Source apportionment and ozone formation mechanism of VOCs considering photochemical loss in Guangzhou, China.

Understanding the sources and impact of volatile organic compounds (VOCs) on ozone formation is challenging when the traditional method does not account for their photochemical loss. In this study, online monitoring of 56 VOCs was carried out in summer and autumn during high ozone pollution episodes. The photochemical age method was used to evaluate the atmospheric chemical loss of VOCs and to analyze the effects on characteristics, sources, and ozone formation of VOC components. The initial concentrations during daytime were 5.12 ppbv and 4.49 ppbv higher than the observed concentrations in the summer and autumn, respectively. The positive matrix factorization (PMF) model identified 5 major emission sources. However, the omission of the chemical loss of VOCs led to underestimating the contributions of sources associated with highly reactive VOC components, such as those produced by biogenic emissions and solvent usage. Conversely it resulted in overestimating the contributions from VOC components with lower chemical activity such as liquefied petroleum gas (LPG) usage, vehicle emissions, and gasoline evaporation. Furthermore, the estimation of ozone formation may be underestimated when the atmospheric photochemical loss is not taken into account. The ozone formation potential (OFP) method and propylene-equivalent concentration method both underestimated ozone formation by 53.24 ppbv and 47.25 ppbc, respectively, in the summer, and by 40.34 ppbv and 26.37 ppbc, respectively, in the autumn. The determination of the ozone formation regime based on VOC chemical loss was more acceptable. In the summer, the ozone formation regime changed from the VOC-limited regime to the VOC-NOx transition regime, while in the autumn, the ozone formation regime changed from the strong VOC-limited regime to the weak VOC-limited regime. To obtain more thorough and precise conclusions, further monitoring and analysis studies will be conducted in the near future on a wider variety of VOC species such as oxygenated VOCs (OVOCs).

Average and statistical properties of coherent radiation from steady-state microbunching.

A promising accelerator light source mechanism called steady-state microbunching (SSMB) is being actively studied. With the combination of strong coherent radiation from microbunching and high repetition rate of a storage ring, high-average-power narrow-band radiation can be anticipated from an SSMB storage ring, with wavelengths ranging from THz to soft X-ray. Such a novel light source could provide new opportunities for accelerator photon science like high-resolution angle-resolved photoemission spectroscopy and industrial applications like extreme ultraviolet (EUV) lithography. In this paper, a theoretical and numerical study of the average and statistical properties of coherent radiation from SSMB are presented. The results show that 1 kW average-power quasi-continuous-wave EUV radiation can be obtained from an SSMB ring provided that an average current of 1 A and a microbunch train with bunch length of 3 nm can be formed at the radiator which is assumed to be an undulator. Together with the narrow-band feature, the EUV photon flux can reach 6 × 1015 photons s-1 within a 0.1 meV energy bandwidth, which is three orders of magnitude higher than that in a conventional synchrotron source and is appealing for fundamental condensed matter physics and other research. In this theoretical investigation, we have generalized the definition and derivation of the transverse form factor of an electron beam which can quantify the impact of its transverse size on coherent radiation. In particular, it has been shown that the narrow-band feature of SSMB radiation is strongly correlated with the finite transverse electron beam size. Considering the pointlike nature of electrons and quantum nature of radiation, the coherent radiation fluctuates from microbunch to microbunch, or for a single microbunch from turn to turn. Some important results concerning the statistical properties of SSMB radiation are presented, with a brief discussion on its potential applications, for example the beam diagnostics. The presented work is of value for the development of SSMB to better serve potential synchrotron radiation users. In addition, this also sheds light on understanding the radiation characteristics of free-electron lasers, coherent harmonic generation, etc.

Hsa-miR-34a-5p reverses multidrug resistance in gastric cancer cells by targeting the 3'-UTR of SIRT1 and inhibiting its expression.

Multidrug resistance (MDR) is a major obstacle to chemotherapy, which leads to ineffective chemotherapy, an important treatment strategy for gastric cancer (GC). The abnormality of microRNAs (miRNAs) is critical to the occurrence and progression of MDR in various tumors. In this study, hsa-miR-34a-5p was found to be decreased in multidrug resistant GC cells SGC-7901/5-Fluorouracil (SGC-7901/5-Fu) compared to the parental SGC-7901 cells. Overexpression of hsa-miR-34a-5p in SGC-7901/5-Fu cells promoted apoptosis and decreased migration and invasiveness after chemotherapy. In addition, overexpression of hsa-miR-34a-5p suppressed the growth of drug-resistant tumor in vivo. The mechanism of the effects of hsa-miR-34a-5p could include the regulation of the expression of Sirtuin 1 (SIRT1), P-glycoprotein (P-gp) or Multidrug resistance-related protein 1 (MRP1) through direct binding to the 3'-untranslated region (UTR) of SIRT1. Functional gain-and-loss experiments indicated that hsa-miR-34a-5p enhances the chemotherapy sensitivity of MDR GC cells by inhibiting SIRT1, P-gp and MRP1. In conclusion, hsa-miR-34a-5p can reverse the MDR of GC cells by inhibiting the expression of SIRT1, P-gp or MRP1.

