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Comparison of lipoprotein analysis by agarose gel and paper electrophoresis with analytical ultracentrifugation  

Microsoft Academic Search

A comparison has been made of human serum lipoprotein analysis by agarose gel and paper electrophoresis with a standard method\\u000a of analytical ultracentrifugation. Samples were obtained from 28 patients with various disorders of lipoprotein metabolism.\\u000a Correspondence was shown between the following electrophoretic and ultracentrifugal fractions: ? and Sf 0–20; pre-? and Sf 20–400; ?1 and total HDL. The deviations observed

R. P. Noble; F. T. Hatch; J. A. Marzimas; F. T. Lindgren; L. C. Jensen; G. L. Adamson



Analytical Ultracentrifugation: Sedimentation Velocity and Sedimentation Equilibrium  

PubMed Central

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

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



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



Detecting RNA tertiary folding by sedimentation velocity analytical ultracentrifugation.  


Analytical Ultracentrifugation (AUC) is a highly sensitive technique for detecting global conformational features of biological molecules and molecular interactions in solution. When operated in a sedimentation velocity (SV) recording mode, it reports precisely on the hydrodynamic properties of a molecule, including its sedimentation and diffusion coefficients, which can be used to calculate its hydrated radius, as well as, to estimate its global shape. This chapter describes the application of SV-AUC to the detection of global conformational changes accompanying equilibrium counterion induced tertiary folding of structured RNA molecules. A brief theoretical background is provided at the beginning, aimed at familiarizing the readers with the operational principle of the technique; then, a detailed set of instructions is provided on how to design, conduct, and analyze the data from an equilibrium RNA folding experiment, using SV-AUC. PMID:24136610

Mitra, Somdeb



Comparison of ultracentrifugation and gel filtration for the isolation of bovine lipoproteins  

Microsoft Academic Search

Lipoproteins from the plasma of three nonlactating Holstein cows were isolated using either preparative ultracentrifugation\\u000a or gel filtration chromatography. Lipoprotein classes obtained by ultracentrifugation were very low density plus chylomicra,\\u000a 1, 1.040–1.063 g\\/ml; and high density, 1.064–1.22 g\\/ml. These lipoprotein classes were individually applied to an agarose gel\\u000a column to determine at what volume they eluted in comparison to lipoproteins

R. R. Grummer; C. L. Davis; H. M. Hegarty



Assembly, Loading, and Alignment of an Analytical Ultracentrifuge Sample Cell  

PubMed Central

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.

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



Screening for serum lipoprotein abnormalities: Comparison of ultracentrifugal, paper and thin-layer starch-gel electrophoresis techniques  

Microsoft Academic Search

Three methods for evaluation of serum lipoprotein abnormalities were compared: paper electrophoresis using buffer containing\\u000a albumin, ultracentrifugation at d 1.21, and thin-layer starch-gel electrophoresis. Analyses by paper electrophoresis and by\\u000a ultracentrifugation of 109 sera of patients with cholesterol levels between 78 and 1150 mg\\/100 ml showed that the electrophoretic\\u000a procedure while not quantitative was an effective procedure for detecting and

Lena A. Lewis



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

Microsoft Academic Search

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

Patrick H. Brown; Andrea Balbo; Peter Schuck



Gel chromatography and analytical ultracentrifugation to determine the extent of detergent binding and aggregation, and Stokes radius of membrane proteins using sarcoplasmic reticulum Ca2+–ATPase as an example  

Microsoft Academic Search

For structural studies of integral membrane proteins, including their 3D crystallization, the judicious use of detergent for solubilization and purification is required. Detergent binding by the solubilized protein is an important parameter to determine the hydrodynamic properties in terms of size and aggregational (monomeric\\/oligo(proto)meric) state of the protein. Detergent binding can be measured by gel filtration chromatography under equilibrium conditions

Bertrand Arnou; Claus Olesen; Dominique Georgin; Christine Ebel; Jesper V Møller; Marc le Maire



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

PubMed Central

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



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

NASA Astrophysics Data System (ADS)

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

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



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

NASA Astrophysics Data System (ADS)

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

Brown, Patrick H.; Schuck, Peter



Rapid precision interferometry for the analytical ultracentrifuge. I. A laser controller based on a phase-lock-loop circuit.  


This is the first of a series of manuscripts presenting methods to enable rapid reduction of data from the Rayleigh interference optical system of the Beckman Model E analytical ultracentrifuge. Here we present a pulsed laser controller for the ultracentrifuge. This laser controller uses a phase-lock-loop to provide properly timed light pulses over the speed range of 3000 to 60,000 rpm; it effectively resolves one rotor revolution into 4096 discrete angular positions. The circuit has been designed so that the laser light bursts occur at selectable angular positions of the rotor that are independent of rotor speed even under conditions of maximum acceleration or deceleration. We have used this controller in our laboratory over a 7-year period for both photographic and real-time collection at interferometric data from the ultracentrifuge. PMID:6614453

Laue, T M; Domanik, R A; Yphantis, D A



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


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

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



An analytical ultracentrifugation based study on the conformation of lambda carrageenan in aqueous solution.  


The conformation and heterogeneity of lambda-carrageenan, a sulphonated galactan from red seaweed, solubilised in aqueous solvent with the assistance of microwave irradiation, has been assessed by a combination of analytical ultracentrifugation, size-exclusion chromatography, light scattering and capillary viscometry. Preparations appeared generally unimodal on the basis of sedimentation coefficient distributions from sedimentation velocity although at the highest concentrations a shoulder appears with a sedimentation coefficient approximately 1.1 times greater than that of the main component. Even under conditions commensurate with charge suppression simple linear regression was insufficient to represent non-ideal concentration dependence and the extraction of the Grálen concentration dependence parameter ks. A more general fitting algorithm was therefore employed. Mark-Houwink-Kuhn-Sakurada analysis of the change in intrinsic viscosity [?] with molecular weight, together with the Wales-van Holde ratio (combination of ks with [?]) point to an extended flexible conformation for lambda-carrageenan in the (weight average) molecular weight range Mw=340,000-870,000g/mol. The origin of the larger sedimentation coefficient component appearing at the higher concentrations is considered. PMID:23769538

Almutairi, Fahad M; Adams, Gary G; Kök, Mehmet S; Lawson, Christopher J; Gahler, Roland; Wood, Simon; Foster, Timothy J; Rowe, Arthur J; Harding, Stephen E



Investigation of ?-carotene–gelatin composite particles with a multiwavelength UV\\/vis detector for the analytical ultracentrifuge  

Microsoft Academic Search

A multiwavelength UV\\/vis detector for the analytical ultracentrifuge (MWL-AUC) has been developed recently. In this work,\\u000a ?-carotene–gelatin composite particles are investigated with MWL-AUC. Band centrifugation with a Vinograd cell is used to\\u000a ensure maximum sample separation. Spectral changes of the system are observed in dependence of the sedimentation coefficient\\u000a and are attributed to a previously unknown inhomogeneity of the ?-carotene

Engin Karabudak; Wendel Wohlleben; Helmut Cölfen



An Optical Thermometer for Direct Measurement of Cell Temperature in the Beckman Instruments XL-A Analytical Ultracentrifuge  

Microsoft Academic Search

An optical thermometer has been evaluated for use in the Beekman Instruments Optima XL-A Analytical Ultracentrifuge. A thermochromic solution of CoCl2·6H2O was used as the temperature sensing material. The dehydration of CoCl2·6H2O is temperature dependent resulting a highly temperature dependent absorption peak at 660 nm. Spectra of 0.1 M CoCl2·6H2O in an alcohol-water mixture were measured at different temperature settings

S. Liu; W. F. Stafford



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

PubMed Central

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

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



Analytical ultracentrifugation studies of oligomerization and DNA-binding of TtCarH, a Thermus thermophilus coenzyme B12-based photosensory regulator.  


Thermus thermophilus transcriptional factor TtCarH belongs to a newly discovered class of photoreceptors that use 5'-deoxyadenosylcobalamin (AdoB12) as the light-sensing chromophore. Photoregulation relies on the repressor activity of AdoB12-bound oligomers in the dark, which light counteracts by oligomer disruption due to AdoB12 photolysis. In this study, we investigated TtCarH self-association and binding to DNA in the dark and in the light using analytical ultracentrifugation (AUC) methods, both sedimentation velocity (SV) as well as equilibrium (SE). From a methodological point of view, this study shows that AUC can provide hydrodynamic insights in cases where light is a crucial determinant of solution properties. For the light-sensitive TtCarH, absorbance as well as interference AUC data yielded comparable results. Sedimentation coefficients and whole-body hydrodynamic analysis from SV experiments indicate that in solution apo-TtCarH and light-exposed AdoB12-TtCarH are predominantly aspherical, ellipsoidal monomers, in accord with SE data. By comparison, AdoB12-TtCarH exists as a more compact tetramer in the dark, with smaller forms such as dimers or monomers remaining undetected and low levels of larger oligomers appearing at higher protein concentrations. AUC analyses indicate that in the dark AdoB12-TtCarH associates as a tetramer with DNA but forms smaller complexes in the apo form or if exposed to light. The self-association and DNA-binding properties of TtCarH deduced from AUC are consistent with data from size-exclusion and DNA-binding gel-shift assays. AUC analyses together with hydrodynamic modeling provide insights into the AdoB12- and light-dependent self-association and DNA-binding of TtCarH. PMID:23512413

Díez, Ana I; Ortiz-Guerrero, Juan Manuel; Ortega, Alvaro; Elías-Arnanz, Montserrat; Padmanabhan, S; García de la Torre, José



Size distribution analysis of single and bi-component polymer and inorganic particle systems by comparison of two analysis methods in analytical ultracentrifuge.  


Sedimentation velocity runs were performed on organic and inorganic particles with analytical ultracentrifugation and the diameter and diameter distribution analysis was carried out with Sedfit and VelXLAI data analysis programs. The particles were measured either as pure components or as mixtures of different organic or inorganic particles using different weight ratios of these components. Polymer particles with peak diameters of ?15 and 32-35 nm and inorganic particles with peak diameters of ?5 and ?32 nm were used and the particles also differed in the extent of polydispersity. The mixtures of particles in the weight ratios of 50:50, 90:10 and 95:5 of smaller to larger particles or vice versa were studied. The aim was to compare the performance of the analysis programs to characterize the various polymer and inorganic particle samples of varying complexity. The analysis programs were compared with each other not only for peak particle diameters and their size distributions, but also for the cumulative fractions of components of the particle mixtures. PMID:21227446

Mittal, V; Lechner, M D



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)



Interaction of the DNA-binding domain of Drosophila heat shock factor with its cognate DNA site: a thermodynamic analysis using analytical ultracentrifugation.  

PubMed Central

Heat shock transcription factor (HSF) mediates the activation of heat shock genes by binding to its cognate sites with high affinity and specificity. The high-affinity binding of HSF is dependent on the formation of an HSF homotrimer, which interacts specifically with the heat shock response element (HSE), comprised of 3 inverted repeats of the 5-bp sequence NGAAN. In order to investigate the thermodynamic basis of the interaction between HSF and HSE, we have overexpressed and purified a polypeptide (dHSF(33-163)) encompassing only the DNA-binding domain of HSF from Drosophila and analyzed its binding to DNA by equilibrium analytical ultracentrifugation using a multiwavelength scan technique. We demonstrate that dHSF(33-163) can bind as a monomer with 1:1 stoichiometry to a synthetic 13-bp DNA containing a single NGAAN sequence. The values of the thermodynamic parameters obtained from the temperature dependence of the equilibrium binding constants indicate that the changes of free energy for the binding of dHSF(33-163) to the wild-type site and a mutant DNA site are predominantly characterized by substantial negative changes of enthalpy. Binding to the wild-type DNA is characterized by a significant positive change of entropy, whereas binding to the mutant DNA is distinguished by a negative change of entropy of comparable magnitude. The binding to the mutant DNA was also highly sensitive to increasing salt concentrations, indicating a dominance of ionic interactions. The sequence-specific, 1:1 binding of dHSF(33-163) to the NGAAN sequence provides a basis for the analysis of higher order interactions between HSF trimers and the HSE.

Kim, S. J.; Tsukiyama, T.; Lewis, M. S.; Wu, C.



Sequential assembly of the wedge of the baseplate of phage T4 in the presence and absence of gp11 as monitored by analytical ultracentrifugation.  


The baseplate wedge of bacteriophage T4 consists of seven gene products, namely, gp11, gp10, gp7, gp8, gp6, gp53, and gp25, which assemble strictly in this order with an exception that gp11 can bind to gp10 at any stage of the assembly. In this study, all the seven corresponding genes are expressed as recombinant proteins and all the possible combinations of the gene products are tested for interactions by analytical ultracentrifugation. No interactions among gene products that violate the strict sequential binding are observed except that gp6, gp53, and gp25 interact with each other weakly, but significantly. However, when gp6 is previously bound to the precursor complex, only gp53 binds to gp6 strongly and then gp25 binds to complete the wedge formation. This result indicates that the strict sequential association is based on the conformational change of the complex upon addition of each gene product. The binding constant between subunits in the intermediate complexes is too high to be measured. In fact, the binding of gp11 to gp10 is so tight that the binding constant could not be determined by trace sedimentation equilibrium. Also, no indication of dissociation of the intermediate complexes is found in sedimentation velocity, which indicates that other subunit interactions in the intermediate complexes are also strong. The 43.7 S complex, which formed upon addition of gp53, is a hexamer of the wedge complex and resembles the star-shaped baseplate. The s-value of the baseplate-like complex decreased to 40.6 S upon association with gp11 in spite of the increased molecular weight, which is reflected in the sharper edges of the baseplate-like structure which would have a higher friction. PMID:20593364

Yap, Moh Lan; Mio, Kazuhiro; Ali, Said; Minton, Allen; Kanamaru, Shuji; Arisaka, Fumio



Characterization of Triglyceride Rich Lipoproteins with Very Light Density by Ultracentrifugation and Agarose Gel Electrophoresis using Triglyceride and Cholesterol-Staining  

Microsoft Academic Search

Hypertriglyceridemia is an independent risk factor for atherosclerosis. This risk is most likely due to accumulation of circulating triglyceride rich lipoproteins with heterogeneous particles. The identification and characterization of these triglyceride rich lipoproteins is important to detect abnormality of triglyceride metabolism. In the present study, we developed a new method that combines ultra- centrifugation and agarose gel electrophoresis with triglyceride-

Hiroya Hidaka; Minoru Tozuka; Barbara Meyer; Kazuyoshi Yamauchi; Mitsutoshi Sugano; Tetsuo Nakabayashi; Tsutomu Katsuyama


The dimeric assembly of Photobacterium leiognathi and Salmonella typhimurium SodC1 Cu,Zn superoxide dismutases is affected differently by active site demetallation and pH: an analytical ultracentrifuge study.  


To establish whether the species-specific variations at the subunit interface of bacterial Cu,Zn superoxide dismutases affect dimer assembly, the association state of the Photobacterium leiognathi (PlSOD) and Salmonella typhimurium (StSOD) enzymes, which differ in 11 out of 19 interface residues, was investigated by analytical ultracentrifugation. The same linkage pattern correlates quaternary assembly, active site metallation, and pH in the two enzymes albeit with quantitative differences. Both holo-enzymes are stable dimers at pH 6.8 and 8.0, although their shape is altered at alkaline pH. In contrast, dimer stability is affected differently by metal removal. Thus, apo-StSOD is a stable dimer at pH 6.8 whereas apo-PlSOD is in reversible monomer-dimer equilibrium. In both apoproteins a pH increase to 8.0 favors monomerization. These effects prove the existence of long-range communication between the active site and the subunit interface and provide a structural explanation for the known functional differences between the two enzymes. PMID:18179768

Catacchio, B; D'Orazio, M; Battistoni, A; Chiancone, E




PubMed Central

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

Chiles, James A.; Severinghaus, Aura E.



Use of analytical techniques for identification of inorganic polymer gel composition  

Microsoft Academic Search

In the present experimental study, a number of analytical techniques were used to identify the composition of gel and thus\\u000a elucidate to a certain extent the mechanisms involved during synthesis of inorganic polymers. The raw materials used, low\\u000a calcium slag from a ferronickel plant and commercial glass, were alkali activated by Na2SiO3 and KOH solutions. X-ray diffraction (XRD) is used

D. Zaharaki; K. Komnitsas; V. Perdikatsis



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



Electrostatic interactions between polyelectrolytes within an ultracentrifuge  

Microsoft Academic Search

The authors characterize electrostatic and other polymer-polymer interactions within an ultracentrifuge cell using a new electrochemical transport model. Applying conservation of mass and momentum of solutes and solvent, and Maxwell's equations valid in the electroquasistatic limit, together with initial and boundary conditions on solute (and electrolyte) distribution, the authors predict the transient (nonequilibrium) and equilibrium solute (and electrolyte) distributions, net

P. J. Basser; A. J. Grodzinsky



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 and quantitation of cholesterol carriers in native bile by ultracentrifugation.  


The vesicular and micellar carriers of biliary cholesterol were isolated and quantitated from native bile by a simple and short isopyknic ultracentrifugal method. The method was designed to decrease the potential pitfalls of classic ultracentrifugation: osmotic effects of the centrifugation media and hydrostatic pressure effects generated in the centrifuge tube. This was accomplished by using metrizamide as an inert centrifugation medium for isopyknic separation and a vertical rotor. The buoyant density of vesicles isolated from human native bile varied between 1.010 and 1.030 gm/ml, as determined in preformed bile-metrizamide density gradients after 285 min of centrifugation. When 16% metrizamide was directly dissolved in bile, its density increased to 1.060 gm/ml. After 120 min of centrifugation, it was found that more than 95% of total vesicular cholesterol floated at the top of the centrifuge tube. This fraction appeared as one or two white opalescent bands. The present ultracentrifugal method was validated by gel filtration chromatography. It was found that more than 95% of vesicular cholesterol migrated to the top 0.4 ml of the centrifuge tube after the short-run centrifugation. Approximately 5% of total biliary cholesterol present in the vesicular fractions was in fact solubilized in mixed micelles as assessed by gel filtration chromatography. Although the proportion of vesicles and micelles estimated with the present ultracentrifugal method is in the range reported by other authors using the more common chromatographic method, we believe that our method has two major advantages. First, it eliminates the dilutional effect of buffers necessary for gel filtration chromatography.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2210640

Amigo, L; Covarrubias, C; Nervi, F



Influence of Nafion in Titania Sol-gel Matrix on Analytical Characteristic of Amperometric Phenol Biosensor Based on Tyrosinase.  


For detection of phenolic compounds a simple amperometric biosensor based on tyrosinase immobilized in titania sol-gel/Nafion composite was employed. Titania sol-gel was mixed with Nafion (v/v) in ratios 1:1 (TiO2/NF-1/1) and 2:1 (TiO2/NF-2/1), v/v. Morphology of immobilization composites was characterized by scanning electron microscopy. Analytical performance of biosensors with Nafion and based only on titania sol-gel (TiO2) was compared. Apart from sensitivity, linear range and detection limit also repeatability, reproducibility and storage stability were evaluated. The biosensor based on titania sol mixed with Nafion in ratio 1:1 (v/v) exhibited the best analytical parameters in terms of sensitivity: 2.84 µA L µmol-1, corresponding LOD, 0.056 µmol L-1, and the long-term stability within 20 days: it retained 80% of initial activity. PMID:24061356

Kochana, Jolanta



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


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

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



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



Biologist's perspective on analytical imaging systems as applied to protein gel electrophoresis  

Microsoft Academic Search

High-resolution two-dimensional polyacrylamide gel electrophoresis entails the separation of proteins in the first dimension according to their charge and in the second dimension according to their relative mobility (RF). The technique is capable of simultaneously resolving thousands of polypeptides as a constellation pattern of spots. Ultimately, the level of success in the analysis of such protein patterns depends upon the

Wayne F. Patton



Generalization of the Radial Dilution Square Law in Ultracentrifugation  

Microsoft Academic Search

The classical square law of radial dilution, which relates the concentration of a single component to the boundary position in the ultracentrifuge cell, has been examined and found to be valid for a single component as well as for a multicomponent system even though the sedimentation rates are dependent on concentration.The square law has been generalized to give corrected concentrations

Rodes Trautman; Verne Schumaker




PubMed Central

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

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



Cytoplasmic and Chloroplast Ribosomes of Chlamydomonas: Ultracentrifugal Characterization  

Microsoft Academic Search

Ribosomes isolated from the cytoplasmic and chloroplast fractions of Chlamydomonas were characterized in the ultracentrifuge. The cytoplasmic ribosomes belong to the 80S class of ribosomes, and, like animal ribosomes, dissociate to 60, 50, and 40S subunits. However, like the ribosomes of micro-organisms, they contain smaller RNA's, 24 and 16S, and require 0.01 mole of magnesium ions per liter for stability.

Ruth Sager; Mary G. Hamilton



Oligomerization state of S100B at nanomolar concentration determined by large-zone analytical gel filtration chromatography.  

PubMed Central

S100B is a Ca(2+)-binding protein known to be a non-covalently associated dimer, S100B(beta beta), at high concentrations (0.2-3.0 mM) under reducing conditions. The solution structure of apo-S100B (beta beta) shows that the subunits associate in an antiparallel manner to form a tightly packed hydrophobic core at the dimer interface involving six of eight helices and the C-terminal loop (Drohat AC, Amburgey JC, Abildgaard F, Starich MR, Baldisseri D, Weber DJ. 1996. Solution structure of rat apo-S100B (beta beta) as determined by NMR spectroscopy. Biochemistry 35:11577-11588). The C-terminal loop, however, is also known to participate in the binding of S100B to target proteins, so its participation in the dimer interface raises questions as to the physiological relevance of dimeric S100B (beta beta). Therefore, we investigated the oligomerization state of S100B at low concentrations (1-10,000 nM) using large-zone analytical gel filtration chromatography with 35S-labeled S100B. We found that S100B exists (> 99%) as a non-covalently associated dimer, S100B (beta beta), at 1 nM subunit concentration (500 pM dimer) in the presence or absence of saturating levels of Ca2+, which implies a dissociation constant in the picomolar range or lower. These results demonstrate for the first time that in reducing environments and at physiological concentrations, S100B exists as dimeric S100B (beta beta) in the presence or absence of Ca2+, and that the non-covalent dimer is most likely the form of S100B presented to target proteins.

Drohat, A. C.; Nenortas, E.; Beckett, D.; Weber, D. J.



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


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

Beretta, Giangiacomo; Malacco, Matteo



Sedimentation velocity ultracentrifugation analysis for hydrodynamic characterization of G-quadruplex structures.  


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

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



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

PubMed Central

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

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



Characterization of chick serum lipoproteins isolated by density gradient ultracentrifugation.  


