不同能量电子辐照下星用瑞侃导线性能退化研究

目的研究卫星上外露导线在空间辐射环境下的耐受能力。方法通过分析GEO轨道下在轨10年航天器外露瑞侃导线的辐照环境,研究低能和高能电子对导线性能的影响,地面模拟试验参数选择能量分别为45 keV和1 MeV,注量率均为8.3×10^10 e/(cm^2·s),总注量均为2×10^16 e/cm^2。考察瑞侃导线力学性能(断裂伸长率、拉伸强度)和电性能(击穿电压)的退化情况,并用XPS和SEM测试分析手段,对其电子辐照损伤机理进行研究。结果在不同能量电子辐照下,瑞侃导线的力学性能均略有下降,没有显著区别,而电学性能严重退化,且低能电子较高能电子对其电学性能影响更为严重,其击穿电压分别下降了100%和50%。结论通过剂量-深度分布计算,45 keV入射电子能量全部沉积在样品表层下数微米的深度范围内,完全被导线外皮吸收,对样品的损伤较大;而1 MeV入射电子能量绝大部分穿透表皮沉积在样品铜芯中,因而其性能退化情况相对低能电子较小。进一步的,通过SEM和XPS测试和分析发现,电子辐照造成瑞侃导线分子链降解,形成自由基以及气体,自由基的再交联是造成瑞侃导线损伤的重要机理。     

基于PBPK模型的大鼠体内镉分布的比较:联合暴露及单独暴露

环境中同时存在着多种重金属元素,联合暴露与单独暴露时,重金属在体内的蓄积分布情况也可能有所差异。为探究重金属元素(汞、铬、砷、铅)对镉(Cd)在体内分布的影响,建立了大鼠在Cd暴露下的药代动力学(PBPK)模型,并进行了包括Cd在内5种重金属的联合毒性实验,比较了Cd单独给药与重金属混合物给药2种方式下大鼠肝脏、肾脏中的Cd浓度水平。结果表明,联合暴露高(Hg Cl23.67 mg·kg~(-1),NaAsO_2 3.67 mg·kg~(-1),CdCl_2 10.55 mg·kg~(-1),K_2Cr_2O_7 6.40 mg·kg~(-1),Pb(OOCCH_3)_2·3H_2O 133.33 mg·kg~(-1))、中(HgCl_20.367 mg·kg~(-1),NaAsO_2 0.367 mg·kg~(-1),CdCl_2 1.055 mg·kg~(-1),K2Cr2O70.640 mg·kg~(-1),Pb(OOCCH_3)_2·3H_2O 13.333 mg·kg~(-1))、低(HgCl_2 0.0367 mg·kg~(-1),Na As O20.0367 mg·kg~(-1),Cd Cl20.1055 mg·kg~(-1),K_2Cr_2O_7 0.0640 mg·kg~(-1),Pb(OOCCH3)2·3H2O 1.3333 mg·kg~(-1))剂量组大鼠肝脏中Cd浓度分别为13.37、0.78和0.06μg·g~(-1);肾脏中Cd浓度分别为14.41、1.64和0.15μg·g~(-1)。与对照组相比,暴露组中Cd浓度有显著升高,且不同剂量组之间均有显著性差异。同剂量Cd单独暴露的PBPK模拟结果显示,肝脏及肾脏中的Cd浓度水平落在联合毒性实验结果的浓度范围内,初步推断其他4种重金属的联合暴露并没有影响Cd在大鼠肾脏和肝脏中的浓度分布。     

