共查询到20条相似文献，搜索用时 15 毫秒
1.
2.
研究地质流体的物理化学性质和地球化学行为是地球系统科学研究所面对的挑战性课题之一。与诸如实验和物理化学建模等传统研究方法相比，分子水平上的计算机模拟在解决极端条件下流体体系物理化学性质方面表现出明显的优势，成为定量研究地球内部不同层圈中地质流体特点及其作用规律的有效途径。本论文简要介绍了我们把计算机模拟技术应用到地质流体研究中的成果，主要可概括为：（1）利用蒙特卡罗计算机模拟方法，我们成功地模拟了地质流体体系相平衡和相变，取得了与实验一致的结果，从而在计算机上实现了相平衡研究，与花费昂贵的实验相比具有方法学上的先进性；（2）通过分子动力学模拟研究水的物理化学性质，我们把水的PVT数据从实验所允许的温压范围（温度小于1873.15 K、压力低于5万大气压）扩展到2000 K、20万大气压，并提出了一个适用于宽广温压条件下的状态方程；（3）通过分子动力学和蒙特卡罗模拟，我们建立了一个CO2分子模型，它能同时准确预测CO2的各种物理化学性质和行为（PVT性质、相平衡、潜热、结构性质和动力学性质）；（4）通过分子动力学模拟研究氯化锂在溶液中的离子水化和缔合性质，我们得到了与实验和量子力学模拟一致的结果，与此同时还揭示了离子水化和缔合过程的微观机制。 相似文献
3.
4.
H.S.W Massey 《Endeavour》1980,4(2):78-84
The reaction of an electron with a molecule AB which leads to dissociation of the molecule into a neutral component and a negative ion, is known as dissociative attachment. Such reactions are important sources of negative ions and may be used for the design of very sensitive detectors for certain compounds. They are of basic importance in determining the high dielectric strength of certain gases and vapours as well as in the design of gaseous lasers. The detailed study of the reactions leads to insight into reaction mechanisms and provides new information about molecular parameters. This article reviews the application of modern experimental and theoretical techniques to the subject. 相似文献
5.
Zhizhi Sheng Mengchuang Zhang Jing Liu Paolo Malgaretti Jianyu Li Shuli Wang Wei Lv Rongrong Zhang Yi Fan Yunmao Zhang Xinyu Chen Xu Hou 《国家科学评论(英文版)》2021,8(5)
Collective dynamics of confined colloids are crucial in diverse scenarios such as self-assembly and phase behavior in materials science, microrobot swarms for drug delivery and microfluidic control. Yet, fine-tuning the dynamics of colloids in microscale confined spaces is still a formidable task due to the complexity of the dynamics of colloidal suspension and to the lack of methodology to probe colloids in confinement. Here, we show that the collective dynamics of confined magnetic colloids can be finely tuned by external magnetic fields. In particular, the mechanical properties of the confined colloidal suspension can be probed in real time and this strategy can be also used to tune microscale fluid transport. Our experimental and theoretical investigations reveal that the collective configuration characterized by the colloidal entropy is controlled by the colloidal concentration, confining ratio and external field strength and direction. Indeed, our results show that mechanical properties of the colloidal suspension as well as the transport of the solvent in microfluidic devices can be controlled upon tuning the entropy of the colloidal suspension. Our approach opens new avenues for the design and application of drug delivery, microfluidic logic, dynamic fluid control, chemical reaction and beyond. 相似文献
6.
7.
SONG Jianlan 《中国科学院院刊(英文版)》2009,23(2):103-108
Enchanted by the glamour of the fascinating effects resulting from the collisions between the molecules of hydrogen, deuteride and fluorine, Prof. YANG Xueming never expects to attract too many spotlights. However, over the past few years after his returning to the Dalian Institute of Chemical Physics （DICP）, CAS, his team was frequently caught by the media on the center stage. Discoveries made by his team ranked top 10 S＆T advancements of China consecutively in 2006 and 2007. Significant progress was also made in 2008 by this group in the research field of molecular reaction dynamics, and he himself has won a number of important awards and prizes. 相似文献
8.
