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Challenges for the modern analytical ultracentrifuge analysis of polysaccharides  

Microsoft Academic Search

This article reviews some of the recent advances in analytical ultracentrifugation and how these advances have impacted—and can impact—on our understanding of the size, shape through conformation modelling, interactions and charge properties of polysaccharides in solution, particularly when used in combination with other solution techniques and also imaging techniques. Specifically we look at (1) polysaccharide polydispersity and simple shape analysis

Stephen E. Harding



Improved measurement of the rotor temperature in analytical ultracentrifugation.  


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

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



Analytical Ultracentrifugation as a Tool for Studying Protein Interactions  

PubMed Central

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



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


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

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



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


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

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



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

PubMed Central

Analytical ultracentrifugation allows one to measure in real-time the concentration gradients arising from the application of a centrifugal force to macromolecular mixtures in solution. In the last decade, the ability to efficiently solve the partial differential equation governing the ultracentrifugal sedimentation and diffusion process, the Lamm equation, has spawned significant progress in the application of sedimentation velocity analytical ultracentrifugation for the study of biological macromolecules, for example, the characterization of protein oligomeric states and the study of reversible multi-protein complexes in solution. The present work describes a numerical algorithm that can provide an improvement in accuracy or efficiency over existing algorithms by more than one order of magnitude, and thereby greatly facilitate the practical application of sedimentation velocity analysis, in particular, for the study of multi-component macromolecular mixtures. It is implemented in the public domain software SEDFIT for the analysis of experimental data. PMID:18196178

Brown, Patrick H.; Schuck, Peter



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. PMID:21654635

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



Recorded Scan Times Can Limit the Accuracy of Sedimentation Coefficients in Analytical Ultracentrifugation  

PubMed Central

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 at present 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 two years. Many of the recently published sedimentation coefficients may need to be re-examined. The problem can be easily recognized by comparing the file time-stamps provided by the operating system with the elapsed scan times recorded within the data files. We therefore 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



Measuring the grafting density of nanoparticles in solution by analytical ultracentrifugation and total organic carbon analysis.  


Many of the solution phase properties of nanoparticles, such as their colloidal stability and hydrodynamic diameter, are governed by the number of stabilizing groups bound to the particle surface (i.e., grafting density). Here, we show how two techniques, analytical ultracentrifugation (AUC) and total organic carbon analysis (TOC), can be applied separately to the measurement of this parameter. AUC directly measures the density of nanoparticle-polymer conjugates while TOC provides the total carbon content of its aqueous dispersions. When these techniques are applied to model gold nanoparticles capped with thiolated poly(ethylene glycol), the measured grafting densities across a range of polymer chain lengths, polymer concentrations, and nanoparticle diameters agree to within 20%. Moreover, the measured grafting densities correlate well with the polymer content determined by thermogravimetric analysis of solid conjugate samples. Using these tools, we examine the particle core diameter, polymer chain length, and polymer solution concentration dependence of nanoparticle grafting densities in a gold nanoparticle-poly(ethylene glycol) conjugate system. PMID:22967239

Benoit, Denise N; Zhu, Huiguang; Lilierose, Michael H; Verm, Raymond A; Ali, Naushaba; Morrison, Adam N; Fortner, John D; Avendano, Carolina; Colvin, Vicki L



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


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



A short-run new analytical ultracentrifugal micromethod for determining low-density lipoprotein sub-fractions using Schlieren refractometry.  


We have developed a new analytical ultracentrifugal micromethod for the determination of serum low-density lipoprotein (LDL) subclasses directly from ultracentrifugal Schlieren scans. We have used special software for the analysis of this type of single-spin density-gradient ultracentrifugation. The flotation of LDL patterns was obtained by underlayering a physiological salt solution with serum or isolated lipoprotein fractions raised to a density of 1.3 g/mL in the spinning ultracentrifugation capillary band-forming cell. The repeated analysis of Schlieren curves of the same sample from 10 to 100 microL in the 60-100 min full-speed interval time resulted in quite reproducible results. We obtained quantitative results by measuring the Schlieren areas between the sample curves and the reference baseline curve by using computerised numerical and graphic techniques. The decomposition of the integrated curve was carried out using a nonlinear regression program followed by deconvolution algorithm analysis in order to determine the parameters of the composing Gaussian subclasses. The LDL particle concentrations were calculated from the area under the integral of the Gaussian curve using a calibration data constant. The flotation range of the LDL Schlieren curves in the cell was identified with serum from which LDL had been removed by means of precipitation reagents and with centrifugation of isolated LDL aliquots. With this technique, we measured the concentration of LDL and analysed its polydispersity without the need for preceding sequential isolation of the LDL. On the basis of the Schlieren curves, the LDL samples were either physically paucidisperse, having a symmetrical peak within a narrow density range, or were polydisperse, showing an asymmetrical pattern distributed over a broader density region. The described method proved to be useful for a clear and immediate visual presentation of the concentration values of the LDL and for the identification of the heterogeneity of LDL variants without the need for the preparative isolation of that density class. PMID:11288837

Bozóky, Z; Fülöp, L; Köhidai, L



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


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



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


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



Damaged starch characterisation by ultracentrifugation  

Microsoft Academic Search

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

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



Critical velocities of ultracentrifuges  

NASA Technical Reports Server (NTRS)

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

Sokolov, V I



Sol-gel matrices for direct colorimetric detection of analytes  


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)



Sol-Gel Matrices For Direct Colorimetric Detection Of Analytes  


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)



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

E-print Network

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

Holmgreen, Richard J



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



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



Separation of the principal HDL subclasses by iodixanol ultracentrifugation.  


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

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



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

Microsoft Academic Search

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

Vivek Babu Kandimalla; Vijay Shyam Tripathi; Huangxian Ju



Sorption of iron(II) and ruthenium(III)-triazine complexes on silica gel and its analytical applicability  

Microsoft Academic Search

2,4,6-Tri(2?-pyridyl)-s-triazine (TPTZ) complexes with iron(II) and ruthenium(III) were prepared. Their sorption and desorption features on silica gel have been investigated. Both complexes were strongly adsorbed. This has been utilized for separating and preconcentrating iron(II) and ruthenium(III) using TPTZ-impregnated silica gel. The chromatographic behavior of TPTZ on silica gel column was examined and found to be effective modifier for silica gel

El-Sayed A. K. Yacoub; Abdel-Ghany El-Kourashy; M. A. Al-Hajjaji


Solid-state NMR of proteins sedimented by ultracentrifugation  

PubMed Central

Relatively large proteins in solution, spun in NMR rotors for solid samples at typical ultracentrifugation speeds, sediment at the rotor wall. The sedimented proteins provide high-quality solid-state-like NMR spectra suitable for structural investigation. The proteins fully revert to the native solution state when spinning is stopped, allowing one to study them in both conditions. Transiently sedimented proteins can be considered a novel phase as far as NMR is concerned. NMR of transiently sedimented molecules under fast magic angle spinning has the advantage of overcoming protein size limitations of solution NMR without the need of sample crystallization/precipitation required by solid-state NMR. PMID:21670262

Bertini, Ivano; Luchinat, Claudio; Parigi, Giacomo; Ravera, Enrico; Reif, Bernd; Turano, Paola



On the use of ultracentrifugal devices for sedimented solute NMR.  


We have recently proposed sedimented solute NMR (SedNMR) as a solid-state method to access biomolecules without the need of crystallization or other sample manipulation. The drawback of SedNMR is that samples are intrinsically diluted and this is detrimental for the signal intensity. Ultracentrifugal devices can be used to increase the amount of sample inside the rotor, overcoming the intrinsic sensitivity limitation of the method. We designed two different devices and we here report the directions for using such devices and the relevant equations for determining the parameters for sedimentation. PMID:22872367

Bertini, Ivano; Engelke, Frank; Gonnelli, Leonardo; Knott, Benno; Luchinat, Claudio; Osen, David; Ravera, Enrico



Solid-state NMR of proteins sedimented by ultracentrifugation.  


Relatively large proteins in solution, spun in NMR rotors for solid samples at typical ultracentrifugation speeds, sediment at the rotor wall. The sedimented proteins provide high-quality solid-state-like NMR spectra suitable for structural investigation. The proteins fully revert to the native solution state when spinning is stopped, allowing one to study them in both conditions. Transiently sedimented proteins can be considered a novel phase as far as NMR is concerned. NMR of transiently sedimented molecules under fast magic angle spinning has the advantage of overcoming protein size limitations of solution NMR without the need of sample crystallization/precipitation required by solid-state NMR. PMID:21670262

Bertini, Ivano; Luchinat, Claudio; Parigi, Giacomo; Ravera, Enrico; Reif, Bernd; Turano, Paola



High precision fractionator for use with density gradient ultracentrifugation.  


The recent application of density gradient ultracentrifugation (DGU) for structural sorting of single-walled carbon nanotube samples has created a need for highly selective extraction of closely spaced layers formed in the centrifuged tube. We describe a novel computer-controlled device designed for this purpose. Through the use of fine needles, systematic needle motions, and slow flow rates, multiple sample layers can be aspirated under program control with minimal cross contamination between layers. The fractionator's performance is illustrated with DGU-sorted samples of single-walled carbon nanotubes. PMID:25325436

Kadria-Vili, Yara; Canning, Griffin; Bachilo, Sergei M; Weisman, R Bruce



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

E-print Network

' 'TIGHT vs. FOAM' F. ~ 4. 90 1. 33 1. 42 3. 45 1. 07 3. 69 F( b 2. 48 2. 48 2. 48 2. 48 2. 48 2. 48 28 CONCLUSIONS AND RECOMMENDATIONS The basic premise of this research was that packing a tighter silica gel bed or replacing glass wool... PAPER GLASS TUBE I 4, 8 mm (Ld. ) BACKUP PRIMARY SECTION SECTION 200 mg 400 mg 20-40 MESH WASHED SILICA GEL (14) SPECIFICATIONS FOR THE STANDARD NIOSH SILICA SAMPLING TUBE 35 TABLE B-1 Weight of ORBO Silica Gel Tube Sections in mg ORBO...

Anna, Daniel Howard



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


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

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



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



Non-denaturing polyacrylamide gradient gel electrophoresis for the diagnosis of dysbetalipoproteinemia  

Microsoft Academic Search

Dysbetalipoproteinemia, an uncommon but highly atherogenic mixed hyperlipidemia due to the accumulation of remnants of triglyceride-rich lipoproteins, is characterized by cholesterol-enriched VLDL that migrates in the ? -position on agarose gels. The demonstration of a broad ? -band on agarose gel electrophoresis of plasma is an insensitive method and ultracentrifugation is an impractical method of diagnosing this condition. Non-denaturing polyacrylamide

Dirk J. Blom; Pamela Byrnes; Sheena Jones; A. David Marais



Molecular weight distribution analysis by ultracentrifugation: adaptation of a new approach for mucins.  


Mucins are the key macromolecular component of mucus, nature's natural lubricant, and one of the most important physical properties is their molecular weight distribution. A new approach for polydisperse polymers was recently published based on sedimentation velocity in the analytical ultracentrifuge and converts a distribution of sedimentation coefficient g(s) vs. s plot into a distribution of molecular weight utilising the power-law or scaling relationship between the sedimentation coefficient and molecular weight, s=?sMw(b) where s is the sedimentation coefficient, Mw is the weight average molecular weight and ?s and b are characteristic coefficients related to conformation. We investigate the possibility of using a large database of previously published values of s an M to define ?s and b for both aqueous solution and aqueous solution supplemented by 6M guanidine hydrochloride (a solvent which helps to minimise sample degradation). These values are then applied to a study of the molecular weight distributions of preparations of human gastric mucin in the different solvents and at different stages of purification. PMID:23465917

Gillis, Richard B; Adams, Gary G; Wolf, Bettina; Berry, Monica; Besong, Tabot M D; Corfield, Anthony; Kök, Samil M; Sidebottom, Ray; Lafond, David; Rowe, Arthur J; Harding, Stephen E



sequential ultracentrifugation. ApoHDLs were identified after migration in area-gel  

E-print Network

H and then transferred on PVDF membranes before sequencing. Amino acid (AA) composition of goose apoA-1 was very similar (LPL). Goose apoCb exhibited two isoforms due to dif- ferences in the electric charge, Cb, and Cb2' Cbj isoforms were detected in 20%, 28% and 52% of the geese, respectively. Their transmission mode

Paris-Sud XI, Université de


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

Microsoft Academic Search

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

A. N. Siakotos; George Rouser



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

PubMed Central

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

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



A television scanner for the ultracentrifuge. II. Multiple cell operation.  


The "Optical Multichannel Analyzer" (OMA) is a commercially available instrument that with the absorption optical system of the ultracentrifuge, provides an entire 500 channel intensity profile of a cell in real time. With its own analog-todigital converter, the OMA integrates a selectable number of 32.8 msec scans to provide a time-averaged image in digital form. This paper describes an interface-controller for operation of the OMA with single- and double-sector cells in multi-cell rotors, simulating double-beam measurement required for absorbance determinations. The desired sector is selected by "gating" the intensifier stage of a "Silicon Intensified Target" vidicon (SIT) used as the light detector. The cell location in the rotor and the position of the gate relative to the cell centerline is obtained from a phase-locked loop circuit which divides each rotation of the rotor into 3600 parts independent of rotor speed. (This circuit employed with photo-multiplier scanners would select the gate position for integration of photomultiplier pulses.) From examination of appropriate signals with an oscilloscope, it was verified that gate positions and widths are located with an accuracy of 0.1degree or better and with a precision of +/- 0.1 mus. The light intensity profile for any desired cell can be examined in "real time", even during acceleration of the rotor. Additional circuits employing a 10 MHz crystal clock 1) control the automatic collection of data for all sectors in multicell rotors at digitally selected time intervals, 2) display the rotor speed, and 3) indicate the elapsed time of the experiment. Constructed but not tested are additional circuits for pulsing a laser into the absorption or Rayleigh optical system. The accuracy of the pulsed SIT has been demonstrated by measurement of absorbances of solutions and also by sedimentation equilibrium experiments with myoglobin. The estimated error is 0.003 for absorbances ranging from 0 to 1. The interface-controller operates extremely well, but problems related to the pulsed SIT (optimum gate position relative to the sector opening shape of high-voltage pulse, slight pincushion distortion) require more work. PMID:963223

Rockholt, D L; Royce, C R; Richards, E G



Effect of Oxalate and Urea upon Ultracentrifugation Properties of Raw and Heated Skimmilk Casein Micelles1  

Microsoft Academic Search

The effect of oxalate aud urea treat- meats upon casein micelles sedimented from raw and heated skimmilk was ex- amined by ultracentrifugation, to deter- mine the relative importance of calcium and hydrogen or hydrophobic bonds in de- termining their structure. A model was proposed for the native casein mieelle which consists of numerous loosely packed calcium easeinate complex units joined

C. V. Morr



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


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



Isolation of serum chylomicrons prior to density gradient ultracentrifugation of other serum lipoprotein classes.  


A method for the removal of serum chylomicrons before density gradient ultracentrifugation of the other serum lipoproteins using an SW 41 swinging bucket rotor is presented. In a preliminary spin, the chylomicrons with an Sf greater than 400 X 10(-13) s float to the top of the gradient, whereas the other lipoproteins are retained in the infranatant fraction. After removal of the chylomicrons, the other serum lipoproteins are subsequently fractionated by isopycnic density gradient ultracentrifugation. Analysis of the separated lipoprotein fractions suggested that this procedure permits isolation of a chylomicron fraction consisting solely of chylomicrons but that the very low density lipoprotein fraction subsequently isolated also contains chylomicrons or chylomicron remnants with an Sf less than 400 X 10(-13) s, and that there is considerable overlap in flotation rate and particle size of very low density lipoproteins and chylomicrons. PMID:4083481

Terpstra, A H



Purification of human respiratory syncytial virus by ultracentrifugation in iodixanol density gradient.  


Ultracentrifugation in sucrose density gradient remains the most commonly used technique for hRSV purification. However, the high viscosity and hyper-osmotic property of sucrose can cause damage to the extremely labile virus leading to loss of infectivity. To overcome these limitations, an alternative purification technique was developed using iodixanol as gradient medium, incorporating MgSO(4) as a stabilizing agent and EDTA to disaggregate the virus prior to infectivity assay. Virus particles were banded at the 20-36% interface after purification of polyethylene glycol-concentrated viruses by rate zonal ultracentrifugation on a 20-52% discontinuous iodixanol gradient. The presence of the virus was confirmed by viral fusion glycoprotein content using ELISA. After further purification by buoyant density ultracentrifugation on a 20-52% continuous gradient, the virus was recovered in the region of density 1.15-1.19 g/ml and this was confirmed by the coincidence of the infectivity titre, viral genome and fusion glycoprotein peaks. Analysis of recovery rates showed that the use of iodixanol increased the virus yield up to 69%. Iodixanol was also found to be non-toxic to HeLa cells used in infectivity assay, eliminating the need of its downstream removal by dialysis. PMID:18029032

Gias, E; Nielsen, S U; Morgan, L A F; Toms, G L



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



Effect of the initial concentration of emulsifying agents on the ultracentrifugal stability of oil-in-water emulsions  

Microsoft Academic Search

The rate of loss of oil from 50% Nujol-50% water emulsions stabilized with varying concentrations of Tween 20 or Triton X-100,\\u000a and from 50% olive oil-50% water emulsions stabilized with sodium dodecyl sulfate (SDS), was determined by ultracentrifugation\\u000a at 39,460 rpm. In all cases the ultracentrifugal stability increased with increasing initial concentration of emulsifier,\\u000a although, unlike the behavior of Nujol-water-SDS

Kashmiri L. Mittal; Robert D. Vold



Ultracentrifugation of single-domain magnetite particles and the De Gennes-Pincus approach to ferromagnetic colloids in the dilute regime.  


We report an analytical ultracentrifugation study on sedimentation in dilute stable dispersions of uniform, magnetic iron oxide (Fe3O4) colloids. On increase of the dipolar coupling constant, tuned by the average particle size, the linear concentration dependence of the sedimentation velocity shows an abrupt transition from the hindered sedimentation expected for hard spheres to a marked acceleration already for weak dipolar interactions. This transition is not reproduced by sedimentation theory derived from an effective, isotropic pair correlation function of the type proposed by De Gennes and Pincus, for reasons which are made clear. Accelerated settling, instead, follows a scaling based on the mass action law for dimer formation with dipoles in head-to-tail configuration. Our work illustrates that orientational averaging of dipole interactions of ferromagnetic colloids in the dilute regime is inapplicable, with an obvious implication for the possible existence of isotropic gas-liquid criticality for such colloids. PMID:19673139

Planken, Karel L; Klokkenburg, Mark; Groenewold, Jan; Philipse, Albert P



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. PMID:25018865

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



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

NASA Astrophysics Data System (ADS)

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

Arnquist, Isaac J.; Holcombe, James A.



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.



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

E-print Network

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

Roberto Piazza; Stefano Buzzaccaro; Eleonora Secchi; Alberto Parola



Structure of halophilic malate dehydrogenase in multimolar KCl solutions from neutron scattering and ultracentrifugation.  


The structure and solvent interactions of malate dehydrogenase from Halobacterium marismortui in multimolar KCl solvents are found to be similar to those in multimolar NACl solvents reported previously (G. Zaccai, E. Wachtel and H. Eisenberg, J. Mol. Biol. 190 (1986) 97). KCl rather than NaCl is predominant in physiological medium. At salt concentrations up to about 3.0 M, the protein (a dimer of M 87000 g/mol) can be considered to occupy an invariant volume in which it is associated with about 4100 molecules of water and about 520 molecules of salt. At very low resolution, the enzyme particle appears to have a compact protein core and protruding protein parts in interaction with the water and salt components, structural features that are not observed in non-halophilic mitochondrial malate dehydrogenase. The above conclusions were drawn from the analysis of neutron scattering and ultracentrifugation data, and the complementarity of these approaches is discussed extensively. PMID:17010283

Calmettes, P; Eisenberg, H; Zaccai, G



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

E-print Network

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

Piazza, Roberto; Secchi, Eleonora; Parola, Alberto



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.



Polyelectrolyte gels  

SciTech Connect

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

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



Polyelectrolyte gels  

Microsoft Academic Search

Polyelectrolyte (PE) gels are swollen polymer\\/solvent networks that undergo a reversible volume collapse\\/expansion through various types of stimulation. Applications that could exploit this large deformation and solvent expulsion\\/absorption characteristics include robotic {open_quotes}fingers{close_quotes} and drug delivery systems. The goals of the research were to first explore the feasibility of using the PE gels as {open_quotes}smart materials{close_quotes} - materials whose response can

D. J. Segalman; W. R. Witkowski



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


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

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



Experimental measurement of the mass distribution of petroleum asphaltene aggregates using ultracentrifugation and small-angle X-ray scattering  

Microsoft Academic Search

Fractionation of petroleum asphaltene in toluene has been carried out using ultracentrifugation. The separated asphaltenes are examined by small-angle X-ray scattering (SAXS). The radii of gyration and molar mass of the separated asphaltenes range over a wide scale that provides a good indication of the self-similar structure of asphaltene aggregates. The relations between mass and radius of gyration (M?RGD) and

D. Fenistein; L. Barré



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

PubMed Central

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

McCallum, Margaret A.; Spragg, S. P.



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.



Correlation of in vitro and in vivo plasma protein binding using ultracentrifugation and UPLC-tandem mass spectrometry.  


The aim of the present study is to develop and demonstrate the correlation between in vitro and in vivo Plasma Protein Binding (PPB) using the ultracentrifugation method for its validation by using marketed compounds like atenolol, theophylline and phenytoin. In this study, in vitro PPB is carried out using ultracentrifugation, by spiking the selected marketed compounds at concentrations of 5 and 15 ?M in plasma. In an in vivo study, rats (n = 3) were given a single oral dose (10 mg kg(-1)) and post-dose samples were subjected to ultracentrifugation to obtain the protein-free fraction. A rapid and highly sensitive method was developed and validated for determining the free fraction of marketed compounds in rat plasma using protein precipitation and analysis using an ultra performance liquid chromatography electrospray ionization (ESI) tandem mass spectrometer system (UPLC-MS/MS). The in vitro free fraction (fup) values were 0.93 ± 0.07 for atenolol, 0.31 ± 0.03 for theophylline and 0.09 ± 0.02 for phenytoin which correlated well with the corresponding in vivo values of 0.91 ± 0.03 for atenolol, 0.25 ± 0.02 for theophylline and 0.09 ± 0.01 for phenytoin with a coefficient of variation less than 11.06%, 11.45% and 13.67%, respectively. Therefore the validated high-throughput in vitro PPB study is expected to have a powerful impact on reducing the cost as well as time in the drug discovery process. PMID:23964358

Srikanth, Cheruvu Hanumanth; Chaira, Tridib; Sampathi, Sunitha; V B, Sreekumar; Bambal, Ramesh B



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


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

Li, Xuhang; Donowitz, Mark



STUDIES ON ISOLATED CELL COMPONENTS: XVI. The Distribution of Acid Phenyl Phosphatase Activities in Rat Liver Brei Fractionated in the Zonal Ultracentrifuge  

Microsoft Academic Search

The zonal ultracentrifuge has been used to separate the major components of rat liver brei (soluble phase, ribosomes, microsomes, mitochondria, membranous fragments, and nuclei) during one ccntrifugation, by using a 1200 ml sucrose gradient varying linearly with radius from 17 to 55 per cent (w\\/w) with a \\




Difference gel electrophoresis.  


DIGE is a protein labelling and separation technique allowing quantitative proteomics of two or more samples by optical fluorescence detection of differentially labelled proteins that are electrophoretically separated on the same gel. DIGE is an alternative to quantitation by MS-based methodologies and can circumvent their analytical limitations in areas such as intact protein analysis, (linear) detection over a wide range of protein abundances and, theoretically, applications where extreme sensitivity is needed. Thus, in quantitative proteomics DIGE is usually complementary to MS-based quantitation and has some distinct advantages. This review describes the basics of DIGE and its unique properties and compares it to MS-based methods in quantitative protein expression analysis. PMID:19003860

Timms, John F; Cramer, Rainer



Analytical Results Analytical Model  

E-print Network

Analytical Results Analytical Model Current Status PhD Timeline Preliminary Conclusions High Providing self-adaptation features for partial replication over SANs START END NOW Lsd Distributed Systems on the number of replicas. · Hybrid partial replication scales slightly better than full replication. · High

Narasayya, Vivek


An Investigation on Gel Electrophoresis with Quantum Dots End-labeled DNA  

E-print Network

Invented in the 1950s, gel electrophoresis has now become a routine analytical method to verify the size of nucleic acids and proteins in molecular biology labs. Conventional gel electrophoresis can successfully separate DNA fragments from several...

