Journal articles: 'Thermodynamic homogeneity'

1

Guseinov, G. M., D. M. Babanly, F. M. Sadygov, and M. B. Babanly. "Thermodynamic properties and homogeneity regions of Tl6SCl4 and Tl5Se2Cl." Inorganic Materials 45, no. 2 (February 2009): 129–34. http://dx.doi.org/10.1134/s0020168509020046.

Full text

APA, Harvard, Vancouver, ISO, and other styles

2

Wang, Jian Li, Bi Yang Tuo, Xun Pu Hu, and Zhu Lin Liu. "Thermodynamic Properties and Thermodynamic Assessment of Ta-Sn System." Advanced Materials Research 821-822 (September 2013): 849–53. http://dx.doi.org/10.4028/www.scientific.net/amr.821-822.849.

Full text

Abstract:

For the little thermodynamic information of Ta-Sn system, the liquid mixing enthalpy of Ta-Sn system, and the formation enthalpy of Ta2Sn3 and Ta3Sn were calculated by Miedema model. The Ta-Sn phase diagram was modeled using CALPHAD technology to obtain a reliable thermodynamic description of the system. Two intermetallic compounds Ta2Sn and Ta3Sn were treated as stoichiometric compounds for the very narrow homogeneity ranges. The higher temperature phase diagram of Ta-Sn system was constructed according to Nb-Sn system for the empty information. The optimization process was carried out using the PARRAT software including in Thermo-Calc database system. The thermodynamic calculated Ta-Sn phase diagram is agreement with the evaluated phase diagram, and the calculated mixing enthalpies of molten Ta-Sn system match well with the Miedema data. The formation enthalpies of the two intermetallic compounds Ta2Sn and Ta3Sn are compared with the Miedema values.

APA, Harvard, Vancouver, ISO, and other styles

3

Kale, G. B. "Thermodynamic Diffusion Coefficients." Defect and Diffusion Forum 279 (August 2008): 39–52. http://dx.doi.org/10.4028/www.scientific.net/ddf.279.39.

Full text

Abstract:

A new form of diffusion coefficient termed as thermodynamic diffusion coefficient is introduced in this paper. Conventionally, diffusion coefficients are evaluated using concentration gradient as driving force. But truly, chemical potential gradient is the actual driving force that determines the material flow in any part of the system. Thermodynamic diffusion coefficients are based on chemical potential gradient as driving force. The relation between thermodynamic diffusion coefficients and phenomenological coefficients has been established. The advantages of thermodynamic diffusion coefficients have been underlined, especially, in the cases of line compounds where concentration difference across the phase is zero or in case of intermetallic compounds with narrow homogeneity range. The intrinsic thermodynamic diffusion coefficients are equal to tracer diffusion coefficients. This helps in estimating tracer diffusivities in cases where tracers are not easily available. The advantages of thermodynamic diffusion coefficients are shown in binary and ternary systems by illustrating them in Ni-Al and Fe-Ni-Cr systems.

APA, Harvard, Vancouver, ISO, and other styles

4

IDER, Muhsin. "Thermodynamic stability and homogeneity of cuprous selenide by emf and coulometric titration." Solid State Ionics 329 (January 2019): 140–48. http://dx.doi.org/10.1016/j.ssi.2018.11.018.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Janiš, Václav, and Lenka Zdeborová. "Replica Trick with Real Replicas: A Way to Build in Thermodynamic Homogeneity." Progress of Theoretical Physics Supplement 157 (2005): 99–102. http://dx.doi.org/10.1143/ptps.157.99.

Full text

APA, Harvard, Vancouver, ISO, and other styles

6

Tsvetkov, Dmitry S., Ivan L. Ivanov, Dmitry A. Malyshkin, Anton L. Sednev, Vladimir V. Sereda, and Andrey Yu Zuev. "Double perovskites REBaCo2−xMxO6−δ (RE=La, Pr, Nd, Eu, Gd, Y; M=Fe, Mn) as energy-related materials: an overview." Pure and Applied Chemistry 91, no. 6 (June 26, 2019): 923–40. http://dx.doi.org/10.1515/pac-2018-1103.

Full text

Abstract:

Abstract This work, based on the experimental and theoretical research carried out by the authors during the last decade, presents an overview of formation, stability and defect thermodynamics, crystal structure, oxygen nonstoichiometry, chemical strain and transport properties of the double perovskites REBaCo2−xMxO6−δ (RE = La, Pr, Nd, Eu, Gd, Y; M = Fe, Mn). These mixed-conducting oxides are widely regarded as promising materials for various energy conversion and storage devices. Attention is focused on (i) thermodynamics of formation and disordering, oxygen nonstoichiometry, crystal and defect structure of the double perovskites REBaCo2−xMxO6−δ, as well as their thermodynamic stability and the homogeneity ranges of solid solutions, (ii) their overall conductivity and Seebeck coefficient as functions of temperature and oxygen partial pressure and (iii) the anisotropic chemical strain of their crystal lattice. The relationships between the peculiarities of the defect structure and related properties of the double perovskites are analysed.

APA, Harvard, Vancouver, ISO, and other styles

7

Idbenali, Mohamed, Colette Servant, and M’barek Feddaoui. "Thermodynamic assessment of Hafnium Iridium binary system." Metallurgical Research & Technology 115, no. 5 (2018): 503. http://dx.doi.org/10.1051/metal/2018001.

Full text

Abstract:

The Hf–Ir system has been thermodynamically modeled by the CALPHAD approach. Hf2Ir, αHfIr, βHfIr, γHfIr (high temperature phase) and HfIr3 which have a homogeneity range, were treated as the formula (Hf,Ir)x:(Ir,Hf)1−x by a two-sublattice model with a mutual substitution of Hf and Ir in both sublattices.Hf5Ir3 has been treated as a stoichiometric compound while a solution model has been used for the description of the FCC (Ir) solid solution. Additionally, two different models describing the excess Gibbs energy for the liquid and for the solid solutions (BCC, FCC and HCP) were used and their predictions are compared. The calculations based on the thermodynamic modeling are in good agreement with the phase diagram data and experimental thermodynamic values available in the literature.

APA, Harvard, Vancouver, ISO, and other styles

8

Andryushin, Konstantin, Inna Andryshina, Lidiya Shilkina, Svetlana Dudkina, Iliya Verbenko, Larisa Reznichenko, Mihail Mazuritskiy, et al. "Thermodynamic Prehistory in the Formation of the Internal Structure of Highly Stable Ferroelectric Materials." Applied Sciences 8, no. 10 (October 12, 2018): 1897. http://dx.doi.org/10.3390/app8101897.

Full text

Abstract:

We investigated and presented our results for the dependence of the characteristics of the crystalline and grain structures of the PCR-13 material (based on the lead zirconate titanate (PZT) system), which was sintered in various ways, on the regulations for its preparation. The data from the microfluorescence analysis of the surface of ceramic materials were provided, which allowed us to state that micro X-ray fluorescence spectrometry (MICRO–XRF), supplemented by mathematical statistics, allows us to trace even small changes in the chemical composition of ceramic samples, reliably characterize the degree of surface homogeneity and provide strict mathematical conclusions related to the reproducibility of the properties of manufactured piezoelectric ceramic materials. Based on the obtained data, the optimal conditions for ceramics have been selected, which ensure homogeneity, high-density structure and reproducibility of the characteristics. This allows us to reliably use the material in frequency-selective equipment.

APA, Harvard, Vancouver, ISO, and other styles

9

Bondarenko, Yu O., N. F. Voronina, and O. A. Shmatko. "Kinetic and Thermodynamic Precipitation Parameters of the Pb-Sn Solid Solutions." Defect and Diffusion Forum 277 (April 2008): 193–98. http://dx.doi.org/10.4028/www.scientific.net/ddf.277.193.

