imaging polymer gel dosimeters using x-ray CT imaging, ultrasound, and radiation-induced changes in gel mechanical properties. In addition, recent work in the area of Raman tomographic imaging of canine bone, in conjunction with past efforts in Raman imaging of polymer gel dosimeters, raises new possibilities for new polymer gel imaging techniques.

  19. A new method for HDL particle sizing by polyacrylamide gradient gel electrophoresis using whole plasma.

    PubMed

    Pérusse, M; Pascot, A; Després, J P; Couillard, C; Lamarche, B

    2001-08-01

    Low plasma levels of HDL cholesterol have been associated with an increased risk of coronary heart disease. HDL particles are heterogeneous with respect to size and apolipoprotein content. The objective of the present study was to develop a method to generate lipid-stainable calibrators that would allow the assessment of HDL particle size from whole plasma, using polyacrylamide gradient gel electrophoresis (PAGGE). Lipid-stainable HDL calibrators were obtained by subjecting isolated red blood cells to hemolysis either by freezing at -20 or -80 degrees C overnight or by rapid exposure to liquid nitrogen and mixing of the hemolysis products with plasma aliquots. All three methods were highly reproducible in producing Sudan black lipid-stainable HDL calibrators ranging from 75 to 200 A. The assessment of HDL particle size with these lipid-stainable HDL calibrators was also highly reproducible, with a coefficient of variation below 5.5%. These lipid-stainable HDL calibrators simplify the assessment of HDL particle size by PAGGE using whole plasma, without the need for costly, time-consuming ultracentrifugation procedures. PMID:11483636

  20. TOPICAL REVIEW: Polymer gel dosimetry

    NASA Astrophysics Data System (ADS)

    Baldock, C.; De Deene, Y.; Doran, S.; Ibbott, G.; Jirasek, A.; Lepage, M.; McAuley, K. B.; Oldham, M.; Schreiner, L. J.

    2010-03-01

    Polymer gel dosimeters are fabricated from radiation sensitive chemicals which, upon irradiation, polymerize as a function of the absorbed radiation dose. These gel dosimeters, with the capacity to uniquely record the radiation dose distribution in three-dimensions (3D), have specific advantages when compared to one-dimensional dosimeters, such as ion chambers, and two-dimensional dosimeters, such as film. These advantages are particularly significant in dosimetry situations where steep dose gradients exist such as in intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery. Polymer gel dosimeters also have specific advantages for brachytherapy dosimetry. Potential dosimetry applications include those for low-energy x-rays, high-linear energy transfer (LET) and proton therapy, radionuclide and boron capture neutron therapy dosimetries. These 3D dosimeters are radiologically soft-tissue equivalent with properties that may be modified depending on the application. The 3D radiation dose distribution in polymer gel dosimeters may be imaged using magnetic resonance imaging (MRI), optical-computerized tomography (optical-CT), x-ray CT or ultrasound. The fundamental science underpinning polymer gel dosimetry is reviewed along with the various evaluation techniques. Clinical dosimetry applications of polymer gel dosimetry are also presented.

  1. Topical Review: Polymer gel dosimetry

    PubMed Central

    Baldock, C; De Deene, Y; Doran, S; Ibbott, G; Jirasek, A; Lepage, M; McAuley, K B; Oldham, M; Schreiner, L J

    2010-01-01

    Polymer gel dosimeters are fabricated from radiation sensitive chemicals which, upon irradiation, polymerize as a function of the absorbed radiation dose. These gel dosimeters, with the capacity to uniquely record the radiation dose distribution in three-dimensions (3D), have specific advantages when compared to one-dimensional dosimeters, such as ion chambers, and two-dimensional dosimeters, such as film. These advantages are particularly significant in dosimetry situations where steep dose gradients exist such as in intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery. Polymer gel dosimeters also have specific advantages for brachytherapy dosimetry. Potential dosimetry applications include those for low-energy x-rays, high-linear energy transfer (LET) and proton therapy, radionuclide and boron capture neutron therapy dosimetries. These 3D dosimeters are radiologically soft-tissue equivalent with properties that may be modified depending on the application. The 3D radiation dose distribution in polymer gel dosimeters may be imaged using magnetic resonance imaging (MRI), optical-computerized tomography (optical-CT), x-ray CT or ultrasound. The fundamental science underpinning polymer gel dosimetry is reviewed along with the various evaluation techniques. Clinical dosimetry applications of polymer gel dosimetry are also presented. PMID:20150687

  2. 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.

  3. 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.

  4. Thixotropic gel for vadose zone remediation

    SciTech Connect

    Riha, Brian D.; Looney, Brian B.

    2015-10-27

    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.

  5. NMR mechanisms in gel dosimetry

    NASA Astrophysics Data System (ADS)

    Schreiner, L. J.

    2009-05-01

    Nuclear magnetic resonance was critical to the development of gel dosimetry, as it established the potential for three dimensional dosimetry with chemical dosimeter systems through magnetic resonance imaging [1]. In the last two decades MRI has served as the gold standard for imaging, while NMR relaxometry has played an important role in the development and understanding of the behaviour of new gel dosimetry systems. Therefore, an appreciation of the relaxation mechanisms determining the NMR behaviour of irradiated gel dosimeters is important for a full comprehension of a considerable component of the literature on gel dosimetry. A number of excellent papers have presented this important theory, this brief review will highlight some of the salient points made previously [1-5]. The spin relaxation of gel dosimeters (which determines the dose dependence in most conventional MR imaging) is determined principally by the protons on water molecules in the system. These water protons exist in different environments, or groups (see Figure 1): on bulk water, on water hydrating the chemical species that are being modified under irradiation, and on water hydrating the gel matrix used to spatially stabilize the dosimeter (e.g., gelatin, agarose, etc). The spin relaxation depends on the inherent relaxation rate of each spin group, that is, on the relaxation rate which would be observed for the specific group if it were isolated. Also, the different water environments are not isolated from each other, and the observed relaxation rate also depends on the rate of exchange of magnetization between the groups, and on the fraction of protons in each group. In fact, the water exchanges quickly between the environments, so that relaxation is in what is usually termed the fast exchange regime. In the limit of fast exchange, the relaxation of the water protons is well characterized by a single exponential and hence by a single apparent relaxation rate. In irradiated gel dosimeters this observed rate is a function of the absorbed dose. In this review I will first develop the fast exchange model for the spin lattice relaxation Fricke gel dosimeter system, as this is conceptually the simpler system. Fundamental concepts such as relaxivity (which specifies the ability of some species to enhance the relaxation of water protons) and chemical yield will be presented. The linear dose relationship for Fricke gel dosimeters, and the reduced dose sensitivity of Fricke dosimeters containing chelators, will be explained. The model will then be extended to the spin-spin relaxation of polymer gel systems and the main differences discussed. The reasons for the enhanced dose sensitivy and dynamic range for spin-spin (R2) rather than spin-lattice (R1) relaxation will be presented.

  6. 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

  7. Capillary fracture of soft gels

    E-print Network

    Bostwick, Joshua B

    2013-01-01

    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 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 $L\\propto t^{3/4}$. 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 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 impo...

  8. Capillary fracture of soft gels

    E-print Network

    Joshua B. Bostwick; Karen E. Daniels

    2013-10-16

    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 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 $L\\propto t^{3/4}$. 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 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.

  9. Inorganic Sensing Using Organofunctional Sol-Gel Materials

    PubMed Central

    Carrington, Nathan A.; Xue, Zi-Ling

    2007-01-01

    This Account describes recent work in the development and applications of sol-gel sensors for concentrated strong acids/bases and metal ions. The use of sol-gel films doped with organic indicators for the optical sensing of concentrated strong acids (HCl 1-10 M) and bases (NaOH 1-10 M) has been explored, and the development of dual optical sensor approaches for ternary systems (HCl-salt-H2O and NaOH-alcohol-H2O) to give acid and salt as well as base and alcohol concentrations is discussed. The preparation of transparent, ligand-grafted sol-gel monoliths is also described, and their use in the analysis of both metal cations (Cu2+) and anions [Cr(VI)] is presented. A new model using both metal ion diffusion and immobilization by the ligands in such monoliths has been developed to give metal concentrations using the optical monolith sensors. In addition to optical sensing, a method utilizing ligand-grafted sol-gel films for analyte preconcentration in the electrochemical determination of Cr(VI) has been explored and is discussed. PMID:17465520

  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. Deformation of Unentangled Swollen Gels

    NASA Astrophysics Data System (ADS)

    Sariyer, Ozan; Panyukov, Sergey; Rubinstein, Michael

    2014-03-01

    We study the deformation characteristics (Poisson's ratios and stress-strain relations) of unentangled gels swollen and uniaxially or biaxially deformed in excess solvent by considering the balance of osmotic pressure and elastic stress in unconstrained dimensions. Our scaling theory predicts a crossover from theta solvent behavior to marginal solvent behavior upon stretching gels that are in concentrated regime at swelling equilibrium - a phenomenon that was experimentally observed long ago, but not understood theoretically. For gels that are in the semidilute good solvent regime at swelling equilibrium, we predict a crossover to theta solvent behavior upon compression and a crossover to marginal solvent behavior upon stretching. Our theory reproduces the previously known results for equilibrium swelling degree as well as known deformation characteristics in theta and athermal solvents.

  12. 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.

  13. 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.

  14. Gel Injections May Help Heart Failure Patients

    MedlinePLUS

    ... news/fullstory_155818.html Gel Injections May Help Heart Failure Patients But larger study needed to assess ... 19, 2015 THURSDAY, Nov. 19, 2015 (HealthDay News) -- Heart failure patients who had beads of gel injected ...

  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. 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 ...

  17. Flexible peptides and cytoplasmic gels

    PubMed Central

    Bray, Dennis

    2005-01-01

    Recent progress in predicting protein structures has revealed a surprising abundance of proteins that are significantly unfolded under physiological conditions. Unstructured, flexible polypeptides are likely to be functionally important and may cause local cytoplasmic regions to become gel-like. PMID:15774032

  18. Formaldehyde RNA Gel Wear gloves.

    E-print Network

    Aris, John P.

    H20. Dilute 30% H202 to 3%. Fill apparatus with 3% H202. Submerge comb and dams. Treat for 10 minutes buffer. Do not add ethidium bromide to gel or running buffer. 2. Have up to 5 µg RNA in 2 µl DEPC-dH2O

  19. Polyelectrolyte intelligent gels. Design and applications

    E-print Network

    Piero Chiarelli; Danilo De Rossi

    2012-06-21

    In this chapter polyelectrolyte intelligent gels are examined along three broad lines. The effects of different physical, chemical and biological stimuli on gels response are analysed and mechanisms of response are outlined. The broad range of biomedical applications of smart gels is reviewed and limits and perspectives of the proposed techniques and devices are crititically discussed. Finally, continuous modelling of gel electromechanochemistry is described, providing quantitative tools to assess swelling equilibrium conditions and coupled kinetics.

  20. 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

  1. 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

  2. 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

  3. 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.

  4. 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.

  5. In vitro studies of the efficacy of reversed phase silica gel as a sorbent for hemo- and plasmaperfusion.

    PubMed

    Murugavel, S

    1992-01-01

    The clearance capacities of reversed phase silica gel, widely used in analytical chemistry, were studied in vitro. The plasma clearances of amitriptyline, quinidine, digoxin, digitoxin, methaqualone, phenobarbital and phenytoin were determined at typical toxic plasma levels. Between 88.8 and 99.5% of the drugs were eliminated from plasma by reversed phase silica gel, which compares favorably with amberlite XAD-4 and coated activated charcoal. The biocompatibility of reversed phase silica gel was also evaluated in vitro. Thrombocytopenia and leukopenia were noted while coagulation parameters, electrolytes, acid-base balance, glucose, urea, creatinine, uric acid, total protein, albumin, bilirubin, cholesterol and triglycerides were not significantly affected. Preliminary results in vitro support the high clearance capacity of reversed phase silica gel and suggest a biocompatibility similar to that of other sorbents currently in use. Further investigation of the clearance capacities and biocompatibility of reversed phase silica gel seems justified. PMID:1311776

  6. SDS agarose gels for analysis of proteins.

    PubMed

    Wu, M; Kusukawa, N

    1998-04-01

    A new agarose-based protein electrophoresis gel system is described. The system consists of a highly resolving agarose, MetaPhor XR (FMC BioProducts, Rockland, ME, USA) dissolved in urea and TBE buffer and a stacking gel composed of a high gel-strength agarose, SeaKem Gold (FMC BioProducts). TBE containing sodium dodecyl sulfate (SDS) is used as electrophoresis buffer. The disadvantages of traditional agarose gels have been overcome, and several advantages over polyacrylamide gels have been demonstrated. The system is capable of high-resolution separation of small proteins and has a dynamic separation range equivalent to a 4%-20% gradient polyacrylamide gel. Furthermore, the staining of protein bands by Coomassie Brilliant Blue is very uniform in this gel, and depending on the protein, higher detection sensitivity can be obtained compared to SDS polyacrylamide gels. In Western blotting, proteins are more efficiently transferred to the membrane from the agarose gel than from polyacrylamide gels. Finally, the exceptional stability of agarose allows for gels to be precast and stored for a year. PMID:9564543

  7. Nanocrystal/sol-gel nanocomposites

    DOEpatents

    Klimov, Victor L.; Petruska, Melissa A.

    2010-05-25

    The present invention is directed to a process for preparing a solid composite having colloidal nanocrystals dispersed within a sol-gel matrix, the process including admixing colloidal nanocrystals with an amphiphilic polymer including hydrophilic groups selected from the group consisting of --COOH, --OH, --SO.sub.3H, --NH.sub.2, and --PO.sub.3H.sub.2 within a solvent to form an alcohol-soluble colloidal nanocrystal-polymer complex, admixing the alcohol-soluble colloidal nanocrystal-polymer complex and a sol-gel precursor material, and, forming the solid composite from the admixture. The present invention is also directed to the resultant solid composites and to the alcohol-soluble colloidal nanocrystal-polymer complexes.

  8. The Swelling of Olympic Gels

    NASA Astrophysics Data System (ADS)

    Lang, Michael; Fischer, Jakob; Werner, Marco; Sommer, Jens-Uwe

    2014-03-01

    The swelling equilibrium of Olympic gels is studied by Monte Carlo Simulations. We observe that gels consisting of flexible cyclic molecules of a higher degree of polymerization N show a smaller equilibrium swelling degree Q ~N - 0 . 28?0- 0 . 72 for the same monomer volume fraction ?0 at network preparation. This observation is explained by a disinterpenetration process of overlapping non-concatenated polymers upon swelling. In the limit of a sufficiently large number of concatenations per cyclic molecule we expect that the equilibrium degree of swelling becomes proportional to ?0- 1 / 2 independent of N. Our results challenge current textbook models for the equilibrium degree of swelling of entangled polymer networks. Now at: Bio Systems Analysis Group, Jena Centre for Bioinformatics (JCB) and Department for Mathematics and Computer Sciences, Friedrich Schiller University of Jena, 07743 Jena, Germany.

  9. Analytics for Education

    ERIC Educational Resources Information Center

    MacNeill, Sheila; Campbell, Lorna M.; Hawksey, Martin

    2014-01-01

    This article presents an overview of the development and use of analytics in the context of education. Using Buckingham Shum's three levels of analytics, the authors present a critical analysis of current developments in the domain of learning analytics, and contrast the potential value of analytics research and development with real world…

  10. Text + Time Search & Analytics

    E-print Network

    Waldmann, Uwe

    Text + Time Search & Analytics Klaus Berberich (kberberi@mpi-inf.mpg.de) #12;Text + Time Search & Analytics ­ Klaus Berberich / 40 Text + Time 2 The New York Times June 2nd, 1889 #12;Text + Time Search & Analytics ­ Klaus Berberich / 40 Text + Time 2 Wikipedia April 23rd, 2001 #12;Text + Time Search & Analytics

  11. Let's Talk... Analytics

    ERIC Educational Resources Information Center

    Oblinger, Diana G.

    2012-01-01

    Talk about analytics seems to be everywhere. Everyone is talking about analytics. Yet even with all the talk, many in higher education have questions about--and objections to--using analytics in colleges and universities. In this article, the author explores the use of analytics in, and all around, higher education. (Contains 1 note.)

  12. "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.

  13. 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

  14. Metal-silica sol-gel materials

    NASA Technical Reports Server (NTRS)

    Stiegman, Albert E. (Inventor)

    2002-01-01

    The present invention relates to a single phase metal-silica sol-gel glass formed by the co-condensation of a transition metal with silicon atoms where the metal atoms are uniformly distributed within the sol-gel glass as individual metal centers. Any transition metal may be used in the sol-gel glasses. The present invention also relates to sensor materials where the sensor material is formed using the single phase metal-silica sol-gel glasses. The sensor materials may be in the form of a thin film or may be attached to an optical fiber. The present invention also relates to a method of sensing chemicals using the chemical sensors by monitoring the chromatic change of the metal-silica sol-gel glass when the chemical binds to the sensor. The present invention also relates to oxidation catalysts where a metal-silica sol-gel glass catalyzes the reaction. The present invention also relates to a method of performing oxidation reactions using the metal-silica sol-gel glasses. The present invention also relates to organopolymer metal-silica sol-gel composites where the pores of the metal-silica sol-gel glasses are filled with an organic polymer polymerized by the sol-gel glass.

  15. 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

  16. 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.

  17. Gel barrier formation in unsaturated porous media

    NASA Astrophysics Data System (ADS)

    Kim, Meejeong; Corapcioglu, M. Yavuz

    2002-05-01

    The gel barrier formation by a gelling liquid (Colloidal Silica) injection in an unsaturated porous medium is investigated by developing a mathematical model and conducting numerical simulations. Gelation process is initiated by adding electrolytes such as NaCl, and the gel phase consisting of cross-linked colloidal silica particles grows as the gelation process proceeds. The mathematical model describing the transport and gelation of Colloidal Silica (CS) is based on coupled mass balance equations for the gel mixture (the sol phase plus the gel phase), gel phase (cross-linked colloidal silica particles plus water captured between cross-linked particles), and colloidal silica particles (discrete and cross-linked) and NaCl in the sol (suspension of discrete colloidal silica particles in water) and gel phases. The solutions in terms of volumetric fraction of the gel phase yield the gel mixture viscosity via the dependency on the volumetric fraction of gel phase. This dependency is determined from a kinetic gelation model with time-normalized viscosity curves. The proposed model is verified by comparing experimentally and numerically determined hydraulic conductivities of gel-treated soil columns at different CS injection volumes. The numerical experiments indicate that an impermeable gel layer is formed within the time period twice the gel-point in a one-dimensional flow system. At the same normalized time corresponding to twice the gel-point, the CS solutions with lower NaCl concentrations result in further migration and poor performance in plugging the pore space. The viscosity computation proposed in this study is compared with another method available in the literature. It is observed that the other method estimates the viscosity at the mixing zone higher than the one proposed by the authors. The proposed model can simulate realistic injection scenarios with various combinations of operating parameters such as NaCl concentration and NaCl mixing time, and thus providing guidelines in performing this technology on site.

  18. Gel barrier formation in unsaturated porous media.

    PubMed

    Kim, Meejeong; Corapcioglu, M Yavuz

    2002-05-01

    The gel barrier formation by a gelling liquid (Colloidal Silica) injection in an unsaturated porous medium is investigated by developing a mathematical model and conducting numerical simulations. Gelation process is initiated by adding electrolytes such as NaCl, and the gel phase consisting of cross-linked colloidal silica particles grows as the gelation process proceeds. The mathematical model describing the transport and gelation of Colloidal Silica (CS) is based on coupled mass balance equations for the gel mixture (the sol phase plus the gel phase), gel phase (cross-linked colloidal silica particles plus water captured between cross-linked particles), and colloidal silica particles (discrete and cross-linked) and NaCl in the sol (suspension of discrete colloidal silica particles in water) and gel phases. The solutions in terms of volumetric fraction of the gel phase yield the gel mixture viscosity via the dependency on the volumetric fraction of gel phase. This dependency is determined from a kinetic gelation model with time-normalized viscosity curves. The proposed model is verified by comparing experimentally and numerically determined hydraulic conductivities of gel-treated soil columns at different CS injection volumes. The numerical experiments indicate that an impermeable gel layer is formed within the time period twice the gel-point in a one-dimensional flow system. At the same normalized time corresponding to twice the gel-point, the CS solutions with lower NaCl concentrations result in further migration and poor performance in plugging the pore space. The viscosity computation proposed in this study is compared with another method available in the literature. It is observed that the other method estimates the viscosity at the mixing zone higher than the one proposed by the authors. The proposed model can simulate realistic injection scenarios with various combinations of operating parameters such as NaCl concentration and NaCl mixing time, and thus providing guidelines in performing this technology on site. PMID:12076024

  19. Characteristics of polyacrylamide gel with THPC and Turnbull Blue gel dosimeters evaluated using optical tomography

    NASA Astrophysics Data System (ADS)

    Pila?ová (Vávr?), Kate?ina; Kozubíková, Petra; Šolc, Jaroslav; Sp?vá?ek, Václav

    2014-11-01

    The purpose of this study was to compare characteristics of radiochromic gel - Turnbull Blue gel (TB gel) with polymer gel - polyacrylamide gel and tetrakis hydroxymethyl phosphonium chloride (PAGAT) using optical tomography. Both types of gels were examined in terms of dose sensitivity, dose response linearity and background value of spectrophotometric absorbance. The calibration curve was obtained for 60Co irradiation performed on Gammacell 220 at predefined gamma dose levels between 0 and 140 Gy for TBG and 0-15 Gy for PAGAT. To measure relative dose distributions from stereotactic irradiation, dosimeters were irradiated on Leksell Gamma Knife Perfexion. The cylindrical glass housings filled with gel were attached to the stereotactic frame. They were exposed with single shot and 16 mm collimator by 65 Gy to a 50% prescription isodose for TB gel and 4 Gy to a 50% prescription isodose for PAGAT. Evaluations of dosimeters were performed on an UV-vis Spectrophotometer Helios ? and an optical cone beam homemade tomography scanner with a 16-bit astronomy CCD camera with a set of color filters. The advantages and potential disadvantages for both types of gel dosimeters were summarized. Dose distribution in central slice and measured profiles of 16 mm shot shows excellent correspondence with treatment planning system Leksell GammaPlan® for both PAGAT and Turnbull Blue gels. Gel dosimeters are suitable for steep dose gradient verification. An optical tomography evaluation method is successful. Dose response characteristics of TB gel and PAGAT gel are presented.

  20. GEM printer: 3D gel printer for free shaping of functional gel engineering materials

    NASA Astrophysics Data System (ADS)

    Furukawa, Hidemitsu; Muroi, Hisato; Yamamoto, Kouki; Serizawa, Ryo; Gong, Jin

    2013-04-01

    In the past decade, several high-strength gels have been developed. 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. The gels have both low surface friction and well permeability due to a large amount of water absorbed in the gels, which are superiority of the gels compering to the polyester fibers. It is, however, difficult for gels to be forked structure or cavity structure by using cutting or mold. Consequently, it is necessary to develop the additive manufacturing device to synthesize and mode freely gels at the same time. Here we try to develop an optical 3D gel printer that enables gels to be shaped precisely and freely. For the free forming of high-strength gels, the 1st gels are ground to particles and mixed with 2nd pregel solution, and the mixed solution is gelled by the irradiation of UV laser beam through an optical fiber. The use of the optical fiber makes one-point UV irradiation possible. Since the optical fiber is controlled by 3D-CAD, the precise and free molding in XYZ directions is easily realized. We successfully synthesized tough gels using the gel printer.

  1. Development of novel Sol-Gel Indicators (SGI's) for in-situ environmental measurements: Part 1, Program and a new pH Sol-Gel Indicator

    SciTech Connect

    Livingston, R.R.; Baylor, L.; Wicks, G.G.

    1992-11-03

    The feasibility of incorporating analytical indicators into a sol-gel glassy matrix and then coating substrates with this composite material has bee demonstrated. Substrates coated include paper, wood, glass, and the lens of an analytical probe. The first SRTC sol-gel indicator, comprising bromophenol blue dispersed in a silica matrix, was fabricated and successfully used to measure solution pH in the range of pH 3.0 to 7.5. material exhibited a quick response time, as measured by color changes both qualitatively and quantitatively, and the measuring device was reversible or reusable. Additional indicators with responses over other ranges as well as indicators sensitive to the presence of elements of interest, are also under development. The new SGI composites possess promising properties and an excellent potential for performing a variety important in-situ environmental measurements and area discussed in this report.

  2. 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.

  3. Kinetics of phase separation of thermoreversible gels

    NASA Astrophysics Data System (ADS)

    Solis, Francisco J.; Leon, Christine; Vernon, Brent

    2009-03-01

    We study the kinetics of phase separation and thermoreversible gel formation of LCST-type polymers. A large number of NIPAM-based polymers exhibit transitions near room temperature from a liquid phase to a two-phase state. In the two phase-region of the phase diagram, a polymer dilute phase coexists with a gel. The corresponding shrinking transition for chemically-linked gels has been extensively studied in both its thermodynamic and kinetic aspects. We show that, in the thermoreversible case, the formation of the gel phase proceeds in a similar way. Upon entrance to the two-phase region, the gel volume follows a double exponential decay. The gel undergoes a fast shrinking associated with water ejection, followed by a slower reorganization regime.

  4. Active Gel Model of Amoeboid Cell Motility

    E-print Network

    Callan-Jones, A C

    2013-01-01

    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.

  5. Active gel model of amoeboid cell motility

    NASA Astrophysics Data System (ADS)

    Callan-Jones, A. C.; Voituriez, R.

    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-substrate 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.

  6. 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.

  7. Gadolinium ferromagnetic mesoparticles from gels

    SciTech Connect

    Blanco, E.; Esquivias, L.; Dominguez, M.

    1995-12-31

    Gadolinium/silica composites have been obtained by the sol-gel method. Ultrasound energy was employed for hydrolysis and polycondensation silica alkoxyde activation. Composites magnetic behavior has been studied by a Faraday magnetometer. Low temperature magnetization has been followed by a SQUID magnetometer working at 2K. X-ray diffraction and transmission electron microscopy (TEM) have been used for samples characterization. Results show that there are ferromagnetic gadolinium mesoparticles (<50 nm) embedded in a diamagnetic silica matrix. The magnetization of this composite upon external magnetic field after zero field cooling (ZFC) down to the liquid He temperature shows the characteristic behavior of a dispersed meso-scale ferromagnet.

  8. Analytical Challenges in Biotechnology.

    ERIC Educational Resources Information Center

    Glajch, Joseph L.

    1986-01-01

    Highlights five major analytical areas (electrophoresis, immunoassay, chromatographic separations, protein and DNA sequencing, and molecular structures determination) and discusses how analytical chemistry could further improve these techniques and thereby have a major impact on biotechnology. (JN)

  9. 21 CFR 866.4900 - Support gel.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...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)...

  10. Food gels: gelling process and new applications.

    PubMed

    Banerjee, Soumya; Bhattacharya, Suvendu

    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 hydrogen bonds, electrostatic forces, Van der Waals forces, and hydrophobic interactions. Polysaccharides including hydrocolloids are strongly hydrated in aqueous medium but they tend to have less ordered structures. The mechanism of gelation depends on the nature of the gelling agent(s) and on the conditions of gel formation like the temperature, the presence of ions, the pH, and the concentration of gelling agents, etc. Characterization of gels can be performed in several ways of which rheological measurements are frequently practiced. Multi-component or mixed gel system is an important area of interest in which two or more gelling components are simultaneously used to achieve certain specific structural and functional characteristics. We here discuss about the different gels and gelling agents, the characterization of gels, and the mechanism of gelation with an emphasis on mixed or multi-component gels that would have significant commercial applications. PMID:22332597

  11. Ionic liquid based multifunctional double network gel

    NASA Astrophysics Data System (ADS)

    Ahmed, Kumkum; Higashihara, Tomoya; Arafune, Hiroyuki; Kamijo, Toshio; Morinaga, Takashi; Sato, Takaya; Furukawa, Hidemitsu

    2015-04-01

    Gels are a promising class of soft and wet materials with diverse application in tissue engineering and bio-medical purpose. In order to accelerate the development of gels, it is required to synthesize multi-functional gels of high mechanical strength, ultra low surface friction and suitable elastic modulus with a variety of methods and new materials. Among many types of gel ionic gel made from ionic liquids (ILs) could be used for diverse applications in electrochemical devices and in the field of tribology. IL, a promising materials for lubrication, is a salt with a melting point lower than 100 °C. As a lubricant, ILs are characterized by an extremely low vapor pressure, high thermal stability and high ion conductivity. In this work a novel approach of making double network DN ionic gel using IL has been made utilizing photo polymerization process. A hydrophobic monomer Methyl methacrylate (MMA) has been used as a first network and a hydrophobic IL monomer, N,N-diethyl-N-(2-mthacryloylethyl)-N-methylammonium bistrifluoromethylsulfonyl)imide (DEMM-TFSI) has been used as a second network using photo initiator benzophenon and crosslinker triethylene glycol dimethacrylate (TEGDMA). The resulting DN ionic gel shows transparency, flexibility, high thermal stability, good mechanical toughness and low friction coefficient value which can be a potential candidate as a gel slider in different mechanical devices and can open a new area in the field of gel tribology.

  12. Tissue simulating gel for medical research

    NASA Technical Reports Server (NTRS)

    Companion, John A. (Inventor)

    1991-01-01

    A tissue simulating gel and a method for preparing the tissue simulating gel are disclosed. The tissue simulating gel is prepared by a process using water, gelatin, ethylene glycol, and a cross-linking agent. In order to closely approximate the characteristics of the type of tissue being simulated, other material has been added to change the electrical, sound conducting, and wave scattering properties of the tissue simulating gel. The result of the entire process is a formulation that will not melt at the elevated temperatures involved in hyperthermia medical research. Furthermore, the tissue simulating gel will not support mold or bacterial growth, is of a sufficient mechanical strength to maintain a desired shape without a supporting shell, and is non-hardening and non-drying. Substances have been injected into the tissue simulating gel prior to the setting-up thereof just as they could be injected into actual tissue, and the tissue simulating gel is translucent so as to permit visual inspection of its interior. A polyurethane spray often used for coating circuit boards can be applied to the surface of the tissue simulating gel to give a texture similar to human skin, making the tissue simulating gel easier to handle and contributing to its longevity.

  13. Structure of chitosan gels mineralized by sorption

    NASA Astrophysics Data System (ADS)

    Modrzejewska, Z.; Skwarczy?ska, A.; Douglas, T. E. L.; Binia?, D.; Maniukiewicz, W.; Sielski, J.

