Arson presents a challenging crime scene for fire investigators worldwide. Key to the investigation of suspected arson cases is the analysis of fire debris for the presence of accelerants or ignitable liquids. This st...Arson presents a challenging crime scene for fire investigators worldwide. Key to the investigation of suspected arson cases is the analysis of fire debris for the presence of accelerants or ignitable liquids. This study has investigated the application and method development of vapor phase mid-Infrared (mid-IR) spectroscopy using a field portable quantum cascade laser (QCL) based system for the detection and identification of accelerant residues such as gasoline, diesel, and ethanol in fire debris. A searchable spectral library of various ignitable fluids and fuel components measured in the vapor phase was constructed that allowed for real-time identification of accelerants present in samples using software developed in-house. Measurement of vapors collected from paper material that had been doused with an accelerant followed by controlled burning and then extinguished with water showed that positive identification could be achieved for gasoline, diesel, and ethanol. This vapor phase mid-IR QCL method is rapid, easy to use, and has the sensitivity and discrimination capability that make it well suited for non-destructive crime scene sample analysis. Sampling and measurement can be performed in minutes with this 7.5 kg instrument. This vibrational spectroscopic method required no time-consuming sample pretreatment or complicated solvent extraction procedure. The results of this initial feasibility study demonstrate that this portable fire debris analyzer would greatly benefit arson investigators performing analysis on-site.展开更多
Bilayer (BL) molybdenum disulfide (MoS_(2)) is one of the most important electronic structures not only in valleytronics but also in realizing twistronic systems on the basis of the topological mosaics in moiré s...Bilayer (BL) molybdenum disulfide (MoS_(2)) is one of the most important electronic structures not only in valleytronics but also in realizing twistronic systems on the basis of the topological mosaics in moiré superlattices. In this work, BL MoS_(2) on sapphire substrate with 2H-stacking structure is fabricated. We apply the terahertz (THz) time-domain spectroscopy (TDS) for examining the basic optoelectronic properties of this kind of BL MoS_(2). The optical conductivity of BL MoS_(2) is obtained in temperature regime from 80 K to 280 K. Through fitting the experimental data with the theoretical formula, the key sample parameters of BL MoS_(2) can be determined, such as the electron density, the electronic relaxation time and the electronic localization factor. The temperature dependence of these parameters is examined and analyzed. We find that, similar to monolayer (ML) MoS_(2), BL MoS_(2) with 2H-stacking can respond strongly to THz radiation field and show semiconductor-like optoelectronic features. The theoretical calculations using density functional theory (DFT) can help us to further understand why the THz optoelectronic properties of BL MoS_(2) differ from those observed for ML MoS_(2). The results obtained from this study indicate that the THz TDS can be applied suitably to study the optoelectronic properties of BL MoS_(2) based twistronic systems for novel applications as optical and optoelectronic materials and devices.展开更多
Background Stroke is a devastating disease,including intracerebral haemorrhage(ICH)and ischaemic stroke.Emerging evidences indicate that systemic inflammatory cascades after stroke contribute to brain damage.However,t...Background Stroke is a devastating disease,including intracerebral haemorrhage(ICH)and ischaemic stroke.Emerging evidences indicate that systemic inflammatory cascades after stroke contribute to brain damage.However,the direct effects and features of systemic inflammation on brain injury,especially comparing between ischaemic and haemorrhagic stroke,are still obscure.Methods Pertussis toxin(PT)was used to build a pro-inflammatory milieu after ICH and ischaemic stroke in mouse model.The neurodeficits,stroke lesion,immune response and blood–brain barrier(BBB)destruction were assessed.Results In ICH mouse model,PT-induced systemic inflammation exacerbated neurological deficits,and enlarged haemorrhage lesion and perihaematomal oedema.We also found promoted leucocyte infiltration and inflammatory cytokine release into the brain after PT treatment.Moreover,the integrity of the BBB was further disrupted after receiving PT.Furthermore,we demonstrated that PT enhanced brain inflammation and aggravated stroke severity in middle cerebral artery occlusion mouse model.Conclusions Our results suggest that PT increases inflammatory response that exacerbates brain injury after ICH or ischaemic stroke in mouse model.展开更多
Stem cells(SCs)are cells with strong proliferation ability,multilineage differentiation potential and self-renewal capacity.SC transplantation represents an important therapeutic advancement for the treatment strategy...Stem cells(SCs)are cells with strong proliferation ability,multilineage differentiation potential and self-renewal capacity.SC transplantation represents an important therapeutic advancement for the treatment strategy of neurological diseases,both in the preclinical experimental and clinical settings.Innovative and breakthrough SC labelling and tracking technologies are widely used to monitor the distribution and viability of transplanted cells non-invasively and longitudinally.Here we summarised the research progress of the main tracers,labelling methods and imaging technologies involved in current SC tracking technologies for various neurological diseases.Finally,the applications,challenges and unresolved problems of current SC tracing technologies were discussed.展开更多
