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1

Preparative ultracentrifugation and analytic ultracentrifugation of plasma lipoproteins  

SciTech Connect

There are several chapters and a book dealing with both preparative and analytical ultracentrifugation (AnUC) of plasma lipoproteins. However, what we would like to present are the procedures as currently done here at Donner Laboratory. They have been modified and improved since the earliest lipoprotein flotation was demonstrated in 1949, and this will present a combined, practical up-date of our chapter on AnUC in Blood Lipids and Lipoproteins (1972) and our chapter on preparative procedures in the American Oil Chemists' Society (AOCS) book, Analysis of Lipids and Lipoproteins (1975). This information is intended as a practical laboratory guide to anyone who wishes to do preparative and AnUC of plasma lipoproteins. 10 refs., 6 figs., 1 tab.

Orr, J.R.; Adamson, G.L.; Lindgren, F.T.

1990-03-01

2

Brownian dynamics simulation of analytical ultracentrifugation experiments  

PubMed Central

Background We have devised a protocol for the Brownian dynamics simulation of an analytical ultracentrifugation experiment that allows for an accurate and efficient prediction of the time-dependent concentration profiles, c(r, t) in the ultracentrifuge cell. The procedure accounts for the back-diffusion, described as a Brownian motion that superimposes to the centrifugal drift, and considers the sector-shaped geometry of the cell and the boundaries imposed by the meniscus and bottom. Results Simulations are carried out for four molecules covering a wide range of the ratio of sedimentation and diffusion coefficients. The evaluation is done by extracting the molecular parameters that were initially employed in the simulation by analyzing the profiles with an independent tool, the well-proved SEDFIT software. The code of simulation algorithm has been parallelized in order to take advantage of current multi-core computers. Conclusions Our Brownian dynamics simulation procedure may be considered as an alternative to other predictors based in numerical solutions of the Lamm equation, and its efficiency could make it useful in the most relevant, inverse problem, which is that of extracting the molecular parameters from experimentally determined concentration profiles.

2011-01-01

3

Comparison of gradient gel electrophoresis and zonal ultracentrifugation for quantitation of high density lipoproteins  

Microsoft Academic Search

The study was conducted to compare gradient gel electrophoresis (GGE) and zonal ultracentrifugation for quanti- tation of human plasma high density lipoproteins (HDL). Plasma samples were obtained from seven normal subjects consuming a high fat diet (65% total calories) followed by a high carbohydrate diet (65% total calories). HDL were fractionated into HDL2 and HDLS by zonal ultracentrifugation and lipid

Constance A. McNerney; Moti L. Kashyap; Roger L. Barnhart

4

Analytical Ultracentrifugation as a Tool for Studying Protein Interactions.  

PubMed

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

Schuck, Peter

2013-06-01

5

Osmotic pressure and phase boundary determination of multiphase systems by analytical ultracentrifugation.  

PubMed

We show that analytical ultracentrifugation can be applied to derive full equations of state of colloids in a single sedimentation equilibrium experiment, by determination of single-phase boundaries as well as of osmotic pressure versus concentration at fixed temperatures. A continuous dependence of the osmotic pressure, over orders of magnitude between at least approximately 10(1) and 10(4) Pa, and a wide concentration range, are determined in agreement with standard theoretical considerations. Two model experimental colloidal systems are investigated: For a well-known synthetic clay system (laponite), it is shown that two regimes-counter-ion ideal gas and interacting double layers-can easily be identified in the equation of state, whereas metastable glass- or microphase-separated gel states previously encountered in osmotic stress measurements of laponite are circumvented. For the case of rigid, crystallized catanionic bilayers, single phase domains can be identified. Osmotic pressure results in this case disagree with results obtained using the classical osmotic stress technique, as a result of sample adhesion to the ultracentrifuge cell windows and uncertainty due to possible micromolar ion contamination. PMID:18383058

Page, Miles G; Zemb, Thomas; Dubois, Monique; Cölfen, Helmut

2008-04-21

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

Model independent determination of colloidal silica size distributions via analytical ultracentrifugation.  

PubMed

We report a method to determine the particle size distribution of small colloidal silica spheres via analytical ultracentrifugation and show that the average particle size, variance, standard deviation, and relative polydispersity can be obtained from a single sedimentation velocity (SV) analytical ultracentrifugation (AUC) experiment. The particle size distribution (psd) from the enhanced van Holde-Weischet (vHW) analysis accounts for the dynamic light scattering results quite well. In addition, the vHW psd equals the psd from a continuous distribution of sedimentation coefficients analysis where whole sedimentation velocity boundaries are fitted. The SV AUC interference optical data also yield the specific particle volume such that distributions of sedimentation coefficients for colloidal spheres can be converted directly to particle size distributions. Our results show that SV AUC experiments may yield a quantitative particle size distribution without a priori knowledge of the particle size and the shape of the size distribution. PMID:19551925

Planken, Karel L; Kuipers, Bonny W M; Philipse, Albert P

2008-12-01

8

A Bayesian Approach for Quantifying Trace Amounts of Antibody Aggregates by Sedimentation Velocity Analytical Ultracentrifugation  

Microsoft Academic Search

Sedimentation velocity analytical ultracentrifugation (SV-AUC) has become an important tool for the characterization of the\\u000a purity of protein therapeutics. The work presented here addresses a need for methods orthogonal to size-exclusion chromatography\\u000a for ensuring the reliable quantitation of immunogenic oligomers, for example, in antibody preparations. Currently the most\\u000a commonly used approach for SV-AUC analysis is the diffusion-deconvoluted sedimentation coefficient distribution

Patrick H. Brown; Andrea Balbo; Peter Schuck

2008-01-01

9

Alternative light sources for the Schlieren optical system of analytical ultracentrifuges  

Microsoft Academic Search

This paper presents alternative light sources to the rather unreliable high pressure mercury lamps, commonly used for the\\u000a schlieren optical system of Analytical Ultracentrifuges. The alternatives are an ultra-bright light emitting diode (LED) and\\u000a a halogen lamp, which are both commonly available and very cheap. The non-uniform light emitted by these light sources is\\u000a either transformed to uniform diffuse light

H. Cölfen; P. Husbands; S. Harding

10

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

PubMed Central

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

Latner, A L; Hodson, A W

1976-01-01

11

Measurement of the temperature of the resting rotor in analytical ultracentrifugation.  

PubMed

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

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

2014-08-01

12

Using prior knowledge in the determination of macromolecular size distributions by analytical ultracentrifugation  

PubMed Central

Analytical ultracentrifugation has reemerged as a widely used tool for the study of ensembles of biological macromolecules to understand, for example, their size-distribution and interactions in free solution. Such information can be obtained from the mathematical analysis of the concentration and signal gradients across the solution column and their evolution in time generated as a result of the gravitational force. In sedimentation velocity analytical ultracentrifugation, this analysis is frequently conducted using high resolution, diffusion-deconvoluted sedimentation coefficient distributions. They are based on Fredholm integral equations, which are ill-posed unless stabilized by regularization. In many fields, maximum entropy and Tikhonov-Phillips regularization are well-established and powerful approaches that calculate the most parsimonious distribution consistent with the data and prior knowledge, in accordance with Occam’s razor. In the implementations available in analytical ultracentrifugation, to date, the basic assumption implied is that all sedimentation coefficients are equally likely, and that the information retrieved should be condensed to the least amount possible. Frequently, however, more detailed distributions would be warranted by specific detailed prior knowledge on the macromolecular ensemble under study, such as, the expectation of the sample to be monodisperse or paucidisperse, or the expectation for the migration to establish a bimodal sedimentation pattern based on Gilbert & Jenkins’ theory for the migration of chemically reacting systems. So far, such prior knowledge has remained largely unused in the calculation of the sedimentation coefficient or molecular weight distributions, or was only applied as constraints. In the present paper, we examine how prior expectations can be built directly into the computational data analysis, conservatively in a way that honors the complete information of the experimental data, whether or not consistent with the prior expectation. Consistent with analogous results in other fields, we find that use of available prior knowledge can have a dramatic effect on the resulting molecular weight, sedimentation coefficient and size-and-shape distributions, and significantly increase both their sensitivity and resolution. Further, the use of multiple alternative priors allows to probe the range of possible interpretations consistent with the data.

Brown, Patrick H.; Balbo, Andrea; Schuck, Peter

2007-01-01

13

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

PubMed Central

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

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

2011-01-01

14

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

PubMed Central

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

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

2011-01-01

15

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.

2009-01-01

16

Size and density measurement of core-shell Si nanoparticles by analytical ultracentrifugation  

NASA Astrophysics Data System (ADS)

Si nanocrystals, terminated with cyclohexane and allylamine, were analyzed using analytical ultracentrifugation (AUC), dynamic light scattering (DLS) and transmission electron microscopy. We found that AUC yielded equivalent particle size distribution data to other nanoparticle characterization techniques, while also providing important information not probed by techniques such as DLS regarding the relative size of the particle core and shell components and the overall effective particle density. Estimates of particle core and shell dimensions are consistent with the particle’s optical properties within the quantum confinement representation and available theoretical Si nanocrystal models. Measurement of sedimentation velocity in several solvents with different densities presents a way to circumvent the ambiguity of simultaneous fitting of particle density and sedimentation coefficient and allows us to significantly reduce the uncertainty in the estimates of particle hydrodynamic diameter by finding the effective particle density value.

Nontapot, Kanokwan; Rastogi, Vinayak; Fagan, Jeffrey A.; Reipa, Vytas

2013-04-01

17

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

NASA Astrophysics Data System (ADS)

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

Brown, Patrick H.; Schuck, Peter

2008-01-01

18

Atomic force microscopy and analytical ultracentrifugation for probing nanomaterial protein interactions.  

PubMed

Upon contact with the human body, nanomaterials are known to interact with the physiological surroundings, especially with proteins. In this context, we explored analytical methods to provide biologically relevant information, in particular for manufactured nanomaterials as produced by the chemical industry. For this purpose, we selected two batches of SiO(2) nanoparticles as well as four batches of CeO(2) nanoparticles, each of comparably high chemical purity and similar physicochemical properties. Adsorption of serum proteins and bovine serum albumin (BSA) was quantified by SDS-PAGE in combination with densitometry and further investigated by atomic force microscopy (AFM) and analytical ultracentrifugation (AUC). The protein adsorption to SiO(2) nanoparticles was below the limit of detection, regardless of adjusting pH or osmolality to physiological conditions. In contrast, the four CeO(2) nanomaterials could be classified in two groups according to half-maximal protein adsorption. Measuring the work of adhesion and indention by AFM for the BSA-binding CeO(2) nanomaterials revealed the same classification, pointing to alterations in shape of the adsorbed protein. The same trend was also reflected in the agglomeration behavior/dispersibility of the four CeO(2) nanomaterials as revealed by AUC. We conclude that even small differences in physicochemical particle properties may nevertheless lead to differences in protein adsorption, possibly implicating a different disposition and other biological responses in the human body. Advanced analytical methods such as AFM and AUC may provide valuable additional information in this context. PMID:22577818

Schaefer, Jens; Schulze, Christine; Marxer, Elena Eva Julianne; Schaefer, Ulrich Friedrich; Wohlleben, Wendel; Bakowsky, Udo; Lehr, Claus-Michael

2012-06-26

19

Recorded scan times can limit the accuracy of sedimentation coefficients in analytical ultracentrifugation.  

PubMed

We report systematic and large inaccuracies in the recorded elapsed time in data files from the analytical ultracentrifuge, leading to overestimates of the sedimentation coefficients of up to 10%. This far exceeds previously considered factors contributing to the uncertainty in this parameter and has significant ramifications for derived parameters such as hydrodynamic shape and molar mass estimates. The source of this error is currently unknown, but we found it to be quantitatively consistent across different instruments, increasing with rotor speed. Furthermore, its occurrence appears to correlate with the use of the latest data acquisition software from the manufacturer, in use in some of our laboratories for nearly 2 years. Many of the recently published sedimentation coefficients may need to be reexamined. The problem can be easily recognized by comparing the file timestamps provided by the operating system with the elapsed scan times recorded within the data files. Therefore, we implemented a routine in SEDFIT that can automatically examine the data files, alert the user to significant discrepancies, and correct the scan times accordingly. This eliminates errors in the recorded scan times. PMID:23458356

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

2013-06-01

20

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.

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

2013-01-01

21

Tools for the quantitative analysis of sedimentation boundaries detected by fluorescence optical analytical ultracentrifugation.  

PubMed

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

22

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

PubMed

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

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

1997-01-01

23

A bayesian approach for quantifying trace amounts of antibody aggregates by sedimentation velocity analytical ultracentrifugation.  

PubMed

Sedimentation velocity analytical ultracentrifugation (SV-AUC) has become an important tool for the characterization of the purity of protein therapeutics. The work presented here addresses a need for methods orthogonal to size-exclusion chromatography for ensuring the reliable quantitation of immunogenic oligomers, for example, in antibody preparations. Currently the most commonly used approach for SV-AUC analysis is the diffusion-deconvoluted sedimentation coefficient distribution c(s) method, previously developed by us as a general purpose technique and implemented in the software SEDFIT. In both practical and theoretical studies, different groups have reported a sensitivity of c(s) for trace oligomeric fractions well below the 1% level. In the present work we present a variant of c(s) designed for the purpose of trace detection, with customized Bayesian regularization. The original c(s) method relies on maximum entropy regularization providing the most parsimonious distribution consistent with the data. In the present paper, we use computer simulations of an antibody system as example to demonstrate that the standard maximum entropy regularization, due to its design, leads to a theoretical lower limit for the detection of oligomeric traces and a consistent underestimate of the trace populations by approximately 0.1% (dependent on the level of regularization). This can be overcome with a recently developed Bayesian extension of c(s) (Brown et al., Biomacromolecules, 8:2011-2024, 2007), utilizing the known regions of sedimentation coefficients for the monomer and oligomers of interest as prior expectation for the peak positions in the distribution. We show that this leads to more clearly identifiable and consistent peaks and lower theoretical limits of quantization by approximately an order of magnitude for some experimental conditions. Implications for the experimental design of SV-AUC and practical detection limits are discussed. PMID:18814037

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

2008-09-01

24

On the analysis of protein self-association by sedimentation velocity analytical ultracentrifugation.  

PubMed

Analytical ultracentrifugation is one of the classical techniques for the study of protein interactions and protein self-association. Recent instrumental and computational developments have significantly enhanced this methodology. In this paper, new tools for the analysis of protein self-association by sedimentation velocity are developed, their statistical properties are examined, and considerations for optimal experimental design are discussed. A traditional strategy is the analysis of the isotherm of weight-average sedimentation coefficients s(w) as a function of protein concentration. From theoretical considerations, it is shown that integration of any differential sedimentation coefficient distribution c(s), ls-g(*)(s), or g(s(*)) can give a thermodynamically well-defined isotherm, as long as it provides a good model for the sedimentation profiles. To test this condition for the g(s(*)) distribution, a back-transform into the original data space is proposed. Deconvoluting diffusion in the sedimentation coefficient distribution c(s) can be advantageous to identify species that do not participate in the association. Because of the large number of scans that can be analyzed in the c(s) approach, its s(w) values are very precise and allow extension of the isotherm to very low concentrations. For all differential sedimentation coefficients, corrections are derived for the slowing of the sedimentation boundaries caused by radial dilution. As an alternative to the interpretation of the isotherm of the weight-average s value, direct global modeling of several sedimentation experiments with Lamm equation solutions was studied. For this purpose, a new software SEDPHAT is introduced, allowing the global analysis of several sedimentation velocity and equilibrium experiments. In this approach, information from the shape of the sedimentation profiles is exploited, which permits the identification of the association scheme and requires fewer experiments to precisely characterize the association. Further, under suitable conditions, fractions of incompetent material that are not part of the reversible equilibrium can be detected. PMID:12895474

Schuck, Peter

2003-09-01

25

Analytical ultracentrifugation studies of translin: analysis of protein-DNA interactions using a single-stranded fluorogenic oligonucleotide.  

PubMed

Translin is a recently identified nucleic acid binding protein that appears to be involved in the recognition of conserved sequences found at many chromosomal breakpoints. Previous reports indicate that, based on gel filtration analysis and electron microscopy of protein-DNA complexes, translin forms an octameric structure that binds the DNA. In this study, we further examine the possibility of self-association of translin and its interactions with DNA by analytical ultracentrifugation. Sedimentation velocity analysis of translin indicates that the predominant species sediments with a sedimentation coefficient of 8.5 S and has a frictional ratio, f/f(omicron), of 1.35; these data are consistent with the presence of an octamer with an ellipsoidal configuration; a small amount of a component with significantly higher mass is also present. Equilibrium sedimentation studies of translin at three different protein concentrations also indicate that the predominant species present is an octamer with a minor fraction of aggregated species. Neither monomer nor dimer was detected. Sedimentation equilibrium studies of translin with an FITC-labeled single-stranded oligonucleotide were performed to examine the interaction. A novel analysis method has been developed to analyze protein-nucleic acid interactions based on global fitting of scans of 280 and 490 nm to appropriate mathematical models. Utilizing this method, it was determined that the DNA binding species of translin is an octamer binding a single-stranded oligonucleotide with a DeltaG degrees value of -9.49 +/- 0.12 kcal/mol, corresponding to a dissociation constant, K(d), of 84 +/- 17 nM. On the basis of this evidence and electron microscopy, it is envisioned that translin forms an annular structure of eight subunits, hydrodynamically an oblate ellipsoid, which binds DNA at chromosomal breakpoints. PMID:11705401

Lee, S P; Fuior, E; Lewis, M S; Han, M K

2001-11-20

26

Evaluation of rat and rabbit sera lipoproteins in experimentally induced hyperlipidemia by analytical ultracentrifugation  

Microsoft Academic Search

Animals of various species are widely used as models with which to study atherosclerosis and the lipoprotein metabolism. The\\u000a objective of this study was to investigate the lipoprotein profiles in Wistar rats and New Zealand white rabbits with experimentally\\u000a induced hyperlipidemia by means of ultracentrifugation. The Schlieren curves were utilized to compare suckling and adult rat\\u000a sera to determine whether

Z. Bozóky; L. Balogh; D. Máthé; L. Fülöp; Gy. A. Jánoki

2006-01-01

27

The effect of a point mutation on the stability of IgG4 as monitored by analytical ultracentrifugation.  

PubMed

There is presently considerable interest in the state of aggregation and biophysical integrity of antibody preparations, and recent advances in the analysis of data from the analytical ultracentrifuge renders it a powerful probe of these stability phenomena, under both storage and freeze-thaw conditions. Solutions of a wild-type IgG4 antibody and a single amino acid hinge mutant IgG4m (serine residue 241 converted to proline) were exposed to different accelerated stress conditions, namely (i) elevated temperature storage for various periods (up to 59 days at 37 degrees C) or (ii) a series of freeze-thaw cycles (storage at -80 degrees C then incubation at 20 degrees C for 1 h under different conditions). Analysis using the nondisruptive probe of sedimentation velocity in the analytical ultracentrifuge indicated that for both antibodies the monomer was always the most common species present whatever storage regime had been used. Sedimentation coefficient distribution analysis showed that other higher oligomer species and half-antibodies were present, and appeared to be not in chemical equilibrium with each other. Solution heterogeneity was found to increase considerably with treatment for both native and hinge-mutant antibodies although the latter appeared to be more resistant to freeze-thaw-induced aggregation. PMID:17722105

Lu, Yanling; Harding, Stephen E; Rowe, Arthur J; Davis, Kenneth G; Fish, Brendan; Varley, Paul; Gee, Chris; Mulot, Sandrine

2008-02-01

28

Probing the Oligomeric Assemblies of Pea Porphobilinogen Synthase by Analytical Ultracentrifugation  

PubMed Central

The enzyme porphobilinogen synthase (PBGS) can exist in different non-additive homo-oligomeric assemblies and, under appropriate conditions, the distribution of these assemblies can respond to ligands such as metals or substrate. PBGS from most organisms was believed to be octameric until work on a rare allele of human PBGS revealed an alternate hexameric assembly, which is also available to the wild type enzyme at elevated pH. Herein, we establish that the distribution of pea PBGS quaternary structures also contains octamers and hexamers, using both sedimentation velocity and sedimentation equilibrium experiments. We report results in which the octamer dominates under purification conditions and discuss conditions that influence the octamer:hexamer ratio. As predicted by PBGS crystal structures from related organisms, in the absence of magnesium, the octameric assembly is significantly destabilized and the oligomeric distribution is dominated largely by the hexameric assembly. Although the PBGS hexamer-to-octamer oligomeric rearrangement is well document under some conditions, both assemblies are very stable (under AUC conditions) in the timeframe of our ultracentrifuge experiments.

Kokona, Bashkim; Rigotti, Daniel J.; Wasson, Andrew S.; Lawrence, Sarah H.; Jaffe, Eileen K.; Fairman, Robert

2008-01-01

29

Analysis of the complex formation of heparin with protamine by light scattering and analytical ultracentrifugation: implications for blood coagulation management.  

PubMed

Heparin, a linear glycosaminoglycan, is used in different forms in anticoagulation treatment. Protamine, a highly positive charged peptide containing about 32 amino acids, acts as an antagonist for heparin to restore normal blood coagulation. The complex formation of protamine with heparin was analyzed by a combination of analytical ultracentrifugation and light scattering. Titration of heparin with protamine in blood plasma preparations results in a drastic increase of turbidity, indicating the formation of nanoscale particles. A similar increase of turbidity was observed in physiological saline solution with or without human serum albumin (HSA). Particle size analysis by analytical ultracentrifugation revealed a particle radius of approximately 30 nm for unfractionated heparin and of approximately 60 nm for low molecular weight heparin upon complexation with excess protamine, in agreement with atomic force microscopy data. In the absence of HSA, larger and more heterogeneous particles were observed. The particles obtained were found to be stable for hours. The particle formation kinetics was analyzed by light scattering at different scattering angles and was found to be complete within several minutes. The time course of particle formation suggests a condensation reaction, with sigmoidal traces for low heparin concentrations and quasi-first-order reaction for high heparin concentrations. Under all conditions, the final scattering intensity reached after several minutes was found to be proportional to the amount of heparin in the blood plasma or buffer solution, provided that excess protamine was available and no multiple scattering occurred. On the basis of a direct relation between particle concentration and the heparin concentration present before protaminization, a light scattering assay was developed which permits the quantitative analysis of the heparin concentration in blood plasma and which could complement or even replace the activated clotting time test, which is currently the most commonly used method for blood coagulation management. PMID:21186806

Maurer, Jürgen; Haselbach, Stephanie; Klein, Oliver; Baykut, Doan; Vogel, Vitali; Mäntele, Werner

2011-02-01

30

Use of the novel technique of analytical ultracentrifugation with fluorescence detection system identifies a 77S monosomal translation complex  

PubMed Central

A fundamental problem in proteomics is the identification of protein complexes and their components. We have used analytical ultracentrifugation with a fluorescence detection system (AU-FDS) to precisely and rapidly identify translation complexes in the yeast Saccharomyces cerevisiae. Following a one-step affinity purification of either poly(A)-binding protein (PAB1) or the large ribosomal subunit protein RPL25A in conjunction with GFP-tagged yeast proteins/RNAs, we have detected a 77S translation complex that contains the 80S ribosome, mRNA, and components of the closed-loop structure, eIF4E, eIF4G, and PAB1. This 77S structure, not readily observed previously, is consistent with the monosomal translation complex. The 77S complex abundance decreased with translational defects and following the stress of glucose deprivation that causes translational stoppage. By quantitating the abundance of the 77S complex in response to different stress conditions that block translation initiation, we observed that the stress of glucose deprivation affected translation initiation primarily by operating through a pathway involving the mRNA cap binding protein eIF4E whereas amino acid deprivation, as previously known, acted through the 43S complex. High salt conditions (1M KCl) and robust heat shock acted at other steps. The presumed sites of translational blockage caused by these stresses coincided with the types of stress granules, if any, which are subsequently formed.

Wang, Xin; Zhang, Chongxu; Chiang, Yueh-Chin; Toomey, Shaun; Power, Matthew P; Granoff, Mitchell E; Richardson, Roy; Xi, Wen; Lee, Darren J; Chase, Susan; Laue, Thomas M; Denis, Clyde L

2012-01-01

31

Rod hydrodynamics and length distributions of single-wall carbon nanotubes using analytical ultracentrifugation.  

PubMed

Because of their repetitive chemical structure, extreme rigidity, and the separability of populations with varying aspect ratio, SWCNTs are excellent candidates for use as model rodlike colloids. In this contribution, the sedimentation velocities of length and density sorted single-wall carbon nanotubes (SWCNTs) are compared to predictions from rod hydrodynamic theories of increasing complexity over a range of aspect ratios from <50 to >400. Independently measuring all contributions to the sedimentation velocity besides the shape factor, excellent agreement is found between the experimental findings and theoretical predictions for numerically calculated hydrodynamic radius values and for multiterm analytical expansion approximations; values for the hydrodynamic radii in these cases are additionally found to be consistent with the apparent hydrated particle radius determined independently by buoyancy measurements. Lastly, we utilize this equivalency to calculate the apparent distribution of nanotube lengths in each population from their sedimentation coefficient distribution without adjustable parameters, achieving excellent agreement with distributions from atomic force microscopy. The method developed herein provides an alternative for the ensemble measurement of SWCNT length distributions and others rodlike particles. PMID:24707888

Batista, Carlos A Silvera; Zheng, Ming; Khripin, Constantine Y; Tu, Xiaomin; Fagan, Jeffrey A

2014-05-01

32

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

33

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

34

Ultracentrifugation deforms unfixed influenza A virions  

PubMed Central

Negatively stained influenza virions sometimes show irregular morphology and are often referred to as pleomorphic. However, this irregular morphology has not been visualized when ultrathin-section transmission and scanning electron microscopies are used. This study focused on the effects of ultracentrifugation on influenza A virion morphology, as negative staining often involves ultracentrifugation to concentrate or purify virions. The morphologies of unfixed, glutaraldehyde-fixed and osmium tetroxide-fixed virions were quantitatively compared before and after ultracentrifugation, and it was found that, without chemical fixation, approximately 30?% of virions were altered from oval to irregular shapes following ultracentrifugation. By contrast, most glutaraldehyde-fixed virions remained uniformly elliptical, even after ultracentrifugation. When a virus with an 11 aa deletion at the C terminus of its M2 cytoplasmic tail was ultracentrifuged, its morphology was appreciably deformed compared with that of the wild-type virus. These results demonstrate that the native morphology of influenza A virions is regular but is disrupted by ultracentrifugation, and that the cytoplasmic tail of M2 is important for virion integrity.

Sugita, Yukihiko; Sagara, Hiroshi

2011-01-01

35

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

36

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

Microsoft Academic Search

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

Peter Schuck

2000-01-01

37

Studies on the bioactivity of radioiodinated highly purified bovine thyrotropin: analytical polyacrylamide gel electrophoresis  

SciTech Connect

Highly purified bovine TSH (stored in solution at -70 C) was radioiodinated by the stoichiometric chloroamine-T method. The iodinated material ws subjected to analytical polyacrylamide disc gel electrophoresis. TSH was eluted from gel slices (1 mm width) and was analyzed for radioactivity and bioactivity. The latter was determined using the cultured thyroid cell cAMP response assay. Radioactivity in the TSH preparation migrated separately from bioactivity, but concordant with the protein bands observed in gels run in parallel. Further studies performed on bovine TSH purified in our laboratory, as well as on a different TSH preparation of exceptionally high potency (both stored as lyophilized powder) revealed a different pattern, with TSH bioactivity and radioactivity eluting concurrently. Iodination of TSH did not alter its electrophoretic migration on disc gel electrophoresis. In all preparations polymorphism of TSH bioactivity was observed, with at least four separate protein bands containing TSH bioactivity being present in our preparation. The relationship between the degree of iodination and retention of TSH bioactivity was examined. Incorporation of /sup 125/I into TSH was greatly different at two different concentrations of chloramine-T. Despite this, however, the progressive loss of TSH bioactivity was similar at both concentrations, indicating that incorporation of iodine into the TSH molecule is not itself responsible for the decrease in bioactivity. These studies indicate variability among different TSH preparations in terms of their retention of bioactivity. Significant loss of TSH bioactivity appears to occur during storage in solution. The damage to the biological activity of TSH during the iodination procedure is more likely related to the oxidation process than to the incorporation of iodine.

Takai, N.A.; Filetti, S.; Rapoport, B.

1981-01-01

38

Gram-scale fractionation of nanodiamonds by density gradient ultracentrifugation  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

39

Gram-scale fractionation of nanodiamonds by density gradient ultracentrifugation.  

