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Background:  Microsurgical training should be implemented with consideration of operative difficulties that occur in actual clinical situations. We evaluated the effectiveness of a novel clinical scenario simulator for step-by-step microsurgical training that progressed from conventional training to escalated training with additional obstacles., Methods:  A training device was designed according to multiple and intricate clinical microsurgery scenarios. Twenty surgical residents with no experience in microsurgery were randomly assigned to either the control group (conventional training curricula, n  = 10) or the experimental group (step-by-step training courses, n  = 10). After 4 weeks of laboratory practice, the participants were scheduled to perform their first microvascular anastomoses on patients in an operating room. The Global Rating Scale (GRS) scores and operative duration were used to compare microsurgical skills between the two groups., Results:  There were no significant differences in the participants' baseline characteristics before microsurgical training between the groups with respect to age, sex, postgraduate year, surgical specialty, or mean GRS score ( p  < 0.05). There were also no significant differences in recipient sites between the two groups ( p  = 0.735). After training, the GRS scores in both groups were significantly improved ( p  = 0.000). However, in the actual microsurgical situations, the GRS scores were significantly higher in the experimental than control group ( p  < 0.05). There was no significant difference in the operative duration between the two groups ( p  < 0.13)., Conclusion:  Compared with a traditional training program, this step-by-step microsurgical curriculum based on our clinical scenario simulator results in significant improvement in acquisition of microsurgical skills., Competing Interests: None declared., (Thieme. All rights reserved.)

Objective: Conventional second window indocyanine green (SWIG) technique has been widely attempted in near-infrared fluorescence (NIRF) imaging for intraoperative navigation of tumor radical resection. Nevertheless, the overuse of indocyanine green (ICG) led to an increased risk of drug lethal allergy and high medical cost. This prospective study was to explore clinical application of modified low-dose SWIG technique in guiding dermatofibrosarcoma protuberans (DFSPs) radical resection., Method: Patients with DFSPs were randomly assigned to control and experimental group. The ICG was injected intravenously 24 h before surgery, at a dose of 3.5 mg/kg in the control group and 25 mg/patient in the experiment group, respectively. Intraoperative NIRF imaging included serial views of gross tumor, tumor bed and cross-sectional specimen., Results: Although NIRF imaging of gross tumor and tumor bed in the experimental group demonstrated similar sensitivity and negative predictive value, the specificity and positive predictive value were obviously higher compared to control group. The tumor-to-background ratios of cross-sectional specimens in the experimental group was significantly higher than in the control group ( P  = 0.000). Data in both groups displayed that there was a positive correlation of tumor size in cross-sections between integrated histopathologic photomicrographs and NIRF imaging of specimen views ( P  = 0.000). NIRF imaging of cross-sectional specimens had a significant decrease in time cost, and an increase in the ability of examining more surgical margins ( P  = 0.000)., Conclusion: This is the first study to demonstrate that a low-dose SWIG technique could improve the accuracy of near-infrared fluorescence image-guided dermatofibrosarcoma protuberans resection. Clinical Trial Registration: ChiCTR2100050174; date of registration: August 18, 2021 followed by "retrospectively registered"., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2022 Cui, Wang, Li, Song, Pu, Zhang, Jiang, Kou, Tan, Tao, Han and Han.)

Background: The goal of the current study was to explore the application of preoperative three-dimensional reconstruction (3DR) based on thin-slice magnetic resonance imaging (MRI) in the simultaneous guidance of en bloc tumor resection and adjacent perforator flap elevation., Methods: The prospective cohort included 35 patients diagnosed with either soft tissue sarcoma or squamous cell skin cancer between 2019 and 2021. The preoperative 3DR based on thin-slice MRI illustrated the spatial anatomical relationship among the tumor, underlying muscle, adjacent perforator vessels, and bone around the surgical region. The accuracy of preoperative imaging data was verified by intraoperative vessel dissection and postoperative pathological measurements., Results: Tumor size from 3DR data showed relatively high concordance rates with pathological measurements within the 95% limits of agreement. An average of three perforators (range: 1-7) with a mean diameter of 0.32 cm (range: 0.18-0.74 cm) from the 3DR were present in our study. The average distance between tumor boundary and perforator piercing sites on the 3DR was 2.2 cm (range: 1.2-7.7 cm). The average length of artery perforator coursing along the subcutaneous tissue was 5.8 cm (range: 3.3-25.1 cm). The mean flap harvest time was 55 mins (range: 36-97 min). The average flap size was 92.2 cm 2 (range: 32-126 cm 2 ). One perforator flap occurred distal partial necrosis., Conclusion: A thorough understanding of anatomical structures in the surgical region according to full-field 3DR based on thin-slice MRI can improve the performance of radical resection of the tumor and adjacent perforator flap transfer, especially for junior surgeons with a poor experience., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2022 Cui, Jiang, Zhang, Wang, Han, Pu, Shao, Guo, Tao and Han.)

