Green’s function methods within many-body perturbation theory provide a general framework for treating electronic correlations in excited states and spectra. Here, we develop the cumulant form of the ...one-electron Green’s function using a real-time coupled-cluster equation-of-motion approach, in an extension of our previous study (Rehr J.; et al. J. Chem. Phys. 2020, 152, 174113). The approach yields a nonperturbative expression for the cumulant in terms of the solution to a set of coupled first-order, nonlinear differential equations. The method thereby adds nonlinear corrections to traditional cumulant methods, which are linear in the self-energy. The approach is applied to the core-hole Green’s function and is illustrated for a number of small molecular systems. For these systems, we find that the nonlinear contributions yield significant improvements, both for quasiparticle properties such as core-level binding energies and for inelastic losses that correspond to satellites observed in photoemission spectra.
The increasing complexity and dynamism of construction projects have imposed substantial uncertainties and subjectivities in the risk analysis process. Most of the real-world risk analysis problems ...contain a mixture of quantitative and qualitative data; therefore quantitative risk assessment techniques are inadequate for prioritizing risks. This article presents a risk assessment methodology based on the Fuzzy Sets Theory, which is an effective tool to deal with subjective judgement, and on the Analytic Hierarchy Process (AHP), which is used to structure a large number of risks. The proposed methodology incorporates knowledge and experience acquired from many experts, since they carry out the risks identification and their structuring, and also the subjective judgements of the parameters which are considered to assess the overall risk factor: risk impact, risk probability and risk discrimination. All of these factors are expressed by qualitative scales which are defined by trapezoidal fuzzy numbers to capture the vagueness in the linguistic variables. The most notable differences with other fuzzy risk assessment methods are the use of an algorithm to handle the inconsistencies in the fuzzy preference relation when pair-wise comparison judgements are necessary, and the use of trapezoidal fuzzy numbers until the defuzzification step. An illustrative example on risk assessment of a rehabilitation project of a building is used to demonstrate the proposed methodology.
Many-body excitations in X-ray photoemission spectra have been difficult to simulate from first principles. We have recently developed a cumulant-based one-electron Green’s function method using the ...real-time coupled-cluster-singles equation-of-motion approach (RT-EOM-CCS) that provides a general framework for treating these problems. Here we extend this approach to include double excitations in the ground-state energy and in the coupled cluster amplitudes, which have been implemented using subroutines generated by the Tensor Contraction Engine (TCE). As in the case of the singles approximation, RT-EOM-CCSD yields a nonperturbative cumulant form of the Green’s function in terms of the time-dependent cluster amplitudes, adding nonlinear corrections to the traditional cumulant forms. The extended approach is applied to the core-hole spectral function for small molecular systems. We find that, when core-optimized basis sets are used, the doubles contributions reduce the mean absolute errors in the core binding energies of the 10e systems from 0.8 to 0.3 eV. They also significantly improve the quasiparticle–satellite gap by reducing its overestimation from about 3–5 to about 0–1 eV in CH4, NH3, and H2O, and also improving the overall shape of the satellite features. Finally, we demonstrate the application of the new implementation to the larger, classical XPS ESCA series of molecules and show that the singles approximation can be paired with a modest basis set to study carbon speciation.