Geographical distribution of ozone seasonality over China.

Up to now, a nation-wide scale study of surface ozone (O3) concentrations in China was limited due to scarce observation. Thanks to the establishment of national air quality monitoring network in 2013, surface O3 data from 1402 stations during 2014-2017 were collected to investigate O3 seasonality. Our analysis reveals that the variations of monthly O3 averaged from daily mean concentration during a year show different temporal profiles depending on latitude. A unimodal structure (UMS) is generally found for latitudes over 35°N, whereas a bimodal structure (BMS) is in most of the cases identified south of 35°N. The peak of UMS is found in the period of May to July, whereas the first and second peaks of BMS are found from April to June, and from July to October, respectively. In addition, the seasonality of O3 presents a strong dependence on pseudo-equivalent potential temperature and monsoonal clouds. The onset and retreat of warm and wet air are correlated to the summer minimum in BMS cases and to the sharp decrease of UMS in July. As far as the relationships between O3 and carbon monoxide are concerned, the effects of clean maritime air masses on the summer trough of O3 are not significant for inland sites. Overall, summer monsoon bringing warm and moist air and subsequent clouds leads to the suppression of photochemical production, thereby contributing directly to the geographical distribution of O3 seasonality.

The relative impact of urbanization and precipitation on long-term water level variations in the Yangtze River Delta.

The combined and individual hydrological impacts of climate variation and urbanization have been extensively discussed over the past few decades, yet little is known about the relative impact of each. In this paper we took one of the most developed regions worldwide, Yangtze River Delta, as an example to analyse the long-term relative impacts of precipitation and urbanization change on water level alterations, based on precipitation, water level series, and annual impervious area data from 1960 to 2015. Abrupt changes detection in the water level series divided the data into the pre-impact period (1960-1988) and impacted period (1989-2015), and relative impacts of precipitation and urbanization on the water level increase from pre-impacted to impacted period, as well as their spatial and seasonal variations were estimated with the elasticity method. The results indicated that the urbanization change showed no distinct influence on the water level rise in the pre-impact period, while the precipitation played distinct roles only during summer months in the impacted period; the precipitation dominated two thirds of the water level rise in flood season, and in non-flood season the urbanization controlled the two thirds of the water level rise; spatially, the water level variations in old and new urban area were dominated by precipitation and urbanization process respectively; compared with precipitation amount, the water level correlated more strongly to the contribution ratio of precipitation. The results would provide a good reference for flood control and water resource management in the river basin, especially in the economically developed areas.

Transport paths and vertical exchange characteristics of haze pollution in Southern China.

Transport paths and vertical exchange characteristics are important factors for understanding the long-term transport, dispersion capability for haze prediction. Many previous studies revealed that the Pearl River Delta (PRD) region, one of the major polluted areas in China, is largely affected by the long-range pollution transport. However, mostly of these studies focused on the source apportionment or horizontal transport path of pollutants by using short-term data, and the vertical exchange characteristics had been rarely analyzed. In this study, using HYSPLIT model, the transport paths and the vertical exchange characteristics of haze episodes over four sub-region of Guangdong (GD) Province in southern China of dry season and wet season were analyzed by using 10years data from 2005 to 2014. Three major transport paths can be statistically summarized based on the long-term data. The haze episodes in PRD and North-GD were distinguished by the characteristics of high frequency and long duration, while the West-GD and East-GD are relatively clean. The haze over North-GD and PRD were mainly influenced by the airflows from northern path, which could bring the pollution from Jiangxi, Anhui, and also influenced by the airflows from coastal path, which could bring the pollution of eastern coastal from Zhejiang and Fujian to Guangdong, while regional transport contributions from Guangdong province and adjacent areas can also be clearly observed. The haze pollution from the identified two major transport paths were mainly transported within the mixing layer (>80% trajectories, <500m), whereas the probability of haze trajectories across mixing layer was relatively low and generally associated with much longer transport distance and higher terrain height over Western China. Combing the vertical exchange analysis, results also show that Wuyi Mountains and Nanling Mountains played a role as barrier to obstruct the haze airflows from other regions of China to the Guangdong province.

Assessment of regional air quality resulting from emission control in the Pearl River Delta region, southern China.

