In petroleum industry, creep behavior of rocks can affect the fracture conductivity, well productivity and ultimate recovery of the reservoir, in shale formations in particular. To get a better insight into this phenomenon, in this study, we applied grid nanoindentation method as a function of time to quantify creep behavior of shale rocks which is a complex material. The deconvolution results from statistical analysis of the data showed that shale samples could be distinguished by three mechanical phases where the mechanical phase with the largest hardness value exhibits the least creep deformation. Burgers models was applied to characterize the creep behavior of our shale samples. We realized as creep time increases, the creep time constant value increases, therefore, a logarithmic function can be used to quantify their correlations. This study showed that as the creep time increases, Young's modulus, hardness, and fracture toughness will decrease. Finally, we concluded, shale samples become softer and more prone to fracture growth as the creep time increases.
Pharmaceutically active compounds (PhACs) are widely detected emerging contaminants in water environments and possess high potential risks to human health and aquatic life; however, conventional water treatment processes cannot remove them sufficiently. The boom in nanoscience and nanotechnology offers opportunities to leapfrog on the back of these new technologies to develop innovative techniques in the field of water treatment. The extraordinary properties of nanomaterials, such as large surface area, quantum effect, electrochemical and magnetic properties, and other size-dependent physical and chemical properties, offer nanotechnologies great advantages over conventional technologies. To date, nanomaterials have been extensively applied or investigated in adsorption, photocatalysis, catalytic ozonation and filtration processes and have been shown to have many promising potential application prospects. Among the various nanomaterials, graphene and carbon nanotubes have shown a superior adsorption capacity for the removal of PhACs and possess great potential for modifying photocatalysts; moreover, they can also act as highly efficient catalysts for ozonation. The nano-sized photocatalysts, i.e. nano-TiO2, graphitic carbon nitride, MoS2 nanosheets, and ZnO, generally exhibit higher photocatalytic activity than bulk photocatalysts. The involvement of nanomaterials in a membrane can improve the permeability, selectivity, and anti-fouling properties of the membrane for improved filtration processes. However, some challenges, such as high cost, poor separation performance and environmental risks, are still impeding their engineering application. Aiming to provide readers with a comprehensive insight into the application of nanotechnologies for PhACs' remediation, the current review summarizes the recent advances and breakthroughs made in nanotechnology for PhACs' removal, highlights the modification methods for improving the effectiveness of treatment methods using nanomaterials, and proposes a number of possible further research directions.
In this paper, an empirical correlation is modified and applied to predict the CO2 bubble-rising velocity (BRV) in the light crude oil. On a basis of the predicted BRVs, the minimum miscibility pressures (MMPs) of three light crude oil−CO2 systems are estimated by using the BRV criterion with the rising-bubble apparatus (RBA). First, a correction term of s·2PρL0.5 is added into the BRV correlation in order to reflect the velocity of falling liquid film in velocity field by applying the Bernoulli’s theorem. The modified correlation is tuned to match the BRVs of the dead light oil–pure and impure CO2 systems from the literature and two respective numerical coefficients s of −0.00046 and −0.00028 are determined by using the non-linear least-square method. It is found that the BRV is positive proportionally increased with the bubble diameter, interfacial tension, and density difference. Second, the predicted BRVs are used to estimate the MMPs by using the BRV criterion. Two respective MMPs of the dead light oil–pure and impure CO2 systems are found to be 12.4 MPa and 23.7 MPa at Tres = 53.0 °C, which agree well with 12.4–12.9 MPa from the coreflood tests and 23.4 MPa from the RBA tests or 23.4–23.5 MPa from the vanishing interfacial tension (VIT) technique. In addition, a live light oil–pure CO2 system is added to validate the modified BRV correlation. By means of the predicted BRVs, the MMP of the live oil–pure CO2 system is estimated to be 15.5 MPa, which matches well with 15.2–15.4 MPa from the slim-tube tests. The modified empirical correlation can improve the efficiency and capability of the BRV criterion.
