Non-Gradient Blue Native Polyacrylamide Gel Electrophoresis.

PubMed

Luo, Xiaoting; Wu, Jinzi; Jin, Zhen; Yan, Liang-Jun

2017-02-02

Gradient blue native polyacrylamide gel electrophoresis (BN-PAGE) is a well established and widely used technique for activity analysis of high-molecular-weight proteins, protein complexes, and protein-protein interactions. Since its inception in the early 1990s, a variety of minor modifications have been made to this gradient gel analytical method. Here we provide a major modification of the method, which we call non-gradient BN-PAGE. The procedure, similar to that of non-gradient SDS-PAGE, is simple because there is no expensive gradient maker involved. The non-gradient BN-PAGE protocols presented herein provide guidelines on the analysis of mitochondrial protein complexes, in particular, dihydrolipoamide dehydrogenase (DLDH) and those in the electron transport chain. Protocols for the analysis of blood esterases or mitochondrial esterases are also presented. The non-gradient BN-PAGE method may be tailored for analysis of specific proteins according to their molecular weight regardless of whether the target proteins are hydrophobic or hydrophilic. © 2017 by John Wiley & Sons, Inc. Copyright © 2017 John Wiley & Sons, Inc.

Application of temperature-gradient gel electrophoresis for detection of prion protein gene polymorphisms in Polish Swiniarka sheep.

PubMed

Jasik, Agnieszka; Reichert, Michal

2006-05-01

This study presents preliminary data on the polymorphism in the prion protein gene of Swiniarka sheep using temperature gradient gel electrophoresis (TGGE). Available data indicate that sensitivity to scrapie is associated with polymorphisms in three codons of prion protein gene: 136,154, and 171. The TGGE method was used to detect point mutations in these codons responsible for sensitivity or resistance to scrapie. This study revealed presence of an allele encoding valine (V) in codon 136, which is associated with high sensitivity to scrapie and occurred in the form of heterozygous allele together with alanine (AV). The highest variability was observed in codon 171, with presence of arginine (R) and glutamine (Q) in the homozygous (RR or QQ) as well as the heterozygous form (RQ). The results of examination of fifty sheep DNA samples with mutations in codons 136, 154, and 171 demonstrated that TGGE can be used as a simple and rapid method to detect mutations in the PrP gene of sheep. Several samples can be run at the same time, making TGGE ideal for the screening of large numbers of samples.

The effect of solute concentration on hindered gradient diffusion in polymeric gels

NASA Astrophysics Data System (ADS)

Buck, Kristan K. S.; Dungan, Stephanie R.; Phillips, Ronald J.

1999-10-01

The effect of solute concentration on hindered diffusion of sphere-like colloidal solutes in stiff polymer hydrogels is examined theoretically and experimentally. In the theoretical development, it is shown that the presence of the gel fibres enhances the effect of concentration on the thermodynamic driving force for gradient diffusion, while simultaneously reducing the effect of concentration on the hydrodynamic drag. The result is that gradient diffusion depends more strongly on solute concentration in gels than it does in pure solution, by an amount that depends on the partition coefficient and hydraulic permeability of the gel solute system. Quantitative calculations are made to determine the concentration-dependent diffusivity correct to first order in solute concentration. In order to compare the theoretical predictions with experimental data, rates of diffusion have been measured for nonionic micelles and globular proteins in solution and agarose hydrogels at two gel concentrations. The measurements were performed by using holographic interferometry, through which one monitors changes in refractive index as gradient diffusion takes place within a transparent gel. If the solutes are modelled as spheres with short-range repulsive interactions, then the experimentally measured concentration dependence of the diffusivities of both the protein and micelles is in good agreement with the theoretical predictions.

Effect of egg albumen protein addition on physicochemical properties and nanostructure of gelatin from fish skin.

PubMed

Cai, Luyun; Feng, Jianhui; Peng, Xichun; Regenstein, Joe M; Li, Xiuxia; Li, Jianrong; Zhao, Wei

2016-12-01

The physicochemical properties and nanostructure of mixtures of egg albumen protein (EAP) and gelatin from under-utilised grass carp ( Ctenopharyngodon idella ) skins were studied. The gelatin with 1% EAP had an acceptable gel strength. The addition of 5% EAP significantly increased the melting and gelling temperatures of gelatin gels. Additionally, the colour turned white and the crystallinity was higher in gelatin gels with gradient concentrations of EAP (1, 3, and 5%). Gelatin with 5% EAP had the highest G' values while gelatin with 1% EAP had the lowest G' values. Atomic force microscopy showed the heterogeneous nanostructure of fish gelatin, and a simple coacervate with a homogeneous distribution was only observed with the addition of 1% EAP, indicating interaction between gelatin and EAP. These results showed that EAP effect fish gelatin's physicochemical and nanostructure properties and has potential applications in foods and pharmaceuticals.

Method for producing small hollow spheres

DOEpatents

Rosencwaig, Allen; Koo, Jackson C.; Dressler, John L.

1981-01-01

A method for producing small hollow spheres of glass having an outer diameter ranging from about 100.mu. to about 500.mu. with a substantially uniform wall thickness in the range of about 0.5-20.mu.. The method involves introducing aqueous droplets of a glass-forming solution into a long vertical drop oven or furnace having varying temperature regions. In one embodiment, one of the temperature regions is lower than both the preceeding region and the subsequent region. One region utilizes a temperature of at least 200.degree. C. higher than the melting point of the glass-forming material in the solution and, for example, may be at least 3 times higher than the temperature of the preceeding region. In addition, there is a sharp temperature gradient between these regions. As each droplet of solution passes through a first region it forms into a gel membrane having a spherical shape and encapsulates the rest of the drop retained in the elastic outer surface and the water entrapped within diffuses rapidly through the thin gel membrane which causes more of the glass-forming material to go out of solution and is incorporated into the gel membrane causing it to grow in size and become hollow. thus produced hollow glass sphere has a sphericity, concentricity, and wall uniformity of better than 5%. The sphere is capable of retaining material of up to at least 100 atmospheres therein over long periods of time. In one embodiment.

Microfluidic device having an immobilized pH gradient and PAGE gels for protein separation and analysis

DOEpatents

Sommer, Gregory J.; Hatch, Anson V.; Singh, Anup K.; Wang, Ying-Chih

2012-12-11

Disclosed is a novel microfluidic device enabling on-chip implementation of a two-dimensional separation methodology. Previously disclosed microscale immobilized pH gradients (IPG) are combined with perpendicular polyacrylamide gel electrophoresis (PAGE) microchannels to achieve orthogonal separations of biological samples. Device modifications enable inclusion of sodium dodecyl sulfate (SDS) in the second dimension. The device can be fabricated to use either continuous IPG gels, or the microscale isoelectric fractionation membranes we have also previously disclosed, for the first dimension. The invention represents the first all-gel two-dimensional separation microdevice, with significantly higher resolution power over existing devices.

Microfluidic device having an immobilized pH gradient and page gels for protein separation and analysis

DOEpatents

Sommer, Gregory J; Hatch, Anson V; Singh, Anup K; Wang, Ying-Chih

2014-05-20

Disclosed is a novel microfluidic device enabling on-chip implementation of a two-dimensional separation methodology. Previously disclosed microscale immobilized pH gradients (IPG) are combined with perpendicular polyacrylamide gel electrophoresis (PAGE) microchannels to achieve orthogonal separations of biological samples. Device modifications enable inclusion of sodium dodecyl sulfate (SDS) in the second dimension. The device can be fabricated to use either continuous IPG gels, or the microscale isoelectric fractionation membranes we have also previously disclosed, for the first dimension. The invention represents the first all-gel two-dimensional separation microdevice, with significantly higher resolution power over existing devices.

Conformal thermal therapy using planar ultrasound transducers and adaptive closed-loop MR temperature control: demonstration in gel phantoms and ex vivo tissues

NASA Astrophysics Data System (ADS)

Tang, K.; Choy, V.; Chopra, R.; Bronskill, M. J.

2007-05-01

MRI-guided transurethral ultrasound therapy offers a minimally invasive approach for the treatment of localized prostate cancer. Integrating a multi-element planar transducer with active MR temperature feedback can enable three-dimensional conformal thermal therapy of a target region within the prostate gland while sparing surrounding normal tissues. Continuous measurement of the temperature distribution in tissue enables dynamic compensation for unknown changes in blood flow and tissue properties during treatment. The main goal of this study was to evaluate the feasibility of using active temperature feedback on a clinical 1.5 T MR imager for conformal thermal therapy. MR thermometry was performed during heating in both gel phantoms and excised tissue with a transurethral heating applicator, and the rotation rate and power were varied based on the thermal measurements. The capability to produce a region of thermal damage that matched a target boundary was evaluated. The influence of a cooling gradient (to simulate cooling of the rectum or urethra) on the desired pattern of thermal damage was also investigated in gel phantoms. Results showed high correlation between the desired target boundary and the 55 °C isotherm generated during heating with an average distance error of 0.9 mm ± 0.4 mm (n = 6) in turkey breasts, 1.4 mm ± 0.6 mm (n = 4) in gel phantoms without rectal cooling and 1.4 mm ± 0.6 mm (n = 3) in gel phantoms with rectal cooling. The results were obtained using a temporal update rate of 5 s, a spatial resolution of 3 × 3 × 10 mm for the control point, and a temperature uncertainty of approximately 1 °C. The performance of the control algorithm under these conditions was comparable to that of simulations conducted previously by our group. Overall, the feasibility of generating targeted regions of thermal damage with a transurethral heating applicator and active MR temperature feedback has been demonstrated experimentally. This method of treatment appears capable of accounting for unpredictable and varying tissue properties during the treatment.

Molecular diagnostics of periodontitis.

PubMed

Korona-Głowniak, Izabela; Siwiec, Radosław; Berger, Marcin; Malm, Anna; Szymańska, Jolanta

2017-01-28

The microorganisms that form dental plaque are the main cause of periodontitis. Their identification and the understanding of the complex relationships and interactions that involve these microorganisms, environmental factors and the host's health status enable improvement in diagnostics and targeted therapy in patients with periodontitis. To this end, molecular diagnostics techniques (both techniques based on the polymerase chain reaction and those involving nucleic acid analysis via hybridization) come increasingly into use. On the basis of a literature review, the following methods are presented: polymerase chain reaction (PCR), real-time polymerase chain reaction (real-time PCR), 16S rRNA-encoding gene sequencing, checkerboard and reverse-capture checkerboard hybridization, microarrays, denaturing gradient gel electrophoresis (DGGE), temperature gradient gel electrophoresis (TGGE), as well as terminal restriction fragment length polymorphism (TRFLP) and next generation sequencing (NGS). The advantages and drawbacks of each method in the examination of periopathogens are indicated. The techniques listed above allow fast detection of even small quantities of pathogen present in diagnostic material and prove particularly useful to detect microorganisms that are difficult or impossible to grow in a laboratory.

Loss of an actin crosslinker uncouples cell spreading from cell stiffening on gels with a gradient of stiffness

NASA Astrophysics Data System (ADS)

Wen, Qi; Byfield, Fitzroy J.; Nordstrom, Kerstin; Arratia, Paulo E.; Miller, R. Tyler; Janmey, Paul A.

2009-03-01

We use microfluidics techniques to produce gels with a gradient of stiffness to show the essential function of the actin crosslinker filamin A in cell responses to mechanical stimuli. M2 melanoma cells null for filamin A do not alter their adherent area in response to increased substrate stiffness when they link to the substrate only through collagen receptors, but change adherent area normally when bound through fibronectin receptors. In contrast, filamin A-replete A7 cells change adherent area on both substrates and respond more strongly to collagen 1-coated gels than to fibronectin-coated gels. A7 cells alter their stiffness, as measured by atomic force microscopy, to match the elastic modulus of the substrate immediately adjacent to them on the gradient. M2 cells, in contrast, maintain a constant stiffness on all substrates that is as low as that of A7 cells on the softest gels achievable (1000 Pa). By contrasting the responses of these cell types to different adhesive substrates, cell spreading can be dissociated from stiffening.

Complex magnetic properties of TbMn{sub 1-x}Fe{sub x}O{sub 3} (x = 0.1 and 0.2) nanoparticles prepared by the sol-gel method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Das, A.; Chatterjee, S.; Das, D., E-mail: ddas@alpha.iuc.res.in

2016-05-23

TbMn{sub 1-x}Fe{sub x}O{sub 3} nanoparticles (NPs) with x = 0, 0.1 and 0.2 have been prepared by adopting the chemical sol-gel method. Phase identification and particle size estimation are done by XRD analysis. M-H measurements at 5 K indicate a complete ferromagnetic behaviour in the Fe-doped samples with large coercivity whereas the pristine sample shows presence of both ferromagnetic and antiferromagnetic orders. ZFC and FC magnetization curves of all samples show signature of antiferromagnetic ordering of both terbium and manganese magnetic moments along with a systematic shift of ordering temperatures with Fe substitution. {sup 57}Fe Mössbauer spectroscopic measurements of the Fe-dopedmore » samples at room temperature confirm the paramagnetic behaviour and reduction of electric field gradient around Fe probe atoms with increase of Fe concentration.« less

Combination of Multiplex PCR and PCR-Denaturing Gradient Gel Electrophoresis for Monitoring Common Sourdough-Associated Lactobacillus Species

PubMed Central

Settanni, Luca; Valmorri, Sara; van Sinderen, Douwe; Suzzi, Giovanna; Paparella, Antonello; Corsetti, Aldo

2006-01-01

A combination of denaturing gradient gel electrophoresis (DGGE) and a previously described multiplex PCR approach was employed to detect sourdough lactobacilli. Primers specific for certain groups of Lactobacillus spp. were used to amplify fragments, which were analyzed by DGGE. DGGE profiles obtained from Lactobacillus type strains acted as standards to analyze lactobacilli from four regional Abruzzo (central Italy) sourdoughs. PMID:16672538

The use of poloxamer hydrogels for the assessment of biofilm susceptibility towards biocide treatments.

PubMed

Gilbert, P; Jones, M V; Allison, D G; Heys, S; Maira, T; Wood, P

1998-12-01

Poloxamer F127 is a non-toxic, di-block copolymer of polyoxyethylene and polyoxypropylene. Aqueous solutions (30% w/v) show thermoreversible gelation, being liquid at temperatures < 15 degrees C and robust gels at temperatures > 15 degrees C. Chilled poloxamer (30% in tryptone soya broth) was mixed with an inoculum of Pseudomonas aeruginosa (10(4) cfu ml-1) and placed as 100 microliters drops onto separate glass cover-slips. These were placed into sealed Petri dishes containing moistened cotton wool and incubated at 35 degrees C. Viable counts could be performed on the poloxamer gels by transfer of the coverslips to diluents at < 15 degrees C. Growth curves in the gels and in liquid batch cultures were indistinguishable from one another with stationary phase cell densities, being approximately 5 x 10(10) cfu ml-1 in each at 16 h. SDS-PAGE of cell envelope preparations showed the poloxamer-grown cells to exhibit a biofilm rather than planktonic phenotype. Susceptibility towards various concentrations of chlorhexidine, iodine and hydrogen peroxide was assessed for 10 min at 35 degrees C for suspensions of broth-grown cells and for incubated poloxamer-gels (1 and 16 h). The gels were immersed in biocide, on their glass supports, before transfer to neutralizer at 10 degrees C where dissolution was complete within 5 min. Further serial dilutions and plate counts were made. While modest decreases in susceptibility towards all biocides were associated with incorporation of the inoculum with the gel (1 h incubation), substantial changes were noted after prolonged incubation and adaptation to a biofilm phenotype (16 h incubation). The gel populations mimic the localized high cell densities observed in biofilms and will also be subject to the same nutrient and chemical gradients as found within natural biofilms. Thermoreversible gelation enables complete recovery of the test inoculum without further trauma. They therefore provide an effective model for assessing biofilm susceptibility towards biocides and would be suitable for screening programmes.

Molecular diversity and tools for deciphering the methanogen community structure and diversity in freshwater sediments.

PubMed

Chaudhary, Prem Prashant; Brablcová, Lenka; Buriánková, Iva; Rulík, Martin

2013-09-01

Methanogenic archaeal communities existing in freshwater sediments are responsible for approximately 50 % of the total global emission of methane. This process contributes significantly to global warming and, hence, necessitates interventional control measures to limit its emission. Unfortunately, the diversity and functional interactions of methanogenic populations occurring in these habitats are yet to be fully characterized. Considering several disadvantages of conventional culture-based methodologies, in recent years, impetus is given to molecular biology approaches to determine the community structure of freshwater sedimentary methanogenic archaea. 16S rRNA and methyl coenzyme M reductase (mcrA) gene-based cloning techniques are the first choice for this purpose. In addition, electrophoresis-based (denaturing gradient gel electrophoresis, temperature gradient gel electrophoresis, and terminal restriction fragment length polymorphism) and quantitative real-time polymerase chain reaction techniques have also found extensive applications. These techniques are highly sensitive, rapid, and reliable as compared to traditional culture-dependent approaches. Molecular diversity studies revealed the dominance of the orders Methanomicrobiales and Methanosarcinales of methanogens in freshwater sediments. The present review discusses in detail the status of the diversity of methanogens and the molecular approaches applied in this area of research.

Thermo-sensitive hydrogel for preventing bowel injury in percutaneous renal radiofrequency ablation.

PubMed

Wang, Xin; Zhao, Xiaozhi; Lin, Tingsheng; Guo, Hongqian

2016-10-01

Percutaneous radiofrequency ablation (PRFA) has been used to ablate renal neoplasms with good outcome. However, if bowel lies adjacent to a tumor, ablation increases the risk of thermal bowel injury, and the consequences could be fatal. We describe the technique, effectiveness and safety of using thermo-sensitive hydrogel as insulation to displace the bowel away during PRFA. The study was divided into two main parts: the in vitro and in vivo studies. In in vitro study, to explore the heat insulation of hydrogel, the rabbit kidney was entirely embedded in hydrogel, and then radiofrequency ablation was performed; the temperature on the gel-air and gel-kidney interfaces was measured. In in vivo study, hydrogel of poloxamer 407, 25 % concentration (w/v), was instilled into the perinephric space of 10 rabbits under CT guidance to separate the kidney from adjacent bowel before PRFA performed in the targeted parenchyma in the gel group. For the control group, PRFA was performed in similar portions of 10 rabbits without instillation of hydrogel. Some parameters were recorded such as kidney-to-bowel and electrode-to-bowel distance. Immediately after PRFA, distribution of hydrogel was evaluated and the dimension of radiofrequency ablation zone was measured; bowel thermal injury was compared between the gel and control groups by gross anatomy and histopathological examination. To assess safety, two additional follow-up groups with 10 rabbits in each were set; after PRFA, CT scan was performed every 2 days; gel absorption, thermal damage and some other complications were evaluated during the period. In in vitro study, temperature was significantly lower at the gel-air than gel-kidney interface (P < .05), and the temperature gradient was positively associated with gel thickness. In in vivo study, hydrogel was instilled successfully in all rabbits in the gel group. The kidney-to-bowel and electrode-to-bowel distances were larger in the gel than control group [(1.1 ± 0.6 cm vs 0.1 ± 0.0 cm, P < .01), (1.8 ± 0.4 cm vs 0.5 ± 0.1 cm, P < .01), respectively]. The gel and control groups did not differ in size of the ablation zones (0.80 ± 0.2 cm vs 0.75 ± 0.3 cm, P > .05). Thermal injury in adjacent bowel was more serious in the control than gel group (P < .01). As for the follow-up, rabbits with gel instillation showed good condition and gel was absorbed gradually within 5 days. Those rabbits with no bowel displacement by gel got significantly lower survival rate and high complication rate (P < .01). Hydrogel-dissection by means of thermo-sensitive hydrogel instillation is valuable for protecting the bowel adjacent to ablation area against thermal injury during PRFA.

Analysis of spatial diffusion of ferric ions in PVA-GTA gel dosimeters through magnetic resonance imaging

NASA Astrophysics Data System (ADS)

Marrale, Maurizio; Collura, Giorgio; Gallo, Salvatore; Nici, Stefania; Tranchina, Luigi; Abbate, Boris Federico; Marineo, Sandra; Caracappa, Santo; d'Errico, Francesco

2017-04-01

This work focused on the analysis of the temporal diffusion of ferric ions through PVA-GTA gel dosimeters. PVA-GTA gel samples, partly exposed with 6 MV X-rays in order to create an initial steep gradient, were mapped using magnetic resonance imaging on a 7T MRI scanner for small animals. Multiple images of the gels were acquired over several hours after irradiation and were analyzed to quantitatively extract the signal profile. The spatial resolution achieved is 200 μm and this makes this technique particularly suitable for the analysis of steep gradients of ferric ion concentration. The results obtained with PVA-GTA gels were compared with those achieved with agarose gels, which is a standard dosimetric gel formulation. The analysis showed that the diffusion process is much slower (more than five times) for PVA-GTA gels than for agarose ones. Furthermore, it is noteworthy that the diffusion coefficient value obtained through MRI analysis is significantly consistent with that obtained in separate study Marini et al. (Submitted for publication) using a totally independent method such as spectrophotometry. This is a valuable result highlighting that the good dosimetric features of this gel matrix not only can be reproduced but also can be measured through independent experimental techniques based on different physical principles.

Composition gradient optimization and electrical characterization of (Pb, Ca)TiO3 thin films

NASA Astrophysics Data System (ADS)

Bao, Dinghua; Mizutani, Nobuyasu; Zhang, Liangying; Yao, Xi

2001-01-01

Compositionally graded (Pb, Ca)TiO3 thin films were prepared by a monoethanolamine-modified sol-gel technique on platinum-coated silicon substrates at the annealing temperature of 600 °C. The composition gradient of the films was greatly improved by a modified annealing method. The dielectric constants, for up-graded and down-graded films annealed at 600 °C for 60 min, were found to be 469 and 355, respectively. Both were larger than those reported for conventional (Pb, Ca)TiO3 thin films. The compositionally graded films had large polarization offsets in hysteresis loops when excited by an alternating electric field. The more smooth the composition gradient of the graded film, the larger the polarization offset. This was consistent with a theoretical model reported previously by Mantese and coworkers [Appl. Phys. Lett. 71, 2047 (1997)]. The magnitude of polarization offset displayed a power-law dependence on the electric field, and the direction of the offset depended on the direction of the composition gradient with respect to the substrate. Both up-graded and down-graded films had good leakage current characteristics.

Unfolding of a branched double-helical DNA three-way junction with triple-helical ends.

PubMed

Hüsler, P L; Klump, H H

1994-08-15

We have designed three oligonucleotides (33 mers) which when mixed in a 1:1:1 ratio form double-helical DNA three-way junctions with triple helical ends in the pH interval pH 4 to 5.5. The triplex to coil transition is initiated by raising the temperature and was recorded by temperature gradient gel electrophoresis, uv melting, and differential scanning calorimetry. The transitions can be deconvoluted into three subtransitions representing the independent thermal denaturation of each of the arms. We have proposed a model for the unfolding pathway and give the thermodynamic parameters for each step as calculated using the formalism outlined in the appendix.

System for loading slab-gel holders for electrophoresis separation

DOEpatents

Anderson, Norman G.; Anderson, Norman L.

1979-01-01

A slab-gel loading system includes a prismatic chamber for filling a plurality of slab-gel holders simultaneously. Each slab-gel holder comprises a pair of spaced apart plates defining an intermediate volume for gel containment. The holders are vertically positioned in the chamber with their major surfaces parallel to the chamber end walls. A liquid inlet is provided at the corner between the bottom and a side wall of the chamber for distributing a polymerizable monomer solution or a coagulable colloidal solution into each of the holders. The chamber is rotatably supported so that filling can begin with the corner having the liquid inlet directed downwardly such that the solution is gently funneled upwardly, without mixing, along the diverging side and bottom surfaces. As filling proceeds, the chamber is gradually rotated to position the bottom wall in a horizontal mode. The liquid filling means includes a plastic envelope with a septum dividing it into two compartments for intermixing two solutions of different density and thereby providing a liquid flow having a density gradient. The resulting gels have a density gradient between opposite edges for subsequent use in electrophoresis separations.

tuf-PCR-temporal temperature gradient gel electrophoresis for molecular detection and identification of staphylococci: application to breast milk and neonate gut microbiota.

PubMed

Filleron, Anne; Simon, Margaux; Hantova, Stefaniya; Jacquot, Aurélien; Cambonie, Gilles; Marchandin, Hélène; Jumas-Bilak, Estelle

2014-03-01

Coagulase negative staphylococci (CoNS) are a leading cause of infections in preterm infants, mostly involved in late-onset infection in low birth weight neonates. The epidemiology and pathophysiology of these infections remain unclear, notably because the causing agents are gathered in the artificial CoNS group. The aim of this work was to optimize the study of Staphylococcus species diversity in human breast milk and neonate stool, two sample types with bacterial communities dominated by CoNS, using PCR-temporal temperature gel electrophoresis based on the tuf gene. The optimized protocol identified 18 Staphylococcus species involved in neonate gut microbiota and infections and was applied to cultivation-independent study of breast milk and neonate stool. The efficiency, sensitivity, specificity and species discrimination of the proposed protocol appears suitable for patient follow-up in order to link microbiological data at the community level in milk and stool and interpret them from epidemiological and pathophysiological points of view. Copyright © 2014 Elsevier B.V. All rights reserved.

SU-F-T-304: Complex Multi-PTV Treatment Evaluation Using a Remotely Processed 3D Gel Dosimeter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoisak, J; Dragojevic, I; Sutlief, S

Purpose: A new 3D gel dosimeter (ClearView™, Modus Medical Systems) was investigated for use as a QA tool for stereotactic radiosurgery (SRS) plans exhibiting high dose gradients and spatially separated treatment targets. The unique feature of this gel dosimeter is the remote processing service provided by Modus Medical Systems. Methods: The gel dosimeters were filled in either 10 cm diameter or 15 cm diameter clear plastic jars. The jars were then shipped in ice-cooled containers to our department for irradiation. Clinical SRS plans for treatment of multiple metastases and plans with simulated concave structures were applied to a CT scanmore » of the gel dosimeter. The gel was irradiated in treatment position using modulated arcs and then returned in the cooled container for processing. The 3D gel dose was compared to the DICOM-RT dose from the treatment plan to assess dosimetric and geometric agreement. Results: There was no discernible difference between the planned and measured dose for dose gradients as high as 10%/mm, which was the highest gradient we evaluated. Geometric agreement for distant metastases separated by 6 cm was within 1.5 mm. Among three identically irradiated gels using a plan intended for nine metastases, the 3%/3mm gamma passing rate was 84.5% with a range of 14.7%, measured over the entire volume of the dosimeter. Regions of larger gamma values correlated with geometric offsets between the planned and measured data. Conclusion: The gel dosimeter exhibits the dosimetric and geometric characteristics necessary for 3D evaluation of treatment plan deliverability. The range of observed gamma passing rates suggests a high sensitivity to geometric registration. With proper management of geometric registration between planned and measured data, this service should enable a radiation oncology department to use 3D dosimetry in end-to-end testing or patient plan delivery QA without the expense of an in-house processing system.« less

Low density lipoprotein fraction assay for cardiac disease risk

DOEpatents

Krauss, Ronald M.; Blanche, Patricia J.; Orr, Joseph

1999-01-01

A variable rate density gradient electrophoric gel is described which separate LDL subfractions with the precision of ultracentrifugation techniques. Also, an innovative bottom inlet mixing chamber particularly useful for producing these gels is described.

[Influence of implants on human body during MRI examinations: fundamental experiment using metal balls].

PubMed

Muranaka, Hiroyuki; Nakamura, Osamu; Usui, Shuji; Ueda, Yoshitake; Morikawa, Kaoru

2005-07-20

It is increasingly the case that patients who have implants feel pain during high-field MRI examinations. A probable reason for the pain is the generation by irradiation of RF pulses and changing of the magnetic field gradient. As a fundamental study on the effect of implants on the human body under MRI procedures, temperature measurements were obtained from metal balls incorporated into gel-filled phantoms by using two kinds of measuring instruments, a copper-constantan thermocouple and a fluorescence fiber thermometer. At first we pursued a correlation between a copper-constantan thermocouple (absolute measurement) and fluoroptic thermometer and confirmed the precision and stability of the fluoroptic thermometer under MRI procedures. When a stainless steel ball with or without a loop antenna was used, only in the former case did the temperature rise during RF pulse irradiation. There was no significant difference between the magnetic field gradient ON and OFF. Furthermore, differences in metal (steel, aluminum, brass, stainless steel, copper) and size (5, 10, 20 mmPhi) were affected according to the increase of temperature. In conclusion, both RF pulse irradiation and a loop antenna are necessary for heat generation on the surface of metals.

Low density lipoprotein fraction assay for cardiac disease risk

DOEpatents

Krauss, R.M.; Blanche, P.J.; Orr, J.

1999-07-20

A variable rate density gradient electrophoric gel is described which separates LDL subfractions with the precision of ultracentrifugation techniques. Also, an innovative bottom inlet mixing chamber particularly useful for producing these gels is described. 8 figs.

A novel production process for optically pure L-lactic acid from kitchen refuse using a bacterial consortium at high temperatures.

PubMed

Tashiro, Yukihiro; Matsumoto, Hiroko; Miyamoto, Hirokuni; Okugawa, Yuki; Pramod, Poudel; Miyamoto, Hisashi; Sakai, Kenji

2013-10-01

We investigated L-lactic acid production in static batch fermentation of kitchen refuse using a bacterial consortium from marine-animal-resource (MAR) composts at temperatures ranging from 30 to 65 °C. At relatively low temperatures butyric acid accumulated, whereas at higher temperatures L-lactic acid was produced. In particular, fermentation at 50 °C produced 34.5 g L(-1) L-lactic acid with 90% lactic acid selectivity and 100% optical purity. Denaturing gradient gel electrophoresis indicated that dominant bacteria present in the original MAR composts diminished rapidly and Bacillus coagulans strains became the dominant contributors to L-lactic acid production at 45, 50 and 55 °C. This is the first report of the achievement of 100% optical purity of L-lactic acid using a bacterial consortium. Copyright © 2013 Elsevier Ltd. All rights reserved.

Diversity, geographic distribution, and habitat-specific variations of microbiota in natural populations of the chicken mite, Dermanyssus gallinae.

PubMed

Moro, Claire Valiente; Thioulouse, Jean; Chauve, Claude; Zenner, Lionel

2011-07-01

Dermanyssus gallinae is considered to be the most economically significant ectoparasite to affect egg-laying poultry in Europe. This mite can also act as a vector for a number of pathogens. The array of bacteria associated with D. gallinae mites could provide insight into the biology and population dynamics of arthropods, but at the present time little information is available. To understand the intra- and interpopulation diversity of its associated microbiota, we analyzed the whole internal bacterial community of natural populations of D. gallinae originating from two types of poultry farm habitats (standard and free-range) in two regions of France (Brittany and the Rhone-Alpes). Total DNA was extracted from individual or pooled mites, and polymerase chain reaction temporal temperature gradient gel electrophoresis of 16S rRNA was then done to separate bacterial DNA fragments associated with the host arthropod. A large diversity of bacteria was detected, but principally firmicutes and gamma-Proteobacteria. Between-group analyses of temporal temperature gradient gel electrophoresis-banding patterns revealed that bacterial populations clustered into categories according to their geographic origin and the habitat specifics of the farms. Some degree of stability of bacterial populations was observed within a specific time scale. These results suggest that environmental factors either recent (e.g., poultry farming practices) or long-standing (e.g., geographic isolation) may affect the bacterial communities present in D. gallinae. Further knowledge of the microbiota associated with D. gallinae and its variation would indeed offer new perspectives for biological control methods to prevent the establishment, proliferation, and transmission of pathogenic bacteria.

Characterization of Free Surface-Bound and Entrapped Water Environments in Poly(N-Isopropyl Acrylamide) Hydrogels via 1H HRMAS PFG NMR Spectroscopy

DOE PAGES

Alam, Todd Michael; Childress, Kimberly Kay; Pastoor, Kevin; ...

2014-09-19

We found that different water environments in poly(N-isopropyl acrylamide) (PNIPAAm) hydrogels are identified and characterized using 1H high resolution magic angle spinning (HRMAS) nuclear magnetic resonance (NMR). Local water environments corresponding to a “free” highly mobile species, along with waters showing restricted dynamics are resolved in these swollen hydro-gels. For photo-initiated polymerized PNIPAAm gels, an additional entrapped water species is observed. Spin–spin R 2 relaxation experiments support the argument of reduced mobility in the restricted and entrapped water species. Furthermore, by combining pulse field gradient techniques with HRMAS NMR it is possible to directly measure the self-diffusion rate for thesemore » different water environments. The behavior of the heterogeneous water environments through the lower critical solution temperature transition is described.« less

Development of novel separation techniques for biological samples in capillary electrophoresis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Huan -Tsung

1994-07-27

This dissertation includes three different topics: general introduction of capillary electrophoresis (CE); gradient in CE and CE in biological separations; and capillary gel electrophoresis (CGE) for DNA separation. Factors such as temperature, viscosity, pH, and the surface of capillary walls affecting the separation performance are demonstrated. A pH gradient between 3.0 and 5.2 is useful to improve the resolution among eight different organic acids. A flow gradient due to the change in the concentration of surfactant, which is able to coat to the capillary wall to change the flow rate and its direction, is also shown as a good waymore » to improve the resolution for organic compounds. A temperature gradient caused by joule heat is shown by voltage programming to enhance the resolution and shorten the separation time for several phenolic compounds. The author also shows that self-regulating dynamic control of electroosmotic flow in CE by simply running separation in different concentrations of surfactant has less matrix effect on the separation performance. One of the most important demonstrations in this dissertation is that the author proposes on-column reaction which gives several advantages including the use of a small amount of sample, low risk of contamination, and time saving and kinetic features. The author uses this idea with laser induced fluorescence (LIF) as a detection mode to detect an on-column digestion of sub-ng of protein. This technique also is applied to single cell analysis in the group.« less

[Effect of temperature on performance of microbial fuel cell using beer wastewater].

PubMed

Wang, Xin; Feng, Yu-Jie; Qu, You-Peng; Li, Dong-Mei; Li, He; Ren, Nan-Qi

2008-11-01

The effects of temperature on performance and biological community structure were investigated in air-cathode microbial fuel cells (MFCs) using beer wastewater amended with 50 mmol/L phosphate buffer solution (PBS). The maximum power density decreased from 483 mW/m2 to 435 mW/m2 when the temperature varied from 30 degrees C to 20 degrees C, meanwhile just a little decreasing on coulombic efficiency and the COD removal rate were observed. Decreasing of temperature resulted in effects both on cathode potential and anode potential, but cathode potential behaved much more sensitive to temperature. The half-saturation constants (Ks) obtained from the fit of Monod-type equation were 228 mg/L (30 degrees C) and 293 mg/L (20 degrees C) respectively. Denaturing gradient gel electrophoresis (DGGE) analysis indicated that operating temperature not only affected the predominant population of the anodic bacterial community, but also had a great impact on the diversity of the cathodic microbial population.

Molecular identification of the microbiota of French sourdough using temporal temperature gradient gel electrophoresis.

PubMed

Ferchichi, Mounir; Valcheva, Rosica; Prévost, Hervé; Onno, Bernard; Dousset, Xavier

2007-01-01

The microbiota of four industrial French sourdoughs (BF, GO, VB and RF) was characterized by PCR temporal temperature gel electrophoresis (TTGE). The TTGE technique reveals differences in the 16S rDNA V6-V8 regions of these bacteria. DNA was extracted directly from sourdough samples. A specific TTGE fingerprint was determined for 30 bacterial species, including members of the genera Lactobacillus, Leuconostoc and Weissella, all known to be present in sourdough. These sourdoughs contain different species of lactic acid bacteria (LAB) depending on ecological conditions prevailing in the different sourdough fermentations. Only a few LAB species were found to be competitive and became dominant. Lactobacillus sanfranciscensis was observed as the most frequently found species. In sourdough GO, L. sanfranciscensis, Lactobacillus panis and two new species, Lactobacillus nantensis and Lactobacillus hammesii, were detected. Sourdough BF contain L. sanfranciscensis, Lactobacillus spicheri and Lactobacillus pontis. In sourdough VB, which differed in the process temperature, we identified exclusively L. sanfranciscensis and Leuconostoc mesenteroïdes subsp. mesenteroïdes. Lactobacillus frumenti, L. hammesii and Lacobacillus paralimentarius became the predominant species in sourdough RF. Compared with conventional bacteriological methods, the use of this new molecular approach to analyze the sourdough ecosystem should therefore allow a more complete and rapid assessment of its specific microbiota.

Gel-based coloration technique for the submillimeter-scale imaging of labile phosphorus in sediments and soils with diffusive gradients in thin films.

PubMed

Ding, Shiming; Wang, Yan; Xu, Di; Zhu, Chungang; Zhang, Chaosheng

2013-07-16

We report a highly promising technique for the high-resolution imaging of labile phosphorus (P) in sediments and soils in combination with the diffusive gradients in thin films (DGT). This technique was based on the surface coloration of the Zr-oxide binding gel using the conventional molybdenum blue method following the DGT uptake of P to this gel. The accumulated mass of the P in the gel was then measured according to the grayscale intensity on the gel surface using computer-imaging densitometry. A pretreatment of the gel in hot water (85 °C) for 5 d was required to immobilize the phosphate and the formed blue complex in the gel during the color development. The optimal time required for a complete color development was determined to be 45 min. The appropriate volume of the coloring reagent added was 200 times of that of the gel. A calibration equation was established under the optimized conditions, based on which a quantitative measurement of P was obtained when the concentration of P in solutions ranged from 0.04 mg L(-1) to 4.1 mg L(-1) for a 24 h deployment of typical DGT devices at 25 °C. The suitability of the coloration technique was well demonstrated by the observation of small, discrete spots with elevated P concentrations in a sediment profile.

Smart membranes: Hydroxypropyl cellulose for flavor delivery

NASA Astrophysics Data System (ADS)

Heitfeld, Kevin A.

2007-12-01

This work focuses on the use of temperature responsive gels (TRGs) (polymeric hydrogels with a large temperature-dependent change in volume) for flavor retention at cooking temperatures. Specifically, we have studied a gel with a lower critical solution temperature (LCST) that swells at low temperatures and collapses at high temperatures. In the collapsed state, the polymer acts as a transport barrier, keeping the volatile flavors inside. An encapsulation system was designed to utilize the solution (phase separation) behavior of a temperature responsive gel. The gel morphology was understood and diffusive properties were tailored through morphology manipulation. Heterogeneous and homogeneous gels were processed by understanding the effect of temperature on gel morphology. A morphology model was developed linking bulk diffusive properties to molecular morphology. Flavor was encapsulated within the gel and the emulsifying capability was determined. The capsules responded to temperature similarly to the pure polymer. The release kinetcs were compared to commercial gelatin capsules and the temperature responsive polymer took longer to release.

Karyotype analysis of anuran trypanosomes by pulsed-field gradient gel electrophoresis.

PubMed

Lun, Z R; Desser, S S

1995-12-01

The chromosomes of 12 species and isolates of anuran trypanosomes were investigated by pulsed-field gradient gel electrophoresis. Twelve to 16 chromosomes ranging from 0.45 to 2.2 megabase pairs were found in each of these trypanosomes. Minichromosomes were not observed in any of the examined isolates. Results indicate that different species of anuran trypanosomes display distinct karyotype patterns, and that isolates from the same region are similar. Our findings also reveal that most chromosome profiles of these trypanosomes are in accordance with isoenzyme and random amplified polymorphic DNA analysis data.

Behavior of variable V3 region from 16S rDNA of lactic acid bacteria in denaturing gradient gel electrophoresis.

PubMed

Ercolini, D; Moschetti, G; Blaiotta, G; Coppola, S

2001-03-01

Separation of amplified V3 region from 16S rDNA by denaturing gradient gel electrophoresis (DGGE) was tested as a tool for differentiation of lactic acid bacteria commonly isolated from food. Variable V3 regions of 21 reference strains and 34 wild strains referred to species belonging to the genera Pediococcus, Enterococcus, Lactococcus, Lactobacillus, Leuconostoc, Weissella, and Streptococcus were analyzed. DGGE profiles obtained were species-specific for most of the cultures tested. Moreover, it was possible to group the remaining LAB reference strains according to the migration of their 16S V3 region in the denaturing gel. The results are discussed with reference to their potential in the analysis of LAB communities in food, besides shedding light on taxonomic aspects.

Soil Microbial Community Structure across a Thermal Gradient following a Geothermal Heating Event

PubMed Central

Norris, Tracy B.; Wraith, Jon M.; Castenholz, Richard W.; McDermott, Timothy R.

2002-01-01

In this study microbial species diversity was assessed across a landscape in Yellowstone National Park, where an abrupt increase in soil temperature had occurred due to recent geothermal activity. Soil temperatures were measured, and samples were taken across a temperature gradient (35 to 65°C at a 15-cm depth) that spanned geothermally disturbed and unimpacted soils; thermally perturbed soils were visually apparent by the occurrence of dead or dying lodgepole pine trees. Changes in soil microbial diversity across the temperature gradient were qualitatively assessed based on 16S rRNA sequence variation as detected by denaturing gradient gel electrophoresis (DGGE) using both ribosomal DNA (rDNA) and rRNA as PCR templates and primers specific for the Bacteria or Archaea domain. The impact of the major heating disturbance was apparent in that DGGE profiles from heated soils appeared less complex than those from the unaffected soils. Phylogenetic analysis of a bacterial 16S rDNA PCR clone library from a recently heated soil showed that a majority of the clones belonged to the Acidobacterium (51%) and Planctomyces (18%) divisions. Agar plate counts of soil suspensions cultured on dilute yeast extract and R2A agar media incubated at 25 or 50°C revealed that thermophile populations were two to three orders of magnitude greater in the recently heated soil. A soil microcosm laboratory experiment simulated the geothermal heating event. As determined by both RNA- and DNA-based PCR coupled with DGGE, changes in community structure (marked change in the DGGE profile) of soils incubated at 50°C occurred within 1 week and appeared to stabilize after 3 weeks. The results of our molecular and culture data suggest that thermophiles or thermotolerant species are randomly distributed in this area within Yellowstone National Park and that localized thermal activity selects for them. PMID:12450855

Soil microbial community structure across a thermal gradient following a geothermal heating event.

PubMed

Norris, Tracy B; Wraith, Jon M; Castenholz, Richard W; McDermott, Timothy R

2002-12-01

In this study microbial species diversity was assessed across a landscape in Yellowstone National Park, where an abrupt increase in soil temperature had occurred due to recent geothermal activity. Soil temperatures were measured, and samples were taken across a temperature gradient (35 to 65 degrees C at a 15-cm depth) that spanned geothermally disturbed and unimpacted soils; thermally perturbed soils were visually apparent by the occurrence of dead or dying lodgepole pine trees. Changes in soil microbial diversity across the temperature gradient were qualitatively assessed based on 16S rRNA sequence variation as detected by denaturing gradient gel electrophoresis (DGGE) using both ribosomal DNA (rDNA) and rRNA as PCR templates and primers specific for the Bacteria or Archaea domain. The impact of the major heating disturbance was apparent in that DGGE profiles from heated soils appeared less complex than those from the unaffected soils. Phylogenetic analysis of a bacterial 16S rDNA PCR clone library from a recently heated soil showed that a majority of the clones belonged to the Acidobacterium (51%) and Planctomyces (18%) divisions. Agar plate counts of soil suspensions cultured on dilute yeast extract and R2A agar media incubated at 25 or 50 degrees C revealed that thermophile populations were two to three orders of magnitude greater in the recently heated soil. A soil microcosm laboratory experiment simulated the geothermal heating event. As determined by both RNA- and DNA-based PCR coupled with DGGE, changes in community structure (marked change in the DGGE profile) of soils incubated at 50 degrees C occurred within 1 week and appeared to stabilize after 3 weeks. The results of our molecular and culture data suggest that thermophiles or thermotolerant species are randomly distributed in this area within Yellowstone National Park and that localized thermal activity selects for them.

Plasma protein denaturation with graded heat exposure.

PubMed

Vazquez, R; Larson, D F

2013-11-01

During cardiopulmonary bypass (CPB), perfusion at tepid temperatures (33-35 °C) is recommended to avoid high temperature cerebral hyperthermia during and after the operation. However, the ideal temperature for uncomplicated adult cardiac surgery is an unsettled question. Typically, the heat exchanger maximum temperature is monitored between 40-42 °C to prevent denaturation of plasma proteins, but studies have not been performed to make these conclusions. Therefore, our hypothesis was to determine the temperature in which blood plasma protein degradation occurs after 2 hours of heat exposure. As a result, blood plasma proteins were exposed to heat in the 37-50 °C range for 2 hours. Plasma protein samples were loaded onto an 8-12% gradient gel for SDS-PAGE and low molecular weight plasma protein degradation was detected with graded heat exposure. Protein degradation was first detected between 43-45 °C of heat exposure. This study supports the practice of monitoring the heat exchanger between 40-42 °C to prevent denaturation of plasma proteins.

Preferential paths in yield stress fluid flow through a porous medium

NASA Astrophysics Data System (ADS)

Guasto, Jeffrey; Waisbord, Nicolas; Stoop, Norbert; Dunkel, Jörn

2016-11-01

A broad range of biological, geological, and industrial materials with complex rheological properties are subjected to flow through porous media in applications ranging from oil recovery to food manufacturing. In this experimental study, we examine the flow of a model yield stress fluid (Carbopol micro-gel) through a quasi-2D porous medium, fabricated in a microfluidic channel. The flow is driven by applying a precisely-controlled pressure gradient and measured by particle tracking velocimetry, and our observations are complemented by a pore-network model of the yield stress fluid flow. While remaining unyielded at small applied pressure, the micro-gel begins to yield at a critical pressure gradient, exhibiting a single preferential flow path that percolates through the porous medium. As the applied pressure gradient increases, we observe a subsequent coarsening and invasion of the yielded, fluidized network. An examination of both the yielded network topology and pore-scale flow reveal that two cooperative phenomena are involved in sculpting the preferential flow paths: (1) the geometry of the porous microstructure, and (2) the adhesive surface interactions between the micro-gel and substrate. NSF CBET-1511340.

Some rheological properties of sodium caseinate-starch gels.

PubMed

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

2005-03-23

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

Feasibility of CBCT dosimetry for IMRT using a normoxic polymethacrylic-acid gel dosimeter

NASA Astrophysics Data System (ADS)

Bong, Ji Hye; Kwon, Soo-Il; Kim, Kum Bae; Kim, Mi Suk; Jung, Hai Jo; Ji, Young Hoon; Ko, In Ok; Park, Ji Ae; Kim, Kyeong Min

2013-09-01

The purpose of this study is to evaluate the availability of cone-beam computed tomography(CBCT) for gel dosimetry. The absorbed dose was analyzed by using intensity-modulated radiation therapy(IMRT) to irradiate several tumor shapes with a calculated dose and several tumor acquiring images with CBCT in order to verify the possibility of reading a dose on the polymer gel dosimeter by means of the CBCT image. The results were compared with those obtained using magnetic resonance imaging(MRI) and CT. The linear correlation coefficients at doses less than 10 Gy for the polymer gel dosimeter were 0.967, 0.933 and 0.985 for MRI, CT and CBCT, respectively. The dose profile was symmetric on the basis of the vertical axis in a circular shape, and the uniformity was 2.50% for the MRI and 8.73% for both the CT and the CBCT. In addition, the gradient in the MR image of the gel dosimeter irradiated in an H shape was 109.88 while the gradients of the CT and the CBCT were 71.95 and 14.62, respectively. Based on better image quality, the present study showed that CBCT dosimetry for IMRT could be restrictively performed using a normoxic polymethacrylic-acid gel dosimeter.

Method of making a functionally graded material

DOEpatents

Lauf, Robert J.; Menchhofer, Paul A.; Walls, Claudia A.; Moorhead, Arthur J.

2002-01-01

A gelcasting method of making an internally graded article alternatively includes the steps of: preparing a slurry including a least two different phases suspended in a gelcasting solution, the phases characterized by having different settling characteristics; casting the slurry into a mold having a selected shape; allowing the slurry to stand for a sufficient period of time to permit desired gravitational fractionation in order to achieve a vertical compositional gradient in the molded slurry; gelling the slurry to form a solid gel while preserving the vertical compositional gradient in the molded slurry; drying the gel to form a dried green body; and sintering the dry green body to form a solid object, at least one property thereof varying along the vertical direction because of the compositional gradient in the molded slurry.

Development and Validation of PCR Primers To Assess the Diversity of Clostridium spp. in Cheese by Temporal Temperature Gradient Gel Electrophoresis

PubMed Central

Le Bourhis, Anne-Gaëlle; Saunier, Katiana; Doré, Joël; Carlier, Jean-Philippe; Chamba, Jean-François; Popoff, Michel-Robert; Tholozan, Jean-Luc

2005-01-01

A nested-PCR temporal temperature gradient gel electrophoresis (TTGE) approach was developed for the detection of bacteria belonging to phylogenetic cluster I of the genus Clostridium (the largest clostridial group, which represents 25% of the currently cultured clostridial species) in cheese suspected of late blowing. Primers were designed based on the 16S rRNA gene sequence, and the specificity was confirmed in PCRs performed with DNAs from cluster I and non-cluster I species as the templates. TTGE profiles of the PCR products, comprising the V5-V6 region of the 16S rRNA gene, allowed us to distinguish the majority of cluster I species. PCR-TTGE was applied to analyze commercial cheeses with defects. All cheeses gave a signal after nested PCR, and on the basis of band comigration with TTGE profiles of reference strains, all the bands could be assigned to a clostridial species. The direct identification of Clostridium spp. was confirmed by sequencing of excised bands. C. tyrobutyricum and C. beijerinckii contaminated 15 and 14 of the 20 cheese samples tested, respectively, and C. butyricum and C. sporogenes were detected in one cheese sample. Most-probable-number counts and volatile fatty acid were determined for comparison purposes. Results obtained were in agreement, but only two species, C. tyrobutyricum and C. sporogenes, could be isolated by the plating method. In all cheeses with a high amount of butyric acid (>100 mg/100 g), the presence of C. tyrobutyricum DNA was confirmed by PCR-TTGE, suggesting the involvement of this species in butyric acid fermentation. These results demonstrated the efficacy of the PCR-TTGE method to identify Clostridium in cheeses. The sensitivity of the method was estimated to be 100 CFU/g. PMID:15640166

Functionalization of quantum rods with oligonucleotides for programmable assembly with DNA origami

NASA Astrophysics Data System (ADS)

Doane, Tennyson L.; Alam, Rabeka; Maye, Mathew M.

2015-02-01

The DNA-mediated self-assembly of CdSe/CdS quantum rods (QRs) onto DNA origami is described. Two QR types with unique optical emission and high polarization were synthesized, and then functionalized with oligonucleotides (ssDNA) using a novel protection-deprotection approach, which harnessed ssDNA's tailorable rigidity and denaturation temperature to increase DNA coverage by reducing non-specific coordination and wrapping. The QR assembly was programmable, and occurred at two different assembly zones that had capture strands in parallel alignment. QRs with different optical properties were assembled, opening up future studies on orientation dependent QR FRET. The QR-origami conjugates could be purified via gel electrophoresis and sucrose gradient ultracentrifugation. Assembly yields, QR stoichiometry and orientation, as well as energy transfer implications were studied in light of QR distances, origami flexibility, and conditions.The DNA-mediated self-assembly of CdSe/CdS quantum rods (QRs) onto DNA origami is described. Two QR types with unique optical emission and high polarization were synthesized, and then functionalized with oligonucleotides (ssDNA) using a novel protection-deprotection approach, which harnessed ssDNA's tailorable rigidity and denaturation temperature to increase DNA coverage by reducing non-specific coordination and wrapping. The QR assembly was programmable, and occurred at two different assembly zones that had capture strands in parallel alignment. QRs with different optical properties were assembled, opening up future studies on orientation dependent QR FRET. The QR-origami conjugates could be purified via gel electrophoresis and sucrose gradient ultracentrifugation. Assembly yields, QR stoichiometry and orientation, as well as energy transfer implications were studied in light of QR distances, origami flexibility, and conditions. Electronic supplementary information (ESI) available: Experimental conditions, DNA origami blueprint and sequences, FRET calculations. Additional Fig. S1-S13. See DOI: 10.1039/c4nr07662a

Intraoperative use of a reflective blanket (Sirius rescue sheet) for temperature management in dogs less than 10 kg.

PubMed

Tünsmeyer, J; Bojarski, I; Nolte, I; Kramer, S

2009-07-01

To compare the effects of the Sirius rescue sheet with gel pads versus gel pads alone on intraoperative body temperature in dogs less than 10 kg. Forty small breed dogs undergoing elective surgical procedures were randomly assigned to two groups. One group was intraoperatively laid on warmed gel pads, and the other group was additionally wrapped in a Sirius rescue sheet. Oesophageal body temperature was determined every 10 minutes and compared between groups. Temperature of gel pads was measured preoperatively and postoperatively to compare heat loss of the gel pads between groups. The body temperature of dogs wrapped with the Sirius rescue sheet increased intraoperatively. In dogs just lying on warmed gel pads, a decrease in mean body temperature was revealed and mean body temperatures differed between groups after 40 minutes. Extent of heat loss from the gel pads did not differ between the groups. The Sirius rescue sheet, used in addition to warmed gel pads, led to higher intraoperative body temperatures in small breed dogs undergoing surgical procedures to the extremities and the head. The cost-effectiveness and ease of handling make this a useful addition to clinical practice.

Effect of storage and drying temperature on the gelation behavior and structural characteristics of sericin.

PubMed

Jo, Yoon Nam; Park, Byung-Dae; Um, In Chul

2015-11-01

Owing to unique properties, including the wound healing effect, sericin gel and films have attracted significant attention in the biomedical and cosmetic fields. The structural characteristics and properties of sericin gels and films are especially important owing to their effect on the performance of sericin in biomedical and cosmetic applications. In the present study, the effect of temperature on the gelation behavior, gel disruption, and sol-gel transition of sericin was examined using rheometry. In addition, the effect of the drying temperature on the structural characteristics of the sericin film was determined via Fourier transform infrared (FTIR) spectroscopy. The strength of the sericin gel increased and the gelation process was prolonged with decreasing storage temperatures. FTIR and differential scanning calorimetry (DSC) results also revealed that the crystallinity and the thermal decomposition temperature of the sericin film increased with decreasing drying temperature. The sericin gels were disrupted at a storage time of 40min when they were stored at temperatures higher than 50°C, and the corresponding gel strength decreased with increasing temperature. Furthermore, the thermo-reversible nature of gel-sol transition of sericin was confirmed by rheological and FTIR measurements. Copyright © 2015 Elsevier B.V. All rights reserved.

Real-time volumetric relative dosimetry for magnetic resonance—image-guided radiation therapy (MR-IGRT)

NASA Astrophysics Data System (ADS)

Lee, Hannah J.; Kadbi, Mo; Bosco, Gary; Ibbott, Geoffrey S.

2018-02-01

The integration of magnetic resonance imaging (MRI) with linear accelerators (linac) has enabled the use of 3D MR-visible gel dosimeters for real-time verification of volumetric dose distributions. Several iron-based radiochromic 3D gels were created in-house then imaged and irradiated in a pre-clinical 1.5 T-7 MV MR-Linac. MR images were acquired using a range of balanced-fast field echo (b-FFE) sequences during irradiation to assess the contrast and dose response in irradiated regions and to minimize the presence of MR artifacts. Out of four radiochromic 3D gel formulations, the FOX 3D gel was found to provide superior MR contrast in the irradiated regions. The FOX gels responded linearly with respect to real-time dose and the signal remained stable post-irradiation for at least 20 min. The response of the FOX gel also was found to be unaffected by the radiofrequency and gradient fields created by the b-FFE sequence during irradiation. A reusable version of the FOX gel was used for b-FFE sequence optimization to reduce artifacts by increasing the number of averages at the expense of temporal resolution. Regardless of the real-time MR sequence used, the FOX 3D gels responded linearly to dose with minimal magnetic field effects due to the strong 1.5 T field or gradient fields present during imaging. These gels can easily be made in-house using non-reusable and reusable formulations depending on the needs of the clinic, and the results of this study encourage further applications of 3D gels for MR-IGRT applications.

Separation and characterization of high-density lipoprotein subpopulations by gel permeation chromatography.

PubMed

Clifton, P M; MacKinnon, A M; Barter, P J

1987-02-20

High-density lipoproteins (HDL) contain at least five distinct subpopulations when analyzed by gradient gel electrophoresis. This report represents the first description of a simple technique for isolating these subpopulations of HDL in quantities sufficient to enable characterization in terms of particle size, apolipoprotein AI and apolipoprotein AII content and chemical composition. Lipoproteins were separated and subfractionated on a column of Superose 6B using a fast protein liquid chromatography system. Five normal subjects were studied: HDL2b and HDL3a were isolated as essentially single subpopulations from all subjects, while HDL2a could be isolated from only three of the subjects. HDL3b was isolated in a relatively impure form (70%) from all subjects. Identical subpopulations were identified in each subject by gradient gel electrophoresis of unseparated HDL.

Monitoring the Bacterial Population Dynamics in Sourdough Fermentation Processes by Using PCR-Denaturing Gradient Gel Electrophoresis

PubMed Central

Meroth, Christiane B.; Walter, Jens; Hertel, Christian; Brandt, Markus J.; Hammes, Walter P.

2003-01-01

Four sourdoughs (A to D) were produced under practical conditions by using a starter mixture of three commercially available sourdough starters and a baker's yeast constitutively containing various species of lactic acid bacteria (LAB). The sourdoughs were continuously propagated until the composition of the LAB flora remained stable. Two LAB-specific PCR-denaturing gradient gel electrophoresis (DGGE) systems were established and used to monitor the development of the microflora. Depending on the prevailing ecological conditions in the different sourdough fermentations, only a few Lactobacillus species were found to be competitive and became dominant. In sourdough A (traditional process with rye flour), Lactobacillus sanfranciscensis and a new species, L. mindensis, were detected. In rye flour sourdoughs B and C, which differed in the process temperature, exclusively L. crispatus and L. pontis became the predominant species in sourdough B and L. crispatus, L. panis, and L. frumenti became the predominant species in sourdough C. On the other hand, in sourdough D (corresponding to sourdough C but produced with rye bran), L. johnsonii and L. reuteri were found. The results of PCR-DGGE were consistent with those obtained by culturing, except for sourdough B, in which L. fermentum was also detected. Isolates of the species L. sanfranciscensis and L. fermentum were shown by randomly amplified polymorphic DNA-PCR analysis to originate from the commercial starters and the baker's yeast, respectively. PMID:12514030

Feasibility of Actively Cooled Silicon Nitride Airfoil for Turbine Applications Demonstrated

NASA Technical Reports Server (NTRS)

Bhatt, Ramakrishna T.