Serum lipoproteins from 12h fasted male chicks (15-day-old) were separated into 20 fractions by isopycnic density gradient ultracentrifugation. A new procedure was described by collecting the different fractions from the bottom of tube instead of by aspiration from the meniscus of each tube. Analyses of chemical composition of serum lipoproteins have permitted to reevaluate the density limits of major classes: VHDL, d greater than 1.132 g/ml; HDL, d 1.132-1.084 g/ml; LDL, d 1.084-1.038; IDL, d 1.038-1.022; and VLDL d less than 1.022. HDL fractions clearly predominated (approx. 77% of total lipoproteins) while IDL and VLDL were present at low percentage. LDL was the fraction richest in cholesterol; triacylglycerol content clearly increased from HDL to VLDL, while protein content decreased. All the chemical components of chick serum lipoproteins were accumulated in HDL, although triacylglycerol was relatively distributed in all the lipoprotein classes. PMID:1380327

Rodriguez-Vico, F; Lopez, J M; Castillo, M; Zafra, M F; Garcia-Peregrin, E


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



Differentiation of liquid analytes in gel films by permeability-modulated double-layer chemo-chips.  


A double-layer chemo-chip for the characterization of liquid analytes by rapid fluorimetric imaging is described. The chemo-chip consists of an array of polymeric micro-spots prepared on a glass slide. Each spot is composed of a thin indicator layer made of PVA doped with an immobilized fluorescence dye and a top layer polymer spot with different permeation properties. The analytes can be differentiated by variations in the optical response rate of the indicator dye after its application. Consequently, different cross-linker concentrations were applied using the Nano-Plotter((TM)) which formed top layers of varying permeability. The chemo-chips were tested with the aqueous solutions of two model liquids (aqueous solutions of malonic acid and phenanthroline hydrochloride). It was found that the transition time of response had changed considerably (up to a factor of about 10) depending on different local cross linking degrees. This has resulted in time-dependent fluorescent patterns of the fluorescence images of the micro-array. The response was fast and the transition times were in the range between a few seconds to 30 s. PMID:19173068

Thete, Aniket R; Gross, G Alexander; Koehler, J Michael



Ultracentrifugation Studies with Absorption Optics. V. Analysis of Interacting Systems Involving Macromolecules and Small Molecules.  

National Technical Information Service (NTIS)

From both theoretical and experimental points of view the ultracentrifugal methods presented have much to commend them for the evaluation of interactions between large and small molecules. The theory for the sedimentation equilibrium technique is rigorous...

I. Z. Steinberg H. K. Schachman



Variability in purified dysfunctional C1(-)-inhibitor proteins from patients with hereditary angioneurotic edema. Functional and analytical gel studies.  

PubMed Central

C1(-)-inhibitor (C1(-)-INH) proteins from normal persons and members of eight different kindred with dysfunctional C1(-)-INH proteins associated with hereditary angioneurotic edema (HANE) were compared with respect to their inhibitory activity against purified preparations of C1s-, plasma kallikrein, activated forms of Hageman factor, and plasmin. Each dysfunctional C1(-)-INH protein showed a unique spectrum of inhibitory activity against these enzymes. Although none of the dysfunctional C1(-)-INH proteins significantly impaired amidolysis by plasmin, all but one inhibited activated Hageman factor. One purified dysfunctional C1(-)-INH (Ta) inhibited purified C1s- to a normal degree. Another C1(-)-INH (Za) had almost seven times as much inhibitory activity as normal C1(-)-INH against activated Hageman factor, but had decreased activity against C1s- and no activity against plasmin. Analyses of mixtures of plasmin and C1(-)-INH proteins in SDS gel electrophoresis revealed variability in the patterns of complex formation and cleavage of dysfunctional proteins after exposure to C1s- and plasmin. Some bound to plasmin and were cleaved, even though none significantly impaired the amidolytic activity of plasmin. Two were cleaved by C1s-, whereas neither normal or other dysfunctional C1(-)-INH were cleaved. Dysfunctional C1(-)-INH proteins from patients with HANE are thus heterogeneous in their inhibitory properties and there must be different structural requirements for the inhibition of the various plasma enzymes that can be regulated by normal C1(-)-INH. The data suggest that in addition to common sites of interactions between these proteases and C1(-)-INH, there are also points of contact that are specific for each protease. Genetic mutations leading to structural changes at some of these sites may have differing effects on the interaction between individual proteases and abnormal C1(-)-INH proteins. These alterations may allow these proteins to serve as probes for structural requirements for inhibitory actions of normal C1(-)-INH. Images

Donaldson, V H; Harrison, R A; Rosen, F S; Bing, D H; Kindness, G; Canar, J; Wagner, C J; Awad, S



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



Kinetic Data Determination by Means of the Analytical Ultracentrifuge, for Optimization of the PUREX Process.  

National Technical Information Service (NTIS)

As the uranyl nitrate uptake by the organic phase requires the formation of the extractable species in the form of the neutral UO/sub 2/(NO/sub 3/)/sub 2/ 2TBP complex, addition of nitric acid or neodymium nitrate, which increases the nitrate concentratio...

V. Friehmelt



System for Gel Electrophoretic Immunoassay.  

National Technical Information Service (NTIS)

A micro-analytical platform for performing electrophoresis-based immunoassays was developed by integrating photopolymerized cross-linked polyacrylamide gels within a microfluidic device. The microfluidic immunoassays are performed by gel electrophoretic s...

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



Sol–gel immobilized cyano-polydimethylsiloxane coating for capillary microextraction of aqueous trace analytes ranging from polycyclic aromatic hydrocarbons to free fatty acids  

Microsoft Academic Search

Sol–gel coating containing highly polar cyanopropyl and nonpolar poly(dimethylsiloxane) components (sol–gel CN-PDMS coating) was developed for capillary microextraction (CME). The sol–gel chemistry provided an efficient means to immobilize the CN-PDMS coating by establishing chemical anchorage between the coating and the fused silica capillary inner surface. This chemical bond provided excellent thermal and solvent stability to the created sol–gel coating. For

Sameer Kulkarni; Li Fang; Khalid Alhooshani; Abdul Malik



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

PubMed Central

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

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



[Identification of the mink alpha2-lipoprotein Lpm-allotypes by the method of preparatory ultracentrifugation].  


The density class accessory of 8 mink alpha2-lipoprotein allotypes are determined by means of preparative ultracentrifugation. It is found that Lpm1, Lpm2, Lpm2, Lpm3, Lpm4, Lpm5, Lpm7 and Lpm8 are determinants of lipoproteins with density exceeding 1.210, i.e. they are VHDL. The allotypic marker 6, which has been earlier assigned by other criteria to Lpm group, belongs to mink lipoprotein, which distributes during ultracentrifugation at the region of low and, partially, high density. PMID:196979

Baranov, O K; Ermolaev, V I; Savina, M A



The Effects of Ultra-centrifuging the Oocytes of Lumbricus terrestris  

Microsoft Academic Search

DURING the last fifty years a large amount of work has been carried out on the cytoplasmic inclusions of the germ-cells of invertebrates. Many of the conclusions expressed in this work were contradictory, and until the advent of the ultra-centrifuge it seemed as if some of the conflicting points would never be cleared up. PREVIOUS WORK WITH THE CENTRIFUGE. Conklin

Gertrude M. Norminton


Very fast ultracentrifugation of serum lipoproteins: influence on lipoprotein separation and composition  

Microsoft Academic Search

A very short run time and small sample volumes in the separation of lipoproteins by preparative ultracentrifugation are needed for several investigations. Recently, a very fast sequential separation method was described that needs only 100 min for one run in a centrifugal field of 625 000 × g. We studied the influence of centrifugal fields of this dimension on lipoprotein

Jens Pietzsch; Sabine Subat; Sigrid Nitzsche; Wolfgang Leonhardt; Klaus-Ulrich Schentke; Markolf Hanefeld



Effective Separation of Carbon Nanotubes and Metal Particles from Pristine Raw Soot by Ultracentrifugation  

NASA Astrophysics Data System (ADS)

A quick and effective method for the separation of single-wall carbon nanotubes (SWCNTs) from impurity particles has been demonstrated. High-purity SWCNTs and impurities, such as metal particles and amorphous carbons, were separated by ultracentrifugation from raw soot containing SWCNTs. The purity of each component was evaluated by scanning electron microscopy, thermogravimetric analysis, and Raman spectroscopy. The advantage of this method is that the impurity particles can be collected as residual soot in the ultracentrifugation process without any loss, while the impurity particles are more or less chemically modified or disappeared in previous purification protocols. The present technique can provide suitable samples for the research of both SWCNTs and impurity particles, particularly for nano-risk assessment.

Nishide, Daisuke; Miyata, Yasumitsu; Yanagi, Kazuhiro; Tanaka, Takeshi; Kataura, Hiromichi



Chemistry and processability of crude oil asphaltenes as studied by ultracentrifugation  

SciTech Connect

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

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



Purification of very high density lipoproteins by differential density gradient ultracentrifugation.  


Differential density gradient ultracentrifugation procedures, utilizing a vertical rotor, were developed for the preparative purification of very high density lipoproteins (VHDL, density greater than 1.21 g/ml). The VHDLs of several insect species were purified as follows. An initial density gradient ultracentrifugation step removed lipoproteins of lower density from the VHDL-fraction, which partially separated from the nonlipoproteins present in the infranatant. A complete separation was achieved by a second centrifugation step employing a modified gradient system. The use of a vertical rotor and specially designed discontinuous gradients allows a relatively fast, efficient, and economical isolation of the class of very high density lipoproteins. Similar gradient systems should be useful for the detection and purification of VHDLs from other sources. PMID:3578796

Haunerland, N H; Ryan, R O; Law, J H; Bowers, W S



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

Microsoft Academic Search

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

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



Method and Apparatus for Gel Electrophoretic Immunoassay.  

National Technical Information Service (NTIS)

A micro-analytical platform for performing electrophoresis-based immunoassays was developed by integrating photopolymerized cross-linked polyacrylamide gels within a microfluidic device. The microfluidic immunoassays are performed by gel electrophoretic s...

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



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.



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

NASA Astrophysics Data System (ADS)

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

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



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

Microsoft Academic Search

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

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



Advanced high-temperature ultracentrifuge apparatus for mega-gravity materials science  

NASA Astrophysics Data System (ADS)

An ultracentrifuge apparatus, which can generate an ultra-strong gravitational field even >1 000 000 (1 million) G (1 G=9.8 m/s2) over a wide temperature range up to >500 °C with high stability control, was developed for new materials science research. The system consists of an air turbine motor with ceramic ball bearings and dumper section, a sample rotor with an outer diameter of up to 160 mm, a vacuum chamber, and a heating system. The nonbored rotor and the double-structural dumper bushing are used to raise the maximum rotational speed and to improve the stability. The samples can be heated by radiant heat. A maximum rotational speed of 190 000 rpm using a 70 mm diam rotor was recorded despite a short time where the maximum gravitational field was >1 2000 000 G. Long and high-temperature ultracentrifuge experiments using 70 and 80 mm diam rotors made of titanium alloy with rotational speeds of up to 170 000 rpm even at temperatures of over 200 °C for 100 h with ripples of <0.05% and <1°, respectively, were successfully performed, where the maximum gravitational field of the sample was >1 000 000 G. The potential energy and sample volume were increased by factors of >2 and >4, respectively, compared with those in the Kumamoto University study [T. Mashimo, S. Okazaki, and S. Tashiro, Rev. Sci. Instrum. 67, 3170 (1996)].

Mashimo, Tsutomu; Huang, Xinsheng; Osakabe, Toyotaka; Ono, Masao; Nishihara, Masamichi; Ihara, Hirotaka; Sueyoshi, Masanori; Shibasaki, Koji; Shibasaki, Shiro; Mori, Nobuo



HDL3 and HDL2 determination by a combined ultracentrifugation and precipitation procedure.  


The aim of the present study was to evaluate a method to separate lipoproteins by ultracentrifugation simultaneously at density 1.006 and 1.125. This procedure combined with heparin-MnCl2 precipitation would facilitate the simultaneous determination of lipid levels of high density lipoproteins (HDL) and its main subfractions (HDL2 and HDL3, including very high density lipoproteins (VHDL)) and of very low (VLDL) and low density lipoprotein (LDL) fractions. Centrifugation at 105 500 X g (mean) for 24 h in a Beckman L5-50 ultracentrifuge with a Ti50 rotor seemed to give an adequate separation. The correlation coefficients for duplicate samples were 0.95 and 0.96 for HDL3-cholesterol and HDL3-phospholipids, respectively. The error of the method for HDL, HDL2 and HDL3 lipids was around half that of the intra-individual variation and comparable to the results for determination of conventional lipoprotein fractions. Therefore the suggested method seems applicable for evaluation of HDL2 and HDL3 levels in selected clinical material. PMID:7296888

Wallentin, L; Fåhraeus, L



The usefulness of the analytical electrofocusing in a thin-layer polyacrylamide gel (PAG) in the histochemistry of enzymes cleaving peptide bonds  

Microsoft Academic Search

The usefulness of the analytical electrofocusing in a thin-layer polyacrylamide (PAG) plate is shown on the basis of experiments with 10%–20% homogenates of various rat, rabbit and human organs as well as in lysates of isolated human lymphocytes and leucocytes in 2% Triton X100. 0.1–0.3 µl of 12000 g supernatants were applied on LKB Ampholine PAG plates pH range 3.5–9.5

Z. Lojda; J. Kulich



Formulating a Sulfonated Anti-Viral Dendrimer in a Vaginal Microbicidal Gel having Dual Mechanisms of Action  

PubMed Central

SPL7013 is the sodium salt of a sulfonated dendrimer that has potent antiviral properties. VivaGel®, a topical gel containing 3% w/w SPL7013, has been shown to be safe and well-tolerated in human clinical studies. BufferGel® is a Carbopol®-based acidic buffering gel that enhances the natural protective action of the vagina to produce a broad-spectrum microbicidal environment. The positive attributes of both gels were combined into a combination vaginal microbicidal gel having dual mechanisms of action. A 3% w/w SPL7013 combination gel, pH 3.7, was developed and fully characterized, and was shown to have more than 2-fold greater acidic buffering capacity than BufferGel. Ultracentrifugation experiments demonstrated that SPL7013 was not sequestered or entropically trapped in the viscous gel, thereby confirming, along with viral challenge studies, that SPL7013 has sufficient mobility in the viscous gel to exert antiviral properties.

Mumper, Russell J.; Bell, Michael A.; Worthen, David R.; Cone, Richard A.; Lewis, Gareth R.; Moench, Thomas R.



Human low density lipoprotein subfractions separated by gradient gel electrophoresis: composition, distribution, and alterations induced by cholesteryl ester transfer protein  

Microsoft Academic Search

Low density lipoprotein (LDL) subfractions were studied in sera from 208 normolipidemic, 22 hypercholester- olemic, and 33 hypertriglyceridemic subjects. Whole serum without preliminary ultracentrifugation was submitted to elec- trophoresis in a nondenaturing polyacrylamide gel. Three main LDL patterns were observed in normolipidemic sera: type 1, characterized by the presence of only one major band; type 2, characterized by the presence

Philippe Gambert; Catherine Bouzerand-Gambert; Anne Athias; Michel Farnier; Christian Lallemant


Very-fast ultracentrifugation of human plasma lipoproteins: influence of the centrifugal field on lipoprotein composition.  


A short run-time in separation of lipoproteins by preparative ultracentrifugation is desirable for several reasons. Recently, a method was described that needs only 100 min for one run in a centrifugal field of 625,000 x g. It is assumed that lipoprotein separation depends on the rotor speed but this has not been systematically studied in centrifugal fields of this order. We performed such a study. Rotor speeds of 120, 90, 60 and 30 x 10(3) rev./min and run-times of 100 min, 3 h, 6.7 h and 27 h were selected in such a way that the product of centrifugal field and run-time remained constant. The first conditions correspond to the 'very fast ultracentrifugation' (VFU) procedure with a centrifugal field of 625,000 x g. The Optima tabletop ultracentrifuge, the rotor TLA-120.2 and thick wall open tubes for 1 ml were used. Thirteen different plasma samples covering a wide range of cholesterol and triglyceride concentrations were separated into VLDL, LDL and HDL in the course of two centrifugal runs at densities of 1.006 and 1.063. The constituents of the lipoproteins were calculated considering the mass of the tube contents after slicing. Recoveries of cholesterol, triglycerides and protein were 97%, 98% and 90%, respectively. The influence of the rotor speed on the apparent composition of the lipoproteins was small. With increasing rotor speed, VLDL-cholesterol became higher (by 14%, P < 0.001), VLDL-triglyceride became lower (by 6%, P < 0.012), LDL-cholesterol became lower (by 9%, P < 0.000). The effects on LDL-triglyceride and on HDL-cholesterol and HDL-triglyceride, did not reach statistical significance. Protein in VLDL and in LDL decreased and increased in 'HDL' (the subnatant of the LDL run). As checked by SDS-PAGE the protein effects were due to complete disappearance of albumin from VLDL and LDL while the apolipoproteins B-100, E and C-I to C-III remained unaffected. It is concluded that the main advantages of VFU are the short run-time and the disappearance of albumin from VLDL and LDL. The other compositional changes need to be further investigated. PMID:8174275

Leonhardt, W; Pietzsch, J; Nitzsche, S



Raman spectroscopy of blue gel pen inks  

Microsoft Academic Search

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

Williams David Mazzella; Patrick Buzzini



Metal ion complexes of EDTA as solutes for density gradient ultracentrifugation: influence of metal ions.  


In the study reported here, we study the nature of the metal ion complexes of EDTA as solute systems for analysis of lipoproteins by density gradient ultracentrifugation (DGU) by varying both the complexing metal ion and the counterion. Specifically, the sodium and cesium salts of complexes of Bi/EDTA, Pb/EDTA, Cd/EDTA, Fe/EDTA, and Cu/EDTA were chosen for this study. We show that useful gradients can be formed within a few hours beginning with a homogeneous solution. Data are presented that provide insight into the nature of how these gradients are formed from these complexes and how the selection of a specific complex can be used to enhance particular regions of the lipoprotein density profile for clinical studies. We also examine the use of equilibrium sedimentation theory to correlate the measured density profiles generated by these complexes with their molecular weight. PMID:16255609

Johnson, Jeffery D; Bell, Natalie J; Donahoe, Erin L; Macfarlane, Ronald D



A Tetramer–Octamer Equilibrium in Mycobacterium leprae and Escherichia coli RuvA by Analytical Ultracentrifugation  

Microsoft Academic Search

In the context of the bacterial RuvABC system, RuvA protein binds to and is involved in the subsequent processing of a four-way DNA structure called Holliday junction that is formed during homologous recombination. Four crystal structures of RuvA from Escherichia coli (EcoRuvA) showed that it was tetrameric, while neutron scattering and two other crystal structures for RuvA from Mycobacterium leprae

Yie Chia Lee; Rashpal Flora; James A. McCafferty; Jayesh Gor; Irina R. Tsaneva; Stephen J. Perkins



Basic amphipathic model peptides: Structural investigations in solution, studied by circular dichroism, fluorescence, analytical ultracentrifugation and molecular modelling  

NASA Astrophysics Data System (ADS)

A twenty amino acid residue long amphipathic peptide made of ten leucine and ten lysine residues and four derivatives, in which a tryptophan, as a fluorescent probe, is substituted for a leucine, are studied. The peptides in water are mainly in an unordered conformation (~90%), and undergo a two state reversible transition upon heating, leading to a partially helical conformation (cold denaturation). Time resolved fluorescence results show that fluorescence decay for the four Trp containing peptides is best described by triple fluorescence decay kinetics. In TFE/water mixture, peptides adopt a single ?-helix conformation but the Leu-Trp9 substitution leads to an effective helix destabilizing effect. In salted media, the peptides are fully helical and present a great tendency to self associate by bringing the hydrophobic faces of helices into close contact. This proceeds in non-cooperative multisteps leading to the formation of ? helix aggregates with various degrees of complexation. Using modelling, the relative hydrophobic surface areas accessible to water molecules in n-mer structures are calculated and discussed. Nous avons étudié un peptide amphipathique composé de dix lysine et dix leucine, ainsi que quatre dérivés comportant un résidu tryptophane pour les études par fluorescence. Dans l'eau, les peptides ne sont pas structurés (~90%), et se structurent partiellement en hélice ? par chauffage (dénaturation froide). Les mesures de déclin de fluorescence font apparaître une cinétique à trois temps de vie. Dans un mélange eau/TFE, les peptides adoptent une conformation en hélice ?, mais la substitution Leu-Trp9 possède un effet déstabilisant. En mileu salin, les peptides sont totalement hélicoïdaux et ont tendance à s'agréger de façon à regrouper leur face hydrophobe. Ce processus se fait en plusieurs étapes avec des agrégats de taille variable. L'existence de tels agrégats est discutée sur la base de la modélisation moléculaire complétée par des calculs d'accessibilité des surfaces hydrophobes.

Mangavel, C.; Sy, D.; Reynaud, J. A.



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

SciTech Connect

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

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



Application of an Ultracentrifugation-based Method for Detection of Feline Calicivirus (a Norovirus Surrogate) in Experimentally Contaminated Delicatessen Meat Samples  

Microsoft Academic Search

The aim of this study was the application of an ultracentrifugation-based method for detection of feline calicivirus (FCV)\\u000a in experimentally contaminated meat samples of roast pork chop, salami and gammon. Virus particles were liberated from food\\u000a items by washing in 0.5-M glycine containing 1% bovine albumin. Food debris were removed by slow-speed centrifugation, and\\u000a viruses were subsequently sedimented by ultracentrifugation.

Artur Rze?utka; Marta Chroboci?ska; Agnieszka Kaupke; Beata Mizak



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



Chemistry and processability of crude oil asphaltenes as studied by ultracentrifugation  

Microsoft Academic Search

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

W. L. McBride



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



Testosterone Gel REMS  

Center for Drug Evaluation (CDER)

Text VersionPage 1. Initial REMS Approval: 02/2012 Testosterone Gel CIII Drug Class and Formulation: Testosterone Gel Products ... use of testosterone gel. II. ... More results from


Apolipoprotein B determination in the dissolved precipitate obtained after precipitation of LDL with polyvinylsulphate. An alternative method for the determination of LDL apolipoprotein B without using ultracentrifugation.  


