Anomalous recurring slope lineae on Mars: Implications for formation mechanisms

Icarus ◽  
2020 ◽  
pp. 114129
Author(s):  
L.H. Lark ◽  
C. Huber ◽  
J.W. Head
Keyword(s):  
Formation Mechanisms ◽  
Recurring Slope Lineae

Evaluation of wet and dry recurring slope lineae (RSL) formation mechanisms based on quantitative mapping of RSL in Garni Crater, Valles Marineris, Mars

Icarus ◽  
2020 ◽  
Vol 335 ◽  
pp. 113420 ◽  
Author(s):  
David E. Stillman ◽  
Brian D. Bue ◽  
Kiri L. Wagstaff ◽  
Katherine M. Primm ◽  
Tim I. Michaels ◽  
...  
Keyword(s):  
Formation Mechanisms ◽  
Valles Marineris ◽  
Quantitative Mapping ◽  
Recurring Slope Lineae

Do Martian slopes with Recurring Slope Lineae (RSL) have a distinct topographic signature?

2021 ◽  
Author(s):  
Aharon Adam ◽  
Itai Haviv ◽  
Dan G. Blumberg ◽  
Shimrit Maman ◽  
Amit Mushkin
Keyword(s):  
Solar Irradiation ◽  
Formation Mechanisms ◽  
Rock Weathering ◽  
Dust Layer ◽  
Geomorphic Mapping ◽  
Weathering Rates ◽  
Topographic Slope ◽  
Morphologic Characteristics ◽  
Recurring Slope Lineae ◽  
Hillslope Scale

<p>Recurring Slope Lineae (RSL) are dynamic, low-albedo, slope-parallel surface features on Mars that occur mainly on steep (>25°) slopes. RSL typically display seasonal dynamics as they appear during late Martian spring, progressively grow during summer, and subsequently fade as summer ends. RSL formation mechanisms remain under debate with proposed mechanisms involving either water/brines (‘wet theories’) vs. dry granular flows within a surficial dust layer (‘dry theories’). In an attempt to distinguish between plausible RSL mechanisms, this study compares the topographic and morphologic characteristics of hillslopes with and without RSL. We suggest that a distinct topographic signature for RSL hillslopes would argue against the ‘dry’ RSL mechanisms, as RSL dynamics within a thin dust layer are not expected to significantly impact the hillslope-scale topography. In contrast, the presence of fluids on RSL hillslopes could conceivably accelerate rock weathering rates, which in turn may impact the hillslope-scale topography. Our analyses are based on HiRISE, CTX and HRSC digital terrain models (DTMs) together with geomorphic mapping using high-resolution orbital images. We focus on inner crater hillslopes and compare the topographic characteristics of RSL vs. non-RSL slopes. In addition, in order to account for the potential influence of aspect-dependent solar irradiation on hillslope processes, we also applied our analysis on adjacent ‘control’ craters that are devoid of RSL activity. Preliminary results from Palikir (-41.6°/ 202.1°E) and Rauna (35.2°/ 328°E) craters reveal that the topographic slope distribution along crater walls with RSL activity is distinct from the slope distribution along crater walls which are devoid of RSL activity. Our results appear to support increased rock-weathering rates on crater walls that presently experience RSL activity.</p><p> </p><p> </p>

The dislocation structure of a 10° [110] tilt boundary in silicon

1983 ◽  
Vol 41 ◽  
pp. 114-115
Author(s):  
B. Cunningham ◽  
D.G. Ast
Keyword(s):  
Dislocation Structure ◽  
Tilt Angle ◽  
Imaging Technique ◽  
Diamond Lattice ◽  
Tilt Boundary ◽  
Formation Mechanisms ◽  
Diffraction Contrast ◽  
Lattice Fringe ◽  
Tilt Boundaries ◽  
Chemically Vapor Deposited

There have Been a number of studies of low-angle, θ < 4°, [10] tilt boundaries in the diamond lattice. Dislocations with Burgers vectors a/2<110>, a/2<112>, a<111> and a<001> have been reported in melt-grown bicrystals of germanium, and dislocations with Burgers vectors a<001> and a/2<112> have been reported in hot-pressed bicrystals of silicon. Most of the dislocations were found to be dissociated, the dissociation widths being dependent on the tilt angle. Possible dissociation schemes and formation mechanisms for the a<001> and a<111> dislocations from the interaction of lattice dislocations have recently been given.The present study reports on the dislocation structure of a 10° [10] tilt boundary in chemically vapor deposited silicon. The dislocations in the boundary were spaced about 1-3nm apart, making them difficult to resolve by conventional diffraction contrast techniques. The dislocation structure was therefore studied by the lattice-fringe imaging technique.

Formation Mechanisms for Multiply Twinned Particles During Nucleation in the Au/MICA System

1975 ◽  
Vol 33 ◽  
pp. 84-85
Author(s):  
Eal H. Lee ◽  
Helmut Poppa
Keyword(s):  
Deposition Time ◽  
High Vacuum ◽  
Dark Field ◽  
Ultra High Vacuum ◽  
Formation Mechanisms ◽  
Heat Treated ◽  
Cluster Density ◽  
Diffraction Patterns ◽  
Crystal Particle ◽  
Multiply Twinned Particles

The formation of thin films of gold on mica has been studied in ultra-high vacuum (5xl0-10 torr) . The mica substrates were heat-treated for 24 hours at 375°C, cleaved, and annealed for 15 minutes at the deposition temperature of 300°C prior to deposition. An impingement flux of 3x1013 atoms cm-2 sec-1 was used. These conditions were found to give high number densities of multiple twin particles and are based on a systematic series of nucleation experiments described elsewhere. Individual deposits of varying deposition time were made and examined by bright and dark field TEM after "cleavage preparation" of highly transparent specimens. In the early stages of growth, the films generally consist of small particles which are either single crystals or multiply twinned; a strong preference for multiply twinned particles was found whenever the particle number densities were high. Fig. 1 shows the stable cluster density ns and the variation with deposition time of multiple twin particle and single crystal particle densities, respectively. Corresponding micrographs and diffraction patterns are shown in Fig. 2.