Chen, Xiaojia



Change in chain stiffness in viscometric and ultracentrifugal fields: Cellulose diacetate in N, N-dimethylacetamide dilute solution  

NASA Astrophysics Data System (ADS)

The molecular characteristics and the chain stiffness were investigated for fractionated samples of cellulose diacetate (CDA, degree of substitution DS = 2.40) in N, N-dimethylacetamide (DMAc) through the partial specific volume, the viscometric, the sedimentation velocity, and the sedimentation equilibrium measurements at 30 °C. It was found that CDA dispersed molecularly in DMAc under the external field such as in the viscometric and the sedimentation experiments. The molecular weight dependence of the intrinsic viscosity [?] and the sedimentation coefficient at infinite dilution s0 of the single CDA molecule were expressed by the relation [?] = 1.10×10-2Mw0.85 (cm3 g-1) and s0=2.25×10-14Mw0.20 (s), which exhibit the stiff, or semiflexible chain nature. The semiflexible chain parameters were evaluated by the Yamakawa-Fujii (YF) theory of the unperturbed wormlike cylinder model, first via a combination of the viscosity and the partial specific volume data (method A) and second via a combination of the sedimentation and the partial specific volume data (method B). Method A gave the chain parameters that q = 8.0 nm, ML = 523 nm-1, and d = 0.89 nm, whereas method B gave q = 48 nm, ML = 560 nm-1, and d = 0.93 nm. Here q is the persistence length, ML is the molecular weight per unit contour length, and d is the chain diameter of the wormlike cylinder model. Methods A and B deduce, independent of the method, the definite ML and d values, which are very consistent with the ordinary reported values. However, q estimated by the two methods differs by about six times the other. This fact suggests that the CDA molecule in the ultracentrifugal field has a conformation different from that in the viscometric shear field: The CDA chain may be highly stiff in the ultracentrifuge because of the situation that the adjacent glucose residues are stuck in a rigid conformation by the double stapled hydrogen bonds between the intramolecular hydroxyls and oxygens.

Kawanishi, Hiroyuki; Tsunashima, Yoshisuke; Okada, Shinichi; Horii, Fumitaka



Solution structure of halophilic malate dehydrogenase from small-angle neutron and X-ray scattering and ultracentrifugation.  


Data from small-angle X-ray and neutron scattering and ultracentrifugation experiments on solutions of malate dehydrogenase from Halobacterium maris mortui are analysed together to yield a model for the enzyme particle formed by the protein and its interactions with water and salt in the solvent. The halophilic enzyme is stable only in high concentrations of salt and the model has structural features that are absent from non-halophilic malate dehydrogenase. The complementarity of the information derived from the three experimental methods is discussed extensively and quantitatively. It derives from the fact that mass density (ultracentrifugation), electron density (X-rays) and neutron scattering density are independent of each other. Each method gives a different "view" of the same particle, and an analysis of the combined data provided thermodynamic and structural parameters with, apart from the chemical composition of the solutions, only one other assumption: a constant partial specific volume for water equal to 1.00 cm3 g-1. Both the insights gained by this novel approach and its limitations are carefully pointed out. In solvents between 1 M and 5 M-NaCl, the enzyme forms a particle of invariant volume, consisting of a protein dimer (87,000 g mol-1) with which are associated 0.87 g of water and 0.35 g of salt per gram of protein. The partial specific volume of the protein calculated from the combined experimental data is 0.753(+/- 0.030) cm3 g-1, in good agreement with the value calculated from the amino acid composition. The particle has a radius of gyration of 32 A and an equivalent Stokes radius of 43 A. By combining the data from the X-ray and neutron scattering studies, the radii of gyration of the protein moiety alone and of the associated water and salt distribution were calculated. They are 28 A and about 40 A, respectively. The large-angle scattering curves show that the shapes of the particle and of the protein moiety alone are similar. At very low resolution they can be approximated by an ellipsoid of axial ratio 1:1:0.6 (or 1:1:1.5). At higher resolution, it becomes apparent that the particle has a significantly larger interface with solvent than an homogeneous ellipsoid or globular protein. The model has a globular protein core similar to non-halophilic malate dehydrogenase, with about 20% of the protein extending loosely out of the core, forming the large interface with solvent. The main interactions with water and salt take place on this outer part. PMID:3783699

Zaccai, G; Wachtel, E; Eisenberg, H



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.



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


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



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



Self-assembly of 3,6-bis(4-triazolyl)pyridazine ligands with copper(I) and silver(I) ions: time-dependant 2D-NOESY and ultracentrifuge measurements.  


Two 3,6-bis(R-1H-1,2,3-triazol-4-yl)pyridazines (R = mesityl, monodisperse (CH(2)-CH(2)O)(12)CH(3)) were synthesized by the copper(I)-catalyzed azide-alkyne cycloaddition and self-assembled with tetrakis(acetonitrile)copper(I) hexafluorophosphate and silver(I) hexafluoroantimonate in dichloromethane. The obtained copper(I) complexes were characterized in detail by time-dependent 1D [(1)H, (13)C] and 2D [(1)H-NOESY] NMR spectroscopy, elemental analysis, high-resolution ESI-TOF mass spectrometry, and analytical ultracentrifugation. The latter characterization methods, as well as the comparison to analog 3,6-di(2-pyridyl)pyridazine (dppn) systems and their corresponding copper(I) and silver(I) complexes indicated that the herein described 3,6-bis(1H-1,2,3-triazol-4-yl)pyridazine ligands form [2×2] supramolecular grids. However, in the case of the 3,6-bis(1-mesityl-1H-1,2,3-triazol-4-yl)pyridazine ligand, the resultant red-colored copper(I) complex turned out to be metastable in an acetone solution. This behavior in solution was studied by NMR spectroscopy, and it led to the conclusion that the copper(I) complex transforms irreversibly into at least one different metal complex species. PMID:21344663

Happ, Bobby; Pavlov, Georges M; Altuntas, Esra; Friebe, Christian; Hager, Martin D; Winter, Andreas; Görls, Helmar; Günther, Wolfgang; Schubert, Ulrich S



Dna electrophoresis in photopolymerized polyacrylamide gels on a microfluidic device  

E-print Network

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

Lo, Chih-Cheng



Running an Agarose Gel  

NSDL National Science Digital Library

This video adapted from the University of Leicester provides step-by-step instructions for loading samples into an agarose gel and then running the gel to separate DNA molecules according to their size.

Foundation, Wgbh E.



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. PMID:24009879

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



Characterization and Purification of Supramolecular Metal Complexes Using Gel-Permeation Chromatography  

E-print Network

Characterization and Purification of Supramolecular Metal Complexes Using Gel-Permeation Received July 25, 2003 Gel-permeation chromatography (GPC) has been used to analyze transition, also known as gel- permeation chromatography (GPC), is an analytical technique in which the separation


Solution-Based Structural Analysis of the Decaheme Cytochrome, MtrA, by Small-Angle X-ray Scattering and Analytical Ultracentrifugation  

E-print Network

The potential exploitation of metal-reducing bacteria as a means for environmental cleanup or alternative fuel is an exciting prospect; however, the cellular processes that would allow for these applications need to be ...

Firer-Sherwood, Mackenzie A.


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

E-print Network

Silver nitrate Sodium acetate Sodium bicarbonate Sodium bromide Sodium carbonate Sodium chloride Sodium Sodium thiocyanate Sodium thiosulfate Sodium tungstate Strontium chloride Sucrose Sulfuric acid Tartaric Ammonium chloride Ammonium hydroxide Ammonium sulfate Barium chloride Cadmium chloride Cadmium sulfate

Chan, Hue Sun


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

E-print Network

Sodium chloride Sodium citrate Sodium diatrizoate Sodium dichromate Sodium ferrocyanide Sodium hydroxide sulfate Sodium tartrate Sodium thiocyanate Sodium thiosulfate Sodium tungstate Strontium chloride Sucrose-Propanol Acetic Acid Acetone Ammonium chloride Ammonium hydroxide Ammonium sulfate Barium chloride Cadmium

Chan, Hue Sun



SciTech Connect

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

Randall S. Seright




SciTech Connect

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

Randall S. Seright



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).


Comparative fluorescence two-dimensional gel electrophoresis using a gel strip sandwich assembly for the simultaneous on-gel generation of a reference protein spot grid.  


The comparison of proteins separated on 2DE is difficult due to gel-to-gel variability. Here, a method named comparative fluorescence gel electrophoresis (CoFGE) is presented, which allows the generation of an artificial protein grid in parallel to the separation of an analytical sample on the same gel. Different fluorescent stains are used to distinguish sample and marker on the gel. The technology combines elements of 1DE and 2DE. Special gel combs with V-shaped wells are placed in a stacking gel above the pI strip. Proteins separated on the pI strip are electrophoresed at the same time as marker proteins (commercially available purified protein of different molecular weight) placed in V-wells. In that way, grids providing approximately 100 nodes as landmarks for the determination of protein spot coordinates are generated. Data analysis is possible with commercial 2DE software capable of warping. The method improves comparability of 2DE protein gels, because they are generated in combination with regular in-gel anchor points formed by protein standards. This was shown here for two comparative experiments with three gels each using Escherichia coli lysate. For a set of 47 well-defined samples spots, the deviation of the coordinates was improved from 7% to less than 1% applying warping using the marker grid. Conclusively, as long as the same protein markers, the same size of pI-strips and the same technology are used, gel matching is reproducibly possible. This is an important advancement for projects involving comparison of 2DE-gels produced over several years and in different laboratories. PMID:22648808

Ackermann, Doreen; Wang, Weiqun; Streipert, Benjamin; Geib, Birgit; Grün, Lothar; König, Simone



Modeling chemoresponsive polymer gels.  


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

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




SciTech Connect

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




Agarose Gel Demos  

NSDL National Science Digital Library

This video, presented by WGBH, is a great overview of how to prepare Agarose gel for electrophoresis. The video goes in-depth with the finer points including how to insert the pipette as to not disturb the gel and get the best results. This video would be useful for anyone in biochemistry or molecular biology fields. This video would also be helpful for instructors looking to provide their students with an overview on how to prepare Agarose gel. Educators will also find a background essay, discussion questions, and standards alignment for the material.



Preparation of chitosan gel  

NASA Astrophysics Data System (ADS)

Aerogel conditioning of the chitosan makes it possible to prepare porous solids of significant specific surface. The increase in the chitosan concentration or the degree of acetylation decreases the specific surface of the synthesized chitosan gel. Whereas drying with supercritical CO2 more effectively makes it possible to preserve the volume of the spheres of gel and to have a more significant specific surface in comparison with evaporative drying.

Moussaoui, Y.; Mnasri, N.; Elaloui, E.; Ben Salem, R.; Lagerge, S.; de Menorval, L. C.



Conformance Improvement Using Gels  

SciTech Connect

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

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



Electrically controlled polymeric gel actuators  

Microsoft Academic Search

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

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



Electrically controlled polymeric gel actuators  

Microsoft Academic Search

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

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



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



Analytical interferences and analytical quality  

Microsoft Academic Search

In today's health care system the prevalence of medical errors is high as stated by the report of the Institute of Medicine. A varying error rate of <10% in clinical medical laboratories has been reported in the literature. Most of these errors occur in the pre-analytical phase. Only a small number of errors will be seen in the analytical phase.

Oswald Sonntag



The turbid specimen as an analytical medium: hemoglobin determination as a model.  


The quantitation of chemical constituents in lipemic samples is a major problem confronting the clinical laboratory. Currently, a number of cumbersome and time-consuming methods are used to clarify samples before analysis. However, the use of enzymic hydrolysis of triglycerides along with efficient chemical removal of the formed non-esterified fatty acids is exemplified here as an excellent alternative to the current methods of clarification such as ultracentrifugation, extraction or chemical precipitation of low density and very low density lipoproteins. This method of clarifying milky serum has been used by us to assay hemoglobin in severely lipemic blood samples as an analytical model. PMID:3987056

Sharma, A; Artiss, J D; Strandbergh, D R; Zak, B



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.



Gel electrophoresis of intact subcellular particles.  


The review describes the application of gel electrophoresis to the characterization and separation of viruses, ribosomes, vesicles and other subcellular particles. The preparation of the sample, the choice of the buffer, the gel medium, the apparatus and the detection of the particle (staining and scanning) as well as the necessary theory are discussed. This includes the mathematical evaluation of experimental data on the basis of Ferguson plots using the extended Ogston theory. Simple methods and sophisticated computer simulation techniques are described and exemplified in application to the determination of particle size and charge, the pore size of the gel (unpublished data) and the two-dimensional agarose electrophoresis (unpublished). It is shown that the nature of the particle (e.g. spherical or rod-shaped, pliable or rigid texture) determines the shape of the non-linear Ferguson plot. In addition, the review gives a number of practical applications of gel electrophoresis, isoelectric focusing, titration curves and immuno-electrophoresis to subcellular particles. Pros and cons are evaluated. A comparison with other analytical procedures is made. The review is concluded by a futuristic outlook. PMID:3305546

Tietz, D



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.



Running an Agarose Gel  

NSDL National Science Digital Library

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

Hinkley, Craig



Preparing an Agarose Gel  

NSDL National Science Digital Library

This video from CUNY Kingsborough Community College describes the technique of preparing 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 3:10.

Shun Ho, Ivan



Pouring an Agarose Gel  

NSDL National Science Digital Library

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

Hinkley, Craig



Transdermal delivery of paeonol using cubic gel and microemulsion gel  

PubMed Central

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

Luo, Maofu; Shen, Qi; Chen, Jinjin



Analytical Microscopy  

SciTech Connect

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

Not Available



Polyacrylamide gels synthesized in the presence of surfactants  

NASA Astrophysics Data System (ADS)

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

Chakrapani, Mukundan


Equity Analytics  

NSDL National Science Digital Library

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


Analytical Chemistry  

NSDL National Science Digital Library

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

Hardy, James K.



MAGIC Gel Dosimetry  

NASA Astrophysics Data System (ADS)

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

Mifflin, Rachel; Shahnazi, Kambiz; Jesseph, Rick



Gastrointestinal Mucus Gel Barrier  

Microsoft Academic Search

A family of glycoproteins, known as gel-forming mucins, endow gastrointestinal mucus with its characteristic viscoelastic\\u000a and biological properties. In the mucus, these large oligomeric glycoproteins are organized into entangled networks that occasionally\\u000a can be stabilized by non-covalent interactions as in the stomach lumen. This network is a formidable chemical and physical\\u000a barrier that not only protects the underlying epithelia but

Juan Perez-Vilar


Ocular tolerance of sertaconazole gel.  


The in vitro and in vivo tolerance of sertaconazole gel, a new topical azole antifungal, was studied. Ketoconazole gel (Panfungol) was used as a reference substance. The methods applied for tolerance assessment were the bovine corneal opacity and permeability test for the in vitro assay and a modified Draize test for the in vivo assay. The results obtained show that both substances can be classified as slightly irritant and with acceptable tolerance. However, unlike ketoconazole gel, sertaconazole gel did not cause a positive lesion index in vivo. Ketoconazole was 5.25 times more irritant in vitro than sertaconazole gel, whose effect was similar to that of saline solution. Consequently, the negligible irritant effect of sertaconazole gel on a type of epithelium that is extremely sensitive, i.e. the cornea, confirms the good tolerance of this new antifungal gel on other structures such as the skin and mucous membranes. PMID:8786760

Romero, A; Grau, M T; Villamayor, F; Zapatero, J; Mayordomo, L; Tortajada, A; Sacristán, A; Ortiz, J A



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)



Analytical Chemistry  

NSDL National Science Digital Library

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

Henderson, David E.



High transparent shape memory gel  

NASA Astrophysics Data System (ADS)

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

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



Foam and gel decontamination techniques  

SciTech Connect

The Savannah River Site is investigating decontamination technology to improve current decontamination techniques, and thereby reduce radiation exposure to plant personnel, reduce uptake of radioactive material, and improve safety during decontamination and decommissioning activities. When decontamination chemicals are applied as foam and gels, the contact time and cleaning ability of the chemical increases. Foam and gel applicators apply foam or gel that adheres to the surface being decontaminated for periods ranging from fifteen minutes (foam) to infinite contact (gel). This equipment was started up in a cold environment. The desired foam and gel consistency was achieved, operators were trained in its proper maintenance and operation, and the foam and gel were applied to walls, ceilings, and hard to reach surfaces. 17 figs.

McGlynn, J.F.; Rankin, W.N.



Mechanical properties of biological gels  

NASA Astrophysics Data System (ADS)

The rheological properties of biological gels are illustrated by reviewing measurements made on samples containing polymer networks reconstituted from cytoskeletal constitutents. Although these networks are crosslinked by non-covalent interactions which may lead to transient gel behavior, the early-time (rapid) mechanical response of the gels can be characterized by the instantaneous shear modulus. A theory for the latter is described, and used to examine the relationship between the cortical f-actin content and the stiffening of activated polymorphonuclear leukocytes.

Nossal, Ralph



Polyoxometalate-based Supramolecular Gel  

PubMed Central

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

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



Electrically controlled polymeric gel actuators  


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.



Electrically controlled polymeric gel actuators  


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)



Luminescence effects in gels containing organo-aluminum complexes  

SciTech Connect

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

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



Nanocrystal/sol-gel nanocomposites  


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

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



Nanocrystal/sol-gel nanocomposites  


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

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



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.



Living bacteria in silica gels  

NASA Astrophysics Data System (ADS)

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

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



Sonication-triggered instantaneous gel-to-gel transformation.  


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

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



Business Intelligence & Analytics  

E-print Network

with "deep analytical skills," as well as another 1.5 million "managers and analysts to analyze big data Analytics BIA 658 Social Network Analytics BIA 660 Web Analytics BIA 680 Applied Analytics in the Life their understanding of specific areas of data, web and social analytics, and their ability to manage data

Yang, Eui-Hyeok


Characterization of rehydrated gelatin gels.  


Five percent glutaraldehyde cross-linked gels have shown excellent blood compatibility as coatings for cardiac prostheses. A method was developed for producing thin dehydrated coatings using a proprietary dehydration procedure and ethylene oxide (EO) sterilization. The swollen surfaces of rehydrates versus wet (original) gels were compared. Within 30 min of saline rehydration, dry 30-50-microns films on textured surfaces became smooth, uniform, and comparable to original gelatin gels. Mechanical test results after rehydration showed values for strain remain unchanged (39.3 + 10.0 to 40.0 + 7.8%), but stress increased (2.79 + 1.21 to 4.22 + 1.60 dyne/cm2; p less than 0.01). The contact angle data reported gamma C values of 26.1 and 30.4 dyne/cm for original and rehydrated gels. Using a coulometric titrimeter, the measured water content of original gels was reduced from 85 to 3.4% after drying. Dried and saline rehydrated gels had a 73.2% moisture content. Gels shrank 8.8% of their original length after rehydration; however, the thickness of all pump coatings remained stable. Two-hour incubations with bovine platelet rich plasma showed no differences in platelet reactivity or morphology when compared to original gels. Light microscopy and scanning electron microscopy (SEM) showed no evidence of gel cracking or surface defects after pump endurance testing for 3 and 5 weeks. The process of dehydration eliminates the wet storage and sterility problems of such hydrogels and provides a stable film coating for a variety of blood-contacting substrates. PMID:1998488

Emoto, H; Kambic, H; Chen, J F; Nosé, Y



Adhesive, elastomeric gel impregnating composition  


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)



An agarose gel electrophoretic method for analysis of sulfated glycosaminoglycans of cultured cells.  


Agarose disc gel electrophoresis has been adapted to achieve the separation of the major sulfated glycosaminoglycans produced by cells in culture. By use of buffers containing barium ion, mixtures of chondroitin sulfate, dermatan sulfate, and heparan sulfate are well resolved into discrete bands. The technique can be used preparatively as well as analytically to separate quantities of glycosaminoglycans up to a milligram in a 6-mm diameter gel. PMID:9762132

Funderburgh, J L; Chandler, J W



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

Microsoft Academic Search

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

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



Self polymerising ionic liquid gel.  


A novel self-polymerised ionic liquid (IL) gel was prepared at room temperature (RT), without light or heat or addition of initiator, using a new IL, choline formate (CF), and 2-hydroxyethyl methacrylate (HEMA). PMID:19462080

Winther-Jensen, Orawan; Vijayaraghavan, R; Sun, Jiazeng; Winther-Jensen, Bjorn; MacFarlane, Douglas R



A conjugated polymer plastic gel  

E-print Network

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

Alcazar Jorba, Daniel



Colloidal gels: Clay goes patchy  

NASA Astrophysics Data System (ADS)

Empty liquids and equilibrium gels have so far been only theoretical possibilities, predicted for colloids with patchy interactions. But evidence of both has now been found in Laponite, a widely studied clay.

Kegel, Willem K.; Lekkerkerker, Henk N. W.



Raft Instability of Biopolymer Gels  

E-print Network

Following recent X-ray diffraction experiments by Wong, Li, and Safinya on biopolymer gels, we apply Onsager excluded volume theory to a nematic mixture of rigid rods and strong ``$\\pi/2$'' cross-linkers obtaining a long-ranged, highly anisotropic depletion attraction between the linkers. This attraction leads to breakdown of the percolation theory for this class of gels, to breakdown of Onsager's second-order virial method, and to formation of heterogeneities in the form of raft-like ribbons.

I. Borukhov; R. F. Bruinsma



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



Synthesis and characterization of nitric oxide-releasing sol-gel microarrays.  


Diazeniumdiolate-modified sol-gel microarrays capable of releasing low levels of nitric oxide are reported as a viable means for improving the blood compatibility of a surface without fully modifying the underlying substrate. Several parameters are characterized including: (1) NO surface flux as a function of sol-gel composition and microarray geometry; (2) microstructure dimensions and spacing for optimal blood compatibility; and (3) the effect of sol-gel surface modification on analyte accessibility to platinum electrodes. The sol-gel microarrays release biologically relevant levels of NO under physiological conditions for >24 h. In vitro platelet adhesion assays indicate that a NO surface flux of 2.2 pmol cm(-2) s(-1) effectively reduces platelet adhesion to glass substrates modified with sol-gel microstructures separated by 50 microm. The blood compatibility observed for these micropatterned surfaces is comparable to NO-releasing sol-gel films. When the separation between NO-releasing microstructures is reduced to 10 microm, the NO surface flux required to reduce platelet adhesion is lowered to 0.4 pmol cm(-2) s(-1). Finally, the oxygen response of platinum electrodes modified with NO-releasing sol-gel microarrays indicates that selective modification via micropatterning enhances analyte accessibility to the sensor surface. PMID:15518528

Robbins, Mary E; Hopper, Erin D; Schoenfisch, Mark H



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


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



Pre-Cast Gel Electrophoresis Guide  

E-print Network

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

Kirschner, Marc W.


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.



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



Capillary fracture of soft gels  

E-print Network

A liquid droplet resting on a soft gel substrate can deform that substrate to the point of material failure, whereby fractures develop on the gel surface that propagate outwards from the contact-line in a starburst pattern. In this paper, we characterize i) the initiation process in which the number of arms in the starburst is controlled by the ratio of surface tension contrast to the gel's elastic modulus and ii) the propagation dynamics showing that once fractures are initiated they propagate with a universal power law $L\\propto t^{3/4}$. We develop a model for crack initiation by treating the gel as a linear elastic solid and computing the deformations within the substrate from the liquid/solid wetting forces. The elastic solution shows that both the location and magnitude of the wetting forces are critical in providing a quantitative prediction for the number of fractures and, hence, an interpretation of the initiation of capillary fractures. This solution also reveals that the depth of the gel is an impo...

Bostwick, Joshua B



Capillary fracture of soft gels  

E-print Network

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

Joshua B. Bostwick; Karen E. Daniels



Copolymers For Capillary Gel Electrophoresis  


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)



Tracer diffusion in colloidal gels  

E-print Network

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

Sujin Babu; Jean Christophe Gimel; Taco Nicolai



Analytics for Education  

ERIC Educational Resources Information Center

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

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



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.



Challenges in Video Analytics  

NASA Astrophysics Data System (ADS)

Video analytics technology has matured and found application in a variety of fields over the past decade. This chapter discusses the current state-ofthe-art, and describes challenges for future video analytics implementations. Current applications and markets for video analytics are described in the context of a processing pipeline. Application-specific challenges are described with potential solutions to those challenges. This chapter also lists some implementation considerations for embedded video analytics and concludes with future and emerging applications of video analytics.

Gagvani, Nikhil


Gluing gels: A nanoparticle solution  

NASA Astrophysics Data System (ADS)

Synthetic polymer gels with certain surface chemistries can be glued together by a simple and inexpensive method that uses commercially available silica nanoparticles. Biological tissues can also be joined by this nanotechnological route, eliminating the need for sutures, additional adhesives or chemical reactions.

Appel, Eric A.; Scherman, Oren A.



Electromechanical coupling in polyelectrolyte gels  

Microsoft Academic Search

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

Katsiaryna I. Prudnikova



Gel Electrophoresis Lab: DNA Fingerprinting  

NSDL National Science Digital Library

This lab activity from the Biotechnology Alliance for Suncoast Biology Educators introduces the methods of RFLP analysis, or DNA fingerprinting, by using gel electrophoresis. Students will learn the role of restriction enzymes in DNA fingerprinting. Required materials, procedure and instructions are provided. This lesson plan may be downloaded in Microsoft Word document file format.

Ehlers, Megan



Gel Electrophoresis Lab: Paternity Case  

NSDL National Science Digital Library

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



Description of analytical problems arising from elevated serum solids.  


