scholarly journals Breyite inclusions in diamond: experimental evidence for possible dual origin

2020 ◽  
Vol 32 (1) ◽  
pp. 171-185 ◽  
Author(s):  
Alan B. Woodland ◽  
Andrei V. Girnis ◽  
Vadim K. Bulatov ◽  
Gerhard P. Brey ◽  
Heidi E. Höfer
Keyword(s):  
Melting Temperature ◽  
Oxygen Fugacity ◽  
Natural Diamond ◽  
High Water ◽  
Experimental Series ◽  
Stability Field ◽  
Maximum Pressure ◽  
Casio3 Perovskite ◽  
Lower Temperature ◽  
Dual Origin

Abstract. Inclusions of breyite (previously known as walstromite-structured CaSiO3) in diamond are usually interpreted as retrogressed CaSiO3 perovskite trapped in the transition zone or the lower mantle. However, the thermodynamic stability field of breyite does not preclude its crystallization together with diamond under upper-mantle conditions (6–10 GPa). The possibility of breyite forming in subducted sedimentary material through the reaction CaCO3 + SiO2 = CaSiO3 + C + O2 was experimentally evaluated in the CaO–SiO2–C–O2 ± H2O system at 6–10 GPa, 900–1500 ∘C and oxygen fugacity 0.5–1.0 log units below the Fe–FeO (IW) buffer. One experimental series was conducted in the anhydrous subsystem and aimed at determining the melting temperature of the aragonite–coesite (or stishovite) assemblage. It was found that melting occurs at a lower temperature (∼1500 ∘C) than the decarbonation reaction, which indicates that breyite cannot be formed from aragonite and silica under anhydrous conditions and an oxygen fugacity above IW – 1. In the second experimental series, we investigated partial melting of an aragonite–coesite mixture under hydrous conditions at the same pressures and redox conditions. The melting temperature in the presence of water decreased strongly (to 900–1200 ∘C), and the melt had a hydrous silicate composition. The reduction of melt resulted in graphite crystallization in equilibrium with titanite-structured CaSi2O5 and breyite at ∼1000 ∘C. The maximum pressure of possible breyite formation is limited by the reaction CaSiO3 + SiO2 = CaSi2O5 at ∼8 GPa. Based on the experimental results, it is concluded that breyite inclusions found in natural diamond may be formed from an aragonite–coesite assemblage or carbonate melt at 6–8 GPa via reduction at high water activity.

scholarly journals PENCITRAAN PEMETAAN PANAS PENYERAPAN RADIASI TERAHERTZ (THz) DALAM JARINGAN BIOLOGIS MENGGUNAKAN MODEL SIMULINK-MATLAB

2020 ◽  
Vol 6 (2) ◽  
pp. 252
Author(s):  
Dewi Kurnia ◽  
Muhammmad Hamdi ◽  
Juandi M
Keyword(s):  
Muscle Tissue ◽  
Biological Networks ◽  
Biological Tissue ◽  
Imaging Techniques ◽  
High Water ◽  
High Water Content ◽  
Thz Radiation ◽  
Fat Tissue ◽  
Lower Temperature ◽  
Thz Power