2001-01-01

Nickel-base superalloys currently limit gas turbine engine performance. Active cooling has extended the temperature range of service of nickel-base superalloys in current gas turbine engines, but the margin for further improvement appears modest. Therefore, significant advancements in materials technology are needed to raise turbine inlet temperatures above 2400 F to increase engine specific thrust and operating efficiency. Because of their low density and high-temperature strength and thermal conductivity, in situ toughened silicon nitride ceramics have received a great deal of attention for cooled structures. However, the high processing costs and low impact resistance of silicon nitride ceramics have proven to be major obstacles for widespread applications. Advanced rapid prototyping technology in combination with conventional gel casting and sintering can reduce high processing costs and may offer an affordable manufacturing approach. Researchers at the NASA Glenn Research Center, in cooperation with a local university and an aerospace company, are developing actively cooled and functionally graded ceramic structures. The objective of this program is to develop cost-effective manufacturing technology and experimental and analytical capabilities for environmentally stable, aerodynamically efficient, foreign-object-damage-resistant, in situ toughened silicon nitride turbine nozzle vanes, and to test these vanes under simulated engine conditions. Starting with computer aided design (CAD) files of an airfoil and a flat plate with internal cooling passages, the permanent and removable mold components for gel casting ceramic slips were made by stereolithography and Sanders machines, respectively. The gel-cast part was dried and sintered to final shape. Several in situ toughened silicon nitride generic airfoils with internal cooling passages have been fabricated. The uncoated and thermal barrier coated airfoils and flat plates were burner rig tested for 30 min without and with air cooling. Without cooling, the surface temperature of the flat plate reached approximately 2350 F. Starting with computer aided design (CAD) files of an airfoil and a flat plate with internal cooling passages, the permanent and removable mold components for gel casting ceramic slips were made by stereolithography and Sanders machines, respectively. The gel-cast part was dried and sintered to final shape. Several in situ toughened silicon nitride generic airfoils with internal cooling passages have been fabricated. The uncoated and thermal barrier coated airfoils and flat plates were burner rig tested for 30 min without and with air cooling. Without cooling, the surface temperature of the flat plate reached approximately 2350 F. With cooling, the surface temperature decreased to approximately 1910 F--a drop of approximately 440 F. This preliminary study demonstrates that a near-net-shape silicon nitride airfoil can be fabricated and that silicon nitride can sustain severe thermal shock and the thermal gradients induced by cooling and, thus, is a viable candidate for cooled components.

Elevation of liquidus temperature in a gel-derived Na2O-SiO2 glass

NASA Technical Reports Server (NTRS)

Weinberg, M. C.; Neilson, G. F.

1983-01-01

The liquidus temperatures of a 19 wt% soda-silica glass prepared by gel and conventional techniques were determined. X-ray diffraction measurements of the glasses which were heat-treated at several temperatures were used to experimentally determine the liquidus temperatures. It was found that the gel-derived glass has an elevated liquidus. This result is discussed in relation to the previous discovery that the immiscibility temperature of this gel-derived glass is elevated

Consequences of ions and pH on the supramolecular organization of sphingomyelin and sphingomyelin/cholesterol bilayers.

PubMed

Chemin, Caroline; Bourgaux, Claudie; Péan, Jean-Manuel; Pabst, Georg; Wüthrich, Patrick; Couvreur, Patrick; Ollivon, Michel

2008-06-01

For drug delivery purpose the anticancer drug S12363 was loaded into ESM/Chol-liposomes using either a pH or an ammonium gradient. Association between the drug and the liposome depends markedly on the liposome membrane structure. Thus, ESM and ESM/Chol bilayer organization had been characterized by coupled DSC and XRDT as a function of both cholesterol concentration and aqueous medium composition. ESM bilayers exhibited a ripple lamellar gel phase P(beta') below the melting temperature and adopted a L(beta)-like gel phase upon Chol insertion. Supramolecular organization of ESM and ESM/Chol bilayers was not modified by citrate buffer or ammonium sulfate solution whatever the pH (3< or = pH < or =7). Nevertheless, in ESM bilayer, ammonium sulfate salt induced a peculiar organization of head groups, leading to irregular d-spacing and weakly correlated bilayers. Moreover, in the presence of salts, a weakening of van der Waals attraction forces was seen and led to a swelling of the water layer.

Raw Cow Milk Bacterial Population Shifts Attributable to Refrigeration

PubMed Central

Lafarge, Véronique; Ogier, Jean-Claude; Girard, Victoria; Maladen, Véronique; Leveau, Jean-Yves; Gruss, Alexandra; Delacroix-Buchet, Agnès

2004-01-01

We monitored the dynamic changes in the bacterial population in milk associated with refrigeration. Direct analyses of DNA by using temporal temperature gel electrophoresis (TTGE) and denaturing gradient gel electrophoresis (DGGE) allowed us to make accurate species assignments for bacteria with low-GC-content (low-GC%) (<55%) and medium- or high-GC% (>55%) genomes, respectively. We examined raw milk samples before and after 24-h conservation at 4°C. Bacterial identification was facilitated by comparison with an extensive bacterial reference database (∼150 species) that we established with DNA fragments of pure bacterial strains. Cloning and sequencing of fragments missing from the database were used to achieve complete species identification. Considerable evolution of bacterial populations occurred during conservation at 4°C. TTGE and DGGE are shown to be a powerful tool for identifying the main bacterial species of the raw milk samples and for monitoring changes in bacterial populations during conservation at 4°C. The emergence of psychrotrophic bacteria such as Listeria spp. or Aeromonas hydrophila is demonstrated. PMID:15345453

Apparatus for investigating the reactions of soft-bodied invertebrates to controlled humidity gradients

PubMed Central

Russell, Joshua; Pierce-Shimomura, Jonathan T.

2015-01-01

Background While many studies have assayed behavioral responses of animals to chemical, temperature and light gradients, fewer studies have assayed how animals respond to humidity gradients. Our novel humidity chamber has allowed us to study the neuromolecular basis of humidity sensation in the nematode Caenorhabditis elegans (Russell et al. 2014). New Method We describe an easy-to-construct, low-cost humidity chamber to assay the behavior of small animals, including soft-bodied invertebrates, in controlled humidity gradients. Results We show that our humidity-chamber design is amenable to soft-bodied invertebrates and can produce reliable gradients ranging 0.3–8% RH/cm across a 9-cm long x 7.5-cm wide gel-covered arena. Comparison with Existing Method(s) Previous humidity chambers relied on circulating dry and moist air to produce a steep humidity gradient in a small arena (e.g. Sayeed & Benzer, 1996). To remove the confound of moving air that may elicit mechanical responses independent of humidity responses, our chamber controlled the humidity gradient using reservoirs of hygroscopic materials. Additionally, to better observe the behavioral mechanisms for humidity responses, our chamber provided a larger arena. Although similar chambers have been described previously, these approaches were not suitable for soft-bodied invertebrates or for easy imaging of behavior because they required that animals move across wire or fabric mesh. Conclusion The general applicability of our humidity chamber overcomes limitations of previous designs and opens the door to observe the behavioral responses of soft-bodied invertebrates, including genetically powerful C. elegans and Drosophila larvae. PMID:25176025

Bioprinting 3D cell-laden hydrogel microarray for screening human periodontal ligament stem cell response to extracellular matrix.

PubMed

Ma, Yufei; Ji, Yuan; Huang, Guoyou; Ling, Kai; Zhang, Xiaohui; Xu, Feng

2015-12-22

Periodontitis is an inflammatory disease negatively affecting up to 15% of adults worldwide. Periodontal ligament stem cells (PDLSCs) hold great promises for periodontal tissue regeneration, where it is necessary to find proper extracellular matrix (ECM) materials (e.g., composition, concentration). In this study, we proposed a bioprinting-based approach to generate nano-liter sized three-dimensional (3D) cell-laden hydrogel array with gradient of ECM components, through controlling the volume ratio of two hydrogels, such as gelatin methacrylate (GelMA) and poly(ethylene glycol) (PEG) dimethacrylate. The resulting cell-laden array with a gradient of GelMA/PEG composition was used to screen human PDLSC response to ECM. The behavior (e.g., cell viability, spreading) of human PDLSCs in GelMA/PEG array were found to be depended on the volume ratios of GelMA/PEG, with cell viability and spreading area decreased along with increasing the ratio of PEG. The developed approach would be useful for screening cell-biomaterial interaction in 3D and promoting regeneration of functional tissue.

Contribution of PCR Denaturing Gradient Gel Electrophoresis Combined with Mixed Chromatogram Software Separation for Complex Urinary Sample Analysis.

PubMed

Kotásková, Iva; Mališová, Barbora; Obručová, Hana; Holá, Veronika; Peroutková, Tereza; Růžička, Filip; Freiberger, Tomáš

2017-01-01

Complex samples are a challenge for sequencing-based broad-range diagnostics. We analysed 19 urinary catheter, ureteral Double-J catheter, and urine samples using 3 methodological approaches. Out of the total 84 operational taxonomic units, 37, 61, and 88% were identified by culture, PCR-DGGE-SS (PCR denaturing gradient gel electrophoresis followed by Sanger sequencing), and PCR-DGGE-RM (PCR- DGGE combined with software chromatogram separation by RipSeq Mixed tool), respectively. The latter approach was shown to be an efficient tool to complement culture in complex sample assessment. © 2017 S. Karger AG, Basel.

Microbial response to environmental gradients in a ceramic-based diffusion system.

PubMed

Wolfaardt, G M; Hendry, M J; Birkham, T; Bressel, A; Gardner, M N; Sousa, A J; Korber, D R; Pilaski, M

2008-05-01

A solid, porous matrix was used to establish steady-state concentration profiles upon which microbial responses to concentration gradients of nutrients or antimicrobial agents could be quantified. This technique relies on the development of spatially defined concentration gradients across a ceramic plate resulting from the diffusion of solutes through the porous ceramic matrix. A two-dimensional, finite-element numerical transport model was used to predict the establishment of concentration profiles, after which concentration profiles of conservative tracers were quantified fluorometrically and chemically at the solid-liquid interface to verify the simulated profiles. Microbial growth responses to nutrient, hypochloride, and antimicrobial concentration gradients were then quantified using epifluorescent or scanning confocal laser microscopy. The observed microbial response verified the establishment and maintenance of stable concentration gradients along the solid-liquid interface. These results indicate the ceramic diffusion system has potential for the isolation of heterogeneous microbial communities as well as for testing the efficacy of antimicrobial agents. In addition, the durability of the solid matrix allowed long-term investigations, making this approach preferable to conventional gel-stabilized systems that are impeded by erosion as well as expansion or shrinkage of the gel. Copyright 2008 Wiley Periodicals, Inc.

Study on Movable gel Profiling/Flooding System Optimization at Boundary Temperature

NASA Astrophysics Data System (ADS)

Gao, Shanshan; Xie, Gang; Zhang, Tiantian; Wang, Zhiqiang; Jiang, Peijun; Wei, Junjie; Gu, Yi; Lei, Xiaoyang; Guo, Suzhen; Lei, Shi

2017-12-01

65-75°C is the boundary temperature of phenol-formaldehyde resin and organic chrome crosslink with HPAM to generate movable gel. Generally speaking, when the reservoir temperature is below 65-75°C, the crosslinking agent is Organic chrome. Phenol-formaldehyde resin is used when the temperature is above 65-75°C. In this paper the gelation properties of phenol-formaldehyde resin and organic chrome were compared at 70°C. The experiment results showed that the crosslinking time of phenol-formaldehyde resin gel was longer and more conducive to field injection. In addition the phenol-formaldehyde resin gel had greater viscosity, adhesion and shearing resistance compared with the organic chrome gel. So the phenol-formaldehyde resin was chosen for further optimization. The crosslinking time was shortened and the gel viscosity increased with the increase of the polymer concentration. As the polymer crosslinker proportion increased The crosslinking time was shortened and the gel viscosity increased first and then decreased. Reinforcer NC and stabilizer WG were added to improve the temperature and salt tolerance of the gel. The gel formula suitable for the boundary temperature was obtained. The optimum polymer concentration is 1200mg/L, the polymer crosslinker proportion is 1:1.1, the best reinforcer concentration is 400mg/L and the concentration of the stabilizer is 150mg/L. The crosslinking time is 31h, the gel viscosity is above 2100mPa·s. The gel did not shrink and no water separation was observed at 70°C for 150 days. The viscosity retention rate was more than 70%.

Heated Ultrasound Gel and Patient Satisfaction with Bedside Ultrasound Studies: The HUGS Trial

PubMed Central

Krainin, Benjamin M.; Thaut, Lane C.; April, Michael D.; Curtis, Ryan A.; Kaelin, Andrea L.; Hardy, Garrett B.; Weymouth, Wells L.; Srichandra, Jonathan; Chin, Eric J.; Summers, Shane M.

2017-01-01

Introduction Our goal was to determine if heated gel for emergency department (ED) bedside ultrasonography improves patient satisfaction compared to room-temperature gel. Methods We randomized a convenience sample of ED patients determined by their treating physician to require a bedside ultrasound (US) study to either heated gel (102.0° F) or room-temperature gel (82.3° F). Investigators performed all US examinations. We informed all subjects that the study entailed investigation into various measures to improve patient satisfaction with ED US examinations but did not inform them of our specific focus on gel temperature. Investigators wore heat-resistant gloves while performing the examinations to blind themselves to the gel temperature. After completion of the US, subjects completed a survey including the primary outcome measure of patient satisfaction as measured on a 100-mm visual analogue scale (VAS). A secondary outcome was patient perceptions of sonographer professionalism measured by an ordinal scale (1–5). Results We enrolled 124 subjects; 120 completed all outcome measures. Of these, 59 underwent randomization to US studies with room-temperature gel and 61 underwent randomization to heated US gel. Patient 100-mm VAS satisfaction scores were 83.9 among patients undergoing studies with room-temperature gel versus 87.6 among subjects undergoing studies with heated gel (effect size 3.7, 95% confidence interval −1.3–8.6). There were similarly no differences between the two arms with regard to patient perceptions of sonographer professionalism. Conclusion The use of heated ultrasound gel appears to have no material impact on the satisfaction of ED patients undergoing bedside ultrasound studies. PMID:29085538

The role of temperature in forming sol-gel biocomposites containing polydopamine.

PubMed

Dyke, Jason Christopher; Hu, Huamin; Lee, Dong Joon; Ko, Ching-Chang; You, Wei

2014-11-28

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.

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

Gelatinization and freeze-concentration effects on recrystallization in corn and potato starch gels.

PubMed

Ronda, Felicidad; Roos, Yrjö H

2008-04-07

Freeze-concentration of starch gels was controlled by temperature and gelatinization with glucose and lactose. The aim of the study was to evaluate the effects of freezing temperature and gel composition on starch recrystallization behaviour of corn and potato starch gels (water content 70%, w/w) in water or glucose or lactose (10%, w/w) solutions. Starch gels were obtained by heating in differential scanning calorimetry (DSC). Samples of starch gels were frozen at -10 degrees C, -20 degrees C and -30 degrees C for 24h and, after thawing, stored at +2 degrees C for 0, 1, 2, 4 and 8 days. The extent of starch recrystallization was taken from the enthalpy of melting of the recrystallized starch by DSC. Freezing temperatures, glucose, lactose and the origin of the starch affected the recrystallization behaviour greatly. The recrystallization of amorphous starch during storage was enhanced by freeze-concentration of gels at temperatures above T'(m). Molecular mobility was enhanced by unfrozen water and consequently molecular rearrangements for nucleation could take place. Further storage at a higher temperature enhanced the growth and the maturation of crystals. In particular, glucose decreased the T'(m) of the gels and consequently lower freezing temperatures were needed to reduce enhanced recrystallization during storage. Freeze-concentration temperatures also showed a significant effect on the size and the perfection of crystals formed in starch recrystallization.

Effects of storage temperature on bacterial growth rates and community structure in fresh retail sushi.

PubMed

Hoel, S; Jakobsen, A N; Vadstein, O

2017-09-01

This study was conducted to assess the effects of different storage temperatures (4-20°C), on bacterial concentrations, growth rates and community structure in fresh retail sushi, a popular retail product with a claimed shelf life of 2-3 days. The maximum specific growth rate based on aerobic plate count (APC) at 4°C was 0·06 h -1 and displayed a sixfold increase (0·37 h -1 ) at 20°C. Refrigeration resulted in no growth of hydrogen sulphide (H 2 S)-producing bacteria, but this group had the strongest temperature response. The bacterial community structure was determined by PCR/DGGE (denaturing gradient gel electrophoresis). Multivariate analysis based on Bray-Curtis similarities demonstrated that temperature alone was not the major determinant for the bacterial community structure. The total concentration of aerobic bacteria was the variable that most successfully explained the differences between the communities. The dominating organisms, detected by sequencing of DNA bands excised from the DGGE gel, were Brochothrix thermosphacta and genera of lactic acid bacteria (LAB). The relationship between growth rates and storage temperatures clearly demonstrates that these products are sensitive to deviations from optimal storage temperature, possibly resulting in loss of quality during shelf life. Regardless of the storage temperature, the bacterial communities converged towards a similar structure and density, but the storage temperature determined how fast the community reached its carrying capacity. Little information is available on the microbial composition of ready-to-eat food that are prepared with raw fish, subjected to contamination during handling, and susceptible to microbial growth during cold storage. Moreover, the data are a good first possibility to simulate growth of APC, H 2 S-producing bacteria and LAB under different temperature scenarios that might occur during production, distribution or storage. © 2017 The Society for Applied Microbiology.

Quantitative Analysis of Cancer Cell Migration in Gradients Of EGF, HGF, and SDF-alpha Using a Microfluidic Chemotaxis Device

DTIC Science & Technology

2005-01-01

Quantitative Analysis of Cancer Cell Migration in Gradients of EGF, HGF, and SDF-alpha Using a Microfluidic Chemotaxis Device The University of California...allowing for parallel analysis . Additionally, simple methods of localizing gels into microdevices are demonstrated. The device was characterized by...To overcome some of these drawbacks, several approaches have utilized free diffusion to produce gradients in static environ - ments.5-9 However

Hydrolysis of triolein in phospholipid vesicles and microemulsions by a purified rat liver acid lipase.

PubMed

Burrier, R E; Brecher, P

1983-10-10

An acid lipase was purified from rat liver lysosomes. Lipase purification involved affinity chromatography, gel filtration, and stabilization of the purified preparation using ethylene glycol and Triton X-100. A molecular weight of 67,000-69,000 was determined independently using density gradient centrifugation, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and gel filtration. To study enzyme action, model substrates were prepared by incorporating radiolabeled triolein into either unilamellar vesicles or microemulsions. Substrates were prepared by cosonicating aqueous dispersions of lecithin and triolein. Formation of vesicles or emulsions depended on the relative amount of each lipid and on sonication conditions. Vesicles were prepared at molar ratios between 70:1 and 26:1 (lecithin:triolein) and the microemulsion preparation at a molar ratio of 1:1. The substrate particles were of similar size (220-250 A) as determined by Bio-Gel A-15m chromatography. Hydrolysis of triolein contained in vesicles or emulsions was similar with respect to pH, temperature, and reaction products. Kinetic studies on vesicles with increasing triolein content showed progressively greater Vmax values (0-0.6 mumol/min/mg), and Vmax for the emulsion was 3.1 mumol/min/mg. Addition of human very low or low density lipoprotein produced a dose-dependent inhibition with both substrates. The results show that synthetically prepared microemulsions are stable and effective substrates for the acid lipase and indicate that surface-oriented triolein is hydrolyzed in both preparations.

ANALYSIS OF BACTERIAL COMMUNITIES IN SEAGRASS BED SEDIMENTS BY DOUBLE-GRADIENT DENATURING GRADIENT GEL ELECTROPHORESIS OF PCR-AMPLIFIED 16SRRNA GENES

EPA Science Inventory

Bacterial communities associated with seagrass bed sediments are not well studied. The work presented here investigated several factors, including the presence or absence of vegetation, depth into sediment, and season, and their impact on bacterial community diversity. Double gra...

Evaluations of Different Hypervariable Regions of Archaeal 16S rRNA Genes in Profiling of Methanogens by Archaea-Specific PCR and Denaturing Gradient Gel Electrophoresis▿

PubMed Central

Yu, Zhongtang; García-González, Rubén; Schanbacher, Floyd L.; Morrison, Mark

2008-01-01

Different hypervariable (V) regions of the archaeal 16S rRNA gene (rrs) were compared systematically to establish a preferred V region(s) for use in Archaea-specific PCR-denaturing gradient gel electrophoresis (DGGE). The PCR products of the V3 region produced the most informative DGGE profiles and permitted identification of common methanogens from rumen samples from sheep. This study also showed that different methanogens might be detected when different V regions are targeted by PCR-DGGE. Dietary fat appeared to transiently stimulate Methanosphaera stadtmanae but inhibit Methanobrevibacter sp. strain AbM4 in rumen samples. PMID:18083874

A Simple Experiment for Visualizing Diffusion

ERIC Educational Resources Information Center

Helseth, L. E.

2011-01-01

We propose a simple and fascinating experiment for studying diffusion in gels using a pH-sensitive dye. By doping agar with methyl red, we obtain a gel which rapidly reacts to changes in pH by changing its absorption spectrum. The pH gradients can be followed using a digital camera, and we demonstrate here that the pH-sensitive colour changes can…

3D conformal MRI-controlled transurethral ultrasound prostate therapy: validation of numerical simulations and demonstration in tissue-mimicking gel phantoms.

PubMed

Burtnyk, Mathieu; N'Djin, William Apoutou; Kobelevskiy, Ilya; Bronskill, Michael; Chopra, Rajiv

2010-11-21

MRI-controlled transurethral ultrasound therapy uses a linear array of transducer elements and active temperature feedback to create volumes of thermal coagulation shaped to predefined prostate geometries in 3D. The specific aims of this work were to demonstrate the accuracy and repeatability of producing large volumes of thermal coagulation (>10 cc) that conform to 3D human prostate shapes in a tissue-mimicking gel phantom, and to evaluate quantitatively the accuracy with which numerical simulations predict these 3D heating volumes under carefully controlled conditions. Eleven conformal 3D experiments were performed in a tissue-mimicking phantom within a 1.5T MR imager to obtain non-invasive temperature measurements during heating. Temperature feedback was used to control the rotation rate and ultrasound power of transurethral devices with up to five 3.5 × 5 mm active transducer elements. Heating patterns shaped to human prostate geometries were generated using devices operating at 4.7 or 8.0 MHz with surface acoustic intensities of up to 10 W cm(-2). Simulations were informed by transducer surface velocity measurements acquired with a scanning laser vibrometer enabling improved calculations of the acoustic pressure distribution in a gel phantom. Temperature dynamics were determined according to a FDTD solution to Pennes' BHTE. The 3D heating patterns produced in vitro were shaped very accurately to the prostate target volumes, within the spatial resolution of the MRI thermometry images. The volume of the treatment difference falling outside ± 1 mm of the target boundary was, on average, 0.21 cc or 1.5% of the prostate volume. The numerical simulations predicted the extent and shape of the coagulation boundary produced in gel to within (mean ± stdev [min, max]): 0.5 ± 0.4 [-1.0, 2.1] and -0.05 ± 0.4 [-1.2, 1.4] mm for the treatments at 4.7 and 8.0 MHz, respectively. The temperatures across all MRI thermometry images were predicted within -0.3 ± 1.6 °C and 0.1 ± 0.6 °C, inside and outside the prostate respectively, and the treatment time to within 6.8 min. The simulations also showed excellent agreement in regions of sharp temperature gradients near the transurethral and endorectal cooling devices. Conformal 3D volumes of thermal coagulation can be precisely matched to prostate shapes with transurethral ultrasound devices and active MRI temperature feedback. The accuracy of numerical simulations for MRI-controlled transurethral ultrasound prostate therapy was validated experimentally, reinforcing their utility as an effective treatment planning tool.

Thermal heterogeneity within aqueous materials quantified by 1H NMR spectroscopy: Multiparametric validation in silico and in vitro

NASA Astrophysics Data System (ADS)

Lutz, Norbert W.; Bernard, Monique

2018-02-01

We recently suggested a new paradigm for statistical analysis of thermal heterogeneity in (semi-)aqueous materials by 1H NMR spectroscopy, using water as a temperature probe. Here, we present a comprehensive in silico and in vitro validation that demonstrates the ability of this new technique to provide accurate quantitative parameters characterizing the statistical distribution of temperature values in a volume of (semi-)aqueous matter. First, line shape parameters of numerically simulated water 1H NMR spectra are systematically varied to study a range of mathematically well-defined temperature distributions. Then, corresponding models based on measured 1H NMR spectra of agarose gel are analyzed. In addition, dedicated samples based on hydrogels or biological tissue are designed to produce temperature gradients changing over time, and dynamic NMR spectroscopy is employed to analyze the resulting temperature profiles at sub-second temporal resolution. Accuracy and consistency of the previously introduced statistical descriptors of temperature heterogeneity are determined: weighted median and mean temperature, standard deviation, temperature range, temperature mode(s), kurtosis, skewness, entropy, and relative areas under temperature curves. Potential and limitations of this method for quantitative analysis of thermal heterogeneity in (semi-)aqueous materials are discussed in view of prospective applications in materials science as well as biology and medicine.

Method of making a functionally graded material

DOEpatents

Lauf, Robert J.; Menchhofer, Paul A.; Walls, Claudia A.

2001-01-01

A gelcasting method of making an internally graded article includes the steps of: preparing at least two slurries, each of the slurries including a different gelcastable powder suspended in a gelcasting solution, the slurries characterized by having comparable shrinkage upon drying and sintering thereof; casting the slurries into a mold having a selected shape, wherein relative proportions of the slurries is varied in at least one direction within the selected shape; gelling the slurries to form a solid gel while preserving the variation in relative proportions of the slurries; drying the gel to form a dried green body; and sintering the dry green body to form a solid object, at least one property thereof varying because of the variation in relative proportions of the starting slurries. A gelcasting method of making an internally graded article alternatively includes the steps of: preparing a slurry including a least two different phases suspended in a gelcasting solution, the phases characterized by having different settling characteristics; casting the slurry into a mold having a selected shape; allowing the slurry to stand for a sufficient period of time to permit desired gravitational fractionation in order to achieve a vertical compositional gradient in the molded slurry; gelling the slurry to form a solid gel while preserving the vertical compositional gradient in the molded slurry; drying the gel to form a dried green body; and sintering the dry green body to form a solid object, at least one property thereof varying along the vertical direction because of the compositional gradient in the molded slurry.

Novel chitosan derivative for temperature and ultrasound dual-sensitive liposomal microbubble gel.

PubMed

Chen, Daquan; Yu, Hongyun; Mu, Hongjie; Wei, Junhua; Song, Zhenkun; Shi, Hong; Liang, Rongcai; Sun, Kaoxiang; Liu, Wanhui

2013-04-15

In this study, a novel liposome-loaded microbubble gel based on N-cholesteryl hemisuccinate-O-sulfate chitosan (NCHOSC) was designed. The structure of the NCHOSC was characterized by FTIR and (1)H NMR. The liposomal microbubble gel based on NCHOSC with a high encapsulation efficiency of curcumin was formed and improved the solubility of curcumin. The diameter of most liposomal microbubble was about 950 nm. The temperature-sensitive CS/GP gel could be formulated at room temperature and would form a gel at body temperature. Simultaneously, the ultrasound-sensitive induced release of curcumin was 85% applying ultrasound. The results of cytotoxicity assay indicated that encapsulated curcumin in Cur-LM or Cur-LM-G was less toxic. The anti-tumor efficacy in vivo suggested that Cur-LM-G by ultrasound suppressed tumor growth most efficiently. These findings have shed some light on the potential NCHOSC material used to liposome-loaded microbubble gel for temperature and ultrasound dual-sensitive drug delivery. Copyright © 2013 Elsevier Ltd. All rights reserved.

Novel diffusive gradients in thin films technique to assess labile sulfate in soil.

PubMed

Hanousek, Ondrej; Mason, Sean; Santner, Jakob; Chowdhury, Md Mobaroqul Ahsan; Berger, Torsten W; Prohaska, Thomas

2016-09-01

A novel diffusive gradients in thin films (DGT) technique for sampling labile soil sulfate was developed, based on a strong basic anion exchange resin (Amberlite IRA-400) for sulfate immobilization on the binding gel. For reducing the sulfate background on the resin gels, photopolymerization was applied instead of ammonium persulfate-induced polymerization. Agarose cross-linked polyacrylamide (APA) hydrogels were used as diffusive layer. The sulfate diffusion coefficient in APA gel was determined as 9.83 × 10(-6) ± 0.35 × 10(-6) cm(2) s(-1) at 25 °C. The accumulated sulfate was eluted in 1 mol L(-1) HNO3 with a recovery of 90.9 ± 1.6 %. The developed method was tested against two standard extraction methods for soil sulfate measurement. The obtained low correlation coefficients indicate that DGT and conventional soil test methods assess differential soil sulfate pools, rendering DGT a potentially important tool for measuring labile soil sulfate.

A cost-effective device for the rapid transfer of gel-separated proteins onto membranes.

PubMed

Tam, Hann W; Huang, Yu-Chen; Tam, Ming F

2009-03-01

We describe here the fabrication of a cost-effective semi-dry blotting apparatus for the transfer of proteins onto membranes. Graphite sheets were used as electrodes. Protein mixtures were separated on NuPAGE 4% to 12% polyacrylamide gradient gels. With a Tris-bicine buffer, we demonstrated that close to 80% of the proteins with apparent molecular mass of 80kDa or less were removed from the gels after 8min of blotting. The process is much faster than the techniques reported previously in the literature.

Prevalence of Nitrosomonas cluster 7 populations in the ammonia-oxidizing community of a submerged membrane bioreactor treating urban wastewater under different operation conditions.

PubMed

Cerrone, F; Poyatos, J M; Molina-Muñoz, M; Cortés-Lorenzo, C; González-López, J; Rodelas, B

2013-07-01

A pilot-scale ultrafiltration membrane bioreactor (MBR) was used for the aerobic treatment of urban wastewater in four experimental stages influenced by seasonal temperature and different sets of operation conditions. The structure of the ammonia-oxidizing bacteria (AOB) community was profiled by temperature gradient gel electrophoresis (TGGE), based on the amplification and separation of partial ammonia-monoxygenase subunit A (amoA) genes. Canonical correspondence analysis revealed that temperature, hydraulic retention time and percentage of ammonia removal had a significant effect on the fingerprints of AOB communities. Phylogenetic analysis conducted on amoA/AmoA sequences of reamplified TGGE bands showed, however, that closely related ammonia-oxidizing populations inhabited the sludge of the MBR in all experimental stages. Nitrosomonas cluster 7 populations (N. europaea-N. eutropha cluster) prevailed under all conditions tested, even when the MBR was operated under complete biomass retention or at low temperatures, suggesting that the high ammonia concentrations in the system were determinant to select r-strategist AOB.

A sensitive gel-based global O-glycomics approach reveals high levels of mannosyl glycans in the high mass region of the mouse brain proteome.

PubMed

Breloy, Isabelle; Pacharra, Sandra; Aust, Christina; Hanisch, Franz-Georg

2012-08-01

We developed a gel-based global O-glycomics method applicable for highly complex protein mixtures entrapped in discontinuous gradient gel layers. The protocol is based on in-gel proteolysis with pronase followed by (glyco)peptide elution and off-gel reductive β-elimination. The protocol offers robust performance with sensitivity in the low picomolar range, is compatible with gel-based proteomics, and shows superior performance in global applications in comparison with workflows eliminating glycans in-gel or from electroblotted glycoproteins. By applying this method, we analyzed the O-glycome of human myoblasts and of the mouse brain O-glycoproteome. After semipreparative separation of mouse brain proteins by one-dimensional SDS gel electrophoresis, the O-glycans from proteins in different mass ranges were characterized with a focus on O-mannose-based glycans. The relative proportion of the latter, which generally represent a rare modification, increases to comparatively high levels in the mouse brain proteome in dependence of increasing protein masses.

Chemotaxis of active, self-oscillating polymer gels in solution

NASA Astrophysics Data System (ADS)

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

2012-02-01

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

Tandem dye-ligand chromatography and biospecific elution applied to the purification of glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides.

PubMed Central

Hey, Y; Dean, P D

1983-01-01

1. A total of 65 immobilized triazine dyes were screened for their ability to purify the dual-nucleotide-specific glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides. From this screen a 'negative' (Matrex Gel Purple A) and a 'positive' (Matrex Gel Orange B) adsorbent were found to be the best in terms of overall purification and yield and were therefore combined to give the best purification. 2. Glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides was purified approx. 56-fold in a two-step tandem chromatographic system using Matrex Gel Purple A followed by Matrex Gel Orange B chromatography to a specific activity of 228 units/mg of protein in a final yield of 73%. 3. A study of the elution characteristics of glucose-6-phosphate dehydrogenase bound to Matrex Gel Orange B by KCl (pulse and gradient) and biospecific eluents (pulse) was carried out. NADP+, NADPH and adenosine 2',5'-bisphosphate were found to be the only effective biospecific eluents. A pulse of 50 microM-NADP+ (1/2 column vol.) was found to give a better purification than a 0-1 M-KCl gradient and therefore was the preferred method of elution. 4. Presaturation of the enzyme with various nucleotides was carried out to determine the effect on the subsequent binding of glucose-6-phosphate dehydrogenase to Matrex Gel Orange B. The results of these and biospecific-elution studies lead us to propose two possible schemes to explain the mechanism of the dye-protein interaction. 5. Reusability, capacity of the adsorbent and effect of varying the ligand concentration were also studied in the purification of glucose-6-phosphate dehydrogenase on Matrex Gel Orange B. Images Fig. 1. PMID:6847623

Tandem dye-ligand chromatography and biospecific elution applied to the purification of glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides.

PubMed

Hey, Y; Dean, P D

1983-02-01

1. A total of 65 immobilized triazine dyes were screened for their ability to purify the dual-nucleotide-specific glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides. From this screen a 'negative' (Matrex Gel Purple A) and a 'positive' (Matrex Gel Orange B) adsorbent were found to be the best in terms of overall purification and yield and were therefore combined to give the best purification. 2. Glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides was purified approx. 56-fold in a two-step tandem chromatographic system using Matrex Gel Purple A followed by Matrex Gel Orange B chromatography to a specific activity of 228 units/mg of protein in a final yield of 73%. 3. A study of the elution characteristics of glucose-6-phosphate dehydrogenase bound to Matrex Gel Orange B by KCl (pulse and gradient) and biospecific eluents (pulse) was carried out. NADP+, NADPH and adenosine 2',5'-bisphosphate were found to be the only effective biospecific eluents. A pulse of 50 microM-NADP+ (1/2 column vol.) was found to give a better purification than a 0-1 M-KCl gradient and therefore was the preferred method of elution. 4. Presaturation of the enzyme with various nucleotides was carried out to determine the effect on the subsequent binding of glucose-6-phosphate dehydrogenase to Matrex Gel Orange B. The results of these and biospecific-elution studies lead us to propose two possible schemes to explain the mechanism of the dye-protein interaction. 5. Reusability, capacity of the adsorbent and effect of varying the ligand concentration were also studied in the purification of glucose-6-phosphate dehydrogenase on Matrex Gel Orange B.

Electronic speckle pattern interferometry: a tool for determining diffusion and partition coefficients for proteins in gels.

PubMed

Karlsson, David; Zacchi, Guido; Axelsson, Anders

2002-01-01

The aim of this study was to demonstrate electronic speckle pattern interferometry (ESPI) as a powerful tool in determining diffusion coefficients and partition coefficients for proteins in gels. ESPI employs a CCD camera instead of a holographic plate as in conventional holographic interferometry. This gives the advantage of being able to choose the reference state freely. If a hologram at the reference state is taken and compared to a hologram during the diffusion process, an interferometric picture can be generated that describes the refraction index gradients and thus the concentration gradients in the gel as well as in the liquid. MATLAB is then used to fit Fick's law to the experimental data to obtain the diffusion coefficients in gel and liquid. The partition coefficient is obtained from the same experiment from the flux condition at the interface between gel and liquid. This makes the comparison between the different diffusants more reliable than when the measurements are performed in separate experiments. The diffusion and partitioning coefficients of lysozyme, BSA, and IgG in 4% agarose gel at pH 5.6 and in 0.1 M NaCl have been determined. In the gel the diffusion coefficients were 11.2 +/- 1.6, 4.8 +/- 0.6, and 3.0 +/- 0.3 m(2)/s for lysozyme, BSA, and IgG, respectively. The partition coefficients were determined to be 0.65 +/- 0.04, 0.44 +/- 0.06, and 0.51 +/- 0.04 for lysozyme, BSA, and IgG, respectively. The current study shows that ESPI is easy to use and gives diffusion coefficients and partition coefficients for proteins with sufficient accuracy from the same experiment.

Tensile Properties of Poly (N-vinyl caprolactam) Gels

NASA Technical Reports Server (NTRS)

Morgret, Leslie D.; Hinkley, Jeffrey A.

2004-01-01

N-vinyl caprolactam was copolymerized with ethylene glycol dimethacrylate using a free-radical initiator in alcohol/water solution. The resulting gels were thermally-responsive in water, undergoing an approximate fivefold reversible volume shrinkage between room temperature and ca. 50 C. Tensile testing showed that the stress-strain behavior was qualitatively different in the collapsed state above the temperature-induced transition. At the higher temperature, gels were stiffer, more ductile, and showed greater time dependence. Implications for the design of gel actuators are briefly discussed.

Growth and properties of gradient free sol-gel lead zirconate titanate thin films

NASA Astrophysics Data System (ADS)

Calame, F.; Muralt, P.

2007-02-01

Pb(Zrx,Ti1-x)O3 thin films of homogeneous composition were synthesized by means of a modified sol-gel route on Pt(111)/TiOx/SiO2/Si substrates. The gradient in B-site composition as obtained by standard routes could be lowered, reducing Zr concentration fluctuations form ±12to±2.5at.%. The 2μm thick, dense and crack-free films exhibited a {100}-texture index of 98.4%. Grain diameters increased by 50%. Dielectric and piezoelectric properties were remarkably improved. The relative dielectric constant ɛ33,f was obtained as 1620, and the remanent transverse piezoelectric coefficient e31,f was measured as -17.7Cm2.

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

Sol-gel processing with inorganic metal salt precursors

DOEpatents

Hu, Zhong-Cheng

2004-10-19

Methods for sol-gel processing that generally involve mixing together an inorganic metal salt, water, and a water miscible alcohol or other organic solvent, at room temperature with a macromolecular dispersant material, such as hydroxypropyl cellulose (HPC) added. The resulting homogenous solution is incubated at a desired temperature and time to result in a desired product. The methods enable production of high quality sols and gels at lower temperatures than standard methods. The methods enable production of nanosize sols from inorganic metal salts. The methods offer sol-gel processing from inorganic metal salts.

Comparison of polyacrylamide and agarose gel thin-layer isoelectric focusing for the characterization of beta-lactamases.

PubMed

Vecoli, C; Prevost, F E; Ververis, J J; Medeiros, A A; O'Leary, G P

1983-08-01

Plasmid-mediated beta-lactamases from strains of Escherichia coli and Pseudomonas aeruginosa were separated by isoelectric focusing on a 0.8-mm thin-layer agarose gel with a pH gradient of 3.5 to 9.5. Their banding patterns and isoelectric points were compared with those obtained with a 2.0-mm polyacrylamide gel as the support medium. The agarose method produced banding patterns and isoelectric points which corresponded to the polyacrylamide gel data for most samples. Differences were observed for HMS-1 and PSE-1 beta-lactamases. The HMS-1 sample produced two highly resolvable enzyme bands in agarose gels rather than the single faint enzyme band observed on polyacrylamide gels. The PSE-1 sample showed an isoelectric point shift of 0.2 pH unit between polyacrylamide and agarose gel (pI 5.7 and 5.5, respectively). The short focusing time, lack of toxic hazard, and ease of formulation make agarose a practical medium for the characterization of beta-lactamases.

Comparison of polyacrylamide and agarose gel thin-layer isoelectric focusing for the characterization of beta-lactamases.

PubMed Central

Vecoli, C; Prevost, F E; Ververis, J J; Medeiros, A A; O'Leary, G P

1983-01-01

Plasmid-mediated beta-lactamases from strains of Escherichia coli and Pseudomonas aeruginosa were separated by isoelectric focusing on a 0.8-mm thin-layer agarose gel with a pH gradient of 3.5 to 9.5. Their banding patterns and isoelectric points were compared with those obtained with a 2.0-mm polyacrylamide gel as the support medium. The agarose method produced banding patterns and isoelectric points which corresponded to the polyacrylamide gel data for most samples. Differences were observed for HMS-1 and PSE-1 beta-lactamases. The HMS-1 sample produced two highly resolvable enzyme bands in agarose gels rather than the single faint enzyme band observed on polyacrylamide gels. The PSE-1 sample showed an isoelectric point shift of 0.2 pH unit between polyacrylamide and agarose gel (pI 5.7 and 5.5, respectively). The short focusing time, lack of toxic hazard, and ease of formulation make agarose a practical medium for the characterization of beta-lactamases. Images PMID:6605714

Differences in protein expression among five species of stream stonefly (Plecoptera) along a latitudinal gradient in Japan.

PubMed

Gamboa, Maribet; Tsuchiya, Maria Claret; Matsumoto, Suguru; Iwata, Hisato; Watanabe, Kozo

2017-11-01

Proteome variation among natural populations along an environmental gradient may provide insights into how the biological functions of species are related to their local adaptation. We investigated protein expression in five stream stonefly species from four geographic regions along a latitudinal gradient in Japan with varying climatic conditions. The extracted proteins were separated by two-dimensional gel electrophoresis and identified by matrix-assisted laser desorption/ionization of time-of-flight (MALDI TOF/TOF), yielding 446 proteins. Low interspecies variation in the proteome profiles was observed among five species within geographical regions, presumably due to the co-occurring species sharing the environments. However, large spatial variations in protein expression were found among four geographic regions, suggesting strong regulation of protein expression in heterogeneous environments, where the spatial variations were positively correlated with water temperature. We identified 21 unique proteins expressed specifically in a geographical region and six common proteins expressed throughout all regions. In warmer regions, metabolic proteins were upregulated, whereas proteins related to cold stress, the photoperiod, and mating were downregulated. Oxygen-related and energy-production proteins were upregulated in colder regions with higher altitudes. Thus, our proteomic approach is useful for identifying and understanding important biological functions related to local adaptations by populations of stoneflies. © 2017 Wiley Periodicals, Inc.

A Comprehensive Quality Evaluation System for Complex Herbal Medicine Using PacBio Sequencing, PCR-Denaturing Gradient Gel Electrophoresis, and Several Chemical Approaches

PubMed Central

Zheng, Xiasheng; Zhang, Peng; Liao, Baosheng; Li, Jing; Liu, Xingyun; Shi, Yuhua; Cheng, Jinle; Lai, Zhitian; Xu, Jiang; Chen, Shilin

2017-01-01

Herbal medicine is a major component of complementary and alternative medicine, contributing significantly to the health of many people and communities. Quality control of herbal medicine is crucial to ensure that it is safe and sound for use. Here, we investigated a comprehensive quality evaluation system for a classic herbal medicine, Danggui Buxue Formula, by applying genetic-based and analytical chemistry approaches to authenticate and evaluate the quality of its samples. For authenticity, we successfully applied two novel technologies, third-generation sequencing and PCR-DGGE (denaturing gradient gel electrophoresis), to analyze the ingredient composition of the tested samples. For quality evaluation, we used high performance liquid chromatography assays to determine the content of chemical markers to help estimate the dosage relationship between its two raw materials, plant roots of Huangqi and Danggui. A series of surveys were then conducted against several exogenous contaminations, aiming to further access the efficacy and safety of the samples. In conclusion, the quality evaluation system demonstrated here can potentially address the authenticity, quality, and safety of herbal medicines, thus providing novel insight for enhancing their overall quality control. Highlight: We established a comprehensive quality evaluation system for herbal medicine, by combining two genetic-based approaches third-generation sequencing and DGGE (denaturing gradient gel electrophoresis) with analytical chemistry approaches to achieve the authentication and quality connotation of the samples. PMID:28955365

A Comprehensive Quality Evaluation System for Complex Herbal Medicine Using PacBio Sequencing, PCR-Denaturing Gradient Gel Electrophoresis, and Several Chemical Approaches.

PubMed

Zheng, Xiasheng; Zhang, Peng; Liao, Baosheng; Li, Jing; Liu, Xingyun; Shi, Yuhua; Cheng, Jinle; Lai, Zhitian; Xu, Jiang; Chen, Shilin

2017-01-01

Herbal medicine is a major component of complementary and alternative medicine, contributing significantly to the health of many people and communities. Quality control of herbal medicine is crucial to ensure that it is safe and sound for use. Here, we investigated a comprehensive quality evaluation system for a classic herbal medicine, Danggui Buxue Formula, by applying genetic-based and analytical chemistry approaches to authenticate and evaluate the quality of its samples. For authenticity, we successfully applied two novel technologies, third-generation sequencing and PCR-DGGE (denaturing gradient gel electrophoresis), to analyze the ingredient composition of the tested samples. For quality evaluation, we used high performance liquid chromatography assays to determine the content of chemical markers to help estimate the dosage relationship between its two raw materials, plant roots of Huangqi and Danggui. A series of surveys were then conducted against several exogenous contaminations, aiming to further access the efficacy and safety of the samples. In conclusion, the quality evaluation system demonstrated here can potentially address the authenticity, quality, and safety of herbal medicines, thus providing novel insight for enhancing their overall quality control. Highlight : We established a comprehensive quality evaluation system for herbal medicine, by combining two genetic-based approaches third-generation sequencing and DGGE (denaturing gradient gel electrophoresis) with analytical chemistry approaches to achieve the authentication and quality connotation of the samples.

Detection by denaturing gradient gel electrophoresis of ammonia-oxidizing bacteria in microcosms of crude oil-contaminated mangrove sediments.

PubMed

dos Santos, A C F; Marques, E L S; Gross, E; Souza, S S; Dias, J C T; Brendel, M; Rezende, R P

2012-01-27

Currently, the effect of crude oil on ammonia-oxidizing bacterium communities from mangrove sediments is little understood. We studied the diversity of ammonia-oxidizing bacteria in mangrove microcosm experiments using mangrove sediments contaminated with 0.1, 0.5, 1, 2, and 5% crude oil as well as non-contaminated control and landfarm soil from near an oil refinery in Camamu Bay in Bahia, Brazil. The evolution of CO(2) production in all crude oil-contaminated microcosms showed potential for mineralization. Cluster analysis of denaturing gradient gel electrophoresis-derived samples generated with primers for gene amoA, which encodes the functional enzyme ammonia monooxygenase, showed differences in the sample contaminated with 5% compared to the other samples. Principal component analysis showed divergence of the non-contaminated samples from the 5% crude oil-contaminated sediment. A Venn diagram generated from the banding pattern of PCR-denaturing gradient gel electrophoresis was used to look for operational taxonomic units (OTUs) in common. Eight OTUs were found in non-contaminated sediments and in samples contaminated with 0.5, 1, or 2% crude oil. A Jaccard similarity index of 50% was found for samples contaminated with 0.1, 0.5, 1, and 2% crude oil. This is the first study that focuses on the impact of crude oil on the ammonia-oxidizing bacterium community in mangrove sediments from Camamu Bay.

Quantitative ultra-fast MRI of HPMC swelling and dissolution.

PubMed

Chen, Ya Ying; Hughes, L P; Gladden, L F; Mantle, M D

2010-08-01

For the first time quantitative Rapid Acquisition with Relaxation Enhancement (RARE) based ultra-fast two-dimensional magnetic resonance imaging has been used to follow the dissolution of hydroxypropylmethyl cellulose (HPMC) in water. Quantitative maps of absolute water concentration, spin-spin relaxation times and water self-diffusion coefficient are obtained at a spatial resolution of 469 microm in less than 3 min each. These maps allow the dynamic development of the medium release rate HPMC/water system to be followed. It is demonstrated that the evolution of the gel layer and, in particular, the gradient in water concentration across it, is significantly different when comparing the quantitative RARE sequence with a standard (nonquantitative) implementation of RARE. The total gel thickness in the axial direction grows faster than that in the radial direction and that the dry core initially expands anisotropically. Additionally, while HPMC absorbs a large amount of water during the dissolution process, the concentration gradient of water within the gel layer is relatively small. For the first time MRI evidence is presented for a transition swollen glassy layer which resides between the outer edge of the dry tablet core and the inner edge of the gel layer. (c) 2010 Wiley-Liss, Inc. and the American Pharmacists Association

Low temperature synthesis of CaO-SiO2 glasses having stable liquid-liquid immiscibility by sol-gel process

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.

1990-01-01

Calcium silicate glass compositions lying within the liquid-liquid immiscibility dome of the phase diagram, which could not have been prepared by the conventional melting method, were synthesized by the sol-gel process. Hydrolysis and polycondensation of tetraethyl orthosilicate (TEOS) solutions containing up to 20 mol percent calcium nitrate resulted in the formation of clear and transparent gels. The gel formation time decreased with increase in water:TEOS mole ratio, calcium content, and the reaction temperature. Smaller values of gel times in the presence of calcium nitrate are probably caused by lowering of the ionic charge on the sol particles by the salt present. The gelation activation energy, E(sub gel), was evaluated from temperature dependence of the gel time. Presence of Ca(2+) ions or the water:TEOS mole ratio did not have an appreciable effect on the value of E(sub gel). Presence of glycerol in the solution helped in the formation of crack-free monolithic gel specimens. Chemical and structural changes occurring in the gels, as a function of the heat treatments, have been monitored using DTA, TGA, IR-spectroscopy, x ray diffraction, surface area and pore size distribution measurements.

Low temperature synthesis of CaO-SiO2 glasses having stable liquid-liquid immiscibility by the sol-gel process

NASA Technical Reports Server (NTRS)

Bansal, N. P.

1992-01-01

Calcium silicate glass compositions lying within the liquid-liquid immiscibility dome of the phase diagram, which could not have been prepared by the conventional melting method, were synthesized by the sol-gel process. Hydrolysis and polycondensation of tetraethyl orthosilicate (TEOS) solutions containing up to 20 mol percent calcium nitrate resulted in the formation of clear and transparent gels. The gel formation time decreased with increase in water: TEOS mole ratio, calcium content, and the reaction temperature. Smaller values of gel times in the presence of calcium nitrate are probably caused by lowering of the ionic charge on the sol particles by the salt present. The gelation activation energy, E(sub gel), was evaluated from temperature dependence of the gel time. Presence of Ca(2+) ions or the water:TEOS mole ratio did not have an appreciable effect on the value of E(sub gel). Presence of glycerol in the solution helped in the formation of crack-free monolithic gel specimens. Chemical and structural changes occurring in the gels, as a function of the heat treatments, have been monitored using DTA, TGA, IR-spectroscopy, X-ray diffraction, surface area and pore size distribution measurements.

Can a commercial gel dosimetry system be used to verify stereotactic spinal radiotherapy treatment dose distributions?

NASA Astrophysics Data System (ADS)

Kairn, T.; Asena, A.; Crowe, S. B.; Livingstone, A.; Papworth, D.; Smith, S.; Sutherland, B.; Sylvander, S.; Franich, R. D.; Trapp, J. V.

2017-05-01

This study investigated the use of the TruView xylenol-orange-based gel and VISTA optical CT scanner (both by Modus Medical Inc, London, Canada), for use in verifying the accuracy of planned dose distributions for hypo-fractionated (stereotactic) vertebral treatments. Gel measurements were carried out using three stereotactic vertebral treatments and compared with planned doses calculated using the Eclipse treatment planning system (Varian Medical Systems, Palo Alto, USA) as well as with film measurements made using Gafchromic EBT3 film (Ashland Inc, Covington, USA), to investigate the accuracy of the gel system. The gel was calibrated with reference to a moderate-dose gradient region in one of the gel samples. Generally, the gel measurements were able to approximate the close agreement between the doses calculated by the treatment planning system and the doses measured using film (which agreed with each other within 2%), despite lower resolution and bit depth. Poorer agreement was observed when the dose delivered to the gel exceeded the range of doses delivered in the calibration region. This commercial gel dosimetry system may be used to verify hypo-fractionated treatments of vertebral targets, although separate gel calibration measurements are recommended.

Sources, isolation, characterisation and evaluation of probiotics.

PubMed

Fontana, Luis; Bermudez-Brito, Miriam; Plaza-Diaz, Julio; Muñoz-Quezada, Sergio; Gil, Angel

2013-01-01

According to the FAO and the WHO, probiotics are 'live microorganisms which, when administered in adequate amounts, confer a health benefit on the host'. The strains most frequently used as probiotics include lactic acid bacteria and bifidobacteria, which are isolated from traditional fermented products and the gut, faeces and breast milk of human subjects. The identification of microorganisms is the first step in the selection of potential probiotics. The present techniques, including genetic fingerprinting, gene sequencing, oligonucleotide probes and specific primer selection, discriminate closely related bacteria with varying degrees of success. Additional molecular methods, such as denaturing gradient gel electrophoresis/temperature gradient gel electrophoresis and fluorescence in situ hybridisation, are employed to identify and characterise probiotics. The ability to examine fully sequenced genomes has accelerated the application of genetic approaches to the elucidation of the functional roles of probiotics. One of the best-demonstrated clinical benefits of probiotics is the prevention and treatment of acute and antibiotic-associated diarrhoea;however, there is mounting evidence for a potential role for probiotics in the treatment of allergies and intestinal, liver and metabolic diseases. There are various mechanisms by which probiotics exert their beneficial effects: regulation of intestinal permeability, normalisation of host intestinal microbiota, improvement of gut immune barrier function, and adjustment between pro- and anti-inflammatory cytokines. The number of studies carried out to test the effects of probiotics in vitro and in animals is enormous. However, the most reliable method of assessing the therapeutic benefits of any probiotic strain is the use of randomised, placebo-controlled trials, which are reviewed in this article [corrected].

Range-Wide Latitudinal and Elevational Temperature Gradients for the World's Terrestrial Birds: Implications under Global Climate Change

PubMed Central

La Sorte, Frank A.; Butchart, Stuart H. M.; Jetz, Walter; Böhning-Gaese, Katrin

2014-01-01

Species' geographical distributions are tracking latitudinal and elevational surface temperature gradients under global climate change. To evaluate the opportunities to track these gradients across space, we provide a first baseline assessment of the steepness of these gradients for the world's terrestrial birds. Within the breeding ranges of 9,014 bird species, we characterized the spatial gradients in temperature along latitude and elevation for all and a subset of bird species, respectively. We summarized these temperature gradients globally for threatened and non-threatened species and determined how their steepness varied based on species' geography (range size, shape, and orientation) and projected changes in temperature under climate change. Elevational temperature gradients were steepest for species in Africa, western North and South America, and central Asia and shallowest in Australasia, insular IndoMalaya, and the Neotropical lowlands. Latitudinal temperature gradients were steepest for extratropical species, especially in the Northern Hemisphere. Threatened species had shallower elevational gradients whereas latitudinal gradients differed little between threatened and non-threatened species. The strength of elevational gradients was positively correlated with projected changes in temperature. For latitudinal gradients, this relationship only held for extratropical species. The strength of latitudinal gradients was better predicted by species' geography, but primarily for extratropical species. Our findings suggest threatened species are associated with shallower elevational temperature gradients, whereas steep latitudinal gradients are most prevalent outside the tropics where fewer bird species occur year-round. Future modeling and mitigation efforts would benefit from the development of finer grain distributional data to ascertain how these gradients are structured within species' ranges, how and why these gradients vary among species, and the capacity of species to utilize these gradients under climate change. PMID:24852009

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

NASA Astrophysics Data System (ADS)

Vandecasteele, Jan; De Deene, Yves

2013-09-01

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

Aperture-Tolerant, Chemical-Based Methods to Reduce Channeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Randall S. Seright

2007-09-30

This final technical progress report describes work performed from October 1, 2004, through May 16, 2007, for the project, 'Aperture-Tolerant, Chemical-Based Methods to Reduce Channeling'. We explored the potential of pore-filling gels for reducing excess water production from both fractured and unfractured production wells. Several gel formulations were identified that met the requirements--i.e., providing water residual resistance factors greater than 2,000 and ultimate oil residual resistance factors (F{sub rro}) of 2 or less. Significant oil throughput was required to achieve low F{sub rro} values, suggesting that gelant penetration into porous rock must be small (a few feet or less) formore » existing pore-filling gels to provide effective disproportionate permeability reduction. Compared with adsorbed polymers and weak gels, strong pore-filling gels can provide greater reliability and behavior that is insensitive to the initial rock permeability. Guidance is provided on where relative-permeability-modification/disproportionate-permeability-reduction treatments can be successfully applied for use in either oil or gas production wells. When properly designed and executed, these treatments can be successfully applied to a limited range of oilfield excessive-water-production problems. We examined whether gel rheology can explain behavior during extrusion through fractures. The rheology behavior of the gels tested showed a strong parallel to the results obtained from previous gel extrusion experiments. However, for a given aperture (fracture width or plate-plate separation), the pressure gradients measured during the gel extrusion experiments were much higher than anticipated from rheology measurements. Extensive experiments established that wall slip and first normal stress difference were not responsible for the pressure gradient discrepancy. To explain the discrepancy, we noted that the aperture for gel flow (for mobile gel wormholing through concentrated immobile gel within the fracture) was much narrower than the width of the fracture. The potential of various approaches were investigated for improving sweep in parts of the Daqing Oil Field that have been EOR targets. Possibilities included (1) gel treatments that are directed at channeling through fractures, (2) colloidal dispersion gels, (3) reduced polymer degradation, (4) more viscous polymer solutions, and (5) foams and other methods. Fractures were present in a number of Daqing wells (both injectors and producers). Because the fractures were narrow far from the wellbore, severe channeling did not occur. On the contrary, fractures near the wellbore aided reservoir sweep. In the February 2006 issue of the Journal of Petroleum Technology, a 'Distinguished-Author-Series' paper claimed that a process using aqueous colloidal dispersion gels (CDG gels) performed superior to polymer flooding. Unfortunately, this claim is misleading and generally incorrect. Colloidal dispersion gels, in their present state of technological development, should not be advocated as an improvement to, or substitute for, polymer flooding.« less

Transport characteristics of nanoparticle-based ferrofluids in a gel model of the brain

PubMed Central

Basak, Soubir; Brogan, David; Dietrich, Hans; Ritter, Rogers; Dacey, Ralph G; Biswas, Pratim

2009-01-01

A current advance in nanotechnology is the selective targeting of therapeutics by external magnetic field-guided delivery. This is an important area of research in medicine. The use of magnetic forces results in the formation of agglomerated structures in the field region. The transport characteristics of these agglomerated structures are explored. A nonintrusive method based on in situ light-scattering techniques is used to characterize the velocity of such particles in a magnetic field gradient. A transport model for the chain-like agglomerates is developed based on these experimental observations. The transport characteristics of magnetic nanoparticle drug carriers are then explored in gel-based simulated models of the brain. Results of such measurements demonstrate decreased diffusion of magnetic nanoparticles when placed in a high magnetic field gradient. PMID:19421367

Detection and Identification of Gastrointestinal Lactobacillus Species by Using Denaturing Gradient Gel Electrophoresis and Species-Specific PCR Primers

PubMed Central

Walter, J.; Tannock, G. W.; Tilsala-Timisjarvi, A.; Rodtong, S.; Loach, D. M.; Munro, K.; Alatossava, T.

