Equation of state for He bubbles in W and model of He bubble growth and bursting near W{100} surfaces derived from molecular dynamics simulations.

Molecular dynamics (MD) simulations are performed to derive an equation of state (EOS) for helium (He) bubbles in tungsten (W) and to study the growth of He bubbles under a W(100) surface until they burst. We study the growth as a function of the initial nucleation depth of the bubbles. During growth, successive loop-punching events are observed, accompanied by shifts in the depth of the bubble towards the surface.

Investigation of interfacial strength in nacre-mimicking tungsten heavy alloys for nuclear fusion applications.

Tungsten heavy alloys have been proposed as plasma facing material components in nuclear fusion reactors and require experimental investigation in their confirmation. For this purpose, a 90W-7Ni-3Fe alloy has been selected and microstructurally manipulated to present a multiphase brick-and-mortar structure of W-phase 'bricks' surrounded by a ductile 'mortar'. This work draws inspiration from nature to artificially imitate the extraordinary combination of strength and stiffness exhibited by mollusks and produce a nacre-mimicking metal matrix composite capable of withstanding the extremely hostile environment of the reactor interior and maintaining structural integrity.

Effect of helium flux on near-surface helium accumulation in plasma-exposed tungsten.

We report results of object kinetic Monte Carlo (OKMC) simulations to understand the effect of helium flux on the near-surface helium accumulation in plasma-facing tungsten, which is initially pristine, defect-free, and has a (100) surface orientation. These OKMC simulations are performed at 933 K for fluxes ranging from 10to 4 × 10He/m s with 100 eV helium atoms impinging on a (100) surface up to a maximum fluence of 4 × 10He/m. In the near-surface region, helium clusters interact elastically with the free surface.

Double Culprits in a Patient with ST Elevation Myocardial Infarction: A Challenging But Rewarding Case.

Myocardial infarction simultaneously involving two or more culprit lesions is extremely rare and usually has a poor clinical outcomes including mortality. Management of this complicated condition is challenging and limited time. Nevertheless, autopsy studies revealed that thrombotic occlusion of more than one major epicardium coronary artery is not uncommon.

Grain boundary phases in bcc metals.

We report a computational discovery of novel grain boundary structures and multiple grain boundary phases in elemental body-centered cubic (bcc) metals represented by tungsten, tantalum and molybdenum. While grain boundary structures created by the γ-surface method as a union of two perfect half crystals have been studied extensively, it is known that the method has limitations and does not always predict the correct ground states. Herein, we use a newly developed computational tool, based on evolutionary algorithms, to perform a grand-canonical search of high-angle symmetric tilt and twist boundaries, and we find new ground states and multiple phases that cannot be described using the conventional structural unit model.

Multifaceted Modularity: A Key for Stepwise Building of Hierarchical Complexity in Actinide Metal-Organic Frameworks.

Growing necessity for efficient nuclear waste management is a driving force for development of alternative architectures toward fundamental understanding of mechanisms involved in actinide (An) integration inside extended structures. In this manuscript, metal-organic frameworks (MOFs) were investigated as a model system for engineering radionuclide containing materials through utilization of unprecedented MOF modularity, which cannot be replicated in any other type of materials. Through the implementation of recent synthetic advances in the MOF field, hierarchical complexity of An-materials was built stepwise, which was only feasible due to preparation of the first examples of actinide-based frameworks with "unsaturated" metal nodes.

Cascade morphology transition in bcc metals.

Energetic atom collisions in solids induce shockwaves with complex morphologies. In this paper, we establish the existence of a morphological transition in such cascades. The order parameter of the morphology is defined as the exponent, b, in the defect production curve as a function of cascade energy (N(F) ~ E(MD)(b)).

Ab initio study of H, He, Li and Be impurity effect in tungsten Σ3{1 1 2} and Σ27{5 5 2} grain boundaries.