Using a commercially available test for LDL cholesterol (Boehringer Mannheim), a method was developed for determination of LDL apolipoprotein B without using ultracentrifugation. The infranatant obtained by precipitation of serum with polyvinylsulphate was redissolved in a saline citrate solution and incubated with phospholipase A2, phospholipase C, phospholipase D or triglyceride lipase, respectively. When the saline-citrate redissolved precipitate was monitored by electron microscopy, it appeared as a fibriform network. The additional incubation with phospholipase A2, C, D, or triglyceride lipase resulted in a molecularization of LDL particles. By electron microscopy these particles could not be distinguished from LDL particles isolated by ultracentrifugation. In radial immunodiffusion tests, the additional incubation of the redissolved precipitate with phospholipase C or phospholipase D resulted in a total loss of the slight immunoreactivity observed before phospholipase incubation. However, additional incubation with triglyceride lipase resulted in a significant increase in immunoreactivity. Only the additional incubation of the redissolved precipitate with phospholipase A2 resulted in an immunoprecipitation reaction comparable to that with LDL particles isolated by ultracentrifugation. Using a resolubilized and phospholipase A2-incubated precipitate of a pool serum as apolipoprotein B standard, a good correlation was obtained between apolipoprotein B values measured in this dissolved precipitate and those measured in the d greater than 1.006 kg/l fraction isolated by ultracentrifugation (r = 0.95; y = 0.95x + 0.018; n = 44). PMID:3734704

Schriewer, H; Nolte, W; Robenek, H; Assmann, G



A one-step separation of human serum high density lipoproteins 2 and 3 by rate-zonal density gradient ultracentrifugation in a swinging bucket rotor  

Microsoft Academic Search

A method was developed for the separation of the high density lipoprotein subclasses HDLn and HDLs from hu- man serum. Six serum samples are fractionated in a single- step ultracentrifugal procedure using the Beckman (SW-40) swinging bucket rotor. The method is based on a difference in flotation rate of the high density lipoprotein subclasses. Sep- aration of HDLp and HDLs

P. H. E. Groat; L. M. Scheek; L. Havekes; W. L. van Noort


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



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

PubMed Central

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

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



Analytical Searching.  

ERIC Educational Resources Information Center

Discusses analytical searching, a process that enables searchers of electronic resources to develop a planned strategy by combining words or phrases with Boolean operators. Defines simple and complex searching, and describes search strategies developed with Boolean logic and truncation. Provides guidelines for teaching students analytical

Pappas, Marjorie L.



Analytical Weights  

Microsoft Academic Search

\\u000a Analytical weights did not come up from empty space. In fact, our idea was taken from Hugo Riemann’s definition of metrical\\u000a weights: Meter relates to weights. So it was decided to generate an output in the form of numerical weights for any analytical\\u000a engine.

Guerino Mazzola


Nondenaturing electrophoresis of lipoproteins in agarose and polyacrylamide gradient gels  

Microsoft Academic Search

The plasma lipoproteins frequently are classified according to density and\\/or electrophoretic mobility. The lipoprotein classes differ characteristically also in particle size and apolipoprotein composition. Each class is heterogeneous in size and composition as well. Nondenaturing electrophoresis in agarose gels and polyacrylamide gradient gels are complementary analytical methods for classification of lipoproteins and determining distribution profiles of the major classes. In



Secondary Structural Studies of Bovine Caseins: Structure and Temperature Dependence of ?-Casein Phosphopeptide (1-25) as Analyzed by Circular Dichroism, FTIR Spectroscopy, and Analytical Ultracentrifugation  

Microsoft Academic Search

The defining structural feature of all of the caseins is their common phosphorylation sequence. In milk, these phosphoserine residues combine with inorganic calcium and phosphate to form colloidal complexes. In addition, nutritional benefits have been ascribed to the phosphopeptides from casein. To obtain a molecular basis for the functional, chemical, and biochemical properties of these casein peptides, the secondary structure

H. M. Farrell; P. X. Qi; E. D. Wickham; J. J. Unruh



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.



Studies of the bulbo-urethral (Cowper's)-gland mucin and seminal gel of the boar  

PubMed Central

1. Moving-boundary electrophoresis of the mucin from the Cowper's gland of the boar revealed a sharp single peak at pH values from 1.1 to 9.0 and an isoelectric point of 1.1. 2. Neuraminidase treatment of the mucin, which removed at least 96% of the sialic acid groups, decreased the electrophoretic mobility at pH4 from ?7.4×10?5 (for the mucin) to ?0.64×10?5cm2V?1s?1. 3. Ultracentrifugal sedimentation values of s20,w showed a marked dependence on concentration. A hyperfine peak, similar to that given by ovine submaxillary secretion, persisted throughout the run at higher concentrations. Ultracentrifugal studies further showed a very low value for the diffusion coefficient (D20,w ?1.57×10?8cm2/s). 4. Calculation of the approximate molecular weight from comparable s20,w and D20,w values gave a provisional value of 6.5×106. 5. Two proteins present in the boar vesicular secretion known as protein A and protein H (the haemagglutinating protein) were shown to promote the swelling of the mucin to form the characteristic rigid elastic gel of boar semen. It is suggested that protein A molecules particularly (mol.wt. 2.8×104) cross-link with the long molecules of the mucin to form the seminal gel. ImagesFig. 2.Fig. 3.

Boursnell, J. C.; Hartree, E. F.; Briggs, P. A.



Gel drying methods.  


For some instances, protein gels need to be dried after SDS-PAGE, for example, if autoradiography should be performed from radioactive-labeled proteins after their separation on SDS-polyacrylamide gels. Another reason may be to simply store the gel in the laboratory book. Aside from expensive commercial solutions, especially for storage of the dried gel in the lab book, the simple and cheap drying protocol here presented may be sufficient. PMID:22585507

Stamova, Slava; Michalk, Irene; Bartsch, Holger; Bachmann, Michael



Nondenaturing electrophoresis of lipoproteins in agarose and polyacrylamide gradient gels  

SciTech Connect

The plasma lipoproteins frequently are classified according to density and/or electrophoretic mobility. The lipoprotein classes differ characteristically also in particle size and apolipoprotein composition. Each class is heterogeneous in size and composition as well. Nondenaturing electrophoresis in agarose gels and polyacrylamide gradient gels are complementary analytical methods for classification of lipoproteins and determining distribution profiles of the major classes. In addition, gradient gel electrophoresis (GGE) has a high resolving capability for subfractionating each class according to particle size. Combination of gel electrophoresis with immunoblotting yields information on heterogeneity in apolipoprotein distribution. 14 refs., 6 figs., 3 tabs.

Shore, V.G.



Analytical Technology  

SciTech Connect

Characterizing environmental samples has been exhaustively addressed in the literature for most analytes of environmental concern. One of the weak areas of environmental analytical chemistry is that of radionuclides and samples contaminated with radionuclides. The analysis of samples containing high levels of radionuclides can be far more complex than that of non-radioactive samples. This chapter addresses the analysis of samples with a wide range of radioactivity. The other areas of characterization examined in this chapter are the hazardous components of mixed waste, and special analytes often associated with radioactive materials. Characterizing mixed waste is often similar to characterizing waste components in non-radioactive materials. The largest differences are in associated safety precautions to minimize exposure to dangerous levels of radioactivity. One must attempt to keep radiological dose as low as reasonably achievable (ALARA). This chapter outlines recommended procedures to safely and accurately characterize regulated components of radioactive samples.

Goheen, Steven C.



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


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

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




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 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 toxicology  

Microsoft Academic Search

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

Hans H. Maurer



Microsoft Academic Search

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

Randall S. Seright




SciTech Connect

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

Randall S. Seright




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.



EPIDUO Gel Labeling  

Center for Biologics Evaluation and Research (CBER)

Text Version... treated with EPIDUO Gel were dry skin, contact ... of topical products with a strong drying effect can ... Weather extremes, such as wind or cold, may be ... More results from


Periodic mesoporous silica gels  

SciTech Connect

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

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



Active DNA gels  

NASA Astrophysics Data System (ADS)

Research into the mechanics and fluctuations of living cells has revealed the key role played by the cytoskeleton, a gel of stiff filaments driven out of equilibrium by force-generating motor proteins. Inspired by the extraordinary mechanical functions that the cytoskeleton imparts to the cell, we sought to create an artificial gel with similar characteristics. We identified DNA, and DNA-based motor proteins, as functional counterparts to the constituents of the cytoskeleton. We used DNA selfassembly to create a gel, and characterized its fluctuations and mechanics both before and after activation by the motor. We found that certain aspects of the DNA gel quantitatively match those of cytoskeletal networks, indicating the universal features of motor-driven, non-equilibrium networks.

Saleh, Omar A.; Fygenson, Deborah K.; Bertrand, Olivier J. N.; Park, Chang Young



Multicomponent biopolymer gels  

Microsoft Academic Search

The structure—property relationship and application of multicomponent protein—polysaccharide and polysaccharide 1—polysaccharide 2 gels are considered. Attention is focused on gels based on mixed solutions of gelatin with dextran, human serum albumin, sodium caseinate, ovalbumin, agarose, methylcellulose, calcium alginate or sodium alginate. The thermodynamic incompatibility of and the formation of complexes by food hydrocolloids greatly affect mechanical and other physicochemical properties

D. V. Zasypkin; E. E. Braudo; V. B. Tolstoguzov



Fluorescent staining of gels.  


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

Buxbaum, Engelbert



Gels with magnetic properties  

Microsoft Academic Search

Materials producing strain in magnetic field are known as magnetoelastic or magneto strictive materials. A new type has been\\u000a developed by preparing magnetic field sensitive gels, called ferrogels. Single domain, magnetic particles of colloidal size\\u000a are incorporated into chemically cross-linked polyvinyl-alcohol hydrogels. The finely distributed colloidal particles having\\u000a superparamgnetic behavior couple the shape of the gel to the nonuniform external

L. Barsi; A. Biiki; D. Szabó; M. Zrinyi


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



Crystallization from Gels  

NASA Astrophysics Data System (ADS)

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

Narayana Kalkura, S.; Natarajan, Subramanian


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




SciTech Connect

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

Randall S. Seright



Spinodal decomposition in gels  

Microsoft Academic Search

We construct a Ginzburg-Landau model for gels undergoing spinodal decomposition in terms of the polymer volume fraction and a deformation tensor. We numerically demonstrate that the domain growth is extremely slowed down in late stages, where the surface tension force, which drives the coarsening in usual fluids, is cancelled by the elastic force. The patterns closely resemble those observed in

A. Onuki; S. Puri



[Pharmaceutical hydrophilic gels].  


From the pharmacopoeial standpoint, gels, together with ointments, creams, pastes, cataplasmata, and medicated plasters, rank among the group of topical semisolid preparations applied to the skin. They are bicoherent systems composed of the internal phase made of a polymer producing a coherent three-dimensional net-like structure, which fixes the liquid vehicle as the external phase. Intermolecular forces bind the molecules of the solvent to a polymeric net, thus decreasing the mobility of these molecules and producing a structured system with increased viscosity. The physical and chemical bonds binding the particles of the internal phase provide a relatively stable structure, which can originate by swelling of solid polymers, or by decreasing the solubility of the polymer in a solution. An important group of gels used in pharmacy are hydrophylic gels, or hydrogels, usually made of hydrophyilc polymers, which under certain conditions and polymer concentration, jellify. Attention of pharmaceutical research now concentrates primarily on hydrophilic gels, as this dosage form seems to be prospective for the development of modern drugs based on systems with prolonged and controlled release of active ingredients. PMID:15895965

Chalupová, Z; Masteiková, R; Savickas, A



Blue Native Polyacrylamide Gel Electrophoresis (BN-PAGE) for Analysis of Multiprotein Complexes from Cellular Lysates  

PubMed Central

Multiprotein complexes (MPCs) play a crucial role in cell signalling, since most proteins can be found in functional or regulatory complexes with other proteins (Sali, Glaeser et al. 2003). Thus, the study of protein-protein interaction networks requires the detailed characterization of MPCs to gain an integrative understanding of protein function and regulation. For identification and analysis, MPCs must be separated under native conditions. In this video, we describe the analysis of MPCs by blue native polyacrylamide gel electrophoresis (BN-PAGE). BN-PAGE is a technique that allows separation of MPCs in a native conformation with a higher resolution than offered by gel filtration or sucrose density ultracentrifugation, and is therefore useful to determine MPC size, composition, and relative abundance (Schägger and von Jagow 1991); (Schägger, Cramer et al. 1994). By this method, proteins are separated according to their hydrodynamic size and shape in a polyacrylamide matrix. Here, we demonstrate the analysis of MPCs of total cellular lysates, pointing out that lysate dialysis is the crucial step to make BN-PAGE applicable to these biological samples. Using a combination of first dimension BN- and second dimension SDS-PAGE, we show that MPCs separated by BN-PAGE can be further subdivided into their individual constituents by SDS-PAGE. Visualization of the MPC components upon gel separation is performed by standard immunoblotting. As an example for MPC analysis by BN-PAGE, we chose the well-characterized eukaryotic 19S, 20S, and 26S proteasomes.

Fiala, Gina J.



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

PubMed Central

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

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



Borate-gum gel breakers  

Microsoft Academic Search

This is a delayed action gel breaker for borate-gum gels. Water-base fracturing fluid is widely used in hydraulic fracturing operations. Borate ions and certain natural gums having cis di-diol groups or adjcent cis hydroxyl units form a gel in water to produce a satisfactory fracturing fluid. The gel must retain its high viscosity and particle suspending qualities from 1 to

R. E. Wyant; T. K. Perkins; T. F. Moore



Phase Transitions in Ionic Gels  

Microsoft Academic Search

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

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



Polyacrylamide/graphite and polyacrylamide/titanium dioxide gel electrodes  

SciTech Connect

Polyacrylamide (pacr) gels have attractive properties that are the basis for several important applications in bioanalytical chemistry. For example, they provide a hydrophilic environment with a controllable pore size that allows for the entrapment and immobilization of biopolymers in their active forms. Pacr gels have long been used as matrices for gel electrophoresis and gel permeation chromatography. Recently, they described the construction of an enzyme electrode, based on the ideas of Hill and co-workers, that consisted of an enzyme/mediator system entrapped in a pacr interface between a carbon support bed and the solution. These pacr-modified electrodes mediated the direct and specific amperometric oxidation of glucose. Others have studied pacr-modified electrodes, and a variety of applications based on the electrochemically driven swelling of polyelectrolyte gels can be envisioned. Thus these electrodes show promise as permeable, multicomponent interfaces between an electrode substrate and solution. The purpose of the work described here was 3-fold: first, to study charge transport through the ferrocene/graphite/pacr gel composite; second, to document preliminary investigations of the photoactivation process occurring in the ferrocene/TiO/sub 2//pacr gel; and third, to examine the analytical utility of the pacr electrode.

Lange, M.A.; Chambers, J.Q.



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



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.



Analytical chemistry instrumentation  

Microsoft Academic Search

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




Factors influencing alginate gel biocompatibility.  


Alginate remains the most popular polymer used for cell encapsulation, yet its biocompatibility is inconsistent. Two commercially available alginates were compared, one with 71% guluronate (HiG), and the other with 44% (IntG). Both alginates were purified, and their purities were verified. After 2 days in the peritoneal cavity of C57BL/6J mice, barium (Ba)-gel and calcium (Ca)-gel beads of IntG alginate were clean, while host cells were adhered to beads of HiG alginate. IntG gel beads, however, showed fragmentation in vivo while HiG gel beads stayed firm. The physicochemical properties of the sodium alginates and their gels were thoroughly characterized. The intrinsic viscosity of IntG alginate was 2.5-fold higher than that of HiG alginate, suggesting a greater molecular mass. X-ray photoelectron spectroscopy indicated that both alginates were similar in elemental composition, including low levels of counterions in all gels. The wettabilities of the alginates and gels were also identical, as measured by contact angles of water on dry films. Ba-gel beads of HiG alginate resisted swelling and degradation when immersed in water, much more than the other gel beads. These results suggest that the main factors contributing to the biocompatibility of gels of purified alginate are the mannuronate/guluronate content and/or intrinsic viscosity. PMID:21523903

Tam, Susan K; Dusseault, Julie; Bilodeau, Stéphanie; Langlois, Geneviève; Hallé, Jean-Pierre; Yahia, L'Hocine



Gel for retarding water flow  

SciTech Connect

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

Marrocco, M.L.



Polyoxometalate-based Supramolecular Gel  

PubMed Central

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

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



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)



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.



Pesticide Analytical Manual (PAM)  

Center for Food Safety and Applied Nutrition (CFSAN)

The Pesticide Analytical Manual (PAM) is published by FDA as a repository of the analytical methods used in FDA laboratories to examine food for ... More results from


Ultracentrifuge for separating fluid mixtures  


1. A centrifuge for the separation of fluid mixtures having light and heavy fractions comprising a cylindrical rotor, disc type end-plugs closing the ends of the rotor, means for mounting said rotor for rotation about its cylindrical axis, a housing member enclosing the rotor, a vacuum chamber in said housing about the central portion of the rotor, a collection chamber at each end of the housing, the innermost side of which is substantially formed by the outer face of the end-plug, means for preventing flow of the fluid from the collection chambers to said vacuum chamber, at least one of said end-plugs having a plurality of holes therethrough communicating between the collection chamber adjacent thereto and the inside of the rotor to induce countercurrent flow of the fluid in the centrifuge, means for feeding fluid to be processed into the centrifuge, means communicating with the collection chambers to extract the light and heavy separated fractions of the fluid, and means for rotating the rotor.

Lowry, Ralph A. (Charlottesville, VA)



Analyticity without Differentiability  

ERIC Educational Resources Information Center

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

Kirillova, Evgenia; Spindler, Karlheinz



Silicone gel including antimicrobial agent.  


Silicone gel sheets containing Ofloxacin (OFLX), that provide a continual drug delivery system from a wound dressing to the wound so as to prevent infection and to promote healing, are described. It was found that silicone gel sheets without added medication did not inhibit microbial growth but that gel sheets containing 0.02% and 0.2% of OFLX had a positive antimicrobial effect against Staphylococcus aureus and Pseudomonas aeruginosa in a dose-dependent fashion in vitro. Further, this antimicrobial efficacy was greatly increased in a silicone gel sheet that contained 0.02% of OFLX and an additional 10% of silicone oil. In animal experiments, a silicone gel sheet containing OFLX prevented microbiol growth and promoted rapid epithelialisation in wounds to which Staphylococcus aureus had been applied, whereas wounds covered only with OpSite all resulted in continued infection. PMID:2107010

Sawada, Y; Suzuki, T; Hatayama, I; Sone, K



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



Gel electrophoresis of linear and star-branched DNA.  


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

Lau, Henry W; Archer, Lynden A



Polyphenol oxidase activity staining in polyacrylamide electrophoresis gels.  


An analytical method allowing the detection of polyphenol oxidase activity on polyacrylamide gel electrophoresis (PAGE) is described. The method is rapid, sensitive and specific and is based on a coupling reaction between 4-tert-butyl-o-benzoquinone and the aromatic amine, 4-amino-N,N-diethylaniline sulphate. Catecholase activity of polyphenol oxidase appears as blue stained bands on a colourless background. PMID:9178091

Rescigno, A; Sollai, F; Rinaldi, A C; Soddu, G; Sanjust, E



Characterization of fish acid proteases by substrate-gel electrophoresis  

Microsoft Academic Search

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

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


Bouncing gel balls: Impact of soft gels onto rigid surface  

NASA Astrophysics Data System (ADS)

After being thrown onto a solid substrate, very soft spherical gels bounce repeatedly. Separate rheological measurements suggest that these balls can be treated as nearly elastic. The Hertz contact deformation expected in the static (elastic) limit was observed only at very small impact velocities. For larger velocities, the gel ball deformed into flattened forms like a pancake. We measured the size of the gel balls at the maximal deformation and the contact time as a function of velocities for samples different in the original spherical radius and the Young modulus. The experimental results revealed a number of scaling relations. To interpret these relations, we developed scaling arguments to propose a physical picture.

Tanaka, Y.; Yamazaki, Y.; Okumura, K.



Structural evolution and stability of sol gel biocatalysts  

NASA Astrophysics Data System (ADS)

Immobilisation strategies for catalytic enzymes are important as they allow recovery and reuse of the biocatalysts. In this work, sol gel matrices have been used to immobilise Candida antarctica lipase B (CALB), a commonly used industrial enzyme. The sol gel bioencapsulate is produced through fluoride-catalysed hydrolysis of mixtures of tetramethylorthosilicate (TMOS) and methyltrimethoxysilane (MTMS) in the presence of CALB, yielding materials with controlled pore sizes and surface chemistries. Sol gel matrices prolong the catalytic life and enhance the activity of CALB, although the molecular basis for this effect has yet to be elucidated due to the limitations of analytical techniques applied to date. Small angle neutron scattering (SANS) allows such multi-component systems to be characterised through contrast matching. In the sol gel bioencapsulate system at the contrast match point for silica, residual scattering intensity is due to the CALB and density fluctuations in the matrix. A SANS contrast variation series found the match point for the silica matrix, both with and without enzyme present, to be around 35%. The model presented here proposes a mechanism for the interaction between CALB and the surrounding sol gel matrix, and the observed improvement in enzyme activity and matrix strength. Essentially, the inclusion of CALB modulates silicate speciation during evolution of the inorganic network, leading to associated variations in SANS contrast. The SANS protocol developed here may be applied more generally to other encapsulated enzyme systems.

Rodgers, L. E.; Knott, R. B.; Holden, P. J.; Pike, K. J.; Hanna, J. V.; Foster, L. J. R.; Bartlett, J. R.



Symmetry breaking in actin gels - Implications for cellular motility  

NASA Astrophysics Data System (ADS)

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

John, Karin; Peyla, Philippe; Misbah, Chaouqi



Microchannel gel electrophoretic separation systems and methods for preparing and using  


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

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



Introduction to Agarose Gel Electrophoresis  

NSDL National Science Digital Library

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

Bioengineering, Climb: C.


Sol-gel encapsulation for controlled drug release and biosensing  

NASA Astrophysics Data System (ADS)

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

Fang, Jonathan


A Modified Polyacrylamide Gel Slicer.  

National Technical Information Service (NTIS)

The polyacrylamide gel slicer described by Goldberger in 1968 contained two critical parts which are no longer commercially available. Design changes are presented which allow for construction of this device at reduced cost, using readily available parts....

G. L. Moore C. D. Purpura



Aqueous Acrylamide Gel Duplicating Material.  

National Technical Information Service (NTIS)

An aqueous acrylamide gel duplicating material was developed by modification of a commercially available acrylamide material. A synthetic calcium silicate was added for purposes of lowering the per cent strain from 35 to 24 per cent. A potassium alignate ...

E. R. Dootz R. G. Craig F. A. Peyton



Kurnakov and analytical chemistry  

Microsoft Academic Search

The paper appreciates the role of Academician N.S. Kurnakov in holding the All-Union Conference on Analytical Chemistry (1939)\\u000a and creating the Commission on Analytical Chemistry at the Academy of Sciences of the USSR. The scientific works of Kurnakov\\u000a relating to chemical analysis are indicated; brief review is given to studies on analytical chemistry that were carried out\\u000a in the collectives

Yu. A. Zolotov



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



Polysaccharide gel with multiple emulsion  

Microsoft Academic Search

The aim of the present work was to investigate the possibility of using a semicrystalline oil phase in W\\/O\\/W to modify the release of encapsulated hydrophilic compounds from polysaccharide gels with embedded multiple emulsions.l-Tryptophan was enclosed within the W1-phase of an W1\\/O\\/W2-emulsion, which itself was homogeneously distributed in a Ca2+-alginate gel with maltodextrin (D.E. 6.5) as a bulking agent. Various

Julia Weiss; Inta Scherze; Gerald Muschiolik



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



Topical Review: Polymer gel dosimetry  

PubMed Central

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

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



TOPICAL REVIEW: Polymer gel dosimetry  

NASA Astrophysics Data System (ADS)

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

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



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

PubMed Central

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

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



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

Microsoft Academic Search

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

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



NMR mechanisms in gel dosimetry  

NASA Astrophysics Data System (ADS)

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

Schreiner, L. J.



