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Sample records for alkali-silica reaction gel

  1. Microwave material characterization of alkali-silica reaction (ASR) gel in cementitious materials

    NASA Astrophysics Data System (ADS)

    Hashemi, Ashkan

    Since alkali-silica reaction (ASR) was recognized as a durability challenge in cement-based materials over 70 years ago, numerous methods have been utilized to prevent, detect, and mitigate this issue. However, quantifying the amount of produced ASR byproducts (i.e., ASR gel) in-service is still of great interest in the infrastructure industry. The overarching objective of this dissertation is to bring a new understanding to the fundamentals of ASR formation from a microwave dielectric property characterization point-of-view, and more importantly, to investigate the potential for devising a microwave nondestructive testing approach for ASR gel detection and evaluation. To this end, a comprehensive dielectric mixing model was developed with the potential for predicting the effective dielectric constant of mortar samples with and without the presence of ASR gel. To provide pertinent inputs to the model, critical factors on the influence of ASR gel formation on dielectric and reflection properties of several mortar samples were investigated at R, S, and X-band. Effects of humidity, alkali content, and long-term curing conditions on ASR-prone mortars were also investigated. Additionally, dielectric properties of chemically different synthetic ASR gel were also determined. All of these, collectively, served as critical inputs to the mixing model. The resulting developed dielectric mixing model has the potential to be further utilized to quantify the amount of produced ASR gel in cement-based materials. This methodology, once becomes more mature, will bring new insight to the ASR reaction, allowing for advancements in design, detection and mitigation of ASR, and eventually has the potential to become a method-of-choice for in-situ infrastructure health-monitoring of existing structures.

  2. Microwave NDE method for health-monitoring of concrete structures containing alkali-silica reaction (ASR) gel

    NASA Astrophysics Data System (ADS)

    Hashemi, A.; Hatfield, S.; Donnell, K. M.; Zoughi, R.; Kurtis, K. E.

    2014-02-01

    The presence of reactive aggregates combined with sufficient moisture and concentration of alkalis are the three basic requirements for damage due alkali-silica reaction (ASR) gel formation and expansion in concrete. For health-monitoring of concrete structures, and in order to investigate the potential for detecting ASR gel formation in existing structures, one potential technique involves studying changes in the temporal complex dielectric constant of concrete structures. In this paper, a microwave nondestructive testing approach is proposed which involves soaking two hardened mortar samples and measuring the change in their temporal complex dielectric constant in order to distinguish between the sample containing ASR gel and the one devoid of it. Part of the free water becomes bound in the sample containing ASR gel and since a portion of the microcracks in this sample contain ASR gel, the rate of evaporation of water of the two samples is expected to be different. The complex dielectric constant of the samples is significantly dependent upon the volumetric level and movement (in and out of the samples) of free water. Therefore, studying the relative different temporal rate of change in this parameter is expected to yield information about the presence or absence of ASR gel.

  3. The effects of lithium hydroxide solution on alkali silica reaction gels created with opal

    SciTech Connect

    Mitchell, Lyndon D.; Beaudoin, James J.; Grattan-Bellew, Patrick

    2004-04-01

    The reaction of Nevada opal with calcium hydroxide, potassium hydroxide and lithium hydroxide solutions was investigated. In addition, opal was exposed to a combined solution of these three hydroxides. The progress of the three reactions was followed using X-ray diffraction (XRD), {sup 29}Si nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM). The XRD results indicated the presence of a low-angle peak exclusive to the lithium-based reactions. The NMR results suggested a change in the silicate structure in the presence of lithium. These techniques indicated that the reaction of the alkali with the opal starting material is inhibited and perhaps stopped in the presence of lithium hydroxide. SEM revealed that the morphology of the reaction products on the surface of the reacted opal grains is markedly different invariably. It was concluded that evidence to support the theory of a protective layer exists and that the nature of the layer varies with ion type.

  4. In situ alkali-silica reaction observed by x-ray microscopy

    SciTech Connect

    Kurtis, K.E.; Monteiro, P.J.M.; Brown, J.T.; Meyer-Ilse, W.

    1997-04-01

    In concrete, alkali metal ions and hydroxyl ions contributed by the cement and reactive silicates present in aggregate can participate in a destructive alkali-silica reaction (ASR). This reaction of the alkalis with the silicates produces a gel that tends to imbibe water found in the concrete pores, leading to swelling of the gel and eventual cracking of the affected concrete member. Over 104 cases of alkali-aggregate reaction in dams and spillways have been reported around the world. At present, no method exists to arrest the expansive chemical reaction which generates significant distress in the affected structures. Most existing techniques available for the examination of concrete microstructure, including ASR products, demand that samples be dried and exposed to high pressure during the observation period. These sample preparation requirements present a major disadvantage for the study of alkali-silica reaction. Given the nature of the reaction and the affect of water on its products, it is likely that the removal of water will affect the morphology, creating artifacts in the sample. The purpose of this research is to observe and characterize the alkali-silica reaction, including each of the specific reactions identified previously, in situ without introducing sample artifacts. For observation of unconditioned samples, x-ray microscopy offers an opportunity for such an examination of the alkali-silica reaction. Currently, this investigation is focusing on the effect of calcium ions on the alkali-silica reaction.

  5. Alkali-silica reaction products: Comparison between samples from concrete structures and laboratory test specimens

    SciTech Connect

    Sachlova, Sarka Prikryl, Richard; Pertold, Zdenek

    2010-12-15

    Alkali-silica gels (ASG) were investigated in concrete from bridge structures (constructed from the 1920s to 2000), as well as in experimental specimens; employing optical microscopy, petrographic image analysis, and scanning electron microscopy combined with energy dispersive spectroscopy (SEM/EDS). The main differences were found in the chemical composition and morphology of the ASGs. ASGs which had formed in older concrete samples (50-80 years old) show a partly crystalline structure and higher Ca{sup 2+} content, indicating their aging and maturation. Younger concrete samples and experimental test specimens exhibit the presence of amorphous ASG. The chemistry of ASG from experimental specimens reflects the chemical composition of accelerating solutions. - Research Highlights: {yields} Quantitative analysis of alkali-silica gels {yields} Comparison of ASR in experimental conditions with ASR in bridge structures {yields} Investigation of factors affecting alkali-silica reaction {yields} Investigation of ASR of different types of aggregates.

  6. Detection of alkali-silica reaction swelling in concrete by staining

    DOEpatents

    Guthrie, Jr., George D.; Carey, J. William

    1998-01-01

    A method using concentrated aqueous solutions of sodium cobaltinitrite and rhodamine B is described which can be used to identify concrete that contains gels formed by the alkali-silica reaction (ASR). These solutions present little health or environmental risk, are readily applied, and rapidly discriminate between two chemically distinct gels; K-rich, Na--K--Ca--Si gels are identified by yellow staining, and alkali-poor, Ca--Si gels are identified by pink staining.

  7. Detection of alkali-silica reaction swelling in concrete by staining

    DOEpatents

    Guthrie, G.D. Jr.; Carey, J.W.

    1998-04-14

    A method using concentrated aqueous solutions of sodium cobalt nitrite and rhodamine B is described which can be used to identify concrete that contains gels formed by the alkali-silica reaction (ASR). These solutions present little health or environmental risk, are readily applied, and rapidly discriminate between two chemically distinct gels; K-rich, Na-K-Ca-Si gels are identified by yellow staining, and alkali-poor, Ca-Si gels are identified by pink staining.

  8. Automated Detection of Alkali-silica Reaction in Concrete using Linear Array Ultrasound Data

    SciTech Connect

    Santos-Villalobos, Hector J; Clayton, Dwight A; Ezell, N Dianne Bull; Clayton, Joseph A; Baba, Justin S

    2017-01-01

    Alkali-silica reaction (ASR) is a chemical reaction in either concrete or mortar between hydroxyl ions of the alkalis (sodium and potassium) from hydraulic cement (or other sources), and certain siliceous minerals present in some aggregates. The reaction product, an alkali-silica gel, is hygroscopic having a tendency to absorb water and swell, which under certain circumstances, leads to abnormal expansion and cracking of the concrete. This phenomenon affects the durability and performance of concrete structures severely since it can cause significant loss of mechanical properties. Developing reliable methods and tools that can evaluate the degree of the ASR damage in existing structures, so that informed decisions can be made toward mitigating ASR progression and damage, is important to the long term operation of nuclear power plants especially if licenses are extended beyond 60 years. This paper examines an automated method of determining the extent of ASR damage in fabricated concrete specimens.

  9. Alkali-silica reaction resistant concrete using pumice blended cement

    NASA Astrophysics Data System (ADS)

    Ramasamy, Uma

    Durability of structures is a major challenge for the building industry. One of the many types of concrete deterioration that can affect durability is alkali-silica reaction (ASR). ASR has been found in most types of concrete structures, including dams, bridges, pavements, and other structures that are 20 to 50 years old. The degradation mechanism of ASR produces a gel that significantly expands in the presence of water as supplied from the surrounding environment. This expansion gel product can create high stresses and cracking of the concrete, which can lead to other forms of degradation and expensive structural replacement costs. The four essential factors that produce an expansive ASR gel in concrete are the presence of alkalis, siliceous aggregate, moisture, and free calcium hydroxide (CH). If concrete is starved of any one of these essential components, the expansion can be prevented. Reducing CH through the use of a supplementary cementitious material (SCM) such as natural pozzolan pumice is the focus of this research. By using a pozzolan, the amount of CH is reduced with time based on the effectiveness of the pozzolan. Many pozzolans exist, but one such naturally occurring pozzolanic material is pumice. This research focuses on determining the effect of a finely ground pumice as a SCM in terms of its resistance to ASR expansion, as well as improving resistance to other potential concrete durability mechanisms. In spite of having high alkali contents in the pumice, mixtures containing the SCM pumice more effectively mitigated the ASR expansion reaction than other degradation mechanisms. Depending on the reactivity of the aggregates and fineness of the pumice, 10-15% replacement of cement with the pumice was found to reduce the ASR expansion to the acceptable limits. The amount of CH remaining in the concrete was compared to the ASR expansion in order to improve understanding of the role of CH in the ASR reaction. Thermo-gravimetric analysis (TGA) and X

  10. The effects of potassium and rubidium hydroxide on the alkali-silica reaction

    SciTech Connect

    Shomglin, K.; Turanli, L.; Wenk, H.-R.; Monteiro, P.J.M.; Sposito, G

    2003-11-01

    Expansion of mortar specimens prepared with an aggregate of mylonite from the Santa Rosa mylonite zone in southern California was studied to investigate the effect of different alkali ions on the alkali-silica reaction in concrete. The expansion tests indicate that mortar has a greater expansion when subjected to a sodium hydroxide bath than in a sodium-potassium-rubidium hydroxide bath. Electron probe microanalysis (EPMA) of mortar bars at early ages show that rubidium ions, used as tracer, were present throughout the sample by the third day of exposure. The analysis also shows a high concentration of rubidium in silica gel from mortar bars exposed to bath solutions containing rubidium. The results suggest that expansion of mortar bars using ASTM C 1260 does not depend on the diffusion of alkali ions. The results indicate that the expansion of alkali-silica gel depends on the type of alkali ions present. Alkali-silica gel containing rubidium shows a lower concentration of calcium, suggesting competition for the same sites.

  11. Crystallized alkali-silica gel in concrete from the late 1890s

    SciTech Connect

    Peterson, Karl . E-mail: cee@mtu.edu; Gress, David . E-mail: dlgress@unh.edu; Van Dam, Tom . E-mail: cee@mtu.edu; Sutter, Lawrence . E-mail: cee@mtu.edu

    2006-08-15

    The Elon Farnsworth Battery, a concrete structure completed in 1898, is in an advanced state of disrepair. To investigate the potential for rehabilitation, cores were extracted from the battery. Petrographic examination revealed abundant deposits of alkali silica reaction products in cracks associated with the quartz rich metasedimentary coarse aggregate. The products of the alkali silica reaction are variable in composition and morphology, including both amorphous and crystalline phases. The crystalline alkali silica reaction products are characterized by quantitative X-ray energy dispersive spectrometry (EDX) and X-ray diffraction (XRD). The broad extent of the reactivity is likely due to elevated alkali levels in the cements used.

  12. Influence of lithium hydroxide on alkali-silica reaction

    SciTech Connect

    Bulteel, D.; Garcia-Diaz, E.; Degrugilliers, P.

    2010-04-15

    Several papers show that the use of lithium limits the development of alkali-silica reaction (ASR) in concrete. The aim of this study is to improve the understanding of lithium's role on the alteration mechanism of ASR. The approach used is a chemical method which allowed a quantitative measurement of the specific degree of reaction of ASR. The chemical concrete sub-system used, called model reactor, is composed of the main ASR reagents: reactive aggregate, portlandite and alkaline solution. Different reaction degrees are measured and compared for different alkaline solutions: NaOH, KOH and LiOH. Alteration by ASR is observed with the same reaction degrees in the presence of NaOH and KOH, accompanied by the consumption of hydroxyl concentration. On the other hand with LiOH, ASR is very limited. Reaction degree values evolve little and the hydroxyl concentration remains about stable. These observations demonstrate that lithium ions have an inhibitor role on ASR.

  13. Alkali-Silica Reaction in Concrete from Fontana Dam, North Carolina, Tennessee Valley Authority.

    DTIC Science & Technology

    1986-09-01

    crossed polarized 1.482 > n < 1.502 light. Alternating growth layers of clear and of tan translucent 1.480 > n < 1.520 gel; some of the clear material is... vermiculite was present in one piece of aggregate; a small amount of amphibole was tentatively identified in several pieces. Small amounts of iron sulfide were...the alkali-silica reaction, which is present in all the cores from block 31 examined here, contribute to the stress developed, to growth in height, and

  14. Laser scanning confocal microscopy for in situ monitoring of alkali-silica reaction.

    PubMed

    Collins, C L; Ideker, J H; Kurtis, K E

    2004-02-01

    Alkali-silica reaction (ASR) occurs in concrete between reactive siliceous components in the aggregate and the strongly alkaline pore solution, resulting in the formation of a potentially expansive gel product. Lithium additives have been shown to reduce expansion associated with ASR, but the mechanism(s) by which lithium reduces expansion have not been understood. Therefore, development of an in situ method to observe reactions associated with ASR is highly desirable, as it will allow for non-destructive observation of the reaction product formation and damage evolution over time, as the reaction progresses. A technique to image into mortar through glass aggregate by laser scanning confocal microscopy (LSCM), producing three-dimensional representations of the sample was developed. This LSCM technique was utilized to monitor the progress of alkali-silica reaction in mortar samples prepared with alkali-reactive glass aggregate both in the presence and in the absence of lithium additives: LiNO3, LiCl or LiOH. The method proved to be effective in qualitatively monitoring crack formation and growth and product formation, within cracks and at the paste/aggregate interface. In particular, dendritic products were observed at the paste/aggregate interface only in those samples containing lithium, suggesting that these products may play a role in ASR mitigation.

  15. A simple environmentally friendly, and chemically specific method for the identification and evaluation of the alkali-silica reaction

    SciTech Connect

    Guthrie, G.D. Jr.; Carey, J.W.

    1997-09-01

    One of the principal mechanisms of premature degradation of concrete is the alkali silica reaction, in which an alkali-rick silica gel froms around and within some reactive aggregate grains, in pores, along fractures, and within paste. A rapid, dual staining method is described whereby reaction products associated with the alkali-silica reaction (ASR) are readily identified by their pink or yellow color following treatment in the laboratory or field. The method is based on both the compositional and physical characteristics of the ASR gel; hence, it provides greater information than non-chemical-specific techniques (such as the uranyl acetate method). In addition, the chemicals used in the staining method pose minimal health risks and are environmentally benign.

  16. Microstructural Changes Due to Alkali-Silica Reaction during Standard Mortar Test

    SciTech Connect

    Shin, Jun-Ho; Struble, Leslie; Kirkpatrick, R.

    2015-12-01

    The microstructural development of mortar bars with silica glass aggregate undergoing alkali-silica reaction (ASR) under the conditions of American Society for Testing and Materials (ASTM) Standard Test C1260 was analyzed using scanning electron microscopy and qualitative X-ray microanalysis. Cracking in the aggregate, the hydrated paste, and the paste-aggregate interface was important in the development of the microstructure. Cracks were characterized according to their location, their relationship to other cracks, and whether they are filled with ASR gel. Expansion of the bars was approximately 1% at 12 days and 2% at 53 days. They fell apart by 63 days. The bars contained two zones, an inner region that was undergoing ASR and an outer and much more highly damaged zone that extended further inward over time. Evidence of ASR was present even during the period when specimens were immersed in water, prior to immersion in NaOH solution.

  17. Microstructural Changes Due to Alkali-Silica Reaction during Standard Mortar Test

    DOE PAGES

    Shin, Jun-Ho; Struble, Leslie; Kirkpatrick, R.

    2015-12-01

    The microstructural development of mortar bars with silica glass aggregate undergoing alkali-silica reaction (ASR) under the conditions of American Society for Testing and Materials (ASTM) Standard Test C1260 was analyzed using scanning electron microscopy and qualitative X-ray microanalysis. Cracking in the aggregate, the hydrated paste, and the paste-aggregate interface was important in the development of the microstructure. Cracks were characterized according to their location, their relationship to other cracks, and whether they are filled with ASR gel. Expansion of the bars was approximately 1% at 12 days and 2% at 53 days. They fell apart by 63 days. The barsmore » contained two zones, an inner region that was undergoing ASR and an outer and much more highly damaged zone that extended further inward over time. Evidence of ASR was present even during the period when specimens were immersed in water, prior to immersion in NaOH solution.« less

  18. Use of ground clay brick as a pozzolanic material to reduce the alkali-silica reaction

    SciTech Connect

    Turanli, L.; Bektas, F.; Monteiro, P.J.M

    2003-10-01

    The objective of this experimental study was to use ground clay brick (GCB) as a pozzolanic material to minimize the alkali-silica reaction expansion. Two different types of clay bricks were finely ground and their activity indices were determined. ASTM accelerated mortar bar tests were performed to investigate the effect of GCB when used to replace cement mass. The microstructure of the mortar was investigated using scanning electron microscopy (SEM). The results showed that the GCBs meet the strength activity requirements of ASTM. In addition, the GCBs were found to be effective in suppressing the alkali-silica reaction expansion. The expansion decreased as the amount of GCBs in the mortar increased.

  19. Alkali-silica reaction and pore solution composition in mortars in sea water

    SciTech Connect

    Kawamura, Mitsunori; Takeuchi, Katsunobu

    1996-12-01

    The promotion of expansion of mortars containing a reactive aggregate in 1N NaCl solution at 38 C was attributed to a rise of OH{sup {minus}} ion concentration in the pore solution in the mortars. However, it is ambiguous whether the promotion of expansion of mortars in sea water at a room temperature can be explained in the same way as in NaCl solution at an elevated temperature. This study aims at pursuing the expansion behavior of mortars containing a reactive aggregate relating it to their pore solution composition and the extent of alkali-silica reaction occurring within reactive grains. The alkali-silica reaction in mortars in sea water and 0.5 1N NaCl solution at 20 C appears to progress differently from that in mortars in 1N NaCl solution at an elevated temperature of 38 C. The promotion of expansion of mortars in sea water at 20 C was found to be responsible for an effect of Cl{sup {minus}} ions in the alkali-silica reaction at early stages of immersion. Only when OH{sup {minus}} ion concentration in the pore solution was relatively high, NaCl and sea water could accelerate the alkali-silica reaction in mortars at 20 C.

  20. Examination of the concrete from an old Portuguese dam: Texture and composition of alkali-silica gel

    SciTech Connect

    Fernandes, Isabel Noronha, Fernando Teles, Madalena

    2007-11-15

    Exudations and pop-outs were identified in the interior galleries of a large dam built in the 1960s. The samples collected were examined by a Scanning Electron Microscope. A dense material with a smooth surface and drying shrinkage cracks or a spongy texture were observed in the samples. The semi-quantitative composition was obtained by energy dispersive spectrometry (EDS) and it was concluded that this material corresponds to alkali-silica gel, composed of SiO{sub 2}-Na{sub 2}O-K{sub 2}O-CaO. A viscous white product in contact with an aggregate particle in a cone sampled from a pop-out was observed through use of the scanning electron microscope and it has characteristics similar to the gel present in the exudations and cavities. Reference is made to the potential alkali reactivity of the aggregate present in the concrete. The texture and composition of the products probably resulting from an alkali-silica reaction are presented, set out in ternary diagrams, and discussed.

  1. Investigation of structural properties associated with alkali-silica reaction by means of macro- and micro-structural analysis

    SciTech Connect

    Mo Xiangyin . E-mail: moxiangyin@njnu.edu.cn; Fournier, Benoit

    2007-02-15

    Structural properties associated with alkali-silica reaction were systematically investigated by means of macro-structural accelerated mortar prism expansion levels testing, combined with micro-structural analysis. One part of this study is to determine the reactivity of the aggregate by means of accelerated mortar bar tests, and also to evaluate perlite aggregate constituents, especially the presence of deleterious components and find main causes of the alkali-silica reaction, which was based on the petrographic studies by optical microscope and the implication of X-ray diffraction on the aggregate. Results implied that the aggregate was highly alkali-silica reactive and the main micro-crystalline quartz-intermediate character and matrix that is mainly composed of chalcedony are potentially suitable for alkali-silica reaction. The other part is to study the long-term effect of lithium salts against alkali-silica reaction by testing accelerated mortar prism expansion levels. The macro-structural results were also consistent with the micro-structural mechanisms of alkali-silica reaction of mortar prisms containing this aggregate and the effect of chemical admixtures by means of the methods of scanning electron microscope-X-ray energy-dispersive spectroscopy and X-ray diffraction. It was indicated by these techniques that lithium salts, which were introduced into concrete containing reactive aggregate at the mixing stage, suppressed the alkali-silica reaction by producing non-expansive crystalline materials.

  2. New observations on the mechanism of lithium nitrate against alkali silica reaction (ASR)

    SciTech Connect

    Feng, X.; Thomas, M.D.A.; Bremner, T.W.; Folliard, K.J.; Fournier, B.

    2010-01-15

    In the current study, in order to elucidate the mechanisms for the favorable effects of lithium nitrate in controlling alkali silica reaction (ASR), vycor glass disk immersion specimens and glass disk-cement paste sandwich specimens were prepared and examined by XRD, SEM and Laser Ablation Induction Coupled Plasma Mass Spectrometry (LA-ICP-MS). Results showed that when glass disk was immersed in only NaOH solution, the glass was attacked by hydroxyl ions but no solid reaction product was found, thus the presence of calcium was essential for the formation of ASR gel. In the presence of lithium, the glass surface was covered by a thick layer of Li-Si crystal. With the addition of Ca(OH){sub 2}, the glass surface was completely covered by Li-Si crystal and a lithium-bearing low Ca-Na-(K)-Si gel. These two phases either form a dense matrix with Li-Si crystal serving as the framework, and the gel filling in the void space, or the Li-Si crystal serving as the foundation to completely cover the entire reactive SiO{sub 2} surface, and the gel sitting on top of these crystal particles. Hence, the suppressive effects of LiNO{sub 3} were attributed to the formation of a layer of Li-Si crystals intimately at the reactive SiO{sub 2} particle surface and the formation of Li-bearing low-Ca ASR gel products. The Li-bearing low-Ca ASR gels may have a dense and rigid structure, thus having low capacity to absorb moisture from the surrounding paste, and exhibiting a non-swelling property.

  3. Petrography study on altered flint aggregate by alkali-silica reaction

    SciTech Connect

    Bulteel, D. . E-mail: bulteel@ensm-douai.fr; Rafai, N.; Degrugilliers, P.; Garcia-Diaz, E.

    2004-11-15

    The aim of our study is to improve our understanding of an alkali-silica reaction (ASR) via petrography. We used a chemical concrete subsystem: flint aggregate, portlandite and KOH. The altered flint aggregate is followed by optical microscopy and scanning electron microscopy (SEM) before and after acid treatment at different intervals. After acid treatment, the observations showed an increase in aggregate porosity and revealed internal degradation of the aggregate. This degradation created amorphous zones. Before acid treatment, the analyses on polished sections by scanning electron microscopy coupled with energy dispersive spectroscopy (EDS) enabled visualization of K{sup +} and Ca{sup 2+} penetration into the aggregate. The appearance of amorphous zones and penetration of positive ions into the aggregate are correlated with the increase in the molar fraction of silanol sites. This degradation is specific to the alkali-silica reaction.

  4. Methods for Controlling Effects of Alkali-Silica Reaction in Concrete.

    DTIC Science & Technology

    1987-02-01

    trioxide were determined gravimetrically by fusing portions of the samples with sodium carbonate. The other oxides were determined by an AA after fusing...minimizing the effects of alkali-silica reaction in concrete. Ten pozzolans were tested to determine how they could most effec- tively be used to...the work included determination of pessimum aggregate levels. The word "pessimum" is used to denote the most reactive amount of reactive material in an

  5. Influence of stress restraint on the expansive behaviour of concrete affected by alkali-silica reaction

    SciTech Connect

    Berra, M.; Faggiani, G.; Mangialardi, T.; Paolini, A.E.

    2010-09-15

    The primary objective of this study was to ascertain whether the Threshold Alkali Level (TAL) of the concrete aggregates may be taken as a suitable reactivity parameter for the selection of aggregates susceptible of alkali-silica reaction (ASR), even when ASR expansion in concrete develops under restrained conditions. Concrete mixes made with different alkali contents and two natural siliceous aggregates with very different TALs were tested for their expansivity at 38 {sup o}C and 100% RH under unrestrained and restrained conditions. Four compressive stress levels over the range from 0.17 to 3.50 N/mm{sup 2} were applied by using a new appositely designed experimental equipment. The lowest stress (0.17 N/mm{sup 2}) was selected in order to estimate the expansive pressure developed by the ASR gel under 'free' expansion conditions. It was found that, even under restrained conditions, the threshold alkali level proves to be a suitable reactivity parameter for designing concrete mixes that are not susceptible of deleterious ASR expansion. An empirical relationship between expansive pressure, concrete alkali content and aggregate TAL was developed in view of its possible use for ASR diagnosis and/or safety evaluation of concrete structures.

  6. Quantitative diagnosis and prognosis framework for concrete degradation due to alkali-silica reaction

    NASA Astrophysics Data System (ADS)

    Mahadevan, Sankaran; Neal, Kyle; Nath, Paromita; Bao, Yanqing; Cai, Guowei; Orme, Peter; Adams, Douglas; Agarwal, Vivek

    2017-02-01

    This research is seeking to develop a probabilistic framework for health diagnosis and prognosis of aging concrete structures in nuclear power plants that are subjected to physical, chemical, environment, and mechanical degradation. The proposed framework consists of four elements: monitoring, data analytics, uncertainty quantification, and prognosis. The current work focuses on degradation caused by ASR (alkali-silica reaction). Controlled concrete specimens with reactive aggregate are prepared to develop accelerated ASR degradation. Different monitoring techniques — infrared thermography, digital image correlation (DIC), mechanical deformation measurements, nonlinear impact resonance acoustic spectroscopy (NIRAS), and vibro-acoustic modulation (VAM) — are studied for ASR diagnosis of the specimens. Both DIC and mechanical measurements record the specimen deformation caused by ASR gel expansion. Thermography is used to compare the thermal response of pristine and damaged concrete specimens and generate a 2-D map of the damage (i.e., ASR gel and cracked area), thus facilitating localization and quantification of damage. NIRAS and VAM are two separate vibration-based techniques that detect nonlinear changes in dynamic properties caused by the damage. The diagnosis results from multiple techniques are then fused using a Bayesian network, which also helps to quantify the uncertainty in the diagnosis. Prognosis of ASR degradation is then performed based on the current state of degradation obtained from diagnosis, by using a coupled thermo-hydro-mechanical-chemical (THMC) model for ASR degradation. This comprehensive approach of monitoring, data analytics, and uncertainty-quantified diagnosis and prognosis will facilitate the development of a quantitative, risk informed framework that will support continuous assessment and risk management of structural health and performance.

  7. Cathodoluminescence microscopy and petrographic image analysis of aggregates in concrete pavements affected by alkali-silica reaction

    SciTech Connect

    Stastna, A.; Sachlova, S.; Pertold, Z.; Prikryl, R.; Leichmann, J.

    2012-03-15

    Various microscopic techniques (cathodoluminescence, polarizing and electron microscopy) were combined with image analysis with the aim to determine a) the modal composition and degradation features within concrete, and b) the petrographic characteristics and the geological types (rocks, and their provenance) of the aggregates. Concrete samples were taken from five different portions of Highway Nos. D1, D11, and D5 (the Czech Republic). Coarse and fine aggregates were found to be primarily composed of volcanic, plutonic, metamorphic and sedimentary rocks, as well as of quartz and feldspar aggregates of variable origins. The alkali-silica reaction was observed to be the main degradation mechanism, based upon the presence of microcracks and alkali-silica gels in the concrete. Use of cathodoluminescence enabled the identification of the source materials of the quartz aggregates, based upon their CL characteristics (i.e., color, intensity, microfractures, deformation, and zoning), which is difficult to distinguish only employing polarizing and electron microscopy. - Highlights: Black-Right-Pointing-Pointer ASR in concrete pavements on the Highways Nos. D1, D5 and D11 (Czech Republic). Black-Right-Pointing-Pointer Cathodoluminescence was combined with various microscopic techniques and image analysis. Black-Right-Pointing-Pointer ASR was attributed to aggregates. Black-Right-Pointing-Pointer Source materials of aggregates were identified based on cathodoluminescence characteristics. Black-Right-Pointing-Pointer Quartz comes from different volcanic, plutonic and metamorphic parent rocks.

  8. Petrography study of two siliceous limestones submitted to alkali-silica reaction

    SciTech Connect

    Monnin, Y. . E-mail: monnin@ensm-douai.fr; Degrugilliers, P.; Bulteel, D.; Garcia-Diaz, E.

    2006-08-15

    This study presents the contribution of petrography to the comprehension of the alkali-silica reaction mechanism applied to two siliceous limestones. A petrography study was made on the two aggregates before reaction to define their relative proportions and types of reactive silica and to observe their distribution in the microstructure. Then a model reactor, constituted by the reactive siliceous limestone aggregate, portlandite and NaOH, was used to measure the swelling due to reaction of the silica with alkalis and the free expansion of the aggregates. The volume evolution between both aggregates was very different and could be explained by the preliminary petrographic study. It appears that the swelling of the aggregates is conditioned by the microstructure of the carbonated matrix, the quantity and the distribution of the reactive silica.

  9. Effect of moisture conditions and transfers on alkali silica reaction damaged structures

    SciTech Connect

    Multon, Stephane; Toutlemonde, Francois

    2010-06-15

    The aim of this paper is to point out the water driving effect on the alkali silica reaction (ASR) expansion and particularly when modifications of moisture conditions occur. After being submitted to a unidirectional moisture gradient during 14 months, the upper faces of ASR reactive beams were covered by water for 9 months. This late water supply on the upper face rapidly produced large expansions, which mainly occurred along the transverse and the vertical directions resulting in large longitudinal cracks. Companion nonreactive specimens were kept in the same environmental conditions in order to quantify the basic characteristics of moisture-dependent expansive behaviour of the material. The paper focuses on the effects of late water supply or late drying on already ASR-damaged concrete, which is a significant concern for real-life structures. Both structural effects of late water supply on ASR progress in already damaged structures and interpretation of such phenomena are described.

  10. Insights into alkali-silica reaction damage in mortar through acoustic nonlinearity

    NASA Astrophysics Data System (ADS)

    Rashidi, M.; Kim, J.-Y.; Jacobs, L. J.; Kurtis, K. E.

    2016-02-01

    The progression of damage as a result of alkali-silica reaction in mortar samples is monitored by using the Nonlinear Impact Resonance Acoustic Spectroscopy (NIRAS) method and expansion measurements, which were performed daily. Results of this study show a strong correlation between the cumulative average nonlinearity parameter and expansion for each sample type, and a strong linear relationship between fourteen-day expansion and the cumulative average nonlinearity of among sample types. In addition to the cumulative average nonlinearity parameter, the standard deviation of average nonlinearity parameter shows strong correlation with the fourteen-day expansion of sample types. Results provide insights to the relationship with the acoustic nonlinearity and damage caused by the ASR.

  11. Relation of expansion due to alkali silica reaction to the degree of reaction measured by SEM image analysis

    SciTech Connect

    Haha, M. Ben; Gallucci, E. Guidoum, A.; Scrivener, K.L.

    2007-08-15

    Scanning Electron Microscopy Image Analysis (SEM-IA) was used to quantify the degree of alkali silica reaction in affected microbars, mortar and concrete prisms. It was found that the degree of reaction gave a unique correlation with the macroscopic expansion for three different aggregates, stored at three temperatures and with two levels of alkali. The relationships found for the concretes and the mortars overlap when normalised by the aggregate content. This relationship seems to be linear up to a critical reaction degree which coincides with crack initiation within the reactive aggregates.

  12. A chemo-mechanical model for the acoustic nonlinearity change in concrete with alkali-silica reactions

    NASA Astrophysics Data System (ADS)

    Liu, M.; Jacobs, L. J.; Qu, J.

    2013-01-01

    Experimental data have demonstrated that damage induced by alkali-silica reaction (ASR) in concrete, even in its very early stage, can cause changes in the acoustic nonlinearity parameter β. This provides a means to characterize ASR damage in concrete nondestructively. However, there is currently no model that explains the relationship between the acoustic nonlinearity parameter and ASR damage. In this work, we present a micromechanics-based chemo-mechanical model that relates the acoustic nonlinearity parameter to ASR damage. The mechanical part of the model is developed based on a modified version of the generalized self-consistent theory. The chemical part of the model accounts for two opposing diffusion processes. One is the diffusion of alkali ions in the pore solution into aggregates, and the other is the permeation of ASR gel from the aggregate surface into the surrounding porous cement matrix. Furthermore, a fracture model is used to simulate crack initiation and growth, so that the crack density and total expansion can be obtained. Finally, the acoustic nonlinearity parameter is determined as a function of exposure time by accounting for the gel pressure and the crack density. This model provides a way to quantitatively predict the changes in the acoustic nonlinearity parameter due to ASR damage, which can be used to guide experimental measurements for nondestructive evaluation of ASR damage.

  13. Monitoring, Modeling, and Diagnosis of Alkali-Silica Reaction in Small Concrete Samples

    SciTech Connect

    Agarwal, Vivek; Cai, Guowei; Gribok, Andrei V.; Mahadevan, Sankaran

    2015-09-01

    Assessment and management of aging concrete structures in nuclear power plants require a more systematic approach than simple reliance on existing code margins of safety. Structural health monitoring of concrete structures aims to understand the current health condition of a structure based on heterogeneous measurements to produce high-confidence actionable information regarding structural integrity that supports operational and maintenance decisions. This report describes alkali-silica reaction (ASR) degradation mechanisms and factors influencing the ASR. A fully coupled thermo-hydro-mechanical-chemical model developed by Saouma and Perotti by taking into consideration the effects of stress on the reaction kinetics and anisotropic volumetric expansion is presented in this report. This model is implemented in the GRIZZLY code based on the Multiphysics Object Oriented Simulation Environment. The implemented model in the GRIZZLY code is randomly used to initiate ASR in a 2D and 3D lattice to study the percolation aspects of concrete. The percolation aspects help determine the transport properties of the material and therefore the durability and service life of concrete. This report summarizes the effort to develop small-size concrete samples with embedded glass to mimic ASR. The concrete samples were treated in water and sodium hydroxide solution at elevated temperature to study how ingress of sodium ions and hydroxide ions at elevated temperature impacts concrete samples embedded with glass. Thermal camera was used to monitor the changes in the concrete sample and results are summarized.

  14. Stability of cenospheres in lightweight cement composites in terms of alkali-silica reaction

    SciTech Connect

    Wang Junyan Zhang Minhong; Li Wei; Chia, Kok-Seng; Liew, Richard J.Y.

    2012-05-15

    This paper presents an experimental study on characteristics and stability of cenospheres used in lightweight cement composites. ASTM C227 and C1260 tests were used to evaluate if cenospheres are potentially deleterious due to alkali-silica reaction (ASR). Natural sand was used as control. Examination by scanning electron microscope with energy-dispersive X-ray spectroscopy and analyses by X-ray diffractometer and thermogravimetry were conducted on samples with cenospheres after 9-month C227 and C1260 tests to better understand the behavior of cenospheres exposed to high alkaline environments and higher temperatures in these tests. Results indicate that cenospheres are not potentially deleterious due to ASR. Expansion of the mortar specimens tested to ASTM C227 and C1260 seems to be affected by the pozzolanic reactivity of cenospheres. Fine cenospheres showed limited pozzolanic reactivity at 28-30 Degree-Sign C and 38 Degree-Sign C, but exhibited significant pozzolanic reactivity at 80 Degree-Sign C with aluminum tobermorite [Ca{sub 5}Si{sub 5}Al(OH)O{sub 17} Bullet-Operator 5H{sub 2}O] identified as the main reaction product.

  15. Measurement of alkali-silica reaction progression by ultrasonic waves attenuation

    SciTech Connect

    Saint-Pierre, Francois; Rivard, Patrice . E-mail: Patrice.Rivard@Usherbrooke.ca; Ballivy, Gerard

    2007-06-15

    Development of non-destructive methods, developed specifically for assessing the damage induced by alkali-silica reaction (ASR) in concrete structures, is needed in order to carry out a systematic evaluation of the concrete condition. The aim of this study is to monitor the evolution of the ASR-damage in laboratory with concrete samples with ultrasonic pulse velocity and attenuation of ultrasonic waves methods. For this study, results of both methods were compared with expansion and mass variation. One reactive concrete mixture was made with reactive aggregate, and one other mixture, incorporating non-reactive aggregate, was made as a control. Specimens were kept at 38 deg. C in a 1 mol l{sup -1} NaOH solution to accelerate the reaction. Attenuation of transmitted ultrasonic waves appeared to be more appropriate for the evaluation of ASR-damage compared with pulse velocity. The attenuation of accelerated reactive concrete cylinders increased by 90% after 1 year while it increased by 40% for the non-reactive concrete used as a control. Major part of the attenuation increase in the non-reactive concrete is due to liquid absorption. This work suggests that in-situ non-destructive techniques based on ultrasonic wave attenuation, like ultrasonic attenuation tomography, should be developed in order to evaluate the development of ASR in concrete structures. Petrographic examination confirmed that damage to concrete is associated with ASR.

  16. Microscopy and Cathodoluminescence Spectroscopy Characterization of Quartz Exhibiting Different Alkali-Silica Reaction Potential.

    PubMed

    Kuchařová, Aneta; Götze, Jens; Šachlová, Šárka; Pertold, Zdeněk; Přikryl, Richard

    2016-02-01

    Different quartz types from several localities in the Czech Republic and Sweden were examined by polarizing microscopy combined with cathodoluminescence (CL) microscopy, spectroscopy, and petrographic image analysis, and tested by use of an accelerated mortar bar test (following ASTM C1260). The highest alkali-silica reaction potential was indicated by very fine-grained chert, containing significant amounts of fine-grained to cryptocrystalline matrix. The chert exhibited a dark red CL emission band at ~640 nm with a low intensity. Fine-grained orthoquartzites, as well as fine-grained metamorphic vein quartz, separated from phyllite exhibited medium expansion values. The orthoquartzites showed various CL of quartz grains, from blue through violet, red, and brown. Two CL spectral bands at ~450 and ~630 nm, with various intensities, were detected. The quartz from phyllite displayed an inhomogeneous dark red CL with two CL spectral bands of low intensities at ~460 and ~640 nm. The massive coarse-grained pegmatite quartz from pegmatite was assessed to be nonreactive and displayed a typical short-lived blue CL (~480 nm). The higher reactivity of the fine-grained hydrothermal quartz may be connected with high concentrations of defect centers, and probably with amorphized micro-regions in the quartz, respectively; indicated by a yellow CL emission (~570 nm).

  17. Classification of alkali-silica reaction and corrosion distress using acoustic emission

    NASA Astrophysics Data System (ADS)

    Abdelrahman, Marwa; ElBatanouny, Mohamed; Serrato, Michael; Dixon, Kenneth; Larosche, Carl; Ziehl, Paul

    2016-02-01

    The Nuclear Regulatory Commission regulates approximately 100 commercial nuclear power reactor facilities that contribute about 20% of the total electric energy produced in the United States. Half of these reactor facilities are over 30 years old and are approaching their original design service life. Due to economic and durability considerations, significant portions of many of the facilities were constructed with reinforced concrete, including the containment facilities, cooling towers, and foundations. While most of these concrete facilities have performed exceptionally well throughout their initial expected service life, some are beginning to exhibit different forms of concrete deterioration. In this study, acoustic emission (AE) is used to monitor two main concrete deterioration mechanisms; alkali-silica reaction (ASR) distress and corrosion of reinforcing steel. An accelerated ASR test was conducted where specimens were continuously monitored with AE. The results show that AE can detect and classify damage due to ASR distress in the specimens. AE was also used to remotely monitor active corrosion regions in a reactor facility. AE monitoring of accelerated corrosion testing was also conducted on a concrete block specimen cut from a similar reactor building. Electrochemical measurements were conducted to correlate AE activity to quantifiable corrosion measurements and to enhance capabilities for service life prediction.

  18. Assessment of Alkali-Silica Reaction Damage in Mortars with Nonlinear Ultrasonic Techniques

    NASA Astrophysics Data System (ADS)

    Chen, J.; Jayapalan, A. R.; Kurtis, K. E.; Kim, J.-Y.; Jacobs, L. J.

    2008-02-01

    In this work, a nonlinear ultrasonic modulation technique is employed to assess the damage state of portland cement mortar samples induced by alkali-silica reaction (ASR). Due to the nonlinear interaction of propagating waves caused by distributed microcracks that are agitated from its equilibrium state, the ultrasonic responses of samples produce sideband frequencies around the frequency of propagating waves. The amplitude of the sidebands depends on the amplitude of the input signals and is particularly sensitive to the state of damage evolved in the sample. Therefore, the development of internal microcracks with increasing duration of exposure to aggressive conditions can be quantitatively related to the variation of external ultrasonic measurements. The ultrasonic results are compared with results from standard ASR expansion measurements (ASTM C 1260), and a proportionally increasing relation was found in the early stages. In addition, aggregates with different alkali-reactivity (i.e., low reactivity or high reactivity) were examined in a similar manner. The results indicate that the nonlinear parameter obtained from ultrasonic tests directly reflects the difference of aggregate reactivity. This clearly indicates that the developed nonlinear ultrasonic method is potentially a good alternative for a more rapid and still reliable assessment of aggregate alkali-reactivity.

  19. A Demonstration of Concrete Structural Health Monitoring Framework for Degradation due to Alkali-Silica Reaction

    SciTech Connect

    Mahadevan, Sankaran; Agarwal, Vivek; Neal, Kyle; Nath, Paromita; Bao, Yanqing; Cai, Guowei; Orme, Peter; Adams, Douglas; Kosson, David

    2016-04-01

    Assessment and management of aging concrete structures in nuclear power plants require a more systematic approach than simple reliance on existing code margins of safety. Structural health monitoring of concrete structures aims to understand the current health condition of a structure based on heterogeneous measurements to produce high-confidence actionable information regarding structural integrity that supports operational and maintenance decisions. This ongoing research project is seeking to develop a probabilistic framework for health diagnosis and prognosis of aging concrete structures in a nuclear power plant that is subjected to physical, chemical, environment, and mechanical degradation. The proposed framework consists of four elements: monitoring, data analytics, uncertainty quantification and prognosis. This report focuses on degradation caused by ASR (alkali-silica reaction). Controlled specimens were prepared to develop accelerated ASR degradation. Different monitoring techniques – thermography, digital image correlation (DIC), mechanical deformation measurements, nonlinear impact resonance acoustic spectroscopy (NIRAS), and vibro-acoustic modulation (VAM) -- were used to detect the damage caused by ASR. Heterogeneous data from the multiple techniques was used for damage diagnosis and prognosis, and quantification of the associated uncertainty using a Bayesian network approach. Additionally, MapReduce technique has been demonstrated with synthetic data. This technique can be used in future to handle large amounts of observation data obtained from the online monitoring of realistic structures.

  20. Modeling Time-Dependent Behavior of Concrete Affected by Alkali Silica Reaction in Variable Environmental Conditions

    PubMed Central

    Alnaggar, Mohammed; Di Luzio, Giovanni; Cusatis, Gianluca

    2017-01-01

    Alkali Silica Reaction (ASR) is known to be a serious problem for concrete worldwide, especially in high humidity and high temperature regions. ASR is a slow process that develops over years to decades and it is influenced by changes in environmental and loading conditions of the structure. The problem becomes even more complicated if one recognizes that other phenomena like creep and shrinkage are coupled with ASR. This results in synergistic mechanisms that can not be easily understood without a comprehensive computational model. In this paper, coupling between creep, shrinkage and ASR is modeled within the Lattice Discrete Particle Model (LDPM) framework. In order to achieve this, a multi-physics formulation is used to compute the evolution of temperature, humidity, cement hydration, and ASR in both space and time, which is then used within physics-based formulations of cracking, creep and shrinkage. The overall model is calibrated and validated on the basis of experimental data available in the literature. Results show that even during free expansions (zero macroscopic stress), a significant degree of coupling exists because ASR induced expansions are relaxed by meso-scale creep driven by self-equilibriated stresses at the meso-scale. This explains and highlights the importance of considering ASR and other time dependent aging and deterioration phenomena at an appropriate length scale in coupled modeling approaches. PMID:28772829

  1. Alkali-silica reaction (ASR) detection in concrete from frequency dependent ultrasonic attenuation

    NASA Astrophysics Data System (ADS)

    Gong, Peng; Patton, Mark E.; Greve, David W.; Harley, Joel B.; Liu, Chang; Oppenheim, Irving J.

    2014-02-01

    The alkali-silica reaction (ASR) occurs between the reactive aggregates and the alkaline cement paste in concrete, eventually producing damage such as swelling and cracking. This research uses mechanical tests and ultrasonic tests to detect ASR onset in concrete specimens. The test specimens are fabricated in pairs, one specimen typically subjected to an accelerated ASR environment (immersion in 1 N NaOH solution at 80°C) and the second specimen comparable but not exposed to the accelerated ASR environment. In mechanical tests, the transverse and longitudinal resonant frequencies are measured. Results show that ASR damage would lower the resonant frequencies. In the ultrasonic test, broadband excitations are used and pitch-catch records are obtained. The presence of ASR damage in concrete is shown to cause frequency dependent ultrasonic attenuation. Signals from ASR damaged specimens show strong attenuation at high frequencies and weak attenuation at low frequencies. In contrast, signals frompaired non-ASR specimens show comparable energy over the entire range of measured frequencies. The cumulative distribution function of frequency components (CDF) is used to characterize the ultrasonic passband changes caused by ASR damage and detect the existence of ASR damage in frequency domain.

  2. Relationship between Degree of Deformation in Quartz and Silica Dissolution for the Development of Alkali-Silica Reaction in Concrete

    PubMed Central

    Gomes, Marcia E. B.; Dal Molin, Denise C. C.; Hasparyk, Nicole P.; Monteiro, Paulo J. M.

    2017-01-01

    This paper presents research on the influence of quartz deformation in aggregates for the development of the alkali-silica reaction in concrete and its relationship with silica dissolution. The study also compares these characteristics with the field behavior of such rocks in concrete. The paper proposes parameters to classify the different degrees of deformation of quartz. Transmission electron microscopy showed the presence of walls even in slightly deformed quartz, which indicate the presence of the internal paths available to react with the alkaline concrete pore solutions and point to the potential development of an alkali-silica reaction. The presence of the deformation bands in the quartz grains leads to the alkali aggregate reaction occurring more rapidly. The visible spectrophotometer test was performed to evaluate the dissolution potential of the different samples of deformed quartz, which confirmed that the reactivity of the quartz increases as the deformation of the crystalline structure increases. The parameters established in the present study could be verified by analyzing the behavior of reactive and innocuous aggregates from the buildings. PMID:28869559

  3. Elastic Modulus of the Alkali-Silica Reaction Rim in a Simplified Calcium-Alkali-Silicate System Determined by Nano-Indentation

    PubMed Central

    Zheng, Kunpeng; Lukovic, Mladena; De Schutter, Geert; Ye, Guang; Taerwe, Luc

    2016-01-01

    This work aims at providing a better understanding of the mechanical properties of the reaction rim in the alkali-silica reaction. The elastic modulus of the calcium alkali silicate constituting the reaction rim, which is formed at the interface between alkali silicate and Ca(OH)2 in a chemically-idealized system of the alkali-silica reaction, was studied using nano-indentation. In addition, the corresponding calcium to silica mole ratio of the calcium alkali silicate was investigated. The results show that the elastic modulus of the calcium alkali silicate formed at the interface increased with the increase of the calcium to silica mole ratio and vice versa. Furthermore, the more calcium that was available for interaction with alkali silicate to form calcium alkali silicate, the higher the calcium to silica mole ratio and, consequently, the higher the elastic modulus of the formed calcium alkali silicate. This work provides illustrative evidence from a mechanical point of view on how the occurrence of cracks due to the alkali-silica reaction (ASR) is linked to the formation of the reaction rim. It has to be highlighted, however, that the simplified calcium-alkali-silicate system in this study is far from the real condition in concrete. PMID:28773907

  4. Elastic Modulus of the Alkali-Silica Reaction Rim in a Simplified Calcium-Alkali-Silicate System Determined by Nano-Indentation.

    PubMed

    Zheng, Kunpeng; Lukovic, Mladena; De Schutter, Geert; Ye, Guang; Taerwe, Luc

    2016-09-20

    This work aims at providing a better understanding of the mechanical properties of the reaction rim in the alkali-silica reaction. The elastic modulus of the calcium alkali silicate constituting the reaction rim, which is formed at the interface between alkali silicate and Ca(OH)₂ in a chemically-idealized system of the alkali-silica reaction, was studied using nano-indentation. In addition, the corresponding calcium to silica mole ratio of the calcium alkali silicate was investigated. The results show that the elastic modulus of the calcium alkali silicate formed at the interface increased with the increase of the calcium to silica mole ratio and vice versa. Furthermore, the more calcium that was available for interaction with alkali silicate to form calcium alkali silicate, the higher the calcium to silica mole ratio and, consequently, the higher the elastic modulus of the formed calcium alkali silicate. This work provides illustrative evidence from a mechanical point of view on how the occurrence of cracks due to the alkali-silica reaction (ASR) is linked to the formation of the reaction rim. It has to be highlighted, however, that the simplified calcium-alkali-silicate system in this study is far from the real condition in concrete.

  5. Development of microwave and impedance spectroscopy methods for in-situ nondestructive evaluation of alkali silica reaction in concrete

    NASA Astrophysics Data System (ADS)

    Heifetz, Alexander; Bakhtiari, Sasan; Lu, Juan; Aranson, Igor S.; Vinokur, Valerii M.; Bentivegna, Anthony F.

    2017-02-01

    Aging concrete degradation due to alkali silica reaction (ASR) is a challenge to sustainability of critical infrastructure, such as nuclear power plants. Currently, there is no standard, nondestructive method for detecting ASR in concrete. We report on the progress in developing electromagnetic (EM) methods, consisting of microwave and impedance spectroscopy techniques, for nondestructive detection of ASR. The microwave and impedance spectroscopy methods are complementary since they provide information about material electrical properties in GHz and Hz to KHz EM spectral bands, respectively. Preliminary studies were conducted using accelerated testing concrete prism specimens developed according to ASTM C1293 standard. Microwave and impedance spectroscopy measurements were performed on ASR specimens at the first and the second month maturity level, as well as on age-matched controls. Microwave tests consisted of reflection and transmission measurements using dielectric-loaded antennas, with the focus on X-band spectrum. Impedance measurements were performed using flexible electrode patches. Measurement results by both microwave and impedance spectroscopy methods indicate observable differences in electrical properties between reactive and non-reactive specimens. In addition, trends in measurement data obtained with the two complementary EM techniques are consistent and correlate with ASR progression in specimens.

  6. Chemo-mechanical modeling for prediction of alkali silica reaction (ASR) expansion

    SciTech Connect

    Multon, Stephane Sellier, Alain; Cyr, Martin

    2009-06-15

    The effect of the size of the aggregate on ASR expansion has already been well illustrated. This paper presents a microscopic model to analyze the development of ASR expansion of mortars containing reactive aggregate of different sizes. The attack of the reactive silica by alkali was determined through the mass balance equation, which controls the diffusion mechanism in the aggregate and the fixation of the alkali in the ASR gels. The mechanical part of the model is based on the damage theory in order to assess the decrease of stiffness of the mortar due to cracking caused by ASR and to calculate the expansion of a Representative Elementary Volume (REV) of concrete. Parameters of the model were estimated by curve fitting the expansions of four experimental mortars. The paper shows that the decrease of expansion with the size of the aggregate and the increase of the expansion with the alkali content are reproduced by the model, which is able to predict the expansions of six other mortars containing two sizes of reactive aggregate and cast with two alkali contents.

  7. GRIZZLY Model of Multi-Reactive Species Diffusion, Moisture/Heat Transfer and Alkali-Silica Reaction for Simulating Concrete Aging and Degradation

    SciTech Connect

    Huang, Hai; Spencer, Benjamin W.; Cai, Guowei

    2015-09-01

    Concrete is widely used in the construction of nuclear facilities because of its structural strength and its ability to shield radiation. The use of concrete in nuclear power plants for containment and shielding of radiation and radioactive materials has made its performance crucial for the safe operation of the facility. As such, when life extension is considered for nuclear power plants, it is critical to have accurate and reliable predictive tools to address concerns related to various aging processes of concrete structures and the capacity of structures subjected to age-related degradation. The goal of this report is to document the progress of the development and implementation of a fully coupled thermo-hydro-mechanical-chemical model in GRIZZLY code with the ultimate goal to reliably simulate and predict long-term performance and response of aged NPP concrete structures subjected to a number of aging mechanisms including external chemical attacks and volume-changing chemical reactions within concrete structures induced by alkali-silica reactions and long-term exposure to irradiation. Based on a number of survey reports of concrete aging mechanisms relevant to nuclear power plants and recommendations from researchers in concrete community, we’ve implemented three modules during FY15 in GRIZZLY code, (1) multi-species reactive diffusion model within cement materials; (2) coupled moisture and heat transfer model in concrete; and (3) anisotropic, stress-dependent, alkali-silica reaction induced swelling model. The multi-species reactive diffusion model was implemented with the objective to model aging of concrete structures subjected to aggressive external chemical attacks (e.g., chloride attack, sulfate attack, etc.). It considers multiple processes relevant to external chemical attacks such as diffusion of ions in aqueous phase within pore spaces, equilibrium chemical speciation reactions and kinetic mineral dissolution/precipitation. The moisture

  8. Amorphisation mechanism of a flint aggregate during the alkali-silica reaction: X-ray diffraction and X-ray absorption XANES contributions

    SciTech Connect

    Verstraete, J.; Khouchaf, L.; Bulteel, D.; Garcia-Diaz, E.; Flank, A.M; Tuilier, M.H

    2004-04-01

    Flint samples at different stages of the Alkali-Silica Reaction were prepared and analyzed by X-ray diffraction (XRD) and silicon K-edge X-ray absorption near edge structure techniques (XANES). The results are compared to those of measurements performed on alpha quartz c-SiO{sub 2} and rough flint aggregate. The molar fraction of Q{sub 3} sites is determined as a function of the time of reaction. Up to 14 h of attack, the effect of the reaction seems of little importance. From 30 to 168 h, we showed an acceleration of the effect of the reaction on the crystal structure of the aggregate resulting in an amorphisation of the crystal. During this period, the amorphous fraction increases linearly with the number of Q{sub 3} sites. The results of the XANES confirm the amorphisation of the aggregate during the reaction and show the presence of silicon in a tetrahedral environment of oxygen whatever the time of attack.

  9. Alkali-silica reactions of mortars produced by using waste glass as fine aggregate and admixtures such as fly ash and Li2CO3.

    PubMed

    Topçu, Ilker Bekir; Boğa, Ahmet Raif; Bilir, Turhan

    2008-01-01

    Use of waste glass or glass cullet (GC) as concrete aggregate is becoming more widespread each day because of the increase in resource efficiency. Recycling of wastes is very important for sustainable development. When glass is used as aggregate in concrete or mortar, expansions and internal stresses occur due to an alkali-silica reaction (ASR). Furthermore, rapid loss in durability is generally observed due to extreme crack formation and an increase in permeability. It is necessary to use some kind of chemical or mineral admixture to reduce crack formation. In this study, mortar bars are produced by using three different colors of glass in four different quantities as fine aggregate by weight, and the effects of these glass aggregates on ASR are investigated, corresponding to ASTM C 1260. Additionally, in order to reduce the expansions of mortars, 10% and 20% fly ash (FA) as mineral admixture and 1% and 2% Li(2)CO(3) as chemical admixture are incorporated by weight in the cement and their effects on expansion are examined. It is observed that among white (WG), green (GG) and brown glass (BG) aggregates, WG aggregate causes the greatest expansion. In addition, expansion increases with an increase in amount of glass. According to the test results, it is seen that over 20% FA and 2% Li(2)CO(3) replacements are required to produce mortars which have expansion values below the 0.2% critical value when exposed to ASR. However, usages of these admixtures reduce expansions occurring because of ASR.

  10. Summary of research on the effect of LiNO{sub 3} on alkali-silica reaction in new concrete

    SciTech Connect

    Feng, X.; Thomas, M.D.A.; Bremner, T.W.; Folliard, K.J.; Fournier, B.

    2010-04-15

    This paper summarizes findings from a research study conducted at the University of New Brunswick in collaboration with the University of Texas at Austin, and CANMET-MTL, on the effect of LiNO{sub 3} on ASR in new concrete. The studies included expansion testing, silica dissolution measurements and microstructural examinations of cement systems containing glass and two different reactive aggregates (NB and NS). Only a small proportion of the data are presented here for the purpose of highlighting the principal findings of this investigation. Based on these findings, it is proposed that the inhibiting effect of LiNO{sub 3} against ASR in new concrete is attributed to the formation of two reaction products in the presence of lithium, these being a crystalline lithium silicate compound (Li{sub 2}SiO{sub 3}) crystal and a Li-bearing, low Ca silica gel. These two phases could serve as a diffusion barrier and protective layer to prevent the reactive silica from further attack by alkalis. It was found that the reason the two reactive aggregates selected responded differently to LiNO{sub 3} was due to the difference in their textural features. The NB aggregate contained reactive volcanic glass particles, the surface of which was immediately and equally available to sodium, potassium and lithium, and thus a Li-Si barrier was able to form quickly. The reactive phase in the NS aggregate was microcrystalline and strained quartz, which was embedded in a dense matrix of a non-reactive predominantly alumino-silicate phase and was not easily accessible to lithium.

  11. Application of micro X-ray diffraction to investigate the reaction products formed by the alkali silica reaction in concrete structures

    SciTech Connect

    Dähn, R.; Arakcheeva, A.; Schaub, Ph.; Pattison, P.; Chapuis, G.; Grolimund, D.; Wieland, E.; Leemann, A.

    2015-12-21

    Alkali–silica reaction (ASR) is one of the most important deterioration mechanisms in concrete leading to substantial damages of structures worldwide. Synchrotron-based micro-X-ray diffraction (micro-XRD) was employed to characterize the mineral phases formed in micro-cracks of concrete aggregates as a consequence of ASR. This particular high spatial resolution technique enables to directly gain structural information on ASR products formed in a 40-year old motorway bridge damaged due to ASR. Micro-X-ray-fluorescence was applied on thin sections to locate the reaction products formed in veins within concrete aggregates. Micro-XRD pattern were collected at selected points of interest along a vein by rotating the sample. Rietveld refinement determined the structure of the ASR product consisting of a new layered framework similar to mountainite and rhodesite. Furthermore, it is conceivable that understanding the structure of the ASR product may help developing new technical treatments inhibiting ASR.

  12. Increasing Class C fly ash reduces alkali silica reactivity

    SciTech Connect

    Hicks, J.K.

    2007-07-01

    Contrary to earlier studies, it has been found that incremental additions of Class C fly ash do reduce alkali silica reactivity (ASR), in highly reactive, high alkali concrete mixes. AST can be further reduced by substituting 5% metakaolin or silica fume for the aggregate in concrete mixes with high (more than 30%) Class C fly ash substitution. The paper reports results of studies using Class C fly ash from the Labadie Station plant in Missouri which typically has between 1.3 and 1.45% available alkalis by ASTM C311. 7 figs.

  13. Alkali-aggregate reaction in concrete containing high-alkali cement and granite aggregate

    SciTech Connect

    Owsiak, Z

    2004-01-01

    The paper discusses results of the research into the influence of high-alkali Portland cement on granite aggregate. The deformation of the concrete structure occurred after 18 months. The research was carried out by means of a scanning electron microscope equipped with a high-energy dispersive X-ray analyzer that allowed observation of unpolished sections of concrete bars exhibiting the cracking pattern typical of the alkali-silica reaction. Both the microscopic observation and the X-ray elemental analysis confirm the presence of alkali-silica gel and secondary ettringite in the cracks.

  14. Geochemical Methods for the Identification of ASR Gel

    SciTech Connect

    Guthrie, G.D.; Carey, J.W.

    1998-07-01

    This paper presents a geochemical method for staining various products of the alkali-silica reaction. The method is based on both the composition of ASR gel and one of its properties (the ability to exchange cations with a fluid). The stained concrete can be observed in normal light and serves as both a rapid field screening method and a useful aid for detailed petrographic examinations.

