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In this paper, a quartz glass with low hydroxyl groups was prepared by combining the advantages of various processes, using a plasma heat source as the flame and high-purity quartz sand as the raw material. The purity of the quartz sand was 99.997%. The number of air bubbles in the quartz glass prepared using high-purity quartz sand was lower. The hardness and tensile strength of the quartz glass were 737.7–767.1 GPa and 6.88–9.64 MPa, respectively. The hydroxyl content of the sample was only 4.11 ppm, and the hydroxyl content of the homogenized quartz glass was reduced to 2.64 ppm, which was an improvement of about 35%. After homogenization, the fictive temperature (Tf) of the quartz glass was determined to be 1253 cm−1, and the variation of the Tf value along the radial direction was reduced, indicating a more homogeneous glass structure. The stress distribution in the quartz glass was significantly improved. These results indicate that the preparation of quartz glass from high-purity quartz sand using a plasma heat source as the flame opens up new avenues for optical applications. [ABSTRACT FROM AUTHOR]

Using voltammetry to readout potentiometrically the solution acidity requires easy pH tunability of the probe's redox properties. In this work, tri‐hydroxyphenyl porphyrin (POH3) was synthesized as the electrochemically active probe to develop a voltammetrically potentiometric sensor (VPS) with a pH‐sensitive response. By comparing POH3 with control di‐ and mono‐hydroxyphenyl porphyrins (POH2 and POH1), we found that protonation of the pyrrole macrocycle, electron communication of the para‐hydroxyl groups with the pyrrole nitrogens during structure tautomerization, and the presence of multiple ionizable hydroxyl groups are the critical factors to report reversibly the pH‐sensitive VPS response at the appropriate potential range. Common metal ions have negligible effects on the sensor performance. In comparison to the conventional potentiometric sensor (CPS), our VPS strategy benefits from the advantage that the electrode modification is not required. Thus, the complex phase boundary models necessary for CPS are unnecessarily involved in explaining the potential response. [ABSTRACT FROM AUTHOR]

When observing the Sun with RATAN-600 radio telescope using a spectropolarimetric complex in the range 1–3 GHz, as well as when observing coronal rain, absorption in the radio emission was discovered in the spectral region 1.5–1.65 GHz in active solar regions located under a cold filament or on the limb under a prominence. The observed line structure corresponds to the hyperfine splitting frequencies in the ground state of X²Π₃/₂ hydroxyl (OH) 1612–1720 MHz. When the observed active region passes through the knife-shaped beam pattern of the telescope antenna, the absorption band shifts in frequency due to a shift in the energy levels of the OH molecule in a magnetic field, which changes along the filament.

Hydrous Cr‐bearing uvarovite garnets are rare in natural occurrences and belong to the ugrandite series and exist in binary solid solutions with grossular and andradite garnets. Here, we report the occurrence of hydrous uvarovite garnet having Cr2O3 upto 19.66 wt% and CaO of 32.12–35.14 wt% in the serpentinized mantle peridotites of Naga Hills Ophiolite (NHO), India. They occur in association with low‐Cr diopsides. They are enriched in LILE (Ba, Sr), LREEs, with fractionating LREE‐MREE [avg. (La/Sm)N = 2.16] with flat MREE/HREE patterns [avg. (Sm/Yb)N = 0.95]. Raman spectra indicate the presence of hydroxyl (OH–) peaks from 3500 to 3700 cm–1. Relative abundances in fluid mobile elements and their close association with clinopyroxenes are suggestive of the formation of uvarovite garnets through low temperature metasomatic alteration of low‐Cr diopsides by hydrothermal slab fluids. The high LREE concentration and absence of Eu anomaly in the garnet further attest to alkaline nature of the transporting slab dehydrated fluid rather the involvement of low‐pH solution. The chemical characteristics of the hydroxyl bearing uvarovite hosted by the mantle peridotite of NHO deviate from the classical features of uvarovite garnet, and their origin is attributed to the fluid‐induced metasomatism of the sub arc mantle wedge in a suprasubduction zone regime. [ABSTRACT FROM AUTHOR]

Aiming to optimize the product distribution of the Cu–Al catalytic system in the oxalate hydrogenation reaction as a way to optimize and improve the product structure of the coal-to-ethylene glycol process (Coal-Oxalate-EG), the researchers have investigated the two anchoring sites for anchoring the Cu component that is available in the Al2O3 support. The results show that the catalyst xSB synthesized from Al2O3 enriched with surface –OH functional groups is superior to the catalyst xSol synthesized from Al2O3 enriched with Al3+Penta sites for oxalate conversion, whereas xSol outperforms the xSB catalyst for the formation of alcohol-ether ester chemicals. Using diethyl oxalate (DEO) as feedstock, the reaction temperature of the 1Sol catalyst (235 °C) was higher than that of the 1SB catalyst (205 °C) for the conversion of the same amount of DEO at the same Cu loading. Meanwhile, the chemical selectivity of alcohol ether esters was higher for the 1Sol catalyst (~ 35%) than for the 1SB (~ 20%). Detailed characterization (XRD, NH3-TPD, XPS, in-situ FTIR, TEM, etc.) shows that the Al3+Penta sites are mainly present in the bulk phase of Al2O3, and the number of Al3+Penta sites present on the surface of the carriers is only sufficient to maintain the low content of Cu species in a highly dispersed state. A certain number of Al–OH is still required for the anchoring of the Cu species to the Al2O3 support surface. Therefore, hydroxyl-rich SB carriers are more favorable for the high dispersion of Cu species. Meanwhile, the stronger LAS distributed on the surface of the hydroxyl-rich SB carrier will lead to the decomposition or dehydration of the raw materials and intermediates during the reaction process, resulting in the formation of lower molecular weight products, which is unfavorable to the formation of the alcohol-ether ester products. Based on the detailed reaction data and characterization, a more complete product formation pathway of oxalate in the Cu–Al catalytic system is given, which provides a certain theoretical basis for the development of new coal-based chemical pathways. [ABSTRACT FROM AUTHOR]

For designing single-molecule devices that have both conjugation systems and structural flexibility, a hyperconjugated molecule with a σ–π bond interaction is considered an ideal candidate. In the investigation of conductance at the single-molecule level, since few hyperconjugation systems have been involved, the strategy of building hyperconjugation systems and the mechanism of electron transport within this system remain unexplored. Based on the skipped-conjugated structure, we present a rational approach to construct a hyperconjugation molecule using a hydroxyl group, which serves as a bridge to interact with the conjugated fragments. The measurement of single-molecule conductance reveals a two-fold conductance enhancement of the hyperconjugation system having the 'bridging' hydroxyl group compared to hydroxyl-free derivatives. Theoretical studies demonstrate that the hydroxyl group in the hyperconjugation system connects the LUMO of the two conjugated fragments and opens a through-space channel for electron transport to enhance the conductance. [ABSTRACT FROM AUTHOR]

Abstract Because of its global abundance and reactivity with hydroxyl radicals (OH•), tropospheric carbon monoxide indirectly impacts the lifetimes of other OH•‐reactive gases, in particular methane and reactive hydrocarbons. The origin and chemistry of atmospheric CO have been studied using stable isotopes. Both 13CO and C18O undergo isotopic fractionation during its main chemical loss reaction, CO + OH•. The kinetic isotope effect (KIE) for 13CO is mass dependent, with a value of ∼5‰; 12CO reacts faster than 13CO with OH. Whereas C18O + OH• exhibits an inversely mass dependent KIE ∼−10‰. We hypothesize these KIEs result in a relative depletion of 13C18O, a CO clumped isotope. To test this, we collected CO from air samples on Long Island, NY, and discovered a −3 to −8‰ difference in the clumped isotope ratio, Δ31, relative to a random distribution of 13C and 18O in CO. A clear negative trend between [CO] and Δ31 is driven by two factors: (a) the atmospheric addition of CO from either a primary or secondary source with a Δ31 of ∼0‰ and (b) the continuing reaction of CO with OH•, leaving the remaining CO pool relatively depleted in 13C18O. This is analogous to the mechanism that determines CO Δ17O values. This study is among the first to show clumped isotope fractionation resulting from atmospheric chemistry and not thermal equilibration, which may inform the identification of clumped isotope KIEs in other atmospheric trace gases. These first Δ31 observations motivate future experimental and observational studies targeted at characterizing the clumped isotopes of CO sources, background CO, and experimentally fractionated CO.

