Continuous shear rheometry of o/w emulsions; control of evaporation in cone/plate geometry.

PubMed

Orafidiya, L O

1989-05-01

Volatile solvents may evaporate during cone/plate viscometry so that false rheograms develop. This surface evaporation was prevented in a cod-liver oil-in-water emulsion stabilized with zanthoxylum gum by layering a film of cod-liver oil on the exposed surface of the emulsion test sample. The oil layer effectively prevented evaporation and did not alter significantly the rheological behaviour of the test material.

Synthesis of Hydroxy-Terminated Dinitropropyl Acrylate Polymers and Improved Characterization of Hydroxy-Terminated Prepolymers

DTIC Science & Technology

1983-03-01

Carbonate GPC Gel Permeation Chromatography HEDS Hydroxyethyl Disulfide HPLC High Pressure Liquid Chromatography NMIM N-methyl imidazole NPGA Neopentyl... analysis and intrinsic viscosity determination by a capillary viscometry shows promise as a reliable approach for the determination of the molecular...more reliable and meaningful data than GPC analysis alone. 3.2.3 Determination of Number Average Functionality of Prepolymer of fp < 2.0 The number

Contactless laser viscometer for flowing liquid films

NASA Astrophysics Data System (ADS)

Michels, Alexandre F.; Menegotto, Thiago; Grieneisen, Hans-Peter; Horowitz, Flavio

2005-12-01

This work briefly reviews recent progress in interferometric monitoring of spin and of dip coating, from a unified point of view, and its application for contactless viscometry of liquid films. Considering the associated models and measurement uncertainties, the method was validated for both coating processes with oil standards of known viscosities and constant refractive indices. Limitations and perspectives for application of the laser viscometer to liquid films with a varying refractive index are also discussed.

Microfluidic viscometers for shear rheology of complex fluids and biofluids

PubMed Central

Wang, William S.; Vanapalli, Siva A.

2016-01-01

The rich diversity of man-made complex fluids and naturally occurring biofluids is opening up new opportunities for investigating their flow behavior and characterizing their rheological properties. Steady shear viscosity is undoubtedly the most widely characterized material property of these fluids. Although widely adopted, macroscale rheometers are limited by sample volumes, access to high shear rates, hydrodynamic instabilities, and interfacial artifacts. Currently, microfluidic devices are capable of handling low sample volumes, providing precision control of flow and channel geometry, enabling a high degree of multiplexing and automation, and integrating flow visualization and optical techniques. These intrinsic advantages of microfluidics have made it especially suitable for the steady shear rheology of complex fluids. In this paper, we review the use of microfluidics for conducting shear viscometry of complex fluids and biofluids with a focus on viscosity curves as a function of shear rate. We discuss the physical principles underlying different microfluidic viscometers, their unique features and limits of operation. This compilation of technological options will potentially serve in promoting the benefits of microfluidic viscometry along with evincing further interest and research in this area. We intend that this review will aid researchers handling and studying complex fluids in selecting and adopting microfluidic viscometers based on their needs. We conclude with challenges and future directions in microfluidic rheometry of complex fluids and biofluids. PMID:27478521

Facile synthesis of fluoro, methoxy, and methyl substituted ferrocene-based urea complexes as potential therapeutic agents.

PubMed

Asghar, Faiza; Badshah, Amin; Lal, Bhajan; Zubair, Shumaila; Fatima, Saira; Butler, Ian S

2017-06-01

In the present work, the synthesis, characterization (FT-IR, multinuclear ( 1 H and 13 C) NMR, AAS, Raman, and elemental analysis), DNA binding (cyclic voltammetry, UV-Vis spectroscopy and viscometry), and in vitro biological assessment of nine new ferrocene-based ureas are reported. The desulphurization of ferrocenyl thioureas to the corresponding oxo analogues using aqueous sodium hydroxide and mercuric chloride led to the ferrocenyl ureas (F1-F9) in high yields. The DNA binding studies performed by cyclic voltammetry and UV-Vis spectroscopy produced results that are in close agreement with one another for the binding constants (K) and an electrostatic mode of interaction was observed. The nature and the extent of interaction with DNA was further investigated by viscometry. The DFT/B3LYP method was used to determine the charge distribution and HOMO/LUMO energies of the optimized structure. The DFT calculated HOMO and LUMO energies correlate well with the experimentally determined redox potential values. The synthesized ferrocenyl derivatives exhibited good scavenging activity against 1,1-diphenyl-2-picrylhydrazyl radical (DPPH). These complexes were also scanned for their in vitro cytotoxicity against human carcinoma cell line THP-1 (leukemia cells). The results showed a moderate level of cytotoxicity against the subjected cancer cell line as compared with the standard chemotherapeutic drug (cisplatin). Copyright © 2017 Elsevier Inc. All rights reserved.

Exact-solution for cone-plate viscometry

NASA Astrophysics Data System (ADS)

Giacomin, A. J.; Gilbert, P. H.

2017-11-01

The viscosity of a Newtonian fluid is often measured by confining the fluid to the gap between a rotating cone that is perpendicular to a fixed disk. We call this experiment cone-plate viscometry. When the cone angle approaches π/2 , the viscometer gap is called narrow. The shear stress in the fluid, throughout a narrow gap, hardly departs from the shear stress exerted on the plate, and we thus call cone-plate flow nearly homogeneous. In this paper, we derive an exact solution for this slight heterogeneity, and from this, we derive the correction factors for the shear rate on the cone and plate, for the torque, and thus, for the measured Newtonian viscosity. These factors thus allow the cone-plate viscometer to be used more accurately, and with cone-angles well below π/2 . We find cone-plate flow field heterogeneity to be far slighter than previously thought. We next use our exact solution for the velocity to arrive at the exact solution for the temperature rise, due to viscous dissipation, in cone-plate flow subject to isothermal boundaries. Since Newtonian viscosity is a strong function of temperature, we expect our new exact solution for the temperature rise be useful to those measuring Newtonian viscosity, and especially so, to those using wide gaps. We include two worked examples to teach practitioners how to use our main results.

Determining the solution conformational entropy of oligosaccharides by SEC with on-line viscometry detection.

PubMed

Morris, Mallory J; Striegel, André M

2014-06-15

Introduced here is a method for determining the solution conformational entropy of oligosaccharides (-ΔS) that relies on the on-line coupling of size-exclusion chromatography (SEC), an entropically-controlled separation technique, and differential viscometry (VISC). Results from this SEC/VISC method were compared, for the same injections of the same sample dissolutions and under identical solvent/temperature conditions, to results from a benchmark SEC/differential refractometry (SEC/DRI) method which has been applied successfully over the last decade to determining -ΔS of a variety of mono-, di-, and oligosaccharides. The accuracy (as compared to SEC/DRI) and precision of SEC/VISC were found to be excellent, as was the sensitivity of the viscometer in the oligomeric region. The experiments presented here contrast three sets of (1→4)-β-d-oligosaccharides, namely manno-, cello-, and N-acetylchitooligosaccharides of degree of polymerization (DP) 2 through 6. For each series, the dependence of -ΔS on DP was found to be monotonic while, between series, differences at each DP could be ascribed to either the additional degrees of freedom imparted by large, multi-atomic substituent groups, or to the presence or absence of additional intramolecular hydrogen bonds, depending on the axial versus equatorial arrangement of particular hydroxyl groups. An hypothesis is advanced to explain the unexpectedly high sensitivity of viscometric detection for low-molar-mass analytes. The method presented can be extended to the analysis of oligosaccharides other than those studied here. Published by Elsevier Ltd.

The physicochemical properties of the low-temperature ionic liquid silver bromide-1-butyl-3-methylimidazolium bromide

NASA Astrophysics Data System (ADS)

Grishina, E. P.; Ramenskaya, L. M.; Pimenova, A. M.

2009-11-01

The physicochemical properties of the low-temperature ionic liquid based on 1-butyl-3-methylimidazolium bromide (BMImBr) and silver bromide were studied. Differential scanning calorimetry, Fourier transform IR spectroscopy, densimetry, viscometry, and conductometry measurements were performed to determine the dependences of the parameters under study on the concentration of AgBr. It was shown that the temperature and concentration behavior of the physicochemical properties of BMImBr-AgBr melts characterized the interaction between the system components with the formation of complex particles.

Temperature transition of human hemoglobin at body temperature: effects of calcium.

PubMed Central

Kelemen, C; Chien, S; Artmann, G M

2001-01-01

We studied the effects of calcium ion concentration on the temperature dependence of rheological behavior of human red blood cells (RBCs) and concentrated hemoglobin solutions. Our previous study (G. M. Artmann, C. Kelemen, D. Porst, G. Büldt, and S. Chien, 1998, Biophys. J., 75:3179-3183) showed a critical temperature (Tc) of 36.4 +/- 0.3 degrees C at which the RBCs underwent a transition from non-passage to passage through 1.3 microm micropipettes in response to an aspiration pressure of -2.3 kPa. An increase in intracellular Ca2+ concentration by using the ionophore A23187 reduced the passability of intact RBCs through small micropipettes above T(c); the micropipette diameter needed for >90% passage increased to 1.7 microm. Viscometry of concentrated hemoglobin solutions (45 and 50 g/dl) showed a sudden viscosity transition at 36 +/- 1 degrees C (Tc(eta)) at all calcium concentrations investigated. Below Tc(eta), the viscosity value of the concentrated hemoglobin solution at 1.8 mM Ca(2+) was higher than that at other concentrations (0.2 microM, 9 mM, and 18 mM). Above Tc(eta), the viscosity was almost Ca2+ independent. At 1.8 mM Ca2+ and 36 +/- 1 degrees C, the activation energy calculated from the viscometry data showed a strong dependence on the hemoglobin concentration. We propose that the transition of rheological behavior is attributable to a high-to-low viscosity transition mediated by a partial release of the hemoglobin-bound water. PMID:11371439

Features of Extrusion Processing of Ultrahigh Molecular Weight Polyethylene. Experiment and Theory

NASA Astrophysics Data System (ADS)

Skul‧skii, O. I.; Slavnov, E. V.

2018-05-01

Experimental studies have been made of the permissible regimes of processing ultrahigh molecular weight polyethylene GUR 2122 with molecular mass of 4.5 million g/moles in a laboratory extruder with an auger diameter 32 mm and a ratio L/D = 20 at temperatures of 155-165oC. On the basis of rotational viscometry, the rheological properties of the melt are described. A mathematical model and a numerical method for calculating the motion of ultrahigh molecular weight polyethylene melt in the auger and in the moulding rigging are proposed. The velocity and stress fields have been determined.

Synthesis and Thermal Degradation Studies of Melamine Formaldehyde Resins

PubMed Central

Ullah, Sami; Bustam, M. A.; Nadeem, M.; Tan, W. L.; Shariff, A. M.

2014-01-01

Melamine formaldehyde (MF) resins have been synthesized at different reaction temperature and pH values. Different molar ratios of melamine and formaldehyde were used to synthesize the corresponding resins. The prepared resin samples were characterized by using molecular weight determination viscometry and thermogravimetric analysis (TGA). The maximum percentage of solid content (69.7%) was obtained at pH 8.5 and 75°C temperature. The molecular weight of MF resin was increased with an increase of melamine monomer concentration. The highest residual weight 14.125 wt.% was obtained with sample 10. PMID:25436237

Pressure-viscosity measurements for several lubricants to 5.5 x 10 to the 8th power Newtons per square meter (8 x 10 to the 4th psi) and 149 C (300 F)

NASA Technical Reports Server (NTRS)

Jones, W. R.; Johnson, R. L.; Winer, W. O.; Sanborn, D. M.

1974-01-01

A capillary viscometer was used to measure viscosity as a function of pressure, temperature, and shear stress for a number of lubricants. The conditions under which the measurements were made are specified. The results obtained for each material are analyzed. It was determined that all pressure-viscosity coefficients decreased with increasing temperature. Data from other techniques such as optical elastohydrodynamics, oscillating crystal, and low shear capillary viscometry were compared with the results obtained.

Synthesis of (azelaic-co-dodecanedioic) polyanhydride by microwave technique

NASA Astrophysics Data System (ADS)

Gutiérrez, M.; Sierra, C.; Acevedo Morantes, M.; Herrera, A. P.

2016-02-01

A polyanhydride was synthesized through microwave radiation using azelaic acid and dodecanedioic dicarboxylic acid at concentrations of 75:25, 50:50, and 25:75%w/w with acetic anhydride as crosslinking agent. Polymerization was carried out during 3 and 5 minutes. The copolymer with the highest molecular weight was selected using the intrinsic viscometry technique and by Huggin/Kraemer and Solomon/Ciuta methods. Based on these measurements, the 50:50 copolymer was selected with a polymerization time of 3 minutes in the microwave. This sample displayed the highest intrinsic viscosity (41.82cm3/g), demonstrating the relevance of the microwave technique for the synthesis of biopolymers.

DNA binding studies of Sunset Yellow FCF using spectroscopy, viscometry and electrochemical techniques

NASA Astrophysics Data System (ADS)

Asaadi, Sara; Hajian, Reza

2017-10-01

Color is one of the important factors in food industry. All food companies use synthetic pigments to improve the aesthetic of products. Studies on the interaction between deoxyribonucleic acid (DNA) and food dye molecules is important because DNA is responsible for some processes including replication and transcription of cells, mutations, genetic diseases, and some synthetic chemical nucleases. In this study, the molecular interaction between Sunset Yellow FCF (SY) as a common food coloring additive and calf thymus DNA (ct-DNA) has been studied using UV-Vis spectrophotometry, spectrofluorometry, Fourier transform infrared (FTIR) spectroscopy, cyclic voltammetry and viscometry techniques. The binding constant between ct-DNA and SY in phosphate buffer solution (pH 7.4) was calculated as 2.09 × 103 L mol-1. The non-electrostatic bonding constant (K0t) was almost consistent and the ratio of K0t/Kb increased by increasing the ionic strength in the range of 0.01-0.1 mol L-1 of KCl. This observation shows that, the molecular bonding of SY to ct-DNA is a combination of electrostatic and intercalation interactions. In the electrochemical studies, an oxidation peak at 0.71 V and a reduction peak at about 0.63 V was observed with the peak potential difference (ΔEp) of 0.08 V, showing a reversible process. The oxidation and reduction peaks were significantly decreased in the presence of ct-DNA and the reduction peak current shifted to negative values. In spectrofluorometric study, the fluorescence intensity of SY increased dramatically after successive addition of DNA due to the increasing of molecular surface area and decreasing of impact frequency between solvent and SY-DNA adduct. Moreover, viscometric study shows that the increasing of viscosity for SY solution in the presence of DNA is due to the intercalation mechanism with double strand DNA (ds-DNA).

Measurement and correlation of jet fuel viscosities at low temperatures

NASA Technical Reports Server (NTRS)

Schruben, D. L.

1985-01-01

Apparatus and procedures were developed to measure jet fuel viscosity for eight current and future jet fuels at temperatures from ambient to near -60 C by shear viscometry. Viscosity data showed good reproducibility even at temperatures a few degrees below the measured freezing point. The viscosity-temperature relationship could be correlated by two linear segments when plotted as a standard log-log type representation (ASTM D 341). At high temperatures, the viscosity-temperature slope is low. At low temperatures, where wax precipitation is significant, the slope is higher. The breakpoint between temperature regions is the filter flow temperature, a fuel characteristic approximated by the freezing point. A generalization of the representation for the eight experimental fuels provided a predictive correlation for low-temperature viscosity, considered sufficiently accurate for many design or performance calculations.

GTP regeneration influences interactions of microtubules, neurofilaments, and microtubule-associated proteins in vitro.

PubMed

Flynn, G; Purich, D L

1987-11-15

Interactions of microtubules, neurofilaments, and microtubule-associated proteins were investigated by turbidity and falling-ball viscometry measurements. We found evidence of endogenous GTPase activity in neurofilaments and microtubule-associated proteins (MAPs) in preparations that do not include urea or heat treatment, respectively. The absence or presence of either adenyl-5'-yl imidodiphosphonic acid or a GTP-regenerating system markedly influenced observed polymerization and gelation characteristics. Most significantly, the apparent viscosity of neurofilament and microtubule samples did not display a biphasic optimal MAP concentration profile when a GTP-regenerating system was operant. Likewise, GTP regeneration promoted the recovery of gelation following mechanical disruption of neurofilament/MAP/microtubule mixtures. These and other observations require some reassessment of proposed roles for microtubule-associated proteins in modulating neurofilament-microtubule interactions in vitro.

Responsive copolymers for enhanced petroleum recovery. Quarterly technical progress report, June 23--September 21, 1994

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

McCormick, C.; Hester, R.

Summaries are given on the technical progress on three tasks of this project. Monomer and polymer synthesis discusses the preparation of 1(7-aminoheptyloxymethyl)naphthalene and poly(maleic anhydride-alt-ethyl vinyl ether). Task 2, Characterization of molecular structure, discusses terpolymer solution preparation, UV analysis, fluorescence analysis, low angle laser light scattering, and viscometry. The paper discusses the effects of hydrophobic groups, the effect of pH, the effect of electrolyte addition, and photophysical studies. Task 3, Solution properties, describes the factorial experimental design for characterizing polymer solutions by light scattering, the light scattering test model, orthogonal factorial test design, linear regression in coded space, confidence levelmore » for coded space test mode coefficients, coefficients of the real space test model, and surface analysis of the model equations.« less

3-[(E)-(acridin-9‧-ylmethylidene)amino]-1-substituted thioureas and their biological activity

NASA Astrophysics Data System (ADS)

Bečka, Michal; Vilková, Mária; Salem, Othman; Kašpárková, Jana; Brabec, Viktor; Kožurková, Mária

2017-06-01

This paper describes the synthesis of a novel series of acridine thiosemicarbazones through a two-step reaction between various isothiocyanates and hydrazine followed by treatment with acridin-9-carbaldehyde. The properties of this series of seven new derivatives are studied using NMR and biochemical techniques, and the DNA-binding properties of the compounds are determined using spectrophotometric studies (UV-vis absorption, fluorescence, and circular/linear dichroism) and viscometry. The binding constants K are estimated as being in the range of 2.2 to 7.8 × 104 M- 1 and the percentage of hypochromism was found to be 22.11-49.75% (from UV-vis spectral titration). Electrophoretic experiments prove that the novel compounds demonstrate moderate inhibitory effects against Topo I activity at a concentration of 60 × 10- 6 M.

Megasupramolecules for safer, cleaner fuel by end association of long telechelic polymers

NASA Astrophysics Data System (ADS)

Wei, Ming-Hsin; Li, Boyu; David, R. L. Ameri; Jones, Simon C.; Sarohia, Virendra; Schmitigal, Joel A.; Kornfield, Julia A.

2015-10-01

We used statistical mechanics to design polymers that defy conventional wisdom by self-assembling into “megasupramolecules” (≥5000 kg/mol) at low concentration (≤0.3 weight percent). Theoretical treatment of the distribution of individual subunits—end-functional polymers—among cyclic and linear supramolecules (ring-chain equilibrium) predicts that megasupramolecules can form at low total polymer concentration if, and only if, the backbones are long (>400 kg/mol) and end-association strength is optimal. Viscometry and scattering measurements of long telechelic polymers having polycyclooctadiene backbones and acid or amine end groups verify the formation of megasupramolecules. They control misting and reduce drag in the same manner as ultralong covalent polymers. With individual building blocks short enough to avoid hydrodynamic chain scission (weight-average molecular weights of 400 to 1000 kg/mol) and reversible linkages that protect covalent bonds, these megasupramolecules overcome the obstacles of shear degradation and engine incompatibility.

Synthesis, characterization, and rheological studies of model water-soluble graft copolymers for application in enhanced oil recovery

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

Park, L.S.

1982-12-01

Model water-soluble graft copolymers have been synthesized with acrylamide as the major grafting monomer and dextran as the substrate in order to define more clearly the structural parameters that are important in enhanced oil recovery applications. The structures of the model graft copolymer samples were studied by aqueous size exclusion chromatography, viscometry, elemental analysis, and selective hydrolysis of the graft copolymer backbone. The grafting systems with selected grafting monomers included Fe(II)/H/sub 2/O/sub 2/ with acrylamide, and Ce(IV)/HNO/sub 3/ with acrylamide, acrylamide/2-acrylamido-2-meth propane sulfonic acid, or acrylamide/diacetone acrylamide. The viscosity and pseudoplasticity of the resulting graft copolymers were affected by bothmore » total molecular weight and length of grafted chains; however, the latter was apparently more important when behavior was compared to linear counterparts.« less

Unveiling the Interplay Between Diffusing CO2 and Ethanol Molecules in Champagne Wines by Classical Molecular Dynamics and (13)C NMR Spectroscopy.

PubMed

Bonhommeau, David A; Perret, Alexandre; Nuzillard, Jean-Marc; Cilindre, Clara; Cours, Thibaud; Alijah, Alexander; Liger-Belair, Gérard

2014-12-18

The diffusion coefficients of carbon dioxide (CO2) and ethanol (EtOH) in carbonated hydroalcoholic solutions and Champagne wines are evaluated as a function of temperature by classical molecular dynamics (MD) simulations and (13)C NMR spectroscopy measurements. The excellent agreement between theoretical and experimental diffusion coefficients suggest that ethanol is the main molecule, apart from water, responsible for the value of the CO2 diffusion coefficients in typical Champagne wines, a result that could likely be extended to most sparkling wines with alike ethanol concentrations. CO2 and EtOH hydrodynamical radii deduced from viscometry measurements by applying the Stokes-Einstein relationship are found to be mostly constant and in close agreement with MD predictions. The reliability of our approach should be of interest to physical chemists aiming to model transport phenomena in supersaturated aqueous solutions or water/alcohol mixtures.

Megasupramolecules for safer, cleaner fuel by end association of long telechelic polymers.

PubMed

Wei, Ming-Hsin; Li, Boyu; David, R L Ameri; Jones, Simon C; Sarohia, Virendra; Schmitigal, Joel A; Kornfield, Julia A

2015-10-02

We used statistical mechanics to design polymers that defy conventional wisdom by self-assembling into "megasupramolecules" (≥5000 kg/mol) at low concentration (≤0.3 weight percent). Theoretical treatment of the distribution of individual subunits—end-functional polymers—among cyclic and linear supramolecules (ring-chain equilibrium) predicts that megasupramolecules can form at low total polymer concentration if, and only if, the backbones are long (>400 kg/mol) and end-association strength is optimal. Viscometry and scattering measurements of long telechelic polymers having polycyclooctadiene backbones and acid or amine end groups verify the formation of megasupramolecules. They control misting and reduce drag in the same manner as ultralong covalent polymers. With individual building blocks short enough to avoid hydrodynamic chain scission (weight-average molecular weights of 400 to 1000 kg/mol) and reversible linkages that protect covalent bonds, these megasupramolecules overcome the obstacles of shear degradation and engine incompatibility. Copyright © 2015, American Association for the Advancement of Science.

