Abstract The mechanism of aggregation-induced emission, which overcomes the common aggregation-caused quenching problem in organic optoelectronics, is revealed by monitoring the real time structural evolution and dynamics of electronic excited state with frequency and polarization resolved ultrafast UV/IR spectroscopy and theoretical calculations. The formation of Woodward?Hoffmann cyclic intermediates upon ultraviolet excitation is observed in dilute solutions of tetraphenylethylene and its derivatives but not in their respective solid. The ultrafast cyclization provides an efficient nonradiative relaxation pathway through crossing a conical intersection. Without such a reaction mechanism, the electronic excitation is preserved in the molecular solids and the molecule fluoresces efficiently, aided by the very slow intermolecular charge and energy transfers due to the well separated molecular packing arrangement. The mechanisms can be general for tuning the properties of chromophores in different phases for various important applications.
Over the past few decades, anaerobic ammonium oxidation (anammox) has been extensively documented at different scales in natural ecosystems. Previous studies have stated that the community composition of anammox bacteria is shaped mainly by environmental factors, whereas spatial factors have been largely overlooked. This study investigated biogeographical patterns of anammox bacterial communities using 42 sediment samples along a 4300-km stretch of the Yangtze River, the longest river in Asia. A significant distance-decay relationship was observed for anammox bacterial community similarity, which was significantly influenced by mean dendritic distance rather than environmental factors. This implied that dispersal limitation plays an important role in shaping biogeographical pattern of anammox community. Furthermore, our results revealed that neutral processes played vital role in shaping community assembly of anammox bacteria, and their communities were seriously dispersal limited. These findings contrast with previous studies on community similarities between broad taxonomic groups, which are mainly determined by niche-based selection owing to greater niche distances within broad taxonomic groups than in anammox bacteria. Importantly, the slope of the distance-decay curve was much steeper than previously reported for whole bacteria, which indicating the species turnover rate of anammox bacterial community was significantly higher than that of the whole bacterial community. Anammox bacteria harbor strong adhesion ability and low dispersal potential, and ultimately exhibited a high species turnover rate. Together, in the context of biogeography, our results highlight the importance of dispersal limitation in shaping the biogeographical pattern of anammox bacterial community.
223 surface soil samples from conservation areas of the Miyun Reservoir were collected for detecting the concentration of organochlorine pesticides (OCPs) residues.The pollution characteristics,spatial distribution,influencing factors,origins of OCPs,and ecological risks were systematically explored.The results showed that the concentration of HCHs and DDTs in the soil samples ranged from ND to 2.10ng/g and ND to 526ng/g,respectively.The HCHs and DDTs in the Miyun reservoir presented zonal and discrete distribution characteristics,and the maximal values appeared in areas with dense population and developed agriculture.Moreover,both land use pattern and soil physical-chemical properties significantly impacted on the distribution of HCHs and DDTs.Highest concentration was found in farmland,and pH value was found to have greatest effect on the OCPs distribution.Furthermore,the OCPs residues in soils were mainly originated from the historical residues,atmospheric precipitation and recent inputs.Compared with other similar soil samples from different regions,the concentration of HCHs and DDTs in soil samples of the Miyun reservoir were at medium-low level,which suggested that HCHs and DDTs in the Miyun reservoir were in a state of low danger.以密云水库水源保护区为研究区域,对采集的223个表层土壤样品开展了有机氯农药残留浓度的测定,并对其污染特征、空间分布、影响因素、污染来源及生态风 险进行了探讨.结果表明,研究区域内HCHs和DDTs的总量变化范围分别在ND-2.10ng/g和ND-526ng/g之间,gamma-HCH、p ,p'-DDE和p,p'-DDT的检出率较高.HCHs和DDTs在空间上的分布呈现带状和离散性分布特征,浓度极值出现在人口密集和农业发达的地区. 土地利用方式和土壤理化性质均会对HCHs和DDTs的分布产生较大影响,其中耕地残留量最高,土壤pH值影响最大.HCHs和DDTs主要来源于早期残 留、大气的干湿沉降及近期的农药输入等.与国内外其他类似区域表层土壤相比,密云水库保护区土壤有机氯农药处于中等偏低水平,区域内总体生态风险较小,个 别点位可能存在潜在生态风险.
