scholarly journals Unable to distinguish between hydroxyl radicals from water ice and hydroxyl groups from methanol using lunar spectral detection--- A problem of sufficient urgency and significance

2020 ◽  
Author(s):  
Tianxi Sun
Keyword(s):  
Hydroxyl Radicals ◽  
Hydroxyl Groups ◽  
Water Ice ◽  
Spectral Detection

scholarly journals Is There Water Ice in the Lunar Polar Craters?

2020 ◽  
Author(s):  
Tianxi Sun
Keyword(s):  
Solar Wind ◽  
Solid State ◽  
Hydroxyl Radicals ◽  
Low Temperatures ◽  
Hydroxyl Groups ◽  
The Moon ◽  
Water Ice ◽  
Spectral Identity ◽  
The One

This literature review found that it is doubtful that there is water ice in the polar craters on the Moon. In the course of this review, the following findings were found: (1) The absorption strength of hydroxyl radicals and hydroxyl groups are all 2.9μm, so it is easy to confuse hydroxyl radicals and hydroxyl groups when interpreting M3 spectra data. I do not doubt the ability of LCROSS to detect OH from water, but only suspect that LCROSS is unable to distinguish between hydroxyl radicals from water ice and hydroxyl groups from Moon's methanol due to ignore their spectral identity; (2) The water brought by comets and asteroids and the one caused by solar wind has been exhausted by reacts with the widespread methanol on the Moon in the presence of Pt/α-MoC or Pt/C catalysts. These reacts form large amount of hydrogen, thus clarifying a question NASA raised that "Scientists have long speculated about the source of vast quantities of hydrogen that have been observed at the lunar poles"; (3) The vast quantities of hydrogen in lunar polar craters at extremely low temperatures might be in liquid or solid state now, easy to confuse with water ice. It seems that all our previous misconceptions about water ice in the lunar polar craters might be due to the neglect of the widespread chemical role of lunar methanol. It is necessary to conduct in-depth research in this field in the future.

Investigating the relationship between ozone and water-ice in the martian atmosphere

2020 ◽  
Author(s):  
Megan Brown ◽  
Manish Patel ◽  
Stephen Lewis ◽  
Amel Bennaceur
Keyword(s):  
Carbon Dioxide ◽  
Water Vapour ◽  
Hydroxyl Radicals ◽  
Atmospheric Chemistry ◽  
Martian Atmosphere ◽  
Reaction Rates ◽  
Chemical Processes ◽  
Ice Clouds ◽  
Water Ice ◽  
The Relationship

<p>This project maps ozone and ice-water clouds detected in the martian atmosphere to assess the atmospheric chemistry between ozone, water-ice and hydroxyl radicals. Hydroxyl photochemistry may be indicated by a non-negative or fluctuating correlation between ozone and water-ice. This will contribute to understanding the stability of carbon dioxide and atmospheric chemistry of Mars.</p><p>Ozone (O<sub>3</sub>) can be used for tracking general circulation of the martian atmosphere and other trace chemicals, as well as acting as a proxy for water vapour. The photochemical break down of water vapour produces hydroxyl radicals known to participate in the destruction of ozone. The relationship between water vapour and ozone is therefore negatively correlated. Atmospheric water-ice concentrations may also follow this theory. The photochemical reactions between ozone, water-ice clouds and hydroxyl radicals are poorly understood in the martian atmosphere due to the short half-life and rapid reaction rates of hydroxyl radicals. These reactions destroy ozone, as well as indirectly contributing to the water cycle and stability of carbon dioxide (measured by the CO<sub>2</sub>–CO ratio). However, the detection of ozone in the presence of water-ice clouds suggests the relationship between them is not always anti-correlated. Global climate models (GCMs) struggle to describe the chemical processes occurring within water-ice clouds. For example, the heterogeneous photochemistry described in the LMD (Laboratoire de Météorologie Dynamique) GCM did not significantly improve the model. This leads to the following questions:<em> what is the relationship between water-ice clouds and ozone, and can the chemical reactions of hydroxyl radicals occurring within water-ice clouds be determined through this relationship?</em></p><p>This project aims to address these questions using nadir and occultation retrievals of ozone and water-ice clouds, potentially using retrievals from the UVIS instrument aboard NOMAD (Nadir and Occultation for Mars Discovery), ExoMars Trace Gas Orbiter. Analysis will include temporal and spatial binning of data to help identify any patterns present. Correlation tests will be conducted to determine the significance of any relationship at short term and seasonal scales along a range of zonally averaged latitude photochemical model from the LMD-UK GCM will be used to further explore the chemical processes.</p><p>Interactions between hydroxyl radicals and the surface of water-ice clouds are poorly understood. Ozone abundance is greatest in the winter at the polar regions, which also coincides with the appearance of the polar hood clouds. The use of nadir observations will enable the comparison between total column of ozone abundance at high latitudes (>60°S) in a range of varying water-ice cloud opacities, as well as the equatorial region (30°S – 30°N) during aphelion. Water-ice clouds may remove hydroxyl radicals responsible for the destruction of ozone and thus the previously assumed anticorrelation between ozone and water-ice will not hold. The project will therefore assess the hypothesis that: <em>water-ice clouds may act as a sink for hydroxyl radicals.</em></p>