There has always been a problem with the collection of data and interpretation of the results obtained from any biological fluid in which the solids content was increased to a great extent. Of these solids, the triglycerides of the lipids may cause a plasma (serum) to vary in appearance from opalescent to milky. This condition of the specimen and the concomitant turbidity upon its addition to reagents creates the well-documented optical aberrations of spectrophotometric measurements. In addition, the lipids, in conjunction with the proteins, can act as diluents when they are elevated, thereby decreasing what might be termed the residual true plasma volume. Thus the water content of an aliquot sampled for a particular analytical procedure is diminished, and by that means a situation is created in which a short sample is drawn. This dilution effect by the solids results in a lowering of the assay values obtained for the measured constituents of such a serum sample. An associated phenomenon of high concentrations of solids, especially proteins, is the increase in viscosity of a specimen, a condition that also causes an error of short sampling when certain peristaltic pumping devices are used. This review considers several aspects of problems encountered when dealing with a number of circumstances that are critical to the measurement of analytes in severely hyperlipemic and/or hyperproteinemic specimens. These include the problems of short sampling; the potential amelioration of the problem by corrective mathematics, extraction of the lipids, or ultracentrifugation of the true plasma from the lipids; the important need to include most analytes into our considerations; the difference in reference base values for the calculation of concentrations of lipids of serum versus other analytes; the concept of the use of ratios when the reference base values differ, numerator analyte from denominator analyte; and the problems of using serum blanks when necessary corrective action for the solids volume is neglected. Thus, in the final analysis, problems with underestimated volumes of samples used for many spectrophotometric determinations are considered here along with the other difficulties encountered when the need to measure analytes in serums with extremely high solids content presents. PMID:6528966

McGowan, M W; Artiss, J D; Zak, B



Commercial applications of block copolymer photonic gels  

E-print Network

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

Lou, Sally S



Capillary fracture of soft gels.  


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



Radiological properties of normoxic polymer gel dosimeters  

Microsoft Academic Search

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

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



Spring-loaded polymeric gel actuators  


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

Shahinpoor, Mohsen (Albuquerque, NM)



Frictional properties of high functional gel materials  

NASA Astrophysics Data System (ADS)

The frictional behavior of the four kinds of high functional gels, which are double network (DN) gels, particle-double network gels (P-DN), shape memory gels (SMG), LA-shape memory gels (LA-SMG) and was studied. The velocity dependence looks similar for both the DN gels and the SMG, however the details of the dependence are different. The coefficient of the DN gels is smaller than that of the SMGs. The coefficient decreases as the normal force increases. This normal force dependence was observed for the DN gels previously, however for the first time for the SMGs. The velocity dependence looks similar for both the DN gels and the SMG, however the details of the dependence are different. The coefficient of the DN gels is smaller than that of the SMGs. The difference of the dependences is possibly related to the different softness by the temperature change of the gels. The temperature dependence of the coefficient of friction in LA-SMG was observed. Increase of the perpendicular load and the surface softness were influenced by coefficient of friction increase. In addition, the frictional coefficient of P-DN that different particle size was measured for the first time. The difference of the friction behavior of LA-SMG by the particle size was clear. Therefore, we show frictional coefficient of various high functional gels.

Wada, Masato; Yamada, Kohei; Yamada, Naoya; Makino, Masato; Gong, Jin; Furukawa, Hidemitsu



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



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


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

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



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

PubMed Central

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

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



Cumulative irritation potential among metronidazole gel 1%, metronidazole gel 0.75%, and azelaic acid gel 15%.  


Topical therapy for rosacea aims to reduce inflammatory lesions and decrease erythema but can carry side effects such as stinging, pruritus, and burning. Metronidazole and azelaic acid gel 15% are U.S. Food and Drug Administration-approved for the treatment of rosacea. The current study was conducted to assess the cumulative irritation potential of 2 formulations of metronidazole 0.75% gel and 1% gel--and azelaic acid gel 15% over 21 days (N=36). Results of this study demonstrated a significantly greater poten tial for irritation from azelaic acid compared with metronidazole gel 0.75% (P < .0001), which had significantly greater potential for irritation compared with metronidazole gel 1% (P = .0054). Metronidazole gel 1% had a similar profile to white petrolatum. PMID:17500380

Colón, Luz E; Johnson, Lori A; Gottschalk, Ronald W



Analytic pulsar models  

NASA Technical Reports Server (NTRS)

An analytical procedure is given for solving the Einstein equations of a rotating fluid body. It is demonstrated that an analytic model of uniform denisty, representing a slowly rotating neutron star, can describe both differentially and uniformly rotating stars.

Adams, R. C.; Cohen, J. M.; Adler, R. J.; Sheffield, C.



Analytical Sciences Digital Library  

NSDL National Science Digital Library

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



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.



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


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

SciTech Connect

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

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



Structural change of ?-carrageenan gel near sol-gel transition point  

NASA Astrophysics Data System (ADS)

The structural change of ?-carrageenan gel in the gel-to-sol transition was observed with the small-angle neutron scattering (SANS). The SANS intensity decreases on approaching to the transition point from the gel phase. On the other hand, the observed gyration radius does not change in the whole region of the gel phase. The fact means that the number of the cross link points decreases but their size keeps almost unchanged in the gel-to-sol transition.

Masaaki Sugiyama; Chikanori Yuasa; Kazuhiro Hara; Nobuyasu Hiramatsu; Atsushi Nakamura; Yasushi Hayakawa; Yutaka Maeda


Equations of state for ideal elastomeric gels  

NASA Astrophysics Data System (ADS)

Submerged in a solvent-containing environment and subject to applied forces, a covalent polymer network absorbs the solvent and deforms, forming an elastomeric gel. The equations of state are derived under two assumptions. First, the amount of the solvent in the gel varies when the gel changes volume, but remains constant when the gel changes shape. Second, the Helmholtz free energy of the gel is separable into the contribution due to stretching the network and that due to mixing the polymer and the solvent. We demonstrate that these equations of state fit several sets of experimental data in the literature remarkably well.

Cai, Shengqiang; Suo, Zhigang



Demonstration of the solar gel pond  

NASA Astrophysics Data System (ADS)

Viscous polymeric gels that act as a thermal insulator and produce high energy collection and storage efficiencies were deveoped. These polymer gels were tested in a small-scale solar pond. The highest bottom temperature was achieved with the bottom layer filled with a salt solution and covered with a top layer of 16 cm polymer gel. By covering the gel layer with a thin layer of water, dirt and debris falling onto the pond can be skimmed, and evaporation can be retarded. The highest bottom temperature and satisfactory efficiency (72%) were obtained with the addition of a gel layer 16 cm thick as an insulation on the top of the saline.

Wilkins, E. S.



Microsoft Analytics Platform System  

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nodes, and the Hadoop Distributed File System (HDFS) storage. By integrating HDInsight with APS, you canBase Integrated Hadoop performance through HDInsight (optional) Introduction Microsoft Analytics Platform SystemMicrosoft Analytics Platform System Solution Brief #12;Microsoft Analytics Platform System

Chaudhuri, Surajit



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

Raja, Anita


Polymer networks and gels: Simulation and theory  

NASA Astrophysics Data System (ADS)

The purpose of this research is to understand the molecular origins of the dynamic and swelling properties of polymer networks and gels. Our approach has been to apply computer simulations techniques to off-lattice, near-perfect, trifunctional and tetrafunctional network models. The networks are constructed by endlinking freely-jointed, tangent-hard-sphere chains. Equilibrium discontinuous molecular dynamics techniques are employed to simulate the relaxation of large networks of chain lengths ranging from N = 20 to N = 150 at a packing fraction of 0.43. The simulation trajectories are used to calculate the radius of gyration and end-to-end distance of the network chains, the static structure factor of the crosslinks, the mean-squared displacement of the crosslinks and chain inner segments, the intermediate scattering function of the chains and the elastic modulus of the network. The structure and properties of the networks are shown to depend heavily on the manner in which the network is initially constructed. The dynamics of the network crosslinks and chain inner segments are similar to those of melt chains at short times and show evidence of spatial localization at long times. The results from the elastic moduli and long-time crosslink and chain displacement calculations indicate that entanglement constraints act in conjunction with crosslink constraints to reduce crosslink and chain mobility. The presence of entanglements appears to cause the magnitude of the elastic modulus to be larger than the affine/phantom model predictions. The pressure-volume behavior and the chain configurational properties of deformed networks are investigated over a range of packing fractions. The variation of network pressure with density is found to be similar to that of uncrosslinked chain systems of the same chain length, except at low densities where the network pressures become negative due to elastic effects. We derive a simple, mean-field network equation of state in which the network pressure is treated as the sum of liquid-like and elastic components. The liquid-like component is obtained by extending the Generalized Flory-Dimer theory to networks, and the elastic component is obtained by treating the network as a set of interpenetrated tree-like structures and using a ideal chain-spring analogy to calculate the free energy. The theoretical predictions for network pressure are in very good agreement with simulation data. Our simulation results for the network chain properties show that the chain end-to-end vectors scale affinely with macroscopic deformation at large densities, but show a weaker-than-affine scaling at low densities. A combined discontinuous molecular dynamics and Monte Carlo simulation technique is used to study the swelling of trifunctional networks of chain lengths 20 and 35 in an athermal solvent. The swelling simulations are conducted under conditions of constant pressure and chemical potential. The gel packing fraction and solvent fraction at swelling equilibrium were found to increase with pressure as expected. We present a simple, analytical theory for gel swelling, grounded in our previous theoretical work for solvent-free networks. The predictions of this theory for the gel properties at swelling equilibrium show remarkably good agreement with simulation results.

Kenkare, Nirupama Ramamurthy



Sodium dodecyl sulfate micelles in polyacrylamide gels.  

NASA Astrophysics Data System (ADS)

Polyacrylamide gels have been made in the presence of sodium dodecyl sulfate (SDS) micelles. The use of these gels for electrophoresis, after removal of the SDS, has demonstrated that the micelles modify the internal gel structure(R. Rill, B. Locke, Y. Liu, J. Dharia, D Van Winkle, Electrophoresis 17), 1304 (1996).. The phase diagram of SDS in buffer exhibits several transitions as a function of concentration and ionic strength. The SDS concentration used for templating gels is quite high, on the order of 20 - 30% by weight. This is the range in which the micellar system undergoes phase transitions. X-ray and light scattering experiments on gels with and without SDS and in SDS-buffer solutions were performed to understand the structure of the templated pores left after SDS removal. These experiments indicate the characteristic length scales associated with SDS micelles in gels changes from 3 to 15 nm as the gel and the SDS concentrations are varied.

van Winkle, David H.; Kettwig, Franz; Rill, Randolph L.; Liu, Yingjie; Locke, Bruce R.



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


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



Generative force of self-oscillating gel.  


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

Hara, Yusuke; Mayama, Hiroyuki; Morishima, Keisuke



Photorefractive sol-gel materials  

SciTech Connect

The authors report the synthesis and characterization of photorefractive sol-gel materials that possess covalently attached push-pull azobenzene and carbazole moieties. Molecular structural characterization of the modified silane monomers was achieved by {sup 1}H NMR and infra red spectroscopy. The second-order nonlinear optical properties of the organic-inorganic hybrid films prepared from modified silane monomers were evaluated by second-harmonic generation. The stabilized value of the second harmonic coefficient, d{sub 33}, of films poled by corona discharge, at 1,064 nm fundamental wavelength was found to be 107 pm/V. Photorefractivity was clearly displayed from a two beam coupling experiment.

Chaput, F.; Boilot, J.P.; Gacoin, T. [Ecole Polytechnique, Palaiseau (France); Darracq, B.; Riehl, D.; Canva, M.; Levy, Y.; Brun, A. [CNRS, Orsay (France)



Forces on an attractive surface generated from a thermoresponsive polymer gel  

NASA Astrophysics Data System (ADS)

Interaction between polymers and soft-matter surfaces in the biological cell is a common yet incompletely understood phenomenon. This work investigates a generic situation where a thermoresponsive polymer gel is placed in the vicinity of an adsorbing surface, and starts contracting. The force is mediated by polymer chains that partially attach to the surface and partially to the contracting gel. The main goal was to understand how the force generated by the transforming polymer gel depends on key parameters that describe the system, most importantly, the concentration of the polymer, the length of the force-mediating polymer, and the the distance between the surface and the outer border of the contracting polymer gel. The key result of the paper is the Laplace transform (with regard to the polymer length) of the pulling force expression. Analytical approximations for the force have been obtained, and the exact expression for the pulling force is presented for the situation when the gel starts contracting. In depth analysis of the force behavior revealed several phases adopted by the polymer during the gel contraction.

Konkoli, Zoran; Wegrzyn, Ilona; Jesorka, Aldo



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

NASA Astrophysics Data System (ADS)

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

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



Automated apparatus for producing gradient gels  


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

Anderson, Norman L. (Clarendon Hills, IL)



Automated apparatus for producing gradient gels  


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.



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



Blue emission in tetraethoxysilane and silica gels  

Microsoft Academic Search

Tetraethoxysilane (TEOS), a well-known SiO2 precursor, and silica gels prepared with it were characterized in terms of their optical properties in the 200–800 nm range. A distinctive blue emission is detected not only in the gels but also in the TEOS itself. Further heat treatments of the gels allowed the evolution of the blue signal to be followed; the origin

J. M. García; M. A. Mondragón; C. S. Téllez; A. Campero; V. M. Castaño



Gel time of calcium acrylate grouting material.  


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



21 CFR 866.4900 - Support gel.  

Code of Federal Regulations, 2010 CFR




21 CFR 866.4900 - Support gel.  

Code of Federal Regulations, 2013 CFR




Preparation of C[sub 70]-doped solid silica gel via sol-gel process  

Microsoft Academic Search

In this paper, the authors report a successful fabrication of C[sub 70]-doped silica solid gel via the sol-gel technique. The sol-gel process is a technique that can be used to prepare transparent oxide glasses by hydrolysis and condensation of alkoxide precursors. Little or no heating is required, and consequently the gel can be doped with molecules whose poor thermal stability

S. Dai; J. P. Young; R. N. Compton; G. Mamantov



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


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



Modeling of fibrin gels based on confocal microscopy and light-scattering data.  


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 D(m) = 1), for the overall system 1gels made of cylindrical sticks of diameter d, density ?, and average length , 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 D(m) ?1.2-1.6. The in silico gels' structure is quantitatively analyzed by its 3D spatial correlation function g(3D)(r) and corresponding power spectrum I(q) = FFT(3D[g3D(r)]), from which ?, d, D(m), ?, and ?0 can be extracted. In particular, ?0 provides an excellent estimate of the gel mesh size. The in silico gels' I(q) compares quite well with real gels' elastic light-scattering measurements. We then derived an analytical form factor for accurately fitting the scattering data, which allowed us to directly recover the gels' structural parameters. PMID:23473498

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



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

Microsoft Academic Search

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

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



Preparation of SnO2 Monolithic Gel by Sol-Gel Method  

Microsoft Academic Search

The effects of aging of a wet gel at room temperature and a use of a drying control chemical additive (DCCA) were investigated on the prevention of cracking of the gel during drying. N,N-Dimethylformamide (DMF) having low surface tension was used as a DCCA in this study. Before drying, the aged wet gel was immersed in DMF for several days

Haruhisa Shiomi; Chisato Kakimoto; Atsushi Nakahira; Shinichi Takeda



IBM Software Business Analytics  

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. It raises your profile as part of an elite group of cutting-edge analytics experts. Plus, we offer many ways· and the industry. You'll learn from other organizations as they learn from you.· You'll join an elite group ... Customer case study: highlight your organization, your business· challenges, the IBM Business Analytics


Against Analytic Moral Functionalism  

Microsoft Academic Search

I argue against the analytic moral functionalist view propounded by Frank Jackson and Philip Pettit. I focus on the 'input' clauses of our alleged 'folk moral theory'. I argue that the examples they give of such input clauses cannot plausibly be interpreted as analytic truths. They are in fact substantive moral claims about the moral 'domain'. It is a substantive

Nick Zangwill



Selectivity in Analytical Chemistry  

NSDL National Science Digital Library

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



Selectivity in Analytical Chemistry  

NSDL National Science Digital Library

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



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



[Serum protein electrophoresis: comparison of capillary zone electrophoresis Capillarys (Sebia) and agarose gel electrophoresis Hydrasys (Sebia)].  


Since several years, serum proteins electrophoresis became a routine analysis, mainly performed by agarose gel electrophoresis, frequently semi-automated. We compared the new fully automated capillary electrophoresis system from Sebia, Capillarys, with our reference method, agarose gel electrophoresis Hydrasys (Sebia). This study focused on the evaluation of both the analytical performances and some practical aspects such as ease of use, rapidity, costs. It appears clearly from that study that both methods give similar results for the detection of monoclonal proteins. We notice that the capillary electrophoresis (Capillarys) displays higher sensitivity (97.2%) than the agarose gel electrophoresis Hydrasys (93.5%), however with a lower specificity (93.7 versus 98.9%). On the other hand, the Capillarys method displays obvious practical advantages such as full automation, ease of use and rapidity. PMID:14671753

Lissoir, B; Wallemacq, P; Maisin, D



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


Aerosol Penetration through Silica Gel Tubes  

Microsoft Academic Search

Silica gel is commonly used by industrial hygienists to collect gases and vapors in the work place, in particular air contaminants with high polarity. The collected air pollutants are then treated and analyzed to identify their type and to determine the concentration using various methods and instrumentations. In addition to collection of gaseous pollutants, the silica gel tubes are also

Chih-Chieh Chen; Chen-Hsiung Wu; Sheng-Hsiu Huang; Yu-Mei Kuo



Cytoplasmic gel and water relations of axon  

Microsoft Academic Search

Summary A previous method of measuring the swelling pressure (??g) of the cytoplasmic gel of the giant axon ofLoligo vulgaris was refined. The estimates of??g made with the improved method were consistent with those made with the earlier method. In these methods the activity of the solvent in the gel is measured by increasing the activity of the solvent in

C. S. Spyropoulos



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.



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

NASA Astrophysics Data System (ADS)

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

Karino, Takeshi; Shibayama, Mitsuhiro; Ito, Kohzo



Intelligent gels and cryogels with entrapped emulsions.  


Smart thermoresponsive gels and cryogels with incorporated emulsions have been synthesized and studied. The gels were obtained by three-dimensional copolymerization of N-isopropylacrylamide and N,N'-methylene-bis-acrylamide or N,N'-bis(acryloyl)cystamine in the presence of dispersion of tetradecane stabilized with sodium dodecylsulfate. Polymerization was performed at room temperature and below the water crystallization temperature. Both composite gels and cryogels were capable of heat-induced collapse. The extent of the collapse of the composite gel prepared at room temperature was much smaller and without squeezing of the lipophilic phase out of the shrunk composite gel. In contrast, shrinking of the composite cryogel was accompanied by release of tetradecane emulsion. PMID:18386880

Komarova, Galina A; Starodubtsev, Sergey G; Lozinsky, Vladimir I; Kalinina, Elena V; Landfester, Katharina; Khokhlov, Alexei R



Volume phase transitions of smectic gels  

NASA Astrophysics Data System (ADS)

We present a mean-field theory to describe volume phase transitions of side-chain liquid crystalline (LC) gels, accompanied by isotropic-nematic-smectic- A phase transitions. Three different uniaxial nematic phases ( N1 , N2 , and N3 ) and smectic- A phases ( S1 , S2 , and S3 ) are defined by using orientational order parameter Sm of side-chain liquid crystals (mesogens), Sb of semiflexible backbone chains, and a translational order parameter ? for a smectic- A phase. We derive the free energy for smectic- A phases of side-chain LC gels dissolved in an isotropic solvent and examine the swelling curve of the LC gel, the orientational order parameters, and the deformation of the LC gel as a function of temperature. We find that the LC gel discontinuously changes the volume at an isotropic-nematic, an isotropic-smectic- A , and a nematic-smectic- A phase transition.

Matsuyama, Akihiko



Improving immobilized biocatalysts by gel phase polymerization  

SciTech Connect

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

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



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.



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

SciTech Connect

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

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



Sol-gel chemical sensors for surface-enhanced Raman spectroscopy  

NASA Astrophysics Data System (ADS)

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

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



Augmentation of Cooling Output by Silica Gel-Water Adsorption Cycle Utilizing the Waste Heat of GHP  

NASA Astrophysics Data System (ADS)

The GHP (Gas engine Heat Pump) system is expected to have high energy-efficiency in utilizing the waste heat exhausted from a gas engine. In summer season, a silica gel-water adsorption cooling unit driven by the exhaust heat is considered as a cooling system for saving energy. In this work, an attempt was made to improve the COP of a silica gel-water adsorption cooling system by enhancing heat and mass transfer in the silica gel adsorption layer. A unit cell was introduced as a simplified model of adsorber for analyzing the phenomena of heat and mass transfer in the adsorbent. This cell was composed of a single tube with a silica gel layer bonded on its external surface. Optimization of heat and mass transfer characteristics for the unit cell was carried out by experimental and analytical approach.

Homma, Hiroki; Araki, Nobuyuki


Enzymes in Analytical Chemistry.  

ERIC Educational Resources Information Center

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

Fishman, Myer M.



Ultrasound in analytical chemistry  

Microsoft Academic Search

Ultrasound is a type of energy which can help analytical chemists in almost all their laboratory tasks, from cleaning to detection.\\u000a A generic view of the different steps which can be assisted by ultrasound is given here. These steps include preliminary operations\\u000a usually not considered in most analytical methods (e.g. cleaning, degassing, and atomization), sample preparation being the\\u000a main area

F. Priego Capote; M. D. Luque de Castro



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. PMID:21487480



Improving immobilized biocatalysts by gel phase polymerization  

SciTech Connect

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

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



Sol-Gel Manufactured Energetic Materials  


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)



Electroacoustics of Particles Dispersed in Polymer Gel  

SciTech Connect

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

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



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.



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.


Comparative study of sol gel-hydrothermal and sol gel synthesis of titania silica composite nanoparticles  

NASA Astrophysics Data System (ADS)

Titania-silica composite nanoparticles were prepared by sol-gel-hydrothermal and sol-gel routes, respectively, and their physico-chemical and photocatalytic properties were compared. The results of XRD, TEM and BET surface areas showed that sol-gel-hydrothermal route led to anatase titania-silica composite nanoparticles with large specific surface area, but the sol-gel route tended to form mixture of anatase and rutile. The composite nanoparticles prepared by sol-gel-hydrothermal route had better thermal stability against phase transformation from anatase to rutile, agglomeration and particle growth than those prepared by sol-gel route. On the basis of XRD, FT-IR, XPS and 29Si MAS-NMR, a strong interaction was found between SiO 2 and TiO 2, and Ti-O-Si bonds formed during both the two routes. But more Ti-O-Si bonds formed in the composite nanoparticles prepared by sol-gel-hydrothermal route than those prepared by sol-gel route. As a result, the titania-silica composite nanoparticles prepared by sol-gel-hydrothermal route exhibited higher photocatalytic activity in decomposition of methylene blue than that prepared by sol-gel route, and it had excellent photocatalytic activity even after calcined at 1000 °C.

Li, Zhijie; Hou, Bo; Xu, Yao; Wu, Dong; Sun, Yuhan; Hu, Wei; Deng, Feng



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.  


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



Advances in sol-gel coating technologies  

SciTech Connect

Sol-gel coatings are thin, oxide layers applied from aqueous and non-aqueous media. In a dipping operation, the layer is typically less than one micron thick. This approach to depositing oxide layers has been used primarily in optical and electronic applications. Uses of these coatings in areas of wear and corrosion are known only in a few cases, such as semiconductor passivation layers or infiltrated fiber composites. The prospects for using sol-gel coatings for wear and corrosion are improving with new studies of electrochemical infiltration of gel layers and organic/inorganic hybrid layers. 57 refs., 6 figs., 2 tabs.

Klein, L.C. [Rutgers-The State Univ., Piscataway, NJ (United States). Ceramics Dept.; Sheppard, K. [Stevens Inst. of Technology, Hoboken, NJ (United States)



Reusable gels for germanium-68 sources.  


Two water-soluble gels, gelatin and Carbowax, were mixed with radioactive 68Ge solutions and evaluated for their use as long-lived (half-life, 280 days) radioactive sources. These gels melt at 40-50 degrees C and solidify at room temperature. The amount of 68Ge mixed with them can be increased or decreased as needed, eliminating waste of 68Ge. These gel sources also may replace short-lived 68Ga (half-life 68 min) as attenuation correction sources in positron emission tomography (PET) and reduce frequency of source preparation, thus reducing exposure of PET operators to radiation. PMID:1667318

Tilbury, R S; Broussard, W F; Youngerman, M J; Nguyen, D; Kim, E E



Degradation of gel in tray whitening.  


This article will address the breakdown or lowering of active bleaching agent concentration during use in the mouth. A greater than expected degradation occurs during the first 5 minutes followed by an exponential rate loss. Subjects have a large variation in degradation rates. After 2 and 6 hours there was 52% and 24% respectively, of the active agent present in a carbamide peroxide gel. The presence or absence of the pellicle did not affect the rate of degradation. The relationship of gel degradation to the whitening capability of a gel is yet to be determined. PMID:11908345

Matis, B A



Heterogeneous integration of gels into microfluidics using a mesh carrier.  