2000-01-01

Denaturing gradient gel electrophoresis (DGGE) of DNA fragments obtained by PCR amplification of the V2-V3 region of the 16S rRNA gene was used to detect the presence of Lactobacillus species in the stomach contents of mice. Lactobacillus isolates cultured from human and porcine gastrointestinal samples were identified to the species level by using a combination of DGGE and species-specific PCR primers that targeted 16S-23S rRNA intergenic spacer region or 16S rRNA gene sequences. The identifications obtained by this approach were confirmed by sequencing the V2-V3 region of the 16S rRNA gene and by a BLAST search of the GenBank database. PMID:10618239

In vitro study of prebiotic properties of levan-type exopolysaccharides from Lactobacilli and non-digestible carbohydrates using denaturing gradient gel electrophoresis.

PubMed

Bello, F D; Walter, J; Hertel, C; Hammes, W P

2001-07-01

Batch cultures inoculated with human faeces were used to study the prebiotic properties of levan-type exopolysaccharides (EPS) from Lactobacillus sanfranciscensis as well as levan, inulin, and fructooligosaccharide (FOS). Denaturing gradient gel electrophoresis of 16S rDNA fragments generated by PCR with universal primers was used to analyse the cultures. Characteristic changes were revealed in the composition of the gut bacteria during fermentation of the carbohydrates. An enrichment of Bifidobacterium spp. was found for the EPS and inulin but not for levan and FOS. The bifidogenic effect of the EPS was confirmed by culturing on selective medium. In addition, the use of EPS and FOS resulted in enhanced growth of Eubacterium biforme and Clostridium perfringens, respectively.

Low temperature synthesis of monolithic transparent Ta2O5 gels from hydrolysis of metal alkoxide

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.

1993-01-01

Tantalum oxide gels in the form of transparent monoliths and powder were prepared from hydrolysis of tantalum pentaethoxide under controlled conditions using different mole ratios of Ta(OC2H5)5:C2H50H:H20:HCl. Alcohol acts as the mutual solvent and HCl as the deflocculating agent. For a fixed alkoxide:water:HCl ratio, time of gel formation increased with the alcohol to alkoxide mole ratio. Thermal evolution of the physical and structural changes in the gel was monitored by differential thermal analysis, thermogravimetric analysis, x-ray diffraction, and infrared spectroscopy. On heating to approximately 400 C, the amorphous gel crystallized into the low temperature orthorhombic phase Beta-Ta2O5, which transformed into the high temperature tetragonal phase Alpha-Ta2O5 when further heated to approximately 1450 C. The volume fraction of the crystalline phase increased with the firing temperature. The Alpha-Ta205 converted back into the low temperature phase, Beta-Ta2O5, on slow cooling through the transformation temperature of 1360 C indicating a slow but reversible transformation.

A preliminary study of the thermal measurement with nMAG gel dosimeter by MRI

NASA Astrophysics Data System (ADS)

Chuang, Chun-Chao; Shao, Chia-Ho; Shih, Cheng-Ting; Yeh, Yu-Chen; Lu, Cheng-Chang; Chuang, Keh-Shih; Wu, Jay

2014-11-01

The methacrylic acid (nMAG) gel dosimeter is an effective tool for 3-dimensional quality assurance of radiation therapy. In addition to radiation induced polymerization effects, the nMAG gel also responds to temperature variation. In this study, we proposed a new method to evaluate the thermal response in thermal therapy using nMAG gel and magnetic resonance image (MRI) scans. Several properties of nMAG have been investigated including the R2 relaxation rate, temperature sensitivity, and temperature linearity of the thermal dose response. nMAG was heated by the double-boiling method in the range of 37-45 °C. MRI scans were performed with the head coil receiver. The temperature to R2 response curve was analyzed and simple linear regression was performed with an R-square value of 0.9835. The measured data showed a well inverse linear relationship between R2 and temperature. We conclude that the nMAG polymer gel dosimeter shows great potential as a technique to evaluate the temperature rise during thermal surgery.

Rapid detection of common Chinese glucose-6-phosphate dehydrogenase (G6PD) mutations by denaturing gradient gel electrophoresis (DGGE).

PubMed

Lam, V M; Huang, W; Lam, S T; Yeung, C Y; Johnson, P H

1996-03-01

We describe here the use of denaturing gradient gel electrophoresis (DGGE) to detect the most common Chinese glucose-6-phosphate dehydrogenase (G6PD) variants, which are the single point mutations: G-->T at nt 1376, G-->A at 1388 both in exon 12 and A-->G at nt 95 in exon 02. In each case, the mutant allele resolves well from the normal allele(s). The distinct heteroduplex bands are characteristic of a particular genotype suggesting that this feature is very useful for identifying all heterozygous carriers for this and other X-linked diseases. When the analysis is extended to other exons, DGGE scans the gene and coupled with direct sequencing, it leads to the identification of new G6PD variation(s). With this approach, we identified a mutation in exon 9 which had not been reported in Hong Kong. Since DGGE can rapidly screen many unknown samples in one gel, this approach could be used to diagnose these G6PD mutations and to identify the at-risk for counselling.

Preparation of fast response superabsorbent hydrogels by radiation polymerization and crosslinking of N-isopropylacrylamide in solution

NASA Astrophysics Data System (ADS)

Abd El-Mohdy, H. L.; Safrany, Agnes

2008-03-01

Macroporous temperature-responsive poly( N-isopropylacrylamide) (PNIPAAm) hydrogels with high equilibrium swelling and fast response rates were obtained by a 60Co γ- and electron beam (EB) irradiation of aqueous N-isopropylacrylamide (NIPAAm) monomer solutions. The effect of irradiation temperatures, the dose, the addition of a pore-forming agent on the swelling ratio, and the kinetics of swelling and shrinking of the PNIPAAm gels was studied. The gels synthesized above the LCST exhibited the highest equilibrium swelling (300-400) and fastest response rate measured by minutes. Scanning electron microscope (SEM) pictures revealed that the gels synthesized above the LCST have larger pores than those prepared at temperatures below the LCST. The gels showed a reversible response to cyclical changes in temperature and might be used in a pulsed drug delivery device. The gels synthesized above the LCST exhibited the highest testosterone propionate release.

Thermo-responsive gels that absorb moisture and ooze water.

PubMed

Matsumoto, Kazuya; Sakikawa, Nobuki; Miyata, Takashi

2018-06-13

The water content of thermo-responsive hydrogels can be drastically altered by small changes in temperature because their polymer chains change from hydrophilic to hydrophobic above their low critical solution temperature (LCST). In general, such smart hydrogels have been utilized in aqueous solutions or in their wet state, and no attempt has been made to determine the phase-transition behavior of the gels in their dried states. Here we demonstrate an application of the thermo-responsive behavior of an interpenetrating polymer network (IPN) gel comprising thermo-responsive poly(N-isopropylacrylamide) and hydrophilic sodium alginate networks in their dried states. The dried IPN gel absorbs considerable moisture from air at temperatures below its LCST and oozes the absorbed moisture as liquid water above its LCST. These phenomena provide energy exchange systems in which moisture from air can be condensed to liquid water using the controllable hydrophilic/hydrophobic properties of thermo-responsive gels with a small temperature change.

Monte Carlo simulation of two-component bilayers: DMPC/DSPC mixtures.

PubMed Central

Sugár, I P; Thompson, T E; Biltonen, R L

1999-01-01

In this paper, we describe a relatively simple lattice model of a two-component, two-state phospholipid bilayer. Application of Monte Carlo methods to this model permits simulation of the observed excess heat capacity versus temperature curves of dimyristoylphosphatidylcholine (DMPC)/distearoylphosphatidylcholine (DSPC) mixtures as well as the lateral distributions of the components and properties related to these distributions. The analysis of the bilayer energy distribution functions reveals that the gel-fluid transition is a continuous transition for DMPC, DSPC, and all DMPC/DSPC mixtures. A comparison of the thermodynamic properties of DMPC/DSPC mixtures with the configurational properties shows that the temperatures characteristics of the configurational properties correlate well with the maxima in the excess heat capacity curves rather than with the onset and completion temperatures of the gel-fluid transition. In the gel-fluid coexistence region, we also found excellent agreement between the threshold temperatures at different system compositions detected in fluorescence recovery after photobleaching experiments and the temperatures at which the percolation probability of the gel clusters is 0.36. At every composition, the calculated mole fraction of gel state molecules at the fluorescence recovery after photobleaching threshold is 0.34 and, at the percolation threshold of gel clusters, it is 0.24. The percolation threshold mole fraction of gel or fluid lipid depends on the packing geometry of the molecules and the interchain interactions. However, it is independent of temperature, system composition, and state of the percolating cluster. PMID:10096905

Optimization of the diffusive gradients in thin films (DGT) method for simultaneous assay of potassium and plant-available phosphorus in soils.

PubMed

Zhang, Yulin; Mason, Sean; McNeill, Ann; McLaughlin, Michael J

2013-09-15

Potassium (K) and phosphorus (P) are two important macronutrients for crops, and are usually applied to soils as granular fertilizer before seeding. Therefore, accurate soil tests prior to planting to predict crop response to fertilizers are important in optimizing crop yields. Traditional methods used for testing both available K and P in soils, which are based on chemical extraction procedures, are to be soil-type dependent, and the predictive relationships across a broad range of soils are generally poor. The diffusive gradients in thin films (DGT) technique, based on diffusion theory, is extensively used to measure the diffusive supply of trace elements, metals and some nutrients in soils and water. When DGT is used to assess plant-available P in soils, a good relationship is found between crop response to P fertilizer and concentrations of P in soil measured by DGT, and therefore the DGT method provides a more precise recommendation of P fertilizer requirements. Adaptation of the DGT method to measure plant-available K in soils has already been attempted [1], but limitations were reported due to the non-uniform size of the resin gel, decreased K binding rate of the gel at long deployment times and a limited ability to measure a wide range of K concentrations. To eliminate these problems, a new resin gel has been developed by combining Amberlite and ferrihydrite. This mixed Amberlite and ferrihydrite (MAF) gel has improved properties in terms of handling and even distribution of Amberlite in the gel. The elution efficiencies of the MAF gel for K and P were 90% and 96%, respectively. The diffusion coefficient of K through the diffusive gel was 1.30 × 10(-5)cm(2)s(-1) at 22 ± 1°C and was stable through time. Since ferrihydrite is already used in DGT P testing, the ability of the MAF gel to assess available P simultaneously was also assessed. The MAF gel performed the same as the traditional ferrihydrite gel for available P assessment in a wide variety of agricultural soils. This means that the newly developed gel has the potential to measure K and plant-available P in soils simultaneously. Copyright © 2013 Elsevier B.V. All rights reserved.

The effect of polymer composition on the gelation behavior of PLGA-g-PEG biodegradable thermoreversible gels.

PubMed

Tarasevich, B J; Gutowska, A; Li, X S; Jeong, B-M

2009-04-01

Graft copolymers consisting of a poly(D,L-lactic acid-co-glycolic acid) backbone grafted with polyethylene glycol side chains were synthesized and formed thermoreversible gels in aqueous solutions that exhibited solution behavior at low temperature and sol-to-gel transitions at higher temperature. The composition of the polymer and relative amounts of polylactic acid, glycolic acid, and ethylene glycol were varied by controlling the precursor concentrations and reaction temperature. The gelation temperature could be systematically tailored from 15 to 34 degrees C by increasing the concentration of polyethylene glycol in the graft copolymer. The gelation temperature also depended on the polymer molecular weight and concentration. This work has importance for the development of water soluble gels with tailored compositions and gelation temperatures for use in tissue engineering and as injectable depots for drug delivery. Copyright 2008 Wiley Periodicals, Inc.

Effect of temperature gradient on liquid-liquid phase separation in a polyolefin blend.

PubMed

Jiang, Hua; Dou, Nannan; Fan, Guoqiang; Yang, Zhaohui; Zhang, Xiaohua

2013-09-28

We have investigated experimentally the structure formation processes during phase separation via spinodal decomposition above and below the spinodal line in a binary polymer blend system exposed to in-plane stationary thermal gradients using phase contrast optical microscopy and temperature gradient hot stage. Below the spinodal line there is a coupling of concentration fluctuations and thermal gradient imposed by the temperature gradient hot stage. Also under the thermal gradient annealing phase-separated domains grow faster compared with the system under homogeneous temperature annealing on a zero-gradient or a conventional hot stage. We suggest that the in-plane thermal gradient accelerates phase separation through the enhancement in concentration fluctuations in the early and intermediate stages of spinodal decomposition. In a thermal gradient field, the strength of concentration fluctuation close to the critical point (above the spinodal line) is strong enough to induce phase separation even in one-phase regime of the phase diagram. In the presence of a temperature gradient the equilibrium phase diagrams are no longer valid, and the systems with an upper critical solution temperature can be quenched into phase separation by applying the stationary temperature gradient. The in-plane temperature gradient drives enhanced concentration fluctuations in a binary polymer blend system above and below the spinodal line.

Evidence of native α-synuclein conformers in the human brain.

PubMed

Gould, Neal; Mor, Danielle E; Lightfoot, Richard; Malkus, Kristen; Giasson, Benoit; Ischiropoulos, Harry

2014-03-14

α-Synuclein aggregation is central to the pathogenesis of several brain disorders. However, the native conformations and functions of this protein in the human brain are not precisely known. The native state of α-synuclein was probed by gel filtration coupled with native gradient gel separation, an array of antibodies with non-overlapping epitopes, and mass spectrometry. The existence of metastable conformers and stable monomer was revealed in the human brain.

Diversity of bacteria and archaea from two shallow marine hydrothermal vents from Vulcano Island.

PubMed

Antranikian, Garabed; Suleiman, Marcel; Schäfers, Christian; Adams, Michael W W; Bartolucci, Simonetta; Blamey, Jenny M; Birkeland, Nils-Kåre; Bonch-Osmolovskaya, Elizaveta; da Costa, Milton S; Cowan, Don; Danson, Michael; Forterre, Patrick; Kelly, Robert; Ishino, Yoshizumi; Littlechild, Jennifer; Moracci, Marco; Noll, Kenneth; Oshima, Tairo; Robb, Frank; Rossi, Mosè; Santos, Helena; Schönheit, Peter; Sterner, Reinhard; Thauer, Rudolf; Thomm, Michael; Wiegel, Jürgen; Stetter, Karl Otto

2017-07-01

To obtain new insights into community compositions of hyperthermophilic microorganisms, defined as having optimal growth temperatures of 80 °C and above, sediment and water samples were taken from two shallow marine hydrothermal vents (I and II) with temperatures of 100 °C at Vulcano Island, Italy. A combinatorial approach of denaturant gradient gel electrophoresis (DGGE) and metagenomic sequencing was used for microbial community analyses of the samples. In addition, enrichment cultures, growing anaerobically on selected polysaccharides such as starch and cellulose, were also analyzed by the combinatorial approach. Our results showed a high abundance of hyperthermophilic archaea, especially in sample II, and a comparable diverse archaeal community composition in both samples. In particular, the strains of the hyperthermophilic anaerobic genera Staphylothermus and Thermococcus, and strains of the aerobic hyperthermophilic genus Aeropyrum, were abundant. Regarding the bacterial community, ε-Proteobacteria, especially the genera Sulfurimonas and Sulfurovum, were highly abundant. The microbial diversity of the enrichment cultures changed significantly by showing a high dominance of archaea, particularly the genera Thermococcus and Palaeococcus, depending on the carbon source and the selected temperature.

A PLGA-PEG-PLGA Thermosensitive Gel Enabling Sustained Delivery of Ropivacaine Hydrochloride for Postoperative Pain Relief.

PubMed

Fu, Xudong; Zeng, Huilin; Guo, Jiaping; Liu, Hong; Shi, Zhen; Chen, Huhai; Li, Dezong; Xie, Xiangyang; Kuang, Changchun

2017-01-01

Postoperative pain is a complex physiological response to disease and tissue injury. Moderate-to-severe pain typically occurs within 48 h after surgery. Amino amide local anesthetics are widely applied to manage postoperative pain, and they have high efficacy, a low risk for addiction and limited side effects. However, these anesthetics also have short half-lives, often necessitating continuous injection to obtain satisfactory pain relief. In the current work, we used a poly(lactic-co-glycolic acid) (PLGA)-polyethylene glycol (PEG)-PLGA (PLGA-PEG-PLGA) temperature-sensitive gel to deliver a local anesthetic, ropivacaine hydrochloride (RP), to prolong its analgesic effect. We investigated the influence of polymer and drug concentration on gelation temperature and the in vitro drug release rate from the temperature-sensitive gel. RP-loaded PLGA-PEG-PLGA solution is a liquid at room temperature and forms a gel at temperatures slightly lower than body temperature. With regard to the gel's drug release rate, 37.5, 51.3 and 72.6% of RP was released at 12, 24 and 48 h, respectively. This in vitro drug release profile conformed to the Higuchi equation. To assess pain control efficacy when using the gel, we evaluated the mechanical paw withdrawal reflex threshold, thermal pain threshold and incision cumulative pain scores in a rat incisional model. The results showed that the anti-pain effect of a single injection of RP-loaded gel at the incision site lasted for 48 h, which is significantly longer than the effect produced by injection of RP solution alone. The use of RP-loaded thermosensitive gels could provide a promising method for managing postoperative pain.

Hydrogen Production by Steam Reforming of Ethanol over Nickel Catalysts Supported on Sol Gel Made Alumina: Influence of Calcination Temperature on Supports

PubMed Central

Yaakob, Zahira; Bshish, Ahmed; Ebshish, Ali; Tasirin, Siti Masrinda; Alhasan, Fatah H.

2013-01-01

Selecting a proper support in the catalyst system plays an important role in hydrogen production via ethanol steam reforming. In this study, sol gel made alumina supports prepared for nickel (Ni) catalysts were calcined at different temperatures. A series of (Ni/AlS.G.) catalysts were synthesized by an impregnation procedure. The influence of varying the calcination temperature of the sol gel made supports on catalyst activity was tested in ethanol reforming reaction. The characteristics of the sol gel alumina supports and Ni catalysts were affected by the calcination temperature of the supports. The structure of the sol gel made alumina supports was transformed in the order of γ → (γ + θ) → θ-alumina as the calcination temperature of the supports increased from 600 °C to 1000 °C. Both hydrogen yield and ethanol conversion presented a volcano-shaped behavior with maximum values of 4.3 mol/mol ethanol fed and 99.5%, respectively. The optimum values were exhibited over Ni/AlS.G800 (Ni catalyst supported on sol gel made alumina calcined at 800 °C). The high performance of the Ni/AlS.G800 catalyst may be attributed to the strong interaction of Ni species and sol gel made alumina which lead to high nickel dispersion and small particle size. PMID:28809270

Enzymatic liquefaction of agarose above the sol-gel transition temperature using a thermostable endo-type β-agarase, Aga16B.

PubMed

Kim, Jung Hyun; Yun, Eun Ju; Seo, Nari; Yu, Sora; Kim, Dong Hyun; Cho, Kyung Mun; An, Hyun Joo; Kim, Jae-Han; Choi, In-Geol; Kim, Kyoung Heon

2017-02-01

The main carbohydrate of red macroalgae is agarose, a heterogeneous polysaccharide composed of D-galactose and 3,6-anhydro-L-galactose. When saccharifying agarose by enzymes, the unique physical properties of agarose, namely the sol-gel transition and the near-insolubility of agarose in water, limit the accessibility of agarose to the enzymes. Due to the lower accessibility of agarose to enzymes in the gel state than to the sol state, it is important to prevent the sol-gel transition by performing the enzymatic liquefaction of agarose at a temperature higher than the sol-gel transition temperature of agarose. In this study, a thermostable endo-type β-agarase, Aga16B, originating from Saccharophagus degradans 2-40 T , was characterized and introduced in the liquefaction process. Aga16B was thermostable up to 50 °C and depolymerized agarose mainly into neoagarooligosaccharides with degrees of polymerization 4 and 6. Aga16B was applied to enzymatic liquefaction of agarose at 45 °C, which was above the sol-gel transition temperature of 1 % (w/v) agarose (∼35 °C) when cooling agarose. This is the first systematic demonstration of enzymatic liquefaction of agarose, enabled by determining the sol-gel temperature of agarose under specific conditions and by characterizing the thermostability of an endo-type β-agarase.

Hydrogen Production by Steam Reforming of Ethanol over Nickel Catalysts Supported on Sol Gel Made Alumina: Influence of Calcination Temperature on Supports.

PubMed

Yaakob, Zahira; Bshish, Ahmed; Ebshish, Ali; Tasirin, Siti Masrinda; Alhasan, Fatah H

2013-05-30

Selecting a proper support in the catalyst system plays an important role in hydrogen production via ethanol steam reforming. In this study, sol gel made alumina supports prepared for nickel (Ni) catalysts were calcined at different temperatures. A series of (Ni/Al S.G. ) catalysts were synthesized by an impregnation procedure. The influence of varying the calcination temperature of the sol gel made supports on catalyst activity was tested in ethanol reforming reaction. The characteristics of the sol gel alumina supports and Ni catalysts were affected by the calcination temperature of the supports. The structure of the sol gel made alumina supports was transformed in the order of γ → (γ + θ) → θ-alumina as the calcination temperature of the supports increased from 600 °C to 1000 °C. Both hydrogen yield and ethanol conversion presented a volcano-shaped behavior with maximum values of 4.3 mol/mol ethanol fed and 99.5%, respectively. The optimum values were exhibited over Ni/Al S.G800 (Ni catalyst supported on sol gel made alumina calcined at 800 °C). The high performance of the Ni/Al S.G800 catalyst may be attributed to the strong interaction of Ni species and sol gel made alumina which lead to high nickel dispersion and small particle size.

Microchannel gel electrophoretic separation systems and methods for preparing and using

DOEpatents

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

2015-02-24

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

Microchannel gel electrophoretic separation systems and methods for preparing and using

DOEpatents

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

2013-09-03

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

Organization versus frustration: low temperature transitions in a gelatine-based gel

NASA Astrophysics Data System (ADS)

Philipp, M.; Müller, U.; Sanctuary, R.; Baller, J.; Krüger, J. K.

2008-09-01

A commercial physical gel composed of gelatine, water and glycerol shows a sol-gel transition which has been resolved by optical rotation measurements by step-wise heating the gel. This transition is not observable in the longitudinal acoustic mode measured at hypersonic frequencies with Brillouin spectroscopy. Depending on the thermal treatment of the investigated material during the sol-gel transition and within the gel state, Brillouin spectroscopy reflects tremendously different hypersonic dynamics. These distinct dynamics are responsible for the formation of different glassy states at low temperatures including that of a glass-ceramic. The large variety of super-cooled and glassy states is attributed to distinct distributions of the gel's constituents within the samples. Surprisingly, the same gel state can be produced either by annealing the gel over months or by the non-equilibrium effect of thermo-diffusion (Soret effect) in the course of some minutes.

Towards real-time thermometry using simultaneous multislice MRI

NASA Astrophysics Data System (ADS)

Borman, P. T. S.; Bos, C.; de Boorder, T.; Raaymakers, B. W.; Moonen, C. T. W.; Crijns, S. P. M.

2016-09-01

MR-guided thermal therapies, such as high-intensity focused ultrasound (MRgHIFU) and laser-induced thermal therapy (MRgLITT) are increasingly being applied in oncology and neurology. MRI is used for guidance since it can measure temperature noninvasively based on the proton resonance frequency shift (PRFS). For therapy guidance using PRFS thermometry, high temporal resolution and large spatial coverage are desirable. We propose to use the parallel imaging technique simultaneous multislice (SMS) in combination with controlled aliasing (CAIPIRINHA) to accelerate the acquisition. We compare this with the sensitivity encoding (SENSE) acceleration technique. Two experiments were performed to validate that SMS can be used to increase the spatial coverage or the temporal resolution. The first was performed in agar gel using LITT heating and a gradient-echo sequence with echo-planar imaging (EPI), and the second was performed in bovine muscle using HIFU heating and a gradient-echo sequence without EPI. In both experiments temperature curves from an unaccelerated scan and from SMS, SENSE, and SENSE/SMS accelerated scans were compared. The precision was quantified by a standard deviation analysis of scans without heating. Both experiments showed a good agreement between the temperature curves obtained from the unaccelerated, and SMS accelerated scans, confirming that accuracy was maintained during SMS acceleration. The standard deviations of the temperature measurements obtained with SMS were significantly smaller than when SENSE was used, implying that SMS allows for higher acceleration. In the LITT and HIFU experiments SMS factors up to 4 and 3 were reached, respectively, with a loss of precision of less than a factor of 3. Based on these results we conclude that SMS acceleration of PRFS thermometry is a valuable addition to SENSE, because it allows for a higher temporal resolution or bigger spatial coverage, with a higher precision.

Phase equilibrium and preparation, crystallization and viscous sintering of glass in the alumina-silica-lanthanum phosphate system

NASA Astrophysics Data System (ADS)

He, Feng

The phase equilibrium, viscosity of melt-quenched glasses, and processing of sol-gel glasses of the alumina-silica-lanthanum phosphate system were studied. These investigations were directed towards serving the objective of synthesizing nano-structured ceramic-matrix-composites via controlled crystallization of glass precursors. The thermal stability, phase equilibrium, and liquidus temperatures of the alumina- and mullite-lanthanum phosphate systems are determined. An iridium wire heater was constructed to anneal samples up to 2200°C. Phosphorus evaporation losses were significant at high temperatures, especially over 1800°C. The tentative phase diagrams of the two quasi-binary systems were presented. The viscosity of the melt-quenched mullite-lanthanum phosphate glasses was measured by three different methods, including viscous sintering of glass powder compacts, neck formation between two Frenkel glass beads, and thermal analysis of the glass transition. Improved methodologies were developed for applying the interpretative mathematical models to the results of the sintered powder and thermal analytical experiments. Good agreement was found between all three methods for both absolute values and temperature dependence. A sol-gel process was developed as a low temperature route to producing glasses. A unique, single phase mullite gel capable of low temperature (575°C) mullitization was made from tetraethoxysilane and aluminum isopropoxide at room temperature in three days. Low temperature crystallization was attributed to the avoidance of phase segregation during gel formation and annealing. This was greatly enhanced by a combination of low temperature preheating in the amorphous state, a high heating rate during crystallization and low water content. The Al2O3 content in mullite (61-68 mol%) depended on the highest annealing temperature. Two mullite-lanthanum phosphate gels were made based upon modifying the chemical procedures used for the homogeneous single phase and heterogeneous diphasic mullite gels from same starting chemicals. Amorphous powders were obtained after optimized calcinations. Their different crystallization routes and sintering behavior were investigated and correlated with the different homogeneities of precursor gels. Structurally stable open, porous ceramics (up to 80% porosity) were produced from the single-phase gel derived powder, where gases exsolved during calcination caused foaming coincident with sintering. Translucent, dense glass ceramic was made from the calcined diphasic gel by hot-pressing.

Separation of the principal HDL subclasses by iodixanol ultracentrifugation

PubMed Central

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

2013-01-01

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

Yeast Diversity and Persistence in Botrytis-Affected Wine Fermentations

PubMed Central

Mills, David A.; Johannsen, Eric A.; Cocolin, Luca

2002-01-01

Culture-dependent and -independent methods were used to examine the yeast diversity present in botrytis-affected (“botrytized”) wine fermentations carried out at high (∼30°C) and ambient (∼20°C) temperatures. Fermentations at both temperatures possessed similar populations of Saccharomyces, Hanseniaspora, Pichia, Metschnikowia, Kluyveromyces, and Candida species. However, higher populations of non-Saccharomyces yeasts persisted in ambient-temperature fermentations, with Candida and, to a lesser extent, Kluyveromyces species remaining long after the fermentation was dominated by Saccharomyces. In general, denaturing gradient gel electrophoresis profiles of yeast ribosomal DNA or rRNA amplified from the fermentation samples correlated well with the plating data. The direct molecular methods also revealed a Hanseniaspora osmophila population not identified in the plating analysis. rRNA analysis also indicated a large population (>106 cells per ml) of a nonculturable Candida strain in the high-temperature fermentation. Monoculture analysis of the Candida isolate indicated an extreme fructophilic phenotype and correlated with an increased glucose/fructose ratio in fermentations containing higher populations of Candida. Analysis of wine fermentation microbial ecology by using both culture-dependent and -independent methods reveals the complexity of yeast interactions enriched during spontaneous fermentations. PMID:12324335

Preliminary map of temperature gradients in the conterminous United States

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guffanti, M.; Nathenson, M.

1980-09-01

Temperature gradients have been determined from temperature/depth measurements made in drill holes deeper than 600 m and used in the construction of a temperature-gradient map of the conterminous United States. The map displays temperature gradients (in /sup 0/C/km) that can be expected to exist regionally in a conductive thermal regime to a depth of 2 km. The major difference between this map and the AAPG-USGS temperature-gradient map is in the midcontinental region where the AAPG-USGS map does not demarcate a division between colder eastern and warmer western thermal regimes. A comparison with the heat-flow map of Sass et al. (1980)more » indicates that temperature gradients commonly reflect regional heat flow, and the gross east-west division of the United States on the basis of heat flow is also expressed by temperature gradient.« less

Combined solvent- and non-uniform temperature-programmed gradient liquid chromatography. I - A theoretical investigation.

PubMed

Gritti, Fabrice

2016-11-18

An new class of gradient liquid chromatography (GLC) is proposed and its performance is analyzed from a theoretical viewpoint. During the course of such gradients, both the solvent strength and the column temperature are simultaneously changed in time and space. The solvent and temperature gradients propagate along the chromatographic column at their own and independent linear velocity. This class of gradient is called combined solvent- and temperature-programmed gradient liquid chromatography (CST-GLC). The general expressions of the retention time, retention factor, and of the temporal peak width of the analytes at elution in CST-GLC are derived for linear solvent strength (LSS) retention models, modified van't Hoff retention behavior, linear and non-distorted solvent gradients, and for linear temperature gradients. In these conditions, the theory predicts that CST-GLC is equivalent to a unique and apparent dynamic solvent gradient. The apparent solvent gradient steepness is the sum of the solvent and temperature steepness. The apparent solvent linear velocity is the reciprocal of the steepness-averaged sum of the reciprocal of the actual solvent and temperature linear velocities. The advantage of CST-GLC over conventional GLC is demonstrated for the resolution of protein digests (peptide mapping) when applying smooth, retained, and linear acetonitrile gradients in combination with a linear temperature gradient (from 20°C to 90°C) using 300μm×150mm capillary columns packed with sub-2 μm particles. The benefit of CST-GLC is demonstrated when the temperature gradient propagates at the same velocity as the chromatographic speed. The experimental proof-of-concept for the realization of temperature ramps propagating at a finite and constant linear velocity is also briefly described. Copyright © 2016 Elsevier B.V. All rights reserved.

pH and temperature dual-sensitive liposome gel based on novel cleavable mPEG-Hz-CHEMS polymeric vaginal delivery system

PubMed Central

Chen, Daquan; Sun, Kaoxiang; Mu, Hongjie; Tang, Mingtan; Liang, Rongcai; Wang, Aiping; Zhou, Shasha; Sun, Haijun; Zhao, Feng; Yao, Jianwen; Liu, Wanhui

2012-01-01

Background In this study, a pH and temperature dual-sensitive liposome gel based on a novel cleavable hydrazone-based pH-sensitive methoxy polyethylene glycol 2000-hydrazone-cholesteryl hemisuccinate (mPEG-Hz-CHEMS) polymer was used for vaginal administration. Methods The pH-sensitive, cleavable mPEG-Hz-CHEMS was designed as a modified pH-sensitive liposome that would selectively degrade under locally acidic vaginal conditions. The novel pH-sensitive liposome was engineered to form a thermogel at body temperature and to degrade in an acidic environment. Results A dual-sensitive liposome gel with a high encapsulation efficiency of arctigenin was formed and improved the solubility of arctigenin characterized by Fourier transform infrared spectroscopy and differential scanning calorimetry. The dual-sensitive liposome gel with a sol-gel transition at body temperature was degraded in a pH-dependent manner, and was stable for a long period of time at neutral and basic pH, but cleavable under acidic conditions (pH 5.0). Arctigenin encapsulated in a dual-sensitive liposome gel was more stable and less toxic than arctigenin loaded into pH-sensitive liposomes. In vitro drug release results indicated that dual-sensitive liposome gels showed constant release of arctigenin over 3 days, but showed sustained release of arctigenin in buffers at pH 7.4 and pH 9.0. Conclusion This research has shed some light on a pH and temperature dual-sensitive liposome gel using a cleavable mPEG-Hz-CHEMS polymer for vaginal delivery. PMID:22679372

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

Energy-Efficient Bioalcohol Recovery by Gel Stripping

NASA Astrophysics Data System (ADS)

Godbole, Rutvik; Ma, Lan; Hedden, Ronald

2014-03-01

Design of energy-efficient processes for recovering butanol and ethanol from dilute fermentations is a key challenge facing the biofuels industry due to the high energy consumption of traditional multi-stage distillation processes. Gel stripping is an alternative purification process by which a dilute alcohol is stripped from the fermentation product by passing it through a packed bed containing particles of a selectively absorbent polymeric gel material. The gel must be selective for the alcohol, while swelling to a reasonable degree in dilute alcohol-water mixtures. To accelerate materials optimization, a combinatorial approach is taken to screen a matrix of copolymer gels having orthogonal gradients in crosslinker concentration and hydrophilicity. Using a combination of swelling in pure solvents, the selectivity and distribution coefficients of alcohols in the gels can be predicted based upon multi-component extensions of Flory-Rehner theory. Predictions can be validated by measuring swelling in water/alcohol mixtures and conducting h HPLC analysis of the external liquid. 95% + removal of butanol from dilute aqueous solutions has been demonstrated, and a mathematical model of the unsteady-state gel stripping process has been developed. NSF CMMI Award 1335082.

A novel polymerase chain reaction (PCR) - denaturing gradient gel electrophoresis (DGGE) for the identification of Micrococcaceae strains involved in meat fermentations. Its application to naturally fermented Italian sausages.

PubMed

Cocolin, L; Manzano, M; Aggio, D; Cantoni, C; Comi, G

2001-05-01

A new molecular method consisting of polymerase chain reaction (PCR) amplification and denaturing gradient gel electrophoresis (DGGE) of a small fragment from the 16S rRNA gene identified the Micrococcaceae strains isolated from natural fermented Italian sausages. Lactic acid bacteria, total aerobic mesophilic flora, Enterobacteriaceae and faecal enterococci were also monitored. Micrococcaceaea control strains from international collections were used to optimise the method and 90 strains, isolated from fermented sausages, were identified by biochemical tests and PCR-DGGE. No differences were observed between the methods used. The results reported in this paper prove that Staphylococcus xylosus is the main bacterium involved in fermented sausage production, representing, from the tenth day of ripening, the only Micrococcaceaea species isolated.

Culture-Independent Analysis of Probiotic Products by Denaturing Gradient Gel Electrophoresis

PubMed Central

Temmerman, R.; Scheirlinck, I.; Huys, G.; Swings, J.

2003-01-01

In order to obtain functional and safe probiotic products for human consumption, fast and reliable quality control of these products is crucial. Currently, analysis of most probiotics is still based on culture-dependent methods involving the use of specific isolation media and identification of a limited number of isolates, which makes this approach relatively insensitive, laborious, and time-consuming. In this study, a collection of 10 probiotic products, including four dairy products, one fruit drink, and five freeze-dried products, were subjected to microbial analysis by using a culture-independent approach, and the results were compared with the results of a conventional culture-dependent analysis. The culture-independent approach involved extraction of total bacterial DNA directly from the product, PCR amplification of the V3 region of the 16S ribosomal DNA, and separation of the amplicons on a denaturing gradient gel. Digital capturing and processing of denaturing gradient gel electrophoresis (DGGE) band patterns allowed direct identification of the amplicons at the species level. This whole culture-independent approach can be performed in less than 30 h. Compared with culture-dependent analysis, the DGGE approach was found to have a much higher sensitivity for detection of microbial strains in probiotic products in a fast, reliable, and reproducible manner. Unfortunately, as reported in previous studies in which the culture-dependent approach was used, a rather high percentage of probiotic products suffered from incorrect labeling and yielded low bacterial counts, which may decrease their probiotic potential. PMID:12513998

Nanoporous Silica Thermal Insulation for Space Shuttle Cryogenic Tanks: A Case Study

NASA Technical Reports Server (NTRS)

Noever, David A.

1999-01-01

Nanoporous silica (with typical 10-50 nm porous radii) has been benchmarked for thermal insulators capable of maintaining a 150 K/cm temperature gradient. For cryogenic use in aerospace applications, the combined features for low-density, high thermal insulation factors, and low temperature compatibility are demonstrated in a prototype sandwich structure between two propulsion tanks. Theoretical modelling based on a nanoscale fractal structure suggest that the thermal conductivity scales proportionally (exponent, 1.7) with the material density-lower density increases the thermal insulation rating. Computer simulations, however, support the optimization tradeoff between material strength (Young moduli, proportional to density with exponent, 3.7), the characteristic (colloidal silica, less than 5 nm) particle size, and the thermal rating. The results of these simulations indicate that as nanosized particles are incorporated into the silica backbone, the resulting physical properties will be tailored by the smallest characteristic length and their fractal interconnections (dimension and fractal size). The application specifies a prototype panel which takes advantage of the processing flexibility inherent in sol-gel chemistry.

[Fungal community structure in phase II composting of Volvariella volvacea].

PubMed

Chen, Changqing; Li, Tong; Jiang, Yun; Li, Yu

2014-12-04

To understand the fungal community succession during the phase II of Volvariella volvacea compost and clarify the predominant fungi in different fermentation stages, to monitor the dynamic compost at the molecular level accurately and quickly, and reveal the mechanism. The 18S rDNA-denaturing gradient gel electrophoresis (DGGE) and sequencing methods were used to analyze the fungal community structure during the course of compost. The DGGE profile shows that there were differences in the diversity of fungal community with the fermentation progress. The diversity was higher in the stages of high temperature. And the dynamic changes of predominant community and relative intensity was observed. Among the 20 predominant clone strains, 9 were unknown eukaryote and fungi, the others were Eurotiales, Aspergillus sp., Melanocarpus albomyces, Colletotrichum sp., Rhizomucor sp., Verticillium sp., Penicillium commune, Microascus trigonosporus and Trichosporon lactis. The 14 clone strains were detected in the stages of high and durative temperature. The fungal community structure and predominant community have taken dynamic succession during the phase II of Volvariella volvacea compost.

Influence of Space Flight Factors on the Genetic Properties of Streptomyces Lividans 66 (PIJ702)

NASA Technical Reports Server (NTRS)

Tabakov, V. Yu.; Voeikova, T. A.; Tairbekov, M. G.; Goins, T. L.; Martinson, V. G.; Pyle, B. H.

2006-01-01

Gram-positive Streptomyces bacteria display genetic instability in response to external factors. Strain S. lividans 66 harbors the multicopy plasmid pIJ702 with selective and differential marker genes for antibiotic thiostrepton resistance and melanin production. Culture plates of modified ISP agar medium with and without thiostrepton were flown on Foton-M2. Suboptimal flight temperatures, which were simulated for asynchronous ground controls, resulted in slow growth and failure to differentiate and sporulate. Flight samples and asynchronous controls showed a high frequency of failing to express plasmid markers compared to laboratory controls. This was associated with loss of plasmid DNA and likely resulted from suboptimal temperatures for flight cultures and controls. Neither restriction fragment length polymorphism, nor polymerase chain reaction amplification coupled with denaturing gradient gel electrophoresis, revealed differences between pIJ702 DNA from flight vs. control clones. Mutations of the plasmid marker genes resulting from specific spaceflight factors, e.g., microgravity and radiation, were not detected.

Effects of oxytetracycline on the abundance and community structure of nitrogen-fixing bacteria during cattle manure composting.

PubMed

Sun, Jiajun; Qian, Xun; Gu, Jie; Wang, Xiaojuan; Gao, Hua

2016-09-01

The effects of oxytetracycline (OTC) on nitrogen-fixing bacterial communities were investigated during cattle manure composting. The abundance and community structure of nitrogen-fixing bacteria were determined by qPCR and denaturing gradient gel electrophoresis (DGGE), respectively. The matrix was spiked with OTC at four levels: no OTC, 10mg/kg dry weight (DW) OTC (L), 60mg/kg DW OTC (M), and 200mg/kg DW OTC (H). The high temperature period of composting was shorter with M and H, and the decline in temperature during the cooling stage was accelerated by OTC. OTC had a concentration-dependent inhibitory effect on the nitrogenase activity during early composting, and the nifH gene abundance declined significantly during the later composting stage. The DGGE profile and statistical analysis showed that OTC changed the nitrogen-fixing bacterial community succession and reduced the community richness and dominance. The nitrogen-fixing bacterial community structure was affected greatly by the high level of OTC. Copyright © 2016. Published by Elsevier Ltd.

Preparation and anti-bacterial properties of a temperature sensitive gel containing silver nanoparticles

USDA-ARS?s Scientific Manuscript database

The purpose of this study was to prepare a novel temperature-sensitive spray gel containing silver nanoparticles and investigate its anti-bacterial properties in vitro. Methods: The aqueous complex gel was prepared by Pluronic F127 (18-22%) and Pluronic F68 (3-9%) through a cold method to obtain a p...

Fractional order analysis of Sephadex gel structures: NMR measurements reflecting anomalous diffusion

NASA Astrophysics Data System (ADS)

Magin, Richard L.; Akpa, Belinda S.; Neuberger, Thomas; Webb, Andrew G.

2011-12-01

We report the appearance of anomalous water diffusion in hydrophilic Sephadex gels observed using pulse field gradient (PFG) nuclear magnetic resonance (NMR). The NMR diffusion data was collected using a Varian 14.1 Tesla imaging system with a home-built RF saddle coil. A fractional order analysis of the data was used to characterize heterogeneity in the gels for the dynamics of water diffusion in this restricted environment. Several recent studies of anomalous diffusion have used the stretched exponential function to model the decay of the NMR signal, i.e., exp[-( bD) α], where D is the apparent diffusion constant, b is determined the experimental conditions (gradient pulse separation, durations and strength), and α is a measure of structural complexity. In this work, we consider a different case where the spatial Laplacian in the Bloch-Torrey equation is generalized to a fractional order model of diffusivity via a complexity parameter, β, a space constant, μ, and a diffusion coefficient, D. This treatment reverts to the classical result for the integer order case. The fractional order decay model was fit to the diffusion-weighted signal attenuation for a range of b-values (0 < b < 4000 s mm -2). Throughout this range of b values, the parameters β, μ and D, were found to correlate with the porosity and tortuosity of the gel structure.

Dynamic Scaling of Colloidal Gel Formation at Intermediate Concentrations

DOE PAGES

Zhang, Qingteng; Bahadur, Divya; Dufresne, Eric M.; ...

2017-10-25

Here, we have examined the formation and dissolution of gels composed of intermediate volume-fraction nanoparticles with temperature-dependent short-range attractions using small-angle x-ray scatter- ing (SAXS), x-ray photon correlation spectroscopy (XPCS), and rheology to obtain nanoscale and macroscale sensitivity to structure and dynamics. Gel formation after temperature quenches to the vicinity of the rheologically-determined gel temperature, T gel, was characterized via the slow-down of dynamics and changes in microstructure observed in the intensity autocorrelation functions and structure factor, respectively, as a function of quench depth (ΔT = T quench - T gel), wave vector, and formation time (t f). We findmore » similar patterns in the slow-down of dynamics that maps the wave-vector-dependent dynamics at a particular ΔT and t f to that at other ΔTs and t fs via an effective scaling temperature, Ts. A single Ts applies to a broad range of ΔT and tf but does depend on the particle size. The rate of formation implied by the scaling is a far stronger function of ΔT than that of the attraction strength between colloids. Finally, we interpret this strong temperature de- pendence in terms of changes in cooperative bonding required to form stable, energetically favored, local structures.« less

Dynamic Scaling of Colloidal Gel Formation at Intermediate Concentrations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Qingteng; Bahadur, Divya; Dufresne, Eric M.

Here, we have examined the formation and dissolution of gels composed of intermediate volume-fraction nanoparticles with temperature-dependent short-range attractions using small-angle x-ray scatter- ing (SAXS), x-ray photon correlation spectroscopy (XPCS), and rheology to obtain nanoscale and macroscale sensitivity to structure and dynamics. Gel formation after temperature quenches to the vicinity of the rheologically-determined gel temperature, T gel, was characterized via the slow-down of dynamics and changes in microstructure observed in the intensity autocorrelation functions and structure factor, respectively, as a function of quench depth (ΔT = T quench - T gel), wave vector, and formation time (t f). We findmore » similar patterns in the slow-down of dynamics that maps the wave-vector-dependent dynamics at a particular ΔT and t f to that at other ΔTs and t fs via an effective scaling temperature, Ts. A single Ts applies to a broad range of ΔT and tf but does depend on the particle size. The rate of formation implied by the scaling is a far stronger function of ΔT than that of the attraction strength between colloids. Finally, we interpret this strong temperature de- pendence in terms of changes in cooperative bonding required to form stable, energetically favored, local structures.« less

Temperature-sensitive microemulsion gel: an effective topical delivery system for simultaneous delivery of vitamins C and E.

PubMed

Rozman, Branka; Zvonar, Alenka; Falson, Francoise; Gasperlin, Mirjana

2009-01-01

Microemulsions (ME)--nanostructured systems composed of water, oil, and surfactants--have frequently been used in attempts to increase cutaneous drug delivery. The primary objective addressed in this work has been the development of temperature-sensitive microemulsion gel (called gel-like ME), as an effective and safe delivery system suitable for simultaneous topical application of a hydrophilic vitamin C and a lipophilic vitamin E. By changing water content of liquid o/w ME (o/w ME), a gel-like ME with temperature-sensitive rheological properties was formed. The temperature-driven changes in its microstructure were confirmed by rotational rheometry, viscosity measurements, and droplet size determination. The release studies have shown that the vitamins' release at skin temperature from gel-like ME were comparable to those from o/w ME and were much faster and more complete than from o/w ME conventionally thickened with polymer (o/w ME carbomer). According to effectiveness in skin delivery of both vitamins, o/w ME was found the most appropriate, followed by gel-like ME and by o/w ME carbomer, indicating that no simple correlation between vitamins release and skin absorption could be found. The cytotoxicity studies revealed good cell viability after exposure to ME and confirmed all tested microemulsions as nonirritant.

Formulation Development of High Strength Gel System and Evaluation on Profile Control Performance for High Salinity and Low Permeability Fractured Reservoir

PubMed Central

Zhang, Chengli; Qu, Guodong

2017-01-01

For the large pores and cracks of reservoirs with low temperatures, high salinity, and low permeability, a new type of high strength gel ABP system is developed in this paper. The defects of conventional gels such as weak gel strength, no gelling, and easy dehydration are overcome under the conditions of low temperature and high salinity. The temperature and salt resistance, plugging characteristics, and EOR of the gel system are studied. Under the condition of 32°C and 29500 mg/L salinity, the ABP system formulation is for 0.3% crosslinking agent A + 0.09% coagulant B + 3500 mg/L polymer solution P. The results show that when the temperature was increased, the delayed crosslinking time of the system was shortened and the gel strength was increased. The good plugging characteristics of the ABP system were reached, and the plugging rate was greater than 99% in cores with different permeability. A good profile control performance was achieved, and the recovery rate was improved by 19.27% on the basis of water flooding. In the practical application of the gel system, the salinity of formation water and the permeability of fractures are necessary to determine the appropriate formulation. PMID:28592971

Conductive heat exchange with a gel-coated circulating water mattress.

PubMed

Bräuer, Anselm; Pacholik, Larissa; Perl, Thorsten; English, Michael John Murray; Weyland, Wolfgang; Braun, Ulrich

2004-12-01

The use of forced-air warming is associated with costs for the disposable blankets. As an alternative method, we studied heat transfer with a reusable gel-coated circulating water mattress placed under the back in eight healthy volunteers. Heat flux was measured with six calibrated heat flux transducers. Additionally, mattress temperature, skin temperature, and core temperature were measured. Water temperature was set to 25 degrees C, 30 degrees C, 35 degrees C, and 41 degrees C. Heat transfer was calculated by multiplying heat flux by contact area. Mattress temperature, skin temperature, and heat flux were used to determine the heat exchange coefficient for conduction. Heat flux and water temperature were related by the following equation: heat flux = 10.3 x water temperature - 374 (r(2) = 0.98). The heat exchange coefficient for conduction was 121 W . m(-2) . degrees C(-1). The maximal heat transfer with the gel-coated circulating water mattress was 18.4 +/- 3.3 W. Because of the small effect on the heat balance of the body, a gel-coated circulating water mattress placed only on the back cannot replace a forced-air warming system.

Sol-gel derived fluor-hydroxyapatite biocoatings on zirconia substrate.

PubMed

Kim, Hae-Won; Kong, Young-Min; Bae, Chang-Jun; Noh, Yoon-Jung; Kim, Hyoun-Ee

2004-07-01

Fluor-hydroxyapatite (FHA) film was coated on a zirconia (ZrO(2)) substrate by a sol-gel method. An appropriate amount of F ions was incorporated into the hydroxyapatite (HA) during the preparation of the sols. The apatite phase began to crystallize after heat treatment at 400 degrees C, and increased in intensity above 500 degrees C. No decomposition was detected by X-ray diffraction analyses up to 800 degrees C, which illustrates the high thermal stability of the FHA films. The films showed a uniform and dense morphology with a thickness of approximately 1 microm after a precisely controlled heat treatment process. These FHA films adhered firmly to the zirconia substrate, representing notable adhesion strengths of approximately 70 MPa after heat treatment above 500 degrees C. The dissolution rate of the FHA coating layer varied according to the heat treatment temperature, which was closely related to the film crystallinity. The dissolution rate of the FHA film was lower than that of the HA film, suggesting the possibility of a functional gradient coating of HA and FHA. The MG63 cells seeded onto the FHA films proliferated in a similar manner to those seeded onto pure HA ceramic and a plastic control.

Process for preparing fine grain silicon carbide powder

DOEpatents

Wei, G.C.

Finely divided silicon carbide powder is obtained by mixing colloidal silica and unreacted phenolic resin in either acetone or methanol, evaporating solvent from the obtained solution to form a gel, drying and calcining the gel to polymerize the phenolic resin therein, pyrolyzing the dried and calcined gel at a temperature in the range of 500 to 1000/sup 0/C, and reacting silicon and carbon in the pyrolyzed gel at a temperature in the range of 1550 to 1700/sup 0/C to form the powder.

Inter-crosslinking network gels having both shape memory and high ductility

NASA Astrophysics Data System (ADS)

Amano, Yoshitaka; Hidema, Ruri; Furukawa, Hidemitsu

2012-04-01

Medical treatment for injuries should be easy and quick in many accidents. Plasters or bandages are frequently used to wrap and fix injured parts. If plasters or bandages have additional smart functions, such as cooling, removability and repeatability, they will be much more useful and effective. Here we propose innovative biocompatible materials, that is, nontoxic high-strength shape-memory gels as novel smart medical materials. These smart gels were prepared from two monomers (DMAAm and SA), a polymer (HPC), and an inter-crosslinking agent (Karenz-MOI). In the synthesis of the gels, 1) a shape-memory copolymer network is made from the DMAAm and the SA, and 2) the copolymer and the HPC are crosslinked by the Karenz-MOI. Thus the crosslinking points are connected only between the different polymers. This is our original technique of developing a new network structure of gels, named Inter-Crosslinking Network (ICN). The ICN gels achieve high ductility, going up to 700% strain in tensile tests, while the ICN gels contain about 44% water. Moreover the SA has temperature dependence due to its crystallization properties; thus the ICN gels obtain shape memory properties and are named ICN-SMG. While the Young's modulus of the ICN-SMG is large below their crystallization temperature and the gels behave like plastic materials, the modulus becomes smaller above the temperature and the gels turn back to their original shape.

Identification and characterization of Vibrio cholerae surface proteins by radioiodination.

PubMed Central

Richardson, K; Parker, C D

1985-01-01

Whole cells and isolated outer membrane from Vibrio cholerae (Classical, Inaba) were radiolabeled with Iodogen or Iodo-beads as catalyst. Radiolabeling of whole cells was shown to be surface specific by sodium dodecyl sulfate-urea polyacrylamide gel electrophoresis of whole cells and cell fractions. Surface-labeled whole cells regularly showed 16 distinguishable protein species, of which nine were found in radiolabeled outer membrane preparations obtained by a lithium chloride-lithium acetate procedure. Eight of these proteins were found in outer membranes prepared by sucrose density gradient centrifugation and Triton X-100 extraction of radiolabeled whole cells. The mobility of several proteins was shown to be affected by temperature, and the major protein species exposed on the cell surface was shown to consist of at least two different peptides. Images PMID:3980099

Temperature-dependent self-assembly and rheological behavior of a thermoreversible pmma-P n BA-PMMA triblock copolymer gel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zabet, Mahla; Mishra, Satish; Boy, Ramiz

Self-assembly and mechanical properties of triblock copolymers in a mid-block selective solvent are of interest in many applications. Herein, we report physical assembly of an ABA triblock copolymer, [PMMA–PnBA–PMMA] in two different mid-block selective solvents, n-butanol and 2-ethyl-1-hexanol. Gel formation resulting from end-block associations and the corresponding changes in mechanical properties have been investigated over a temperature range of -80 °C to 60 °C, from near the solvent melting points to above the gelation temperature. Shear-rheometry, thermal analysis, and small-angle neutron scattering data reveal formation and transition of structure in these systems from a liquid state to a gel statemore » to a percolated cluster network with decrease in temperature. The aggregated PMMA end-blocks display a glass transition temperature. Our results provide new understanding into the structural changes of a self-assembled triblock copolymer gel over a large length scale and wide temperature range.« less

43 CFR 3252.14 - How must I complete a temperature gradient well?

Code of Federal Regulations, 2013 CFR

2013-10-01

... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false How must I complete a temperature gradient... LEASING Conducting Exploration Operations § 3252.14 How must I complete a temperature gradient well? Complete temperature gradient wells to allow for proper abandonment, and to prevent interzonal migration of...

43 CFR 3252.14 - How must I complete a temperature gradient well?

Code of Federal Regulations, 2012 CFR

2012-10-01

... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false How must I complete a temperature gradient... LEASING Conducting Exploration Operations § 3252.14 How must I complete a temperature gradient well? Complete temperature gradient wells to allow for proper abandonment, and to prevent interzonal migration of...

43 CFR 3252.14 - How must I complete a temperature gradient well?

Code of Federal Regulations, 2011 CFR

2011-10-01

... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false How must I complete a temperature gradient... LEASING Conducting Exploration Operations § 3252.14 How must I complete a temperature gradient well? Complete temperature gradient wells to allow for proper abandonment, and to prevent interzonal migration of...

43 CFR 3252.14 - How must I complete a temperature gradient well?

Code of Federal Regulations, 2014 CFR

2014-10-01

... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false How must I complete a temperature gradient... LEASING Conducting Exploration Operations § 3252.14 How must I complete a temperature gradient well? Complete temperature gradient wells to allow for proper abandonment, and to prevent interzonal migration of...

Lipid Bilayers in the Gel Phase Become Saturated by Triton X-100 at Lower Surfactant Concentrations Than Those in the Fluid Phase

PubMed Central

Ahyayauch, Hasna; Collado, M. Isabel; Alonso, Alicia; Goñi, Felix M.

2012-01-01

It has been repeatedly observed that lipid bilayers in the gel phase are solubilized by lower concentrations of Triton X-100, at least within certain temperature ranges, or other nonionic detergents than bilayers in the fluid phase. In a previous study, we showed that detergent partition coefficients into the lipid bilayer were the same for the gel and the fluid phases. In this contribution, turbidity, calorimetry, and 31P-NMR concur in showing that bilayers in the gel state (at least down to 13–20°C below the gel-fluid transition temperature) become saturated with detergent at lower detergent concentrations than those in the fluid state, irrespective of temperature. The different saturation may explain the observed differences in solubilization. PMID:22713566

Rapid step-gradient purification of mitochondrial DNA.

PubMed

Welter, C; Meese, E; Blin, N

1988-01-01

A convenient modification of the step gradient (CsCl/ethidium bomide) procedure is described. This rapid method allows isolation of covalently closed circular DNA separated from contaminating proteins, RNA and chromosomal DNA in ca. 5 h. Large scale preparations can be performed for circular DNA from eukaryotic organelles (mitochondria). The protocol uses organelle pelleting/NaCl-sarcosyl incubation steps for mitochondria followed by a CsCl step gradient and exhibits yields equal to the conventional procedures. It results in DNA sufficiently pure to be used for restriction endonuclease analysis, subcloning, 5'-end labeling, gel retention assays, and various types of hybridization.

Scalable synthesis of mesoporous titania microspheres via spray-drying method.

PubMed

Pal, Manas; Wan, Li; Zhu, Yongheng; Liu, Yupu; Liu, Yang; Gao, Wenjun; Li, Yuhui; Zheng, Gengfeng; Elzatahry, Ahmed A; Alghamdi, Abdulaziz; Deng, Yonghui; Zhao, Dongyuan

2016-10-01

Mesoporous TiO2 has several potential applications due to its unique electronic and optical properties, although its structures and morphologies are typically difficult to tune because of its uncontrollable and fast sol-gel reaction. In this study we have coupled the template-directed-sol-gel-chemistry with the low-cost, scalable, and environmentally benign aerosol (spray-drying) one-pot preparation technique for the fabrication of hierarchically mesoporous TiO2 microspheres and Fe3O4@mesoporous TiO2-x microspheres in a large scale. Parameters during the pre-hydrolysis and spray-drying treatment were varied to successfully control the bead diameter, morphology, monodispersity, surface area and pore size for improving their effectiveness for better application. Unlike to the previous aerosol synthetic approaches, where mainly quite a high temperature gradient with the strict control of spray-drying precursor concentration is implied, our strategy is lying on comparatively low drying temperature with an additional post-ultrasonication (further hydrolysis and condensation) route of the pre-calcined TiO2 samples. As-synthesized mesoporous microspheres have a size distribution from 500nm to 5μm, specific surface areas ranging from 150 to 162m(2)g(-1) and mean pore sizes of several nanometers (4-6nm). Further Fe3O4@mesoporous TiO2-x microspheres were observed to show remarkable selective phosphopeptide-enrichment activity which might have significant importance in disease diagnosis and other biomedical applications. Copyright © 2016. Published by Elsevier Inc.

