285 research outputs found
Two center multipole expansion method: application to macromolecular systems
We propose a new theoretical method for the calculation of the interaction
energy between macromolecular systems at large distances. The method provides a
linear scaling of the computing time with the system size and is considered as
an alternative to the well known fast multipole method. Its efficiency,
accuracy and applicability to macromolecular systems is analyzed and discussed
in detail.Comment: 23 pages, 7 figures, 1 tabl
Modeling of nanoparticle coatings for medical applications
Abstract Gold nanoparticles (AuNPs) have been shown to possess properties beneficial for the treatment of cancerous tumors by acting as radiosensitizers for both photon and ion radiation. Blood circulation time is usually increased by coating the AuNPs with poly(ethylene glycol) (PEG) ligands. The effectiveness of the PEG coating, however, depends on both the ligand surface density and length of the PEG molecules, making it important to understand the structure of the coating. In this paper the thickness, ligand surface density, and density of the PEG coating is studied with classical molecular dynamics using the software package MBN Explorer. AuNPs consisting of 135 atoms (approximately 1.4 nm diameter) in a water medium have been studied with the number of PEG ligands varying between 32 and 60. We find that the thickness of the coating is only weakly dependent on the surface ligand density and that the degree of water penetration is increased when there is a smaller number of attached ligands
Molecular Dynamics Simulations of Bio-Nano Systems with MBN Explorer
AbstractWe present results of molecular dynamics simulations performed using a multi-purpose computer code MBN Explorer. In particular we consider the process of laser induced acoustic desorption of lysine amino acids from the surface of a nickel foil. We analyze the rate of lysine desorption from the nickel foil at different foil accelerations and suggest a simple theoretical model to describe the observed results. We note that despite the universality, the computational efficiency of MBN Explorer is comparable (and in some cases even higher) than the computational efficiency of other software packages, making MBN Explorer a possible alternative to the available codes
Special issue: Dynamics of systems on the nanoscale (2018). Editorial
The structure, formation and dynamics of both animate and inanimate matter on the nanoscale are a highly interdisciplinary field of rapidly emerging research engaging a broad community encompassing experimentalists, theorists, and technologists. It is relevant for a large variety of molecular and nanosystems of different origin and composition and concerns numerous phenomena originating from physics, chemistry, biology, or materials science. This Topical Issue presents a collection of original research papers devoted to different aspects of structure and dynamics on the nanoscale. Some of the contributions discuss specific applications of the research results in several modern technologies and in next generation medicine. Most of the works of this topical issue were reported at the Fifth International Conference on Dynamics of Systems on the Nanoscale (DySoN) – the premier forum for the presentation of cutting-edge research in this field that was held in Potsdam, Germany in October of 2018
Finslerian 3-spinors and the generalized Duffin-Kemmer equation
The main facts of the geometry of Finslerian 3-spinors are formulated. The
close connection between Finslerian 3-spinors and vectors of the 9-dimensional
linear Finslerian space is established. The isometry group of this space is
described. The procedure of dimensional reduction to 4-dimensional quantities
is formulated. The generalized Duffin-Kemmer equation for a Finslerian 3-spinor
wave function of a free particle in the momentum representation is obtained.
From the viewpoint of a 4-dimensional observer, this 9-dimensional equation
splits into the standard Dirac and Klein-Gordon equations.Comment: LaTeX2e, 11 pages, no figures, will be published in "Fundamental and
Applied Mathematics
Ab initio study of alanine polypeptide chains twisting
We have investigated the potential energy surfaces for alanine chains
consisting of three and six amino acids. For these molecules we have calculated
potential energy surfaces as a function of the Ramachandran angles Phi and Psi,
which are widely used for the characterization of the polypeptide chains. These
particular degrees of freedom are essential for the characterization of
proteins folding process. Calculations have been carried out within ab initio
theoretical framework based on the density functional theory and accounting for
all the electrons in the system. We have determined stable conformations and
calculated the energy barriers for transitions between them. Using a
thermodynamic approach, we have estimated the times of characteristic
transitions between these conformations. The results of our calculations have
been compared with those obtained by other theoretical methods and with the
available experimental data extracted from the Protein Data Base. This
comparison demonstrates a reasonable correspondence of the most prominent
minima on the calculated potential energy surfaces to the experimentally
measured angles Phi and Psi for alanine chains appearing in native proteins. We
have also investigated the influence of the secondary structure of polypeptide
chains on the formation of the potential energy landscape. This analysis has
been performed for the sheet and the helix conformations of chains of six amino
acids.Comment: 24 pages, 10 figure
A multi-scale approach to the physics of ion beam cancer therapy
We propose a multi-scale approach to understanding physics related to the
ion/proton-beam cancer therapy and calculation of the probability of the DNA
damage as a result of irradiation of patients with energetic (up to 430 MeV/u)
ions. This approach is inclusive with respect to different scales starting from
the long scale defined by the ion stopping followed by a smaller scale defined
by secondary electrons and radicals ending with the shortest scale defined by
interactions of secondaries with the DNA. We present calculations of the
probabilities of single and double strand breaks of the DNA and suggest a way
of further elaboration of such calculations.Comment: submitted to RADAM2008 proceedings. 8 pages,5 Figures, class files
for AIP include
Influence of the litter features on pedogenesis in forests of the middle Dniprо flood-lands
Узагальнено сучасний стан лісових біогеоценозів заплави середньої течії Дніпра на прикладі Дніпровсько-Орільського природного заповідника. Наведено дані про якісні зміни рівня трофності ґрунтів у ході сукцесій лісової рослинності заплави Дніпра. Узагальнено сучасний стан лісових біогеоценозів заплави середньої течії Дніпра на прикладі Дніпровсько-Орільського природного заповідника. Наведено дані про якісні зміни рівня трофності ґрунтів у ході сукцесій лісової рослинності заплави ДніпраThe modern status of forest ecosystems of the middleDnieperflood-lands is characterized by the example of Dniprovsko-Orelsky nature reserve. The data of qualitative changes of the soil fertility in the course of wood vegetation’s succession in theDnieperflood-lands are presented
Physics of ion beam cancer therapy: a multi-scale approach
We propose a multi-scale approach to understand the physics related to
ion-beam cancer therapy. It allows the calculation of the probability of DNA
damage as a result of irradiation of tissues with energetic ions, up to 430
MeV/u. This approach covers different scales, starting from the large scale,
defined by the ion stopping, followed by a smaller scale, defined by secondary
electrons and radicals, and ending with the shortest scale, defined by
interactions of secondaries with the DNA. We present calculations of the
probabilities of single and double strand breaks of DNA, suggest a way to
further expand such calculations, and also make some estimates for glial cells
exposed to radiation.Comment: 18 pag,5 fig, submitted to PR
Role of exchange interaction in self-consistent calculations of endohedral fullerenes
Results of the self-consistent calculation of electronic structure of
endohedral fullerene Ar@C within the Hartree-Fock and the local density
approximations are presented. Hartree-Fock approximation is used for the
self-consistent description for the first time. It is shown that the accurate
account of the exchange interaction between all electrons of the compound leads
to the significant modification of the atomic valent shell which causes the
noticeable charge redistribution inside the endohedral compound.Comment: 5 figures, Proceedings of the 5th Conference on Elementary Processes
in Atomic Systems (CEPAS 2011), submitted to Nuclear Instruments and Methods
in Physics Research Section
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