scholarly journals Dissolution of pyrochlore and microlite in alkaline, sub-aluminous and high-aluminous granitoid melts

2019 ◽  
Vol 489 (6) ◽  
pp. 626-630
Author(s):  
V. Yu. Chevychelov, ◽  
A. A. Virus ◽  
Yu. B. Shapovalov
Keyword(s):  
Experimental Data ◽  
High Alumina ◽  
Chemical Models ◽  
Physico Chemical ◽  
Quantitative Characteristics ◽  
Nb Content

The represented experimental data on the Ta and Nb contents in acidic magmatic melts of different compositions, when dissolving pyrochlore and microlite at T = 650850 C and P = 100400 MPa, make it possible to obtain quantitative characteristics to create physico-chemical models of the genesis of TaNb deposits. At pyrochlore dissolution in granitoid melts at P = 100 MPa, the highest Nb content (0,71,9 wt.%) is obtained in alkaline melts, it decreases to 0,060,38 wt.% in sub-aluminous melts, and then slightly increases to 0,110,41 wt.% in high-alumina melts. An increase in temperature increases the dissolution of pyrochlore, and an increase in pressure decreases its. In high-alumina granite melts the pyrochlore is unstable. At the microlite dissolves with the increase in the alumina-rich melt, the Nb/Ta ratio in the melt increases approximately doubles.

Identifying Physico-Chemical Laws from the Robotically Collected Data

2019 ◽  
Author(s):  
Liwei Cao ◽  
Danilo Russo ◽  
Vassilios S. Vassiliadis ◽  
Alexei Lapkin
Keyword(s):  
Experimental Data ◽  
Numerical Models ◽  
Predictor Variable ◽  
Physical Models ◽  
Training Data ◽  
Mixed Integer ◽  
Physico Chemical ◽  
Data Points ◽  
Future Work ◽  
The Relationship

<p>A mixed-integer nonlinear programming (MINLP) formulation for symbolic regression was proposed to identify physical models from noisy experimental data. The formulation was tested using numerical models and was found to be more efficient than the previous literature example with respect to the number of predictor variables and training data points. The globally optimal search was extended to identify physical models and to cope with noise in the experimental data predictor variable. The methodology was coupled with the collection of experimental data in an automated fashion, and was proven to be successful in identifying the correct physical models describing the relationship between the shear stress and shear rate for both Newtonian and non-Newtonian fluids, and simple kinetic laws of reactions. Future work will focus on addressing the limitations of the formulation presented in this work, by extending it to be able to address larger complex physical models.</p><p><br></p>

scholarly journals Radiation thermo-chemical models of protoplanetary disks

2019 ◽  
Vol 632 ◽  
pp. A44 ◽  
Author(s):  
W. F. Thi ◽  
G. Lesur ◽  
P. Woitke ◽  
I. Kamp ◽  
Ch. Rab ◽  
...  
Keyword(s):  
Dead Zone ◽  
Cosmic Ray ◽  
Rotational Line ◽  
Viscous Heating ◽  
Gas Phase Reactions ◽  
Chemical Models ◽  
Physico Chemical ◽  
Chemical Heating ◽  
Polycyclic Aromatic ◽  
The Dead

Context. Disks around pre-main-sequence stars evolve over time by turbulent viscous spreading. The main contender to explain the strength of the turbulence is the magnetorotational instability model, whose efficiency depends on the disk ionization fraction. Aims. Our aim is to compute self-consistently the chemistry including polycyclic aromatic hydrocarbon (PAH) charge chemistry, the grain charging, and an estimate of an effective value of the turbulence α parameter in order to find observational signatures of disk turbulence. Methods. We introduced PAH and grain charging physics and their interplay with other gas-phase reactions in the physico-chemical code PRODIMO. Non-ideal magnetohydrodynamics effects such as ohmic and ambipolar diffusion are parametrized to derive an effective value for the turbulent parameter αeff. We explored the effects of turbulence heating and line broadening on CO isotopologue submillimeter lines. Results. The spatial distribution of αeff depends on various unconstrained disk parameters such as the magnetic parameter βmag or the cosmic ray density distribution inside the protoplanetary disk s. The inner disk midplane shows the presence of the so-called dead zone where the turbulence is almost inexistent. The disk is heated mostly by thermal accommodation on dust grains in the dead zone, by viscous heating outside the dead zone up to a few hundred astronomical units, and by chemical heating in the outer disk. The CO rotational lines probe the warm molecular disk layers where the turbulence is at its maximum. However, the effect of turbulence on the CO line profiles is minimal and difficult to distinguish from the thermal broadening. Conclusions. Viscous heating of the gas in the disk midplane outside the dead zone is efficient. The determination of α from CO rotational line observations alone is challenging.

