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1

Analytical Ultracentrifugation: Sedimentation Velocity and Sedimentation Equilibrium  

PubMed Central

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

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

2009-01-01

2

Improved measurement of the rotor temperature in analytical ultracentrifugation.  

PubMed

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

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

2014-04-15

3

Analytical Ultracentrifugation as a Tool for Studying Protein Interactions  

PubMed Central

The last two decades have led to significant progress in the field of analytical ultracentrifugation driven by instrumental, theoretical, and computational methods. This review will highlight key developments in sedimentation equilibrium (SE) and sedimentation velocity (SV) analysis. For SE, this includes the analysis of tracer sedimentation equilibrium at high concentrations with strong thermodynamic non-ideality, and for ideally interacting systems the development of strategies for the analysis of heterogeneous interactions towards global multi-signal and multi-speed SE analysis with implicit mass conservation. For SV, this includes the development and applications of numerical solutions of the Lamm equation, noise decomposition techniques enabling direct boundary fitting, diffusion deconvoluted sedimentation coefficient distributions, and multi-signal sedimentation coefficient distributions. Recently, effective particle theory has uncovered simple physical rules for the co-migration of rapidly exchanging systems of interacting components in SV. This has opened new possibilities for the robust interpretation of the boundary patterns of heterogeneous interacting systems. Together, these SE and SV techniques have led to new approaches to study macromolecular interactions across the entire the spectrum of affinities, including both attractive and repulsive interactions, in both dilute and highly concentrated solutions, which can be applied to single-component solutions of self-associating proteins as well as the study of multi-protein complex formation in multi-component solutions. PMID:23682298

2013-01-01

4

USE OF SHORT ANALYTICAL ULTRACENTRIFUGATION RUNS FOR THE ISOPYCNIC DETERMINATION OF FOOT-AND-MOUTH DISEASE  

E-print Network

USE OF SHORT ANALYTICAL ULTRACENTRIFUGATION RUNS FOR THE ISOPYCNIC DETERMINATION OF FOOT-AND-MOUTH de l'état d'équilibre a été envisagée, mais a été écartée- Isopycnic analysis of Foot and Mouth

Paris-Sud XI, Université de

5

Determination of molecular weights of humic substances by analytical (UV scanning) ultracentrifugation  

NASA Astrophysics Data System (ADS)

Samples of peat humic acid (PHA) and surface water humic (WBHA) and fulvic (WBFA) acids have been extracted from Whitray Beck in North Yorkshire, U.K. The molecular weights of the extracts have been investigated by sedimentation equilibrium using an analytical ultracentrifuge equipped with a UV scanning system. The system allows measurements to be made at low concentrations of humic substances, comparable to those existing in natural humic-rich water. A method is described for correcting UV scanning data for changes in the optical properties of the materials with changing molecular weight. Measurements have also been made on reference samples of Suwannee river humic (SRHA) and fulvic (SRFA) acids from the International Humic Substances Society (IHSS). The weight-average molecular weights of the extracted samples range from approximately 2000 to 17000 and follow a series PHA > WBHA > WBFA. Apparent specific volumes of these materials were in a range from 0.45 to 0.58 cm 3 g -1 as measured by digital densimetry. All the samples studied were analysed by gel filtration, but the molecular weights determined by this method based on a globular protein calibration are not in good accord with the absolute determinations by the sedimentation-equilibrium technique. The molecular weight of the SRHA determined by sedimentation equilibrium is in good agreement with that reported by BECKETT (1987) et al., based on flow field-flow fractionation.

Reid, Patrick M.; Wilkinson, Alan E.; Tipping, Edward; Jones, Malcolm N.

1990-01-01

6

Determination of molecular weights of humic substances by analytical (UV scanning) ultracentrifugation  

SciTech Connect

Samples of peat humic acid (PHA) and surface water humic (WBHA) and fulvic (WBFA) acids have been extracted from Whitray Beck in North Yorkshire, U.K. The molecular weights of the extracts have been investigated by sedimentation equilibrium using an analytical ultracentrifuge equipped with a UV scanning system. The system allows measurements to be made at low concentrations of humic substances, comparable to those existing in natural humic-rich water. A method is described for correcting UV scanning data for changes in the optical properties of the materials with changing molecular weight. Measurements have also been made on reference samples of Suwannee river humic (SRHA) and fulvic (SRFA) acids from the International Humic Substances Society (IHSS). The weight-average moleuclar weights of the extracted samples range from approximately 2,000 to 17,000 and follow a series PHA > WBHA > WBFA. Apparent specific volumes of these materials were in a range from 0.45 to 0.58 cm{sup 3} g{sup {minus}1} as measured by digital densimetry. Al the samples studied were analysed by gel filtration, but the molecular weights determined by this method based on a globular protein calibration are not in good accord with the absolute determinations by the sedimentation-equilibrium technique. The molecular weight of the SRHA determined by sedimentation equilibrium is in good agreement with that reported by BECKETT (1987) et al., based on flow field-flow fractionation.

Reid, P.M.; Wilkinson, A.E.; Tipping, E.; Jones, M.N. (Univ. of Manchester (England) Freshwater Biological Association, Ambleside, Cumbria (England))

1990-01-01

7

On computational approaches for size-and-shape distributions from sedimentation velocity analytical ultracentrifugation  

Microsoft Academic Search

Sedimentation velocity analytical ultracentrifugation has become a very popular technique to study size distributions and\\u000a interactions of macromolecules. Recently, a method termed two-dimensional spectrum analysis (2DSA) for the determination of\\u000a size-and-shape distributions was described by Demeler and colleagues (Eur Biophys J 2009). It is based on novel ideas conceived for fitting the integral equations of the size-and-shape distribution to experimental

Peter Schuck

2010-01-01

8

On computational approaches for size-and-shape distributions from sedimentation velocity analytical ultracentrifugation  

PubMed Central

Sedimentation velocity analytical ultracentrifugation has become a very popular technique to study size distributions and interactions of macromolecules. Recently, a method termed two-dimensional spectrum analysis (2DSA) for the determination of size-and-shape distributions was described by Demeler and colleagues (Eur Biophys J 2009). It is based on novel ideas conceived for fitting the integral equations of the size-and-shape distribution to experimental data, illustrated with an example but provided without proof of the principle of the algorithm. In the present work, we examine the 2DSA algorithm by comparison with the mathematical reference frame and simple well-known numerical concepts for solving Fredholm integral equations, and test the key assumptions underlying the 2DSA method in an example application. While the 2DSA appears computationally excessively wasteful, key elements also appear to be in conflict with mathematical results. This raises doubts about the correctness of the results from 2DSA analysis. PMID:19806353

2009-01-01

9

Tools for the Quantitative Analysis of Sedimentation Boundaries Detected by Fluorescence Optical Analytical Ultracentrifugation  

PubMed Central

Fluorescence optical detection in sedimentation velocity analytical ultracentrifugation allows the study of macromolecules at nanomolar concentrations and below. This has significant promise, for example, for the study of systems of high-affinity protein interactions. Here we describe adaptations of the direct boundary modeling analysis approach implemented in the software SEDFIT that were developed to accommodate unique characteristics of the confocal fluorescence detection system. These include spatial gradients of signal intensity due to scanner movements out of the plane of rotation, temporal intensity drifts due to instability of the laser and fluorophores, and masking of the finite excitation and detection cone by the sample holder. In an extensive series of experiments with enhanced green fluorescent protein ranging from low nanomolar to low micromolar concentrations, we show that the experimental data provide sufficient information to determine the parameters required for first-order approximation of the impact of these effects on the recorded data. Systematic deviations of fluorescence optical sedimentation velocity data analyzed using conventional sedimentation models developed for absorbance and interference optics are largely removed after these adaptations, resulting in excellent fits that highlight the high precision of fluorescence sedimentation velocity data, thus allowing a more detailed quantitative interpretation of the signal boundaries that is otherwise not possible for this system. PMID:24204779

Zhao, Huaying; Casillas, Ernesto; Shroff, Hari; Patterson, George H.; Schuck, Peter

2013-01-01

10

Determination of the Lateral Dimension of Graphene Oxide Nanosheets Using Analytical Ultracentrifugation.  

PubMed

In this paper, a method to determine the lateral dimensions of 2D nanosheets directly in suspension by analytical ultracentrifugation (AUC) is shown. The basis for this study is a well-characterized and stable dispersion of graphene oxide (GO) monolayers in water. A methodology is developed to correlate the sedimentation coefficient distribution measured by AUC with the lateral size distribution of the 2D GO nanosheets obtained from atomic force microscopy (AFM). A very high accuracy can be obtained by virtue of counting several thousand sheets, thereby minimizing any coating effects or statistical uncertainties. The AFM statistics are further used to fit the lateral size distribution obtained from the AUC to determine the unknown hydrodynamic sheet thickness or density. It is found that AUC can derive nanosheet diameter distributions with a relative error of the mean sheet diameter of just 0.25% as compared to the AFM analysis for 90 mass% of the particles in the distribution. The standard deviation of the size-dependent error for the total distribution is found to be 3.25%. Based on these considerations, an expression is given to calculate the cut size of 2D nanosheets in preparative centrifugation experiments. PMID:25201557

Walter, Johannes; Nacken, Thomas J; Damm, Cornelia; Thajudeen, Thaseem; Eigler, Siegfried; Peukert, Wolfgang

2014-09-01

11

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

PubMed

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

Krayukhina, Elena; Uchiyama, Susumu; Fukui, Kiichi

2012-09-29

12

Analysis of High Affinity Self-Association by Fluorescence Optical Sedimentation Velocity Analytical Ultracentrifugation of Labeled Proteins: Opportunities and Limitations  

PubMed Central

Sedimentation velocity analytical ultracentrifugation (SV) is a powerful first-principle technique for the study of protein interactions, and allows a rigorous characterization of binding stoichiometry and affinities. A recently introduced commercial fluorescence optical detection system (FDS) permits analysis of high-affinity interactions by SV. However, for most proteins the attachment of an extrinsic fluorophore is an essential prerequisite for analysis by FDS-SV. Using the glutamate receptor GluA2 amino terminal domain as a model system for high-affinity homo-dimerization, we demonstrate how the experimental design and choice of fluorescent label can impact both the observed binding constants as well as the derived hydrodynamic parameter estimates for the monomer and dimer species. Specifically, FAM (5,6-carboxyfluorescein) was found to create different populations of artificially high-affinity and low-affinity dimers, as indicated by both FDS-SV and the kinetics of dimer dissociation studied using a bench-top fluorescence spectrometer and Frster Resonance Energy Transfer. By contrast, Dylight488 labeled GluA2, as well as GluA2 expressed as an EGFP fusion protein, yielded results consistent with estimates for unlabeled GluA2. Our study suggests considerations for the choice of labeling strategies, and highlights experimental designs that exploit specific opportunities of FDS-SV for improving the reliability of the binding isotherm analysis of interacting systems. PMID:24358283

Zhao, Huaying; Lomash, Suvendu; Glasser, Carla; Mayer, Mark L.; Schuck, Peter

2013-01-01

13

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

PubMed Central

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

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

2009-01-01

14

Damaged starch characterisation by ultracentrifugation  

Microsoft Academic Search

The relative molecular size distributions of a selection of starches (waxy maize, pea and maize) that had received differing amounts of damage from ball milling (as quantified by susceptibility to ?-amylase) were compared using analytical ultracentrifugation. Starch samples were solubilised in 90% dimethyl sulfoxide, and relative size distributions were determined in terms of the apparent distribution of sedimentation coefficients g?(s)

Richard F. Tester; Trushar Patel; Stephen E. Harding

2006-01-01

15

The dimeric and trimeric solution structures of the multidomain complement protein properdin by X-ray scattering, analytical ultracentrifugation and constrained modelling.  

PubMed

Properdin regulates the alternative pathway of the complement system of immune defence by stabilising the C3 convertase complex. It contains six thrombospondin repeat type I (TSR-1 to TSR-6) domains and an N-terminal domain. Properdin exists as either a dimer, trimer or tetramer. In order to determine the solution structure of multiple TSR domains, the molecular structures of dimeric and trimeric properdin were studied by X-ray scattering and analytical ultracentrifugation. Guinier analyses showed that the dimer and trimer have radii of gyration R(G) values of 7.5 nm and 10.3 nm, respectively, and cross-sectional radii of gyration R(XS) values of 1.3 nm and 1.5 nm, respectively. Distance distribution functions showed that the maximum lengths of the dimer and trimer were 25 nm and 30 nm, respectively. Analytical ultracentrifugation gave sedimentation coefficients of 5.1S and 5.2S for the dimer and trimer forms, respectively. Homology models for the TSR domains were constructed using the crystal structure of the TSP-2 and TSP-3 domains in human thrombospondin as templates. Properdin could be represented by seven TSR domains, not six as believed, since the crystal structure determined for TSP-2 and TSP-3 showed that the N-terminal domain (TSR-0) could be represented by a truncated TSR domain with the same six conserved Cys residues found in TSR-1 to TSR-6. Automated constrained molecular modelling revealed the solution conformations of multiple TSR domains in properdin at medium resolution. The comparison of 3125 systematically generated conformational models for the trimer with the X-ray data showed that good curve fits could be obtained by assuming that the linker between adjacent TSR domains possessed limited flexibility. Good trimer models correspond to partially collapsed triangular structures, and extended triangular shapes do not fit the data. The corresponding 3125 models for the dimer revealed a similar outcome in which a partially collapsed TSR structure gave good fits. The models account for the effect of mutations that cause properdin deficiencies, and suggest that the biologically active TSR-4, TSR-5 and TSR-6 domains are exposed for protein-protein interactions. The role of the other TSR domains in properdin may be to act as spacers to make TSR-4, TSR-5 and TSR-6 accessible for function. PMID:15491616

Sun, Zhe; Reid, Kenneth B M; Perkins, Stephen J

2004-11-01

16

Extended and flexible domain solution structure of the extracellular matrix protein anosmin-1 by X-ray scattering, analytical ultracentrifugation and constrained modelling.  

PubMed

Kallmann's syndrome corresponds to a loss of sense of smell and hypogonadotrophic hypogonadism. Defects in anosmin-1 result in the X-linked inherited form of Kallmann's syndrome. Anosmin-1 is an extracellular matrix protein comprised of an N-terminal, cysteine-rich (Cys-box) domain and a whey acidic protein-like (WAP) domain, followed by four fibronectin type III (FnIII) domains. The solution structures of recombinant proteins containing the first three domains (PIWF1) and all six domains (PIWF4) were determined by X-ray scattering and analytical ultracentrifugation. Guinier analyses showed that PIWF1 and PIWF4 have different radii of gyration (R(G)) values of 3.1 nm and 6.7 nm, respectively, but similar cross-sectional radii of gyration (R(XS)) values of 1.5 nm and 1.9 nm, respectively. Distance distribution functions showed that the maximum lengths of PIWF1 and PIWF4 were 11 nm and 23 nm, respectively. Analytical ultracentrifugation gave sedimentation coefficients of 2.52 S and 3.55 S for PIWF1 and PIWF4, respectively. The interpretation of the scattering data by constrained modelling requires homology models for all six domains in anosmin-1. While models were already available for the WAP and FnIII domains, searches suggested the Cys-box domain may resemble the cysteine-rich region of the insulin-like growth factor receptor. Automated constrained molecular modelling based on joining the anosmin-1 domains with structurally randomised linkers resulted in 10,000 models for anosmin-1. A trial-and-error search showed that about 0.1-1.4% of these models fitted the X-ray data. The best models showed that the three domains and six domains in PIWF1 and PIWF4, respectively, were extended. The inter-domain linkers in anosmin-1 could not all be extended at the same time, and there was evidence for inter-domain flexibility. Models with folded-back domain arrangements do not fit the data. These solution structures account for the known biological function of anosmin-1, in particular its ability to interact with its three macromolecular ligands. PMID:15949815

Hu, Youli; Sun, Zhe; Eaton, Julian T; Bouloux, Pierre M G; Perkins, Stephen J

2005-07-15

17

Sol-gel matrices for direct colorimetric detection of analytes  

DOEpatents

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.

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

2000-01-01

18

Sol-Gel Matrices For Direct Colorimetric Detection Of Analytes  

DOEpatents

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.

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

2002-11-26

19

Solution-based structural analysis of the decaheme cytochrome, MtrA, by small-angle X-ray scattering and analytical ultracentrifugation.  

PubMed

The potential exploitation of metal-reducing bacteria as a means for environmental cleanup or alternative fuel is an exciting prospect; however, the cellular processes that would allow for these applications need to be better understood. MtrA is a periplasmic decaheme c-type cytochrome from Shewanella oneidensis involved in the reduction of extracellular iron oxides and therefore is a critical element in Shewanella ability to engage in extracellular charge transfer. As a relatively small 333-residue protein, the heme content is surprisingly high. MtrA is believed to obtain electrons from the inner membrane-bound quinol oxidoreductase, CymA, and shuttle them across the outer membrane to MtrC, another decaheme cytochrome that directly interacts with insoluble metal oxides. How MtrA is able to perform this task is a question of interest. Here through the use of two solution-based techniques, small-angle X-ray scattering (SAXS) and analytical ultracentrifugation (AUC), we present the first structural analysis of MtrA. Our results establish that between 0.5 and 4 mg/mL, MtrA exists as a monomeric protein that is shaped like an extended molecular "wire" with a maximum protein dimension (D(max)) of 104 and a rod-like aspect ratio of 2.2 to 2.5. This study contributes to a greater understanding of how MtrA fulfills its role in the redox processes that must occur before electrons reach the outside of the cell. PMID:21838277

Firer-Sherwood, Mackenzie A; Ando, Nozomi; Drennan, Catherine L; Elliott, Sean J

2011-09-29

20

Analysis of RNA by analytical polyacrylamide gel electrophoresis.  

PubMed

Polyacrylamide gel electrophoresis (PAGE) is a powerful tool for analyzing RNA samples. Denaturing PAGE provides information on the sample composition and structural integrity of the individual RNA species. Nondenaturing gel electrophoresis allows separation of the conformers and alternatively folded RNA species. It also can be used to resolve RNA protein complexes and to detect RNA complex formation by analyzing changes in the electrophoretic mobility of the RNA. RNA can be visualized within gels by different methods depending on the nature of the detection reagent. RNA molecules can be stained with various dyes, including toluidine blue, SYBR green, and ethidium bromide. Radioactively labeled RNA molecules are visualized by autoradiography, and fluorescently labeled RNA molecules can be observed with a fluorescence scanner. Generally, gels between 0.4 and 1.5mm thick are used for analytical PAGE. Gels thinner than 1mm are fragile and thus usually are not stained but rather are used for radiolabeled RNA. The gels are dried and the radiolabeled RNA is visualized by autoradiography. PMID:24034328

Petrov, Alexey; Tsa, Albet; Puglisi, Joseph D

2013-01-01

21

Gel pad array chip for high throughput and multi-analyte microbead-based immunoassays.  

PubMed

We present here a gel pad array chip for high-throughput and multi-analyte microbead-based immunoassays. The chip is fabricated by photo-patterning of two polymeric gels, polyacrylamide gel and polyethylene glycol (PEG) gel, on a glass slide. The resulting chip consists of 40 polyacrylamide gel pad array units for the immobilization of microbeads and each gel pad array is surrounded with a PEG micropillar ring to confine the samples within the microarray. As a proof of concept, this chip was tested for quantitative immunoassays for two model cancer markers, human chorionic gonadotropin (hCG) and prostate specific antigen (PSA), in serum samples. Detection limits below the physiological threshold level for cancer diagnosis were achieved with good inter- and intra-chip reproducibility. Moreover, by using spatial encoded microbeads, simultaneous detection of both hCG and PSA on each gel pad array is achieved with single filter fluorescence imaging. This gel pad array chip is easy to use, easy to fabricate with low cost materials and minimal equipment and reusable. It could be a useful tool for common biolabs to customize their own microbead array for multi-analyte immunoassays. PMID:25463645

Zhu, Qingdi; Trau, Dieter

2015-04-15

22

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

E-print Network

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

Xiaoyi Chen; Hui-Hui Dai

2014-10-30

23

A Sedimentation Experiment Using a Preparative Ultracentrifuge  

ERIC Educational Resources Information Center

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)

Boudreau, Raymond E.; And Others

1975-01-01

24

Analytical Application of Silica Gel Modified with Didecylaminoethyl-beta-Tridecylammonium Iodide.  

PubMed

Sorption of a high molecular weight quaternary ammonium salt, didecylaminoethyl-beta-tridecylammonium iodide (DDATD) on different types of sorbents was investigated. The nature of reagent adsorption on silica gel was examined by spectroscopic and computer methods. The sorption of anionic metal complexes of cobalt, copper, zinc and manganese on silica gel modified with DDATD was studied. The possibility of recovery of cobalt and copper thiocyanate complexes and their further atomic absorption determination is shown. Modified sorbent was applied to cobalt chemiluminescence and determined in natural water and a nickel preparation (detection limit, 2 mug/l.). PMID:18966172

Zaporozhets, O A; Nadzhafova, O Y; Zubenko, A I; Sukhan, V V

1994-12-01

25

ULTRACENTRIFUGATION STUDIES OF YELLOW FEVER VIRUS  

PubMed Central

1. It was possible to study in the ultracentrifuge by optical methods the behavior of yellow fever virus particles directly in the unaltered serum from infected monkeys. 2. The virus showed an extremely high light absorption in the spectral range of 320 to 440 m, which seemed to be its intrinsic property. In a 1 cm. thickness of fluid, the small amount of virus present in unaltered infective serum absorbed about as much light (approximately 25 per cent) in the middle of this range as did all the normal serum proteins present in a combined concentration some 1000 times as great. 3. The concentration of virus in the unaltered serum was found to be of the order of 0.00005 gm. per cc. 1 cc. of a 109 dilution, which, as has been shown, may constitute a minimal infective dose for monkeys, would contain approximately 10,000 virus particles. The probability that most of the virus particles were in the inactive form is discussed. 4. In infective serum having a viscosity of 14 millipoises, the particles sediment with a blurred boundary at rates lying between approximately 18 and 30 x 1013 cm./sec./dyne. Evidence indicates that this spread is the result of an aggregation or association phenomenon. 5. Computations of size are in approximate agreement with those made from ultrafiltration studies. On the assumption that the density of the virus particle is near that of protein, its volume is computed to be at least that of a spherical particle having a diameter of 12 m. An assumed density of 1.15 gm. per cc. yields a diameter of 19 m, considering the shape as spherical. PMID:19870992

Pickels, Edward G.; Bauer, Johannes H.

1940-01-01

26

A combination of ultracentrifugation and solid-phase extraction with subsequent chromatographic analysis of ?-tocopherol in erythrocyte membranes.  

PubMed

A novel and rapid sample pre-treatment technique based on a combination of ultracentrifugation and solid-phase extraction for the determination of ?-tocopherol in human erythrocyte membranes by high-performance liquid chromatography with ultraviolet detection is presented in this work. Red blood cell samples were ultracentrifuged (288000g, 3minutes, 4C) in the presence of d-mannitol, 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid and calcium chloride. The ?-tocopherol was then extracted from the erythrocyte membranes by solid-phase extraction with n-hexane in the presence of ascorbic acid. Tocopherol acetate was used as the internal standard. The extract was dissolved in methanol and separated on themonolithic column Chromolith Performance RP-18e (100 4.6 mm) using100% methanol as the mobile phase. The absorbance of ?-tocopherol was measured at a wavelength of 295 nm. The method was validated and showed sufficient accuracy and precision, ranging from 96.4 to 100.8% and from 4.5 to 6.3%, respectively. Moreover, the developed method was applied to the determination of erythrocyte ?-tocopherol in real samples from patients. The combined ultracentrifugation and solid-phase extraction technique substantially decreased the time for the sample pre-treatment step compared to liquid-liquid extraction and could be applicable for quantitation of other analytes in erythrocyte membranes. This article is protected by copyright. All rights reserved. PMID:25476725

Plek, Ji?; Pospchalov, Na?a; Khalikova, Maria; Aufartov, Jana; Solichov, Dagmar; Kr?mov, Lenka Kujovsk; Solich, Petr

2014-12-01

27

Large-gel two-dimensional electrophoresis-matrix assisted laser desorption/ionization-time of flight-mass spectrometry: an analytical challenge for studying complex protein mixtures.  

PubMed

The large-gel two-dimensional electrophoresis (2-DE) technique, developed by Klose and co-workers over the past 25 years, provides the resolving power necessary to separate crude proteome extracts of higher eukaryotes. Matrix assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS) provides the sample throughput necessary to identify thousands of different protein species in an adequate time period. Spot excision, in situ proteolysis, and extraction of the cleavage products from the gel matrix, peptide purification and concentration as well as the mass spectrometric sample preparation are the crucial steps that interface the two analytical techniques. Today, these routines and not the mass spectrometric instrumentation determine how many protein digests can be analyzed per day per instrument. The present paper focuses on this analytical interface and reports on an integrated protocol and technology developed in our laboratory. Automated identification of proteins in sequence databases by mass spectrometric peptide mapping requires a powerful search engine that makes full use of the information contained in the experimental data, and scores the search results accordingly. This challenge is heading a second part of the paper. PMID:11565779

Nordhoff, E; Egelhofer, V; Giavalisco, P; Eickhoff, H; Horn, M; Przewieslik, T; Theiss, D; Schneider, U; Lehrach, H; Gobom, J

2001-08-01

28

Influence of fibrinogen on fibrin polymerization. Ultracentrifugation studies.  

PubMed

During the transformation of fibrinogen to fibrin, excess fibrinogen suppresses further polymerization of fibrin, thereby enabling the nascent fibrin to be transported in a soluble form in blood. The question of possible complex formation between fibrin and fibrinogen was addressed by analyzing fibrin/fibrinogen (1:20, mol/mol) mixtures in the presence of calcium ions in stable linear sucrose density gradients by ultracentrifugation at 37 degrees C. During the period of ultracentrifugation in independent experiments, 40% of desAA-fibrin and 30% of desAABB-fibrin, respectively, precipitated without the participation of fibrinogen. The desAABB-fibrin, recovered in the gradient fractions, appeared as high-molecular-weight polymers (22 S), whereas the recovered desAA-fibrin exhibited only a slight increase in molecular weight (9 S) compared to fibrinogen (8 S). In contrast to this finding, both types of fibrin were totally recovered in gradient fractions provided that fibrinogen was present in the gradient at a uniform concentration of 2 mg/ml. In addition, the presence of fibrinogen but not human serum albumin reduced the size of desAABB-fibrin polymers (17 S). However, stable fibrin-fibrinogen complexes could not be demonstrated, since cosedimentation of differently labelled desAABB-fibrin and fibrinogen was not detectable. These studies suggest a specific but weak interaction of the solubilizing fibrinogen with the soluble fibrin polymers as demonstrated by a rapid exchange of both macromolecules. PMID:4005267

Preissner, K T; Rtker, J; Selmayr, E; Fasold, H; Mller-Berghaus, G

1985-07-01

29

Analytical Study of Thermal Annealing Behaviour of Erbium Emission in Er2O3-Sol-Gel Silica Films  

E-print Network

Room-temperature 1535-nm-band photoluminescence in ~126 nm silica films (6 at. % doping), produced by spin-coating an Er2O3 and tetraethylorthosilicate sol-gel formulation on silicon substrates, was studied as a function of vacuum furnace annealing (500 to 1050 degrees C). Emission is strongly enhanced for annealing near 850 degrees C, which is shown by modeling the temperature dependence as arising from thermally-activated removal of hydroxyl ions. Suitability of such a process for silicon-based applications is discussed.

Abedrabbo, Sufian; Fiory, Anthony; 10.1088/0022-3727/44/31/315401

2012-01-01

30

Analytical separation of nonlipid water soluble substances and gangliosides from other lipids by dextran gel column chromatography  

Microsoft Academic Search

A column chromatographic procedure is reported utilizing a dextran gel (Sephadex) for the complete separation of the major\\u000a lipid classes from water-soluble nonlipids. Lipids other than gangliosides are eluted first with chloroform\\/methanol 19\\/1\\u000a saturated with water, gangliosides with chloroform\\/methanol\\/water containing acetic acid, and water-soluble nonlipids with\\u000a methanol\\/water 1\\/1. Results for adult human whole brain, grey and white matter, and normal

A. N. Siakotos; George Rouser

1965-01-01

31

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

PubMed Central

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

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

2014-01-01

32

On the general concept of buoyancy in sedimentation and ultracentrifugation  

NASA Astrophysics Data System (ADS)

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.

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

2013-08-01

33

On the general concept of buoyancy in sedimentation and ultracentrifugation.  

PubMed

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

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

2013-08-01

34

Sol-gel approach for fabrication of coated anodized titanium wire for solid-phase microextraction: highly efficient adsorbents for enrichment of trace polar analytes.  

PubMed

Nanotubular titania film was prepared in situ on titanium wire and was used as the fiber substrate for solid-phase microextraction (SPME) because of its high surface-to-volume ratio, easy preparation, and mechanical stability. Three different functional coatings, ?-cyclodextrin (?-CD), ?-cyclodextrin-co-poly(ethylenepropylene glycol) (?-CD/PEG), and polyethylene glycol (PEG)-based sorbents were chemically bonded to the nanostructured wire surface via sol-gel technology to further enhance the absorbing capability and extraction selectivity. Coupled to gas chromatography-flame ionic detection (GC-FID), the prepared SPME fibers were investigated using diverse compounds. The results indicated that the fibers showed good mechanical strength, excellent thermal stability, and wonderful capacity and selectivity to polar compounds, including polar aromatic compounds, alcohols, and ketones. Combining the superior hydrophilic property of a bonded functional molecule and the highly porous structure of a fiber coating, the prepared PEG-coated SPME fiber showed much higher adsorption affinity to ephedrine and methylephedrine than ?-CD and ?-CD/PEG fibers. The as-established PEG-coated SPME-GC analytical method provided excellent sensitivity (LODs, 0.004 and 0.001 ng mL(-1) for ephedrine and methylephedrine, respectively) and better linear range (0.01-2 000 ?g L(-1)). In addition, it has surprising repeatability and reproducibility. Finally, the present approach was used to analyze ephedrine and methylephedrine from real urine samples, and reliable results were obtained. PMID:24682230

Jia, Jing; Xu, Lili; Wang, Shuai; Wang, Licheng; Liu, Xia

2014-05-01

35

Enrichment of calcifying extracellular vesicles using density-based ultracentrifugation protocol  

PubMed Central

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 100,000g, 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

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

2014-01-01

36

Generation of high-titer viral preparations by concentration using successive rounds of ultracentrifugation  

PubMed Central

Background Viral vectors provide a method of stably introducing exogenous DNA into cells that are not easily transfectable allowing for the ectopic expression or silencing of genes for therapeutic or experimental purposes. However, some cell types, in particular bone marrow cells, dendritic cells and neurons are difficult to transduce with viral vectors. Successful transduction of such cells requires preparation of highly concentrated viral stocks, which permit a high virus concentration and multiplicity of infection (MOI) during transduction. Pseudotyping with the vesicular stomatitis virus G (VSV-G) envelope protein is common practice for both lentiviral and retroviral vectors. The VSV-G glycoprotein adds physical stability to retroviral particles, allowing concentration of virus by high-speed ultracentrifugation. Here we describe a method report for concentration of virus from large volumes of culture supernatant by means of successive rounds of ultracentrifugation into the same ultracentrifuge tube. Method Stable retrovirus producer cell lines were generated and large volumes of virus-containing supernatant were produced. We then tested the transduction ability of virus following varying rounds of concentration by ultra-centrifugation. In a second series of experiments lentivirus-containing supernatant was produced by transient transfection of 297T/17 cells and again we tested the transduction ability of virus following multiple rounds of ultra-centrifugation. Results We report being able to centrifuge VSV-G coated retrovirus for as many as four rounds of ultracentrifugation while observing an additive increase in viral titer. Even after four rounds of ultracentrifugation we did not reach a plateau in viral titer relative to viral supernatant concentrated to indicate that we had reached the maximum tolerated centrifugation time, implying that it may be possible to centrifuge VSV-G coated retrovirus even further should it be necessary to achieve yet higher titers for specific applications. We further report that VSV-G coated lentiviral particles may also be concentrated by successive rounds of ultracentrifugation (in this case four rounds) with minimal loss of transduction efficiency. Conclusion This method of concentrating virus has allowed us to generate virus of sufficient titers to transduce bone marrow cells with both retrovirus and lentivirus, including virus carrying shRNA constructs. PMID:21849073

2011-01-01

37

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

E-print Network

Nanoparticles are finding many research and industrial applications, yet their characterization remains a challenge. Their cores are often polydisperse and coated by a stabilizing shell that varies in size and composition. ...