  15. Alkali-Silica Reaction Mitigation: State-of-the-Art

    DTIC Science & Technology

    2001-10-01

    Opal 0.5% max • Natural volcanic glass 3% max Hence, it appears that in Washington State, it is sufficient that only a single test...potential reactivity of the aggregates is of no concern (Heijnen and Larbi, 1999). 2.3.5. Australia The Queensland Department of Main Roads (1999... volcanic glass, argillites, phyllites, metamorphic graywackes and quartz, etc. The maximum amount of these components can then be limited (e.g. see

  16. Alkali-silica reactivity of expanded glass granules in structure of lightweight concrete

    NASA Astrophysics Data System (ADS)

    Bumanis, G.; Bajare, D.; Locs, J.; Korjakins, A.

    2013-12-01

    Main component in the lightweight concrete, which provides its properties, is aggregate. A lot of investigations on alkali silica reaction (ASR) between cement and lightweight aggregates have been done with their results published in the academic literature. Whereas expanded glass granules, which is relatively new product in the market of building materials, has not been a frequent research object. Therefore lightweight granules made from waste glass and eight types of cement with different chemical and mineralogical composition were examined in this research. Expanded glass granules used in this research is commercially available material produced by Penostek. Lightweight concrete mixtures were prepared by using commercial chemical additives to improve workability of concrete. The aim of the study is to identify effect of cement composition to the ASR reaction which occurs between expanded glass granules and binder. Expanded glass granules mechanical and physical properties were determined. In addition, properties of fresh and hardened concrete were determined. The ASR test was processed according to RILEM AAR-2 testing recommendation. Tests with scanning electron microscope and microstructural investigations were performed for expanded glass granules and hardened concrete specimens before and after exposing them in alkali solution.

  17. A nonlinear wave mixing method for detecting Alkali-Silica reactivity of aggregates

    NASA Astrophysics Data System (ADS)

    Liu, M.; Tang, G.; Jacobs, L. J.; Qu, J.

    2012-05-01

    Alkali-silica reaction (ASR) is a deleterious reaction in concrete. Significant ASR damage could undermine the durability of concrete structures and may result in reduced service life. Several nondestructive techniques based on ultrasound have been used to assess ASR damage. It has been shown that nonlinear ultrasound is more sensitive to internal stresses as well as to micro-cracks induced by ASR damage. In this investigation, we developed a co-linear wave mixing method for assessing ASR damage in concrete. By mixing two longitudinal waves, a new longitudinal wave with a lower frequency is generated. The amplitude of this new wave is proportional to the acoustic nonlinear parameter β which can then be obtained from the frequency spectrum of the newly generated longitudinal wave. Our experimental results show that (i) the acoustic nonlinearity parameter is closely correlated to ASR damage in concrete, (ii) the nonlinear wave mixing technique developed here is capable of measuring the changes in the acoustic nonlinearity parameter caused by ASR damage, even in its early stages, and (iii) the nonlinear wave mixing method has the potential to identify the different stages of ASR damage and to track the intrinsic characteristics of the ASR damage.

  18. Microscopic analysis of alkali-aggregate reaction products in a 50-year-old concrete

    SciTech Connect

    Fernandes, Isabel . E-mail: ifernand@fc.up.pt; Noronha, Fernando . E-mail: fmnoronh@fc.up.pt; Teles, Madalena . E-mail: mteles@fe.up.pt

    2004-11-15

    Fifty-year-old concrete from a large dam was examined in the scope of an investigation program concerning the properties of granite as aggregate material for concrete. Site inspection, which was developed in order to detect possible signs of deterioration of the concrete, revealed the existence of efflorescence and exudations. Scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) analyses were attempted to identify the composition of these materials and their morphology. From the analyses, it was concluded that some of the exudations were composed by alkali-silica gel. In these samples, an interesting behavior was observed in different moments after a 3-month interval. It was noticed that the initially noncrystalline alkali-silica gel transformed into sodium-rich needles and tablets after a few months kept in a desiccator in the laboratory. Therefore, it was concluded that the materials identified corresponded to different stages of evolution of an alkali-aggregate reaction product.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

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

    PubMed Central

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

    2015-01-01

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

  1. Linear Array Ultrasonic Test Results from Alkali-Silica Reaction (ASR) Specimens

    SciTech Connect

    Clayton, Dwight A; Khazanovich, Dr. Lev; Salles, Lucio

    2016-04-01

    The purpose of the U.S. Department of Energy Office of Nuclear Energy’s Light Water Reactor Sustainability (LWRS) Program is to develop technologies and other solutions that can improve the reliability, sustain the safety, and extend the operating lifetimes of nuclear power plants (NPPs) beyond 60 years. Since many important safety structures in an NPP are constructed of concrete, inspection techniques must be developed and tested to evaluate the internal condition. In-service containment structures generally do not allow for the destructive measures necessary to validate the accuracy of these inspection techniques. This creates a need for comparative testing of the various nondestructive evaluation (NDE) measurement techniques on concrete specimens with known material properties, voids, internal microstructure flaws, and reinforcement locations.This report presents results of the ultrasound evaluation of four concrete slabs with varying levels of ASR damage present. This included an investigation of the experimental results, as well as a supplemental simulation considering the effect of ASR damage by elasto-dynamic wave propagation using a finite integration technique method. It was found that the Hilbert Transform Indicator (HTI), developed for quantification of freeze/thaw damage in concrete structures, could also be successfully utilized for quantification of ASR damage. internal microstructure flaws, and reinforcement locations.

  2. Use of Fly Ash in the Mitigation of Alkali-Silica Reaction in Concrete

    DTIC Science & Technology

    2010-11-12

    Page 1.1 – Severe ASR crack in concrete slab ......................................................................................... 3 1.2...the expansive pressure exceeds the tensile capacity of the concrete, cracking may occur. Once cracking occurs, external water can more easily...thaw attack to further deteriorate the concrete. Figure 1.1 displays a crack formed from ASR in a concrete footing exposed to outdoor conditions in

  3. Reaction associated with a silicone rubber gel: an experimental study.

    PubMed

    Rigdon, R H; Dricks, A

    1975-11-01

    A blend of Silastic 382 (Room Temperature Vulcanizing, RTV) Medical Grade silicone oil and a catalyst was prepared in vitro, in both the catalyzed and noncatalyzed state, and injected subcutaneously in mice, rats, and rabbits. When properly blended, this catalyzed material, referred to as "silicone gel," formed a soft rubbery mass that remained at the site of injection. Properly catalyzed silicone rubber gel produces no macroscopic inflammatory reaction, attracts few polymorphonuclear leucocytes, and after 5-6 days a thin fibrous capsule begins to form aroung the gel. No degeneration of the silicone gel was observed during the 62 days of this experiment. Additional rats with this silicone gel have been under observation for 8 months and clinically have shown no changes in the local mass of silicone. If the catalyst is partly oxidized when added to the silicone fluid, the degree of gelling is much less. A local mass usually forms at the site of injection with some of the fluid diffusing into the tissue, forming minute cysts. The inflammatory reaciton is characterized by polymorphonuclear leucocytes, associated with many macrophages and giant cells phagocytizing oil droplets and particles of the diatomaceous earth. The pathogenesis of the inflammatory reaction is discussed, referring to the ionic change and the emigration of polymorphonuclear leucocytes to particles of plastics embedded in tissue.

  4. Cloning of DNA fragments: ligation reactions in agarose gel.

    PubMed

    Furtado, Agnelo

    2014-01-01

    Ligation reactions to ligate a desired DNA fragment into a vector can be challenging to beginners and especially if the amount of the insert is limiting. Although additives known as crowding agents, such as PEG 8000, added to the ligation mixes can increase the success one has with ligation reactions, in practice the amount of insert used in the ligation can determine the success or the failure of the ligation reaction. The method described here, which uses insert DNA in gel slice added directly into the ligation reaction, has two benefits: (a) using agarose as the crowding agent and (b) reducing steps of insert purification. The use of rapid ligation buffer and incubation of the ligation reaction at room temperature greatly increase the efficiency of the ligation reaction even for blunt-ended ligation.

  5. Miscible viscous fingering involving production of gel by chemical reactions

    NASA Astrophysics Data System (ADS)

    Nagatsu, Yuichiro; Hoshino, Kenichi

    2015-11-01

    We have experimentally investigated miscible viscous fingering with chemical reactions producing gel. Here, two systems were employed. In one system, sodium polyacrylate (SPA) solution and aluminum ion (Al3 +) solution were used as the more and less viscous liquids, respectively. In another system, SPA solution and ferric ion (Fe3 +) solution were used as the more and less viscous liquids, respectively. In the case of Al3 +, displacement efficiency was smaller than that in the non-reactive case, whereas in the case of Fe3 +, the displacement efficiency was larger. We consider that the difference in change of the patterns in the two systems will be caused by the difference in the properties of the gels. Therefore, we have measured the rheological properties of the gels by means of a rheometer. We discuss relationship between the VF patterns and the rheological measurement.

  6. Effect of exposure conditions on the long-term dielectric properties of mortar samples containing ASR gel

    NASA Astrophysics Data System (ADS)

    Hashemi, A.; Donnell, K. M.; Zoughi, R.; Rashidi, M.; Kurtis, K. E.

    2017-02-01

    Alkali-silica reaction (ASR) is a chemical reaction between alkalis present in portland cement and amorphous or otherwise disordered siliceous minerals in particular aggregates. Through this reaction, reactive silica binds with hydroxyl and alkali ions and forms a gel, known as ASR gel. Recently, microwave materials characterization techniques have shown great potential for detecting ASR in mortar. However, the comprehensive understanding of variables that affect the extent of ASR in mortar and their interaction with microwave signals, in particular the effect of environmental exposure conditions requires more investigations. Therefore, parameters related to these conditions must be considered when using microwave techniques for ASR detection and evaluation. In this paper, the effect of exposure conditions on ASR gel formation and microwave dielectric properties of mortar samples is investigated. To this end, extended measurements of the complex dielectric constants of three different sets of mortar samples are presented at S-band (2.6 - 3.95 GHz). The samples were cast with potentially reactive ASR-aggregates and subjected to different environmental conditions. The results show slightly different permittivities for the differently stored samples, potentially indicating different amount of ASR gel. This observation was corroborated through UV fluorescence microscopy, where different amounts of ASR gel were observed in the samples. Moreover, the results indicate that ASR gel evolution may be better tracked through loss factor measurements, while pre-existing-gel may be better detected through permittivity measurements.

  7. Effects of lithium salts on ASR gel composition and expansion of mortars

    SciTech Connect

    Kawamura, Mitsunori; Fuwa, Hirohito

    2003-06-01

    Suppression of alkali-silica reaction (ASR) expansion in mortar and concrete by the addition of lithium salts has been confirmed by some workers. It has been revealed that lithium hydroxide tended to reduce the reaction between sodium or potassium hydroxide and reactive silica, and that the ASR gel incorporating lithium was less expansive. However, it has not been reported how the addition of a lithium salt influenced the composition of the ASR gel. The calcium in ASR gel is considered to play an important role in the expansion of the gel. Thus, it is significant to characterize ASR gel composition in mortars containing lithium salts by BSE-EDS analysis. This study aims to discuss the mechanisms of suppression of ASR expansion in mortar by lithium salts from the viewpoint of ASR gel composition. The average CaO/SiO{sub 2} ratio in ASR gels decreased with increasing amount of added lithium salts. It should be noted that the extent of variations in the CaO/SiO{sub 2} ratio in ASR gels significantly decreased with increasing amount of lithium salts. The addition of relatively small amounts of LiOH and Li{sub 2}CO{sub 3} resulted in increased expansion. We also obtained an unexpected result that ASR gels became homogeneous with respect to their CaO contents at high dosage levels. However, the reduction in average CaO/SiO{sub 2} ratios and the homogenization in the CaO content of ASR gels due to the addition of lithium salts may not be related to the expansion of mortars.

  8. Switching the BZ reaction with a strong-acid-free gel.

    PubMed

    Hara, Yusuke; Yamaguchi, Yoshinori; Mayama, Hiroyuki

    2014-01-16

    In the present study, a novel gel with a semi-interpenetrating polymer network (semi-IPN) that undergo the Belousov-Zhabotinsky (BZ) reaction without the addition of a strong acid (HNO3 or H2SO4) was developed. The required concentrations of the BZ substrates, sodium bromate (NaBrO3) and malonic acid (MA), under these conditions were higher than under the normal BZ reaction conditions, involving the addition of a strong acid. The period of the BZ reaction with the novel gel (semi-IPN BZ gel) decreased with increasing concentrations of NaBrO3 and MA. Moreover, the connection of the semi-IPN BZ gel to a conventional BZ gel facilitated the reaction in the latter through the propagation of the intermediates from the former to the latter. The BZ reaction stopped when the conventional BZ gel was disconnected from the semi-IPN BZ gel. These results demonstrate that the BZ reaction in the conventional BZ gel underwent on-off switching, controlled by its attachment to the semi-IPN BZ gel. This on-off switching mechanism would be valuable in controlling actuators and robots without strong acids.

  9. Chemomechanical oscillations in a responsive gel induced by an autocatalytic reaction

    SciTech Connect

    Li, Kai; Wu, Peiyi; Cai, Shengqiang

    2014-07-28

    In this article, we investigate dynamic behaviors of a gel layer attached to a rigid substrate and submerged in a continuous stirred tank reactor. With a continuous feed of fresh reactants in the reactor, the concentrations of reactants stay constant on the surface of the gel layer. However, the concentrations of reactants inside the gel are inhomogeneous and vary with time, which are determined by the diffusion and chemical reactions of the reactants. Additionally, both monotonic and oscillatory swelling-shrinking dynamics are predicted in the gel if the swelling capability of the gel depends on the concentration of a reactant. Based on autocatalytic reaction, kinetic model, and nonequilibrium thermodynamic theory of gels, in this article, we investigate the effect of the thickness of the gel layer, lateral prestretches in the gel and the initial concentrations of reactants in the gel on its dynamic behaviors. We have also calculated the evolution of the swelling force that the gel layer exerts on its constrained substrate. The results of this article may find potential applications in using responsive gels to make chemo-mechanical sensors, actuators, biomimetic devices, and even drug delivery systems.

  10. Silica gel-promoted tandem addition-cyclization reactions of 2-alkynylbenzenamines with isothiocyanates.

    PubMed

    Ding, Qiuping; Cao, Banpeng; Zong, Zhenzhen; Peng, Yiyuan

    2010-05-10

    Tandem addition-cyclization reactions of 2-alkynylbenzenamines with isothiocyanates promoted by silica gel are described. This reaction proceeds smoothly at 80 degrees C under metal- and solvent-free conditions, which provides an efficient and practical route for the generation of 2,4-dihydro-1H-benzo[d][1,3]thiazines. The recovered silica gel could be reused for several times.

  11. Double diffusion in gel reactions with antigens insoluble in aqueous media.

    PubMed

    Milgrom, Felix; Loza, Ulana; Czechowski, Donna

    2004-08-01

    Ethanol-soluble, but saline-insoluble antigens were prepared as saline suspensions and studied in double diffusion reactions in a soft agarose gel. Positive reactions were observed with syphilis and SLE sera tested against the Kahn antigen as well as against commercial cardiolipin reagents. Also, ethanol-soluble brain antigen was studied for organ-specific reactions with rabbit immune sera. It was shown that double diffusion in gel can be employed as an analytical procedure for studies on reactions of saline suspensions of ethanol-soluble antigens.

  12. Periodic reciprocating motion of a polymer gel on an aqueous phase synchronized with the Belousov-Zhabotinsky reaction.

    PubMed

    Nakata, Satoshi; Yoshii, Miyu; Suzuki, Seiichi; Yoshida, Ryo

    2014-01-21

    A self-oscillating gel induced by the Belousov-Zhabotinsky (BZ) reaction was investigated on an aqueous phase. When the Ru-catalyst in the gel was rapidly oxidized, the gel was accelerated in a direction opposite to the side of oxidation. The gel then returned to its original position while the Ru-catalyst in the gel was slowly reduced. To clarify the mechanism of this periodic reciprocation of the gel, the contact angle between a sessile bubble and the gel and the time-variation of the adhesive force of the gel on the aqueous phase were measured. The experimental results suggest that the periodic reciprocation of the gel is driven by the periodic change in the contact angle of the gel induced by the BZ reaction.

  13. Polymerase chain reaction amplification products separated on rehydratable polyacrylamide gels and stained with silver.

    PubMed

    Allen, R C; Graves, G; Budowle, B

    1989-01-01

    Separation of polymerase chain reaction (PCR) amplification of specific fragment length polymorphisms was carried out on rehydratable polyacrylamide gels on a horizontal flat slab system. A discontinuous sulfate-borate buffer system was employed on 5-8% T gels crosslinked with 3.5% C. Samples were diluted in leading sulfate ion buffer at 1/10 the ionic strength of the separating gel buffer and placed directly onto the surface of the rehydrated gels in 0.5-10 microliters volumes. The trailing ion and counterion were contained in a gel plug and placed directly onto the anodal and cathodal ends of the gel, and the electrodes placed directly onto the surface of the gel plugs. Filter paper wicks, soaked in diluted leading ion buffer, were placed along each side to lower the ionic strength of the edges, thereby increasing mobility at the edge and thus preventing smile effects. The gel-gel contact of the plug and separating gel prevent the production of a junction potential which occurs between dissimilar materials such as a paper wick and the gel. Ten- to 20-cm separations were carried out from 2-5 h, respectively, and resolution in the 20 cm system was 1.6-4 bp (base pairs) between 100 and 500 bp, 4-7 bp between 500 and 1000 bp, 12-20 bp between 1000 and 2000 bp and about 50 bp between 2000 and 3000 bp. Between 3000 and 4000 bp, resolution fell off to +/- 100 bp. Sensitivity, using a silver stain, indicated that one could readily distinguish less than 10 pg of DNA per mm width on the gels.(ABSTRACT TRUNCATED AT 250 WORDS)

  14. Characterization of the Rheological and Swelling Properties of Synthetic Alkali Silicate Gels in Order to Predict Their Behavior in ASR Damaged Concrete

    NASA Astrophysics Data System (ADS)

    Vayghan, Asghar Gholizadeh

    Alkali-silica reaction (ASR) is a major concrete durability concern that is responsible for the deterioration of concrete infrastructure in the world. The resultant of the reaction between the cement alkali hydroxides and the metastable silicates in the aggregates is a hygroscopic and expansive alkali-silicate gel (referred to as ASR gel in this document). The swelling behavior of ASR gels determines the extent of damage to concrete structures and, as such, mitigation of ASR relies on understanding these gels and finding ways to prevent them either from formation, or from swelling after formation. This dissertation focuses on the synthesis and characterization of ASR gels with wide ranges of compositions similar to what has been reported for the filed ASR gels in the literature. The experimental work consisted of three phases as follow. Phase I: Investigation of rheology, chemistry and physics of ASR gels produced through sol-method. Inspired from the existing literature, two sol-gel methods have been developed for the synthesis of ASR gels. The rheological (primarily gelation time, yield stress, and equilibrium stress), chemical (pore solution pH, pore solution composition, osmotic pressure, solid phase composition, stoichiometry of gelation reactions) and physical (evaporable water, solid content, etc.) properties of synthetic ASR gels have been extensively investigated in this phase. Ca/Si, Na/Si and K/Si, and water content were considered as the main chemical composition variables. In order to investigate the suppressing effects of lithium on the swelling properties of ASR gels, the gels were added with lithium in a part of the experimental program. The results strongly suggested that Ca/Si has a positive effect on the yield stress of the gels and their rate of gelation. Na/Si was found to have a decreasing effect on the yield stress and gelation rate (especially at low Ca/Si levels). K/Si and Li/Si had second-order (i.e., polynomial) effects on the yield

  15. Effect of two-step sol-gel reaction on the mesoporous silica structure.

    PubMed

    Choi, Dae-Geun; Yang, Seung-Man

    2003-05-01

    In the present study, we investigated the effects of two-step sol-gel reaction by abrupt pH change on the SBA-15 and mesocellular silica foams (MCF). Mesoporous silica was fabricated by using triblock copolymer templates (poly(ethylene oxide) and poly(propylene oxide)). The prepared silica structure was characterized by X-ray diffraction, transmission electron microscopy, and N(2) sorption experiment. Specifically, we prepared SBA-15 with long-range two-dimensional hexagonal arrangement of 3 to 6-nm feature spacing and MCF with larger pores of a few tens of nanometers. The pore size and ordering were influenced by pH change in a two-step sol-gel reaction and the concentration of organic solvent. Although well-ordered hexagonal arrangement of mesopores was prevalent in acidic conditions, the materials synthesized by a single-step reaction in neutral or basic conditions possessed gel-like structure without mesopores. However, the present two-step reaction (low pH sol-gel reaction followed by high pH reaction) not only produced mesoporous materials but also provided controllability of the pore size. In particular, mesoporous structures with pore sizes as large as those of MCF were successfully fabricated by the two-step reaction without using organic swelling agents. As expected, when xylene was added as a swelling agent, the pore size increased with the xylene/copolymer weight ratio.

  16. Study of the racemization observed in the amide bond forming reaction on silica gel.

    PubMed

    Norick, Amanda L; Li, Tingyu

    2005-01-01

    Racemization resulting from the coupling of N-(3,5-dinitrobenzoyl)-L-leucine and 3-aminopropyl silica gel with several amide-coupling reagents is further investigated in order to explain the much higher degree of racemization on silica gel, as compared with the similar reaction in solution. Based on experiments using different types of solid supports, limited pore access and surface microchemical environment are ruled out as the possible reason for the higher degree of racemization that occurred on silica gel. Steric hindrance of the solid support is thought to have caused the amino group to be more basic relative to its nucleophilicity, leading to a higher degree of racemization.

  17. Effects of degree of hydrolysis and shear on gelation reaction kinetics and gel strength. [Polyacrylamides

    SciTech Connect

    Gao, Hong W.

    1991-02-01

    Gelation tests were conducted to investigate the effect of the degree of hydrolysis on gelation reaction kinetics and gel strength using four low-molecular-weight polyacrylamides (MW = 400,000 daltons), which were 10% (HPAM1-10), 20% (HPAM1-20), 30% (HAPM1-30), and 40% (HPAM-40) hydrolyzed, and Cr-3 (pH = 4.8) and Al-3 (pH = 7.0) crosslinkers. Results showed that for polymer/Cr-3 gel systems, samples prepared with a low-molecular-weight polyacrylamide polymer, which was 20% hydrolyzed, gelled at a faster rate and retained higher gel strength than those prepared with a low-molecular-weight polyacrylamide polymer, which was 10% hydrolyzed. Under the screening condition, no viscosity enhancement was observed in samples prepared with polymers having a degree of hydrolysis equal to or greater than 30%. For polymer/Al-3 gel systems, samples prepared with a low-molecular-weight polyacrylamide polymer, which was 20% hydrolyzed, gelled at the fastest rate and retained the strongest gel strength among the polymer/Al-3 gel systems prepared with four low-molecular-weight polyacrylamide polymers, which were 10, 20, 30, and 40% hydrolyzed, respectively. Gelation tests of gel systems in glass bead packs showed that high shear favored the gelation of a gel system that had a fast rate of gelation, but had an adverse effect on the gelation of three gel systems that had a slow rate of gelation. Weak gels were found to be injectable through porous media. Weak gels were degradable under high shear condition and regained viscosity under low shear conditions. 17 refs., 8 figs., 1 tab.

  18. Self-oscillating gels driven by the Belousov-Zhabotinsky reaction as novel smart materials.

    PubMed

    Yoshida, Ryo

    2010-08-17

    So far stimuli-responsive polymer gels and their application to smart materials have been widely studied; this research has contributed to progress in gel science and engineering. For their development as a novel biomimetic polymer, studies of polymers with an autonomous self-oscillating function have been carried out since the first reports in 1996. The development of novel self-oscillating polymers and gels have been successful utilizing the oscillating reaction, called the Belousov-Zhabotinsky (BZ) reaction, which is recognized as a chemical model for understanding several autonomous phenomena in biological systems. The self-oscillating polymer is composed of a poly(N-isopropylacrylamide) network in which the catalyst for the BZ reaction is covalently immobilized. In the presence of the reactants, the polymer undergoes spontaneous cyclic soluble-insoluble changes or swelling-deswelling changes (in the case of gel) without any on-off switching of external stimuli. Potential applications of the self-socillating polymers and gels include several kinds of functional material systems, such as biomimetic actuators and mass transport surface.

  19. Three-dimensional model for chemoresponsive polymer gels undergoing the Belousov-Zhabotinsky reaction.

    PubMed

    Kuksenok, Olga; Yashin, Victor V; Balazs, Anna C

    2008-10-01

    We develop a computational model to capture the complex, three-dimensional behavior of chemoresponsive polymer gels undergoing the Belousov-Zhabotinsky reaction. The model combines components of the finite difference and finite element techniques and is an extension of the two-dimensional gel lattice spring model recently developed by two of us [V. V. Yashin and A. C. Balazs, J. Chem. Phys. 126, 124707 (2007)]. Using this model, we undertake the first three-dimensional (3D) computational studies of the dynamical behavior of chemoresponsive BZ gels. For sufficiently large sample sizes and a finite range of reaction parameters, we observe regular and nonregular oscillations in both the size and shape of the sample that are coupled to the chemical oscillations. Additionally, we determine the critical values of these reaction parameters at the transition points between the different types of observed behavior. We also show that the dynamics of the chemoresponsive gels drastically depends on the boundary conditions at the surface of the sample. This 3D computational model could provide an effective tool for designing gel-based, responsive systems.

  20. Effects of gel properties produced by chemical reactions on viscous fingering

    NASA Astrophysics Data System (ADS)

    Ujiie, Tomohiro; Nagatsu, Yuichiro; Ban, Mitsumasa; Iwata, Shuichi; Kato, Yoshihito; Tada, Yutaka

    2011-11-01

    We have experimentally investigated viscous fingering with chemical reaction producing gel. Here, two systems were employed. In one system, sodium polyacrylate (SPA) solution and ferric ion solution were used as the more and less viscous liquids, respectively. In another system, xthantan gum (XG) solution and the ferric ion solution were used as the more and less viscous liquids, respectively. For high concentration of ferric ion, viscous fingering pattern was changed into spiral pattern in the former system, whereas into fracture pattern in the latter system. We consider that the difference in the change of the patterns in the two systems will be caused by the difference in the properties of the gels. Therefore, we have measured the rheological properties of the gels by means of a rheometer. We have found that the gel in the former case is more elastic. Furthermore, we have discussed the relationship between the measured rheological properties and the observed spiral or fracturing patterns.

  1. Reactions driving conformational movements (molecular motors) in gels: conformational and structural chemical kinetics.

    PubMed

    Otero, Toribio F

    2017-01-18

    In this perspective the empirical kinetics of conducting polymers exchanging anions and solvent during electrochemical reactions to get dense reactive gels is reviewed. The reaction drives conformational movements of the chains (molecular motors), exchange of ions and solvent with the electrolyte and structural (relaxation, swelling, shrinking and compaction) gel changes. Reaction-driven structural changes are identified and quantified from electrochemical responses. The empirical reaction activation energy (Ea), the reaction coefficient (k) and the reaction orders (α and β) change as a function of the conformational energy variation during the reaction. This conformational energy becomes an empirical magnitude. Ea, k, α and β include and provide quantitative conformational and structural information. The chemical kinetics becomes structural chemical kinetics (SCK) for reactions driving conformational movements of the reactants. The electrochemically stimulated conformational relaxation model describes empirical results and some results from the literature for biochemical reactions. In parallel the development of an emerging technological world of soft, wet, multifunctional and biomimetic tools and anthropomorphic robots driven by reactions of the constitutive material, as in biological organs, can be now envisaged being theoretically supported by the kinetic model.

  2. Controlling thermo-reversibility of gelatin gels through a peroxidase-catalyzed reaction under mild conditions for mammalian cells.

    PubMed

    Sakai, Shinji; Moriyama, Kousuke; Kawakami, Koei

    2011-01-01

    A variety of cross-linking methods is used for obtaining gelatin gels having a tolerance to thermo-reversible gel-sol transition at physiological temperature. In this paper, we investigated the applicability of horseradish peroxidase-catalyzed cross-linking of tyrosine residues originally contained in native gelatin molecules for preparing such gelatin gels. The gelatin gels obtained through exposure to the enzymatic reaction showed a higher resistance to thermo-reversibility at 37°C than gels obtained through a thermally-induced gelation alone. In addition, the resistance property to thermo-reversible gel-sol transition was tunable by controlling enzymatic reaction conditions: higher peroxidase concentration and thermally-induced pre-gelation accomplished by cooling the gelatin solution prior to the enzymatic reaction produced gels with higher resistance to thermo-reversibility. Fibroblast cells enclosed in the gelatin gels obtained through the enzymatic reaction with thermally-induced pre-gelation showed 93% viability. These results demonstrate the feasibility of peroxidase-catalyzed reaction for obtaining gelatin gels having a tolerance to thermo-reversible gel-to-sol transition at physiological temperature toward applications in biomedical and biopharmaceutical fields.

  3. Suppression of viscous fingering instability by a chemical reaction producing gel

    NASA Astrophysics Data System (ADS)

    Nagatsu, Yuichiro; Kanbara, Toshizo; Taniguchi, Masafumi

    2016-11-01

    Viscous fingering (VF) is a well-known hydrodynamic instability which is observed when a more viscous fluid is displaced by another less viscous one in porous media or Hele-Shaw cell. In such a situation, the interface between two fluids formed finger-like patterns. Recently, several techniques for suppress VF instability has been developed, which include time-dependent injection, addition of permeability gradient, and use of viscoelastic plates of Hele-Shaw cell. Here, we demonstrate our trial to suppress VF by chemical reaction producing gel. We have succeeded to find a system of solutions and reaction in which the reaction producing a gel is able to completely suppress VF. In addition, we have performed rheological measurement of the gel produced at the reactive interface. The VF experiment and the rheological measurement have been performed by varying concentrations of the reactants. We show the storage modulus (G') of the gel, which corresponds to elastic response to small amplitude oscillatory shear, is responsible for the ability of suppression of VF in the present reactive system.

  4. Spiral pattern in a radial displacement involving a reaction-producing gel

    NASA Astrophysics Data System (ADS)

    Nagatsu, Yuichiro; Hayashi, Atsushi; Ban, Mitsumasa; Kato, Yoshihito; Tada, Yutaka

    2008-08-01

    We have shown experimentally that the pattern created by the displacement of a more viscous fluid by a less viscous one in a radial Hele-Shaw cell develops not radially but spirally when a more viscous sodium polyacrylate solution is displaced by a less viscous trivalent iron ion (Fe3+) solution with a sufficiently high concentration of Fe3+ . Another experiment revealed that an instantaneous chemical reaction takes place between the two fluids, and at high Fe3+ concentrations it produces a film of the gel at the contact plane. The gel film is proposed to be responsible for the spiral pattern.

  5. Spatial confinement controls self-oscillations in polymer gels undergoing the Belousov-Zhabotinsky reaction.

    PubMed

    Kuksenok, Olga; Yashin, Victor V; Balazs, Anna C

    2009-11-01

    Chemoresponsive gels undergoing the Belousov-Zhabotinsky (BZ) reaction exhibit self-sustained pulsations, which can be harnessed to perform mechanical work. In technological applications, the gels would typically be confined between hard surfaces and thus, it is essential to establish how confinement affects these distinctive oscillations. Using theory and simulation, we pinpoint regions in phase space where the dynamic behavior of BZ gels critically depends on the presence of confining walls. We then illustrate how the wave propagation within thin samples can be tailored by selectively introducing "cut outs" in the bounding surfaces. The oscillations in the latter films are localized in specified areas, so the system contains well-defined oscillatory and nonoscillatory regions. The cut outs provide an effective means of tuning the mechanical action within the film and provide a route for tailoring the functionality of the material.

  6. Knoevenagel reaction in water catalyzed by amine supported on silica gel.

    PubMed

    Isobe, Kohei; Hoshi, Takashi; Suzuki, Toshio; Hagiwara, Hisahiro

    2005-01-01

    An environmentally benign and sustainable Knoevenagel reaction of aldehyde with ethyl cyanoacetate has been achieved at ambient temperature in water employing 3-aminopropylated silica gel (NAP) as a catalyst. Wide applicability of the reaction is illustrated by the results that not only arylaldehydes of both electronic characters but also aliphatic aldehydes afforded the products. The reaction condition was so mild that aldehydes having acid- or base-sensitive substituents provided substituted alpha-cyano-alpha, beta-unsaturated esters. The catalyst has been efficiently recycled more than five times without any pre-treatment. Catalyst loading was successfully reduced to 0.0029 mmol% (TON = up to 9,226). This protocol was also applicable to the Knoevenagel reaction of malononitrile in good yields in water.

  7. Does crystal or gel matter to stereochemistry of a reaction? Silver complexation-promoted solid-state [2+2] reaction of an unsymmetrical olefin.

    PubMed

    Samai, Suman; Ghosh, Prabir; Biradha, Kumar

    2013-05-14

    Head-to-tail and head-to-head [2+2] photodimerization of an unsymmetrical olefin containing benzimidazole and pyridyl groups was achieved by irradiating Ag(I) complexed olefin in crystalline state and gel state, respectively, in stereoselective manner. The [2+2] reaction indicates that the molecular arrangement in a gel is different from that of a xerogel.

  8. Model creation of moving redox reaction boundary in agarose gel electrophoresis by traditional potassium permanganate method.

    PubMed

    Xie, Hai-Yang; Liu, Qian; Li, Jia-Hao; Fan, Liu-Yin; Cao, Cheng-Xi

    2013-02-21

    A novel moving redox reaction boundary (MRRB) model was developed for studying electrophoretic behaviors of analytes involving redox reaction on the principle of moving reaction boundary (MRB). Traditional potassium permanganate method was used to create the boundary model in agarose gel electrophoresis because of the rapid reaction rate associated with MnO(4)(-) ions and Fe(2+) ions. MRB velocity equation was proposed to describe the general functional relationship between velocity of moving redox reaction boundary (V(MRRB)) and concentration of reactant, and can be extrapolated to similar MRB techniques. Parameters affecting the redox reaction boundary were investigated in detail. Under the selected conditions, good linear relationship between boundary movement distance and time were obtained. The potential application of MRRB in electromigration redox reaction titration was performed in two different concentration levels. The precision of the V(MRRB) was studied and the relative standard deviations were below 8.1%, illustrating the good repeatability achieved in this experiment. The proposed MRRB model enriches the MRB theory and also provides a feasible realization of manual control of redox reaction process in electrophoretic analysis.

  9. Acemannan-containing wound dressing gel reduces radiation-induced skin reactions in C3H mice

    SciTech Connect

    Roberts, D.B.; Travis, E.L.

    1995-07-15

    To determine (a) whether a wound dressing gel that contains acemannan extracted from aloe leaves affects the severity of radiation-induced acute skin reactions in C3H mice; (b) if so, whether other commercially available gels such as a personal lubricating jelly and a healing ointment have similar effects; and (c) when the wound dressing gel should be applied for maximum effect. Male C3H mice received graded single doses of gamma radiation ranging from 30 to 47.5 Gy to the right leg. In most experiments, the gel was applied daily beginning immediately after irradiation. Dose-response curves were obtained by plotting the percentage of mice that reached or exceeded a given peak skin reaction as a function of dose. Curves were fitted by logit analysis and ED{sub 50} values, and 95% confidence limits were obtained. The average peak skin reactions of the wound dressing gel-treated mice were lower than those of the untreated mice at all radiation doses tested. The ED{sub 50} values for skin reactions of 2.0-2.75 were approximately 7 Gy higher in the wound dressing gel-treated mice. The average peak skin reactions and the ED{sub 50} values for mice treated with personal lubricating jelly or healing ointment were similar to irradiated control values. Reduction in the percentage of mice with skin reactions of 2.5 or more was greatest in the groups that received wound dressing gel for at least 2 weeks beginning immediately after irradiation. There was no effect if gel was applied only before irradiation or beginning 1 week after irradiation. Wound dressing gel, but not personal lubricating jelly or healing ointment, reduces acute radiation-induced skin reactions in C3H mice if applied daily for at least 2 weeks beginning immediately after irradiation. 31 refs., 4 figs., 1 tab.

  10. Modified lignin: Preparation and use in reversible gel via Diels-Alder reaction.

    PubMed

    Zhou, Wanpeng; Zhang, Hui; Chen, Fangeng

    2017-09-18

    In this study, popular soda lignin was modified with either furan or maleimide ring, and the modified lignins were subjected to reversible Diels-Alder reaction. A new process was proposed to prepare the functionalized lignin. A long chain was introduced to the hydroxyl groups of lignin, and then either the furan or maleimide ring was added to the other end of the chain. The test results confirmed that either the furan ring or the maleimide ring was bound to lignin. Furan- and maleimide-functionalized lignins were also combined to generate crosslinking via Diels-Alder [4+2] cycloaddition reaction. Under appropriate conditions, the formation of a gel was identified, which reverted to liquid state after retro Diels-Alder reaction upon heating at 120°C. This study reveals the significant versatility and potential of the developed strategy for the utilization of lignin-based recyclable networks. Copyright © 2017. Published by Elsevier B.V.

  11. Structural Modification of Sol-Gel Materials through Retro Diels-Alder Reaction

    SciTech Connect

    SHALTOUT,RAAFAT M.; LOY,DOUGLAS A.; MCCLAIN,MARK D.; PRABAKAR,SHESHASAYANA; GREAVES,JOHN; SHEA,KENNETH J.

    1999-12-08

    Hydrolysis and condensation of organically bridged bis-triethoxysilanes, (EtO){sub 3}Si-R-Si(OEt){sub 3}, results in the formation of three dimensional organic/inorganic hybrid networks (Equation 1). Properties of these materials, including porosity, are dependent on the nature of the bridging group, R. Flexible groups (akylene-spacers longer than five carbons in length) polymerize under acidic conditions to give non-porous materials. Rigid groups (such as arylene-, alkynylene-, or alkenylene) form non-porous, microporous, and macroporous gels. In many cases the pore size distributions are quite narrow. One of the motivations for preparing hybrid organic-inorganic materials is to extend the range of properties available with sol-gel systems by incorporating organic groups into the inorganic network. For example, organically modified silica gels arc either prepared by co-polymerizing an organoalkoxysilane with a silica precursor or surface silylating the inorganic gel. This can serve to increase hydrophobicity or to introduce some reactive organic functionality. However, the type and orientation of these organic functionalities is difficult to control. Furthermore, many organoalkoxysilanes can act to inhibitor even prevent gelation, limiting the final density of organic functionalities. We have devised a new route for preparing highly functionalized pores in hybrid materials using bridging groups that are thermally converted into the desired functionalities after the gel has been obtained. In this paper, we present the preparation and characterization of bridged polysilsesquioxanes with Diels-Alder adducts as the bridging groups from the sol-gel polymerization of monomers 2 and 4. The bridging groups are constructed such that the retro Diela-Alder reaction releases the dienes and leaves the dienophiles as integral parts of the network polymers. In the rigid architecture of a xerogel, this loss of organic functionality should liberate sufficient space to modify the

  12. Chemistry of the silica surface: liquid-solid reactions of silica gel with trimethylaluminum.

    PubMed

    Li, Jianhua; DiVerdi, Joseph A; Maciel, Gary E

    2006-12-27

    The reaction of trimethylaluminum and dry, high-surface-area (500 m2/g) silica gel in a mixed slurry was studied using multinuclear, solid-state NMR spectroscopy. The products of the initial reaction were characterized, and their progress through subsequent washing with diethyl ether and reactions with measured amounts of water was followed. The quantitative distribution of different chemical forms of carbon deposited on the silica surface by the initial reaction was measured. The products of the initial reaction are dominated by methyl species of the types Al(CH3)n (with Si-O-Al linkages), Si-O-CH3, and (Si-O)4-nSi(CH3)n; aluminum is seen to exist predominantly as a five-coordinate species. Subsequent treatment with diethyl ether fails to remove any surface species, but instead the ether becomes strongly associated with the surface and highly resistant to removal. Stepwise additions of water hydrolyze the Al-CH3 and Si-O-CH3 moieties, leading to conversion of five-coordinate aluminum to four- and six-coordinate aluminum, and affect the partial release of the surface-associated diethyl ether; Si-CH3 moieties remain. The effect of aromatic and saturated solvents on the initial reaction was examined and found to cause a small but significant change in the distribution of products. Structures of aluminum-centered species on the silica surface consistent with the spectroscopic data are proposed.

  13. The Use of Gel Electrophoresis to Study the Reactions of Activated Amino Acids with Oligonucleotides

    NASA Technical Reports Server (NTRS)

    Zieboll, Gerhard; Orgel, Leslie E.

    1994-01-01

    We have used gel electrophoresis to study the primary covalent addition of amino acids to oligonu-cleotides or their analogs and the subsequent addition of further molecules of the amino acids to generate peptides covalently linked to the oligonucleotides. We have surveyed the reactions of a variety of amino acids with the phosphoramidates derived from oligonucleotide 5 inches phosphates and ethylenediamine. We find that arginine and amino acids can interact with oligonucleotidesl through stacking interactions react most efficiently. D- and L-amino acids give indistinguishable families of products.

  14. The Use of Gel Electrophoresis to Study the Reactions of Activated Amino Acids with Oligonucleotides

    NASA Technical Reports Server (NTRS)

    Zieboll, Gerhard; Orgel, Leslie E.

    1994-01-01

    We have used gel electrophoresis to study the primary covalent addition of amino acids to oligonu-cleotides or their analogs and the subsequent addition of further molecules of the amino acids to generate peptides covalently linked to the oligonucleotides. We have surveyed the reactions of a variety of amino acids with the phosphoramidates derived from oligonucleotide 5 inches phosphates and ethylenediamine. We find that arginine and amino acids can interact with oligonucleotidesl through stacking interactions react most efficiently. D- and L-amino acids give indistinguishable families of products.

  15. An Inexpensive Gel Electrophoresis-Based Polymerase Chain Reaction Method for Quantifying mRNA Levels

    PubMed Central

    2005-01-01

    In order to engage their students in a core methodology of the new genomics era, an ever-increasing number of faculty at primarily undergraduate institutions are gaining access to microarray technology. Their students are conducting successful microarray experiments designed to address a variety of interesting questions. A next step in these teaching and research laboratory projects is often validation of the microarray data for individual selected genes. In the research community, this usually involves the use of real-time polymerase chain reaction (PCR), a technology that requires instrumentation and reagents that are prohibitively expensive for most undergraduate institutions. The results of a survey of faculty teaching undergraduates in classroom and research settings indicate a clear need for an alternative approach. We sought to develop an inexpensive and student-friendly gel electrophoresis-based PCR method for quantifying messenger RNA (mRNA) levels using undergraduate researchers as models for students in teaching and research laboratories. We compared the results for three selected genes measured by microarray analysis, real-time PCR, and the gel electrophoresis-based method. The data support the use of the gel electrophoresis-based method as an inexpensive, convenient, yet reliable alternative for quantifying mRNA levels in undergraduate laboratories. PMID:15917874

  16. Diffusion in cell-free and cell immobilising kappa-carrageenan gel beads with and without chemical reaction

    PubMed

    Mateus; Alves; da Fonseca MM

    1999-06-05

    Diffusion into and from kappa-carrageenan gel beads was studied, both in the absence and presence of bacterial cells, both with and without biochemical reaction. The solutes were indole, L-serine, and L-tryptophan. The reaction was that of indole and L-serine to give L-tryptophan. Established theory concerning diffusion of a single solute in cell-free gels was found to describe well the effect of the gel on diffusivity. Simultaneous diffusion of the three solutes resulted in lower diffusivities than those for individual solutes, suggesting the need to use multicomponent diffusion theory. The effect of cells on diffusion could only be accounted for by models assuming permeable cells. Diffusion with chemical reaction was reasonably well described by an effectiveness factor calculated using an effective diffusivity estimated from diffusion data without reaction. Copyright 1999 John Wiley & Sons, Inc.

  17. Acemannan-containing wound dressing gel reduces radiation-induced skin reactions in C3H mice.

    PubMed

    Roberts, D B; Travis, E L

    1995-07-15

    To determine (a) whether a wound dressing gel that contains acemannan extracted from aloe leaves affects the severity of radiation-induced acute skin reactions in C3H mice; (b) if so, whether other commercially available gels such as a personal lubricating jelly and a healing ointment have similar effects; and (c) when the wound dressing gel should be applied for maximum effect. Male C3H mice received graded single doses of gamma radiation ranging from 30 to 47.5 Gy to the right leg. In most experiments, the gel was applied daily beginning immediately after irradiation. To determine timing of application for best effect, gel was applied beginning on day -7, 0, or +7 relative to the day of irradiation (day 0) and continuing for 1, 2, 3, 4, or 5 weeks. The right inner thigh of each mouse was scored on a scale of 0 to 3.5 for severity of radiation reaction from the seventh to the 35th day after irradiation. Dose-response curves were obtained by plotting the percentage of mice that reached or exceeded a given peak skin reaction as a function of dose. Curves were fitted by logit analysis and ED50 values, and 95% confidence limits were obtained. The average peak skin reactions of the wound dressing gel-treated mice were lower than those of the untreated mice at all radiation doses tested. The ED50 values for skin reactions of 2.0-2.75 were approximately 7 Gy higher in the wound dressing gel-treated mice. The average peak skin reactions and the ED50 values for mice treated with personal lubricating jelly or healing ointment were similar to irradiated control values. Reduction in the percentage of mice with skin reactions of 2.5 or more was greatest in the groups that received wound dressing gel for at least 2 weeks beginning immediately after irradiation. There was no effect if gel was applied only before irradiation or beginning 1 week after irradiation. Wound dressing gel, but not personal lubricating jelly or healing ointment, reduces acute radiation-induced skin

  18. Novel Nano Boehmite prepared by Solvothermal reaction of aluminum hydroxide gel in Monoethanolamine

    NASA Astrophysics Data System (ADS)

    Ohta, Yasuhiro; Hayakawa, Tomokatsu; Inomata, Tomohiko; Ozawa, Tomohiro; Masuda, Hideki

    2017-07-01

    Solvothermal reaction of aluminum hydroxide gel (AHG) in monoethanolamine (MEA) was studied at several temperatures (100, 120, 150, and 200 °C) in several reaction times (2, 3, 4, 5, 6, and 13 h). The reaction product prepared at a low temperature of 120 °C in the reaction time more than 6 h gave a blue photoluminescence nanoboehmite intercalated with monoethanolamine derivatives (BM-MEA) in the colloidal solution, which showed a photoluminescence emission centered at 420 nm with an excitation of 360 nm. The powdery samples recovered from the reaction products were characterized by using elemental analysis, XRD analysis, IR spectroscopy, thermogravimetric (TG)-DTA, 13C and 27Al CP/MAS NMR spectroscopies, N2 gas adsorption/desorption isotherm, SEM and TEM images, and photoluminescence spectroscopy. The X-ray diffraction revealed that the basal space in BM-MEA was expanded from 0.61 to 1.2 nm by intercalation of MEA derivatives to boehmite, and the IR and 13C CP/MAS NMR spectra determined that the intercalated MEA derivatives are protonated- and carbamate-substituted MEAs, which are formed in the layers through a covalent bond with Al-OH groups on boehmite surface. The empirical formula of BM-MEA was estimated to be AlO(OH)0.82(OCH2CH2NH3 +)0.05(OCH2CH2NHCOO-)0.13 on the basis of the elemental TG-DTA and IR spectral analyses. We discuss the reaction mechanism of a unique blue photoluminescence BM-MEA formed by proceeding in CO2-H2O-alkanolamine system.

  19. Acrylate-silica polymer nanocomposites obtained by sol-gel reactions. Structure, properties and scaffold preparation

    NASA Astrophysics Data System (ADS)

    Rodriguez Hernandez, Jose Carlos

    The manuscript deals with the development and characterization of hybrid materials based on poly(hydroxyethyl acrylate) (hereafter PHEA) reinforced by the inclusion of an amorphous silica phase. Both phases were simultaneously synthesized: the organic phase underwent a free radical polymerization reaction induced by the small addition of a thermal initiator (benzoyl peroxide); besides, silica (SiO2) was polymerized by an acid catalyzed sol-gel reaction of the silicon alkoxide tetraethoxysilane (hereafter TEOS). The sol-gel reaction conditions where silicon dioxide is formed influence the final silica structure: degree of condensation, linear versus branched intermediate species, average size, and so on. Some of the key parameters to control SiO2 topology on sol-gel derived composites include the catalyst nature used to increase the alkoxide reactivity (as well as its amount, pH), the available water to hydrolyze the silica precursor (referred to the stoichiometric amount needed to fully hydrolyze one molecule of TEOS) and ratio between the organic and inorganic phases on the final hybrid. The former (catalyst) and the second (water) conditions were fixed so as to synthesize materials with silica average sizes around tens of nanometres (nanocomposites); the latter, the relative ratio between organic and inorganic phases, was systematically changed. Besides, it is introduced a methodology to prepare a new kind of scaffolds made by nanocomposites whose pore morphology consists of a cylindrical channel mesh, which are perpendicular between themselves. The procedure is based on the well-known method of intermediate templates, this time prepared by a stack of woven fabrics which are first pressed and afterwards sintered. After the filling of the holes left inside the template by the monomeric solution and subsequent thermal polymerization, templates are removed by the selective solvent of the material it is made up. A suitable template preparation is found to be crucial

  20. Alkali-aggregate reaction under the influence of deicing salts in the Hokuriku district, Japan

    SciTech Connect

    Katayama, Tetsuya . E-mail: katayamat@kge.co.jp; Tagami, Masahiko; Sarai, Yoshinori; Izumi, Satoshi; Hira, Toshikatsu

    2004-11-15

    Concrete cores taken from highway bridges and culverts undergoing alkali-silica reaction (ASR) were investigated petrographically by means of core scanning, point counting, polarizing microscopy, scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), electron-probe microanalysis with energy-dispersive spectrometry, in conjunction with wet chemical analyses and expansion tests. Field damage was roughly proportional to the content of andesite in the gravel aggregates due to the presence of highly reactive cristobalite and tridymite. Electron-probe microanalyzer analysis of unhydrated cement phases in the concrete revealed that the cement used had contained at least 0.5% to 1.0% alkali (Na{sub 2}Oeq) and that both the aggregates and the deicing salts had supplied part of the water-soluble alkali to concrete toward the threshold of producing ASR (Na{sub 2}O{sub eq} 3.0 kg/m{sup 3}). An accelerated concrete core expansion test (1 M NaOH, 80 deg. C) of the damaged structures mostly gave core expansions of >0.10% at 21 days (or >0.05% at 14 days), nearly comparable to those of a slow expansion test with saturated NaCl solution (50 deg. C, 91 days) which produced Cl-containing ASR gel.

  1. Rapid verification of candidate serological biomarkers using gel-based, label-free multiple reaction monitoring.

    PubMed

    Tang, Hsin-Yao; Beer, Lynn A; Barnhart, Kurt T; Speicher, David W

    2011-09-02

    Stable isotope dilution-multiple reaction monitoring-mass spectrometry (SID-MRM-MS) has emerged as a promising platform for verification of serological candidate biomarkers. However, cost and time needed to synthesize and evaluate stable isotope peptides, optimize spike-in assays, and generate standard curves quickly becomes unattractive when testing many candidate biomarkers. In this study, we demonstrate that label-free multiplexed MRM-MS coupled with major protein depletion and 1D gel separation is a time-efficient, cost-effective initial biomarker verification strategy requiring less than 100 μL of serum. Furthermore, SDS gel fractionation can resolve different molecular weight forms of targeted proteins with potential diagnostic value. Because fractionation is at the protein level, consistency of peptide quantitation profiles across fractions permits rapid detection of quantitation problems for specific peptides from a given protein. Despite the lack of internal standards, the entire workflow can be highly reproducible, and long-term reproducibility of relative protein abundance can be obtained using different mass spectrometers and LC methods with external reference standards. Quantitation down to ~200 pg/mL could be achieved using this workflow. Hence, the label-free GeLC-MRM workflow enables rapid, sensitive, and economical initial screening of large numbers of candidate biomarkers prior to setting up SID-MRM assays or immunoassays for the most promising candidate biomarkers.

  2. A tunable isoelectric focusing via moving reaction boundary for two-dimensional gel electrophoresis and proteomics.

    PubMed

    Guo, Chen-Gang; Shang, Zhi; Yan, Jian; Li, Si; Li, Guo-Qing; Liu, Rong-Zhong; Qing, Ying; Fan, Liu-Yin; Xiao, Hua; Cao, Cheng-Xi

    2015-05-01

    Routine native immobilized pH gradient isoelectric focusing (IPG-IEF) and two-dimensional gel electrophoresis (2DE) are still suffering from unfortunate reproducibility, poor resolution (caused by protein precipitation) and instability in characterization of intact protein isoforms and posttranslational modifications. Based on the concept of moving reaction boundary (MRB), we firstly proposed a tunable non-IPG-IEF system to address these issues. By choosing proper pairs of catholyte and anolyte, we could achieve desired cathodic and anodic migrating pH gradients in non-IPG-IEF system, effectively eliminating protein precipitation and uncertainty of quantitation existing in routine IEF and 2DE, and enhancing the resolution and sensitivity of IEF. Then, an adjustable 2DE system was developed by combining non-IPG-IEF with polyacrylamide gel electrophoresis (PAGE). The improved 2DE was evaluated by testing model proteins and colon cancer cell lysates. The experiments revealed that (i) a tunable pH gradient could be designed via MRB; (ii) up to 1.65 fold improvement of resolution was achieved via non-IPG-IEF; (iii) the sensitivity of developed techniques was increased up to 2.7 folds; and (iv) up to about 16.4% more protein spots could be observed via the adjustable 2DE as compared with routine one. The developed techniques might contribute to complex proteome research, especially for screening of biological marker and analysis of extreme acidic/alkaline proteins.

  3. Evaluation of the precipitation-in-gel reaction in the diagnosis of smallpox*

    PubMed Central

    Mitra, A. C.; Sarkar, J. K.; Mukherjee, M. K.; Chakravarty, M. S.

    1973-01-01

    Specimens of vesicular or pustular fluids and of scabs from patients with smallpox as well as emulsions of variola-infected chorioallantoic membrane (CAM) were tested for virus titres and by the precipitation-in-gel (PIG) reaction. They were also tested after exposing them directly to sunlight and after keeping them at temperatures of -20°C, 4°C, and 25°C. It was found that when extracts of fresh specimens were diluted to the point where the PIG reaction became negative there was still a titre of 104-105 infectivity in the swab extracts and 103-104 infectivity in the scab extracts. It was also found that the PIG reactions were all negative on specimens that were kept for 14 days at 25°C, and that several were negative after only 7 days; the loss in infectivity titre, however, was only slight in all the specimens tested. It is concluded that the laboratory diagnosis of smallpox by virus inoculation of CAM is more reliable than by the PIG test. PMID:4374321

  4. TiO2 nanosized powders controlling by ultrasound sol-gel reaction.

    PubMed

    Latt, Kyaing Kyaing; Kobayashi, Takaomi

    2008-04-01

    We studied that anatase-TiO2 powders prepared from sol-gel process of titanium tetra-isopropoxide (TTIP) were developed under ultrasonic irradiation with different frequency of 28, 45 and 100 kHz. The irradiated ultrasound (US) was controlled by using semi-cylindrical reflection plate that was placed onto the vicinity of reaction vessel. The focused US influenced the reduction of particles size and increased the surface area of resultant nanosized TiO2 powders. We also examined photodegradation of rhodamine 640 dye (Rh-640) solution by the resultant TiO2 under UV light exposure. It was observed that low frequency for TiO2 photocatalyst preparation and low calcination temperature were more affected onto the photodegradation of the dye.

  5. Combining ligation reaction and capillary gel electrophoresis to obtain reliable long DNA probes.

    PubMed

    García-Cañas, Virginia; Mondello, Monica; Cifuentes, Alejandro

    2011-05-01

    New DNA amplification methods are continuously developed for sensitive detection and quantification of specific DNA target sequences for, e.g. clinical, environmental or food applications. These new applications often require the use of long DNA oligonucleotides as probes for target sequences hybridization. Depending on the molecular technique, the length of DNA probes ranges from 40 to 450 nucleotides, solid-phase chemical synthesis being the strategy generally used for their production. However, the fidelity of chemical synthesis of DNA decreases for larger DNA probes. Defects in the oligonucleotide sequence result in the loss of hybridization efficiency, affecting the sensitivity and selectivity of the amplification method. In this work, an enzymatic procedure has been developed as an alternative to solid-phase chemical synthesis for the production of long oligonucleotides. The enzymatic procedure for probe production was based on ligation of short DNA sequences. Long DNA probes were obtained from smaller oligonucleotides together with a short sequence that acts as bridge stabilizing the molecular complex for DNA ligation. The ligation reactions were monitored by capillary gel electrophoresis with laser-induced fluorescence detection (CGE-LIF) using a bare fused-silica capillary. The capillary gel electrophoresis-LIF method demonstrated to be very useful and informative for the characterization of the ligation reaction, providing important information about the nature of some impurities, as well as for the fine optimization of the ligation conditions (i.e. ligation cycles, oligonucleotide and enzyme concentration). As a result, the yield and quality of the ligation product were highly improved. The in-lab prepared DNA probes were used in a novel multiplex ligation-dependent genome amplification (MLGA) method for the detection of genetically modified maize in samples. The great possibilities of the whole approach were demonstrated by the specific and sensitive

  6. Relationship between severity of the local skin reactions and the rate of local skin reaction resolution in patients treated with ingenol mebutate gel

    PubMed Central

    Jim On, Shelbi C; Knudsen, Kim Mark; Skov, Torsten; Lebwohl, Mark

    2016-01-01

    Background Ingenol mebutate gel is a topical field treatment for actinic keratosis (AK). The treatment elicits application-site reactions in most patients. This analysis evaluated the relationship between the severity of reactions and the speed of their resolution. Methods Patients in Phase III studies were treated for AKs on the face (n=218), scalp (n=56), and trunk and extremities (n=209). All of the patients were treated with either ingenol mebutate gel 0.015% once daily for three consecutive days (face/scalp) or ingenol mebutate gel 0.05% once daily for two consecutive days (trunk/extremities). Local skin reactions (LSRs) were assessed on a 5-point scale from 0 to 4 in six categories, yielding composite scores in the range of 0 to 24. Results The composite LSR score on the day after the last application of ingenol mebutate gel was an important predictor of the speed of resolution of LSRs. The rate of resolution was greatest for AKs treated on the face, followed by the scalp, and then the trunk and extremities. All patients were expected to have minimal LSR scores for the face and scalp at 2 weeks, and for the trunk and extremities at 4 weeks. Conclusion The absolute reduction in LSR scores was proportional to the composite LSR score on the day after the last application of ingenol mebutate gel treatment. The rate of resolution for LSRs was dependent on the anatomic site treated as well as the day 4 composite score. PMID:27601928

  7. Detection of equine infectious anemia virus in a horse with an equivocal agar gel immunodiffusion test reaction.

    PubMed

    Issel, C J; Adams, W V

    1982-02-01

    A horse whose serum reacted equivocally in the agar gel immunodiffusion (AGID) test for equine infectious anemia was studied over a 3-year period. The horse remained afebrile and virus was detected in only 1 of 6 horse inoculation tests. The intensity of AGID test reactions increased temporarily following this evidence for virus. Although the AGID test reaction was equivocal and 5 of the 6 transmission attempts failed, the 1 successful transmission proved the horse was infected.

  8. Alteration of alkali reactive aggregates autoclaved in different alkali solutions and application to alkali-aggregate reaction in concrete

    SciTech Connect

    Lu Duyou; Xu Zhongzi; Tang Mingshu; Fournier, Benoit

    2006-06-15

    Surface alteration of typical aggregates with alkali-silica reactivity and alkali-carbonate reactivity, i.e. Spratt limestone (SL) and Pittsburg dolomitic limestone (PL), were studied by XRD and SEM/EDS after autoclaving in KOH, NaOH and LiOH solutions at 150 deg. C for 150 h. The results indicate that: (1) NaOH shows the strongest attack on both ASR and ACR aggregates, the weakest attack is with LiOH. For both aggregates autoclaved in different alkali media, the crystalline degree, morphology and distribution of products are quite different. More crystalline products are formed on rock surfaces in KOH than that in NaOH solution, while almost no amorphous product is formed in LiOH solution; (2) in addition to dedolomitization of PL in KOH, NaOH and LiOH solutions, cryptocrystalline quartz in PL involves in reaction with alkaline solution and forms typical alkali-silica product in NaOH and KOH solutions, but forms lithium silicate (Li{sub 2}SiO{sub 3}) in LiOH solution; (3) in addition to massive alkali-silica product formed in SL autoclaved in different alkaline solutions, a small amount of dolomite existing in SL may simultaneously dedolomitize and possibly contribute to expansion; (4) it is promising to use the duplex effect of LiOH on ASR and ACR to distinguish the alkali-silica reactivity and alkali-carbonate reactivity of aggregate when both ASR and ACR might coexist.