scholarly journals Influence of galactic arm scale dynamics on the molecular composition of the cold and dense ISM III. Elemental depletion and shortcomings of the current physico-chemical models

2020 ◽  
Vol 497 (2) ◽  
pp. 2309-2319
Author(s):  
V Wakelam ◽  
W Iqbal ◽  
J-P Melisse ◽  
P Gratier ◽  
M Ruaud ◽  
...  
Keyword(s):  
Gas Phase ◽  
Molecular Form ◽  
Dense Medium ◽  
Chemical Model ◽  
Physical Conditions ◽  
Dense Cores ◽  
Chemical Models ◽  
Physico Chemical ◽  
Galactic Model ◽  
Elemental Depletion

ABSTRACT We present a study of the elemental depletion in the interstellar medium. We combined the results of a Galactic model describing the gas physical conditions during the formation of dense cores with a full-gas-grain chemical model. During the transition between diffuse and dense medium, the reservoirs of elements, initially atomic in the gas, are gradually depleted on dust grains (with a phase of neutralization for those which are ions). This process becomes efficient when the density is larger than 100 cm−3. If the dense material goes back into diffuse conditions, these elements are brought back in the gas phase because of photo-dissociations of the molecules on the ices, followed by thermal desorption from the grains. Nothing remains on the grains for densities below 10 cm−3 or in the gas phase in a molecular form. One exception is chlorine, which is efficiently converted at low density. Our current gas–grain chemical model is not able to reproduce the depletion of atoms observed in the diffuse medium except for Cl, which gas abundance follows the observed one in medium with densities smaller than 10 cm−3. This is an indication that crucial processes (involving maybe chemisorption and/or ice irradiation profoundly modifying the nature of the ices) are missing.

Analysis and Interpretation of Microstructures after Liquid Oxide Corrosion

2010 ◽  
Vol 70 ◽  
pp. 114-129
Author(s):  
Jacques Poirier
Keyword(s):  
Experimental Data ◽  
High Temperature ◽  
Room Temperature ◽  
Local Thermodynamic Equilibrium ◽  
High Alumina ◽  
Essential Information ◽  
Phase Rule ◽  
Liquid Oxide ◽  
Chemical Profiles ◽  
Solid Phases

Corrosion by liquid oxides is one of the most severe modes of degradations which limit the lifetime of the refractory linings. The study of the microstructures of corroded refractories provides essential information. However, the interpretation of the microscopic observations is difficult : - The refractories are multi-component and heterogeneous ceramics, - The microscopic observations are carried out at room temperature. They are not representative of the mineral and vitreous phases existing at high temperature, - During cooling, new solid phases appear by crystallization of liquid oxides. The composition of the vitreous phases also evolves with the temperature. Consequently, the information obtained is often limited. In this paper , we will present a method to analyse and interpret the microstructures of refractories after use. The concept of local thermodynamic equilibrium and the use of the phase rule make it possible to interpret the microstructures of corroded refractories, to explain the observed mineral zonation and to quantify the composition of the liquid phase at high temperature from chemical profiles established by S.E.M. Experimental data from corrosion of MgO-C, Al2O3-MgO and high alumina refractories will illustrate and validate this theoretical approach.