Formulation and Characterization of a Plasma Sterilized, Pharmaceutical Grade Chitosan Powder

PubMed Central

Crofton, Andrew R; Hudson, Samuel M; Howard, Kristy; Pender, Tyler; Abdelgawad, Abdelrahman; Wolski, Daniel; Kirsch, Wolff M

2016-01-01

Chitosan has great potential as a pharmaceutical excipient. In this study, chitosan flake was micronized using cryo-ball and cryo-jet milling and subsequently sterilized with nitrogen plasma. Micronized chitosan was characterized by laser diffraction, scanning electron microscopy (SEM), conductometric titration, viscometry, loss on drying, FTIR, and limulus amebocyte lysate (LAL) assays. Cryo-jet milling produced mean particle size of 16.05 μm, 44% smaller than cryo-ball milling. Cryomilled chitosan demonstrated increased hygroscopicity, but reduced molecular weight and degree of deacetylation (DD). SEM imaging showed highly irregular shapes. FTIR showed changes consistent with reduced DD and an unexplained shift at 1100 cm−1. Plasma treated chitosan was sterile with <2.5 EU/g after low-pressure plasma and <1.3 EU/g after atmospheric pressure plasma treatment. Plasma treatment decreased the reduced viscosity of chitosan flake and powder, with a greater effect on powder. In conclusion, pharmaceutical grade, sterile chitosan powder was produced with cryo-jet milling and plasma sterilization. PMID:27112892

Structure and characteristics of acid and pepsin-solubilized collagens from the skin of cobia (Rachycentron canadum).

PubMed

Zeng, Shaokui; Yin, Juanjuan; Yang, Shuqi; Zhang, Chaohua; Yang, Ping; Wu, Wenlong

2012-12-01

Acid-solubilized collagen (ASC) and pepsin-solubilized collagen (PSC) were extracted from the skin of cobia (Rachycentron canadum). The yields of ASC and PSC were 35.5% and 12.3%, respectively. Based on the protein patterns and carboxymethyl-cellulose chromatography, ASC and PSC were composed of α1α2α3 heterotrimers and were characterised as type I collagen with no disulfide bond. Their amounts of imino acids were 203 and 191 residues per 1000 residues, respectively. LC-MS/MS analysis demonstrated the high sequences similarities of ASC and PSC. Fourier transform infrared spectroscopy spectra showed that the amide I, II and III peaks of PSC were obtained at a lower wave number compared with ASC. The thermal denaturation temperatures of ASC and PSC, as measured by viscometry, were 34.62 and 33.97°C, respectively. The transition temperatures (T(max)) were 38.17 and 36.03°C, respectively, as determined by differential scanning calorimetry (DSC). Both collagens were soluble at acidic pH and below 2% (w/v) NaCl concentration. Copyright © 2012 Elsevier Ltd. All rights reserved.

Rheological and nuclear magnetic resonance (NMR) study of the hydration and heating of undeveloped wheat doughs.

PubMed

Lopes-da-Silva, J A; Santos, Dora M J; Freitas, Andreia; Brites, Carla; Gil, Ana M

2007-07-11

The undeveloped doughs of two wheat flours differing in technological performance were characterized at the supramolecular level, by fundamental small-deformation oscillatory rheology and shear viscometry, and at the molecular level, by nuclear magnetic resonance (NMR) spectroscopy. For the harder variety, the higher storage moduli indicated lower mobility of the protein/water matrix in the 0.001-100 s range. Conversely, 1H NMR indicated higher molecular mobility in the sub-microsecond range for protein/water, whereas starch was found to be generally more hindered. It is suggested that faster protein/water motions are at the basis of the higher structural rearrangement indicated by tan delta for the harder variety. Rheological effects of heating-cooling reflect mainly starch behavior, whereas 1H NMR spectra and relaxation times give additional information on component mixing and molecular mobility. The heated softer variety dough formed a rigid lattice and, although a similar tendency was seen for the hard variety, all of its components remained more mobile. About 60% of starch crystallizes in both varieties, which may explain their similar rheological behaviors upon cooling.

Purification, physicochemical characterisation and anticancer activity of a polysaccharide from Cyclocarya paliurus leaves.

PubMed

Xie, Jian-Hua; Liu, Xin; Shen, Ming-Yue; Nie, Shao-Ping; Zhang, Hui; Li, Chang; Gong, De-Ming; Xie, Ming-Yong

2013-02-15

A Cyclocarya paliurus (Batal.) Iljinskaja polysaccharide (CPP) was isolated and purified by hot water extraction, ethanol precipitation, deproteinisation and anion-exchange chromatography. Its physicochemical properties were characterised by gel permeation chromatography (GPC), gas chromatography-mass spectrometry (GC-MS), thermal gravimetric analysis (TGA), Fourier transform infrared spectrometry (FTIR), UV-visible spectrophotometry, dynamic light scattering (DLS) and viscometry analysis. The anticancer effect of CPP in human gastric cancer HeLa cells was also evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The results showed that the molecular weight of CPP was 900 kDa, and it contained 64.8% total sugar, 23.5% uronic acid, 9.26% protein, and six kinds of monosaccharides, including glucose, rhamnose, arabinose, xylose, mannose and galactose, with molar percentages of 32.7%, 9.33%, 30.6%, 3.48%, 10.4%, and 13.5%, respectively. Furthermore, the results showed that CPP exhibited a strong inhibition effect on the growth of human gastric cancer HeLa cells. Copyright © 2012 Elsevier Ltd. All rights reserved.

Isolation of a 5-Kilodalton Actin-Sequestering Peptide from Human Blood Platelets

NASA Astrophysics Data System (ADS)

Safer, Daniel; Golla, Rajasree; Nachmias, Vivianne T.

1990-04-01

Resting human platelets contain ≈0.3 mM unpolymerized actin. When freshly drawn and washed platelets are treated with saponin, 85-90% of the unpolymerized actin diffuses out. Analysis by polyacrylamide gel electrophoresis under nondenaturing conditions shows that the bulk of this unpolymerized actin migrates with a higher mobility than does pure G-actin, profilactin, or actin-gelsolin complex. When muscle G-actin is added to fresh or boiled saponin extract, the added muscle actin is shifted to the high-mobility form. The saponin extract contains an acidic peptide having a molecular mass in the range of 5 kDa, which has been purified to homogeneity by reverse-phase HPLC. This peptide also shifts muscle actin to the high-mobility form. Addition of either boiled saponin extract or the purified peptide to muscle G-actin also strongly and stoichiometrically inhibits salt-induced polymerization, as assayed by falling-ball viscometry and by sedimentation. We conclude that this peptide binds to the bulk of the unpolymerized actin in platelets and prevents it from polymerizing.

Boric Acid Induced Transient Cross-Links in Lactose-Modified Chitosan (Chitlac).

PubMed

Sacco, Pasquale; Furlani, Franco; Cok, Michela; Travan, Andrea; Borgogna, Massimiliano; Marsich, Eleonora; Paoletti, Sergio; Donati, Ivan

2017-12-11

The present paper explores the effect of boric acid on Chitlac, a lactose-modified chitosan which had previously shown interesting biological and physical-chemical features. The herewith-reported experimental evidences demonstrated that boric acid binds to Chitlac, producing conformational and association effects on the chitosan derivative. The thermodynamics of boric acid binding to Chitlac was explored by means of 11 B NMR, circular dichroism (CD), and UV-vis spectroscopy, while macromolecular effects were investigated by means of viscometry and dynamic light scattering (DLS). The experimental results revealed a chain-chain association when limited amounts of boric acid were added to Chitlac. However, upon exceeding a critical boric acid limit dependent on the polysaccharide concentration, the soluble aggregates disentangle. The rheological behavior of Chitlac upon treatment with boric acid was explored showing a dilatant behavior in conditions of steady flow. An uncommonly high dependence in the scaling law between the zero-shear viscosity and the concentration of Chitlac was found, i.e., η 0 ∝ C CTL 5.8 , pointing to interesting potential implications of the present system in biomaterials development.

DNA interaction studies of sesamol (3,4-methylenedioxyphenol) food additive.

PubMed

Kashanian, Soheila; Tahmasian Ghobadi, Ameneh; Roshanfekr, Hamideh; Shariati, Zohreh

2013-02-01

The interaction of native calf thymus DNA (CT-DNA) with sesamol (3,4-methylenedioxyphenol) in Tris-HCl buffer at neutral pH 7.4 was monitored by absorption spectrophotometry, viscometry and spectrofluorometry. It is found that sesamol molecules could interact with DNA outside and/or groove binding modes, as are evidenced by: hyperchromism in UV absorption band, very slow decrease in specific viscosity of DNA, and small increase in the fluorescence of methylene blue (MB)-DNA solutions in the presence of increasing amounts of sesamol, which indicates that it is able to partially release the bound MB. Furthermore, the enthalpy and entropy of the reaction between sesamol and CT-DNA showed that the reaction is enthalpy-favored and entropy-disfavored (ΔH = -174.08 kJ mol(-1); ΔS = -532.92 J mol(-1) K(-1)). The binding constant was determined using absorption measurement and found to be 2.7 × 10(4) M(-1); its magnitude suggests that sesamol interacts to DNA with a high affinity.

Investigation of bacterial resistance to the immune system response: cepacian depolymerisation by reactive oxygen species.

PubMed

Cuzzi, Bruno; Cescutti, Paola; Furlanis, Linda; Lagatolla, Cristina; Sturiale, Luisa; Garozzo, Domenico; Rizzo, Roberto

2012-08-01

Reactive oxygen species (ROS) are part of the weapons used by the immune system to kill and degrade infecting microorganisms. Bacteria can produce macromolecules, such as polysaccharides, that are able to scavenge ROS. Species belonging to the Burkholderia cepacia complex are involved in serious lung infection in cystic fibrosis patients and produce a characteristic polysaccharide, cepacian. The interaction between ROS and bacterial polysaccharides was first investigated by killing experiments, where bacteria cells were incubated with sodium hypochlorite (NaClO) with and without prior incubation with cepacian. The results showed that the polysaccharide had a protective effect towards bacterial cells. Cepacian was then treated with different concentrations of NaClO and the course of reactions was followed by means of capillary viscometry. The degradation products were characterised by size-exclusion chromatography, NMR and mass spectrometry. The results showed that hypochlorite depolymerised cepacian, removed side chains and O-acetyl groups, but did not cleave the glycosidic bond between glucuronic acid and rhamnose. The structure of some oligomers produced by NaClO oxidation is reported.

Synthesis of Eugenol–Lauryl Methacrylate Copolymers via Cationic Polymerization

NASA Astrophysics Data System (ADS)

Fajrin, A.; Marliana, SD; Handayani, D. S.

2018-04-01

Eugenol is one of the most abundant natural resources in Indonesia. The recently bio-based polymer resin is created based on eugenol because eugenol is functionalized with the polymerizable group. In order to improve the functional properties of eugenol, in this research Eugenol–Lauryl Methacrylate copolymers (co-poly(Eg-LMA)) were synthesized by cationic polymerization using H2SO4 as an initiator under the nitrogen atmosphere. Structure identification of the copolymer showed the absorption of the vinyl group from the monomers disappear at the analysis through FTIR at the wave number 1637-1639 and 985-995 cm-1 and also 1H-NMR on the chemical shift 5,97 and 5,08 ppm. The resulting copolymers obtained brown powder in 32.03 % yieldsand melting point at 96 – 97 °C. Solubility test of the co-poly(Eg-LMA) showed that the polymer couldnot soluble in water but soluble in chloroform, diethyl ether, and benzene. Average molecular weight of co-poly(Eg-LMA) Led Ostwald viscometry was obtained 42020 with the degree of polymerization by 200.

Size exclusion chromatography and viscometry in paper degradation studies. New Mark-Houwink coefficients for cellulose in cupri-ethylenediamine.

PubMed

Łojewski, Tomasz; Zieba, Katarzyna; Lojewska, Joanna

2010-10-15

The paper deals with the application of size exclusion chromatography (SEC) for the studies of paper degradation phenomena. The goal is to solve some of the technical problems connected with the calibration of multi-detector SEC system and to find the correlation between SEC and viscometric results of degree of polymerization of cellulose. The results gathered for the paper samples degraded by acidic air pollutant (NO(2)) are used as an example of SEC-MALLS application. From the correlation between intrinsic viscosities and absolute value of molecular masses obtained with SEC/MALLS (Multi Angle Laser Light Scattering) technique, Mark-Houwink coefficients for cellulose in cupri-ethylenediamine solution were determined. Thus obtained coefficients were used for the determination of viscometric degree of polymerization (molecular mass) of the aged samples. An excellent correlation was found between the chromatographic values of molecular masses obtained with SEC-UV/VIS detection and the viscometric ones utilizing the improved values of Mark-Houwink coefficients. Copyright © 2010 Elsevier B.V. All rights reserved.

Solution properties of a heteropolysaccharide extracted from pumpkin (Cucurbita pepo, lady godiva).

PubMed

Song, Yi; Zhao, Jing; Ni, Yuanying; Li, Quanhong

2015-11-05

A water-soluble galactoglucofucomannan was extracted from pumpkin (Cucurbita pepo, lady godiva variety). GC-MS analysis indicated that the polysaccharide was composed of 1,6-linked-glucosyl, 1,2,6-linked-mannosyl, 1,3,6-linked-mannosyl, 1,2,6-linked-galactosyl, 1,2,6-linked-galactosyl, terminal fucosyl and terminal glucose. The solution properties of the polysaccharide were studied systematically by using size-exclusion chromatography combined with multi-angle laser light scattering, viscometry and dynamic light scattering at 25 °C. The weight average molecular masses (Mw), intrinsic viscosity [η], radius of gyration (Rg) and hydrodynamic radius (Rh) were found to be 12.7 × 10(5)g/mol, 780 ml/g, 68 nm and 116 nm, respectively. The fraction dimension and value of ρ (Rg/Rh) of the polysaccharide revealed that it existed in a sphere-like conformation in distilled water. The dependence of zero shear specific viscosity on the coil overlap parameter was analyzed using different models. Furthermore, degradation of samples upon autoclaving has been observed and quantified by intrinsic viscosity determination and SEC-MALLS. Copyright © 2015 Elsevier Ltd. All rights reserved.

Gel-like properties of MCM-41 material and its transformation to MCM-50 in a caustic alkaline surround

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

Saputra, Hens; Othman, Raihan, E-mail: raihan@iium.edu.my; Sutjipto, A.G.E.

2012-03-15

Highlights: Black-Right-Pointing-Pointer MCM-41 material transforms gradually into MCM-50 lamellar gel upon controlled exposure to 6 M KOH. Black-Right-Pointing-Pointer The formation of MCM-50 ordered gel structure occurs at KOH weight content of 40-70 wt. %. Black-Right-Pointing-Pointer MCM gel phase shows pseudoplastic behavior and possesses homogeneous matrix texture. -- Abstract: MCM-41 material, prepared by sol-gel method, reveals gel-like properties in a caustic alkaline environment, i.e., 6 M potassium hydroxide (KOH) electrolyte. The gellation of MCM-41 starts at a KOH weight ratio of 40 wt.%. The structural change of the material is verified with X-Ray diffractograms and supported by observation using Scanning Electronmore » Microscope (SEM). As the KOH weight ratio increases, the MCM-41 hexagonal arrays structure gradually transforms into MCM-50 lamellar structure before disappearing completely at 80 wt.% KOH. The MCM gel phase is further characterized by rotational viscometry and texture analysis. The gel phase shows shear thinning or pseudoplastic behavior and possesses homogeneous matrix structure.« less

Methods of viscosity measurements in sealed ampoules

NASA Astrophysics Data System (ADS)

Mazuruk, Konstantin

1999-07-01

Viscosity of semiconductors and metallic melts is usually measured by oscillating cup method. This method utilizes the melts contained in vacuum sealed silica ampoules, thus the problems related to volatility, contamination, and high temperature and pressure can be alleviate. In a typical design, the time required for a single measurement is of the order of one hour. In order to reduce this time to a minute range, a high resolution angular detection system is implemented in our design of the viscometer. Furthermore, an electromagnet generating a rotational magnetic field (RMF) is incorporated into the apparatus. This magnetic field can be used to remotely and nonintrusively measure the electrical conductivity of the melt. It can also be used to induce a well controlled rotational flow in the system. The transient behavior of this flow can potentially yield of the fluid. Based on RMF implementation, two novel viscometry methods are proposed in this work: a) the transient torque method, b) the resonance method. A unified theoretical approach to the three methods is presented along with the initial test result of the constructed apparatus. Advantages of each of the method are discussed.

Crosslinkable coatings from phosphorylcholine-based polymers.

PubMed

Lewis, A L; Cumming, Z L; Goreish, H H; Kirkwood, L C; Tolhurst, L A; Stratford, P W

2001-01-01

2-Methacryloyloxyethyl phosphorylcholine (MPC) was synthesised and then used in the preparation of crosslinked polymer membranes with lauryl methacrylate, hydroxypropyl methacrylate and trimethoxysilylpropyl methacrylate (crosslinker) comonomers. Some physical aspects of the membrane properties were evaluated in order to establish the basis for the synthesis of a series of post-crosslinkable polymers. These materials were made by copolymerisation of the constituent monomers via a free radical method, and characterised using NMR, FT-IR, viscometry and elemental analysis. The optimum crosslink density and conditions required for curing coatings of these polymers were investigated using atomic force microscopy (AFM) and showed the inclusion of 5 mol% silyl crosslinking agent to be ideal. A nanoindentation technique was employed to determine if the coating developed elasticity upon crosslinking. The biological properties of the coatings were evaluated using a variety of protein adsorption assays and blood contacting experiments, and an enzyme immunoassay was developed to detect E. coli in order to assess the level of bacterial adhesion to these biomaterials. Polymers of this type were shown to be very useful as coating materials for improving the biocompatibility of, or reducing the levels of adherent bacteria to medical devices.

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

Tao Zhu; Jack A. Walker; J. Liang

Due to increasing oil demand, oil companies are moving into arctic environments and deep-water areas for oil production. In these regions of lower temperatures, wax deposits begin to form when the temperature in the wellbore falls below wax appearance temperature (WAT). This condition leads to reduced production rates and larger pressure drops. Wax problems in production wells are very costly due to production down time for removal of wax. Therefore, it is necessary to develop a solution to wax deposition. In order to develop a solution to wax deposition, it is essential to characterize the crude oil and study phasemore » behavior properties. The main objective of this project was to characterize Alaskan North Slope crude oil and study the phase behavior, which was further used to develop a dynamic wax deposition model. This report summarizes the results of the various experimental studies. The subtasks completed during this study include measurement of density, molecular weight, viscosity, pour point, wax appearance temperature, wax content, rate of wax deposition using cold finger, compositional characterization of crude oil and wax obtained from wax content, gas-oil ratio, and phase behavior experiments including constant composition expansion and differential liberation. Also, included in this report is the development of a thermodynamic model to predict wax precipitation. From the experimental study of wax appearance temperature, it was found that wax can start to precipitate at temperatures as high as 40.6 C. The WAT obtained from cross-polar microscopy and viscometry was compared, and it was discovered that WAT from viscometry is overestimated. From the pour point experiment it was found that crude oil can cease to flow at a temperature of 12 C. From the experimental results of wax content, it is evident that the wax content in Alaskan North Slope crude oil can be as high as 28.57%. The highest gas-oil ratio for a live oil sample was observed to be 619.26 SCF/STB. The bubblepoint pressure for live oil samples varied between 1600 psi and 2100 psi. Wax precipitation is one of the most important phenomena in wax deposition and, hence, needs to be modeled. There are various models present in the literature. Won's model, which considers the wax phase as a non-ideal solution, and Pedersen's model, which considers the wax phase as an ideal solution, were compared. Comparison indicated that Pedersen's model gives better results, but the assumption of wax phase as an ideal solution is not realistic. Hence, Won's model was modified to consider different precipitation characteristics of the various constituents in the hydrocarbon fraction. The results obtained from the modified Won's model were compared with existing models, and it was found that predictions from the modified model are encouraging.« less

Synthesis, characterization and DNA-binding studies of mono and heterobimetallic complexes Cu sbnd Sn 2/Zn sbnd Sn 2 and their DNA cleavage activity

NASA Astrophysics Data System (ADS)

Arjmand, Farukh; Sayeed, Fatima

2010-02-01

Heterobimetallic complexes C 6H 24N 4O 6CuSn 2Cl 63, C 6H 24N 4O 6ZnSn 2Cl 64 have been synthesized from their monometallic analogs C 6H 16N 4O 2CuCl 21, C 6H 16N 4O 2ZnCl 22, and were characterized by various spectroscopic and analytical methods. The complexes 1-4 reveal an octahedral geometry for both central metal ions Cu/Zn as well as for Sn metal ion. The interaction of complexes 1-4 with CT-DNA, were investigated by using absorption, emission, cyclic voltammetry, viscometry and DNA cleavage studies. The emission quenching of 3 and 4 by [Fe(CN) 6] 4- depressed greatly when bound to CT-DNA. The results of spectroscopic, viscometric and cyclic voltammetry of complexes 3 and 4 revealed electrostatic mode of binding of the complexes with CT-DNA. These results revealed that 4 bind more avidly in comparison to 3 with CT-DNA. Gel electrophoresis of DNA with complexes 3 and 4 demonstrated that the complexes exhibit excellent cleavage activity under physiological conditions.

Erythrocyte interactions - Comparison of the aggregation power of polymer molecules used in medicine - Not only size does matter.

PubMed

Jovtchev, S; Alexandrov, S; Hristova-Avakumova, N; Miteva, S; Traikov, L; Gerasimova, D; Stoeff, S

2016-01-01

Different colloids are used as a part of solutions for fluid resuscitation and organ preservation: hydroxyethyl starches (HES), dextran (Dx), polyethylene glycols (PEG), polyvinyl pyrrolidone (PVP). Some of the problems associated with their application are addressed to alteration in erythrocyte (ERY) rheology. We intended to estimate in vitro and compare the aggregation power (AP) of these molecules related to ERY interactions. Washed human ERY are used during the study. The zeta sedimentation technique is used to quantify the cell aggregation. Zeta sedimentation ratio (ZSR) based indices (AI) are calculated. The hydrodynamic radius (Rh) of the polymer molecules is determined using viscometry. For all polymers tested a linear range in the relationship AI - concentration was found. The slope of the calculated line was interpreted as measure of the molecule's AP. The following ranking was obtained: PEG >PVP >DX >HES. Within the same chemical type of polymer, increasing Rh of the molecules leads to elevated AI. Comparison of the AP of molecules with similar Rh reveals a significant dependence on their chemical nature. Our results show that molecule's AP is significantly dependent on their chemical nature - i.e. not only molecular size does matter.

DNA-binding studies of a tetraalkyl-substituted porphyrin and the mutually adaptive distortion principle.

PubMed

Ghimire, Srijana; Fanwick, Phillip E; McMillin, David R

2014-10-20

This investigation explores DNA-binding interactions of various forms of an alkyl-substituted cationic porphyrin, H2TC3 (5,10,15,20-tetra[3-(3'-methylimidazolium-1'-yl)]porphyrin). The motivating idea is that incorporating alkyl rather than aryl substituents in the meso positions will enhance the prospects for intercalative as well as external binding to DNA hosts. The ligands may also be applicable for photodynamic and/or anticancer therapy. Methods employed include absorbance, circular dichroism, and emission spectroscopies, as well as viscometry and X-ray crystallography. By comparison with the classical H2T4 system, H2TC3 exhibits a higher molar extinction coefficient but is more prone to self-association. Findings of note include that the copper(II)-containing form Cu(TC3) is adept at internalizing into single-stranded as well as B-form DNA, regardless of the base composition. Surprisingly, however, external binding of H2TC3 occurs within domains that are rich in adenine-thymine base pairs. The difference in the deformability of H2TC3 versus Cu(TC3) probably accounts for the reactivity difference. Finally, Zn(TC3) binds externally, as the metal center remains five-coordinate.