Full text

Abstract:

Stages of cellular precipitation for the supersaturated Pb-Sn solid solutions were analyzed. This was done for almost the whole homogeneity interval. Literary heritage as well as the data of the present authors concerning kinetic and thermodynamic parameters of cellular precipitation for these solid solutions were compared and summarized. It was shown that the segregation factor, which characterizes the impurity atoms behavior at the grain boundary, decreases with solid solution supersaturation increase.

APA, Harvard, Vancouver, ISO, and other styles

10

Hu, Z., C. Huang, J. Tu, Y. Huang, and A. Dong. "Thermodynamic modeling of the In-Sc and In-Y systems supported by first-principles calculations." Journal of Mining and Metallurgy, Section B: Metallurgy 54, no. 2 (2018): 161–67. http://dx.doi.org/10.2298/jmmb171121004h.

Full text

Abstract:

Based on an assessment of the phase equilibria and thermodynamic data in the literature, the thermodynamic modeling of the In?Sc and In?Y systems was carried out by means of the calculation of phase diagram (CALPHAD) method supported by first-principles calculations. The solution phases, i.e., liquid, (In), (?Sc), (?Sc), (?Y) and (?Y), were modeled with the substitutional regular solution model. Ten intermetallic compounds, including InSc3, InSc2, In4Sc5, InSc, In2Sc, In3Sc, InY2, InY, In5Y3, and In3Y were described as stoichiometric phases, while In3Y5 was modeled with a sublattice model with respect to its homogeneity range. The enthalpies of formation of the intermetallic compounds at 0 K were computed using firstprinciple calculations and were used as input for the thermodynamic optimization. A set of self-consistent thermodynamic parameters for both the In?Sc and In?Y systems were obtained and the calculated phase diagrams are in good agreement with the experimental data.

APA, Harvard, Vancouver, ISO, and other styles

11

Babanly, M. B., F. N. Guseinov, G. B. Dashdyeva, and Yu A. Yusibov. "Homogeneity ranges and thermodynamic properties of ternary phases in the SnTe-Bi2Te3-Te system." Inorganic Materials 47, no. 3 (March 2011): 235–39. http://dx.doi.org/10.1134/s0020168511030022.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Eom, Youngho, Hyejin Ju, Yeonju Park, Dong Wook Chae, Young Mee Jung, Byoung Chul Kim, and Han Gi Chae. "Effect of dissolution pathways of polyacrylonitrile on the solution homogeneity: Thermodynamic- or kinetic-controlled dissolution." Polymer 205 (September 2020): 122697. http://dx.doi.org/10.1016/j.polymer.2020.122697.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Viswanathan, R., M. Sai Baba, T. S. Lakshmi Narasimhan, R. Balasubramanian, D. Darwin Albert Raj, and C. K. Mathews. "Homogeneity ranges and thermodynamic properties of the Te-rich phases in the CrTe system." Journal of Alloys and Compounds 206, no. 2 (May 1994): 201–10. http://dx.doi.org/10.1016/0925-8388(94)90036-1.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Schatz, Konrad, Horst-Heino von Borzeszkowski, and Thoralf Chrobok. "Non-Perfect-Fluid Space-Times in Thermodynamic Equilibrium and Generalized Friedmann Equations." Journal of Gravity 2016 (November 17, 2016): 1–11. http://dx.doi.org/10.1155/2016/4597905.

Full text

Abstract:

We determine the energy-momentum tensor of nonperfect fluids in thermodynamic equilibrium and, respectively, near to it. To this end, we derive the constitutive equations for energy density and isotropic and anisotropic pressure as well as for heat-flux from the corresponding propagation equations and by drawing on Einstein’s equations. Following Obukhov on this, we assume the corresponding space-times to be conform-stationary and homogeneous. This procedure provides these quantities in closed form, that is, in terms of the structure constants of the three-dimensional isometry group of homogeneity and, respectively, in terms of the kinematical quantities expansion, rotation, and acceleration. In particular, we find a generalized form of the Friedmann equations. As special cases we recover Friedmann and Gödel models as well as nontilted Bianchi solutions with anisotropic pressure. All of our results are derived without assuming any equations of state or other specific thermodynamic conditions a priori. For the considered models, results in literature are generalized to rotating fluids with dissipative fluxes.

APA, Harvard, Vancouver, ISO, and other styles

15

Huang, G., L. Liu, L. Zhang, and Z. Jin. "Thermodynamic description of the Al-Cu-Yb ternary system supported by first-principles calculations." Journal of Mining and Metallurgy, Section B: Metallurgy 52, no. 2 (2016): 177–83. http://dx.doi.org/10.2298/jmmb150709013h.

Full text

Abstract:

Phase relationships of the ternary Al-Cu-Yb system have been assessed using a combination of CALPHAD method and first principles calculations. A self-consistent thermodynamic parameter was established based on the experimental and theoretical information. Most of the binary intermetallic phases, except Al3Yb, Al2Yb, Cu2Yb and Cu5Yb, were assumed to be zero solubility in the ternary system. Based on the experimental data, eight ternary intermetallic compounds were taken into consideration in this system. Among them, three were treated as line compounds with large homogeneity ranges for Al and Cu. The others were treated as stoichiometric compounds. The calculated phase diagrams were in agreement with available experimental and theoretical data.

APA, Harvard, Vancouver, ISO, and other styles

16

Wiedemeier, H., and D. Chandra. "A thermodynamic model of The Hg0.8Cd0.2Te-Iodine Transport System. II. Source material composition within the homogeneity range." Zeitschrift f�r anorganische und allgemeine Chemie 545, no. 2 (February 1987): 109–17. http://dx.doi.org/10.1002/zaac.19875450212.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Stein, F., C. He, and N. Dupin. "Melting behaviour and homogeneity range of B2 CoAl and updated thermodynamic description of the Al–Co system." Intermetallics 39 (August 2013): 58–68. http://dx.doi.org/10.1016/j.intermet.2013.03.011.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

JIGALOV, Anatoliy N., Valeriy K. SHELEG, and Dmitriy D. BOGDAN. "THERMODYNAMIC MODEL OF AERODYNAMIC SOUND HARDENING METHOD." Mechanics of Machines, Mechanisms and Materials 4, no. 53 (December 2020): 65–69. http://dx.doi.org/10.46864/1995-0470-2020-4-53-65-69.

Full text

Abstract:

As a result of scientific research, a method of aerodynamic sound hardening (ADH) has been developed and patented, which makes it possible to achieve improved properties of hard alloys by reducing their defectiveness, improving the homogeneity of the structure. The physics of the ADH process is that the hardened product is preheated to an acceptable temperature at which the hard alloy does not lose the plasticity and hardness acquired during manufacture. Then the product is exposed to sound frequency waves, reduced in the range of 140...160 Hz into a resonant state, in which the formation of a resonant amplitude increased by several hundred times occurs. The article gives a description of the essence of the created ADH method. The dependence for determining the action energy on a hardened solid by ADH is provided. A thermodynamic model of the ADH method is presented, based on energy thermal and wave effects on the hardened structure. On the basis of the thermodynamic explanation, the ADH method is reduced to a change in the initial structure of the hard alloy under the influence of temperature and wave resonant energy fluxes on it, through which activating and dissipative processes of energy outflow are excited in the hardening object in the mode of an open thermodynamic system. In addition, the quasi-static process of wave energy transfer, carried out in a non-equilibrium medium, significantly exceeds the relaxation time of the strengthening system. When hardening by ADH, the impact toughness increases by 19–23 % in hard alloys, while the values of impact toughness equal to 39.54–42.05 kJ/m2 are achieved, the hardness according to the HRC parameter increases by 3.0–5.2 %.

APA, Harvard, Vancouver, ISO, and other styles

19

Trabelsi, M., K. Madih, and J. P. Coulomb. "Thermodynamic and structural properties of thin N2and Co films adsorbed on ionic substrate of high surface homogeneity MgO (100)." Phase Transitions 30, no. 1-4 (April 1991): 103–5. http://dx.doi.org/10.1080/01411599108207968.

