Narrow Results

In liquid mixtures or analogous binary systems at low temperatures the pure phases may coexist, separated by an interface. The interface tension vanishes according to σ=σ₀(1−T/T_c)^µ as the temperature T approaches the critical point from below. Similarly the correlation length diverges as ξ=ξ₀(T/T_c−1)^−ν. For three-dimensional systems the dimensionless product R=σ₀(ξ₀)² is universal. This and related universal quantities are investigated by means of a semiclassical expansion in the framework of Φ⁴ theory, as well as by Monte Carlo calculations in the three-dimensional Ising model.

In the SU(3) pure gauge theory the high temperature deconfinement phase transition is first order. At the transition the confined phase coexists with three distinct deconfined phases. The interfaces separating the various phases show universal critical behavior when the confined phase completely wets the deconfined-deconfined interfaces. The critical exponents of complete wetting are derived from an interface solution of a Z(3) symmetric effective theory for the Polyakov loop. When complete wetting occurs in the pure glue theory the deconfinement transition proceeds via domain wall splitting. When quarks are present wetting disappears and the standard bubble nucleation scenario applies.

The transfer matrix method to describe finite size effects due to tunneling are worked out for Z(2)- and Z(3)-symmetric models. We used this method to extract the surface tension σ in the SU(3) gauge theory at the finite temperature phase transition on lattices with an extent T=2 in the euclidean time direction. We also discuss if the confined phase completely wets the deconfined phase at this first order phase transition.

The free energy distribution across the interface of coexisting quark and hadron mat-ter is studied in the framework of lattice QCD. We calculate the interface tension α with the “differential method” for pure SU(3) gauge theory and in the presence of dynamical quarks with four flavors. Using lattices with spatial volume 8²×16 it turns out that α is very small and compatible with zero. The chiral condensate indicates the same width of the domain wall as the Polyakov loop distribution and the other thermodynamical observables.

At low temperature, the Potts models can have interfaces between domains ordered to different directions. We use the difference of periodic and twisted boundary conditions to study planar order-order interfaces. We show that the interface tension, energy and width display critical properties as one approaches the critical point. We measure the critical exponents connected to their power like singular behaviour at the critical point.

We present a multicanonical algorithm for the SU(3) pure gauge theory at the deconfinement phase transition. We measure the tunneling times for lattices of size L²×2 for L=8, 10, and 12. In contrast to the canonical algorithm the tunneling time increases only moderately with L. Finally, we determine the interfacial free energy applying the multicanonical algorithm.

This paper focuses on effects of roughness on wettability. According to Wenzel's equation, the transition of theoretical wetting contact angles is 90°, whereas many experimental results have indicated that such a transition takes place at contact angles smaller than 90°. A new model of wetting on roughness surface is established in this paper. The model indicates that the influencing factors of wetting on roughness surface include not only equilibrium contact angle θ₀ and surface roughness, but also the system of liquids and solid substrates. There is a corresponding transition angle for every surface roughness, and the transition angle is lower than 90°. Surface roughness is propitious to improve the contact angle only when θ₀ is lower than the transition angle. The effect of surface roughness on the contact angle increases with the increase of r_E. To engineer the surface with different roughnesses, a Ti test sample is polished with sandpaper with abrasive number 350, 500, 1000 and 2000; the contact angles of water on Ti are measured by the sessile drop method. The results of the theoretical analysis agree with experimental ones.

This work aimed to evaluate the potential of biosurfactant produced by Rhdotorula glutinis using industrial wastes as substrates. The production was made in flasks (250 ml) containing 100 ml of means of production according to an experimental kind CCRD, varying the concentration of cassava wastewater, waste corn steep liquor and ice cream. Later, he was selected the best condition to make the factorial design optimization. Production was transferred to the reactor with a capacity of dual-shirt 2L under the same conditions. Were inoculated 5% of the pre-inoculum (Sabouraud Dextrose Broth), fermentation took place for 72 hours, 150 rpm at 28°C. Were determined the surface tension and interfacial fluid cell-free metabolic, obtaining surface tension de28, 2 mN/m interfacial 5.1 mN/m. Has been demonstrated effective stability of biosurfactant at different pH’s, temperatures and salinity determined by tensão. Subsequently was determined emulsification index of stability. The results obtained for biosurfactant production by R. glutinis using industrial waste is an alternative that comes to the economy and contribute to the preservation of the environment