The airborne occurrence, isomer profiles, and phase distribution of perfluoroalkyl acids (PFAAs), including perfluoroalkyl carboxylates (PFCAs) and sulfonates (PFSAs), have received little scientific attention to date. Here we collected gaseous and particulate phase (PM2.5) samples in China, between June and November 2013, using alkalized annular denuders and downstream filters toavoid sampling artefacts associated with traditional air sampling. We analysed the concentrations of 18 linear PFAAs and the branched isomers of perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS). Concentra- tions of total PFAAs were dominated by PFCAs, with a range of 6.6e610 pg/m3 in the gaseous phase and 2.3e290 pg/m3 in the particulate phase. Concentrations of total PFCAs were higher in summer than winter in both phases. Branched PFOA isomers accounted for 10e22% of total PFOA in the gaseous phase and 13e24% in the particulate phase, which is close to, but slightly lower than, their abundance in the commercial PFOA mixtures manufactured using the electrochemical fluorination (ECF) process. In con- tract, branched PFOS isomers accounted for 26-63% of total PFOS in the gaseous phase and 39-77% in the particulate phase, which is much higher than their abundance in commercial PFOS mixtures manufac- tured by ECF. Most PFCAs had mean particle-associated fractions (F) higher than 0.5. PFHxS had a much higher mean F (0.65) than linear PFOS (0.31). We hypothesise that PFAAs observed in Beijing air may originate from the local water bodies through processes such as aerosol generation, although trans- formation of precursors also contribute.
We derive the definition of the Berry phase for adiabatic transport of a composite Fermion (CF) in a half-filled composite Fermi-liquid (CFL). It is found to be different from that adopted in previous investigations by Geraedts et al. With the definition, the numerical evaluation of the Berry phase becomes robust and free of extraneous phase factors. We show that the two forms of microscopic wave-functions of the CFL, i.e., the Jain-Kamilla type wave function and the standard CF wave function, yield different distributions of the Berry curvature in the momentum space. For the former, the Berry curvature has a continuous distribution inside the Fermi sea and vanishes outside, whereas for the latter, the Berry curvature is uniform in the whole momentum space. To facilitate an analytic derivation for the latter, we reveal a simple structure of standard CF wave functions by establishing their connections to the Segal-Bargmann transform. We conclude that the CF with respect to both the microscopic wave-functions is not a massless Dirac particle.
Abstract Identifying hotspots of species richness/rarity is the most commonly used approach worldwide for defining areas of high conservation importance. However, the use of the hotspot method limits one's ability to protect or exclude particular species as all species are treated equally. Particularly, range-restricted species require high conservation attention because they are more vulnerable than common species. However, the efficiency of the hotspot method in capturing range-restricted species is yet to be explored, although it is known that this method provides low species coverage. Here, using a comprehensive database of Chinese woody plants, we mapped the diversity pattern of 11,405 species at the spatial resolution of 50 × 50 km2 and identified hotspot areas using 1, 2.5, 5, 10, 25, and 50% thresholds. We then evaluated the proportion of range-restricted versus common species captured/missed by each hotspot threshold. We found that the commonly used hotspot thresholds (5 and 10%) failed to capture 41–45% of range-restricted species, which indicates that using the hotspot method for conservation prioritization exposes range-restricted species to high extinction risk. Relying entirely on the hotspot method to prioritize conservation areas, therefore, can be risky not only because it provides low species coverage but also because the missed species are mostly range-restricted species. We advocate adopting more efficient methods, such as systematic conservation planning, rather than the hotspot method, to increase the coverage of range-restricted species in designated priority areas and balance the needs of biodiversity conservation and economic development.
A branching random walk algorithm for many-body Wigner equations and its numerical applications for quantum dynamics in phase space are proposed and analyzed in this paper. Using an auxiliary function, the truncated Wigner equation and its adjoint form are cast into integral formulations, which can be then reformulated into renewal-type equations with probabilistic interpretations. We prove that the first moment of a branching random walk is the solution for the adjoint equation. With the help of the additional degree of freedom offered by the auxiliary function, we are able to produce a weighted-particle implementation of the branching random walk. In contrast to existing signed-particle implementations, this weighted-particle one shows a key capacity of variance reduction by increasing the constant auxiliary function and has no time discretization errors. Several canonical numerical experiments on the 2D Gaussian barrier scattering and a 4D Helium-like system validate our theoretical findings, and demonstrate the accuracy, the efficiency, and thus the computability of the proposed weighted-particle Wigner branching random walk algorithm.
Abstract By designing a plasmonic waveguide–slit structure (a nanoslit etched in a silver nanowire) on a silver substrate, an ultrahigh Purcell factor and ultralarge figure of merit (FOM) are numerically predicted. Because of the large field enhancement (>150 times the incident field) and the ultrasmall optical volume (V ≈ 2 × 10−5λ3) of the resonant mode in the metallic nanoslit, the simulations show that the Purcell factor in the system can reach up to FP = 1.68 × 105, which is more than ten times the maximum Purcell factor in previous work (by placing metallic nanoparticles on a metal surface with a nanogap). Because of the utilization of a silver substrate rather than the common dielectric substrate, the mode cutoff of the surface plasmon polariton (SPP) waveguide mode is completely eliminated, which provides a large selection range of the nanowire radii to support the resonant mode in the nanoslit. Moreover, the SPP propagation length is significantly increased by more than 30 times. As a result, an ultralarge FOM of 1.40 × 107 is obtained, which is more than 80 times the maximum FOM in previous work where the metallic nanowire is placed on or surrounded by dielectric materials.
Carbon nanotubes (CNTs) and trace contaminants often co-occur in natural waters and wastewaters, and they may become the precursors of disinfection byproducts (DBPs). However, the effects of CNTs on the formation of DBPs during chlorination of co-existed organic pollutants are unknown. This study compared the effects of three types of CNTs on the formation of DBPs during chlorination of bisphenol A (BPA). The results showed that, compared with the single system of BPA, CNTs significantly decreased the initial rate (Ri) and the second-order rate constant (k) of trihalomethanes (THMs) formation in the binary systems of CNTs and BPA. For example, Ri for the binary system (38.7–49.6 µg/(L·h)) was much lower than that for the single system of BPA (63.1 µg/(L·h)). Furthermore, the suppression effects depended not only on the type but also on the concentration of CNTs: the suppression of Ri and k by CNTs followed the order of pristine CNTs > hydroxyl CNTs > carboxylic CNTs, and increased with rising concentration of CNTs. The adsorption experiments and density functional theory (DFT) calculation further revealed that higher adsorption and stronger binding of BPA to CNTs resulted in greater suppression degree of Ri and k by CNTs.
Causal relations can be presented as subjective, involving someone's reasoning, or objective, depicting a real- world cause-consequence relation. Subjective relations require longer processing times than objective relations. We hypothesize that the extra time is due to the involvement of a Subject of Consciousness (SoC) in the mental representation of subjective information. To test this hypothesis, we conducted a Visual World Paradigm eye- tracking experiment on Dutch and Chinese connectives that differ in the degree of subjectivity they encode. In both languages, subjective connectives triggered an immediate increased attention to the SoC, compared to objective connectives. Only when the subjectivity information was not expressed by the connective, modal verbs presented later in the sentence induced an increase in looks at the SoC. This focus on the SoC due to the linguistic cues can be explained as the tracking of the information source in the situation models, which continues throughout the sentence.
