Functional planning and occupational safety of milk production in cold loose housing barns

The study charted the most serious occupational hazards of cold loose housing barns. Furthermore, the study gave a good general picture of cold loose housing barns (CLHB) in dairy production. The study was a thesis for the Department of Agricultural Engineering and Household Technology in the University of Helsinki

Systematic comparison of force fields for microscopic simulations of NaCl in aqueous solutions: Diffusion, free energy of hydration and structural properties

In this paper we compare different force fields that are widely used (Gromacs, Charmm-22/x-Plor, Charmm-27, Amber-1999, OPLS-AA) in biophysical simulations containing aqueous NaCl. We show that the uncertainties of the microscopic parameters of, in particular, sodium and, to a lesser extent, chloride translate into large differences in the computed radial-distribution functions. This uncertainty reflects the incomplete experimental knowledge of the structural properties of ionic aqueous solutions at finite molarity.We discuss possible implications on the computation of potential of mean force and effective potentials.Comment: Revised and extended manuscrip

Anomalously slow phase transitions in self-gravitating systems

Kinetics of collapse and explosion transitions in microcanonical self-gravitating ensembles is analyzed. A system of point particles interacting via an attractive soft Coulomb potential and confined to a spherical container is considered. We observed that for 100--200 particles collapse takes $10^3$ -- $10^4$ particle crossing times to complete, i. e., it is by 2-3 orders of magnitude slower than velocity relaxation. In addition, it is found that the collapse time decreases rapidly with the increase of the softcore radius. We found that such an anomalously long collapse time is caused by the slow energy exchange between a higher-temperature compact core and relatively cold diluted halo. The rate of energy exchange between the faster modes of the core particles and slower-moving particles of the halo is exponentially small in the ratio of the frequencies of these modes. As the softcore radius increases, and the typical core modes become slower, the ratio of core and halo frequencies decreases and the collapse accelerates. Implications to astrophysical systems and phase transition kinetics are discussed.Comment: 6 pages, 5 figure

Multiphase density functional theory parameterization of the Gupta potential for silver and gold

The ground state energies of Ag and Au in the face-centered cubic (FCC), body-centered cubic (BCC), simple cubic (SC) and the hypothetical diamond-like phase, and dimer were calculated as a function of bond length using density functional theory (DFT). These energies were then used to parameterize the many-body Gupta potential for Ag and Au. This parameterization over several phases of Ag and Au was performed to guarantee transferability of the potentials and to make them appropriate for studies of related nanostructures. Depending on the structure, the energetics of the surface atoms play a crucial role in determining the details of the nanostructure. The accuracy of the parameters was tested by performing a 2 ns MD simulation of a cluster of 55 Ag atoms -- a well studied cluster of Ag, the most stable structure being the icosahedral one. Within this time scale, the initial FCC lattice was found to transform to the icosahedral structure at room temperature. The new set of parameters for Ag was then used in a temperature dependent atom-by-atom deposition of Ag nanoclusters of up to 1000 atoms. We find a deposition temperature of 500 $\pm$50 K where low energy clusters are generated, suggesting an optimal annealing temperature of 500 K for Ag cluster synthesis

Stability of charge inversion, Thomson problem and application to electrophoresis

We analyse charge inversion in colloidal systems at zero temperature using stability concepts, and connect this to the classical Thomson problem of arranging electrons on sphere. We show that for a finite microion charge, the globally stable, lowest energy state of the complex formed by the colloid and the oppositely charged microions is always overcharged. This effect disappears in the continuous limit. Additionally, a layer of at least twice as many microions as required for charge neutrality is always locally stable. In an applied external electric field the stability of the microion cloud is reduced. Finally, this approach is applied to a system of two colloids at low but finite temperature

Getting excited: Challenges in quantum-classical studies of excitons in polymeric systems

A combination of classical molecular dynamics (MM/MD) and quantum chemical calculations based on the density functional theory (DFT) was performed to describe conformational properties of diphenylethyne (DPE), methylated-DPE and poly para phenylene ethynylene (PPE). DFT calculations were employed to improve and develop force field parameters for MM/MD simulations. Many-body Green's functions theory within the GW approximation and the Bethe-Salpeter equation were utilized to describe excited states of the systems. Reliability of the excitation energies based on the MM/MD conformations was examined and compared to the excitation energies from DFT conformations. The results show an overall agreement between the optical excitations based on MM/MD conformations and DFT conformations. This allows for calculation of excitation energies based on MM/MD conformations