Probabilistic Feature Attention as an Alternative to Variables in Phonotactic Learning

Since Halle (1962), explicit algebraic variables (often called alpha notation) have been commonplace in phonological theory. However, Hayes and Wilson (2008) proposed a variable-free model of phonotactic learning, sparking a debate about whether such algebraic representations are necessary to capture human phonological acquisition. While past experimental work has found evidence that suggested a need for variables in models of phonology (Berent et al. 2012, Moreton 2012, Gallagher 2013), this paper presents a novel mechanism, Probabilistic Feature Attention (PFA), that allows a variable-free model of phonotactics to predict a number of these phenomena. Additionally, experimental results involving phonological generalization that cannot be explained by variables are captured by this novel approach. These results cast doubt on whether variables are necessary to capture human-like phonotactic learning and provide a useful alternative to such representations.

Experimental constraints on dynamic fragmentation as a dissipative process during seismic slip

Various fault damage fabrics, from gouge in the principal slip zone to fragmented and pulverized rocks in the fault damage zone, have been attributed to brittle deformation at high strain rates during earthquake rupture. Past experimental work has shown that there exists a critical threshold in stress–strain rate space through which rock failure transitions from failure along a few discrete fracture planes to intense fragmentation. We present new experimental results on Arkansas Novaculite (AN) and Westerly Granite (WG) in which we quantify fracture surface area produced by dynamic fragmentation under uniaxial compressive loading and examine the controls of pre-existing mineral anisotropy on dissipative processes at the microscale. Tests on AN produced substantially greater new fracture surface area (approx. 6.0 m 2 g −1 ) than those on WG (0.07 m 2 g −1 ). Estimates of the portion of energy dissipated into brittle fracture were significant for WG (approx. 5%), but appeared substantial in AN (10% to as much as 40%). The results have important implications for the partitioning of dissipated energy under extreme loading conditions expected during earthquakes and the scaling of high-speed laboratory rock mechanics experiments to natural fault zones. This article is part of the themed issue ‘Faulting, friction and weakening: from slow to fast motion’.

Improvisation as a Way of Knowing

This paper proposes a theory of improvisation as a way of knowing. Different musicians may know about similar musical structures in different ways; different ways of knowing facilitate particular kinds of perception and cognition that underlie different performance behaviors. Some of these ways of knowing can facilitate improvisatory performance practices. The details of these improvisatory ways of knowing can be characterized by psychological and neuroscientific experimental work that compares differences in perception and cognition between groups of musicians depending on their training methods and performance experiences. In particular, perception-action coupling is a promising place to begin making such comparisons. This approach provides an alternative operationalization of improvisation for scientific study that is not susceptible to the problems that arise when describing cognitive processes in culturally contingent and music-theoretically relative terms such as novelty, spontaneity, and freedom, as past experimental work has done. Its hypotheses are also more readily falsifiable. This perspective can also connect an understanding of musical improvisation to other domains of improvisation and to historical and ethnomusicological work, as well as square it with more general theories in cognitive science, such as perception-action coupling. Finally, such a formulation has productive implications for work on improvisation thatdoesengage with concepts like novelty, spontaneity, and freedom that are traditionally invoked in improvisation discourse.

Static Mode Seeding of Summer Cumuli—A Review

A review of the state of knowledge of the physics of the static mode seeding hypothesis for convective clouds is presented. The central thesis of the review is that the results of past experimental work are diverse but valid and that credibility of the science depends on understanding the physical reasons for the diverse results. Areas of uncertainty and conflicts in evidence associated with the statement of physical hypothesis, the concept of seedability, the seeding operation, and the chain of physical events following seeding are highlighted to identify what issues need to be resolved to further progress in precipitation enhancement research and application. It is concluded that the only aspect of static seeding that meets scientific standards of cause-and-effect relationships and repeatability is that glaciogenic seeding agents can produce distinct “seeding signatures” in clouds. However, the reviewer argues that a body of inferential physical evidence has been amassed that provides a better understanding of which clouds are seedable (susceptible to precipitation enhancement by artificial seeding) and which are not, even though the tools for recognizing and properly treating them are imperfect. In particular, the inferred evidence appears to support the claims of physical plausibility for the positive statistical results of the Israeli experiments. It is suggested that future work continue to be designed for physical understanding and evaluation through comprehensive field studies and numerical modeling. Duplicating the Israeli experiments in another location should receive high priority but, in general, future experiments should move upscale from cumulus congestus to convective complexes. In doing so, a new, more complex physical hypothesis that accounts for cloud–environment and microphysical–dynamical interactions and their response to seeding will have to be developed.

On combustion generated noise

Upon review of past experimental results and theoretical efforts it is apparent that the mechanism by which combustion noise is generated is not well understood. A theory of combustion noise is developed in this paper which follows rigorously from the principles of fluid mechanics. Lighthill's approach, used in his studies of aerodynamic noise, is closely followed in the present work. The sound radiated from open, turbulent flames is found to depend strongly upon the structure of such flames; at present their structure is not well known. However, meaningful bounds and scaling rules for the sound power output and spectral content are derived based upon the present limited knowledge. A framework is developed which explains past experimental work and the origin of combustion noise.