Structure of hadron matter: Hierarchy,democracy, or potentiality?

An attempt is made to give a methodological and physical characterization to the concept of the structure of matter. The methodological status of theories describing the structure of hadrons is discussed. A parallelism is drawn between the quark model as a theory of the mathematical composite structure of hadrons and Plato's theory of matter. The merger of the bootstrap idea with a quark substructure of hadrons is discussed. A third approach to the structure of hadron matter is presented. It resembles the Aristotelian conception of primary matter on which form is imprinted potentially.     

Bond breaking coupled with translation in rolling of covalently bound molecules

The response of a C60 molecule to manipulation across a surface displays a long range periodicity which corresponds to a rolling motion. A period of three or four lattice constants is observed and is accompanied by complex subharmonic structure due to molecular hops through a regular, repeating sequence of adsorption states. Combining experimental data and ab initio calculations, we show that this response corresponds to a rolling motion in which two of the four Si-C60 covalent bonds act as a pivot over which the molecule rotates while moving through one lattice constant and identify a sequence of C60 bonding configurations that accounts for the periodic structure.     

Structure factor of ferrofluids with chain aggregates: Theory and computer simulations

In this paper we present theoretical and simulation results on the structure factor of mono- and bidisperse ferrofluids with chain aggregates, both with and without an applied external magnetic field. Chain distribution is obtained by the density functional theory (DFT). The radial distribution function (RDF) is calculated directly on the basis of the chain distribution and Fourier transformed to calculate the structure factor. An extensive comparison of the theoretical predictions to the results of the molecular dynamics computer simulations is provided. The proposed combined approach allows to elucidate the connection between experimentally observed small angle neutron scattering (SANS) images and the ferrofluid microstructure.     

Homopairing possibilities of the DNA base thymine and the RNA base uracil: an ab initio density functional theory study

All planar homopairings of the DNA base thymine and the RNA base uracil are reported for the first time in this study. Using the idea of binding sites discussed in our previous work (Kelly et al. J. Phys. Chem. B 2005, 109, 11933; J. Phys. Chem. B 2005, 109, 22045) and ab initio density functional theory, we predict and relax 10 thymine and 10 uracil homopairs. The stabilization energies of the homopairs vary from just below zero to -0.82 eV. The results on the pair geometry and energetics are compared with those available in the literature. The collected data on all planar thymine and uracil homopairs can be used to construct the thymine and uracil superstructures seen experimentally on various surfaces.     

Two-dimensional supramolecular nanopatterns formed by the coadsorption of guanine and uracil at the liquid/solid interface

A novel supramolecular nanostructure formed by the coadsorption of the complementary nucleobases guanine (G) and uracil (U) at the liquid (1-octanol solvent)/solid (graphite) interface is revealed by scanning tunneling microscopy (STM). The GU supramolecular structure is distinctly different from the structures observed by STM when the individual nucleobases (NB) are adsorbed on graphite in the control experiments. Using a systematic methodology and ab initio density functional theory (DFT), an atomistic structural model is proposed for the supramolecular coadsorbed GU structure, which consists of a periodic repetition of cyclic units based on the strongest GU base pairing.     

Structure formation and phase behaviour in ferrofluid monolayers: theory and computer simulations

In order to investigate the peculiarities brought by the quasi-2D geometry into the aggregation processes in ferrofluids, a combination of density functional theory (DFT), and molecular dynamics (MD) simulations is presented. The microstructure formation and the phase behaviour of monodisperse ferrofluid monolayers is studied. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Tip models and force definitions in molecular dynamics simulations of scanning force microscopy

The definition of the time varying force on a tip with internal degrees of freedom in atomistic molecular dynamics (MD) simulations of scanning force microscopy experiments is discussed. We show that the static expression for the tip force is inadequate for calculating force fluctuations within the MD simulations and suggest a different method of calculating the tip force. By studying the size of tip force fluctuations for different tip models and various tip positions with respect to the surface, we demonstrate that the new method works equally well in both static and dynamic cases.     

Inclusion of delay effects in the collision integral by means of continuous integration. I

Representation of the casual two-body Green's function in the form of a double (with respect to the external fields and the trajectories) continuous integral with a subsequent density expansion and integration with respect to the external fields is used to construct a non-Markovian collision integral for a quantum gas with binary scalar coupling. The nondissipative contribution of coupling is included in the Born approximation according to [1,2].Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 114–118, April, 1976.The author thanks L. Ya. Kobelev for suggesting the topic and for useful criticism.