Signals: Applying Academic Analytics  

ERIC Educational Resources Information Center

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

Arnold, Kimberly E.



Extreme Scale Visual Analytics  

SciTech Connect

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

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



Validating Analytical Methods  

ERIC Educational Resources Information Center

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

Ember, Lois R.



Learning Analytics Considered Harmful  

ERIC Educational Resources Information Center

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

Dringus, Laurie P.



Advances in analytical chemistry  

Microsoft Academic Search

The requirement to increase our understanding and control of processes has accelerated development of chemical sensor and analyzer technology. Analytical chemists anticipated the requirement to reduce the time between sampling and reporting the results. Multivariate statistical analyses when implemented on dedicated computers controlling modern instruments provide a mechanism for real time monitors. Implementation of these advanced techniques of analytical chemistry

William F. Arendale; Gary L. Workman



Analytical mass spectrometry  

SciTech Connect

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

Not Available



Analytical mass spectrometry. Abstracts  

SciTech Connect

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

Not Available




Technology Transfer Automated Retrieval System (TEKTRAN)

The measurement of triglyceride (TG)-rich particles after an oral fat challenge has been used to provide a measure of risk for coronary artery disease independent of the fasting plasma triglyceride concentration. The analytical "gold standard" for measuring TG-rich lipoproteins uses density gradient...


Gel placement in fractured systems  

SciTech Connect

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

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



Inorganic Sensing Using Organofunctional Sol-Gel Materials  

PubMed Central

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

Carrington, Nathan A.; Xue, Zi-Ling



Microbubble tunneling in gel phantoms  

PubMed Central

Insonified microbubbles were observed in vessels within a gel with a Young’s modulus similar to that of tissue, demonstrating shape instabilities, liquid jets, and the formation of small tunnels. In this study, tunnel formulation occurred in the direction of the propagating ultrasound wave, where radiation pressure directed the contact of the bubble and gel, facilitating the activity of the liquid jets. Combinations of ultrasonic parameters and microbubble concentrations that are relevant for diagnostic imaging and drug delivery and that lead to tunnel formation were applied and the resulting tunnel formation was quantified.

Caskey, Charles F.; Qin, Shengping; Dayton, Paul A.; Ferrara, Katherine W.



Workforce Planning and Analytics.  

National Technical Information Service (NTIS)

Workforce planning -- the process of getting the right people, with the right competencies, in the right jobs at the right time. Analytics -- using numbers and contexts to explain the present and predict the future.

J. More C. Presta



Visual Analytics: Why Now?  

SciTech Connect

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

Thomas, James J.



Analytic ICF Hohlraum Energetics.  

National Technical Information Service (NTIS)

We apply recent analytic solutions to the radiation diffusion equation to problems of interest for ICF hohlraums. The solutions provide quantitative values for absorbed energy which are of use for generating a desired radiation temperature vs. time within...

M. Rosen J. Hammer



Selectivity in Analytical Isotachophoresis.  

National Technical Information Service (NTIS)

Selectivity in isotachophoretic (ITP) separation, automatic signal processing, and analytical applications are discussed. The suitability of ITP as a reference method was investigated for the determination of sodium in human serum. Aspects of sample pretr...

A. A. G. Lemmens



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.



Adhesive Properties of Thermoreversible Gels  

NASA Astrophysics Data System (ADS)

Fracture mechanics analysis based on JKR theory provides a useful method to investigate the adhesive behavior of low modulus materials, such as acrylic elastomers diluted with solvent. We have developed a thermoreversible system based on a triblock copolymer with poly(methyl methacrylate) (PMMA) endblocks and a poly(n-butyl acrylate) midblock, in which we are able to explore its interfacial properties. These low modulus gels are formed when the triblock copolymer is dissolved in warm 2-ethyl hexanol, a selective solvent for the midblock, and cooled to room temperature. As shown through dynamic rheological studies, this thermoreversible gel exhibits a linearly elastic response, thus, making it an excellent model system for JKR experiments. In these trials, hemispherical lenses formed from 5 to 10 volume percent polymer, are loaded and unloaded against a variety of substrates including flat, rigid surfaces coated with polystyrene and PMMA. Results obtained from measuring the contact area and lens displacement throughout loading cycles, indicate that these gels have no adhesion hysteresis and are completely elastic. Furthermore, by applying this fracture mechanics approach to this system, we are able to obtain estimates of the gel's modulus as a function of composition, which are consistent with rheological experiments for these highly diluted copolymers.

Mowery, C. L.; Shull, K. R.



Fracture of model gel networks  

Microsoft Academic Search

A random central force network model of a gel is constructed by relaxation of a bond diluted simple cubic lattice of Hooke's law springs under tension. The bond dilution procedure, which defines the model, involves the random removal of bonds connecting nodes, at least one of which has a value greater than a prescribed maximum value. The fracture of such

Malcolm J. Grimson



Phase transitions in ionic gels  

Microsoft Academic Search

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

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



Gel-Silica Hybrid Optics.  

National Technical Information Service (NTIS)

Sol-gel processing is used to make two new types of silica optics, Type V fully dense silica and Type VI optically transparent ultra-porous silica. Type VI silica is an ideal matrix for impregnation with second phases that are optically active, resulting ...

L. L. Hench J. K. West B. F. Zhu R. Ochoa



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


Stress field in actin gel growing on spherical substrate.  


Polymerization of actin to form an elastic gel is one of the main mechanisms responsible for cellular motility. The particular problem addressed here stems from the need to model theoretically the growth of actin gel under controlled conditions, as observed in experiments. A biomimetic in vitro system which consists of a spherical latex bead, coated by the enzymatic protein ActA, and a reconstituted cytoplasm within which such beads are placed, induces polymerization of actin on the surface of the bead in the form of successive elastic thin spherical layers. Each newly formed layer pushes outward, and is pushed inward by, the already formed spherical layers which altogether constitute an elastic spherical shell of thickness h varying with time. Thus, a stress field is created in the shell which in turn affects the rate of polymerization as well as that of dissociation of actin gel. Given this bio-chemo-mechanical coupling, the accurate determination of the stress field becomes a subject of great importance for the understanding of the process, and it is the main objective of this work. The problem is addressed by first assuming appropriate constitutive laws for the actin gel elastic material, and then solving the only non-trivial stress equilibrium differential equation along the radial direction assuming spherical symmetry. A linear and a non-linear constitutive model for isotropic elasticity is used, appropriate for small and finite strains, respectively, and the solution is found in closed analytical forms in both cases. Two important conclusions are reached. First, the stress field depends strongly on the compressibility of the actin gel medium via the value of the Poisson ratio, for both linear and non-linear analysis. Second, the linear and non-linear solutions are very close for small strains, but they diverge progressively as the strains increase from small to large. Guided by available experimental data on the observed strain levels, the analytical results are illustrated by selected graphs of stress variation along the radial direction. At the end some comments and suggestions on the bio-chemo-mechanical coupling of actin gel growth and resorption are presented, where the role of properly defined joint isotropic invariants of stress and a unit vector along the predominant direction of free ends of actin filaments at the polymerization site is introduced. PMID:18058144

Dafalias, Yannis F; Pitouras, Zacharias



Regenerative medicine: Noodle gels for cells  

NASA Astrophysics Data System (ADS)

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

Deming, Timothy J.



Analytical chemistry of PCBs  

SciTech Connect

This book provides a comprehensive review of the analytical chemistry of PCBs. The book is an invaluable resource for both chemists with no experience in PCB analysis and seasoned PCB researchers by reviewing possible approaches to analytical problems, serving as a compendium of the literature, and presenting comparisons of available techniques. The book contains 10 chapters that address such topics as the various properties of PCBs; the discrete steps of analysis, including sampling, extraction, cleanup, determination, data reduction, and quality assurance; and collaborative testing, which is the ultimate step in method validation. Analytical chemists, lawyers, environmental scientists, and environmental regulators should consider this book an important reference resource for understanding the complicated process of PCB analysis.

Erickson, M.D. (Argonne National Lab., IL (United States))



Study of Fricke gel dosimeter response for different gel quality  

NASA Astrophysics Data System (ADS)

The Fricke xylenol gel (FXG) dosimeter has been studied for application in radiotherapy because it is capable of to measure the spatial distribution of radiation doses. The dosimetry is based on the oxidation of ferrous (Fe2+) to ferric (Fe3+) ions radiation induced, related to the radiation dose. The gel material usually employed is the 300 Bloom gelatin, which is imported and very expensive in Brazil. Aiming to analyze the viability of to use a locally produced and low cost gel material, in this work the spectrophotometric responses of FXG solutions prepared using 270 Bloom gelatin commercially available and 300 Bloom gelatin imported were compared. The absorption spectra of solutions prepared with 5% by weight 270 and 300 Bloom gelatins non-irradiated and irradiated with 60Co gamma radiation in the dose range between 0.5 and 100 Gy were analysed, the dose-response curves were evaluated and the useful dose range was established. The obtained results indicate that the FXG solution prepared with 270 Bloom gelatin presents good performance, similar to that presented by the FXG solution prepared with 300 Bloom gelatin and its use can be recommended owing to the low cost and the availability in local market.

Cavinato, C. C.; Campos, L. L.



Laboratory evaluation of silica gel sorbent tubes for sampling hydrogen fluoride.  


The NIOSH sampling and analytical method for inorganic acids employs a silica gel sorbent tube for the collection of five common inorganic acids with simultaneous determination of these acids in a single sample by ion chromatography. When the method was extended to the determination of hydrogen fluoride (HF) the sampled HF reacted with the silica gel and glass fiber of the sampler, but the reaction products remained trapped on the sorbent. Silica gel samplers were evaluated for the collection of HF from laboratory generated atmospheres. Factors tested included capacity, storage stability, humidity, accuracy and precision. Based on comparison with impinger collection, the mean recovery of HF from silica gel tube samples was 100.7% with a precision of 0.144. PMID:3010691

Cassinelli, M E



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

NASA Astrophysics Data System (ADS)

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

Mohammadi, Aliasghar



Analytic Trajectory Visualizer Model  

NSDL National Science Digital Library

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

Christian, Wolfgang; Belloni, Mario



Automated Apparatus for Producing Gradient Gels.  

National Technical Information Service (NTIS)

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...

N. L. Anderson



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)



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. 5 figs.

Shahinpoor, M.



Rheology and molecular structure of HPG gels  

SciTech Connect

Hydroxypropyl guar (HPG) polymer solutions crosslinked with titanates (Ti) are used in hydraulic fracturing operations. The rheology of these gels arise from the complex interaction of polymer chemistry, metal ion chemistry, and flow history. The authors have employed several techniques (steady shear viscosity, dynamic oscillatory shear, Laser Doppler Anemometry, and freeze fracture electron microscopy) to develop a consistent picture of the factors controlling gel rheology. An impingement mixing technique has been developed to prepare uniform HPG gels and reproducible rheological data has bee obtained. Dynamic oscillatory rheological measurements have been used as diagnostic probes of gel structure, and are shown to be useful in understanding chemical effects on gel structure. Laser Doppler Anemometry, a non-invasive technique for measuring velocity distributions, has been used to measure velocity profiles for gels under flow. Classical wall slip is not observed, rather distortions of the velocity profiles are observed for gels that have gelled under quiescent conditions. For gels made with impingement mixing linear velocity profiles are observed. Freeze fracture electron microscopy has been used to image gel structure and the results show the fracture of gel structure by shear. These observations demonstrate the mechaism of temperature stabilization of the viscosity of cross-linked gels. Temperature stability measurements of gel viscosity have been made using a novel reciprocating capillary viscometer.

Kramer, J.; Chu, A.; Prud'homme, R.K.



Food gels: Gelling process and new applications  

Microsoft Academic Search

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




Food Gels: Gelling Process and New Applications  

Microsoft Academic Search

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

Soumya Banerjee; Suvendu Bhattacharya



Structure and dynamics of ovalbumin gels: II. Gels induced by heat treatment at 80°C  

Microsoft Academic Search

Dynamic viscoelastic measurements were made on ovalbumin gels prepared by two different thermal denaturation methods for a study of their gel structures. Results are discussed in the light of the fractal concept developed for the critical gel structure of synthetic polymers at the sol–gel transition point. Especially, a role of added salt on association kinetics of denatured proteins as well

Akihiro Koike; Akihiko Takada; Norio Nemoto



Viscoelasticity of Cowpea Starch Gels  

Microsoft Academic Search

Cereal Chem. 77(3):309-314 The mechanical behavior of cowpea starch gels (10%, w\\/v) at small and large deformations were investigated in comparison with acorn, corn, and potato starches in storage at 4°C for seven days. The rapid visco- grams of starch paste (7%, w\\/v) revealed that cowpea starch had a larger setback (1,135 cP) than other starches (465-830 cP), although peak

So-Yoon Won; WonSeok Choi; Hyesook S. Lim; Ki-Yul Cho; Seung-Taik Lim



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



Analytical applications of aptamers  

Microsoft Academic Search

So far, several bio-analytical methods have used nucleic acid probes to detect specific sequences in RNA or DNA targets through hybridisation. More recently, specific nucleic acids, aptamers, selected from random sequence pools, have been shown to bind non-nucleic acid targets, such as small molecules or proteins. The development of in vitro selection and amplification techniques has allowed the identification of

S. Tombelli; M. Minunni; M. Mascini



Miniaturization of analytical systems  

Microsoft Academic Search

Miniaturization has been a long-term trend in clinical diagnostics instrumentation. Now a range of new tech- nologies, including micromachining and molecular self- assembly, are providing the means for further size reduction of analyzers to devices with micro- to nano- meter dimensions and submicroliter volumes. Many analytical techniques (e.g., mass spectrometry and elec- trophoresis) have been successfully implemented on microchips made

Larry J. Kricka



Social Learning Analytics  

ERIC Educational Resources Information Center

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

Buckingham Shum, Simon; Ferguson, Rebecca



Challenges for Visual Analytics  

SciTech Connect

Visual analytics has seen unprecedented growth in its first five years of mainstream existence. Great progress has been made in a short time, yet great challenges must be met in the next decade to provide new technologies that will be widely accepted by societies throughout the world. This paper sets the stage for some of those challenges in an effort to provide the stimulus for the research, both basic and applied, to address and exceed the envisioned potential for visual analytics technologies. We start with a brief summary of the initial challenges, followed by a discussion of the initial driving domains and applications, as well as additional applications and domains that have been a part of recent rapid expansion of visual analytics usage. We look at the common characteristics of several tools illustrating emerging visual analytics technologies, and conclude with the top ten challenges for the field of study. We encourage feedback and collaborative participation by members of the research community, the wide array of user communities, and private industry.

Thomas, James J.; Kielman, Joseph



Avatars in Analytical Gaming  

Microsoft Academic Search

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

Andrew J. Cowell; Amanda K. Cowell




EPA Science Inventory

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


Social Learning Analytics  

ERIC Educational Resources Information Center

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

Buckingham Shum, Simon; Ferguson, Rebecca



Advances in analytical chemistry  

Microsoft Academic Search

Interest in chemical sensor and analyzer technology has sky rocketed in recent years due to a growing desire to increase our understanding and control of processes. Through advances in instrumentation, analytical chemists can provide analyses for smaller samples and more dilute solutions. Implementation of computer programs based on multivariate statistical algorithms makes possible obtaining reliable information from long data vectors

William F. Arendale; Richard T. Congo; Bruce J. Nielsen



Analytical Probability Theory.  

National Technical Information Service (NTIS)

Research results under the grant have been summarized in fifteen research articles, six of which have been published and the other nine of which have been submitted for publication. The research results are in the general area of analytic probability theo...

E. Lukacs



Social media analytics  

Microsoft Academic Search

Online social media represent a fundamental shift of how information is being produced, transferred and consumed. The present tutorial investigates techniques for social media modeling, analytics and optimization. First we present methods for collecting large scale social media data and then discuss techniques for coping with and correcting for the effects arising from missing and incomplete data. We proceed by

Jure Leskovec



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



Biosensors: Future Analytical Tools  

Microsoft Academic Search

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

C S Pundir



Urea Process Analytical Study.  

National Technical Information Service (NTIS)

In an effort to help determine the feasibility of the Urea process for production of the amine fuels, AFRPL established an in-house program to develop a useful analytical technique for monitoring the critical DMU to UDMH reaction. It was the absence of su...

L. A. Dee S. G. Wax



Analytical Chemistry in Poland  

Microsoft Academic Search

The paper presents the main achievements of analytical chemistry in Poland on the basis of papers published mainly in the last decade. The selection is somewhat arbitrary but should show the most important directions of research. The citations generally refer to papers published in regular journals. The following topics were discussed: general aspects, chemical methods and reagents, spectrophotometry, speciation studies,

Adam Hulanicki; Zygfryd Witkicewicz



Selective gel system for permeability profile control  

SciTech Connect

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

Shu, P.



Mechanical characterization of active polymer gels  

NASA Astrophysics Data System (ADS)

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

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



Reduction of Gas and Water Permeabilities Using Gels  

Microsoft Academic Search

The authors investigated how different types of gels reduce permeability to water and gases in porous rock. Five types of gels were studied, including (1) a ``weak`` resorcinol-formaldehyde gel, (2) a ``strong`` resorcinol-formaldehyde gel, (3) a Cr(III)-xanthan gel, (4) a Cr(III)-acetate-HPAM gel, and (5) a colloidal-silica gel. For all gels, extensive coreflood experiments were performed to assess the permeability-reduction characteristics

R. S. Seright



Nuclear analytical chemistry  

SciTech Connect

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

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



Analytical applications of aptamers  

NASA Astrophysics Data System (ADS)

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

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



Ultrasound in analytical chemistry.  


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

Priego Capote, F; Luque de Castro, M D



Analytic holographic superconductor  

SciTech Connect

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.

Herzog, Christopher P. [Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States)



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



Analyticity and phase retrieval  

Microsoft Academic Search

Summary  The general problem of constructing a spectrumg(v) from the knowledge of the magnitude of its Fourier transform ¦ ?(?\\u000a r) ¦ is considered. The question reduces to locating the zeros of the analytic continuation ?(?) in the upper half-plane. It is shown that ifg(v) is real, the complex zeros of ?(?) in the u.h.p. either are on the imaginary axis

P. Roman; A. S. Marathay



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



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



Molecular imprinting in sol-gel matrix.  


Molecular imprinting is a newly developed methodology which provides molecular assemblies of desired structures and properties and is being increasingly used for several applications such as in separation processes, microreactors, immunoassays and antibody mimics, catalysis, artificial enzymes, biosensor recognition elements and bio- and chemo-sensors. The ambient processing conditions and versatility of the sol-gel process makes sol-gel glassy matrix suitable for molecular imprinting. The progress of sol-gel based molecular imprinted polymers (MIPs) for various applications can be seen from the growing number of publications. The main focus of the review is molecular imprinting in sol-gel matrix and applications of molecular imprinted sol-gel derived materials for the development of sensors. Combining sol-gel process with molecular imprinting enables to procure the sensors with greater sensitivity and selectivity necessary for sensing applications. The merits, problems, challenges and factors affecting molecular imprinting in sol-gel matrix have been discussed. Considerable attention has been drawn on recent developments like use of organically modified silane precursors (ORMOSILS) for the synthesis of hybrid molecular imprinted polymers (HMIPs) and applying surface sol-gel process for molecular imprinting. The development of molecular imprinted sol-gel nanotubes for biochemical separation and bio-imprinting is a new advancement and is under progress. Templated xerogels and molecularly imprinted sol-gel films provide a good platform for various sensor applications. PMID:18692561

Gupta, Radha; Kumar, Ashok



Visual Analytics: How Much Visualization and How Much Analytics?  

SciTech Connect

The term Visual Analytics has been around for almost five years by now, but still there are on-going discussions about what it actually is and in particular what is new about it. The core of our view on Visual Analytics is the new enabling and accessible analytic reasoning interactions supported by the combination of automated and visual analytics. In this paper, we outline the scope of Visual Analytics using two problem and three methodological classes in order to work out the need for and purpose of Visual Analytics. Thereby, the respective methods are explained plus examples of analytic reasoning interaction leading to a glimpse into the future of how Visual Analytics methods will enable us to go beyond what is possible when separately using the two methods.

Keim, Daniel; Mansmann, Florian; Thomas, James J.



Swine liver L-leucine aminopeptidase: improved purification procedure.  


An L-leucine aminopeptidase, having a specificity toward the substrate L-leucine amide, was purified 1084-fold from swine liver with a yield of 50.7 per cent. Purification procedure was carried out using successively centrifugation at 105 000 X g, fractionation by ammonium sulfate, DEAE Sephacel chromatography and zonal ultracentrifugation. Enzyme homogeneity and purity studies were carried out by analytical ultracentrifugation and polyacrylamide gel electrophoresis. In SDS-gel polyacrylamide, a single band was observed. It corresponded to a 55 000 molecular weight protein. PMID:6733155

Vincent-Fiquet, O; Rogez, J C; Plaquet, R



Local analytic first integrals of planar analytic differential systems  

NASA Astrophysics Data System (ADS)

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

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



Visual analytics: how much visualization and how much analytics?  

Microsoft Academic Search

The term Visual Analytics has been around for almost ve years by now, but still there are on-going discussions about what it actually is and in particular what is new about it. The core of our view on Visual Analytics is the new enabling and accessible analytic reasoning interactions supported by the combination of automated and visual analysis. In this

Daniel A. Keim; Florian Mansmann; James J. Thomas



Principles of Gel Permeation Chromatography  

NSDL National Science Digital Library

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


Selective gel system for permeability profile control  

SciTech Connect

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

Shu, P.



Applications of CE SDS gel in development of biopharmaceutical antibody-based products.  


CE SDS gel technique offers many advantages over the traditional labor-intensive SDS PAGE slab gel technology. The CE-based method has increasingly been applied to many protein analysis applications. Specific examples are provided for monoclonal antibody (mAb), though the technique can be adapted to many other therapeutic protein products. Applications of CE SDS gel method using Beckman PA800 with UV detection are presented and discussed with respect to mAb analysis, such as purity, quantitation of non-glycosylated heavy chain (NGHC) peak, identity, and stability. The stability of mAb is evaluated with respect to formulation buffer, accelerated temperature stress, UV light-exposure, and high pH conditions. Both reducing and non-reducing CE SDS gel conditions were applied and optimized to characterize mAb products. The data presented provides a "taste" of what CE SDS gel method can do to support the development of mAb products from early clone screening for product quality to the final product characterization. Since the CE SDS gel method is automatable, quantitative, robust, and allows for relatively high throughput, it provides both great analytical capacity and product coverage for a wide spectrum of protein product development in biopharmaceutical industry. PMID:18803223

Rustandi, Richard R; Washabaugh, Michael W; Wang, Yang



Mars Analytical Microimager  

NASA Astrophysics Data System (ADS)

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

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


[Electron microscopy study of artificial vitreous gel].  