To evaluate the impact of emission control measures on the air quality in the Pearl River Delta (PRD) region of South China, statistic data including atmospheric observations, emissions and energy consumptions during 2006-2014 were analyzed, and a Weather Research and Forecasting - Community Multi-scale Air Quality (WRF-CMAQ) model was used for various scenario simulations. Although energy consumption doubled from 2004 to 2014 and vehicle number significantly increased from 2006 to 2014, ambient SO2, NO2 and PM10 were reduced by 66%, 20% and 24%, respectively, mainly due to emissions control efforts. In contrast, O3 increased by 19%. Model simulations of three emission control scenarios, including a baseline (a case in 2010), a CAP (a case in 2020 assuming control strength followed past control tendency) and a REF (a case in 2020 referring to the strict control measures based on recent policy/plans) were conducted to investigate the variations of air pollutants to the changes in NOx, VOCs and NH3 emissions. Although the area mean concentrations of NOx, nitrate and PM2.5 decreased under both NOx CAP (reduced by 1.8%, 0.7% and 0.2%, respectively) and NOx REF (reduced by 7.2%, 1.8% and 0.3%, respectively), a rising of PM2.5 was found in certain areas as reducing NOx emissions elevated the atmospheric oxidizability. Furthermore, scenarios with NH3 emission reductions showed that nitrate was sensitive to NH3 emissions, with decreasing percentages of 0-10.6% and 0-48% under CAP and REF, respectively. Controlling emissions of VOCs reduced PM2.5 in the southwestern PRD where severe photochemical pollution frequently occurred. It was also found that O3 formation in PRD was generally VOCs-limited while turned to be NOx-limited in the afternoon (13:00-17:00), suggesting that cutting VOCs emissions would reduce the overall O3 concentrations while mitigating NOx emissions in the afternoon could reduce the peak O3 levels.

An optimized method of venous anastomosis for right donor kidney transplantation in rat.

BACKGROUND: Insufficient length of right renal vein (RV) increases the difficulty of venous anastomosis and blocks the promotion of transplantation of both kidneys, which could significantly reduce operative time and donor numbers. This study sought to discover a quick, safe method of venous anastomosis for right kidney donation. METHODS: Three venous anastomotic methods (n = 20 in each group) were used for right donor kidney heterotopic transplantation: End-to-side, vena cava bypass, and modified end-to-end, namely, harvesting the right donor kidney with a part of the vena cava and then anastomosing the proximal end to the recipient RV followed by a ligation of the distal end. The conventional end-to-end venous anastomosis was used for left donor kidney orthotopic transplantation as a control (n = 60). We compared operative times and complications. RESULTS: The operative time of the modified end-to-end group (18.45 ± 0.69 minutes) and end-to-side group (17.95 ± 1.54 minutes) were both less than the vena caval bypass group (32.60 ± 2.84 minutes); (P < .05), but equal to the control group (17.60 ± 1.89; P > .05). The overall complication rate among the modified end-to-end group (2/20) was less than those for the end-to-side (8/20) and vena caval bypass groups (9/20; P < .05), but similar to the control group (7/60; P > .05). CONCLUSION: A modified end-to-end technique is the preferred venous anastomotic method for right donor kidney transplantation.

Substance use, sexual behaviours, and suicidal ideation and attempts among adolescents: findings from the 2004 Guangzhou Youth Risk Behaviour Survey.

OBJECTIVES: To investigate the prevalence of substance use, sexual behaviours, and suicidal ideation and attempts among adolescents in Guangzhou, China, and to explore the associations between these risk behaviours and demographics. STUDY DESIGN: A two-stage stratified cluster sample design produced a representative sample of 12-19-year-old students in Grades 1-6 who attended public middle schools in Guangzhou. METHODS: Prevalence estimates and 95% confidence intervals were calculated using SUDDAN statistical software. Logistic regression was used to examine the associations between health risk behaviours and demographics. RESULTS: In total, 5988 students (45.5% males, 54.5% females) were included in this study. Overall, 17.6% of students had tried cigarette smoking, 63.1% of students had had at least one drink of alcohol, 1.7% of students had used marijuana, 3.5% of students had experienced sexual intercourse, 17.6% of students had seriously considered attempting suicide and 3.2% had attempted suicide. Male gender was positively associated with substance use and sexual risk behaviours, but negatively associated with feeling sad or hopeless and suicide ideation. Being in Grades 4-6 was positively associated with lifetime cigarette use, lifetime alcohol use, current alcohol use, episodic heavy drinking and marijuana use, but negatively associated with suicide attempts. Higher parental education was positively associated with lifetime alcohol use, current alcohol use, lifetime marijuana use, feeling sad or hopeless, and suicidal ideation, but negatively associated with lifetime cigarette use and current cigarette use. CONCLUSIONS: Gender, school grade and parental education were found to be significantly associated with certain risk behaviours.