PubMed

Size is a defining characteristic of nanoparticles; it influences their optical and electronic properties as well as their interactions with molecules and macromolecules. Producing nanoparticles with narrow size distributions remains one of the main challenges to their utilization. At this time, the number of practical approaches to optimize the size distribution of nanoparticles in many interesting materials systems, including diamond nanocrystals, remains limited. Diamond nanocrystals synthesized by detonation protocols - so-called detonation nanodiamonds (DNDs) - are promising systems for drug delivery, photonics, and composites. DNDs are composed of primary particles with diameters mainly <10 nm and their aggregates (ca. 10-500 nm). Here, we introduce a large-scale approach to rate-zonal density gradient ultracentrifugation to obtain monodispersed fractions of nanoparticles in high yields. We use this method to fractionate a highly concentrated and stable aqueous solution of DNDs and to investigate the size distribution of various fractions by dynamic light scattering, analytical ultracentrifugation, transmission electron microscopy and powder X-ray diffraction. This fractionation method enabled us to separate gram-scale amounts of DNDs into several size ranges within a relatively short period of time. In addition, the high product yields obtained for each fraction allowed us to apply the fractionation method iteratively to a particular size range of particles and to collect various fractions of highly monodispersed primary particles. Our method paves the way for in-depth studies of the physical and optical properties, growth, and aggregation mechanism of DNDs. Applications requiring DNDs with specific particle or aggregate sizes are now within reach. PMID:23636671

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

2013-06-01

40

Stability studies of common biochemical analytes in serum separator tubes with or without gel barrier subjected to various storage conditions  

PubMed Central

Introduction The collected and shipped blood samples are exposed to a various extra-analytical factors prior to analysis. The aim of the study was to determine the stability of analytes in serum gel tubes and plain tubes exposed to a range of storage temperatures and times after centrifugation. Materials and methods: Fifteen healthy volunteers were recruited and venous blood was collected into four tubes, two with and two without gel separator. Analyzing the baseline samples in 30 min, all were stored at 4ºC or 24ºC for 6, 12, 18, 24, 30, 36, 48 and 72 hours and 1 week. Sixteen biochemical anaytes were measured on each sample. Variations remained under the desirable bias considered as clinically insignificant. Results: On day three, most analytes remained stable including albumin, protein, creatinine, cholesterol, triglycerides, gamma-glutamyl transferase (GGT), alkaline phosphatase (ALP), alanine aminotransferase (ALT), creatine kinase (CK), lactate dehydrogenase (LD) regardless of tube types. Glucose concentration decreased markedly (P = 0.001) beginning from the first hours of storage in plain serum. The stability maximized for the analytes including glucose, total bilirubin, urea nitrogen (BUN), uric acid stored at 4 ºC in gel tubes. Aspartate aminotransferase (AST) activity increased significantly (P = 0.002) up to 48-h, however bias was not significant clinically. High density lipoprotein (HDL) concentration was stable in gel tubes at 24 ºC, in plain tubes at 4 ºC stored up to 36-h. Conclusion: Serum gel or non-gel tubes might be used interchangeably for 11 analytes chilled or at 24 ºC, whereas some restrictions must be applied for glucose, AST, BUN, HDL, and uric acid.

Cuhadar, Serap; Atay, Aysenur; Koseoglu, Mehmet; Dirican, Ahmet; Hur, Aysel

2012-01-01

41

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 mµ, 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 10–9 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 10–13 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 mµ. An assumed density of 1.15 gm. per cc. yields a diameter of 19 mµ, considering the shape as spherical.

Pickels, Edward G.; Bauer, Johannes H.

1940-01-01

42

Chromatographic, ultracentrifugal, and related studies of fibrinogen "Baltimore"  

PubMed Central

Chromatographic, ultracentrifugal, and related studies of the fibrinogen of a patient with a congenital disorder of fibrinogen (fibrinogen “Baltimore” have provided evidence of structural differences from normal. Diethylaminoethyl-cellulose (DEAE-cellulose) gradient elution chromatography demonstrated two major peaks in the elution pattern of fibrinogen Baltimore as was the case for normal fibrinogen. However, the first peak of fibrinogen Baltimore was somewhat broader and more symmetrical and was eluted significantly later in the chromatogram than the corresponding peak of normal fibrinogen. Additionally, in some elution patterns, a shoulder on the ascending limb of peak 1 was present, suggesting the presence of chromatographically “normal” fibrinogen. Thrombin time determinations of eluted column fractions from a chromatogram of propositus fibrinogen supported this conclusion by demonstrating that fibrinogen from the ascending portion of peak 1 behaved functionally more like normal than that later in the chromatogram. Chromatograms of mixtures of propositus and normal fibrinogen confirmed the ability of this technique to distinguish normal from Baltimore fibrinogen. Chromatograms of fibrinogen isolated from two affected daughters displayed the characteristic increased anionic binding of peak 1 fibrinogen. Sedimentation velocity experiments indicated that the So20, [unk] of fibrinogen Baltimore was slightly greater (8.13S vs. 7.85S) than that of normal fraction I-4. Differences in concentration dependence (- 0.65 c vs. - 1.30 c for normal) of the sedimentation coefficient could be attributable in part to spatial conformational differences. Molecular sieving experiments in acrylamide gels indicated that the molecular weight of propositus fraction I-2 was about the same as that of normal fibrinogen of comparable solubility (i.e. I-4, mol wt 325,000). Studies of the UV spectra, tyrosine/tryptophan ratios, sialic acid and hexose content, and N-terminal amino acids demonstrated no consistent significant differences from normal fraction I-4.

Mosesson, M. W.; Beck, E. A.

1969-01-01

43

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

PubMed

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

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

2012-11-01

44

Purification of anatid herpesvirus 1 particles by tangential-flow ultrafiltration and sucrose gradient ultracentrifugation.  

PubMed

Anatid herpesvirus 1 (AHV-1) infection causes substantial economic losses to the world-wide waterfowl production. However, little is known about the efficient method used to study the purification of AHV-1 and the negative staining morphology of the purified virus particles. This lack of knowledge is one of the important factors that have affected the progress of research studies on AHV-1 molecular virology to such an extent that they are lagging far behind those on other members of the same family Herpesviridae. Therefore, an efficient method for purifying AHV-1 from cell-culture medium has been developed. Abundant AHV-1 particles, whose morphological features match those of herpesvirus, were obtained by using the following procedures: (1) conventional differential centrifugation for removal of debris after cell disruption, (2) tangential-flow ultrafiltration coupled with sucrose density gradient ultracentrifugation for isolation of the virus, and (3) conventional differential ultracentrifugation for virus concentration. The purified AHV-1 particles were subjected to transmission electron microscopy (TEM), infectivity and recovery tests, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), immunoblotting assay, and agar gel diffusion test (AGDT). The results of examinations revealed that purified AHV-1 particles were free of visible contamination or degradation. The purified AHV-1 particles were biologically active and were successful in initiating infection upon inoculation into susceptible duck embryo fibroblast. The procedures are reliable technically and feasible for purification of large volumes of viruses. PMID:19152808

Guo, Yufei; Cheng, Anchun; Wang, Mingshu; Zhou, Yi

2009-10-01

45

Macroscopic electric field and osmotic pressure in ultracentrifugal sedimentation diffusion equilibria of charged colloids  

NASA Astrophysics Data System (ADS)

Sedimentation-diffusion (SD) equilibria from analytical ultracentrifugation of well-characterized charged silica spheres in ethanol deviate strongly from a barometric profile and demonstrate the existence and substantial effects of a recently predicted internal macroscopic electric field (van Roij 2003 J. Phys.: Condens. Matter 15 S3569). Experimental SD-profiles yield the gradient of the electrostatic potential energy of the colloids, which clearly manifests an almost homogeneous macroscopic electric field. Electrochemical Donnan potential measurements confirm a difference in electrical potential between the top and bottom of the profiles. A 'non-barometric' limiting law derived from electroneutrality explains the trends in the SD-profiles quite well. Our analysis of osmotic pressures (obtained from integrating SD-profiles) beyond this simple law includes, among other things, colloid-ion attractions and extra volume terms in the free energy.

Rasa, M.; Erné, B. H.; Zoetekouw, B.; van Roij, R.; Philipse, A. P.

2005-04-01

46

Capillary gel electrophoresis-coupled aptamer enzymatic cleavage protection strategy for the simultaneous detection of multiple small analytes.  

PubMed

This novel, multi small-analyte sensing strategy is the result of combining the target-induced aptamer enzymatic protection approach with the CGE-LIF (capillary gel electrophoresis with laser-induced fluorescence) technique. The implemented assay principle is based on an analysis of the phosphodiesterase I (PDE I)-mediated size variation of a fluorescein-labeled aptamer (FApt), the enzyme catalyzing the removal of nucleotides from DNA in the 3' to 5' direction. In the absence of the target, the unfolded aptamer was enzymatically cleaved into short DNA fragments. Upon target binding, the DNA substrate was partially protected against enzymatic hydrolysis. The amount of bound aptamer remaining after the exonuclease reaction was proportional to the concentration of the target. The CGE technique, which was used to determine the separation of FApt species from DNA digested products, permitted the quantification of adenosine (A), ochratoxin A (O), and tyrosinamide (T) under the same optimized enzymatic conditions. This assay strategy was subsequently applied to the simultaneous detection of A, O, and T in a single capillary under buffered conditions using corresponding FApt probes of different lengths (23, 36, and 49 nucleotides, respectively). Additionally, the detection of these three small molecules was successfully achieved in a complex medium (diluted, heat-treated human serum) showing a good recovery. It is worth noting that the multiplexed analysis was accomplished for targets with different charge states by using aptamers possessing various structural features. This sensing platform constitutes a rationalized and reliable approach with an expanded potential for a high-throughput determination of small analytes in a single capillary. PMID:24716781

Perrier, Sandrine; Zhu, Zhenyu; Fiore, Emmanuelle; Ravelet, Corinne; Guieu, Valérie; Peyrin, Eric

2014-05-01

47

Chemical and physicochemical properties of the high cohesive silicone gel from Poly Implant Prothèse (PIP) breast prostheses after explantation: a preliminary, comparative analytical investigation.  

PubMed

Aim of this work was to gain a deeper insight into the analytical profile of the macromolecular and LMW fractions of polymeric silicones present in breast implants. The study was conducted on silicone gel samples from (i) breast prostheses (Poly Implant Prothèse, PIP) explanted from a patient that needed their therapeutical removal, (ii) from a virgin Mc Ghan 410 MX prosthesis and (iii) from a sample of technical-grade non-cohesive silicone. The gels were analysed using rheological techniques, attenuated total reflectance infrared spectroscopy (ATR-FT-IR), nuclear magnetic resonance ((1)H NMR), gas chromatography coupled to mass spectrometry (GC-MS) and flow injection electrospray mass spectrometry (FI-ESI-MS). Our results demonstrate that, compared to the virgin McGhan gel, the silicone present the PIP prostheses lacks a significant part of the cross-linking sites necessary for the high-cohesive properties of the gel, significant amounts of cholesterol have been absorbed from the breast tissue by the silicone material, demonstrating the lack of impermeability of its elastomer shell. The potential implications and consequences of these analytical results are discussed. PMID:23454600

Beretta, Giangiacomo; Malacco, Matteo

2013-05-01

48

A density gradient ultracentrifugation analysis of carbon nanotube soot  

NASA Astrophysics Data System (ADS)

Knowing the absolute amounts of carbon nanotubes (CNTs) and carbonaceous impurities in commercial CNT soot is important for supporting and enabling advances in countless nanotechnology applications involving CNTs. However, the physiochemical characterization of CNTs and carbonaceous impurities in heterogeneous soot samples is very challenging because both components comprise sp2- and sp3-hybridized carbons; in particular, CNTs with open ends and/or defect sides could possess sp3-hybridization. Herein, we present the use of density gradient ultracentrifugation (DGU) to separate and quantify single-walled carbon nanotubes (SWNTs) and nontubular carbon (NTC) impurities in CoMoCAT(TM) soot, and the development of protocols to analyze the DGU fractions. While a complete separation of SWNTs and NTCs could not be obtained, important discoveries were made. Primarily, CoMoCAT(TM) soot contains spherical fullerenes and graphite even though no prior reports have indicated the presence of these species in this material.

Jacobsen, Nancy S.

49

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

50

Molecular fractionation of starch by density-gradient ultracentrifugation.  

PubMed

Amylose and amylopectin in corn and potato starches were fractionated by centrifugation at 124,000g for 3-72 h at 40 degrees C in a gradient media, Nycodenz, based on their sedimentation rate differences. The fractions were collected from a centrifuge tube, and then analyzed by the phenol-sulfuric acid method and iodine-binding test. Amylopectin, a large and highly branched starch molecule, migrated faster than amylose and quickly reached its isopycnic point with a buoyant density of about 1.25 g/mL, exhibiting a sharp and stable carbohydrate peak. Amylose, which is a relatively small and linear molecule, however, migrated slowly in a broad density range and continued moving to higher density regions, eventually overlapping with amylopectin peak as the centrifugation continued. This could indicate that the buoyant density of amylose is similar to that of amylopectin. Under centrifugal conditions of 3 h and 124,000g, amylose and amylopectin molecules were clearly separated, and the presence of intermediate starch molecules (11.5 and 7.7% for corn and potato starch, respectively) was also observed between amylose and amylopectin fractions. The amylose content of corn and potato starches was 22.6 and 21.1%, respectively, based on the total carbohydrate analysis after the ultracentrifugation for 3 h. In alkaline gradients (pH 11 or 12.5), the sedimentation rate of starch molecules and the buoyant density of amylopectin were reduced, possibly due to the structural changes induced by alkali. PMID:12644374

Yoon, Jae Wook; Lim, Seung Taik

2003-03-28

51

LC-MS/MS Analysis of Canine Lipoproteins Fractionated Using the Ultracentrifugation-Precipitation Method  

PubMed Central

ABSTRACT Due to the lack of a gold standard method in canine lipoprotein analysis, it is unclear whether canine high-density lipoprotein (HDL) and low-density lipoprotein (LDL) can be accurately evaluated by the lipoprotein analysis methods used for dogs. This study investigated whether the ultracentrifugation-precipitation (U-P) method was suitable as a gold standard method for analyzing canine lipoprotein. First, the U-P method was compared with a gel permeation high-performance liquid chromatography system (GP-HPLC). The concentrations of canine HDL cholesterol (HDL-C) and LDL cholesterol (LDL-C) determined by the U-P method correlated closely with those determined by GP-HPLC. However, the canine HDL-C concentration determined by the U-P method was lower than that determined by GP-HPLC, and the canine LDL-C concentration determined by the U-P method was higher than that determined by GP-HPLC. This study showed that some canine HDL could be precipitated with heparin manganese chloride solution. Second, the HDL and LDL fractions separated by the U-P method were analyzed by LC-MS/MS. The HDL fraction was found to contain only apolipoprotein A-I, which is an apolipoprotein of HDL, whereas the LDL fraction contained both apolipoprotein A-I and apolipoprotein B-100, which is an apolipoprotein of LDL. This data showed that a certain lipoprotein that includes apolipoprotein A-I might precipitate with canine LDL when using heparin manganese chloride solution. These results indicated that the U-P method is not currently a gold standard method for analyzing canine lipoproteins.

SUTO, Asuka; YAMASAKI, Masahiro; TAKASAKI, Yukari; FUJITA, Yasuyuki; ABE, Riichiro; SHIMIZU, Hiroshi; OHTA, Hiroshi; TAKIGUCHI, Mitsuyoshi

2013-01-01

52

NMR spectroscopic and analytical ultracentrifuge analysis of membrane protein detergent complexes  

PubMed Central

Background Structural studies of integral membrane proteins (IMPs) are hampered by inherent difficulties in their heterologous expression and in the purification of solubilized protein-detergent complexes (PDCs). The choice and concentrations of detergents used in an IMP preparation play a critical role in protein homogeneity and are thus important for successful crystallization. Results Seeking an effective and standardized means applicable to genomic approaches for the characterization of PDCs, we chose 1D-NMR spectroscopic analysis to monitor the detergent content throughout their purification: protein extraction, detergent exchange, and sample concentration. We demonstrate that a single NMR measurement combined with a SDS-PAGE of a detergent extracted sample provides a useful gauge of the detergent's extraction potential for a given protein. Furthermore, careful monitoring of the detergent content during the process of IMP production allows for a high level of reproducibility. We also show that in many cases a simple sedimentation velocity measurement provides sufficient data to estimate both the oligomeric state and the detergent-to-protein ratio in PDCs, as well as to evaluate the homogeneity of the samples prior to crystallization screening. Conclusion The techniques presented here facilitate the screening and selection of the extraction detergent, as well as help to maintain reproducibility in the detergent exchange and PDC concentration procedures. Such reproducibility is particularly important for the optimization of initial crystallization conditions, for which multiple purifications are routinely required.

Maslennikov, Innokentiy; Kefala, Georgia; Johnson, Casey; Riek, Roland; Choe, Senyon; Kwiatkowski, Witek

2007-01-01

53

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

PubMed Central

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

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

2002-01-01

54

System for Gel Electrophoretic Immunoassay.  

National Technical Information Service (NTIS)

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 s...

A. E. Herr A. K. Singh D. J. Throckmorton

2005-01-01

55

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

56

Multidimensional proteomic analysis of photosynthetic membrane proteins by liquid extraction-ultracentrifugation-liquid chromatography-mass spectrometry.  

PubMed

The membrane protein components of photosystem I (PSI) and II (PSII) from different species were prefractionated by liquid extraction and sucrose gradient ultracentrifugation and subsequently analyzed by reversed-phase high-performance liquid chromatography-electrospray ionization-mass spectrometry (RP-HPLC-ESI-MS) using poly-(styrene-divinylbenzene)-based monolithic capillary columns. The analytical method was shown to be very flexible and enabled the identification of antenna proteins as well as most of the proteins of the reaction center from PSI and PSII in various plant species with few RP-HPLC-ESI-MS analyses necessitating only minor adaptations in the gradients of acetonitrile in 0.05% aqueous trifluoroacetic acid. The membrane proteins, ranging in molecular mass (Mr) from 4196 (I protein) to more than 80,000 (PSI A/B) as well as isoforms were identified on the basis of their intact Mr and comparison with Mr deduced from known DNA or protein sequences. High quality mass spectra enabled the identification and quantitation of the nonphosphorylated and phosphorylated reaction center subunits D1, D2, and CP43 of PSII, containing five to seven membrane-spanning alpha-helices. Because of its high flexibility and suitability for proteins having a very wide range of Mr and hydrophobicities, the method is generally applicable to the analysis of complex mixtures of membrane proteins. PMID:15449339

Huber, Christian G; Walcher, Wolfgang; Timperio, Anna-Maria; Troiani, Sonia; Porceddu, Andrea; Zolla, Lello

2004-12-01

57

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

58

Co-isolation of extracellular vesicles and high-density lipoproteins using density gradient ultracentrifugation  

PubMed Central

Extracellular vesicles (EVs) facilitate intercellular communication by carrying bioactive molecules such as proteins, messenger RNA, and micro (mi)RNAs. Recently, high-density lipoproteins (HDL) isolated from human plasma were also reported to transport miRNA to other cells. HDL, when isolated from human plasma, ranges in density between 1.063 and 1.21 g/mL, which grossly overlap with the reported density of EVs. Consequently, HDL and EV will be co-isolated when using density gradient ultracentrifugation. Thus, more stringent isolation/separation procedures of EV and HDL are essential to know their relative contribution to the pool of circulating bioactive molecules.

Yuana, Yuana; Levels, Johannes; Grootemaat, Anita; Sturk, Auguste; Nieuwland, Rienk

2014-01-01

59

Two-dimensional nanodiamond monolayers deposited by combined ultracentrifugation and electrophoresis techniques  

NASA Astrophysics Data System (ADS)

Dense detonation nanodiamonds deposit has been obtained through a coupled process: Electrophoretic deposition was applied to an ultracentrifugated detonation nanodiamonds suspension. The resulting coating exhibits nearly complete 5 nm thick monolayer coverage of the substrate. The described process is a soft and easily tunable approach, particularly suitable for the development of sensors or the growth of high performance nanodiamond films. The proximity of the adsorbed nanoparticles on the substrate was demonstrated by scanning probe techniques, such as atomic force microscopy and scanning tunneling microscopy.

Schmidlin, L.; Pichot, V.; Josset, S.; Pawlak, R.; Glatzel, T.; Kawai, S.; Meyer, E.; Spitzer, D.

2012-12-01

60

In VitroCulture of TrichogrammaSpp. on Artificial Diets Containing Yeast Extract and Ultracentrifuged Chicken Egg Yolk but Devoid of Insect Components  

Microsoft Academic Search

Trichogramma minutumRiley andTrichogramma brassicaeBezdenko (Hymenoptera: Trichogrammatidae) were culturedin vitrofrom eggs to adults on artificial diets, which contained no insect components. The diets contained ultracentrifuged chicken egg yolk, milk, Grace's insect medium, and yeast extract. The most important components were the yeast extract and ultracentrifuged chicken egg yolk. Addition of the sediment of ultracentrifuged chicken egg yolk to a diet containing

Zhong-Neng Xie; Zhi-Xin Wu; William C. Nettles; Guadalupe Saldaña; Donald A. Nordlund

1997-01-01

61

Combining Ultracentrifugation and Peptide Termini Group-specific Immunoprecipitation for Multiplex Plasma Protein Analysis  

PubMed Central

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

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

2012-01-01

62

Treatment of olive mill waste-water by aerobic biodegradation: an analytical study using gel permeation chromatography, ultraviolet-visible and Fourier transform infrared spectroscopy.  

PubMed

Liquid waste from olive oil mills was digested following inoculation with soil microorganisms and fractionated through various grades of gel. The fractionation showed the range of sizes of the molecules in the waste. In addition, the disappearance of the low molecular weight fraction, which is retained by the gel, and the increase of the high molecular weight fraction, which is excluded by the gel, during the last stages of the microbial treatment, indicates polymerisation of the low-molecular-weight subunits. Characterization of the fractions by UV-visible and FTIR spectroscopy confirmed the increase in their degree of polymerisation during the treatment. This is paralleled by a reduction in the amount of aliphatic components and a concomitant increase in aromatic structures. PMID:17224272

El Hajjouji, H; Fakharedine, N; Ait Baddi, G; Winterton, P; Bailly, J R; Revel, J C; Hafidi, M

2007-12-01

63

Method and Apparatus for Gel Electrophoretic Immunoassay.  

National Technical Information Service (NTIS)

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 s...

A. E. Herr A. K. Singh D. J. Throckmorton

2005-01-01

64

Large Scale Preparation by Zonal Gradient Ultracentrifugation of Hepatitis B Purified Core Antigen from Autopsy Liver Tissue.  

National Technical Information Service (NTIS)

Large scale production of purified HBcAg from autopsied livers by zonal density gradient ultracentrifugation is reported. The preliminary results show that it is the method of choice for the preparation of purified hepatitis B core antigen which is used f...

T. Qimin F. Baifang W. Jingi L. Xinfu L. Yuzhen

1981-01-01

65

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

PubMed Central

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

Cao, Weiming; Demeler, Borries

2008-01-01

66

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

67

Purification of infectious adenovirus in two hours by ultracentrifugation and tangential flow filtration  

SciTech Connect

Adenoviruses are excellent vectors for gene transfer and are used extensively for high-level expression of the products of transgenes in living cells. The development of simple and rapid methods for the purification of stable infectious recombinant adenoviruses (rAds) remains a challenge. We report here a method for the purification of infectious adenovirus type 5 (Ad5) that involves ultracentrifugation on a cesium chloride gradient at 604,000g for 15 min at 4 deg C and tangential flow filtration. The entire procedure requires less than two hours and infectious Ad5 can be recovered at levels higher than 64% of the number of plaque-forming units (pfu) in the initial crude preparation of viruses. We have obtained titers of infectious purified Ad5 of 1.35 x 10{sup 10} pfu/ml and a ratio of particle titer to infectious titer of seven. The method described here allows the rapid purification of rAds for studies of gene function in vivo and in vitro, as well as the rapid purification of Ad5.

Ugai, Hideyo; Yamasaki, Takahito; Hirose, Megumi; Inabe, Kumiko; Kujime, Yukari; Terashima, Miho [Gene Engineering Division, BioResource Center, Tsukuba Institute, RIKEN - Institute of Physical and Chemical Research, 3-1-1 Koyadai, Tsukuba, Ibaraki 305-0074 (Japan); Liu, Bingbing [Gene Engineering Division, BioResource Center, Tsukuba Institute, RIKEN - Institute of Physical and Chemical Research, 3-1-1 Koyadai, Tsukuba, Ibaraki 305-0074 (Japan)]|[Department of Internal Medicine, China Medical University, Shenyang 20031 (China); Tang, Hong [Gene Engineering Division, BioResource Center, Tsukuba Institute, RIKEN - Institute of Physical and Chemical Research, 3-1-1 Koyadai, Tsukuba, Ibaraki 305-0074 (Japan)]|[Institute of Biochemistry and Cell Biology, Shanghai Institute for Biological Science, Chinese Academy of Sciences, Shanghai 20031 (China); Zhao, Mujun [Institute of Biochemistry and Cell Biology, Shanghai Institute for Biological Science, Chinese Academy of Sciences, Shanghai 20031 (China); Murata, Takehide [Gene Engineering Division, BioResource Center, Tsukuba Institute, RIKEN - Institute of Physical and Chemical Research, 3-1-1 Koyadai, Tsukuba, Ibaraki 305-0074 (Japan); Kimura, Makoto; Pan, Jianzhi [Gene Engineering Division, BioResource Center, Tsukuba Institute, RIKEN - Institute of Physical and Chemical Research, 3-1-1 Koyadai, Tsukuba, Ibaraki 305-0074 (Japan); Obata, Yuichi [Department of Biological Systems, Tsukuba Institute, RIKEN - Institute of Physical and Chemical Research, 3-1-1 Koyadai, Tsukuba, Ibaraki 305-0074 (Japan); Hamada, Hirofumi [Department of Molecular Medicine, Sapporo Medical University, Sapporo, Hokkaido 060-8556 (Japan); Yokoyama, Kazunari K. [Gene Engineering Division, BioResource Center, Tsukuba Institute, RIKEN - Institute of Physical and Chemical Research, 3-1-1 Koyadai, Tsukuba, Ibaraki 305-0074 (Japan)]. E-mail: kazu@brc.riken.jp

2005-06-17

68

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

69

Ultracentrifugation of Serum Samples Allows Detection of Hepatitis C Virus RNA in Patients with Occult Hepatitis C?  

PubMed Central

Occult hepatitis C virus (HCV) infection of patients with abnormal liver function tests of unknown origin who are anti-HCV and serum HCV RNA negative but who have HCV RNA in the liver has been described. As HCV replicates in the liver cells of these patients, it could be that the amount of circulating viral particles is under the detection limit of the most sensitive techniques. To prove this hypothesis, serum samples from 106 patients with occult HCV infection were analyzed. Two milliliters of serum was ultracentrifuged over a 10% sucrose cushion for 17 h at 100,000 × gav, where av means average, and HCV RNA detection was performed by strand-specific real-time PCR. Out of the 106 patients, 62 (58.5%) had detectable serum HCV RNA levels after ultracentrifugation, with a median load of 70.5 copies/ml (range, 18 to 192). Iodixanol density gradient studies revealed that HCV RNA was positive at densities of 1.03 to 1.04 and from 1.08 to 1.19 g/ml, which were very similar to those found in the sera of patients with classical chronic HCV infection. Antigenomic HCV RNA was found in the livers of 56 of 62 (90.3%) patients with detectable serum HCV RNA levels after ultracentrifugation, compared to 27 of 44 (61.4%) negative patients (P < 0.001). No differences in the median loads of antigenomic HCV RNA between patients with an those without serum HCV RNA (4.5 × 104 [range, 7.9 × 102 to 1.0 × 106] versus 2.3 × 104 [range, 4.0 × 102 to 2.2 × 105]) were found. Alanine aminotransferase and gamma-glutamyl transpeptidase levels, liver necroinflammatory activity, and fibrosis did not differ between both groups. In conclusion, HCV RNA can be detected in the sera of patients with occult HCV infection after circulating viral particles are concentrated by ultracentrifugation.

Bartolome, Javier; Lopez-Alcorocho, Juan Manuel; Castillo, Inmaculada; Rodriguez-Inigo, Elena; Quiroga, Juan Antonio; Palacios, Ricardo; Carreno, Vicente

2007-01-01

70

Preparative and quantitative isolation of plasma lipoproteins: rapid, single discontinuous density gradient ultracentrifugation in a vertical rotor  

Microsoft Academic Search

A rapid method has been developed for separa- tion of the major plasma lipoproteins from up to 96 ml of plasma by a single ultracentrifugation step. This separa- tion was achieved by a discontinuous density gradient centrifugation between the density range of 1.006 and 1.30 g\\/ml in Sorvall vertical rotors. Each lipoprotein fraction was sharply banded with VLDL at the

Byung H. Chung; Thomas Wilkinson; Jack C. Geer; Jere P. Segrest

71

PlasmaHigh-DensityLipoproteinCholesterolConcentrations Determinedafter Removalof Other Lipoproteinsby Heparin\\/ ManganesePrecipitationor by Ultracentrifugation  

Microsoft Academic Search

isolated preparations of the lipoprotein are only partly precipitated under the test conditions. in the presentstudy, the procedure as applied to plasma tolerated rather wide variations in heparin and MnCI2concentrations without significant effects on theassayedvalues in severalplasma pools tested. The procedure was further tested on 129 individual samples by comparison with an ultracentrifugal method in which high-density lipoprotein-cholesterol is assumed

P. S. Bachorik; P. D. Wood; J. J. Albers; P. Steiner; M. Dempsey; K. Kuba

72

Gel Electrophoresis  

NSDL National Science Digital Library

In the early days of DNA manipulation, DNA fragments were laboriously separated by gravity. In the 1970s, the powerful tool of DNA gel electrophoresis was developed. This process uses electricity to separate DNA fragments by size as they migrate through a gel matrix. This animation from Cold Spring Harbor Laboratory's Dolan DNA Learning Center presents Gel Electrophoresis through a series of illustrations of the processes involved.