应用分子动力学模拟的方法,研究了纳米金刚石颗粒的导热系数对温度和颗粒尺寸的依存关系。为了得到较为准确的模拟结果,采用了平衡态分子动力学模拟的方法。计算了较长时间的热流自相关函数,并得到了导热系数的收敛结果。结果表明,纳米金刚石颗粒由于尺寸的影响,导热系数低于体材料金刚石的导热系数;随温度的升高,导热系数出现一个峰值,该峰值点的温度小于体材料金刚石出现峰值点的温度;随颗粒尺寸的增大,导热系数增加,我们预测导热系数将在一定的颗粒尺寸时收敛于体材料金刚石的导热系数。 相似文献
9.
Intracellular drug delivery by rapid squeezing is one of the most recent and simple cell membrane disruption-mediated drug encapsulation approaches. In this method, cell membranes are perforated in a microfluidic setup due to rapid cell deformation during squeezing through constricted channels. While squeezing-based drug loading has been successful in loading drug molecules into various cell types, such as immune cells, cancer cells, and other primary cells, there is so far no comprehensive understanding of the pore opening mechanism on the cell membrane and the systematic analysis on how different channel geometries and squeezing speed influence drug loading. This article aims to develop a three-dimensional computational model to study the intracellular delivery for compound cells squeezing through microfluidic channels. The Lattice Boltzmann method, as the flow solver, integrated with a spring-connected network via frictional coupling, is employed to capture compound capsule dynamics over fast squeezing. The pore size is proportional to the local areal strain of triangular patches on the compound cell through mathematical correlations derived from molecular dynamics and coarse-grained molecular dynamics simulations. We quantify the drug concentration inside the cell cytoplasm by introducing a new mathematical model for passive diffusion after squeezing. Compared to the existing models, the proposed model does not have any empirical parameters that depend on operating conditions and device geometry. Since the compound cell model is new, it is validated by simulating a nucleated cell under a simple shear flow at different capillary numbers and comparing the results with other numerical models reported in literature. The cell deformation during squeezing is also compared with the pattern found from our compound cell squeezing experiment. Afterward, compound cell squeezing is modeled for different cell squeezing velocities, constriction lengths, and constriction widths. We reported the instantaneous cell center velocity, variations of axial and vertical cell dimensions, cell porosity, and normalized drug concentration to shed light on the underlying physics in fast squeezing-based drug delivery. Consistent with experimental findings in the literature, the numerical results confirm that constriction width reduction, constriction length enlargement, and average cell velocity promote intracellular drug delivery. The results show that the existence of the nucleus increases cell porosity and loaded drug concentration after squeezing. Given geometrical parameters and cell average velocity, the maximum porosity is achieved at three different locations: constriction entrance, constriction middle part, and outside the constriction. Our numerical results provide reasonable justifications for experimental findings on the influences of constriction geometry and cell velocity on the performance of cell-squeezing delivery. We expect this model can help design and optimize squeezing-based cargo delivery. 相似文献
10.
以刻划著名的Belousov Zhabotinsky化学反应的俄勒冈振子为数学模型 ,研究解决了激励介质中一些悬而未决的理论问题 (如波的存在性和稳定性等 ) ,进一步完善了激励介质的非线性波型动力学的理论体系 .通过Painlev啨分析 ,B¨acklund变换和奇异摄动方法 ,分析地给出了一些常见的波型解 (如行波 ,螺旋波 ,靶型波 ,V 型波 ,涡卷波等 ) .在波前的邻域内 ,通过引进新的运动坐标系 ,获得了波在直角坐标下的运动方程 .特别是定量地给出了刻划小幅波的组织中心沿轴向和径向运动的规律 ,并由此可判定波的组织中心何时沿径向呈现膨胀或收缩 ,何时沿轴向有正向或反向漂移 .这一结果很好地与实验和数值模拟结果相吻合 .此外 ,研究了耦合的俄勒冈振子 ,解决了Tyson于 1 979年提出的一个猜想 (即对耦合的俄勒冈振子 ,稳定的回声波可以和稳定的正定态共存 ) ,提出了一套解决类似问题的一般方法 . 相似文献
11.
二氧化铀是一种稳定的陶瓷燃料,它具有熔点高和物理化学性质稳定的特性,作为核燃料二氧化铀的导热性能将直接影响核燃料芯块内的温度分布和芯块中心的最高温度,分析比较了二氧化铀热导率的实验研究结果和关联式,发现已有实验结果间的差异已经缩小.通过开展非平衡分子动力学模拟分析表明,二氧化铀热导率在中温区模拟较为准确可靠.在低温区时,需对能量输运粒子的动能计算进行量子修正;在高温区,需建立声子能量输运模型、电子气能量输运模型和光子辐射部分的能量输运模型,进一步建立二氧化铀的热导率计算程序. 相似文献
12.
