Switchable synchronisation of pirouetting motions in a redox-active [3]rotaxane

In this study, the crown/ammonium [3]rotaxane R2 is reported which allows a switchable synchronisation of wheel pirouetting motions. The rotaxane is composed of a dumbbell-shaped axle molecule with two mechanically interlocked macrocycles which are decorated with a redox-active tetrathiafulvalene (TTF) unit. Electrochemical, spectroscopic, and electron paramagnetic resonance experiments reveal that rotaxane R2 can be reversibly switched between four stable oxidation states (R2, R2˙+, R22(˙+), and R24+). The oxidations enable non-covalent, cofacial interactions between the TTF units in each state—including a stabilised mixed-valence (TTF2)˙+ and a radical-cation (TTF˙+)2 dimer interaction—which dictate a syn (R2, R2˙+, and R22(˙+)) or anti (R24+) ground state co-conformation of the wheels in the rotaxane. Furthermore, the strength of these wheel–wheel interactions varies with the oxidation state, and thus electrochemical switching allows a controllable synchronisation of the wheels’ pirouetting motions. DFT calculations explore the potential energy surface of the counter-rotation of the two interacting wheels in all oxidation states. The controlled coupling of pirouetting motions in rotaxanes can lead to novel molecular gearing systems which transmit rotational motion by switchable non-covalent interactions

Comparison of structure, regeneration and dead wood in virgin forest remnant and managed forest on Grmecˇ Mountain in Western Bosnia

This paper compares the forest structure, regeneration and distribution of dead wood in a virgin forest remnant and a close-to-nature managed beech–conifer mixture situated on Grmecˇ Mountain inWestern Bosnia. The investigations were carried out in a 1 ha permanent sample plot and 35 circular plots (20m radius) in the virgin forest and in 17 circular plots (25m radius) in managed forests. The number of trees in the managed forest was significantly ( p ¼ 0.05) higher than that in virgin forest and the distribution of the number of trees per diameter classes had a decreasing trend, but with a different shape in the virgin forest compared to the managed stands. In the lower diameter classes, the stock volume recorded in virgin forest was half of that in the managed forest, whilst for higher diameter classes the cumulated volume of the growing stock was almost double in virgin forest. The young crops had a significantly lower presence in the virgin forest and a larger volume of dead wood was identified in the virgin forest than in managed stands. The study results are important in assessing the consequences of close-to-nature management on the forest structure and regeneration when compared to the condition in virgin forests

A healthy diet in women is associated with less facial wrinkles in a large Dutch population-based cohort

Public Health and primary carePrevention, Population and Disease management (PrePoD

Increased scalp hair cortisol concentrations in obese children

Context: Pathologically increased cortisol exposure induces obesity, but it is not known whether relatively high cortisol within the physiological range is related to childhood obesity. Objective: The aim of the study was to compare hair cortisol concentrations between obese and normal-weight c

Ventricular response to dobutamine stress relates to the change in peak oxygen uptake during the 5-year follow-up in young patients with repaired tetralogy of Fallot

Cardiolog