Spatially resolved pump-probe study of single-layer graphene produced by chemical vapor deposition

Carrier dynamics in single-layer graphene grown by chemical vapor deposition (CVD) is studied using spatially and temporally resolved pump-probe spectroscopy by measuring both differential transmission and differential reflection. By studying the expansion of a Gaussian spatial profile of carriers excited by a 1500-nm pump pulse with a 1761-nm probe pulse, we observe a diffusion of hot carriers of 5500 square centimeter per second. We also observe that the expansion of the carrier density profile decreases to a slow rate within 1 ps, which is unexpected. Furthermore, by using an 810-nm probe pulse we observe that both the differential transmission and reflection change signs, but also that this sign change can be permanently removed by exposure of the graphene to femtosecond laser pulses of relatively high fluence. This indicates that the differential transmission and reflection at later times may not be directly caused by carriers, but may be from some residue material from the sample fabrication or transfer process.Comment: 9 pages, 3 figure

Deciphering the pathogenic role of rare RAF1 heterozygous missense mutation in the late-presenting DDH

BackgroundDevelopmental Dysplasia of the Hip (DDH) is a skeletal disorder where late-presenting forms often escape early diagnosis, leading to limb and pain in adults. The genetic basis of DDH is not fully understood despite known genetic predispositions.MethodsWe employed Whole Genome Sequencing (WGS) to explore the genetic factors in late-presenting DDH in two unrelated families, supported by phenotypic analyses and in vitro validation.ResultsIn both cases, a novel de novo heterozygous missense mutation in RAF1 (c.193A>G [p.Lys65Glu]) was identified. This mutation impacted RAF1 protein structure and function, altering downstream signaling in the Ras/ERK pathway, as demonstrated by bioinformatics, molecular dynamics simulations, and in vitro validations.ConclusionThis study contributes to our understanding of the genetic factors involved in DDH by identifying a novel mutation in RAF1. The identification of the RAF1 mutation suggests a possible involvement of the Ras/ERK pathway in the pathogenesis of late-presenting DDH, indicating its potential role in skeletal development

Enhanced interfacial interaction, mechanical properties and thermal stability of basalt fiber/epoxy composites with multi-scale reinforcements

In this work, epoxy (EP) resin composites with multi-scale reinforcements were prepared by hand lay-up and hot-pressing. The epoxy was reinforced with basalt fibers (BF) modified with a silane coupling agent (KH560). Carboxylated multi-walled carbon nanotubes (CNTs) were also grafted onto the surface of the modified BF using an impregnation method to achieve BF/CNTs multi-scale reinforcement. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) showed that KH560 was successfully grafted onto the BF surface. Scanning electron microscopy (SEM), indicated a better resin adhesion on the BF and thus a stronger interfacial interaction in the BF/CNTs-reinforced composite. It was observed that the mass fraction of KH560 was a significant parameter in achieving desirable CNT immobilization and mechanical properties of the composites. At an optimal mass fraction of KH560 (5%), the tensile, flexural, and interlaminar shear strength (ILSS) of the modified composite (BF-5%KH560-CNT/EP) increased by 12.5%, 20.9%, and 25.5% respectively compared with the BF-washed/EP composite due to more efficient load transfer. In addition, compared with BF-washed/EP, the decomposition onset temperature of BF-5%KH560-CNT/EP increased from 387°C to 396°C, the maximum decomposition rate temperature increased from 400°C to 408°C, and the residual weight increased by 5.8%

Nitrogen isotope composition of ammonium in PM 2.5 in the Xiamen, China: impact of non-agricultural ammonia

Abstract(#br)Since NH 3 is a significant precursor to ammonium in PM 2.5 and contributes significantly to atmospheric nitrogen deposition but largely remains unregulated in China, the insight into the source of NH 3 emissions by the isotopic investigation is important in controlling NH 3 emissions. In this study, atmospheric concentrations of NH 3 and water-soluble ion composition in PM 2.5 as well as nitrogen isotope ratios in NH 4 + (δ 15 N-NH 4 + ) in Xiamen, China, were measured. Results showed that average NH 3 concentration for the five sites in Xiamen was 7.9 μg m −3 with distinct higher values in the warm season and lower values in the cold season, and PM 2.5 concentration for the two sites (urban and suburban) was 59.2 μg m −3 with lowest values in summer. In the PM 2.5 , NH 4 +..

