Small angle neutron scattering (SANS) analysis was performed on six Bakken Shale samples with different maturities to reveal the complexities in the pore structure. Pore size distribution (PSD), porosity and specific surface area (SSA) were calculated from SANS data via the Polydisperse Spherical Pore (PDSP) model and compared with the data from N2 adsorption and mercury intrusion. The results showed that the Bakken samples have a very small porosity value (less than 1%) and a very larger specific surface area (larger than 180995 cm−1) in the measuring pore size range (pore diameter: 1–200 nm). SANS and N2 adsorption can detect pores in the similar size range (2–200 nm). The SSA measured by SANS and mercury intrusion was found larger than the one detected by N2 adsorption. Pore structure information that is obtained from SANS, N2 adsorption, and mercury intrusion methods exhibited a fractal and multifractal behavior. Moreover, the pore size distribution that is calculated from SANS data was the most heterogeneous. Finally, the effects of rock composition on pore structures demonstrated that organic matter hosts some isolated pores while clay minerals do not host a large quantity of pores that are either connected or isolated.
Inhalation exposure to flame retardants used as additives to minimize fire risk and plasticizers is ubiquitous in human daily activities, but has not been adequately assessed. To address this research gap, the present study conducted an assessment of human health risk for four age groups through inhalation exposure to size fractionated particle-bound and gaseous halogenated flame retardants (polybrominated diphenyl ethers (PBDEs) and alternative halogenated flame retardants (AHFRs)) and organophosphate esters (OPEs) at indoor and outdoor environments (school, office, and residence) in three districts of a megacity (Guangzhou, China). Results demonstrated that OPEs were the dominant components among all targets. Indoor daily intakes of PBDEs and OPEs were 13-16 times greater than outdoor levels for all age groups. Gaseous OPEs contributed significantly greater than particle-bound compounds to daily intakes of all target compounds. Based on the different life scenarios, hazard quotient (HQ) and incremental life cancer risk (ILCR) from adults exposure to PBDEs and OPEs in indoor and outdoor settings were the greatest, followed by adolescents, children, and seniors. The estimated HQ and ILCR for all age groups both indoors and outdoors were lower than the safe level (HQ= 1 and ILCR= 10(-6)), indicating that the potential health risk for local residents in Guangzhou via inhalation exposure to atmospheric halogenated flame retardants and OPEs was low. (C) 2019 Elsevier Ltd. All rights reserved.
In this paper, confined fluid interfacial tensions (IFTs) in nanopores and their influential factors are studied. First, a new generalized equation of state (EOS) considering the pore radius, intermolecular interactions, and wall effect is developed analytically for calculating the thermodynamic phase behaviour of confined pure and mixing fluids in nanopores. Second, the modified model based on the new EOS and coupled with the parachor model, which also takes account for the capillary pressure and shifts of critical properties, is applied to calculate the IFTs in nanopores at different conditions. Third, the following four important factors are specifically studied to evaluate their effects on the IFTs in nanopores: feed gas to liquid ratio (FGLR), temperature, pore radius, and wall-effect distance. The newly-developed model is found to be accurate for vapour–liquid equilibrium (VLE) and IFT calculations in bulk phase and nanopores by comparing with the measured and calculated data in the literature. The IFTs in bulk phase of the pure and mixing hydrocarbon (HC) systems are always higher than those in nanopores. At low pressures, the calculated IFTs in nanopores from the new model are higher than those from the previously modified EOS, whereas they become almost equivalent at high pressures. The calculated IFTs of the simple HC systems in nanopores keep constant at different FGLRs while they are decreased by reducing the FGLRs for a multicomponent mixing HC system. Moreover, at low pressures, the gaseous CO2–mixing HC IFTs in bulk phase and nanopores are inferred to be lowered by increasing the temperature while the liquid/supercritical CO2–mixing HC IFTs may be increased. The temperature effect on the IFTs are weakened in nanopores at most pressures except for some extremely high pressure cases. The IFTs in nanopores are decreased with the reduction of pore radius but keep constant at δp/rp ≥ 1.0.