  9. Mecanismes d'action des fines et des granulats de verre sur la reaction alcali-silice et la reaction pouzzolanique

    NASA Astrophysics Data System (ADS)

    Idir, Rachida

    Recycling composite glass with different colours in order to be manufactured into new glass products is at present not economically viable. Therefore, the search for new issues other than stockpile areas or dumping sites could be a serious opportunity. To a certain extent, one of the possible solutions is to use the recycled glass in manufacturing cements and in the preparation of concrete mixtures. However, it is essential to manage the two main behaviours that the glass can have when used in cement-based materials: (1) the use of glass as coarse aggregates reveals harmful behaviour related to alkali-silica reaction; (2) on the other hand, it can result in useful behaviour related to pozzolanic reaction if used as fine particles. Furthermore, the significant alkali content should not be overlooked as their mass corresponds to about 13% of the total mass of the glass and as they may activate the alkali-silica reaction. An experimental programme was conducted to provide answers to the various questions raised about the use of glass in cement-based materials. The first part of this work was primarily devoted to the evaluation of the reactive potential of glass in mortars (alkali and pozzolanic reactions). At this stage, nine classes of glass particles ranging from 3mum to 2.5 mm were considered. Then, fine glass particles were used in order to counteract the negative effect of some classes of coarse aggregates having revealed alkali-reactive behaviour. The second part of this work was performed to study the mechanisms that could explain the behaviours of fine and coarse particles in aqueous and concentrated environments. Different answers have been proposed to explain the observed behaviour in terms of grain sizes of glass. Keywords: Glass, Powder, Pozzolan, aggregates, alkali-reaction, alkali-aggregate reaction, alkali-silica reaction, Pouzzolanicity, alkalis, Mortars

  10. Experimenting with a Visible Copper-Aluminum Displacement Reaction in Agar Gel and Observing Copper Crystal Growth Patterns to Engage Student Interest and Inquiry

    ERIC Educational Resources Information Center

    Xu, Xinhua; Wu, Meifen; Wang, Xiaogang; Yang, Yangyiwei; Shi, Xiang; Wang, Guoping

    2016-01-01

    The reaction process of copper-aluminum displacement in agar gel was observed at the microscopic level with a stereomicroscope; pine-like branches of copper crystals growing from aluminum surface into gel at a constant rate were observed. Students were asked to make hypotheses on the pattern formation and design new research approaches to prove…

  11. Experimenting with a Visible Copper-Aluminum Displacement Reaction in Agar Gel and Observing Copper Crystal Growth Patterns to Engage Student Interest and Inquiry

    ERIC Educational Resources Information Center

    Xu, Xinhua; Wu, Meifen; Wang, Xiaogang; Yang, Yangyiwei; Shi, Xiang; Wang, Guoping

    2016-01-01

    The reaction process of copper-aluminum displacement in agar gel was observed at the microscopic level with a stereomicroscope; pine-like branches of copper crystals growing from aluminum surface into gel at a constant rate were observed. Students were asked to make hypotheses on the pattern formation and design new research approaches to prove…

  12. Effect of the exothermal polymerization reaction on polymer gel dosimetric measurements

    NASA Astrophysics Data System (ADS)

    Sedaghat, Mahbod; Bujold, Rachel; Lepage, Martin

    2010-11-01

    Discrepancies in polymer gel dosimetric measurements have been observed between containers of different sizes receiving the same radiation dose. We hypothesized that these deviations are caused by a change in the rate of polymerization due to internal heat increase in the gel containers resulting from the exothermic polymerization of monomers. Here, we test this hypothesis in a polyacrylamide gel dosimeter by recording the temperature in glass phantoms of different sizes during and after irradiation. The dose response of the samples was determined with magnetic resonance imaging. The difference of R2 values along the depth of the containers was below ±1%. We discuss that this small difference can be attributed to variations in the rate of gelatin cooling during manufacture rather than to the measured heat increase during irradiation.

  13. Computer model of the diffusion/reaction interplay in the gel acupuncture method

    NASA Astrophysics Data System (ADS)

    Otálora, Fermín; García-Ruiz, Juan M.

    1996-11-01

    A numerical model is presented to simulate the growth of protein crystals by the gel acupuncture method. The model includes simultaneous transport, nucleation and growth/dissolution and shows itself as a powerful tool in getting insight into the complex interplay of the three processes. The output data allow us to describe simulated experiments both in terms of number, size and distribution of the crystals obtained, and the physicochemical parameters controlling them. The initial protein concentration and the penetration depth of the capillary into the gel define the amplitude and gradient of a supersaturation wave. This wave travels across the system producing the typical distribution of crystals in gel acupuncture in a self-organised way. The existence of this one-dimensional wave imposes a spatio-temporal order in the events, producing crystals in such a way that large crystals of good quality are formed in the middle of the capillary.

  14. Thermal denaturation of double-stranded nucleic acids: prediction of temperatures critical for gradient gel electrophoresis and polymerase chain reaction.

    PubMed Central

    Steger, G

    1994-01-01

    A program is described which calculates the thermal stability and the denaturation behaviour of double-stranded DNAs and RNAs up to a length of 1000 base pairs. The algorithm is based on recursive generation of conditional and a priori probabilities for base stacking. Output of the program may be compared directly to experimental results; thus the program may be used to optimize the nucleic acid fragments, the primers and the experimental conditions prior to experiments like polymerase chain reactions, temperature-gradient gel electrophoresis, denaturing-gradient gel electrophoresis and hybridizations. The program is available in three versions; the first version runs interactively on VAXstations producing graphics output directly, the second is implemented as part of the HUSAR package at GENIUSnet, the third runs on any computer producing text output which serves as input to available graphics programs. Images PMID:8052531

  15. NO reactions with sol-gel and solution phase samples of the ferric nitrite derivative of HbA

    PubMed Central

    Roche, Camille J.; Friedman, Joel M.

    2010-01-01

    The reaction of nitric oxide (NO) with the ferric (met) nitrite derivative of human adult hemoglobin Hb is probed for both solution phase and sol-gel encapsulated populations. The evolution of both the Q band absorption spectrum and fitted populations of Hb derivatives are used to show the sequence of events occurring when NO interacts with nitrite bound to a ferric heme in Hb. The sol-gel is used to compare the evolving populations as a function of quaternary state for the starting met nitrite populations. The redox status of intermediates is probed using the CN− anion to trap ferric heme species. The emergent presence of reactive NO species such as N2O3 during the course of the reaction is probed using the fluorescent probe DAF-2 whereas the fluorophore Chemi-fluor is used as an indirect measure of the ability of the reaction to create S-nitrosothiols on glutathione. The results are consistent with the formation of a stable reactive intermediate capable of generating bioactive forms of NO. The patterns observed are consistent with a proposed mechanism whereby NO reacts with the ferric nitrite derivative to generate N2O3. PMID:19919854

  16. Discovery of protein- and DNA-imperceptible nanoparticle hard coating using gel-based reaction tuning.

    PubMed

    Welsher, Kevin; McManus, Simon A; Hsia, Chih-Hao; Yin, Shuhui; Yang, Haw

    2015-01-21

    The seemingly inevitable protein corona appears to be an insurmountable obstacle to wider application of functional nanomaterials in biotechnology. The accumulation of serum proteins can block targeting functionalities and alter the in vivo fate of these nanomaterials. Here we demonstrate a method to generate non-stick, robustly passivated functional nanoparticles (NPs) using a tailored silica coating. We apply agarose gel electrophoresis to sensitively evaluate protein binding to NPs with different surface chemistry. Using gel banding and retardation as a read-out for protein adsorption, we optimize the surface chemistry to yield a mixed charge surface which displays remarkable binding resistance to a wide range of serum proteins and nucleic acids. The hard silica shell also protects the functional NP core in harsh environments (down to pH 1) while still showing the ability to be targeted for cellular uptake with little or no non-specific binding.

  17. Topochemical Azide-Alkyne Cycloaddition Reaction in Gels: Size-Tunable Synthesis of Triazole-Linked Polypeptides.

    PubMed

    Krishnan, Baiju P; Sureshan, Kana M

    2017-02-01

    Though topochemical reactions are attractive, the difficulty associated with crystallization such as low yield, unsuitability for large-scale synthesis, etc. warranted the exploitation of other self-assembled media for topochemical reactions. We synthesized a dipeptide gelator decorated with azide and alkyne at its termini, N3-Ala-Val-NHCH2-C≡CH, which is designed to self-assemble through intermolecular hydrogen bonds to β-sheets thereby placing the azide and alkyne motifs in proximity. As anticipated, this peptide forms gels in organic solvents and water via hydrogen-bonded β-sheet assembly as evidenced from IR spectroscopy and PXRD profiling. The microscopic fibers present in organogel and hydrogel have different morphology as was evident from scanning electron microscopy (SEM) imaging of their xerogels, XGh (xerogel made from hydrogel) and XGo (xerogel made from organogel). Heating of xerogels at 80 °C resulted in the topochemical azide-alkyne cycloaddition (TAAC) polymerization to 1,4-triazole-linked oligopeptides. Under identical conditions, XGo produced larger oligopeptides, and XGh produced smaller peptides, as evidenced from MALDI-TOF spectrometry. We have also shown that degree of TAAC polymerization can be controlled by changing gel fiber thickness, which in turn can be controlled by concentration. SEM studies suggested the morphological intactness of the fibers even after the reaction, and their PXRD profiles revealed that both XGh and XGo undergo fiber-to-fiber oligomerization without losing their crystallinity. In contrast to crystals, the xerogels undergo TAAC polymerization in two distinct stages as shown by DSC analyses. Interestingly, XGh and XGo undergo spontaneous TAAC polymerization at room temperature; the latter shows faster kinetics. This is not only the first demonstration of the use of xerogels for thermally induced topochemical polymerization but also the first report on a spontaneous topochemical reaction in xerogels.

  18. Analysis of chicken bile by gel precipitation reactions using a lectin in the place of antibody.

    PubMed

    Cotter, P F

    2000-09-01

    A lectin obtained from black turtle beans (BTB) was precipitated with IgA in chicken bile samples in various forms of agarose gel systems. Ouchterlony-type double-diffusion (ODD) precipitation patterns between the lectin, bile IgA, and heavy chain-specific antibody contained spurs of the type suggestive of partial immunologic identity. The immunoelectrophoresis precipitation patterns between the same three reactants were mirror images and fused on the cathodic side of the immunoelectrophoresis origin. In addition to use in ODD-type gels, BTB could also be incorporated into agarose gels suitable for Mancini (radial immunodiffusion) or Laurell-type rocket electrophoresis. Bile samples obtained from Cornell lines OS and C, broiler breeder males, and University of California-Davis congenic lines were investigated using BTB- and antibody-based methods. The results of this study indicated that IgA was the most frequently detected isotype in bile, occurring in 139 of 156 (89%) samples. Most bile samples (128/156; 82%) also contained IgG, whereas fewer (19/156; 12%) contained IgM. Cornell lines appeared to differ from broiler breeders, having a higher frequency of IgM-positive samples. Of the total bile samples studied, 11% (17/156) of samples from broiler breeders and the Cornell lines appeared to be devoid of IgA; the bile of one broiler breeder was found to be devoid of all three isotypes. Instances were found in which bile samples shown to be negative for IgA by antibody-ODD were shown to be positive by BTB-ODD. Thus BTB appears to be a suitable adjunct to antibody for the study of IgA.

  19. Semi-quantitative digital analysis of polymerase chain reaction-electrophoresis gel: Potential applications in low-income veterinary laboratories

    PubMed Central

    Antiabong, John F.; Ngoepe, Mafora G.; Abechi, Adakole S.

    2016-01-01

    Aim: The interpretation of conventional polymerase chain reaction (PCR) assay results is often limited to either positive or negative (non-detectable). The more robust quantitative PCR (qPCR) method is mostly reserved for quantitation studies and not a readily accessible technology in laboratories across developing nations. The aim of this study was to evaluate a semi-quantitative method for conventional PCR amplicons using digital image analysis of electrophoretic gel. The potential applications are also discussed. Materials and Methods: This study describes standard conditions for the digital image analysis of PCR amplicons using the freely available ImageJ software and confirmed using the qPCR assay. Results and Conclusion: Comparison of ImageJ analysis of PCR-electrophoresis gel and qPCR methods showed similar trends in the Fusobacterium necrophorum DNA concentration associated with healthy and periodontal disease infected wallabies (p≤0.03). Based on these empirical data, this study adds descriptive attributes (“more” or “less”) to the interpretation of conventional PCR results. The potential applications in low-income veterinary laboratories are suggested, and guidelines for the adoption of the method are also highlighted. PMID:27733792

  20. Fabrication of three-dimensional nanostructured titania materials by prism holographic lithography and the sol-gel reaction.

    PubMed

    Park, Sung-Gyu; Jeon, Tae Yoon; Yang, Seung-Man

    2013-08-06

    We present a simple, easy method for fabricating high-quality titania inverted replicas of 3D holographically featured structures. A combination of single-prism holographic lithography and sol-gel chemistry was used to prepare 3D titania inverse structures with flat and completely open surfaces without the use of additional postprocessing steps, such as reactive ion etching, ion-beam milling, and/or polishing steps. A hydrophobic, stable liquid titania precursor facilitated the complete infiltration of the precursor into the hydrophobic 3D SU-8 polymer template, which produced very uniform high-quality titania inverse structures. Although the degree of film shrinkage during the calcination process was large (∼34%), the optical strength of the 3D titania inverse photonic crystals doubled because of the high-refractive-index contrast. Compared to titania inverse opal structures, the filling fraction (∼27%) of titania materials has been doubled. This is the first work to fabricate titania inverse photonic crystals with a high filling fraction by utilizing prism holographic lithography and the sol-gel chemistry reaction of a stable titania precursor. The X-ray diffraction patterns indicated the presence of a crystalline anatase or rutile phase depending on the calcination temperature.

  1. Semi-quantitative digital analysis of polymerase chain reaction-electrophoresis gel: Potential applications in low-income veterinary laboratories.

    PubMed

    Antiabong, John F; Ngoepe, Mafora G; Abechi, Adakole S

    2016-09-01

    The interpretation of conventional polymerase chain reaction (PCR) assay results is often limited to either positive or negative (non-detectable). The more robust quantitative PCR (qPCR) method is mostly reserved for quantitation studies and not a readily accessible technology in laboratories across developing nations. The aim of this study was to evaluate a semi-quantitative method for conventional PCR amplicons using digital image analysis of electrophoretic gel. The potential applications are also discussed. This study describes standard conditions for the digital image analysis of PCR amplicons using the freely available ImageJ software and confirmed using the qPCR assay. Comparison of ImageJ analysis of PCR-electrophoresis gel and qPCR methods showed similar trends in the Fusobacterium necrophorum DNA concentration associated with healthy and periodontal disease infected wallabies (p≤0.03). Based on these empirical data, this study adds descriptive attributes ("more" or "less") to the interpretation of conventional PCR results. The potential applications in low-income veterinary laboratories are suggested, and guidelines for the adoption of the method are also highlighted.

  2. Performance of ZnO synthesized by sol-gel as photocatalyst in the photooxidation reaction of NO.

    PubMed

    Luévano-Hipólito, E; Martínez-de la Cruz, A; López Cuéllar, E

    2017-03-01

    ZnO samples were prepared by sol-gel method applying a factorial design in order to improve the photocatalytic properties of the semiconductor oxide in the NO photooxidation reaction. The concentrations of zinc acetate and ammonium hydroxide were selected as critical variables in the synthesis of ZnO. Nine samples of ZnO were obtained as product of the factorial design and were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, diffuse reflectance spectroscopy, and N2 adsorption-desorption isotherms. The photocatalytic activity of ZnO samples was associated with the physical properties developed by each sample according to its respective conditions of synthesis. Some photocatalytic reaction parameters, such as mass of photocatalyst, irradiance, and relative humidity, were modified in order to evaluate its effect in the photocatalytic conversion of NO. As a relevant point, the relative humidity played an important role in the increase of the selectivity of the NO photooxidation reaction to innocuous nitrate ions when ZnO was used as photocatalyst.

  3. Multistimuli responsive organogels based on a new gelator featuring tetrathiafulvalene and azobenzene groups: reversible tuning of the gel-sol transition by redox reactions and light irradiation.

    PubMed

    Wang, Cheng; Chen, Qun; Sun, Fei; Zhang, Deqing; Zhang, Guanxin; Huang, Yanyan; Zhao, Rui; Zhu, Daoben

    2010-03-10

    For the development of multistimuli responsive organogels, the new organic gelator LMWG 1, featuring electroactive TTF and photoresponsive azobenzene groups, was designed and studied. By manipulating the redox state of the TTF group in LMWG 1, the gel-sol transition for organogels with the LMWG 1 can be reversibly tuned by either chemical or electrochemical oxidation/reduction reactions. Alternatively, the photoisomerization of the azobenzene group in LMWG 1 can also trigger the gel-sol transition. Therefore, organogels with LMWG 1 respond not only to thermal stimuli but also to redox reactions and light irradiation.

  4. Comparison of the morphology of alkali–silica gel formed in limestones in concrete affected by the so-called alkali–carbonate reaction (ACR) and alkali–silica reaction (ASR)

    SciTech Connect

    Grattan-Bellew, P.E.; Chan, Gordon

    2013-05-15

    The morphology of alkali–silica gel formed in dolomitic limestone affected by the so-called alkali–carbonate reaction (ACR) is compared to that formed in a siliceous limestone affected by alkali–silica reaction (ASR). The particle of dolomitic limestone was extracted from the experimental sidewalk in Kingston, Ontario, Canada that was badly cracked due to ACR. The siliceous limestone particle was extracted from a core taken from a highway structure in Quebec, affected by ASR. Both cores exhibited marked reaction rims around limestone particles. The aggregate particles were polished and given a light gold coating in preparation for examination in a scanning electron microscope. The gel in the ACR aggregate formed stringers between the calcite crystals in the matrix of the rock, whereas gel in ASR concrete formed a thick layer on top of the calcite crystals, that are of the same size as in the ACR aggregate.

  5. Study of the sol-gel reaction mechanism in supercritical CO2 for the formation of SiO2 nanocomposites.

    PubMed

    Charpentier, Paul A; Li, Xinsheng; Sui, Ruohong

    2009-04-09

    Direct sol-gel reactions in supercritical CO2 (scCO2) have attracted significant interest for synthesizing nanomaterials by reacting alkoxides with a carboxylic acid. In this study, the hydrolysis of silicon alkoxides (TEOS or TMOS) was carried out using scCO2 as the solvent to generate silica nanoparticles within the matrix of polyethylene for the synthesis of polymeric nanocomposites. This methodology provides advantages of combining the sol-gel reactions and drying into a one-step process for producing polymer nanocomposites. The synthesized polymer silica composites were characterized by SEM, FTIR, and XPS. When the TEOS loading was below 10 wt % Si content, nanometer-sized silica particles were formed that were well dispersed within the polyethylene matrix. The mechanism of the silicon alkoxides reacting with acetic acid in scCO2 was further studied using online GC-MS and offline 13C NMR. Oligomer structures with a bridging methoxyl group between the two silicon atoms and the acetate monodentate were observed. This study suggests a new sol-gel pathway in scCO2 that is different from the hydrolysis-condensation reactions using the conventional sol-gel process.

  6. Detection of bacteria in normal adult nasal cavity based on polymerase chain reaction-denaturing gradient gel electrophoresis.

    PubMed

    Cho, Jae Hoon; Jung, Min Young; Kim, Jin Kook; Chang, Young-Hyo

    2011-01-01

    This study investigated the bacterial diversity in a normal adult nasal cavity using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) of 16S ribosomal RNA (rRNA) gene fragments and compared the results with those of a culture-based method. We swabbed the inferior turbinate from 19 normal volunteers. The transport media was divided by two, one for bacterial culture and another direct extraction for bacterial DNA. PCR-DGGE was performed from the bacterial DNA and all of the sequences were compared with the reference organism by using the BLAST program (a genome database of GenBank in the National Center for Biotechnology Information, Bethesda, MD). All 224 colonies were obtained from 19 samples by using a culture-based method; however, only 9 kinds of bacteria were detected. Staphylococcus epidermidis was the most frequently detected bacteria, and Staphylococcus aureus was the second most. The detection rates of other bacteria were very low. On the other hand, the PCR-DGGE from direct DNA extraction revealed 34 different bands that corresponded to 23 different kinds of bacteria. There were nine genera, viz., Staphylococcus, Bacillus, Enterobacter, Corynebacterium, Actinobacterium, Hafnia, Moraxella, Dolosigranulum, and Clostridium. Among them, unspecific Staphylococcus species and Enterobacter aerogenes were detected most frequently. Compared with the previous culture-based method, PCR-DGGE can detect much more diversity of bacteria in the nasal cavity.

  7. Determination of fluoride and oxalate using the indicator reaction of Zr(IV) with methylthymol blue adsorbed on silica gel.

    PubMed

    Zaporozhets, Olga A; Tsyukalo, Lyudmila Ye

    2007-07-30

    Solid-phase spectrophotometric and visual test-methods of fluoride and oxalate determination are proposed. The methods are based on the competitive reactions of ZrOCl2 with methylthymol blue immobilized on silica gel and fluoride or oxalate in solution. Absorbance of the solid-phase reagent at 590 nm decreases with the growth of fluoride and oxalate contents in solution. The developed methods demonstrate high selectivity. The interference of Bi(III) and SO4(2-), PO4(3-) is eliminated by the addition of 0.01 mol L(-1) solution of ascorbic acid and 0.01 mol L(-1) of BaCl2, respectively. To eliminate the fluoride interference with oxalate determination 1x10(-3) mol L(-1) solution of Ca(NO3)2 at pH 1.5 was added. The anions of the organic acids were destructed prior to F- determination by ultrasonic exposition (44 kHz, intensity of < or = 10 W cm(-2) for 3 min). The proposed methods were applied to the analysis of mineral water, toothpaste and biological fluids.

  8. A study of the electrochemical lithium intercalation behavior of porous LiNiO 2 electrodes prepared by solid-state reaction and sol-gel methods

    NASA Astrophysics Data System (ADS)

    Choi, Young-Min; Pyun, Su-Il; Moon, Seong-In; Hyung, Yoo-Eup

    The electrochemical lithium intercalation behavior of porous LiNiO 2 electrodes prepared by solid-state reaction and sol-gel methods is investigated by using X-ray diffractometry (XRD), a galvanostatic intermittent charge-discharge experiment, electrochemical impedance spectroscopy(EIS), and a charge-discharge cycling test. The ultrafine LiNiO 2 powder is prepared by the sol-gel method in order to overcome the disadvantage of the conventional solid-state reaction method. From the results of XRD, the layered LiNiO 2 phase proves to be stable above 400°C. The conventional oxide electrode suffers a larger capacity loss, a greater instantaneous IR drop during the first intermittent discharge, and a smaller chemical diffusivity than the gel-derived electrode. The results are discussed with respect to the marked cation mixing effect in the former electrode. Furthermore, the charge-discharge cycling test shows that the cell Li/organic electrolyte/gel-derived LiNiO 2 electrode displays improved performance, i.e., an initial specific capacity of 150 Ah kg -1 and a specific energy density above 500 Wh kg -1.

  9. Metal chalcogenide nanoparticle gel networks: Their formation mechanism and application for novel material generation and heavy metal water remediation via cation exchange reactions

    NASA Astrophysics Data System (ADS)

    Palhares, Leticia F.

    The dissertation research is focused on (1) uncovering the mechanism of metal chalcogenide nanoparticle gel formation; (2) extending the cation exchange reaction protocol to zinc sulfide gel networks, with the goal of accessing new aerogel chemistries and understanding the factors that drive the process; and (3) conducting a quantitative analysis of the ability of ZnS aerogels to remove heavy metal ions from aqueous solutions. The mechanism of metal chalcogenide nanoparticle gel formation was investigated using Raman spectroscopy and X-ray Photoelectron Spectroscopy to probe the chemical changes that occur during the gelation process. These techniques suggest that the bonding between the particles in the CdSe nanoparticle gels is due to the oxidation of surface selenide species, forming covalent Se--Se bonds. Treating the gel networks with a suitable reducing agent, such as a thiol, breaks the covalent bond and disperses the gel network. The addition of sodium borohydride, a "pure" reducing agent, also breaks down the gel network, strengthening the hypothesis that the reducing character of the thiols, not their ligation ability, is responsible for the gel network breakdown. UV-Vis spectroscopy, Transmission Electron Microscopy and Powder X-ray Diffraction were used to analyze the particles after successive gelation-dispersion cycles. The primary particle size decreases after repeated oxidation-reduction cycles, due to nanoparticle surface etching. This trend is observed for CdSe and CdS gel networks, allowing for the proposition that the oxidative-reductive mechanism responsible for the formation-dispersion of the gels is general, applying to other metal chalcogenide nanocrystals as well. The cation exchange reaction previously demonstrated for CdSe gels was extended to ZnS gel networks. The exchange occurs under mild reaction conditions (room temperature, methanol solvent) with exchanging ions of different size, charge and mobility (Ag+, Pb2+, Cd2+ , Cu2+). The

  10. The preparation of Zn2+-doped TiO(2) nanoparticles by sol-gel and solid phase reaction methods respectively and their photocatalytic activities.

    PubMed

    Liu, Guoguang; Zhang, Xuezhi; Xu, Yajie; Niu, Xinshu; Zheng, Liqing; Ding, Xuejun

    2005-06-01

    The photocatalytic oxidation of the organic pollutants with TiO(2) as photocatalyst has been widely studied in the world, and many achievements have been made. The degradation of pollutants is highly related to the photocatalytic activity of TiO(2). It is demonstrated that doping ions to TiO(2) is one way to enhance the photocatalytic activity of TiO(2). In this paper, Zn(2+)-doped TiO(2) nanoparticles were prepared through sol-gel and solid phase reaction methods, characterized by means of X-ray diffraction (XRD) and transmission electron microscopy (TEM). The photocatalytic activity of the elaborated powders was studied following the degradation of Rhodamine B. The results showed that the photocatalytic activity of Zn(2+)-doped TiO(2) prepared by sol-gel method is close to that of pure TiO(2) particles, however, the photocatalytic activity of Zn(2+)-doped TiO(2) prepared by solid phase reaction method is much higher than that of pure TiO(2) particles. The most efficient degradation of Rhodamine B was found with TiO(2) particles doped with 0.5% Zn(2+) in mole and calcined at 500 degrees C. Also the reason for the enhancement of the photocatalytic activity of TiO(2) by Zn(2+) doping through solid phase reaction method was discussed.

  11. Development of cross-linked polystyrene-supported chiral amines featuring a fluorinated linker for gel-phase 19F NMR spectrometry monitoring of reactions.

    PubMed

    Hourdin, Marie; Gouhier, Géraldine; Gautier, Arnaud; Condamine, Eric; Piettre, Serge R

    2005-01-01

    Ten cross-linked polystyrene-supported, protected chiral amines featuring both a spacer, comprising from 5 to 15 atoms, and a fluorinated linker have been successfully prepared. The development of the monitoring technique by gel-phase 19F NMR spectrometry on cross-linked polystyrene derivatives proved to be of high value in four steps of the process, as shown by the comparison of data gathered from both a classic NMR spectrometer and elemental analysis. Gel-phase 19F NMR spectrometry, thus, constitutes a useful technique that complements IR and 13C NMR spectrometries for the qualitative monitoring of reactions. In addition, quantitative determination of the conversion in a given transformation is possible, provided that 19F chemical shifts of the substrate and the product be different enough (Deltadelta>base width), as illustrated by the Mitsunobu coupling process (16-->17). The technique is nondestructive, and the samples used to monitor the reactions may be returned to the reaction medium. Deprotection of the above amines was achieved and furnished eight of the final resins in good to acceptable purity for future applications.

  12. In-Gel Determination of L-Amino Acid Oxidase Activity Based on the Visualization of Prussian Blue-Forming Reaction

    PubMed Central

    Zhou, Ning; Zhao, Chuntian

    2013-01-01

    L-amino acid oxidase (LAAO) is attracting increasing attention due to its important functions. Diverse detection methods with their own properties have been developed for characterization of LAAO. In the present study, a simple, rapid, sensitive, cost-effective and reproducible method for quantitative in-gel determination of LAAO activity based on the visualization of Prussian blue-forming reaction is described. Coupled with SDS-PAGE, this Prussian blue agar assay can be directly used to determine the numbers and approximate molecular weights of LAAO in one step, allowing straightforward application for purification and sequence identification of LAAO from diverse samples. PMID:23383337

  13. Reaction mechanism and optimal conditions for preparation of high-quality vanadium oxide films by organic sol-gel for optoelectronic applications

    NASA Astrophysics Data System (ADS)

    Sun, Minghui; Wen, Yuejiang; Xu, Xiangdong; Wang, Meng; He, Qiong; Jiang, Yadong; Dai, Zelin; Gu, Yu; Chen, Zhegeng

    2016-03-01

    Although vanadium oxides (VO x ) are important functional materials for academic research and industrial applications, the reaction mechanism of VO x prepared by organic sol-gel remains unclear. In order to investigate this mechanism, VO x organic sols were reacted at different temperatures, by which various VO x thin films were prepared. The products were systematically characterized by infrared spectroscopy, Raman spectroscopy, UV-vis spectroscopy, thermogravimetric analysis, scanning electron microscopy, x-ray diffraction, and a high resistance meter. Results reveal that vanadium alkoxides are created through an alcoholysis reaction of V2O5 powder and isobutyl alcohol, and then a condensation reaction of the vanadium alkoxides leads to the formation of VO x networks. The as-prepared sols are strongly temperature-dependent, causing different chemical structures and physical properties for the resulting VO x films. Particularly, a moderate temperature of 110 °C prompts both alcoholysis and condensation reactions, and thus the VO x films that are produced by the sol reacted at 110 °C possess a low resistivity of 23 Ω cm, a high temperature coefficient resistance (TCR) of  -3.2% K-1, and a low average transmittance of 54% in 580-1100 nm, compared with those prepared by the sols reacted at lower or higher temperatures. Therefore, 110 °C is a desirable sol temperature for producing VO x films serving as high-quality bolometric materials for uncooled infrared detectors. This work discloses not only the reaction mechanism of VO x films prepared by organic sol-gel, but also the route to yield desirable VO x films for optoelectronic applications.

  14. A Theoretical and Experimental Analysis of Double Diffusion Precipitin Reactions in Gels, and its Application to Characterization of Antigens

    PubMed Central

    Allison, A. C.; Humphrey, J. H.

    1960-01-01

    The distribution of antigen and antibody in radial double diffusion systems was studied by means of materials labelled with 131I or 14C. These studies showed that, once a precipitate begins to form, the assumption that antigen and antibody obey the laws of free diffusion is invalid. They also showed that, in the systems used, no antigen and very little antibody diffused past the zone of visible precipitation. It was found that accurate estimates of the diffusion constants of antigens could be obtained by allowing antigen and antibody to diffuse from troughs set at right angles and by measuring the angle of the precipitin line. Examples of the use of this method, and a theoretical treatment are given. An alternative method for estimating the size of antigens is to use the `molecular sieve' properties of gelatin gels, which are sharply graded with the concentration of the gel. ImagesFIG. 3 PMID:13792817

  15. Preparation and Characterization of Polyurethanes with Cross-Linked Siloxane in the Side Chain by Sol-Gel Reactions

    PubMed Central

    Zhao, Hui; Hao, Tong-Hui; Hu, Guo-Hua; Shi, Dean; Huang, Da; Jiang, Tao; Zhang, Qun-Chao

    2017-01-01

    A series of novel polyurethanes containing cross-linked siloxane in the side chain (SPU) were successfully synthesized through a sol-gel process. The SPU was composed of 0%–20% N-(n-butyl)-3-aminopropyltriethoxysilane (HDI-T) modified hexamethylene diisocynate homopolymer. The effects of HDI-T content on both the structure and properties of SPU were investigated by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), mechanical properties tests, gel content test, water contact angle measurement and water absorption test. FT-IR, XPS and XRD results confirmed the successful incorporation of HDI-T onto polyurethanes and the formation of Si–O–Si. The surface roughness and the Si content of SPU enhanced with the increase of HDI-T content. Both crystallization and melting temperature shifted to a lower point after the incorporation of HDI-T. The hydrophobicity, tensile strength, Young’s modulus and pencil hardness overall increased with the increasing of HDI-T content, whereas the thermal stability and the elongation at break of SPU slightly decreased. PMID:28772607

  16. The differences in colonic mucosal microbiota between normal individual and colon cancer patients by polymerase chain reaction-denaturing gradient gel electrophoresis.

    PubMed

    Huipeng, Wang; Lifeng, Gong; Chuang, Ge; Jiaying, Zhao; Yuankun, Cai

    2014-02-01

    The aim of this study was to analyze the differences in the intestinal composition between normal individuals and colon cancer patients. To establish the criteria for screening a normal individual for colon cancer, human colonic biopsies were obtained at routine colonoscopy. For patients with colon cancer, samples were obtained from cancerous regions. For normal individuals, colonic biopsies were taken from 3 sites of large intestine (descending, transverse, and ascending colon). Thereafter, a comparison of the microbiota structure by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) was carried out. At last, bacterial species were identified by sequencing special bands from DGGE gels and comparing data with sequence databases. With PCR-DGGE, we have discovered that the diversity and richness of the bacterial community from colon cancer patient's colonic mucosa were lower than that of the normal individual's sample. Then, a special DGGE band was found in the colon cancer patients. After sequencing, we confirmed that it had a high level of similarity with bacteroides. Colon cancers are closely related with the alteration of intestinal flora such as the reduction of biodiversity and richness of the bacterial community. Furthermore, the increase in proportion of bacteroides may be directly associated with colon cancer.

  17. Fabrication of SiO2/TiO2 double-shelled hollow nanospheres with controllable size via sol-gel reaction and sonication-mediated etching.

    PubMed

    Lee, Jungsup; Hwang, Sun Hye; Yun, Juyoung; Jang, Jyongsik

    2014-09-10

    Size-controllable double-shell SiO2/TiO2 hollow nanoparticles (DS HNPs) were fabricated using a simple sol-gel reaction and sonication-mediated etching. The size of the DS HNPs was controlled using SiO2 core templates of various sizes. Moreover, monodisperse DS HNPs were produced on a large scale (10 g per 1 batch) using the sol-gel method. The surface area and porosity of intrashell and inner-cavity pores were measured by Brunauer-Emmett-Teller analysis. As a result, 240 nm DS HNPs (240 DS HNPs) exhibited the highest surface area of 497 m(2) g(-1) and a high porosity. Additionally, DS HNPs showed excellent light-scattering ability as a scattering layer in dye-sensitized solar cells due to their structural properties, such as a composite, double-shell, hollow structure, as well as intrashell and inner cavity pores. The DSSCs incorporating 240 DS HNPs demonstrated an 18.3% enhanced power conversion efficiency (PCE) compared to TiO2 nanoparticles.

  18. Multiplex polymerase chain reaction-capillary gel electrophoresis: a promising tool for GMO screening--assay for simultaneous detection of five genetically modified cotton events and species.

    PubMed

    Nadal, Anna; Esteve, Teresa; Pla, Maria

    2009-01-01

    A multiplex polymerase chain reaction assay coupled to capillary gel electrophoresis for amplicon identification by size and color (multiplex PCR-CGE-SC) was developed for simultaneous detection of cotton species and 5 events of genetically modified (GM) cotton. Validated real-time-PCR reactions targeting Bollgard, Bollgard II, Roundup Ready, 3006-210-23, and 281-24-236 junction sequences, and the cotton reference gene acp1 were adapted to detect more than half of the European Union-approved individual or stacked GM cotton events in one reaction. The assay was fully specific (<1.7% of false classification rate), with limit of detection values of 0.1% for each event, which were also achieved with simulated mixtures at different relative percentages of targets. The assay was further combined with a second multiplex PCR-CGE-SC assay to allow simultaneous detection of 6 cotton and 5 maize targets (two endogenous genes and 9 GM events) in two multiplex PCRs and a single CGE, making the approach more economic. Besides allowing simultaneous detection of many targets with adequate specificity and sensitivity, the multiplex PCR-CGE-SC approach has high throughput and automation capabilities, while keeping a very simple protocol, e.g., amplification and labeling in one step. Thus, it is an easy and inexpensive tool for initial screening, to be complemented with quantitative assays if necessary.

  19. Development of a polymerase chain reaction and capillary gel electrophoresis method for the detection of chicken or turkey meat in heat-treated pork meat mixtures.

    PubMed

    Hernández-Chávez, Juan F; González-Córdova, Aarón F; Rodríguez-Ramírez, Roberto; Vallejo-Cordoba, Belinda

    2011-12-05

    A polymerase chain reaction and capillary gel electrophoresis (PCR-CGE) method with ultraviolet (UV) or laser induced fluorescence detection (LIF) was established for the detection of chicken or turkey in heat-treated pork meat mixtures. Mitochondrial DNA samples extracted from heat treated meat were amplified with their corresponding specific primers yielding PCR products between 200 and 300 bp. LIF detection was superior than UV detection in terms of precision and sensitivity for the study of DNA fragments. The CGE-LIF method was highly reproducible and accurate for determining DNA fragment size. The PCR-CGE-LIF was sensitive since a significant fluorescent signal was obtained at the minimum admixture level employed of 1% in meat mixtures. Thus, the PCR-CGE-LIF method established was useful for the detection of chicken or turkey in heat treated meat mixtures and may prove to be useful for the detection of poultry meat in pork processed products.

  20. pH-oscillations in the bromate-sulfite reaction in semibatch and in gel-fed batch reactors

    NASA Astrophysics Data System (ADS)

    Poros, Eszter; Kurin-Csörgei, Krisztina; Szalai, István; Rábai, Gyula; Orbán, Miklós

    2015-06-01

    The simplest bromate oxidation based pH-oscillator, the two component BrO3--SO32- flow system was transformed to operate under semibatch and closed arrangements. The experimental preconditions of the pH-oscillations in semibatch configuration were predicted by model calculations. Using this information as guideline large amplitude (ΔpH˜3), long lasting (11-24 h) pH-oscillations accompanied with only a 20% increase of the volume in the reactor were measured when a mixture of Na2SO3 and H2SO4 was pumped into the solution of BrO3- with a very low rate. Batch-like pH-oscillations, similar in amplitude and period time appeared when the sulfite supply was substituted by its dissolution from a gel layer prepared previously in the reactor in presence of high concentration of Na2SO3. The dissolution vs time curve and the pH-oscillations in the semibatch and closed systems were successfully simulated. Due to the simplicity in composition and in experimental technique, the semibatch and batch-like BrO3--SO32- pH-oscillators may become superior to their CSTR (continuous flow stirred tank reactor) version in some present and future applications.

  1. Sol-gel reaction stability studied: Influence in the formation temperature and properties of ferroelectric thin films

    SciTech Connect

    Perez, J. Vilarinho, P.M.; Kholkin, A.L.; Almeida, A.

    2009-03-05

    Lead zirconium titanate (PZT) sol-gel solutions were prepared based on distilled lead acetate precursor solutions. A detailed analysis of the distillation effect on the lead precursor and the final PZT solution were carried out by Infrared and Raman techniques. It was found that the increase in the number of distillation steps experienced by the lead precursor solutions removes the constitutional water and increases the lead acetate-2-methoxyethanol interconnectivity; thus improving stability and avoiding the aging effect of the resulting PZT solutions. The thermal decomposition process of the PZT solutions was analyzed based on the thermogravimetric (TG) and differential thermogravimetric analysis (DTA) measurements. It was found that as the number of distillation steps in the lead precursor solutions increases, the decomposition rate increases and the formation temperature of pure perovskite PZT films decreases. X-ray diffraction (XRD) technique was used to study the film phase formation. A pure perovskite phase at 500 deg. C was found by the XRD analysis after the second distillation step. Scanning electron microscope technique was used to carry out the microstructural analysis. Dense microstructure was found in all analyzed films and an incipient columnar grain growth was revealed in PZT films prepared based on lead precursor solution with more than three distillation steps. The dependence of the dielectric, ferroelectric and piezoelectric properties on the number of distillation steps was revealed and a correlation between the distillation process, film microstructure properties and electrical performance was established.

  2. pH-oscillations in the bromate–sulfite reaction in semibatch and in gel-fed batch reactors

    SciTech Connect

    Poros, Eszter; Kurin-Csörgei, Krisztina; Szalai, István; Orbán, Miklós; Rábai, Gyula

    2015-06-15

    The simplest bromate oxidation based pH-oscillator, the two component BrO{sub 3}{sup −}–SO{sub 3}{sup 2–} flow system was transformed to operate under semibatch and closed arrangements. The experimental preconditions of the pH-oscillations in semibatch configuration were predicted by model calculations. Using this information as guideline large amplitude (ΔpH∼3), long lasting (11–24 h) pH-oscillations accompanied with only a 20% increase of the volume in the reactor were measured when a mixture of Na{sub 2}SO{sub 3} and H{sub 2}SO{sub 4} was pumped into the solution of BrO{sub 3}{sup −} with a very low rate. Batch-like pH-oscillations, similar in amplitude and period time appeared when the sulfite supply was substituted by its dissolution from a gel layer prepared previously in the reactor in presence of high concentration of Na{sub 2}SO{sub 3}. The dissolution vs time curve and the pH-oscillations in the semibatch and closed systems were successfully simulated. Due to the simplicity in composition and in experimental technique, the semibatch and batch-like BrO{sub 3}{sup −}–SO{sub 3}{sup 2–} pH-oscillators may become superior to their CSTR (continuous flow stirred tank reactor) version in some present and future applications.

  3. Analysis of microbial diversity on deli slicers using polymerase chain reaction and denaturing gradient gel electrophoresis technologies.

    PubMed

    Koo, O K; Mertz, A W; Akins, E L; Sirsat, S A; Neal, J A; Morawicki, R; Crandall, P G; Ricke, S C

    2013-02-01

    Cross-contamination of pathogenic and spoilage bacteria from food-contact surfaces to food products is a serious public health issue. Bacteria may survive and attach to food-contact surfaces by residual food components and/or background bacteria which may subsequently transfer to other food products. Deli slicers, generally used for slicing ready-to-eat products, can serve as potential sources for considerable bacterial transfer. The objective of this study was to assess the extent and distribution of microbial diversity of deli slicers by identification of pathogenic and background bacteria. Slicer-swab samples were collected from restaurants in Arkansas and Texas in the United States. Ten surface areas for each slicer were swabbed using sterile sponges. Denaturing gradient gel electrophoresis (DGGE) was applied to investigate the fingerprint of samples, and each band was further identified by sequence analysis. Pseudomonads were identified as the dominant bacteria followed by Enterobacteriaceae family, and lactic acid bacteria such as Lactococcus lactis and Streptococcus thermophilus were also found. Bacterial distribution was similar for all surface areas, while the blade guard exhibited the greatest diversity. This study provides a profile of the microbial ecology of slicers using DGGE to develop more specific sanitation practices and to reduce cross-contamination during slicing. © 2012 The Society for Applied Microbiology.

  4. Supramolecular gel-assisted synthesis of double shelled Co@CoO@N-C/C nanoparticles with synergistic electrocatalytic activity for the oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Wu, Zexing; Wang, Jie; Han, Lili; Lin, Ruoqian; Liu, Hongfang; Xin, Huolin L.; Wang, Deli

    2016-02-01

    Investigating active, stable, and low-cost materials for the oxygen reduction reaction is one of the key challenges in fuel-cell research. In this work, we describe the formation of N-doped carbon shell coated Co@CoO nanoparticles supported on Vulcan XC-72 carbon materials (Co@CoO@N-C/C) based on a simple supramolecular gel-assisted method. The double-shelled Co@CoO@N-C/C core-shell nanoparticles exhibit superior electrocatalytic activities for the oxygen reduction reaction compared to N-doped carbon and cobalt oxides, demonstrating the synergistic effect of the hybrid nanomaterials. Notably, the Co@CoO@N-C/C nanoparticles give rise to a comparable four-electron selectivity, long-term stability, and high methanol tolerance; all show a multi-fold improvement over the commercial Pt/C catalyst. The progress is of great importance in exploring advanced non-precious metal-based electrocatalysts for fuel cell applications.Investigating active, stable, and low-cost materials for the oxygen reduction reaction is one of the key challenges in fuel-cell research. In this work, we describe the formation of N-doped carbon shell coated Co@CoO nanoparticles supported on Vulcan XC-72 carbon materials (Co@CoO@N-C/C) based on a simple supramolecular gel-assisted method. The double-shelled Co@CoO@N-C/C core-shell nanoparticles exhibit superior electrocatalytic activities for the oxygen reduction reaction compared to N-doped carbon and cobalt oxides, demonstrating the synergistic effect of the hybrid nanomaterials. Notably, the Co@CoO@N-C/C nanoparticles give rise to a comparable four-electron selectivity, long-term stability, and high methanol tolerance; all show a multi-fold improvement over the commercial Pt/C catalyst. The progress is of great importance in exploring advanced non-precious metal-based electrocatalysts for fuel cell applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07929b

  5. Supramolecular gel-assisted synthesis of double shelled Co@CoO@N-C/C nanoparticles with synergistic electrocatalytic activity for the oxygen reduction reaction

    SciTech Connect

    Wu, Zexing; Wang, Jie; Han, Lili; Lin, Ruogian; Liu, Hongfang; Xin, Huolin L.; Wang, Deli

    2016-01-19

    Investigating active, stable, and low-cost materials for the oxygen reduction reaction is one of the key challenges in fuel-cell research. In this work, we describe the formation of N-doped carbon shell coated Co@CoO nanoparticles supported on Vulcan XC-72 carbon materials (Co@CoO@N–C/C) based on a simple supramolecular gel-assisted method. The double-shelled Co@CoO@N–C/C core–shell nanoparticles exhibit superior electrocatalytic activities for the oxygen reduction reaction compared to N-doped carbon and cobalt oxides, demonstrating the synergistic effect of the hybrid nanomaterials. Notably, the Co@CoO@N–C/C nanoparticles give rise to a comparable four-electron selectivity, long-term stability, and high methanol tolerance; all show a multi-fold improvement over the commercial Pt/C catalyst. As a result, the progress is of great importance in exploring advanced non-precious metal-based electrocatalysts for fuel cell applications.

  6. Supramolecular gel-assisted synthesis of double shelled Co@CoO@N-C/C nanoparticles with synergistic electrocatalytic activity for the oxygen reduction reaction

    DOE PAGES

    Wu, Zexing; Wang, Jie; Han, Lili; ...

    2016-01-19

    Investigating active, stable, and low-cost materials for the oxygen reduction reaction is one of the key challenges in fuel-cell research. In this work, we describe the formation of N-doped carbon shell coated Co@CoO nanoparticles supported on Vulcan XC-72 carbon materials (Co@CoO@N–C/C) based on a simple supramolecular gel-assisted method. The double-shelled Co@CoO@N–C/C core–shell nanoparticles exhibit superior electrocatalytic activities for the oxygen reduction reaction compared to N-doped carbon and cobalt oxides, demonstrating the synergistic effect of the hybrid nanomaterials. Notably, the Co@CoO@N–C/C nanoparticles give rise to a comparable four-electron selectivity, long-term stability, and high methanol tolerance; all show a multi-fold improvement overmore » the commercial Pt/C catalyst. As a result, the progress is of great importance in exploring advanced non-precious metal-based electrocatalysts for fuel cell applications.« less

  7. Structural and magnetic properties of magnesium ferrite nanoparticles prepared via EDTA-based sol-gel reaction

    NASA Astrophysics Data System (ADS)

    Hussein, Shaban I.; Elkady, Ashraf S.; Rashad, M. M.; Mostafa, A. G.; Megahid, R. M.

    2015-04-01

    Magnesium ferrite (MgFe2O4) nanoparticles have been prepared, for the first time, by ethylene diamine tetraacetic acid (EDTA)-based sol-gel combustion method. The prepared ferrite system is calcined at 400, 500 and 600 °C. Thermo-gravimetric and differential thermal analysis (TGA-DTA), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, high resolution transmission electron microscopy (HRTEM) and vibrating sample magnetometry (VSM) were applied for elucidating the structural and magnetic properties of the prepared system. XRD patterns revealed that the prepared system have two spinel MgFe2O4 structures, namely cubic and tetragonal phases that are dependent on calcination temperature (Tc). The crystallite sizes varied from 8.933 to 41.583 nm, and from 1.379 to 292.565 nm for the cubic and tetragonal phases respectively depending on Tc. The deduced lattice parameters for the cubic and (tetragonal) systems are a=8.368, 8.365 and 8.377 and (a=7.011, 5.922, 5.908 and c=6.622, 8.456, 8.364) Å at Tc=400, 500 and 600 °C respectively. While the cation distribution of the cubic phase is found to be mixed spinel and Tc-dependent, it is an inverse spinel in the tetragonal phase where the Fe3+ ions occupy both the tetrahedral A- and octahedral B-sites in almost equal amount; the Mg2+ ions are found to occupy only the B-sites. The HRTEM and selected-area electron diffraction (SAED) revealed the detailed morphology of the nanoparticles, and confirmed their crystalline spinel structure. VSM indicated the existence of an appreciable fraction of superparamagnetic particles at room temperature, with pure superparamagnetic behavior observed for samples calcined at 400 °C. Besides, the magnetic properties are found to change by thermal treatment as a result of the varied phase concentration, cation distribution and lattice parameters. Thus, the new synthesis route used in this study by applying EDTA as an organic precursor for preparing MgFe2O4 nanoparticles at

  8. Separation of single-walled carbon nanotubes by gel-based chromatography using surfactant step-gradient techniques and development of new instrumentation for studying SWCNT reaction processes

    NASA Astrophysics Data System (ADS)

    Breindel, Leonard M.

    Single-walled carbon nanotube (SWCNT) synthesis methods such as CoMoCATTM, HiPcoTM, pulsed laser vaporization (PLV), and catalytic chemical vapor deposition (CCVD) produce several different distributions of (n,m) SWCNT structures, where ( n,m) defines the nanotube diameter and chiral wrapping angle. Post-synthesis processing such as functionalization and/or separations must therefore be employed to yield high purity electronic or single (n,m) samples. Through the use of a surfactant gradient across a gel-based chromatographic column, separations of single (n,m) species can be achieved. Anionic surfactants such as SDS, SDBS, and AOT display different separation effectiveness for single (n,m) species. Results of near-infrared optical absorption for separated SWCNT surfactant suspensions will be discussed, leading to a broader understanding of the important factors necessary for the gel chromatography separation technique. In particular, the effects of SWCNT/surfactant micelle structure are found to be key to achieving fast, simple SWCNT electronic type separations. Additionally, development of new instrumentation for the near-infrared spectrofluorimetric analysis (NIR-SFA) of SWCNTs is useful to the advancement of fundamental SWCNT research and applications. NIR-SFA, for instance, allows for the (n,m) structures of a sample to be identified and monitored during the progress of a chemical reaction or separation experiment. Seeking to achieve the time resolutions necessary for such experiments, the design and optimizations of a system utilizing single-wavelength excitation by diode lasers coupled with a fast NIR detection system are presented.

  9. Simultaneous phase- and size-controlled synthesis of TiO(2) nanorods via non-hydrolytic sol-gel reaction of syringe pump delivered precursors.

    PubMed

    Koo, Bonil; Park, Jongnam; Kim, Yukyeong; Choi, Sang-Hyun; Sung, Yung-Eun; Hyeon, Taeghwan

    2006-12-07

    The simultaneous phase- and size-controlled synthesis of TiO(2) nanorods was achieved via the non-hydrolytic sol-gel reaction of continuously delivered two titanium precursors using two separate syringe pumps. As the injection rate was decreased, the length of the TiO(2) nanorods was increased and their crystalline phase was simultaneously transformed from anatase to rutile. When the reaction was performed by injecting titanium precursors contained in two separate syringes into a hot oleylamine surfactant solution with an injection rate of 30 mL/h, anatase TiO(2) nanorods with dimensions of 6 nm (thickness) x 50 nm (length) were produced. When the injection rate was decreased to 2.5 mL/h, star-shaped rutile TiO(2) nanorods with dimensions of 25 nm x 200 nm and a small fraction of rod-shaped anatase TiO(2) nanorods with dimensions of 9 nm x 100 nm were synthesized. Pure star-shaped rutile TiO(2) nanorods with dimensions of 25 nm x 450 nm were synthesized when the injection rate was further decreased to 1.25 mL/h. The simultaneous phase transformation and length elongation of the TiO(2) nanorods were achieved. Under optimized reaction conditions, as much as 3.5 g of TiO(2) nanorods were produced. The TiO(2) nanorods were used to produce dye-sensitized solar cells, and the photoconversion efficiency of the mixture composed of star-shaped rutile TiO(2) nanorods and a small fraction of anatase nanorods were comparable to that of Degussa P-25.

  10. Synthesis of organic-inorganic hybrid sols with nano silica particles and organoalkoxysilanes for transparent and high-thermal-resistance coating films using sol-gel reaction.

    PubMed

    Na, Moonkyong; Park, Hoyyul; Ahn, Myeongsang; Lee, Hyeonhwa; Chung, Ildoo

    2010-10-01

    Organic-inorganic hybrid sols were synthesized from nano silica particles dispersed in water and from organoalkoxysilanes, using the sol-gel reaction. This work focuses on the effects of the three multifunctional organoalkoxysilanes dimethyldimethoxysilane (DMDMS), methyltrimethoxysilane (MTMS), and tetramethoxysilane (TMOS) to form a transparent and high-thermal-resistance coating film. The stability of the hybrid sol was evaluated as a function of the reaction time for 10 d through the variation of the viscosity. The viscosity of the silica/DMDMS and silica/MTMS sol was slightly increased for 10 d. The multifunctional organoalkoxysilanes formed dense silica networks through hydrolysis and condensation reaction, which enhanced the thermal resistance of the coating films. No thermal degradation of the silica/DMDMS sample occurred up to 600 degrees C, and none of the silica/MTMS and silica/TMOS samples occurred either up to 700 degrees C. The organic-inorganic hybrid sols were coated on the glass substrate using a spin-coating procedure. The organic-inorganic hybrid sols formed flat coating films without cracks. The transmittance of the hybrid sol coating films using MTMS and DMDMS was shown to be over 90%. The transmittance of the silica/TMOS sol coating film reacted for 10 d abruptly decreased due to faster gelation. The silica/DMDMS and silica/MTMS hybrid sols formed smooth coating films while the surface roughness of the silica/TMOS coating film markedly increased when the hybrid sol reacted for 10 d. The increase of the surface roughness of the silica/TMOS coating film can be attributed to the degradation of the stability of the hybrid sol and to the loss of transmittance of the coating film. It was confirmed in this study that the use of organic-inorganic hybrid sol can yield transparent and high-thermal-resistance coating films.

  11. Fluorescent and colorimetric magnetic microspheres as nanosensors for Hg2+ in aqueous solution prepared by a sol-gel grafting reaction and host-guest interaction

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Zhang, Yue; Yang, Qingbiao; Sun, Mingda; Fei, Xiaoliang; Song, Yan; Zhang, Yingmu; Li, Yaoxian

    2013-05-01

    Fluorescent sensing TSRh6G-β-cyclodextrin fluorophore/adamantane-modified inclusion complex magnetic nanoparticles (TFIC MNPs) have been synthesized via the cooperation of a host-guest interaction and sol-gel grafting reaction. Powder X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, and UV-visible absorption and emission spectroscopy have been employed to characterize the material. Fluorescence and UV-visible spectra have shown that the resultant multifunctional nanoparticle sensors exhibit selective `turn-on' type fluorescent enhancements and a clear color change from light brown to pink with Hg2+. Owing to a larger surface area and high permeability, TFIC MNPs exhibit remarkable selectivity and sensitivity for Hg2+, and its detection limit measures up to the micromolar level in aqueous solution. Most importantly, magnetic measurements have shown that TFIC magnetic nanoparticles are superparamagnetic and they can be separated and collected easily using a commercial magnet. These results not only solve the limitations in practical sensing applications of nanosensors, but also enable the fabrication of other multifunctional nanostructure-based hybrid nanomaterials.Fluorescent sensing TSRh6G-β-cyclodextrin fluorophore/adamantane-modified inclusion complex magnetic nanoparticles (TFIC MNPs) have been synthesized via the cooperation of a host-guest interaction and sol-gel grafting reaction. Powder X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, and UV-visible absorption and emission spectroscopy have been employed to characterize the material. Fluorescence and UV-visible spectra have shown that the resultant multifunctional nanoparticle sensors exhibit selective `turn-on' type fluorescent enhancements and a clear color change from light brown to pink with Hg2+. Owing to a larger surface area and high permeability, TFIC MNPs exhibit remarkable selectivity and sensitivity for Hg2

  12. How to identify carbonate rock reactions in concrete

    SciTech Connect

    Katayama, Tetsuya . E-mail: katayamat@kge.co.jp

    2004-11-15

    This paper summarizes the modern petrographic techniques used to diagnose carbonate rock reactions in concrete. Concrete microbar specimens of the prototype RILEM AAR-5 test, provided by the Austrian Cement Research Institute, and typical Canadian concrete that had undergone alkali-carbonate reaction (ACR) were examined. Scanning electron microscopy, element mapping and quantitative analysis using electron-probe microanalyzer with energy-dispersive spectrometry (EPMA/EDS: around x 2000, <0.1 nA) were made of polished thin sections after completing polarizing microscopy. Dedolomitization produced a myrmekitic texture, composed of spotted brucite (<3 {mu}m) and calcite within the reaction rim, along with a carbonate halo of calcite in the surrounding cement paste. However, no evidence was detected that dedolomitization had produced the expansion cracks in the cement paste, while the classical definition of alkali-carbonate reaction postulates their development. It was found that the alkali-silica reaction (ASR) due to cryptocrystalline quartz hidden in the matrix, always associated with dedolomitization in all the carbonate aggregates tested, was responsible for the expansion of both the laboratory and field concretes, even with the Canadian dolomitic limestone from Kingston, the reference material for alkali-carbonate reaction. It is suggested that the term alkali-carbonate reaction is misleading.

  13. [A preliminary analysis of changes in composition of intestinal microbiota during infancy using polymerase chain reaction-denaturing gradient gel electrophoresis].

    PubMed

    Li, Shan-Shan; Miao, Jun-Jie; Wu, Zi-Xi; Yao, Jian-Rong; Li, Ming; Yu, Qian; He, Fang

    2017-03-01

    To investigate the composition of bacteria in the stools of infants and the colonization of intestinal microbiota during infancy. Fresh stools were collected from 15 healthy infants at 0, 2, 4, 7, 10, 14, and 28 days and 3, 6, and 12 months after birth. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) was used to analyze the composition of intestinal microbiota, perform sequencing of dominant bacteria, and to analyze the changes in the composition of intestinal microbiota during infancy. DGGE fingerprint showed that the composition of intestinal microbiota during infancy changed significantly over time after birth. The cloning and sequencing results indicated that Proteobacteria colonized the earliest, mainly the obligate aerobes Enterobacter and Pseudomonas, followed by the obligate anaerobes (Clostridium hathewayi and Veillonella parvula) and the facultative anaerobe Clostridium ramosum in Firmicutes, and Verrucomicrobia. Actinobacteria colonized the latest, mainly Bifidobacterium, and gradually became dominant bacteria. During infancy, obligate aerobes colonize the intestinal tract the earliest, followed by obligate anaerobes and facultative anaerobes. Proteobacteria colonizes the earliest, followed by Firmicutes and Verrucomicrobia, and Actinobacteria, mainly Bifidobacterium, colonizes the latest.

  14. [Comparative investigation of fructosobisphosphatases of Bacillus subtilis and pale-green dwarfism pathogens of cereals in the reaction of double diffusion in gel according to Ouchterlony].

    PubMed

    Skrypal', I H; Malynovs'ka, L P; Tokovenko, I P; Iastrebova, O V; Panchenko, L P

    2007-01-01

    Serological properties of fructosobisphosphatases (FBPases) of Bacillus subtilis 668 and PGD agent of cereals--the mollicute Acholplasma laidlawii var. granulum st. 118 (Alg 118) were studied in a comparative aspect with the help of the reaction of double diffusion in gel according to Ouchterlony. It was established for each of microorganisms that their extracellular and intracellular enzymes are similar in serologic respect, and each of them is composed of two antigens, one of them being identical in the both microorganisms, while the other displays only partial identity, since it reacts with antibodies in heterological systems with formation of a precipitation line looking as a "spur". That indicates to the fact that antisera to those enzymes contain antibodies both to general determinants of antigens which are compared (FBPases here), and to the determinant absent in one of them. Basing on the investigation results it is concluded that FBPase of B. subtilis is rather similar than identical, in serological aspect, to the enzyme Alg 118 of the same name.

  15. Unified ZnO Q-dot growth mechanism from simultaneous UV-Vis and EXAFS monitoring of sol-gel reactions induced by different alkali base

    NASA Astrophysics Data System (ADS)

    Caetano, Bruno L.; Silva, Marlon N.; Santilli, Celso V.; Briois, Valérie; Pulcinelli, Sandra H.

    2016-11-01

    This article aims to give experimental evidences of the universality of main steps involved in ZnO nanoparticles formation and growth from sol-gel process. In this way, we revisit the effect of the alkali base (LiOH, NaOH, KOH) used to induce the hydrolysis-condensation reaction in order to unfold the ZnO Q-dot formation mechanisms by using simultaneous time resolved monitoring of zinc species and Q-dot size by combining EXAFS and UV-Vis spectroscopy. Irrespective of the alkali base used, nucleation and growth of ZnO Q-dots occur by consumption of zinc oxy-acetate precursor. Higher amounts of ZnO nanocrystal are produced as the strength of the base increases. After achieving the steady state equilibrium regime the Q-dot growth occurs initially by oriented attachment coalescence mechanism followed by the Ostwald ripening coarsening. The dependence of the formation and growth mechanisms on the base strength allows the fine tuning of the Q-dot size and photoluminescence properties.

  16. Fluorescent and colorimetric magnetic microspheres as nanosensors for Hg2+ in aqueous solution prepared by a sol-gel grafting reaction and host-guest interaction.