Bakken shale samples were studied for distribution of adsorbed water using low-pressure nitrogen sorption. By comparing results between dry and wet samples, the distribution of adsorbed water in shale was determined. Two of the isolated kerogen samples show a striking change of pore size distribution (PSD) in large pores (>16 nm), indicating the pronounced distribution of adsorbed water in large pores of organic matter. As for the bulk shale, water can adsorb in both small (16 nm) depending on hydrophilic sites. However, hydrophilic sites in small pores are mainly contributed by inorganic matter, while hydrophilic sites in large pores are composed of inorganic or organic matter. The overall results therefore clarify the contribution of inorganic and organic matter to water adsorption in shale and provide a better understanding of the significance of adsorbed water in shale.
BACKGROUND: DNA methylation (DNAm) may play a role in age-related outcomes. It is not yet known which DNAm-based biomarkers of age acceleration (BoAA) has the strongest association with age-related endpoints. METHODS: We collected the blood samples from two independent cohorts: the Normative Ageing Study, and the Cooperative Health Research in the Region of Augsburg cohort. We measured epigenome-wide DNAm level, and generated five DNAm BoAA at baseline. We used Cox proportional hazards model to analyze the relationships between BoAA and all-cause death. We applied the Fine and Gray competing risk model to estimate the risk of BoAA on myocardial infarction (MI), stroke, and cancer, accounting for death of other reasons as the competing risks. We used random-effects meta-analyses to pool the individual results, with adjustment for multiple testing. FINDINGS: The mean chronological ages in the two cohorts were 74, and 61, respectively. Baseline GrimAgeAccel, and DNAm-related mortality risk score (DNAmRS) both had strong associations with all-cause death, MI, and stroke, independent from chronological age. For example, a one standard deviation (SD) increment in GrimAgeAccel was significantly associated with increased risk of all-cause death [hazard ratio (HR): 2.01; 95% confidence interval (CI), 1.15, 3.50], higher risk of MI (HR: 1.44; 95% CI, 1.16, 1.79), and elevated risk of stroke (HR: 1.42; 95% CI, 1.06, 1.91). There were no associations between any BoAA and cancer. INTERPRETATION: From the public health perspective, GrimAgeAccel is the most useful tool for identifying at-risk elderly, and evaluating the efficacy of anti-aging interventions. FUNDING: National Institute of Environmental Health Sciences of U.S., Harvard Chan-NIEHS Center for Environmental Health, German Federal Ministry of Education and Research, and the State of Bavaria in Germany.
Past studies typically have focused on whether people perceive more rare risk after experiencing catastrophic disasters. We show that people can also feel less risk with unexpected "lucky" disaster experience. By exploring a novel identification strategy based on households' expectations, we find that households perceive less (more) risk when they experience disasters that have lower (higher) actual fatalities than what was expected. This opposite experience effect of rare disasters is substantial: a one standard deviation increase in the negative (positive) experience shock is associated with a 1.71% decrease (a 1.31% increase) in the life insurance-to-portfolio ratio. We discuss three possible mechanisms to account for our empirical findings: incomplete information learning, salience theory, and change in risk preferences.
Abstract Aim Sexual systems strongly influence angiosperm evolution and play important roles in community assembly and species responses to climate change. However, geographical variation in proportions of different sexual systems (dioecy, monoecy and hermaphroditism) in response to changes in climate, life-history traits and evolutionary age remains poorly understood. Here, we map the geographical variation in proportions of different sexual systems and hypothesize that the prevalence of hermaphrodites increases with aridity owing to their advantages in colonizing harsh environments, whereas dioecy is most successful in humid regions with tall-canopy vegetation and old floras. Location China. Time period Current. Major taxa studied Woody angiosperms. Methods Using data on sexual systems and distributions of 10,449 woody species in China, we estimated the proportions of different sexual systems in local floras (50 km × 50 km grid cells). Spatial linear models, phylogenetic general linear models and structural equation models were used to compare the relative influences of climate, plant height and evolutionary age on geographical variation in proportions of different sexual systems. Results We found contrasting geographical patterns in the proportions of different sexual systems. The proportions of dioecy and monoecy increased with plant height and were highest in humid regions with older floras, whereas that of hermaphroditism decreased with plant height and was highest in arid regions with younger floras. Plant height was the strongest correlate of sexual system frequency. Climate influenced sexual system frequency both directly and indirectly via its effects on plant height. Main conclusions Our study provides the first continuous map of sexual system composition in woody floras over a large spatial scale. Our findings suggest that mature plant height, reflecting plant longevity, dominates geographical variation in sexual systems and that the proportions of different sexual systems in local floras might reflect their correlated evolution with traits in response to climate changes.