Functional liquid crystal films selectively recognize amine vapours and simultaneously change their colour

During recent years, cholesteric liquid crystals have found only a few applications, one of them being temperature detection; in this study, however, we intend to show that the combination of cholesteric liquid crystals and molecules with a trifluoroacetyl function can be applied to optically detect amine vapours.     

Catalytic enantioselective stereoablative reactions: an unexploited approach to enantioselective catalysis

Approaches to the preparation of enantioenriched materials via catalytic methods that destroy stereogenic elements of a molecule are discussed. Although these processes often decrease overall molecular complexity, there are several notable advantages including material recycling, enantiodivergence and convergence, and increased substrate scope. Examples are accompanied by discussion of the critical design elements required for the success of these methods.     

(tBu2SnAsH)2 und (tBu2SnAsH)3: Zwei neue ring-oligomere Stannylarsine

(^tBu₂SnAsH)₂ and (^tBu₂SnAsH)₃: Two Novel Ring-Oligomeric Stannylarsines ^tBu₂SnCl₂ reacts with NaAsH₂ in liquid ammonia to give the four-membered As–H-functional stannylarsine (^tBu₂SnAsH)₂ ( 1 ). The oligomeric six-membered heterocycle (^tBu₂SnAsH)₃ ( 2 ) is obtained by transamination of ^tBu₂Sn(NH^tBu)₂ with AsH₃. The novel compounds are characterized by NMR (¹H, ¹¹⁹Sn) and mass spectroscopy and their molecule structures determined by X-ray crystallography. In the solid state both compounds contain molecules with planar tin-arsenic rings ( 1 : space group P2₁/n, Z = 2; 2 : space group P6₃/m, Z = 2).     

Understanding the Dynamic Behaviour of a Tennis Racket under Play Conditions

The ‘feel’ of tennis rackets is of increasing importance to manufacturers seeking product differentiation in a context where further performance enhancements are prevented by a combination of mechanical limits and regulations imposed to protect the integrity of the sport. Vibrations excited during a shot contribute greatly to the perception of ‘feel’. Previous studies have been reported but none has covered the full set of mode families or the frequency range in this study. In-plane vibrations associated with the routine use of topspin shots in modern tennis have not been documented so far in the literature. To consider modal behaviour, multiple measurements during play conditions are required but this is practically impossible. This paper proposes an alternative approach and successfully relates a comprehensive modal analysis on a freely suspended racket to vibration measurements under play conditions. This is achieved through an intermediate stage comprising a necessarily more limited modal analysis on a hand-gripped racket and use of the mass modification modal analysis tool. This stage confirmed the prevailing view that hand-gripping can be considered as a mass modification distributed along the handle of the freely suspended racket but the associated mass was much lower than that of an actual hand and the hand also increased the damping ratio of frame modes significantly. Furthermore, in frame vibration measurements during forehand groundstrokes, a greater reduction in bending mode frequencies was observed, consistent with a mass-loading of around 25 % of the actual hand as a consequence of the tighter grip. In these play tests, the first two bending modes, the first torsional mode, the first eight stringbed modes, the first three hoop modes and the third in-plane bending mode were identified, with the stringbed modes being particularly prominent.     

Preparation and structural characterization of rare-earth doped lead lanthanum zirconate titanate ceramics

A new preparation route towards rare-earth (RE) doped polycrystalline lead lanthanum zirconate titanate (PLZT) ceramics (RE = Y³⁺, Nd³⁺, Yb³⁺), based on the use of doped lanthanum oxide or zirconia, is reported. Structural characterization by X-ray powder diffraction reveals that secondary phase formation can be substantially diminished in comparison to conventional preparation methods. The distribution of the rare-earth dopants was investigated as a function of concentration by static ²⁰⁷Pb spin echo NMR spectra, using Fourier Transformation of Carr–Purcell–Meiboom–Gill spin echo trains. For the Nd- and Yb-doped materials, the interaction of the ²⁰⁷Pb nuclei with the unpaired electron spin density results in significant broadening and shifting of the NMR signal, whereas these effects are absent in the diamagnetic Y³⁺ doped materials. Based on different concentration dependences of the NMR lineshape parameters, we conclude that the structural role of the Nd³⁺ dopants differs significantly from that of Yb³⁺. While the Nd³⁺ ions appear to be statistically distributed in the PLZT lattice, incorporation of Yb³⁺ into PLZT appears to be limited by the appearance of doped cubic zirconia as a secondary phase.