Beijing is suffering from serious particulate matter pollution, and the atmosphere boundary layer (ABL) has important direct and indirect effects on human activities. This research analyzed the ...characteristics of the ABL in Beijing and discussed the impacts of meteorological factors on atmosphere boundary layer height (ABLH) during winter heavy pollution events in Beijing. The data observed by Mie lidar in the winter of 2014 to 2016 were used to estimate the ABLH by employing image edge detection. In addition, a weather research and forecasting (WRF) model was used to simulate the meteorological field in the same period. Ground and vertical data indicated that the average ABLH decreased from 0.63 km to 0.53 km in three consecutive years. In addition, a significant negative correlation existed between ABLH and PM2.5, and the effect of low ABLH on the vertical diffusion capacity of pollutants was greater than that of high ABLH. Relative humidity was negatively correlated with ABLH, increasing during the three years at a rate of 61%. In the winter of 2014, the atmosphere was dominated by instability, which was beneficial to the development of ABL. In contrast, many stable stratifications occurred in the upper air during the winters of 2015 and 2016; however, these were not conducive to the development of ABL. The northwest wind decreased by 11.35% and the south wind increased by 11.41%. Moreover, the time of near-surface wind speed below 2 m s−1 increased by 34.74%, and the frequency of occurrence above 4 m s−1 decreased by 8.19%. The decrease in ground wind speed was unfavorable for the development of ABL. The sea level pressure remained at 1027.68 ± 17.32 hPa, and the ABLH was found to be generally positively correlated with sea level pressure.
•Characteristics of the atmosphere boundary layer during heavy pollution episodes in winter in Beijing were analyzed.•Effects of meteorological factors on atmosphere boundary layer height were discussed.•High humidity, low wind and inversion are unfavorable to the development of boundary layer height.•The results improve our understanding of the formation of heavy pollution events in Beijing.
Ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) and lidar measurements were performed in Shanghai, China, during May 2016 to investigate the vertical distribution of ...summertime atmospheric pollutants. In this study, vertical profiles of aerosol extinction coefficient, nitrogen dioxide (NO2) and formaldehyde (HCHO) concentrations were retrieved from MAX-DOAS measurements using the Heidelberg Profile (HEIPRO) algorithm, while vertical distribution of ozone (O3) was obtained from an ozone lidar. Sensitivity study of the MAX-DOAS aerosol profile retrieval shows that the a priori aerosol profile shape has significant influences on the aerosol profile retrieval. Aerosol profiles retrieved from MAX-DOAS measurements with Gaussian a priori profile demonstrate the best agreements with simultaneous lidar measurements and vehicle-based tethered-balloon observations among all a priori aerosol profiles. Tropospheric NO2 vertical column densities (VCDs) measured with MAX-DOAS show a good agreement with OMI satellite observations with a Pearson correlation coefficient (R) of 0.95. In addition, measurements of the O3 vertical distribution indicate that the ozone productions do not only occur at surface level but also at higher altitudes (about 1.1 km). Planetary boundary layer (PBL) height and horizontal and vertical wind field information were integrated to discuss the ozone formation at upper altitudes. The results reveal that enhanced ozone concentrations at ground level and upper altitudes are not directly related to horizontal and vertical transportation. Similar patterns of O3 and HCHO vertical distributions were observed during this campaign, which implies that the ozone productions near the surface and at higher altitudes are mainly influenced by the abundance of volatile organic compounds (VOCs) in the lower troposphere.
Abstract
Hydrogels have been extensively favored as drug and cell carriers for the repair of knee cartilage defects. Recruiting mesenchymal stem cells (MSCs) in situ to the defect region could reduce ...the risk of contamination during cell delivery, which is a highly promising strategy to enhance cartilage repair. Here, a cell-free cartilage tissue engineering (TE) system was developed by applying an injectable chitosan/silk fibroin hydrogel. The hydrogel system could release first stromal cell-derived factor-1 (SDF-1) and then kartogenin (KGN) in a unique sequential drug release mode, which could spatiotemporally promote the recruitment and chondrogenic differentiation of MSCs. This system showed good performance when formulated with SDF-1 (200 ng/mL) and PLGA microspheres loaded with KGN (10 μΜ). The results showed that the hydrogel had good injectability and a reticular porous structure. The microspheres were distributed uniformly in the hydrogel and permitted the sequential release of SDF-1 and KGN. The results of in vitro experiments showed that the hydrogel system had good cytocompatibility and promoted the migration and differentiation of MSCs into chondrocytes. In vivo experiments on articular cartilage defects in rabbits showed that the cell-free hydrogel system was beneficial for cartilage regeneration. Therefore, the composite hydrogel system shows potential for application in cell-free cartilage TE.