Full text

APA, Harvard, Vancouver, ISO, and other styles

20

Han, Jung Hoon. "Tunneling Spectra of Inhomogeneous d-Wave Superconductor." International Journal of Modern Physics B 17, no. 18n20 (August 10, 2003): 3484–92. http://dx.doi.org/10.1142/s0217979203021253.

Full text

Abstract:

The tunneling spectrum of an inhomogeneous d-wave superconductor is discussed in the framework of self-consistent slave-boson mean-field theory. Distinct from the usual BCS-type mean-field theory, an electron is now described using both fermionic and bosonic degree of freedom. We show that one can define two types of tunneling spectra in this theory, which also corresponds to two ways of calibrating the STM spectra. In good agreement with the experimental observation, we show that one type of tunneling spectrum remains inhomogeneous while the other type shows a remarkable degree of homogeneity at low energy, despite the underlying disorder. Physical implications of this result, in particular in relation to thermodynamic measurement such as heat capacity, are discussed.

APA, Harvard, Vancouver, ISO, and other styles

21

Kumar, Bhupendra, Manas Paliwal, Chandra Sekhar Tiwary, and Min-Kyu Paek. "Thermodynamic Optimization of the Ternary Ga-Sn-Te System Using Modified Quasichemical Model." Metals 11, no. 9 (August 30, 2021): 1363. http://dx.doi.org/10.3390/met11091363.

Full text

Abstract:

Thermoelectric (TE) materials are of great interest to many researchers because they directly convert electric and thermal energy in a solid state. Various materials such as chalcogenides, clathrates, skutterudites, eutectic alloys, and intermetallic alloys have been explored for TE applications. The Ga-Sn-Te system exhibits promising potential as an alternative to the lead telluride (PbTe) based alloys, which are harmful to environments because of Pb toxicity. Therefore, in this study, thermodynamic optimization and critical evaluation of binary Ga-Sn, binary Sn-Te, and ternary Ga-Sn-Te systems have been carried out over the whole composition range from room temperature to above liquidus temperature using the CALPHAD method. It is observed that Sn-Te and Ga-Te liquids show the strong negative deviation from the ideal solution behavior. In contrast, the Ga-Sn liquid solution has a positive mixing enthalpy. These different thermodynamic properties of liquid solution were explicitly described using Modified Quasichemical Model (MQM) in the pair approximation. The asymmetry of ternary liquid solution in the Ga-Sn-Te system was considered by adopting the toop-like interpolation method based on the intrinsic property of each binary. The solid phase of SnTe was optimized using Compound Energy Formalism (CEF) to explain the high temperature homogeneity range, whereas solid solution, Body-Centered Tetragonal (BCT) was optimized using a regular solution model. Thermodynamic properties and phase diagram in the Ga-Sn-Te and its sub-systems were reproduced successfully by the optimized model parameters. Using the developed database, we also suggested several ternary eutectic compositions for designing TE alloy with improved properties.

APA, Harvard, Vancouver, ISO, and other styles

22

Mir, Arash, Giang Dinh Nguyen, and Abdul H. Sheikh. "A Continuum Model with an Embedded Fracture Process Zone Modelled as a Cohesive Frictional Interface." Applied Mechanics and Materials 846 (July 2016): 360–65. http://dx.doi.org/10.4028/www.scientific.net/amm.846.360.

Full text

Abstract:

Failure in quasi-brittle materials, such as concrete and rock, usually develops in a fracture process zone (FPZ), in which dissipative processes takes place. At the onset of bifurcation or upon formation of FPZ the homogeneity of kinematic fields is lost and the stress field is redistributed which gives rise to the so called deterministic size effect problem. The total strain energy stored within a specimen of quasi-brittle materials will scale with its size; however, the amount of dissipated energy does not depend on the specimen size but only on the width of the FPZ. This width is related to the microstructure of the material and is considered a characteristic of the material. In this paper, a cohesive frictional interface is used to model the dissipative behaviour of material inside FPZ. Fundamental micro-mechanisms of energy dissipation such as micro-crack opening in mode I and frictional sliding between micro-crack surfaces are formulated within the frame work of Thermodynamic with internal variables (TIV) to ensure the thermodynamics admissibility of the model. The link between the material behaviour inside and outside FPZ is given through the continuity of tractions along the boundaries of FPZ. It is shown that although the shape of the post-peak stress-strain varies, for specimens of different slenderness, the amount of dissipated energy remains the same in all cases.

APA, Harvard, Vancouver, ISO, and other styles

23

Zavyalova, Elena, Valeriia Legatova, Rugiya Alieva, Arthur Zalevsky, Vadim Tashlitsky, Alexander Arutyunyan, and Alexey Kopylov. "Putative Mechanisms Underlying High Inhibitory Activities of Bimodular DNA Aptamers to Thrombin." Biomolecules 9, no. 2 (January 24, 2019): 41. http://dx.doi.org/10.3390/biom9020041.

Full text

Abstract:

Nucleic acid aptamers are prospective molecular recognizing elements. Similar to antibodies, aptamers are capable of providing specific recognition due to their spatial structure. However, the apparent simplicity of oligonucleotide folding is often elusive, as there is a balance between several conformations and, in some cases, oligomeric structures. This research is focused on establishing a thermodynamic background and the conformational heterogeneity of aptamers taking a series of thrombin DNA aptamers having G-quadruplex and duplex modules as an example. A series of aptamers with similar modular structures was characterized with spectroscopic and chromatographic techniques, providing examples of the conformational homogeneity of aptamers with high inhibitory activity, as well as a mixture of monomeric and oligomeric species for aptamers with low inhibitory activity. Thermodynamic parameters for aptamer unfolding were calculated, and their correlation with aptamer functional activity was found. Detailed analysis of thrombin complexes with G-quadruplex aptamers bound to exosite I revealed the similarity of the interfaces of aptamers with drastically different affinities to thrombin. It could be suggested that there are some events during complex formation that have a larger impact on the affinity than the states of initial and final macromolecules. Possible mechanisms of the complex formation and a role of the duplex module in the association process are discussed.

APA, Harvard, Vancouver, ISO, and other styles

24

Nehru, L. C., and C. Sanjeeviraja. "Microwave-Assisted Combustion Synthesis of Nanocrystalline ZnO Powders Using Zinc Nitrate and Various Amount of Organic Fuels as Reactants: Influence of Reactant Parameters - A Status Review." Nano Hybrids 6 (February 2014): 75–110. http://dx.doi.org/10.4028/www.scientific.net/nh.6.75.

Full text

Abstract:

Nanocrystalline ZnO powders have been synthesized by a novel and simple microwave-assisted combustion synthesis method using urea, glycine, carbohydrazine and citric acid as fuels and zinc nitrate as oxidant. The starting materials were directly mixed and a slurry precursor with high homogeneity was formed due to the hygroscopicity of the reactants. The precursor could be ignited at room temperature, resulting in dry, loose and voluminous ZnO powders. An interpretation based on an adiabatic flame temperature, amount of gases produced during reaction for various fuel-to-oxidizer molar ratios (ψ), has been proposed for the nature of combustion and its correlation with the characteristics of as-synthesized product. The variation of adiabatic flame temperature (Tad) with the ψ value was calculated theoretically according to the thermodynamic concept. The reaction process of the precursor was investigated by XRD techniques.

APA, Harvard, Vancouver, ISO, and other styles

25

Radha, A. V., Sergey V. Ushakov, and Alexandra Navrotsky. "Thermochemistry of lanthanum zirconate pyrochlore." Journal of Materials Research 24, no. 11 (November 2009): 3350–57. http://dx.doi.org/10.1557/jmr.2009.0401.