The biochemical stability of typical biomarkers from the free lipid extract of different plant chars during biotic degradation was examined using pyrogenic organic matter (PyOM) derived from rye ...grass (Lolium perenne; Gr) and pine wood (Pinus sylvestris; P) heated at 350°C for 1 (1M) and 4min (4M) under oxic conditions. The composition of the n-alkanes and n-fatty acids (FA) as well as the contents of the molecular markers levoglucosan and vanillin were determined and related to charring intensity and stability to microbial reworking. Our results confirmed that charring of plant residues results in typical thermal breakdown processes of n-alkanes and FA. Prolonged charring reduced the average chain length of n-alkanes by up to four carbons and shifted the characteristic odd/even predominance of fresh plants towards a balanced odd/even distribution. The unsaturated FA fraction was more prone to heat degradation than the saturated counterparts. Especially, linoleic acid (C18:2) and α-linolenic acid (C18:3) were depleted in the severely charred grass, whereas oleic acid (C18:1) was still present. Levoglucosan was detectable in all PyOMs, but the pine wood charred for 1min (P1M) contained the largest amount. Progressive heating resulted in a strong depletion of levoglucosan for both plant materials. The pine char showed a relative accumulation of vanillin, supporting that some lignin-derived structures can survive charring. Microbial decomposition of the chars within a soil matrix for seven weeks demonstrates that during initial PyOM biodegradation, n-alkanes and FA series are rapidly modified by microbial reworking and biosynthesis. After the incubation, the pine chars were enriched in octadecane (C18) and homologues in the range from C22 to C26. The n-alkanes and FA of the grass chars were more severely affected than those of the pine chars. Levoglucosan was efficiently decomposed, indicating that care has to be taken if these compounds are used as char tracer in soils, since their instability against biodegradation may hamper the identification of charcoal residues.
► Lignin components can survive charring of plant residues. ► Lipid pattern of char in soils is microbially altered during post-fire recovery. ► The lipid pattern in post-fire soils changes due to degradation and resynthesis. ► Levoglucans are rapidly decomposed during post-fire microbial activities.
This article presents a longitudinal panel study analyzing the evolution of a sample of more than 1000 informants in the language practices with peers during the period between the end of primary ...education and the end of secondary education in Catalonia. Results led to the identification of five clusters of informants according to their linguistic trajectories. Three of them, which together accounted for 75% of all informants, combined the strong predominance of a single language -respectively Catalan, Castilian, and other languages- and a remarkable stability in patterns of language choice during the five years' period under scrutiny. The other 25% of informants, grouped in two different clusters, declared more bilingual/multilingual behavior and underwent more significant changes that may be related to linguistic mudes Pujolar, Joan, and Isaac Gonzàlez. 2013. 'Linguistic "Mudes" and the Deethnicization of Language Choice in Catalonia.' International Journal of Bilingual Education and Bilingualism. The study also explores the relevance of the transition between primary and secondary education as a social moment favorable for linguistic mudes and concludes thata small but still significant percentage of informants went through such changes in that transition.
The amount and compositional characteristics of black carbon in soils (mollisol and vertisol), charred biomass (laboratory produced; rice, chestnut), and soils (southern Spain) affected by forest ...fire have been determined using a combination of thermogravimetry (TG), TG coupled with isotope ratio mass spectrometry (IRMS), solid state 13C nuclear magnetic resonance (NMR) spectroscopy, and pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS). Samples affected by fire had higher total organic matter content, and this was enriched in aromatic components. Good agreement was observed between the content of refractory organic matter (ROM) determined by TG analysis and the aromatic content measured by 13C NMR. Py‐GC/MS demonstrated the presence of aromatic compounds in samples rich in black carbon, the absence of furans (derived from carbohydrates) in soils affected by fire, and the detection of methoxyphenols (derived from lignin) in artificially charred grass and wood. Some of the characteristic peaks obtained by analytical pyrolysis in combination with TG analysis and NMR 13C spectra could be used as markers in the detection of black carbon. This is the first study in which TG‐differential scanning calorimetry (DSC)‐IRMS has been used to detect black carbon formed during artificial smoldering and natural combustion processes.