    2015-10-01

    The paper presents the structural studies of mineralized chitosan hydrogels. Hydrogels produced by using sodium beta-glycerophosphate (Na-?-GP) as a neutralizing agent. Mineralization was performed method "post loading", which consisted in sorption to the gels structure Ca ions. In order to obtain - in the structure of gels - compounds similar to the hydroxyapatites present naturally in bone tissue, gels after sorption were modified in: pH 7 buffer and sodium hydrogen phosphate. In order to determine the structural properties of the gels, the following methods were used: infrared spectroscopy with Fourier transformation, FTIR, X-ray diffractometry, XRD, scanning electron microscopy, SEM.

  14. Modeling of Fibrin Gels Based on Confocal Microscopy and Light-Scattering Data

    PubMed Central

    Magatti, Davide; Molteni, Matteo; Cardinali, Barbara; Rocco, Mattia; Ferri, Fabio

    2013-01-01

    Fibrin gels are biological networks that play a fundamental role in blood coagulation and other patho/physiological processes, such as thrombosis and cancer. Electron and confocal microscopies show a collection of fibers that are relatively monodisperse in diameter, not uniformly distributed, and connected at nodal points with a branching order of ?3–4. Although in the confocal images the hydrated fibers appear to be quite straight (mass fractal dimension Dm = 1), for the overall system 1gels made of cylindrical sticks of diameter d, density ?, and average length ?L?, joined at randomly distributed nodal points. The resulting 3D network strikingly resembles real fibrin gels and can be sketched as an assembly of densely packed fractal blobs, i.e., regions of size ?, where the fiber concentration is higher than average. The blobs are placed at a distance ?0 between their centers of mass so that they are overlapped by a factor ? = ?/?0 and have Dm ?1.2–1.6. The in silico gels’ structure is quantitatively analyzed by its 3D spatial correlation function g3D(r) and corresponding power spectrum I(q) = FFT3D[g3D(r)], from which ?, d, Dm, ?, and ?0 can be extracted. In particular, ?0 provides an excellent estimate of the gel mesh size. The in silico gels’ I(q) compares quite well with real gels’ elastic light-scattering measurements. We then derived an analytical form factor for accurately fitting the scattering data, which allowed us to directly recover the gels’ structural parameters. PMID:23473498

  15. Stacking gels: A method for maximising output for pulsed-field gel electrophoresis.

    PubMed

    Heng, See Kah; Heng, Chua Kek; Puthucheary, S D

    2009-01-01

    Pulsed field gel electrophoresis (PFGE), the gold standard of molecular typing methods, has a major disadvantage of an unusually long electrophoretic time. From the original protocol of 6 days, it was modified to 3 days and subsequently to a single day. We describe the procedure of stacking five to six gels one on top of another in order to increase and maximize the output in a shorter time without compromising the resolution and reproducibility. All the variables that affect pulsed field gels during electrophoresis were taken into consideration. We firstly optimized the parameters to be used and secondly determined whether stacking of five to six gels had any effect on the molecular separation during electrophoresis in comparison with a single gel run. DNA preparation, restriction, electrophoresis, staining and gel documentation was carried out based on previously published methods. Gels were analysed using BioNumerics and dice coefficient and unweighted pair group methods were used to generate dendrograms based on 1.5% tolerance values. Identical band profiles and band resolution-separation were seen in the PFGE patterns with single gel and multiple stacking gels. Cluster analysis further strengthened the fact that results from stacking gels were reproducible and comparable with a single gel run. This method of stacking gels saves time and maximizes the output at the same time. The run time for a single gel was about 28 hours, but with six stacked gels the run time was 54 hours compared with 28 x 6 = 168 hours if they were run separately as single gels thus saving time of 67.86%. Beside the big factor of saving time, stacking gels save resources (electricity, reagents, water, chemicals and working time) by increasing the sample throughput in a shorter time without compromising on quality of data. But optimization of working parameters is vital depending on the PFGE system used. PMID:19384038

  16. enhancements Operational analytics and

    E-print Network

    Chaudhuri, Surajit

    In database analytics at massive scale 30X In-memory OLTP As the biggest leap forward in Microsoft's data apps for Windows, iOS and Android. New modern reports for all browsers. Advanced Analytics at massive" algorithms directly in SQL Server. Expand your analytics library with Microsoft Azure Marketplace. HYPERSCALE

  17. 01101011011 Competing on Analytics

    E-print Network

    Yu, Sheng-Tao

    of Big Data, but extracting value from Big Data is no ordinary task. Big Data management and analytics University has established the WSU Big Data & Business Analytics Group. Our goal is to be the Midwest's premier center of innovation in Big Data science and business analytics. To do this, we must have a strong

  18. Silver Staining SDS Gels Remove the stacking gel before the first fixative step.

    E-print Network

    Aris, John P.

    37 Silver Staining SDS Gels · Remove the stacking gel before the first fixative step. · Do, for frequent silver staining: make up solutions as 10X stocks ahead of time. 1. Fix in 50% methanol, 10% acetic. Replace silver nitrate solution in same tray and gently agitate for 15 minutes again. 6. Rinse the gel 2 X

  19. 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

  20. MECHANICAL PROPERTIES OF COLLOIDAL GELS SUBJECT TO PARTICLE REARRANGEMENT

    E-print Network

    Aksay, Ilhan A.

    Technology Center, Washington Technology Centers, University of Washington, Seattle, WA 98195 INTRODUCTION is formed. Colloidal gels may be divided into hard gels and soft gels. 1 Hard gels are those formed by fine modulus G' of a hard gel remains constant at small strain and increases in a power-law fashion

  1. Terpolymer smart gels: synthesis and characterizations

    NASA Astrophysics Data System (ADS)

    Bag, Dibyendu S.; Alam, Sarfaraz; Mathur, G. N.

    2004-10-01

    Two smart terpolymer gels, MS-1 and MS-2, were synthesized such that the same gel can respond to more than one external environmental condition, such as pH, temperature, solvent composition, electric field. So two terpolymers gels of vinyl monomers such as sodium acrylate, acrylamide and N-isopropyl acrylamide were synthesized by using ammonium persulfate (APS) as an initiator, N,N,N',N'-tetramethyl ethylene diamine (TMEDA) as an accelerator and methylene bisacrylamide as a cross-linker. These terpolymers were characterized by elemental and Fourier transform infrared analysis. The swelling behavior of these terpolymer smart gels was evaluated by changing the pH, temperature and solvent composition. The variation of the swelling behavior with time was evaluated in an aqueous medium at room temperature. The time taken for maximum swelling (tm) was about 20 min for the gel MS-2. However the tm value for the gel MS-1 is higher than that of MS-2. The swelling behavior remains almost unchanged over a temperature range of 22-50 °C for both the gels. The discontinuous volume transitions were observed at pH 7.6 and 8.2 for the two gels, MS-1 and MS-2, respectively. The gel MS-1 suddenly shrinks below and swells above pH 7.6. Correspondingly, the pH is 8.2 for the case of MS-2. Volume transitions in an acetone-water mixture were also observed for these gels. The swelling behaviors of these two smart gels are almost parallel above the 40% acetone concentration.

  2. 21 CFR 866.4900 - Support gel.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Support gel. 866.4900 Section 866.4900 Food and Drugs 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....

  3. 21 CFR 866.4900 - Support gel.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Support gel. 866.4900 Section 866.4900 Food and Drugs 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....

  4. 21 CFR 866.4900 - Support gel.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Support gel. 866.4900 Section 866.4900 Food and Drugs 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....

  5. 21 CFR 866.4900 - Support gel.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Support gel. 866.4900 Section 866.4900 Food and Drugs 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....

  6. 21 CFR 866.4900 - Support gel.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Support gel. 866.4900 Section 866.4900 Food and Drugs 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....

  7. Fixing and Drying PAGE Gels 1. Fixation

    E-print Network

    Aris, John P.

    MM paper on gel. Place on metal screen and invert quickly. Place white porous sheet on top. Place on absorbant pad. Cut away excess. Invert sandwich so that gel is face up. Cover with plastic wrap. Fold up edges. 5. Set up dryer as follows. Follow instructions posted near dryer. Metal Screen (centered) White

  8. 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…

  9. Thermotropic nanostructured "gel in gel" systems for improved oil recovery and water shutoff

    NASA Astrophysics Data System (ADS)

    Altunina, L. K.; Kuvshinov, V. A.; Stasyeva, L. A.

    2015-10-01

    Thermotropic nanostructured system with two gel-forming components has been created based on inorganic hydroxypolymer and organic polymer with a lower critical solution temperature of "aluminum salt-cellulose ether-carbamide-water", forming at heating a bound-dispersed nano-sized "gel in gel" structure. The studies on the kinetics of gelation and rheological properties of solutions and gels in this system have shown that the gels have a higher viscosity and elasticity and thereby are promising for creating deflecting screens in oil reservoirs, redistribution of filtration flows, improved oil recovery and for water shutoff.

  10. A new polymer gel dosimeter composed of methacrylic acid, agarose gel and THPC with gelatin

    NASA Astrophysics Data System (ADS)

    Yoshioka, M.; Hayashi, S.; Usui, S.; Haneda, K.; Numasaki, H.; Teshima, T.; Tominaga, T.

    2009-05-01

    In this paper, a new type of methacrylic acid based gel dosimeter is presented. This gel contains both agarose and gelatin with deferent roles respectively. The agarose conducts itself as a gelling agent, while the gelatin relates to the graft reaction of methacrylic acid. This new type of gel excels in the long-term stability of R2 after irradiation. The characteristics of this gel were studied by the measurements of R2 with MRI and the direct measurements of temperature in the gel during the irradiation.

  11. 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.

  12. 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

  13. Generation of inkjet drop of particulate gel

    NASA Astrophysics Data System (ADS)

    Yoo, Hansol; Kim, Chongyoup

    2015-08-01

    The generation of inkjet drops of colloidal gels is studied experimentally. Particle suspensions are prepared by dispersing spherical polystyrene particles of 620 nm in the 1:1 mixture of deionized water and ethylene glycol. The gels are prepared by adding polyethylene oxide to the suspensions by inducing the depletion interaction between particles. It is demonstrated that inkjet drops can be generated by using the colloidal gels. It is found that the ligament extended from the inkjet nozzle is stabilized so that the drop can be generated without satellite droplets behind the main drop and the velocity of the gel drop is faster than that of the polymer solution at the same concentration. The gel drop generation characteristics are found to be sensitive to input voltage.

  14. Improving immobilized biocatalysts by gel phase polymerization

    SciTech Connect

    Kuu, W.Y.; Polack, J.A.

    1983-08-01

    A new method is presented for the treatment of gel-type supports, used for immobilizing microbial cells and enzymes, to obtain high mechanical strength. It is particularly useful for ethanol fermentation over gel beads containing immobilized viable cells, where the beads can be ruptured by gas production and the growth of cells within the gels. This method consists of treating agar or carrageenan gel with polyacrylamide to form a rigid support which retains the high catalytic activity characteristic of the untreated biocatalysts. The size and shape of the biocatalyst is unaffected by this treatment. The method involves the diffusion of acrylamide, N,N'-methylenebisacrylamide and BETA-dimethylaminopropionitrile (or N,N,N',N'-tetramethylethylenediamine) into the preformed biocatalyst beads followed by the addition of an initiator to cause polymerization within the beads. Treated gels have been used for the continuous fermentation of glucose to ethanol in a packed column for over two months.

  15. 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.

  16. Viscoelastic Properties of Vitreous Gel

    NASA Astrophysics Data System (ADS)

    Pirouz Kavehpour, H.; Sharif-Kashani, Pooria

    2010-11-01

    We studied the rheological properties of porcine vitreous humor using a stressed-control shear rheometer. All experiments were performed in a closed environment at body temperature to mimic in-vivo conditions. We modeled the creep deformation using a two-element retardation spectrum model. By associating each element of the model to an individual biopolymeric system in the vitreous gel, a separate response to the applied stress was obtained from each component. The short time scale was associated with the collagen structure, while the longer time scale was related to the microfibrilis and hyaluronan network. We were able to distinguish the role of each main component from the overall rheological properties. Knowledge of this correlation enables us to relate the physical properties of vitreous to its pathology, as well as optimize surgical procedures such as vitrectomy.

  17. Silver nanowires embedded gel electrodes

    NASA Astrophysics Data System (ADS)

    Abe, Yuta; Gong, Jin; Furukawa, Hidemitsu

    2013-04-01

    The polyelectrolyte of high-strength gels was made to improve the mechanical properties in our previous study. In the field of electronic devices, the demand of polymer electrodes, which have high conductivity, high flexibility and transparence, is increasing. In this study, we attempt to make a transparent polymer electrode by laminating polymer thin film and silver nanowire (AgNW). High transparenct poly(methyl methacrylate) (PMMA) film, which is produced by using solvent cast method is used. AgNW is prepared by reacting Silver chloride (AgCl) with Silver nitrate (AgNO3) based on previous study. The AgNWs taking on different shapes were obtained. Fibrous AgNWs are formed by using high molecular weight polyvinylpyrrolidone (PVP). These results showed a possibility of developing the polymer electrode with high conductivity, high flexibility and transparence.

  18. Radiological properties of normoxic polymer gel dosimeters

    SciTech Connect

    Venning, A.J.; Nitschke, K.N.; Keall, P.J.; Baldock, C.

    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.

  19. 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.

  20. Sol-gel chemical sensors for surface-enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Lee, Vincent Y.; Farquharson, Stuart; Kwon, Hueong-Chan; Shahriari, Mahmoud R.; Rainey, Petrie M.

    1999-02-01

    Surface-enhanced Raman spectroscopy (SERS) promises to be one of the most sensitive methods for chemical detection. Unfortunately, the inability of SERS to perform quantitative chemical analysis has slowed its general use in laboratories. This is largely due to the difficulty of manufacturing either active surfaces that yield reproducible enhancements, or surfaces that are capable of reversible chemical adsorption, or both. In an effort to meet this need, we have developed metal-doped sol-gels that provide surface-enhancement of Raman scattering. The porous silica network offers a unique environment for stabilizing SER active metal particles and the high surface area increases the interaction between the analyte and metal particles. This eliminates the need to concentrate the analyte on the surface by evaporating the solvent. The sol-gel is easily coated on a variety of surfaces, such as fiber optics, glass slides, or glass tubing, and can be designed into sample flow systems. Here we present the development of both gold- and silver-doped sol-gels, which have been used to coat the inside walls of glass sample vials for SERS applications. The performance of the metal-doped sol-gels was evaluated using p-aminobenzoic acid, to establish enhancement factors, detection limits, dynamic response range, reversibility, reproducibility, and suitability to commercial spectrometers. Measurements of trace chemicals, such as adenine and cocaine, are also presented.

  1. 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)

  2. Water equivalence of polymer gel dosimeters

    NASA Astrophysics Data System (ADS)

    Sellakumar, P.; James Jebaseelan Samuel, E.; Supe, Sanjay S.

    2007-07-01

    To evaluate the water equivalence and radiation transport properties of polymer gel dosimeters over the wide range of photon and electron energies 14 different types of polymer gels were considered. Their water equivalence was evaluated in terms of effective atomic number ( Zeff), electron density ( ?e), photon mass attenuation coefficient ( ?/?), photon mass energy absorption coefficient ( ?en/?) and total stopping power (S/?)tot of electrons using the XCOM and the ESTAR database. The study showed that the effective atomic number of polymer gels were very close ( <1%) to that of water except PAGAT, MAGAT and NIPAM which had the variation of 3%, 2% and 3%, respectively. The value of ?/? and ?en/? for all polymer gels were in close agreement ( <1%) with that of water beyond 80 keV. The value of (S/?)tot of electrons in polymer gel dosimeters were within 1% agreement with that of water. From the study we conclude that at lower energy ( <80 keV) the polymer gel dosimeters cannot be considered water equivalent and study has to be carried out before using the polymer gel for clinical application.

  3. Electroacoustics of Particles Dispersed in Polymer Gel

    SciTech Connect

    Bhosale, Prasad S.; Chun, Jaehun; Berg, John C.

    2011-06-27

    This study examines the acoustic electrophoresis of particles dispersed in polymer hydrogels, with the particle size either less than or greater than the gel mesh size. When the particles are smaller than the gel mesh size, their acoustic vibration is resisted by only the background water medium, and the measured dynamic electrophoretic mobility, ?d (obtained in terms of colloid vibration current, CVI), is the same as in water. For the case of particles larger than the gel mesh size, ?d is decreased due to trapping, and the net decrease depends on the viscoelastic properties of the gel. The gel mesh size was varied by varying its crosslink density, the latter being characterized as the storage modulus, G’. The dependence of mobility on G’, for systems of a given particle size, and on particle size, for gels of a given G’, are investigated. The measured mobility remains constant as G’ is increased (i.e., mesh size is decreased) up to a value of approximately 300 Pa, beyond which it decreases. In the second set of measurements, the trapped particle size was increased in a gel medium of constant mesh size, with G’ approximately 100 Pa. In this case, the measured ?d is found to be effectively constant over the particle size range studied (14-120 nm), i.e., it is independent of the degree of trapping as expressed by the ratio of the particle size to the mesh size.

  4. Improving immobilized biocatalysts by gel phase polymerization

    SciTech Connect

    Kuu, W.Y.; Polack, J.A.

    1983-08-01

    A new method is presented for the treatment of gel-type supports, used for immobilizing microbial cells and enzymes, to obtain high mechanical strength. It is particularly useful for ethanol fermentation over gel beads containing immobilized viable cells, where the beads can be ruptured by gas production and the growth of cells within the gels. This method consists of treating agar or carrageenan gel with polyacrylamide to form a rigid support which retains the high catalytic activity characteristic of the untreated biocatalysts. The size and shape of the biocatalyst is unaffected by this treatment. The method involves the diffusion of acrylamide, N,N'-methylenebisacrylamide and ..beta..-dimethylaminopropionitrile (or N,N,N',N'-tetramethylethylenediamine) into the preformed biocatalyst beads followed by the addition of an initiator to cause polymerization within the beads. Treated gels have been used for the continuous fermentation of glucose to ethanol in a packed column for over two months. During this operation, the gel beads maintained their rigidity, and the maximum productivity was as high as 50 gh/sup -1/ L/sup -1/ gel. There was no appreciable decay of cell activity.

  5. Sol-Gel Manufactured Energetic Materials

    DOEpatents

    Simpson, Randall L. (Livermore, CA); Lee, Ronald S. (Livermore, CA); Tillotson, Thomas M. (Tracy, CA); Hrubesh, Lawrence W. (Pleasanton, CA); Swansiger, Rosalind W. (Livermore, CA); Fox, Glenn A. (Livermore, CA)

    2005-05-17

    Sol-gel chemistry is used for the preparation of energetic materials (explosives, propellants and pyrotechnics) with improved homogeneity, and/or which can be cast to near-net shape, and/or made into precision molding powders. The sol-gel method is a synthetic chemical process where reactive monomers are mixed into a solution, polymerization occurs leading to a highly cross-linked three dimensional solid network resulting in a gel. The energetic materials can be incorporated during the formation of the solution or during the gel stage of the process. The composition, pore, and primary particle sizes, gel time, surface areas, and density may be tailored and controlled by the solution chemistry. The gel is then dried using supercritical extraction to produce a highly porous low density aerogel or by controlled slow evaporation to produce a xerogel. Applying stress during the extraction phase can result in high density materials. Thus, the sol-gel method can be used for precision detonator explosive manufacturing as well as producing precision explosives, propellants, and pyrotechnics, along with high power composite energetic materials.

  6. Sol-gel manufactured energetic materials

    DOEpatents

    Simpson, Randall L.; Lee, Ronald S.; Tillotson, Thomas M.; Hrubesh, Lawrence W.; Swansiger, Rosalind W.; Fox, Glenn A.

    2003-12-23

    Sol-gel chemistry is used for the preparation of energetic materials (explosives, propellants and pyrotechnics) with improved homogeneity, and/or which can be cast to near-net shape, and/or made into precision molding powders. The sol-gel method is a synthetic chemical process where reactive monomers are mixed into a solution, polymerization occurs leading to a highly cross-linked three dimensional solid network resulting in a gel. The energetic materials can be incorporated during the formation of the solution or during the gel stage of the process. The composition, pore, and primary particle sizes, gel time, surface areas, and density may be tailored and controlled by the solution chemistry. The gel is then dried using supercritical extraction to produce a highly porous low density aerogel or by controlled slow evaporation to produce a xerogel. Applying stress during the extraction phase can result in high density materials. Thus, the sol-gel method can be used for precision detonator explosive manufacturing as well as producing precision explosives, propellants, and pyrotechnics, along with high power composite energetic materials.

  7. In-gel peptide IEF sample preparation for LC/MS analysis.

    PubMed

    Berkelman, Tom; Bandhakavi, Sricharan; Paulus, Aran

    2015-01-01

    The technique of proteolytically digesting a sample and identifying its protein components by liquid chromatography followed by mass spectrometry (LC-MS) is a widely used analytical tool. Prior fractionation by isoelectric focusing (IEF) may be performed to increase the depth of proteome coverage. Here, we describe a method for in-gel IEF separation of a proteolytic digest that utilizes commercially available immobilized pH gradient (IPG) strips and a widely used IEF instrument. PMID:25820734

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    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.

  10. 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.

  11. 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.

  12. 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.

  13. Chemical sensing using sol-gel derived planar waveguides and indicator phases

    SciTech Connect

    Yang, L.; Saavedra, S.S.

    1995-04-15

    A new optical sensing platform based on a combination of planar waveguiding and sol-gel processing technologies is described. The sensing element consists of two, submicrometer thick glass layers supported on an optically thick glass substrate; both layers were fabricated using a sol-gel coating method. The lower layer is a densified glass that functions as a planar integrated optical waveguide (IOW). The upper layer is an undensified glass of lower index doped with an optical indicator that is immobilized, yet remains sterically accessible to analytes that diffuse into the pore network. Formation of a complex between the analyte and indicator is detected via attenuated total reflection (ATR) of light guided in the IOW. Feasibility was evaluated by constructing IOW-ATR sensors for Pb{sup 2+} and pH, based on immobilized xylenol orange and bromocresol purple, respectively. The response of both sensors was sensitive and rapid, features that are difficult to achieve simultaneously in monolithic sol-gel glass sensors. In the IOW-ATR geometry, these features are realized simultaneously because the primary axes of light propagation and analyte diffusion are orthogonal. The overall approach is technically simple, inexpensive, and applicable to a wide variety of indicator chemistries. 48 refs., 8 figs.

  14. Optical sensors based on sol-gel derived, laminate planar waveguide structures

    SciTech Connect

    Yang, Lin; Armstrong, N.R.; Dunphy, D.R.; Saavedra, S.S.

    1995-12-31

    A new optical sensing platform based on a combination of planar and sol-gel processing technologies is described. The sensing element is a planar integrated optical waveguide (IOW) composed of two, submicron thick glass layers coated on glass substrate; both layers are fabricated via the sol-gel method. The lower layer is a densified titania-silica composite. The upper layer is an undensified silica doped with an optical indicator that is physically entrapped yet sterically accessible to dissolved analytes that can diffuse into the pore network. Formation of an analyte-indicator complex is detected via attenuated total reflection (ATR) of light guided in the IOW. The sensor response is both sensitive and rapid, features that are difficult to achieve simultaneously in monolithic sol-gel glass sensors. In the IOW-ATR geometry, these features are realized simultaneously because the primary axes of light propagation and analyte diffusion are orthogonal. The overall approach is technically simple, inexpensive, and applicable to a wide variety of indicator chemistries.

  15. Phase diagram of a reentrant gel of patchy particles

    SciTech Connect

    Roldán-Vargas, Sándalo; Smallenburg, Frank; Sciortino, Francesco; Kob, Walter

    2013-12-28

    We study the phase diagram of a binary mixture of patchy particles which has been designed to form a reversible gel. For this we perform Monte Carlo and molecular dynamics simulations to investigate the thermodynamics of such a system and compare our numerical results with predictions based on the analytical parameter-free Wertheim theory. We explore a wide range of the temperature-density-composition space that defines the three-dimensional phase diagram of the system. As a result, we delimit the region of thermodynamic stability of the fluid. We find that for a large region of the phase diagram the Wertheim theory is able to give a quantitative description of the system. For higher densities, our simulations show that the system is crystallizing into a BCC structure. Finally, we study the relaxation dynamics of the system by means of the density and temperature dependences of the diffusion coefficient. We show that there exists a density range where the system passes reversibly from a gel to a fluid upon both heating and cooling, encountering neither demixing nor phase separation.

  16. Sol-gel based sensor for selective formaldehyde determination.

    PubMed

    Bunkoed, Opas; Davis, Frank; Kanatharana, Proespichaya; Thavarungkul, Panote; Higson, Séamus P J

    2010-02-01

    We report the development of transparent sol-gels with entrapped sensitive and selective reagents for the detection of formaldehyde. The sampling method is based on the adsorption of formaldehyde from the air and reaction with beta-diketones (for example acetylacetone) in a sol-gel matrix to produce a yellow product, lutidine, which was detected directly. The proposed method does not require preparation of samples prior to analysis and allows both screening by visual detection and quantitative measurement by simple spectrophotometry. The detection limit of 0.03 ppmv formaldehyde is reported which is lower than the maximum exposure concentrations recommended by both the World Health Organisation (WHO) and the Occupational Safety and Health Administration (OSHA). This sampling method was found to give good reproducibility, the relative standard deviation at 0.2 and 1 ppmv being 6.3% and 4.6%, respectively. Other carbonyl compounds i.e. acetaldehyde, benzaldehyde, acetone and butanone do not interfere with this analytical approach. Results are provided for the determination of formaldehyde in indoor air. PMID:20103132

  17. Dynamics of Swollen Gel Layers Anchored to Solid Surfaces

    NASA Astrophysics Data System (ADS)

    Fytas, George; Gianneli, Maria; Roskamp, Robert; Jonas, Ulrich; Koynov, Kaloian; Knoll, Wolfgang; Loppinet, Benoit

    2008-03-01

    Thin responsive hydrogel films are currently under development for biosensor applications. Photocrosslinkable poly(N-isopropylacrylamide) (PNIPAAm) based chains are spin coated as thin films (about 1 micron) and UV irradiated with variable doses to control the crosslink density. The obtained anchored gel layers can swell in ethanol or water up to about 10 microns for low crosslinking densities. Dynamics of the swollen layers and diffusion of different tracers (as analyte mimicks) are studied by dynamic light scattering (PCS) and fluorescence correlation spectroscopy (FCS). PCS resolved fast and slow diffusions, attributed to cooperative diffusion and long range concentration heterogeneities. Higher crosslink densities give rise to faster cooperative diffusion, i.e. short dynamic mesh sizes. FCS revealed the importance of electrostatic interactions between probe and negatively charged network. While a negatively charged dye senses local dynamics with a moderate slow down, a positively charged dye exhibited substantially retarded diffusion. Larger tracers are used to assess the size dependent gel penetrability, whereas large particles, trapped into the network, expectedly follow the network dynamics.

  18. 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)

  19. 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)

  20. 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…

  1. Microsoft Analytics Platform System

    E-print Network

    Chaudhuri, Surajit

    | Solution Brief Contents 4 Introduction 4 Microsoft Analytics Platform System 5 Enterprise-ready Big Data 7;Microsoft Analytics Platform System | Solution Brief 4 For decades, the data warehouse has been accessibility to keep up with enterprise demand in this world of Big Data. Microsoft is ready to help

  2. 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.

  3. 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…

  4. Validating Analytical Methods

    ERIC Educational Resources Information Center

    Ember, Lois R.

    1977-01-01

    The procedures utilized by the Association of Official Analytical Chemists (AOAC) to develop, evaluate, and validate analytical methods for the analysis of chemical pollutants are detailed. Methods validated by AOAC are used by the EPA and FDA in their enforcement programs and are granted preferential treatment by the courts. (BT)

  5. Cell motility: a viscous fingering analysis of active gels

    E-print Network

    M. Ben Amar; O. V. Manyuhina; G. Napoli

    2011-02-08

    The symmetry breaking of the actin network from radial to longitudinal symmetry has been identified as the major mechanism for keratocytes (fish cells) motility on solid substrate. For strong friction coefficient, the two dimensional actin flow which includes the polymerisation at the edge and depolymerisation in the bulk can be modelled as a Darcy flow, the cell shape and dynamics being then modelled by standard complex analysis methods. We use the theory of active gels to describe the orientational order of the filaments which varies from the border to the bulk. We show analytically that the reorganisation of the cortex is enough to explain the motility of the cell and find the velocity as a function of the orientation order parameter in the bulk.

  6. Manual control of catalytic reactions: Reactions by an apoenzyme gel and a cofactor gel

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    Enzymes play a vital role in catalysing almost all chemical reactions that occur in biological systems. Some enzymes must form complexes with non-protein molecules called cofactors to express catalytic activities. Although the control of catalytic reactions via apoenzyme–cofactor complexes has attracted significant attention, the reports have been limited to the microscale. Here, we report a system to express catalytic activity by adhesion of an apoenzyme gel and a cofactor gel. The apoenzyme and cofactor gels act as catalysts when they form a gel assembly, but they lose catalytic ability upon manual dissociation. We successfully construct a system with switchable catalytic activity via adhesion and separation of the apoenzyme gel with the cofactor gel. We expect that this methodology can be applied to regulate the functional activities of enzymes that bear cofactors in their active sites, such as the oxygen transport of haemoglobin or myoglobin and the electron transport of cytochromes.

  7. Manual control of catalytic reactions: Reactions by an apoenzyme gel and a cofactor gel

    PubMed Central

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

    2015-01-01

    Enzymes play a vital role in catalysing almost all chemical reactions that occur in biological systems. Some enzymes must form complexes with non-protein molecules called cofactors to express catalytic activities. Although the control of catalytic reactions via apoenzyme–cofactor complexes has attracted significant attention, the reports have been limited to the microscale. Here, we report a system to express catalytic activity by adhesion of an apoenzyme gel and a cofactor gel. The apoenzyme and cofactor gels act as catalysts when they form a gel assembly, but they lose catalytic ability upon manual dissociation. We successfully construct a system with switchable catalytic activity via adhesion and separation of the apoenzyme gel with the cofactor gel. We expect that this methodology can be applied to regulate the functional activities of enzymes that bear cofactors in their active sites, such as the oxygen transport of haemoglobin or myoglobin and the electron transport of cytochromes. PMID:26537172

  8. 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.