Carney, Randy P.

38

Simultaneous Determination of Residual Saturation and Capillary Pressure Curves Utilizing the Ultracentrifuge  

Microsoft Academic Search

Residual saturation and capillary pressure curves are important for modelling reservoir and laboratory processes. Knowledge of the residual saturation curve is necessary to determine the ultimate production from a tertiary recovery process. Capillary pressure is required to interpret laboratory core floods and to describe multi-phase reservoir fluid flow. The ultracentrifuge provides a rapid means of determining capillary pressure and residual

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

1986-01-01

39

Gel Electrophoresis  

NSDL National Science Digital Library

This interactive activity from the Dolan DNA Learning Center illustrates the process of gel electrophoresis, in which DNA fragments are separated by size as they migrate at different rates through a gel matrix.

Foundation, Wgbh E.

2007-04-19

40

Proteomic analysis of normal human urinary proteins isolated by acetone precipitation or ultracentrifugation  

Microsoft Academic Search

Proteomic analysis of normal human urinary proteins isolated by acetone precipitation or ultracentrifugation.BackgroundProteomic techniques have recently become available for large-scale protein analysis. The utility of these techniques in identification of urinary proteins is poorly defined. We constructed a proteome map of normal human urine as a reference protein database by using two differential fractionated techniques to isolate the proteins.MethodsProteins were

Visith Thongboonkerd; Kenneth R. Mcleish; John M. Arthur; Jon B. Klein

2002-01-01

41

A density gradient ultracentrifugal procedure for the isolation of the major lipoprotein classes from human serum  

Microsoft Academic Search

A density gradient ultracentrifugal procedure is described for the rapid and reproducible isolation of the major lipoprotein classes, VLDL, LDL, HDb, and HDL3, from human serum. A step gradient is constructed from four NaCUKBr solutions varying in density from 1.006 to 1.24 g\\/ml and from 3 ml of serum adjusted to d 1.2 1 glml. Separation is achieved after a

M. John Chapman; Sonia Goldstein; Dominique Lagrange; P. Michel

42

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

Microsoft Academic Search

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

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

1972-01-01

43

Raman spectroscopy of blue gel pen inks  

Microsoft Academic Search

Raman spectroscopy is becoming a tool of major importance in forensic science. It is a non-invasive, non-destructive analytical method allowing samples to be examined without any preparation. This paper demonstrates the use of the technique as a general tool for gel pen inks analysis. For this purpose, 55 blue gel pen inks, of different brands and models representative of gel

Williams David Mazzella; Patrick Buzzini

2005-01-01

44

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

NASA Astrophysics Data System (ADS)

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.

Arnquist, Isaac J.; Holcombe, James A.

2012-10-01

45

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

E-print Network

. 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

Wenseleers, Wim

46

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

E-print Network

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.

Piazza, Roberto; Secchi, Eleonora; Parola, Alberto

2012-01-01

47

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

E-print Network

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.

Roberto Piazza; Stefano Buzzaccaro; Eleonora Secchi; Alberto Parola

2012-05-28

48

Gel Electrophoresis  

NSDL National Science Digital Library

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

Yu, Julie

2007-01-01

49

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

50

AN IMPROVED AIR-DRIVEN TYPE OF ULTRACENTRIFUGE FOR MOLECULAR SEDIMENTATION  

PubMed Central

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 2C. 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

Bauer, Johannes H.; Pickels, Edward G.

1937-01-01

51

Temperature responsive gel displays  

NASA Astrophysics Data System (ADS)

Synthesis and application of engineered surface patterns on environmentally responsive polymer gels are reported here. N-isopropylacrylamide (NIPA) gel was deposited on the masked-surface of an acrylamide gel using photo-initiated polymerization method. The pattern of the NIPA deposited area can be either visible or invisible by simply switching temperature above or below the low critical solution temperature (LCST) of the NIPA gel. Such gels can be used as displays.

Zheng, Yindong; Wang, Changjie; Hu, Zhibing; Li, Yong

1999-10-01

52

An efficient process for the purification of helper-dependent adenoviral vector and removal of helper virus by iodixanol ultracentrifugation.  

PubMed

The preparation of large amount of purified helper-dependent adenoviral vector material is hampered by the lack of development of downstream processes with proven records on separation and recovery efficiencies. In order to facilitate the use of clinical-grade helper-dependent virus material for large-scale in vivo studies, a three-step purification scheme consisting of (1) an anion-exchange chromatography for initial capturing of virus, (2) a shallow iodixanol density gradient ultracentrifugation for the removal of helper virus from helper-dependent virus, and (3) a size-exclusion chromatography for the removal of iodixanol and residual protein contaminants as a polishing step was developed. The use of a fast iodixanol density ultracentrifugation step was highly effective in separating infectious helper-dependent virus from contaminating helper virus. The overall downstream processing scheme gave 80% infectious particle yield. The contamination ratio of helper virus in the helper-dependent virus preparation are reduced from 2.57 to 0.03% corresponding to a reduction of helper virus by factors of 85 by two iodixanol purification steps. It was also demonstrated that size-exclusion chromatography is an excellent step for the removal of iodixanol and polishing of the final helper-dependent virus preparation. PMID:20116403

Dormond, Edwige; Chahal, Parminder; Bernier, Alice; Tran, Rosa; Perrier, Michel; Kamen, Amine

2010-04-01

53

A high molecular weight chemoattractant generated from C5 by ultracentrifugation of mouse serum without activation of complement.  

PubMed

After ultracentrifugation of normal mouse serum, we found chemoattractant activity in the high molecular weight protein region at the bottom of the tube, which was comparable in amount and potency to the attractant in endotoxin-activated serum. This was not a pre-formed attractant, but was generated from serum reactants at least one of which was inactivated by heating at 56 degrees C. Analysis of sera from 10 different mouse strains for hemolytic C5 activity and for capacity to generate chemoattractant on ultracentrifugation showed that the 4 strains without C5 were the only strains that failed to generate the attractant. Thus, the attractant precursor is C5. Since the activity was generated in the presence of 0.01 M EDTA, classical or alternative complement activation was not required. The chemoattractant product had a mol. wt of approximately 170,000; it was therefore not free C5a. These results, and data recently published on digestion of purified human C5 by trypsin, suggest that limited proteolysis of C5 can produce a chemoattractant molecule without release of free C5a. PMID:6410183

Leonard, E J; Skeel, A

1983-06-01

54

Fundamentals of gel dosimeters  

NASA Astrophysics Data System (ADS)

Fundamental chemical and physical phenomena that occur in Fricke gel dosimeters, polymer gel dosimeters, micelle gel dosimeters and genipin gel dosimeters are discussed. Fricke gel dosimeters are effective even though their radiation sensitivity depends on oxygen concentration. Oxygen contamination can cause severe problems in polymer gel dosimeters, even when THPC is used. Oxygen leakage must be prevented between manufacturing and irradiation of polymer gels, and internal calibration methods should be used so that contamination problems can be detected. Micelle gel dosimeters are promising due to their favourable diffusion properties. The introduction of micelles to gel dosimetry may open up new areas of dosimetry research wherein a range of water-insoluble radiochromic materials can be explored as reporter molecules.

McAuley, K. B.; Nasr, A. T.

2013-06-01

55

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

PubMed

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

Oh-Ishi, Masamichi; Maeda, Tadakazu

2007-04-15

56

Dna electrophoresis in photopolymerized polyacrylamide gels on a microfluidic device  

E-print Network

DNA gel electrophoresis is a critical analytical step in a wide spectrum of genomic analysis assays. Great efforts have been directed to the development of miniaturized microfluidic systems (lab-on-a-chip systems) to perform low-cost, high...

Lo, Chih-Cheng

2009-05-15

57

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

NASA Astrophysics Data System (ADS)

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.

Moreno, Abel; Jurez-Martnez, Gabriela; Hernndez-Prez, Toms; Batina, Nikola; Mundo, Manuel; McPherson, Alexander

1999-09-01

58

Polymer gel: Kinetic, dynamic studies and its applications as biomaterials  

NASA Astrophysics Data System (ADS)

The polymer gels especially hydrogels have a very special structure and useful features such as unusual volume phase transition, compatibility with biological systems, and sensitivity to environmental stimuli (temperature, pH value, electric field, light and more), which lead to many potential applications in physical and biochemical fields. This research includes: (1) the theoretical and experimental studies of polymer gels on swelling kinetics, spinodal decomposition, and solution convection in gel matrix; (2) applications of polymer gels in wound dressing, tissue-simulating optical phantom and gel display. The kinetics of gel swelling has been theoretically analyzed by considering coupled motions of both solvent and polymer network. Analytical solutions of the solvent and the network movement are derived from collective diffusion equations for a long cylindrical and a large disk gel. Kinetics of spinodal decomposition of N-isopropylacrylamide (NIPA) polymer gel is investigated using turbidity and ultrasonic techniques. By probing movement of domains, a possible time-dependent gel structure in the spinodal decomposition region is presented. Theoretical studies of solution convection in gel matrix have been done and more analysis on dimensionless parameters is provided. To enhance the drug uptake and release capacity of silicone rubber (SR), NIPA hydrogel particles have been incorporated into a SR membrane. This SR/NIPA composite gel has promising attributes for wound dressing and other uses. Tissue-simulating optical phantom has been synthesized and studied using NIPA solution trapped inside a hydrogel. Polymer gels with engineered surface patterns were implemented. NIPA gel deposited on the surface of an acrylamide gel can be used as responsive gel display. A dynamically measurement technique of local shear modulus and swelling ratio of gel is presented based on an engineered periodic surface pattern as square array.

Wang, Changjie

59

Unified Theory for Gel Electrophoresis and Gel Filtration  

Microsoft Academic Search

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

David Rodbard; Andreas Chrambach

1970-01-01

60

Graphical analysis of nonideal monomer N-mer, isodesmic, and type II indefinite self-associating systems by equilibrium ultracentrifugation.  

PubMed Central

A graphical procedure is described by which one can obtain in principle the monomer molecular weight, stoichiometry, equilibrium constant, and second virial coefficient of nonideal monomer N-mer, isodesmic, and type II indefinite self-associating systems. In addition, a method is presented for obtaining both the equilibrium constant and the second virial coefficient from the maximum in a plot of apparent molecular weight vs. concentration if the monomer molecular weight and stoichiometry are known. The usefulness and limitations of the methods are discussed, as well as the quality and range of data required for determination of the relevant parameters. The techniques described are applicable to analysis of self-associating systems by osmotic pressure and light scattering, as well as equilibrium ultracentrifugation measurements. PMID:7260244

Stafford, W F

1980-01-01

61

Examination of the Protein Composition of the Cell Envelope of Escherichia coli by Polyacrylamide Gel Electrophoresis  

PubMed Central

An envelope preparation containing the cell wall and cytoplasmic membrane of Escherichia coli was obtained by breaking the cells with a French pressure cell and sedimentating the envelope fraction by ultracentrifugation. This fraction was prepared for polyacrylamide gel electrophoresis by dissolving the protein in an acidified N,N?-dimethylformamide, removing lipids by gel filtration in the same organic solvent and removing the solvent by dialysis against aqueous urea solutions. More than 80% of the total protein of the envelope fraction was recovered in soluble form. Electrophoresis on sodium dodecyl sulfate-containing gels yielded from 20 to 30 well-resolved bands of protein. One major protein band was observed on the gels. This protein had a molecular weight of 44,000 and accounted for as much as 40% of the total protein of the envelope fraction. A double-labeling technique was used to examine the protein composition of the envelope fraction from cells grown under different sets of conditions which result in large changes in the levels of membrane-bound oxidative enzymes. These changes in growth conditions resulted in only minor alterations in the protein profiles observed on the gels, suggesting that this organism is able to adapt to changes in growth environment with only minor modifications of the major proteins of the cell envelope. PMID:4923077

Schnaitman, Carl A.

1970-01-01

62

Sol-Gel Glasses  

NASA Technical Reports Server (NTRS)

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.

Mukherjee, S. P.

1985-01-01

63

CONFORMANCE IMPROVEMENT USING GELS  

SciTech Connect

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.

Randall S. Seright

2003-09-01

64

Surfactant Templated Polyacrylamide Gels  

NASA Astrophysics Data System (ADS)

The controlled modification of gel structure by using surfactant self-assemblies as templates provides new opportunities in the development of novel materials. Polyacrylamide gels were synthesized in the presence of tetradecyltrimethylammonium bromide (TTAB) surfactant. Small-angle X-ray scattering (SAXS) results indicate that acrylamide monomer does not prevent the self-assembly of TTAB surfactants. Dynamic rheology measurements indicated a transition from an isotropic micellar phase to a hexagonal columnar phase occurred about 10% higher TTAB concentration in the presence of acrylamide (the transition occurs at 35% (by weight) for TTAB in buffer solution). The presence of surfactant during the gelation profoundly affected the final gel structure. Real time rheology measurements showed evidence of a demixing of the polymer and the surfactant phase in gels formed in the presence of high TTAB concentration (> 30% by weight) leading to the formation of highly macroporous gels. Bulk structure characterization using SAXS showed that TTAB micelles were separated by about 10 nm in gels synthesized in the presence of low and moderate TTAB concentration (< 30%). Protein separation on gels templated by TTAB surfactants showed significant improvements over conventional gels.

Chakrapani, Mukundan; van Winkle, D. H.; Rill, R. L.

2003-03-01

65

Modeling chemoresponsive polymer gels.  

PubMed

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

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

2014-01-01

66

Periodic mesoporous silica gels  

SciTech Connect

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.

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

1996-06-01

67

Electrophoresis and Gel Analysis  

NSDL National Science Digital Library

In this animation produced by WGBH and Digizyme, Inc., see how molecules of DNA are separated using gel electrophoresis, and how this process enables scientists to compare the molecular variations of two or more DNA samples.

2011-08-05

68

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

PubMed

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

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

2014-01-01

69

Crystallization from Gels  

NASA Astrophysics Data System (ADS)

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.

Narayana Kalkura, S.; Natarajan, Subramanian

70

Conformance Improvement Using Gels  

SciTech Connect

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.

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

2002-09-26

71

Polymer gel dosimetry.  

PubMed

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

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

2010-03-01

72

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

E-print Network

Hydrochloric acid Inulin Lactic acid Lactose Lanthanum nitrate Lead nitrate Lithium chloride Magnesium chloride Ammonium chloride Ammonium hydroxide Ammonium sulfate Barium chloride Cadmium chloride Cadmium sulfate Calcium chloride Cesium chloride Citric acid Cobaltous chloride Creatinine Cupric sulfate EDTA disodium

Chan, Hue Sun

73

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

chloride Magnesium chloride Magnesium sulfate Maltose Manganous sulfate Mannitol Methanol Nickel sulfate-Propanol Acetic Acid Acetone Ammonium chloride Ammonium hydroxide Ammonium sulfate Barium chloride Cadmium chloride Cadmium sulfate Calcium chloride Cesium chloride Citric acid Cobaltous chloride Creatinine Cupric

Chan, Hue Sun

74

[Isolation of flagellin antigens of salmonellae by the method of ultracentrifugation and their use for preparation of erythrocytic H-diagnostic agents].  

PubMed

Flagellar preparations were obtained from 6 salmonellae strains by differential ultracentrifugation; they were characterized by morphological, immunochemical, and serological tests. The results of investigations showed that the preparations possessed high serological activity; somatic antigen admixture was insignificant. Flagellins extracted from the flagellae were used to prepare erythrocytic H-diagnostic agents. The results of their use in the examination of sera of healthy persons, and of those suffering from typhoid fever and salmonellosis indicated the expediency of using passive H-hemagglutination for diagnostic purposes. PMID:331767

Rukhadze, E Z; Levenson, V I; Subbotina, Iu L; Trushina, V V; Kapuka, L P

1977-05-01

75

Gel Electrophoresis of Dyes  

NSDL National Science Digital Library

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

Stephens, Janice; Leach, Jan

2011-01-01

76

Swelling of Olympic Gels  

NASA Astrophysics Data System (ADS)

The swelling equilibrium of Olympic gels, which are composed of entangled cyclic polymers, is studied by Monte Carlo simulations. In contrast to chemically cross-linked polymer networks, we observe that Olympic gels made of chains with a larger degree of polymerization, N, exhibit a smaller equilibrium swelling degree, Q?N-0.28?0-0.72, at the same polymer volume fraction ?0 at network preparation. This observation is explained by a desinterspersion (reorganization with release of nontrapped entanglements) process of overlapping nonconcatenated rings upon swelling.

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

2014-06-01

77

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

SciTech Connect

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.

Koutney, L.B.

1992-09-09

78

Analytical testing  

NASA Technical Reports Server (NTRS)

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.

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

1981-01-01

79

Transdermal delivery of paeonol using cubic gel and microemulsion gel  

PubMed Central

Background The aim of this study was to develop new systems for transdermal delivery of paeonol, in particular microemulsion gel and cubic gel formulations. Methods Various microemulsion vehicles were prepared using isopropyl myristate as an oil phase, polyoxyethylated castor oil (Cremophor EL) as a surfactant, and polyethylene glycol 400 as a cosurfactant. In the optimum microemulsion gel formulation, carbomer 940 was selected as the gel matrix, and consisted of 1% paeonol, 4% isopropyl myristate, 28% Cremophor EL/polyethylene glycol 400 (1:1), and 67% water. The cubic gel was prepared containing 3% paeonol, 30% water, and 67% glyceryl monooleate. Results A skin permeability test using excised rat skins indicated that both the cubic gel and microemulsion gel formulations had higher permeability than did the paeonol solution. An in vivo pharmacokinetic study done in rats showed that the relative bioavailability of the cubic gel and microemulsion gel was enhanced by about 1.51-fold and 1.28-fold, respectively, compared with orally administered paeonol suspension. Conclusion Both the cubic gel and microemulsion gel formulations are promising delivery systems to enhance the skin permeability of paeonol, in particular the cubic gel. PMID:21904450

Luo, Maofu; Shen, Qi; Chen, Jinjin

2011-01-01

80

Calcium tartrate gel.  

PubMed

A method for preparation of a gel for chromatography has been developed. The adsorbent is calcium tartrate treated with potassium phosphate. By changing the temperature of synthesis (10-65 degrees C) and concentration of the salts (calcium chloride and sodium potassium tartrate) from 0.3 to 3.0 M, we have been able to prepare adsorbent crystals of definite sizes in the range 35-200 microns. In all cases, for synthesis of adsorbent, the Ca2+/K+Na+ ratio was greater than 1. After treatment of calcium tartrate crystals with 0.075-1.5 M potassium phosphate at 80-100 degrees C and pH 8.5-9.0, an appropriate chromatographic adsorbent was prepared. The chromatographic properties of calcium tartrate gel have been studied. The adsorbent permits flow rates of 25-150 ml/h, depending on the particle size. The capacity of calcium tartrate gel for binding BSA, RNA, and DNA was similar to that of Tiselius' hydroxyapatite (A. Tiselius, S. Hjerten, O. Levin (1956) Arch. Biochem. Biophys. 65, 132-155). The spheric shape of gel particles permits uniform and compact packing of adsorbent under the conditions of column chromatography. PMID:2757203

Akhrem, A A; Drozhdenyuk, A P

1989-05-15

81

Polyacrylamide gels synthesized in the presence of surfactants  

NASA Astrophysics Data System (ADS)

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.

Chakrapani, Mukundan

82

Analytical Microscopy  

SciTech Connect

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.

Not Available

2006-06-01

83

Analytical toxicology.  

PubMed

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

Maurer, Hans H

2010-01-01

84

Linear electrochemical gel actuators  

NASA Astrophysics Data System (ADS)

By using electroactive monomers it is possible to produce gels that respond to oxidation or reduction by swelling and deswelling in the presence of solvent. By the inclusion of an appropriate biasing element such as a spring, it is possible to produce linear, reversible actuation. The process can be driven electrochemically in a standard cell, with driving voltages under +/- 1 V. For many systems, the intrinsic conductivity of the gel, leading to poor or no performance. This can be overcome by blending conductive carbon nanotubes at 1% concentration, which give reasonable conductivity without affecting mechanical performance. Extensions of up to 40% are possible, against an external pressure of 30 kPa. The process is slow, taking up to 160 minutes per cycle due to slow ionic diffusion. The electrochemical cell can be cycled many times without degradation.

Goswami, Shailesh; McAdam, C. John; Hanton, Lyall R.; Moratti, Stephen C.

2011-11-01

85

Linear electrochemical gel actuators  

NASA Astrophysics Data System (ADS)

By using electroactive monomers it is possible to produce gels that respond to oxidation or reduction by swelling and deswelling in the presence of solvent. By the inclusion of an appropriate biasing element such as a spring, it is possible to produce linear, reversible actuation. The process can be driven electrochemically in a standard cell, with driving voltages under +/- 1 V. For many systems, the intrinsic conductivity of the gel, leading to poor or no performance. This can be overcome by blending conductive carbon nanotubes at 1% concentration, which give reasonable conductivity without affecting mechanical performance. Extensions of up to 40% are possible, against an external pressure of 30 kPa. The process is slow, taking up to 160 minutes per cycle due to slow ionic diffusion. The electrochemical cell can be cycled many times without degradation.

Goswami, Shailesh; McAdam, C. John; Hanton, Lyall R.; Moratti, Stephen C.

2012-04-01

86

Equity Analytics  

NSDL National Science Digital Library

Equity Analytics, Ltd, an independent consulting firm, has created this useful directory. The annotated index includes information on government statistical releases, futures and commodities, financial planning, software downloads, and a discounted bookstore. Each directory entry links to rich articles and to valuable information for those looking for guidance in financial matters.

87

Analytical sedimentology  

SciTech Connect

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

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

1994-01-01

88

Analytical toxicology  

Microsoft Academic Search

\\u000a This paper reviews procedures for screening, identification and quantification of drugs, poisons and their metabolites in\\u000a biosamples, and the corresponding work-up procedures. Gas chromatography-mass spectrometry and liquid chromatography-mass\\u000a spectrometry are mostly used today in analytical toxicology. Selection of the most appropriate biosample, e.g., ante\\/postmortem\\u000a blood, urine, or tissues or alternative matrices like hair, sweat and oral fluid, nails or meconium,

Hans H. Maurer

89

Analytical Chemistry  

NSDL National Science Digital Library

This document contains a list of detailed lecture notes covering a wide range of topics including equilibrium, titrations, sample preparation, acids and bases, buffers, spectrophotometry, potentiometry and chromatography. This site is part of a collection of notes from a general chemistry course taught at the State University of West Georgia. This document gives supplementary material that could be useful to intermediate chemistry majors in an analytical chemistry course or new faculty developing a course.

Henderson, David E.

90

Nanoparticle gel electrophoresis: bare charged spheres in polyelectrolyte hydrogels.  

PubMed

Nanoparticle gel electrophoresis has recently emerged as an attractive means of separating and characterizing nanoparticles. Consequently, a theory that accounts for electroosmotic flow in the gel, and coupling of the nanoparticle and hydrogel electrostatics and hydrodynamics, is required, particularly for gels in which the mesh size is comparable to or smaller than the particle radii. Here, we present an electrokinetic model for charged, spherical colloidal particles undergoing electrophoresis in charged (polyelectrolyte) hydrogels: the gel-electrophoresis analogue of Henry's theory for electrophoresis in Newtonian electrolytes. We compare numerically exact solutions of the model with several independent asymptotic approximations, identifying regions in the parameter space where these approximations are accurate or break down. As previously assumed in the literature, Henry's formula, modified by the addition of a constant electroosmotic flow mobility, is accurate only for nanoparticles that are small compared to the hydrogel mesh size. We derived an exact analytical solution of the full model by judiciously modifying the theory of Allison et al. for uncharged gels, drawing on the superposition methodology of Doane et al. to account for hydrogel charge. This furnishes accurate and economical mobility predictions for the entire parameter space. The present model suggests that nanoparticle size separations (with diameters ?40 nm) are optimal at low ionic strength, with a gel mesh size that is selected according to the particle charging mechanism. For weakly charged particles, optimal size separation is achieved when the Brinkman screening length is matched to the mean particle size. PMID:23153681

Li, Fei; Hill, Reghan J

2013-03-15

91

New effect in ionic polymeric gels: the ionic flexogelectric effect  

NASA Astrophysics Data System (ADS)

Reported are a number of quantitative observations and analytical modeling of a new effect in ionic polymeric gels such as poly(2-acrylamido-2-methylpropanesulfonic acid) or PAMPS, polyacrylic acid plus sodium acrylate cross-linked with bisacrylamide (PAAM), or various chemically doped combinations of polyacrylic acid plus polyvinyl alcohol (PAA-PVA). This new effect, hereafter, referred to as `flexogelectric effect' is basically the inverse of the effect originally reported in 1965 by three GE researchers, namely, Hamlen, Kent, and Shafer in which the imposition of an electric field on an ionic polymeric gel fiber produced extension or contraction. Here it is shown, both theoretically and experimentally, that mechanically induced nonhomogeneous deformations, and in particular bending of strips of such ionic gels, can produce an electric field and the associated voltage. For typical samples of such gels (4 X 4 X 40 mm) with copper or platinum foil electrodes snugly contacting a pair of opposite sides (4 X 40 mm) of the strip, the difference in voltage measured between the electrodes for extreme bending configurations of the gel is typically in the 10s of millivolts range. This voltage difference which is quite significant for many engineering applications, such as large strain and deformation sensing, is still an order of magnitude smaller than the voltage necessary to induce similar deformations in the gel itself. A plausible explanation is also presented for such discrepancies.

Shahinpoor, Mohsen

1995-05-01

92

Clarification Procedure for Gels  

NASA Technical Reports Server (NTRS)

Procedure developed to obtain transparent gels with consistencies suitable for crystal growth, by replacing sodium ions in silicate solution with potassium ions. Clarification process uses cation-exchange resin to replace sodium ions in stock solution with potassium ions, placed in 1M solution of soluble potassium salt. Slurry stirred for several hours to allow potassium ions to replace all other cations on resin. Supernatant solution decanted through filter, and beads rinsed with distilled water. Rinsing removes excess salt but leaves cation-exchange beads fully charged with potassium ions.

Barber, Patrick G.; Simpson, Norman R.

1987-01-01

93

High transparent shape memory gel  

NASA Astrophysics Data System (ADS)

Gels are a new material having three-dimensional network structures of macromolecules. They possess excellent properties as swellability, high permeability and biocompatibility, and have been applied in various fields of daily life, food, medicine, architecture, and chemistry. In this study, we tried to prepare new multi-functional and high-strength gels by using Meso-Decoration (Meso-Deco), one new method of structure design at intermediate mesoscale. High-performance rigid-rod aromatic polymorphic crystals, and the functional groups of thermoreversible Diels-Alder reaction were introduced into soft gels as crosslinkable pendent chains. The functionalization and strengthening of gels can be realized by meso-decorating the gels' structure using high-performance polymorphic crystals and thermoreversible pendent chains. New gels with good mechanical properties, novel optical properties and thermal properties are expected to be developed.

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

2014-03-01

94

Gel for retarding water flow  

SciTech Connect

A process is described for forming, in situ, a gel in a porous structure comprising: introducing an effective amount of a gel-forming composition into pores of a porous structure; and allowing the gel-forming composition to form a gel in the pores. The thusly formed gel is capable of being formed by reacting an aqueous solution comprising a first substance selected from the group consisting of polyvinyl alcohols, polyvinyl alcohol copolymers, and mixtures thereof. A second substance comprises aldehyde operable for effecting a crosslinking reaction with the first substance, wherein the total amount of aldehyde is from about 0.005 to about 2.5% of the weight of the gel.

Marrocco, M.L.

1987-05-12

95

Polyoxometalate-based Supramolecular Gel  

PubMed Central

Self-assemblyings of surfactant-encapsulated Wells-Dawson polyoxometalates (SEPs) nanobuilding blocks in butanone and esters yielded supramolecular gels showing thermo and photo responsive properties. The gels can be further polymerized if unsaturated esters were used and subsequently electrospinned into nanowires and non-woven mats. The as-prepared non-woven mats have a Young's modulus as high as 542.55?MPa. It is believed that this supramolecular gel is a good platform for polyoxometalates processing. PMID:23666013

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

2013-01-01

96

Polyoxometalate-based Supramolecular Gel  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

97

Electrically controlled polymeric gel actuators  

DOEpatents

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.

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

1993-10-05

98

Gel polymer electrolytes for batteries  

DOEpatents

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.

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

2014-11-18

99

Luminescence effects in gels containing organo-aluminum complexes  

SciTech Connect

The fluorescence behavior of metal organic complex-doped sol-gel media is an area of great interest to those conducting research related to opto-chemical sensors and materials associated novel photonic device architectures. The sol-gel method comprises a low temperature preparative approach which is readily used to synthesize glassy materials containing chromophoric dopants. Di-(sec-butoxy)aluminoxytriethoxysilane (DBATES) is an especially useful sol-gel precursor, as it represents a double alkoxide which can be used to synthesize compositionally novel alumina-silica gel ``copolymers``. Derivatives of 8-hydroxyquinoline, such as 8-hydroxyquinoline-5-sulfonic acid (HQS) have been used as fluorometric analytical reagents for the detection of metal ions such as aqueous Al{sup 3+}. The unmodified HQS molecule is, itself, virtually non-luminescent. The authors have performed preliminary experiments involving the preparation of luminescent quinolinato-aluminoxysilane complexes, which may be used as precursors in sol-gel derived media. The system under investigation is based on the complex-formation HQS molecule and the aluminum-containing DBATES alkoxide sol-gel precursor. The resultant alkoxide was observed to possess intense blue luminescence which is believed to result from complexation of the bidentate ligand to the Al{sup 3+} center. The modified DBATES precursor was subsequently hydrolyzed and allowed to gel. The luminescence behavior of the modified alkoxide and the resultant gels was studied through the use of absorbance and fluorescence (continuous and time-resolved) spectroscopy. The results of those experiments are subsequently described.

Arbuthnot, D.; Wang, X.J.; Knobbe, E.T. [Oklahoma State Univ., Stillwater, OK (United States)

1994-12-31

100

Deformation and fracture of cross-linked polymer gels  

NASA Astrophysics Data System (ADS)

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 35C. 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.

