scholarly journals Evidence for different behaviors of atmospheric glass alteration as a function of glass composition

2020 ◽  
Vol 4 (1) ◽  
Author(s):  
Fanny Alloteau ◽  
Odile Majérus ◽  
Valentina Valbi ◽  
Isabelle Biron ◽  
Patrice Lehuédé ◽  
...  
Keyword(s):  
Glass Composition ◽  
Significant Proportion ◽  
Accelerated Ageing ◽  
Atmospheric Conditions ◽  
Experimental Conditions ◽  
Hydrated Layer ◽  
Stable Glass ◽  
Network Of Hydrogen Bonds ◽  
Ageing Period ◽  
Glass Compositions

AbstractThe glass composition is a determining parameter that influences the glass chemical durability, particularly in atmospheric conditions (defined by the relative humidity, RH, < 100%). This is obvious in the field of the cultural heritage (CH), where some glass compositions qualified as unstable show advanced signs of degradation under atmosphere, while others seem, on the contrary, stable. This study investigates the differences between stable and unstable glass compositions regarding the phenomenology of the atmospheric glass alteration, by means of accelerated ageing of three glass replicas followed by the characterization of their alteration layers at different scales. Over the same ageing period and experimental conditions, the two glass compositions qualified as unstable develop thick hydrated layers and a thin top layer of carbonate precipitates. Their hydrated layers are depolymerized, and they remarkably retain alkalis and non-bridging oxygens in a dense network of hydrogen bonds, as demonstrated by 29Si and 1H MAS NMR. On the contrary, the stable glass composition shows a considerably thinner hydrated layer and, relatively, a higher amount of carbonates on the surface. In unstable glasses, the retention of a significant proportion of alkalis and NBOs, probably by maintaining a basic character to the hydrated layer, seems comparatively a destabilizing factor sustaining hydration by fast network hydrolysis.

scholarly journals Obsidian pyroclasts in the Yellowstone-Snake River Plain ignimbrites are dominantly juvenile in origin

2021 ◽  
Vol 83 (4) ◽  
Author(s):  
L. R. Monnereau ◽  
B. S. Ellis ◽  
D. Szymanowski ◽  
O. Bachmann ◽  
M. Guillong
Keyword(s):  
Glass Composition ◽  
Snake River Plain ◽  
Explosive Eruptions ◽  
Snake River ◽  
Pyroclastic Deposits ◽  
Volcanic Conduit ◽  
Trace Elemental ◽  
Multiple Cycles ◽  
River Plain ◽  
Glass Compositions

AbstractDense, glassy pyroclasts found in products of explosive eruptions are commonly employed to investigate volcanic conduit processes through measurement of their volatile inventories. This approach rests upon the tacit assumption that the obsidian clasts are juvenile, that is, genetically related to the erupting magma. Pyroclastic deposits within the Yellowstone-Snake River Plain province almost without exception contain dense, glassy clasts, previously interpreted as hyaloclastite, while other lithologies, including crystallised rhyolite, are extremely rare. We investigate the origin of these dense, glassy clasts from a coupled geochemical and textural perspective combining literature data and case studies from Cougar Point Tuff XIII, Wolverine Creek Tuff, and Mesa Falls Tuff spanning 10 My of silicic volcanism. These results indicate that the trace elemental compositions of the dense glasses mostly overlap with the vesiculated component of each deposit, while being distinct from nearby units, thus indicating that dense glasses are juvenile. Textural complexity of the dense clasts varies across our examples. Cougar Point Tuff XIII contains a remarkable diversity of clast appearances with the same glass composition including obsidian-within-obsidian clasts. Mesa Falls Tuff contains clasts with the same glass compositions but with stark variations in phenocryst content (0 to 45%). Cumulatively, our results support a model where most dense, glassy clasts reflect conduit material that passed through multiple cycles of fracturing and sintering with concurrent mixing of glass and various crystal components. This is in contrast to previous interpretations of these clasts as entrained hyaloclastite and relaxes the requirement for water-magma interaction within the eruptive centres of the Yellowstone-Snake River Plain province.