  9. 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.

  10. 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].

  11. 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.

  12. 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....

  13. 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.

  14. 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

  15. Gel pad application for automated breast sonography.

    PubMed

    Kim, Yun Ju; Kim, Sung Hun; Jeh, Su Kyung; Choi, Jae Jeong; Kang, Bong Joo; Song, Byung Joo

    2015-04-01

    The purpose of this study was to describe the technical aspects of gel pad application for automated breast sonography and to show its effects on pain relief, scan coverage, and image quality. Twenty patients underwent 2 sets of automated breast sonography with and without gel pad application and were then asked to provide feedback on the examination-related pain. Scan coverage and image quality were compared quantitatively and qualitatively. The degree of pain was significantly decreased after gel pad application (P < .0001). The scan coverage was expanded particularly at the mid-portion of the breast. Image quality was satisfactory without significant differences between the sets. Gel pad application for automated breast sonography is easy and provides significant pain relief. The scan coverage was expanded, while the image quality was maintained. PMID:25792588

  16. 2-DE Gel Analysis: The Spot Detection.

    PubMed

    Martinotti, Simona; Ranzato, Elia

    2016-01-01

    The abundance of different proteins on a 2-DE gel is reflected by the shape, size, and intensity of the corresponding spots. Protein quantitation requires the conversion of an analog gel image into digital data, resulting into a catalog of individual spots listed as x, y positions, shape parameters, and quantitative values. So, it is possible to carry out objective comparisons of equivalent spots on different gels, determining whether a particular protein is more or less abundant in one sample compared with another.Unfortunately, spots on protein gels are not uniform in shape, size, or density, and detection, quantitation, and comparison can be challenging without intervention.Once a processed image is available, a number of different algorithms can be applied to detect and quantitate individual spots. PMID:26611414

  17. Buckling of paramagnetic chains in soft gels.

    PubMed

    Huang, Shilin; Pessot, Giorgio; Cremer, Peet; Weeber, Rudolf; Holm, Christian; Nowak, Johannes; Odenbach, Stefan; Menzel, Andreas M; Auernhammer, Günter K

    2015-12-16

    We study the magneto-elastic coupling behavior of paramagnetic chains in soft polymer gels exposed to external magnetic fields. To this end, a laser scanning confocal microscope is used to observe the morphology of the paramagnetic chains together with the deformation field of the surrounding gel network. The paramagnetic chains in soft polymer gels show rich morphological shape changes under oblique magnetic fields, in particular a pronounced buckling deformation. The details of the resulting morphological shapes depend on the length of the chain, the strength of the external magnetic field, and the modulus of the gel. Based on the observation that the magnetic chains are strongly coupled to the surrounding polymer network, a simplified model is developed to describe their buckling behavior. A coarse-grained molecular dynamics simulation model featuring an increased matrix stiffness on the surfaces of the particles leads to morphologies in agreement with the experimentally observed buckling effects. PMID:26463270

  18. Fluorography of polyacrylamide gels containing tritium.

    PubMed

    Waterborg, J H; Matthews, H R

    1984-01-01

    Fluorography is the term used for the process of determining radioactivity in gels and other media by a combination of fluorescence and photography. Since most of the radiation of a low energy emitter will largely be absorbed by the gel, in the technique of fluorography a fluor (e.g., PPO) is infiltrated into the gel where it can absorb the radiation and re-emit light that will pass through the gel to the film. The resulting photographic image is analogous to an autoradiograph, but for a low energy beta-emitting isotope like (3)H, the sensitivity of fluorography is many times the sensitivity of autoradiography. The fluorograph may be used directly, as a qualitative picture of the radioactivity on the gel. It may also be used to locate radioactive bands or spots that can then be cut from the original gel for further analysis, or be scanned to give quantitative information about the distribution of radioactivity. Figure 1 shows an example of a gel that was stained with Coomassie blue and then fluorographed. Notice that there is no loss of resolution in the fluorography of thin gels of normal size. Fig. 1. This shows two examples of fluorography of protein bands labeled with (3)H. Basic nuclear proteins were isolated from the slime mold, Physarum polycephalum, pulse-labeled with (3)H-acetate in either S phase or G(2) phase of the naturally synchronous cell cycle. The proteins were analyzed by acrylamide gel electrophoresis in acetic acid, urea, and Triton X-100. After electrophoresis, the gel was stained with Coomassie blue, photographed, and then fluorographed. Individual lanes of the gel image were cut from the photograph (negative) and the fluorograph and then printed side-by-side to give the figure shown. Notice that the stain patterns of the two lanes are practically identical, except for the loading, while the radioactivity patterns show major differences, for example, the absence of label in his-tones H2A and H2B in G2 phase (4). PMID:20512684

  19. The fundamental radiation properties of normoxic polymer gel dosimeters: a comparison between a methacrylic acid based gel and acrylamide based gels

    NASA Astrophysics Data System (ADS)

    DeDeene, Y.; Vergote, K.; Claeys, C.; DeWagter, C.

    2006-02-01

    Polymer gel dosimeters offer a wide range of applications in the three-dimensional verification of complex dose distributions such as in intensity-modulated radiotherapy. One of the major difficulties with polymer gel dosimeters is their sensitivity to oxygen, as oxygen inhibits the radiation-induced polymerization reaction. For several years, oxygen was removed from the gels by bubbling the sol with inert gases for several hours during the gel fabrication. Also, the gel had to be poured in containers with low oxygen permeability and solubility. Recently, it was found that these technical difficulties can easily be solved by adding an antioxidant to the gel. These gels are called 'normoxic' gels as they can be produced under normal atmospheric conditions. In this study several properties of polymer gel dosimeters have been investigated: the dose sensitivity, the temporal and spatial stability of the gel, the sensitivity of the dose response to temperature during irradiation and during MR imaging, the energy dependence and the dose-rate dependence. This study reveals that the normoxic polymer gel dosimeter based on methacrylic acid (nMAG) studied in this work has inferior radiation properties as compared to the polyacrylamide gelatine (PAG) gel dosimeters. It is shown that from the three different gel dosimeters investigated in this study, the nPAG gel dosimeter results in a less sensitive gel dosimeter but with superior radiation properties as compared to the nMAG gel dosimeter. The importance of investigating relevant radiation properties of gel dosimeters apart from the radiation sensitivity—prior to their use for dosimetric validation experiments—is illustrated and emphasized throughout this study. Other combinations of monomer and gelling agent may result in more reliable normoxic polymer gel dosimeters.

  20. A Practical Use for FXG Gel Dosimetry

    NASA Astrophysics Data System (ADS)

    Olding, T.; Salomons, G.; Darko, J.; Schreiner, L. J.

    2010-11-01

    In-phantom Fricke-xylenol orange-gelatin (FXG) gel dosimetry yields three dimensional (3D) dose data for intensity modulated radiation therapy (IMRT) treatment plan verification within 18-24 hours from the point of request. The information obtained from a 3% dose difference, 3 mm distance-to-agreement gamma function comparison between treatment plan dose and gel-measured dose then provides a useful secondary 3D quality assurance check of the treatment plan prior to delivery.

  1. Tissue-Simulating Gel For Medical Research

    NASA Technical Reports Server (NTRS)

    Companion, John A.

    1992-01-01

    Nonhardening, translucent gel more nearly simulates soft human or animal tissue. Modified to be softer or harder by altering proportions of ingredients. Fillers added to change electrical, mechanical, heat-conducting, or sound-conducting/scattering properties. Molded to any desired shape and has sufficient mechanical strength to maintain shape without supporting shell. Because of its thermal stability, gel especially useful for investigation of hyperthermia as treatment for cancer.

  2. Spontaneous flow transition in active polar gels

    E-print Network

    R. Voituriez; J-F Joanny; J. Prost

    2005-03-16

    We study theoretically the effects of confinement on active polar gels such as the actin network of eukaryotic cells. Using generalized hydrodynamics equations derived for active gels, we predict, in the case of quasi one-dimensional geometry, a spontaneous flow transition from a homogeneously polarized immobile state for small thicknesses, to a perturbed flowing state for larger thicknesses. The transition is not driven by an external field but by the activity of the system. We suggest several possible experimental realizations.

  3. Natural gels in the Yucca Mountain Area, Nevada, USA

    SciTech Connect

    Levy, S.S.

    1991-12-31

    Relict gels at Yucca Mountain include pore- and fracture-fillings of silica and zeolite related to diagenetic and hydrothermal alteration of vitric tuffs. Water-rich free gels in fractures at Rainier Mesa consist of smectite with or without silica-rich gel fragments. Gels are being studied for their potential role in transport of radionuclides from a nuclear-waste repository.

  4. Basic investigations on LCV micelle gel

    NASA Astrophysics Data System (ADS)

    Ebenezer, S. B.; Rafic, M. K.; Ravindran, P. B.

    2013-06-01

    The aim of this study was to investigate the feasibility of using Leuco Crystal Violet (LCV) based micelle gel dosimeter as a quality assurance tool in radiotherapy applications. Basic properties such as absorption coefficient and diffusion of LCV gel phantom over time were evaluated. The gel formulation consisted of 25 mM Trichloroacetic acid, 1mM LCV, 4 mM Triton X-100, 4% gelatin by mass and distilled water. The advantages of using this gel are its tissue equivalence, easy and less preparation time, lower diffusion rate and it can be read with an optical scanner. We were able to reproduce some of the results of Babic et al. The peak absorption was found to be at 600 nm and hence a matrix of yellow LEDs was used as light source. The profiles obtained from projection images confirmed the diffusion of LCV gel after 6 hours of irradiation. Hence the LCV gel phantom should be read before 6 hours post irradiation to get accurate dose information as suggested previously.

  5. 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.

  6. Gels de poly(octylthiophène) : cristallisation

    NASA Astrophysics Data System (ADS)

    Pépin-Donat, B.; Sixou, B.; de Geyer, A.; Viallat, A.; Fah. Hin, L. Won

    1998-06-01

    The study of conjugated poly(octylthiophene) gels by x-ray diffraction and differential calorimetry shows that these networks are semi-crystalline. State of crystallinity, transport properties and large scale heterogeneity seem to be correlated. The determination of this correlation requires a detailed study of the mechanisms of crystallization of these polymer gels, the first results of which are reported here. They show that crystallinity ratios and crystallization rates can be determined by NMR and, as expected, strongly depend on the gels thermodynamic history. L'étude de gels conjugués de poly(octylthiophène) par diffraction des rayons X et par calorimétrie différentielle montre que ces réseaux sont semi-cristallins. Etat de cristallinité, propriétés de transport et état d'hétérogénéité à grande échelle semblent être corrélés. La détermination de cette corrélation nécessite une étude approfondie des mécanismes de cristallisation de ces gels polymères dont les premiers résultats sont reportés ici. Ils montrent que taux de cristallinité et vitesses de cristallisation peuvent être déterminés par RMN et, comme attendu, dépendent fortement de l'histoire thermodynamique des gels.

  7. Swelling instabilities in patterned, microscale gels

    NASA Astrophysics Data System (ADS)

    Toomey, Ryan; Dupont, Samuel

    2012-02-01

    Hydrogels facilitate reconfigurable structures with response integrated at the material level. Response is engendered by a competing mechanism: the elasticity of the network ounterbalances expansion by the solvent. If the strength of expansion can be controlled by an environmental cue, the hydrogel can be adjusted in situ. The equilibrium state occurs when the osmotic stress exerted by the solvent in the gel equals the osmotic pressure of the solvent outside the gel. For a free structure, the equilibrium state corresponds to homogenous swelling. If a free surface of the gel is mechanically constrained, however, the dimensions available for the relief of the osmotic stress are reduced, resulting in non-uniform or inhomogeneous swelling. In this study, we demonstrate how mechanical constraints impose differential gel swelling and buckling in patterned gels. Depending on the initial geometry of the constrained gel, three general modes of swelling-induced deformation can be observed: lateral differential swelling, bulk sinusoidal buckling, and surface wrinkling. Through confocal microscopy and 3D image rendering, the mechanics of swelling has been evaluated in the context of linear elasticity theory.

  8. 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.

  9. 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

  10. Uncertainty in 3D gel dosimetry

    NASA Astrophysics Data System (ADS)

    De Deene, Yves; Jirasek, Andrew

    2015-01-01

    Three-dimensional (3D) gel dosimetry has a unique role to play in safeguarding conformal radiotherapy treatments as the technique can cover the full treatment chain and provides the radiation oncologist with the integrated dose distribution in 3D. It can also be applied to benchmark new treatment strategies such as image guided and tracking radiotherapy techniques. A major obstacle that has hindered the wider dissemination of gel dosimetry in radiotherapy centres is a lack of confidence in the reliability of the measured dose distribution. Uncertainties in 3D dosimeters are attributed to both dosimeter properties and scanning performance. In polymer gel dosimetry with MRI readout, discrepancies in dose response of large polymer gel dosimeters versus small calibration phantoms have been reported which can lead to significant inaccuracies in the dose maps. The sources of error in polymer gel dosimetry with MRI readout are well understood and it has been demonstrated that with a carefully designed scanning protocol, the overall uncertainty in absolute dose that can currently be obtained falls within 5% on an individual voxel basis, for a minimum voxel size of 5 mm3. However, several research groups have chosen to use polymer gel dosimetry in a relative manner by normalizing the dose distribution towards an internal reference dose within the gel dosimeter phantom. 3D dosimetry with optical scanning has also been mostly applied in a relative way, although in principle absolute calibration is possible. As the optical absorption in 3D dosimeters is less dependent on temperature it can be expected that the achievable accuracy is higher with optical CT. The precision in optical scanning of 3D dosimeters depends to a large extend on the performance of the detector. 3D dosimetry with X-ray CT readout is a low contrast imaging modality for polymer gel dosimetry. Sources of error in x-ray CT polymer gel dosimetry (XCT) are currently under investigation and include inherent limitations in dosimeter homogeneity, imaging performance, and errors induced through post-acquisition processing. This overview highlights a number of aspects relating to uncertainties in polymer gel dosimetry.

  11. Analytical Chemistry Applied Mathematics

    E-print Network

    Heller, Barbara

    Geoenvironmental Engineering Geotechnical Engineering Health Physics Industrial Technology & Operations Information Science Manufacturing Engineering Materials Chemistry Materials Science & Engineering Mathematical FinanceAnalytical Chemistry Applied Mathematics Architectural Engineering Architecture Architecture

  12. Extreme Scale Visual Analytics

    SciTech Connect

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

    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.

  13. Hydrodynamic examination of the dimeric cytoplasmic domain of the human erythrocyte anion transporter, band 3.

    PubMed Central

    Cölfen, H; Harding, S E; Boulter, J M; Watts, A

    1996-01-01

    Solution studies of the cytoplasmic domain (molecular mass approximately 40kDa) of band 3, the anion exchanger from human erythrocyte membranes, previously suggested a dimeric molecule on the basis of the relative techniques of calibrated gel filtration and calibrated preparative ultracentrifugation. This dimeric behavior is firmly established on an absolute basis by a combination of calibrated gel chromatography and absolute ultracentrifugation techniques. Sedimentation velocity in the analytical ultracentrifuge combined with calibrated gel chromatography give a molecular mass M of (77 +/- 4) kDa, a value confirmed by low-speed sedimentation equilibrium. Velocity sedimentation in the analytical ultracentrifuge gave a single sedimenting species with an s o 20,w of (3.74 +/- 0.07)S. Sedimentation equilibrium analysis was also used to establish the strength of the binding via the dissociation constant Kd, with a value from direct fitting of the concentration distribution curves of (2.8 +/- 0.5) microM, confirmed by a value of approximately 3 microM obtained from fitting a plot of molecular weight Mw,app versus cell loading concentration. Hydrodynamic calculations based on the classical translational frictional ratio showed that the protein was highly asymmetric, with an axial ratio of approximately 10:1, consistent with observations from electron microscopy. PMID:8874035

  14. Recycling of superfine resolution agarose gel.

    PubMed

    Seng, T-Y; Singh, R; Faridah, Q Z; Tan, S-G; Alwee, S S R S

    2013-01-01

    Genetic markers are now routinely used in a wide range of applications, from forensic DNA analysis to marker-assisted plant and animal breeding. The usual practice in such work is to extract the DNA, prime the markers of interest, and sift them out by electrically driving them through an appropriate matrix, usually a gel. The gels, made from polyacrylamide or agarose, are of high cost, limiting their greater applications in molecular marker work, especially in developing countries where such technology has great potential. Trials using superfine resolution (SFR) agarose for SSR marker screening showed that it is capable of resolving SSR loci and can be reused up to 14 times, thus greatly reducing the cost of each gel run. Furthermore, for certain applications, low concentrations of agarose sufficed and switching to lithium borate buffer, instead of the conventional Tris-borate-ethylenediaminetetraacetic acid buffer, will further save time and cost. The 2.5% gel was prepared following the Agarose SFR(TM) manual by adding 2.5 g agarose powder into 100 mL 1X lithium borate buffer in a 250-mL flask with rapid stirring. Two midigels (105 x 83 mm, 17 wells) or 4 minigels (50 x 83 mm, 8 wells), 4 mm thickness can be prepared from 100 mL gel solution. A total of 1680 PCR products amplified using 140 SSR markers from oil palm DNA samples were tested in this study using SFR recycled gel. As average, the gel can be recycled 8 times with good resolution, but can be recycled up to 14 times before the resolutions get blurred. PMID:23546970

  15. Mechanical stability of fractal colloidal gels

    NASA Astrophysics Data System (ADS)

    Manley, Suliana

    Colloidal particles with attraction diffuse and stick to form highly disordered aggregates whose structures are well-described as mass fractals. Thus, even at low particle volume fractions, ?, aggregates grow to fill space and form an elastic network. In this study, we focus on understanding the mechanical properties of colloid gels. In the process, we explore the limits to gelation and gel stability. In Chapter 2, we discuss the limits to gelation at low-?. We show that the dynamics of large fractal colloid aggregates are well described by a combination of translational and rotational diffusion and internal elastic fluctuations, allowing both the aggregate size and internal elasticity to be determined by dynamic light scattering. We find that gravitational stress limits the cluster growth on earth, even under near buoyancy-matched conditions, whereas thermal fluctuations limit the growth of fractal structures in the absence of gravity. In Chapter 3, we study the mechanical properties of gels formed from strongly aggregating silica colloids. Surprisingly, we find that their elastic moduli, G', continue to increase long after network formation, leading to an increase in elasticity of several orders of magnitude over a few hours. We present a model based on the sintering of the particles which accounts for the observed time dependence. In Chapter 4, we examine the collapse of silica colloidal gels; this occurs when the gravitational stress exerted on the lower part of a sample is greater than its yield stress. We show that the collapse dynamics are related to the rheological properties of the gel as it yields. In Chapter 5, we study the effects of surfactant concentration on a model concentrated emulsion. Surfactant concentration helps to set droplet sizes; thus, it plays an important role in determining the mechanical properties and stability of these kinds of gels. Gel networks are generally out-of-equilibrium systems; similar to glasses, they undergo aging. In Chapter 6, we discuss preliminary work on aging as it depends on attraction and ?.

  16. SRL online Analytical Development

    SciTech Connect

    Jenkins, C.W.

    1991-12-31

    The Savannah River Site is operated by the Westinghouse Savannah River Co. for the Department of Energy to produce special nuclear materials for defense. R&D support for site programs is provided by the Savannah River Laboratory, which I represent. The site is known primarily for its nuclear reactors, but actually three fourths of the efforts at the site are devoted to fuel/target fabrication, fuel/target reprocessing, and waste management. All of these operations rely heavily on chemical processes. The site is therefore a large chemical plant. There are then many potential applications for process analytical chemistry at SRS. The Savannah River Laboratory (SRL) has an Analytical Development Section of roughly 65 personnel that perform analyses for R&D efforts at the lab, act as backup to the site Analytical Laboratories Department and develop analytical methods and instruments. I manage a subgroup of the Analytical Development Section called the Process Control & Analyzer Development Group. The Prime mission of this group is to develop online/at-line analytical systems for site applications.

  17. SRL online Analytical Development

    SciTech Connect

    Jenkins, C.W.

    1991-01-01

    The Savannah River Site is operated by the Westinghouse Savannah River Co. for the Department of Energy to produce special nuclear materials for defense. R D support for site programs is provided by the Savannah River Laboratory, which I represent. The site is known primarily for its nuclear reactors, but actually three fourths of the efforts at the site are devoted to fuel/target fabrication, fuel/target reprocessing, and waste management. All of these operations rely heavily on chemical processes. The site is therefore a large chemical plant. There are then many potential applications for process analytical chemistry at SRS. The Savannah River Laboratory (SRL) has an Analytical Development Section of roughly 65 personnel that perform analyses for R D efforts at the lab, act as backup to the site Analytical Laboratories Department and develop analytical methods and instruments. I manage a subgroup of the Analytical Development Section called the Process Control Analyzer Development Group. The Prime mission of this group is to develop online/at-line analytical systems for site applications.

  18. Evolution of gel structure during thermal processing of Na-geopolymer gels.

    PubMed

    Duxson, Peter; Lukey, Grant C; van Deventer, Jannie S J

    2006-10-10

    The present work examines how the gel structure and phase composition of Na-geopolymers derived from metakaolin with varied Si/Al ratio evolve with exposure to temperatures up to 1000 degrees C. Gels were thermally treated and characterized using quantitative XRD, DTA, and FTIR to elucidate the changes in gel structure, phase composition, and porosity at each stage of heating. It is found that the phase stability, defined by the amount and onset temperature of crystallization, is improved at higher Si/Al ratios. Two different mechanisms of densification have been isolated by FTIR, related to viscous flow and collapse of the highly distributed pore network in the gel. Gels with low Si/Al ratio only experience viscous flow that correlates with low thermal shrinkage. Gels at a higher Si/Al ratio, which have a homogeneous microstructure composed of a highly distributed porosity, undergo both densification processes corresponding to a large extent of thermal shrinkage during densification. This work elucidates the intimate relationship between gel microstructure, chemistry, and thermal evolution of Na-geopolymer gels. PMID:17014113

  19. Denaturing Urea PAGE -Small Gel 1. Prepare denaturing polyacrylamide gel solution. Use Gibco/BRL apparatus.

    E-print Network

    Aris, John P.

    31 Denaturing Urea PAGE - Small Gel 1. Prepare denaturing polyacrylamide gel solution. Use Gibco denatures nucleic acids. 4. Denature samples. To RNA, add an equal volume of sample buffer (100 µl formamide water in bath). Chill on ice. Spin briefly. Thaw frozen RNA samples just before denaturation and loading

  20. 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.

  1. Structural Properties of Silk Electro-Gels

    NASA Astrophysics Data System (ADS)

    Tabatabai, A. P.; Urbach, J. S.; Blair, D. L.; Kaplan, D. L.

    2013-03-01

    The interest in Bombyx Mori silk emerges from its biocompatibility and its structural superiority to synthetic polymers. Our particular interest lies in understanding the capabilities of silk electro-gels because of their reversibility and tunable adhesion. We create an electro-gel by applying a DC electric potential across a reconstituted silk fibroin solution derived directly from Bombyx Mori cocoons. This process leads to the intermolecular self-assembly of fibroin proteins into a weak gel. In this talk we will present our results on the effects of applied shear on electro-gels. We quantify the structural properties while dynamically imaging shear induced fiber formation; known as fibrillogenesis. It is observed that the mechanical properties and microstructure of these materials are highly dependent on shear history. We will also discuss the role of surface modification, through micro-patterning, on the observed gel structure. Our results provide an understanding of both the viscoelastiticity and microstucture of reconstituted silks that are being utilized as tissue scaffolds. This work is supported by a grant from the AFOSR FA9550-07-1-0130.

  2. Long time response of soft magnetorheological gels.

    PubMed

    An, Hai-Ning; Sun, Bin; Picken, Stephen J; Mendes, Eduardo

    2012-04-19

    Swollen physical magnetorheological (MR) gels were obtained by self-assembling of triblock copolymers containing dispersed soft magnetic particles. The transient rheological responses of these systems were investigated experimentally. Upon sudden application of a homogeneous magnetic field step change, the storage modulus of MR gels continued to increase with time. Such increase trend of the storage modulus could be expressed by a double-exponential function with two distinct modes, a fast and a slow one. The result was compared with the transient rheological response of equivalent MR fluids (paraffin oil without copolymer) and a MR elastomer (PDMS) and interpreted as the consequence of strong rearrangement of the original particle network under magnetic field. Similar to the structure evolution of MR fluids, the ensemble of results suggests that "chaining" and "clustering" processes are also happening inside the gel and are responsible for the rheological behavior, provided they are happening on a smaller length scale (long chains and clusters are hindered). We show that response times of several minutes are typical for the slow response of MR gels. The characteristic time t(2) for the slow process is significantly dependent on the magnetic flux density, the matrix viscoelastic property, particle volume fraction, and sample's initial particle distribution. In order to validate our results, the role of dynamic strain history was clarified. We show that, in the linear viscoelastic region, the particle rearrangement of MR gels was not hindered or accelerated by the dynamic strain history. PMID:22439870

  3. 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

  4. A Sol-Gel-Modified Poly(methyl methacrylate) Electrophoresis Microchip with a Hydrophilic Channel Wall

    SciTech Connect

    Chen, Gang; Xu, Xuejiao; Lin, Yuehe; Wang, Joseph

    2007-07-27

    A sol-gel method was employed to fabricate a poly(methyl methacrylate) (PMMA) electrophoresis microchip that contains a hydrophilic channel wall. To fabricate such a device, tetraethoxysilane (TEOS) was injected into the PMMA channel and was allowed to diffuse into the surface layer for 24 h. After removing the excess TEOS, the channel was filled with an acidic solution for 3 h. Subsequently, the channel was flushed with water and was pretreated in an oven to obtain a sol-gel-modified PMMA microchip. The water contact angle for the sol-gel-modified PMMA was 27.4° compared with 66.3° for the pure PMMA. In addition, the electro-osmotic flow increased from 2.13×10-4 cm2 V-1 s-1 for the native-PMMA channel to 4.86×10-4 cm2 V-1 s-1 for the modified one. The analytical performance of the sol-gel-modified PMMA microchip was demonstrated for the electrophoretic separation of several purines, coupled with amperometric detection. The separation efficiency of uric acid increased to 74 882.3 m-1 compared with 14 730.5 m-1 for native-PMMA microchips. The result of this simple modification is a significant improvement in the performance of PMMA for microchip electrophoresis and microfluidic applications.

  5. Gel-Filled Holders For Ultrasonic Transducers

    NASA Technical Reports Server (NTRS)

    Companion, John A.

    1992-01-01

    In new technique, ultrasonic transducer embedded in rubbery, castable, low-loss gel to enable transducer to "look" into surface of test object or human body at any desired angle. Composed of solution of water and ethylene glycol in collagen matrix. Provides total contact of water bath, also used on bodies or objects too large for water baths, even if moving. Also provides look angles of poly(methyl methacrylate) angle block with potential of reduced acoustic impedance and refraction. Custom-tailored to task at hand, and gel sufficiently inexpensive to be discarded upon completion. Easy to couple ultrasound in and out of gel, minimizing losses and artifacts of other types of standoffs employed in ultrasonic testing.

  6. Preparation and characterization of hydrophobic superparamagnetic gel.

    SciTech Connect

    Liu, X.; Kaminski, M. D.; Guan, Y.; Chen, H.; Liu, H.; Rosengart, A. J.; Chemical Engineering; Univ. of Chicago; Pritzker School of Medicine; Chinese Academy of Sciences

    2006-01-01

    The present study describes the preparation and analysis of a highly concentrated hydrophobic oleic acid-coated magnetite gel. By contrast to conventional techniques to prepare magnetic fluids, herein the oleic acid was introduced as a reactant during the initial crystallization phase of magnetite that was obtained by the co-precipitation of Fe(II) and Fe(III) salts by addition of ammonium hydroxide. The resulting gelatinous hydrophobic magnetite was characterized in terms of morphology, particle size, magnetic properties, crystal structure, and hydrophobicity/hydrophilicity. This magnetic gel exhibited superparamagnetism with a saturation magnetization of 46.0 emu/g at room temperature and could be well dispersed both in polar and nonpolar carrier liquids. This protocol produced highly concentrated hydrophobic magnetic gel for biopolymer encapsulations.

  7. Writing in the granular gel medium

    PubMed Central

    Bhattacharjee, Tapomoy; Zehnder, Steven M.; Rowe, Kyle G.; Jain, Suhani; Nixon, Ryan M.; Sawyer, W. Gregory; Angelini, Thomas E.

    2015-01-01

    Gels made from soft microscale particles smoothly transition between the fluid and solid states, making them an ideal medium in which to create macroscopic structures with microscopic precision. While tracing out spatial paths with an injection tip, the granular gel fluidizes at the point of injection and then rapidly solidifies, trapping injected material in place. This physical approach to creating three-dimensional (3D) structures negates the effects of surface tension, gravity, and particle diffusion, allowing a limitless breadth of materials to be written. With this method, we used silicones, hydrogels, colloids, and living cells to create complex large aspect ratio 3D objects, thin closed shells, and hierarchically branched tubular networks. We crosslinked polymeric materials and removed them from the granular gel, whereas uncrosslinked particulate systems were left supported within the medium for long times. This approach can be immediately used in diverse areas, contributing to tissue engineering, flexible electronics, particle engineering, smart materials, and encapsulation technologies. PMID:26601274

  8. Nail damage from gel polish manicure.

    PubMed

    Chen, Andrea F; Chimento, Stacy M; Hu, Shasa; Sanchez, Margaret; Zaiac, Martin; Tosti, Antonella

    2012-03-01

    Manicures can result in nail damage via instrumentation, nail polish, nail polish removers, and artificial nails. We report nail weakness, brittleness, and thinning in five subjects after the application of a new manicure system called gel polish and removal with acetone and manual peeling. All subjects complained that the polish was very difficult to remove and that their nails became much thinner after the procedure. Pseudoleukonychia and onychoschizia lamellina were noted on examination. One subject underwent ultrasound and reflectance confocal microscopy (RCM) measurements of nail plate before and after the gel polish application, which showed thinned nail plate (0.063 vs. 0.050 cm and 0.059 vs. 0.030 cm, respectively). Overall, we call attention to the adverse effects of gel polish manicures in five subjects. In addition, our case illustrates potential utility of ultrasound and RCM in measuring nail plate thickness. PMID:22360331

  9. Kinetics of water flow through polymer gel

    E-print Network

    Yasuo Y. Suzuki; Masayuki Tokita; Sata-atsu Mukai

    2008-11-13

    The water flow through the poly(acrylamide) gel under a constant water pressure is measured by newly designed apparatus. The time evolution of the water flow in the gel, is calculated based on the collective diffusion model of the polymer network coupled with the friction between the polymer network and the water. The friction coefficient are determined from the equilibrium velocity of water flow. The Young modulus and the Poisson's ratio of the rod shape gels are measured by the uni-axial elongation experiments, which determine the longitudinal modulus independently from the water flow experiments. With the values of the longitudinal modulus and of the friction determined by the experiments, the calculated results are compared with the time evolution of the flow experiments. We find that the time evolution of the water flow is well described by a single characteristic relaxation time predicted by the collective diffusion model coupled with the water friction.