Plants have evolved an array of specific photoreceptors to acclimate to the light environment. By sensing light signals, photoreceptors modulate plant morphology, carbon- and water-physiology, crop ...yield and quality of harvestable organs, among other responses. Many cultural practices and crop management decisions alter light quantity and quality perceived by plants cultivated in the field. Under full sunlight, phytochromes perceive high red to far red ratios (R:FR; 1.1), whereas overhead or lateral low R:FR (below 1.1) are sensed in the presence of plant shade or neighboring plants, respectively. Grapevine is one of the most important fruit crops in the world. To date, studies on grapevine response to light focused on different Photosynthetic Active Radiation (PAR) levels; however, limited data exist about its response to light quality. In this study we aimed to investigate morphological, biochemical, and hydraulic responses of Vitis vinifera to variations in R:FR. Therefore, we irradiated Syrah and Torrontés Riojano plants, grown in a glasshouse, with lateral FR light (low lateral R:FR treatment), while others, that were kept as controls, were not irradiated (ambient lateral R:FR treatment). In response to the low lateral R:FR treatment, grapevine plants did not display any of the SAS morphological markers (i.e. stem length, petiole length and angle, number of lateral shoots) in any of the cultivars assessed, despite an increase in gibberelins and auxin concentrations in leaf tissues. Low lateral R:FR did not affect dry matter partitioning, water-related traits (stomata density and index, wood anatomy), or water-related physiology (plant conductance, transpiration rate, stem hydraulic conductivity, stomatal conductance). None of the Vitis vinifera varieties assessed displayed the classical morphological and hydraulic responses associated to SAS induced by phytochromes. We discuss these results in the context of natural grapevine environment and agronomical relevance.
X-ray photoemission spectra generally exhibit satellite features beyond the main peak due to many-body excitations. However, the satellites associated with charge-transfer excitations in correlated ...materials have proved difficult to calculate from first principles and their interpretation has been controversial. Here we show that these satellites can be attributed to local density fluctuations in response to a suddenly created core hole. Our approach is based on a cumulant representation of the core-hole Green's function with a real-time, time-dependent density functional theory calculation of the cumulant. This approach includes effects that cannot be accounted for by cluster methods and yields a direct real-space, real-time interpretation. Illustrative results for TiO sub(2) and NiO are in good agreement with XPS experiment.
English has achieved a hegemonic position in the field of science and technology and is gaining ground as the means of instruction in higher education. These developments have raised concern in ...numerous circles about the effects of the reduction of multilingualism in the academic fields, and some authors have warned against a possible scientific diglossia that might reduce all language but English to the status of non-academic languages. In this paper we argue that this approach is insufficient because it misses two fundamental points: on the one hand, it reduces the scientific field to only one of its dimensions, namely publication in scholarly articles, whereas academic life includes many other scholarly activities; on the other hand, the number of academic languages has actually increased in the last decades. Confronting these approaches, we propose to understand the aforementioned evolution in terms of a socioeconomic transformation which has triggered a number of new language choices. Plurilingualism has been a traditional feature of communities with an academic language, and we illustrate this plurilingualism with Catalan, a language that regained the status of academic language in the 1970s and is currently used side by side with Castilian and with English. To finish, some considerations are raised about the risk that English goes beyond its role of academic lingua franca and becomes appropriated as a legitimate vehicle of in-group interaction among members of other communities.
The real‐space Green's function code FEFF has been extensively developed and used for calculations of X‐ray and related spectra, including X‐ray absorption (XAS), X‐ray emission (XES), inelastic ...X‐ray scattering, and electron energy‐loss spectra. The code is particularly useful for the analysis and interpretation of the XAS fine‐structure (EXAFS) and the near‐edge structure (XANES) in materials throughout the periodic table. Nevertheless, many applications, such as non‐equilibrium systems, and the analysis of ultra‐fast pump–probe experiments, require extensions of the code including finite‐temperature and auxiliary calculations of structure and vibrational properties. To enable these extensions, we have developed in tandem a new version FEFF10 and new FEFF‐based workflows for the Corvus workflow manager, which allow users to easily augment the capabilities of FEFF10 via auxiliary codes. This coupling facilitates simplified input and automated calculations of spectra based on advanced theoretical techniques. The approach is illustrated with examples of high‐temperature behavior, vibrational properties, many‐body excitations in XAS, super‐heavy materials, and fits of calculated spectra to experiment.
A new approach to facilitate advanced calculations of X‐ray spectroscopies using the RSGF X‐ray spectroscopy code FEFF10 and the Corvus workflow tool is presented.
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