Abstract Aim Quantifying niche shifts of non-native species and their interactions with natives is vital in evaluating invasion risk yet remains difficult. Climate filtering and competition with native congeners are two important processes impacting niche changes and yielding contradictory predictions for the coexistence of non-native and native species. Closely related species representing the Eastern Asia (EA)?Eastern North America (ENA) floristic disjunction provide a powerful yet unexplored system for assessing the relative roles of these two processes. Here, we tested three niche change scenarios (unfilling, expansion and stable) using EA species naturalized in ENA. We aim to answer: (1) which scenario is observed for naturalized species? and (2) how has niche overlap between EA and ENA congeners changed after naturalization? Location ENA and EA. Time Period Present. Major Taxa Studied Angiosperms. Methods Niches were estimated using both occurrences and predictions generated by ecological niche models. Niche changes of naturalized species and their niche overlap with natives were measured using Schoener's D. Contributions of niche expansion and unfilling on niche changes of naturalized niches were evaluated using hierarchical partitioning and linear regressions. We further measured pairwise phylogenetic distances among EA and ENA congeners and evaluated the association with niche overlap. Results Unfilling-dominated postintroduction niche changes of the naturalized species. EA species naturalized in ENA exhibited lower niche overlap with ENA native congeners compared with native range populations in EA. These results remain when considering time since introduction and potential physical dispersal limitations interpreted by projecting suitable niche space between EA and ENA. However, dispersal limitation may contribute to the degree of niche unfilling. Main Conclusions Using intercontinental disjunct species as a study system, we found that naturalization is shaped jointly by climate filtering and competition with native congeners, providing valuable insights for evaluating invasion risk underlying global floristic exchanges.
An approach to generalize any kind of collinear functional in density functional theory to noncollinear functionals is proposed. This approach satisfies the correct collinear limit for any kind of functional, guaranteeing that the exact collinear functional after generalization is still exact for collinear spins. Besides, it has well-defined and numerically stable functional derivatives, a desired feature for noncollinear and spin-flip time-dependent density functional theory. Furthermore, it provides local torque, hinting at its applications in spin dynamics.
Nonlocal modeling has drawn more and more attention and becomes steadily more powerful in scientific computing. In this paper, we demonstrate the superiority of a first-principle nonlocal model—Wigner function—in treating singular potentials which are often used to model the interaction between point charges in quantum science. The nonlocal nature of the Wigner equation is fully exploited to convert the singular potential into the Wigner kernel with weak or even no singularity, and thus highly accurate numerical approximations are achievable, which are hardly designed when the singular potential is taken into account in the local Schrödinger equation. The Dirac delta function, the logarithmic, and the inverse power potentials are considered. Numerically converged Wigner functions under all these singular potentials are obtained with a fourth-order accurate operator splitting spectral method, and display many interesting quantum behaviors as well.
In this work, an excitonic energy transfer (EET) based non-radical mechanism was proposed for the degradation of organic pharmaceuticals by graphitic carbon nitride (g-C3N4) under visible light irradiation. Using diclofenac (DCF) as a model molecule, the competition between single electron transfer (SET) and EET was studied through modulating the exciton binding energy of g-C3N4. The different mechanisms of SET and EET for DCF degradation were predicted by DFT calculation, and further confirmed by their different degradation pathways. When EET played an important role, the rationality of some very popular radical scavengers, such as p-BQ, TEMPOL and furfuryl alcohol must be reconsidered. In addition, humic acid (HA) had a distinct effect on EET and SET. Specifically, HA enhanced the EET process through photosensitization, but suppressed SET through radical quenching effect. The effect of HA on DCF degradation depended on the contribution ratio of SET and ET.
Fracture-cave carbonate reservoirs represent a significant amount of oil and gas resources worldwide, while their intrinsic complex pore network, large caves and tectonic fractures bring challenges to reservoir characterizations and productions. Many models have been proposed to solve the pressure transient analysis (PTA) solutions for such reservoirs. With recent explorations, the position of fractures and caves can be determined by seismic data. However, models using the position information with the coexistence of discrete fractures and caves were not reported in the literature. This paper proposes a novel semi-analytical model based on the Boundary Element Method (BEM), to describe the transient pressure behavior of the fracture-cave carbonate reservoirs. Basically, the proposed model treats the cave edge as an inner boundary and includes the fracture-cave fluid interchanges. As a results, the model's solution is proved to be flexible for arbitrary cave and reservoir shape. A typical system consisting of one fracture and one case is discussed in detail. The result indicates the well location is the key factor to the pressure response, where the pressure response is mostly affected by the cave volume and fracture conductivity when the well is on the cave and fracture, respectively. The sensitivities of three major parameters on the pressure response are analyzed. In addition, the proposed model is applied in two field cases. The result shows the proposed model is reliable and accurate.
