Morphological instability, evolution, and scaling in strained epitaxial films: An amplitude equation analysis of the phase field crystal model

Morphological properties of strained epitaxial films are examined through a mesoscopic approach developed to incorporate both the film crystalline structure and standard continuum theory. Film surface profiles and properties, such as surface energy, liquid-solid miscibility gap and interface thickness, are determined as a function of misfit strains and film elastic modulus. We analyze the stress-driven instability of film surface morphology that leads to the formation of strained islands. We find a universal scaling relationship between the island size and misfit strain which shows a crossover from the well-known continuum elasticity result at the weak strain to a behavior governed by a "perfect" lattice relaxation condition. The strain at which the crossover occurs is shown to be a function of liquid-solid interfacial thickness, and an asymmetry between tensile and compressive strains is observed. The film instability is found to be accompanied by mode coupling of the complex amplitudes of the surface morphological profile, a factor associated with the crystalline nature of the strained film but absent in conventional continuum theory.Comment: 16 pages, 10 figures; to be published in Phys. Rev.

Entanglement and the modern Australian rhythm method: Lantana's lessons in policing sexuality and gender

Film in Australia, as with many other nations, is often seen as an important cultural medium where national stories about belonging and identity can be (re)produced in pleasurable and, at times, complicated ways. One such film is Ray Lawrence’s Lantana. Although striking a chord in Australia as a good film about ‘ basically good people’, people that rang ‘brilliantly’ true (Lantana DVD 2002), this paper argues that, at the same time as it produces a fantasy of a ‘good’ Australia, the film also conducts a regulation of what constitutes Australianness. In many ways the imaginary of Australia offered in this film, to its contemporary, urban, professional and intellectual elite audience, still draws on and (re)produces a vision of an Australian community that uses the same narrative frameworks of protection and control as the cruder discourses of ‘white Australia’ offered to an earlier generation of cinema-goers. This film’s central motif of the lantana bush, the out of control weed, that is known as both foreign and local is here emblematic of tensions about belonging, place and otherness. Yet while, within the film’s knowingly reflexive purview any remaining potential for racism is understood and itself under control – we know how to be good mutliculturalists –it is the trope of sexuality in Lantana that provides the real sense of edginess and anxiety about belonging. It is in this arena that the film sets up an idea of danger and –less self-consciously, and in the end more aggressively – marks out who is and who is not part of the community. In this context the motif of lantana signals an ambivalence about difference and the exotic. Lantana is both desirable because of the difference in its attractive Latin looks and repulsive or feared because of other qualities inherent within its difference: a refusal to behave and a propensity to get out-of control, spread and potentially take over. The film here explores desire for a taste of the other (a gay man, a newly separated woman, a Latin dance teacher). However, these fantasies are in the end emphatically shut down as the film ends by producing a vision of subtly normalised hetero, mono, familial (though not necessarily happy) forms of desiring, loving and reproducing in contemporary Australia

Phase field crystal dynamics for binary systems: Derivation from dynamical density functional theory, amplitude equation formalism, and applications to alloy heterostructures

The dynamics of phase field crystal (PFC) modeling is derived from dynamical density functional theory (DDFT), for both single-component and binary systems. The derivation is based on a truncation up to the three-point direct correlation functions in DDFT, and the lowest order approximation using scale analysis. The complete amplitude equation formalism for binary PFC is developed to describe the coupled dynamics of slowly varying complex amplitudes of structural profile, zeroth-mode average atomic density, and system concentration field. Effects of noise (corresponding to stochastic amplitude equations) and species-dependent atomic mobilities are also incorporated in this formalism. Results of a sample application to the study of surface segregation and interface intermixing in alloy heterostructures and strained layer growth are presented, showing the effects of different atomic sizes and mobilities of alloy components. A phenomenon of composition overshooting at the interface is found, which can be connected to the surface segregation and enrichment of one of the atomic components observed in recent experiments of alloying heterostructures.Comment: 26 pages, 5 figures; submitted to Phys. Rev.

Snowex 2017 Community Snow Depth Measurements: A Quality-Controlled, Georeferenced Product

Snow depth was one of the core ground measurements required to validate remotely-sensed data collected during SnowEx Year 1, which occurred in Colorado. The use of a single, common protocol was fundamental to produce a community reference dataset of high quality. Most of the nearly 100 Grand Mesa and Senator Beck Basin SnowEx ground crew participants contributed to this crucial dataset during 6-25 February 2017. Snow depths were measured along ~300 m transects, whose locations were determined according to a random-stratified approach using snowfall and tree-density gradients. Two-person teams used snowmobiles, skis, or snowshoes to travel to staked transect locations and to conduct measurements. Depths were measured with a 1-cm incremented probe every 3 meters along transects. In shallow areas of Grand Mesa, depth measurements were also collected with GPS snow-depth probes (a.k.a. MagnaProbes) at ~1-m intervals. During summer 2017, all reference stake positions were surveyed with <10 cm accuracy to improve overall snow depth location accuracy. During the campaign, 193 transects were measured over three weeks at Grand Mesa and 40 were collected over two weeks in Senator Beck Basin, representing more than 27,000 depth values. Each day of the campaign depth measurements were written in waterproof field books and photographed by National Snow and Ice Data Center (NSIDC) participants. The data were later transcribed and prepared for extensive quality assessment and control. Common issues such as protocol errors (e.g., survey in reverse direction), notebook image issues (e.g., halo in the center of digitized picture), and data-entry errors (sloppy writing and transcription errors) were identified and fixed on a point-by-point basis. In addition, we strove to produce a georeferenced product of fine quality, so we calculated and interpolated coordinates for every depth measurement based on surveyed stakes and the number of measurements made per transect. The product has been submitted to NSIDC in csv format. To educate data users, we present the study design and processing steps that have improved the quality and usability of this product. Also, we will address measurement and design uncertainties, which are different in open vs. forest areas