  10. Low-Reynolds number swimming in gels

    E-print Network

    Henry C. Fu; Vivek B. Shenoy; Thomas R. Powers

    2010-04-08

    Many microorganisms swim through gels, materials with nonzero zero-frequency elastic shear modulus, such as mucus. Biological gels are typically heterogeneous, containing both a structural scaffold (network) and a fluid solvent. We analyze the swimming of an infinite sheet undergoing transverse traveling wave deformations in the "two-fluid" model of a gel, which treats the network and solvent as two coupled elastic and viscous continuum phases. We show that geometric nonlinearities must be incorporated to obtain physically meaningful results. We identify a transition between regimes where the network deforms to follow solvent flows and where the network is stationary. Swimming speeds can be enhanced relative to Newtonian fluids when the network is stationary. Compressibility effects can also enhance swimming velocities. Finally, microscopic details of sheet-network interactions influence the boundary conditions between the sheet and network. The nature of these boundary conditions significantly impacts swimming speeds.

  11. Effectiveness of Gel Repellents on Feral Pigeons

    PubMed Central

    Stock, Birte; Haag-Wackernagel, Daniel

    2013-01-01

    Simple Summary Feral pigeons live in close association in urban areas. They constitute serious health risks to humans and also lead to high economic loss due to costly damage to buildings, historic monuments, statues and even vegetation. While numerous avian repellent systems are regularly introduced onto the market, scientific proof of efficacy and their use from the point of view of animal welfare is lacking. Therefore, two avian gel repellents were studied on free-living feral pigeons in this study. The focus was set on repellent efficacy and animal welfare concerns. This study’s aim is to contribute to a better understanding of feral pigeon management in our cities. Abstract Millions of feral pigeons (Columba livia) live in close association with the human population in our cities. They pose serious health risks to humans and lead to high economic loss due to damage caused to buildings. Consequently, house owners and city authorities are not willing to allow pigeons on their buildings. While various avian repellents are regularly introduced onto the market, scientific proof of efficacy is lacking. This study aimed at testing the effectiveness of two avian gel repellents and additionally examined their application from animal welfare standpoint. The gels used an alleged tactile or visual aversion of the birds, reinforced by additional sensory cues. We mounted experimental shelves with the installed repellents in a pigeon loft and observed the behavior of free-living feral pigeons towards the systems. Both gels showed a restricted, transient repellent effect, but failed to prove the claimed complete effectiveness. Additionally, the gels’ adhesive effect remains doubtful in view of animal welfare because gluing of plumage presents a risk to feral pigeons and also to other non-target birds. This study infers that both gels lack the promised complete efficacy, conflict with animal welfare concerns and are therefore not suitable for feral pigeon management in urban areas. PMID:26479881

  12. Initial investigation of a novel light-scattering gel phantom for evaluation of optical CT scanners for radiotherapy gel dosimetry

    NASA Astrophysics Data System (ADS)

    Bosi, Stephen; Naseri, Pourandokht; Puran, Alicia; Davies, Justin; Baldock, Clive

    2007-05-01

    There is a need for stable gel materials for phantoms used to validate optical computerized tomography (CT) scanners used in conjunction with radiation-induced polymerizing gel dosimeters. Phantoms based on addition of light-absorbing dyes to gelatine to simulate gel dosimeters have been employed. However, to more accurately simulate polymerizing gels one requires phantoms that employ light-scattering colloidal suspensions added to the gel. In this paper, we present the initial results of using an optical CT scanner to evaluate a novel phantom in which radiation-exposed polymer gels are simulated by the addition of colloidal suspensions of varying turbidity. The phantom may be useful as a calibration transfer standard for polymer gel dosimeters. The tests reveal some phenomena peculiar to light-scattering gels that need to be taken into account when calibrating polymer gel dosimeters.

  13. 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.

  14. 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.

  15. 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.

  16. Aggregation-structure-elasticity relationship of gels

    NASA Astrophysics Data System (ADS)

    Ma, Hang-Shing

    Aerogel is a mesoporous, low-density material which is desirable for applications like thermal insulation and low-k interlayer dielectric. However, its lack of mechanical integrity hinders its development. Experiments have shown that aerogels exhibit a scaling relationship E ? rho m between modulus E and density rho, with the exponent m usually between 3 and 4. The objective of the dissertation is to use computer modeling to understand how the random aggregation process accounts for the fractal structure and the compliant nature of aerogels. Model gels were created by the diffusion-limited cluster-cluster aggregation (DLCA), which simulates random aggregation leading to the sol-gel transition. Then each resulting structure was modeled as an elastic beam network and numerically compressed using the finite element method (FEM). Analyses showed that the DLCA gels reproduced the scaling relationship after trimming the non-contributive dangling branches from the mechanically efficient looped networks. The dangling bond deflection (DEF) model was therefore developed to model the random rotational movement of the dangling branches and the subsequent loop structure formation. Model gels with extensive loops and negligible dangling branches were simulated by combining the DLCA and DEF models. Representation of the aerogel networks by the DLCADEF models was validated for the resemblance of the fractal geometry and elastic behavior. The lack of mechanical integrity in aerogels is a natural consequence of the random aggregation and the resulting fractal structure. Fractal clusters are created in the early stage of aggregation, each of which is characterized by a dense core and sparse perimeter. These clusters grow in size until they percolate at the gel point by knitting together at the perimeters. The gel structure possesses a "blob-and-link" architecture, with the blobs representing the rigid cores of the fractal clusters, and the links corresponding to the tenuous chains formed between the clusters at percolation. Finite element analysis illustrates that the strain energy always localizes at the links in the DLCADEF gels. Therefore the stiffness of an aerogel is reduced by the presence of these compliant links. The key to synthesizing stiffer gels is to homogenize the distribution and cross-linking of mass during the formation of the network.

  17. 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.

  18. 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.

  19. Free forming of the gel by 3D gel printer SWIM-ER

    NASA Astrophysics Data System (ADS)

    Okada, Koji; Tase, Taishi; Saito, Azusa; Makino, Masato; Gong, Jin; Kawakami, Masaru; Furukawa, Hidemitsu

    2015-04-01

    Gels, soft and wet materials, have unique properties such as material permeability, biocompatibility and low friction, which are hardly found in hard and dry materials. These superior characteristics of hydrogels promise to expand the medical applications. In recent years, the optical 3D gel printer named SWIM-ER (Soft and Wet Industrial - Easy Realizer) was developed by our team in order to fabricate tough gels with free form. We are aiming to create artificial blood vessel of the gel material by 3D gel printer. Artificial blood vessel is expected to be used for vascular surgery practice. The artificial blood vessel made by 3D gel printer can be create to free form on the basis of the biological data of the patient. Therefore, we believe it is possible to contribute to increasing the success rate and safety of vascular surgery by creating artificial blood vessel with 3D gel printer. The modeling method of SWIM-ER is as follow. Pregel solution is polymerized by one-point UV irradiation with optical fiber. The irradiation area is controlled by computer program, so that exact 3D free forming is realized. In this study, synthesis conditions are re-examined in order to improve the degree of freedom of fabrication. The dimensional accuracy in height direction is improved by increasing the cross linker concentration. We examined the relationship of resolution to the pitch and UV irradiation time in order to improve the modeling accuracy.

  20. Gel-expanded to gel-condensed transition in neurofilament networks revealed by direct force measurements

    NASA Astrophysics Data System (ADS)

    Beck, Roy; Deek, Joanna; Jones, Jayna B.; Safinya, Cyrus R.

    2010-01-01

    Neurofilaments (NF)-the principal cytoskeletal constituent of myelinated axons in vertebrates-consist of three molecular-weight subunit proteins NF-L (low), NF-M (medium) and NF-H (high), assembled to form mature filaments with protruding unstructured C-terminus side arms. Liquid-crystal gel networks of side-arm-mediated neurofilament assemblies have a key role in the mechanical stability of neuronal processes. Disruptions of the neurofilament network, owing to neurofilament over-accumulation or incorrect side-arm interactions, are a hallmark of motor-neuron diseases including amyotrophic lateral sclerosis. Using synchrotron X-ray scattering, we report on a direct measurement of forces in reconstituted neurofilament gels under osmotic pressure (P). With increasing pressure near physiological salt and average phosphorylation conditions, NF-LMH, comprising the three subunits near in vivo composition, or NF-LH gels, undergo for P>Pc~10kPa, an abrupt non-reversible gel-expanded to gel-condensed transition. The transition indicates side-arm-mediated attractions between neurofilaments consistent with an electrostatic model of interpenetrating chains. In contrast, NF-LM gels remain in a collapsed state for Pgel-condensed state at P>Pc. These findings, which delineate the distinct roles of NF-M and NF-H in regulating neurofilament interactions, shed light on possible mechanisms for disruptions of optimal mechanical network properties.

  1. 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

  2. Frontiers in analytical chemistry

    SciTech Connect

    Amato, I.

    1988-12-15

    Doing more with less was the modus operandi of R. Buckminster Fuller, the late science genius, and inventor of such things as the geodesic dome. In late September, chemists described their own version of this maxim--learning more chemistry from less material and in less time--in a symposium titled Frontiers in Analytical Chemistry at the 196th National Meeting of the American Chemical Society in Los Angeles. Symposium organizer Allen J. Bard of the University of Texas at Austin assembled six speakers, himself among them, to survey pretty widely different areas of analytical chemistry.

  3. 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.

  4. 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.

  5. Modeling the dynamics of a tracer particle in an elastic active gel

    E-print Network

    Isaac, E Ben; Visco, P; van Wijland, F; Gov, N S

    2015-01-01

    The internal dynamics of active gels, both in artificial (in-vitro) model systems and inside the cytoskeleton of living cells, has been extensively studied by experiments of recent years. These dynamics are probed using tracer particles embedded in the network of biopolymers together with molecular motors, and distinct non-thermal behavior is observed. We present a theoretical model of the dynamics of a trapped active particle, which allows us to quantify the deviations from equilibrium behavior, using both analytic and numerical calculations. We map the different regimes of dynamics in this system, and highlight the different manifestations of activity: breakdown of the virial theorem and equipartition, different elasticity-dependent "effective temperatures" and distinct non-Gaussian distributions. Our results shed light on puzzling observations in active gel experiments, and provide physical interpretation of existing observations, as well as predictions for future studies.

  6. Modeling the dynamics of a tracer particle in an elastic active gel

    E-print Network

    E. Ben Isaac; É. Fodor; P. Visco; F. van Wijland; N. S. Gov

    2015-07-03

    The internal dynamics of active gels, both in artificial (in-vitro) model systems and inside the cytoskeleton of living cells, has been extensively studied by experiments of recent years. These dynamics are probed using tracer particles embedded in the network of biopolymers together with molecular motors, and distinct non-thermal behavior is observed. We present a theoretical model of the dynamics of a trapped active particle, which allows us to quantify the deviations from equilibrium behavior, using both analytic and numerical calculations. We map the different regimes of dynamics in this system, and highlight the different manifestations of activity: breakdown of the virial theorem and equipartition, different elasticity-dependent "effective temperatures" and distinct non-Gaussian distributions. Our results shed light on puzzling observations in active gel experiments, and provide physical interpretation of existing observations, as well as predictions for future studies.

  7. Modeling the dynamics of a tracer particle in an elastic active gel.

    PubMed

    Ben-Isaac, E; Fodor, É; Visco, P; van Wijland, F; Gov, Nir S

    2015-07-01

    The internal dynamics of active gels both in artificial (in vitro) model systems and inside the cytoskeleton of living cells has been extensively studied with experiments of recent years. These dynamics are probed using tracer particles embedded in the network of biopolymers together with molecular motors, and distinct nonthermal behavior is observed. We present a theoretical model of the dynamics of a trapped active particle, which allows us to quantify the deviations from equilibrium behavior, using both analytic and numerical calculations. We map the different regimes of dynamics in this system and highlight the different manifestations of activity: breakdown of the virial theorem and equipartition, different elasticity-dependent "effective temperatures," and distinct non-Gaussian distributions. Our results shed light on puzzling observations in active gel experiments and provide physical interpretation of existing observations, as well as predictions for future studies. PMID:26274211

  8. Modeling the dynamics of a tracer particle in an elastic active gel

    NASA Astrophysics Data System (ADS)

    Ben-Isaac, E.; Fodor, É.; Visco, P.; van Wijland, F.; Gov, Nir S.

    2015-07-01

    The internal dynamics of active gels both in artificial (in vitro) model systems and inside the cytoskeleton of living cells has been extensively studied with experiments of recent years. These dynamics are probed using tracer particles embedded in the network of biopolymers together with molecular motors, and distinct nonthermal behavior is observed. We present a theoretical model of the dynamics of a trapped active particle, which allows us to quantify the deviations from equilibrium behavior, using both analytic and numerical calculations. We map the different regimes of dynamics in this system and highlight the different manifestations of activity: breakdown of the virial theorem and equipartition, different elasticity-dependent "effective temperatures," and distinct non-Gaussian distributions. Our results shed light on puzzling observations in active gel experiments and provide physical interpretation of existing observations, as well as predictions for future studies.

  9. Social Learning Analytics

    ERIC Educational Resources Information Center

    Buckingham Shum, Simon; Ferguson, Rebecca

    2012-01-01

    We propose that the design and implementation of effective "Social Learning Analytics (SLA)" present significant challenges and opportunities for both research and enterprise, in three important respects. The first is that the learning landscape is extraordinarily turbulent at present, in no small part due to technological drivers. Online social…

  10. Analytical Services Management System

    SciTech Connect

    2005-03-30

    Analytical Services Management System (ASMS) provides sample management services. Sample management includes sample planning for analytical requests, sample tracking for shipping and receiving by the laboratory, receipt of the analytical data deliverable, processing the deliverable and payment of the laboratory conducting the analyses. ASMS is a web based application that provides the ability to manage these activities at multiple locations for different customers. ASMS provides for the assignment of single to multiple samples for standard chemical and radiochemical analyses. ASMS is a flexible system which allows the users to request analyses by line item code. Line item codes are selected based on the Basic Ordering Agreement (BOA) format for contracting with participating laboratories. ASMS also allows contracting with non-BOA laboratories using a similar line item code contracting format for their services. ASMS allows sample and analysis tracking from sample planning and collection in the field through sample shipment, laboratory sample receipt, laboratory analysis and submittal of the requested analyses, electronic data transfer, and payment of the laboratories for the completed analyses. The software when in operation contains business sensitive material that is used as a principal portion of the Kaiser Analytical Management Services business model. The software version provided is the most recent version, however the copy of the application does not contain business sensitive data from the associated Oracle tables such as contract information or price per line item code.

  11. Ada & the Analytical Engine.

    ERIC Educational Resources Information Center

    Freeman, Elisabeth

    1996-01-01

    Presents a brief history of Ada Byron King, Countess of Lovelace, focusing on her primary role in the development of the Analytical Engine--the world's first computer. Describes the Ada Project (TAP), a centralized World Wide Web site that serves as a clearinghouse for information related to women in computing, and provides a Web address for…

  12. Introducing the Analytical Perspective.

    ERIC Educational Resources Information Center

    Atkinson, George F.

    1982-01-01

    A flow chart is used to illustrate analytical chemistry as a component of a problem-solving process. Beginning with a problem, the flow chart proceeds to the question, experimental design, experiments, data treatment, answer, and solution. Another flow chart is used to expand on experimental design. (Author/SK)

  13. 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.

  14. Analytical Chemistry Laboratory

    NASA Technical Reports Server (NTRS)

    Anderson, Mark

    2013-01-01

    The Analytical Chemistry and Material Development Group maintains a capability in chemical analysis, materials R&D failure analysis and contamination control. The uniquely qualified staff and facility support the needs of flight projects, science instrument development and various technical tasks, as well as Cal Tech.

  15. 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...

  16. Analytical Services Management System

    Energy Science and Technology Software Center (ESTSC)

    2005-03-30

    Analytical Services Management System (ASMS) provides sample management services. Sample management includes sample planning for analytical requests, sample tracking for shipping and receiving by the laboratory, receipt of the analytical data deliverable, processing the deliverable and payment of the laboratory conducting the analyses. ASMS is a web based application that provides the ability to manage these activities at multiple locations for different customers. ASMS provides for the assignment of single to multiple samples for standardmore »chemical and radiochemical analyses. ASMS is a flexible system which allows the users to request analyses by line item code. Line item codes are selected based on the Basic Ordering Agreement (BOA) format for contracting with participating laboratories. ASMS also allows contracting with non-BOA laboratories using a similar line item code contracting format for their services. ASMS allows sample and analysis tracking from sample planning and collection in the field through sample shipment, laboratory sample receipt, laboratory analysis and submittal of the requested analyses, electronic data transfer, and payment of the laboratories for the completed analyses. The software when in operation contains business sensitive material that is used as a principal portion of the Kaiser Analytical Management Services business model. The software version provided is the most recent version, however the copy of the application does not contain business sensitive data from the associated Oracle tables such as contract information or price per line item code.« less

  17. Application of surface analytical methods in thin film analysis

    NASA Astrophysics Data System (ADS)

    Wen, Xingu

    Self-assembly and the sol-gel process are two promising methods for the preparation of novel materials and thin films. In this research, these two methods were utilized to prepare two types of thin films: self-assembled monolayers of peptides on gold and SiO2 sol-gel thin films modified with Ru(II) complexes. The properties of the resulting thin films were investigated by several analytical techniques in order to explore their potential applications in biomaterials, chemical sensors, nonlinear optics and catalysis. Among the analytical techniques employed in the study, surface analytical techniques, such as X-ray photoelectron spectroscopy (XPS) and grazing angle reflection absorption Fourier transform infrared spectroscopy (RA-FTIR), are particularly useful in providing information regarding the compositions and structures of the thin films. In the preparation of peptide thin films, monodisperse peptides were self-assembled on gold substrate via the N-terminus-coupled lipoic acid. The film compositions were investigated by XPS and agreed well with the theoretical values. XPS results also revealed that the surface coverage of the self-assembled films was significantly larger than that of the physisorbed films and that the chemisorption between the peptides and gold surface was stable in solvent. Studies by angle dependent XPS (ADXPS) and grazing angle RA-FTIR indicated that the peptides were on average oriented at a small angle from the surface normal. By using a model of orientation distribution function, both the peptide tilt angle and film thickness can be well calculated. Ru(II) complex doped SiO2 sol-gel thin films were prepared by low temperature sol-gel process. The ability of XPS coupled with Ar + ion sputtering to provide both chemical and compositional depth profile information of these sol-gel films was evaluated. This technique, together with UV-VIS and electrochemical measurements, was used to investigate the stability of Ru complexes in the composite films. The stability of Ru complexes with respect to dopant leaching was dependent on the film microstructures. Three methods aiming to improve the dopant stability were also explored. In addition, the ion exchange properties of the composite films, upon exposure to various ions in aqueous solutions, were investigated by XPS, and the ion exchange mechanism was elucidated.

  18. Multicomponent gels: Remote control for self-assembly

    NASA Astrophysics Data System (ADS)

    Kar, Haridas; Ghosh, Suhrit

    2015-10-01

    A patterned, spatially resolved gel has now been devised. The two-component gel is formed by sequential assembly of two independent networks of fibres, and the subsequent selective removal of one network by irradiation.

  19. 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 ...

  20. 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.

  1. Elastic interactions in nematic elastomers and gels

    NASA Astrophysics Data System (ADS)

    Uchida, N.; Onuki, A.

    1999-02-01

    We investigate elastic interactions in nematic elastomers and gels using a Ginzburg-Landau model for the isotropic-nematic transition. We propose an elastic origin of the "four-leaf clover" pattern observed in depolarised light scattering from polydomain nematic elastomers. We also investigate the director fluctuation in the nematic phase. Aligned nematic states are found to be unstable below a critical elongation.

  2. 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.

  3. Gel injection successfully shuts off excess water

    SciTech Connect

    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.

  4. 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…

  5. 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.

  6. 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…

  7. Development of novel Sol-Gel Indicators (SGI`s) for in-situ environmental measurements: Part 1, Program and a new pH Sol-Gel Indicator

    SciTech Connect

    Livingston, R.R.; Baylor, L.; Wicks, G.G.

    1992-11-03

    The feasibility of incorporating analytical indicators into a sol-gel glassy matrix and then coating substrates with this composite material has bee demonstrated. Substrates coated include paper, wood, glass, and the lens of an analytical probe. The first SRTC sol-gel indicator, comprising bromophenol blue dispersed in a silica matrix, was fabricated and successfully used to measure solution pH in the range of pH 3.0 to 7.5. material exhibited a quick response time, as measured by color changes both qualitatively and quantitatively, and the measuring device was reversible or reusable. Additional indicators with responses over other ranges as well as indicators sensitive to the presence of elements of interest, are also under development. The new SGI composites possess promising properties and an excellent potential for performing a variety important in-situ environmental measurements and area discussed in this report.

  8. Encapsulation of nanoclusters in dried gel materials via an inverse micelle/sol gel synthesis

    DOEpatents

    Martino, Anthony (Albuquerque, NM); Yamanaka, Stacey A. (Dallas, TX); Kawola, Jeffrey S. (Albuquerque, NM); Showalter, Steven K. (Albuquerque, NM); Loy, Douglas A. (Albuquerque, NM)

    1998-01-01

    A dried gel material sterically entrapping nanoclusters of a catalytically active material and a process to make the material via an inverse micelle/sol-gel synthesis. A surfactant is mixed with an apolar solvent to form an inverse micelle solution. A salt of a catalytically active material, such as gold chloride, is added along with a silica gel precursor to the solution to form a mixture. To the mixture are then added a reducing agent for the purpose of reducing the gold in the gold chloride to atomic gold to form the nanoclusters and a condensing agent to form the gel which sterically entraps the nanoclusters. The nanoclusters are normally in the average size range of from 5-10 nm in diameter with a monodisperse size distribution.

  9. Encapsulation of nanoclusters in dried gel materials via an inverse micelle/sol gel synthesis

    DOEpatents

    Martino, A.; Yamanaka, S.A.; Kawola, J.S.; Showalter, S.K.; Loy, D.A.

    1998-09-29

    A dried gel material sterically entrapping nanoclusters of a catalytically active material and a process to make the material via an inverse micelle/sol-gel synthesis are disclosed. A surfactant is mixed with an apolar solvent to form an inverse micelle solution. A salt of a catalytically active material, such as gold chloride, is added along with a silica gel precursor to the solution to form a mixture. To the mixture are then added a reducing agent for the purpose of reducing the gold in the gold chloride to atomic gold to form the nanoclusters and a condensing agent to form the gel which sterically entraps the nanoclusters. The nanoclusters are normally in the average size range of from 5--10 nm in diameter with a monodisperse size distribution. 1 fig.

  10. Gel-forming reagents and uses thereof for preparing microarrays

    DOEpatents

    Golova, Julia (Burr Ridge, IL); Chernov, Boris (Burr Ridge, IL); Perov, Alexander (Woodridge, IL)

    2010-11-09

    New gel-forming reagents including monomers and cross-linkers, which can be applied to gel-drop microarray manufacturing by using co-polymerization approaches are disclosed. Compositions for the preparation of co-polymerization mixtures with new gel-forming monomers and cross-linker reagents are described herein. New co-polymerization compositions and cross-linkers with variable length linker groups between unsaturated C.dbd.C bonds that participate in the formation of gel networks are disclosed.

  11. Methods of Manufacturing Bioactive Gels from Extracellular Matrix Material

    NASA Technical Reports Server (NTRS)

    Kentner, Kimberly A. (Inventor); Stuart, Katherine A. (Inventor); Janis, Abram D. (Inventor)

    2014-01-01

    The present invention is directed to methods of manufacturing bioactive gels from ECM material, i.e., gels which retain bioactivity, and can serve as scaffolds for preclinical and clinical tissue engineering and regenerative medicine approaches to tissue reconstruction. The manufacturing methods take advantage of a new recognition that bioactive gels from ECM material can be created by digesting particularized ECM material in an alkaline environment and neutralizing to provide bioactive gels.

  12. Methods of Manufacturing Bioactive Gels from Extracellular Matrix Material

    NASA Technical Reports Server (NTRS)

    Kentner, Kimberly A. (Inventor); Stuart, Katherine A. (Inventor); Janis, Abram D. (Inventor)

    2015-01-01

    The present invention is directed to methods of manufacturing bioactive gels from ECM material, i.e., gels which retain bioactivity, and can serve as scaffolds for preclinical and clinical tissue engineering and regenerative medicine approaches to tissue reconstruction. The manufacturing methods take advantage of a new recognition that bioactive gels from ECM material can be created by digesting particularized ECM material in an alkaline environment and neutralizing to provide bioactive gels.

  13. Reformulated tenofovir gel for use as a dual compartment microbicide

    PubMed Central

    Dezzutti, Charlene S.; Rohan, Lisa C.; Wang, Lin; Uranker, Kevin; Shetler, Cory; Cost, Marilyn; Lynam, J. D.; Friend, David

    2012-01-01

    Objectives Coital use of 1% tenofovir gel was shown to be modestly effective at preventing HIV transmission when applied vaginally in the CAPRISA 004 trial. Because the gel is hyperosmolar, which would reduce the integrity of the epithelium and induce fluid movement into the lumen, rectal use may not be acceptable. This study evaluated the pre-clinical safety and efficacy of a reformulated (reduced osmolality) tenofovir gel product. Methods Reduced glycerine (RG)-tenofovir gel was compared with the original tenofovir gel for physiochemical characteristics, product safety and anti-HIV-1 activity. Results The formulations were similar in all characteristics except for osmolality and spreadability/firmness. The RG-tenofovir gel had a 73% lower osmolality, a 29.6% increase in spreadability and a 27% decrease in firmness as compared with the original tenofovir gel. When applied to epithelial cell monolayers, tenofovir gel showed a transient reduction in the transepithelial resistance while the RG-tenofovir gel did not. Both gels retained ectocervical and colorectal explant viability. However, tenofovir gel treatment resulted in epithelial stripping that was absent after RG-tenofovir gel treatment of the polarized explants. Anti-HIV-1 activity was confirmed by lack of HIV-1 infection in polarized explants treated with either gel as compared with the control explants. Conclusions Reducing the osmolality of the tenofovir gel resulted in improved epithelial integrity, which suggests better safety upon rectal use. The improved gel safety did not compromise drug release or anti-HIV-1 activity. These data support the use of this gel as a dual compartment microbicide. PMID:22581908

  14. Metal-doped organic gels and method thereof

    DOEpatents

    Satcher, Jr., Joe H.; Baumann, Theodore F.

    2003-09-02

    Disclosed herein is a sol-gel polymerization process for synthesizing metal-doped organic gels. The process polymerizes metal salts of hydroxylated benzenes or hydroxylated benzene derivatives with alkyl or aryl aldehydes to form metal-doped, wet, organic gels. The gels can then be dried by supercritical solvent extraction to form metal-doped aerogels or by evaporation to form metal-doped xerogels. The aerogels and xerogels can then be pyrolyzed.

  15. Metal-doped organic gels and method thereof

    DOEpatents

    Satcher, Jr., Joe H. (Patterson, CA); Baumann, Theodore F. (Tracy, CA)

    2007-10-23

    Disclosed herein is a sol-gel polymerization process for synthesizing metal-doped organic gels. The process polymerizes metal salts of hydroxylated benzenes or hydroxylated benzene derivatives with alkyl or aryl aldehydes to form metal-doped, wet, organic gels. The gels can then be dried by supercritical solvent extraction to form metal-doped aerogels or by evaporation to form metal-doped xerogels. The aerogels and xerogels can then be pyrolyzed.

  16. 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.

  17. Solid phase extraction using silica gel modified with murexide for preconcentration of uranium (VI) ions from water samples.

    PubMed

    Sadeghi, S; Sheikhzadeh, E

    2009-04-30

    Murexide was chemically bonded to silica gel surface immobilized 3-aminopropyl trimethoxysilane (APMS) to produce the new sorbent. A solid phase extraction method using the new sorbent has been developed to separate and concentrate trace amount of uranium (VI) from aqueous samples for the measurement by spectrophotometry method using Arsenazo III reagent. The influences of some analytical parameters on the quantitative recoveries of the analyte were investigated both in batch and column methods. Quantitative recovery of U(VI) was achieved by stripping with 0.1 mol L(-1) HCl. The maximum sorption capacity of the modified silica gel was 1.13 mmol g(-1) U(VI). A high preconcentration factor value of 400 with a lower limit of detection of 1 microg L(-1) was obtained for U(VI). The practical applicability of the developed sorbent was examined using synthetic and real samples such as sea/ground water samples. PMID:18755546

  18. Reuse of denaturing polyacrylamide gels for short tandem repeat analysis.

    PubMed

    Tereba, A; Micka, K A; Schumm, J W

    1998-11-01

    Denaturing polyacrylamide gel electrophoretic analysis of amplified polymorphic short tandem repeat (STR) loci using fluorescent markers is a mainstay of forensic and paternity testing. To reduce the drawback of preparing gels or using expensive precast gels, we have developed a simple and rapid method to reuse gels between 2 and 8 times over a period of several days. Following the initial electrophoresis and scan, the original samples are removed from the gel by a 1-1.5-h reverse-electrophoresis step. This step heats the gel for the next set of samples and can be performed several days after the initial electrophoresis. Sample bands remain sharp on subsequent runs, but edge effects (frowning of the outside lanes) become progressively worse and ultimately limit gel reuse. Well distortions and separation of the gel from the plates become problems if the gel is used more than twice. However, degassing the gel solution and bonding the gel to both plates eliminate these problems. Precast gels also can be used multiple times. Using this technique, we have successfully analyzed samples amplified with a nine-locus multiplex system and characterized the separated products using a fluorescent scanner and software. PMID:9821592

  19. 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.

