Pressure dependence of size effects in superfluid 4He

We show that the depression of the fourth sound velocity due to size effects over the range 1.4 ? T ? 1.8 K and 0 ? P ? 25 bar can be represented by a function of the displacement thickness δ of Roberts et al. A simple phenomenological model yields values of the healing length which agree with δ within a normalization constant.     

On the heat capacity at constant volume near the superfluid transition

Available experimental results forC_ν nearT_λ are examined for consistency with other thermodynamic measurements, and are compared with current theories.     

The superfluid fraction near Tλ in dilute solutions of 3He in 4He

Existing second-sound velocity measurements are interpreted to imply an unexpectedly strong concentration dependence for the amplitude of $\text{?}{}_{\mathrm{s}}\text{?}$.     

Stability and stabilization of 2H martensite in Cu–Zn–Al single crystals

The stabilization of the 2H martensitic phase in Cu–Zn–Al single crystals with an electron concentration e/a?=?1.53 was investigated. This orthorhombic 2H martensite was first induced from the cubic β phase by the direct β?→?2H or the indirect β?→?18R?→?2H transformations. On loading the 2H martensite, a transition without hysteresis is observed at a stress which was denoted σ_T1. It was found that this stress is associated with a change in the behaviour of the 2H martensite. A high stabilization of the 2H martensite, around 300?K, is only obtained if an ageing is performed at a stress above σ_T1. Additionally, the stresses of the transformation to another martensitic phase, called 18R₂, were found to be constant when the value of σ_T1 is below the retransformation stress. The 2H martensite and its behaviour on ageing were studied by dilatometry, calorimetry, mechanical testing, optical microscopy and transmission electron microscopy (TEM). Models accounting for the stabilization of the 2H martensite on ageing are proposed.     

Transition to the ultimate state of turbulent Rayleigh-Bénard convection

Measurements of the Nusselt number Nu and of a Reynolds number Re(eff) for Rayleigh-Bénard convection (RBC) over the Rayleigh-number range 10(12)?Ra?10(15) and for Prandtl numbers Pr near 0.8 are presented. The aspect ratio Γ≡D/L of a cylindrical sample was 0.50. For Ra?10(13) the data yielded Nu∝Ra(γ(eff)) with γ(eff)?0.31 and Re(eff)∝Ra(ζ(eff)) with ζ(eff)?0.43, consistent with classical turbulent RBC. After a transition region for 10(13)?Ra?5×10(14), where multistability occurred, we found γ(eff)?0.38 and ζ(eff)=ζ?0.50, in agreement with the results of Grossmann and Lohse for the large-Ra asymptotic state with turbulent boundary layers which was first predicted by Kraichnan.     

Clustering in a precipitate-free GeMn magnetic semiconductor

We present the first study relating structural parameters of precipitate-free Ge0.95Mn0.05 films to magnetization data. Nanometer-sized clusters--areas with increased Mn content on substitutional lattice sites compared to the host matrix--are detected in transmission electron microscopy analysis. The films show no overall spontaneous magnetization at all down to 2 K. The TEM and magnetization results are interpreted in terms of an assembly of superparamagnetic moments developing in the dense distribution of clusters. Each cluster individually turns ferromagnetic below an ordering temperature which depends on its volume and Mn content.     

Metathesis at an Implausible Site: A Formal Total Synthesis of Rhizoxin D

The new approach to the anticancer agent rhizoxin D described herein does not cohere with the conventional logic of metathesis, according to which macrocycles are best closed at a disubstituted olefinic site; rather, the trisubstituted C11?C12 alkene flanked by an allylic ‐OH group served as the pivot point for synthesis. This motif was attained in good yield and excellent selectivity by a sequence of alkyne metathesis, trans‐hydrostannation and cross coupling. Because the exact same substructure is prominently featured in numerous other natural products, the underpinning strategy, though unusual, might bear more general relevance.