121,010 research outputs found
DNA Nanorobotics
This paper presents a molecular mechanics study for new nanorobotic
structures using molecular dynamics (MD) simulations coupled to virtual reality
(VR) techniques. The operator can design and characterize through molecular
dynamics simulation the behavior of bionanorobotic components and structures
through 3-D visualization. The main novelty of the proposed simulations is
based on the mechanical characterization of passive/active robotic devices
based on double stranded DNA molecules. Their use as new DNA-based nanojoint
and nanotweezer are simulated and results discussed.Comment: Submitted on behalf of TIMA Editions
(http://irevues.inist.fr/tima-editions
Visualization and Simulation of Laser-Induced Fullerene Fragmentation
The benefit from the research of carbon, an element with one of the highest variety of binding possibilities that is essential for life, has a strong impact in many fields in science as well as in industry. A molecule that is suited to explore more complex systems of carbon atoms due to its highly symmetrical hollow sphere-like structure is C60, one of the best known fullerenes. Still, its dynamics is far from being understood, especially its interaction with ultrashort and strong laser pulses. Simulations can help us to get insights into the dynamics of molecules. In combination with visualization, these dynamics can be analyzed and understood. Leaned to laser experiments with fullerene, performed at LCLS to get further insights into the dynamics of fullerene, this work examines some of their experiments by means of molecular dynamics simulations, which we analyze by our developed visualization techniques. The focus is on the fragmentation dynamics, induced by laser pulses that are used in the experiments. The contribution of this work can be summarized into simulation and visualization. Simulations are required to imitate the experiment, including the modeling of C60 by the choice of force field potentials, the modeling of laser pulses, and their intensities. The results of our simulations are adapted based on results from the experiments. Goals in the visualization are the development of novel analysis techniques. These techniques are for the fragmentation process of fullerene, the fragmentation dynamics by exibility methods, the reconstruction of diffraction images, which can be used as additional medium for the physical analysis, as well as the analysis of the achieved results of this work
WavePacket: A Matlab package for numerical quantum dynamics. I: Closed quantum systems and discrete variable representations
WavePacket is an open-source program package for the numerical simulation of
quantum-mechanical dynamics. It can be used to solve time-independent or
time-dependent linear Schr\"odinger and Liouville-von Neumann-equations in one
or more dimensions. Also coupled equations can be treated, which allows to
simulate molecular quantum dynamics beyond the Born-Oppenheimer approximation.
Optionally accounting for the interaction with external electric fields within
the semiclassical dipole approximation, WavePacket can be used to simulate
experiments involving tailored light pulses in photo-induced physics or
chemistry.The graphical capabilities allow visualization of quantum dynamics
'on the fly', including Wigner phase space representations. Being easy to use
and highly versatile, WavePacket is well suited for the teaching of quantum
mechanics as well as for research projects in atomic, molecular and optical
physics or in physical or theoretical chemistry.The present Part I deals with
the description of closed quantum systems in terms of Schr\"odinger equations.
The emphasis is on discrete variable representations for spatial discretization
as well as various techniques for temporal discretization.The upcoming Part II
will focus on open quantum systems and dimension reduction; it also describes
the codes for optimal control of quantum dynamics.The present work introduces
the MATLAB version of WavePacket 5.2.1 which is hosted at the Sourceforge
platform, where extensive Wiki-documentation as well as worked-out
demonstration examples can be found
From complex data to clear insights: visualizing molecular dynamics trajectories
Advances in simulations, combined with technological developments in high-performance computing, have made it possible to produce a physically accurate dynamic representation of complex biological systems involving millions to billions of atoms over increasingly long simulation times. The analysis of these computed simulations is crucial, involving the interpretation of structural and dynamic data to gain insights into the underlying biological processes. However, this analysis becomes increasingly challenging due to the complexity of the generated systems with a large number of individual runs, ranging from hundreds to thousands of trajectories. This massive increase in raw simulation data creates additional processing and visualization challenges. Effective visualization techniques play a vital role in facilitating the analysis and interpretation of molecular dynamics simulations. In this paper, we focus mainly on the techniques and tools that can be used for visualization of molecular dynamics simulations, among which we highlight the few approaches used specifically for this purpose, discussing their advantages and limitations, and addressing the future challenges of molecular dynamics visualization
WavePacket: A Matlab package for numerical quantum dynamics. II: Open quantum systems, optimal control, and model reduction
WavePacket is an open-source program package for numeric simulations in
quantum dynamics. It can solve time-independent or time-dependent linear
Schr\"odinger and Liouville-von Neumann-equations in one or more dimensions.