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

Eker, Bilge; Temiz, Yuksel; Delamarche, Emmanuel



Silica Gel Coated with Schiff's Base: Synthesis and Application as an Adsorbent for Cadmium, Copper, Zinc, and Nickel Determination after Preconcentration by Flame Atomic Absorption Spectrometry  

Microsoft Academic Search

A method for the preconcentration of Cd(II), Cu(II), Zn(II), and Ni(II) is proposed using a minicolumn filled with silica gel modified by Schiff's base. The retained analytes on the ligand-coated silica gel were recovered with a small volume of HNO3 (nitric acid). The metal ions in the eluent were determined by flame atomic absorption spectrometer (FAAS). Different factors, including the

Farzaneh. Shemirani; Aazam Alsadat. Mirroshandel; Masood. Salavati Niasari; Reyhaneh Rahnama Kozani



Difference gel electrophoresis: a single gel method for detecting changes in protein extracts.  


We describe a modification of two-dimensional (2-D) polyacrylamide gel electrophoresis that requires only a single gel to reproducibly detect differences between two protein samples. This was accomplished by fluorescently tagging the two samples with two different dyes, running them on the same 2-D gel, post-run fluorescence imaging of the gel into two images, and superimposing the images. The amine reactive dyes were designed to insure that proteins common to both samples have the same relative mobility regardless of the dye used to tag them. Thus, this technique, called difference gel electrophoresis (DIGE), circumvents the need to compare several 2-D gels. DIGE is reproducible, sensitive, and can detect an exogenous difference between two Drosophila embryo extracts at nanogram levels. Moreover, an inducible protein from E. coli was detected after 15 min of induction and identified using DIGE preparatively. PMID:9420172

Unlü, M; Morgan, M E; Minden, J S



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)



Sol-gel antireflective coating on plastics  


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

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



Formation of Anisotropic Block Copolymer Gels  

NASA Astrophysics Data System (ADS)

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

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



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.



Sol-gel antireflective coating on plastics  


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.



Turbidimetric studies of Limulus coagulin gel formation.  

PubMed Central

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

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



Instrumental texture profile analysis of gelatin gel extracted from grouper skin and commercial (bovine and porcine) gelatin gels.  


Mechanical compression was used to study the gelling characteristics of gelatin gels. Texture profile analysis (TPA) showed that the hardness of fish and mammalian gelatin increased significantly as the concentrations of gels increased. TPA attributes of 10% fish skin gel showed significant differences from those obtained from 20% and 30% gels. In bovine and porcine cases, such generic trends were not observed. Mechanical characteristics of 10% gels of gelatin from fish skin, determined from one cycle compression, were significantly lower than other sources of gelatin gels, while bovine and porcine gels did not show any significant differences. In the case of TPA, hardness of bovine gelatin gel was highest at 41 N for 10% gel, followed by porcine (30 N) then fish skin (5 N) gelatin gels. The gels prepared from different sources did not show any generic trends when all other mechanical attributes were considered. PMID:19521895

Rahman, Mohammad Shafiur; Al-Mahrouqi, Abdullah Issa



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.



Characterization of gels prepared from silicon ethoxide  

E-print Network

CHAPTER I INTRODUCTION CHAPTER II LITERATURE REVIEW 2, 1. Sol-gel process 2. 1. 1. Raw materials 2. 1. 2. Geladon process 2. 1. 3. Effect of operating conditions 2. 2. Drying 2. 2. 1. Crack development 2. 2. 2. Drying techniques 2. 2. 3... particles 2. b. A chain like aggregate 3, a Schematic representation of initial sol formation by polymeirc page 3. b. Schematic representation of gel structure before and after desiccation 4. The effect of salts( other than flourides...

Yun, Su-Jin



Sol-gel based biofuel cell architectures  

Microsoft Academic Search

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.

James Robert Lim



Adhesive Gels from Marine Gastropods (Mollusca)  

Microsoft Academic Search

\\u000a The structure and properties of gastropod gels are strikingly different from common commercial glues. Commercial glues are\\u000a generally solids; they may be applied in liquid form and then solidify or they may be deformable, tacky solids. In either\\u000a case, their final form consists entirely of polymers or cross-linked materials. In contrast, adhesive gels typically consist\\u000a of dilute polymer networks that

Hermann Ehrlich


Annular gel reactor for chemical pattern formation  


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); Horsthemke, Werner (Austin, TX); McCormick, William D. (Austin, TX); Swinney, Harry L. (Austin, TX); Tam, Wing Y. (Austin, TX)



An Analytic Holographic Superconductor  

E-print Network

We investigate a holographic superconductor that admits an analytic treatment near the phase transition. In the dual 3+1 dimensional field theory, the phase transition occurs when a scalar operator of scaling dimension two gets a vacuum expectation value. We calculate current-current correlation functions along with the speed of second sound near the critical temperature. We also make some remarks about critical exponents. An analytic treatment is possible because an underlying Heun equation describing the zero mode of the phase transition has a polynomial solution. Amusingly, the treatment here may generalize for an order parameter with any integer spin, and we propose a Lagrangian for a spin two holographic superconductor.

Christopher P. Herzog



Microstructure and phase diagrams of polymer gels  

NASA Astrophysics Data System (ADS)

Recently we developed [Panyukov and Rabin, Macromolecules 29 (1996) 7960] a phenomenological theory of randomly cross-linked polymer networks, based on the separation of solid-like and liquid-like degrees of freedom and taking into account the frozen inhomogeneity of network structure. We calculated the scattering spectra of weakly charged, randomly cross-linked polymer gels in good, poor and in ? solvents [Panyukov and Rabin, Macromolecules 29 (1996) 8530; Rabin and Panyukov, Macromolecules 30 (1996) 301]. For some values of the thermodynamic parameters, the competition between poor solubility, electrostatics and network elasticity leads to the divergence of the structure factor at a wave vector q ?, signaling the onset of microphase separation in the gel. Depending on the choice of thermodynamic parameters, the characteristic wavelength 1/q ? varies from microscopic to macroscopic length scales. We have shown that the presence of long range elastic interactions in the network affects the phase diagrams of polymer gels in poor solvent. Weakly charged gels deswell continuously upon decreasing the quality of solvent. At intermediate degrees of ionization the gel undergoes a first order volume transition between two homogeneous states, which takes place at the spinodal. Strong hysteresis is predicted for the swelling and the deswelling transitions in this regime. Further increase of the charge on the gel leads to the formation of an anisotropically deformed phase on the surface of the isotropic bulk phase.

Panyukov, Sergei; Rabin, Yitzhak


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. PMID:23271807

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



Linear and bending actuation of bucky gel  

NASA Astrophysics Data System (ADS)

In 2003 Takuzo Aida and coworkers reported that single-walled carbon nanotubes (SW-CNTs), when ground with imidazolium based ionic liquids (ILs), create a physical gel, named "bucky gel"1. This gel was used to prepare bimorph electrochemical actuators using a polymer-supported internal IL electrolyte layer2. These actuators can operate in air at low voltage showing improved frequency response and strain. Usual bucky gel actuators rely on a bimorph configuration where the electrodes are used alternatively as cathode and anode thus producing a bending motion. This kind of motion is limiting the possible applications, especially when, like in artificial muscles, linear strain and motion are required. We present a new design for bucky gel actuators capable of both linear and bending motion that uses a three electrode configuration with two active electrodes and a third passive one, made from a metal spring (serpentine shaped), acting as counter plate. We have built such a device and report here its linear and bending actuation performance. In these preliminary experiments we have obtained a linear strain of 0.6% and a bending strain difference between two bucky gel electrodes of 0.25%.

Biso, Maurizio; Ansaldo, Alberto; Vintera, Veronica; Ricci, Davide



Gel electrolyte for lithium-ion batteries.  

SciTech Connect

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

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



Treatment of osteochondral injuries with platelet gel  

PubMed Central

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

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



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



Kinetic resolution of racemic mixtures in gel media  

Microsoft Academic Search

The goal of this research was to investigate the effect of chiral gels on the chiral crystal nucleation and growth and assess the gels' potential as media for kinetic separation of racemic mixtures. The morphologies of asparagine monohydrate and sodium bromate crystals grown in different gel media were examined in order to discern the effect of gel structure and density

Rositza Iordanova Petrova



Preparation and in vitro percutaneous penetration of simvastatin ethosome gel.  


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

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



Ada & the Analytical Engine.  

ERIC Educational Resources Information Center

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

Freeman, Elisabeth



Statistics for Analytical Chemistry  

NSDL National Science Digital Library

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

Van Bramer, Scott E.



Analytical Probability Distributions  

Microsoft Academic Search

This note introduces four analytical probability distributions and the underlying uncertain processes from which they can be derived. It demonstrates that, when we can build a reasonable model of an uncertain process, we can use the model to derive the probability distribution from fundamental principles and forgo the chore of estimating the distribution subjectively by assessing fractiles. The probability distributions

Dana Clyman


Data Analytics Engineering  

E-print Network

S h l f Applied OR Data Analytics School of Operations Financial Engineering Information Research and Information Manufacturing Strategic Technology Engineering Operations Systems Engineering Master of E i iEngineering of the Master of Engineering Program................... . 1 II. MASTER OF ENGINEERING PROGRAM REQUIREMENTS A

Keinan, Alon


Synthetic and analytical thinking  

Microsoft Academic Search

It is shown that scientific research is not a linear process of information gaining, of accumulating data and facts, but is rather to be characterized by a model showing the cyclic structure of data gathering and construction of theories, of inductive and deductive methods. Analytical and synthetic methods are linked together and are building inseparable components of the texture of

Franz M. Wuketits



Analytics: Changing the Conversation  

ERIC Educational Resources Information Center

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

Oblinger, Diana G.



Structural change of?-carrageenan gel near solgel transition point  

NASA Astrophysics Data System (ADS)

The structural change of ?-carrageenan gel in the gel-to-sol transition was observed with the small-angle neutron scattering (SANS). The SANS intensity decreases on approaching to the transition point from the gel phase. On the other hand, the observed gyration radius does not change in the whole region of the gel phase. The fact means that the number of the cross link points decreases but their size keeps almost unchanged in the gel-to-sol transition.

Sugiyama, Masaaki; Yuasa, Chikanori; Hara, Kazuhiro; Hiramatsu, Nobuyasu; Nakamura, Atsushi; Hayakawa, Yasushi; Maeda, Yutaka



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

E-print Network

37 Silver Staining SDS Gels · Remove the stacking gel before the first fixative step. · Do, for frequent silver staining: make up solutions as 10X stocks ahead of time. 1. Fix in 50% methanol, 10% acetic seconds. Repeat the change of developer solution once again. Agitate gently until the desired staining

Aris, John P.


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

Microsoft Academic Search

Gel destaining following Coomassie Brilliant Blue (CBB) staining involves the use of toxic reagents. Here we demonstrate the efficacy of various paper adsorbents in adsorbing CBB. Kimwipes adsorbed the best, followed by Teri towels, multifold towels, and Whatman numbers 1 and 3 filter papers. Three Kimwipes completely adsorbed the dye released from a CBB-stained mini-gel. Nonradioactive destain solution can, therefore,

Yaser Dorri; Biji T. Kurien



Motion design of a starfish-shaped gel robot made of electro-active polymer gel  

Microsoft Academic Search

This paper proposes a method to generate novel motions of mollusk-type deformable robots made of electro-active polymer gel. Simulation and experimental results show that large transformations can be obtained with multiple electrodes in a planar configuration. We have designed a starfish-shaped gel robot that can turn over using spatially varying electric fields.

Mihoko Otake; Yoshiharu Kagami; Masayuki Inaba; Hirochika Inoue



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


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



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

PubMed Central

The use of conducting gels to mimic brain and other tissues is of increasing interest in the development of new medical devices. Currently, there are few such models that can be utilized at physiologic temperatures. In this work, the conductivities of agar, agarose and gelatin gels were manipulated by varying NaCl concentration from 0–1 mg/ml. The AC conductivity was measured at room and physiological temperatures (37°C) in the 100–500 Hz frequency range. Conductivity (?) was nearly independent of frequency but increased linearly with NaCl concentration and was higher at physiological temperatures in these gels. A formula for predicting conductivity as a function of NaCl concentration was derived for each gel type. The overall goal is to develop a ‘brain gel model’, for studying low frequency electrical properties of the brain and other tissues at physiological temperatures. PMID:23139442

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



Reprogramming cellular phenotype by soft collagen gels.  


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

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



Sol-gel processing of metal sulfides  

NASA Astrophysics Data System (ADS)

Metal sulfides were synthesised via a sol-gel process using various metal alkoxides and hydrogen sulfide in toluene. Colloidal gels were prepared from germanium ethoxide, germanium isopropoxide, zinc tert-butoxide and tungsten (VI) ethoxide, whereas colloidal powder was produced from tungsten (V) dichloride ethoxide. Special precautions were necessary to protect the reaction mixture from water contamination which produced metal oxides. Results indicated that the main source of water is the hydrogen sulfide gas. In addition, synthesis of metal sulfides from a mixture of metal oxide and sulfide was demonstrated by the example of monoclinic germanium disulfide. It was produced by reaction of the sol-gel product with sulfur. Heat treatment of the sol-gel product and sulfur yielded single phase GeSsb2. The sol-gel prepared materials and their heat treated products were characterized by various methods. A chemical kinetics study of the functional groups -OR, -SH and Ssp{2-} was carried out for the sol-gel processing of GeSsb2 from of hydrogen sulfide and two different alkoxides, germanium ethoxide and germanium isopropoxide. The study was performed for different concentrations of precursors at different molar ratios and temperatures. The results indicate that the proposed reaction mechanism was simplified under appropriate reaction conditions. Experimentally determined rate constants of thiolysis and condensations demonstrate that thiolysis is slow and that condensations are fast steps, regardless of the studied reaction conditions. A study of the temperature effect on the reaction rate constant shows that it increases with temperature in accord with both Arrhenius law and transition-state theory. Activation energies, Esba, and activation parameters DeltaSsp{ddagger}, DeltaHsp{ddagger} and DeltaGsp{ddagger}, were determined for thiolysis and condensation reactions. The potentiometric tiration method was used for quantitative determination of germanium sulfide and germanium mercaptide evolved during the sol-gel processing of GeSsb2. The titrations were performed in 2-propanol or in a 50-50 vol % mixture of 2-propanol and toluene. The ion selective Ag/Agsb2S electrode was used for equivalence point detection. Study of the Nernst equation shows that complexes were formed at the electrode surface. However, the titration equivalence point volume clearly demonstrates the formation of Agsb2S and Ge(SAg)sbn. In order to explain this discrepancy a new electrode reaction mechanism and a modified Ag/Agsb2S electrode potential equation are proposed. Effects of hydrogen sulfide and germanium ethoxide concentrations, the concentration ratio and temperature on the microstructure of the prepared GeSsb2 gels were studied. It was found that the concentrations of the reactants have the most significant influence on gel structure.

Stanic, Vesha


Traveling Waves in a Reactive Polymer Gel  

NASA Astrophysics Data System (ADS)

We consider a theoretical model of a polymer gel, which exhibits a swelling-deswelling behavior in response to the Belousov-Zhabotinsky (BZ) reaction. The BZ reaction generates periodic redox changes of a metal catalyst, and a wide variety of spatiotemporal structures have been observed in the course of the BZ reaction in solution. If the catalyst is covalently bonded to a responsive hydrogel soaked in a solution containing the rest of the BZ reagents, then the metal redox changes may cause variations in the gel volume. The self-oscillation of the gel volume and the traveling chemical waves accompanied by the local swelling have been experimentally observed by Yoshida and co-workers. Here, we present a simplified theoretical description of a hydrogel with the BZ reaction. The description is based on the Oregonator model of the BZ reaction, and on the two-fluid model of the gel dynamics. The formulated model is applied to studying one-dimensional wave trains in the reactive gel. We focus on the dispersion law as it reflects the inherent coupling between the chemical and mechanical degrees of freedom.

Yashin, Victor V.



Nonlinear elasticity and yielding of depletion gels  

NASA Astrophysics Data System (ADS)

A microscopic activated barrier hopping theory of the viscoelasticity of colloidal glasses and gels has been generalized to treat the nonlinear rheological behavior of particle-polymer suspensions. The quiescent cage constraints and depletion bond strength are quantified using the polymer reference interaction site model theory of structure. External deformation (strain or stress) distorts the confining nonequilibrium free energy and reduces the barrier. The theory is specialized to study a limiting mechanical description of yielding and modulus softening in the absence of thermally induced barrier hopping. The yield stress and strain show a rich functional dependence on colloid volume fraction, polymer concentration, and polymer-colloid size asymmetry ratio. The yield stress collapses onto a master curve as a function of the polymer concentration scaled by its ideal mode-coupling gel boundary value, and sufficiently deep in the gel is of an effective power-law form with a universal exponent. A similar functional and scaling dependence of the yield stress on the volume fraction is found, but the apparent power-law exponent is nonuniversal and linearly correlated with the critical gel volume fraction. Stronger gels are generally, but not always, predicted to be more brittle in the strain mode of deformation. The theoretical calculations appear to be in accord with a broad range of observations.

Kobelev, Vladimir; Schweizer, Kenneth S.



Field Analytic Technologies Encyclopedia  

NSDL National Science Digital Library

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



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.



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



Analytical blind channel identification  

Microsoft Academic Search

A novel analytical blind single-input single-output (SISO) identification algorithm is presented, based on the noncircular second-order statistics of the output. It is shown that statistics of order higher than two are not mandatory to restore identifiability. Our approach is valid, for instance, when the channel is excited by phase shift keying (PSK) inputs. It is shown that the channel taps

Olivier Grellier; P. Comon; B. Mourrain; P. Trebuchet



Competing on talent analytics.  


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



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


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



Nail damage from gel polish manicure.  


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

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



Low-Reynolds-number swimming in gels  

NASA Astrophysics Data System (ADS)

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

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



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.



Preparation and characterization of hydrophobic superparamagnetic gel.  

SciTech Connect

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

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



Pouring and running a protein gel by reusing commercial cassettes.  


The evaluation of proteins using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis is a common technique used by biochemistry and molecular biology researchers. For laboratories that perform daily analyses of proteins, the cost of commercially available polyacrylamide gels (~$10/gel) can be considerable over time. To mitigate this cost, some researchers prepare their own polyacrylamide gels. Traditional methods of pouring these gels typically utilize specialized equipment and glass gel plates that can be expensive and preclude pouring many gels and storing them for future use. Furthermore, handling of glass plates during cleaning or gel pouring can result in accidental breakage creating a safety hazard, which may preclude their use in undergraduate laboratory classes. Our protocol demonstrates how to pour multiple protein gels simultaneously by recycling Invitrogen Nupage Novex minigel cassettes, and inexpensive materials purchased at a home improvement store. This economical and streamlined method includes a way to store the gels at 4°C for a few weeks. By re-using the plastic gel cassettes from commercially available gels, labs that run frequent protein gels can save significant costs and help the environment. In addition, plastic gel cassettes are extremely resistant to breakage, which makes them ideal for undergraduate laboratory classrooms. PMID:22349047

Hwang, Alexander C; Grey, Paris H; Cuddy, Katrina; Oppenheimer, David G



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


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

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



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


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.



MSc in Analytical Science Analytical Science: Methods and  

E-print Network

such as the life sciences (including pharmaceutical and environmental science), and materials science, and weAS:MIT MSc in Analytical Science Analytical Science: Methods and Instrumental Techniques Warwick Centre for Analytical Science An EPSRC approved masters training package at the University of Warwick www

Davies, Christopher


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.



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

E-print Network

, such as anthropology (1,2), evo- lution (3,4), population genetics (4), and human meta- bolic disease (5). Unlike- istics result in mtDNA polymorphisms whose maternal lineage can be followed to study population dispersal is described that detects even single base pair changes in mitochondrial DNA (mtDNA). In this method

Ernst, Susan G.


Phase Equilibria and Computer Simulation of Polymer Gels and Related Systems.  

NASA Astrophysics Data System (ADS)

A number of the properties of gels are examined from a microscopic viewpoint through application of equilibrium statistical mechanics. Particular emphasis is placed on the phase equilibrium characteristics of polymer gels and the properties related to the formation of colloidal gels. A lattice model is proposed to describe the swelling behavior and first-order volume phase transitions of polymer gels in binary solvent mixtures. The model is a spin-1 Ising model coupled with an elastic equation of state. It is solved numerically to obtain the degree of swelling of the gel as a function of the solvent concentration. Results are obtained for a range of interaction energies and degrees of cross-linking to determine the effects on the transitions. These results demonstrate that a simple lattice model is capable of producing swelling curves, including first-order transitions, similar to those seen in some experimental systems. Monte Carlo simulations are developed and applied to an N-isopropylacrylamide gel in water that exhibits a first-order swelling transition with changes in temperature. In the simulation, polymer and solvent are described by detailed site-site potentials. These simulations show, for the first time, phase transitions in polymer gels, and demonstrate, semi-quantitatively, the forces that are important for the presence or absence of swelling transitions. The formation of colloidal gels via the clustering of particles is examined through a continuum percolation model. Connectedness Ornstein-Zernike integral equations are solved numerically in the Percus-Yevick approximation for the square-well potential system to obtain cluster distributions and locate the percolation transition. Additional results are presented for studies of the thermodynamic properties and phase equilibria of simple fluid mixtures. The adhesive-sphere potential is used to analytically compute excess free energies via the Percus -Yevick approximation in order to examine the predictive abilities of commonly-used excess property theories which are based on particle clustering or local composition. A graphical technique for computing vapor-liquid phase coexistence for multicomponent solutions is also presented, and is demonstrated using a binary van der Waals mixture.

Netemeyer, Stephen C.


Analytical Instruments and Spectroscopic Concepts  

NSDL National Science Digital Library

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

Chasteen, Thomas G.



Electrochemical impedimetric sensor based on molecularly imprinted polymers/sol-gel chemistry for methidathion organophosphorous insecticide recognition.  


We report here a novel method to detect methidathion organophosphorous insecticides. The sensing platform was architected by the combination of molecularly imprinted polymers and sol-gel technique on inexpensive, portable and disposable screen printed carbon electrodes. Electrochemical impedimetric detection technique was employed to perform the label free detection of the target analyte on the designed MIP/sol-gel integrated platform. The selection of the target specific monomer by electrochemical impedimetric methods was consistent with the results obtained by the computational modelling method. The prepared electrochemical MIP/sol-gel based sensor exhibited a high recognition capability toward methidathion, as well as a broad linear range and a low detection limit under the optimized conditions. Satisfactory results were also obtained for the methidathion determination in waste water samples. PMID:25159412

Bakas, Idriss; Hayat, Akhtar; Piletsky, Sergey; Piletska, Elena; Chehimi, Mohamed M; Noguer, Thierry; Rouillon, Régis



(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.



Bioactive nanocrystalline sol-gel hydroxyapatite coatings.  


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

Chai, C S; Ben-Nissan, B



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



Gel bead composition for metal adsorption  


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)



Gel bead composition for metal adsorption  


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)



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.



Sol-gel Chemistry in Medicinal Science  

Microsoft Academic Search

The sol-gel process is an inorganic polymerization process taking place in mild conditions, allowing the association of mineral phases with organic or biological systems. The possibility to immobilize drugs, enzymes, antibodies and even whole cells without loss of their biological activity led to the development of diagnostic tools, drug delivery carriers as well as new hosts for artificial organ design.

Thibaud Coradin; Michel Boissiere; Jacques Livage



Rheology of ?-carrageenan and ?-lactoglobulin mixed gels  

Microsoft Academic Search

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

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



How to scan polymer gels with MRI?  

Microsoft Academic Search

The absorbed radiation dose fixated in a polymer gel dosimeter can be read out by several methods such as magnetic resonance imaging (MRI), optical CT, X-ray CT and ultrasound with MRI being the first method that was explored. Although MRI was considered as an elegant scanning technique, readily available in most hospitals, it was later found that using a non-optimized

Yves De Deene



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)



Electrochemical Growth Of Crystals In Gels  

NASA Technical Reports Server (NTRS)

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

Barber, Patrick G.; Coleman, James



Microstructure and microhardness in alumina gel monoliths  

Microsoft Academic Search

Alumina gel monoliths prepared from aluminium isopropoxide through hydrolysis and chemical polymerization are porous, transparent, and consist of ultrafine particles. The monolithic xerogels exhibit lamellar, cellular and fractal microstructures which are found to arise due to instabilities during drying. Phase separation can occur during ageing and drying and influence the microstructure. The Vickers indentation hardness shows a power-law dependence on

V. Saraswati; Indira Gandhi



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.



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.



Non-diffusing radiochromic micelle gel  

NASA Astrophysics Data System (ADS)

The addition of Laponite, a synthetic clay nanoparticle material to radiochromic leuco Malachite Green micelle hydrogel eliminates diffusion of the cationic dye by electrostatic binding. The clay nanoparticles also increased dose sensitivity ten-fold relative to the parent gel formulation. This material is a suitable 3D water equivalent dosimeter with optical CT readout.

Jordan, Kevin; Sekimoto, Masaya



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


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.