Improving the colloidal stability of magnetite nanoparticles (MNPs) is essential for their successful applications. In this study, the surface zeta potential and particle size evolutions of citric acid coated magnetite nanoparticles (CA-MNPs) were measured under varied aqueous conditions using dynamic light scattering (DLS). The effects of pH (5.0–9.0), ionic strength (IS), cations (Na+ and Ca2+), anions (phosphate, sulfate, and chloride) and humic acid on the aggregation behaviors of CA-MNPs were explored. Compared with bare MNPs, the stability of CA-MNPs were greatly improved over the typical pH range of natural aquatic environments (pH = 5.0–9.0), as the coated CA-MNPs were highly negatively charged over the pH range due to the low pKa1 value (3.13) of citrate acid. CA-MNPs were more stable in the presence of monovalent cation (Na+) compared with divalent cation (Ca2+), as Ca2+ could neutralize the surface charge of MNPs more significantly than Na+. In the presence of anions, the surface charges of CA-MNPs became more negative, and the stability of CA-MNPs followed the order: in phosphate > sulfate > chloride. The observed aggregation trend could be explained by the differences in the valences of the anions and their adsorption behaviors onto CA-MNPs, which altered the surface charges of CA-MNPs. The measured critical coagulation concentrations (CCC) values of CA-MNPs in these electrolyte solutions agreed well with Derjaguin–Landau–Verwey–Overbeek (DLVO) calculations. With the addition of Humic acid (HA), the aggregation of CA-MNPs was inhibited in all electrolyte solutions even with the critical coagulation concentrations. This is due to the adsorption of HA onto CA-MNPs, which enhanced the electrostatic and steric repulsive forces between CA-MNPs. Considering the good stability of CA-MNPs in solutions with varied pH and electrolyte compositions, as well as with the easy synthesis of CA-MNPs and their non-toxicity, this study suggested CA coating as a good strategy to increase the stability of MNPs.
An increasing number of policy makers in developing countries have made the mass expansion of upper-secondary vocational education and training (VET) a top priority. The goal of this study is to examine whether VET fulfills these objectives of building skills and abilities along multiple dimensions and further identify which school-level factors help vocational students build these skills and abilities. To fulfill this goal, we analyzed representative, longitudinal data that we collected on more than 12,000 students from 118 schools in one province of central China. First, descriptive analysis shows that approximately 90 percent of VET students do not make any gains in vocational or general skills. In addition, negative behaviors (misbehavior in the classroom, antisocial behavior, and other risky behaviors) are highly prevalent among VET students. A nontrivial proportion of student internships also fail to meet minimum government requirements for student safety and well-being. Perhaps as a result of these outcomes, more than 60 percent of students express dissatisfaction with their VET programs, as evidenced by either self-reports or dropping out. Finally, using a multilevel model, we find that school inputs (such as school size, teacher qualifications, and per pupil expenditures) are not correlated with vocational and general skill at the end of the school year, or student dropout in the academic year.
Although a number of studies have assessed the occurrence of atmospheric polycyclic aromatic hydrocarbons (PAHs) in indoor environment, few studies have systemically examined the indoor-outdoor interplay of size-dependent particulate PAHs and potential health risk based on daily lifestyles. In the present study, size-dependent particle and gaseous samples were collected both indoors and outdoors within selected schools, offices and residences located in three districts of Guangzhou, China with different urbanization levels during the dry and wet weather seasons. Results from measurements of PAHs showed that higher total PAH concentrations occurred in residential areas than in other settings and in indoor than in outdoor environments. Compositional profiles and size distribution patterns of particle-bound PAHs were similar indoors and outdoors, predominated by 4-and 5-ring PAHs and the 0.56-1.0 sm particle fraction. Statistical analyses indicated that outdoor sources may have contributed to 38-99% and 62-100% of the variations for indoor particle-bound and gaseous PAH concentrations, respectively. Incremental life cancer risk (ILCR) from human exposure to indoor and outdoor PAHs based on different lifestyles followed the order of adults > children > adolescents > seniors. All average ILCR values for four age groups were below the lower limit of the Safe Acceptable Range (10(-6)). In addition, the ILCR value for adults (average: 7.2 x 10(-7); 95% CI: 5.4 x 10(-8) -2.5 x 10(-6)), estimated from outdoor air PAH levels with 24-h exposure time, was significantly higher than our assessment results (average: 5.9 x 10(-7); 95% Cl: 6.3 x 10(-8)-1.9 x 10(-6)), suggesting the significance of assessing human inhalation exposure risks of indoor and outdoor PAHs in urban air based on daily lifestyles. (C) 2018 Elsevier Ltd. All rights reserved.