Also coupled equations can be treated, which allows, e.g., to simulate
molecular quantum dynamics beyond the Born-Oppenheimer approximation.
Optionally accounting for the interaction with external electric fields within
the semi-classical dipole approximation, WavePacket can be used to simulate
experiments involving tailored light pulses in photo-induced physics or
chemistry. Being highly versatile and offering visualization of quantum
dynamics 'on the fly', WavePacket is well suited for teaching or research
projects in atomic, molecular and optical physics as well as in physical or
theoretical chemistry. Building on the previous Part I which dealt with closed
quantum systems and discrete variable representations, the present Part II
focuses on the dynamics of open quantum systems, with Lindblad operators
modeling dissipation and dephasing. This part also describes the WavePacket
function for optimal control of quantum dynamics, building on rapid
monotonically convergent iteration methods. Furthermore, two different
approaches to dimension reduction implemented in WavePacket are documented
here. In the first one, a balancing transformation based on the concepts of
controllability and observability Gramians is used to identify states that are
neither well controllable nor well observable. Those states are either
truncated or averaged out. In the other approach, the H2-error for a given
reduced dimensionality is minimized by H2 optimal model reduction techniques,
utilizing a bilinear iterative rational Krylov algorithm
Dataflow programming for the analysis of molecular dynamics with AViS, an analysis and visualization software application
The study of molecular dynamics simulations is largely facilitated by
analysis and visualization toolsets. However, these toolsets are often designed
for specific use cases and those only, while scripting extensions to such
toolsets is often exceedingly complicated. To overcome this problem, we
designed a software application called AViS which focuses on the extensibility
of analysis. By utilizing the dataflow programming (DFP) paradigm, algorithms
can be defined by execution graphs, and arbitrary data can be transferred
between nodes using visual connectors. Extension nodes can be implemented in
either Python, C++, and Fortran, and combined in the same algorithm. AViS
offers a comprehensive collection of nodes for sophisticated visualization
state modifications, thus greatly simplifying the rules for writing extensions.
Input files can also be read from the server automatically, and data is fetched
automatically to improve memory usage. In addition, the visualization system of
AViS uses physically-based rendering techniques, improving the 3D perception of
molecular structures for interactive visualization. By performing two case
studies on complex molecular systems, we show that the DFP workflow offers a
much higher level of flexibility and extensibility when compared to legacy
workflows. The software source code and binaries for Windows, MacOS, and Linux
are freely available at https://avis-md.github.io/.Comment: 13 pages, 8 figures, additional figures and example code in
supplementary material
Physics-based visual characterization of molecular interaction forces
Molecular simulations are used in many areas of biotechnology, such as drug design and enzyme engineering. Despite the development of automatic computational protocols, analysis of molecular interactions is still a major aspect where human comprehension and intuition are key to accelerate, analyze, and propose modifications to the molecule of interest. Most visualization algorithms help the users by providing an accurate depiction of the spatial arrangement: the atoms involved in inter-molecular contacts. There are few tools that provide visual information on the forces governing molecular docking. However, these tools, commonly restricted to close interaction between atoms, do not consider whole simulation paths, long-range distances and, importantly, do not provide visual cues for a quick and intuitive comprehension of the energy functions (modeling intermolecular interactions) involved. In this paper, we propose visualizations designed to enable the characterization of interaction forces by taking into account several relevant variables such as molecule-ligand distance and the energy function, which is essential to understand binding affinities. We put emphasis on mapping molecular docking paths obtained from Molecular Dynamics or Monte Carlo simulations, and provide time-dependent visualizations for different energy components and particle resolutions: atoms, groups or residues. The presented visualizations have the potential to support domain experts in a more efficient drug or enzyme design process.Peer ReviewedPostprint (author's final draft
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