scholarly journals Temperature uniformity in the CERN CLOUD chamber

2017 ◽  
Vol 10 (12) ◽  
pp. 5075-5088 ◽  
Author(s):  
António Dias ◽  
Sebastian Ehrhart ◽  
Alexander Vogel ◽  
Christina Williamson ◽  
João Almeida ◽  
...  
Keyword(s):  
Steady State ◽  
Air Temperature ◽  
Elevated Temperatures ◽  
Trace Gases ◽  
Vertical Direction ◽  
Cloud Chamber ◽  
Temperature Uniformity ◽  
Atmospheric Conditions ◽  
Cloud Droplets ◽  
Experimental Conditions

Abstract. The CLOUD (Cosmics Leaving OUtdoor Droplets) experiment at CERN (European Council for Nuclear Research) investigates the nucleation and growth of aerosol particles under atmospheric conditions and their activation into cloud droplets. A key feature of the CLOUD experiment is precise control of the experimental parameters. Temperature uniformity and stability in the chamber are important since many of the processes under study are sensitive to temperature and also to contaminants that can be released from the stainless steel walls by upward temperature fluctuations. The air enclosed within the 26 m3 CLOUD chamber is equipped with several arrays (strings) of high precision, fast-response thermometers to measure its temperature. Here we present a study of the air temperature uniformity inside the CLOUD chamber under various experimental conditions. Measurements were performed under calibration conditions and run conditions, which are distinguished by the flow rate of fresh air and trace gases entering the chamber at 20 and up to 210 L min−1, respectively. During steady-state calibration runs between −70 and +20 °C, the air temperature uniformity is better than ±0.06 °C in the radial direction and ±0.1 °C in the vertical direction. Larger non-uniformities are present during experimental runs, depending on the temperature control of the make-up air and trace gases (since some trace gases require elevated temperatures until injection into the chamber). The temperature stability is ±0.04 °C over periods of several hours during either calibration or steady-state run conditions. During rapid adiabatic expansions to activate cloud droplets and ice particles, the chamber walls are up to 10 °C warmer than the enclosed air. This results in temperature differences of ±1.5 °C in the vertical direction and ±1 °C in the horizontal direction, while the air returns to its equilibrium temperature with a time constant of about 200 s.

scholarly journals Laboratory study on new particle formation from the reaction OH + SO<sub>2</sub>: influence of experimental conditions, H<sub>2</sub>O vapour, NH<sub>3</sub> and the amine tert-butylamine on the overall process

2010 ◽  
Vol 10 (3) ◽  
pp. 6447-6484 ◽  
Author(s):  
T. Berndt ◽  
F. Stratmann ◽  
M. Sipilä ◽  
J. Vanhanen ◽  
T. Petäjä ◽  
...  
Keyword(s):  
Relative Humidity ◽  
High Sensitivity ◽  
Particle Growth ◽  
Counting Efficiency ◽  
Oh Radicals ◽  
Atmospheric Conditions ◽  
Promoting Effect ◽  
Experimental Conditions ◽  
H2so4 Concentration ◽  
Tert Butylamine

Abstract. Nucleation experiments starting from the reaction of OH radicals with SO2 have been performed in the IfT-LFT flow tube under atmospheric conditions at 293±0.5 K for a relative humidity of 13–61%. The presence of different additives (H2, CO, 1,3,5-trimethylbenzene) for adjusting the OH radical concentration and resulting OH levels in the range (4–300)·105 molecule cm−3 did not influence the nucleation process itself. The number of detected particles as well as the threshold H2SO4 concentration needed for nucleation was found to be strongly dependent on the counting efficiency of the used counting devices. High-sensitivity particle counters allowed the measurement of freshly nucleated particles with diameters down to about 1.5 nm. A parameterization of the experimental data was developed using power law equations for H2SO4 and H2O vapour. The exponent for H2SO4 from different measurement series was in the range of 1.7–2.1 being in good agreement with those arising from analysis of nucleation events in the atmosphere. For increasing relative humidity, an increase of the particle number was observed. The exponent for H2O vapour was found to be 3.1 representing a first estimate. Addition of 1.2·1011 molecule cm−3 or 1.2·1012 molecule cm−3 of NH3 (range of atmospheric NH3 peak concentrations) revealed that NH3 has a measureable, promoting effect on the nucleation rate under these conditions. The promoting effect was found to be more pronounced for relatively dry conditions. NH3 showed a contribution to particle growth. Adding the amine tert-butylamine instead of NH3, the enhancing impact for nucleation and particle growth appears to be stronger.

