scholarly journals Experimental Etching of Diamonds: Extrapolation to Impact Diamonds from the Popigai Crater (Russia)

Minerals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1229
Author(s):  
Valeri Sonin ◽  
Egor Zhimulev ◽  
Aleksei Chepurov ◽  
Ivan Gryaznov ◽  
Anatoly Chepurov ◽  
...  
Keyword(s):  
Large Range ◽  
Ambient Pressure ◽  
Inert Gases ◽  
Oxidation States ◽  
Silicate Melts ◽  
Etch Pits ◽  
Diamond Crystals ◽  
Surface Graphitization ◽  
O2 Diffusion ◽  
The Impact

Diamond etching in high-temperature ambient-pressure experiments has been performed aimed to assess possible postimpact effects on diamonds in impact craters, for the case of the Popigai crater in Yakutia (Russia). The experiments with different etchants, including various combinations of silicate melts, air, and inert gases, demonstrated the diversity of microstructures on {111} diamond faces: negative or positive trigons, as well as hexagonal, round, or irregularly shaped etch pits and striation. The surface features obtained after etching experiments with kimberlitic diamonds are similar to those observed on natural impact diamonds with some difference due to the origin of the latter as a result of a martensitic transformation of graphite in target rocks. Extrapolated to natural impact diamonds, the experimental results lead to several inferences: (1) Diamond crystals experienced natural oxidation and surface graphitization during the pressure decrease after the impact event, while the molten target rocks remained at high temperatures. (2) Natural etching of diamonds in silicate melts is possible in a large range of oxidation states controlled by O2 diffusion. (3) Impact diamonds near the surface of molten target rocks oxidized at the highest rates, whereas those within the melt were shielded from the oxidizing agents and remained unchanged.

scholarly journals Experimental and Computational Investigation of binary drop collisions under elevated pressure

2017 ◽  
Author(s):  
Jan Breitenbach ◽  
Louis Maximilian Reitter ◽  
Muyuan Liu ◽  
Kuan-Ling Huang ◽  
Dieter Bothe ◽  
...  
Keyword(s):  
Relative Velocity ◽  
Computational Study ◽  
Ambient Pressure ◽  
Experimental System ◽  
Elevated Pressure ◽  
Computational Investigation ◽  
Ambient Conditions ◽  
Influencing Parameters ◽  
Gas Layer ◽  
The Impact

Spray systems often operate under extreme ambient conditions like high pressure, which can have a significant influence on important spray phenomena. One of these phenomena is binary drop collisions. Such collisions, depending on the relative velocity and the impact parameter (eccentricity of the collision), can lead to drop bouncing, coalescence or breakup. This experimental and computational study is focused on the description of the phenomenon of drop bouncing, which is caused by a thin gas layer preventing the drops coalescence. To identify the main influencing parameters of this phenomenon, experiments on binary drop collisions are performed in a pressure chamber. This experimental system allows us to investigate the effect of an ambient pressure (namely the density and viscosity of the surrounding gas) on the bouncing/coalescence threshold.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4758

Assessing the effects of positive buoyancy on rainbow trout (Oncorhynchus mykiss) held in gas supersaturated water

1990 ◽  
Vol 68 (5) ◽  
pp. 969-973 ◽  
Author(s):  
J. M. Shrimpton ◽  
D. J. Randall ◽  
L. E. Fidler
Keyword(s):  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Ambient Pressure ◽  
Large Change ◽  
Bladder Volume ◽  
Bladder Pressure ◽  
Small Fish ◽  
Swim Bladder ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
The Impact

We examined the effects of swim bladder overinflation associated with dissolved gas supersaturation on rainbow trout (Oncorhynchus mykiss). The change in swim bladder volume with increased swim bladder pressure was measured in fish subjected to a decrease in ambient pressure. An expansion of swim bladder volume occurs that is related to the excess swim bladder pressure. The volume change results in a decrease in density and positive buoyancy in the fish. Small fish are adversely affected when exposed to gas supersaturated water because of the high swim bladder pressure required to force gas out the pneumatic duct. Changes in behaviour and depth distribution of fish held in gas supersaturated water were measured in a 2 m deep observation column. A large change in density caused small fish to increase depth and compensate for the swim bladder expansion. Although swim bladder inflation occurs for all sizes of trout held in gas supersaturated water, the impact is greatest for small fish and they must compensate by seeking depth. However, adequate depth to compensate for positive buoyancy may not always exist. In such a case, fish must swim continuously in a head down position to overcome excess buoyancy. The power necessary for a fish to swim with an overinflated swim bladder is greatest for small fish that show the largest change in density.