The Computable General Equilibrium (CGE) model could capture the full range of interaction and feedback effects among different agents in the economic system. This study analyzes the economic impacts of differentiated carbon reduction targets by using a two-region CGE model in Tianjin Municipal City of China (hereafter “Tianjin”). Firstly, based on a business-as-usual (BaU) scenario and seven proposed carbon reduction scenarios, this paper quantifies the macroeconomic impacts of different carbon reduction targets in both regions, especially the carbon reduction costs and industrial output. Furthermore, several typical industries in Tianjin are chosen to explore how their competitiveness is affected under different carbon allocation scenarios. The results show that compared with the BaU scenario, the Gross Domestic Product (GDP) in Tianjin would achieve the highest growth rate if the carbon intensity reduction target is set at 65% in Tianjin whereas 55% in the rest of China (ROC). Meanwhile, residents’ welfare loss in Tianjin will be the largest if carbon intensity reduction target in 2030 is set to be 65% in Tianjin and 75% in ROC. Also, the local pillar industries (including electronic sector and the metal smelting sector) would benefit from the carbon reduction policy, while the paper sector would be negatively influenced. Policy recommendations are raised, in which several factors should be fully considered, including development stages, resource endowments, technical levels and local environmental carrying capacity.
Background: Adverse effects of ambient fine particles (PM2.5) on sperm quality and oocyte fertilization have been identified by previous research. However, insufficient human studies tested associations between PM2.5 and decreased fertility rates.Methods: We associated long-term exposure to PM2.5 and county-level fertility rates reported by 2010 census across China. Exposure assessments were based on PM2.5 maps (2009-2010) with a spatial resolution of 0.1 degrees derived from satellite remote sensing data from another published study. We used a Poisson regression to examine the relationship between PM2.5 and fertility rates with adjustment of potential confounders including county-level socioeconomic factors (e.g. sex ratio) and a spatially smoothed trend.Results: We found that fertility rates were significantly decreased by 2.0% (95% confidence interval: 1.8%, 2.1%) per 10 mu g/m(3) increment of PM2.5. We also found a geographical variation of the associations.Conclusions: The study add to epidemiological evidences on adverse effects of PM2.5 on fertility rates. (C) 2018 Elsevier Ltd. All rights reserved.
The association between maternal exposure to PM2.5 and birthweight varies geographically, which may be caused by susceptibility. Whether this population-level association is a function of mixtures of individuals with different susceptibilities is unclear. We investigated the probability distribution of individuals with different susceptibilities to PM2.5-related birthweight change, and evaluated spatial variation of the effect across the United States (US). We estimated the individual-level susceptibility using the effect of PM2.5 among a homogenous subpopulation, which was defined by a specific combination of modifiers. According to frequencies for all combinations, we derived the probability distribution of differential susceptibilities across the US and by states. From birth certificates across the US (1999-2004), we analyzed a total of 18,317,707 samples of singletons. Of the samples, 54-55% were assigned valid exposures, and linked to PM2.5. The subpopulation-specific associations of PM2.5 on birthweight change (i.e., susceptibilities) ranged from negative to positive. For the firsttrimester exposure, 61.4% of the associations were negative, and the mean was - 1.01 g (95% confidence interval, CI: - 1.63, - 0.38) of birthweight change per 5 mu g/m(3) increase of PM2.5. The state-level associations varied (from - 2.04 g - 2.76, -1.31] in New Hampshire to - 0.30 g [-1.01, 0.41] in Texas) with demographic compositions in the US. The between-state variations of maternal race and education level were the greatest contributors to the spatial heterogeneity. Our findings may be useful to the policymaker in planning interventions for subpopulations susceptible to ambient pollution.