Surface and satellite observations of atmospheric methane show smooth seasonal behavior in the Southern Hemisphere driven by loss from the hydroxyl (OH) radical. However, observations in the Northern Hemisphere show a sharp mid‐summer increase that is asymmetric with the Southern Hemisphere and not captured by the default configuration of the GEOS‐Chem chemical transport model. Using an ensemble of 22 OH model estimates and 24 wetland emission inventories in GEOS‐Chem, we show that the magnitude, latitudinal distribution, and seasonality of Northern Hemisphere wetland emissions are critical for reproducing the observed seasonality of methane in that hemisphere, with the interhemispheric OH ratio playing a lesser role. Reproducing the observed seasonality requires a wetland emission inventory with ∼80 Tg a−1 poleward of 10°N including significant emissions in South Asia, and an August peak in boreal emissions persisting into autumn. In our 24‐member wetland emission ensemble, only the LPJ‐wsl MERRA‐2 inventory has these attributes. Plain Language Summary: The amount of methane, a powerful greenhouse gas, has been growing in Earth's atmosphere during the last decade, and scientists disagree about which methane sources and sinks are responsible for the growth. One clue into understanding methane's sources and sinks is their seasonality—their month‐to‐month cycles that happen every year. Measurements of atmospheric methane taken at the Earth's surface and using satellite instruments show a steep increase each summer in the Northern Hemisphere that is not replicated when methane is simulated in a global chemical transport model, indicating missing information about source and sink seasonalities. To investigate, we use that model to simulate 24 representations of methane's largest source, emissions from wetlands, and 22 representations of its largest sink, chemical loss by the hydroxyl radical (OH). We find that OH is unlikely to cause the summer increase and model bias, but the amount, spatial distribution, and seasonal cycles of global wetland emissions are the strongest drivers. We suggest that these characteristics are linked to the underlying mechanisms determining wetland area and methane production in wetland models. The results unveil the role of global wetlands in driving methane's seasonality and inform research to analyze methane's long‐term trends. Key Points: Northern Hemisphere atmospheric methane shows a summer increase not replicated by the GEOS‐Chem model with its default sources and sinksThe summer increase's timing and magnitude is determined by the magnitude, seasonality, and spatial distribution of NH wetland emissionsInversions of atmospheric methane observations should use a suitable wetland emission inventory and optimize hemispheric OH concentrations [ABSTRACT FROM AUTHOR]

The present study investigated the phytochemical, total phenolic, flavonoid content and in vitro antioxidant of the methanolic extract of the leaf of Ipomoea hederifolia Linn. In vitro antioxidant activity was determined using 2,2-diphenyl-1-picrylhydrazyl, hydroxyl radical, reducing power and phosphomolybdenum method. The total phenolic and total flavonoid contents were also determined using Folin Ciocalteau's and aluminium chloride method respectively. The preliminary phytochemical screening showed the presence of alkaloids, glycosides, steroids, triterpenoids, flavonoids, phenols and tannins. Results indicated that the total phenolic and flavonoid content were found to be 101.28±0.9238 mg of gallic acid equivalents/g and 14.91±0.672 quercetin equivalent/g respectively. The half-maximal inhibitory concentration values of the extract based on the 2,2-diphenyl-1-picrylhydrazyl was 20.33 µg/ml as compared to standard (ascorbic acid) which is 18.30 µg/ml while the half-maximal inhibitory concentration values of the methanolic extract of Ipomoea hederifolia and standard (ascorbic acid) for hydroxyl scavenging activity were found to be 104.9 µg/ml and 16.88 µg/ml respectively. The reducing power of methanolic extract and standard (ascorbic acid) at 25 µg/ml were found to be 0.183±0.002 and 0.396±0.001 respectively and the total antioxidant capacity of methanolic extract and standard (ascorbic acid) at 100 µg/ml and were found to be 0.094±0.0002 and 0.368±0.002 respectively. [ABSTRACT FROM AUTHOR]

Despite its importance for the global oxidative capacity, spatially resolved trends and variability of the hydroxyl radical (OH) are poorly constrained. We demonstrate the utility of a tropospheric column OH (TCOH) product, created from machine learning and satellite proxy data, in determining the spatial variability in trends of tropical OH over the oceans during September through November. While OH increases domain‐wide by 2.1%/decade from 2005–2019, we find significant spatial heterogeneity in regional trends, with decreases in some areas of 2.5%/decade. Our analysis of the trends in the proxy data indicate anthropogenic‐driven changes in emissions of OH drivers as well as increasing temperatures cause these trends. This OH product is potentially a significant advance in constraining OH spatial variability and serves as a useful complement to existing tools in understanding the atmospheric oxidative capacity. Comprehensive observations of TCOH are required to assess the fidelity of this method. Plain Language Summary: Hydroxyl is a chemical that removes many gases from the atmosphere, including methane, an important greenhouse gas. To understand recent trends in methane, we must also understand recent trends in hydroxyl. Because of various limitations, we unfortunately do not have long‐term, direct observations of hydroxyl. To address this problem, we have developed a machine learning model that uses satellite observations of variables relevant to hydroxyl chemistry and variability to calculate hydroxyl. We demonstrate that this product can be used to understand trends and variability of hydroxyl over the tropical oceans. While, on average, hydroxyl increases from 2005–2019, we show that this is not a universal trend and that hydroxyl actually decreases in multiple regions over the same time period. Using satellite observations of various chemicals, we demonstrate that changes in emissions due to human activity and increases in temperature cause many of these trends. This product is potentially a significant advance in understanding changes in hydroxyl and could be a useful complement to more traditional methods in understanding atmospheric methane. Key Points: Satellite proxies can constrain the spatial distribution of trends and variability of the hydroxyl radical in the tropicsChanges in biomass burning, temperature, and other emissions lead to large spatial heterogeneity in hydroxyl radical trendsMore direct observations of the hydroxyl radical and its drivers are needed to further validate the fidelity of our methodology [ABSTRACT FROM AUTHOR]

Glass sagging is a subsequent process to the CVD process used for large‐size and high‐purity silica glass synthesis. Physical phenomena taking place in this process are complicated which need an in‐depth understanding for better control. In this paper, a comprehensive study is conducted for the sagging process using a level‐set and enthalpy‐porosity coupled model. With this model, the deforming behavior of glass ingot and evolution of OH uniformly distributed region are well predicted. Then, two performance indices (the effective yield rate and maximum extension radius of OH uniformly distributed region) are proposed based on different applications, and important factors, including geometrical parameters (the ingot initial length, crucible diameter and pedestal height) and operating parameter (the heater power allocation scheme), are explored for their effects on the two indices. The orthogonal test design method is adopted to further determine the collective effects of the four factors. According to the range analysis results, the initial ingot length has the greatest effect, while the crucible diameter has the least effect on the effective yield rate; and for the maximum extension radius, the crucible diameter becomes the major factor, while the pedestal height is the most insensitive factor. The corresponding optimal schemes are proposed for the two indices finally, which are believed to provide useful guidance for improving the sagging process. [ABSTRACT FROM AUTHOR]

