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Transport Cross Sections and Collision Integrals for O(3 P)–O(3 P) Interaction
Get PDFNew collision integrals and transport cross sections for O(3P)–O(3P) interaction are reported in the 300–30000 K range. Those values are based on a new set of potential energy curves (PECs) calculated with the multireference configuration interaction method. The results of the classical and semiclassical WKB (Wentzel–Kramers–Brillouin) methods are compared, excellent performance of the classical approach is shown (discrepancy much lower than 1% even at room temperature). In particular, the classical and WKB methods agree very well for the repulsive potentials effectively reducing overall uncertainty
Implementation and application of an improved phase spectrum determination scheme for Fourier transform spectrometry
Get PDFCorrect determination of the phase spectrum is a highly relevant task in Fourier transform spectrometry for concluding which spectral distribution most likely gave rise to the measured interferogram. We present implementation of an improved scheme for phase determination in the operational Collaborative Carbon Column Observing Network (COCCON) processor. We introduce a robust unwrapping scheme for retrieving a spectrally smooth phase spectrum at intermediate spectral resolution, which uses all spectral positions carrying enough signal to allow a significant determination of the phase. In the second step, we perform a least-squares fit of model parameters of a suitable analytical phase spectrum model through all reliable phase values constructed in the first step. The model fit exploits the fact that we expect the phase to be spectrally smooth. Still, it can be refined to reflect specific characteristics inherent to the optical and electronic layout of the interferometer. The proposed approach avoids the problems of the classical phase reconstruction method, which enforces a spectrally smooth phase by directly limiting spectral resolution when calculating the complex phase. Thereby, the phase is created from a very low number of interferogram points around the centerburst of the interferogram, which results in a suboptimal noise propagation from the interferogram into the spectral domain. Moreover, the interpolation of the phase spectrum across spectral subsections with reduced spectral signal is not well behaved, and results depend strongly on the numerical apodization function used for creating the low-resolution phase
Plantations of native tree species in Africa: a synthesis of tree survival and growth across plantation methods in the Guineo-Congolian region
No full textIn the rainforests of the Guineo-Congolian region, several native tree species have been tested in plantations established with different silvicultural methods and objectives. The results of these experiments remained scattered, hampering our ability to identify the key drivers of variability in survival and growth of planted species. In this study, we carried out a systematic review of the literature. From 45 selected studies, a database was compiled of 89 native tree species planted in different forest types (evergreen, semideciduous and transition). The data included plantation age, survival, height and diameter growth. For each species, information was collected on the planting method (understorey, line planting, gap, degraded area, regrowth and clear-cut), and species functional traits (species guild, dispersal mode, wood density and leaf phenology). Tree survival, height and diameter growth were modelled using linear mixed-effect models. Tree survival depended mainly on plantation age, and mortality was the highest in the seven first years. However, survival did not significantly depend on planting method or species traits. In the study plantations, height and diameter growth depended on planting method and species guild. Diameter growth was negatively correlated with wood density. Pioneer, non-pioneer light-demanding and shade-tolerant species grew faster in diameter when planted in degraded areas and clear-cuts. Pioneer species grew the fastest in gaps. Although we did not find an effect of forest type on tree survival and growth, the variability between sites was substantial. This study provides empirical evidence that planting methods need to be adapted to the species guild
Modeling of Ionization and Recombination Processes in Plasma with Arbitrary Non-Maxwellian Electron Distribution
Get PDFIn astronomical environments, the high-temperature emission of plasma mainly depends on ion charge states, requiring accurate analysis of the ionization and recombination processes. For various phenomena involving energetic particles, non-Maxwellian distributions of electrons exhibiting high-energy tails can significantly enhance the ionization process. Therefore, accurately computing ionization and recombination rates with non-Maxwellian electron distributions is essential for emission diagnostic analysis. In this work, we report two methods for fitting various non-Maxwellian distributions by using the Maxwellian decomposition strategy. For standard κ-distributions, the calculated ionization and recombination rate coefficients show comparable accuracy to other public packages. Additionally, our methods support arbitrary electron