Designing gradient coils with reduced hot spot temperatures.

PubMed

While, Peter T; Forbes, Larry K; Crozier, Stuart

2010-03-01

Gradient coil temperature is an important concern in the design and construction of MRI scanners. Closely spaced gradient coil windings cause temperature hot spots within the system as a result of Ohmic heating associated with large current being driven through resistive material, and can strongly affect the performance of the coils. In this paper, a model is presented for predicting the spatial temperature distribution of a gradient coil, including the location and extent of temperature hot spots. Subsequently, a method is described for designing gradient coils with improved temperature distributions and reduced hot spot temperatures. Maximum temperature represents a non-linear constraint and a relaxed fixed point iteration routine is proposed to adjust coil windings iteratively to minimise this coil feature. Several examples are considered that assume different thermal material properties and cooling mechanisms for the gradient system. Coil winding solutions are obtained for all cases considered that display a considerable drop in hot spot temperature (>20%) when compared to standard minimum power gradient coils with equivalent gradient homogeneity, efficiency and inductance. The method is semi-analytical in nature and can be adapted easily to consider other non-linear constraints in the design of gradient coils or similar systems. Crown Copyright (c) 2009. Published by Elsevier Inc. All rights reserved.

Locally targeted delivery of a micron-size radiation therapy source using temperature-sensitive hydrogel.

PubMed

Kim, Yusung; Seol, Dong Rim; Mohapatra, Sucheta; Sunderland, John J; Schultz, Michael K; Domann, Frederick E; Lim, Tae-Hong

2014-04-01

To propose a novel radiation therapy (RT) delivery modality: locally targeted delivery of micron-size RT sources by using temperature-sensitive hydrogel (RT-GEL) as an injectable vehicle. Hydrogel is a water-like liquid at room temperature but gels at body temperature. Two US Food and Drug Administration-approved polymers were synthesized. Indium-111 (In-111) was used as the radioactive RT-GEL source. The release characteristics of In-111 from polymerized RT-GEL were evaluated. The injectability and efficacy of RT-GEL delivery to human breast tumor were tested using animal models with control datasets of RT-saline injection. As proof-of-concept studies, a total of 6 nude mice were tested by injecting 4 million tumor cells into their upper backs after a week of acclimatization. Three mice were injected with RT-GEL and 3 with RT-saline. Single-photon emission computed tomography (SPECT) and CT scans were performed on each mouse at 0, 24, and 48 h after injection. The efficacy of RT-GEL was determined by comparison with that of the control datasets by measuring kidney In-111 accumulation (mean nCi/cc), representing the distant diffusion of In-111. RT-GEL was successfully injected into the tumor by using a 30-gauge needle. No difficulties due to polymerization of hydrogel during injection and intratumoral pressure were observed during RT-GEL injection. No back flow occurred for either RT-GEL or RT-saline. The residual tumor activities of In-111 were 49% at 24 h (44% at 48 h, respectively) for RT-GEL and 29% (22%, respectively) for RT-saline. Fused SPECT-CT images of RT-saline showed considerable kidney accumulation of In-111 (2886%, 261%, and 262% of RT-GEL at 0, 24, and 48 h, respectively). RT-GEL was successfully injected and showed much higher residual tumor activity: 170% (200%, respectively), than that of RT-saline at 24 h (48 h, respectively) after injection with a minimal accumulation of In-111 to the kidneys. Preliminary data of RT-GEL as a delivery modality of a radiation source to a local tumor are promising. Published by Elsevier Inc.

Characterization of thermotropism in primary roots of maize: dependence on temperature and temperature gradient, and interaction with gravitropism

NASA Technical Reports Server (NTRS)

Poff, K. L.

1991-01-01

Thermotropism in primary roots of Zea mays L. was studied with respect to gradient strength (degrees C cm-1), temperature of exposure within a gradient, pre-treatment temperature, and gravitropic stimulation. The magnitude of the response decreased with gradient strength. Maximum thermotropism was independent of gradient strength and pre-treatment temperature. The range of temperature for positive and negative thermotropism did not change with pre-treatment temperature. However, the exact range of temperatures for positive and negative thermotropism varied with gradient strengths. In general, temperatures of exposure lower than 25 degrees C resulted in positive tropic responses while temperatures of exposure of 39 degrees C or more resulted in negative tropic responses. Thermotropism was shown to modify and reverse the normal gravitropic curvature of a horizontal root when thermal gradients were applied opposite the 1 g vector. It is concluded that root thermotropism is a consequence of thermal sensing and that the curvature of the primary root results from the interaction of the thermal and gravitational sensing systems.

A general strategy for performing temperature-programming in high performance liquid chromatography--prediction of segmented temperature gradients.

PubMed

Wiese, Steffen; Teutenberg, Thorsten; Schmidt, Torsten C

2011-09-28

In the present work it is shown that the linear elution strength (LES) model which was adapted from temperature-programming gas chromatography (GC) can also be employed to predict retention times for segmented-temperature gradients based on temperature-gradient input data in liquid chromatography (LC) with high accuracy. The LES model assumes that retention times for isothermal separations can be predicted based on two temperature gradients and is employed to calculate the retention factor of an analyte when changing the start temperature of the temperature gradient. In this study it was investigated whether this approach can also be employed in LC. It was shown that this approximation cannot be transferred to temperature-programmed LC where a temperature range from 60°C up to 180°C is investigated. Major relative errors up to 169.6% were observed for isothermal retention factor predictions. In order to predict retention times for temperature gradients with different start temperatures in LC, another relationship is required to describe the influence of temperature on retention. Therefore, retention times for isothermal separations based on isothermal input runs were predicted using a plot of the natural logarithm of the retention factor vs. the inverse temperature and a plot of the natural logarithm of the retention factor vs. temperature. It could be shown that a plot of lnk vs. T yields more reliable isothermal/isocratic retention time predictions than a plot of lnk vs. 1/T which is usually employed. Hence, in order to predict retention times for temperature-gradients with different start temperatures in LC, two temperature gradient and two isothermal measurements have been employed. In this case, retention times can be predicted with a maximal relative error of 5.5% (average relative error: 2.9%). In comparison, if the start temperature of the simulated temperature gradient is equal to the start temperature of the input data, only two temperature-gradient measurements are required. Under these conditions, retention times can be predicted with a maximal relative error of 4.3% (average relative error: 2.2%). As an example, the systematic method development for an isothermal as well as a temperature gradient separation of selected sulfonamides by means of the adapted LES model is demonstrated using a pure water mobile phase. Both methods are compared and it is shown that the temperature-gradient separation provides some advantages over the isothermal separation in terms of limits of detection and analysis time. Copyright © 2011 Elsevier B.V. All rights reserved.

Shear rheological characterization of gel healing response and construction of rheo-PIV system

NASA Astrophysics Data System (ADS)

Bawiskar, Abhishek D.

Thermo-reversible gels are solvent-filled 3D networks of polymer chains interconnected by physical (transient) crosslinks. On applying a high shear stress, the crosslinks are broken and these gels show a typical stress-strain behavior due to cohesive fracture of the gel. When heated above a critical temperature and cooled back to room temperature, all the crosslinks are re-formed. Interestingly, partial to full recovery of broken crosslinks is also observed by simply letting the gel stand at room temperature. In this study, the fracture and healing behavior of a model acrylic triblock copolymer gel has been characterized by shear rheometry. A mathematical model has also been proposed to better understand the mechanics at the molecular level and predict the healing time of a system. A rheo-PIV system was built as part of the project, to observe and confirm the bulk healing process in situ. Spontaneous self-healing behavior has immense potential in controlled drug delivery systems, coatings, food and various other applications.

Radiation hardening of sol gel-derived silica fiber preforms through fictive temperature reduction.

PubMed

Hari Babu, B; Lancry, Matthieu; Ollier, Nadege; El Hamzaoui, Hicham; Bouazaoui, Mohamed; Poumellec, Bertrand

2016-09-20

The impact of fictive temperature (T_f) on the evolution of point defects and optical attenuation in non-doped and Er³⁺-doped sol-gel silica glasses was studied and compared to Suprasil F300 and Infrasil 301 glasses before and after γ-irradiation. To this aim, sol-gel optical fiber preforms have been fabricated by the densification of erbium salt-soaked nanoporous silica xerogels through the polymeric sol-gel technique. These γ-irradiated fiber preforms have been characterized by FTIR, UV-vis-NIR absorption spectroscopy, electron paramagnetic resonance, and photoluminescence measurements. We showed that a decrease in the glass fictive temperature leads to a decrease in the glass disorder and strained bonds. This mainly results in a lower defect generation rate and thus less radiation-induced attenuation in the UV-vis range. Furthermore, it was found that γ-radiation "hardness" is higher in Er³⁺-doped sol-gel silica compared to un-doped sol-gel silica and standard synthetic silica glasses. The present work demonstrates an effective strategy to improve the radiation resistance of optical fiber preforms and glasses through glass fictive temperature reduction.

Markers and mapping revisited: finding your gene.

PubMed

Jones, Neil; Ougham, Helen; Thomas, Howard; Pasakinskiene, Izolda

2009-01-01

This paper is an update of our earlier review (Jones et al., 1997, Markers and mapping: we are all geneticists now. New Phytologist 137: 165-177), which dealt with the genetics of mapping, in terms of recombination as the basis of the procedure, and covered some of the first generation of markers, including restriction fragment length polymorphisms (RFLPs), random amplified polymorphic DNA (RAPDs), simple sequence repeats (SSRs) and quantitative trait loci (QTLs). In the intervening decade there have been numerous developments in marker science with many new systems becoming available, which are herein described: cleavage amplification polymorphism (CAP), sequence-specific amplification polymorphism (S-SAP), inter-simple sequence repeat (ISSR), sequence tagged site (STS), sequence characterized amplification region (SCAR), selective amplification of microsatellite polymorphic loci (SAMPL), single nucleotide polymorphism (SNP), expressed sequence tag (EST), sequence-related amplified polymorphism (SRAP), target region amplification polymorphism (TRAP), microarrays, diversity arrays technology (DArT), single-strand conformation polymorphism (SSCP), denaturing gradient gel electrophoresis (DGGE), temperature gradient gel electrophoresis (TGGE) and methylation-sensitive PCR. In addition there has been an explosion of knowledge and databases in the area of genomics and bioinformatics. The number of flowering plant ESTs is c. 19 million and counting, with all the opportunity that this provides for gene-hunting, while the survey of bioinformatics and computer resources points to a rapid growth point for future activities in unravelling and applying the burst of new information on plant genomes. A case study is presented on tracking down a specific gene (stay-green (SGR), a post-transcriptional senescence regulator) using the full suite of mapping tools and comparative mapping resources. We end with a brief speculation on how genome analysis may progress into the future of this highly dynamic arena of plant science.

Thermosetting gels with modulated gelation temperature for ophthalmic use: the rheological and gamma scintigraphic studies.

PubMed

Wei, Gang; Xu, Hui; Ding, Ping Tian; Li, San Ming; Zheng, Jun Min

2002-09-18

For ophthalmic drug delivery, Pluronic F127 solutions have a phase transition temperature too low for them to be instilled into the eye at room temperature. Refrigerator storage is usually required to make administration easier, whereas the potential irritation of cold to the sensitive ocular tissues may result in poor topical bioavailability. The purpose of this study is to develop a thermosetting gel with a suitable phase transition temperature by combining Pluronic analogs and to examine the influence of incorporating mucoadhesive polysaccharide, sodium hyaluronate (HA-Na), on the ocular retention of the gel. Dynamic rheological method and single photon emission computing tomography (SPECT) technique were used to ex/in vivo evaluate the thermosetting gels, respectively. An optimized formulation containing 21% F127 and 10% F68 increased the phase transition temperature by 9 degrees C as evaluated by elasticity modulus compared to that of individual 21% F127 solution. Rheological behaviors of the Pluronic solutions showed that the combined Pluronic formulation was free flowing liquid below 25 degrees C and converted to a firm gel under the physiological condition. Furthermore, this formulation possessed the highest viscosity both before and after tear dilution at 35 degrees C. Gamma scintigraphic data demonstrated that the clearance of the thermosetting gel labeled with 99mTc-DTPA was significantly delayed with respect to the phosphate buffered solution, and at least a threefold increase of the corneal residence time was achieved. However, no further improvement in the ocular retention was observed when adding HA-Na into the thermosetting gel due to the substantially decreased gel strength. Copyright 2002 Elsevier Science B.V.

Microscopic Description of Thermodynamics of Lipid Membrane at Liquid-Gel Phase Transition

NASA Astrophysics Data System (ADS)

Kheyfets, B.; Galimzyanov, T.; Mukhin, S.

2018-05-01

A microscopic model of the lipid membrane is constructed that provides analytically tractable description of the physical mechanism of the first order liquid-gel phase transition. We demonstrate that liquid-gel phase transition is cooperative effect of the three major interactions: inter-lipid van der Waals attraction, steric repulsion and hydrophobic tension. The model explicitly shows that temperature-dependent inter-lipid steric repulsion switches the system from liquid to gel phase when the temperature decreases. The switching manifests itself in the increase of lateral compressibility of the lipids as the temperature decreases, making phase with smaller area more preferable below the transition temperature. The model gives qualitatively correct picture of abrupt change at transition temperature of the area per lipid, membrane thickness and volume per hydrocarbon group in the lipid chains. The calculated dependence of phase transition temperature on lipid chain length is in quantitative agreement with experimental data. Steric repulsion between the lipid molecules is shown to be the only driver of the phase transition, as van der Waals attraction and hydrophobic tension are weakly temperature dependent.

Quantification of the effect of temperature gradients in soils on subsurface radon signal

NASA Astrophysics Data System (ADS)

Haquin, Gustavo; Ilzycer, Danielle; Kamai, Tamir; Zafrir, Hovav; Weisbrod, Noam

2017-04-01

Temperature gradients that develop in soils due to atmospheric temperature cycles are factors of primary importance in determining the rates and directions of subsurface gas flow. Models including mechanisms of thermal convection and thermal diffusion partially explain the impact of temperature gradients on subsurface radon transport. However, the overall impact of temperature gradients on subsurface radon transport is still not well understood. A laboratory setup was designed and built to experimentally investigate the influence of temperature gradients on radon transport under well controlled conditions. A 60 cm diameter and 120 cm tall column was thermally insulated except from the atmosphere-soil interface, such that it was constructed to simulate field conditions where temperature gradients in soils are developed following atmospheric temperature cycles. The column was filled with fine grinded phosphate rock which provided the porous media with radon source. Radon in soil-air was continuously monitored using NaI gamma detectors positioned at different heights along the column. Soil temperature, differential pressure, and relative humidity were monitored along the column. Experiments based on steep and gradual stepwise changes in ambient temperature were conducted. Absolute changes on radon levels in the order of 10-30% were measured at temperature gradients of up to ±20oC/m. Results showed a non-linear correlation between the temperature gradient and the subsurface radon concentration. An asymmetric relationship between the radon concentration and the temperature gradients for ΔT>0 and ΔT<0 was also observed. Laboratory simulations of the time- and depth-dependent temperature wave functions with frequencies ranged from a daily cycle to few days were performed. In response to the harmonic temperature behaviour radon oscillations at similar frequencies were detected correspondingly. In this work a quantitative relationship between radon and temperature gradients will be presented for cases beyond the classical conditions for thermal convection and thermal diffusion.

[In vitro evaluation of the gels properties prepared thermosensitive polymers as vehicles for administration substance by injection].

PubMed

Karolewicz, Bozena; Owczarek, Artur; Pluta, Janusz

2011-01-01

The aim of this study was to prepare a thermoresponsive formulations, which are a carrier for substance administered directly into site of action and which obtain sol-gel transitions at physiological ranges of temperature. The investigated formulations of liquid consistency at room temperature were obtained in sterile conditions on the basis of nonionic polymers Pluronic F-127, Pluronic F-68 and anionic polymer hyaluronic acid in different concentrations. The sol-gel transition temperature of the formulations was investigated and their physicochemical properties such as pH, density, osmotic pressure, sol-gel transition temperature, texture and release of vancomycin hydrochloride were studied. In vitro release experiments indicated that the optimised platform was able to prolong vancomycin hydrochloride release and their physico-chemical properties allow for application by injection form.

Biodegradability of poly(butylene succinate-co-butylene adipate) (PBSA) controlled by temperature during the dried-gel process

NASA Astrophysics Data System (ADS)

Yamazaki, Hana; Maeda, Tomoki; Hotta, Atsushi

Currently there is a growing interest in biodegradable plastics that can be readily degraded into H2O and CO2. Among them, poly(butylene succinate-co-butylene adipate)(PBSA) is one of the mechanically attractive materials that can be biodegraded by surrounding water molecules and microorganisms after the disposal of the plastics. In order to expand the use of PBSA, the proper and effective control of the biodegradability of PBSA should be realized. In this work, the dried-gel process of the PBSA was carefully studied considering the temperature of the process. Three different types of dried PBSA gels were prepared at three different gel-process temperatures. From the biodegradability testing by immersing the PBSA samples in NaOH aq., it was found that the percentage of the weight loss of the PBSA was increased, indicating that the biodegradability was enhanced as the gel preparation temperature became lower. In fact, smaller spherocrystals were observed in PBSA dried at cooler temperature, studied by the scanning electron microscopy (SEM). It was therefore concluded that the microstructures of PBSA could be well controlled by changing the gel preparation temperatures for the precise control of the biodegradability of PBSA. This work was supported by a Grant-in-Aid for Scientific Research (A) (No. 15H02298 to A.H.) and a Grant-in-Aid for Research Activity Start-up (No.15H06586 to T.M.) from JSPS: KAKENHI\\x9D.

Thermosensitive and mucoadhesive in situ gel based on poloxamer as new carrier for rectal administration of nimesulide.

PubMed

Yuan, Yuan; Cui, Ying; Zhang, Li; Zhu, Hui-Ping; Guo, Yi-Sha; Zhong, Bo; Hu, Xia; Zhang, Ling; Wang, Xiao-Hui; Chen, Li

2012-07-01

Poloxamer 407 has excellent thermo-sensitive gelling properties. Nevertheless, these gels possess inadequate poor bioadhesiveness and high permeability to water, which limited its' application as a thermoresponsive matrix. The main aim of the present investigation was to develop thermosensitive and mucoadhesive rectal in situ gel of nimesulide (NM) by using mucoadhesive polymers such as sodium alginate (Alg-Na) and HPMC. These gels were prepared by addition of mucoadhesive polymers (0.5%) to the formulations of thermosensitive gelling solution containing poloxamer 407 (18%) and nimesulide (2.0%). Polyethylene glycol (PEG) was used to modify gelation temperature and drug release properties. The gelation temperature and drug release rate of the prepared in situ gels were evaluated. Gelation temperature was significantly increased with incorporation of nimesulide (2.0%) in the poloxamer solution, while the addition of the mucoadhesive polymers played a reverse role on gelation temperature. The addition of PEG polymers increased the gelation temperature and the drug release rate. Among the formulations examined, the poloxamer 407/nimesulide/sodium alginate/PEG 4000 (18/2.0/0.5/1.2%) exhibited the appropriate gelation temperature, acceptable drug release rate and rectal retention at the administration site. Furthermore, the micrographic results showed that in situ gel, given at the dose of 20mg/kg, was safe for no mucosa irritation. In addition, it resulted in significantly higher initial serum concentrations, C(max) and AUC of NM compared to the solid suppository. Copyright © 2012 Elsevier B.V. All rights reserved.

Administration of a Sol-Gel Formulation of Phenylephrine Using Low-Temperature Hollow Microneedle for Treatment of Intermittent Fecal Incontinence.

PubMed

Lee, Hyunji; Park, Jung-Hwan; Park, Jung Ho

2017-12-01

A low temperature hollow microneedle system was devised to deliver sol-gel transition formulation near the surface of the skin for extended release and local delivery of drug by a non-invasive method. This new system can improve treatment of intermittent fecal incontinence. The low-temperature system was integrated with a hollow microneedle to maintain the low temperature of the sol formulation. Various sol-gel formulations using Pluronic F-127 (PF-127) and Hydroxy-propyl-methyl-cellulose (HPMC) were prepared, and their gelation temperature, flow property, and diffusion retardation were observed. Resting anal sphincter pressure in response to a phenylephrine (PE) sol-gel formulation was measured using an air-charged catheter. The biocompatibility of the sol-gel PE formulation was evaluated by observing the immunological response. When the PF-127 25%, HPMC 1% and PE formulation (PF25-HPMC1-PE) was injected through the peri-anal skin of the rat in vivo, the highest pressure on the anal sphincter muscle occurred at 6-8 h and anal pressure increased and lasted twice as long as with the phosphate-buffered saline (PBS)-PE formulation. There was no significant difference in the number of mast cells after administration into the rat in vivo between the PF25-HPMC1-PE formulation and the PBS-PE formulation. The combination of a low-pain hollow microneedle system and an injectable sol-gel formulation improved the efficacy of treatment of intermittent fecal incontinence. A low-temperature hollow microneedle system using a sol-gel formulation has many applications in medical treatments that require depot effect, local targeting, and pain control.

Dosimetric characteristics of PASSAG as a new polymer gel dosimeter with negligible toxicity

NASA Astrophysics Data System (ADS)

Farhood, Bagher; Abtahi, Seyed Mohammad Mahdi; Geraily, Ghazale; Ghorbani, Mehdi; Mahdavi, Seied Rabi; Zahmatkesh, Mohammad Hasan

2018-06-01

Despite many advantages of polymer gel dosimeters, their clinical use is only not realized now. Toxicity of polymer gel dosimeters can be considered as one of their main limitations for use in routine clinical applications. In the current study, a new polymer gel dosimeter is introduced with negligible toxicity. For this purpose, 2-Acrylamido-2-Methy-1-PropaneSulfonic acid (AMPS) sodium salt monomer was replaced instead of acrylamide monomer used in PAGAT gel dosimeter by using %6 T and %50 C to the gel formula and the new formulation is called PASSAG (Poly AMPS Sodium Salt and Gelatin) polymer gel dosimeter. The irradiation of gel dosimeters was carried out using a Co-60 therapy machine. MRI technique was used to quantify the dose responses of the PASSAG gel dosimeter. Then, the MRI responses (R2) of the gel dosimeter was analyzed at different dose values, post-irradiation times, and scanning temperatures. The results showed that the new gel formulation has a negligible toxicity and it is also eco-friendly. In addition, carcinogenicity and genetic toxicity tests are negative for the monomer used in PASSAG. The radiological properties of PASSAG gel dosimeter showed that this substance can be considered as a soft tissue/water equivalent material. Furthermore, dosimetric evaluation of the new polymer gel dosimeter revealed an excellent linear R2-dose response in the evaluated dose range (0-15 Gy). The R2-dose sensitivity and dose resolution of PASSAG gel dosimeter were 0.081 s-1Gy-1 (in 0-15 Gy dose range) and 1 Gy (in 0-10 Gy dose range), respectively. Moreover, it was shown that the R2-dose sensitivity and dose resolution of the new gel dosimeter improves over time after irradiation. It was also found that the R2 response of the PASSAG gel dosimeter has less dependency to the 18, 20, and 24 °C scanning temperature in comparison to that of room temperature (22 °C).

Extraction of espresso coffee by using gradient of temperature. Effect on physicochemical and sensorial characteristics of espresso.

PubMed

Salamanca, C Alejandra; Fiol, Núria; González, Carlos; Saez, Marc; Villaescusa, Isabel

2017-01-01

Espresso extraction is generally carried out at a fixed temperature within the range 85-95°C. In this work the extraction of the espressos was made in a new generation coffee machine that enables temperature profiling of the brewing water. The effect of using gradient of temperature to brew espressos on physicochemical and sensorial characteristics of the beverage has been investigated. Three different extraction temperature profiles were tested: updrawn gradient (88-93°C), downdrawn gradient (93-88°C) and fixed temperature (90°C). The coffee species investigated were Robusta, Arabica natural and Washed Arabica. Results proved that the use of gradient temperature for brewing espressos allows increasing or decreasing the extraction of some chemical compounds from coffee grounds. Moreover an appropriate gradient of temperature can highlight or hide some sensorial attributes. In conclusion, the possibility of programming gradient of temperature in the coffee machines recently introduced in the market opens new expectations in the field of espresso brewing. Copyright © 2016 Elsevier Ltd. All rights reserved.

The effectiveness of low-intensity red laser for activating a bleaching gel and its effect in temperature of the bleaching gel and the dental pulp.

PubMed

Pleffken, Patrícia Rondon; Borges, Alessandra Bühler; Gonçalves, Sérgio Eduardo D E Paiva; Rocha Gomes Torres, Carlos

2012-04-01

The effectiveness of low-intensity red laser for activating a bleaching gel and its effect in pulp temperature was not investigated in dental literature. The objective of this study was to assess the effectiveness of low-intensity red laser for activating a bleaching gel, as well as its effect in temperature of the bleaching gel and the dental pulp. Forty extracted bovine teeth were immersed in a solution of coffee 14 days for darkening. The initial colors were recorded by spectrophotometric analysis. The specimens were randomly distributed into two groups (N = 20): the control, which did not receive light and the experimental group that received light from an appliance fitted with three red light-emitting laser diodes (λ = 660 nm). A green-colored, 35% H(2) O(2) -based bleaching gel was applied for 30 minutes, and changed three times. After bleaching, the colors were again measured to obtain the L*a*b* values. Color variation was calculated (ΔE) and the data submitted to the non-paired t-test (5%). To assess temperature, 10 human incisors were prepared, in which one thermocouple was placed on the bleaching gel applied on the surface of the teeth and another inside the pulp chamber. There was a significant difference between the groups (p = 0.016), and the experimental group presented a significantly higher mean variation (7.21 ± 2.76) in comparison with the control group (5.37 ± 1.76). There was an increase in pulp temperature, but it was not sufficient to cause damage to the pulp. Bleaching gel activation with low-intensity red laser was capable of increasing the effectiveness of bleaching treatment and did not increase pulp temperature to levels deleterious to the pulp. © 2011 Wiley Periodicals, Inc.

Processing temperature and moisture content effects on the texture and microscopic appearance of cooked fowl meat gels.

PubMed

Voller, L M; Dawson, P L; Han, I Y

1996-12-01

New aseptic processes are being used and refined to produce convenient, shelf stable liquid products containing meat particles. These processes utilize high temperature, short time thermal treatments to minimize food quality change; however, little research has been conducted on the effects of this process on the texture of meat from mature hens traditionally used for canning. The objective of this study was to examine textural and structural changes in meat structure due to different high temperature (HT) heat treatments and meat moisture contents were examined by use of electron microscopy and torsion analyses. Cooked gels of different moisture contents (71.2 to 74.8%) were formulated from spent fowl breast meat and exposed to processing temperatures of 120 or 124 C. The HT processing resulted in stronger (tougher) meat gels that were more deformable (more chewy) than gels that were not processed by HT. Water added prior to cooking was not retained in samples that were cooked and then processed at 124 C, but was retained in the samples processed at 120 C. Electron micrographs showed a more organized and open gel structure in the samples with higher moisture content and lower temperature (120 C) processing compared to the lower moisture and higher (124 C) temperature treatments.

Correlation between ion diffusional motion and ionic conductivity for different electrolytes based on ionic liquid.

PubMed

Kaur, Dilraj Preet; Yamada, K; Park, Jin-Soo; Sekhon, S S

2009-04-23

Room temperature ionic liquid 2,3-dimethyl-1-hexylimidazolium bis(trifluoromethane sulfonyl)imide (DMHxImTFSI) has been synthesized and used in the preparation of polymer gel electrolytes containing polymethylmethacrylate and propylene carbonate (PC). The onset of ion diffusional motion has been studied by (1)H and (19)F NMR spectroscopy and the results obtained for ionic liquid, liquid electrolytes, and polymer gel electrolytes have been correlated with the ionic conductivity results for these electrolytes in the 100-400 K temperature range. The temperature at which (1)H and (19)F NMR lines show motional narrowing and hence ion diffusional motion starts has been found to be closely related to the temperature at which a large increase in ionic conductivity has been observed for these electrolytes. Polymer gel electrolytes have high ionic conductivity over a wide range of temperatures. Thermogravimetric analysis/differential scanning calorimetry studies show that the ionic liquid (DMHxImTFSI) used in the present study is thermally stable up to 400 degrees C, whereas the addition of PC lowers the thermal stability of polymer gel electrolytes containing the ionic liquid. Different electrolytes have been observed to show high ionic conductivity in different range of temperatures, which can be helpful in the design of polymer gel electrolytes for specific applications.

Analysis of Chromatin Organisation

ERIC Educational Resources Information Center

Szeberenyi, Jozsef

2011-01-01

Terms to be familiar with before you start to solve the test: chromatin, nucleases, sucrose density gradient centrifugation, melting point, gel electrophoresis, ethidium bromide, autoradiography, Southern blotting, Northern blotting, Sanger sequencing, restriction endonucleases, exonucleases, linker DNA, chloroform extraction, nucleosomes,…

Investigating Freshwater Periphyton Community Response to Uranium with Phospholipid Fatty Acid and Denaturing Gradient Gel Electrophoresis Analyses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Small, Jack A.; Bunn, Amoret L.; McKinstry, Craig A.

2008-04-01

Periphyton communities can be used as monitors of ecosystem health and as indicators of contamination in lotic systems. Measures of biomass, community structure and genetic diversity were used to investigate impacts of uranium exposure on periphyton. Laboratory exposures of periphyton in river water amended with uranium were performed for 5 days, followed by 2 days of uranium depuration in unamended river water. Productivity as measured by biomass was not affected by concentrations up to 100 µg L-1 uranium. Phospholipid fatty acid (PLFA) profiles and denaturing gradient gel electrophoresis (DGGE) banding patterns found no changes in community or genetic structure relatedmore » to uranium exposure. We suggest that the periphyton community as a whole is not impacted by exposures of uranium up to a dose of 100 µg L-1. These findings have significance for the assessment and prediction of uranium impacts on aquatic ecosystems.« less

One-step separation and purification of hydrolysable tannins from Geranium wilfordii Maxim by adsorption chromatography on cross-linked 12% agarose gel.

PubMed

Liu, Dan; Ma, Yan; Wang, Ye; Su, Zhiguo; Gu, Ming; Janson, Jan-Christer

2011-05-01

The hydrolysable tannins corilagin and geraniin, the major active components of the traditional Chinese medicine Geranium wilfordii Maxim, have been separated and purified from crude extracts in one step by adsorption chromatography on cross-linked 12% agarose gel (Superose 12 10/300 GL). The separation was achieved by gradient elution using mobile phase A composed of 5% ethanol and 5% acetic acid and mobile phase B composed of 30% ethanol and 30% acetic acid. The gradients were composed as follows: 0-240 mL, 0-25% B; 240-480 mL, 25-40% B; after 480 mL, 100% B. The purities of the collected corilagin and geraniin were 92.4 and 87.2%, and the corresponding yields were 88.0 and 76.8%, respectively. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microstructure and rheology of thermoreversible nanoparticle gels.

PubMed

Ramakrishnan, S; Zukoski, C F

2006-08-29

Naïve mode coupling theory is applied to particles interacting with short-range Yukawa attractions. Model results for the location of the gel line and the modulus of the resulting gels are reduced to algebraic equations capturing the effects of the range and strength of attraction. This model is then applied to thermo reversible gels composed of octadecyl silica particles suspended in decalin. The application of the model to the experimental system requires linking the experimental variable controlling strength of attraction, temperature, to the model strength of attraction. With this link, the model predicts temperature and volume fraction dependencies of gelation and modulus with five parameters: particle size, particle volume fraction, overlap volume of surface hairs, and theta temperature. In comparing model predictions with experimental results, we first observe that in these thermal gels there is no evidence of clustering as has been reported in depletion gels. One consequence of this observation is that there are no additional adjustable parameters required to make quantitative comparisons between experimental results and model predictions. Our results indicate that the naïve mode coupling approach taken here in conjunction with a model linking temperature to strength of attraction provides a robust approach for making quantitative predictions of gel mechanical properties. Extension of model predictions to additional experimental systems requires linking experimental variables to the Yukawa strength and range of attraction.

Insights into the mechanical properties of a silicone oil gel with a 'latent' gelator, 1-octadecylamine, and CO(2) as an 'activator'.

PubMed

Carretti, Emiliano; George, Mathew; Weiss, Richard G

2010-10-15

A detailed study of the rheological properties of silicone oil gels, made from a low-molecular-mass organic gelator, a combination of 1-octadecylamine (a latent gelator) and carbon dioxide (an 'activating' molecule), is reported. Information gleaned from the mechanical measurements is used to characterize the gel networks and how they respond to temperature and strain. It is shown, for example, that very precise measurements of the gel-to-sol transitions can be obtained from plots of viscosity versus temperature.

Spatially resolved speckle-correlometry of sol-gel transition

NASA Astrophysics Data System (ADS)

Isaeva, A. A.; Isaeva, E. A.; Pantyukov, A. V.; Zimnyakov, D. A.

2018-04-01

Sol-gel transition was studied using the speckle correlometry method with a localized light source and spatial filtering of backscattered radiation. Water solutions of technical or food gelatin with added TiO2 nanoparticles were used as studied objects. Structural transformation of "sol-gel" system was studied at various temperatures from 25°C to 50°C using analysis of the correlation and structure functions of speckle intensity fluctuations. The characteristic temperatures of "sol - gel" transition were evaluated for studied systems. Obtained results can be used for various applications in biomedicine and food industry.

Polymer gel dosimeters with reduced toxicity: a preliminary investigation of the NMR and optical dose response using different monomers

NASA Astrophysics Data System (ADS)

Senden, R. J.; DeJean, P.; McAuley, K. B.; Schreiner, L. J.

2006-07-01

In this work, three new polymer gel dosimeter recipes were investigated that may be more suitable for widespread applications than polyacrylamide gel dosimeters, since the extremely toxic acrylamide has been replaced with the less harmful monomers N-isopropylacrylamide (NIPAM), diacetone acrylamide and N-vinylformamide. The new gel dosimeters studied contained gelatin (5 wt%), monomer (3 wt%), N,N'-methylene-bis-acrylamide crosslinker (3 wt%) and tetrakis (hydroxymethyl) phosphonium chloride antioxidant (10 mM). The NMR response (R2) of the dosimeters was analysed for conditions of varying dose, dose rate, time post-irradiation, and temperature during irradiation and scanning. It was shown that the dose-response behaviour of the NIPAM/Bis gel dosimeter is comparable to that of normoxic polyacrylamide gel (PAGAT) in terms of high dose-sensitivity and low dependence on dose rate and irradiation temperature, within the ranges considered. The dose-response (R2) of NIPAM/Bis appears to be linear over a greater dose range than the PAGAT gel dosimeter. The effects of time post-irradiation (temporal instability) and temperature during NMR scanning on the R2 response were more significant for NIPAM/Bis dosimeters. Diacetone acrylamide and N-vinylformamide gel dosimeters possessed considerably lower dose-sensitivities. The optical dose-response, measured in terms of the attenuation coefficient for each polymer gel dosimeter, showed potential for the use of optical imaging techniques in future studies.

Spectroscopic studies of triethoxysilane sol-gel and coating process.

PubMed

Li, Ying-Sing; Ba, Abdul

2008-10-01

Silica sol-gels have been prepared under different conditions using triethoxysilane (TES) as precursor. The prepared sol-gels have been used to coat aluminum for corrosion protection. Vibrational assignments have been made for most vibration bands of TES, TES sol-gel, TES sol-gel-coated aluminum and xerogel. It has been noticed that air moisture may have helped the hydrolysis of the thin coating films. Xerogels have been obtained from the sol-gel under different temperature conditions and the resulting samples have been characterized by using infrared and Raman spectroscopic methods. IR data indicate that the sol-gel process is incomplete under the ambient conditions although an aqueous condition can have slightly improved the process. Two nonequivalent silicon atoms have been identified from the collected 29Si NMR spectra for the sol-gel, supporting the result derived from the IR data. The frequency of Si-H bending vibration has been found to be more sensitive to the skeletal structure than that of the Si-H stretching vibration. A higher temperature condition could favor the progression of hydrolysis and condensation. A temperature higher than 300 degrees C would cause sample decomposition without seriously damaging the silica network. From infrared intensity measurements and thermo-gravimetric analyses, the fractions of incomplete hydrolysis and condensation species have been estimated to be 4% and 3%, respectively. Electrochemical data have shown that the sol-gel coating significantly improves the corrosion protection properties of aluminum.

The low temperature synthesis, characterization and properties of ferroelectrics

NASA Astrophysics Data System (ADS)

Xu, Jie

2000-10-01

PZT 50:50 xerogels prepared by two different sol-gel routes crystallized in a similar fashion to give a mixture of tetragonal and rhombohedral at high temperature (1000°C). Both the diffraction and EXAFS data suggest that the compositional inhomogeneity of the samples prepared by the two routes is similar. The crystallization of CZT gels is complicated. Crystalline CaCO 3 was always detected in the dry gels regardless of the sample composition and preparation methods. At intermediate temperatures a fluorite related phase was always formed and it transformed to perovskite at higher temperatures. The EXAFS data suggest that perovskite CZT samples prepared using alkoxide sol-gel chemistry may not be random solid solutions. All the solution processed ZrTiO4 materials crystallized in the range 600--700°C. The KTN samples prepared using a conventional alkoxide sol-gel route crystallized completely to perovskite at lower temperatures than those prepared using prehydrolyzed precursors. The EXAFS data for the KTN samples prepared using a conventional alkoxide sol-gel route are consistent with a random distribution of tantalum and niobium in the solid solution. However, materials prepared using the inhomogeneous sol-gel route and by the direct reaction of mixed oxides were shown to be compositionally inhomogeneous. The heterogeneity could not be removed by regrinding and heating the mixed oxide samples several times. K2Ta4-xNbxO11 (x = 0, 2, 4) samples were prepared using alkoxide sol-gel chemistry and their crystallization was examined by powder X-ray diffraction. A Rietveld structure analysis of the pyrochlore formed from a gel with bulk composition K2Ta 2Nb2O11 indicated that it was rich in potassium relative to the bulk sample. On heating to high temperatures tetragonal tungsten bronzes were formed. A Rietveld analysis was also performed for K2Ta 2Nb2O11 with tetragonal tungsten bronze structure. The defect pyrochlores "AgTaO3" and GaTaO 3 were synthesized by ion-exchange using pyrochlore KTaO3 as a starting material. The structures of the pyrochlores were examined using the Rietveld method. The pyrochlore-to-perovskite transformations were also explored.

43 CFR 3252.13 - How long may I collect information from my temperature gradient well?

Code of Federal Regulations, 2011 CFR

2011-10-01

... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false How long may I collect information from my temperature gradient well? 3252.13 Section 3252.13 Public Lands: Interior Regulations Relating to Public Lands... temperature gradient well? You may collect information from your temperature gradient well for as long as your...

43 CFR 3252.13 - How long may I collect information from my temperature gradient well?

Code of Federal Regulations, 2013 CFR

2013-10-01

... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false How long may I collect information from my temperature gradient well? 3252.13 Section 3252.13 Public Lands: Interior Regulations Relating to Public Lands... temperature gradient well? You may collect information from your temperature gradient well for as long as your...

43 CFR 3252.13 - How long may I collect information from my temperature gradient well?

Code of Federal Regulations, 2014 CFR

2014-10-01

... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false How long may I collect information from my temperature gradient well? 3252.13 Section 3252.13 Public Lands: Interior Regulations Relating to Public Lands... temperature gradient well? You may collect information from your temperature gradient well for as long as your...

43 CFR 3252.13 - How long may I collect information from my temperature gradient well?

Code of Federal Regulations, 2012 CFR

2012-10-01

... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false How long may I collect information from my temperature gradient well? 3252.13 Section 3252.13 Public Lands: Interior Regulations Relating to Public Lands... temperature gradient well? You may collect information from your temperature gradient well for as long as your...

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.

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.

Optical Fiber Chemical Sensor with Sol-Gel Derived Refractive Material as Transducer for High Temperature Gas Sensing in Clean Coal Technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shiquan Tao

2006-12-31

The chemistry of sol-gel derived silica and refractive metal oxide has been systematically studied. Sol-gel processes have been developed for preparing porous silica and semiconductor metal oxide materials. Micelle/reversed micelle techniques have been developed for preparing nanometer sized semiconductor metal oxides and noble metal particles. Techniques for doping metal ions, metal oxides and nanosized metal particles into porous sol-gel material have also been developed. Optical properties of sol-gel derived materials in ambient and high temperature gases have been studied by using fiber optic spectroscopic techniques, such as fiber optic ultraviolet/visible absorption spectrometry, fiber optic near infrared absorption spectrometry and fibermore » optic fluorescence spectrometry. Fiber optic spectrometric techniques have been developed for investigating the optical properties of these sol-gel derived materials prepared as porous optical fibers or as coatings on the surface of silica optical fibers. Optical and electron microscopic techniques have been used to observe the microstructure, such as pore size, pore shape, sensing agent distribution, of sol-gel derived material, as well as the size and morphology of nanometer metal particle doped in sol-gel derived porous silica, the nature of coating of sol-gel derived materials on silica optical fiber surface. In addition, the chemical reactions of metal ion, nanostructured semiconductor metal oxides and nanometer sized metal particles with gas components at room temperature and high temperatures have also been investigated with fiber optic spectrometric methods. Three classes of fiber optic sensors have been developed based on the thorough investigation of sol-gel chemistry and sol-gel derived materials. The first group of fiber optic sensors uses porous silica optical fibers doped with metal ions or metal oxide as transducers for sensing trace NH{sub 3} and H{sub 2}S in high temperature gas samples. The second group of fiber optic sensors uses sol-gel derived porous silica materials doped with nanometer particles of noble metals in the form of fiber or coating for sensing trace H{sub 2}, NH{sub 3} and HCl in gas samples at for applications ambient temperature. The third classes of fiber optic sensors use sol-gel derived semiconductor metal oxide coating on the surface of silica optical fiber as transducers for selectively sensing H{sub 2}, CH{sub 4} and CO at high temperature. In addition, optical fiber temperature sensors use the fluorescence signal of rare-earth metal ions doped porous silica optical fiber or the optical absorption signal of thermochromic metal oxide materials coated on the surface of silica optical fibers have also been developed for monitoring gas temperature of corrosive gas. Based on the results obtained from this project, the principle of fiber optic sensor techniques for monitoring matrix gas components as well as trace components of coal gasification derived syngas has been established. Prototype sensors for sensing trace ammonia and hydrogen sulfide in gasification derived syngas have been built up in our laboratory and have been tested using gas samples with matrix gas composition similar to that of gasification derived fuel gas. Test results illustrated the feasibility of these sensors for applications in IGCC processes.« less

TEMPERATURE-GRADIENT INCUBATOR FOR DETERMINING THE TEMPERATURE RANGE OF GROWTH OF MICROORGANISMS

PubMed Central

Elliott, R. Paul

1963-01-01

Elliott, R. Paul (U.S. Department of Agriculture, Albany, Calif.). Temperature-gradient incubator for determining the temperature range of growth of microorganisms. J. Bacteriol. 85:889–894. 1963.—The temperature-gradient incubator consists of an aluminum bar with troughs for media, with controlled temperatures at each end, and with insulation to prevent heat transfer. The resulting linear temperature gradient provides a means for determining minimal or maximal growth temperatures of microorganisms in any desired range and at any desired gradient. The operation of the incubator is unaffected by line-voltage variations or by ambient temperature. Media do not dehydrate seriously even during prolonged periods of operation. The incubator can be used to determine water activity of media by an adjustment to permit partial freezing. Either thermocouples or thermistors may be used to measure temperatures. Images PMID:14044959

Accelerated cell sheet detachment by copolymerizing hydrophilic PEG side chains into PNIPAm nanocomposite hydrogels.

PubMed

Liu, Dan; Wang, Tao; Liu, Xinxing; Tong, Zhen

2012-10-01

One-end-connected short poly(ethylene glycol) (PEG) side chains were facilely introduced into the poly(N-isopropylacrylamide) (PNIPAm) nanocomposite hydrogel (NC gel) via in situ copolymerization of NIPAm monomer and PEG macromonomer in the aqueous suspension of hectorite clay Laponite XLS. The NC gels were characterized with Fourier transform infrared and x-ray photoelectron spectroscopy for the composition, DSC and transmittance for the phase separation temperature, dynamic mechanical spectra and swelling ratio for the interaction. Increasing the PEG content led to a small increase in the storage modulus and the lower critical solution temperature (LCST) of the copolymerized NC gels, and the LCST of the copolymerized NC gels was still below 37 °C. The L929 cell adhesion and proliferation on the surface of these NC gels were not suppressed by the incorporation of hydrophilic PEG side chains. By lowering temperature below the LCST, the cell sheet spontaneously detached from the copolymerized NC gels. The surface morphology and surface wettability of the NC gels were detected by atom force microscope and contact angle measurement. A rough and hydrophilic surface induced by a small amount of PEG side chains was found to be favorable to accelerate the cell sheet detachment, probably due to the enhanced water permeation into the gel-cell sheet interface.

Minimizing hot spot temperature in asymmetric gradient coil design.

PubMed

While, Peter T; Forbes, Larry K; Crozier, Stuart

2011-08-01

Heating caused by gradient coils is a considerable concern in the operation of magnetic resonance imaging (MRI) scanners. Hot spots can occur in regions where the gradient coil windings are closely spaced. These problem areas are particularly common in the design of gradient coils with asymmetrically located target regions. In this paper, an extension of an existing coil design method is described, to enable the design of asymmetric gradient coils with reduced hot spot temperatures. An improved model is presented for predicting steady-state spatial temperature distributions for gradient coils. A great amount of flexibility is afforded by this model to consider a wide range of geometries and system material properties. A feature of the temperature distribution related to the temperature gradient is used in a relaxed fixed point iteration routine for successively altering coil windings to have a lower hot spot temperature. Results show that significant reductions in peak temperature are possible at little or no cost to coil performance when compared to minimum power coils of equivalent field error.

Magnetoelectrets prepared by using temperature gradient method

NASA Astrophysics Data System (ADS)

Ojha, Pragya; Qureshi, M. S.; Malik, M. M.

2015-05-01

A novel Temperature Gradient method for preparation of magnetoelectret is proposed. Non uniform magnetic field and temperature gradient are expected to be the main cause for the formation of magnetoelectrets (MEs). Being bad conductors of heat, during their formation, there is a possibility for the existence of a temperature gradient along the dielectric electrode interface. In this condition, the motion of, molecules and charge carriers are dependent on Temperature Gradient in a preferred direction. To increase this temperature gradient on both sides of the sample novel method for the preparation of MEs is developed for the first time. For this method the special sample holders are designed in our laboratory. MEs are prepared in such a way that one surface is cooled and the other is heated, during the process. With the help of XRD analysis using Type-E orientation pattern and surface charge studies on magnetoelectrets, the two main causes Non uniform magnetic field and temperature gradient for the formation of magnetoelectrets (MEs), are authenticated experimentally.

Population dynamics of two antilisterial cheese surface consortia revealed by temporal temperature gradient gel electrophoresis

PubMed Central

2010-01-01

Background Surface contamination of smear cheese by Listeria spp. is of major concern for the industry. Complex smear ecosystems have been shown to harbor antilisterial potential but the microorganisms and mechanisms involved in the inhibition mostly remain unclear, and are likely related to complex interactions than to production of single antimicrobial compounds. Bacterial biodiversity and population dynamics of complex smear ecosystems exhibiting antilisterial properties in situ were investigated by Temporal temperature gradient gel electrophoresis (TTGE), a culture independent technique, for two microbial consortia isolated from commercial Raclette type cheeses inoculated with defined commercial ripening cultures (F) or produced with an old-young smearing process (M). Results TTGE revealed nine bacterial species common to both F and M consortia, but consortium F exhibited a higher diversity than consortium M, with thirteen and ten species, respectively. Population dynamics were studied after application of the consortia on fresh-produced Raclette cheeses. TTGE analyses revealed a similar sequential development of the nine species common to both consortia. Beside common cheese surface bacteria (Staphylococcus equorum, Corynebacterium spp., Brevibacterium linens, Microbacterium gubbeenense, Agrococcus casei), the two consortia contained marine lactic acid bacteria (Alkalibacterium kapii, Marinilactibacillus psychrotolerans) that developed early in ripening (day 14 to 20), shortly after the growth of staphylococci (day 7). A decrease of Listeria counts was observed on cheese surface inoculated at day 7 with 0.1-1 × 102 CFU cm-2, when cheeses were smeared with consortium F or M. Listeria counts went below the detection limit of the method between day 14 and 28 and no subsequent regrowth was detected over 60 to 80 ripening days. In contrast, Listeria grew to high counts (105 CFU cm-2) on cheeses smeared with a defined surface culture. Conclusions This work reports the first population dynamics study of complex smear ecosystems exhibiting in situ antilisterial activity. TTGE revealed the presence of marine lactic acid bacteria that are likely related to the strong Listeria inhibition, as their early development in the smear occurred simultaneously with a decrease in Listeria cell count. PMID:20222967

Influence of smooth temperature variation on hotspot ignition

NASA Astrophysics Data System (ADS)

Reinbacher, Fynn; Regele, Jonathan David

2018-01-01

Autoignition in thermally stratified reactive mixtures originates in localised hotspots. The ignition behaviour is often characterised using linear temperature gradients and more recently constant temperature plateaus combined with temperature gradients. Acoustic timescale characterisation of plateau regions has been successfully used to characterise the type of mechanical disturbance that will be created from a plateau core ignition. This work combines linear temperature gradients with superelliptic cores in order to more accurately account for a local temperature maximum of finite size and the smooth temperature variation contained inside realistic hotspot centres. A one-step Arrhenius reaction is used to model a H2-air reactive mixture. Using the superelliptic approach a range of behaviours for temperature distributions are investigated by varying the temperature profile between the gradient only and plateau and gradient bounding cases. Each superelliptic case is compared to a respective plateau and gradient case where simple acoustic timescale characterisation may be performed. It is shown that hot spots equivalent with excitation-to-acoustic timescale ratios sufficiently greater than unity exhibit behaviour very similar to a simple plateau-gradient model. However, for larger hot spots with timescale ratios sufficiently less than unity the reaction behaviour is highly dependent on the smooth temperature profile contained within the core region.

Effect of calcium source on structure and properties of sol-gel derived bioactive glasses.

PubMed

Yu, Bobo; Turdean-Ionescu, Claudia A; Martin, Richard A; Newport, Robert J; Hanna, John V; Smith, Mark E; Jones, Julian R

2012-12-18

The aim was to determine the most effective calcium precursor for synthesis of sol-gel hybrids and for improving homogeneity of sol-gel bioactive glasses. Sol-gel derived bioactive calcium silicate glasses are one of the most promising materials for bone regeneration. Inorganic/organic hybrid materials, which are synthesized by incorporating a polymer into the sol-gel process, have also recently been produced to improve toughness. Calcium nitrate is conventionally used as the calcium source, but it has several disadvantages. Calcium nitrate causes inhomogeneity by forming calcium-rich regions, and it requires high temperature treatment (>400 °C) for calcium to be incorporated into the silicate network. Nitrates are also toxic and need to be burnt off. Calcium nitrate therefore cannot be used in the synthesis of hybrids as the highest temperature used in the process is typically 40-60 °C. Therefore, a different precursor is needed that can incorporate calcium into the silica network and enhance the homogeneity of the glasses at low (room) temperature. In this work, calcium methoxyethoxide (CME) was used to synthesize sol-gel bioactive glasses with a range of final processing temperatures from 60 to 800 °C. Comparison is made between the use of CME and calcium chloride and calcium nitrate. Using advanced probe techniques, the temperature at which Ca is incorporated into the network was identified for 70S30C (70 mol % SiO(2), 30 mol % CaO) for each of the calcium precursors. When CaCl(2) was used, the Ca did not seem to enter the network at any of the temperatures used. In contrast, Ca from CME entered the silica network at room temperature, as confirmed by X-ray diffraction, (29)Si magic angle spinning nuclear magnetic resonance spectroscopy, and dissolution studies. CME should be used in preference to calcium salts for hybrid synthesis and may improve homogeneity of sol-gel glasses.

Microbial Community Structure of Korean Cabbage Kimchi and Ingredients with Denaturing Gradient Gel Electrophoresis.

PubMed

Hong, Sung Wook; Choi, Yun-Jeong; Lee, Hae-Won; Yang, Ji-Hee; Lee, Mi-Ai

2016-06-28

Kimchi is a traditional Korean fermented vegetable food, the production of which involves brining of Korean cabbage, blending with various other ingredients (red pepper powder, garlic, ginger, salt-pickled seafood, etc.), and fermentation. Recently, kimchi has also become popular in the Western world because of its unique taste and beneficial properties such as antioxidant and antimutagenic activities, which are derived from the various raw materials and secondary metabolites of the fermentative microorganisms used during production. Despite these useful activities, analysis of the microbial community present in kimchi has received relatively little attention. The objective of this study was to evaluate the bacterial community structure from the raw materials, additives, and final kimchi product using the culture-independent method. Specifically, polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) was used to analyze the 16S rRNA partial sequences of the microflora. One primer set for bacteria, 341F(GC)-518R, reliably produced amplicons from kimchi and its raw materials, and these bands were clearly separated on a 35-65% denaturing gradient gel. Overall, 117 16S rRNA fragments were identified by PCR-DGGE analysis. Pediococcus pentosaceus, Leuconostoc citreum, Leuconostoc gelidum, and Leuconostoc mesenteroides were the dominant bacteria in kimchi. The other strains identified were Tetragenococcus, Pseudomonas, Weissella, and uncultured bacterium. Comprehensive analysis of these microorganisms could provide a more detailed understanding of the biologically active components of kimchi and help improve its quality. PCR-DGGE analysis can be successfully applied to a fermented food to detect unculturable or other species.

Thermoelectrically cooled temperature-gradient apparatus for comparative cell and virus temperature studies.

PubMed

Clark, H F; Kaminski, F; Karzon, D T

1970-05-01

Establishment of a near-linear temperature gradient in an incubator has been accomplished by the application of heat to one terminus of a conducting body, normally a metal bar, and the removal of heat from the other terminus of the conducting body. Such incubators have been complex and unwieldy because of the need for mechanical refrigeration. We have described a simplified temperature gradient incubator which uses thermoelectric module cooling coupled with electric heating. Along the gradient, 20 stations in two parallel rows of 10, each accommodating a 30-ml plastic cell culture flask, were continually monitored by an electronic thermometer, and the temperatures were recorded. By manipulation of two simple potentiometer controls, any temperature gradient between 0 and 50 C could be obtained. Minor deviations which occurred between theoretically perfect and obtained temperature gradients were reproducible and readily measured. The gradient incubator was particularly applicable to (i) simultaneously studying a given biological activity over the entire temperature range supporting the growth of a given cell, virus, or microorganism, or (ii) precisely defining the upper or lower temperature limits of a biological system by 10-point determinations. Preliminary experiments have demonstrated the usefulness of the apparatus in characterizing the temperature limits for growth in vitro of cells of reptilian cell lines. The gradient incubator was also successfully utilized for the characterization of the effect of temperature on the efficiency of plating of amphibian viruses and possible temperature variants of those viruses.

Electron temperature critical gradient and transport stiffness in DIII-D

DOE PAGES

Smith, Sterling P.; Petty, Clinton C.; White, Anne E.; ...

2015-07-06

The electron energy flux has been probed as a function of electron temperature gradient on the DIII-D tokamak, in a continuing effort to validate turbulent transport models. In the scan of gradient, a critical electron temperature gradient has been found in the electron heat fluxes and stiffness at various radii in L-mode plasmas. The TGLF reduced turbulent transport model [G.M. Staebler et al, Phys. Plasmas 14, 055909 (2007)] and full gyrokinetic GYRO model [J. Candy and R.E. Waltz, J. Comput. Phys. 186, 545 (2003)] recover the general trend of increasing electron energy flux with increasing electron temperature gradient scale length,more » but they do not predict the absolute level of transport at all radii and gradients. Comparing the experimental observations of incremental (heat pulse) diffusivity and stiffness to the models’ reveals that TGLF reproduces the trends in increasing diffusivity and stiffness with increasing electron temperature gradient scale length with a critical gradient behavior. Furthermore, the critical gradient of TGLF is found to have a dependence on q 95, contrary to the independence of the experimental critical gradient from q 95.« less

A simplified model for equilibrium and transient swelling of thermo-responsive gels.

PubMed

Drozdov, A D; deClaville Christiansen, J

2017-11-01

A simplified model is developed for the elastic response of thermo-responsive gels subjected to swelling under an arbitrary deformation with finite strains. The constitutive equations involve five adjustable parameters that are determined by fitting observations in equilibrium water uptake tests and T-jump transient tests on thin gel disks. Two scenarios for water release under heating are revealed by means of numerical simulation. When the final temperature in a T-jump test is below the volume-phase transition temperature, deswelling is characterized by smooth distribution of water molecules and small tensile stresses. When the final temperature exceeds the critical temperature, a gel disk is split into three regions (central part with a high concentration of water molecules and two domains near the boundaries with low water content) separated by sharp interfaces, whose propagation is accompanied by development of large (comparable with the elastic modulus) tensile stresses. Copyright © 2017 Elsevier Ltd. All rights reserved.

Directional Bleb Formation in Spherical Cells under Temperature Gradient

PubMed Central

Oyama, Kotaro; Arai, Tomomi; Isaka, Akira; Sekiguchi, Taku; Itoh, Hideki; Seto, Yusuke; Miyazaki, Makito; Itabashi, Takeshi; Ohki, Takashi; Suzuki, Madoka; Ishiwata, Shin'ichi

2015-01-01

Living cells sense absolute temperature and temporal changes in temperature using biological thermosensors such as ion channels. Here, we reveal, to our knowledge, a novel mechanism of sensing spatial temperature gradients within single cells. Spherical mitotic cells form directional membrane extensions (polar blebs) under sharp temperature gradients (≥∼0.065°C μm−1; 1.3°C temperature difference within a cell), which are created by local heating with a focused 1455-nm laser beam under an optical microscope. On the other hand, multiple nondirectional blebs are formed under gradual temperature gradients or uniform heating. During heating, the distribution of actomyosin complexes becomes inhomogeneous due to a break in the symmetry of its contractile force, highlighting the role of the actomyosin complex as a sensor of local temperature gradients. PMID:26200871

Transportation of perishable and refrigerated foods in mylar foil bags and insulated containers: a time-temperature study.

