Lattice Green's function for crystals containing a planar interface

Flexible boundary condition methods couple an isolated defect to a harmonically responding medium through the bulk lattice Green's function; in the case of an interface, interfacial lattice Green's functions. We present a method to compute the lattice Green's function for a planar interface with arbitrary atomic interactions suited for the study of line defect/interface interactions. The interface is coupled to two different semi-infinite bulk regions, and the Green's function for interface-interface, bulk-interface and bulk-bulk interactions are computed individually. The elastic bicrystal Green's function and the bulk lattice Green's function give the interaction between bulk regions. We make use of partial Fourier transforms to treat in-plane periodicity. Direct inversion of the force constant matrix in the partial Fourier space provides the interface terms. The general method makes no assumptions about the atomic interactions or crystal orientations. We simulate a screw dislocation interacting with a $(10\bar{1}2)$ twin boundary in Ti using flexible boundary conditions and compare with traditional fixed boundary conditions results. Flexible boundary conditions give the correct core structure with significantly less atoms required to relax by energy minimization. This highlights the applicability of flexible boundary conditions methods to modeling defect/interface interactions by \textit{ab initio} methods

High-Risk Deviant Decisions: Does Neutralization Still Play a Role?

Extant research has shown that neutralization processes can enable potential IS security policy violators to justify their behavior and overcome the deterrence effect of sanctions in order to engage in unethical behaviors. However, such sanctions are typically moderate and not career ending. We test the boundary conditions of this theory by evaluating whether neutralization plays a role in overcoming the impact of extreme levels of deterrence. We extend the Siponen and Vance (2010) framework within a professional context that assigns extreme sanctions to violators. Using the scenario-based factorial survey method common in IS security research, we collected data from future auditors who understand these extreme sanctions. We test the reasons that auditors may use to form intentions to falsify information concerning an information security issue with a company’s accounting information system, thereby jeopardizing data integrity and security by modifying working papers to hide irregularities and, by doing so, violating their professional standards, which could result in career-ending sanctions. We empirically validated and tested the theoretical model. Our results show that sanctions play an important role in reducing employees’ intentions to violate policy but that, even under extreme boundary conditions, employees might seek to rationalize their unethical behavior by denying responsibility for their actions through, for example, arguing that their supervisors pressured them into performing the violations. We also establish that messages heightening the awareness and perceptions of the certainty and severity of organizational punishment are likely to attenuate such deviant behaviors. We discuss the implications of these findings and suggest future avenues for research

Convergence rate for numerical computation of the lattice Green's function

Flexible boundary condition methods couple an isolated defect to bulk through the bulk lattice Green's function. The inversion of the force-constant matrix for the lattice Green's function requires Fourier techniques to project out the singular subspace, corresponding to uniform displacements and forces for the infinite lattice. Three different techniques--relative displacement, elastic Green's function, and discontinuity correction--have different computational complexity for a specified numerical error. We calculate the convergence rates for elastically isotropic and anisotropic cases and compare them to analytic results. Our results confirm that the discontinuity correction is the most computationally efficient method to compute the lattice Green's function.Comment: 12 pages, 4 figure

DETC2005-85266 A TIME-STEPPING SCHEME FOR QUASISTATIC MULTIBODY SYSTEMS *

Abstract Two new instantaneous-time models for predicting the motion and contact forces of three-dimensiona

NOPdb: Nucleolar Proteome Database

The Nucleolar Proteome Database (NOPdb) archives data on >700 proteins that were identified by multiple mass spectrometry (MS) analyses from highly purified preparations of human nucleoli, the most prominent nuclear organelle. Each protein entry is annotated with information about its corresponding gene, its domain structures and relevant protein homologues across species, as well as documenting its MS identification history including all the peptides sequenced by tandem MS/MS. Moreover, data showing the quantitative changes in the relative levels of ∼500 nucleolar proteins are compared at different timepoints upon transcriptional inhibition. Correlating changes in protein abundance at multiple timepoints, highlighted by visualization means in the NOPdb, provides clues regarding the potential interactions and relationships between nucleolar proteins and thereby suggests putative functions for factors within the 30% of the proteome which comprises novel/uncharacterized proteins. The NOPdb () is searchable by either gene names, nucleotide or protein sequences, Gene Ontology terms or motifs, or by limiting the range for isoelectric points and/or molecular weights and links to other databases (e.g. LocusLink, OMIM and PubMed)

Thermal Stabilization of the HCP Phase in Titanium

We have used a tight-binding model that is fit to first-principles electronic-structure calculations for titanium to calculate quasi-harmonic phonons and the Gibbs free energy of the hexagonal close-packed (hcp) and omega crystal structures. We show that the true zero-temperature ground-state is the omega structure, although this has never been observed experimentally at normal pressure, and that it is the entropy from the thermal population of phonon states which stabilizes the hcp structure at room temperature. We present the first completely theoretical prediction of the temperature- and pressure-dependence of the hcp-omega phase transformation and show that it is in good agreement with experiment. The quasi-harmonic approximation fails to adequately treat the bcc phase because the zero-temperature phonons of this structure are not all stable