From the latest PNAS:

A superior descriptor of random textures and its predictive capacity

Y Jiao et al

Two-phase random textures abound in a host of contexts, including porous and composite media, ecological structures, biological media, and astrophysical structures. Questions surrounding the spatial structure of such textures continue to pose many theoretical challenges. For example, can two-point correlation functions be identified that can be manageably measured and yet reflect nontrivial higher-order structural information about the textures? We present a solution to this question by probing the information content of the widest class of different types of two-point functions examined to date using inverse “reconstruction” techniques. This enables us to show that a superior descriptor is the two-point cluster function C2(r), which is sensitive to topological connectedness information. We demonstrate the utility of C2(r) by accurately reconstructing textures drawn from materials science, cosmology, and granular media, among other examples. Our work suggests a theoretical pathway to predict the bulk physical properties of random textures and that also has important ramifications for atomic and molecular systems.

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A new resolution standard for spherical and chromatic aberration corrected electron microscopy has apparently been set; here is the commentary.

A few papers from scripta

October 7, 2009

[1] Do bainitic and Widmanstätten ferrite grow with different mechanisms?

M Hillert et al

Caballero et al. recently presented new evidence for different growth mechanisms of Widmanstätten and bainitic ferrite. The argument was based on Zener’s hypothesis of diffusionless growth of bainitic ferrite. It is now demonstrated that Bhadeshia’s model, based on Zener’s hypothesis, predicts that some of the new measurements, claimed to fall above Bs and to be due to Widmanstätten ferrite, actually fall within the predicted temperature range of bainite, indicating that they cannot be used as new support for Bhadeshia’s model.

[2] Nucleation of nanosize particles following the spinodal decomposition in the pseudo-ternary Ge0.6Sn0.1Pb0.3Te compound

B Dado et al

Demixing following a spinodal decomposition, takes place in Sn-lean compounds in the pseudo-ternary (Ge, Sn, Pb)Te system, giving rise to both Pb- and Ge-rich telluride areas. After quenching from the high-temperature single cubic phase in the course of an aging treatment at 663 K, a Ge0.6Sn0.1Pb0.3Te sample undergoes several microstructural stages. The last stage consists of nucleation and growth of nanosize particles which maintain their dimensional stability for relatively extended periods of time.

[3] Twin boundary nucleation and motion in Ni–Mn–Ga magnetic shape memory material with a low twinning stress

E Aaltio et al

The twin boundary motion in the Ni–Mn–Ga single crystal 10M martensite magnetic shape memory material was studied by mechanical twinning stress and magnetic measurements at ambient temperature. The compressive stress required to trigger the movement of the twin boundaries was higher in the sample with the single variant state than in that with the multivariant state. Magnetometer measurements confirmed that the energy needed to move the twin boundaries in a high-quality single crystal 10M Ni–Mn–Ga is lower than that for the nucleation of a twin boundary.