The State of Water in the Isolated Toad Bladder in the Presence and Absence of Vasopressin

An attempt has been made to assess the validity of applying the frictional and viscous coefficients of bulk water to the movement of water and solutes through the urinary bladder of the toad. The temperature dependence of diffusion of THO, C14-urea, C14-thiourea, and net water transfer across the bladder was determined in the presence and absence of vasopressin. The activation energy for diffusion of THO was 9.8 kcal per mole in the absence of vasopressin and 4.1 kcal per mole with the hormone present. Activation energies simultaneously determined following vasopressin for diffusion and net transfers of water were similar, and in the same range as known activation energies for diffusion and viscous flow in water. Urea had activation energies for diffusion of 4.1 and 3.9 kcal per mole in the absence and presence of vasopressin, respectively. Thiourea had a high activation energy for diffusion of 6.3 kcal per mole, which was unchanged, 6.6 kcal per mole, following hormone. These findings suggest that in its rate-limiting permeability barrier, water is present in a structured state, offering a high resistance to penetration by water. Vasopressin enlarges the aqueous channels so that the core of water they contain possesses the physical properties of ordinary bulk water. Urea penetrates the tissue via these aqueous channels while thiourea is limited by some other permeability barrier.

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High-Temperature Deformation of Naturally Aged 7010 Aluminum Alloy

Metals ◽

10.3390/met11040581 ◽

2021 ◽

Vol 11 (4) ◽

pp. 581

Author(s):

Abdulhakim A. Almajid

Keyword(s):

Activation Energy ◽

Aluminum Alloy ◽

High Temperature ◽

Threshold Stress ◽

Activation Energies ◽

Temperature Deformation ◽

High Temperature Range ◽

Temperature Range ◽

True Activation Energy ◽

Two Temperatures

This study is focused on the deformation mechanism and behavior of naturally aged 7010 aluminum alloy at elevated temperatures. The specimens were naturally aged for 60 days to reach a saturated hardness state. High-temperature tensile tests for the naturally aged sample were conducted at different temperatures of 573, 623, 673, and 723 K at various strain rates ranging from 5 × 10−5 to 10−2 s−1. The dependency of stress on the strain rate showed a stress exponent, n, of ~6.5 for the low two temperatures and ~4.5 for the high two temperatures. The apparent activation energies of 290 and 165 kJ/mol are observed at the low, and high-temperature range, respectively. These values of activation energies are greater than those of solute/solvent self-diffusion. The stress exponents, n, and activation energy observed are rather high and this indicates the presence of threshold stress. This behavior occurred as a result of the dislocation interaction with the second phase particles that are existed in the alloy at the testing temperatures. The threshold stress decreases in an exponential manner as temperature increases. The true activation energy was computed by incorporating the threshold stress in the power-law relation between the stress and the strain. The magnitude of the true activation energy, Qt dropped to 234 and 102 kJ/mol at the low and high-temperature range, respectively. These values are close to that of diffusion of Zinc in Aluminum and diffusion of Magnesium in Aluminum, respectively. The Zener–Hollomon parameter for the alloy was developed as a function of effective stress. The data in each region (low and high-temperature region) coalescence in a segment line in each region.

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Effect of CaO on catalytic combustion of semi-coke

Green Processing and Synthesis ◽

10.1515/gps-2021-0002 ◽

2021 ◽

Vol 10 (1) ◽

pp. 011-020

Author(s):

Luyao Kou ◽

Junjing Tang ◽

Tu Hu ◽

Baocheng Zhou ◽

Li Yang

Keyword(s):

Activation Energy ◽

Apparent Activation Energy ◽

Combustion Rate ◽

Activation Energies ◽

Combustion Reaction ◽

Tg Analysis ◽

Conversion Rates ◽

Apparent Activation Energies ◽

Ozawa Integral Method ◽

Addition Amount

Abstract Generally, adding a certain amount of an additive to pulverized coal can promote its combustion performance. In this paper, the effect of CaO on the combustion characteristics and kinetic behavior of semi-coke was studied by thermogravimetric (TG) analysis. The results show that adding proper amount of CaO can reduce the ignition temperature of semi-coke and increase the combustion rate of semi-coke; with the increase in CaO content, the combustion rate of semi-coke increases first and then decreases, and the results of TG analysis showed that optimal addition amount of CaO is 2 wt%. The apparent activation energy of CaO with different addition amounts of CaO was calculated by Coats–Redfern integration method. The apparent activation energy of semi-coke in the combustion reaction increases first and then decreases with the increase in CaO addition. The apparent activation energies of different samples at different conversion rates were calculated by Flynn–Wall–Ozawa integral method. It was found that the apparent activation energies of semi-coke during combustion reaction decreased with the increase in conversion.

