Modeling Grain Boundaries using a Phase Field Technique

We propose a two dimensional frame-invariant phase field model of grain impingement and coarsening. One dimensional analytical solutions for a stable grain boundary in a bicrystal are obtained, and equilibrium energies are computed. We are able to calculate the rotation rate for a free grain between two grains of fixed orientation. For a particular choice of functional dependencies in the model the grain boundary energy takes the same analytic form as the microscopic (dislocation) model of Read and Shockley.Comment: 4 pages, 2 figure

Economic and Environmental Impacts of Adoption of Genetically Modified Rice in California

Crop Production/Industries, Research and Development/Tech Change/Emerging Technologies,

Thermodynamic phase-field model for microstructure with multiple components and phases: the possibility of metastable phases

A diffuse-interface model for microstructure with an arbitrary number of components and phases was developed from basic thermodynamic and kinetic principles and formalized within a variational framework. The model includes a composition gradient energy to capture solute trapping, and is therefore suited for studying phenomena where the width of the interface plays an important role. Derivation of the inhomogeneous free energy functional from a Taylor expansion of homogeneous free energy reveals how the interfacial properties of each component and phase may be specified under a mass constraint. A diffusion potential for components was defined away from the dilute solution limit, and a multi-obstacle barrier function was used to constrain phase fractions. The model was used to simulate solidification via nucleation, premelting at phase boundaries and triple junctions, the intrinsic instability of small particles, and solutal melting resulting from differing diffusivities in solid and liquid. The shape of metastable free energy surfaces is found to play an important role in microstructure evolution and may explain why some systems premelt at phase boundaries and phase triple junctions while others do not.Comment: 14 pages, 8 figure

Realising the technological promise of smartphones in addiction research and treatment: An ethical review

Background Smartphone technologies and mHealth applications (or apps) promise unprecedented scope for data collection, treatment intervention, and relapse prevention when used in the field of substance abuse and addiction. This potential also raises new ethical challenges that researchers, clinicians, and software developers must address. Aims This paper aims to identify ethical issues in the current uses of smartphones in addiction research and treatment. Methods A search of three databases (PubMed, Web of Science and PsycInfo) identified 33 studies involving smartphones or mHealth applications for use in the research and treatment of substance abuse and addiction. A content analysis was conducted to identify how smartphones are being used in these fields and to highlight the ethical issues raised by these studies. Results Smartphones are being used to collect large amounts of sensitive information, including personal information, geo-location, physiological activity, self-reports of mood and cravings, and the consumption of illicit drugs, alcohol and nicotine. Given that detailed information is being collected about potentially illegal behaviour, we identified the following ethical considerations: protecting user privacy, maximising equity in access, ensuring informed consent, providing participants with adequate clinical resources, communicating clinically relevant results to individuals, and the urgent need to demonstrate evidence of safety and efficacy of the technologies. Conclusions mHealth technology offers the possibility to collect large amounts of valuable personal information that may enhance research and treatment of substance abuse and addiction. To realise this potential researchers, clinicians and app-developers must address these ethical concerns to maximise the benefits and minimise risks of harm to users

Is Sue and be Sued Language a Clear and Unambiguous Waiver of Immunity.

Because “sue and be sued” language is ambiguous at best, courts should not find that this language is a waiver of immunity. Under Texas law, governmental entities—including the state, its agencies, and political subdivisions—are entitled to sovereign immunity from both suit and liability. For sovereign immunity to be applicable to governmental entities, sovereign immunity applies unless the legislature has clearly and unambiguously waived it. Although numerous Texas appellate courts have held that “sue and be sued” language is a waiver of sovereign immunity, the Texas Supreme Court has squarely addressed the issue only once, in Missouri Pacific Railroad Co. v. Brownsville Navigation District. According to the Texas Supreme Court in Missouri Pacific, the “sue and be sued” language is a waiver of immunity from suit. Subsequent appellate cases following Missouri Pacific, however, disagree with the Texas Supreme Court’s decision. There are convincing arguments to be made that the Court in Missouri Pacific did not apply the clear and unambiguous standard that is now an unquestionable requirement of the law on sovereign immunity. Thus, the Court\u27s ruling in Missouri Pacific is ripe for reconsideration. Until the Texas Supreme Court revisits the issue or the legislature further addresses the matter, attorneys representing governmental entities will continue to argue that sue and be sued language is not a clear and unambiguous waiver of immunity from suit. Moreover, uncertainty about the meaning and effect of the language will continue to cloud both existing and prospective contracts between governmental entities and private parties

Is Sue and be Sued Language a Clear and Unambiguous Waiver of Immunity.