Real-time BTEX(including benzene, toluene, ethylbenzene, m -, p -, and o -xylenes) were measured continuously in Tianjin urban site in July 2019 and January 2020 using a Syntech Spectras GC955 analyzer. The BTEX concentration levels, composition, and evolutionary mechanisms during typical pollution episodes were investigated. The potential sources of BTEX were analyzed qualitatively using the diagnostic ratios method. Finally, the BTEX health risk was evaluated by using the human exposure analysis and evaluation method according to US EPA. The averaged total mixing ratio of BTEX were 1.32×10 -9 and 4.83×10 -9 during ozone pollution and haze episodes, respectively. Benzene was the most abundant species, followed by toluene. The mixing ratio of BTEX was largely affected by short southwestern distance transportation in January, while local emissions in July. In addition, the BTEX mixing ratio depended on the influence of temperature and relative humidity(RH) in July, while the concentration was more sensitive to changes in RH when the temperature was low in January. Diagnostic ratios and source implications suggested that the BTEX was affected mainly by biomass/biofuel/coal burning during haze episodes. The traffic related emissions also had an impact except for the influence of biomass/biofuel/coal burning in July. The averaged hazard quotient(HQ) values were 0.072 and 0.29 during ozone pollution and haze episodes, respectively, which were in the upper safety range limit recommended by the US EPA. The carcinogenic risk posed by benzene in both cleaning and pollution processes was higher than the safety threshold set by the US EPA, which should be monitored carefully.

The characteristics of meteorological conditions and pollutant concentrations were analyzed based on two pollution episodes before and after city heating in Beijing during February to March of 2019. The backward trajectory and WRF-CAMx models were used to analyze the evolution of pollutants before and after city heating, and the influences of meteorological conditions, regional transport, and secondary transformation on the episodes were discussed. There was little difference in the average ρ (PM 2.5 ) between February 21-24 (episode 1) and March 18-20 (episode 2), with concentrations of 100.1 μg·m -3 and 97.2 μg·m -3 , respectively. However, compared with that of episode 2, in episode 1 the average peak value was higher with two peak stages, the diurnal variation was clearer, and the process developed much more rapidly. Moreover, episode 1 was regional pollution, while episode 2 was more related to local pollution in Beijing. The SO 2 concentrations in both episodes were not higher than 16 μg·m -3 , thereby indicating the effectiveness of coal-burning treatment and other measures. In addition, two peaks occurred in the diurnal fluctuation of SO 2 in episode 1, whereas only one peak occurred for episode 2. In episode 1, the CO concentration was high and the ratio of ρ (CO)/ ρ (SO 2 ) increased around February 22-23 (phase 1); moreover, the pollutant concentrations in the central and southern areas of the Beijing-Tianjin-Hebei region and those in the background sites located in the southern part of the Beijing plain were higher than those in the urban area, thereby indicating that the diffusion conditions of episode 1 were unfavorable and the first PM 2.5 peak was mainly affected by regional transport. A high ratio of ρ (PM 2.5 )/ ρ (CO) in episode 2 suggested a slightly larger proportion of secondary generation for PM 2.5 , whereas higher ratios of ρ (NO 2 )/ ρ (CO), ρ (SO 2 )/ ρ (CO), and ρ (SO 4 2- )/ ρ (PM 2.5 ) in episode 2 and the similar SOR value to that of episode 1 demonstrated that episode 1 was more advantageous for gas phase transformation and episode 2 was more affected by the coal industry. Phased analysis of episode 1 showed that the indicators of second generation for PM 2.5 in phase 2 (around February 23-24) of episode 1 and episode 2 were similar, and both were higher than that in phase 1 of episode 1, which implied that the second PM 2.5 peaks of episode 1 and episode 2 were mainly related to local emissions and chemical conversion. Both WRF-CAMx with and without assimilation experiments could better reproduce the temporal variation in pollutants, and the correlation between the simulation and observations increased but with lower values after assimilation. The model performance for the PM 2.5 trend simulation significantly increased with data assimilation, and the simulated lower NO 2 in February and higher NO 2 in March as well as the overestimated SO 2 were also improved. In addition, the pollutant concentration simulation in Beijing was more sensitive to that of Hebei in episode 1, which suggested that episode 1 was more affected by regional transport. The simulation ability for the rapid growth of pollutants needs to be promoted, and the response of pollutant types to emission reduction and the feedback related to the atmospheric oxidant and aerosol properties may be important for the simulation effect, which all require further study.

