Geometry, topology and dynamics of geodesic flows on noncompact polygonal surfaces

We establish the background for the study of geodesics on noncompact polygonal surfaces. For illustration, we study the recurrence of geodesics on ?-periodic polygonal surfaces. We prove, in particular, that almost all geodesics on a topologically typical ?-periodic surface with a boundary are recurrent.     

Towards a Unified Turbulence Simulation Approach for Wall-Bounded Flows

A hybrid Reynolds-averaged Navier–Stokes/Large-Eddy Simulation (RANS/LES) methodology has received considerable attention in recent years, especially in its application to wall-bounded flows at high-Reynolds numbers. In the conventional zonal hybrid approach, eddy-viscosity-type RANS and subgrid scale models are applied in the RANS and LES zones, respectively. In contrast, the non-zonal hybrid approach uses only a generalized turbulence model, which provides a unified simulation approach that spans the continuous spectrum of modeling/simulation schemes from RANS to LES. A particular realization of the non-zonal approach, known as partially resolved numerical simulation (PRNS), uses a generalized turbulence model obtained from a rescaling of a conventional RANS model through the introduction of a resolution control function F _R , where F _R is used to characterize the degree of modeling required to represent the unresolved scales of turbulent motion. A new generalized functional form for F _R in PRNS is proposed in this study, and its performance is compared with unsteady RANS (URANS) and LES computations for attached and separated wall-bounded turbulent flows. It is demonstrated that PRNS behaves similarly to LES, but outperforms URANS in general.     

Studies Related to Biological Detoxification of Kraft Pulp Mill Effluent. VI. The Biodegradation of 12,14-dichlorodehydroabietic acid with mortierella isabellina

A detailed study of the biodegradation of one of the fish toxic chlorinated resin acids, 12,14-dichlorodehydroabietic acid

1 The correct IUPAC-name is 12,14-dichloro-8,9,11,12-tetradehydro-7,8-dihydroabietic acid.

( 3 ) is presented. When exposed to the fungus Mortierella isabellina, 3 is converted into a number of hydroxylated and keto derivatives which show low levels of toxicity to fish. These metabolites were isolated and characterized.