Repetitive inductions of bioluminescence of Pseudomonas putida TVA8 immobilised by adsorption on optical fibre

2016 ◽  
Vol 70 (7) ◽  
Author(s):  
Jakub Zajíc ◽  
Milan Bittner ◽  
Tomáš Brányik ◽  
Andrey Solovyev ◽  
Stanislav Šabata ◽  
...  
Keyword(s):  
Pseudomonas Putida ◽  
Optical Fibre ◽  
Contact Angles ◽  
Solid Surfaces ◽  
Zeta Potentials ◽  
Chemical Models ◽  
Physico Chemical

AbstractPhysico–chemical models of the interactions of cells with solid surfaces, which use contact angles and zeta potentials, indicated more facile adsorption of cells of

scholarly journals Tracing the cold and warm physico-chemical structure of deeply embedded protostars: IRAS 16293−2422 vs. VLA 1623−2417

2018 ◽  
Vol 617 ◽  
pp. A120 ◽  
Author(s):  
N. M. Murillo ◽  
E. F. van Dishoeck ◽  
M. H. D. van der Wiel ◽  
J. K. Jørgensen ◽  
M. N. Drozdovskaya ◽  
...  
Keyword(s):  
Chemical Structure ◽  
Cavity Wall ◽  
Key Factors ◽  
Chemical Complexity ◽  
Chemical Structures ◽  
Chemical Models ◽  
Physico Chemical ◽  
Envelope Material ◽  
Low Mass ◽  
Dust Distribution

Context. Much attention has been placed on the dust distribution in protostellar envelopes, but there are still many unanswered questions regarding the physico-chemical structure of the gas. Aims. Our aim is to start identifying the factors that determine the chemical structure of protostellar regions, by studying and comparing low-mass embedded systems in key molecular tracers. Methods. The cold and warm chemical structures of two embedded Class 0 systems, IRAS 16293−2422 and VLA 1623−2417 were characterized through interferometric observations. DCO+, N2H+, and N2D+ were used to trace the spatial distribution and physics of the cold regions of the envelope, while c-C3H2 and C2H from models of the chemistry are expected to trace the warm (UV-irradiated) regions. Results. The two sources show a number of striking similarities and differences. DCO+ consistently traces the cold material at the disk-envelope interface, where gas and dust temperatures are lowered due to disk shadowing. N2H+ and N2D+, also tracing cold gas, show low abundances toward VLA 1623−2417, but for IRAS 16293−2422, the distribution of N2D+ is consistent with the same chemical models that reproduce DCO+. The two systems show different spatial distributions c-C3H2 and C2H. For IRAS 16293−2422, c-C3H2 traces the outflow cavity wall, while C2H is found in the envelope material but not the outflow cavity wall. In contrast, toward VLA 1623−2417 both molecules trace the outflow cavity wall. Finally, hot core molecules are abundantly observed toward IRAS 16293−2422 but not toward VLA 1623−2417. Conclusions. We identify temperature as one of the key factors in determining the chemical structure of protostars as seen in gaseous molecules. More luminous protostars, such as IRAS 16293−2422, will have chemical complexity out to larger distances than colder protostars, such as VLA 1623−2417. Additionally, disks in the embedded phase have a crucial role in controlling both the gas and dust temperature of the envelope, and consequently the chemical structure.

scholarly journals INTERACTION OF RECOMBINANT TATA-BINDING PROTEIN WITH MAMMALS GENES PROMOTER TATA

2007 ◽  
Vol 5 (2) ◽  
pp. 44-49 ◽  
Author(s):  
Ludmila K Savinkova ◽  
Irina A Drachkova ◽  
Michail P Ponomarenko ◽  
Marina V Lysova ◽  
Tatiana V Arshinova ◽  
...  
Keyword(s):  
Experimental Data ◽  
Promoter Region ◽  
Binding Protein ◽  
Tata Binding Protein ◽  
Tata Element ◽  
Quantitative Characteristics

Quantitative characteristics of interaction recombinant TATA-binding protein (TBP) with oligonucleotides identical to natural TATA-containing promoter region genes of mammals are received. In particular, new experimental data about the importance guanine in 8-th position of the TATA-element for affinity to TBP are received. The experimental data, testifying that raised maintenance G and С nucleotides in flanks of TATA-element does the contribution to affinity to TBP are received.

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