Lin, Wei-Chun

101

Theory and simulation of the swelling of polymer gels  

SciTech Connect

A combined discontinuous molecular dynamics and Monte Carlo simulation technique is used to study the swelling of athermal, continuous-space, near-perfect, trifunctional polymer networks containing hard chains of lengths 20 and 35 immersed in an athermal hard-sphere solvent. The swelling simulations are conducted under conditions of constant pressure and chemical potential. A simple, analytical theory for gel swelling is presented in which the gel free energy is calculated as the sum of an elastic, affine-type term, and a liquidlike mixing term that is based on the generalized-Flory dimer equation of state. The theory shows good agreement with our simulation results for the gel properties at swelling equilibrium. (c) 2000 American Institute of Physics.

Kenkare, N. R. [Department of Chemical Engineering, Box 7905, North Carolina State University, Raleigh, North Carolina 27695-7905 (United States)] [Department of Chemical Engineering, Box 7905, North Carolina State University, Raleigh, North Carolina 27695-7905 (United States); Hall, C. K. [Department of Chemical Engineering, Box 7905, North Carolina State University, Raleigh, North Carolina 27695-7905 (United States)] [Department of Chemical Engineering, Box 7905, North Carolina State University, Raleigh, North Carolina 27695-7905 (United States); Khan, S. A. [Department of Chemical Engineering, Box 7905, North Carolina State University, Raleigh, North Carolina 27695-7905 (United States)] [Department of Chemical Engineering, Box 7905, North Carolina State University, Raleigh, North Carolina 27695-7905 (United States)

2000-07-01

102

Nanocrystal/sol-gel nanocomposites  

SciTech Connect

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

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

2012-06-12

103

Nanocrystal/sol-gel nanocomposites  

DOEpatents

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.

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

2007-06-05

104

Multiple phases of protien gels  

Microsoft Academic Search

A multiple phase transition was observed in gels made by covalently cross-linking proteins in either native or denatured state. The enzymatic activity of the gels prepared from native alpha-chymotrypsin was determined for each of the multiple phases. The reversibility of the swelling degrees and the enzymatic reaction rates upon phase transition suggests that the protein is at a free energy

Masahiko Annaka; Toyoichi Tanaka

1994-01-01

105

Electromechanical nonionic gels  

NASA Astrophysics Data System (ADS)

The electrically induced bending of nonionic polyvinyl alcohol gels, bending over 90 within 100 ms, is the fastest motion in the field of electroactuation of polymers. This rapid bending produces initial mechanical vibrations followed by a durable displacement that contrasts highly with the relaxation observed with elastomer- and polyelectrolyte-based actuators. Here, we characterize the bending process using video imaging and laser detecting technology and establish a physical model for the electromechanical conversion, based on our observation of an induced solvent migration. Our results show excellent agreement between the measurements and calculations. This study provides general rules for understanding the electrically induced bending of isotropic dielectrics and may also shed light on nonmuscular biological engines.

Zheng, J.; Xu, C.; Hirai, T.

2008-02-01

106

Living bacteria in silica gels  

NASA Astrophysics Data System (ADS)

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

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

2002-09-01

107

Methylthymol blue in Fricke gels  

NASA Astrophysics Data System (ADS)

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.

Penev, K. I.; Mequanint, K.

2015-01-01

108

Collapse of Gels in an Electric Field  

Microsoft Academic Search

An infinitesimal change in electric potential across a polyelectrolyte gel produces a discrete, reversible volume change. The volume of the collapsed gel can be several hundred times smaller than that of the swollen gel.

Toyoichi Tanaka; Izumi Nishio; Shao-Tang Sun; Shizue Ueno-Nishio

1982-01-01

109

Sonication-triggered instantaneous gel-to-gel transformation.  

PubMed

Two new peptide-based isomers containing cholesterol and naphthalic groups have been designed and synthesized. We found that the position of L-alanine in the linker could tune the gelation properties and morphologies. The molecule with the L-alanine residue positioned in the middle of the linker (1b) shows better gelation behavior than that with L-alanine directly linked to the naphthalimido moiety (1a). As a result, a highly thermostable organogel of 1b with a unique core-shell structure was obtained at high temperature and pressure in acetonitrile. Moreover, the gels of 1a and 1b could undergo an instantaneous gel-to-gel transition triggered by sonication. Ultrasound could break the core-shell microsphere of 1b and the micelle structure of 1a into entangled fibers. By studying the mechanism of the sonication-triggered gel-to-gel transition process of these compounds, it can be concluded that ultrasound has a variety of effects on the morphology, such as cutting, knitting, unfolding, homogenizing, and even cross-linking. Typically, ultrasound can cleave and homogenize pi-stacking and hydrophobic interactions among the gel molecules and then reshape the morphologies to form a new gel. This mechanism of morphology transformation triggered by sonication might be attractive in the field of material storage and controlled release. PMID:20572172

Yu, Xudong; Liu, Qian; Wu, Junchen; Zhang, Mingming; Cao, Xinhua; Zhang, Song; Wang, Qi; Chen, Liming; Yi, Tao

2010-08-01

110

Detection of Nitroaromatic Explosives with Fluorescent Molecular Assemblies and ?-Gels.  

PubMed

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

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

2014-10-29

111

Sol-gel encapsulation for controlled drug release and biosensing  

NASA Astrophysics Data System (ADS)

The main focus of this dissertation is to investigate the use of sol-gel encapsulation of biomolecules for controlled drug release and biosensing. Controlled drug release has advantages over conventional therapies in that it maintains a constant, therapeutic drug level in the body for prolonged periods of time. The anti-hypertensive drug Captopril was encapsulated in sol-gel materials of various forms, such as silica xerogels and nanoparticles. The primary objective was to show that sol-gel silica materials are promising drug carriers for controlled release by releasing Captopril at a release rate that is within a therapeutic range. We were able to demonstrate desired release for over a week from Captopril-doped silica xerogels and overall release from Captopril-doped silica nanoparticles. As an aside, the antibiotic Vancomycin was also encapsulated in these porous silica nanoparticles and desired release was obtained for several days in-vitro. The second part of the dissertation focuses on immobilizing antibodies and proteins in sol-gel to detect various analytes, such as hormones and amino acids. Sol-gel competitive immunoassays on antibody-doped silica xerogels were used for hormone detection. Calibration for insulin and C-peptide in standard solutions was obtained in the nM range. In addition, NASA-Ames is also interested in developing a reagentless biosensor using bacterial periplasmic binding proteins (bPBPs) to detect specific biomarkers, such as amino acids and phosphate. These bPBPs were doubly labeled with two different fluorophores and encapsulated in silica xerogels. Ligand-binding experiments were performed on the bPBPs in solution and in sol-gel. Ligand-binding was monitored by fluorescence resonance energy transfer (FRET) between the two fluorophores on the bPBP. Titration data show that one bPBP has retained its ligand-binding properties in sol-gel.

Fang, Jonathan

112

Microchannel gel electrophoretic separation systems and methods for preparing and using  

DOEpatents

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.

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

2013-09-03

113

Adhesive, elastomeric gel impregnating composition  

DOEpatents

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.

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

2002-01-01

114

Tetrameric structure of thermostable direct hemolysin from vibrio parahaemolyticus revealed by ultracentrifugation, small-angle X-ray scattering and electron microscopy.  

PubMed

The thermostable direct hemolysin (TDH) is a major virulence factor of Vibrio parahaemolyticus. We have characterized the conformational properties of TDH by small-angle X-ray scattering (SAXS), ultracentrifugation and transmission electron microscopy. Sedimentation equilibrium and velocity studies revealed that the protein is tetrameric in aqueous solvents. The Guinier plot derived from SAXS data provided a radius of gyration of 29.0 A. The elongated pattern with a shoulder of a pair distance distribution function derived from SAXS data suggested the presence of molecules with an anisotropic shape having a maximum diameter of 98 A. Electron microscopic image analysis of the negatively stained TDH oligomer showed the presence of C(4) symmetric particles with edge and diagonal lengths of 65 A and 80 A, respectively. Shape reconstruction was carried out by ab initio calculations using the SAXS data with a C(4) symmetric approximation. These results suggested that the tetrameric TDH assumes an oblate structure. The hydrodynamic parameters predicted from the ab initio model differed slightly from the experimental values, suggesting the presence of flexible segments. PMID:17056060

Hamada, Daizo; Higurashi, Takashi; Mayanagi, Kouta; Miyata, Tomoko; Fukui, Takashi; Iida, Tatsuya; Honda, Takeshi; Yanagihara, Itaru

2007-01-01

115

Electrostatics and aggregation: How charge can turn a crystal into a gel  

PubMed Central

The crystallization of proteins or colloids is often hindered by the appearance of aggregates of low fractal dimension called gels. Here we study the effect of electrostatics upon crystal and gel formation using an analytic model of hard spheres bearing point charges and short range attractive interactions. We find that the chief electrostatic free energy cost of forming assemblies comes from the entropic loss of counterions that render assemblies charge-neutral. Because there exists more accessible volume for these counterions around an open gel than a dense crystal, there exists an electrostatic entropic driving force favoring the gel over the crystal. This driving force increases with increasing sphere charge, but can be counteracted by increasing counterion concentration. We show that these effects cannot be fully captured by pairwise-additive macroion interactions of the kind often used in simulations, and we show where on the phase diagram to go in order to suppress gel formation. PMID:21895221

Schmit, Jeremy D.; Whitelam, Stephen; Dill, Ken

2011-01-01

116

Electrostatics and aggregation: how charge can turn a crystal into a gel.  

PubMed

The crystallization of proteins or colloids is often hindered by the appearance of aggregates of low fractal dimension called gels. Here we study the effect of electrostatics upon crystal and gel formation using an analytic model of hard spheres bearing point charges and short range attractive interactions. We find that the chief electrostatic free energy cost of forming assemblies comes from the entropic loss of counterions that render assemblies charge-neutral. Because there exists more accessible volume for these counterions around an open gel than a dense crystal, there exists an electrostatic entropic driving force favoring the gel over the crystal. This driving force increases with increasing sphere charge, but can be counteracted by increasing counterion concentration. We show that these effects cannot be fully captured by pairwise-additive macroion interactions of the kind often used in simulations, and we show where on the phase diagram to go in order to suppress gel formation. PMID:21895221

Schmit, Jeremy D; Whitelam, Stephen; Dill, Ken

2011-08-28

117

DNA gel particles: an overview.  

PubMed

A general understanding of interactions between DNA and oppositely charged compounds forms the basis for developing novel DNA-based materials, including gel particles. The association strength, which is altered by varying the chemical structure of the cationic cosolute, determines the spatial homogeneity of the gelation process, creating DNA reservoir devices and DNA matrix devices that can be designed to release either single- (ssDNA) or double-stranded (dsDNA) DNA. This review covers recent developments on the topic of DNA gel particles formed in water-water emulsion-type interfaces. The degree of DNA entrapment, particle morphology, swelling/dissolution behavior and DNA release responses are discussed as functions of the nature of the cationic agent used. On the basis of designing DNA gel particles for therapeutic purposes, recent studies on the determination of the surface hydrophobicity and the hemolytic and the cytotoxic assessments of the obtained DNA gel particles have been also reported. PMID:24119768

Morn, M Carmen; Vinardell, M Pilar; Infante, M Rosa; Miguel, M Graa; Lindman, Bjrn

2014-03-01

118

Agarose Gel Electrophoresis of RNA  

Microsoft Academic Search

\\u000a Gel electrophoresis is one of the most important techniques currently available for the fractionation of RNA. The experimental\\u000a procedure is relatively simple, but nevertheless achieves very reproducible results and high resolution. RNA is a polyanion\\u000a and will therefore migrate toward the positive electrode in an electric field. If the migration occurs through a gel matrix\\u000a of carefully chosen pore size,

Robert J. Slater

119

TOPICAL REVIEW: Polymer gel dosimetry  

NASA Astrophysics Data System (ADS)

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.

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

2010-03-01

120

Topical Review: Polymer gel dosimetry  

PubMed Central

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

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

2010-01-01

121

Pre-Cast Gel Electrophoresis Guide  

E-print Network

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

Kirschner, Marc W.

122

Surface grafted chitosan gels. Part II. Gel formation and characterization.  

PubMed

Responsive biomaterial hydrogels attract significant attention due to their biocompatibility and degradability. In order to make chitosan based gels, we first graft one layer of chitosan to silica, and then build a chitosan/poly(acrylic acid) multilayer using the layer-by-layer approach. After cross-linking the chitosan present in the polyelectrolyte multilayer, poly(acrylic acid) is partly removed by exposing the multilayer structure to a concentrated carbonate buffer solution at a high pH, leaving a surface-grafted cross-linked gel. Chemical cross-linking enhances the gel stability against detachment and decomposition. The chemical reaction between gluteraldehyde, the cross-linking agent, and chitosan was followed in situ using total internal reflection Raman (TIRR) spectroscopy, which provided a molecular insight into the complex reaction mechanism, as well as the means to quantify the cross-linking density. The amount of poly(acrylic acid) trapped inside the surface grafted films was found to decrease with decreasing cross-linking density, as confirmed in situ using TIRR, and ex situ by Fourier transform infrared (FTIR) measurements on dried films. The responsiveness of the chitosan-based gels with respect to pH changes was probed by quartz crystal microbalance with dissipation (QCM-D) and TIRR. Highly cross-linked gels show a small and fully reversible behavior when the solution pH is switched between pH 2.7 and 5.7. In contrast, low cross-linked gels are more responsive to pH changes, but the response is fully reversible only after the first exposure to the acidic solution, once an internal restructuring of the gel has taken place. Two distinct pKa's for both chitosan and poly(acrylic acid), were determined for the cross-linked structure using TIRR. They are associated with populations of chargeable groups displaying either a bulk like dissociation behavior or forming ionic complexes inside the hydrogel film. PMID:25006685

Liu, Chao; Thormann, Esben; Claesson, Per M; Tyrode, Eric

2014-07-29

123

Thixotropic gel for vadose zone remediation  

DOEpatents

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.

Rhia, Brian D. (Augusta, GA)

2011-03-01

124

Capillary fracture of soft gels  

NASA Astrophysics Data System (ADS)

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

Bostwick, Joshua B.; Daniels, Karen E.

2013-10-01

125

Inorganic Sensing Using Organofunctional Sol-Gel Materials  

PubMed Central

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

Carrington, Nathan A.; Xue, Zi-Ling

2007-01-01

126

Copolymers For Capillary Gel Electrophoresis  

DOEpatents

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.

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

2005-08-09

127

Tracer diffusion in colloidal gels  

E-print Network

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.

Sujin Babu; Jean Christophe Gimel; Taco Nicolai

2007-05-09

128

Tracer diffusion in colloidal gels.  

PubMed

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 approximately 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. PMID:18171042

Babu, Sujin; Gimel, Jean Christophe; Nicolai, Taco

2008-01-24

129

Gelatin gels in deuterium oxide  

Microsoft Academic Search

Gelatin gels formed in D2O have greater rigidity than gels of equal concentration formed in H2O. In D2O the junction zones (regions of collagen triple helix structure) were smaller (i.e. involved fewer amino acid residues) than in H2O. The contribution per amino acid residue to the free energy of formation of junction zones was ?0.51kJ\\/mol in D2O compared with ?0.34kJ\\/mol

David Oakenfull; Alan Scott

2003-01-01

130

Screening effect on nanostructure of charged gel  

NASA Astrophysics Data System (ADS)

Charge screening effects on nanostructures of N-isopropylacrylamide-sodium acrylate (NIPA-SA) and -acrylic acid (NIPA-AAc) gels are investigated with small-angle neutron scattering. The NIPA-SA and NIPA-AAc gels with low water content exhibit microphase separations with different dimensions. The dehydrated NIPA-SA gel also makes the microphase separation but the dehydrated NIPA-AAc gel does not. These results indicate that ionic circumstance around charged bases strongly affects the nanostructures both of the dehydrated gel and the gel with low water content.

Sugiyama, Masaaki; Annaka, Masahiko; Hino, Masahiro; Fukunaga, Toshiharu; E. Vigild, Martin; Hara, Kazuhiro

2004-07-01

131

Analytics for Education  

ERIC Educational Resources Information Center

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

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

2014-01-01

132

Elasticity of c*Gels  

Microsoft Academic Search

A junction affine network model is solved for chains following a Redner des Cloizeaux distribution. In a gel at c^* the network strands behave as isolated chains. In a good solvent their elastic properties cannot be obtained from Gaussian statistics as in the classical models of rubber elasticity. Instead the Redner-des Cloizeaux distribution is employed, which is known to be

Ralf Everaers

1995-01-01

133

Gel Electrophoresis Lab: Paternity Case  

NSDL National Science Digital Library

This lab activity from the Biotechnology Alliance for Suncoast Biology Educators provides instructions for conducting a gel electrophoresis lab. Students will try to solve a paternity case with this activity by obtaining a DNA fingerprint from each potential father, the mother and the child. This activity may be downloaded in PDF file format. A data collection sheet and student questions are also included.

2013-07-05

134

Calculating Percent Gel For Process Control  

NASA Technical Reports Server (NTRS)

Reaction state of thermosetting resin tracked to assure desired properties. Rate of gel determined as function of temperature by measuring time to gel of part of graphite fabric impregnated with Hexcel R120 (or equivalent) phenolic resin.

Webster, Charles Neal; Scott, Robert O.

1988-01-01

135

Regenerative medicine: Noodle gels for cells  

NASA Astrophysics Data System (ADS)

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.

Deming, Timothy J.

2010-07-01

136

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

NASA Astrophysics Data System (ADS)

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

Mohammadi, Aliasghar

2013-08-01

137

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

PubMed

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

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

2014-01-01

138

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

PubMed Central

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 Ficks law. PMID:25338049

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

2014-01-01

139

Advanced gel propulsion controls for kill vehicles  

Microsoft Academic Search

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

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

1993-01-01

140

Spring-loaded polymeric gel actuators  

DOEpatents

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.

Shahinpoor, Mohsen (Albuquerque, NM)

1995-01-01

141

Food gels: Gelling process and new applications  

Microsoft Academic Search

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

SOUMYA BANERJEE; SUVENDU BHATTACHARYA

2011-01-01

142

Food Gels: Gelling Process and New Applications  

Microsoft Academic Search

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

Soumya Banerjee; Suvendu Bhattacharya

2012-01-01

143

A clarified gel for crystal growth  

NASA Technical Reports Server (NTRS)

A procedure for preparing clarified sodium silicate gels suitable for crystal growth is described. In the method described here, the silicate stock is clarified by pretreating it with cation exchange resins before preparing the gels. Also, a modified recipe is proposed for preparing gels to achieve improved transparency.

Barber, P. G.; Simpson, N. R.

1985-01-01

144

Spring-loaded polymeric gel actuators  

DOEpatents

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.

Shahinpoor, M.

1995-02-14

145

Pro-Q Diamond Phosphoprotein Gel Stain  

E-print Network

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

Lebendiker, Mario

146

Nongradient blue native gel analysis of serum proteins and in-gel detection of serum esterase activities.  

PubMed

The objective of the present study was to analyze serum protein complexes and detect serum esterase activities using nongradient blue native polyacrylamide gel electrophoresis (BN-PAGE). For analysis of potential protein complexes, serum from rat was used. Results demonstrate that a total of 8 gel bands could be clearly distinguished after Coomassie blue staining, and serum albumin could be isolated nearly as a pure protein. Moreover, proteins in these bands were identified by electrospray mass spectrometry and low-energy collision induced dissociation (CID)-MS/MS peptide sequencing and the existence of serum dihydrolipoamide dehydrogenase (DLDH) was confirmed. For studies of in-gel detection of esterase activities, serum from rat, mouse, and human was used. In-gel staining of esterase activity was achieved by the use of either ?-naphthylacetate or ?-naphthylacetate in the presence of Fast blue BB salt. There were three bands exhibiting esterase activities in the serum of both rat and mouse. In contrast, there was only one band showing esterase activity staining in the human serum. When serum samples were treated with varying concentrations of urea, esterase activity staining was abolished for all the bands except the one containing esterase 1 (Es1) protein that is known to be a single polypeptide enzyme, indicating that majority of these esterases were protein complexes or multimeric proteins. We also identified the human serum esterase as butyrylcholinesterase following isolation and partial purification using ammonium sulfate fractioning and ion exchange column chromatographies. Where applicable, demonstrations of the gel-based method for measuring serum esterase activities under physiological or pathophysiological conditions were illustrated. Results of the present study demonstrate that nongradient BN-PAGE can serve as a feasible analytical tool for proteomic and enzymatic analysis of serum proteins. PMID:21237726

Thangthaeng, Nopporn; Sumien, Nathalie; Forster, Michael J; Shah, Ruchir A; Yan, Liang-Jun

2011-02-15

147

The use of analytical sedimentation velocity to extract thermodynamic linkage  

PubMed Central

For 25 years, the Gibbs Conference on Biothermodynamics has focused on the use of thermodynamics to extract information about the mechanism and regulation of biological processes. This includes the determination of equilibrium constants for macromolecular interactions by high precision physical measurements. These approaches further reveal thermodynamic linkages to ligand binding events. Analytical ultracentrifugation has been a fundamental technique in the determination of macromolecular reaction stoichiometry and energetics for 85 years. This approach is highly amenable to the extraction of thermodynamic couplings to small molecule binding in the overall reaction pathway. In the 1980s this approach was extended to the use of sedimentation velocity techniques, primarily by the analysis of tubulin-drug interactions by Na and Timasheff. This transport method necessarily incorporates the complexity of both hydrodynamic and thermodynamic nonideality. The advent of modern computational methods in the last 20 years has subsequently made the analysis of sedimentation velocity data for interacting systems more robust and rigorous. Here we review three examples where sedimentation velocity has been useful at extracting thermodynamic information about reaction stoichiometry and energetics. Approaches to extract linkage to small molecule binding and the influence of hydrodynamic nonideality are emphasized. These methods are shown to also apply to the collection of fluorescence data with the new Aviv FDS. PMID:21703752

Cole, James L.; Correia, John J.; Stafford, Walter F.

2011-01-01

148

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

SciTech Connect

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

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

1995-08-01

149

Elasticity of c*-Gels  

NASA Astrophysics Data System (ADS)

A junction affine network model is solved for chains following a Redner des Cloizeaux distribution. In a gel at c^* the network strands behave as isolated chains. In a good solvent their elastic properties cannot be obtained from Gaussian statistics as in the classical models of rubber elasticity. Instead the Redner-des Cloizeaux distribution is employed, which is known to be an excellent approximation to the end to end distance distribution of flexible polymer chains in a good solvent. The implications of using non-linear entropic springs, the role of fluctuations and the quality of the affine approximation are worked out for a Flory-Rehner model. The applicability to swollen networks and the elasticity of two dimensional c^*-gels are briefly discussed.

Everaers, Ralf

1995-10-01

150

Fluctuations in strained polymer gels  

SciTech Connect

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

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

1993-12-31

151

Hylan gel composition for percutaneous embolization.  

PubMed

Viscoelastic, pseudoplastic, radiopaque injectable hylan gel for percutaneous embolization was developed and evaluated by in vitro and in vivo tests. The embolization gel is composed of cross-linked hylan (hyaluronan, hyaluronate), tantalum, microcrystalline cellulose, hexamethonium chloride, and thrombin. Upon delivery through small-lumen catheters to the appropriate vascular site, the gel induces formation of a solid blood/gel coagulum. Results from animal studies (rat aorta, rabbit auricular artery) demonstrate that formation of complete and long-lasting arterial blockage is readily achievable without complications due to blood flow, partial vessel obstruction, uncontrolled polymerization, or movement of the gel or its components (specifically thrombin and hexamethonium chloride) into the circulation. Microscopic evaluation indicates that arterial occlusion initially occurs as a result of the injected gel and formed fibrin; at 7 weeks and beyond, arteries are occluded by injected gel, inflammatory cells and fibrosis (scar tissue). PMID:1874755

Larsen, N E; Leshchiner, E A; Parent, E G; Hendrikson-Aho, J; Balazs, E A; Hilal, S K

1991-06-01

152

Analyticity without Differentiability  

ERIC Educational Resources Information Center

In this article we derive all salient properties of analytic functions, including the analytic version of the inverse function theorem, using only the most elementary convergence properties of series. Not even the notion of differentiability is required to do so. Instead, analytical arguments are replaced by combinatorial arguments exhibiting

Kirillova, Evgenia; Spindler, Karlheinz

2008-01-01

153

CHARLOTTE: BIG DATA & ANALYTICS  

E-print Network

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

Raja, Anita

154

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

PubMed

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

Victorov, A; Radke, C; Prausnitz, J

2006-01-14

155

Bacterial cellulose gels with high mechanical strength.  

PubMed

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

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

2015-02-01

156

Metal-silica sol-gel materials  

NASA Technical Reports Server (NTRS)

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.

Stiegman, Albert E. (Inventor)

2002-01-01

157

Generative force of self-oscillating gel.  

PubMed

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

Hara, Yusuke; Mayama, Hiroyuki; Morishima, Keisuke

2014-03-01

158

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

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.

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

1992-11-03

159

Intercomparison of small biomolecules by gel filtration and small angle scattering  

SciTech Connect

This paper describes how small angle neutron scattering (SANS) can be used to confirm that gel filtration results are free of dimerization effects. After characterization by analytical gel filtration, concentrated solutions (in heavy water, D2O) of a cobra neurotoxin, a cytotoxin, and a cytotoxin analog are studied by SANS. Small differences in shape are shown to be discernible by means of least-square fits to ellipsoidal models. The parallel axis theorem is then invoked to assess dimerization levels statistically. The results are briefly discussed on the basis of function in relation to structure.

Martel, P.; Stepanik, T.M.; Szabo, A.G. (Atomic Energy of Canada Limited, Chalk River Nuclear Laboratories, Ontario (Canada))

1990-05-01

160

Automated apparatus for producing gradient gels  

DOEpatents

Apparatus for producing a gradient gel which serves as a standard medium for a two-dimensional analysis of proteins, the gel having a density gradient along its height formed by a variation in gel composition, with the apparatus including first and second pumping means each including a plurality of pumps on a common shaft and driven by a stepping motor capable of providing small incremental changes in pump outputs for the gel ingredients, the motors being controlled, by digital signals from a digital computer, a hollow form or cassette for receiving the gel composition, means for transferring the gel composition including a filler tube extending near the bottom of the cassette, adjustable horizontal and vertical arms for automatically removing and relocating the filler tube in the next cassette, and a digital computer programmed to automatically control the stepping motors, arm movements, and associated sensing operations involving the filling operation.

Anderson, Norman L. (Clarendon Hills, IL)

1986-01-01

161

Automated apparatus for producing gradient gels  

DOEpatents

Apparatus for producing a gradient gel which serves as a standard medium for a two-dimensional analysis of proteins, the gel having a density gradient along its height formed by a variation in gel composition, with the apparatus including first and second pumping means each including a plurality of pumps on a common shaft and driven by a stepping motor capable of providing small incremental changes in pump outputs for the gel ingredients, the motors being controlled, by digital signals from a digital computer, a hollow form or cassette for receiving the gel composition, means for transferring the gel composition including a filler tube extending near the bottom of the cassette, adjustable horizontal and vertical arms for automatically removing and relocating the filler tube in the next cassette, and a digital computer programmed to automatically control the stepping motors, arm movements, and associated sensing operations involving the filling operation.

Anderson, N.L.

1983-11-10

162

Active gel model of amoeboid cell motility  

NASA Astrophysics Data System (ADS)

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.

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

2013-02-01

163

Western Blot Protocol 1. Cast Gel  

E-print Network

resolution gel (recipe) and mix Make stacking gel (recipe) à diwater--acrylamide/bis Add 7.5ml of res gel __________________________ul in plates and rock 1hr. (Could stop here and put in 4 o over night.) ***SAVE AB*** Add 10ml ______________________________ul à Rock 30 min. / pour out milk Add 10ml milkà rock 10 min. / pour out Repeat Wash with 15ml

Ye, Jianping

164

Determination of diclazuril, toltrazuril and its two metabolites in poultry tissues and eggs by gel permeation chromatographyliquid chromatographytandem mass spectrometry  

Microsoft Academic Search

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

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

2011-01-01

165

Solution structure determination of monomeric human IgA2 by X-ray and neutron scattering, analytical ultracentrifugation and constrained modelling: a comparison with monomeric human IgA1.  

PubMed

Immunoglobulin A (IgA), the most abundant human immunoglobulin, mediates immune protection at mucosal surfaces as well as in plasma. It exists as two subclasses IgA1 and IgA2, and IgA2 is found in at least two allotypic forms, IgA2m(1) or IgA2m(2). Compared to IgA1, IgA2 has a much shorter hinge region, which joins the two Fab and one Fc fragments. In order to assess its solution structure, monomeric recombinant IgA2m(1) was studied by X-ray and neutron scattering. Its Guinier X-ray radius of gyration R(G) is 5.18 nm and its neutron R(G) is 5.03 nm, both of which are significantly smaller than those for monomeric IgA1 at 6.1-6.2 nm. The distance distribution function P(r)for IgA2m(1) showed a broad peak with a subpeak and gave a maximum dimension of 17 nm, in contrast to the P(r) curve for IgA1, which showed two distinct peaks and a maximum dimension of 21 nm. The sedimentation coefficients of IgA1 and IgA2m(1) were 6.2S and 6.4S, respectively. These data show that the solution structure of IgA2m(1) is significantly more compact than IgA1. The complete monomeric IgA2m(1) structure was modelled using molecular dynamics to generate random IgA2 hinge structures, to which homology models for the Fab and Fc fragments were connected to generate 10,000 full models. A total of 104 compact best-fit IgA2m(1) models gave good curve fits. These best-fit models were modified by linking the two Fab light chains with a disulphide bridge that is found in IgA2m(1), and subjecting these to energy refinement to optimise this linkage. The averaged solution structure of the arrangement of the Fab and Fc fragments in IgA2m(1) was found to be predominantly T-shaped and flexible, but also included Y-shaped structures. The IgA2 models show full steric access to the two FcalphaRI-binding sites at the Calpha2-Calpha3 interdomain region in the Fc fragment. Since previous scattering modelling had shown that IgA1 also possessed a flexible T-shaped solution structure, such a T-shape may be common to both IgA1 and IgA2. The final models suggest that the combination of the more compact IgA2m(1) and the more extended IgA1 structures will enable human IgA to access a broader range of antigens than either acting alone. The hinges of both IgA subclasses appear to show reduced flexibility when compared to their equivalents in IgG, and this may be important for maintaining an extended IgA structure. PMID:15111057

Furtado, Patricia B; Whitty, Patrick W; Robertson, Alexis; Eaton, Julian T; Almogren, Adel; Kerr, Michael A; Woof, Jenny M; Perkins, Stephen J

2004-05-14

166

21 CFR 866.4900 - Support gel.  

Code of Federal Regulations, 2014 CFR

...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)...

2014-04-01

167

21 CFR 866.4900 - Support gel.  

Code of Federal Regulations, 2011 CFR

...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)...

2011-04-01

168

21 CFR 866.4900 - Support gel.  

Code of Federal Regulations, 2012 CFR

...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)...

2012-04-01

169

21 CFR 866.4900 - Support gel.  

Code of Federal Regulations, 2010 CFR

...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)...

