Context.
The chemical composition of the Sun is a fundamental yardstick in astronomy, relative to which essentially all cosmic objects are referenced. As such, having accurate knowledge of the solar ...elemental abundances is crucial for an extremely broad range of topics.
Aims.
We reassess the solar abundances of all 83 long-lived elements, using highly realistic solar modelling and state-of-the-art spectroscopic analysis techniques coupled with the best available atomic data and observations.
Methods.
The basis for our solar spectroscopic analysis is a three-dimensional (3D) radiative-hydrodynamical model of the solar surface convection and atmosphere, which reproduces the full arsenal of key observational diagnostics. New complete and comprehensive 3D spectral line formation calculations taking into account of departures from local thermodynamic equilibrium (non-LTE) are presented for Na, Mg, K, Ca, and Fe using comprehensive model atoms with reliable radiative and collisional data. Our newly derived abundances for C, N, and O are based on a 3D non-LTE analysis of permitted and forbidden atomic lines as well as 3D LTE calculations for a total of 879 molecular transitions of CH, C
2
, CO, NH, CN, and OH. Previous 3D-based calculations for another 50 elements are re-evaluated based on updated atomic data, a stringent selection of lines, improved consideration of blends, and new non-LTE calculations available in the literature. For elements where spectroscopic determinations of the quiet Sun are not possible, the recommended solar abundances are revisited based on complementary methods, including helioseismology (He), solar wind data from the Genesis sample return mission (noble gases), sunspot observations (four elements), and measurements of the most primitive meteorites (15 elements).
Results.
Our new improved analysis confirms the relatively low solar abundances of C, N, and O obtained in our previous 3D-based studies: log
ϵ
C
= 8.46 ± 0.04, log
ϵ
N
= 7.83 ± 0.07, and log
ϵ
O
= 8.69 ± 0.04. Excellent agreement between all available atomic and molecular indicators is achieved for C and O, but for N the atomic lines imply a lower abundance than for the molecular transitions for unknown reasons. The revised solar abundances for the other elements also typically agree well with our previously recommended values, with only Li, F, Ne, Mg, Cl, Kr, Rb, Rh, Ba, W, Ir, and Pb differing by more than 0.05 dex. The here-advocated present-day photospheric metal mass fraction is only slightly higher than our previous value, mainly due to the revised Ne abundance from Genesis solar wind measurements:
X
surface
= 0.7438 ± 0.0054,
Y
surface
= 0.2423 ± 0.0054,
Z
surface
= 0.0139 ± 0.0006, and
Z
surface
/
X
surface
= 0.0187 ± 0.0009. Overall, the solar abundances agree well with those of CI chondritic meteorites, but we identify a correlation with condensation temperature such that moderately volatile elements are enhanced by ≈0.04 dex in the CI chondrites and refractory elements possibly depleted by ≈0.02 dex, conflicting with conventional wisdom of the past half-century. Instead, the solar chemical composition more closely resembles that of the fine-grained matrix of CM chondrites with the expected exception of the highly volatile elements.
Conclusions.
Updated present-day solar photospheric and proto-solar abundances are presented for 83 elements, including for all long-lived isotopes. The so-called solar modelling problem – a persistent discrepancy between helioseismology and solar interior models constructed with a low solar metallicity similar to that advocated here – remains intact with our revised solar abundances, suggesting shortcomings with the computed opacities and/or treatment of mixing below the convection zone in existing standard solar models. The uncovered trend between the solar and CI chondritic abundances with condensation temperature is not yet understood but is likely imprinted by planet formation, especially since a similar trend of opposite sign is observed between the Sun and solar twins.
North China registers frequent air pollution episodes from high PM
concentrations. Shijiazhuang is located at the intensive industrial zone of this region, but there is insufficient data on the ...chemical composition of PM
and its sources in this city. In this study, the chemical and seasonal characteristics of PM
in Shijiazhuang were investigated based on 12-h integrated PM
measurements made over eight 1-month periods in each season between June 2014 and April 2016 (486 samples). The eight-season average concentration of PM
was 138.8 μg m
, and the major chemical components were secondary inorganic aerosol (SIA) species of sulfate, nitrate, and ammonium (41.5%), followed by organic matter (25.9%). The mass concentration and most of the chemical components of PM
showed clear seasonal variation, with a winter-high and summer-low pattern. SO
and NO
were the dominant components at each pollution level in summer and autumn (18.1%-30.6% and 14.2%-27.0%, respectively). Sufficient gaseous oxidants (O
) concentrations and suitable meteorology conditions were observed in these two seasons. Highest SOR (0.61), SO
/EC(10.8) and NOR (0.58), NO
/EC (5.9) were found in summer and autumn, which indicated intense secondary transformation in these two seasons. Organic matter was the dominant species in winter, which increased from 17.1 μg m
for clean days (28.7% of PM
) to 169.1 μg m
(38.4% of PM
). The accumulation of primary emissions (coal combustion and biomass burning) was responsible for the increasing OM trend (especially for POC). The highest and leading proportion of mineral dust occurred in spring (20.3%-46.5%) as a result of higher wind speeds (up to 3 m/s). Potential source contribution function (PSCF) analyses implied that the border areas of Hebei, Henan and Shandong Provinces, together with the central area of Shanxi Province, contributed significantly to the PM
pollution in Shijiazhuang, especially in autumn and winter.