ABSTRAKRadiasi THz memiliki sifat yang membuatnya lebih menarik dan efektif dalam bidang teknik pencitraan biomedis. Hal ini dikarenakan radiasi THz tidak mengionisasi dan merusak jaringan. Penelitian ini menggunakan sampel jaringan biologis sapi yaitu  jaringan kulit, lemak, tumor dan otot. Tujuan dari penelitian untuk mengetahui suatu jaringan terindikasi abnormal atau normal dengan melihat pemetaan panas yang dihasilkan dari penyerapan radiasi THz dalam jaringan biologis sapi dengan cara pemodelan. Penelitian ini menggunakan teknik komputasi biofisik dengan medel simulink-matlab. Rentang frekuensi radiasi THz yang digunakan 0,1 - 1 THz, daya 50 – 150 mW serta kerapatan daya 5 - 25 mW/mm3. Rasio dan temperatur dari masing-masing jaringan yaitu lemak 0,25 T/25 oC (T = 6,25 oC ), kulit 0,432 T/25oC (10,8 oC), otot 0,675 T/25oC (16,88 oC) dan Tumor 0,9 T/25oC (22,50 oC). Hasil penelitian menunjukkan bahwa Jaringan lemak memiliki produksi panas yang lebih kecil dan temperatur yang lebih rendah dari jaringan kulit dan otot. Hal ini dikarenakan jaringan lemak memiliki kadar air yang tinggi dengan konsentrasi yang lebih encer sehingga radiasi THz lebih banyak terserap dengan energi yang lebih cepat habis sesuai penetrasi jaringan. Kata kunci:  terahertz; pemetaan panas; jaringan biologis; simulink-matlab.                                                                                                                                       ABSTRACTTerahertz (THz) radiation has properties that make it more attractive and effective in the field of biomedical imaging techniques. This is because THz radiation does not ionize and damage tissue. This study used a sample of bovine biological tissue, namely skin, fat, tumor and muscle tissue. The aim of this research is to find out whether a tissue is indicated as abnormal or normal by looking at the heat mapping generated from the absorption of THz radiation in the biological tissue of cattle by means of modeling. This study uses biophysical computation techniques with the simulink-matlab method. The range of THz radiation frequency used is 0.1 - 1 THz, power 50 - 150 mW and power density 5 - 25 mW / mm3. The ratio and temperature of each tissue were fat 0.25 T / 25 oC (T = 6.25 oC), skin 0.432 T / 25oC (10.8 oC), muscle 0.675 T / 25oC (16.88 oC) and Tumor 0.9 T / 25oC (22.50 oC). The results showed that fat tissue has less heat production and a lower temperature than skin and muscle tissue. This is because the fat tissue has a high water content with a more dilute concentration so that more THz radiation is absorbed with energy that runs out faster according to tissue penetration. Keywords: terahertz; heat mapping; biological networks; simulink-matlab.

scholarly journals Effect of Different Modifiers on Melting Points and pH under Leaching in Nuclear Waste Glasses in Borosilicate and Phosphate Systems

2012 ◽  
Vol 9 (1) ◽  
pp. 105-109 ◽  
Author(s):  
Patit P. Malik ◽  
Partha Mitra ◽  
Tanmay Das3*
Keyword(s):  
Ambient Temperature ◽  
Melting Temperature ◽  
Nuclear Waste ◽  
Melting Points ◽  
Time Intervals ◽  
Ionic Radii ◽  
Silicate System ◽  
Leachate Solution ◽  
Ionic Size ◽  
Lower Temperature

Glasses were melted in three systems viz., borosilicate, phosphate and pure silicate system. In the present work we could melt the glass at much lower temperature (800-950oC) with a soaking period of 30 min-1 hr which were earlier reported to be melted not below 1000o C. The effect of different modifier ions like Pb2+, Ba2+, Na+, Fe3+, Al3+, Y3+, Ca2+, Ce4+ and Sr2+ on melting temperature and time of melting in each system has been found to be evident. The pH determination in the range 6.43 to 8.18 of the leachate solution at ambient temperature under varying time intervals shows interesting and regular variations. The findings have been corroborated in terms of ionic size, ionic radii and hence ionic potential of the modifier ions.

Temperature-dependent Rutile Solubility in Garnet and Clinopyroxene from Mantle Eclogite: Implications for Continental Crust Formation and V-based Oxybarometry

2020 ◽  
Vol 61 (6) ◽  
Author(s):  
Sonja Aulbach
Keyword(s):  
Low Temperature ◽  
Continental Crust ◽  
Oxygen Fugacity ◽  
Oceanic Crust ◽  
Tetrahedral Site ◽  
Bulk Composition ◽  
Distribution Coefficients ◽  
Accessory Mineral ◽  
Stability Field ◽  
Increasing Temperature

