Ab initio simulation of a tensile test in MoSi\u3csub\u3e2\u3c/sub\u3e and WSi\u3csub\u3e2\u3c/sub\u3e

The tensile test in transition metal disilicides with C11b structure is simulated by ab initio electronic structure calculations using full potential linearized augmented plane wave method (FLAPW). Full relaxation of both external and internal parameters is performed. The theoretical tensile strength of MoSi2 and WSi2 for [001] loading is determined and compared with those of other materials

Monte Carlo Analysis of Stress-Directed Phase Segregation in Binary Thin Film Alloys Under Nonisothermal Annealing

The use of patterned stress fields to direct phase separation in thin film alloys is investigated computationally with Monte Carlo simulations in which atomic interactions are represented by a Lennard-Jones potential. We show that careful design of annealing schedules based on consideration of the system phase diagram can lead to vastly enhanced patterning kinetics. In particular, by avoiding the low temperature formation of highly stable nuclei within the entire system, the kinetics of patterning are accelerated by rapid monomerdiffusion, rather than classical Ostwald ripening in which small precipitates must dissolve to feed larger ones

Atomistic Analysis of Phase Segregation Patterning in Binary Thin Films Using Applied Mechanical Fields

The patterned compositional evolution in thin films of a binary alloy controlled by modulated stress fields is studied by employing Monte Carlo simulations. General features of stress-patterned phase segregation are probed using a binary Lennard-Jones potential in which the lattice misfit between the two components of the alloy is varied systematically. In general, patterning of the microstructure is found to be more robust in the low-mismatch binary systems because large lattice mismatch promotes plastic, and therefore, irreversible relaxation, during annealing. It is shown that some control over the relaxation process can be achieved by careful design of the applied thermal annealing history. Additional calculations have been performed using two other potentials for binary metallic systems, an embedded-atom method (EAM) potential for Cu–Ag and a modified embedded-atom method (MEAM) potential for Cu–Ni that represent examples of high and low-mismatched systems, respectively. The results obtained with generic Lennard-Jones potentials are in excellent agreement with those from the EAM and MEAM potentials suggesting that it is possible to derive general guidelines for accomplishing stress-patterned segregation in a variety of thin films of binary alloys

High-resolution genome-wide scan of genes, gene-networks and cellular systems impacting the yeast ionome

Peer reviewedPublisher PD

Prediction and Observation of the bcc Structure in Pure Copper at a \u3cem\u3e\u3cstrong\u3eΣ\u3c/strong\u3e\u3c/em\u3e3 Grain Boundary

We have used molecular dynamics and simulated annealing to study an asymmetrical Σ3 tilt grain boundary with ⟨211⟩ rotation axis in Cu. The boundary plane was inclined at 84° with respect to the {}(111) plane. A simple central force N-body interatomic potential was used. The most stable configuration shows a broad band of predominantly bcc structure in the boundary region. Samples of the bicrystal with the same misorientation and inclination of the boundary plane were observed in a 1250 kV transmission electron microscope, confirming the predicted structure with atomic resolution

Status Update on the Threat of Babesiosis Returning to the United States

Babesiosis is a hemolytic disease caused by protozoan parasites in the genus Babesia, transmitted through the saliva of infected ticks. The most economically important species, Babesia bigemina and B. bovis, infect cattle and are the etiological agents of bovine babesiosis. In the southern United States, eradication efforts directed against the tick vectors, Boophilus spp., began in the early 1900s. A quarantine zone in south Texas along the US/Mexico border was subsequently established following the eradication of the disease in the US. The permanent quarantine zone, spanning approximately 33% of the total shared border between Texas and Mexico, has helped limit the reintroduction of the vector and disease, and reduced the incidence of the tick vectors. Further, a strict regimen of broad monitoring and surveillance activities coupled with a rapid response and systematic application of containment procedures under the joint jurisdiction of the Texas Animal Health Commission and the United States Department of Agriculture has proven effective in enforcing the permanent quarantine zone and preventing the emergence of babesiosis into the United States. However, the presence of exotic game animals has helped facilitate the spread of the tick vectors and, when coupled with expanding populations of native deer that can host the tick vectors, the prevalence of Boophilus spp. ticks suggests an increased risk of the return of bovine babesiosis to the United States. This mini-review will examine the efforts in south Texas during 2018 to prevent the spread of cattle fever ticks

Generalized stacking fault energy surfaces and dislocation properties of aluminum

We have employed the semidiscrete variational generalized Peierls-Nabarro model to study the dislocation core properties of aluminum. The generalized stacking fault energy surfaces entering the model are calculated by using first-principles Density Functional Theory (DFT) with pseudopotentials and the embedded atom method (EAM). Various core properties, including the core width, splitting behavior, energetics and Peierls stress for different dislocations have been investigated. The correlation between the core energetics and dislocation character has been explored. Our results reveal a simple relationship between the Peierls stress and the ratio between the core width and atomic spacing. The dependence of the core properties on the two methods for calculating the total energy (DFT vs. EAM) has been examined. The EAM can give gross trends for various dislocation properties but fails to predict the finer core structures, which in turn can affect the Peierls stress significantly (about one order of magnitude).Comment: 25 pages, 12 figure

DESIGNING MICROARRAYS

Microarrays allow the simultaneous assessment of expression levels for thousands of genes across various treatment conditions and time. It has been shown that in these experiments expression levels can also be affected by factors in the printing of the slide, in the hybridization process, and in the post-hybridization process. Recently, variations of the incomplete block design were proposed as a way to avoid confounding the expression levels of interest with several of these nuisance factors. In this paper, we propose additional design procedures to remove factors that contribute to the spatial variability on a slide. This approach requires the use of replication, and involves designing how the replicates are to be positioned on the slide. We demonstrate these techniques using an experiment involving sixty-four genes, four replicates per slide, and five treatment conditions

The influence of transition metal solutes on dislocation core structure and values of Peierls stress and barrier in tungsten

Several transition metals were examined to evaluate their potential for improving the ductility of tungsten. The dislocation core structure and Peierls stress and barrier of $1/2$ screw dislocations in binary tungsten-transition metal alloys (W$_{1-x}$TM$_{x}$) were investigated using first principles electronic structure calculations. The periodic quadrupole approach was applied to model the structure of $1/2$ dislocation. Alloying with transition metals was modeled using the virtual crystal approximation and the applicability of this approach was assessed by calculating the equilibrium lattice parameter and elastic constants of the tungsten alloys. Reasonable agreement was obtained with experimental data and with results obtained from the conventional supercell approach. Increasing the concentration of a transition metal from the VIIIA group, i.e. the elements in columns headed by Fe, Co and Ni, leads to reduction of the $C^\prime$ elastic constant and increase of elastic anisotropy A=$C_{44}/C^\prime$. Alloying W with a group VIIIA transition metal changes the structure of the dislocation core from symmetric to asymmetric, similar to results obtained for W$_{1-x}$Re$_{x}$ alloys in the earlier work of Romaner {\it et al} (Phys. Rev. Lett. 104, 195503 (2010))\comments{\cite{WRECORE}}. In addition to a change in the core symmetry, the values of the Peierls stress and barrier are reduced. The latter effect could lead to increased ductility in a tungsten-based alloy\comments{\cite{WRECORE}}. Our results demonstrate that alloying with any of the transition metals from the VIIIA group should have similar effect as alloying with Re.Comment: 12 pages, 8 figures, 3 table