Synthesis and Engineering Materials Properties of Fluid Phase Chemical Hydrogen Storage Materials for Automotive Applications

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

Choi, Young Joon; Westman, Matthew P.; Karkamkar, Abhijeet J.

Among candidates for chemical hydrogen storage in PEM fuel cell automotive applications, ammonia borane (AB, NH3BH3) is considered to be one of the most promising materials due to its high practical hydrogen content of 14-16 wt%. This material is selected as a surrogate chemical for a hydrogen storage system. For easier transition to the existing infrastructure, a fluid phase hydrogen storage material is very attractive and thus, we investigated the engineering materials properties of AB in liquid carriers for a chemical hydrogen storage slurry system. Slurries composed of AB and high temperature liquids were prepared by mechanical milling and sonicationmore » in order to obtain stable and fluidic properties. Volumetric gas burette system was adopted to observe the kinetics of the H2 release reactions of the AB slurry and neat AB. Viscometry and microscopy were employed to further characterize slurries engineering properties. Using a tip-sonication method we have produced AB/silicone fluid slurries at solid loadings up to 40wt% (6.5wt% H2) with viscosities less than 500cP at 25°C.« less

Self-sorted photoconductive xerogels† †Electronic supplementary information (ESI) available: Full experimental details, rheological data, pK a titrations, further NMR data, full details of the photoconductivity set-up, further photoconductivity measurements. See DOI: 10.1039/c6sc02644c Click here for additional data file.

PubMed Central

Draper, Emily R.; Lee, Jonathan R.; Wallace, Matthew; Jäckel, Frank; Cowan, Alexander J.

2016-01-01

We show that a perylene bisimide (PBI)-based gelator forms self-sorted mixtures with a stilbene-based gelator. To form the self-sorted gels, we use a slow pH change induced by the hydrolysis of glucono-δ-lactone (GdL) to gluconic acid. We prove that self-sorting occurs using NMR spectroscopy, UV-Vis spectroscopy, rheology, and viscometry. The corresponding xerogels are photoconductive. Importantly, the wavelength dependence of the photoconductive films is different to that of the films formed from the perylene bisimide alone. Transient absorption spectroscopy of the xerogels reveals changes in the spectrum of the PBI on the picosecond timescale in the presence of stilbene with a PBI radical anion being formed within 10 ps when the stilbene is present. The ability to form the PBI radical anion under visible light leads to the enhanced spectral response of the multicomponent gels. These systems therefore have potential as useful visible-active optoelectronics. PMID:28451108

The effect of gamma irradiation on chitosan and its application as a plant growth promoter in Chinese kale (Brassica alboglabra)

NASA Astrophysics Data System (ADS)

Isa, Mohd Hafez Mohd; Yasir, Muhamad Samudi; Hasan, Abu Bakar; Fadilah, Nur Izzah Md; Hassan, Abdul Rahman

2016-01-01

This research project was conducted to study the effects of irradiation on chitosan and its potential application as a plant growth promoter. Chitosan in the form of flakes was irradiated with gamma rays at irradiation dosage of 50 kGy, 100 kGy, 200 kGy and 400 kGy. The effect of irradiation on chitosan in terms of intrinsic viscosity and average molecular weight was measured using Ubbelohde capillary viscometry technique and the results obtained showed irradiation at doses of up to 50 kGy had caused an extremely significant reduction of both parameters and this trend continued at higher irradiation doses, although the decrease were not significant. The effect of various concentrations of chitosan and irradiated chitosan on growth promotion of Chinese kale (Brassica alboglabra) was hydroponically grown and cultivated for 50 days. Statistical analysis showed addition of 10 ppm of irradiated chitosan of 200 kGy and 400 kGy, respectively, resulted in an extremely significant increase in the percentage weight gain of Chinese kale (Brassica alboglabra). Results obtained in this study showed the potential use of irradiated chitosan as a plant growth promoter for plants grown hydroponically.

Toward comprehensive studies of liquids at high pressures and high temperatures: Combined structure, elastic wave velocity, and viscosity measurements in the Paris-Edinburgh cell

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

Kono, Yoshio; Park, Changyong; Kenney-Benson, Curtis

2014-08-19

Techniques for measuring liquid structure, elastic wave velocity, and viscosity under high pressure have been integrated using a Paris–Edinburgh cell at Beamline 16-BM-B, HPCAT of the Advanced Photon Source. The Paris–Edinburgh press allows for compressing large volume samples (up to 2 mm in both diameter and length) up to ~7 GPa and 2000 °C. Multi-angle energy dispersive X-ray diffraction provides structure factors of liquid to a large Q of ~19 Å. Ultrasonic techniques have been developed to investigate elastic wave velocity of liquids combined with the X-ray imaging. Falling sphere viscometry, using high-speed X-ray radiography (>1000 frames/s), enables us tomore » investigate a wide range of viscosity, from those of high viscosity silicates or oxides melts to low viscosity (<1 mPa s) liquids and fluids such as liquid metals or salts. The integration of these multiple techniques has promoted comprehensive studies of structure and physical properties of liquids as well as amorphous materials at high pressures and high temperatures, making it possible to investigate correlations between structure and physical properties of liquids in situ.« less

The Tribological Properties of Several Silahydrocarbons for Use in Space Mechanisms

NASA Technical Reports Server (NTRS)

Jones, W. R., Jr.; Jansen, M. J.; Gschwender, L. J.; Snyder, C. E., Jr.; Sharma, S. K.; Predmore, R. E.; Dube, M. J.

2001-01-01

Silahydrocarbons are members of a relatively new class of liquid lubricants with great potential for use in space mechanisms. They are unimolecular species consisting of silicon, carbon, and hydrogen. They possess unique wear, viscosity, and volatility properties while retaining the ability to solubilize conventional additives. The tribological properties of several members of this class, including tri, tetra- and penta-compounds, are presented. These properties include: viscosity-temperature (ASTM D446), viscosity-pressure coefficient, vapor pressure, volatility, lubricant lifetimes, traction, reciprocating and four ball wear rates and bearing performance. Lubricant lifetimes were determined using a vacuum ball bearing simulator, the spiral orbit tribometer (SOT). Wear was measured using a Cameron Plint reciprocating tribometer and wear rates with a vacuum four ball tribometer. Conventional viscometry was used for viscosity-temperature measurements and a Knudsen cell for vapor pressure. Vacuum Thermogravimetric Analysis (TGA) was also used for volatility measurements. Pressure viscosity coefficients (a values) were estimated from EHL (elastohydrodynamic lubrication) film thickness measurements. Traction coefficients were measured with a twin disk traction rig. Bearing tests were performed in a vacuum bearing test facility. These properties are compared to existing state-of-the-art space lubricants.

Synthesis, spectroscopic characterization, biological screenings, DNA binding study and POM analyses of transition metal carboxylates.

PubMed

Uddin, Noor; Sirajuddin, Muhammad; Uddin, Nizam; Tariq, Muhammad; Ullah, Hameed; Ali, Saqib; Tirmizi, Syed Ahmed; Khan, Abdur Rehman

2015-04-05

This article contains the synthesis of a novel carboxylic acid derivative, its transition metal complexes and evaluation of biological applications. Six carboxylate complexes of transition metals, Zn(II) and Hg(II), have been successfully synthesized and characterized by FT-IR and NMR (1H, 13C). The ligand, HL, (4-[(2,6-Diethylphenyl)amino]-4-oxobutanoic acid) was also characterized by single crystal X-ray analysis. The complexation occurs via oxygen atoms of the carboxylate moiety. FT-IR date show the bidentate nature of the carboxylate moiety of the ligand as the Δν value in all complexes is less than that of the free ligand. The ligand and its complexes were screened for antifungal and antileishmanial activities. The results showed that the ligand and its complexes are active with few exceptions. UV-visible spectroscopy and viscometry results reveal that the ligand and its complexes interact with the DNA via intercalative mode of interaction. A new and efficient strategy to identify the pharmacophores and anti-pharmacophores sites in carboxylate derivatives for the antibacterial/antifungal activity using Petra, Osiris and Molinspiration (POM) analyses was also carried out. Copyright © 2014 Elsevier B.V. All rights reserved.

Synthesis, spectroscopic characterization, biological screenings, DNA binding study and POM analyses of transition metal carboxylates

NASA Astrophysics Data System (ADS)

Uddin, Noor; Sirajuddin, Muhammad; Uddin, Nizam; Tariq, Muhammad; Ullah, Hameed; Ali, Saqib; Tirmizi, Syed Ahmed; Khan, Abdur Rehman

2015-04-01

This article contains the synthesis of a novel carboxylic acid derivative, its transition metal complexes and evaluation of biological applications. Six carboxylate complexes of transition metals, Zn(II) and Hg(II), have been successfully synthesized and characterized by FT-IR and NMR (1H, 13C). The ligand, HL, (4-[(2,6-Diethylphenyl)amino]-4-oxobutanoic acid) was also characterized by single crystal X-ray analysis. The complexation occurs via oxygen atoms of the carboxylate moiety. FT-IR date show the bidentate nature of the carboxylate moiety of the ligand as the Δν value in all complexes is less than that of the free ligand. The ligand and its complexes were screened for antifungal and antileishmanial activities. The results showed that the ligand and its complexes are active with few exceptions. UV-visible spectroscopy and viscometry results reveal that the ligand and its complexes interact with the DNA via intercalative mode of interaction. A new and efficient strategy to identify the pharmacophores and anti-pharmacophores sites in carboxylate derivatives for the antibacterial/antifungal activity using Petra, Osiris and Molinspiration (POM) analyses was also carried out.

Methods of Viscosity Measurements in Sealed Ampoules

NASA Technical Reports Server (NTRS)

Mazuruk, Konstantin

1999-01-01

Viscosity of semiconductor and metallic melts is usually measured by oscillating cup method. This method utilizes the melts contained in vacuum sealed silica ampoules, thus the problems related to volatility, contamination, and high temperature and pressure can be alleviated. In a typical design, the time required for a single measurement is of the order of one hour. In order to reduce this time to a minute range, a high resolution (0.05 arc.sec) angular detection system is implemented in our design of the viscometer. Furthermore, an electromagnet generating a rotational magnetic field (RMF) is incorporated into the apparatus. This magnetic field can be used to remotely and non intrusively measure the electrical conductivity of the melt. It can also be used to induce a well controlled rotational flow in the system. The transient behavior of this flow can potentially yield the viscosity of the fluid. Based on RMF implementation, two novel viscometry methods are proposed in this work: a) the transient torque method, b) the resonance method. A unified theoretical approach to the three methods (oscillating cup, transient torque, and resonance) is presented along with the initial test results of the constructed apparatus. Advantages of each of the method are discussed.

A glycoconjugate of Haemophilus influenzae Type b capsular polysaccharide with tetanus toxoid protein: hydrodynamic properties mainly influenced by the carbohydrate.

PubMed

Abdelhameed, Ali Saber; Adams, Gary G; Morris, Gordon A; Almutairi, Fahad M; Duvivier, Pierre; Conrath, Karel; Harding, Stephen E

2016-02-26

Three important physical properties which may affect the performance of glycoconjugate vaccines against serious disease are molar mass (molecular weight), heterogeneity (polydispersity), and conformational flexibility in solution. The dilute solution behaviour of native and activated capsular polyribosylribitol (PRP) polysaccharides extracted from Haemophilus influenzae type b (Hib), and the corresponding glycoconjugate made by conjugating this with the tetanus toxoid (TT) protein have been characterized and compared using a combination of sedimentation equilibrium and sedimentation velocity in the analytical ultracentrifuge with viscometry. The weight average molar mass of the activated material was considerably reduced (Mw ~ 0.24 × 10(6) g.mol(-1)) compared to the native (Mw ~ 1.2 × 10(6) g.mol(-1)). Conjugation with the TT protein yielded large polydisperse structures (of Mw ~ 7.4 × 10(6) g.mol(-1)), but which retained the high degree of flexibility of the native and activated polysaccharide, with frictional ratio, intrinsic viscosity, sedimentation conformation zoning behaviour and persistence length all commensurate with highly flexible coil behaviour and unlike the previously characterised tetanus toxoid protein (slightly extended and hydrodynamically compact structure with an aspect ratio of ~3). This non-protein like behaviour clearly indicates that it is the carbohydrate component which mainly influences the physical behaviour of the glycoconjugate in solution.

Technological optimization of manufacture of probiotic whey cheese matrices.

PubMed

Madureira, Ana R; Brandão, Teresa; Gomes, Ana M; Pintado, Manuela E; Malcata, F Xavier

2011-03-01

In attempts to optimize their manufacture, whey cheese matrices obtained via thermal processing of whey (leading to protein precipitation) and inoculated with probiotic cultures were tested. A central composite, face-centered design was followed, so a total of 16 experiments were run using fractional addition of bovine milk to feedstock whey, homogenization time, and storage time of whey cheese as processing parameters. Probiotic whey cheese matrices were inoculated with Lactobacillus casei LAFTIL26 at 10% (v/v), whereas control whey cheese matrices were added with skim milk previously acidified with lactic acid to the same level. All whey cheeses were stored at 7 °C up to 14 d. Chemical and sensory analyses were carried out for all samples, as well as rheological characterization by oscillatory viscometry and textural profiling. As expected, differences were found between control and probiotic matrices: fractional addition of milk and storage time were the factors accounting for the most important effects. Estimation of the best operating parameters was via response surface analysis: milk addition at a rate of 10% to 15% (v/v), and homogenization for 5 min led to the best probiotic whey cheeses in terms of texture and organoleptic properties, whereas the best time for consumption was found to be by 9 d of storage following manufacture.

Micro-Electromechanical Affinity Sensor for the Monitoring of Glucose in Bioprocess Media

PubMed Central

Theuer, Lorenz; Lehmann, Micha; Junne, Stefan; Neubauer, Peter; Birkholz, Mario

2017-01-01

An affinity-viscometry-based micro-sensor probe for continuous glucose monitoring was investigated with respect to its suitability for bioprocesses. The sensor operates with glucose and dextran competing as binding partner for concanavalin A, while the viscosity of the assay scales with glucose concentration. Changes in viscosity are determined with a micro-electromechanical system (MEMS) in the measurement cavity of the sensor probe. The study aimed to elucidate the interactions between the assay and a typical phosphate buffered bacterial cultivation medium. It turned out that contact with the medium resulted in a significant long-lasting drift of the assay’s viscosity at zero glucose concentration. Adding glucose to the medium lowers the drift by a factor of eight. The cglc values measured off-line with the glucose sensor for monitoring of a bacterial cultivation were similar to the measurements with an enzymatic assay with a difference of less than ±0.15 g·L−1. We propose that lectin agglomeration, the electro-viscous effect, and constitutional changes of concanavalin A due to exchanges of the incorporated metal ions may account for the observed viscosity increase. The study has demonstrated the potential of the MEMS sensor to determine sensitive viscosity changes within very small sample volumes, which could be of interest for various biotechnological applications. PMID:28594350

Quasi-Solid-State Single-Atom Transistors.

PubMed

Xie, Fangqing; Peukert, Andreas; Bender, Thorsten; Obermair, Christian; Wertz, Florian; Schmieder, Philipp; Schimmel, Thomas

2018-06-21

The single-atom transistor represents a quantum electronic device at room temperature, allowing the switching of an electric current by the controlled and reversible relocation of one single atom within a metallic quantum point contact. So far, the device operates by applying a small voltage to a control electrode or "gate" within the aqueous electrolyte. Here, the operation of the atomic device in the quasi-solid state is demonstrated. Gelation of pyrogenic silica transforms the electrolyte into the quasi-solid state, exhibiting the cohesive properties of a solid and the diffusive properties of a liquid, preventing the leakage problem and avoiding the handling of a liquid system. The electrolyte is characterized by cyclic voltammetry, conductivity measurements, and rotation viscometry. Thus, a first demonstration of the single-atom transistor operating in the quasi-solid-state is given. The silver single-atom and atomic-scale transistors in the quasi-solid-state allow bistable switching between zero and quantized conductance levels, which are integer multiples of the conductance quantum G 0  = 2e 2 /h. Source-drain currents ranging from 1 to 8 µA are applied in these experiments. Any obvious influence of the gelation of the aqueous electrolyte on the electron transport within the quantum point contact is not observed. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hemorheological changes and characteristic parameters derived from whole blood viscometry in chronic heroin addicts.

PubMed

Antonova, N; Zvetkova, E; Ivanov, I; Savov, Y

2008-01-01

A group of 15 chronic opioid addicts (DA) with mean age 26.5+/-7.3 years was studied by means of a rotational Contraves Low Shear 30 viscometer and the results have been compared with a control group of 19 healthy subjects. It was found that the mean whole blood viscosity values of the investigated group of heroin abusers (n=15) were elevated compared to that of healthy persons (n=19) over the whole shear rate range and fell by more than ten orders of magnitude (Savov et al., 2006). The present investigation uses the coefficients of the models of Ostwald-de-Walle (power law) and Herschel-Bulkley law, which describe whole blood flow curves (tau-gamma) within the shear rates range from 10(-2) to 10(2) s(-1) and itself incorporate whole blood viscosity data in the entire shear rate range. A significant difference in the mean yield shear stress tau(0) values of the drug abusers' group compared to the controls was found. A strong positive linear correlation was determined between the parameters of RBC aggregation in the group of heroin addicts confirming our previous results (Ivanov and Antonova, 2005; Savov, Zvetkova et al., 2007; Savov, Antonova et al., 2007) for intensive RBC and platelet aggregation and morphological changes in DA group.

Effects of surfactant micelles on viscosity and conductivity of poly(ethylene glycol) solutions

NASA Astrophysics Data System (ADS)

Wang, Shun-Cheng; Wei, Tzu-Chien; Chen, Wun-Bin; Tsao, Heng-Kwong

2004-03-01

The neutral polymer-micelle interaction is investigated for various surfactants by viscometry and electrical conductometry. In order to exclude the well-known necklace scenario, we consider aqueous solutions of low molecular weight poly(ethylene glycol) (2-20)×103, whose radial size is comparable to or smaller than micelles. The single-tail surfactants consist of anionic, cationic, and nonionic head groups. It is found that the viscosity of the polymer solution may be increased several times by micelles if weak attraction between a polymer segment and a surfactant exists, ɛ

The effect of gamma irradiation on chitosan and its application as a plant growth promoter in Chinese kale (Brassica alboglabra)

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

Isa, Mohd Hafez Mohd, E-mail: m.hafez@usim.edu.my; Hasan, Abu Bakar; Fadilah, Nur Izzah Md

This research project was conducted to study the effects of irradiation on chitosan and its potential application as a plant growth promoter. Chitosan in the form of flakes was irradiated with gamma rays at irradiation dosage of 50 kGy, 100 kGy, 200 kGy and 400 kGy. The effect of irradiation on chitosan in terms of intrinsic viscosity and average molecular weight was measured using Ubbelohde capillary viscometry technique and the results obtained showed irradiation at doses of up to 50 kGy had caused an extremely significant reduction of both parameters and this trend continued at higher irradiation doses, although themore » decrease were not significant. The effect of various concentrations of chitosan and irradiated chitosan on growth promotion of Chinese kale (Brassica alboglabra) was hydroponically grown and cultivated for 50 days. Statistical analysis showed addition of 10 ppm of irradiated chitosan of 200 kGy and 400 kGy, respectively, resulted in an extremely significant increase in the percentage weight gain of Chinese kale (Brassica alboglabra). Results obtained in this study showed the potential use of irradiated chitosan as a plant growth promoter for plants grown hydroponically.« less

Interaction of thionine with triple-, double-, and single-stranded RNAs.

PubMed

Lozano, Héctor J; García, Begoña; Busto, Natalia; Leal, José M

2013-01-10

The interaction of thionine with triple, double, and single RNA helices has been fully characterized by thermodynamic and kinetic methods. The nature of the interaction of thionine with the synthetic polynucleotides poly(rU), poly(rA)·poly(rU), and poly(rA)·2poly(rU) has been studied at pH = 7.0 and 25 °C by UV absorbance, fluorescence, circular dichroism spectroscopy, viscometry, differential scanning calorimetry, and T-jump kinetic measurements. The results show that at I = 0.1 M thionine binds to a single poly(rU) strand, destabilizes the poly(rA)·2poly(rU) triplex by external binding, and intercalates into poly(rA)·poly(rU) with similar affinity to the thionine/DNA intercalated complex (Paul, P.; Kumar, G. S. J. Fluoresc. 2012, 22, 71-80). On the other hand, the differential scanning calorimetry measurements performed with thionine display a point in which the heat capacity remains unaltered, revealing the equilibrium of isothermal denaturation: thionine/poly(rA)·2poly(rU) + thionine ⇌ thionine/poly(rA)·poly(rU) + thionine/poly(rU), an outcome supported by the other techniques used. The denaturation equilibrium constant, K(D) (25 °C) = 522 M(-1), was evaluated from the affinity with the single, duplex, and triplex RNA.

An interlaboratory comparison of measurements from filament-stretching rheometers using common test fluids

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

Anna, Shelley L.; McKinley, Gareth H.; Nguyen, Duc A.

2001-01-01

Following development of a filament-stretching extensional rheometer at Monash University, similar rheometers have been designed and built in other laboratories. To help validate the basic technique, a collaborative program was undertaken to compare results from several instruments. First, three test fluids prepared at the University of California at Berkeley were characterized in steady and transient shear flows there and at the Massachusetts Institute of Technology (M.I.T.), and then tested in extensional rheometers at M.I.T., Monash and the University of Toronto. Each fluid is a constant-viscosity solution of narrow-molecular-weight-distribution polystyrene dissolved in oligomeric polystyrene. The solute molecular weights are 2.0, 6.5,more » and 20 million g/mol, and the polymer concentration in each fluid is 0.05 wt.%. From linear viscoelastic measurements, the Zimm relaxation times of the fluids are found to be 3.7, 31, and 150 s, respectively. The scaling of relaxation times with molecular weight indicates better-than-theta solvent quality, a finding consistent with independent intrinsic viscometry measurements of equilibrium coil size. Each fluid was tested in the three filament stretching rheometers at similar Deborah numbers. Despite variations in instrument design and the general difficulty of the technique, transient Trouton ratios measured in the three instruments are shown to agree quantitatively.« less

Effect of selected non-ionic surfactants on the flow behavior of aqueous veegum suspensions.

PubMed

Kennedy, Ross A; Kennedy, Michelle L

2007-03-30

The aim of this work was to investigate the influence of some non-ionic surfactants, Tween 80 and Brij 98, on the viscosity and flow behavior of a commercial montmorillonite clay, Veegum Granules. The effect of different concentrations of the surfactants on the shear stress-shear rate rheograms of hydrated concentrated clay suspensions was determined by shear viscometry. The addition of either surfactant increased the plastic viscosity and the yield stress of the suspensions. Furthermore, both surfactants altered the thixotropy of the suspensions to an extent that depended on both the surfactant concentration and the time of equilibration of the surfactant and Veegum. Brij 98 had a greater and more rapid effect. It is proposed that the surfactant polar head-groups anchor at the tetrahedral sheet surface, leaving the alkyl chains extending away from the edges and faces. Consequently, the alkyl chains undergo hydrophobic interactions that facilitate the association between the platelets and increase the physical structure within the suspension. Stereochemical differences between the polar groups may lead to differences in the way the surfactants associate with the tetrahedral sheet and hence their ultimate effect on the rheological behavior. There is a significant interaction between these surfactants and montmorillonite clays, and the rheological changes that occur could have a major impact on any pharmaceutical formulation that uses these ingredients.