  20. MP 33354 Pro-Q Sapphire 532 Oligohistidine Gel Stain

    E-print Network

    Lebendiker, Mario

    MP 33354 Pro-Q® Sapphire 532 Oligohistidine Gel Stain Product Information Storage upon receipt: · 6­ polyacrylamide gel electrophoresis (PAGE) and Western blot analysis. With Molecular Probes Pro-Q® Sapphire 532­polyacrylamide gel, eliminating the need to blot the protein to a membrane (Figure 1, top). Pro-Q Sapphire 532

  1. Biomimetic ratcheting motion of a soft, slender, sessile gel

    E-print Network

    Chaudhury, Manoj K.

    Biomimetic ratcheting motion of a soft, slender, sessile gel L. Mahadevan* , S. Daniel , and M. K-breaking bifurcations of a simple base state associated with periodic longitudinal oscillations of a slender gel deformation waves lead to the generation of periodic pulses in a soft, slender gel rod on a substrate. Motion

  2. 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.

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

    DOEpatents

    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.

  4. Developments in analytical instrumentation

    NASA Astrophysics Data System (ADS)

    Petrie, G.

    The situation regarding photogrammetric instrumentation has changed quite dramatically over the last 2 or 3 years with the withdrawal of most analogue stereo-plotting machines from the market place and their replacement by analytically based instrumentation. While there have been few new developments in the field of comparators, there has been an explosive development in the area of small, relatively inexpensive analytical stereo-plotters based on the use of microcomputers. In particular, a number of new instruments have been introduced by manufacturers who mostly have not been associated previously with photogrammetry. Several innovative concepts have been introduced in these small but capable instruments, many of which are aimed at specialised applications, e.g. in close-range photogrammetry (using small-format cameras); for thematic mapping (by organisations engaged in environmental monitoring or resources exploitation); for map revision, etc. Another innovative and possibly significant development has been the production of conversion kits to convert suitable analogue stereo-plotting machines such as the Topocart, PG-2 and B-8 into fully fledged analytical plotters. The larger and more sophisticated analytical stereo-plotters are mostly being produced by the traditional mainstream photogrammetric systems suppliers with several new instruments and developments being introduced at the top end of the market. These include the use of enlarged photo stages to handle images up to 25 × 50 cm format; the complete integration of graphics workstations into the analytical plotter design; the introduction of graphics superimposition and stereo-superimposition; the addition of correlators for the automatic measurement of height, etc. The software associated with this new analytical instrumentation is now undergoing extensive re-development with the need to supply photogrammetric data as input to the more sophisticated G.I.S. systems now being installed by clients, instead of the data being used mostly in the digital mapping systems operated in-house by mapping organisations. These various new hardware and software developments are reported upon and analysed in this Invited Paper presented to ISPRS Commission II at the 1988 Kyoto Congress.

  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. Analytical applications of aptamers

    NASA Astrophysics Data System (ADS)

    Tombelli, S.; Minunni, M.; Mascini, M.

    2007-05-01

    Aptamers are single stranded DNA or RNA ligands which can be selected for different targets starting from a library of molecules containing randomly created sequences. Aptamers have been selected to bind very different targets, from proteins to small organic dyes. Aptamers are proposed as alternatives to antibodies as biorecognition elements in analytical devices with ever increasing frequency. This in order to satisfy the demand for quick, cheap, simple and highly reproducible analytical devices, especially for protein detection in the medical field or for the detection of smaller molecules in environmental and food analysis. In our recent experience, DNA and RNA aptamers, specific for three different proteins (Tat, IgE and thrombin), have been exploited as bio-recognition elements to develop specific biosensors (aptasensors). These recognition elements have been coupled to piezoelectric quartz crystals and surface plasmon resonance (SPR) devices as transducers where the aptamers have been immobilized on the gold surface of the crystals electrodes or on SPR chips, respectively.

  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. Industrial Analytics Corporation

    SciTech Connect

    Industrial Analytics Corporation

    2004-01-30

    The lost foam casting process is sensitive to the properties of the EPS patterns used for the casting operation. In this project Industrial Analytics Corporation (IAC) has developed a new low voltage x-ray instrument for x-ray radiography of very low mass EPS patterns. IAC has also developed a transmitted visible light method for characterizing the properties of EPS patterns. The systems developed are also applicable to other low density materials including graphite foams.

  9. Exploratory data analysis groupware for qualitative and quantitative electrophoretic gel analysis over the Internet-WebGel.

    PubMed

    Lemkin, P F; Myrick, J M; Lakshmanan, Y; Shue, M J; Patrick, J L; Hornbeck, P V; Thornwal, G C; Partin, A W

    1999-12-01

    Many scientists use quantitative measurements to compare the presence and amount, of various proteins and nucleotides among series of one- and two-dimensional (1-D and 2-D) electrophoretic gels. These gels are often scanned into digital image files. Gel spots are then quantified using stand-alone analysis software. However, as more research collaborations take place over the Internet, it has become useful to share intermediate quantitative data between researchers. This allows research group members to investigate their data and share their work in progress. We developed a World Wide Web group-accessible software system, WebGel, for interactively exploring qualitative and quantitative differences between electrophoretic gels. Such Internet databases are useful for publishing quantitative data and allow other researchers to explore the data with respect to their own research. Because intermediate results of one user may be shared with their collaborators using WebGel, this form of active data-sharing constitutes a groupware method for enhancing collaborative research. Quantitative and image gel data from a stand-alone gel image processing system are copied to a database accessible on the WebGel Web server. These data are then available for analysis by the WebGel database program residing on that server. Visualization is critical for better understanding of the data. WebGel helps organize labeled gel images into montages of corresponding spots as seen in these different gels. Various views of multiple gel images, including sets of spots, normalization spots, labeled spots, segmented gels, etc. may also be displayed. These displays are active and may be used for performing database operations directly on individual protein spots by simply clicking on them. Corresponding regions between sets of gels may be visually analyzed using Flicker-comparison (Electrophoresis 1997, 18, 122-140) as one of the WebGel methods for qualitative analysis. Quantitative exploratory data analysis can be performed by comparing protein concentration values between corresponding spots for multiple samples run in separate gels. These data are then used to generate reports on statistical differences between sets of gels (e.g., between different disease states such as benign or metastatic cancers, etc.). Using combined visual and quantitative methods, WebGel can help bridge the analysis of dissimilar gels which are difficult to analyze with stand-alone systems and can serve as a collaborative Internet tool in a groupware setting. PMID:10612275

  10. Dielectric properties of gel collected from shark electrosensors

    NASA Astrophysics Data System (ADS)

    Hughes, Mary E.; Brown, Brandon R.; Hutchison, John C.; Murray, Royce W.

    2003-03-01

    To investigate the physical mechanism of the electric sense, we present an initial characterization of the dielectric properties of the glycoprotein gel that fills the electrosensitive organs of marine elasmobranches (sharks, skates, and rays). To ascertain the properties of the gel, low-frequency impedance spectroscopy is used. The impedance data collected from a dialyzed sample show large values of static permittivity and a loss peak corresponding to a long relaxation time (about 1 ms). Impedance measurements of the native (nondialyzed) gel reliable to 0.1 Hz will be presented and compared to the dialyzed gel. Ramifications of the gel's dielectric properties for the electric sense will be explored.

  11. Antimicrobial activity and the mechanism of silver nanoparticle thermosensitive gel

    PubMed Central

    Chen, Meiwan; Yang, Zhiwen; Wu, Hongmei; Pan, Xin; Xie, Xiaobao; Wu, Chuanbin

    2011-01-01

    Purpose The purpose of the present study was to elucidate the antimicrobial activity and mechanism of silver nanoparticles incorporated into thermosensitive gel (S-T-Gel) on Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. Patients and methods This study investigated the growth, permeability, and morphology of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa cells in order to observe the action of S-T-Gel on the membrane structure of these three bacteria. The cell morphology of normal and treated bacteria cells was assessed by transmission electron microscopy (TEM), and the effects of S-T-Gel on genome DNA of bacterial cells were evaluated by agarose gel electrophoresis. Results S-T-Gel showed promising activity against Staphylococcus aureus and moderate activity against Escherichia coli and Pseudomonas aeruginosa. The observation with TEM suggested that S-T-Gel may destroy the structure of bacterial cell membranes in order to enter the bacterial cell. S-T-Gel then condensed DNA and combined and coagulated with the cytoplasm of the damaged bacteria, resulting in the leakage of the cytoplasmic component and the eventual death of these three bacteria. In addition, the analysis of agarose gel electrophoresis demonstrated that S-T-Gel could increase the decomposability of genome DNA. Conclusion These results about promising antimicrobial activity and mechanism of S-T-Gel may be useful for further research and development in in-vivo studies. PMID:22131833

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. Antioxidant effect of green tea on polymer gel dosimeter

    NASA Astrophysics Data System (ADS)

    Samuel, E. J. J.; Sathiyaraj, P.; Deena, T.; Kumar, D. S.

    2015-01-01

    Extract from Green Tea (GTE) acts as an antioxidant in acrylamide based polymer gel dosimeter. In this work, PAGAT gel was used for investigation of antioxidant effect of GTE.PAGAT was called PAGTEG (Polyacrylamide green tea extract gel dosimeter) after adding GTE. Free radicals in water cause pre polymerization of polymer gel before irradiation. Polyphenols from GTE are highly effective to absorb the free radicals in water. THPC is used as an antioxidant in polymer gel dosimeter but here we were replaced it by GTE and investigated its effect by spectrophotometer. GTE added PAGAT samples response was lower compared to THPC added sample. To increase the sensitivity of the PAGTEG, sugar was added. This study confirmed that THPC was a good antioxidant for polymer gel dosimeter. However, GTE also can be used as an antioxidant in polymer gel if use less quantity (GTE) and add sugar as sensitivity enhancer.

  17. Ultrasound evaluation of polymer gel dosimeters

    NASA Astrophysics Data System (ADS)

    Mather, Melissa L.; Whittaker, Andrew K.; Baldock, Clive

    2002-05-01

    A new method for the evaluation of radiotherapy 3D polymer gel dosimeters has been developed using ultrasound to assess the significant structural changes that occur following irradiation of the dosimeters. The ultrasonic parameters of acoustic speed of propagation, attenuation and transmitted signal intensity were measured as a function of absorbed radiation dose. The dose sensitivities for each parameter were determined as 1.8 × 10-4 s m-1 Gy-1, 3.9 dB m-1 Gy-1 and 3.2 V-1 Gy-1 respectively. All parameters displayed a strong variation with absorbed dose that continued beyond absorbed doses of 15 Gy. The ultrasonic measurements demonstrated a significantly larger dynamic range in dose response curves than that achieved with previously published magnetic resonance imaging (MRI) dose response data. It is concluded that ultrasound shows great potential as a technique for the evaluation of polymer gel dosimeters.

  18. Ultrasonic Wave Propagation in Particle Compounded Gels

    NASA Astrophysics Data System (ADS)

    Ueba, Shizuko; Matsukawa, Mami; TakahikoOtani, TakahikoOtani

    1999-05-01

    Attenuation and sound velocity in particle compounded agar weremeasured by an ultrasonic wave transmission technique at frequenciesranging from 1 MHz to 8 MHz. The observed values were discussed usingUrick's theory for viscous suspensions. The measured values ofattenuation and sound velocity were in good agreement with thecalculated values using Urick's theory up to a particle concentrationof 10%. This means that Urick's theory can be applied not only tosuspensions, but also to particle compounded gels. Furthermore, fromthe investigation of the experimental results obtained using thistheory, it was clarified that the attenuation depends on the particledensity. In particular, it should be noted that n depends on theparticle diameter (the attenuation ? can be expressed with theequation ?= ?0fn, where ?0 and n are constants and f isfrequency). All measured and calculated results suggested that theacoustic properties in these kinds of particle compounded gels could beestimated theoretically.

  19. Novel carboxy functionalized sol-gel precursors

    SciTech Connect

    Wolter, H.; Storch, W.; Gellermann, C.

    1996-12-31

    A novel family of inorganic-organic copolymers (ORMOCER`s) derived from urethane- and thioether(meth)acrylate alkoxysilanes has been successfully exploited for a variety of diverse applications. In order to widen the range of applications an additional functionality (carboxy group) has been incorporated int his silane type. Conventional sol-gel processing facilitates the formation of an inorganic Si-O-Si-network via hydrolysis and polycondensation reactions of alkoxysilyl moieties and in addition, the (meth)acrylate groups are available for radically induced polymerization to obtain a complementary organic polymer structure. The presence of a carboxy group would appear to have great potential for a range of diverse areas of application, such as an internal catalyst for the sol-gel process, complexation of elements such as Zr and Ti, increasing the adhesion to various substrates and modification of solubility. A number of novel silanes and their syntheses will be described in this paper.

  20. Electrodeposited gels prepared from protein alloys

    PubMed Central

    Lin, Yinan; Wang, Siran; Chen, Ying; Wang, Qianrui; Burke, Kelly A; Spedden, Elise M; Staii, Cristian; Weiss, Anthony S; Kaplan, David L

    2015-01-01

    Aim Silk-tropoelastin alloys, composed of recombinant human tropoelastin and regenerated Bombyx mori silk fibroin, are an emerging, versatile class of biomaterials endowed with tunable combinations of physical and biological properties. Electrodeposition of these alloys provides a programmable means to assemble functional gels with both spatial and temporal controllability. Materials & methods Tropoelastin-modified silk was prepared by enzymatic coupling between tyrosine residues. Hydrogel coatings were electrodeposited using two wire electrodes. Results & discussion Mechanical characterization and in vitro cell culture revealed enhanced adhesive capability and cellular response of these alloy gels as compared with electrogelled silk alone. Conclusion These electro-depositable silk-tropoelastin alloys constitute a suitable coating material for nanoparticle-based drug carriers and offer a novel opportunity for on-demand encapsulation/release of nanomedicine. PMID:25816881

  1. GEL, a DNA sequencing project management system.

    PubMed Central

    Clayton, J; Kedes, L

    1982-01-01

    We have developed an automated system for management of DNA sequencing projects. The system, named GEL, can handle data from both random sequences and from fragments whose relative positions are known. The system is highly interactive, self-documenting, and forgiving; it is designed for use by computer-naive molecular biologists. An editor designed specifically for sequences allows simple entry of data. Special functions allow direct checking and immediate editing of paired readings of the same gel. Merging of new random fragment sequences into the project as a whole is semi-automated. The user is shown probable overlaps if they exist, and can edit either the sequences or the consensus. Heuristic approaches to limiting the kinds of searches made in the merging process reduces the problem of combinatoric data overload as sequencing projects grow large. Complete histories of all entries, editing changes, and generation of consensus sequences are automatically prepared. PMID:7063403

  2. Analytical Scientist The Epic Saga

    E-print Network

    Kounaves, Samuel P.

    , analytical science is truly ubiquitous. It is practiced in forensics, agriculture, pharmaceutics, commerce science" ­ covering more rigorously error analysis, precision, accuracy, statistics, samplingthe Analytical Scientist The Epic Saga Quantitative analysis and the essence of doing good science

  3. ANALYTICAL METHODS in CHEMICAL ECOLOGY

    E-print Network

    ANALYTICAL METHODS in CHEMICAL ECOLOGY a post graduate course (doktorandkurs) when: February 10 ­ 28, 2014 where: Chemical Ecology, Plant Protection Biology, Swedish University of Agriculture (SLU to modern analytical methods used in Chemical Ecological and Ecotoxicological research, such as: methods

  4. Analytical Division Questions CPT Criteria.

    ERIC Educational Resources Information Center

    Hercules, David M.

    1978-01-01

    The Analytical Division of the American Chemical Society (ACS) questions criteria established by the Committee on Professional Training of the same organization concerning the role of analytical chemistry in freshman level courses. (CP)

  5. Ring-Resonator/Sol-Gel Interferometric Immunosensor

    NASA Technical Reports Server (NTRS)

    Bearman, Gregory; Cohen, David

    2007-01-01

    A proposed biosensing system would be based on a combination of (1) a sensing volume containing antibodies immobilized in a sol-gel matrix and (2) an optical interferometer having a ring resonator configuration. The antibodies would be specific to an antigen species that one seeks to detect. In the ring resonator of the proposed system, light would make multiple passes through the sensing volume, affording greater interaction length and, hence, greater antibody- detection sensitivity.

  6. 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/.

  7. The formation and structure of Olympic gels

    NASA Astrophysics Data System (ADS)

    Fischer, J.; Lang, M.; Sommer, J.-U.

    2015-12-01

    Different methods for creating Olympic gels are analyzed using computer simulations. First ideal reference samples are obtained from freely interpenetrating semi-dilute solutions and melts of cyclic polymers. The distribution of pairwise concatenations per cyclic molecule is given by a Poisson-distribution and can be used to describe the elastic structure of the gels. Several batches of linear chains decorated with different selectively binding groups at their ends are mixed in the "DNA Origami" technique and network formation is realized. While the formation of cyclic molecules follows mean field predictions below overlap of the precursor molecules, an enhanced ring formation above overlap is found that is not explained by mean field arguments. The "progressive construction" method allows to create Olympic gels with a single reaction step from a concentrated mixture of large compressed rings with a low weight fraction of short chains that are below overlap concentration. This method, however, is limited by the difficulty to obtain a sufficiently high degree of polymerization of the large rings.

  8. The yielding dynamics of a colloidal gel

    E-print Network

    Thomas Gibaud; Frelat Damien; Sébastien Manneville

    2009-11-06

    Attractive colloidal gels display a solid-to-fluid transition as shear stresses above the yield stress are applied. This shear-induced transition is involved in virtually any application of colloidal gels. It is also crucial for controlling material properties. Still, in spite of its ubiquity, the yielding transition is far from understood, mainly because rheological measurements are spatially averaged over the whole sample. Here, the instrumentation of creep and oscillatory shear experiments with high-frequency ultrasound opens new routes to observing the local dynamics of opaque attractive colloidal gels. The transition proceeds from the cell walls and heterogeneously fluidizes the whole sample with a characteristic time whose variations with applied stress suggest the existence of an energy barrier linked to the gelation process. The present results provide new test grounds for computer simulations and theoretical calculations in the attempt to better understand the yielding transition. The versatility of the technique should also allow extensive mesoscopic studies of rupture mechanisms in soft solids ranging from crystals to glassy materials.

  9. Sol-gel method for encapsulating molecules

    DOEpatents

    Brinker, C. Jeffrey (Albuquerque, NM); Ashley, Carol S. (Albuquerque, NM); Bhatia, Rimple (Albuquerque, NM); Singh, Anup K. (San Francisco, CA)

    2002-01-01

    A method for encapsulating organic molecules, and in particular, biomolecules using sol-gel chemistry. A silica sol is prepared from an aqueous alkali metal silicate solution, such as a mixture of silicon dioxide and sodium or potassium oxide in water. The pH is adjusted to a suitably low value to stabilize the sol by minimizing the rate of siloxane condensation, thereby allowing storage stability of the sol prior to gelation. The organic molecules, generally in solution, is then added with the organic molecules being encapsulated in the sol matrix. After aging, either a thin film can be prepared or a gel can be formed with the encapsulated molecules. Depending upon the acid used, pH, and other processing conditions, the gelation time can be from one minute up to several days. In the method of the present invention, no alcohols are generated as by-products during the sol-gel and encapsulation steps. The organic molecules can be added at any desired pH value, where the pH value is generally chosen to achieve the desired reactivity of the organic molecules. The method of the present invention thereby presents a sufficiently mild encapsulation method to retain a significant portion of the activity of the biomolecules, compared with the activity of the biomolecules in free solution.

  10. Gel Electrophoresis of Gold-DNA Nanoconjugates

    DOE PAGESBeta

    Pellegrino, T.; Sperling, R. A.; Alivisatos, A. P.; Parak, W. J.

    2007-01-01

    Gold-DNA conjugates were investigated in detail by a comprehensive gel electrophoresis study based on 1200 gels. A controlled number of single-stranded DNA of different length was attached specifically via thiol-Au bonds to phosphine-stabilized colloidal gold nanoparticles. Alternatively, the surface of the gold particles was saturated with single stranded DNA of different length either specifically via thiol-Au bonds or by nonspecific adsorption. From the experimentally determined electrophoretic mobilities, estimates for the effective diameters of the gold-DNA conjugates were derived by applying two different data treatment approaches. The first method is based on making a calibration curve for the relation between effectivemore »diameters and mobilities with gold nanoparticles of known diameter. The second method is based on Ferguson analysis which uses gold nanoparticles of known diameter as reference database. Our study shows that effective diameters derived from gel electrophoresis measurements are affected with a high error bar as the determined values strongly depend on the method of evaluation, though relative changes in size upon binding of molecules can be detected with high precision. Furthermore, in this study, the specific attachment of DNA via gold-thiol bonds to Au nanoparticles is compared to nonspecific adsorption of DNA. Also, the maximum number of DNA molecules that can be bound per particle was determined.« less

  11. Mars Analytical Microimager

    NASA Astrophysics Data System (ADS)

    Batory, Krzysztof J.; Govindjee; Andersen, Dale; Presley, John; Lucas, John M.; Sears, S. Kelly; Vali, Hojatollah

    Unambiguous detection of extraterrestrial nitrogenous hydrocarbon microbiology requires an instrument both to recognize potential biogenic specimens and to successfully discriminate them from geochemical settings. Such detection should ideally be in-situ and not jeopardize other experiments by altering samples. Taken individually most biomarkers are inconclusive. For example, since amino acids can be synthesized abiotically they are not always considered reliable biomarkers. An enantiomeric imbalance, which is characteristic of all terrestrial life, may be questioned because chirality can also be altered abiotically. However, current scientific understanding holds that aggregates of identical proteins or proteinaceous complexes, with their well-defined amino acid residue sequences, are indisputable biomarkers. Our paper describes the Mars Analytical Microimager, an instrument for the simultaneous imaging of generic autofluorescent biomarkers and overall morphology. Autofluorescence from ultraviolet to near-infrared is emitted by all known terrestrial biology, and often as consistent complex bands uncharacteristic of abiotic mineral luminescence. The MAM acquires morphology, and even sub-micron morphogenesis, at a 3-centimeter working distance with resolution approaching a laser scanning microscope. Luminescence is simultaneously collected via a 2.5-micron aperture, thereby permitting accurate correlation of multi-dimensional optical behavior with specimen morphology. A variable wavelength excitation source and photospectrometer serve to obtain steady-state and excitation spectra of biotic and luminescent abiotic sources. We believe this is the first time instrumentation for detecting hydrated or desiccated microbiology non-destructively in-situ has been demonstrated. We have obtained excellent preliminary detection of biota and inorganic matrix discrimination from terrestrial polar analogues, and perimetric morphology of individual magnetotactic bacteria. Proposed analytical components for enhanced detection are: fluorescence anisotropy which analyzes chromophore-based proteins, anisotropy depletion to detect the presence of a fluid environment, anisotropy excitation spectrum for augmented characterization, and fluorescence-detected circular dichroism. Because all its analytical components are independent of chirality and amino acid types, life detection ability of the MAM is not limited to the terrestrial core biomolecular subsets.

  12. MERRA Analytic Services

    NASA Astrophysics Data System (ADS)

    Schnase, J. L.; Duffy, D. Q.; McInerney, M. A.; Tamkin, G. S.; Thompson, J. H.; Gill, R.; Grieg, C. M.

    2012-12-01

    MERRA Analytic Services (MERRA/AS) is a cyberinfrastructure resource for developing and evaluating a new generation of climate data analysis capabilities. MERRA/AS supports OBS4MIP activities by reducing the time spent in the preparation of Modern Era Retrospective-Analysis for Research and Applications (MERRA) data used in data-model intercomparison. It also provides a testbed for experimental development of high-performance analytics. MERRA/AS is a cloud-based service built around the Virtual Climate Data Server (vCDS) technology that is currently used by the NASA Center for Climate Simulation (NCCS) to deliver Intergovernmental Panel on Climate Change (IPCC) data to the Earth System Grid Federation (ESGF). Crucial to its effectiveness, MERRA/AS's servers will use a workflow-generated realizable object capability to perform analyses over the MERRA data using the MapReduce approach to parallel storage-based computation. The results produced by these operations will be stored by the vCDS, which will also be able to host code sets for those who wish to explore the use of MapReduce for more advanced analytics. While the work described here will focus on the MERRA collection, these technologies can be used to publish other reanalysis, observational, and ancillary OBS4MIP data to ESGF and, importantly, offer an architectural approach to climate data services that can be generalized to applications and customers beyond the traditional climate research community. In this presentation, we describe our approach, experiences, lessons learned,and plans for the future.; (A) MERRA/AS software stack. (B) Example MERRA/AS interfaces.

  13. Dynamics around the sol-gel transition in thermoreversible polymer gels

    NASA Astrophysics Data System (ADS)

    Mattsson, Johan; Dasgupta, Bivash; Matic, Aleksandar; Bergman, Rikard; Nystrom, Bo; Weitz, David A.

    2004-03-01

    Recently, a number of intriguing similarities have been found between the dynamical behaviour of gel- and glass-forming materials [1-3]. For instance, both the glass and gel transitions are reversible, they show typical kinetic features and occur as a result of the physical arrest of either molecules or molecular structures. An obvious difference between glasses and gels is one of length and correspondingly time scales, with those of gels being much longer than those of glasses. In order to investigate what similarities and indeed differences that exist between thermoreversible gelation and glass formation we have investigated the dynamics around the sol-gel transition in two different thermoreversibly gelling systems: poly(N-acetamido acrylamide) in water and atactic polystyrene in toluene. The studies include a wide range of experimental techniques including dynamic light scattering, diffusing wave spectroscopy, rheology, calorimetry,quasi-elastic neutron scattering and dielectric spectrocopy. The results will be discussed in the light of models and theories suggested to describe gelation in these types of systems. [1] Ren, S.Z. And Sorensen, C.M., Phys. Rev. Lett., 70, 1727 (1993) [2] Ikkai, F. and Shibayama, M., Phys. Rev. Lett. 82, 4946 (1999) [3] Kumar, S. and Douglas, J.F., Phys. Rev. Lett., 87, 188301 (2001)

  14. 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.

  15. 01101011011 From Analytics to Action

    E-print Network

    Yu, Sheng-Tao

    of Big Data, but extracting value from Big Data is no ordinary task. Big Data management and analytics University has established the WSU Big Data & Business Analytics Group. Our goal is to be the Midwest's premier center of innovation in Big Data science and business analytics. To do this, we must have a strong

  16. 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…

  17. Phenyl Functionalized Sol-gel Silica Sorbent for Capillary Microextraction and Chromia-Based Sol-gel Ucon Stationary Phase for Capillary Gas Chromatography

    NASA Astrophysics Data System (ADS)

    McLean, Michael M.

    The first chapter of this thesis presents an introduction to sol-gel methodology whose usefulness as a synthetic route will be demonstrated with two applications in chromatography. The first application involves the fabrication of a capillary micro-extraction (CME) device by coating a phenyl functionalized extracting phase on the inner surface of a fused silica capillary for analyte pre-concentration. The device was coupled on-line to a RP-HPLC system and practicality was demonstrated using allergens as target analytes. The allergens chosen as model analytes are typically found in fragrance products and food. Most of the 26 fragrance allergens that are monitored by various government authorities have a phenyl organic moiety (a strong chromophore), thus making them appropriate probes for exploring the extraction efficiency of the coating using a UV detector. The CME device showed ppt level limit of detection which makes it suitable for trace analyses of allergens and similar compounds in a variety of matrices. The second application explores the feasibility of using sol-gel derived chromia-based stationary phase in gas chromatographic columns. The organic moiety of the stationary phase was derived from Ucon 75-H-90,000 while the inorganic backbone was prepared using chromium(III) dichloride hydroxide - methacrylic acid - aqua complex, 40% in isopropanol/acetone . Usefulness of prepared chromia-based GC stationary phase was examined for petrochemical application. Promising results were obtained using aliphatic-aromatics, polyaromatic hydrocarbons, BTEX test mixture, cycloalkanes, branched alkanes and akylbenzenes. The column was able to perform without degradation despite being rinsed multiples times sequentially with the following solvents: dichloromethane, methanol, water and finally methanol again. Maximum theoretical plate number calculated is around 2,400 plates/m. The plate number clearly needs improvement but is a promising result for the newly explored chromia-based stationary phase. The maximum programmable temperature is 250°C which is comparable with similar commercially available polar stationary phases.

  18. Ionogel Electrolytes through Sol-Gel Processing

    NASA Astrophysics Data System (ADS)

    Horowitz, Ariel I.

    Electrical energy needs have intensified due to the ubiquity of personal electronics, the decarbonization of energy services through electrification, and the use of intermittent renewable energy sources. Despite developments in mechanical and thermal methods, electrochemical technologies are the most convenient and effective means of storing electrical energy. These technologies include both electrochemical cells, commonly called batteries, and electrochemical double-layer capacitors, or "supercapacitors", which store energy electrostatically. Both device types require an ion-conducting electrolyte. Current devices use solutions of complex salts in organic solvents, leading to both toxicity and flammability concerns. These drawbacks can be avoided by replacing conventional electrolytes with room-temperature molten salts, known as ionic liquids (ILs). ILs are non-volatile, non-flammable, and offer high conductivity and good electrochemical stability. Device mass can be reduced by combining ILs with a solid scaffold material to form an "ionogel," further improving performance metrics. In this work, sol-gel chemistry is explored as a means of forming ionogel electrolytes. Sol-gel chemistry is a solution-based, industrially-relevant, well-studied technique by which solids such as silica can be formed in situ. Previous works used a simple acid-catalyzed sol-gel reaction to create brittle, glassy ionogels. Here, both the range of products that can be accomplished through sol-gel processing and the understanding of interactions between ILs and the sol-gel reaction network are greatly expanded. This work introduces novel ionogel materials, including soft and compliant silica-supported ionogels and PDMS-supported ionogels. The impacts of the reactive formulation, IL identity, and casting time are detailed. It is demonstrated that variations in formulation can lead to rapid gelation and open pore structures in the silica scaffold or slow gelation and more dense silica morphologies. The IL identity is shown to have an impact on the apparent strength of the acid catalyst, leading to significant shifts in gelation time. Delayed casting is proven to be an optimal technique for avoiding pore blockage when combining ionogels with high surface area electrodes for supercapacitor applications. Finally, a simple recycling process is proposed, establishing that ILs can be easily reclaimed from silica-supported ionogels and reused, thereby validating the reputation of ILs as "green" materials.

