This study was carried out to characterize three aldehydes of health concern (formaldehyde, acetaldehyde, and acrolein) at a central Beijing site in the summer and early fall of 2008 (from June to October). Aldehydes in polluted atmospheres come from both primary and secondary sources, which limits the control strategies for these reactive compounds. Measurements were made before, during, and after the Beijing Olympics to examine whether the dramatic air pollution control measures implemented during the Olympics had an impact on concentrations of the three aldehydes and their underlying primary and secondary sources. Average concentrations of formaldehyde, acetaldehyde and acrolein were 29.3+/-15.1 mug/m(3), 27.1+/-15.7 mug/m(3) and 2.3+/-1.0 mug/m(3), respectively, for the entire period of measurements, all being at the high end of concentration ranges measured in cities around the world in photochemical smog seasons. Formaldehyde and acrolein increased during the pollution control period compared to the pre-Olympic Games, followed the changing pattern of temperature, and were significantly correlated with ozone and with a secondary formation factor identified by principal component analysis (PCA). In contrast, acetaldehyde had a reduction in mean concentration during the Olympic air pollution control period compared to the pre-Olympic period and was significantly correlated with several pollutants emitted from local emission sources (e.g., NO2, CO, and PM2.5). Acetaldehyde was also more strongly associated with primary emission sources including vegetative burning and oil combustion factors identified through the PCA. All three aldehydes were lower during the post-Olympic sampling period compared to the before and during Olympic periods, likely due to seasonal and regional effects. Our findings point to the complexity of source control strategies for secondary pollutants.
The hollow core of a carbon nanotube (CNT) provides a unique opportunity to explore the physics, chemistry, biology, and metallurgy of different materials confined in such nanospace. Here, we investigate the nonequilibrium metallurgical processes taking place inside CNTs by in situ transmission electron microscopy using CNTs as nanoscale resistively heated crucibles having encapsulated metal nanowires/crystals in their channels. Because of nanometer size of the system and intimate contact between the CNTs and confined metals, an efficient heat transfer and high cooling rates (similar to 10(13) K/s) were achieved as a result of a flash bias pulse followed by system natural quenching, leading to the formation of disordered amorphous-like structures in iron, cobalt, and gold. An intermediate state between crystalline and amorphous phases was discovered, revealing a memory effect of local short-to-medium range order during these phase transitions. Furthermore, subsequent directional crystallization of an amorphous iron nano wire formed by this method was realized under controlled Joule heating. High-density crystalline defects were generated during crystallization due to a confinement effect from the CNT and severe plastic deformation involved.
The majority of children with Dravet syndrome (DS) are caused by de novo SCN1A mutations. To investigate the origin of the mutations, we developed and applied a new method that combined deep amplicon resequencing with a Bayesian model to detect and quantify allelic fractions with improved sensitivity. Of 174 SCN1A mutations in DS probands which were considered “de novo” by Sanger sequencing, we identified 15 cases (8.6%) of parental mosaicism. We identified another five cases of parental mosaicism that were also detectable by Sanger sequencing. Fraction of mutant alleles in the 20 cases of parental mosaicism ranged from 1.1% to 32.6%. Thirteen (65% of 20) mutations originated paternally and seven (35% of 20) maternally. Twelve (60% of 20) mosaic parents did not have any epileptic symptoms. Their mutant allelic fractions were significantly lower than those in mosaic parents with epileptic symptoms (P = 0.016). We identified mosaicism with varied allelic fractions in blood, saliva, urine, hair follicle, oral epithelium, and semen, demonstrating that postzygotic mutations could affect multiple somatic cells as well as germ cells. Our results suggest that more sensitive tools for detecting low‐level mosaicism in parents of families with seemingly “de novo” mutations will allow for better informed genetic counseling.
The employment quality of college graduates is a recent topic of heated discussion in China. Given the differences in the talent development goals of academic and vocational institutions and in individual job search approaches, this research compares the differences between the job search approaches and actual employment outcomes of graduates of undergraduate and vocational institutions, and analyzes the correspondence of vocational graduates' job search approaches with their job search outcomes to identify the effect of higher vocational education on employment. Using the proposed methods, this study finds a significant gap in job search approaches between the two types of graduates and that higher vocational education significantly affects employment approaches and outcomes. The job search approaches of vocational graduates also influence their employment outcomes. The study concludes that the employment quality of vocational graduates is not necessarily worse than that of
The idea of single particle aerosol mass spectrometry was first proposed in the 1970s and then developed quickly in recent two decades. Because it can simultaneously provide much information including particle size distribution, composition of multiple chemical species and mixing state for each single particle with high-time resolution, single particle aerosol mass spectrometry has been widely applied in the area of environmental monitoring and fine particulate matter research. This review aims to (1) provide an introduction of the development history and progress of single particle aerosol time-of-flight mass spectrometry, (2) summarize its principle, methods for data analysis, output of results and its applications in environmental measurement and research using two major commercialized instruments (ATOFMS and SPAMS), and (3) provide suggestions for future research.
The debonding of particle/matrix interfaces has an important effect on the behavior of composite materials. During last decades, great efforts have been made to simulate the behavior of the interface. Boundary element method, as an alternative effective numerical method, has great advantages in simu...
