scholarly journals Venus: key to understanding the evolution of terrestrial planets

2021 ◽  
Author(s):  
Colin F. Wilson ◽  
Thomas Widemann ◽  
Richard Ghail
Keyword(s):  
High Temperature ◽  
High Resolution ◽  
Radar Imaging ◽  
Space Science ◽  
Interior Surface ◽  
Extended Surface ◽  
Earth Like Planets ◽  
Orbital Mission

AbstractIn this paper, originally submitted in answer to ESA’s “Voyage 2050” call to shape the agency’s space science missions in the 2035–2050 timeframe, we emphasize the importance of a Venus exploration programme for the wider goal of understanding the diversity and evolution of habitable planets. Comparing the interior, surface, and atmosphere evolution of Earth, Mars, and Venus is essential to understanding what processes determined habitability of our own planet and Earth-like planets everywhere. This is particularly true in an era where we expect thousands, and then millions, of terrestrial exoplanets to be discovered. Earth and Mars have already dedicated exploration programmes, but our understanding of Venus, particularly of its geology and its history, lags behind. Multiple exploration vehicles will be needed to characterize Venus’ richly varied interior, surface, atmosphere and magnetosphere environments. Between now and 2050 we recommend that ESA launch at least two M-class missions to Venus (in order of priority): a geophysics-focussed orbiter (the currently proposed M5 EnVision orbiter – [1] – or equivalent); and an in situ atmospheric mission (such as the M3 EVE balloon mission – [2]). An in situ and orbital mission could be combined in a single L-class mission, as was argued in responses to the call for L2/L3 themes [3–5]. After these two missions, further priorities include a surface lander demonstrating the high-temperature technologies needed for extended surface missions; and/or a further orbiter with follow-up high-resolution surface radar imaging, and atmospheric and/or ionospheric investigations.

In situsynchrotron powder diffraction study of active belite clinkers

2007 ◽  
Vol 40 (6) ◽  
pp. 999-1007 ◽  
Author(s):  
Ángeles G. De la Torre ◽  
Khadija Morsli ◽  
Mohammed Zahir ◽  
Miguel A.G. Aranda
Keyword(s):  
High Temperature ◽  
High Resolution ◽  
Powder Diffraction ◽  
Polymorphic Transformation ◽  
High Energy ◽  
Dicalcium Silicate ◽  
Polymorphic Transformations ◽  
X Ray ◽  
High Temperature Reactions

The clinkerization processes to form belite clinkers, with theoretical compositions close to 60 wt% of Ca2SiO4, have been studiedin situby high-resolution high-energy (λ = 0.30 Å) synchrotron X-ray powder diffraction. In order to obtain active belite cements, different amounts of K2O, Na2O and SO3have been added. The existence range of the high-temperature phases has been established and, furthermore, Rietveld quantitative phase analyses at high temperature have been performed for all patterns. The following high-temperature reactions have been investigated: (i) polymorphic transformations of dicalcium silicate, \alpha_{\rm L}'-Ca2SiO4↔ \alpha_{\rm H}'-Ca2SiO4from 1170 to 1230 K, and \alpha_{\rm H}'-Ca2SiO4↔ α-Ca2SiO4from 1500 to 1600 K; (ii) melting of the aluminates phases, Ca3Al2O6and Ca4(Al2Fe2)O10, above ∼1570 K; and (iii) reaction of Ca2SiO4with CaO to yield Ca3SiO5above ∼1550 K. Moreover, in all the studied compositions the temperature of the polymorphic transformation \alpha_{\rm H}'-Ca2SiO4↔ α-Ca2SiO4has decreased with the addition of activators. Finally, active belite clinkers were produced as the final samples contained α-belite phases.

scholarly journals Experimental observation of carousel-like phason flips in the decagonal quasicrystal Al60Cr20Fe10Si10

2021 ◽  
Vol 77 (5) ◽  
Author(s):  
Zhanbing He ◽  
Jean-Luc Maurice ◽  
Haikun Ma ◽  
Yanguo Wang ◽  
Hua Li ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Temperature ◽  
High Resolution ◽  
Translational Symmetry ◽  
Long Range Order ◽  
Decagonal Quasicrystal ◽  
Microscopy Imaging ◽  
Transmission Electron

Quasicrystals have special crystal structures with long-range order, but without translational symmetry. Unexpectedly, carousel-like successive flippings of groups of atoms inside the ∼2 nm decagonal structural subunits of the decagonal quasicrystal Al60Cr20Fe10Si10 were directly observed using in situ high-temperature high-resolution transmission electron microscopy imaging. The observed directionally successive phason flips occur mainly clockwise and occasionally anticlockwise. The origin of these directional phason flips is analyzed and discussed.