Density functional theory calculations were performed to investigate the effect of H, He, Li and Be impurities on the intergranular cohesion of W Σ3〈1 1 0〉{1 1 2} and Σ27〈1 1 0〉{5 5 2} grain boundaries (GBs). A rigorous search of unique interstices was performed to reveal a range of impurity behaviors. It was found that He exhibits the largest defect formation energy, however it is Li that shows the strongest tendency to segregate towards the GBs.

An apparatus for studying scintillator properties at high isostatic pressures.

We describe the design and operation of a unique hydraulic press for the study of scintillator materials under isostatic pressure. This press, capable of developing a pressure of a gigapascal, consists of a large sample chamber pressurized by a two-stage hydraulic amplifier. The optical detection of the scintillation light emitted by the sample is performed, through a large aperture optical port, by a photodetector located outside the pressure vessel.

A search model for topological insulators with high-throughput robustness descriptors.

Topological insulators (TI) are becoming one of the most studied classes of novel materials because of their great potential for applications ranging from spintronics to quantum computers. To fully integrate TI materials in electronic devices, high-quality epitaxial single-crystalline phases with sufficiently large bulk bandgaps are necessary. Current efforts have relied mostly on costly and time-consuming trial-and-error procedures.

Diagnosis and management of acromegaly: giant invasive adenoma.

Acromegaly is a rare disorder caused by excessive growth hormone. Majority of acromegaly are due to pituitary adenoma. It is estimated that 5% of pituitary adenoma become invasive and may grow to gigantic sizes (>4 cm in diameter).

High-throughput combinatorial database of electronic band structures for inorganic scintillator materials.

For the purpose of creating a database of electronic structures of all the known inorganic compounds, we have developed a computational framework based on high-throughput ab initio calculations (AFLOW) and an online repository (www.aflowlib.org).

Structures and topological transitions of hydrocarbon films on quasicrystalline surfaces.

Lubricants can affect quasicrystalline coating surfaces by modifying the commensurability of the interfaces. We report results of the first computer simulation studies of physically adsorbed hydrocarbons on a quasicrystalline surface: methane, propane, and benzene on decagonal Al-Ni-Co. The grand canonical Monte Carlo method is employed, using novel embedded-atom method potentials generated from ab initio calculations, and standard hydrocarbon interactions.

Reduced carbon solubility in Fe nanoclusters and implications for the growth of single-walled carbon nanotubes.

Fe nanoclusters are becoming the standard catalysts for growing single-walled carbon nanotubes via chemical vapor decomposition. Contrary to the Gibbs-Thompson model, we find that the reduction of the catalyst size requires an increase of the minimum temperature necessary for the growth. We address this phenomenon in terms of solubility of C in Fe nanoclusters and, by using first-principles calculations, we devise a simple model to predict the behavior of the phases competing for stability in Fe-C nanoclusters at low temperature.

Evolution of topological order in Xe films on a quasicrystal surface.

We report results of the first computer simulation studies of a physically adsorbed gas on a quasicrystalline surface Xe on decagonal Al-Ni-Co. The grand canonical Monte Carlo method is employed, using a semiempirical gas-surface interaction, based on conventional combining rules, and the usual Lennard-Jones Xe-Xe interaction. The resulting adsorption isotherms and calculated structures are consistent with the results of LEED experimental data.

Nanotube electronics: large-scale assembly of carbon nanotubes.

Nanoscale electronic devices made from carbon nanotubes, such as transistors and sensors, are much smaller and more versatile than those that rely on conventional microelectronic chips, but their development for mass production has been thwarted by difficulties in aligning and integrating the millions of nanotubes required. Inspired by biomolecular self-assembly processes, we have created chemically functionalized patterns on a surface, to which pre-grown nanotubes in solution can align themselves in huge numbers. This method allows wafer-scale fabrication of millions of carbon-nanotube circuits with single-nanotube precision, and may enable nanotube-based devices, such as computer chips and high-density sensor arrays, to be produced industrially.