    PubMed

    Wang, Wei; Zhang, Yue; Yang, Qingbiao; Sun, Mingda; Fei, Xiaoliang; Song, Yan; Zhang, Yingmu; Li, Yaoxian

    2013-06-07

    Fluorescent sensing TSRh6G-β-cyclodextrin fluorophore/adamantane-modified inclusion complex magnetic nanoparticles (TFIC MNPs) have been synthesized via the cooperation of a host-guest interaction and sol-gel grafting reaction. Powder X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, and UV-visible absorption and emission spectroscopy have been employed to characterize the material. Fluorescence and UV-visible spectra have shown that the resultant multifunctional nanoparticle sensors exhibit selective 'turn-on' type fluorescent enhancements and a clear color change from light brown to pink with Hg(2+). Owing to a larger surface area and high permeability, TFIC MNPs exhibit remarkable selectivity and sensitivity for Hg(2+), and its detection limit measures up to the micromolar level in aqueous solution. Most importantly, magnetic measurements have shown that TFIC magnetic nanoparticles are superparamagnetic and they can be separated and collected easily using a commercial magnet. These results not only solve the limitations in practical sensing applications of nanosensors, but also enable the fabrication of other multifunctional nanostructure-based hybrid nanomaterials.

  17. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE): a promising tool to diagnose bacterial infections in diabetic foot ulcers.

    PubMed

    Dunyach-Remy, C; Cadière, A; Richard, J-L; Schuldiner, S; Bayle, S; Roig, B; Sotto, A; Lavigne, J-P

    2014-12-01

    The diagnosis of diabetic foot infections is difficult due to limitations of conventional culture-based techniques. The objective of this study was to evaluate the contribution of denaturing gradient gel electrophoresis (DGGE) in the microbiological diagnosis of diabetic foot ulcers in comparison to conventional techniques, and also to evaluate the need to perform a biopsy sample for this diagnosis. Twenty diabetic patients (types 1 and 2) with foot ulcers (grades 1-4) were included. After debridement of their wounds, samples were taken in duplicate by surface swabbing and deep-tissue biopsy. The samples were analyzed by conventional culture and by a new molecular biology tool, DGGE technology. Polymerase chain reaction (PCR)-DGGE led to the identification of more bacteria than did conventional cultures (mean: 2.35 vs 0.80, respectively). In 11 cases, the technology detected pathogenic species not isolated by classical cultures. PCR-DGGE also identified significantly more pathogenic species at deep levels compared with species detected at superficial levels (87% vs 58%, respectively; P = 0.03). In 9/20 cases, pathogenic bacteria were detected only in deep samples, revealing the need to perform tissue biopsy sampling. DGGE, achievable in 48h, could be a useful technique for the bacteriological diagnosis of diabetic foot infections. It may help to identify pathogenic bacteria in deeply infected ulcers, thereby contributing to a more appropriate use of antibiotics. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

  18. CONFORMANCE IMPROVEMENT USING GELS

    SciTech Connect

    Randall S. Seright

    2004-09-30

    ) 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.

  19. Separation of intron 22 inversion type 1 and 2 of hemophilia A by modified inverse-shifting polymerase chain reaction and capillary gel electrophoresis.

    PubMed

    Pan, Tzu-Yu; Chiou, Shyh-Shin; Wang, Chun-Chi; Wu, Shou-Mei

    2014-12-01

    An inverse-shifting polymerase chain reaction (IS-PCR) combined with short-end capillary gel electrophoresis (CGE) was developed for genotyping of intron 22 inversion Type 1 (Inv22-1) and Type 2 (Inv22-2) of hemophilia A (HA). Severe HA cases are affected by intron 22 inversion around 45-50%. Inv22-1 has higher frequency than Inv22-2. The aim of this study is to distinguish them by genotyping. In order to improve Inv22 genotyping efficiency, five primers were designed and applied to differentiate the wild type, Inv22-1, Inv22-2 and carrier. Three amplicons of 405, 457 and 512 bp were recognized for wild type; 333, 457 and 584 bp for Inv22-1; 385, 405 and 584 bp for Inv22-2. The Inv22-1 carrier has 5 amplicons including 333, 405, 457, 512, 584 bp and Inv22-2 carrier is differentiated by 385, 405, 457, 512 and 584 bp. The amplicons between Inv22-1 and Inv22-2 carriers are only different in 333 bp for Inv22-1 carrier and 385 bp for Inv22-2 carrier. Capillary gel electrophoresis (CGE) was used for separation within 5 min. The separation voltage was set at 8 kV (cathode at detector), and the temperature was kept at 25°C. The sieving matrix was 89 mM Tris, 89 mM boric acid, 2mM EDTA containing 0.4% (w/v) HPMC and 1 μM of YO-PRO(®)-1 Iodide. Total of 50 HA patients (including 35 non-Inv22, 14 Inv22-1, and one Inv22-2 patients) and 7 HA carriers were diagnosed in the application. Seven random samples (5 patients and 2 carriers) were subjected to comparison and gave identical results of DNA sequencing and this modified IS-PCR.

  20. Calculating Percent Gel For Process Control

    NASA Technical Reports Server (NTRS)

    Webster, Charles Neal; Scott, Robert O.

    1988-01-01

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

  1. Detection of Helicobacter species in liver and stomach tissues of patients with chronic liver diseases using polymerase chain reaction-denaturing gradient gel electrophoresis and immunohistochemistry.

    PubMed

    Stalke, Piotr; Al-Soud, Waleed Abu; Bielawski, Krzysztof P; Bakowska, Alicja; Trocha, Hanna; Stepinski, Jan; Wadström, Torkel

    2005-09-01

    Helicobacter DNA has been detected in the hepatobiliary tree of patients with chronic liver diseases (CLD). The presence of H. pylori in the stomach compared with in the liver of the same patients with CLD has not been studied, therefore to the aim of this study was to investigate the presence of Helicobacter DNA and antigens in the liver and stomach of Polish patients with chronic liver diseases using molecular and immunological methods. Gastric mucosa and liver tissue samples and sera were collected from 97 Polish patients with CLD. Anti-H. pylori antibodies were detected by enzyme immunoassay (EIA), and H. pylori-like antigens detected by immunohistochemistry. Helicobacter DNA was detected in stomach and liver samples using a semi-nested Helicobacter genus-specific polymerase chain reaction (PCR) assay, and Helicobacter species identified by denaturing gradient gel electrophoresis (DGGE) and sequencing analysis of amplified PCR products. H. pylori was identified by DGGE and sequence analysis in 60/62 (97%) and 25/25 (100%) of the gastric and liver Helicobacter genus-positive samples, respectively, whereas DNA of H. heilmannii was detected in 2/62 (3%) of the Helicobacter genus-positive gastric samples. H. pylori cagA gene was detected in 23/62 (36%) and 3/25 (12%) gastric and liver tissue samples, respectively. H. pylori-like antigens were detected in 61/97 (63%) gastric mucosa and in 40/97 (41%) liver tissue samples. H. pylori-like organisms appeared to dominate the gastric mucosa and liver tissue of Polish patients with CLD. The prevalence of the cagA gene was higher in stomach compared with liver samples, which suggests a possible role of cagA negative H. pylori-like organisms in CLD. On the other hand, no significant correlation was found between the presence of H. pylori-like DNA and antigens in the liver and liver function tests.

  2. Comparison of automated repetitive-sequence-based polymerase chain reaction and spa typing versus pulsed-field gel electrophoresis for molecular typing of methicillin-resistant Staphylococcus aureus.

    PubMed

    Church, Deirdre L; Chow, Barbara L; Lloyd, Tracie; Gregson, Daniel B

    2011-01-01

    Automated repetitive polymerase chain reaction (PCR) (DiversiLab, bioMérieux, St. Laurent, Quebec, Canada) and single locus sequence typing of the Staphylococcus protein A (spa) gene with spa-type assignment by StaphType RIDOM software were compared to pulsed-field gel electrophoresis (PFGE) as the "gold standard" method for methicillin-resistant Staphylococcus aureus (MRSA) typing. Fifty-four MRSA isolates were typed by all methods: 10 of known PFGE CMRSA type and 44 clinical isolates. Correct assignment of CMRSA type or cluster occurred for 47 of 54 (87%) of the isolates when using a rep-PCR similarity index (SI) of ≥95%. Rep-PCR gave 7 discordant results [CMRSA1 (3), CMRSA2 (1), CMRSA4 (1), and CMRSA10 (2)], and some CMRSA clusters were not distinguished (CMRSA10/5/9, CMRSA 7/8, and CMRSA3/6). Several spa types occurred within a single PFGE or repetitive PCR types among the 19 different spa types found. spa type t037 was shared by CMRSA3 and CMRSA6 strains, and CMRSA9 and most CMRSA10 strains shared spa type t008. Time to results for PFGE, repetitive PCR, and spa typing was 3-4 days, 24 h, and 48 h, respectively. The annual costs of using spa or repetitive PCR were 2.4× and 1.9× higher, respectively, than PFGE but routine use of spa typing would lower annual labor costs by 0.10 full-time equivalents compared to PFGE. Repetitive PCR is a good method for rapid outbreak screening, but MRSA isolates that share the same repetitive PCR or PFGE patterns can be distinguished by spa typing. Copyright © 2011 Elsevier Inc. All rights reserved.

  3. Polyurethane-silica hybrid foams from a one-step foaming reaction, coupled with a sol-gel process, for enhanced wound healing.

    PubMed

    Song, Eun-Ho; Jeong, Seol-Ha; Park, Ji-Ung; Kim, Sukwha; Kim, Hyoun-Ee; Song, Juha

    2017-10-01

    Polyurethane (PU)-based dressing foams have been widely used due to their excellent water absorption capability, optimal mechanical properties, and unequaled economic advantage. However, the low bioactivity and poor healing capability of PU limit the applications of PU dressings in complex wound healing cases. To resolve this problem, this study was carried out the hybridization of bioactive silica nanoparticles with PU through a one-step foaming reaction that is coupled with the sol-gel process. The hybridization with silica did not affect the intrinsically porous microstructure of PU foams with silica contents of up to 10wt% and where 5-60nm silica nanoparticles were well dispersed in the PU matrix, despite slight agglomerations. The incorporated silica enhanced the mechanical performance of PU by proffering better flexibility and durability as well as maintaining good water absorption capabilities and the WVTR characteristics of pure PU foam. The silica of PU-10wt% Si foams was gradually dissolved and released under physiological conditions during a 14-day immersion period. The in vitro cell attachment and proliferation tests showed significant improvements in terms of the biocompatibility of PU-Si hybrid foams and demonstrated the effects of silica on cell growth. More significantly, the superior healing capability of PU-Si as a wound dressing in comparison to PU-treated wounds was verified through in vivo animal tests. Full-thickness wounds treated with PU-Si foams exhibited faster wound closure rates as well as accelerated collagen and elastin fiber regeneration in newly formed dermis, which was ultimately completely covered by a new epithelial layer. It is clear that PU-Si hybrid foams have considerable potential as a wound dressing material geared for accelerated, superior wound healing. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Polyacrylamide gel electrophoresis.

    PubMed

    Chrambach, A; Rodbard, D

    1971-04-30

    Polyacrylamide gel electrophoresis (PAGE) provides a versatile, gentle, high resolution method for fractionation and physical-chemical characterization of molecules on the basis of size, conformation, and net charge. The polymerization reaction can be rigorously controlled to provide uniform gels of reproducible, measurable pore size over a wide range. This makes it possible to obtain reproducible relative mobility (Rf) values as physical-chemical constants. Application and extension of Ogston's (random fiber) model for a gel allows for calculation of molecular volume, surface area, or radius, free mobility, and valence from RJ measurements at several gel concentrations, to calculate gel concentration for optimal resolution, and to predict behavior of macromolecules on gel gradients by computerized methods. Extension of classical moving boundary theory has been used to generate multiphasic buffer systems (providing selective stacking, unstacking, restacking, and preparative steady-state-stacking) with known operating characteristics for any pH at 0 degrees and 25 degrees C. A general strategy for isolation of macromolecules and for macromolecular mapping has been developed. Preparative scale PAGE is operational for milligram loads and feasible for gram quantities.

  5. Mineralogy, geochemistry and expansion testing of an alkali-reactive basalt from western Anatolia, Turkey

    SciTech Connect

    Copuroglu, Oguzhan; Andic-Cakir, Ozge; Broekmans, Maarten A.T.M.; Kuehnel, Radko

    2009-07-15

    In this paper, the alkali-silica reaction performance of a basalt rock from western Anatolia, Turkey is reported. It is observed that the rock causes severe gel formation in the concrete microbar test. It appears that the main source of expansion is the reactive glassy phase of the basalt matrix having approximately 70% of SiO{sub 2}. The study presents the microstructural characteristics of unreacted and reacted basalt aggregate by optical and electron microscopy and discusses the possible reaction mechanism. Microstructural analysis revealed that the dissolution of silica is overwhelming in the matrix of the basalt and it eventually generates four consequences: (1) Formation of alkali-silica reaction gel at the aggregate perimeter, (2) increased porosity and permeability of the basalt matrix, (3) reduction of mechanical properties of the aggregate and (4) additional gel formation within the aggregate. It is concluded that the basalt rock is highly prone to alkali-silica reaction. As an aggregate, this rock is not suitable for concrete production.

  6. High transparent shape memory gel

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  7. Characterisation of Maillard reaction products derived from LEKFD--a pentapeptide found in β-lactoglobulin sequence, glycated with glucose--by tandem mass spectrometry, molecular orbital calculations and gel filtration chromatography coupled with continuous photodiode array.

    PubMed

    Yamaguchi, Keiko; Homma, Takeshi; Nomi, Yuri; Otsuka, Yuzuru

    2014-02-15

    Maillard reaction peptides (MRPs) contribute to taste, aroma, colour, texture and biological activity. However, peptide degradation or the cross-linking of MRPs in the Maillard reaction has not been investigated clearly. A peptide of LEKFD, a part of β-lactoglobulin, was heated at 110 °C for 24h with glucose and the reaction products were analysed by HPLC with ODS, ESI-MS, ESI-MS/MS and HPLC with gel-filtration column and DAD detector. In the HPLC fractions, an imminium ion of LEK*FD, a pyrylium ion or a hydroxymethyl furylium ion of LEK*FD, and KFD and EK were detected by ESI-MS. Therefore, those products may be produced by the Maillard reaction. The molecular orbital of glycated LEKFD at the lysine epsilon-amino residue with Schiff base form was calculated by MOPAC. HPLC with gel-filtration column showed cross-linking and degradation of peptides. Copyright © 2013 Elsevier Ltd. All rights reserved.

  8. Retrospective study of radiotherapy-induced skin reactions in breast cancer patients: reduced incidence of moist desquamation with a hydroactive colloid gel versus dexpanthenol.

    PubMed

    Censabella, Sandrine; Claes, Stefan; Orlandini, Marc; Braekers, Roel; Thijs, Herbert; Bulens, Paul

    2014-10-01

    Dermatitis is a very frequent and distressing side effect of radiation therapy that may necessitate a treatment interruption when evolving towards more severe forms such as moist desquamation (MD). The aim of this study was to compare the efficacy of two topical agents, a dexpanthenol cream vs a hydroactive colloid gel combining absorbing and moisturising properties, in preventing MD in breast cancer patients. This retrospective study compared two successive groups of breast cancer patients undergoing radiotherapy after breast-sparing surgery between 2008 and 2012. A group of 267 patients applied a 5% dexpanthenol cream on the irradiated zone throughout the course of their radiotherapy. Another group of 216 patients applied first the dexpanthenol cream then replaced it by the hydroactive colloid gel after 11-14 days of radiotherapy. Radiation treatment (total dose, technique, and equipment) was the same for the two groups. The clinical outcomes were the occurrence and time to onset of moist desquamation. The overall incidence of MD was significantly lower in patients who applied the hydroactive colloid gel (16%) than in those who applied the dexpanthenol cream (32%, odds-ratio = 0.35). Also, MD occurred significantly later with the hydroactive colloid gel than with the dexpanthenol cream (hazard ratio = 0.39). Compared with the dexpanthenol cream, the hydroactive colloid gel significantly reduced the risk of developing MD in patients undergoing radiotherapy for breast cancer. These promising results warrant further research on the efficacy of hydroactive colloid gels in managing radiation dermatitis. Copyright © 2014 Elsevier Ltd. All rights reserved.

  9. Reaction calorimetry for coal chemistry and catalysis. Quarterly report, February 1, 1985-April 30, 1985. [Heats of immersion of triphenylsilanol and silica gel

    SciTech Connect

    Arnett, E.M.

    1985-01-01

    Extension of the thermochemical approach to the study of hydrogen bond interactions on silica gel and its homogeneous analogue, triphenylsilanol, is presented here. This thermochemical study is analogous to that presented by R. Haaksma in previous reports (i.e., Annual Report August 1983 to July 1984). Heats of immersion were determined on the Setaram C-80 Tian-Calvet Calorimeter. While Haaksma used Dowex and p-toluene sulfonic acid as models for Broensted (proton transfer) processes in the thermochemical comparison, we are testing silica gel and triphenylsilanol as models for hydrogen bonding interactions. 9 refs., 3 figs., 5 tabs.

  10. Detection Of Concrete Deterioration By Staining

    DOEpatents

    Guthrie, Jr., George D.; Carey, J. William

    1999-09-21

    A method using concentrated aqueous solutions of sodium cobaltinitrite and a rhodamine dye is described which can be used to identify concrete that contains gels formed by the alkali-silica reaction (ASR), and to identify degraded concrete which results in a porous or semi-permeable paste due to carbonation or leaching. These solutions present little health or environmental risk, are readily applied, and rapidly discriminate between two chemically distinct gels; K-rich, Na--K--Ca--Si gels are identified by yellow staining, and alkali-poor, Ca--Si gels are identified by pink staining.

  11. The Flögel-three-component reaction with dicarboxylic acids – an approach to bis(β-alkoxy-β-ketoenamides) for the synthesis of complex pyridine and pyrimidine derivatives

    PubMed Central

    Bera, Mrinal K; Domínguez, Moisés; Hommes, Paul

    2014-01-01

    Summary An extension of the substrate scope of the Flögel-three-component reaction of lithiated alkoxyallenes, nitriles and carboxylic acids is presented. The use of dicarboxylic acids allowed the preparation of symmetrical bis(β-ketoenamides) from simple starting materials in moderate yields. Cyclocondensations of these enamides to 4-hydroxypyridine derivatives or to functionalized pyrimidines efficiently provided symmetrically and unsymmetrically substituted fairly complex (hetero)aromatic compounds containing up to six conjugated aryl and hetaryl groups. In addition, subsequent functionalizations of the obtained heterocycles by palladium-catalyzed couplings or by oxidations are reported. We also describe the simple synthesis of a structurally interesting macrocyclic bispyrimidine derivative incorporating a 17-membered ring, whose configuration was elucidated by DFT calculations and by subsequent reactions. PMID:24605160

  12. Multiple phases of protien gels

    NASA Astrophysics Data System (ADS)

    Annaka, Masahiko; Tanaka, Toyoichi

    1994-03-01

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

  13. Adhesive, elastomeric gel impregnating composition

    DOEpatents

    Shaw, David Glenn; Pollard, John Randolph; Brooks, Robert Aubrey

    2002-01-01

    An improved capacitor roll with alternating film and foil layers is impregnated with an adhesive, elastomeric gel composition. The gel composition is a blend of a plasticizer, a polyol, a maleic anhydride that reacts with the polyol to form a polyester, and a catalyst for the reaction. The impregnant composition is introduced to the film and foil layers while still in a liquid form and then pressure is applied to aid with impregnation. The impregnant composition is cured to form the adhesive, elastomeric gel. Pressure is maintained during curing.

  14. Aerosol gels

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

  15. Synthesis and characterization of Nafion/SiO2 - MOx (M= Ti, Zr, W) nanocomposite membranes by sol-gel reaction for fuel cells

    NASA Astrophysics Data System (ADS)

    Shahzadi, Ambreen; Ahmed, Riaz; Siddiq, Muhammad

    2014-06-01

    Development of efficient and durable cation exchange membranes for fuel cells is important particularly a method for inhibiting the volatility of water at higher temperature is a crucial issue. Nafion composite membranes were prepared by impregnation with SiO2, SiO2 -TiO2, SiO2 - WO3, and SiO2 - ZrO2 by immersing these in-situ sol-gel solution and stirring. The sol-gel solution mixture served to swell the pores of the membrane to maximize the adsorption of the precursor solution. The composite membranes have been characterized by X-ray diffraction, scanning electron microscopy, water uptake, ion exchange capacity and conductivity. XRD studies showed the crystallinity and particle sizes of oxides. FTIR showed the bond formation in oxide mixtures. SEM provides information about the morphology of the particles. Water uptake increased gradually from pure membrane to SiO2, SiO2 - TiO2, SiO2 -WO3, and SiO2 - ZrO2 particles added membranes and was maximum for SiO2 - ZrO2 added membrane. Composite membranes exhibited higher water uptake, ion exchange capacity, conductivity and can improve the efficiency and durability of PEM fuel cells considerably.

  16. Seasonal variation in communities of ammonia-oxidizing bacteria based on polymerase chain reaction - denaturing gradient gel electrophoresis in a biofilm reactor for drinking water pretreatment.

    PubMed

    Zhang, Xiao-Wen; Qin, Ying-Ying; Ren, Hong-Qiang; Li, Dao-Tang; Yang, Hong

    2008-05-01

    The diversity and variation of total and active ammonia-oxidizing bacteria in a full-scale aerated submerged biofilm reactor for drinking water pretreatment were characterized by clone libraries and denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA and its gene during a whole year. Sequences obtained from clone libraries affiliated with the Nitrosomonas oligotropha lineage and the Nitrosomonas communis lineage. An uncultured subgroup of Nitrosomonas communis lineage was also detected. Seasonal variations in both total and active ammonia-oxidizing bacteria communities were observed in the DGGE profiles, but an RNA-based analysis reflected more obvious dynamic changes in ammonia-oxidizer community than a DNA-based approach. Statistical study based on canonical correspondence analysis showed that a community shift of active ammonia oxidizers was significantly influenced by temperature and pH, but no significant correlation was found between environmental variables and total ammonia-oxidizer community shift.

  17. Discriminative detection of low-abundance point mutations using a PCR/ligase detection reaction/capillary gel electrophoresis method and fluorescence dual-channel monitoring.

    PubMed

    Hamada, Mariko; Shimase, Koji; Tsukagoshi, Kazuhiko; Hashimoto, Masahiko

    2014-04-01

    We applied a facile LIF dual-channel monitoring system recently developed and reported by our group to the polymerase chain reaction/ligase detection reaction/CGE method for detecting low-abundance point mutations present in a wild-type sequence-dominated population. Mutation discrimination limits and signaling fidelity of the analytical system were evaluated using three mutant variations in codon 12 of the K-ras oncogene that have high diagnostic value for colorectal cancer. We demonstrated the high sensitivity of the present method by detecting rare mutations present among an excess of wild-type alleles (one mutation among ~100 normal sequences). This method also simultaneously interrogated the allelic compositions of the test samples with high specificity through spectral discrimination of the dye-tagged ligase detection reaction products using the dual-channel monitoring system.

  18. Metal-silica sol-gel materials

    NASA Technical Reports Server (NTRS)

    Stiegman, Albert E. (Inventor)

    2002-01-01

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

  19. Preparation of YBa 2Cu 3O 7- x superconducting solutions and films from alkoxide-based precursors using sol-gel method and investigation of their chemical reaction mechanisms

    NASA Astrophysics Data System (ADS)

    Mutlu, Ibrahim Halil; Acun, Hediye; Celik, Erdal; Turkmen, Hasan

    2007-01-01

    In the development of coated superconductors sol-gel technique has been widely used as an effective processing method, especially in making long-length wires and tapes. However, one drawback associated with the deposition of YBa2Cu3O7-x and Gd2O3 buffer layer on Ni tape is the adhesion characteristic at interfaces YBCO-Gd2O3 and Gd2O3-NiO and NiO-Ni substrate. In this paper, two strategies for adhesion enhancement of multilayered ceramic oxide coatings on Ni substrate were proposed: (1) formation of chemical bonds through surface condensation reactions, and development of ceramic networks through diffusion of alkoxide precursors. The current research has focused on the fabrication and adhesion of YBCO coatings on buffered Ni substrate using nine solutions prepared from Y, Ba and Cu alkoxides, solvent and chelating agent. Only two of YBCO solutions were successfully obtained while the rest of them were unsuccessful. Among these solutions we scrutinized chemical reaction mechanisms of a successful and an unsuccessful solution for comparison. How the chemical bonds and solubility were affected by the acids, base and solvents used in the solutions was demonstrated. It was shown that pH of the solution, homogeneity of the solution and gelation, steric affect of the chemicals in sol-gel solutions are significant issues to obtain high quality superconducting YBCO thin films. In addition, X-ray diffraction (XRD) was used to analyze phase structure of YBCO and compare results of chemical reactions obtained by a chemdraw programme. Scanning electron microscope (SEM) studies was carried out to examine microstructures of YBCO films produced from alkoxide precursors, solvent, chelating agent and modifying liquid chemical materials such as triethanolamine or ammonium hydroxide. It was found to be YBCO, Gd2O3, NiO and Ni phases in YBCO/Gd2O3/Ni sample from XRD analysis. That the solution prepared by using triethanolamine provided the best film quality and adhesion was determined

  20. Dynamic changes of yak (Bos grunniens) gut microbiota during growth revealed by polymerase chain reaction-denaturing gradient gel electrophoresis and metagenomics.

    PubMed

    Nie, Yuanyang; Zhou, Zhiwei; Guan, Jiuqiang; Xia, Baixue; Luo, Xiaolin; Yang, Yang; Fu, Yu; Sun, Qun

    2017-07-01

    To understand the dynamic structure, function, and influence on nutrient metabolism in hosts, it was crucial to assess the genetic potential of gut microbial community in yaks of different ages. The denaturing gradient gel electrophoresis (DGGE) profiles and Illumina-based metagenomic sequencing on colon contents of 15 semi-domestic yaks were investigated. Unweighted pairwise grouping method with mathematical averages (UPGMA) clustering and principal component analysis (PCA) were used to analyze the DGGE fingerprint. The Illumina sequences were assembled, predicted to genes and functionally annotated, and then classified by querying protein sequences of the genes against the Kyoto encyclopedia of genes and genomes (KEGG) database. Metagenomic sequencing showed that more than 85% of ribosomal RNA (rRNA) gene sequences belonged to the phylum Firmicutes and Bacteroidetes, indicating that the family Ruminococcaceae (46.5%), Rikenellaceae (11.3%), Lachnospiraceae (10.0%), and Bacteroidaceae (6.3%) were dominant gut microbes. Over 50% of non-rRNA gene sequences represented the metabolic pathways of amino acids (14.4%), proteins (12.3%), sugars (11.9%), nucleotides (6.8%), lipids (1.7%), xenobiotics (1.4%), coenzymes, and vitamins (3.6%). Gene functional classification showed that most of enzyme-coding genes were related to cellulose digestion and amino acids metabolic pathways. Yaks' age had a substantial effect on gut microbial composition. Comparative metagenomics of gut microbiota in 0.5-, 1.5-, and 2.5-year-old yaks revealed that the abundance of the class Clostridia, Bacteroidia, and Lentisphaeria, as well as the phylum Firmicutes, Bacteroidetes, Lentisphaerae, Tenericutes, and Cyanobacteria, varied more greatly during yaks' growth, especially in young animals (0.5 and 1.5 years old). Gut microbes, including Bacteroides, Clostridium, and Lentisphaeria, make a contribution to the energy metabolism and synthesis of amino acid, which are essential to the normal growth

  1. Dynamic changes of yak (Bos grunniens) gut microbiota during growth revealed by polymerase chain reaction-denaturing gradient gel electrophoresis and metagenomics

    PubMed Central

    Nie, Yuanyang; Zhou, Zhiwei; Guan, Jiuqiang; Xia, Baixue; Luo, Xiaolin; Yang, Yang; Fu, Yu; Sun, Qun

    2017-01-01

    Objective To understand the dynamic structure, function, and influence on nutrient metabolism in hosts, it was crucial to assess the genetic potential of gut microbial community in yaks of different ages. Methods The denaturing gradient gel electrophoresis (DGGE) profiles and Illumina-based metagenomic sequencing on colon contents of 15 semi-domestic yaks were investigated. Unweighted pairwise grouping method with mathematical averages (UPGMA) clustering and principal component analysis (PCA) were used to analyze the DGGE fingerprint. The Illumina sequences were assembled, predicted to genes and functionally annotated, and then classified by querying protein sequences of the genes against the Kyoto encyclopedia of genes and genomes (KEGG) database. Results Metagenomic sequencing showed that more than 85% of ribosomal RNA (rRNA) gene sequences belonged to the phylum Firmicutes and Bacteroidetes, indicating that the family Ruminococcaceae (46.5%), Rikenellaceae (11.3%), Lachnospiraceae (10.0%), and Bacteroidaceae (6.3%) were dominant gut microbes. Over 50% of non-rRNA gene sequences represented the metabolic pathways of amino acids (14.4%), proteins (12.3%), sugars (11.9%), nucleotides (6.8%), lipids (1.7%), xenobiotics (1.4%), coenzymes, and vitamins (3.6%). Gene functional classification showed that most of enzyme-coding genes were related to cellulose digestion and amino acids metabolic pathways. Conclusion Yaks’ age had a substantial effect on gut microbial composition. Comparative metagenomics of gut microbiota in 0.5-, 1.5-, and 2.5-year-old yaks revealed that the abundance of the class Clostridia, Bacteroidia, and Lentisphaeria, as well as the phylum Firmicutes, Bacteroidetes, Lentisphaerae, Tenericutes, and Cyanobacteria, varied more greatly during yaks’ growth, especially in young animals (0.5 and 1.5 years old). Gut microbes, including Bacteroides, Clostridium, and Lentisphaeria, make a contribution to the energy metabolism and synthesis of amino acid

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

    PubMed

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

    2014-07-29

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

  3. Sol-gel antireflective coating on plastics

    DOEpatents

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

    1988-01-26

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

  4. Sol-gel antireflective coating on plastics

    DOEpatents

    Ashley, Carol S.; Reed, Scott T.

    1990-01-01

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

  5. Sol-gel antireflective coating on plastics

    DOEpatents

    Ashley, Carol S.; Reed, Scott T.

    1990-01-01

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

  6. Lithological influence of aggregate in the alkali-carbonate reaction

    SciTech Connect

    Lopez-Buendia, A.M. . E-mail: angel.lopez@aidico.es; Climent, V. . E-mail: vcliment@grupogla.com; Verdu, P.

    2006-08-15

    The reactivity of carbonate rock with the alkali content of cement, commonly called alkali-carbonate reaction (ACR), has been investigated. Alkali-silica reaction (ASR) can also contribute in the alkali-aggregate reaction (AAR) in carbonate rock, mainly due to micro- and crypto-crystalline quartz or clay content in carbonate aggregate. Both ACR and ASR can occur in the same system, as has been also evidenced on this paper. Carbonate aggregate samples were selected using lithological reactivity criteria, taking into account the presence of dedolomitization, partial dolomitization, micro- and crypto-crystalline quartz. Selected rocks include calcitic dolostone with chert (CDX), calcitic dolostone with dedolomitization (CDD), limestone with chert (LX), marly calcitic dolostone with partial dolomitization (CD), high-porosity ferric dolostone with clays (FD). To evaluate the reactivity, aggregates were studied using expansion tests following RILEM AAR-2, AAR-5, a modification using LiOH AAR-5Li was also tested. A complementary study was done using petrographic monitoring with polarised light microscopy on aggregates immersed in NaOH and LiOH solutions after different ages. SEM-EDAX has been used to identify the presence of brucite as a product of dedolomitization. An ACR reaction showed shrinkage of the mortar bars in alkaline solutions explained by induced dedolomitization, while an ASR process typically displayed expansion. Neither shrinkage nor expansion was observed when mortar bars were immersed in solutions of lithium hydroxide. Carbonate aggregate classification with AAR pathology risk has been elaborated based on mechanical behaviours by expansion and shrinkage. It is proposed to be used as a petrographic method for AAR diagnosis to complement the RILEM AAR1 specifically for carbonate aggregate. Aggregate materials can be classified as I (non-reactive), II (potentially reactive), and III (probably reactive), considering induced dedolomitization ACR

  7. Optical fiber chemical sensors with sol-gel derived nanomaterials for monitoring high temperature/high pressure reactions in clean energy technologies

    NASA Astrophysics Data System (ADS)

    Tao, Shiquan

    2010-04-01

    The development of sensor technologies for in situ, real time monitoring the high temperature/high pressure (HTP) chemical processes used in clean energy technologies is a tough challenge, due to the HTP, high dust and corrosive chemical environment of the reaction systems. A silica optical fiber is corrosive resistance, and can work in HTP conditions. This paper presents our effort in developing fiber optic sensors for in situ, real time monitoring the concentration of trace ammonia and hydrogen in high temperature gas samples. Preliminary test results illustrate the feasibility of using fiber optic sensor technologies for monitoring HTP processes for next generation energy industry.

  8. Optically transparent dense colloidal gels

    PubMed Central

    Zupkauskas, M.; Lan, Y.; Joshi, D.; Ruff, Z.

    2017-01-01

    Traditionally it has been difficult to study the porous structure of dense colloidal gels and (macro) molecular transport through them simply because of the difference in refractive index between the colloid material and the continuous fluid phase surrounding it, rendering the samples opaque even at low colloidal volume fractions. Here, we demonstrate a novel colloidal gel that can be refractive index-matched in aqueous solutions owing to the low refractive index of fluorinated latex (FL)-particles (n = 1.37). Synthesizing them from heptafluorobutyl methacrylate using emulsion polymerization, we demonstrate that they can be functionalized with short DNA sequences via a dense brush-layer of polystyrene-b-poly(ethylene oxide) block-copolymers (PS-PEO). The block-copolymer, holding an azide group at the free PEO end, was grafted to the latex particle utilizing a swelling–deswelling method. Subsequently, DNA was covalently attached to the azide-end of the block copolymer via a strain-promoted alkyne–azide click reaction. For comparison, we present a structural study of single gels made of FL-particles only and composite gels made of a percolating FL-colloid gel coated with polystyrene (PS) colloids. Further we demonstrate that the diffusivity of tracer colloids dispersed deep inside a refractive index matched FL-colloidal gel can be measured as function of the local confinement using Dynamic Differential Microscopy (DDM). PMID:28970935

  9. Electrochemical chloride extraction: efficiency and side effects

    SciTech Connect

    Orellan, J.C.; Escadeillas, G.; Arliguie, G

    2004-02-01

    Some specimens of reinforced concrete cast with an alkali-resistant aggregate, previously maintained in a solution of NaCl, were subjected to an electrochemical chloride extraction (ECE). The chloride profiles before and after treatment were determined. Likewise, alkali ions profiles before and after treatment were determined. After treatment, some specimens were stored in a controlled atmosphere (60 deg. C and 100% RH) in order to accelerate the alkali-silica reaction, if any. Results of chloride content after treatment show that about 40% of the initial chloride is removed within 7 weeks. About one-half of the chloride close to steel was removed, but at the same time, significant amounts of alkali ions were observed around the steel. Microstructural observations by scanning electron microscopy (SEM) showed that after treatment, new cementitious phases containing higher concentrations of sodium, aluminum and potassium were formed. Moreover, alkali-silica gel was observed in the specimens stored at 60 deg. C and 100% RH. It may be possible that the ECE accumulates locally high amounts of alkali ions that stimulate the alkali-silica reaction even though the concrete contained nominally inert siliceous aggregates. The specimen expansions were not recorded, but no cracks were observed.

  10. Controlled Synthesis of Uniform, Micrometer-Sized Ruthenium-Functionalized Poly(N-Isopropylacrylamide) Gel Particles and their Application to the Catalysis of the Belousov-Zhabotinsky Reaction.

    PubMed

    Hu, Yuandu; Pérez-Mercader, Juan

    2017-02-01

    Ruthenium-functionalized poly(N-isopropyl acrylamide)-based chemically oscillating microgels with diameters between 1 and 6 µm are synthesized by a modified precipitation polymerization approach. It is found that the initial amount of N-isopropyl acrylamide (NIPAAm) can significantly affect the final sizes of the microgels. 2.5 g of initial NIPAAm results in microgels with maximum average diameter of ≈6 ± 0.5 µm. Making use of their fluorescence due to their ruthenium contents and their larger sizes compared to microgels prepared using other traditional methods, the impact of changes in the NaBrO3 concentrations on their microscopic behavior is studied using a combination of fluorescence microscopy and dynamic light scattering techniques. When increasing the concentration of NaBrO3 in a solution, the microgels first experience a decrease in size followed by aggregation that leads to the loss of colloidal stability. Finally, the redox potential behavior and optical performance of the Belousov-Zhabotinsky reaction catalyzed by these microgels are studied by electrochemical and spectroscopic means.

  11. Gel-sol synthesis of rutile nanoparticles.

    PubMed

    Verhovšek, Dejan; Lešnik, Maja; Veronovski, Nika; Samardžija, Zoran; Žagar, Kristina; Čeh, Miran

    2014-01-01

    Titanium dioxide (TiO(2)) rutile nanoparticles were synthesized at temperatures below 100 °C using a gel-sol process that provides control of the final particles' characteristics, such as the nanoparticle size, morphology, crystal structure and crystallinity. The synthesized rutile nanoparticles were analyzed using X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that the gel-sol process allows control over the final nanoparticle characteristics with the proper choice of reaction parameters. The most profound influence on the nanoparticles' properties is achieved by the type and concentration of the acid used in the reaction mixture. The gel-sol synthesis resulted in anisotropic rutile nanoparticles that are 60-160 nm long, depending on the reaction parameters, and have an aspect ratio of about 5. A reaction mechanism is presented, explaining the influence of various reaction parameters on the characteristics of the TiO(2) nanoparticles.

  12. Self-oscillating gels beating like a heart muscle

    PubMed Central

    Yoshida, Ryo

    2012-01-01

    So far stimuli-responsive polymer gels and their application to smart materials have been widely studied. On the other hand, as a novel biomimetic gel, we developed gels with an autonomous self-oscillating function like a heart muscle, which was firstly reported in 1996. We designed the self-oscillating polymers and gels by utilizing the oscillating reaction, called the Belousov-Zhabotinsky (BZ) reaction. The self-oscillating polymer is composed of a poly(N-isopropylacrylamide) network in which the catalyst for the BZ reaction is covalently immobilized. In the presence of the reactants, the polymer gel undergoes spontaneous cyclic swelling–deswelling changes without any on–off switching of external stimuli. Potential applications of the self-oscillating polymers and gels include several kinds of functional material systems, such as bio-mimetic actuators and mass transport surface. In this review, recent progress on the polymer gels is introduced. PMID:27493533

  13. Photocatalytic activity of nanostructured {gamma}-Al{sub 2}O{sub 3}/TiO{sub 2} composite powder formed via a polyelectrolyte-multilayer-assisted sol-gel reaction

    SciTech Connect

    Logar, Manca; Kocjan, Andraz; Dakskobler, Ales

    2012-01-15

    Highlights: Black-Right-Pointing-Pointer PEM assisted synthesis for {gamma}-Al{sub 2}O{sub 3}/TiO{sub 2} composite powder is developed. Black-Right-Pointing-Pointer Nanoparticulate TiO{sub 2} layer results in high specific surface area composite powder. Black-Right-Pointing-Pointer {gamma}-Al{sub 2}O{sub 3}/TiO{sub 2} composite powder exhibit enhanced photocatalytic activity. -- Abstract: Nanostructured, {gamma}-Al{sub 2}O{sub 3}/TiO{sub 2} composite powder was fabricated via an in situ, sol-gel reaction of titanium iso-propoxide in a self-assembled, polyelectrolyte multilayer (PEM) formed on the surface of high-specific-area, polycrystalline, {gamma}-Al{sub 2}O{sub 3} lamellas. The infiltration of the titanium precursor into the PEM, followed by the hydrolysis and condensation reactions with the water absorbed in the PEM after annealing, resulted in the formation of a nanostructured TiO{sub 2} layer on the surface of the {gamma}-Al{sub 2}O{sub 3} lamellas. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) were employed to evaluate the morphology, the chemical composition and the crystallinity of the {gamma}-Al{sub 2}O{sub 3}/TiO{sub 2} particles of the composite powder. The as-formed, nanostructured, {gamma}-Al{sub 2}O{sub 3}/TiO{sub 2} composite powder exhibited a 2.7-times-higher photo-activity in the near-UV region compared to commercially available TiO{sub 2} (Degusa P25), as monitored by the photo-decomposition of a methylene blue (MB) dye.

  14. Electrochemical Performance of LiNi0.5Mn1.5O4 by Sol-gel Self-combustion Reaction Method in Different Kinds of Electrolyte for High-voltage Rechargeable Lithium Cells

    NASA Astrophysics Data System (ADS)

    Liang, Xinghua; Shi, Lin; Liu, Yusi; Zeng, Shuaibo; Ye, Chaochao

    2015-07-01

    LiNi0.5Mn1.5O4 cathode material was synthesized through sol-gel self-combustion reaction method. LiNi0.5Mn1.5O4 powders were subsequently characterized as cathode materials in a Li-ion coin cell comprising a Li anode with electrolyte A or electrolyte B. 1.0 mol/L Lithium Hexafluorophosphate (LiPF6) dissolved in volume ration of ethylene carbonate (EC) to ethyl methyl carbonate (EMC) to diethyl carbonate (DEC) corresponded to 4:3:3as electrolyte A, 1.0 mol/L LiPF6 dissolved in volume ration of EC to EMC to DEC corresponded to 4:2:4 as electrolyte B. Electrochemical performance of lithium cells was evaluated. These tests showed that no matter the cells with electrolyte A or electrolyte B has good discharge platform in 4.7V range (3.5V-4.75V) at the rate of 0.1C, the initial discharge capacity of cell with electrolyte B was higher than that with electrolyte A.

  15. Fundamentals of gel dosimeters

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

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

  16. Annular gel reactor for chemical pattern formation

    DOEpatents

    Nosticzius, Zoltan; Horsthemke, Werner; McCormick, William D.; Swinney, Harry L.; Tam, Wing Y.

    1990-01-01

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

  17. Self-Oscillating Polymer Gels as Smart Materials

    NASA Astrophysics Data System (ADS)

    Yoshida, Ryo

    2013-12-01

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

  18. A gel electrophoresis loading system to prevent laboratory contamination by amplification products.

    PubMed

    Adey, Nils B; Emery, Dale B; Bosh, Derek D; Parry, Robert J

    2014-10-01

    Pipet tip loading of polymerase chain reaction (PCR) and other amplification products into an electrophoresis gel represents a potential source of laboratory contamination. We have developed a prototype of the gel contamination control system (GelCCS) that enables gel loading by bottom puncture of PCR tubes. Puncture occurs within a sealed gel casing, preventing contamination of the surrounding environment. The system was designed for inexpensive manufacture so that after the results are visualized, the gel casing and PCR tubes are discarded intact with the amplification products sealed inside. We demonstrate that gel loading is reliable and that the resulting bands are equivalent in appearance to manually loaded gels.

  19. Sol-Gel Glasses

    NASA Technical Reports Server (NTRS)

    Mukherjee, S. P.

    1985-01-01

    Multicomponent homogeneous, ultrapure noncrystalline gels/gel derived glasses are promising batch materials for the containerless glass melting experiments in microgravity. Hence, ultrapure, homogeneous gel precursors could be used to: (1) investigate the effect of the container induced nucleation on the glass forming ability of marginally glass forming compositions; and (2) investigate the influence of gravity on the phase separation and coarsening behavior of gel derived glasses in the liquid-liquid immiscibility zone of the nonsilicate systems having a high density phase. The structure and crystallization behavior of gels in the SiO2-GeO2 as a function of gel chemistry and thermal treatment were investigated. As are the chemical principles involved in the distribution of a second network former in silica gel matrix being investigated. The procedures for synthesizing noncrystalline gels/gel-monoliths in the SiO2-GeO2, GeO2-PbO systems were developed. Preliminary investigations on the levitation and thermal treatment of germania silicate gel-monoliths in the Pressure Facility Acoustic Levitator were done.

  20. Investigating potential physicochemical errors in polymer gel dosimeters

    NASA Astrophysics Data System (ADS)

    Sedaghat, Mahbod; Bujold, Rachel; Lepage, Martin

    2011-09-01

    Measurement errors in polymer gel dosimetry can originate either during irradiation or scanning. One concern related to the exothermic nature of polymerization reaction was that the heat released in polymer gel dosimeters during irradiation modifies their dose response. In this paper, the effect of heat released from the exothermal polymerization reaction on the dose response of a number of dosimeters was studied. In addition, we investigated whether heat-generated geometric distortion existed in newly proposed gel dosimeters that contain highly thermoresponsive polymers. Our results suggest that despite a significant internal temperature increase in some gel compositions, their dose responses are not affected when oxygen is well expelled mechanically from the gel mixture. We also report on significant pre-irradiation instability in some recently developed polymer gel dosimeters but that geometric distortions were not observed. Data obtained by a set of small calibration vials are compared to those obtained from larger phantoms, and potential physicochemical causes of deviations between them are identified.

  1. Simultaneous immunoblotting analysis with activity gel electrophoresis and 2-D gel electrophoresis.

    PubMed

    Lee, Der-Yen; Chang, Geen-Dong

    2015-01-01

    Diffusion blotting method can couple immunoblotting analysis with another biochemical technique in a single polyacrylamide gel, however, with lower transfer efficiency as compared to the conventional electroblotting method. Thus, with diffusion blotting, protein blots can be obtained from an SDS polyacrylamide gel for zymography assay, from a native polyacrylamide gel for electrophoretic mobility shift assay (EMSA) or from a 2-D polyacrylamide gel for large-scale screening and identification of a protein marker. Thereafter, a particular signal in zymography, electrophoretic mobility shift assay, and 2-dimensional gel can be confirmed or identified by simultaneous immunoblotting analysis with a corresponding antiserum. These advantages make diffusion blotting desirable when partial loss of transfer efficiency can be tolerated or be compensated by a more sensitive immunodetection reaction using enhanced chemiluminescence detection.

  2. Combinatorial methods in sol-gel technology

    NASA Astrophysics Data System (ADS)

    Rantala, Juha T.; Kololuoma, Terho K.; Kivimaki, L.

    2000-05-01

    Sol-gel processing consists several variable parameters during materials synthesis and post processing steps. The sol-gel synthesis is rather sensitive for the parameters such as pH, temperature, type of catalyst, reaction time etc. However, this sensitivity can be taken as an advantage when developing and studying new materials and their properties. Furthermore, since the sol-gel technology mainly describes the fabrication of solid state materials from a liquid phase by applying metal alkoxides or metal salts as precursors, the post processing such as sintering has critical effects on the final form and properties of the solid material. Combinatorial chemistry and methods are valuable tools to estimate the effects of different variables and to build-up combinatorial libraries for the sol-gel technique. This paper generally describes potentials and the usage motivation of combinatorial chemistry in the sol-gel technology by taking into account some major steps in the synthesis and processing which are valuable for the estimation of the final product properties. Different kind of post processing steps in the combinatorial manner are studied in details. As an example the post processing of sol-gel derived semiconductor oxides and photosensitivity of hybrid sol-gel glasses are presented. The combinatorial treatment and measurement methods for these materials are explained.

  3. Liquid crystalline gel beads of curdlan.

    PubMed

    Dobashi, Toshiaki; Yoshihara, Hiromi; Nobe, Masahiro; Koike, Michiru; Yamamoto, Takao; Konno, Akira

    2005-01-04

    Curdlan beads consisting of liquid crystalline gel (LCG) and amorphous gel (AG) in alternating layers in a wide range of diameters were newly prepared by interfacial insolubilization reactions using calcium chloride as the setting reagent. The thickness of the liquid crystalline layer was proportional to the diameter of the gel bead, and the proportional constant agreed with that determined for the cylindrical gel prepared by a dialysis method. The proportional constant initially increased with increasing calcium concentration of the dispersing medium and saturated at a high concentration limit. These results suggest that the mechanisms for forming the alternating LCG/AG structures prepared with different boundary conditions are the same. The LCG/AG structure could be controlled by calcium concentration.

  4. Sol-gel science

    SciTech Connect

    Brinker, C.J. ); Scherer, G.W. )

    1990-01-01

    Although the science and technology of sol-gel processing has experienced enormous growth in the last decade, few books have been available to help researchers cope with the flood of results published in various journals and conference proceedings. This book presents and understanding of sol-gel processing. Following the sol-gel processing sequence from beginning to end, it includes discussions on the chemistry of hydrolysis and condensation of metalorganics and inorganic salts, the growth of polymeric or particulate species in sols, gelation, aging of gels, drying, structure of gels, and sintering. In addition, it compares the properties of gel-derived and conventionally prepared ceramics, examines films in detail, and presents a variety of applications.

  5. Pulse Field Gel Electrophoresis

    PubMed Central

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

    2015-01-01

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

  6. Pulse Field Gel Electrophoresis.

    PubMed

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

    2016-01-01

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

  7. CONFORMANCE IMPROVEMENT USING GELS

    SciTech Connect

    Randall S. Seright

    2003-09-01

    This report describes work performed during the second year of the project, ''Conformance Improvement Using Gels.'' The project has two objectives. The first objective is to identify gel compositions and conditions that substantially reduce flow through fractures that allow direct channeling between wells, while leaving secondary fractures open so that high fluid injection and production rates can be maintained. The second objective is to optimize treatments in fractured production wells, where the gel must reduce permeability to water much more than that to oil. Pore-level images from X-ray computed microtomography were re-examined for Berea sandstone and porous polyethylene. This analysis suggests that oil penetration through gel-filled pores occurs by a gel-dehydration mechanism, rather than a gel-ripping mechanism. This finding helps to explain why aqueous gels can reduce permeability to water more than to oil. We analyzed a Cr(III)-acetate-HPAM gel treatment in a production well in the Arbuckle formation. The availability of accurate pressure data before, during, and after the treatment was critical for the analysis. After the gel treatment, water productivity was fairly constant at about 20% of the pre-treatment value. However, oil productivity was stimulated by a factor of 18 immediately after the treatment. During the six months after the treatment, oil productivity gradually decreased to approach the pre-treatment value. To explain this behavior, we proposed that the fracture area open to oil flow was increased substantially by the gel treatment, followed by a gradual closing of the fractures during subsequent production. For a conventional Cr(III)-acetate-HPAM gel, the delay between gelant preparation and injection into a fracture impacts the placement, leakoff, and permeability reduction behavior. Formulations placed as partially formed gels showed relatively low pressure gradients during placement, and yet substantially reduced the flow capacity of

  8. Self-oscillating surface of gel for autonomous mass transport.

    PubMed

    Yoshida, Ryo; Murase, Yoko

    2012-11-01

    As a novel biomimetic gels deffering from conventonal stimuli-responsive polymer gels, we have developed a "self-oscillating" gel that swells and deswells periodically under constant condition without on-off switching of external stimuli. The gel is composed of poly(N-isopropylacrylamide) to which the catalyst of the oscillating chemical reaction, called Belousov-Zhabotinsky reaction, is covalently immobilized. The chemical oscillation is converted to the mechanical oscillation of the gel through the change in hydrophilicity of polymer chains with the redox changes of the immobilized catalyst. By utilizing the self-oscillating gel, several kinds of functional material systems such as biomimetic actuators, etc. are expected. Here we review a potential application to functional surface to realize autonomous mass-transport by utilizing the peristaltic motion of the gel. With the propagation of the chemical wave, the loaded cargo is autonomously transported on the surface. In order to fabricate the self-driven gel conveyer for a wider use including biomedical applications, the interactions between the self-oscillating gel and the loaded gel cargo were investigated and their influence on the transport phenomena were evaluated.

  9. Slow Release Of Reagent Chemicals From Gel Matrices

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

  10. Electrochemical Growth Of Crystals In Gels

    NASA Technical Reports Server (NTRS)

    Barber, Patrick G.; Coleman, James

    1988-01-01

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

  11. Supramolecular Gel-Templated In Situ Synthesis and Assembly of CdS Quantum Dots Gels

    NASA Astrophysics Data System (ADS)

    Zhu, Lili; He, Jie; Wang, Xiaoliang; Li, Dawei; He, Haibing; Ren, Lianbing; Jiang, Biwang; Wang, Yong; Teng, Chao; Xue, Gi; Tao, Huchun

    2017-01-01

    Although many studies have attempted to develop strategies for spontaneously organizing nanoparticles (NPs) into three-dimensional (3D) geometries, it remains a fascinating challenge. In this study, a method for in situ synthesis and self-assembly of a CdS quantum dots (QDs) gel using a Cd supramolecular gel as a scaffold was demonstrated. During the QDs formation process, the Cd ions that constituted the Cd gels served as the precursors of the CdS QDs, and the oleic acid (OA) that ligated with the Cd in the supramolecular gels was capped on the surface of the CdS QDs in the form of carboxylate. The OA-stabilized CdS QDs were in situ synthesized in the entangled self-assembled fibrillar networks (SAFIN) of the Cd gels through reactions between the gelator and H2S. As a result, the QDs exactly replicated the framework of the SAFIN in the CdS QD gels instead of simply assembling along the SAFIN of the supramolecular gels. Moreover, the CdS QDs showed extraordinary sensitivity in the fluorescence detection of IO4 - anions. The facile one-step method developed here is a new approach to assembling nanostructured materials into 3D architectures and has general implications for the design of low molecular mass gelators to bring desired functionality to the developed supramolecular gels.

  12. An Experimental Study of the Liesegang Phenomenon and Crystal Growth in Silica Gels.

    ERIC Educational Resources Information Center

    Sharbaugh, Amandus H., III; Sharbaugh, Amandus H., Jr.

    1989-01-01

    Reports on a 30-year-old longitudinal study of reactions in gels. Described are reactions and crystal growth in silica gels and diffusion studies of the Liesegang ring formation. Color photographs showing the reactions and graphs upon the diffusions are presented. (YP)

  13. Cumulative irritation potential of metronidazole gel compared to azelaic acid gel after repeated applications to healthy skin.

    PubMed

    Ziel, Kristin; Yelverton, Christopher B; Balkrishnan, Rajesh; Feldman, Steven R

    2005-01-01

    Metronidazole 0.75% gel and azelaic acid 15% gel are commonly used to treat rosacea. Irritation is a common side effect. To assess the cumulative irritation potential of metronidazole 0.75% gel and azelaic acid 15% gel. Metronidazole 0.75% gel, azelaic acid 15% gel, and a white petrolatum negative control were applied under occlusive conditions to the upper back of a total of 33 healthy subjects. There were twelve 24-hour applications (4 times a week) and three 72-hour applications on weekends during a 3-week period. Skin reactions (erythema score +/- other local reaction) were assessed within 15 to 30 minutes of removal of the products. The mean cumulative irritancy index of metronidazole 0.75% gel was significantly lower than that of azelaic acid 15% gel and not significantly higher than the negative control product. There was increasing cumulative irritancy with azelaic acid; no cumulative irritancy was seen for either metronidazole or white petrolatum. Metronidazole 0.75% gel is less irritating in sustained use than azelaic acid 15% gel.

  14. CONFORMANCE IMPROVEMENT USING GELS

    SciTech Connect

    Randall S. Seright

    2004-03-01

    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

  15. Actuator device utilizing a conductive polymer gel

    DOEpatents

    Chinn, Douglas A.; Irvin, David J.

    2004-02-03

    A valve actuator based on a conductive polymer gel is disclosed. A nonconductive housing is provided having two separate chambers separated by a porous frit. The conductive polymer is held in one chamber and an electrolyte solution, used as a source of charged ions, is held in the second chamber. The ends of the housing a sealed with a flexible elastomer. The polymer gel is further provide with electrodes with which to apply an electrical potential across the gel in order to initiate an oxidation reaction which in turn drives anions across the porous frit and into the polymer gel, swelling the volume of the gel and simultaneously contracting the volume of the electrolyte solution. Because the two end chambers are sealed the flexible elastomer expands or contracts with the chamber volume change. By manipulating the potential across the gel the motion of the elastomer can be controlled to act as a "gate" to open or close a fluid channel and thereby control flow through that channel.

  16. Gels and gel-derived glasses in the system Na2O-B2O3-SiO2

    NASA Technical Reports Server (NTRS)

    Mukherjee, S. P.

    1983-01-01

    The containerless melting of high-purity multicomponent homogeneous gels and gel monoliths offers a unique approach to making ultrapure multicomponent optical glasses in the reduced gravity environment of space. Procedures for preparing and characterizing gels and gel-derived glasses in the system Na2O-B2O3-SiO2 are described. Preparation is based on the polymerization reactions of alkoxysilane with trimethyl borate or boric acid and a suitable sodium compound. The chemistry of the gelling process is discussed in terms of process parameters and the gel compositions. The physicochemical nature of gels prepared by three different procedures was found to be significantly different. Infrared absorption spectra indicate finite differences in the molecular structures of the different gels. The melting of the gel powders and the transformation of porous gel monoliths to transparent 'glass' without melting are described.

  17. Gels and gel-derived glasses in the Na2O-B2O3-SiO2 system. [containerless melting in space

    NASA Technical Reports Server (NTRS)

    Mukherjee, S. P.

    1982-01-01

    The containerless melting of high-purity multicomponent homogeneous gels and gel-monoliths offers a unique approach to making ultrapure multicomponent optical glasses in the reduced gravity environment of space. Procedures for preparing and characterizing gels and gel-derived glasses in the Na2O-B2O3-SiO2 system are described. Preparation is based on the polymerization reactions of alkoxysilane with trimethyl borate or boric acid and a suitable sodium compound. The chemistry of the gelling process is discussed in terms of process parameters and the gel compositions. The physicochemical nature of gels prepared by three different procedures were found to be significantly different. IR absorption spectra indicate finite differences in the molecular structures of the different gels. The melting of the gel powders and the transformation of porous gel-monoliths to transparent 'glass' without melting are described.

  18. Gels and gel-derived glasses in the Na2O-B2O3-SiO2 system. [containerless melting in space

    NASA Technical Reports Server (NTRS)

    Mukherjee, S. P.

    1982-01-01

    The containerless melting of high-purity multicomponent homogeneous gels and gel-monoliths offers a unique approach to making ultrapure multicomponent optical glasses in the reduced gravity environment of space. Procedures for preparing and characterizing gels and gel-derived glasses in the Na2O-B2O3-SiO2 system are described. Preparation is based on the polymerization reactions of alkoxysilane with trimethyl borate or boric acid and a suitable sodium compound. The chemistry of the gelling process is discussed in terms of process parameters and the gel compositions. The physicochemical nature of gels prepared by three different procedures were found to be significantly different. IR absorption spectra indicate finite differences in the molecular structures of the different gels. The melting of the gel powders and the transformation of porous gel-monoliths to transparent 'glass' without melting are described.

  19. Drying SDS-Polyacrylamide Gels.

    PubMed

    Sambrook, Joseph; Russell, David W

    2006-09-01

    INTRODUCTIONThis protocol describes a method for drying SDS-polyacrylamide gels. Gels containing proteins radiolabeled with (35)S-labeled amino acids must be dried before autoradiographic images can be obtained. Nonradioactive gels can also be preserved by drying.

  20. Agarose gel electrophoresis.

    PubMed

    Smith, D R

    1993-01-01

    After digestion of DNA with a restriction enzyme (Chapter 50), it is usually necessary, for both preparative and analytical purposes, to separate and visualize the products. In most cases, where the products are between 200 and 20,000 bp long, this is achieved by agarose gel electrophoresis. Agarose is a linear polymer that is extracted from seaweed and sold as a white powder. The powder is melted in buffer and allowed to cool, whereby the agarose forms a gel by hydrogen bonding. The hardened matrix contains pores, the size of which depends on the concentration of agarose. The concentration of agarose is referred to as a percentage of agarose to volume of buffer (w/v), and agarose gels are normally in the range of 0.3 to 3%. Many different apparatus arrangements have been devised to run agarose gels; for example, they can be run horizontally or vertically, and the current can be conducted by wicks or the buffer solution. However, today, the "submarine" gel system is almost universally used. In this method, the agarose gel is formed on a supporting plate, and then the plate is submerged into a tank containing a suitable electrophoresis buffer. Wells are preformed in the agarose gel with the aid of a "comb" that is inserted into the cooling agarose before the agarose has gelled. Into these wells are loaded the sample to be analyzed, which has been mixed with a dense solution (a loading buffer) to ensure that the sample sinks into the wells.

  1. Radiolucent prosthetic gel.

    PubMed

    Beisang, A A; Geise, R A; Ersek, R A

    1991-05-01

    The successful use of silicone breast implants is complicated by their interference with mammography. We have evaluated clinically available implant filling materials and found that a new Bio-Oncotic gel approximates the radiolucency of normal breast tissue. Silicone implants completely obscure areas of the breast in mammography. Recently proposed as a filler material, peanut oil is significantly more radiolucent than normal tissue. Physiologic saline solution compares favorably as a tissue-density-simulating substance. However, saline's lack of lubricating properties results in leakage, making it less than optimal. Bio-Oncotic gel is biologically compatible. We conclude that this gel is the most appropriate filler for breast prostheses. Clinical studies are indicated.

  2. Cyanocobalamin Nasal Gel

    MedlinePlus

    ... B12 can cause anemia (condition in which the red blood cells do not bring enough oxygen to the organs) ... be treated with vitamin B12 injections. After the red blood cells have returned to normal, cyanocobalamin nasal gel can ...