High-temperature high-resolution in-situ microscopy of grain boundary migration and structure change

1990 ◽  
Vol 48 (4) ◽  
pp. 514-515
Author(s):  
Hideki Ichinose ◽  
Tokuji Kizuka ◽  
Yoichi Ishida
Keyword(s):  
High Temperature ◽  
High Resolution ◽  
Grain Boundary ◽  
High Stability ◽  
Boundary Migration ◽  
Structure Change ◽  
Objective Lens ◽  
Video Tape ◽  
Grain Boundary Migration

A high resolution high temperature specimen stage of 200kV HRTEM was newly designed and produced in order to investigate the physical and mechanical nature of materials at high temperature.The atomic process of silicon grain boundary migration and the structure change was successfully observed in-situ at 1000K by the new specimen stage.The high temperature specimen stage consists of a heating specimen holder, a high stability power supply and a high stability current controller. Heat is provided by an induction free double spiral coil heater which is made of tungsten. Excellent current stability, better than 10−6 , prevents the objective lens from the magnetic disturbance which is caused by heating current. The highest temperature of the specimen is designed to be 1100K. The accuracy of the temperature measurement is checked by the melting test of tin. In order to keep the high resolution of the microscope(JEM-200CX) at such high temperature as 1100K an objective lens is also newly designed and produced. Aberration constants of the new lens are respectively Cs=0.7mm and Cc=1.2mm. Resulted resolution at high temperature is as same level as the that of the original JEM-200CX at room temperature. Images are recorded by a video tape recorder.

scholarly journals Connecting Lost Baryons and Dark Galaxies via QSO Absorption Lines

2007 ◽  
Vol 3 (S244) ◽  
pp. 63-72
Author(s):  
Todd M. Tripp
Keyword(s):  
High Resolution ◽  
Absorption Lines ◽  
Ultraviolet Spectroscopy ◽  
Low Density ◽  
Metal Enrichment ◽  
Complementary Information ◽  
Physical Conditions ◽  
Galactic Winds

AbstractQSO absorption lines are sensitive to very low density gas, and consequently, QSO spectroscopy provides a powerful tool for measuring the distribution, physical conditions, and metal enrichment of baryons in the intergalactic medium and in “dark galaxies”. However, ultraviolet spectroscopy is required to study QSO absorbers in the nearby universe where the connections between the absorbing gas and galaxies/environment can be probed. This talk reviewed several recent studies of low-zQSO absorbers in order to demonstrate the value of combining high-resolution ultraviolet spectroscopy with complementary information on the absorber environment, e.g., mapping of 21 cm emission in the vicinity of the absorbers; some notes on these examples are presented in this paper. The absorbers probed range from high-N(H I) damped Lyman α absorbers down to very low-column Lyα forest clouds with logN(H I) < 13.5. The high-N(H I) systems are candidate “dark galaxies” – these systems are more metal enriched than the high-zIGM, possibly due to in-situ star formation, and some of the absorbers are highly metal enriched. However, we have obtained follow-up 21cm emission mapping with the VLA and deep optical imaging, and while we do find H I clouds associated with the absorbers in 21cm emission, we often do not find any evidence of in-situ stars. At this juncture, it seems more likely that these low-zabsorbers were enriched with metals within galaxies and were subsequently transported out into the IGM, e.g., by tidal stripping or galactic winds. This contribution also summarizes some recent results on the search for lost baryons in the “warm-hot” (shock-heated) low-redshift IGM.

scholarly journals A multiscale in situ high temperature high resolution transmission electron microscopy study of ThO2 sintering

