Metadata management for distributed first principles calculations in VLab—A collaborative cyberinfrastructure for materials computation

This paper describes the metadata and metadata management algorithms necessary to handle the concurrent execution of multiple tasks from a single workflow, in a collaborative service oriented architecture environment. Metadata requirements are imposed by the distributed workflow that calculates thermoelastic properties of materials at high pressures and temperatures. The scientific relevance of this workflow is also discussed. We explain the basic metaphor, the receipt, underlying the metadata management. We show the actual java representation of the receipt, and explain how it is converted to XML in order to be transferred between servers, and stored in a database. We also discuss how the collaborative aspect of user activity on running workflows could potentially lead to race conditions, how this affects requirements on metadata, and how these race conditions are precluded. Finally we describe an additional metadata structure, complementary to the receipts, that contains general information about the workflow.     

Rapid Generation of Biologically Relevant Hydrogels Containing Long‐Range Chemical Gradients

Many biological processes are regulated by gradients of bioactive chemicals. Thus, the generation of materials with embedded chemical gradients may be beneficial for understanding biological phenomena and generating tissue‐mimetic constructs. Here a simple and versatile method to rapidly generate materials containing centimeter‐long gradients of chemical properties in a microfluidic channel is described. The formation of a chemical gradient is initiated by a passive‐pump‐induced forward flow and further developed during an evaporation‐induced backward flow. The gradient is spatially controlled by the backward flow time and the hydrogel material containing the gradient is synthesized via photopolymerization. Gradients of a cell‐adhesion ligand, Arg‐Gly‐Asp‐Ser (RGDS), are incorporated in poly(ethylene glycol)‐diacrylate (PEG‐DA) hydrogels to test the response of endothelial cells. The cells attach and spread along the hydrogel material in a manner consistent with the RGDS‐gradient profile. A hydrogel containing a PEG‐DA concentration gradient and constant RGDS concentration is also shown. The morphology of cells cultured on such hydrogel changes from round in the lower PEG‐DA concentration regions to well‐spread in the higher PEG‐DA concentration regions. This approach is expected to be a valuable tool to investigate the cell–material interactions in a simple and high‐throughput manner and to design graded biomimetic materials for tissue engineering applications.     

Fabrication of a Thermoelectric Nanocomposite via Multiple Roll Bonding of Cast Bi-22at.%Sb Alloy

A Bi-22at.%Sb alloy was water-quenched from 973 K; its microstructure was dendritic with primary Sb-rich arms up to 50 μm in diameter. The cast alloy was first rolled to tape, then cut into equal lengths and subjected to multiple roll bonding (MRB) processes. The evolution of the microstructure during deformation was followed by optical microscopy, scanning electron microscopy (SEM), field-emission scanning electron microscopy (FESEM), differential scanning calorimetry (DSC), and x-ray diffraction analysis. After three MRB cycles, an overall area reduction ratio of 4 × 10³ was achieved. Due to the relatively low process temperature, a relevant fraction of dendrites was preserved. Plastic strain caused dendritic arms to elongate in the rolling direction and to flatten in the transverse direction. As a result of different starting size and orientation, the dendritic arms were transformed into Sb-rich inclusions of various shapes and dimensions at the end of the MRB process. In particular, inclusions with a transverse size down to 20 nm were observed.     

Transformation kinetics for nucleus clusters

A rigorous mathematical approach based on stochastic geometry concepts is presented to extend previous Johnson–Mehl, Avrami, Kolmogorov treatment of transformation kinetics to situations in which nuclei are not homogeneously located in space but are located in clusters. An exact analytical solution is presented here for the first time assuming that nucleation sites follow a Matérn cluster process. The influence of Matérn cluster process parameters on subsequent growth kinetics and the microstructural path are illustrated by means of numerical examples. Moreover, using the superposition principle, exact analytical solutions are also obtained when nucleation takes place by a combination of a Matérn cluster process and an inhomogeneous Poisson point process. The new solutions presented here significantly increase the number of exactly solvable cases available to formal kinetics.     

Binary integer programming formulations for scheduling in market-driven foundries

This paper describes the development and solution of binary integer formulations for production scheduling problems in market-driven foundries. This industrial sector is comprised of small and mid-sized companies with little or no automation, working with diversified production, involving several different metal alloy specifications in small tailor-made product lots. The characteristics and constraints involved in a typical production environment at these industries challenge the formulation of mathematical programming models that can be computationally solved when considering real applications. However, despite the interest on the part of these industries in counting on effective methods for production scheduling, there are few studies available on the subject. The computational tests prove the robustness and feasibility of proposed models in situations analogous to those found in production scheduling at the analyzed industrial sector.     

MOSFET simulation with quantum effects and nonlocal mobility model

We present a state-of-the-art two-dimensional (2-D) device simulator suitable for highly doped n-MOSFETs. Quantization effects in the inversion channel are accounted for by a self-consistent solution of the Poisson, current-continuity and Schrodinger equations. The electron charge is given by a density of electrons in the bounded levels plus a density of classically-distributed carriers. Consequently, different mobility models are used. For the former, we adopted a nonlocal, newly-developed mobility model, thus overcoming the deficiency of currently-used mobility models in the high-doping limit. We instead retained a standard local model for the classical regime. Results of the simulations are in good agreement with the experiments     

Anti-inflammatory activity of American yam Dioscorea trifida L.f. in food allergy induced by ovalbumin in mice

Tropical ecosystems are particularly rich in edible plant species with different bioactive substances. Among the plants with promising benefits for health are species from the genus Dioscorea (Dioscoreaceae), especially those named yam. Recent studies have shown the beneficial effects of different species of Dioscorea, and its main constituent, diosgenine, in the treatment of food allergy. In this study we evaluated the potential of D. trifida, the only yam native from South America, in the treatment of ovalbumin (OVA) induced food allergy in Balb/c mice. HPLC/DAD analysis showed the presence of three very distinctive groups of natural products in extracts and fractions: (I) very polar substances, including allantoin, (II) phenolic substances as flavonoids and phenolic acids and (III) diosgenin and derivatives. Sensitive mice received casein feed with supplementation of crude extract (CE) and fractions. The supplementation with all products from D. trifida reduced IGE, intestinal oedema and mucus production, parameters observed in OVA allergic mice. The results showed the potential of this food to prevent or treat this disease and the necessity to be better explored.