2012-01-20

73

Sedimentation equilibrium of detergent-solubilized membrane proteins in the preparative ultracentrifuge.  

PubMed

Working with detergent-solubilized bacteriorhodopsin we have used a table top preparative centrifuge for determination of M(r) of membrane proteins by sedimentation equilibrium. We demonstrate the use of two new methods to measure protein concentration as a function of distance from rotor axis: (i) peak integration after HPLC on silica gel, and (ii) microdensitometry after sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Coomassie blue staining. These methods, although somewhat lengthier than conventional spectrophotometric methods, are more reliable, especially in the presence of a large amount of detergent and small amount of protein. In addition they provide independent information on the status of the protein after sedimentation equilibrium, the association of the solubilized units being readily detected by gel chromatography and proteolytic cleavage by SDS-PAGE. PMID:8452225

Garrigos, M; Centeno, F; Deschamps, S; Møller, J V; le Maire, M

1993-02-01

74

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

PubMed

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

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

2013-07-01

75

Chemistry and processability of crude oil asphaltenes as studied by ultracentrifugation  

Microsoft Academic Search

One of the problems encountered during high severity hydrocracking of resids is asphaltene precipitation on the catalyst, in reactor effluent lines, and in product blends. Asphaltenes from different crudes show surprising differences in their response to hydrogen processing. Some asphaltenes are remarkably refractory while others are readily destroyed. These differences are very difficult to relate to analytically determined properties for

W. L. McBride

1979-01-01

76

Fluorescence detection for gel and capillary electrophoresis  

SciTech Connect

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

Hogan, B.

1992-07-21

77

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

78

Aerosol gels  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

79

The repton model of gel electrophoresis  

NASA Astrophysics Data System (ADS)

We discuss the repton model of agarose gel electrophoresis of DNA. We review previous results, both analytic and numerical, as well as presenting a new numerical algorithm for the efficient simulation of the model, and suggesting a new approach to the model's analytic solution.

Barkema, G. T.; Newman, M. E. J.

1997-02-01

80

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

PubMed

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

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

2012-09-01

81

Meningococcal endotoxin in lethal septic shock plasma studied by gas chromatography, mass-spectrometry, ultracentrifugation, and electron microscopy.  

PubMed Central

We have compared gas chromatography and mass spectrometry (GC-MS) analysis with the Limulus amebocyte lysate (LAL) assay to quantify native meningococcal lipopolysaccharides (LPS) in five patient plasmas containing greater than 5 micrograms/liter by LAL. 3-Hydroxy lauric acid (3-OH-12:0) was used as a specific lipid A marker of neisserial LPS. The quantitative LAL results were confirmed by GC-MS (r = 0.98, P = 0.006). Seven patient plasmas were centrifuged at 103,000 g and the sedimentation behavior of native LPS compared with reference plasma proteins and with apo A1 and apo B100 representing high and low density lipoproteins. After 15 min of centrifugation, 84 +/- 2% (mean +/- SE) of the recovered LPS were found in the lower one-third of the centrifuged volume, whereas 6 +/- 1% remained in the upper one-third volume, indicating that meningococcal endotoxin circulates as complexes with high sedimentation coefficients. Bacterial outer membrane fragments were detected in the bottom fractions of three patient plasmas examined by means of electron microscopy. In three patient plasmas ultracentrifuged for 60 min at 103,000 g, the levels of apo A1 and apo B100 revealed minor changes, whereas only 1 +/- 1% of the recovered LPS remained in the upper one-third and 91 +/- 2% were found in the lower one-third volume. Few bioreactive LPS appear to be complexed with high and low density lipoproteins in meningococcal septic shock plasma. Images

Brandtzaeg, P; Bryn, K; Kierulf, P; Ovsteb?, R; Namork, E; Aase, B; Jantzen, E

1992-01-01

82

Detection of rotavirus A in sewage samples using multiplex qPCR and an evaluation of the ultracentrifugation and adsorption-elution methods for virus concentration.  

PubMed

Group A rotaviruses (RV-A) are the most common agents of viral gastroenteritis in children worldwide. The goal of this study was to compare two different methods to concentrate RV-A from sewage samples and to improve the detection and quantification of RV-A using a multiplex quantitative PCR assay with an internal control. Both RV-A and the internal control virus, bacteriophage PP7, were seeded into wastewater and then concentrated using either an ultrafiltration-based adsorption-elution protocol or an ultracentrifugation-based protocol. Real time multiplex quantitative PCR was used to quantify the purified RV-A and PP7, and the results of the multiplex assay were compared with the results of the monoplex assays. The ultracentrifugation-based method had a mean recovery rate of 47% (range: 34-60%), while the ultrafiltration-based adsorption-elution method had a mean recovery rate of 3.5% (range: 1.5-5.5%). These results demonstrate that ultracentrifugation is a more appropriate method for recovering RV-A from wastewater. This method together with the multiplex qPCR assay may be suitable for routine laboratory use. PMID:20804786

Fumian, Tulio M; Leite, José Paulo G; Castello, Alejandro A; Gaggero, Aldo; Caillou, Maria Susana L de; Miagostovich, Marize P

2010-12-01

83

Analytical performance and clinical usefulness of two binding assays for growth hormone binding protein (GHBP) measurement: high performance liquid chromatography (HPLC)-gel filtration and dextran-coated charcoal adsorption  

Microsoft Academic Search

We compared two binding assays for growth hormone binding protein (GHBP) measurements, which differ in the method of bound and free GH separation: HPLC-gel filtration or dextran coated-charcoal adsorption (DCC). Two pools of sera (high and medium GHBP activity) were used for quality-control assessment. Moreover, 62 samples from 34 children and 28 adults with different nutritional status were studied. Total,

Maria Antonia Llopis; Maria Luisa Granada; Laura Aud??; Anna Sanmart??; Joan Bel; Luis Sánchez-Planell; Xavier Formiguera; Fernando Marin; August Corominas

1997-01-01

84

Diverse subpopulations of vesicles secreted by different intracellular mechanisms are present in exosome preparations obtained by differential ultracentrifugation  

PubMed Central

Exosomes are extracellular vesicles of 50 to 100 nm in diameter, released by many cell types. Exosomes are formed inside the cell in intracellular endosomal compartments and are secreted upon fusion of these compartments with the plasma membrane. Cells also secrete other types of membrane vesicles, for instance, by outward budding from the plasma membrane, and although some of them clearly differ from exosomes by their structural features (larger size), others are possibly more difficult to separate. Here, using Rab27a inhibition to modulate exosome secretion, we show the existence of at least 2 distinct populations of vesicles after purification by classical ultracentrifugation from mouse tumor cell conditioned medium. Rab27a inhibition lead to decreased vesicular secretion of some conventional markers of exosomes (CD63, Tsg101, Alix and Hsc70) but did not affect secretion of others (CD9 and Mfge8). By electron microscopy, CD9 was observed on vesicles of various sizes, ranging from 30 nm to more than 150 nm in diameter. Flotation onto sucrose gradients showed different proportions of CD63, CD9 and Mfge8 not only in fractions of densities classically described for exosomes (around 1.15 g/ml) but also in fractions of densities over 1.20 g/ml, indicating the presence of heterogenous vesicle populations. CD9 and Mfge8 were also found in large vesicles pelleted at low speed and can thus not be considered as specific components of endosome-derived vesicles. We propose that the most commonly used protocols for exosome preparations co-purify vesicles from endosomal and other origins, possibly the plasma membrane. Future work will be required to improve techniques for accurate purification and characterization of the different populations of extracellular vesicles.

Bobrie, Angelique; Colombo, Marina; Krumeich, Sophie; Raposo, Graca; Thery, Clotilde

2012-01-01

85

Analytical Microscopy.  

National Technical Information Service (NTIS)

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 ...

2006-01-01

86

Analytical Sciences  

NSDL National Science Digital Library

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

87

Two-dimensional gel isoelectric focusing.  

PubMed

Two-dimensional gel isoelectric focusing (2-D gel IEF) is presented as the combination of the same separation method used consecutively in two directions of the same gel. In this new method, after completion of IEF process in the first dimension the gel was cut into the separate strips, each containing selected analytes together with the appropriate part of the original broad pH gradient, and the strips were rotated by 90 degrees (with regard to the first IEF) and left to diffuse overnight. After diffusion the strips were subjected to the second IEF. During the second IEF, the corresponding narrow part of pH gradient in each strip was restored again, however, now along the strip. The progress of the separation process can be monitored visually by using colored low-molecular-weight isoelectric point (pI) markers loaded into the gel simultaneously with proteins. The unique properties of IEF, focusing and resolution power were enhanced by using the same technique twice. Two forms of beta-lactoglobulin (pI values 5.14 and 5.31, respectively) non-separated in the first IEF were successfully separated in the second dimension at relatively low voltage (330 V) with the resolution power comparable to the high-resolution gels requiring the high voltage during the run and long separation time. Glucose oxidase loaded as diluted solution into ten positions across the gel was finally focused into a single band during 2-D gel IEF. Since the first and second IEF are carried out on the same gel, no losses and contamination of analyte occur. The suggested method can be used for separation/fractionation of complex biological mixtures, similarly as other multidimensional separation techniques applied in proteomics, and can be followed by further processing, e.g., mass spectrometry analysis. The focusing properties of IEF could be useful especially in separation of mixtures, where components are at low concentration levels. PMID:16100746

Stastná, Miroslava; Slais, Karel

2005-09-01

88

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

89

Molecular Growth Pathways in Silica Sol-Gel Polymerization.  

National Technical Information Service (NTIS)

An analytical protocol involving gas chromatography (GC), gas chromatography-mass spectrometry (GCMS), and sup 29 Si//sup 1/H/ NMR spectroscopy, was developed to determine the structures of the polysilicate intermediates formed during silica sol-gel polym...

S. D. Ramamurthi

1989-01-01

90

Ultracentrifugation as a direct method to concentrate viruses in environmental waters: virus-like particle enumeration as a new approach to determine the efficiency of recovery.  

PubMed

Some health important enteric viruses are considered to be emerging waterborne pathogens and so the improvement of detection of these viruses in the aquatic environment is one of the most important steps in dealing with these pathogens. Since these viruses may be present in low numbers in water, it is necessary to concentrate water samples before viral detection. Although there are several methods to concentrate viruses in environmental waters, all present some drawbacks and consequently the method should be chosen that, despite its limitations, is adequate to achieve the aim of each study. As the effectiveness of the concentration methods is evaluated by determining the efficiency of viral recovery after concentration, it is important to use a simple and effective approach to evaluate their recovery efficiency. In this work ultracentrifugation, usually used as a secondary step for virus concentration, was evaluated as the main method to concentrate directly viruses in environmental water samples, using the microscopic enumeration of virus-like particles (VLP) as a new approach to estimate the efficiency of recovery. As the flocculation method is currently employed to concentrate viruses in environmental waters, it was also used in this study to assess the efficiency of the ultracentrifugation as the main viral concentration method in environmental waters. The results of this study indicate that ultracentrifugation is an adequate approach to concentrate viruses directly from environmental waters (recovery percentages between 66 and 72% in wastewaters and between 66 and 76% in recreational waters) and that the determination of VLP by epifluorescence microscopy is a simple, fast and cheap alternative approach to determine the recovery efficiency of the viral concentration methods. PMID:22113738

Prata, Catarina; Ribeiro, Andreia; Cunha, Ângela; Gomes, Newton C M; Almeida, Adelaide

2012-01-01

91

Statistical physics of polymer gels  

NASA Astrophysics Data System (ADS)

This work presents a comprehensive analysis of the statistical mechanics of randomly cross-linked polymer gels, starting from a microscopic model of a network made of instantaneously cross-linked Gaussian chains with excluded volume, and ending with the derivation of explicit expressions for the thermodynamic functions and for the density correlation functions which can be tested by experiments. Using replica field theory we calculate the mean field density in replica space and show that this solution contains statistical information about the behavior of individual chains in the network. The average monomer positions change affinely with macroscopic deformation and fluctuations about these positions are limited to length scales of the order of the mesh size. We prove that a given gel has a unique state of microscopic equilibrium which depends on the temperature, the solvent, the average monomer density and the imposed deformation. This state is characterized by the set of the average positions of all the monomers or, equivalently, by a unique inhomogeneous monomer density profile. Gels are thus the only known example of equilibrium solids with no long-range order. We calculate the RPA density correlation functions that describe the statistical properties of small deviations from the average density, due to both static spatial heterogeneities (which characterize the inhomogeneous equilibrium state) and thermal fluctuations (about this equilibrium). We explain how the deformation-induced anisotropy of the inhomogeneous equilibrium density profile is revealed by small angle neutron scattering and light scattering experiments, through the observation of the butterfly effect. We show that all the statistical information about the structure of polymer networks is contained in two parameters whose values are determined by the conditions of synthesis: the density of cross-links and the heterogeneity parameter. We find that the structure of instantaneously cross-linked gels becomes increasingly inhomogeneous with the approach to the cross-link saturation threshold at which the heterogeneity parameter diverges. Analytical expressions for the correlators of deformed gels are derived in both the long wavelength and the short wavelength limits and an exact expression for the total static structure factor, valid for arbitrary wavelengths, is obtained for gels in the state of preparation. We adapt the RPA results to gels permeated by free labelled chains and to gels in good solvents (in the latter case, excluded volume effects are taken into account exactly) and make predictions which can be directly tested by scattering and thermodynamic experiments. Finally, we discuss the limitations and the possible extensions of our work.

Panyukov, Sergei; Rabin, Yitzhak

1996-05-01

92

Applications of gel dosimetry  

Microsoft Academic Search

Gel dosimetry has been examined as a clinical dosimeter since the 1950s. During the last two decades, however, a rapid increase in the number of investigators has been seen, and the body of knowledge regarding gel dosimetry has expanded considerably. Gel dosimetry is still considered a research project, and the introduction of this tool into clinical use is proceeding slowly.

Geoffrey S Ibbott

2004-01-01

93

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

94

Analytical performance and clinical usefulness of two binding assays for growth hormone binding protein (GHBP) measurement: high performance liquid chromatography (HPLC)-gel filtration and dextran-coated charcoal adsorption.  

PubMed

We compared two binding assays for growth hormone binding protein (GHBP) measurements, which differ in the method of bound and free GH separation: HPLC-gel filtration or dextran coated-charcoal adsorption (DCC). Two pools of sera (high and medium GHBP activity) were used for quality-control assessment. Moreover, 62 samples from 34 children and 28 adults with different nutritional status were studied. Total, between- and intra-iodination coefficients of variation (CVs) from the two methods were not different. Although percentage binding measured in the pool sera significantly differed, the concentrations assessed by Scatchard plot were comparable. Results obtained by the two methods in the 62 sera were significantly correlated (r = 0.77, P < 0.001). With both methods GHBP activity correlated with chronological age and body mass index (BMI) and differed among groups with different nutritional status. Although HPLC and DCC separation methods for GHBP measurement differ in their practicability, our study demonstrates that performance and the clinical usefulness of the two methods are comparable. PMID:9469251

Llopis, M A; Granada, M L; Audí, L; Sanmartí, A; Bel, J; Sánchez-Planell, L; Formiguera, X; Marin, F; Corominas, A

1997-11-28

95

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

96

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

97

High Purity and Yield Separation of Semiconducting Single-Walled Carbon Nanotubes Dispersed in Aqueous Solutions with Density Gradient Ultracentrifugation Using Mixed Dispersants of Polysaccharides and Surfactants  

NASA Astrophysics Data System (ADS)

The heterogeneity of as-synthesized single-walled carbon nanotubes (SWNTs) prevents their potential applications in high-resolution field-effect transistors, nanoscale sensors, and conductive films. In the present study, we demonstrate the development of a new selective-separation procedure for collecting semiconducting single-walled carbon nanotubes (s-SWNTs) with a high purity from as-synthesized SWNTs individually dispersed with mixed dispersing agents consisting of carboxymethylcellulose (CMC) and sodium dodecyl sulfate (SDS) in water using density gradient ultracentrifugation (DGU). Ultraviolet--visible--near infrared (UV--vis--NIR) absorption, resonance Raman, and NIR photoluminescence spectroscopies revealed that the s-SWNTs were enriched to a purity of more than 97%, and that the recovery was approximately 40% through the DGU treatment. This separation strategy is expected to impact the application fields using s-SWNTs.

Tsuchiya, Koji; Uchida, Katsumi; Kaminosono, Yoshiya; Shimizu, Kazushi; Ishii, Tadahiro; Yajima, Hirofumi

2013-03-01

98

Analytical applications of positrons  

SciTech Connect

In using positrons as analytical tools the experimenter has two quite different options. The first and more obvious is to duplicate electron methods with positrons and see what differences (if any) result. The second is to exploit a unique characteristic of positrons, such as the formation and decay of the positronium atom, to study chemical composition and surface characteristics. Because positrons do not exist freely in our world, they must be obtained from radioactive sources or nuclear interactions. Source intensity has consequently been a limiting factor in experiments that attempt to duplicate electron applications. Some methods of producing and moderating positrons that have been developed here (and elsewhere) are described as well as results from studies using the sources. Surface measurements require less intense sources and yield useful data on materials such as xeolites, silica gels, graphite and alumina. Experimental apparatus, data and interpretation are discussed.

Dale, J.M.; Hulett, L.D.; Pendyala, S.; Lyon, W.S.

1985-01-01

99

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

100

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

101

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.

Foundation, Wgbh E.

2011-09-22

102

Mechanochromic photonic gels.  

PubMed

Polymer gels are remarkable materials with physical structures that can adapt significantly and quite rapidly with changes in the local environment, such as temperature, light intensity, electrochemistry, and mechanical force. An interesting phenomenon observed in certain polymer gel systems is mechanochromism - a change in color due to a mechanical deformation. Mechanochromic photonic gels are periodically structured gels engineered with a photonic stopband that can be tuned by mechanical forces to reflect specific colors. These materials have potential as mechanochromic sensors because both the mechanical and optical properties are highly tailorable via incorporation of diluents, solvents, nanoparticles, or polymers, or the application of stimuli such as temperature, pH, or electric or strain fields. Recent advances in photonic gels that display strain-dependent optical properties are discussed. In particular, this discussion focuses primarily on polymer-based photonic gels that are directly or indirectly fabricated via self-assembly, as these materials are promising soft material platforms for scalable mechanochromic sensors. PMID:23754505

Chan, Edwin P; Walish, Joseph J; Urbas, Augustine M; Thomas, Edwin L

2013-08-01

103

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

104

CONFORMANCE IMPROVEMENT USING GELS  

SciTech Connect

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

Randall S. Seright

2002-02-28

105

A rapid 3% polyacrylamide slab gel electrophoresis method for high through put screening of LDL phenotype  

PubMed Central

Background Small dense LDL is reported to be associated with increased coronary artery disease risk by various epidemiological studies. The gold standard for separation and identification of LDL subtypes in plasma is ultracentrifugation which is a lengthy procedure and difficult to perform. Various other methods like NMR, HPLC, gradient gel electrophoresis (GGE) have been reported for LDL sub fractionation all of which require specialized equipments and expertise. We report here a high throughput 3% polyacrylamide slab gel electrophoresis method (PASGE) for sub fractionation of LDL which was compared with GGE, a commonly used method for LDL sub fractionation. Results The 3% PASGE method compared well with the GGE method There was a good correlation between LDL particle diameter identified by the PASGE and GGE (Pearson correlation coefficient = 0.950). A 100% concordance was found when samples were classified as per LDL phenotypes in subjects with A and B phenotype by the two methods with the concordance being 66% in subjects with intermediate (I) phenotype. The electrophoresis apparatus was optimized and designed for running twenty eight samples at a time compared to twelve to fourteen by the conventional PASGE and eight to twelve by disc electrophoresis. Conclusion The rapid 3% polyacrylamide slab gel electrphoresis method developed is simple to perform, cost-effective and can be used for the identification LDL sub fractionation and phenotyping in large epidemiological studies.

Singh, Yogendra; Lakshmy, Ramakrishnan; Gupta, Ruby; Kranthi, Vemparala

2008-01-01

106

Polymer gel dosimetry technique  

SciTech Connect

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

Maryanski, M.J.

1995-12-31

107

Patterns in shrinking gels  

NASA Astrophysics Data System (ADS)

POLYMER gels can undergo a volume phase transition (either continuous or discontinuous) when an external condition, such as temperature or solvent composition, is altered1-3. During this transition, the volume may change by a factor of several thousand, and various patterns develop in the gel. The patterns arising from swelling and shrinking differ in both their appearance and their physical mechanisms. The mechanism for the formation and evolution of patterns on swelling gels has been established as being due to a single kind of mechanical instability4-7 in contrast, the shrinking patterns seem to be sensitive to both the initial and final states of the transition. Here we classify the various shrinking patterns in the form of a phase diagram, and explain the poly-morphism in terms of macroscopic phase separation.

Matsuo, Eriko Sato; Tanaka, Toyoichi

1992-08-01

108

Gel-silica science  

SciTech Connect

Sol-gel techniques can be used to produce two new types of optical silicas, termed Type V for the full density material and Type VI for the optically transparent porous material. This paper summarizes the processing differences between these six types of commercial silicas. The primary emphasis of this paper is to discuss the scientific basis for the processing of Types V and VI optical silica. First, however, the use of sol-gel processing of other systems will be briefly reviewed. The controlled hydrolysis of alkoxides has also been used to produce submicrometer TiO{sub 2}, doped TiO{sub 2} (17), ZrO{sub 2} (18), doped ZrO{sub 2} (18), doped SiO{sub 2} (19), SrTiO{sub 3} (20), and corderite (20) powders. Emulsions have been employed to produce spherical powders of mixed cation oxides, such as yttrium aluminum garnets (YAG) and many other systems (20). Sol-gel powder processes have also been applied to fissile elements (21) where spray form sols UO{sub 2}, and rigid gel spheres of UO-PuO{sub 2} are formed during passage through a column of heated liquid. Both crystalline and vitreous ceramic fibers have been prepared using the sol-gel method. Compositions include TiO{sub 2}-SiO{sub 2} and ZrO{sub 2}-SiO{sub 2} glass fibers (22), high purity SiO{sub 2} waveguide fibers (23), Al{sub 2}O{sub 3}, ZrO{sub 2}, ThO{sub 2}, MgO, TiO{sub 2}, ZrSiO{sub 4}, 3AlO{sub 3}-2SiO{sub 2} fibers (24). Sol-gel derived alumina grains are important commercial products (25).

Hench, L.L.; Vasconcelos, W. (Advanced Materials Research Center, Univ. of Florida, Gainesville, FL (US))

1990-01-01

109

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

110

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

111

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

112

Peculiarities of diffusion in gels  

NASA Astrophysics Data System (ADS)

An optical method was applied to study the peculiarities of diffusion in gel: this method provides real-time visualization of spreading of solutes brought into the gel. It was shown that spectral characteristics of reflected light give additional information about nature of diffusive spreading of solutes and about state of the gel. Gels with different densities and lifetime were studied. These parameters have strong influence on the velocity of diffusion. The study demonstrated critical differences for diffusion process in gels with true solutions and with solutions with nanoparticles. Experiments discovered the anisotropy in 3D diffusion of solutes in gels; physical explanation of this phenomenon was proposed.

Pokusaev, B. G.; Karlov, S. P.; Vyazmin, A. V.; Nekrasov, D. A.

2013-12-01

113

Peculiarities of diffusion in gels  

NASA Astrophysics Data System (ADS)

An optical method was applied to study the peculiarities of diffusion in gel: this method provides real-time visualization of spreading of solutes brought into the gel. It was shown that spectral characteristics of reflected light give additional information about nature of diffusive spreading of solutes and about state of the gel. Gels with different densities and lifetime were studied. These parameters have strong influence on the velocity of diffusion. The study demonstrated critical differences for diffusion process in gels with true solutions and with solutions with nanoparticles. Experiments discovered the anisotropy in 3D diffusion of solutes in gels; physical explanation of this phenomenon was proposed.

Pokusaev, B. G.; Karlov, S. P.; Vyazmin, A. V.; Nekrasov, D. A.

2014-12-01

114

Preparation of Homogeneous Aluminosilicate Gels by Sol/Gel Techniques.  

National Technical Information Service (NTIS)

The factors affecting the production of homogeneous aluminosilicate gels from alkoxide precursors were investigated. Aluminosilicate gels were made in acidic conditions with a prepolymerization of the silicate precursors followed by the addition of the al...

M. Reese J. Sanchez A. V. McCormick

1993-01-01

115

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

116

Nanostructured Magnetorheological Fluids and Gels.  

National Technical Information Service (NTIS)

Magnetorheological materials having a supramolecular polymer gel as a component of the carrier are disclosed. Useful supramolecular polymers for gels include those having terpyridine ligands which can participate in metal coordination bonding. The magneti...

A. Fuchs B. Hu B. Kavlicoglu F. Gordaninejad

2004-01-01

117

Clinical Applications of Gel Dosimeters  

NASA Astrophysics Data System (ADS)

This paper reviews the characteristics of gel dosimetry that make it desirable for clinical use, the postulated and demonstrated applications of gel dosimetry, and some complications, setbacks, and failures that have contributed to the slow introduction into routine clinical use.

Ibbott, Geoffrey S.

2006-12-01

118

Phase Transitions in Ionic Gels  

Microsoft Academic Search

The polymer network of a gel, under certain conditions, undergoes a discrete transition in equilibrium volume with changes in solvent composition or temperature. This Letter demonstrates that ionization of the gel network plays an essential role in the phase transition. The volume collapse is also observed when the pH within the gel is varied.

Toyoichi Tanaka; David Fillmore; Shao-Tang Sun; Izumi Nishio; Gerald Swislow; Arati Shah

1980-01-01

119

Microfluidics with Gel Emulsions  

Microsoft Academic Search

Microfluidic processing is usually achieved using single phase liquids. Instead, we use monodisperse emulsions to compartment liquids within microchannel geometries. At low continuous phase volume fractions, droplets self-organize to form well-defined arrangements, analogous to foam. While it is well-known that confined geometries can induce rearrangement of foam compartments at the millimeter-scale, similar dynamics are also expected for gel emulsions. We

Craig Priest; Enkhtuul Surenjav; Stephan Herminghaus; Ralf Seemann

2006-01-01

120

Gel architectures and their complexity.  

PubMed

Gels have made the transition from brittle materials with few potential applications to high performance systems with mechanical properties approaching that of rubber. They have a wide variety of structures and provide the opportunity to tailor these structures to achieve well-controlled properties over a range of length scales. In this review we consider and compare the structures and properties of a range of gels that have been studied in recent years. In comparing these gels we highlight the importance of key structural parameters in defining gel mechanical properties. It is hoped that this article will provide authors who discover new gels a resource that will easily enable them to determine the differences of their new gels to existing gels. PMID:24705716

Richtering, Walter; Saunders, Brian R

2014-06-01

121

Let's Talk... Analytics  

ERIC Educational Resources Information Center

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

Oblinger, Diana G.

2012-01-01

122

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

123

Compartmentalization of electrophoretically separated analytes in a multiphase microfluidic platform.  

PubMed

Herein, we describe the monolithic integration of a multiphase microfluidic system to a microcapillary gel electrophoresis (?CGE) architecture for the complete isolation and storage of separated analyte bands. Within this platform, analyte molecules are separated using microchannel gel electrophoresis, and the eluted bands are stored in a sequence of approximately 40-600 encapsulating microdroplets. Importantly, employing such a system allows for total control of droplet size, shape, and composition. This approach is utilized to separate, optically detect, and encapsulate two fluorescent analytes from a composite sample mixture. Further to this, we subsequently investigate the potential of the system to be used as a concentration gradient generator through analysis of the segmented analyte bands and droplet composition. PMID:22656086

Draper, Mark C; Niu, Xize; Cho, Soongwon; James, David I; Edel, Joshua B

2012-07-01

124

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

125

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.

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

2013-01-01

126

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

127

Electrically controlled polymeric gel actuators  

DOEpatents

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

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

1993-01-01

128

Photopatterned free-standing polyacrylamide gels for microfluidic protein electrophoresis.  

