Confinement-induced phase transitions in simple liquids

The liquid-to-solid transition of a simple model liquid confined between two surfaces was studied as a function of surface separation. From large surface separations (more than 1000 angstroms) down to a separation corresponding to seven molecular layers, the confined films displayed a liquid-like shear viscosity. When the surface separation was further decreased by a single molecular spacing, the films underwent an abrupt, reversible transition to a solid. At the transition, the rigidity of the confined films (quantified in terms of an "effective viscosity") increased reversibly by at least seven orders of magnitude.     

A hybridization model for the plasmon response of complex nanostructures

We present a simple and intuitive picture, an electromagnetic analog of molecular orbital theory, that describes the plasmon response of complex nanostructures of arbitrary shape. Our model can be understood as the interaction or "hybridization" of elementary plasmons supported by nanostructures of elementary geometries. As an example, the approach is applied to the important case of a four-layer concentric nanoshell, where the hybridization of the plasmons of the inner and outer nanoshells determines the resonant frequencies of the multilayer nanostructure.     

A simple model for neutrino cooling of the large magellanic cloud supernova

A simplified analytic model of a cooling hot neutron star, motivated by detailed computer calculations, describes well the neutrinos detected from the recent supernova in the Large Magellanic Cloud. The observations do not require explanations that invoke exotic physics or complicated astrophysics. The parameters in this simple model are not severely constrained: 6.1(-3.6)(+3.5) x 10(52) ergs emitted in electron antineutrinos, a peak temperature of 4.2(-0.8)(+1.2) megaelectron volts, a radius of 27(-15)(+17) kilometers, and a cooling time of 4.5(-2.0)(+1.7) seconds.     

Engineering complex dynamical structures: sequential patterns and desynchronization

We used phase models to describe and tune complex dynamic structures to desired states; weak, nondestructive signals are used to alter interactions among nonlinear rhythmic elements. Experiments on electrochemical reactions on electrode arrays were used to demonstrate the power of mild model-engineered feedback to achieve a desired response. Applications are made to the generation of sequentially visited dynamic cluster patterns similar to reproducible sequences seen in biological systems and to the design of a nonlinear antipacemaker for the destruction of pathological synchronization of a population of interacting oscillators.     

森林资源可持续性的内在动力机制及其模型

森林资源可持续性是森林资源系统对人类满足其需求的约束 ,其内在动力机制在于森林资源系统的内在持续能力和外部支撑调控能力的统一 ,以及各种内部和外部结构、功能和效益的协同 .其实质是人 -森林资源系统协同关系的反映 ,这种协同关系可以用人地协同论原理描述     

Chaos versus noisy periodicity: alternative hypotheses for childhood epidemics

Whereas case rates for some childhood diseases (chickenpox) often vary according to an almost regular annual cycle, the incidence of more efficiently transmitted infections such as measles is more variable. Three hypotheses have been proposed to account for such fluctuations. (i) Irregular dynamics result from random shocks to systems with stable equilibria. (ii) The intrinsic dynamics correspond to biennial cycles that are subject to stochastic forcing. (iii) Aperiodic fluctuations are intrinsic to the epidemiology. Comparison of real world data and epidemiological models suggests that measles epidemics are inherently chaotic. Conversely, the extent to which chickenpox outbreaks approximate a yearly cycle depends inversely on the population size.     

一种快速高效适于柑桔AFLP分析的DNA提取方法

利用改进的CTAB法提取了柑类、桔类、橙类及部分柑桔杂交实生后代等120多个品种的基因组,结果表明:该方法提取的DNA溶液无色透明,紫外分光光度计测得A260/A280为1.8～1.9,1%琼脂糖凝胶电泳为清晰的一条带,RNA去除干净,无降解现象,DNA的纯度和质量能满足AFLP分析要求.     

Topological transitions in metamaterials

Light-matter interactions can be controlled by manipulating the photonic environment. We uncovered an optical topological transition in strongly anisotropic metamaterials that results in a dramatic increase in the photon density of states-an effect that can be used to engineer this interaction. We describe a transition in the topology of the iso-frequency surface from a closed ellipsoid to an open hyperboloid by use of artificially nanostructured metamaterials. We show that this topological transition manifests itself in increased rates of spontaneous emission of emitters positioned near the metamaterial. Altering the topology of the iso-frequency surface by using metamaterials provides a fundamentally new route to manipulating light-matter interactions.     

High-accuracy ab initio rotation-vibration transitions for water

The spectrum of water vapor is of fundamental importance for a variety of processes, including the absorption and retention of sunlight in Earth's atmosphere. Therefore, there has long been an urgent need for a robust and accurate predictive model for this spectrum. In our work on the high-resolution spectrum of water, we report first-principles calculations that approach experimental accuracy. To achieve this, we performed exceptionally large electronic structure calculations and considered a variety of effects, including quantum electrodynamics, which have routinely been neglected in studies of small many-electron molecules. The high accuracy of the resulting ab initio procedure is demonstrated for the main isotopomers of water.     

一种适用于PCR的环境友好型植物DNA提取方法(英文)

改进DNA提取方法,利用含2%CTAB、1%SDS、2%PVP、100mmol/LTris-Cl(pH8.0)、20mmol/LEDTA(pH8.0)和1.4mol/LNaCl的DNA提取缓冲液,提取了不同种属12种植物的DNA,并对其进行了PCR检测.结果显示,所提取的DNA符合PCR试验要求,用真核生物ITS4/ITS5通用引物均能扩增出清晰的条带.该方法无需酚仿抽提,简单、高效、环保,特别适合大规模植物DNA的提取.