13.
Caitlin M. Austin William Stoy Peter Su Marie C. Harber J. Patrick Bardill Brian K. Hammer Craig R. Forest 《Biomicrofluidics》2014,8(3)
Biosensors exploiting communication within genetically engineered bacteria are becoming
increasingly important for monitoring environmental changes. Currently, there are a variety of
mathematical models for understanding and predicting how genetically engineered bacteria respond to
molecular stimuli in these environments, but as sensors have miniaturized towards microfluidics and
are subjected to complex time-varying inputs, the shortcomings of these models have become apparent.
The effects of microfluidic environments such as low oxygen concentration, increased biofilm
encapsulation, diffusion limited molecular distribution, and higher population densities strongly
affect rate constants for gene expression not accounted for in previous models. We report a
mathematical model that accurately predicts the biological response of the autoinducer N-acyl
homoserine lactone-mediated green fluorescent protein expression in reporter bacteria in
microfluidic environments by accommodating these rate constants. This generalized mass action model
considers a chain of biomolecular events from input autoinducer chemical to fluorescent protein
expression through a series of six chemical species. We have validated this model against
experimental data from our own apparatus as well as prior published experimental results. Results
indicate accurate prediction of dynamics (e.g., 14% peak time error from a pulse input) and with
reduced mean-squared error with pulse or step inputs for a range of concentrations
(10 μM–30 μM). This model can help advance the design of
genetically engineered bacteria sensors and molecular communication devices. 相似文献
14.
A basic understanding of the transport mechanisms of nanostructures in a polymer brush-modified nanochannel as well as the brush-nanostructure interactions at molecular level is important to design and fabricate emerging smart nano/microfluidic channels. In this work, we report coarse-grained molecular dynamics simulations of the translocation of nanoparticles through a cylindrical nanochannel coated with the polymer brush. The effects of the interparticle interaction and grafting density on the distribution and electrokinetic transport of nanoparticles are addressed in detail. Analysis of the distribution and velocity profiles of nanoparticles from the simulations indicate that the location of nanoparticles along the radial direction and their migration velocity are very sensitive to the change of interparticle interaction. We find complicated transport dynamics of nanoparticles under the influence of various grafting densities. The nanoparticles show markedly different translocation behavior upon increasing the grafting density, which depends on the counterion distribution, free room within the brush, nanoparticle-polymer friction, and brush configuration. Our results may serve as a useful starting point for the transport of nanostructures in polymer-modified channels and help to guide the design of novel smart nanofluidic channels for controlling the migration behavior of nanostructures. 相似文献
15.
Visualizing single DNA dynamics in flow provides a wealth of physical insights in biophysics and complex flow study. However, large signal fluctuations, generated from diversified conformations, deformation history dependent dynamics and flow induced stochastic tumbling, often frustrate its wide adoption in single molecule and polymer flow study. We use a hybrid field microfluidic (HFM) approach, in which an electric field is imposed at desired locations and appropriate moments to balance the flow stress on charged molecules, to effectively regulate the initial conformations and the deformation dynamics of macromolecules in flow. With λ-DNA and a steady laminar shear flow as the model system, we herein studied the performance of HFM on regulating DNA trapping, relaxation, coil-stretch transition, and accumulation. DNA molecules were found to get captured in the focused planes when motions caused by flow, and the electric field were balanced. The trapped macromolecules relaxed in two different routes while eventually became more uniform in size and globule conformations. When removing the electric field, the sudden stretching dynamics of DNA molecules exhibited a more pronounced extension overshoot in their transient response under a true step function of flow stress while similar behaviors to what other pioneering work in steady shear flow. Such regulation strategies could be useful to control the conformations of other important macromolecules (e.g., proteins) and help better reveal their molecular dynamics. 相似文献
16.