scholarly journals Laser filament-induced aerosol formation

2013 ◽  
Vol 13 (9) ◽  
pp. 4593-4604 ◽  
Author(s):  
H. Saathoff ◽  
S. Henin ◽  
K. Stelmaszczyk ◽  
M. Petrarca ◽  
R. Delagrange ◽  
...  
Keyword(s):  
Particle Production ◽  
Ambient Air ◽  
Particle Formation ◽  
Oxygen Mixture ◽  
Atmospheric Conditions ◽  
Aerosol Formation ◽  
Experimental Conditions ◽  
Particle Yield ◽  
The Given ◽  
Terawatt Laser

Abstract. Using the aerosol and cloud simulation chamber AIDA, we investigated the laser filament induced particle formation in ambient air, humid synthetic air, humid nitrogen, argon–oxygen mixture, and pure argon in order to simulate the particle formation under realistic atmospheric conditions as well as to investigate the influence of typical gas-phase atmospheric constituents on the particle formation. Terawatt laser plasma filaments generated new particles in the size range 3 to 130 nm with particle production rates ranging from 1 × 107 to 5 × 109 cm−3 plasma s−1 for the given experimental conditions. In all cases the particle formation rates increased exponentially with the water content of the gas mixture. Furthermore, the presence of a few ppb of trace gases like SO2 and α-pinene clearly enhanced the particle yield by number, the latter also by mass. Our findings suggest that new particle formation is efficiently supported by oxidized species like acids generated by the photoionization of both major and minor components of the air, including N2, NH3, SO2 and organics.

The Threshold for Sudden Changes in the Velocity of a Seen Object

1950 ◽  
Vol 2 (1) ◽  
pp. 33-41 ◽  
Author(s):  
W. E. Hick
Keyword(s):  
Initial Velocity ◽  
Moving Objects ◽  
Significant Proportion ◽  
Difference Threshold ◽  
Experimental Conditions ◽  
Velocity Change ◽  
The Mean ◽  
The Difference ◽  
Velocity Changes ◽  
Method Of Constant Stimuli

The difference threshold for the velocity of a seen object was measured by the method of constant stimuli, using two categories. An approximate correspondence with Weber's law was found, the divergence from it appearing, in general, as an increase of the threshold at both ends of the range of initial velocities. The Mean Threshold (0·5 probability of perception, corrected for guessing) was, in favourable conditions, about 12 per cent, of the initial velocity. Whether the stimulus was an increase or a decrease of velocity made no marked difference. With two moving objects, which converged, crossed, and then diverged, both suffering the same change of velocity, the threshold was higher. Velocity changes as low as 2 · 5 per cent, elicited a significant proportion of correct responses. Some theoretical points in connection with this are discussed. Responses to blank stimuli showed a strong tendency to guess “slower,” which tendency differed significantly in degree between most of the experimental conditions. Tests with reduced exposure times showed that exposures could be as short as 0 · 5 second (the velocity change occurring in the middle of the exposure) without appreciable detriment.

Trace Detection of Nitrocompounds by ArF Laser Photofragmentation/Ionization Spectrometry

1993 ◽  
Vol 47 (11) ◽  
pp. 1907-1912 ◽  
Author(s):  
Josef B. Simeonsson ◽  
George W. Lemire ◽  
Rosario C. Sausa
Keyword(s):  
Ground State ◽  
Multiphoton Ionization ◽  
Ionization Mass ◽  
Trace Detection ◽  
Atmospheric Conditions ◽  
Experimental Conditions ◽  
Detection Range ◽  
Arf Laser ◽  
Free Environment ◽  
193 Nm

A new method for detecting trace vapors of NO2-containing compounds near atmospheric conditions has been demonstrated with the use of one-color-laser photofragmentation/ionization spectrometry. An ArF laser is employed to both photolytically fragment the target molecules in a collision-free environment and ionize the characteristic NO fragments. The production of NO is hypothesized to result from a combination of two NO2 unimolecular fragmentation pathways, one yielding NO in its X2II electronic ground state and the other in its A2Σ+ excited state. Ionization of ground-state NO molecules is accomplished by resonance-enhanced multiphoton ionization processes via its A2Σ+ ← X2II (3, 0), B2II ← X2II (7, 0) and/or D2Σ+ ← X2II (0, 1) bands at 193 nm. The analytical utility of this method is demonstrated in a molecular beam time-of-flight apparatus. Limits of detection range from the parts-per-million (ppm) to parts-per-billion (ppb) level for NO, NO2, CH3NO2, dimethylnitramine (DMNA), ortho- and meta-nitrotoluene, nitrobenzene, and trinitrotoluene (TNT). Under effusive beam experimental conditions, discrimination between structural isomers, ortho-nitrotoluene and meta-nitrotoluene, has been demonstrated with the use of their characteristic photofragmentation/ionization mass spectra.

Influence of body weight, swimming characteristics, and water temperature on the cost of swimming in brook trout (Salvelinus fontinalis)

2000 ◽  
Vol 57 (7) ◽  
pp. 1482-1488 ◽  
Author(s):  
Ming Tang ◽  
Daniel Boisclair ◽  
Chantal Ménard ◽  
John A Downing
Keyword(s):  
Experimental Data ◽  
Water Temperature ◽  
Brook Trout ◽  
Salvelinus Fontinalis ◽  
Significant Proportion ◽  
Average Difference ◽  
Fish Swimming ◽  
Experimental Conditions ◽  
Fish Weight ◽  
The Cost

We performed respirometry experiments to estimate the spontaneous swimming costs of brook trout (Salvelinus fontinalis) for 24 combinations of fish weight (3.5, 17, and 32 g), water temperature (4, 12, and 18°C), and respirometer size (27, 54, and 108 L). Fish swimming characteristics were estimated for each experiment using videocamera recordings and image analysis. Under our experimental conditions, average swimming characteristics of fish, such as swimming speed and turning and acceleration rates, varied from 2.5- to 29-fold. Our data, alone or combined with similar published results on brook trout weighing 1 g, indicated that fish weight was the only variable that could explain a statistically significant proportion of the variations of spontaneous swimming costs for that species (r2 = 0.91). Our work confirms, with a wider range of experimental data, that spontaneous swimming costs of fish are 3- to 22-fold (8-fold average difference) more energy demanding than predicted by forced swimming models developed using fish swimming at constant speeds and directions in flumes.

scholarly journals Environmental effects on arsenosugars and arsenolipids in Ectocarpus (Phaeophyta)

2016 ◽  
Vol 13 (1) ◽  
pp. 21 ◽  
Author(s):  
Ásta H. Pétursdóttir ◽  
Kyle Fletcher ◽  
Helga Gunnlaugsdóttir ◽  
Eva Krupp ◽  
Frithjof C. Küpper ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Mass Spectrometry ◽  
Inductively Coupled Plasma ◽  
High Performance ◽  
Natural Habitat ◽  
Significant Proportion ◽  
Stress Factors ◽  
Experimental Conditions ◽  
Inductively Coupled ◽  
Plasma Mass Spectrometry

Environmental context Arsenolipids, which are present in seaweed, can show high toxicity, emphasising the need for more information on these compounds. We investigated the effects of different stress factors on the arsenic compounds formed by cultures of brown algae, and compared the results with those from field-collected samples. We show that the arsenolipid and arsenosugar profiles differ depending on the experimental conditions, and that a deficiency in phosphate has a direct positive effect on the biosynthesis of arsenic-containing phospholipids. Abstract Seaweeds have recently been shown to contain a significant proportion of arsenic in the form of arsenolipids (AsLp). Three strains of the filamentous brown alga Ectocarpus species were grown in the laboratory with different simulations of environmental stress: control conditions (1/2 Provasoli-enriched seawater), low nitrate (30% of the amount of nitrates in the control), low phosphate (30% of the amount of phosphate in the control) and under oxidative stress levels (2mM H2O2). Generally, the major AsLp was an arsenic-containing hydrocarbon, AsHC360 (50–80%), but additionally, several arsenic-containing phospholipids (AsPL) were identified and quantified using high-performance liquid chromatography–inductively coupled plasma mass spectrometry and electrospray ionisation mass spectrometry (HPLC-ICP-MS/ESI-MS). The AsLps in cultures were compared with AsLps in Ectocarpus found in its natural habitat as well as with other brown filamentous algae. The AsLp and arsenosugar profiles differed depending on the experimental conditions. Under low phosphate conditions, a significant reduction of phosphorus-containing arsenosugars was noticed, and a significant increase of phosphate-containing AsLps was found when compared with the controls. Strains grown under oxidative stress showed a significant increase in AsLps as well as clear physiological changes.

scholarly journals Characterisation and Properties of Lithium Disilicate Glass Ceramics in the SiO2-Li2O-K2O-Al2O3System for Dental Applications

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Naruporn Monmaturapoj ◽  
Pornchanok Lawita ◽  
Witoon Thepsuwan
Keyword(s):  
Glass Composition ◽  
Glass Ceramics ◽  
Lithium Disilicate ◽  
Nucleating Agents ◽  
Fine Grained ◽  
Melting Glass ◽  
Heterogenous Nucleation ◽  
Dental Applications ◽  
Slight Amount ◽  
Glass Compositions

This work proposes four different glass formulas derived from the SiO2-Li2O-K2O-Al2O3system to investigate the effect of glass composition on their crystal formations and properties. Glass LD1 was SiO2-Li2O-K2O-Al2O3system with the addition of P2O5and CaF2as nucleating agents. In Glass LD2, a slight amount of MgO was mixed in order to increase the viscosity of the melting glass. Finally, the important factor of Si : Li ratio was increased in Glasses LD3 and LD4 with compositions otherwise the same as LD1 and LD2. The results found that P2O5and CaF2served as a nucleating site for lithium phosphate and fluorapatite to encourage heterogenous nucleation and produce a fine-grained interlocking microstructure of lithium disilicate glass ceramics. MgO content in this system seemed to increase the viscosity of the melting glass and thermal expansion coefficient including the chemical solubility. Increasing the Si : Li ratio in glass compositions resulted in the change of the microstructure of Li2Si2O5crystals.

Structural Properties of Strontium Vanadate Glasses

2000 ◽  
Vol 15 (4) ◽  
pp. 995-999 ◽  
Author(s):  
S. Sen ◽  
A. Ghosh
Keyword(s):  
Single Phase ◽  
Glass Composition ◽  
Charge Carriers ◽  
Resonance Structure ◽  
Oxide Content ◽  
X Ray ◽  
Spin Resonance ◽  
Component Line ◽  
Vanadate Glasses ◽  
Glass Compositions

Structural studies of the strontium vanadate glasses of compositions xV2O5–(100 − x)SrO are reported. X-ray diffractograms, density, and oxygen molar volume, etc., of the glasses show that single-phase and homogeneous glasses were obtained in the composition domain x = 50 to 90 mol%. The network structure for the glass compositions with 90 and 80 mol% V2O5 is built up of the VO5 polyhedra, while the other glass compositions consist of the VO4 polyhedra. Density and glass transition temperature are observed to decrease with an increase in the V2O5 content. The magnetic susceptibility of the glasses shows an increase of concentration of the reduced V4+ ion with the increase of vanadium oxide content in the compositions. The well-resolved electron spin resonance structure observed for the glass composition with 50 mol% V2O5 gradually becomes poor and reduces to a single component line, which has been attributed to the increase of the hopping rate of charge carriers with the increase of the V2O5 content in the compositions.

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