Solvation and ionization of hydroxyl groups in water–ice layers on silver (110)

1999 ◽  
Vol 425 (2-3) ◽  
pp. 233-244 ◽  
Author(s):  
D.S.-W Lim ◽  
E.M Stuve
Keyword(s):  
Hydroxyl Groups ◽  
Water Ice

scholarly journals Study on the cleavage of alkyl-O-aryl bonds by in situ generated hydroxyl radicals on an ORR cathode

RSC Advances ◽  
2017 ◽  
Vol 7 (81) ◽  
pp. 51419-51425 ◽  
Author(s):  
Lei Wang ◽  
Yongmei Chen ◽  
Shuangyan Liu ◽  
Haomin Jiang ◽  
Linan Wang ◽  
...  
Keyword(s):  
Hydroxyl Radicals ◽  
Active Sites ◽  
Bond Cleavage ◽  
Phenolic Hydroxyl ◽  
Hydroxyl Groups ◽  
Phenolic Hydroxyl Groups

˙OH selectively attacks the active sites opposite to phenolic hydroxyl groups and leads to bond-cleavage of ether bonds.

scholarly journals Behavior of Hydroxyl Radicals on Water Ice at Low Temperatures

2021 ◽  
Vol 54 (3) ◽  
pp. 471-480
Author(s):  
Masashi Tsuge ◽  
Naoki Watanabe
Keyword(s):  
Hydroxyl Radicals ◽  
Low Temperatures ◽  
Water Ice

A comparative study on the degradation of cotton linters induced by carbonate and hydroxyl radicals generated from peroxynitrite

Holzforschung ◽  
2005 ◽  
Vol 59 (2) ◽  
pp. 132-142 ◽  
Author(s):  
Magnus Carlsson ◽  
David Stenman ◽  
Gábor Merényi ◽  
Torbjörn Reitberger
Keyword(s):  
Hydrogen Atom ◽  
Comparative Study ◽  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Cellulose Degradation ◽  
Hydroxyl Groups ◽  
Cotton Linter ◽  
Carbonate Radical ◽  
Radical Degradation ◽  
Cotton Linters

Abstract Carbonate (CO3 •−) and hydroxyl (HO•) radicals were chemically produced in cotton linter suspensions using peroxynitrite as a radical precursor. Both radicals could degrade cotton linters, as shown by viscosity and GPC-SEC measurements. As evidenced by the viscosity measurements, the presence of oxygen during the cotton linter treatments slightly increased cellulose degradation by both radicals. For the carbonate radical, more than 90% of the viscosity losses could be recovered by reductive NaBH4 treatment before measuring the viscosity, whereas only approximately 40% of the viscosity was recovered after hydroxyl radical degradation and subsequent NaBH4 treatment. This indicates that carbonate radicals mainly abstract H-atoms adjacent to hydroxyl groups, i.e., at C2, C3 and C6. This intramolecular selectivity may reflect a polar effect, whereby hydrogen atom abstractions from these positions are favoured. In addition, abstraction at C6 would be sterically and statistically favoured.