PubMed

Li, Yanyan; Schrade, John P; Su, Haiyan; Specchio, John J

2014-08-01

Data are lacking on the temperature changes of food during transport without the use of refrigerated trucks. The purpose of this study was to evaluate the ability of several insulated and noninsulated containers with or without frozen gel packs to keep perishable and refrigerated foods within the temperature safe zone in relationship to duration of transport. The study was designed to duplicate the practices exhibited by customers purchasing perishable food products from a cash-and-carry business. Approximately 40 perishable food items were evaluated. Four types of containers were tested: a mylar foil bag, a commercial insulated bag, a generic insulated bag, and a commercial insulated blanket. Mixed foods were placed into these containers with or without frozen gel packs, transported in unrefrigerated vehicles, and monitored for 4 h for temperature changes. Two environmental temperatures, room temperature of 21.1°C and a stress temperature of 37.8°C, were evaluated. The internal temperature and surface temperature of the food products in these containers increased slowly but remained well below the U.S. Food and Drug Administration Food Code requirements. The various containers were similar in their ability to retain coolness. The presence of frozen gel packs dramatically enhanced the cold-holding capacity of the containers. The temperature of foods increased more rapidly when stressed in a heated environment. The containers tested used with the frozen gel packs can keep the surface and internal temperatures of various perishable foods (starting at 4.4°C or less) within the Food Code recommendation of under 21.1°C for 4 h. Cash-and-carry businesses should strongly encourage their retail customers to utilize these containers with frozen gel packs to safely transport perishable foods.

Temperature-dependent self-assembly and rheological behavior of a thermoreversible pmma-P n BA-PMMA triblock copolymer gel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zabet, Mahla; Mishra, Satish; Boy, Ramiz

We present that self-assembly and mechanical properties of triblock copolymers in a mid-block selective solvent are of interest in many applications. Herein, we report physical assembly of an ABA triblock copolymer, [PMMA–PnBA–PMMA] in two different mid-block selective solvents, n-butanol and 2-ethyl-1-hexanol. Gel formation resulting from end-block associations and the corresponding changes in mechanical properties have been investigated over a temperature range of -80 °C to 60 °C, from near the solvent melting points to above the gelation temperature. Shear-rheometry, thermal analysis, and small-angle neutron scattering data reveal formation and transition of structure in these systems from a liquid state tomore » a gel state to a percolated cluster network with decrease in temperature. The aggregated PMMA end-blocks display a glass transition temperature. Finally, our results provide new understanding into the structural changes of a self-assembled triblock copolymer gel over a large length scale and wide temperature range.« less

Temperature-dependent self-assembly and rheological behavior of a thermoreversible pmma-P n BA-PMMA triblock copolymer gel

DOE PAGES

Zabet, Mahla; Mishra, Satish; Boy, Ramiz; ...

2017-03-25

We present that self-assembly and mechanical properties of triblock copolymers in a mid-block selective solvent are of interest in many applications. Herein, we report physical assembly of an ABA triblock copolymer, [PMMA–PnBA–PMMA] in two different mid-block selective solvents, n-butanol and 2-ethyl-1-hexanol. Gel formation resulting from end-block associations and the corresponding changes in mechanical properties have been investigated over a temperature range of -80 °C to 60 °C, from near the solvent melting points to above the gelation temperature. Shear-rheometry, thermal analysis, and small-angle neutron scattering data reveal formation and transition of structure in these systems from a liquid state tomore » a gel state to a percolated cluster network with decrease in temperature. The aggregated PMMA end-blocks display a glass transition temperature. Finally, our results provide new understanding into the structural changes of a self-assembled triblock copolymer gel over a large length scale and wide temperature range.« less

Different elution modes and field programming in gravitational field-flow fractionation. III. Field programming by flow-rate gradient generated by a programmable pump.

PubMed

Plocková, J; Chmelík, J

2001-05-25

Gravitational field-flow fractionation (GFFF) utilizes the Earth's gravitational field as an external force that causes the settlement of particles towards the channel accumulation wall. Hydrodynamic lift forces oppose this action by elevating particles away from the channel accumulation wall. These two counteracting forces enable modulation of the resulting force field acting on particles in GFFF. In this work, force-field programming based on modulating the magnitude of hydrodynamic lift forces was implemented via changes of flow-rate, which was accomplished by a programmable pump. Several flow-rate gradients (step gradients, linear gradients, parabolic, and combined gradients) were tested and evaluated as tools for optimization of the separation of a silica gel particle mixture. The influence of increasing amount of sample injected on the peak resolution under flow-rate gradient conditions was also investigated. This is the first time that flow-rate gradients have been implemented for programming of the resulting force field acting on particles in GFFF.

Thermodynamic analysis of sol-gel transition of gelatin in terms of water activity in various solutions.

PubMed

Miyawaki, Osato; Omote, Chiaki; Matsuhira, Keiko

2015-12-01

Sol-gel transition of gelatin was analyzed as a multisite stoichiometric reaction of a gelatin molecule with water and solute molecules. The equilibrium sol-gel transition temperature, Tt , was estimated from the average of gelation and melting temperature measured by differential scanning calorimetry. From Tt and the melting enthalpy, ΔHsol , the equilibrium sol-to-gel ratio was estimated by the van't Hoff equation. The reciprocal form of the Wyman-Tanford equation, which describes the sol-to-gel ratio as a function of water activity, was successfully applied to obtain a good linear relationship. From this analysis, the role of water activity on the sol-gel transition of gelatin was clearly explained and the contributions of hydration and solute binding to gelatin molecules were separately discussed in sol-gel transition. The general solution for the free energy for gel-stabilization in various solutions was obtained as a simple function of solute concentration. © 2015 Wiley Periodicals, Inc.

Relative humidity preference and survival of starved Formosan subterranean termites (Isoptera: Rhinotermitidae) at various temperature and relative humidity conditions.

PubMed

Gautam, Bal K; Henderson, Gregg

2011-10-01

Foraging groups of Formosan subterranean termites, Coptotermes formosanus Shiraki were tested for their relative humidity (RH) preference in a humidity gradient arena in the laboratory at a constant temperature of 26°C. Five RH levels (9%, 33%, 53%, 75%, and 98%) were maintained in the test arena comprising of a series of closed containers by using dry silica gel, saturated salt solutions, or distilled water alone. Termites gradually aggregated to the highest RH chamber in the arena. After 1 h, a significantly greater percentage of termites (≈46%) aggregated to the highest RH chamber (98%) than to the lower RH chambers (≤75%). After 12 h, > 97% of the termites aggregated to the 98% RH chamber. In survival tests, where termites were exposed to 15 combinatorial treatments of five RH levels (9%, 33%, 53%, 75%, and 98%) and three temperatures (20°C, 28°C, and 36°C) for a week, the survival was significantly influenced by RH, temperature, and their interaction. A significantly higher mortality was observed on termites exposed to ≤75% RH chambers than to 98% RH chamber at the three temperatures and significantly lower survival was found at 36°C than at 28°C or 20°C. The combination of temperature and RH plays an important role in the survival of C. formosanus.

Application of the diffusive gradients in thin films technique for available potassium measurement in agricultural soils: effects of competing cations on potassium uptake by the resin gel.

PubMed

Zhang, Yulin; Mason, Sean; McNeill, Ann; McLaughlin, Michael J

2014-09-09

The utilization of Amberlite (IRP-69 ion-exchange resin, 100-500 wet mesh) as the binding phase in the diffusive gradients in thin films (DGT) technique has shown potential to improve the assessment of plant-available K in soils. The binding phase has recently been optimized by using a mixed Amberlite and ferrihydrite (MAF) gel which results in linear K uptake over extended deployment periods and in solutions with higher K concentrations. As restriction of K uptake by Ca on the Amberlite based resin gel has been previously proposed, potential competing effects of Ca(2+), Mg(2+) and NH(4+) on K uptake by the MAF gel were investigated. These cations had no effect on K elution efficiency which was 85%. However, K uptake by the MAF gel was restricted in the presence of competing cations in solution. Consequently, the diffusion coefficient of K decreased in the presence of cations compared to previous studies but was stable at 1.12×10(-5)cm(2)s(-1) at 25°C regardless of cation concentrations. Uptake of K by the DGT device was affected by the presence of excessive Ca in more than 30% of twenty typical Australian agricultural soils. However, this problem could be circumvented by using a shorter deployment time than the normal 24 h. Moderate correlation of concentrations of K extracted by DGT with Colwell K (extracted by NaHCO(3), R(2)=0.69) and NH4OAc K (R(2)=0.61) indicates that DGT measures a different pool of K in soils than that measured by the standard extractants used. In addition, the MAF gel has the ability to measure Ca and Mg simultaneously. Copyright © 2014 Elsevier B.V. All rights reserved.

Investigation of water mobility and diffusivity in hydrating micronized low-substituted hydroxypropyl cellulose, hydroxypropylmethyl cellulose, and hydroxypropyl cellulose matrix tablets by magnetic resonance imaging (MRI).

PubMed

Kojima, Masazumi; Nakagami, Hiroaki

2002-12-01

The water mobility and diffusivity in the gel-layer of hydrating low-substituted hydroxypropyl cellulose (LH41) tablets with or without a drug were investigated by magnetic resonance imaging (MRI) and compared with those properties in the gel-layer of hydroxypropylmethyl cellulose (HPMC) and hydroxypropyl cellulose (HPC) tablets. For this purpose, a localized image-analysis method was newly developed, and the spin-spin relaxation time (T(2)) and apparent self-diffusion coefficient (ADC) of water in the gel-layer were visualized in one-dimensional maps. Those maps showed that the extent of gel-layer growth in the tablets was in the order of HPC>HPMC>LH41, and there was a water mobility gradient across the gel-layers of all three tablet formulations. The T(2) and ADC in the outer parts of the gel-layers were close to those of free water. In contrast, these values in the inner parts of the gel-layer decreased progressively; suggesting that the water mobility and diffusivity around the core interface were highly restricted. Furthermore, the correlation between the T(2) of (1)H proton in the gel-layer of the tablets and the drug release rate from the tablets was observed.

Thermal stability and degradation kinetics of kenaf/sol-gel silica hybrid

NASA Astrophysics Data System (ADS)

Yusof, F. A. M.; Hashim, A. S.; Tajudin, Z.

2017-12-01

Thermal stability and degradation kinetics of kenaf/sol-gel silica hybrid materials was investigated by thermogravimetric analysis (TGA). Model-free iso-conversion Flynn-Wall-Ozawa (FWO) and Coats-Redfern-modified (CRm) were chosen to evaluate the activation energy of the kenaf (KF) and kenaf/sol-gel silica (KFS) at heating rates (β) of 10, 20, 30 and 40 °C/min. The results shows that an apparent activation energy was increased for the kenaf/sol-gel silica hybrid (211.59 kJ/mol for FWO and 191.55 kJ/mol for CRm) as compared to kenaf fiber (202.84 kJ/mol for FWO and 186.20 kJ/mol for CRm). Other parameters such as integral procedure decomposition temperature (IPDT), final residual weight (Rf), temperature of maximum degradation rate (Tmax) and residual at maximum temperature (RTmax) were obtained from TGA curves, additionally confirmed the thermal stability of the kenaf/sol-gel silica hybrid. These activation energy values and other findings developed the simplified approach in order to understand the thermal stability and degradation kinetics behavior of kenaf/sol-gel silica hybrid materials.

Gradient structure-induced temperature responsiveness in styrene/methyl methacrylate gradient copolymers micelles.

PubMed

Zheng, Chao; Huang, Haiying; He, Tianbai

2014-02-01

In this work, micelles are formed by gradient copolymer of styrene and methyl methacrylate in acetone-water mixture and their temperature responsiveness is investigated in a narrow range near room temperature. Three different kinds of structural transitions could be induced by temperature: unimers to micelle transition, shrinkage/stretching of micelles, and morphological transition from spherical micelles to vesicles. In addition, a model analysis on the interface of gradient copolymer micelle is made to better understand these phenomena. It is found that both position and composition of the interface could alter in response to the change in temperature. According to the experiments and model analysis, it is proposed that temperature responsiveness might be an intrinsic and universal property of gradient copolymer micelles, which only originates from the gradient structure. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermal gradients for the stabilization of a single domain wall in magnetic nanowires.

PubMed

Mejía-López, J; Velásquez, E A; Mazo-Zuluaga, J; Altbir, D

2018-08-24

By means of Monte Carlo simulations we studied field driven nucleation and propagation of transverse domain walls (DWs) in magnetic nanowires subjected to temperature gradients. Simulations identified the existence of critical thermal gradients that allow the existence of reversal processes driven by a single DW. Critical thermal gradients depend on external parameters such as temperature, magnetic field and wire length, and can be experimentally obtained through the measurement of the mean velocity of the magnetization reversal as a function of the temperature gradient. Our results show that temperature gradients provide a high degree of control over DW propagation, which is of great importance for technological applications.

Evidence of counter-gradient growth in western pond turtles (Actinemys marmorata) across thermal gradients

Treesearch

Melissa L. Snover; Michael J. Adams; Donald T. Ashton; Jamie B. Bettaso; Hartwell H. Welsh

2015-01-01

Summary1. Counter-gradient growth, where growth per unit temperature increases as temperature decreases, can reduce the variation in ectothermic growth rates across environmental gradients. Understanding how ectothermic species respond to changing temperatures is essential to their conservation and management due to human-altered habitats and changing...

Influence of smooth temperature variation on hotspot ignition

DOE PAGES

Reinbacher, Fynn; Regele, Jonathan David

2017-10-06

Autoignition in thermally stratified reactive mixtures originates in localised hotspots. The ignition behaviour is often characterised using linear temperature gradients and more recently constant temperature plateaus combined with temperature gradients. Acoustic timescale characterisation of plateau regions has been successfully used to characterise the type of mechanical disturbance that will be created from a plateau core ignition. This work combines linear temperature gradients with superelliptic cores in order to more accurately account for a local temperature maximum of finite size and the smooth temperature variation contained inside realistic hotspot centres. A one-step Arrhenius reaction is used to model a H 2–airmore » reactive mixture. Using the superelliptic approach a range of behaviours for temperature distributions are investigated by varying the temperature profile between the gradient only and plateau and gradient bounding cases. Each superelliptic case is compared to a respective plateau and gradient case where simple acoustic timescale characterisation may be performed. It is shown that hot spots equivalent with excitation-to-acoustic timescale ratios sufficiently greater than unity exhibit behaviour very similar to a simple plateau-gradient model. Furthermore, for larger hot spots with timescale ratios sufficiently less than unity the reaction behaviour is highly dependent on the smooth temperature profile contained within the core region.« less

Influence of smooth temperature variation on hotspot ignition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reinbacher, Fynn; Regele, Jonathan David

Autoignition in thermally stratified reactive mixtures originates in localised hotspots. The ignition behaviour is often characterised using linear temperature gradients and more recently constant temperature plateaus combined with temperature gradients. Acoustic timescale characterisation of plateau regions has been successfully used to characterise the type of mechanical disturbance that will be created from a plateau core ignition. This work combines linear temperature gradients with superelliptic cores in order to more accurately account for a local temperature maximum of finite size and the smooth temperature variation contained inside realistic hotspot centres. A one-step Arrhenius reaction is used to model a H 2–airmore » reactive mixture. Using the superelliptic approach a range of behaviours for temperature distributions are investigated by varying the temperature profile between the gradient only and plateau and gradient bounding cases. Each superelliptic case is compared to a respective plateau and gradient case where simple acoustic timescale characterisation may be performed. It is shown that hot spots equivalent with excitation-to-acoustic timescale ratios sufficiently greater than unity exhibit behaviour very similar to a simple plateau-gradient model. Furthermore, for larger hot spots with timescale ratios sufficiently less than unity the reaction behaviour is highly dependent on the smooth temperature profile contained within the core region.« less

High-mobility low-temperature ZnO transistors with low-voltage operation

NASA Astrophysics Data System (ADS)

Bong, Hyojin; Lee, Wi Hyoung; Lee, Dong Yun; Kim, Beom Joon; Cho, Jeong Ho; Cho, Kilwon

2010-05-01

Low voltage high mobility n-type thin film transistors (TFTs) based on sol-gel processed zinc oxide (ZnO) were fabricated using a high capacitance ion gel gate dielectric. The ion gel gated solution-processed ZnO TFTs were found to exhibit excellent electrical properties. TFT carrier mobilities were 13 cm2/V s, ON/OFF current ratios were 105, regardless of the sintering temperature used for the preparation of the ZnO thin films. Ion gel gated ZnO TFTs are successfully demonstrated on plastic substrates for the large area flexible electronics.

Insights into the mechanical properties of a silicone oil gel with a ‘latent’ gelator, 1-octadecylamine, and CO2 as an ‘activator’

PubMed Central

George, Mathew

2010-01-01

Summary A detailed study of the rheological properties of silicone oil gels, made from a low-molecular-mass organic gelator, a combination of 1-octadecylamine (a latent gelator) and carbon dioxide (an ‘activating’ molecule), is reported. Information gleaned from the mechanical measurements is used to characterize the gel networks and how they respond to temperature and strain. It is shown, for example, that very precise measurements of the gel-to-sol transitions can be obtained from plots of viscosity versus temperature. PMID:21085496

Bacterial and Archaeal Communities Variability Associated with Upwelling and Anthropogenic Pressures in the Protection Area of Arraial do Cabo (Cabo Frio region - RJ).

PubMed

Coelho-Souza, Sergio A; Araújo, Fábio V; Cury, Juliano C; Jesus, Hugo E; Pereira, Gilberto C; Guimarães, Jean R D; Peixoto, Raquel S; Dávila, Alberto M R; Rosado, Alexandre S

2015-09-01

Upwelling systems contain a high diversity of pelagic microorganisms and their composition and activity are defined by factors like temperature and nutrient concentration. Denaturing gradient gel electrophoresis (DGGE) technique was used to verify the spatial and temporal genetic variability of Bacteria and Archaea in two stations of the Arraial do Cabo coastal region, one under upwelling pressure and another under anthropogenic pressure. In addition, biotic and abiotic variables were measured in surface and deep waters from three other stations between these stations. Six samplings were done during a year and adequately represented the degrees of upwelling and anthropogenic pressures to the system. Principal Component Analysis (PCA) showed negative correlations between the concentrations of ammonia and phosphorous with prokaryotic secondary production and the total heterotrophic bacteria. PCA also showed negative correlation between temperature and the abundance of prokaryotic cells. Bacterial and archaeal compositions were changeable as were the oceanographic conditions, and upwelling had a regional pressure while anthropogenic pressure was punctual. We suggest that the measurement of prokaryotic secondary production was associated with both Bacteria and Archaea activities, and that substrate availability and temperature determine nutrients cycling.

Effect of fermentation temperature on hydrogen production from cow waste slurry by using anaerobic microflora within the slurry.

PubMed

Yokoyama, Hiroshi; Waki, Miyoko; Moriya, Naoko; Yasuda, Tomoko; Tanaka, Yasuo; Haga, Kiyonori

2007-02-01

We examined hydrogen production from a dairy cow waste slurry (13.4 g of volatile solids per liter) by batch cultures in a temperature range from 37 to 85 degrees C, using microflora naturally present within the slurry. Without the addition of seed bacteria, hydrogen was produced by simply incubating the slurry, using the microflora within the slurry. Interestingly, two peaks of fermentation temperatures for hydrogen production from the slurry were observed at 60 and 75 degrees C (392 and 248 ml H2 per liter of slurry, respectively). After the termination of the hydrogen evolution, the microflora cultured at 60 degrees C displayed hydrogen-consuming activity, but hydrogen-consuming activity of the microflora cultured at 75 degrees C was not detected, at least for 24 days. At both 60 and 75 degrees C, the main by-product was acetate, and the optimum pH of the slurry for hydrogen production was around neutral. Bacteria related to hydrogen-producing moderate and extreme thermophiles, Clostridium thermocellum and Caldanaerobacter subterraneus, were detected in the slurries cultured at 60 and 75 degrees C, respectively, by denaturing gradient gel electrophoresis analyses, using the V3 region of 16S rDNA.

Site-Specific Pre-Swelling-Directed Morphing Structures of Patterned Hydrogels.

PubMed

Wang, Zhi Jian; Hong, Wei; Wu, Zi Liang; Zheng, Qiang

2017-12-11

Morphing materials have promising applications in various fields, yet how to program the self-shaping process for specific configurations remains a challenge. Herein we show a versatile approach to control the buckling of individual domains and thus the outcome configurations of planar-patterned hydrogels. By photolithography, high-swelling disc gels were positioned in a non-swelling gel sheet; the swelling mismatch resulted in out-of-plain buckling of the disc gels. To locally control the buckling direction, masks with holes were used to guide site-specific swelling of the high-swelling gel under the holes, which built a transient through-thickness gradient and thus directed the buckling during the subsequent unmasked swelling process. Therefore, various configurations of an identical patterned hydrogel can be programmed by the pre-swelling step with different masks to encode the buckling directions of separate domains. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Temperature-induced sol-gel transition and microgel formation in α-actinin cross-linked actin networks: A rheological study

NASA Astrophysics Data System (ADS)

Tempel, M.; Isenberg, G.; Sackmann, E.

1996-08-01

We have studied the sol-gel transition, the viscoelastic and the structural properties of networks constituted of semiflexible actin filaments cross-linked by α-actinin. Cross-linking was regulated in a reversible way by varying the temperature through the association-dissociation equilibrium of the actin-α-actinin system. Viscoelastic parameters [shear storage modulus G'(ω), phase shift tan(Φ)(ω), creep compliance J(t)] were measured as a function of temperature and actin-to-cross-linker ratio by a magnetically driven rotating disc rheometer. G'(ω) and tan(Φ)(ω) were studied at a frequency ω corresponding to the elastic plateau regime of the G'(ω) versus ω spectrum of the purely entangled solution. The microstructure of the networks was viewed by negative staining electron microscopy (EM). The phase shift tan(Φ) (or equivalently the viscosity η) diverges and reaches a maximum when approaching the apparent gel point from lower and higher temperatures, and the maximum defines the gel point (temperature Tg). The elastic plateau modulus G'N diverges at temperatures beyond this gel point TTg. The cross-linking transition (corresponding to a sol-gel transition at zero frequency) is interpreted in terms of a percolation model and the divergence of G'N at TTg), (2) that microscopic segregation takes place at T<=Tg leading to local formation of clusters (a state termed microgel), and (3) that at low actin-α-actinin ratios (rAα<=10) and low temperatures (T<=10 °C) macroscopic segregation into bundles of cross-linked actin filaments and a diluted solution of actin filaments is observed. The three regimes of network structure are represented by an equivalent phase diagram.

Combining high-throughput MALDI-TOF mass spectrometry and isoelectric focusing gel electrophoresis for virtual 2D gel-based proteomics.

PubMed

Lohnes, Karen; Quebbemann, Neil R; Liu, Kate; Kobzeff, Fred; Loo, Joseph A; Ogorzalek Loo, Rachel R

2016-07-15

The virtual two-dimensional gel electrophoresis/mass spectrometry (virtual 2D gel/MS) technology combines the premier, high-resolution capabilities of 2D gel electrophoresis with the sensitivity and high mass accuracy of mass spectrometry (MS). Intact proteins separated by isoelectric focusing (IEF) gel electrophoresis are imaged from immobilized pH gradient (IPG) polyacrylamide gels (the first dimension of classic 2D-PAGE) by matrix-assisted laser desorption/ionization (MALDI) MS. Obtaining accurate intact masses from sub-picomole-level proteins embedded in 2D-PAGE gels or in IPG strips is desirable to elucidate how the protein of one spot identified as protein 'A' on a 2D gel differs from the protein of another spot identified as the same protein, whenever tryptic peptide maps fail to resolve the issue. This task, however, has been extremely challenging. Virtual 2D gel/MS provides access to these intact masses. Modifications to our matrix deposition procedure improve the reliability with which IPG gels can be prepared; the new procedure is described. Development of this MALDI MS imaging (MSI) method for high-throughput MS with integrated 'top-down' MS to elucidate protein isoforms from complex biological samples is described and it is demonstrated that a 4-cm IPG gel segment can now be imaged in approximately 5min. Gel-wide chemical and enzymatic methods with further interrogation by MALDI MS/MS provide identifications, sequence-related information, and post-translational/transcriptional modification information. The MSI-based virtual 2D gel/MS platform may potentially link the benefits of 'top-down' and 'bottom-up' proteomics. Copyright © 2016 Elsevier Inc. All rights reserved.

Improved Characterization of Groundwater Flow in Heterogeneous Aquifers Using Granular Polyacrylamide (PAM) Gel as Temporary Grout

NASA Astrophysics Data System (ADS)

Klepikova, Maria V.; Roques, Clement; Loew, Simon; Selker, John

2018-02-01

The range of options for investigation of hydraulic behavior of aquifers from boreholes has been limited to rigid, cumbersome packers, and inflatable sleeves. Here we show how a new temporary borehole sealing technique using soft grains of polyacrylamide (PAM) gel as a sealing material can be used to investigate natural groundwater flow dynamics and discuss other possible applications of the technology. If no compressive stress is applied, the gel packing, with a permeability similar to open gravel, suppresses free convection, allowing for local temperature measurements and chemical sampling through free-flowing gel packing. Active heating laboratory and field experiments combined with temperature measurements along fiber optic cables were conducted in water-filled boreholes and boreholes filled with soft grains of polyacrylamide gel. The gel packing is shown to minimize the effect of free convection within the well column and enable detection of thin zones of relatively high or low velocity in a highly transmissive alluvial aquifer, thus providing a significant improvement compared to temperature measurements in open boreholes. Laboratory experiments demonstrate that under modest compressive stress to the gel media the permeability transitions from highly permeable to nearly impermeable grouting. Under this configuration the gel packing could potentially allow for monitoring local response pressure from the formation with all other locations in the borehole hydraulically isolated.

Isothermal transitions of a thermosetting system

NASA Technical Reports Server (NTRS)

Gillham, J. K.; Benci, J. A.; Noshay, A.

1974-01-01

A study of the curing reactions of a cycloaliphatic epoxy resin/anhydride system by torsional braid analysis showed the existence of two critical isothermal temperatures - namely, the maximum glass transition temperature of the thermoset system and the glass transition temperature of the material at its gel point. Two rheologically active kinetic transitions occur during isothermal cure which correspond to gelation and vitrification. Three types of isothermal behavior occur. Methods for determining the time to gel and the time to vitrify, and also the two above-mentioned critical isothermal temperatures, have been developed. The time to gel obeyed the Arrhenius relationship, whereas the time to vitrify passed through a minimum. Application of these results to thermosetting systems in general is discussed in terms of the influence of molecular structure on the values of the critical isothermal temperatures.

Polymer gel dosimeter with AQUAJOINT® as hydrogel matrix

NASA Astrophysics Data System (ADS)

Maeyama, Takuya; Ishida, Yasuhiro; Kudo, Yoshihiro; Fukasaku, Kazuaki; Ishikawa, Kenichi L.; Fukunishi, Nobuhisa

2018-05-01

We report a polymer gel dosimeter based on a new gel matrix (AQUAJOINT®) that is a thermo-irreversible hydrogel formed by mixing two types of water-based liquids at room temperature. Normoxic N-vinylpyrrolidone-based polymer gels were prepared with AQUAJOINT® instead of gelatin. This AQUAJOINT®-based gel dosimeter exhibits a 2.5-fold increase in sensitivity over a gelatin-based gel dosimeter and a linear dose-response in the dose range of 0-8 Gy. This gel has heat resistance in a jar and controlled gel properties such as viscoelastic and mechanical characters, which may be useful for deformable polymer gel dosimetry.

Effect of light-enhanced bleaching on in vitro surface and intrapulpal temperature rise.

PubMed

Baik, J W; Rueggeberg, F A; Liewehr, F R

2001-01-01

This study investigated the effect of the presence, absence, and aging of a heat-enhancing compound (colorant) added to bleaching gel on the temperature rise of the gel itself, as well as the temperature rise within the pulp chamber, when a tooth was exposed to a variety of light-curing units in vitro. An extracted human upper central incisor was fitted with thermocouples placed in the pulp chamber as well as on the facial tooth surface. A temperature-controlled simulated intrapulpal fluid flow was provided to the tooth, and bleaching agent (Opalesence XTRA, Ultradent) containing heat-enhancing colorant, aged colorant, or no colorant was applied to the facial surface. The tooth and light-curing unit were placed in a thermostatically controlled oven at 37 degrees C, and real-time gel and intrapulpal temperature values were recorded digitally. Light-curing units used were a plasma arc light (PAC) (PowerPac, ADT), a conventional quartz tungsten halogen source (QTH) (Optilux 501, Demetron/Kerr), the QTH light used in high-power (bleaching) mode, and an argon ion laser (AccuCure 3000, LaserMed). An exposure scenario simulating light-enhanced bleaching of 10 upper teeth was developed. Temperature rise over the pre-exposure, baseline value associated with the last light exposure in the bleaching sequence was calculated for each curing and bleaching combination. Five replications for each test condition were made. Temperature rise values were compared using analysis of variance (ANOVA) at a preset alpha of 0.05. When fresh colorant-containing bleach was used, the PAC light increased bleach temperature 39.3 degrees C above baseline. With no added colorant, temperature rise was 37.1 degrees C. The QTH light in bleach mode resulted in gel temperature 24.8 degrees C above baseline, whereas the temperature increase was only 11.5 degrees C when no colorant was used. Conventional QTH light use increased fresh bleach temperature by 17.7 degrees C, whereas an increase of only 11.1 degrees C was measured without colorant. The argon ion laser produced equivalent temperature rise regardless of the presence or freshness of the colorant, approximately 9.4 degrees C. Intrapulpal temperatures were all significantly lower than those recorded in the bleaching gel and ranged from 5 degrees to 8 degrees C. As a rule, the presence of fresh heat-enhancing colorant in the bleaching gel resulted in a significant intrapulpal temperature increase (approximately 1 degrees C) over that reached using other lights. The PAC and the QTH light used in bleach mode induced greater intrapulpal temperature rise than the laser. Freshness of bleaching agent incorporating light-activated, heat-enhancing colorant influences temperature rise of bleaching gel and also may increase intrapulpal temperature values. Use of intense lights does elevate bleach temperature and also results in increased intrapulpal temperature that may further impact on patient sensitivity and pulpal health resulting from this treatment.

Dehydration and crystallization kinetics of zirconia-yttria gels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramanathan, S.; Muraleedharan, R.V.; Roy, S.K.

1995-02-01

Zirconia and zirconia-yttria gels containing 4 and 8 mol% yttria were obtained by coprecipitation and drying at 373 K. The dehydration and crystallization behavior of the dried gels was studied by DSC, TG, and XRD. The gels undergo elimination of water over a wide temperature range of 373--673 K. The peak temperature of the endotherm corresponding to dehydration and the kinetic constants for the process were not influenced by the yttria content of the gel. The enthalpy of dehydration observed was in good agreement with the heat of vaporization data. The dehydration was followed by a sharp exothermic crystallization process.more » The peak temperature of the exotherm and the activation energy of the process increased with an increase in yttria content, while the enthalpy of crystallization showed a decrease. The ``glow effect`` reduced with increasing yttria content. Pure zirconia crystallizes in the tetragonal form while the zirconia containing 4 and 8 mol% yttria appears to crystallize in the cubic form.« less

Heat-induced gelation of casein micelles in aqueous suspensions at different pH.

PubMed

Thomar, Peggy; Nicolai, Taco

2016-10-01

Heat-induced gelation of casein micelles in aqueous solution was investigated between pH 5.2 and pH 6.7 over a wide range of protein concentrations (C=25-160gL(-1)). For C≥40gL(-1) the casein micelles rapidly formed a self-supporting gel above a critical temperature (Tc). At C=160gL(-1), Tc decreased from 90°C at pH 6.5 to 30°C at pH 5.4 and increased with decreasing protein concentration. Oscillatory shear measurements during heating showed that the elastic modulus (Gel) of the gels increased strongly with increasing protein concentration, but was insensitive to the pH and the heating temperature except close to Tc where Gel decreased sharply with decreasing temperature. The microstructure of the gels was observed by confocal scanning laser microscopy. Heat-induced gelation of casein micelles was compared with that of sodium caseinate solutions free of calcium phosphate. Copyright © 2016 Elsevier B.V. All rights reserved.

The role of hydrogels in the radical production of the Fricke-gel-dosimeter

NASA Astrophysics Data System (ADS)

Lazzaroni, S.; Liosi, G. M.; D'Agostino, G.; Marconi, R. P.; Mariani, M.; Buttafava, A.; Dondi, D.

2018-01-01

The radiolysis mechanism of the Fricke-gel-dosimeters has been investigated in order to evaluate the role of hydrogels in the radical production. For this purpose, electron paramagnetic resonance (EPR) spectra were acquired for samples frozen and irradiated at 77 K. The analysis was performed by increasing stepwise the temperature and acquiring the EPR spectra at 120 K in order to follow the radical reaction mechanism. The comparison between aqueous- and gel- dosimeters were performed. Both gelatin from porcine skin and PVA (polyvinyl alcohol) were investigated as gel matrix. Different radical species were identified and qualitatively compared. For gel matrix, peroxyl radicals, stemming from the hydrogel, play an important role in the survival of radicals at higher temperature. Moreover, the Fe3+ EPR signal has been studied and compared with the radicals concentration. From this comparison, it is evident the increase of Fe3+ concentration is shifted toward higher temperatures with respect to the radical decay. To explain this phenomenon, the intervention of EPR silent species like peroxides is supposed.

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.

Geologic and geophysical data for wells drilled at Raft River Valley, Cassia County, Idaho, in 1977-1978 and data for wells drilled previously

USGS Publications Warehouse

Nathenson, Manuel; Urban, Thomas C.; Covington, Harry R.

2014-01-01

For purposes of defining the thermal anomaly for the geothermal system, temperature gradients are calculated over long depth intervals on the basis of the appearance of reasonable linear segments on a temperature versus plot depth.  Temperature versus depth data for some drill holes can be represented by a single gradient, whereas others require multiple gradients to match the data.  Data for some drill holes clearly reflect vertical flows of water in the formation surrounding the drill holes, and water velocities are calculated for these drill holes.  Within The Narrows area, temperature versus depth data show reversals at different depth in different drill holes.  In the main thermal area, temperatures in intermediate-depth drill holes vary approximately linearly but with very high values of temperature gradient.  Temperature gradients on a map of the area can be reasonable divided into a large area of regional gradients and smaller areas defining the thermal anomalies.

Adhesive Properties of Polyacrylate Gels

NASA Astrophysics Data System (ADS)

Flanigan, Cynthia; Shull, Kenneth

1998-03-01

Soft, low-modulus gels provide an interesting opportunity to examine small adhesive interactions between two bodies in contact. As shown through dynamic rheological studies, our materials undergo a rapid gelation as they are cooled from a viscous liquid at elevated temperatures to a soft, elastic solid at room temperature. At low temperatures, the gels exhibit a linearly elastic response and display moduli close to 100Pa, thereby forming materials with great potential for quantifying weak adhesive interactions with a variety of bodies ranging from polymer surfaces to biological entities. Our current studies focus on investigating interfacial effects by performing axisymmetric adhesion tests with a model polyacrylate gel formed by diluting the copolymer poly(methyl methacrylate)-poly(n-butyl acrylate)-poly(methyl methacrylate) to a 5-15 percent solution in 2-ethyl hexanol, a selective solvent for the midblock. We have explored two different experimental geometries including a hemispherical rigid indenter of glass pressed into a gel layer of varying thicknesses, and a soft, gel cap in contact with a rigid polymer surface. By simultaneously measuring the applied load, displacement between the two bodies, and contact area during loading cycles, we are able to employ a linearly elastic fracture mechanics analysis to obtain estimates of the gel's modulus over a range of polymer concentrations, and G, the energy release rate.

Aircraft symmetric flight optimization. [gradient techniques for supersonic aircraft control

NASA Technical Reports Server (NTRS)

Falco, M.; Kelley, H. J.

1973-01-01

Review of the development of gradient techniques and their application to aircraft optimal performance computations in the vertical plane of flight. Results obtained using the method of gradients are presented for attitude- and throttle-control programs which extremize the fuel, range, and time performance indices subject to various trajectory and control constraints, including boundedness of engine throttle control. A penalty function treatment of state inequality constraints which generally appear in aircraft performance problems is outlined. Numerical results for maximum-range, minimum-fuel, and minimum-time climb paths for a hypothetical supersonic turbojet interceptor are presented and discussed. In addition, minimum-fuel climb paths subject to various levels of ground overpressure intensity constraint are indicated for a representative supersonic transport. A variant of the Gel'fand-Tsetlin 'method of ravines' is reviewed, and two possibilities for further development of continuous gradient processes are cited - namely, a projection version of conjugate gradients and a curvilinear search.

Effect of temperature and pH on the properties of skim milk gels made from a tamarillo (Cyphomandra betacea) coagulant and rennet.

PubMed

Li, Z; Scott, K; Otter, D; Zhou, P; Hemar, Y

2018-06-01

Reconstituted skim milk was gelled with a crude protease extract from tamarillo [Cyphomandra betacea or Solanum betacea (syn.)] fruit and compared with gels prepared with calf rennet. The effects of temperature and pH on the gelation of skim milk were investigated by small deformation oscillatory rheology. The tamarillo extract-induced gels had a faster rate of increase in the elastic modulus (G') at the early stage of gelation than rennet-induced milk gels. This was probably due to the broader proteolytic activity of tamarillo protease extracts as shown by sodium dodecyl sulfate-PAGE analysis. Confocal microscopy also showed that the milk gels resulting from the addition of tamarillo extracts had larger voids than rennet-induced milk gels. The proteolytic activity of tamarillo extracts was found to be optimal at pH 11. For both rennet and tamarillo extracts, the aggregation time was similar between pH 6.7 and 6.5, but the aggregation time of rennet-induced milk gels was lower than that of milk gels obtained by the addition of tamarillo extracts at pH lower than 6.5. An increase in temperature was found to have a significant effect on aggregation time, particularly at 20°C, where rennet did not coagulate milk in 3 h but the tamarillo extracts coagulated milk within 2 h. The results of this study suggest that extracts from tamarillo fruit could be used for milk gelation, particularly under lower temperature or high pH conditions. Copyright © 2018 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

The Effect of Temperature on Moisture Transport in Concrete.

PubMed

Wang, Yao; Xi, Yunping

2017-08-09

Most concrete structures and buildings are under temperature and moisture variations simultaneously. Thus, the moisture transport in concrete is driven by the moisture gradient as well as the temperature gradient. This paper presents an experimental approach for determining the effect of different temperature gradients on moisture distribution profiles in concrete. The effect of elevated temperatures under isothermal conditions on the moisture transport was also evaluated, and found not to be significant. The non-isothermal tests show that the temperature gradient accelerates the moisture transport in concrete. The part of increased moisture transfer due to the temperature gradient can be quantified by a coupling parameter D HT , which can be determined by the present test data. The test results indicated that D HT is not a constant but increases linearly with the temperature variation. A material model was developed for D HT based on the experimental results obtained in this study.

The Effect of Temperature on Moisture Transport in Concrete

PubMed Central

Wang, Yao; Xi, Yunping

2017-01-01

Most concrete structures and buildings are under temperature and moisture variations simultaneously. Thus, the moisture transport in concrete is driven by the moisture gradient as well as the temperature gradient. This paper presents an experimental approach for determining the effect of different temperature gradients on moisture distribution profiles in concrete. The effect of elevated temperatures under isothermal conditions on the moisture transport was also evaluated, and found not to be significant. The non-isothermal tests show that the temperature gradient accelerates the moisture transport in concrete. The part of increased moisture transfer due to the temperature gradient can be quantified by a coupling parameter DHT, which can be determined by the present test data. The test results indicated that DHT is not a constant but increases linearly with the temperature variation. A material model was developed for DHT based on the experimental results obtained in this study. PMID:28792460

Temperature Gradients on the Cell Wall in the Critical Viscosity Experiment

NASA Technical Reports Server (NTRS)

Berg, Robert F.; Moldover, Michael R.

1993-01-01

Because of the diverging susceptibility delta rho/delta Tau near the liquid-vapor critical point, temperature gradients must be kept small to maintain adequate sample homogeneity. In our Science Requirements Document we paid particular attention to radial density gradients caused by equilibration of the xenon sample. Axial density gradients were addressed through the requirement that the cell's copper wall have a gradient less than 22 microK/m. This report re-examines the cell wall's temperature distribution in more detail by estimating all known significant contributions to temperature differences on the cell's wall.

Tripolar vortex formation in dense quantum plasma with ion-temperature-gradients

NASA Astrophysics Data System (ADS)

Qamar, Anisa; Ata-ur-Rahman, Mirza, Arshad M.

2012-05-01

We have derived system of nonlinear equations governing the dynamics of low-frequency electrostatic toroidal ion-temperature-gradient mode for dense quantum magnetoplasma. For some specific profiles of the equilibrium density, temperature, and ion velocity gradients, the nonlinear equations admit a stationary solution in the form of a tripolar vortex. These results are relevant to understand nonlinear structure formation in dense quantum plasmas in the presence of equilibrium ion-temperature and density gradients.

Gels with exceptional thermal stability formed by bis(amino acid) oxalamide gelators and solvents of low polarity.

PubMed

Makarević, Janja; Jokić, Milan; Frkanec, Leo; Katalenić, Darinka; Zinić, Mladen

2002-10-07

Some bis (amino acid) oxalamide gelators form common thermo-reversible gels with various organic solvents but also gels of exceptional thermal stability with some solvents of medium and low polarity; the latter gels can be heated up to 50 degrees C higher temperatures than the bp of the solvent without apparent gel-to-sol transition.

Bacterial analysis of combined periodontal-endodontic lesions by polymerase chain reaction-denaturing gradient gel electrophoresis.

PubMed

Xia, Minghui; Qi, Qingguo

2013-01-01

We used denaturing gradient gel electrophoresis (DGGE) to compare bacterial profiles in periodontium and root canals of teeth with combined periodontal-endodontic lesions. Samples of dental plaque and necrotic pulp were collected from thirteen extracted teeth with advanced periodontitis. Genomic DNA was extracted for polymerase chain reaction (PCR) analysis using universal bacterial primers. The PCR products were then loaded onto DGGE gels to obtain fractionated bands. Characteristic DGGE bands were excised and DNA was cloned and sequenced. The number of bands, which indicates the number of bacterial species, was compared between dental plaques and necrotic pulp tissues from the same tooth. Although the difference was statistically significant (P < 0.01), there was no positive correlation; similarity (Dice coefficient) was 13.1% to 62.5%. Some bacteria species were present in both the periodontal pockets and root canals of the same tooth; however, periodontal bacteria did not always invade the root canals, and some bacteria in root canals were not present in periodontal pockets of the same tooth. In some teeth, unique bacteria in root canals had not passed from periodontal pockets. A basic local alignment search tool (BLAST) sequence search in Genbank indicated that new bacteria species were present in periodontal pockets and root canals. Their characteristics must thus be further analyzed.

Glass shell manufacturing in space

NASA Technical Reports Server (NTRS)

Downs, R. L.; Ebner, M. A.; Nolen, R. L., Jr.

1981-01-01

Highly-uniform, hollow glass spheres (shells), which are used for inertial confinement fusion targets, were formed from metal-organic gel powder feedstock in a vertical furnace. As a result of the rapid pyrolysis caused by the furnace, the gel is transformed to a shell in five distinct stages: (a) surface closure of the porous gel; (b) generation of a closed-cell foam structure in the gel; (c) spheridization of the gel and further expansion of the foam; (d) coalescence of the closed-cell foam to a single-void shell; and (e) fining of the glass shell. The heat transfer from the furnace to the falling gel particle was modeled to determine the effective heating rate of the gel. The model predicts the temperature history for a particle as a function of mass, dimensions, specific heat, and absorptance as well as furnace temperature profile and thermal conductivity of the furnace gas. A model was developed that predicts the gravity-induced degradation of shell concentricity in falling molten shells as a function of shell characteristics and time.

Preparation and evaluation of gelling granules to improve oral administration.

PubMed

Ito, Ikumi; Ito, Akihiko; Unezaki, Sakae

2015-06-01

We investigated the preparation of oral granules that are solid when stored and that will swell and gel via water absorption, to address problems experienced by patients when taking medication. Important physical properties of gelling granules include elasticity that is normally smooth, quick water absorption and swelling properties that allow easy swallowing. We selected gelatin (GEL), succinylated gelatin (SUC-GEL) and ι-carrageenan (CAR) as matrix polymers that can undergo gelation at room temperature or at cold temperatures. Saccharide and polyethylene glycol (PEG) were added to prepare the experimental granules. The best matrix gelling granule was SUC-GEL. When xylitol (XYL), sorbitol (SOR) and maltitol (MAL) were added, elasticity was improved, and PEG improved the granule's water absorption behavior, which is an important element involved in gelation. The best granules were prepared by selecting SUC-GEL as the matrix and adding a small amount of PEG and XYL in amounts equal to that of SUC-GEL.

Fabrication and characterization of poly(L-lactic acid) gels induced by fibrous complex crystallization with solvents

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsuda, Yasuhiro; Fukatsu, Akinobu; Wang, Yangyang

2014-01-01

Complex crystal induced gelation of poly(L-lactic acid) (PLLA) solutions was studied for a series of solvents, including N,N-dimethylformamide (DMF). By cooling the solutions prepared at elevated temperatures, PLLA gels were produced in solvents that induced complex crystals ( -crystals) with PLLA. Fibrous structure of PLLA in the gel with DMF was observed by polarizing optical microscopy, field emission electron microscopy, and atomic force microscopy. Upon heating, the crystal form of PLLA in the DMF gel changed from -crystal to a-crystal, the major crystal form in common untreated PLLA films, but the morphology and high elastic modulus of the gel remainedmore » until the a-crystal dissolved at higher temperature. In addition, a solvent exchanging method was developed, which allowed PLLA gels to be prepared in other useful solvents that do not induce -crystals without losing the morphology and mechanical properties.« less

Biodiversity of Bacterial Ecosystems in Traditional Egyptian Domiati Cheese▿

PubMed Central

El-Baradei, Gaber; Delacroix-Buchet, Agnès; Ogier, Jean-Claude

2007-01-01

Bacterial biodiversity occurring in traditional Egyptian soft Domiati cheese was studied by PCR-temporal temperature gel electrophoresis (TTGE) and PCR-denaturing gradient gel electrophoresis (DGGE). Bands were identified using a reference species database (J.-C. Ogier et al., Appl. Environ. Microbiol. 70:5628-5643, 2004); de novo bands having nonidentified migration patterns were identified by DNA sequencing. Results reveal a novel bacterial profile and extensive bacterial biodiversity in Domiati cheeses, as reflected by the numerous bands present in TTGE and DGGE patterns. The dominant lactic acid bacteria (LAB) identified were as follows: Leuconostoc mesenteroides, Lactococcus garvieae, Aerococcus viridans, Lactobacillus versmoldensis, Pediococcus inopinatus, and Lactococcus lactis. Frequent non-LAB species included numerous coagulase-negative staphylococci, Vibrio spp., Kocuria rhizophila, Kocuria kristinae, Kocuria halotolerans, Arthrobacter spp./Brachybacterium tyrofermentans. This is the first time that the majority of these species has been identified in Domiati cheese. Nearly all the dominant and frequent bacterial species are salt tolerant, and several correspond to known marine bacteria. As Domiati cheese contains 5.4 to 9.5% NaCl, we suggest that these bacteria are likely to have an important role in the ripening process. This first systematic study of the microbial composition of Domiati cheeses reveals great biodiversity and evokes a role for marine bacteria in determining cheese type. PMID:17189434

Biodiversity of bacterial ecosystems in traditional Egyptian Domiati cheese.

PubMed

El-Baradei, Gaber; Delacroix-Buchet, Agnès; Ogier, Jean-Claude

2007-02-01

Bacterial biodiversity occurring in traditional Egyptian soft Domiati cheese was studied by PCR-temporal temperature gel electrophoresis (TTGE) and PCR-denaturing gradient gel electrophoresis (DGGE). Bands were identified using a reference species database (J.-C. Ogier et al., Appl. Environ. Microbiol. 70:5628-5643, 2004); de novo bands having nonidentified migration patterns were identified by DNA sequencing. Results reveal a novel bacterial profile and extensive bacterial biodiversity in Domiati cheeses, as reflected by the numerous bands present in TTGE and DGGE patterns. The dominant lactic acid bacteria (LAB) identified were as follows: Leuconostoc mesenteroides, Lactococcus garvieae, Aerococcus viridans, Lactobacillus versmoldensis, Pediococcus inopinatus, and Lactococcus lactis. Frequent non-LAB species included numerous coagulase-negative staphylococci, Vibrio spp., Kocuria rhizophila, Kocuria kristinae, Kocuria halotolerans, Arthrobacter spp./Brachybacterium tyrofermentans. This is the first time that the majority of these species has been identified in Domiati cheese. Nearly all the dominant and frequent bacterial species are salt tolerant, and several correspond to known marine bacteria. As Domiati cheese contains 5.4 to 9.5% NaCl, we suggest that these bacteria are likely to have an important role in the ripening process. This first systematic study of the microbial composition of Domiati cheeses reveals great biodiversity and evokes a role for marine bacteria in determining cheese type.

Neurotrophic factor - Characterization and partial purification

NASA Technical Reports Server (NTRS)

Popiela, H.; Ellis, S.

1981-01-01

Recent evidence suggests that neurotrophic activity is required for the normal proliferation and development of muscle cells. The present paper reports a study of the purification and characterization of a neurotrophic factor (NTF) from adult chicken ischiatic-peroneal nerves using two independent quantitative in vitro assay systems. The assays were performed by the measurement of the incorporation of tritiated thymidine or the sizes of single-cell clones by chick muscle cells grown in culture. The greatest amount of neutrotrophic activity is found to be extracted at a pH of 8; aqueous suspensions of the activity are stable to long-term storage at room temperature. The specific activity of the substance is doubled upon precipitation with ammonium sulfate or after gel filtration, and increase 4 to 5 fold after salt gradient elution from DEAE cellulose columns. The active fraction obtained after gel filtration and rechromatography on DEAE cellulose exhibits a 7 to 10-fold increase in specific activity. Electrophoresis of the most highly purified material yields a greatly concentrated band at around 80,000 daltons. Although NTF is purified almost 10-fold as indicated by the increase in specific activity, the maximum activity of the partially purified material is greatly reduced, possibly due to a requirement for a cofactor for the expression of maximum activity.

Evidence for retrovirus infections in green turtles Chelonia mydas from the Hawaiian islands

USGS Publications Warehouse

Casey, R.N.; Quackenbush, S.L.; Work, Thierry M.; Balazs, G.H.; Bowser, P.R.; Casey, J.W.

1997-01-01

Apparently normal Hawaiian green turtles Chelonia mydas and those displaying fibropapillomas were analyzed for infection by retroviruses. Strikingly, all samples were positive for polymerase enhanced reverse transcriptase (PERT) with levels high enough to quantitate by the conventional reverse transcriptase (RT) assay. However, samples of skin, even from asymptomatic turtles, were RT positive, although the levels of enzyme activity in healthy turtles hatched and raised in captivity were much lower than those observed in asymptomatic free-ranging turtles. Turtles with fibropapillomas displayed a broad range of reverse transcriptase activity. Skin and eye fibropapillomas and a heart tumor were further analyzed and shown to have reverse transcriptase activity that banded in a sucrose gradient at 1.17 g ml-1. The reverse transcriptase activity purified from the heart tumor displayed a temperature optimum of 37??C and showed a preference for Mn2+ over Mg2+. Sucrose gradient fractions of this sample displaying elevated reverse transcriptase activity contained primarily retrovitalsized particles with prominent envelope spikes, when negatively stained and examined by electron microscopy. Sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of gradient-purified virions revealed a conserved profile among 4 independent tumors and showed 7 prominent proteins having molecular weights of 116, 83, 51, 43, 40, 20 and 14 kDa. The data suggest that retroviral infections are widespread in Hawaiian green turtles and a comprehensive investigation is warranted to address the possibility that these agents cause green turtle fibropapillomatosis (GTFP).

Exhaled nitric oxide in mylar balloons: influence of storage time, humidity and temperature.

PubMed Central

Bodini, Alessandro; Pijnenburg, Mariëlle W H; Boner, Atillio L; de Jongste, Johan C

2003-01-01

BACKGROUND: Mylar balloons are used to collect exhaled air for analysis of fractional nitric oxide concentration (FENO). AIM: We studied the effect of storage conditions on the stability of nitric oxide (NO) in mylar balloons. METHODS: Exhaled air samples and calibration gases were stored in mylar balloons at 4, 21 and 37 degrees C, with or without silica gel. NO was measured after 0, 6, 9, 24 and 48 h. Scheffe F-tests were used to compare NO values. RESULTS: NO remained stable in balloons for 9 h at all temperatures, without silica gel. NO increased between 9 and 48 h, but only with low initial FENO. Silica gel increased variability. CONCLUSIONS: FENO in mylar balloons is stable for at least 9 h. The storage temperature is not critical, but silica gel increases variability. PMID:12745548

Crystalline-gel-molten phase transitions of water in calcium dipicolinate (Ca-DPA)

NASA Astrophysics Data System (ADS)

Tiwari, Subodh; Mishra, Ankit; Sheng, Chunyang; Rajak, Pankaj; Kalia, Rajiv; Nakano, Aiichiro; Vashishta, Priya

The heat resistance of bacterial spores directly correlates to the protoplast dehydration and presence of dipicolinic acid (DPA) and its associated metal salts at the core. Bacteria's structural integrity in moist heat conferred by high concentration of DPA and calcium DPA salts depends on the properties are additional water molecules and temperature. In our reactive MD simulations, we characterize different possible phases and the transport properties of water molecules. We observed solid-gel and gel-liquid phase transitions of the hydrated Ca-DPA system. These simulations reveal monotonically decreasing solid-gel-liquid transition temperatures with increasing cell hydration, reflecting the experimental trend of moist-heat resistance of bacterial spores. We also observed that the calcification of bacterial spores further increases the transition temperatures. This research is supported by DTRA Grant No. HDTRA1-14-1-0074.

A gel probe equilibrium sampler for measuring arsenic porewater profiles and sorption gradients in sediments: I. Laboratory development

USGS Publications Warehouse

Campbell, K.M.; Root, R.; O'Day, P. A.; Hering, J.G.

2008-01-01

A gel probe equilibrium sampler has been developed to study arsenic (As) geochemistry and sorption behavior in sediment porewater. The gels consist of a hydrated polyacrylamide polymer, which has a 92% water content. Two types of gels were used in this study. Undoped (clear) gels were used to measure concentrations of As and other elements in sediment porewater. The polyacrylamide gel was also doped with hydrous ferric oxide (HFO), an amorphous iron (Fe) oxyhydroxide. When deployed in the field, HFO-doped gels introduce a fresh sorbent into the subsurface thus allowing assessment of in situ sorption. In this study, clear and HFO-doped gels were tested under laboratory conditions to constrain the gel behavior prior to field deployment. Both types of gels were allowed to equilibrate with solutions of varying composition and re-equilibrated in acid for analysis. Clear gels accurately measured solution concentrations (??1%), and As was completely recovered from HFO-doped gels (??4%). Arsenic speciation was determined in clear gels through chromatographic separation of the re-equilibrated solution. For comparison to speciation in solution, mixtures of As(III) and As(V) adsorbed on HFO embedded in gel were measured in situ using X-ray absorption spectroscopy (XAS). Sorption densities for As(III) and As(V) on HFO embedded in gel were obtained from sorption isotherms at pH 7.1. When As and phosphate were simultaneously equilibrated (in up to 50-fold excess of As) with HFO-doped gels, phosphate inhibited As sorption by up to 85% and had a stronger inhibitory effect on As(V) than As(III). Natural organic matter (>200 ppm) decreased As adsorption by up to 50%, and had similar effects on As(V) and As(III). The laboratory results provide a basis for interpreting results obtained by deploying the gel probe in the field and elucidating the mechanisms controlling As partitioning between solid and dissolved phases in the environment. ?? 2008 American Chemical Society.

PCR-DGGE Analysis on Microbial Community Structure of Rural Household Biogas Digesters in Qinghai Plateau.

PubMed

Han, Rui; Yuan, Yongze; Cao, Qianwen; Li, Quanhui; Chen, Laisheng; Zhu, Derui; Liu, Deli

2018-05-01

To investigate contribution of environmental factor(s) to microbial community structure(s) involved in rural household biogas fermentation at Qinghai Plateau, we collected slurry samples from 15 digesters, with low-temperature working conditions (11.1-15.7 °C) and evenly distributed at three counties (Datong, Huangyuan, and Ledu) with cold plateau climate, to perform polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and further sequencing. The bacterial communities in the total 15 digesters were classified into 38 genera with Mangroviflexus (12.1%) as the first dominant, and the archaeal communities into ten genera with Methanogenium (38.5%) as the most dominant. For each county, the digesters with higher biogas production, designated as HP digesters, exclusively had 1.6-3.1 °C higher fermentation temperature and the unique bacterial structure composition related, i.e., unclassified Clostridiales for all the HP digesters and unclassified Marinilabiliaceae and Proteiniclasticum for Ledu HP digesters. Regarding archaeal structure composition, Methanogenium exhibited significantly higher abundances at all the HP digesters and Thermogymnomonas was the unique species only identified at Ledu HP digesters with higher-temperature conditions. Redundancy analysis also confirmed the most important contribution of temperature to the microbial community structures investigated. This report emphasized the correlation between temperature and specific microbial community structure(s) that would benefit biogas production of rural household digesters at Qinghai Plateau.

A general strategy for performing temperature-programming in high performance liquid chromatography--further improvements in the accuracy of retention time predictions of segmented temperature gradients.