Two heavy rainfall events occurred over the Pearl River Delta during 20-22 May 2020:the first was a warm-sector event and the second a frontal event.Based on ERA5 reanalysis data and observations from wind profilers a...Two heavy rainfall events occurred over the Pearl River Delta during 20-22 May 2020:the first was a warm-sector event and the second a frontal event.Based on ERA5 reanalysis data and observations from wind profilers and Doppler weather radars,the structures and roles of low-level jets(LLJs)during these two heavy rainfall events were analyzed.The results show that:(1)South China was affected by a low-level vortex and a low-level shear line during the two processes.The two heavy rainfall events were both associated with a synoptic-system-related low-level jet(SLLJ)and a boundary layer jet(BLJ).The coupling of the convergence at the exit of the BLJ and the divergence at the entrance of the SLLJ produced strong lifting for the warm-sector heavy rainfall,and the strong convergence between the LLJs and northerly winds as the cold front moved southwards was the main lifting reason for the frontal heavy rainfall.(2)The BLJ was the main transport of water vapor during the two processes.The coupling of the BLJ and SLLJ caused the water vapor convergence to be concentrated in the boundary layer during the first process,whereas the strong convergence between the LLJs and northerly winds led to the lower and middle troposphere having strong water vapor convergence during the second process.(3)During the period of these two heavy rainfall events,the lower and middle troposphere remained unstable.Further analysis show that the differences in the intensity,location,and direction between the BLJ and SLLJ resulted in the pseudo-equivalent potential temperature advection in the boundary layer being significantly larger than in the lower and middle troposphere,which compensated for the energy loss caused by heavy rainfall and maintained the convective instability.These findings add to our knowledge on the roles of LLJs in the pre-summer rainfall over South China.展开更多
文摘Arson presents a challenging crime scene for fire investigators worldwide. Key to the investigation of suspected arson cases is the analysis of fire debris for the presence of accelerants or ignitable liquids. This study has investigated the application and method development of vapor phase mid-Infrared (mid-IR) spectroscopy using a field portable quantum cascade laser (QCL) based system for the detection and identification of accelerant residues such as gasoline, diesel, and ethanol in fire debris. A searchable spectral library of various ignitable fluids and fuel components measured in the vapor phase was constructed that allowed for real-time identification of accelerants present in samples using software developed in-house. Measurement of vapors collected from paper material that had been doused with an accelerant followed by controlled burning and then extinguished with water showed that positive identification could be achieved for gasoline, diesel, and ethanol. This vapor phase mid-IR QCL method is rapid, easy to use, and has the sensitivity and discrimination capability that make it well suited for non-destructive crime scene sample analysis. Sampling and measurement can be performed in minutes with this 7.5 kg instrument. This vibrational spectroscopic method required no time-consuming sample pretreatment or complicated solvent extraction procedure. The results of this initial feasibility study demonstrate that this portable fire debris analyzer would greatly benefit arson investigators performing analysis on-site.
基金supported by the National Natural Science Foundation of China(NSFC)(Grant Nos.U2230122 and U2067207)Shenzhen Science and Technology Program(No.KQTD20190929173954826).
文摘Bilayer (BL) molybdenum disulfide (MoS_(2)) is one of the most important electronic structures not only in valleytronics but also in realizing twistronic systems on the basis of the topological mosaics in moiré superlattices. In this work, BL MoS_(2) on sapphire substrate with 2H-stacking structure is fabricated. We apply the terahertz (THz) time-domain spectroscopy (TDS) for examining the basic optoelectronic properties of this kind of BL MoS_(2). The optical conductivity of BL MoS_(2) is obtained in temperature regime from 80 K to 280 K. Through fitting the experimental data with the theoretical formula, the key sample parameters of BL MoS_(2) can be determined, such as the electron density, the electronic relaxation time and the electronic localization factor. The temperature dependence of these parameters is examined and analyzed. We find that, similar to monolayer (ML) MoS_(2), BL MoS_(2) with 2H-stacking can respond strongly to THz radiation field and show semiconductor-like optoelectronic features. The theoretical calculations using density functional theory (DFT) can help us to further understand why the THz optoelectronic properties of BL MoS_(2) differ from those observed for ML MoS_(2). The results obtained from this study indicate that the THz TDS can be applied suitably to study the optoelectronic properties of BL MoS_(2) based twistronic systems for novel applications as optical and optoelectronic materials and devices.