  3. Conformance Improvement Using Gels

    SciTech Connect

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

    2002-09-26

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

  4. Conformance Improvement Using Gels

    SciTech Connect

    Seright, Randall S.; Schrader; II Hagstrom, John; Wang, Ying; Al-Dahfeeri, Abdullah; Marin, Amaury

    2002-09-26

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

  5. Crystallization from Gels

    NASA Astrophysics Data System (ADS)

    Narayana Kalkura, S.; Natarajan, Subramanian

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

  6. Ultraflexible organic amplifier with biocompatible gel electrodes.

    PubMed

    Sekitani, Tsuyoshi; Yokota, Tomoyuki; Kuribara, Kazunori; Kaltenbrunner, Martin; Fukushima, Takanori; Inoue, Yusuke; Sekino, Masaki; Isoyama, Takashi; Abe, Yusuke; Onodera, Hiroshi; Someya, Takao

    2016-04-29

    In vivo electronic monitoring systems are promising technology to obtain biosignals with high spatiotemporal resolution and sensitivity. Here we demonstrate the fabrication of a biocompatible highly conductive gel composite comprising multi-walled carbon nanotube-dispersed sheet with an aqueous hydrogel. This gel composite exhibits admittance of 100 mS cm(-2) and maintains high admittance even in a low-frequency range. On implantation into a living hypodermal tissue for 4 weeks, it showed a small foreign-body reaction compared with widely used metal electrodes. Capitalizing on the multi-functional gel composite, we fabricated an ultrathin and mechanically flexible organic active matrix amplifier on a 1.2-μm-thick polyethylene-naphthalate film to amplify (amplification factor: ∼200) weak biosignals. The composite was integrated to the amplifier to realize a direct lead epicardial electrocardiography that is easily spread over an uneven heart tissue.

  7. Ultraflexible organic amplifier with biocompatible gel electrodes

    PubMed Central

    Sekitani, Tsuyoshi; Yokota, Tomoyuki; Kuribara, Kazunori; Kaltenbrunner, Martin; Fukushima, Takanori; Inoue, Yusuke; Sekino, Masaki; Isoyama, Takashi; Abe, Yusuke; Onodera, Hiroshi; Someya, Takao

    2016-01-01

    In vivo electronic monitoring systems are promising technology to obtain biosignals with high spatiotemporal resolution and sensitivity. Here we demonstrate the fabrication of a biocompatible highly conductive gel composite comprising multi-walled carbon nanotube-dispersed sheet with an aqueous hydrogel. This gel composite exhibits admittance of 100 mS cm−2 and maintains high admittance even in a low-frequency range. On implantation into a living hypodermal tissue for 4 weeks, it showed a small foreign-body reaction compared with widely used metal electrodes. Capitalizing on the multi-functional gel composite, we fabricated an ultrathin and mechanically flexible organic active matrix amplifier on a 1.2-μm-thick polyethylene-naphthalate film to amplify (amplification factor: ∼200) weak biosignals. The composite was integrated to the amplifier to realize a direct lead epicardial electrocardiography that is easily spread over an uneven heart tissue. PMID:27125910

  8. Ultraflexible organic amplifier with biocompatible gel electrodes

    NASA Astrophysics Data System (ADS)

    Sekitani, Tsuyoshi; Yokota, Tomoyuki; Kuribara, Kazunori; Kaltenbrunner, Martin; Fukushima, Takanori; Inoue, Yusuke; Sekino, Masaki; Isoyama, Takashi; Abe, Yusuke; Onodera, Hiroshi; Someya, Takao

    2016-04-01

    In vivo electronic monitoring systems are promising technology to obtain biosignals with high spatiotemporal resolution and sensitivity. Here we demonstrate the fabrication of a biocompatible highly conductive gel composite comprising multi-walled carbon nanotube-dispersed sheet with an aqueous hydrogel. This gel composite exhibits admittance of 100 mS cm-2 and maintains high admittance even in a low-frequency range. On implantation into a living hypodermal tissue for 4 weeks, it showed a small foreign-body reaction compared with widely used metal electrodes. Capitalizing on the multi-functional gel composite, we fabricated an ultrathin and mechanically flexible organic active matrix amplifier on a 1.2-μm-thick polyethylene-naphthalate film to amplify (amplification factor: ~200) weak biosignals. The composite was integrated to the amplifier to realize a direct lead epicardial electrocardiography that is easily spread over an uneven heart tissue.

  9. CONFORMANCE IMPROVEMENT USING GELS

    SciTech Connect

    Randall S. Seright

    2002-02-28

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

  10. Continuum Models of Stimuli-responsive Gels

    NASA Astrophysics Data System (ADS)

    Hong, Wei

    Immersed in a solution of small molecules and ions, a network of long-chain polymers may imbibe the solution and swell, resulting in a polymeric gel. Depending on the molecular structure of the polymers, the amount of swelling can be regulated by moisture, mechanical forces, ionic strength, electric field, pH value, and many other types of stimuli. Starting from the basic principles of non-equilibrium thermodynamics, this chapter formulates a field theory of the coupled large deformation and mass transportation in a neutral polymeric gel. The theory is then extended to study polyelectrolyte gels with charge-carrying networks by accounting for the electromechanical coupling and migration of solute ions. While the theoretical framework is adaptable to various types of material models, some representative ones are described through specific free-energy functions and kinetic laws. A specific material law for pH-sensitive gels—a special type of polyelectrolyte gels—is introduced as an example of incorporating chemical reactions in modeling stimuli-responsive gels. Finally, a simplified theory for the equilibrium but inhomogeneous swelling of a polymeric gel is deduced. The theory and the specific material models are illustrated through several examples.

  11. Method of making ionic liquid mediated sol-gel sorbents

    DOEpatents

    Malik, Abdul; Shearrow, Anne M.

    2017-01-31

    Ionic liquid (IL)-mediated sol-gel hybrid organic-inorganic materials present enormous potential for effective use in analytical microextraction. One obstacle to materializing this prospect arises from high viscosity of ILs significantly slowing down sol-gel reactions. A method was developed which provides phosphonium-based, pyridinium-based, and imidazolium-based IL-mediated advanced sol-gel organic-inorganic hybrid materials for capillary microextraction. Scanning electron microscopy results demonstrate that ILs can serve as porogenic agents in sol-gel reactions. IL-mediated sol-gel coatings prepared with silanol-terminated polymers provided up to 28 times higher extractions compared to analogous sol-gel coatings prepared without any IL in the sol solution. This study shows that IL-generated porous morphology alone is not enough to provide effective extraction media: careful choice of the organic polymer and the precursor with close sol-gel reactivity must be made to ensure effective chemical bonding of the organic polymer to the created sol-gel material to be able to provide the desired sorbent characteristics.

  12. Gel integration for microfluidic applications.

    PubMed

    Zhang, Xuanqi; Li, Lingjun; Luo, Chunxiong

    2016-05-21

    Molecular diffusive membranes or materials are important for biological applications in microfluidic systems. Hydrogels are typical materials that offer several advantages, such as free diffusion for small molecules, biocompatibility with most cells, temperature sensitivity, relatively low cost, and ease of production. With the development of microfluidic applications, hydrogels can be integrated into microfluidic systems by soft lithography, flow-solid processes or UV cure methods. Due to their special properties, hydrogels are widely used as fluid control modules, biochemical reaction modules or biological application modules in different applications. Although hydrogels have been used in microfluidic systems for more than ten years, many hydrogels' properties and integrated techniques have not been carefully elaborated. Here, we systematically review the physical properties of hydrogels, general methods for gel-microfluidics integration and applications of this field. Advanced topics and the outlook of hydrogel fabrication and applications are also discussed. We hope this review can help researchers choose suitable methods for their applications using hydrogels.

  13. Schiff base mediated sol-gel polymerization

    SciTech Connect

    Lindquist, D.A.; Harrison, C.M.; Williams, B.; Morris, R.D.

    1996-12-31

    Formation of a Schiff base imine by reacting a primary amine with either an aldehyde or ketone was initiated by an aluminum compound acting as a Lewis acid catalyst. The water byproduct of the reaction then was used as an in situ reagent for subsequent hydrolysis and sol-gel condensation of the aluminum species. These reactions yielded a gel network containing the entrained Schiff base. Two examples of this synthetic approach are described with two different aluminum catalyst/reagents: a diethylaluminum diethylphosphate ester [(CH{sub 3}CH{sub 2}){sub 2}Al-O-P(O)(OCH{sub 2}CH{sub 3}){sub 2}] and triethyl aluminum [Al(CH{sub 3}CH{sub 2}){sub 3}]. Anhydrous ammonia and acetone were used as the Schiff base precursors.

  14. Patterns in shrinking gels

    NASA Astrophysics Data System (ADS)

    Matsuo, Eriko Sato; Tanaka, Toyoichi

    1992-08-01

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

  15. Nematic Nanotubes Gels

    NASA Astrophysics Data System (ADS)

    Yodh, A. G.; Islam, M. F.; Alsayed, A. M.; Dogic, Z.; Zhang, J.; Lubensky, T. C.

    2003-03-01

    Composites of aligned single wall carbon nanotubes (SWNTs) are among the most sought after materials in nanotube science. We report the production of one such medium, containing large domains of oriented SWNTs. We call these materials nematic nanotube gels. We have created them by first dispersing SWNTs at low volume fraction in a gel, and then inducing a volume-compression transition of the gel. We identify hallmark liquid crystalline defects in these materials, as well as a novel buckling of the walls accompanying defect formation. Quantitative measurements of the tube order parameter reveal a concentration-dependent crossover from isotropic to nematic phases. This work has been partially supported by the NSF through the MRSEC grant DMR 00-79909, DMR-0203378, and by NASA through grant NAG8-2172.

  16. Gel electrolytes and electrodes

    DOEpatents

    Fleischmann, Sven; Bunte, Christine; Mikhaylik, Yuriy V.; Viner, Veronika G.

    2017-09-05

    Gel electrolytes, especially gel electrolytes for electrochemical cells, are generally described. In some embodiments, the gel electrolyte layers comprise components a) to c). Component a) may be at least one layer of at least one polymer comprising polymerized units of: a1) at least one monomer containing an ethylenically unsaturated unit and an amido group and a2) at least one crosslinker. Component b) may be at least one conducting salt and component c) may be at least one solvent. Electrodes may comprise the components a), d) and e), wherein component a) may be at least one layer of at least one polymer as described herein. Component d) may be at least one electroactive layer and component e) may be at least one ceramic layer. Furthermore, electrochemical cells comprising component a) which may be at least one layer of at least one polymer as described herein, are also provided.

  17. Spatially resolved multicomponent gels

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  18. Electroblotting from Polyacrylamide Gels.

    PubMed

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

    2015-11-02

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

  19. Swelling of Olympic Gels

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    The swelling equilibrium of Olympic gels, which are composed of entangled cyclic polymers, is studied by Monte Carlo simulations. In contrast to chemically cross-linked polymer networks, we observe that Olympic gels made of chains with a larger degree of polymerization, N, exhibit a smaller equilibrium swelling degree, Q∝N-0.28ϕ0-0.72, at the same polymer volume fraction ϕ0 at network preparation. This observation is explained by a desinterspersion (reorganization with release of nontrapped entanglements) process of overlapping nonconcatenated rings upon swelling.

  20. Variable mineral composition of metamorphic rocks from a single quarry compared to their ASR potential (Bohemian Massif, Czech Republic)

    NASA Astrophysics Data System (ADS)

    Stastna, Aneta; Sachlova, Sarka; Pertold, Zdenek; Nekvasilova, Zuzana; Prikryl, Richard

    2013-04-01

    The alkali-silica reaction (ASR) is one of the most damaging factors for concrete structures. ASR originates due to the presence of reactive silica (SiO2) that reacts with alkaline ions under wet conditions. The reaction mechanism consists of four different steps: initial attack of OH- compounds on SiO2 at aggregate-cement paste boundary; formation of silanol groups at SiO2 surface; formation of siloxane groups and their polymerization; adsorption of alkaline and Ca2+ ions and formation of alkali-silica gels. Alkali-silica gels tend to absorb water molecules and swell causing increasing internal pressures in concrete and microcracking. The most reactive aggregates are mainly composed of amorphous and/or fine-grained SiO2-rich phases. In the Czech Republic, ASR was observed in deteriorating concrete structures containing very fine-grained quartz (quartz in tuffaceous sandstones and greywackes), as well as quartz indicating variable degree of deformation (quartz in quartzite, granodiorite and various metamorphic rock types). In this study, mineralogical-petrographic methods (polarizing, electron and cathodoluminescence microscopy) were combined with the accelerated mortar bar test (following the standard ASTM C1260), with the aim to quantify the ASR potential, as well as to distinguish reactive mineral phases. Different aggregate varieties from the Těchobuz quarry (Moldanubian Zone, Czech Republic) have been compared. Mineralogical-petrographic characteristics permit a distinction between 1) medium-grained plagioclase quartzite and 2) fine-grained biotite-plagioclase-quartz paragneiss and 3) fine-grained calc-silicate rock. Mineralogical composition of the first type is quartz + Ca-plagioclase + K-feldspar + biotite + chlorite + diopside + pyrite + apatite + titanite ± calcite. The second type has mineral assemblage including quartz + Ca-plagioclase + K-feldspar + biotite + chlorite + pyrite + tourmaline + apatite + titanite ± calcite. The third type contains

  1. Comparison of dosimetry gels prepared by agar and bovine gelatine

    NASA Astrophysics Data System (ADS)

    Sağsöz, M. E.; Korkut, Ö.; Alemdar, N.; Aktaş, S.; Çalı, E. B.; Kantarcı, M.

    2016-04-01

    Gel dosimeters are unique materials capable of showing three dimensional (3D) dose distributions of therapeutic or diagnostic exposures. Fricke gel dosimeters can be considered as chemical dosimeters that rely on a radiation-induced chemical reaction. Dose distribution of Fricke solutions containing Fe+2 ions determines the transformation of acidic, oxygen saturated Fe+2 ions to Fe+3 ions by the ionizing radiation in aqueous solutions. In this study we produced two different types of gel dosimeters using agar and bovine gelatin with similar fabrication methods. We compared the magnetic resonance (MR) T1 imaging responses of these two gel dosimeters to acquire a dose dependency of MR intensities. In conclusion agar gel dosimeters found to be produced easily and more consistent.

  2. Gravitational compression of colloidal gels

    NASA Astrophysics Data System (ADS)

    Liétor-Santos, J. J.; Kim, C.; Lu, P. J.; Fernández-Nieves, A.; Weitz, D. A.

    2009-02-01

    We study the compression of depletion gels under the influence of a gravitational stress by monitoring the time evolution of the gel interface and the local volume fraction, φ , inside the gel. We find φ is not constant throughout the gel. Instead, there is a volume fraction gradient that develops and grows along the gel height as the compression process proceeds. Our results are correctly described by a non-linear poroelastic model that explicitly incorporates the φ -dependence of the gravitational, elastic and viscous stresses acting on the gel.

  3. Gravitational compression of colloidal gels.

    PubMed

    Liétor-Santos, J J; Kim, C; Lu, P J; Fernández-Nieves, A; Weitz, D A

    2009-02-01

    We study the compression of depletion gels under the influence of a gravitational stress by monitoring the time evolution of the gel interface and the local volume fraction, φ, inside the gel. We find φ is not constant throughout the gel. Instead, there is a volume fraction gradient that develops and grows along the gel height as the compression process proceeds. Our results are correctly described by a non-linear poroelastic model that explicitly incorporates the φ-dependence of the gravitational, elastic and viscous stresses acting on the gel.

  4. Electrochemical mechanism of ion current rectification of polyelectrolyte gel diodes.

    PubMed

    Yamamoto, Tetsuya; Doi, Masao

    2014-06-17

    Polyelectrolyte gel diodes that are double layers of two oppositely charged polyelectrolyte gels, sandwiched by two symmetric electrodes, are emergent ionic devices. These diodes are designed to rectify ion currents with a physical mechanism that is analogous to conventional semiconductor diodes-the asymmetry in the permeability of ions across the interfaces between the two oppositely charged gels. Here we show that polyelectrolyte gel diodes indeed rectify steady currents with a physical mechanism that is very different from conventional diodes by using a simple electrochemical model; electric currents are limited by electrochemical reactions that are driven by potential drops at electrodes and these potential drops markedly change with changing the direction of applied voltages due to the redistribution of non-reactive counterions, leading to rectified ion currents. This concept is relatively generic and thus may provide insight in the physics of analogous ionic and biomimetic systems that show electrochemical reactions.

  5. Rheology of Active Gels

    NASA Astrophysics Data System (ADS)

    Chen, Daniel

    2015-03-01

    Active networks drive a diverse range of critical processes ranging from motility to division in living cells, yet a full picture of their rheological capabilities in non-cellular contexts is still emerging, e.g., How does the rheological response of a network capable of remodeling under internally-generated stresses differ from that of a passive biopolymer network? In order to address this and other basic questions, we have engineered an active gel composed of microtubules, bidirectional kinesin motors, and molecular depletant that self-organizes into a highly dynamic network of active bundles. The network continually remodels itself under ATP-tunable cycles of extension, buckling, fracturing, and self-healing. Using confocal rheometry we have simultaneously characterized the network's linear and non-linear rheological responses to shear deformation along with its dynamic morphology. We find several surprising and unique material properties for these active gels; most notably, rheological cloaking, the ability of the active gel to drive large-scale fluid mixing over several orders of flow magnitude while maintaining an invariant, solid-like rheological profile and spontaneous flow under confinement, the ability to exert micro-Newton forces to drive persistent directed motion of the rheometer tool. Taken together, these results and others to be discussed highlight the rich stress-structure-dynamics relationships in this class of biologically-derived active gels.

  6. Giant Volume Change of Active Gels under Continuous Flow

    DTIC Science & Technology

    2014-04-21

    communication17 of BZ droplets and chemical self-organiza- tion,18 the properties and potential of self-oscillating gels in a microfluidic system have yet to be...active gels driven by the Belousov−Zhabotinsky reaction. These results demon- strate that microfluidics offers a useful and facile experimental...soft materials and microfluidic systems. ■ INTRODUCTION This paper reports the use of a continuous reactant flow in a microfluidic system to achieve

  7. Time and frequency dependent rheology of reactive silica gels.

    PubMed

    Wang, Miao; Winter, H Henning; Auernhammer, Günter K

    2014-01-01

    In a mixture of sodium silicate and low concentrated sulfuric acid, nano-sized silica particles grow and may aggregate to a system spanning gel network. We studied the influence of the finite solubility of silica at high pH on the mechanical properties of the gel with classical and piezo-rheometers. Direct preparation of the gel sample in the rheometer cell avoided any pre-shear of the gel structure during the filling of the rheometer. The storage modulus of the gel grew logarithmically with time with two distinct growth laws. The system passes the gel point very quickly but still shows relaxation at low frequency, typically below 6 rad/s. We attribute this as a sign of structural rearrangements due to the finite solubility of silica at high pH. The reaction equilibrium between bond formation and dissolution maintains a relatively large bond dissolution rate, which leads to a finite life time of the bonds and behavior similar to physical gels. This interpretation is also compatible with the logarithmic time dependence of the storage modulus. The frequency dependence was more pronounced for lower water concentrations, higher temperatures and shorter reaction times. With two relaxation models (the modified Cole-Cole model and the empirical Baumgaertel-Schausberger-Winter model) we deduced characteristic times from the experimental data. Both models approximately described the data and resulted in similar relaxation times.

  8. Oxide Ceramic Fibers by the Sol-Gel Methods

    DTIC Science & Technology

    1989-02-10

    prepared by the sol-gel method . 3 Table 2. List of candidates for fibers via the sol-gel method . 4 Table 3. Solvents, raw materials and catalysts ...reaction chemistry. The synthesis method will be discussed in Section 3.1.3 Using commercially available precursors the production of lanthanum chromite via...AFWAL-TR-88-4199 OXIDE CERAMIC FIBERS BY THE SOL-GEL METHOD J. D. Mackenzie If) K. Ono The Regents of the University of California (Los Angeles) V

  9. A macroscopic reaction: direct covalent bond formation between materials using a Suzuki-Miyaura cross-coupling reaction.

    PubMed

    Sekine, Tomoko; Kakuta, Takahiro; Nakamura, Takashi; Kobayashi, Yuichiro; Takashima, Yoshinori; Harada, Akira

    2014-09-18

    Cross-coupling reactions are important to form C-C covalent bonds using metal catalysts. Although many different cross-coupling reactions have been developed and applied to synthesize complex molecules or polymers (macromolecules), if cross-coupling reactions are realized in the macroscopic real world, the scope of materials should be dramatically broadened. Here, Suzuki-Miyaura coupling reactions are realized between macroscopic objects. When acrylamide gel modified with an iodophenyl group (I-gel) reacts with a gel possessing a phenylboronic group (PB-gel) using a palladium catalyst, the gels bond to form a single object. This concept can also be adapted for bonding between soft and hard materials. I-gel or PB-gel selectively bonds to the glass substrates whose surfaces are modified with an electrophile or nucleophile, respectively.

  10. Preparation of carbon nanotube-alginate nanocomposite gel for tissue engineering.

    PubMed

    Kawaguchi, Minoru; Fukushima, Tadao; Hayakawa, Toru; Nakashima, Naotoshi; Inoue, Yusuke; Takeda, Shoji; Okamura, Kazuhiko; Taniguchi, Kunihisa

    2006-12-01

    A novel scaffold material based on an alginate hydrogel which contained carbon nanotubes (CNTs) was prepared, and its mechanical property and biocompatibility evaluated. Soluble CNTs were prepared with acid treatment and dispersed in sodium alginate solution as a cross-linker. After which, the mechanical property (elastic deformation), saline sorption, histological reaction, and cell viability of the resultant nanocomposite gel (CNT-Alg gel) were evaluated. The CNT-Alg gel showed faster gelling and higher mechanical strength than the conventional alginate gel. Saline sorption amount of freeze-dried CNT-Alg gel was equal to that of the alginate gel. In terms of histological evaluation and cell viability assay, CNT-Alg gel exhibited a mild inflammatory response and non-cytotoxicity. These results thus suggested that CNT-Alg gel could be useful as a scaffold material in tissue engineering with the sidewalls of CNTs acting as active sites for chemical functionalization.

  11. Investigation of preparation and mechanisms of a dispersed particle gel formed from a polymer gel at room temperature.

    PubMed

    Zhao, Guang; Dai, Caili; Zhao, Mingwei; You, Qing; Chen, Ang

    2013-01-01

    A dispersed particle gel (DPG) was successfully prepared from a polymer gel at room temperature. The polymer gel system, morphology, viscosity changes, size distribution, and zeta potential of DPG particles were investigated. The results showed that zirconium gel systems with different strengths can be cross-linked within 2.5 h at low temperature. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) results showed that the particles were polygonal particles with nano-size distribution. According to the viscosity changes, the whole preparation process can be divided into two major stages: the bulk gel cross-linking reaction period and the DPG particle preparation period. A polymer gel with a 3-dimensional network was formed in the bulk gel cross-linking reaction period whereas shearing force and frictional force were the main driving forces for the preparation of DPG particles, and thus affected the morphology of DPG particles. High shearing force and frictional force reduced the particle size distribution, and then decreased the zeta potential (absolute value). The whole preparation process could be completed within 3 h at room temperature. It could be an efficient and energy-saving technology for preparation of DPG particles.

  12. Investigation of Preparation and Mechanisms of a Dispersed Particle Gel Formed from a Polymer Gel at Room Temperature

    PubMed Central

    Zhao, Guang; Dai, Caili; Zhao, Mingwei; You, Qing; Chen, Ang

    2013-01-01

    A dispersed particle gel (DPG) was successfully prepared from a polymer gel at room temperature. The polymer gel system, morphology, viscosity changes, size distribution, and zeta potential of DPG particles were investigated. The results showed that zirconium gel systems with different strengths can be cross-linked within 2.5 h at low temperature. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) results showed that the particles were polygonal particles with nano-size distribution. According to the viscosity changes, the whole preparation process can be divided into two major stages: the bulk gel cross-linking reaction period and the DPG particle preparation period. A polymer gel with a 3-dimensional network was formed in the bulk gel cross-linking reaction period whereas shearing force and frictional force were the main driving forces for the preparation of DPG particles, and thus affected the morphology of DPG particles. High shearing force and frictional force reduced the particle size distribution, and then decreased the zeta potential (absolute value). The whole preparation process could be completed within 3 h at room temperature. It could be an efficient and energy-saving technology for preparation of DPG particles. PMID:24324817

  13. Large deformation of self-oscillating polymer gel

    NASA Astrophysics Data System (ADS)

    Maeda, Shingo; Kato, Terukazu; Otsuka, Yuji; Hosoya, Naoki; Cianchetti, Matteo; Laschi, Cecilia

    2016-01-01

    A self-oscillating gel is a system that generates an autonomous volume oscillation. This oscillation is powered by the chemical energy of the Belousov-Zhabotinsky (BZ) reaction, which demonstrates metal ion redox oscillation. A self-oscillating gel is composed of Poly-N -isopropylacrylamide (PNIPAAm) with a metal ion. In this study, we found that the displacement of the volume oscillation in a self-oscillating gel could be controlled by its being subjected to a prestraining process. We also revealed the driving mechanism of the self-oscillating gel from the point of view of thermodynamics. We observed that the polymer-solvent interaction parameter χ is altered by the redox changes to the metal ion incorporated in the self-oscillating gel. The prestraining process leads to changes in χ and changes in enthalpy and entropy when the self-oscillating gel is in a reduced and oxidized state. We found that nonprestrained gel samples oscillate in a poor solution (χ >0.5 ) and prestrained gel samples oscillate in a good solution (χ <0.5 ).

  14. Creating Reconfigurable Materials Using ``Colonies'' of Oscillating Polymer Gels

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    Species ranging from single-cell organisms to social insects can undergo auto-chemotaxis, where the entities move towards a chemo-attractant that they themselves emit. This mode of signaling allows the organisms to form large-scale structures. Using computational modeling, we show that millimeter-sized polymer gels can display similar auto-chemotaxis. In particular, we demonstrate that gels undergoing the self-oscillating Belousov-Zhabotinsky (BZ) reaction not only respond to a chemical signal from the surrounding solution, but also emit this signal and thus, multiple gel pieces can spontaneously self-aggregate. We focus on the collective behavior of ``colonies'' of BZ gels and show that communication between the individual pieces critically depends on all the neighboring gels. We isolate the conditions at which the BZ gels can undergo a type of self-recombining: if a larger gel is cut into distinct pieces that are moved relatively far apart, then their auto-chemotactic behavior drives them to move and autonomously recombine into a structure resembling the original, uncut sample. These findings reveal that the BZ gels can be used as autonomously moving building blocks to construct multiple structures and thus, provide a new route for creating dynamically reconfigurable materials.

  15. Polymer gel dosimeters with PVA-GA matrix.

    PubMed

    Abtahi, Seyed Mohammad Mahdi; Sadeghi Abandansari, Hamid

    2017-07-27

    Properties of a new polymer gel with cross-linked polyvinyl alcohol as a gelatinous matrix were investigated. The new polymer gel dosimeter was named PVABAT. The irradiation was performed using a calibrated (60)Co beam. The dose responses of the PVABAT formulations were quantified with MRI transverse relaxation rate (R2) measurements. The results show that the PVABAT gel responds linearly to the absorbed dose for doses from 30 up to 45 Gy. The maximal amount of [Formula: see text] of PVABAT polymer gel dosimeter was about 0.19 Gy which was indicated on a better resolution in comparison with previously reported acrylamide-based polymer gel dosimeters formulations. Furthermore, the gel response remains stable in the investigated time (192 h) after the irradiation. The effective atomic number and electron density of the new gel showed a maximum difference of 3.2 and 2% with soft tissue respectively. The melting point also increased significantly for new formulation. Furthermore, the new gel formulation has an elemental tissue equivalency for dosimetry applications involving nuclear reactions.

  16. Biopolymer gels containing fructooligosaccharides.

    PubMed

    Silva, Karen Cristina Guedes; Sato, Ana Carla Kawazoe

    2017-11-01

    The influence of the addition of fructooligosaccharide (FOS) in an external gelated alginate/gelatin biopolymer matrix, was evaluated in order to produce biopolymeric structures with functional effects. Solutions were characterized regarding their rheological properties, macrogels regarding their microstructure and mechanical properties and microgels were characterized in relation to their particle size distribution and morphology. Close relationship was found between the microstructure, rheological and mechanical properties of the biopolymeric systems. An increased viscosity and accentuated elastic and pseudoplastic behavior were associated to denser microstructures. The FOS addition caused changes in the evaluated properties, resulting in more cohesive structures, with smaller pores and higher viscosity, compared to alginate-gelatin gels. The addition of 3% FOS to biopolymeric system provided an optimal condition, allowing the formation of stronger gels, with smaller pores and beads with smaller sizes, indicating the potential use of these functional systems as texture modifiers or encapsulation systems. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Bi-Sr-Co-O thermoelectrics prepared by sol-gel methods with modified gel decomposition

    NASA Astrophysics Data System (ADS)

    Rubešová, K.; Hlásek, T.; Jakeš, V.; Sedmidubský, D.; Hejtmánek, J.

    2012-02-01

    We prepared misfit Bi2Sr2Co1.8Ox (Bi-222) phase as a member of a Bi-Sr-Co-O family. Two water based sol-gel methods were chosen with regard to the presence of a strongly hydrolysing Bi3+ ion - chelating route combining EDTA (ethylenediaminetetraacetic acid) and TEA (triethanolamine) and, secondly, water soluble polymer method using PEI (polyethylenimine). We focused on the influence of gel decomposition process on the grain size of precursor and, consequently, on the bulk density of the final samples. We tested decomposition in N2 atmosphere followed by a treatment in pure oxygen. The precursors decomposed in "N2/O2" regime were mainly composed of Bi2O3, SrCO3 and cobalt oxides with the grain size of approximately 50-100 nm. The powders arising from gel decomposition in air contained the desired Bi-Sr-Co-O oxide as the major phase independently of the chosen sol-gel method. The final sintered samples were almost single-phase with traces of the other pseudoternary phase Bi2Sr2CoOx independently of the decomposition atmosphere. For comparison, samples were also prepared by solid state reaction. The sol-gel prepared samples were always of higher bulk density with larger grains, moreover partly microstructurally ordered. These facts were also reflected in transport thermoelectric measurements.

  18. Solvent-induced lysozyme gels: rheology, fractal analysis, and sol-gel kinetics.

    PubMed

    da Silva, Marcelo A; Arêas, Elizabeth P G

    2005-09-15

    In this work, the gelation kinetics and fractal character of lysozyme gel matrices developed in tetramethylurea (TMU)-water media were investigated. Gelation times were determined from the temporal crossover point between the storage, G', and loss, G'', moduli, as a function of the binary solvent composition and of protein concentration. The inverse dependence of the upper limit of the linear viscoelastic region (gamma0) on protein concentration indicate that the lysozyme gels belong to the "strong link" kind, a gel category where interparticle links are stronger than intraparticle ones. Lysozyme gel fractal dimensions (Df) were determined from the analysis of rheological data according to a scaling theory by Shih et al. [Phys. Rev. A 42 (1990) 4772-4779] and were found to be compatible with a diffusion-limited cluster-aggregation kinetics (DLCA) for lysozyme gels formed at the TMU mass fraction in the binary organic-aqueous solvent, wTMU=0.9, and with a reaction-limited cluster aggregation kinetics (RLCA) for wTMU in the 0.6< or =wTMU< or =0.8 range.

  19. Designing Active Coatings and Multilayer Composites: Harnessing Mechano-chemical Transduction in Responsive Gels

    DTIC Science & Technology

    2011-03-02

    Gels; Funding: $364, 000 awarded for July 1, 2007 – July 1, 2010 Polymer gels undergoing the Belousov - Zhabotinsky reaction —the BZ gels—are currently... Zhabotinsky Reaction ” Nonlinear Dynamics with Polymers, J. Pojman and Q. Tran-Cong-Miyata, Eds., John Wiley, Chapter 8, (2010) 135-161. ...Combining this approach with our previously derived kinetic equations for the BZ reaction in polymers2,3, we undertook the first three-dimensional

  20. Dapsone gel 5% in combination with adapalene gel 0.1%, benzoyl peroxide gel 4% or moisturizer for the treatment of acne vulgaris: a 12-week, randomized, double-blind study.

    PubMed

    Fleischer, Alan B; Shalita, Alan; Eichenfield, Lawrence F; Abramovits, William; Lucky, Anne; Garrett, Steven

    2010-01-01

    To evaluate the safety and efficacy of dapsone gel 5% in the treatment of acne when used in combination with adapalene gel 0.1%, benzoyl peroxide gel 4% or moisturizer. This was a twelve-week, randomized, double-blind study. Patients aged 12 years and older (n=301) applied dapsone gel twice daily and were randomly assigned (1:1:1) to one of three additional treatments, applied once daily. By week 12, dapsone gel combined with any of the three additional treatments reduced the mean number of inflammatory lesions. However, the authors did not detect a significant difference in the reduction of inflammatory lesions when dapsone was used in combination with adapalene gel or with benzoyl peroxide gel compared to the dapsone plus moisturizer combination group (P=0.052 for both versus moisturizer combination). Patients treated with dapsone gel combined with adapalene showed a significantly better response in reduction in non-inflammatory and total acne lesion count than those who received the moisturizer combination. Local adverse reactions in all three treatment groups were minimal and generally mild in severity. Dapsone gel in combination with adapalene gel or benzoyl peroxide gel is safe and well tolerated for the treatment of acne vulgaris.

  1. Alteration of alkali reactive aggregates autoclaved in different alkali solutions and application to alkali-aggregate reaction in concrete (II) expansion and microstructure of concrete microbar

    SciTech Connect

    Lu Duyou . E-mail: duyoulu@njut.edu.cn; Mei Laibao; Xu Zhongzi; Tang Mingshu; Mo Xiangyin; Fournier, Benoit

    2006-06-15

    The effect of the type of alkalis on the expansion behavior of concrete microbars containing typical aggregate with alkali-silica reactivity and alkali-carbonate reactivity was studied. The results verified that: (1) at the same molar concentration, sodium has the strongest contribution to expansion due to both ASR and ACR, followed by potassium and lithium; (2) sufficient LiOH can completely suppress expansion due to ASR whereas it can induce expansion due to ACR. It is possible to use the duplex effect of LiOH on ASR and ACR to clarify the ACR contribution when ASR and ACR may coexist. It has been shown that a small amount of dolomite in the fine-grained siliceous Spratt limestone, which has always been used as a reference aggregate for high alkali-silica reactivity, might dedolomitize in alkaline environment and contribute to the expansion. That is to say, Spratt limestone may exhibit both alkali-silica and alkali-carbonate reactivity, although alkali-silica reactivity is predominant. Microstructural study suggested that the mechanism in which lithium controls ASR expansion is mainly due to the favorable formation of lithium-containing less-expansive product around aggregate particles and the protection of the reactive aggregate from further attack by alkalis by the lithium-containing product layer.

  2. Calcium and fibrin gel structure.

    PubMed

    Okada, M; Blombäck, B

    1983-02-01

    Calcium ions (Ca), when present in the gel forming system, were shown to influence liquid permeation of the gels formed, as judged from the Ks-values (permeability coefficients) of the final gels. On increasing Ca concentration, the Ks-values for Fibrin I and Fibrin II gels increase and a maximum is reached at about 10-20 mM for gels formed at ionic strengths between 0.18 and 0.24. For both gels, clotting times (Ct) were shortened on increasing Ca concentration and the shortening was accompanied by increase in Ks. Magnesium also shortened Ct but had no appreciable effect on Ks. The rate of activation of fibrinogen (release of FPA and FPB) was not much affected by Ca, but the activation required for gelation at Ct, decreased with increasing Ca concentration. After the gels were formed, the removal of Ca by EDTA did not change the flow properties. Our results showed that Ca is of importance for formation of the fibrin gel structure, but it may be of minor importance for preservation of the gel structure after its formation. There is a difference between Fibrin I and Fibrin II gels with regard to Ca dependence. The role of calcium in gelation as well as its physiological implications is discussed.

  3. Clarification Procedure for Gels

    NASA Technical Reports Server (NTRS)

    Barber, Patrick G.; Simpson, Norman R.

    1987-01-01

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

  4. Staining Proteins in Gels

    PubMed Central

    Gallagher, Sean; Chakavarti, Deb

    2008-01-01

    Following separation by electrophoretic methods, proteins in a gel can be detected by several staining methods. This unit describes protocols for detecting proteins by four popular methods. Coomassie blue staining is an easy and rapid method. Silver staining, while more time consuming, is considerably more sensitive and can thus be used to detect smaller amounts of protein. Fluorescent staining is a popular alternative to traditional staining procedures, mainly because it is more sensitive than Coomassie staining, and is often as sensitive as silver staining. Staining of proteins with SYPRO Orange and SYPRO Ruby are also demonstrated here. PMID:19066521

  5. Staining proteins in gels.

    PubMed

    Gallagher, Sean; Chakavarti, Deb

    2008-07-08

    Following separation by electrophoretic methods, proteins in a gel can be detected by several staining methods. This unit describes protocols for detecting proteins by four popular methods. Coomassie blue staining is an easy and rapid method. Silver staining, while more time consuming, is considerably more sensitive and can thus be used to detect smaller amounts of protein. Fluorescent staining is a popular alternative to traditional staining procedures, mainly because it is more sensitive than Coomassie staining, and is often as sensitive as silver staining. Staining of proteins with SYPRO Orange and SYPRO Ruby are also demonstrated here.

  6. Mineral-water reactions in metamorphism and volcanism

    USGS Publications Warehouse

    Barnes, I.

    1985-01-01

    Low-temperature (120??C and less) metamorphism of graywacke, granite and andesite yields zeolites and precursor gels by reaction with fresh water but low-greenschist facies by reaction with salt (sea)water. ?? 1985.

  7. Optical detection of parasitic protozoa in sol-gel matrices

    NASA Astrophysics Data System (ADS)

    Livage, Jacques; Barreau, J. Y.; Da Costa, J. M.; Desportes, I.

    1994-10-01

    Whole cell parasitic protozoa have been entrapped within sol-gel porous silica matrices. Stationary phase promastigote cells of Leishmania donovani infantum are mixed with a silica sol before gelation occurs. They remain trapped within the growing oxide network and their cellular organization appears to be well preserved. Moreover protozoa retain their antigenic properties in the porous gel. They are still able to detect parasite specific antibodies in serum samples from infected patients via an enzyme linked immunosorbent assay (ELISA). Antigen- antibody associations occurring in the gel are optically detected via the reactions of a peroxidase conjugate with ortho-phenylenediamine leading to the formation of a yellow coloration. A clear-cut difference in optical density is measured between positive and negative sera. Such an entrapment of antigenic species into porous sol-gel matrices avoids the main problems due to non specific binding and could be advantageously used in diagnostic kits.

  8. Preparation and clinical application of indomethacin gel for medical treatment of stomatitis.

    PubMed

    Momo, Kenji; Shiratsuchi, Tatsuko; Taguchi, Hiroyuki; Hashizaki, Kaname; Saito, Yoshihiro; Makimura, Mizue; Ogawa, Naotake

    2005-05-01

    The preparation and clinical applications of indomethacin (IM) gel were investigated in the treatment of stomatitis resulting from chemotherapy and radiotherapy for cancer. IM gel was prepared by adding various water-soluble polymers [hydroxypropyl cellulose (HPC), etc.] to IM aqueous solution. The release rate of IM from IM gels was found to decrease with increasing polymer concentration and viscosity and to follow a first-order reaction rate equation. The release rate of IM from the IM gel with HPC was decreased gradually with increasing polymer concentration and to be easily controllable compared with gels with other polymers. The time before pain relief occurred after application of the IM gel was slightly shorter and the duration of pain relief was longer compared with the IM aqueous solution. It was confirmed that IM gel is useful in the treatment of stomatitis.

  9. Effect of gravity and diffusion interface proximity on the morphology of collagen gels.

    PubMed

    Roedersheimer, M T; Bateman, T A; Simske, S J

    1997-11-01

    Collagen solutions (0.25% w/v) were polymerized in microgravity (STS-77, 10 days) along with simultaneous ground controls. Assembly conditions were achieved by the passage of buffer ions across a dialysis membrane into a reaction chamber containing the dissolved collagen. The gels were analyzed macroscopically and microscopically to assess the influence of gravity and the oriented diffusion of buffer ions on the resulting product. Double-blind rankings based on visual observation of the gels established that all of the flight gels (n = 8) were more uniform in appearance than all of the ground gels (n = 6). Photography using side illumination of the gels revealed the more granular appearance of the ground gels relative to the highly uniform appearance of the flight gels. Scanning electron microscopy established this difference at the microscopic level. Proximity to the dialysis interface and the presence or absence of gravity were both found to control the porosity and uniformity of the matrix.

  10. Polyoxometalate-based Supramolecular Gel

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

    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.

  11. Silver nitrate based gel dosimeter

    NASA Astrophysics Data System (ADS)

    Titus, D.; Samuel, E. J. J.; Srinivasan, K.; Roopan, S. M.; Madhu, C. S.

    2017-05-01

    A new radiochromic gel dosimeter based on silver nitrate and a normoxic gel dosimeter was investigated using UV-Visible spectrophotometry in the clinical dose range. Gamma radiation induced the synthesis of silver nanoparticles in the gel and is confirmed from the UV-Visible spectrum which shows an absorbance peak at around 450 nm. The dose response function of the dosimeter is found to be linear upto12Gy. In addition, the gel samples were found to be stable which were kept under refrigeration.

  12. Gel polymer electrolytes for batteries

    DOEpatents

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

    2014-11-18

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

  13. Electrically controlled polymeric gel actuators

    DOEpatents

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

    1993-10-05

    Electrically controlled polymeric gel actuators or synthetic muscles are described capable of undergoing substantial expansion and contraction when subjected to changing pH environments, temperature, or solvent. The actuators employ compliant containers for the gels and their solvents. The gels employed may be cylindrical electromechanical gel fibers such as polyacrylamide fibers or a mixture of poly vinyl alcohol-polyacrylic acid arranged in a parallel aggregate and contained in an electrolytic solvent bath such as salt water. The invention includes smart, electrically activated devices exploiting this phenomenon. These devices are capable of being manipulated via active computer control as large displacement actuators for use in adaptive structure such as robots. 11 figures.

  14. Electrically controlled polymeric gel actuators

    DOEpatents

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

    1993-01-01

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

  15. Modeling the entrainment of self-oscillating gels to periodic mechanical deformation

    NASA Astrophysics Data System (ADS)

    Yashin, Victor V.; Levitan, Steven P.; Balazs, Anna C.

    2015-06-01

    Polymer gels undergoing the oscillatory Belousov-Zhabotinsky (BZ) reaction are one of the few synthetic materials that exhibit biomimetic mechano-chemical transduction, converting mechanical input into chemical energy. Here, we consider self-oscillating BZ gels that are subjected to periodic mechanical forcing, and model the entrainment of the oscillatory gel dynamics to this external stimulus. The gel size is assumed to be sufficiently small that the chemo-mechanical oscillations are spatially uniform. The behavior of the system is captured by equations describing the kinetics of the oscillatory BZ reaction in the gel coupled to equations for the variations in gel size due to the inherent reaction and imposed force. We employ the phase dynamics approach for analyzing the entrainment of the BZ gel to force- and strain-controlled compressive deformations. The phase response curves are obtained using Malkin's method, and time-averaging is applied to extract the slow phase dynamics caused by the periodic forcing. We demonstrate that the entrainment of the self-oscillating BZ gel is sensitive to the chemo-mechanical coupling in gel, the mode of deformation, and the level of static compression. Kuramoto's model of phase oscillators is shown to be applicable if the external forcing is purely harmonic.

  16. Homogeneity of gels and gel-derived glasses

    NASA Technical Reports Server (NTRS)

    Mukherjee, S. P.

    1984-01-01

    The significance and implications of gel preparation procedures in controlling the homogeneity of multicomponent oxide gels are discussed. The role of physicochemical factors such as the structure and chemical reactivities of alkoxides, the formation of double-metal alkoxides, and the nature of solvent(s) are critically analyzed in the context of homogeneity of gels during gelation. Three procedures for preparing gels in the SiO2-B2O3-Na2O system are examined in the context of cation distribution. Light scattering results for glasses in the SiO2-B2O3-Na2O system prepared by both the gel technique and the conventional technique are examined.

  17. Homogeneity of gels and gel-derived glasses

    NASA Technical Reports Server (NTRS)

    Mukherjee, S. P.

    1984-01-01

    The significance and implications of gel preparation procedures in controlling the homogeneity of multicomponent oxide gels are discussed. The role of physicochemical factors such as the structure and chemical reactivities of alkoxides, the formation of double-metal alkoxides, and the nature of solvent(s) are critically analyzed in the context of homogeneity of gels during gelation. Three procedures for preparing gels in the SiO2-B2O3-Na2O system are examined in the context of cation distribution. Light scattering results for glasses in the SiO2-B2O3-Na2O system prepared by both the gel technique and the conventional technique are examined.

  18. Active gel physics

    NASA Astrophysics Data System (ADS)

    Prost, J.; Jülicher, F.; Joanny, J.-F.

    2015-02-01

    The mechanical behaviour of cells is largely controlled by a structure that is fundamentally out of thermodynamic equilibrium: a network of crosslinked filaments subjected to the action of energy-transducing molecular motors. The study of this kind of active system was absent from conventional physics and there was a need for both new theories and new experiments. The field that has emerged in recent years to fill this gap is underpinned by a theory that takes into account the transduction of chemical energy on the molecular scale. This formalism has advanced our understanding of living systems, but it has also had an impact on research in physics per se. Here, we describe this developing field, its relevance to biology, the novelty it conveys to other areas of physics and some of the challenges in store for the future of active gel physics.

  19. Ionogel Electrolytes through Sol-Gel Processing

    NASA Astrophysics Data System (ADS)

    Horowitz, Ariel I.

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

  20. Microscopic examination of volcanic rocks subjected to alkaline leaching

    NASA Astrophysics Data System (ADS)

    Seidlova, Z.; Prikryl, R.; Sachlova, S.

    2012-04-01

    Volcanic rocks supply one third of crushed stone in the Czech Republic. Some of these rocks significantly contribute to concrete damage by alkali silica reaction (ASR) as has been recognised by previous studies in several concrete constructions (dams, highways, bridges). In recent study, volcanic rocks (basalts, spilites, melaphyres, phonolites, rhyolites, diabases) were subjected to several test procedures aiming to evaluate their ASR potential. The experimental study employed accelerated mortar bar test (following the standard ASTM C1260), chemical test (following the standard ASTM C289), and microscopic techniques (polarising microscopy, scanning electron microscopy combined with energy dispersive analysis). The interaction of cement paste and aggregate under high alkaline solution and increasing temperature conditions takes place during the accelerated mortar bar test. Microscopic techniques applied on mortar bar specimens enabled identification of ASR products (alkali-silica gels). Chemical test quantified ASR potential based on the amount of Si4+ leached into the solution within 24 hours testing period and contemporaneous reduction of alkalinity. Volcanic particles leached in alkaline solution were subjected to microscopic analysis with the aim to find minerals (phases) affecting their ASR potential. ASR of volcanic rocks was found highly variable connected to the mineral composition. The highest degree of ASR was found in connection with melaphyres, rhyolites and one sample of spilite. The main factor influencing ASR of investigated aggregates is regarded in the presence of SiO2-rich phases (e.g. SiO2-rich glass).

  1. Nanocrystal/sol-gel nanocomposites

    DOEpatents

    Petruska, Melissa A [Los Alamos, NM; Klimov, Victor L [Los Alamos, NM

    2012-06-12

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

  2. Nanocrystal/sol-gel nanocomposites

    DOEpatents

    Petruska, Melissa A [Los Alamos, NM; Klimov, Victor L [Los Alamos, NM

    2007-06-05

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

  3. Crystallization of steroids in gels

    NASA Astrophysics Data System (ADS)

    Kalkura, S. Narayana; Devanarayanan, S.

    1991-03-01

    The crystal growth and characterization of certain steriods, viz., cholesterol, cholesteryl acetate, β-sitosterol, progesterone and testosterone, in a silica gel medium is discussed. The present study shows that the single test tube diffusion method can be used to grow crystals of steroids in a silica gel medium by the reduction of steroid solubility.

  4. A new agarose gel model

    SciTech Connect

    Hasenfeld, A.; Pepke, E.; Lim, H.A.; Cantor, C.R.

    1993-12-31

    A new agarose gel model is introduced, which corresponds to what the authors believe agarose gels look like microscopically. While the scientific literature is filled with studies of the microscopic structure of agarose, the fact remains that there is no unambiguous and exact model of its underlying structure. Given this, the authors are left to construct their own model numerically.

  5. Living bacteria in silica gels

    NASA Astrophysics Data System (ADS)

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

    2002-09-01

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

  6. Product-selective blot: a technique for measuring enzyme activities in large numbers of samples and in native electrophoresis gels

    SciTech Connect

    Thompson, G.A.; Davies, H.M.; McDonald, N.

    1985-08-01

    A method termed product-selective blotting has been developed for screening large numbers of samples for enzyme activity. The technique is particularly well suited to detection of enzymes in native electrophoresis gels. The principle of the method was demonstrated by blotting samples from glutaminase or glutamate synthase reactions into an agarose gel embedded with ion-exchange resin under conditions favoring binding of product (glutamate) over substrates and other substances in the reaction mixture. After washes to remove these unbound substances, the product was measured using either fluorometric staining or radiometric techniques. Glutaminase activity in native electrophoresis gels was visualized by a related procedure in which substrates and products from reactions run in the electrophoresis gel were blotted directly into a resin-containing image gel. Considering the selective-binding materials available for use in the image gel, along with the possible detection systems, this method has potentially broad application.

  7. Bouncing gel balls: Impact of soft gels onto rigid surface

    NASA Astrophysics Data System (ADS)

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

    2003-07-01

    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.

  8. Gels based on cyclic polymers.

    PubMed

    Zhang, Ke; Lackey, Melissa A; Cui, Jun; Tew, Gregory N

    2011-03-23

    Cyclic poly(5-hydroxy-1-cyclooctene) (PACOE) was synthesized by ring-expansion metathesis polymerization (REMP), and thiol-ene chemistry was used to cross-link the internal double bonds in the PACOE backbone. This created a novel network material (gels formed from cyclic polymers) with unique structural units, where the cyclic PACOE main chains, which serve as secondary topological cross-linkages, were connected by primary intermolecular chemical cross-linkages. The resulting properties were notably different from those of traditional chemically cross-linked linear PACOE gels, whose gel fraction (GF) and modulus (G) increased while the swelling ratio (Q) decreased with increasing initial polymer concentration in the gel precursor solution (C(0)). For the gels formed from cyclic polymers, however, the GF, Q, and G all simultaneously increased as C(0) increased at the higher range. Furthermore, at the same preparation state (same C(0)), the swelling ability and the maximum strain at break of the gels formed from cyclic polymers were always greater than those of the gels formed from linear polymers, and these differences became more pronounced as C(0) increased.

  9. Blood grouping based on PCR methods and agarose gel electrophoresis.

    PubMed

    Sell, Ana Maria; Visentainer, Jeane Eliete Laguila

    2015-01-01

    The study of erythrocyte antigens continues to be an intense field of research, particularly after the development of molecular testing methods. More than 300 specificities have been described by the International Society for Blood Transfusion as belonging to 33 blood group systems. The polymerase chain reaction (PCR) is a central tool for red blood cells (RBC) genotyping. PCR and agarose gel electrophoresis are low cost, easy, and versatile in vitro methods for amplifying defined target DNA (RBC polymorphic region). Multiplex-PCR, AS-PCR (Specific Allele Polymerase Chain Reaction), and RFLP-PCR (Restriction Fragment Length Polymorphism-Polymerase Chain Reaction) techniques are usually to identify RBC polymorphisms. Furthermore, it is an easy methodology to implement. This chapter describes the PCR methodology and agarose gel electrophoresis to identify the polymorphisms of the Kell, Duffy, Kidd, and MNS blood group systems.

  10. Mechanical Failure in Colloidal Gels

    NASA Astrophysics Data System (ADS)

    Kodger, Thomas Edward

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

  11. The effect of residual water on antacid properties of sucralfate gel dried by microwaves.

    PubMed

    Gainotti, Alessandro; Losi, Elena; Colombo, Paolo; Santi, Patrizia; Sonvico, Fabio; Baroni, Daniela; Massimo, Gina; Colombo, Gaia; Del Gaudio, Pasquale

    2006-01-20

    The aim of this work was to study the acid neutralization characteristics of microwave-dried sucralfate gel in relation to the water content and physical structure of the substance. Several dried sucralfate gels were compared with humid sucralfate gel and sucralfate nongel powder in terms of neutralization rate and buffering capacity. Humid sucralfate gel and microwave-dried gel exhibited antacid effectiveness. In particular, the neutralization rate of dried gel powders was inversely related to the water content: as the water content of dried powders decreased, the acid reaction rate linearly increased. The relationship was due to the different morphology of dried sucralfate gels. In fact, the porosity of the dried samples increased with the water reduction. However, the acid neutralization equivalent revealed that the dried sucralfate gel became more resistant to acid attack in the case of water content below 42%. Then, the microwave drying procedure had the opposite effect on the reactivity of the aluminum hydroxide component of dried sucralfate gel powders, since the rate of the reaction increased whereas the buffering capacity decreased as the amount of water was reduced.

  12. Harnessing interfacially-active nanorods to regenerate severed polymer gels.

    PubMed

    Yong, Xin; Kuksenok, Olga; Matyjaszewski, Krzysztof; Balazs, Anna C

    2013-01-01

    With newly developed computational approaches, we design a nanocomposite that enables self-regeneration of the gel matrix when a significant portion of the material is severed. The cut instigates the dynamic cascade of cooperative events leading to the regrowth. Specifically, functionalized nanorods localize at the new interface and initiate atom transfer radical polymerization with monomers and cross-linkers in the outer solution. The reaction propagates to form a new cross-linked gel, which can be tuned to resemble the uncut material.

  13. Synthesis of polyferromethylsiloxane sorbents using a sol gel method

    NASA Astrophysics Data System (ADS)

    Zub, Yuriy Leonidovych; Roesky, Herbert W.; Malyar, Mariana Mykolaivna; Chuiko, Alexei Alexeyevich; Jaroniec, Mietek; Murugavel, Ramaswamy

    2001-02-01

    Trivalent iron complexes which could be easily converted into materials are formed by the reaction of FeCl 3 with K 3[O 3SiMe] in a highly concentrated aqueous alkaline solution. The presence of the liquid glass as an additive and decreasing the pH results in solutions that give rise to homogeneous gels. Polycondensation proceeds very rapidly in the higher pH range (viz. pH 9-10) and substantially slower in an acidic medium (pH 2-3). Xerogels were obtained having microporous structure after treatment of polyferromethylsiloxane gels obtained from acidic medium or mesoporous structure when obtained from alkaline medium.

  14. Polyoxometalate-based Supramolecular Gel

    PubMed Central

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

    2013-01-01

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

  15. Hydrothermal preparation of diatomaceous earth combined with calcium silicate hydrate gels.

    PubMed

    Maeda, Hirotaka; Ishida, Emile Hideki

    2011-01-30

    A novel composite for the removal of color in waste water was prepared by subjecting slurries consisting diatomaceous earth and slaked lime to a hydrothermal reaction at 180 °C. Subsequently, calcium silicate hydrate gels covered the surface of diatomaceous earth due to the reaction between the amorphous silica of diatomaceous earth and slaked lime. The formation of calcium silicate hydrate gels led to an increase in the specific surface area. The composites showed higher methylene blue adsorption capacity compared with diatomaceous earth. The improved adsorption capacity of the composites depended on the amount of the calcium silicate hydrate gels and their silicate anion chain-lengths.

  16. Design of Self-Oscillating Gels and Application to Biomimetic Actuators

    PubMed Central

    Yoshida, Ryo

    2010-01-01

    As a novel biomimetic polymer, we have developed polymer gels with an autonomous self-oscillating function. This was achieved by utilizing oscillating chemical reactions, called the Belousov-Zhabotinsky (BZ) reaction, which is recognized as a chemical model for understanding several autonomous phenomena in biological systems. Under the coexistence of the reactants, the polymer gel undergoes spontaneous swelling-deswelling changes without any on-off switching by external stimuli. In this review, our recent studies on the self-oscillating polymer gels and application to biomimetic actuators are summarized. PMID:22294901

  17. Meso-decorated self-healing gels: network structure and properties

    NASA Astrophysics Data System (ADS)

    Gong, Jin; Sawamura, Kensuke; Igarashi, Susumu; Furukawa, Hidemitsu

    2013-04-01

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

  18. Ultrapure glass optical waveguide development in microgravity by the sol-gel process

    NASA Technical Reports Server (NTRS)

    Mukherjee, S. P.; Holman, R. A.

    1981-01-01

    Multicomponent, homogeneous, noncrystalline oxide gels can be prepared by the sol-gel process and these gels are promising starting materials for melting glasses in the space environment. The sol-gel process referred to here is based on the polymerization reaction of alkoxysilane with other metal alkoxy compounds or suitable metal salts. Many of the alkoxysilanes or other metal alkoxides are liquids and thus can be purified by distillation. The use of gels offers several advantages such as high purity and lower melting times and temperatures. The sol-gel process is studied for utilization in the preparation of multicomponent ultrapure glass batches for subsequent containerless melting of the batches in space to prepare glass blanks for optical waveguides.

  19. Making a choice of catheterisation gel and the role of chlorhexidine.

    PubMed

    Williams, Cath

    2017-07-02

    It is estimated that over 90 000 people in the UK community live with an indwelling catheter ( Wilson, 2016 ). It is essential that a lubricating gel is used during catheterisation, as this helps to reduce the risk of pain, trauma and infection ( Loveday et al, 2014 ; National Institute for Health and Care Excellence, 2012 ). Chlorhexidine is an antiseptic contained in many catheterisation gels. Evidence demonstrates that increasing numbers of patients are experiencing hypersensitivity reactions to this ingredient ( Australian and New Zealand College of Anaesthetists, 2014 ). This article considers the range of catheterisation gel choices available to clinicians and the importance of selecting the correct gel for each patient. It addresses the benefits of using OptiLube Active CHG Free (with lidocaine 2%) - the only catheterisation gel currently available in the UK that contains the benefits of local anaesthetic without chlorhexidine - and recommends that this should be the gel of choice for non-specialist staff conducting catheterisations without individual patient assessments.

  20. DETERMINING DRUG SENSITIVITY—Use of the Gel Diffusion Method

    PubMed Central

    Chambers, Van Vleck

    1960-01-01

    A study was carried out to determine whether the double diffusion gel test when applied to the serum of patients with clear-cut penicillin reactions of various types, might be useful for demonstrating the presence of precipitating antibody. Results did not demonstrate the antibody. The difference in results with this test obtained by various workers was not explained by the observations in this study. Other approaches to determination of the mechanism of the penicillin reaction are discussed, and it is noted that the hemagglutination test, newly applied to the penicillin reaction problem, may be useful after further investigation. PMID:13692231

  1. Dynamics of a DNA Gel

    NASA Astrophysics Data System (ADS)

    Adhikari, Ramesh; Bhattacharya, Aniket; Dogariu, Aristide

    We study in silico the properties of a gel consisting of DNA strands (modeled as semi-flexible chains) and linkers of varying flexibility, length, and topology. These linkers are envisioned and modeled as active components with additional attributes so as to mimic properties of a synthetic DNA gel containing motor proteins. We use Brownian dynamics to directly obtain frequency dependent complex shear moduli of the gel. We further carry out force spectroscopy on these computer generated gels and study the relaxation properties as a function of the important parameters of the model, e.g., densities and relative ratios of the DNAs and the linkers, the average life time of a link, etc. Our studies are relevant for designing synthetic bio-materials for both materials and medical applications.

  2. Diffusion of polymer gel implants.

    PubMed

    Davis, B K

    1974-08-01

    Crosslinked polyacrylamide and polyvinylpyrrolidone gels have been used to subcutaneously implant (125)I-labeled immunoglobulin, (125)I-labeled luteinizing hormone, (125)I-labeled bovine serum albumin, (125)I-labeled insulin, [(3)H]prostaglandin F(2alpha), and Na(125)I into hamsters. From the rates of absorption of the solutes, their diffusion coefficients were determined. The diffusion coefficients showed a logarithmic dependence on implant polymer concentration and solute molecular weight. Release of the solutes from gel preparations incubated 10 mM phosphate buffer (pH 7.2) at 37 degrees revealed a similar relationship between solute diffusion coefficient, molecular weight, and the concentration of polymer. A general equation was derived that gives the expected diffusion coefficient of a substance in a polymer gel from its molecular weight, diffusion coefficient in solvent, and polymer concentration of the gel.

  3. Actuation performances of anisotropic gels

    NASA Astrophysics Data System (ADS)

    Nardinocchi, P.; Teresi, L.

    2016-12-01

    We investigated the actuation performances of anisotropic gels driven by mechanical and chemical stimuli, in terms of both deformation processes and stroke-curves, and distinguished between the fast response of gels before diffusion starts and the asymptotic response attained at the steady state. We also showed as the range of forces that an anisotropic hydrogel can exert when constrained is especially wide; indeed, changing fiber orientation allows us to induce shear as well as transversely isotropic extensions.

  4. Rheological characterization of hydroxypropylcellulose gels.

    PubMed

    Ramachandran, S; Chen, S; Etzler, F

    1999-02-01

    The present paper describes the rheological properties of hydroxypropylcellulose (HPC) gels formulated in propylene glycol (PG), water, ethanol, and mixtures of these components. The effects of molecular weight, polymer concentration, and solvent composition on the apparent viscosity and flow characteristics have been studied by continuous shear rheometry. The HPC gels are shear thinning and do not exhibit significant yield or hysteresis in their rheograms. The apparent viscosity increases with increasing molecular weight and concentration of the polymer, as expected. Although not so pronounced at lower concentrations (< or = 1.5%), HPC gels tend to become increasingly non-Newtonian with increasing molecular weight at higher polymer concentrations (3%). A mathematical model has been proposed for the prediction of viscosities of HPC gels. There exists a high degree of dependence on molecular interactions between various solvent molecules in the prediction of mixture viscosities in ternary systems. The effects of solvent composition on the viscoelastic behavior of these gels have also been examined by dynamic mechanical analysis. The HPC gels are highly viscoelastic and exhibit greater degrees of elasticity with increased PG content in ternary solvent mixtures with water and ethanol. The study also suggests that dynamic mechanical analysis could prove to be a useful tool in the determination of zero-shear viscosities, viscosities that are representative of most realistic situations.