Artificial gels prepared from Cu2+-ions and hyaluronic acid were studied in the electron microscope and compared with the native vitreous body. Additionally, the authors attempted to produce transparent gels from the native constituents of the vitreous body, namely collagen and hyaluronic acid. Mixing of solutions of these constituents formed no gels but white precipitates. The ultrastructure of these precipitates was also studied in the electron microscope. PMID:3723971

Ehgartner, E M; Schmut, O; Hofmann, H



Polymer gel electrolytes for lithium batteries  

NASA Astrophysics Data System (ADS)

The data on the most promising polymer gel electrolytes for lithium batteries published in the past decade are surveyed and described systematically. Gel electrolytes with matrices of polyethylene oxide, poly(vinylidene fluoride) and its copolymer with hexafluoropropylene, poly(methyl methacrylate), polyacrylonitrile, poly(vinyl chloride) and polyacrylates are discussed. A special section is devoted to gel electrolytes with ionic liquids as the solvents. The bibliography includes 160 references.

Baskakova, Yu V.; Yarmolenko, Ol'ga V.; Efimov, Oleg N.



Sol–gel materials for electrochemical biosensors  

Microsoft Academic Search

An overview is presented of the state-of-the art of electrochemical biosensors employing sol–gel materials. Low-temperature, porous sol–gel ceramics represent a relatively new class of materials for the immobilization of biomolecules. The rational design of sol–gel sensing materials, based on the judicious choice of the starting alkoxide, encapsulated reagents, and preparation conditions, allows tailoring of material properties in a wide range,

Joseph Wang



Gel-Based Microchips: History and Prospects  

Microsoft Academic Search

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

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



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



21 CFR 866.4900 - Support gel.  

Code of Federal Regulations, 2013 CFR




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


Role of fluorine ions in the formation of silica gel structure and gel glass  

Microsoft Academic Search

Fluorine containing silica gels can be used as precursors of anhydrous glasses for fibre optics. The silica gels were prepared by the sol-gel process including the following stages: hydrolysis of tetraethylor- thosilicate (TEOS) in a four-component system Si(OC2H5)-C2H5OH-H2O-HCl, addition of fumed silica (aerosil) into the sol, sono-activation, centrifugal separation, neutralization by the ammonia solution, gelation, washing the gels in distilled



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.



Coulomb expansion: analytical solutions.  


Exact and approximate analytical solutions are presented, describing expansion of a cloud of charged particles in one, two, and three dimensions (assuming the planar, axial, and spherical symmetries, respectively). The expansion occurs in a gas or dilute plasma, where the screening is unimportant, so that particles interact with each other via Coulomb repulsive forces. It is shown that, irrespective of dimensionality, the density distribution remains homogeneous across the cloud and the velocity increases linearly towards the cloud boundary. The density evolution obeys a universal dependence, asymptotically decreasing with time as t(-1). It is also shown that in the presence of an inhomogeneous external field the interparticle repulsion becomes negligible at an early stage of expansion and then the density decreases with time exponentially. PMID:23496647

Ivlev, A V




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)



Comparison of lipoprotein fractionation by sequential density gradient ultracentrifugation with precipitation or fast phase liquid chromatography ? ? Names are necessary to report factually on available data; however, the US Department of Agriculture neither guarantees nor warrants the standard of the product, and the use of a name implies no approval of the product to the exclusion of others that may also be suitable  

Microsoft Academic Search

Lipoprotein fractions, i.e. very low density (VLDL, ?=0.93?1.019), low density (LDL, ?=1.019?1.063), and high density lipoprotein (HDL, ?=1.063?1.21) were separated by sequential gradient density ultracentrifugation (SDGU) and their cholesterol values were determined and compared with values determined by fast phase liquid chromatography (FPLC) or HDL cholesterol by phosphotungstic acid-MgCl2 (PTMg) precipitation in hamsters fed diets containing various levels of cholesterol.

Talwinder S Kahlon; Ruping Xu; Faye I Chow



Protein-alginate gel for enzyme immobilisation  

Microsoft Academic Search

Propylene glycol alginate forms strong, covalently bonded gel when mixed with certain proteins in alkaline conditions. Enzymes can be immobilised onto the alginate ester before gelating with protein to form the above gel. Some data on the immobilisation of ß-glucosidase are presented.

Abu Bakar Salleh; Suhaila Mohamed



A Short-Duration Gel Diffusion Experiment.  

ERIC Educational Resources Information Center

Described is a gel diffusion experiment that permits the completion of duplicate diffusion runs within a three-hour laboratory session. Information included for the short-duration gel diffusion experiment is the diffusion cell, the experiment, data treatment, and the expected results of the experiment. (Author/DS)

Mulcahy, D. E.



Effect of iron gel on dentin permeability.  


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

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



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


Gel bead composition for metal adsorption  

SciTech Connect

This patent describes a gel bead consisting essentially of a sufficient amount of water and propylene glycol alginate to allow for bead formation and a sufficient amount of bone gelatin to allow for metal absorption and chemically crosslinked in an alkaline medium to form a stable structure. A gel bead contained therein a biological absorbent capable of removing metals from solution.

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



Oil recovery process using a polyacrylamide gel  

SciTech Connect

A polymer gel is formulated by adding a cross-linking agent containing a polyvalent metal cation to an aqueous solution of undried partially hydrolyzed polyacrylamide. The resulting gel is dissolved or suspended in an aqueous medium and injected via a well into a subterranean hydrocarbon-bearing formation to improve oil recovery from the formation.

Norton, C. J.; Falk, D. O.; Hill, A. D.



Polymers and Gels as Molecular Recognition Agents  

Microsoft Academic Search

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

Nicholas A. Peppas; Yanbin Huang



An XML standard for the dissemination of annotated 2D gel electrophoresis data complemented with mass spectrometry results  

Microsoft Academic Search

BACKGROUND: Many proteomics initiatives require a seamless bioinformatics integration of a range of analytical steps between sample collection and systems modeling immediately assessable to the participants involved in the process. Proteomics profiling by 2D gel electrophoresis to the putative identification of differentially expressed proteins by comparison of mass spectrometry results with reference databases, includes many components of sample processing, not

Romesh Stanislaus; Liu Hong Jiang; Martha Swartz; John Arthur; Jonas S. Almeida



Photoswitchable gel assembly based on molecular recognition.  


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

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



Polymer gel dosimetry using computed tomography  

NASA Astrophysics Data System (ADS)

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

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



Radiological properties of normoxic polymer gel dosimeters.  


The radiological properties of the normoxic polymer gel dosimeters MAGIC, MAGAS, and MAGAT [methacrylic and ascorbic acid in gelatin initiated by copper; methacrylic acid gelatine gel with ascorbic acid; and methacrylic acid gelatine and tetrakis (hydroxymethyl) phosphonium chloride, respectively] have been investigated. The radiological water equivalence was determined by comparing the polymer gel macroscopic photon and electron interaction cross sections over the energy range from 10 keV to 20 MeV and by Monte Carlo modeling of depth doses. Normoxic polymer gel dosimeters have a high gelatine and monomer concentration and therefore mass density (kg m(-3)) up to 3.8% higher than water. This results in differences between the cross-section ratios of the normoxic polymer gels and water of up to 3% for the attenuation, energy absorption, and collision stopping power coefficient ratios through the Compton dominant energy range. The mass cross-section ratios were within 2% of water except for the mass attenuation and energy absorption coefficients ratios, which showed differences with water of up to 6% for energies less than 100 keV. Monte Carlo modeling was undertaken for the polymer gel dosimeters to model the electron and photon transport resulting from a 6 MV photon beam. The absolute percentage differences between gel and water were within 1% and the relative percentage differences were within 3.5%. The results show that the MAGAT gel formulation is the most radiological water equivalent of the normoxic polymer gel dosimeters investigated due to its lower mass density measurement compared with MAGAS and MAGIC gels. PMID:15895589

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



Determination of mechanical parameters related to the kinetics of swelling in an electrically activated contractile gel  

Microsoft Academic Search

We report on an analytical model and related experiments to determine the mechanical parameters governing the kinetics of\\u000a mechanical readjustment of a thermally crosslinked polyacrylic acid (20% by weight) and polyvinylalcohol (80% by weight) (PAA-PVA)\\u000a gel.\\u000a \\u000a Either thin films on spherical samples have been used in the experiments. The characteristic time of swelling in the case\\u000a of a thin film

P. Chiarelli; D. De Rossi


Sol–gel derived ZnO\\/PVP nanocomposite thin film for superoxide radical sensor  

Microsoft Academic Search

Pure ZnO films and ZnO nanoparticle-dispersed polyvinylpyrrolidone (PVP) composite films are prepared on Pyrex glass substrates by the sol–gel dip-coating technique utilizing zinc acetate precursor. The thin films are extensively characterized for surface morphology, chemistry, and nanocrystallite size using various advanced analytical techniques including Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). For the

Tianbao Du; Hongwei Song; Olusegun J. Ilegbusi



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.


Composite sol-gel ceramics  

NASA Astrophysics Data System (ADS)

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

Yang, Quanzu



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.



21 CFR 872.1730 - Electrode gel for pulp testers.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Electrode gel for pulp testers. 872.1730... Diagnostic Devices § 872.1730 Electrode gel for pulp testers. (a) Identification. An electrode gel for pulp testers is a device...



Water equivalence of polymer gel dosimeters  

NASA Astrophysics Data System (ADS)

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

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



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



RenaGel (Geltex Pharmaceuticals Inc).  


RenaGel, developed by GelTex, is a polymer that binds and removes dietary phosphate from the intestinal tract without being absorbed into the bloodstream. A US NDA for control of hyperphosphatemia in patients with chronic renal failure was filed in October 1997 and accepted for review in January 1998. Marketing approval was granted in November 1998. The compound has also achieved part B status in Europe. Merrill Lynch predict RenaGel will achieve worldwide sales of $220 million by 2001. PMID:16160949

von Appen, K



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


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

Vandecasteele, Jan; De Deene, Yves



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

NASA Astrophysics Data System (ADS)

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

Vandecasteele, Jan; De Deene, Yves



Phase transition behavior of an amphoteric polymer gel  

NASA Astrophysics Data System (ADS)

In order to characterize the deformation behavior of polymer gels for actuators, spatial distribution of deformation of anionic, cationic and amphoteric gels under the electric field was measured. Amphoteric gel was found to be a promising material for inducing symmetric deformation, compared with anionic and cationic gels. It was also found that the deformation of electro-active gels was mainly attributed to interfacial phenomenon between gel-electrode. It can be concluded that by the use of as many amphoteric gel-electrode interfaces as possible will provide us with electro-active polymer gels that are fast responsive, largely deformable with symmetric deformation mode.

Tamagawa, Hirohisa; Popovic, Suzana; Taya, Minoru



Analytical techniques for cell fractions  

SciTech Connect

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

Pearson, T.; Anderson, L.



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



Social learning analytics: five approaches  

Microsoft Academic Search

This paper proposes that Social Learning Analytics (SLA) can be usefully thought of as a subset of learning analytics approaches. SLA focuses on how learners build knowledge together in their cultural and social settings. In the context of online social learning, it takes into account both formal and informal educational environments, including networks and communities. The paper introduces the broad

Rebecca Ferguson; Simon Buckingham Shum



Visual Analytics Law Enforcement Toolkit  

Microsoft Academic Search

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

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



Philosophical aspects on analytical chemistry  

Microsoft Academic Search

This contribution is neither a cosmetic “facelifting” of an old but loved and admired lady nor is it an advertisement for “Selling new lamps for old“. It is simply a trial to clarify the actual situation and position of analytical chemistry and its paradigmatic change to analytics and its general role in our building of knowledge of nature. Taken this

H. Malissa



Charles Babbage's Analytical Engine, 1838  

Microsoft Academic Search

Charles Babbage commenced work on the design of the Analytical Engine in 1834 following the collapse of the project to build the Difference Engine. His ideas evolved rapidly, and by 1838 most of the important concepts used in his later designs were established. This paper introduces the design of the Analytical Engine as it stood in early 1838, concentrating on

Allan G. Bromley



Charles Babbage's Analytical Engine, 1838  

Microsoft Academic Search

Charles Babbage commenced work on the design of the Analytical Engine in 1834, following the collapse of the project to build the Difference Engine. His ideas evolved rapidly, and by 1838, most of the important concepts used in his later designs were established. The paper introduces the design of the Analytical Engine as it stood in early 1838, concentrating on

Allan G. Bromley



Semiconductor lasers in analytical chemistry  

Microsoft Academic Search

Laser spectroscopy has become a widely used popular technique in analytical chemistry during the laser decade. Numerous studies have documented the results of the advantages of lasers (low detection limits, for example); however, most of the applications have focused on the use of relatively expensive lasers. Much less effort has been directed toward the development of analytical methods using semiconductor

Gabor Patonay; Miquel D. Antoine; A. E. Boyer



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.



Rotor for Centrifugal Testing of Electrophoresis Gel.  

National Technical Information Service (NTIS)

The patent application describes a rotor for the preparation of identical electrophoresis gels where the liquid is permitted to flow into a rotor bowl under dynamic conditions. The rotor comprises a cylindrical body, a sealable closure, a central core, an...



Colloidal gel filtration: Experiment and theory  

SciTech Connect

The filtration of colloidal gels, consisting of octadecyl-coated silica spheres in hexadecane, is examined experimentally using CAT scanning. A number of interparticle strengths are explored, with significant differences in qualitative behavior relative to the filtration of stable dispersions. For stiff gels, the transmission of stresses from the cell wall to the dispersion results in a fracturing phenomenon during consolidation on a length scale substantially larger than the particle size. For more pliant gels, the radial propagation of stress is more local to the wall region and gravitational effects play a prominent role. The existing theory of network consolidation is compared against the experimental results for pliant gels, independent of the form of the constitutive functions for the sedimentation velocity and yield stress. Though the measurements seem consistent with the theory at early times, deviations at later moments question whether a compressive yield stress is actually present.

Shen, C.; Russel, W.B. (Princeton Univ., NJ (United States). Dept. of Chemical Engineering); Auzerais, F.M. (Schlumberger-Doll Research, Ridgefield, CT (United States))



Textural properties of sol-gel silicoaluminates  

Microsoft Academic Search

Silicoaluminates were synthesized from Al and Si alkoxides by the sol-gel method and characterized by FTIR spectroscopy and specific BET areas. The water and aluminate ion concnetration effects were studied.

Tessy Lopez; Metropolitana Iztapalapa



An Investigation of the Rheology of Gels.  

National Technical Information Service (NTIS)

The report describes work accomplished on the rising sphere rheometer and efforts to develop a standard gel to be used for interlaboratory comparisons both on the rising sphere and on the Brookfield viscometer. The construction details and wiring for the ...

J. H. Blatt B. D. Allan



Prepartially crosslinked gel for retarding fluid flow  

SciTech Connect

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

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



Molecular Recognition in Gels, Monolayers, and Solids.  

National Technical Information Service (NTIS)

This paper describes work in four area:affinity electrophoresis of carbonic anhydrase in cross-linked polyacrylamide-derived gels containing immobilized derivatives of aryl sulfonamides; inhibition of the hemagglutination of erythrocytes induced by influe...

K. L. Prime Y. H. Chu W. Schmid C. T. Seto J. K. Chen



Large deformation analysis of gellan gels  

NASA Astrophysics Data System (ADS)

Gellan gel, a typical polysaccharide gel, is ruptured with different deformation behaviors from gelatin gel or rubber. It exhibits both strain hardening and softening; hardening is observed for moderate strain and softening occurs for larger strain. From the analyses of stress-strain curves of gellan gels, we propose forms of strain energy function. The fit with the proposed equation was excellent, while the existing models fail because they consider only one of hardening or softening effect. Furthermore, these equations are shown to be capable of extracting the hardening and softening effects separately from the observed stress-strain curves. By using these fitting equations, the concentration dependences of hardening and softening are investigated. It is shown that the degrees of hardening and softening both increase with increasing gellan concentration.

Kawai, Shinnosuke; Nitta, Yoko; Nishinari, Katsuyoshi



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)



Dip coating of sol-gels.  

National Technical Information Service (NTIS)

Dip coating is the primary means of depositing sol-gel films for precision optical coatings. Sols are typically multicomponent systems consisting of an inorganic phase dispersed in a solvent mixture, with each component differing in volatility and surface...

A. J. Hurd C. J. Brinker P. R. Schunk



Sol-gel deposited electrochromic coatings  

SciTech Connect

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

Ozer, N.; Lampert, C.M.



Sol-gel deposited electrochromic coatings.  

National Technical Information Service (NTIS)

Electrochromic devices have increasing application in display devices, switchable mirrors and smart windows. A variety of vacuum deposition technologies have been used to make electrochromic devices. The sol- gel process offers an alternative approach to ...

N. Ozer C. M. Lampert



Optical analysis of gel dosimeters: Comparison of Fricke and normoxic polymer gels  

NASA Astrophysics Data System (ADS)

The dosimetry method based on optical analysis of gel layers has been experienced utilising both Fricke and polymer (normoxic) gels. The aim of the work was that of investigating the potentiality of a normoxic polymer gel and of performing a further verification of the reliability of Fricke gel dosimeters. Optical absorbance was measured, both with a spectrophotometer and by imaging light transmittance detected with a CCD camera. The results of the study of sensitivity, linearity of the response and reproducibility of the polymer gel dosimeter have shown acceptable performances, except for doses below 2 Gy. The linearity range extends up to 20 Gy. On the other side, dose images and profiles have shown noticeable differences when compared to those calculated or measured with ionisation chambers or Fricke gel dosimeters. Such Fricke dosimeters have given further confirmation of their reliability.

Gambarini, G.; Carrara, M.; Mariani, M.; Pirola, L.; Tomatis, S.; Valente, M.; Vanossi, E.



Magnetization transfer imaging for polymer gel dosimetry  

Microsoft Academic Search

Off-resonance RF pre-saturation was used to obtain contrast in MRI images of polymer gel dosimeters irradiated to doses up to 50 Gy. Two different polymer gel dosimeters composed of 2-hydroxyethyl-acrylate or methacrylic acid monomers mixed with N, N'-methylene-bisacrylamide (BIS), dispersed in an aqueous gelatin matrix were evaluated. Radiation-induced polymerization of the co-monomers generates a fast-relaxing insoluble polymer. Saturation of the

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



Sol-gel technology for biomedical engineering  

Microsoft Academic Search

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



Absorption, luminescent and lasing properties of laser dyes in silica gel matrices and thin gel films  

SciTech Connect

The absorption and emission properties of eight organic compounds in silica gel matrices of different chemical compositions and different types (bulk samples and thin films) are studied upon excitation by a XeCl laser and the second harmonic of a Nd:YAG laser. The mechanisms of the laser-induced changes in the spectral parameters of molecules in silica gel matrices are discussed and the photostability of the laser dyes in silica gel films is estimated. (active media)

Shaposhnikov, A A; Kuznetsova, Rimma T; Kopylova, T N; Maier, G V; Tel'minov, E N [V.D. Kuznetsov Siberian Physical-Technical Institute, Tomsk (Russian Federation); Pavich, T A; Arabei, S M [Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, Minsk (Belarus)



Basic investigations on LCV micelle gel  

NASA Astrophysics Data System (ADS)

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

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



Swelling instabilities in patterned, microscale gels  

NASA Astrophysics Data System (ADS)

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

Toomey, Ryan; Dupont, Samuel



A new silver sulfadiazine water soluble gel.  


Silver sulfadiazine is the most commonly used topical antibacterial agent for the treatment of burn wounds. It has many clinical advantages, including a broad spectrum of antimicrobial activity, low toxicity, and minimal pain on application. The current formulation of silver sulfadiazine contains a lipid soluble carrier, polypropylene glycol, that has certain disadvantages, including pseudo-eschar formation and the need for twice daily application. The purpose of this investigation was to describe a new formulation of silver sulfadiazine in a water soluble gel, poloxamer 188. The antibacterial activity of this new gel has been compared to that of the commercially available silver sulfadiazine cream by in vitro and in vivo testing. The results of the in vitro antibacterial testing of these two different agents demonstrated the superiority of the new gel formulation. In experimental wounds, the antibacterial activity of the gel and the commercially available silver sulfadiazine cream were not significantly different when applied once a day. The antibacterial activity of the gel when applied once a day was comparable to that encountered by twice daily applications of the silver sulfadiazine cream by experimental wounds. The major advantage of this gel was its ease of application and removal that is attributed to its water solubility. PMID:9426907

Gear, A J; Hellewell, T B; Wright, H R; Mazzarese, P M; Arnold, P B; Rodeheaver, G T; Edlich, R F



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



Phase separation in calcium alginate gels.  


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

Straatmann, A; Borchard, W



Analytical spectroscopy. Analytical Chemistry Symposia Series, Volume 19  

Microsoft Academic Search

This book contains papers covering several fields in analytical chemistry including lasers, mass spectrometry, inductively coupled plasma, activation analysis and emission spectroscopy. Separate abstracting and indexing was done for 64 papers in this book.



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.



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



Investigations in x-ray computed tomography polyacrylamide gel dosimetry  

Microsoft Academic Search

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

Michelle Louise Hilts



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.



Analytic Models of Multitask Processes.  

National Technical Information Service (NTIS)

Asynchronous multitask processes occur in a wide variety of control applications ranging from industrial control to computer operating systems, yet no analytical methods are available for studying their detailed behavior. The preliminary results reported ...

T. L. Johnson



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.



Total Diet Study - Analytical Results  

Center for Food Safety and Applied Nutrition (CFSAN)

Results of the Total Diet Study from mind-1991 to the present for elemental analytes, radionuclides, pesticide residues, industrial chemicals, mercury ... More results from


Visual Analytics Technology Transition Progress  

SciTech Connect

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

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



Diffusion anomaly from analytical formula  

NASA Astrophysics Data System (ADS)

An analytic expression is derived for the diffusion coefficient of a sorbate in a crystalline porous solid with bottlenecks. The diffusion coefficients obtained from the analytic expression is found to agree well with the molecular dynamics results. It is also found to reproduce the temperature dependence of the levitation effect for zeolites Y and A. The present calculations provide a strong theoretical support for the levitation effect obtained so far purely from molecular dynamics calculations.

Sarkar, Subir; Kumar, A. V. Anil; Yashonath, Subramanian



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



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



Nonlinear elasticity and yielding of depletion gels.  


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. PMID:16268723

Kobelev, Vladimir; Schweizer, Kenneth S



[Comparison evaluation of polymer gel with a water phantom.].  


