Viscosities of dilute aqueous suspensions of montmorillonite and kaolinite clays

1986 ◽  
Vol 64 (9) ◽  
pp. 1919-1924 ◽  
Author(s):  
Kim L. Kasperski ◽  
Charles T. Hepler ◽  
Loren G. Hepler
Keyword(s):  
Einstein Equation ◽  
Colloidal Particles ◽  
Effect Of Temperature ◽  
Previous Knowledge ◽  
Swelling Clay ◽  
Clay Particles ◽  
Previous Evidence ◽  
Aqueous Suspensions ◽  
Increasing Temperature

We have measured viscosities and densities of dilute aqueous suspensions of Na-kaolinite (25 °C), of Na-montmorillonite (25–55 °C), and of mixtures of Na-kaolinite/Na-montmorillonite (25 °C). Results of the measurements at 25 °C have been analyzed in terms of the Einstein equation with conclusions that are consistent with previous knowledge that colloidal particles of these clays are non-spherical and that montmorillonite is a swelling clay. Viscosities of mixed clay systems are nearly consistent with a simple additivity model; the small non-additivities are in accord with previous evidence that relatively small montmorillonite particles are adsorbed on the surface of relatively large kaolinite particles. The effect of temperature on the viscosities of suspensions of montmorillonite is consistent with the idea that aggregation of clay particles diminishes with increasing temperature.

scholarly journals Theoretical Effect of Temperature on Threshold in the Hodgkin-Huxley Nerve Model

1966 ◽  
Vol 49 (5) ◽  
pp. 989-1005 ◽  
Author(s):  
Richard Fitzhugh
Keyword(s):  
Relaxation Time ◽  
Relaxation Times ◽  
Giant Axon ◽  
Temperature Curve ◽  
Effect Of Temperature ◽  
Threshold Temperature ◽  
Ionic Conductances ◽  
And Shifts ◽  
The Right ◽  
Increasing Temperature

In the squid giant axon, Sjodin and Mullins (1958), using 1 msec duration pulses, found a decrease of threshold with increasing temperature, while Guttman (1962), using 100 msec pulses, found an increase. Both results are qualitatively predicted by the Hodgkin-Huxley model. The threshold vs. temperature curve varies so much with the assumptions made regarding the temperature-dependence of the membrane ionic conductances that quantitative comparison between theory and experiment is not yet possible. For very short pulses, increasing temperature has two effects. (1) At lower temperatures the decrease of relaxation time of Na activation (m) relative to the electrical (RC) relaxation time favors excitation and decreases threshold. (2) For higher temperatures, effect (1) saturates, but the decreasing relaxation times of Na inactivation (h) and K activation (n) factor accommodation and increased threshold. The result is a U-shaped threshold temperature curve. R. Guttman has obtained such U-shaped curves for 50 µsec pulses. Assuming higher ionic conductances decreases the electrical relaxation time and shifts the curve to the right along the temperature axis. Making the conductances increase with temperature flattens the curve. Using very long pulses favors effect (2) over (1) and makes threshold increase monotonically with temperature.

scholarly journals DFT calculation for the electronic properties and quantum capacitance of pure and doped Zr2CO2 as electrode of supercapacitors

2021 ◽  
Author(s):  
Shuo Xu ◽  
Shi-Jie Wang ◽  
Li Xiao-Hong ◽  
Hong-Ling Cui
Keyword(s):  
Electronic Properties ◽  
Electrode Materials ◽  
Chemical Properties ◽  
Effect Of Temperature ◽  
Quantum Capacitance ◽  
Substitutional Site ◽  
Level Shifts ◽  
Dirac Distribution ◽  
Increasing Temperature ◽  
Physical And Chemical

Defect and doping are effective methods to modulate the physical and chemical properties of materials. In this report, we investigated the structural stability, electronic properties and quantum capacitance (Cdiff) of Zr2CO2 by changing the dopants of Si, Ge, Sn, N, B, S and F in the substitutional site. The doping of F, N, and S atoms makes the system undergo the semiconductor-to-conductor transition, while the doping of Si, Ge, and Sn maintains the semiconductor characteristics. The Cdiff of the doped systems are further explored. The B-doped system can be used as cathode materials, while the systems doped by S, F, N, Sn atoms are promising anode materials of asymmetric supercapacitors, especially for the S-doped system. The improved Cdiff mainly originates from Fermi-level shifts and Fermi-Dirac distribution by the introduction of the dopant. The effect of temperature on Cdiff is further explored. The result indicates that the maximum Cdiff of the studied systems gradually decreases with the increasing temperature. Our investigation can provide useful theoretical basis for designing and developing the ideal electrode materials for supercapacitors.