Full text

Abstract:

A thermodynamic study was carried out to resolve discrepancies in the enthalpy of formation and related parameters for lanthanum zirconate pyrochlore. The homogeneity field for single phase pyrochlore formation was determined to be ∼33–35 mol% La2O3 at 1500 °C. High-temperature oxide melt drop solution calorimetry was performed in sodium molybdate and lead borate solvents on three compositions ranging from La1.98Zr2.01O7 to La2.07Zr1.95O7. The enthalpy of formation from oxides at 25 °C, ΔH0f,ox, for stoichiometric lanthanum zirconate pyrochlore is −107.3 ± 5.1 kJ/mol, and the standard enthalpy of formation from elements, ΔH0f,el, is −4102.2 ± 6.0 kJ/mol. La2Zr2O7 pyrochlore was found by differential thermal analysis to be stable up to its melting point. The melting point and the fusion enthalpy of La2Zr2O7 pyrochlore were measured as 2295 ± 10 °C and ∼350 kJ/mol, respectively.

APA, Harvard, Vancouver, ISO, and other styles

26

Ma, Chen-Chi M., Hew-Der Wu, Peter P. Chu, and Han-Thing Tseng. "Prediction of Thermodynamic Properties of Novolak-Type Phenolic Resin and Aliphatic Polyester Blends: Painter−Coleman Association Model Study of Compositional Homogeneity." Macromolecules 30, no. 18 (September 1997): 5443–49. http://dx.doi.org/10.1021/ma961251o.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Meng, X., S. Lu, T. Zhang, Y. Ao, S. Li, Y. Bao, L. Wen, and S. Luo. "Impacts of inhomogeneous landscapes in oasis interior on the oasis self-maintaining mechanism by integrating numerical model with satellite data." Hydrology and Earth System Sciences Discussions 9, no. 2 (February 14, 2012): 1979–2004. http://dx.doi.org/10.5194/hessd-9-1979-2012.

Full text

Abstract:

Abstract. Mesoscale meteorological modeling is an important tool to help understand the energy budget of the oasis. While basic dynamic and thermodynamic processes for oasis self-maintaining in the desert environment is well investigated, influence of heterogeneous landscapes of oasis interior on the processes are still important and remain to be investigated. In this study, two simulations are designed for investigating the influence of inhomogeneity. In the first case, land surface parameters including land-use types, vegetation cover fraction, and surface layer soil moisture are derived by satellite remote sensing data from EOS/MODIS, and then be used specify the respective options in the MM5 model, to describe a real inhomogeneity for the oasis interior. In the other run, land use types are set to MM5 default, in which landscapes in the oasis interior is relative uniform, and then surface layer soil moisture and vegetation fraction is set to be averages of the first case for the respective oasis and desert surface lying, to represent a relative homogeneity. Results show that the inhomogeneity leads to a weaker oasis "cold-wet island" effect and a stronger turbulence over the oasis interior, both of which will reduce the oasis-desert secondary circulation and increase the evaporation over the oasis, resulting in a negative impact on the oasis self-protecting mechanism. The simulation of homogeneity indicates that the oasis may be more stable even with relative lower soil moisture if landscapes in the oasis interior are comparatively uniform.

APA, Harvard, Vancouver, ISO, and other styles

28

Allemann, J. A., Y. Xia, R. E. Morriss, A. P. Wilkinson, H. Eckert, J. S. Speck, C. G. Levi, F. F. Lange, and S. Anderson. "Crystallization behavior of Li1–5x Ta1+xO3 glasses synthesized from liquid precursors." Journal of Materials Research 11, no. 9 (September 1996): 2376–87. http://dx.doi.org/10.1557/jmr.1996.0301.

Full text

Abstract:

The crystallization of amorphous oxides synthesized by pyrolytic decomposition of mixed Li and Ta 2-ethylhexanoates and alkoxides has been investigated. The study was motivated by thermodynamic considerations that, in the light of experience in other systems, suggest the potential for metastable extension of the LiTaO3 homogeneity range. Materials investigated are described by the general stoichiometry Li1–5xTa1+xO3 and include Li2O contents from 0 to 70 mol% (20.18 ≤ x ≤ 0.2). The samples were prepyrolyzed at 400 °C and subsequently crystallized by heat treatments in air at 550–700 °C for 0.1–100 h. The first product of crystallization for compositions from 30 to 65% Li2O is always the LiTaO3 phase. Extensive characterization by x-ray and neutron diffraction, as well as 7Li-NMR spectroscopy, revealed that this phase evolves with a structure and stoichiometry close to equilibrium. For Li+-deficient compositions, excess Ta5+ is rejected to the amorphous constituent during crystallization and eventually gives rise to the evolution of Ta2O5, with the LiTa3O8 phase suppressed in all cases. Similar observations were made for the Li+-rich compositions, but the evolving second phase is the equilibrium Li3TaO4. The absence of solubility extension in LiTaO3, which appears feasible from a thermodynamic viewpoint, is ascribed to the large differences in mobilities of the Li and Ta species in the parent amorphous oxide resulting from pyrolysis.

APA, Harvard, Vancouver, ISO, and other styles

29

Casamiquela, L., Y. Tarricq, C. Soubiran, S. Blanco-Cuaresma, P. Jofré, U. Heiter, and M. Tucci Maia. "Differential abundances of open clusters and their tidal tails: Chemical tagging and chemical homogeneity." Astronomy & Astrophysics 635 (February 28, 2020): A8. http://dx.doi.org/10.1051/0004-6361/201936978.

Full text

Abstract:

Context. Well studied open clusters (OCs) of the solar neighborhood are frequently used as reference objects to test galactic and stellar theories. For that purpose, their chemical composition needs to be known with a high level of confidence. It is also important to clarify if each OC is chemically homogeneous and if it has a unique chemical signature. Aims. The aims of this work are (1) to determine accurate and precise abundances of 22 chemical species (from Na to Eu) in the Hyades, Praesepe, and Rupecht 147 by using a large number of stars at different evolutionary states, (2) to evaluate the level of chemical homogeneity of these OCs, and (3) to compare their chemical signatures. Methods. We gathered ∼800 high resolution and high signal-to-noise spectra of ∼100 members in the three clusters, which were obtained with the latest memberships based on Gaia DR2 data. We built a pipeline, which computes atmospheric parameters and strictly line-by-line differential abundances among twin stars in our sample. With this method, we were able to reach a very high precision in the abundances (0.01–0.02 dex in most of the elements). Results. We find large differences in the absolute abundances in some elements, which can be attributed to diffusion, non-local thermodynamic equilibrium (non-LTE) effects, or systematics in the analysis. For the three OCs, we find strong correlations in the differential abundances between different pairs of elements. According to our experiment with synthetic data, this can be explained by some level of chemical inhomogeneity. We compare differential abundances of several stars from the Hyades and Praesepe tails: The stars that differ more in chemical abundances also have distinct kinematics, even though they have been identified as members of the tail. Conclusions. It is possible to obtain high precision abundances using a differential analysis even when mixing spectra from different instruments. With this technique, we find that the Hyades and Preasepe have the same chemical signature when G dwarfs and K giants are considered. Despite a certain level of inhomogeneity in each cluster, it is still possible to clearly distinguish the chemical signature of the older cluster Ruprecht 147 when compared to the Hyades and Praesepe.

APA, Harvard, Vancouver, ISO, and other styles

30

Sokov, V. N., and A. A. Kulibaev. "Intensification of foam technology by the energy of the electrohydrothermalpower field. Part 2. Regularities of optimization of the structure of lightweight foam material under the influence of EHTPF." NOVYE OGNEUPORY (NEW REFRACTORIES), no. 7 (September 18, 2020): 63–66. http://dx.doi.org/10.17073/1683-4518-2020-7-63-66.

Full text

Abstract:

The formation of the structure of lightweight foam material is determined by the course of complex processes of a three-phase heterogeneous system. The article studies the control factor ― electric heating, which provides a forced decrease in the moisture content of the foam mass with the acceleration of structuring processes. A model of a gas pore with force vectors is proposed. Internal and external factors affecting the air space during electric heating are analyzed. Thermodynamic changes in the foam system and the phenomena of heat and mass transfer in it are considered. The state of the foam system is determined by variables: temperature, overpressure and electric voltage. Due to the complex effect on the EHTPF foam mass, cavities and stratification are eliminated and the homogeneity of the macrostructure is achieved. The choice of the foaming agent according to the pH and electrical conductivity of the surfactant solution has been substantiated.