Vehicle emissions are affected by factors such as vehicle type, fuel quality, and engine repair. Therefore, mobile source profiles should be established based on a characteristic fleet for a specific ...region. This study characterised the chemical composition of PM
emitted from motor vehicles that are commonly used in Xi'an through dynamometer tests. The tested fleet included light duty diesel vehicles (LDDVs; eight sample sets), heavy duty diesel vehicles (HDDVs; six sample sets), light duty gasoline vehicles (LDGVs; eight sample sets), one natural gas vehicle (NGV; four sample sets) and one methanol vehicle (MV; two sample sets). Similarities and differences among the source profiles were compared and evaluated. Overall, carbon species (13.14-59.11%) were the major components of PM
for each type of vehicle, and the content of organic carbon (OC) was generally higher than that of elemental carbon (EC). Moreover, NO
(18.577-220.062 mg·g
) was the dominant water-soluble ion and the Ca
(2.429-17.209 mg·g
) and Na
(1.966-20.798 mg·g
) contents in PM
were high. In terms of elements, the PM
emitted from various types of vehicles consisted of abundant Al (2.183-94.949 mg·g
), Fe (0.567-12.297 mg·g
), and Zn (0.659-5.195 mg·g
). In addition, the PM
profiles were significantly affected by fuel type. In general, emissions from the LDGVs and NGV exhibited higher contents of OC (477.0-479.1 mg·g
). The greatest fractions of water-soluble ions (32.94%) and total elements (11.74%) were observed in emissions from the NGV and MV, respectively. For the same type of vehicle, the OC/EC ratio was possibly dependent on the emission standards. The PM
emitted from the LDDVs with stricter emission standards exhibited higher OC/EC ratios, whereas the OC/EC ratios displayed a decreasing trend for the LDGVs under more stringent emission standards.
Antifogging (AF) structure materials found in nature have great potential for enabling novel and emerging products and technologies to facilitate the daily life of human societies, attracting ...enormous research interests owing to their potential applications in display devices, traffics, agricultural greenhouse, food packaging, solar products, and other fields. The outstanding performance of biological AF surfaces encourages the rapid development and wide application of new AF materials. In fact, AF properties are inextricably associated with their surface superwettability. Generally, the superwettability of AF materials depends on a combination of their surface geometrical structures and surface chemical compositions. To explore their general design principles, recent progresses in the investigation of bioinspired AF materials are summarized herein. Recent developments of the mechanism, fabrication, and applications of bioinspired AF materials with superwettability are also a focus. This includes information on constructing superwetting AF materials based on designing the topographical structure and regulating the surface chemical composition. Finally, the remaining challenges and promising breakthroughs in this field are also briefly discussed.
Bioinspired antifogging materials with superwettability have great potential for inspiring novel products and technologies to facilitate human life, such as in eyeglasses, vehicles, solar products, and so on. The outstanding performance of biological antifogging surfaces encourages the rapid development and wide application of new antifogging materials. The mechanism, fabrication, progress, challenges, and perspectives of this material are reviewed.
The Current Status of MOF and COF Applications Freund, Ralph; Zaremba, Orysia; Arnauts, Giel ...
Angewandte Chemie International Edition,
November 2, 2021, Letnik:
60, Številka:
45
Journal Article
Recenzirano
Odprti dostop
The amalgamation of different disciplines is at the heart of reticular chemistry and has broadened the boundaries of chemistry by opening up an infinite space of chemical composition, structure, and ...material properties. Reticular design has enabled the precise prediction of crystalline framework structures, tunability of chemical composition, incorporation of various functionalities onto the framework backbone, and as a consequence, fine‐tuning of metal–organic framework (MOF) and covalent organic framework (COF) properties beyond that of any other material class. Leveraging the unique properties of reticular materials has resulted in significant advances from both a fundamental and an applied perspective. Here, we wish to review the milestones in MOF and COF research and give a critical view on progress in their real‐world applications. Finally, we briefly discuss the major challenges in the field that need to be addressed to pave the way for industrial applications.