2010-04-01

170

21 CFR 866.4900 - Support gel.  

Code of Federal Regulations, 2013 CFR

...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)...

2013-04-01

171

Food gels: gelling process and new applications.  

PubMed

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

Banerjee, Soumya; Bhattacharya, Suvendu

2012-01-01

172

Conducting Polymer Electrodes for Gel Electrophoresis  

PubMed Central

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

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

2014-01-01

173

Gel catalysts that switch on and off.  

PubMed

We report development of a polymer gel with a catalytic activity that can be switched on and off when the solvent composition is changed. The gel consists of two species of monomers. The major component, N-isopropylacrylamide, makes the gel swell and shrink in response to a change in composition of ethanol/water mixtures. The minor component, vinylimidazole, which is capable of catalysis, is copolymerized into the gel network. The reaction rate for catalytic hydrolysis of p-nitrophenyl caprylate was small when the gel was swollen. In contrast, when the gel was shrunken, the reaction rate increased 5 times. The activity changes discontinuously as a function of solvent composition, thus the catalysis can be switched on and off by an infinitesimal change in solvent composition. The kinetics of catalysis by the gel in the shrunken state is well described by the Michaelis-Menten formula, indicating that the absorption of the substrate by the hydrophobic environment created by the N-isopropylacrylamide polymer in the shrunken gel is responsible for enhancement of catalytic activity. In the swollen state, the rate vs. active site concentration is linear, indicating that the substrate absorption is not a primary factor determining the kinetics. Catalytic activity of the gel is studied for substrates with various alkyl chain lengths; of those studied the switching effect is most pronounced for p-nitrophenyl caprylate. PMID:10954747

Wang, G; Kuroda, K; Enoki, T; Grosberg, A; Masamune, S; Oya, T; Takeoka, Y; Tanaka, T

2000-08-29

174

Tissue simulating gel for medical research  

NASA Technical Reports Server (NTRS)

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.

Companion, John A. (Inventor)

1991-01-01

175

Population dynamics of chesapeake bay virioplankton: total-community analysis by pulsed-field gel electrophoresis  

PubMed

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

Wommack; Ravel; Hill; Chun; Colwell

1999-01-01

176

Principles of Gel Permeation Chromatography  

NSDL National Science Digital Library

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

177

ANALYTICAL SCIENCES 2001, VOL.17 SUPPLEMENT i193 2001 The Japan Society for Analytical Chemistry  

E-print Network

has been no systematic comparison among different systems. Such comparisons would require uniform includes a lack of comparison between biological and synthetic polyelectrolytes. The focus of work- sensor, and ultracentrifugation. Many of these are separation methods, e.g. size exclusion chromatography

Dubin, Paul D.

178

ANALYTIC CELL DECOMPOSITION AND ANALYTIC MOTIVIC ...  

E-print Network

model theoretic setting. Another necessary ingredient for cell decomposition is an analysis of analytic ... result is new also in the algebraic case, and is used in [4] to prove a change of variables formula ..... Note that ? extends coefficient-wise to.

2005-03-30

179

Business Analytics and Optimization  

E-print Network

of an ongoing commitment by IBM Global Business Services to provide analysis and viewpoints that help companiesBusiness Analytics and Optimization IBM Institute for Business Value IBM Global Business Services Business Analytics and Optimization for the Intelligent Enterprise #12;IBM Institute for Business Value IBM

180

Selectivity in Analytical Chemistry  

NSDL National Science Digital Library

The International Union of Pure and Applied Chemistry (IUPAC) has put online a draft of recommendations for the correct use of the terms "selectivity" and "specificity" in analytical chemistry. The provisional report, available for download in .pdf format, was drafted by the IUPAC's Analytical Division Task Force, and reader comments are welcomed until September 30, 2001.

2001-01-01

181

Learning Analytics Considered Harmful  

ERIC Educational Resources Information Center

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

Dringus, Laurie P.

2012-01-01

182

Signals: Applying Academic Analytics  

ERIC Educational Resources Information Center

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

Arnold, Kimberly E.

2010-01-01

183

Analytical testing techniques  

NASA Technical Reports Server (NTRS)

Structural dynamic analytical testing techniques can be a tool to determine the source of structural dynamic problems and the solution to these problems. Analytical testing techniques are based upon dynamic testing methods and analysis of test results. These methods apply primarily to constructed wind turbine systems. A summary of these methods is presented.

Jones, R.

1978-01-01

184

Selectivity in Analytical Chemistry  

NSDL National Science Digital Library

The International Union of Pure and Applied Chemistry (IUPAC) has put online a draft of recommendations for the correct use of the terms "selectivity" and "specificity" in analytical chemistry. The provisional report, available for download in .pdf format, was drafted by the IUPAC's Analytical Division Task Force, and reader comments are welcomed until September 30, 2001.

2005-11-01

185

Equilibrium swelling and mesoscopic structure of a diblockcopolymer gel in a selective solvent  

SciTech Connect

Our previous analytic model of a block-copolymer gel swollen in selective solvent was obtained from self-consistent field theory in the strong-segregation approximation; it takes into account the structure of the gel on the mesoscopic scale but is restricted to the case where the solvent-selective polymer subchains are located in the inner (minority) domains. In this work, the model is generalized to include swollen outer domains. The dependence of the equilibrium microdomain size on solvent uptake has been established. We calculate equilibrium swelling and determine relative stabilities for gels of different morphologies. Predicted equilibrium profiles of polymer segments are compared with computer simulation. Based on the average-solvent-fraction approximation, results obtained for an athermal solvent are very close to those from equilibrium profiles. Attention is given to the effect of partial restrictions in self-assembly of polymer chains on microdomain spacing and on equilibrium swelling.

Victorov, Alexey; Radke, Clay; Prausnitz, John

2005-01-05

186

Morphology and CO uptake in Tobermorite gel  

Microsoft Academic Search

Tobermorite gels have been synthesized in various degrees of crystallinity by a number of techniques. In this article, it is shown that a tobermorite gel may absorb carbon dioxide from the atmosphere to a level over 20% CO by wt, with virtually no change in morphology. The marked changes in crystallinity and infrared absorption which occur during this process are

T. Baird; A. G. Cairns-Smith; D. S. Snell

1975-01-01

187

Alumina precursors produced by gel combustion  

Microsoft Academic Search

Alumina precursor produced by a gel combustion method using aluminum nitrate and citric acid as raw materials was investigated. Thermodynamic calculation of the combustion reaction shows that as the citrate-to-nitrate ratio ? increases, the enthalpy of reaction and adiabatic flame temperatures also increase. The DSC analysis indicates that the combustion temperature of the gel decreases, as the citrate content in

Jiang Li; Yusong Wu; Yubai Pan; Jingkun Guo

2007-01-01

188

A Simple Vertical Slab Gel Electrophoresis Apparatus.  

ERIC Educational Resources Information Center

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

Carter, J. B.; And Others

1983-01-01

189

Drying compressed natural gas with silica gel  

Microsoft Academic Search

In order to determine the feasibility of using the heat of compressed natural gas to regenerate the sorbent, an investigation of gas drying with silica gel at 20 MPa and regeneration of the silica gel at relatively low temperature in a pilot unit was performed. Prior to this drying method, in automotive gas-filling compressor stations, compressed natural gas was subjected

G. V. Vyalkina; Z. A. Nabutovskii; V. I. Popov; E. N. Torevskii

1986-01-01

190

Microporous gel electrolyte Li-ion battery  

Microsoft Academic Search

This paper describes the fabrication and performance of microporous gel electrolyte (MGE) Li-ion batteries. Fabrication of the MGE battery includes three steps: (1) making a microporous membrane separator by the phase inversion method, (2) activating the battery with a liquid electrolyte, and (3) forming MGE in situ by cycling the battery. The MGE contains three phases: liquid electrolyte, gel electrolyte,

S. S. Zhang; K. Xu; D. L. Foster; M. H. Ervin; T. R. Jow

2004-01-01

191

Sol-gel kinetics by NMR  

SciTech Connect

The chemical synthesis of advanced ceramic and glass materials by the sol-gel process has become an area of increasing activity in the field of material science. The sol-gel process provides a means to prepare homogeneous, high purity materials with tailored chemical and physical properties. This paper surveyed the nuclear magnetic resonance (NMR) studies of silicon-based sol-gel kinetics. A review of the various models which have been used to analyze the chemical kinetics of various sol-gel systems was presented. The utility of NMR spectroscopy was demonstrated in investigating the influence that various reaction conditions have on the reaction pathways by which sol-gel derived materials are synthesized. By observing in a direct fashion the chemical pathway of the sol-gel, it is often possible to relate the final properties of the material to the formulation and reaction conditions of the sol-gel. The study of reaction kinetics by NMR is expected to play an increasingly important role in understanding sol-gel processing and material properties. 15 refs. (DP)

Assink, R.A.; Kay, B.D.

1991-01-01

192

Crosslinked acid gels offer advantages  

SciTech Connect

Acid polymer gels having a pH less than one have been crosslinked for retarding the chemical and physical activity of hydrochloric acid on calcareous formations. Hydrochloric acid concentrations from /one quarter/% to 28% have been successfully crosslinked. This unique stimulation fluid offers high viscosity with adequate shear stability, perfect support for propants, and clay stabilization. Additionally, the fluid provided effective fluid loss control and retardation of acid reaction enabling live acid to penetrate deeper into the formation for better conductivity; furthermore, there is practically a residue free break for rapid cleanup of the well after the job. Results of lab and field tests show this new acid crosslinked system to be an effective stimulation fluid for acidizing and acid fracturing in calcareous and sandstone formations having low permeability. 5 refs.

Pabley, A.S.; Holcomb, D.L.

1981-09-28

193

Slide-ring gel: Topological gel with freely movable cross-links  

NASA Astrophysics Data System (ADS)

The structure of slide-ring (SR) gel was investigated by means of small angle neutron scattering (SANS). The SR gel was synthesized by coupling of ?-cyclodextrin molecules on polyrotaxane chains. A cross-linking point of SR gel has a shape of figure-of-eight. Two-dimensional SANS patterns for uniaxially stretched SR gels showed a normal butterfly pattern. This result indicates that the cross-links slide along the polymer chain so as to minimize the local strain as a pulley. The pulley effect was found to be significant to reduce spatial inhomogeneities inherent in polymer gels.

Karino, Takeshi; Shibayama, Mitsuhiro; Ito, Kohzo

2006-11-01

194

Catalytic control over supramolecular gel formation  

NASA Astrophysics Data System (ADS)

Low-molecular-weight gels show great potential for application in fields ranging from the petrochemical industry to healthcare and tissue engineering. These supramolecular gels are often metastable materials, which implies that their properties are, at least partially, kinetically controlled. Here we show how the mechanical properties and structure of these materials can be controlled directly by catalytic action. We show how in situ catalysis of the formation of gelator molecules can be used to accelerate the formation of supramolecular hydrogels, which drastically enhances their resulting mechanical properties. Using acid or nucleophilic aniline catalysis, it is possible to make supramolecular hydrogels with tunable gel-strength in a matter of minutes, under ambient conditions, starting from simple soluble building blocks. By changing the rate of formation of the gelator molecules using a catalyst, the overall rate of gelation and the resulting gel morphology are affected, which provides access to metastable gel states with improved mechanical strength and appearance despite an identical gelator composition.

Boekhoven, Job; Poolman, Jos M.; Maity, Chandan; Li, Feng; van der Mee, Lars; Minkenberg, Christophe B.; Mendes, Eduardo; van Esch, Jan H.; Eelkema, Rienk

2013-05-01

195

Radiological properties of normoxic polymer gel dosimeters  

SciTech Connect

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.

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

2005-04-01

196

Dewatering fine coal slurries by gel extraction  

SciTech Connect

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.

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

1990-01-01

197

Sol-gel chemical sensors for surface-enhanced Raman spectroscopy  

NASA Astrophysics Data System (ADS)

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.

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

1999-02-01

198

Sol-Gel Manufactured Energetic Materials  

DOEpatents

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.

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

199

Electroacoustics of Particles Dispersed in Polymer Gel  

SciTech Connect

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.

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

2011-06-27

200

Gel phantom in selective laser phototherapy  

NASA Astrophysics Data System (ADS)

Tissue-simulating gel phantoms have been used in selective laser photothermal interaction. The gelatin phantom provides a uniform tissue-simulating medium for analyzing thermal performance under laser radiation. The gelatin phantom gel is used particularly in measurements of thermal reactions in laser thermology. The gelatin phantom is made from gelatin and Liposyn. A special gel sphere with Indocyanine Green (ICG) laser absorption enhancement dye is embedded in normal gel to simulate the dye-enhanced tumor in normal tissue. The concentration of ICG within the dye sphere is optimized using simulation for selective phototherapy. As a first attempt, the concentration of ICG and laser power density was optimized using a temperature ratio of target tissue versus surrounding tissue. The gel thermal performance is also monitored using MRI thermology imaging technology. The thermal imaging shows in vivo, 3D temperature mapping inside the gel. The study of thermal distribution using gel phantom provides information to guide the future selective laser photothermal thermal therapy.

Chen, Yichao; Bailey, Christopher A.; Cowan, Thomas M.; Wu, Feng; Liu, Hong; Towner, Rheal A.; Chen, Wei R.

2008-02-01

201

Analytical techniques: A compilation  

NASA Technical Reports Server (NTRS)

A compilation, containing articles on a number of analytical techniques for quality control engineers and laboratory workers, is presented. Data cover techniques for testing electronic, mechanical, and optical systems, nondestructive testing techniques, and gas analysis techniques.

1975-01-01

202

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

PubMed

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

Vandecasteele, Jan; De Deene, Yves

2013-09-21

203

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

NASA Astrophysics Data System (ADS)

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.

Vandecasteele, Jan; De Deene, Yves

2013-09-01

204

Extreme Scale Visual Analytics  

SciTech Connect

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.

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

2013-01-01

205

Strain Hardening of Fractal Colloidal Gels  

NASA Astrophysics Data System (ADS)

We report on experiments on the rheology of gels formed by diffusion-limited aggregation of neutrally buoyant colloidal particles. These gels form very weak solids, with the elastic modulus, G'\\(?\\), larger than the loss modulus, G''\\(?\\), and with both G'\\(?\\) and G''\\(?\\) exhibiting only a very weak frequency dependence. Upon small but finite strains ?<0.45 the elastic modulus increases roughly exponentially with ?2. We explain the observed strain hardening with the highly nonlinear elastic response of the rigid backbone of the gel to elongational deformation.

Gisler, T.; Ball, R. C.; Weitz, D. A.

1999-02-01

206

Energy dependence of Fricke-xylenol orange gel and gel based on Turnbull blue for low-energy photons  

NASA Astrophysics Data System (ADS)

The paper describes the energy dependence of two types of radiochromic gels, a Fricke-xylenol orange gel (FX gel) and a gel based on Turnbull blue (TB gel), on low energy photons between 14 and 145 keV. Gel samples were irradiated at reference photon fields at the Czech Metrology Institute and evaluated by two independent optical methods. Measurements revealed that the response of the TB gel is independent on photon energy down to at least 14 keV photons, while the FX gel is energy dependent for photons below roughly 50 keV.

olc, Jaroslav; Sochor, Vladimr; Kozubkov, Petra

2015-01-01

207

SRL online Analytical Development  

SciTech Connect

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.

Jenkins, C.W.

1991-12-31

208

SRL online Analytical Development  

SciTech Connect

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.

Jenkins, C.W.

1991-01-01

209

Heterogeneous integration of gels into microfluidics using a mesh carrier.  

PubMed

The incorporation of hydrogels inside microfluidics is a promising method for localizing receptors inside microfluidic structures for many bio-analytical applications as well as for working with cells. However, current methods rely on the in situ polymerization of hydrogels and therefore necessitate optical masks and extensive post-polymerization steps for example for washing uncrosslinked gel precursors and receptors. Here, we report a simple and efficient method for the integration of hydrogels to microfluidic chips. Small volumes of poly(ethylene)glycol-based acrylamide (PEGACA) hydrogels are photopolymerized on a mesh, rinsed, partially dried and transferred to microfluidic structures by simple contact. The gels can be derivatized before transfer with receptors such as streptavidin, antibodies, or can entrap beads as small as 200 nm. We detail the role of meshes relative to the mesh density and wettability and demonstrate how hydrogels can be transferred into capillary-driven microfluidic chips, which are easily sealed using a dry-film resist. By analogy to microfabrication strategies wherein critical components are produced separately and then combined, our method introduces the concept of heterogeneous integration of critical (bio)chemicals to microfluidic chips using an intermediate mesh carrier. PMID:24999091

Eker, Bilge; Temiz, Yuksel; Delamarche, Emmanuel

2014-12-01

210

Phase diagram of a reentrant gel of patchy particles  

SciTech Connect

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.

Roldn-Vargas, Sndalo; Smallenburg, Frank; Sciortino, Francesco [Department of Physics, Sapienza, Universit di Roma, Piazzale Aldo Moro 2, I-00185 Roma (Italy)] [Department of Physics, Sapienza, Universit di Roma, Piazzale Aldo Moro 2, I-00185 Roma (Italy); Kob, Walter [Laboratoire Charles Coulomb, UMR 5221, CNRS and Universit Montpellier 2, 34095 Montpellier (France)] [Laboratoire Charles Coulomb, UMR 5221, CNRS and Universit Montpellier 2, 34095 Montpellier (France)

2013-12-28

211

Frictional properties of gel engineering materials with laser surface texturing  

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

212

Complex Analytic and Differential Geometry  

E-print Network

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

Demailly, Jean-Pierre

213

Colloidal gels under shear: Strain rate effects  

NASA Astrophysics Data System (ADS)

Attractive colloidal particles are trapped in metastable states such as colloidal gels at high attraction strengths and attractive glasses and high volume fractions. Under shear such states flow via a two step yielding process that relates to bond and cluster or cage breaking. We discuss the way the structural properties and related stress response are affected by the shear rate. At low rates colloidal gels yield during start-up shear essentially in a single step, exhibiting a single stress overshoot due to creation of compact flowing clusters. With increasing shear rate a second stress overshoot, linked with further cluster breaking up to individual particles, is becoming more pronounced. We further present the age dependence of the two step yielding and wall slip effects often taking place during rheological experiments of colloidal gels. The latter is related both with the shear rate dependent gel structure as well as the time evolution of the near wall structure.

Koumakis, N.; Ballesta, P.; Besseling, R.; Poon, W. C. K.; Brady, J. F.; Petekidis, G.

2013-02-01

214

Turbidimetric studies of Limulus coagulin gel formation.  

PubMed Central

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

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

1996-01-01

215

Advanced gel propulsion controls for kill vehicles  

NASA Astrophysics Data System (ADS)

A gel propulsion control concept for tactical applications is reviewed, and the status of the individual component technologies currently under development at the Aerojet Propulsion Division is discussed. It is concluded that a gel propellant Divert and Attitude Control Subsystem (DACS) provides a safe, insensitive munitions compliant alternative to current liquid Theater Missile Defense (TMD) DACS approaches. The gel kill vehicle (KV) control system packages a total impulse typical of a tactical weapon interceptor for the ground- or sea-based TMD systems. High density packaging makes it possible to increase firepower and to eliminate long-term high pressure gas storage associated with bipropellant systems. The integrated control subsystem technologies encompass solid propellant gas generators, insulated composite overwrapped propellant tanks, lightweight endoatmospheric thrusters, and insensitive munition gel propellants, which meet the requirements of a deployable, operationally safe KV.

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

1993-06-01

216

Magnetic Hyperthermia in ferrofluid-gel composites  

NASA Astrophysics Data System (ADS)

Magnetic hyperthermia is the generation of heat by an external magnetic field using superparamagnetic nanoparticles. However, there are still questions concerning magnetic hyperthermia in tissue; in particular the confinement of the nanoparticles at mesoscopic scales. We used Agarose and Alginate gels as models for human tissue and embedded magnetic nanoparticles in them. We report the synthesis and characterization of dextran coated iron oxide (Fe3O4) nanoparticles. Characterization of these nanoparticles was done using X-ray diffraction, transmission electron microscopy, magnetometry, and hyperthermia measurements. Temperature dependent susceptibility measurements reveal a sharp anomaly in the ferrofluid sample at the freezing temperature. This is conspicuously absent in the ferrofluid-gel composites. Heat generation studies on these superparamagnetic gel-composites revealed a larger heat production in the ferrofluids(4W/g) as compared to the gels(1W/g), which we attribute to a reduction in Brownian relaxation for the nanoparticles embedded in Agarose and Alginate.

Nemala, Humeshkar; Wadehra, Anshu; Dixit, Ambesh; Regmi, Rajesh; Vaishnava, Prem; Lawes, Gavin; Naik, Ratna

2012-02-01

217

Sol-gel antireflective coating on plastics  

DOEpatents

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.

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

1990-01-01

218

Sol-gel antireflective coating on plastics  

DOEpatents

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.

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

1988-01-26

219

[Formulation of benzethonium chloride into gels].  

PubMed

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

Cimrik, Jozef; Vitkov, Zuzana; Herdov, Petra; Kodadov, Alexandra; Vmi, Daniel

2014-06-01

220

Gel electrolyte candidates for electrochromic devices (ECDs)  

NASA Astrophysics Data System (ADS)

A comparison of key parameters of seven different gel electrolytes for use in electrochromic devices (ECD) is reported. The ionic conductivity, transmittance, and stability of the gel electrolytes are important considerations for smart window applications. The gel electrolytes were prepared by combining polymethylmethacrylate (PMMA) with a salt and a solvent combination. Two different salts, lithium perchlorate (LiClO4) and trifluorosulfonimide (LiN(CF3SO2)2), and three solvent combinations, acetonitrile and propylene carbonate (ACN and PC), ethylene carbonate and propylene carbonate (EC and PC), and Gamma-butyrolactone and propylene carbonate (GBL and PC) were investigated. Results show that gel electrolytes composed of a LiClO4 and GBL+PC combination and a LiClO4 and EC+PC combination are the best candidates for a smart window device based on its high conductivity over time and various temperatures, as well as its electrochemical stability and high transmittance.

Legenski, Susan E.; Xu, Chunye; Liu, Lu; Le Guilly, Marie O.; Taya, Minoru

2004-07-01

221

Procedure to prepare transparent silica gels  

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

222

Prepartially crosslinked gel for retarding fluid flow  

SciTech Connect

This patent describes a subterranean formation having channels which have a high permeability to the flow of fluids. A process for retarding fluid flow in the channels comprises: providing a gel-forming composition which when substantially completely gelled in the high permeability channels is operable for retarding fluid flow therein. The gel-forming composition comprises: an aqueous solution comprising a first substance selected from the group consisting of polyvinyl alcohol, a polyvinyl alcohol copolymer, and mixtures thereof, and an effective amount of a second substance selected from the group consisting of aldehydes, aldehyde generating substances, acetals, acetal generating substances, and mixtures thereof capable of crosslinking with the first substance through the formation of acetal crosslinkages. The second substance is operable for forming a gel with the aqueous solution when the gel-forming composition is acidic.

Sandiford, B.B.; Chiou, C.S.

1987-05-19

223

Polymer Gels as Temperature-responsive Attenuator  

NASA Astrophysics Data System (ADS)

The ultrasonic attenuation in N-isopropylacrylamide (NIPA) gel has been measured as a function of temperature at various frequencies. It is found that at room temperature, the attenuation of a longitudinal ultrasonic wave in the gel is small and close to that of pure water. However, as the temperature increases above the spinodal phase transition point of the gel, the attenuation increases drastically. This change of the attenuation is completely reversible and due to the micro-domains formed in the NIPA gel above its phase transition temperature. The change of attenuation at 15 MHz in the temperature range between 26 and 45 ^0C is about 26 dB/cm. The rate of attenuation change is within 5 minutes for a sample with diameter 1 cm and height 0.8 cm. The results reported here may have potential applications from ultrasonic assistant drug-release to a switch for ultrasonic signals.

Yuan, Kaihua; Hu, Zhibing; Li, Yong

1998-10-01

224

Sol-Gel Manufactured Energetic Materials  

Microsoft Academic Search

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

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

2005-01-01

225

Particle size analysis of PAGAT gel dosimetry  

NASA Astrophysics Data System (ADS)

This work represents the response of PAGAT gel dosimeter using UV-Visible Spectrophotometry. The particle size and optimal wavelength of the gel sample were analyzed from the obtained spectrum. In addition, the compressibility was estimated using Ultrasonic Interferometer. The results showed that the particle size of the PAGAT varied appreciably with respect to the dose applied but did not vary significantly with the post irradiation time.

Samuel, E. J. J.; Sathiyaraj, P.; Titus, D.; Kumar, D. S.

2015-01-01

226

Tissue-Simulating Gel For Medical Research  

NASA Technical Reports Server (NTRS)

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.

Companion, John A.

1992-01-01

227

Mechanical phase diagram of shrinking cylindrical gels  

NASA Astrophysics Data System (ADS)

When polymer gels are subjected to an external stimulus such as temperature or solvent change, they undergo a phase transition often driving pattern formation. In this paper, we use an elastic model to investigate the linear stability of shrinking cylindrical NIPA gels. This model exhibits bubble and bamboo patterns. The wavelengths of these patterns and their phase diagram are in agreement with the experiment of Matsuo and Tanaka [Nature (London) 358, 482 (1992)].

Boudaoud, Arezki; Chaeb, Sahraoui

2003-08-01

228

The use of highly ordered vesicle gels as template for the formation of silica gels.  

PubMed

A spontaneously forming gel of unilamellar vesicles based on sodium oleate (Na oleate) and 1-octanol as amphiphiles has been employed as a template in the formation of a silica gel formed by the hydrolysis of the inorganic precursor tetraethyl orthosilicate (TEOS). Up to about 10 wt % TEOS can be incorporated into this vesicle gel without phase separation and in a fully homogeneous formation process by simple mixing of the components. The process itself relies solely upon the self-organizing properties of this amphiphilic template system. The formation process was followed by means of time-resolved turbidity, rheology, and small-angle neutron scattering (SANS) experiments. It can be concluded that the presence of the precursor TEOS affects the kinetics of the process but the original vesicle gel structure is retained even up to highest TEOS content. The kinetic studies confirm that under the chosen conditions the vesicle formation proceeds much faster than the hydrolysis of TEOS and the subsequent formation of the silica gel. SANS displays in the low q-range an additional scattering due to the silica gel network, i.e., a hybrid material of an amphiphilic vesicle gel and an inorganic oxide gel is formed. Thus, this method is a very facile novel route of forming a highly ordered silica/vesicle gel by employing a self-organizing amphiphilic system as template and the formation of the silica network proceeds in a fully homogeneous fashion under kinetic control. PMID:21692463

Oppel, Claudia; Prvost, Sylvain; Noirez, Laurence; Gradzielski, Michael

2011-07-19

229

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

NASA Astrophysics Data System (ADS)

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

Zheng, Yindong; Wang, Changjie; Hu, Zhibing

1998-10-01

230

Gel electrolyte for lithium-ion batteries.  

SciTech Connect

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.

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

2008-03-10

231

Binary diamondoid building blocks for molecular gels.  

PubMed

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

Zhang, Mengwen; Zukoski, Charles F

2014-07-01

232

Treatment of osteochondral injuries with platelet gel  

PubMed Central

OBJECTIVES: Treatments for injured articular cartilage have not advanced to the point that efficient regeneration is possible. However, there has been an increase in the use of platelet-rich plasma for the treatment of several orthopedic disorders, including chondral injuries. Our hypothesis is that the treatment of chondral injuries with platelet gel results in higher-quality repair tissue after 180 days compared with chondral injuries not treated with gel. METHODS: A controlled experimental laboratory study was performed on 30 male rabbits to evaluate osteochondral injury repair after treatment with or without platelet gel. Osteochondral injuries were surgically induced in both knees of each rabbit at the medial femoral condyle. The left knee injury was filled with the platelet gel, and the right knee was not treated. Microscopic analysis of both knee samples was performed after 180 days using a histological grading scale. RESULTS: The only histological evaluation criterion that was not significantly different between treatments was metachromasia. The group that was treated with platelet gel exhibited superior results in all other criteria (cell morphology, surface regularity, chondral thickness and repair tissue integration) and in the total score. CONCLUSION: The repair tissue was histologically superior after 180 days in the study group treated with platelet gel compared with the group of untreated injuries. PMID:25518022

Danieli, Marcus Vinicius; da Rosa Pereira, Hamilton; de S Carneiro, Carlos Augusto; Felisbino, Srgio Luiz; Deffune, Elenice

2014-01-01

233

Natural gels in the Yucca Mountain Area, Nevada, USA  

Microsoft Academic Search

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.

Levy

1991-01-01

234

Sampling and Sensing Systems for High Priority Analytes  

SciTech Connect

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.

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

1999-04-01

235

COMPLEX ANALYTIC GEOMETRY AND ANALYTIC-GEOMETRIC CATEGORIES  

E-print Network

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

236

Preparation and in vitro percutaneous penetration of simvastatin ethosome gel.  

PubMed

To prepare ethosome gel containing simvastatin ethosome and investigate the permeation behavior of simvastatin from ethosome gel. Cumulative permeation quantity in unit area and intradermal retention were the indicators to evaluate the effects of simvastatin in vitro percutaneous permeation behavior. Cumulative permeation quantity in unit area of simvastatin ethosome gel was significantly higher than other agents (P < 0.05), the intradermal retention of simvastatin ethosome gel, simvastatin gel containing 1%, and 3% menthol were significantly higher than simvastatin gel (P < 0.05). Ethosome gel could enhance the skin permeation and accumulation in a depot of simvastatin. PMID:23305447

An, Keyao; Sun, Yong; Wu, Yan; Yuan, Haicheng; Cui, Zhaoyuan; Xu, Lisa

2013-10-01

237

Uncertainty in 3D gel dosimetry  

NASA Astrophysics Data System (ADS)

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.

De Deene, Yves; Jirasek, Andrew

2015-01-01

238

A newly developed chromium(III) gel technology  

SciTech Connect

Laboratory testing of a recently developed chromium(III) (Cr(III)) gel technology is reported. The gels can be used in conjunction with a number of oilfield treatments. The single-fluid acrylamide-polymer/Cr(III)-carboxylate aqueous gels are formed by crosslinking acrylamide polymer with a Cr(III)-carboxylate-complex crosslinking agent. Representative gel compositions and associated gel properties are discussed.

Sydansk, R.D. (Marathon Oil Co., Littleton, CO (USA). Research Div.)

1990-08-01

239

Recycling of superfine resolution agarose gel.  

PubMed

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

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

2013-01-01

240

Mechanical stability of fractal colloidal gels  

NASA Astrophysics Data System (ADS)

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 ?.

Manley, Suliana

241

Carbonate hydroxyapatite gel monolith formation and drying.  