Repairing extensive bone defects that cannot self-heal has been a clinical challenge. The construction of scaffolds with osteogenic activity through tissue engineering can provide an effective ...strategy for bone regeneration. This study utilized gelatin, silk fibroin, and Si3N4 as scaffold materials to prepare silicon-functionalized biomacromolecules composite scaffolds using three-dimensional printing (3DP) technology. This system delivered positive outcomes when Si3N4 levels were 1 % (1SNS). The results showed that the scaffold had a porous reticular structure with a pore size of 600–700 μm. The Si3N4 nanoparticles were distributed uniformly in the scaffold. The scaffold could release Si ions for up to 28 days. In vitro experiments showed that the scaffold had good cytocompatibility, promoting the osteogenic differentiation of mesenchymal stem cells (MSCs). In vivo experiments on bone defects in rats showed that the 1SNS group facilitated bone regeneration. Therefore, the composite scaffold system showed potential for application in bone tissue engineering.
Fine particle with diameter <2.5 μm (PM2.5) have important direct and indirect effects on human life and activities. However, the studies of fine particle were limited by the lack of monitoring data ...obtained with multiple fixed site sampling strategies. Mobile monitoring has provided a means for broad measurement of fine particles. In this research, the potential use of mobile lidar to map the distribution and transport of fine particles was discussed. The spatial and temporal distributions of particle extinction, PM2.5 mass concentration and regional transport flux of fine particle in the planetary boundary layer were investigated with the use of vehicle-based mobile lidar and wind field data from north China. Case studies under different pollution levels in Beijing were presented to evaluate the contribution of regional transport. A vehicle-based mobile lidar system was used to obtain the spatial and temporal distributions of particle extinction in the measurement route. Fixed point lidar and a particulate matter sampler were operated next to each other at the University of Chinese Academy of Science (UCAS) in Beijing to determine the relationship between the particle extinction coefficient and PM2.5 mass concentration. The correlation coefficient (R2) between the particle extinction coefficient and PM2.5 mass concentration was found to be over 0.8 when relative humidity (RH) was less than 90%. A mesoscale meteorological model, the Weather Research and Forecasting (WRF) model, was used to obtain profiles of the horizontal wind speed, wind direction and relative humidity. A vehicle-based mobile lidar technique was applied to estimate transport flux based on the PM2.5 profile and vertical profile of wind data. This method was applicable when hygroscopic growth can be neglected (relatively humidity<90%). Southwest was found to be the main pathway of Beijing during the experiments.
•Characteristics of the vertical distribution of fine particles in Beijing were observed.•Transport fluxes of Beijing were estimated based on a vehicle-based mobile lidar.•Southwest was an important regional transport pathway of Beijing.
The polarization–Raman Lidar combined sun photometer is a powerful method for separating dust and urban haze backscatter, extinction, and mass concentrations. The observation was performed in Beijing ...during the 2019 National Day parade, the particle depolarization ratio at 532 nm and Lidar ratio at 355 nm are 0.13 ± 0.05 and 52 ± 9 sr, respectively. It is the typical value of a mixture of dust and urban haze. Here we quantify the contributions of cross-regional transported natural dust and urban haze mass concentrations to Beijing’s air quality. There is a significant correlation between urban haze mass concentrations and surface PM2.5 (R = 0.74, p < 0.01). The contributions of local emissions to air pollution during the 2019 National Day parade were insignificant, mainly affected by regional transport, including urban haze in North China plain and Guanzhong Plain (Hebei, Tianjin, Shandong, and Shanxi), and dust aerosol in Mongolia regions and Xinjiang. Moreover, the trans-regional transmission of natural dust dominated the air pollution during the 2019 National Day parade, with a relative contribution to particulate matter mass concentrations exceeding 74% below 4 km. Our results highlight that controlling anthropogenic emissions over regional scales and focusing on the effects of natural dust is crucial and effective to improve Beijing’s air quality.