Because “sue and be sued” language is ambiguous at best, courts should not find that this language is a waiver of immunity. Under Texas law, governmental entities—including the state, its agencies, and political subdivisions—are entitled to sovereign immunity from both suit and liability. For sovereign immunity to be applicable to governmental entities, sovereign immunity applies unless the legislature has clearly and unambiguously waived it. Although numerous Texas appellate courts have held that “sue and be sued” language is a waiver of sovereign immunity, the Texas Supreme Court has squarely addressed the issue only once, in Missouri Pacific Railroad Co. v. Brownsville Navigation District. According to the Texas Supreme Court in Missouri Pacific, the “sue and be sued” language is a waiver of immunity from suit. Subsequent appellate cases following Missouri Pacific, however, disagree with the Texas Supreme Court’s decision. There are convincing arguments to be made that the Court in Missouri Pacific did not apply the clear and unambiguous standard that is now an unquestionable requirement of the law on sovereign immunity. Thus, the Court\u27s ruling in Missouri Pacific is ripe for reconsideration. Until the Texas Supreme Court revisits the issue or the legislature further addresses the matter, attorneys representing governmental entities will continue to argue that sue and be sued language is not a clear and unambiguous waiver of immunity from suit. Moreover, uncertainty about the meaning and effect of the language will continue to cloud both existing and prospective contracts between governmental entities and private parties

Atomistic Simulations of Metallic Cluster Coalescence

A new computational method is introduced to investigate the stresses developed in the island-coalescence stage of polycrystalline film formation during deposition. The method uses molecular dynamics to examine the behavior of clusters of atoms both in free space and on substrates. Continuum treatments used in previous models may not be applicable at small length scales or low dimensionality. In atomistic simulations, the effects of surface diffusion, bond straining and defect formation can be directly studied. TEM experiments will be used to evaluate the validity of the simulation model.Singapore-MIT Alliance (SMA

Metallic Cluster Coalescence: Molecular Dynamics Simulations of Boundary Formation

During the evaporative deposition of polycrystalline thin films, the development of a tensile stress at small film thicknesses is associated with island coalescence. Several continuum models exist to describe the magnitude of this tensile stress but the coalescence stress becomes significant at small enough thicknesses to draw the continuum models into question. For nanometer-sized islands, we perform atomistic simulations of island coalescence to determine if the atomistic methods and continuum models are mutually consistent. The additional detail provided by the atomistic simulations allows for study of the kinetics of island coalescence and the treatment of different crystallographic orientations. We find that the atomistic simulations are consistent with the continuum models. We also note that the atomistic simulations predict extremely fast coalescence times and include the possibility of island rotations during coalescence.Singapore-MIT Alliance (SMA

Percolation of diffusionally evolved two-phase systems

Percolation thresholds and critical exponents for universal scaling laws are computed for microstructures that derive from phase-transformation processes in two dimensions. The computed percolation threshold for nucleation and growth processes, p[subscript c] ≈0.6612, is similar to those obtained by random placement of disks and greater than that of spinodal decomposition, p[subscript c] ≈0.4987. Three critical exponents for scaling behavior were computed and do not differ significantly from universal values. The time evolution of a characteristic microstructural length was also computed: For spinodal decomposition, this length grows according to a power law after a short incubation period; for nucleation and growth, there are several transitions in the nature of the growth law. We speculate that the transitions in nucleation and growth derive from competing effects of coalescence at short times and then subsequent coarsening. Short-range order is present, but different, for both classes of microstructural evolution. © 2011 American Physical Society.National Science Foundation (U.S.) (Contract DMR-0855402