Marine-derived fungi: a chemically and biologically diverse group of microorganisms

A diverse array of secondary metabolites have been isolated and characterized from marine-derived fungi. The structures and biological activities of these metabolites are presented. Additionally, some basic principles of mycology are covered. Overall, 273 structures are presented and the review contains 162 references     

Natural Product-Derived Phosphonic Acids as Corrosion Inhibitors for Iron and Steel

Organic acids, typically derived from an oil-based value chain, are frequently used as corrosion inhibitors in industrial metal working fluids. The criteria for selection of these corrosion inhibitors have changed in the last decades, and are today not only performance-driven, but influenced by ecological considerations, toxicity and regulatory standards. We present scalable semisynthetic approaches to organic corrosion inhibitors based on phosphonic acids from renewable resources. They have been evaluated by chip filter assay, potentiodynamic polarization measurements, electrochemical impedance measurements and gravimetry for corrosion protection of iron and steel in an aqueous environment at slightly alkaline pH. The efficacy of several phosphonic acids tested was found to be strongly dependent on structural features influencing molecular self-assembly of protective layers, and the solubility of salts formed with di- and trivalent cations from the media or formed during corrosion. A carboxyphosphonic acid (derived from castor oil) was found to have remarkable anticorrosive effects in all media tested. We attribute the anticorrosion properties of this carboxyphosphonic acid to the formation of particularly stable protective layers on the metal surface. It might thus serve as a commercially attractive substitute for current acidic corrosion inhibitors, derived from renewable resources.     

A Functional Model of Cytochrome c Oxidase: Thermodynamic Implications

The environment of the Cu ^I ion in the distal ligand group decides the fate of the reduction of O₂ by the two analogues 1 and 2 of the heme a₃ Cu_B center in cytochrome c oxidase. The fourfold coordination by N in 1 favors the Cu^II oxidation state and leads to a 4 e⁻–4 H⁺ reduction and the formation of H₂O under physiological conditions, while with 2 a 2 e⁻–2 H⁺ reduction occurs to form the cytotoxic H₂O₂.     

On the second cohomology group in semi-abelian categories

We develop some new aspects of cohomology in the context of semi-abelian categories: we establish a Hochschild-Serre 5-term exact sequence extending the classical one for groups and Lie algebras; we prove that an object is perfect if and only if it admits a universal central extension; we show how the second Barr-Beck cohomology group classifies isomorphism classes of central extensions; we prove a universal coefficient theorem to explain the relationship with homology.     

Modeling slow deformation of polygonal particles using DEM

We introduce two improvements in the numerical scheme to simulate collision and slow shearing of irregular particles. First, we propose an alternative approach based on simple relations to compute the frictional contact forces. The approach improves efficiency and accuracy of the Discrete Element Method （DEM） when modeling the dynamics of the granular packing. We determine the proper upper limit for the integration step in the standard numerical scheme using a wide range of material parameters. To this end, we study the kinetic energy decay in a stress controlled test between two particles. Second, we show that the usual way of defining the contact plane between two polygonal particles is, in general, not unique which leads to discontinuities in the direction of the contact plane while particles move. To solve this drawback, we introduce an accurate definition for the contact plane based on the shape of the overlap area between touching particles, which evolves continuously in time.     

Multidimensional optimization of structural changes of molecules upon lonization in Franck-Condon factor calculations

Two different iterative methods, namely, the conjugate gradients method and the pattern search method, are applied to Franck-Condon factor calculations using the Coon et al. method (J. B. Coon, R. E. DeWames, and C. M. Loyd, J. Mol. Spectrosc.8, 235–299 (1962)) and the generating function method (T. E. Sharp and H. M. Rosenstock, J. Chem. Phys.41, 3453–3463 (1964); R. Botter, V. H. Dibeler, J. A. Walker, and H. M. Rosenstock, J. Chem. Phys.44, 1271–1278 (1966)). In such treatment, either the changes in normal coordinates or the changes in internal symmetry displacement coordinates are refined automatically until the weighted sum of square deviation between the calculated and the observed Franck-Condon factors is minimized. Some properties of the methods used are given and their applications to several cases are discussed in detail.