We have investigated the properties of three polymergels: G gel, A gel, and C gel. These polymer gels changed only the chemical reagent for the gel. The water equivalence was determined by comparing the polymer gels macroscopic photon and electron interaction cross sections over the energy range from 10 KeV to 50 MeV and by Monte Carlo modeling of percentage depth doses. Polymer gels have a chemical reagent for the gel and monomer concentration and therefore their mass density is up to 1.70-2.91 % higher than water. This results in differences between the cross section ratios of the polymer gels and water of up to 0.01-3.00 % for the attenuation coefficients ratio and relative stopping power throughout the energy range. Monte Carlo modeling was done for the polymer gels to model the electron and photon transport resulting from a 6 MV photon beam. The absolute percentage differences between each gel and water were within 1 % of the relative percentage differences. The results showed that the A gel formulation had the most suitable water equivalence of the polymer gels investigated due to its lower mass density measurement compared with G gel and C gel. PMID:17634738

Haneda, Kiyofumi; Okudo, Hiroki; Yoshioka, Munenori; Hayashi, Shin-Ichiro; Usui, Shuji; Tominaga, Takahiro



Crack buckling in soft gels under compression  

NASA Astrophysics Data System (ADS)

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

Long, Rong; Hui, Chung-Yuen



Gel composition and method of treatment  

SciTech Connect

This patent describes a method of treating at least one of formations intersected by a well bore. It comprises: introducing into one of the plurality of formations which has a permeability which differs from another of the formations a first aqueous solution comprising a polymeric material selected from a biopolymer or a synthetic polymer, a crosslinking agent comprising a chromic carboxylate complex, a solvent selected from water or brine and a gel breaker consisting essentially of ethylenediaminetetraacetic acid, the polymeric material crosslinking with the chromic carboxylate complex to form a gel impervious to fluid flow, the ethylenediaminetetraacetic acid being present in amount sufficient to break the gel after a predetermined period of time to a predetermined degree whereby limited permeability is restored to the one of the plurality of formations, the limited permeability more closely matching the permeability of the another of the formations.

Falk, D.O.



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




Microsoft Academic Search

C70 is incorporated in gel by a sol-gel process with using 3-amino-propyltriethoxysilane (NH2(CH2)3Si(OC2H5)3, APTS) and 3-glycidoxypropltrimethoxysilane (CH2OCHCH2O(CH2)3Si(OCH3)3, GPTMS) as precursors. C70 is firstly mixed with APTS to form C70-NH2(CH2)3Si(OC2H5)3 compound by the reaction between C70 and amino-group of APTS, and then the compound is hybridized with GPTMS to form solid gel. The linkage of C70 and APTS is estimated and

Haiping Xia; Qiuhua Nie; Jianli Zhang; Yueping Zhang



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

SciTech Connect

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

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



Hybrid sol-gel optical materials  


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

Zeigler, J.M.



Simple cloud chambers using gel ice packs  

NASA Astrophysics Data System (ADS)

Although cloud chambers are highly regarded as teaching aids for radiation education, school teachers have difficulty in using cloud chambers because they have to prepare dry ice or liquid nitrogen before the experiment. We developed a very simple and inexpensive cloud chamber that uses the contents of gel ice packs which can substitute for dry ice or liquid nitrogen. The gel can be frozen in normal domestic freezers, and can be used repeatedly by re-freezing. The tracks of alpha-ray particles can be observed continuously for about 20 min, and the operation is simple and easy.

Kamata, Masahiro; Kubota, Miki



Advances in biomedical applications of pectin gels.  


Pectin, due to its simple and cytocompatible gelling mechanism, has been recently exploited for different biomedical applications including drug delivery, gene delivery, wound healing and tissue engineering. Recent studies involving pectin for the biomedical field are reviewed, with the aim to capture the state of art on current research about pectin gels for biomedical applications, moving outside the traditional fields of application such as the food industry or pharmaceutics. Pectin structure, sources and extraction procedures have been discussed focussing on the properties of the polysaccharide that can be tuned to optimize the gels for a desired application and possess a fundamental role in application of pectin in the biomedical field. PMID:22776748

Munarin, F; Tanzi, M C; Petrini, P



Neutron detector using sol-gel absorber  


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

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



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



Analytical Sociology: A Bungean Appreciation  

NASA Astrophysics Data System (ADS)

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

Wan, Poe Yu-Ze



Reduction of gas and water permeabilities using gels  

SciTech Connect

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

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



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.



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



Molecularly imprinted sol-gels for nafcillin determination in milk-based products.  


A study has been made of the analytical application of a nafcillin-imprinted sol-gel to the direct determination of the beta-lactamic antibiotic in spiked milk-based samples using a room temperature phosphorescent flow-through system. The influence of the sample matrix on the transduction and the recognition processes was statistically determined, and results demonstrated that the imprinted sol-gel optosensing system could be effectively applied to real sample analysis. The analytical performance characteristics were as follows: The detection limit results for aqueous and skimmed milk were 5.8 x 10(-6) and 3.3 x 10(-5) mol L(-1), respectively, and a relative standard deviation less than 5% was found for both matrices. Statistical analysis of variance studies have been shown to have no significant effect on different skimmed milk commercial products over the imprinted material recognition. This fact provides an indicator of the ruggedness/robustness of the proposed analytical system and the possibility to use external real matrix calibration. Application of the method to nafcillin analysis in other milk-based samples is outlined. PMID:17263442

Guardia, Laura; Badía, Rosana; Díaz-García, Marta E



Binding of Ubiquitin Conjugates to Proteasomes as Visualized with Native Gels  

PubMed Central

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

Elsasser, Suzanne; Shi, Yuan; Finley, Daniel



The effective diffusion coefficient of a small molecule in a two-phase gel medium  

NASA Astrophysics Data System (ADS)

Using simple theoretical arguments and exact numerical lattice calculations, Hickey et al. [J. Chem. Phys. 124, 204903 (2006)] derived and tested an expression for the effective diffusion coefficient of a probe molecule in a two-phase medium consisting of a hydrogel with large gel-free inclusions. Although providing accurate predictions, this expression neglects important characteristics that such two-phase systems can present. In this article, we extend the previously derived expression in order to include local interactions between the gel and the analyte, interfacial effects between the main phase and the inclusions, and finally a possible incomplete separation between the two phases. We test our new, generalized expressions using exact numerical calculations. These generalized equations should be a useful tool for the development of novel multiphase systems for specific applications, such as drug-delivery platforms.

Kingsburry, Christine; Slater, Gary W.



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

NASA Astrophysics Data System (ADS)

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

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



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

SciTech Connect

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

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



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.

Hetrick, Evan M.



A Survey of Risk Analytics  

NASA Astrophysics Data System (ADS)

Risk Analytical Units within Wall Street firms are responsible for developing the methods used to quantify the different forms of risk inherent in the firms' activities. This talk is an overview of risk analytics. It will cover: the function and validation of valuation models; the measurement of market risk; and the measurement of the different aspects of and forms of credit risk, including the simulation of the potential counterparty credit exposure of derivatives, the estimation of obligor default probability and the simulation of the potential loss distribution of loan portfolios. Risk Analytics is an applied field that integrates finance theory, mathematics and statistical analysis. It is a field in that has attracted many physicists and one in which many physicists have flourished. The talk will conclude with an analysis of why this is so.

Picoult, Evan



Analyticity, scaling and renormalization for some complex analytic dynamical systems  

NASA Astrophysics Data System (ADS)

We review some results about the analytic structure of Lindstedt series for some complex analytic dynamical systems: in particular, we consider Hamiltonian maps (like the standard map and its generalizations), the semi-standard map and Siegel's problem of the linearization of germs of holomorphic diffeomorphisms of (C, 0). The analytic structure of those series can be studied numerically using Padé approximants, and one can show the existence of natural boundaries for real, diophantine values of the rotation number; by complexifying the rotation number, we show how these natural boundaries arise from the accumulation of singularities due to resonances, providing a new intuitive insight into the mechanism of the break-down of invariant KAM curves. Moreover, we study the Lindstedt series at resonances, i.e. for rational values of the rotation number, by suitably rescaling to 0 the value of the perturbative parameter, and a simple analytic structure emerges. Finally, we present some proofs for the simplest models and relate these results to renormalization ideas.

Berretti, Alberto



Analytical, Visual, and Interactive Concepts for Geo-Visual Analytics  

Microsoft Academic Search

Supporting the visual analysis of structured multivariate geo-spatial data is a challenging task involving many different aspects. In this paper, we describe a systematic view of this task based on Chi's data state reference model. The analytical, visual and interaction components of the systematic view will be instantiated with specific examples that demonstrate how their tight interconnection facilitates exploration and

Heidrun Schumann; Christian Tominski



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.



Liposomal gels for vaginal drug delivery.  


The aim of our study was to develop a liposomal drug carrier system, able to provide sustained and controlled release of appropriate drug for local vaginal therapy. To optimise the preparation of liposomes with regards to size and entrapment efficiency, liposomes containing calcein were prepared by five different methods. Two optimal liposomal preparations (proliposomes and polyol dilution liposomes) were tested for their in vitro stability in media that simulate human vaginal conditions (buffer, pH 4.5). To be closer to in vivo application of liposomes and to achieve further improvement of their stability, liposomes were incorporated in vehicles suitable for vaginal self-administration. Gels of polyacrylate were chosen as vehicles for liposomal preparations. Due to their hydrophilic nature and bioadhesive properties, it was possible to achieve an adequate pH value corresponding to physiological conditions as well as desirable viscosity. In vitro release studies of liposomes incorporated in these gels (Carbopol 974P NF or Carbopol 980 NF) confirmed their applicability as a novel drug carrier system in vaginal delivery. Regardless of the gel used, even 24 h after the incubation of liposomal gel in the buffer pH 4.5 more than 80% of the originally entrapped substance was still retained. PMID:11337174

Paveli?, Z; Skalko-Basnet, N; Schubert, R



Cell viability in a wet silica gel.  


A modified two-step sol-gel route using silicon ethoxide (TEOS) has been used to synthesize amorphous sol-gel-derived silica, which has been successfully used as a cell encapsulation matrix for 3T3 mouse fibroblasts and CRL-2595 epithelial cells due to its non-toxicity. The sol-gel procedure comprised a first, low pH hydrolysis step, followed by a neutral condensation-gelation step. A high water-to-TEOS ratio and the addition of d-glucose as a porogen and source of nutrients were chosen to minimize silica dissolution and improve the biocompatibility of the process. Indeed, the cell integrity in the encapsulation process was preserved by alcohol removal from the starting solution. Cells were then added in a buffered medium, causing rapid gelation and entrapment of the cells within a randomly structured siloxane matrix in the shape of a monolith, which was maintained in the wet state. MTT and alamarBlue assays were used to check the cytotoxicity of the silica gels and the viability of entrapped cells at initial times in contact with silica. To improve cell attachment, cell clumping experiments - where groups of cells were formed - were designed, rendering improved viability. The obtained materials are therefore excellent candidates for designing tissue-culture scaffolds and implantable bioreactors for biomedical applications. PMID:19481618

Nieto, Alejandra; Areva, Sami; Wilson, Timothy; Viitala, Reeta; Vallet-Regi, Maria



Correlations predict friction pressures of fracturing gels  

Microsoft Academic Search

Friction pressure calculations are very important in the design of any hydraulic fracturing treatment. They are useful in determining horsepower requirements, bottomhole treating pressure, and maximum wellhead pressure. This article presents a classical approach in which flow data of various gels in multiple pipes are presented as two dimensionless quantities, Fanning friction factor and generalized Reynolds number. These dimensionless quantities




Sudden collapse of a colloidal gel.  


Metastable gels formed by weakly attractive colloidal particles display a distinctive two-stage time-dependent settling behavior under their own weight. Initially, a space-spanning network is formed that, for a characteristic time, which we define as the lag time ?(d), resists compaction. This solidlike behavior persists only for a limited time. Gels whose age t(w) is greater than ?(d) yield and suddenly collapse. We use a combination of confocal microscopy, rheology, and time-lapse video imaging to investigate both the process of sudden collapse and its microscopic origin in a refractive-index matched emulsion-polymer system. We show that the height h of the gel in the early stages of collapse is well described by the surprisingly simple expression, h(?)=h(0)-A?(3/2), with h(0) the initial height and ?=t(w)-?(d) the time counted from the instant where the gel first yields. We propose that this unexpected result arises because the colloidal network progressively builds up internal stress as a consequence of localized rearrangement events, which leads ultimately to collapse as thermal equilibrium is reestablished. PMID:22463209

Bartlett, Paul; Teece, Lisa J; Faers, Malcolm A



Autologous platelet gel in plastic surgery  

Microsoft Academic Search

Autologous platelet gel is now being used in many surgical specialties. It is appropriate for use in plastic surgery procedures that entail a significant risk of hematoma, such as breast surgery, face lifts, nasal surgery, and skin grafting. Advantages include adhesive benefits, a reduction in risk of bleeding, and the added bonus of increased leukocyte concentration. (Aesthetic Surg J 2001;21:377-379.)

Edward P. Melmed



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. 4 tabs.

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




Technology Transfer Automated Retrieval System (TEKTRAN)

Polyethylene glycol (PEG) and citric acid (CA) are crystalline solids at room temperature. The materials are opaque, hard, brittle materials. However, blending the PEG and CA shows that a clear, soft 'gel' is formed at certain concentrations. Rheology, differential scanning calorimetry (DSC), FT-...


Macroscopic dynamics of uniaxial magnetic gels  

Microsoft Academic Search

We present the derivation of the macroscopic equations for uniaxial ferrogels. In addition to the usual hydrodynamic variables for gels we introduce the magnetization and the relative rotations between the magnetization and the network as macroscopic variables. The relative rotations introduced here for a system with magnetic degrees of freedom are the analog of the relative rotations introduced by de

S. Bohlius; H. R. Brand; H. Pleiner



Simple Cloud Chambers Using Gel Ice Packs  

ERIC Educational Resources Information Center

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

Kamata, Masahiro; Kubota, Miki



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



Sudden collapse of a colloidal gel  

NASA Astrophysics Data System (ADS)

Metastable gels formed by weakly attractive colloidal particles display a distinctive two-stage time-dependent settling behavior under their own weight. Initially, a space-spanning network is formed that, for a characteristic time, which we define as the lag time ?d, resists compaction. This solidlike behavior persists only for a limited time. Gels whose age tw is greater than ?d yield and suddenly collapse. We use a combination of confocal microscopy, rheology, and time-lapse video imaging to investigate both the process of sudden collapse and its microscopic origin in a refractive-index matched emulsion-polymer system. We show that the height h of the gel in the early stages of collapse is well described by the surprisingly simple expression, h(?)=h0-A?(3)/(2), with h0 the initial height and ?=tw-?d the time counted from the instant where the gel first yields. We propose that this unexpected result arises because the colloidal network progressively builds up internal stress as a consequence of localized rearrangement events, which leads ultimately to collapse as thermal equilibrium is reestablished.

Bartlett, Paul; Teece, Lisa J.; Faers, Malcolm A.




Technology Transfer Automated Retrieval System (TEKTRAN)

In order to develop pectins as delivery carriers for the controlled release of volatile chemicals, two types of pectin formulations were prepared and studied: pectin gels from pectins with various degrees of esterification (D.E.) and calcium cross-linked pectin microparticles. Citronellal, a model...


Optical bonding with fast sol-gel  

NASA Astrophysics Data System (ADS)

We investigate here the properties of fast sol-gel for optical bonding. The precursors of the fast sol-gel material are organically modified alkoxides generating a transparent hybrid (organic-inorganic) substance with silica glass-like properties whose index of refraction can be modified by the addition of various metal-oxides. The fast sol-gel method consists of rapid fabrication of a viscous resin and its subsequent dilution for long shelf life use. This material, when used as an adhesive offers the option of either a thermal or UV curing procedure. We demonstrate a bonding strength of ~ 10 MPa when a 15 ?m layer is applied between two glass elements. The bonding remained stable after an extensive -40°C - 120°C temperature cycling with minimal residual solvent evaporation at 150°C. The fast sol-gel material was tested for optical bonding between silica bulks, between silica bulk and silicon wafers and as an adhesive in silica fibre couplers.

Gvishi, R.; Pokrass, M.; Strum, G.



Thermosensitive sol–gel reversible hydrogels  

Microsoft Academic Search

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

Byeongmoon Jeong; Sung Wan Kim; You Han Bae



Dielectric losses and breakdown in silicone gel  

Microsoft Academic Search

Silicone gels are used for the packaging and insulation of power electronic components such as high voltage IGBT modules, mainly due to their good mechanical and thermal properties. Nevertheless, the knowledge of their dielectric properties is still uncompleted. The aim of this paper is to present the results of measurements of dielectric losses versus frequency, as well as breakdown field

M. T. Do; J.-L. Auge; O. Lesaint



Mechanical properties and morphology of polymer gels  

NASA Astrophysics Data System (ADS)

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

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



Egg yolk protein gels and emulsions  

Microsoft Academic Search

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

V Kiosseoglou



Lattice model for colloidal gels and glasses.  


We study a lattice model of attractive colloids. It is exactly solvable on sparse random graphs. As the pressure and temperature are varied, it reproduces many characteristic phenomena of liquids, glasses, and colloidal systems such as ideal gel formation, liquid-glass phase coexistence, jamming, or the re-entrance of the glass transition. PMID:18999686

Krzakala, Florent; Tarzia, Marco; Zdeborová, Lenka



Sol-Gel Based Electrochemical Biosensors.  

National Technical Information Service (NTIS)

This work is based on the use of the sol-gel process to encapsulate biomolecules in a porous silicate matrix. The porosity of the matrix is such that small molecules and ions can readily diffuse into the materials while the much larger proteins remain tra...

B. C. Dave B. Dunn J. S. Valentine J. I. Zink



Structure and elasticity of model gel networks  

Microsoft Academic Search

A random central force network model of a gel is constructed by relaxation of a bond diluted simple cubic lattice of Hooke's law springs under tension. The bond dilution procedure, which defines the model, involves the random removal of bonds connecting nodes at least one of which has a value greater than a prescribed maximum value. The structure and elastic

Malcolm J. Grimson



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 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.



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


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


There is a need for stable gel materials for phantoms used to validate optical computerized tomography (CT) scanners used in conjunction with radiation-induced polymerizing gel dosimeters. Phantoms based on addition of light-absorbing dyes to gelatine to simulate gel dosimeters have been employed. However, to more accurately simulate polymerizing gels one requires phantoms that employ light-scattering colloidal suspensions added to the gel. In this paper, we present the initial results of using an optical CT scanner to evaluate a novel phantom in which radiation-exposed polymer gels are simulated by the addition of colloidal suspensions of varying turbidity. The phantom may be useful as a calibration transfer standard for polymer gel dosimeters. The tests reveal some phenomena peculiar to light-scattering gels that need to be taken into account when calibrating polymer gel dosimeters. PMID:17473358

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



New insight into agarose gel mechanical properties.  


The current study focuses on the effects of the molecular weight on the mechanical behavior of agarose gels. The small strain rheology and large strain deformation/failure behavior of three different molecular weight agarose gels have been examined, with the results expressed in term of molar concentration. For small deformation strains, the gelation temperature at low concentrations and the critical concentration for gel formation are strongly affected by the molecular weight. In addition, the elasticity of the network is also very sensitive to this parameter. It has been demonstrated that the experimental gelation cure curves can be superimposed on a universal gelation master curve, independent of the cure time. This would indicate self-similarity of the network at different scales, irrespective of concentration. A relationship between the elastic modulus and the molecular weight has been extracted from these results, where the molecular weight dependence exhibits a power law exponent of 2.42. For large deformation strains, the Poisson ratio has been estimated to be 0.5 for each of the agarose types examined, which indicates that these gels are incompressible. The strain at failure is largely dependent on the molecular weight, and is essentially independent of the biopolymer concentration. This result highlights the fact that the strain at failure is sensitive to the connectivity distances in the gel network. However, the failure stress and Young's modulus of agarose gels show a dependence on both concentration and molecular weight. The observations regarding Young's modulus are in good agreement with those found for small deformation strain rheology for the shear modulus. One of the primary advantages of using the lowest molecular weight agarose is that higher molar concentrations can be reached (more molecules per unit volume). However, the mechanical response of agarose gels is very sensitive to the molecular weight at fixed molar concentration, and if the present results are extrapolated to very low molecular weight, it can be suggested that below a limiting molecular weight a percolating network will not be formed, as suggested by the Cascade model (Carbohydr. Polym. 1994, 23, 247-251). This speculation is based on the influence of the "connectivity" at long distances, which influences the strain at failure (when the strain at failure is zero, the system is not connective). PMID:11710204

Normand, V; Lootens, D L; Amici, E; Plucknett, K P; Aymard, P



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.



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.



AndroGel® (testosterone gel) 1% CIII NDA 21-015 Pediatric ...  

Center for Biologics Evaluation and Research (CBER)

Text Version... the androgen class may promote retention of sodium and water. ... related to AndroGel administration), depression, sadness, memory loss, elevated ... More results from


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

Microsoft Academic Search

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

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



(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.



Entrepreneurship: An analytical thermodynamic theory  

Microsoft Academic Search

In this paper, we present a newly developed analytical thermodynamic theory and show that it offers a simple understanding of entrepreneurship. The approach we present in the paper is different from previous work on the subject in that we not only borrow the mathematical tools from, and the analogy to thermodynamic but treat economics in general and entrepreneurship in particular

Jing Chen; Tsvi Vinig



Serious Gaming for Predictive Analytics  

Microsoft Academic Search

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

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




EPA Science Inventory

This project focused on the development of an analytical method for the analysis of phenols in drinking water. The need for this project is associated with the recently published Contaminant Candidate List (CCL). The following phenolic compounds are listed on the current CCL, a...


Analytical dynamics of multibody systems  

Microsoft Academic Search

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

Peter Maisser



Substituted hydroxylamines as analytical reagents.  