Ambient pollutants are associated with clinical and sub-clinical indicators of infertility, such as poor sperm quality. However, the link between the ambient fine particle (PM2.5) concentration and the fertility rate (FR) is unclear. In this epidemiological study, we examined the association between PM2.5 concentration and childlessness in the United States (US). We conducted a nationwide spatiotemporal study of ~29 million births in 520 US counties from 2003 to 2011. We obtained monthly numbers and demographic data of newborns from the Centers for Disease Control and Prevention, and PM2.5 estimates from a downscaling model of in situ observations and outputs from the Community Multiscale Air Quality Model. We evaluated the association between the mean PM2.5 concentration and the FR during the gestational (0–8 months before birth) and pre-gestational (9–11 months before birth) periods using a Poisson model with demographic and socioeconomic covariates. We found a significant association between the FR and PM2.5 exposure during pre-gestation but not gestation. Each 5 μg/m3 increase in pre-gestational PM2.5 exposure was associated with a 0.7% (0.0%, 1.4%) reduction in the FR. Nonlinear analysis suggested a sublinear association between the reduction in the FR and PM2.5 concentration without a safety threshold. Additionally, an annual mean reduction of 1.16 (1.15, 1.17) births per 1000 females aged 15–44 years was attributable to PM2.5. This study established, for the first time, an association in the US between the FR and PM2.5 concentration, a finding that adds to the extant epidemiological evidence of the effects of ambient pollutants on fertility, and extends the scope of the impact of low air quality on health.
Hypertensive disorders in pregnancy harm both maternal and infant health and have been linked to ambient particulate matter. However, existing studies are restricted to a local scale and remain inconsistent. A large-scale study is required to enrich the epidemiological evidence and explore the potential sources of the inconsistency. Making use of US birth certificates (1999-2004), and monitoring data from the environmental protection agency air quality networks, we associated hypertensive disorders in pregnancy with maternal exposure to fine particles or coarse particles using logistic regression analysis after adjusting for many covariates among >5 million subjects in the contiguous United States. Additional analyses were conducted to examine variations in the associations according to (1) census divisions; (2) individual-level factors; (3) a socioeconomic indicator, county-level poverty; and (4) the concentration of ambient particles. The results indicated that hypertensive disorders in pregnancy were robustly linked to maternal exposure to fine particles with an adjusted odds ratio of 1.10 (95% confidence intervals, 1.08-1.12) per 5 mu g/m(3) increment in terms of the entire pregnancy mean. Stronger associations were found among white mothers. There were also considerable variations in the association by census division or poverty level among counties. Nonlinear analysis indicated a sublinear dose-response function with a threshold concentration of 9 g/m(3). Based on the national study, we calculated the population attributable fractions and found that 8.1% (6.8%-9.4%) of hypertensive disorder cases were attributable to an entire pregnancy exposure of fine particles. These findings can help policymakers to plan related interventions.
In this review paper, we synthesize the current knowledges about bacteria in atmospheric waters, e.g., cloud, fog, rain, and snow, most of which were obtained very recently. First, we briefly describe the importance of bacteria in atmospheric waters, i.e., the essentiality of studying bacteria In atmospheric waters in understanding aerosol-cloud-precipitation-climate interactions in the Earth system. Next, approaches to collect atmospheric water samples for the detection of bacteria and methods to identify the bacteria are summarized and compared. Then the available data on the abundance, viability and community composition of bacteria in atmospheric waters are summarized. The average bacterial concentration in cloud water was usually on the order 10(4)-10(5) cells mL(-1), while that in precipitation on the order 10(3)-10(4) cells mL(-1). Most of the bacteria were viable or metabolically active. Their community composition was highly diverse and differed at various sites. Factors potentially influencing the bacteria, e.g., air pollution levels and sources, meteorological conditions, seasonal effect, and physicochemical properties of atmospheric waters, are described. After that, the implications of bacteria present in atmospheric waters, including their effect on nucleation in clouds, atmospheric chemistry, ecosystems and public health, are briefly discussed. Finally, based on the current knowledges on bacteria in atmospheric waters, which in fact remains largely unknown, we give perspectives that should be paid attention to in future studies.
Monolayer transition metal dichalcogenides (TMDs) have become essential two-dimensional materials for their perspectives in engineering next-generation electronics. For related applications, the controlled growth of large-area uniform monolayer TMDs is crucial, while it remains challenging. Herein, we report the direct synthesis of 6-inch uniform monolayer molybdenum disulfide on the solid soda-lime glass, through a designed face-to-face metal-precursor supply route in a facile chemical vapor deposition process. We find that the highly uniform monolayer film, with the composite domains possessing an edge length larger than 400 µm, can be achieved within a quite short time of 8 min. This highly efficient growth is proven to be facilitated by sodium catalysts that are homogenously distributed in glass, according to our experimental facts and density functional theory calculations. This work provides insights into the batch production of highly uniform TMD films on the functional glass substrate with the advantages of low cost, easily transferrable, and compatible with direct applications.