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


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)



Optimization of topical gels with betamethasone dipropionate: selection of gel forming and optimal cosolvent system.  


The purpose of these studies was to develop a 0.05% betamethasone gel characterized by physical-chemical stability and good release properties. The preliminary studies were designed to select the gel-forming agents and the excipients compatible with betamethasone dipropionate. In order to formulate a clear gel without particles of drug substances in suspension, a solvent system for the drug substance was selected. The content of drug substance released, the rheological and in vitro release tests were the tools used for the optimal formulation selection. A stable carbomer gel was obtained by solubilization of betamethasone dipropionate in a vehicle composed by 40% PEG 400, 10% ethanol and 5% Transcutol. PMID:21870764

B?i?an, Mariana; Lionte, Mihaela; Moisuc, L?cr?mioara; Gafi?anu, Eliza



Sol-Gel Synthesis of Au-Nanoparticle Dispersed Bicontinuous Macroporous Siloxane Gel  

NASA Astrophysics Data System (ADS)

We synthesized Au-nanoparticle dispersed siloxane gel with well-defined bicontinuous macroporous morphologies. We employed methyltrimethoxysilane (MTMS) as a precursor of the gel skeleton, and also employed hydrogen tetrachloroaurate(III) as both a precursor of Au nanoparticles and an acid catalyst for hydrolysis/condensation of methoxysilanes. The effect of adding (3-mercaptopropyl)trimethoxysilane (MPTMS) as a starting material on the obtained structure was also investigated. It is found that Au nanoparticles of 20-30 nm in grain size are uniformly dispersed on the gel surface in the system containing MPTMS; in contrast, Au nanoparticles assembled in the pits in the MPTMS-free system. All the heat-treated MPTMS-containing gels showed surface plasmon absorption, and the peaks shifted from 550 to 520 nm with increasing the calcination temperature.

Hamada, Y.; Nishi, M.; Shimotsuma, Y.; Miura, K.; Hirao, K.



Prescribed Pattern Transformation in Swelling Gel Tubes by Elastic Instability  

E-print Network

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

Lee, Howon


Sol-Gel Alumina Nano Composites for Functional Applications.  

E-print Network

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

Jayasankar, M



Synthetic and Biopolymer Gels - Similarities and Difference.  

NASA Astrophysics Data System (ADS)

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

Horkay, Ferenc



Comparison of dye adsorption by mesoporous hybrid gels: Understanding the interactions between dyes and gel surfaces  

Microsoft Academic Search

Without using any templating agents, mesoporous hybrid gels were prepared using mixtures of tetraethoxysilane (TEOS) with n-propyltriethoxysilane (PTES), bis(trimethoxysilyl)hexane (TSH), or bis(trimethoxysilylpropyl)amine (TSPA) as precursors. Fourier transform infrared (FTIR), N2 adsorption\\/desorption, thermogravimetry (TG), point of zero charge (PZC), and water vapor adsorption measurements were used to characterize the gels. The adsorption of methyl orange (MO), methyl red (MR), bromocresol purple

Zhijian Wu; Laijiang You; Hong Xiang; Yan Jiang



Tribological Properties and Film Formation Behavior of Thermoreversible Gel Lubricants  

Microsoft Academic Search

The tribological properties of a new and unique thermoreversible gel lubricant (TR gel lube) were investigated. TR gel lube, which includes 10–40% of amide-type gelling agent in base fluid, is able to repeatedly alter or convert phase from gel state to liquid state at the melting point of the gelling agent. High-pressure rheological tests were performed in order to characterize

Nobuyoshi Ohno; Sobahan Mia; Kazuo Masuhara; Kentaro Sonoda; Yuji Yamashita; Yoshitaka Tamura; Shigeki Morita; Yuji Shitara



Photophysical properties of cyanine dyes in sol-gel matrices  

Microsoft Academic Search

Planar and twisted cyanine dyes with different pKa values are examined concerning their protonation equilibrium in sol-gel matrices. In the sol-gel matrix the equilibrium between the cation and the dicationic form shifts to the dication pointing to acid-base reactions of sol-gel walls with cyanine dyes. The colorless dicationic species is not found for pseudoisocyanine and in sol-gel bulks prepared with

U. De Rossi; S. Daehne; R. Reisfeld



Recent Progress in Gel Theory: Ring, Excluded Volume, and Dimension  

Microsoft Academic Search

Recent developments in gel research are reviewed with emphasis on the gel point problem. We will describe in due course how\\u000a the gel point equation can be deduced from first principles. First we review briefly the industrial development of gel science\\u000a in Japan (Sect. 1) and a central aspect of the classical theory of gelation (Sect. 2). In Sect. 3,

Kazumi Suematsu


Low temperature and UV curable sol-gel coatings for long lasting optical fiber biosensors  

NASA Astrophysics Data System (ADS)

The use of optical fibers as sensing element is increasing in clinical, pharmaceutical and industrial applications. Excellent light delivery, long interaction length, low cost and ability not only to excite the target molecules but also to capture the emitted light from the targets are the hallmarks of optical fiber as biosensors. In biosensors based on fiber optics the interaction with the analyte can occur within an element of the optical fiber. One of the techniques for this kind of biosensors is to remove the fiber optic cladding and substitute it for biological coatings that will interact with the parameter to sensorize. The deposition of these layers can be made by sol-gel technology. The sol-gel technology is being increasingly used mainly due to the high versatility to tailor their optical features. Incorporation of suitable chemical and biochemical sensing agents have allowed determining pH, gases, and biochemical species, among others. Nonetheless, the relatively high processing temperatures and short lifetime values mean severe drawbacks for a successful exploitation of sol-gel based coated optical fibres. With regard to the latter, herein we present the design, preparation and characterization of novel sol-gel coated optical fibres. Low temperature and UV curable coating formulations were optimized to achieve a good adhesion and optical performance. The UV photopolymerizable formulation was comprised by glycidoxypropyltrimethoxysilane (GLYMO), Tetraethylorthosilicate (TEOS) and an initiator. While the thermoset coating was prepared by using 3-aminopropyltrimethoxysilane, GLYMO, and TEOS as main reagents. Both curable sol-gel coated fibres were analysed by FTIR, SEM and optical characterization. Furthermore, in the present work a new technique for silica cladding removal has been developed by ultra-short pulses laser processing, getting good dimensional accuracy and surface integrity.

Otaduy, D.; Villar, A.; Gomez-Herrero, E.; Goitandia, A. M.; Gorritxategi, E.; Quintana, I.



Monolithic diphasic gels of mullite by sol-gel process under ultrasound stimulation.  


Diphasic gel in the mullite composition was prepared from a colloidal sol of boehmite mixed with a hydrolyzed tetraethoxisilane (TEOS) solution. The boehmite sol was obtained by peptization of a poorly crystallized or very small mean crystallite size (approximately 34 A) precipitate, resulting from the reaction between solutions of aluminum sulfate and sodium hydroxide. Ultrasound was utilized in the processes of the TEOS hydrolysis and the boehmite peptization, and also for complete homogenization of the mixture to gel. The wet gel is almost clear and monolithic. The gel transparency is lost on drying, when syneresis has ended, so that the interlinked pore structure starts to empty and is recovered upon water re-absorption. Cracking closely accompanies this critical drying process. Differential thermal analysis (DTA) and X-ray diffraction (XRD) show that the solid structure of the gel is composed of an amorphous silica phase, as a matrix, and a colloidal sized crystalline phase of boehmite. Upon heat treatment, the boehmite phase within the gel closely follows the same transition sequence as in pure alumina shifted towards higher temperatures. Orthorhombic mullite formation was detected at 1300 degrees C. PMID:11270341

Vollet, D R; Donatti, D A; Domingos, R N; de Oliveira, I



21 CFR 520.1720d - Phenylbutazone gel.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Phenylbutazone gel. 520.1720d Section 520.1720d Food...ANIMAL DRUGS § 520.1720d Phenylbutazone gel. (a) Specifications. Each 30 grams of gel contains 4 grams of phenylbutazone....



Material characterization of fluorosilicone gels for automotive application  

Microsoft Academic Search

Fluorosilicone gel is commonly used in die passivation. This paper studies the characteristics of fluorosilicone gel applied on the manifold air pressure (MAP) sensor die. The cure mechanism and material characterization of the three types of gels were analyzed using differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), and rheometer. The temperature and time relationships were derived for each material type.

J. C. C. Fay; A. Lee; Lee Choon Liang; R. Neo



The sol-gel glass transformation of silica  

Microsoft Academic Search

Large monolithic xerogel silica glasses were successfully made from tetramethyl-orthosilicate and distilled water using the combination of an acidic drying control chemical additive (DCCA) and a specially designed drying chamber. The acidic DCCA increases the gel strength by formation of a fibrillar ultrastructure, and the drying chamber reduces the catastrophic capillary forces inside the wet gel body.Partially densified monolithic gels

L. L. Hench; S. H. Wang




E-print Network


Brinker, C. Jeffrey


Swelling of scleroglucan gels in binary DMSO\\/water solvents  

Microsoft Academic Search

The aim of the present study is to investigate the correspondence between volume transitions of scleroglucan gels and the reported conformational properties of the uncrosslinked polymer chains. The swelling behaviour of scleroglucan gels in binary solvent consisting of water and dimethylsulphoxide (DMSO) was investigated by first crosslinking aqueous scleroglucan in cylindrical tubes. The resulting cylindrical gels were cut into small

Bo Guo; Bjørn T. Stokke; Arnljot Elgsaeter



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


Cervical ripening with intravaginal prostaglandin E2 gel  

Microsoft Academic Search

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

I Z MacKenzie; M P Embrey




SciTech Connect

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

Cash, Webster [Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309 (United States)



Normality in Analytical Psychology  

PubMed Central

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

Myers, Steve



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


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



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



SANS study on pulley effect of slide-ring gel  

NASA Astrophysics Data System (ADS)

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

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



Dielectric properties of gel collected from shark electrosensors  

NASA Astrophysics Data System (ADS)

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

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



Strip-Loaded Sol-Gel Waveguides  

NASA Astrophysics Data System (ADS)

Sol-gel is one of the most attractive techniques for production of silica-on-silicon integrated optical devices. In fact, it combines low cost with flexibility and ease of doping; thus, nonlinear and active compounds can be effectively included in the silica matrix. Here, the feasibility of applying the sol-gel technique to the realization of an erbium-doped optical amplifier is reported on, operating in the third telecommunication window. In particular, the development of an optimum strategy for the design and fabrication of a guiding structure in the strip-loaded configuration is described. Design optimization results, as well as fabrication results and measured characteristics, are described and discussed.

Forastiere, Michele A.; Pelli, Stefano; Righini, Giancarlo C.; Guglielmi, Massimo; Martucci, Alessandro; Ahmad, Munir M.; McCarthy, Orla; Yeatman, Eric; Vannucci, Antonello


Similarity of wet granular packing to gels  

NASA Astrophysics Data System (ADS)

To date, there is still no general consensus on the fundamental principle that governs glass transition. Colloidal suspensions are ordinarily utilized as model systems to study the dynamical arrest mechanisms in glass or gels. Here, we tackle the problem using athermal granular particles. Slow dynamics and structural evolution of granular packing upon tapping are monitored by fast X-ray tomography. When the packing are wet and short-range attractive interactions exist, we find a large amount of locally favoured structures with fivefold symmetry, which bear great structural similarity to colloidal gels. In addition, these structures are almost absent in dry packing with similar packing fractions. The study leads strong support for the geometrical frustration mechanism for dynamic arrest in both thermal and athermal systems with attractive interactions. It also suggests nontrivial structural mechanism, if exists, for dynamic arrest in systems with purely repulsive interactions.

Li, Jindong; Cao, Yixin; Xia, Chengjie; Kou, Binquan; Xiao, Xianghui; Fezzaa, Kamel; Wang, Yujie



Gel-log flocculants treat drainage  

SciTech Connect

Sedimentation ponds are often located at sites difficult to access and where electricity is not available. The problem of flocculant treatment to increase settling rates and of monitoring the system can be met by a new form of flocculant presentation in gel logs. Each log weighs 40 lbs and measures 18 in by 9 in diameter. It is wrapped in wire mesh and placed in the channel feeding the retention pond. The log gradually dissolves at a rate determined by its surface area, the water flow in contact with the gel and the water temperature. Some trial and error is necessary to achieve the correct dosage rate, but the method has been used satisfactorily for over a year.

Not Available



Structural Hierarchy Governs Fibrin Gel Mechanics  

PubMed Central

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

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



Similarity of wet granular packing to gels.  


To date, there is still no general consensus on the fundamental principle that governs glass transition. Colloidal suspensions are ordinarily utilized as model systems to study the dynamical arrest mechanisms in glass or gels. Here, we tackle the problem using athermal granular particles. Slow dynamics and structural evolution of granular packing upon tapping are monitored by fast X-ray tomography. When the packing are wet and short-range attractive interactions exist, we find a large amount of locally favoured structures with fivefold symmetry, which bear great structural similarity to colloidal gels. In addition, these structures are almost absent in dry packing with similar packing fractions. The study leads strong support for the geometrical frustration mechanism for dynamic arrest in both thermal and athermal systems with attractive interactions. It also suggests nontrivial structural mechanism, if exists, for dynamic arrest in systems with purely repulsive interactions. PMID:25247441

Li, Jindong; Cao, Yixin; Xia, Chengjie; Kou, Binquan; Xiao, Xianghui; Fezzaa, Kamel; Wang, Yujie



Gel ointment of verapamil for percutaneous absorption.  


A gel ointment of verapamil designed for systemic action by transdermal absorption was prepared. The amount of drug released in vitro decreased progressively when increasing amounts (from 20 to 50%) of ethanol-propylene glycol (2:1, v/v) were incorporated into the ointment. Transdermal absorption of the drug in vivo was studied in rats. Verapamil was found in the systemic circulation, and plasma drug levels were maintained at a plateau for 12 hours after application. The effect of two additives on absorption was also examined. Azone, a cycloheptanone derivative, increased plasma levels of verapamil up to tenfold, the effect being greatly dependent on the amount of alcohols in the formulation. Isopropyl myristate did not influence systemic absorption, but it effectively increased absorption into skin. We conclude that the gel ointment can be used for transdermal drug delivery when an adequate absorption promoter is added. PMID:3509338

Sekine, T; Machida, Y; Nagai, T



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

Microsoft Academic Search

Polymer gel dosimeters offer a wide range of applications in the three-dimensional verification of complex dose distributions such as in intensity-modulated radiotherapy. One of the major difficulties with polymer gel dosimeters is their sensitivity to oxygen, as oxygen inhibits the radiation-induced polymerization reaction. For several years, oxygen was removed from the gels by bubbling the sol with inert gases for

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



Sol-Gel PZT for MEMS Applications  

Microsoft Academic Search

Thin-film piezoelectric materials offer an alternative transduction mechanism to electrostatic actuation and capacitive sensing with many attractive advantages for applications in microelectromechanical systems (MEMS). Researchers at the U.S. Army Research Laboratory are utilizing sol-gel deposited lead zirconate titanate (PZT) thin-films in developing several new MEMS technologies, including high frequency filters, magnetometers, micropumps, and pressure sensors. The fabrication procedure and an

Brett Piekarski; Madan Dubey; Eugene Zakar; Ronald Polcawich; Don Devoe; Dennis Wickenden



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


Sol–gel processing of hydroxyapatite  

Microsoft Academic Search

Hydroxyapatite, a calcium phosphate-based compound with numerous applications in the biological field was synthesized using the sol–gel processing route. The formation of hydroxyapatite and other compounds during the heat-treatment cycle were identified and characterized using thermal analyses and X-ray diffraction together with infrared and Raman spectroscopy. The influence of the addition of various organic alcohols (R–OH, R=CH3–, C2H5– and C3H8–)

A. Jillavenkatesa; R. A. Condrate SR



Activity staining of endoglucanases in polyacrylamide gels.  


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



Hydrocolloid Gel Particles: Formation, Characterization, and Application  

Microsoft Academic Search

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

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



Gastropod Secretory Glands and Adhesive Gels  

Microsoft Academic Search

\\u000a Gastropod molluscs are known for slime, yet the complexity and variety of their slimes is not always appreciated. These snails\\u000a and slugs secrete visco-elastic mucous gels with functions that include feeding, protection, reproduction, locomotion, lubrication,\\u000a defense, and adhesion (Denny, 1983). While the functional demands of such disparate tasks obviously vary widely, there has been little work on the biochemical\\u000a variations

Andrew M. Smith


Ultrasensitive fluorescence detection of DNA sequencing gels  

SciTech Connect

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

Mathies, R.A.



Dynamic light-scattering monitoring of a transient biopolymer gel  

NASA Astrophysics Data System (ADS)

We performed dynamic light-scattering (DLS) monitoring and a rheological study to characterize the formation and destruction of a transient (limited lifetime) gel formed from the biopolymers chitosan and gelatin. Gel formation, initiated by the enzyme tyrosinase, is followed by spontaneous gel breakage. Our DLS results demonstrate that this material passes through five stages in which the gel forms, consolidates, “lives”, softens, and eventually breaks. We speculate that the existence of the transient gel is caused by a competition between two processes: a fast-rate chemical reaction leading to formation of a branched-copolymer network and a slow-rate diffusion-like rearrangement of the gelatin branches resulting in eventual gel breakage. Despite a dramatic difference in the characteristic times of the gel formation ( tg) and gel breakage ( tb)-the ratio tb/ tg is of the order 10 3-DLS has revealed an intrinsic monitoring-time symmetry in the formation and destruction of the gel provided that a proper physical choice of the reduced temporal scale is used. In this scale the slow-mode relaxation time for both sides of the process, gel formation and gel destruction, exhibits a power law in the spirit of percolation theory.

Kostko, A. F.; Chen, T.; Payne, G. F.; Anisimov, M. A.



Gel Encapsulation of Glucose Nanosensors for Prolonged In Vivo Lifetime  

PubMed Central

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

Balaconis, Mary K.; Clark, Heather A.



Bucky gel actuators optimization towards haptic applications  

NASA Astrophysics Data System (ADS)

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

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



Sol-gel based optical chemical sensors  

NASA Astrophysics Data System (ADS)

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

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



Highly-correlated charges in polyelectrolyte gels  

NASA Astrophysics Data System (ADS)

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

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



Sol-gel method for encapsulating molecules  


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

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



Pair Analytics: Capturing Reasoning Processes in Collaborative Visual Analytics  

Microsoft Academic Search

Studying how humans interact with abstract, visual representations of massive amounts of data provides knowledge about how cognition works in visual analytics. This knowledge provides guidelines for cognitive-aware design and evaluation of visual analytic tools. Different methods have been used to capture and conceptualize these processes including protocol analysis, experiments, cognitive task analysis, and field studies. In this article, we

Richard Arias-Hernández; Linda T. Kaastra; Tera Marie Green; Brian D. Fisher



Autologous Platelet-Poor Plasma Gel for Injection Laryngoplasty  

PubMed Central

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

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



Direct Force Measurements on Neurofilaments: Gel Expanded to Gel Condensed Transition  

NASA Astrophysics Data System (ADS)

Neurofilaments (NFs)--the major cytoskeletal constituent of axons in vertebrates, consist of three subunit proteins assembled to form filaments with protruding unstructured C-terminus sidearms. Liquid crystal gel networks of sidearm-mediated NF assemblies play a key role in the mechanical while disruptions of this network, due to over-accumulation or incorrect sidearm interactions, are a hallmark of motor neuron diseases. Using synchrotron SAXS [1,2] and microscopy techniques [1,3] we report a direct force measurement of reconstituted NF-gels under osmotic pressure (P), which revealed the role of subunit sidearms on structure and interaction of NFs. With increasing P, near physiological condition, the gels undergo an abrupt nonreversible gel expanded to gel condensed transition that indicates sidearm-mediated attractions between NFs. This attraction is consistent with an electrostatic model of interpenetrating chains.[4pt] [1] J.B. Jones, C.R. Safinya, Biophys. J. 95, 823 (2008);[0pt] [2] R. Beck et al., Nature Mat. (2009) in press;[0pt] [3] H. Hess et al. Langmuir 24, 8397 (2008)

Beck, R.; Deek, J.; Jones, J. B.; Safinya, C. R.



Responsive Gel-Gel Phase Transitions in Artificially Engineered Protein Hydrogels  

NASA Astrophysics Data System (ADS)

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

Olsen, B. D.



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


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



Investigations on gel forming media for use in low gravity bioseparations research  

NASA Astrophysics Data System (ADS)

Microgravity research includes investigations designed to gain insight on methods of separating living cells. During a typical separation certain real-time measurements can be made by optical methods, but some materials must also be subjected to subsequent analyses, sometimes including cultivation of the separated cells. In the absence of on-orbit analytical or fraction collecting procedures, some means is required to ``capture'' cells after separation. The use of solutions that form gels was therefore investigated as a means of maintaining cells and/or macromolecules in the separated state after two types of simple ground-based experiments. Microgravity electrophoresis experiments were simulated by separating model cell types (rat, chicken, human and rabbit erythrocytes) in a vertical density gradient containing low-conductivity buffer, 1.7%-6.5% Ficoll, 6.8-5.0% sucrose, and 1% SeaPrep low-melting temperature agarose and demonstrating that, upon cooling, a gel formed in the column, and cells could be captured in the positions to which they had migrated. Two-phase extraction experiments were simulated by choosing two-polymer solutions in which phase separation occurs in normal saline at temperatures compatible with cell viability and in which one or both phases form a gel upon cooling. Suitable polymers included commercial agaroses (1-2%), maltodextrin (5-7%) and gelatin (5-20%).

Todd, Paul; Szlag, David C.; Plank, Lindsay D.; Delcourt, Scott G.; Kunze, M. Elaine; Kirkpatrick, Francis H.; Pike, Roland G.


Excluded volume effects on ionic partitioning in gels and microgels: a simulation study.  


In this work the effect of volume exclusion on ionic partitioning in swollen and moderately collapsed gels has been studied through coarse-grained simulations. Our results show that finite size effects yield deviations from the classical theory of Donnan exclusion. At low or moderate reservoir electrolyte concentration these discrepancies become important if one of the ions has diameters of just a few nanometers. When the reservoir electrolyte concentration grows, volume exclusion can lead to a drastic failure of the ideal Donnan exclusion even for conventional hydrated monoatomic ions. In addition, an approximate analytical expression for the partition coefficient of ionic species including the volume exclusion associated with the polymer network and the neutralizing counterions has been proposed and tested. This theoretical approach also provides an expression for the Donnan potential difference that takes such effects into account. Good agreement between theory and simulations is found for slightly and moderately charged gels (both at low and high reservoir electrolyte concentrations). The theory also works acceptably for highly charged gels at high salt concentrations or for electrolytes with large counterions. PMID:25343312

Ahualli, Silvia; Martín-Molina, Alberto; Quesada-Pérez, Manuel



Data-base techniques for multiple two-dimensional polyacrylamide gel electrophoresis analyses.  


Two-dimensional protein electrophoresis can benefit from a powerful set of computer-supported image processing and data structure/management procedures. Detection of quantitative differences is complicated by local inhomogeneities in the polyacrylamide base; biochemical changes and variations in temperature and preparative technique also make the between-gel density and x-y coordinate correspondences quite imprecise. The program presented here provides local alignment and computer-controlled variable "flicker" rates for multiple gels, with use of an interactive display system. Manual spot densitometry, referred to a National Bureau of Standards density wedge, can be complemented by a set of automatic densitometry routines for previously established lists of spots. The ability to establish a set of local landmarks, either by included standards or user identification, provides a basis for automatic n-way gel comparison for subsets or for the entire set of spots. Automatic segmentatin algorithms allow isolatin of spots and separation of touching and partially overlapping regions. Various analytical and statistical facilities are part of the user's access to the interactively developed data base. The data-structure and image-manipulation techniques developed here allow for user-directed and heuristic comparisons with online presentation of intermediate and final results. PMID:6996868

Lipkin, L E; Lemkin, P F



Rare earth doped optical fiber fabrication by standard and sol-gel derived granulated oxides  

NASA Astrophysics Data System (ADS)

We present our progress in the production of ytterbium (Yb) doped optical fibers fabricated by two variants of the granulated aluminophosphosilicate method. We show advantages and disadvantages of mixing rare earth and aluminophosphosilicate granulated oxides directly (variant 1) or by using the sol-gel method to produce doped granulate material (variant 2). For both methods we studied the effects of varying the dopant concentrations and of introducing iterative melting and milling procedures. In particular, the sol-gel based method eases the inclusion of P2O5 and thus, in combination with Al2O3, higher dopant concentration of Yb and Er are possible. Sintering the sol-gel material at high temperature eliminated bubbles in the core. We fabricated optical fibers that, piecewise, between individual strong scatterers, exhibited attenuation losses as low as 0.35dB/m. For our comparative study we determined volume percentage and distribution of chemical elements in the fabricated fiber glasses by the analytical technique of Energy-Dispersive X-ray, Electro Probe Microanalysis and the degree of crystallization by X-Ray Diffraction analysis. Furthermore we measured fluctuations of the refractive index profile and scattering losses of the fiber core.

Etissa, D.; Neff, M.; Pilz, S.; Ryser, M.; Romano, V.