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

Shendrikar, A D



Analytical chemistry of perfluoroalkylated substances  

Microsoft Academic Search

Polyfluorinated alkylated substances have recently gained scientific interest because they have been found to be present in appreciable concentrations in human serum, in surface waters, and in tissues of wildlife from remote areas. The developments in analytical chemistry of these mainly neutral or anionic surface-active compounds are reviewed in this paper. Problems associated with the determination of polyfluorinated alkylated compounds

Pim de Voogt; Mónica Sáez



Learning designs and learning analytics  

Microsoft Academic Search

Government and institutionally-driven reforms focused on quality teaching and learning in universities emphasize the importance of developing replicable, scalable teaching approaches that can be evaluated. In this context, learning design and learning analytics are two fields of research that may help university teachers design quality learning experiences for their students, evaluate how students are learning within that intended learning context

Lori Lockyer; Shane Dawson



Collaborative Sensemaking in Learning Analytics  

Microsoft Academic Search

Learning Analytics (LA) is a new educational tool aimed at improving learning processes and outcomes via the analysis of, and feedback regarding, student trace data. Implementation has often involved visualizations for sensemaking. However, these visualizations are complicated by their wide range of audiences - from governmental, down to individual pupils. Furthermore, the needs and abilities of these various stakeholders are

Simon Knight; Simon Buckingham Shum; Karen Littleton



Discourse-centric learning analytics  

Microsoft Academic Search

Drawing on sociocultural discourse analysis and argumentation theory, we motivate a focus on learners' discourse as a promising site for identifying patterns of activity which correspond to meaningful learning and knowledge construction. However, software platforms must gain access to qualitative information about the rhetorical dimensions to discourse contributions to enable such analytics. This is difficult to extract from naturally occurring

Anna De Liddo; Simon Buckingham Shum; Ivana Quinto; Michelle Bachler; Lorella Cannavacciuolo



Analytic Model of Reactive Flow  

Microsoft Academic Search

A simple analytic model allows prediction of rate constants and size effect behavior before a hydrocode run if size effect data exists. At infinite radius, it defines not only detonation velocity but also average detonation rate, pressure and energy. This allows the derivation of a generalized radius, which becomes larger as the explosive becomes more non-ideal. The model is applied

P C Souers; P Vitello



Advanced analytics: opportunities and challenges  

Microsoft Academic Search

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

Ranjit Bose



Functional Analytic Psychotherapy and Supervision  

ERIC Educational Resources Information Center

The interpersonal behavior therapy, Functional Analytic Psychotherapy (FAP) has been empirically investigated and described in the literature for a little over a decade. Still, little has been written about the process of supervision in FAP. While there are many aspects of FAP supervision shared by other contemporary behavior therapies and…

Callaghan, Glenn M.



Visual Analytics Science and Technology  

SciTech Connect

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

Wong, Pak C.



Visual analytics of brain networks.  


Identification of regions of interest (ROIs) is a fundamental issue in brain network construction and analysis. Recent studies demonstrate that multimodal neuroimaging approaches and joint analysis strategies are crucial for accurate, reliable and individualized identification of brain ROIs. In this paper, we present a novel approach of visual analytics and its open-source software for ROI definition and brain network construction. By combining neuroscience knowledge and computational intelligence capabilities, visual analytics can generate accurate, reliable and individualized ROIs for brain networks via joint modeling of multimodal neuroimaging data and an intuitive and real-time visual analytics interface. Furthermore, it can be used as a functional ROI optimization and prediction solution when fMRI data is unavailable or inadequate. We have applied this approach to an operation span working memory fMRI/DTI dataset, a schizophrenia DTI/resting state fMRI (R-fMRI) dataset, and a mild cognitive impairment DTI/R-fMRI dataset, in order to demonstrate the effectiveness of visual analytics. Our experimental results are encouraging. PMID:22414991

Li, Kaiming; Guo, Lei; Faraco, Carlos; Zhu, Dajiang; Chen, Hanbo; Yuan, Yixuan; Lv, Jinglei; Deng, Fan; Jiang, Xi; Zhang, Tuo; Hu, Xintao; Zhang, Degang; Miller, L Stephen; Liu, Tianming



Surface-Specific Analytical Techniques  

Microsoft Academic Search

Many new surface analytical techniques have appeared over the last few years, and their proliferation has led to some confusion about what sort of information is provided by each, and what is the appropriate field of application. In this paper those techniques that are surface-specific are described and discussed, i.e. those that give information about the surface only, the surface

J. C. Riviere



Analytical Chemistry and the Microchip.  

ERIC Educational Resources Information Center

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

Lowry, Robert K.



Model-driven Visual Analytics  

Microsoft Academic Search

We describe a Visual Analytics (VA) infrastructure, rooted on techniques in machine learning and logic-based deductive reason- ing that will assist analysts to make sense of large, complex data sets by facilitating the generation and validation of models repre- senting relationships in the data. We use Logic Programming (LP) as the underlying computing machinery to encode the relations as rules

Supriya Garg; Julia Eunju Nam; I. V. Ramakrishnan; Klaus Mueller



Analytical Sociology: A Bungean Appreciation  

ERIC Educational Resources Information Center

|Analytical sociology, an intellectual project that has garnered considerable attention across a variety of disciplines in recent years, aims to explain complex social processes by dissecting them, accentuating their most important constituent parts, and constructing appropriate models to understand the emergence of what is observed. To achieve…

Wan, Poe Yu-ze



Analytic Approximations for Spread Options  

Microsoft Academic Search

This paper expresses the price of a spread option as the sum of the prices of two compound options. One compound option is to exchange vanilla call options on the two underlying assets and the other is to exchange the corresponding put options. This way we derive a new analytic approximation for the price of a European spread option, and

Carol Alexander; Aanand Venkatramanan



Deepest regression in analytical chemistry  

Microsoft Academic Search

Recently the concept of regression depth has been introduced [J. Am. Stat. Assoc. 94 (1999) 388]. The deepest regression (DR) is a method for linear regression which is defined as the fit with the best depth relative to the data. In this paper we explain the properties of the DR and give some applications of DR in analytical chemistry which

P. J. Rousseeuw; S. Van Aelst; B. Rambali; J. Smeyers-Verbeke



Ionic Liquids in Analytical Chemistry  

Microsoft Academic Search

The role of ionic liquids (ILs) in analytical chemistry is increasing substantially every year. A decade ago there were but a handful of papers in this area of research that were considered curiosities at best. Today, those publications are recognized as seminal articles that gave rise to one of the most rapidly expanding areas of research in chemical analysis. In

Renee J. Soukup-Hein; Molly M. Warnke; Daniel W. Armstrong



Literature documentation in analytical chemistry  

Microsoft Academic Search

67 Abstracts from 1978 and 1979 of 23 original papers in different journals from 1978 were selected as random samples from Anal. Abstr., Chem. Abstr. and Fresenius Z. Anal. Chem. for examination of information content and structure. A generally applied principle of structure for abstracts could not be recognized in any of these journals. The statements on analytically relevant results

Georg Schwedt



Deepest Regression in Analytical Chemistry  

Microsoft Academic Search

Recently the concept of regression depth has been introduced (1). The deepest regression (DR) is a method for linear regression which is defined as the fit with the best depth relative to the data. In this paper we explain the properties of the DR and give some applications of deepest regression in analytical chemistry which involve regression through the origin,

P. J. Rousseeuw; S. Van Aelst; B. Rambalib; J. Smeyers-Verbekeb


Wavelets — something for analytical chemistry?  

Microsoft Academic Search

Wavelets have shown great applicability in many diverse fields of science, and are now becoming of interest in analytical chemistry. This paper is intended as a first reading, introducing fundamentals of wavelets and wavelet transforms, and some applications thereof, such as signal compression and denoising, image processing, data set compression and the modeling of multivariate data sets.

D. L Massart



Analytical aspects of environmental chemistry  

Microsoft Academic Search

This book is 64th in the series of monographs on Chemical Analysis edited by Elving and Winefordner. Chapter I deals with chemical separation. The analytical techniques for the determination of organometallic species of Sb, As, Cu, Ge, Pb, Hg, S, Se, and Sn are discussed. The second chapter presents a well-structured general review of column parameters and selective detectors for

D. F. Natusch; P. K. Hopke



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


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

Day, I N; Humphries, S E



Enhancement of proteolysis through the silica-gel-derived microfluidic reactor.  


An on-chip enzymatic reactor providing rapid protein digestion is presented. Trypsin-embedding stationary phase within the microchannel has been prepared by the sol-gel method. Such a microfluidic reactor has been used for low-level protein digestion at 16 fmol per analysis. The analytical potential of the microreactor combined with the strong cation exchange and RPLC ESI-MS/MS for the identification of real samples from the cytoplasma of the human liver tissue has been demonstrated. PMID:17407177

Liu, Yun; Qu, Haiyun; Xue, Yan; Wu, Zhonglin; Yang, Pengyuan; Liu, Baohong



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


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

Humann-Ziehank, E; Ganter, M



Analytical Plan for Roman Glasses  

SciTech Connect

Roman glasses that have been in the sea or underground for about 1800 years can serve as the independent “experiment” that is needed for validation of codes and models that are used in performance assessment. Two sets of Roman-era glasses have been obtained for this purpose. One set comes from the sunken vessel the Iulia Felix; the second from recently excavated glasses from a Roman villa in Aquileia, Italy. The specimens contain glass artifacts and attached sediment or soil. In the case of the Iulia Felix glasses quite a lot of analytical work has been completed at the University of Padova, but from an archaeological perspective. The glasses from Aquileia have not been so carefully analyzed, but they are similar to other Roman glasses. Both glass and sediment or soil need to be analyzed and are the subject of this analytical plan. The glasses need to be analyzed with the goal of validating the model used to describe glass dissolution. The sediment and soil need to be analyzed to determine the profile of elements released from the glass. This latter need represents a significant analytical challenge because of the trace quantities that need to be analyzed. Both pieces of information will yield important information useful in the validation of the glass dissolution model and the chemical transport code(s) used to determine the migration of elements once released from the glass. In this plan, we outline the analytical techniques that should be useful in obtaining the needed information and suggest a useful starting point for this analytical effort.

Strachan, Denis M.; Buck, Edgar C.; Mueller, Karl T.; Schwantes, Jon M.; Olszta, Matthew J.; Thevuthasan, Suntharampillai; Heeren, Ronald M.



21 CFR 520.1453 - Moxidectin and praziquantel gel.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 false Moxidectin and praziquantel gel. 520.1453 Section 520...DRUGS § 520.1453 Moxidectin and praziquantel gel. (a) Specifications ...moxidectin and 125 mg (12.5 percent) praziquantel. (b) Sponsor . See No....



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

National Technical Information Service (NTIS)

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

E. L. Mosser D. A. Clark



US EPA, Pesticide Product Label, TILT GEL FUNGICIDE, 04 ...  

EPA Pesticide Factsheets

... DIB'lB)'1 18 EPA R;~~\\~ni~~~~;7 ,. .:' Tilt Gel Fungicide ~ .. -: ... A stamped copy for each product, Tilt ~ ~~~~ Gel, is enclosed for your records. ...



Executive Summary Silicone Gel-Filled Breast Implants ...  

Center for Biologics Evaluation and Research (CBER)

Text VersionExecutive Summary Silicone Gel-Filled Breast Implants General Issues Panel ... Silicone gel-filled breast implants were introduced to the US in 1962. ... More results from


Zone Electrophoresis of Human Parotid Saliva in Acrylamide Gel.  

National Technical Information Service (NTIS)

The report concerns an examination of acrylamide gel as another medium for the zone electrophoresis of parotid saliva proteins. Preliminary experiments with acrylamide-gel strips yielded protein patterns in which twenty or more fractions could be visually...

T. S. Meyer B. L. Lamberts



Reformulated tenofovir gel for use as a dual compartment microbicide  

PubMed Central

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

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



Pattern Formation Theory for Electroactive Polymer Gel Robots  

Microsoft Academic Search

Abstract— This paper proposes the mathematical model of deformation for gel robots and develops the pattern formation theory. The robots are made of surfactant-driven ionic polymer gel in constant electric fields, which is a typical electroactive poly- mer gel containing poly 2-acrylamido-2-metylpropane sulfonic acid (PAMPS). A beam of gel in uniform electric fields develops wave forms through penetration of the

Mihoko Otake; Yoshihiko Nakarnura; Hirochika Inoue



DC Electrical Field Effects on Plant Tissues and Gels  

Microsoft Academic Search

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

Amos Nussinovitch; Ronit Zvitov


Evaluation of the dosimetric performance of BANG3® polymer gel  

NASA Astrophysics Data System (ADS)

New radiotherapy techniques call for three-dimensional dosimetric methods with high spatial resolution. Radiation sensitive gels read out using MRI T2 mapping provide an extremely promising option, and commercially available BANG® polymer gels provide a convenient route into gel dosimetry. Gel dosimetry is dependent on the ability to calibrate gel response against radiation dose. This in turn is dependent on the reproducibility of response both between gels irradiated to the same dose and for a single gel sample over time. This study aims to evaluate the performance of a commercially available BANG® gel. Our experimental arrangement gave excellent precision of radiation delivery (<0.2%) and reproducibility of T2 measurement (<0.5%). Seven groups of 10 test tubes containing BANG3® gel were irradiated in 0.5 Gy steps between 0 and 3 Gy. A further four groups of four samples were irradiated in 2 Gy steps between 4 and 10 Gy. The gel samples were identical and derived from the same manufacturing batch. MR imaging was carried out four days after irradiation and then at weekly intervals for four weeks. Short-term variation in gel response can readily be corrected using reference samples. Longer term systematic drift of the gel calibration curve was observed relative to reference samples prepared in-house for quality assurance purposes. This implies that read-out of the calibration gels and dosimetry phantom must be performed at the same time after irradiation, or errors of up to 25% may be incurred. Precision of gel response did not change significantly over time. The observation of significantly different T2 values both prior to irradiation and following irradiation to the same dose (variation up to 15%) illustrates the current difficulties associated with BANG3® gel calibration and constrains the practical utility of these commercially available gels for clinical radiation dosimetry.

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



Gel-coated membranes for lithium-ion polymer batteries  

Microsoft Academic Search

A membrane-supported gel polymer electrolyte for a lithium-ion polymer battery was prepared and characterized. This electrolyte was prepared by coating a gel polymer electrolyte onto a porous polyethylene membrane. The gel-coated membrane electrolytes exhibited a high ionic conductivity, and excellent mechanical and good adhesive properties. The gel polymer electrolyte coated on both sides of the membrane was demonstrated to encapsulate

Dong-Won Kim; Bookeun Oh; Jin-Hwan Park; Yang-Kook Sun



Characterization of gelatin gels induced by high pressure  

Microsoft Academic Search

Gelatin gels made from cod and megrim skins were formed using high pressure and subsequent cooling at 7°C during 16–18h. Pressure treatments were carried out at two temperatures (20 and 7°C) and 200, 300 and 400MPa. Turbidity, gel strength and viscoelastic properties of these gels were studied. Gelatin gels from megrim showed lower degree of turbidity, independent of the treatment,

P. Montero; M. D. Fernández-D??az; M. C. Gómez-Guillén



Electric field-induced deformation of polyelectrolyte gels  

SciTech Connect

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

Adolf, D.; Hance, B.G.



Gel-forming reagents and uses thereof for preparing microarrays  


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

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



Analytical chemistry in a new analytical hot cell facility  

Microsoft Academic Search

The Remote Analytical Laboratory is a new facility at the Idaho Chemical Processing Plant designed to handle samples from the processing of spent nuclear fuel. It consists of a cold laboratory for analyzing process make-up samples, a warm laboratory for analyzing low-level (<100 mR\\/h) radioactive samples, and a hot cell for analyzing high-level radioactive samples. The hot cell is built

M. A. Wade; F. W. Dykes; J. H. Goettsche; A. L. Lewis; P. C. Lewis; P. C. Marushia; J. A. Murphy; S. D. Reeder; D. R. Trannell; L. E. Trejo



Tuning of sol-gel derived PZT MEMS resonators  

NASA Astrophysics Data System (ADS)

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

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



Preparative and Analytical Purification of DNA from Agarose  

NASA Astrophysics Data System (ADS)

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

Vogelstein, Bert; Gillespie, David



Minimum pore size obtainable in a silica gel during drying.  

National Technical Information Service (NTIS)

The pore size r(sub p) in a gel is determined by the extent of shrinkage of the gel network during drying. Shrinkage is driven by the collapse of the gel network in response to the capillary pressure P(sub c) exerted by the pore fluid. The extent of shrin...

S. Wallace C. J. Brinker D. M. Smith



Chirp-Z analysis for sol–gel transition monitoring  

Microsoft Academic Search

Gelation is a complex reaction that transforms a liquid medium into a solid one: the gel. In gel state, some gel materials (DMAP) have the singular property to ring in an audible frequency range when a pulse is applied. Before the gelation point, there is no transmission of slow waves observed; after the gelation point, the speed of sound in

Emmanuel Caplain; Stéphane Serfaty; Pascal Griesmar; Gérard Gouedard; Marcel Gindre



Electrochemical stimulation and control of electroactive polymer gels  

NASA Astrophysics Data System (ADS)

Direct effects of electrical currents on polyelectrolyte gels are always associated with changes in their Donnan potential. Thus electrical stimulation of gels can be only completely understood if the direct effect of electric fields on the potential profile within the gels are known. The purpose of this study is to present recordings of Donnan potentials in electroactive gels of various compositions, especially under the influence of electric fields. An important finding is that opposite alterations in the Donnan potential simultaneously occur at the current inflow and outflow region of the gel. In anionic gels hyperpolarization, i.e. higher negativity, is induced on the anode-side of the gel, whereas depolarization is found on the cathode-side. As these shifts in the potential are supposed to affect swelling or deswelling of polyelectrolyte gels, they will primarily promote bending motions of the gel. To demonstrate the opposite bending behavior of anionic and cationic polymer gels under the influence of an electric field a short video sequence of an EAP gripper in action is presented. It is made exclusively of polyelectrolyte gel strips taking advantage of the fact that anionic and cationic polyacrylamide gels can be attached firmly to each other without any adhesive.

Guelch, Rainer W.; Holdenried, Jens; Weible, Andrea; Wallmersperger, Thomas; Kroeplin, Bernd



Formulation and method for preparing gels comprising hydrous cerium oxide  


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

Collins, Jack L; Chi, Anthony



DTA and TGA characterization of sol-gel hydrotalcites  

Microsoft Academic Search

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

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



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


Polyacrylamide gels synthesized in the presence of surfactants  

Microsoft Academic Search

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

Mukundan Chakrapani



Persimmon peel gel for the selective recovery of gold  

Microsoft Academic Search

The use of persimmon peel gel for the recovery of Au(III) from aqueous chloride medium was investigated. By comparing with the adsorption of some other metal ions, the gel was found to be selective only for Au(III). The XRD analysis and the digital micrograph of the gel taken after adsorption supported the formation of gold particles during adsorption process. High

Durga Parajuli; Hidetaka Kawakita; Katsutoshi Inoue; Keisuke Ohto; Kumiko Kajiyama



Antimicrobial efficacy of alcohol-based hand gels.  


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

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



Swelling, mechanical properties and effect of annealing of scleroglucan gels  

Microsoft Academic Search

Scleroglucan gels were made by alkaline denaturation and subsequent renaturation of the scleroglucan triple helix by in situ neutralization. Gels prepared from 4 to 5% scleroglucan solutions were incubated in aqueous solutions and dependence of pH, temperature and ionic strength, I, were studied. (i) The scleroglucan gels were observed to be stable for more than 600 days in solutions of

Einar Aasprong; Olav Smidsrød; Bjørn Torger Stokke



Interpenetration twinning in gel-grown gypsum single crystals  

Microsoft Academic Search

Crystallographers are exploiting the art of growing crystals having low and high solubilities in water, tn gel medium derived from the diffusion of reactants of very high solubilities [1-4]. The fact that larger crystals grow in gel proves that supersaturation near the surface of these crystals must be much higher in the gel than in the solution. The explanation therefore

K. S. Raju



Hydroxyapatite incorporated into collagen gels for mesenchymal stem cell culture.  


Collagen gels could be used as carriers in tissue engineering to improve cell retention and distribution in the defect. In other respect hydroxyapatite could be added to gels to improve mechanical properties and regulate gel contraction. The aim of this work was to analyze the feasibility to incorporate hydroxyapatite into collagen gels and culture mesenchymal stem cells inside it. Human bone marrow mesenchymal stem cells (hMSC-BM) were used in this study. Gels were prepared by mixing rat tail type I collagen, hydroxyapatite microparticles and MSCs. After polymerization gels were kept in culture while gel contraction and mechanical properties were studied. In parallel, cell viability and morphology were analyzed. Gels became free-floating gels contracted from day 3, only in the presence of cells. A linear rapid contraction phase was observed until day 7, then a very slow contraction phase took place. The incorporation of hydroxyapatite improved gel stability and mechanical properties. Cells were randomly distributed on the gel and a few dead cells were observed all over the experiment. This study shows the feasibility and biocompatibility of hydroxyapatite supplemented collagen gels for the culture of mesenchymal stem cells that could be used as scaffolds for cell delivery in osteoarticular regenerative medicine. PMID:23798652

Laydi, F; Rahouadj, R; Cauchois, G; Stoltz, J-F; de Isla, N



Formulation and method for preparing gels comprising hydrous hafnium oxide  


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

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



A fundamental study of tethered polymer chains in gel systems  

Microsoft Academic Search

Two types of tethered polymers in the gel system were studied in this work. One involved polymer Chains grafted on the gel surface, while the other Consisted of the gel itself where mesh chains were tethered on each other through their chain ends. ^ Surface-tethered polymer chains were studied both theoretically and experimentally with the consideration of their application as

Yanbin Huang



Smart polymeric gels: Redefining the limits of biomedical devices  

Microsoft Academic Search

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

Somali Chaterji; Il Keun Kwon



DNA-origami technique for olympic gels  

NASA Astrophysics Data System (ADS)

Taking advantage of the specific base-pairing interaction of DNA, I propose a robust method for creating melt topological or "olympic" gels. Flexible polymers which have been end-decorated with complimentary base-pair sequences will undergo end-closing reactions with either themselves (forming loops) or with neighboring chains (creating linear, but lengthened chains). The loop-forming or chain-forming process can be controlled by how many distinct ligand pairs occur in the system. A gel formed of these interlocking rings will display a sensitivity to dissolve when brought into contact with a large concentration of DNA fragments, thus giving a biologically-specific trigger for drug delivery by olympic microgels.

Pickett, G. T.



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.

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



Molecular recognition in gels, monolayers, and solids  

NASA Astrophysics Data System (ADS)

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

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



Hydraulic fracturing process using a polymer gel  

SciTech Connect

This patent describes a fracturing process applied to a subterranean hydrocarbon-bearing formation below an earthen surface in fluid communication with a wellbore comprising: (a) premixing a fracturing fluid at the surface comprising a gel breaker and a gelation solution consisting essentially of an aqueous solvent, a water-soluble acrylamide polymer selected from the group consisting of polyacrylamide and partially hydrolyzed polyacrylamide, and a crosslinking agent formed of at least one chromium III species complexed with at least one carboxylate species selected from the group consisting of propionate, acetate, lactate, and mixtures thereof; (b) at least partially gelling the gelation solution at the surface to form a gel; and (c) injecting the fracturing fluid into the formation via the wellbore at a pressure sufficient to hydraulically fracture the formation.

Sydansk, R.D.