Viscosity characteristics of selected volcanic rock melts

NASA Astrophysics Data System (ADS)

Hobiger, Manuel; Sonder, Ingo; Büttner, Ralf; Zimanowski, Bernd

2011-02-01

A basic experimental study of the behavior of magma rheology was carried out on remelted volcanic rocks using wide gap viscometry. The complex composition of magmatic melts leads to complicated rheologic behavior which cannot be described with one simple model. Therefore, measurement procedures which are able to quantify non-Newtonian behavior have to be employed. Furthermore, the experimental apparatus must be able to deal with inhomogeneities of magmatic melts. We measured the viscosity of a set of materials representing a broad range of volcanic processes. For the lower viscous melts (low-silica compositions), non-Newtonian behavior is observed, whereas the high-silica melts show Newtonian behavior in the measured temperature and shear rate range (T = 1423 K - 1623 K, γ˙ = 10 - 2 s - 1 - 20 s - 1 ). The non-Newtonian materials show power-law behavior. The measured viscosities η and power-law indexes m lie in the intervals 8 Pa s ≤ η ≤ 210 3 Pa s, 0.71 ≤ m ≤ 1.0 (Grímsvötn basalt), 0.9 Pa s ≤ η ≤ 350 Pa s, 0.61 ≤ m ≤ 0.93 (Hohenstoffeln olivine-melilitite), and 8 Pa s ≤ η ≤ 1.510 4 Pa s, 0.55 ≤ m ≤ 1.0 (Sommata basalt). Measured viscosities of the Newtonian high-silica melts lie in the range 10 4 Pa s ≤ η ≤ 310 5 Pa s.

1-anilino-8-naphthalene sulfonate as a protein conformational tightening agent.

PubMed

Matulis, D; Baumann, C G; Bloomfield, V A; Lovrien, R E

1999-05-01

1-Anilino-8-naphthalene sulfonate (ANS) anion is conventionally considered to bind to preexisting hydrophobic (nonpolar) surfaces of proteins, primarily through its nonpolar anilino-naphthalene group. Such binding is followed by an increase in ANS fluorescence intensity, similar to that occurring when ANS is dissolved in organic solvents. It is generally assumed that neither the negative sulfonate charge on the ANS, nor charges on the protein, participate significantly in ANS-protein interaction. However, titration calorimetry has demonstrated that most ANS binding to a number of proteins occurs through electrostatic forces, in which ion pairs are formed between ANS sulfonate groups and cationic groups on the proteins (D. Matulis and R. E. Lovrien, Biophys. J., 1998, Vol. 74, pp. 1-8). Here we show by viscometry and diffusion coefficient measurements that bovine serum albumin and gamma-globulin, starting from their acid-expanded, most hydrated conformations, undergo extensive molecular compaction upon ANS binding. As the cationic protein binds negatively charged ANS anion it also takes up positively charged protons from water to compensate the effect of the negative charge, and leaves the free hydroxide anions in solution thus shifting pH upward (the Scatchard-Black effect). These results indicate that ANS is not always a definitive reporter of protein molecular conformation that existed before ANS binding. Instead, ANS reports on a conformationally tightened state produced by the interplay of ionic and hydrophobic characters of both protein and ligand.

Synthesis, Structural, DNA Binding and Cleavage Studies of Cu(II) Complexes Containing Benzothiazole Cored Schiff Bases.

PubMed

Tejaswi, Somapangu; Kumar, Marri Pradeep; Rambabu, Aveli; Vamsikrishna, Narendrula; Shivaraj

2016-11-01

Novel benzothiazole Schiff bases L 1 [1-((4,6-difluorobenzo[d]thiazol-2-ylimino)methyl) naphthalen-2-ol], L 2 [3-((4,6-difluorobenzo[d]thiazol-2-ylimino) methyl)benzene-1,2-diol], L 3 [2-((4,6-difluorobenzo[d]thiazol-2-ylimino)methyl)-5-methoxyphenol], L 4 [2-((4,6-difluorobenzo[d]thiazol-2-ylimino)methyl)-4-chlorophenol] and their binary Cu(II) complexes were synthesized. The structures of all the compounds have been discussed on the basis of elemental analysis, FT-IR, NMR, UV-Visible, ESI-Mass, TGA, ESR, SEM, powder XRD and magnetic moments. Based on the analytical and spectral data a square planar geometry has been assigned to all complexes in which the Schiff bases act as monobasic bidentate ligands, coordinating through the azomethine nitrogen and phenolic oxygen atom. DNA binding ability of these complexes was studied on CT-DNA by using UV-Vis absorption, fluorescence and viscometry. DNA cleavage ability of the complexes was examined on pBR322 DNA by using gel electrophoresis method. All the DNA binding studies reveal that they are good intercalators. The bioefficacy of the ligands and their complexes was examined against the growth of bacteria and fungi in vitro to evaluate their antimicrobial potential. The screening data revealed that the complexes showed more antimicrobial activity than the corresponding free ligands.

Human Growth Hormone Delivery with a Microneedle Transdermal System: Preclinical Formulation, Stability, Delivery and PK of Therapeutically Relevant Doses

PubMed Central

Ameri, Mahmoud; Kadkhodayan, Miryam; Nguyen, Joe; Bravo, Joseph A.; Su, Rebeca; Chan, Kenneth; Samiee, Ahmad; Daddona, Peter E.

2014-01-01

This study evaluated the feasibility of coating formulated recombinant human growth hormone (rhGH) on a titanium microneedle transdermal delivery system, Zosano Pharma (ZP)-hGH, and assessed preclinical patch delivery performance. Formulation rheology and surface activity were assessed by viscometry and contact angle measurement. rhGH liquid formulation was coated onto titanium microneedles by dip-coating and drying. The stability of coated rhGH was determined by size exclusion chromatography-high performance liquid chromatography (SEC-HPLC). Preclinical delivery and pharmacokinetic studies were conducted in female hairless guinea pigs (HGP) using rhGH coated microneedle patches at 0.5 and 1 mg doses and compared to Norditropin® a commercially approved rhGH subcutaneous injection. Studies demonstrated successful rhGH formulation development and coating on microneedle arrays. The ZP-hGH patches remained stable at 40 °C for six months with no significant change in % aggregates. Pharmacokinetic studies showed that the rhGH-coated microneedle patches, delivered with high efficiency and the doses delivered indicated linearity with average Tmax of 30 min. The absolute bioavailability of the microneedle rhGH patches was similar to subcutaneous Norditropin® injections. These results suggest that ZP-transdermal microneedle patch delivery of rhGH is feasible and may offer an effective and patient-friendly alternative to currently marketed rhGH injectables. PMID:24838219

Hydrodynamic properties of human cervical-mucus glycoproteins in 6M-guanidinium chloride.

PubMed Central

Sheehan, J K; Carlstedt, I

1984-01-01

Cervical mucins and fragments thereof were studied by sedimentation-velocity, rotatory viscometry and laser light-scattering performed as photon-correlation spectroscopy as well as low-angle total-intensity measurements. The Mr of the whole mucins is 10 X 10(6)-15 X 10(6), whereas fragments obtained after reduction of disulphide bonds ('subunits') have Mr 2.1 X 10(6)-2.9 X 10(6), depending on the method used. Subsequent trypsin digestion of subunits afforded glycopeptides with Mr approx. 0.4 X 10(6). The high frictional ratio for the whole mucins is interpreted as a large degree of expansion. The Stokes radius calculated from the diffusion coefficient is approx. 110nm for the whole mucins, which is in agreement with that estimated from the radius of gyration (130nm) by using the concept of the equivalent hydrodynamic sphere. The ratio of the concentration-dependence parameter for the reciprocal sedimentation coefficient (Ks) to the intrinsic viscosity ( [eta] ) for the whole mucins is 1.42, suggesting that the individual macromolecule occupies a spheroidal domain in solution. The relationship between [eta] and Mr for whole mucins, subunits and T-domains suggests that they are linear flexible macromolecules behaving as somewhat 'stiff' random coils. This conclusion is supported by the relationships between the sedimentation coefficients, the diffusion coefficients and the Mr. The hydrodynamic behaviour of the mucins is thus close to that expected for coiling macromolecules entrapping a lot of solvent, which is consistent with the postulated polymeric structure. PMID:6696734

Synthesis of N-vinylpyrrolidone modified acrylic acid copolymer in supercritical fluids and its application in dental glass-ionomer cements.

PubMed

Moshaverinia, Alireza; Roohpour, Nima; Billington, Richard W; Darr, Jawwad A; Rehman, Ihtesham U

2008-07-01

Compressed fluids such as supercritical CO(2) offer marvellous opportunities for the synthesis of polymers, particularly in applications in medicine and dentistry. It has several advantages in comparison to conventional polymerisation solvents, such as enhanced kinetics and simplified solvent removal process. In this study, poly(acrylic acid-co-itaconic acid-co-N-vinylpyrrolidone) (PAA-IA-NVP), a modified glass-ionomer polymer, was synthesised in supercritical CO(2) (sc-CO(2)) and methanol as a co-solvent. The synthesised polymer was characterized by (1)H-NMR, Raman and FT-IR spectroscopy and viscometry. The molecular weight of the final product was also measured using static light scattering method. The synthesised polymers were subsequently used in several glass ionomer cement formulations (Fuji II commercial GIC) in which mechanical strength (compressive strength (CS), diametral tensile strength (DTS) and biaxial flexural strength (BFS)) and handling properties (working and setting time) of the resulting cements were evaluated. The polymerisation reaction in sc-CO(2)/methanol was significantly faster than the corresponding polymerisation reaction in water and the purification procedures were simpler for the former. Furthermore, glass ionomer cement samples made from the terpolymer prepared in sc-CO(2)/methanol exhibited higher CS and DTS and comparable BFS compared to the same polymer synthesised in water. The working properties of glass ionomer formulations made in sc-CO(2)/methanol were comparable and in selected cases better than the values of those made from polymers synthesised in water.

A new insight into the interaction of ZnO with calf thymus DNA through surface defects.

PubMed

Das, Sumita; Chatterjee, Sabyasachi; Pramanik, Srikrishna; Devi, Parukuttyamma Sujatha; Kumar, Gopinatha Suresh

2018-01-01

Experimental evidences on the binding interaction of ZnO and Calf Thymus (CT) DNA using several biophysical techniques are the centre of interest of the present study. The interaction of ZnO with CT DNA has been investigated in detail by absorption spectral study, fluorescence titration, Raman analysis, zeta potential measurement, viscometric experiment along with thermal melting study and microscopic analysis. Steady-state fluorescence study revealed the quenching (48%) of the surface defect related peak intensity of ZnO on interaction with DNA. The optimized concentration of ZnO and DNA to obtain this level of quenching has been found to be 0.049mM and 1.027μM, respectively. Additional fluorescence study with 8-hydroxy-5-quinoline (HQ) as a fluorescence probe for Zn 2+ ruled out the dissolution effect of ZnO under the experimental conditions. DNA conjugation on the surface of ZnO was also supported by Raman study. The quantitative variation in conductivity as well as electrophoretic mobility indicated significant interaction of ZnO with the DNA molecule. Circular dichroism (CD) and viscometry titrations provided clear evidence in support of the conformational retention of the DNA on interaction with ZnO. The binding interaction was found to be predominantly entropy driven in nature. The bio-physical studies presented in this paper exploring ZnO-CT DNA interaction could add a new horizon to understand the interaction between metal oxide and DNA. Copyright © 2017. Published by Elsevier B.V.

Thermal and rheological properties of a family of botryosphaerans produced by Botryosphaeria rhodina MAMB-05.

PubMed

Fonseca, Paulo R M S; Dekker, Robert F H; Barbosa, Aneli M; Silveira, Joana L M; Vasconcelos, Ana F D; Monteiro, Nilson K; Aranda-Selverio, Gabriel; da Silva, Maria de Lourdes Corradi

2011-09-02

Differential scanning calorimetry (DSC), thermogravimetry (TG) and Fourier-transform infra-red spectroscopy (FT-IR) analyses were performed to investigate changes in the physico-chemical properties of botryosphaerans, a family of exopolysaccharides (EPS) produced by the fungus Botryosphaeria rhodina MAMB-05 grown on glucose (EPS(GLC)), sucrose (EPS(SUC)) and fructose (EPS(FRU)). A slight endothermic transition and small mass loss attributable to the removal of water of hydration were observed in the DSC and TG analyses, respectively, for the three EPS samples. The FT-IR spectra confirmed no structural changes occurred during thermal treatment. Viscometry was utilized to obtain information on the rheological behaviour of the EPS in aqueous solutions. The Power Law and Cross Equations determined the natural pseudoplastic characteristics of the EPS. Comparatively, results obtained for EPS produced when B. rhodina MAMB-05 was grown on each of the three carbohydrate sources demonstrated similar apparent viscosity values for EPS(GLC) and EPS(SUC), while EPS(FRU) displayed the lowest apparent viscosity of the three botryosphaerans, suggesting a higher degree of ramification and lower Mw. EPS(GLC) and EPS(SUC) possessed similar degrees of ramification. The slight differences found in their viscosities can be explained by the differences in the type of branching among the three botryosphaerans, thus varying the strength of intermolecular interactions and consequently, consistency and viscosity. The physico-chemical studies of botryosphaerans represent the originality of this work, and the knowledge of these properties is an important criterion for potential applications.

Formulation and in vitro/in vivo evaluation of chitosan-based film forming gel containing ketoprofen.

PubMed

Oh, Dong-Won; Kang, Ji-Hyun; Lee, Hyo-Jung; Han, Sang-Duk; Kang, Min-Hyung; Kwon, Yie-Hyuk; Jun, Joon-Ho; Kim, Dong-Wook; Rhee, Yun-Seok; Kim, Ju-Young; Park, Eun-Seok; Park, Chung-Woong

2017-11-01

The film forming gel, adhered to skin surfaces upon application and formed a film, has an advantage onto skin to provide protection and continuous drug release to the application site. This study aimed to prepare a chitosan-based film forming gel containing ketoprofen (CbFG) and to evaluate the CbFG and film from CbFG (CbFG-film). CbFG were prepared with chitosan, lactic acid and various skin permeation enhancers. The physicochemical characteristics were evaluated by texture analysis, viscometry, SEM, DSC, XRD and FT-IR. To identify the mechanism of skin permeation, in vitro skin permeation study was conducted with a Franz diffusion cell and excised SD-rat and hairless mouse dorsal skin. In vivo efficacy assessment in mono-iodoacetate (MIA)-induced rheumatoid arthritis animal model was also conducted. CbFG was successfully prepared and, after applying CbFG to the excised rat dorsal skin, the CbFG-film was also formed well. The physicochemical characteristics of CbFG and CbFG-film could be explained by the grafting of oleic acid onto chitosan in the absence of catalysts. In addition, CbFG containing oleic acid had a higher skin permeation rate in comparison with any other candidate enhancers. The in vivo efficacy study also confirmed significant anti-inflammatory and analgesic effects. Consequently, we report the successful preparation of chitosan-based film forming gel containing ketoprofen with excellent mechanical properties, skin permeation and anti-inflammatory and analgesic effects.

Are Non-Newtonian Effects Important in Hemodynamic Simulations of Patients With Autogenous Fistula?

PubMed Central

Javid Mahmoudzadeh Akherat, S. M.; Cassel, Kevin; Boghosian, Michael; Dhar, Promila; Hammes, Mary

2017-01-01

Given the current emphasis on accurate computational fluid dynamics (CFD) modeling of cardiovascular flows, which incorporates realistic blood vessel geometries and cardiac waveforms, it is necessary to revisit the conventional wisdom regarding the influences of non-Newtonian effects. In this study, patient-specific reconstructed 3D geometries, whole blood viscosity data, and venous pulses postdialysis access surgery are used as the basis for the hemodynamic simulations of renal failure patients with native fistula access. Rheological analysis of the viscometry data initially suggested that the correct choice of constitutive relations to capture the non-Newtonian behavior of blood is important because the end-stage renal disease (ESRD) patient cohort under observation experience drastic variations in hematocrit (Hct) levels and whole blood viscosity throughout the hemodialysis treatment. For this purpose, various constitutive relations have been tested and implemented in CFD practice, namely Quemada and Casson. Because of the specific interest in neointimal hyperplasia and the onset of stenosis in this study, particular attention is placed on differences in nonhomeostatic wall shear stress (WSS) as that drives the venous adaptation process that leads to venous geometric evolution over time in ESRD patients. Surprisingly, the CFD results exhibit no major differences in the flow field and general flow characteristics of a non-Newtonian simulation and a corresponding identical Newtonian counterpart. It is found that the vein's geometric features and the dialysis-induced flow rate have far greater influence on the WSS distribution within the numerical domain. PMID:28249082

Are Non-Newtonian Effects Important in Hemodynamic Simulations of Patients With Autogenous Fistula?

PubMed

Javid Mahmoudzadeh Akherat, S M; Cassel, Kevin; Boghosian, Michael; Dhar, Promila; Hammes, Mary

2017-04-01

Given the current emphasis on accurate computational fluid dynamics (CFD) modeling of cardiovascular flows, which incorporates realistic blood vessel geometries and cardiac waveforms, it is necessary to revisit the conventional wisdom regarding the influences of non-Newtonian effects. In this study, patient-specific reconstructed 3D geometries, whole blood viscosity data, and venous pulses postdialysis access surgery are used as the basis for the hemodynamic simulations of renal failure patients with native fistula access. Rheological analysis of the viscometry data initially suggested that the correct choice of constitutive relations to capture the non-Newtonian behavior of blood is important because the end-stage renal disease (ESRD) patient cohort under observation experience drastic variations in hematocrit (Hct) levels and whole blood viscosity throughout the hemodialysis treatment. For this purpose, various constitutive relations have been tested and implemented in CFD practice, namely Quemada and Casson. Because of the specific interest in neointimal hyperplasia and the onset of stenosis in this study, particular attention is placed on differences in nonhomeostatic wall shear stress (WSS) as that drives the venous adaptation process that leads to venous geometric evolution over time in ESRD patients. Surprisingly, the CFD results exhibit no major differences in the flow field and general flow characteristics of a non-Newtonian simulation and a corresponding identical Newtonian counterpart. It is found that the vein's geometric features and the dialysis-induced flow rate have far greater influence on the WSS distribution within the numerical domain.

Supercooled smectic nanoparticles: a potential novel carrier system for poorly water soluble drugs.

PubMed

Kuntsche, J; Westesen, K; Drechsler, M; Koch, M H J; Bunjes, H

2004-10-01

The possibility of preparing nanoparticles in the supercooled thermotropic liquid crystalline state from cholesterol esters with saturated acyl chains as well as the incorporation of model drugs into the dispersions was investigated using cholesteryl myristate (CM) as a model cholesterol ester. Nanoparticles were prepared by high-pressure melt homogenization or solvent evaporation using phospholipids, phospholipid/ bile salt, or polyvinyl alcohol as emulsifiers. The physicochemical state and phase behavior of the particles was characterized by particle size measurements (photon correlation spectroscopy, laser diffraction with polarization intensity differential scattering), differential scanning calorimetry, X-ray diffraction, and electron and polarizing light microscopy. The viscosity of the isotropic and liquid crystalline phases of CM in the bulk was investigated in dependence on temperature and shear rate by rotational viscometry. CM nanoparticies can be obtained in the smectic phase and retained in this state for at least 12 months when stored at 230C in optimized systems. The recrystallization tendency of CM in the dispersions strongly depends on the stabilizer system and the particle size. Stable drug-loaded smectic nanoparticles were obtained after incorporation of 10% (related to CM) ibuprofen, miconazole, etomidate, and 1% progesterone. Due to their liquid crystalline state, colloidal smectic nanoparticles offer interesting possibilities as carrier system for lipophilic drugs. CM nanoparticles are suitable model systems for studying the crystallization behavior and investigating the influence of various parameters for the development of smectic nanoparticles resistant against recrystallization upon storage.

Modeling the reversible kinetics of neutrophil aggregation under hydrodynamic shear.

PubMed Central

Neelamegham, S; Taylor, A D; Hellums, J D; Dembo, M; Smith, C W; Simon, S I

1997-01-01

Neutrophil emigration into inflamed tissue is mediated by beta 2-integrin and L-selectin adhesion receptors. Homotypic neutrophil aggregation is also dependent on these molecules, and it provides a model system in which to study adhesion dynamics. In the current study we formulated a mathematical model for cellular aggregation in a linear shear field based on Smoluchowski's two-body collision theory. Neutrophil suspensions activated with chemotactic stimulus and sheared in a cone-plate viscometer rapidly aggregate. Over a range of shear rates (400-800 s-1), approximately 90% of the single cells were recruited into aggregates ranging from doublets to groupings larger than sextuplets. The adhesion efficiency fit to these kinetics reached maximum levels of > 70%. Formed aggregates remained intact and resistant to shear up to 120 s, at which time they spontaneously dissociated back to singlets. The rate of cell disaggregation was linearly proportional to the applied shear rate, and it was approximately 60% lower for doublets as compared to larger aggregates. By accounting for the time-dependent changes in adhesion efficiency, disaggregation rate, and the effects of aggregate geometry, we succeeded in predicting the reversible kinetics of aggregation over a wide range of shear rates and cell concentrations. The combination of viscometry with flow cytometry and mathematical analysis as presented here represents a novel approach to differentiating between the effects of hydrodynamics and the intrinsic biological processes that control cell adhesion. Images FIGURE 3 FIGURE 5 PMID:9083659

Partial purification of coriolus versicolor's extracellular polyphenol oxidase (PPO)

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

Moore, N.L.; Dashek, W.V.

1993-05-01

Coriolus versicolor, a white-rot basidiomycete, secretes ligno-celluloytic enzymes. Because these are valuable to paper-pulp agricultural industries, trials are in progress to substrate induce these enzymes enhance their secretions. Reported are attempts to develop an extracellular PPO (o-diphenols to 0-diquinones) purification protocol applicable to [open quote]batch-cultured[close quote] C. versicolor. Whereas dialysis (MW [open quote]cut-off[close quote], 14,000) of 13 day growth medium (GM) resulted in 2.17 fold PPO spc. act. increase, dialysis plus a 0-30% (NH[sub 4])[sub 2]SO[sub 4] [open quote]cut[close quote] yielded a 3.27 fold enhancement. Subsequent GM chromatography on DEAE CM-Sephadexes revealed that PPO exchanged with DEAE's counterion without enhancingmore » spc. act. Gel filtration of GM commercial PPOs on G-150 resulted in similar elutions indicating a substitute for ion exchange chromatography. Time-dependent fungal growth in liquid medium followed by viscometry utilizing CMC revealed a GM endocellulase 2 days after inoculation an activity rise to day 12. Filteration of Onozuka cellulase on G-150 yielded an elution profile similar to those of GM authentic PPO's compounding C. versicolor's PPO purification. SDS-PAGE of dialyzed GM revealed 4 proteins, one of which was removed by the (NH[sub 4])[sub 2]SO[sub 4]. The m[sub TS] of commercial Sigma's PPO Onozuka cellulase were 0.76 0.59, respectively, for comparison to C. versicolor's PPO. Affinity, hydroxylapatite hydrophobic interaction chromatographies may yield a single SDS-PAGE PPO band.« less

A Dictyostelium mutant deficient in severin, an F-actin fragmenting protein, shows normal motility and chemotaxis

PubMed Central

1989-01-01

A severin deficient mutant of Dictyostelium discoideum has been isolated by the use of colony immunoblotting after chemical mutagenesis. In homogenates of wild-type cells, severin is easily detected as a very active F-actin fragmenting protein. Tests for severin in the mutant, HG1132, included viscometry for the assay of F- actin fragmentation in fractions from DEAE-cellulose columns, labeling of blots with monoclonal and polyclonal antibodies, and immunofluorescent-labeling of cryosections. Severin could not be detected in the mutant using these methods. The mutation in HG1132 is recessive and has been mapped to linkage group VII. The mutant failed to produce the normal severin mRNA, but small amounts of a transcript that was approximately 100 bases larger than the wild-type mRNA were detected in the mutant throughout all stages of development. On the DNA level a new Mbo II restriction site was found in the mutant within the coding region of the severin gene. The severin deficient mutant cells grew at an approximately normal rate, aggregated and formed fruiting bodies with viable spores. By the use of an image processing system, speed of cell movement, turning rates, and precision of chemotactic orientation in a stable gradient of cyclic AMP were quantitated, and no significant differences between wild-type and mutant cells were found. Thus, under the culture conditions used, severin proved to be neither essential for growth of D. discoideum nor for any cell function that is important for aggregation or later development. PMID:2537840

Spherical LDH-Ag°-montmorillonite heterocoagulated system with a pH-dependent sol-gel structure for controlled accessibility of AgNPs immobilized on the clay lamellae.