[Display omitted] Various adsorbents for CO 2 capture have been developed to mitigate the greenhouse effect. In this work, a novel CO 2 adsorbent was fabricated by depositing triethanolamine (TEOA) onto the surface of nickel-cobalt-aluminum layered double oxide (NiCoAl-LDO) via the impregnation method. The CO 2 capacity of the TEOA-LDO composite reached 1.27 mmol/g at 0 °C and 100 kPa, which was twice that of unmodified NiCoAl-LDO. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) showed that the hydroxyl groups (–OH) on the surface of NiCoAl-LDO played a significant role in facilitating CO 2 adsorption, similar to CO 2 adsorption in the presence of H 2 O, where CO 2 is not converted to carbamates but to bicarbonates through base-catalyzed hydration. This bicarbonate pathway doubles the theoretical amine efficiency, increases the CO 2 capacity, and reduces the energy consumption during CO 2 desorption. The work provides valuable insights into the development of CO 2 adsorbents with high capacity, excellent cycling stability, and low regeneration energy. [ABSTRACT FROM AUTHOR]

Curcumin is found in the medicinal plant turmeric and has a wide range of pharmacological activities. To improve their low stability, poor solubility, and low bioavailability, their monocarbonyl derivatives (MACs) modification has received much attention from researchers. In this study, MACs (1a–1e) were investigated with the help of density functional theory (DFT). The equilibrium geometries were optimized and then the predictions of vibration frequencies, conceptual density functional indices, antioxidant activity, and aromaticity were carried out. The results showed that the hydroxyl substitution at o- and p-positions in MACs exhibited strong reactivity, especially the substitution at the p-position significantly improved the electrophilic and antioxidant activity of compounds. This work also found that aqueous solutions had a booster effect on the reactivity of MACs. In contrast, the effect of hydroxyl at the m-position on the structure and properties was not significant. Furthermore, the molecular docking results show that the presence of hydroxyl group in MACs facilitates the enhancement of the interaction between MACs and the receptor. Results of this work introduce new and important information that contributes to the understanding of the potential properties of MACs and provides references and directions for the design of this type of drugs. [ABSTRACT FROM AUTHOR]

The crystal structure of the title compound was determined at 120 K. It crystallizes in the triclinic space group P\overline{1} with four independent molecules in the asymmetric unit. In the crystal, each symmetry-unique molecule forms π–π stacks on itself, giving four unique π–π stacking interactions. Intermolecular hydrogen bonding is observed between each pair of independent molecules, where each hydroxy group can act as a hydrogen-bond donor and acceptor.

In this paper, a quartz glass with low hydroxyl groups was prepared by combining the advantages of various processes, using a plasma heat source as the flame and high-purity quartz sand as the raw material. The purity of the quartz sand was 99.997%. The number of air bubbles in the quartz glass prepared using high-purity quartz sand was lower. The hardness and tensile strength of the quartz glass were 737.7–767.1 GPa and 6.88–9.64 MPa, respectively. The hydroxyl content of the sample was only 4.11 ppm, and the hydroxyl content of the homogenized quartz glass was reduced to 2.64 ppm, which was an improvement of about 35%. After homogenization, the fictive temperature (Tf) of the quartz glass was determined to be 1253 cm−1, and the variation of the Tf value along the radial direction was reduced, indicating a more homogeneous glass structure. The stress distribution in the quartz glass was significantly improved. These results indicate that the preparation of quartz glass from high-purity quartz sand using a plasma heat source as the flame opens up new avenues for optical applications.

The oxidation behavior of Tyranno® Grade-S SiC-tows was investigated under ambient air in the 450–1140 °C range. Below 650 °C, a linear oxidation rate was identified for oxide scale thicknesses up to 1.2 µm, attributed to the hydroxyl (Si-OH) groups degrading the silica structure as shown by 1H and 1H–29Si CP/MAS NMR. Above this temperature, the classical parabolic oxidation rate (diffusion controlled) was identified with a dehydroxylated silica scale. These results bring new insights to interpret the slow crack growth (SCG) transition observed at 650 °C. Above 650 °C the activation energies (Ea) for oxidation and SCG are close to 50 kJ mol−1 indicating the diffusion might be the rate limiting factor; whereas for lower temperatures Ea SCG < Ea oxidation as a consequence of the stress-enhanced chemical reactivity. The oxide thicknesses at failure time (predicted with power or exponential laws) were assessed and highlight some incoherencies in the lifetime projection to lower stresses. [Display omitted] • Oxidation kinetics for Grade S fibers under ambient air from 450° to 1140°C. • Oxidation rate below 650 °C exclusively linear, regardless of silica thickness. • Dehydroxylation of the silica shell observed from 550° to 950°C. • Identical SiO 2 growth rate under static oxidation and static fatigue conditions. • Ea ox ≈ Ea SCG (slow crack growth) above 650 °C and Ea ox > Ea SCG below 650 °C. [ABSTRACT FROM AUTHOR]

Cerium oxide (CeO 2) is well known to be reducible by hydrogen (H 2), yet the diffusion and solution properties of hydrogen in ceria at elevated temperatures have remained challenging to evaluate. We therefore fabricated nanometer-thin (∼100 nm) cerium oxide films on Si(111) substrates by pulsed laser deposition (PLD) and quantitatively investigated the H depth distributions therein by means of resonant 1H(15N,αγ)12C nuclear reaction analysis (NRA) before and after annealing in H 2 gas at 773–973 K. X-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) reveal that the as-deposited films exhibit single phase CeO 2 structure and partially reduced stoichiometry (CeO 1.69). H 2 annealing does not largely change the H content of the as-deposited films; in all conditions several atomic percent of hydroxyl (OH) are found to exist in a thin (∼4 nm) surface layer, whereas stably bound hydrogen in the bulk of the films is almost uniformly distributed and of much smaller quantity (∼0.2 at.%) than the oxygen vacancy concentration in the partially reduced ceria. Its low concentration and high thermal stability identify this bulk H species as likely being strongly bound to defects in the polycrystalline films rather than as a hydride species that interacts weakly with O-vacancies. The H diffusion coefficient and activation energy in the ceria films are determined as > 10−18 m2 s−1 at 773–973 K and <1.69 eV, respectively. The observed diffusion activation energy is somewhat larger than theoretical predictions for thermal diffusion of H in stoichiometric bulk CeO 2 , suggesting that defects and oxygen vacancies in the PLD-fabricated ceria thin films possibly have an impact on the H mobility. [Display omitted] • As-deposited films (∼100 nm) are partially reduced stoichiometry (CeO 1.69). • H 2 annealing of CeO 2-x films at 773–973 K results in a partial depletion of OH groups. • H is quite stable as OH in the surface layer up to about 4 nm, but not as hydride in the bulk. • The H species observed in the bulk of the films are rather small abundance (∼0.2 at.%). • Imperfections and vacancies are likely routes for hydrogen diffusion in CeO 2-x thin films. [ABSTRACT FROM AUTHOR]