In situ gels improve formation acidizing  

SciTech Connect

Viscosity-controlled acid effectively improves acid placement, provides more uniform damage removal, improves surface etching, and controls acid fluid loss. Viscosity-controlled acid (VCA) contains gels that break back to original viscosity 1 day after being pumped. These acids have been used for: matrix-acidizing long horizontal and vertical well intervals; controlling fluid loss in fracture acidizing to obtain longer fractures and deeper live-acid penetration. Fluid pH controls gel formation and breaking. In one operator`s horizontal wells, viscosity-controlled acid increased production by 2.5--6 fold. In carbonate formation fracture-acidizing, these acids have shown production improvements of 170 to 375%. VCA acid can be used in both cased or open hole, in vertical or deviated/horizontal wells.

Yeager, V.; Shuchart, C. [Halliburton Energy Services, Duncan, OK (United States)



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


New rapid gel sequencing method for RNA  

Microsoft Academic Search

METHODS for sequencing nucleic acids have improved significantly in the last few years due to the development of rapid `read-off' gel methods. The first method to be developed was the `plus and minus' copying method for DNA1 and an analogous copying method for RNA now exists2. A different and more direct method for sequencing DNA has been developed3, but no

A. Simoncsits; G. G. Brownlee; R. S. Brown; J. R. Rubin; H. Guilley



Gels, monomer solutions fix pinhole casing leaks  

Microsoft Academic Search

Sodium silicate gel and in situ polymerizing monomer (IPM) solutions have had nearly 100% success in repairing pinhole casing leaks. These methods are an alternative to small-particle cement squeeze jobs and can be used in both producing and injection wells. The particles in small-particle or fine-grind cement average 5 microns in diameter compared to the 50 micron particles in Portland

P. Creel; R. Crook



Sol-gels and chemical sensors  

Microsoft Academic Search

We review the principles of optical and electrochemical sensors based on the use of the sol-gel technique, in particular their\\u000a fabrication, working principles, and various configurations. We also report on potential applications, e.g. to environmental\\u000a and clinical analysis, to gas sensing, and to bioprocess monitoring. Methods are critically reviewed for making such sensors,\\u000a how to encapsulate organic, inorganic and biological

Otto S. Wolfbeis; Renata Reisfeld; Ines Oehme


Catalyst Doped Sol-Gel Materials  

Microsoft Academic Search

\\u000a An important subject in catalysis is the synthesis of metallic supported catalysts. The structural and textural modification\\u000a of this materials can improve the activity, selectivity or catalyst lifetime. Research groups have recently shown a great\\u000a interest in the preparation of metal doped catalysts by the well known sol-gel method. This process consists in the hydrolysis\\u000a and condensation of an alkoxide

Tessy López; Ricardo Gómez


DNA-origami technique for olympic gels  

Microsoft Academic Search

Taking advantage of the specific base-pairing interaction of DNA, I propose a robust method for creating melt topological or “olympic” gels. Flexible polymers which have been end-decorated with complimentary base-pair sequences will undergo end-closing reactions with either themselves (forming loops) or with neighboring chains (creating linear, but lengthened chains). The loop-forming or chain-forming process can be controlled by how many

G. T. Pickett



Sol-gel synthesis of manganese oxides  

Microsoft Academic Search

Transparent and stable manganese dioxide gels are obtained upon reduction of permanganate aqueous solutions AMnO4 [A = Li, Na, K, NH4, N(CH3)4] by fumaric acid. All xerogels are amorphous when dried at room temperature. Their thermal behavior however depends on the nature of the counter cation A+. Ammonium permanganates lead to the formation of alpha- or gamma-Mn2O3 while AMnO2 mixed

S. Bach; M. Henry; N. Baffier; J. Livage



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



New gel polyelectrolytes for rechargeable lithium batteries  

Microsoft Academic Search

New polyelectrolytes were synthesized by grafting the allyl group containing lithium salt, lithium bis(allylmalonato)borate (LiBAMB), onto poly[pentaethylene glycol methyl ether acrylate-co-allyoxyethyl acrylate] through hydrosilylation chemistry. Gel polyelectrolytes were obtained by adding 50 wt.% of different 1\\/1 (wt\\/wt) mixtures of propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC) and tetraethyleneglycol dimethyl ether (TEGDME). The highest ambient conductivity was 2.7×10?8 S

Xiao-Guang Sun; Gao Liu; Jiangbing Xie; Yongbong Han; John B. Kerr



Swelling\\/deswelling of anionic copolymer gels  

Microsoft Academic Search

Studies of dynamic and equilibrium swelling of ionic gels are important in understanding the diffusion of physiologically important fluids in materials for site-specific controlled drug delivery applications. The dynamic and equilibrium swelling properties of dry glassy poly(2-hydroxyethyl methacrylate-comethacrylic acid) and poly(2-hydroxyethyl methacrylate-co-acrylic acid) polymeric networks were studied as a function of pH, ionic strength, nature of the counterion and buffer

Atul R. Khare; Nikolaos A. Peppas



Adsorption of chlorinated hydrocarbons on silica gel  

SciTech Connect

A survey of indoor air pollutants was conducted in this study. A gravimetrical adsorption apparatus was designed and used to study the adsorption and diffusion of chlorinated hydrocarbons in silica gel. A new theoretical heterogeneous isotherm, using local Jovanovic isotherm and a Morse-type probability density function, was developed and tested. The new adsorption isotherm as well as the Langmuir and the BET models were then used to correlate the experimental adsorption data for the six chlorinated hydrocarbons investigated in this study. The diffusion coefficients of six chlorinated hydrocarbons in spherical silica gel beads were also investigated using the same gravimetrical adsorption apparatus. Results suggested that silica gel can be effectively used to both dehumidify and remove pollutants. A comparison of the new model with other heterogeneous isotherm equations showed that the new model gives a more accurate and yet simpler description of adsorption behavior on heterogeneous adsorbents. The new isotherm equation also correlated the experimental data extremely well. The Langmuir model provided better correlations for the isotherm data for the heavier adsorbates than for lighter ones, while the BET model provided good correlations for the isotherm data only up to 35% saturation pressure for each adsorbate. Diffusion studies of the chlorinated hydrocarbons in spherical silica gel beads showed that the diffusion rate controlling step was surface diffusion while the effects of gas and Knudsen diffusions were found to be less significant. Surface diffusion coefficients were found to be within an order of magnitude of the liquid phase diffusion coefficients, which suggests that surface diffusion exhibits liquid-like characteristics for multilayer coverage of the solids.

Kuo, S.L.



A gel polymer electrolyte of magnesium triflate  

Microsoft Academic Search

Investigations leading to understanding and development of solid state rechargeable magnesium batteries are important in view of the fact that the Mg is free from hazards, it’s stability is high and it’s natural resources are abundant. A Mg2+ ion conducting gel polymer electrolyte (GPE) is investigated for a possible application in solid state rechargeable Mg battery. The GPE consists of

G. Girish Kumar; N Munichandraiah



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


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

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



Reflections on the science of analytical chemistry: competition “analytical chemistry — today's definition and interpretation”  

Microsoft Academic Search

This paper discusses the significance of Analytical Chemistry within the whole field of chemistry in terms of economy, productivity and impact of analytical innovations on the development of Chemistry as a science. It then reports about the competition to define and interpret Analytical Chemistry and raises the question of the future designation of the discipline: Analytics, Analytical Sciences or still

Manfred Grasserbauer



Analytical Spectroscopy Using Modular Systems  

NASA Astrophysics Data System (ADS)

This article describes the development of three analytical spectroscopy experiments that compare the determination of salicylic acid (SA) content in aspirin tablets. The experiments are based on UV vis, fluorescence, and Raman spectroscopies and utilize modular spectroscopic components. Students assemble their own instruments, optimize them with respect to signal-to-noise, generate calibration curves, determine the SA content in retail aspirin tablets, and assign features in the respective spectra to functional groups within the active material. Using this approach in the discovery-based setting, the students gain invaluable insight into method-specific parameters, such as instrumental components, sample preparation, and analytical capability. In addition, the students learn the fundamentals of fiber optics and signal processing using the low-cost CCD based spectroscopic components.

Patterson, Brian M.; Danielson, Neil D.; Lorigan, Gary A.; Sommer, André J.



Analytically solvable processes on networks  

NASA Astrophysics Data System (ADS)

We introduce a broad class of analytically solvable processes on networks. In the special case, they reduce to random walk and consensus process, the two most basic processes on networks. Our class differs from previous models of interactions (such as the stochastic Ising model, cellular automata, infinite particle systems, and the voter model) in several ways, the two most important being (i) the model is analytically solvable even when the dynamical equation for each node may be different and the network may have an arbitrary finite graph and influence structure and (ii) when local dynamics is described by the same evolution equation, the model is decomposable, with the equilibrium behavior of the system expressed as an explicit function of network topology and node dynamics.

Smilkov, Daniel; Kocarev, Ljupco



New routes to food gels and glasses.  


We describe the possibility to create solid-like protein samples whose structural and mechanical properties can be varied and tailored over an extremely large range in a very controlled way through an arrested spinodal decomposition process. We use aqueous lysozyme solutions as a model globular protein system. A combination of video microscopy, small-angle neutron and X-ray scattering and reverse Monte Carlo modeling is used to characterize the structure of the bicontinuous network with two coexisting phases of a dilute protein solution and a glassy or arrested dense protein backbone at all relevant length scales. Rheological measurements are then used to determine the complex mechanical response of these protein gels as a function of protein concentration and quench temperature. While in particular the origin of the dependence of the mechanical properties on quench depth and concentration is not well understood currently, it seems ultimately connected to the particular bicontinuous structure of the arrested spinodal network created by the interplay between the early stage of a spinodal decomposition and the position of the glass line. We then generalize this behavior and discuss how this could open up new routes to prepare gel-like food systems with adjustable structural and mechanical properties. We present results from a first feasibility study where we use a depletion interaction caused by the addition of small non-adsorbing polymers to suspensions of casein micelles in order to create food gels with tunable structural and mechanical properties through an arrested spinodal decomposition process. PMID:23234170

Gibaud, Thomas; Mahmoudi, Najet; Oberdisse, Julian; Lindner, Peter; Pedersen, Jan Skov; Oliveira, Cristiano L P; Stradner, Anna; Schurtenberger, Peter



Magnetization transfer imaging for polymer gel dosimetry  

NASA Astrophysics Data System (ADS)

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

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



Modeling of optical gel electroactive response  

NASA Astrophysics Data System (ADS)

In this paper a model is postulated to describe the optical response of an electroactive polymer hydrogel due to applied electrical fields. This model consists of a series of several modules: an electrical module that identifies the relationship between the applied voltage/current, electrode location and material and applied electrical field; a chemical module that correlates the percentage monomer in the gel, percentage cross linker, solvent ionic strength and pH; a mechanical module that employs the output of the chemical module to calculate deformation, taking into consideration experimentally measured elastic and viscoelastic characteristics; an optical module that will incorporate results from the previous modules to yield important optical characteristics (such as focal length and refractive index). It is anticipated that ultimately this model will set the required voltage to produce particular optical characteristics. Using an elastic modulus of 2160 Pa, a Poisson's ratio of 0.33 and experimentally measured gel response force of 0.1 N has resulted in a mechanical module which fully describes the gel motion. This result is promising; however, the mechanical module is currently using elastic properties, whereas viscoelastic properties are ideally needed.

Paxton, Robert A.; Al-Jumaily, Ahmed M.; Ramos, Maximiano V.; Easteal, Allan J.



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



Semi-analytical MBS Pricing  

Microsoft Academic Search

This paper presents a multi-factor valuation model for fixed-rate callable mortgage backed securities (MBS). The model yields\\u000a semi-analytic solutions for the value of MBS in the sense that the MBS value is found by solving a system of ordinary differential\\u000a equations. Instead of modelling the conditional prepayment rate (CPR), as is customary, the pool size is the primary modelling\\u000a object.

Niels Rom-Poulsen



Analytical pitfalls in hair testing  

Microsoft Academic Search

This review focuses on possible pitfalls in hair testing procedures. Knowledge of such pitfalls is useful when developing\\u000a and validating methods, since it can be used to avoid wrong results as well as wrong interpretations of correct results. In\\u000a recent years, remarkable advances in sensitive and specific analytical techniques have enabled the analysis of drugs in alternative\\u000a biological specimens such

Frank Musshoff; Burkhard Madea



Scalable Data-Intensive Analytics  

Microsoft Academic Search

To effectively handle the scale of processing required in information extraction and analytical tasks in an era of information\\u000a explosion, partitioning the data streams and applying computation to each partition in parallel is the key. Even though the\\u000a concept of MapReduce has been around for some time and is well known in the functional programming literatures, it is Google\\u000a which

Meichun Hsu; Qiming Chen



Analytic bounds on transmission probabilities  

SciTech Connect

We develop some new analytic bounds on transmission probabilities (and the related reflection probabilities and Bogoliubov coefficients) for generic one-dimensional scattering problems. To do so we rewrite the Schroedinger equation for some complicated potential whose properties we are trying to investigate in terms of some simpler potential whose properties are assumed known, plus a (possibly large) 'shift' in the potential. Doing so permits us to extract considerable useful information without having to exactly solve the full scattering problem.

Boonserm, Petarpa, E-mail: [Department of Mathematics, Faculty of Science Chulalongkorn University, Phayathai Rd., Pathumwan Bangkok 10330 (Thailand); Visser, Matt, E-mail: [School of Mathematics, Statistics, and Operations Research, Victoria University of Wellington (New Zealand)



Analytical methods under emergency conditions  

SciTech Connect

This lecture discusses methods for the radiochemical determination of internal contamination of the body under emergency conditions, here defined as a situation in which results on internal radioactive contamination are needed quickly. The purpose of speed is to determine the necessity for medical treatment to increase the natural elimination rate. Analytical methods discussed include whole-body counting, organ counting, wound monitoring, and excreta analysis. 12 references. (ACR)

Sedlet, J.



Analyte detection using an active assay  


Analytes using an active assay may be detected by introducing an analyte solution containing a plurality of analytes to a lacquered membrane. The lacquered membrane may be a membrane having at least one surface treated with a layer of polymers. The lacquered membrane may be semi-permeable to nonanalytes. The layer of polymers may include cross-linked polymers. A plurality of probe molecules may be arrayed and immobilized on the lacquered membrane. An external force may be applied to the analyte solution to move the analytes towards the lacquered membrane. Movement may cause some or all of the analytes to bind to the lacquered membrane. In cases where probe molecules are presented, some or all of the analytes may bind to probe molecules. The direction of the external force may be reversed to remove unbound or weakly bound analytes. Bound analytes may be detected using known detection types.

Morozov, Victor (Manassas, VA); Bailey, Charles L. (Cross Junction, VA); Evanskey, Melissa R. (Potomac Falls, VA)



A randomized controlled trial comparing topical piroxicam gel with a homeopathic gel in osteoarthritis of the knee  

Microsoft Academic Search

Objective. To evaluate the efficacy and safety of a homeopathic gel vs an NSAID (piroxicam) gel in the treatment of osteoarthritis of the knee. Method. One hundred and eighty-four out-patients with radiographically confirmed symptomatic osteoarthritis of the knee were entered into a pragmatic, randomized, double- blind controlled trial and treated with 1 g of gel three times daily for 4

R. A. van Haselen; P. A. G. Fisher



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.



Methyl modified siloxane melting gels for hydrophobic films  

Microsoft Academic Search

Hybrid melting gels were prepared by a sol–gel process, starting with a mono-substituted siloxane and a di-substituted siloxane.\\u000a Methyl-modified melting gels were prepared using (a) methyltriethoxysilane (MTES) with dimethyldiethoxysilane (DMDES) and\\u000a (b) methyltrimethoxysilane (MTMS) together with dimethyldimethoxysilane (DMDMS). The gels with MTES–DMDES were prepared with\\u000a concentrations between 50–50 and 75–25 mol%. The gels with MTMS–DMDMS were prepared with concentrations between 50–50

Andrei Jitianu; John Doyle; Glenn Amatucci; Lisa C. Klein



Copper phthalocyanine bonding with gel and their optical properties  

Microsoft Academic Search

(Tetracarboxyphalocyaninato)copper(II), (CuPc(COOH)4) is incorporated in gel by a sol–gel process with using 3-aminopropyltriethoxysilane (NH2(CH2)3Si(OC2H5)3, APTS) and 3-glycidoxypropl-trimethoxysilane (CH2OCHCH2O(CH2)3Si(OCH3)3, GPTMS) as precursors. The starting compound and the gel are in the dimer forms of copper phthalocyanine, which are identified from their UV\\/visible spectra. The aggregation of copper phthalocyanine dyes from sol to gel is effectively prevented by tethering them to sol–gel

Haiping Xia; Masayuki Nogami



The Molecular Dimensions of Guinea Pig Lymphotoxin.  

National Technical Information Service (NTIS)

The molecular dimensions of guinea pig lymphotoxin were studied by means of gel filtration, sucrose density gradient ultracentrifugation, and CsCl isopycnic ultracentrifugation. Lymphotoxin was produced by stimulating immune lymph node cells with the spec...

M. K. Gately M. M. Mayer



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.



Modelling of the inhomogeneous interior of polymer gels  

NASA Astrophysics Data System (ADS)

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

Shew, Chwen-Yang; Iwaki, Takafumi



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 103-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.



Fabrication, modeling and optimization of an ionic polymer gel actuator  

NASA Astrophysics Data System (ADS)

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

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



Photo- and electroactive color changeable acrylamide gel actuator  

NASA Astrophysics Data System (ADS)

Polyacrylamide hydrogels containing bis-[4- {dimethylamine}phenyl]{4-vinyl-phenyl}methyl leucohydroxide which is so called vinyl derivative of Malachite Green have been studied as color changeable gels. The response times of the color and the volume changes of the gel were measured under 6 and 2 different stimuli, respectively. We found a way to increase their color change speed upon applied electric current (E-current), and designed a gel actuator using Nafion film as a separator between two compartments and as a cation conductor. In addition acrylamide gel swollen with Na2SO4 solution was used as a medium for increasing electric conductivity. We varied the concentration of dvMG in the gel to control the degree of color change. Furthermore, we have studied the influence of gel thickness on the color change rate. In light of the results obtained, we have proposed one device consisting of this color changeable gel.

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



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


Capillary blotting of glycosaminoglycans on nitrocellulose membranes after agarose-gel electrophoresis separation.  


A method for the blotting and immobilizing of several nonsulfated and sulfated complex polysaccharides on membranes made hydrophilic and positively charged by cationic detergent after their separation by conventional agarose gel electrophoresis is illustrated. This new approach to the study of glycosaminoglycans (GAGs) utilizes the capacity of agarose gel electrophoresis to separate single species of polysaccharides from mixtures and the membrane technology for further preparative and analytical uses.Nitrocellulose membranes are derivatized with the cationic detergent cetylpyridinium chloride and mixtures of GAGs are capillary blotted after their separation in agarose gel electrophoresis. Single purified species of variously sulfated polysaccharides are transferred on derivatized membranes with an efficiency of 100% and stained with alcian blue (irreversible staining) and toluidine blue (reversible staining). This enables a lower amount limit of detection of 0.1 microg. Nonsulfated polyanions, for example hyaluronic acid, may also be transferred to membranes with a limit of detection of approximately 0.1-0.5 microg after irreversible or reversible staining. The membranes may be stained with reversible staining and the same lanes are used for immunological detection or other applications. PMID:19378049

Volpi, Nicola; Maccari, Francesca



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


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

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



Autologous platelet-poor plasma gel for injection laryngoplasty.  


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°C 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; Lee, Sang-Hyuk; Jeong, Han-Sin



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.

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



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

SciTech Connect

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

Craig Joseph Fontenot



A review on development of solid phase microextraction fibers by sol-gel methods and their applications.  


Solid phase microextraction (SPME) is an innovative, solvent free technology that is fast, economical and versatile. SPME is a fiber coated with a liquid (polymer), a solid (sorbent) or a combination of both. The fiber coating takes up the compounds from the sample by absorption in the case of liquid coatings or adsorption in the case of solid coatings. The SPME fiber is then transferred with the help of a syringe like device into the analytical instrument for desorption and analysis of the target analytes. The sol-gel process provides a versatile method to prepare size, shape and charge selective materials of high purity and homogeneity by means of preparation techniques different from the traditional ones, for the chemical analysis. This review is on the current state of the art and future trends in the developments of solid phase microextraction (SPME) fibers using sol-gel method. To achieve more selective determination of different compound classes, the variety of different coating material for SPME fibers has increased. Further developments in SPME as a highly efficient extraction technique, will greatly depend on new breakthroughs in the area of new coating material developments for the SPME fibers. In sol-gel approach, appropriate sol-gel precursors and other building blocks can be selected to create a stationary phase with desired structural and surface properties. This approach is efficient in integrating the advantageous properties of organic and inorganic material systems and thereby increasing and improving the extraction selectivity of the produced amalgam organic-inorganic stationary phases. This review is mainly focused on recent advanced developments in the design, synthesis, characterisation, properties and application of sol-gel in preparation of coatings for the SPME fibers. PMID:18267134

Kumar, Ashwini; Gaurav; Malik, Ashok Kumar; Tewary, Dhananjay Kumar; Singh, Baldev



Characterization of a composite gradient gel for the electrophoretic separation of lipoproteins  

Microsoft Academic Search

We describe a protocol for making a new type of gradient gel, the Composite gradient gel, that was designed to resolve plasma lipoproteins using nondenaturing gradient gel electrophoresis. The new gel format allows analysis both of high density lipoproteins (HDLs) and low density lipopro- teins (LDLs) on the same gel. The gel gave highly repeatable ( r2 = 0.999) size

David L. Rainwater; Perry H. Moore; Wendy R. ShelIedy; Thomas D. Dyer; Susan H. Slifer


Analytic Methods in Open String Field Theory  

NASA Astrophysics Data System (ADS)

We review the basics of recent developments of analytic methods in open string field theory. We in particular explain Schnabl's analytic solution for tachyon condensation in detail, assuming only the basic knowledge on conformal field theory.

Okawa, Y.



Urban Runoff Characteristics. Volume I. Analytical Studies.  

National Technical Information Service (NTIS)

The report is on analytical studies and field investigations for the characterization of urban runoff and combined sewer overflows. The report is divided into two volumes as follows: Volume I - Analytical Studies; Volume II - Field Investigations. Volume ...

H. C. Preul C. N. Papadakis



Approximate analytical method for groundwater modelling.  

National Technical Information Service (NTIS)

The approximate analytical method described in this report is a combined analytical and numerical analysis method for obtaining an approximate solution to a groundwater model which usually consists of partial differential equation(s). The attractive featu...

G. L. Moltyaner



Fluorescent Protein Sensors for Detection of Analytes.  

National Technical Information Service (NTIS)

Fluorescent indicators including a binding protein moiety, a donor fluorescent protein moiety, and an acceptor fluorescent protein moiety are described. The binding protein moiety has an analyte-binding region which binds an analyte and causes the indicat...

A. Miyawaki R. Y. Tsien



40 CFR 1065.750 - Analytical gases.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Analytical gases. 1065.750 Section 1065...CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Engine Fluids, Test Fuels, Analytical Gases and Other Calibration Standards...