  5. TOPICAL REVIEW: Polymer gel dosimetry

    NASA Astrophysics Data System (ADS)

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

    2010-03-01

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

  6. Topical Review: Polymer gel dosimetry

    PubMed Central

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

    2010-01-01

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

  7. Precise Tuning of Facile One-Pot Gelatin Methacryloyl (GelMA) Synthesis

    PubMed Central

    Shirahama, Hitomi; Lee, Bae Hoon; Tan, Lay Poh; Cho, Nam-Joon

    2016-01-01

    Gelatin-methacryloyl (GelMA) is one of the most commonly used photopolymerizable biomaterials in bio-applications. However, GelMA synthesis remains suboptimal, as its reaction parameters have not been fully investigated. The goal of this study is to establish an optimal route for effective and controllable GelMA synthesis by systematically examining reaction parameters including carbonate-bicarbonate (CB) buffer molarity, initial pH adjustment, MAA concentration, gelatin concentration, reaction temperature, and reaction time. We employed several analytical techniques in order to determine the degree of substitution (DS) and conducted detailed structural analysis of the synthesized polymer. The results enabled us to optimize GelMA synthesis, showing the optimal conditions to balance the deprotonation of amino groups with minimizing MAA hydrolysis, which led to nearly complete substitution. The optimized conditions (low feed ratio of MAA to gelatin (0.1 mL/g), 0.25 M CB buffer at pH 9, and a gelatin concentration of 10–20%) enable a simplified reaction scheme that produces GelMA with high substitution with just one-step addition of MAA in one pot. Looking forward, these optimal conditions not only enable facile one-pot GelMA synthesis but can also guide researchers to explore the efficient, high methacrylation of other biomacromolecules. PMID:27503340

  8. Precise Tuning of Facile One-Pot Gelatin Methacryloyl (GelMA) Synthesis

    NASA Astrophysics Data System (ADS)

    Shirahama, Hitomi; Lee, Bae Hoon; Tan, Lay Poh; Cho, Nam-Joon

    2016-08-01

    Gelatin-methacryloyl (GelMA) is one of the most commonly used photopolymerizable biomaterials in bio-applications. However, GelMA synthesis remains suboptimal, as its reaction parameters have not been fully investigated. The goal of this study is to establish an optimal route for effective and controllable GelMA synthesis by systematically examining reaction parameters including carbonate-bicarbonate (CB) buffer molarity, initial pH adjustment, MAA concentration, gelatin concentration, reaction temperature, and reaction time. We employed several analytical techniques in order to determine the degree of substitution (DS) and conducted detailed structural analysis of the synthesized polymer. The results enabled us to optimize GelMA synthesis, showing the optimal conditions to balance the deprotonation of amino groups with minimizing MAA hydrolysis, which led to nearly complete substitution. The optimized conditions (low feed ratio of MAA to gelatin (0.1 mL/g), 0.25 M CB buffer at pH 9, and a gelatin concentration of 10–20%) enable a simplified reaction scheme that produces GelMA with high substitution with just one-step addition of MAA in one pot. Looking forward, these optimal conditions not only enable facile one-pot GelMA synthesis but can also guide researchers to explore the efficient, high methacrylation of other biomacromolecules.

  9. Manufacture of Regularly Shaped Sol-Gel Pellets

    NASA Technical Reports Server (NTRS)

    Leventis, Nicholas; Johnston, James C.; Kinder, James D.

    2006-01-01

    An extrusion batch process for manufacturing regularly shaped sol-gel pellets has been devised as an improved alternative to a spray process that yields irregularly shaped pellets. The aspect ratio of regularly shaped pellets can be controlled more easily, while regularly shaped pellets pack more efficiently. In the extrusion process, a wet gel is pushed out of a mold and chopped repetitively into short, cylindrical pieces as it emerges from the mold. The pieces are collected and can be either (1) dried at ambient pressure to xerogel, (2) solvent exchanged and dried under ambient pressure to ambigels, or (3) supercritically dried to aerogel. Advantageously, the extruded pellets can be dropped directly in a cross-linking bath, where they develop a conformal polymer coating around the skeletal framework of the wet gel via reaction with the cross linker. These pellets can be dried to mechanically robust X-Aerogel.

  10. Magnetic Characterization of Iron Oxide Cross Linked Hydro gels

    NASA Astrophysics Data System (ADS)

    Senaratne, U.; Powell, N.; Kroll, E.; Tsoi, G.; Naik, R.; Naik, V.; Vaishnava, P. P.; Wenger, L. E.

    2004-03-01

    Magnetic hydro gels have potential applications in drug delivery, cells sorting, sensors, and actuating technologies. Iron oxide alginate nanocomposites were synthesized following the method of Kroll et al^1 by cross linking sodium alginate with Fe^2+ and Fe^3+ in methanol: water. The ion-cross linked alginate hydro gels are oxidized in an alkaline solution. The resulting hydro gel consists of iron oxide cross linked alginate. The alginate hydro gels are inert to the reaction conditions and therefore the reaction sequence can be repeated. The multiple loadings result in an increase in the amount of iron oxide and the size of the iron oxide nanoparticles in the cross linked hydro gels. The third and sixth loaded iron oxide alginate hydro gels were dried and characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), and Superconducting Quantum Interference Device (SQUID) magnetometry. The XRD patterns have characteristic features of γ- Fe_2O3 or Fe_3O4 phases. The average particle size, calculated from the XRD peaks, for third loaded iron oxide alginate was 2 nm. The zero-field-cooled and field-cooled SQUID measurements show the iron oxide nanoparticles are superparamagnetic with blocking temperature (T_B) of approximately 35 K. Above the blocking temperature, the inverse susceptibility versus temperature relationship does not follow the Curie-Weiss law, indicating strong inter-particle interactions. The M vs. H data above the blocking temperature was fitted with a modified Langevin function to obtain additional information about the iron oxide particle size. Details of the relationship between coercive field and temperature as well as the particle size distribution obtained from XRD and TEM measurements will be presented. *Research supported by NSF grant # DGE ˜980720 **Supported by NSF REU grant # EEC-0097736 ^1E. Kroll, F.M. Winnik, and R.F. Ziolo, Chem. Mater, 8, 1594 (1996).

  11. Gel-based versus gel-free proteomics: a review.

    PubMed

    Baggerman, Geert; Vierstraete, Evy; De Loof, Arnold; Schoofs, Liliane

    2005-12-01

    With the sequencing of the genome of over 150 organisms, the field of biology has been revolutionised. Instead of studying one gene or protein at the time, it is now possible to study the effect of physiological or pathological changes on the expression of all genes or proteins in the organism. Proteomics aims at the simultaneous analysis of all proteins expressed by a cell, tissue or organism in a specific physiological condition. Because proteins are the effector molecules in all organisms, it is evident that changes in the physiological condition of an organism will be reflected by changes in protein expression and/or processing. Since the formulation of the concept of proteomics in the mid 90's proteomics has relied heavily on 2 dimensional gel electrophoresis (2DGE) for the separation and visualization of proteins. 2DGE, however, has a number of inherent drawbacks. 2DGE is costly, fairly insensitive to low copy proteins and cannot be used for the entire proteome. Therefore, over the years, several gel-free proteomics techniques have been developed to either fill the gaps left by 2DGE or to entirely abolish the gel based techniques. This review summarizes the most important gel-free and gel-based proteomics techniques and compares their advantages and drawbacks.

  12. Light scattering study of partially ionized poly(acrylic acid) systems : comparison between gels and solutions

    NASA Astrophysics Data System (ADS)

    Moussaid, A.; Munch, J. P.; Schosseler, F.; Candau, S. J.

    1991-06-01

    Static and quasielastic light scattering experiments have been performed on the reaction bath of partially neutralized poly(acrylic acid) solutions and gels. The intensity scattered from gels is independent on the scattering wavevector, giving thus evidence that the gels are homogeneous at the scale of the wavelength of the light, contrary to what is generally observed in neutral gels. The comparison of the time and ensemble averages of the autocorrelation function of scattered light intensity shows that the gels behave with respect to that experiment as ergodic media. The variations of the intensity scattered from gels and solutions, with the ionization degree and the polymer concentration were found to be in good agreement with those predicted from simple theoretical arguments. The variations of the cooperative diffusion with these same parameters were found similar for gels and solutions. Des mesures de diffusion statique et quasiélastique de la lumière ont été effectuées sur des solutions et des gels d'acide poly(acrylique) partiellement ionisés. L'intensité diffusée par les gels est indépendante du vecteur d'onde de transfert, ce qui montre leur homogénéité, contrairement au cas des gels neutres. La comparaison des moyennes temporelle et spatiale de la fonction d'autocorrélation de l'intensité de la lumière diffusée montre que ces gels se comportent comme des milieux ergodiques. Les variations de l'intensité diffusée par les gels et les solutions en fonction de la concentration en polymère et du degré d'ionisation sont en bon accord avec les prédictions théoriques. Les variations du coefficient de diffusion avec ces mêmes paramètres sont identiques pour les gels et les solutions.

  13. Does nitrogen gas bubbled through a low density polymer gel dosimeter solution affect the polymerization process?

    PubMed Central

    Shahbazi-Gahrouei, Daryoush; Gholami, Mehrdad; Pourfallah, Tayyeb Allahverdi; Keshtkar, Mohammad

    2015-01-01

    Background: On account of the lower electron density in the lung tissue, the dose distribution in the lung cannot be verified with the existing polymer gel dosimeters. Thus, the aims of this study are to make a low density polymer gel dosimeter and investigate the effect of nitrogen gas bubbles on the R2 responses and its homogeneity. Materials and Methods: Two different types of low density polymer gel dosimeters were prepared according to a composition proposed by De Deene, with some modifications. In the first type, no nitrogen gas was perfused through the gel solution and water. In the second type, to expel the dissolved oxygen, nitrogen gas was perfused through the water and gel solution. The post-irradiation times in the gels were 24 and 5 hours, respectively, with and without perfusion of nitrogen gas through the water and gel solution. Results: In the first type of gel, there was a linear correlation between the doses and R2 responses from 0 to 12 Gy. The fabricated gel had a higher dynamic range than the other low density polymer gel dosimeter; but its background R2 response was higher. In the second type, no difference in R2 response was seen in the dose ranges from 0 to 18 Gy. Both gels had a mass density between 0.35 and 0.45 g.cm-3 and CT values of about -650 to -750 Hounsfield units. Conclusion: It appeared that reactions between gelatin-free radicals and monomers, due to an increase in the gel temperature during rotation in the household mixer, led to a higher R2-background response. In the second type of gel, it seemed that the collapse of the nitrogen bubbles was the main factor that affected the R2-responses. PMID:26015914

  14. Nonlinear Ultrasonic Diagnosis and Prognosis of ASR Damage in Dry Cask Storage

    SciTech Connect

    Qu, Jianmin; Bazant, Zdenek; Jacobs, Laurence; Guimaraes, Maria

    2015-11-30

    Alkali-silica reaction (ASR) is a deleterious chemical process that may occur in cement-based materials such as mortars and concretes, where the hydroxyl ions in the highly alkaline pore solution attack the siloxane groups in the siliceous minerals in the aggregates. The reaction produces a cross-linked alkali-silica gel. The ASR gel swells in the presence of water. Expansion of the gel results in cracking when the swelling-induced stress exceeds the fracture toughness of the concrete. As the ASR continues, cracks may grow and eventually coalesce, which results in reduced service life and a decrease safety of concrete structures. Since concrete is widely used as a critical structural component in dry cask storage of used nuclear fuels, ASR damage poses a significant threat to the sustainability of long term dry cask storage systems. Therefore, techniques for effectively detecting, managing and mitigating ASR damage are needed. Currently, there are no nondestructive methods to accurately detect ASR damage in existing concrete structures. The only current way of accurately assessing ASR damage is to drill a core from an existing structure, and conduct microscopy on this drilled cylindrical core. Clearly, such a practice is not applicable to dry cask storage systems. To meet these needs, this research is aimed at developing (1) a suite of nonlinear ultrasonic quantitative nondestructive evaluation (QNDE) techniques to characterize ASR damage, and (2) a physics-based model for ASR damage evolution using the QNDE data. Outcomes of this research will provide a nondestructive diagnostic tool to evaluate the extent of the ASR damage, and a prognostic tool to estimate the future reliability and safety of the concrete structures in dry cask storage systems

  15. Capability of NIPAM polymer gel in recording dose from the interaction of (10)B and thermal neutron in BNCT.

    PubMed

    Khajeali, Azim; Reza Farajollahi, Ali; Kasesaz, Yaser; Khodadadi, Roghayeh; Khalili, Assef; Naseri, Alireza

    2015-11-01

    The capability of N-isopropylacrylamide (NIPAM) polymer gel to record the dose resulting from boron neutron capture reaction in BNCT was determined. In this regard, three compositions of the gel with different concentrations of (10)B were prepared and exposed to gamma radiation and thermal neutrons. Unlike irradiation with gamma rays, the boron-loaded gels irradiated by neutron exhibited sensitivity enhancement compared with the gels without (10)B. It was also found that the neutron sensitivity of the gel increased by the increase of concentration of (10)B. It can be concluded that NIPAM gel might be suitable for the measurement of the absorbed dose enhancement due to (10)B and thermal neutron reaction in BNCT. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Structural Evolution of Silica Gel and Silsesquioxane Using Thermal Curing.

    PubMed

    Hu, Nan; Rao, YuanQiao; Sun, Shengtong; Hou, Lei; Wu, Peiyi; Fan, Shaojuan; Ye, Bangjiao

    2016-08-01

    The curing of coatings of two types of siloxane containing materials, silica gel and silsesquioxane, at a modest temperature (<280℃) was studied with in situ heating Fourier transform infrared spectroscopy (FT-IR) in combination with perturbation correlation moving window (PCMW) and two-dimensional correlation spectroscopy (2D-COS) analyses. The result revealed detailed structural evolution of these two different gels. When the silica gel was heated, (Si-O)6 rings appeared from the random Si-O-Si network formed after sol gel reaction, followed by condensation of silanol groups. Upon further heating, the existing (Si-O)4 rings were broken down and converted into (Si-O)6 structures, and finally isolated silanols appeared. The transition from (Si-O)4 rings to (Si-O)6 rings was observed by IR and further confirmed with positron annihilation lifetime spectroscopy (PALS). In comparison, during the curing of hybrid silsesquioxane, the condensation of silanols happens immediately upon heating without the rearrangement of Si-O-Si network. Afterwards, the fraction of (Si-O)6 ring structure increased. (Si-O)4 structures exhibited higher stability in hybrid silsesquioxanes. In addition, the amount of silanols in silsesquioxane continued to reduce without the generation of isolated silanol in the end. The different curing behavior of silsesquioxanes from silica gel originates from the organic groups in silsesquioxanes, which lowers the cross-linking density and reduces the rigidity of siloxane network.

  17. Nanoparticle solutions as adhesives for gels and biological tissues

    NASA Astrophysics Data System (ADS)

    Rose, Séverine; Prevoteau, Alexandre; Elzière, Paul; Hourdet, Dominique; Marcellan, Alba; Leibler, Ludwik

    2014-01-01

    Adhesives are made of polymers because, unlike other materials, polymers ensure good contact between surfaces by covering asperities, and retard the fracture of adhesive joints by dissipating energy under stress. But using polymers to `glue' together polymer gels is difficult, requiring chemical reactions, heating, pH changes, ultraviolet irradiation or an electric field. Here we show that strong, rapid adhesion between two hydrogels can be achieved at room temperature by spreading a droplet of a nanoparticle solution on one gel's surface and then bringing the other gel into contact with it. The method relies on the nanoparticles' ability to adsorb onto polymer gels and to act as connectors between polymer chains, and on the ability of polymer chains to reorganize and dissipate energy under stress when adsorbed onto nanoparticles. We demonstrate this approach by pressing together pieces of hydrogels, for approximately 30 seconds, that have the same or different chemical properties or rigidities, using various solutions of silica nanoparticles, to achieve a strong bond. Furthermore, we show that carbon nanotubes and cellulose nanocrystals that do not bond hydrogels together become adhesive when their surface chemistry is modified. To illustrate the promise of the method for biological tissues, we also glued together two cut pieces of calf's liver using a solution of silica nanoparticles. As a rapid, simple and efficient way to assemble gels or tissues, this method is desirable for many emerging technological and medical applications such as microfluidics, actuation, tissue engineering and surgery.

  18. Posing for a picture: vesicle immobilization in agarose gel

    PubMed Central

    Lira, Rafael B.; Steinkühler, Jan; Knorr, Roland L.; Dimova, Rumiana; Riske, Karin A.

    2016-01-01

    Taking a photo typically requires the object of interest to stand still. In science, imaging is potentiated by optical and electron microscopy. However, living and soft matter are not still. Thus, biological preparations for microscopy usually include a fixation step. Similarly, immobilization strategies are required for or substantially facilitate imaging of cells or lipid vesicles, and even more so for acquiring high-quality data via fluorescence-based techniques. Here, we describe a simple yet efficient method to immobilize objects such as lipid vesicles with sizes between 0.1 and 100 μm using agarose gel. We show that while large and giant unilamellar vesicles (LUVs and GUVs) can be caged in the pockets of the gel meshwork, small molecules, proteins and micelles remain free to diffuse through the gel and interact with membranes as in agarose-free solutions, and complex biochemical reactions involving several proteins can proceed in the gel. At the same time, immobilization in agarose has no adverse effect on the GUV size and stability. By applying techniques such as FRAP and FCS, we show that the lateral diffusion of lipids is not affected by the gel. Finally, our immobilization strategy allows capturing high-resolution 3D images of GUVs. PMID:27140695

  19. Rheology of the gel formed in the California Mastitis Test.

    PubMed

    Verbeek, C Johan R; Xia, Stephen S; Whyte, David

    2008-11-01

    The California Mastitis Test has previously been adapted for use in an inline, cow-side sensor and relies on the fact that the viscosity of the gel formed during the test is proportional to the somatic cell concentration. In this paper, the use of capillary and rotational viscometry was compared in light of the expected rheology of the gel formed during the test. It was found that the gel is non-Newtonian, but the initial phase of viscosity increase was not due to shear dependence, but rather due to the gelation reaction. The maximum apparent viscosity of the gel was shear dependent while the time it took to reach the maximum was not truly shear dependent, but was rather dependent on the degree of mixing during gelation. This was confirmed by introducing a delay time prior to viscosity measurement, in both capillary and rotational viscometry. It was found that by mixing the reagent and infected milk, then delaying viscosity measurement for 30 s, shortened the time it took to reach maximum viscosity by more than 60 s. The maximum apparent viscosity, however, was unaffected. It was found that capillary viscometry worked well to correlate relative viscosity with somatic cell count, but that it was sensitive to the reagent concentration. It can therefore be deduced that the rheology of the gel is complicated not only by it being non-Newtonian, but also by the strong dependence on test conditions. These make designing a successful sensor much more challenging.

  20. Posing for a picture: vesicle immobilization in agarose gel

    NASA Astrophysics Data System (ADS)

    Lira, Rafael B.; Steinkühler, Jan; Knorr, Roland L.; Dimova, Rumiana; Riske, Karin A.

    2016-05-01

    Taking a photo typically requires the object of interest to stand still. In science, imaging is potentiated by optical and electron microscopy. However, living and soft matter are not still. Thus, biological preparations for microscopy usually include a fixation step. Similarly, immobilization strategies are required for or substantially facilitate imaging of cells or lipid vesicles, and even more so for acquiring high-quality data via fluorescence-based techniques. Here, we describe a simple yet efficient method to immobilize objects such as lipid vesicles with sizes between 0.1 and 100 μm using agarose gel. We show that while large and giant unilamellar vesicles (LUVs and GUVs) can be caged in the pockets of the gel meshwork, small molecules, proteins and micelles remain free to diffuse through the gel and interact with membranes as in agarose-free solutions, and complex biochemical reactions involving several proteins can proceed in the gel. At the same time, immobilization in agarose has no adverse effect on the GUV size and stability. By applying techniques such as FRAP and FCS, we show that the lateral diffusion of lipids is not affected by the gel. Finally, our immobilization strategy allows capturing high-resolution 3D images of GUVs.

  1. Nanoparticle solutions as adhesives for gels and biological tissues.

    PubMed

    Rose, Séverine; Prevoteau, Alexandre; Elzière, Paul; Hourdet, Dominique; Marcellan, Alba; Leibler, Ludwik

    2014-01-16

    Adhesives are made of polymers because, unlike other materials, polymers ensure good contact between surfaces by covering asperities, and retard the fracture of adhesive joints by dissipating energy under stress. But using polymers to 'glue' together polymer gels is difficult, requiring chemical reactions, heating, pH changes, ultraviolet irradiation or an electric field. Here we show that strong, rapid adhesion between two hydrogels can be achieved at room temperature by spreading a droplet of a nanoparticle solution on one gel's surface and then bringing the other gel into contact with it. The method relies on the nanoparticles' ability to adsorb onto polymer gels and to act as connectors between polymer chains, and on the ability of polymer chains to reorganize and dissipate energy under stress when adsorbed onto nanoparticles. We demonstrate this approach by pressing together pieces of hydrogels, for approximately 30 seconds, that have the same or different chemical properties or rigidities, using various solutions of silica nanoparticles, to achieve a strong bond. Furthermore, we show that carbon nanotubes and cellulose nanocrystals that do not bond hydrogels together become adhesive when their surface chemistry is modified. To illustrate the promise of the method for biological tissues, we also glued together two cut pieces of calf's liver using a solution of silica nanoparticles. As a rapid, simple and efficient way to assemble gels or tissues, this method is desirable for many emerging technological and medical applications such as microfluidics, actuation, tissue engineering and surgery.

  2. Bleach gel: a simple agarose gel for analyzing RNA quality.

    PubMed

    Aranda, Patrick S; LaJoie, Dollie M; Jorcyk, Cheryl L

    2012-01-01

    RNA-based applications requiring high-quality, non-degraded RNA are a foundational element of many research studies. As such, it is paramount that the integrity of experimental RNA is validated prior to cDNA synthesis or other downstream applications. In the absence of expensive equipment such as microfluidic electrophoretic devices, and as an alternative to the costly and time-consuming standard formaldehyde gel, RNA quality can be quickly analyzed by adding small amounts of commercial bleach to TAE buffer-based agarose gels prior to electrophoresis. In the presence of low concentrations of bleach, the secondary structure of RNA is denatured and potential contaminating RNases are destroyed. Because of this, the 'bleach gel' is a functional approach that addresses the need for an inexpensive and safe way to evaluate RNA integrity and will improve the ability of researchers to rapidly analyze RNA quality.

  3. Protection of bifidobacteria encapsulated in polysaccharide-protein gel beads against gastric juice and bile.

    PubMed

    Guérin, Daniel; Vuillemard, Jean-Christophe; Subirade, Muriel

    2003-11-01

    Bifidobacterium cells were encapsulated in a mixed gel composed of alginate, pectin, and whey proteins. Two kinds of capsules were obtained: gel beads without membranes and gel beads with two membranes formed by the transacylation reaction. In vitro studies were carried out to determine the effects of simulated gastric pH and bile salts on the survival of free and encapsulated Bifidobacterium bifidum. The protective effects of gel beads without membranes and gel beads coated with two membranes formed by the transacylation reaction were evaluated. After 1 h in an acidic solution (pH 2.5), the free-cell counts decreased by 4.75 log units, compared with a <1-log decrease for entrapped cells. The free cells did not survive after 2 h of incubation at pH 2.5, while immobilized-cell counts decreased by about 2 log units. After incubation (1 or 3 h) in 2 and 4% bile salt solutions, the bifidobacterium mortality level for membrane-free gel beads (4 to 7 log units) was higher than that for free cells (2 to 3 log units). However, counts of bifidobacteria immobilized in membrane-coated gel beads decreased by <2 log units. Cell encapsulation in membrane-coated protein-polysaccharide gel beads could be used to increase the survival of healthy probiotic bacteria during their transit through the gastrointestinal tract.

  4. Thixotropic gel for vadose zone remediation

    DOEpatents

    Riha, Brian D.

    2012-07-03

    A thixotropic gel suitable for use in subsurface bioremediation is provided along with a process of using the gel. The thixotropic gel provides a non-migrating injectable substrate that can provide below ground barrier properties. In addition, the gel components provide for a favorable environment in which certain contaminants are preferentially sequestered in the gel and subsequently remediated by either indigenous or introduced microorganisms.

  5. Thixotropic gel for vadose zone remediation

    DOEpatents

    Riha, Brian D.; Looney, Brian B.

    2015-10-27

    A thixotropic gel suitable for use in subsurface bioremediation is provided along with a process of using the gel. The thixotropic gel provides a non-migrating injectable substrate that can provide below ground barrier properties. In addition, the gel components provide for a favorable environment in which certain contaminants are preferentially sequestered in the gel and subsequently remediated by either indigenous or introduced microorganisms.

  6. Thixotropic gel for vadose zone remediation

    DOEpatents

    Rhia, Brian D [Augusta, GA

    2011-03-01

    A thixotropic gel suitable for use in subsurface bioremediation is provided along with a process of using the gel. The thixotropic gel provides a non-migrating injectable substrate that can provide below ground barrier properties. In addition, the gel components provide for a favorable environment in which certain contaminants are preferentially sequestered in the gel and subsequently remediated by either indigenous or introduced microorganisms.

  7. Estimation of polymerization efficiency in the formation of polyacrylamide gel, using continuous optical scanning during polymerization.

    PubMed

    Chen, B; Chrambach, A

    1979-05-01

    The Ferguson plot and 'quantitative' gel electrophoresis (based on the Ferguson plot) depend on a knowledge of accurate gel concentrations. The easiest way to estimate accuracy of gel concentrations, in terms of the degree of completion of the polymerization reaction which gives rise to a gel, is by spectrophometry. Making use of the apparatus for continuous optical scanning of polyacrylamide gels, the extent and rate of polymerization of cross-linked polyacrylamide were estimated by measuring the absorbance at 275 nm of the reaction mixture subsequent to free radical initiation of polymerization. Under appropriate conditions of monomer concentration, initiator levels and temperature, absorbance decreased monotonically after a lag period of 10 min, and after 20--30 min of reaction the absorbance reached a plateau value which provided a measure of polymerization efficiency. Application of a standard curve of absorbance vs. monomer concentration allowed one to quantitate concentrations of residual monomer throughout the course of polymerization. Under a set of arbitrary polymerization conditions (e.g. 6--20% total gel concentration), the reaction went to 63--96% completion. The rate of polymerization was approximately proportional to the square of the monomer concentration (2nd-order reaction kinetics). Absorbance decrease subsequent to the initiation of the polymerization reaction appeared suitable as a measure of efficiency of polymerization since: (a) absorbance spectra of monomers at 0.5 %T and residual monomers in a 10 %T gel, at a time when polymerization seemed terminated, coincided; (b) values of residual monomer obtained were reasonable (10--30%); (c) bimolecular reaction kinetics were found, in agreement with expectation; and (d) absorbance of incomplete polymerization mixtures, deficient in either initiators or monomers, was constant with time.

  8. Capillary fracture of soft gels

    NASA Astrophysics Data System (ADS)

    Bostwick, Joshua B.; Daniels, Karen E.

    2013-10-01

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

  9. Amorphous sol-gel insulating films

    SciTech Connect

    Brinker, C.J. |; Warren, W.L.; Logan, M.N.; Ashley, C.S.

    1993-05-01

    The porosity of sol-gel thin films may be tailored for specific applications through control of the size and structure of inorganic polymers within the coating sol, the extent of polymer reaction and interpenetration during film formation, and the magnitude of the capillary pressure exerted during the final stage of drying. By maximizing the capillary pressure and avoiding excessive condensation, dense insulating films may be prepared as passivation layers on silicon substrates. Such films can exhibit excellent dielectric integrity, viz., low interface trap densities and insulating properties approaching those of thermally grown SiO{sub 2}. Alternatively, through exploitation of the scaling relationship of mass and density of fractal objects, silica films can be prepared that show a variation in porosity (7--29 %) and refractive index (1.42--1.31) desired for applications in sensors, membranes, and photonics.

  10. Amorphous sol-gel insulating films

    SciTech Connect

    Brinker, C.J. New Mexico Univ., Albuquerque, NM . Center for Micro-Engineered Ceramics); Warren, W.L.; Logan, M.N.; Ashley, C.S. )

    1993-01-01

    The porosity of sol-gel thin films may be tailored for specific applications through control of the size and structure of inorganic polymers within the coating sol, the extent of polymer reaction and interpenetration during film formation, and the magnitude of the capillary pressure exerted during the final stage of drying. By maximizing the capillary pressure and avoiding excessive condensation, dense insulating films may be prepared as passivation layers on silicon substrates. Such films can exhibit excellent dielectric integrity, viz., low interface trap densities and insulating properties approaching those of thermally grown SiO[sub 2]. Alternatively, through exploitation of the scaling relationship of mass and density of fractal objects, silica films can be prepared that show a variation in porosity (7--29 %) and refractive index (1.42--1.31) desired for applications in sensors, membranes, and photonics.

  11. Molecularly imprinted sol-gel nanotubes membrane for biochemical separations.

    PubMed

    Yang, Huang-Hao; Zhang, Shu-Qiong; Yang, Wei; Chen, Xiao-Lan; Zhuang, Zhi-Xia; Xu, Jin-Gou; Wang, Xiao-Ru

    2004-04-07

    In this study, we report a simple procedure for applying molecular imprinting functional groups to the inner surfaces of the template-synthesized sol-gel nanotubes for chemical separation of estrone. The silica nanotubes were synthesized within the pores of nanopore alumina template membranes using a sol-gel method by simultaneous hydrolysis of a silica monomer-imprinted molecule complex and tetraethoxysilane (TEOS). A covalent imprinting strategy was employed by generating a sacrificial spacer through the reaction of the isocyanate group of 3-(triethoxysilyl)propyl isocyanate and a phenol moiety of estrone to form a thermally cleavable urethane bond. This allowed us to remove the imprinted estrone by simple thermal reaction and to simultaneously introduce functional groups into the cavity formed by the silica nanotubes. Experiments indicated that estrone could be bound selectively by such an approach and have a binding affinity of 864 +/- 137 (n = 3).

  12. Using stability analyses to predict dynamic behaviour of self-oscillating polymer gels

    NASA Astrophysics Data System (ADS)

    Palkar, Vaibhav; Srivastava, Gaurav; Kuksenok, Olga; Balazs, Anna C.; Dayal, Pratyush

    2015-03-01

    Use of chemo-mechanical transduction to produce locomotion is one of the significant characteristics of biological systems. Polymer gels, intrinsically powered by oscillatory Belousov-Zhabotinsky (BZ) reaction, are biomimetic materials that exhibit rhythmic self-sustained mechanical oscillations by chemo-mechanical transduction. Via simulations, based on the 3D gel lattice spring model, we have successfully captured the dynamic behaviour of BZ gels. We have demonstrated that it is possible to direct the movement of BZ gels along complex paths, guiding them to bend, reorient and turn. From a mathematical perspective, the oscillations in the BZ gels occur when the gel's steady states loose stability by virtue of Hopf bifurcations (HB). Through the use of stability analyses, we predict the conditions under which gel switches from stationary to oscillatory mode and vice versa. In addition, we characterize the nature of HB and also identify other types of bifurcations that play a critical role in governing the dynamic behaviour of BZ gels. Also, we successfully predict the frequency of chemo-mechanical oscillations and characterize its dependency on the model parameters. Our approach not only allows us to establish optimal conditions for the motion of BZ gels, but also can be used to design other dynamical systems. IIT Gandhinagar and DST-SERB for funding.

  13. Sol-gel synthesis of magnesium oxide-silicon dioxide glass compositions

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1988-01-01

    MgO-SiO2 glasses containing up to 15 mol pct MgO, which could not have been prepared by the conventional glass melting method due to the presence of stable liquid-liquid immiscibility, were synthesized by the sol-gel technique. Clear and transparent gels were obtained from the hydrolysis and polycondensation of silicon tetraethoxide (TEOS) and magnesium nitrate hexahydrate when the water/TEOS mole ratio was four or more. The gelling time decreased with increase in magnesium content, water/TEOS ratio, and reaction temperature. Magnesium nitrate hexahydrate crystallized out of the gels containing 15 and 20 mol pct MgO on slow drying. This problem was partially alleviated by drying the gels quickly at higher temperatures. Monolithic gel samples were prepared using glycerol as the drying control additive. The gels were subjected to various thermal treatments and characterized by several methods. No organic groups could be detected in the glasses after heat treatments to approx. 800 C, but trace amounts of hydroxyl groups were still present. No crystalline phase was found from X-ray diffraction in the gel samples to approx. 890 C. At higher temperatures, alpha quartz precipitated out as the crystalline phase in gels containing up to 10 mol pct MgO. The overall activation energy for gel formation in 10MgO-90SiO2 (mol pct) system for water/TEOS mole ratio of 7.5 was calculated to be 58.7 kJ/mol.

  14. Sol-gel synthesis of magnesium oxide-silicon dioxide glass compositions

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1988-01-01

    MgO-SiO2 glasses containing up to 15 mol pct MgO, which could not have been prepared by the conventional glass melting method due to the presence of stable liquid-liquid immiscibility, were synthesized by the sol-gel technique. Clear and transparent gels were obtained from the hydrolysis and polycondensation of silicon tetraethoxide (TEOS) and magnesium nitrate hexahydrate when the water/TEOS mole ratio was four or more. The gelling time decreased with increase in magnesium content, water/TEOS ratio, and reaction temperature. Magnesium nitrate hexahydrate crystallized out of the gels containing 15 and 20 mol pct MgO on slow drying. This problem was partially alleviated by drying the gels quickly at higher temperatures. Monolithic gel samples were prepared using glycerol as the drying control additive. The gels were subjected to various thermal treatments and characterized by several methods. No organic groups could be detected in the glasses after heat treatments to approx. 800 C, but trace amounts of hydroxyl groups were still present. No crystalline phase was found from X-ray diffraction in the gel samples to approx. 890 C. At higher temperatures, alpha quartz precipitated out as the crystalline phase in gels containing up to 10 mol pct MgO. The overall activation energy for gel formation in 10MgO-90SiO2 (mol pct) system for water/TEOS mole ratio of 7.5 was calculated to be 58.7 kJ/mol.

  15. Copolymers For Capillary Gel Electrophoresis

    DOEpatents

    Liu, Changsheng; Li, Qingbo

    2005-08-09

    This invention relates to an electrophoresis separation medium having a gel matrix of at least one random, linear copolymer comprising a primary comonomer and at least one secondary comonomer, wherein the comonomers are randomly distributed along the copolymer chain. The primary comonomer is an acrylamide or an acrylamide derivative that provides the primary physical, chemical, and sieving properties of the gel matrix. The at least one secondary comonomer imparts an inherent physical, chemical, or sieving property to the copolymer chain. The primary and secondary comonomers are present in a ratio sufficient to induce desired properties that optimize electrophoresis performance. The invention also relates to a method of separating a mixture of biological molecules using this gel matrix, a method of preparing the novel electrophoresis separation medium, and a capillary tube filled with the electrophoresis separation medium.

  16. Deformation of Unentangled Swollen Gels

    NASA Astrophysics Data System (ADS)

    Sariyer, Ozan; Panyukov, Sergey; Rubinstein, Michael

    2014-03-01

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

  17. Sol-gel derived sorbents

    DOEpatents

    Sigman, Michael E.; Dindal, Amy B.

    2003-11-11

    Described is a method for producing copolymerized sol-gel derived sorbent particles for the production of copolymerized sol-gel derived sorbent material. The method for producing copolymerized sol-gel derived sorbent particles comprises adding a basic solution to an aqueous metal alkoxide mixture for a pH.ltoreq.8 to hydrolyze the metal alkoxides. Then, allowing the mixture to react at room temperature for a precalculated period of time for the mixture to undergo an increased in viscosity to obtain a desired pore size and surface area. The copolymerized mixture is then added to an immiscible, nonpolar solvent that has been heated to a sufficient temperature wherein the copolymerized mixture forms a solid upon the addition. The solid is recovered from the mixture, and is ready for use in an active sampling trap or activated for use in a passive sampling trap.

  18. Nasal gel and olfactory cleft.

    PubMed

    Herranz González-Botas, Jesús; Padín Seara, Anselmo

    2012-01-01

    To evaluate whether a nasal gel, administrated using a radial-hole inhaler, reaches the olfactory cleft and if a different administration method influences distribution. Sixteen healthy volunteers underwent a nasal endoscopy at 1 and 7minutes after the administration of a intranasal gel, with a different method in each fossa. No dye deposition was identified at the olfactory cleft, middle turbinate or middle meatus. In all cases the gel was identified at the nasal vestibule. On the right side, the second most frequent dye identification area was the inferior turbinate, with a rate of 87% at the first minute and 75% at 7 minutes. It was followed by the septum (75 and 62%) and the inferior meatus (6.2 and 12.5%). On the left side, the second most frequent stained area was the septum (18.7 and 13.5%), followed by the inferior meatus (6.5 and 65%). No inferior turbinate staining was found in the left side. There was a significant difference in the deposition rate at the septum (P<.01) and inferior turbinate (P<.001), when both administration methods were compared. No nasal gel, administrated using a radial-hole inhaler, was found at the olfactory cleft, middle turbinate or middle meatus. Gel distribution was located at the anterior and inferior portion of the nose, independent of the administration method used. Significantly different gel distribution rates were found at the septum and inferior turbinate when the 2 administration methods were compared. Copyright © 2012 Elsevier España, S.L. All rights reserved.

  19. Synthesis of zirconium oxide nanoparticle by sol-gel technique

    SciTech Connect

    Lim, H. S.; Ahmad, A.; Hamzah, H.

    2013-11-27

    Zirconium oxide nanoparticle is synthesized using sol-gel technique. Various mole ratio of ammonia solution and nitric acid relative to zirconium propoxide is added in the reaction to study the effect on the crystallinity and particle size on zirconium oxide particle. Zirconium oxide synthesized with nitric acid have the smallest particle size under FESEM image and show the increasing formation of crystalline tetragonal phase under XRD diffractogram.

  20. Supramolecular Construction of Multifluorescent Gels: Interfacial Assembly of Discrete Fluorescent Gels through Multiple Hydrogen Bonding.

    PubMed

    Ji, Xiaofan; Shi, Bingbing; Wang, Hu; Xia, Danyu; Jie, Kecheng; Wu, Zi Liang; Huang, Feihe

    2015-12-22

    Multifluorescent supramolecular gels with complex structures are constructed from discrete fluorescent gels, which serve as the building blocks, through hydrogen bonding interactions at interfaces. The multifluorescent gel can realize rapid healing within only ≈100 s.

  1. Microbubble tunneling in gel phantoms

    PubMed Central

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

    2009-01-01

    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. PMID:19425620

  2. Statistical physics of polymer gels

    NASA Astrophysics Data System (ADS)

    Panyukov, Sergei; Rabin, Yitzhak

    1996-05-01

    This work presents a comprehensive analysis of the statistical mechanics of randomly cross-linked polymer gels, starting from a microscopic model of a network made of instantaneously cross-linked Gaussian chains with excluded volume, and ending with the derivation of explicit expressions for the thermodynamic functions and for the density correlation functions which can be tested by experiments. Using replica field theory we calculate the mean field density in replica space and show that this solution contains statistical information about the behavior of individual chains in the network. The average monomer positions change affinely with macroscopic deformation and fluctuations about these positions are limited to length scales of the order of the mesh size. We prove that a given gel has a unique state of microscopic equilibrium which depends on the temperature, the solvent, the average monomer density and the imposed deformation. This state is characterized by the set of the average positions of all the monomers or, equivalently, by a unique inhomogeneous monomer density profile. Gels are thus the only known example of equilibrium solids with no long-range order. We calculate the RPA density correlation functions that describe the statistical properties of small deviations from the average density, due to both static spatial heterogeneities (which characterize the inhomogeneous equilibrium state) and thermal fluctuations (about this equilibrium). We explain how the deformation-induced anisotropy of the inhomogeneous equilibrium density profile is revealed by small angle neutron scattering and light scattering experiments, through the observation of the butterfly effect. We show that all the statistical information about the structure of polymer networks is contained in two parameters whose values are determined by the conditions of synthesis: the density of cross-links and the heterogeneity parameter. We find that the structure of instantaneously cross

  3. Preparation of adsorbent for phosphate recovery from aqueous solutions based on condensed tannin gel.

    PubMed

    Ogata, Takeshi; Morisada, Shintaro; Oinuma, Yasumi; Seida, Yoshimi; Nakano, Yoshio

    2011-08-30

    We have synthesized an iron-loaded tannin gel as an adsorbent for phosphate recovery in aqueous solutions. The use of the tannin gel prepared from condensed tannin, which is a ubiquitous and inexpensive natural polymer, is not only cost effective and environment-friendly, but interesting because the phosphate-adsorbed gel can be expected to use directly as a fertilizer. The amount of iron loaded into the tannin gel oxidized by nitric acid was much larger than that into the non-oxidized tannin gel. This increase in the amount of the loaded iron resulted in the significant increase in the adsorption amount of phosphate onto the gel. Mössbauer spectroscopy indicated that the morphology of iron in the gel is a mono-type complex, which is formed as a result of the reaction between Fe(III) and the oxidized tannin gel with carbonyl groups. The iron-loaded tannin gel showed the adsorption selectivity for phosphate over other anions and the pH independence of phosphate adsorption in the wide range of initial pH 3-12. The phosphate adsorption isotherm for the iron-loaded tannin gel followed the Freundlich equation with constants of K(F)=2.66 and 1/n=0.31, rather than the Langmuir equation. The adsorption amount of phosphate on iron weight basis for the iron-loaded tannin gel is 31.3mg-P/g-Fe, which indicates that iron in the gel was efficiently used for the phosphate adsorption compared with other phosphate adsorbents, such as iron hydroxides. Copyright © 2011 Elsevier B.V. All rights reserved.

  4. Buckling instabilities in photopolymerised gels

    NASA Astrophysics Data System (ADS)

    Hennessy, Matthew; Cabral, Joao; Matar, Omar

    2014-11-01

    Frontal photopolymerisation (FPP) is a process whereby solid polymer networks are created by illuminating a monomer-rich bath with collimated light. In practice, FPP can be used to rapidly fabricate intricate small-scale structures. Due to the attenuation of light as it propagates through the bath, polymerisation occurs in a wave-like fashion from the illuminated surface into the bulk. At low temperatures, the polymerisation front remains planar; however, at higher temperatures, it can undergo large deformations. We believe this is due the buckling of a thin gel layer that forms between the polymer-rich and solvent-rich phases. The gel is thought to buckle due to high compressive stresses that are generated as it absorbs solvent and swells. In this talk, we will present a mathematical model for gel formation which captures the phenomenon of buckling due to swelling. The gel is treated as a deformable porous medium and the solvent is assumed to flow according to Darcy's law. We will also examine the buckling patterns that emerge from the model and compare them with experiments. EPSRC Grant Number EP/L022176/1.

  5. Nonlinear elasticity of alginate gels

    NASA Astrophysics Data System (ADS)

    Hashemnejad, Seyed Meysam; Kundu, Santanu

    Alginate is a naturally occurring anionic polysaccharide extracted from brown algae. Because of biocompatibility, low toxicity, and simple gelation process, alginate gels are used in biomedical and food applications. Here, we report the rheological behavior of ionically crosslinked alginate gels, which are obtained by in situ gelation of alginates with calcium salts, in between two parallel plates of a rheometer. Strain stiffening behavior was captured using large amplitude oscillatory shear (LAOS) experiments. In addition, negative normal stress was observed for these gels, which has not been reported earlier for any polysaccharide networks. The magnitude of negative normal stress increases with applied strain and can exceed that of the shear stress at large strain. Rheological results fitted with a constitutive model that considers both stretching and bending of chains indicate that nonlinearity is likely related to the stretching of the chains between the crosslink junctions. The results provide an improved understanding of the deformation mechanism of ionically crosslinked alginate gel and the results will be important in developing synthetic extracellular matrix (ECM) from these materials.

  6. Liquid-crystalline physical gels.

    PubMed

    Kato, Takashi; Hirai, Yuki; Nakaso, Suguru; Moriyama, Masaya

    2007-12-01

    Liquid-crystalline (LC) physical gels are a new class of dynamically functional materials consisting of liquid crystals and fibrous aggregates of molecules that are called "gelators". Liquid-crystalline physical gels, which are macroscopically soft solids, exhibit induced or enhanced electro-optical, photochemical, electronic properties due to the combination of two components that form phase-separated structures. In this tutorial review, we describe the materials design and structure-property relationships of the LC physical gels. The introduction of self-assembled fibers into nematic liquid crystals leads to faster responses in twisted nematic (TN) mode and high contrast switching in light scattering mode. Furthermore, the LC physical gels can be exploited as a new type of materials for electro-optical memory. This function is achieved by the control of reversible aggregation processes of gelators under electric fields in nematic liquid crystals. Electronic properties such as hole mobilities are improved by the introduction of fibrous aggregates into triphenylene-based columnar liquid crystals. The incorporation of photochromic azobenzenes or electroactive tetrathiafulvalenes into the chemical structures of gelators leads to the preparation of ordered functional materials.

  7. [Gel immobilization of human genome].

    PubMed

    Pan, Yingqiu; Zhang, Wei; Chen, Shuqing

    2013-01-01

    To develop a solid phase PCR method by covalent single point immobilization for recycle utilization of human genome. Polymethacrylamide gel was selected as a solid PCR carrier based on DNA-hydrogel copolymer chemistry presented by Mirzabekov. (CH2)6NH2 amino-modified PCR product and randomly fractured formic acid-modified plasmid pGEM-T-HLA-G were used as templates. The specificity of the attachment chemistry was characterized by acrylamide gel electrophoresis, and the thermal stability of method was demonstrated by PCR. This method was applied for the recycle utilization of human genome. Sequencing was used to exclude the possibility of introduced mutations during modification and immobilization procedures. The PCR detections of plasmid DNA and human genome DNA immobilized by polymethacrylamide gel was successful. The thermal stability of method was successfully demonstrated by performing PCR after 16 rounds of standard 36 PCR cycles. And the sequencing was found no mutation. The DNA immobilization method with polymethacrylamide gel as a solid phase carrier is stable and specific, which can be a possible approach for realizing recycle utilization of human genome for whole-genome sequencing and SNP detection.

  8. Hydrous manganese oxide doped gel probe sampler for measuring in situ reductive dissolution rates. 1. Laboratory development.

    PubMed

    Farnsworth, Claire E; Hering, Janet G

    2010-01-01

    Reductive dissolution of redox-sensitive minerals such as manganese (Mn) oxides in natural sediments is an important mechanism for trace element mobilization into groundwater. A gel probe sampler has been constructed to study in situ reductive dissolution of Mn oxides. The gel consists of a polyacrylamide polymer matrix doped with hydrous Mn oxide (HMO). Gel slabs are mounted into a probe, which is designed to be inserted into the sediments. The amount of Mn released from the gel by reductive dissolution is determined by comparing the amount of Mn initially embedded into the gel with the amount remaining in the gel after exposure to conditions in the sediments or, in laboratory studies, to reducing agents. In this laboratory study, the performance of the gel probes was examined using the model reductant ascorbate and the Mn-reducing bacteria Shewanella oneidensis strain MR-1. In addition, a 1-D model was used to relate the reaction rates observed for HMO embedded in gels to those for HMO in suspension. One limitation of the HMO-doped gels for assessing microbial reduction rates is that the gels prevent direct contact between the microbes and the HMO and hence preclude enzymatic reduction at the cell surface. Nonetheless, the HMO-doped gel probes offer the possibility to establish a lower bound for Mn-reduction capacity in sediments.

  9. Gel/Space Ratio Evolution in Ternary Composite System Consisting of Portland Cement, Silica Fume, and Fly Ash.

    PubMed

    Wu, Mengxue; Li, Chen; Yao, Wu

    2017-01-11

    In cement-based pastes, the relationship between the complex phase assemblage and mechanical properties is usually described by the "gel/space ratio" descriptor. The gel/space ratio is defined as the volume ratio of the gel to the available space in the composite system, and it has been widely studied in the cement unary system. This work determines the gel/space ratio in the cement-silica fume-fly ash ternary system (C-SF-FA system) by measuring the reaction degrees of the cement, SF, and FA. The effects that the supplementary cementitious material (SCM) replacements exert on the evolution of the gel/space ratio are discussed both theoretically and practically. The relationship between the gel/space ratio and compressive strength is then explored, and the relationship disparities for different mix proportions are analyzed in detail. The results demonstrate that the SCM replacements promote the gel/space ratio evolution only when the SCM reaction degree is higher than a certain value, which is calculated and defined as the critical reaction degree (CRD). The effects of the SCM replacements can be predicted based on the CRD, and the theological predictions agree with the test results quite well. At low gel/space ratios, disparities in the relationship between the gel/space ratio and the compressive strength are caused by porosity, which has also been studied in cement unary systems. The ratio of cement-produced gel to SCM-produced gel ( G C to G S C M ratio) is introduced for use in analyzing high gel/space ratios, in which it plays a major role in creating relationship disparities.

  10. Gel/Space Ratio Evolution in Ternary Composite System Consisting of Portland Cement, Silica Fume, and Fly Ash

    PubMed Central

    Wu, Mengxue; Li, Chen; Yao, Wu

    2017-01-01

    In cement-based pastes, the relationship between the complex phase assemblage and mechanical properties is usually described by the “gel/space ratio” descriptor. The gel/space ratio is defined as the volume ratio of the gel to the available space in the composite system, and it has been widely studied in the cement unary system. This work determines the gel/space ratio in the cement-silica fume-fly ash ternary system (C-SF-FA system) by measuring the reaction degrees of the cement, SF, and FA. The effects that the supplementary cementitious material (SCM) replacements exert on the evolution of the gel/space ratio are discussed both theoretically and practically. The relationship between the gel/space ratio and compressive strength is then explored, and the relationship disparities for different mix proportions are analyzed in detail. The results demonstrate that the SCM replacements promote the gel/space ratio evolution only when the SCM reaction degree is higher than a certain value, which is calculated and defined as the critical reaction degree (CRD). The effects of the SCM replacements can be predicted based on the CRD, and the theological predictions agree with the test results quite well. At low gel/space ratios, disparities in the relationship between the gel/space ratio and the compressive strength are caused by porosity, which has also been studied in cement unary systems. The ratio of cement-produced gel to SCM-produced gel (GC to GSCM ratio) is introduced for use in analyzing high gel/space ratios, in which it plays a major role in creating relationship disparities. PMID:28772420

  11. Sol-Gel Synthesis and Characterization of Neodymium-Ion Doped Nanostructured Titania Thin Films

    DTIC Science & Technology

    2001-11-01

    reactions, which break down harmful organic pollutants to relatively harmless constituent chemicals. Semiconductor photocatalysis takes advantage of the...UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADP012201 TITLE: Sol-Gel Synthesis and Characterization of Neodymium-Ion...Society V5.2 SOL-GEL SYNTHESIS AND CHARACTERIZATION OF NEODYMIUM-ION DOPED NANOSTRUCTURED TITANIA THIN FILMS Andrew Burns~ln, W. Li("t, C. Baker"l) and

  12. Ultrasound-assisted sol-gel synthesis of ZrO2.

    PubMed

    Guel, Marlene Lariza Andrade; Jiménez, Lourdes Díaz; Hernández, Dora Alicia Cortés

    2017-03-01

    Synthesis of tetragonal ZrO2 by both conventional sol-gel and ultrasound-assisted sol-gel methods and using a non-ionic surfactant Tween-20, was performed. A porous microstructure composed of nanometric particles was observed. Tetragonal ZrO2 was obtained using a low heat treatment temperature of powders, 500°C by both methods. A higher crystallinity and a shorter reaction time were observed when ultrasound was used in the sol-gel method due to the cavitation phenomenon. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. A catalytic chiral gel microfluidic reactor assembled via dynamic covalent chemistry.

    PubMed

    Liu, Haoliang; Feng, Juan; Zhang, Jianyong; Miller, Philip W; Chen, Liuping; Su, Cheng-Yong

    2015-04-16

    A novel dynamic covalent gel strategy is reported to immobilize an asymmetric catalyst within the channels of a microfluidic flow reactor. A layer of a catalytically active Mn-salen dynamic covalent imine gel matrix was coated onto a functionalized capillary. Mn-salen active moiety was incorporated into dynamic covalent imine gel matrix via the reaction of a chiral Mn-salen dialdehyde unit with a tetraamine linker. The catalytic activity of the capillary reactor has been demonstrated in enantioselective kinetic resolution of secondary alcohols.

  14. Hydroponics gel as a new electrolyte gelling agent for alkaline zinc-air cells

    NASA Astrophysics Data System (ADS)

    Othman, R.; Basirun, W. J.; Yahaya, A. H.; Arof, A. K.

    The viability of hydroponics gel as a new alkaline electrolyte gelling agent is investigated. Zinc-air cells are fabricated employing 12 wt.% KOH electrolyte immobilised with hydroponics gel. The cells are discharged at constant currents of 5, 50 and 100 mA. XRD and SEM analysis of the anode plates after discharge show that the failure mode is due to the formation of zinc oxide insulating layers and not due to any side reactions between the gel and the plate or the electrolyte.

  15. Drug Reactions

    MedlinePlus

    ... or diabetes. But medicines can also cause unwanted reactions. One problem is interactions, which may occur between ... more serious. Drug allergies are another type of reaction. They can be mild or life-threatening. Skin ...

  16. Bleach Gel: A Simple Agarose Gel for Analyzing RNA Quality

    PubMed Central

    Aranda, Patrick S.; LaJoie, Dollie M.; Jorcyk, Cheryl L.

    2013-01-01

    RNA-based applications requiring high quality, non-degraded RNA are a foundational element of many research studies. As such, it is paramount that the integrity of experimental RNA is validated prior to cDNA synthesis or other downstream applications. In the absence of expensive equipment such as microfluidic electrophoretic devices, and as an alternative to the costly and time-consuming standard formaldehyde gel, RNA quality can be quickly analyzed by adding small amounts of commercial bleach to TAE buffer-based agarose gels prior to electrophoresis. In the presence of low concentrations of bleach, the secondary structure of RNA is denatured and potential contaminating RNases are destroyed. Because of this, the ‘bleach gel’ is a functional approach that addresses the need for an inexpensive and safe way to evaluate RNA integrity and will improve the ability of researchers to rapidly analyze RNA quality. PMID:22222980

  17. Clindamycin phosphate 1% gel in acne vulgaris.

    PubMed

    Rizer, R L; Sklar, J L; Whiting, D; Bucko, A; Shavin, J; Jarratt, M

    2001-01-01

    A 12-week study compared Clindagel, a unique water-based gel formulation of clindamycin phosphate 1%, administered once daily, and Cleocin T, a slightly different gel formulation indicated for twice-daily use, in the treatment of acne vulgaris. Clindagel was safe and effective and equivalent to Cleocin T gel, albeit with a better tolerability profile. Clindagel is a viable alternative to Cleocin T gel.

  18. Study of Fricke gel dosimeter response for different gel quality

    NASA Astrophysics Data System (ADS)

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

    2010-11-01

    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.

  19. Preparation and characterization of Ag nanoparticle-embedded blank and ligand-anchored silica gels.

    PubMed

    Im, Hee-Jung; Lee, Byung Cheol; Yeon, Jei-Won

    2013-11-01

    Ag nanoparticles, used for halogen (especially iodine) adsorption and an evaluation of halogen behavior, were embedded in synthesized inorganic-organic hybrid gels. In particular, an irradiation method using an electron beam plays a part in introducing Ag nanoparticles to the organofunctionalized silica gels from AgNO3 solutions in a simple way at atmospheric pressure and room temperature. For preparation of the Ag nanoparticle-embedded inorganic-organic hybrid gels, ligands of ethylenediamine (NH2CH2CH2NH-, TMSen) and mercapto (HS-) functionalized three-dimensional porous SiO2 sol-gels were first synthesized through hydrolysis and condensation reactions, and Ag nanoparticles were then embedded into the ethylenediamine- and mercapto-anchored silica gels each, through electron-beam irradiation. The addition of ligands yielded larger average pore sizes than the absence of any ligand. Moreover, the ethylenediamine ligand led to looser structures and better access of the Ag nanoparticles to the ethylenediamine-anchored gel. As a result, more Ag nanoparticles were introduced into the ethylenediamine-anchored gel. The preparation and characterization of Ag nanoparticle-embedded blank and ligand-anchored silica gels are discussed in detail.

  20. Method for separating constituents from solution employing a recyclable Lewis acid metal-hydroxy gel

    SciTech Connect

    Alexander, D.H.

    1995-12-31

    This invention permits radionuclides, heavy metals, and organics to be extracted from solution by scavenging them with an amorphous gel. In the preferred embodiment, a contaminated solution (e.g. from soil washing, decontamination, or groundwater pumping) is transferred to a reaction vessel. The contaminated solution is contacted by the sequestering reagent which might contain for example, aluminate and EDTA anions in a 2.5 M NaOH solution. The pH of the reagent bearing solution is lowered on contact with the contaminated solution, or for example by bubbling carbon dioxide through it, causing an aluminum hydroxide gel to precipitate as the solution drops below the range of 1.8 to 2.5 molar NaOH (less than pH 14). This precipitating gel scavenges waste contaminants as it settles through solution leaving a clean supernatant which is then separated from the gel residue by physical means such as centrifugation, or simple settling. The gel residue containing concentrated contaminants is then redissolved releasing contaminants for separations and processing. This is a critical point: the stabilized gel used in this invention is readily re-dissolved by merely increasing the pH above the gels phase transition to aqueous anions. Thus, concentrated contaminants trapped in the gel can be released for convenient separation from the sequestering reagent, and said reagent can then be recycled.

  1. Stability analyses of the model for photosensitive self-oscillating polymer gels

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    Via theory and simulations, we investigate the behavior of polymer gels undergoing Belousov-Zhabotinsky (BZ) reaction. Driven by periodic reduction and oxidation of the ruthenium catalyst, which is grafted to the polymer network, BZ gels undergo rhythmic mechanical oscillations and thereby exhibit chemo-mechanical transduction. The oscillations within the BZ gels, however, can be completely suppressed with light of a certain intensity and wavelength. We simulate the behavior of photosensitive BZ gels by our 3D gel lattice spring model. Using this model we have successfully demonstrated that it is possible to direct the movement of BZ gels, along complex paths, guiding them to bend, reorient and turn. The mechanism of chemo-mechanical transduction, however, works for a particular set of conditions. Through linear stability and normal form analyses, we isolate parameters for which the gel switches from oscillatory mode to stationary mode and vice versa. Specifically, we characterize the nature of Hopf bifurcations and identify regimes where this bifurcation is subcritical or supercritical. We also determine several other types of bifurcations within our system. These analyses allow us to establish optimal conditions required to guide the movement of BZ gels along complex paths.

  2. Spring-loaded polymeric gel actuators

    DOEpatents

    Shahinpoor, M.

    1995-02-14

    Spring-loaded electrically controllable polymeric gel actuators are disclosed. The polymeric gels can be polyvinyl alcohol, polyacrylic acid, or polyacrylamide, and are contained in an electrolytic solvent bath such as water plus acetone. The action of the gel is mechanically biased, allowing the expansive and contractile forces to be optimized for specific applications. 5 figs.

  3. Spring-loaded polymeric gel actuators

    DOEpatents

    Shahinpoor, Mohsen

    1995-01-01

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

  4. Effects of Aggregate Microfines and Potassium Acetate Interactions on Concrete Performance

    NASA Astrophysics Data System (ADS)

    Silva, Jessica Marie Sanfilippo

    The principal objective of this research is to elucidate the role that microfines from coarse and fine aggregates play in the development of the Alkali Silica Reaction (ASR) related distress observed in airport pavements subject to anti-icing agents. As a secondary objective, it was proposed to identify other potential impacts of microfines and deicers on concrete durability. It was determined that combinations of microfines at less than 5% of the total aggregate weight and potassium acetate deicer (KAC Deicer) exposure caused significant deterioration of concrete that may be mistaken for ASR cracking and expansion. However, our analyses suggest it was not ASR, at least as traditionally diagnosed through the presence of ASR gel and reaction rims around aggregates. Expansions in modified ASTM C1293 produced expansions from 0.05% to 0.70% at one year depending on the type of microfine. Expansions of specimens containing microfines but not exposed to KAc Deicer produced negligible expansion. Expansions were larger with base aggregate known to be prone to ASR, but significant expansions (up to 0.50% at one year) also occurred in specimens with unreactive aggregates. Degradation combined with the reduction in entrained air content led to dramatic loss of freeze-thaw durability. These degradations were associated with specific mineralogical profiles of microfines in the presence of KAc Deicer and these profiles consistently were associated with corresponding levels of degradation. The KAc Deicer transformed in the concrete pore solutions to form potassium sulfate and calcium-bearing potassium sulfate compounds. During the transformation of the potassium acetate the level of hydroxide increases dramatically in the pore solution and can lead to reformation of silica species released by the microfines and the aggregates. While these reactions do not appear to be the classical alkali silica reaction, they may exhibit some similarity and create an environment where expansion

  5. Preparation and gel properties of low molecular weight curdlan by hydrolysis of curdlan with commercial α-amylase.

    PubMed

    Chen, Yi-Feng; Zhu, Qin; Wu, Sheng-Jun

    2014-11-26

    Low molecular weight curdlan (LMWC) was prepared by hydrolysis of curdlan with commercial α-amylase. The hydrolysis reaction was conducted using 31.94 mg α-amylase per 500 mL reaction mixture, which contained 5 g curdlan. The hydrolysis was performed at pH 5.98 and 55.92 °C for 10 min. The molecular weight and structure of LMWC were characterized by high-performance liquid chromatography and Fourier transform infrared spectroscopy, respectively. Generally, LMWC showed lower gel strength than high molecular weight curdlan (HMWC). Unlike HMWC, LMWC could form into a gel at 50 °C. By contrast, HMWC could form into a gel at pH 11, but LMWC gel failed to form at this pH level. The strength of LMWC and HMWC gels increased with increasing temperature and decreased with increasing pH level.