The photochemistry of native proteins

1951 ◽  
Vol 205 (1082) ◽  
pp. 391-408 ◽  
Keyword(s):  
Molecular Weight ◽  
Free Radicals ◽  
Serum Albumin ◽  
Hydroxyl Radicals ◽  
Hydroxyl Groups ◽  
Native Proteins ◽  
Oxidative Breakdown ◽  
Peptide Linkage ◽  
Protein Molecules ◽  
Mechanism And Kinetics

The photochemistry of serum albumin has been studied in detail. Evidence has been obtained showing that approximately 5 % of the radiation absorbed by the protein at 2537 Å wavelength is directly absorbed at the keto-imino linkage. It has been shown that irradiation of the protein in an atmosphere of nitrogen causes aggregation to give protein molecules of high molecular weight. Although there is some initial aggregation during irradiation in oxygen, this is quickly superseded by a photo-oxidative decomposition of the protein. The aggregation mechanism and kinetics have been elucidated. Absorption of radiation quanta by the keto-imino linkage causes fission of that linkage and the consequent production of two free radicals. These free radicals then react with the carboxyl and hydroxyl groups of other protein molecules forming aggregates. The free radicals have been detected, as has also their reaction with the carboxyl and hydroxyl groups. A theoretical equation for the rate of aggregation has been determined and shown to agree with that determined experimentally. It has also been possible to determine the quantum efficiency for the process in terms of the number of quanta absorbed by the peptide linkage. The photo-oxidative breakdown of the protein has been shown to be due to the formation in the solution of hydroxyl radicals. These react with the free radicals formed by the protein, thereby preventing aggregation.

scholarly journals Hydroxyl Radical-Suppressing Mechanism and Efficiency of Melanin-Mimetic Nanoparticles

2018 ◽  
Vol 19 (8) ◽  
pp. 2309
Author(s):  
Koichiro Hayashi ◽  
Atsuto Tokuda ◽  
Wataru Sakamoto
Keyword(s):  
Free Radicals ◽  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Kupffer Cells ◽  
Treatment Efficacy ◽  
Hepatic Cirrhosis ◽  
In Vivo Studies ◽  
Hydroxyl Groups ◽  
Treatment Methods

Harnessing melanins to scavenge free radicals in vivo may yield treatment methods for inflammatory disorders. Furthermore, elucidation of the mechanism underlying melanin-mediated suppression of free radicals, which is yet unclear, is warranted. Herein, we chemically synthesized melanin-mimetic nanoparticles (MeNPs) and investigated the mechanism underlying their use. MeNPs efficiently suppressed hydroxyl radicals by converting some MeNP hydroxyl groups to ketone groups. Furthermore, they suppressed hydroxyl radicals produced by lipopolysaccharide-treated Kupffer cells involved in hepatic cirrhosis pathogenesis, without causing significant cytotoxicity. The present results indicate the suitability of MeNPs to treat hepatic cirrhosis; however, further in vivo studies are warranted to determine their treatment efficacy.

Temporal evolution of the permanent shadowed regions at Mercury poles: applications for spectral detection of ices by SIMBIOSYS-VIHI on BepiColombo mission

2020 ◽  
Vol 498 (1) ◽  
pp. 1308-1318 ◽  
Author(s):  
Gianrico Filacchione ◽  
Alessandro Frigeri ◽  
Andrea Raponi ◽  
Mauro Ciarniello ◽  
Fabrizio Capaccioni ◽  
...  
Keyword(s):  
Near Infrared ◽  
Temporal Evolution ◽  
Signal To Noise Ratio ◽  
Polar Regions ◽  
Volatile Species ◽  
Imaging Spectrometer ◽  
Water Ice ◽  
The Earth ◽  
Spectral Detection ◽  
Spectrometer Channel

ABSTRACT Radar observations from the Earth and multi-instrument measurements by MESSENGER mission have indicated the presence of large quantities of ices within the permanent shadowed regions (PSRs) located at Mercury poles. The detection and mapping of the distribution of volatile species on PSRs are among the primary scientific goals of the Spectrometer and IMagers for MPO Bepicolombo Integrated Observatory SYStem (SIMBIO-SYS) suite aboard ESA’s BepiColombo mission. We report about a three-steps preparatory study mainly focusing on SIMBIO-SYS/Visible and near Infrared Hyperspectral Imager (VIHI) 0.4–2.0 μm imaging spectrometer aiming (1) to render the solar illumination temporal evolution occurring on polar regions and in particular on Prokofiev and Kandinsky craters by studying the effects of shadows and penumbras caused by the finite apparent solar disc; (2) to simulate the spectral reflectance of various mixtures of average Mercury terrain and water ice in the spectral range of the VIHI imaging spectrometer channel in direct illumination, penumbra and shadowed illumination conditions; and (3) to verify the resulting VIHI signal-to-noise ratio during the different phases of the BepiColombo mission.

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