PubMed

Deák, Ágota; Janovák, László; Tallósy, Szabolcs Péter; Bitó, Tamás; Sebők, Dániel; Buzás, Norbert; Pálinkó, István; Dékány, Imre

2015-02-17

Aqueous suspensions of spherical ZnMgAl-layered double hydroxides [LDH(sph)] and antibacterial silver nanoparticles (AgNPs) deposited on the lamellae of montmorillonite were used for the synthesis of composites, which behave like coherent gels at low pH (≲4.5) and incoherent sols at higher pH (≳4.5). The composition of the composite was chosen as LDH(sph)/Ag°-montm. = 25:75 wt % in order to ensure a sol-gel transition that can also be characterized by viscometry. This pH-sensitive heterocoagulated system consisting of oppositely charged colloid particles was suitable for the release of antimicrobial AgNPs immobilized on the clay lamellae via a pH-controlled gel-sol transition. The heterocoagulation process was also characterized by surface charge titration measurements. Spherical LDH/Ag°-montmorillonite composite samples were identified by X-ray diffraction (XRD) measurements. The morphological properties of the composites were studied, and the presence of the heterocoagulated structure was confirmed by scanning electron microscopy (SEM). The nanoscale structure of the LDH(sph)-Ag°-montmorillonite composite obtained was also verified by small-angle X-ray scattering (SAXS), and the rheological characteristics were studied at various pH values. The viscosity and yield value of the composite decreased by an order of magnitude upon increasing the pH from 3.0 to 5.5. The sol-gel transition of the composite suspension was reversible in the previously mentioned pH range.

The molar hydrodynamic volume changes of factor VIIa due to GlycoPEGylation.

PubMed

Plesner, Bitten; Westh, Peter; Hvidt, Søren; Nielsen, Anders D

2011-06-01

The effects of GlycoPEGylation on the molar hydrodynamic volume of recombinant human rFVIIa were investigated using rFVIIa and two GlycoPEGylated recombinant human FVIIa derivatives, a linear 10kDa PEG and a branched 40kDa PEG, respectively. Molar hydrodynamic volumes were determined by capillary viscometry and mass spectrometry. The intrinsic viscosities of rFVIIa, its two GlycoPEGylated compounds, and of linear 8kDa, 10kDa, 20kDa and branched 40kDa PEG polymers were determined. The measured intrinsic viscosity of rFVIIa is 6.0mL/g, while the intrinsic viscosities of 10kDa PEG-rFVIIa and 40kDa PEG-rFVIIa are 29.5mL/g and 79.0mL/g, respectively. The intrinsic viscosities of the linear PEG polymers are 20, 22.6 and 41.4mL/g for 8, 10, and 20kDa, respectively, and 61.1mL/g for the branched 40kDa PEG. From the results of the intrinsic viscosity and MALDI-TOF measurements it is evident, that the molar hydrodynamic volume of the conjugated protein is not just an addition of the molar hydrodynamic volume of the PEG and the protein. The molar hydrodynamic volume of the GlycoPEGylated protein is larger than the volume of its composites. These results suggest that both the linear and the branched PEG are not wrapped around the surface of rFVIIa but are chains that are significantly stretched out when attached to the protein. Copyright © 2011 Elsevier B.V. All rights reserved.

Interaction of small molecules with double-stranded RNA: spectroscopic, viscometric, and calorimetric study of hoechst and proflavine binding to PolyCG structures.

PubMed

Sinha, Rangana; Hossain, Maidul; Kumar, Gopinatha Suresh

2009-04-01

Design and synthesis of new small molecules binding to double-stranded RNA necessitate complete understanding of the molecular aspects of the binding of many existing molecules. Toward this goal, in this work we evaluated the biophysical aspects of the interaction of a DNA intercalator (proflavine) and a minor groove binder (hoechst 33258) with two polymorphic forms of polyCG, namely, the right-handed Watson-Crick base paired A-form and the left-handed Hoogsteen base paired H(L)-form, by absorption, fluorescence, and viscometry experiments. The energetics of the interaction of these molecules with the RNA structures has also been elucidated by isothermal titration calorimetry (ITC). Results suggest that proflavine strongly intercalates in both forms of polyCG, whereas hoechst shows mainly groove-binding modes. The binding of both drugs to both forms of RNA resulted in significant conformational change to the RNA structure with the bound molecules being placed in the chiral RNA helix. ITC profiles for both proflavine and hoechst show two binding sites. Binding of proflavine to both forms of RNA is endothermic and entropy driven in the first site and exothermic and enthalpy driven in the second site, whereas hoechst binding to both forms of RNA is exothermic and enthalpy driven in the first site and endothermic and entropy driven in the second site. This study suggests that the binding affinity characteristics and energetics of interaction of these DNA binding molecules with the RNA conformations are significantly different and may serve as data for future development of effective structure-selective RNA-based drugs.

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

Fauzi, Iqbal, E-mail: arcana@chem.itb.ac.id; Arcana, I Made, E-mail: arcana@chem.itb.ac.id

Recently, the need of secondary battery application continues to increase. The secondary battery which using a liquid electrolyte was indicated had some weakness. A solid polymer electrolyte is an alternative electrolytes membrane which developed in order to replace the liquid electrolyte type. In the present study, the effect of phosphorylation on to polymer electrolyte membrane which synthesized from chitosan and lithium perchlorate salts was investigated. The effect of the component’s composition respectively on the properties of polymer electrolyte, was carried out by analyzed of it’s characterization such as functional groups, ion conductivity, and thermal properties. The mechanical properties i.e tensilemore » resistance and the morphology structure of membrane surface were determined. The phosphorylation processing of polymer electrolyte membrane of chitosan and lithium perchlorate was conducted by immersing with phosphoric acid for 2 hours, and then irradiated on a microwave for 60 seconds. The degree of deacetylation of chitosan derived from shrimp shells was obtained around 75.4%. Relative molecular mass of chitosan was obtained by viscometry method is 796,792 g/mol. The ionic conductivity of chitosan membrane was increase from 6.33 × 10{sup −6} S/cm up to 6.01 × 10{sup −4} S/cm after adding by 15 % solution of lithium perchlorate. After phosphorylation, the ionic conductivity of phosphorylated lithium chitosan membrane was observed 1.37 × 10{sup −3} S/cm, while the tensile resistance of 40.2 MPa with a better thermal resistance. On the strength of electrolyte membrane properties, this polymer electrolyte membrane was suggested had one potential used for polymer electrolyte in field of lithium battery applications.« less

Viscoelastic properties of bovine orbital connective tissue and fat: constitutive models

PubMed Central

Yoo, Lawrence; Gupta, Vijay; Lee, Choongyeop; Kavehpore, Pirouz

2012-01-01

Reported mechanical properties of orbital connective tissue and fat have been too sparse to model strain–stress relationships underlying biomechanical interactions in strabismus. We performed rheological tests to develop a multi-mode upper convected Maxwell (UCM) model of these tissues under shear loading. From 20 fresh bovine orbits, 30 samples of connective tissue were taken from rectus pulley regions and 30 samples of fatty tissues from the posterior orbit. Additional samples were defatted to determine connective tissue weight proportion, which was verified histologically. Mechanical testing in shear employed a triborheometer to perform: strain sweeps at 0.5–2.0 Hz; shear stress relaxation with 1% strain; viscometry at 0.01–0.5 s−1 strain rate; and shear oscillation at 1% strain. Average connective tissue weight proportion was 98% for predominantly connective tissue and 76% for fatty tissue. Connective tissue specimens reached a long-term relaxation modulus of 668 Pa after 1,500 s, while corresponding values for fatty tissue specimens were 290 Pa and 1,100 s. Shear stress magnitude for connective tissue exceeded that of fatty tissue by five-fold. Based on these data, we developed a multimode UCM model with variable viscosities and time constants, and a damped hyperelastic response that accurately described measured properties of both connective and fatty tissues. Model parameters differed significantly between the two tissues. Viscoelastic properties of predominantly connective orbital tissues under shear loading differ markedly from properties of orbital fat, but both are accurately reflected using UCM models. These viscoelastic models will facilitate realistic global modeling of EOM behavior in binocular alignment and strabismus. PMID:21207094

Crystallohydrodynamics of Protein Assemblies: Combining Sedimentation, Viscometry, and X-Ray Scattering

PubMed Central

Lu, Yanling; Longman, Emma; Davis, Kenneth G.; Ortega, Álvaro; Grossmann, J. Günter; Michaelsen, Terje E.; de la Torre, José García; Harding, Stephen E.

2006-01-01

Crystallohydrodynamics describes the domain orientation in solution of antibodies and other multidomain protein assemblies where the crystal structures may be known for the domains but not the intact structure. The approach removes the necessity for an ad hoc assumed value for protein hydration. Previous studies have involved only the sedimentation coefficient leading to considerable degeneracy or multiplicity of possible models for the conformation of a given protein assembly, all agreeing with the experimental data. This degeneracy can be considerably reduced by using additional solution parameters. Conformation charts are generated for the three universal (i.e., size-independent) shape parameters P (obtained from the sedimentation coefficient or translational diffusion coefficient), ν (from the intrinsic viscosity), and G (from the radius of gyration), and calculated for a wide range of plausible orientations of the domains (represented as bead-shell ellipsoidal models derived from their crystal structures) and after allowance for any linker or hinge regions. Matches are then sought with the set of functions P, ν, and G calculated from experimental data (allowing for experimental error). The number of solutions can be further reduced by the employment of the Dmax parameter (maximum particle dimension) from x-ray scattering data. Using this approach we are able to reduce the degeneracy of possible solution models for IgG3 to a possible representative structure in which the Fab domains are directed away from the plane of the Fc domain, a structure in accord with the recognition that IgG3 is the most efficient complement activator among human IgG subclasses. PMID:16766619

Cleavage of the main carbon chain backbone of high molecular weight polyacrylamide by aerobic and anaerobic biological treatment.

PubMed

Song, Wenzhe; Zhang, Yu; Gao, Yingxin; Chen, Dong; Yang, Min

2017-12-01

High molecular weight partially hydrolyzed polyacrylamide (PAM) can be bio-hydrolyzed on the amide side group, however, solid evidence regarding the biological cleavage of its main carbon chain backbone is limited. In this study, viscometry, flow field-flow fractionation multi-angle light scattering (FFF-MALS), and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) analysis were used to investigate the biodegradability of PAM with a nominal molecular weight of 2 × 10 7  Da (Da) in two suspended aerobic (25 and 40 °C) and two upflow anaerobic blanket reactors (35 and 55 °C) operated for 470 d under a hydraulic residence time (HRT) of 2 d. Both anaerobic and aerobic biological treatment reduced the viscosity from 2.02 cp in the influent to 1.45-1.60 cp, and reduced the molecular weight of PAM using FFF-MALS from 2.17 × 10 7  Da to less than one-third its original size. The removals of both the amide group and carbon chain backbone in the PAM molecule were further supported by the FTIR analysis. In comparison with the other conditions, thermophilic anaerobic treatment exhibited higher efficiency for PAM biodegradation. Batch test excluded the influence of temperature on the molecular weight of PAM over the range 25-55 °C, suggesting that cleavage of the main carbon chain backbone was attributed to biological degradation. Our results suggested that high molecular weight PAM was biodegradable, but mineralization did not occur. Copyright © 2017 Elsevier Ltd. All rights reserved.

Size and shape of soil humic acids estimated by viscosity and molecular weight.

PubMed

Kawahigashi, Masayuki; Sumida, Hiroaki; Yamamoto, Kazuhiko

2005-04-15

Ultrafiltration fractions of three soil humic acids were characterized by viscometry and high performance size-exclusion chromatography (HPSEC) in order to estimate shapes and hydrodynamic sizes. Intrinsic viscosities under given solute/solvent/temperature conditions were obtained by extrapolating the concentration dependence of reduced viscosities to zero concentration. Molecular mass (weight average molecular weight (M (w)) and number average molecular weight (M (n))) and hydrodynamic radius (R(H)) were determined by HPSEC using pullulan as calibrant. Values of M (w) and M (n) ranged from 15 to 118 x 10(3) and from 9 to 50 x 10(3) (g mol(-1)), respectively. Polydispersity, as indicated by M (w)/M (n), increased with increasing filter size from 1.5 to 2.4. The hydrodynamic radii (R(H)) ranged between 2.2 and 6.4 nm. For each humic acid, M (w) and [eta] were related. Mark-Houwink coefficients calculated on the basis of the M (w)-[eta] relationships suggested restricted flexible chains for two of the humic acids and a branched structure for the third humic acid. Those structures probably behave as hydrated sphere colloids in a good solvent. Hydrodynamic radii of fractions calculated from [eta] using Einstein's equation, which is applicable to hydrated sphere colloids, ranged from 2.2 to 7.1 nm. These dimensions are fit to the size of nanospaces on and between clay minerals and micropores in soil particle aggregates. On the other hand, the good agreement of R(H) values obtained by applying Einstein's equation with those directly determined by HPSEC suggests that pullulan is a suitable calibrant for estimation of molecular mass and size of humic acids by HPSEC.

Sealed Gravitational Capillary Viscometry of Dimethyl Ether and Two Next-Generation Alternative Refrigerants

PubMed Central

Cousins, Dylan S.; Laesecke, Arno

2012-01-01

The viscosities of dimethyl ether (DME, C2H6O) and of the fluorinated propene isomers 2,3,3,3-tetrafluoroprop-1-ene (R1234yf, C3H2F4) and trans-1,3,3,3-tetrafluoropropene (R1234ze(E)) were measured in a combined temperature range from 242 K to 350 K at saturated liquid conditions. The instrument was a sealed gravitational capillary viscometer developed at NIST for volatile liquids. Calibration and adjustment of the instrument constant were conducted with n-pentane. The repeatability of the measurements was found to be approximately 1.5 %, leading to a temperature-dependent estimated combined standard uncertainty of the experimental data between 5.7 % at 242 K for dimethyl ether and 2.6 % at 340 K for R1234yf. The measurements were supplemented by ab initio calculations of the molecular size, shape, and charge distributions of the measured compounds. The viscosity results for dimethyl ether were compared with literature data. One other data set measured with a sealed capillary viscometer and exceeding the present results by up to 7 % could be reconciled by applying the vapor buoyancy correction. Then, all data agreed within the estimated uncertainty of the present results. Viscosities for the fluorinated propene isomers deviate up to 4 % from values predicted with the NIST extended corresponding-states model. The viscosities of the two isomers do not scale with their dipole moments. While the measured viscosity of R1234ze(E) with the lower dipole moment is close to that of R134a, the refrigerant to be replaced, that of R1234yf with the higher dipole moment is up to 25 % lower. The viscosity of dimethyl ether is compared with those of water and methanol. PMID:26900526

Reactive processing of textile-natural fiber reinforced anionic polyamide-6 composites

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

Kan, Ze; Chen, Peng; Liu, Zhengying

Nowadays natural fiber, used in reinforced composites, is widely concerned. However, no natural fiber reinforced reactive thermoplastic polymer grades had been prepared so far. Through our studies, it was demonstrated that there was a severe retardation and discoloration occurred in the reactive processing between anionic polyamide-6 (APA-6) and natural fiber, which result in incomplete polymerization when put together. In order to solve the problem, two methods were adopted in this paper, which are fiber pretreatment and usage of a new-style initiator called caprolactam magnesium bromide. The former is to remove sizing agent and impurities on the surface of fiber, andmore » the latter is to weaken the side reactions between APA-6 and natural fiber by the nature of its lower reactivity and weaker alkaline. In cooperation with both methods, the severe retardation and discoloration had been improved significantly, so that the polymerization of APA-6 in natural fiber was occurred smoothly. Following textile-natural fiber reinforced APA-6 composites with an average thickness of 2.5 mm and a fiber volume content of 50% was prepared by vacuum assisted resin transfer molding (VARTM). The soxhlet extraction, dilute solution viscometry and differential scanning calorimeter (DSC) measurements respectively suggested the degree of conversion, viscosity-average molar mass and crystallization of composites was up to 94%, 11.3×104 and 50%. Remarkable improvement of mechanical properties were achieved through dynamic mechanical analysis (DMA), tensile and three-point bending test. Favorable interfacial adhesion and wettability were revealed by scanning electron microscopy (SEM) observation. Therefore, all of the above good performance make this new-style and environmentally friendly composites have broad application prospects.« less

Rheological Studies of Komatiite Liquids by In-Situ Falling Sphere Viscometry

NASA Astrophysics Data System (ADS)

O Dwyer, L.; Lesher, C. E.; Baxter, G.; Clark, A.; Fuss, T.; Tangeman, J.; Wang, Y.

2005-12-01

The rheological properties of komatiite liquids at high pressures and temperatures are being investigated by the in situ falling sphere technique, using the T-25 multianvil apparatus at the GSECARS 13 ID-D-D beamline at the Advanced Photon Source, ANL. The refractory and fluid nature of komatiite and other ultramafic liquids relevant to the Earth's deep interior, presents unique challenges for this approach. To reduce the density contrast between the melt and the marker sphere, and thus increase the Stoke's travel time, we have begun testing various composite spheres composed of refractory silicates and metals. Two successful custom designs are zirconia silicate mantled by Pt and Pt mantled by forsterite. These custom spheres contain sufficient Pt to absorb x-rays, while containing sufficient low-density refractory silicate so that marker sphere densities are in the range of 4-6 g/cc. These relatively more buoyant spheres increase travel time. These custom spheres, together with Re or Pt marker spheres, have been used to determine the viscosity of Gorgona anhydrous komatiite around 1600 ° C between 3.5 and 6 GPa. Initial experiments yield viscosities of 2.8 Pa s at 3.5 GPa, 5.3 Pa s at 4.6 GPa and 7.6 Pa s at 6 GPa. The observed positive pressure dependence of viscosity is consistent with recent results on pyrolite composition liquids and suggests that the activation volume for highly depolymerized melts will be positive for at least upper mantle conditions. The development of low-density, x-ray detectable marker spheres has applications in studies of melt density, whereby in situ detection of sink-float behavior during heating and compression cycles may be possible.

Interactions of tetracationic porphyrins with DNA and their effects on DNA cleavage

NASA Astrophysics Data System (ADS)

Lebedeva, Natalya Sh.; Yurina, Elena S.; Gubarev, Yury A.; Syrbu, Sergey A.

2018-06-01

The interaction of tetracationic porphyrins with DNA was studied using UV-Vis absorption, fluorescence spectroscopy and viscometry, and the particle sizes were determined. Аs cationic porphyrins, two isomer porphyrins, 3,3‧,3″,3‴-(5,10,15,20-Porphyrintetrayl)tetrakis(1-methylpyridinium) (TMPyP3) and 4,4‧,4″,4‴-(5,10,15,20-Porphyrintetrayl)tetrakis(1-methylpyridinium) (TMPyP4), were studied. They differ in the position of NCH3+ group in phenyl ring of the porphyrins and hence, in degree of freedom of rotation of the phenyl rings about the central macrocycle. It was found that intercalated complexes are formed at DNA/porphyrin molar ratios (R) of 2.2 and 3.9 for TMPyP3 и TMPyP4, respectively. Decreasing R up to 0.4 and 0.8 for TMPyP3 и TMPyP4, respectively, leads mainly to formation of outside complexes due to π-π stacking between the porphyrin chromophores interacting electrostatically with phosphate framework of DNA. Each type of the obtained complexes was characterized using Scatchard approach. It was ascertained that the affinity of TMPyP4 to DNA is stronger than TMPyP3, meanwhile the wedge effect of the latter is higher. The differences between the porphyrin isomers become more evident at irradiation of their complexes with DNA. It was established that irradiation of the intercalated complexes results in DNA fragmentation. In the case of TMPyP4, DNA fragments of different size are formed. The irradiation of the outside DNA/porphyrin complexes leads to cleavage of DNA (TMPyP3 and TMPyP4) and partial destruction of the complex due to photolysis of the porphyrin (TMPyP3).

In Vitro Evaluation of the Link Between Cell Activation State and Its Rheological Impact on the Microscale Flow of Neutrophil Suspensions

PubMed Central

Akenhead, Michael L.; Horrall, Nolan M.; Rowe, Dylan; Sethu, Palaniappan; Shin, Hainsworth Y.