  19. Interionic interactions of binary gels consisting of pyrrolidinium-based zwitterionic compounds and lithium salts.

    PubMed

    Park, HoSeok; Kim, Hoon Sik; Jung, Young Mee

    2011-03-01

    We demonstrated thermal transitions and physical gelation of binary ionic salts through interionic interactions, which consist of pyrrolidinium-N-propanesulfonate zwitterionic compound (PyrZIC) and lithium bis(trifluorosulfonyl)imide (LiTFSI). The transition behaviors of binary ionic gels were attributed to conformational changes in the cations and anions of PyrZIC and LiTFSI as analyzed by density functional theory (DFT), principal component analysis (PCA), and two-dimensional infrared correlation spectroscopy (2D IR COS). Furthermore, the geometries of binary PyrZIC-LiTFSI systems were strongly influenced by the electrostatic interactions between two ionic salts. The different dynamic processes in the PyrZIC- and LiTFSI-rich phases, which are classified by the transition point of PCA plots, were induced by the conformational changes in the respective interaction fields, as shown by 2D correlation spectra. In particular, LiTFSI-rich binary gels revealed characteristic four-leaf-clover and butterfly patterns under their unique chemical circumstances, which were different from those of PyrZIC-rich gels. Consequently, these computational and experimental investigations provide an analytical tool to understand the physical phenomenon and interactions occurring in the unveiled and complicated systems. PMID:21291183

  20. 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.

  1. Investigation of the Peroxovanadate Sol-Gel Process and Characterization of the Gels

    SciTech Connect

    Craig Joseph Fontenot

    2001-12-31

    In general, the peroxovanadate solution sol-gel process can be thought of as consisting of two parts: (1) the decomposition of the peroxo species and (2) cation hydrolysis leading to gelation. By controlling the synthesis conditions, both layered and amorphous compounds can be created. However, the type of water coordination observed in these gels was found to be identical no matter what the long-range order. The current work clarified many of the discrepancies found in the literature and offered much new valuable information. Highlights include the types of vanadium environments present at various stages of hydration, the role of adsorbed water, oxygen exchange from adsorbed water into the gel sites, and the ability to create metastable VMoO solid solution phases. These results could have a variety of impacts on future catalysis research.

  2. The Biophysical Properties of Basal Lamina Gels Depend on the Biochemical Composition of the Gel

    PubMed Central

    Pflieger, Kerstin; Boettcher, Kathrin; Zahler, Stefan; Lieleg, Oliver

    2015-01-01

    The migration of cells within a three-dimensional extracellular matrix (ECM) depends sensitively on the biochemical and biophysical properties of the matrix. An example for a biological ECM is given by reconstituted basal lamina gels purified from the Engelbreth-Holm-Swarm sarcoma of mice. Here, we compare four different commercial variants of this ECM, which have all been purified according to the same protocol. Nevertheless, in those gels, we detect strong differences in the migration behavior of leukocyte cells as well as in the Brownian motion of nanoparticles. We show that these differences correlate with the mechanical properties and the microarchitecture of the gels which in turn arise from small variations in their biochemical composition. PMID:25689062

  3. 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

  4. Analysis of variations in band positions for normalization in across-gel denaturing gradient gel electrophoresis.

    PubMed

    Matsushita, Yuko; Yamamura, Kohji; Morimoto, Sho; Bao, Zhihua; Kurose, Daisuke; Sato, Ikuo; Yoshida, Shigenobu; Tsushima, Seiya

    2015-05-01

    Variation in band position between gels is a well-known problem in denaturing gradient gel electrophoresis (DGGE). However, few reports have evaluated the degree of variation in detail. In this study, we investigated the variation in band positions of DNA samples extracted from soil, normalized using reference positions within marker lanes for DGGE in three organismal (bacterial, fungal, and nematode) conditions. For sample lanes, marker DNA (as a control) and sample DNA were used. The test for normality of distribution showed that the position data of a large percentage of bands were normally distributed but not for certain bands. For the normally-distributed data, their variations [standard deviation of marker bands (SDM) and standard deviation of sample bands (SDS), respectively] were assessed. For all organismal conditions, the degree of within-gel variation were similar between SDMs and SDSs, while between-gel variations in SDSs were larger than those in SDMs. Due to the large effect of between-gel variations, the total variations in SDSs were more varied between sample bands, and the mean variations of all sample bands were higher than those in the markers. We found that the total variation in the fungal and nematode SDSs decreased when the intervals between marker bands were narrowed, suggesting that band interval is important for reducing total variation in normalized band positions. For the non-normally distributed data, the distribution was examined in detail. This study provided detailed information on the variation of band positions, which could help to optimize markers for reducing band position variation, and could aid in the accurate identification of bands in across-gel DGGE analyses. PMID:25725304

  5. Sol-gel processing to form doped sol-gel monoliths inside hollow core optical fiber and sol-gel core fiber devices made thereby

    NASA Technical Reports Server (NTRS)

    Shaw, Harry C. (Inventor); Ott, Melanie N. (Inventor); Manuel, Michele V. (Inventor)

    2002-01-01

    A process of fabricating a fiber device includes providing a hollow core fiber, and forming a sol-gel material inside the hollow core fiber. The hollow core fiber is preferably an optical fiber, and the sol-gel material is doped with a dopant. Devices made in this manner includes a wide variety of sensors.

  6. Normality in Analytical Psychology

    PubMed Central

    Myers, Steve

    2013-01-01

    Although C.G. Jung’s interest in normality wavered throughout his career, it was one of the areas he identified in later life as worthy of further research. He began his career using a definition of normality which would have been the target of Foucault’s criticism, had Foucault chosen to review Jung’s work. However, Jung then evolved his thinking to a standpoint that was more aligned to Foucault’s own. Thereafter, the post Jungian concept of normality has remained relatively undeveloped by comparison with psychoanalysis and mainstream psychology. Jung’s disjecta membra on the subject suggest that, in contemporary analytical psychology, too much focus is placed on the process of individuation to the neglect of applications that consider collective processes. Also, there is potential for useful research and development into the nature of conflict between individuals and societies, and how normal people typically develop in relation to the spectrum between individuation and collectivity. PMID:25379262

  7. VERDE Analytic Modules

    SciTech Connect

    2008-01-15

    The Verde Analytic Modules permit the user to ingest openly available data feeds about phenomenology (storm tracks, wind, precipitation, earthquake, wildfires, and similar natural and manmade power grid disruptions and forecast power outages, restoration times, customers outaged, and key facilities that will lose power. Damage areas are predicted using historic damage criteria of the affected area. The modules use a cellular automata approach to estimating the distribution circuits assigned to geo-located substations. Population estimates served within the service areas are located within 1 km grid cells and converted to customer counts by conversion through demographic estimation of households and commercial firms within the population cells. Restoration times are estimated by agent-based simulation of restoration crews working according to utility published prioritization calibrated by historic performance.

  8. VERDE Analytic Modules

    Energy Science and Technology Software Center (ESTSC)

    2008-01-15

    The Verde Analytic Modules permit the user to ingest openly available data feeds about phenomenology (storm tracks, wind, precipitation, earthquake, wildfires, and similar natural and manmade power grid disruptions and forecast power outages, restoration times, customers outaged, and key facilities that will lose power. Damage areas are predicted using historic damage criteria of the affected area. The modules use a cellular automata approach to estimating the distribution circuits assigned to geo-located substations. Population estimates servedmore »within the service areas are located within 1 km grid cells and converted to customer counts by conversion through demographic estimation of households and commercial firms within the population cells. Restoration times are estimated by agent-based simulation of restoration crews working according to utility published prioritization calibrated by historic performance.« less

  9. Normality in analytical psychology.

    PubMed

    Myers, Steve

    2013-12-01

    Although C.G. Jung's interest in normality wavered throughout his career, it was one of the areas he identified in later life as worthy of further research. He began his career using a definition of normality which would have been the target of Foucault's criticism, had Foucault chosen to review Jung's work. However, Jung then evolved his thinking to a standpoint that was more aligned to Foucault's own. Thereafter, the post Jungian concept of normality has remained relatively undeveloped by comparison with psychoanalysis and mainstream psychology. Jung's disjecta membra on the subject suggest that, in contemporary analytical psychology, too much focus is placed on the process of individuation to the neglect of applications that consider collective processes. Also, there is potential for useful research and development into the nature of conflict between individuals and societies, and how normal people typically develop in relation to the spectrum between individuation and collectivity. PMID:25379262

  10. ANALYTIC MODELING OF STARSHADES

    SciTech Connect

    Cash, Webster

    2011-09-01

    External occulters, otherwise known as starshades, have been proposed as a solution to one of the highest priority yet technically vexing problems facing astrophysics-the direct imaging and characterization of terrestrial planets around other stars. New apodization functions, developed over the past few years, now enable starshades of just a few tens of meters diameter to occult central stars so efficiently that the orbiting exoplanets can be revealed and other high-contrast imaging challenges addressed. In this paper, an analytic approach to the analysis of these apodization functions is presented. It is used to develop a tolerance analysis suitable for use in designing practical starshades. The results provide a mathematical basis for understanding starshades and a quantitative approach to setting tolerances.

  11. Analytical applications of dithizone

    SciTech Connect

    Irving, H.M.N.H.

    1980-01-01

    The organic reagent best known under its common name dithizone was introduced into analytical practice by Hellmuth Fischer just over 50 years ago. By virtue of its thiol group, it can form formally unchanged chelate complexes with a small group of metals (notably, Co, Ni, Zn, Pd, Ag, Cd, In, Sn, Pt, Au, Hg, Tl, Pb, and Bi) and organometallic ions (such as R/sub 2/Tl/sup +/, R/sub 3/Su/sup +/, R/sub 2/Pb/sup 2 +/, RHg/sup +/) and since, like the reagent itself, these are intensely colored and very sparingly soluble in water though soluble in chloroform, carbon tetrachloride, and other water-immiscible organic solvents, dithizone lends itself to liquid-liquid extraction procedures and the spectrophotometric determination of trace metals at around the microgram level. With the increasing popularity of atomic abosption spectrophotometry, this technique has tended to supplant spectrophotometry as the preferred finish in quantitative trace-metal determinations, but many other physical procedures are in current use. The ability to preconcentrate certain metals by liquid-liquid extraction of their dithizonates plays an increasing role in environmental analysis, and chromatographic techniques now extend from thin layer chromatography to the use of columns for specific separations. The present review summarizes the basic analytical applications of dithizone that have become well established in the past half-century but highlights the more recent developments through a detailed review of papers published during the last 10 years. Particular attention is paid to the applications of dithizone in preconcentration and separation techniques, in electroanalytical procedures, in substoichiometry and in the design of liquid-membrane ion-selective electrodes. 4 figures, 4 tables.

  12. A simple gel electrophoresis method for separating polyhedral gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Kim, Suhee; Lee, Hye Jin

    2015-07-01

    In this paper, a simple approach to separate differently shaped and sized polyhedral gold nanoparticles (NPs) within colloidal solutions via gel electrophoresis is described. Gel running parameters for separating efficiently gold NPs including gel composition, added surfactant types and applied voltage were investigated. The plasmonic properties and physical structure of the separated NPs extracted from the gel matrix were then investigated using transmission electron microscopy (TEM) and UV-vis spectrophotometry respectively. Data analysis revealed that gel electrophoresis conditions of a 1.5 % agarose gel with 0.1 % sodium dodecyl sulfate (SDS) surfactant under an applied voltage of 100 V resulted in the selective isolation of ~ 50 nm polyhedral shaped gold nanoparticles. Further efforts are underway to apply the method to purify biomolecule-conjugated polyhedral Au NPs that can be readily used for NP-enhanced biosensing platforms.

  13. Method for imparting selectivity to polymeric gel systems

    SciTech Connect

    Hoskin, D.H.; Sifferman, T.R.

    1992-10-20

    This patent describes a method for imparting selectivity to an in-situ gel-forming composition for placement within a subterranean oil-bearing formation having relatively high permeability zones and relatively low permeability zones. It comprises: preparing an aqueous-based mixture comprising: a first stage gel-forming composition; at least one second stage in-situ gel-forming composition comprising a water-dispersible polymer and a crosslinking agent for the water-dispersible polymer in an amount effective to form a stable gel; and gelling the first stage gel-forming composition exsitu by reacting the Xanthomonas campestris NCIB 1185 heteropolysaccharide with the crosslinking agent for the heteropolysaccharide; wherein the mixture exhibits greater selectivity than would a like mixture in the absence of the first stage selective gel-forming composition.

  14. Polyacrylamide gel with switchable trypsin activity for analysis of proteins.

    PubMed

    Liu, Fangjie; Ye, Mingliang; Wang, Chunli; Hu, Zhengyan; Zhang, Yi; Qin, Hongqiang; Cheng, Kai; Zou, Hanfa

    2013-08-01

    Trypsin was immobilized on a variety of materials to improve digestion efficiency. However, because the immobilized trypsin will digest proteins during electrophoresis, direct immobilization of active trypsin in polyacrylamide gel will compromise the protein separation. To overcome this problem, here we report a novel polyacrylamide gel with switchable trypsin activity. It was prepared by copolymerization of the PEG-trypsin-aprotinin complex during the gel-casting step. Because the inhibitor aprotinin binds strongly with trypsin at alkaline pH, this novel gel does not display hydrolytic activity during electrophoresis. After electrophoresis, the activity of trypsin embedded in gel could be recovered by simply washing away the bound inhibitor at a low pH. It was demonstrated that this unique switchable activity design allowed high resolution of the complex protein mixture during electrophoresis and highly efficient digestion of the separated proteins in situ in the gel after electrophoresis. PMID:23855779

  15. Analytic integrable systems: Analytic normalization and embedding flows

    NASA Astrophysics Data System (ADS)

    Zhang, Xiang

    In this paper we mainly study the existence of analytic normalization and the normal form of finite dimensional complete analytic integrable dynamical systems. More details, we will prove that any complete analytic integrable diffeomorphism F(x)=Bx+f(x) in (Cn,0) with B having eigenvalues not modulus 1 and f(x)=O(|) is locally analytically conjugate to its normal form. Meanwhile, we also prove that any complete analytic integrable differential system x?=Ax+f(x) in (Cn,0) with A having nonzero eigenvalues and f(x)=O(|) is locally analytically conjugate to its normal form. Furthermore we will prove that any complete analytic integrable diffeomorphism defined on an analytic manifold can be embedded in a complete analytic integrable flow. We note that parts of our results are the improvement of Moser's one in J. Moser, The analytic invariants of an area-preserving mapping near a hyperbolic fixed point, Comm. Pure Appl. Math. 9 (1956) 673-692 and of Poincaré's one in H. Poincaré, Sur l'intégration des équations différentielles du premier order et du premier degré, II, Rend. Circ. Mat. Palermo 11 (1897) 193-239. These results also improve the ones in Xiang Zhang, Analytic normalization of analytic integrable systems and the embedding flows, J. Differential Equations 244 (2008) 1080-1092 in the sense that the linear part of the systems can be nonhyperbolic, and the one in N.T. Zung, Convergence versus integrability in Poincaré-Dulac normal form, Math. Res. Lett. 9 (2002) 217-228 in the way that our paper presents the concrete expression of the normal form in a restricted case.

  16. Pulsed field gel electrophoresis for dairy propionibacteria.

    PubMed

    Chuat, Victoria; de Freitas, Rosangela; Dalmasso, Marion

    2015-01-01

    Pulsed field gel electrophoresis (PFGE) is a technique using alternating electric fields to migrate high molecular weight DNA fragments with a high resolution. This method consists of the digestion of bacterial chromosomal DNA with rare-cutting restriction enzymes and in applying an alternating electrical current between spatially distinct pairs of electrodes. DNA molecules migrate at different speeds according to the size of the fragments. Among other things, this technique is considered as the "gold standard" for genotyping, genetic fingerprinting, epidemiological studies, genome size estimation, and studying radiation-induced DNA damage and repair. This chapter describes a PFGE method that can be used to differentiate dairy propionibacteria. PMID:25862063

  17. 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.

  18. Silver staining DNA in polyacrylamide gels.

    PubMed

    Bassam, Brant J; Gresshoff, Peter M

    2007-01-01

    This protocol describes a simple silver staining method used to visualize DNA fragments and other organic molecules with unsurpassed detail following traditional polyacrylamide gel electrophoresis (PAGE). Sensitivity rivals radioisotopic methods and DNA in the picogram range can be reliably detected. The described protocol is fast (approximately 1 h) and is implemented using readily available chemicals and materials. To achieve the sensitivity and visual clarity expected, quality reagents and clean handling are important. The updated protocol described here is based on the widely used method of Bassam et al. (1991), but provides improved image contrast and less risk of staining artefacts. PMID:18007600

  19. GelApp: Mobile gel electrophoresis analyser Jia-Zhi Sim1,*

    E-print Network

    Cai, Long

    ://www.achartengine.org/) for the generation of logarithmic graphs; and Itseez's OpenCV (http://opencv.org/) for the Gabor filter, threshold and Gaussian blur. GelApp for iOS was developed using XCode 6, Itseez's Open CV, and Kishikawa Katsumi

  20. A constitutive theory for visco-hyperelastic gels

    NASA Astrophysics Data System (ADS)

    Chester, Shawn

    2012-02-01

    Many gels operate in chemically saturated environments in a variety of applications. Most constitutive theories for gels are formulated using large deformation hyperelasticity coupled with fluid transport. However, in most cases the mechanical response of such gels show hysteresis and other dissipative effects which are not accounted for in present constitutive theories. We have recently developed a three dimensional continuum level theory to describe the coupled fluid permeation and large deformation response of visco-hyperelastic materials. In this work, we apply our theory and numerical simulation capability to study the indentation response among others of visco-hyperelastic gels.

  1. GEL FORMATION: PHASE DIAGRAMS USING TABLETOP RHEOLOGY AND CALORIMETRY

    E-print Network

    Raghavan, Srinivasa

    Chapter 8 GEL FORMATION: PHASE DIAGRAMS USING TABLETOP RHEOLOGY AND CALORIMETRY Srinivasa R: In particular, differential scanning calorimetry (DSC). We will now consider these two techniques systematically

  2. Inclusion type radiochromic gel dosimeter for threedimensional dose verification

    NASA Astrophysics Data System (ADS)

    Usui, Shuji; Yoshioka, Munenori; Hayashi, Shin-ichiro; Tominaga, Takahiro

    2015-01-01

    For the verification of 3D dose distributions in modern radiation therapy, a new inclusion type radiochromic gel detector has been developed. In this gel, a hydrophobic leuco dye (leucomalachite green: LMG) was dissolved in water as an inclusion complex with highly branched cyclic dextrin. The radiation induced radical oxidation property of the LMG gel with various sensitizers was investigated. As a result, the optical dose responses were enhanced by the addition of bromoacetic acid and manganese (II) chloride. Unfavorable auto-oxidation of the gel was reduced when it was stored at 4°C.

  3. 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.

  4. Author's personal copy Large deformation and electrochemistry of polyelectrolyte gels

    E-print Network

    Hong, Wei

    Author's personal copy Large deformation and electrochemistry of polyelectrolyte gels Wei Hong and electrochemistry. A specific material model is described, including the effects of stretching the network, mixing

  5. Creating analysts, creating analytic patients.

    PubMed

    Levine, Howard B

    2010-12-01

    This paper applies a contemporary, 'two-track'- transformational as well as archaeological - perspective on psychoanalytic process to clinical issues in the creation of analytic patients: case finding, recommending analysis, and recommending and negotiating the intensification of frequency of sessions in analytic psychotherapy. Central importance is assigned to the role of the mind and analytic identity of the analyst, including the analyst's capacity to maintain an internal analytic frame and analyzing attitude from the very first contact with the patient and throughout the treatment, the analyst's confidence in and conviction about the usefulness of analysis for a given analytic dyad and the role of the analyst's theory, which must be broad and consistent enough to allow the analyst to feel that he or she is operating analytically when addressing non-neurotic (unrepresented and weakly represented mental states) as well as neurotic structures. PMID:21133904

  6. Preparation of highly luminescent hybrid gel incorporating NAC-capped CdTe quantum dots through sol-gel processing

    NASA Astrophysics Data System (ADS)

    Bu, Hang-Beom; Watanabe, Taichi; Hizume, Masayuki; Takagi, Tomomi; Sobue, Susumu; Kawai, Shoichi; Okuno, Eiichi; Kim, DaeGwi

    2015-03-01

    Highly photoluminescent gel was prepared by embedding water soluble quantum dots (QDs) in an inorganic-organic hybrid gel matrix using a conventional sol-gel process. Aminopropyltrimethoxysilane and citric acid (CA) were found to be the best combination for the gel preparation. 13C-NMR and FT-IR studies indicated hydrogen bond formation between the amine group of APS and the carboxyl group of CA. IR-light radiation curing was comparable to thermal curing and reduced the gelation time to a considerable extent (71 %). The resulting composite formed a hybrid gel phosphor with excellent transparency by embedding CdTe QDs into the matrix and emitted light of various colors with high photoluminescence efficiency (40 %). The gel phosphor retained the PL properties after storage in air for one year. In addition, the strength of the hybrid phosphor was demonstrated by a coin-flipping test.

  7. The behaviour of BHK cells and neutrophil leukocytes on collagen gels of defined mechanical strength.

    PubMed

    Reid, G G; Lackie, J M; Gorham, S D

    1990-11-01

    This study demonstrates how the mechanical strength of a series of collagen/composite gels can be measured using a penetrometer. It was found that the presence of fibrin in collagen gels resulted in increased gel strength. Similarly hyaluronic acid was found to increase the strength of collagen gels. Addition of heparin weakened collagen gels as did chondroitin-6-sulphate. Neutrophil migration into collagen gels was found to be inversely proportional to gel strength. Fibrin and hyaluronic acid containing gels inhibited neutrophil migration while the presence of heparin and chondroitin sulphate increased neutrophil migration. BHK gel contraction experiments demonstrated how the presence of fibrin prevents gel contraction. Despite increasing gel strength the presence of hyaluronic acid appeared to have no effect on BHK contraction of collagen gels. Similarly the presence of heparin or chondroitin sulphate had no effect on gel contraction by BHK cells. PMID:2126224

  8. Analytic Feminism: A Brief Introduction

    E-print Network

    Cudd, Ann E.

    1995-01-01

    with such very differing views as Donna Haraway, Sandra Harding, and Helen Longino. One article is in moral epistemology. Margaret Little's "Seeing and Caring: The Role of Affect in Feminist Epistemology" examines the epistemic role of caring in ethics... essays take on feminists' criticisms of analytic philosophical concepts directly. In "Feminism, Objectivity, and Analytic Philosophy," Sara Worley defends analytic epistemology against critiques by Susan Bordo and Evelyn Fox Keller, arguing...

  9. Purification of recombinant growth hormone by clear native gels for conformational analyses: preservation of conformation and receptor binding.

    PubMed

    Chen, Wei-Qiang; Salmazo, Anita; Myllykoski, Matti; Sjöblom, Björn; Bidlingmaier, Martin; Pollak, Arnold; Baumgärtel, Peter; Djinovic-Carugo, Kristina; Kursula, Petri; Lubec, Gert

    2010-08-01

    Most protein preparations require purification steps prior to biophysical analysis assessing protein stability, secondary structure and degree of folding. It was, therefore, the aim of this study to develop a system to separate and purify a protein from a commercially available medicinal product, recombinant human growth hormone (rhGH) and show preservation of conformation and function following the gel-based procedure. The rhGH was run on clear native (CN) gels and recovered from the gels by electroelution using D-Tube Dialyzer Midi under rigorous cooling. Melting point studies indicated preservation of the structural integrity. This finding was confirmed by synchrotron radiation circular dichroism spectroscopy (SRCD) revealing an identical folding pattern for the sample before and after electrophoretic separation and purification. Synchrotron small-angle X-ray scattering (SAXS) indicated that the sample was folded and monomeric, both before and after separation and purification, and that its shape corresponded well to the known crystal structure of GH. Binding properties of rhGH to a receptor-model system before and after clear native electrophoresis were comparable. This analytical and preparative approach to purify and concentrate a protein preserving conformation and function may be helpful for many applications in analytical, protein and stereochemistry. PMID:20238132

  10. Probing convection and diffusion in macromolecular gels

    NASA Astrophysics Data System (ADS)

    de Rosa, Enrica; Netti, Paolo Antonio

    2005-03-01

    Transport of molecules within three-dimensional biological tissue occurs by both diffusion and convection. While diffusion is relatively well studied in the literature, there is a paucity of data on convection parameters, even if is the most effective transport mechanism for large molecules. Pressure-driven flow through complex macromolecular gels can provide different probe velocity depending on the diffusant molecule and matrix interaction and so far no specific measurements have been performed. Furthermore the complexity or heterogeneity of the system may cause differences with the position in the convection properties of the sample. In this study both diffusion coefficient and velocity of several fluorescent probes in macromolecular gels have been measured with a high spatial resolution (100?m). The macromolecular velocity has been evaluated by adopting the video-FRAP technique, through an algorithm to separate the fluorescence recovery due to the brownian motion and that due to a bulk convection. Combination of the two transport process is very relevant in tissue engineering and drug delivery application.

  11. Block copolymer ion gels for gas separation

    NASA Astrophysics Data System (ADS)

    Gu, Yuanyan; Lodge, Timothy

    2012-02-01

    Carbon dioxide removal from light gases (eg. N2, CH4, and H2) is a very important technology for industrial applications such as natural gas sweetening, CO2 capture from coal-fire power plant exhausts and hydrogen production. Current CO2 separation method uses amine-absorption, which is energy-intensive and requires frequent maintenance. Membrane separation is a cost-effective solution to this problem, especially in small-scale applications. Ionic liquids have recently received increasing interest in this area because of their selective solubility for CO2 and non-volatility. However, ionic liquid itself lacks the persistent structure and mechanical integrity to withstand the high pressure for gas separation. Here, we report the development and gas separation performances of physically crosslinked ion gels based on self-assembly of ABA-triblock copolymers in ionic liquids. Three different types of polymers was used to achieve gelation in ionic liquids. Specifically, a triblock copolymer ion gel with a polymerized ionic liquid mid-block shows performances higher than the upper bound of well-known ``Robeson Plot'' for CO2/N2.

  12. Microfluidic dielectrophoretic sorter using gel vertical electrodes

    PubMed Central

    Luo, Jason; Nelson, Edward L.; Li, G. P.; Bachman, Mark

    2014-01-01

    We report the development and results of a two-step method for sorting cells and small particles in a microfluidic device. This approach uses a single microfluidic channel that has (1) a microfabricated sieve which efficiently focuses particles into a thin stream, followed by (2) a dielectrophoresis (DEP) section consisting of electrodes along the channel walls for efficient continuous sorting based on dielectric properties of the particles. For our demonstration, the device was constructed of polydimethylsiloxane, bonded to a glass surface, and conductive agarose gel electrodes. Gold traces were used to make electrical connections to the conductive gel. The device had several novel features that aided performance of the sorting. These included a sieving structure that performed continuous displacement of particles into a single stream within the microfluidic channel (improving the performance of downstream DEP, and avoiding the need for additional focusing flow inlets), and DEP electrodes that were the full height of the microfluidic walls (“vertical electrodes”), allowing for improved formation and control of electric field gradients in the microfluidic device. The device was used to sort polymer particles and HeLa cells, demonstrating that this unique combination provides improved capability for continuous DEP sorting of particles in a microfluidic device. PMID:24926390

  13. Deoxyribonuclease zymography adapted to the precast PhastGel electrophoresis media.

    PubMed

    Straetkvern, K O; Raae, A J

    1990-04-01

    A set-up for casting fluorescent indicator agarose gels on ultrathin polyacrylamide microelectrophoresis gel media (Pharmacia PhastGel media) is described. The zymogram system allows a rapid and sensitive detection of deoxyribonuclease in various gel media, following isoelectric focusing, native and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. PMID:1692791

  14. Analytics for Metabolic Engineering

    PubMed Central

    Petzold, Christopher J.; Chan, Leanne Jade G.; Nhan, Melissa; Adams, Paul D.

    2015-01-01

    Realizing the promise of metabolic engineering has been slowed by challenges related to moving beyond proof-of-concept examples to robust and economically viable systems. Key to advancing metabolic engineering beyond trial-and-error research is access to parts with well-defined performance metrics that can be readily applied in vastly different contexts with predictable effects. As the field now stands, research depends greatly on analytical tools that assay target molecules, transcripts, proteins, and metabolites across different hosts and pathways. Screening technologies yield specific information for many thousands of strain variants, while deep omics analysis provides a systems-level view of the cell factory. Efforts focused on a combination of these analyses yield quantitative information of dynamic processes between parts and the host chassis that drive the next engineering steps. Overall, the data generated from these types of assays aid better decision-making at the design and strain construction stages to speed progress in metabolic engineering research. PMID:26442249

  15. Symmetries of Analytic Paths

    E-print Network

    Christian Fleischhack

    2015-03-21

    The symmetries of paths in a manifold $M$ are classified with respect to a given pointwise proper action of a Lie group $G$ on $M$. Here, paths are embeddings of a compact interval into $M$. There are at least two types of symmetries: Firstly, paths that are parts of an integral curve of a fundamental vector field on $M$ (continuous symmetry). Secondly, paths that can be decomposed into finitely many pieces, each of which is the translate of some free segment, where possibly the translate is cut at the two ends of the paths (discrete symmetry). Here, a free segment is a path $e$ whose $G$-translates either equal $e$ or intersect it in at most finitely many points. Note that all the statements above are understood up to the parametrization of the paths. We will show, for the category of analytic manifolds, that each path is of exactly one of either types. For the proof, we use that the overlap of a path $\\gamma$ with one of its translates is encoded uniquely in a mapping between subsets of $\\dom\\gamma$. Running over all translates, these mappings form the so-called reparametrization set to $\\gamma$. It will turn out that, up to conjugation with a diffeomorphism, any such set is given by the action of a Lie subgroup of $O(2)$ on $S^1$, restricted in domain and range to some compact interval on $S^1$. Now, the infinite subgroups correspond to the continuous symmetry above, finite ones to the discrete symmetry.

  16. Spot volume vs. amount of protein loaded onto a gel: a detailed, statistical comparison of two gel electrophoresis systems.

