We discuss an alternative approach to quintessence modifying the usual equation of state of the cosmological fluid in order to see if going further than the approximation of perfect fluid allows to better reproduce the available data. We consider a cosmological model comprising only two fluids, namely baryons (modelled as dust) and dark matter with a Van der Waals equation of state. First, the ...

By the inclusion of an additional term, non-linear in the scalar curvature R, it is tested if dark energy could rise as a geometrical effect in 3D gravitational formulations. We investigate a cosmological fluid obeying a non-polytropic equation of state (the van der Waals equation) that is used to construct the energy-momentum tensor of the sources, representing the hypothetical inflaton in gra...

2 Different Types of Bonds 7 2.1 Covalent Bonding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.2 Ionic Bonding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.2.1 Madelung Sums . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.3 Metallic Bonding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.4 Van der Waals Bonds . . . . . . . . . . . ....

The derivation of the van der Waals parameters for the aliphatic CH united atoms of the GROMOS96 force field is presented. The parameters n have been adjusted to reproduce the experimental enthalpies of vaporization and vapor pressures or densities of a set of nine alkanes in the liquid state at 298 Ž . K or at the boiling point in the case of methane , using a cutoff radius for the van der Waa...

We study the dependence of the heat transfer and the van der Waals friction between two semi-infinite solids on the dielectric properties of the bodies. We show that the heat transfer and van der Waals friction at short separation between the solids may increase by many orders of magnitude when the surfaces are covered by adsorbates, or can support low-frequency surface plasmons. In this case t...

The nature of the physical interactions between Escherichia coli JM109 and a model surface (silicon nitride) was investigated in water via atomic force microscopy (AFM). AFM force measurements on bacteria can represent the combined effects of van der Waals and electrostatic forces, hydrogen bonding, steric interactions, and perhaps ligand-receptor type bonds. It can be difficult to decouple the...

The energetic barriers that atoms and molecules often experience when binding to surfaces are incredibly important to a myriad of chemical and physical processes. However, these barriers are difficult to describe accurately with current computer simulation approaches. Two prominent contemporary challenges faced by simulation are the role of van der Waals forces and nuclear quantum effects. Here...

Multi-walled hollow nanoparticles made from tungsten disulphide (WS2) show exceptional tribological performance as additives to liquid lubricants due to effective transfer of low shear strength material onto the sliding surfaces. Using a scaling approach based on continuum elasticity theory for shells and pairwise summation of van der Waals interactions, we show that van der Waals interactions ...

A recently proposed general density functional for asymptotic van der Waals forces is used to calculate van der Waals coefficients and reference-plane positions for realistic low-indexed Al surfaces. Results are given for a number of atoms and molecules outside the surfaces, as well as for the interaction between the surfaces themselves. The densities and static image-plane positions that are n...

The interaction between charged particles via the Coulomb interaction is one of the most important features in physics and is familiar to any student of the subject. The way in which electrons and protons bind to form the hydrogen atom is also well known and is a staple of any quantum mechanics course. However, less familiar is the interaction between such bound systems at separation R, which i...