Towards Dynamic Control of Wettability by Using Functionalized Altitudinal Molecular Motors on Solid Surfaces

We report the synthesis of altitudinal molecular motors that contain functional groups in their rotor part. In an approach to achieve dynamic control over the properties of solid surfaces, a hydrophobic perfluorobutyl chain and a relatively hydrophilic cyano group were introduced to the rotor part of the motors. Molecular motors were attached to quartz surfaces by using interfacial 1,3‐dipolar cycloadditions. To test the effect of the functional groups on the rotary motion, photochemical and thermal isomerization studies of the motors were performed both in solution and when attached to the surface. We found that the substituents have no significant effect on the thermal and photochemical processes, and the functionalized motors preserved their rotary function both in solution and on a quartz surface. Preliminary results on the influence of the functional groups on surface wettability are also described.     

Systematics of inner-shell photo-ionization X-ray lasers with constant pump rates

Population-rate equations are analytically solved for constant pump rates. Conditions for population inversions are developed for this simplified case. Numbers appropriate for inner-shell photo-ionization of magnesium and neon are used. These allow back-of-the envelope calculations for predicting lasing duration. Pump-rate thresholds are also given which permit lasing for the duration of the pumping. Blackbody-source temperatures associated with such pump rates are calculated. A method of using the solution of the small-signal population-rate equations to determine the saturated intensity when the lower lasing level has a decay channel is given. This method is applied to the case of constant pump rates. An analytic expression for the saturated intensity is developed for this case.     

Asymmetric NMR spectra of weakly coupled nuclei: A common characteristic in the 13C NMR spectra of [U-13C]-labeled molecules and in natural abundance protoncoupled 13C spectra

Typically encountered proton-decoupled spectra of [U-¹³C]-labeled molecules or proton-coupled spectra of natural abundance or singly labeled molecules contain many nuclei which satisfy the weak coupling approximation. The spectra of such nuclei are frequently highly asymmetric and often appear to exhibit the skewed intensity distribution characteristic of strongly coupled spins. Analysis of typical cases indicates that such effects arise in the presence of at least one moderately strong coupling interaction in the spin system (Jδν ～ 1/3), and the apparent intensity asymmetry reflects small differences in the spacing of unresolved components of the observed resonance. This effect is analogous to the case of ‘virtual coupling’ in which weakly coupled spins cannot be analyzed as first order spectra; however; the ABX spin system which generally serves as a model for such systems does not predict the existence of spectral asymmetry for the X resonances. Prediction of this asymmetry requires a spin system of at least four spins with at least ABMX complexity, and can be treated generally using the effective Hamiltonian approach of Poeple and Schaefer.     

Ueber die Polarfiguren der ebenen Curven dritter Ordnung

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