A comprehensive study involving numerical analysis and experimental validation of temperature transients within a microchamber was performed for thermocycling operation in an integrated centrifugal microfluidic platform for polymerase chain reaction (PCR) amplification. Controlled heating and cooling of biological samples are essential processes in many sample preparation and detection steps for micro-total analysis systems. Specifically, the PCR process relies on highly controllable and uniform heating of nucleic acid samples for successful and efficient amplification. In these miniaturized systems, the heating process is often performed more rapidly, making the temperature control more difficult, and adding complexity to the integrated hardware system. To gain further insight into the complex temperature profiles within the PCR microchamber, numerical simulations using computational fluid dynamics and computational heat transfer were performed. The designed integrated centrifugal microfluidics platform utilizes thermoelectrics for ice-valving and thermocycling for PCR amplification. Embedded micro-thermocouples were used to record the static and dynamic thermal responses in the experiments. The data collected was subsequently used for computational validation of the numerical predictions for the system response during thermocycling, and these simulations were found to be in agreement with the experimental data to within ∼97%. When thermal contact resistance values were incorporated in the simulations, the numerical predictions were found to be in agreement with the experimental data to within ∼99.9%. This in-depth numerical modeling and experimental validation of a complex single-sided heating platform provide insights into hardware and system design for multi-layered polymer microfluidic systems. In addition, the biological capability along with the practical feasibility of the integrated system is demonstrated by successfully performing PCR amplification of a Group B Streptococcus gene. 相似文献
17.
We use molecular dynamics simulations with a dissipative particle dynamics thermostat to study the behavior of nanosized inclusions (colloids) in a polymer brush under shear whereby the solvent is explicitly included in the simulation. The brush is described by a bead-spring model for flexible polymer chains, grafted on a solid substrate, while the polymer-soluble nanoparticles in the solution are taken as soft spheres whose diameter is about three times larger than that of the chain segments and the solvent. We find that the brush number density profile, as well as the density profiles of the nanoinclusions and the solvent, remains insensitive to strong shear although the grafted chains tilt in direction of the flow. The thickness of the penetration layer of nanoinclusions, as well as their average concentration in the brush, stays largely unaffected even at the strongest shear. Our result manifests the remarkable robustness of polymer brushes with embedded nanoparticles under high shear which could be of importance for technological applications. 相似文献
18.
Roger A. Grey Author Vitae 《Journal of The Franklin Institute》2004,341(3):197-205
Throughout his distinguished career of over 40 years, Robin Hochstrasser has made significant contributions to several areas of science in the fields of chemical and biochemical physics. He has been at the forefront and made fundamental contributions to the fields of photochemistry, solid-state chemistry, ultra-fast laser spectroscopies, and protein dynamics. He has been a prolific researcher, producing over 560 publications. His work has been characterized by experts in the fields as “a constant stream of experiments of lasting significance” (J. Phys. Chem. 100 (1996) 11791).Robin began his career in the 1960s using a variety of magnetic and electric field measurements to study crystals at low temperatures to understand spin quantization in solids and electron exchanged-mediated energy transfer. This work, described as a “classic contribution” (J. Phys. Chem. 100 (1996) 11791) was the basis for much of the subsequent experimental and theoretical work on the effect of magnetic fields on molecular spectra and on the measurements of dipole moments.In the late 1970s, Robin recognized the power of laser technology for the study of molecules and soon became a leader in the field investigating solid, gas phase, and condensed phase systems. He developed and applied various ultra-fast laser techniques to study the structure and dynamics of complex molecules in liquid phase, chemical, and biochemical reactions. He made seminal contributions to the development of two-dimensional infrared spectroscopy (2D IR) on a time scale of a picosecond or less. This 2D IR spectroscopy measures coupling between two functional groups in a large molecule and can thus be used to measure distances, as for example, two amide carbonyl groups in a peptide molecule. On the ultra-fast timescale, one application of 2D IR is to gain information on the rate of protein folding and unfolding in solution. Some of Robin's greatest contributions to understanding biomolecules are said to be in the experimental studies on the picosecond and femtosecond dynamics of heme proteins. Using techniques he developed he was able to observe the interactions of oxygen, carbon monoxide, and nitric oxide with hemoglobin inside the protein. 相似文献
19.
物联网三元空间域中传播动力学的形成与演化机制 总被引：1，自引：0，他引：1
基于物联网环境下"人(H)-机(M)-物(T)"3类主体所对应的{用户需求域,信息空间域,物理空间域}的三元体系架构,以及贯穿其间的{控制流,数据流,感知流}的动态交互模式,按照"模式构建—决策分析—形态推演"逐层递进的分析思路提出物联网三元空间域的传播动力学模型,从而定量刻画三元网络空间中传播行为的发生发展过程以及由此形成的系统演化状态;最后基于物联传播的模拟仿真环境,对其传播动力学特性进行算例分析。实验研究结果符合预期,验证了传播决策模型的合理性。 相似文献