PubMed

Designed for compatibility with slab-gel polyacrylamide gel electrophoresis (PAGE) reagents and instruments, we detail development of free-standing polyacrylamide gel (fsPAG) microstructures supporting electrophoretic performance rivalling that of microfluidic platforms. For the protein electrophoresis study described here, fsPAGE lanes are comprised of a sample reservoir and contiguous separation gel. No enclosed microfluidic channels are employed. The fsPAG devices (120 ?m tall) are directly photopatterned atop of and covalently attached to planar polymer or glass surfaces. Leveraging the fast <1 h design-prototype-test cycle - significantly faster than mold based fabrication techniques - we optimize the fsPAG architecture to minimize injection dispersion for rapid (<1 min) and short (1 mm) protein separations. The facile fabrication and prototyping of the fsPAGE provides researchers a powerful tool for developing custom analytical assays. We highlight the utility of assay customization by fabricating a polyacrylamide gel with a spatial pore-size distribution and demonstrate the resulting enhancement in separation performance over a uniform gel. Further, we up-scale from a unit separation to an array of 96 concurrent fsPAGE assays in 10 min run time driven by one electrode pair. The fsPAG array layout matches that of a 96-well plate to facilitate integration of the planar free standing gel array with multi-channel pipettes while remaining compatible with conventional slab-gel PAGE reagents, such as staining for label-free protein detection. Notably, the entire fsPAGE workflow from fabrication, to operation, and readout uses readily available materials and instruments - making this technique highly accessible. PMID:23609800

Duncombe, Todd A; Herr, Amy E

2013-06-01

129

Creases and wrinkles on the surface of a swollen gel  

NASA Astrophysics Data System (ADS)

Consider a layer of a gel attached to a rigid substrate, immersed in a solvent, and swelling in the thickness direction. The flat surface of the gel remains stable if the swelling ratio is small, but becomes unstable if the swelling ratio is large. While creases have been commonly observed, wrinkles have also been observed under certain conditions. We compare the critical conditions for the onset of creases and wrinkles by using a nonlinear field theory of gels. The critical swelling ratio for the onset of creases is calculated by using a finite element method, and that for wrinkles is calculated by using an analytical method. We find that the critical swelling ratio for the onset of creases is significantly lower than that for wrinkles.

Weiss, François; Cai, Shengqiang; Hu, Yuhang; Kyoo Kang, Min; Huang, Rui; Suo, Zhigang

2013-08-01

130

Reversible Dimer Formation and Stability of the Anti-tumour Single-chain Fv Antibody MFE-23 by Neutron Scattering, Analytical Ultracentrifugation, and NMR and FT-IR Spectroscopy  

Microsoft Academic Search

MFE-23 is a single chain Fv (scFv) antibody molecule used to target colorectal cancer through its high affinity for the tumour marker carcinoembryonic antigen (CEA). ScFv molecules are formed from peptide-linked antibody VH and VL domains, and many of these form dimers. Our recent crystal structure for MFE-23 showed that this formed an unusual symmetric back-to-back association of two monomers

Yie Chia Lee; Mark K. Boehm; Kerry A. Chester; Richard H. J. Begent; Stephen J. Perkins

2002-01-01

131

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

132

Analytical Challenges in Biotechnology.  

ERIC Educational Resources Information Center

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

Glajch, Joseph L.

1986-01-01

133

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

134

A cholesterol-isopropanol gel  

Microsoft Academic Search

IN the course of measuring solubilities of cholesterol in pure and mixed solvents we have observed the formation of a transparent gel in the cholesterol+isopropanol system. Because of the historical importance of liquid crystals of cholesteryl esters1 and the biological importance of cholesterol, we are reporting here some observations on the properties of this gel. Liquid crystals of cholesterol with

William E. Acree; Gary L. Bertrand

1977-01-01

135

Living bacteria in silica gels  

Microsoft Academic Search

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

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

2002-01-01

136

Analyte detection assay  

US Patent & Trademark Office Database

A rapid and sensitive analyte detection assay is based on whispering gallery modes of fluorescently labelled microspheroidal particles. Ligands for the analyte, such as nucleic acids, are anchored to the particles. The fluorescent labels may comprise fluorophores or quantum dots. In the latter case, the particles may comprise melamine formaldehyde. The assay may be used to detect analytes in aqueous samples.

2013-12-31

137

Good Analytical Research  

Microsoft Academic Search

The purpose of this commentary is to address the issues raised by Ohlson from the point of view of analytical accounting research. The aim is not only to provide some input to young researchers who are going to publish good research using analytical methods, but also to give some hints to help users of analytical accounting research to understand and

John Christensen

2011-01-01

138

Characterization of fish acid proteases by substrate-gel electrophoresis  

Microsoft Academic Search

Several analytical techniques based upon the use of substrate-polyacrylamide gel electrophoresis were evaluated to achieve characterization of aspartate proteases in fish stomach. Since aspartate proteases of fish are more stable at high pH than mammalian pepsins, the most accurate technique for activity assessment is electrophoresis at neutral pH and revealing of such activity at low pH with hemoglobin as substrate.

Manuel Diaz-Lopez; Francisco J. Moyano-Lopez; F. Javier Alarcon-Lopez; Fernando L. Garcia-Carreno; M. Angeles; Navarrete del Toro

139

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

140

Poroviscoelastic characterization of particle-reinforced gelatin gels using indentation and homogenization.  

PubMed

Hydrogels are promising materials for bioengineering applications, and are good model materials for the study of hydrated biological tissues. As these materials often have a structural function, the measurement of their mechanical properties is of fundamental importance. In the present study gelatin gels reinforced with ceramic microspheres are produced and their poroviscoelastic response in spherical indentation is studied. The constitutive responses of unreinforced gels are determined using inverse finite element modeling in combination with analytical estimates of material parameters. The behavior of composite gels is assessed by both analytical and numerical homogenization. The results of the identification of the constitutive parameters of unreinforced gels show that it is possible to obtain representative poroviscoelastic parameters by spherical indentation without the need for additional mechanical tests. The agreement between experimental results on composite gelatin and the predictions from homogenization modeling show that the adopted modeling tools are capable of providing estimates of the poroviscoelastic response of particle-reinforced hydrogels. PMID:21396610

Galli, Matteo; Fornasiere, Elvis; Cugnoni, Joël; Oyen, Michelle L

2011-05-01

141

Protein gel staining methods: an introduction and overview.  

PubMed

Laboratory scientists who encounter protein biochemistry in many of its myriad forms must often ask: is my protein pure? The most frequent response: run a denaturing SDS polyacrylamide gel. Running this gel raises another series of considerations regarding detection, quantitation, and characterization and so the next questions invariably center on suitable protein gel staining and detection methods. A total protein profile can be determined with the colorimetric methods embodied in Coomassie Blue and silver staining methods, or increasingly, with fluorescent stains. Protein quantitation can be done following staining, with fluorescence- and instrumentation-based methods offering the greatest sensitivity and linear dynamic range. Protein posttranslational modifications such as phosphorylation and glycosylation can be reliably determined with several fluorescence-based protocols. Staining and detection with two or more different stains can be done in series to establish relative profiles of modified versus total protein or to assess purity at two levels of quantitative sensitivity. The choice of staining method and protocol depends on the required rigor of detection and quantitation combined with available instrumentation and documentation capabilities. Other considerations for staining methods include intended downstream analytical procedures such as mass spectrometry or peptide sequencing, which preclude some methods. Nonfixative staining methods allow western blotting after gel staining. Laboratory custom and budget or intellectual curiosity may be the ultimate determinate of the chosen gel staining protocol. PMID:19892191

Steinberg, Thomas H

2009-01-01

142

Symmetry breaking in actin gels - Implications for cellular motility  

NASA Astrophysics Data System (ADS)

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

John, Karin; Peyla, Philippe; Misbah, Chaouqi

2007-03-01

143

Protein diffusion in charged polyacrylamide gels. Visualization and analysis.  

PubMed

Protein diffusion in anionic, cross-linked polyacrylamide-based gels supported in fused-silica capillaries was characterized by a direct visualization method. Microphotography was used to obtain transient protein concentration profiles in these gels using cytochrome c as a probe molecule. Gels based on acrylamido-methylpropane sulfonic acid with 2.5-10% N,N'-methylene-bisacrylamide as a cross-linker and with a total polymer concentration of 0.21 g/cm3 yielded diffuse protein concentration profiles which were quantitatively consistent with a Fickian diffusion model. An analytical method was developed to calculate the diffusivity as a function of protein concentration in the gel from the experimental profiles. The diffusivity was found to assume values in the range 2.5-5.5x10(-8) cm2/s and varied somewhat with the protein concentration in the gel. The effects of some of the polymer properties, such as cross-link density, polymer concentration and charge, were also investigated for a limited range of conditions to derive qualitative trends. Results showed that the transport rates increased with a decrease in the cross-link density, were extremely reduced when the polymer concentration was doubled, and were slightly increased when the charge density was decreased by half by polymerizing a 1:1 mixture of acrylamide and acrylamido-methylpropane sulfonic acid monomers. PMID:10674938

Lewus, R K; Carta, G

1999-12-31

144

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

145

[Thin layer chromatographic detection of aflatoxins on ready-made silica gel plates].  

PubMed

Silica gel instant plates with an aluminium reflection foil as the carrier material (Silufol) were tested for their suitability for the thin-layer chromatographic separation of aflatoxins in comparison with conventiol silica gel G coated glass plates. Besides the well-knwon merits of instant plates, the Silufol plates offer remarkable analytical advantages; increased sensibility and shorter time of development. For this reason, the Silufol plates may be recommended for routine examinations of foods for aflatoxins. PMID:854082

Thurm, V

1977-01-01

146

Sedimentation equilibria of ferrofluids: I. Analytical centrifugation in ultrathin glass capillaries.  

PubMed

Analytical centrifugation is used for the first time to measure sedimentation equilibrium concentration profiles of a ferrofluid, a concentrated colloidal dispersion of strongly absorbing magnetic nanoparticles. To keep the optical absorbance from becoming too strong, the optical path length is restricted to 50 ?m by placing the dispersion in a flat glass capillary. The concentration profile is kept from becoming too steep, despite the relatively high buoyant mass of the nanoparticles, by making novel use of a low-velocity analytical centrifuge that was not designed to measure equilibrium profiles. The experimental approach is validated by comparison with profiles obtained using an analytical ultracentrifuge. At concentrations of a few hundred grams per liter, the osmotic pressures calculated from the equilibrium profiles are lower than expected for hard spheres or non-interacting particles, due to magnetic dipolar interactions. By following the presented experimental approach, it will now also be possible to characterize the interparticle interactions of other strongly absorbing colloidal particles not studied before by analytical centrifugation. PMID:22617483

Luigjes, Bob; Thies-Weesie, Dominique M E; Philipse, Albert P; Erné, Ben H

2012-06-20

147

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

148

Introduction to Agarose Gel Electrophoresis  

NSDL National Science Digital Library

In this module, developed as part of Cornell's Learning Initiative in Medicine and Bioengineering (CLIMB), students are introduced to the concepts of gel electrophoresis without requiring all the equipment needed to run a full gel electrophoresis experiment. The goal is to have students understand how gels are made for DNA separation and how altering the composition can affect the experimental parameters. This module contains a teacher's guide, classroom activity, and suggestions for extended activities. This lab is a precursor to Cornellâs Institute for Biology Teachers labâs entitled DNA Profiling â Paternity Testing, which is linked within the teacher's guide. CLIMB is part of the NSF GK-12 program.

Bioengineering, Climb: C.

149

DNA electronic switches based on analyte-responsive aptamers.  

PubMed

Aptamers have proven to be very useful as high-affinity and -specificity molecular recognition elements in analytical sensors of various forms. Herein, we describe a general process for creating an aptamer-based sensor that functions as an analyte-responsive, nano-sized, electronic switch. These sensors can provide an electrochemical readout, by switching through-DNA charge transfer across a DNA three-way junction from "off" to "on" in response to the binding of a target ligand to the sensor's aptamer domain. We detail the general design principles for such sensors, as well as the biochemical charge transfer assays used to identify functional sensors. In these gel electrophoresis-based assays, analyte-responsive conductivity switching is detected conveniently through biochemical experiments that characterize oxidative DNA damage patterns in sequencing PAGE gels. PMID:24318900

Thomas, Jason M; Yu, Hua-Zhong; Sen, Dipankar

2014-01-01

150

Bifurcation of a Swelling Gel with a Mechanical Load and Geometric Constraint  

NASA Astrophysics Data System (ADS)

We present an analysis of the bifurcation phenomenon of a gel in contact with a solvent. When a Mooney—Rivlin form-free energy function is introduced, an asymmetric swelling may appear for a gel swelling under uniaxial constraint or subjected to equal dead loads, which results in an interesting pitchfork bifurcation phenomenon. We present an analytical investigation of this problem based on the classical theory of continuum mechanics. The bifurcation points are obtained for different values of the chemical potential of the solvent molecules. The results demonstrate that the free swelling of the gel under uniaxial constraint will not result in the bifurcation unless further mechanical loads are applied.

Xue, Feng; Yong, Hua-Dong; Zhou, You-He

2011-11-01

151

Diffusion in Polymer Gel Implants  

PubMed Central

Crosslinked polyacrylamide and polyvinylpyrrolidone gels have been used to subcutaneously implant 125I-labeled immunoglobulin, 125I-labeled luteinizing hormone, 125I-labeled bovine serum albumin, 125I-labeled insulin, [3H]prostaglandin F2?, and Na125I into hamsters. From the rates of absorption of the solutes, their diffusion coefficients were determined. The diffusion coefficients showed a logarithmic dependence on implant polymer concentration and solute molecular weight. Release of the solutes from gel preparations incubated 10 mM phosphate buffer (pH 7.2) at 37° revealed a similar relationship between solute diffusion coefficient, molecular weight, and the concentration of polymer. A general equation was derived that gives the expected diffusion coefficient of a substance in a polymer gel from its molecular weight, diffusion coefficient in solvent, and polymer concentration of the gel.

Davis, B. K.

1974-01-01

152

Multiple phases of protien gels  

NASA Astrophysics Data System (ADS)

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 ?-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 minimum and thus in a phase.

Annaka, Masahiko; Tanaka, Toyoichi

1994-03-01

153

TOPICAL REVIEW: Polymer gel dosimetry  

Microsoft Academic Search

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

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

2010-01-01

154

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.

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

2010-01-01

155

Science Update: Analytical Chemistry.  

ERIC Educational Resources Information Center

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

Worthy, Ward

1980-01-01

156

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

157

Four Analytics in Educational Planning  

ERIC Educational Resources Information Center

Deals with four major skill areas: (1) the analytics of categorization, (2) the analytics of priority assessment, (3) the analytics of time and transition, and (4) the analytics of decision strategy. (Author)

McNamara, James F.; Rick, Zelda L.

1976-01-01

158

Silver stains for protein in gels  

US Patent & Trademark Office Database

A silver stain method for polypeptides in gels comprising the sequential steps of photo-reversing the polypeptide-gel by treatment with an oxidizing agent, forming a latent stain image by treating the polypeptide-gel with a photosensitive salt, and developing the stain image by treating the polypeptide-gel with a reducing agent.

1983-09-20

159

Thermoreversible konjac glucomannan gel crosslinked by borax  

Microsoft Academic Search

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

Shanjun Gao; Jinming Guo; Katsuyoshi Nishinari

2008-01-01

160

Alternative imaging modalities for polymer gel dosimetry  

NASA Astrophysics Data System (ADS)

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

Jirasek, Andrew

2010-11-01

161

Frozen Gel Slicing Method and Apparatus.  

National Technical Information Service (NTIS)

The patent discloses a method and apparatus for obtaining highly uniform slices of gel containing bands of RNA by freezing the gel in a cylindrical tube and then introducing the frozen cylindrical gel into a cylindrical sample handling mechanism and a gel...

F. L. Schaffer M. E. Soergel D. C. Straube

1974-01-01

162

Polytetrahydrofuran- and dendrimer- based novel sol-gel coatings for capillary microextraction (cme) providing parts per trillion (ppt) and parts per quadrillion (ppq) level detection limits in conjunction with gas chromatography and flame ionization detection (fid)  

Microsoft Academic Search

Sol-gel capillary microextraction (CME) is a new direction in solvent-free extraction and preconcentration of trace analytes. CME presents significant interest in environmental, pharmaceutical, petrochemical, biomedical, agricultural, food, flavor, and a host of other important areas. Sol-gel CME utilizes advanced material properties of organic-inorganic hybrid sol-gel polymers to perform efficient extraction and enrichment of target analytes from a variety of matrices.

Abuzar Kabir

2005-01-01

163

Extreme Scale Visual Analytics  

SciTech Connect

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

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

2012-05-08

164

Analytical mass spectrometry. Abstracts  

SciTech Connect

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

Not Available

1990-12-31

165

Analytical mass spectrometry  

SciTech Connect

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

Not Available

1990-01-01

166

Validating Analytical Methods  

ERIC Educational Resources Information Center

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

Ember, Lois R.

1977-01-01

167

Teaching the Analytical Life  

ERIC Educational Resources Information Center

Using a survey of 138 writing programs, I argue that we must be more explicit about what we think students should get out of analysis to make it more likely that students will transfer their analytical skills to different settings. To ensure our students take analytical skills with them at the end of the semester, we must simplify the task we…

Jackson, Brian

2010-01-01

168

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

169

Accelerating business analytics applications  

Microsoft Academic Search

Business text analytics applications have seen rapid growth, driven by the mining of data for various decision making processes. Regular expression processing is an important component of these applications, consuming as much as 50% of their total execution time. While prior work on accelerating regular expression processing has focused on Network Intrusion Detection Systems, business analytics applications impose different requirements

Valentina Salapura; Tejas Karkhanis; Priya Nagpurkar; Jose Moreira

2012-01-01

170

Optical Sensors for Biomolecules Using Nanoporous Sol-Gel Materials  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

171

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

172

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

173

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

174

Antibiotic gels for periodontal disease.  

PubMed

Periodontal disease is a major cause of tooth loss. The underlying pathology is inflammation caused by bacterial plaque affecting the supporting structures of the teeth. Conventional treatment involves mechanical debridement of calcified plaque (calculus) by the dentist combined with meticulous oral hygiene by the patient. A more recent approach is to apply antimicrobial drugs locally to the diseased gingival tissue after debridement. Two antibiotic preparations, minocycline 2% gel (Dentomycin-Lederle) and metronidazole 25% gel (Elyzol-Dumex), are now licensed for the treatment of patients with periodontal disease. Are these treatments an advance on conventional therapy? PMID:7635031

1994-06-16

175

On-line preconcentration and determination of cobalt by DPTH-gel chelating microcolumn and flow injection inductively coupled plasma atomic emission spectrometry  

Microsoft Academic Search

This paper reports the development of a new methodology for the determination of cobalt in biological samples by using a flow injection system with loaded DPTH-gel as solid phase to preconcentrate analytes. The procedure is based on the on-line preconcentration of cobalt on a microcolumn of 1,5-bis(di-2-pyridyl)methylene thiocarbohydrazide immobilized on silica gel (DPTH-gel). The trapped cobalt is then eluted with

Mohammed Zougagh

2004-01-01

176

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

177

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

178

Visual analytics for immunologists  

PubMed Central

Visual analytics is the science of analytical reasoning that facilitates research through the use of interactive visual interfaces. New techniques of visual analytics are designed to aid the understanding of complex systems versus traditional blind-context rules to explore massive volumes of interrelated data. Nowhere else is visualization more important in analysis than in the emerging fields of life sciences, where amounts of collected data grow increasingly in exponential rates. The complexity of the immune system in immunology makes visual analytics especially important for understanding how this system works. In this context, our effort should be focused on avoiding accurate but potentially misleading use of visual interfaces. The proposed approach of data compression and visualization that reveal structural and functional features of immune responses enhances systemic and comprehensive description and provides the platform for hypothesis generation. Further, this approach can evolve into a powerful visual-analytical tool for prospective and real-time monitoring and can provide an intuitive and interpretable illustration of vital dynamics that govern immune responses in an individual and populations. The undertaken explorations demonstrate the critical role of novel techniques of visual analytics in stimulating research in immunology and other life sciences and in leading us to understanding of complex biological systems and processes.

2010-01-01

179

Perfluoropolyether characterization by nuclear magnetic resonance spectroscopy and gel permeation chromatography  

Microsoft Academic Search

Perfluoropolyethers (PFPEs) are vital lubricants in the aerospace and magnetic recording industry, and they have potential applications in micro-electromechanical and optoelectronic devices. Precise control of their physical properties requires analytical tools, such as nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC) to characterize, chain composition end groups, and molecular weight distribution. The 19F chemical shifts for Z-, D-

T. E. Karis; B. Marchon; D. A. Hopper; R. L. Siemens

2002-01-01

180

Phase transitions in ionic gels  

Microsoft Academic Search

It has been reported that under certain conditions the polymer network of acrylamide gels immersed in acetone—water mixtures undergoes a discrete transition in equilibrium volume with changes in acetone concentration or temperature. In the present work, the physical and chemical basis of this phase transition is identified. The magnitude of the collapse can increase substantially when a small percentage of

Toyoichi Tanaka; Shao-Tang Sun; Izumi Nishio; Gerald Swislow; Arati Shah

1980-01-01

181

Capillary fracture of soft gels.  

PubMed

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

Bostwick, Joshua B; Daniels, Karen E

2013-10-01

182

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

183

Polymeric Gels as an Environment for Electrochemistry.  

National Technical Information Service (NTIS)

The program Objectives are to study (1) the transport of ions and molecules in polymeric gels; (2) volume phase transitions of gels and their influence on the transport properties of ions and molecules; (3) electrochemical generation of volume phase trans...

M. Ciszkowska

1998-01-01

184

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

185

Two-dimensional Gel Electrophoresis (2DE)  

NASA Astrophysics Data System (ADS)

The chemical compounds, which are present in the environment, increasingly cause bad effects on health. The most serious effects are tumors and various mutations at the cellular level. Such compounds, from the analytical point of view, can serve the function of biomarkers, constituting measurable changes in the organism's cells and biochemical processes occurring therein. The challenge of the twenty-first century is therefore searching for effective and reliable methods of identification of biomarkers as well as understanding bodily functions, which occur in living organisms at the molecular level. The irreplaceable tool for these examinations is proteomics, which includes both quality and quantity analysis of proteins composition, and also makes it possible to learn their functions and expressions. The success of proteomics examinations lies in the usage of innovative analytical techniques, such as electromigration technique, two-dimensional electrophoresis in polyacrylamide gel (2D PAGE), liquid chromatography, together with high resolution mass spectrometry and bio-informatical data analysis. Proteomics joins together a number of techniques used for analysis of hundreds or thousands of proteins. Its main task is not the examination of proteins inside the particular tissue but searching for the differences in the proteins' profile between bad and healthy tissues. These differences can tell us a lot regarding the cause of the sickness as well as its consequences. For instance, using the proteomics analysis it is possible to find relatively fast new biomarkers of tumor diseases, which in the future will be used for both screening and foreseeing the course of illness. In this chapter we focus on two-dimensional electrophoresis because as it seems, it may be of enormous importance when searching for biomarkers of cancer diseases.

K?odzi?ska, Ewa; Buszewski, Bogus?aw

186

Oilfield Applications of Colloidal Silica Gel  

Microsoft Academic Search

This paper reports on a practical reservoir fluid-flow control system based on colloidal silica gel that was developed. Colloidal silica gel is an environmentally benign system that provides easy surface handling, reliable gel-time control at temperatures up to 250° F, and high in-situ performance. Extensive laboratory testing was completed and is discussed elsewhere. Colloidal silica gel has been used in

J. J. Jurinak; L. E. Summers

1991-01-01

187

Improving calibration accuracy in gel dosimetry  

Microsoft Academic Search

A new method of calibrating gel dosimeters (applicable to both Fricke and polyacrylamide gels) is presented which has intrinsically higher accuracy than current methods, and requires less gel. Two test-tubes of gel (inner diameter 2.5 cm, length 20 cm) are irradiated separately with a field end-on in a water bath, such that the characteristic depth-dose curve is recorded in the

M. Oldham; M. McJury; I. B. Baustert; S. Webb; M. O. Leach

1998-01-01

188

Determination of association constants between 5'-guanosine monophosphate gel and aromatic compounds by capillary electrophoresis.  

PubMed

Hydro gel formed by 5'-guanosine monophosphate (GMP) in the presence of a potassium ion is expected to exhibit interesting selectivity in capillary electrophoretic separations. Here, we estimated the conditional association constants between the hydro gel (G-gel) and aromatic compounds by capillary electrophoresis in order to investigate the separation selectivity that is induced by the G-gel. Several aromatic compounds were separated in a solution containing GMP and potassium ion at different concentrations. The association constants were calculated by correlating the electrophoretic mobilities of the analytes obtained experimentally using a concentration of G-gel. During semi-quantitative estimation, naphthalene derivatives had larger association constants (Kass=10.3-16.8) compared with those of benzene derivatives (Kass=3.91-5.31), which means that the binding sites of G-gel match better to a naphthalene ring than to a benzene ring. A hydrophobic interaction was also found when the association constants for alkyl resorcinol were compared with those of different hydrocarbon chains. The association constants of nucleobases and tryptophan ranged from 6.05 to 12.6, which approximated the intermediate values between benzene and naphthalene derivatives. Consequently, the selective interaction between G-gel and aromatic compounds was classified as one of three types: (1) an intercalation into stacked planar GMP tetramers; (2) a hydrophobic interaction with a long alkyl chain; or, (3) a small contribution of steric hindrance and/or hydrogen bonding with functional groups such as amino and hydroxyl groups. PMID:23522259

Yamaguchi, Kaori; Takeyasu, Nobuyuki; Kaneta, Takashi

2013-05-01

189

Testim ® Gel: Review of Clinical Data  

Microsoft Academic Search

Late-onset hypogonadism is a medical condition characterized by testosterone deficiency in ageing men, accompanied by clinical symptoms, that can negatively affect quality of life and multiple organ systems. The condition is generally managed using testosterone substitution. Many formulations of testosterone are available, including deep-muscle injections, buccal formulations, transdermal patches, and topical gels. Testim® Gel 1% testosterone gel (Auxilium Pharmaceuticals –

Tom A. McNicholas

2005-01-01

190

Gel phantom in selective laser phototherapy  

Microsoft Academic Search

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

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

2008-01-01

191

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

192

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

193

Improving immobilized biocatalysts by gel phase polymerization  

Microsoft Academic Search

A new method is presented for the treatment of gel-type supports, used for immobilizing microbial cells and enzymes, to obtain high mechanical strength. It is particularly useful for ethanol fermentation over gel beads containing immobilized viable cells, where the beads can be ruptured by gas production and the growth of cells within the gels. This method consists of treating agar

W. Y. Kuu; J. A. Polack

1983-01-01

194

Analytical terahertz spectroscopy.  

PubMed

Recent progress in analytical terahertz (THz) spectroscopy is reviewed with illustrative examples showing that it is an effective method for detecting and identifying intermolecular interactions in chemical compounds, such as hydrogen bonds. The unique and characteristic properties of THz waves, their significance to both science and industry, and the bases of one of the successful fields of analytical THz spectroscopy, namely THz time-domain spectroscopy and THz imaging for chemical analysis, are described. Preliminary quantitative studies are presented to show the potential of THz spectroscopy for the detection and identification of intermolecular hydrogen bonds in unknown mixture samples. The selective detection of intramolecular hydrogen bonds and the detection of intramolecular interactions in ice are also introduced. Some brief remarks are provided on future developments, the main issues, and the prospects for analytical THz spectroscopy. PMID:18270407

Ueno, Yuko; Ajito, Katsuhiro

2008-02-01

195

Advances in analytical chemistry  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

196

Frontiers in analytical chemistry  

SciTech Connect

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

Amato, I.

1988-12-15

197

Analytic Trajectory Visualizer Model  

NSDL National Science Digital Library

The Analytic Animator allows instructors to create two-dimensional single-particle kinematics models for teaching. Instructors set two functions, x(t) and y(t), and the model displays the position-space particle motion as well as position, velocity, and acceleration graphs and tables. The customized simulation is then saved with associated curricular as a new jar file that can be redistributed. The Analytic Trajectory Animator Model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_newton_TabletopProjectile.jar file will run the program if Java is installed.

Christian, Wolfgang; Belloni, Mario

2012-05-15

198

Analytical Chemistry Springboard  

NSDL National Science Digital Library

The Analytical Chemistry Springboard Web site is provided by Umea University Department of Chemistry. The metadata site provides a large number of annotated links that relate to analytical chemistry. Categories include Atomic Spectroscopy, Chemometrics, Electron Spectroscopy, Mass Spectrometry, Nuclear Magnetic Resonance, X-Ray Spectroscopy, and many more. Another section on the site provides links to informational resources such as newsgroups, nonprofit organizations, and scientific literature sources. Each site has a brief description, a direct link, and informational icons that tell if the site is new, updated, or contains graphics -- all of which culminate in a simple but very helpful resource for those working in a related field.

1995-01-01

199

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

200

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

201

Avatars in Analytical Gaming  

Microsoft Academic Search

This paper discusses the design and use of anthropomorphic computer characters as nonplayer characters (NPC's) within analytical games. These new environments allow avatars to play a central role in supporting training and education goals instead of playing the supporting cast role. This new `science' of gaming, driven by high-powered but inexpensive computers, dedicated graphics processors and realistic game engines, enables

Andrew J. Cowell; Amanda K. Cowell

2009-01-01

202

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

203

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

204

Extending XQuery for analytics  

Microsoft Academic Search

XQuery is a query language under development by the W3C XML Query Working Group. The language contains constructs for navigating, searching, and restructuring XML data. With XML gaining importance as the standard for representing business data, XQuery must support the types of queries that are common in business analytics. One such class of queries is OLAP-style aggregation queries. Although these

Kevin S. Beyer; Don Chambérlin; Latha S. Colby; Fatma Özcan; Hamid Pirahesh; Yu Xu

2005-01-01

205

SDS agarose gels for analysis of proteins.  

PubMed

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

Wu, M; Kusukawa, N

1998-04-01

206

Smart Polymeric Gels: Redefining the Limits of Biomedical Devices  

PubMed Central

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

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

2007-01-01

207

Direct response to proton beam linear energy transfer (LET) in a novel polymer gel dosimeter formulation.  

