The GraVent DDT database

An open-access online platform containing data from experiments on deflagration-to-detonation transition conducted at the Institute of Thermodynamics, Technical University of Munich, has been developed and is accessible at http://www.td.mw.tum.de/ddt. The database provides researchers working on explosion dynamics with data for theoretical analyses and for the validation of numerical simulations.     

Second generation of primaquine ureas and bis-ureas as potential antimycobacterial agents

Molecular Diversity - Here, we describe design and synthesis of twelve novel compounds bearing primaquine motif and hydroxy- or halogenamine linked by an urea or bis-urea spacer. Preparation of...     

A Dogma in Doubt: Hydrolysis of Equatorial Ligands of PtIV Complexes under Physiological Conditions

Due to their high kinetic inertness and consequently reduced side reactions with biomolecules, Pt^IV complexes are considered to define the future of anticancer platinum drugs. The aqueous stability of a series of biscarboxylato Pt^IV complexes was studied under physiologically relevant conditions. Unexpectedly and in contrast to the current chemical understanding, especially oxaliplatin and satraplatin complexes underwent fast hydrolysis in equatorial position (even in cell culture medium and serum). Notably, the resulting hydrolysis products strongly differ in their reduction kinetics, a crucial parameter for the activation of Pt^IV drugs, which also changes the anticancer potential of the compounds in cell culture. The discovery that intact Pt^IV complexes can hydrolyze at equatorial position contradicts the dogma on the general kinetic inertness of Pt^IV compounds and needs to be considered in the screening and design for novel platinum‐based anticancer drugs.     

Conformal Operators on Forms and Detour Complexes on Einstein Manifolds

For even dimensional conformal manifolds several new conformally invariant objects were found recently: invariant differential complexes related to, but distinct from, the de Rham complex (these are elliptic in the case of Riemannian signature); the cohomology spaces of these; conformally stable form spaces that we may view as spaces of conformal harmonics; operators that generalise Branson’s Q-curvature; global pairings between differential form bundles that descend to cohomology pairings. Here we show that these operators, spaces, and the theory underlying them, simplify significantly on conformally Einstein manifolds. We give explicit formulae for all the operators concerned. The null spaces for these, the conformal harmonics, and the cohomology spaces are expressed explicitly in terms of direct sums of subspaces of eigenspaces of the form Laplacian. For the case of non-Ricci flat spaces this applies in all signatures and without topological restrictions. In the case of Riemannian signature and compact manifolds, this leads to new results on the global invariant pairings, including for the integral of Q-curvature against the null space of the dimensional order conformal Laplacian of Graham et al.     

Turbulence structure in a diabatically heated forest canopy composed of fractal Pythagoras trees

We investigate the turbulent flow through a heterogeneous forest canopy by high-resolution numerical modeling. For this purpose, a novel approach to model individual trees is implemented in our large-eddy simulation (LES). A group of sixteen fractal Pythagoras trees is placed in the computational domain and the tree elements are numerically treated as immersed boundaries. Our objective is to resolve the multiscale flow response starting at the diameter of individual tree elements up to the depth of the atmospheric surface layer. A reference run, conducted for the forest flow under neutral thermal stratification, produces physically meaningful turbulence statistics. Our numerical results agree quantitatively with data obtained from former field-scale LESs and wind tunnel experiments. Furthermore, the numerical simulations resolve vortex shedding behind individual branches and trunks as well as the integral response of the turbulent flow through the heterogeneous forest canopy. A focus is the investigation of the turbulence structure of the flow under stable thermal stratification and in response to the heating of the fractal tree crowns. For the stratified flows, statistical quantities, e.g. turbulent kinetic energy and vorticity, are presented and the turbulent exchange processes of momentum and heat are considered in detail. The onset and formation of coherent structures such as elevated shear layers above the diabatically heated forest canopy are analyzed. For the stably stratified flow, temperature ramps above the forest canopy were simulated in agreement with previous observations. Thermally driven vortices with a typical diameter of the canopy height were simulated when the tree crowns were diabatically heated. The impact of the coherent flow structures on the heat flux is investigated.     

Preparation of undecamethylated and hexamethylated 1‐halocarba‐closo‐dodecaborate anions

We report an improved synthesis of 1‐halocarba‐closo‐dodecaborate anions 1‐Hal–CB₁₁H and their efficient conversion to the undecamethylated anions 1‐Hal–CB₁₁Me (Hal = Cl, Br, I) and the hexamethylated anions 1‐Hal‐(7–12)‐(CH₃)₆–CB₁₁H (Hal = F, Cl) by treatment with methyl triflate in sulfolane in the presence of calcium hydride to remove the triflic acid byproduct. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:217–223, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20224     

High-pressure foaming properties of carbon dioxide-saturated emulsions

The aeration of emulsions with tailored properties and structure is of widespread importance in processing of foods and cosmetics. This report addresses the micro-cellular foam formation of carbon dioxide-saturated oil-in-water emulsions triggered by the application of a controlled pressure drop. The experimental setup combines a stirred pressure vessel with a pressure cell-equipped rheometer and pneumatic expansion valves. This allows to systematically study the process of gas dissolution, bubble nucleation, and growth under defined pressure, temperature, and flow conditions. Investigations on the impact of relevant process parameters show that dissolved gas fraction, emulsion viscosity, and shear rate have a major influence on foam formation. Dissolution of carbon dioxide leads to a viscosity reduction of the emulsion which and is described by a viscosity reduction factor. The point of bubble nucleation is derived from rheological patterns during depressurization. Experiments show that lower emulsion viscosity and higher shear rate favor bubble nucleation upon pressure release. Rheological results are supported by video analysis as the setup allows capturing nucleation, growth, and destabilization of bubbles as a function of pressure, supersaturation, and time. The results of this work yield the understanding of the high-pressure foaming mechanism from a rheological perspective and foster the design of such processes.