The first and second cinchona rearrangement. Two fundamental transformations of alkaloid chemistry

Stereochemistry, products, and driving forces of the "first and second Cinchona rearrangement" have been investigated and a unified theory is presented. The first cage expansion affords [3.2.2]azabicyclic alpha-amino ether and is formulated via a configurationally stable bridgehead iminium ion and quasiequatorial nucleophilic attack. The second cage expansion affords beta-functionalized [3.2.2]azabicycles. In this case a nonclassical nitrogen-bridged cation is postulated to account for retention of configuration and potential reversibility of the cage expansion. The second rearrangement is favored for the so-called cinch bases (6'-R = H) in trifluoroethanol. Stereoelectronic factors, electron demand at C9, ground state conformation, and solvent type are crucial in all cases. A two-step protocol for preparing 9-epi-configured Cinchona alkaloids from 9-nat precursors is described.     

An efficient method for the fabrication of temperature-sensitive hydrogel microactuators

In this article a new method for the photolithographical deposition of temperature-sensitive hydrogels is presented. The method can be used in conjunction with standard 365 nm UV-photolithography to accurately dimension and position temperature-sensitive hydrogel microactuators in a highly parallel fashion. A number of characteristics of the hydrogels were investigated. These include: the photolithographical reproduction quality, the effect of the crosslinking density in the hydrogels on their swelling behavior, the swelling hysteresis behavior, the effect of dimensional constraints on the swelling of the hydrogels and the effect of copolymerization with an ionizable comonomer on the temperature behavior of the hydrogels. The method presents a considerable improvement in the microfabrication of temperature-sensitive hydrogel microactuators and has potential for the mass-fabrication of these interesting microactuators.     

Does ignorance promote norm compliance?

A large extent of undetected norm violations may have positive effects for society. If many norm violations are hidden, society seems to be in good order so that actors are more willing to comply with the norms themselves. In this sense, ignorance promotes norm compliance. We challenge this view by arguing that in scenarios, in which norms are controlled and enforced by third parties who receive rewards for their success, the opposite is true: Ignorance promotes norm violations. The reason is that unsuspicious inspectors who believe that little hidden norm violations are committed will spend less effort for detection, some formerly detected norm violations will go undetected, norm targets will be less deterred from the lower detection probability and will commit more norm violations over time. This article develops a respective mathematical model and confirms the above described intuition.     

Chemical bonding in view of electron charge density and kinetic energy density descriptors

Stalke's dilemma, stating that different chemical interpretations are obtained when one and the same density is interpreted either by means of natural bond orbital (NBO) and subsequent natural resonance theory (NRT) application or by the quantum theory of atoms in molecules (QTAIM), is reinvestigated. It is shown that within the framework of QTAIM, the question as to whether for a given molecule two atoms are bonded or not is only meaningful in the context of a well‐defined reference geometry. The localized‐orbital‐locator (LOL) is applied to map out patterns in covalent bonding interaction, and produces results that are consistent for a variety of reference geometries. Furthermore, LOL interpretations are in accord with NBO/NRT, and assist in an interpretation in terms of covalent bonding. © 2008 Wiley Periodicals, Inc.J Comput Chem, 2009.     

On the analysis of intermediate–energy Coulomb excitation experiments

In a recent publication [C.A. Bertulani, G. Cardella, M. De Napoli, G. Raciti, E. Rapisarda, Phys. Lett. B 650 (2007) 233] the validity of analysis methods used for intermediate-energy Coulomb excitation experiments was called into question. Applying a refined theory large corrections of results in the literature seemed needed. We show that this is not the case and that the large deviations observed in above mentioned reference are due to the use of the wrong experimental parameters in that publication. We furthermore show that an approximate expression derived in above mentioned reference is in fact equivalent to the theory of Winther and Alder, an analysis method often used in the literature.     

Analyzing the sustainability of harvesting behavior and the relationship to personality traits in a simulated Lotka–Volterra biotope

For the analysis presented in this paper we use experiments to study human behavior in a simulation environment based on a simple Lotka–Volterra predator–prey ecology. The aim is to study the influence of different harvesting strategies and of certain personality traits derived from the Hamburg Personality Inventory (HPI) [Andresen, B., 2002. HPI – Hamburger Persönlichkeitsinventar. Hogrefe, Göttingen] on the outcome in terms of sustainability and economic performance.     

Preparation and Conformation of Organo‐Bridged Bis[tris(arylchalcogenolato)tin] Compounds – An Experimental and Quantum Chemical Study

Seven organo‐bridged bis[tris(arylchalcogenolato)tin] compounds with the general formulae (R′E)₃Sn–R–Sn(ER′)₃ (R = –(CH₂)₄–, 1,4‐bis(methyl)benzene, 4,4′‐bis(methyl)biphenyl; R′ = Ph, 1‐Np, 2‐Np; E = S, Se) were synthesized and characterized by means of X‐ray diffractometry as well as NMR spectroscopy. Three different conformations of the arylchalcogenolato groups ER′ with respect to the bridging group R were rationalized and explained by means of quantum chemical investigations.