Ultralong-range polaron-induced quenching of excitons in isolated conjugated polymers

In conjugated polymers, radiative recombination of excitons (electron-hole pairs) competes with nonradiative thermal relaxation pathways. We visualized exciton quenching induced by hole polarons in single-polymer chains in a device geometry. The distance-scale for quenching was measured by means of a new subdiffraction, single-molecule technique--bias-modulated intensity centroid spectroscopy--which allowed the extraction of a mean centroid shift of 14 nanometers for highly ordered, single-polymer nanodomains. This shift requires energy transfer over distances an order of magnitude greater than previously reported for bulk conjugated polymers and far greater than predicted by the standard mechanism for exciton quenching, the unbiased diffusion of free excitons to quenching sites. Instead, multistep "energy funneling" to trapped, localized polarons is the probable mechanism for polaron-induced exciton quenching.     

Principles of design of fluid transport systems in zoology

Fluid transport systems mediate the transfer of materials both within an organism and between an organism and its environment. The architecture of fluid transport systems is determined by the small distances over which transfer processes are effective and by hydrodynamic and energetic constraints. All fluid transport systems within organisms exhibit one of two geometries, a simple tube interrupted by a planar transfer region or a branched network of vessels linking widely distributed transfer regions; each is determined by different morphogenetic processes. By exploiting the signal inherent in local shear stress on the vessel walls, animals have repeatedly evolved a complex branching hierarchy of vessels approximating a globally optimal system that minimizes the costs of the construction and maintenance of the fluid transport system.     

Tryptophan-accelerated electron flow through proteins

Energy flow in biological structures often requires submillisecond charge transport over long molecular distances. Kinetics modeling suggests that charge-transfer rates can be greatly enhanced by multistep electron tunneling in which redox-active amino acid side chains act as intermediate donors or acceptors. We report transient optical and infrared spectroscopic experiments that quantify the extent to which an intervening tryptophan residue can facilitate electron transfer between distant metal redox centers in a mutant Pseudomonas aeruginosa azurin. Cu(I) oxidation by a photoexcited Re(I)-diimine at position 124 on a histidine(124)-glycine(123)-tryptophan(122)-methionine(121) beta strand occurs in a few nanoseconds, fully two orders of magnitude faster than documented for single-step electron tunneling at a 19 angstrom donor-acceptor distance.     

Long-range electron transfer in heme proteins

Kinetic experiments have conclusively shown that electron transfer can take place over large distances (greater than 10 angstroms) through protein interiors. Current research focuses on the elucidation of the factors that determine the rates of long-range electron-transfer reactions in modified proteins and protein complexes. Factors receiving experimental and theoretical attention include the donor-acceptor distance, changes in geometry of the donor and acceptor upon electron transfer, and the thermodynamic driving force. Recent experimental work on heme proteins indicates that the electron-transfer rate falls off exponentially with donor-acceptor distance at long range. The rate is greatly enhanced in proteins in which the structural changes accompanying electron transfer are very small.     

Gravitational Lens of the Sun: Its Potential for Observations and Communications over Interstellar Distances

The gravitational field of the sun acts as a spherical lens to magnify the intensity of radiation from a distant source along a semi-infinite focal line. A spacecraft anywhere on that line in principle could observe, eavesdrop, and communicate over interstellar distances, using equipment comparable in size and power with what is now used for interplanetary distances. If one neglects coronal effects, the maximum magnification factor for coherent radiation is inversely proportional to the wavelength, being 100 million at 1 millimeter. The principal difficulties are that the nearest point on the focal half-line is about 550 times the sun-earth distance, separate spacecraft would be needed to work with each stellar system of interest, and the solar corona would severely limit the intensity of coherent radiation while also restricting operations to relatively short wavelengths.     