scholarly journals Short- and long-term effects of diving on pulmonary function

2017 ◽  
Vol 26 (143) ◽  
pp. 160097 ◽  
Author(s):  
Kay Tetzlaff ◽  
Paul S. Thomas
Keyword(s):  
Lung Function ◽  
Pulmonary Function ◽  
Ambient Pressure ◽  
Small Airways ◽  
Long Term Effects ◽  
Cold Temperatures ◽  
Factors Associated ◽  
Stress Changes ◽  
The Impact

The diving environment provides a challenge to the lung, including exposure to high ambient pressure, altered gas characteristics and cardiovascular effects on the pulmonary circulation. Several factors associated with diving affect pulmonary function acutely and can potentially cause prolonged effects that may accumulate gradually with repeated diving exposure. Evidence from experimental deep dives and longitudinal studies suggests long-term adverse effects of diving on the lungs in commercial deep divers, such as the development of small airways disease and accelerated loss of lung function. In addition, there is an accumulating body of evidence that diving with self-contained underwater breathing apparatus (scuba) may not be associated with deleterious effects on pulmonary function. Although changes in pulmonary function after single scuba dives have been found to be associated with immersion, ambient cold temperatures and decompression stress, changes in lung function were small and suggest a low likelihood of clinical significance. Recent evidence points to no accelerated loss of lung function in military or recreational scuba divers over time. Thus, the impact of diving on pulmonary function largely depends on factors associated with the individual diving exposure. However, in susceptible subjects clinically relevant worsening of lung function may occur even after single shallow-water scuba dives.

Intramicroparticle nitrogen dioxide is a bubble nucleation site leading to decompression-induced neutrophil activation and vascular injury

2013 ◽  
Vol 114 (5) ◽  
pp. 550-558 ◽  
Author(s):  
Stephen R. Thom ◽  
Ming Yang ◽  
Veena M. Bhopale ◽  
Tatyana N. Milovanova ◽  
Marina Bogush ◽  
...  
Keyword(s):  
Nitrogen Dioxide ◽  
Ex Vivo ◽  
Ambient Pressure ◽  
Annexin V ◽  
Nucleation Site ◽  
Bubble Nucleation ◽  
Neutrophil Activation ◽  
Inert Gases ◽  
Wild Type ◽  
Inos Inhibitor

Inert gases diffuse into tissues in proportion to ambient pressure, and when pressure is reduced, gas efflux forms bubbles due to the presence of gas cavitation nuclei that are predicted based on theory but have never been characterized. Decompression stress triggers elevations in number and diameter of circulating annexin V-coated microparticles (MPs) derived from vascular cells. Here we show that ∼10% MPs from wild-type (WT) but not inflammatory nitric oxide synthase-2 (iNOS) knockout (KO) mice increase in size when exposed to elevated air pressure ex vivo. This response is abrogated by a preceding exposure to hydrostatic pressure, demonstrating the presence of a preformed gas phase. These MPs have lower density than most particles, 10-fold enrichment in iNOS, and generate commensurately more reactive nitrogen species (RNS). Surprisingly, RNS only slowly diffuse from within MPs unless particles are subjected to osmotic stress or membrane cholesterol is removed. WT mice treated with iNOS inhibitor and KO mice exhibit less decompression-induced neutrophil activation and vascular leak. Contrary to injecting naïve mice with MPs from wild-type decompressed mice, injecting KO MPs triggers fewer proinflammatory events. We conclude that nitrogen dioxide is a nascent gas nucleation site synthesized in some MPs and is responsible for initiating postdecompression inflammatory injuries.

scholarly journals The Dissolution Dilemma for low Pt Loading Polymer Electrolyte Membrane Fuel Cell Catalysts