A comprehensive experiment was devised focusing on the preparation, characterization, and antiscalant performance of fluorescent and hydroxy-modified polyaspartic acid. Initially, a water-soluble fluorescent material and polysuccinimide (PSI) were synthesized. The PSI was then modified using the fluorescent material and ethanolamine, followed by alkaline hydrolysis to obtain the target antiscalant. The antiscalant was characterized using 1H NMR, gel permeation chromatography, and fluorescence spectrophotometry, and its antiscalant efficacy was evaluated through static scaling tests. This experiment integrates concepts from polymer chemistry, organic chemistry, and analytical chemistry, embodying the scientific research process of "synthesis-characterization-analysis". It emphasizes the research thinking model of "substance-structure-property", aiming to cultivate students' experimental proficiency and research capabilities. [ABSTRACT FROM AUTHOR]

Metastasis is the process by which cancer cells move from the primary location to establish themselves in a new location in the human body. It is still a significant challenge in cancer management because it is responsible for 90% of cancer‐related deaths. In this work, we present an idea to use shear stress encountered by all metastasizing cells as an elegant means to deactivate metastasizing cancer cells. Shear‐induced ROS and cross‐talk between ROS and miRNA play crucial roles in deactivating metastasizing cancer cells. In addition, there exists a vast therapeutic potential for miRNAs. Therefore, this study explores the effect of shear on miRNAs and reactive oxygen species (ROS), the two molecular mediators in the proposed {shear‐stress}–{miRNA}–{metastasizing‐cancer‐cell‐deactivation} approach. In this context, to understand the effect of defined shear on HCT116 colon cancer cells, they were cultivated in a defined shear environment provided by an appropriately designed and fabricated cone‐and‐plate device. Shear rate affected the culture growth characteristics and the specific intracellular reactive oxygen species level (si‐ROS). HCT116 cell growth was observed at 0 and 0.63 s−1 but not at 1.57 s−1 or beyond. Shear rate induced upregulation of the hsa‐miR‐335‐5p but induced downregulation of hsa‐miR‐34a‐5p. Furthermore, the specific levels of hsa‐miR‐335‐5p, hsa‐miR‐26b‐5p, and hsa‐miR‐34a‐5p negatively correlated with specific intracellular (si)‐hydroxyl radical levels. In addition, some messenger RNAs (mRNAs) in HCT116 cells showed a differential expression under shear stress, notably the ROS‐associated mRNA of PMAIP1. The above miRNAs (and possibly some mRNAs) could be targeted to manage colon cancer metastasis. [ABSTRACT FROM AUTHOR]

We report the highest altitude detection of water vapor on Mars to date. The daytime limb observations by the Imaging Ultraviolet Spectrograph (IUVS) on the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft are of hydroxyl (OH) prompt emission near 308 nm, which is excited directly from the photodissociation of water vapor by the solar Lyman‐α flux. Average IUVS daytime water vapor densities near 130 km are 3 × 107 cm−3 around perihelion. The water vapor densities diurnally vary with a peak near midday and no detection at sunrise and sunset. To evaluate the large daytime water vapor densities for self‐consistency, we also report the simultaneous observation of OH solar fluorescence emission near 308 nm in the thermosphere, which enables the retrieval of OH densities. Using a one‐dimensional photochemical model initialized with the daytime IUVS water vapor densities, modeled peak OH densities are in good agreement with the observed IUVS peak OH densities. Because the observed thermospheric temperatures are controlled by solar insolation and cross the water frost point during the day, we suggest that the IUVS observed water vapor is created by the daily sublimation of water ice particles supplied from below. We discuss the implications of the IUVS observations on the present day loss of water vapor from Mars in the form of atomic hydrogen. Plain Language Summary: The loss of water from Mars is a compelling topic of study that helps trace its transformation from a warm and wet planet to the cold and dry planet that exists today. Water loss is greatly facilitated by water vapor transport to altitudes above 100 km during the dust storm season on Mars. We report the highest altitude detection of water vapor on Mars to date. Daytime observations between 110 and 150 km altitude indicate a strong diurnal variation of water vapor there, with a peak near midday. The observations are made by the Imaging Ultraviolet Spectrograph (IUVS) on NASA's Mars Atmosphere and Volatile Evolution spacecraft currently orbiting Mars. Simultaneous IUVS observations of hydroxyl, a product of water vapor destruction by solar ultraviolet radiation, reveal a self‐consistent picture of daytime water vapor variability. We suggest that the water is lofted to these high altitudes from below as ice particles before they reach altitudes where the temperatures are high enough to release the water in the vapor phase. The IUVS daytime water vapor densities in the upper atmosphere indicate that its escape to space is more efficient than previously thought. Key Points: OH prompt emission observations provide the highest altitude detection of water vapor on Mars to dateThermospheric water vapor concentrations are diurnally dependent, with a peak near midday at perihelionDiurnal temperature variations are consistent with nighttime sequestration of water as ice, followed by its daytime sublimation to vapor [ABSTRACT FROM AUTHOR]

Biochar is a promising remediation agent for heavy metal contaminated soils, and its immobilization effect on heavy metals depends not only on its structure composition but also on its interaction with soil components such as soil minerals. In this study, we investigated the effect of two typical soil iron minerals, hematite and goethite, on Pb2+ immobilization by barley grass–derived biochar through batch adsorption and model fitting, meanwhile elucidated the underlying mechanisms through XRD, FTIR, and SEM-EDS by dividing biochar into undissolvable biochar and dissolvable biochar. Dissolvable biochar had more excellent Pb2+ removal capacity than undissolvable biochar (Gmax in Langmuire model were 0.356 mmol L−1 and 0.288 mmol L−1, respectively). The presence of goethite increased Pb2+ removal rates by 70.8% and 72.2% for undissolvable and dissolvable biochar, respectively, while hematite slightly reduced their Pb2+ removal rates. The main mechanism was the formation of a ternary complex of biochar-goethite-Pb through -OH groups on the surface of goethite and biochar. Above novel findings emphasized that the dissolvable organic fraction in biochar played an important role in immobilizing Pb2+, and the interaction between biochar and soil iron minerals significantly affected final remediation effect. [ABSTRACT FROM AUTHOR]

Abstract Surface and satellite observations of atmospheric methane show smooth seasonal behavior in the Southern Hemisphere driven by loss from the hydroxyl (OH) radical. However, observations in the Northern Hemisphere show a sharp mid‐summer increase that is asymmetric with the Southern Hemisphere and not captured by the default configuration of the GEOS‐Chem chemical transport model. Using an ensemble of 22 OH model estimates and 24 wetland emission inventories in GEOS‐Chem, we show that the magnitude, latitudinal distribution, and seasonality of Northern Hemisphere wetland emissions are critical for reproducing the observed seasonality of methane in that hemisphere, with the interhemispheric OH ratio playing a lesser role. Reproducing the observed seasonality requires a wetland emission inventory with ∼80 Tg a−1 poleward of 10°N including significant emissions in South Asia, and an August peak in boreal emissions persisting into autumn. In our 24‐member wetland emission ensemble, only the LPJ‐wsl MERRA‐2 inventory has these attributes.

Abstract Despite its importance for the global oxidative capacity, spatially resolved trends and variability of the hydroxyl radical (OH) are poorly constrained. We demonstrate the utility of a tropospheric column OH (TCOH) product, created from machine learning and satellite proxy data, in determining the spatial variability in trends of tropical OH over the oceans during September through November. While OH increases domain‐wide by 2.1%/decade from 2005–2019, we find significant spatial heterogeneity in regional trends, with decreases in some areas of 2.5%/decade. Our analysis of the trends in the proxy data indicate anthropogenic‐driven changes in emissions of OH drivers as well as increasing temperatures cause these trends. This OH product is potentially a significant advance in constraining OH spatial variability and serves as a useful complement to existing tools in understanding the atmospheric oxidative capacity. Comprehensive observations of TCOH are required to assess the fidelity of this method.