    PubMed

    Zhan, Xianquan; Desiderio, Dominic M

    2003-06-01

    The long-term goal of this research program is to clarify the molecular mechanisms that participate in the formation of human pituitary macroadenomas. One approach to that goal is to characterize the differentially expressed proteins that are found by a comparison of the proteomes of control pituitary vs. macroadenoma tissues. In order to accurately perform a comparative proteomics study, based on the combination of two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) and PDQuest 2-D analysis software, a reproducible 2-DE separation system with a wide linear dynamic measure range is needed. A typical horizontal system is the Multiphor II system that analyzes one gel at a time, using a precast gradient gel (180 x 245 x 0.5 mm); a typical vertical system is the Dodeca system that analyzes up to 12 gels at a time on a single-concentration gel (190 x 205 x 1.0 mm). We have evaluated (Zhan and Desiderio, Electrophoresis 2003, 24, 1834-1846) the spatial and quantitative reproducibility of the two second-dimensional gel systems to separate a human pituitary proteome; that study showed a higher reproducibility for the Dodeca gel system. This present study investigated the relationship between the spot volume and the amount of protein loaded onto the gel for those two 2-D systems. The results demonstrated that the Dodeca gel system provides a wider linear dynamic range to measure the changes in the protein abundance in pituitary proteome. PMID:12783459

  17. Kinetics of swelling of polyelectrolyte gels: Fixed degree of ionization.

    PubMed

    Sen, Swati; Kundagrami, Arindam

    2015-12-14

    The swelling kinetics of uncharged and charged polymer (polyelectrolyte) gels in salt-free conditions is studied in one dimension by solving the constitutive equation of motion (Newton's law for the elementary gel volume) of the displacement variable by two theoretical methods: one in which the classical definition of stress is used with the bulk modulus taken as a parameter, and the other in which a phenomenological expression of the osmotic stress as a function of polymer density and degree of ionization is taken as an input to the dynamics. The time-evolution profiles for spatially varying polymer density and stress, along with the location of the gel-solvent interface, are obtained from the two methods. We show that both the polymer density (volume fraction) and stress inside the gel follow expected behaviours of being maximum for the uniformly shrunken gel, and relaxing slowly to the lowest values as the gel approaches equilibrium. We further show that, by comparing the temporal profiles of the gel-solvent interface and other variables between the two methods, one may attempt to assign an effective bulk modulus to the polyelectrolyte gel as a function of the degree of ionization and other parameters of the gel such as hydrophobicity, cross-link density, and the temperature. The major result we get is that the effective bulk modulus of a polyelectrolyte gel increases monotonically with its degree of ionization. In the process of identifying the parameters for a monotonic swelling, we calculated using a well-known expression of the free energy the equilibrium results of two-phase co-existence and the critical point of a polyelectrolyte gel with a fixed degree of ionization. PMID:26671401

  18. Beating polymer gels coupled with a nonlinear chemical reaction

    NASA Astrophysics Data System (ADS)

    Yoshida, Ryo; Kokufuta, Etsuo; Yamaguchi, Tomohiko

    1999-06-01

    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 BZ reaction, is covalently bonded to the polymer chain. The poly[NIPAAm-co-Ru(bpy)3] gel provides an open system where the BZ reaction proceeds, when immersed in an aqueous solution containing the reactants of the BZ reaction (with the exception of a catalyst). The chemical oscillation in the BZ reaction generates the periodical changes of the charge of Ru(bpy)3 in the gel network between reduced [Ru(II)] and oxidized [Ru(III)] states. The gel swells at the oxidized state because the hydrophilicity of the polymer chains increases, while at the reduced state the gel deswells. Thus, the chemical energy is transduced into the mechanical energy to drive the polymer gel oscillation with a period of about 5 min, depending on the composition of the surrounding solution. The oscillation mode of the gel depends on its size scaled by the wavelength of the BZ pattern. Sufficiently small bead-like gels demonstrate isotropic beating. A large rectangular gel shows mechanical oscillation with a peristaltic motion coupled with the propagating chemical waves. The dynamic behavior of the chemical and mechanical oscillations have been analyzed with a model simulation.

  19. 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.

  20. 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.

  1. Analytical laboratory quality audits

    SciTech Connect

    Kelley, William D.

    2001-06-11

    Analytical Laboratory Quality Audits are designed to improve laboratory performance. The success of the audit, as for many activities, is based on adequate preparation, precise performance, well documented and insightful reporting, and productive follow-up. Adequate preparation starts with definition of the purpose, scope, and authority for the audit and the primary standards against which the laboratory quality program will be tested. The scope and technical processes involved lead to determining the needed audit team resources. Contact is made with the auditee and a formal audit plan is developed, approved and sent to the auditee laboratory management. Review of the auditee's quality manual, key procedures and historical information during preparation leads to better checklist development and more efficient and effective use of the limited time for data gathering during the audit itself. The audit begins with the opening meeting that sets the stage for the interactions between the audit team and the laboratory staff. Arrangements are worked out for the necessary interviews and examination of processes and records. The information developed during the audit is recorded on the checklists. Laboratory management is kept informed of issues during the audit so there are no surprises at the closing meeting. The audit report documents whether the management control systems are effective. In addition to findings of nonconformance, positive reinforcement of exemplary practices provides balance and fairness. Audit closure begins with receipt and evaluation of proposed corrective actions from the nonconformances identified in the audit report. After corrective actions are accepted, their implementation is verified. Upon closure of the corrective actions, the audit is officially closed.

  2. VIASAT PROPRIETARY Big Data Analytics

    E-print Network

    Mohsenian-Rad, Hamed

    VIASAT PROPRIETARY Big Data Analytics for Smart Grid Security Intelligence November 4, 2015 Stefan Sensors Activity & Assets BigData Analytics/Orchestration Engine Collect process Analyze Enrich correlate information · Batch paradigm - pull · Query Driven Big Data Computing · Application & Data Centric · Speed

  3. Understanding Education Involving Geovisual Analytics

    ERIC Educational Resources Information Center

    Stenliden, Linnea

    2013-01-01

    Handling the vast amounts of data and information available in contemporary society is a challenge. Geovisual Analytics provides technology designed to increase the effectiveness of information interpretation and analytical task solving. To date, little attention has been paid to the role such tools can play in education and to the extent to which…

  4. Yielding of colloidal gels under steady and oscillatory shear

    NASA Astrophysics Data System (ADS)

    Petekidis, George; Moghimi, Esmaeel; Koumakis, Nick; Forth Team

    2015-03-01

    The structural and rheological properties of intermediate volume fraction colloid polymer gels are examined during and after steady and oscillatory shear flow using rheometry, confocal microscopy, light scattering and Brownian Dynamics simulations. Our main objective is to rationalize the microscopic mechanisms through which one can tune the mechanical properties of such metastable colloidal gels by imposing different types of external shear and flow. Experimentally, the gels consist of model hard sphere particle dispersions of ? = 0.44 with the addition of non-adsorbing linear chains, while BD simulations are conducted for hard spheres with the superposition of an AO potential for depletion attractions. Structural analysis shows that variation of the applied shear rate produces strong changes in the structure of the gels both when under shear and during gel reformation at cessation. Larger rates are characterized by disperse particles and the total breakage of structures at rest, which after cessation evolve with time into strong solids with relatively homogeneous structures. However, smaller rates show large inhomogeneous structures under flow, which do not evolve after cessation and additionally exhibit reduced elasticity and as such are weaker solids. Furthermore oscillatory shear is far more efficient than steady shear creating gels with stronger differences in their elastic modulus. Thus by tuning the way a gel is sheared, one may vary the final strength and structure of the resulting gel. Work in collaboration with R. Besseling, W. C. K. Poon and J. F. Brady

  5. 21 CFR 872.1730 - Electrode gel for pulp testers.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Electrode gel for pulp testers. 872.1730 Section 872.1730 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Diagnostic Devices § 872.1730 Electrode gel for pulp testers....

  6. Subtractive Methods for Forming Microfluidic Gels of Extracellular Matrix Proteins

    E-print Network

    Tien, Joe

    Street, Boston, MA 02215 235 Key terms microfluidic networks gel fibrin collagen gelatin channels. We have established two methods for forming microscale channels within collagen and fibrin gels. Both) proteins type I collagen and fibrin [1, 2]. It details methods for establishing and maintaining per- fusion

  7. 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.

  8. 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 ...

  9. 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…

  10. In-gel technology for PCR genotyping and pathogen detection.

    PubMed

    Atrazhev, Alexey; Manage, Dammika P; Stickel, Alexander J; Crabtree, H John; Pilarski, Linda M; Acker, Jason P

    2010-10-01

    This work describes the use of polyacrylamide gel and PCR reagents photopolymerized in a mold to create an array of semisolid posts that serve as reaction vessels for parallel PCR amplification of an externally added template. DNA amplification occurred in a cylindrical, self-standing 9 × 9 array of gel posts each less than 1 ?L in volume. Photopolymerization of the gel with an intercalating dye added prior to polymerization permitted acquisition of real-time PCR data and melting curve analysis data without the need for any type of post-PCR staining procedures. PCR was equally efficient and reproducible when template DNA was polymerized within the gel or when exogenous template was added atop precast gel posts. PCR amplification occurred with template from purified DNA or from raw urine of patients with BK viruria. Multiple primer sets can be utilized per gel post array with no detectable cross contamination. As few as 34 BK virus templates were consistently detected by PCR in an individual gel post. Amplification of HPA1 and FGFR2 genes in human genomic DNA (gDNA) required as little as 2-5 ng of gDNA template/gel post. The device prototype includes a Peltier element for PCR thermal cycling and a CCD camera to capture fluorescence for product detection. Our technology is amenable to integration in point of care microdevices. PMID:20809605

  11. Quantitative characterization of developing collagen gels using optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Levitz, David; Hinds, Monica T.; Choudhury, Niloy; Tran, Noi T.; Hanson, Stephen R.; Jacques, Steven L.

    2010-03-01

    Nondestructive optical imaging methods such as optical coherence tomography (OCT) have been proposed for characterizing engineered tissues such as collagen gels. In our study, OCT was used to image collagen gels with different seeding densities of smooth muscle cells (SMCs), including acellular gels, over a five-day period during which the gels contracted and became turbid with increased optical scattering. The gels were characterized quantitatively by their optical properties, specified by analysis of OCT data using a theoretical model. At 6 h, seeded cell density and scattering coefficient (?s) were correlated, with ?s equal to 10.8 cm-1/(106 cells/mL). Seeded cell density and the scattering anisotropy (g) were uncorrelated. Over five days, the reflectivity in SMC gels gradually doubled with little change in optical attenuation, which indicated a decrease in g that increased backscatter, but only a small drop in ?s. At five days, a subpopulation of sites on the gel showed substantially higher reflectivity (approximately a tenfold increase from the first 24 h). In summary, the increased turbidity of SMC gels that develops over time is due to a change in the structure of collagen, which affects g, and not simply due to a change in number density of collagen fibers due to contraction.

  12. 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…

  13. How it all began: a personal history of gel electrophoresis.

    PubMed

    Smithies, Oliver

    2012-01-01

    Arne Tiselius' moving boundary electrophoresis method was still in general use in 1951 when this personal history begins, although zonal electrophoresis with a variety of supporting media (e.g., filter paper or starch grains) was beginning to replace it. This chapter is an account of 10 years of experiments carried out by the author during which molecular sieving gel electrophoresis was developed and common genetic variants of two proteins, haptoglobin and transferrin, were discovered in normal individuals. Most of the figures are images of pages from the author's laboratory notebooks, which are still available, so that some of the excitement of the time and the humorous moments are perhaps apparent. Alkaline gels, acidic gels with and without denaturants, vertical gels, two-dimensional gels, and gels with differences in starch concentration are presented. The subtle details that can be discerned in these various gels played an indispensable role in determining the nature of the change in the haptoglobin gene (Hp) that leads to the polymeric series characteristic of Hp ( 2 ) /Hp ( 2 ) homozygotes. Where possible, the names of scientific friends who made this saga of gel electrophoresis so memorable and enjoyable are gratefully included. PMID:22585472

  14. 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...

  15. 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.

  16. Transfer printing of thermoreversible ion gels for flexible electronics.

    PubMed

    Lee, Keun Hyung; Zhang, Sipei; Gu, Yuanyan; Lodge, Timothy P; Frisbie, C Daniel

    2013-10-01

    Thermally assisted transfer printing was employed to pattern thin films of high capacitance ion gels on polyimide, poly(ethylene terephthalate), and SiO2 substrates. The ion gels consisted of 20 wt?% block copolymer poly(styrene-b-ethylene oxide-b-styrene and 80 wt?% ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)amide. Patterning resolution was on the order of 10 ?m. Importantly, ion gels containing the block polymer with short PS end blocks (3.4 kg/mol) could be transfer-printed because of thermoreversible gelation that enabled intimate gel-substrate contact at 100 °C, while gels with long PS blocks (11 kg/mol) were not printable at the same temperature due to poor wetting contact between the gel and substrates. By using printed ion gels as high-capacitance gate insulators, electrolyte-gated thin-film transistors were fabricated that operated at low voltages (<1 V) with high on/off current ratios (?10(5)). Statistical analysis of carrier mobility, turn-on voltage, and on/off ratio for an array of printed transistors demonstrated the excellent reproducibility of the printing technique. The results show that transfer printing is an attractive route to pattern high-capacitance ion gels for flexible thin-film devices. PMID:24028461

  17. Quantitative evaluation of polymer gel dosimeters by broadband ultrasound attenuation

    NASA Astrophysics Data System (ADS)

    Khoei, S.; Trapp, J. V.; Langton, C. M.

    2013-06-01

    Ultrasound has been examined previously as an alternative readout method for irradiated polymer gel dosimeters, with authors reporting varying dose response to ultrasound transmission measurements. In this current work we extend previous work to measure the broadband ultrasound attenuation (BUA) response of irradiated PAGAT gel dosimeters, using a novel ultrasound computed tomography system.

  18. Photopolymerized Sol-Gel Monoliths for Capillary Electrochromatography

    E-print Network

    Zare, Richard N.

    Photopolymerized Sol-Gel Monoliths for Capillary Electrochromatography Maria T. Dulay, Joselito P.d. capillary to prepare a porous monolithic sol-gel column by a one-step, in situ, process. The photopoly fabrication problems, surface-functionalized open-tubular capillary columns6,8-10 and monolithic capillaries6

  19. Rheology of reconstituted type I collagen gel in confined compression

    E-print Network

    Petzold, Linda R.

    Rheology of reconstituted type I collagen gel in confined compression David M. Knapp, Victor H 1996; final version received 10 June 1997) Synopsis Collagen gels are used extensively for studying to bulk deformation of the sparse network of long, highly entangled collagen fibrils and syneresis

  20. The Micromechanics of Three-Dimensional Collagen-I Gels

    E-print Network

    The Micromechanics of Three-Dimensional Collagen-I Gels ANDREW M. STEIN,1 DAVID A. VADER,2 DAVID A June 2010 We study the micromechanics of collagen-I gel with the goal of bridging the gap between labeled collagen are obtained by confocal microscopy, and the network geometry is extracted using a 3D

  1. Pore-Level Examination of Gel Destruction During Oil Flow

    E-print Network

    New York at Stoney Brook, State University of

    Pore-Level Examination of Gel Destruction During Oil Flow R.S. Seright, SPE, New Mexico Petroleum-scale X-ray computed microtomography (XMT) images were obtained at a variety of oil (hexadecane(III)-acetate-hydrolyzed polyacrylamide (HPAM) gel]. For each pore in our image volume, we followed oil and water saturations

  2. Long-range forces extending from polymer-gel surfaces

    E-print Network

    Jian-ming Zheng; Gerald H. Pollack

    2003-05-05

    Aqueous suspensions of microspheres were infused around gels of varying composition. The solutes were excluded from zones on the order of 100 micrometers from the gel surface. We present evidence that this finding is not an artifact, and that solute-repulsion forces exist at distances far greater than conventional theory predicts. The observations imply that solutes may interact over an unexpectedly long range.

  3. A Silica Gel Based Method for Extracting Insect Surface Hydrocarbons

    E-print Network

    Ramírez, Santiago

    . Bees . Cuticular hydrocarbons . Silica gel . Extraction . Solid-phase microextraction . Bioassay profiles of Euglossa dilemma obtained via silica-rubbing and solid phase microextraction (SPME). ComparisonA Silica Gel Based Method for Extracting Insect Surface Hydrocarbons Dong-Hwan Choe & Santiago R

  4. Preparation and characterization of cellulose gels from corn cobs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aqueous cellulose gels were prepared by extraction of ground corn cobs with hot aqueous sodium hydroxide/sodium hypochlorite and shearing. Initial shearing in a blender broke up cob tissue structure into individual cells and resulted in a gel. Subsequent shearing in a high pressure homogenizer incre...

  5. Preparation and Characterization of Cellulose Gels from Corn Cobs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aqueous cellulose gels were prepared by extraction of ground corn cobs with hot aqueous sodium hydroxide/sodium hypochlorite and shearing. Initial shearing in a blender broke up cob tissue structure into individual cells and resulted in a gel. Subsequent shearing in a high pressure homogenizer incre...

  6. 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...

  7. 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…

  8. 21 CFR 872.1730 - Electrode gel for pulp testers.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Electrode gel for pulp testers. 872.1730 Section 872.1730 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Diagnostic Devices § 872.1730 Electrode gel for pulp testers....

  9. 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

  10. Spinodal decomposition in gels and S. Puri2,3

    E-print Network

    Spinodal decomposition in gels A. Onuki1 and S. Puri2,3 1 Department of Physics, Kyoto University August 1998 We construct a Ginzburg-Landau model for gels undergoing spinodal decomposition in terms undergo spinodal decomposition with enhancement of small scale fluctuations and that the resultant two

  11. EXAFS analysis of a human Cu,Zn SOD isoform focused using non-denaturing gel electrophoresis

    NASA Astrophysics Data System (ADS)

    Chevreux, Sylviane; Solari, Pier Lorenzo; Roudeau, Stéphane; Deves, Guillaume; Alliot, Isabelle; Testemale, Denis; Hazemann, Jean Louis; Ortega, Richard

    2009-11-01

    Isoelectric point isoforms of a metalloprotein, copper-zinc superoxide dismutase (CuZnSOD), separated on electrophoresis gels were analyzed using X-ray Absorption Spectroscopy. Mutations of this protein are involved in familial cases of amyotrophic lateral sclerosis. The toxicity of mutants could be relied to defects in the metallation state. Our purpose is to establish analytical protocols to study metallation state of protein isoforms such as those from CuZnSOD. We previously highlighted differences in the copper oxidation state between CuZnSOD isoforms using XANES. Here, we present the first results for EXAFS analyses performed at Cu and Zn K-edge on the majoritary expressed isoform of human CuZnSOD separated on electrophoresis gels.

  12. GelScape: a web-based server for interactively annotating, manipulating, comparing and archiving 1D and 2D gel images.

    PubMed

    Young, Nelson; Chang, Zhan; Wishart, David S

    2004-04-12

    GelScape is a web-based tool that permits facile, interactive annotation, comparison, manipulation and storage of protein gel images. It uses Java applet-servlet technology to allow rapid, remote image handling and image processing in a platform-independent manner. It supports many of the features found in commercial, stand-alone gel analysis software including spot annotation, spot integration, gel warping, image resizing, HTML image mapping, image overlaying as well as the storage of gel image and gel annotation data in compliance with Federated Gel Database requirements. PMID:14764570

  13. Tunable dynamics of microtubule-based active isotropic gels

    PubMed Central

    Henkin, Gil; DeCamp, Stephen J.; Chen, Daniel T. N.; Sanchez, Tim; Dogic, Zvonimir

    2014-01-01

    We investigate the dynamics of an active gel of bundled microtubules (MTs) 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, MT volume fraction, as well as the stoichiometry of the constituent motor clusters. Our results show that the dynamical and structural properties of MT-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. PMID:25332391

  14. 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.

  15. Keggin-type polyoxometalate-based ionic liquid gels.

    PubMed

    Huang, Tianpei; Tian, Naiqin; Wu, Qingyin; Yan, Wenfu

    2015-06-14

    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

  16. Foam and gel methods for the decontamination of metallic surfaces

    DOEpatents

    Nunez, Luis; Kaminski, Michael Donald

    2007-01-23

    Decontamination of nuclear facilities is necessary to reduce the radiation field during normal operations and decommissioning of complex equipment. In this invention, we discuss gel and foam based diphosphonic acid (HEDPA) chemical solutions that are unique in that these solutions can be applied at room temperature; provide protection to the base metal for continued applications of the equipment; and reduce the final waste form production to one step. The HEDPA gels and foams are formulated with benign chemicals, including various solvents, such as ionic liquids and reducing and complexing agents such as hydroxamic acids, and formaldehyde sulfoxylate. Gel and foam based HEDPA processes allow for decontamination of difficult to reach surfaces that are unmanageable with traditional aqueous process methods. Also, the gel and foam components are optimized to maximize the dissolution rate and assist in the chemical transformation of the gel and foam to a stable waste form.

  17. Gutenberg-Richter's law in sliding friction of gels

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Tetsuo; Morishita, Masatoshi; Doi, Masao; Hori, Takane; Sakaguchi, Hide; Ampuero, Jean-Paul

    2011-12-01

    We report on experimental studies of spatio-temporally heterogeneous stick-slip motions in the sliding friction between a hard polymethyl methacrylate (PMMA, plexiglass) block and a soft poly-dimethyl siloxane (PDMS, silicone) gel plate. We perform experiments on two PDMS gels with different viscoelastic properties. For the less viscous gel, large and rapid events are preceded by an alternation of active and less active periods. For the more viscous gel, successive slow slip events take place continuously. The probability distributions of the force drop, a quantity analogous to seismic moment, obey a power law similar to Gutenberg-Richter's empirical law for the frequency-size statistics of earthquakes, and the exponents of the power law vary with the plate velocity and the viscosity of the gel. We propose a simple model to explain the dependence of the power law exponent on the plate velocity, which agrees with experimental results.

  18. Volume phase transitions of cholesteric liquid crystalline gels.

    PubMed

    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. PMID:25956120

  19. 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.

  20. Fricke Gel Dosimeter Tissue-Equivalence a Monte Carlo Study

    NASA Astrophysics Data System (ADS)

    Valente, M.; Bartesaghi, G.; Gambarini, G.; Brusa, D.; Castellano, G.; Carrara, M.

    2008-06-01

    Gel dosimetry has proved to be a valuable technique for absorbed dose distribution measurements in radiotherapy. FriXy-gel dosimeters consist of Fricke (ferrous sulphate) solution infused with xylenol orange. The solution is incorporated to a gel matrix in order to fix it to a solid structure allowing good spatial resolution and is imaged with a transportable optical system, measuring visible light transmittance before and after irradiation. This paper presents an evaluation of total photon mass attenuation coefficients at energies in the range of 50 keV-10MeV for the radiochromic FriXy gel dosimeter sensitive material. Mass attenuation coefficient estimations have been performed by means of Monte Carlo (PENELOPE) simulations. These calculations have been carried out for the FriXy gel sensitive material as well as for soft tissue (ICRU) and pure liquid water; a comparison of the obtained data shows good agreement between the different materials.

  1. 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.

  2. 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.

  3. Gel Mobility Shift Assays to Detect Protein–RNA Interactions

    PubMed Central

    Yakhnin, Alexander V.; Yakhnin, Helen; Babitzke, Paul

    2015-01-01

    The gel mobility shift assay is a powerful technique for detecting and quantifying protein–RNA interactions. While other techniques such as filter binding and isothermal titration calorimetry (ITC) are available for quantifying protein–RNA interactions, gel shift analysis provides the added advantage that you can visualize the protein–RNA complexes. In the gel shift assay, protein–RNA complexes are typically separated from the unbound RNA using native polyacrylamide gels in Tris/borate/EDTA buffer, although an alternative Tris-glycine buffering system is superior in many situations. Here, we describe both gel shift methods, along with strategies to improve separation of protein–RNA complexes from free RNA, which can be a particular challenge for small RNA binding proteins. PMID:22736005

  4. Volume phase transitions of cholesteric liquid crystalline gels

    SciTech Connect

    Matsuyama, Akihiko

    2015-05-07

    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.

  5. Gel-based immunotest for simultaneous detection of 2,4,6-trichlorophenol and ochratoxin A in red wine.

    PubMed

    Beloglazova, N V; Goryacheva, I Yu; Rusanova, T Yu; Yurasov, N A; Galve, R; Marco, M-P; De Saeger, S

    2010-07-01

    A new rapid method which allows simultaneous one step detection of two analytes of different nature (2,4,6,-trichlorophenol (TCP) and ochratoxin A (OTA)) in red wine was developed. It was based on a column test with three separate immunolayers: two test layers and one control layer. Each layer consisted of sepharose gel with immobilized anti-OTA (OTA test layer), anti-TCP (TCP test layer) or anti-HRP (control layer) antibodies. Analytes bind to the antibodies in the corresponding test layer while sample flows through the column. Then a mixture of OTA-HRP and TCP-HRP in appropriate dilutions was used, followed by the application of chromogenic substrate. Colour development of the test layer occurred when the corresponding analyte was absent in the sample. HRP-conjugates bound to anti-HRP antibody in the control layer independently of presence or absence of analytes and a blue colour developed in the control layer. Cut-off values for both analytes were 2 microg L(-1). The described method was applied to the simultaneous detection of TCP and OTA in wine samples. To screen the analytes in red wine samples, clean-up columns were used for sample pre-treatment in combination with the test column. Results were confirmed by chromatographic methods. PMID:20579481

  6. Polymer gel dosimeter based on itaconic acid.

    PubMed

    Mattea, Facundo; Chacón, David; Vedelago, José; Valente, Mauro; Strumia, Miriam C

    2015-11-01

    A new polymeric dosimeter based on itaconic acid and N, N'-methylenebisacrylamide was studied. The preparation method, compositions of monomer and crosslinking agent and the presence of oxygen in the dosimetric system were analyzed. The resulting materials were irradiated with an X-ray tube at 158cGy/min, 226cGymin and 298cGy/min with doses up to 1000Gy. The dosimeters presented a linear response in the dose range 75-1000Gy, sensitivities of 0.037 1/Gyat 298cGy/min and an increase in the sensitivity with lower dose rates. One of the most relevant outcomes in this study was obtaining different monomer to crosslinker inclusion in the formed gel for the dosimeters where oxygen was purged during the preparation method. This effect has not been reported in other typical dosimeters and could be attributed to the large differences in the reactivity among these species. PMID:26275817

  7. 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.

  8. Sol-gel synthesis of protoenstatite

    SciTech Connect

    Jones, S.A.; Burlitch, J.M.

    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.

  9. How to scan polymer gels with MRI?

    NASA Astrophysics Data System (ADS)

    De Deene, Y.

    2013-06-01

    The absorbed radiation dose fixated in a polymer gel dosimeter can be read out by several methods such as magnetic resonance imaging (MRI), optical CT, X-ray CT and ultrasound with MRI being the first method that was explored. Although MRI was considered as an elegant scanning technique, readily available in most hospitals, it was later found that using a non-optimized imaging protocol may result in unacceptable deviations in the obtained dose distribution. Although most medical physicists have an understanding of the basic principles of magnetic resonance imaging (MRI), the optimization of quantitative imaging sequences and protocols is often perceived as the work of MRI experts. In this paper, we aim at providing the reader with some easy guidelines in how to obtain reliable quantitative MRI maps.

  10. How to scan polymer gels with MRI?

    NASA Astrophysics Data System (ADS)

    De Deene, Yves

    2010-11-01

    The absorbed radiation dose fixated in a polymer gel dosimeter can be read out by several methods such as magnetic resonance imaging (MRI), optical CT, X-ray CT and ultrasound with MRI being the first method that was explored. Although MRI was considered as an elegant scanning technique, readily available in most hospitals, it was later found that using a non-optimized imaging protocol may result in unacceptable deviations in the obtained dose distribution. Although most medical physicists have an understanding of the basic principles of magnetic resonance imaging (MRI), the optimization of quantitative imaging sequences and protocols is often perceived as the work of MRI experts. In this paper, we aim at providing the reader with some easy guidelines in how to obtain reliable quantitative MRI maps.

  11. 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.

  12. 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.

  13. How deeply cells feel: methods for thin gels

    NASA Astrophysics Data System (ADS)

    Buxboim, Amnon; Rajagopal, Karthikan; Brown, Andre'E. X.; Discher, Dennis E.

    2010-05-01

    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 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 (e.g. 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.

  14. 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.

  15. Analytic QCD - a short review

    E-print Network

    Gorazd Cvetic; Cristian Valenzuela

    2008-04-10

    Analytic versions of QCD are those whose coupling alpha_s(Q^2) does not have the unphysical Landau singularities on the space-like axis (-q^2=Q^2 > 0). The coupling is analytic in the entire complex plane except the time-like axis (Q^2 < 0). Such couplings are thus suitable for application of perturbative methods down to energies of order GeV. We present a short review of the activity in the area which started with a seminal paper of Shirkov and Solovtsov ten years ago. Several models for analytic QCD coupling are presented. Strengths and weaknesses of some of these models are pointed out. Further, for such analytic couplings, constructions of the corresponding higher order analytic couplings (the analogs of the higher powers of the perturbative coupling) are outlined, and an approach based on the renormalization group considerations is singled out. Methods of evaluation of the leading-twist part of space-like observables in such analytic frameworks are described. Such methods are applicable also to the inclusive time-like observables. Two analytic models are outlined which respect the ITEP Operator Product Expansion philosophy, and thus allow for an evaluation of higher-twist contributions to observables.

  16. Investigations in x-ray computed tomography polyacrylamide gel dosimetry

    SciTech Connect

    Hilts, Michelle . E-mail: mhilts@bccancer.bc.ca

    2005-09-15

    Polyacrylamide gels (PAGs) are radiosensitive materials currently under development for use as three-dimensional (3D) dosimeters in radiation therapy. Dose information is recorded in the gels and extracted through imaging. X-ray computed tomography (CT) has emerged as a promising gel imaging method due to a change in gel density that occurs upon irradiation. The accessibility of CT technology to cancer hospitals makes CT read out clinically attractive; however, the technique remains of limited clinical use due in part to poor dose resolution. This thesis investigates the use of CT for extracting dose information from PAGs with an overall goal of improving achievable dose resolution. Thesis results are divided into three studies: a gel-compositional study, a study of noise and dose resolution, and a digital filtering study. The first study investigates the effects of gel composition on PAG CT dose response and the underlying density change. Results indicate dramatic variation in CT dose response sensitivity and range with gel composition. A model is developed to describe gel density change with dose, revealing two fundamental properties of the density to dose response: the density change per unit polymer yield is highest for gels with low and high concentrations of crosslinking molecules, and dose response sensitivity is linearly dependent on the total concentration of monomers in the gel. The second study investigates strategies for minimizing noise in CT polymer gel dosimetry and assesses system performance. Specifically, the effects of phantom design, scanning technique, and voxel size on image noise are investigated and the effect of scanning protocol on imaging time is established. The dose resolution achievable with an optimized system is then calculated, given voxel size and imaging time constraints, and compared with published values for magnetic resonance imaging (MRI) and optical CT gel dosimetry. The third study investigates the potential of image filtering for improved dose resolution in CT gel dosimetry. CT image noise is characterized and appropriate filters are tested on a CT image of a PAG irradiated with a clinically relevant dose distribution. Filter performance is found to vary dramatically, with the best filters more than halving the dose resolution without significantly distorting the spatial distribution of dose. In summary, this thesis provides insight into the fundamental nature of PAG density to dose response, develops strategies for minimizing image noise, quantifies system performance, and demonstrates that digital image filtering is an effective tool to provide additional improvements to dose resolution.