Thermal shock is the physical process of rapid cooling of a hot object. The physical and mechanical properties of rocks that have undergone thermal shock will change. This variation can be applied to ...the development of geothermal in limestone reservoirs and serve as an effective means of enhancing heat exchange capacity. The essence of this is rock thermal shock rupture. The reason for the change in rock properties due to thermal shock is distinguished from other factors and is a process of instantaneous impact thermal stress caused by non-constant heat transfer, resulting in rock damage from microscopic damage to macroscopic damage. In order to study the variation of physical and mechanical properties of limestone with heating and cooling temperatures under the effect of thermal shock, a self-developed thermal shock test device was used to test the physical and mechanical properties of limestone heated to 100 °C~600 °C after thermal shock. The results strongly suggest that the heating temperature under the effect of thermal shock is the main factor affecting the evolution of basic physical properties of limestone; with the increase in heating temperature, the color of the specimen changes from off-white to white, the mass decreases and the volume nonlinearly increases, with a maximum reduction of 1.39% in mass and a maximum expansion of 2.79% in volume at 600 °C. Indeed, 500 °C is the temperature of abrupt mass loss. The heating temperature and the cooling medium temperature act together to deteriorate the mechanical properties of limestone. With increasing heating temperature (decreasing cooling temperature), the uniaxial compressive strength of limestone decreased by 39.5% (19.3%), modulus of elasticity by 59.5% (22.9%), tensile strength by 42.9% (7.6%), and cohesion by 43.2% (22.5%). The peak strain increases by 74.2% and the angle of internal friction increases by 27% (25.9%). The above data are average values. The empirical equations of the compressive strength, modulus of elasticity, tensile strength of limestone under the action of thermal shock versus heating temperature were obtained. The differences in the physical and mechanical properties of limestone after two heat treatments (thermal shock and high-temperature heating) were compared and analyzed, and the results showed that the physical and mechanical properties of limestone deteriorated more severely after thermal shock compared to high-temperature heating. The research results can provide technical support for the drilling of geothermal development and wellbore stability assessment in limestone reservoirs, and enrich the theory of high-temperature rock mechanics.
Persistent heavy haze episodes have repeatedly shrouded North China in recent years. Besides anthropogenic emissions, natural dust also contributes to the aerosols in this region. Through continuous ...observation by a dual-wavelength Raman lidar, the primary aerosol types and their contributions to air pollution in North China were determined. The following three aerosol types can be classified: natural dust, anthropogenic aerosols, and the mixture of anthropogenic aerosols and dust (polluted dust). The classification results are basically consistent with the classification results from the cloud–aerosol lidar and infrared pathfinder satellite observations (CALIPSO) satellite measurements. The relative bias of the lidar ratio between the Raman lidar and CALIPSO is less than 25% over 90% of the cases, indicating that the CALIPSO lidar ratio selection algorithm is reasonable. The classification results show that approximately 45% of aerosols below 1.8 km are contributed by polluted dust during our one year observations. The contribution of dust increased with height, from 6% at 500 m to 28% at 1,800 m, while the contribution of anthropogenic aerosols decreased from 49% to 25%. In addition, polluted dust is the major aerosol subtype below 1.0 km in spring (over 60%) and autumn (over 70%). Anthropogenic aerosols contribute more than 75% of air pollution in summer. In winter, anthropogenic aerosols prevailed (over 80%) in the lower layer, while polluted dust (around 60%) dominated the upper layer. Our results identified the primarily aerosol types to assess the contributions of anthropogenic and natural sources to air pollution in North China, and highlight that natural dust plays a crucial role in lower-layer air pollution in spring and autumn, while controlling anthropogenic aerosols will significantly improve air quality in winter.
A water-soluble fluorescence sensor (SA) was facilely synthesized via a one-step condensation reaction between commercially available salicylaldehyde and 2-(2-aminoethylamino)ethanol with high yield. ...The addition of Zn2+ and Al3+ to SA showed drastic enhancements of the emission intensities at 458 nm and 376 nm, respectively, while exhibiting negligible interference in the presence of typical competitive ions such as Fe3+, Cr3+, Hg2+ and Cd2+. This phenomenon indicates that SA may be helpful for rapid, quantitative and qualitative detection of Zn2+ and Al3+.
Different therapies are adopted for the treatment of deep seated tumours in combination or as an alternative to surgical removal or chemotherapy: radiotherapy with photons (RT), particle therapy (PT) ...with protons or even heavier ions like
C, are now available in clinical centres. In addition to these irradiation modalities, the use of Very High Energy Electron (VHEE) beams (100-200 MeV) has been suggested in the past, but the diffusion of that technique was delayed due to the needed space and budget, with respect to standard photon devices. These disadvantages were not paired by an increased therapeutic efficacy, at least when comparing to proton or carbon ion beams. In this contribution we investigate how recent developments in electron beam therapy could reshape the treatments of deep seated tumours. In this respect we carefully explored the application of VHEE beams to the prostate cancer, a well-known and studied example of deep seated tumour currently treated with high efficacy both using RT and PT. The VHEE Treatment Planning System was obtained by means of an accurate Monte Carlo (MC) simulation of the electrons interactions with the patient body. A simple model of the FLASH effect (healthy tissues sparing at ultra-high dose rates), has been introduced and the results have been compared with conventional RT. The study demonstrates that VHEE beams, even in absence of a significant FLASH effect and with a reduced energy range (70-130 MeV) with respect to implementations already explored in literature, could be a good alternative to standard RT, even in the framework of technological developments that are nowadays affordable.
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