There is a kind of serious air pollution case occurring in the situation of northerly flow at the levels above 850 hPa in Beijing area. Meteorological data, NCEP reanalysis data and PM2.5 concentration survey were used to analyze the roles of meteorological mechanism in this kind of air pollution case. The results showed that the stable stratification did not exist all the time during the gradual increase of PM2.5 concentration. The favorable meteorological conditions in PM2.5 accumulation came from the layered structure of vertical speed and convergence in vertical direction. From the surface to the middle level of troposphere, the vertical velocity showed an updraft-downdraft-updraft distribution. And the divergence displayed a convergence-divergence-convergence structure. The convergence at lower levels led to the gathering of the polluted air from the surrounding and the ascending current brought it upwards. However, the polluted air could not go further up due to the prolonged downdraft layer above. As the result, PM2.5 near the surface was concentrated gradually. The vertical speed in layer structure was attributed to the high level northerly flow without invading into the boundary layer. In such case, the wind was still in southerly direction or kept calm at the surface. The weak cold air or no cold air at all was the main reason that the northerly flow could not hit the surface. The developed downdraft layer was relative to the convergence above which was resulted from the wind speed pulses in the northerly flow at upper levels. In conclusion, the air dynamical effect played a key role in the pollution type of northerly flow at upper levels. Therefore, it will be beneficial to enhance our capability in the analysis and forecasting of this kind of pollution case by focusing on 24 hours temperature variation at the middle and lower troposphere as well as the vertical distribution of vertical velocity and divergence.

The impact of transport pathways on aerosol properties at Shangdianzi (SDZ) background station was analyzed using the back trajectory analysis method with the observation of PM2.5 concentration and aerosol scattering coefficients ( σ(sp)) during 2005-2010. The results showed that the pollutant level at SDZ was influenced by both the direction and motion state of air masses. The southerly transport pathways of air masses had higher PM2.5 concentration and σ(sp) than those of northerly pathways. The air masses with lower moving speed and altitude generally corresponded to higher PM2.5 concentration and σ(sp). Air masses originated from the North China Plain in spring, summer and autumn, and air masses from the north of North China region in winter had a significant contribution to PM2.5 concentration and σ (sp) at SDZ. Dust aerosol appeared frequently in spring, and the mean scattering efficiency (α(sp)) was 0.78 m2 x g(-1). The mean α(sp) of anthropogenic aerosol of four seasons was 4.00 m2 x g(-1) with the highest value in winter and the lowest in spring. The west-northwest, southerly pathways, and the northerly pathways with low moving speed in spring, summer and autumn correspond to higher α(sp) ( > 4.0 m2 x g(-1)). This indicated that these pathways were affected by the emissions form human activities. However, the α(sp) in winter kept at a high level among all pathways, which suggested that the emission effect was relatively uniform in surrounding regions in winter. The other northerly pathways in spring, summer and autumn were affected by anthropogenic pollutants mixed with dust.

A study on the PM2.5 pollution and aerosol optical properties in haze-fog days was carried out from Sep. 1st to Dec. 7th, 2011 in Beijing area by using PM2.5 concentration, aerosol scattering coefficient (sigma sca) and absorption coefficient (sigma abs) measured under urban and rural environment. The effect of weather condition on the PM25 pollution and aerosol optical properties was discussed as well. The results showed that the PM2.5 concentration, sigma sca and sigma abs, were evidently higher in haze-fog days than those in non-haze-fog days. The average PM2.5 concentrations in haze-fog days with values of 97.6 microg m-3 and 64.4 microg.m-3 were as 3.3 and 4.8 times as those in non-haze-fog days at urban and rural stations, respectively. The higher PM2.5 concentration in urban area resulted in the more frequent fog and haze phenomena than that in rural area. The PM25 concentration, sigma sca, and sigma abs were significantly higher in urban area than that in rural area in mist days, while relatively close in mist-haze days. This difference suggested that the effect of regional transport of pollution was relatively evident in mist-haze days but weak in mist day. In fog days the sigma sca showed no evident difference between urban and rural area, and was the highest in all types of fog and haze weather. The scattering property of aerosol was the strongest in fog days. The different weather conditions resulted in various characteristics of spatial distribution of PM2.5 concentration, sigma sca and sigma abs, as well as the strength of PM2,5 pollution and aerosol extinction. The pollutants transported by the strong southwest wind above the boundary layer and subsided in the boundary layer companying with the local accumulation of pollutants due to the weak diffusion resulted in the most serious haze-fog episode with the strongest PM2.5 pollution and aerosol extinction.

A study on the effect of weather condition on the aerosol scattering property has been carried out using one year measurement data sets of aerosol scattering coefficient (ASC) and meteorological parameters at Shangdianzi (SDZ). The results showed that the ASC was highest in haze-fog day with 608.4 Mm(-1) and higher in fog day with 500.6 Mm(-1) and haze day with 423.7 Mm (-1) those were 6.4-9.2 times higher than the ASC in normal day. The ASC was highest in summer in all kinds of weather conditions. The lower ASC in fog day and haze-fog day was observed in autumn and winter, respectively. There was no evident difference of the ASC between other three seasons in haze day and normal day. Pronounced seasonal variation of the mass scattering efficiency (MSE) of PM2.5 was observed in fog day with the highest value in summer. Significant diurnal variations in ASC were observed in haze-fog day and normal day with a unimodal pattern and a bimodal pattern, respectively. The wind was the most important factor for the ASC at SDZ. The transport of aerosol particles by the strong southwest wind should be responsible for the higher level of ASC in SDZ area and regional scale in low visibility weather conditions. The northeast wind was favourable to the reduction of ASC, especially in normal day.