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

SciTech Connect

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

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



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.



Aligned human microvessels formed in 3D fibrin gel by constraint of gel contraction.  


This study aimed to form microvessels in fibrin gels, which is of interest both for studying the fundamental cell-matrix interactions as well as for tissue engineering purposes, and to align the microvessels, which would provide natural inlet and outlet sides for perfusion. The data reported here demonstrate the formation of highly interconnected microvessels in fibrin gel under defined medium conditions and the ability to align them using two methods, both of which involved anchoring the gel at both ends to constrain the cell-induced compaction. The first method used only defined medium and resulted in moderate alignment. The second method used defined and serum-containing media sequentially to achieve high levels of microvessel alignment. PMID:23938272

Morin, Kristen T; Smith, Annie O; Davis, George E; Tranquillo, Robert T



Microdetermination of protease activity in humic bands of different sizes after analytical isoelectric focusing  

Microsoft Academic Search

Extracellular benzoyl-l,-argininamide (BAA)-hydrolysing protease was extracted with neutral pyrophosphate from an arable soil and fractionated by membrane ultrafiltration. There were three fractions: A1 (molecular weight > 105), AII (molecular weight 104–105), and R (molecular weight 4). Analytical isoelectric focusing (IEF) of the fractions was carried out on polyacrylamide gels with a restricted pH gradient of 4.0 to 5.0. Two extracellular

B. Ceccanti; M. Bonmati-Pont; P. Nannipieri




E-print Network

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


Analytic Geometry, A Tentative Guide.  

ERIC Educational Resources Information Center

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

Helwig, G. Alfred; And Others


Macroscopic structure and properties of aqueous methylcellulose gels  

NASA Astrophysics Data System (ADS)

Cold semi-dilute aqueous methylcellulose (MC) solutions are known to undergo thermoreversible gelation when warmed. Here, studies on two MC materials, which contrast in thermal gelation performance (gel temperature, hot gel modulus etc.) even though they were prepared with similar methyl ether substitution levels and molecular weight distributions are presented. Small-angle neutron scattering (SANS)* measurements reveal differences in their gel structures which presumably are relevant to their thermal gelation performances. MC gel with higher gel temperature and lower hot gel modulus contains a single temperature invariant characteristic length (˜ 1000 å). However, besides this length scale, an additional and distinct smaller structure is also observed for the material with the lower gel temperature and the higher hot gel modulus. Further, in this case, the characteristic length scale decreases as temperature rises where as, the other length scale (smaller in size) remain almost temperature-invariant. The smaller domain size of the gel structure leads to the higher hot gel modulus for these methylcellulose materials. *Performed at NG3 beamline, NCNR, NIST.

Chatterjee, Tirtha; Adden, Roland; Brackhagen, Meinolf; Nakatani, Alan I.; Redwine, David; Sammler, Robert L.



Design of tenofovir-UC781 combination microbicide vaginal gels.  


Tenofovir (TFV) is a proven microbicide when administered topically as a vaginal gel. To improve its efficacy, TFV was combined with the nonnucleoside reverse-transcriptase inhibitor UC781 in a vaginal gel. Mixture design of experiments theory was used to define a range of gel compositions with varying rheological properties and to assess in vitro drug release and tissue retention. Experiments and computations led to the specification of three different gels referred to as a spreading gel (SG), an intermediate spreading gel (ISG), and a bolus gel (BG). These three gels, all containing 1.0% TFV and 0.1% micronized UC781, were evaluated for in vitro release, in vitro tissue retention and safety, and in vivo pharmacokinetics in the rabbit. There were some differences in in vitro release rates of UC781 (the higher the gel viscosity, the slower the release rate) across gels, while release of TFV was independent of gel type. In an organotypic human vaginal-ectocervical (VEC) tissue model, the amounts of tissue-associated TFV and UC781 were several orders of magnitude higher than their in vitro half-maximal inhibitory concentration. There were no differences in VEC tissue concentrations of TFV or UC781 between the SG, ISG, and BG. All three gels were well tolerated in the VEC model as assessed by tissue viability, electrical resistance, histology, and cytokine (interleukin-8 and interleukin-1 beta) release. The local vaginal tissue concentrations in rabbits following a single dose or seven once-daily doses were variable and generally lower than those found in the VEC tissue model. The approach described herein provides a rational schema to design and evaluate vaginal gels for use as microbicides. PMID:22359356

Kiser, Patrick F; Mahalingam, Alamelu; Fabian, Judit; Smith, Eric; Damian, Festo R; Peters, Jennifer J; Katz, David F; Elgendy, Hoda; Clark, Meredith R; Friend, David R



Bradyrhizobium japonicum Survival in and Soybean Inoculation with Fluid Gels  

PubMed Central

The utilization of gels, which are used for fluid drilling of seeds, as carriers of Bradyrhizobium japonicum for soybean (Glycine max (L.) Merr.) inoculation was studied. Gels of various chemical composition (magnesium silicate, potassium acrylate-acrylamide, grafted starch, and hydroxyethyl cellulose) were used, although the hydroxyethyl cellulose gels were more extensively investigated. Gel inocula were prepared by mixing gel powder with liquid cultures of B. japonicum (2% [wt/vol]). The population of B. japonicum USDA 110 did not change in each gel type during 8 days of incubation at 28°C. These fluid gels were prepared with late-exponential-growth-phase cells that were washed and suspended in physiological saline. Mid-exponential-growth-phase B. japonicum USDA 110, 123, and 138 grew in cellulose gels prepared with yeast extract-mannitol broth as well as or better than in yeast extract-mannitol broth alone for the first 10 days at 28°C. Populations in these cellulose gels after 35 days were as large as when the gels had originally been prepared, and survival occurred for at least 70 days. Soybeans grown in sand in the greenhouse had greater nodule numbers, nodule weights, and top weights with gel inoculants compared with a peat inoculant. In soil containing 103 indigenous B. japonicum per g of soil, inoculation resulted in increased soybean nodule numbers, nodule weights, and top weights, but only nodule numbers were greater with gel than with peat inoculation. The gel-treated seeds carried 102 to 103 more bacteria per seed (107 to 108) than did the peat-treated seeds. PMID:16347870

Jawson, Michael D.; Franzluebbers, Alan J.; Berg, Robert K.



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

NASA Technical Reports Server (NTRS)

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

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



Adsorption of pesticidal compounds bearing a single carboxyl functional group and biogenic amines by humic fraction-immobilized silica gel.  


Fractions collected from humic acids under acidic and basic conditions were immobilized on silica gel and used as adsorbents for a variety of agricultural pesticide compounds bearing a single carboxyl functional group and biogenic amines in acetonitrile. Among these compounds examined under the same conditions, the percentage of adsorption varies considerably from 0 to almost 100%. The percentage is found to be highly related to the structure of the analyte and the type of functional group attached to it. The adsorption, better performed on adsorbent immobilized with the fraction collected under acidic conditions, is believed to result from the reversible interaction between the functional moieties of the analyte and humic acids (e.g., amino or carboxyl group of analyte vs carboxyl group of humic acids, etc.) as no adsorption is observed under the same conditions for analytes that are derivatives of alcohol, amide, and ester. Given the nature of the analyte, the time needed to reach the maximum percent of adsorption decreases as the amount of adsorbent is increased. Also, the longer the time that has elapsed, the higher the percentage of analyte adsorbed, thus indicating that the adsorption process is surface-oriented. Factors such as the acidic or basic origin of the additive in the liquid phase of the matrix also affect the percentage of analyte adsorbed. PMID:23521499

Chen, Cheng-Sheng; Chen, Shushi



Platelet gel: applications in dental regenerative surgery  

PubMed Central

Background Platelet growth factors obtained from platelet-rich plasma (PRP) are used in prosthetic and periodontal regenerative therapy in dentistry. Increased microvascular proliferation in the first 20 days is followed by enhanced osteoblast activity and immature osteoid formation within 3–6 weeks, improving the quality and quantity of newly formed bone tissue. The aim of this study was to evaluate, through three-dimensional X-ray monitoring, the amount of bone obtained after bone regeneration treatment with platelet gel from autologous PRP. Materials and methods Patients eligible for regenerative treatment of atrophic alveolar bone of the maxilla or mandible were studied. The patients’ autologous whole blood was collected at the Department of Immunology and Transfusion of San Matteo Hospital for the preparation of platelet gel. The bone at the treated sites was analysed prior to and 4 months after the treatment using the three-dimensional X-ray system Galileos. Results Over a period of 6 years, 133 patients were treated: 304 implants were inserted and there were five cases of failure. The regenerated bone area consisted of histologically immature osteoid tissue composed of thin trabeculae of vital bone and nuclei of osteocytes, associated with fibro-connective tissue. Discussion This co-operative trial between the Transfusion Centre, for standardised production and validation of the platelet gel, and the Dental Surgery room for its application showed that the technique appears effective and safe. Although difficulties were encountered because of the small sample size and the inability to carry out long-term histological controls, the use of small amounts of PRP (5–10%) combined with autologous bone (15–20%) and alloplastic material appears to reduce the need for bone grafting. PMID:22790266

Forni, Franco; Marzagalli, Massimo; Tesei, Patrizia; Grassi, Alessandra



Biotechnology Laboratory: Gel Electrophoresis of Dyes  

NSDL National Science Digital Library

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



Soluble polymers in sol-gel silica  

NASA Astrophysics Data System (ADS)

In the last few years, the inherent versatility of sol-gel processing has led to a significant research effort on inorganic/organic materials. One method of incorporating an organic phase into sol-gel silica is dissolving an organic polymer in a tetraethylorthosilicate (TEOS) solution, followed by in situ polymerization of silica in the presence of organic polymer. The first part of the study involved the development of a two-step (acid-base) synthesis procedure to allow systematic control of acidity in TEOS solutions. With this procedure, it was possible to increase the pH of the TEOS solution while correlating the acidity and properties. The properties were the gelation time, syneresis rate, drying behavior, and xerogel pore structure, as determined by nitrogen sorption. Furthermore, controlling the acidity was shown to control the silica xerogel pore structure. In the second part of the study, the two-step procedure was used to synthesize silica/poly(ethylene glycol) (PEG), and silica/poly(vinyl acetate) (PVAc) composite materials. The content of organic polymer and the molecular weight were varied. The gelation time, the syneresis rate, the drying behavior, and the pore structure were determined for compositions with 10% PEG (M.W. 2,000), 5, 10, and 15% PEG (M.W. 3,400), and 10 and 25% PVAc (M.W. 83,000). Other compositions and molecular weights of PEG lead to sedimentation. In the PEG compositions, the tendency to phase separate was correlated with the effects of the processing variables on the segregation strength and polymerization rate. The PVAc compositions did not show any visible phase separation during processing, giving the composite xerogels an appearance similar to pure silica. The property differences between gels with PEG and gels with PVAc show the relative strength of the interactions with silica. Both polymers exhibit hydrogen bonding between the phases. In the case of PEG, hydrogen bonding between the ether oxygens of the polymer and silanol groups of the hydrolyzed TEOS reduce the gelation time. In the case of PVAc, hydrogen bonding between carbonyl groups of the polymer and silanol groups delay gelation and may physically interfere with condensation. As the competition between the rates of condensation and phase separation are a function of processing conditions, we obtained xerogels that ranged from transparent to opaque.

Beaudry, Christopher Laurent


The use of laser induced breakdown spectroscopy for the determination of Li in organic wash solutions during the preparation of lithium based oxide ceramics by sol-gel  

NASA Astrophysics Data System (ADS)

Laser induced breakdown spectroscopy (LIBS) has been investigated for the determination of lithium in various streams generated during the preparation of lithium titanate microspheres employing internal gelation in Sol-gel. Important parameters including laser energy and acquisition delay were optimized to achieve the best signal to noise ratio during the LIBS analysis using filter paper as a solid support. The usefulness of different analytical emission lines of lithium was investigated. The developed LIBS methodology was found to be useful in developing the sol-gel process for preparing the lithium based microspheres for fusion based R&D programs.

Sarkar, Arnab; Alamelu, D.; Vittal Rao, T. V.; Bamankar, Y. R.; Mukerjee, S. K.; Aggarwal, Suresh K.



A rapid, high resolution DNA sequencing gel system.  


We have developed a simple method which significantly increases the efficiency of manual DNA sequencing. This method increases both the ease of gel preparation and the quality of fragment resolution. Our system involves (i) casting of gels horizontally, without sealing around the plates; (ii) the use of a self-forming buffer gradient to stack bands in the lower part of the gel; (iii) separation of the samples on two 0.2-mm-thick acrylamide gels (4.5 and 4%) with overlapping readings; (iv) "nonsmiling" electrophoresis with very simple, self-made electrophoresis stands; and (v) prior to exposure in situ dry fixation of the gel matrix to the glass support without previous covalent binding of the gel. On average, we are able to read from nucleotide position 50 to position 600 without ambiguity. PMID:2221359

Lang, B F; Burger, G



Static and dynamic properties of a reversible gel  

E-print Network

We study a microscopically realistic model of a physical gel and use computer simulations to investigate its static and dynamic properties at thermal equilibrium. The phase diagram comprises a sol phase, a coexistence region ending at a critical point, a gelation line, and an equilibrium gel phase unrelated to phase separation. The global structure of the gel is homogeneous, but the stress is supported by a fractal network. Gelation results in a dramatic slowing down of the dynamics, which can be used to locate the transition, which otherwise shows no structural signatures. Moreover, the equilibrium gel dynamics is highly heterogeneous as a result of the presence of particle families with different mobilities. An analysis of gel dynamics in terms of mobile and arrested particles allows us to elucidate several differences between the dynamics of equilibrium gels and that of glass-formers.

Pablo I. Hurtado; Pinaki Chaudhuri; Ludovic Berthier; Walter Kob



Surface sliding friction of negatively charged polyelectrolyte gels.  


The friction between two polyelectrolyte gels carrying the same or opposite sign of charges has been investigated using a rheometer. It is found that the friction was strongly dependent on the interfacial interaction between two gel surfaces. In the repulsive interaction case, especially, the friction was extremely low. The friction behavior is attempted to be described in terms of the hydrodynamic lubrication of the solvent layer between two like-charged gel surfaces, which is formed due to the electrostatic repulsion of the two gel surfaces. From the theoretical analysis (hydrodynamic mechanism), the friction behaviors were explained qualitatively, all of the experimental results, nevertheless, could not be understood well. The viscoelastic feature of the gel and the non-Newtonian behavior of water at the friction interface are considered to be important to elucidate the gel friction. PMID:17137762

Kagata, Go; Gong, Jian Ping



Non-affine deformation in semi-flexible polymer gels  

NASA Astrophysics Data System (ADS)

Compared to flexible polymer gels, semi-flexible filamentous biopolymer networks generally have larger elastic moduli, marked strain-stiffening behavior, and a pronounced negative normal stress when deformed under shear. Theoretical models based on either entropic stretching or enthalpic bending of polymer segments can capture these unusual behaviors to some extent but differ in their predictions about whether the deformation of these materials is affine. We test the validity of this affine assumption by embedding fluorescent tracer beads of different sizes within different bio-polymer gels and quantifying their displacements under shear deformation using confocal microscopy. Gels studied include fibrin and collagen gels. Fiber concentration and pH of the gels are systematically varied to understand the effect of network mesh-size, filament thickness and persistence length on non-affinity. The gels are studied under a wide range of applied strain, well into the strain-stiffening regimes.

Basu, Anindita; Qi, Wen; Mao, Xiaoming; Lubensky, Tom; Janmey, Paul; Yodh, Arjun



Working Smarter with Analytics. Working smarter with analytics  

E-print Network

? And yet, in this brutal economy working smarter is a matter of survival. Slow sales cycles, cutbacks, minimize customer churn, detect fraud and increase campaign effectiveness #12;Broad analytics capabilities


Methods to electrophoretically stretch DNA: microcontractions, gels, and hybrid gel-microcontraction devices  

E-print Network

``fingerprinting'' and medical diagnostics rely on a very low resolution view of a DNA's gene map.1 HoweverMethods to electrophoretically stretch DNA: microcontractions, gels, and hybrid gelc The ability to controllably and continuously stretch large DNA molecules in a microfluidic format

Doyle, Patrick S.


Diffusion Equation Analytic Solution Model  

NSDL National Science Digital Library

The Diffusion Equation Analytic Solution Model shows the analytic solution of the one dimensional diffusion equation. A delta pulse at the origin is set as the initial function. This setup approximately models the temperature increase in a thin, long wire that is heated at the origin by a short laser pulse. The analytic solution is a Gaussian spreading in time. Its integral is constant, which means that the laser pulse heating energy is conserved in the diffusion process. Calculus Models are part of âLearning and Teaching Mathematics using Simulations â Plus 2000 Examples from Physicsâ ISBN 978-3-11-025005-3, Walter de Gruyter GmbH & Co. KG

Roess, Dieter



The Science of Analytic Reporting  

SciTech Connect

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

Chinchor, Nancy; Pike, William A.



Absolute calibration of polymer gel dosimeters using scintillating fibers  

NASA Astrophysics Data System (ADS)

Accurate dose distributions are still difficult to obtain using polymer gel dosimetry. While the causes for observed discrepancies are being tracked and understood in details, solutions remain elusive. Causes for discrepancies in absolute dose distributions obtained by polymer gel dosimetry include imaging artefacts and errors associated with the calibration procedure. In this preliminary study, we wanted to verify whether scintillation fiber detectors could be used to improve the accuracy of dose distributions determined by polymer gel dosimeters.

Archambault, Louis; Leclerc, Ghyslain; Beaulieu, Luc; Lepage, Martin



Formation of magnetite nanoparticles in poly(acrylamide) gels  

Microsoft Academic Search

Magnetic gels with magnetite nanoparticles incorporated in a matrix of poly(acrylamide) gel were studied. Magnetite was synthesized through coprecipitation of Fe(II) and Fe(III) in the gel phase, in the solution of linear polymer and in aqueous solution without polymer in alkaline media. The effects of network structure and of the concentration of iron salts in the swollen networks on the

Sergey G Starodubtsev; Evheniy V Saenko; Maxim E Dokukin; Viktor L Aksenov; Vera V Klechkovskaya; Irina S Zanaveskina; Alexei R Khokhlov



Modeling mechanochemical transduction in chemo-responsive gels  

Microsoft Academic Search

Using the recently developed gel lattice spring model, we study mechanochemical transduction in chemo-responsive gels undergoing the Belousov-Zhabotinsky reaction. More specifically, we examine how to harness an applied mechanical force to trigger the propagation of traveling chemical waves, which then lead to oscillations within gels that were initially non-oscillating. In our two dimensional simulations, we introduce the presence of an

Olga Kuksenok; Victor Yashin; Anna C. Balazs



Ion-exchange chromatography by dicarboxyl cellulose gel  

Microsoft Academic Search

A new column packing material for ion-exchange chromatography was prepared from cellulose gel by periodate oxidation followed by chlorite oxidation to form spatially paired carboxyl groups (dicarboxyl cellulose, DCC). The carboxyl group was quantitatively introduced to spherical cellulose gel by controlling the extent of oxidation. The DCC gels were examined for their ion-exchange activity for various amines at pH of

Ung-Jin Kim; Shigenori Kuga



Spectroscopic study of sulforhodamine 640-doped sol–gel silica  

Microsoft Academic Search

The sol–gel process is a technique which provides a low-temperature route for the preparation of organic dye-doped porous silica glass. Extended UV transmission was observed for HCl-catalysed sol–gel silica. Properties of a solute may differ greatly between a free solution and that solution confined in pores of a sol–gel glass. Absorption and fluorescence properties of sulforhodamine 640-doped silica samples prepared

Haider Abbas; K. P. Tiwary; L. S. S. Singh; Mohd. Zulfequar; Z. H. Zaidi; M. Husain



Responsive supramolecular gels constructed by crown ether based molecular recognition.  


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

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



Autostoichiometric vapor-gel deposition of ferroelectric thin films  

NASA Astrophysics Data System (ADS)

An autostoichiometric vapor gel deposition approach is demonstrated for ferroelectric LiTaO3 and LiNbO3 thin films. This approach utilizes the partial hydrolysis of hygroscopic alkoxide in the vapor phase, and the subsequent polycondensation on a heated substrate. Epitaxial films with precisely controlled stoichiometry were obtained. Ultra low temperature deposition was achieved taking advantage of the inherently low temperature sol-gel chemistry. The vapor phase hydrolysis of alkoxides provided a mild deposition reaction that allows for the autostoichiometric deposition. The vapor gel method appears to possess the combined advantages of sol- gel processing and MOCVD.

Xu, Ren



Adsorption of midmolecular peptides by fullerene modified silica gel  

NASA Astrophysics Data System (ADS)

The adsorption properties of raw and processed silica gels and of silica gels modified with fullerene (fullerene-silica gel nanosystems) toward serum midmolecular peptides of ischemic origin were examined. A high adsorption capacity of the nanosorbents was found. The influence of fullerenes on the condition of silica gel was studied by solid-state NMR, and an increase in the silanol fraction at the adsorbent surface was demonstrated. It was shown that presence of fullerene C60 in nanosorbents enables oxidation reaction of the adsorbed peptides, i.e., sorption of metabolites.

Melenevskaya, E. Yu.; Gribanov, A. V.; Podosenova, N. G.



Silica scintillating materials prepared by sol-gel methods  

SciTech Connect

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 methanol at the sol stage of gel formation. The silica sol-gel matrix is very rad-hard. The radiation stability of silica scintillators prepared by this method is dye-limited. Transient radioluminescence was measured following excitation with 30 ps pulses of 20 MeV electrons.

Werst, D.W.; Sauer, M.C. Jr.; Cromack, K.R.; Lin, Y.; Tartakovsky, E.A.; Trifunac, A.D.



Development of nonaqueous polymer gels that exhibit broad temperature performance  

NASA Astrophysics Data System (ADS)

While significant work has focused on aqueous hydrogels for biotechnology applications, hydrogels suffer from a limited operating temperature range due to the moderate freezing point and high volatility of water. In this work, a nonaqueous, chemically cross-linked polybutadiene gel has been designed which exhibits stable properties over a temperature range of -60-70°C. A combination of rheology, neutron scattering, and tack adhesion testing was utilized to characterize the gel properties. The methodology employed to design the polybutadiene gel can be generalized to a variety of gel materials and applications.

Lenhart, Joseph L.; Cole, Phillip J.; Unal, Burcu; Hedden, Ronald



Highly porous thin films obtained by spray-gel technique  

NASA Astrophysics Data System (ADS)

Combining the spray pyrolysis and the sol-gel techniques (spray-gel) gives the possibility to produce very rough and highly diffuse films. This technique is suitable for producing multifunctional metal oxides for gas-sensing, electrochromism, microbattery, and photocatalysis applications; due to the fact that it yields a large interface between a solid and a gaseous/liquid medium. The process basically consists in producing an aerosol from a gel, which is sprayed over a hot substrate, where the film is going to grow. In this work we present the results on highly porous SnO2, WO3, and phosphotungstic acid (PWA) thin films obtained by spray-gel.

Solis, J. L.; Rodriguez, J.; Estrada, W.



Acid Base Equilibrium in a Lipid/Water Gel  

NASA Astrophysics Data System (ADS)

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

Streb, Kristina K.; Ilich, Predrag-Peter



Trial participation disclosure and gel use behavior in the CAPRISA 004 tenofovir gel trial  

PubMed Central

Disclosure, or open communication, by female microbicide trial participants of their trial participation and use of an investigational HIV prevention drug to a sexual partner may affect participants' trial product usage behavior and contribute to poor adherence. With mixed results from recent microbicide clinical trials being linked to differing participant adherence, insights into the communication dynamics between trial participants and their sexual partners are particularly important. We examined the quantitative association between (1) communication of trial participation to a partner and participant adherence to gel and (2) communication of trial participation to a partner and participant HIV status. An in-depth adherence and product acceptability assessment was administered to the women participating in the CAPRISA 004 trial. Additionally, we collected qualitative data related to communication of trial participation and gel use. Qualitatively, among 165 women who had reported that they had discussed trial participation with others, most (68%) stated that they communicated participation to their sexual partner. Most of the women who had communicated study participation with their partners had received a positive/neutral response from their partner. Some of these women stated that gel use was easy; only a small number said that gel use was difficult. Among women who did not communicate their study participation to their partners, difficulty with gel use was more common and some women stated that they feared communicating their participation. Quantitatively, there was no statistically significant difference in the proportions of women who had communicated study participation to a partner across different adherence levels or HIV status. A deeper knowledge of the dynamics surrounding trial participation communication to male partners will be critical to understanding the spectrum of trial product usage behavior, and ultimately to designing tailored strategies to assist trial participants with product adherence. PMID:25285564

Succop, Stacey M.; MacQueen, Kathleen M.; van Loggerenberg, Francois; Majola, Nelisile; Karim, Quarraisha Abdool; Karim, Salim S. Abdool



Catanionic gels based on cholic acid derivatives.  


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

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



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

NASA Astrophysics Data System (ADS)

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

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



Cautions Concerning Electronic Analytical Balances.  

ERIC Educational Resources Information Center

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

Johnson, Bruce B.; Wells, John D.



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.



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.



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.