2015-01-01

Activated neutrophils have been reported to affect peripheral resistance, for example, by plugging capillaries or adhering to the microvasculature. In vivo and ex vivo data indicate that activated neutrophils circulating in the blood also influence peripheral resistance. We used viscometry and microvascular mimics for in vitro corroboration. The rheological impact of differentiated neutrophil-like HL-60 promyelocytes (dHL60s) or human neutrophil suspensions stimulated with 10 nM fMet-Leu-Phe (fMLP) was quantified using a cone-plate rheometer (450 s−1 shear rate). To evaluate their impact on microscale flow resistance, we used 10-μm Isopore® membranes to model capillaries as well as single 200 × 50 μm microchannels and networks of twenty 20 × 50 μm microfluidic channels to mimic noncapillary microvasculature. Stimulation of dHL60 and neutrophil populations significantly altered their flow behavior as evidenced by their impact on suspension viscosity. Notably, hematocrit abrogated the impact of leukocyte activation on blood cell suspension viscosity. In micropore filters, activated cell suspensions enhanced flow resistance. This effect was further enhanced by the presence of erythrocytes. The resistance of our noncapillary microvascular mimics to flow of activated neutrophil suspensions was significantly increased only with hematocrit. Notably, it was elevated to a higher extent within the micronetwork chambers compared to the single-channel chambers. Collectively, our findings provide supportive evidence that activated neutrophils passing through the microcirculation may alter hemodynamic resistance due to their altered rheology in the noncapillary microvasculature. This effect is another way neutrophil activation due to chronic inflammation may, at least in part, contribute to the elevated hemodynamic resistance associated with cardiovascular diseases (e.g., hypertension and hypercholesterolemia). PMID:26065495

The synthesis and characterization of 7-hydroxy-4-methylcoumarin and the investigation of the fluorescence properties of its 7-hydroxy-4-methylcoumarin-chitosan films

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

Wahyuningrum, Deana, E-mail: deana@chem.itb.ac.id; Zulqarnaen, Muhammad; Suendo, Veinardi

Chitosan fluorescent films containing 7-hydroxy-4-methylcoumarin (7H4MC) have been successfully prepared. Used chitosan was obtained from chitin isolated from skin of tiger prawns (Penaeus monodon) through the deproteination, demineralization, and deacetylation process. The yields of chitin and chitosan are 10.66% and 23.83%, respectively. The chitosan has 55.00% degree of deacetylation based on FTIR spectroscopy. Average molecular mass of chitosan which was determined by Ostwald viscometry method is 8.55 × 10{sup 6} g/mol. The 7H4MC was synthesized from resorcinol and ethyl acetoacetate using amberlyst-15 as catalyst based on Pechmann reaction with chemical yields of 90.01% and the melting point of 189–190°C. Themore » FTIR, {sup 1}H–NMR, and {sup 13}C–NMR spectroscopies confirmed the structure which corresponds to the structure of 7H4MC. The films of chitosan containing 7H4MC were prepared by solvent evaporation method in 2% (v/v) acetic acid. The 7H4MC content in each film was 0% (blank), 0.2%, 0.4%, 0.6%, and 0.8% (w/w). The UV-Vis spectrum of 7H4MC in methanol showed λ{sub max} at 235 and 337 nm. The observed fluorescence is the fluorescence color of cyan. The excitation wavelengths are 200, 235, 275, 337, and 365 nm. The highest intensity of cyan color fluorescence of chitosan containing 7H4MC films was obtained at the concentration of 0.2% of 7-hydroxy-4-methylcoumarin at the excitation wavelength of 275 nm.« less

Investigating the evolution of the phase behavior of AOT-based w/o microemulsions in dodecane as a function of droplet volume fraction.

PubMed

Ganguly, R; Choudhury, N

2012-04-15

AOT-based water in oil (w/o) microemulsions are one of the most extensively studied reverse micellar systems because of their rich phase behavior and their ability to form in the absence of any co-surfactant. The aggregation characteristics and interaction of the microemulsion droplets in these systems are known to be governed by AOT-oil compatibility and water to AOT molar ratio (w). In this manuscript by using Dynamic Light Scattering (DLS) and viscometry techniques, we show that droplet volume fraction too plays an important role in shaping the phase behavior of these microemulsions in dodecane. The phase separation characteristics and the evolution of the viscosity and the hydrodynamic radius of the microemulsion droplets on approaching the cloud points have thus been found to undergo complete transformation as one goes from low to high droplet volume fraction even at a fixed 'w'. Modeling of the DLS data attributes this to the weakening of inter droplet attractive interaction caused by the growing dominance of the excluded volume effect with increase in droplet volume fraction. In the literature, the inter droplet attractive interaction driven phase separation in these microemulsions is explained based on gas-liquid type phase transition, conceptualized in the framework of Baxter adhesive hard sphere theory. The modeling of our viscosity data, however, does not support such proposition as the characteristic stickiness parameter (τ(-1)) of the microemulsion droplets in this system remains much lower than the critical value (τ(c)(-1)≈10.25) required to enforce such phase transition. Copyright © 2012 Elsevier Inc. All rights reserved.

Varicocele and concomitant dilation of the periprostatic venous plexus: effects on semen viscosity sperm parameters.

PubMed

Condorelli, R A; Calogero, A E; Mongioi', L; Vicari, E; Russo, G I; Lanzafame, F; La Vignera, S

2016-05-01

Since varicocele is often associated with other venous abnormalities, this study was undertaken to evaluate the frequency of dilation of the periprostatic venous plexus (DPVP) in these patients and the effects of this association on sperm parameters before and after varicocelectomy. Sperm parameters were evaluated using the conventional WHO criteria, and seminal fluid viscosity was further evaluated by quantitative viscometry, in 50 patients (aged 20-38 years) who underwent surgical treatment for grade III bilateral varicocele. Thirty patients with varicocele had also DPVP (DPVP+) (60 %). Sperm concentration and the percentage of spermatozoa with normal morphology did not differ significantly in patients with DPVP- or DPVP+ before or after surgical repair. On the other hand, sperm progressive motility was low in all patients and increased significantly after varicocele repair, but only in DPVP- patients. Before varicocele treatment, a significantly higher number of DPVP+ patients (25/30 = 83.3 %) had seminal fluid hyperviscosity compared to DPVP- patient (2/20 = 10.0 %). Viscosity quantitative measurement was significantly higher in DPVP+ patients both before and after varicocele repair compared to DPVP- patients. These latter showed a statistically significant reduction of sperm viscosity after varicocele surgical repair compared to pretreatment values. Finally, periprostatic venous plexus diameter and seminal fluid viscosity correlated directly in DPVP+ patients. In conclusion, these results showed that a large number of patients with varicocele had a concomitant DPVP. This subset of patients did not take advantage from varicocele surgical repair since only DPVP- varicocele patients showed a significant improvement of sperm progressive motility and seminal fluid viscosity. These findings suggest the evaluation of the periprostatic venous plexus and seminal fluid viscosity before patients with varicocele undergo surgical repair for asthenozoospemia.

Viscoelastic properties of bovine orbital connective tissue and fat: constitutive models.

PubMed

Yoo, Lawrence; Gupta, Vijay; Lee, Choongyeop; Kavehpore, Pirouz; Demer, Joseph L

2011-12-01

Reported mechanical properties of orbital connective tissue and fat have been too sparse to model strain-stress relationships underlying biomechanical interactions in strabismus. We performed rheological tests to develop a multi-mode upper convected Maxwell (UCM) model of these tissues under shear loading. From 20 fresh bovine orbits, 30 samples of connective tissue were taken from rectus pulley regions and 30 samples of fatty tissues from the posterior orbit. Additional samples were defatted to determine connective tissue weight proportion, which was verified histologically. Mechanical testing in shear employed a triborheometer to perform: strain sweeps at 0.5-2.0 Hz; shear stress relaxation with 1% strain; viscometry at 0.01-0.5 s(-1) strain rate; and shear oscillation at 1% strain. Average connective tissue weight proportion was 98% for predominantly connective tissue and 76% for fatty tissue. Connective tissue specimens reached a long-term relaxation modulus of 668 Pa after 1,500 s, while corresponding values for fatty tissue specimens were 290 Pa and 1,100 s. Shear stress magnitude for connective tissue exceeded that of fatty tissue by five-fold. Based on these data, we developed a multi-mode UCM model with variable viscosities and time constants, and a damped hyperelastic response that accurately described measured properties of both connective and fatty tissues. Model parameters differed significantly between the two tissues. Viscoelastic properties of predominantly connective orbital tissues under shear loading differ markedly from properties of orbital fat, but both are accurately reflected using UCM models. These viscoelastic models will facilitate realistic global modeling of EOM behavior in binocular alignment and strabismus.

In Vitro Evaluation of the Link Between Cell Activation State and Its Rheological Impact on the Microscale Flow of Neutrophil Suspensions.

PubMed

Akenhead, Michael L; Horrall, Nolan M; Rowe, Dylan; Sethu, Palaniappan; Shin, Hainsworth Y

2015-09-01

Activated neutrophils have been reported to affect peripheral resistance, for example, by plugging capillaries or adhering to the microvasculature. In vivo and ex vivo data indicate that activated neutrophils circulating in the blood also influence peripheral resistance. We used viscometry and microvascular mimics for in vitro corroboration. The rheological impact of differentiated neutrophil-like HL-60 promyelocytes (dHL60s) or human neutrophil suspensions stimulated with 10 nM fMet-Leu-Phe (fMLP) was quantified using a cone-plate rheometer (450 s(-1) shear rate). To evaluate their impact on microscale flow resistance, we used 10-μm Isopore® membranes to model capillaries as well as single 200 × 50 μm microchannels and networks of twenty 20 × 50 μm microfluidic channels to mimic noncapillary microvasculature. Stimulation of dHL60 and neutrophil populations significantly altered their flow behavior as evidenced by their impact on suspension viscosity. Notably, hematocrit abrogated the impact of leukocyte activation on blood cell suspension viscosity. In micropore filters, activated cell suspensions enhanced flow resistance. This effect was further enhanced by the presence of erythrocytes. The resistance of our noncapillary microvascular mimics to flow of activated neutrophil suspensions was significantly increased only with hematocrit. Notably, it was elevated to a higher extent within the micronetwork chambers compared to the single-channel chambers. Collectively, our findings provide supportive evidence that activated neutrophils passing through the microcirculation may alter hemodynamic resistance due to their altered rheology in the noncapillary microvasculature. This effect is another way neutrophil activation due to chronic inflammation may, at least in part, contribute to the elevated hemodynamic resistance associated with cardiovascular diseases (e.g., hypertension and hypercholesterolemia).

Nutritional and metabolic determinants of blood rheology differ between trained and sedentary individuals.

PubMed

Varlet-Marie, Emmanuelle; Guiraudou, Marie; Fédou, Christine; Raynaud de Mauverger, Eric; Durand, Fabienne; Brun, Jean-Frédéric

2013-01-01

Body composition and nutrition have been reported to be correlated with blood rheology. However, in sedentary and in physically active individuals these relationships seem to be not exactly similar. This study investigated whether exercise training status influences these relationships. 32 athletes (ATH) (age: 25 ± 0.7 yr; body mass index (BMI): 23.75 ± 0.23 kg/m2) were compared to 21 sedentary subjects (SED) (age: 45.19 ± 2.90; BMI = 33.41 ± 1.33) with nutritional assessment (autoquestionnaire), bioelectrical impedancemetry, viscometry at high shear rate (MT90) and Myrenne aggregometer. Subjects differ according to age, weight and adiposity parameters. Their eating behavior is different: ATH eat a higher percentage of protein (p < 0.005), a lower percentage of lipid (p < 0.05), and a higher total amount of carbohydrate (+31% p < 0.02). Their viscosity factors are similar except plasma viscosity which is higher in SED than ATH (1.51 ± 0.03 vs 1.43 ± 0.02 mPa.s, p < 0.05). In both ATH and SED, abdominal obesity (waist-to-hip ratio or WHR) is associated with impairments in blood rheology, but not exactly the same. In ATH, WHR is associated with an increase in hematocrit (r = 0.647; p = 0.009), plasma viscosity (r = 0.723; p = 0.002), and caloric (and CHO) intake moderately increase RBC rigidity (r = 0.5405; p = 0.0251) and aggregability (r = 0.3366 p = 0.0596). In SED the picture is different, adiposity increases hematocrit (r = 0.460; p = 0.048), abdominal fatness increases blood viscosity independent of hematocrit, and CHO intake is associated with lower RBC aggregability (r = -0.493; p = 0.0319).

Reactive processing of textile-natural fiber reinforced anionic polyamide-6 composites

NASA Astrophysics Data System (ADS)

Kan, Ze; Chen, Peng; Liu, Zhengying; Feng, Jianmin; Yang, Mingbo

2015-05-01

Nowadays natural fiber, used in reinforced composites, is widely concerned. However, no natural fiber reinforced reactive thermoplastic polymer grades had been prepared so far. Through our studies, it was demonstrated that there was a severe retardation and discoloration occurred in the reactive processing between anionic polyamide-6 (APA-6) and natural fiber, which result in incomplete polymerization when put together. In order to solve the problem, two methods were adopted in this paper, which are fiber pretreatment and usage of a new-style initiator called caprolactam magnesium bromide. The former is to remove sizing agent and impurities on the surface of fiber, and the latter is to weaken the side reactions between APA-6 and natural fiber by the nature of its lower reactivity and weaker alkaline. In cooperation with both methods, the severe retardation and discoloration had been improved significantly, so that the polymerization of APA-6 in natural fiber was occurred smoothly. Following textile-natural fiber reinforced APA-6 composites with an average thickness of 2.5 mm and a fiber volume content of 50% was prepared by vacuum assisted resin transfer molding (VARTM). The soxhlet extraction, dilute solution viscometry and differential scanning calorimeter (DSC) measurements respectively suggested the degree of conversion, viscosity-average molar mass and crystallization of composites was up to 94%, 11.3×104 and 50%. Remarkable improvement of mechanical properties were achieved through dynamic mechanical analysis (DMA), tensile and three-point bending test. Favorable interfacial adhesion and wettability were revealed by scanning electron microscopy (SEM) observation. Therefore, all of the above good performance make this new-style and environmentally friendly composites have broad application prospects.

Viscosity Determination of Molten Ash from Low-Grade US Coals

DOE PAGES

Zhu, Jingxi; Nakano, Jinichiro; Kaneko, Tetsuya Kenneth; ...

2012-10-01

In entrained slagging gasifiers, the fluidity of the molten ash is a critical factor for process control since it affects slag formation, the capture of inorganic constituents, refractory wear, and slag drainage along the gasification chamber walls. The use of western coal, or mixtures of eastern and western coals as gasifier feedstock, is likely to occur as western coals become available and technological issues that hinder their use are being resolved. In the present work, the viscosity of synthetic slags with ash chemistries simulating the western U.S. coals, was experimentally measured at a Po 2 = 10 - 8 atmmore » in the temperature range of 1773–1573 K (1500–1300 °C) using a rotating-bob viscometer. Alumina spindles and containment crucibles of both alumina and zirconia were used. Crystallization studies of this slag using a confocal scanning laser microscope found that a (Mg,Fe)Al 2O 4-based spinel precipitated at temperatures below 1723 K (1450 °C), and this agreed with FactSage equilibrium phase prediction. The same spinels were observed in the post-viscometry experiment slags when ZrO 2 crucibles were used and assumed to be in equilibrium with the slag at the higher temperatures. Zirconia dissolution resulted in a slight increase in the solid fraction present in slags at lower temperatures, compared to spinel fraction. Crystal precipitation changed the apparent activation energy and required a longer stabilization times for viscosity measurements. The viscosity results were used in predictive equations based on Veytsman and Einstein's models, with critical nucleation temperatures and the solid fraction calculated with FactSage. In the simulated eastern/western coal feedstock blends based on ash compositions, the fractions of the solid precipitates were also calculated using the thermodynamic program FactSage for each blend composition, and the plastic viscosity of each eastern/western coal slag blend was predicted using Veytsman's model and compared to available experimental data.« less

DNA binding studies of a new dicationic porphyrin. Insights into interligand interactions.

PubMed

Shelton, Alexander H; Rodger, Alison; McMillin, David R

2007-08-07

Cationic porphyrins have an affinity for DNA and potential for applications in the fields of photodynamic therapy and cellular imaging. This report describes a new dicationic porphyrin, 5,15-dimethyl-10,20-di(N-methylpyridinium-4-yl)porphyrin, abbreviated H2tMe2D4. Although tetrasubstituted, H2tMe2D4 presents modest steric requirements and forms in reasonable yield by a "2+2" synthetic method. Accordingly, studies of the zinc(II)- and copper(II)-containing derivatives, Zn(tMe2D4) and Cu(tMe2D4), have also been possible. Methods used to characterize DNA-binding motifs include absorption, emission, linear, and circular dichroism spectroscopies, as well as viscometry. An unusually detailed picture of porphyrin uptake emerges. As the ratio of DNA to porphyrin increases during a typical titration, H2tMe2D4 or Cu(tMe2D4) initially aggregates on the host and then shifts to intercalative binding at close quarters before finally dispersing into non-interacting intercalation sites of the host. Emission studies of the copper(II) porphyrin have been very valuable. The existence of a measurable signal is diagnostic of intercalative binding, and the saturation behavior establishes that internalization typically monopolizes approximately three base pairs. In the moderate loading regime, emission data are most telling because dipole-dipole interactions between near-neighbor porphyrins tend to confuse other spectroscopic assays. The third ligand, Zn(tMe2D4), behaves differently in that the uptake is a strictly cooperative process. The mode of binding also varies with the base content of the DNA host. When the DNA is rich in A=T base pairs, the porphyrin remains five-coordinate and binds externally; however, Zn(tMe2D4) loses its axial ligand and binds by intercalation if the host contains only G[triple bond]C base pairs.

Interactive effect of chondroitin sulphate C and hyaluronan on fluid movement across rabbit synovium

PubMed Central

Sabaratnam, S; Coleman, P J; Badrick, E; Mason, R M; Levick, J R

2002-01-01

The polysaccharide hyaluronan (HA) conserves synovial fluid by keeping outflow low and almost constant over a wide pressure range (‘buffering’), but only at concentrations associated with polymer domain overlap. We therefore tested whether polymer interactions can cause buffering, using HA-chondroitin sulphate C (CSC) mixtures. Also, since it has been found that capillary filtration is insensitive to the Starling force interstitial osmotic pressure in frog mesenteries, this was assessed in synovium. Hyaluronan at non-buffering concentrations (0.50–0.75 mg ml−1) and/or 25 mg ml−1 CSC (osmotic pressure 68 cmH2O) was infused into knees of anaesthetised rabbits in vivo. Viscometry and chromatography confirmed that HA interacts with CSC. Pressure (Pj) versus trans-synovial flow (Q̇s) relations were measured. Q̇s was outwards for HA alone (1.2 ± 0.9 μl min−1 at 3 cmH2O, mean ± s.e.m.; n = 6). CSC diffused into synovium and changed Q̇s to filtration at low Pj (−4.1 μl min−1, 3 cmH2O, n = 5, P < 0.02, t test). Filtration ceased upon circulatory arrest (n = 3). At higher Pj, 0.75 mg ml−1 HA plus CSC buffered Q̇s to ∼3 μl min−1 over a wide range of Pj, with an outflow increase of only 0.04 ± 0.02 μl min−1 cmH2O−1 (n = 4). With HA or CSC alone, buffering was absent (slopes 0.57 ± 0.04 μl min−1 cmH2O−1 (n = 4) and 0.86 ± 0.05 μl min−1 cmH2O−1 (n = 5), respectively). Therefore, polymer interactions can cause outflow buffering in joints. Also, interstitial osmotic pressure promoted filtration in fenestrated synovial capillaries, so the results for frog mesentery capillaries cannot be generalised. The difference is attributed to differences in pore ultrastructure. PMID:11927686

Effects of N-vinylpyrrolidone (NVP) containing polyelectrolytes on surface properties of conventional glass-ionomer cements (GIC).

PubMed

Moshaverinia, Alireza; Roohpour, Nima; Ansari, Sahar; Moshaverinia, Maryam; Schricker, Scott; Darr, Jawwad A; Rehman, Ihtesham U

2009-10-01

It has been found that polyacids containing an N-vinylpyrrolidinone (NVP) comonomer produces a glass inomer cement with improved mechanical and handling properties. The objective of this study was to investigate the effect of NVP modified polyelectrolytes on the surface properties and shear bond strength to dentin of glass ionomer cements. Poly(acrylic acid (AA)-co-itaconic acid (IA)-co-N-vinylpyrrolidone) was synthesized by free radical polymerization. The terpolymer was characterized using (1)H NMR, FTIR spectroscopy and viscometry for solution properties. The synthesized polymers were used in glass ionomer cement formulations (Fuji II commercial GIC). Surface properties (wettability) of modified cements were studied by water contact angle measurements as a function of time. Work of adhesion values of different surfaces was also determined. The effect of NVP modified polyacid, on bond strength of glass-ionomer cement to dentin was also investigated. The mean data obtained from contact angle and bonding strength measurements were subjected to one- and two-way analysis of variance (ANOVA) at alpha=0.05. Results showed that NVP modified glass ionomer cements showed significantly lower contact angles (theta=47 degrees) and higher work of adhesion (WA=59.4 erg/cm(2)) in comparison to commercially available Fuji II GIC (theta=60 degrees and WA=50.3 erg/cm(2), respectively). The wettability of dentin surfaces conditioned with NVP containing terpolymer was higher (theta=21 degrees, WA=74.2 erg/cm(2)) than dentin conditioned with Fuji conditioner (theta=30 degrees, WA=69 erg/cm(2)). The experimental cement also showed higher but not statistically significant values for shear bond strength to dentin (7.8 MPa), when compared to control group (7.3 MPa). It was concluded that NVP containing polyelectrolytes are better dentin conditioners than the commercially available dentin conditioner (Fuji Cavity Conditioner, GC). NVP containing terpolymers can enhance the surface properties of GICs and also increase their bond strength to the dentin.

Bingham fluid behavior of plagioclase-bearing basaltic magma: Approach from laboratory viscosity measurements

NASA Astrophysics Data System (ADS)

Ishibashi, H.; Sato, H.

2010-12-01

Datasets of one atmosphere high temperature rotational viscometry of the Fuji 1707 basalt (Ishibashi, 2009) were analyzed based on the Bingham fluid model, and both yield stress and Bingham viscosity were determined. Reproducibility of the dataset by the Bingham fluid model was slightly better than that by the power law fluid modes adopted in our previous study although both the fluid models well represent the dataset in practical perspective. The relation between Bingham viscosity and crystallinity was compared with the Krieger-Dougherty equation, and both the maximum packing fraction of crystals and intrinsic viscosity for Bingham viscosity were determined ca. 0.45 and ca. 5.25, respectively, revealing that the maximum packing fraction decreased and intrinsic viscosity increased concomitantly with the increase in shape-anisotropy of crystals. However, the obtained value of the product of the maximum packing fraction and intrinsic viscosity (= ca. 2.36) was similar to that of uniform, isotropic-shaped particles (= 2.5), indicating that the effect of crystal shape-anisotropy on Bingham viscosity might be predicted only by change of the maximum packing fraction. Finite yield stress was detected for crystallinity larger than 0.133; it increased with crystallinity which suggests that critical crystallinity for onset of yield stress is at least lower than 0.133. The upper limit value of the critical crystallinity resembles the value calculated numerically for randomly oriented uniform particles by Saar et al. (2001) (0.10-0.15 for width/length ratio of 0.1-0.2, which is similar to the ratios in the basalt) whereas crystals in the basalt were moderately parallel arranged and their sizes vary significantly. That fact might be explained as follows; effects of parallel arrangement and size variation of crystals on the critical crystallinity are offset by the effect of variation in crystal shape-anisotropy, which suggests that shape-anisotropy distribution of crystals must be a critical factor for the onset of yield stress. Keywords: magma, viscosity, Bingham fluid, yield stress, plagioclase

Effects of ionizing radiation on extracellular matrix

NASA Astrophysics Data System (ADS)

Mohamed, F.; Bradley, D. A.; Winlove, C. P.

2007-09-01

The extracellular matrix is a ubiquitous and important component of tissues. We investigated the effects of ionizing radiation on the physical properties of its principal macromolecular components, pericardial collagen, ligament elastin and hyaluronan, a representative glycosaminoglycan. Samples were exposed to X-rays from an electron linear accelerator in the range of 10-100 Gy to cover the range of irradiation exposure during radiotherapy. A uniaxial mechanical testing protocol was used to characterize the fibrous proteins. For pericardial tissue the major change was an increase in the elastic modulus in the toe region of the curve (⩽20% strain), from 23±18 kPa for controls to 57±22 kPa at a dose of 10 Gy ( p=0.01, α=0.05). At larger strain (⩾20% strain), the elastic modulus in the linear region decreased from 1.92±0.70 MPa for control pericardium tissue to 1.31±0.56 MPa ( p=0.01, α=0.05) for 10 Gy X-irradiated sample. Similar observations have been made previously on tendon collagen at larger strains. For elastin, the stress-strain relationship was linear up to 30% strain, but the elastic modulus decreased significantly with irradiation (controls 626±65 kPa, irradiated 474±121 kPa ( p=0.02, α=0.05), at 10 Gy X-irradiation). The results suggest that for collagen the primary effect of irradiation is generation of additional cross-links, while for elastin chain scissions are important. The viscosity of HA (at 1.25% w/v and 0.125% w/v) was measured by both cone and plate and capillary viscometry, the former providing measurement at uniform shear rate and the latter providing a more sensitive indication of changes at low viscosity. Both techniques revealed a dose-dependent reduction in viscosity (from 3400±194 cP for controls to 1500±88 cP at a shear rate of 2 s -1 and dose of 75 Gy), again suggesting depolymerization.