PubMed

Wiese, Steffen; Teutenberg, Thorsten; Schmidt, Torsten C

2012-01-27

In the present work it is shown that the linear elution strength (LES) model which was adapted from temperature-programming gas chromatography (GC) can also be employed for systematic method development in high-temperature liquid chromatography (HT-HPLC). The ability to predict isothermal retention times based on temperature-gradient as well as isothermal input data was investigated. For a small temperature interval of ΔT=40°C, both approaches result in very similar predictions. Average relative errors of predicted retention times of 2.7% and 1.9% were observed for simulations based on isothermal and temperature-gradient measurements, respectively. Concurrently, it was investigated whether the accuracy of retention time predictions of segmented temperature gradients can be further improved by temperature dependent calculation of the parameter S(T) of the LES relationship. It was found that the accuracy of retention time predictions of multi-step temperature gradients can be improved to around 1.5%, if S(T) was also calculated temperature dependent. The adjusted experimental design making use of four temperature-gradient measurements was applied for systematic method development of selected food additives by high-temperature liquid chromatography. Method development was performed within a temperature interval from 40°C to 180°C using water as mobile phase. Two separation methods were established where selected food additives were baseline separated. In addition, a good agreement between simulation and experiment was observed, because an average relative error of predicted retention times of complex segmented temperature gradients less than 5% was observed. Finally, a schedule of recommendations to assist the practitioner during systematic method development in high-temperature liquid chromatography was established. Copyright © 2011 Elsevier B.V. All rights reserved.

Evaluation of hybrid SART  +  OS  +  TV iterative reconstruction algorithm for optical-CT gel dosimeter imaging

NASA Astrophysics Data System (ADS)

Du, Yi; Wang, Xiangang; Xiang, Xincheng; Wei, Zhouping

2016-12-01

Optical computed tomography (optical-CT) is a high-resolution, fast, and easily accessible readout modality for gel dosimeters. This paper evaluates a hybrid iterative image reconstruction algorithm for optical-CT gel dosimeter imaging, namely, the simultaneous algebraic reconstruction technique (SART) integrated with ordered subsets (OS) iteration and total variation (TV) minimization regularization. The mathematical theory and implementation workflow of the algorithm are detailed. Experiments on two different optical-CT scanners were performed for cross-platform validation. For algorithm evaluation, the iterative convergence is first shown, and peak-to-noise-ratio (PNR) and contrast-to-noise ratio (CNR) results are given with the cone-beam filtered backprojection (FDK) algorithm and the FDK results followed by median filtering (mFDK) as reference. The effect on spatial gradients and reconstruction artefacts is also investigated. The PNR curve illustrates that the results of SART  +  OS  +  TV finally converges to that of FDK but with less noise, which implies that the dose-OD calibration method for FDK is also applicable to the proposed algorithm. The CNR in selected regions-of-interest (ROIs) of SART  +  OS  +  TV results is almost double that of FDK and 50% higher than that of mFDK. The artefacts in SART  +  OS  +  TV results are still visible, but have been much suppressed with little spatial gradient loss. Based on the assessment, we can conclude that this hybrid SART  +  OS  +  TV algorithm outperforms both FDK and mFDK in denoising, preserving spatial dose gradients and reducing artefacts, and its effectiveness and efficiency are platform independent.

Subsurface temperatures and geothermal gradients on the North Slope, Alaska

USGS Publications Warehouse

Collett, Timothy S.; Bird, Kenneth J.; Magoon, Leslie B.

1989-01-01

Geothermal gradients as interpreted from a series of high-resolution stabilized well-bore-temperature surveys from 46 North Slope, Alaska, wells vary laterally and vertically throughout the near-surface sediment (0-2,000 m). The data from these surveys have been used in conjunction with depths of ice-bearing permafrost, as interpreted from 102 well logs, to project geothermal gradients within and below the ice-bearing permafrost sequence. The geothermal gradients calculated from the projected temperature profiles are similar to the geothermal gradients measured in the temperature surveys. Measured and projected geothermal gradients in the ice-bearing permafrost sequence range from 1.5??C/100m in the Prudhoe Bay area to 5.1??C/100m in the National Petroleum Reserve in Alaska (NPRA).

Assessment of the effects of CT dose in averaged x-ray CT images of a dose-sensitive polymer gel

NASA Astrophysics Data System (ADS)

Kairn, T.; Kakakhel, M. B.; Johnston, H.; Jirasek, A.; Trapp, J. V.

2015-01-01

The signal-to-noise ratio achievable in x-ray computed tomography (CT) images of polymer gels can be increased by averaging over multiple scans of each sample. However, repeated scanning delivers a small additional dose to the gel which may compromise the accuracy of the dose measurement. In this study, a NIPAM-based polymer gel was irradiated and then CT scanned 25 times, with the resulting data used to derive an averaged image and a "zero-scan" image of the gel. Comparison between these two results and the first scan of the gel showed that the averaged and zero-scan images provided better contrast, higher contrast-to- noise and higher signal-to-noise than the initial scan. The pixel values (Hounsfield units, HU) in the averaged image were not noticeably elevated, compared to the zero-scan result and the gradients used in the linear extrapolation of the zero-scan images were small and symmetrically distributed around zero. These results indicate that the averaged image was not artificially lightened by the small, additional dose delivered during CT scanning. This work demonstrates the broader usefulness of the zero-scan method as a means to verify the dosimetric accuracy of gel images derived from averaged x-ray CT data.

Thermal Gradient Fining of Glass

NASA Technical Reports Server (NTRS)

Wilcox, W.

1983-01-01

Molten glass fined (cleared of bubbles) by heating with suitable temperature gradient, according to preliminary experiments. Temperature gradient produces force on gas bubbles trapped in molten glass pushing bubbles to higher temperature region where they are collected. Concept demonstrated in experiments on Earth and on rocket.

Comparison of the canine corneal epithelial cell sheets cultivated from limbal stem cells on canine amniotic membrane, atelocollagen gel, and temperature-responsive culture dish.

PubMed

Nam, Eunryel; Fujita, Naoki; Morita, Maresuke; Tsuzuki, Keiko; Lin, Hsing Yi; Chung, Cheng Shu; Nakagawa, Takayuki; Nishimura, Ryohei

2015-07-01

The current study compared canine corneal epithelial cell sheets cultivated from limbal stem cells on amniotic membrane, atelocollagen gel, and temperature-responsive culture dish. We collected limbal epithelial cells from the intact eyes of beagles and cultivated the cells on denuded canine amniotic membranes, temperature-responsive cell culture labware, and collagen gel with 3T3 feeder cells. Immunofluorescence staining for Ki-67 was used to analyze the capacity of cell proliferation in the sheets. Immunofluorescence staining was also performed for the corneal epithelium-specific marker cytokeratin 3 and putative stem cell markers ABCG2 and p63. Reverse-transcription polymerase chain reaction (RT-PCR) was performed to detect ABCG2 and p63. The growth rates of the cultivated cells, or the times it took them to reach confluency, were different for the three scaffolds. The cultivated sheet on the temperature-responsive dish consisted of 2-3 layers, while those on the collagen gel and on the amniotic membrane consisted of 5-8 layers. The basal layer cells grown on all three scaffolds expressed putative stem cell markers. In real-time RT-PCR analysis, the highest level of p63 was observed in the sheets grown on collagen gel. In this study, the cells cultured on the collagen gel demonstrated a capacity for cell proliferation, and the expressions of stem cells in the sheets suggested that collagen gel is the most suitable carrier for clinical use. © 2014 American College of Veterinary Ophthalmologists.

Seasonal variation of plankton communities influenced by environmental factors in an artificial lake

NASA Astrophysics Data System (ADS)

Li, Xuemei; Yu, Yuhe; Zhang, Tanglin; Feng, Weisong; Ao, Hongyi; Yan, Qingyun

2012-05-01

We evaluated the seasonal variation in plankton community composition in an artificial lake. We conducted microscopic analysis and denaturing gradient gel electrophoresis (DGGE) of PCR-amplified partial 16S rRNA and 18S rRNA genes to characterize the plankton community. The clustering of unweighted pair group method with arithmetic mean (UPGMA) was then used to investigate the similarity of these plankton communities. DGGE fingerprinting revealed that samples collected at the different sites within a season shared high similarity and were generally grouped together. In contrast, we did not observe any seasonal variation based on microscopic analysis. Redundancy analysis (RDA) of the plankton operational taxonomic units (OTUs) in relation to environmental factors revealed that transparency was negatively correlated with the first axis ( R=-0.931), and temperature and total phosphorus (TP) were positively correlated with the first axis ( R=0.736 and R=0.660, respectively). In conclusion, plankton communities in the artificial lake exhibited significant seasonal variation. Transparency, phosphorus and temperature appear to be the major factors driving the differences in plankton composition.

Use of Psychrotolerant Lactic Acid Bacteria (Lactobacillus spp. and Leuconostoc spp.) Isolated from Chinese Traditional Paocai for the Quality Improvement of Paocai Products.

PubMed

Liu, Aiping; Li, Xiaoyan; Pu, Biao; Ao, Xiaolin; Zhou, Kang; He, Li; Chen, Shujuan; Liu, Shuliang

2017-03-29

To improve the quality of Chinese traditional Paocai, two psychrotolerant lactic acid bacteria (LAB) strains were isolated from Paocai, and the quality of Chinese Paocai product using these two strains as starter cultures was compared to a control sample fermented with aged brine at 10 °C. The results suggested that the physicochemical and sensory features of Paocai fermented with psychrotolerant LAB were more suitable for industrial applications. The nitrite content of Paocai fermented with psychrotolerant LAB was 1 mg/kg, which was significantly lower than that of the control Paocai (P < 0.05). Low-temperature fermentation with the starter cultures of psychrotolerant LAB could effectively prevent overacidity and over-ripening of the Paocai products. Additionally, Paocai fermented with psychrotolerant LAB harbored relatively simple microbial flora as revealed by polymerase chain reaction-denaturing gradient gel electrophoresis. This study provides a basis for improving the quality of Chinese traditional Paocai and the large-scale production of low-temperature Chinese traditional Paocai products.

Molecular Level Understanding of Sodium Dodecyl Sulfate (SDS) Induced Sol-Gel Transition of Pluronic F127 Using Fisetin as a Fluorescent Molecular Probe.

PubMed

Mishra, Jhili; Swain, Jitendriya; Mishra, Ashok Kumar

2018-01-11

The thermoreversible sol-gel transition of pluronic F127 is markedly altered even with addition of submicellar concentration of sodium dodecyl sulfate (SDS) surfactant. Multiple fluorescence parameters like fluorescence intensity, fluorescence anisotropy and fluorescence lifetime of both the prototropic forms (anion (A - *) and phototautomer FT*) of the photoprototropic fluorescent probe fisetin has been efficiently used to understand the molecular level properties like polarity and microviscosity of the PF127-SDS system as a function of temperature. The SDS-induced increase in the interfacial hydrophobicity level is seen to affect the sol-gel phase transition of PF127 (21-18 °C). The E T (30) polarity parameter value of anionic emission of fisetin suggests that there is a considerable decrease in the polarity of the PF127 medium with increase in temperature and with the addition of SDS. The microviscosity progressively increases from ∼5 mPa s (sol state, 10 °C) to ∼22.01 mPa s (gel state 35 °C) in aqueous solution of PF127. The variation in microviscosity with addition of SDS in PF127-SDS mixed system is significant in sol phase whereas in gel phase this variation is significantly less. Temperature dependent fluorescence lifetime of FT* indicates that there is heterogeneity in distribution of fisetin molecules at different domains of PF127. This work also show-cases the sensitivity of fisetin toward change in polarity and change in sol-gel transition temperature of copolymer PF127 with variation in temperature (both forward and reverse directions) and SDS.

Rheological study of physical cross-linked quaternized cellulose hydrogels induced by β-glycerophosphate.

PubMed

You, Jun; Zhou, Jinping; Li, Qian; Zhang, Lina

2012-03-20

As a weak base, β-glycerophosphate (β-GP) was used to spontaneously initiate gelation of quaternized cellulose (QC) solutions at body temperature. The QC/β-GP solutions are flowable below or at room temperature but gel rapidly under physiological conditions. In order to clarify the sol-gel transition process of the QC/β-GP systems, the complex was investigated by dynamic viscoelastic measurements. The shear storage modulus (G') and loss modulus (G″) as a function of (1) concentration of β-GP (c(β-GP)), (2) concentration of QC (c(QC)), (3) degree of substitution (DS; i.e., the average number of substituted hydroxyl groups in the anhydroglucose unit) of QC, (4) viscosity-average molecular weight (M(η)) of QC, and (5) solvent medium were studied by the oscillatory rheology. The sol-gel transition temperature of QC/β-GP solutions decreased with an increase of c(QC) and c(β-GP), the M(η) of QC, and a decrease of the DS of QC and pH of the solvent. The sol-gel transition temperature and time could be easily controlled by adjusting the concentrations of QC and β-GP, M(η) and DS of QC, and the solvent medium. Gels formed after heating were irreversible; i.e., after cooling to lower temperature they could not be dissolved to become liquid again. The aggregation and entanglement of QC chains, electrostatic interaction, and hydrogen bonding between QC and β-GP were the main factors responsible for the irreversible sol-gel transition behavior of QC/β-GP systems.

Biocompatible patterning of proteins on wettability gradient surface by thermo-transfer printing.

PubMed

Kim, Sungho; Ryu, Yong-Sang; Suh, Jeng-Hun; Keum, Chang-Min; Sohn, Youngjoo; Lee, Sin-Doo

2014-08-01

We develop a simple and biocompatible method of patterning proteins on a wettability gradient surface by thermo-transfer printing. The wettability gradient is produced on a poly(dimethylsiloxane) (PDMS)-modified glass substrate through the temperature gradient during thermo-transfer printing. The water contact angle on the PDMS-modified surface is found to gradually increase along the direction of the temperature gradient from a low to a high temperature region. Based on the wettability gradient, the gradual change in the adsorption and immobilization of proteins (cholera toxin B subunit) is achieved in a microfluidic cell with the PDMS-modified surface.

43 CFR 3252.12 - How deep may I drill a temperature gradient well?

Code of Federal Regulations, 2012 CFR

2012-10-01

... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false How deep may I drill a temperature... RESOURCE LEASING Conducting Exploration Operations § 3252.12 How deep may I drill a temperature gradient well? (a) You may drill a temperature gradient well to any depth that we approve in your exploration...

43 CFR 3252.12 - How deep may I drill a temperature gradient well?

Code of Federal Regulations, 2013 CFR

2013-10-01

... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false How deep may I drill a temperature... RESOURCE LEASING Conducting Exploration Operations § 3252.12 How deep may I drill a temperature gradient well? (a) You may drill a temperature gradient well to any depth that we approve in your exploration...

43 CFR 3252.12 - How deep may I drill a temperature gradient well?

Code of Federal Regulations, 2014 CFR

2014-10-01

... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false How deep may I drill a temperature... RESOURCE LEASING Conducting Exploration Operations § 3252.12 How deep may I drill a temperature gradient well? (a) You may drill a temperature gradient well to any depth that we approve in your exploration...

43 CFR 3252.12 - How deep may I drill a temperature gradient well?

Code of Federal Regulations, 2011 CFR

2011-10-01

... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false How deep may I drill a temperature... RESOURCE LEASING Conducting Exploration Operations § 3252.12 How deep may I drill a temperature gradient well? (a) You may drill a temperature gradient well to any depth that we approve in your exploration...

Fully kinetic Biermann battery and associated generation of pressure anisotropy

NASA Astrophysics Data System (ADS)

Schoeffler, K. M.; Loureiro, N. F.; Silva, L. O.

2018-03-01

The dynamical evolution of a fully kinetic, collisionless system with imposed background density and temperature gradients is investigated analytically. The temperature gradient leads to the generation of temperature anisotropy, with the temperature along the gradient becoming larger than that in the direction perpendicular to it. This causes the system to become unstable to pressure anisotropy driven instabilities, dominantly to the electron Weibel instability. When both density and temperature gradients are present and nonparallel to each other, we obtain a Biermann-like linear-in-time magnetic field growth. Accompanying particle-in-cell numerical simulations are shown to confirm our analytical results.

Process for preparing silicon carbide foam

DOEpatents

Whinnery, LeRoy Louis; Nichols, Monte Carl; Wheeler, David Roger; Loy, Douglas Anson

1997-01-01

A method of preparing near net shape, monolithic, porous SiC foams is disclosed. Organosilicon precursors are used to produce polymeric gels by thermally induced phase separation, wherein, a sufficiently concentrated solution of an organosilicon polymer is cooled below its solidification temperature to form a gel. Following solvent removal from the gel, the polymer foam is pretreated in an oxygen plasma in order to raise its glass transition temperature. The pretreated foam is then pyrolized in an inert atmosphere to form a SiC foam.

Process for preparing silicon carbide foam

DOEpatents

Whinnery, L.L.; Nichols, M.C.; Wheeler, D.R.; Loy, D.A.

1997-09-16

A method of preparing near net shape, monolithic, porous SiC foams is disclosed. Organosilicon precursors are used to produce polymeric gels by thermally induced phase separation, wherein, a sufficiently concentrated solution of an organosilicon polymer is cooled below its solidification temperature to form a gel. Following solvent removal from the gel, the polymer foam is pretreated in an oxygen plasma in order to raise its glass transition temperature. The pretreated foam is then pyrolyzed in an inert atmosphere to form a SiC foam. 9 figs.

L-cysteine-derived ambidextrous gelators of aromatic solvents and ethanol/water mixtures.

PubMed

Pal, Amrita; Dey, Joykrishna

2013-02-19

A series of L-cysteine-derived double hydrocarbon chain amphiphilic gelators L-(3-alkyl-carbamoylsulfanyl)-2-(3-alkylurido)propionic acid with different hydrocarbon chain lengths (C6-C16) was designed and synthesized. These gelators efficiently gelate only aromatic solvents. The gelation ability increased with the increase of chain length up to C14, but then it dropped with further increase of chain length. The C12 and C14 derivatives also gelled ethanol/water mixtures. The gels were characterized by a number of methods, including FT-IR, NMR, and XRD spectroscopy, electron microscopy, and rheology. The amphiphiles were observed to form either flat lamellar or ribbonlike aggregates in aromatic solvents as well as in ethanol/water mixtures. The gelation in all the solvents employed was observed to be thermoreversible. The gel-to-sol transition temperature as well as mechanical strength of the organogels were observed to increase with the hydrocarbon chain length. Both types of gels of C8-C16 amphiphiles have gel-to-sol transition temperatures above the physiological temperature (310 K). FT-IR and variable temperature (1)H NMR measurements suggested that van der Waals interactions have major contribution in the gelation process. The gel-to-sol transition temperature and mechanical strength of the organogels in ethanol/water mixtures was observed to be higher than those of benzene organogel.

Determination of total arsenic using a novel Zn-ferrite binding gel for DGT techniques: Application to the redox speciation of arsenic in river sediments.

PubMed

Gorny, Josselin; Lesven, Ludovic; Billon, Gabriel; Dumoulin, David; Noiriel, Catherine; Pirovano, Caroline; Madé, Benoît

2015-11-01

A new laboratory-made Zn-ferrite (ZnFe2O4) binding gel is fully tested using Diffusive Gradient in Thin films (DGT) probes to measure total As [including inorganic As(III) and As(V), as well as MonoMethyl Arsenic Acid (MMAA(V)) and DiMethyl Arsenic Acid (DMAA(V))] in river waters and sediment pore waters. The synthesis of the binding gel is easy, cheap and its insertion into the acrylamide gel is not problematic. An important series of triplicate tests have been carried out to validate the use of the Zn-ferrite binding gel in routine for several environmental matrixes studies, in order to test: (i) the effect of pH on the accumulation efficiency of inorganic As species; (ii) the reproducibility of the results; (iii) the accumulation efficiency of As species; (iv) the effects of the ionic strength and possible competitive anions; and (v) the uptake and the elution efficiency of As species after accumulation in the binding gel. All experimental conditions have been reproduced using two other existing binding gels for comparison: ferrihydrite and Metsorb® HMRP 50. We clearly demonstrate that the Zn-ferrite binding gel is at least as good as the two other binding gels, especially for pH values higher than 8. In addition, by taking into consideration the diffusion rates of As(III) and As(V) in the gel, combining the 3-mercaptopropyl [accumulating only As(III)] with the Zn-ferrite binding gels allows for performing speciation studies. An environmental study along the Marque River finally illustrates the ability of the new binding gel to be used for field studies. Copyright © 2015. Published by Elsevier B.V.

Analysis of the response of PVA-GTA Fricke-gel dosimeters with clinical magnetic resonance imaging

NASA Astrophysics Data System (ADS)

Collura, Giorgio; Gallo, Salvatore; Tranchina, Luigi; Abbate, Boris Federico; Bartolotta, Antonio; d'Errico, Francesco; Marrale, Maurizio

2018-01-01

Fricke gel dosimeters produced with a matrix of Poly-vinyl alcohol (PVA) cross-linked with glutaraldehyde (GTA) were analyzed with magnetic resonance imaging (MRI). Previous studies based on spectrophotometry showed valuable dosimetric features of these gels in terms of X-ray sensitivity and diffusion of the ferric ions produced after irradiation. In this study, MRI was performed on the gels at 1.5 T with a clinical scanner in order to optimize the acquisition parameters and obtain high contrast between irradiated and non-irradiated samples. The PVA gels were found to offer good linearity in the range of 0-10 Gy and a stable signal for several hours after irradiation. The sensitivity was about 40% higher compared to gels produced with agarose as gelling agent. The effect of xylenol orange (XO) on the MRI signal was also investigated: gel dosimeters made without XO show higher sensitivity to x-rays than those made with XO. The dosimetric accuracy of the 3D gels was investigated by comparing their MRI response to percentage depth dose and transversal dose profile measurements made with an ionization chamber in a water phantom. The comparison of PVA-GTA gels with and without XO showed that the chelating agent reduces the MRI sensitivity of the gels. Depth-dose and transversal dose profiles acquired by PVA-GTA gels without XO are more accurate and consistent with the ionization chamber data. However, diffusion effects hinder accurate measurements in the steep dose gradient regions and they should be further reduced by modifying the gel matrix and/or by minimizing the delay between irradiation and imaging.

[Establishment and evaluation of an in vitro method for neutrophil extracellular trap generation and degradation].

PubMed

Li, Jinlong; Zhang, Yidan; Zhou, Xin; Ji, Wenjie; Zhao, Jihong; Wei, Luqing; Li, Yuming

2014-09-01

To evaluate a novel method for in vitro generation and degradation of neutrophil extracellular traps (NETs), which are a newly recognized structure that is involved in the pathogenesis of autoimmune diseases and thrombosis. Neutrophils from peripheral blood of healthy donors were obtained by Ficoll-Histopaque gradient separation. NET release was initiated by phorbol myristate acetate (PMA) and validated by immunofluorescence staining and agarose gel electrophoresis. NETs degraded by DNase I and healthy human plasma were quantified by fluorescence spectrometry after staining with PicoGreen. HE staining showed that the purity of neutrophils was up to 95% after Ficoll-Histopaque gradient separation. NET immunofluorescent staining revealed that the network structure was mainly composed of DNA and histones, with molecular length more than 10 kb as demonstrated by agarose gel electrophoresis. Moreover, both DNase and healthy human plasma could induce the degradation of NETs, in varying degrees. This work established an efficient method for in vitro generation and degradation of human NETs.

Deep coverage of the beer proteome.

PubMed

Grochalová, Martina; Konečná, Hana; Stejskal, Karel; Potěšil, David; Fridrichová, Danuše; Srbová, Eva; Ornerová, Kateřina; Zdráhal, Zbyněk

2017-06-06

We adopted an approach based on peptide immobilized pH gradient-isoelectric focusing (IPG-IEF) separation, coupled with LC-MS/MS, in order to maximize coverage of the beer proteome. A lager beer brewed using traditional Czech technology was degassed, desalted and digested. Tryptic peptides were separated by isoelectric focusing on an immobilized pH gradient strip and, after separation, the gel strip was divided into seven equally sized parts. Peptides extracted from gel fractions were analyzed by LC-MS/MS. This approach resulted in a three-fold increase in the number of proteins identified (over 1700) when compared to analysis of unfractionated beer processed by a filter-aided sample preparation (FASP). Over 1900 protein groups (PGs) in total were identified by both approaches. The study significantly extends knowledge about the beer proteome and demonstrates its complexity. Detailed knowledge of the protein content, especially gluten proteins, will enhance the evaluation of potential health risks related to beer consumption (coeliac disease) and will contribute to improving beer quality. Copyright © 2017 Elsevier B.V. All rights reserved.

Microchip capillary gel electrophoresis using programmed field strength gradients for the ultra-fast analysis of genetically modified organisms in soybeans.

PubMed

Kim, Yun-Jeong; Chae, Joon-Seok; Chang, Jun Keun; Kang, Seong Ho

2005-08-12

We have developed a novel method for the ultra-fast analysis of genetically modified organisms (GMOs) in soybeans by microchip capillary gel electrophoresis (MCGE) using programmed field strength gradients (PFSG) in a conventional glass double-T microchip. Under the programmed electric field strength and 0.3% poly(ethylene oxide) sieving matrix, the GMO in soybeans was analyzed within only 11 s of the microchip. The MCGE-PFSG method was a program that changes the electric field strength during GMO analysis, and was also applied to the ultra-fast analysis of PCR products. Compared to MCGE using a conventional and constantly applied electric field, the MCGE-PFSG analysis generated faster results without the loss of resolving power and reproducibility for specific DNA fragments (100- and 250-bp DNA) of GM-soybeans. The MCGE-PFSG technique may prove to be a new tool in the GMO analysis due to its speed, simplicity, and high efficiency.

Analysis of DGGE profiles to explore the relationship between prokaryotic community composition and biogeochemical processes in deep subseafloor sediments from the Peru Margin.

PubMed

Fry, John C; Webster, Gordon; Cragg, Barry A; Weightman, Andrew J; Parkes, R John

2006-10-01

The aim of this work was to relate depth profiles of prokaryotic community composition with geochemical processes in the deep subseafloor biosphere at two shallow-water sites on the Peru Margin in the Pacific Ocean (ODP Leg 201, sites 1228 and 1229). Principal component analysis of denaturing gradient gel electrophoresis banding patterns of deep-sediment Bacteria, Archaea, Euryarchaeota and the novel candidate division JS1, followed by multiple regression, showed strong relationships with prokaryotic activity and geochemistry (R(2)=55-100%). Further correlation analysis, at one site, between the principal components from the community composition profiles for Bacteria and 12 other variables quantitatively confirmed their relationship with activity and geochemistry, which had previously only been implied. Comparison with previously published cell counts enumerated by fluorescent in situ hybridization with rRNA-targeted probes confirmed that these denaturing gradient gel electrophoresis profiles described an active prokaryotic community.

Formulation and method for preparing gels comprising hydrous aluminum oxide

DOEpatents

Collins, Jack L.

2014-06-17

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

Formulation and method for preparing gels comprising hydrous cerium oxide

DOEpatents

Collins, Jack L; Chi, Anthony

2013-05-07

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

Effects of temperature on anaerobic decomposition of high-molecular weight organic matter under sulfate-reducing conditions

NASA Astrophysics Data System (ADS)

Matsui, Takato; Kojima, Hisaya; Fukui, Manabu

2013-03-01

Most sedimentary mineralization occurs along coasts under anaerobic conditions. In the absence of oxygen, high-molecular weight organic matter in marine sediments is gradually decomposed by hydrolysis, fermentation and sulfate reduction. Because of the different responses of the respective steps to temperature, degradation may be specifically slowed or stopped in certain step. To evaluate the effect of temperature on cellobiose degradation, culture experiments were performed at six different temperatures (3 °C, 8 °C, 13 °C, 18 °C, 23 °C, and 28 °C) under sulfate-reducing conditions. This study measured the concentrations of sulfide, dissolved organic carbon (DOC), and organic acids during that degradation. Degradation patterns were divided into three temperature groups: 3 °C, 8/13 °C, and 18/23/28 °C. The decrease in DOC proceeded in two steps, except at 3 °C. The length of the stagnant phase separating these two steps differed greatly between temperatures of 8/13 °C and 18/23/28 °C. In the first step, organic carbon was consumed by hydrolysis, fermentation and sulfate reduction. In the second step, acetate accumulated during the first step was oxidized by sulfate reduction. Bacterial communities in the cultures were analyzed by denaturing gradient gel electrophoresis (DGGE); the major differences among the three temperature groups were attributed to shifts in acetate-using sulfate reducers of the genus Desulfobacter. This suggests that temperature characteristics of dominant acetate oxidizers are important factors in determining the response of carbon flow in coastal marine sediments in relation to the changes in temperature.

Thermal Gradient During Vacuum-Deposition Dramatically Enhances Charge Transport in Organic Semiconductors: Toward High-Performance N-Type Organic Field-Effect Transistors.

PubMed

Kim, Joo-Hyun; Han, Singu; Jeong, Heejeong; Jang, Hayeong; Baek, Seolhee; Hu, Junbeom; Lee, Myungkyun; Choi, Byungwoo; Lee, Hwa Sung

2017-03-22

A thermal gradient distribution was applied to a substrate during the growth of a vacuum-deposited n-type organic semiconductor (OSC) film prepared from N,N'-bis(2-ethylhexyl)-1,7-dicyanoperylene-3,4:9,10-bis(dicarboxyimide) (PDI-CN2), and the electrical performances of the films deployed in organic field-effect transistors (OFETs) were characterized. The temperature gradient at the surface was controlled by tilting the substrate, which varied the temperature one-dimensionally between the heated bottom substrate and the cooled upper substrate. The vacuum-deposited OSC molecules diffused and rearranged on the surface according to the substrate temperature gradient, producing directional crystalline and grain structures in the PDI-CN2 film. The morphological and crystalline structures of the PDI-CN2 thin films grown under a vertical temperature gradient were dramatically enhanced, comparing with the structures obtained from either uniformly heated films or films prepared under a horizontally applied temperature gradient. The field effect mobilities of the PDI-CN2-FETs prepared using the vertically applied temperature gradient were as high as 0.59 cm 2 V -1 s -1 , more than a factor of 2 higher than the mobility of 0.25 cm 2 V -1 s -1 submitted to conventional thermal annealing and the mobility of 0.29 cm 2 V -1 s -1 from the horizontally applied temperature gradient.

Physicochemical characterization of diclofenac sodium-loaded poloxamer gel as a rectal delivery system with fast absorption.

PubMed

Yong, Chul Soon; Sah, Hongkee; Jahng, Yurngdong; Chang, Hyeun Wook; Son, Jong-Keun; Lee, Seung Ho; Jeong, Tae Cheon; Rhee, Jong-Dal; Baek, Suk Hwan; Kim, Chong-Kook; Choi, Han-Gon

2003-05-01

Rectal poloxamer gel systems composed of poloxamers and bioadhesive polymers were easy to administer to the anus and were mucoadhesive to the rectal tissues without leakage after the dose. However, a poloxamer gel containing diclofenac sodium could not be developed using bioadhesive polymers, since the drug was precipitated in this preparation. To develop a poloxamer gel using sodium chloride instead of bioadhesive polymers, the physicochemical properties such as gelation temperature, gel strength, and bioadhesive force of various formulations composed of diclofenac sodium, poloxamers, and sodium chloride were investigated. Furthermore, the pharmacokinetic study of diclofenac sodium delivered by the poloxamer gel was performed. Diclofenac sodium significantly increased the gelation temperature and weakened the gel strength and bioadhesive force, while sodium chloride did the opposite. The poloxamer gels with less than 1.0% sodium chloride, in which the drug was not precipitated, were inserted into the rectum without difficulty and leakage, and were retained in the rectum of rats for at least 6 hr. Furthermore, poloxamer gel gave significantly higher initial plasma concentrations and faster Tmax of diclofenac sodium than did solid suppository, indicating that drug from poloxamer gel could be absorbed faster than that from the solid one in rats. Our results suggested that a rectal poloxamer gel system with sodium chloride and poloxamers was a more physically stable, convenient, and effective rectal dosage form for diclofenac sodium.

Real-time Fluorescence Polarization Microscopy of the Moving Boundary in Cross-Gradient SDS-PAGE

NASA Astrophysics Data System (ADS)

Hwang, Jeeseong; Giulian, Gary

2003-03-01

Real-time Fluorescence Polarization Microscopy of the Moving Boundary in Cross-Gradient SDS-PAGE Jeeseong Hwang, Jeffrey R. Krogmeier, Angela M. Bardo, Scott N. Goldie, Lori S. Goldner; Optical Technology Division, National Institute of Standards and Technology, Gaithersburg, MD 20899 Gary G. Giulian, Carl R. Merril; National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892 Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE) is a popular method to separate proteins by their apparent molecular weight. However, it is a limited technique due, in part, to its low spatial resolution. In order to improve the resolution and to enhance the detection sensitivity of proteins separated by SDS-PAGE we are studying the detergent properties at the moving boundary of precast Tris-Tricine-Acetate cross-gradient gels using fluorescent cationic and pH indicating dyes. We have developed real-time full-field fluorescence polarization microscopy to monitor the dynamic fluorescence anisotropy from the cationic tetramethylindocarbocyanine dyes localized in the "extended stack", a concentrated detergent zone. We will present quantitative results of the fluorescence anisotropy. Our system is capable of analyzing local structures of the detergent molecules in the moving boundary of SDS-PAGE and the microenvironment(s) near the boundary. We will discuss the significance of these results and their potential role in enhanced protein separation.

Eye patches: Protein assembly of index-gradient squid lenses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cai, J.; Townsend, J. P.; Dodson, T. C.

A parabolic relationship between lens radius and refractive index allows spherical lenses to avoid spherical aberration. We show that in squid, patchy colloidal physics resulted from an evolutionary radiation of globular S-crystallin proteins. Small-angle x-ray scattering experiments on lens tissue show colloidal gels of S-crystallins at all radial positions. Sparse lens materials form via low-valence linkages between disordered loops protruding from the protein surface. The loops are polydisperse and bind via a set of hydrogen bonds between disordered side chains. Peripheral lens regions with low particle valence form stable, volume-spanning gels at low density, whereas central regions with higher averagemore » valence gel at higher densities. The proteins demonstrate an evolved set of linkers for self-assembly of nanoparticles into volumetric materials.« less

Continuous gradient temperature Raman spectroscopy of oleic and linoleic acids from -100 to 50°C

USDA-ARS?s Scientific Manuscript database

Gradient Temperature Raman spectroscopy (GTRS) applies the temperature gradients utilized in differential scanning calorimetry (DSC) to Raman spectroscopy, providing a straightforward technique to identify molecular rearrangements that occur near and at phase transitions. Herein we apply GTRS and DS...

Lateral Temperature-Gradient Method for High-Throughput Characterization of Material Processing by Millisecond Laser Annealing.

PubMed

Bell, Robert T; Jacobs, Alan G; Sorg, Victoria C; Jung, Byungki; Hill, Megan O; Treml, Benjamin E; Thompson, Michael O

2016-09-12

A high-throughput method for characterizing the temperature dependence of material properties following microsecond to millisecond thermal annealing, exploiting the temperature gradients created by a lateral gradient laser spike anneal (lgLSA), is presented. Laser scans generate spatial thermal gradients of up to 5 °C/μm with peak temperatures ranging from ambient to in excess of 1400 °C, limited only by laser power and materials thermal limits. Discrete spatial property measurements across the temperature gradient are then equivalent to independent measurements after varying temperature anneals. Accurate temperature calibrations, essential to quantitative analysis, are critical and methods for both peak temperature and spatial/temporal temperature profile characterization are presented. These include absolute temperature calibrations based on melting and thermal decomposition, and time-resolved profiles measured using platinum thermistors. A variety of spatially resolved measurement probes, ranging from point-like continuous profiling to large area sampling, are discussed. Examples from annealing of III-V semiconductors, CdSe quantum dots, low-κ dielectrics, and block copolymers are included to demonstrate the flexibility, high throughput, and precision of this technique.

Potential efficacy of a delta 5-aminolevulinic acid thermosetting gel formulation for use in photodynamic therapy of lesions of the gastrointestinal tract.

PubMed

Bourre, Ludovic; Thibaut, Sonia; Briffaud, Amelie; Lajat, Youenn; Patrice, Thierry

2002-02-01

Photodynamic therapy (PDT) using 5-aminolevulinic acid (ALA)-induced protoporphyrin IX may play a role in the treatment of dysplastic Barrett's oesophagus. An ALA thermosetting gel Pluronic F-127) was developed and evaluated in an in vivo mouse model for potential use in PDT of Barrett's mucosa. In vitro studies of the influence of Pluronic F-127 percentage on thermosetting gel temperature, followed by the influence of ALA concentration on thermosetting temperature and ALA-gel stability as a function of time or temperature were studied. In vivo relationships between ALA doses and fluorescence were studied to determine the optimal concentration. Fluorescence measurement in vivo showed that ALA concentration and time had a nonlinear influence on protoporphyrin IX synthesis. For ALA-gel applications longer than 30 min a plateau fluorescence was reached, the maximum fluorescence being obtained after 4 h whatever the time of contact. The maximum intensity (2824 counts s(-1)) was found with 40 mg mL(-1) ALA-gel, and fluorescence intensities differed with time, reaching a maximum after 3-4 h. ALA-Pluronic F-127 is a suitable formulation for treatment of Barrett's oesophagus, allowing easy application in liquid form at 4 degrees C and good adhesion in the oesophagus in gel form, with efficient diffusion of ALA into treated mucosa. Copyright 2002 Elsevier Science Ltd.

Cold hands, warm feet: sleep deprivation disrupts thermoregulation and its association with vigilance.

PubMed

Romeijn, Nico; Verweij, Ilse M; Koeleman, Anne; Mooij, Anne; Steimke, Rosa; Virkkala, Jussi; van der Werf, Ysbrand; Van Someren, Eus J W

2012-12-01

Vigilance is affected by induced and spontaneous skin temperature fluctuations. Whereas sleep deprivation strongly affects vigilance, no previous study examined in detail its effect on human skin temperature fluctuations and their association with vigilance. In a repeated-measures constant routine design, skin temperatures were assessed continuously from 14 locations while performance was assessed using a reaction time task, including eyes-open video monitoring, performed five times a day for 2 days, after a normal sleep or sleep deprivation night. Participants were seated in a dimly lit, temperature-controlled laboratory. Eight healthy young adults (five males, age 22.0 ± 1.8 yr (mean ± standard deviation)). One night of sleep deprivation. Mixed-effect regression models were used to evaluate the effect of sleep deprivation on skin temperature gradients of the upper (ear-mastoid), middle (hand-arm), and lower (foot-leg) body, and on the association between fluctuations in performance and in temperature gradients. Sleep deprivation induced a marked dissociation of thermoregulatory skin temperature gradients, indicative of attenuated heat loss from the hands co-occurring with enhanced heat loss from the feet. Sleep deprivation moreover attenuated the association between fluctuations in performance and temperature gradients; the association was best preserved for the upper body gradient. Sleep deprivation disrupts coordination of fluctuations in thermoregulatory skin temperature gradients. The dissociation of middle and lower body temperature gradients may therefore be evaluated as a marker for sleep debt, and the upper body gradient as a possible aid in vigilance assessment when sleep debt is unknown. Importantly, our findings suggest that sleep deprivation affects the coordination between skin blood flow fluctuations and the baroreceptor-mediated cardiovascular regulation that prevents venous pooling of blood in the lower limbs when there is the orthostatic challenge of an upright posture.

Harnessing Thermoresponsive Aptamers and Gels To Trap and Release Nanoparticles

NASA Astrophysics Data System (ADS)

Liu, Ya; Kuksenok, Olga; He, Ximin; Aizenberg, Michael; Aizenberg, Joanna; Balazs, Anna

We use computational modeling to design a device that can controllably trap and release particles in solution in response to variations in temperature. The system exploits the thermoresponsive properties of end-grafted fibers and the underlying gel substrate. The fibers mimic the temperature-dependent behavior of biological aptamers, which form a hairpin structure at low temperatures (T) and unfold at higher T, consequently losing their binding affinity. The gel substrate exhibits a lower critical solution temperature and thus, expands at low tempertures and contracts at higher T. By developing a new dissipative particle dynamics simulation, we examine the behavior of this hybrid system in a flowing fluid that contains buoyant nanoparticles. Our findings provide guidelines for creating fluidic devices that are effective at purifying contaminated solutions or trapping cells for biological assays.

RESPONSE OF HATCHLING AND YEARLING TURTLES TO THERMAL GRADIENTS: COMPARISON OF CHELYDRA SERPENTINA AND TRACHEMYS SCRIPTA

EPA Science Inventory

In laboratory test, young Chelydra serpentina and Trachemys scripta altered their distribution in the presence of a temperature gradient. Selection of temperatures in the gradient for hatchlings and yearlings showed that body temperature (Tbs) of C. serpentina were lower tha...

Thermotropism by primary roots of maize

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fortin, M.-C.; Poff, K.L.

1990-05-01

Sensing in the roots of higher plants has long been recognized to be restricted mainly to gravitropism and thigmotropism. However, root responses to temperature gradients have not been extensively studied. We have designed experiments under controlled conditions to test if and how root direction of maize can be altered by thermal gradients perpendicular to the gravity vector. Primary roots of maize grown on agar plates exhibit positive thermotropism (curvature toward the warmer temperature) when exposed to gradients of 0.5 to 4.2{degree}C cm{sup {minus}1}. The extent of thermotropism depends on the temperature gradient and the temperature at which the root ismore » placed within the gradient. The curvature cannot be accounted for by differential growth as a direct effect of temperature on each side of the root.« less

Skin temperature and core-peripheral temperature gradient as markers of hemodynamic status in critically ill patients: a review.

PubMed

Schey, Bernadette M; Williams, David Y; Bucknall, Tracey

2010-01-01

To examine the evidential basis underpinning the monitoring of skin temperature and core-peripheral temperature gradient as elements of hemodynamic assessment in critically ill and adult cardiac surgical patients. Twenty-six studies examining the efficacy of skin temperature or temperature gradient as markers of hemodynamic status were selected as part of an integrative review. Evidence pertaining to the efficacy of these parameters as markers of cardiac function is equivocal and has not been well appraised in the adult cardiac surgical population. Skin temperature and systemic vascular resistance are also affected by factors other than cardiac output. Skin temperature and core-peripheral temperature gradient should not be considered in isolation from other hemodynamic parameters when assessing cardiac status until they are validated by further large-scale prospective studies. 2010. Published by Mosby, Inc.

Subsurface temperatures and geothermal gradients on the north slope of Alaska

USGS Publications Warehouse

Collett, T.S.; Bird, K.J.; Magoon, L.B.

1993-01-01

On the North Slope of Alaska, geothermal gradient data are available from high-resolution, equilibrated well-bore surveys and from estimates based on well-log identification of the base of ice-bearing permafrost. A total of 46 North Slope wells, considered to be in or near thermal equilibrium, have been surveyed with high-resolution temperatures devices and geothermal gradients can be interpreted directly from these recorded temperature profiles. To augment the limited North Slope temperature data base, a new method of evaluating local geothermal gradients has been developed. In this method, a series of well-log picks for the base of the ice-bearing permafrost from 102 wells have been used, along with regional temperature constants derived from the high-resolution stabilized well-bore temperature surveys, to project geothermal gradients. Geothermal gradients calculated from the high-resolution temperature surveys generally agree with those projected from known ice-bearing permafrost depths over most of the North Slope. Values in the ice-bearing permafrost range from ??? 1.5??C 100 m in the Prudhoe Bay area to ??? 4.5??C 100 m in the east-central portion of the National Petroleum Reserve in Alaska. Geothermal gradients below the ice-bearing permafrost sequence range from ??? 1.6??C 100 m to ??? 5.2??C 100 m. ?? 1993.

Investigation of phase evolution of CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) by in situ synchrotron high-temperature powder diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ouyang, Xin; Huang, Saifang; School of Materials Science and Technology, China University of Geosciences

2014-03-15

In situ synchrotron X-ray powder diffraction was used to study the high-temperature phase evolution of CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) precursors prepared via solid-state and sol–gel methods. After the precursors are heated to 1225 °C, the CCTO phase is the main phase observed in the calcined powder, with the presence of some minor impurities. Comparing the two precursors, we found that the onset temperature for the CCTO phase formation is 800 °C in the sol–gel precursor, lower than that in the solid-state precursor (875 °C). Intermediate phases were only observed in the sol–gel precursor. Both precursors are able to bemore » calcined to sub-micrometric sized powders. Based on the synchrotron data along with differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA), the phase formation sequence and mechanism during calcination are proposed in this study. -- Graphical abstract: The in situ synchrotron HT-XRD patterns of CCTO sol–gel and solid-state precursor. Highlights: • Phase formation sequence/mechanism in two CCTO precursors has been established. • Formation temperature of CCTO via sol–gel method is lower than solid-state method. • Intermediate phases are only observed in the sol–gel precursor. • Both precursors are able to be calcined into sub-micrometric sized powders.« less

Influence of temperature gradients on charge transport in asymmetric nanochannels.

PubMed

Benneker, Anne M; Wendt, Hans David; Lammertink, Rob G H; Wood, Jeffery A

2017-10-25

Charge selective asymmetric nanochannels are used for a variety of applications, such as nanofluidic sensing devices and energy conversion applications. In this paper, we numerically investigate the influence of an applied temperature difference over tapered nanochannels on the resulting charge transport and flow behavior. Using a temperature-dependent formulation of the coupled Poisson-Nernst-Planck and Navier-Stokes equations, various nanochannel geometries are investigated. Temperature has a large influence on the total ion transport, as the diffusivity of ions and viscosity of the solution are strongly affected by temperature. We find that the selectivity of the nanochannels is enhanced with increasing asymmetry ratios, while the total current is reduced at higher asymmetry cases. Most interestingly, we find that applying a temperature gradient along the electric field and along the asymmetry direction of the nanochannel enhances the selectivity of the tapered channels even further, while a temperature gradient countering the electric field reduces the selectivity of the nanochannel. Current rectification is enhanced in asymmetric nanochannels if a temperature gradient is applied, independent of the direction of the temperature difference. However, the degree of rectification is dependent on the direction of the temperature gradient with respect to the channel geometry and the electric field direction. The enhanced selectivity of nanochannels due to applied temperature gradients could result in more efficient operation in energy harvesting or desalination applications, motivating experimental investigations.

Synthesis of Hollow Sphere and 1D Structural Materials by Sol-Gel Process.

PubMed

Li, Fa-Liang; Zhang, Hai-Jun

2017-08-25

The sol-gel method is a simple and facile wet chemical process for fabricating advanced materials with high homogeneity, high purity, and excellent chemical reactivity at a relatively low temperature. By adjusting the processing parameters, the sol-gel technique can be used to prepare hollow sphere and 1D structural materials that exhibit a wide application in the fields of catalyst, drug or gene carriers, photoactive, sensors and Li-ion batteries. This feature article reviewed the development of the preparation of hollow sphere and 1D structural materials using the sol-gel method. The effects of calcination temperature, soaking time, pH value, surfactant, etc., on the preparation of hollow sphere and 1D structural materials were summarized, and their formation mechanisms were generalized. Finally, possible future research directions of the sol-gel technique were outlined.

Synthesis of Hollow Sphere and 1D Structural Materials by Sol-Gel Process

PubMed Central

Li, Fa-Liang; Zhang, Hai-Jun

2017-01-01

The sol-gel method is a simple and facile wet chemical process for fabricating advanced materials with high homogeneity, high purity, and excellent chemical reactivity at a relatively low temperature. By adjusting the processing parameters, the sol-gel technique can be used to prepare hollow sphere and 1D structural materials that exhibit a wide application in the fields of catalyst, drug or gene carriers, photoactive, sensors and Li-ion batteries. This feature article reviewed the development of the preparation of hollow sphere and 1D structural materials using the sol-gel method. The effects of calcination temperature, soaking time, pH value, surfactant, etc., on the preparation of hollow sphere and 1D structural materials were summarized, and their formation mechanisms were generalized. Finally, possible future research directions of the sol-gel technique were outlined. PMID:28841188

Correlations between quasi-coherent fluctuations and the pedestal evolution during the inter-edge localized modes phase on DIII-D

DOE PAGES

Diallo, A.; Groebner, R. J.; Rhodes, T. L.; ...

2015-05-15

Direct measurements of the pedestal recovery during an edge-localized mode cycle provide evidence that quasi-coherent fluctuations (QCFs) play a role in the inter-ELM pedestal dynamics. When using fast Thomson scattering measurements, we found that the pedestal density and temperature evolutions are probed on sub-millisecond time scales to show a fast recovery of the density gradient compared to the temperature gradient. The temperature gradient appears to provide a drive for the onset of quasi-coherent fluctuations (as measured with the magnetic probe and the density diagnostics) localized in the pedestal. The amplitude evolution of these QCFs tracks the temperature gradient evolution includingmore » its saturation. Such correlation suggests that these QCFs play a key role in limiting the pedestal temperature gradient. Moreover, the saturation of the QCFs coincides with the pressure gradient reaching the kinetic-ballooning mode (KBM) critical gradient as predicted by EPED1. Furthermore, linear microinstability analysis using GS2 indicates that the steep gradient is near the KBM threshold. Finally, the modeling and the observations together suggest that QCFs are consistent with dominant KBMs, although microtearing cannot be excluded as subdominant.« less

Crystal growth and annealing method and apparatus

DOEpatents

Gianoulakis, Steven E.; Sparrow, Robert

2001-01-01

A method and apparatus for producing crystals that minimizes birefringence even at large crystal sizes, and is suitable for production of CaF.sub.2 crystals. The method of the present invention comprises annealing a crystal by maintaining a minimal temperature gradient in the crystal while slowly reducing the bulk temperature of the crystal. An apparatus according to the present invention includes a thermal control system added to a crystal growth and annealing apparatus, wherein the thermal control system allows a temperature gradient during crystal growth but minimizes the temperature gradient during crystal annealing. An embodiment of the present invention comprises a secondary heater incorporated into a conventional crystal growth and annealing apparatus. The secondary heater supplies heat to minimize the temperature gradients in the crystal during the annealing process. The secondary heater can mount near the bottom of the crucible to effectively maintain appropriate temperature gradients.

Relating Paleoclimate Data and Past Temperature Gradients: Some Suggestive Rules

NASA Technical Reports Server (NTRS)

Rind, David

1999-01-01

Understanding tropical sensitivity is perhaps the major concern confronting researchers, for both past and future climate change issues. Tropical data has been beset by contradictions, and many techniques applicable to the extratropics are either unavailable or fraught with uncertainty when applied at low latitudes. Paleoclimate data, if interpreted within the context of the latitudinal temperature gradient data they imply, can be used to estimate what happened to tropical temperatures in the past, and provide a first guess for what might happen in the future. The approach is made possible by the modeling result that atmospheric dynamical changes, and the climate impacts they produce, respond primarily to temperature gradient changes. Here we review some "rules" obtained from GCM (General Circulation Model) experiments with different sea surface temperature gradients and different forcing, that can be used to relate paleoclimate reconstructions to the likely temperature gradient changes they suggest.

Association of Stremptomyces community composition determined by PCR-denaturing gradient gel electrophoresis with indoor mold status.

EPA Science Inventory

Abstract Both Streptomyces species and mold species have previously been isolated from moisture-damaged building materials; however, an association between these two groups of microorganisms in indoor environments is not clear. In this study, we used a cultureindependent met...

Interfacial free energy and stiffness of aluminum during rapid solidification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, Nicholas T.; Martinez, Enrique; Qu, Jianmin

Using molecular dynamics simulations and the capillary fluctuation method, we have calculated the anisotropic crystal-melt interfacial free energy and stiffness of aluminum in a rapid solidification system where a temperature gradient is applied to enforce thermal non-equilibrium. To calculate these material properties, the standard capillary fluctuation method typically used for systems in equilibrium has been modified to incorporate a second-order Taylor expansion of the interfacial free energy term. The result is a robust method for calculating interfacial energy, stiffness and anisotropy as a function of temperature gradient using the fluctuations in the defined interface height. This work includes the calculationmore » of interface characteristics for temperature gradients ranging from 11 to 34 K/nm. The captured results are compared to a thermal equilibrium case using the same model and simulation technique with a zero gradient definition. We define the temperature gradient as the change in temperature over height perpendicular to the crystal-melt interface. The gradients are applied in MD simulations using defined thermostat regions on a stable solid-liquid interface initially in thermal equilibrium. The results of this work show that the interfacial stiffness and free energy for aluminum are dependent on the magnitude of the temperature gradient, however the anisotropic parameters remain independent of the non-equilibrium conditions applied in this analysis. As a result, the relationships of the interfacial free energy/stiffness are determined to be linearly related to the thermal gradient, and can be interpolated to find material characteristics at additional temperature gradients.« less

Interfacial free energy and stiffness of aluminum during rapid solidification

DOE PAGES

Brown, Nicholas T.; Martinez, Enrique; Qu, Jianmin

2017-05-01

Using molecular dynamics simulations and the capillary fluctuation method, we have calculated the anisotropic crystal-melt interfacial free energy and stiffness of aluminum in a rapid solidification system where a temperature gradient is applied to enforce thermal non-equilibrium. To calculate these material properties, the standard capillary fluctuation method typically used for systems in equilibrium has been modified to incorporate a second-order Taylor expansion of the interfacial free energy term. The result is a robust method for calculating interfacial energy, stiffness and anisotropy as a function of temperature gradient using the fluctuations in the defined interface height. This work includes the calculationmore » of interface characteristics for temperature gradients ranging from 11 to 34 K/nm. The captured results are compared to a thermal equilibrium case using the same model and simulation technique with a zero gradient definition. We define the temperature gradient as the change in temperature over height perpendicular to the crystal-melt interface. The gradients are applied in MD simulations using defined thermostat regions on a stable solid-liquid interface initially in thermal equilibrium. The results of this work show that the interfacial stiffness and free energy for aluminum are dependent on the magnitude of the temperature gradient, however the anisotropic parameters remain independent of the non-equilibrium conditions applied in this analysis. As a result, the relationships of the interfacial free energy/stiffness are determined to be linearly related to the thermal gradient, and can be interpolated to find material characteristics at additional temperature gradients.« less

Formulation and method for preparing gels comprising hydrous hafnium oxide

DOEpatents

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

2013-08-06

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

Preparation and mechanical characterization of a PNIPA hydrogel composite.

PubMed

Liu, Kaifeng; Ovaert, Timothy C; Mason, James J

2008-04-01

A poly (N-isopropylacrylamide) (PNIPA) hydrogel was synthesized by free radical polymerization and reinforced with a polyurethane foam to make a hydrogel composite. The temperature dependence of the elastic modulus of the PNIPA hydrogel and the composite due to volume phase transition was found using a uniaxial compression test, and the swelling property was investigated using an equilibrium swelling ratio experiment. The gel composite preserves the ability to undergo the volume phase transition and its elastic modulus has strong temperature dependence. The temperature dependence of the elastic modulus and swelling ratio of the gel composite were compared to the PNIPA hydrogel. Not surprisingly, the modulus and swelling ratio of the composite were less dramatic than in the gel.

Comparative study of energy-transducing properties of cytoplasmic membranes from mesophilic and thermophilic Bacillus species.

PubMed Central

De Vrij, W; Bulthuis, R A; Konings, W N

1988-01-01

The properties of enzymes involved in energy transduction from a mesophilic (Bacillus subtilis) and a thermophilic (B. stearothermophilus) bacterium were compared. Membrane preparations of the two organisms contained dehydrogenases for NADH, succinate, L-alpha-glycerophosphate, and L-lactate. Maximum NADH and cytochrome c oxidation rates were obtained at the respective growth temperatures of the two bacteria. The enzymes involved in the oxidation reactions in membranes of the thermophilic species were more thermostable than those of the mesophilic species. The apparent microviscosities of the two membrane preparations were studied at different temperatures. At the respective optimal growth temperatures, the apparent microviscosities of the membranes of the two organisms were remarkably similar. The transition from the gel to the liquid-crystalline state occurred at different temperatures in the two species. In the two species, the oxidation of physiological (NADH) and nonphysiological (N,N,N',N'-tetramethyl-p-phenylenediamine or phenazine methosulfate) electron donors led to generation of a proton motive force which varied strongly with temperature. At increasing temperatures, the efficiency of energy transduction declined because of increasing H+ permeability. At the growth temperature, the efficiency of energy transduction was lower in B. stearothermophilus than in the mesophilic species. Extremely high respiratory activities enabled B. stearothermophilus to maintain a high proton motive force at elevated temperatures. The pH dependence of proton motive force generation appeared to be similar in the two membrane preparations. The highest proton motive forces were generated at low external pH, mainly because of a high pH gradient. At increasing external pH, the proton motive force declined. PMID:2834342

Temperature and deflection data from the asymmetric heating of cross-ply composite tubes

NASA Technical Reports Server (NTRS)

Hyer, Michael W.; Cooper, David E.; Tompkins, S. S.; Cohen, David

1987-01-01

Data generated while heating several cross-ply graphite-epoxy tubes on one side, along their lengths, and cooling them on the other side are presented. This heating arrangement produces a circumferential temperature gradient, and the data show that the gradient can be represented by a cosinusoidal temperature distribution. The thermally induced bending deflections caused by the temperature gradient are also presented.

Rheology-A pre-formulation tool for evaluating mechanical and thermal properties of transdermal formulations

NASA Astrophysics Data System (ADS)

Modi, Nisarg

Rheological characterization of pharmaceutical gel is of importance as it provides fundamental information required for the assessment of some of the final properties of a product such as viscosity, elasticity, quality and physical storage stability. The effect of formulation and process variables on product characteristics such as consistency, drug release, and physical stability can also be attained. Moreover, some of the transdermal patch problems such as leaking from reservoir patch or cold flow in matrix patch can also be estimated using rheological characterization. During this research, various tests were employed to characterize the mechanical properties of gel such as oscillation test (Frequency and Amplitude Sweep), flow and viscosity curves and yield point measurements, as well as temperature sweep and temperature ramp test. The present studies evaluate rheological properties of hydroxypropyl cellulose (Klucel HF) gels prepared containing fatty acids with different carbon chain length at different homogenization speed. A controlled stress rheometer was used to study the effect of different number of carbon chain fatty acids, homogenization speed and storage period on the rheological properties and microstructure of transdermal gels. The studies demonstrated that as the carbon chain length increased (C10-C 18) the thixotropic area decreased, which suggested that the stability of gel structure was increased with increase in carbon chain of fatty acids. Cohesive Energy was affected by the homogenization speed and carbon chain of fatty acids. There was decreased in cohesive energy as increase in carbon chain of fatty acids. Temperature sweep data revealed that gels prepared with oleic acid (C18) at 25000 RPM gave the best thermal stability after the longest storage period (60-Days) compare to the capric(C10) acid and Lauirc (C12) acid. There was only 31% decreased in temperature loop area for oleic (C18) acid as compare to 54% and 86% for capric (C10) acid and lauric acid (C12) respectively. During different mixing speeds at initial time period (t=0), oleic acid showed lowest temperature loop area, which was not affected by storage period. Furthermore, by applying power law model to frequency sweep data, mechanical propereties of transdermal gels were evaluated. Transdermal gels are "physical gels" in nature which showed both frequency dependency and also had a cross-over point. Moreover, the value of n is less than 1. Time Temperature superposition principle can apply to the rheological data of Transdermal gels to obtain the thermal properties of formulations. Thermal properties of transdermal gels are very difficult to measure using traditional DSC equipment. By applying TTS principle, frequency sweep data were obtained between 5-50 °C and extrapolated to achieve the glass transition temperature, free volume and thermal expansion co-efficient of the formulations. Last but not least, In-vitro studies using human cadaver skin showed that Capric acid is the best permeability enhancing agent for escitalopram oxalate in current formulations. Furthermore, increase in carbon chain length of fatty acids decreased the permeability enhancing effect of Escitalopram Oxalate through human cadaver skin during In-vitro diffusion studies.