distributions and can be easily extended to updated atomic databases. We apply the above methods to two specific non-Maxwellian distribution scenarios: (i) accelerated electron distributions due to magnetic reconnection revealed in a combined MHD–particle simulation; and (ii) the high-energy truncated κ-distribution predicted by the exospheric model of the solar wind. During the electron acceleration process, we show that the ionization rates of high-temperature iron ions increase significantly compared to their initial Maxwellian distribution, while the recombination rates may decrease due to the electron distribution changes in low-energy ranges. This can potentially lead to an overestimation of the plasma temperature when analyzing the Fe emission lines under the Maxwellian distribution assumption. For the truncated κ-distribution in the solar wind, our results show that the ionization rates are lower than those for the standard κ-distribution, while the recombination rates remain similar. This leads to an overestimation of the plasma temperature when assuming a κ-distribution
Dynamic water vapor sorption: a helpful tool for preventive conservation of salt contaminated built heritage
Get PDFThe presence of salts and related salt-induced damage represent one of the major threats to the preservation of our built heritage. Identifying critical relative humidity values that facilitate crystallization cycles is essential for understanding damage risks and extents. This knowledge helps in developing recommendations for favorable, damage-avoiding climates, particularly in controllable indoor environments. While for single salts their deliquescence humidity is known, for multi-ion mixtures relevant for the built heritage multiple transitions happen over a range of relative humidity. Modeling of equilibrium crystallization pathways is possible, e.g. using the Pitzer formalism. However, for complex mixtures, only predictions can be given, which need to be validated through experimental results. This work focuses on the use of dynamic water vapor sorption measurements to investigate phase transitions in salt mixtures, demonstrating its applicability, scrutinizing different influencing factors and an appropriate interpretation of results. Additionally, presenting an experimental design that delivers reliable results for the conservation of cultural heritage is crucial. In addition to single salts, mixtures from the common hygroscopic system Na+–K+–Mg2+–Ca2+–Cl––NO3––H2O are investigated, including their behavior in a stone material. The identified transitions are compared to the calculated behavior using the ECOS–Runsalt model. The presented results are accurate and reproducible. They show the ability to determine the critical relative humidity ranges (in bulk and in porous materials) and validate thermodynamic models
Die eyckischen Miniaturen im Turin-Mailänder Stundenbuch
No full textKatalog erschienen aus Anlass der Austellung "Van Eyck. Eine optische Revolution", Museum voor Schone Kunsten Gent, 1. Februar-30. April 202
République Démocratique du Congo, Carte administrative , Province du Kasaï-Central, Territoire de Kazumba
No full textValidation and assessment of satellite-based columnar CO2 and CH4 mixing ratios from GOSAT and OCO-2 satellites over India
Get PDFSatellite observations of column-averaged carbon dioxide (XCO2) and methane (XCH4) mixing ratios provide essential data for monitoring greenhouse gas (GHG) emissions. However, the accuracy of emission estimates depends on the precision and bias of satellite retrievals, which require validation against ground-based reference measurements. This study presents a systematic validation of XCO2 and XCH4 data from GOSAT (Greenhouse gases Observing SATellite) and OCO-2 (Oribiting Carbon Observatory-2) satellites over South India using ground-based Fourier transform spectrometer (FTS) observations at Gadanki (13.5° N, 79.2° E) collected from October 2015 to July 2016. Satellite products from National Institute for Environmental Studies, Japan (NIES), NASA's Atmospheric CO2 Observations from Space (ACOS) project, USA (ACOS), and the University of Leicester, UK (UoL) were evaluated using a three-step spatial-temporal pairing method. Results show that the UoL's proxy XCH4 product meets the European Space Agency's Climate Change Initiative (ESA CCI) bias requirement (<10 ppb) across all spatial windows, while the NIES XCH4 product meets the requirement only for intermediate spatial scales. For XCO2, NASA ACOS and OCO-2 products meet the CCI bias requirement (<0.5 ppm), while NIES XCO2 exceeds this threshold. All products satisfy the precision requirement (<8 ppm for XCO2 and <34 ppb for XCH4) with substantial margins. In addition, FLEXPART model simulations using regional emission inventories revealed that agricultural activities dominate seasonal methane enhancements, contributing approximately 55 %, followed by waste and wetland emissions. The model captured seasonal trends but underestimated the amplitude of observed variations, highlighting the influence of changing background methane levels. These findings demonstrate the suitability of recent satellite products for regional GHG monitoring and emphasise the need for expanding ground-based FTS networks across South Asia to support improved emission assessments