2020 ◽  
Author(s):  
Daniel John Seale Sandbeck ◽  
Niklas Mørch Secher ◽  
Masanori Inaba ◽  
Jonathan Quinson ◽  
Jakob Ejler Sørensen ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Polymer Electrolyte ◽  
Inductively Coupled Plasma ◽  
Polymer Electrolyte Membrane ◽  
Oxidation States ◽  
Metal Loading ◽  
Electrolyte Membrane ◽  
On Line ◽  
Low Pt Loading ◽  
The Impact

Cost and lifetime currently hinder widespread commercialization of polymer electrolyte<br>membrane fuel cells (PEMFCs). Reduced electrode Pt loadings lower costs; however, the impact<br>of metal loading (on the support) and its relation to degradation (lifetime) remain unclear. The<br>limited research on these parameters stems from synthetic difficulties and lack of in situ<br>analytics. This study addresses these challenges by synthesizing 2D and 3D Pt/C model catalyst<br>systems via two precise routes and systematically varying the loading. Pt dissolution was<br>monitored using on-line inductively coupled plasma mass spectrometry (on-line-ICP-MS), while<br>X-ray spectroscopy techniques were applied to establish the oxidation states of Pt in correlation<br>with metal loading. Dissolution trends emerge which can be explained by three particle<br>proximity dependent mechanisms: (1) shifts in the Nernst dissolution potential, (2) redeposition,<br>and (3) alteration of Pt oxidation states. These results identify engineering limitations, which<br>should be considered by researchers in fuel cell development and related fields. <br>

In Situ Characterization of Ceria Oxidation States in High-Temperature Electrochemical Cells with Ambient Pressure XPS

2010 ◽  
Vol 114 (46) ◽  
pp. 19853-19861 ◽  
Author(s):  
Steven C. DeCaluwe ◽  
Michael E. Grass ◽  
Chunjuan Zhang ◽  
Farid El Gabaly ◽  
Hendrik Bluhm ◽  
...  
Keyword(s):  
High Temperature ◽  
Ambient Pressure ◽  
Oxidation States ◽  
Electrochemical Cells ◽  
In Situ Characterization ◽  
Ambient Pressure Xps

The chemical nature of ion-bombarded carbon: a photoelectron spectroscopic study of 'cleaned’ surfaces of diamond and graphite

1977 ◽  
Vol 353 (1672) ◽  
pp. 103-120 ◽  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Ion Bombardment ◽  
Spectroscopic Studies ◽  
Oxygen Species ◽  
Diamond Crystals ◽  
Before And After ◽  
Surface Graphitization ◽  
Carbon Surfaces ◽  
Fe Ions ◽  
Comparative Electron

The effects of ion-bombardment on single-crystal carbon surfaces have been studied by X-ray photoelectron spectroscopy (X. p. s.) partly to establish whether, as previously suggested, the bombardment of diamond leads to surface graphitization. Changes in the x. p. s. of graphite were monitored as a function of exposure to both Ar and 57 Fe ions; and the chemical natures of ion-bombarded diamond and graphite were examined in comparative electron spectroscopic studies of their uptakes of various oxygen species. X. p. s. revealed significant differences between Ar-ion bombarded diamond and graphite both in their C 1s spectra (which also differed significantly from that of cleaved graphite) and in the 2p binding energy of the embedded argon. The C 1s spectra of the 57 Fe implanted graphite specimens (10 15 -10 16 cm -2 , 12.5-85 kV) were identical with those of Ar-ion bombarded graphite, although the Fe was buried beneath the X. p. s. sampling depth. These results show that ion bombardment produces partially disordered but nevertheless structurally distinct surface phases on graphite and diamond crystals. The bombarded surfaces were rather unreactive to O 2 taking up only a small fraction of a monolayer, although exposure to oxygen (or, more effectively, nitric oxide) excited by a microwave discharge resulted in the uptake of several monolayer equivalents of oxygen. Embedded Ar was only very slowly lost during oxidation, confirming the expected low erosion rate under the conditions used. The O 1s X. p. s. from the two substrates showed significant differences although the rates of uptake of oxygen were closely similar. The O 1s peaks were broad, indicating the presence of a minimum of two major oxygen species. Our results, taken in conjunction with others, suggest that >C=O and —>C—O—C<— surface groups were probably present in roughly equal concentrations on the oxygenated carbon surfaces. He ǀ and He ǁ spectra of Ar-ion bombarded diamond obtained before and after oxidation are also intelligible on this basis.