APA, Harvard, Vancouver, ISO, and other styles

31

Kodentsov, Alexander. "Interdiffusion Studies in β- and γ′-Intermetallic Phases of the Binary Ni-Al System." Diffusion Foundations 13 (November 2017): 56–97. http://dx.doi.org/10.4028/www.scientific.net/df.13.56.

Full text

Abstract:

A critical review of interdiffusion processes in the binary β-NiAl and γ'-Ni3Al intermetallic compounds is presented. The molar volume changes associated with interdiffusion and partial molar volumes of the reacting species, required for the determination of the diffusion parameters, are found using lattice parameter data and, in the case of NiAl, the available information about vacancy concentration within homogeneity range of the β-phase. The presented treatment is purely phenomenological, and its use is convenient since no exlicit assumption of the underlying mechanisms required. A critical analysis of diffusion data for β-NiAl and γ'-Ni3Al ordered phases is followed by discussion of error sources encountered in the interdiffusion experiments. From Kirkendall marker experiments with incremental diffusion couples, information about relative mobilities of species in the intermetallic phases can be obtained, and tracer diffusion coefficients can be deduced using pertinent thermodynamic data on the nickel aluminides. Contribution of the vacancy wind effect to the calculated tracer diffusivities can also be estimated. The Kirkendall plane bifurcation in the Ni41.7Al58.3/Ni72.24Al27.76 reaction couple, in which a single-phased layer of β-NiAl intermatallic is formed during interdiffusion from its adjacent phases, is directly related to the growth of grains of the reaction product at a location in between interfaces with starting materials. This diffusion phenomenon can be rationallised using a corresponding Kirkendall velocity diagram. Changes in magnitude and sign of the difference in intrinsic mobilities of the components inside the homogeneity range of the β-NiAl lead to a velocity curve that makes bifurcation of the Kirkendall marker plane possible.

APA, Harvard, Vancouver, ISO, and other styles

32

Harding, S. E., and P. Johnson. "Physicochemical studies on turnip-yellow-mosaic virus. Homogeneity, relative molecular masses, hydrodynamic radii and concentration-dependence of parameters in non-dissociating solvents." Biochemical Journal 231, no. 3 (November 1, 1985): 549–55. http://dx.doi.org/10.1042/bj2310549.

Full text

Abstract:

Turnip-yellow-mosaic virus, with its stable, highly spherical and monodisperse character, was chosen as a suitable model substance with which to test hydrodynamic theories of transport. Sedimentation coefficients, diffusion coefficients (obtained through photon correlation spectroscopy) and viscosities were measured accurately as a function of concentration in well-defined and nearly neutral buffer systems. Ancillary information was also obtained from very-low-speed sedimentation-equilibrium experiments. The coefficients expressing the variation in sedimentation and diffusion coefficients with weight concentration were obtained, and by combination with other data it was possible to avoid assumptions concerning solvation and transform such regression coefficients into the form appropriate to volume fractions. Some measure of support for Batchelor's [(1972) J. Fluid Mech. 52, 245-268] calculations was thus obtained, but over most of the pH range the coefficients were significantly smaller than those calculated from his theory. It seems likely that electrostatic interactions are responsible for the discrepancies. Hydrodynamic radii (from diffusion coefficients) were in very fair agreement with those calculated from the thermodynamic excluded-volume term, but were higher than indicated by electron microscopy and X-ray diffraction, a discrepancy ascribable to solvation.

APA, Harvard, Vancouver, ISO, and other styles

33

Chernov, A. A., J. J. De Yoreo, L. N. Rashkovich, and P. G. Vekilov. "Step and Kink Dynamics in Inorganic and Protein Crystallization." MRS Bulletin 29, no. 12 (December 2004): 927–34. http://dx.doi.org/10.1557/mrs2004.262.

Full text

Abstract:

AbstractRevived interest in crystal growth from solutions is driven by a variety of demands, including the need to develop an understanding of biomineralization processes in bones, teeth, and shells;and efforts to characterize large optically nonlinear crystals, perfect crystals of proteins, nucleic acids, and complexes such as viruses. Producing and purifying drugs, food, paint, fertilizers, and other polycrystalline materials in industry are other expanding areas that rely on crystal growth from solution. These general practical incentives have activated in-depth studies that revealed new phenomena and raised new fundamental questions: Are thermal fluctuations of steps on a crystal face always fast enough to assure the step propagation at the rate controlled just by molecular incorporation at kinks? Is the Gibbs–Thomson capillarity shift of thermodynamic equilibrium always applicable to evaluate the crystallization driving force of polygonized steps? Is it possible to eliminate the step bunching on a growing crystal face that compromises crystal homogeneity, or at least to mitigate it? In this overview, we will discuss experimental findings and provide state-of-the-art answers to these questions.

APA, Harvard, Vancouver, ISO, and other styles

34

Marsland, Simon, and Jörg-Olaf Wolff. "East Antarctic seasonal sea-ice and ocean stability: a model study." Annals of Glaciology 27 (1998): 477–82. http://dx.doi.org/10.3189/1998aog27-1-477-482.

Full text

Abstract:

A high-resolution primitive equation ocean model has been coupled to a dynamic/thermodynamic sea-ice model and applied to a region of the Southern Ocean south of Australia. The model is found to be very sensitive to the surface fresh-water flux! A stable seasonal cycle of sea-ice advance and retreat is simulated only for sufficient surface fresh-water fluxes. For fresh-water fluxes below a threshold value of around 40 cm a−1 the coupled system enters a thermal mode characterised by vertical homogeneity of the oceanic temperature and salinity fields. Such an ocean has a surface temperature that is too warm for a sea-ice cover to develop. Spatial and temporal variability of the oceanic heat llux into the upper model layer iS examined for the stable simulations. High values of this oceanic heat flux (~40Wm−2) occur during the sea-ice formation period (March-June), with values as low as 5 wM−2 occurring in November. The source of this heat is primarily convective, a process induced by brine rejection during ice growth.

APA, Harvard, Vancouver, ISO, and other styles

35

Di Liberto, L., F. Angelini, I. Pietroni, F. Cairo, G. Di Donfrancesco, A. Viola, S. Argentini, et al. "Estimate of the Arctic Convective Boundary Layer Height from Lidar Observations: A Case Study." Advances in Meteorology 2012 (2012): 1–9. http://dx.doi.org/10.1155/2012/851927.

Full text

Abstract:

A new automated small size lidar system (microlidar or MULID) has been developed and employed to perform aerosol measurements since March 2010 at Ny Ålesund (78.9°N,11.9°E), Svalbard. The lidar observations have been used to estimate the PBL height by using the gradient method based on abrupt changes in the vertical aerosol profile and monitor its temporal evolution. The scope of the present study is to compare several approaches to estimate the PBL height, by using lidar observations, meteorological measurements by radio soundings, and a zero-order one-dimensional model based on a parameterization of the turbulent kinetic energy budget within the mixing layer, under the assumptions of horizontal homogeneity, and neglecting radiation and latent heat effects. A case study is presented here for a convective PBL, observed in June 2010 in order to verify whether the Gradient Method can be applied to lidar measurements in the Arctic region to obtain the PBL height. The results obtained are in good agreement with the PBL height estimated by the analysis of thermodynamic measurements obtained from radio sounding and with the model.

APA, Harvard, Vancouver, ISO, and other styles

36

Jabar, Sharhid, John A. Siefert, Martin Strangwood, and Geoff D. West. "The Effect of Micro-Segregation on the Quantification of Microstructural Parameters in Grade 91 Steel." Metallurgical and Materials Transactions A 52, no. 1 (November 15, 2020): 426–37. http://dx.doi.org/10.1007/s11661-020-06062-y.