Bio-solids (biological sludge) from wastewater treatment plants are a significant source of the emission of microplastics (MPs) into the environment. Weakening the structure of MPs before they enter the environment may accelerate their degradation and reduce the environmental exposure time. Therefore, we studied the effect of UV-A and UV-C, applied at 70 °C, on three types of MPs, polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET), that are commonly found in sewage sludge, using three shapes (fibers, lines, granules). The MPs were exposed to UV radiation in bio-solid suspensions, and to air and water as control. The structural changes in and degradation of the MPs were investigated using Attenuated Total Reflectance–Fourier Transform Infrared Spectrometry (ATR-FTIR) and surface morphology was performed with SEM analysis. UV exposure led to the emergence of carbonyl and hydroxyl groups in all of the PP samples. In PE and PET, these groups were formed only in the bio-solid suspensions. The presence of carbonyl and hydroxyl groups increased with an increasing exposure time. Overall, UV radiation had the greatest impact on the MPs in the bio-solids suspension. Due to the surface-to-volume ratio of the tested samples, which influences the degradation rate, the fibers were more degraded than the other two plastic shapes. UV-A was slightly more effective at degrading the MPs than UV-C. These findings show that ultraviolet radiation in combination with an elevated temperature affects the structure of polymers in wastewater bio-solids, which can accelerate their degradation. [ABSTRACT FROM AUTHOR]

MIL-53(Fe) and MIL-53(Fe)-2OH were prepared by solvothermal method, and the adsorption properties for Cr(VI) in solution were studied. The adsorption process of the two materials for Cr(VI) followed the pseudo-first-order (PFO) kinetic model, which belonged to physical adsorption. The adsorption for Cr(VI) on MIL-53(Fe)-2OH fitted to the Freundlich isotherm equation. The surface morphology of the MIL-53(Fe)-2OH changed after modified with double hydroxyl. The specific surface area (SSA) and total pore volume (TPV) increased from 7.7 m2/g and 0.016 cc/g to 16.77 m2/g and 0.045 cc/g. The adsorption performance of the materials improved with the content of hydroxyl functional group increased. Adsorption amount of the MIL-53(Fe)-2OH can reach 143.8 mg/g according to the kinetic fitting which was nearly three times that of MIL-53(Fe). The adsorption mechanism was mainly electrostatic attraction. [ABSTRACT FROM AUTHOR]

Gemini surfactants, composed of two surfactant monomers, are likely to self-assemble into viscoelastic fluids in water at low concentrations. Here, the aggregation behaviors of quaternary ammonium gemini surfactant with a hydroxyl group on the spacer (16-3OH-16) have been studied in the dilute aqueous system by rheological techniques, small angle X-ray scattering (SAXS), scanning electron microscopy (SEM) and other characterizations. At room temperature, the samples behave as elastic gels. The structure and morphology of gels were confirmed by SAXS and SEM characterizations. Due to the hydroxyl group on the spacer of 16-3OH-16, the gels are more stable than those formed by 16-3-16. At high temperature, the gels transform into wormlike micelles and behave as viscoelastic fluids. The obtained results would help to construct complexed fluids with structure tailorable gemini surfactants. The elastic Lβ gel showing good thixotropic behavior was constructed by the cationic gemini surfactant 16-3OH-16 with a hydroxyl group on the spacer. The alkyl chains of 16-3OH-16 would cross to form the hydrophobic domains while water could be confined in the solvent layer. [ABSTRACT FROM AUTHOR]

Lepidolite is widespread in the upper crust and can be used as a lithium ore. In the present study, in-situ high-temperature Raman and infrared spectroscopic measurements of natural Rb/Cs-free 2M2 lepidolite in pegmatite were conducted up to 700 °C for investigating the thermal response of lepidolite. In addition, single-crystal X-ray diffraction and electron microprobe analyses were also conducted to determine the polytype and composition of the lepidolite sample. The results show that (1) in the temperature range from 25 to 700 °C, the crystal structure of 2M2 lepidolite is not expected to undergo remarkable transformations upon heating and cooling; (2) the stabilities of hydroxyls in high-charge environments are lower than those in low-charge environments at elevated temperatures up to 700 °C. As a result, hydrogen ions in 2M2 lepidolite can transfer from the non-silicate oxygens in high-charge environments to those in low-charge environments during heating; (3) the transfers of the hydrogen ions between non-silicate oxygens in high-charge and low-charge environments may lead to the dehydration of lepidolite. Thus, lepidolites in subduction zones at temperatures below 700 °C can be sufficient to trigger partial melting and result in the release of lithium in subducted oceanic and continental slabs during subduction and exhumation. [ABSTRACT FROM AUTHOR]

Biosurfactants are amphipathic compounds that are produced by many microorganisms and show a wide range of biological activities due to their unique characteristics. This study aimed to determine the antioxidant and antimicrobial potential of the biosurfactants isolated from Lactobacillus plantarum, Lactobacillus pentosus, and Lactobacillus casei. The antioxidant activity of biosurfactant was evaluated in vitro conditions using the ability to inhibit 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl free radicals and antimicrobial activities using the diffusion method in agar wells against pathogenic bacteria. The results showed that the inhibitory activity of DPPH and hydroxyl of biosurfactants at a concentration of 5 mg/ml was 78.51-81.99% and 69.51-71.56%, respectively, and the highest antioxidant activity was related to Lactobacillus plantarum (P

For designing single-molecule devices that have both conjugation systems and structural flexibility, a hyperconjugated molecule with a σ–π bond interaction is considered an ideal candidate. In the investigation of conductance at the single-molecule level, since few hyperconjugation systems have been involved, the strategy of building hyperconjugation systems and the mechanism of electron transport within this system remain unexplored. Based on the skipped-conjugated structure, we present a rational approach to construct a hyperconjugation molecule using a hydroxyl group, which serves as a bridge to interact with the conjugated fragments. The measurement of single-molecule conductance reveals a two-fold conductance enhancement of the hyperconjugation system having the ‘bridging’ hydroxyl group compared to hydroxyl-free derivatives. Theoretical studies demonstrate that the hydroxyl group in the hyperconjugation system connects the LUMO of the two conjugated fragments and opens a through-space channel for electron transport to enhance the conductance.

The presence of hydroxyl (OH) groups on the photocatalyst surface is crucial for the volatile organic compounds' (VOCs) degradation. However, there is still limited knowledge on how OH groups are formed and their role in the magnetic-field-dependent photocatalytic degradation process. In this work, magnetic-field-assisted photocatalytic degradation of toluene was built by taking magnetic semiconductor material ZnFe2O4 nanospheres as the photocatalyst. Through a combination of experimental techniques, in situ DRIFTS analysis, and DFT calculations, we discovered that applying a vertical magnetic field activated the OH groups on the surface of ZnFe2O4, leading to an increase in the adsorption capacity of toluene. Additionally, the magnetic-field-induced Lorentz force facilitated the conversion of toluene to benzaldehyde, a significant step in the degradation process. As the magnetic field intensity increased, the way in which toluene was adsorbed changed. Overall, our study provides a valuable view for the role of OH groups and the effect of magnetic fields in the VOCs' photocatalytic degradation. [ABSTRACT FROM AUTHOR]