Measurement of Particulate n-alkanes and PAHs Inside and Outside a Temple in Xiamen, China

Total suspended particles samples inside and outside the South Pu-Tuo Temple (SPT), a traditional Buddhist temple in Xiamen, China were collected and further analyzed for n-alkanes and polycyclic aromatic hydrocarbons (PAHs) during the periods of worship. It was observed that the concentrations of particulate n-alkanes at SPT were abnormally higher compared to the surrounding bus terminus and campus. In addition, benzo[a]pyrene (BaP) equivalent concentrations at SPT (7.1-26.3 ng/m(3)) were significantly higher than those at the bus terminus (5.1-6.9 ng/m(3)) although the PAH concentrations were comparable. The hazard potential of PAHs in terms of the carcinogenicity of BaP inside SPT is not acceptable because the indoor air quality standard of BaP recommended by the State Environmental Protection Administration of China is 1 ng/m(3) (daily mean). Ratios of fluoranthene to fluoranthene plus pyrene, indeno[1,2,3-cd] pyrene to indeno[1,2,3-cd] pyrene plus benzo[g,h,i] perylene and 1,7-DMP (dimethylphenanthrene) to 2,6-DMP plus 1,7-DMP were further calculated; the values of these three together with the ratio of retene to phenanthrene separated the SPT samples from the bus terminus samples, in that SPT samples showed a strong influence of wood burning (such as bamboo sticks, stick coatings, and joss paper).National Science Foundation of China [20777060

Nitrogen isotope composition of ammonium in PM2.5 in the Xiamen, China: impact of non-agricultural ammonia.

Since NH3 is a significant precursor to ammonium in PM2.5 and contributes significantly to atmospheric nitrogen deposition but largely remains unregulated in China, the insight into the source of NH3 emissions by the isotopic investigation is important in controlling NH3 emissions. In this study, atmospheric concentrations of NH3 and water-soluble ion composition in PM2.5 as well as nitrogen isotope ratios in NH4+ (δ15N-NH4+) in Xiamen, China, were measured. Results showed that average NH3 concentration for the five sites in Xiamen was 7.9 μg m-3 with distinct higher values in the warm season and lower values in the cold season, and PM2.5 concentration for the two sites (urban and suburban) was 59.2 μg m-3 with lowest values in summer. In the PM2.5, NH4+ concentrations were much lower than NH3 and showed a stronger positive correlation with NO3- than that with SO42- suggesting the formation of NH4NO3 and equilibrium between NH3 and NH4+. Although the concentrations of NH3 at the urban site were significantly higher than those at the suburban site, no significant spatial difference in NH4+ and δ15N-NH4+ was obtained. The distinct heavier δ15N-NH4+ values in summer than in other seasons correlated well with the equilibrium isotopic effects between NH3 and NH4+ which depend on temperature. The initial δ15N-NH3 values were in the range of waste treatment (- 25.42‰) and fossil fuel combustion (- 2.5‰) after accounting for the isotope fractionation. The stable isotope mixing model showed that fossil fuel-related NH3 emissions (fossil fuel combustion and NH3 slip) contributed more than 70% to aerosol NH4+. This finding suggested that the reduction of NH3 emissions from urban transportation and coal combustion should be a priority in the abatement of PM2.5 pollution in Xiamen

Effect of Surfactant on the Volatilization of Organochlorine Pesticides from Still Artificial Seawater

[摘要]：研究了阴离子表面活性剂十二烷基苯磺酸钠( SDBS) 对17 种有机氯农药(OCPs) 在模拟静海水水面挥发的影响及机制. 结 果表明, 低浓度SDBS的存在能抑制OCPs 的挥发, 抑制能力有随SDBS 浓度增加而增加的趋势, 且经盐常数校正后的气2水分配 系数与挥发速率常数在对数散点图上存在很好的正相关关系. OCPs 化合物挥发阻力分析表明, 低浓度SDBS 形成的表面膜不 会对OCPs 的挥发阻力产生直接影响, 但却增加了大气中OCPs 化合物在液面的沉降, 造成净挥发量减少, 且挥发性相对较强的 化合物受表面活性膜的影响更大.[ABstract]:The effect of sodium dodecylbenzene sulfonate ( SDBS) on the volatilization of 17 organochlorine pesticides ( OCPs) from still artificial seawater has been examined. The results show that SDBS at low concentration can retard the volatilization of OCPs compared to / clean0 surface. The retarding influence ismore pronounced for high level of SDBS than it is for low level of SDBS. A good positive correlation between the gas2seawater partition coefficients and the measured volatilization rates of OCPs is observed. Although the SDBS films present no significant, direct resistance to transfer, the films can absorb more OCPs from the above atmosphere with respect to the / clean0 surface and reduce the net volatilization flux from the still artificial seawater. The effect of the film is more pronounced for volatilization of more volatile OCPs than it is for less volatile OCPs.国家自然科学基金项目( 40603020) ; 中国博士后科学基金 项目(20060390186