Osteointegration of PLGA implants with nanostructured or microsized β-TCP particles in a minipig model.

PubMed

Kulkova, Julia; Moritz, Niko; Suokas, Esa O; Strandberg, Niko; Leino, Kari A; Laitio, Timo T; Aro, Hannu T

2014-12-01

Bioresorbable suture anchors and interference screws have certain benefits over equivalent titanium-alloy implants. However, there is a need for compositional improvement of currently used bioresorbable implants. We hypothesized that implants made of poly(l-lactide-co-glycolide) (PLGA) compounded with nanostructured particles of beta-tricalcium phosphate (β-TCP) would induce stronger osteointegration than implants made of PLGA compounded with microsized β-TCP particles. The experimental nanostructured self-reinforced PLGA (85L:15G)/β-TCP composite was made by high-energy ball-milling. Self-reinforced microsized PLGA (95L:5G)/β-TCP composite was prepared by melt-compounding. The composites were characterized by gas chromatography, Ubbelohde viscometry, scanning electron microscopy, laser diffractometry, and standard mechanical tests. Four groups of implants were prepared for the controlled laboratory study employing a minipig animal model. Implants in the first two groups were prepared from nanostructured and microsized PLGA/β-TCP composites respectively. Microroughened titanium-alloy (Ti6Al4V) implants served as positive intra-animal control, and pure PLGA implants as negative control. Cone-shaped implants were inserted in a random order unilaterally in the anterior cortex of the femoral shaft. Eight weeks after surgery, the mechanical strength of osteointegration of the implants was measured by a push-out test. The quality of new bone surrounding the implant was assessed by microcomputed tomography and histology. Implants made of nanostructured PLGA/β-TCP composite did not show improved mechanical osteointegration compared with the implants made of microsized PLGA/β-TCP composite. In the intra-animal comparison, the push-out force of two PLGA/β-TCP composites was 35-60% of that obtained with Ti6Al4V implants. The implant materials did not result in distinct differences in quality of new bone surrounding the implant. Copyright © 2014 Elsevier Ltd. All rights reserved.

Comparison of the rheological properties of ready-to-serve and powdered instant food-thickened beverages at different temperatures for dysphagic patients.

PubMed

Adeleye, Bernice; Rachal, Corryn

2007-07-01

Dysphagia, or difficulty swallowing, affects an estimated 15 million Americans. Its management may include use of instant food thickener (IFT) to modify beverage consistency to minimize the risk of aspiration and prevent dehydration. However, inconsistencies with the desired viscosity of these thickened liquids occur both within and across product lines for both ready-to-serve commercially packaged prethickened (CPPT) and IFT-thickened beverages. To examine the rheological property differences between CPPT and similar IFT-thickened beverages, and to assess the stability of these products at two temperature ranges using three viscosity measurement techniques. The rheological properties of five CPPT and IFT-thickened beverages at both nectar- and honey-like consistencies were evaluated at 10 degrees C (50 degrees F) and 20 degrees C (68 degrees F) using the line spread, funnel, and viscometry methods. One-way analysis of variance was used for data analysis. When a significant difference was observed, Tukey's test was used to separate the means. Each viscosity measurement technique showed the CPPT nectar- and honey-like consistency beverages were significantly more viscous (P<0.0001) at both temperatures compared with their IFT counterparts. Moreover, CPPT beverages at nectar and honey consistencies were almost always more viscous than the National Dysphagia Diet Task Force-defined standards, whereas the IFT-thickened beverages were more frequently within those standards. A reevaluation of the viscosity of CPPT beverages with reference to the National Dysphagia Diet Task Force set standard ranges needs to be considered. A strong need also exists for development of a standard protocol on product labels that includes the expected rheological properties of CPPT and IFT-thickened beverages. To the clinicians, especially registered dietitians, it is an important clinical consideration to recognize that CPPT products may be thicker than IFT-thickened products and also may be more viscous than the National Dysphagia Diet Task Force-defined standards.

Emplacement dynamics and timescale of a Holocene flow from the Cima Volcanic Field (CA): Insights from rheology and morphology

NASA Astrophysics Data System (ADS)

Soldati, Arianna; Beem, Jordon; Gomez, Francisco; Huntley, John Warren; Robertson, Timothy; Whittington, Alan

2017-11-01

We present a rheological and morphological study of a Holocene lava flow emitted by a monogenetic cinder cone in the Cima Volcanic Field, eastern California. Our field observations focused on surface morphology, which transitions from smooth core extrusions near the vent to jagged 'a'ā blocks over the majority of the flow, and on channel and levée dimensions. We collected airborne photogrammetry data and used it to generate a digital elevation model. From this, the total flow volume was estimated and surface roughness was quantified in terms of standard deviation of the real surface (5 cm resolution) from the software-generated 1 m-average plane. Sample textural analyses revealed that the near-vent portion of the flow is significantly more crystalline (ϕxtal = 0.95 ± 0.04) than the main flow body (ϕxtal = 0.66 ± 0.11). The rheology of Cima lavas was determined experimentally by concentric cylinder viscometry between 1550 °C and 1160 °C, including the first subliquidus rheology measurements for a continental intraplate trachybasaltic lava. The experimentally determined effective viscosity increases from 54 Pa·s to 1361 Pa·s during cooling from the liquidus ( 1230 °C) to 1160 °C, where crystal fraction is 0.11. The lava viscosity over this range is still lower than most basaltic melts, due to the high alkali content of Cima lavas ( 6 wt% Na2O + K2O). Monte Carlo simulations were used to account for and propagate experimental uncertainties, and to determine which rheological model (Bingham, power law, or Herschel-Bulkley) provides the best-fit of the obtained rheological data. Results suggest that Bingham and Herschel-Bulkley models are statistically indistinguishable from each other, and that both fit the data better than a power law model. By combining field observations and experimental results, we reconstructed the eruption temperature and few days-long emplacement history of the Cima flow.

In situ evaluation of supersolidus liquid phase sintering phenomena of stainless steel 316L: Densification and distortion

NASA Astrophysics Data System (ADS)

Bollina, Ravi

Supersolidus liquid phase sintering (SLPS) is a variant of liquid phase sintering. In SLPS, prealloyed powders are heated between the solidus and liquidus temperature of the alloy. This thesis focuses on processing of stainless steel 316L via SLPS by adding boron. Various amounts of boron were added to study the effect of boron on densification and distortion. The sintering window for water atomized 316L with 0.2% boron ranges from 1430 to 1435°C and 1225 to 1245°C for water atomized 316L with 0.8% boron. The rate of change of liquid content with temperature dVL/dt decreases from 1.5%/°C to 0.1%/°C for in increase in boron content from 0 to 0.8%, giving a wider range and better control during sintering. Further; effect of boron on mechanical properties and corrosion properties was researched. It was possible to achieve tensile strength of 476+/-21 MPa and an yield strength of 250+/-5 MPa with an elongation of 15+/-2 % in water atomized 316L with 0.8% boron. Fracture analysis indicates the presence of a brittle boride phase along the grain boundary causing intergranular fracture resulting in poor ductility. The crux of this thesis discusses the evolution of apparent viscosity and its relation to the microstructure. Beam bending viscometry was successfully used to evaluate the in situ apparent viscosity evolution of water atomized 316L with 0.2 and 0.8% boron additions. The apparent viscosity drops from 174 GPa.s at 1200°C to 4 GPa.s at 1275°C with increasing fractional liquid coverage in the water atomized 316L with 0.8% boron. The apparent viscosity calculated from bending beam and was used as an input into a finite element model (FEM) derived from constitutive equations and gives an excellent, fit between simulation and experiment. The densification behavior of boron doped stainless steel was modelled using Master Sintering Curve (MSC) (based on work of sintering) for the first time. It is proven that MSC can be used to identify change in densification rate upon liquid formation during SLPS.

Characterizing string-of-pearls colloidal silica by multidetector hydrodynamic chromatography and comparison to multidetector size-exclusion chromatography, off-line multiangle static light scattering, and transmission electron microscopy.

PubMed

Brewer, Amandaa K; Striegel, André M

2011-04-15

The string-of-pearls-type morphology is ubiquitous, manifesting itself variously in proteins, vesicles, bacteria, synthetic polymers, and biopolymers. Characterizing the size and shape of analytes with such morphology, however, presents a challenge, due chiefly to the ease with which the "strings" can be broken during chromatographic analysis or to the paucity of information obtained from the benchmark microscopy and off-line light scattering methods. Here, we address this challenge with multidetector hydrodynamic chromatography (HDC), which has the ability to determine, simultaneously, the size, shape, and compactness and their distributions of string-of-pearls samples. We present the quadruple-detector HDC analysis of colloidal string-of-pearls silica, employing static multiangle and quasielastic light scattering, differential viscometry, and differential refractometry as detection methods. The multidetector approach shows a sample that is broadly polydisperse in both molar mass and size, with strings ranging from two to five particles, but which also contains a high concentration of single, unattached "pearls". Synergistic combination of the various size parameters obtained from the multiplicity of detectors employed shows that the strings with higher degrees of polymerization have a shape similar to the theory-predicted shape of a Gaussian random coil chain of nonoverlapping beads, while the strings with lower degrees of polymerization have a prolate ellipsoidal shape. The HDC technique is contrasted experimentally with multidetector size-exclusion chromatography, where, even under extremely gentle conditions, the strings still degraded during analysis. Such degradation is shown to be absent in HDC, as evidenced by the fact that the molar mass and radius of gyration obtained by HDC with multiangle static light scattering detection (HDC/MALS) compare quite favorably to those determined by off-line MALS analysis under otherwise identical conditions. The multidetector HDC results were also comparable to those obtained by transmission electron microscopy (TEM). Unlike off-line MALS or TEM, however, multidetector HDC is able to provide complete particle analysis based on the molar mass, size, shape, and compactness and their distributions for the entire sample population in less than 20 min. © 2011 American Chemical Society

D-DIA High Pressure Facility at the Australian Synchrotron: First Results

NASA Astrophysics Data System (ADS)

Rushmer, T. A.; Wykes, J.

2016-12-01

The recent acquisition of a D-DIA type cubic multi-anvil apparatus for use at the Australian Synchrotron provides exciting opportunities for conducting a wide range of in situ experiments at high pressure and temperature. The MQ-AS D-DIA apparatus was designed as a mobile system capable of moving between beamlines. The apparatus was installed at the XAS beamline in May, 2016 and experiments performed since then include 1) a proof-of-concept in situ U and Th L3-edge XANES study of MORB liquid; 2) a proof-of-concept falling sphere viscometry of silicate liquid; and 3) room temperature transmission XANES in the high pressure assembly at energies as low as the Ga K-edge and as high as Sb K-edge. The MQ-AS D-DIA apparatus comprises a 350 ton ram in a four post press frame. The press is installed on a positioning table with motorised X-Y-Z-θ axes capable of positioning accuracy of <10 microns. The Rockland Research D-DIA module is equipped with 4 mm and 6 mm TEL anvils, capable of producing maximum sample pressure of 6 GPa. Stepper motors drive the main and differential ram hydraulic pressure generators in a control loop closed by pressure transducers. Samples are heated by graphite resistance furnaces driven by a Eurotherm 3504 PID controller driving a 5 V 200 A step down transformer via a phase angle power controller. Temperature is monitored via a thermocouple and power by true RMS voltage and current transducers. The XAS beamline at the Australian Synchrotron comprises a 1.9 T 40 pole wiggler, a bendable collimating mirror, a Si(111) / Si(311) DCM and a toroidal focussing mirror. Accessible energies are 5-34 keV with photon fluxes of 108-1012 photons/sec at the sample. Here we present an overview of our recent results. More detailed results of the in situ U and Th L3-edge XANES study are presented by Mallmann et al. (this meeting). In situ imaging and XRD experiments with the D-DIA apparatus on the AS Imaging and Medical Beamline are planned for the coming year.

FOR STIMUL-RESPONSIVE POLYMERS WITH ENHANCED EFFICIENCY IN RESERVOIR RECOVERY PROCESSES

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

Charles McCormick; Roger Hester

This report contains a series of terpolymers containing acrylic acid, methacrylamide and a twin-tailed hydrophobic monomer that were synthesized using micellar polymerization methods. These polymer systems were characterized using light scattering, viscometry, and fluorescence methods. Viscosity studies indicate that increasing the nonpolar character of the hydrophobic monomer (longer chain length or twin tailed vs. single tailed) results in enhanced viscosity in aqueous solutions. The interactions of these polymers with surfactants were investigated. These surfactants include sodium dodecyl sulfate (SDS), cetyl trimethyl ammonium bromide (CTAB), Triton X-100. Viscosity measurements of DiC{sub 6}AM and DiC{sub 8}AM mixtures indicate little interaction with SDS,more » gelation with CTAB, and hemimicelle formation followed by polymer hydrophobe solubilization with Triton X-100. The DiC{sub 10}Am terpolymer shows similar interaction behavior with CTAB and Triton X-100. However, the enhanced hydrophobic nature of the DiC{sub 10} polymer allows complex formation with SDS as confirmed by surface tensiometry. Fluorescence measurements performed on a dansyl labeled DiC{sub 10}Am terpolymer in the presence of increasing amounts of each of the surfactant indicate relative interaction strengths to be CTAB>Triton X-100>SDS. A modified model based on Yamakawa-Fujii and Odjik-Skolnick-Fixman theories was found to describe the contribution of electrostatic forces to the excluded volume of a polyelectrolyte in solution. The model was found to be valid for flexible polymer coils in aqueous salt solutions where intermolecular interactions are minimal. The model suggested that a dimensionless group of parameters termed the dimensionless viscosity should be proportional to the dimensionless ratio of solution screening length to polyion charge spacing. Several sets of experimental data from the literature and from our laboratory have been analyzed according to the model and the results suggest that the two dimensionless groups are indeed related by a universal constant. This model has identified the parameters that are important to fluid mobility, thereby revealing methods to enhance solution performance when using polyions solutions as displacing fluids in oil reservoirs.« less

Emplacement Dynamics and Timescale of a Holocene Flow from the Cima Volcanic Field (CA): Insights from Rheology and Morphology

NASA Astrophysics Data System (ADS)

Soldati, A.; Beem, J. R.; Gomez, F.; Huntley, J. W.; Robertson, T.; Whittington, A. G.

2017-12-01

We present a rheological and morphological study of a Holocene lava flow emitted by a monogenetic cinder cone in the Cima Volcanic Field, eastern California. By combining field observations and experimental results, we reconstructed the few weeks-long emplacement timeline of the Cima flow. Sample textural analyses revealed that the near-vent portion of the flow is significantly more crystalline (fxtal=0.95±0.04) than the main flow body (fxtal=0.66±0.11), which reveals a multi-stage emplacement history. Airborne photogrammetry data were used to generate a digital elevation model, which allowed us to estimate the flow volume. The rheology of Cima lavas was determined experimentally by concentric cylinder viscometry between 1550 °C and 1160 °C, including the first subliquidus rheology measurements for a continental intraplate trachybasaltic lava. The experimentally determined effective viscosity increases from 54 Pa·s to 1,361 Pa·s during cooling from the liquidus ( 1230 ˚C) to 1160 ˚C, where crystal fraction is 0.11. Flow curves fitted to measurements at different strain rates indicate a Herschel-Bulkley rheological behavior, combining shear-thinning with a yield strength negligible at the higher measured temperatures but increasing up to 357±41 Pa at 1160˚C. The lava viscosity over this range is still lower than most basaltic melts, due to the high alkali content of Cima lavas ( 6 wt% Na2O+K2O). We determined that the morphological pahoehoe to `a'ā transition of this trachybasalt occurs at a temperature of 1160±10 ˚C, similar to that observed for Hawaiian tholeiitic lavas, but at higher apparent viscosity values. Monogenetic volcanism in the Western United States is typically characterized by low effusion rates and eruption on sub-horizontal desert plains. Under these low strain-rate conditions, the pahoehoe to `a'ā transition is likely to occur abruptly upon minimal cooling, i.e. very close to the vent, but lava tubes may transport fluid lava to flow fronts rapidly, allowing breakouts to extend the flow length, as we infer happened for the Cima flow.

Experimental and Theoretical Investigations on Viscosity of Fe-Ni-C Liquids at High Pressures

NASA Astrophysics Data System (ADS)

Chen, B.; Lai, X.; Wang, J.; Zhu, F.; Liu, J.; Kono, Y.

2016-12-01

Understanding and modeling of Earth's core processes such as geodynamo and heat flow via convection in liquid outer cores hinges on the viscosity of candidate liquid iron alloys under core conditions. Viscosity estimates from various methods of the metallic liquid of the outer core, however, span up to 12 orders of magnitude. Due to experimental challenges, viscosity measurements of iron liquids alloyed with lighter elements are scarce and conducted at conditions far below those expected for the outer core. In this study, we adopt a synergistic approach by integrating experiments at experimentally-achievable conditions with computations up to core conditions. We performed viscosity measurements based on the modified Stokes' floating sphere viscometry method for the Fe-Ni-C liquids at high pressures in a Paris-Edinburgh press at Sector 16 of the Advanced Photon Source, Argonne National Laboratory. Our results show that the addition of 3-5 wt.% carbon to iron-nickel liquids has negligible effect on its viscosity at pressures lower than 5 GPa. The viscosity of the Fe-Ni-C liquids, however, becomes notably higher and increases by a factor of 3 at 5-8 GPa. Similarly, our first-principles molecular dynamics calculations up to Earth's core pressures show a viscosity change in Fe-Ni-C liquids at 5 GPa. The significant change in the viscosity is likely due to a liquid structural transition of the Fe-Ni-C liquids as revealed by our X-ray diffraction measurements and first-principles molecular dynamics calculations. The observed correlation between structure and physical properties of liquids permit stringent benchmark test of the computational liquid models and contribute to a more comprehensive understanding of liquid properties under high pressures. The interplay between experiments and first-principles based modeling is shown to be a practical and effective methodology for studying liquid properties under outer core conditions that are difficult to reach with the current static high-pressure capabilities. The new viscosity data from experiments and computations would provide new insights into the internal dynamics of the outer core.

Effect of pressure on viscosity of liquid Fe-alloys up to 16 GPa

NASA Astrophysics Data System (ADS)

Terasaki, H.; Ohtani, E.; Suzuki, A.; Nishida, K.; Sakamaki, T.; Shindo, S.; Funakoshi, K.

2005-12-01

Viscosity of liquid Fe-alloy is closely related to a convection behavior of the Earth's liquid outer core and also time scale of planetary core formation. In previous studies, viscosity of liquid Fe-S has been measured up to 7 GPa using X-ray radiography falling sphere method [Terasaki et al. 2001]. However, some technical problems, such as chemical reaction between the metal marker sphere and the Fe-alloy sample and insufficient image recording time for less viscous material, have been suggested. In this study, we have measured the viscosity of Fe-S and Fe-C liquids without those problems by using novel techniques combined with in situ X-ray radiography falling sphere method and extended the pressure range to 16 GPa. Falling sphere viscometry was carried out under high pressure and temperature using high speed CCD camera with 1500 ton Kawai-type multi-anvil device at BL04B1, SPring-8 in Japan. Starting compositions of Fe-alloy were Fe78S22 and Fe86C14 which correspond to near eutectic compositions at the experimental pressures. Viscosity marker sphere, which was made of Re or Pt, was coated by alumina in order to prevent the reaction between the sphere and the Fe-alloy sample. Falling sphere images were obtained with recording rate of 50 - 125 frame/second. Viscosity of liquid Fe-S was measured up to 16.1 GPa and 1763 K. Measured viscosity coefficients were in the range of 8.8 - 9.2 mPa-s which indicates that the activation volume of viscous flow is approximately a half of the previous estimations (1.5 cm3/mol). Viscosity of liquid Fe-C was measured up to 5 GPa and 1843 K. Viscosity coefficients are 4.7 - 4.9 mPa-s. Activation volume of Fe-C liquid is estimated to be 0.8 cm3/mol. This pressure dependence is consistent with the result of Lucas (1964) measured at ambient pressure. Consequently, viscosity of Fe-alloy liquids are likely to stay small in the Earth's interior and there is no large difference in viscosity coefficient and activation volume between Fe-S and Fe-C eutectic liquids in the range of measurements.

Ties of Heat and Mass Transport Properties in Glasses and Melts, with Emphasis on Natural Lava Compositions

NASA Astrophysics Data System (ADS)

Hofmeister, A. M.; Whittington, A. G.; Robert, G.; Sehlke, A.

2016-12-01

We have discovered strong ties of mass and heat transport properties in glasses and melts via coordinated measurements of thermal diffusivity (D) and viscosity (η). Over the course of several studies we have compared over 50 remelted natural lavas, tektites, and synthetic glasses and melts, with substantially different chemical compositions, e.g., from 50 to 100% silica, and with slight variations in H and Fe cations and the presence/absence of Al. We use laser flash analysis to obtain D, which avoids contact and radiative errors and constrain η over a wide range of temperature (T). We use a combination of parallel-plate and concentric-cylinder viscometry to obtain η from the glass transition to above the liquidus. Our most recent studies include differential scanning calorimetric measurements of heat capacity (CP) to calculate their thermal conductivity (k), and we are now measuring thermal expansivity using dilatometry. The combined datasets show consistent macroscopic behavior, providing an improved understanding of microscopic behavior, particularly of heat transport properties, which have been misunderstood. Both viscosity and the glass transition temperature decrease with decreasing melt polymerization. Clear correlations exist between D of glass or melt with Si content, density, NBO/T, and, most strongly, with fragility (obtained from η). Glass thermal diffusivity is represented by D = FT-G +HT, where F, G and H are fitting parameters. For melts, D drops upon melting but we could only resolve D/T for a small number of samples. The results show that high-T behavior is controlled by Fe oxidation state and polymerization and involves radiative transfer (HT) but at infrared frequencies. In disordered materials, acoustic scattering is less important to heat transfer than is IR absorption/re-emissions. We find that k for glasses is described by a Maier-Kelly formula, consistent with the T response being dominated by CP. Trends in k are irregular due to k being the convolution of three physical properties. Nonetheless, basaltic melts are constrained to k 1.4±0.1 Wm-1k-1. Low values for thermal diffusivity and viscosity for basaltic melts suggests that basalts transfer heat much more efficiently by advection than by conduction alone, which pertains to upper mantle processes.

Density and Viscosity Measurement of Liquid FeS at High Pressure and High Temperature Using Synchrotron X-ray

NASA Astrophysics Data System (ADS)

Yu, T.; Long, H.; Young, C.; Wang, L.; Chen, J.