基于高通量测序的工业园区地下水和土壤细菌群落结构比较研究

为探究工业园区地下水和土壤细菌群落结构、多样性变化特征,采用高通量测序技术对地下水和土壤细菌16S r RNA基因高变区域进行序列测定。通过对Alpha多样性、物种组成、丰度和群落结构的分析,比较地下水和土壤细菌群落结构的异同。Alpha多样性的比较结果表明,土壤细菌群落多样性和丰富度明显高于地下水,地下水细菌群落多样性指数反映出地下水已受到周边污染源的影响。物种注释结果表明,地下水样品共检出48个细菌门,土壤样品共检出50个细菌门。变形菌门(Proteobacteria)、拟杆菌门(Bacteroidetes)和厚壁菌门(Firmicutes)是地下水细菌群落的优势类群,共占93.54%,且该工业园区地下水细菌群落呈现出典型的淡水种群特征;土壤中优势细菌门为Proteobacteria、放线菌门(Actinobacteria)、酸杆菌门(Acidobacteria)、Firmicutes和芽单胞菌门(Gemmatimonadetes),共占85.21%。由于地下水和土壤两者的生态系统和理化环境的差异,致使Actinobacteria、Acidobacteria、绿弯菌门(Chloroflexi)、硝化螺旋菌门(Nitrospirae)、α-变形菌纲(Alphaproteobacteria)、δ-变形菌纲(Deltaproteobacteria)和Gemmatimonadetes占比在地下水和土壤细菌群落间差异显著,同时使地下水和土壤细菌群落各含有一些特有的优势细菌属(地下水2个,土壤4个)。基于高通量测序技术对工业园区样品的测序结果可以为地下水和土壤环境的生态评价提供方法依据。     

Aerosol transmission,an indispensable route of COVID-19 spread: case study of a department-store cluster

• Aerosol transmission is an indispensable route of COVID-19 spread. • Different outbreak sites have different epidemiologic feature. • SRAS-CoV-2 can exist for a long time in aerosol. • SRAS-CoV-2 RNA can be detected in aerosol in diverse places. • Some environmental factors can impact SARS-CoV-2 transportation in aerosol. Patients with COVID-19 have revealed a massive outbreak around the world, leading to widespread concerns in global scope. Figuring out the transmission route of COVID-19 is necessary to control further spread. We analyzed the data of 43 patients in Baodi Department Store (China) to supplement the transmission route and epidemiological characteristics of COVID-19 in a cluster outbreak. Incubation median was estimated to endure 5.95 days (2–13 days). Almost 76.3% of patients sought medical attention immediately upon illness onset. The median period of illness onset to hospitalization and confirmation were 3.96 days (0–14) and 5.58 days (1–21), respectively. Patients with different cluster case could demonstrate unique epidemiological characteristics due to the particularity of outbreak sites. SRAS-CoV-2 can be released into the surrounding air through patient’s respiratory tract activities, and can exist for a long time for long-distance transportation. SRAS-CoV-2 RNA can be detected in aerosol in different sites, including isolation ward, general ward, outdoor, toilet, hallway, and crowded public area. Environmental factors influencing were analyzed and indicated that the SARS-CoV-2 transportation in aerosol was dependent on temperature, air humidity, ventilation rate and inactivating chemicals (ozone) content. As for the infection route of case numbers 2 to 6, 10, 13, 16, 17, 18, 20 and 23, we believe that aerosol transmission played a significant role in analyzing their exposure history and environmental conditions in Baodi Department Store. Aerosol transmission could occur in some cluster cases when the environmental factors are suitable, and it is an indispensable route of COVID-19 spread.     

Neighborhood form and CO2 emission: evidence from 23 neighborhoods in Jinan, China

To understand the household C02 emission level in China, as well as how much the neighborhoods＇ socio-economic or design factors could influence the CO2 emission, 23 neighborhoods in Jinan were investigated in 2009 and 2010. These neighborhoods fall into four different types： superblock, enclave, grid and traditional. The household CO2 emission includes sources of both in- home energy use and passenger transportation. The average CO2 emission per household is 7.66 t.a^-1, including 6.87 t in-home operational emission and 792 kg transportation emission. The household CO2 emission by neighborhood categories is 10.97, 5.65, 6.49, 5.40 t-household-1. a-1 for superblock, enclave, grid and tradi- tional respectively. Superblock has the highest average emission and also the highest percent （more than 25%） of transportation emission among four different types of neighborhoods. The residential CO2 emission of superb- lock neighborhoods in Jinan has already reached the level in developed countries nearly ten years ago. It is predictable that more superblock neighborhoods would be built in China with the fast urbanization. How to avoid the rapid household CO2 emission growth in the future would be a systematic issue. The study also found that in addition to income and apartment area, household density, land use mix and accessibility to public transportation are three primary factors which have significant impacts on CO2 emission. High density, mixed land use and convenient accessibility to public transportation tend to reduce household CO2 emission.     