Full text

Abstract:

AbstractThe quantification of key microstructural parameters as a function of aging or creep exposure time is commonplace in the assessment of 9Cr Creep Strength Enhanced Ferritic (CSEF) power-plant steels. In these studies, the sample is either assumed chemically homogenous at the micro-scale or that a material average will be achieved by collecting enough images at random locations. In this paper, the micro-scale chemical homogeneity of two ex-service boiler components, a pipe and a forging, are quantitatively assessed using high sensitivity chemical mapping from µ-XRF. The compositional variation was as expected most pronounced in the larger elements Mo and Nb, where a > 20 pct difference in composition was present between positively and negatively segregated areas. The effect of this micro-segregation on local variations in Laves phase particle characteristics was investigated using SEM images. This showed a factor of two difference in the number of particles and the area coverage between positively and negatively Mo-segregated regions. This result was consistent with the thermodynamic equilibrium predictions of the phase content based on the observed level of segregation.

APA, Harvard, Vancouver, ISO, and other styles

37

binti Che Ibrahim, Nurul Syazwina, Sivakumar Ramakrishan, Sheikh Abdul Rezan, Norlia binti Baharun, Reza Alizadeh, and Parham Roohi. "Non-Isothermal Kinetic Modelling for Hydrogen Reduction of Ferric Oxide Using Matlab." Materials Science Forum 819 (June 2015): 3–8. http://dx.doi.org/10.4028/www.scientific.net/msf.819.3.

Full text

Abstract:

Reduction of iron oxide by hydrogen is important in the production of direct reduced iron. This method of iron production is gaining increasing significance as an alternative route to the blast furnace technology with the many difficult issues facing the latter, the most important being the problem related to environmental. In order to reduce the emission of greenhouse gases CO2, particularly for iron making, the production of Direct Reduced Iron (DRI) using hydrogen as the reducing gas instead of carbon monoxide is being considered. Reduction of pure hematite by hydrogen was studied at the laboratory scale, varying the experimental conditions like temperature (700oC and 800oC) and porosity (20% and 40%). Then, a Kinetic Modelling was conducted using Matlab software based on independently measured physical and thermodynamic properties of the reaction system and experimentally measured properties of the reactant solid (Fe2O3), gas phase (H2) and reactant product (Fe). There is a gap that occurs between the predicted result and the experimental result although the model explicated the trend and the behaviour of the reduction rate of Ferric Oxide and indicated a good homogeneity to the experimental conditions used in this research.

APA, Harvard, Vancouver, ISO, and other styles

38

El-Bindary, A. A., A. F. Shoair, H. A. Kiwaan, and A. R. Hawas. "Preparation, characterization, and application of synthesized thiourea formaldehyde-calcium alginate in removal of Reactive Black 5." Canadian Journal of Chemistry 96, no. 12 (December 2018): 1101–14. http://dx.doi.org/10.1139/cjc-2017-0767.

Full text

Abstract:

Thiourea formaldehyde calcium alginate (TFCA) composite was successfully synthesized and used for removal of Reactive Black 5 (RB5) dye. The synthesized composite was applied and characterized by Fourier transform infrared spectrometer (FTIR) spectra, scanning electron microscope (SEM)/EDS, energy dispersive X-ray analysis (EDX), and X-ray diffraction (XRD). SEM and EDX analyses confirm the homogeneity of the sorbent in term of composition. Batch adsorption experiments were performed to evaluate the adsorption conditions such as pH value, dye concentration, contact time, temperature, and sorbent dose, as well as the ionic strength effect. Experimental data have been modeled by using Langmuir, Freundlich, Dubinin Radushkevich (D–R), and Temkin isotherms. Kinetic adsorption data modeled using PFORE, PSORE, Morris Weber, and Elovich in order to determine thermodynamic parameters (ΔG, ΔH, and ΔS) for the dye adsorbent systems. These data indicated an exothermic spontaneous adsorption process that kinetically followed the pseudo second-order adsorption process and removal of RB5 dye from aqueous solution. The results showed that the maximum adsorption capacity was 0.2 mmol g−1, observed at pH 1 and temperature 25 °C. Equilibrium adsorption was achieved within 60 min.

APA, Harvard, Vancouver, ISO, and other styles

39

Thebti, Wajdi, Yosra Riahi, and Omrane Belhadj. "Purification and Characterization of a New Thermostable, Haloalkaline, Solvent Stable, and Detergent Compatible Serine Protease fromGeobacillus toebiiStrain LBT 77." BioMed Research International 2016 (2016): 1–8. http://dx.doi.org/10.1155/2016/9178962.

Full text

Abstract:

A new thermostable, haloalkaline, solvent stable SDS-induced serine protease was purified and characterized from a thermophilicGeobacillus toebiiLBT 77 newly isolated from a Tunisian hot spring. This study reveals the potential of the protease fromGeobacillus toebiiLBT 77 as an additive to detergent with spectacular proprieties described for the first time. The protease was purified to homogeneity by ammonium sulfate precipitation followed by Sephadex G-75 and DEAE-Cellulose chromatography. It was a monomeric enzyme with molecular weight of 30 kDa. The optimum pH, temperature, and NaCl for maximum protease activity were 13.0, 95°C, and 30%, respectively. Activity was stimulated by Ca2+, Mg2+, DTNB,β-mercaptoethanol, and SDS. The protease was extremely stable even at pH 13.25, 90°C, and 30% NaCl and in the presence of hydrophilic, hydrophobic solvents at high concentrations. The high compatibility with ionic, nonionic, and commercial detergents confirms the utility as an additive to cleaning products. Kinetic and thermodynamic characterization of protease revealedKm=1 mg mL−1, Vmax=217.5 U mL−1,Kcat/Km=99 mg mL−1 S−1,Ea=51.5 kJ mol−1, andΔG⁎=56.5 kJ mol−1.

APA, Harvard, Vancouver, ISO, and other styles

40

Cernat, Alexandru, Constantin Pana, and Niculae Negurescu. "Aspects of in-Cylinder Mixture Formation Study for a Diesel Engine Fuelled with LPG by Diesel-Gas Method." Applied Mechanics and Materials 809-810 (November 2015): 1043–48. http://dx.doi.org/10.4028/www.scientific.net/amm.809-810.1043.

Full text

Abstract:

The Liquid Petroleum Gas can be use for diesel engine fuelling with significant result in term of pollutant emissions improvement, with important reduction of nitrous oxides and smoke for a LPG dual fuelled diesel engine. Beside this the LPG fuelling affects the combustion process inside the cylinder and also the mixture forming. High degree of homogeneity of the air-LPG mixtures will accelerate the in-cylinder mixture forming between air-LPG and diesel fuel jets, since the LPG-air mixture combustion starts. The paper presents the results of a zero-dimensional, one-zone thermodynamic model developed by authors for diesel fuel jets vaporization and combustion at dual fuelling. The model shows the diesel fuel jet characteristic, the break-up period, the mass flow of vaporized substance on the particle surface, drops vaporization time, air-fuel mixture forming speed, drops combustion time and flame position, showing a significant influence of LPG cycle dose on their characteristic parameters. The drops vaporization and combustion duration decrease for dual fuelling and the flame radius increases. Thus, based on the experimental data, an evaluation model for mixture forming was developed for an automotive diesel engine fuelled with LPG and diesel fuel by diesel-gas method.

APA, Harvard, Vancouver, ISO, and other styles

41

Vončina, Maja, Kristijan Kresnik, Darja Volšak, and Jožef Medved. "Effects of Homogenization Conditions on the Microstructure Evolution of Aluminium Alloy EN AW 8006." Metals 10, no. 3 (March 24, 2020): 419. http://dx.doi.org/10.3390/met10030419.

