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.
Background Firearm-related death rates and years of potential life lost (YPLL) vary widely between population subgroups and states. However, changes or inflections in temporal trends within subgroups and states are not fully documented. We assessed temporal patterns and inflections in the rates of firearm deaths and %YPLL due to firearms for overall and by sex, age, race/ethnicity, intent, and states in the United States between 1999 and 2016. Methods We extracted age-adjusted firearm mortality and YPLL rates per 100,000, and %YPLL from 1999 to 2016 by using the WONDER (Wide-ranging Online Data for Epidemiologic Research) database. We used Joinpoint Regression to assess temporal trends, the inflection points, and annual percentage change (APC) from 1999 to 2016. Results National firearm mortality rates were 10.3 and 11.8 per 100,000 in 1999 and 2016, with two distinct segments; a plateau until 2014 followed by an increase of APC = 7.2% (95% CI 3.1, 11.4). YPLL rates were from 304.7 and 338.2 in 1999 and 2016 with a steady APC increase in %YPLL of 0.65% (95% CI 0.43, 0.87) from 1999 to an inflection point in 2014, followed by a larger APC in %YPLL of 5.1% (95% CI 0.1, 10.4). The upward trend in firearm mortality and YPLL rates starting in 2014 was observed in subgroups of male, non-Hispanic blacks, Hispanic whites and for firearm assaults. The inflection points for firearm mortality and YPLL rates also varied across states. Conclusions Within the United States, firearm mortality rates and YPLL remained constant between 1999 and 2014 and has been increasing subsequently. There was, however, an increase in firearm mortality rates in several subgroups and individual states earlier than 2014.
After the founding of P. R. China, land use in rural China was organized under two successive paradigms: state-directed collectivization from 1958–1984 (the Collective Era), and privatization after 1984 (the Household Land Contract Period, HLCP). Taking Nileke County of Xinjiang as a case study, this research analyzed the livelihood changes of agro-pastoralists over the two periods using quantitative household livelihood assets—financial, physical, natural, human, and social capital—as indicators. Using annual series data of the five livelihood capitals, a comprehensive livelihood assets index (CLAI) was calculated by two-stage factor analysis. Higher CLAI scores meant better living and reduced poverty for agro-pastoralists. Quantitative results were validated and detailed with semi-structured household interviews. The results showed that CLAI slightly increased during the HLCP in comparison to the Collective Era, mainly due to increases in financial and physical capital. In contrast, natural and social capital showed downward trends, indicating that alleviation of poverty came at the cost of natural resources and social justice. Natural capital was the main contributor to agro-pastoralist livelihoods during the Collective Era, but diminished and was replaced by financial capital during the HLCP. Based on the findings, we put forward policy suggestions to improve community land management and sustainable livelihoods as part of future poverty alleviation efforts.
Research on unconventional shale reservoirs has increased dramatically due to the decline of shale production from conventional reserves. Pore structure analysis can assist in accurately understanding the storage and migration properties of the gas and oil that are very critical for the numerical simulation and overall production estimation. In this chapter, three methods (field emission scanning electron microscope (FESEM), nitrogen adsorption, and mercury intrusion capillary pressure (MICP)) are introduced and applied to analyze the microstructures of shale rocks. Pore information is derived and analyzed using the three methods. Limitations and strengths of the three methods are also described in this chapter. The results showed that nanopores were widely distributed in the shale samples. FESEM is a straightforward way to view the pores but is limited in characterizing the pores in two dimensions. Nitrogen adsorption can quantify the pores that are <200nm in size. MICP can detect pores with a broad size range from a few nanometers to few hundred micrometers. The pore information from the MICP method reflects the pore throat characteristics.
Biomass burning (BB) seriously affect air pollution, human health and global climate. A severe pollution episode (PE) caused by BB was investigated in the southern Sichuan Basin (SSB), one of the most polluted areas in China. Hourly variations in criteria air pollutants (PM2.5, PM10, SO2, NO2, CO, and O3), chemical components, and sources of PM2.5 before, during, and after the severe regional air PE were characterized at three sites, namely Neijiang (NJ), Zigong (ZG), and Yibin (YB). The results showed that combination of intensive pollution from BB, stable meteorological conditions, and the basin topography caused this severe regional PE in the SSB. The average daily concentrations of PM2.5 during the PE were 1.8–6 times those measured during the periods before and after the PE, and 4.0–7.4 times that of World Health Organization air quality guidelines in the SSB. The highest PM levels occurred in ZG, where the peak values of PM2.5 and PM10 reached 536 μg m−3 and 578 μg m−3 at night, respectively. PM10, NO2, and CO also increased dramatically at night in the SSB. O3 formation was affected by BB, showing lower levels at night but higher levels in the day during the PE than before and after the PE, whereas SO2 levels were not affected. Sulfate–nitrate–ammonium in PM2.5 was the main chemical compositions before the PE, whereas organic matter (OM) and K+ became characteristics compositions during and after the PE. Higher OC/EC and Kexcess/EC ratios were observed during the PE and Kexcess/EC ratio was a better indicator of BB in the SSB than OC/EC ratio. The results of a positive matrix factorization model indicated that BB was the most significant contributor to PM2.5 during the PE, accounting for 58% in NJ, 65% in ZG, and 56% in YB. Backward trajectory analysis confirmed that the SSB is susceptible to pollutants from Chongqing and other surrounding cities, especially in ZG and NJ, due to the unique topography of the basin. Our findings suggest that BB in the basin topography can cause severe regional air pollution events at night, thus supporting the critical need for BB control in the basin to improve regional air quality.
