Numerical Simulation Studies of the Long-term Evolution of a CO<Subscript>2</Subscript> Plume in a Saline Aquifer with a Sloping Caprock

We have used the TOUGH2-MP/ECO2N code to perform numerical simulation studies of the long-term behavior of CO₂ stored in an aquifer with a sloping caprock. This problem is of great practical interest, and is very challenging due to the importance of multi-scale processes. We find that the mechanism of plume advance is different from what is seen in a forced immiscible displacement, such as gas injection into a water-saturated medium. Instead of pushing the water forward, the plume advances because the vertical pressure gradients within the plume are smaller than hydrostatic, causing the groundwater column to collapse ahead of the plume tip. Increased resistance to vertical flow of aqueous phase in anisotropic media leads to reduced speed of up-dip plume advancement. Vertical equilibrium models that ignore effects of vertical flow will overpredict the speed of plume advancement. The CO₂ plume becomes thinner as it advances, but the speed of advancement remains constant over the entire simulation period of up to 400 years, with migration distances of more than 80 km. Our simulations include dissolution of CO₂ into the aqueous phase and associated density increase, and molecular diffusion. However, no convection develops in the aqueous phase because it is suppressed by the relatively coarse (sub-) horizontal gridding required in a regional-scale model. A first crude sub-grid-scale model was developed to represent convective enhancement of CO₂ dissolution. This process is found to greatly reduce the thickness of the CO₂ plume, but, for the parameters used in our simulations, does not affect the speed of plume advancement.     

Open Chain Chiral Macrolide Building Blocks by Opening of Deoxygenated 1,6-Anhydrosugars with 1,3-Propanedithiol

Chiral building blocks for macrolides and related natural products are obtained from 1,6-anhydrosugars by conversion of the bicyclic acetals 2 or 12 into the open chain chiral 1,3-dithianes 6 and 13. Branched precursors can be obtained by opening of the ?erný epoxide 1 with the 1,3-dithiane anion to yield 7, followed by ring opening with 1,3-propanedithiol to the bis-1,3-dithiane 8.     

Random Broken Lines That Weakly Converge to a Fractional Ornstein-Uhlenbeck Process

We study the behavior of sequences of continuous random broken lines that are constructed from increased sums of stationary sequences. We obtain conditions of weak convergence of these random broken lines to Gaussian processes of types of a fractional Ornstein-Uhlenbeck process and the fractional Brownian motion. Sequences of moving averages are considered as the main examples of the investigated stationary sequences. Bibliography: 8 titles.__________Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 298, 2003, pp. 134–149.     

Global G-Manifold Reductions and Resolutions

The purpose of this note is to exhibit some simple and basic constructions for smooth compact transformation groups, and some of their most immediate applications to geometry.     

Polynome über endlichen Körpern mit gleichem Wurzelraum

Ohne Zusammenfassung     

Novel triazolopeptides: chirospecific synthesis and conformational studies of proline derived analogs

Replacing the backbone amide function by a heterocyclic bioisostere, [3+2] azide-alkyne cycloaddition has been applied for the construction of biologically relevant peptidomimetics. Starting from aminoalkynoates, triazole formation was accomplished by addition of hydrazoic acid. NMR studies displayed that the newly developed 4,5-triazolopeptides, which incorporate a biomimetic triazole NH-function as polar constraint element, showed a substantially higher tendency to form a cis-prolyl-geometry than a comparable native peptide sequence.