PubMed

Linear energy transfer (LET) of clinical proton beams is an important parameter influencing the biological effects of radiation. This work demonstrates LET-induced response enhancement in novel formulations of polymer gel dosimeters, potentially useful for LET mapping of clinical proton beams. A series of four polymer gel dosimeters (labeled A through D), prepared based on the BANG3-Pro2 formulation, but with varying concentrations of polymerization modifiers, were irradiated by a clinical proton beam with a spread out Bragg peak modulation (SOBP) and read out using the OCTOPUS-IQ optical CT scanner. The evaluation of optical density profiles in the SOBP (constant physical dose) revealed response deviations at the distal end consistent with variations in gel composition. Maximum response deviations were as follows: -3% (under-response) for gel A, and over-response of 2%, 12%, and 17% for gels B, C, and D, respectively, relative to the mean dose in the center of the SOBP. This enhancement in optical response was correlated to LET by analytical calculations. Gels A and B showed no measurable dependence on LET. Gel C responded linearly in the limited range from 1.5 to 3.5 keV/?m. LET response of gel D was linear up to at least 5.5 keV/?m, with the threshold at about 1.3 keV/?m. These results suggest that it may be possible to develop a polymer gel system with direct optical response to LET for mapping of LET distributions for particle therapy beams. PMID:22568627

Lopatiuk-Tirpak, O; Su, Z; Li, Z; Zeidan, O A; Meeks, S L; Maryanski, M J

2012-10-01

208

Synthesis of oligomeric models of coal-derived materials for use with GPC calibration. Quarterly report, June-August 1982. [Gel permeation chromatography  

SciTech Connect

One important facet of the characterization of coal-derived materials is that of molecular weight determination. Number average molecular weight is usually obtained by vapor pressure osmometry measurements. However, no satisfactory method is available for determining weight average molecular weights. The latter values are useful in predicting rheological properties. Gel permeation chromatography (GPC) is a technique which should be most readily adaptable for this measurement. The other techniques of ultracentrifugation and light scattering are not as readily available as GPC. At this time, satisfactory GPC calibration standards which possess chemical structures similar to coal derived mterials are non-existent. The purpose of this study is to develop a useful set of GPC calibration standards for asphaltene and preaspaltene analyses. Our previous results suggest models in which coal derived preasphaltenes and asphaltenes are composed of oligomeric aromatic ethers of both diaryl and furan types. We plan to synthesize a series of model oligomers that are in agreement with the average structural formulas of some selected coal preasphaltenes as determined by pmr, elemental analyses and various oxygen derivatization procedures. These model compounds will be tested for use as calibration standards for both high pressure gel permeation chromatographic and vapor pressure osmometric procedures. Their response and retention times will be compared with coal preasphaltenes to determine the suitability of the model compounds as calibration standards.

Baltisberger, R J; Jones, M B

1982-09-01

209

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

210

Analytical caustic surfaces  

NASA Technical Reports Server (NTRS)

This document discusses the determination of caustic surfaces in terms of rays, reflectors, and wavefronts. Analytical caustics are obtained as a family of lines, a set of points, and several types of equations for geometries encountered in optics and microwave applications. Standard methods of differential geometry are applied under different approaches: directly to reflector surfaces, and alternatively, to wavefronts, to obtain analytical caustics of two sheets or branches. Gauss/Seidel aberrations are introduced into the wavefront approach, forcing the retention of all three coefficients of both the first- and the second-fundamental forms of differential geometry. An existing method for obtaining caustic surfaces through exploitation of the singularities in flux density is examined, and several constant-intensity contour maps are developed using only the intrinsic Gaussian, mean, and normal curvatures of the reflector. Numerous references are provided for extending the material of the present document to the morphologies of caustics and their associated diffraction patterns.

Schmidt, R. F.

1987-01-01

211

Ultrasound in analytical chemistry.  

PubMed

Ultrasound is a type of energy which can help analytical chemists in almost all their laboratory tasks, from cleaning to detection. A generic view of the different steps which can be assisted by ultrasound is given here. These steps include preliminary operations usually not considered in most analytical methods (e.g. cleaning, degassing, and atomization), sample preparation being the main area of application. In sample preparation ultrasound is used to assist solid-sample treatment (e.g. digestion, leaching, slurry formation) and liquid-sample preparation (e.g. liquid-liquid extraction, emulsification, homogenization) or to promote heterogeneous sample treatment (e.g. filtration, aggregation, dissolution of solids, crystallization, precipitation, defoaming, degassing). Detection techniques based on use of ultrasonic radiation, the principles on which they are based, responses, and the quantities measured are also discussed. PMID:17103146

Priego Capote, F; Luque de Castro, M D

2007-01-01

212

Avatars in Analytical Gaming  

SciTech Connect

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

Cowell, Andrew J.; Cowell, Amanda K.

2009-08-29

213

Analytical applications of aptamers  

NASA Astrophysics Data System (ADS)

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

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

2007-06-01

214

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

215

Industrial Analytics Corporation  

SciTech Connect

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

Industrial Analytics Corporation

2004-01-30

216

Aspects of analytic deduction  

Microsoft Academic Search

Let ? be the ordinary deduction relation of classical first-order logic. We provide an “analytic” subrelation ?3 of ? which for propositional logic is defined by the usual “containment” criterion \\u000a$$\\\\Gamma \\\\vdash ^a \\\\varphi iff \\\\Gamma \\\\vdash \\\\varphi and Atom(\\\\varphi ) \\\\subseteq Atom(\\\\Gamma ),$$\\u000a whereas for predicate logic, ?a is defined by the extended criterion \\u000a$$\\\\Gamma \\\\vdash ^a \\\\varphi iff

Athanassios Tzouvaras

1996-01-01

217

Business Process Analytics  

Microsoft Academic Search

\\u000a Business Process Management systems (BPMS) are a rich source of events that document the execution of processes and activities\\u000a within these systems. Business Process Management analytics is the family of methods and tools that can be applied to these\\u000a event streams in order to support decision making in organizations. The analysis of process events can focus on the behavior\\u000a of

Michael Mühlen; Robert Shapiro

218

Sol/gel transition of chitosan solutions.  

PubMed

This work studies the occurrence of sol/gel transition and the gel rheology for chitosan solution under various conditions. Experiments were conducted in an oscillatory shear apparatus with small amplitude, using a Rheometrics SR-5 rheometer, with Couette and parallel plate geometries. The experimental results demonstrate that the sol/gel transition concentration and the elastic modulus (G') for CS gel decrease as the pH value and the molecular weight (Mw) increase. However, the sol/gel transition concentration and G' became independent of Mw when Mw exceeded a threshold. The higher ionization constant, Kp, is responsible for the higher sol/gel transition concentration in a formic acid solution than in an acetic acid solution with equivalent molar concentration. The elastic modulus G' of a CS gel increases with temperature, which relationship differs from that for many polysaccharides, and can be understood through classical rubber elastic theory. Finally, a gel whose concentration was barely above the sol/gel point exhibited aging, and its G' and G" declined rather than increase with time, accompanied by a reversal from the sol/gel state back to the sol state. This is an uncommon aging behavior for a polysaccharide and a detailed explanation is provided. PMID:16370243

Rwei, S P; Chen, T Y; Cheng, Y Y

2005-01-01

219

Competing on talent analytics.  

PubMed

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

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

2010-10-01

220

Denaturing gradient gel electrophoresis (DGGE).  

PubMed

Denaturing Gradient Gel Electrophoresis (DGGE) is a technique used to separate short- to medium-length DNA fragments based on their melting characteristics. It has been used frequently for identifying single-nucleotide polymorphisms without the need for DNA sequencing and as a molecular fingerprinting method for complex ecosystem communities, in particular in conjunction with amplification of microbial 16S rRNA genes. Here, the principles of DGGE, based on partial DNA strand separation at a given position in a gradient of chemical denaturant, are described, and an example protocol, optimized for fingerprinting of 200-300 bp fragments of bacterial 16S rRNA genes, is given. PMID:23913290

Strathdee, Fiona; Free, Andrew

2013-01-01

221

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

222

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

223

Reconfigurable assemblies of active, autochemotactic gels  

PubMed Central

Using computational modeling, we show that self-oscillating Belousov–Zhabotinsky (BZ) gels can both emit and sense a chemical signal and thus drive neighboring gel pieces to spontaneously self-aggregate, so that the system exhibits autochemotaxis. To the best of our knowledge, this is the closest system to the ultimate self-recombining material, which can be divided into separated parts and the parts move autonomously to assemble into a structure resembling the original, uncut sample. We also show that the gels’ coordinated motion can be controlled by light, allowing us to achieve selective self-aggregation and control over the shape of the gel aggregates. By exposing the BZ gels to specific patterns of light and dark, we design a BZ gel “train” that leads the movement of its “cargo.” Our findings pave the way for creating reconfigurable materials from self-propelled elements, which autonomously communicate with neighboring units and thereby actively participate in constructing the final structure.

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

2013-01-01

224

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

225

Spectrophotometric analysis of molecular transport in gels  

Microsoft Academic Search

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

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

1999-01-01

226

Gel time of calcium acrylate grouting material.  

PubMed

Calcium acrylate is a polymerized grout, and can polymerize in an aqueous solution. The polymerization reaction utilizes ammonium persulfate as a catalyst and sodium thiosulfate as the activator. Based on the theory of reaction kinetics, this study on the relation between gel time and concentration of activator and catalyst showed that gel time of calcium acrylate is inversely proportional to activator and catalyst concentration. A formula of gel time is proposed, and an example is provided to verify the proposed formula. PMID:15236477

Han, Tong-Chun

2004-08-01

227

Gel-Based Microchips: History and Prospects  

Microsoft Academic Search

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

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

2004-01-01

228

Chain Release Behavior of Gellan Gels  

Microsoft Academic Search

\\u000a The chain release behavior from gellan gels was studied by immersing the gel into water and monitoring the mass loss as a\\u000a function of time. Concentration of released gellan in the external solution was determined for gels of different sizes using\\u000a phenol-sulfuric acid method. The chain release process became faster with increasing total surface area and volume. However\\u000a the concentration

Khandker S. Hossain; Katsuyoshi Nishinari

2009-01-01

229

Nonlinear elasticity in biological gels  

NASA Astrophysics Data System (ADS)

The mechanical properties of soft biological tissues are essential to their physiological function and cannot easily be duplicated by synthetic materials. Unlike simple polymer gels, many biological materials-including blood vessels, mesentery tissue, lung parenchyma, cornea and blood clots-stiffen as they are strained, thereby preventing large deformations that could threaten tissue integrity. The molecular structures and design principles responsible for this nonlinear elasticity are unknown. Here we report a molecular theory that accounts for strain-stiffening in a range of molecularly distinct gels formed from cytoskeletal and extracellular proteins and that reveals universal stress-strain relations at low to intermediate strains. The input to this theory is the force-extension curve for individual semi-flexible filaments and the assumptions that biological networks composed of these filaments are homogeneous, isotropic, and that they strain uniformly. This theory shows that systems of filamentous proteins arranged in an open crosslinked mesh invariably stiffen at low strains without requiring a specific architecture or multiple elements with different intrinsic stiffness.

Storm, Cornelis; Pastore, Jennifer J.; Mackintosh, F. C.; Lubensky, T. C.; Janmey, Paul A.

2005-05-01

230

Nonlinear Elasticity in Biological Gels  

NASA Astrophysics Data System (ADS)

The mechanical properties of soft biological tissues are essential to their physiologic function and cannot easily be duplicated by synthetic materials. Unlike simple polymer gels, many biological materials including blood vessels, mesentery tissue, lung parenchyma, cornea and blood clots, stiffen as they are deformed, or strained. Stiffening under deformation allows tissues to be compliant at small strains and strengthen at larger deformations that could threaten tissue integrity. The molecular structures and design principles responsible for this non-linear elasticity are unknown. I will outline a molecular theory that accounts for strain-stiffening in a range of molecularly distinct gels formed from cytoskeletal and extracellular proteins and reveals universal stress-strain relations at low to intermediate strains. The input to this theory is the force-extension curve for individual semi- flexible filaments and the assumptions that networks composed of them are isotropic and that their elastic response is affine. The theory shows that systems of filamentous proteins arranged in an open crosslinked meshwork invariably stiffen at low strains without requiring a specific architecture or multiple elements with different intrinsic stiffness.

Storm, Cornelis

2006-03-01

231

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.

232

Conducting polymer electrodes for gel electrophoresis.  

PubMed

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

233

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

234

MERRA Analytic Services  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

235

Analytics for Cyber Network Defense.  

National Technical Information Service (NTIS)

This report provides a brief survey of analytics tools considered relevant to cyber network defense (CND). Ideas and tools come from fields such as statistics, data mining, and knowledge discovery. Some analytics are considered standard mathematical or st...

T. D. Plantenga T. G. Kolda

2011-01-01

236

Analytical Division Questions CPT Criteria.  

ERIC Educational Resources Information Center

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

Hercules, David M.

1978-01-01

237

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

238

Sampling and Analytical Methods for the Determination of Monochloroacetic Acid in Air  

Microsoft Academic Search

A personal sampling and analytical method has been developed for the determination of monochloroacetic acid (MCA) vapor in air. The sampling procedure is the collection of MCA with a solid sorbent sampling tube packed with silica gel. The MCA is leached from the exposed sorbent into distilled, deionized water and quantitated by ion chromatographic analysis. The method has been validated

DAVID W. MASON; H. KENNETH DILLON; ROBERT A. GLASER

1986-01-01

239

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

PubMed Central

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

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

2013-01-01

240

Magnetically Suspended Vacuum-Type Ultracentrifuge  

Microsoft Academic Search

A centrifuge rotor constructed of steel and Duralumin ST-14 weighing 4.93 kilograms and having a radius of 65 mm to the center of the standard centrifuge cell, which contains the material to be centrifuged, is suspended magnetically in a high vacuum (pressure less than 10?5 mm Hg). The rotor is driven to running speed by an air turbine below the

J. W. Beams; J. D. Ross; J. F. Dillon

1951-01-01

241

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

PubMed

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

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

2009-01-01

242

Parts per quadrillion level ultra-trace determination of polar and nonpolar compounds via solvent-free capillary microextraction on surface-bonded sol–gel polytetrahydrofuran coating and gas chromatography–flame ionization detection  

Microsoft Academic Search

Sol–gel polytetrahydrofuran (poly-THF) coating was developed for high-sensitivity sample preconcentration by capillary microextraction (CME). Parts per quadrillion (ppq) level detection limits were achieved for both polar and nonpolar analytes through sample preconcentration on sol–gel poly-THF coated microextraction capillaries followed by gas chromatography (GC) analysis of the extracted compounds using a flame ionization detector (FID). The sol–gel coating was in situ

Abuzar Kabir; Christina Hamlet; Abdul Malik

2004-01-01

243

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

PubMed

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

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

2014-02-28

244

Sol-gel chemistry and electrochemical properties of vanadium oxide gels  

Microsoft Academic Search

Vanadium oxide gels can be synthesized either from vanadic acid or vanadium alkoxides. The chemical nature, the structure and the properties of the resulting materials can then be quite different. The aqueous route, or a high hydrolysis ratio, leads to ordered gels with a layered structure. These gels behave as a host structure for intercalation. They exhibit improved properties as

J. Livage

1996-01-01

245

Fractionation of SWNT/nucleic acid complexes by agarose gel electrophoresis  

NASA Astrophysics Data System (ADS)

We show that aqueous dispersions of single-walled carbon nanotubes (SWNTs), prepared with the aid of nucleic acids (NAs) such as RNA or DNA, can be separated into fractions using agarose gel electrophoresis. In a DC electric field, SWNT/NA complexes migrate in the gel in the direction of positive potential to form well-defined bands. Raman spectroscopy as a function of band position shows that nanotubes having different spectroscopic properties possess different electrophoretic mobilities. The migration patterns for SWNT/RNA and SWNT/DNA complexes differ. Parallel elution of the SWNT/NA complexes from the gel during electrophoresis and subsequent characterization by AFM reveals differences in nanotube diameter, length and curvature. The results suggest that fractionation of nanotubes can be achieved by this procedure. We discuss factors affecting the mobility of the nanotube complexes and propose analytical applications of this technique.

Vetcher, Alexandre A.; Srinivasan, Srimeenakshi; Vetcher, Ivan A.; Abramov, Semen M.; Kozlov, Mikhail; Baughman, Ray H.; Levene, Stephen D.

2006-08-01

246

Evaluation of the dosimetric performance of BANG3? polymer gel  

Microsoft Academic Search

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

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

2005-01-01

247

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

248

Viscoelastic Properties of Vitreous Gel  

NASA Astrophysics Data System (ADS)

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

Pirouz Kavehpour, H.; Sharif-Kashani, Pooria

2010-11-01

249

New Developments in Sol-Gel Imaging.  

National Technical Information Service (NTIS)

This paper addresses the properties of sol-gel silica in relation to its potential to provide new devices for optical imaging. Although the sol-gel method opens the door to unprecedented levels of purity of silica materials, it is also beset with problems...

N. J. Phillips

1992-01-01

250

Halogen-bonding-triggered supramolecular gel formation.  

PubMed

Supramolecular gels are topical soft materials involving the reversible formation of fibrous aggregates using non-covalent interactions. There is significant interest in controlling the properties of such materials by the formation of multicomponent systems, which exhibit non-additive properties emerging from interaction of the components. The use of hydrogen bonding to assemble supramolecular gels in organic solvents is well established. In contrast, the use of halogen bonding to trigger supramolecular gel formation in a two-component gel ('co-gel') is essentially unexplored, and forms the basis for this study. Here, we show that halogen bonding between a pyridyl substituent in a bis(pyridyl urea) and 1,4-diiodotetrafluorobenzene brings about gelation, even in polar media such as aqueous methanol and aqueous dimethylsulfoxide. This demonstrates that halogen bonding is sufficiently strong to interfere with competing gel-inhibitory interactions and create a 'tipping point' in gel assembly. Using this concept, we have prepared a halogen bond donor bis(urea) gelator that forms co-gels with halogen bond acceptors. PMID:23247176

Meazza, Lorenzo; Foster, Jonathan A; Fucke, Katharina; Metrangolo, Pierangelo; Resnati, Giuseppe; Steed, Jonathan W

2013-01-01

251

Morphology and COâ 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% COâ 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

252

Effect of iron gel on dentin permeability.  

PubMed

This study evaluated in vitro the effect of an experimental gel containing iron on the reduction of hydraulic conductance of dentin. Thirty-six 1-mm-thick dentin discs obtained from extracted human third molars were divided into 3 groups of 10 specimens each. The groups corresponded to the following experimental materials: 1.23% acidulated phosphate fluoride gel, pH 4.1; 3% potassium oxalate gel, pH 4.1 (Oxa-Gel®); and iron sulfate gel (10 mmol/L FeSO4), pH 4.1. The gels were applied to dentin under the following conditions: after 37% phosphoric acid and before 6% citric acid. Data were analyzed statistically by ANOVA and Tukey's test at 5% significance level. There was no significant differences (p<0.05) among the groups in any of the conditions for hydraulic conductance reduction, except for smear layer presence. The active agents reduced dentin permeability, but they produced significantly lower (p<0.05) reduction in hydraulic conductance when compared to presence of smear layer. The effectiveness in reducing dentin permeability was not significantly different (p>0.05) among the gels. This study suggests that the iron gel promoted reduction in dentin permeability comparable to that of the other agents and thus may be considered a good clinical alternative for the treatment of dentin hypersensitivity. PMID:21915516

Sales-Peres, Sílvia Helena de Carvalho; Reinato, João Victor Donazan; Sales-Peres, André de Carvalho; Marsicano, Juliane Avansini

2011-01-01

253

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

254

Fundamentals of MRI measurements for gel dosimetry  

Microsoft Academic Search

In radiotherapy gel dosimetry a humanoid phantom is irradiated according to the planned treatment of a patient. This results in a three-dimensional dose distribution. In order to read-out the gel dosimeter phantom, magnetic resonance imaging (MRI) is often used. Due to specific disturbances both the spatial and the dose reliability can be compromised. It is essential that the measurement sequence

Y. DeDeene

2004-01-01

255

Chain Release Behavior of Gellan Gels  

NASA Astrophysics Data System (ADS)

The chain release behavior from gellan gels was studied by immersing the gel into water and monitoring the mass loss as a function of time. Concentration of released gellan in the external solution was determined for gels of different sizes using phenol-sulfuric acid method. The chain release process became faster with increasing total surface area and volume. However the concentration of released chain normalized by surface area and volume suggests that the chain release itself is governed not only by the ionic effect and the amount of unassociated chains in gel but other factors such as osmotic pressure may play an important role on the chain release from the gels. The diffusion coefficient was estimated from the chain release process which is in the same order of magnitude reported for an isolated gellan chain by light scattering. Rheological measurements also suggest that the unassociated gellan chains are released out when immersed in pure water while unassociated chains are restricted to release out when immersed in salt solution due to the intrusion of cations which is responsible for further association of the unassociated gellan chains being in agreement with the previously published results. The elastic modulus of gels was increased by immersion of gels in water and in salt solutions, which can be attributed as the stiffening of network chains due to gel swelling and the conversion from free and unassociated chains into network chains, respectively, leading to an increase in elastic modulus with time.

Hossain, Khandker S.; Nishinari, Katsuyoshi

256

Fast Dissolving Tablets of Aloe Vera Gel  

Microsoft Academic Search

Purpose : The objective of this work was to prepare and evaluate fast dissolving tablets of the nutraceutical, freeze dried Aloe vera gel. Methods: Fast dissolving tablets of the nutraceutical, freeze-dried Aloe vera gel, were prepared by dry granulation method. The tablets were evaluated for crushing strength, disintegration time, wetting time, friability, drug content and drug release. A 3 2

Jyotsana Madan; AK Sharma; Ramnik Singh

257

Polymers and Gels as Molecular Recognition Agents  

Microsoft Academic Search

Synthetic polymers and gels capable of molecular recognition are very useful in designing novel intelligent biomaterials. In this article we review the recent progress in both theoretical and experimental studies toward making heteropolymers and gels with biomimetic properties, specifically in relation to protein recognition. Knowledge obtained from protein-folding studies sheds much light on our understanding of the heteropolymer behavior. Consequently,

Nicholas A. Peppas; Yanbin Huang

2002-01-01

258

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, Yuan-Hsiang; Farquharson, Stuart; Kwon, Hueong-Chan; Shahriari, Mahmoud R.; Rainey, Petrie M.

1999-02-01

259

Photoswitchable gel assembly based on molecular recognition  

PubMed Central

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

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

2012-01-01

260

Mechanical properties of active polyacrylonitrile gels  

NASA Astrophysics Data System (ADS)

The ability of some polymeric gels to shrink and swell with changes in their environment makes them of interest in many applications such as artificial muscles and drug delivery systems. While much work has been done to study the behavior and properties of these gels, little information is available regarding the full constitutive description of the mechanical and actuation properties. This work is focused on developing constitutive descriptions of the mechanical properties of such gels, and to determine how these properties change due to changes in the environment. Since these gels can undergo finite elastic deformations, uniaxial tests do not provide sufficient property information and a combination of loading conditions must be used. A biaxial testing system has been developed to test thin sheets of these films, and includes the ability to monitor and change the environmental conditions around the specimen. Initial tests were performed on latex to determine the quality of the testing apparatus. Preliminary results on a polyacrylonitrile gel are presented.

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

1999-05-01

261

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

262

Polymer gel dosimetry using computed tomography  

NASA Astrophysics Data System (ADS)

Polymer gel dosimeter (PGD) is a type of integrating chemical dosimeter that, with the use of a suitable phantom, can be used for evaluation of the absorbed dose (dose distribution) deposited into a polymer gel by various irradiation modalities. Using suitable compounds of gel and appropriate parameters affecting the quality of the final image, evaluation using computed tomography (CT) should become a more advantageous alternative to magnetic resonance (MR), which is the most frequently applied method for the purposes of polymer gel dosimetry so far. In our work, several compositions of polymer gels (PG) were tested; evaluation was made via CT and MR, and values of dose and relative dose resolution were calculated. The optimal protocol for CT imaging and comparison of results from CT and MR are discussed.

Ornová, D.; Šemnická, J.; Sp?vá?ek, V.; Kon?ek, O.

2011-10-01

263

Method for quantitating cholesterol in subfractions of serum lipoproteins separated by gradient gel electrophoresis  

Microsoft Academic Search

Extensive heterogeneity in particle size distribution of serum lipoproteins of baboons was resolved by a procedure that combined\\u000a Sudan black B prestaining, polyacrylamide gradient gel electrophoresis (GGE), and quantitative densitometry. Each densitometric\\u000a scan represented a continuous distribution of the relative amount of cholesterol in a serum sample, as a function of the lipoprotein\\u000a particle size. For analytical purposes, each scan

M.-L. Cheng; C. M. Kammerer; W. F. Lowe; B. Dyke; J. L. VandeBerg

1988-01-01

264

Iron specificity of a biosensor based on fluorescent pyoverdin immobilized in sol-gel glass  

Microsoft Academic Search

Two current technologies used in biosensor development are very promising: 1. The sol-gel process of making microporous glass\\u000a at room temperature, and 2. Using a fluorescent compound that undergoes fluorescence quenching in response to a specific analyte.\\u000a These technologies have been combined to produce an iron biosensor. To optimize the iron (II or III) specificity of an iron\\u000a biosensor, pyoverdin

Michael F Yoder; William S Kisaalita

2011-01-01

265

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

266

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

267

Universal method for synthesis of artificial gel antibodies by the imprinting approach combined with a unique electrophoresis technique for detection of minute structural differences of proteins, viruses, and cells (bacteria): Ia. gel antibodies against proteins (transferrins).  

PubMed

Artificial antibodies in the form of gel granules were prepared by the molecular imprinting technique from the monomers acrylamide and N,N'-methylene-bis-acrylamide. Gel granules, freed from the selectively adsorbed protein (the antigen), are neutral and, accordingly, do not migrate in an electrical field. However, upon selective interaction with the antigen at a pH different from its pI, the granules become charged. The selectivity of the gel antibodies was studied by free zone electrophoresis in a tube with inside diameter larger than the size of the granules. Such electrophoretic analyses showed that gel antibodies against iron-free transferrin had a high selectivity for this protein, although some crossreaction took place with iron-saturated transferrin, indicating that these artificial antibodies can easily distinguish the minute differences in the 3-D structure of the transferrins. Analogously, gel antibodies against iron-saturated transferrin were highly selective for this protein with some crossreaction with iron-free transferrin. The mobilities of iron-free and iron-saturated transferrin are very similar, and, therefore, capillary free zone electrophoresis cannot distinguish between these structurally related proteins. However, significant differences in the mobilities of the selective gel granules can be observed depending on their interaction with iron-free or iron-saturated transferrin, i.e., the artificial gel antibodies may become powerful analytical tools. PMID:17305242

Takátsy, Anikó; Kilár, Anikó; Kilár, Ferenc; Hjertén, Stellan

2006-12-01

268

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

SciTech Connect

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

Yang, L.; Saavedra, S.S. [Univ. of Arizona, Tucson, AZ (United States)

1995-04-15

269

Parts per quadrillion level ultra-trace determination of polar and nonpolar compounds via solvent-free capillary microextraction on surface-bonded sol-gel polytetrahydrofuran coating and gas chromatography-flame ionization detection.  

PubMed

Sol-gel polytetrahydrofuran (poly-THF) coating was developed for high-sensitivity sample preconcentration by capillary microextraction (CME). Parts per quadrillion (ppq) level detection limits were achieved for both polar and nonpolar analytes through sample preconcentration on sol-gel poly-THF coated microextraction capillaries followed by gas chromatography (GC) analysis of the extracted compounds using a flame ionization detector (FID). The sol-gel coating was in situ created on the inner walls of a fused silica capillary using a sol solution containing poly-THF as an organic component, methyltrimethoxysilane (MTMOS) as a sol-gel precursor, trifluoroacetic acid (TFA, 5% water) as a sol-gel catalyst, and hexamethyldisilazane (HMDS) as a deactivating reagent. The sol solution was introduced into a hydrothermally-treated fused silica capillary and the sol-gel reactions were allowed to take place inside the capillary for 60 min. A wall-bonded coating was formed due to the condensation of silanol groups residing on the capillary inner surface with those on the sol-gel network fragments evolving in close vicinity of the capillary walls. Poly-THF is a medium polarity polymer, and was found to be effective in carrying out simultaneous extraction of both polar and nonpolar analytes. Efficient extraction of a wide range of trace analytes from aqueous samples was accomplished using sol-gel poly-THF coated fused silica capillaries for further analysis by GC. The test analytes included polycyclic aromatic hydrocarbons (PAHs), aldehydes, ketones, chlorophenols, and alcohols. To our knowledge, this is the first report on the use of a poly-THF based sol-gel material in analytical microextraction. Sol-gel poly-THF coated CME capillaries showed excellent solvent and thermal stability (>320 degrees C). PMID:15481455

Kabir, Abuzar; Hamlet, Christina; Malik, Abdul

2004-08-20

270

Electromechanical coupling in polyelectrolyte gels  

NASA Astrophysics Data System (ADS)

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

Prudnikova, Katsiaryna I.

271

Precorneal sampling techniques for ophthalmic gels.  