Phthalate esters, commonly used as plasticizers, can be found indoors in the gas phase, in airborne particulate matter, in dust, and on surfaces. The dynamic behavior of phthalates indoors is not fully understood. In this study, time-resolved measurements of airborne phthalate concentrations and associated gas-particle partitioning data were acquired in a normally occupied residence. The vapor pressure and associated gas-particle partitioning of measured phthalates influenced their airborne dynamic behavior. Concentrations of higher vapor pressure phthalates correlated well with indoor temperature, with little discernible influence from direct occupant activity. Conversely, occupant-related behaviors substantially influenced the concentrations and dynamic behavior of a lower vapor pressure compound, diethylhexyl phthalate (DEHP), mainly through production of particulate matter during cooking events. The proportion of airborne DEHP in the particle phase was experimentally observed to increase under higher particle mass concentrations and lower indoor temperatures in correspondence with theory. Experimental observations indicate that indoor surfaces of the residence are large reservoirs of phthalates. The results also indicate that two key factors influenced by human behavior—temperature and particle mass concentration—cause short-term changes in airborne phthalate concentrations.
Abstract We investigate source characteristics and emission dynamics of volatile organic compounds (VOCs) in a single-family house in California utilizing time- and space-resolved measurements. About 200 VOC signals, corresponding to more than 200 species, were measured during 8 weeks in summer and five in winter. Spatially resolved measurements, along with tracer data, reveal that VOCs in the living space were mainly emitted directly into that space, with minor contributions from the crawlspace, attic, or outdoors. Time-resolved measurements in the living space exhibited baseline levels far above outdoor levels for most VOCs; many compounds also displayed patterns of intermittent short-term enhancements (spikes) well above the indoor baseline. Compounds were categorized as ?high-baseline? or ?spike-dominated? based on indoor-to-outdoor concentration ratio and indoor mean-to-median ratio. Short-term spikes were associated with occupants and their activities, especially cooking. High-baseline compounds indicate continuous indoor emissions from building materials and furnishings. Indoor emission rates for high-baseline species, quantified with 2-hour resolution, exhibited strong temperature dependence and were affected by air-change rates. Decomposition of wooden building materials is suggested as a major source for acetic acid, formic acid, and methanol, which together accounted for \~75% of the total continuous indoor emissions of high-baseline species.
Carbonyl compounds (carbonyls) play important roles in atmospheric photochemistry, serving as reservoirs of radicals (OH, HO2, and RO2) and precursors of secondary organic aerosols (SOA). Field measurements of gaseous and particulate carbonyls were taken over urban Beijing during summer and winter, and field-measured gas-particle partitioning coefficients (Kp ) were determined. Compared with theoretical values, field-measured Kp values were 4–6 orders of magnitude higher for the six detected carbonyls, which underlined the importance of heterogeneous reactions. In winter, the Kp values of carbonyl compounds were one order of magnitude higher than those in summer owing to the effect of temperature. This study applied the positive matrix factorization (PMF) model to the source apportionment of carbonyl compounds. Five factors were identified for both summer and winter, whereas the biogenic factor was only identified in summer and coal burning was only found in winter. In summer, secondary formation was the largest contributor (39%) to the measured total carbonyl compounds levels. In contrast, vehicular exhaust was the largest source of the measured total carbonyl compounds in winter (37%), although secondary formation still had an important contribution of 31%. The contribution of coal burning to ambient carbonyls was reduced by half compared with prior results. As the most abundant carbonyl compound in the atmosphere, formaldehyde in summer mainly came from secondary production (42%) and primary anthropogenic emissions (48%), while biogenic sources had a minor contribution (10%). However, 78% of formaldehyde was attributed to primary anthropogenic emissions in winter, which indicated that these winter emissions were more important sources of carbonyl compounds. Glyoxal was always dominated by secondary formation, with contributions of 56% in summer and 52% in winter.
The efficient ternary all-polymer solar cells (PSCs) are designed and fabricated, using a polymer acceptor of NDP-V-C7 and analogue co-donors containing a chlorinated polymer PBClT and classical PTB7-Th. PBClT and PTB7-Th possess very similar chemical structure and matched energy levels to form the cascade of the co-donors. Meanwhile, benefiting from those analogous polymer structures, there is little influence of the morphology in blend film compared to their pristine polymer films. The binary PBClT:NDP-V-C7 devices exhibit a high open-circuit voltage (Voc) due to the deep HOMO level of PBClT. The Voc of all-PSCs could be finely manipulated by adjusting the content of PBClT in blend film. The ternary all-PSCs have the more balanced charge mobility and prolonged carrier lifetime compared to the binary devices. The PBClT also help improve the miscibility of ternary blend and suppress crystallization in films, bringing about favorable morphology with appropriate orientation and surface roughness in blend film. With the optimal processing, the champion ternary all-PSCs obtain a high PCE of 9.03%, which is about 10% enhancement compared to that of binary device. The results indicate that the ternary approach using analogue co-donors is a practical method to enhance the performance of all-PSCs.