初生仔猪大肠的位置排列及测量

采用民猪和哈白猪的初生仔猪（生后５天以内）各１５头,观察总结了大肠的形态、位置和排列的各种不同类型,并对两品种大肠各段的长度、重量和周长进行测量比较。     

Epidermal electronics

We report classes of electronic systems that achieve thicknesses, effective elastic moduli, bending stiffnesses, and areal mass densities matched to the epidermis. Unlike traditional wafer-based technologies, laminating such devices onto the skin leads to conformal contact and adequate adhesion based on van der Waals interactions alone, in a manner that is mechanically invisible to the user. We describe systems incorporating electrophysiological, temperature, and strain sensors, as well as transistors, light-emitting diodes, photodetectors, radio frequency inductors, capacitors, oscillators, and rectifying diodes. Solar cells and wireless coils provide options for power supply. We used this type of technology to measure electrical activity produced by the heart, brain, and skeletal muscles and show that the resulting data contain sufficient information for an unusual type of computer game controller.     

应用变频器使多台油泵软启动

如何实现用一台变频器使多台油泵软启动,其关键问题是逆变器与工频电源之间的双向切换。为了克服设备运行工况不稳定和电机二次启动冲击电流给电网带来的危害,必须实现平滑无冲击切换,这就要求切换的瞬间,逆变器输出电源的频率、相位、幅度与工频电网的频率、相位、幅度相一致。为实现平滑无冲击切换,研制出了单台切换器和适用于多台电机启动的配电线路及多台切换控制线路。切换器由相位鉴别器、幅度鉴别器、50周好检测电路、允许门电路、输出控制电路等五部分组成。经用户一年多实践证明,生产样机完全达到了设计要求,既保证了飞机加油又可进行油库装卸和输转作业,且从未出现故障。     

Direct visualization of horizontal gene transfer

Conjugation allows bacteria to acquire genes for antibiotic resistance, novel virulence attributes, and alternative metabolic pathways. Using a fluorescent protein fusion, SeqA-YFP, we have visualized this process in real time and in single cells of Escherichia coli. We found that the F pilus mediates DNA transfer at considerable cell-to-cell distances. Integration of transferred DNA by recombination occurred in up to 96% of recipients; in the remaining cells, the transferred DNA was fully degraded by the RecBCD helicase/nuclease. The acquired integrated DNA was tracked through successive replication rounds and was found to occasionally split and segregate with different chromosomes, leading to the inheritance of different gene clusters within the cell lineage. The incidence of DNA splitting corresponds to about one crossover per cell generation.     

白藜芦醇与牛血清白蛋白相互作用的研究

采用荧光猝灭光谱、同步荧光光谱和紫外-可见吸收光谱,研究了白藜芦醇与牛血清白蛋白(BSA)的相互作用。结果表明白藜芦醇对BSA有较强的荧光猝灭作用,荧光猝灭机理属于二者形成复合物所引起的静态猝灭和非辐射能量转移;根据不同温度下防己诺林碱对BSA的荧光猝灭作用,利用Stern-Volmer方程处理实验数据,得到白藜芦醇与BSA之间的结合常数KA为6.11×104(25℃)、4.46×104(35℃)和3.84×104(45℃)。根据F rster非辐射能量转移理论,求出了白藜芦醇与BSA之间的结合距离为2.36 nm(25℃)、2.73 nm(35℃)和2.48 nm(45℃)。通过计算热力学参数,可知该药物与牛血清白蛋白的相互作用是一个吉布斯自由能降低的自发过程,且二者之间的主要作用力类型为疏水作用力,同时用同步荧光光谱探讨了白藜芦醇对BSA构象的影响。     

Coils and polygonal crust in the Athabasca Valles region, Mars, as evidence for a volcanic history

Athabasca Valles is a near-equatorial martian outflow channel that contains many well-preserved features whose formation and composition have been a point of contention. Large plates of terrain that have clearly fractured and drifted may have once been ice rafts or the rocky solidification crust of a large lava flow. We have identified 269 spiral coils ranging from 5 to 30 meters wide on the polygonally patterned interplate terrain that are morphologically consistent with terrestrial lava coils that form in zones of flow shear. This patterned terrain also exhibits signs of fracture and drift, indicating that it is platelike as well. The coils in the Athabasca region are inconsistent with ice rheology, and the plates, spirals, and polygons are interpreted to be of volcanic origin.     

