Observing High‐Pressure Chemistry in Graphene Bubbles

Using IR spectroscopy, high‐pressure reactions of molecules were observed in liquids entrapped by graphene nanobubbles formed at the graphene–diamond interface. Nanobubbles formed on graphene as a result of thermally induced bonding of its edges with diamond are highly impermeable, thus providing a good sealing of solvents within. Owing to the optical transparency of graphene and diamond, high‐pressure chemical reactions within the bubbles can be probed with vibrational spectroscopy. By monitoring the conformational changes of pressure‐sensitive molecules, the pressure within the nanobubble can be calibrated as a function of temperature and it is about 1 GPa at 600 K. The polymerization of buckministerfullerene (C₆₀), which is symmetrically forbidden under ambient conditions, is observed to proceed in well‐defined stages in the pressurized nanobubbles.     

Computational Insights into Allosteric Conformational Modulation of P-Glycoprotein by Substrate and Inhibitor Binding

The ATP-binding cassette (ABC) transporter P-glycoprotein (P-gp) is a physiologically essential membrane protein that protects many tissues against xenobiotic molecules, but limits the access of chemotherapeutics into tumor cells, thus contributing to multidrug resistance. The atomic-level mechanism of how substrates and inhibitors differentially affect the ATP hydrolysis by P-gp remains to be elucidated. In this work, atomistic molecular dynamics simulations in an explicit membrane/water environment were performed to explore the effects of substrate and inhibitor binding on the conformational dynamics of P-gp. Distinct differences in conformational changes that mainly occurred in the nucleotide-binding domains (NBDs) were observed from the substrate- and inhibitor-bound simulations. The binding of rhodamine-123 can increase the probability of the formation of an intermediate conformation, in which the NBDs were closer and better aligned, suggesting that substrate binding may prime the transporter for ATP hydrolysis. By contrast, the inhibitor QZ-Leu stabilized NBDs in a much more separated and misaligned conformation, which may result in the deficiency of ATP hydrolysis. The significant differences in conformational modulation of P-gp by substrate and inhibitor binding provided a molecular explanation of how these small molecules exert opposite effects on the ATPase activity. A further structural analysis suggested that the allosteric communication between transmembrane domains (TMDs) and NBDs was primarily mediated by two intracellular coupling helices. Our computational simulations provide not only valuable insights into the transport mechanism of P-gp substrates, but also for the molecular design of P-gp inhibitors.     

2D Oligosilyl Metal–Organic Frameworks as Multi‐state Switchable Materials

We report the synthesis of a set of 2D metal–organic frameworks (MOFs) constructed with organosilicon‐based linkers. These oligosilyl MOFs feature linear Si_nMe_2n(C₆H₄CO₂H)₂ ligands (lin‐Si_n, n=2, 4) connected by Cu paddlewheels. The stacking arrangement of the 2D sheets is dictated by van der Waals interactions and is tunable by solvent exchange, leading to reversible structural transformations between many crystalline and amorphous phases.     

安庆天柱山机场鸟类群落季节性变化与鸟击防范

在2008年2月至2009年2月间,对安庆天柱山机场及其周边地区的鸟类种类、种群数量进行了为期一年的调查.调查共记录到鸟类102种,隶属于12个目29个科,其中留鸟38种,占总数37.25%;夏候鸟28种,占总数27.45%;冬候鸟25种,占总数24.51%;旅鸟11种,占总数14.39%.在地理类型上,机场地区鸟类呈现古北界与东洋界过渡地带的特点,其中广布种37种,占总数36.27%;东洋界种类有34种,占总数33.33%;古北界种类31种,占总数30.39%.在机场及周边地区,春季观察到鸟类物种数要明显多于秋季及冬季,春季鸟类多样性也要高于秋季与冬季.在机场地区,每年5~6月份与10~11月份鸟类活动比较频繁.机场鸟击防范工作,应该根据鸟类活动特点,通过对重点区域栖息地的改造,降低生物多样性,从而减少鸟类在机场地区的活动,避免鸟击事件的发生.     