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The Effect of α-Al(MnCr)Si Dispersoids on Activation Energy and Workability of Al-Mg-Si-Cu Alloys during Hot Deformation

Advances in Materials Science and Engineering ◽

10.1155/2020/3471410 ◽

2020 ◽

Vol 2020 ◽

pp. 1-12

Author(s):

Xiaoguo Wang ◽

Jian Qin ◽

Hiromi Nagaumi ◽

Ruirui Wu ◽

Qiushu Li

Keyword(s):

Activation Energy ◽

Aluminum Alloys ◽

Constitutive Equation ◽

Hot Deformation ◽

Flow Instability ◽

Void Formation ◽

Activation Energies ◽

Compression Tests ◽

Softening Mechanism ◽

Dynamic Softening

The hot deformation behaviors of homogenized direct-chill (DC) casting 6061 aluminum alloys and Mn/Cr-containing aluminum alloys denoted as WQ1 were studied systematically by uniaxial compression tests at various deformation temperatures and strain rates. Hot deformation behavior of WQ1 alloy was remarkably changed compared to that of 6061 alloy with the presence of α-Al(MnCr)Si dispersoids. The hyperbolic-sine constitutive equation was employed to determine the materials constants and activation energies of both studied alloys. The evolution of the activation energies of two alloys was investigated on a revised Sellars’ constitutive equation. The processing maps and activation energy maps of both alloys were also constructed to reveal deformation stable domains and optimize deformation parameters, respectively. Under the influence of α dispersoids, WQ1 alloy presented a higher activation energy, around 40 kJ/mol greater than 6061 alloy’s at the same deformation conditions. Dynamic recrystallization (DRX) is main dynamic softening mechanism in safe processing domain of 6061 alloy, while dynamic recovery (DRV) was main dynamic softening mechanism in WQ1 alloy due to pinning effect of α-Al(MnCr)Si dispersoids. α dispersoids can not only resist DRX but also increase power required for deformation of WQ1 alloy. The microstructure analysis revealed that the flow instability was attributed to the void formation and intermetallic cracking during hot deformation of both alloys.

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Front instability in a condensed phase combustion model

Advances in Nonlinear Analysis ◽

10.1515/anona-2014-0018 ◽

2015 ◽

Vol 4 (3) ◽

pp. 153-176 ◽

Cited By ~ 2

Author(s):

Alexis Bonnet ◽

Fathi Dkhil ◽

Elisabeth Logak

Keyword(s):

Activation Energy ◽

Condensed Phase ◽

Linear Instability ◽

Combustion Model ◽

Energy Limit ◽

High Activation ◽

Front Solution ◽

High Activation Energy ◽

Linearized Problem ◽

Existence Of Zeros

AbstractWe consider a condensed phase (or solid) combustion model and its linearization around the travelling front solution. We construct an Evans function to characterize the eigenvalues of the linearized problem. We estimate this functional in the high activation energy limit. We deduce the existence of zeros with nonnegative real part for high activation energy, which proves the linear instability of the travelling front solution.

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Observation of Rheed Intensity Oscillations During PbSe/CaF2/Si(111) MBE

MRS Proceedings ◽

10.1557/proc-441-51 ◽

1996 ◽

Vol 441 ◽

Cited By ~ 2

Author(s):

W. K. Liu ◽

X. M. Fang ◽

P. J. McCann ◽

M. B. Santos

Keyword(s):

Activation Energy ◽

Melting Point ◽

Substrate Temperature ◽

High Melting ◽

Arrhenius Behavior ◽

High Activation ◽

High Melting Point ◽

Mbe Growth ◽

Sublimation Energy ◽

Initial Nucleation

AbstractRHEED intensity oscillations observed during MBE growth of CaF2 on Si(111) and PbSe on CaF2/Si(111) are presented. The effects of substrate temperature and initial nucleation procedure are investigated. Strong temporal oscillations of the specular beam intensity are found to be most readily observed at temperatures below 200°C for both CaF2 and PbSe. Growth rates measured as a function of cell temperatures exhibit Arrhenius behavior with activation energies of 5.0 eV and 1.93 eV for CaF2 and PbSe, respectively. The relatively high activation energy obtained for CaF2 is consistent with the high melting point and sublimation energy of ionic fluorides.

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New experiments on the relationship between light-induced defects and photoconductivity degradation

MRS Proceedings ◽

10.1557/proc-664-a12.2 ◽

2001 ◽

Vol 664 ◽

Cited By ~ 2

Author(s):

Stephan Heck ◽

Howard M. Branz

Keyword(s):

