Environment-Assisted Modulation of Heat Flux in a Bio-Inspired System Based on Collision Model

The high energy transfer efficiency of photosynthetic complexes has been a topic of research across many disciplines. Several attempts have been made in order to explain this energy transfer enhancement in terms of quantum mechanical resources such as energetic and vibration coherence and constructive effects of environmental noise. The developments in this line of research have inspired various biomimetic works aiming to use the underlying mechanisms in biological light harvesting complexes for the improvement of synthetic systems. In this article, we explore the effect of an auxiliary hierarchically structured environment interacting with a system on the steady-state heat transport across the system. The cold and hot baths are modeled by a series of identically prepared qubits in their respective thermal states, and we use a collision model to simulate the open quantum dynamics of the system. We investigate the effects of system-environment, inter-environment couplings and coherence of the structured environment on the steady state heat flux and find that such a coupling enhances the energy transfer. Our calculations reveal that there exists a non-monotonic and non-trivial relationship between the steady-state heat flux and the mentioned parameters.     

滑块碰撞动力学与圆周率的关联

滑块碰撞与圆周率π看似不相关的两个事物却具有某种联系,本文研究了滑块碰撞动力学,利用计算工具MATLAB,发现在理想情况下,滑块的碰撞次数与π有一定的关联,并在理论上证明了计算结果。     

Galilean炮在刚性壁上的回弹1)

研究了Galilean炮——即若干个直径递增的弹性球组成的球链---撞击刚性壁回弹的问题。采用三种力学模型：分离刚体的多次"弹性"碰撞、多刚体的接触碰撞、以及有限元模拟,对球链撞击问题进行了分析,旨在给出碰撞结束后末端小球的飞离速度与入射速度的比值。研究表明：球链碰撞反弹后将会散开,末端小球的飞离速度明显大于球链入射速度;当入射球链间存在间隙时,末端小球的速度增幅更加明显。通过实验展现了这种末端小球回弹速度增加的现象。     

球链中冲击扰动的传播

采用Hertz 接触理论处理牛顿摆中球与球之间的相互接触,建立球链碰撞模型,观察到碰撞过程中类似孤立波的传播现象。为了便于处理“n 对m”碰撞的计算,编写了带有GUI (graphic user interface) 界面的计算程序,可以研究不同撞击球个数对撞击过程的影响,包括球心位置、球心速度以及相邻小球间的变形量与相互作用力随时间的变化规律。进一步比较了一维球链模型和三维有限元模型的结果,并实验观察了碰撞过程的细节,得到一致性结论。     

轿车冲撞行人过程的力学分析

通过建立力学模型,分析轿车冲撞行人的力学过程,对此进行了计算和讨论,进而得到与实验结果相吻合的使行人发生倒立时轿车车速的临界值.并提供了一种有效估算临界车速的方法.     

Tracking the Electrocatalytic Activity of a Single Palladium Nanoparticle for the Hydrogen Evolution Reaction

The nanoparticle-based electrocatalysts’ performance is directly related to their working conditions. In general, a number of nanoparticles are uncontrollably fixed on a millimetre-sized electrode for electrochemical measurements. However, it is hard to reveal the maximum electrocatalytic activity owing to the aggregation and detachment of nanoparticles on the electrode surface. To solve this problem, here, we take the hydrogen evolution reaction (HER) catalyzed by palladium nanoparticles (Pd NPs) as a model system to track the electrocatalytic activity of single Pd NPs by stochastic collision electrochemistry and ensemble electrochemistry, respectively. Compared with the nanoparticle fixed working condition, Pd NPs in the nanoparticle diffused working condition results in a 2–5 orders magnitude enhancement of electrocatalytic activity for HER at various bias potential. Stochastic collision electrochemistry with high temporal resolution gives further insights into the accurate study of NPs’ electrocatalytic performance, enabling to dramatically enhance electrocatalytic efficiency.     

Combined Chemical Modification and Collision Induced Unfolding Using Native Ion Mobility-Mass Spectrometry Provides Insights into Protein Gas-Phase Structure

Native mass spectrometry is now an important tool in structural biology. Thus, the nature of higher protein structure in the vacuum of the mass spectrometer is an area of significant interest. One of the major goals in the study of gas-phase protein structure is to elucidate the stabilising role of interactions at the level of individual amino acid residues. A strategy combining protein chemical modification together with collision induced unfolding (CIU) was developed and employed to probe the structure of compact protein ions produced by native electrospray ionisation. Tractable chemical modification was used to alter the properties of amino acid residues, and ion mobility-mass spectrometry (IM-MS) utilised to monitor the extent of unfolding as a function of modification. From these data the importance of specific intramolecular interactions for the stability of compact gas-phase protein structure can be inferred. Using this approach, and aided by molecular dynamics simulations, an important stabilising interaction between K6 and H68 in the protein ubiquitin was identified, as was a contact between the N-terminus and E22 in a ubiquitin binding protein UBA2.     