Potential influence of water level changes on energy flows in a lake food web

Large seasonal water-level fluctuations may influence isotopic signatures of primary producers and the types and amounts of these potential food sources accessible to aquatic fauna of Poyang Lake,the largest freshwater lake in China.In this study,the isotopic signatures of primary producers and consumers were determined,stable carbon and nitrogen isotope analysis and mixing models were combined to investigate the influence of water levels on the diet and isotopic composition of Poyang Lake fish and inverteb...     

北京市海淀公园绿地CO2通量变化特征

为了定量评估城市绿地吸收CO2改善城市生态环境的效果,2006年4月—2007年3月在北京海淀公园绿地使用涡度相关系统连续观测CO2通量、总辐射、大气温度,并使用冠层分析仪测量叶面积指数,研究CO2通量的变化及其影响因素.结果表明,绿地CO2通量受植被生物活动的影响呈现明显的季节变化特征,晴天天气状况下CO2通量日均值FCO2在4—10月为负值,绿地是CO2汇,在6—9月是CO2强吸收汇,FCO2约-0.100—-0.120mg/m2.s,而在11—3月FCO2为正值,绿地为CO2源,12—2月是CO2强排放源,FCO2约0.100mg/m2.s.绿地CO2通量受总辐射、LAI、大气温度的显著影响,净辐射的影响明显大于大气温度,净辐射越大、LAI越大、大气温度越高,绿地光合作用吸收CO2的能力越强.观测期间一年海淀公园绿地CO2的净吸收量约为615gCO2/m2.     

太阳高年期间海南电离层扩展F出现的起始时间研究

电离层扩展F与电离层闪烁现象密切相关,它们出现的起始时间存在着很大程度上的一致性,因此研究电离层扩展F出现的起始时间将对闪烁预报模型的建立具有重要的应用价值.将太阳高年（2002年3月-2003年2月）期间海南地区DPS-4测高仪观测到的扩展F按照频率、区域、混合和强区域扩展等分为四种类型,对其出现的起始时间进行了分析研究.结果表明：频率扩展和混合扩展的起始时间分别集中在0200LT-0800LT和0000LT-0600LT;而区域扩展和强区域扩展出现的起始时间分别集中在2000LT-0200LT和2000LT-2200LT.     

地面目标红外特性及其隐身技术研究

随着红外搜索与制导技术的飞速发展,对于地面目标红外特征及其隐身技术的研究具有越来越重要的军事意义.在简化目标传热模型的基础之上,计算出目标的瞬时温度变化,并与背景的温度比较发现,目标与背景在一天之中均存在明显温差,最大温差可达10℃.从目标与背景的辐射对比度出发,分析了辐射对比度与目标表面发射率以及目标与背景温差的关系,发现了当目标与背景温差控制在±4℃之内时,采用固定发射率涂料可以使目标达到红外隐身的目的.     

西北太平洋热带气旋气候特征及其变化研究的若干进展

为了对我国气象工作者全面了解和参与热带气旋的研究有所帮助,在大量阅读和调研的基础上,介绍了近20年西北太平洋热带气旋活动在季节、年际和年代际尺度上研究的若干主要成果.重点阐述了EN-SO与热带气旋的关系,温室效应热带气旋的数值模拟和观测研究等的最新动态.     

季节性商品的促销定价模型与算法

研究了季节性商品在促销前提下的定价问题.在综合考虑季节性商品的销售特点、销售折扣率、商品库存、商品周期衰退、商品价格等问题的基础上,建立了以利润损失最小为目标的动态定价模型,以商家需处理的货物量为约束条件,基于改进遗传算法和粒子群算法,找到了成本最优的商品定价.并通过仿真,分析了商品定价对利润损失的影响,为大中型企业的促销决策提供了重要依据.