The Chinese government has adopted Payment for Ecosystem Services (PES) as a main approach for preventing or restoring rangelands perceived as undergoing degradation on a massive scale. Using the PES project, known as the 'retire livestock, restore rangeland' project in Alxa of Inner Mongolia as an example, the long-term ecological consequences of such projects is assessed, and the causes of the associated problems from the perspective of social-ecological system explored. Study findings demonstrate that PES, as used in the case study area, is unlikely to achieve the expected outcome of rangeland restoration in the long term. The root cause of such failure is that the PES approach focuses on end-point ecosystem services (outputs), while at the same time decoupling the feedbacks among social and ecological systems that are the key to generating such services. This drives the overall social-ecological system into an undesirable basin of attraction. It is concluded that a PES program for pastoral systems should aim to improve resilience of such a coupled social-ecological system to external shocks and changes, instead of simply maintaining ecological services without considering the origins of such services in the inter-relationship of humans and environment. It is argued that 'Payment for Ecosystem Services' should be displaced by 'Payment for Social-ecological System Resilience' in future policy discussions.;The Chinese government has adopted Payment for Ecosystem Services (PES) as a main approach for preventing or restoring rangelands perceived as undergoing degradation on a massive scale. Using the PES project, known as the 'retire livestock, restore rangeland' project in Alxa of Inner Mongolia as an example, the long-term ecological consequences of such projects is assessed, and the causes of the associated problems from the perspective of social-ecological system explored. Study findings demonstrate that PES, as used in the case study area, is unlikely to achieve the expected outcome of rangeland restoration in the long term. The root cause of such failure is that the PES approach focuses on end-point ecosystem services (outputs), while at the same time decoupling the feedbacks among social and ecological systems that are the key to generating such services. This drives the overall social-ecological system into an undesirable basin of attraction. It is concluded that a PES program for pastoral systems should aim to improve resilience of such a coupled social-ecological system to external shocks and changes, instead of simply maintaining ecological services without considering the origins of such services in the inter-relationship of humans and environment. It is argued that 'Payment for Ecosystem Services' should be displaced by 'Payment for Social-ecological System Resilience' in future policy discussions. Additional keywords: Inner Mongolia, payment for ecosystem services, rangeland conservation, social-ecological system.;
In this paper, the shear-improved Smagorinsky model (SISM) is assessed in a K-type transitional channel flow. Our numerical simulation results show that the original SISM model is still too dissipative to predict the transitional channel flow. Two former reported empirical correction approaches, including a low-Reynolds-number correction and a shape-factor-based intermittency correction, are applied to further promote the capability of the SISM model in simulating the transition process. Numerical tests show that the shape-factor-based intermittency correction approach can correctly improve the transition-prediction capability of the SISM model, while the low-Reynolds-number correction approach fails. Furthermore, the shape-factor-based intermittency-corrected SISM model can capture the vortical structures during the transitional process very well and possesses the grid-insensitive characteristics.
It is not known whether exposure to air pollutants causes systemic oxidative stress in children. We investigated the association between exposure to air pollution and biomarkers of oxidative stress in relation to a governmental air quality intervention implemented during the 2008 Beijing Olympic Games. We studied 36 schoolchildren during 5 time periods before and during the Olympic Games in Beijing (June 2007-September 2008). The oxidative stress biomarkers 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and malondialdehyde were measured in urine samples collected daily during each period. Generalized estimating equations were used to examine the relationship between repeated biomarker measurements and ambient air pollutant levels. During the Olympic intervention period, substantial reductions in air pollution (-19% to -72%), urinary 8-oxodG concentrations (-37.4%; 95% confidence interval: -53.5, -15.7), and urinary malondialdehyde concentrations (-25.3%; 95% confidence interval: -34.3, -15.1) were found. Malondialdehyde and 8-oxodG were significantly associated with concentrations of black carbon, fine particulate matter with an aerodynamic with diameter less than 2.5 mu m, sulfur dioxide, nitrogen dioxide, and carbon monoxide. Biomarker changes per each interquartile-range increase in pollutants were largest at lag 0 or lag 1. In a 2-pollutant model, the most robust associations were for black carbon. These findings suggest that exposure to black carbon leads to systemic oxidative stress in children.
STUDY QUESTION: Is polycystic ovary syndrome (PCOS) associated with increased serum levels of typical organic pollutants? summary answer: PCOS in Han females from Northern China was significantly associated with elevated serum levels of pollutants, including polychlorinated biphenyls (PCBs), organochlorine pesticides and polycyclic aromatic hydrocarbons (PAHs). what is known already: PCOS is arguably the most common endocrinopathy in females of reproductive age. The etiology of PCOS is thought to be multifactorial. study design, size, duration: This was a preliminary case-control study undertaken at the Division of Reproductive Center, Peking University Third Hospital. Fifty participants affected by PCOS and 30 normal controls were recruited between August and October 2012 from Northern China. All participants were Han women. participants/materials, setting, methods: PCOS participants were diagnosed according to the 2003 Rotterdam criteria. The control participants were non-pregnant females unable to conceive solely due to male azoospermia. Serum levels of a wide range of organic pollutants, including PCBs, organochlorine pesticides, PAHs and more than 20 phenolic pollutants, were analyzed using gas chromatographic mass spectrometry. main results and the role of chance: Serum levels of PCBs, pesticides and PAHs were significantly higher in the PCOS group than the control group. Concentrations of PCBs, p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE) and PAHs in serum above median levels were associated with PCOS with odds ratios of 3.81 [95% confidence interval (CI), 1.45-10.0], 4.89 (95% CI, 1.81-13.2) and 2.39 (95% CI, 0.94-6.05), respectively. Partial least-squares-discriminant analysis (PLS-DA) confirmed that serum levels of organic pollutants were associated with PCOS, especially for p, p'-DDE and PCBs. limitations, reasons for caution: Some other possible covariates (e.g. dietary and income) were missed in this study, although education and occupation have been considered as an indicator of personal income. The PLS-DA model allowed a quasi-exposome analysis with over 60 kinds of typical organic pollutants; however, the possibility of other pollutants involved in the PCOS still could not be excluded. wider implications of the findings: Our study identified that bodily retention of environmental organic pollutants-including PCBs, pesticides (especially p, p'-DDE) and PAHs-was associated with PCOS.