Phase transformation study of Cu2S

The phase transformations of crystalline Cu₂S in the temperature range 50?C to 600?C have been studied through electric quadrupole interactions of¹¹¹Cd impurities observed by time-differential perturbed angular correlations. The Cd is subject to no discernable quadrupolar interaction in the cubic phase above 430?C. In the hexagonal phase between approximately 103?C and 430?C, a single-site, weakly temperature dependent, axially symmetric quadrupolar interaction is found. At lower temperature, the structure is complex with a number of different sites. These data were taken with a microcomputer-controlled TDPAC spectrometer with logical steering that allows a standard 4-detector spectrometer to collect simultaneously 12 channels of data.     

An examination of the parameters that govern the acoustic behavior of sea bed sediments containing gas bubbles.

The acoustic properties of sea bed sediments containing occluded gas are dominated by the volume of gas contained in bubbles, the size of bubbles, and the elastic properties of the soil matrix. This study evaluated current theory developed by Anderson and Hampton to determine the sound speed and resonance frequency of gassy soils, and the models they used to determine the elastic properties of the soils. It compared calculated sound speeds, based on material properties simulated by the models, with measured sound speeds on "large bubble" laboratory soils produced in a similar manner to natural sea bed gassy soils. There was some evidence that the Anderson and Hampton equations accurately predicted sound speed at lower frequencies of bubbles resonance and below, but results were sensitive to inappropriate values for the elastic and damping properties of the soil. The bounds of sound speed based on the elastic properties of models that simulate "compressible fluid" or "suspension" behavior were grossly misleading when applied to large bubble soils. Conversely, sound speed based on models that correctly simulate the "bulk" or "matrix" properties of large bubble soils, at strain magnitudes and strain rates equivalent to acoustic signals, agreed well with measured data.     

Cosmological natural selection and the purpose of the universe

The cosmological natural selection (CNS) hypothesis holds that the fundamental constants of nature have been fine‐tuned by an evolutionary process in which universes produce daughter universes via the formation of black holes. Here, we formulate the CNS hypothesis using standard mathematical tools of evolutionary biology. Specifically, we capture the dynamics of CNS using Price's equation, and we capture the adaptive purpose of the universe using an optimization program. We establish mathematical correspondences between the dynamics and optimization formalisms, confirming that CNS acts according to a formal design objective, with successive generations of universes appearing designed to produce black holes. © 2013 Wiley Periodicals, Inc. Complexity 18: 48–56, 2013