2005-12-01

From previous experimental and theoretical studies, sulfur has been considered one of the possible light elements in the core that might be responsible for the large density deficit when compared with the theoretical pure Fe core (Ganapathy and Anders, 1974; Ahrens and Jeanloz, 1987). Therefore, understanding the physical properties of liquid FeS will help us reveal the details of the Earth?|s core. This study focused on the liquid state of sulfur in iron due to sulfur?|s lack of amount in the mantle; easiness to alloy with iron; and the predicted 5 wt% ~10 wt% amount of this light element in the core (Ahrens, 1979; Sherman, 1997). Modern development of the multi-anvil high pressure apparatus limits the pressure range of the experiments (<30 GPa). It is somewhat low if comparing with the outer core pressure condition. Therefore, extrapolation of data derived at low pressure range to the condition of the outer core (>130 GPa) has to be applied, and may produce results that are far from the true numbers. However, at the point while the techniques are limited, studying the physical properties of the liquid-phase FeS at relatively low pressures still provides us a better picture of the physical behavior of the outer core comparing with data derived from solid state FeS experiments. Pervious studies on the viscosity of the Fe-FeS system (LeBlanc and Secco, 1996; Dobson et al., 2000; Urakawa et al., 2001; Secco et al., 2002) have presented different values of viscosity numbers with a maximum difference of two orders of magnitude. We have conducted the density measurements of liquid FeS (~36 wt% of S) up to 5.6 GPa in pressure and 1673K in temperature using the in-situ synchrotron-source x-ray absorption setup at Beamline X17B2, NSLS. The viscosity measurements were conducted by the x-ray radiograph technique combined with the falling sphere method. The falling sphere method applied at the experiment is suitable for liquids with viscosities between 10-3 Pa-s and 105 Pa-s (LeBlanc et al., 1999). We used tungsten spheres in our viscosity measurement experiments. We analyzed the sphere falling motion in the sample chamber at high pressure and high temperature. And by applying our density compression curve of liquid FeS to the Stokes?| viscometry method, we were able to derive the viscosity of liquid FeS.

The Anatomy of the Blue Dragon: Changes in Lava Flow Morphology and Physical Properties Observed in an Open Channel Lava Flow as a Planetary Analogue

NASA Astrophysics Data System (ADS)

Sehlke, A.; Kobs-Nawotniak, S. E.; Hughes, S. S.; Sears, D. W. G.; Downs, M.; Whittington, A. G.; Lim, D. S. S.; Heldmann, J. L.

2017-12-01

Lava terrains on other planets and moons exhibit morphologies similar to those found on Earth, such as smooth pāhoehoe transitioning to rough `a`ā terrains based on the viscosity - strain rate relationship of the lava. Therefore, the morphology of lava flows is governed by eruptive conditions such as effusion rate, underlying slope, and the fundamental thermo-physical properties of the lava, including temperature (T), composition (X), viscosity (η), fraction of crystals (φc) and vesicles (φb), as well as bulk density (ρ). These textural and rheological changes were previously studied for Hawaiian lava, where the lava flow started as channelized pāhoehoe and transitioned into `a`ā, demonstrating a systematic trend in T, X, η, φc, φb, and ρ. NASA's FINESSE focuses on Science and Exploration through analogue research. One of the field sites is Craters of the Moon, Idaho. We present field work done at a 3.0 km long lava flow belonging to the Blue Dragon lavas erupted from a chain of spatter cones, which then coalesced into channelized flows. We acquired UAV imagery along the entire length of the flow, and generated a high resolution DTM of 5 cm/pixel, from which we derived height profiles and surface roughness values. Field work included mapping the change in surface morphology and sample collection every 150 meters. In the laboratory, we measured φc, φb, and ρ for all collected samples. Viscosity measurements were carried out by concentric cylinder viscometry at subliquidus temperatures between 1310ºC to 1160ºC to study the rheology of the lava, enabling us to relate changes in flow behavior to T and φc. Our results are consistent with observations made for Hawaiian lava, including increasing bulk density downflow, and porosity changing from connected to isolated pore space. Crystallinity increases downflow, and the transition from pāhoehoe to `a`ā occurs between 1230ºC to 1150ºC, which is prompted by nucleation and growth of plagioclase microcrystals, strongly increasing the viscosity of the lava several orders of magnitude. The results of this study allows us to correlate T, X, η, φc, φb, and ρ to the lava flow morphology expressed as surface roughness, which can then be used as a tool to infer these physical properties of the rocks for open channel lava flows on other airless bodies, such as the Moon and Mercury, based on DTMs.

The viscosity of pāhoehoe lava: In situ syn-eruptive measurements from Kilauea, Hawaii

NASA Astrophysics Data System (ADS)

Chevrel, Magdalena Oryaëlle; Harris, Andrew J. L.; James, Mike R.; Calabrò, Laura; Gurioli, Lucia; Pinkerton, Harry

2018-07-01

Viscosity is one of the most important physical properties controlling lava flow dynamics. Usually, viscosity is measured in the laboratory where key parameters can be controlled but can never reproduce the natural environment and original state of the lava in terms of crystal and bubble contents, dissolved volatiles, and oxygen fugacity. The most promising approach for quantifying the rheology of molten lava in its natural state is therefore to carry out direct field measurements by inserting a viscometer into the lava while it is flowing. Such in-situ syn-eruptive viscosity measurements are notoriously difficult to perform due to the lack of appropriate instrumentation and the difficulty of working on or near an active lava flow. In the field, rotational viscometer measurements are of particular value as they have the potential to measure the properties of the flow interior rather than an integration of the viscosity of the viscoelastic crust + flow interior. To our knowledge only one field rotational viscometer is available, but logistical constraints have meant that it has not been used for 20 yr. Here, we describe new viscosity measurements made using the refurbished version of this custom-built rotational viscometer, as performed on active pāhoehoe lobes from the 61G lava flow of Kilauea's Pu'u 'Ō'ō eruption in 2016. We successfully measured a viscosity of ∼380 Pa s at strain-rates between 1.6 and 5 s-1 and at 1144 °C. Additionally, synchronous lava sampling allowed us to provide detailed textural and chemical characterization of quenched samples. Application of current physico-chemical models based on this characterization (16 ± 4 vol.% crystals; 50 ± 6 vol.% vesicles), gave viscosity estimates that were approximately compatible with the measured values, highlighting the sensitivity of model-based viscosity estimates on the effect of deformable bubbles. Our measurements also agree on the range of viscosities in comparison to previous field experiments on Hawaiian lavas. Conversely, direct comparison with sub-liquidus rheological laboratory measurements on natural lavas was unsuccessful because recreating field conditions (in particular volatile and bubble content) is so far inaccessible in the laboratory. Our work shows the value of field rotational viscometry fully-integrated with sample characterization to quantify three-phase lava viscosity. Finally, this work suggests the need for the development of a more versatile instrument capable of recording precise measurements at low torque and low strain rate, and with synchronous temperature measurements.

Synthesis and characterization of lactose-based homopolymers, hydrophilic/hydrophobic copolymers, and hydrogels

NASA Astrophysics Data System (ADS)

Zhou, Wenjing

The focus of this dissertation is the synthesis and characterization of lactose-based functional polymers. Currently 60% of lactose, a by-product from the cheese industry, is being utilized and the remaining fraction represents a serious disposal problem because of the high biological oxygen demand. Therefore, further development of utilization of lactose is an important issue both for industry and environment. Herein, the syntheses of lactose-based polymers such glycopolymers, hydrophilic/hydrophobic copolymers, and hydrogels are reported. A brief review of lactose formation, physical properties, and production is presented in Chapter 1. Syntheses and applications of lactose derivatives such as lactitol, lactulose, lactaime, lactosylurea, lactosylamine, lactone, and barbituric derivative are documented. Previous work in lactose-based polymers include: (1) hydrogels from cross linking of LPEP, borate complexation of lactose-containing polymer, and copolymerization of lactose monomer with crosslinkers; (2) lactose-based polyurethane rigid foams and adhesives; and (3) lactose-containing glycopolymers are also included. Chapter 2 documents the synthesis of acrylamidolactamine and the free radical copolymerization of this monomer with N-isopropylacrylamide in the presence of BisA to make hydrogels. Swelling behavior of the hydrogels at different temperatures as well as DSC study of these hydrogels are also carried out to characterize the swelling transition and the organization of water in the copolymer hydrogels. In Chapter 3, novel monomer syntheses of N-lactosyl- N'-(4-vinylbenzyl)urea or N '-lactosyl-N,N-methyl(4-vinylbenzyl)urea are described. Polymerization of these new urea monomers using a redox initiator gave water-soluble homopolymers with molecular weights in the range of 1.9 x 103 to 5.3 x 106. Synthesis and polymerization of lactose-O-(p-vinylbenzyl)hydroxime are documented in Chapter 4. The resulting polymers had high molecular weight (106) and narrow polydispersity (Mw/Mn: 1.20--1.35). The Mark-Houwink equation was obtained as [eta] = 2.15 x 10-4Mv0.73. Hydrogels produced in the presence of N,N'-methylenebisacrylamide swelled as much as 21-fold in deionized water. Copolymerization of styrene with lactose-O-(vinylbenzyl)oxime in dimethylsulfoxide-toluene (1:1, v/v) using 2,2'-azobisisobutyronitrile as the initiator are discussed in Chapter 5. The resulting hydrophilic/hydrophobic copolymers were characterized by viscometry, TGA, DSC, GPC, and solubility tests in solvents of varied polarities. Chapter 6 documents the preparation of polystyrene beads with different length of oligo(ethylene glycol) crosslinkers. Swelling in different solvents, solvent accessibility, and reagent diffusion of these beads with different crosslinking density were studied and the results indicated that the PEG-crosslinked polymers showed slightly better solvent accessibility in polar solvents than the analogous DVB-crosslinked networks.

A Non-Arrhenian Viscosity Model for Natural Silicate Melts with Applications to Volcanology

NASA Astrophysics Data System (ADS)

Russell, J. K.; Giordano, D.; Dingwell, D. B.

2005-12-01

Silicate melt viscosity is the most important physical property in volcanic systems. It governs styles and rates of flow, velocity distributions in flowing magma, rates of vesiculation, and, ultimately, sets limits on coherent(vs. fragmented or disrupted) flow. The prediction of melt viscosity over the range of conditions found on terrestrial planets remains a challenge. However, the extraordinary increase in number and quality of published measurements of melt viscosity suggests the possibility of new models. Here we review the attributes of previous models for silicate melt viscosity and, then, present a new predictive model natural silicate melts. The importance of silicate melt viscosity was recognized early [1] and culminated in 2 models for predicting silicate melt viscosity [2,3]. These models used an Arrhenian T-dependence; they were limited by a limited experimental database dominated by high-T measurements. Subsequent models have aimed to: i) extend the compositional range of Arrhenian T-dependent models [4,5]; ii) to develop non-Arrhenian models for limited ranges of composition [6,7,8], iii) to develop new strategies for modelling the composition and T-dependence of viscosity [9,10,11], and, finally, to create chemical models for the non-Arrhenian T-dependence of natural melts [12]. We present a multicomponent model for the compositional and T dependence of silicate melt viscosity based on data spanning a wide range of anhydrous melt compositions. The experimental data include micropenetration and concentric cylinder viscometry measurements covering a viscosity range of 10-1 to 1012 Pa s and a T-range from 700 to 1650°C. These published data provide a high- quality database comprising ~ 800 experimental data on 44 well-characterized melt compositions. Our model uses the Adam-Gibbs equation to capture T-dependence: log η = A + B/[T · log (T/C)] where A, B, and C are adjustable parameters that vary for different melt compositions. We assume that all silicate melts converge to a common, but unknown, high-T limit (e.g., A) and that all compositional dependence is accommodated for by B and C. We adopt a linear compositional dependence for B and C: B = σi=1..n [xi βi] C = σi=1..n [xi γi] where xi's are the mole fractions of oxide components (n=8) and βi and γi are adjustable parameters. The model, therefore, comprises 2 · n+1 adjustable parameters which are optimized for against the experimental database including a common value of A and compositional coefficeints for B and C. The new model reproduces the original database to within experimental uncertainty and can predict the viscosity of silicate melts across the full range of conditions found in Nature. References Cited: [1] Friedman et al., 1963. J Geophys Res 68, 6523-6535. [2] Bottinga Y & Weill D 1972. Am J Sci 272, 438- 475. [3] Shaw HR 1972. Am J Sci 272, 438- 475. [4] Persikov ES 1991. Adv Phys Geochem 9, 1-40. [5] Prusevich AA 1988. Geol Geofiz 29, 67-69. [6] Baker DR 1996. Am Min 81, 126-134. [7] Hess KU & Dingwell DB 1996. Am Min 81, 1297- 1300. [8] Zhang, et al. 2003. Am min 88, 1741- 1752. [9] Russell et al. 2002. Eur J Min 14, 417-428. [10] Russell et al. 2003. Am Min 8, 1390- 1394. [11] Russell JK & Giordano D In Press. Geochim Cosmochim Acta. [12] Giordano D & Dingwell DB 2003. Earth Planet. Sci. Lett. 208, 337-349.

Surface Modification of Nanocellulose Substrates

NASA Astrophysics Data System (ADS)

Zoppe, Justin Orazio

Cellulose fibers constitute an important renewable raw material that is utilized in many commercial applications in non-food, paper, textiles and composite materials. Chemical functionalization is an important approach for improving the properties of cellulose based materials. Different approaches are used to graft polymeric chains onto cellulose substrates, which can be classified by two principal routes, namely 'grafting onto' or 'grafting from' methods. Never-dried cellulose nanocrystals (CNCs) or nanowhiskers produced from sulfuric acid hydrolysis of ramie fibers were used as substrates for surface chemical functionalization with various macromolecules. In addition, the use of cellulose nanocrystals to reinforce poly(epsilon-caprolactone) (PCL) nanofibers was studied. Chemical grafting with low molecular weight polycaprolactone diol onto cellulose nanocrystals was carried out in an attempt to improve the interfacial adhesion with the fiber matrix. Significant improvements in the mechanical properties of the nanofibers after reinforcement with unmodified cellulose nanocrystals were confirmed. Fiber webs from PCL reinforced with 2.5% unmodified CNCs showed ca. 1.5-fold increase in Young's modulus and ultimate strength compared to PCL webs. The CNCs were also grafted with poly(N-isopropylacrylamide) (poly(NiPAAm)) brushes via surface-initiated single-electron transfer living radical polymerization (SI-SETLRP) under various conditions at room temperature. The grafting process depended on the initiator and/or monomer concentrations used. No observable damage occurred to the CNCs after grafting, as determined by X-ray diffraction. Size exclusion chromatography analyses of polymer chains cleaved from the cellulose nanocrystals indicated that a higher degree of polymerization was achieved by increasing initiator or monomer loading, most likely caused by local heterogeneities yielding higher rates of polymerization. In addition, the colloidal stability and thermo-responsive behavior of poly(NiPAAm) brushes grafted from nanoparticles of CNCs of varying graft densities and molecular weights was investigated. Halo areas surrounding grafted CNCs that were adsorbed on silica and imaged with an AFM were indicative of the grafted polymer brushes. Aggregation of nanoparticles carrying grafts of high degree of polymerization was observed. The responsiveness of CNCs in liquid medium and as spin-coated films was determined by using light scattering, viscometry and Colloidal Probe Microscopy (CPM). Light transmittance measurements showed temperaturedependent aggregation originating from the different graft densities and molecular weights and a sharp increase in dispersion viscosity as the temperature approached the LCST. The lower critical solution temperature (LCST) of grafted poly(NiPAAm) brushes was found to decrease with the ionic strength as is the case of neat poly(NiPAAm) in aqueous solution. CPM in aqueous media for asymmetric systems consisting of thin films of CNCs and a colloidal silica probe showed the distinctive effects of the grafted polymer brushes on the interaction (repulsive and adhesive) forces. The origin of such forces was mainly electrostatic and steric in the case of bare and grafted CNCs, respectively. A decrease in the onset of attractive and adhesion forces of grafted CNCs films was observed with the ionic strength of the aqueous solution medium. The decreased mobility of polymer brushes upon partial collapse and decreased availability of hydrogen bonding sites with higher electrolyte concentration were hypothesized as main reasons for the less prominent polymer bridging between interacting surfaces. Finally, poly(NiPAAm)-g-CNCs were utilized as a Pickering emulsions stabilizer. All emulsions formed were oil-in-water confirmed by a drop test. Various drop sizes were obtained as characterized by laser scattering particle size analysis and optical microscopy. Anisotropic colloidal assemblies of grafted CNCs at the oil-water interface were observed in freeze-fractured samples via Transmission Electron Microscopy. Emulsions were stable for over three months at the time of writing this thesis, however rapidly broke above the LCST as determined by rheometry.

EDITORIAL: MST Best Paper Award for 2003

NASA Astrophysics Data System (ADS)

Gill, Patrick

2004-09-01

For the last 12 years, Measurement Science and Technology has awarded a Best Paper prize. The Editorial Board of the journal believes that such a prize is an opportunity to thank authors for submitting their work, and serves as an integral part of the on-going quality review of the journal. An Editorial Board working party, comprising Patrick Gill (Chairman), Ralph Tatam and David Birch, was convened to determine a single contributed paper describing new and significant work, well aligned with the measurement scope of the journal, and presented in clear and rigorous form. They received a number of recommendations from the Editorial and International Advisory Board Members, and they would like to record their thanks to the Members for these recommendations, as they form an all-important first stage in the assessment process. There were responses from some 12 Board Members. In total, there were 31 papers nominated. To aid the process, additional information in the form of the 2003 MST papers top rated by referees, and the top papers ranked by most electronic accesses, was accessed. Reviews, and papers which included a Board Member as an author, were automatically excluded. From the totality of nominations and working party deliberations, there emerged a clear winner. Thus the paper recommended by the working party for the MST Best Paper Award for 2003 is: 'Extension of the torsional crystal viscometer to measurements in the time domain' by Richard F Hafer and Arno Laesecke, 14 663-673 (2003) This paper describes a significant advance in viscosity measurement using torsional vibration in piezoelectric rods. The method reported here demonstrates the use of free-decay time-domain measurements as opposed to the more established steady-state forced-mode resonance technique. The time domain technique is faster and more sensitive, with the potential for improved accuracy due to the lack of large time constants necessary for the interpretation of forced mode data. It offers a more direct approach which has the potential for absolute viscosity measurements and the establishment of a primary instrument for the measurement of viscosity standards, but also has potentially wider application for industrial viscosity measurement and process control. The paper is well structured and clearly written, with a good outline of the background to the work, a comparison of theoretical description of both forced mode and free-decay operation, and a clear description of the device. Results and data analysis are presented for both types of operation of the viscometer; the viscometer is characterized in vacuo, followed by validation with SF6 as a test fluid. The much reduced timescale for gathering the free decay data, coupled with available bench-top PC computing power, led to a significant advantage for 'on-line' data analysis, and has enabled the avoidance of non-linear operating regimes which were difficult to deal with under forced mode operation. Even without immediate knowledge and expertise in this area, the readership can gain a useful insight into the state of the art in viscometry due to the lucidity of the paper. This is illustrated in the top level quality rating that was accorded the paper at the refereeing stage. We therefore recommend this paper for the MST 2003 Best Paper Award. The working party decided also that the following article was the best Design Note in MST for 2003: 'A dispersion-free high-speed beam chopper for ultrafast-pulsed-laser applications' by J F Holzman and A Y Elezzabi, 14 N41-N44 (2003) This design note reports the development of a chopper for use at frequencies ~100 kHz, well above those possible with conventional choppers, and offers an alternative in the medium to high frequency range to electro-optic and acousto-optic modulation techniques, which can suffer from material dispersion problems and propagation-induced pulse broadening effects.

Fabrication de structures tridimensionnelles de nanocomposites polymeres charges de nanotubes de carbone a simple paroi

NASA Astrophysics Data System (ADS)

Laberge Lebel, Louis

There is currently a worldwide effort for advances in micro and nanotechnologies due to their high potential for technological applications in fields such as microelectromechanical systems (MEMS), organic electronics and structural microstructures for aerospace. In these applications, carbon nanotube/polymer nanocomposites represent interesting material options compared to conventional resins for their enhanced mechanical and electrical properties. However, several significant scientific and technological challenges must first be overcome in order to rapidly and cost-effectively fabricate nanocomposite-based microdevices. Fabrication techniques have emerged for fabricating one- of two-dimensional (1D/2D) nanocomposite structures but few techniques are available for three-dimensional (3D) nanocomposite structures. The overall objective of this thesis is the development of a manufacturing technique allowing the fabrication of 3D structures of single-walled carbon nanotube (C-SWNT)/polymer nanocomposite. This thesis reports the development of a direct-write fabrication technique that greatly extends the fabrication space for 3D carbon nanotube/polymer nanocomposite structures. The UV-assisted direct-write (UV-DW) technique employs the robotically-controlled micro-extrusion of a nanocomposite filament combined with a UV exposure that follows the extrusion point. Upon curing, the increased rigidity of the extruded filament enables the creation of multi-directional shapes along the trajectory of the extrusion point. The C-SWNT material is produced by laser ablation of a graphite target and purified using a nitric acid reflux. The as-grown and purified material is characterized under transmission electron microscopy and Raman spectroscopy. The purification procedure successfully graphed carboxylic groups on the surface of the C-SWNTs, shown by X-ray photoelectron spectroscopies. An incorporation procedure in the polymer is developed involving a non-covalent functionalization of the nanotubes by zinc protoporphyrin IX molecule and high shear mixing using a three-roll mill. The incorporation of the C-SWNTs into the resin led to an increase of the viscosity and the apparition of a shear thinning behaviour, characterized by capillary viscometry. The nanocomposite UV-curing behavior is characterized under differential scanning calorimetry coupled with a UV source. A further adjustment of the shear thinning behavior using fumed silica enabled the UV-DW fabrication of microbeams. Mechanical characterization reveals significant increase in both strength (by ˜64%) and modulus (by more than 15 times). These mechanical enhancements are attributed to both the covalent and the non-covalent functionalizations of the C-SWNTs. Nanocomposite spring networks composed of three micro-coils fabricated using the UV-DW technique are mechanically tested under compression and show a rigidity of ˜11.5 mN/mm. A micro-coil is also deposited between two uneven electrodes and a 10-6 S/cm electrical conductivity is measured. Nanocomposite scaffold structures are also deposited using the UV-DW technique. This thesis also reports the fabrication of 3D micro structured beams reinforced with the C-SWNT/polymer nanocomposite by using an approach based on the infiltration of 3D microfluidic networks. The 3D microfluidic network is first fabricated by the direct-write assembly method, which consists of the robotized deposition of fugitive ink filaments on an epoxy substrate, forming a 3D micro structured scaffold. After encapsulating the 3D micro-scaffold structure with an epoxy resin, the fugitive ink is liquefied and removed, resulting in a 3D network of interconnected microchannels. This microfluidic network is then infiltrated by the C-SWNT/polyurethane nanocomposite and subsequently cured. The final samples consist of rectangular beams having a complex 3D-skeleton structure of C-SWNT/polyrner nanocomposite fibers, adapted to offer better performance under flexural solicitation. Dynamic mechanical analysis in flexion show an increase of 12.5% in the storage modulus under 35°C compared to the resin infiltrated beams. The manufacturing techniques demonstrated here, i.e. UV assisted direct writing and the infiltration of 3D microfluidic networks, open new prospects for the achievement of 3D reinforced micro structures that could find application in organic electronics, MEMS, sensor, tissue engineering scaffolds and aerospace.