  17. Kinetic resolution of racemic mixtures in gel media

    NASA Astrophysics Data System (ADS)

    Petrova, Rositza Iordanova

    The goal of this research was to investigate the effect of chiral gels on the chiral crystal nucleation and growth and assess the gels' potential as media for kinetic separation of racemic mixtures. The morphologies of asparagine monohydrate and sodium bromate crystals grown in different gel media were examined in order to discern the effect of gel structure and density on the relative growth rates of those materials. Different crystal habits were observed when the gel chemical composition, density and solute concentration were varied. These studies showed that the physical properties of the gel, such as gel density and pore size, as well as its chemical composition affect the crystal habit. The method of kinetic resolution in gel media was first applied to sodium chlorate, which is achiral in solution but crystallizes in a chiral space group. Crystallization in agarose gels yielded an enantiomorphic bias, the direction and magnitude of which could be affected by changing the temperature or by the addition of an achiral cosolvent. Aqueous gels at 6°C produced crystalline mixtures enriched with the d-enantiomorph, while crystallization under MeOH diffusion favored l-crystals. Optimized conditions yielded e.e. of 53% of l-enantiomorph. The method was next applied to the organic molecular crystals of asparagine monohydrate and threonine. Asparagine monohydrate growth in aqueous agarose and iota-carrageenan gels produced crystal mixtures enriched with D-enantiomer. The degree of resolution was higher when the total amount of asparagine crystallized was low. The success of the resolution depends strongly on the concentrations of solute and the geling substance. Growth from agarose gels yielded e.e. of 44% under optimized conditions. The same method was applied to the resolution of Thr, albeit with modest success. In an effort to improve the resolution of asparagine monohydrate, agarose was synthetically modified by esterifying its side chains with homochiral asparagyl groups and used as a kinetic resolution media. The crystallization from L-Asn-agarose favored crystallization of L-enantiomer (28% e.e.), while D-Asn-agarose favored D-enantiomer (40% e.e.). The degree of resolution was sensitive to the concentrations of the gel and the total amount of crystallized asparagine, but the media was no better than that in pure agarose.

  18. Gel permeation chromatography-high performance liquid chromatography combination as an automated clean-up technique for the multiresidue analysis of fats.

    PubMed

    Rimkus, G G; Rummler, M; Nausch, I

    1996-06-14

    The well-known and almost universally utilizable clean-up technique of gel permeation chromatography (GPC) and subsequent conventional silica-gel column chromatography was automated by an on-line solvent evaporation of the GPC fraction, followed by normal-phase HPLC separation. The ternary solvent system n-hexane-toluene-acetone (88:10:2, v/v/v) was used as the mobile phase which resulted in only one HPLC fraction for all relevant analytes. The HPLC column was cleaned automatically after each sample by backflushing with polar solvents. The recoveries and reproducibilities of 35 analytes (mainly organochlorine compounds) were in the range of 77-90% and 3-7%, respectively; the high efficiency of the HPLC separation provide very clean extracts for the GC analysis. This automated clean-up technique is routinely used for the multiresidue analysis of various fat-containing food and biota samples. PMID:8777464

  19. 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

  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. Probe diffusion in phase-separated bicontinuous biopolymer gels.

    PubMed

    Wassén, Sophia; Bordes, Romain; Gebäck, Tobias; Bernin, Diana; Schuster, Erich; Lorén, Niklas; Hermansson, Anne-Marie

    2014-11-01

    Probe diffusion was determined in phase separated bicontinuous gels prepared by acid-induced gelation of the whey protein isolate-gellan gum system. The topological characterization of the phase-separated gel systems is achieved by confocal microscopy and the diffusion measurements are performed using pulsed field gradient (PFG) NMR and fluorescence recovery after photo-bleaching (FRAP). These two techniques gave complementary information about the mass transport at different time- and length scales, PFG NMR provided global diffusion rates in the gel systems, while FRAP enabled the measurements of diffusion in different phases of the phase-separated gels. The results revealed that the phase-separated gel with the largest characteristic wavelength had the fastest diffusion coefficient, while the gel with smaller microstructures had a slower probe diffusion rate. By using the diffusion data obtained by FRAP and the structural data from confocal microscopy, modelling through the lattice-Boltzmann framework was carried out to simulate the global diffusion and verify the validity of the experimental measurements. With this approach it was found that discrepancies between the two experimental techniques can be rationalized in terms of probe distribution between the different phases of the system. The combination of different techniques allowed the determination of diffusion in a phase-separated biopolymer gel and gave a clearer picture of this complex system. We also illustrate the difficulties that can arise if precautions are not taken to understand the system-probe interactions. PMID:25189146

  2. 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

  3. 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.

  4. Creating coordination-based cavities in a multiresponsive supramolecular gel.

    PubMed

    Wei, Shi-Chao; Pan, Mei; Fan, Yuan-Zhong; Liu, Haoliang; Zhang, Jianyong; Su, Cheng-Yong

    2015-05-11

    Creating cavities in varying levels, from molecular containers to macroscopic materials of porosity, have long been motivated for biomimetic or practical applications. Herein, we report an assembly approach to multiresponsive supramolecular gels by integrating photochromic metal-organic cages as predefined building units into the supramolecular gel skeleton, providing a new approach to create cavities in gels. Formation of discrete O-Pd2 L4 cages is driven by coordination between Pd(2+) and a photochromic dithienylethene bispyridine ligand (O-PyFDTE). In the presence of suitable solvents (DMSO or MeCN/DMSO), the O-Pd2 L4 cage molecules aggregate to form nanoparticles, which are further interconnected through supramolecular interactions to form a three-dimensional (3D) gel matrix to trap a large amount of solvent molecules. Light-induced phase and structural transformations readily occur owing to the reversible photochromic open-ring/closed-ring isomeric conversion of the cage units upon UV/visible light radiation. Furthermore, such Pd2 L4 cage-based gels show multiple reversible gel-solution transitions when thermal-, photo-, or mechanical stimuli are applied. Such supramolecular gels consisting of porous molecules may be developed as a new type of porous materials with different features from porous solids. PMID:25876958

  5. Gels composed of sodium-aluminium silicate, lake magadi, kenya.

    PubMed

    Eugster, H P; Jones, B F

    1968-07-12

    Sodium-aluminum silicate gels are found in surficial 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 degrees to 82 degrees C; pH, about 9) with alkali trachyte flows and their detritus, rather than by direct precipitation. In the process, Na(2)O 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. PMID:17770594

  6. Two-dimensional gel electrophoresis: vertical isoelectric focusing.

    PubMed

    Dorri, Yaser

    2012-01-01

    Two-dimensional gel electrophoresis (2-DE) is one of the most powerful tools for separating proteins based on their size and charge. 2-DE is very useful to separate two proteins with identical molecular weights but different charges, which cannot be achieved with just sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Here, a simpler and easier version of 2-DE is presented which is also faster than all the currently available techniques. In this modified version of 2-DE, isoelectric focusing is carried out in the first dimension using a vertical SDS-PAGE apparatus. Following the first-dimensional IEF, each individual lane is excised from the IEF gel and, after a 90° rotation, is inserted into a second-dimensional SDS-PAGE, which can be stained with Coomassie Brilliant Blue for protein analysis or immunoblotted for further analysis. This version of IEF can be run in less than 2 h compared to the overnight run required by O'Farrell's method. Difficult tube gel casting and gel extrusion as well as tube gel distortion are eliminated in our method. This method is simpler, faster, and inexpensive. Both dimensions can be done on the same SDS-PAGE apparatus, and up to ten samples can be run simultaneously using one gel. PMID:22585490

  7. Analytic Methods in Investigative Geometry.

    ERIC Educational Resources Information Center

    Dobbs, David E.

    2001-01-01

    Suggests an alternative proof by analytic methods, which is more accessible than rigorous proof based on Euclid's Elements, in which students need only apply standard methods of trigonometry to the data without introducing new points or lines. (KHR)

  8. Cautions Concerning Electronic Analytical Balances.

    ERIC Educational Resources Information Center

    Johnson, Bruce B.; Wells, John D.

    1986-01-01

    Cautions chemists to be wary of ferromagnetic samples (especially magnetized samples), stray electromagnetic radiation, dusty environments, and changing weather conditions. These and other conditions may alter readings obtained from electronic analytical balances. (JN)

  9. An analytic Lifshitz black hole

    E-print Network

    Balasubramanian, Koushik

    A Lifshitz point is described by a quantum field theory with anisotropic scale invariance (but not Galilean invariance). In 8, gravity duals were conjectured for such theories. We construct analytically a black hole that ...

  10. Laboratory Workhorse: The Analytical Balance.

    ERIC Educational Resources Information Center

    Clark, Douglas W.

    1979-01-01

    This report explains the importance of various analytical balances in the water or wastewater laboratory. Stressed is the proper procedure for utilizing the equipment as well as the mechanics involved in its operation. (CS)

  11. Analytical Chemistry: A Literary Approach.

    ERIC Educational Resources Information Center

    Lucy, Charles A.

    2000-01-01

    Provides an anthology of references to descriptions of analytical chemistry techniques from history, popular fiction, and film which can be used to capture student interest and frame discussions of chemical techniques. (WRM)

  12. Wednesday, March 11, 2015 Competing on Analytics

    E-print Network

    Yu, Sheng-Tao

    Perspective IHS Case Study: A Big Data Platform ­ The Foundation to Advanced Analytics Michelle Eissele Senior Business Ad Hoc Production Analytics Cyclical Jobs Linking & Integration Existing IHS Data Existing Polk Data Analytics & Visualization Outputs to Applications/ Customers Analytics Sandbox Data Analytics

  13. Visual Analytics Technology Transition Progress

    SciTech Connect

    Scholtz, Jean; Cook, Kristin A.; Whiting, Mark A.; Lemon, Douglas K.; Greenblatt, Howard

    2009-09-23

    The authors provide a description of the transition process for visual analytic tools and contrast this with the transition process for more traditional software tools. This paper takes this into account and describes a user-oriented approach to technology transition including a discussion of key factors that should be considered and adapted to each situation. The progress made in transitioning visual analytic tools in the past five years is described and the challenges that remain are enumerated.

  14. Functionalized magnetic nanoparticle analyte sensor

    DOEpatents

    Yantasee, Wassana; Warner, Maryin G; Warner, Cynthia L; Addleman, Raymond S; Fryxell, Glen E; Timchalk, Charles; Toloczko, Mychailo B

    2014-03-25

    A method and system for simply and efficiently determining quantities of a preselected material in a particular solution by the placement of at least one superparamagnetic nanoparticle having a specified functionalized organic material connected thereto into a particular sample solution, wherein preselected analytes attach to the functionalized organic groups, these superparamagnetic nanoparticles are then collected at a collection site and analyzed for the presence of a particular analyte.

  15. Structural Investigation of Supertough Polymer Gels by Small-Angle Neutron Scattering Measurement

    NASA Astrophysics Data System (ADS)

    Shibayama, Mitsuhiro

    2009-04-01

    Various types of supertough polymer gels capable of high recoverable deformability and/or with high shear/compressive moduli are investigated by small-angle neutron scattering (SANS) and mechanical measurements. These gels have unique structures, such as sliding cross-links (slide-ring gels), plane cross-links by clay platelets (nanocomposite gels; NC gels), and tetrahedral networks (tetra-PEG gels). One of the common features of these gels is that frozen inhomogeneities inherent to polymer gels are negligible. This fact, observed by SANS measurements, indicates that cross-links are introduced very effectively. Hence, the mechanical properties of these gels are expected to be well predicted by the theories of rubber elasticity. In this review, we discuss the relationship between the structure and mechanical properties of supertough polymer gels. Furthermore, we address the necessary conditions for high-performance polymer gels in the analogy of rubber.

  16. Fracture of a biopolymer gel as a viscoplastic disentanglement process

    E-print Network

    Tristan Baumberger; Christiane Caroli; David Martina

    2006-07-05

    We present an extensive experimental study of mode-I, steady, slow crack dynamics in gelatin gels. Taking advantage of the sensitivity of the elastic stiffness to gel composition and history we confirm and extend the model for fracture of physical hydrogels which we proposed in a previous paper (Nature Materials, doi:10.1038/nmat1666 (2006)), which attributes decohesion to the viscoplastic pull-out of the network-constituting chains. So, we propose that, in contrast with chemically cross-linked ones, reversible gels fracture without chain scission.

  17. Water equivalence of micelle gels for x-ray beams

    NASA Astrophysics Data System (ADS)

    Gorjiara, T.; Hill, R.; Kuncic, Z.; Bosi, S.; Baldock, C.

    2013-06-01

    Micelle gel is a radiochromic hydrogel with the potential to be used as a three dimensional (3D) radiation dosimeter. Since an ideal dosimeter should present water equivalent properties, in this study the water equivalence of two formulations of micelle gel has been investigated by calculating electron density, effective atomic number, fractional interaction probabilities, mass attenuation coefficient. The depth doses for kilovoltage and megavoltage x-ray beams have also modelled using Monte Carlo code. Based on the results of this work, micelle gels can be considered as water equivalent dosimeters.

  18. Improving gel properties of hairtail surimi by electron irradiation

    NASA Astrophysics Data System (ADS)

    Lin, Xianping; Yang, Wenge; Xu, Dalun; Jie, Zhen; Liu, Wen

    2015-05-01

    Hairtail surimi was subjected to electron irradiation for doses up to 9 kGy. At 7 kGy highest gel strength was achieved. The irradiation also increased lightness and expressible water amount. Scanning electron micrographs showed that 7 kGy irradiation made the surimi protein gel network more compact. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed the degradation of myosin heavy chain (MHC) as the irradiation dose increased, particularly at the 7 and 9 kGy doses. Radiation processing may become a new effective tool in surimi production.

  19. Theory and experiment at the sol-gel phase transition

    NASA Astrophysics Data System (ADS)

    Stauffer, D.

    1981-03-01

    Many physicists believe that the gel-sol phase transition for branching polymers is described by percolation theory, as far as critical phenomena are concerned. But in chemistry most researchers believe theories of the Flory-Stockmayer type which neglect cyclic bonds. The talk is a general review of the predictions by competing theories and of relevant experimental results. For example, if the gel fraction G and the weight-average molecular weight M are measured in the gel phase, then close to the phase transition one expects M ? G1-?, where ? = 2 in “chemistry” and ? ? 5 in “physics”. The reasons why chemistry mistrusts physics are reviewed.

  20. Sol-gel processing with inorganic metal salt precursors

    DOEpatents

    Hu, Zhong-Cheng

    2004-10-19

    Methods for sol-gel processing that generally involve mixing together an inorganic metal salt, water, and a water miscible alcohol or other organic solvent, at room temperature with a macromolecular dispersant material, such as hydroxypropyl cellulose (HPC) added. The resulting homogenous solution is incubated at a desired temperature and time to result in a desired product. The methods enable production of high quality sols and gels at lower temperatures than standard methods. The methods enable production of nanosize sols from inorganic metal salts. The methods offer sol-gel processing from inorganic metal salts.

  1. Gel Electrophoresis of Gold-DNA Nano-Conjugates

    SciTech Connect

    Pellegrino, T.; Sperling, R.A.; Alivisatos, A.P.; Parak, W.J.

    2006-01-10

    Single stranded DNA of different lengths and different amounts was attached to colloidal phosphine stabilized Au nanoparticles. The resulting conjugates were investigated in detail by a gel electrophoresis study based on 1200 gels. We demonstrate how these experiments help to understand the binding of DNA to Au particles. In particular we compare specific attachment of DNA via gold-thiol bonds with nonspecific adsorption of DNA. The maximum number of DNA molecules that can be bound per particle was determined. We also compare several methods to used gel electrophoresis for investigating the effective diameter of DNA-Au conjugates, such as using a calibration curve of particles with known diameters and Ferguson plots.

  2. 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.

  3. Tensile Properties of Poly (N-vinyl caprolactam) Gels

    NASA Technical Reports Server (NTRS)

    Morgret, Leslie D.; Hinkley, Jeffrey A.

    2004-01-01

    N-vinyl caprolactam was copolymerized with ethylene glycol dimethacrylate using a free-radical initiator in alcohol/water solution. The resulting gels were thermally-responsive in water, undergoing an approximate fivefold reversible volume shrinkage between room temperature and ca. 50 C. Tensile testing showed that the stress-strain behavior was qualitatively different in the collapsed state above the temperature-induced transition. At the higher temperature, gels were stiffer, more ductile, and showed greater time dependence. Implications for the design of gel actuators are briefly discussed.

  4. A systematic study of field inversion gel electrophoresis.

    PubMed Central

    Heller, C; Pohl, F M

    1989-01-01

    The mobilities of oligomers of phage lambda DNA and of yeast chromosomes in agarose gels during field inversion gel electrophoresis (FIGE) were measured at different pulse times and electric fields. Also the ratios between forward and backward pulse times and/or field gradients were varied. The problem of 'band inversion' during FIGE, leading to an ambiguity in the mobility of large DNA fragments, was solved by using two dimensional gel electrophoresis with different parameters in the first and second dimension. The results are compared with those obtained with other pulsed electrophoresis systems and with a theoretical model. Images PMID:2528121

  5. Note: A gel based imaging technique of the iridocorneal angle for evaluation of angle-closure glaucoma

    NASA Astrophysics Data System (ADS)

    Shinoj, V. K.; Murukeshan, V. M.; Baskaran, M.; Aung, T.

    2014-06-01

    Noninvasive medical imaging techniques have high potential in the field of ocular imaging research. Angle closure glaucoma is a major disease causing blindness and a possible way of detection is the examination of the anterior chamber angle in eyes. Here, a simple optical method for the evaluation of angle-closure glaucoma is proposed and illustrated. The light propagation from the region associated with the iridocorneal angle to the exterior of eye is considered analytically. The design of the gel assisted probe prototype is carried out and the imaging of iridocorneal angle is performed on an eye model.

  6. 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.

  7. 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.

  8. Synthesis of high-surface-area titanium dioxide by sol-gel process for DSSC

    NASA Astrophysics Data System (ADS)

    Wahyuningsih, S.; Ramelan, A. H.; Juliana, G.; Khoirunisa, A. R.; Rahardjo, S. B.; Pramono, E.; Suharyana, S.; Suryana, R.; Supriyanto, A.

    2014-05-01

    Mesoporous TiO2 material was synthesized from dissolution ilmenite as well as from titanium chloride precursor via a sol-gel process in acidic aqueous solution. The properties of these materials were characterized with several analytical techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), wide angle X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis, and Barrett-Joyner-Halenda (BJH) analysis. The mesoporous TiO2 materials calcinated at various temperatures were found to have high value surface areas. The photovoltaic of photo-anode build from the mesoporous TiO2 was characterized with I-V Keitley Multimeter, and it was found that photovoltaics fabricated using the mesoporous TiO2 have a good performance. Such a high photovoltaic activity is explained with large surface area and small crystal size.

  9. Molecular analysis of chromosomal rearrangements using pulsed field gel electrophoresis and somatic cell hybrids

    SciTech Connect

    Davis, L.M. )

    1991-01-01

    Many human genetic diseases, including some cancers, are characterized by consistent chromosome abnormalities, such as deletions and translocations. Analyses of these mutations often prove crucial to the eventual cloning and characterization of the gene(s) responsible for the disease. Two methods for analyzing these chromosome abnormalities have been developed in recent years: somatic cell hybridization and pulsed field gel electrophoresis (PFGE). Somatic cell hybridization is a technique for segregating an aberrant chromosome from its normal homologue in a cell derived from an unrelated species, which is usually a rodent. Demonstrations of these analytic techniques are presented, using as an example chromosomal abnormalities involving human chromosome band 11p13, the locus for the Wilms' tumor, aniridia, genitourinary abnormality, and mental retardation (WAGR) syndrome.

  10. Proteomic profiling of the mesenteric lymph after hemorrhagic shock: Differential gel electrophoresis and mass spectrometry analysis

    PubMed Central

    2011-01-01

    Experiments show that upon traumatic injury the composition of mesenteric lymph changes such that it initiates an immune response that can ultimately result in multiple organ dysfunction syndrome (MODS). To identify candidate protein mediators of this process we carried out a quantitative proteomic study on mesenteric lymph from a well characterized rat shock model. We analyzed three animals using analytical 2D differential gel electrophoresis. Intra-animal variation for the majority of protein spots was minor. Functional clustering of proteins revealed changes arising from several global classes that give novel insight into fundamental mechanisms of MODS. Mass spectrometry based proteomic analysis of proteins in mesenteric lymph can effectively be used to identify candidate mediators and loss of protective agents in shock models. PMID:21906351

  11. Visual Analytics at the Pacific Northwest

    E-print Network

    makes big, complex data useful through skillful visual design, compelling interaction, sound analytic AND TECHNOLOGIES PNNL creates interactive analytical environments that address dynamically changing data, allowing; create categories and correlations of data types; and more. PNNL has deployed visual analytics

  12. Laser microbeam CT scanning of dosimetry gels

    NASA Astrophysics Data System (ADS)

    Maryanski, Marek J.; Ranade, Manisha K.

    2001-06-01

    A novel design of an optical tomographic scanner is described that can be used for 3D mapping of optical attenuation coefficient within translucent cylindrical objects with spatial resolution on the order of 100 microns. Our scanner design utilizes the cylindrical geometry of the imaged object to obtain the desired paths of the scanning light rays. A rotating mirror and a photodetector are placed at two opposite foci of the translucent cylinder that acts as a cylindrical lens. A He-Ne laser beam passes first through a focusing lens and then is reflected by the rotating mirror, so as to scan the interior of the cylinder with focused and parallel paraxial rays that are subsequently collected by the photodetector to produce the projection data, as the cylinder rotates in small angle increments between projections. Filtered backprojection is then used to reconstruct planar distributions of optical attenuation coefficient in the cylinder. Multiplanar scans are used to obtain a complete 3D tomographic reconstruction. Among other applications, the scanner can be used in radiation therapy dosimetry and quality assurance for mapping 3D radiation dose distributions in various types of tissue-equivalent gel phantoms that change their optical attenuation coefficients in proportion to the absorbed radiation dose.

  13. Elastomeric Photopolymers: Shaping Polymer Gels with Light

    NASA Astrophysics Data System (ADS)

    Kornfield, Julia

    2008-03-01

    Polymer gels that possess a latent ability to change shape, which can be triggered in a spatially resolved manner using light---``elastomeric photopolymers''---have been developed to meet the need for materials that can be reshaped without direct contact, e.g., to non-invasively adjust an implanted lens in the human eye. The physics of diffusion and swelling in elastomers are applied to create a transparent silicone suitable for making a foldable intraocular lens that can be reshaped using near ultraviolet light. A crosslinked silicone matrix dictates the initial shape of the lens, while ``macromers''--short silicone chains with polymerizable end groups—and photoinitiator enable shape adjustment using light: polymerization of the macromer in the irradiated regions, followed by diffusion of free macromer causes local swelling. To predict shape change directly from irradiation profile, a theoretical treatment is presented that captures 1. shape change with no external forces, 2. coupling between diffusion and deformation, and 3. connection between thermodynamics, constitutive equations and equations of motion. Using continuum mechanics complemented with thermodynamics within the auspices of the finite element method, we develop a steady-state model which successfully captures the coupling between diffusion and deformation. Parameter values are drawn from our prior experimental studies of the mechanical properties, equilibrium swelling, penetrant diffusivities and interaction parameters in systematically varied polydimethylsiloxane (PDMS) networks and acrylate endcapped PDMS macromers. Preliminary computational studies show qualitative agreement with experimentally observed phenomena.

  14. Strain-induced alignment in collagen gels

    E-print Network

    D. Vader; A. Kabla; D. Weitz; L. Mahadevan

    2009-07-10

    Collagen is the most abundant extracellular-network-forming protein in animal biology and is important in both natural and artificial tissues, where it serves as a material of great mechanical versatility. This versatility arises from its almost unique ability to remodel under applied loads into anisotropic and inhomogeneous structures. To explore the origins of this property, we develop a set of analysis tools and a novel experimental setup that probes the mechanical response of fibrous networks in a geometry that mimics a typical deformation profile imposed by cells in vivo. We observe strong fiber alignment and densification as a function of applied strain for both uncrosslinked and crosslinked collagenous networks. This alignment is found to be irreversibly imprinted in uncrosslinked collagen networks, suggesting a simple mechanism for tissue organization at the microscale. However, crosslinked networks display similar fiber alignment and the same geometrical properties as uncrosslinked gels, but with full reversibility. Plasticity is therefore not required to align fibers. On the contrary, our data show that this effect is part of the fundamental non-linear properties of fibrous biological networks.

  15. Sol-gel synthesis of manganese oxides

    SciTech Connect

    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{sub 4} (A = Li, Na, K, NH{sub 4}, N(CH{sub 3}){sub 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{sup +}. Ammonium permanganates lead to the formation of {alpha}- or {gamma}-Mn{sub 2}O{sub 3} while AMnO{sub 2} mixed oxides are obtained at high temperature when A = Li, Na, K. Other crystalline phases such as LiMn{sub 2}O{sub 4} or Na{sub 0.7}MnO{sub 2} are also formed at lower temperature around 500{degree}C. Oxidation of these mixed oxides into sulfuric acid lead to the formation of {lambda}- or {delta}-MnO{sub 2} while A{sup +} and Mn{sup 2+} ions are released into the solution. Such manganese dioxides could be good candidates for making reversible cathodes in nonaqueous lithium batteries.

  16. Micropatterning of bioactive self-assembling gels

    PubMed Central

    Mata, Alvaro; Hsu, Lorraine; Capito, Ramille; Aparicio, Conrado; Henrikson, Karl

    2009-01-01

    Microscale topographical features have been known to affect cell behavior. An important target in this area is to integrate top down techniques with bottom up self-assembly to create three-dimensional (3D) patterned bioactive mimics of extracellular matrices. We report a novel approach toward this goal and demonstrate its use to study the behavior of human mesenchymal stem cells (hMSCs). By incorporating polymerizable acetylene groups in the hydrophobic segment of peptide amphiphiles (PAs), we were able to micro-pattern nanofiber gels of these bioactive materials. PAs containing the cell adhesive epitope arginine–glycine–aspartic acid–serine (RGDS) were allowed to self-assemble within microfabricated molds to create networks of either randomly oriented or aligned ~30 nm diameter nanofiber bundles that were shaped into topographical patterns containing holes, posts, or channels up to 8 ?m in height and down to 5 ?m in lateral dimensions. When topographical patterns contained nanofibers aligned through flow prior to gelation, the majority of hMSCs aligned in the direction of the nanofibers even in the presence of hole microtextures and more than a third of them maintained this alignment when encountering perpendicular channel microtextures. Interestingly, in topographical patterns with randomly oriented nanofibers, osteoblastic differentiation was enhanced on hole microtextures compared to all other surfaces. PMID:20047022

  17. Sol-gel-derived percolative copper film

    SciTech Connect

    Szu Sungping Cheng, C.-L.

    2008-10-02

    Cu-SiO{sub 2} films were prepared by the sol-gel method. Two-dimensional fractal copper films were formed after the films were thermally treated in reducing atmosphere. dc resistances of the films decrease 12 orders of magnitude as the content of copper increases from 70 to 80 mol%. During the resistance measurement under argon atmosphere, samples showed a sharp increase or decrease of resistance at a transition temperature which is ascribed to the oxidation of Cu into CuO. The oxidation was also observed in the in situ high temperature X-ray diffraction under vacuum condition. The evolution of the morphology of the films was studied by scanning electron microscopy. As the content of copper increases, the forms of copper particles change from discrete to aggregate then to interconnecting. The coverage coefficients of the copper range from 23 to 55% and the fractal dimensions range from 1.65 to 1.77. The percolation thresholds for the coverage coefficient and the fractal dimension are about 33% and 1.71, respectively, which corresponds to the sample containing 72.5 mol% of Cu.

  18. A Biophysical Analysis of the Ocr Protein Gel 

    E-print Network

    Higham, Richard G

    2007-01-01

    Ocr is unusual among proteins in its ability to form a transparent gel at high ammonium sulphate concentrations. This transition was investigated using a combination of spectroscopic, microscopic and rheological techniques. ...

  19. Inhibition of collagenase and metalloproteinases by aloins and aloe gel.

    PubMed

    Barrantes, Esther; Guinea, María

    2003-01-01

    The effects of Aloe barbadensis gel and aloe gel constituents on the activity of microbial and human metalloproteinases have been investigated. Clostridium histolyticum collagenase (ChC) results dose-dependently inhibited by aloe gel and the activity-guided fractionation led to an active fraction enriched in phenolics and aloins. Aloins have been shown to be able to bind and to inhibit ChC reversibly and non-competitively. Aloe gel and aloins are also effective inhibitors of stimulated granulocyte matrix metalloproteinases (MMPs). The remarkable structural resemblances between aloins and the pharmacophore structure of inhibitory tetracyclines, suggest that the inhibitory effects of aloins are via an interaction between the carbonyl group at C(9) and an adjacent hydroxyl group of anthrone (C(1) or C(8)) at the secondary binding site of enzyme, destabilizing the structure of granulocyte MMPs. PMID:12479983

  20. Oxidizer gels for detoxification of chemical and biological agents

    DOEpatents

    Hoffman, Dennis M. (Livermore, CA); McGuire, Raymond R. (Brentwood, CA)

    2002-01-01

    A gel composition containing oxidizing agents and thickening or gelling agents is used to detoxify chemical and biological agents by application directly to a contaminated area. The gelling agent is a colloidal material, such as silica, alumina, or alumino-silicate clays, which forms a viscous gel that does not flow when applied to tilted or contoured surfaces. Aqueous or organic solutions of oxidizing agents can be readily gelled with less than about 30% colloidal material. Gel preparation is simple and suitable for field implementation, as the gels can be prepared at the site of decontamination and applied quickly and uniformly over an area by a sprayer. After decontamination, the residue can be washed away or vacuumed up for disposal.