  6. Nanocrystal/sol-gel nanocomposites

    DOEpatents

    Klimov, Victor L.; Petruska, Melissa A.

    2010-05-25

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

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

    PubMed

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

    2007-04-01

    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.

  8. Designing Dual-functionalized Gels for Self-reconfiguration and Autonomous Motion

    DOE PAGES

    Kuksenok, Olga; Balazs, Anna C.

    2015-04-30

    Human motion is enabled by the concerted expansion and contraction of interconnected muscles that are powered by inherent biochemical reactions. One of the challenges in the field of biomimicry is eliciting this form of motion from purely synthetic materials, which typically do not generate internalized reactions to drive mechanical action. Moreover, for practical applications, this bio-inspired motion must be readily controllable. Herein, we develop a computational model to design a new class of polymer gels where structural reconfigurations and internalized reactions are intimately linked to produce autonomous motion, which can be directed with light. These gels contain both spirobenzopyran (SP)more » chromophores and the ruthenium catalysts that drive the oscillatory Belousov-Zhabotinsky (BZ) reaction. Importantly, both the SP moieties and the BZ reaction are photosensitive. When these dual-functionalized gels are exposed to non-uniform illumination, the localized contraction of the gel (due to the SP moieties) in the presence of traveling chemical waves (due to the BZ reaction) leads to new forms of spontaneous, self-sustained movement, which cannot be achieved by either of the mono-functionalized networks.« less

  9. Designing Dual-functionalized Gels for Self-reconfiguration and Autonomous Motion

    SciTech Connect

    Kuksenok, Olga; Balazs, Anna C.

    2015-04-30

    Human motion is enabled by the concerted expansion and contraction of interconnected muscles that are powered by inherent biochemical reactions. One of the challenges in the field of biomimicry is eliciting this form of motion from purely synthetic materials, which typically do not generate internalized reactions to drive mechanical action. Moreover, for practical applications, this bio-inspired motion must be readily controllable. Herein, we develop a computational model to design a new class of polymer gels where structural reconfigurations and internalized reactions are intimately linked to produce autonomous motion, which can be directed with light. These gels contain both spirobenzopyran (SP) chromophores and the ruthenium catalysts that drive the oscillatory Belousov-Zhabotinsky (BZ) reaction. Importantly, both the SP moieties and the BZ reaction are photosensitive. When these dual-functionalized gels are exposed to non-uniform illumination, the localized contraction of the gel (due to the SP moieties) in the presence of traveling chemical waves (due to the BZ reaction) leads to new forms of spontaneous, self-sustained movement, which cannot be achieved by either of the mono-functionalized networks.

  10. Designing Dual-functionalized Gels for Self-reconfiguration and Autonomous Motion

    NASA Astrophysics Data System (ADS)

    Kuksenok, Olga; Balazs, Anna C.

    2015-04-01

    Human motion is enabled by the concerted expansion and contraction of interconnected muscles that are powered by inherent biochemical reactions. One of the challenges in the field of biomimicry is eliciting this form of motion from purely synthetic materials, which typically do not generate internalized reactions to drive mechanical action. Moreover, for practical applications, this bio-inspired motion must be readily controllable. Herein, we develop a computational model to design a new class of polymer gels where structural reconfigurations and internalized reactions are intimately linked to produce autonomous motion, which can be directed with light. These gels contain both spirobenzopyran (SP) chromophores and the ruthenium catalysts that drive the oscillatory Belousov-Zhabotinsky (BZ) reaction. Importantly, both the SP moieties and the BZ reaction are photosensitive. When these dual-functionalized gels are exposed to non-uniform illumination, the localized contraction of the gel (due to the SP moieties) in the presence of traveling chemical waves (due to the BZ reaction) leads to new forms of spontaneous, self-sustained movement, which cannot be achieved by either of the mono-functionalized networks.

  11. Designing Dual-functionalized Gels for Self-reconfiguration and Autonomous Motion

    PubMed Central

    Kuksenok, Olga; Balazs, Anna C.

    2015-01-01

    Human motion is enabled by the concerted expansion and contraction of interconnected muscles that are powered by inherent biochemical reactions. One of the challenges in the field of biomimicry is eliciting this form of motion from purely synthetic materials, which typically do not generate internalized reactions to drive mechanical action. Moreover, for practical applications, this bio-inspired motion must be readily controllable. Herein, we develop a computational model to design a new class of polymer gels where structural reconfigurations and internalized reactions are intimately linked to produce autonomous motion, which can be directed with light. These gels contain both spirobenzopyran (SP) chromophores and the ruthenium catalysts that drive the oscillatory Belousov-Zhabotinsky (BZ) reaction. Importantly, both the SP moieties and the BZ reaction are photosensitive. When these dual-functionalized gels are exposed to non-uniform illumination, the localized contraction of the gel (due to the SP moieties) in the presence of traveling chemical waves (due to the BZ reaction) leads to new forms of spontaneous, self-sustained movement, which cannot be achieved by either of the mono-functionalized networks. PMID:25924823

  12. Protein microchips : use for immunoassay and enzymatic reactions.

    SciTech Connect

    Arenkov, P.; Kukhtin, A.; Gemmell, A.; Voloschuk, S.; Chupeeva, V.; Mirzabekov, A.; Biochip Technology Center; Russian Academy of Sciences

    2000-02-15

    Different proteins such as antibodies, antigens, and enzymes were immobilized within the 100 x 100 x 20-{mu}m gel pads of protein microchips. A modified polyacrylamide gel has been developed to accommodate proteins of a size up to 400,000 daltons. Electrophoresis in the microchip reaction chamber speeded up antigen-antibody interactions within the gel. Protein microchips were used in immunoassays for detection of antigens or antibodies, as well as to carry out enzymatic reactions and to measure their kinetics in the absence or presence of an inhibitor. A protein microchip can be used several times in different immunoassays and enzymatic kinetic measurements.

  13. Basics of quantitative polymerase chain reaction: 2. Electrophoresis and quantitation of polymerase chain reaction products.

    PubMed

    Sundfors, C; Collan, Y

    1996-01-01

    The performance of agarose and polyacrylamide (PAGE) gels in quantitating polymerase chain reaction (PCR) amplified c-erbB2 and p53 gene sequences (213 and 133 base pairs, respectively) was studied by applying image analysis on photographed ethidium bromide stained gels. The 5 mm thick agarose gels were more insensitive than the 1 mm thin PAGE gels and already started to show saturation effects within a narrow concentration range. The explanation is the greater dilution of band-associated products within the volume of the gel and the inefficient penetration of exciting UV light through the gel. Such effects produced inconsistency and dramatic variations in the band ratio estimates. In the system used by us, agarose electrophoresis and also electrophoresis using 5 mm thick PAGE gels have only a limited value in quantitation of PCR products with the band density ratios, but both can be used well in qualitative work. The far thinner (1 mm) PAGE gels, which did not markedly absorb UV light, performed better in the light of band density ratio estimates. The linear or approximately linear range of concentrations was wider. The coefficient of variation of band ratio, when estimated from the same gels, after loading them with aliquots of identical DNA from several PCR amplified tubes, was in the range of 4%. The absolute values of band densities had a more remarkable variation (than 4%) in both agarose and PAGE gels. Our recommendation is that quantitation of PCR products be done with band density ratio estimates, and in thin PAGE gels.

  14. Multiscale modeling of polyelectrolyte gels

    NASA Astrophysics Data System (ADS)

    Wallmersperger, Thomas; Wittel, Falk K.; Kröplin, Bernd H.

    2006-03-01

    Electrolyte polymer gels are a very attractive class of actuation materials with remarkable electronic and mechanical properties having a great similarity to biological contractile tissues. They consist of a polymer network with ionizable groups and a liquid phase with mobile ions. Absorption and delivery of solvent lead to a considerably large change of volume. Due to this capability, they can be used as actuators for technical applications, where large swelling and shrinkage is desired. In the present work chemically and electrically stimulated polymer gels in a solution bath are investigated. To describe the different complicated phenomena occurring in these gels adequately, the modeling can be conducted on different scales. Therefore, models based on the statistical theory and porous media theory, as well as a multi-field model and a discrete element formulation are derived. A refinement of the different theories from global macroscopic to microscopic are presented in this paper: The statistical theory is a macroscopic theory capable to describe the global swelling or bending e.g. of a gel film, while the general theory of porous media (TPM) is a macroscopic continuum theory which is based on the theory of mixtures extended by the concept of volume fractions. The TPM is a homogenized model, i.e. all geometrical and physical quantities can be seen as statistical averages of the real quantities. The presented chemo-electro-mechanical multi-field formulation is a mesoscopic theory. It is capable of giving the concentrations and the electric potential in the whole domain. Finally the (micromechanical) discrete element (DE) theory is employed. In this case, the continuum is represented by distributed particles with local interaction relations combined with balance equations for the chemical field. This method is predestined for problems involving large displacements, strains and discontinuities. The presented formulations are compared and conclusions on their

  15. The gel electrophoresis markup language (GelML) from the Proteomics Standards Initiative.

    PubMed

    Gibson, Frank; Hoogland, Christine; Martinez-Bartolomé, Salvador; Medina-Aunon, J Alberto; Albar, Juan Pablo; Babnigg, Gyorgy; Wipat, Anil; Hermjakob, Henning; Almeida, Jonas S; Stanislaus, Romesh; Paton, Norman W; Jones, Andrew R

    2010-09-01

    The Human Proteome Organisation's Proteomics Standards Initiative has developed the GelML (gel electrophoresis markup language) data exchange format for representing gel electrophoresis experiments performed in proteomics investigations. The format closely follows the reporting guidelines for gel electrophoresis, which are part of the Minimum Information About a Proteomics Experiment (MIAPE) set of modules. GelML supports the capture of metadata (such as experimental protocols) and data (such as gel images) resulting from gel electrophoresis so that laboratories can be compliant with the MIAPE Gel Electrophoresis guidelines, while allowing such data sets to be exchanged or downloaded from public repositories. The format is sufficiently flexible to capture data from a broad range of experimental processes, and complements other PSI formats for MS data and the results of protein and peptide identifications to capture entire gel-based proteome workflows. GelML has resulted from the open standardisation process of PSI consisting of both public consultation and anonymous review of the specifications.

  16. Controlling chemical oscillations in heterogeneous Belousov-Zhabotinsky gels via mechanical strain.

    PubMed

    Yashin, Victor V; Van Vliet, Krystyn J; Balazs, Anna C

    2009-04-01

    We performed theoretical and computational studies to determine the effect of an applied mechanical strain on the dynamic behavior of heterogeneous polymer gels undergoing the oscillatory Belousov-Zhabotinsky (BZ) reaction. In these spatially heterogeneous gels, the catalyst for the reaction is localized in specific patches within the polymer network and the BZ reaction only occurs within these catalyst-containing patches, which we refer to as BZ patches. We focused on a model for a one-dimensional system, and further assumed that the BZ reaction did not affect the degree of swelling within the gel. For gels having one and two BZ patches, we found that a tensile or compressive strain could induce transitions between the oscillatory and nonoscillatory, steady-state regimes of the system. For certain values of the BZ stoichiometric parameter f , these transitions could exhibit a hysteresis. In systems having two oscillating BZ patches, an applied strain could cause a switching between the in-phase and out-of-phase synchronization of the oscillations. The ability to controllably alter the dynamic behavior of BZ gels through mechanical deformations opens up the possibility of using these materials in the design of chemo-mechanical sensors.

  17. Bio-barcode gel assay for microRNA

    NASA Astrophysics Data System (ADS)

    Lee, Hyojin; Park, Jeong-Eun; Nam, Jwa-Min

    2014-02-01

    MicroRNA has been identified as a potential biomarker because expression level of microRNA is correlated with various cancers. Its detection at low concentrations would be highly beneficial for cancer diagnosis. Here, we develop a new type of a DNA-modified gold nanoparticle-based bio-barcode assay that uses a conventional gel electrophoresis platform and potassium cyanide chemistry and show this assay can detect microRNA at aM levels without enzymatic amplification. It is also shown that single-base-mismatched microRNA can be differentiated from perfectly matched microRNA and the multiplexed detection of various combinations of microRNA sequences is possible with this approach. Finally, differently expressed microRNA levels are selectively detected from cancer cells using the bio-barcode gel assay, and the results are compared with conventional polymerase chain reaction-based results. The method and results shown herein pave the way for practical use of a conventional gel electrophoresis for detecting biomolecules of interest even at aM level without polymerase chain reaction amplification.

  18. Sol gel-fluorination synthesis of amorphous magnesium fluoride

    NASA Astrophysics Data System (ADS)

    Krishna Murthy, J.; Groß, Udo; Rüdiger, Stephan; Kemnitz, Erhard; Winfield, John M.

    2006-03-01

    The sol-gel fluorination process is discussed for the reaction of magnesium alkoxides with HF in non-aqueous solvents to give X-ray amorphous nano-sized magnesium fluoride with high surface areas in the range of 150-350 m 2/g (HS-MgF 2). The H2 type hysteresis of nitrogen adsorption-desorption BET-isotherms is indicative for mesoporous solids. A highly distorted structure causes quite high Lewis acidity, shown by NH 3 temperature-programmed desorption (NH 3-TPD) and catalytic test reactions. XPS data of amorphous and conventionally crystalline MgF 2 are compared, both show octahedral coordination at the metal site. Thermal analysis, F-MAS NMR- and IR-spectroscopy give information on composition and structure of the precursor intermediate as well as of the final metal fluoride. The preparation of complex fluorides, M +MgF 3-, by the sol-gel route is reported. From the magnesium fluoride gel of the above process thin films for optical application are obtained by, e.g., spin coating.

  19. Mechanical characterization of active polymer gels

    NASA Astrophysics Data System (ADS)

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

    2000-06-01

    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.

  20. Combined gel filtration, biuret/copper method compared with an immunochemical method for urinary protein measurement.

    PubMed

    Peele, J D; Gadsden, R H; Loadholt, C B

    1977-01-01

    We compared an immunochemical method specific for plasma proteins with a chemical method, in which interfering substances are separated by gel filtration and "total" urinary protein is determined by the biuret reaction followed by reaction of protein-bound copper with diethyldithiocarbamate after a second gel filtration to remove nonprotein-bound copper. More than 250 24-h urine samples were analyzed by each method. There was linear agreement and a correlation of 0.96 between the two methods, but urinary protein values determined by the immunochemical method, especially for patients with multiple myeloma, were lower than by the chemical method.

  1. Fibrin gels and their clinical and bioengineering applications

    PubMed Central

    Janmey, Paul A; Winer, Jessamine P; Weisel, John W

    2008-01-01

    Fibrin gels, prepared from fibrinogen and thrombin, the key proteins involved in blood clotting, were among the first biomaterials used to prevent bleeding and promote wound healing. The unique polymerization mechanism of fibrin, which allows control of gelation times and network architecture by variation in reaction conditions, allows formation of a wide array of soft substrates under physiological conditions. Fibrin gels have been extensively studied rheologically in part because their nonlinear elasticity, characterized by soft compliance at small strains and impressive stiffening to resist larger deformations, appears essential for their function as haemostatic plugs and as matrices for cell migration and wound healing. The filaments forming a fibrin network are among the softest in nature, allowing them to deform to large extents and stiffen but not break. The biochemical and mechanical properties of fibrin have recently been exploited in numerous studies that suggest its potential for applications in medicine and bioengineering. PMID:18801715

  2. Synchronization of oscillations in hybrid gel-piezoelectric active materials

    NASA Astrophysics Data System (ADS)

    Yashin, Victor V.; Levitan, Steven P.; Balazs, Anna C.

    We model the hybrid gel-piezoelectric active material that could perform oscillator based unconventional computing tasks (``materials that compute''). The material is assumed to have a cellular structure, where each cell contains a polymer gel, which undergoes cyclic swelling and deswelling due to the oscillatory Belousov-Zhabotinsky (BZ) reaction, and is coupled to a piezoelectric (PZ) film. Upon electrical connection, oscillations in the BZ-PZ units get synchronized, and the mode of synchronization is shown to depend on the number of units in the system, type of circuit connection, etc. Introduction of capacitors into the circuits allows us to further manipulate the synchronization modes, i.e., the distinctive patterns in phase of oscillations. The results indicate the BZ-PZ systems could be used for spatio-temporal pattern recognition.

  3. DEVELOPMENT OF POLYMER GEL SYSTEMS TO IMPROVE VOLUMETRIC SWEEP AND REDUCE PRODUCING WATER/OIL RATIOS

    SciTech Connect

    G. Paul Willhite; Stan McCool; Don W. Green; Min Cheng; Rajeev Jain; Tuan Nguyen

    2003-11-01

    Gelled polymer treatments are applied to oil reservoirs to increase oil production and to reduce water production by altering the fluid movement within the reservoir. This report describes the results of the first year of a three-year research program that is aimed at the understanding of the chemistry of gelation and the fundamental mechanisms that alter the flows of oil and water in reservoir rocks after a gel treatment. Work has focused on a widely-applied system in field applications, the partially hydrolyzed polyacrylamide-chromium acetate gel. Gelation occurs by network formation through the crosslinking of polyacrylamide molecules as a result of reaction with chromium acetate. The initial reaction between chromium acetate and one polymer is referred to as the uptake reaction. The uptake reaction was studied as functions of chromium and polymer concentrations and pH values. Experimental data were regressed to determine a rate equation that describes the uptake reaction of chromium by polyacrylamide. Pre-gel aggregates form and grow as the reactions between chromium acetate and polyacrylamide proceed. A statistical model that describes the growth of pre-gel aggregates was developed using the theory of branching processes. The model gives molecular weight averages that are expressed as functions of the conversion of the reactive sites on chromium acetate or on the polymer molecule. Results of the application of the model correlate well with experimental data of viscosity and weight-average molecular weight and gives insights into the gelation process. A third study addresses the flow of water and oil in rock material after a gel treatment. Previous works have shown that gel treatments usually reduce the permeability to water to a greater extent than the permeability to oil is reduced. This phenomenon is referred to as disproportionate permeability reduction (DPR). Flow experiments were conducted to determine the effect of polymer and chromium concentrations on

  4. User`s guide and documentation manual for ``PC-Gel`` simulator

    SciTech Connect

    Chang, Ming-Ming; Gao, Hong W.

    1993-10-01

    PC-GEL is a three-dimensional, three-phase (oil, water, and gas) permeability modification simulator developed by incorporating an in-situ gelation model into a black oil simulator (BOAST) for personal computer application. The features included in the simulator are: transport of each chemical species of the polymer/crosslinker system in porous media, gelation reaction kinetics of the polymer with crosslinking agents, rheology of the polymer and gel, inaccessible pore volume to macromolecules, adsorption of chemical species on rock surfaces, retention of gel on the rock matrix, and permeability reduction caused by the adsorption of polymer and gel. The in-situ gelation model and simulator were validated against data reported in the literature. The simulator PC-GEL is useful for simulating and optimizing any combination of primary production, waterflooding, polymer flooding, and permeability modification treatments. A general background of permeability modification using crosslinked polymer gels is given in Section I and the governing equations, mechanisms, and numerical solutions of PC-GEL are given in Section II. Steps for preparing an input data file with reservoir and gel-chemical transport data, and recurrent data are described in Sections III and IV, respectively. Example data inputs are enclosed after explanations of each input line to help the user prepare data files. Major items of the output files are reviewed in Section V. Finally, three sample problems for running PC-GEL are described in Section VI, and input files and part of the output files of these problems are listed in the appendices. For the user`s reference a copy of the source code of PC-GEL computer program is attached in Appendix A.

  5. Ternary Phase-Separation Investigation of Sol-Gel Derived Silica from Ethyl Silicate 40.

    PubMed

    Wang, Shengnan; Wang, David K; Smart, Simon; da Costa, João C Diniz

    2015-09-28

    A ternary phase-separation investigation of the ethyl silicate 40 (ES40) sol-gel process was conducted using ethanol and water as the solvent and hydrolysing agent, respectively. This oligomeric silica precursor underwent various degrees of phase separation behaviour in solution during the sol-gel reactions as a function of temperature and H2O/Si ratios. The solution composition within the immiscible region of the ES40 phase-separated system shows that the hydrolysis and condensation reactions decreased with decreasing reaction temperature. A mesoporous structure was obtained at low temperature due to weak drying forces from slow solvent evaporation on one hand and formation of unreacted ES40 cages in the other, which reduced network shrinkage and produced larger pores. This was attributed to the concentration of the reactive sites around the phase-separated interface, which enhanced the condensation and crosslinking. Contrary to dense silica structures obtained from sol-gel reactions in the miscible region, higher microporosity was produced via a phase-separated sol-gel system by using high H2O/Si ratios. This tailoring process facilitated further condensation reactions and crosslinking of silica chains, which coupled with stiffening of the network, made it more resistant to compression and densification.

  6. Ternary Phase-Separation Investigation of Sol-Gel Derived Silica from Ethyl Silicate 40

    NASA Astrophysics Data System (ADS)

    Wang, Shengnan; Wang, David K.; Smart, Simon; Diniz da Costa, João C.

    2015-09-01

    A ternary phase-separation investigation of the ethyl silicate 40 (ES40) sol-gel process was conducted using ethanol and water as the solvent and hydrolysing agent, respectively. This oligomeric silica precursor underwent various degrees of phase separation behaviour in solution during the sol-gel reactions as a function of temperature and H2O/Si ratios. The solution composition within the immiscible region of the ES40 phase-separated system shows that the hydrolysis and condensation reactions decreased with decreasing reaction temperature. A mesoporous structure was obtained at low temperature due to weak drying forces from slow solvent evaporation on one hand and formation of unreacted ES40 cages in the other, which reduced network shrinkage and produced larger pores. This was attributed to the concentration of the reactive sites around the phase-separated interface, which enhanced the condensation and crosslinking. Contrary to dense silica structures obtained from sol-gel reactions in the miscible region, higher microporosity was produced via a phase-separated sol-gel system by using high H2O/Si ratios. This tailoring process facilitated further condensation reactions and crosslinking of silica chains, which coupled with stiffening of the network, made it more resistant to compression and densification.

  7. Ternary Phase-Separation Investigation of Sol-Gel Derived Silica from Ethyl Silicate 40

    PubMed Central

    Wang, Shengnan; Wang, David K.; Smart, Simon; Diniz da Costa, João C.

    2015-01-01

    A ternary phase-separation investigation of the ethyl silicate 40 (ES40) sol-gel process was conducted using ethanol and water as the solvent and hydrolysing agent, respectively. This oligomeric silica precursor underwent various degrees of phase separation behaviour in solution during the sol-gel reactions as a function of temperature and H2O/Si ratios. The solution composition within the immiscible region of the ES40 phase-separated system shows that the hydrolysis and condensation reactions decreased with decreasing reaction temperature. A mesoporous structure was obtained at low temperature due to weak drying forces from slow solvent evaporation on one hand and formation of unreacted ES40 cages in the other, which reduced network shrinkage and produced larger pores. This was attributed to the concentration of the reactive sites around the phase-separated interface, which enhanced the condensation and crosslinking. Contrary to dense silica structures obtained from sol-gel reactions in the miscible region, higher microporosity was produced via a phase-separated sol-gel system by using high H2O/Si ratios. This tailoring process facilitated further condensation reactions and crosslinking of silica chains, which coupled with stiffening of the network, made it more resistant to compression and densification. PMID:26411484

  8. Adsorption of Cu and Mn on covalently cross-linked alginate gel beads.

    PubMed

    Gotoh, Takeshi; Matsushima, Keiei; Kikuchi, Ken-Ichi

    2004-04-01

    The covalently cross-linked alginate gel beads were prepared by the reactions of Ca(2+)-doped alginate gel beads, which were formed by spraying a viscous alginate solution into a calcium chloride solution, with cyanogen bromide and following 1,6-diaminohexane. The cross-linking of alginate matrix decreased the mean bead diameter by about 30% and made the beads durable in some extent under alkaline conditions. The adsorption of metal ions on the covalently cross-linked alginate gel beads was rapid and reached at equilibrium within 30 min at 25 degrees C. Adsorption isotherms of Cu(II), Mn(II), and Ca2+ on the beads possessed a stepwise shape, which was firstly determined by Rorrer et al. [Ind. Eng. Chem. Res. 32 (1993) 2170] for cross-linked chitosan gel beads and explained by a pore-blockage mechanism. Higher selectivity was determined against Cu(II) over Mn(II) and Ca2+, especially at a low concentration region. These metal adsorption profiles for the covalently cross-linked alginate gel beads was almost the same as those for the un-cross-linked beads, indicating that the cross-linking reactions were performed without interfering the adsorption characteristics of alginate gel beads.

  9. Molecular imprinting in sol-gel matrix.

    PubMed

    Gupta, Radha; Kumar, Ashok

    2008-01-01

    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.

  10. Effect of solvent on melting gel behavior

    NASA Astrophysics Data System (ADS)

    Degnah, Ahmed Abdulaziz

    Melting gel and hybrid glass are organic-inorganic materials derived from sol gel processing. The behavior of the melting gel is that it is a solid at room temperature, but when the melting gel is reheated to 110°C (T1) it becomes fluid. The melting gel has reversible behavior due to incomplete crosslinking between polysiloxane chains. When the melting gel is heated to its consolidation temperature of 150°C (T2) the gel no longer softens (T2>T1), because crosslinking is completed. The melting gel at the consolidation temperature becomes hybrid glass. Melting gel coatings were applied to titanium alloy substrates. Melting gels were prepared containing phenyl substitutions with 1.0 mole Phenyltrimethoxysilane (PhTMS) in ratio to 0.25 moles of Diphenyldimethoxysilane (DPhDMS). The methanol to DPhDMS ratio was varied to change the thickness of the coatings. The coatings were inspected visually to see that there is good adhesion between the coating and the substrate. Nanoindenter tests were performed to determine hardness. The coated samples were placed in an oven and heated to 150ºC for 24, 48 or 96 hours before cooling back to room temperature, which took about 4 hours. The measurements of the hardness on samples containing 3 levels of solvent and heat treatment were collected by indentation technique. The best combination of solvent and temperature was 1:8 PhTMS:MeOH for all temperatures.

  11. Nondenaturing agarose gel electrophoresis of RNA.

    PubMed

    Rio, Donald C; Ares, Manuel; Hannon, Gregory J; Nilsen, Timothy W

    2010-06-01

    INTRODUCTION Perhaps the most important and certainly the most often used technique in RNA analysis is gel electrophoresis. Because RNAs are negatively charged, they migrate toward the anode in the presence of electric current. The gel acts as a sieve to selectively impede the migration of the RNA in proportion to its mass, given that its mass is generally proportional to its charge. Because mass is approximately related to chain length, the length of an RNA is more generally determined by its migration. In addition, topology (i.e., circularity) can affect migration, making RNAs appear longer on the gel than they actually are. There are two common types of gel: polyacrylamide and agarose. For most applications involving RNAs of < or =600 nucleotides, denaturing acrylamide gels are most appropriate. In contrast, agarose gels are generally used to analyze RNAs of > or =600 nucleotides, and are especially useful for analysis of mRNAs (e.g., by Northern blotting). RNA analysis on agarose gels is essentially identical to DNA analysis (except that the gel boxes used must be dedicated to RNA work or to other ribonuclease-free work). Here we describe the use of straightforward Tris borate, EDTA (TBE) gels for routine analysis. These gels are appropriate for determining the quantity and integrity of RNA before using it for other applications. This procedure should not be used to determine size with accuracy, because the RNA will not remain in its extended state throughout the run.

  12. Tailoring the properties of supramolecular gels

    NASA Astrophysics Data System (ADS)

    Buerkle, Lauren

    Supramolecular gels created from low molecular weight species (gelators) have gathered wide attention over the past few decades on account of their highly ordered assembly and ability to respond to external stimuli. These properties make such gels highly promising candidates for a diverse range of applications including biomaterials, viscosity modifiers, sensors, and liquid crystalline materials. We have focused on the design and tailoring of guanosine (the ribonucleoside of the nucleobase guanine) hydrogels. It is well known that in an aqueous environment, guanosine forms circular hydrogen-bonded quartets around a monovalent metal ion, most commonly potassium. These quartets then stack to form high-aspect ratio fibers that entangle and branch to form gels. Despite facile gel formation, crystallization of the guanosine molecules out of the gel is a common occurrence that leads to gel collapse within hours of fabrication. In addition, guanosine and related gelators often require a high potassium concentration or acidic pH to gel, which presents limited practical use in our target application of tissue engineering. We have focused on the modification and analysis of guanosine gels via an additive and/or a change in chemical structure to inhibit crystallization and promote gelation at physiological salt concentrations. Additionally, initial cell culture experiments suggest that these gel materials show great potential as an easily accessible and inexpensive tissue engineering scaffold. We also examined the potential for supramolecular gels for use in personal care formulations as electrolyte-resistant rheology modifiers for aqueous systems. Sugar-based gels fit the necessary criteria; however, many of these molecules also crystallize from the gel over time. We achieved lifetime stabilization again via a mixing approach and examined the resulting properties of the stabilized gels.

  13. Testim 1% testosterone gel for the treatment of male hypogonadism.

    PubMed

    Bouloux, Pierre

    2005-03-01

    The aim of this work was to review the pharmacokinetic and clinical profile of Testim (Auxilium Pharmaceuticals, Norristown, Pennsylvania) 1% gel formulation of testosterone for the treatment of male hypogonadism. An English-language search of the medical literature was conducted using PubMed (1998-December 2004) and EMBASE (1998-December 2004). Search terms included ag(e)ing male, male hypogonadism, late-onset hypogonadism, testosterone, testosterone deficiency, testosterone therapy, testosterone replacement therapy, androgen therapy, testosterone gel, and Testim. Bibliographies of retrieved articles were also reviewed. Five published clinical studies were reviewed. Testim 50 mg showed clear pharmacokinetic differences from AndroGel (known as Testogel in Europe; Unimed Pharmaceuticals, Inc., and Solvay Pharmaceuticals, Inc., Marietta, Georgia) 1% testosterone gel 50 mg, with increases of 30% (90% CI, 8%-57%) and 47% (90% CI, 20%-79%) versus AndroGel, respectively, in AUC(0-24h) for total serum testosterone and free testosterone. In a 30-day study of 638 men with hypogonadism, sexual desire scores and sexual motivation scores increased after Testim treatment at weeks 1, 2, 3, and 4 (each, P < 0.001). During 12 months of treatment with Testim 50 or 100 mg in 371 men with hypogonadism, total serum testosterone levels were raised to and maintained within the normal adult range, lean body mass increased by 2.2 kg (P < 0.001), fat mass fell by 2.1% (P < 0.001), and bone mineral density increased by 2.58% (P < 0.001). Mean scores for sexual desire, performance, motivation, and spontaneous erections were all significantly higher (all, P < 0.001) than at baseline for all time points during 12-month studies of Testim. In 2 studies comparing Testim with different testosterone patches, treatment with the gel resulted in 10-fold fewer application-site reactions than either patch. In men with hypogonadism, Testim gel raised and maintained serum testosterone levels to within the

  14. Photorefractive sol-gel materials

    SciTech Connect

    Chaput, F.; Boilot, J.P.; Gacoin, T.; Darracq, B.; Riehl, D.; Canva, M.; Levy, Y.; Brun, A.

    1996-12-31

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

  15. Using in situ rheology to characterize the microstructure in photopolymerized polyacrylamide gels for DNA electrophoresis.

    PubMed

    Wang, Jian; Ugaz, Victor M

    2006-09-01

    Photopolymerized cross-linked polyacrylamide hydrogels are attractive sieving matrix formulations for DNA electrophoresis owing to their rapid polymerization times and the potential to locally tailor the gel pore structure through spatial variation of illumination intensity. This capability is especially important in microfluidic systems, where photopolymerization allows gel matrices to be precisely positioned within complex microchannel networks. Separation performance is also directly related to the nanoscale gel pore structure, which is in turn strongly influenced by polymerization kinetics. Unfortunately, detailed studies of the interplay among polymerization kinetics, mechanical properties, and structural morphology are lacking in photopolymerized hydrogel systems. In this paper, we address this issue by performing a series of in situ dynamic small-amplitude oscillatory shear measurements during photopolymerization of cross-linked polyacrylamide electrophoresis gels to investigate the relationship between rheology and parameters associated with the gelation environment including UV intensity, monomer and cross-linker composition, and reaction temperature. In general, we find that the storage modulus G' increases with increasing initial monomer concentration, cross-linker concentration, and polymerization temperature. The steady-state value of G', however, exhibits a more complex dependence on UV intensity that varies with gel concentration. A simple model based on rubber elasticity theory is used to obtain estimates of the average gel pore size that are in surprisingly good agreement with corresponding data obtained from analysis of DNA electrophoretic mobility in gels cast under identical polymerization conditions.

  16. Aloe vera gel protects liver from oxidative stress-induced damage in experimental rat model.

    PubMed

    Nahar, Taslima; Uddin, Borhan; Hossain, Shahdat; Sikder, Abdul Mannan; Ahmed, Sohel

    2013-05-07

    Aloe vera is a semi-tropical plant of Liliaceae family which has a wide range of applications in traditional medicine. In the present study, we sought to investigate the heptaoprotective potential of Aloe vera gel as a diet supplement. To achieve this goal, we have designed in vitro and in vivo experimental models of chemical-induced liver damage using male Sprague-Dawley rat. In the in vitro model, its effect was evaluated on Fenton's reaction-induced liver lipid peroxidation. Co-incubation with gel significantly reduced the generation of liver lipid peroxide (LPO). Next, to see the similar effect in vivo, gel was orally administered to rats once daily for 21 successive days. Following 1 hour of the last administration of gel, rats were treated with intra-peritoneal injection of CCl4. Dietary gel showed significant hepatoprotection against CCl4-induced damage as evident by restoration of liver LPO, serum transaminases, alkaline phosphatase, and total bilirubin towards near normal. The beneficial effects were pronounced with the doses used (400 and 800 mg/kg body weight). Besides, we did not observe any significant drop in serum albumin, globulin as well as total protein levels of gel-administered rats. Histopathology of the liver tissue further supported the biochemical findings confirming the hepatoprotective potential of dietary gel.

  17. Two-dimensional polyacrylamide gel analysis of Plodia interpunctella granulosis virus

    SciTech Connect

    Russell, D.L.; Consigli, R.A.

    1986-10-01

    The structural polypeptides of purified Plodia interpunctella granulosis virus were analyzed by three different two-dimensional gel systems. Isoelectric focusing followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis allowed resolution of 53 acidic polypeptides in the enveloped nucleocapsid of the virus ranging in molecular weight from 97,300 to 8000. Nine of these polypeptides were shown to be glycoproteins by the technique of radiolabeled lectin blotting. Separation of the granulin in this system allowed resolution of five species, all of which have identical tryptic peptide maps. This matrix protein was demonstrated to be a phosphoglycoprotein by radiolabeled lectin blotting and acid phosphatase dephosphorylation. Nonequilibrium pH gel electrophoresis followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis allowed resolution of the major basic protein of the virus, VP12, from a more acidic protein of the same molecular weight. Tryptic peptide analysis demonstrated that these two proteins were indeed different and acid urea gels followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis allowed localization of the acidic protein to the envelope and the basic protein to the nucleocapsid of the virus. Finally, probing of the separated envelope nucleocapsid proteins in both the isoelectric focusing and nonequilibrium pH gel electrophoresis two-dimensional systems after transfer to nitrocellulose with iodinated, purified viral proteins allowed further insight into reactions which may be important in the maintenance of the virion structure.

  18. Porating anion-responsive copolymeric gels.

    PubMed

    England, Dustin; Yan, Feng; Texter, John

    2013-09-24

    A polymerizable ionic liquid surfactant, 1-(11-acryloyloxyundecyl)-3-methylimidiazolium bromide (ILBr), was copolymerized with methyl methacrylate (MMA) in aqueous microemulsions at 30% (ILBr w/w) and various water to MMA ratios. The ternary phase diagram of the ILBr/MMA/water system was constructed at 25 and 60 °C. Homopolymers and copolymers of ILBr and MMA were produced by thermally initiated chain radical microemulsion polymerization at various compositions in bicontinuous and reverse microemulsion subdomains. Microemulsion polymerization reaction products varied from being gel-like to solid, and these materials were analyzed by thermal and scanning electron microscopy methods. Microemulsion polymerized materials were insoluble in all solvents tested, consistent with light cross-linking. Ion exchange between Br(-) and PF6(-) in these copolymeric materials resulted in the formation of open-cell porous structures in some of these materials, as was confirmed by scanning electron microscopy (SEM). Several compositions illustrate the capture of prepolymerization nanoscale structure by thermally initiated polymerization, expanding the domain of compositions exhibiting this feat and yet to be demonstrated in any other system. Regular cylindrical pores in interpenetrating ILBr-co-MMA and PMMA networks are produced by anion exchange in the absence of templates. A percolating cluster/bicontinuous transition is "captured" by SEM after using anion exchange to visualize the mixed cluster/pore morphology. Some design principles for achieving this capture and for obtaining stimuli responsive solvogels are articulated, and the importance of producing solvogels in capturing the nanoscale is highlighted.

  19. Thermochromic gels for control of insolation

    SciTech Connect

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

    1993-05-01

    Thermochromic gels consist of a mixture of water, gelling agent, and a polyether reaction compound. They show a drastic increase of scattering when a characteristic switching temperature is surpassed. The hemispherical transmission consequently decreases from about 90 to 50% for a 1-mm-thick layer sandwiched between two glass panes. The increase in scattering is caused by a dramatic increase in number density and particle size of created scattering centers. The latter consists of agglomerated polyether chains with reduced water content, i.e., increased index of refraction. Our measurements cover the directional-directional transmission, as well as the directional-hemispherical transmission and reflection, using a double- beam spectrophotometer with an integrating sphere. For structural information a light-scattering apparatus was employed. Multiflux calculations allow predictions of the switching behaviour for nonvertical incidence and for arbitrarily thick layers. The thermochromic material is a low-cost, nontoxic product. The achieved switching action is reliable however, it may need improvement to allow application in solar architecture.

  20. The role of temperature in forming sol-gel biocomposites containing polydopamine

    PubMed Central

    Dyke, Jason Christopher; Hu, Huamin; Lee, Dong Joon; Ko, Ching-Chang; You, Wei

    2014-01-01

    To further improve the physical strength and biomedical applicability of bioceramicsbuilt on hydroxyapatite-gelatin (HAp-Gel) and siloxane sol-gel reactions, we incorporated mussel adhesive inspired polydopamine (PD) into our original composite based on HAp-Gel cross-linked with siloxane. Surprisingly, with the addition of PD, we observed that the processing conditions and temperatures play an important role in the structure and performance of these materials. A systematic study to investigate this temperature dependence behavior discloses that the rate of crosslinking of silane during the sol-gel process is significantly influenced by the temperature, whereas the polymerization of the dopamine only shows minor temperature dependence. With this discovery, we report an innovative thermal process for the design and application of these biocomposites. PMID:25485111

  1. Ultrapure glass optical waveguide development in microgravity by the sol-gel process

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Containerless melting of glasses in space for the preparation of ultrapure homogeneous glass for optical waveguides is discussed. The homogenization of the glass using conventional raw materials is normally achieved on Earth either by the gravity induced convection currents or by the mechanical stirring of the melt. Because of the absence of gravity induced convection currents, the homogenization of glass using convectional raw materials is difficult in the space environment. Multicomponent, homogeneous, noncrystalline oxide gels can be prepared by the sol-gel process and these gels are promising starting materials for melting glasses in the space environment. The sol-gel process is based on the polymerization reaction of alkoxysilane with other metal alkoxy compounds or suitable metal salts. Many of the alkoxysilanes or other metal alkoxides are liquids and thus can be purified by distillation.

  2. Automated apparatus for producing gradient gels

    DOEpatents

    Anderson, N.L.

    1983-11-10

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

  3. Active gel model of amoeboid cell motility

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

    We develop a model of amoeboid cell motility based on active gel theory. Modeling the motile apparatus of a eukaryotic cell as a confined layer of finite length of poroelastic active gel permeated by a solvent, we first show that, due to active stress and gel turnover, an initially static and homogeneous layer can undergo a contractile-type instability to a polarized moving state in which the rear is enriched in gel polymer. This agrees qualitatively with motile cells containing an actomyosin-rich uropod at their rear. We find that the gel layer settles into a steadily moving, inhomogeneous state at long times, sustained by a balance between contractility and filament turnover. In addition, our model predicts an optimal value of the gel-substrate adhesion leading to maximum layer speed, in agreement with cell motility assays. The model may be relevant to motility of cells translocating in complex, confining environments that can be mimicked experimentally by cell migration through microchannels.

  4. Tunable Gas Sensing Gels by Cooperative Assembly.

    PubMed

    Hussain, Abid; Semeano, Ana T S; Palma, Susana I C J; Pina, Ana S; Almeida, José; Medrado, Bárbara F; Pádua, Ana C C S; Carvalho, Ana L; Dionísio, Madalena; Li, Rosamaria W C; Gamboa, Hugo; Ulijn, Rein V; Gruber, Jonas; Roque, Ana C A

    2017-07-19

    The cooperative assembly of biopolymers and small molecules can yield functional materials with precisely tunable properties. Here, the fabrication, characterization, and use of multicomponent hybrid gels as selective gas sensors are reported. The gels are composed of liquid crystal droplets self-assembled in the presence of ionic liquids, which further coassemble with biopolymers to form stable matrices. Each individual component can be varied and acts cooperatively to tune gels' structure and function. The unique molecular environment in hybrid gels is explored for supramolecular recognition of volatile compounds. Gels with distinct compositions are used as optical and electrical gas sensors, yielding a combinatorial response conceptually mimicking olfactory biological systems, and tested to distinguish volatile organic compounds and to quantify ethanol in automotive fuel. The gel response is rapid, reversible, and reproducible. These robust, versatile, modular, pliant electro-optical soft materials possess new possibilities in sensing triggered by chemical and physical stimuli.

  5. Automated apparatus for producing gradient gels

    DOEpatents

    Anderson, Norman L.

    1986-01-01

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

  6. Gel trapping of dense colloids.

    PubMed

    Laxton, Peter B; Berg, John C

    2005-05-01

    Phase density differences in sols, foams, or emulsions often lead to sedimentation or creaming, causing problems for materials where spatial uniformity over extended periods of time is essential. The problem may be addressed through the use of rheology modifiers in the continuous phase. Weak polymer gels have found use for this purpose in the food industry where they appear to be capable of trapping dispersoid particles in a three-dimensional matrix while displaying water-like viscosities at low shear. Attempts to predict sedimentation stability in terms of particle properties (size, shape, density difference) and gel yield stress have led to qualitative success for suspensions of large particles. The effect of particle size, however, in particular the case in which colloidal dimensions are approached, has not been investigated. The present work seeks to determine useful stability criteria for colloidal dispersions in terms of readily accessible viscoelastic descriptors. Results are reported for systems consisting of 12 microm poly(methyl methacrylate) (PMMA) spheres dispersed in aqueous gellan gum. Monovalent salt concentration is varied to control rheological properties, and sedimentation/centrifugation experiments are performed to determine dispersion stability. Necessary conditions for stability consist of a minimum yield stress together with a value of tan delta less than unity.

  7. Self-Pumping Active Gel

    NASA Astrophysics Data System (ADS)

    Wu, Kun-Ta; Hishamunda, Jean Bernard; Fraden, Seth; Dogic, Zvonimir

    Isotropic active gels are the network which is consist of cross-linked building blocks and the structure of which changes randomly and isotropically with time. Dogic et. al. show that pairs of anti-parallel microtubules form extensile bundles, which merge, extend, and buckle. In an unconfined system, the dynamics of these bundles causes spontaneous turbulent-like flow driven by motion of microscopic molecular motors. We found that confining these active gels in a millimeter sized toroids causes a transition into a new dynamical state characterized by circulation currents persisting for hours until ATP is depleted. We show how toroid dimensions impact the properties of self-organized circular currents, how directions of circulation can be designed by engineering ratchet-shaped boundaries, and how circulations of connected toroids can be either synchronized or antisynchronized. Furthermore, we demonstrate that the flow rate in the circulation is independent of curvature and length of flow path. The flow rate persists for centimeters without decay, disregarding conventional pipe flow resistance. Such findings pave the path to self-pumping pipe transport and performing physical work with biological system.

  8. Effectiveness of mineral admixtures in reducing ASR expansion

    SciTech Connect

    Xu, G.J.Z.; Watt, D.F.; Hudec, P.P.

    1995-08-01

    This paper investigates the effectiveness of eight mineral admixtures in reducing the alkali silica(te) reactivity of cement mortar. The admixtures include one class F fly ash, a condensed silica fume, a ground fiberglass, three glass containing waste materials, and two inert fillers (carbon and calcium carbonate). Mortar bar expansion, the change in evaporable water content, the evidence of reaction and the composition of reaction products were studied. It was found that shale is the only reactive component of the sand and the effectiveness of admixtures in reducing alkali-silica reaction depends largely on the chemical composition of the admixtures. Ground fiberglass is very effective in controlling the alkali silica reaction, while inert fillers have only a dilution effect. It is thought that admixtures reduce ASR expansion by two reactions: (1) pozzolanic reaction that reduces the permeability of concrete and entraps some fraction of the alkali ions; (2) alkali silica reaction that consumes most of the available alkali ions and thereby prevents the reaction between alkalis and aggregate.

  9. Human glans penis augmentation using injectable hyaluronic acid gel.

    PubMed

    Kim, J J; Kwak, T I; Jeon, B G; Cheon, J; Moon, D G

    2003-12-01

    Although augmentation phalloplasty is not an established procedure, some patients still need enlargement of their penis. Current penile augmentation is girth enhancement of penile body by dermofat graft. We performed this study to identify the efficacy and the patient's satisfaction of human glans penis augmentation with injectable hyaluronic acid gel. In 100 patients of subjective small penis (Group I) and 87 patients of small glans after dermofat graft (Group II), 2 cm(3) of hyaluronic acid gel was injected into the glans penis, subcutaneously. At 1 y after injection, changes of glandular diameter were measured by tapeline. Patient's visual estimation of glandular size (Gr 0-4) and patient's satisfaction (Grade (Gr) 0-4) were evaluated, respectively. Any adverse reactions were also evaluated. The mean age of patients was 42.2 (30-70) y in Group I and 42.13 (28-61) y in Group II. The maximal glandular circumference was significantly increased compared to basal circumference of 9.13+/-0.64 cm in Group I (P<0.01) and 9.49+/-1.05 cm in Group II (P<0.01) at 1 y after injection. Net increase of maximal glandular circumference after glans augmentation was 14.93+/-0.80 mm in Group I and 14.78+/-0.89 mm in Group II. In patient's visual estimation, more than 50% of injected volume was maintained in 95% of Group 1 and 100% of Group II. The percentage of postoperative satisfaction (Gr 4, 5) was 77% in Group 1 and 69% in Group II. There was no abnormal reaction in area feeling, texture, and color. In most cases, initial discoloration by glandular swelling recovered to normal within 2 weeks. There were no signs of inflammation and no serious adverse reactions in all cases. These results suggest that injectable hyaluronic acid gel is a safe and effective material for augmentation of glans penis.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

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

    NASA Astrophysics Data System (ADS)

    Pilařová (Vávrů), Kateřina; Kozubíková, Petra; Šolc, Jaroslav; Spěváček, Václav

    2014-11-01

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

  12. Dermal tolerance and effect on skin hydration of a new ethanol-based hand gel.

    PubMed

    Kampf, G; Muscatiello, M; Häntschel, D; Rudolf, M

    2002-12-01

    We studied the dermal tolerance (repetitive occlusive patch test; ROPT) and the skin hydrating properties of a new ethanol-based gel [85% (w/w)], Sterillium Gel. For the ROPT, 53 participants were studied. Gel was applied to one site on the back under an occlusive patch during an induction phase (nine applications over three weeks) and two weeks later to a virgin site on the back during a challenge phase (one application). Twenty-four hours after the removal of the patches (induction phase and challenge phase), then 48 and 72 h later (challenge phase) sites were graded for skin reactions using a standardized scale. In the induction phase none of the 53 participants had a skin reaction. In the challenge phase one participant had a barely perceptible skin reaction, and one had mild erythema at one time point. To evaluate skin hydrating properties of the gel, treated skin of 21 participants was compared to untreated skin. The gel was applied twice a day to the forearm for 14 days. Control corneometer values were taken before application of the gel (mean: 32.7 +/- 5.0) and after one (36.3 +/- 4.4) and two weeks (36.1 +/- 5.4). Relative skin hydration on treated skin in comparison with an untreated control field was significantly higher after one week by 6.85% (P = 0.0031; paired t -test for dependent samples) and after two weeks by 4.47% (P = 0.0153). Sterillium Gel did not demonstrate a clinically relevant potential for dermal irritation or sensitization, and significantly increased skin hydration after repetitive use, and so could enhance compliance with hand hygiene among healthcare workers.

  13. Food gels: gelling process and new applications.

    PubMed

    Banerjee, Soumya; Bhattacharya, Suvendu

    2012-01-01

    Food gels are viscoelastic substances and several gelled products are manufactured throughout the world. The gelling agents in foods are usually polysaccharides and proteins. In food gels, the polymer molecules are not cross-linked by covalent bonds with the exception of disulphide bonds in some protein gels. Instead, the molecules are held together by a combination of weak inter-molecular forces like hydrogen bonds, electrostatic forces, Van der Waals forces, and hydrophobic interactions. Polysaccharides including hydrocolloids are strongly hydrated in aqueous medium but they tend to have less ordered structures. The mechanism of gelation depends on the nature of the gelling agent(s) and on the conditions of gel formation like the temperature, the presence of ions, the pH, and the concentration of gelling agents, etc. Characterization of gels can be performed in several ways of which rheological measurements are frequently practiced. Multi-component or mixed gel system is an important area of interest in which two or more gelling components are simultaneously used to achieve certain specific structural and functional characteristics. We here discuss about the different gels and gelling agents, the characterization of gels, and the mechanism of gelation with an emphasis on mixed or multi-component gels that would have significant commercial applications.

  14. Ionic liquid based multifunctional double network gel

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  15. Conducting Polymer Electrodes for Gel Electrophoresis

    PubMed Central

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

    2014-01-01

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

  16. Tissue simulating gel for medical research

    NASA Technical Reports Server (NTRS)

    Companion, John A. (Inventor)

    1989-01-01

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

  17. Tissue simulating gel for medical research

    NASA Technical Reports Server (NTRS)

    Companion, John A. (Inventor)

    1991-01-01

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

  18. Conducting polymer electrodes for gel electrophoresis.

    PubMed

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

    2014-01-01

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

  19. Sol-Gel synthesis of MgO-SiO2 glass compositions having stable liquid-liquid immiscibility

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1987-01-01

    MgO-SiO2 glasses containing up to 15 mol % MgO, which could not have been prepared by the conventional glass melting method due to the presence of stable liquid-liquid immiscibility, were synthesized by the sol-gel technique. Clear and transparent gels were obtained from the hydrolysis and polycondensation of silicon tetraethoxide (TEOS) and magnesium nitrate hexahydrate when the water/TEOS mole ratio was four or more. The gelling time decreased with increase in magnesium content, water/TEOS ratio, and reaction temperature. Magnesium nitrate hexahydrate crystallized out of the gels containing 15 and 20 mol % MgO on slow drying. This problem was partially alleviated by drying the gels quickly at higher temperatures. Monolithic gel samples were prepared using glycerol as the drying control additive. The gels were subjected to various thermal treatments and characterized by several methods. No organic groups could be detected in the glasses after heat treatments to approx. 800 C, but trace amounts of hydroxyl groups were still present. No crystalline phase was found from X-ray diffraction in the gel samples to approx. 890 C. At higher temperatures, alpha quartz precipitated out as the crystalline phase in gels containing up to 10 mol % MgO. The overall activation energy for gel formation in 10MgO-90SiO2 (mol %) system for water/TEOS mole ratio of 7.5 was calculated to be 58.7 kJ/mol.

  20. A gel-based solid-phase amplification and its application for SNP typing and sequencing on-chip.

    PubMed

    Huang, Huan; Xiao, Pengfeng; Qi, Zongtai; Bu, Ying; Liu, Wenbo; Zhou, Guohua

    2009-12-01

    As conventional solid-phase amplification (SPA) on a two-dimensional slide has a low amplification capacity due to a limited amount of immobilized primers, we propose a three-dimensional SPA by immobilizing primers in hydrogel attached to a slide. One of the PCR primers, modified with an acrylamide group at the 5'-terminal, was copolymerized with both polyacrylamide gel and an acryl-modified glass slide, resulting in a high amplification capacity. The immobilization process was carried out by adding the catalysis reagent N,N,N',N'-tetramethylethylenediamine (TEMED) volatilized in vacuum, with uniform sample-concentration and gel-viscosity in the course of one-step nucleic acid immobilization. The porous structure of polyacrylamide gel, which allows PCR reagents such as Taq DNA polymerase, primers, dNTPs and DNA templates to freely enter the gel matrix, provides a homogeneous solution-mimicking environment for SPA on the interface or the inside of gel pads. Based on gel-based SPA, genotypes of different samples were accurately discriminated by either dual-color fluorescence hybridization or BAMPER (Bioluminometric Assay coupled with Modified Primer Extension Reactions). Pyrosequencing was also successfully carried out on SPA products. As the linkage between DNA molecules and gel is very strong, SPA products immobilized on gel pads could be reused several times if extended strands were removed by electrophoresis. Thus, the gel-based SPA provides a powerful tool for directly using on-chip amplicons for parallel detection.

  1. Achieving synchronization with active hybrid materials: Coupling self-oscillating gels and piezoelectric films

    NASA Astrophysics Data System (ADS)

    Yashin, Victor V.; Levitan, Steven P.; Balazs, Anna C.

    Our goal is to develop materials that compute by using non-linear oscillating chemical reactions to perform spatio-temporal recognition tasks. The material of choice is a polymer gel undergoing the oscillatory Belousov-Zhabotinsky reaction. The novelty of our approach is in employing hybrid gel-piezoelectric micro-electro-mechanical systems (MEMS) to couple local chemo-mechanical oscillations over long distances by electrical connection. Our modeling revealed that (1) interaction between the MEMS units is sufficiently strong for synchronization; (2) the mode of synchronization depends on the number of units, type of circuit connection (serial of parallel), and polarity of the units; (3) each mode has a distinctive pattern in phase of oscillations and generated voltage. The results indicate feasibility of using the hybrid gel-piezoelectric MEMS for oscillator based unconventional computing.

  2. Monte Carlo verification of polymer gel dosimetry applied to radionuclide therapy: a phantom study.

    PubMed

    Gear, J I; Charles-Edwards, E; Partridge, M; Flux, G D

    2011-11-21

    This study evaluates the dosimetric performance of the polymer gel dosimeter 'Methacrylic and Ascorbic acid in Gelatin, initiated by Copper' and its suitability for quality assurance and analysis of I-131-targeted radionuclide therapy dosimetry. Four batches of gel were manufactured in-house and sets of calibration vials and phantoms were created containing different concentrations of I-131-doped gel. Multiple dose measurements were made up to 700 h post preparation and compared to equivalent Monte Carlo simulations. In addition to uniformly filled phantoms the cross-dose distribution from a hot insert to a surrounding phantom was measured. In this example comparisons were made with both Monte Carlo and a clinical scintigraphic dosimetry method. Dose-response curves generated from the calibration data followed a sigmoid function. The gels appeared to be stable over many weeks of internal irradiation with a delay in gel response observed at 29 h post preparation. This was attributed to chemical inhibitors and slow reaction rates of long-chain radical species. For this reason, phantom measurements were only made after 190 h of irradiation. For uniformly filled phantoms of I-131 the accuracy of dose measurements agreed to within 10% when compared to Monte Carlo simulations. A radial cross-dose distribution measured using the gel dosimeter compared well to that calculated with Monte Carlo. Small inhomogeneities were observed in the dosimeter attributed to non-uniform mixing of monomer during preparation. However, they were not detrimental to this study where the quantitative accuracy and spatial resolution of polymer gel dosimetry were far superior to that calculated using scintigraphy. The difference between Monte Carlo and gel measurements was of the order of a few cGy, whilst with the scintigraphic method differences of up to 8 Gy were observed. A manipulation technique is also presented which allows 3D scintigraphic dosimetry measurements to be compared to polymer

  3. Monte Carlo verification of polymer gel dosimetry applied to radionuclide therapy: a phantom study

    NASA Astrophysics Data System (ADS)

    Gear, J. I.; Charles-Edwards, E.; Partridge, M.; Flux, G. D.

    2011-11-01

    This study evaluates the dosimetric performance of the polymer gel dosimeter 'Methacrylic and Ascorbic acid in Gelatin, initiated by Copper' and its suitability for quality assurance and analysis of I-131-targeted radionuclide therapy dosimetry. Four batches of gel were manufactured in-house and sets of calibration vials and phantoms were created containing different concentrations of I-131-doped gel. Multiple dose measurements were made up to 700 h post preparation and compared to equivalent Monte Carlo simulations. In addition to uniformly filled phantoms the cross-dose distribution from a hot insert to a surrounding phantom was measured. In this example comparisons were made with both Monte Carlo and a clinical scintigraphic dosimetry method. Dose-response curves generated from the calibration data followed a sigmoid function. The gels appeared to be stable over many weeks of internal irradiation with a delay in gel response observed at 29 h post preparation. This was attributed to chemical inhibitors and slow reaction rates of long-chain radical species. For this reason, phantom measurements were only made after 190 h of irradiation. For uniformly filled phantoms of I-131 the accuracy of dose measurements agreed to within 10% when compared to Monte Carlo simulations. A radial cross-dose distribution measured using the gel dosimeter compared well to that calculated with Monte Carlo. Small inhomogeneities were observed in the dosimeter attributed to non-uniform mixing of monomer during preparation. However, they were not detrimental to this study where the quantitative accuracy and spatial resolution of polymer gel dosimetry were far superior to that calculated using scintigraphy. The difference between Monte Carlo and gel measurements was of the order of a few cGy, whilst with the scintigraphic method differences of up to 8 Gy were observed. A manipulation technique is also presented which allows 3D scintigraphic dosimetry measurements to be compared to polymer

  4. Sol-gel chemistry-based Ucon-coated columns for capillary electrophoresis.

    PubMed

    Hayes, J D; Malik, A

    1997-07-18

    A sol-gel chemistry-based novel approach for the preparation of a Ucon-coated fused-silica capillary column in capillary electrophoresis is presented. In this approach the sol-gel process is carried out inside 25 microm I.D. fused-silica capillaries. The sol solution contained appropriate quantities of an alkoxide-based sol-gel precursor, a polymeric coating material (Ucon), a crosslinking reagent, a surface derivatizing reagent, controlled amounts of water and a catalyst dissolved in a suitable solvent system. The coating procedure involves filling a capillary with the sol solution and allowing the sol-gel process to proceed for an optimum period. Hydrolysis of the alkoxide precursor and polycondensation of the hydrolyzed products with the surface silanol groups and the hydroxy-terminated Ucon molecules lead to the formation of a surface-bonded sol-gel coating on the inner walls of the capillary. The thickness of the coated film can be controlled by varying the reaction time, coating solution composition and experimental conditions. Commercial availability of high purity sol-gel precursors (e.g., TEOS 99.999%), the ease of coating, run-to-run and column-to-column reproducibility, and long column lifetimes make sol-gel coating chemistry very much suitable for being applied in analytical microseparations column technology. Test samples of basic proteins and nucleotides were used to evaluate the column performance. These results show that the sol-gel coating scheme has allowed for the generation of bio-compatible surfaces characterized by high separation efficiencies in CE. For different types of solutes, the sol-gel coated Ucon column consistently provided migration time R.S.D. values of the order of 0.5%.

  5. Ultrafast Sol-Gel Synthesis of Graphene Aerogel Materials

    SciTech Connect

    Lim, Mathew; Hu, Matthew; Manandhar, Sandeep; Sakshaug, Avery; Strong, Adam; Riley, Leah; Pauzauskie, Peter J.

    2015-12-01

    Graphene aerogels derived from graphene-oxide (GO) starting materials recently have been shown to exhibit a combination of high electrical conductivity, chemical stability, and low cost that has enabled a range of electrochemical applications. Standard synthesis protocols for manufacturing graphene aerogels require the use of sol-gel chemical reactions that are maintained at high temperatures for long periods of time ranging from 12 hours to several days. Here we report an ultrafast, acid-catalyzed sol-gel formation process in acetonitrile in which wet GO-loaded gels are realized within 2 hours at temperatures below 45°C. Spectroscopic and electrochemical analysis following supercritical drying and pyrolysis confirms the reduction of the GO in the aerogels to sp2 carbon crystallites with no residual carbon–nitrogen bonds from the acetonitrile or its derivatives. This rapid synthesis enhances the prospects for large-scale manufacturing of graphene aerogels for use in numerous applications including sorbents for environmental toxins, support materials for electrocatalysis, and high-performance electrodes for electrochemical capacitors and solar cells.