PubMed

The effect of carbonate in reducing the crystal size of precipitated hydroxyapatite by approximately an order of magnitude has not been used previously in the preparation of gel monoliths for the fabrication of carbonate hydroxyapatite ceramics. The aim of this study was to devise a method whereby gel monoliths of carbonate hydroxyapatite could be repeatably produced without cracking. A precipitation reaction was used for the preparation of carbonate hydroxyapatities with carbonate contents of 5.8 and 7.8 wt%. Biaxial vacuum filtration was used to form disc shaped monoliths. The rate of filtration of a 7.8 wt% carbonate hydroxyapatite sol was measured throughout the gelation process. Gel monoliths were dried slowly in air and the mass and dimensions of the gel were recorded once approximately every 24 hours. Using this data, the permeability, water volume fraction with time, rate of water loss, gelation point and gel density were determined. The pore size distribution was measured using mercury porosimetry for a carbonate apatite gel and a pressed powder pellet of a commercial hydroxyapatite. In tact monoliths were formed with masses up to 9.9 g. It was found that gelation behaviour was independent of monolith size and carbonate content and the final green density of all monoliths was 37%. Gelation was found to occur at 50-55 vol% water. Gel monoliths were found to have a monomodal pore size distribution with a mean pore size of 9.1 nm, whereas a pressed pellet of hydroxyapatite had a bimodal pore size distribution. PMID:8761520

Barralet, J E; Best, S M; Bonfield, W

1996-01-01

242

Pseudomonas aeruginosa exotoxin: purification by preparative polyacrylamide gel electrophoresis and the development of a highly specific antitoxin serum.  

PubMed Central

Pseudomonas aeruginosa exotoxin has been purified to a specific activity of 12,000 to 16,000 mouse median lethal doses/mg of protein. Total recovery was about 25%, and the degree of purification was approximately 3,000-fold. Preparative polyacrylamide gel electrophoresis greatly facilitated purification. As judged by analytical disc gel electrophoresis, the purified toxin contained one major band of protein and only a negligible amount of contamination. Antiserum prepared against the purified toxin neutralized the lethal activity of crude toxin preprations and reacted by double immunodiffusion with a single component of concentrated broth cultures of P. aeruginosa isolates obtained from a clinical source. Images PMID:820647

Callahan, L T

1976-01-01

243

Analytics: Changing the Conversation  

ERIC Educational Resources Information Center

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

Oblinger, Diana G.

2013-01-01

244

Analytical Electrochemistry: Potentiometry  

NSDL National Science Digital Library

This courseware module is structured for either a lecture presentation or self-study tutorial on analytical potentiometry. The level of presentation spans upper high school to college students. Topics include historical background, theory/principles, instrumentation, pH electrodes, experimental examples, and troubleshooting tips.

Cannon, Donald M.; Gross, Erin M.; Kelly, Richard S.

2011-04-04

245

Social Learning Analytics  

ERIC Educational Resources Information Center

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

Buckingham Shum, Simon; Ferguson, Rebecca

2012-01-01

246

Analytical techniques in scattering  

Microsoft Academic Search

Summary form only given. There are very few geometries for which exact analytical solutions of a scattering problem are available, and these are almost all limited to bodies whose surface is a complete coordinate surface in one of the six coordinate systems for which the vector wave equation is separable. At the dawn of the last century, the Mie series

T. B. A. Senior

2000-01-01

247

Applications of Analytical Cartography  

Microsoft Academic Search

Several applications of analytical cartography are presented. They include terrain visibili- ty (including visibility indices, viewsheds, and intervisibility), map overlay (including solving roundoff errors with C++ class libraries and computing polygon areas from incomplete informa- tion), mobility, and interpolation and approximation of curves and of terrain (including curves and surfaces in CAD\\/CAM, smoothing terrains with overdetermined systems of equations, and

Wm Randolph Franklin

2000-01-01

248

Ada & the Analytical Engine.  

ERIC Educational Resources Information Center

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

Freeman, Elisabeth

1996-01-01

249

Flavonoids as Analytical Reagents  

Microsoft Academic Search

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

Krystyna Pyrzynska; Anna P?kal

2011-01-01

250

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

PubMed

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

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

2006-10-10

251

Application of denaturing gradient gel electrophoresis (DGGE) and temperature gradient gel electrophoresis (TGGE) in microbial ecology  

Microsoft Academic Search

Here, the state of the art of the application of denaturing gradient gel electrophoresis (DGGE) and temperature gradient gel electrophoresis (TGGE) in microbial ecology will be presented. Furthermore, the potentials and limitations of these techniques will be discussed, and it will be indicated why their use in ecological studies has become so important. Abbreviations: ARDRA - amplified ribosomal DNA restriction

Gerard Muyzer; Kornelia Smalla

1998-01-01

252

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

E-print Network

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

Aris, John P.

253

Comparison of electrical conductivities of various brain phantom gels: Developing a Brain Gel Model  

PubMed Central

The use of conducting gels to mimic brain and other tissues is of increasing interest in the development of new medical devices. Currently, there are few such models that can be utilized at physiologic temperatures. In this work, the conductivities of agar, agarose and gelatin gels were manipulated by varying NaCl concentration from 01 mg/ml. The AC conductivity was measured at room and physiological temperatures (37C) in the 100500 Hz frequency range. Conductivity (?) was nearly independent of frequency but increased linearly with NaCl concentration and was higher at physiological temperatures in these gels. A formula for predicting conductivity as a function of NaCl concentration was derived for each gel type. The overall goal is to develop a brain gel model, for studying low frequency electrical properties of the brain and other tissues at physiological temperatures. PMID:23139442

Kandadai, Madhuvanthi A.; Raymond, Jason L.; Shaw, George J.

2012-01-01

254

New polymer gel dosimeters consisting of less toxic monomers with radiation-crosslinked gel matrix  

NASA Astrophysics Data System (ADS)

New polymer gel dosimeters consisting of less toxic methacrylate-type monomers such as 2-hydroxymethyl methacrylate (HEMA) and polyethylene glycol 400 dimethacrylate (9G) with hydroxypropyl cellulose (HPC) gel were prepared. The HPC gels were obtained by using a radiation-induced crosslinking technique to be applied in a matrix instead of a gelatin, which is conventionally used in earlier dosimeters, for the polymer gel dosimeters. The prepared polymer gel dosimeters showed cloudiness by exposing to 60Co ?-ray, in which the cloudiness increased with the dose up to 10 Gy. At the same dose, the increase in the cloudiness appeared with increasing concentration of 9G. As a result of the absorbance measurement, it was found that the dose response depended on the composition ratio between HEMA and 9G.

Hiroki, A.; Yamashita, S.; Sato, Y.; Nagasawa, N.; Taguchi, M.

2013-06-01

255

Reprogramming cellular phenotype by soft collagen gels.  

PubMed

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

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

2014-11-28

256

Missing values in gel-based proteomics.  

PubMed

Gel-based proteomics is a widely applied technique to measure abundances of proteins in various biological systems. Comparison of two or more biological groups involves matching of 2-D gels. Depending on the software, this can result in spots showing missing values on several gels. Most studies ignore this fact or substitute all missing data by zero. Since a couple of years, scientists have realized that this is not the optimal way of analyzing their data and several studies were published presenting methods of imputing missing proteomics data. Most of these methods have already been applied to microarray data before; the phenomenon of missing data is well known in this field, too. With this review, we intend to further raise awareness of the problem of missing values in gel-based proteomics. We summarize reasons for missing values and explore their distribution in data sets. We also provide a comparison and evaluation of hitherto proposed imputation methods for gel-based proteomics data. PMID:20077407

Albrecht, Daniela; Kniemeyer, Olaf; Brakhage, Axel A; Guthke, Reinhard

2010-03-01

257

Growing an actin gel on spherical surfaces.  

PubMed Central

Inspired by the motility of the bacteria Listeria monocytogenes, we have experimentally studied the growth of an actin gel around spherical beads grafted with ActA, a protein known to be the promoter of bacteria movement. On ActA-grafted beads F-actin is formed in a spherical manner, whereas on the bacteria a "comet-like" tail of F-actin is produced. We show experimentally that the stationary thickness of the gel depends on the radius of the beads. Moreover, the actin gel is not formed if the ActA surface density is too low. To interpret our results, we propose a theoretical model to explain how the mechanical stress (due to spherical geometry) limits the growth of the actin gel. Our model also takes into account treadmilling of actin. We deduce from our work that the force exerted by the actin gel on the bacteria is of the order of 10 pN. Finally, we estimate from our theoretical model possible conditions for developing actin comet tails. PMID:10692348

Noireaux, V; Golsteyn, R M; Friederich, E; Prost, J; Antony, C; Louvard, D; Sykes, C

2000-01-01

258

A New Standard-Based Polynomial Interpolation (SBPIn) Method to Address Gel-to-Gel Variability for the Comparison of Multiple Denaturing Gradient Gel Electrophoresis Profile Matrices  

PubMed Central

The Standard-Based Polynomial Interpolation (SBPIn) method is a new simple three-step protocol proposed to address common gel-to-gel variations for the comparison of sample profiles across multiple DGGE gels. The advantages of this method include no requirement for additional software or modification of the standard DGGE protocol. PMID:23234884

Valentn-Vargas, Alexis; Chorover, Jon; Maier, Raina M.

2013-01-01

259

Separation performance of single-stranded DNA electrophoresis in photopolymerized cross-linked polyacrylamide gels.  

PubMed

Considerable effort has been directed toward optimizing performance and maximizing throughput in ssDNA electrophoresis because it is a critical analytical step in a variety of genomic assays. Ultimately, it would be desirable to quantitatively determine the achievable level of separation resolution directly from measurements of fundamental physical properties associated with the gel matrix rather than by the trial and error process often employed. Unfortunately, this predictive capability is currently lacking, due in large part to the need for a more detailed understanding of the fundamental parameters governing separation performance (mobility, diffusion, and dispersion). We seek to address this issue by systematically characterizing electrophoretic mobility, diffusion, and dispersion behavior of ssDNA fragments in the 70-1,000 base range in a photopolymerized cross-linked polyacrylamide matrix using a slab gel DNA sequencer. Data are collected for gel concentrations of 6, 9, and 12%T at electric fields ranging from 15 to 40 V/cm, and resolution predictions are compared with corresponding experimentally measured values. The data exhibit a transition from behavior consistent with the Ogston model for small fragments to behavior in agreement with the biased reptation model at larger fragment sizes. Mobility data are also used to estimate the mean gel pore size and compare the predictions of several models. PMID:16331587

Lo, Roger C; Ugaz, Victor M

2006-02-01

260

Cooperative Processes in Restructuring Gel Networks  

NASA Astrophysics Data System (ADS)

Colloidal gel networks are disordered elastic solids that can form even in extremely dilute particle suspensions. Similarly to other network-forming soft materials, including many with important biological function or technological potential, they can locally restructure via breaking and reforming interparticle bonds. Although controlling the link between local restructuring and mechanical response bears enormous potential for designing smart nanocomposites, there is at present little understanding of how local bond changes affect the dynamics of the gel network and the stress transmission through it. Here, using numerical simulations of a model system and a space-resolved analysis of dynamical heterogeneities, we show that bond breaking has non-local consequences and induces cooperative relaxation further away along the network. This provides explicit microscopic insight into why non-local constitutive relations are required to rationalize the non-trivial mechanical response of colloidal gels.

Colombo, Jader; Widmer-Cooper, Asaph; Del Gado, Emanuela

2013-03-01

261

Gel-Filled Holders For Ultrasonic Transducers  

NASA Technical Reports Server (NTRS)

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.

Companion, John A.

1992-01-01

262

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

PubMed

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

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

2014-08-01

263

Compressive Modulus of Ferrite Containing Polymer Gels  

NASA Astrophysics Data System (ADS)

The mechanical properties of magnetic gel have been investigated. Magnetic gels, which consist of finely dispersed powder of barium ferrite (BaFe12O19) and poly vinyl alcohol (PVA), have been synthesized. The diameter of barium ferrite is less than 45 ?m. The magnetic gels varying with ferrite concentration, crosslinking densities were prepared by mixing 10 wt.% PVA aqueous solution and barium ferrite using glutaraldehyde as a crosslinking agent in the presence of HCl. The diameter of barium ferrite is large enough to have a permanent magnetic moment. We applied a 10 kOe magnetic field in order to saturate the magnetic moment of barium ferrite. After magnetization, the compressive modulus was estimated with an ultrasonic method in order to find the influence of magnetization. Ultrasonic measurements were carried out using burst waves at 10 MHz and 295.5 K. The modulus of magnetized gel was found to depend on the concentration of magnetic substance, the crosslinking density, and the degree of swelling. It was clear that the modulus of magnetized gel was higher than the gel without magnetization for all samples. The change in modulus to the initial modulus ?M'/M'o for 10 wt.% and 15 wt.% of ferrite concentration was about 0.28% and 0.4% in a lower density region, respectively. Moreover, the change in modulus ?M'/M'o was constant in a lower density region however it strongly depends on the density in a higher density region. When the stress direction is perpendicular to the magnetization, the change in modulus increased. On the contrary, the change in modulus decreased when the stress direction is parallel to the magnetization. As increasing the density, the distance between magnetic substances become short and therefore the magnetic interaction is more significant in a higher density region.

Mitsumata, Tetsu; Furukawa, Kenta; Juliac, Etienne; Iwakura, Kenji; Koyama, Kiyohito

264

Sol-gel based biofuel cell architectures  

NASA Astrophysics Data System (ADS)

Sol-gel based biofuel cell architectures were investigated and quantified for electrochemical performance. The flexible solution chemistry of the sol-gel process has been used to synthesize bio-hybrid materials in which a wide variety of biomolecules are encapsulated in a transparent, inorganic matrix. These biomolecules retain their characteristic reactivities and spectroscopic properties despite being immobilized in the pores of the inorganic matrix. Stability of the biomolecules is also improved because of the confinement in the rigid inorganic network. Sol-gel immobilization serves as the basis for the electrode architecture used in enzymatic biofuel cells. In this dissertation, the fabrication and characterization of an enzymatic glucoseoxygen biofuel cell that incorporates nanostructured silica sol-gel/carbon nanotube composite electrodes was evaluated. These novel electrodes combine the benefits of sol-gel encapsulation with the use of carbon nanotubes which provide enhanced electronic conduction pathways and increase the effective surface area of the electrode. With this immobilization approach, the silica sol-gel is sufficiently porous that both glucose and oxygen have access to enzymes and yet provide a protective cage that preserves biological structure and function, offers long-term stability and perhaps enables operation at elevated temperatures. In addition, direct electron transfer was exhibited by a nanostructured cathode. More notably, these nanostructured composites were developed for power generation. Analysis of electron transfer rates and enzyme kinetics were used to quantify encapsulation properties and explore potential opportunities for optimization. Another topic for biofuel cells is miniaturization. Through miniaturization, biofuel cell design and integration are major considerations for increasing power density and performance.

Lim, James Robert

265

Phase transition in strongly stretched polymer gels  

NASA Astrophysics Data System (ADS)

We will present the volume phase transition of cylindrical poly N-isopropylacrylamide (NIPA) gels under large distortion along the uniaxial direction. The neutral and slightly ionized NIPA gels were synthesized in submillimeter diameter. The gel was stretched along the uniaxial direction with the longitudinal deformation ratio, ?? (the ratio of the stretched length to the equilibrium length in the swollen state at 30 C). By keeping the longitudinal length constant, we have simultaneously measured the equilibrium diameter and the force as functions of temperature. The swelling curves of the neutral NIPA gels including the volume phase transition temperature were obtained for several deformations in the range between ??=1 and ??=6. With increasing ??, the transition temperature increased up to 1 C in the small deformation below ??3.5, and it saturated and slightly decreased in the large ?? above ??4. At the transition temperature on heating, the force to keep the length constant increased discontinuously in the smaller region below ??3.5. The magnitude of this steplike change in the force began to decrease in the vicinity of ??3.5, and hereafter exhibited negative change above ??4. In the case of the slightly ionized NIPA gels, these effects came into play at an earlier stage, that is, at smaller ??, because of the prestretching due to the ionic pressure. The present observations, especially for the strong deformation above ??4, were discussed by the equation of states of strongly stretched hydrophobic gels on the basis of the extended Flory-type free energy taken into account the non-Gaussian effect.

Suzuki, A.; Sanda, K.; Omori, Y.

1997-10-01

266

Requirements for Predictive Analytics  

SciTech Connect

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.

Troy Hiltbrand

2012-03-01

267

Field Analytic Technologies Encyclopedia  

NSDL National Science Digital Library

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

2005-12-08

268

Avatars in Analytical Gaming  

SciTech Connect

This paper discusses the design and use of anthropomorphic computer characters as nonplayer characters (NPCs) 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.

Cowell, Andrew J.; Cowell, Amanda K.

2009-08-29

269

Nuclear analytical chemistry  

SciTech Connect

This book covers the general theories and techniques of nuclear chemical analysis, directed at applications in analytical chemistry, nuclear medicine, radiophysics, agriculture, environmental sciences, geological exploration, industrial process control, etc. The main principles of nuclear physics and nuclear detection on which the analysis is based are briefly outlined. An attempt is made to emphasise the fundamentals of activation analysis, detection and activation methods, as well as their applications. The book provides guidance in analytical chemistry, agriculture, environmental and biomedical sciences, etc. The contents include: the nuclear periodic system; nuclear decay; nuclear reactions; nuclear radiation sources; interaction of radiation with matter; principles of radiation detectors; nuclear electronics; statistical methods and spectral analysis; methods of radiation detection; neutron activation analysis; charged particle activation analysis; photon activation analysis; sample preparation and chemical separation; nuclear chemical analysis in biological and medical research; the use of nuclear chemical analysis in the field of criminology; nuclear chemical analysis in environmental sciences, geology and mineral exploration; and radiation protection.

Brune, D.; Forkman, B.; Persson, B.

1984-01-01

270

Analytic chemistry of molybdenum  

SciTech Connect

Electrochemical, colorimetric, gravimetric, spectroscopic, and radiochemical methods for the determination of molybdenum are summarized in this book. Some laboratory procedures are described in detail while literature citations are given for others. The reader is also referred to older comprehensive reviews of the analytical chemistry of molybdenum. Contents, abridged: Gravimetric methods. Titrimetric methods. Colorimetric methods. X-ray fluorescence. Voltammetry. Catalytic methods. Molybdenum in non-ferrous alloys. Molydbenum compounds.

Parker, G.A.

1983-01-01

271

Hybrid sol-gel optical materials  

DOEpatents

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.

Zeigler, J.M.

1993-04-20

272

Hybrid sol-gel optical materials  

DOEpatents

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.

Zeigler, John M. (Albuquerque, NM)

1993-01-01

273

Hybrid sol-gel optical materials  

DOEpatents

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.

Zeigler, John M. (Albuquerque, NM)

1992-01-01

274

Neutron detector using sol-gel absorber  

DOEpatents

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.

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

1999-01-01

275

Dynamic Light Scattering From Colloidal Gels  

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

276

Pre-Analytical Requirements  

PubMed Central

Summary Correct test selection: a test must have the potential to alter patient management and have the specificity and sensitivity appropriate to the pretest probability of disease.Correct dynamic test procedure: dynamic tests may assist diagnosis and protocols must be readily available.Correct patient preparation: fasting, or other patient preparation, may reduce variability. Clear communication, to both patients and staff, of any such requirements is essential.Correct sample collection: the tube type (for blood) or container (for urine) must be appropriate for the analyte; there must be sufficient volume, avoidance of venous stasis, contaminants and haemolysis; and adequate labelling.Correct sample handling: the time and temperature before and after separation, and the centrifugation and separation procedures, must be suitable for the analyte. Accept/reject criteria must be defined.Methods require thorough evaluation of patient-related pre-analytical factors, and quantification of the effects of time, temperature, haemolysis, anticoagulant type and minimum allowable volume on sample suitability. PMID:18852848

Livesey, John H; Ellis, M Jane; Evans, Margaret J

2008-01-01

277

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

NASA Astrophysics Data System (ADS)

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.

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

2010-01-01

278

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

NASA Astrophysics Data System (ADS)

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.

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

2012-05-01

279

Complex analytic geometry and analytic-geometric categories  

Microsoft Academic Search

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

Ya'acov Peterzil; Sergei Starchenko

2009-01-01

280

Local analytic first integrals of planar analytic differential systems  

NASA Astrophysics Data System (ADS)

We study the existence of local analytic first integrals of a class of analytic differential systems in the plane, obtained from the Chua's system studied in L.O. Chua (1992, 1995), N.V. Kuznetsov et al. (2011), G.A. Leonov et al. (2012) [6,7,11,13]. The method used can be applied to other analytic differential systems.

Colak, Ilker E.; Llibre, Jaume; Valls, Claudia

2013-06-01

281

Analytical Instruments and Spectroscopic Concepts  

NSDL National Science Digital Library

This webpage includes primers for a variety of different analytical techniques. Links to animations and audio descriptions of analytically related concepts are also provided. Techniques include atomic absorption, spectrophotometry, chemiluminescence, gas chromatography, mass spectrometry, and atomic emission.

Chasteen, Thomas G.

282

Analytic Feminism: A Brief Introduction  

E-print Network

This essay introduces the subject of this special issue by offering a characterization of analytic feminism in terms of its context, methods, and problem areas. I argue that analytic feminism is a legitimate sub-field both ...

Cudd, Ann E.

1995-01-01

283

Mechanical properties and morphology of polymer gels  

NASA Astrophysics Data System (ADS)

Understanding morphology and mechanical response of polymeric gels is of particular importance to design materials with required energy dissipation characteristics. We will present our latest results for polymer gels based on 1) self-assembled block copolymers and 2) chemically cross-linked polymers. The dissipative particle dynamics (DPD) was used to predict morphology in good agreement with atomic force microscopy. We have performed DPD non-equilibrium oscillatory shear calculations predicting elastic modulus of unentangled gels that correlates well with experimental rheology data. However, this methodology fails to predict mechanics of entangled polymer networks due to unphysical chain crossing brought by the soft potentials used in DPD simulations. Recently, we have introduced an improved segmental repulsion potential that removes the bond crossing allowing for reptation dynamics. The improved DPD method was used in simulations for entangled gels to explore impact of branched architecture of solvent on the mechanical response to the tensile deformation. Novel architectures of solvent resulting in a dramatic increase of the elastic modulus were identified. The topological analysis was applied to understand contributions of chemical cross-links and entanglements to the stress.

Sliozberg, Yelena; Sirk, Timothy; Brennan, John; Andzelm, Jan; Mrozek, Randy; Lenhart, Joseph

2012-02-01

284

Simple Cloud Chambers Using Gel Ice Packs  

ERIC Educational Resources Information Center

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

Kamata, Masahiro; Kubota, Miki

2012-01-01

285

Characterization of sol-gel entrapped chlorophyllase.  

PubMed

Immobilization of membrane proteins remains a challenge compared to soluble proteins. The membrane protein-chlorophyllase was successful entrapped in tetramethoxysilane (TMOS)-based sol-gel in the presence of lipid. Activity was examined against mixing rate, incubation temperature, time, substrate, acetone, and canola oil concentration. The external mass transfer of chlorophyll is not the rate-limiting step at higher mixing rates. Stability against temperature and acetone as denaturant was enhanced. In spite of the fact that an initial reaction lag phase was observed, 20% more chlorophyll was hydrolyzed, compared to reaction with free enzyme by the end of a 12 h assay. The initial lower activity demonstrated by entrapped chlorophyllase is likely due to the diffusion resistance of chlorophyll into and within the entrapment matrix. This hypothesis was substantiated by a low diffusion coefficient on the order of 10(-14) m(2)/s obtained for chlorophyll in nanoporous sol-gel particles. Pore size distribution of nanoporous wet TMOS-based sol-gel with or without protein was determined by thermoporometry. The change in pore morphology upon doping with chlorophyllase suggests that protein acts as a template during the sol-gel process. PMID:16804946

Yi, Yunyu; Kermasha, Selim; Neufeld, Ronald

2006-12-01

286

Electrochemical Growth Of Crystals In Gels  

NASA Technical Reports Server (NTRS)

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

Barber, Patrick G.; Coleman, James

1988-01-01

287

Sol-Gel Synthesis Of Aluminoborosilicate Powders  

NASA Technical Reports Server (NTRS)

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

Bull, Jeffrey; Leiser, Daniel; Selvaduray, Guna

1992-01-01

288

Sol-Gel Derived Hafnia Coatings  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

289

Electrophoretic Porosimetry of Sol-Gels  

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

290

Thermosensitive solgel reversible hydrogels  

Microsoft Academic Search

Aqueous polymer solutions that are transformed into gels by changes in environmental conditions, such as temperature and pH, thus resulting in in situ hydrogel formation, have recently attracted the attention of many investigators for scientific interest and for practical biomedical or pharmaceutical applications. When the hydrogel is formed under physiological conditions and maintains its integrity for a desired period of

Byeongmoon Jeong; Sung Wan Kim; You Han Bae

2002-01-01

291

Gel beads from novel ionic polysaccharides  

Microsoft Academic Search

Stable gelling systems were obtained by mixing polyanion solutions with solutions containing suitable polycations. Carboxymethyl cellulose was chosen as the polyanion, whilst a number of polycations, with different molecular weights and charge densities, were tested. In particular, both low molecular weight polyamines and new synthetically aminated polysaccharides, derived from pullulan and scleroglucan, were used. Stable gels, in the absence of

M Miani; R Gianni; G Liut; R Rizzo; R Toffanin; F Delben

2004-01-01

292

Brownian dynamics simulations of aging colloidal gels  

NASA Astrophysics Data System (ADS)

The aging of colloidal gels is investigated using very long duration Brownian dynamics simulations. The Asakura-Oosawa description of the depletion interaction is used to model a simple colloid polymer mixture. Several regimes are identified during gel formation. The intermediate scattering function displays a double decay characteristic of systems where some kinetic processes are frozen. The ? relaxation at short times is explained in terms of the Krall-Weitz model for the decorrelation due to the elastic modes present. The ? relaxation at long times is well described by a stretched exponential, showing a wide spectrum of relaxation times for which the q dependence is ??=q-2.2, lower than for diffusion. For the shortest waiting times, a combination of two stretched exponentials is used, suggesting a bimodal distribution. The extracted relaxation times vary with waiting time as ??=?0.66w, more slowly than in the simple aging case. The real space displacements are found to be strongly non-Gaussian, correlated in space and time. We were unable to find clear evidence that the gel aging was driven by internal stresses. Rather, we hypothesize that in this case of weakly interacting gels, the aging behavior arises due to the thermal diffusion of strands, constrained by the percolating network, which ruptures discontinuously. Although the mechanisms differ, the similarity of some of the results to aging of glasses is striking.

D'Arjuzon, Rodolphe J.; Frith, William; Melrose, John R.

2003-06-01

293

Gel Filtration Chromatography: A Laboratory Experiment.  

ERIC Educational Resources Information Center

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

Hurlbut, Jeffrey A.; Schonbeck, Niels D.

1984-01-01

294

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

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.

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

1992-11-03

295

Physics of liquid crystals embedded in silica gels  

E-print Network

Octylcyanobiphenyl (8CB) embedded in silica aerosil gels have been studied by means of high resolution X-ray scattering experiments. The silica particles form a hydrogen-bonded fractal gel network that introduces quenched ...

Park, Sungil, 1967-

2001-01-01

296

Prescribed Pattern Transformation in Swelling Gel Tubes by Elastic Instability  

E-print Network

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 ...

Lee, Howon

297

Sol-Gel Alumina Nano Composites for Functional Applications.  

E-print Network

??The thesis entitled "Sol-Gel Alumina Nano Composites for Functional Applications" investigate sol-gel methods of synthesis of alumina nanocomposites special reference to alumina-aluminium titanate and alumina-lanthanum (more)

Jayasankar, M

2009-01-01

298

Process Analytical Chemistry  

SciTech Connect

This review of process analytical chemistry is an update to the previous review on this subject published in 1995(A2). The time period covered for this review includes publications written or published from late 1994 until early 1999, with the addition of a few classic references pointing to background information critical to an understanding of a specific topic area. These older references have been critically included as established fundamental works. New topics covered in this review not previously treated as separate subjects in past reviews include sampling systems, imaging (via optical spectroscopy), and ultrasonic analysis.

Veltkamp, David J. (VISITORS); Doherty, Steve D. (BCO); Anderson, B B. (VISITORS); Koch, Mel (University of Washington); Bond, Leonard J. (BATTELLE (PACIFIC NW LAB)); Burgess, Lloyd W. (VISITORS); Ullman, Alan H. (UNKNOWN); Bamberger, Judith A. (BATTELLE (PACIFIC NW LAB)); Greenwood, Margaret S. (BATTELLE (PACIFIC NW LAB))

1999-06-15

299

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

DOEpatents

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.

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

1998-09-29

300

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

DOEpatents

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.

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

301

Quality Indicators for Learning Analytics  

ERIC Educational Resources Information Center

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

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

2014-01-01

302

Learning Analytics: Readiness and Rewards  

ERIC Educational Resources Information Center

This position paper introduces the relatively new field of learning analytics, first by considering the relevant meanings of both "learning" and "analytics," and then by looking at two main levels at which learning analytics can be or has been implemented in educational organizations. Although integrated turnkey systems or

Friesen, Norm

2013-01-01

303

q-analytic functions, fractals and generalized analytic functions  

NASA Astrophysics Data System (ADS)

We introduce a new class of complex functions of complex argument which we call q-analytic functions. These functions satisfy q-Cauchy-Riemann equations and have real and imaginary parts as q-harmonic functions. We show that q-analytic functions are not the analytic functions. However some of these complex functions fall in the class of generalized analytic functions. As a main example we study the complex q-binomial functions and their integral representation as a solution of the D-bar problem. In terms of these functions the complex q-analytic fractal, satisfying the self-similar q-difference equation is derived. A new type of quantum states as q-analytic coherent states and corresponding q-analytic Fock-Bargmann representation are constructed. As an application, we solve quantum q-oscillator problem in this representation, and show that the wave functions of quantum states are given by complex q-binomials.

Pashaev, Oktay K.; Nalci, Sengul

2014-01-01

304

The relationship of agarose gel structure to the sieving of spheres during agarose gel electrophoresis.  

PubMed Central

To understand the organization of fibers in an agarose gel, digitized electron micrographs are used here to determine the frequency distribution of interfiber distance (2Pc) in thin sections of agarose gels. For a preparation of underivatized agarose, a 1.5% gel has a Pc distribution that is indistinguishable from the Pc distribution of a computer-generated, random-fiber gel; the log of the occurrence frequency (F) decreases linearly as a function of Pc. As the agarose concentration decreases below 1.5%, the semilogarithmic F versus Pc plot becomes progressively less linear. Two straight lines represent the data; the plot is steeper at the lower Pc values. As the percentage of agarose increases above 1.5%, the semilogarithmic F versus Pc plot becomes steeper at the higher Pc values. This change in the shape of semilogarithmic F versus Pc plots is possibly explained by the existence in agarose gels of two zones, one whose Pc distribution is more sensitive to the average agarose concentration than the other. To compare the structure of agarose gels to their sieving during electrophoresis, the root mean square value of Pc (Pc) is compared to the sieving-based radius of the effective pore (PE; Griess et. al. (16)) for both underivatized agarose and a derivatized agarose that has a smaller PE at any given agarose percentage. For 0.8-2.0% gels of either underivatized or derivatized agarose, PE/Pc is a constant within experimental error. Deviations from this constant are observed at lower gel percentages. This relationship of PE to Pc constrains theoretical descriptions of the motion of spheres in fibrous networks. Images FIGURE 1 FIGURE 2 FIGURE 3 PMID:8369423

Griess, G A; Guiseley, K B; Serwer, P

1993-01-01

305

Metal-doped organic gels and method thereof  

DOEpatents

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.