Diurnal Variations of Particle-bound PAHs at a Traffic Site in Xiamen, China

To improve our current understanding of the fate of particle-bound PAHs, which include potent mutagens and carcinogens, diurnal measurements of these compounds were carried out from 23 Oct to 31 Dec 2008 at a busy traffic site in Xiamen, China. The sum of 19 PAH concentrations showed a just noticeable day-night difference in the warmer period (from 23 Oct to 25 Nov) to a remarkable day-night difference in the colder period (from 26 Nov to 31 Dec). However, the average profiles of the 19 PAHs in the warmer and colder periods were very similar for both day and night samples. Atmospheric mixing seemed to have more influence on the diurnal variations in PAHs than photodecomposition resulting from solar radiation, because PAH concentrations showed negative correlation with air temperature but significantly positive correlation with the ratios of reactive to stable PAHs, such as benz[a] anthracene to chrysene and benzo[a] pyrene to benzo[e] pyrene. Based on the diagnostic ratios of indeno[1,2,3-cd]pyrene to indeno[1,2,3-cd] pyrene plus benzo[g, h, i]perylene and fluoranthene to fluoranthene plus pyrene, the results showed that no significant differences were observed in PAHs sources between the warm and cold periods and a combination of grass, wood or coal combustion and petroleum sources in airborne particles might be the most significant contributors of PAHs. Gas-phase PAHs were calculated based on the theoretical gas/particle partitioning coefficients for 19 PAHs and a high fraction of daily exposure was attributed to particle-phase PAHs in most cases. The excess lifetime cancer risk in colder period was generally higher than in the warmer period. The total uncertainties were computed based on the simpler average error transfer formula.Natural Science Foundation (NSFC) [40971257, 20777060

Seasonal variation for the ratio of BaP to BeP at different sites in Great Xiamen Bay

From March 2008 to February 2009, PM10 samples were collected and analyzed for polycyclic aromatic hydrocarbons (PAHs) at eight sampling sites in Great Xiamen Bay, China. Analyses of the seasonal and spatial variations of these compounds revealed the following results. Significantly high levels of PAHs were found in the winter compared to the summer, sometimes exceeding 100 ng m(-3), and the spatial variations were influenced most by the sampling site surroundings. Composition profiles of PAHs of an urban and a rural site were shown to be very similar with a positive correlation coefficient larger than 0.9 at the 0.01 level of significance for the same season. Diagnostic ratios, together with principal component and multiple linear regression analysis, showed that more PAHs were from grass/wood/coal combustion in winter than in other seasons. The ratios of benzo[a]pyrene to benzo[e]pyrene (BaP-BeP) in winter and fall were 0.6-1.7 times higher than those in spring and summer, suggesting the importance of local emissions of PAHs. The BaP-BeP ratios in Kinmen were generally lower than those in Xiamen, indicating that the aging degree of PAHs was higher in Kinmen than in Xiamen. The external input of PAHs from upwind urban and industrial areas was one of the key factors causing high levels of PAHs in PM10 in Great Xiamen Bay in winter.National Natural Science Foundation of China [40971257, 41171365]; Environmental Nonprofit Research and Special Project of China [201009004]; Program for Changjiang Scholars and Innovative Research Team in University (PCSIRT

P ollution of an ion ic surfactan t and PCB in coasta l surfa ce seawa ter of Fujian Lprovince

[摘要]：用亚甲蓝分光光度法和GC2ECD 法分别对福建近岸表层海水中的阴离子表面活性剂和PCBs进行了分析, 初步探 讨了表层海水中这两类污染物的来源。表层海水中阴离子表面活性剂浓度范围为0. 04~ 1. 987 mg/L, 较高浓度值站点主要 位于九龙江口、闽江口和湄洲湾海域。PCBs的浓度在3. 9 ~ 367. 1 ng/L之间, 整体上近岸站点浓度值比离岸站点高, 中北部 浓度值比南部高。与其他地区的研究结果及海水水质标准进行比较, 福建沿海表层海水中阴离子表面活性剂和PCB的污染 都较为严重。[Abstract]:The an ion ic surfactant and PCB in the coasta l su rface seawater of Fu jian p rovin ce were analyzed bymethylene blue sp ectro2 photometricmethod andGC2ECD, respectively. Th e concen trations ofmethylene b lu e act ive substan ce (MBAS) in th e surface seawater ranged from 0. 04 to 1. 987mg /L with the h ighest value found at the p ipe ou tlet near X iamen Un iversity. The elevated concentrat ions ofMBASwere observed in J iu long jiang, M in jiang Estuary andMeizhou Bay, poss ib ly du e to the d ischarge of sewage. Th e concentrat ions of totalPCBs ( d issolved p lu s particu late phase) ranged from 3. 9 to 367. 1 ng/L in th e surface L seawater and increased concentrat ions were ob served from offsh ore to inshore and from sou th to north. Th e pollut ion of an ion ic surfactan ts and PCBs in the coastal su rface sea2 water of Fu j ian P rovin ce is a seriou s prob lem comparingw ith other values reported andU S and Canada seawater2qu ality criteria.中国博士后科学基金( 20060390186); 国家自然科学基金项目( 40603020