Comparison of thermoregulatory devices used during anesthesia of C57BL/6 mice and correlations between body temperature and physiologic parameters.

PubMed

Caro, Adam C; Hankenson, F Claire; Marx, James O

2013-09-01

General anesthesia affects several body systems, including thermoregulation. Decreased body temperature during anesthesia has potential negative effects, including delayed recovery to consciousness. Thermoregulatory support devices are used to maintain temperature in anesthetized rodents. We analyzed 2 novel thermoregulatory devices, thermogenic gel packs and reflective foils, to compare their effectiveness in maintaining temperatures with that of a standard circulating-warm-water blanket (CWWB) in C57BL/6 mice. Mice were grouped randomly: control (no thermal support), reflective foil, gel pack, gel pack plus reflective foil, CWWB on medium setting, CWWB on high setting, and CWWB on high setting plus reflective foil. Mice were anesthetized with isoflurane for 30 min, and temperature and heart and respiratory rates were monitored. Results indicated that the temperatures of mice with reflective foil only (start temperature, 36.2 ± 0.38 °C; end temperature, 28.8 ± 0.78 °C) did not differ significantly from those of control mice; however, the inclusion of foil heightened thermogenic properties when combined with other devices. Thermogenic gel packs and CWWB on high setting, both with and without reflective foil, caused significant temperature increases (that is, 1.6 °C to 4.4 °C) in mice. CWWB on medium setting (blanket temperature, 37.5 °C) maintained mice at temperatures within 1 °C of the 36.1 °C baseline. Strong correlations existed between temperature, heart and respiratory rates, and recovery time to consciousness. This information provides guidance regarding the use of thermoregulatory devices in anesthetized rodents and demonstrates the effect of maintaining a consistent core temperature on physiologic parameters.

Comparison of Thermoregulatory Devices Used during Anesthesia of C57BL/6 Mice and Correlations between Body Temperature and Physiologic Parameters

PubMed Central

Caro, Adam C; Hankenson, F Claire; Marx, James O

2013-01-01

General anesthesia affects several body systems, including thermoregulation. Decreased body temperature during anesthesia has potential negative effects, including delayed recovery to consciousness. Thermoregulatory support devices are used to maintain temperature in anesthetized rodents. We analyzed 2 novel thermoregulatory devices, thermogenic gel packs and reflective foils, to compare their effectiveness in maintaining temperatures with that of a standard circulating-warm–water blanket (CWWB) in C57BL/6 mice. Mice were grouped randomly: control (no thermal support), reflective foil, gel pack, gel pack plus reflective foil, CWWB on medium setting, CWWB on high setting, and CWWB on high setting plus reflective foil. Mice were anesthetized with isoflurane for 30 min, and temperature and heart and respiratory rates were monitored. Results indicated that the temperatures of mice with reflective foil only (start temperature, 36.2 ± 0.38 °C; end temperature, 28.8 ± 0.78 °C) did not differ significantly from those of control mice; however, the inclusion of foil heightened thermogenic properties when combined with other devices. Thermogenic gel packs and CWWB on high setting, both with and without reflective foil, caused significant temperature increases (that is, 1.6 °C to 4.4 °C) in mice. CWWB on medium setting (blanket temperature, 37.5 °C) maintained mice at temperatures within 1 °C of the 36.1 °C baseline. Strong correlations existed between temperature, heart and respiratory rates, and recovery time to consciousness. This information provides guidance regarding the use of thermoregulatory devices in anesthetized rodents and demonstrates the effect of maintaining a consistent core temperature on physiologic parameters. PMID:24041214

Whey protein isolate modified by transglutaminase aggregation and emulsion gel properties

NASA Astrophysics Data System (ADS)

Qi, Weiwei; Chen, Chong; Liu, Mujun; Yu, Guoping; Cai, Xinghang; Guo, Peipei; Yao, Yuxiu; Mei, Sijie

2015-07-01

Whey protein isolate and commercial soybean salad oil were used to produce the WPI emulsion dispersions. The properties of TG-catalyzed emulsion gelation produced from WPI emulsion dispersions were investigated by the amount of TG, temperature, pH and reaction time. Specifically, the texture properties (hardness and springiness), water-holding capacity and rheological properties (G' and G") were assessed. The result of Orthogonal tests showed WPI emulsion can form better hardness and springiness gel when the ratio of TG and WPI was 20U/g, pH 7.5, treatment temperature and time were 50°C and 3 h, respectively. The microstructure of TG emulsion gels was more compact, gel pore is smaller, distribution more uniform, the oil droplets size smaller compared with untreated emulsion gels. Compared to the control of rheological properties, G' and G" were significantly increased and G' > G", results showed that the gel was solid state, and TG speeded up the process of gelation.

Crosslinking of polysaccharides in room temperature ionic liquids by ionizing radiation

NASA Astrophysics Data System (ADS)

Kimura, Atsushi; Nagasawa, Naotsugu; Shimada, Akihiko; Taguchi, Mitsumasa

2016-07-01

Crosslinking of polysaccharides in room temperature ionic liquids (RTILs) by ionizing radiation were investigated by the scavenging method, fluorescent and X-ray photoelectron spectroscopy (XPS) analysis. Radiation chemical yields of hydroxyl radicals inducing the crosslinking of cellulose were estimated with phenol as a scavenger, and increased with water content in 1-ethyl-3-methylimidazolium acetate (EMI-acetate). Cellulose gel was also produced in fluorescent carboxylate-based RTILs, 1,3-dibutylimidazolium acetate (DBI-acetate). Light emission from DBI-acetate in cellulose gel was observed and 20-nm red shifted at a maximum wavelength of 415 nm when excited at 323 nm. Expected elements of carbon and oxygen were detected in neat cellulose by XPS, while additional nitrogen was detected in radiation-crosslinked cellulose gel produced in EMI-acetate. These results indicate that RTILs is incorporated in the cellulose gel. Chitin gel was first obtained in 1-butyl-3-methyimidazolium chloride by γ-ray irradiations, and its gel fraction increased with the dose and reached 86% at 60 kGy.

Room temperature ferromagnetism of tin oxide nanocrystal based on synthesis methods

NASA Astrophysics Data System (ADS)

Sakthiraj, K.; Hema, M.; Balachandrakumar, K.

2016-04-01

The experimental conditions used in the preparation of nanocrystalline oxide materials play an important role in the room temperature ferromagnetism of the product. In the present work, a comparison was made between sol-gel, microwave assisted sol-gel and hydrothermal methods for preparing tin oxide nanocrystal. X-ray diffraction analysis indicates the formation of tetragonal rutile phase structure for all the samples. The crystallite size was estimated from the HRTEM images and it is around 6-12 nm. Using optical absorbance measurement, the band gap energy value of the samples has been calculated. It reveals the existence of quantum confinement effect in all the prepared samples. Photoluminescence (PL) spectra confirms that the luminescence process originates from the structural defects such as oxygen vacancies present in the samples. Room temperature hysteresis loop was clearly observed in M-H curve of all the samples. But the sol-gel derived sample shows the higher values of saturation magnetization (Ms) and remanence (Mr) than other two samples. This study reveals that the sol-gel method is superior to the other two methods for producing room temperature ferromagnetism in tin oxide nanocrystal.

Sound control by temperature gradients

NASA Astrophysics Data System (ADS)

Sánchez-Dehesa, José; Angelov, Mitko I.; Cervera, Francisco; Cai, Liang-Wu

2009-11-01

This work reports experiments showing that airborne sound propagation can be controlled by temperature gradients. A system of two heated tubes is here used to demonstrate the collimation and focusing of an ultrasonic beam by the refractive index profile created by the temperature gradients existing around the tubes. Numerical simulations supporting the experimental findings are also reported.

43 CFR 3252.16 - How must I abandon a temperature gradient well?

Code of Federal Regulations, 2012 CFR

2012-10-01

... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false How must I abandon a temperature gradient well? 3252.16 Section 3252.16 Public Lands: Interior Regulations Relating to Public Lands (Continued... LEASING Conducting Exploration Operations § 3252.16 How must I abandon a temperature gradient well? (a...

43 CFR 3252.15 - When must I abandon a temperature gradient well?

Code of Federal Regulations, 2013 CFR

2013-10-01

... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false When must I abandon a temperature gradient well? 3252.15 Section 3252.15 Public Lands: Interior Regulations Relating to Public Lands (Continued... LEASING Conducting Exploration Operations § 3252.15 When must I abandon a temperature gradient well? When...

43 CFR 3252.16 - How must I abandon a temperature gradient well?

Code of Federal Regulations, 2014 CFR

2014-10-01

... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false How must I abandon a temperature gradient well? 3252.16 Section 3252.16 Public Lands: Interior Regulations Relating to Public Lands (Continued... LEASING Conducting Exploration Operations § 3252.16 How must I abandon a temperature gradient well? (a...

43 CFR 3252.16 - How must I abandon a temperature gradient well?

Code of Federal Regulations, 2011 CFR

2011-10-01

... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false How must I abandon a temperature gradient well? 3252.16 Section 3252.16 Public Lands: Interior Regulations Relating to Public Lands (Continued... LEASING Conducting Exploration Operations § 3252.16 How must I abandon a temperature gradient well? (a...

43 CFR 3252.15 - When must I abandon a temperature gradient well?

Code of Federal Regulations, 2014 CFR

2014-10-01

... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false When must I abandon a temperature gradient well? 3252.15 Section 3252.15 Public Lands: Interior Regulations Relating to Public Lands (Continued... LEASING Conducting Exploration Operations § 3252.15 When must I abandon a temperature gradient well? When...

43 CFR 3252.16 - How must I abandon a temperature gradient well?

Code of Federal Regulations, 2013 CFR

2013-10-01

... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false How must I abandon a temperature gradient well? 3252.16 Section 3252.16 Public Lands: Interior Regulations Relating to Public Lands (Continued... LEASING Conducting Exploration Operations § 3252.16 How must I abandon a temperature gradient well? (a...

43 CFR 3252.15 - When must I abandon a temperature gradient well?

Code of Federal Regulations, 2012 CFR

2012-10-01

... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false When must I abandon a temperature gradient well? 3252.15 Section 3252.15 Public Lands: Interior Regulations Relating to Public Lands (Continued... LEASING Conducting Exploration Operations § 3252.15 When must I abandon a temperature gradient well? When...

43 CFR 3252.15 - When must I abandon a temperature gradient well?

Code of Federal Regulations, 2011 CFR

2011-10-01

... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false When must I abandon a temperature gradient well? 3252.15 Section 3252.15 Public Lands: Interior Regulations Relating to Public Lands (Continued... LEASING Conducting Exploration Operations § 3252.15 When must I abandon a temperature gradient well? When...

Poloxamer-Based Thermoreversible Gel for Topical Delivery of Emodin: Influence of P407 and P188 on Solubility of Emodin and Its Application in Cellular Activity Screening.

PubMed

Ban, Eunmi; Park, Mijung; Jeong, Seonghee; Kwon, Taekhyun; Kim, Eun-Hee; Jung, Kiwon; Kim, Aeri

2017-02-07

Emodin is a component in a Chinese herb, Rheum officinale Baill, traditionally used for diabetes and anticancer. Its poor solubility is one of the major challenges to pharmaceutical scientists. We previously reported on thermoreversible gel formulations based on poloxamer for the topical delivery of emodin. The present study was to understand the effect of poloxamer type on emodin solubility and its application in cellular activity screening. Various gel formulations composed of poloxamer 407 (P407), poloxamer 188 (P188) and PEG400 were prepared and evaluated. Major evaluation parameters were the gelation temperature (Tgel) and solubility of emodin. The emodin solubility increased with increasing poloxamer concentration and the Tgel was modulated by the proper combination of P407. In particular, this study showed that the amount of P407 in thermoreversible poloxamer gel (PG) was the dominant factor in enhancing solubility and P188 was effective at fixing gelation temperature in the desired range. A thermoreversible emodin PG was selected as the proper composition with the liquid state at room temperature and gel state at body temperature. The gel showed the solubility enhancement of emodin at least 100-fold compared to 10% ethanol or water. The thermoreversible formulation was applied for in vitro cellular activity screening in the human dermal fibroblast cell line and DLD-1 colon cancer cell line after dilution with cell culture media. The thermoreversible gel formulation remained as a clear solution in the microplate, which allowed reliable cellular activity screening. In contrast, emodin solution in ethanol or DMSO showed precipitation at the corresponding emodin concentration, complicating data interpretation. In conclusion, the gel formulation is proposed as a useful prototype topical formulation for testing emodin in vivo as well as in vitro.

Single photon counting fluorescence lifetime detection of pericellular oxygen concentrations

NASA Astrophysics Data System (ADS)

Hosny, Neveen A.; Lee, David A.; Knight, Martin M.

2012-01-01

Fluorescence lifetime imaging microscopy offers a non-invasive method for quantifying local oxygen concentrations. However, existing methods are either invasive, require custom-made systems, or show limited spatial resolution. Therefore, these methods are unsuitable for investigation of pericellular oxygen concentrations. This study describes an adaptation of commercially available equipment which has been optimized for quantitative extracellular oxygen detection with high lifetime accuracy and spatial resolution while avoiding systematic photon pile-up. The oxygen sensitive fluorescent dye, tris(2,2'-bipyridyl)ruthenium(II) chloride hexahydrate [Ru(bipy)3]2+, was excited using a two-photon excitation laser. Lifetime was measured using a Becker & Hickl time-correlated single photon counting, which will be referred to as a TCSPC card. [Ru(bipy)3]2+ characterization studies quantified the influences of temperature, pH, cellular culture media and oxygen on the fluorescence lifetime measurements. This provided a precisely calibrated and accurate system for quantification of pericellular oxygen concentration based on measured lifetimes. Using this technique, quantification of oxygen concentrations around isolated viable chondrocytes, seeded in three-dimensional agarose gel, revealed a subpopulation of cells that exhibited significant spatial oxygen gradients such that oxygen concentration reduced with increasing proximity to the cell. This technique provides a powerful tool for quantifying spatial oxygen gradients within three-dimensional cellular models.

Single photon counting fluorescence lifetime detection of pericellular oxygen concentrations.

PubMed

Hosny, Neveen A; Lee, David A; Knight, Martin M

2012-01-01

Fluorescence lifetime imaging microscopy offers a non-invasive method for quantifying local oxygen concentrations. However, existing methods are either invasive, require custom-made systems, or show limited spatial resolution. Therefore, these methods are unsuitable for investigation of pericellular oxygen concentrations. This study describes an adaptation of commercially available equipment which has been optimized for quantitative extracellular oxygen detection with high lifetime accuracy and spatial resolution while avoiding systematic photon pile-up. The oxygen sensitive fluorescent dye, tris(2,2'-bipyridyl)ruthenium(II) chloride hexahydrate [Ru(bipy)(3)](2+), was excited using a two-photon excitation laser. Lifetime was measured using a Becker & Hickl time-correlated single photon counting, which will be referred to as a TCSPC card. [Ru(bipy)(3)](2+) characterization studies quantified the influences of temperature, pH, cellular culture media and oxygen on the fluorescence lifetime measurements. This provided a precisely calibrated and accurate system for quantification of pericellular oxygen concentration based on measured lifetimes. Using this technique, quantification of oxygen concentrations around isolated viable chondrocytes, seeded in three-dimensional agarose gel, revealed a subpopulation of cells that exhibited significant spatial oxygen gradients such that oxygen concentration reduced with increasing proximity to the cell. This technique provides a powerful tool for quantifying spatial oxygen gradients within three-dimensional cellular models.

Application of Sol-Gel Method as a Protective Layer on a Specular Reflective Surface for Secondary Reflector in a Solar Receiver

DOE Office of Scientific and Technical Information (OSTI.GOV)

Afrin, Samia; Dagdelen, John; Ma, Zhiwen

Highly-specular reflective surfaces that can withstand elevated-temperatures are desirable for many applications including reflective heat shielding in solar receivers and secondary reflectors, which can be used between primary concentrators and heat collectors. A high-efficiency, high-temperature solar receiver design based on arrays of cavities needs a highly-specular reflective surface on its front section to help sunlight penetrate into the absorber tubes for effective flux spreading. Since this application is for high-temperature solar receivers, this surface needs to be durable and to maintain its optical properties through the usable life. Degradation mechanisms associated with elevated temperatures and thermal cycling, which include cracking,more » delamination, corrosion/oxidation, and environmental effects, could cause the optical properties of surfaces to degrade rapidly in these conditions. Protected mirror surfaces for these applications have been tested by depositing a thin layer of SiO2 on top of electrodeposited silver by means of the sol-gel method. To obtain an effective thin film structure, this sol-gel procedure has been investigated extensively by varying process parameters that affect film porosity and thickness. Endurance tests have been performed in a furnace at 150 degrees C for thousands of hours. This paper presents the sol-gel process for intermediate-temperature specular reflective coatings and provides the long-term reliability test results of sol-gel protected silver-coated surfaces.« less

Evaluation of tilapia skin gelatin as a mammalian gelatin replacer in acid milk gels and low-fat stirred yogurt.

PubMed

Pang, Zhihua; Deeth, Hilton; Yang, Hongshun; Prakash, Sangeeta; Bansal, Nidhi

2017-05-01

Tilapia skin gelatin (TSG) was studied in a 3-stage process (cooling, annealing, and heating) for pure gelatin gels and in a 4-stage process (acidification, cooling, annealing, and heating) for acid milk gels and cultured yogurt. The aim was to evaluate the use of TSG as a replacement for mammalian gelatin in yogurt. In pure TSG gels, stronger gels with higher melting temperatures were formed with increasing TSG concentrations. Compared with bovine gelatin (BG), which gelled at a concentration of 2.5%, TSG gels had lower gelling (14.1°C) and melting (24°C) temperatures but comparable storage moduli during annealing. In acid milk gels, addition of TSG increased the firmness of the gels with increasing concentration. Gelling and melting points of TSG in milk gels were observed at sufficient concentrations during cooling and heating. Strands and sheets were observed in the electron micrographs of milk gels with 1% TSG and a very dense structure was observed with 2.5% TSG. Yogurt with 0.4% TSG had similar viscosity, consistency, pseudoplasticity, and thixotropy as yogurt containing 0.4% BG; no difference was perceived by sensory panelists according to a triangle test. Addition of 0.4% TSG completely prevented whey separation from the acid milk gel and yogurt. The results suggest that TSG could be a suitable replacement for mammalian gelatin in low-fat stirred yogurt. Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Temperature logging of groundwater in bedrock wells for geothermal gradient characterization in New Hampshire, 2012

USGS Publications Warehouse

Degnan, James; Barker, Gregory; Olson, Neil; Wilder, Leland

2012-01-01

Maximum groundwater temperatures at the bottom of the logs were between 11.7 and 17.3 degrees Celsius. Geothermal gradients were generally higher than typically reported for other water wells in the United States. Some of the high gradients were associated with high natural gamma emissions. Groundwater flow was discernible in 5 of the 10 wells studied but only obscured the portion of the geothermal gradient signal where groundwater actually flowed through the well. Temperature gradients varied by mapped bedrock type but can also vary by differences in mineralogy or rock type within the wells.

SIMILARITY OF PARTICLE-ASSOCIATED AND FREE-LIVING BACTERIAL COMMUNITIES IN NORTHERN SAN FRANCISCO BAY, CALIFORNIA

EPA Science Inventory

We used denaturing gradient gel electrophoresis (DGGE) of 16S rDNA PCR amplicons to analyze the composition of Bacteria communities in samples collected during the summer, low flow season from northern San Francisco Bay, California. There were clear compositional differences in ...

TEMPERATURE-GRADIENT PLATES FOR GROWTH OF MICROORGANISMS

PubMed Central

Landman, Otto E.; Bausum, Howard T.; Matney, Thomas S.

1962-01-01

Landman, Otto E. (Fort Detrick, Frederick, Md.), Howard T. Bausum, and Thomas S. Matney. Temperature-gradient plates for growth of microorganisms. J. Bacteriol. 83:463–469. 1962.—Different temperature-gradient plates have been devised for the study of microbial growth on solid media through continuous temperature ranges or in liquid media at finely graded temperatures. All plates are made of heavy-gauge aluminum; heat supplied at one end is dissipated along the length of the metal so that a gradient is produced. The shape and range of the gradient depends on the amount of heat supplied, the insulation, the ambient temperature, and other factors. Differences of 0.2 C in temperature sensitivity between bacterial strains can be detected. The plates are simple to construct and operate. The dimensions of the aluminum, the mode of temperature measurement, and the method of heating may all be modified without diminishing the basic utility of the device. A sharp growth front develops at the maximal temperature of growth of bacteria. In most strains, all bacteria below the front form colonies and all bacteria above the front are killed, except for a few temperature-resistant mutants. Images PMID:14461975

Bioinspired Programmable Polymer Gel Controlled by Swellable Guest Medium.

PubMed

Deng, Heng; Dong, Yuan; Su, Jheng-Wun; Zhang, Cheng; Xie, Yunchao; Zhang, Chi; Maschmann, Matthew R; Lin, Yuyi; Lin, Jian

2017-09-13

Responsive materials with functions of forming three-dimensional (3D) origami and/or kirigami structures have a broad range of applications in bioelectronics, metamaterials, microrobotics, and microelectromechanical (MEMS) systems. To realize such functions, building blocks of actuating components usually possess localized inhomogeneity so that they respond differently to external stimuli. Previous fabrication strategies lie in localizing nonswellable or less-swellable guest components in their swellable host polymers to reduce swelling ability. Herein, inspired by ice plant seed capsules, we report an opposite strategy of implanting swellable guest medium inside nonswellable host polymers to locally enhance the swelling inhomogeneity. Specifically, we adopted a skinning effect induced surface polymerization combined with direct laser writing to control gradient of swellable cyclopentanone (CP) in both vertical and lateral directions of the nonswellable SU-8. For the first time, the laser direct writing was used as a novel strategy for patterning programmable polymer gel films. Upon stimulation of organic solvents, the dual-gradient gel films designed by origami or kirigami principles exhibit reversible 3D shape transformation. Molecular dynamics (MD) simulation illustrates that CP greatly enhances diffusion rates of stimulus solvent molecules in the SU-8 matrix, which offers the driving force for the programmable response. Furthermore, this bioinspired strategy offers unique capabilities in fabricating responsive devices such as a soft gripper and a locomotive robot, paving new routes to many other responsive polymers.

Identifying Time Periods of Minimal Thermal Gradient for Temperature-Driven Structural Health Monitoring.

PubMed

Reilly, John; Glisic, Branko

2018-03-01

Temperature changes play a large role in the day to day structural behavior of structures, but a smaller direct role in most contemporary Structural Health Monitoring (SHM) analyses. Temperature-Driven SHM will consider temperature as the principal driving force in SHM, relating a measurable input temperature to measurable output generalized strain (strain, curvature, etc.) and generalized displacement (deflection, rotation, etc.) to create three-dimensional signatures descriptive of the structural behavior. Identifying time periods of minimal thermal gradient provides the foundation for the formulation of the temperature-deformation-displacement model. Thermal gradients in a structure can cause curvature in multiple directions, as well as non-linear strain and stress distributions within the cross-sections, which significantly complicates data analysis and interpretation, distorts the signatures, and may lead to unreliable conclusions regarding structural behavior and condition. These adverse effects can be minimized if the signatures are evaluated at times when thermal gradients in the structure are minimal. This paper proposes two classes of methods based on the following two metrics: (i) the range of raw temperatures on the structure, and (ii) the distribution of the local thermal gradients, for identifying time periods of minimal thermal gradient on a structure with the ability to vary the tolerance of acceptable thermal gradients. The methods are tested and validated with data collected from the Streicker Bridge on campus at Princeton University.

Temperature gradient effects on vapor diffusion in partially-saturated porous media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Webb, S.W.

1999-07-01

Vapor diffusion in porous media in the presence of its own liquid may be enhanced due to pore-scale processes, such as condensation and evaporation across isolated liquid islands. Webb and Ho (1997) developed one-and two-dimensional mechanistic pore-scale models of these processes in an ideal porous medium. For isothermal and isobaric boundary conditions with a concentration gradient, the vapor diffusion rate was significantly enhanced by these liquid island processes compared to a dry porous media. The influence of a temperature gradient on the enhanced vapor diffusion rate is considered in this paper. The two-dimensional pore network model which is used inmore » the present study is shown. For partially-saturated conditions, a liquid island is introduced into the top center pore. Boundary conditions on the left and right sides of the model are specified to give the desired concentration and temperature gradients. Vapor condenses on one side of the liquid island and evaporates off the other side due to local vapor pressure lowering caused by the interface curvature, even without a temperature gradient. Rather than acting as an impediment to vapor diffusion, the liquid island actually enhances the vapor diffusion rate. The enhancement of the vapor diffusion rate can be significant depending on the liquid saturation. Vapor diffusion is enhanced by up to 40% for this single liquid island compared to a dry porous medium; enhancement factors of up to an order of magnitude have been calculated for other conditions by Webb and Ho (1997). The dominant effect on the enhancement factor is the concentration gradient; the influence of the temperature gradient is smaller. The significance of these results, which need to be confirmed by experiments, is that the dominant model of enhanced vapor diffusion (EVD) by Philip and deVries (1957) predicts that temperature gradients must exist for EVD to occur. If there is no temperature gradient, there is no enhancement. The present results indicate that EVD is predominantly driven by concentration gradients; temperature gradients are less important. Therefore, the EVD model of Philip and deVries may need to be modified to reflect these results.« less

Sound beam manipulation based on temperature gradients

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qian, Feng; School of Physics & Electronic Engineering, Changshu Institute of Technology, Changshu 215500; Quan, Li

Previous research with temperature gradients has shown the feasibility of controlling airborne sound propagation. Here, we present a temperature gradients based airborne sound manipulation schemes: a cylindrical acoustic omnidirectional absorber (AOA). The proposed AOA has high absorption performance which can almost completely absorb the incident wave. Geometric acoustics is used to obtain the refractive index distributions with different radii, which is then utilized to deduce the desired temperature gradients. Since resonant units are not applied in the scheme, its working bandwidth is expected to be broadband. The scheme is temperature-tuned and easy to realize, which is of potential interest tomore » fields such as noise control or acoustic cloaking.« less

Protein structural development of threadfin bream ( Nemipterus spp.) surimi gels induced by glucose oxidase.

PubMed

Wang, Lei; Fan, Daming; Fu, Lulu; Jiao, Xidong; Huang, Jianlian; Zhao, Jianxin; Yan, Bowen; Zhou, Wenguo; Zhang, Wenhai; Ye, Weijian; Zhang, Hao

2018-01-01

This study investigated the effect of glucose oxidase on the gel properties of threadfin bream surimi. The gel strength of surimi increased with the addition of 0.5‰ glucose oxidase after two-step heating. Based on the results of the chemical interactions, the hydrophobic interaction and disulfide bond of glucose oxidase-treated surimi samples increased compared with the control samples at the gelation temperature and gel modori temperature. The surface hydrophobicity of samples with glucose oxidase and glucose increased significantly ( p < 0.05) and total sulfhydryl groups decreased significantly ( p < 0.05). The analysis of Raman spectroscopy shows that the addition of glucose oxidase induced more α-helixes to turn into a more elongated random and flocculent structure. Glucose oxidase changes the secondary structure of the surimi protein, making more proteins depolarize and stretch and causing actomyosin to accumulate to each other, resulting in the formation of surimi gel.

Lipid diffusion in alcoholic environment.

PubMed

Rifici, Simona; Corsaro, Carmelo; Crupi, Cristina; Nibali, Valeria Conti; Branca, Caterina; D'Angelo, Giovanna; Wanderlingh, Ulderico

2014-08-07

We have studied the effects of a high concentration of butanol and octanol on the phase behavior and on the lateral mobility of 1,2-palmitoyl-sn-glycero-3-phosphocholine (DPPC) by means of differential scanning calorimetry and pulsed-gradient stimulated-echo (PGSTE) NMR spectroscopy. A lowering of the lipid transition from the gel to the liquid-crystalline state for the membrane-alcohol systems has been observed. NMR measurements reveal three distinct diffusions in the DPPC-alcohol systems, characterized by a high, intermediate, and slow diffusivity, ascribed to the water, the alcohol, and the lipid, respectively. The lipid diffusion process is promoted in the liquid phase while it is hindered in the interdigitated phase due to the presence of alcohols. Furthermore, in the interdigitated phase, lipid lateral diffusion coefficients show a slight temperature dependence. To the best of our knowledge, this is the first time that lateral diffusion coefficients on alcohol with so a long chain, and at low temperatures, are reported. By the Arrhenius plots of the temperature dependence of the diffusion coefficients, we have evaluated the apparent activation energy in both the liquid and in the interdigitated phase. The presence of alcohol increases this value in both phases. An explanation in terms of a free volume model that takes into account also for energy factors is proposed.

Rpn9 Is Required for Efficient Assembly of the Yeast 26S Proteasome

PubMed Central

Takeuchi, Junko; Fujimuro, Masahiro; Yokosawa, Hideyosi; Tanaka, Keiji; Toh-e, Akio

1999-01-01

We have isolated the RPN9 gene by two-hybrid screening with, as bait, RPN10 (formerly SUN1), which encodes a multiubiquitin chain receptor residing in the regulatory particle of the 26S proteasome. Rpn9 is a nonessential subunit of the regulatory particle of the 26S proteasome, but the deletion of this gene results in temperature-sensitive growth. At the restrictive temperature, the Δrpn9 strain accumulated multiubiquitinated proteins, indicating that the RPN9 function is needed for the 26S proteasome activity at a higher temperature. We analyzed the proteasome fractions separated by glycerol density gradient centrifugation by native polyacrylamide gel electrophoresis and found that a smaller amount of the 26S proteasome was produced in the Δrpn9 cells and that the 26S proteasome was shifted to lighter fractions than expected. The incomplete proteasome complexes were found to accumulate in the Δrpn9 cells. Furthermore, Rpn10 was not detected in the fractions containing proteasomes of the Δrpn9 cells. These results indicate that Rpn9 is needed for incorporating Rpn10 into the 26S proteasome and that Rpn9 participates in the assembly and/or stability of the 26S proteasome. PMID:10490597

Method of improving heterogeneous oil reservoir polymer flooding effect by positively-charged gel profile control

NASA Astrophysics Data System (ADS)

Zhao, Ling; Xia, Huifen

2018-01-01

The project of polymer flooding has achieved great success in Daqing oilfield, and the main oil reservoir recovery can be improved by more than 15%. But, for some strong oil reservoir heterogeneity carrying out polymer flooding, polymer solution will be inefficient and invalid loop problem in the high permeability layer, then cause the larger polymer volume, and a significant reduction in the polymer flooding efficiency. Aiming at this problem, it is studied the method that improves heterogeneous oil reservoir polymer flooding effect by positively-charged gel profile control. The research results show that the polymer physical and chemical reaction of positively-charged gel with the residual polymer in high permeability layer can generate three-dimensional network of polymer, plugging high permeable layer, and increase injection pressure gradient, then improve the effect of polymer flooding development. Under the condition of the same dosage, positively-charged gel profile control can improve the polymer flooding recovery factor by 2.3∼3.8 percentage points. Under the condition of the same polymer flooding recovery factor increase value, after positively-charged gel profile control, it can reduce the polymer volume by 50 %. Applying mechanism of positively-charged gel profile control technology is feasible, cost savings, simple construction, and no environmental pollution, therefore has good application prospect.

Applications and Properties of Ionic Liquid- Based Gels and Soft Solid Composites

NASA Astrophysics Data System (ADS)

Voss, Bret Alan McGinness

2011-12-01

Solid-liquid composites (gels) have a combination of properties that afford new material applications in which high solute diffusion is desirable. These composites have a soft-solid mechanical integrity and will not flow under gravity, but entrain a liquid matrix (i.e. 60-98 mass %) which allows for high diffusion and high reactivity. Room temperature ionic liquid (RTILs) are molten organic salts with a melting point below room temperature and negligible vapor pressure. If the RTILs are used as the liquid component of a gel, then the gel matrix will not evaporate (unlike other organic solvents) and may be used for long term applications. This thesis research applies RTIL gels for two new applications; carbon dioxide/nitrogen separation and chemical warfare agent (CWA) barrier and decontamination. Separating CO2 from the flue gas of coal and gas fired power-plants is an increasingly economically and environmentally important gas separation. In this first study, RTIL gels are cast in a supported membrane and gas permeability and ideal selectivity are measured. The RTIL matrix has an inherent affinity for CO2 and provides a high diffusion, hence high permeability (i.e. 500-700 barrer). The solidifying component is a low molecular-weight organic gelator (LMOG) which through physical bonding interactions (i.e. hydrogen bonding, pi-pi stacking and van der Walls forces) forms an entangled network which provides mechanical stability (i.e. increase trans-membrane pressure required to expel selective material from the support). In these studies two LMOGs and five RTILs are used to make supported gel membranes and determine gas permeability and temperature dependent trends. The second application for RTIL gels is a decontaminating barrier for CWAs and toxic industrial compounds (TICs). In these studies a layer of RTIL gel is applied on top of a substrate contaminated with a CWA simulant (i.e. chloroethylethylsulfide, CEES). The gel performs well as a barrier, preventing CEES vapor from penetrating the gel. Simultaneously, the RTIL gel actively decontaminated the substrate by reacting CEES with a sacrificial amine. The RTIL gel barrier was able to decontaminate up to 98% of the CEES applied to a painted steel substrate. Two gel barriers are tested: (1) RTIL gel with a LMOG solidifying agent, and (2) RTIL gel with a polymeric cross-linked network solidifying agent. The polymer gel provided a more mechanically robust barrier, however, the LMOG gel decontaminated at a faster rate. These new applications are but two of many possible applications for RTIL gels. Their negligible vapor pressure affords long term application in ambient conditions and their unique chemistry allows them to be tailored for specific applications.

Single cell–resolution western blotting

PubMed Central

Kang, Chi-Chih; Yamauchi, Kevin A; Vlassakis, Julea; Sinkala, Elly; Duncombe, Todd A; Herr, Amy E

2017-01-01

This protocol describes how to perform western blotting on individual cells to measure cell-to-cell variation in protein expression levels and protein state. like conventional western blotting, single-cell western blotting (scWB) is particularly useful for protein targets that lack selective antibodies (e.g., isoforms) and in cases in which background signal from intact cells is confounding. scWB is performed on a microdevice that comprises an array of microwells molded in a thin layer of a polyacrylamide gel (PAG). the gel layer functions as both a molecular sieving matrix during PAGE and a blotting scaffold during immunoprobing. scWB involves five main stages: (i) gravity settling of cells into microwells; (ii) chemical lysis of cells in each microwell; (iii) PAGE of each single-cell lysate; (iv) exposure of the gel to UV light to blot (immobilize) proteins to the gel matrix; and (v) in-gel immunoprobing of immobilized proteins. Multiplexing can be achieved by probing with antibody cocktails and using antibody stripping/reprobing techniques, enabling detection of 10+ proteins in each cell. We also describe microdevice fabrication for both uniform and pore-gradient microgels. to extend in-gel immunoprobing to gels of small pore size, we describe an optional gel de-cross-linking protocol for more effective introduction of antibodies into the gel layer. once the microdevice has been fabricated, the assay can be completed in 4–6 h by microfluidic novices and it generates high-selectivity, multiplexed data from single cells. the technique is relevant when direct measurement of proteins in single cells is needed, with applications spanning the fundamental biosciences to applied biomedicine. PMID:27466711

Making MgO/SiO2 Glasses By The Sol-Gel Process

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.

1989-01-01

Silicon dioxide glasses containing 15 mole percent magnesium oxide prepared by sol-gel process. Not made by conventional melting because ingredients immiscible liquids. Synthesis of MgO/SiO2 glass starts with mixing of magnesium nitrate hexahydrate with silicon tetraethoxide, both in alcohol. Water added, and transparent gel forms. Subsequent processing converts gel into glass. Besides producing glasses of new composition at lower processing temperatures, sol-gel method leads to improved homogeneity and higher purity.

Variations in bacterial communities during foliar litter decomposition in the winter and growing seasons in an alpine forest of the eastern Tibetan Plateau.

PubMed

Zhao, Yeyi; Wu, Fuzhong; Yang, Wanqin; Tan, Bo; He, Wei

2016-01-01

Bacterial communities are the primary engineers during litter decomposition and related material cycling, and they can be strongly controlled by seasonal changes in temperature and other environmental factors. However, limited information is available on changes in the bacterial community from winter to the growing season as litter decomposition proceeds in cold climates. Here, we investigated the abundance and structure of bacterial communities using real-time quantitative PCR and denaturing gradient gel electrophoresis (DGGE) during a 2-year field study of the decomposition of litter of 4 species in the winter and growing seasons of an alpine forest of the eastern Tibetan Plateau. The abundance of the bacterial 16S rRNA gene was relatively high during decomposition of cypress and birch litter in the first winter, but for the other litters 16S rRNA abundance during both winters was significantly lower than during the following growing season. A large number of bands were observed on the DGGE gels, and their intensities and number from the winter samples were lower than those from the growing season during the 2-year decomposition experiment. Eighty-nine sequences from the bands of bacteria that had been cut from the DGGE gels were affiliated with 10 distinct classes of bacteria and an unknown group. A redundancy analysis indicated that the moisture, mass loss, and elemental content (e.g., C, N, and P) of the litter significantly affected the bacterial communities. Collectively, the results suggest that uneven seasonal changes in climate regulate bacterial communities and other decomposers, thus affecting their contribution to litter decomposition processes in the alpine forest.

Stem cell migration and mechanotransduction on linear stiffness gradient hydrogels

PubMed Central

Hadden, William J.; Young, Jennifer L.; Holle, Andrew W.; McFetridge, Meg L.; Kim, Du Yong; Wijesinghe, Philip; Taylor-Weiner, Hermes; Wen, Jessica H.; Lee, Andrew R.; Bieback, Karen; Vo, Ba-Ngu; Sampson, David D.; Kennedy, Brendan F.; Spatz, Joachim P.; Choi, Yu Suk

2017-01-01

The spatial presentation of mechanical information is a key parameter for cell behavior. We have developed a method of polymerization control in which the differential diffusion distance of unreacted cross-linker and monomer into a prepolymerized hydrogel sink results in a tunable stiffness gradient at the cell–matrix interface. This simple, low-cost, robust method was used to produce polyacrylamide hydrogels with stiffness gradients of 0.5, 1.7, 2.9, 4.5, 6.8, and 8.2 kPa/mm, spanning the in vivo physiological and pathological mechanical landscape. Importantly, three of these gradients were found to be nondurotactic for human adipose-derived stem cells (hASCs), allowing the presentation of a continuous range of stiffnesses in a single well without the confounding effect of differential cell migration. Using these nondurotactic gradient gels, stiffness-dependent hASC morphology, migration, and differentiation were studied. Finally, the mechanosensitive proteins YAP, Lamin A/C, Lamin B, MRTF-A, and MRTF-B were analyzed on these gradients, providing higher-resolution data on stiffness-dependent expression and localization. PMID:28507138

In situ synthesis of bilayered gradient poly(vinyl alcohol)/hydroxyapatite composite hydrogel by directional freezing-thawing and electrophoresis method.

PubMed

Su, Cui; Su, Yunlan; Li, Zhiyong; Haq, Muhammad Abdul; Zhou, Yong; Wang, Dujin

2017-08-01

Bilayered poly(vinyl alcohol) (PVA)/hydroxyapatite (HA) composite hydrogels with anisotropic and gradient mechanical properties were prepared by the combination of directional freezing-thawing (DFT) and electrophoresis method. Firstly, PVA hydrogels with aligned channel structure were prepared by the DFT method. Then, HA nanoparticles were in situ synthesized within the PVA hydrogels via electrophoresis. By controlling the time of the electrophoresis process, a bilayered gradient hydrogel containing HA particles in only half of the gel region was obtained. The PVA/HA composite hydrogel exhibited gradient mechanical strength depending on the distance to the cathode. The gradient initial tensile modulus ranging from 0.18MPa to 0.27MPa and the gradient initial compressive modulus from 0.33MPa to 0.51MPa were achieved. The binding strength of the two regions was relatively high and no apparent internal stress or defect was observed at the boundary. The two regions of the bilayered hydrogel also showed different osteoblast cell adhesion properties. Copyright © 2017 Elsevier B.V. All rights reserved.

Electrolyte transport in neutral polymer gels embedded with charged inclusions

NASA Astrophysics Data System (ADS)

Hill, Reghan

2005-11-01

Ion permeable membranes are the basis of a variety of molecular separation technologies, including ion exchange, gel electrophoresis and dialysis. This work presents a theoretical model of electrolyte transport in membranes comprised of a continuous polymer gel embedded with charged spherical inclusions, e.g., biological cells and synthetic colloids. The microstructure mimics immobilized cell cultures, where electric fields have been used to promote nutrient transport. Because several important characteristics can, in principle, be carefully controlled, the theory provides a quantitative framework to help tailor the bulk properties for enhanced molecular transport, microfluidic pumping, and physicochemical sensing applications. This talk focuses on the electroosmotic flow driven by weak electric fields and electrolyte concentration gradients. Also of importance is the influence of charge on the effective ion diffusion coefficients, bulk electrical conductivity, and membrane diffusion potential.

Theoretical Design of Multilayer Dental Posts Using CAD-Based Approach and Sol-Gel Chemistry.

PubMed

Maietta, Saverio; De Santis, Roberto; Catauro, Michelina; Martorelli, Massimo; Gloria, Antonio

2018-05-07

A computer-aided design (CAD)-based approach and sol-gel chemistry were used to design a multilayer dental post with a compositional gradient and a Young’s modulus varying from 12.4 to 2.3 GPa in the coronal-apical direction. Specifically, we propose a theoretical multilayer post design, consisting of titanium dioxide (TiO₂) and TiO₂/poly(ε-caprolactone) (PCL) hybrid materials containing PCL up to 24% by weight obtained using the sol-gel method. The current study aimed to analyze the effect of the designed multilayer dental post in endodontically treated anterior teeth. Stress distribution was investigated along and between the post and the surrounding structures. In comparison to a metal post, the most uniform distributions with lower stress values and no significant stress concentration were found when using the multilayer post.

Modification of vital wheat gluten with phosphoric acid to produce high free-solution capacity

USDA-ARS?s Scientific Manuscript database

Wheat gluten reacts with phosphoric acid to produce natural superabsorbent gels. The gel properties are defined by Fourier Transform Infra-red (FTIR) spectroscopy, 2-dimensional gel electrophoresis (2DE), and uptake of water, salt solutions, and aqueous ethanol. Temperatures above 120'C and dry cond...

Ion-temperature-gradient sensitivity of the hydrodynamic instability caused by shear in the magnetic-field-aligned plasma flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mikhailenko, V. V., E-mail: vladimir@pusan.ac.kr; Mikhailenko, V. S.; Faculty of Transportation Systems, Kharkiv National Automobile and Highway University, 61002 Kharkiv

2014-07-15

The cross-magnetic-field (i.e., perpendicular) profile of ion temperature and the perpendicular profile of the magnetic-field-aligned (parallel) plasma flow are sometimes inhomogeneous for space and laboratory plasma. Instability caused either by a gradient in the ion-temperature profile or by shear in the parallel flow has been discussed extensively in the literature. In this paper, (1) hydrodynamic plasma stability is investigated, (2) real and imaginary frequency are quantified over a range of the shear parameter, the normalized wavenumber, and the ratio of density-gradient and ion-temperature-gradient scale lengths, and (3) the role of inverse Landau damping is illustrated for the case of combinedmore » ion-temperature gradient and parallel-flow shear. We find that increasing the ion-temperature gradient reduces the instability threshold for the hydrodynamic parallel-flow shear instability, also known as the parallel Kelvin-Helmholtz instability or the D'Angelo instability. We also find that a kinetic instability arises from the coupled, reinforcing action of both free-energy sources. For the case of comparable electron and ion temperature, we illustrate analytically the transition of the D'Angelo instability to the kinetic instability as (a) the shear parameter, (b) the normalized wavenumber, and (c) the ratio of density-gradient and ion-temperature-gradient scale lengths are varied and we attribute the changes in stability to changes in the amount of inverse ion Landau damping. We show that near a normalized wavenumber k{sub ⊥}ρ{sub i} of order unity (i) the real and imaginary values of frequency become comparable and (ii) the imaginary frequency, i.e., the growth rate, peaks.« less

EFFECTS OF TEMPERATURE ON TRICHLOROETHYLENE DESORPTION FROM SILICA GEL AND NATURAL SEDIMENTS. 2. KINETICS. (R822626)

EPA Science Inventory

Isothermal desorption rates were measured at 15, 30, and 60 src="/ncer/pubs/images/deg.gif">C for trichloroethylene (TCE) on a silica gel,
an aquifer sediment, a soil, a sand fraction, and a clay and silt fraction, all
at 100% relative humidity. Temperature-st...

Reduction of particle deposition on substrates using temperature gradient control

DOEpatents

Rader, Daniel J.; Dykhuizen, Ronald C.; Geller, Anthony S.

2000-01-01

A method of reducing particle deposition during the fabrication of microelectronic circuitry is presented. Reduction of particle deposition is accomplished by controlling the relative temperatures of various parts of the deposition system so that a large temperature gradient near the surface on which fabrication is taking place exists. This temperature gradient acts to repel particles from that surface, thereby producing cleaner surfaces, and thus obtaining higher yields from a given microelectronic fabrication process.

Preparation of nickel oxide thin films at different annealing temperature by sol-gel spin coating method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdullah, M. A. R., E-mail: ameerridhwan89@gmail.com; Mamat, M. H., E-mail: hafiz-030@yahoo.com; Ismail, A. S., E-mail: kyrin-samaxi@yahoo.com

2016-07-06

Preparation of NiO thin films at different annealing temperature by sol-gel method was conducted to synthesize the quality of the surface thin films. The effects of annealing temperature on the surface topology were systematically investigated. Our studies confirmed that the surface roughness of the thin films was increased whenever annealing temperature was increase. NiO thin films morphology structure analysis was confirmed by field emission scanning electron microscope. Surface roughness of the thin films was investigated by atomic force microscopy.

Integrated optical devices based on sol – gel waveguides using the temperature dependence of the effective refractive index

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pavlov, S V; Trofimov, N S; Chekhlova, T K

2014-07-31

A possibility of designing optical waveguide devices based on sol – gel SiO{sub 2} – TiO{sub 2} films using the temperature dependence of the effective refractive index is shown. The dependences of the device characteristics on the parameters of the film and opticalsystem elements are analysed. The operation of a temperature recorder and a temperature limiter with a resolution of 0.6 K mm{sup -1} is demonstrated. The film and output-prism parameters are optimised. (fibreoptic and nonlinear-optic devices)

Athermal silicon optical add-drop multiplexers based on thermo-optic coefficient tuning of sol-gel material.

PubMed

Namnabat, Soha; Kim, Kyung-Jo; Jones, Adam; Himmelhuber, Roland; DeRose, Christopher T; Trotter, Douglas C; Starbuck, Andrew L; Pomerene, Andrew; Lentine, Anthony L; Norwood, Robert A

2017-09-04

Silicon photonics has gained interest for its potential to provide higher efficiency, bandwidth and reduced power consumption compared to electrical interconnects in datacenters and high performance computing environments. However, it is well known that silicon photonic devices suffer from temperature fluctuations due to silicon's high thermo-optic coefficient and therefore, temperature control in many applications is required. Here we present an athermal optical add-drop multiplexer fabricated from ring resonators. We used a sol-gel inorganic-organic hybrid material as an alternative to previously used materials such as polymers and titanium dioxide. In this work we studied the thermal curing parameters of the sol-gel and their effect on thermal wavelength shift of the rings. With this method, we were able to demonstrate a thermal shift down to -6.8 pm/°C for transverse electric (TE) polarization in ring resonators with waveguide widths of 325 nm when the sol-gel was cured at 130°C for 10.5 hours. We also achieved thermal shifts below 1 pm/°C for transverse magnetic (TM) polarization in the C band under different curing conditions. Curing time compared to curing temperature shows to be the most important factor to control sol-gel's thermo-optic value in order to obtain an athermal device in a wide temperature range.

Highly efficient gel-state dye-sensitized solar cells prepared using propionitrile and poly(vinylidene fluoride-co-hexafluoropropylene)

NASA Astrophysics Data System (ADS)

Venkatesan, Shanmuganathan; Hidayati, Noor; Liu, I.-Ping; Lee, Yuh-Lang

2016-12-01

Propionitrile (PPN) solvent based iodide/triiodide liquid-electrolyte is utilized to prepare highly efficient poly (vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) polymer gel electrolytes (PGEs) of dye-sensitized solar cells, aiming at improving the energy conversion efficiency as well as the stability of gel-state DSSCs. The concentrations effect of the PVdF-HFP on the properties of PGEs and the performance of the corresponding cells are studied. The results show that the in-situ gelation is performed for the PVdF-HFP concentration range of 8-18% at room temperature. However, increasing the concentration of polymer in the PGEs triggers a decrease in the diffusivity and conductivity of the PGEs, but an increase in the phase transition temperature of the PGEs. A high phase transition temperature is obtained for the PGEs with 18 wt% PVdF-HFP, which increase the long-term stability of the gel-state DSSC. By using the 18 wt% PVdF-HFP in the presence of 5 wt% TiO2 nanofillers (NFs), gel-state cells with an efficiency of 8.38% can be obtained, which is higher than that achieved by liquid-state cells (7.55%). After 1000 h test at room temperature (RT) and 50 °C, the cell can retain 96% and 82%, respectively, of its initial efficiency.

Experimental feasibility of investigating acoustic waves in Couette flow with entropy and pressure gradients

NASA Technical Reports Server (NTRS)

Parrott, Tony L.; Zorumski, William E.; Rawls, John W., Jr.

1990-01-01

The feasibility is discussed for an experimental program for studying the behavior of acoustic wave propagation in the presence of strong gradients of pressure, temperature, and flow. Theory suggests that gradients effects can be experimentally observed as resonant frequency shifts and mode shape changes in a waveguide. A convenient experimental geometry for such experiments is the annular region between two co-rotating cylinders. Radial temperature gradients in a spinning annulus can be generated by differentially heating the two cylinders via electromagnetic induction. Radial pressure gradients can be controlled by varying the cylinder spin rates. Present technology appears adequate to construct an apparatus to allow independent control of temperature and pressure gradients. A complicating feature of a more advanced experiment, involving flow gradients, is the requirement for independently controlled cylinder spin rates. Also, the boundary condition at annulus terminations must be such that flow gradients are minimally disturbed. The design and construction of an advanced apparatus to include flow gradients will require additional technology development.

Autecology of an arsenite chemolithotroph: sulfide constraints on function and distribution in a geothermal spring.

PubMed

D'Imperio, Seth; Lehr, Corinne R; Breary, Michele; McDermott, Timothy R

2007-11-01

Previous studies in an acid-sulfate-chloride spring in Yellowstone National Park found that microbial arsenite [As(III)] oxidation is absent in regions of the spring outflow channel where H(2)S exceeds approximately 5 microM and served as a backdrop for continued efforts in the present study. Ex situ assays with microbial mat samples demonstrated immediate As(III) oxidation activity when H(2)S was absent or at low concentrations, suggesting the presence of As(III) oxidase enzymes that could be reactivated if H(2)S is removed. Cultivation experiments initiated with mat samples taken from along the H(2)S gradient in the outflow channel resulted in the isolation of an As(III)-oxidizing chemolithotroph from the low-H(2)S region of the gradient. The isolate was phylogenetically related to Acidicaldus and was characterized in vitro for spring-relevant properties, which were then compared to its distribution pattern in the spring as determined by denaturing gradient gel electrophoresis and quantitative PCR. While neither temperature nor oxygen requirements appeared to be related to the occurrence of this organism within the outflow channel, H(2)S concentration appeared to be an important constraint. This was verified by in vitro pure-culture modeling and kinetic experiments, which suggested that H(2)S inhibition of As(III) oxidation is uncompetitive in nature. In summary, the studies reported herein illustrate that H(2)S is a potent inhibitor of As(III) oxidation and will influence the niche opportunities and population distribution of As(III) chemolithotrophs.

Autecology of an Arsenite Chemolithotroph: Sulfide Constraints on Function and Distribution in a Geothermal Spring▿

PubMed Central

D'Imperio, Seth; Lehr, Corinne R.; Breary, Michele; McDermott, Timothy R.

2007-01-01

Previous studies in an acid-sulfate-chloride spring in Yellowstone National Park found that microbial arsenite [As(III)] oxidation is absent in regions of the spring outflow channel where H2S exceeds ∼5 μM and served as a backdrop for continued efforts in the present study. Ex situ assays with microbial mat samples demonstrated immediate As(III) oxidation activity when H2S was absent or at low concentrations, suggesting the presence of As(III) oxidase enzymes that could be reactivated if H2S is removed. Cultivation experiments initiated with mat samples taken from along the H2S gradient in the outflow channel resulted in the isolation of an As(III)-oxidizing chemolithotroph from the low-H2S region of the gradient. The isolate was phylogenetically related to Acidicaldus and was characterized in vitro for spring-relevant properties, which were then compared to its distribution pattern in the spring as determined by denaturing gradient gel electrophoresis and quantitative PCR. While neither temperature nor oxygen requirements appeared to be related to the occurrence of this organism within the outflow channel, H2S concentration appeared to be an important constraint. This was verified by in vitro pure-culture modeling and kinetic experiments, which suggested that H2S inhibition of As(III) oxidation is uncompetitive in nature. In summary, the studies reported herein illustrate that H2S is a potent inhibitor of As(III) oxidation and will influence the niche opportunities and population distribution of As(III) chemolithotrophs. PMID:17827309

Knee temperatures measured in vivo after arthroscopic ACL reconstruction followed by cryotherapy with gel-packs or computer controlled heat extraction.

PubMed

Rashkovska, Aleksandra; Trobec, Roman; Avbelj, Viktor; Veselko, Matjaž

2014-09-01

To obtain in vivo data about intra- and extra-articular knee temperatures to assess the effectiveness of two cryotherapeutic methods-conventional cooling with gel-packs and computer controlled cryotherapy following anterior cruciate ligament (ACL) reconstructive surgery. Twenty patients were arbitrarily assigned for cryotherapy after ACL reconstruction: 8 patients with frozen gel-packs and 12 patients with computer controlled cryotherapy with constant temperatures of the cooling liquid in the knee pads. The treatment was performed for 12 h. Temperatures were measured with two thermo sensors in catheters placed intraarticularly and subcutaneously, four sensors on the skin and one sensor under protective bandage, every second for 16 h after surgery. In the first 2 h of treatment, there were no significant differences (n.s.) between the groups in temperatures in the intracondylar notch. After 4 h of cryotherapy, the temperatures were significantly lower on the skin (24.6 ± 2.8 and 31.4 ± 1.3 °C, p < 0.01) and in the subcutaneous tissue (28.6 ± 5.7 and 34.6 ± 1.4 °C, p = 0.01), and the difference between the temperature in the intracondylar notch and the subcutaneous tissue was significantly greater (4.0 ± 3.0 and 0.8 ± 0.6 °C, p = 0.01) in the computer controlled cryotherapy group compared to the gel-pack group. The cooling effect of the arthroscopy irrigation fluid on the knee temperature is evident in the first 2 h of treatment. The energy extraction is significantly more effective and controllable by computer controlled cryotherapy than with frozen gel-packs. Prospective comparative study, Level II.

Hierarchical Sol-Gel Transition Induced by Thermosensitive Self-Assembly of an ABC Triblock Polymer in an Ionic Liquid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kitazawa, Yuzo; Ueki, Takeshi; McIntosh, Lucas D.

2016-04-29

Here we investigate a hierarchical morphology change and accompanying sol–gel transition using a doubly thermosensitive ABC-triblock copolymer in an ionic liquid (IL). The triblock copolymer contains two different lower critical solution temperature (LCST) thermosensitive polymers, poly(benzyl methacrylate) (PBnMA) and poly(2-phenylethyl methacrylate) (PPhEtMA), as the end blocks and poly(methyl methacrylate) (PMMA) as the middle block (PBnMA-b-PMMA-b-PPhEtMA: BMP). BMP undergoes a hierarchical phase transition corresponding to the self-assembly of each of the thermosensitive blocks in the IL, and a sol–gel transition was observed in concentrated, above 10 wt %, polymer solutions. The gelation behavior was affected by polymer concentration, and at 20more » wt %, the BMP/IL composite showed a phase transition, with increasing temperature, from solution through a jammed micelle suspension to a physically cross-linked gel. For each phase was formed reversibly and rapidly over the corresponding temperature range. Finally, the jammed micelle and cross-linked gel states were characterized using viscoelastic measurements and small-angle X-ray scattering (SAXS).« less

The Influence of Wavelength-Dependent Absorption and Temperature Gradients on Temperature Determination in Laser-Heated Diamond-Anvil Cells

NASA Astrophysics Data System (ADS)

Deng, J.; Lee, K. K. M.; Du, Z.; Benedetti, L. R.

2016-12-01

In situ temperature measurements in the laser-heated diamond-anvil cell (LHDAC) are among the most fundamental experiments undertaken in high-pressure science. Despite its importance, few efforts have been made to examine the alteration of thermal radiation spectra of hot samples by wavelength-dependent absorption of the sample itself together with temperature gradients within samples while laser heating and their influence on temperature measurement. For example, iron-bearing minerals show strong wavelength dependent absorption in the wavelength range used to determine temperature, which, together with temperature gradients can account for largely aliased apparent temperatures (e.g., 1200 K deviation for a 4000 K melting temperature) in some experiments obtained by fitting of detected thermal radiation intensities. As such, conclusions of melting temperatures, phase diagrams and partitioning behavior, may be grossly incorrect for these materials. In general, wavelength-dependent absorption and temperature gradients of samples are two key factors to consider in order to rigorously constrain temperatures, which have been largely ignored in previous LHDAC studies. A reevaluation of temperatures measured in recent high-profile papers will be reviewed.