Abstract Aim Although the effects of climate on species richness are known, regional processes may lead to different species richness?climate relationships across continents resulting in species richness anomalies, especially for tropical groups. Phylogenetic niche conservatism may also influence species richness?climate relationships of different lineages. Here, we tested whether regional effects also exist for temperate lineages using the genus Quercus. Location Northern Hemisphere. Time period Present day. Major taxa studied Quercus (Fagaceae). Methods We used a dated phylogeny and distribution data for Quercus to evaluate its global species richness patterns and phylogenetic niche conservatism. To evaluate the consistency in species richness?climate relationships across continents of the genus Quercus as a whole and the temperate subgenus Quercus, we conducted analyses of covariance with continent as the categorical variable and climate variables as the covariate. We calibrated four widely used models using the global data or data from each continent separately and evaluated the predictive power of each model for different continents using the root mean squared error. Results The relationships between species richness and climate were not significantly different among continents for both the genus Quercus as a whole and the subgenus Quercus. Unlike the models based on European data, those based on North American and eastern Asian data predicted both the global species richness and the richness in other continents. The species richness of a subtropical subgenus Cyclobalanopsis was most influenced by water availability, while that of a temperate subgenus Quercus was most influenced by environmental temperature. Main conclusions In contrast to the subtropical subgenus Cyclobalanopsis, our results showed a consistent richness?climate relationship and absence of regional effects on species richness across continents for the temperate subgenus Quercus, likely suggesting that the species richness of temperate lineages, for example subgenus Quercus, may have reached equilibrium with the contemporary climate in the Northern Hemisphere.
Jia N, Chen Y, Guo D, Liu Y. Construction and application of triangle model for community risk prevention. Xitong Gongcheng Lilun yu Shijian/System Engineering Theory and PracticeXitong Gongcheng Lilun yu Shijian/System Engineering Theory and PracticeXitong Gongcheng Lilun yu Shijian/System Engineering Theory and Practice. 2019;39:2855-2864.Abstract
Biogeographic patterns and drivers of soil microbial diversity have been extensively studied in the past few decades. However, most research has focused on the topsoil, while the subsoil is assumed to have microbial diversity patterns similar to those of the topsoil. Here we compared patterns and drivers of microbial alpha and beta diversity in and between topsoils (0 to 10 cm) and subsoils (30 to 50 cm) of temperate grasslands in Inner Mongolia of China, covering an ∼1,500-km transect along an aridity gradient. Counter to the conventional assumption, we find contrasting biogeographic patterns of diversity and influencing factors for different bacterial and archaeal groups and between depths. While bacterial diversity remains constant or increases with increasing aridity in topsoil and decreases in subsoil, archaeal diversity decreases in topsoil and remains constant in subsoil. Microbial diversity in the topsoil is most strongly influenced by aboveground vegetation and contemporary climate but is most strongly influenced by the factor historical temperature anomaly since the Last Glacial Maximum (LGM) and by soil pH in the subsoil. Moreover, the biogeographic patterns of topsoil-subsoil community dissimilarities vary for different microbial groups and are overall most strongly influenced by soil fertility differences between depths for bacteria and by contemporary climate for archaea. These findings suggest that diversity patterns observed in the topsoil may not be readily applied to the subsoil horizons. For the subsoil in particular, historical climate plays a vital role in the spatial variation of bacterial diversity. Overall, our study provides novel information for understanding and predicting soil microbial diversity patterns at depth.IMPORTANCE Exploring the biogeographic patterns of soil microbial diversity is critical for understanding mechanisms underlying the response of soil processes to climate change. Using top- and subsoils from an ∼1,500-km temperate grassland transect, we find divergent patterns of microbial diversity and its determinants in the topsoil versus the subsoil. Furthermore, we find important and direct legacy effects of historical climate change on the microbial diversity of subsoil yet indirect effects on topsoil. Our findings challenge the conventional assumption of similar geographic patterns of soil microbial diversity along soil profiles and help to improve our understanding of how soil microbial communities may respond to future climate change in different regions with various climate histories.