Nanoscale ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 7362-7374
Author(s):  
R. Podor ◽  
V. Trillaud ◽  
G. I. Nkou Bouala ◽  
N. Dacheux ◽  
C. Ricolleau ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Temperature ◽  
High Resolution ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Transmission Electron Microscopy Study ◽  
Transmission Electron ◽  
Initial Stage

Two-grain systems formed by ThO2 nanospheres are used to study the initial stage of sintering up to 1050 °C using HT-HRTEM. The low temperature crystallite rearrangements as well as grain boundary formation and growth are observed.

mRNA localization by Electron microscopic in situ hybridization

1991 ◽  
Vol 49 ◽  
pp. 430-431
Author(s):  
J. A. Pollock ◽  
M. Martone ◽  
T. Deerinck ◽  
M. H. Ellisman
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Nucleic Acids ◽  
Recombinant Dna ◽  
Light And Electron Microscopy ◽  
Electron Microscopic ◽  
High Voltage Electron Microscopy ◽  
Functional Sites ◽  
Voltage Electron

Localization of specific proteins in cells by both light and electron microscopy has been facilitate by the availability of antibodies that recognize unique features of these proteins. High resolution localization studies conducted over the last 25 years have allowed biologists to study the synthesis, translocation and ultimate functional sites for many important classes of proteins. Recently, recombinant DNA techniques in molecular biology have allowed the production of specific probes for localization of nucleic acids by “in situ” hybridization. The availability of these probes potentially opens a new set of questions to experimental investigation regarding the subcellular distribution of specific DNA's and RNA's. Nucleic acids have a much lower “copy number” per cell than a typical protein, ranging from one copy to perhaps several thousand. Therefore, sensitive, high resolution techniques are required. There are several reasons why Intermediate Voltage Electron Microscopy (IVEM) and High Voltage Electron Microscopy (HVEM) are most useful for localization of nucleic acids in situ.

Ultrastructural analysis of the spatial distribution of MRNA

1992 ◽  
Vol 50 (1) ◽  
pp. 552-553
Author(s):  
Gary Bassell ◽  
Robert H. Singer
Keyword(s):  
Electron Microscopy ◽  
Spatial Distribution ◽  
In Situ Hybridization ◽  
High Resolution ◽  
Nucleic Acids ◽  
Colloidal Gold ◽  
Dna Probe ◽  
Nucleotide Analogs ◽  
Gold Particles

We have been investigating the spatial distribution of nucleic acids intracellularly using in situ hybridization. The use of non-isotopic nucleotide analogs incorporated into the DNA probe allows the detection of the probe at its site of hybridization within the cell. This approach therefore is compatible with the high resolution available by electron microscopy. Biotinated or digoxigenated probe can be detected by antibodies conjugated to colloidal gold. Because mRNA serves as a template for the probe fragments, the colloidal gold particles are detected as arrays which allow it to be unequivocally distinguished from background.

The reaction of amorphous Ni-Nb films with Si in the presence of a native SiO2 layer

1990 ◽  
Vol 48 (4) ◽  
pp. 664-665
Author(s):  
N. Rozhanski ◽  
A. Barg
Keyword(s):  
High Temperature ◽  
Crystallization Temperature ◽  
Diffusion Barriers ◽  
Sio2 Layer ◽  
Si Substrate ◽  
Cross Sectional ◽  
Plan View ◽  
Temperature Range ◽  
Sputter Deposited

Amorphous Ni-Nb alloys are of potential interest as diffusion barriers for high temperature metallization for VLSI. In the present work amorphous Ni-Nb films were sputter deposited on Si(100) and their interaction with a substrate was studied in the temperature range (200-700)°C. The crystallization of films was observed on the plan-view specimens heated in-situ in Philips-400ST microscope. Cross-sectional objects were prepared to study the structure of interfaces.The crystallization temperature of Ni5 0 Ni5 0 and Ni8 0 Nb2 0 films was found to be equal to 675°C and 525°C correspondingly. The crystallization of Ni5 0 Ni5 0 films is followed by the formation of Ni6Nb7 and Ni3Nb nucleus. Ni8 0Nb2 0 films crystallise with the formation of Ni and Ni3Nb crystals. No interaction of both films with Si substrate was observed on plan-view specimens up to 700°C, that is due to the barrier action of the native SiO2 layer.

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