基金This work is supported by the start-up funding from ShanghaiTech University, the Young 1000 Talents Program, the National Natural Science Foundation of China （Nos. U1632118, 21571129, and 21571129）, the National Basic Research Program of China （Nos. 2016YFA0204000 and 2013CB733700）, Science and Technology Commission of Shanghai Municipality （Nos. 16JC1402100 and 16520720700） and the National Natural Science Foundation of China for Creative Research Groups （No. 21421004）. We thank Dr. Yanyan Jia at the testing center at School of Physical Science and Technology, Protein center.
基金supported in part by the National Science Foundation of China(81971094,81771274)the Advanced Innovation Center for Human Brain Protection,Capital Medical University,Beijing,China.
文摘Background Stroke is a devastating disease,including intracerebral haemorrhage(ICH)and ischaemic stroke.Emerging evidences indicate that systemic inflammatory cascades after stroke contribute to brain damage.However,the direct effects and features of systemic inflammation on brain injury,especially comparing between ischaemic and haemorrhagic stroke,are still obscure.Methods Pertussis toxin(PT)was used to build a pro-inflammatory milieu after ICH and ischaemic stroke in mouse model.The neurodeficits,stroke lesion,immune response and blood–brain barrier(BBB)destruction were assessed.Results In ICH mouse model,PT-induced systemic inflammation exacerbated neurological deficits,and enlarged haemorrhage lesion and perihaematomal oedema.We also found promoted leucocyte infiltration and inflammatory cytokine release into the brain after PT treatment.Moreover,the integrity of the BBB was further disrupted after receiving PT.Furthermore,we demonstrated that PT enhanced brain inflammation and aggravated stroke severity in middle cerebral artery occlusion mouse model.Conclusions Our results suggest that PT increases inflammatory response that exacerbates brain injury after ICH or ischaemic stroke in mouse model.
基金by National Science Foundation of China(81801199,81830038,81971094,91949208)Beijing Municipal Science&Technology Commission(Z181100001818001).
文摘Stem cells(SCs)are cells with strong proliferation ability,multilineage differentiation potential and self-renewal capacity.SC transplantation represents an important therapeutic advancement for the treatment strategy of neurological diseases,both in the preclinical experimental and clinical settings.Innovative and breakthrough SC labelling and tracking technologies are widely used to monitor the distribution and viability of transplanted cells non-invasively and longitudinally.Here we summarised the research progress of the main tracers,labelling methods and imaging technologies involved in current SC tracking technologies for various neurological diseases.Finally,the applications,challenges and unresolved problems of current SC tracing technologies were discussed.
基金Supported by the Natural Science Foundation of Guangdong Province(2020A1515010602)Key-Area Research and Development Program of Guangdong Province(2020B1111200001)+1 种基金Guangzhou Municipal Science and Technology Planning Project of China(201903010101)Radar Application and Short-Term Severe-Weather Predictions and Warnings Technology Program(GRMCTD202002)。
文摘Two heavy rainfall events occurred over the Pearl River Delta during 20-22 May 2020:the first was a warm-sector event and the second a frontal event.Based on ERA5 reanalysis data and observations from wind profilers and Doppler weather radars,the structures and roles of low-level jets(LLJs)during these two heavy rainfall events were analyzed.The results show that:(1)South China was affected by a low-level vortex and a low-level shear line during the two processes.The two heavy rainfall events were both associated with a synoptic-system-related low-level jet(SLLJ)and a boundary layer jet(BLJ).The coupling of the convergence at the exit of the BLJ and the divergence at the entrance of the SLLJ produced strong lifting for the warm-sector heavy rainfall,and the strong convergence between the LLJs and northerly winds as the cold front moved southwards was the main lifting reason for the frontal heavy rainfall.(2)The BLJ was the main transport of water vapor during the two processes.The coupling of the BLJ and SLLJ caused the water vapor convergence to be concentrated in the boundary layer during the first process,whereas the strong convergence between the LLJs and northerly winds led to the lower and middle troposphere having strong water vapor convergence during the second process.(3)During the period of these two heavy rainfall events,the lower and middle troposphere remained unstable.Further analysis show that the differences in the intensity,location,and direction between the BLJ and SLLJ resulted in the pseudo-equivalent potential temperature advection in the boundary layer being significantly larger than in the lower and middle troposphere,which compensated for the energy loss caused by heavy rainfall and maintained the convective instability.These findings add to our knowledge on the roles of LLJs in the pre-summer rainfall over South China.