Leveraging the unique properties of reticular materials has resulted in significant advances from both a fundamental and an applied perspective. This Review reports on the milestones in MOF and COF research and gives a critical view on progress in their real‐world applications. The major challenges in the field that need to be addressed to pave the way for industrial applications are also discussed.
Metal species with different size (single atoms, nanoclusters, and nanoparticles) show different catalytic behavior for various heterogeneous catalytic reactions. It has been shown in the literature ...that many factors including the particle size, shape, chemical composition, metal–support interaction, and metal–reactant/solvent interaction can have significant influences on the catalytic properties of metal catalysts. The recent developments of well-controlled synthesis methodologies and advanced characterization tools allow one to correlate the relationships at the molecular level. In this Review, the electronic and geometric structures of single atoms, nanoclusters, and nanoparticles will be discussed. Furthermore, we will summarize the catalytic applications of single atoms, nanoclusters, and nanoparticles for different types of reactions, including CO oxidation, selective oxidation, selective hydrogenation, organic reactions, electrocatalytic, and photocatalytic reactions. We will compare the results obtained from different systems and try to give a picture on how different types of metal species work in different reactions and give perspectives on the future directions toward better understanding of the catalytic behavior of different metal entities (single atoms, nanoclusters, and nanoparticles) in a unifying manner.
Continuously growing world’s energy demand and global climate change due to green house gas emissions have created need to find out renewable and sustainable energy solution. Biodiesel is one of the ...most promising substitute of diesel fuel that can be produced from vegetable oils, animal fats, waste oils etc. It is broadly classified in four generations i.e. edible oils (first generation), non-edible oils (second generation), waste oils (third generation) and advance solar biodiesel (fourth generation). There are some limitations associated with biodiesel as a fuel in diesel engines like cold flow, oxidation stability etc. Selection of biodiesel due to the above reasons is region specific and depends on the specific properties which are mainly governed by fatty acid composition of that oil. This review discusses the physicochemical properties of different generation biodiesel using 52 types of feedstocks. The chemical composition and physicochemical properties of 31 raw oils have also been discussed. As different fatty acid methyl esters (FAME) structures behave differently, it is not possible to develop a unique approach for obtaining optimum composition of FAME. The low concentration of polyunsaturated FAME and long-chain saturated FAME is more favorable for oxidation stability, low-temperature operability, and satisfactory performance. American Society for Testing and Materials (ASTM), European committee for standardization (CEN), Bureau of Indian Standards (BIS), etc. provided the specifications for the biodiesel and their blends.
•Biomass characterization is an important step to obtain process characteristics.•Composition of the main components did not differ significantly between samples.•Average of 7:1 C/H, almost 1:1 C/O, ...166:1 C/N and 8:1 O/H ratios.•Cellulose/hemicelluloses 1.5:1, cellulose/lignin 1.9:1, hemicelluloses/lignin 1.3:1 ratios.•Xylose/arabinose 12:1 and xylose/acetyl groups ratio of approximately 8.8:1.
Brazil, with 185 million tons of solid residues generation per harvest, is the largest producer of sugarcane in the world. The utilization of this biomass ranges from the extraction of sugarcane juice for application in the ethanol and sugar industry to energy generation and bio-based products synthesis.
Sugarcane residues are basically composed of hemicellulose, cellulose and lignin – chemical structures that are tightly linked to each other and are responsible for the integrity of the vegetal biomass. The aim of the present work is to show the different relations of the biomass contents from different varieties, cultivated places, soils, harvest season, and climate. For the chemical and elemental determination, 60 bagasse samples were characterized. The different bagasse samples did not show significant variability in their lignocellulosic contents. The results showed that the biomass characterization is an important step to obtain process characteristics.
The degree of imidization of polyimide used in VIA and PDL materials is important characteristic because of relationship with life cycles in OLED. During the curing process, a polyimide film ...optically changes to a negative C‐plate like sheet structure. The more polyimide chains packed closely, the higher out‐of‐plane retardation (Rth) is. In other words, for analyzing retardation properties of polyimide except for imidization ratio, Rth could be a useful analyzing method. In this study, using polyimide formed from different curing temperature and various chemical compositions, relation between Rth and properties of polyimide film was investigated.
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