Understanding the effect of H2O adsorption on reactant activation is of great importance in heterogeneous catalysis, which remains a grand challenge particularly in oxide catalyst systems with structural complexity. Herein, the effect of D2O adsorption on D2 activation over MgO nanocatalysts at different temperatures has been investigated by transmission Fourier transform infrared (FT-IR) and temperature-programmed desorption (TPD). Two sets of hydride and hydroxyl species produced from D2 dissociation at more active and less active Mg-O pairs can be observed by FT-IR, which all desorb via the product of D2 as confirmed by TPD experiments. We find that the physically adsorbed D2O overlayer does not affect the dissociation of D2 since D2 may pass through the molecular layer and access the surface-active sites. When D2O is partially dissociated on the MgO surface, D2 can only dissociate at the remaining active sites until that dissociated −ODw groups from D2O occupy all active sites. These findings provide a fundamental understanding of the effect of water adsorption on D2 activation on oxide catalysts. [ABSTRACT FROM AUTHOR]

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In this study, grand canonical Monte Carlo simulations (GCMC) and molecular dynamics simulations (MD) were used to construct models of activated carbon with hydroxyl-modified hexachlorobenzene basic unit contents of 0%, 12.5%, 25%, 35% and 50%. The mechanism of adsorption of carbon disulfide (CS2) by hydroxyl-modified activated carbon was then studied. It is found that the introduction of hydroxyl functional groups will improve the adsorption capacity of activated carbon for carbon disulfide. As far as the simulation results are concerned, the activated carbon model containing 25% hydroxyl modified activated carbon basic units has the best adsorption performance for carbon disulfide molecules at 318 K and atmospheric pressure. At the same time, the changes in the porosity, accessible surface area of the solvent, ultimate diameter and maximum pore diameter of the activated carbon model also led to great differences in the diffusion coefficient of carbon disulfide molecules in different hydroxyl-modified activated carbons. However, the same adsorption heat and temperature had little effect on the adsorption of carbon disulfide molecules. [ABSTRACT FROM AUTHOR]

The doping of the second metal Mo is expected to further enhance the carbon deposition resistance of Ni-based catalysts for syngas production via dry reforming of methane (DRM). In this study, the hydroxyapatite (HAP) was used as the support and a small Mo dosage was doped in the Ni-based catalysts to investigate the effect of intrinsic hydroxyl and Mo doping on the catalytic activity and carbon deposition resistance in DRM reaction. The catalyst characterization results show that both Ni and Mo are doped into the HAP structure with relatively uniform dispersion. The basic site strength of Ni4Mo0.2-HAP catalyst containing Mo is significantly higher than that of without Mo. The Mo dopant significantly improves the initial catalytic activity, but has minimal effect on the stability enhancement. Whether the catalyst is pre-reduced or not is crucial to the initial activity of the DRM reaction, the non-pre-reduced catalysts will go through a "self-activation" stage at the beginning of the reaction, where the "hydroxyl group" are proved to play as an "oxygen supply" for the partial oxidation of CH 4 or the oxidation of the carbon deposition in the initial stage. Only trace amount of carbon deposition is found after 100 h of DRM reaction on Ni3Mo0.2-HAP catalyst. The NiMo-HAP catalysts exhibit excellent initial activity and resistance to carbon deposition due to the synergistic effect of Ni–Mo alloy and hydroxyl groups in the hydroxyapatite support. [Display omitted] • The doping of Mo improved the initial activity of the NiMo-HAP catalyst. • NiMo-HAP catalysts exhibited enhanced carbon deposition resistance (during 100 h DRM reaction). • Hydroxyl groups and NiMo alloys synergistically contributed to the DRM catalytic activity and stability. • NiMo-HAP maintained structural stability after 100 h DRM reaction. [ABSTRACT FROM AUTHOR]

Functional liquid fluoroelastomers are in high demand in new energy fields. And these materials have potential applications in high-performance sealing materials and as electrode materials. In this study, a novel high-performance hydroxyl-terminated liquid fluoroelastomer (t-HTLF) with a high fluorine content, temperature resistance, and curing efficiency was synthesised from a terpolymer of vinylidene fluoride (VDF), tetrafluoroethylene (TFE), and hexafluoropylene (HFP). A carboxyl-terminated liquid fluoroelastomer (t-CTLF) with controllable molar mass and end-group content was first prepared from a poly(VDF-ter-TFE-ter-HFP) terpolymer using a unique oxidative degradation method. Subsequently, an efficient "one-step" reduction of the carboxyl groups (COOH) in t-CTLF into hydroxyl groups (OH) was achieved via the functional-group conversion method using lithium aluminium hydride (LiAlH4) as the reductant. Thus, t-HTLF with a controllable molar mass and end-group content and highly active end groups was synthesised. Owing to the efficient curing reaction between OH and isocyanate groups (NCO), the cured t-HTLF exhibits good surface properties, thermal properties, and chemical stability. The thermal decomposition temperature (Td) of the cured t-HTLF reaches 334 °C, and it exhibits hydrophobicity. The oxidative degradation, reduction, and curing reaction mechanisms were also determined. The effects of solvent dosage, reaction temperature, reaction time, and ratio of the reductant to the COOH content on the carboxyl conversion were also systematically investigated. An efficient reduction system comprising LiAlH4 can not only achieve an efficient conversion of the COOH groups in t-CTLF to OH groups but also the in situ hydrogenation and addition reactions of residual double bonds (C=C) groups in the chain, such that the thermal stability and terminal activity of the product are improved while maintaining a high fluorine content. [ABSTRACT FROM AUTHOR]

A structured anodic alumina-supported Pt and Fe composition catalyst was developed to investigate its catalytic performance in carbon monoxide (CO) oxidation reactions. It is found that the hydroxyl-rich structured Pt/Fex/γ-Al2O3/Al catalyst with a mass of 0.58 g achieved 100% removal of CO and exhibited good stability of 60 h by weakening the competition between CO and O2 on the catalyst and decreasing the energy barrier. In addition, a series of explorations were carried out on the changes of relevant functional groups and active sites during catalyst deactivation and regeneration, and the data were explained in detail. Furtherly, it is demonstrated by in situ DRIFT that formate species are the important intermediates, produced by the reaction between hydroxyl group (–OH) on the catalyst and adsorbed CO. To explore the reaction mechanism at the atomic level, the CO oxidation reaction at the interface of Pt, Pt–OH, and Pt–Fe2O3 was analyzed by DFT calculations. [ABSTRACT FROM AUTHOR]

The article compares the interannual variability of the atmosphere at the OH glow height, which can be associated with planetary wave propagation, at stations spaced in latitude. As a characteristic reflecting planetary wave activity we consider standard deviations of the average overnight temperature σpw from its monthly average after taking into account the seasonal variation. Joint mesopause temperature measurements at high latitudes at two optical stations Maimaga (63.04° N, 129.51° E) and Tiksi (71.58° N, 128.77° E) began in 2015. The stations are equipped with identical Shamrock (Andor) high image quality infrared spectrographs for registration of OH (3-1) in the near infrared region (~1.5 μm). The main result of studying the planetary wave activity during the 5-year period of simultaneous observations is that at Tiksi station it slightly (by about 1–2 K) exceeds that at Maimaga station. In average annual activity fluctuations, the presence of quasi-biennial oscillations is traced.