Generation of megawatt optical solitons in hollow-core photonic band-gap fibers

The measured dispersion of a low-loss, hollow-core photonic band-gap fiber is anomalous throughout most of the transmission band, and its variation with wavelength is large compared with that of a conventional step-index fiber. For an air-filled fiber, femtosecond self-frequency--shifted fundamental solitons with peak powers greater than 2megawatts can be supported. For Xe-filled fibers, nonfrequency-shifted temporal solitons with peak powers greater than 5.5 megawatts can be generated, representing an increase in the power that can be propagated in an optical fiber of two orders of magnitude. The results demonstrate a unique capability to deliver high-power pulses in a single spatial mode over distances exceeding 200 meters.     

杏园梅下毛瘿螨Acalitus phloeocoptes(Nalepa)发生规律

【目的】研究新疆轮台县杏园芽瘿发生原因、分析梅下毛瘿螨的发生、转移、扩散规律,确定最佳防治时间。【方法】对杏芽瘿室内镜检,在田间定点、定时选取样株样枝记录危害症状、致瘿因子及田间时空动态;在新老枝条间粘贴胶带及树冠不同高度、方向、距离悬挂粘虫板的方法,记录致瘿因子的转移危害规律、传播的方式及传播距离。【结果】危害杏树芽苞,使其增生畸变成瘿瘤的是瘿螨,经鉴定系梅下毛瘿螨 Acalitus phloeocoptes (Nalepa)。在新疆轮台县该螨主要以成螨在瘿瘤芽苞幼嫩杏鳞叶片内越冬,占调查总数的95.91%;翌年3月下旬杏树开花中期,越冬成螨开始出蛰活动,4月上旬出蛰成螨开始大量产卵,4月下旬至5月上旬是梅下毛瘿螨的产卵高峰期,5月中下旬是成若螨高峰期,9月底随着气温下降,成螨为越冬做准备。梅下毛瘿螨5月上旬开始从芽苞内向外爬行转移,5月下旬是其转移高峰期。风是梅下毛瘿螨被动传播的主要媒介,帮助其远距离传播,传播距离最远可达15 m。在不同高度的粘虫板诱捕螨量存在差异:迎风面>背风面。【结论】杏芽瘿是由梅下毛瘿螨侵染引起,以成螨在瘿瘤芽苞内层越冬,在新疆轮台县3月底至9月下旬均有危害,一年发生10余代,其中4、5和6月危害较严重。5月下旬是其转移高峰期,这一阶段是化学防治的最佳时间。     

Nanoparticles: strained and stiff

Nanoparticles may contain unusual forms of structural disorder that can substantially modify materials properties and thus cannot solely be considered as small pieces of bulk material. We have developed a method to quantify intermediate-range order in 3.4-nanometer-diameter zinc sulfide nanoparticles and show that structural coherence is lost over distances beyond 2 nanometers. The zinc-sulfur Einstein vibration frequency in the nanoparticles is substantially higher than that in the bulk zinc sulfide, implying structural stiffening. This cannot be explained by the observed 1% radial compression and must be primarily due to inhomogeneous internal strain caused by competing relaxations from an irregular surface. The methods developed here are generally applicable to the characterization of nanoscale solids, many of which may exhibit complex disorder and strain.     

内置电热层实木复合地板表面温度变化规律及模拟

目的研究不同电热层位置和不同结构的电热实木复合地板温度变化规律,为电热实木复合地板的电热性能及结构优化提供理论参考。方法采用碳纤维纸作为发热元件,通过热压方式制备具有电热功能的实木复合地板,测试了通电荷载后时间-温度效应、温度不均匀度、电-热辐射转换效率和表面网格温度,分析不同电热层位置对表面温度、温度不均匀度和电-热辐射转换效率的影响,模拟了表面温度二维和三维分布图,探讨不同结构电热实木复合地板正面和背面温度变化规律,拟合了时间-温度变化曲线幂函数方程。结果表面温度均随通电荷载时间的增加而增加,最终趋于稳定,切断电源以后,温度快速下降直至与环境温度平衡。随电热层位置下移,发热稳定后表面温度随之降低,电-热辐射转换效率也相应降低。功率密度为200、300、400和500 W/m2,电热层位于近表层时,表面温度比底层温度分别高了17.2%、21.8%、24.8%和26.8%。随功率密度的增加,温度不均匀度增加,电-热辐射转换效率也随之增加,功率密度达到500 W/m2时,电热层位于近表层的电-热辐射转换效率达95.6%。二维和三维模拟图表明:表面温度分布总体呈中间高、四周低趋势,电热层位于表层尤为明显且存在聚热现象。不同结构电热实木复合地板正面表面温度随通电荷载时间增加而增加,背面木材厚度越厚,正面表面温度越高,反之背面温度越低,拟合方程表明时间-温度变化呈幂函数关系,决定系数最高达0.999 9。结论电热层位置和地板结构对电热实木复合地板表面温度和电-热辐射转换效率影响显著,电热层位于近表层时更有利于电热性能改善。      