Global climate changes urge prompt energy transition for less carbon emissions, from traditional fossil fuels to renewable and sustainable clean energy. However, in reality, the world's energy majority cannot make U-turn immediately to renewables or clean energy due to the immature technology readiness, insufficient resource availability and unstable energy supply. In the next few decades, the fossil fuels, particularly oil and gas, will continue acting as the primary energy sector. Thus, instead of absolutely abandoning fossil fuel and seeking for impractical carbon mitigation technologies, to decarbonise the oil and gas will be definitely feasible and contribute more to net-zero transitions. This study, initially put eyes on the oil and gas decarbonization, critically reviewing the oil and gas resources, technologies, policies, and their futures toward net-zero. Basically, the status of oil and gas resources from different global regions, including the details of reserves, productions, consumptions, are summarized and analyzed. Moreover, the oil and gas technologies are categorized as gas, thermal and non-thermal, new recovery methods, each of which is specifically discussed in the applicable reservoir, mechanism, features and examples. Then, the global carbon emissions are reviewed in perspectives of emissions from fuel types and world regions as well as mitigations policies. Accordingly, the carbon mitigation approaches, specially in the oil and gas industry, are collected and listed from enterprise managements and technology renovations. Lastly, based on all the information and analyses and assisted with IEA energy outlook report, we provide a potential pathway for the oil and gas towards carbon neutral. This paper provides comprehensive overview on the oil and gas pathway to net-zero, which will not only technically guide the oil and gas decarbonisations, also be of interest to wide-range readers who are not experts but intend to understand the energy transitions.
The practical importance of coherent forecasts in hierarchical forecasting has inspired many studies on forecast reconciliation. Under this approach, so-called base forecasts are produced for every series in the hierarchy and are subsequently adjusted to be coherent in a second reconciliation step. Reconciliation methods have been shown to improve forecast accuracy, but will, in general, adjust the base forecast of every series. However, in an operational context, it is sometimes necessary or beneficial to keep forecasts of some variables unchanged after forecast reconciliation. In this paper, we formulate reconciliation methodology that keeps forecasts of a pre-specified subset of variables unchanged or "immutable". In contrast to existing approaches, these immutable forecasts need not all come from the same level of a hierarchy, and our method can also be applied to grouped hierarchies. We prove that our approach preserves unbiasedness in base forecasts. Our method can also account for correlations between base forecasting errors and ensure non-negativity of forecasts. We also perform empirical experiments, including an application to sales of a large scale online retailer, to assess the impacts of our proposed methodology.
Organic peroxides (POs) are organic molecules with one or more peroxide (−O–O−) functional groups. POs are commonly regarded as chemically labile termination products from gas-phase radical chemistry and therefore serve as temporary reservoirs for oxidative radicals (HOx and ROx) in the atmosphere. Owing to their ubiquity, active gas-particle partitioning behavior, and reactivity, POs are key reactive intermediates in atmospheric multiphase processes determining the life cycle (formation, growth, and aging), climate, and health impacts of aerosol. However, there remain substantial gaps in the origin, molecular diversity, and fate of POs due to their complex nature and dynamic behavior. Here, we summarize the current understanding on atmospheric POs, with a focus on their identification and quantification, state-of-the-art analytical developments, molecular-level formation mechanisms, multiphase chemical transformation pathways, as well as environmental and health impacts. We find that interactions with SO2 and transition metal ions are generally the fast PO transformation pathways in atmospheric liquid water, with lifetimes estimated to be minutes to hours, while hydrolysis is particularly important for α-substituted hydroperoxides. Meanwhile, photolysis and thermolysis are likely minor sinks for POs. These multiphase PO transformation pathways are distinctly different from their gas-phase fates, such as photolysis and reaction with OH radicals, which highlights the need to understand the multiphase partitioning of POs. By summarizing the current advances and remaining challenges for the investigation of POs, we propose future research priorities regarding their origin, fate, and impacts in the atmosphere.
Organosulfur compounds (OSCs) are important components of fine particulate matter (PM2.5); however, little information is available on OSCs in urban regions due to their chemical complexity, especially for novel species such as aromatic sulfonates. To supplement the detection technique and systematically identify OSCs, in this study we developed a nontargeted approach based on gas chromatography and high-resolution mass spectrometry (GC-HRMS) to screen OSCs in PM2.5 of urban Beijing and provide field evidence for their source and formation mechanism. 76 OSCs were found through mass difference of sulfur isotopes and characteristic sulfur-containing fragments. 6 species were confirmed as aromatic sulfonates by authentic standards. 32 OSCs showed higher levels in the heating season, presumably because of the intensive emission, especially from coal combustion. While certain species, with 2-sulfobenzoic acid as the representative, were 2.6-times higher in the non-heating season than in the heating season. Such species were significantly correlated with ozone and aerosol liquid water content (r = 0.2–0.8, p < 0.05), implying an oxidation-involved aqueous-phase formation in the atmosphere. In addition, with an average proportion of ∼95 % of the total sulfobenzoic acids, the predominance of the 2-substitution product over its isomers of 3- or 4-sulfobenzoic acid suggests a more plausible mechanism of radical-initiated reaction of phthalic acid followed by sulfonation, with atmospheric reactivity indicated by ozone and temperature as the determining factor. This study provided not only a nontargeted approach for OSCs in ambient PM2.5, but also field evidence on their secondary formation proposed in previous simulation studies.