Competitive homolytic and heterolytic decomposition pathways of gas‐phase negative ions generated from aminobenzoate esters

An alkyl‐radical loss and an alkene loss are two competitive fragmentation pathways that deprotonated aminobenzoate esters undergo upon activation under mass spectrometric conditions. For the meta and para isomers, the alkyl‐radical loss by a homolytic cleavage of the alkyl‐oxygen bond of the ester moiety is the predominant fragmentation pathway, while the contribution from the alkene elimination by a heterolytic pathway is less significant. In contrast, owing to a pronounced charge‐mediated ortho effect, the alkene loss becomes the predominant pathway for the ortho isomers of ethyl and higher esters. Results from isotope‐labeled compounds confirmed that the alkene loss proceeds by a specific γ‐hydrogen transfer mechanism that resembles the McLafferty rearrangement for radical cations. Even for the para compounds, if the alkoxide moiety bears structural motifs required for the elimination of a more stable alkene molecule, the heterolytic pathway becomes the predominant pathway. For example, in the spectrum of deprotonated 2‐phenylethyl 4‐aminobenzoate, m/z 136 peak is the base peak because the alkene eliminated is styrene. Owing to the fact that all deprotonated aminobenzoate esters, irrespective of the size of the alkoxy group, upon activation fragment to form an m/z 135 ion, aminobenzoate esters in mixtures can be quantified by precursor ion discovery mass spectrometric experiments. Copyright © 2016 John Wiley & Sons, Ltd.     

Evidence of self-affine multiplicity fluctuation of particle production in 84Kr--emulsion interactions at 1.7 A GeV

Self-affine multiplicity fluctuation is investigated by using the two-dimensional factorial moment methodology and the concept of the Hurst exponent (H). Investigation on the experimental data of compound particles and target fragments emitted in 84 Kr-AgBr interactions at 1.7 A GeV reveals that the best power law behaviours are exhibited at H=0.7 and 0.6 respectively, and the data for shower particles produced in 84 Kr-emulsion interactions at 1.7 A GeV indicate that the best power law behaviour occurs at H=0.6, all of which show the self-affine multiplicity fluctuation patterns. The multifractality and the non-thermal phase transition occurring during producing the compound particles, the target fragments, and the shower particles in the 84 Kr-AgBr interaction and the 84 Kr-emulsion interaction are also discussed. The multifractality is observed during producing compound particles, target fragments, and shower particles. In the target fragment production, an evidence of non-thermal phase transition is observed, but in the shower particle production and the compound particle production, no evidence of non-thermal phase transition is observed.     

Molecular constants of LiCl(X~1Σ~+) and elastic collisions of two ground-state Cl and Li atoms at low and ultralow temperatures

Interaction potentials for LiCl(X 1 Σ +) are constructed by the highly accurate valence internally contracted mul-tireference configuration interaction in combination with a number of large correlation-consistent basis sets,which are used to determine the spectroscopic parameters (D 0,D e,R e,ω e,ω e χ e,B e and α e).The potentials obtained at the basis sets,i.e.,aug-cc-pV5Z-JKFI for Cl and cc-pV5Z for Li,are selected to study the elastic collision properties of Li and Cl atoms at the impact energies from 1.0×10 12 to 1.0×10 4 a.u.The derived total elastic cross sections are very large and almost constant at ultralow temperatures,and their shapes are mainly dominated by the s-partial wave at very low impact energies.Only one shape resonance can be found in the total elastic cross sections over the present collision energy regime,which is rather strong and obviously broadened by the overlap contributions of the abundant resonances coming from various partial waves.Abundant resonances exist for the elastic partial-wave cross sections until l=22 partial waves.The vibrational manifolds of the LiCl(X 1 Σ +) molecule,which are predicted at the present level of theory and the basis sets cc-pV5Z for Li and the aug-cc-pV5Z-JKFI for Cl,should achieve much high accuracy due to the employment of the large correlation-consistent basis sets.