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

2007-10-23

306

DC Electrical Field Effects on Plant Tissues and Gels  

Microsoft Academic Search

\\u000a Gels (intermediate between a solid and a liquid) have similarities to both animal and vegetative materials. Most food products\\u000a are solids composed of 5090% water, and they can be regarded in many ways as multicomponent gels. Moreover, the cellular\\u000a structure of fruits and vegetables can be considered a foam with a closed-cell geometry, filled with gel. Gels are omnipresent,\\u000a and

Amos Nussinovitch; Ronit Zvitov

307

SEPARATION OF CO-EXISTING PARACETAMOL AND DICLOFENAC SODIUM ON SILICA GEL 'H' LAYERS USING SURFACTANT MEDIATED MOBILE PHASES: IDENTIFICATION OF DICLOFENAC SODIUM FROM HUMAN URINE  

Microsoft Academic Search

Thin layer chromatography (TLC) has been used as an analytical technique for the identification and separation of two different drugs (paracetamol and diclofenac sodium) on silica gel H layers under optimized experimental conditions using surfactant mediated mobile phase systems. Cationic, non-ionic and anionic surfactants at different concentration levels have been used as mobile phases. Among the TLC systems studied, silica

ALI MOHAMMAD; SUDHANSHU SHARMA

2009-01-01

308

Adsorption of OrganicAcidsfromAmnioticFluidandUrineonto SilicaGel beforeAnalysisbyGasChromatography andCombined Gas Chromatography\\/Mass Spectrometry  

Microsoft Academic Search

We describe a method for adsorbing organic acids from amniotic fluid and urine specimens onto a column of silica gel before analysis by gas chromatography and by com- bined gas chromatography\\/mass spectrometry. Analytical recoveries of individual organic acids by our adsorption method compare favorably with those obtained by a more laborious manual extraction with ethyl acetate. Results for specimens of

Vincent P. Williams; Dexter K. Ching

309

Cervical ripening with intravaginal prostaglandin E2 gel  

Microsoft Academic Search

We describe a technique of administering prostaglandin E2 (PGE2) in a viscous cellulose gel into the vagina to ripen the unfavourable cervix in patients requiring induction of labour. A total of 168 primigravidae were studied, of whom 102 received 2 mg PGE2 in 2% gel and 66 received 5 mg PGE2 in 4% gel. In the latter group, the state

I Z MacKenzie; M P Embrey

1977-01-01

310

Acid Base Equilibrium in a Lipid\\/Water Gel  

Microsoft Academic Search

A new and original experiment in which partition of bromophenol blue dye between water and lipid\\/water gel causes a shift in the acid base equilibrium of the dye is described. The dye-absorbing material is a monoglyceride food additive of plant origin that mixes freely with water to form a stable cubic phase gel; the nascent gel absorbs the dye from

Kristina K. Streb; Predrag-Peter Ilich

2003-01-01

311

INCIPIENT DYNAMICS OF SWELLING OF GELS M. Carme Calderer  

E-print Network

are presented too. Key words. Gel swelling, two-component mixture, polymer-solvent friction, type II diffusion of the incipient dynamics of polymer gel swelling. The system that we study is derived from the balance lawsINCIPIENT DYNAMICS OF SWELLING OF GELS By Hang Zhang and M. Carme Calderer IMA Preprint Series

312

Formulation and method for preparing gels comprising hydrous hafnium oxide  

DOEpatents

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.

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

2013-08-06

313

Formulation and method for preparing gels comprising hydrous cerium oxide  

DOEpatents

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.

Collins, Jack L; Chi, Anthony

2013-05-07

314

Formulation and method for preparing gels comprising hydrous aluminum oxide  

SciTech Connect

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.

Collins, Jack L.

2014-06-17

315

MP 33354 Pro-Q Sapphire 532 Oligohistidine Gel Stain  

E-print Network

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

Lebendiker, Mario

316

77 FR 26556 - Determination of Regulatory Review Period for Purposes of Patent Extension; EQUIDONE GEL  

Federal Register 2010, 2011, 2012, 2013, 2014

...Purposes of Patent Extension; EQUIDONE GEL AGENCY: Food and Drug Administration...the regulatory review period for EQUIDONE GEL and is publishing this notice of that determination...marketing the animal drug product EQUIDONE GEL (domperidone). EQUIDONE GEL is...

2012-05-04

317

Strategies and techniques for testing the precision, reliability and reproducibility of computerized two-dimensional gel electrophoresis analysis systems.  

PubMed

A set of test procedures is described for evaluating the reliability, precision and reproducibility of computer systems designed to analyze two-dimensional gel electrophoretograms. The Elsie 4 gel analysis system (Analyt. Biochem., 169, 49-70 (1988) is used to demonstrate the use of these tests. Three major groups of tests are described: analysis of the scanner; analysis of mathematically constructed model gels; and analysis of real gel images. Scanner tests involve evaluating the stability and reproducibility of the scanner. The tests consist primarily of measuring the output of the scanner over a time period to determine its stability, and evaluating the consistency of the scanner at different points in the scanning field. Commonly encountered real gel situations are simulated and analyzed by arranging computer-generated 'ideal spots' in different ways. With such gels we can determine such things as the ability of the computer system to separate closely resolved and/or shoulder spots; whether or not streaks and/or smears are handled correctly; how random noise affects measurements; and, in idealized situation, the accuracy of the quantitation. The idealized spots are generated using the two-dimensional Gaussian as a model of density distribution; other spot models can be used. The Elsie 4 system is capable of finding virtually any spot (if detection parameters are set low enough), and of resolving different-sized spots whose peaks are separated by one and one-half their mean half width). The most significant tests are done on a set of actual gels.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2488595

Miller, M J; Merril, C

1989-01-01

318

The defect of Mk erythrocytes as revealed by sodium dodecylsulphate--polyacrylamide gel electrophoresis.  

PubMed

The membrane glycoprotein defect of Mk red cells was studied using discontinuous sodium dodecylsulphate--polyacrylamide gel electrophoresis, carbohydrate analytical procedures and lectins. The results suggest that Mk erythrocyte membranes contain only about half of the normal amount of the MN and Ss sialoglycoproteins, both molecules being not qualitatively different from normal. The major membrane protein exhibits an increased molecular weight in the above red cells. Some data on Mg and Miltenberger class five cells are presented for comparison. The results on Mk erythrocytes support the operon concept of the MNSs blood group system proposed previously. PMID:894053

Dahr, W; Uhlenbruck, G; Knott, H

1977-06-01

319

Normality in Analytical Psychology  

PubMed Central

Although C.G. Jungs 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 Foucaults criticism, had Foucault chosen to review Jungs work. However, Jung then evolved his thinking to a standpoint that was more aligned to Foucaults own. Thereafter, the post Jungian concept of normality has remained relatively undeveloped by comparison with psychoanalysis and mainstream psychology. Jungs 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

Myers, Steve

2013-01-01

320

Normality in analytical psychology.  

PubMed

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

Myers, Steve

2013-12-01

321

Analytical sensor redundancy assessment  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

322

Analytical applications of dithizone  

SciTech Connect

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.

Irving, H.M.N.H.

1980-01-01

323

Dielectric properties of gel collected from shark electrosensors  

NASA Astrophysics Data System (ADS)

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.

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

2003-03-01

324

SANS study on pulley effect of slide-ring gel  

NASA Astrophysics Data System (ADS)

We have recently developed a novel kind of gel slide-ring (SR) gel, based on polyrotaxane consisting of thread-like molecules of poly(ethylene glycol) and rings of ?-cyclodextrin (CD) molecules. The SR gel has mobile cross-links. In order to improve the unique properties, i.e., sliding motion or pulley effect of the SR gels and to suppress the self-aggregation tendency of CD molecules, methylated polyrotaxane was synthesized by substituting hydroxyl group with methyl group on CD molecules. The structure of SR gel having methylated CD molecules was investigated by small angle neutron scattering.

Karino, Takeshi; Shibayama, Mitsuhiro; Okumura, Yasushi; Ito, Kohzo

2006-11-01

325

Switching friction with thermal- responsive gels.  

PubMed

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

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

2013-11-01

326

Ring-Resonator/Sol-Gel Interferometric Immunosensor  

NASA Technical Reports Server (NTRS)

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.

Bearman, Gregory; Cohen, David

2007-01-01

327

Electroactive polymer gels based on epoxy resin  

Microsoft Academic Search

Five types of epoxy gels have been synthesized from common epoxy resins and hardeners. Fumed silica and nanoclay, respectively, were used as fillers and butyl methacrylate\\/acrylamide were used as monomer(s) for making interpenetrating polymer networks (IPNs) in three compositions. Swelling study, tensile property evaluation, dynamic mechanical thermal analysis, thermo-gravimetric analysis, scanning electron microscopy and electroactive property evaluation were done. The

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

2007-01-01

328

Electron Conducting and Magneto-Sensitive Gels  

Microsoft Academic Search

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

Frdric Fages

329

Dynamic viscoelastic properties of collagen gels with high mechanical strength.  

PubMed

We developed a new method for the preparation of mechanically strong collagen gels by combining successively basic gel formation, followed by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) cross-linking and lyophilization. Gels cross-linked three times with this method showed stronger mechanical properties (G': 37302060 Pa, G?: 28835 Pa) than a conventional gel that was sequentially cross-linked with EDC once (G': 22670 Pa, G?: 214.4 Pa), but not as strong as the same gel with heating for 30 min at 80C (G': 7010830 Pa, G?: 28835 Pa) reported in our previous paper. The conventional collagen gel was cross-linked with EDC once, heated once, and then subjected twice to a lyophilization-gel formation-cross-linking cycle to give three-cycled gel 2. This gel had the strongest mechanical properties (G': 40,20018,000 Pa, G?: 30901400 Pa, Young's modulus: 0.1970.069 MPa) of the gels tested. These promising results suggest possible applications of the gels as scaffolds in tissue engineering research. PMID:23706205

Mori, Hideki; Shimizu, Kousuke; Hara, Masayuki

2013-08-01

330

Scaling Behaviors and Mechanical Properties of Polymer Gels  

NASA Astrophysics Data System (ADS)

Polymer gels undergo a volume phase transition in solvent in response to an infinitesimal environmental change. This remarkable phenomenon has resulted in many potential applications of polymer gels. The understanding of its mechanical properties has both scientific and technological importance. For this purpose, we have developed a novel method for measuring Poisson's ratio, which is one of the most important parameters determining the mechanical property of gels. Using this method, Poisson's ratio in N-isopropyacryl -amide (NIPA) and polyacrylamide (PAAM) gels has been studied. We obtained that Poisson's ratio goes through a negative dip in both neutral and ionic NIPA gels, but positive in the PAAM gels. It was found that the scaling exponent delta depends on the details of chemical ingredients and polymerization process. In the salt solution, the delta depends on both the network ionization and the solvent salt concentration. The study of acoustic attenuation and velocity of NIPA gels reveals the dynamic scaling behavior of NIPA gels near the transition point. It has been found that there are four different pattern regions on the surface of constrained gel films depending on the temperature (or acetone concentration) and ionic strength of the sample, these patterns are associated with the mechanical instability of gel surface. The work presented in this dissertation will help ones both in the theoretical understanding and practical application of the gel system.

Li, Chunfang

331

Anion-switchable supramolecular gels for controlling pharmaceutical crystal growth  

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

332

Antioxidant effect of green tea on polymer gel dosimeter  

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

333

Dynamics of sodium dodecyl sulfate micelles in polyacrylamide gels  

NASA Astrophysics Data System (ADS)

Hydrophilic polyacrylamide gels exhibit interesting elastic properties which can be probed by dynamic light scattering. The dynamic structure factors of such gels and of gels which were polymerized in the presence of high concentrations of sodium dodecyl sulfate (SDS) micelles were measured. It was found that the gels containing SDS decay initially according to a stretched exponential, followed by a long time simple exponential decay, whereas the pure gel decay is single exponential at all times. Furthermore, the initial decays of all SDS/gel systems are nearly identical, while the long-time decays are clearly a function of SDS concentration. We interpret the initial decay as associated with local polyacrylamide elasticity unaffected by the presence of the micelles and the long time decays as characteristic of gel modes slowed by the various densities of SDS micelles.

Reyna, A.; Liu, Yingjie; van Winkle, David H.

1998-03-01

334

State of water in gelatin Gels  

SciTech Connect

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/.

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

1986-03-01

335

Micro-size polyacrylamide gel electrophoresis system  

NASA Astrophysics Data System (ADS)

The development and characterization of a micro-size two-dimensional polyacrylamide gel electrophoresis system is described. Some of the techniques which have evolved with use of the system are also discussed. This apparatus has unique features which provide advantages over other small scale units. Up to ten first- and second-dimension gels can be processed simultaneously with excellent resolution of protein regions. Consistent reproducibility is possible from protein samples as small as 400 ng and individual protein regions as small as 1 pg can be visualized by silver staining of the two-dimensional gels. Similar sensitivities are achieved in autoradiographs of 3H-labeled proteins extracted from the nuclei of cultured cells. The application of this system in conjunction with flow cytometric examination of nuclear DNA and electrostatic cell sorting of specific cell nuclei to provide homogeneous sample populations, allows subtle variations in isotope incorporation in proteins to be detected; whereas many times in generalized tissue samples these changes are masked. Also, these techniques elucidate the effects of external stimuli (chemicals, drugs, or environment) on protein synthesis and phosphorylation for analyses and comparison. Fabrication drawings are available upon request.

Hinson, W. G.; Pipkin, J. L.; Anson, J. F.; Casciano, D. A.; Burns, E. R.

1987-09-01

336

Magnetization transfer imaging for polymer gel dosimetry  

NASA Astrophysics Data System (ADS)

Off-resonance RF pre-saturation was used to obtain contrast in MRI images of polymer gel dosimeters irradiated to doses up to 50 Gy. Two different polymer gel dosimeters composed of 2-hydroxyethyl-acrylate or methacrylic acid monomers mixed with N, N'-methylene-bisacrylamide (BIS), dispersed in an aqueous gelatin matrix were evaluated. Radiation-induced polymerization of the co-monomers generates a fast-relaxing insoluble polymer. Saturation of the polymer using off-resonance Gaussian RF pulses prior to a spin-echo read-out with a short echo time leads to contrast that is dependent on the absorbed dose. This contrast is attributed to magnetization transfer (MT) between free water and the polymer, and direct saturation of water was found to be negligible under the prevailing experimental conditions. The usefulness of MT imaging was assessed by computing the dose resolution obtained with this technique. We found a low value of dose resolution over a wide range of doses could be obtained with a single experiment. This is an advantage over multiple spin echo (MSE) experiments using a single echo spacing where an optimal dose resolution is achieved over only very limited ranges of doses. The results suggest MT imaging protocols may be developed into a useful tool for polymer gel dosimetry.

Lepage, M.; McMahon, K.; Galloway, G. J.; DeDeene, Y.; Bck, S. . J.; Baldock, C.

2002-06-01

337

Research software for radiotherapy gel dosimetry.  

PubMed

Gel dosimetry using magnetic resonance imaging is a technique which allows measurement of three-dimensional absorbed dose distributions in radiation therapy. This paper presents details of a software tool written specifically to provide facilities to perform image processing required in research and development of gel dosimetry. Collections of magnetic resonance images can be converted into either longitudinal or transverse nuclear magnetic resonance relaxation images. The conversions are accomplished by means of a pixel-by-pixel non-linear least squares fitting algorithm. Adjustments can be made to the number of parameters used in the fitting algorithm. Fundamental image manipulation tools such as window width/level display adjustment, zooming, profile and region of interest tools are provided. The software has been developed using MATLAB (The MathWorks Inc., Natick, MA) running on Windows 95. User interaction is via a windows graphical user interface (GUI). Data such as statistics from regions of interest can be exported to other windows applications for further processing. Flexibility is incorporated in the GUI design by taking advantage of the developmental aspects of the MATLAB environment. Although originally designed for gel dosimetry, the software can be used in any application of MRI which requires production and manipulation of relaxation time images. PMID:10979593

Murry, P; Baldock, C

2000-06-01

338

Highly-correlated charges in polyelectrolyte gels  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

339

Fibrillar peptide gels in biotechnology and biomedicine  

PubMed Central

Peptides, peptidomimetics, and peptide derivatives that self-assemble into fibrillar gels have received increasing interest as synthetic extracellular matrices for applications in 3D cell culture and regenerative medicine. Recently, several of these fibrillizing molecules have been functionalized with bioactive components such as cell-binding ligands, degradable sequences, drug-eluting compounds, and chemical modifications for cross-linking, producing gels that can reliably display multiple factors simultaneously. This capacity for incorporating precise levels of many different biological and chemical factors is advantageous given the natural complexity of cell-matrix interactions that many current biomaterial strategies seek to mimic. In this review, recent efforts in the area of fibril-forming peptide materials are described, and advantages of biomaterials containing multiple modular elements are outlined. In addition, a few hurdles and open questions surrounding fibrillar peptide gels are discussed, including issues of the materials structural heterogeneity, challenges in fully characterizing the diversity of their self-assembled structures, and incomplete knowledge of how the materials are processed in vivo. PMID:20091870

Jung, Jangwook P.; Gasiorowski, Joshua Z.; Collier, Joel H.

2012-01-01

340

Sol-gel based optical chemical sensors  

NASA Astrophysics Data System (ADS)

The growing activity in the field of optical chemical sensors has resulted in numerous sensing schemes, new indicator dyes, various polymeric matrix, size and shapes and highly diversified methods of immobilization. The sensor characteristics are dependent upon the choice of indicator, polymer, immobilization technique, and also size. Sol-gel technology provides a low-temperature method for obtaining porous silicate glass matrices. It enables to obtain material in the form of films, powders, monoliths, fibres or nanoparticles. Organic reagents and molecular receptors can be easily immobilized in the matrices. Moreover, one of the unique features of the sol-gel process is that the properties of the final network structure, such as hydrophobicity, thickness, porosity, flexibility, reactivity and stability can be easily tailored by controlling the process conditions, the type and the size of the precursors and catalysis. Here we will report about several sensor designed over the years based on sol-gel materials for monitoring and controlling different parameters, such as heavy metals, amines, phosphates, organophosphates.

Lobnik, Aleksandra; Korent Urek, pela; Turel, Matejka; Fran?i?, Nina

2011-05-01

341

Autologous Platelet-Poor Plasma Gel for Injection Laryngoplasty  

PubMed Central

Purpose To overcome the potential disadvantages of the use of foreign materials and autologous fat or collagen, we introduce here an autologous plasma gel for injection laryngoplasty. The purpose of this study was to present a new injection material, a plasma gel, and to discuss its clinical effectiveness. Materials and Methods From 2 mL of blood, the platelet poor serum layer was collected and heated at 100? for 12 min to form a plasma gel. The plasma gel was then injected into a targeted site; the safety and efficacy thereof were evaluated in 30 rats. We also conducted a phase I/II clinical study of plasma gel injection laryngoplasty in 11 unilateral vocal fold paralysis patients. Results The plasma gel was semi-solid and an easily injectable material. Of note, plasma gel maintains the same consistency for up to 1 year in a sealed bottle. However, exposure to room air causes the plasma gel to disappear within 1 month. In our animal study, the autologous plasma gel remained in situ for 6 months in animals with minimal inflammation. Clinical study showed that vocal cord palsy was well compensated for with the plasma gel in all patients at two months after injection with no significant complications. Jitter, shimmer, maximum, maximum phonation time (MPT) and mean voice handicap index (VHI) also improved significantly after plasma gel injection. However, because the injected plasma gel was gradually absorbed, 6 patients needed another injection, while the gel remained in place in 2 patients. Conclusion Injection laryngoplasty with autologous plasma gel may be a useful and safe treatment option for temporary vocal cord palsy. PMID:24142660

Woo, Seung Hoon; Kim, Jin Pyeong; Park, Jung Je; Chung, Phil-Sang

2013-01-01

342

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

E-print Network

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

Paris-Sud XI, Université de

343

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

PubMed

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

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

2009-08-01

344

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

SciTech Connect

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

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

1983-02-01

345

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

SciTech Connect

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.

Craig Joseph Fontenot

2001-12-31

346

Analytical Chemists Eye Curriculum Revisions.  

ERIC Educational Resources Information Center

Analytical chemists need to revise curricula and make better use of computers to improve the status of their discipline. Highlights of an international panel of leading analytical chemists which addressed topics and issues related to these needs are presented. A chart showing the five-year Soviet chemistry curriculum is included. (JN)

Stinson, Steve

1986-01-01

347

Visual Analytics Law Enforcement Toolkit  

Microsoft Academic Search

We present VALET, a Visual Analytics Law Enforcement Toolkit for analyzing spatiotemporal law enforcement data. VALET provides users with a suite of analytical tools coupled with an interactive visual interface for data exploration and analysis. This system includes linked views and interactive displays that spatiotemporally model criminal, traffic and civil (CTC) incidents and allows officials to observe patterns and quickly

Abish Malik; Ross Maciejewski; Timothy F. Collins; David S. Ebert

2010-01-01

348

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

349

The Case for Assessment Analytics  

ERIC Educational Resources Information Center

Learning analytics is a relatively new field of inquiry and its precise meaning is both contested and fluid (Johnson, Smith, Willis, Levine & Haywood, 2011; LAK, n.d.). Ferguson (2012) suggests that the best working definition is that offered by the first Learning Analytics and Knowledge (LAK) conference: "the measurement, collection,

Ellis, Cath

2013-01-01

350

Understanding Education Involving Geovisual Analytics  

ERIC Educational Resources Information Center

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

Stenliden, Linnea

2013-01-01

351

Analytic Geometry, A Tentative Guide.  

ERIC Educational Resources Information Center

This teacher's guide for a semester course in analytic geometry is based on the text "Analytic Geometry" by W. K. Morrill. Included is a daily schedule of suggested topics and homework assignments. Specific teaching hints are also given. The content of the course includes point and plane vectors, straight lines, point and space vectors, planes,

Helwig, G. Alfred; And Others

352

Analytical Cartography W. R. Tobler  

E-print Network

... - Analytical Cartography W. R. Tobler In the late 19()()'s a new course, entitled Analytical Cartography, was introduced into tile geography pro~ram at the Uni- versity of Michigan. It is the purpose. Cartography has ken a university suhject in the United States since the late thirties of this century

Clarke, Keith

353

Analytical Cartography W. R Tobler  

E-print Network

Analytical Cartography W. R Tobler In the late 1960's a new course, entitled Analytical Cartography, was introduced into the geography program at the University of Michigan. It is the purpose, but some of the flavor may be suggested. An understanding of the situation in geographical cartography

Tobler, Waldo

354

Personal Analytical Calendar Sanaz Tavakkol  

E-print Network

i Personal Analytical Calendar by Sanaz Tavakkol Bachelor of Science, Shahid Beheshti University of the author. #12;ii Supervisory Committee Personal Analytical Calendar by Sanaz Tavakkol Bachelor of Science digital calendars as a platform to integrate productivity related information as they provide beneficial

Tory, Melanie

355

Polymethacrylate Microparticles Gel for Topical Drug Delivery  

Microsoft Academic Search

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

Hagar Ibrahim Labouta; Labiba K. El-Khordagui

2010-01-01

356

Biotechnology Laboratory: Gel Electrophoresis of Dyes  

NSDL National Science Digital Library

A portion of the Partnership for Plant Genomics Education, hosted by the University of California-Davis, this PDF presents a student activity where students will use agarose gel electrophoresis to separate several different dyes. The lab is described as a âprecursor to DNA separationsâ and thus provides an important step in the subject matter. The lab provides for students: detailed instructions, background information, and a quiz and group questions. Answers to the questions, and also the general objective of the lab, are provided for the instructor. Overall, the lab is introductory in nature and perfect for any science classroom.

2008-12-05

357

RNA purification by preparative polyacrylamide gel electrophoresis.  

PubMed

Preparative polyacrylamide gel electrophoresis (PAGE) is a powerful tool for purifying RNA samples. Denaturing PAGE allows separation of nucleic acids that differ by a single nucleotide in length. It is commonly used to separate and purify RNA species after in vitro transcription, to purify naturally occurring RNA variants such as tRNAs, to remove degradation products, and to purify labeled RNA species. To preserve RNA integrity following purification, RNA is usually visualized by UV shadowing or stained with ethidium bromide or SYBR green dyes. PMID:24034329

Petrov, Alexey; Wu, Tinghe; Puglisi, Elisabetta Viani; Puglisi, Joseph D

2013-01-01

358

Hybrid slab-microchannel gel electrophoresis system  

DOEpatents

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.

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

1998-01-01

359

Simple miniaturized gel system for DNA sequence analysis.  

PubMed Central

A simple miniaturized gel system suitable for DNA sequencing is described. Small ultrathin polyacrylamide gels are cast, eight or more at a time, using standard microscope slides. Gels, ready to use, can be stored for approximately 2 weeks. Gels are run horizontally in a standard mini-agarose gel apparatus. Typical run times are 6-8 min. A novel sample loading system permits volumes of standard sequencing reactions as small as 0.1 microl to be analyzed. Sequencing ladders were visualized using 35S-labeled DNA by autoradiography and by colorimetric detection. Band resolution compares favorably with that of large gels. The methods introduced here serve as a step toward the miniaturization of DNA sequencing and are amenable to automated sample loading and detection. PMID:9421499

Stein, A; Hill, S A; Cheng, Z; Bina, M

1998-01-01

360

Self-Oscillating Polymer Gels as Smart Materials  

NASA Astrophysics Data System (ADS)

Stimuli-responsive polymer gels and their application to smart materials have been widely studied. On the other hand, as a novel biomimetic gel, we have been studying gels with an autonomous self-oscillating function, since first reported in 1996. We succeeded in developing novel self-oscillating polymers and gels by utilizing the oscillating reaction, called the Belousov-Zhabotinsky (BZ) reaction. The self-oscillating polymer is composed of a poly(N-isopropylacrylamide) network in which the catalyst for the BZ reaction is covalently immobilized. In the presence of the reactants, the polymer gel undergoes spontaneous cyclic swelling-deswelling changes or soluble-insoluble changes (in the case of uncrosslinked polymer) without any on-off switching of external stimuli. Potential applications of the self-oscillating polymers and gels include several kinds of functional material systems, such as biomimetic actuators and mass transport surface.

Yoshida, Ryo

2013-12-01

361

Structural colored gels for tunable soft photonic crystals.  

PubMed

A periodically ordered interconnecting porous structure can be embodied in chemical gels by using closest-packed colloidal crystals as templates. The interconnecting porosity not only provides a quick response but also endows the porous gels with structural color arising from coherent Bragg optical diffraction. The structural colors revealed by porous gels can be regulated by several techniques, and thus, it is feasible to obtain desirable, smart, soft materials. A well-known thermosensitive monomer, N-isopropylacrylamide (NIPA), and other minor monomers were used to fabricate various structural colored gels. The selection of minor monomers depended on the targeted properties. This review focuses on the synthesis of templates, structural colored porous gels, and the applications of structural colored gel as smart soft materials for tunable photonic crystals. PMID:19306332

Harun-Ur-Rashid, Mohammad; Seki, Takahiro; Takeoka, Yukikazu

2009-01-01

362

Prediction of Gel Modulus using the Gel-Tensile Blob (GTB) Model for Network Structure  

NASA Astrophysics Data System (ADS)

Network structure in gels, as determined by small-angle scattering, bears little resemblance to the structure expected from the Flory-Rehner, c* or other models for gel properties. Scattering shows a universal excess in scattering intensity at moderate-q that displays a size larger than that of a chain between network crosslinks. Further, a substructural size, often associated with the chain-coil of the network mesh, deviates from linear chain scattering. In this presentation, recent developments in the understanding of branch topology (Beaucage 2004, Ramachandran 2008,2009) are applied to networks in order to predict mechanical properties, particularly the modulus of swollen networks. The approach is based on quantification of the minimum dimension and connectivity dimension for gels and coupling of these descriptions with the gel-tensile blob (GTB) model previously described by Sukumaran (2001,2005). Beaucage G, Phys. Rev. E 70 031401 (2004).; Ramachandran R, et al. Macromolecules 41 9802-9806 (2008).; Ramachandran R, et al. Macromolecules, 42 4746-4750 (2009).; Sukumaran SK & Beaucage G Europhys. Lett. 59 714-720 (2002).; Sukumaran SK & Beaucage G, et al. Eur. Phys. J. E 18 29-36 (2005).

Beaucage, Gregory; Sukumaran, Sathish K.

2010-03-01

363

Experimental: Gel Electrolyte The gel mixtures were designed to be cast as  

E-print Network

) adopting organic/inorganic gels as well as a novel dye presenting a conjugated polymer covalently linked harvesting and hole conduction while the ruthenium complex binds to the anatase electrode providing efficient domain, a charge injecting domain and a light harvesting and energy transfer domain was prepare

364

Responsive supramolecular gels constructed by crown ether based molecular recognition.  

PubMed

Responsive supramolecular gels were constructed from crown ether terminated four-arm star poly(epsilon-caprolactone) (PCL-DB24C8) and dibenzylammonium-terminated two-arm PCL-DBAS (see scheme), exploiting the formation of pseudorotaxane linkages between crown ether and ammonium moieties. The resultant supramolecular gels exhibit thermo- and pH-induced reversible gel-sol transition. PMID:19173355

Ge, Zhishen; Hu, Jinming; Huang, Feihe; Liu, Shiyong

2009-01-01

365

Chemical characterisation of the steelgeopolymeric gel interface  

Microsoft Academic Search

Geopolymers could be used as non-combustible adhesives for steel, so that it is important to understand the interaction of stainless steel and pure iron with geopolymeric gel. Different artificial gel forming solutions with varied concentrations of alkali and Si\\/Al ratio were used to investigate the effect of the AlSi precursors on the interactions between the gel and substrates. The gelation

S. L. Yong; D. W. Feng; G. C. Lukey; J. S. J. van Deventer

2007-01-01

366

Clinical efficacy of becaplermin (rhPDGF-BB) gel  

Microsoft Academic Search

The results of four multicenter, randomized, placebo-controlled, parallel group studies of the efficacy of becaplermin gel are reviewed here. The four studies included a total of 922 patients, all of whom received a standardized regimen of good ulcer care. Patients were randomized to receive placebo gel, 30 or 100 ?g\\/g becaplermin gel, or good ulcer care alone.In Studies 1 and

T. Jeffery Wieman

1998-01-01

367

Applications and Nonlinear Mechanical Properties of Thermoreversible Triblock Copolymer Gels  

NASA Astrophysics Data System (ADS)

Thermoreversible triblock copolymer gels display a wide variation in mechanical behavior over a temperature range that is experimentally accessible. At elevated temperatures these gels behave as freely flowing solutions, exhibiting fast relaxation behavior. The relaxation time increases dramatically as temperature is reduced, such that at room temperature the gels become strong elastic materials. The nonlinear mechanical properties of triblock copolymer gels are ultimately dependent on the structure of the underlying physically associating network of triblock copolymer molecules and how this structure evolves during deformation and aging. The aim of this research is to characterize the structure-property relationships of triblock copolymer gels utilizing shear rheometry over a wide range of temperature and deformation rates. Behavior of the gels in the nonlinear regime -- i.e., the stress response during deformation to large strain or strain rate -- is of particular interest. Triblock copolymer gels were successfully applied as model systems for a variety of engineering and biophysical applications. The thermoreversible nature and mechanical strength of the gels was found to be advantageous in a low-temperature casting process for titanium foams of complex shape. The gels were also demonstrated to be excellent synthetic model systems for strain-stiffening biological materials. Additionally, evidence of flow inhomogeneities in the triblock copolymer gels coupled with the well-defined structure of the gels and the wide range of accessible relaxation times makes these gels ideal model systems for future studies of deformation-induced failure in physically associating solutions and complex fluids. The foundation is also being laid for the rheological investigation of two-dimensional layers of self-assembled triblock copolymer molecules with the hope of establishing these physically associating networks as synthetic model systems for biological membranes and thin films.