Abstract Despite its accessory mineral status in metabasaltic rocks, rutile controls the whole-rock Ti, Nb and Ta budget. These are key elements used to trace fluid- and melt-mediated mass transfer across the mantle–crust boundary. Rutile also contains significant amounts of the redox-sensitive element V, which is increasingly used to estimate oxygen fugacity. Kimberlite-borne mantle eclogite xenoliths, which are frequently rutile-bearing, have been interpreted as residues from the extraction of silicic partial melt similar in composition to the average continental crust. Published mineral compositions for eclogite xenoliths from various cratons combined with geothermobarometrical calculations show that TiO2 contents in garnet and clinopyroxene increase with increasing temperature of last residence in the lithospheric mantle, whereas apparent clinopyroxene–garnet distribution coefficients decrease. This implies that (1) increasing TiO2 contents in eclogitic garnet or clinopyroxene are not a signature of increasing metasomatism with depth, (2) whole-rock eclogites reconstructed without rutile will increasingly underestimate TiO2, Nb and Ta contents with decreasing temperature, and (3) low-temperature eclogites are more likely to contain free rutile. Only about a third of the ∼250 samples considered here would have whole-rock TiO2 contents (reconstructed with calculated rutile modes) required for rutile saturation during subduction and partial melting. If there is a role for subducting oceanic crust now sampled as mantle eclogite, the characteristic Ti–Nb–Ta depletion in continental crust may require fluid-dominated processes, where these elements are not efficiently mobilised. In garnet, Ti uptake on the octahedral site is accommodated primarily by coupled substitution with Na and subordinately with a divalent metal cation, and there is no evidence for substitution on the tetrahedral site. For samples equilibrated to the conductive geotherm, Ti in addition to Na enrichment may be indicative of equilibration in the diamond stability field. The jadeite component in clinopyroxene as a function of temperature is a good indicator of the geotherm to which the various samples equilibrated, and can be used to reveal samples within each suite that have been affected by isobaric heating. The distribution of V in eclogitic garnet, clinopyroxene and rutile is affected by bulk composition, temperature and oxygen fugacity. In carefully vetted, low-temperature samples with TiO2 contents >0·8 wt%, V-based oxybarometry may monitor redox conditions prevailing during metamorphism of oceanic crust or, at lower TiO2, during (secular) cooling-related exsolution of rutile from garnet or clinopyroxene, whereas in higher-temperature ilmenite-bearing samples metasomatic conditions may be recorded.

scholarly journals High-Pressure Phase Diagrams of Na2CO3 and K2CO3

Minerals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 599
Author(s):  
Pavel N. Gavryushkin ◽  
Altyna Bekhtenova ◽  
Sergey S. Lobanov ◽  
Anton Shatskiy ◽  
Anna Yu. Likhacheva ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Phase Diagrams ◽  
Diffraction Pattern ◽  
Diamond Anvil Cell ◽  
Stability Field ◽  
Maximum Pressure ◽  
Diamond Anvil ◽  
Diffraction Peaks ◽  
New Phase ◽  
Pressure Phase

The phase diagrams of Na 2 CO 3 and K 2 CO 3 have been determined with multianvil (MA) and diamond anvil cell (DAC) techniques. In MA experiments with heating, γ -Na 2 CO 3 is stable up to 12 GPa and above this pressure transforms to P 6 3 /mcm-phase. At 26 GPa, Na 2 CO 3 - P 6 3 /mcm transforms to the new phase with a diffraction pattern similar to that of the theoretically predicted Na 2 CO 3 - P 2 1 /m. On cold compression in DAC experiments, γ -Na 2 CO 3 is stable up to the maximum pressure reached of 25 GPa. K 2 CO 3 shows a more complex sequence of phase transitions. Unlike γ Na 2 CO 3 , γ -K 2 CO 3 has a narrow stability field. At 3 GPa, K 2 CO 3 presents in the form of the new phase, called K 2 CO 3 -III, which transforms into another new phase, K 2 CO 3 -IV, above 9 GPa. In the pressure range of 9–15 GPa, another new phase or the mixture of phases III and IV is observed. The diffraction pattern of K 2 CO 3 -IV has similarities with that of the theoretically predicted K 2 CO 3 - P 2 1 /m and most of the diffraction peaks can be indexed with this structure. Water has a dramatic effect on the phase transitions of K 2 CO 3 . Reconstruction of the diffraction pattern of γ -K 2 CO 3 is observed at pressures of 0.5–3.1 GPa if the DAC is loaded on the air.