Characteristic volume fractions of different grains in porous media for anomalous dispersion

Anomalous solute transport in porous media is an important issue in groundwater research. In this paper, we explore the relationship between the anomalous solute transport and the volume fractions of different grains in the porous media. Via simulation, we find that there is a maximum and a minimum in the degree of anomalous transport when changing the volume fractions of different grains. Moreover, the characteristic volume fractions corresponding to the anomalous transport maximum and minimum vary little with the flow field and diffusion coefficient of the solute. We also find that the volume fraction corresponding to the most anomalous dispersion is close to the threshold of the site percolation for simple-cubic networks.     

我国自然灾害时空分布及其粮食风险评估

分析了旱灾、水灾、风雹灾、霜冻灾、台风灾和农业病虫害、草害、鼠害8种自然灾害的时空分布情况,计算了其造成的历年粮食减产量,并在此基础上评估2020年自然灾害对粮食产量的影响。结果表明,2020年不同自然灾害对我国各省粮食生产的影响程度不同。旱灾风险区集中在我国北方地区,分布在黄淮海区、西北区等;涝灾风险区集中在我国南方地区,分布在长江中下游区等;风雹灾风险区对我国粮食产量影响相对较小,主要分布在新疆和青海;台风灾风险区集中在我国南方沿海地区;农业病虫害风险区集中在我国的南方地区,分布在华南沿海区和西南区等;而霜冻灾、农业草害、鼠害对粮食生产的影响范围和影响程度较小。     

人类的新噩梦:声波武器

意外发现“死亡之声” 20世纪50年代末,冷战正酣。出生于俄罗斯的机器人发明家加夫雷奥,一天接到了法国国防部的密令：火速研发能打核战争的机器人。     

Diethylenetriaminepentaacetic Acid (DPTA)-modified Magnetic Cellulose Nanocrystals can Efficiently Remove Pb(II) from Aqueous Solution

Journal of Polymers and the Environment - Surface modification of cellulose nanocrystals (CNC) is essential for improving their reactivity and adsorption capacity. Oxidation, as a conventional...     

An antibiotic composite electrode for improving the sensitivity of electrochemically active biofilm biosensor

• Antibiotic azithromycin employed in graphite electrode for EAB biosensor. • Azithromycin at 0.5% dosage increased the sensitivity for toxic formaldehyde. • Azithromycin increased the relative abundance of Geobacter. • Azithromycin regulated thickness of electroactive biofilm. Extensive research has been carried out for improved sensitivity of electroactive biofilm-based sensor (EAB-sensor), which is recognized as a useful tool in water quality early-warning. Antibiotic that is employed widely to treat infection has been proved feasible in this study to regulate the EAB and to increase the EAB-biosensor’s sensitivity. A novel composite electrode was prepared using azithromycin (AZM) and graphite powder (GP), namely AZM@GP electrode, and was employed as the anode in EAB-biosensor. Different dosages of AZM, i.e., 2 mg, 4 mg, and 8 mg, referred to as 0.25%, 0.5% and 1% AZM@GP were under examination. Results showed that EAB-biosensor was greatly benefited from appropriate dosage of AZM (0.5% AZM@GP) with reduced start-up time period, comparatively higher voltage output, more readable electrical signal and increased inhibition rate (30%-65% higher than control sensor with GP electrode) when exposing to toxic formaldehyde. This may be attributed to the fact that AZM inhibited the growth of non-EAM without much influence on the physiologic or metabolism activities of EAM under proper dosage. Further investigation of the biofilm morphology and microbial community analysis suggested that the biofilm formation was optimized with reduced thickness and enriched Geobacter with 0.5% AZM@GP dosage. This novel electrode is easily fabricated and equipped, and therefore would be a promising way to facilitate the practical application of EAB-sensors.