This work investigates spatial and temporal distributions of hydroxyl, OH, in laser-plasma in laboratory air at standard ambient temperature and pressure. Of interest are determination of temperature and density of OH and establishment of a correlation of molecular OH emission spectra with shadow graphs for time delays of 50 to 100 μs, analogous to previous work on shadow graph and emission spectroscopy correlation for cyanide, CN, in gas mixtures and for time delays of the order of 1 μs. Wavelength- and sensitivity-corrected spatiotemporal data analysis focuses on temperature inferences using molecular OH emission spectroscopy. Near-IR radiation from a Q-switched laser device initiates optical breakdown in laboratory air. The laser device provides 6 ns, up to 850 milli Joule, pulses at a wavelength of 1064 nm, and focal irradiance in the range of 1 to 10 terawatt per centimeter-squared. Frequency doubled beams are utilized for capturing shadow graphs for visualization of the breakdown kernel at time delays in the range of 0.1 to 100 μs. OH emission spectra of the laser plasma, spatially resolved along the slit dimension, are recorded in the wavelength range of 298 nm to 321 nm, and with gate widths adjusted to 10 μs for the intensified charge-coupled device that is mounted at the exit plane of a 0.64 m Czerny-Turner configuration spectrometer. Diatomic OH signals occur due to recombination of the plasma and are clearly distinguishable for time delays larger than 50 μs, but are masked by spectra of N2 early in the plasma decay.

The nocturnal mesopause region of the Earth's atmosphere radiates chemiluminescent emission from various roto‐vibrational bands of hydroxyl (OH), which is therefore a good tracer of the chemistry and dynamics at the emission altitudes. Intensity variations can, for example, be caused by the general circulation, gravity waves, tides, planetary waves, and the solar activity. While the basic OH response to the different dynamical influences has been studied quite frequently, detailed comparisons of the various individual lines are still rare. Such studies can improve our understanding of the OH‐related variations as each line shows a different emission profile. We have therefore used about 90,000 spectra of the X‐shooter spectrograph of the Very Large Telescope at Cerro Paranal in Chile in order to study 10 years of variations of 298 OH lines. The analysis focuses on climatologies of intensity, solar cycle effect (SCE), and residual variability (especially with respect to time scales of hours and about 2 days) for day of year and local time. For a better understanding of the resulting variability patterns and the line‐specific differences, we applied decomposition techniques, studied the variability depending on time scale, and calculated correlations. As a result, the mixing of thermalized and nonthermalized OH level populations clearly influences the amplitude of the variations. Moreover, the local times of the variability features shift depending on the effective line emission height, which can mainly be explained by the propagation of the migrating diurnal tide. This behavior also contributes to remarkable differences in the effective SCE. Plain Language Summary: Emission from various lines of the hydroxyl (OH) molecule is an important contribution to the Earth's nighttime radiation in the near‐infrared. The emission mostly originates from altitudes between 80 and 100 km and is therefore a good tracer of the chemistry and dynamics at these altitudes. OH intensity variations can be caused by changes in the atmospheric conditions and passing waves with different time scales. In order to better understand the origin of these variations and their impact on the OH emission, we studied the variability of 298 OH lines measured in 10 years of data from the X‐shooter spectrograph at Cerro Paranal in Chile. The analysis focused on average variations with respect to local time and day of year, that is, climatologies. As the lines show different vertical emission distributions, this study also provides height‐dependent information. The climatologies for intensity, the response to the solar activity cycle of 11 years, and the residual variability (dominated by waves with time scales of a few hours and about 2 days) revealed remarkable patterns which depend on the OH excitation level. The features can partly be explained by the impact of solar tides, particularly with a period of 24 hr. Key Points: Climatologies of intensity, solar cycle effect, and residual variability of 298 OH lines were derived from 10 years of X‐shooter dataThe strongest variations are found for intermediate rotational energies where cold and hot OH populations show similar contributionsTides cause a local time shift of the climatological patterns depending on the effective line emission height [ABSTRACT FROM AUTHOR]

Gas phase reactions between OH radicals and three 2‐Butenes were studied using a flash photolysis resonance‐fluorescence technique over the temperature range 220–370 K and total gas pressures of 0.67 kPa (5 Torr) to 40 kPa (300 Torr). Measured rate constants exhibited weak negative temperature dependences. Most studies were carried out in argon, but some test experiments employed helium or nitrogen as the bath gas. Rate constants of OH reactions with cis‐2‐butene and trans‐2‐butene were found to exhibit a pressure dependence at room temperature and above. Kinetic parameters k0(T)${k}_{0}(T)$ and k∞(T)$k_\infty (T)$ describing termolecular rate constants in Ar bath gas were derived for both reactions and can be used to calculate rate constants at the Earth's atmospheric conditions. The high‐pressure limiting rate constants are k∞Z(T)=5.78×10−11×(298T)1.51$k_\infty ^Z(T) = 5.78 \times {10^{ - 11}} \times {({\frac{{298}}{T}})^{1.51}}$, cm3 molecule−1 s−1 and k∞E(T)=6.59×10−11×(298T)1.54${k}_{\infty}^{E}(T)=6.59\ensuremath{\times{}}{10}^{-11}\ensuremath{\times{}}(\frac{298}{T})^{1.54}$, cm3 molecule−1 s−1 for OH addition reactions with cis‐2‐butene and trans‐2‐butene, respectively. Their rate constants at 1 atm (760 Torr, 101 kPa) pressure can be represented as kZ(T, 1 atm) = 5.93 × 10−11 × (T/298)−1.61 × exp (− 17/T), cm3 molecule−1 s−1 and kE(T, 1 atm) = 6.75 × 10−11 × (T/298)−1.64 × exp (− 16/T), cm3 molecule−1 s−1. The rate constant of the OH addition reaction with 2,3‐dimethyl‐2‐butene was found to be pressure independent under our conditions and can be represented as kTME(T) = 14.08 × 10−11 × (T/298)−1.714 × exp (− 95.7/T), cm3 molecule−1 s−1 with kTME (298 K) = (10.21 ± 0.30) × 10−11, cm3 molecule−1 s−1. Complementary measurements of IR absorption spectra of cis‐2‐butene and trans‐2‐butene were done between 500 and 3300 cm−1. They are presented in Supporting Information. [ABSTRACT FROM AUTHOR]

Chemiluminescent radiation of the vibrationally and rotationally excited hydroxyl (OH) radical, which dominates the nighttime near‐infrared emission of the Earth's atmosphere in wide wavelength regions, is an important tracer of the chemical and dynamical state of the mesopause region between 80 and 100 km. As radiative lifetimes and rate coefficients for collision‐related transitions depend on the OH energy level, line‐dependent emission profiles are expected. However, except for some height differences for whole bands mostly revealed by satellite‐based measurements, there is a lack of data for individual lines. We succeeded in deriving effective emission heights for 298 OH lines thanks to the joint observation of a strong quasi‐2‐day wave (Q2DW) in eight nights in 2017 with the medium‐resolution spectrograph X‐shooter at the Very Large Telescope at Cerro Paranal in Chile and the limb‐sounding SABER radiometer on the TIMED satellite. Our fitting procedure revealed the most convincing results for a single wave with a period of about 44 hr and a vertical wavelength of about 32 km. The line‐dependent as well as altitude‐resolved phases of the Q2DW then resulted in effective heights which differ by up to 8 km and tend to increase with increasing vibrational and rotation excitation. The measured dependence of emission heights and wave amplitudes (which were strongest after midnight) on the line parameters implies the presence of a cold thermalized and a hot non‐thermalized population for each vibrational level. Plain Language Summary: Hydroxyl (OH) is an important molecule in the Earth's atmosphere at altitudes between 80 and 100 km. It is the main source of atmospheric nighttime radiation in the near‐infrared wavelength range and is therefore a valuable tracer of the chemistry and dynamics at high altitudes. The emission spectrum consists of various lines which are related to different levels of vibration and rotation. Although the vertical emission distribution should depend on the given line due to differences in the deactivation of the corresponding energy levels, the line‐specific details have been uncertain until now. We have succeeded in deriving effective time‐averaged emission heights for 298 OH lines based on the combination of ground‐based line‐resolved and space‐based height‐resolved observations of a very strong rising wave with a period close to 2 days and a relatively short vertical wavelength in eight nights in 2017. The resulting heights (obtained via the line‐dependent wave phases) differ by up to 8 km and generally increase with higher molecular vibration and rotation. They are valuable for ground‐based studies of other waves and contribute (combined with conclusions from the wave amplitudes) to a better understanding of the internal processes in OH molecules. Key Points: X‐shooter‐based intensities of 298 hydroxyl (OH) lines from eight nights show a strong quasi‐2‐day wave (Q2DW) in southern summer 2017Fits of the Q2DW phase in the X‐shooter data and Sounding of the Atmosphere using Broadband Emission Radiometry‐based OH emission profiles were used to derive effective OH emission heightsThe line‐dependent wave amplitudes confirm the presence of cold and hot OH populations for each vibrational level [ABSTRACT FROM AUTHOR]