scholarly journals Effects of the Temperature and the pH on the Main Protease of SARS-CoV-2: A Molecular Dynamics Simulation Study

2021 ◽  
Vol 12 (6) ◽  
pp. 7239-7248
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Root Mean Square ◽  
Dynamics Simulation ◽  
Effect Of Temperature ◽  
Water Molecules ◽  
Mean Square ◽  
Main Protease ◽  
Decreasing Ph ◽  
Increasing Temperature

The novel coronavirus, recognized as COVID-19, is the cause of an infection outbreak in December 2019. The effect of temperature and pH changes on the main protease of SARS-CoV-2 were investigated using all-atom molecular dynamics simulation. The obtained results from the root mean square deviation (RMSD) and root mean square fluctuations (RMSF) analyses showed that at a constant temperature of 25℃ and pH=5, the conformational change of the main protease is more significant than that of pH=6 and 7. Also, by increasing temperature from 25℃ to 55℃ at constant pH=7, a remarkable change in protein structure was observed. The radial probability of water molecules around the main protease was decreased by increasing temperature and decreasing pH. The weakening of the binding energy between the main protease and water molecules due to the increasing temperature and decreasing pH has reduced the number of hydrogen bonds between the main protease and water molecules. Finding conditions that alter the conformation of the main protease could be fundamental because this change could affect the virus’s functionality and its ability to impose illness.

scholarly journals Partial purification and properties of the two common inherited forms of human erythrocyte adenylate kinase

1972 ◽  
Vol 130 (3) ◽  
pp. 797-803 ◽  
Author(s):  
C. Brownson ◽  
N. Spencer
Keyword(s):  
Adenylate Kinase ◽  
Effect Of Temperature ◽  
Partial Purification ◽  
Heat Denaturation ◽  
Gel Chromatography ◽  
Molecular Weights ◽  
Purification And Properties ◽  
Increasing Temperature

1. The partial purification of adenylate kinase, types 1 and 2, from human erythrocytes is described. 2. Gel chromatography of both forms of the enzyme gave estimates of the molecular weights in the range 20000–23000. 3. Studies on crude haemolysates at various pH values indicated that the type 2 enzyme was less stable than the type 1. Heat denaturation studies on the partially purified enzymes confirmed these findings. 4. Measurements of rates of inhibition by iodoacetate and iodoacetamide showed that the type 2 enzyme reacts more readily than the type 1 enzyme with both reagents. 5. The effect of temperature on the initial velocity of ADP formation was measured at a single concentration of both AMP and MgATP2-. The two forms of the enzyme responded differently to increasing temperature.

scholarly journals Surface and interfacial tensions of aqueous dispersions of charged colloidal (clay) particles

1994 ◽  
Vol 72 (9) ◽  
pp. 1915-1920 ◽  
Author(s):  
Laurier L. Schramm ◽  
Loren G. Hepler
Keyword(s):  
Interfacial Tension ◽  
Pure Water ◽  
Surface Tensions ◽  
Flow Rates ◽  
Aqueous Dispersions ◽  
Clay Particles ◽  
Interfacial Tensions ◽  
Aqueous Suspensions ◽  
Colloidal Clay ◽  
Effect Of Surface

We have measured (du Nouy ring and maximum bubble pressure methods) suspension–air surface tensions of aqueous suspensions of montmorillonite and have observed that these surface tensions are larger than those of pure water at the same temperatures. Further measurements have shown that dispersed montmorillonite also increases the suspension–toluene interfacial tension compared with that of pure water–toluene. Similar measurements on aqueous suspensions of kaolinite have yielded suspension–air interfacial tensions with uncertainties as large as the observed (small) effect, and also shown that the suspension–toluene interfacial tension is decreased (opposite to the effect of montmorillonite) by amounts larger than the experimental uncertainties. Measurements of maximum bubble pressures at different flow rates have provided information about the effect of surface age on observed surface tensions.