Full text

Abstract:

The industrial production of products, such as foil and aluminium alloy strips, begins with the production of semi-finished products in the form of slabs. These are produced by the continuous casting process, which is quick and does not allow the equilibrium conditions of solidification. Non-homogeneity—such as micro and macro segregation, non-equilibrium phases and microstructural constituents, as well as stresses arising during non-equilibrium solidification—are eliminated by means of homogenization annealing. In this way, a number of technological difficulties in the further processing of semi-finished products can be avoided. The aim of this research was the optimization of the homogenization annealing of the EN AW 8006 alloy. With the Thermo-Calc software, a thermodynamic simulation of equilibrium and non-equilibrium solidification was performed. Differential scanning calorimetry (DSC) was performed on selected samples in as-cast state and after various regimes of homogenization annealing and was used for the simulation of homogenization annealing. Using an optical microscope (OM), a scanning electron microscope (SEM) and an energy dispersion spectrometer (EDS), the microstructure of the samples was examined. Based on the results, it was concluded that homogenization annealing has already taken place after 8 h at 580 °C to the extent, that the material is then suitable for further processing.

APA, Harvard, Vancouver, ISO, and other styles

42

Levkov, Leonid, Dmitry Shurygin, Vladimir Dub, Konstantin Kosyrev, and Alan Balikoev. "New generation of super duplex steels for equipment gas and oil production." E3S Web of Conferences 121 (2019): 04007. http://dx.doi.org/10.1051/e3sconf/201912104007.

Full text

Abstract:

Oil&gas producing industry today is increased production volumes from old deposits on land, offshore and deep-water. The materials used to create modern equipment that meets these trends should be distinguished by increased productivity in conditions of corrosion and high pressure, to ensure trouble-free operation. In such conditions, taking into account the necessary provision of acceptable cost indicators, there is no alternative to duplex steels. Their crystal structure simultaneously allows using the advantages of ferritic and austenitic phases. The report presents the results of using a compositional and technological methods for structure management, the rationale alloying with copper (3.0-3.3%). Application of ESR in the manufacture of steel billets of super duplex steel has demonstrated the ability to simultaneously achieve physical, chemical and structural homogeneity, ensuring high corrosion&mechanical characteristics. The thermodynamic and kinetic conditions for the formation of optimal phase steel composition are determined. Grounded heat treatment regimes, prevent the formation of sigma and psi-phase and contribute to the formation of stable intermetallides (30-300 nm). Based on the test results of “Gazprom-VNIIGAZ” LLC the new steel is recommended for the manufacture of valve bodies and in-vessel internals used in the fields, that containing H2S and CO2 up to 25% in the fluid.

APA, Harvard, Vancouver, ISO, and other styles

43

Hoyoux, A., I. Jennes, P. Dubois, S. Genicot, F. Dubail, J. M. François, E. Baise, G. Feller, and C. Gerday. "Cold-Adapted β-Galactosidase from the Antarctic Psychrophile Pseudoalteromonas haloplanktis." Applied and Environmental Microbiology 67, no. 4 (April 1, 2001): 1529–35. http://dx.doi.org/10.1128/aem.67.4.1529-1535.2001.

Full text

Abstract:

ABSTRACT The β-galactosidase from the Antarctic gram-negative bacteriumPseudoalteromonas haloplanktis TAE 79 was purified to homogeneity. The nucleotide sequence and the NH2-terminal amino acid sequence of the purified enzyme indicate that the β-galactosidase subunit is composed of 1,038 amino acids with a calculated M r of 118,068. This β-galactosidase shares structural properties with Escherichia coli β-galactosidase (comparable subunit mass, 51% amino sequence identity, conservation of amino acid residues involved in catalysis, similar optimal pH value, and requirement for divalent metal ions) but is characterized by a higher catalytic efficiency on synthetic and natural substrates and by a shift of apparent optimum activity toward low temperatures and lower thermal stability. The enzyme also differs by a higher pI (7.8) and by specific thermodynamic activation parameters. P. haloplanktis β-galactosidase was expressed in E. coli, and the recombinant enzyme displays properties identical to those of the wild-type enzyme. Heat-induced unfolding monitored by intrinsic fluorescence spectroscopy showed lower melting point values for both P. haloplanktiswild-type and recombinant β-galactosidase compared to the mesophilic enzyme. Assays of lactose hydrolysis in milk demonstrate that P. haloplanktis β-galactosidase can outperform the current commercial β-galactosidase from Kluyveromyces marxianusvar. lactis, suggesting that the cold-adapted β-galactosidase could be used to hydrolyze lactose in dairy products processed in refrigerated plants.

APA, Harvard, Vancouver, ISO, and other styles

44

Shao, J., H. Shen, and B. Havsteen. "Purification, characterization and binding interactions of the Chinese-cobra (Naja naja atra) serum antitoxic protein CSAP." Biochemical Journal 293, no. 2 (July 15, 1993): 559–66. http://dx.doi.org/10.1042/bj2930559.

Full text

Abstract:

The characterization of the single-chain protein in Chinese-cobra (Naja naja atra) blood serum, which yields strong specific protection against the venom of the same snake, is reported. The protein, CSAP (cobra serum antitoxic protein), was purified to electrophoretic homogeneity. Over the pH range 5-9 it formed stable complexes with the neuro- and the cardio-toxin of the snake. The molecular size of the CSAP was estimated to be 70.3 +/- 0.3 kDa. Tryptic hydrolysis of CSAP yielded several peptides that were able to bind to the toxin. The native CSAP maximally bound 8 +/- 1 toxin molecules/molecule. Six tryptic fragments, containing 5-39 residues, were sequenced. The longest of these displayed sequence similarity to rat serum albumin. The protective effect of the CSAP was demonstrated in vivo on mice and in vitro by measurement of the rate of haemolysis. Kinetic and thermodynamic parameters of the binding interactions of the neurotoxin and the CSAP were determined from the rates of displacement of 125I-labelled toxin from its complexes with the CSAP by unlabelled toxin by using a DEAE-cellulose filter assay for CSAP-toxin complexes. The toxin molecules rapidly dissociated from one type of site and slowly from a second. The binding capacity and concentration of the CSAP suffice to explain the protective effect of the latter against the toxin.

APA, Harvard, Vancouver, ISO, and other styles

45

Jiang, Shimin, Chunhong Li, Weiwen Zhang, Yuanheng Cai, Yunliu Yang, Sheng Yang, and Weihong Jiang. "Directed evolution and structural analysis of N-carbamoyl-D-amino acid amidohydrolase provide insights into recombinant protein solubility in Escherichia coli." Biochemical Journal 402, no. 3 (February 26, 2007): 429–37. http://dx.doi.org/10.1042/bj20061457.

Full text

Abstract:

One of the greatest bottlenecks in producing recombinant proteins in Escherichia coli is that over-expressed target proteins are mostly present in an insoluble form without any biological activity. DCase (N-carbamoyl-D-amino acid amidohydrolase) is an important enzyme involved in semi-synthesis of β-lactam antibiotics in industry. In the present study, in order to determine the amino acid sites responsible for solubility of DCase, error-prone PCR and DNA shuffling techniques were applied to randomly mutate its coding sequence, followed by an efficient screening based on structural complementation. Several mutants of DCase with reduced aggregation were isolated. Solubility tests of these and several other mutants generated by site-directed mutagenesis indicated that three amino acid residues of DCase (Ala18, Tyr30 and Lys34) are involved in its protein solubility. In silico structural modelling analyses suggest further that hydrophilicity and/or negative charge at these three residues may be responsible for the increased solubility of DCase proteins in E. coli. Based on this information, multiple engineering designated mutants were constructed by site-directed mutagenesis, among them a triple mutant A18T/Y30N/K34E (named DCase-M3) could be overexpressed in E. coli and up to 80% of it was soluble. DCase-M3 was purified to homogeneity and a comparative analysis with wild-type DCase demonstrated that DCase-M3 enzyme was similar to the native DCase in terms of its kinetic and thermodynamic properties. The present study provides new insights into recombinant protein solubility in E. coli.

APA, Harvard, Vancouver, ISO, and other styles

46

Doma, Ahmed Salah, Elbadawy A. Kamoun, Sayed Abboudy, Mohammed A. Belal, Sherine N. Khattab, and Ali A. El-Bardan. "Compatibilization of Vulcanized SBR/NBR Blends using Cis-Polybutadiene Rubber: Influence of Blend Ratio on Elastomer Properties." European Journal of Engineering Research and Science 3, no. 12 (January 1, 2019): 135–43. http://dx.doi.org/10.24018/ejers.2018.3.12.958.