Molybdenite-bearing porphyry deposits are the predominant supplier of molybdenum to industrialized society and one of the main hosts of Mo in the upper continental crust. The Mo isotope compositions (delta Mo-98/95, normalized to NIST3134 equals 0 parts per thousand) of molybdenite show considerable variation (-1.62 to + 2.27 parts per thousand), but the factors controlling this variability remain poorly constrained. This information is critical for underpinning genetic models of porphyry deposits, understanding elemental cycling, and utilizing the delta Mo-98/95 of marine sediments as a paleoredox proxy. Using the well-characterized Qulong porphyry Cu-Mo deposit (Tibet) as an example, here we discuss how rapid cooling, facilitated by mixing hot magmatic fluid with cold meteoric water, can be a controlling factor on efficient mineralization, and then tackle how fluid evolution regulates molybdenum isotope fractionation. Molybdenites, which preferentially partition isotopically light Mo (Rayleigh fractionation), precipitated from a single fluid will develop a heavier delta Mo-98/95 composition over time, and this also creates hetero-geneous delta Mo-98/95 between molybdenite grains. Whereas a fluid undergoing multiple episodes of intensive boiling will gradually lose its isotopically heavy Mo to the vapor phase, molybdenites crystallizing successively from the residual liquid will then have lighter delta Mo-98/95 over time. However, when mineralization efficiency becomes too low, a negligible variation in delta Mo-98/95 of molybdenite is observed. Given that the mineralization efficiency (i.e., the amount of Mo crystallized as molybdenite from the fluid) rarely reaches 100% and molybdenite favors isotopically light Mo, the presence of a residual fluid with isotopically heavy Mo is inevitable. This residual fluid may then become trapped in alteration halos; hence, delta Mo-98/95 has the potential to aid in locating the mineralization center (e.g., lighter delta Mo-98/95 toward the orebody). The residual fluid may also feed surface hydrological systems and eventually impact Mo cycling. Our study highlights that understanding the controls of isotope fractionation is critical to bridge the gap between ore formation and elemental cycling, and that other transition metals (e.g., Cu, Fe, and Zn) may follow similar trajectories.
Understanding how defaults correlate across firms is a persistent concern in risk management. In this paper, we apply covariate-dependent copula models to assess the dynamic nature of credit risk dependence, which we define as “credit risk clustering”. We also study the driving forces of the credit risk clustering in CEC business group in China. Our empirical analysis shows that the credit risk clustering varies over time and exhibits different patterns across firm pairs in a business group. We also investigate the impacts of systematic and idiosyncratic factors on credit risk clustering. We find that the impacts of the money supply and the short-term interest rates are positive, whereas the impacts of exchange rates are negative. The roles of the CPI on credit risk clustering are ambiguous. Idiosyncratic factors are vital for predicting credit risk clustering. From a policy perspective, our results not only strengthen the results of previous research but also provide a possible approach to model and predict the extreme co-movement of credit risk in business groups with financial indicators.
Summary Contractile injection systems (CISs) are cell-puncturing nanodevices that share ancestry with contractile tail bacteriophages. Photorhabdus virulence cassette (PVC) represents one group of extracellular CISs that are present in both bacteria and archaea. Here, we report the cryo-EM structure of an intact PVC from P. asymbiotica. This over 10-MDa device resembles a simplified T4 phage tail, containing a hexagonal baseplate complex with six fibers and a capped 117-nanometer sheath-tube trunk. One distinct feature of the PVC is the presence of three variants for both tube and sheath proteins, indicating a functional specialization of them during evolution. The terminal hexameric cap docks onto the topmost layer of the inner tube and locks the outer sheath in pre-contraction state with six stretching arms. Our results on the PVC provide a framework for understanding the general mechanism of widespread CISs and pave the way for using them as delivery tools in biological or therapeutic applications.