Activation Energy ◽

Defect Density ◽

Activation Energies ◽

Dangling Bond ◽

Fast Recovery ◽

Slow Recovery ◽

Degradation Model ◽

Induced Defects ◽

The Relationship ◽

Hydrogenated Amorphous

ABSTRACTWe report experimental results that help settle apparent inconsistencies in earlier work on photoconductivity and light-induced defects in hydrogenated amorphous silicon (a-Si:H) and point toward a new understanding of this subject. After observing that light-induced photoconductivity degradation anneals out at much lower T than the light-induced increase in deep defect density, Han and Fritzsche[1] suggested that two kinds of defects are created during illumination of a-Si:H. In this view, one kind of defect degrades the photoconductivity and the other increases defect sub-bandgap optical absorption. However, the light-induced degradation model of Stutzmann et al.[2] assumes that photoconductivity is inversely proportional to the dangling-bond defect density. We observe two kinds of defects that are distinguished by their annealing activation energies, but because their densities remain in strict linear proportion during their creation, the two kinds of defects cannot be completely independent.In our measurements of photoconductivity and defect absorption (constant photocurrent method) during 25°C light soaking and during a series of isochronal anneals between 25 < T < 190°C, we find that the absorption measured with E ≤1.1 eV, first increases during annealing, then exhibits the usual absorption decrease found for deeper defects. The maximum in this absorption at E ≤1.1eV occurs simultaneously with a transition from fast to slow recovery of photoconductivity. The absorption for E ≤1.1eV shows two distinct annealing activation energies: the signal rises with about 0.87 eV and falls with about 1.15 eV. The 0.87 eV activation energy roughly equals the activation energy for the dominant, fast, recovery of photoconductivity. The 1.15 eV activation energy roughly equals the single activation energy for annealing of the light-induced dangling bond absorption.

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Gas-phase detonation propagation in mixture composition gradients

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2011.0342 ◽

2012 ◽

Vol 370 (1960) ◽

pp. 567-596 ◽

Cited By ~ 27

Author(s):

D. A. Kessler ◽

V. N. Gamezo ◽

E. S. Oran

Keyword(s):

Activation Energy ◽

Reaction Model ◽

Single Step ◽

Mixture Composition ◽

Composition Gradient ◽

Detonation Properties ◽

High Activation ◽

Zone Structure ◽

Detonation Cell ◽

High Activation Energy

The propagation of detonations through several fuel–air mixtures with spatially varying fuel concentrations is examined numerically. The detonations propagate through two-dimensional channels, inside of which the gradient of mixture composition is oriented normal to the direction of propagation. The simulations are performed using a two-component, single-step reaction model calibrated so that one-dimensional detonation properties of model low- and high-activation-energy mixtures are similar to those observed in a typical hydrocarbon–air mixture. In the low-activation-energy mixture, the reaction zone structure is complex, consisting of curved fuel-lean and fuel-rich detonations near the line of stoichiometry that transition to decoupled shocks and turbulent deflagrations near the channel walls where the mixture is extremely fuel-lean or fuel-rich. Reactants that are not consumed by the leading detonation combine downstream and burn in a diffusion flame. Detonation cells produced by the unstable reaction front vary in size across the channel, growing larger away from the line of stoichiometry. As the size of the channel decreases relative to the size of a detonation cell, the effect of the mixture composition gradient is lessened and cells of similar sizes form. In the high-activation-energy mixture, detonations propagate more slowly as the magnitude of the mixture composition gradient is increased and can be quenched in a large enough gradient.

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Crystallization behavior of ion beam sputtered HfO2 thin films and its effect on the laser-induced damage threshold

Journal of the European Optical Society Rapid Publications ◽

10.1186/s41476-021-00147-w ◽

2021 ◽

Vol 17 (1) ◽

Author(s):

Zoltán Balogh-Michels ◽

Igor Stevanovic ◽

Aurelio Borzi ◽

Andreas Bächli ◽

Daniel Schachtler ◽

...

Keyword(s):

Activation Energy ◽

Crystallization Process ◽

Ion Beam ◽

Damage Threshold ◽

High Activation ◽

Quarter Wave ◽

Dimensional Growth ◽

Laser Induced Damage ◽

Significant Increment

AbstractIn this work, we present our results about the thermal crystallization of ion beam sputtered hafnia on 0001 SiO2 substrates and its effect on the laser-induced damage threshold (LIDT). The crystallization process was studied using in-situ X-ray diffractometry. We determined an activation energy for crystallization of 2.6 ± 0.5 eV. It was found that the growth of the crystallites follows a two-dimensional growth mode. This, in combination with the high activation energy, leads to an apparent layer thickness-dependent crystallization temperature. LIDT measurements @355 nm on thermally treated 3 quarter-wave thick hafnia layers show a decrement of the 0% LIDT for 1 h @773 K treatment. Thermal treatment for 5 h leads to a significant increment of the LIDT values.

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Metamorphism of Air Bubbles in a Snow Crystal

Journal of Glaciology ◽

10.3189/s0022143000019778 ◽

1967 ◽

Vol 6 (46) ◽

pp. 561-564

Author(s):

Norikazu Maeno ◽

Daisuke Kuroiwa

Keyword(s):

Activation Energy ◽

Diffusion Processes ◽

Atomic Diffusion ◽

Mechanical Relaxation ◽

Air Bubbles ◽

A Value ◽

Snow Crystal ◽

Activation Energy For Diffusion ◽

Snow Crystals ◽

Natural Snow

RésuméObservations have been made of the modification produced by a temperature gradient in the shape of air bubbles in natural snow crystals, and also of the shrinkage of the bubbles with time. The rate of shrinkage is governed by a constant which is strongly temperature dependent with an activation energy of about 15.1 kcal./mole, a value sufficiently similar to the activation energy for diffusion of tritium, dielectric relaxation and mechanical relaxation to suggest that atomic diffusion processes may be responsible for all of these phenomena.

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