Dimerization of Carboxylic Acids in Solution up to High Pressures and Temperatures. 2. Benzoic Acid

1987 ◽  
Vol 42 (4) ◽  
pp. 406-412 ◽  
Author(s):  
R. Barraza ◽  
E. M. Borschel ◽  
M. Buback
Keyword(s):  
Benzoic Acid ◽  
Quantitative Measurement ◽  
High Pressures ◽  
Equilibrium Constants ◽  
Cyclic Dimer ◽  
Maximum Pressure ◽  
Dilute Solution ◽  
High Pressures And Temperatures ◽  
Lower Temperature ◽  
Hydrogen Bonded

Benzoic acid in dilute solution of n-heptane and of CCl4 is studied via high-pressure hightemperature IR spectroscopy on the C = O and O - H stretching fundamentals. Lambert-Beer’s law is shown to be valid for the C = O modes of the acid monomer and of the hydrogen-bonded cyclic dimer, which enables the quantitative measurement of the dimerization equilibrium to a maximum pressure of 2 kbar and up to 175 °C. At identical pressure and temperature the dimerization equilibrium constant is larger in n-heptane than in CCl4. From the monomer-cyclic dimer equilibrium constants the pressure dependence of the dimerization enthalpy is determined and compared with direct information on both species as derived from their O - H fundamental mode absorption. Toward lower temperature the dimerization volume is decreasingly negative and, in CCl4 solution, ΔV even changes sign around 40 °C. Increasing pressure thus favours the dissociation of the hydrogen-bonded dimer into benzoic acid monomer molecules at ambient temperature.

scholarly journals Modeling the Crystallization and Emplacement Conditions of a Basaltic Trachyandesitic Sill at Mt. Etna Volcano

Minerals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 126 ◽  
Author(s):  
Manuela Nazzari ◽  
Flavio Di Stefano ◽  
Silvio Mollo ◽  
Piergiorgio Scarlato ◽  
Vanni Tecchiato ◽  
...  
Keyword(s):  
Lattice Strain ◽  
Magma Ascent ◽  
Stability Field ◽  
Etna Volcano ◽  
Mt Etna ◽  
Ascent Velocity ◽  
Compositional Variations ◽  
Kinetic Effects ◽  
Lower Temperature ◽  
The Stability

This study documents the compositional variations of phenocrysts from a basaltic trachyandesitic sill emplaced in the Valle del Bove at Mt. Etna volcano (Sicily, Italy). The physicochemical conditions driving the crystallization and emplacement of the sill magma have been reconstructed by barometers, oxygen barometers, thermometers and hygrometers based on clinopyroxene, feldspar (plagioclase + K-feldspar) and titanomagnetite. Clinopyroxene is the liquidus phase, recording decompression and cooling paths decreasing from 200 to 0.1 MPa and from 1050 to 940 °C, respectively. Plagioclase and K-feldspar cosaturate the melt in a lower temperature interval of ~1000–870 °C. Cation exchanges in clinopyroxene (Mg-Fe) and feldspar (Ca-Na) indicate that magma ascent is accompanied by progressive H2O exsolution (up to ~2.2 wt. %) under more oxidizing conditions (up to ΔNNO + 0.5). Geospeedometric constraints provided by Ti–Al–Mg cation redistributions in titanomagnetite indicate that the travel time (up to 23 h) and ascent velocity of magma (up to 0.78 m/s) are consistent with those inferred for other eruptions at Mt. Etna. These kinetic effects are ascribed to a degassing-induced undercooling path caused principally by H2O loss at shallow crustal conditions. Rare earth element (REE) modeling based on the lattice strain theory supports the hypothesis that the sill magma formed from primitive basaltic compositions after clinopyroxene (≤41%) and plagioclase (≤12%) fractionation. Early formation of clinopyroxene at depth is the main controlling factor for the REE signature, whereas subsequent degassing at low pressure conditions enlarges the stability field of plagioclase causing trace element enrichments during eruption towards the surface.