Standardized reaction times used to describe the mechanism of enzyme-induced gelation in whey protein systems

2000 ◽  
Vol 67 (3) ◽  
pp. 403-413 ◽  
Author(s):  
RICHARD IPSEN ◽  
JEANETTE OTTE ◽  
STIG B. LOMHOLT ◽  
KARSTEN B. QVIST
Keyword(s):  
Whey Protein ◽  
Reaction Times ◽  
Enzyme Concentration ◽  
Protein Isolate ◽  
Effect Of Temperature ◽  
Degree Of Hydrolysis ◽  
Thermally Induced ◽  
Constant Degree ◽  
Increasing Temperature ◽  
Rate Limiting

Whey protein isolate (WPI), either untreated or pretreated at 80 °C for 30 min, was incubated with a proteinase from Bacillus licheniformis until a gel was formed. Standardized reaction times, directly linked to the degree of hydrolysis, were obtained from plots of the relative amount of peptides released v. reaction time obtained under different conditions (enzyme concentration, temperature, pH, NaCl addition). This provided a connection between the gelation profile and the degree of hydrolysis. In the case of untreated WPI, gelation occurred at lower degrees of proteolysis when the enzyme concentration was decreased, demonstrating that a rate-limiting aggregation process occurred at the same time as the proteolysis in a manner similar to the renneting of milk. This was not the case for preheated WPI, when gelation was found to take place at a constant degree of proteolysis, independent of the enzyme concentration. In this case, the mechanism could be described by assuming the thermally induced aggregates present in this substrate had progressively more stabilizing peptide segments shaved off, resulting in increased attraction between individual aggregates that ultimately led to gelation. Results obtained at 40–60 °C supported this, as we found no effect of temperature on the degree of proteolysis at gelation for the untreated WPI, whereas the degree of proteolysis decreased with increasing temperature when heated WPI was hydrolysed. The effect of pH and NaCl addition on the process was to reduce repulsion between the aggregating species so that gelation was induced at a decreased degree of proteolysis.

Modeling and Numerical Simulation of the Effect of Temperature on the LCF Behaviour of a CuCrZr Alloy Specimen

2020 ◽  
Vol 50 ◽  
pp. 37-47
Author(s):  
M. Benhaddou ◽  
M. Ghammouri ◽  
Z. Hammouch ◽  
F. Latrache
Keyword(s):  
Test Piece ◽  
Low Cycle Fatigue ◽  
Effect Of Temperature ◽  
Cycle Fatigue ◽  
Alloy Specimen ◽  
Number Of Cycles ◽  
Increasing Temperature ◽  
Relationship Of ◽  
The Relationship ◽  
Cylindrical Test

The main originality of this work consists in investigating low cycle fatigue of cylindrical test piece with wings under imposed constraint and for the temperature 20°c, 200°c, 400°c. Based on a combination between the fatigue parameter of Jiang-Sehitoglu and the relationship of Coffin-Manson, a numerical model for the prediction of the number of cycles at break. It was found that the CuCrZr cylindrical test piece showed a reduction in fatigue life with increasing temperature.

scholarly journals Mineral Composition and Antioxidant Potential in the Common Poppy (Papaver rhoeas L.) Petal Infusions

2020 ◽  
Vol 199 (1) ◽  
pp. 371-381
Author(s):  
Janda Katarzyna ◽  
Jakubczyk Karolina ◽  
Kupnicka Patrycja ◽  
Bosiacki Mateusz ◽  
Gutowska Izabela
Keyword(s):  
Vitamin C ◽  
Mineral Content ◽  
Antioxidant Potential ◽  
Effect Of Temperature ◽  
Total Polyphenol ◽  
Spectrophotometric Methods ◽  
Inflammatory Conditions ◽  
Different Temperatures ◽  
The Common ◽  
Increasing Temperature

AbstractThe flowers of the common poppy are used for medicinal purposes, both internally and externally. They are reported to have antispasmodic and antitussive properties, to alleviate inflammatory conditions and soothe anxiety-related digestive problems. The aim of the study was to determine the antioxidant potential and the content of vitamin C, polyphenols, and minerals in infusions made from the petals of the common poppy at different temperatures. The infusions were made at various temperatures (25 °C, 70 °C, 80 °C, and 90 °C). The antioxidant potential and the content of polyphenols and vitamin C were determined by spectrophotometric methods. The mineral content was determined using the ICP-OES method. The total polyphenol content ranged from 135.2 to 137.24 ppm and that of vitamin C—from 15.47 to 15.78 mg/100 mL. The temperature of the water used to make the infusions did not appear to have a significant effect on these parameters. The temperature did, however, significantly affect the antioxidant potential of the infusions—the highest antioxidant activity (71.21% DPPH inhibition) was observed in the infusion prepared using water at 80 °C. The infusions included in the study contained a number of minerals. No significant effect of temperature was found for the content of K, Zn, Cu, Fe, and Ni in the infusions. On the other hand, the content of Ca in the infusions was significantly correlated with the increasing temperature of the water. It was concluded that poppy petal infusions may serve as a valuable dietary supplement, providing antioxidants and minerals required by the human body to function properly.

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