Aiming at the problems of long period, large floor area and low treatment efficiency of the existing medical wastewater treatment system, using plasma discharge technology, high-frequency and high-voltage power supply, and auxiliary solar power supply, O2 and H2O enter the plasma generator through pretreatment, through the strong electric field ionization discharge, high-energy electrons are obtained to promote the excitation of O2 and H2O, thereby generating a strong oxidant· OH. Use the broad-spectrum lethality of OH to efficiently kill pathogenic microorganisms, degrade organic drugs, etc., and decompose them into H2O, CO2 and inorganic salts at the same time, and the remaining OH will be decomposed into H2O and O2. Causes secondary pollution, can effectively solve the problem of medical wastewater treatment, and achieve zero environmental pollution and zero waste discharge. [ABSTRACT FROM AUTHOR]

This work investigates spatial and temporal distributions of hydroxyl, OH, in laser-plasma in laboratory air at standard ambient temperature and pressure. Of interest are determination of temperature and density of OH and establishment of a correlation of molecular OH emission spectra with shadow graphs for time delays of 50 to 100 μs, analogous to previous work on shadow graph and emission spectroscopy correlation for cyanide, CN, in gas mixtures and for time delays of the order of 1 μs. Wavelength- and sensitivity-corrected spatiotemporal data analysis focuses on temperature inferences using molecular OH emission spectroscopy. Near-IR radiation from a Q-switched laser device initiates optical breakdown in laboratory air. The laser device provides 6 ns, up to 850 milli Joule, pulses at a wavelength of 1064 nm, and focal irradiance in the range of 1 to 10 terawatt per centimeter-squared. Frequency doubled beams are utilized for capturing shadow graphs for visualization of the breakdown kernel at time delays in the range of 0.1 to 100 μs. OH emission spectra of the laser plasma, spatially resolved along the slit dimension, are recorded in the wavelength range of 298 nm to 321 nm, and with gate widths adjusted to 10 μs for the intensified charge-coupled device that is mounted at the exit plane of a 0.64 m Czerny-Turner configuration spectrometer. Diatomic OH signals occur due to recombination of the plasma and are clearly distinguishable for time delays larger than 50 μs, but are masked by spectra of N2 early in the plasma decay. [ABSTRACT FROM AUTHOR]

Widespread contamination of soils by neurotoxic lead ions (Pb) posed a serious risk to food security, but efficient treatment in soil remained a challenge. For the adsorption of Pb, DFT calculations were firstly performed to predict the synergistic effect of sulfhydryl-hydroxyl groups as well as the ability of sulfur ions to strengthen Pb-OH bonding. Consequently, Mn-S functionalized coffee ground biochar (MSBC) was then synthesized utilizing precipitation and impregnation methods. In the soil experiment, the removal efficiency of Pb reached 82.92%, exceeding the previous research results. In addition, it successfully restored the polluted farmland near the mining area and increased the plant height of Swiss chard by 186.23%. Subsequently, synergistic effect of sulfhydryl-hydroxyl groups was confirmed by XPS, FT-IR, and DFT calculations. Furthermore, the factors affecting the structural stability of O-Pb-S were discussed by regression analysis. These reflected that MSBC can enhance the removal efficiency of Pb in soil by mitigating the competition of impurity ions to adsorption sites. These findings may provide new insights into the development of the specific passivation materials for other heavy metals. [Display omitted] • Thiol group can modulate the bonding structure between lead and the hydroxyl group. • Sulfide ion eliminated semi-occupied electrons and enhanced the adsorption. • Bridging effect exhibited selectivity towards borderline acid ions. • Manganese-sulfur functionalized biochar restored the polluted farmland successfully. [ABSTRACT FROM AUTHOR]

Persister cells constitute a bacterial subpopulation able to survive to high concentrations of antibiotics. This phenotype is temporary and reversible, and thus could be involved in the recurrence of infections and emergence of antibiotic resistance. To better understand how persister cells survive to such high antibiotic concentration, we examined changes in their lipid composition. We thus compared the lipidome of Acinetobacter baumannii ATCC 19606T persister cells formed under ciprofloxacin treatment with the lipidome of control cells grown without antibiotic. Using matrix assisted laser desorption ionisation-Fourier transform ion cyclotron resonance mass spectrometry, we observed a higher abundance of short chains and secondary chains without hydroxylation for lipid A in persister cells. Using liquid chromatography-tandem mass spectrometry, we found that persister cells produced particular phosphatidylglycerols, as LPAGPE and PAGPE, but also lipids with particular acyl chains containing additional hydroxyl group or uncommon di-unsaturation on C18 and C16 acyl chains. In order to determine the impact of these multiple lipidome modifications on membrane fluidity, fluorescence anisotropy assays were performed. They showed an increase of rigidity for the membrane of persister cells, inducing likely a decrease membrane permeability to protect cells during dormancy. Finally, we highlighted that A. baumannii persister cells also produced particular wax esters, composed of two fatty acids and a fatty diol. These uncommon storage lipids are key metabolites allowing a rapid bacterial regrow when antibiotic pressure disappears. These overall changes in persister lipidome may constitute new therapeutic targets to combat these particular dormant cells. [Display omitted] • PAGPE, LPAGPE as discriminant lipids in persister cells • Presence of di-unsaturated and hydroxyl fatty acyl chains in lipids of persister cells • Decrease of membrane fluidity of persister cells • Special WE presenting one diol with two acyl chains in persister cells [ABSTRACT FROM AUTHOR]

Low charge separation efficiency (η sep) of TiO 2 impedes its applications of photoelectrochemical (PEC) water splitting. A positive potential pretreatment approach has been developed to construct a surface polarization with −OH groups at a potential of 1.48 V RHE. When the pretreatment time of 6 h is used, the η sep and photocurrent density (J ph) reach up to 54 % (vs. 24 %, TiO 2) and 0.92 mA cm−2 (vs. 0.32 mA cm−2, TiO 2) under AM 1.5 G illumination, respectively. The photovoltage can be increased from 0.17 V to 0.52 V. When the pretreatment time is extended to 22 h, a higher J ph of 1.57 mA cm−2 and η sep of 87 % can be obtained. Furthermore, the positive potential pretreated TiO 2 possesses excellent PEC stability. The PEC improvements can be attributed to the surface polarization with the −OH groups and favorable surface states of Ti-OH, but not to the formation of Ti3+ or oxygen vacancies. [Display omitted] • A positive potential pretreatment method is developed to construct TiO 2 surface polarization with −OH groups. • A higher photocurrent and charge separation efficiency of 1.57 mA cm−2 and 87 % are obtained, respectively. • Positive potential pretreated TiO 2 shows an excellent stability, which greatly vary from the electrochemical reduced TiO 2. [ABSTRACT FROM AUTHOR]