Analytical Solution of Mathieu Equation  

E-print Network

The general solution of the homogeneous damped Mathieu equation in the analytical form, allowing its practical using in many applications, including superconductivity studies, without numerical calculations has been found.

Dmitri Yerchuck; Alla Dovlatova; Yauhen Yerchak; Felix Borovik



Analytic thinking promotes religious disbelief.  


Scientific interest in the cognitive underpinnings of religious belief has grown in recent years. However, to date, little experimental research has focused on the cognitive processes that may promote religious disbelief. The present studies apply a dual-process model of cognitive processing to this problem, testing the hypothesis that analytic processing promotes religious disbelief. Individual differences in the tendency to analytically override initially flawed intuitions in reasoning were associated with increased religious disbelief. Four additional experiments provided evidence of causation, as subtle manipulations known to trigger analytic processing also encouraged religious disbelief. Combined, these studies indicate that analytic processing is one factor (presumably among several) that promotes religious disbelief. Although these findings do not speak directly to conversations about the inherent rationality, value, or truth of religious beliefs, they illuminate one cognitive factor that may influence such discussions. PMID:22539725

Gervais, Will M; Norenzayan, Ara



Array-based disease diagnostics using lipid/polydiacetylene vesicles encapsulated in a sol-gel matrix.  


We demonstrate a novel array-based diagnostic platform comprising lipid/polydiacetylene (PDA) vesicles embedded within a transparent silica-gel matrix. The diagnostic scheme is based upon the unique chromatic properties of PDA, which undergoes blue-red transformations induced by interactions with amphiphilic or membrane-active analytes. We show that constructing a gel matrix array hosting PDA vesicles with different lipid compositions and applying to blood plasma obtained from healthy individuals and from patients suffering from disease, respectively, allow distinguishing among the disease conditions through application of a simple machine-learning algorithm, using the colorimetric response of the lipid/PDA/gel matrix as the input. Importantly, the new colorimetric diagnostic approach does not require a priori knowledge on the exact metabolite compositions of the blood plasma, since the concept relies only on identifying statistically significant changes in overall disease-induced chromatic response. The chromatic lipid/PDA/gel array-based "fingerprinting" concept is generic, easy to apply, and could be implemented for varied diagnostic and screening applications. PMID:22746165

Kolusheva, S; Yossef, R; Kugel, A; Katz, M; Volinsky, R; Welt, M; Hadad, U; Drory, V; Kliger, M; Rubin, E; Porgador, A; Jelinek, R



A facile sol–gel method for the encapsulation of gold nanoclusters in silica gels and their optical properties  

Microsoft Academic Search

A novel process consisting of a synthesis of gold hydrosol using tetrakis (hydroxymethyl) phosphonium chloride (THPC) reduction and a sol–gel process using tetramethylorthosilicate (TMOS) for the encapsulation of gold nanoparticles (Au\\/SiO2: 0.1–1 wt% Au) in a matrix of silica gel without the aid of any external stabilizing agent or organically modified sol–gel monomers is described. The optical absorption spectra showed

S Tamil Selvan; Masayuki Nogami; Arao Nakamura; Yasushi Hamanaka



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

Microsoft Academic Search

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

I. K. Battisha



A basic study of some normoxic polymer gel dosimeters.  


Polymer gel dosimeters offer a wide range of potential applications in the three-dimensional verification of complex dose distribution such as in intensity-modulated radiotherapy (IMRT). Until now, however, polymer gel dosimeters have not been widely used in the clinic. One of the reasons is that they are difficult to manufacture. As the polymerization in polymer gels is inhibited by oxygen, all free oxygen has to be removed from the gels. For several years this was achieved by bubbling nitrogen through the gel solutions and by filling the phantoms in a glove box that is perfused with nitrogen. Recently another gel formulation was proposed in which oxygen is bound in a metallo-organic complex thus removing the problem of oxygen inhibition. The proposed gel consists of methacrylic acid, gelatin, ascorbic acid, hydroquinone and copper(II)sulphate and is given the acronym MAGIC gel dosimeter. These gels are fabricated under normal atmospheric conditions and are therefore called 'normoxic' gel dosimeters. In this study, a chemical analysis on the MAGIC gel was performed. The composition of the gel was varied and its radiation response was evaluated. The role of different chemicals and the reaction kinetics are discussed. It was found that ascorbic acid alone was able to bind the oxygen and can thus be used as an anti-oxidant in a polymer gel dosimeter. It was also found that the anti-oxidants N-acetyl-cysteine and tetrakis(hydroxymethyl)phosphonium were effective in scavenging the oxygen. However, the rate of oxygen scavenging is dependent on the anti-oxidant and its concentration with tetrakis(hydroxymethyl)phosphonium being the most reactive anti-oxidants. Potentiometric oxygen measurements in solution provide an easy way to get a first impression on the rate of oxygen scavenging. It is shown that cupper(II)sulphate operates as a catalyst in the oxidation of ascorbic acid. We, therefore, propose some new normoxic gel formulations that have a less complicated chemical formulation than the MAGIC gel. PMID:12408474

De Deene, Y; Hurley, C; Venning, A; Vergote, K; Mather, M; Healy, B J; Baldock, C



Radiological properties of MAGIC normoxic polymer gel dosimetry  

NASA Astrophysics Data System (ADS)

For a polymer gel dosimeter to be of use in radiation dosimetry, it should display water-equivalent radiological properties. In this study, the radiological properties of the MAGIC (Methacrylic and Ascorbic acid in Gelatin Initiated by Copper) normoxic polymer gels were investigated. The mass density (?) was determined based on Archimedes' principle. The weight fraction of elemental composition and the effective atomic number (Zeff) were calculated. The electron density was also measured with 90° scattering angle at room temperature. The linear attenuation coefficient (?) of unirradiated gel, irradiated gel, and water were determined using Am-241 based on narrow beam geometry. Monte Carlo simulation was used to calculate the depth doses response of MAGIC gel and water for 6MV photon beam. The weight fractions of elements composition of MAGIC gel were close to that for water. The mass density was found to be 1027 ± 2 kg m-3, which is also very close to mass density of muscle tissue (1030 kg m-3) and 2.7% higher than that of water. The electron density (?e) and atomic number (Zeff) were found to be 3.43 × 1029 e m-3 and 7.105, respectively. The electron density measured was 2.6% greater than that for water. The atomic number was very close to that for water. The prepared MAGIC gel was found to be water equivalent based on the study of element composition, mass density, electron density and atomic number. The linear attenuation coefficient of unirradiated gel was very close to that of water. The ? of irradiated gel was found to be linear with dose 2-40 Gy. The depth dose response for MAGIC gel from a 6 MV photon beam had a percentage dose difference to water of less than 1%. Therefore it satisfies the criteria to be a good polymer gel dosimeter for radiotherapy.

Aljamal, M.; Zakaria, A.; Shamsuddin, S.



Self-assembling small molecules for the detection of important analytes.  


Nano-materials formed by the self-assembly of small molecules are very promising for drug delivery, regenerative medicine, and detection of important analytes due to their unique properties, such as self-assembled multivalency, biocompatibility, and fast response to external stimuli. This tutorial review focuses on their applications in detection of important analytes. Self-assembling small molecules can show fast response to external stimuli. Therefore, the gel-sol/sol-gel phase transitions of supramolecular hydrogels that can be easily identified by naked eyes have been applied for the detection of enzymes and enzyme-involving analytes. The supramolecular hydrogels can also provide semi-wet environments that can retain the activity of enzymes and recognition properties of molecular probes. Thus, they provide good platforms for the detection of many biologically and environmentally important analytes. Besides, self-assembling small molecules show big differences in fluorescence or the F-NMR signal between their self-assembled and un-assembled stages. Such small molecules can be rationally designed through the integration of fluorescent dyes or fluorine containing molecules in the self-assembling small molecules. Therefore, extensive recent research efforts have been made to explore their detection applications based on the dis-assembly triggered fluorescence/F-NMR signal turn on or the self-assembly/aggregation induced fluorescence turn on. We believe that the research efforts made to this field will ultimately lead to the development of useful nano-materials for detection applications. PMID:25060777

Ren, Chunhua; Zhang, Jianwu; Chen, Minsheng; Yang, Zhimou



Multilevel thresholding of gel electrophoresis images using firefly algorithm  

Microsoft Academic Search

Gel electrophoresis (GE) is a process of DNA, RNA and protein molecules separation using electric field applied to a gel matrix. This paper describes the image processing techniques applied on GE image to segment the bands from their background. A few pre-processing steps are applied on the image prior to the segmentation technique for the purpose of removing noise in

M. H. Mohd Noor; A. R. Ahmad; Z. Hussain; K. A. Ahmad; A. R. Ainihayati



Denaturing Urea PAGE -Large Gel Preparation of Glass Plates  

E-print Network

with soap and water. Rinse and wipe to dry with EtOH and Kimwipe. 2. Siliconize plates: Using a Pasteur flask. De-gas for 5 minutes with aspirator vacuum (while sealing). Mix by swirling without bubbles. Pour gel solution down middle of glass plates with 25 ml pipette. Do not trap bubbles in gel. Adjust flow

Aris, John P.


Performance of 18 polymers in aluminum citrate colloidal dispersion gels  

SciTech Connect

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

Smith, J.E.



Such ion gels have shown superior performance as gate  

E-print Network

Such ion gels have shown superior performance as gate dielectrics in organic thin-film transistors (5). For many organic semiconductors, device perfor- mance is constrained by the num- ber of charge electric field leads to differential gel swelling and thus to bending. A possible route to accentu- ate

Zeebe, Richard E.


Experimental study of attenuation properties of normoxic polymer gel dosimeters  

Microsoft Academic Search

The change in linear attenuation coefficient with absorbed dose has been investigated for aqueous polyacrylamide, gelatine and tetrakis (PAGAT) and aqueous methacrylic acid, gelatine and tetrakis (MAGAT) normoxic polymer gel dosimeters using tetrakis (hydroxy methyl) phosphonium chloride as the antioxidant. The measured linear attenuation coefficient increased linearly with absorbed dose up to 15 Gy for PAGAT gels and 10 Gy

S Brindha; A J Venning; B Hill; C Baldock



Slow Release Of Reagent Chemicals From Gel Matrices  

NASA Technical Reports Server (NTRS)

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

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



Review of quantitative MRI principles for gel dosimetry  

Microsoft Academic Search

The radiation dose distribution absorbed by polymer gel dosimeters can be read out by several methods such as magnetic resonance imaging (MRI), optical CT, X-ray CT and ultrasound. MRI was the first method that was explored to read out polymer gel dosimeters. Although MRI was soon recognised as a promising technique, limited access to MRI scanners and the often (wrongly

Yves DeDeene



Transport of proteins through gel-filled porous membranes  

Microsoft Academic Search

Membranes with a mean pore diameter of 0.5 ?m were filled with neutral polyacrylamide (PA) gels at fixed crosslink density. The gel was synthesized in the membranes by impregnating the pores with a solution of monomer and crosslinker and then initiating polymerization by ultraviolet radiation. The rate of diffusion and convection (ultrafiltration) of two proteins, ribonuclease A (RNAse) and bovine

Vivek Kapur; John Charkoudian; John L. Anderson



Scaling behavior of the elastic properties of colloidal gels  

Microsoft Academic Search

The scaling behavior of the elastic properties of colloidal gels that are well above the gelation threshold is studied both theoretically and experimentally. A scaling theory was developed by considering the structure of the gel network as a collection of flocs, which are fractal objects closely packed throughout the sample. Two regimes are found based on the relative value of

Wei-Heng Shih; Wan Y. Shih; Seong-Il Kim; Jun Liu; Ilhan A. Aksay



Sol–gel coatings on metals for corrosion protection  

Microsoft Academic Search

Sol–gel protective coatings have shown excellent chemical stability, oxidation control and enhanced corrosion resistance for metal substrates. Further, the sol–gel method is an environmentally friendly technique of surface protection and had showed the potential for the replacement of toxic pretreatments and coatings which have traditionally been used for increasing corrosion resistance of metals. This review covers the recent developments and

Duhua Wang; Gordon. P. Bierwagen



Formation and physical properties of acid milk gels: a review  

Microsoft Academic Search

Acidified milk products like yoghurt are an important food product but there are relatively few reports on the mechanisms involved in gel formation and the effects of processing variables such as heat treatment and gelation temperature on the important physical properties (such as whey separation) of acid-induced gels. Most previous reviews have described the microbiology of the starter cultures and

J. A. Lucey; H. Singh



Pore-Level Examination of Gel Destruction During Oil Flow  

E-print Network

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

New York at Stoney Brook, State University of


Phase behavior and rheological characterization of silica nanoparticle gel  

NASA Astrophysics Data System (ADS)

Preferential injection into high permeability thief zones or fractures can result in early breakthrough at production wells and large unswept areas of high oil saturation, which impact the economic life of a well. A variety of conformance control techniques, including polymer and silica gel treatments, have been designed to block flow through the swept zones. Over a certain range of salinities, silica nanoparticle suspensions form a gel in bulk phase behavior tests. These gels have potential for in situ flow diversion, but in situ flow tests are required to determine their applicability. To determine the appropriate scope of the in situ tests, it is necessary to obtain an accurate description of nanoparticle phase behavior and gel rheology. In this paper, the equilibrium phase behavior of silica nanoparticle solutions in the presence of sodium chloride (NaCl) is presented with four phase regions classified as a function of salinity and nanoparticle concentration. Once the gelation window was clearly defined, rheology experiments of silica nanoparticle gels were also carried out. Gelation time decreases exponentially as a function of silica concentration, salinity, and temperature. Following a power law behavior, the storage modulus, G', increases with particle concentration. Steady shear measurements show that silica nanoparticle gels exhibit non-Newtonian, shear thinning behavior. This comprehensive study of the silica nanoparticle gels has provided a clear path forward for in situ tests to determine the gel's applicability for conformance control operations.

Metin, Cigdem O.; Rankin, Kelli M.; Nguyen, Quoc P.



Gel Electrophoresis--The Easy Way for Students  

ERIC Educational Resources Information Center

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

VanRooy, Wilhelmina; Sultana, Khalida



Quantification of friction force reduction induced by obstetric gels  

Microsoft Academic Search

The objective of this study was to quantify the reduction of friction forces by obstetric gels aimed to facilitate human childbirth. Lubricants, two obstetric gels with different viscosities and distilled water, were applied to a porcine model under mechanical conditions compa- rable to human childbirth. In tests with higher movement speeds of the skin relative to the birth canal, both

Robert Riener; Kerstin Leypold; Andreas Brunschweiler; Andreas Schaub; Ulrich Bleul; Peter Wolf



Review article Radiation dosimetry using polymer gels: methods and  

E-print Network

Review article Radiation dosimetry using polymer gels: methods and applications 1 M MCJURY, PhD, 1 dosimetry, including gel manufacture, imaging, calibration and application to radiotherapy veri and stereotactic radiosurgery. All the studies have con®rmed the value and versatility of the dosimetry technique

Doran, Simon J.


Biocatalysis with Sol-Gel Encapsulated Acid Phosphatase  

ERIC Educational Resources Information Center

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

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



Gels as battery separators for soluble electrode cells  

NASA Technical Reports Server (NTRS)

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

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



Dielectric properties of gel collected from shark electrosensors  

Microsoft Academic Search

To investigate the physical mechanism of the electric sense, we present an initial characterization of the dielectric properties of the glycoprotein gel that fills the electrosensitive organs of marine elasmobranches (sharks, skates, and rays). To ascertain the properties of the gel, low-frequency impedance spectroscopy is used. The impedance data collected from a dialyzed sample show large values of static permittivity

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



New gel phantoms simulating optical properties of biological tissue  

E-print Network

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

Lee, Mija




EPA Science Inventory

The feasiability of using crosslinked gels in a reversible process for extracting pure water from aqueous waste solutions has been investigated. It has potential for concentrating waste streams that contain hazardous chemicals. Near critical gels have been developed which swell a...


A dynamic covalent imine gel as a luminescent sensor.  


A novel dynamic covalent gel has been prepared via the imine bond formation reaction of tetraamine building blocks with luminescent tetraphenylethene tetraaldehyde units. The gel shows high hierarchical porosity (SBET = 512 m(2) g(-1)) and remarkable aggregation-induced emission enhancement, which has been demonstrated to be a selective sensor. PMID:25162069

Luo, Weijun; Zhu, Yixuan; Zhang, Jianyong; He, Jiajun; Chi, Zhenguo; Miller, Philip W; Chen, Liuping; Su, Cheng-Yong



Zirconyl-containing microspheric silica gel surfaces  

NASA Astrophysics Data System (ADS)

The adsorption properties of two samples of zirconyl-containing silica gels derived from zirconium oxychloride, polyetoxysiloxane oligomer 3% ZrOCl2/SiO2 (composite 1) and tetraetoxysilane 5% ZrOCl2/SiO2 (composite 2) were investigated by gas chromatography at low surface coverages. n-Alkanes and n-alkenes (C6-C8), C6H6 were used as test adsorbates, along with polar compounds whose molecules had different donor-acceptor interaction abilities. The dispersion and specific (electron-donor and electronacceptor) components of the energy of intermolecular interactions for the studied systems were determined from the experimental data on chromatographic retention. It was shown that composite 2 had a higher dispersion potential and higher surface energy characteristics of the surface's electron-donating and electronacceptor centers, as compared to composite 1.

Lanin, S. N.; Kabulov, B. D.; Vlasenko, E. V.; Kovaleva, N. V.; Lanina, K. S.; Strepetova, T. A.; Akhundzhanov, K. A.; Yunusov, F. U.



Laser light scattering studies of biological gels  

NASA Astrophysics Data System (ADS)

Several authors have investigated the Rayleigh linewidth of light scattered from the gels of cross-linked flexible polymers such as polyacrylamide14. The width of the spectral broadening varies as sinL(O/2), and diffusion coefficients may be calculated in the same way as for a macromolecular solution5. According to the theory of Tanaka et al.1, this corresponds to freely diffusing fluctuations in polymer segment density and is equal to the ratio of the longitudinal elastic modulus to the force per unit volume required to maintain unit relative velocity between the polymer network and solvent. The degree of spectral broadening has, in general, been found to be small enough (ca. 10%) for the optical beating to be regarded as largely heterodyne, most of the scattered light arising from a stationary component in the density fluctuations.

Burne, P. M.; Sellen, D. B.



How to scan polymer gels with MRI?  

NASA Astrophysics Data System (ADS)

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

De Deene, Y.



Electromechanical studies of a novel polymer gel  

SciTech Connect

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

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



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

NASA Astrophysics Data System (ADS)

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

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



Phyllosilicates and Amorphous Gel in the Nakhlites  

NASA Astrophysics Data System (ADS)

Previous studies of the nakhlite martian meteorites have revealed hydrothermal minerals present within the fractures of the olivine minerals and the mesostasis. The olivine fractures of the Lafayette nakhlite reveal variations with initial deposits of siderite on the fracture walls, followed by crystalline phyllosilicates (smectite), and finishing with a rapidly cooled amorphous silicate gel within the central regions of the fractures. The mesostasis fractures of Lafayette also contain a crystalline phyllosilicate (serpentine). The amorphous gel is the most abundant secondary phase within the fractures of the other nakhlites [1, 2]. By studying nine nakhlite samples, including Lafayette, Governador Valadares, Nakhla, Y-000593, Y-000749, Miller-Range 03346, NWA 817, NWA 998, and NWA 5790, our aim is to constrain the identity of the phyllosilicate secondary phase minerals found throughout the nakhlite martian meteorites. This is achieved using methods including Electron Probe Micro-analysis (EPMA); X-ray Absorption Near-Edge Structure (Fe-K XANES) spectroscopy measured using Beamline I-18 at the Diamond Light Source synchrotron; and the use of Transmission Electron Microscopy (TEM) at the University of Leicester for High-Resolution (HR) imaging and Selected Area Electron Diffraction (SAED). BF studying nine nakhlite samples, including Lafayette, Governador Valadares, Nakhla, Y-000593, Y-000749, Miller-Range 03346, NWA 817, NWA 998, and NWA 5790, our aim is to constrain the identity of the phyllosilicate secondary phase minerals found throughout the nakhlite martian meteorites. This is achieved using methods including Electron Probe Micro-analysis (EPMA); X-ray Absorption Near-Edge Structure (Fe-K XANES) spectroscopy measured using Beamline I-18 at the Diamond Light Source synchrotron; and the use of Transmission Electron Microscopy (TEM) at the University of Leicester for High-Resolution (HR) imaging and Selected Area Electron Diffraction (SAED).

Hicks, L. J.; Bridges, J. C.; Gurman, S. J.



Elastic properties of swollen polyelectrolyte gels in aqueous salt solutions  

NASA Astrophysics Data System (ADS)

The elastic relaxation responding to a uniaxially stretched poly(acrylic acid) rodlike gel in the aqueous NaCl solution was investigated. The relaxation elucidated the shear (?) and bulk (K) moduli and the frictional coefficients (?) of the fully ionized gel at pH above 9 as functions of the degree of swelling, which was controlled by the NaCl concentration (CS) of the solution. Two gels, cross-linked chains of which consist of 500 (GelA500) and 50 (GelA50) monomeric units, were examined to investigate the effect of the chain length on the elastic behavior. The moduli of GelA500 increased with swelling at CS below 100 mM and decreased at CS above it. The ? values of both gels can be characterized by the power function of gel diameter, d as ? ?d?. The ? values being -1 at CS above 100 mM transitionally changed to 1.2 at CS about 100 mM. That is, the dimensionality of space for the chains to distribute, ndim {=(?+5)/(?+2) according to the conventional theory [Sasaki et al., J. Chem. Phys. 102, 5694 (1995)]}, changed from 4 (ndim of ideal chain) to 1.9 at CS=100mM. This indicates that the electrostatic repulsion between gel chains reduces the ndim at CS below 100 mM but not at CS above it. It was found that the K values of GelA500 were well described by the conventional theory but those of GelA50 not. The ?zr/?rr (?zr is an off-diagonal element of the friction coefficient tensor and ?rr is a diagonal element of the friction coefficient tensor) was found to be 2.7×10-2, which was the same as the previously reported value for the swollen poly(acrylamide) gel [Sasaki, J. Chem. Phys. 120, 5789 (2004)]. The ?rr of unit volume of the GelA500 is well explained by the free draining model while the ?rr of GelA50 is less than that of the free draining model, suggesting the slip between water and ionized chain.

Sasaki, Shigeo



Some rheological properties of sodium caseinate-starch gels.  


The influence of sodium caseinate on the thermal and rheological properties of starch gels at different concentrations and from different botanical sources was evaluated. In sodium caseinate-starch gels, for all starches with the exception of potato starch, the sodium caseinate promoted an increase in the storage modulus and in the viscosity of the composite gel when compared with starch gels. The addition of sodium caseinate resulted in an increase in the onset temperature, the gelatinization temperature, and the end temperature, and there was a significant interaction between starch and sodium caseinate for the onset temperature, the peak temperature, and the end temperature. Microscopy results suggested that sodium caseinate promoted an increase in the homogeneity in the matrix of cereal starch gels. PMID:15769164

Bertolini, Andrea C; Creamer, Lawrence K; Eppink, Mieke; Boland, Mike



Hybrid thermoreversible gels from covalent polymers and organogels.  


This paper reports on experiments intended for investigating the feasibility of preparing hybrid thermoreversible gels from covalent polymers and noncovalent self-assembling pi-conjugated molecules. The formation and the degree of dispersion of these hybrid gels have been studied with polystyrenes of various tacticities and oligo(p-phenylenevinylene) molecules (OPV) in different nonpolar organic solvents. Detailed investigations of the systems have been carried out by DSC, SAXS, and AFM. It is shown that no liquid-liquid phase separation is involved, indicating that the systems are highly compatible, and that the growth of one type of gel does not interfere with the other. These studies reveal that the resultant hybrid gels are composed of the intermingled fibrillar architectures of both gels. PMID:19292503

Dasgupta, D; Srinivasan, S; Rochas, C; Ajayaghosh, A; Guenet, J M



Investigation on Pmma-Based Gel Electrolyte for Electrochromic Devices  

NASA Astrophysics Data System (ADS)

Studies were carried out on gel electrolytes based on PMMA and non-aqueous solution of lithium salt, LiClO4 in the mixed solvent of propylene carbonate and ethylene carbonate (PC+EC). This paper reports the influences of polymer concentration and ratios of mixed solvent on the properties of gel electrolytes. The addition of polymer has increased the viscosity considerably without affecting the stable potential window, resulting in thermally stable gels. Result shows that addition of EC increases the conductivity by two order of magnitude as compared to that of PC alone. However conductivity decreases with addition of EC beyond 2:1 ratio of EC:PC. These gel electrolytes showed good room temperature conductivity in the order of 10-3 S/cm with high transmission in the visible region. This makes the gel a very promising electrolyte candidate for electrochromic device application.