Erk, Kendra A.

368

Augmentation of glans penis using injectable hyaluronic acid gel  

Microsoft Academic Search

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

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

2003-01-01

369

Characterization of two germania gels of different coordination  

NASA Technical Reports Server (NTRS)

Two germania gels were synthesized by hydrolytic condensation of germanium ethoxide and by dissolution of germanium dioxide powder in ammonium hydroxide solution. The two gels were characterized using differential scanning calorimetry, X-ray powder diffraction, surface area and weight loss data, and infrared spectroscopy. The results indicate that, in gels, germanium is capable of tetragonal as well as hexagonal coordination, resulting in different crystallization behaviors.

Mukherjee, Shyama P.; Glass, Amy S.; Low, Manfred J. D.

1990-01-01

370

Effect of bloom strength on radiochromic gel dosimeters  

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

371

Inclusion type radiochromic gel dosimeter for threedimensional dose verification  

NASA Astrophysics Data System (ADS)

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 4C.

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

2015-01-01

372

Polyacrylamide gel miniaturization improves protein visualization and autoradiographic detection  

SciTech Connect

Polyacrylamide gels shrink to one-quarter of their original area when soaked in a 50% (w/v) solution of polyethylene glycol. Gel miniaturization improves the contrast of protein bands, with four valuable consequences. (i) A 5- to 10-fold increase in sensitivity for Coomassie blue is observed. (ii) Gels are more durable; i.e., they resist tearing when wet and they do not crack during drying under vacuum. (iii) Shrunken gels give sharper photographic images and provide better interlane protein band comparisons. (iv) Condensed protein bands lead to an increased sensitivity for detecting low-abundance, radioactively-labeled proteins by fluorography.

Mohamed, M.A.; Lerro, K.A.; Prestwich, G.D.

1989-03-01

373

Sol gels. (Latest citations from Materials Business file). Published Search  

SciTech Connect

The bibliography contains citations concerning sol gel derived materials. The citations examine research conducted by universities, corporations and government agencies for the development of novel sol gel processes, and commercial applications of these techniques. Uses of sol gels in the production of glass, ceramics, composites, protective coatings, and hybrid organic/inorganic materials are described. Other topics include new products, expanding markets for sol gel derived materials, and profit potential. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

NONE

1996-01-01

374

Acid Base Equilibrium in a Lipid/Water Gel  

NASA Astrophysics Data System (ADS)

A new and original experiment in which partition of bromophenol blue dye between water and lipid/water gel causes a shift in the acid base equilibrium of the dye is described. The dye-absorbing material is a monoglyceride food additive of plant origin that mixes freely with water to form a stable cubic phase gel; the nascent gel absorbs the dye from aqueous solution and converts it to the acidic form. There are three concurrent processes taking place in the experiment: (a) formation of the lipid/water gel, (b) absorption of the dye by the gel, and (c) protonation of the dye in the lipid/water gel environment. As the aqueous solution of the dye is a deep purple-blue color at neutral pH and yellow at acidic pH the result of these processes is visually striking: the strongly green-yellow particles of lipid/water gel are suspended in purple-blue aqueous solution. The local acidity of the lipid/water gel is estimated by UV vis spectrophotometry. This experiment is an example of host-guest (lipid/water gel dye) interaction and is suitable for project-type biophysics, physical chemistry, or biochemistry labs. The experiment requires three, 3-hour lab sessions, two of which must not be separated by more than two days.

Streb, Kristina K.; Ilich, Predrag-Peter

2003-12-01

375

Synthesis of surface patterns on the gel surface  

NASA Astrophysics Data System (ADS)

The surface structures of hydrogels play important roles for many potential applications in physical, chemical and biomedical fields. Our idea is to precisely control the local properties of the one gel surface by incorporating different materials onto the given areas selected with a mask. We have successfully deposited NIPA polymer gel on the controlled area of the surface of an agarose gel. The pattern of the NIPA deposited area can be either visible or invisible by simply switching temperature above or below the low critical solution temperature (LCST) of the NIPA gel.

Zheng, Yindong; Wang, Changjie; Hu, Zhibing; Li, Yong

1997-10-01

376

Concentration fluctuations in polymer gel investigated by neutron scattering: Static inhomogeneity in swollen gel  

NASA Astrophysics Data System (ADS)

By using small-angle neutron scattering (SANS) and neutron spin echo (NSE), we have quantitatively investigated the static inhomogeneity in poly (N-isopropyl acrylamide) gel (PNIPA) in microscopic length scales of 0.015gel decays more slowly as compared to the PNIPA solution without crosslinks. According to our scenario that the slower decay found for the PNIPA gel is due to the static inhomogeneity coexisting in the swollen gel, small-angle scattering S(q) obtained by SANS has been quantitatively decomposed into thermal and static scattering components, respectively, Sth(q) and Sst(q). It was further revealed that (i) the q-region where Sst(q) becomes dominant is closely related to that for the abnormal butterfly scattering under stretching, and (ii) as the temperature increases toward the temperature for volume phase transition, Sst(q) of a squared Lorentzian shape increases more drastically than Sth(q) of a Lorentzian shape. These findings were quantitatively understood in the theoretical framework by Panyukov and Rabin [Macromolecules 29, 7960 (1996)] or by Onuki [J. Phys. II. France 2, 45 (1992)], taking into account stress-fluctuation coupling under coexistence of the inherent structural heterogeneity in the real gel. We further found that the static inhomogeneity showing Sst(q) seems to relate to the necklacelike microstructure, appearing after a shallow quench into the collapsed phase.

Koizumi, Satoshi; Monkenbusch, Michael; Richter, Dieter; Schwahn, Dietmar; Farago, Bela

2004-12-01

377

Semiconductor Gel in Shark Sense Organs?  

PubMed Central

Sharks can sense bioelectric fields of prey and other animals in seawater using an extraordinary system of sense organs (ampullae of Lorenzini) [9]. A recent study reported that these sense organs also enable sharks to locate prey-rich thermal fronts using a novel mode of temperature reception without ion channels. The study reported that gel extracted from the organs operates as a thermoelectric semiconductor, generating electricity when it is heated or cooled [2]. Here we report biophysical studies that call into question this mechanism of sensory transduction. Our experiments indicate that the material exhibits no unusual thermoelectric or electromechanical properties, and that the thermoelectric response is an artifact caused by temperature effects on the measurement electrodes. No response is seen when non-metallic electrodes (carbon or salt bridges) are used, and ordinary seawater produces the same effect as shark organ gel when silver wire electrodes are used. These data are consistent with the voltages arising from electrochemical electrode potentials rather generated intrinsically within the sample. This new evidence, together with the anatomy of the organs and behavioral studies in the literature, best support the conclusion that the biological function of these sense organs is to detect electric fields. PMID:17904741

Fields, R. Douglas; Fields, Kyle D.; Fields, Melanie C.

2007-01-01

378

Block copolymer ion gels for gas separation  

NASA Astrophysics Data System (ADS)

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.

Gu, Yuanyan; Lodge, Timothy

2012-02-01

379

MSc in Analytical Science Analytical Science: Methods and  

E-print Network

in Materials, Environmental, Biological, Biomedical, and Pharmaceutical Sciences. Clearly, any industrialised and environmental science), and materials science, and we invite applications from students with backgrounds understanding of analytical techniques and excellent practical skills. The MSc qualification provides

Davies, Christopher

380

Fabrications and characterizations of dye-sensitized solar cells (DSSCs) with sol-gel derived gel electrolytes  

NASA Astrophysics Data System (ADS)

Dye Sensitized Solar Cells (DSSCs) have been fabricated by using sol-gel derived polymer gel electrolytes incorporating imidazolium ionic liquid. Two kinds of polymer gel electrolytes have been prepared. The first one is composed of siloxane polymer only, while the second one is composed of blend of siloxane and ethylene glycol polymers. The fabricated DSSC have the same structure configuration, namely ITO/Ti:ZnO/TiO2/Ru-dye/gelelectrolyte/Pt/ITO. DSSCs with the second type of gel electrolyte were found to exhibit much better photovoltaic performance in comparison to those with the first type of gel electrolyte. This fact is in agreement with the results from impedance spectroscopy measurements, which indicate more facile charge transfer process and much smaller ionic polarizations in the cell with the second type of gel electrolyte.

Sukmawati Arsyad, Wa Ode; Pujiarti, Herlin; Tola, Pardi Sampe; Herman, Hidayat, Rahmat

2013-09-01

381

The Science of Analytic Reporting  

SciTech Connect

The challenge of visually communicating analysis results is central to the ability of visual analytics tools to support decision making and knowledge construction. The benefit of emerging visual methods will be improved through more effective exchange of the insights generated through the use of visual analytics. This paper outlines the major requirements for next-generation reporting systems in terms of eight major research needs: the development of best practices, design automation, visual rhetoric, context and audience, connecting analysis to presentation, evidence and argument, collaborative environments, and interactive and dynamic documents. It also describes an emerging technology called Active Products that introduces new techniques for analytic process capture and dissemination.

Chinchor, Nancy; Pike, William A.

2009-09-23

382

Apparatus for the production of gel beads containing a biocatalyst  

DOEpatents

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.

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

1998-03-19

383

Enhanced local anesthetic action of mepivacaine from the bioadhesive gels.  

PubMed

Mepivacaine, an amide-type local anesthetic, has been used to relieve local pain. Among the many drug delivery systems, transdermal drug delivery has some advantages, as it provides controlled drug delivery for an extended period of time. To develop new gel formulations that have suitable bioadhesion, the bioadhesive force of hydroxypropyl methylcellulose (HPMC) was assessed using an auto-peeling tester. The effect of drug concentration on drug release from 2% HPMC gel was studied using synthetic cellulose membrane at 370.5C. The drug concentrations tested were 0.5, 1, 1.5, 2, and 2.5%. The effect of temperature on drug release from the 2% drug gel was evaluated at 27, 32, 37 and 42C. To increase the skin permeation of mepivacaine from HPMC gel, enhancers such as saturated and unsaturated fatty acids, pyrrolidones, propylene glycol derivatives, glycerides, and non-ionic surfactants were incorporated into the mepivacaine-HPMC gels. The enhancing effect of the enhancer on drug permeation was then examined in the modified Keshary-Chien cell. For the efficacy study, the anesthetic action of the formulated mepivacaine gel containing enhancer and vasoconstrictor was evaluated with the tail-flick analgesimeter. Among the various kinds of HPMC, HPMC-K100M gel showed the highest viscosity and bioadhesive force. As the viscosity of the HPMC gels increased, the bioadhesive forces increased. Increasing the drug concentration or temperature increased the drug release rate. Among the enhancers used, polyoxyethylene 2-oleyl ether showed the greatest enhancement of permeation. Based on the area under the efficacy curve of the rat tail flick test curve, mepivacaine gel containing polyoxyethylene 2-oleyl ether and tetrahydrozoline showed prolonged and increased local anesthetic action compared to the control. For bioadhesive mepivacaine gels with enhanced local anesthetic action, mepivacaine gels containing penetration enhancer and vasoconstrictor could be developed with the bioadhesive polymer, HPMC. PMID:21190925

Cho, Cheong-Weon; Choi, Jun-Shik; Shin, Sang-Chul

2011-01-01

384

Apparatus for the production of gel beads containing a biocatalyst  

DOEpatents

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.

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

1998-01-01

385

Reversible adsorption of calcium ions by imprinted temperature sensitive gels  

NASA Astrophysics Data System (ADS)

With the aim of developing polymeric gels sensitive to external stimuli and able to reversibly adsorb and release divalent ions, copolymer gels of N-isopropylacrylamide (NIPA) and methacrylic (MAA) monomers were prepared. We chose calcium as a target divalent ion. Two MAAs form a complex with a calcium ion, and the NIPA component allows the polymers to swell and shrink reversibly in response to temperature. The adsorbing site develops an affinity to target ions when the adsorbing molecules come into proximity, but when they are separated, the affinity diminishes. To enhance the affinity to calcium, an imprinting technique was applied using Ca2+ and Pb2+ ions as templates in methylsulfoxide and dioxane media, respectively. The adsorption capacity of the imprinted gels was compared with that of the nonimprinted gels, and the effects of the templates, the solvents, and the amount of methacrylic monomers used in the synthesis and the medium temperature over the Ca2+ adsorption capacity of the gels from aqueous solutions were evaluated. The analysis of the adsorption revealed that (a) the adsorption can be described by the Langmuir isotherms; (b) there is an approximately linear relationship between saturation and methacrylic monomer concentration; (c) the affinity depends on the degree of gel swelling or shrinkage that can be switched on and off by temperature; (d) in the shrunken state, the affinity depends approximately linearly on the MAA concentration in the imprinted gels, whereas in the nonimprinted gels it is proportional to the square of MAA concentration; (e) the imprinted gels adsorb more than the nonimprinted gels when MAA concentration is less than that of permanent cross linkers. The success of imprinting of CaMAA2 and PbMAA2 complex is evidence for memory of such complex onto the weakly cross-linked gel.

Alvarez-Lorenzo, Carmen; Guney, Orhan; Oya, Taro; Sakai, Yasuzo; Kobayashi, Masatoshi; Enoki, Takashi; Takeoka, Yukikazu; Ishibashi, Toru; Kuroda, Kenichi; Tanaka, Kazunori; Wang, Guoqiang; Grosberg, Alexander Yu.; Masamune, Satoru; Tanaka, Toyoichi

2001-02-01

386

Sol-gel-based molecularly imprinted xerogel for capillary microextraction.  

PubMed

A novel molecularly imprinted xerogel (MIX) based on organically modified silica (ORMOSIL) was successfully prepared for on-line capillary microextraction (CME) coupled with high-performance liquid chromatography (HPLC). The sol-gel-based xerogel was prepared using only one precursor and exhibited extensive selectivity towards triazines along with significant thermal and chemical stability. Atrazine was selected as a model template molecule and 3-(trimethoxysilyl)propylmethacrylate (TMSPMA) as a precursor in which the propylmethacrylate moiety was responsible for van der Waals, dipole-dipole, and hydrogen-bond interactions with the template. This moiety plays a key role in creation of selective sites while methoxysilyl groups in TMSPMA acted as crosslinkers between the template and the propylmethacrylate moiety. Moreover, a non-imprinted xerogel (NIX) was also prepared in the absence of the template for evaluating the extraction efficiency of the prepared MIX. Then, the prepared imprinted and non-imprinted xerogels were used for extraction of three selected analytes of triazines class including atrazine, ametryn, and terbutryn, which have rather similar structures. The extraction efficiency of the prepared xerogel for atrazine, the template molecule, was found to be ten times greater than the efficiency achieved by the non-imprinted one. In the meantime, the extraction efficiency ratio of MIX to NIX for ametryn and terbutryn was also rather significant (eight times). Moreover, other compounds from different classes including dicamba, mecoprop, and estriol were also analyzed to evaluate the selectivity of the prepared MIX towards triazines. The ratio of enrichment factors (EF) of MIX to NIX for atrazine, ametryn, terbutryn, dicamba, mecoprop, and estriol were about 10, 8, 8, 2, 2, and 3, respectively. The linearity for the analytes was in the range of 5-700 ?g L(-1). Limit of detection was in the range of 1-5 ?g L(-1) and the RSD% values (n = 5) were all below 6.6% at the 20 ?g L(-1) level. The developed method was also applied to real water samples and the relative recovery percentages obtained for the spiked water samples were from 92 to 104%. The CME loop, containing the prepared MIX, exhibited a rather long life time due to its remarkable solvent and mechanical stability. Even after 100 runs, no decrease in the peak areas was observed. The developed method could easily provide the possibility of preparing a selective sorbent in a unique way with the lowest possible cost and time. PMID:22752449

Bagheri, Habib; Piri-Moghadam, Hamed

2012-09-01

387

Cautions Concerning Electronic Analytical Balances.  

ERIC Educational Resources Information Center

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)

Johnson, Bruce B.; Wells, John D.

1986-01-01

388

An analytic Lifshitz black hole  

E-print Network

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 ...

Balasubramanian, Koushik

389

Analytical Chemistry: A Literary Approach.  

ERIC Educational Resources Information Center

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)

Lucy, Charles A.

2000-01-01

390

Cambiera: Collaborative Tabletop Visual Analytics  

E-print Network

, "city hall" found 18 documents; each of them is represented as a grey bar on the right side. Each., Kuchar, O., Wolf, K. (2009) Exploring the Analytical Processes of Intelligence Analysts. Proc. CHI, pp 11

Isenberg, Petra

391

Cambiera: Collaborative Tabletop Visual Analytics  

E-print Network

is represented as a grey bar on the right side. Each document is colored by the set of searches that found it-duplication of effort. References [1] Chin, G., Kuchar, O., Wolf, K. (2009) Exploring the Analytical Processes

Paris-Sud XI, Université de

392

Analytic Methods in Investigative Geometry.  

ERIC Educational Resources Information Center

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)

Dobbs, David E.

2001-01-01

393

On the analytic wavelet transform  

Microsoft Academic Search

An exact and general expression for the analytic wavelet transform of a real-valued signal is constructed, resolving the time-dependent effects of non-negligible amplitude and frequency modulation. The analytic signal is first locally represented as a modulated oscillation, demodulated by its own instantaneous frequency, and then Taylor-expanded at each point in time. The terms in this expansion, called the instantaneous modulation

Jonathan M. Lilly; Sofia C. Olhede

2010-01-01

394

Functionalized magnetic nanoparticle analyte sensor  

DOEpatents

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.

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

2014-03-25

395

Visual Analytics Technology Transition Progress  

SciTech Connect

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.

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

2009-09-23

396

Hydrothermal transformation of tobermorite gel to 10 tobermorite  

Microsoft Academic Search

The tobermorite gel, formed by hydrothermal reaction of silica and lime, is transformed either into Z phase if the quantity of lime is less than 37 % or into 10 tobermorite if the quantity of lime is between 37 % and 42 %.The sheets of tobermorite gel are progressively ordered in a direction perpendicular to their plane in a

R. Jauberthie; M. Temimi; M. Laquerbe

1996-01-01

397

Bidisperse Aggregation and Gel Formation via Simultaneous Convection and Diffusion  

E-print Network

Bidisperse Aggregation and Gel Formation via Simultaneous Convection and Diffusion Ian J. Laurenzi-limited aggregation processes with Brownian motion and shear contributing to the collision frequency. To study, the kinetics of the aggregation process and gel point are shown to have a cooperative dependence on shear

398

HermiteLindemann & Gel'fondSchneider Six Exponentials Theorem  

E-print Network

Hermite­Lindemann & Gel'fond­Schneider Six Exponentials Theorem Strong Six Exponentials Theorem://www.math.jussieu.fr/miw/ December 17, 2005 1 / 36 Hermite­Lindemann & Gel'fond­Schneider Six Exponentials Theorem Strong Six Exponentials Theorem Recent results Product of logarithms of algebraic numbers References DION 2005 TIFR

Waldschmidt, Michel

399

Application of gel growth to hanging drop technique  

NASA Astrophysics Data System (ADS)

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

Provost, Karine; Robert, Marie-Claire

1991-03-01

400

Slow Release Of Reagent Chemicals From Gel Matrices  

NASA Technical Reports Server (NTRS)

Procedure developed for slow release of reagent chemicals into solutions. Simple and inexpensive and not subject to failure of equipment. Use of toothpaste-type tube or pump dispenser conceivably provides more controlled technique for storage and dispensation of gel matrix. Possible uses include controlled, slow release of reagents in chemical reactions, crystal growth, space-flight experiments, and preformed gel medications from packets.

Debnam, William J.; Barber, Patrick G.; Coleman, James

1988-01-01

401

Gel Electrophoresis--The Easy Way for Students  

ERIC Educational Resources Information Center

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

VanRooy, Wilhelmina; Sultana, Khalida

2010-01-01

402

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, Kyoto 606, Japan 2 Graduate School of Human and Environmental Studies, Kyoto University, Kyoto 606 August 1998 We construct a Ginzburg-Landau model for gels undergoing spinodal decomposition in terms

403

Growth of single crystals of bismuth sulpho iodide in gel  

Microsoft Academic Search

Single crystals of bismuth sulpho iodide have been grown in sodium silicate gel at room temperature by diffusing suitable reactants. In the first batch of experiments 3 to 7 g solution of BiCl3 was diffused into the gel containing 10 to 15% KI. Platelets of dimensions upto 5 mm were obtained in a period of 30 days. When thiourea of

R. Roop Kumar; G. Raman; F. D. Gnanam

1989-01-01

404

Pore-Level Examination of Gel Destruction During Oil Flow  

E-print Network

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

New York at Stoney Brook, State University of

405

Quality and authenticity of commercial aloe vera gel powders  

Microsoft Academic Search

This study provides a survey of commercial aloe vera gel powders. Nine products, obtained from leading international suppliers, were examined and compared with fresh aloe vera gel. A multi-technique approach was chosen to assess their quality and authenticity. Authenticity was evaluated by nuclear magnetic resonance spectrometry (1H NMR). The absence of adulterants, impurities, and preservatives was also investigated by this

A. Bozzi; C. Perrin; S. Austin; F. Arce Vera

2007-01-01

406

Gels as battery separators for soluble electrode cells  

NASA Technical Reports Server (NTRS)

Gels are formed from silica powders and hydrochloric acid. The gels are then impregnated into a polymeric foam and the resultant sheet material is then used in applications where the transport of chloride ions is desired. Specifically disclosed is the utilization of the sheet in electrically rechargeable redox flow cells which find application in bulk power storage systems.

Sheibley, D. W.; Gahn, R. F. (inventors)

1977-01-01

407

Gel spinning of PVA\\/SWNT composite fiber  

Microsoft Academic Search

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

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

2004-01-01

408

Inexpensive and Safe DNA Gel Electrophoresis Using Household Materials  

ERIC Educational Resources Information Center

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

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

2012-01-01

409

MFR PAPER 1021 Testing the gel-forming capacity  

E-print Network

MFR PAPER 1021 Testing the gel-forming capacity of marine fish muscle proteins is part nutritive value of its muscle protein. In addition to their nutritive value, fish muscle protein their muscle proteins for func- tional properties such as gel-formin g capacity is part of our effort

410

Application of MAGAT polymer gel dosimetry in breast balloon  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

411

Transfer printing of thermoreversible ion gels for flexible electronics.  

PubMed

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

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

2013-10-01

412

Biocatalysis with Sol-Gel Encapsulated Acid Phosphatase  

ERIC Educational Resources Information Center

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

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

2010-01-01

413

Polymer gels with engineered environmentally responsive microstructural surface patterns  

NASA Astrophysics Data System (ADS)

A class of hydrogels with microstructural surface arrays has been synthesized. The sputter-depositing method is used to imprint the surface of an N-isopropylacrylamide (NIPA) gel with a square array of a gold thin film. The periodicity of the array is about 20 ?m and can be varied as a function of temperature or electric field. As the periodicity of the gel surface pattern changes in responsive to the external stimuli, the light diffraction pattern changes accordingly. It is demonstrated that the deformation of a gel under external force can be easily monitored using the gel with the periodic surface array. The temperature-responsive NIPA polymer gel is also deposited on the surface of another non- responsive gel using the method of photosensitized solution polymerization. The patterned area can be rendered invisible reversibly by switching the temperature above or below the low critical solution temperature of the NIPA gel. Furthermore, the patterned area can also change its hydrophilicity with the environment. The gels with engineered microstructural surface patterns may find applications in sensor and display technology.

Hu, Zhibing

1999-06-01

414

Polymer gels with engineered environmentally responsive surface patterns  

NASA Astrophysics Data System (ADS)

The polymer gels called hydrogels may be induced to swell or shrink (taking up or expelling water between the crosslinked polymer chains) in response to a variety of environmental stimuli, such as changes in pH or temperature, or the presence of a specific chemical substrate. These gels are being explored for several technological applications, particularly as biomedical materials. When hydrogels swell or shrink, complex patterns may be generated on their surfaces. Here we report the synthesis and controlled modulation of engineered surface patterns on environmentally responsive hydrogels. We modify the character of a gel surface by selectively depositing another material using a mask. For example, we use sputter deposition to imprint the surface of an N-isopropylacrylamide (NIPA) gel with a square array of gold thin films. The periodicity of the array can be continuously varied as a function of temperature or electric field (which alter the gel's volume), and so such an array might serve as an optical grating for sensor applications. We also deposit small areas of an NIPA gel onthe surface of an acrylamide gel; the patterned area can be rendered invisible reversibly by switching the temperature above or below the lower critical solution temperature of the NIPA gel. We anticipate that these surface patterning techniques may find applications in display and sensor technology.

Hu, Zhibing; Chen, Yuanye; Wang, Changjie; Zheng, Yindong; Li, Yong

1998-05-01

415

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

NASA Astrophysics Data System (ADS)

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.

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

2009-11-01

416

How to scan polymer gels with MRI?  

NASA Astrophysics Data System (ADS)

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.

De Deene, Y.

2013-06-01

417

Hybrid slab-microchannel gel electrophoresis system  

DOEpatents

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.

Balch, J.W.; Carrano, A.V.; Davidson, J.C.; Koo, J.C.

1998-05-05

418

Electromechanical studies of a novel polymer gel  

SciTech Connect

Elastic films (thickness ca. 200 {mu}m) of water-swollen, sulfonated styrene/ethylenelbutylene/styrene triblock polymers (14-69% of the styrene sulfonated) were investigated for their ability to exhibit bending movement in electric fields. Application of electric fields of 1-8 V/cm afforded relatively rapid bending of the films toward the cathode. The gel bending dependence on the solution concentration was studied and a maximum was found at about 0.02 M Na{sub 2}SO{sub 4}, while the swelling kept decreasing with increasing concentration. Bending and swelling increased with the degree of sulfonation. When the applied field strength increased, the bending increased and eventually leveled off although the current continued to increase. Switching of the field direction every few seconds resulted in continuous reversals in the direction of film bending.

Ye, Yijun; Rider, J.N.; Kamler, M. [Rensselaer Polytechnic Institute, Troy, NY (United States)] [and others

1996-10-01

419

Microscopic Picture of Cooperative Processes in Restructuring Gel Networks  

NASA Astrophysics Data System (ADS)

Colloidal gel networks are disordered elastic solids that can form even in extremely dilute particle suspensions. With interaction strengths comparable to the thermal energy, their stress-bearing network can locally restructure via breaking and reforming interparticle bonds. This allows for yielding, self-healing, and adaptive mechanics under deformation. Designing such features requires controlling stress transmission through the complex structure of the gel and this is challenging because the link between local restructuring and overall response of the network is still missing. Here, we use a space resolved analysis of dynamical processes and numerical simulations of a model gel to gain insight into this link. We show that consequences of local bond breaking propagate along the gel network over distances larger than the average mesh size. This provides the missing microscopic explanation for why nonlocal constitutive relations are necessary to rationalize the nontrivial mechanical response of colloidal gels.

Colombo, Jader; Widmer-Cooper, Asaph; Del Gado, Emanuela

2013-05-01

420

Fricke Gel Dosimeter Tissue-Equivalence a Monte Carlo Study  

NASA Astrophysics Data System (ADS)

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.

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

2008-06-01

421

Self-oscillations in chemoresponsive gels: a theoretical approach.  

PubMed

Some gels can swell or shrink in function of the concentration of the solutes contained in the solvent. We develop and discuss an algorithm based on Stefan-Maxwell equations to study the dynamics of a sphere of chemoresponsive gel immersed in a medium kept far from equilibrium. We show that the coupling of the reaction with these volume changes creates some feedback that can lead to chemomechanical instabilities. As a result, a reaction that is not oscillatory in homogeneous conditions or in a nonresponsive gel can induce self-oscillations of volume and concentrations in a responsive gel. We also show that chemical oscillations related to long range activation can be strongly modified in such gels, even when the changes of volume are small. PMID:16035893

Boissonade, J

2005-06-01

422

Engineering cartilage in a photochemically crosslinked collagen gel.  

PubMed

This study's purpose was to investigate whether photochemically crosslinking collagen gel to encapsulate chondrocytes (articular, auricular, costal) would permit new cartilage formation in vivo, and to determine whether this neocartilage had the ability to integrate with existing native cartilage. Chondrocytes from swine were embedded in collagen gel that was photochemically crosslinked using riboflavin and visible light. Controls were collagen gels containing cells that were not crosslinked. Cylindrical implants (0.1 cc) were placed in athymic mice for 4 and 8 weeks. To study integration, the constructs were crosslinked within articular cartilage rings and implanted in the mice. Samples were analyzed in terms of macroscopic, microscopic, and biochemical aspects. Photocrosslinking did not affect the amount of glycosaminoglycan and type II collagen produced by the cells. We found that photochemical crosslinking collagen gel enhances the physical parameters of the gel and permits new cartilage formation that can integrate with existing native cartilage. PMID:19216355

Ibusuki, Shinichi; Papadopoulos, Anestis; Ranka, Milan P; Halbesma, Gertjan J; Randolph, Mark A; Redmond, Robert W; Kochevar, Irene E; Gill, Thomas J

2009-01-01

423

Laser CT evaluation on normoxic PAGAT gel dosimeter  

NASA Astrophysics Data System (ADS)

Optical computed tomography has been shown to be a potentially useful imaging tool for the radiation therapy physicists. In radiation therapy, researchers have used optical CT for the readout of 3D dosimeters. The purpose of this paper is to describe the initial evaluation of a newly fabricated laser CT scanner for 3D gel dosimetry which works using the first generation principle. A normoxic PAGAT (Polyacrylamide Gelatin and Tetrakis) gel is used as a dosimeter for this analysis. When a laser passes through the gel phantom, absorption and scattering of photon take place. The optical attenuation coefficient of the laser can be obtained by measuring its intensity after passing through the gel by a sensor. The scanner motion is controlled by a computer program written in Microsoft Visual C++. Reconstruction and data analysis on the irradiated gel phantom is performed by suitable algorithm using Matlab software.

Kumar, D. S.; Samuel, E. J. J.; Watanabe, Y.

2013-06-01

424

Adsorption Characteristics of Silica Gels Treated with Fluorinated Silylation Agents  

PubMed

Branched-chain polyfluorosilane (monochlorodimethyl[4,4-bis(trifluoromethyl)-5,5,6,6,7,7,7-heptafluoroheptyl)-bonded silica gels were prepared. The surface properties of the silica gels modified with various organic silanes were evaluated by the adsorption density of polar and nonpolar gases calculated from adsorption isotherms of nitrogen, carbon dioxide, and normal butane gases. The polyfluorocarbon-bonded silica gel surface was found to be both hydrophobic and oleophobic in nature, whereas the hydrocarbon-bonded silica gel surface was characterized only as hydrophobic. The trifunctional fluorinated silane provides the silica gel surface with a more hydrophilic nature than the monofunctional silane because of the formation of a denser polymeric coating layer with a larger number of silanols. PMID:9056313

Monde; Nakayama; Yano; Yoko; Konakahara

1997-01-01

425

Preparative and analytical purification of DNA from agarose.  