Method of controlling a resin curing process. [for fiber reinforced composites

NASA Technical Reports Server (NTRS)

Webster, Charles Neal (Inventor); Scott, Robert O. (Inventor)

1989-01-01

The invention relates to an analytical technique for controlling the curing process of fiber-reinforced composite materials that are formed using thermosetting resins. The technique is the percent gel method and involves development of a time-to-gel equation as a function of temperature. From this equation a rate-of-gel equation is then determined, and a percent gel is calculated which is the product of rate-of-gel times time. Percent gel accounting is used to control the proper pressure application point in an autoclave cure process to achieve desired properties in a production composite part.

Analysis of shade, temperature and hydrogen peroxide concentration during dental bleaching: in vitro study with the KTP and diode lasers.

PubMed

Fornaini, C; Lagori, G; Merigo, E; Meleti, M; Manfredi, M; Guidotti, R; Serraj, A; Vescovi, P

2013-01-01

Many dental bleaching techniques are now available, several of them using a laser source. However, the literature on the exact role of coherent light in the biochemical reaction of the whitening process is very discordant. The aims of this in vitro study were: (1) to compare two different laser sources, a KTP laser with a wavelength of 532 nm and a diode laser with a wavelength of 808 nm, during dental bleaching, and (2) to investigate the relationships among changes in gel temperature, tooth shade and hydrogen peroxide (HP) concentration during laser irradiation. Altogether, 116 bovine teeth were bleached using a 30% HP gel, some of them with gel only and others with gel plus one of the two lasers (532 or 808 nm) at two different powers (2 and 4 W). The KTP laser produced a significant shade variation with a minimal temperature increase. The diode laser led to a higher temperature increase with a greater reduction in HP concentration, but the change in shade was only statistically significant with a power of 4 W. At a power of 2 W, the KTP laser caused a greater change in shade than the diode laser. No significant correlations were found among temperature, HP concentration and shade variation. The KTP laser appears to provide better results with less dangerous thermal increases than the diode laser. This might call into question most of the literature affirming that the action of laser bleaching is by increasing the gel temperature and, consequently, the speed of the redox reaction. Further study is required to investigate the correlations between the parameters investigated and efficacy of the bleaching process.

In situ synthesis-gelation at room temperature vs. heating-cooling procedure. Fine tuning of molecular gels derived from succinic acid and L-valine.

PubMed

Fontanillo, Miriam; Angulo-Pachón, César A; Escuder, Beatriu; Miravet, Juan F

2013-12-15

The reaction between succinic anhydride and a diamine derived from L-valine should afford efficiently a molecular gelator. Based on this reaction, it should be feasible to prepare molecular gels at room temperature, avoiding the conventional thermal treatment required for the solubilization of the gelator, by in situ, simultaneous, synthesis and gelation. The gels prepared by in situ and conventional heating-cooling protocols could present important differences relevant for potential practical applications of these materials. The gelator was synthesized by reaction of succinic anhydride and a diamine derived from L-valine, affording two new amide bonds. The molecular gels were studied by IR, NMR, electron microscopy, X-ray diffraction and DSC. The results indicate that different polymorphic fibrillar networks are formed depending on the gel preparation method, highlighting how the properties of molecular gels can be tuned in this way. Significant differences between thermal and in situ gels were found in properties such as thermal stability, thixotropic behavior or release of an entrapped dye. In situ synthesis-gelation has also been shown to provide gels in media such as oleic acid which cannot be jellified by conventional heating-cooling procedures. Copyright © 2013 Elsevier Inc. All rights reserved.

Body Temperature Controlled Optical and Thermal Information Storage Light Scattering Display with Fluorescence Effect and High Mechanical Strength.

PubMed

Chen, Si; Tong, Xiaoqian; He, Huiwen; Ma, Meng; Shi, Yanqin; Wang, Xu

2017-04-05

A kind of body temperature controlled optical and thermal information storage light scattering display based on super strong liquid crystalline physical gel with special "loofah-like gel network" was successfully prepared. Such liquid crystal (LC) gel was obtained by mixing a dendritic gelator (POSS-G1-BOC), an azobenzene compound (2Azo2), and a phosphor tethered liquid crystalline host (5CB), which could show its best contrast ratio at around human body temperature under UV light because of the phosphor's fluorescence effect. The gel also has quite strong mechanical strength, which could be used in wearable device field especially under sunlight, even under the forcing conditions as harsh as being centrifuged for 10 min at the speed of 2000 r/min. The whole production process of such a display is quite simple and could lead to displays at any size through noncontact writing. We believe it will have wide applications in the future.

Naphthalene biodegradation in temperate and arctic marine microcosms.

PubMed

Bagi, Andrea; Pampanin, Daniela M; Lanzén, Anders; Bilstad, Torleiv; Kommedal, Roald

2014-02-01

Naphthalene, the smallest polycyclic aromatic hydrocarbon (PAH), is found in abundance in crude oil, its major source in marine environments. PAH removal occurs via biodegradation, a key process determining their fate in the sea. Adequate estimation of PAH biodegradation rates is essential for environmental risk assessment and response planning using numerical models such as the oil spill contingency and response (OSCAR) model. Using naphthalene as a model compound, biodegradation rate, temperature response and bacterial community composition of seawaters from two climatically different areas (North Sea and Arctic Ocean) were studied and compared. Naphthalene degradation was followed by measuring oxygen consumption in closed bottles using the OxiTop(®) system. Microbial communities of untreated and naphthalene exposed samples were analysed by polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) and pyrosequencing. Three times higher naphthalene degradation rate coefficients were observed in arctic seawater samples compared to temperate, at all incubation temperatures. Rate coefficients at in situ temperatures were however, similar (0.048 day(-1) for temperate and 0.068 day(-1) for arctic). Naphthalene biodegradation rates decreased with similar Q10 ratios (3.3 and 3.5) in both seawaters. Using the temperature compensation method implemented in the OSCAR model, Q10 = 2, biodegradation in arctic seawater was underestimated when calculated from the measured temperate k1 value, showing that temperature difference alone could not predict biodegradation rates adequately. Temperate and arctic untreated seawater communities were different as revealed by pyrosequencing. Geographic origin of seawater affected the community composition of exposed samples.

A chitosan/beta-glycerophosphate thermo-sensitive gel for the delivery of ellagic acid for the treatment of brain cancer.

PubMed

Kim, Sungwoo; Nishimoto, Satoru K; Bumgardner, Joel D; Haggard, Warren O; Gaber, M Waleed; Yang, Yunzhi

2010-05-01

We report here the development of a chitosan/beta-glycerophosphate(Ch/beta-GP) thermo-sensitive gel to deliver ellagic acid (EA) for cancer treatment. The properties of the Ch/beta-GP gels were characterized regarding chemical structure, surface morphology, and viscoelasticity. In vitro EA release rate from the EA loaded Ch/beta-GP gel and chitosan degradation rate were investigated. The anti-tumor effect of the EA loaded Ch/beta-GP gel on brain cancer cells (human U87 glioblastomas and rat C6 glioma cells) was evaluated by examining cell viability. Cell number and activity were monitored by the MTS assay. The Ch/beta-GP solution formed a heat-induced gel at body temperature, and the gelation temperature and time were affected by the final pH of the Ch/beta-GP solution. The lysozyme increased the EA release rate by 2.5 times higher than that in the absence of lysozyme. Dialyzed chitosan solution with final pH 6.3 greatly reduced the beta-GP needed for gelation, thereby significantly improving the biocompatibility of gel (p < 0.001). The chitosan gels containing 1% (w/v) of ellagic acid significantly reduced viability of U87 cells and C6 cells compared with the chitosan gels at 3 days incubation (p < 0.01, and p < 0.001, respectively). Copyright 2010 Elsevier Ltd. All rights reserved.

Chitosan-based thermosensitive hydrogel as a promising ocular drug delivery system: preparation, characterization, and in vivo evaluation.

PubMed

Chen, Xingwei; Li, Xinru; Zhou, Yanxia; Wang, Xiaoning; Zhang, Yanhui; Fan, Yating; Huang, Yanqing; Liu, Yan

2012-11-01

The purpose of this study was to evaluate the feasibility of in situ thermosensitive hydrogel based on chitosan in combination with disodium α-d-Glucose 1-phosphate (DGP) for ocular drug delivery system. Aqueous solution of chitosan/DGP underwent sol-gel transition as temperature increased which was flowing sol at room temperature and then turned into non-flowing hydrogel at physiological temperature. The properties of gels were characterized regarding gelation time, gelation temperature, and morphology. The sol-to-gel phase transition behaviors were affected by the concentrations of chitosan, DGP and the model drug levocetirizine dihydrochloride (LD). The developed hydrogel presented a characteristic of a rapid release at the initial period followed by a sustained release and remarkably enhanced the cornea penetration of LD. The results of ocular irritation demonstrated the excellent ocular tolerance of the hydrogel. The ocular residence time for the hydrogel was significantly prolonged compared with eye drops. The drug-loaded hydrogel produced more effective anti-allergic conjunctivitis effects compared with LD aqueous solution. These results showed that the chitosan/DGP thermosensitive hydrogel could be used as an ideal ocular drug delivery system in terms of the suitable sol-gel transition temperature, mild pH environment in the hydrogel as well as the organic solvent free.

The extrusion test and sensory perception revisited: Some comments on generality and the effect of measurement temperature.

PubMed

Brenner, Tom; Tomczyńska-Mleko, Marta; Mleko, Stanisław; Nishinari, Katsuyoshi

2017-12-01

Relations between sensory perception, extrusion and fracture in shear, extension and compression are examined. Gelatin-based gels are perceived as less firm and less hard than expected based on their mechanical properties compared to polysaccharide gels that have the same mechanical properties at room temperature but melt well above body temperature, underlying the importance of the measurement temperature for gels that melt during mastication. Correlations between parameters from extrusion and compression, extension and shear are verified using mixed polysaccharide gels. We previously reported a high correlation between several sensory attributes and parameters from an extrusion test. The extrusion test showed the most robust correlation, and could be used to assess samples at both extremes of the texture range with respect to elasticity, for example, both samples that could not be extended as their very low elasticity led to their fracture during handling, as well as samples that could not be fractured in compression. Here, we reexamine the validity of the relations reported. We demonstrate the generality of the relations between large deformation tests and extrusion, but the findings underscore the need to take into account the measurement temperature for samples that melt during mastication when correlating instrumental parameters with sensory perception. © 2017 Wiley Periodicals, Inc.

Temperature gradient interaction chromatography of polymers: A molecular statistical model.

PubMed

Radke, Wolfgang; Lee, Sekyung; Chang, Taihyun

2010-11-01

A new model describing the retention in temperature gradient interaction chromatography of polymers is developed. The model predicts that polymers might elute in temperature gradient interaction chromatography in either an increasing or decreasing order or even nearly independent of molar mass, depending on the rate of the temperature increase relative to the flow rate. This is in contrast to solvent gradient elution, where polymers elute either in order of increasing molar mass or molar mass independent. The predictions of the newly developed model were verified with the literature data as well as new experimental data. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rheological, mechanical and degradable properties of injectable chitosan/silk fibroin/hydroxyapatite/glycerophosphate hydrogels.

PubMed

Wu, Jingjing; Liu, Jiaoyan; Shi, Yanmei; Wan, Ying

2016-12-01

Silk fibroin (SF) and hydroxyapatite (HA) were incorporated into chitosan/glycerophosphate (GP) system to prepare new types of hydrogels. The formulated chitosan/SF/GP and chitosan/SF/HA/GP solutions were found to be injectable at room temperature, and able to form into hydrogels at near-physiological temperature and pH. Rheological measurements showed that elastic modulus of certain chitosan/SF/GP and chitosan/SF/HA/GP gels could reach around 1.8 and 15kPa, respectively, and was much higher than their respective viscous modulus. Compressive measurements revealed that some chitosan/SF/GP and chitosan/SF/HA/GP gels had 8 and 20-fold modulus and strength higher than the chitosan/GP gel, respectively, confirming that compressive properties of these gels were greatly improved. Results obtained from in vivo degradation demonstrated that degradation endurance of the optimized chitosan/SF/GP and chitosan/SF/HA/GP gels was significantly enhanced as compared to the chitosan/GP gel, and the degradation rate of the gels could be regulated by the SF component alone or by the combination of SF and HA components. Copyright © 2016 Elsevier Ltd. All rights reserved.

Physically Gelled Room-Temperature Ionic Liquid-Based Composite Membranes for CO2/N-2 Separation: Effect of Composition and Thickness on Membrane Properties and Performance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, PT; Voss, BA; Wiesenauer, EF

2013-07-03

An aspartame-based, low molecular-weight organic gelator (LMOG) was used to form melt-infused and composite membranes with two different imidazolium-based room-temperature ionic liquids (RTILs) for CO2 separation from N-2. Previous work demonstrated that LMOGs can gel RTILs at low, loading levels, and this aspartame-based LMOG was selected because it has been reported to gel a large number of RTILs. The imidazolium-based RTILs were used because of their inherent good properties for CO2/light gas separations. Analysis of the resulting bulk RTIL/LMOG physical gels showed that these materials have high sol-gel transition temperatures (ca. 135 degrees C) suitable for flue gas applications. Gasmore » permeabilities and burst pressure measurements of thick, melt infused membranes revealed a trade-off between high CO2 permeabilities and good mechanical stability as a function of the LMOG loading. Defect-free, composite membranes of the gelled RTILs were successfully fabricated by choosing an appropriate porous membrane support (hydrophobic PTFE) using a suitable coating technique (roller coating). The thicknesses of the applied composite gel layers ranged from 10.3 to 20.7 mu m, which represents an order of magnitude decrease in active layer thickness, compared to the original melt-infused gel RTIL membranes.« less

Diversity and dynamics of lactobacilli populations during ripening of RDO Camembert cheese.

PubMed

Henri-Dubernet, Ségolène; Desmasures, Nathalie; Guéguen, Micheline

2008-03-01

The diversity and dynamics of Lactobacillus populations in traditional raw milk Camembert cheese were monitored throughout the manufacturing process in 3 dairies. Culture-dependent analysis was carried out on isolates grown on acidified de Man - Rogosa - Sharpe agar and Lactobacillus anaerobic de Man Rogosa Sharpe agar supplemented with vancomycin and bromocresol green media. The isolates were identified by polymerase chain reaction - temperature gradient gel electrophoresis (PCR-TGGE) and (or) species-specific PCR and (or) sequencing, and Lactobacillus paracasei and Lactobacillus plantarum isolates were characterized by pulsed field gel electrophoresis (PFGE). Milk and cheese were subjected to culture-independent analysis by PCR-TGGE. Presumed lactobacilli were detected by plate counts throughout the ripening process. However, molecular analysis of total DNA and DNA of isolates failed to detect Lactobacillus spp. in certain cases. The dominant species in the 3 dairies was L. paracasei. PFGE analysis revealed 21 different profiles among 39 L. paracasei isolates. Lactobacillus plantarum was the second most isolated species, but it occurred nearly exclusively in one dairy. The other species isolated were Lactobacillus parabuchneri, Lactobacillus fermentum, Lactobacillus acidophilus, Lactobacillus helveticus, a Lactobacillus psittaci/delbrueckii subsp. bulgaricus/gallinarum/crispatus group, Lactobacillus rhamnosus, Lactobacillus delbrueckii subsp. bulgaricus, L. delbrueckii subsp. lactis, Lactobacillus brevis, Lactobacillus kefiri, and Lactobacillus perolens. Lactobacilli diversity at the strain level was high. Dynamics varied among dairies, and each cheese exhibited a specific picture of species and strains.

Sintering and microstructure of silicon carbide ceramic with Y3Al5O12 added by sol-gel method*

PubMed Central

Guo, Xing-zhong; Yang, Hui

2005-01-01

Silicon carbide (SiC) ceramic with YAG (Y3Al5O12) additive added by sol-gel method was liquid-phase sintered at different sintering temperatures, and the sintering mechanism and microstructural characteristics of resulting silicon carbide ceramics were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and elemental distribution of surface (EDS). YAG (yttrium aluminum garnet) phase formed before the sintering and its uniform distribution in the SiC/YAG composite powder decreased the sintering temperature and improved the densification of SiC ceramic. The suitable sintering temperature was 1860 °C with the specimen sintered at this temperature having superior sintering and mechanical properties, smaller crystal size and fewer microstructure defects. Three characteristics of improved toughness of SiC ceramic with YAG added by sol-gel method were microstructural densification, main-crack deflection and crystal ‘bridging’. PMID:15682507

A sandwich-designed temperature-gradient incubator for studies of microbial temperature responses.

PubMed

Elsgaard, Lars; Jørgensen, Leif Wagner

2002-03-01

A temperature-gradient incubator (TGI) is described, which produces a thermal gradient over 34 aluminium modules (15x30x5 cm) intersected by 2-mm layers of partly insulating graphite foil (SigraFlex Universal). The new, sandwich-designed TGI has 30 rows of six replicate sample wells for incubation of 28-ml test tubes. An electric plate heats one end of the TGI, and the other end is cooled by thermoelectric Peltier elements in combination with a liquid cooling system. The TGI is equipped with 24 calibrated Pt-100 temperature sensors and insulated by polyurethane plates. A PC-operated SCADA (Supervisory Control And Data Acquisition) software (Genesis 4.20) is applied for temperature control using three advanced control loops. The precision of the TGI temperature measurements was better than +/-0.12 degrees C, and for a 0-40 degrees C gradient, the temperature at the six replicate sample wells varied less than +/-0.04 degrees C. Temperatures measured in incubated water samples closely matched the TGI temperatures, which showed a linear relationship to the sample row number. During operation for 8 days with a gradient of 0-40 degrees C, the temperature at the cold end was stable within +/-0.02 degrees C, while the temperatures at the middle and the warm end were stable within +/-0.08 degrees C (n=2370). Using the new TGI, it was shown that the fine-scale (1 degrees C) temperature dependence of S(o) oxidation rates in agricultural soil (0-29 degrees C) could be described by the Arrhenius relationship. The apparent activation energy (E(a)) for S(o) oxidation was 79 kJ mol(-1), which corresponded to a temperature coefficient (Q(10)) of 3.1. These data demonstrated that oxidation of S(o) in soil is strongly temperature-dependent. In conclusion, the new TGI allowed a detailed study of microbial temperature responses as it produced a precise, stable, and certifiable temperature gradient by the new and combined use of sandwich-design, thermoelectric cooling, and advanced control loops. The sandwich-design alone reduced the disadvantageous thermal gradient over individual sample wells by 56%.

Agricultural scene understanding

NASA Technical Reports Server (NTRS)

Landgrebe, D. A. (Principal Investigator); Bauer, M. E.; Silva, L.; Hoffer, R. M.; Baumgardner, M. F.

1977-01-01

The author has identified the following significant results. The LACIE field measurement data were radiometrically calibrated. Calibration enabled valid comparisons of measurements from different dates, sensors, and/or locations. Thermal band canopy results included: (1) Wind velocity had a significant influence on the overhead radiance temperature and the effect was quantized. Biomass and soil temperatures, temperature gradient, and canopy geometry were altered. (2) Temperature gradient was a function of wind velocity. (3) Temperature gradient of the wheat canopy was relatively constant during the day. (4) The laser technique provided good quality geometric characterization.

Broadband reflective liquid crystalline gels due to the ultraviolet light screening made by the liquid crystal

NASA Astrophysics Data System (ADS)

Relaix, Sabrina; Bourgerette, Christian; Mitov, Michel

2006-12-01

It is shown that the natural ultraviolet light absorbing properties of the liquid crystal constituent during the photoinduced elaboration of a liquid crystalline gel induce the broadening of the reflection bandwidth. The polymer component is then included in a resin by preserving its spatial distribution, and transmission electron microscopy investigations of cross sections show the existence of a structure gradient, which is at the origin of the broadening phenomenon. Such reflectors may be of interest for reflective polarizer-free displays or smart windows for the control of solar light for which a broadband reflection is required.

Passive and active sol-gel materials and devices

NASA Astrophysics Data System (ADS)

Andrews, Mark P.; Najafi, S. Iraj

1997-07-01

This paper examines sol-gel materials for photonics in terms of partnerships with other material contenders for processing optical devices. The discussion in four sections identifies semiconductors, amorphous and crystalline inorganic dielectrics, and amorphous and crystalline organic dielectrics as strategic agents in the rapidly evolving area of materials and devices for data communications and telecommunications. With Zyss, we trace the hierarchical lineage that connects molecular hybridization (chemical functionality), through supramolecular hybridization (collective properties and responses), to functional hybridization (device and system level constructs). These three concepts thread their way through discussions of the roles sol-gel glasses might be anticipated to assume in a photonics marketplace. We assign a special place to glass integrated optics and show how high temperature consolidated sol-gel derived glasses fit into competitive glass fabrication technologies. Low temperature hybrid sol-gel glasses that combine attractive features of organic polymers and inorganic glasses are considered by drawing on examples of our own new processes for fabricating couplers, power splitters, waveguides and gratings by combining chemical synthesis and sol-gel processing with simple photomask techniques.

Vibrational spectroscopic studies of (3-mercaptopropyl)trimethoxylsilane sol-gel and its coating.

PubMed

Li, Ying-Sing; Wang, Yu; Tran, Tuan; Perkins, Anshion

2005-10-01

Organosilane sol-gels have been prepared under different conditions from mercaptopropyltrimethoxysilane (MPTMS) and mercaptopropyltriethoxysilane (MPTES). These sol-gels were applied for the thin film coating on aluminum. Vibrational spectroscopy has been employed to trace and to study the proceeding of the sol-gel formation and the curing of the coated films on Al. Based on the group frequencies as well as their spectral behavior under different conditions, vibrational assignments have been made for most of the observed bands. Surface enhanced Raman scattering has revealed the chemical adsorption of MPTMS sol-gel on silver particles. Recorded reflection and absorption infrared (RAIR) spectra of coated tiles cured at different temperatures have indicated that surface reaction may occur at high temperature. The anticorrosion characters of the coated metals have been evaluated with the measured electrochemical data. Results from cyclic voltammographs have indicated that each layer of sol-gel coating would reduce the redox current across the electrode/electrolyte solution interface. Tafel plots have shown that the anodic current of the coated electrode decreases significantly and the corrosion potentials shift to the positive side.

Apparatus for the production of gel beads containing a biocatalyst

DOEpatents

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

1998-03-19

An apparatus is described for the large-scale and continuous production of gel beads containing a biocatalyst. The apparatus is a columnar system based on the chemical cross-linking of hydrocolloidal gels that contain and immobilize a biocatalyst, the biocatalyst being a microorganism or an enzyme. Hydrocolloidal gels, such as alginate, carrageenan, and a mixture of bone gelatin and modified alginate, provide immobilization matrices that can be used to entrap and retain the biocatalyst while allowing effective contact with substrates and release of products. Such immobilized biocatalysts are generally formulated into small spheres or beads that have high concentrations of the biocatalyst within the gel matrix. The columnar system includes a gel dispersion nozzle submerged in a heated non-interacting liquid, typically an organic liquid, that is immiscible with water to allow efficient formation of spherical gel droplets, the non-interacting liquid having a specific gravity that is less than water so that the gel droplets will fall through the liquid by the force of gravity. The heated non-interacting liquid is in direct contact with a chilled upflowing non-interacting liquid that will provide sufficient residence time for the gel droplets as they fall through the liquid so that they will be cooled below the gelling temperature and form solid spheres. The upflowing non-interacting liquid is in direct contact with an upflowing temperature-controlled aqueous solution containing the necessary chemicals for cross-linking or fixing of the gel beads to add the necessary stability. The flow rates of the two liquid streams can be varied to control the proper residence time in each liquid section to accommodate the production of gel beads of differing settling velocities. A valve is provided for continuous removal of the stabilized gel beads from the bottom of the column. 1 fig.

Apparatus and method for the production of gel beads containing a biocatalyst

DOEpatents

Scott, Charles D.; Scott, Timothy C.; Davison, Brian H.

1998-01-01

An apparatus and method for the large-scale and continuous production of gel beads containing a biocatalyst. The apparatus is a columnar system based on the chemical cross-linking of hydrocolloidal gels that contain and immobilize a biocatalyst, the biocatalyst being a microorganism or an enzyme. Hydrocolloidal gels, such as alginate, carrageenan, and a mixture of bone gelatin and modified alginate, provide immobilization matrices that can be used to entrap and retain the biocatalyst while allowing effective contact with substrates and release of products. Such immobilized biocatalysts are generally formulated into small spheres or beads that have high concentrations of the biocatalyst within the gel matrix. The columnar system includes a gel dispersion nozzle submerged in a heated non-interacting liquid, typically an organic liquid, that is immiscible with water to allow efficient formation of spherical gel droplets, the non-interacting liquid having a specific gravity that is less than water so that the gel droplets will fall through the liquid by the force of gravity. The heated non-interacting liquid is in direct contact with a chilled upflowing non-interacting liquid that will provide sufficient residence time for the gel droplets as they fall through the liquid so that they will be cooled below the gelling temperature and form solid spheres. The upflowing non-interacting liquid is in direct contact with an upflowing temperature-controlled aqueous solution containing the necessary chemicals for cross-linking or fixing of the gel beads to add the necessary stability. The flow rates of the two liquid streams can be varied to control the proper residence time in each liquid section to accommodate the production of gel beads of differing settling velocities. A valve is provided for continuous removal of the stabilized gel beads from the bottom of the column.

Apparatus for the production of gel beads containing a biocatalyst

DOEpatents

Scott, Charles D.; Scott, Timothy C.; Davison, Brian H.

1998-01-01

An apparatus for the large-scale and continuous production of gel beads containing a biocatalyst. The apparatus is a columnar system based on the chemical cross-linking of hydrocolloidal gels that contain and immobilize a biocatalyst, the biocatalyst being a microorganism or an enzyme. Hydrocolloidal gels, such as alginate, carrageenan, and a mixture of bone gelatin and modified alginate, provide immobilization matrices that can be used to entrap and retain the biocatalyst while allowing effective contact with substrates and release of products. Such immobilized biocatalysts are generally formulated into small spheres or beads that have high concentrations of the biocatalyst within the gel matrix. The columnar system includes a gel dispersion nozzle submerged in a heated non-interacting liquid, typically an organic liquid, that is immiscible with water to allow efficient formation of spherical gel droplets, the non-interacting liquid having a specific gravity that is less than water so that the gel droplets will fall through the liquid by the force of gravity. The heated non-interacting liquid is in direct contact with a chilled upflowing non-interacting liquid that will provide sufficient residence time for the gel droplets as they fall through the liquid so that they will be cooled below the gelling temperature and form solid spheres. The upflowing non-interacting liquid is in direct contact with an upflowing temperature-controlled aqueous solution containing the necessary chemicals for cross-linking or fixing of the gel beads to add the necessary stability. The flow rates of the two liquid streams can be varied to control the proper residence time in each liquid section to accommodate the production of gel beads of differing settling velocities. A valve is provided for continuous removal of the stabilized gel beads from the bottom of the column.

Sol-gel transition of organogels observed by terahertz spectroscopy

NASA Astrophysics Data System (ADS)

Hoshina, Hiromichi; Ozaki, Atsumi; Itagaki, Yusuke; Yajima, Setsuko; Suzuki, Hal; Ishii, Shinya; Ishida, Misaki; Uchiyama, Tetsuji; Kimura, Keiichi; Otani, Chiko

2014-07-01

Terahertz (THz) absorption spectra of organogels consisting of (1R,2R)-1,2-bis(dodecanoylamino)cyclohexane/2-nitrophenyl octyl ether (RR-BDC/NPOE) and RR-BDC/n-dodecane were measured by Fourier-transform far-infrared (FT-FIR) spectroscopy. The vibrational peaks of the gels were observed at the same frequencies as those of the pure gelator, suggesting that the intermolecular structure around the Nsbnd H⋯Odbnd C hydrogen bond is maintained in the gel phase. Temperature-dependent spectroscopy showed a drastic spectral change at the sol-gel transition temperature, in which the vibrational peak at 3.5 THz disappears and a new peak appears at 2.9 THz. The change in THz vibrational frequency is indicative of the structural collapse of the hydrogen-bonded fibrous architecture in the sol phase.

Comparison of benthic bacterial community composition in nine streams

Treesearch

Xueqing Gao; Ola A. Olapade; Laura G. Leff

2005-01-01

In this study, the abundance of major bacterial taxa (based on fluorescent in situ hybridization, FISH) and the structure of the bacterial community (based on denaturing gradient gel electrophoresis, DGGE) were determined in the benthos of 9 streams in the southeastern and midwestern United States and related to differences in environmental...

Camparison of benthic bacterial community composition in nine streams

Treesearch

Xuqing Gao; Ola A. Olapade; Laura G. Leff

2005-01-01

In this study, the abundance of major bacterial taxa (based on fluorescent in situ hybridization, FISH) and the structure of the bacterial community (based on denaturing gradient gel electrophoresis, DGGE) were determined in the benthos of 9 streams in the southeastern and midwestern United States and related to differences in environmental conditions. Taxa examined...

Denaturing gradient gel electrophoresis-polymerase chain reaction comparison of chitosan effects on anaerobic cultures of broiler cecal bacteria and Salmonella Typhimurium

USDA-ARS?s Scientific Manuscript database

Salmonella colonization and product contamination are major poultry industry problems. Alternatives to traditional antibiotics against Salmonella offer the potential to lessen the development of resistance to antibiotics of importance to human health. The chitin derivative chitosan has drawn substa...

Controlled release from a composite silicone/hydrogel membrane.

PubMed

Hu, Z; Wang, C; Nelson, K D; Eberhart, R C

2000-01-01

To enhance the drug uptake and release capacity of silicone rubber (SR), N-isopropylacrylamide (NIPA) hydrogel particles have been incorporated into a SR membrane. The NIPA particles were thoroughly blended with uncured SR with a certain ratio at room temperature. The mixture was then cast in a Petri dish to 1 mm thickness and cured 10 hours at 90 degrees C. The SR/NIPA composite gel can absorb water approximately equal to its dry weight. Brilliant blue, used as a mock drug, was loaded into the composite gel. Drug release increased exponentially to a final value that is temperature dependent: low at T> =34 degrees C, and high at T< 34 degrees C. This finding is because the hydrophobicity of NIPA changes with temperature. Pulsed release in response to temperature switching between 20 and 39 degrees C has been achieved. Drug uptake and release capability strongly depends upon the structure of the composite gel. The optimal range of NIPA composition is between 75 and 87% by volume. In the cited range, the NIPA particles form an interconnected network that provides a channel for diffusion of drug solution. The SR/NIPA composite gel has promising attributes as a wound dressing and other uses.

Identifying Time Periods of Minimal Thermal Gradient for Temperature-Driven Structural Health Monitoring

PubMed Central

Reilly, John; Glisic, Branko

2018-01-01

Temperature changes play a large role in the day to day structural behavior of structures, but a smaller direct role in most contemporary Structural Health Monitoring (SHM) analyses. Temperature-Driven SHM will consider temperature as the principal driving force in SHM, relating a measurable input temperature to measurable output generalized strain (strain, curvature, etc.) and generalized displacement (deflection, rotation, etc.) to create three-dimensional signatures descriptive of the structural behavior. Identifying time periods of minimal thermal gradient provides the foundation for the formulation of the temperature–deformation–displacement model. Thermal gradients in a structure can cause curvature in multiple directions, as well as non-linear strain and stress distributions within the cross-sections, which significantly complicates data analysis and interpretation, distorts the signatures, and may lead to unreliable conclusions regarding structural behavior and condition. These adverse effects can be minimized if the signatures are evaluated at times when thermal gradients in the structure are minimal. This paper proposes two classes of methods based on the following two metrics: (i) the range of raw temperatures on the structure, and (ii) the distribution of the local thermal gradients, for identifying time periods of minimal thermal gradient on a structure with the ability to vary the tolerance of acceptable thermal gradients. The methods are tested and validated with data collected from the Streicker Bridge on campus at Princeton University. PMID:29494496

Dynamics of a camphoric acid boat at the air-water interface

NASA Astrophysics Data System (ADS)

Akella, V. S.; Singh, Dhiraj K.; Mandre, Shreyas; Bandi, M. M.

2018-05-01

We report experiments on an agarose gel tablet loaded with camphoric acid (c-boat) spontaneously set into motion by surface tension gradients on the water surface. We observe three distinct modes of c-boat motion: harmonic mode where the c-boat speed oscillates sinusoidally in time, a steady mode where the c-boat maintains constant speed, and an intermittent mode where the c-boat maintains near-zero speed between sudden jumps in speed. Whereas all three modes have been separately reported before in different systems, controlled release of Camphoric Acid (CA) from the agarose gel matrix allowed the observation of all the three modes in the same system. These three modes are a result of a competition between the driving (surface tension gradients) and drag forces acting on the c-boat. Moreover we suggest that there exist two time scales corresponding to spreading of CA and boat motion and the mismatch of these two time scales give rise to the three modes in boat motion. We reproduced all the modes of motion by varying the air-water interfacial tension using Sodium Dodecyl Sulfate (SDS).

Succession of bacterial and fungal communities during a traditional pot fermentation of rice vinegar assessed by PCR-mediated denaturing gradient gel electrophoresis.

PubMed

Haruta, Shin; Ueno, Shintaro; Egawa, Isao; Hashiguchi, Kazunori; Fujii, Akira; Nagano, Masanobu; Ishii, Masaharu; Igarashi, Yasuo

2006-05-25

Denaturing gradient gel electrophoresis (DGGE) based on small subunit rRNA gene was applied to a traditional rice vinegar fermentation process in which the conversion of rice starch into acetic acid proceeded in a pot. The fungal DGGE profile indicated that the transition from Aspergillus oryzae to Saccharomyces sp. took place at the initial stage at which alcohol production was observed. The early stage was characterized by the coexistence of Saccharomyces sp. and lactic acid bacteria. Almost all of the bacterial DGGE bands related to lactic acid bacteria were replaced by bands derived from Lactobacillus acetotolerance and Acetobacter pasteurianus at the stage at which acetic acid started to accumulate. The microbial succession, tested in three different pots, was found to be essentially identical. Among the bacteria isolated at the early stage, some species differed from those detected by DGGE. This is the first report to reveal the microbial community succession that occurs during a unique vinegar fermentation process, as determined by a culture-independent method.

Microfludic Device for Creating Ionic Strength Gradients over DNA Microarrays for Efficient DNA Melting Studies and Assay Development

PubMed Central

Petersen, Jesper; Poulsen, Lena; Birgens, Henrik; Dufva, Martin

2009-01-01

The development of DNA microarray assays is hampered by two important aspects: processing of the microarrays is done under a single stringency condition, and characteristics such as melting temperature are difficult to predict for immobilized probes. A technical solution to these limitations is to use a thermal gradient and information from melting curves, for instance to score genotypes. However, application of temperature gradients normally requires complicated equipment, and the size of the arrays that can be investigated is restricted due to heat dissipation. Here we present a simple microfluidic device that creates a gradient comprising zones of defined ionic strength over a glass slide, in which each zone corresponds to a subarray. Using this device, we demonstrated that ionic strength gradients function in a similar fashion as corresponding thermal gradients in assay development. More specifically, we noted that (i) the two stringency modulators generated melting curves that could be compared, (ii) both led to increased assay robustness, and (iii) both were associated with difficulties in genotyping the same mutation. These findings demonstrate that ionic strength stringency buffers can be used instead of thermal gradients. Given the flexibility of design of ionic gradients, these can be created over all types of arrays, and encompass an attractive alternative to temperature gradients, avoiding curtailment of the size or spacing of subarrays on slides associated with temperature gradients. PMID:19277213

Microfludic device for creating ionic strength gradients over DNA microarrays for efficient DNA melting studies and assay development.

PubMed

Petersen, Jesper; Poulsen, Lena; Birgens, Henrik; Dufva, Martin

2009-01-01

The development of DNA microarray assays is hampered by two important aspects: processing of the microarrays is done under a single stringency condition, and characteristics such as melting temperature are difficult to predict for immobilized probes. A technical solution to these limitations is to use a thermal gradient and information from melting curves, for instance to score genotypes. However, application of temperature gradients normally requires complicated equipment, and the size of the arrays that can be investigated is restricted due to heat dissipation. Here we present a simple microfluidic device that creates a gradient comprising zones of defined ionic strength over a glass slide, in which each zone corresponds to a subarray. Using this device, we demonstrated that ionic strength gradients function in a similar fashion as corresponding thermal gradients in assay development. More specifically, we noted that (i) the two stringency modulators generated melting curves that could be compared, (ii) both led to increased assay robustness, and (iii) both were associated with difficulties in genotyping the same mutation. These findings demonstrate that ionic strength stringency buffers can be used instead of thermal gradients. Given the flexibility of design of ionic gradients, these can be created over all types of arrays, and encompass an attractive alternative to temperature gradients, avoiding curtailment of the size or spacing of subarrays on slides associated with temperature gradients.

IMPROVED TEMPERATURE GRADIENT FOR MONITORING BEHAVIORAL THERMOREGULATION IN THE RAT

EPA Science Inventory

Past studies have found that the laboratory rat placed In a temperature gradient prefers temperatures that are markedly below its lower critical ambient temperature (LCT), whereas other rodents (e.g., mouse, hamster, and guinea pig) generally select thermal environments associate...

A neutral branched platinum-acetylide complex possessing a tetraphenylethylene core: preparation of a luminescent organometallic gelator and its unexpected spectroscopic behaviour during sol-to-gel transition.

PubMed

Ren, Yuan-Yuan; Wu, Nai-Wei; Huang, Junhai; Xu, Zheng; Sun, Dan-Dan; Wang, Cui-Hong; Xu, Lin

2015-10-21

A neutral branched platinum-acetylide complex TPA possessing a tetraphenylethylene core was successfully prepared, which was found to form luminescent organometallic gels in ethyl acetate. Stimulated by temperature or F(-), the reversible gel-sol transition was realized. More interestingly, TPA exhibited an unexpected blue shift of the emission during the sol-to-gel transition.

Development, in vitro and in vivo evaluation of novel injectable smart gels of azithromycin for chronic periodontitis.

PubMed

Venkatesh, M P; Kumar, T M Pramod; Avinash, B S; Kumar, G Sheela

2013-04-01

Periodontitis is an inflammatory condition affecting teeth resulting in progressive destruction of periodontal ligaments, resorption of alveolar bone and loss of teeth. Treatment of periodontitis includes surgical and non surgical management. Systemic antibiotics are also used for the treatment of periodontitis. The aim of this research was to formulate smart gel system of azithromycin (AZT) and to evaluate in vitro and in vivo for non-surgical treatment of chronic periodontitis. Azithromycin dihydrate, used systemically in the treatment of periodontitis, was formulated into smart gels using biodegradable, thermosensitive polymer Pluronic® F-127 (PF-127) and Hydroxy Ethyl Cellulose (HEC) as copolymer. The prepared smart gels were evaluated for sterility, content uniformity, gelation temperature and time, syringeability, rheological behavior, in vitro diffusion and in vivo efficacy in human patients. The prepared smart gels were clear and transparent, sterile, thermoresponsive and injectable. Viscosity of gels increased with increase in concentration of polymer/co-polymer and also with temperature. They gelled in short response time below the body temperature. In vitro release studies showed controlled drug release which was influenced significantly by the properties and concentration of PF-127 and HEC. In vivo efficacy studies showed a significant improvement (p <0.001) in clinical parameters such as gingival index, probing pocket depth, clinical attachment level, bleeding index and plaque index. The developed azithromycin smart gel system is a novel approach for the treatment of chronic periodontitis since it reduces the dose and side effects, bypasses the usual surgical procedures and improves patient compliance.

Sol-gel optics for biomeasurements

NASA Astrophysics Data System (ADS)

Lechna-Marczynska, Monika I.; Podbielska, Halina; Ulatowska-Jarza, Agnieszka; Holowacz, Iwona; Andrzejewski, Damian

2001-10-01

Sol-gel technique is a method for producing of glass-like materials without involving a melting process. Organic compounds such as alcoholates of silicon, sodium or calcium can be used. The irregular non-crystalline network forms a gel structure where the metallic atoms are bonded to oxygen atoms. Low-temperature treatment turns this gel into an inorganic glass-like structure. There are numbers of applications of these materials that can be produced in various forms and shapes. Here, silica based sol-gel bulks and thin films optodes for biomedical applications will be presented.

Influence of natural temperature gradients on measurements of xylem sap flow with thermal dissipation probes. 1. Field observations and possible remedies.

PubMed

Do, F; Rocheteau, A

2002-06-01

The thermal dissipation method is simple and widely used for measuring sap flow in large stems. As with several other thermal methods, natural temperature gradients are assumed to be negligible in the sapwood being measured. We studied the magnitude and variability of natural temperature gradients in sapwood of Acacia trees growing in the Sahelian zone of Senegal, analyzed their effects on sap flow measurements, and investigated possible solutions. A new measurement approach employing cyclic heating (45 minutes of heating and 15 minutes of cooling; 45/15) was also tested. Three-day measurement sequences that included 1 day without heating, a second day with continuous heating and a third day with cyclic heating were recorded during a 6.5-month period using probes installed at three azimuths in a tree trunk. Natural temperature gradients between the two probes of the sensor unit, spaced 8 to 10 cm vertically, were rarely negligible (i.e., < 0.2 degrees C): they were positive during the night and negative during the day, with an amplitude ranging from 0.3 to 3.5 degrees C depending on trunk azimuth, day and season. These temperature gradients had a direct influence on the signal from the continuously heated sensors, inducing fluctuations in the nighttime reference signal. The resulting errors in sap flow estimates can be greater than 100%. Correction protocols have been proposed in previous studies, but they were unsuitable because of the high spatial and temporal variability of the natural temperature gradients. We found that a measurement signal derived from a noncontinuous heating system could be an attractive solution because it appears to be independent of natural temperature gradients. The magnitude and variability of temperature gradients that we observed were likely exacerbated by the combination of open stand, high solar radiation and low sap flow rate. However, for all applications of the thermal dissipation method, it is wise to check regularly for natural temperature gradients by switching off the heater.

Detection of acoustic waves by NMR using a radiofrequency field gradient

NASA Astrophysics Data System (ADS)

Madelin, Guillaume; Baril, Nathalie; Lewa, Czeslaw J.; Franconi, Jean-Michel; Canioni, Paul; Thiaudiére, Eric; de Certaines, Jacques D.

2003-03-01

A B1 field gradient-based method previously described for the detection of mechanical vibrations has been applied to detect oscillatory motions in condensed matter originated from acoustic waves. A ladder-shaped coil generating a quasi-constant RF-field gradient was associated with a motion-encoding NMR sequence consisting in a repetitive binomial 1 3¯3 1¯ RF pulse train (stroboscopic acquisition). The NMR response of a gel phantom subject to acoustic wave excitation in the 20-200 Hz range was investigated. Results showed a linear relationship between the NMR signal and the wave amplitude and a spectroscopic selectivity of the NMR sequence with respect to the input acoustic frequency. Spin displacements as short as a few tens of nanometers were able to be detected with this method.

Detection of acoustic waves by NMR using a radiofrequency field gradient.

PubMed

Madelin, Guillaume; Baril, Nathalie; Lewa, Czeslaw J; Franconi, Jean Michel; Canioni, Paul; Thiaudiére, Eric; de Certaines, Jacques D

2003-03-01

A B(1) field gradient-based method previously described for the detection of mechanical vibrations has been applied to detect oscillatory motions in condensed matter originated from acoustic waves. A ladder-shaped coil generating a quasi-constant RF-field gradient was associated with a motion-encoding NMR sequence consisting in a repetitive binomial 13;31; RF pulse train (stroboscopic acquisition). The NMR response of a gel phantom subject to acoustic wave excitation in the 20-200 Hz range was investigated. Results showed a linear relationship between the NMR signal and the wave amplitude and a spectroscopic selectivity of the NMR sequence with respect to the input acoustic frequency. Spin displacements as short as a few tens of nanometers were able to be detected with this method.

Method for fabrication of ceramic dielectric films on copper foils

DOEpatents

Ma, Beihai; Narayanan, Manoj; Dorris, Stephen E.; Balachandran, Uthamalingam

2017-06-14

The present invention provides copper substrate coated with a lead-lanthanum-zirconium-titanium (PLZT) ceramic film, which is prepared by a method comprising applying a layer of a sol-gel composition onto a copper foil. The sol-gel composition comprises a precursor of a ceramic material suspended in 2-methoxyethanol. The layer of sol-gel is then dried at a temperature up to about 250.degree. C. The dried layer is then pyrolyzed at a temperature in the range of about 300 to about 450.degree. C. to form a ceramic film from the ceramic precursor. The ceramic film is then crystallized at a temperature in the range of about 600 to about 750.degree. C. The drying, pyrolyzing and crystallizing are performed under a flowing stream of an inert gas.

Mayenite Synthesized Using the Citrate Sol-Gel Method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ude, Sabina N; Rawn, Claudia J; Meisner, Roberta A

2014-01-01

A citrate sol-gel method has been used to synthesize mayenite (Ca12Al14O33). X-ray powder diffraction data show that the samples synthesized using the citrate sol-gel method contained CaAl2O4 and CaCO3 along with mayenite when fired ex-situ in air at 800 C but were single phase when fired at 900 C and above. Using high temperature x-ray diffraction, data collected in-situ in air at temperatures of 600 C and below showed only amorphous content; however, data collected at higher temperatures indicated the first phase to crystallize is CaCO3. High temperature x-ray diffraction data collected in 4% H2/96% N2 does not show themore » presence of CaCO3, and Ca12Al14O33 starts to form around 850 C. In comparison, x-ray powder diffraction data collected ex-situ on samples synthesized using traditional solid-state synthesis shows that single phase was not reached until samples were fired at 1350 C. DTA/TGA data collected either in a nitrogen environment or air on samples synthesized using the citrate gel method suggest the complete decomposition of metastable phases and the formation of mayenite at 900 C, although the phase evolution is very different depending on the environment. Brunauer-Emmett-Teller (BET) measurements showed a slightly higher surface area of 7.4 0.1 m2/g in the citrate gel synthesized samples compared to solid-state synthesized sample with a surface area of 1.61 0.02 m2/g. SEM images show a larger particle size for samples synthesized using the solid-state method compared to those synthesized using the citrate gel method.« less

Formulation, in-vitro characterization and clinical evaluation of curcumin in-situ gel for treatment of periodontitis.

PubMed

Nasra, Maha M A; Khiri, Heba M; Hazzah, Heba A; Abdallah, Ossama Y

2017-11-01

This study aimed to develop syringeable in-situ curcumin (cur) gel for the treatment of periodontal pockets as well as to evaluate the clinical efficacy of Cur in-situ gel formulation. Different in-situ gel formulations of Cur were prepared using 30% of pluronic F127, and 1% of carbopol P934. The formulations were evaluated regarding gelation temperature, pH, viscosity, syringeability study, in-vitro release and chemical stability of cur. The effect of aging of gel formulations for 3months in refrigerator was investigated. The selected formulation was clinically evaluated through the determination of probing depth, plaque index, and bleeding index at baseline and 1 month after application. The formulations showed accepted gelation temperature ranging from 28 to 34 °C and all had pH value of 4. The viscosity of the formulations at 4 °C ranged from 19 000 to 37 000 cP. All formulations were easily syringeable through 21 gauge needle at cold temperature. Curcumin stability during the release study was maintained. Aging showed no significant effect on release profile, drug content, or the pH after 3 months, while it showed a slight increase in viscosity with concomitant decrease in gelation temperature. Selected formulations delivered into periodontal pocket evaluated clinically showed to be effective. The treated group revealed that the adjunctive use of intracrevicular 2% curcumin in-situ gel adjunct to mechanical treatment in patients with adult periodontitis could aid in significant clinical reduction of probing depth, bleeding index, and to less extent of plaque. This indicates that curcumin in this novel drug delivery system is an excellent candidate for periodontal disease treatment.

Fermentation and microbial population dynamics during the ensiling of native grass and subsequent exposure to air.

PubMed

Zhang, Qing; Wu, Baiyila; Nishino, Naoki; Wang, Xianguo; Yu, Zhu

2016-03-01

To study the microbial population and fermentation dynamics of large needlegrass (LN) and Chinese leymus (CL) during ensiling and subsequent exposure to air, silages were sampled and analyzed using culture-based techniques and denaturing gradient gel electrophoresis (DGGE). A total of 112 lactic acid bacteria (LAB) strains were isolated and identified using the 16S rRNA sequencing method. Lactic acid was not detected in the first 20 days in LN silage and the pH decreased to 6.13 after 45 days of ensiling. The temperature of the LN silage increased after approximately 30 h of air exposure and the CL silage showed a slight temperature variation. Enterococcus spp. were mainly present in LN silage. The proportion of Lactobacillus brevis in CL silage increased after exposure to air. LN silage with a higher proportion of Enterococcus spp. and propionic acid concentration did not show higher fermentation quality or aerobic stability than CL silage, which had a higher concentration of acetic acid, butyric acid and increased proportion of L. brevis after exposure to air. © 2015 Japanese Society of Animal Science.

Microbial community of cyanobacteria mats in the intertidal zone of oil-polluted coast of Saudi Arabia.

PubMed

Al-Thukair, A A; Abed, R M M; Mohamed, L

2007-02-01

Cyanobacterial mats are found at various locations along the coast of the Eastern Province of Saudi Arabia. Those mats were affected by severe oil pollution following 1991 oil spill. In this study, samples from Abu Ali Island were collected at three selected sampling sites across the intertidal zone (Lower, Middle, and Upper) in order to understand the effect of extreme environmental conditions of high salinity, temperature and desiccation on distribution of cyanobacteria along the oil polluted intertidal zone. Our investigation of composition of cyanobacteria and diatoms was carried out using light microscopy, and Denaturant Gradient Gel Electrophoresis (DGGE) technique. Light microscopy identification revealed dominant cyanobacteria to be affiliated with genera Phormidium, Microcoleus, and Schizothrix, and to a lesser extent with Oscillatoria, Halothece, and various diatom species. The analysis of DGGE of PCR-amplified 16S rRNA fragments showed that the diversity of cyanobacteria decreases as we proceed from the lower to the upper intertidal zone. Accordingly, the tidal regime, salinity, elevated ambient air temperature, and desiccation periods have a great influence on the distribution of cyanobacterial community in the oil polluted intertidal zone of Abu Ali Island.

Development of a novel amide-silica stationary phase for the reversed-phase HPLC separation of different classes of phytohormones.

PubMed

Aral, Hayriye; Aral, Tarık; Ziyadanoğulları, Berrin; Ziyadanoğulları, Recep

2013-11-15

A novel amide-bonded silica stationary phase was prepared starting from N-Boc-phenylalanine, cyclohexylamine and spherical silica gel (4 µm, 60 Å). The amide ligand was synthesised with high yield. The resulting amide bonded stationary phase was characterised by SEM, IR and elemental analysis. The resulting selector bearing a polar amide group is used for the reversed-phase chromatography separation of different classes of thirteen phytohormones (plant hormones). The chromatographic behaviours of these analytes on the amide-silica stationary phase were compared with those of RP-C18 column under same conditions. The effects of different separation conditions, such as mobile phase, pH value, flow rate and temperature, on the separation and retention behaviours of the 13 phytohormones in this system were studied. The optimum separation was achieved using reversed-phase HPLC gradient elution with an aqueous mobile phase containing pH=6.85 potassium phosphate buffer (20 mM) and acetonitrile with a 22 °C column temperature. Under these experimental conditions, the 12 phytohormones could be separated and detected at 230 or 270 nm within 26 min. Copyright © 2013 Elsevier B.V. All rights reserved.

Gel-Based Hippocampal Proteomic Analysis 2 Weeks following Traumatic Brain Injury to Immature Rats Using Controlled Cortical Impact

PubMed Central

Kochanek, Ashley R.; Kline, Anthony E.; Gao, Wei-Min; Chadha, Mandeep; Lai, Yichen; Clark, Robert S.B.; Dixon, C. Edward; Jenkins, Larry W.

2009-01-01

Traumatic brain injury (TBI) to postnatal day 17 rats has been shown to produce acute changes in hippocampal global protein levels and spatial learning and memory deficits. The purpose of the present study was to analyze global hippocampal protein changes 2 weeks after a moderate ipsilateral controlled cortical impact in postnatal day 17 rats using 2-dimensional difference gel electrophoresis and mass spectrometry. Paired sham and ipsilateral injured hippocampal lysates were independently labeled with different fluorescent cyanine dyes and coseparated within the same immobilized pH gradient strips and slab gel based on isoelectric point and molecular mass. Significant changes in key proteins involved in glial and neuronal stress, oxidative metabolism, calcium uptake and neurotransmitter function were found 2 weeks after injury, and their potential roles in hippocampal plasticity and cognitive dysfunction were discussed. PMID:16943664

Sol-gel precursors and products thereof

DOEpatents

Warren, Scott C.; DiSalvo, Jr., Francis J.; Weisner, Ulrich B.

2017-02-14

The present invention provides a generalizable single-source sol-gel precursor capable of introducing a wide range of functionalities to metal oxides such as silica. The sol-gel precursor facilitates a one-molecule, one-step approach to the synthesis of metal-silica hybrids with combinations of biological, catalytic, magnetic, and optical functionalities. The single-source precursor also provides a flexible route for simultaneously incorporating functional species of many different types. The ligands employed for functionalizing the metal oxides are derived from a library of amino acids, hydroxy acids, or peptides and a silicon alkoxide, allowing many biological functionalities to be built into silica hybrids. The ligands can coordinate with a wide range of metals via a carboxylic acid, thereby allowing direct incorporation of inorganic functionalities from across the periodic table. Using the single-source precursor a wide range of functionalized nanostructures such as monolith structures, mesostructures, multiple metal gradient mesostructures and Stober-type nanoparticles can be synthesized. ##STR00001##

An electromagnetically actuated fiber optic switch using magnetized ferromagnetic materials

NASA Astrophysics Data System (ADS)

Pandojirao-S, Praveen; Dhaubanjar, Naresh; Phuyal, Pratibha C.; Chiao, Mu; Chiao, J.-C.

2008-03-01

This paper presents the design, fabrication and testing of a fiber optic switch actuated electromagnetically. The ferromagnetic gel coated optical fiber is actuated using external electromagnetic fields. The ferromagnetic gel consists of ferromagnetic powders dispersed in epoxy. The fabrication utilizes a simple cost-effective coating setup. A direct fiberto-fiber alignment eliminates the need for complementary optical parts and the displacement of fiber switches the laser coupling. The magnetic characteristics of magnetized ferromagnetic materials are performed using alternating gradient magnetometer and the magnetic hysteresis curves are measured for different ferromagnetic materials including iron, cobalt, and nickel. Optical fiber switches with various fiber lengths are actuated and their static and dynamic responses for the same volume of ferromagnetic gel are summarized. The highest displacement is 1.345 mm with an input current of 260mA. In this paper, the performance of fiber switches with various coating materials is presented.

Different Effects of Long- and Short-Chain Ceramides on the Gel-Fluid and Lamellar-Hexagonal Transitions of Phospholipids: A Calorimetric, NMR, and X-Ray Diffraction Study

PubMed Central

Sot, Jesús; Aranda, Francisco J.; Collado, M.-Isabel; Goñi, Félix M.; Alonso, Alicia

2005-01-01

The effects on dielaidoylphosphatidylethanolamine (DEPE) bilayers of ceramides containing different N-acyl chains have been studied by differential scanning calorimetry small angle x-ray diffraction and 31P-NMR spectroscopy. N-palmitoyl (Cer16), N-hexanoyl (Cer6), and N-acetyl (Cer2) sphingosines have been used. Both the gel-fluid and the lamellar-inverted hexagonal transitions of DEPE have been examined in the presence of the various ceramides in the 0-25 mol % concentration range. Pure hydrated ceramides exhibit cooperative endothermic order-disorder transitions at 93°C (Cer16), 60°C (Cer6), and 54°C (Cer2). In DEPE bilayers, Cer16 does not mix with the phospholipid in the gel phase, giving rise to high-melting ceramide-rich domains. Cer16 favors the lamellar-hexagonal transition of DEPE, decreasing the transition temperature. Cer2, on the other hand, is soluble in the gel phase of DEPE, decreasing the gel-fluid and increasing the lamellar-hexagonal transition temperatures, thus effectively stabilizing the lamellar fluid phase. In addition, Cer2 was peculiar in that no equilibrium could be reached for the Cer2-DEPE mixture above 60°C, the lamellar-hexagonal transition shifting with time to temperatures beyond the instrumental range. The properties of Cer6 are intermediate between those of the other two, this ceramide decreasing both the gel-fluid and lamellar-hexagonal transition temperatures. Temperature-composition diagrams have been constructed for the mixtures of DEPE with each of the three ceramides. The different behavior of the long- and short-chain ceramides can be rationalized in terms of their different molecular geometries, Cer16 favoring negative curvature in the monolayers, thus inverted phases, and the opposite being true of the micelle-forming Cer2. These differences may be at the origin of the different physiological effects that are sometimes observed for the long- and short-chain ceramides. PMID:15695626

Dynamic behaviors of water contained in calcium-silicate-hydrate gel at different temperatures studied by quasi-elastic neutron scattering spectroscopy

NASA Astrophysics Data System (ADS)

Yi, Zhou; Deng, Pei-Na; Zhang, Li-Li; Li, Hua

2016-10-01

The dynamic behaviors of water contained in calcium-silicate-hydrate (C-S-H) gel with different water content values from 10% to 30% (by weight), are studied by using an empirical diffusion model (EDM) to analyze the experimental data of quasi-elastic neutron scattering (QENS) spectra at measured temperatures ranging from 230 K to 280 K. In the study, the experimental QENS spectra with the whole Q-range are considered. Several important parameters including the bound/immobile water elastic coefficient A, the bound water index BWI, the Lorentzian with a half-width at half-maximum (HWHM) Γ 1(Q) and Γ 2(Q), the self-diffusion coefficients D t1 and D t2 of water molecules, the average residence times τ 01 and τ 02, and the proton mean squared displacement (MSD) are obtained. The results show that the QENS spectra can be fitted very well not only for small Q (≤ 1 Å-1) but also for large Q. The bound/immobile water fraction in a C-S-H gel sample can be shown by the fitted BWI. The distinction between bound/immobile and mobile water, which includes confined water and ultra-confined water, can be seen by the fitted MSD. All the MSD tend to be the smallest value below 0.25 Å2 (the MSD of bound/immobile water) as the Q increases to 1.9 Å-1, no matter what the temperature and water content are. Furthermore, by the abrupt changes of the fitted values of D t1, τ 01, and Γ 1(Q), a crossover temperature at 250 K, namely the liquid-to-crystal-like transition temperature, can be identified for confined water in large gel pores (LGPs) and/or small gel pores (SGPs) contained in the C-S-H gel sample with 30% water content.