Mohamad Mahbor, Kamisah



Photophysical properties of cyanine dyes in sol-gel matrices  

NASA Astrophysics Data System (ADS)

Planar and twisted cyanine dyes with different p Ka values are examined concerning their protonation equilibrium in sol-gel matrices. In the sol-gel matrix the equilibrium between the cation and the dicationic form shifts to the dication pointing to acid-base reactions of sol-gel walls with cyanine dyes. The colorless dicationic species is not found for pseudoisocyanine and in sol-gel bulks prepared with drying control chemical agents (DCCA) indicating the absence of the responsible interaction. The fluorescence lifetimes of cyanine molecules are used to compare the pore size and distribution in sol-gel matrices prepared with and without DCCA. J-aggregation, examined for one dye, depends strongly on environment polarity and pore size.

De Rossi, U.; Daehne, S.; Reisfeld, R.



Microscopic picture of cooperative processes in restructuring gel networks.  


Colloidal gel networks are disordered elastic solids that can form even in extremely dilute particle suspensions. With interaction strengths comparable to the thermal energy, their stress-bearing network can locally restructure via breaking and reforming interparticle bonds. This allows for yielding, self-healing, and adaptive mechanics under deformation. Designing such features requires controlling stress transmission through the complex structure of the gel and this is challenging because the link between local restructuring and overall response of the network is still missing. Here, we use a space resolved analysis of dynamical processes and numerical simulations of a model gel to gain insight into this link. We show that consequences of local bond breaking propagate along the gel network over distances larger than the average mesh size. This provides the missing microscopic explanation for why nonlocal constitutive relations are necessary to rationalize the nontrivial mechanical response of colloidal gels. PMID:23705744

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



Laser CT evaluation on normoxic PAGAT gel dosimeter  

NASA Astrophysics Data System (ADS)

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

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



Thermal and non-thermal fluctuations in active polar gels  

NASA Astrophysics Data System (ADS)

We discuss general features of noise and fluctuations in active polar gels close to and away from equilibrium. We use the single-component hydrodynamic theory of active polar gels built by Kruse and coworkers to describe the cytoskeleton in cells. Close to equilibrium, we calculate the response function of the gel to external fields and introduce Langevin forces in the constitutive equations with correlation functions respecting the fluctuation-dissipation theorem. We then discuss the breakage of the fluctuation-dissipation theorem due to an external field such as the activity of the motors. Active gels away from equilibrium are considered at the scaling level. As an example of application of the theory, we calculate the density correlation function (the dynamic structure factor) of a compressible active polar gel and discuss possible instabilities.

Basu, A.; Joanny, J. F.; Jülicher, F.; Prost, J.



Novel Printing------Using Polymeric Gel as Ink  

NASA Astrophysics Data System (ADS)

Novel printing ink has been developed based on polymeric gel having the nature of gel to sol transition caused by application of electric voltage. The polymeric gel ink consisted of polyvinyl alcohol) (PVA) partially crosslinked with borax, carbon black as a pigment, and water. Printing facilities was also designed. Polymeric gel ink with electric conductivity 4.0 x 10-3 ?-1cm-1 was used. It could offer resolution of more than 200 dots per inch (dpi). Image density was fully controlled from 0.05 to 1.5 as optical density by application of electric voltage of 3 - 12 V. An advantage of this printing system was that polymeric gel ink not only acted as ink but also as the support.

Toyama, Noboru; Fukumoto, Hiroshi; Tanioka, Hiroshi; Arahara, Kohzoh; Koizumi, Norihiko; Yuasa, Toshiya; Kobayashi, Motokazu; Kan, Fumitaka



The transfer of analytical procedures.  


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



Exactly solvable Ogston model of gel electrophoresis. IX. Generalizing the lattice model to treat high field intensities  

NASA Astrophysics Data System (ADS)

Traditionally, the Ogston regime is studied solely in the limit of low field intensities. This explains why the theoretical discussion has focused until now on the relative roles of the fractional volume available to the analyte and the subtleties of the gel architecture. Over the past several years, we have developed a lattice model of gel electrophoresis that has allowed us to revisit the fundamental assumptions of the standard Ogston model. In particular, we demonstrated that the fractional free volume is not the relevant parameter for gel sieving. In this article, we continue the development of this model and we generalize our mathematical approach to treat nonvanishing electric field intensities. To do so, we must revisit the way biased random walks are normally modeled by stochastic processes. Straightforward generalizations based on standard Metropolis-like schemes fail at high field intensities. Moreover, our generalization requires the complete decoupling of the spatial directions parallel and perpendicular to the field direction. We show that our novel theoretical approach makes it possible to calculate exact mobilities in the presence of lattice obstacles. Several two-dimensional examples are then studied, including one that includes topological dead ends that act like traps. In the latter case, we recover results very similar to those reported by Serwer et al. [Biopolymers 29, 1863 (1990)] on the trapping electrophoresis of charged spheres in agarose gels. In the absence of such traps, the mobility is shown to be a very weak function of the electric field, thus validating the historical neglect of the field intensity in the development of obstruction models for the Ogston sieving regime of small analytes. Finally, we describe how the present model could be improved to treat more realistic cases and we discuss the problem of the field dependence of the diffusion coefficient during electrophoresis.

Gauthier, Michel G.; Slater, Gary W.



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


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

Dorri, Yaser; Kurien, Biji T



How deeply cells feel: methods for thin gels  

PubMed Central

Tissue cells lack the ability to see or hear but have evolved mechanisms to feel into their surroundings and sense a collective stiffness. A cell can even sense the effective stiffness of rigid objects that are not in direct cellular contact – like the proverbial princess who feels a pea placed beneath soft mattresses. How deeply a cell feels into a matrix can be measured by assessing cell responses on a controlled series of thin and elastic gels that are affixed to a rigid substrate. Gel elasticity E is readily varied with polymer concentrations of now-standard polyacrylamide hydrogels, but to eliminate wrinkling and detachment of thin gels from an underlying glass coverslip, vinyl groups are bonded to the glass before polymerization. Gel thickness is nominally specified using micron-scale beads that act as spacers, but gels swell after polymerization as measured by z-section, confocal microscopy of fluorescent gels. Atomic force microscopy (AFM) is used to measure E at gel surfaces, employing stresses and strains that are typically generated by cells and yielding values for E that span a broad range of tissue microenvironments. To illustrate cell sensitivities to a series of thin-to-thick gels, the adhesive spreading of mesenchymal stem cells was measured on gel mimics of a very soft tissue (eg. brain, E ~ 1 kPa). Initial results show that cells increasingly respond to the rigidity of an underlying ‘hidden’ surface starting at about 10–20 µm gel thickness with a characteristic tactile length of less than about 5 µm. PMID:20454525

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



Dewatering fine coal slurries by gel extraction. Final report  

SciTech Connect

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

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



40 CFR 721.9680 - Alkaline titania silica gel (generic name).  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Alkaline titania silica gel (generic name...Chemical Substances § 721.9680 Alkaline titania silica gel (generic name...substance identified generically as an alkaline titania silica gel (PMN...



Analytical Chemistry of Nitric Oxide  

PubMed Central

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

Hetrick, Evan M.



Analytical models of dipolarization fronts  

NASA Astrophysics Data System (ADS)

Dipolarization fronts (DFs) are mesoscale structures generated during the transient magnetic reconnection in the Earth's magnetotail. Spacecraft often observe these structures propagating toward the Earth with velocities 300-100 km/s. Modern multispacecraft observations allow reconstruction of 3D configuration of electromagnetic fields of DF: front is strongly curved in the XY plane and spatially localized along the Z axis (in GSM coordinate system). DFs play important role in plasma heating and charged particle acceleration. Thus, the simplified analytical models of 2D and 3D configuration of DF are necessary to model charge particle interaction with fronts. In the present report we propose 3D analytical model of DF. For several given distributions of B _{z} magnetic field component we have found analytical expressions for magnetic fields B _{x}, B _{y} and electric fields E _{x}, E _{y}. We also discuss distribution of electric field, which is due to the polarization of plasma in the vicinity of DF.

Vasko, Ivan; Artemyev, Anton


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.



A Primer on Spreadsheet Analytics  

E-print Network

This paper provides guidance to an analyst who wants to extract insight from a spreadsheet model. It discusses the terminology of spreadsheet analytics, how to prepare a spreadsheet model for analysis, and a hierarchy of analytical techniques. These techniques include sensitivity analysis, tornado charts,and backsolving (or goal-seeking). This paper presents native-Excel approaches for automating these techniques, and discusses add-ins that are even more efficient. Spreadsheet optimization and spreadsheet Monte Carlo simulation are briefly discussed. The paper concludes by calling for empirical research, and describing desired features spreadsheet sensitivity analysis and spreadsheet optimization add-ins.

Grossman, Thomas A



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


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

NASA Astrophysics Data System (ADS)

CdS/silica xerogel glasses were prepared via silica gels containing mixture solution of 0.2 M (CdCl2 and thiourea) with molar ratio 1:1. Doping the gels with this mixture solution and its heat treatment gave transparent yellow silica-gel glasses doped with CdS crystals. X-ray diffraction and transmission electron microscope make it possible to evaluate the nanoparticle size of the prepared samples. The nanoparticle size was dependent on the concentration of the dopant materials and the heating temperature. In the optical transmission spectra, the absorption edge exhibited a blue shift compared to that of the bulk CdS, and its energy shift was reciprocally proportional to the square of the radius. Thus the quantum-size effect could be found for the silica gel containing CdS prepared by the sol-gel process. The energy band gap shifted to higher energy for smaller nanoparticle size.

Battisha, I. K.


Kinetic resolution of racemic mixtures in gel media  

NASA Astrophysics Data System (ADS)

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

Petrova, Rositza Iordanova


Investigations in x-ray computed tomography polyacrylamide gel dosimetry  

SciTech Connect

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

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



Analytical chemistry at the interface between materials science and biology  

NASA Astrophysics Data System (ADS)

This work describes several research efforts that lie at the new interfaces between analytical chemistry and other disciplines, namely materials science and biology. In the materials science realm, the search for new materials that may have useful or unique chromatographic properties motivated the synthesis and characterization of electrically conductive sol-gels. In the biology realm, the search for new surface fabrication schemes that would permit or even improve the detection of specific biological reactions motivated the design of miniaturized biological arrays. Collectively, this work represents some of analytical chemistry's newest forays into these disciplines. This dissertation is divided into six chapters. Chapter 1 is an introductory chapter that provides background information pertinent to several key aspects of the work contained in this dissertation. Chapter 2 describes the synthesis and characterization of electrically conductive sol-gels derived from the acid-catalyzed hydrolysis of a vanadium alkoxide. Specifically, this chapter describes our attempts to increase the conductivity of vanadium sol-gels by optimizing the acidic and drying conditions used during synthesis. Chapter 3 reports the construction of novel antigenic immunosensing platforms of increased epitope density using Fab'-SH antibody fragments on gold. Here, X-ray photoelectron spectroscopy (XPS), thin-layer cell (TLC) and confocal fluorescence spectroscopies, and scanning force microscopy (SFM) are employed to characterize the fragment-substrate interaction, to quantify epitope density, and to demonstrate fragment viability and specificity. Chapter 4 presents a novel method for creating and interrogating double-stranded DNA (dsDNA) microarrays suitable for screening protein:dsDNA interactions. Using the restriction enzyme ECoR1, we demonstrate the ability of the atomic force microscope (AFM) to detect changes in topography that result from the enzymatic cleavage of dsDNA microarrays containing the correct recognition sequence. Chapter 5 explores more fully the microarray fabrication process described in Chapter 4. Specifically, experiments characterizing the effect of deposition conditions on oligonucleotide topography and as well as those that describe array density optimization are presented. Chapter 6 presents general conclusions from the work recorded in this dissertation and speculates on its extension.

O'Brien, Janese Christine


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


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

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



Measuring Dilution of Microbicide Gels with Optical Imaging  

PubMed Central

We present a novel approach for measuring topical microbicide gel dilution using optical imaging. The approach compares gel thickness measurements from fluorimetry and multiplexed low coherence interferometry in order to calculate dilution of a gel. As a microbicide gel becomes diluted at fixed thickness, its mLCI thickness measurement remains constant, while the fluorimetry signal decreases in intensity. The difference between the two measurements is related to the extent of gel dilution. These two optical modalities are implemented in a single endoscopic instrument that enables simultaneous data collection. A preliminary validation study was performed with in vitro placebo gel measurements taken in a controlled test socket. It was found that change in slope of the regression line between fluorimetry and mLCI based measurements indicates dilution. A dilution calibration curve was then generated by repeating the test socket measurements with serial dilutions of placebo gel with vaginal fluid simulant. This methodology can provide valuable dilution information on candidate microbicide products, which could substantially enhance our understanding of their in vivo functioning. PMID:24340006

Drake, Tyler K.; Shah, Tejen; Peters, Jennifer J.; Wax, Adam; Katz, David F.



Pickering stabilized peptide gel particles as tunable microenvironments for biocatalysis.  


We demonstrate the preparation of peptide gel microparticles that are emulsified and stabilized by SiO2 nanoparticles. The gels are composed of aromatic peptide amphiphiles 9-fluorenylmethoxycarbonyldiphenylalanine (Fmoc-FF) coassembled with Fmoc-amino acids with different functional groups (S: serine; D: aspartic acid; K: lysine; and Y: tyrosine). The gel phase provides a highly hydrated matrix, and peptide self-assembly endows the matrix with tunable chemical environments which may be exploited to support and stabilize proteins. The use of Pickering emulsion to stabilize these gel particles is advantageous through avoidance of surfactants that may denature proteins. The performance of enzyme lipase B immobilized in pickering/gel microparticles with different chemical functionalities is investigated by studying transesterification in heptane. We show that the use of Pickering particles enhances the performance of the enzyme, which is further improved in gel-phase systems, with hydrophilic environment provided by Fmoc-FF/S giving rise to the best catalytic performance. The combination of a tunable chemical environment in gel phase and Pickering stabilization described here is expected to prove useful for areas where proteins are to be exploited in technological contexts such as biocatalysis and also in other areas where protein performance and activity are important, such as biosensors and bioinspired solar fuel devices. PMID:24144273

Scott, Gary; Roy, Sangita; Abul-Haija, Yousef M; Fleming, Scott; Bai, Shuo; Ulijn, Rein V



Dynamical arrest: interplay of glass and gel transitions.  


The structural arrest of a polymeric suspension might be driven by an increase of the cross-linker concentration, which drives the gel transition, as well as by an increase of the polymer density, which induces a glass transition. These dynamical continuous (gel) and discontinuous (glass) transitions might interfere, since the glass transition might occur within the gel phase, and the gel transition might be induced in a polymer suspension with glassy features. Here we study the interplay of these transitions by investigating via event-driven molecular dynamics simulation the relaxation dynamics of a polymeric suspension as a function of the cross-linker concentration and the monomer volume fraction. We show that the slow dynamics within the gel phase is characterized by a long sub-diffusive regime, which is due both to the crowding as well as to the presence of a percolating cluster. In this regime, the transition of structural arrest is found to occur either along the gel or along the glass line, depending on the length scale at which the dynamics is probed. Where the two lines meet there is no apparent sign of higher order dynamical singularity. Logarithmic behavior typical of A3 singularity appears inside the gel phase along the glass transition line. These findings seem to be related to the results of the mode coupling theory for the F13 schematic model. PMID:24828914

Khalil, Nagi; de Candia, Antonio; Fierro, Annalisa; Ciamarra, Massimo Pica; Coniglio, Antonio



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

USGS Publications Warehouse

Sodium-aluminum silicate gels are found in surftcial deposits as thick as 5 centimeters in the Magadi area of Kenya. Chemical data indicate they are formed by the interaction of hot alkaline springwaters (67?? to 82??C; pH, about 9) with alkali trachyte flows and their detritus, rather than by direct precipitation. In the process, Na2O is added from and silica is released to the saline waters of the springs. Algal mats protect the gels from erosion and act as thermal insulators. The gels are probably yearly accumulates that are washed into the lakes during floods. Crystallization of these gels in the laboratory yields analcite; this fact suggests that some analcite beds in lacustrine deposits may have formed from gels. Textural evidence indicates that cherts of rocks of the Pleistocene chert series in the Magadi area may have formed from soft sodium silicate gels. Similar gels may have acted as substrates for the accumulation and preservation of prebiological organic matter during the Precambrian.

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



pH-Responsive Swelling of PAMAM Dendrimer-Gels.  

NASA Astrophysics Data System (ADS)

End-linked hydrogels containing high mass fractions of amine-terminated poly(amidoamine) (PAMAM) dendrimers are prepared by reaction of dendrimers with monodisperse, epoxide-terminated linear poly(ethylene glycol) chains. PAMAM dendrimers impart pH-dependent swelling characteristics to the gels, which absorb large amounts of water due to protonation of the dendrimers' amine groups under neutral or weakly acidic conditions. The equilibrium swelling of the gels passes through a maximum at pH of approximately 4.5, due to extensive protonation of the amine groups. Interestingly, the equilibrium swelling ratio is markedly lower at both high external pH and low external pH. We model the swelling behavior by invoking the Donnan equilibrium theory, treating the gels as phantom networks that contain a high concentration of Lewis bases having pKb=3.5 The model captures the maximum in swelling near pH=4.5, though equilibrium swelling ratio is overpredicted in some cases. The collapse of the gels at both high and low external pH is explained in terms of the differential between the concentrations of mobile ions inside and outside the gel. We will discuss recent attempts to prepare stimuli-responsive gels based upon the remarkable swelling characteristics of PAMAM dendrimer-gels.

Hedden, Ronald; Unal, Burcu



Fibril formation from pea protein and subsequent gel formation.  


The objective of this study was to characterize fibrillar aggregates made using pea proteins, to assemble formed fibrils into protein-based gels, and to study the rheological behavior of these gels. Micrometer-long fibrillar aggregates were observed after pea protein solutions had been heated for 20 h at pH 2.0. Following heating of pea proteins, it was observed that all of the proteins were hydrolyzed into peptides and that 50% of these peptides were assembled into fibrils. Changes on a structural level in pea proteins were studied using circular dichroism, transmission electron microscopy, and particle size analysis. During the fibril assembly process, an increase in aggregate size was observed, which coincided with an increase in thioflavin T binding, indicating the presence of ?-sheet aggregates. Fibrils made using pea proteins were more branched and curly. Gel formation of preformed fibrils was induced by slow acidification from pH 7.0 to a final pH of around pH 5.0. The ability of pea protein-based fibrillar gels to fracture during an amplitude sweep was comparable to those of soy protein and whey protein-based fibrillar gels, although gels prepared from fibrils made using pea protein and soy protein were weaker than those of whey protein. The findings show that fibrils can be prepared from pea protein, which can be incorporated into protein-based fibrillar gels. PMID:24564788

Munialo, Claire Darizu; Martin, Anneke H; van der Linden, Erik; de Jongh, Harmen H J



Western Blot of Stained Proteins from Dried Polyacrylamide Gels  

NASA Technical Reports Server (NTRS)

Western blotting of proteins is customarily performed following their separation on polyacrylamide gels, either prior to staining (1) or, as recently reported, following staining (2). We describe here Western blotting with stained gels, which had been dried and some of which had been stored for years. This procedure permits immunological analysis of proteins, to which antisera may have become available only later, or where the application of newly developed sensitive detection methods is desired. Once rehydration of the gels is achieved, proteins can be-transferred to blotting membranes by any appropriate protocol. Proteins stained with Coomassie Blue have to be detected with a non-chromogenic method, such as the film-based enhanced chemiluminescence (ECL)2) procedure (3). Silver stained proteins, which transfer in the colorless form, may be visualized by any detection method, although, because of the usually very low amounts of proteins, detection by ECL is preferable. Blotting of stained proteins from rehydrated gels is as rapid and as quantitative as from freshly prepared gels, in contrast to blotting from wet stained gels, which requires extensive washing and results in low transfer efficiency (2). Together with a photographic record of the gel pattern, unambiguous identification of immunoreactive proteins from complex mixtures is possible. Some further applications of this work are discussed.

Gruber, Claudia; Stan-Lotter, Helga



Probe diffusion in phase-separated bicontinuous biopolymer gels.  


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

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



Performance of electric double layer capacitors with polymer gel electrolytes  

SciTech Connect

Polymer gel electrolytes consisting of poly(vinylidene fluoride) (PVdF), tetraethylammonium tetrafluoroborate (TEABF{sub 4}), and propylene carbonate (PC) as a plasticizer have been investigated for electric double layer capacitors. The PVdF gel electrolytes showed high ionic conductivity (ca. 6 mS/cm at 298 K). To assemble model capacitors with the PVdF gel electrolytes and activated carbon fiber cloth electrodes, a pair of the fixed electrodes was soaked in a precursor solution containing PC, PVdF, and TEABF{sub 4}, followed by evaporation of the PC solvent in a vacuum oven. The resulting gel electrolytes were in good contact with the electrodes. The model capacitors with the PVdF gel electrolytes showed a large value of capacitance and high coulombic efficiency in operation voltage ranges of 1--2 and 1--3 V. It is worth noting that the capacitors with the PVdF electrolytes showed long voltage retention in a self-discharge test. These good characteristics of the gel capacitors were comparable to those of typical double layer capacitors with a liquid organic electrolyte containing PC and TEABF{sub 4}; rather, the voltage retentivity of the PVdF gel capacitors was much superior to that of the capacitors with the organic electrolyte.

Ishikawa, Masashi; Kishino, Takahiro; Katada, Naoji; Morita, Masayuki



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


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

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



Common Lisp Analytical Statistics Package  

E-print Network

for the Common Lisp Instrumentation Package (Clip), a tool for automating data collection and experimen- tationCommon Lisp Analytical Statistics Package: User Manual Scott D. Anderson, Adam Carlson, David L of Massachusetts Amherst, MA 01003-4610 * Replaces TR-90-85 This work was supported by a University Research


Microcomputer Applications in Analytical Chemistry.  

ERIC Educational Resources Information Center

The first part of this paper addresses the following topics: (1) the usefulness of microcomputers; (2) applications for microcomputers in analytical chemistry; (3) costs; (4) major microcomputer systems and subsystems; and (5) which microcomputer to buy. Following these brief comments, the major focus of the paper is devoted to a discussion of…

Long, Joseph W.


Analytical Probability Distributions With Excel  

Microsoft Academic Search

This note introduces four common underlying processes and the analytical probability distribution used to forecast the outcomes of each. The note also illustrates how to use Excel functions to calculate probabilities from the four resulting probability distributions: binomial, normal, Poisson, and exponential.

Sherwood Frey; Phillip Pfeifer


Immunoassays in Environmental Analytical Chemistry  

Microsoft Academic Search

A review is presented which summarizes the recent developments of immunoassays in environmental analytical chemistry.The basic principle of the method and the following steps in the development of an immunoassay procedure are discussed in detail: Synthesis of the immunogen, immunization procedure, synthesis of the labelled antigen (tracer), advantages and drawbacks of radioimmunoassay, fluoroimmunoassay and enzyme immunoassay. A special emphasis is

Margit Schwalbe-fehl



From Metaphor to Analytic Tool  

E-print Network

Process Tracing From Metaphor to Analytic Tool Edited by ANDREW BENNETT and JEFFREY T. CHECKEL mechanisms. This book argues that the method known as process tracing is particularly well suited basis for process tracing � one that captures mainstream uses while simultaneously being open


Characterizing matrix remodeling in collagen gels using optical coherence tomography  

NASA Astrophysics Data System (ADS)

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

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



The instantaneous monitoring of polyacrylamide gels during electrophoresis.  

PubMed Central

The advantages of being able to see protein zones in a gel during electrophoresis (and hence before staining) are pointed out, and a method is described which depends on local increments of refractive index in these zones. The use of local increments of refractive index in polyacrylamide gels for measuring protein concentrations in zones during electrophoresis is briefly considered; it is found that such increments are greater than would be expected from the amount of protein when sodium dodecyl sulphate is present. The enhancement depends on conditions and time of running. This makes quantitative estimates difficult, but the sensitivity of detection of protein zones by observations based on refractive-index changes is greatly increased by this property of sodium dodecyl sulphate. Methods are described for making optically uniform gels (both with uniform and with graded concentrations of polyacrylamide), necessary for observation of small changes in refractive index. A simple dark-field system of observation is described. Examples are given showing protein samples observed with the system during electrophoresis and compared with the same gel stained with Coomassie Blue after completion of the run. Under optimal conditions the optical method is comparable in sensitivity with staining. With the proteins of lower mol.wt. (approx. 15000), the optical method is not so sensitive, becoming less sensitive with longer running time. This loss of sensitivity is greatly decreased by using more concentrated polyacrylamide gels, and graded gels are therefore more suitable for optical observation than are uniform gels. The observation of protein zones during electrophoresis adds nothing to the time needed for making a stained gel and gives much information long before it can be obtained from the stained gel. Images PLATE 1 PLATE 2 PMID:1008832

Elliott, A



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

NASA Astrophysics Data System (ADS)

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

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



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.



Gel Electrophoresis of Gold-DNA Nano-Conjugates  

SciTech Connect

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

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



C60: the first one-component gel?  

E-print Network

Until now, gels have been formed of multicomponent soft matter systems, consisting of a solvent and one or more macromolecular or colloidal species. Here we show that, for sufficient quench rates, the Girifalco model of C60 can form gels which we identify by their slow dynamics and long-lived network structure. These gels are stable at room temperature, at least on the simulation timescale up to 100 ns. At moderate tempera