The Lower Temperature Range of the Wustite Stability Field

1981 ◽  
Vol 124 (2) ◽  
pp. 139-147 ◽  
Author(s):  
J. A. Barbero ◽  
M. A. Blesa ◽  
A. J. G. Maroto
Keyword(s):  
Stability Field ◽  
Temperature Range ◽  
Lower Temperature Range ◽  
Lower Temperature

Effect of Stepped Solution Treatment on Microstructure and Properties of AA7085 Aluminum Alloy

2011 ◽  
Vol 239-242 ◽  
pp. 786-792
Author(s):  
Chun Mei Li ◽  
Zhi Qian Chen ◽  
Su Min Zeng ◽  
Nan Pu Cheng ◽  
Zhen Hua Geng ◽  
...  
Keyword(s):  
Melting Temperature ◽  
Solution Treatment ◽  
Solution Temperature ◽  
Tensile Fracture ◽  
Tensile Fracture Surface ◽  
The Matrix ◽  
Initial Melting ◽  
Statistic Theory ◽  
Lower Temperature ◽  
Multi Phase

The effect of stepped solution treatment on the mechanical properties and the microstructure of AA7085 have been investigated compared to AA7050. Optical and electron microscopy observation and electron probe microanalysis were used to analyze the microstructure and tensile fracture surface of AA7085 and AA7050 processed via various treatment schedules. Besides, X-ray diffractometer and differential scanning calorimeter were used to seek the differences of microstructure characters between AA7085 and AA7050. The results indicate that higher content of Zn along with lower content of Mg and Cu and strictly confined Fe and Si made the matrix of AA7085 get a larger single phase and a higher melting temperature of multi-phase eutectics. By using a lower temperature pretreatment, the initial melting temperature of the alloys can be increased. Consequently complete dissolution of remnant constituents was achieved without overheating. Based on thermodynamics statistic theory, the supersaturation degree of the matrix and the density of cavity may be increased with the elevation of the lattermost solution temperature, which resultes in the increase of fracture toughness and optimization of the microstructure after aging.

Geometrical analysis of elliptical journal bearings and its effects on friction and load capacity

2019 ◽  
Vol 234 (5) ◽  
pp. 743-750
Author(s):  
Ali Ebrahimi ◽  
Saleh Akbarzadeh ◽  
Hassan Moosavi
Keyword(s):  
Friction Force ◽  
Reynolds Equation ◽  
Load Capacity ◽  
Major Axis ◽  
Journal Bearings ◽  
Maximum Pressure ◽  
Geometrical Parameters ◽  
Load Carrying Capacity ◽  
Load Carrying ◽  
Lower Temperature

Elliptical bearings are one type of non-circular journal bearings which has two main advantages over the conventional circular bearings: lower temperature rise and lower vibrations. In this study, the energy equation and Reynolds equation are simultaneously solved under adiabatic boundary conditions. The predicted pressure and temperature are compared to the results of published literature for verification purposes. A parametric study is then conducted on the effect of geometrical parameters of the elliptical journal bearing on the load capacity, friction force, pressure, and oil temperature. Effect of geometric parameters of the bearing on the performance is studied. The results show that non-circularity parameter is the most influential parameter in the bearing, and an increase in the non-circularity results in the decrease in maximum pressure and temperature as well as the friction force. Increasing the eccentricity ratio, on the other hand, will cause an increase in the pressure, temperature, and the friction force. Changes in the angle between the major axis of the bearing and load direction decrease the load-carrying capacity and the non-dimensional pressure and results in an increase in the friction coefficient.

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