PubMed Central

Two procedures were developed for removing DNA from agarose after electrophoretic separation of DNA fragments according to size. Both involve dissolving the DNA-containing agarose in NaI. The preparative technique uses binding of DNA to glass in the presence of NaI. The method is rapid and convenient, and DNA of all molecular weight ranges can be recovered in high yield and without degradation. The DNA is free of agarose and remains susceptible to digestion by restriction enzymes. The analytical technique uses selective precipitation of DNA with acetone and has been adapted to molecular hybridization scans of sequences in agarose gels. The sequence-monitoring system is quantitative, directly measuring the proportion of the probe complementary to a given DNA fragment and vice versa. It is especially suitable for analyzing restriction enzyme digests of DNA in mapping experiments. PMID:284385

Vogelstein, B; Gillespie, D

1979-01-01

426

Low pH induces an interdigitated gel to bilayer gel phase transition in dihexadecylphosphatidylcholine membrane.  

PubMed Central

We have investigated the influence of pH on the structures and phase behaviors of multilamellar vesicles of the ether-linked dihexadecylphosphatidylcholine (DHPC-MLV). This phospholipid is known to be in the interdigitated gel (L(beta)I) phase in excess water at 20 degrees C at neutral pH. The results of X-ray diffraction experiments indicate that a phase transition from L(beta)I phase to the bilayer gel phase occurred in DHPC-MLV in 0.5 M KCl around pH 3.9 with a decrease in pH, and that at low pH values, less than pH 2.2, DHPC-MLVs were in L(beta') phase. The results of fluorescence and light scattering method indicate that the gel to liquid-crystalline phase transition temperature (T(m)) of DHPC-MLV increased with a decrease in pH. On the basis of a thermodynamic analysis, we conclude that the main mechanism of the low-pH induced L(beta)I to bilayer gel phase transition in DHPC-MLV and the increase in its T(m) is connected with the decrease in the repulsive interaction between the headgroups of these phospholipids. As pH decreases, the phosphate groups of the headgroups begin to be protonated, and as a result, the apparent positive surface charges appear. However, surface dipoles decrease and the interaction free energy of the hydrophilic segments with water increases. The latter effect dominates the pure electrostatic repulsion between the charged headgroups, and thereby, the total repulsive interaction in the interface decreases. PMID:10512821

Furuike, S; Levadny, V G; Li, S J; Yamazaki, M

1999-01-01

427

Dewatering fine coal slurries by gel extraction. Final report  

SciTech Connect

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.

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

1990-12-31

428

Environmentally safe removal/disposal of Coomassie Brilliant Blue from gel destain and used gel stain.  

PubMed

Gel destaining following Coomassie Brilliant Blue (CBB) staining involves the use of toxic reagents. Here we demonstrate the efficacy of various paper adsorbents in adsorbing CBB. Kimwipes adsorbed the best, followed by Teri towels, multifold towels, and Whatman numbers 1 and 3 filter papers. Three Kimwipes completely adsorbed the dye released from a CBB-stained mini-gel. Nonradioactive destain solution can, therefore, be recycled for destaining CBB-stained gels. Stain removal with Kimwipes helps in reducing destain use and in reducing organic liquid waste, and it is 7.5-fold cheaper compared with an available method for CBB disposal. Following this, we determined the suitability of this procedure to remove the dye from a used CBB staining solution awaiting proper disposal by our Institutional Safety Office. The dye from a 0.05% CBB staining solution could be removed in 5 to 10 min using 75 Kimwipes. The CBB-adsorbed Kimwipes did not release the stain when squeezed dry even after incubation in various salts over 1week and in water for 5 weeks. The CBB removed allows its easy disposal as solid waste and will not leach out from solid landfills. Thus, stain removal with Kimwipes helps in disposing CBB in an environmentally friendly manner and allows recycling of destaining solution. PMID:20507825

Dorri, Yaser; Kurien, Biji T

2010-09-15

429

Gel-Based and Gel-Free Quantitative Proteomics Approaches at a Glance  

PubMed Central

Two-dimensional gel electrophoresis (2-DE) is widely applied and remains the method of choice in proteomics; however, pervasive 2-DE-related concerns undermine its prospects as a dominant separation technique in proteome research. Consequently, the state-of-the-art shotgun techniques are slowly taking over and utilising the rapid expansion and advancement of mass spectrometry (MS) to provide a new toolbox of gel-free quantitative techniques. When coupled to MS, the shotgun proteomic pipeline can fuel new routes in sensitive and high-throughput profiling of proteins, leading to a high accuracy in quantification. Although label-based approaches, either chemical or metabolic, gained popularity in quantitative proteomics because of the multiplexing capacity, these approaches are not without drawbacks. The burgeoning label-free methods are tag independent and suitable for all kinds of samples. The challenges in quantitative proteomics are more prominent in plants due to difficulties in protein extraction, some protein abundance in green tissue, and the absence of well-annotated and completed genome sequences. The goal of this perspective assay is to present the balance between the strengths and weaknesses of the available gel-based and -free methods and their application to plants. The latest trends in peptide fractionation amenable to MS analysis are as well discussed. PMID:23213324

Abdallah, Cosette; Dumas-Gaudot, Eliane; Renaut, Jenny; Sergeant, Kjell

2012-01-01

430

Tuning viscoelastic properties of supramolecular peptide gels via dynamic covalent crosslinking.  

PubMed

A dynamic covalent crosslinking approach is used to crosslink supramolecular peptide gels. This novel approach facilitates tuning viscoelastic properties of the gel and enhances mechanical stability (storage modulus exceeding 10(5) Pa) of the peptide gels. PMID:25566850

Khalily, Mohammad Aref; Goktas, Melis; Guler, Mustafa O

2015-02-01

431

On the non-analyticity locus of an arc-analytic function  

Microsoft Academic Search

In this paper we show that the non-analyticity locus of an arc-analytic function is arc-symmetric. Recall that a function is called arc-analytic if it is real analytic on each real analytic arc. By a result of Bierstone and Milman a big class of arc-analytic function, namely those that satisfy a polynomial equation with real analytic coefficients, can be made analytic

Krzysztof Kurdyka; Adam Parusinski

2009-01-01

432

Analytical Sociology: A Bungean Appreciation  

NASA Astrophysics Data System (ADS)

Analytical sociology, an intellectual project that has garnered considerable attention across a variety of disciplines in recent years, aims to explain complex social processes by dissecting them, accentuating their most important constituent parts, and constructing appropriate models to understand the emergence of what is observed. To achieve this goal, analytical sociologists demonstrate an unequivocal focus on the mechanism-based explanation grounded in action theory. In this article I attempt a critical appreciation of analytical sociology from the perspective of Mario Bunge's philosophical system, which I characterize as emergentist systemism. I submit that while the principles of analytical sociology and those of Bunge's approach share a lot in common, the latter brings to the fore the ontological status and explanatory importance of supra-individual actors (as concrete systems endowed with emergent causal powers) and macro-social mechanisms (as processes unfolding in and among social systems), and therefore it does not stipulate that every causal explanation of social facts has to include explicit references to individual-level actors and mechanisms. In this sense, Bunge's approach provides a reasonable middle course between the Scylla of sociological reification and the Charybdis of ontological individualism, and thus serves as an antidote to the untenable "strong program of microfoundations" to which some analytical sociologists are committed.

Wan, Poe Yu-ze

2012-10-01

433

The transfer of analytical procedures.  

PubMed

Analytical method transfers are certainly among the most discussed topics in the GMP regulated sector. However, they are surprisingly little regulated in detail. General information is provided by USP, WHO, and ISPE in particular. Most recently, the EU emphasized the importance of analytical transfer by including it in their draft of the revised GMP Guideline. In this article, an overview and comparison of these guidelines is provided. The key to success for method transfers is the excellent communication between sending and receiving unit. In order to facilitate this communication, procedures, flow charts and checklists for responsibilities, success factors, transfer categories, the transfer plan and report, strategies in case of failed transfers, tables with acceptance limits are provided here, together with a comprehensive glossary. Potential pitfalls are described such that they can be avoided. In order to assure an efficient and sustainable transfer of analytical procedures, a practically relevant and scientifically sound evaluation with corresponding acceptance criteria is crucial. Various strategies and statistical tools such as significance tests, absolute acceptance criteria, and equivalence tests are thoroughly descibed and compared in detail giving examples. Significance tests should be avoided. The success criterion is not statistical significance, but rather analytical relevance. Depending on a risk assessment of the analytical procedure in question, statistical equivalence tests are recommended, because they include both, a practically relevant acceptance limit and a direct control of the statistical risks. However, for lower risk procedures, a simple comparison of the transfer performance parameters to absolute limits is also regarded as sufficient. PMID:23978903

Ermer, J; Limberger, M; Lis, K; Wtzig, H

2013-11-01

434

Simultaneous analysis of select pharmaceuticals and personal care products in fish tissue using pressurized liquid extraction combined with silica gel cleanup.  

PubMed

Analytical improvements were developed and validated for measuring select personal care products (PCPs) and two pharmaceuticals in fish tissue. The method was validated using fortified fillet tissue for twelve PCPs including fragrance materials, alkylphenols, photo initiators, and triclosan as well as two pharmaceuticals including carbamazepine (anti-seizure) and diazepam (anti-convulsant). The analytical method utilized pressurized liquid extraction (PLE) combined with silica gel cleanup, gel permeation chromatography, and gas chromatography ion-trap tandem mass spectrometry. Silica gel cleanup was combined with the PLE to produce one automated extraction/cleanup technique. This analytical improvement served to reduce the incurred cost, time, and loss of potential target analytes associated with independent cleanup steps. The combined extraction/cleanup technique resulted in an average increase of 10% in analyte recoveries. Average triplicate recoveries and relative standard deviations for the entire method, using 2.5 g of fish fillet tissue, were 92 9% (recoveries ranged from 64 to 131%). The sensitivity of the analytical methods was improved by optimizing the resonant collision induced dissociation energy to the hundredths place (0.01 V). Improvements in ion production range from 24 to 122% for six of the 12 PCPs. Statistically derived method detection limits (MDLs) were also lowered on average by a factor of 8 and ranged from 1.2 to 38 ng/g wet weight. MDLs for carbamazepine and diazepam were 18 and 3.7 ng/g wet weight, respectively. Galaxolide and tonalide were measured in an environmental sample at concentrations of 81 and 5.5 ng/g wet weight, respectively. PMID:21820663

Subedi, Bikram; Mottaleb, Mohammad A; Chambliss, C Kevin; Usenko, Sascha

2011-09-16

435

Investigations in x-ray computed tomography polyacrylamide gel dosimetry  

SciTech Connect

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.

Hilts, Michelle [Physics and Astronomy, University of British Columbia, British Columbia, Canada and Medical Physics, BC Cancer Agency, Vancouver Centre, British Columbia (Canada)]. E-mail: mhilts@bccancer.bc.ca

2005-09-15

436

Analytical Chemistry of Nitric Oxide  

PubMed Central

Nitric oxide (NO) is the focus of intense research, owing primarily to its wide-ranging biological and physiological actions. A requirement for understanding its origin, activity, and regulation is the need for accurate and precise measurement techniques. Unfortunately, analytical assays for monitoring NO are challenged by NOs unique chemical and physical properties, including its reactivity, rapid diffusion, and short half-life. Moreover, NO concentrations may span pM to M in physiological milieu, requiring techniques with wide dynamic response ranges. Despite such challenges, many analytical techniques have emerged for the detection of NO. Herein, we review the most common spectroscopic and electrochemical methods, with special focus on the fundamentals behind each technique and approaches that have been coupled with modern analytical measurement tools or exploited to create novel NO sensors. PMID:20636069

Hetrick, Evan M.

2013-01-01

437

Analytical approximations for spiral waves  

SciTech Connect

We propose a non-perturbative attempt to solve the kinematic equations for spiral waves in excitable media. From the eikonal equation for the wave front we derive an implicit analytical relation between rotation frequency ? and core radius R{sub 0}. For free, rigidly rotating spiral waves our analytical prediction is in good agreement with numerical solutions of the linear eikonal equation not only for very large but also for intermediate and small values of the core radius. An equivalent ?(R{sub +}) dependence improves the result by Keener and Tyson for spiral waves pinned to a circular defect of radius R{sub +} with Neumann boundaries at the periphery. Simultaneously, analytical approximations for the shape of free and pinned spirals are given. We discuss the reasons why the ansatz fails to correctly describe the dependence of the rotation frequency on the excitability of the medium.

Lber, Jakob, E-mail: jakob@physik.tu-berlin.de; Engel, Harald [Institut fr Theoretische Physik, Technische Universitt Berlin, Hardenbergstrasse 36, EW 7-1, 10623 Berlin (Germany)] [Institut fr Theoretische Physik, Technische Universitt Berlin, Hardenbergstrasse 36, EW 7-1, 10623 Berlin (Germany)

2013-12-15

438

Analytical Applications of NMR: Summer Symposium on Analytical Chemistry.  

ERIC Educational Resources Information Center

Highlights a symposium on analytical applications of nuclear magnetic resonance spectroscopy (NMR), discussing pulse Fourier transformation technique, two-dimensional NMR, solid state NMR, and multinuclear NMR. Includes description of ORACLE, an NMR data processing system at Syracuse University using real-time color graphics, and algorithms for

Borman, Stuart A.

1982-01-01

439

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

PubMed

A new procedure has been described for the extraction of diclazuril (DIZ), toltrazuril (TOZ) and its two main metabolites toltrazuril sulphoxide (TZSO) and toltrazuril sulphone (TZS) from poultry tissues and eggs, using gel permeation chromatography (GPC). The analytes and the deuterated internal standard were extracted from the samples with ethyl acetate. The analytes were measured by LC coupled to an electrospray ionization tandem mass spectrometer operating in the negative ion mode. Excellent linear dynamic range was observed from 1 to 500 ?g/L with the correlation coefficients (R(2)) better than 0.99 for all analytes. The method LOQ of the four analytes in real samples was 1.2 ?g/kg for DIZ and TOZ, and 1.8 ?g/kg for TZSO and TZS. These values are far lower than the maximum residue limits (MRLs) established by several control authorities. The developed method was accurate with overall recoveries in four matrices. PMID:21565565

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

2011-06-15

440

Dried polyacrylamide gel absorption: a method for efficient elimination of the interferences from SDS-solubilized protein samples in mass spectrometry-based proteome analysis.  

PubMed

Sample preparation holds an important place in MS-based proteome analysis. For effective proteolysis and MS analysis, it is essential to eliminate the interferences while extracting the analytes of interest from complex mixtures. To address this, herein we describe a new dried polyacrylamide gel absorption method. In this method, the protein sample prepared using high concentration of SDS was directly and completely absorbed by vacuum-dried polyacrylamide gel, and then the interfering substances including SDS and some other salts were efficiently removed by in-gel washing steps while retaining the denatured proteins in the gel, thus offering a clean environment amenable to downstream buffer exchange, proteolytic digestion and digest recovery, etc. In combination with in-gel digestion and LC-MS/MS, the newly developed method was applied to the proteome analyses of membrane-enriched fraction and whole tissue homogenate. It was demonstrated that the method is suitable for the analysis of a complex biological sample and can be widely used for sample cleanup in shotgun proteome analyses. PMID:21064138

Zhou, Jian; Li, Jianglin; Li, Jianjun; Chen, Ping; Wang, Xianchun; Liang, Songping

2010-12-01

441

Gels composed of sodium-aluminum silicate, Lake Magadi, Kenya  

USGS Publications Warehouse

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.

Eugster, H.P.; Jones, B.F.

1968-01-01

442

Coordination polymer gels with important environmental and biological applications.  

PubMed

Coordination Polymer Gels (CPGs) constitute a subset of solid-like metal ion and bridging organic ligand structures (similar to metal-organic frameworks) that form multi-dimensional networks through a trapped solvent as a result of non-covalent interactions. While physical properties of these gels are similar to conventional high molecular weight organic polymer gels, coordination polymer gel systems are often fully reversible and can be assembled and disassembled in the presence of additional energy (heat, sonication, shaking) to give a solution of solvated gelators. Compared to gels resulting from purely organic self-assembled low molecular weight gelators, metal ions incorporated into the fibrilar networks spanning the bulk solvent can impart CPGs with added functionalities. The solid/liquid nature of the gels allows for species to migrate through the gel system and interact with metals, ligands, and the solvent. Chemosensing, catalysis, fluorescence, and drug-delivery applications are some of the many potential uses for these dynamic systems, taking advantage of the metal ion's coordination, the organic polydentate ligand's orientation and functionality, or a combination of these properties. By fine tuning these systems through metal ion and ligand selection and by directing self-assembly with external stimuli the rational synthesis of practical systems can be envisaged. PMID:23192282

Jung, Jong Hwa; Lee, Ji Ha; Silverman, Julian R; John, George

2013-02-01

443

Current issues in sol-gel reaction kinetics  

SciTech Connect

This paper surveys a few of the current issues in sol-gel reaction kinetics. Many times seemingly modest changes in reactants or reaction conditions can lead to substantial differences in the overall reaction rates and pathways. For example, qualitative features of the reaction kinetics can depend on catalyst concentration. At very high acid-catalyst concentrations, reverse are significant for TMOS sol-gels, while for moderate acid-catalyst concentrations, reverse reactions are substantially reduced. The reaction kinetics are substantially reduced. The reaction kinetics of two similar tetraalkoxysilanes: tetramethoxysilane (TMOS) and tetraethoxysilane (TEOS), can be markedly different under identical reaction conditions. Under acid-catalyzed reaction conditions, a TMOS sol-gel undergoes both water-and alcohol-producing condensation reactions while a TEOS sol-gel undergoes only water-producing condensation. The early time hydrolysis and condensation reactions of a TMOS sol-gel are statistical in nature and can be quantitatively described by a few simple reaction rate constants while the reaction behavior of a TEOS sol-gel is markedly nonstatistical. A comprehensive theory of sol-gel kinetics must address diverse experimental findings. 9 refs., 3 figs., 1 tab.

Assink, R.A.; Kay, B.D.

1990-01-01

444

Chemotaxis of active, self-oscillating polymer gels in solution  

NASA Astrophysics Data System (ADS)

Fighting, fleeing and feeding are hallmarks of all living things; all these activities require some degree of mobility. Herein, we undertake the first computational study of self-oscillating polymer gels and show that this system can ``communicate'' to undergo a biomimetic, collective response to small-scale chemical changes. In this study we harness unique properties of polymer gels that undergo oscillatory Belousov-Zhabotinsky (BZ) reaction. The activator for the reaction is generated within these BZ cilia and diffuses between the neighboring gels. In order to simulate the dynamics of the BZ gels in surrounding fluid we have developed a nonlinear hybrid 3D model which captures the elasto-dynamics of polymer gel and diffusive exchange of BZ reagents between the gel and the fluid. We illustrate that multiple BZ gels in solution exhibit a distinct form of chemotaxis, moving towards the highest activator concentration in the solution. Similar ability to sense and move in response to chemical gradients constitutes a vital function in simple organisms, enabling them to find food and flee from poisons.

Dayal, Pratyush; Bhattacharya, Amitabh; Kuksenok, Olga; Balazs, Anna C.

2012-02-01

445

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

PubMed

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

Eugster, H P; Jones, B F

1968-07-12

446

Electrically Induced Volume Modification of Ionic Porous Gels  

NASA Astrophysics Data System (ADS)

Volume alterations of conventional gels such as N-isopropylacrylamides (NIPA) have been widely tested via several mediums. However, mediums such as temperature and pH are often dependent variables difficult to control in some environments such as the human body. It is for this reason that this team has developed an ionic-porous-gel (IPG) capable of responding to an operatively induced electrical stimuli much rapidly than conventional gels. The volume transition of the IPG is tested for maximum shrinkage and expansion in de-ionized water. Results indicate that the gel has ionization and de-ionization properties similar to that of biological muscle, in that it will re-expand to near original size upon termination of electric field. The volume change is effected by the induced electro-osmolosis through the matrix of the gel. The permeability of IPG permits the transition of ions in and out of the gel, subsequently allowing for the active movement of water through the matrix, hence, affecting volume transitions. This experiment has shown the practicality of an operatively controlled polymer gel and its reactivity to numerous impulses. It is thus easy to discern the potential for further research application such as in the field of synthetic muscle development.

El-Lessy, Hussein N.; Chen, Yuanye; Wang, Changjie; Hu, Zhibing; Li, Yong

1997-10-01

447

Automated dynamic analytical model improvement  

NASA Technical Reports Server (NTRS)

A method is developed and illustrated which finds minimum changes in analytical mass and stiffness matrices to make them consistent with a set of measured normal modes and natural frequencies. The corrected model is an improved base for studies of physical changes, changes in boundary conditions, and for prediction of forced responses. Features of the method are: efficient procedures not requiring solutions of the eigenproblem; the model may have more degrees of freedom than the test data; modal displacements at all the analytical degrees of freedom are obtained; the frequency dependence of the coordinate transformations are properly treated.

Berman, A.

1981-01-01

448

Modern analytical instrumentation used for determining coating quality and investigating coating failures. What state-of-the-art analytical instruments can do for you  

SciTech Connect

Because of the importance of Paints and coatings as the primary means for corrosion protection, increasingly sophisticated analytical instruments being developed and, brought to base monitoring all stages of the coating process. This includes both GA/QC during coatings manufacture and application as well as during the investigation of coating failures years after. Microscopic-FTIR, auger, XPS/ESCA spectroscopy, thermal analysis (including DSC, TGA, and TGA/FTIR), SEM coupled with EDX, as well as gas and gel permeation chromatography are but a few techniques available to the investigator wishing to solve (or prevent) coating problems. These are discussed along with some specific applications and instrumental limitations.

Mills, G. [George Mills and Associates International, Inc., Humble, TX (United States); Sansum, A.; Cox, G. [ITI Anticorrosion, Inc., Houston, TX (United States)

1994-12-31

449

Characterizing matrix remodeling in collagen gels using optical coherence tomography  

NASA Astrophysics Data System (ADS)

Optical coherence tomography (OCT) has shown promise at non-destructively characterizing engineered tissues such as collagen gels. However, as the collagen gels develop, the OCT images lose contrast of structures as the gels develop, making visual assessment difficult. Our group proposed quantitatively characterizing these gels by fitting the optical properties from the OCT signals. In this paper, we imaged collagen gels seeded with smooth muscle cells (SMCs) over a 5-day period and used the data to measure their optical properties. Our results showed that over time, the reflectivity of the samples increased 10-fold, corresponding to a decrease in anisotropy factor g, without much change in the scattering coefficient ?s. Overall, the optical properties appeared to be dominated by scattering from the collagen matrix, not the cells. However, SMCs remodeled the collagen matrix, and this collagen remodeling by the cells is what causes the observed changes in optical properties. Moreover, the data showed that the optical properties were sensitive to the activity of matrix metalloproteinases (MMPs), enzymes that break down local collagen fibrils into smaller fragments. Blocking MMPs in the SMC gels greatly impeded both the remodeling process and change in optical properties at day 5. Treating day 1 acellular gels with MMP-8 for 3 hr managed to partially reproduce the remodeling observed in SMC gels at day 5. Altogether, we conclude that matrix remodeling in general, and MMPs specifically, greatly affect the local optical properties of the sample, and OCT is a unique tool that can assess MMP activity in collagen gels both non-destructively and label free.

Levitz, David; Hinds, Monica T.; Hanson, Stephen R.; Jacques, Steven L.

2010-02-01

450

Structural studies on the yttrium-doped cobalt ferrite powders synthesized by sol-gel combustion method  

NASA Astrophysics Data System (ADS)

Y0.2CoFe1.8O4 nanopowders were prepared using a sol-gel combustion method. Metal nitrates, such as yttrium nitrate, cobalt nitrate and ferric nitrate, were used as the source materials. Citric acid and polyvinyl alcohol were used as the burning agent and agglomeration reducing agent, respectively. The pH of the precursor was maintained at 7. The mean crystallite size of the prepared ferrite was in the range of ?20-70 nm. The inverse spinel structure, cubic morphology, and the identification of functional groups of the yttrium-doped cobalt ferrite were analyzed systematically using several analytical tools.

Shobana, M. K.; Kwon, Hoon; Choe, Heeman

2012-07-01

451

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

452

Pluronic copolymer liquid crystals: unique, replaceable media for capillary gel electrophoresis.  

PubMed

Liquid crystalline solutions of Pluronic copolymers are versatile alternatives to solutions of entangled, random coil polymers as replaceable media for capillary gel electrophoresis (CGE). Pluronic copolymers are tri-block polymers of poly(ethylene oxide) [(EO)x] and poly(propylene oxide) [(PO)y] with the general formula (EO)x(PO)y(EO)x. Large micelles form in aqueous solutions in which central, hydrophobic cores of (PO)y segments are surrounded by "brushes" of hydrated (EO)x tails. Solutions of Pluronic F127 (BASF Performance Chemicals) in a concentration range of about 18-30% are liquids at refrigerator temperatures (< or = 5 degrees C) and are easily introduced into capillaries. A self-supporting, gel-like liquid crystalline phase is formed as the temperature is raised to > or = 20 degrees C. This liquid crystalline phase consists of spherical micelles with diameters of 17-18 nm which pack with local cubic symmetry. CGE in Pluronic F127 liquid crystals separates species within several chemical classes as varied as nucleoside monophosphates and organic dyes, oligonucleotides of 4-60 nucleotides, DNA fragments of 50-3000 base pairs (bp), and supercoiled plasmid DNAs of 2000-10,000 bp. Mechanisms of molecular sieving in polymer liquid crystals must differ in fundamental ways from separations in random polymer gels because molecules move around uncrosslinked obstacles that are larger than the smallest dimensions of typical analytes. Molecular sieving in Pluronic liquid crystals is envisioned to occur as molecules squeeze between hydrated (EO)x strands of micelle brushes, or through brushtips and interstitial spaces between micelles. Small molecules such as nucleotides appear to separate by a different mechanism involving partitioning between hydrophilic and hydrophobic environments. This process is termed "hydrophobic interaction electrophoresis". The unique structures of Pluronic copolymers and their liquid crystalline phases provide new challenges and opportunities in separations science. PMID:9764501

Rill, R L; Liu, Y; Van Winkle, D H; Locke, B R

1998-08-21

453

In-phantom dose imaging with polymer gel layer dosimeters.  

PubMed

Gel dosimeters in form of layers have shown noticeable potentiality for in-phantom dose profiling and imaging in BNCT neutron fields. Such dosimeters give the possibility of achieving spatial dose distributions of each dose contribution in neutron fields. The various dose components are separated by means of pixel-to-pixel manipulations of pairs of images acquired with gel dosimeters having different isotopic compositions. The reliability of polymer-gel-layer dosimeters (PGLD) for BNCT has been studied and their utilisation limits have been inspected. PMID:19375935

Vanossi, E; Carrara, M; Gambarini, G; Negri, A; Mariani, M

2009-07-01

454

Gel Electrophoresis of Gold-DNA Nano-Conjugates  

SciTech Connect

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.

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

2006-01-10

455

Helicoidal precipitation patterns in silica and agarose gels  

NASA Astrophysics Data System (ADS)

Helicoidal patterns grown in agarose and silica gels were studied using reaction-diffusion-precipitation processes with components CuCl2/K2CrO4. We measured the probability PH of the emergence of helicoids as the internal surface area of the gels was varied by changing the concentration for agarose and by modifying pH for silica. In addition, the effects of mixing the two gels were also investigated. Our main result is that the surface area effects parallel the effects of noise, namely increasing the surface area initially enhances the formation of helicoids but further increase leads to downturn in PH due to proliferation of random patterns.

Thomas, Shibi; Varghese, George; Brdfalvy, Dra; Lagzi, Istvn; Rcz, Zoltn

2014-04-01

456

Characteristics of gel alkylene oxide polymer electrolytes containing ?-butyrolactone  

NASA Astrophysics Data System (ADS)

Gel polymer electrolytes consisted of poly(alkylene oxide) (PAO), LiBF 4 or LiClO 4, and aprotic solvents (?-butyrolactone (GBL) and/or ethylene carbonate (EC)) were prepared and the conductivity was measured. The conductivity was very high and similar to that of the organic liquid electrolytes. The performance of Li | gel polymer electrolyte | LiCoO 2 cell was measured and compared to that of the cell with the liquid electrolyte corresponded. The cell with the gel electrolyte showed a decrease of capacity at high-rate discharge and low temperature owing to concentration polarization.

Matsuda, Yoshiharu; Fukushima, Tsuyoshi; Katoh, Yuichi; Ishiko, Eriko; Nishiura, Masahito; Kikuta, Manabu; Kono, Michiyuki

457

Electrical properties of lithium ionic electrolyte using fluorinated gels  

Microsoft Academic Search

The lithium ionic electrolytes of fluorinated gel materials have been found to show high ionic conductivity. We proposed an application to a secondary battery using this gel electrolyte. Non-crosslinked fluorinated gel materials were prepared by reacting fluoroalkanoyl peroxides with 2-acrylamid-2-methylpropanesulfonic acid (AMPS) oligomer containing fluoroalkylated end-capped units {[-RF-(AMPS)q]p-}. Several kinds of lithium salts [LiPF4 , LiBF6, LiCF3SO3, and LiN(CF3-SO2)2] were

J. Kyokane; K. Lee; T. Murano; H. Sawada

1999-01-01

458

Tensile Properties of Poly (N-vinyl caprolactam) Gels  

NASA Technical Reports Server (NTRS)

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.

Morgret, Leslie D.; Hinkley, Jeffrey A.

2004-01-01

459

Fracture of a biopolymer gel as a viscoplastic disentanglement process.  

PubMed

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 Mater. 5, 552 (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. PMID:17093896

Baumberger, T; Caroli, C; Martina, D

2006-09-01

460

C60: the first one-component gel?  

E-print Network

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.

C. Patrick Royall; Stephen R. Williams

2011-02-15

461

Google analytics: Tips for micro-firms  

Microsoft Academic Search

The free web analytics tools launched by some search engines (for example, Google analytics and yahoo web analytics) have the potential to be turned into key marketing tools for small businesses and long tail websites. Web analytics, however, is not just about the number of people visiting a site, but is also about the quality of the traffic and what

Beatriz Plaza

2012-01-01

462

Correction of Wall Adhesion Effects in Batch Settling of Strong Colloidal Gels  

E-print Network

The batch settling test is widely used to estimate the compressive rheology of strongly flocculated colloidal suspensions, in particular the compressive yield strength and hydraulic permeability. Recently it has been discovered that wall adhesion effects in these tests may be significantly greater than previously appreciated, which can introduce unbounded errors in the estimation of these rheological functions. Whilst a methodology to solve the underlying static problem and correct for wall adhesion effects has been developed, this method is quite complex and unwieldy, involving solution of a 2D hyper-elastic constitutive model for strong colloidal gels. In this paper we develop a highly simplified 1D visco-plastic approximation to the hyper-elastic model which admits analytic expressions for the equilibrium solids concentration profile and bed height. These expressions facilitate robust estimation of the compressive yield and wall adhesion strength via nonlinear regression of experimental data in the presence of small measurement errors.

Daniel R. Lester; Richard Buscall

2014-09-30

463

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

464

Clotrimazole nanoparticle gel for mucosal administration.  

PubMed

In this study a formulation suitable to be applied on oral and/or vaginal mucosa has been developed for the treatment of fungal infect