Clinical and molecular cytogenetic characterization of two cases of inverted duplication deletion 8p

2020 ◽  
pp. 41-42
Author(s):  
Д.А. Юрченко ◽  
М.Е. Миньженкова ◽  
Е.Л. Дадали ◽  
Н.В. Шилова
Keyword(s):  
Mental Retardation ◽  
Congenital Heart ◽  
Heart Defects ◽  
Clinical Manifestations ◽  
Formation Mechanisms ◽  
Agenesis Of Corpus Callosum ◽  
Molecular Cytogenetic ◽  
Inverted Duplication ◽  
Cytogenetic Characterization

Синдром инвертированной дупликации короткого плеча хромосомы 8 со смежной терминальной делециенй (inv dup del(8p), ORPHA 96092) - редкая хромосомная аномалия (ХА) с частотой 1/10000-1/30000 живорожденных. В статье представлены клинические и молекулярно-цитогенетические характеристики двух неродственных пациентов с синдромом inv dup del(8p) и уточнены механизмы формирования хромосомного дисбаланса. Inverted duplication deletion 8p syndrome (inv dup del(8p), ORPHA 96092) is a rare chromosomal abnormality with a frequency of 1:10,000 - 30,000 newborns. Clinical manifestations of this syndrome include mental retardation, facial anomalies, hypoplasia/agenesis of corpus callosum, scoliosis and/or kyphosis, hypotonia, congenital heart defects. The article presents the clinical and molecular cytogenetic characteristics of two patients with inv dup del (8p) syndrome and clarifies the formation mechanisms.

Substituent Effects on the Thermal Decomposition of Phosphate Esters on Ferrous Surfaces

2019 ◽  
Author(s):  
James Ewen ◽  
Carlos Ayestaran Latorre ◽  
Arash Khajeh ◽  
Joshua Moore ◽  
Joseph Remias ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Film Formation ◽  
Substituent Effects ◽  
Vapour Phase ◽  
Industrial Applications ◽  
Phosphate Esters ◽  
Antiwear Additives ◽  
Formation Mechanisms ◽  
Phosphate Ester ◽  
Wide Range

<p>Phosphate esters have a wide range of industrial applications, for example in tribology where they are used as vapour phase lubricants and antiwear additives. To rationally design phosphate esters with improved tribological performance, an atomic-level understanding of their film formation mechanisms is required. One important aspect is the thermal decomposition of phosphate esters on steel surfaces, since this initiates film formation. In this study, ReaxFF molecular dynamics simulations are used to study the thermal decomposition of phosphate esters with different substituents on several ferrous surfaces. On Fe<sub>3</sub>O<sub>4</sub>(001) and α-Fe(110), chemisorption interactions between the phosphate esters and the surfaces occur even at room temperature, and the number of molecule-surface bonds increases as the temperature is increased from 300 to 1000 K. Conversely, on hydroxylated, amorphous Fe<sub>3</sub>O<sub>4</sub>, most of the molecules are physisorbed, even at high temperature. Thermal decomposition rates were much higher on Fe<sub>3</sub>O<sub>4</sub>(001) and particularly α-Fe(110) compared to hydroxylated, amorphous Fe<sub>3</sub>O<sub>4</sub>. This suggests that water passivates ferrous surfaces and inhibits phosphate ester chemisorption, decomposition, and ultimately film formation. On Fe<sub>3</sub>O<sub>4</sub>(001), thermal decomposition proceeds mainly through C-O cleavage (to form surface alkyl and aryl groups) and C-H cleavage (to form surface hydroxyls). The onset temperature for C-O cleavage on Fe<sub>3</sub>O<sub>4</sub>(001) increases in the order: tertiary alkyl < secondary alkyl < primary linear alkyl ≈ primary branched alkyl < aryl. This order is in agreement with experimental observations for the thermal stability of antiwear additives with similar substituents. The results highlight surface and substituent effects on the thermal decomposition of phosphate esters which should be helpful for the design of new molecules with improved performance.</p>

TO THE QUESTION ABOUT SPECIAL TYPE OF OCCASIONAL WORDS IN RUSSIAN

2019 ◽  
pp. 305-307
Author(s):  
N.N. Zaitseva
Keyword(s):  
Word Formation ◽  
Formation Mechanisms ◽  
Basic Part ◽  
New Words ◽  
Language System ◽  
Informal Conversation ◽  
Mobile Part

The lexical level is the most mobile part of the language system. This mobility is in many respects caused by word-formation mechanisms. In live informal conversation the process of occurrence of new words is continuous and active. The basic part of new words is created according to productive models. The share of occasional ways in word-formation is less. However, it grows, as the occasional way in itself is more expressive and more emphatic. In the work we will pay attention to the words created by means of one of the ways of occasional word-formation.

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