[Genetic analysis of dominant earliness of rice genic male sterile line 6442S-7].

F1 progenies of a genic male sterile and early maturing indica line 6442S-7 crossed with sixteen medium or late maturing varieties, such as Minghui 63, shared the same heading date as 6442S-7 under long day and short day, suggesting that 6442S-7 has completely dominant earliness. Segregation of heading dates of the F2 and B1F1 populations indicated that the earliness of 6442S-7 is mainly controlled by two dominant major genes. Whereas, heading dates of F1 progenies of 6442S-7 crossed with other four late maturing varieties, i.e. IR68, Xianguo, 9311, and BG1639, closed to the mid-parent value under long day. In F2 populations of 6442S-7 crossed with each of the four late maturing varieties, F1 from three-way crosses between 6442S-7 and each F1 of Minghui 63 crossed with each of the four late maturing varieties, and F1 from three-way crosses between 6442S-7 and each F1 of crosses between each two of the four late maturing varieties, segregation of heading dates showed that an incompletely diminant allelic suppressor for the dominant earliness of 6442S-7 existed in the late maturing varieties, IR68, Xianguo, 9311, and BG1639. It is considered that dominant earliness genes harbored in 6442S-7 have splendid future in rice improvement.

Preparation of graded porous titanium coatings on titanium implant materials by plasma spraying.

Graded porous titanium coatings have been deposited on titanium substrates for dental implants by plasma spraying in an argon atmosphere. X-ray diffraction (XRD), scanning electron microscopy (SEM), surface roughness measurement, and tensile strength tests were performed on graded porous coatings. The results showed that Ti(3)O(5) was formed in the outermost surface of the porous coatings due to oxidation. The graded porous coatings consisted of three layers. The outer layer was full of macropores with a surface roughness of approximately 100 microm. The diameter of many macropores reached and even surpassed 150 microm, which could be beneficial for tissue to grow into the coating. The middle layer consisted of a mixture of micropores and macropores. The inner layer was a very dense and tight interface layer that included mechanical, physical, and metallurgical bonding. In tensile strength tests, testing bars peeled off the coatings, because the adhesive agent fractured, but the coatings remained intact.

Intramucosal cysts in gastric mucosa adjacent to carcinoma and peptic ulcer: a histochemical study.

Histochemical characteristics and the distribution of gastric intramucosal cysts were studied in 50 cancerous and 51 benign gastrectomy specimens. The frequency of such cysts was significantly higher in stomachs with carcinoma (70%) than in stomachs with peptic ulcer (43%) (P less than 0.01). Intramucosal cysts were classified into gastric type, small intestinal type, colonic type and non-mucous type. There were significant differences in the constituent ratios of the four types of cyst between gastric carcinoma and gastric ulcer (P less than 0.01), as well as between intestinal type and diffuse type cancer (P less than 0.001). The present results reveal a close relationship between intramucosal cysts and gastric carcinoma. Cysts of small intestinal, colonic and non-mucous types were associated with intestinal type cancer while cysts of gastric type were related to diffuse type cancer of the stomach.

[Establishment and experimental study of a transplantable hepatocellular carcinoma model in 615-strain mice (H 615)].

H 615, the first transplantable mouse liver carcinoma model established in China, was derived from a spontaneous hepatocellular carcinoma of an inbred 615 mouse and has been successfully propagated for 52 generations during the past 7 years and more. Its biologic and pathologic features are relatively stable. H 615 was a syngenic transplantable tumor model of 615-strain mice with a successful transplantation rate of 85.6% without spontaneous regression. The course of tumor growth after subcutaneous inoculation was divided into 4 stages: latent, slowly growing, rapidly growing and terminal stages. Cancer metastasis was rare. The tumor-bearing host would die of cachexia finally. The mean survival time was 62.2 +/- 11.0 days regardless of sex or age. Histologically and ultrastructurally, H 615 was a well-differentiated hepatocellular carcinoma, rather resembling human liver carcinoma. The short-term primary passage culture of H 615 showed that, in vitro, tumor tissue could easily grow into monolayer, the majority of which appeared as epithelioid cells in cytomorphology. Therapeutic tests of 15 anticancer drugs showed that H 615 was sensitive, in varying degrees, to 5 drugs, i. e. MMC, Thio-Tepa, 5FU, CPT and DACT. The inhibition rate of MMC and Thio-Tepa could be as high as 100%. These experimental results are similar to those of the human liver cancer chemotherapy. Hence, the authors believe that H 615 may be a useful model in experimental study of the liver cancer and screening of anticancer drugs.