Blood velocity measurements in intact subjects

Venous blood velocities in intact human forearms can be measured by the use of nuclear magnetic resonance techniques. In essence, two separated coils are placed over the vein, and the arm is held in a magnetic field. Radio-frequency energy in one coil "flips" over the protons in the blood stream, and the second coil detects the arrival of the "flipped" protons. Human blood in vivo and in vitro has a nominal nuclear magnetic resonance relaxation time of 0.4 second.     

亲本间数量性状遗传距离在高赖氨酸玉米育种中的应用初探

以八个高赖氨酸玉米自交系考查产量品质等16个性状作亲本间遗传距离研究,同时以相应的杂种一代作验证。结果表明,基于性状间遗传相关的主成分值可以较充分地概括众多育种性状的遗传信息,以主成分为基础的遗传距离可以较充分地反映出亲本间的遗传差异,用类平均法比用最短距离法对亲本进行聚类能较好地反映出亲本间的关系。遗传距离与超标优势间不存在明显的相关关系。超亲优势这一参数在高赖氮酸杂种玉米育种中无实际利用价值。一个亲本与其它所有亲本的遗传距离的平均(~2)与该亲本的一般配合力效应(GCA)有曲线关系的趋势。在一定范围内~2与GCA 呈直线关系,r(~2,GCA)=0.7896(P<0.1121)。直线回归方程为GCA=-0.6341+0.8D~2。~2与由该亲本构成的优良组合的比例间存在着显著的线性关系,r(~2,优良组合比例)=0.9027(P<0.05)。因此可望用~2来预测亲本的 GCA 及获得成功的把握性,从而减少实测配合力的大量繁重劳动,提高育种效率。以单位面积赖氨酸产量为指标能较好地概括高赖氮酸玉米育种的目标。     

根系的吸收作用及土壤水分对硝态氮、铵态氮分布的影响

 研究了玉米根系的吸收作用和土壤水分对耕层土壤硝态氮迁移及分布的影响。结果表明，根系发育状况及水分供应明显影响硝态氮的迁移及分布。根系自然生长和灌水处理，距主茎不同距离的各位点硝态氮浓度差异小；而限制根系生长和不灌水处理，则差异较大。距主茎0～10 cm范围的耕层土壤中硝态氮含量的变化趋势是由远到近逐渐降低。这种变化趋势与耕层土壤中根系吸收面积的变化趋势相反。限制根系生长时，各位点土壤硝态氮浓度与土壤水分有相当一致的变化规律，说明随着植物吸水硝态氮作为溶质向根表迁移。与硝态氮不同，铵态氮的迁移和分布不受根系发育状况及水分供应的影响。     

啶酰菌胺对油菜菌核病的作用方式及其田间防效

在室内和田间应用离体和活体方法,研究了啶酰菌胺对油菜菌核病的保护和治疗效果,以及在油菜植株上的传导性和持效期,结果表明:啶酰菌胺在6.25～400.00 mg/L浓度范围内,对油菜菌核病的保护效果为81.66%～100.00%,治疗效果为19.82%～78.88%;由于啶酰菌胺在油菜植株上的传导性较差,对施药叶片的上位和下位叶的保护效果均较低,施药后啶酰菌胺持效期为20 d左右。田间试验表明:啶酰胺施药量为150～350 g/hm2时对油菜菌核病的防治效果在68.89%～86.84%之间,显著优于多菌灵(750 g/hm2)对油菜菌核病的防治效果。     

Earth tides, global heat flow, and tectonics

The power of a heat engine ignited by tidal energy can account for geologically reasonable rates of average magma production and sea floor spreading. These rates control similarity of heat flux over continents and oceans because of an inverse relationship between respective depth intervals for mass transfer and consequent distributions of radiogenic heat production.