  6. Aligning Goals, Assessments, and Activities: An Approach to Teaching PCR and Gel Electrophoresis

    ERIC Educational Resources Information Center

    Phillips, Allison R.; Robertson, Amber L.; Batzli, Janet; Harris, Michelle; Miller, Sarah

    2008-01-01

    Polymerase chain reaction (PCR) and gel electrophoresis have become common techniques used in undergraduate molecular and cell biology labs. Although students enjoy learning these techniques, they often cannot fully comprehend and analyze the outcomes of their experiments because of a disconnect between concepts taught in lecture and experiments…

  7. Aligning Goals, Assessments, and Activities: An Approach to Teaching PCR and Gel Electrophoresis

    ERIC Educational Resources Information Center

    Phillips, Allison R.; Robertson, Amber L.; Batzli, Janet; Harris, Michelle; Miller, Sarah

    2008-01-01

    Polymerase chain reaction (PCR) and gel electrophoresis have become common techniques used in undergraduate molecular and cell biology labs. Although students enjoy learning these techniques, they often cannot fully comprehend and analyze the outcomes of their experiments because of a disconnect between concepts taught in lecture and experiments…

  8. Viscoelastic Properties of Vitreous Gel

    NASA Astrophysics Data System (ADS)

    Pirouz Kavehpour, H.; Sharif-Kashani, Pooria

    2010-11-01

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

  9. Simple procedure for preparation of bluetongue virus and epizootic hemorrhagic disease virus antigens for agar gel immunodiffusion.

    PubMed

    Stott, J L; Osburn, B I

    1983-12-01

    A simplified procedure was developed for preparing soluble antigen from two related orbiviruses, bluetongue and epizootic hemorrhagic disease viruses, for agar gel immunodiffusion. The antigens gave excellent results in both micro-agar gel diffusion (agar gel precipitin) and macro-agar gel diffusion (bluetongue immunodiffusion). Minor modification in the spatial arrangement of reference antisera, commonly utilized in the agar gel immunodiffusion tests, was employed to reduce the possible development of false-positive reactions. The procedures for antigen preparation were inexpensive and did not require elaborate filtration or high-speed centrifugation. Stability of antigen preparations at 5 degrees C was excellent (in excess of 3 years for bluetongue virus and 2 years for epizootic hemorrhagic disease virus).

  10. A Simple Vertical Slab Gel Electrophoresis Apparatus.

    ERIC Educational Resources Information Center

    Carter, J. B.; And Others

    1983-01-01

    Describes an inexpensive, easily constructed, and safe vertical slab gel kit used routinely for sodium dodecyl sulphate-polyacrylamide gel electrophoresis research and student experiments. Five kits are run from a single transformer. Because toxic solutions are used, students are given plastic gloves and closely supervised during laboratory…

  11. A Short-Duration Gel Diffusion Experiment.

    ERIC Educational Resources Information Center

    Mulcahy, D. E.

    1980-01-01

    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)

  12. Flow of colloidal suspensions and gels

    NASA Astrophysics Data System (ADS)

    Zia, Roseanna

    Our recent studies of yield of colloidal gels under shear show that yield in such gels occurs in distinct stages. Under fixed stress, yield follows a finite delay period of slow solid-like creep. Post yield, the gel fluidizes and may undergo long-time viscous flow or, in some cases, may re-solidify. Under imposed strain rate, the transition from equilibrium to long-time flow is characterized by one or more stress overshoots, signifying a yield process here as well. These rheological changes are accompanied by evolution in morphology and dynamics of the gel network. Similar regimes have been observed in gels subjected to gravitational forcing; the gel initially supports its own weight, or perhaps undergoes slow, weak compaction. This may be followed by a sudden transition to rapid compaction or sedimentation. Various models have been put forth to explain these behaviors based on structural evolution, but this detail is difficult to observe in experiment. Here we examine the detailed microstructural evolution and rheology of reversible colloidal gels as they deform under gravity, identifying the critical buoyant force at which yield occurs, the role played by ongoing gel coarsening, and similarities and differences compared to yield under shear. We gratefully acknowledge the support of the NSF XSEDE Computational Resource, the NSF Early CAREER Program, and the Office of Naval Research Young Investigator Program.

  13. Acoustic images of gel dosimetry phantoms

    NASA Astrophysics Data System (ADS)

    Vieira, Silvio L.; Baggio, André; Kinnick, Randall R.; Fatemi, M.; Carneiro, Antonio Adilton O.

    2010-01-01

    This work presents Vibro-acoustography (VA) as a tool to visualize absorbed dose in a polymer gel dosimetry phantom. VA relies on the mechanical excitation introduced by the acoustic radiation force of focused modulated ultrasound in a small region of the object. A hydrophone or microphone is used to measure the sound emitted from the object in response to the excitation, and by using the amplitude or phase of this signal, an image of the object can be generated. To study the phenomena of dose distribution in a gel dosimetry phantom, continuous wave (CW), tone burst and multi-frequency VA were used to image this phantom. The phantom was designed using 'MAGIC' gel polymer with addition of glass microspheres at 2% w/w having an average diameter range between 40-75 μm. The gel was irradiated using conventional 10 MeV X-rays from a linear accelerator. The field size in the surface of the phantom was 1.0×1.0 cm2 and a source-surface distance (SSD) of 100 cm. The irradiated volume corresponds to an approximately 8.0 cm3, where a dose of 50 gray was delivered to the gel. Polymer gel dosimeters are sensitive to radiation-induced chemical changes that occur in the irradiated polymer. VA images of the gel dosimeter showed the irradiate area. It is concluded that VA imaging has potential to visualize dose distribution in a polymer gel dosimeter.

  14. Halogen-bonding-triggered supramolecular gel formation.

    PubMed

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

    2013-01-01

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

  15. SDS-Polyacrylamide Gel Electrophoresis of Proteins.

    PubMed

    Sambrook, Joseph; Russell, David W

    2006-09-01

    INTRODUCTIONThis protocol describes the separation of proteins by SDS-polyacrylamide gel electrophoresis. SDS is used with a reducing agent and heat to dissociate the proteins. SDS-polypeptide complexes form and migrate through the gels according to the size of the polypeptide. By using markers of known molecular weight, the molecular weight of the polypeptide chain(s) can be estimated.

  16. 21 CFR 866.4900 - Support gel.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Support gel. 866.4900 Section 866.4900 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents § 866.4900 Support gel....

  17. 21 CFR 866.4900 - Support gel.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Support gel. 866.4900 Section 866.4900 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents § 866.4900 Support gel....

  18. 21 CFR 866.4900 - Support gel.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Support gel. 866.4900 Section 866.4900 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents § 866.4900 Support gel....

  19. Staining proteins in gels with coomassie blue.

    PubMed

    Simpson, Richard J

    2007-04-01

    INTRODUCTIONThe most commonly used dye for visualizing proteins in SDS-PAGE gels is Coomassie Brilliant Blue R250 (CBR-250) because of its relatively high sensitivity. This protocol describes the standard CBR-250 staining method, along with a simple method for preparing stained gels for long-term storage.

  20. A Simple Vertical Slab Gel Electrophoresis Apparatus.

    ERIC Educational Resources Information Center

    Carter, J. B.; And Others

    1983-01-01

    Describes an inexpensive, easily constructed, and safe vertical slab gel kit used routinely for sodium dodecyl sulphate-polyacrylamide gel electrophoresis research and student experiments. Five kits are run from a single transformer. Because toxic solutions are used, students are given plastic gloves and closely supervised during laboratory…

  1. 21 CFR 866.4900 - Support gel.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Support gel. 866.4900 Section 866.4900 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents § 866.4900 Support gel. (a...

  2. 21 CFR 866.4900 - Support gel.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Support gel. 866.4900 Section 866.4900 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents § 866.4900 Support gel. (a...

  3. How to Use Eye Ointments and Gels

    MedlinePlus

    How to Use Eye Ointments and GelsWash your hands thoroughly with soap and water. Avoid touching the tip of the tube against your eye or ... 0.6- to 1.25-centimeter) ribbon of ointment or gel into the pocket made by the ...

  4. Using Greener Gels to Explore Rheology

    ERIC Educational Resources Information Center

    Garrett, Brendan; Matharu, Avtar S.; Hurst, Glenn A.

    2017-01-01

    A laboratory experiment was developed to investigate the rheological properties of a green calcium-cross-linked alginate gel as an alternative to the traditional borax-cross-linked poly(vinyl alcohol) gel. As borax is suspected of damaging fertility and the unborn child, a safe, green alternative is necessary. The rheological properties of a…

  5. Fluorescence detection for gel and capillary electrophoresis

    SciTech Connect

    Hogan, B.

    1992-07-21

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

  6. Gel bead composition for metal adsorption

    SciTech Connect

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

    1990-12-18

    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.

  7. Mechanical properties of active polyacrylonitrile gels

    NASA Astrophysics Data System (ADS)

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

    1999-05-01

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

  8. Enantioselective Recognition by Chiral Supramolecular Gels.

    PubMed

    Zhang, Li; Jin, Qingxian; Liu, Minghua

    2016-10-06

    Chiral supramolecular gels, in which small organic molecules self-assemble into chiral nanostructures and entangle each other to immobilize solvents through various noncovalent interactions, can work as a matrix for enantioselective recognition on chiral analytes. Through gelation and the formation of well-defined nanostructures, the chiral sense of the component molecules can be accumulated or amplified, and thus, the enantioselective recognition ability can be enhanced. Furthermore, a chiral microenvironment formed in the gel networks could provide additional stereochemical recognition geometry and attribute to efficient recognition. In this focus review, enantioselective recognition on chiral analytes through chiral supramolecular gels, with either amplified signals or the gel-sol phase transition, is discussed. This review is expected to provide useful insights into the design and fabrication of supramolecular gel systems with chiral features and high enantioselectivity.

  9. Catalytic control over supramolecular gel formation

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

  10. Catalytic control over supramolecular gel formation.

    PubMed

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

    2013-05-01

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

  11. Tunable Gas Sensing Gels by Cooperative Assembly

    PubMed Central

    Hussain, Abid; Semeano, Ana T. S.; Palma, Susana I. C. J.; Pina, Ana S.; Almeida, José; Medrado, Bárbara F.; Pádua, Ana C. C. S.; Carvalho, Ana L.; Dionísio, Madalena; Li, Rosamaria W. C.; Gamboa, Hugo; Ulijn, Rein V.; Gruber, Jonas; Roque, Ana C. A.

    2017-01-01

    The cooperative assembly of biopolymers and small molecules can yield functional materials with precisely tunable properties. Here, the fabrication, characterization, and use of multicomponent hybrid gels as selective gas sensors are reported. The gels are composed of liquid crystal droplets self-assembled in the presence of ionic liquids, which further coassemble with biopolymers to form stable matrices. Each individual component can be varied and acts cooperatively to tune gels’ structure and function. The unique molecular environment in hybrid gels is explored for supramolecular recognition of volatile compounds. Gels with distinct compositions are used as optical and electrical gas sensors, yielding a combinatorial response conceptually mimicking olfactory biological systems, and tested to distinguish volatile organic compounds and to quantify ethanol in automotive fuel. The gel response is rapid, reversible, and reproducible. These robust, versatile, modular, pliant electro-optical soft materials possess new possibilities in sensing triggered by chemical and physical stimuli. PMID:28747856

  12. Photoswitchable gel assembly based on molecular recognition

    PubMed Central

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

    2012-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  14. Transparent poly(vinyl acetate)-silica gels by a sol-gel process

    NASA Astrophysics Data System (ADS)

    Wojcik, Anna B.; Klein, Lisa C.

    1993-12-01

    Rod shaped silica-poly(vinyl acetate) (PVAc) gels have been prepared by a sol gel process. In situ polymerization of tetraethoxysilane (TEOS) was accomplished in the presence of low molecular weight PVAc by dissolving various amounts of PVAc in a mixture of TEOS, ethanol, water and hydrochloric acid (HCl). Gelation of this mixture was carried out between room temperature and slightly above. Silica-PVAc rods recovered from cylindrical molds were homogeneous and transparent. Gels with weight percents of PVAc ranging from 2% to 50% were prepared. Silica-PVAc gels have higher flexure strengths, less brittle character and improved water durability in comparison with pure sol- gel silica.

  15. Radiological properties of normoxic polymer gel dosimeters

    SciTech Connect

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

    2005-04-01

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

  16. Indirect fluorescent-antibody and quantitative agar-gel immunodiffusion tests for the serological diagnosis of paracoccidioidomycosis.

    PubMed

    Restrepo, A; Moncada, L H

    1972-07-01

    The value of various serological tests in the diagnosis of paracoccidioidomycosis was studied. Quantitative agar-gel immunodiffusion and indirect immunofluorescent tests were performed, and the results were compared with those of complement fixation and qualitative agar-gel procedures. The quantitative immunodiffusion procedure was found to serve as the simplest and safest quantitative test that could be performed for evaluation purposes, whereas the indirect fluorescent-antibody test gave nonspecific reactions and, as such, proved unsuitable.

  17. Internal structure analysis of particle-double network gels used in a gel organ replica

    NASA Astrophysics Data System (ADS)

    Abe, Mei; Arai, Masanori; Saito, Azusa; Sakai, Kazuyuki; Kawakami, Masaru; Furukawa, Hidemitsu

    2016-04-01

    In recent years, the fabrication of patient organ replicas using 3D printers has been attracting a great deal of attention in medical fields. However, the cost of these organ replicas is very high as it is necessary to employ very expensive 3D printers and printing materials. Here we present a new gel organ replica, of human kidney, fabricated with a conventional molding technique, using a particle-double network hydrogel (P-DN gel). The replica is transparent and has the feel of a real kidney. It is expected that gel organ replicas produced this way will be a useful tool for the education of trainee surgeons and clinical ultrasonography technologists. In addition to developing a gel organ replica, the internal structure of the P-DN gel used is also discussed. Because the P-DN gel has a complex structure comprised of two different types of network, it has not been possible to investigate them internally in detail. Gels have an inhomogeneous network structure. If it is able to get a more uniform structure, it is considered that this would lead to higher strength in the gel. In the present study we investigate the structure of P-DN gel, using the gel organ replica. We investigated the internal structure of P-DN gel using Scanning Microscopic Light Scattering (SMILS), a non-contacting and non-destructive.

  18. Application of melanin-free ink as a new antioxidative gel enhancer in sardine surimi gel.

    PubMed

    Vate, Naveen Kumar; Benjakul, Soottawat; Agustini, Tri Winarni

    2015-08-30

    The squid ink that is discarded as waste during processing can be effectively utilised as a gel enhancer in surimi gels, especially those prepared from dark-fleshed fish which have poor gel properties. It also acts as an antioxidant, inhibiting lipid oxidation. This investigation aimed to study the effect of melanin-free ink (MFI) from splendid squid (Loligo formosana) on properties and oxidative stability of surimi gel from sardine (Sardinella albella). MFI (0-0.1 g kg(-1) surimi) increased the breaking force and deformation of sardine surimi gel in a dose-dependent manner (P < 0.05). The addition of MFI had no effect on whiteness of surimi gels (P > 0.05). The expressible moisture content of gels decreased as the levels of MFI increased (P < 0.05). Based on a microstructure study, gel added with MFI at a level of 0.08 g kg(-1) surimi was denser and finer than that of the control (without MFI). Surimi gels with MFI had lower peroxide values, thiobarbituric acid reactive substances, nonanal and 2-decenal. MFI could improve the properties of sardine surimi gel. Additionally, it was able to prevent lipid oxidation in surimi gels during refrigerated storage. © 2014 Society of Chemical Industry.

  19. Electrophoresis of DNA in agarose gels, polyacrylamide gels and in free solution

    PubMed Central

    Stellwagen, Nancy C.

    2009-01-01

    This review describes the electrophoresis of curved and normal DNA molecules in agarose gels, polyacrylamide gels and in free solution. These studies were undertaken to clarify why curved DNA molecules migrate anomalously slowly in polyacrylamide gels but not in agarose gels. Two milestone papers are cited, in which Ferguson plots were used to estimate the effective pore size of agarose and polyacrylamide gels. Subsequent studies on the effect of the electric field on agarose and polyacrylamide gel matrices, DNA interactions with the two gel matrices, and the effect of curvature on the free solution mobility of DNA are also described. The combined results suggest that the anomalously slow mobilities observed for curved DNA molecules in polyacrylamide gels are due primarily to preferential interactions of curved DNAs with the polyacrylamide gel matrix; the restrictive pore size of the matrix is of lesser importance. In free solution, DNA mobilities increase with increasing molecular mass until leveling off at a plateau value of (3.17 ± 0.01) × 10-4 cm2/Vs in 40 mM Tris-acetate-EDTA buffer at 20°C. Curved DNA molecules migrate anomalously slowly in free solution as well as in polyacrylamide gels, explaining why the Ferguson plots of curved and normal DNAs containing the same number of base pairs extrapolate to different mobilities at zero gel concentration. PMID:19517510

  20. Electrophoresis of DNA in agarose gels, polyacrylamide gels and in free solution.

    PubMed

    Stellwagen, Nancy C

    2009-06-01

    This review describes the electrophoresis of curved and normal DNA molecules in agarose gels, polyacrylamide gels and in free solution. These studies were undertaken to clarify why curved DNA molecules migrate anomalously slowly in polyacrylamide gels but not in agarose gels. Two milestone papers are cited, in which Ferguson plots were used to estimate the effective pore size of agarose and polyacrylamide gels. Subsequent studies on the effect of the electric field on agarose and polyacrylamide gel matrices, DNA interactions with the two gel matrices, and the effect of curvature on the free solution mobility of DNA are also described. The combined results suggest that the anomalously slow mobilities observed for curved DNA molecules in polyacrylamide gels are primarily due to preferential interactions of curved DNAs with the polyacrylamide gel matrix; the restrictive pore size of the matrix is of lesser importance. In free solution, DNA mobilities increase with increasing molecular mass until leveling off at a plateau value of (3.17 +/- 0.01) x 10(-4) cm2/V s in 40 mM Tris-acetate-EDTA buffer at 20 degrees C. Curved DNA molecules migrate anomalously slowly in free solution as well as in polyacrylamide gels, explaining why the Ferguson plots of curved and normal DNAs containing the same number of base pairs extrapolate to different mobilities at zero gel concentration.

  1. Sol-gel composite material characteristics caused by different dielectric constant sol-gel phases

    NASA Astrophysics Data System (ADS)

    Kimoto, Keisuke; Matsumoto, Makoto; Kaneko, Tsukasa; Kobayashi, Makiko

    2016-07-01

    Ultrasonic transducers prepared by a sol-gel composite method have been investigated in the field of nondestructive testing (NDT). Sol-gel composite materials could be ideal piezoelectric materials for ultrasonic transducer applications in the NDT field, and a new sol-gel composite with desirable characteristics has been developed. Three kinds of sol-gel composite materials composed of different dielectric constant sol-gel phases, Pb(Zr,Ti)O3 (PZT), Bi4Ti3O12 (BiT), and BaTiO3 (BT), and the same piezoelectric powder phase, PbTiO3 (PT), were fabricated and their properties were compared quantitatively. As a result, the PT/BT, sol-gel composite with the highest dielectric constant sol-gel phase showed the highest d 33 and signal strength. In addition, only PT/BT was successfully poled by room-temperature corona poling with reasonable signal strength.

  2. Effect of sugarcane biopolymer gel injected in rabbit vocal fold.

    PubMed

    Leão, Rodrigo Augusto de Souza; Assis, Raquel Coelho de; Caldas Neto, Silvio da Silva; Lira, Mariana Montenegro de Melo; Vasconcelos, Silvio José de

    2014-01-01

    Alterations in the vocal folds that involve volume reduction and glottal closure failure result in exaggerated air escape during speech. For such situations, the use of implants or grafts of different materials has been proposed. To define the effect of sugarcane biopolymer gel when implanted in the vocal folds of rabbits. This was an experimental study. The vocal folds of rabbits injected with sugarcane biopolymer and saline solution were histologically evaluated after 21 and 90 days. Mild to moderate inflammation and increased volume were observed in all vocal folds injected with biopolymer, when compared to controls. There were no cases of necrosis or calcification. This study showed higher inflammatory reaction in cases than in controls and biopolymer biointegration to the vocal fold. This fibrogenic response with absence of epithelial repercussions suggests that the biopolymer in its gel form can be bioactive and preserve the normal vibratory function of the epithelium. We show that in spite of producing an inflammatory reaction in vocal fold tissues, the material remained in vocal fold throughout the study period.

  3. Silver-stained fibrin zymography: separation of proteases and activity detection using a single substrate-containing gel.

    PubMed

    Chung, Dong-Min; Kim, Ki Eun; Ahn, Keug-Hyun; Park, Chan-Sun; Kim, Dong-Ho; Koh, Hong Bum; Chun, Hyo Kon; Yoon, Byung-Dae; Kim, Hong Jib; Kim, Min-Soo; Choi, Nack-Shick

    2011-08-01

    A new zymogram method, silver-stained fibrin zymography, for separation of protease bands and activity detection using a single substrate gel, was developed. The method takes advantage of the nanoscale sensitivity of both zymography and silver staining. After SDS-PAGE in a gel containing fibrin, the gel was incubated in enzyme reaction buffer and the zymogram was silver-stained. Bands with protease activity were stained with silver in clear areas where the protein substrate had been degraded. The molecular sizes of proteases were accurately determined. Furthermore, proteases of high molecular weight were clearly and sharply resolved.

  4. A direct method of quantification of maximal chemisorption of 3-aminopropylsilyl groups on silica gel using DRIFT spectroscopy

    NASA Astrophysics Data System (ADS)

    Bukleski, Miha; Ivanovski, Vladimir; Hey-Hawkins, Evamarie

    2015-10-01

    3-Aminopropylsilyl (APS) modified silica gel plays an important role as a precursor for further modifications, where APS acts as a spacer or bridging molecule. A monolayer of APS which is most suitable for this purpose was obtained in anhydrous conditions. The properties of the APS-modified silica gel depend on the amount of molecules chemisorbed on the surface. A direct quantitative method using Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy was proposed. The obtained results were further supported by elemental analysis. The conclusion was that the proposed methodology can be used for the quantification of APS groups chemisorbed on silica gel when the grafting chemical reaction was mainly irreversible.

  5. Agarose gel purification of PCR products for denaturing gradient gel electrophoresis results in GC-clamp deletion.

    PubMed

    Sun, Guowei; Xiao, Jinzhou; Lu, Man; Wang, Hongming; Chen, Xiaobing; Yu, Yongxin; Pan, Yingjie; Wang, Yongjie

    2015-01-01

    The 16S ribosomal RNA (rRNA) gene of marine archaeal samples was amplified using a nested PCR approach, and the V3 region of 16S rRNA gene of crab gut microbiota (CGM) was amplified using the V3 universal primer pair with a guanine and cytosine (GC)-clamp. Unpurified PCR products (UPPs), products purified from reaction solution (PPFSs), and products purified from gel (PPFGs) of above two DNA samples were used for denaturing gradient gel electrophoresis (DGGE) analysis, respectively. In contrast to almost identical band patterns shared by both the UPP and PPFS, the PPFGs were barely observed on the DGGE gel for both the marine archaea and CGM samples. Both PPFS and PPFG of CGM V3 regions were subjected to cloning. A small amount of positive clones was obtained for PPFS, but no positive clones were observed for PPFG. The melt curve and direct sequencing analysis of PPFS and PPFG of E. coli V3 region indicated that the Tm value of PPFG (82.35 ± 0.19 °C) was less than that of PPFS (83.81 ± 0.11 °C), and the number of shorter GC-clamps was significant higher in PPFG than in PPFS. The ultraviolet exposure experiment indicated that the ultraviolet was not responsible for the deletion of the GC-clamps. We conclude that the gel purification method is not suitable for DGGE PCR products or even other GC-rich DNA samples.

  6. Safety and efficacy of testosterone gel in the treatment of male hypogonadism

    PubMed Central

    Lakshman, Kishore M; Basaria, Shehzad

    2009-01-01

    Transdermal testosterone gels were first introduced in the US in 2000. Since then, they have emerged as a favorable mode of testosterone substitution. Serum testosterone levels reach a steady-state in the first 24 hours of application and remain in the normal range for the duration of the application. This pharmacokinetic profile is comparable to that of testosterone patch but superior to injectable testosterone esters that are associated with peaks and troughs with each dose. Testosterone gels are as efficacious as patches and injectable forms in their effects on sexual function and mood. Anticipated increases in prostate-specific antigen with testosterone therapy are not significantly different with testosterone gels, and the risk of polycythemia is lower than injectable modalities. Application site reactions, a major drawback of testosterone patches, occur less frequently with testosterone gels. However, inter-personal transfer is a concern if appropriate precautions are not taken. Superior tolerability and dose flexibility make testosterone gel highly desirable over other modalities of testosterone replacement. Androgel and Testim, the two currently available testosterone gel products in the US, have certain brand-specific properties that clinicians may consider prior to prescribing. PMID:19966909

  7. Rheological characteristics of heat-induced custard pudding gels with high antioxidative activity.

    PubMed

    Sun, Yuanxia; Hayakawa, Shigeru; Jiang, Huihong; Ogawa, Masahiro; Izumori, Ken

    2006-12-01

    Custard pudding gels were prepared from fresh whole egg, milk and sugar. The effects of D-psicose (Psi), a non-calorie rare hexose, on the antioxidative activity and rheological properties of the custard pudding gels were investigated at different temperatures for comparison with those of control sugars (sucrose, Suc; D-fructose, Fru). The rheological behavior of the heat-induced pudding gels was evaluated by using breaking and creep tests. During the heat-induced gel formation, custard pudding containing Psi (15%, wt/wt) demonstrated a stronger breaking strength and higher viscoelasticity than those containing Fru and Suc. The thermodynamic parameters obtained from DSC indicated that the egg white (EW) proteins were made less thermally stable when heated in the presence of Psi than in the presence of Fru and Suc. These findings are consistent with enhanced aggregation of the EW solution in the presence of Psi. Furthermore, the Psi pudding gels possessed higher antioxidative activity than the control sugar pudding gels by using an analysis of the scavenging activity on DPPH radicals and the ferric-reducing antioxidative power. These results suggest that Psi favored cross-linking of Psi-protein molecules through the Maillard reaction which increased the formation of intermediate products to improve functionality. Custard pudding containing Psi could therefore be an effective functional sweet desert with high antioxidative activity and the outstanding gelling characteristics.

  8. Mesoscopic study of the effects of gel concentration and materials on the formation of precipitation patterns.

    PubMed

    Chen, Li; Kang, Qinjun; He, Ya-Ling; Tao, Wen-Quan

    2012-08-14

    A mesoscopic model based on the lattice Boltzmann method (LBM) is proposed to simulate the formation of Liesegang precipitation patterns and investigate the effects of gel on the morphology of the precipitates. In this model, nucleation is introduced on the basis of Ostwald's supersaturation theory, and subsequent crystal growth on the precipitate surface is simulated using a crystal growth model by taking into account the heterogeneous reaction on the surface of the precipitate. This model can capture the porous structures of the precipitates and can take into account the effects of the gel concentration and material by adjusting the gel porosity and nucleation threshold. The density of the precipitate nodes in the model is limited. A wide range of precipitation patterns is predicted under different gel concentrations, including regular bands, treelike patterns, and for the first time with numerical models, transition patterns between regular bands and treelike patterns. Both the spacing law and the width law are carefully investigated with different gel concentrations and gel materials, and the obtained α in the width law (w(n) ≈ x(n)(α), where x(n) and w(n) are the position and the width of the nth band, respectively) is in the range of 0.58-0.67, sandwiched by previously predicted ranges.

  9. Randomized controlled trial on the treatment of otitis externa with one per cent silver nitrate gel.

    PubMed

    van Hasselt, Piet; Gudde, Hugo

    2004-02-01

    Otitis externa (OE) and especially otomycosis can be very persistent and difficult to control. In the present study the efficacy of treatment of OE with a single instillation in the ear canal of one per cent silver nitrate in three per cent hypromellose gel compared to 0.1 per cent silver nitrate gel was tested in a single-blinded randomized controlled parallel group study. The outcome measure was complete resolution of the OE after one week. Forty-four patients with refractory, bacterial as well as fungal, OE entered the study, comprising 30 ears in each treatment arm. Eight patients defaulted from follow-up, five ears in each treatment arm. A single instillation of one per cent silver nitrate gel cured 23 (92 per cent) of 25 ears with OE, whereas with 0.1 per cent silver nitrate gel seven (28 per cent) of 25 ears treated were cured (Fisher-exact test, p-exact = 0.00010). In a non-controlled series of 120 ears 93.3 per cent needed only a single instillation of one per cent silver nitrate gel while another five per cent were cured after a second instillation a week later. There were no adverse reactions. OE can be treated effectively with instillation of one per cent silver nitrate gel and is particularly useful in recalcitrant otomycosis. The treatment method saves both cost and time.

  10. Lip augmentation with a new filler (agarose gel): a 3-year follow-up study.

    PubMed

    Scarano, Antonio; Carinci, Francesco; Piattelli, Adriano

    2009-08-01

    Many fillers have been used to augment lips. Agarose gel is a new and absorbable filler indicated for the correction of soft tissues and lip. This article reviews the results of 68 cases that have undergone lip augmentation with this new filler in the last 3 years. A total of 68 patients received agarose gel for treatment for lip augmentation in a 3-year period from 2005 to 2008. Each of the patients signed an informed consent form. The patients were between 35 and 70 years of age. Three patients were male, and 65 were female. A volume of 0.5-1.0 mL of agarose gel was sufficient for each lip. A bigger volume may result in a dense mass and pain. All patients were successfully treated with injections of agarose gel. Clinical improvement was noted immediately, and only mild bruising was recorded. All of the the patients returned to the clinic 10 days after treatment for follow-up, and all felt that an excellent cosmetic result was obtained. The patients were told to return after an additional month for follow-up and possible reinjection. The results lasted approximately 5 months with a gradual decline to baseline. The agarose gel was very well tolerated with only a few mild adverse reactions that resolved spontaneously. During 3 years of clinical use, agarose gel proved to be a reliable and predictable treatment for lip augmentation.

  11. Electrokinetics of nanoparticle gel-electrophoresis.

    PubMed

    Hill, Reghan J

    2016-09-28

    Gel-electrophoresis has been demonstrated in recent decades to successfully sort a great variety of nanoparticles according to their size, charge, surface chemistry, and corona architecture. However, quantitative theoretical interpetations have been limited by the number and complexity of factors that influence particle migration. Theoretical models have been fragmented and incomplete with respect to their counterparts for free-solution electrophoresis. This paper unifies electrokinetic models that address complex nanoparticle corona architectures, corona and gel charge regulation (e.g., by the local pH), multi-component electrolytes, and non-linear electrostatics and relaxation effects. By comprehensively addressing the electrokinetic aspects of the more general gel-electrophoresis problem, in which short-ranged steric interactions are significant, a stage is set to better focus on the physicochemical and steric factors. In this manner, it is envisioned that noparticle gel-electrophoresis may eventually be advanced from a nanoparticle-characterization tool to one that explicitly probes the short-ranged interactions of nanoparticles with soft networks, such as synthetic gels and biological tissues. In this paper, calculations are undertaken that identify a generalized Hückel limit for nanoparticles in low-conductivity gels, and a new Smoluchowski limit for polyelectrolyte-coated particles in high-conductivity gels that is independent of the gel permeability. Also of fundamental interest is a finite, albeit small, electrophoretic mobility for uncharged particles in charged gels. Electrophoretic mobilities and drag coefficients (with electroviscous effects) for nanoparticles bearing non-uniform coronas show that relaxation effects are typically weak for the small nanoparticles (radius ≈3-10 nm) to which gel-electrophoresis has customarily been applied, but are profound for the larger nanoparticles (radius ≳ 40 nm in low conductivity gels) to which passivated gel

  12. Exploring macrocycles in functional supramolecular gels: from stimuli responsiveness to systems chemistry.

    PubMed

    Qi, Zhenhui; Schalley, Christoph A

    2014-07-15

    be used as a binding site to allow additional stimuli control. To combine different stimuli for triggering gel-sol transitions certainly expands the options for establishing stimuli responsiveness. If, for example, an agent trapped inside the gel is only liberated when two different stimuli are present simultaneously, its release can be controlled with much higher precision and selectivity compared with a gel that responds to one stimulus only. In this Account, the recent progress in the construction of functional macrocycle-containing supramolecular gels is summarized. First, recent strategies to engineer responsiveness into macrocycle-containing gels are discussed. Next, different functions are presented including applications as responsive reaction media, for controlled drug-delivery or tissue engineering, and as self-healing materials. Finally, we highlight the recent progress in designing macrocycle-containing supramolecular gel materials exhibiting complex behavior. This field is part of systems chemistry and still in its infancy but appears to be one of the most promising routes to smart responsive materials.

  13. Preliminary evaluation of a gel tube agglutination major cross-match method in dogs.

    PubMed

    Villarnovo, Dania; Burton, Shelley A; Horney, Barbara S; MacKenzie, Allan L; Vanderstichel, Raphaël

    2016-09-01

    A major cross-match gel tube test is available for use in dogs yet has not been clinically evaluated. This study compared cross-match results obtained using the gel tube and the standard tube methods for canine samples. Study 1 included 107 canine sample donor-recipient pairings cross-match tested with the RapidVet-H method gel tube test and compared results with the standard tube method. Additionally, 120 pairings using pooled sera containing anti-canine erythrocyte antibody at various concentrations were tested with leftover blood from a hospital population to assess sensitivity and specificity of the gel tube method in comparison with the standard method. The gel tube method had a good relative specificity of 96.1% in detecting lack of agglutination (compatibility) compared to the standard tube method. Agreement between the 2 methods was moderate. Nine of 107 pairings showed agglutination/incompatibility on either test, too few to allow reliable calculation of relative sensitivity. Fifty percent of the gel tube method results were difficult to interpret due to sample spreading in the reaction and/or negative control tubes. The RapidVet-H method agreed with the standard cross-match method on compatible samples, but detected incompatibility in some sample pairs that were compatible with the standard method. Evaluation using larger numbers of incompatible pairings is needed to assess diagnostic utility. The gel tube method results were difficult to categorize due to sample spreading. Weak agglutination reactions or other factors such as centrifuge model may be responsible. © 2016 American Society for Veterinary Clinical Pathology.

  14. Titanium (IV) sol-gel chemistry in varied gravity environments

    NASA Astrophysics Data System (ADS)

    Hales, Matthew; Martens, Wayde; Steinberg, Theodore

    Sol-gel synthesis in reduced gravity is a relatively new topic in the literature and further inves-tigation is essential to realise its potential and application to other sol-gel systems. The sol-gel technique has been successfully applied to the synthesis of silica systems of varying porosity for many diverse applications [1-5]. It is proposed that current methods for the synthesis of silica sol-gels in reduced gravity may be applied to titanium sol-gel processing in order to enhance desirable physical and chemical characteristics of the final materials. The physical and chemical formation mechanisms for titanium alkoxide based sol-gels, to date, is not fully understood. However, various authors [6-9] have described potential methods to control the hydrolysis and condensation reactions of titanium alkoxides through the use of chemical inhibitors. A preliminary study of the reaction kinetics of titanium alkoxide sol-gel reaction in normal gravity was undertaken in order to determine reactant mixtures suitable for further testing under varied gravity conditions of limited duration. Through the use of 1H Nuclear Magnetic Resonance spectroscopy (NMR) for structural analysis of precursor materials, Ultra-Violet-Visible spectroscopy (UV-VIS) and viscosity measurements, it was demonstrated that not only could the rate of the chemical reaction could be controlled, but directed linear chain growth within the resulting gel structure was achievable through the use of increased inhibitor concentrations. Two unique test systems have been fabricated to study the effects of varied gravity (reduced, normal, high) on the formation of titanium sol-gels. Whilst the first system is to be used in conjunction with the recently commissioned drop tower facility at Queensland University of Technology in Brisbane, Australia to produce reduced gravity conditions. The second system is a centrifuge capable of providing high gravity environments of up to 70 G's for extended periods of time

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

    SciTech Connect

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

    1986-08-01

    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.

  16. Demonstration of Thermo-Sensitive Tetra-Gel with Implication for Facile and Versatile Platform for a New Class of Smart Gels.

    PubMed

    Matsumoto, Akira; Sato, Shohei; Sakamaki, Tomoko; Sanjo, Mai; Tabata, Miyuki; Goda, Tatsuro; Asoh, Taka-Aki; Kikuchi, Akihiko; Miyahara, Yuji

    2017-04-10

    A tertiary branched poly(N-isopropylacrylamide) with controlled molecular weight, distribution and the end amino-functionalization (tetra-PNIPAAm-NH2) was studied for the ability to form a gel via in situ chain-end reaction with a counterpart tertiary branched poly(ethyleneglycol) bearing N-hydroxysuccinimide end groups (tetra-PEG-NHS), a well-documented class of building block to yield the tetra-gel. Some of these polymers, both comparable and distinct (relative to the counterpart) extended chain length pairs, provided a self-standing and macroscopically homogeneous gel, which was capable of undergoing thermo-sensitive and reversible change in hydration in line with the nature of PNIPAAm. Phantom network model based calculation indicated that a half molar fraction of the polymer chains in the network remained unreacted, revealing further room for optimizing the reaction condition. Since such tetra-PNIPAAm based motif can be readily tailored to a variety of other physicochemical stimuli-responsive analogues, our finding may give important insight into a platform for "smart" tetra-gels with exceptional mechanical properties and potentially highly controllable molecular cut-off capability.

  17. Human platelet lysate gel provides a novel three dimensional-matrix for enhanced culture expansion of mesenchymal stromal cells.

    PubMed

    Walenda, Gudrun; Hemeda, Hatim; Schneider, Rebekka K; Merkel, Rudolf; Hoffmann, Bernd; Wagner, Wolfgang

    2012-12-01

    Cell culture in regenerative medicine needs to facilitate efficient expansion according to good manufacturing practice requirements. Human platelet lysate (HPL) can be used as a substitute for fetal calf serum without the risk of xenogeneic immune reactions or transmission of bovine pathogens. Heparin needs to be added as anticoagulant before addition of HPL to culture medium; otherwise, HPL-medium forms a gel within 1 h. Here, we demonstrated that such HPL-gels provide a suitable 3D-matrix for cell culture that-apart from heparin-consists of the same components as the over-layered culture medium. Mesenchymal stromal cells (MSCs) grew in several layers at the interface between HPL-gel and HPL-medium without contact with any artificial biomaterials. Notably, proliferation of MSCs was much higher on HPL-gel compared with tissue culture plastic. Further, the frequency of initial fibroblastoid colony forming units (CFU-f) increased on HPL-gel. The viscous consistency of HPL-gel enabled passaging with a convenient harvesting and reseeding procedure by pipetting cells together with their HPL-matrix-this method does not require washing steps and can easily be automated. The immunophenotype and in vitro differentiation potential toward adipogenic, osteogenic, and chondrogenic lineage were not affected by culture-isolation on HPL-gel. Taken together, HPL-gel has many advantages over conventional plastic surfaces: it facilitates enhanced CFU-f outgrowth, increased proliferation rates, higher cell densities, and nonenzymatic passaging procedures for culture expansion of MSCs.

  18. Time-resolved and spatially-resolved infrared spectroscopic observation of seeded nucleation controlling geopolymer gel formation.

    PubMed

    Hajimohammadi, Ailar; Provis, John L; van Deventer, Jannie S J

    2011-05-15

    The effect of seeded nucleation on the formation and structural evolution of one-part ("just add water") geopolymer gels is investigated. Gel-forming systems are seeded with each of three different oxide nanoparticles, and seeding is shown to have an important role in controlling the silica release rate from the solid geothermal silica precursor, and in the development of physical properties of the gels. Nucleation accelerates the chemical changes taking place during geopolymer formation. The nature of the seeds affects the structure of the growing gel by affecting the extent of phase separation, identified by the presence of a distinct silica-rich gel in addition to the main, more alumina-rich gel phase. Synchrotron radiation-based infrared microscopy (SR-FTIR) shows the effect of nucleation on the heterogeneous nanostructure and microstructure of geopolymer gels, and is combined with data obtained by time-resolved FTIR analysis to provide a more holistic view of the reaction processes at a level of detail that has not previously been available. While spatially averaged (ATR-FTIR) infrared results show similar spectra for seeded and unseeded samples which have been cured for more than 3 weeks, SR-FTIR results show marked differences in gel structure as a result of seeding.

  19. Sol-Gel Manufactured Energetic Materials

    DOEpatents

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

    2005-05-17

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

  20. Sol-gel manufactured energetic materials

    DOEpatents

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

    2003-12-23

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

  1. Crystallization of lactose from carbopol gels.

    PubMed

    Zeng, X M; Martin, G P; Marriott, C; Pritchard, J

    2000-07-01

    To crystallize lactose under static conditions with a view to preparing crystals of well-defined morphology. et-Lactose monohydrate was crystallized from neutralized Carbopol 934 gels. When the majority of crystals had grown to maturity, the gels were acidified using diluted hydrochloric acid and the crystals were harvested by filtration or centrifugation and washed with ethanol-water mixtures. Crystals prepared from the gel had a consistently narrower size distribution than control crystals, prepared from solution under constant stirring. If crystallization was effected in the gel without sedimentation of the crystals, then the resultant crystals had smooth surfaces without visually detectable surface roughness or asperities viewed by optical microscopy. The crystals from Carbopol gels also exhibited the uniform shape of an elongated tomahawk regardless of the crystallization conditions, in contrast to crystallization under constant stirring, where the crystal shape of lactose changed with crystallization conditions especially as a function of the initial concentration of lactose. All batches of lactose crystals prepared from Carbopol gels existed as alpha-lactose monohydrate, which showed better flowability than the controls of a similar particle size. Crystallization from Carbopol gel produces lactose crystals of uniform size, regular shape, smooth surface, and improved flowability.

  2. Electroacoustics of Particles Dispersed in Polymer Gel

    SciTech Connect

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

    2011-06-27

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

  3. Polymerase chain reaction in liposomes.

    PubMed

    Oberholzer, T; Albrizio, M; Luisi, P L

    1995-10-01

    Compartmentalization of biochemical reactions within a spherically closed bilayer is an important step in the molecular evolution of cells. Liposomes are the most suitable structures to model this kind of chemistry. We have used the polymerase chain reaction (PCR) to demonstrate that complex biochemical reactions such as DNA replication can be carried out inside these compartments. We describe the first example of DNA amplification by the PCR occurring inside liposomes composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), or of a mixture of POPC and phosphatidylserine. We show that these liposomes are stable even under the high temperature conditions used for PCR. Although only a very small fraction of liposomes contains all eight different reagents together, a significant amount of DNA is produced which can be observed by polyacrylamide gel electrophoresis. This work shows that it is possible to carry out complex biochemical reactions within liposomes, which may be germane to the question of the origin of living cells. We have established the parameters and conditions that are critical for carrying out this complex reaction within the liposome compartment.

  4. Biocompatibility of cross-linked hyaluronate (Gel-200) for the treatment of knee osteoarthritis.

    PubMed

    Ishikawa, M; Yoshioka, K; Urano, K; Tanaka, Y; Hatanaka, T; Nii, A

    2014-11-01

    To compare the biocompatibility and immunogenicity of two intra-articular hyaluronan formulations, Gel-200 (Gel-One(®)) and hylan G-F 20 (Synvisc(®) series). A comparison of the biocompatibility of Gel-200 and hylan G-F 20 was made using a rat subcutaneous air pouch model and the knee joint of normal rabbits. Immunogenicity was evaluated using a homologous passive cutaneous anaphylaxis (PCA) assay in guinea pigs. In the air pouch model in rats, characteristic fibrous belts formed in the subcutaneous tissue. Injection of hylan G-F 20 into the air pouch induced granulomatous nodules primarily composed of macrophages, multinucleated giant cells, and eosinophils accompanied with the test material in the center of the nodules in the fibrous belt. Furthermore, the thickness of the fibrous belt in the hylan G-F 20 group increased significantly compared to the saline group. Injection of Gel-200 into the air pouch induced neither granulomatous inflammation nor significant thickening of fibrous belt, while foamy macrophages containing the test material were observed. Intra-articular injection of hylan G-F 20 into the rabbit knee joints induced granulomatous inflammation, eosinophil infiltration, and significant increase in the number of cells in the synovial fluid, while these findings were absent in the Gel-200 group. In the immunogenicity assay, hylan G-F 20 induced a positive PCA reaction, but the Gel-200 did not. Gel-200 showed more favorable biocompatibility and less immunogenicity compared to hylan G-F 20. Gel-200 is expected to be a single injection hyaluronan product with less safety concerns for the treatment of knee osteoarthritis (OA) pain. Copyright © 2014 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

  5. Exploring encapsulation mechanism of DNA and mononucleotides in sol-gel derived silica.

    PubMed

    Kapusuz, Derya; Durucan, Caner

    2017-07-01

    The encapsulation mechanism of DNA in sol-gel derived silica has been explored in order to elucidate the effect of DNA conformation on encapsulation and to identify the nature of chemical/physical interaction of DNA with silica during and after sol-gel transition. In this respect, double stranded DNA and dAMP (2'-deoxyadenosine 5'-monophosphate) were encapsulated in silica using an alkoxide-based sol-gel route. Biomolecule-encapsulating gels have been characterized using UV-Vis, (29)Si NMR, FTIR spectroscopy and gas adsorption (BET) to investigate chemical interactions of biomolecules with the porous silica network and to examine the extent of sol-gel reactions upon encapsulation. Ethidium bromide intercalation and leach out tests showed that helix conformation of DNA was preserved after encapsulation. For both biomolecules, high water-to-alkoxide ratio promoted water-producing condensation and prevented alcoholic denaturation. NMR and FTIR analyses confirmed high hydraulic reactivity (water adsorption) for more silanol groups-containing DNA and dAMP encapsulated gels than plain silica gel. No chemical binding/interaction occurred between biomolecules and silica network. DNA and dAMP encapsulated silica gelled faster than plain silica due to basic nature of DNA or dAMP containing buffer solutions. DNA was not released from silica gels to aqueous environment up to 9 days. The chemical association between DNA/dAMP and silica host was through phosphate groups and molecular water attached to silanols, acting as a barrier around biomolecules. The helix morphology was found not to be essential for such interaction. BET analyses showed that interconnected, inkbottle-shaped mesoporous silica network was condensed around DNA and dAMP molecules.

  6. Polyphenoloxidases immobilized in organic gels: Properties and applications in the detoxification of aromatic compounds

    SciTech Connect

    Crecchio, C.; Ruggiero, P.; Pizzigallo, M.D.R.

    1995-12-20

    Gelatine gels originate from water in oil microemulsions in which the ternary system consists of isooctane/sulfosuccinic acid bis [2-ethyl hexyl] ester/water; the solubilization of gelatin in the water pool of these microemulsions transforms them into viscous gels in which it is possible to cosolubilize various reactive molecules. These gels were used to immobilize two phenoloxidases, a laccase from Trametes versicolor and a tyrosinase from mushroom. The best balance between gel retention and catalytic activity was reached at a gelatine concentration of 2.5% (w/v) in the case of tyrosinase, while laccase immobilization was independent of gelatine concentration. Both enzymes kept the same optimum pH as the corresponding soluble controls, while a partial loss of activity was observed when they were immobilized. Immobilized enzymes showed an increased stability when incubated for several days at 4 C with a very low release from the gels in the incubation solutions. The immobilization of tyrosinase and of laccase enhanced stability to thermal inactivation. Furthermore, gel-entrapped tyrosinase was almost completely preserved from proteolysis: more than 80% of the activity was maintained, while only 25% of the soluble control activity was detected after the same proteolytic treatments. A column packed with gel-immobilized tyrosinase was used to demonstrate that enzymes immobilized with this technique may be reused several times in the same reaction without loosing their efficiency. Finally, gel-entrapped tyrosinase and laccase were capable of removing naturally occurring and xenobiotic aromatic compounds from aqueous suspensions with different degrees of efficiency.

  7. Preparation, characterization, and catalytic activity of zirconocene bridged on surface of silica gel

    NASA Astrophysics Data System (ADS)

    El Majdoub, Lotfia; Shi, Yasai; Yuan, Yuan; Zhou, Annan; Abutartour, Abubaker; Xu, Qinghong

    2015-10-01

    Zirconocene catalyst supported on silica gel was prepared for olefin polymerization by surface modification of calcined silica with SiCl4, and the reaction between the modified silica and cyclopentadienyl sodium and ZrCl4. The catalyst was characterized by using Fourier-transform infrared (FT-IR) spectrometer, thermogravimetric (TG), and differential scanning calorimetric (DSC) analytic spectrometer. It was found that the metallocene structure could be formed and connected on silica surface by chemical bond. Initial catalytic tests showed that the supported metallocene was catalytically active (methylaluminoxane as a cocatalyst), producing polymer with higher molecular weight than the metallocene just immobilized on the surface of silica gel.

  8. Fabrication of SWNT/silica composites by the sol-gel process.

    PubMed

    Babooram, Keshwaree; Narain, Ravin

    2009-01-01

    Single-walled carbon nanotubes (SWNTs) have successfully been incorporated into a silica matrix using the sol-gel process. The SWNTs were first functionalized with 3-aminopropyltriethoxysilane (APTES) through an amide linkage formed between the carboxylic acid groups already present on their surface and the amino group on APTES. The silane moieties were then used to form silica with and without the presence of tetramethylorthosilicate (TMOS) in a sol-gel reaction. The addition of TMOS was found to influence the molecular arrangement of the SWNT in the silica matrix and also to retard the degradation of the silica-SWNT composite.

  9. Penis invalidating cicatricial outcomes in an enlargement phalloplasty case with polyacrylamide gel (Formacryl).

    PubMed

    Parodi, P C; Dominici, M; Moro, U

    2006-01-01

    The present article reports the case of a patient subjected to polyacrylamide polymers-composed gel cutaneous infiltration in the penis for cosmetic purposes, resulting in severe invalidating outcomes. A significant tissue reaction to the subcutaneous injection of polyacrylamide gel for the penis enlargement purpose resulted in permanent and invalidating scars both on the esthetic and functional levels. Such a result must be simply taken into account both singly and in the light of the international literature to exclude this method as standard uro-andrologic activity.

  10. Novel Sol-Gel Based Pt Nanocluster Catalysts for Propane Dehydrogenation

    SciTech Connect

    Boespflug, Elaine; Kawola, Jeffrey S.; Martino, Anthony; Sault, Allen G.

    1999-08-09

    We report propane dehydrogenation behavior of catalysts prepared using two novel synthesis strategies that combine inverse micelle Pt nanocluster technology with silica and alumina sol-gel processing. Unlike some other sol-gel catalyst preparations. Pt particles in these catalysts are not encapsulated in the support structure and the entire Pt particle surface is accessible for reaction. Turnover frequencies (TOF) for these catalysts are comparable to those obtained over Pt catalysts prepared by traditional techniques such as impregnation, yet the resistance to deactivation by carbon poisoning is much greater in our catalysts. The deactivation behavior is more typical of traditionally prepared PtSn catalysts than of pure Pt catalysts.

  11. Some Thoughts on The Definition of a Gel

    NASA Astrophysics Data System (ADS)

    Nishinari, Katsuyoshi

    To avoid the confusion of the concept of a gel frequently encountered in daily markets of food, cosmetics, and other industrial products, the definition of a gel is revisited. Recent proposals of the definition of a gel are overviewed, and classifications of various gels from different points of view are described. Discussion is mainly focused on the gel-sol transition and the difference between the structured liquid and the gel, and the classification of gels by temperature dependence of elastic modulus. Finally, the definition of a gel is proposed as a working hypothesis from rheological and structural view points.

  12. Analysis of gel heterogeneities on a local level

    NASA Astrophysics Data System (ADS)

    Boyne, Philip; Lechenault, Frederic; Daniels, Karen

    2008-10-01

    We study the heterogeneity of gels near the sol-gel transition through measurements of the spatial variations in gel strength. The correlated motion of fluorescent polystyrene microspheres suspended in gels is measured via two-point microrheology. Analysis of this correlated motion provides a local measure of gel heterogeneity. Additionally, we divide the images into micron-wide squares and determine how rheological properties spatially vary as a function of gel concentration. Our results imply that weaker gels exhibit more heterogeneity than stronger gels.

  13. Control of Drug Diffusion Behavior of Xanthan and Locust Bean Gum Gel by Agar Gel.

    PubMed

    Hishikawa, Yoshihiro; Kakino, Yukari; Tsukamoto, Hoshi; Tahara, Kohei; Onodera, Risako; Takeuchi, Hirofumi

    2016-01-01

    Oral gel formulations are known as easy to administer drug products for patients who have problems taking drugs including those with conditions such as dysphagia. In addition, there are numerous commercially available oral gel products, most of which are immediate-release formulation that release their pharmaceutical ingredient content by diffusion. This study is focused on developing oral gel formulations that reduce the dosing frequency and dosage compared to the conventional types. This is with the aim of facilitating the use of gel formulations for producing pharmaceutical agents with different dose regimens, thereby enhancing patient convenience. Here, we used naturally derived high-molecular-weight agar (Ag), xanthan gum (Xa), and locust bean gum (Lo) as gel bases to prepare a variety of gel membranes, and evaluated the diffusion coefficient of the model substances. The result revealed that the Ag content in the Xa-Lo combination gel concentration-dependently increased the diffusion coefficient. Moreover, these findings were applied in an attempt to mask the taste of intensely bitter levofloxacin. The results indicated that the Xa-Lo combination gel exhibited a significantly superior masking effect to that of the Ag gel. This study demonstrates the feasibility of using oral gel formulations to modulate the controlled-release functionality of pharmaceutical agents.

  14. Simple and practical staining of DNA with GelRed in agarose gel electrophoresis.

    PubMed

    Huang, Qing; Baum, Larry; Fu, Wei-Ling

    2010-01-01

    Although SYBR Gold or SYBR Green I have been used in the loading buffer as a DNA stain safer than ethidium bromide for agarose gel electrophoresis, electrophoretic mobility of DNA is altered and thus DNA fragment size cannot be accurately determined. A method using GelRed in the loading buffer was developed to stain DNA fragments in agarose gel electrophoresis. Among various concentrations of GelRed, SYBR Gold, or SYBR Green I tested in the loading buffer, only the highest tested concentration of GelRed, i.e., 100x GelRed, did not change band mobility. Evaluations using various sizes of PCR products at different concentrations further confirmed that 100x GelRed could be used to accurately determine DNA fragment size. The reagent can be stored at 4 degrees C for at least 1 year without a decrease in staining sensitivity. The 100x GelRed is a sensitive and safe alternative to ethidium bromide and better than either SYBR Gold or SYBR Green I for size determination in agarose gel electrophoresis. Our laboratory now uses the GelRed method routinely with great consistency and success.

  15. Muscular Contraction Mimiced by Magnetic Gels

    NASA Astrophysics Data System (ADS)

    Zrínyi, Miklós; Szabó, Dénes

    The ability of magnetic-field-sensitive gels to undergo a quick controllable change of shape can be used to create an artificially designed system possessing sensor- and actuator functions internally in the gel itself. The peculiar magneto-elastic properties may be used to create a wide range of motion and to control the shape change and movement, that are smooth and gentle similar to that observed in muscle. Magnetic field sensitive gels provide attractive means of actuation as artificial muscle for biomechanics and biomimetic applications.

  16. A randomised experiment comparing low-cost ultrasound gel alternative with commercial gel.

    PubMed

    Riguzzi, Christine; Binkowski, Allison; Butterfield, Mike; Sani, Farhad; Teismann, Nathan; Fahimi, Jahan

    2017-04-01

    Point-of-care ultrasound is a portable, relatively low-cost imaging modality with great potential utility in low-resource settings. However, commercially produced ultrasound gel is often cost-prohibitive and unavailable. We investigated whether images obtained using an alternative cornstarch-based gel would be of comparable quality with those using commercial gel. This was a blinded, randomised, cross-over study comparing commercially produced ultrasound gel with home-made cornstarch-based gel. Ultrasound-trained faculty obtained three video clips with each gel type from patients at one urban ED. The clips were evaluated by a radiologist and an ultrasound-trained emergency physician. Images were assessed in terms of overall adequacy (dichotomous) and quality, resolution and detail using a rating scale (0-10). All sonographers and physicians reviewing the images were blinded to the type of gel used. Thirty-four patients were enrolled in the study, producing 204 separate images (102 with each gel). The cornstarch gel clips were deemed accurate in 70.6% (95% CI 63.9% to 76.5%) of the scans, as compared with 65.2% (95% CI 58.4% to 71.4%) of those using commercial gel. There was no difference between the two groups with respect to image detail, resolution or quality. Images produced using the cornstarch-based alternative ultrasound gel were of similar quality to those using commercial gel. The low cost and easy preparation of the cornstarch-based gel make it an attractive coupling medium for use in low-resource settings. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

  17. Mechanical Properties of Gels; Stress from Confined Fluids

    SciTech Connect

    George W. Scherer

    2009-12-01

    Abstract for Grant DE-FG02-97ER45642 Period: 1997-2002 Mechanical Properties of Gels 2002-2008 Stress from Confined Fluids Principal investigator: Prof. George W. Scherer Dept. Civil & Env. Eng./PRISM Eng. Quad. E-319 Princeton, NJ 08544 USA Recipient organization: Trustees of Princeton University 4 New South Princeton, NJ 08544 USA Abstract: The initial stage of this project, entitled Mechanical Properties of Gels, was dedicated to characterizing and explaining the properties of inorganic gels. Such materials, made by sol-gel processing, are of interest for fabrication of films, fibers, optical devices, advanced insulation and other uses. However, their poor mechanical properties are an impediment in some applications, so understanding the origin of these properties could lead to enhanced performance. Novel experimental methods were developed and applied to measure the stiffness and permeability of gels and aerogels. Numerical simulations were developed to reproduce the growth process of the gels, resulting in structures whose mechanical properties matched the measurements. The models showed that the gels are formed by the growth of relatively robust clusters of molecules that are joined by tenuous links whose compliance compromises the stiffness of the structure. Therefore, synthetic methods that enhance the links could significantly increase the rigidity of such gels. The next stage of the project focused on Stress from Confined Fluids. The first problem of interest was the enhanced thermal expansion coefficient of water that we measured in the nanometric pores of cement paste. This could have a deleterious effect on the resistance of concrete to rapid heating in fires, because the excessive thermal expansion of water in the pores of the concrete could lead to spalling and collapse. A series of experiments demonstrated that the expansion of water increases as the pore size decreases. To explain this behavior, we undertook a collaboration with Prof. Stephen

  18. Hydrogen generation systems utilizing sodium silicide and sodium silica gel materials

    DOEpatents

    Wallace, Andrew P.; Melack, John M.; Lefenfeld, Michael

    2015-07-14

    Systems, devices, and methods combine reactant materials and aqueous solutions to generate hydrogen. The reactant materials can sodium silicide or sodium silica gel. The hydrogen generation devices are used in fuels cells and other industrial applications. One system combines cooling, pumping, water storage, and other devices to sense and control reactions between reactant materials and aqueous solutions to generate hydrogen. Multiple inlets of varied placement geometries deliver aqueous solution to the reaction. The reactant materials and aqueous solution are churned to control the state of the reaction. The aqueous solution can be recycled and returned to the reaction. One system operates over a range of temperatures and pressures and includes a hydrogen separator, a heat removal mechanism, and state of reaction control devices. The systems, devices, and methods of generating hydrogen provide thermally stable solids, near-instant reaction with the aqueous solutions, and a non-toxic liquid by-product.

  19. Hydrogen generation systems utilizing sodium silicide and sodium silica gel materials

    DOEpatents

    Wallace, Andrew P.; Melack, John M.; Lefenfeld, Michael

    2017-06-06

    Systems, devices, and methods combine reactant materials and aqueous solutions to generate hydrogen. The reactant materials can sodium silicide or sodium silica gel. The hydrogen generation devices are used in fuels cells and other industrial applications. One system combines cooling, pumping, water storage, and other devices to sense and control reactions between reactant materials and aqueous solutions to generate hydrogen. Multiple inlets of varied placement geometries deliver aqueous solution to the reaction. The reactant materials and aqueous solution are churned to control the state of the reaction. The aqueous solution can be recycled and returned to the reaction. One system operates over a range of temperatures and pressures and includes a hydrogen separator, a heat removal mechanism, and state of reaction control devices. The systems, devices, and methods of generating hydrogen provide thermally stable solids, near-instant reaction with the aqueous solutions, and a non-toxic liquid by-product.

  20. Multifunctional Nanostructured Conductive Polymer Gels: Synthesis, Properties, and Applications.

    PubMed

    Zhao, Fei; Shi, Ye; Pan, Lijia; Yu, Guihua

    2017-07-18

    Conductive polymers have attracted significant interest over the past few decades because they synergize the advantageous features of conventional polymeric materials and organic conductors. With rationally designed nanostructures, conductive polymers can further exhibit exceptional mechanical, electrical, and optical properties because of their confined dimensions at the nanoscale level. Among various nanostructured conductive polymers, conductive polymer gels (CPGs) with synthetically tunable hierarchical 3D network structures show great potential for a wide range of applications, such as bioelectronics, and energy storage/conversion devices owing to their structural features. CPGs retain the properties of nanosized conductive polymers during the assembly of the nanobuilding blocks into a monolithic macroscopic structure while generating structure-derived features from the highly cross-linked network. In this Account, we review our recent progress on the synthesis, properties, and novel applications of dopant cross-linked CPGs. We first describe the synthetic strategies, in which molecules with multiple functional groups are adopted as cross-linkers to cross-link conductive polymer chains into a 3D molecular network. These cross-linking molecules also act as dopants to improve the electrical conductivity of the gel network. The microstructure and physical/chemical properties of CPGs can be tuned by controlling the synthetic conditions such as species of monomers and cross-linkers, reaction temperature, and solvents. By incorporating other functional polymers or particles into the CPG matrix, hybrid gels have been synthesized with tailored structures. These hybrid gel materials retain the functionalities from each component, as well as enable synergic effects to improve mechanical and electrical properties of CPGs. We then introduce the unique structure-derived properties of the CPGs. The network facilitates both electronic and ionic transport owing to the