scholarly journals Structure and magnetism of the A site scandium perovskite (Sc 0.94 Mn 0.06 )Mn 0.65 Ni 0.35 O 3 synthesized at high pressure

2014 ◽  
Vol 372 (2013) ◽  
pp. 20130012 ◽  
Author(s):  
Chris I. Thomas ◽  
Matthew R. Suchomel ◽  
Giap V. Duong ◽  
Andrew M. Fogg ◽  
John B. Claridge ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Room Temperature ◽  
Magnetic Measurements ◽  
Ambient Pressure ◽  
Oxidation States ◽  
Formula Unit ◽  
Triclinic Structure ◽  
Bond Valence Sum ◽  
A Site

Scandium perovskite (Sc 0.94 Mn 0.06 )Mn 0.65 Ni 0.35 O 3 , synthesized at high pressure and high temperature, has a triclinic structure (space group ) at room temperature and ambient pressure with a √2 a p ×√2 a p ×2 a p structure with α ≈90 ° , β ≈89 ° , γ ≈90 ° . Magnetic measurements show that the material displays Curie–Weiss behaviour above 50 K with C =2.11 emu K mol −1 ( μ eff =4.11 μ B per formula unit) and θ =−95.27 K. Bond valence sum analysis of the crystal structure shows that manganese is present in three different oxidation states (+2, +3, +4), with the +2 oxidation state on the A site resulting in a highly tilted perovskite structure (average tilt 21.2 ° compared with 15.7 ° calculated for LaCaMnNbO 6 ), giving the formula .

IMPACTS OF AMBIENT TEMPERATURE AND PRESSURE ON PM2.5 EMISSION PROFILES OF LIGHT-DUTY DIESEL VEHICLES

2012 ◽  
Vol 11 (06) ◽  
pp. 1240037
Author(s):  
CHENYU WANG ◽  
YE WU ◽  
ZHENHUA LI ◽  
JIMING HAO
Keyword(s):  
Ambient Temperature ◽  
Size Distribution ◽  
Ambient Pressure ◽  
Passenger Cars ◽  
Test Range ◽  
Diesel Vehicles ◽  
Light Duty ◽  
Mass Size ◽  
Temperature And Pressure ◽  
The Impact

The impact of the environmental factors on the emissions of particulate matter (PM) number, size distribution and mass size distribution from diesel passenger cars was evaluated. Particle measurements from five modern light-duty diesel vehicles (LDDV) were performed in June and November 2011. Commercial low sulfur diesel fuel (less than 50 ppm) was used during the testing of these vehicles which were not equipped with after-treatment devices. The dynamometer test was based on the Economic Commission of Europe (ECE) 15 cycles. The results indicate that PM2.5 emissions from LDDV are significantly affected by ambient temperature and pressure. A comparison of the emissions concentration of PM2.5 in these two different months showed that the number concentration in June was (3.8 ± 0.69) × 107 cm-3 and (2.5 ± 0.66) × 107 cm-3 in November. The PM concentration of about 30 nm diameter was 25 ± 6% of the total emissions in November while only 14 ± 3% of total emissions in June. In the 60 nm to 2.5 μm test range, November data shows less of a contribution for number than data from June testing. The concentration of mass emissions in June was (325 ± 44) mg/m3 and (92 ± 30) mg/m3 in November. The contribution of the number of PM particles in November testing is lower than testing in June by 34% and the mass concentration in November is 70% lower than that in June. With the decrease of ambient temperature and the increase of ambient pressure, both the oxygen concentration in cylinder and air–fuel ratio are increased, which caused lower particle number and mass emissions during November testing. The size distribution is also altered by these changes: the more efficient in-cylinder combustion resulted in a higher proportion of particles in the 30 nm and smaller range than for other particle sizes.

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