PubMed

Drug-cornea contact time is a critical issue in ocular drug delivery. Existing methods for its experimental determination are developed mainly for eye drops and ointments, and have not been reported for ophthalmic gels. The present study evaluated two tear film sampling techniques (capillary tubes and Schirmer strips) and one recovery technique (cotton swab) for their suitability for the determination of precorneal drug concentration as a function of time for ophthalmic gels. The study was conducted using the rabbit eye model, and the gel studied was a commercial polyacrylate-based gel containing pilocarpine HCl. The three techniques explored yield similar results with respect to drug-cornea contact time, about one hour for the gel studied. The strip method suffers from a gel-carry-over problem at the early time points; therefore it is not recommended for tear sampling until most of the gel is cleared from the cul-de-sac. Successful tear sampling was accomplished using capillary tubes. Drug concentration in the tear film as a function of time determined using this technique reveals not only the duration of contact between the drug and the cornea, but also demonstrates a nonuniform drug distribution in the tear film at the early time points (10 and 30 minutes). Finally the cotton swab technique is gentle, easy, and nondestructive. It recovers total drug remaining in the cul-de-sac but does not yield information for the tear film. PMID:1506756

Ding, S; Chen, C C; Salome-Kesslak, R; Tang-Liu, D D; Himmelstein, K J

1992-01-01

272

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

273

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

274

Perils of analytic continuation  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

275

The Laboratory Technology of Discrete Molecular Separation: The Historical Development of Gel Electrophoresis and the Material Epistemology of Biomolecular Science, 1945–1970  

Microsoft Academic Search

Preparative and analytical methods developed by separation scientists have played an important role in the history of molecular\\u000a biology. One such early method is gel electrophoresis, a technique that uses various types of gel as its supporting medium\\u000a to separate charged molecules based on size and other properties. Historians of science, however, have only recently begun\\u000a to pay closer attention

Howard Hsueh-Hao Chiang

2009-01-01

276

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

277

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

278

Analytical techniques for cell fractions  

SciTech Connect

Disposable microimmunoadsorbent columns containing Staphylococcus Protein A and monoclonal antibodies were used to bind antigenic proteins from a mixture. Eluates from these columns were directly analyzed by electrophoresis on two-dimensional (2-D) gels. In this way, biochemical and biophysical information on the bound antigen and on the specific antibody can be obtained simultaneously. The microimmunoadsorbents are easy to handle and in conjunction with multiple 2-D gel systems provide a means for screening large numbers of myeloma hybrids for specificity to antigens in complex mixtures.

Pearson, T.; Anderson, L.

1980-01-15

279

Analytical laboratory quality audits  

SciTech Connect

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

Kelley, William D.

2001-06-11

280

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

281

Role of Water in Densification of Gels.  

National Technical Information Service (NTIS)

The densification behavior of a gel-derived borosilicate glass was studied. Surface area, thermal gravimetric and infrared measurements were used to calculate the surface hydroxyl coverage as a function of time at several temperatures. Application of a vi...

T. A. Gallo C. J. Brinker L. C. Klein G. W. Scherer

1984-01-01

282

Mobility of microparticles in protein gel  

NASA Astrophysics Data System (ADS)

The hematite Fe2O3 submicron particles, 90 and 170 nm in diameter, exhibit bounded diffusion in water voids formed by gelatin networks in gel. Such particles occupy two different types of local states, distinguished by the microviscosity.

Fornal, Piotr; Stanek, Jan; Wilk, Alicja

2008-07-01

283

K-Basin gel formation studies  

SciTech Connect

A key part of the proposed waste treatment for K Basin sludge is the elimination of reactive uranium metal by dissolution in nitric acid (Fkirnent, 1998). It has been found (Delegard, 1998a) that upon nitric acid dissolution of the sludge, a gel sometimes forms. Gels are known to sometimes impair solid/liquid separation and/or material transfer. The purpose of the work reported here is to determine the cause(s) of the gel formation and to determine operating parameters for the sludge dissolution that avoid formation of gel. This work and related work were planned in (Fkunent, 1998), (Jewett, 1998) and (Beck, 1998a). This report describes the results of the tests in (Beck, 1998a) with non-radioactive surrogates.

Beck, M.A.

1998-07-23

284

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.

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

1996-01-01

285

Sol-gel deposited electrochromic coatings  

SciTech Connect

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

Ozer, N.; Lampert, C.M.

1995-06-01

286

PMMA - Impregnated Silica Gels: Synthesis and Characterization.  

National Technical Information Service (NTIS)

Shaped microporous silica has been prepared by a sol-gel process. The resulting silicas have 50% open porosity. The open porosity is filled by immersing the shapes in methyl methacrylate (MMA) and polymerizing with ultraviolet radiation. The fully impregn...

B. Abramoff L. C. Klein

1990-01-01

287

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

288

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

289

Cohesive gel naturally-shaped breast implants  

Microsoft Academic Search

According to the author, cohesive gel naturally-shaped breast implants provide particular benefits for patients who prefer retromammary implant placement. He discusses his experimence with these implants in 50 patients.

Richard Sadove

2003-01-01

290

Buckling Instability in Liquid Crystalline Physical Gels  

NASA Astrophysics Data System (ADS)

In a nematic gel we observe a low-energy buckling deformation arising from soft and semisoft elastic modes. We prepare the self-assembled gel by dissolving a coil side-group liquid-crystalline polymer coil copolymer in a nematic liquid crystal. The gel has long network strands and a precisely tailored structure, making it ideal for studying nematic rubber elasticity. Under polarized optical microscopy we observe a striped texture that forms when gels uniformly aligned at 35 °C are cooled to room temperature. We model the instability using the molecular theory of nematic rubber elasticity, and the theory correctly captures the change in pitch length with sample thickness and polymer concentration. This buckling instability is a clear example of a low-energy deformation that arises in materials where polymer network strains are coupled to the director orientation.

Verduzco, Rafael; Meng, Guangnan; Kornfield, Julia A.; Meyer, Robert B.

2006-04-01

291

Functional gels based on chemically modified graphenes.  

PubMed

Chemically modified graphene (CMG) materials have been extensively studied because of their unique structures, excellent properties, and potential applications in energy storage and conversion, catalysis, and environment remediation. However, the unique two-dimensional structure and amphiphilicity make CMG sheets easily restack into irregular aggregates, which greatly reduces their accessible surface area, and thereby deteriorates their performance in practical applications. To exploit their inherent properties fully, CMGs usually have to be fabricated or assembled into functional gels with desired three-dimensional (3D) interconnected porous microstructures. In this review, we summarize the recent achievements in the synthesis of CMG-based functional gels, including hydrogels, organogels, aerogels, and their composites. The mechanisms of gel formation and the applications of these functional gels will also be discussed. PMID:24659376

Li, Chun; Shi, Gaoquan

2014-06-01

292

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

293

Process ceramic fibers by Sol-Gel  

Microsoft Academic Search

The Sol-Gel process may transform the materials of construction chemical engineers make and use--thin films, fibers, and powders. The advantage of the Sol-Gel technology is the ability to produce high purity products at low temperatures. For example, silica film is used to passivate integrated circuits. To achieve this, the native silicon substrate now is oxidized at about 1,000C for a

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

1993-01-01

294

Annular gel reactor for chemical pattern formation  

DOEpatents

The present invention is directed to an annular gel reactor suitable for the production and observation of spatiotemporal patterns created during a chemical reaction. The apparatus comprises a vessel having at least a first and second chamber separated one from the other by an annular polymer gel layer (or other fine porous medium) which is inert to the materials to be reacted but capable of allowing diffusion of the chemicals into it.

Nosticzius, Zoltan (Budapest, HU) [Budapest, HU; Horsthemke, Werner (Austin, TX) [Austin, TX; McCormick, William D. (Austin, TX) [Austin, TX; Swinney, Harry L. (Austin, TX) [Austin, TX; Tam, Wing Y. (Austin, TX) [Austin, TX

1990-01-01

295

Sol-gel technology for biomedical engineering  

Microsoft Academic Search

Sol-gel derived silica possess many promising features, including low-temperature preparation procedure, porosity, chemical and physical stability. Applications exploiting porous materials to encapsulate sensor molecules, enzymes and many other compounds, are devel- oping rapidly. In this paper some potential applications, with emphasis on biomedical and environmental ones, are reviewed. The material preparation procedure is described and practical remarks on silica-based sol-gels

H. PODBIELSKA; A. ULATOWSKA-JAR

296

K-Basin gel formation studies  

Microsoft Academic Search

A key part of the proposed waste treatment for K Basin sludge is the elimination of reactive uranium metal by dissolution in nitric acid (Fkirnent, 1998). It has been found (Delegard, 1998a) that upon nitric acid dissolution of the sludge, a gel sometimes forms. Gels are known to sometimes impair solid\\/liquid separation and\\/or material transfer. The purpose of the work

Beck

1998-01-01

297

A Practical Use for FXG Gel Dosimetry  

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

298

Viscoelasticity of near-critical gels  

Microsoft Academic Search

Viscoelastic measurements on gels near the gel point show power-law frequency and time dependences. Using a percolation model, we find that viscoelastic properties are described by the universal exponent \\/Delta\\/= d\\/nu\\/\\/(d\\/nu\\/+k) where k is the viscosity exponent, \\/nu\\/ is the correlation-length exponent, and d is the dimension of space. This expression leads to a theory for the critical growth of

James Martin; Douglas Adolf; Jess Wilcoxon

1988-01-01

299

Magnetization transfer imaging for polymer gel dosimetry  

Microsoft Academic Search

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

M. Lepage; K. McMahon; G. J. Galloway; Y. DeDeene; S. Å. J. Bäck; C. Baldock

2002-01-01

300

Polymeric Gel Electrolytes for Electrochemical Capacitors  

Microsoft Academic Search

Three kinds of the polymer matrix, poly(ethylene oxide)-grafted polymethacrylate (PEO-PMA), poly(vinyldene fluoride) (PVdF) and poly(vinyldene-co-hexafluoropripylene) (PVdF-HFP), were used for gel preparation. A proper amount of organic salts or acids were dissolved in the polymer matrix together with organic plasticizers, dimethylformamide (DMF) and\\/or poly-(efhylene glycol)-dimethylether (PEGDE), without water. Thin films of the polymeric gel were obtained by either direct polymerization of

Masayuki Morita; Jin-Li Qiao; Naoki Ohsumi; Nobuko Yoshimoto; Minato Egashira

2006-01-01

301

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

302

A thermodynamic model of physical gels  

NASA Astrophysics Data System (ADS)

Physical gels are characterized by dynamic cross-links that are constantly created and broken, changing its state between solid and liquid under influence of environmental factors. This restructuring ability of physical gels makes them an important class of materials with many applications, such as in drug delivery. In this article, we present a thermodynamic model for physical gels that considers both the elastic properties of the network and the transient nature of the cross-links. The cross-links' reformation is captured through a connectivity tensor M at the microscopic level. The macroscopic quantities, such as the volume fraction of the monomer ?, number of monomers per cross-link s, and the number of cross-links per volume q, are defined by statistic averaging. A mean-field energy functional for the gel is constructed based on these variables. The equilibrium equations and the stress are obtained at the current state. We study the static thermodynamic properties of physical gels predicted by the model. We discuss the problems of un-constrained swelling and stress driven phase transitions of physical gels and describe the conditions under which these phenomena arise as functions of the bond activation energy Ea, polymer/solvent interaction parameter ?, and external stress p.

An, Yonghao; Solis, Francisco J.; Jiang, Hanqing

2010-12-01

303

Ultrasound increases flow through fibrin gels.  

PubMed

Ultrasound accelerates fibrinolysis in vitro and in animal models of thrombosis. Since transport of fibrinolytic enzymes into clots by permeation may be an important determinant of the rate of fibrinolysis, we examined the effect of ultrasound on permeation through fibrin gels in vitro. Gels of purified fibrin were prepared in plastic tubes, and the rate of pressure-mediated fluid permeation was measured. Exposure to 1 MHz ultrasound at 2 W/cm2 and a duty cycle of 5 msec on, 5 msec off resulted in a significant (p = .005) increase in flow through the gel of 29.0 +/- 4.2% (SEM). The ultrasound-induced flow increase was intensity-dependent, increasing from 17.0 +/- 1.2% at 1 W/cm2 to 30.1 +/- 1.9% at 2.3 W/cm2. Increased flow was not due to heating, detachment of fibrin from the tube wall or fragmentation of the gel resulting in channeling. However, degassing the fluid by autoclaving significantly reduced the ultrasound-induced increase in flow. We conclude that exposure of fibrin gels to ultrasound increases pressure-mediated permeation. This effect may be related to cavitation-induced changes in fibrin gel structure, and could contribute to the accelerated fibrinolysis observed in an ultrasound field. PMID:7667834

Siddiqi, F; Blinc, A; Braaten, J; Francis, C W

1995-03-01

304

Basic investigations on LCV micelle gel  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

305

Dynamics of surfactants spreading on gel layers  

NASA Astrophysics Data System (ADS)

Gel-like materials are of central importance to a large number of engineering, biological, biomedical and day-life applications. This work attempts to investigate the spreading of droplets of surfactant solutions on agar gels, which is accompanied by cracking of the gel layers. The cracking progresses via the formation of patterns that resemble ``starbursts,'' which have been reported recently in the literature by Daniels et al. Marangoni stresses generated by surface tension gradients between the surfactant droplet and the uncontaminated gel layer are identified to be the driving force behind these phenomena. The morphology and dynamics of the starburst patterns are investigated for droplets of different surfactant solutions, including sodiumdodecylsulphate, spreading on gel layers of different strengths. The instability is characterised in terms of the number of arms that form, and their mean width and length as a function of time. In addition, photoelasticity is used to provide information about the stress field of the material, which, combined with the results from our direct visualisation, can elucidate further the mechanisms underlying the pattern formation and the nature of the interactions between the liquid and the gel.

Spandagos, Constantine; Luckham, Paul; Matar, Omar

2009-11-01

306

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; Prévost, Sylvain; Noirez, Laurence; Gradzielski, Michael

2011-07-19

307

Thickening Capacity of Silica Gel in Plastic Lubricants.  

National Technical Information Service (NTIS)

The authors studied the influence of moisture, chemically and physically bound by silica gel, on (the) thickening capacity of the gel and on the stability of silica gel (Si) lubricants. The lubricants were prepared on silica gel specimens, etherified by b...

V. V. Vainshtok R. A. Levento M. B. Bakaleinikov

1970-01-01

308

Dynamic Performance Characterization of Bound, Porous Silica Gel Desiccant.  

National Technical Information Service (NTIS)

Drying of air with silica gel is a well established procedure. However, for the specific use of silica gel in a novel desiccant air conditioning system, which continually cools the silica gel and utilizes solar energy for silica gel regeneration, conventi...

M. Onischak D. Gidaspow S. Perkari T. Sasaki

1979-01-01

309

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

Callahan, L T

1976-01-01

310

Hexagonal phase based gel-emulsion (O/H1 gel-emulsion): formation and rheology.  

PubMed

The formation, stability, and rheological behavior of a hexagonal phase based gel-emulsion (O/H1 gel-emulsion) have been studied in water/C12EO8/hydrocarbon oil systems. A partial phase behavior study indicates that the oil nature has no effect on the phase sequences in the ternary phase diagram of water/C12EO8/oil systems but the domain size of the phases or the oil solubilization capacity considerably changes with oil nature. Excess oil is in equilibrium with the hexagonal phase (H1) in the ternary phase diagram in the H1+O region. The O/H1 gel-emulsion was prepared (formation) and kept at 25 degrees C to check stability. It has been found that the formation and stability of the O/H1 gel-emulsion depends on the oil nature. After 2 min observation (formation), the results show that short chain linear hydrocarbon oils (heptane, octane) are more apt to form a O/H1 gel-emulsion compared to long chain linear hydrocarbon oils (tetradecane, hexadecane), though the stability is not good enough in either system, that is, oil separates within 24 h. Nevertheless, the formation and stability of the O/H1 gel-emulsion is appreciably increased in squalane and liquid paraffin. It is surmised that the high transition temperature of the H1+O phase and the presence of a bicontinuous cubic phase (V1) might hamper the formation of a gel-emulsion. It has been pointed out that the solubilization of oil in the H1 phase could be related to emulsion stability. On the other hand, the oil nature has little or no effect on the formation and stability of a cubic phase based gel-emulsion (O/I1 gel-emulsion). From rheological measurements, it has found that the rheogram of the O/H1 gel-emulsion indicates gel-type structure and shows shear thinning behavior similar to the case of the O/I1 gel-emulsion. Rheological data infer that the O/I1 gel-emulsion is more viscous than the O/H1 gel-emulsion at room temperature but the O/H1 gel-emulsion shows consistency at elevated temperature. PMID:18847293

Alam, Mohammad Mydul; Aramaki, Kenji

2008-11-01

311

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

312

Development and characterization of molecularly imprinted sol-gel materials for the selective detection of DDT.  

PubMed

Molecularly imprinting sol-gel materials for DDT using both a noncovalent and a covalent approach was examined. A nonpolar porous sol-gel network was created through the use of the bridged polysilsesquioxane, bis-(trimethoxysilylethyl)benzene (BTEB), as the principal sol-gel component. Noncovalent molecular imprinting was deemed unsuccessful, presumably because of the lack of strong intermolecular interactions that can be established between the DDT and the sol-gel precursor. A covalent imprinting strategy was employed by generating a sacrificial spacer through the reaction of two 3-isocyanatopropyltriethoxysilanes with one of two different template molecules: 4,4'-ethylenedianiline (EDA) or 4,4'-ethylidenebisphenol (EBP). After formation of the sol-gel, the bonds linking the spacer template to the matrix were cleaved in a manner that generated a pocket of the appropriate size bordered by amine groups that could aid in the binding of DDT through weak hydrogen bonding interactions. Experiments indicated that DDT could be bound selectively by such an approch. To generate a sensor, an environmentally sensitive fluorescent probe, 7-nitrobenz-2-oxa-1,3-diazole, (NBD) located adjacent to the DDT binding site was used to transduce the binding of analyte. EDA-imprinted sol-gels, deposited as films on glass microscope slides, were shown to quantitatively detect DDT in water to a limit-of-detection of 50 ppt with a response time of <60 s. Repeat measurements could be made with the same sensing films after rinsing with acetone between each measurement. The EDA sensing material was selective for DDT and other structurally similar molecules. However, the sensing film design was limited by the relatively minor changes in fluorescence intensity upon binding DDT. This situation may be remedied by an alternative methodology that can facilitate attachment of the NBD fluorophore in an optimal position proximal to the binding pocket. PMID:11811423

Graham, Amy L; Carlson, Catherine A; Edmiston, Paul L

2002-01-15

313

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 CaCl2 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 CaCl2 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 CaCl2 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

314

Control of pore size distribution of silica gel through sol-gel process using inorganic salts and surfactants as additives  

Microsoft Academic Search

For control of the pore size distribution of silica gel, the gel was prepared using the sol-gel process modified by adding several kinds of inorganic salts and surfactants. The addition of any inorganic salt decreased the gel surface area and depressed the formation of mesopores. The surface area and the volume occupied by mesopores changed with the valency of the

Tadahiro Murakata; Shimio Sato; Takashi Ohgawara; Tetushi Watanabe; Tohru Suzuki

1992-01-01

315

Swelling kinetics of poly( N-isopropylacrylamide) gel  

Microsoft Academic Search

In many gel applications the swelling and shrinking kinetics are very important, e.g. in controlled\\/slow release, where the kinetics determine the rate of out-diffusion of the active component, and in gel extraction where the gel is swollen and shrunk several times. In this study swelling kinetics of poly(N-isopropylacrylamide) gel (NiPAAm gel) was determined by monitoring the swelling process using a

Matz Andersson; Anders Axelsson; Guido Zacchi

1998-01-01

316

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.

Gerard Muyzer; Kornelia Smalla

1998-01-01

317

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

318

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

319

Polymeric ionic liquid bucky gels as sorbent coatings for solid-phase microextraction.  

PubMed

Novel cross-linked polymeric ionic liquid (PIL) bucky gels were formed by free-radical polymerization of polymerizable ionic liquids gelled with multi-walled carbon nanotubes (MWCNT) and used as sorbent coatings for solid-phase microextraction (SPME). The combination of PIL with MWCNTs significantly enhanced the ?-? interaction between the sorbent coatings and the aromatic analytes. Compared to the neat PIL-based sorbent coating, the PIL bucky gel sorbent coatings demonstrated higher extraction efficiency for the extraction of polycyclic aromatic hydrocarbons (PAHs). A partitioning extraction mechanism was observed for the PIL/MWCNT-based sorbent coatings indicating that the addition of MWCNTs did not seem to affect the extraction mechanism of the sorbent coating. The analyte-to-coating partition coefficients (logKfs) were estimated and the limits of detection (LOD) for selected PIL bucky gel sorbent coating were determined to be in the range of 1-2.5 ng L(-1). Recovery studies were also performed for PAHs in river and tap water to validate the applicability of the developed method. PMID:24768123

Zhang, Cheng; Anderson, Jared L

2014-05-30

320

Trends in Analytical Scale Separations.  

ERIC Educational Resources Information Center

Discusses recent developments in the instrumentation and practice of analytical scale operations. Emphasizes detection devices and procedures in gas chromatography, liquid chromatography, electrophoresis, supercritical fluid chromatography, and field-flow fractionation. (JN)

Jorgenson, James W.

1984-01-01

321

International Behavior Analysis: Analytical Strategies.  

National Technical Information Service (NTIS)

The objective of the International Behavior Analysis (IBA) Project is to construct and analyze an analytical framework which can provide insight into the actions and interactions of certain states in certain situations. The Project's emphasis is comparati...

G. W. Hopple J. Wilkenfeld P. J. Rossa

1977-01-01

322

Analytical computation of the smear.  

National Technical Information Service (NTIS)

We explain an analytic computation of the map and the ''smear'' for a lattice composed of cells with random sextupole and octupole errors, as well as systematic chromatic sextupoles. Results are presented for the 60(degree) and 90(degree) lattices.

E. Forest

1986-01-01

323

Hollow Cathode Discharges: Analytical Applications.  

National Technical Information Service (NTIS)

The low pressure glow discharges considered in this paper are the hollow cathode (Paschen), and the flat cathode (Grimm). Both discharges have similar voltage--current characteristics which are responsible for their radiation stability. The analytical sam...

R. Mavrodineanu

1983-01-01

324

Laboratory Workhorse: The Analytical Balance.  

ERIC Educational Resources Information Center

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

Clark, Douglas W.

1979-01-01

325

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

326

Analytical Solutions for Heat Conduction.  

National Technical Information Service (NTIS)

Green's functions are found for steady state heat conduction in a composite rectangular parallelepiped (RPP) and in a composite right circular cylinder (RCC) assuming no contact resistance. These Green's functions may then be used to provide analytical so...

S. K. Fraley

1976-01-01

327

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

PubMed

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

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

1998-05-01

328

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

329

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

330

Structural Properties of Silk Electro-Gels  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

331

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.

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

2000-01-01

332

Speciation of protein-bound trace elements by gel electrophoresis and atomic spectrometry.  

PubMed

The metabolism of trace elements, in particular their binding to proteins in biological systems is of great importance in biochemical, toxicological, and pharmacological studies. As a result there has been a sustained interest over the last two decades in the speciation of protein-bound metals. Various analytical approaches have been employed, combining efficient separation of metalloproteins by liquid chromatography or electrophoresis with high-sensitivity elemental detection. Slab-gel electrophoresis (GE) is a key platform for high-resolution protein separation, and has been combined with autoradiography and various atomic spectrometric techniques for in-gel determination of protein-bound metals. Recently, the combination of GE with state-of-the-art inductively coupled plasma-mass spectrometry (ICP-MS), particularly when linked to laser ablation (LA) for direct gel interrogation, has opened up new opportunities for rapid characterization of metalloproteins. The use of GE and atomic spectrometry for the speciation of protein-bound trace elements is reviewed in this paper. Technical requirements for gel electrophoresis/atomic spectrometric measurement are considered in terms of method compatibilities, detection capability and potential usefulness. The literature is also surveyed to illustrate current status and future trends. PMID:15300764

Ma, Renli; McLeod, Cameron W; Tomlinson, Kerry; Poole, Robert K

2004-08-01

333

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

SciTech Connect

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

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

2007-07-27

334

Two-dimensional difference gel electrophoresis.  

PubMed

Two-dimensional difference gel electrophoresis (2D DIGE) is a modified form of 2D electrophoresis (2DE) that allows one to compare two or three protein samples simultaneously on the same gel. The proteins in each sample are covalently tagged with different color fluorescent dyes that are designed to have no effect on the relative migration of proteins during electrophoresis. Proteins that are common to the samples appear as "spots" with a fixed ratio of fluorescent signals, whereas proteins that differ between the samples have different fluorescence ratios. With the appropriate imaging system, difference gel electrophoresis (DIGE) is capable of reliably detecting as little as 0.2 fmol of protein, and protein differences down to ±15%, over a ?20,000-fold protein concentration range. DIGE combined with digital image analysis therefore greatly improves the statistical assessment of proteome variation. Here we describe a protocol for conducting DIGE experiments, which takes 2-3 days to complete. PMID:22585495

Minden, Jonathan S

2012-01-01

335

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

336

Interaction of Surfactants with Block Polyelectrolyte Gels  

NASA Astrophysics Data System (ADS)

We present SANS and rheology for poly(styrene)-poly(acrylic acid) polymers in aqueous solutions. These polymers self-assemble to form spherical micelles in aqueous solutions, and the micelles associate to create elastic, transparent gels at moderate polymer concentrations. The addition of cationic and anionic surfactants (DTAB and SDS) can be used to modify the associative interactions and solution rheology. Addition of an anionic surfactant acts to screen attractive interactions and causes a monotonic decrease in the elastic modulus. However, the addition of a cationic surfactant appears to initially induce a stronger intermicellar attraction, leading to gels with a higher elastic modulus. At higher surfactant concentrations, the cationic surfactant begins to screen intermicellar association, leading to a decrease in the strength of the gel.

Crichton, Mark; Bhatia, Surita

2002-03-01

337

Carboxyalkylation of chitosan in the gel state.  

PubMed

This study presents a new approach for direct carboxyalkylation of chitosan in the gel state by using aza-Michael addition and substitution reactions. Various reagents were applied including acrylic and crotonic acids, and ?-, ?-, ?-, ?-, and ?-halocarboxylic acids. The reaction of chitosan with ?- and ?-halocarboxylic acids showed no target product formation either in solution or in the gel state. In the case of acrylic, crotonic, ?- and ?-halocarboxylic acids, the reaction performed in the gel state (concentration of chitosan 20-40%) shows higher degree of substitution at lower reaction time and temperature than in diluted solutions (concentration of chitosan 0.5-2%). The results were discussed in terms of kinetics of the target and side reactions. (1)H and (13)C NMR confirmed that in all cases the carboxyalkylation of chitosan proceeds exclusively at the amino groups. PMID:22840055

Skorik, Yury A; Pestov, Alexander V; Kodess, Mikhail I; Yatluk, Yury G

2012-10-01

338

Crack buckling in soft gels under compression  

NASA Astrophysics Data System (ADS)

Recent interest in designing soft gels with high fracture toughness has called for simple and robust methods to test fracture behavior. The conventional method of applying tension to a gel sample suffers from a difficulty of sample gripping. In this paper, we study a possible fracture mechanism of soft gels under uni-axial compression. We show that the surfaces of a pre-existing crack, oriented parallel to the loading axis, can buckle at a critical compressive stress. This buckling instability can open the crack surfaces and create highly concentrated stress fields near the crack tip, which can lead to crack growth. We show that the onset of crack buckling can be deduced by a dimensional argument combined with an analysis to determine the critical compression needed to induce surface instabilities of an elastic half space. The critical compression for buckling was verified for a neo-Hookean material model using finite element simulations.

Long, Rong; Hui, Chung-Yuen

2012-08-01

339

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

340

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

341

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

342

Effective Management of FXG Gel Dosimetry  

NASA Astrophysics Data System (ADS)

The details of a calibration basis for the Fricke-xylenol orange-gelatin (FXG) gel dosimeter combined with the fast, easily accessible readout tool of cone beam optical computed tomography (CT) are described in this report. With proper controls in place, the results from a test intensity modulated radiation therapy (IMRT) treatment plan evaluation indicate that greater than 95% Low's gamma function agreement between plan and gel-measured dose using 3% dose and 3 mm distance-to-agreement criteria is achievable.

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

2010-11-01

343

Gel electrophoretic analysis of DNA branched junctions.  