Full text

Abstract:

Blends composed of styrene butadiene rubber (SBR) and acrylonitrile-butadiene rubber (NBR) were fabricated by melt blending technique using two-roll mill blend machine. Cis- polybutadiene rubber (CBR) was used as a compatibilizer for enhancing the homogeneity between SBR and NBR phases in blends. Although, no previous reports were found to discuss improving electrical properties of vulcanized SBR/NBR blends using unfilled rubber system (i.e. no fillers incorporated). Raman spectra and SEM images indicate that a significant compatibility within the rubber matrix is observed, due to using CBR compatibilizer. The effect of SBR/NBR blend ratio on curing characteristics, physico-mechanical properties, and physicochemical properties (e.g. network characteristics and thermodynamic parameters) were studied. SBR/NBR blend showed comparatively better mechanical properties, compared to each other individually rubber system. Curing parameters e.g. Mooney viscosity and hardness were increased, while a reduction in cure time and specific gravity was observed with increasing SBR ratio in blends. Results revealed that increasing SBR resulted in an enhancement of the tensile strength, modulus at 300 % and elongation at break up to 40 phr, and then gradually decreased. The TGA results indicated that SBR/NBR blends were thermally decomposed at a temperature range of 340-520°C. The notable decrease of DC conductivity (σdc) of vulcanized blends is owing to the decrease of NBR, which is a polar portion and is responsible for increasing the conductivity of vulcanized blends. This proved that the targeted industrial applications for vulcanized blends are entirely depending upon SBR/NBR blend in elastomers matrix.

APA, Harvard, Vancouver, ISO, and other styles

47

Rannou, B., M. Mollard, B. Bouchaud, J. Balmain, G. Bonnet, Vladislav Kolarik, and F. Pedraza. "On the Influence of a Heat Treat for an Aluminizing Progress Based on Al Microparticles Slurry for Model Ni and Ni20Cr. Experimental and Theoretical Approaches." Defect and Diffusion Forum 323-325 (April 2012): 373–79. http://dx.doi.org/10.4028/www.scientific.net/ddf.323-325.373.

Full text

Abstract:

The use of thermal barrier coating systems allows superalloys to withstand higher operating temperatures in aeroengine turbines. Aiming at providing oxidation protection to such substrates, an aluminum-rich layer is deposited to form the α-Al2O3scale over which a ceramic layer (i.e. YSZ layer) is applied to provide thermal insulation. A new approach is now being investigated within the FP7 European project « PARTICOAT », in which a single step process is employed by applying micro-sized aluminum particles. The particles are mixed in a binder and deposited by brushing or spraying on the substrate surface. During a heat treatment, the particles sinter and oxidize to form a top coat composed of hollow con-joint alumina spheres and simultaneously, an Al-rich diffusion zone is formed in the substrate. For a better understanding of the diffusion / growth processes, preliminary tests were carried out on pure nickel and Ni20Cr model alloys prior to further application on commercial superalloys. The effect of the heat treatment on the coating characteristics (number of layers, thickness, composition, homogeneity, etc.) was particularly investigated to emphasize the mechanisms of diffusion governing the growth of the coatings. The establishment of the diffused layers occurred very readily even at intermediate temperatures (650 and 700°C). However, the layers formed did not match perfectly with the thermodynamic modeling because of the quick incorporation of Ni into molten Al at intermediate temperatures (650°C). In contrast, at higher temperatures (700 and 1100°C) the phases predicted by Thermocalc are in good agreement with the observed thickness of the diffused layers. The incorporation of Cr as an alloying element restrained Al ingress by segregation of Cr even at very low temperatures aluminizing temperatures (625°C).

APA, Harvard, Vancouver, ISO, and other styles

48

Slesarev, Valery I. "Water: a substance with unique properties." Hygiene and sanitation 100, no. 1 (February 12, 2021): 19–24. http://dx.doi.org/10.47470/0016-9900-2021-100-1-19-24.

Full text

Abstract:

Water is a supramolecular aqua system with a single highly structurally dynamic network of hydrogen bonds. Since this grid is inhomogeneous in properties and structure, a proposed aquamezophase model of water takes into account the indicated heterogeneity and homogeneity of water. The peculiarities of intermolecular interactions for hydration and aquaclatratation, characteristic of water, are described. For the first time, the peculiarities of the chemistry and energy of water during vortex motion were revealed. This made it possible to propose a mechanism of action for vortex tubes, a cyclone of J. Rank, and aqua-vortex heat generators. Due to the vortex movement, the aquatic systems of the living organisms actively show restorative properties and become a source of energy necessary for life. Due to the thermodynamic nonequilibrium, openness, nonlinearity, and self-oscillating properties, water is a source of very weak acoustic and electromagnetic aqua emissions in a wide frequency range from fractions of Hz to 1017 Hz, which are recorded as emissions from the end of the 20th century. Since water is a source of radiation and is sensitive to external radiation, water is an aqua-radio system. Under even weak external influences, water is characterized by phase transitions of the second order under external weak influences, at which its ΔUtotal ≈ 0. At the first resonance stage, a quickly coordinated and conjugated transformation |ΔUfree|↔|ΔUconnect| occurs, which changes the properties of water. The second stage is a slow return to its original state, i.e., structural-temporal hysteresis is observed. The change in the properties of water as a result of a phase transition of the second kind is called aquacommunication. Given that living things in molecular composition consist of 99% of water, all living things are also aqua-systems.

APA, Harvard, Vancouver, ISO, and other styles

49

Orlov, Victor, Leonid Levkov, Vladimir Dub, Alan Balikoev, and Dmitry Shurygin. "New approach to development and manufacturing technologies of duplex steel." E3S Web of Conferences 121 (2019): 04010. http://dx.doi.org/10.1051/e3sconf/201912104010.

Full text

Abstract:

We conducted a brief review of current production and application of duplex and super duplex steels for manufacture of equipment exposed to the hazard of sulphide stress-corrosion cracking, sea water and other corrosive environment. The super duplex steel with enhanced corrosion-mechanical characteristics in comparison with the known steels of austenitic-ferritic class was developed. Based on the concepts of formation of a special structure of two-phase austenitic-ferritic steels in the process of crystallization, the possibilities of compositional, technological, thermal and special impact techniques are considered and advanced ways of controlling physical, chemical, structural homogeneity and properties of super duplex steels are developed. Electroslag remelting with the application of low-frequency alternating current provides effective control over the length of the two-phase area, the size of the primary dendrites of the austenitic and ferritic phases, the average distance between their axes, the parameters of the crystallizing cell, the development of liquation phenomena and the size of the growing non-metallic phases. Within framework of the proposed approach, the thermodynamic and kinetic conditions for the formation and growth of hardening phases are assessed, a new composition and a complex technology for the manufacture of corrosion-resistant super duplex steels for gas and oil production equipment has been developed. Thermodynamically stable, having sizes of 30-300 nm, niobium nitrides and carbonitrides are located inside the grains of the ferritic phase. At the same time, the sigma phase and chromium carbide precipitates at the intergrain boundaries are not observed. The results of the determination of mechanical and corrosion properties in accordance with the NACE TM 0177 standard (method A), tests of corrosion witness-samples in field conditions demonstrate the advantages and prospects of using new super duplex steel for the manufacture of oil and gas production equipment operating in an environment with high H2S content and CO2 under significant mechanical loads, without the risk of brittle fracture.

APA, Harvard, Vancouver, ISO, and other styles

50

Rey de Luna, A., and M. Zamora. "Canonical formalism in equilibrium thermodynamics. II. Homogeneity, stability, and generalized Maxwell relations." Journal of Chemical Physics 84, no. 8 (April 15, 1986): 4619–24. http://dx.doi.org/10.1063/1.449986.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Thermodynamic homogeneity'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles