Role of Heat Accumulation by Reaction Loop Initiated by H2O2 Decomposition for Thermal Ignition

Abstract. Maud Rise polynyas (MRPs) form due to deep convection, which is caused by static instabilities of the water column. Recent studies with the Community Earth System Model (CESM) have indicated that a multidecadal varying heat accumulation in the subsurface layer occurs prior to MRP formation due to the heat transport over the Weddell Gyre. In this study, a conceptual MRP box model, forced with CESM data, is used to investigate the role of this subsurface heat accumulation in MRP formation. Cases excluding and including multidecadal varying subsurface heat and salt fluxes are considered, and multiple polynya events are only simulated in the cases where subsurface fluxes are included. The dominant frequency for MRP events in these results, approximately the frequency of the subsurface heat and salt accumulation, is still visible in cases where white noise is added to the freshwater flux. This indicates the importance and dominance of the subsurface heat accumulation in MRP formation.

Download Full-text

Role of heat accumulation in the multi-shot damage of silicon irradiated with femtosecond XUV pulses at a 1 MHz repetition rate

Optics Express ◽

10.1364/oe.24.015468 ◽

2016 ◽

Vol 24 (14) ◽

pp. 15468 ◽

Cited By ~ 10

Author(s):

Ryszard Sobierajski ◽

Iwanna Jacyna ◽

Piotr Dłużewski ◽

Marcin T. Klepka ◽

Dorota Klinger ◽

...

Keyword(s):

Repetition Rate ◽

Heat Accumulation

Download Full-text

Catalytic activity of nanosized Au/CeO2 catalyst towards H2O2 decomposition and the role of cationic/metallic ratio in its activity

European Journal of Chemistry ◽

10.5155/eurjchem.10.4.317-322.1895 ◽

2019 ◽

Vol 10 (4) ◽

pp. 317-322

Author(s):

Ayman Abd El-Moemen

Keyword(s):

Catalytic Activity ◽

Photoelectron Spectroscopy ◽

Catalytic Decomposition ◽

Metallic Gold ◽

Kinetic Measurements ◽

H2o2 Decomposition ◽

Treatment Conditions ◽

Treated Sample ◽

Pre Treatment

The catalytic decomposition of H2O2 on differently pre-treated Au/CeO2 catalyst was studied by kinetic measurements at 20-50 °C. The prepared catalyst was subjected to pre-treatment by heating either in oxidative (10% O2/N2) or inert (pure N2)atmosphere at 400 °C. The different oxidation states of gold were determined by X-ray photoelectron spectroscopy measurements. The Au/CeO2 catalyst exhibited an excellent catalytic activity towards H2O2 decomposition. The catalytic activity of oxygen pre-treated sample was about twice higher than that measured for nitrogen pre-treated sample. This finding ran parallel to the amount of Aun+ as determined by XPS, indicating the role played by Aun+ species as the most active catalyst’s constituent. However, one cannot overlook the role of metallic gold in catalyzing the H2O2, decomposition showing small activity compared to that of cationic gold. The average crystallites size of metallic gold particles was found to be 7±0.5 nm independent of the pre-treatment conditions. The apparent activation energy of the catalyzed reaction was found to be 46.5 and 47.8 kJ/mol for oxygen and nitrogen pre-treatment, respectively.

Download Full-text

Ab initio and transition state theory study of the OH + HO2 → H2O + O2(3Σg−)/O2(1Δg) reactions: yield and role of O2(1Δg) in H2O2 decomposition and in combustion of H2

Physical Chemistry Chemical Physics ◽

10.1039/c7cp05850k ◽

2018 ◽

Vol 20 (6) ◽

pp. 4478-4489 ◽

Cited By ~ 13

Author(s):

M. Monge-Palacios ◽

S. Mani Sarathy

Keyword(s):

Transition State ◽

Ab Initio ◽

Rate Constants ◽

Transition State Theory ◽

Initial Conditions ◽

Branching Ratio ◽

State Theory ◽

H2o2 Decomposition ◽

P Rate

Rate constants for the reactions OH + HO2 → H2O + O2(3Σg−)/O2(1Δg) have been calculated. The branching ratio to O2(1Δg) is small, and thus particular initial conditions are needed for O2(1Δg) to play a role in combustion.

Download Full-text

Multidecadal Polynya Formation in a Conceptual (Box) Model

10.5194/os-2020-63 ◽

2020 ◽

Author(s):

Daan Boot ◽

René M. Van Westen ◽

Henk A. Dijkstra

Keyword(s):

Deep Convection ◽

Subsurface Layer ◽

Dominant Frequency ◽

Box Model ◽

Freshwater Flux ◽

Heat Accumulation ◽

Community Earth System Model ◽

Maud Rise ◽

Static Instability

Abstract. Maud Rise Polynyas (MRPs) form due to deep convection, which is caused by static instability of the water column. Recent studies with the Community Earth System Model (CESM) have indicated that a multidecadal varying heat accumulation in the subsurface layer occurs prior to MRP formation due to the heat transport over the Weddell gyre. In this study, a conceptual MRP box model, forced with CESM data, is used to investigate the role of this subsurface heat accumulation in MRP formation. Cases excluding and including multidecadal varying subsurface heat and salt fluxes are considered and multiple polynya events are only simulated in the cases where subsurface fluxes are included. The dominant frequency for MRP events in these results, approximately the frequency of the subsurface heat and salt accumulation, is still visible in cases where white noise is added to the freshwater flux. This indicates the importance and dominance of the subsurface heat accumulation in MRP formation.

Download Full-text

Role of hydrogen peroxide in the cytotoxicity of the xanthine/xanthine oxidase system

Biochemical Journal ◽

10.1042/bj2490391 ◽

1988 ◽

Vol 249 (2) ◽

pp. 391-399 ◽

Cited By ~ 62

Author(s):

E M Link ◽

P A Riley

Keyword(s):

Hydrogen Peroxide ◽

Xanthine Oxidase ◽

Cytotoxic Effect ◽

Oxidase System ◽

H2o2 Decomposition ◽

Enzymic Reaction ◽

Single Oxygen ◽

Phosphate Buffered Saline

1. The survival of mammalian epithelial cells exposed in vitro to the xanthine/xanthine oxidase system in phosphate-buffered saline (PBS) or serum-containing medium (SCMEM) was investigated. 2. The cytotoxic effect observed depended on the composition of the medium in which the enzymic reaction was carried out; a surviving fraction of 5 x 10(-5) was found for cells exposed in PBS and 5.2 x 10(-1) for those in SCMEM. 3. The cytotoxic product(s) formed by the xanthine/xanthine oxidase system was relatively stable in PBS; survival of cells incubated after completion of the enzymic reaction was always less than that found for cells exposed during the reaction in the same system. 4. Superoxide dismutase or mannitol present during the enzymic reaction did not inhibit the cytotoxic effect. 5. NaN3 (a single-oxygen quencher and a catalase inhibitor) added to the system in SCMEM caused a reduction in survival to the level observed for cells exposed to the enzymic reaction in PBS. 6. Catalase completely protected cells, but no protection was observed when both catalase and NaN3 were present in the reaction mixture. 7. A similar cytotoxic effect was produced when cells were treated with H2O2 alone. 8. The rate of H2O2 decomposition in medium was accelerated by the presence of serum, but this was completely inhibited by NaN3. 9. It is concluded that H2O2 is the major cytotoxic product formed by the xanthine/xanthine oxidase system.

Download Full-text