PubMed

Gel electrophoresis has provided much of the detailed information we have about the properties of DNA junctions, stable branched molecules formed from oligonucleotide or polynucleotide strands. Here we review these applications, and present the results of an electrophoretic investigation of conformationally restricted junctions formed by covalently connecting two different pairs of strands in a junction with four arms. Native gel electrophoresis is employed to establish the formation and stoichiometry of the multistrand complexes. Ferguson analysis of native gel mobility shows that junctions have retardation coefficients that are distinct from those of linear DNA duplexes. Denaturing gel electrophoresis is the primary tool for characterizing junctions that have been covalently linked together to form both linear and macrocyclic oligomers of junctions (oligojunctions). Radioactively labelled strands enable one to monitor the progress of the ligation reaction: both linear and closed cyclic molecules result, and these can be distinguished by applying Ferguson analysis to denaturing gels. Combinations of exonuclease III, restriction enzymes and sequencing reactions have been applied to oligojunction molecules, and the results are all analyzed on denaturing gels. Junctions containing intramolecular "tethers" that restrict the conformation freedom of the complex comprise a new system for analyzing the conformations of branched molecules. In these tethered junctions, the ability of arms to move relative to each other is restricted substantially by covalently connecting pairs of arms in the original complex with short, flexible loops. The two tethers used here constrain the helical domains of the structure to be roughly parallel or anti-parallel. In this article, we use Ferguson analysis to compare two tethered junctions with an untethered junction. At high gel concentrations, the mobility of the untethered complex is found to be closer to that of the molecule tethered anti-parallel than to the one tethered parallel. Curvature in the Ferguson plots for all three of these junctions is detected over a range of compositions. At low gel concentrations, differences in electrophoretic mobility persist, suggesting that the untethered junction differs in charge as well as conformational freedom from the tethered analogs. We expect that studies of this kind will be able to define the conformational repertoire of junctions of different kinds, and to explore the effects of electrophoresis on these states. PMID:2548837

Seeman, N C; Chen, J H; Kallenbach, N R

1989-01-01

344

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

345

Electroactive polymer gels based on epoxy resin  

NASA Astrophysics Data System (ADS)

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

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

2007-04-01

346

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

347

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

348

Visual Analytic for Improving Human Terrain Understanding.  

National Technical Information Service (NTIS)

Visual analytics are a growing area of research within the Department of Defense that targets the effective interleaving of analytical reasoning with interactive interfaces. Capitalizing on the human capacity for spatial reasoning, visual analytics enhanc...

E. Heilman J. Richardson M. Mittrick T. Hanratty

2013-01-01

349

Binding of Ubiquitin Conjugates to Proteasomes as Visualized with Native Gels  

PubMed Central

Summary The proteasome is an ATP-dependent molecular machine that degrades proteins through the concerted activity of dozens of subunits. It is the yin to the ribosome’s yang, and together these entities mold the protein landscape of the cell. Native gels are generally superior to conventional and affinity purifications for the analytical resolution proteasomal variants, and have thus become a staple of proteasome work. Here we describe the technique of using native gels to observe proteasomes in complex with ubiquitin conjugates. We discuss the consequences of ubiquitin conjugate length and concentration on the migration of these complexes, the use of this mobility shift to evaluate the relative affinity of mutant proteasomes for ubiquitin conjugates, and the effects of deubiquitinating enzymes and competing ubiquitin binding proteins on the interactions of ubiquitin conjugates with the proteasome.

Elsasser, Suzanne; Shi, Yuan; Finley, Daniel

2013-01-01

350

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

351

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

352

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

353

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

354

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; Wätzig, H

2013-11-01

355

Synthesis of thermosensitive poly( N-alkylacrylamide) gels and core–shell type gels  

Microsoft Academic Search

When the poly(acrylic acid) (PAA) gel-1,8-diazabicyclo-[5,4,0]-7-undecene salt (DAA) was placed in N-methyl-2-pyrrolidone containing an excess of alkylamine and triphenylphosphine, selective amidation took place from the outside to give the corresponding poly(N-alkylacrylamide) gel containing a C3 alkyl chain through a DAA–poly(N-alkylacrylamide) type gel capsule consisting of a hydrophilic unreacted core part and an amidated shell layer. The amidation proceeded by a

Takashi Iizawa; Yoshinobu Matsuura; Yukio Onohara

2005-01-01

356

Steps in miniaturizing analytical systems  

NASA Astrophysics Data System (ADS)

The completion of the DNA sequence of several genomes, including the human one, has opened completely new scientific and technological frontiers. The huge amount of genetic information available requires the development of faster and cheaper analytical tools. This can be possible by miniaturising the analytical system itself and by the development of proper analytical procedures, involving fluidic processes. A precise genetic identifying technique is hybridization, that can be accomplished in an array format on very small bidimensional surfaces. In order to automate the fluidic process involved in the DNA hybridization, three micromachining techniques are approached by the authors team, for obtaining reservoirs with volumes ranging from 1nl to 2?l using different materials as polyimide, silicon and glass. Several configurations were proposed targeting a turbulence free fluid flow. A qualitatively fluid flow study was performed and the influence of the reservoir shape was revealed. One obtained device was tested in a Laser Induced Fluorescence detection set-up.

de Bellis, Gianluca; Caramenti, Giancarlo; Ilie, Mihaela; Cianci, Elena; Minotti, Antonio; Foglietti, Vittorio

2003-09-01

357

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

358

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

359

Preparation for Pouring an Agarose Gel  

NSDL National Science Digital Library

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

Hinkley, Craig

2013-06-25

360

Mobility of microparticles in protein gel  

Microsoft Academic Search

The hematite Fe2O3 submicron particles, 90 and 170 nm in diameter, exhibit bounded diffusion in water voids formed by gelatin networks in gel. Such particles occupy two different\\u000a types of local states, distinguished by the microviscosity.

Piotr Fornal; Jan Stanek; Alicja Wilk

2008-01-01

361

Mobility of microparticles in protein gel  

Microsoft Academic Search

The hematite Fe2O3 submicron particles, 90 and 170 nm in diameter, exhibit bounded diffusion in water voids formed by gelatin networks in gel. Such particles occupy two different\\u000a types of local states, distinguished by the microviscosity.

Piotr Fornal; Jan Stanek; Alicja Wilk

362

Thermochromic gels for control of insolation  

Microsoft Academic Search

Thermochromic gels consist of a mixture of water, gelling agent, and a polyether reaction compound. They show a drastic increase of scattering when a characteristic switching temperature is surpassed. The hemispherical transmission consequently decreases from about 90 to 50% for a 1-mm-thick layer sandwiched between two glass panes. The increase in scattering is caused by a dramatic increase in number

A. Beck; T. Hoffmann; W. Koerner; J. Fricke

1993-01-01

363

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

364

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

365

Lanes Detection in PCR Gel Electrophoresis Images  

Microsoft Academic Search

This study aims at development of methods to track the center of and detect lanes as the first step of automated tooì to analyze rose DNA using PCR gel electrophoresis images. Although several research results have been previously reported using projection profiles in a whole image, it is still challenge to track the center of and detect bent lanes using

Sang Cheol Park; In Seop Na; Soo Hyung Kim; Guee Sang Lee; Kang Han Oh; Jeong Hwan Kim; Tae Ho Han

2011-01-01

366

Thermosensitive sol-gel reversible hydrogels.  

PubMed

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 time, the process may provide various advantages over conventional hydrogels. Because of the simplicity of pharmaceutical formulation by solution mixing, biocompatibility with biological systems, and convenient administration, the pharmaceutical and biomedical uses of the water-based sol-gel transition include solubilization of low-molecular-weight hydrophobic drugs, controlled release, labile biomacromolecule delivery, such as proteins and genes, cell immobilization, and tissue engineering. When the formed gel is proven to be biocompatible and biodegradable, producing non-toxic degradation products, it will provide further benefits for in vivo applications where degradation is desired. It is timely to summarize the polymeric systems that undergo sol-gel transitions, particularly due to temperature, with emphasis on the underlying transition mechanisms and potential delivery aspects. This review stresses the polymeric systems of natural or modified natural polymers, N-isopropylacrylamide copolymers, poly(ethylene oxide)/poly(propylene oxide) block copolymers, and poly(ethylene glycol)/poly(D,L-lactide-co-glycolide) block copolymers. PMID:11755705

Jeong, Byeongmoon; Kim, Sung Wan; Bae, You Han

2002-01-17

367

The Genetic Science Learning Center: Gel Electrophoresis  

NSDL National Science Digital Library

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

2007-04-05

368

Viscoelasticity near the sol-gel transition  

Microsoft Academic Search

Measurements of viscoelastic properties near the sol-gel transition demonstrate that viscoelastic phenomena are described by power laws. To describe these phenomena, we derive the distribution of relaxation times for branched polymers, both in the reaction bath and in the dilute solution. From this spectrum we can compute viscoelastic properties such as the shear relaxation modulus G(t) and the complex shear

James E. Martin; Douglas Adolf; Jess P. Wilcoxon

1989-01-01

369

Gel Permeation Chromatography of Fluoroether Polymers  

NASA Technical Reports Server (NTRS)

A Method is described for determining the molecular weight distribution of fluorinated polymers by gel permeation chromatography. Porous silica-packed columns are used with Freon 113 as the chromatographic solvent. Fluoroether oligomers are used for column calibration in the molecular weight range of 1400 to 12000.

Korus, Roger A.; Rosser, Robert W.

1978-01-01

370

Dewatering fine coal slurries by gel extraction  

Microsoft Academic Search

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

S. H. Gehrke; Lii-Hurng. Lyu

1990-01-01

371

Photothermal densitometer for reading electrophoresis gels  

US Patent & Trademark Office Database

A densitometer apparatus for evaluating electrophoresis gel samples based on photothermal techniques. In accordance with this invention, electrophoresis gels are characterized by passing a heating light beam through the gel at a particular location. Light absorbed by the presence of staining dyes in that area causes heat evolution which generates a local index of refraction variation or a "thermal lens". A probe beam is passed through the sample in the area of the thermal lens a predetermined period of time after it is generated and the modification to the beam caused by the thermal lens is evaluated. For example, defocusing of the probe beam can be sensed by a detector which receives transmitted light through a limiting aperture. Various means of separating the heating and probe beams are disclosed, including use of separate lasers, crossed beams, modulation by plane of polarization, etc. One embodiment of this invention is particularly adapted for characterizing dry gels in which the heating beam is absorbed by the sample and the probe beam passes across the sample and is modified by a thermal lens generated in the air above the sample. Several embodiments are related to means for offsetting the probe beam from the heating beam for use with samples that are swept by the photothermal techniques in accordance with this invention offer advantages in terms of sensitivity over conventional transmission-type densitometers. These advantages enable increased sensitivity and facilitate the use of simplified staining techniques.

1990-07-03

372

Gel bead composition for metal adsorption  

DOEpatents

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

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

1990-01-01

373

Gel bead composition for metal adsorption  

DOEpatents

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

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

1991-01-01

374

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

375

Quantitative ultrasonic elastography for gel dosimetry.  

PubMed

Advanced radiation techniques such as intensity-modulated radiotherapy (IMRT) for complex geometries in which targets are close to organs at risk have been introduced in radiation therapy, creating a need for procedures that allow easy three-dimensional (3-D) measurement of dose for verification purposes. Polymer gels that change their material properties when irradiated have been suggested for such use. For example, the change in their magnetic properties has been thoroughly investigated with magnetic resonance imaging (MRI). Also, we have previously shown that the mechanical stiffness, i.e., Young's modulus, of these gels changes with dose. This finding prompted us to assess whether we can image a radiation-induced stiffness distribution with quantitative ultrasound elastography and whether the stiffness distribution is correlated with the dose distribution. A methacrylic-acid-based gel was loaded with scatterers to create an ultrasound echoic signal. It was irradiated to create a rod-like region of increased stiffness with a 10 x 10 mm(2) cross-section. The gel block was compressed in a frame that restricted the movement of the gel to planes orthogonal to the long axis of the irradiated region and ultrasonic echo data were acquired in the central plane during compression. This simplified irradiation pattern and experimental set-up were designed to approximate plane-strain conditions and was chosen for proof of concept. The movement of the gel was tracked from ultrasound images of a different compressional state using cross-correlation, enabling a displacement map to be created. The shear modulus was reconstructed using an inverse algorithm. The role of the magnitude of the regularization parameter in the inverse problem and the boundary conditions in influencing the spatial distribution of stiffness and, thus, final dose contrast was investigated through parametric studies. These parameters were adjusted using prior knowledge about the stiffness in parts of the material, e.g., the background was not irradiated and therefore its stiffness was homogeneous. It was observed that a suitable choice for these reconstruction parameters was essential for a quantitative application of stiffness measurement such as dosimetry. The dose contrast and distribution found with the optimal parameters were close to those obtained with MRI. Initial results reported in this article are encouraging and indicate that with ongoing refinement of ultrasound elastography techniques and accompanying inverse algorithms, this approach could play an important role in gel dosimetry. PMID:19945211

Crescenti, Remo A; Bamber, Jeffrey C; Oberai, Assad A; Barbone, Paul E; Richter, Joseph P; Rivas, Carlos; Bush, Nigel L; Webb, Steve

2010-02-01

376

Single Cell Analytics: An Overview  

Microsoft Academic Search

\\u000a \\u000a Abstract  The research field of single cell analysis is rapidly expanding, driven by developments in flow cytometry, microscopy, lab-on-a-chip\\u000a devices, and many other fields. The promises of these developments include deciphering cellular mechanisms and the quantification\\u000a of cell-to-cell differences, ideally with spatio-temporal resolution. However, these promises are challenging as the analytical\\u000a techniques have to cope with minute analyte amounts and concentrations.

Hendrik Kortmann; Lars M. Blank; Andreas Schmid

377

Optical trapping for analytical biotechnology.  

PubMed

We describe the exciting advances of using optical trapping in the field of analytical biotechnology. This technique has opened up opportunities to manipulate biological particles at the single cell or even at subcellular levels which has allowed an insight into the physical and chemical mechanisms of many biological processes. The ability of this technique to manipulate microparticles and measure pico-Newton forces has found several applications such as understanding the dynamics of biological macromolecules, cell-cell interactions and the micro-rheology of both cells and fluids. Furthermore we may probe and analyse the biological world when combining trapping with analytical techniques such as Raman spectroscopy and imaging. PMID:22154469

Ashok, Praveen C; Dholakia, Kishan

2012-02-01

378

(3-Mercaptopropyl)trimethoxysilane-derived Porous Gel Monolith via Thioacetal Reaction-Assisted Sol-Gel Route  

NASA Astrophysics Data System (ADS)

Porous gel monolith was synthesized by reacting (3-mercaptopropyl)trimethoxysilane (MPTMS) with acetone on acidic conditions. It is known that MPTMS itself is difficult to turn into gel on acidic conditions and instead oligomers are obtained owing to the large mercaptopropyl group. In our system, the gels were obtained since acetone worked as a cross-linker via thioacetal reaction. Additionally, Au ions were selectively adsorbed on the obtained gel. When an obtained white gel was soaked in a chloroauric acid solution, the gel turned brown and was getting dark depending on the soaked time; on the other hand, the color of the solution turned from yellow to colorless.

Ito, S.; Nishi, M.; Kanamori, K.; Nakanishi, K.; Kurahashi, T.; Matsubara, S.; Shimotsuma, Y.; Miura, K.; Hirao, K.

2011-10-01

379

Modification of micro-cantilever sensors with sol-gels to enhance performance and immobilize chemically selective phases  

Microsoft Academic Search

A chemical sensor based on the deflection of a surface modified silicon micro-cantilever is presented. A thin film of sol-gel was applied to one side of the micro-cantilever surface using a spin coating procedure. The sensor has been shown to give different responses to vapor phase analytes of varying chemical composition, as well as to varying concentrations of a given

Bryan C. Fagan; Christopher A. Tipple; Ziling Xue; Michael J. Sepaniak; Panos G. Datskos

2000-01-01

380

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

381

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

382

Structural Evolution During the Gel to Glass Conversion.  

National Technical Information Service (NTIS)

We have used differential scanning calorimetry (DSC) to quantitatively measure enthalpic changes which accompany gel densification and have related these changes to the evolving gel structure using Raman spectroscopy, gas adsorption, and thermal analysis....

C. J. Brinker E. P. Roth G. W. Scherer D. R. Tallant

1984-01-01

383

Silica scintillating materials prepared by sol-gel methods.  

National Technical Information Service (NTIS)

Silica was investigated as a rad-hard alternative to organic polymer hosts for organic scintillators. Silica sol-gels were prepared by hydrolysis of tetramethoxysilane in alcohol solutions. organic dyes were incorporated into the gels by dissolving in met...

D. W. Werst M. C. Sauer K. R. Cromack Y. Lin E. A. Tartakovsky

1993-01-01

384

Electroactive nonionic poly(vinyl alcohol) gel actuator  

NASA Astrophysics Data System (ADS)

A fast (0.8sec), large (>10%) and reversible deformation of Poly(vinyl alcohol) gel (PVA) swollen with dimethyl sulfoxide (DMSO) upon electric field was realized, and the maximum observed strain reached quite high 27% (DP2100). St-PVA gels were found to exhibit more stable and reversible deformation than at-PVA gels. Furthermore, we have studied the macroscopic structure of PVA/DMSO gels and its influence on their strain exhibition. Four differently structured PVA/DMSO gels, monolayer, circular, triple-layered and porous, were prepared. Monolayer gel exhibited the highly reproducible strain behavior. The mechanism of electric actuation of PVA/DMSO gel is proposed. Then a design of gel mechanical switch is shown, which exhibited the fast response to the electric field with a large, stable and reversible stretching deformation.

Popovic, Suzana; Xu, Chunye; Tamagawa, Hirohisa; Taya, Minoru

2001-07-01

385

Image noise in X-ray CT polymer gel dosimetry  

Microsoft Academic Search

This work investigates factors which affect image noise in CT polymer gel dosimetry, discusses techniques that can be used to further improve image noise and provides overall recommendations for the CT imaging of polymer gels.

M. Hilts; C. Duzenli

2004-01-01

386

Lipoprotein Agarose Gel Electrophoresis. Application in HDL-Cholesterol Methodology.  

National Technical Information Service (NTIS)

We perform agarose gel lipoprotein electrophoresis (AGLE) in this laboratory using glass microscope slides to support the agarose gel and 0.025 M barbital buffer for the electrophoresis. This report describes details, including special apparatus used to f...

E. L. Mosser D. A. Clark

1985-01-01

387

Structure and properties of resorcinol-formaldehyde gels.  

National Technical Information Service (NTIS)

The condensation polymerization of resorcinol and formaldehyde catalized by sodium carbonate produces a sol that aggregates to form a gel. Using viscometry the effect of temperature and catalyst concentration on the sol-gel transition was investigated. At...

S. A. Letts S. R. Buckley F. M. Kong E. F. Lindsey M. L. Sattler

1989-01-01

388

Vaginal Gel Might Prevent HIV Hours After Exposure  

MedlinePLUS

... please enable JavaScript. Vaginal Gel Might Prevent HIV Hours After Exposure Lab tests with monkeys look promising, ... from HIV, even if it is applied several hours after sex, animal research suggests. The antimicrobial gel ...

389

Electrophoresis for genotyping: microtiter array diagonal gel electrophoresis on horizontal polyacrylamide gels, hydrolink, or agarose.  

PubMed

Electrophoresis of DNA has been performed traditionally in either an agarose or acrylamide gel matrix. Considerable effort has been directed to improved quality agaroses capable of high resolution, but for small fragments, such as those from polymerase chain reaction (PCR) and post-PCR digests, acrylamide still offers the highest resolution. Although agarose gels can easily be prepared in an open-faced format to gain the conveniences of horizontal electrophoresis, acrylamide does not polymerize in the presence of air and the usual configurations for gel preparation lead to electrophoresis in the vertical dimension. We describe here a very simple device and method to prepare and manipulate horizontal polyacrylamide gels (H-PAGE). In addition, the open-faced horizontal arrangement enables loading of arrays of wells. Since many procedures are undertaken in standard 96-well microtiter plates, we have also designed a device which preserves the exact configuration of the 8 x 12 array and enables electrophoresis in tracks following a 71.6 degrees diagonal between wells (MADGE, microtiter array diagonal gel electrophoresis), using either acrylamide or agarose. This eliminates almost all of the staff time taken in setup, loading, and recordkeeping and offers high resolution for genotyping pattern recognition. The nature and size of the gels allow direct stacking of gels in one tank, so that a tank used typically to analyze 30-60 samples can readily be used to analyze 1000-2000 samples. The gels would also enable robotic loading. Electrophoresis allows analysis of size and charge, parameters inaccessible to liquid-phase methods: thus, genotyping size patterns, variable length repeats, and haplotypes is possible, as well as adaptability to typing of point variations using protocols which create a difference detectable by electrophoresis. PMID:7864363

Day, I N; Humphries, S E

1994-11-01

390

Thermoplastic elastomer gels. I. Effects of composition and processing on morphology and gel behavior  

Microsoft Academic Search

Thermoplastic elastomer gels (TPEGs) composed of a poly(styrene-b-(eth- ylene-co-butylene)-b-styrene) triblock copolymer and a low-volatility, midblock-compat- ible mineral oil have been investigated at different oil concentrations to ascertain the effect of composition on TPEG morphology and mechanical properties. The impact of thermal processing is also examined by comparing gels thermally quenched to 0°C or slowly cooled to ambient temperature. Transmission electron

Jonathan H. Laurer; James F. Mulling; Saad A. Khan; Richard J. Spontak; Rudy Bukovnik

1998-01-01

391

Sol-gel derived TiO[sub 2] microemulsion gels and coatings  

Microsoft Academic Search

Microemulsion gels and coatings have been obtained by the sol-gel method using titanium(IV) isopropoxide. Three types of fine water dispersions have been used as the basis sol: reverse Triton X-100 micelles in cyclohexane; quaternary water-in-oil microemulsions containing cyclohexane, 1-pentanol, sodium dodecyl sulfate, and water; and dispersions of water in pentanol in the presence of sodium dodecyl sulfate. Titanium(IV) isopropoxide was

D. Papoutsi; P. Lianos; P. Yianoulis; P. Koutsoukos

1994-01-01

392

Labor induction with intravaginal misoprostol versus intracervical prostaglandin E 2 gel (Prepidil gel): Randomized comparison  

Microsoft Academic Search

OBJECTIVE: Our purpose was to compare the safety and efficacy of intravaginal prostaglandin E1, misoprostol, with that of intracervical prostaglandin E2 (Prepidil gel) for labor induction.STUDY DESIGN: One hundred three patients with an indication for induction of labor were randomly assigned to induction with prostaglandin E1, 50 ?g intravaginally, or with Prepidil gel, 0.5 mg intracervically, every 4 hours until

Frank J. Chuck; B. Joyce Huffaker

1995-01-01

393

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

394

Pre-analytical factors affecting the results of laboratory blood analyses in farm animal veterinary diagnostics.  

PubMed

The quality of the laboratory diagnostic approach in farm animals can be severely affected by pre-analytical factors of variation. They induce increase/decrease of biochemical and hematological analyte concentrations and, as a consequence, they may cause unsuitable conclusions and decisions for animal health management and research projects. The pre-analytical period covers the preparation of sampling, the sampling procedure itself, as well as all specimen handling until the beginning of the specific laboratory analysis. Pre-analytical factors may have either an animal-related or a technique-related background. Animal-related factors cover daytime/season, meals/fasting, age, gender, altitude, drugs/anesthesia, physical exercise/stress or coinfection. Technique-related factors are the choice of the tube including serum v. plasma, effects of anticoagulants/gel separators, the anticoagulant/blood ratio, the blood collection procedure itself, specimen handling, contamination, labeling, storage and serum/plasma separation, transportation of the specimen, as well as sample preparation before analysis in the laboratory. It is essential to have proper knowledge about the importance and source of pre-analytical factors to alter the entire diagnostic process. Utmost efforts should be made to minimize controllable factors. Analytical results have to be evaluated with care considering that pre-analytical factors of variation are possible causes of misinterpretation. PMID:23031472

Humann-Ziehank, E; Ganter, M

2012-07-01

395

Analytic Theory of the Gyrotron.  

National Technical Information Service (NTIS)

An analytic theory is derived for a gyrotron operating in the linear gain regime. The gyrotron is a coherent source of microwave and millimeter wave radiation based on an electron beam emitting at cyclotron resonance (Omega) in a strong, uniform magnetic ...

P. J. Lentini

1989-01-01

396

Substituted hydroxylamines as analytical reagents.  

PubMed

The review deals with analytical applications of hydroxylamine derivatives. The defects of cupferron and versatility of N-benzoyl-N-phenylhydroxylamine in reaction with various metal ions is discussed. The application of the latter in chemical analysis is summarized and separation factors for some pairs of elements included. Suggestions for further use of this compound and other hydroxylamines are given. PMID:18960466

Shendrikar, A D

1969-01-01

397

An Overview of Learning Analytics  

ERIC Educational Resources Information Center

Learning analytics, the analysis and representation of data about learners in order to improve learning, is a new lens through which teachers can understand education. It is rooted in the dramatic increase in the quantity of data about learners and linked to management approaches that focus on quantitative metrics, which are sometimes antithetical…

Clow, Doug

2013-01-01

398

Analytical Electrochemistry: A Laboratory Manual  

NSDL National Science Digital Library

This labware module contains directions for seven experiments in analytical electrochemistry. The experiments are designed to illustrate fundamentals of electrode reactions as applied to readily accessible redox reactants. They provide insight to dynamic electrochemistry for scientists at all levels of training. Activation procedures to prepare glassy carbon electrodes are provided in a TechNote.

Kuwana, Theodore

2011-06-06

399

Analytical Sociology: A Bungean Appreciation  

ERIC Educational Resources Information Center

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…

Wan, Poe Yu-ze

2012-01-01

400

Analytical dynamics of multibody systems  

Microsoft Academic Search

The dynamic behavior of a three-dimensional open-tree system of rigid bodies connected by physical or geometric links is investigated analytically. A generalized Lagrangian formulation is derived in detail; the use of algebraic methods to check for the existence of first integrals is explained; and the implementation of the algorithm in a set of FORTRAN computer programs is outlined. Results for

Peter Maisser

1988-01-01

401

Analytical study for tube hydroforming  

Microsoft Academic Search

Recently, the tube hydroforming technology has been widely used in manufacturing the high-rigidity structural components in automotive industry. However, many failures like wrinkling, buckling, folding back, and bursting are frequently experienced during the tube hydroforming process under improper forming conditions. In this paper the analytical models are used to determine the forming limits for tube hydroforming process and demonstrate how

Sungtae Kim; Youngsuk Kim

2002-01-01

402

Molodensky's Series and Analytical Continuation.  

National Technical Information Service (NTIS)

It is shown that the Molodensky series solution and the solution of OSU Report 126, based on analytical continuation, are asymptotic series satisfying the basic equations in terms of which the problems are formulated. For the investigation of the second s...

H. Moritz

1970-01-01

403

Analytical Chemistry and the Microchip.  

ERIC Educational Resources Information Center

Analytical techniques used at various points in making microchips are described. They include: Fourier transform infrared spectrometry (silicon purity); optical emission spectroscopy (quantitative thin-film composition); X-ray photoelectron spectroscopy (chemical changes in thin films); wet chemistry, instrumental analysis (process chemicals);…

Lowry, Robert K.

1986-01-01

404

Visual Analytics Science and Technology  

SciTech Connect

It is an honor to welcome you to the first theme issue of information visualization (IVS) dedicated entirely to the study of visual analytics. It all started from the establishment of the U.S. Department of Homeland Security (DHS) sponsored National Visualization and Analytics Center™ (NVAC™) at the Pacific Northwest National Laboratory (PNNL) in 2004. In 2005, under the leadership of NVAC, a team of the world’s best and brightest multidisciplinary scholars coauthored its first research and development (R&D) agenda Illuminating the Path, which defines the study as “the science of analytical reasoning facilitated by interactive visual interfaces.” Among the most exciting, challenging, and educational events developed since then was the first IEEE Symposium on Visual Analytics Science and Technology (VAST) held in Baltimore, Maryland in October 2006. This theme issue features seven outstanding articles selected from the IEEE VAST proceedings and a commentary article contributed by Jim Thomas, the director of NVAC, on the status and progress of the center.

Wong, Pak C.

2007-03-01

405

Advanced analytics: opportunities and challenges  

Microsoft Academic Search

Purpose – Advanced analytics-driven data analyses allow enterprises to have a complete or “360 degrees” view of their operations and customers. The insight that they gain from such analyses is then used to direct, optimize, and automate their decision making to successfully achieve their organizational goals. Data, text, and web mining technologies are some of the key contributors to making

Ranjit Bose

2009-01-01

406

Rhyme Perception: Global or Analytical?  

ERIC Educational Resources Information Center

Preschool, kindergarten, and first-grade Brazilian children who performed well on an easy rhyme-categorization task were given a second such task that seemed to require some analytical ability to perform successfully. Results suggest that children's rhyme detection does not involve attention to word segments but a sensitivity to some sort of…

Cardosa-Martins, Claudia

1994-01-01

407

Numeric-analytical satellite theory  

Microsoft Academic Search

The numeric-analytical (NA) satellite theory is presented. The theory considers the perturbations of the motion of an artificial satellite caused by the following effects: the inhomogeneity of the gravity field of the primary planet; the gravity effects of other celestial bodoes; the Solar radiation pressure (with shadowing effect); and the air drag. The atmospheric density is described by a time-dependent

E. L. Akim; A. R. Golikov

1993-01-01

408

Analytical theory of Earth's rotation  

NASA Astrophysics Data System (ADS)

An analytical theory of the rotation of the rigid Earth is developed in a form compatible with the general planetary theory. Numerical estimates of the constants of integration of the Poisson equations, which are a particular case of the equations of the Earth’s rotation, are given.

Brumberg, V. A.; Ivanova, T. V.

