Physisorption kinetics and equilibrium properties of gas-solid systems approaching monolayer coverage

The quantum statistical theory of phonon-mediated physisorption is extended up to monolayer coverage. Taking the time evolution of the phonon system fully into account we derive the standard rate equation for the coverage in terms of adsorption and desorption rates. An expression for the sticking coefficient S in terms of the desorption time is derived, and the low temperature behavior of S is discussed.     

Instance Optimality of the Adaptive Maximum Strategy

In this paper, we prove that the standard adaptive finite element method with a (modified) maximum marking strategy is instance optimal for the total error, being the square root of the squared energy error plus the squared oscillation. This result will be derived in the model setting of Poisson’s equation on a polygon, linear finite elements, and conforming triangulations created by newest vertex bisection.     

Probing the Binding Requirements of Modified Nucleosides with the DNA Nuclease SNM1A

SNM1A is a nuclease that is implicated in DNA interstrand crosslink repair and, as such, its inhibition is of interest for overcoming resistance to chemotherapeutic crosslinking agents. However, the number and identity of the metal ion(s) in the active site of SNM1A are still unconfirmed, and only a limited number of inhibitors have been reported to date. Herein, we report the synthesis and evaluation of a family of malonate-based modified nucleosides to investigate the optimal positioning of metal-binding groups in nucleoside-derived inhibitors for SNM1A. These compounds include ester, carboxylate and hydroxamic acid malonate derivatives which were installed in the 5′-position or 3′-position of thymidine or as a linkage between two nucleosides. Evaluation as inhibitors of recombinant SNM1A showed that nine of the twelve compounds tested had an inhibitory effect at 1 mM concentration. The most potent compound contains a hydroxamic acid malonate group at the 5′-position. Overall, our studies advance the understanding of requirements for nucleoside-derived inhibitors for SNM1A and indicate that groups containing a negatively charged group in close proximity to a metal chelator, such as hydroxamic acid malonates, are promising structures in the design of inhibitors.     

Exploring the qualitative behavior of uncertain dynamical systems

The global behavior of uncertain nonlinear systems by means of the cell mapping method is investigated. The systems under consideration are governed by ordinary differential equations where uncertainty is characterized by a bounded stationary noise process. In order to make cell mapping methods applicable to this particular situation generalizations of the theory become necessary. The numerical approach is based on a reformulation of the dynamics in terms of a Markov process whose qualitative behavior is analyzed. We demonstrate the usefulness of the presented scheme in the engineering field while addressing an example problem from technical mechanics.     

Designing fluorinated cinchona alkaloids for enantioselective catalysis: controlling internal rotation by a fluorine-ammonium ion gauche effect (φ(NCCF))

The C9 position of cinchona alkaloids functions as a molecular hinge, with internal rotations around the C8-C9 (τ(1)) and C9-C4' (τ(2)) bonds giving rise to four low energy conformers (1; anti-closed, anti-open, syn-closed, and syn-open). By substituting the C9 carbinol centre by a configurationally defined fluorine substituent, a fluorine-ammonium ion gauche effect (σ(C-H) → σ(C-F)*; F(δ-)???N(+)) encodes for two out of the four possible conformers (2). This constitutes a partial solution to the long-standing problem of governing internal rotations in cinchonium-based catalysts relying solely on a fluorine conformational effect.     

Fluorinated organocatalysts for the enantioselective epoxidation of enals: molecular preorganisation by the fluorine-iminium ion gauche effect

The fluorine-iminium ion gauche effect is triggered upon union of a secondary β-fluoroamine and an α,β-unsaturated aldehyde, providing a useful strategy for controlling the molecular topology of intermediates that are central to organocatalytic processes. The β-fluoroamine (S)-2-(fluorodiphenylmethyl)pyrrolidine (1) is an effective catalyst for the enantioselective epoxidation of α,β-unsaturated aldehydes. A process of structural editing has revealed that the efficiency of this catalyst is due to the (fluorodiphenyl)methyl group when it is embedded in a β-fluoroiminium motif. Epoxidations of challenging cyclic α,β-disubstituted, β,β-disubstituted and α,β,β-trisubstituted enals catalysed by 1 proceed with excellent levels of enantiocontrol (up to 98?%?ee).     

Three-Body Physics in a Finite Volume

Three particles with large two-body scattering lengths display universal properties including a spectrum of three-body bound states called “Efimov trimers”. I calculate the spectrum of three identical bosons inside a finite cubic box below the three-body breakup threshold. The dependence of the spectrum on the box size and the effects of the breakdown of spherical symmetry are investigated using effective field theory. The renormalization of the effective field theory in the finite volume is explicitly verified. The study of the three-nucleon system inside a finite cubic volume provides a tool for the understanding of Lattice QCD results. I study the triton in a finite volume at physical and unphysical pion masses.     

Sliding Mode Control of a Remotely Operated Underwater Vehicle with Adaptive Fuzzy Dead-Zone Compensation

Due to the great technological improvement obtained in the last decades, it became possible to use robotic vehicles for underwater exploration. During the execution of a certain task with a remotely operated underwater vehicle, the operator needs to monitor and control a number of parameters. If some of these parameters, as for instance position and attitude, could be controlled automatically, the teleoperation of the vehicle can be enormously facilitated. Based on experimental tests, it was verified that marine thrusters can exhibit dead-zone nonlinearities. This work describes the development of a variable structure control strategy for an underwater vehicle with a thrust system subject to dead-zone input. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Numerical Computation of Parametric Induced Roll Motions in Random Seas

For a vessel in open seas, the sudden appearance of roll motions due to waves from the front or rear leads to dangerous situations up to capsizing. The equations of motion used to analyze the roll motion include the righting lever curve. This curve is set up by means of hydrostatic calculations and approximated by polynomials for further analysis. The irregular waves are modeled in terms of a continuous-time ARMA process. The resulting model of stochastic differential equations is investigated numerically by Local Statistical Linearization. The necessary stochastic moments and their derivatives are computed using Itô's differential rule and Gaussian closure. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)