2009-02-01

409

Serious Gaming for Predictive Analytics  

Microsoft Academic Search

We describe a methodology and architecture to support the development of games in a predictive analytics context. These games serve as part of an overall family of systems designed to gather input knowledge, calculate results of complex predictive technical and social models, and explore those results in an engaging fashion. The games provide an environment shaped and driven in part

Roderick M. Riensche; Patrick R. Paulson; Gary R. Danielson; Stephen D. Unwin; R. Scott Butner; Sarah M. Miller; Lyndsey R. Franklin; Nino Zuljevic

2009-01-01

410

Prenatal Virilization Associated with Paternal Testosterone Gel Therapy  

PubMed Central

Transdermal testosterone gels are used in the treatment of hypoandrogenism of males. Virilization due to exposure to testosterone gels has been reported in children resulting in a US Food and Drug Administration (FDA) warning about secondary exposure to these products. At present, we are unaware of prenatal virilization associated with unintentional testosterone gel exposure. We report prenatal virilization in a female infant due to secondary maternal exposure to the father's testosterone gel. We also describe postnatal virilization of the child's twin sister.

Patel, Anisha; Rivkees, Scott A.

2010-01-01

411

A multistimuli-responsive photochromic metal-organic gel.  

PubMed

A photochromic metal-organic gel with thermo-, photo-, and anion-responsive behavior is obtained. Unusually, heating of the Al-ligand solution leads to gel formation and cooling to room temperature reverses the process to reform the solution. The gel is sensitive to weakly coordinating anions. Additionally, reversible photochromic transformations take place both in the solution and gel states, accompanied by reversibly switched luminescence. PMID:24339174

Wei, Shi-Chao; Pan, Mei; Li, Kang; Wang, Sujuan; Zhang, Jianyong; Su, Cheng-Yong

2014-04-01

412

Gel-filled hollow fiber membranes for water softening  

Microsoft Academic Search

Three different gel-filled microporous poly(propylene) hollow fiber (HF) membranes were prepared by the incorporation of poly(4-vinylpyridinium salt) gels into the fiber walls. The gels were anchored in the pores of the membrane by cross-linking poly(4-vinylpyridine) with ?,??-dichloro-p-xylene, followed by quaternization using benzyl bromide. Different distributions of the gel were achieved by varying the preparation conditions. Energy dispersive X-ray (EDX) analysis

Sriram Suryanarayan; Alicja M. Mika; Ronald F. Childs

2006-01-01

413

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

414

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 50–90% water, and they can be regarded in many ways as multicomponent gels. Moreover, the cellular\\u000a structure of fruits and vegetables can be considered a “foam” with a closed-cell geometry, filled with gel. Gels are omnipresent,\\u000a and

Amos Nussinovitch; Ronit Zvitov

415

Electric field-induced deformation of polyelectrolyte gels  

SciTech Connect

Water-swollen polyelectrolyte gels deform in an electric field. We observed that the sign and magnitude of the deformation is dependent on the nature of the salt bath in which the gel is immersed and electrocuted. These results are compatible with a deformation mechanism based upon creation of ion density gradients by the field which, in turn, creates osmotic pressure gradients within the gel. A consistent interpretation results only if gel mobility is allowed as well as free ion diffusion and migration.

Adolf, D.; Hance, B.G.

1995-08-01

416

Reformulated tenofovir gel for use as a dual compartment microbicide  

PubMed Central

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

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

2012-01-01

417

Outlook for Visual Analytics Research Funding  

Microsoft Academic Search

Visual Analytics has become a rapidly growing field of study. It is also a field that is addressing very significant real world problems in homeland security, business analytics, emergency management, genetics and bioinformatics, investigative analysis, medical analytics, and other areas. For both these reasons, it is attracting new funding and will continue to do so in the future. Visual analytics

Jim Thomas; Daniel A. Keim; Joe Kielman; Larry Rosenblum

2007-01-01

418

Rapid extraction and structural characterization of biomolecules in agarose gels by laser desorption Fourier transform mass spectrometry  

SciTech Connect

A method originally developed for the extraction of biomolecules from agarose gel slices has been utilized as a rapid means of isolating biological compounds from gels for subsequent structural characterization by matrix-assisted laser desorption-ionization Fourier transform mass spectrometry (MALDI/FTMS). This [open quotes]freeze-squeeze[close quotes] extraction method involves pressure extrusion of fluid from frozen gel slices and provides near 50% recovery of analyte in less than 5 min. Experiments were directed at examining the recovery efficiency of the extraction method using [sup 14]C-labeled adenosine monophosphate and investigating the effect of high buffer concentrations on the laser desorption mass spectra. When coupled with this extraction technique, MALDI/FTMS can be used to detect and identify biomolecules at the low picomole level in agarose gel slices. The accurate mass measurements and MS/MS capabilities of the FTMS were exploited to provide detailed structural information at the isomeric level for oligonucleotides electrophoresed into agarose gels. 41 refs., 5 figs., 1 tab.

Dunphy, J.C.; Busch, K.L. (Georgia Inst. of Technology, Atlanta (United States)); Hettich, R.L.; Buchanan, M.V. (Oak Ridge National Lab., TN (United States))

1993-05-15

419

Low-cost, high-sensitivity laser-induced fluorescence detection for DNA sequencing by capillary gel electrophoresis.  

PubMed

A low cost, 0.75-mW helium neon laser, operating in the green region at 534.5 nm, is used to excite fluorescence from tetramethylrhodamine isothiocyanate-labelled DNA fragments that have been separated by capillary gel electrophoresis. The detection limit (3 sigma) for the dye is 500 ymol [1 yoctomole (1 ymol) = 10(-24) mol] or 300 analyte molecules in capillary zone electrophoresis; the detection limit for labeled primer separated by capillary gel electrophoresis is 2 zmol [1 zeptomole (1 zmol) = 10(-21) mol]. The Richardson-Tabor peak-height encoded sequencing technique is used to prepare DNA sequencing samples. In 6% T, 5% C acrylamide, 7 M urea gels, sequencing rates of 300 bases/hour are produced at an electric field strength of 200 V/cm; unfortunately, the data are plagued by compressions. These compressions are eliminated with addition of 20% formamide to the sequencing gel; the gel runs slowly and sequencing data are generated at a rate of about 70 bases/hour. PMID:1761625

Chen, D Y; Swerdlow, H P; Harke, H R; Zhang, J Z; Dovichi, N J

1991-10-18

420

Waste minimization in analytical methods  

SciTech Connect

The US Department of Energy (DOE) will require a large number of waste characterizations over a multi-year period to accomplish the Department`s goals in environmental restoration and waste management. Estimates vary, but two million analyses annually are expected. The waste generated by the analytical procedures used for characterizations is a significant source of new DOE waste. Success in reducing the volume of secondary waste and the costs of handling this waste would significantly decrease the overall cost of this DOE program. Selection of appropriate analytical methods depends on the intended use of the resultant data. It is not always necessary to use a high-powered analytical method, typically at higher cost, to obtain data needed to make decisions about waste management. Indeed, for samples taken from some heterogeneous systems, the meaning of high accuracy becomes clouded if the data generated are intended to measure a property of this system. Among the factors to be considered in selecting the analytical method are the lower limit of detection, accuracy, turnaround time, cost, reproducibility (precision), interferences, and simplicity. Occasionally, there must be tradeoffs among these factors to achieve the multiple goals of a characterization program. The purpose of the work described here is to add waste minimization to the list of characteristics to be considered. In this paper the authors present results of modifying analytical methods for waste characterization to reduce both the cost of analysis and volume of secondary wastes. Although tradeoffs may be required to minimize waste while still generating data of acceptable quality for the decision-making process, they have data demonstrating that wastes can be reduced in some cases without sacrificing accuracy or precision.

Green, D.W.; Smith, L.L.; Crain, J.S.; Boparai, A.S.; Kiely, J.T.; Yaeger, J.S. Schilling, J.B.

1995-05-01

421

Reuse of denaturing polyacrylamide gels for short tandem repeat analysis.  

PubMed

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

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

1998-11-01

422

MAGNETIC RESONANCE ELASTOGRAPHY OF GEL DOSIMETERS: PRELIMINARY STUDY  

Microsoft Academic Search

This preliminary work presents Magnetic Resonance Elastography (MRE) as a novel technique to evaluate the absorbed dose by gel dosimeters. We investigate the feasibility of using MRE to assess the changes of mechanical properties (shear stiffness) in irradiated polymer gel dosimeters and correlate them with the amount of radiation. Three phantoms were made using the 'MAGIC' polymer gel; two of

S. L. Vieira; Y. K. Mariappan; J. P. Fernandes; R. L. Ehman; M. Fatemi

423

The Biochemistry and Mechanics of Gastropod Adhesive Gels  

Microsoft Academic Search

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

Andrew M. Smith

424

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

425

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

426

Zirconium Molybdate Gel as a Generator for Technetium-99M.  

National Technical Information Service (NTIS)

A new sup(99m)Tc generator based on zirconium molybdate gel is described. Essentially the gel is a cation ion exchanger which permits the elution of the pertechnetate ion. The high molybdenum content of this gel, its stability under self-irradiation, and ...

J. V. Evans M. E. Shying

1984-01-01

427

Relationship Between Macroscopic and Microscopic Viscosities in Starch Gels  

Microsoft Academic Search

We investigated the relationship between the macroscopic viscosity lpar;?N ), determined by creep measurement, and the microscopic viscosity, estimated by rotational correlation time (?c) of spin label determined by ESR method, for wheat and potato starch gels. Both ?Nand ?c. Of wheat starch gel increased linearly with an increase of starch concentration. Both ?N and ?c of potato starch gel

Yoshimasa Yamano; Yuuichi Emori; Shoichi Gohtani

1996-01-01

428

Where does gel dosimetry fit in the clinic?  

Microsoft Academic Search

For over a decade our community has considered gel dosimetry a promising technique for the clinic, since it provides a unique methodology for three dimensionally dose measurement of the complex conformal dose distributions achieved by modern techniques such as Intensity Modulated Radiation Therapy. Even with improved gel dosimeters (such as normoxic polymer gel systems) and more accessible imaging for dose

L J Schreiner

2009-01-01

429

Internal calibration of gel dosimeters: A feasibility study  

NASA Astrophysics Data System (ADS)

In this work we test the feasibility of a new calibration method for gel dosimetry. We examine, through Monte Carlo modelling, whether the inclusion of an organic plastic scintillator system at key points within the gel phantom would perturb the dose map. Such a system would remove the requirement for a separate calibration gel, removing many sources of uncertainty.

Trapp, J. V.; Kairn, T.; Crowe, S.; Fielding, A.

2009-05-01

430

DTA and TGA characterization of sol-gel hydrotalcites  

Microsoft Academic Search

Double layered hydroxides with hydrotalcite structure were synthesized by the sol-gel precess using aluminum and magnesium alkoxides as precursors. The thermal decomposition of sol-gel hydrotalcites was studied by TGA and DTA methods. The sol-gel hydrotalcites show thermal stability up to 550 °C.

T. Lopez; E. Ramos; P. Bosch; M. Asomoza; R. Gomez

1997-01-01

431

Tuning of sol-gel derived PZT MEMS resonators  

NASA Astrophysics Data System (ADS)

This paper demonstrates the tunability of resonant frequencies for MEMS piezoelectric resonators acting in the d33 mode by experiment and theoretical analysis. Thin-film MEMS beams made by sol-gel PZT processing are first fabricated and tested to investigate the tuning capability. The three-layered interdigitated-electrode trapezoidal beams are then modeled by finite element analysis for validation. Beam curl and undercutting are also examined to present an alternative way of finding the stress gradient in comparison to Stoney's formula. The experimental and analytical results indicate that piezoelectric MEMS resonators have the ability to passively tune their resonant frequencies between open-circuit and short-circuit frequencies. Tuning of 0.2-0.6% is demonstrated experimentally, which compares with finite element predictions of 1.02-1.08%. Consideration is given to the reason for the differences in experimental percentages versus those predicted numerically, including the use of bulk PZT values in the ANSYS simulations, the undercut and curling effects of fabrication, and the low percentage of piezoelectric poling in the length direction.

Knight, Ryan R.; Frederick, Amanda A.; Mo, Changki; Clark, William W.

2010-12-01

432

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

Microsoft Academic Search

There is a need for stable gel materials for phantoms used to validate optical computerized tomography (CT) scanners used in conjunction with radiation-induced polymerizing gel dosimeters. Phantoms based on addition of light-absorbing dyes to gelatine to simulate gel dosimeters have been employed. However, to more accurately simulate polymerizing gels one requires phantoms that employ light-scattering colloidal suspensions added to the

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

2007-01-01

433

Preparation of transparent non-crystalline stoichiometric magnesium aluminate gel-monolith by the sol-gel process  

Microsoft Academic Search

Transparent non-crystalline stoichiometric magnesium aluminate gel-monolith was prepared by chemical polymerization reaction between aluminium alkoxide and magnesium salt. The reaction mechanisms of gel formation are discussed. The ovendried gel was freed from residual organics by chemical treatment with hydrogen peroxide solution. X-ray analysis of organic-free gel powder after heat treatment for 4h at 2000‡ C did not show any indication

J. C. Debsikdar

1985-01-01

434

Simultaneous determination of catecholamines and serotonin by liquid chromatography, after treatment with boric acid gel.  

PubMed

We describe a liquid-chromatographic method for simultaneously determining norepinephrine, epinephrine, dopamine, and serotonin in 0.5 mL of human plasma. These analytes are purified on boric acid gel from Aldrich, separated on a reversed-phase C18 column, and detected electrochemically at +600 mV. Absolute recoveries of internal standards were 84% for 3,4-dihydroxybenzylamine and 57% for N-methylserotonin. Reproducibility was good to excellent, depending on the concentration of the analytes. A chromatographic run is complete in 40 min, but this can be shortened by about half when the determination of only serotonin is required, by increasing the column temperature from 40 degrees C to 60 degrees C. PMID:3349603

Imai, Y; Ito, S; Maruta, K; Fujita, K

1988-03-01

435

Application of sol-gel and gel-precipitation technology to the preparation of spheres of lithium aluminate.  

National Technical Information Service (NTIS)

A concept for preparing spheres of lithium aluminate by either a sol-gel or gel-precipitation process based on the precipitation of a lithium salt in the pores of an aluminum hydroxide gel has been tested and has proved to be not feasible. The addition of...

C. W. Turner B. C. Clatworthy

1988-01-01

436

High-resolution gel dosimetry of a HDR brachytherapy source using normoxic polymer gel dosimeters: Preliminary study  

Microsoft Academic Search

Polymer gel dosimetry has been shown to be an effective tool in the analysis of radiotherapy treatments in cancer therapy, being used to map the dose distribution around an irradiation pattern of a polymer gel dosimeter. Combined with high-resolution magnetic resonance imaging (MRI), polymer gel dosimetry can be an effective dosimetry tool to map dose distributions with high spatial resolution

C. Hurley; C. McLucas; G. Pedrazzini; C. Baldock

2006-01-01

437

Detection of serum proteins by native polyacrylamide gel electrophoresis using Blue Sepharose CL6B-containing stacking gels  

Microsoft Academic Search

Analysis of serum proteins by native polyacrylamide gel electrophoresis is difficult because albumin is abundant in serum and interferes with the resolution of other proteins, especially ?-antitrypsin which has mobility that is very similar to that of albumin. We present here a method in which serum proteins are separated by polyacrylamide gel electrophoresis using stacking gels containing Blue Sepharose CL-6B,

Haruhiro Muratsubaki; Kaoru Satake; Yasuhisa Yamamoto; Keiichiro Enomoto

2002-01-01

438

Innovative materials based on sol gel technology  

NASA Astrophysics Data System (ADS)

We review the sol-gel based new materials which were prepared in our laboratory including: tunable lasers, active waveguides, luminescent solar concentrators, electrochromic, photochromic and gasochromic plates for smart windows, chemical and biological sensors, semiconductor quantum dots and complexes of rare earth ions. In this paper we present the firstly obtained results of the Eu sulfide nanocrystalline (NCs) powder material and doped in the sol-gel based zirconia films. The powder and films were studied by high resolution transmittance electron microscopy (HRTEM), energy dispersive X-ray spectroscopy analysis (EDS) and luminescence spectroscopy. Eu sulfide nanocrystals (NCs) ranging between 8 and 10 nm were obtained as powder and 3-4 nm incorporated in zirconia film.

Reisfeld, Renata; Saraidarov, Tsiala

2006-01-01

439

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

440

Ballistic penetration of Perma-Gel  

NASA Astrophysics Data System (ADS)

In this study a number of experiments were performed by taking high-speed footage of the firing spherical steel bullets at different speeds into Perma-Gel, a new synthetic thermoplastic material touted to exhibit similar properties to ordnance ballistic gelatin. We found that the gel undergoes very large and recoverable elastic deformations, which could strongly affect the dynamics of the temporary cavity formed behind the projectile. As with ordnance ballistic gelatin, the diameter of the temporary cavity can be many times the diameter of the projectile, in contrast with that of the permanent cavity which is several times smaller.We also observed that the closure of the cavity chokes the air inside, which could affect its dynamics in noticeable ways. Finally, one of the experiments suggest that the precise model of material failure may not be important to determine the dynamics of the temporary cavity.

Ryckman, Raymond Albert; Powell, David Arthur; Lew, Adrian

2012-03-01

441

Freezing D2O clay gels.  

PubMed

To obtain the T1 surface value in smectites/D2O diluted suspensions or gels, as was obtained on a monolayer deuterated clay, we freeze them. The broad Pake's doublets similar to ice doublets and with the same T1 show that we can separate frozen from unfrozen D2O. The latter exhibits a narrower line and a single T1 and is attributed to the liquid surface water layer in rapid exchange with the nearby supercooled water, the quantity of which diminishes with the lowering of the temperature depending on the gel porosity. It is possible to measure the supercooled water quantity and to correct the T1 measured values to extract the T1 surface. The value extrapolated at room temperature allows the complete clay surface area measurement. The example of a montmorillonite is given and a comparison with laponite is made. PMID:9803898

Letellier, M

1998-01-01

442

Dynamics of colloidal glasses and gels.  

PubMed

Many household and industrially important soft colloidal materials, such as pastes, concentrated suspensions and emulsions, foams, slurries, inks, and paints, are very viscous and do not flow over practical timescales until sufficient stress is applied. This behavior originates from restricted mobility of the constituents arrested in disordered structures of varying length scales, termed colloidal glasses and gels. Usually these materials are thermodynamically out of equilibrium, which induces a time-dependent evolution of the structure and the properties. This review presents an overview of the rheological behavior of this class of materials. We discuss the experimental observations and theoretical developments regarding the microstructure of these materials, emphasizing the complex coupling between the deformation field and nonequilibrium structures in colloidal glasses and gels, which leads to a rich array of rheological behaviors with profound implications for various industrial processes and products. PMID:24655137

Joshi, Yogesh M

2014-01-01

443

NOTE: Uncertainty analysis in polymer gel dosimetry  

NASA Astrophysics Data System (ADS)

Verification of advanced radiotherapy treatment modalities requires measurement of three-dimensional absorbed dose distributions with high spatial resolution and precision. Polymer gel dosimeters combined with magnetic resonance imaging may be able to fulfil this requirement. However, verification requires that the uncertainty in the dosimeter is well known. One method of estimating the overall uncertainty in polymer gel dosimeters involves the propagation of the uncertainty in the R2 (nuclear magnetic resonance relaxation rate) map and the uncertainties in the calibration data. This work shows that using this method with current data suggests that the lowest uncertainty currently obtainable is about 3% at 8 Gy and 7% at 2 Gy. Furthermore, the most significant reductions in overall uncertainty will be achieved by reducing the noise in the R2 map.

Baldock, C.; Murry, P.; Kron, T.

1999-11-01

444

Uncertainty analysis in polymer gel dosimetry.  

PubMed

Verification of advanced radiotherapy treatment modalities requires measurement of three-dimensional absorbed dose distributions with high spatial resolution and precision. Polymer gel dosimeters combined with magnetic resonance imaging may be able to fulfil this requirement. However, verification requires that the uncertainty in the dosimeter is well known. One method of estimating the overall uncertainty in polymer gel dosimeters involves the propagation of the uncertainty in the R2 (nuclear magnetic resonance relaxation rate) map and the uncertainties in the calibration data. This work shows that using this method with current data suggests that the lowest uncertainty currently obtainable is about 3% at 8 Gy and 7% at 2 Gy. Furthermore, the most significant reductions in overall uncertainty will be achieved by reducing the noise in the R2 map. PMID:10588291

Baldock, C; Murry, P; Kron, T

1999-11-01

445

Polymeric Gel Electrolytes for Electrochemical Capacitors  

NASA Astrophysics Data System (ADS)

Three kinds of the polymer matrix, poly(ethylene oxide)-grafted polymethacrylate (PEO-PMA), poly(vinyldene fluoride) (PVdF) and poly(vinyldene-co-hexafluoropripylene) (PVdF-HFP), were used for gel preparation. A proper amount of organic salts or acids were dissolved in the polymer matrix together with organic plasticizers, dimethylformamide (DMF) and/or poly-(efhylene glycol)-dimethylether (PEGDE), without water. Thin films of the polymeric gel were obtained by either direct polymerization of the mixed monomer solution or a thermal casting method. The composition of the polymer-electrolyte complex system is optimized to obtain good capacitor performances of the electrochemical capacitor (ECC) system.

Morita, Masayuki; Qiao, Jin-Li; Ohsumi, Naoki; Yoshimoto, Nobuko; Egashira, Minato

2006-06-01

446

Molecular recognition in gels, monolayers, and solids  

NASA Astrophysics Data System (ADS)

This paper describes work in four areas: affinity electrophoresis of carbonic anhydrase in cross-linked polyacrylamide derived gels containing immobilized derivatives of aryl sulfonamides; inhibition of the hemagglutination of erythrocytes induced by influenza virus using water-soluble polyacrylamides bearing sialic acid groups; the application of self-assembled monolayers (SAMs) of alkyl thiolates on gold to the study of protein adsorption on organic surfaces; and the use of networks of hydrogen bonds to generate new classes of non-covalently assembled organic materials, both in solution and in crystals. This paper summarizes research in two areas of molecular recognition: affinity polymers and molecular self assembly. We illustrate these areas by examples drawn from affinity gel electrophoresis, soluble synthetic macromolecular inhibitors of binding of influenza virus to erythrocytes protein adsorption on self assembled monolayers and self assembling hydrogen bonded molecular aggregates.

Prime, Kevin L.; Chu, Yen-Ho; Schmid, Walther; Seto, Christopher T.; Chen, James K.

1991-12-01

447

Gels of DNA nanostars never crystallize.  

PubMed

Using state-of-the-art numerical techniques, we show that, upon lowering the temperature, tetravalent DNA nanostars form a thermodynamically stable, fully bonded equilibrium gel. In contrast to atomic and molecular network formers, in which the disordered liquid is always metastable with respect to some crystalline phase, we find that the DNA nanostar gel has a lower free energy than the diamond crystal structure in a wide range of concentrations. This unconventional behavior, here verified for the first time in a realistic model, arises from the large arm flexibility of the DNA nanostars, a property that can be tuned by design. Our results confirm the thermodynamic stability of the recently experimentally realized DNA hydrogels. PMID:24646041

Rovigatti, Lorenzo; Smallenburg, Frank; Romano, Flavio; Sciortino, Francesco

2014-04-22

448

Surface tension-induced gel fracture. Part 1. Fracture of agar gels.  

PubMed

This work involves an experimental investigation of the spreading of liquids on gel layers in the presence of surfactants. Of primary interest is the instability that accompanies the cracking of gels through the deposition and subsequent spreading of a drop of surfactant solution on their surfaces. This instability manifests itself via the shaping of crack-like spreading "arms", in formations that resemble starbursts. The main aim of this study is to elucidate the complex interactions between spreading surfactants and underlying gels and to achieve a fundamental understanding of the mechanism behind the observed phenomenon of the cracking pattern formation. By spreading SDS and Silwet L-77 surfactant solutions on the surfaces of agar gels, the different ways that system parameters such as the surfactant chemistry and concentration and the gel strength can affect the morphology and dynamics of the starburst patterns are explored. The crack propagation dynamics is fitted to a power law by measuring the temporal evolution of the length of the spreading arms that form each one of the observed patterns. The values of the exponent of the power law are within the predicted limits for Marangoni-driven spreading on thick layers. Therefore, Marangoni stresses, induced by surface tension gradients between the spreading surfactant and the underlying gel layer, are identified to be the main driving force behind these phenomena, whereas gravitational forces were also found to play an important role. A mechanism that involves the "unzipping" of the gel in a manner perpendicular to the direction of the largest surface tension gradient is proposed. This mechanism highlights the important role of the width of the arms in the process; it is demonstrated that a cracking pattern is formed only within the experimental conditions that allow S/?w to be greater than G', where S is the spreading coefficient, ?w is the change in the width of the crack, and G' is the storage modulus of the substrate. PMID:22512657

Spandagos, Constantinos; Goudoulas, Thomas B; Luckham, Paul F; Matar, Omar K

2012-05-01

449

Silver staining of 2D electrophoresis gels.  

PubMed

Silver staining is used to detect proteins after electrophoretic separation on polyacrylamide gels. It -combines excellent sensitivity (in the low nanogram range) with the use of very simple and cheap equipment and chemicals. For its use in proteomics, two important additional features must be considered, compatibility with mass spectrometry and quantitative response. Both features are discussed in this chapter, and optimized silver staining protocols are proposed. PMID:22665294

Rabilloud, Thierry

2012-01-01

450

Sol-gel preparation of nanostructured adsorbents  

Microsoft Academic Search

This paper reports sol-gel synthesis and properties of several major ceramic adsorbents. Nanostructured y-alumina, zirconia and titania adsorbents with uniform pore size distribution and an average pore diameter of about 3 nm are prepared by hydrolysis and condensation of corresponding metalorganic precursors. The as-synthesized adsorbents are in their meta-stable phases, and transform to their stable phases upon heat-treatment. The phase

Y. S. Lin; S. G. Deng

1999-01-01

451

Activity staining of endoglucanases in polyacrylamide gels.  

PubMed

The endoglucanases of Penicillium funiculosum were analyzed for the presence of multiple forms using a modified version of the Congo red method. Postelectrophoretic slab gels were directly incubated in a solution of carboxymethylcellulose for a period as short as 15 min and then the activities were visualized by staining with Congo red. Ten distinct bands of clearances were obtained indicating the presence of at least as many multiple forms. PMID:1280921

Mathew, R; Rao, K K

1992-10-01

452

Human serum protein fractionation by gel filtration  

PubMed Central

The development of a quantitative immunological technique using polyvalent antiserum permits a more logical approach to the fractionation of complex protein mixtures. In this study whole serum was separated by conventional gel filtration and the fractions obtained were analysed. This demonstrates over 60 immunologically distinct serum proteins. Because the current terminology is inadequate to describe this number of proteins, a temporary numerical nomenclature has been used. ImagesPLATE 4PLATE 5PLATE 1PLATE 2PLATE 3

Freeman, T.; Smith, J.

1970-01-01

453

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

454

'Laterally aggregated' polyacrylamide gels for electrophoresis.  

PubMed

A new method is described for producing highly porous polyacrylamide matrices: polymerization in presence of a preformed hydrophilic polymer. If a standard mixture of monomers (e.g., 5%T, 4%C) is polymerized in presence of, e.g., polyethylene glycol (PEG) 10 kDa, lateral chain aggregation occurs, with formation of large pore sizes. In PEG 10 kDa, the transition from a small- to a large-pore gel is clearly apparent at 0.5% PEG addition and reaches a plateau already at 2.5% PEG. Even with shorter PEG fragments (6.2 and 1 kDa) this transition occurs, but with progressively larger amounts of PEG in solution (up to 25% for the 1 kDa species). Other polymers such as hydroxymethyl cellulose (1000 kDa) and polyvinyl-pyrrolidone (360 kDa and 25 kDa) are also able to elicit this phenomenon. It appears that lateral chain aggregation (before the cross-linking event) is induced via intra-chain hydrogen bonding, since urea and temperature strongly inhibit it, whereas tetramethylurea (an agent quenching hydrophobic interactions) does not hamper it. By scanning electron microscope, it is found that the maximum pore size obtained in a 5%T, 4%C gel in presence of 2.5% PEG 10 kDA is of the order of 0.5 micron, whereas the same 5%T, 4%C control gel would have an average pore diameter of 5 nm. Thus, an increment of pore size of about 2 orders of magnitude is obtained: in these new matrices, a 21000 bp DNA fragment exhibits a much greater migration than in a control gel in which the sample is entrapped at the application site. PMID:1459071

Righetti, P G; Caglio, S; Saracchi, M; Quaroni, S

1992-01-01

455

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

Frédéric Fages

456

Quantitative Ultrasonic Elastography for Gel Dosimetry  

Microsoft Academic Search

Advanced radiation techniques such as intensity-modulated radiotherapy (IMRT) for complex geometries in which targets are close to organs at risk have been introduced in radiation therapy, creating a need for procedures that allow easy three-dimensional (3-D) measurement of dose for verification purposes. Polymer gels that change their material properties when irradiated have been suggested for such use. For example, the

Remo A. Crescenti; Jeffrey C. Bamber; Assad A. Oberai; Paul E. Barbone; Joseph P. Richter; Carlos Rivas; Nigel L. Bush; Steve Webb

2010-01-01

457