Al matrix composites reinforced by in situ synthesized graphene–Cu hybrid layers: interface control by spark plasma sintering conditions

Journal of Materials Science - Tremendous impacts are usually made by the synthesis method and consolidation technique on microstructure and interface of graphene/Al composites. In the present...     

Optimization of Gluten-Free Formulations for French-Style Breads

ABSTRACT:  The formulation of gluten-free bread, which will be suitable for patients with coeliac disease, was optimized to provide bread similar to French bread. The effects of the presence of hydrocolloids and the substitution of the flour basis by flour or proteins from different sources were studied. The added ingredients were (1) hydrocolloids (carboxymethylcellulose [CMC], guar gum, hydroxypropylmethylcellulose [HPMC], and xanthan gum), and (2) substitutes (buckwheat flour, whole egg powder, and whey proteins). The bread quality parameters measured were specific volume, dry matter of bread, crust color, crumb hardness, and gas cell size distribution. Specific volume was increased by guar gum and HPMC. Breads with guar gum had color characteristics similar to French bread. Hardness decreased with the addition of hydrocolloids, especially HPMC and guar. Breads with guar gum had the most heterogeneous cell size distribution, and guar gum was therefore selected for further formulations. Bread prepared with buckwheat flour had improved quality: an increased specific volume, a softer texture, color characteristics, and gas-cell size distribution similar to French bread. Bread with 1.9% guar gum (w/w, total flour basis) and 5% buckwheat flour (of all flours and substitutes) mimicked French bread quality attributes.     

Dog-bone copper specimens prepared by one-step spark plasma sintering

Copper dog-bone specimens are prepared by one-step spark plasma sintering (SPS). For the same SPS cycle, the influence of the nature of the die (graphite or WC–Co) on the microstructure, microhardness, and tensile strength is investigated. All samples exhibit a high Vickers microhardness and high ultimate tensile strength. A numerical electro-thermal model is developed, based on experimental data inputs such as simultaneous temperature and electrical measurements at several key locations in the SPS stack, to evaluate the temperature and current distributions for both dies. Microstructural characterizations show that samples prepared using the WC–Co die exhibit a larger grain size, pointing out that it reached a higher temperature during the SPS cycle. This is confirmed by numerical simulations demonstrating that with the WC–Co die, the experimental sample temperature at the beginning of the dwell is higher than the experimental control temperature measured at the outer surface of the die. This difference is mostly ascribed to a high vertical thermal contact resistance and a higher current density flowing through the WC–Co punch/die interface. Indeed, simulations show that current density is maximal just outside the copper sample when using the WC–Co die, whereas by contrast, with the graphite die, current density tends to flow through the copper sample. These results are guidelines for the direct, one-step, preparation of complex-shaped samples by SPS which avoids waste and minimizes machining.     

Dynamic flow behavior measurements in gas–solid fluidized beds using different non-intrusive techniques and polyethylene powder

Pressure fluctuations and X-ray computed tomography (CT) measurements were utilized to characterize the flow behavior of gas–solid fluidized beds using polyethylene particles in three Plexiglas columns with diameters of 10, 20, and 30 cm. Air was used as the gas phase. The gas–solid flow dynamic under ambient conditions was characterized from statistical analysis of pressure fluctuation data and CT images. The time-averaged voidage distribution, bubble-phase area fraction, bubble diameter and bubble number distribution varying with the bed heights were extracted from all the three columns. The bed scales had significant effect on the hydrodynamics. The scale-up effects on the gas–solid two-phase flow behavior were discussed.     

Annealing and ultraviolet treatment of plasma fluorocarbon films for enhanced cohesion and stability

Stents, commonly used for the treatment of cardiovascular diseases, are mainly made of 316L stainless steel. They are, however, prone to corrosion when they are in contact with human body fluid. To prevent this corrosion process and to ameliorate their patencies, in this study, we used a strategy to cover stent materials with a protective fluorocarbon layer deposited by plasma polymerization. In an approach to optimize its cohesion properties and stability, posttreatments, namely, thermal annealing and UV irradiation, were applied on the ultrathin fluorocarbon film. A combination of X‐ray photoelectron spectroscopy, polarized near‐edge X‐ray absorption fine‐structure spectroscopy, and time‐of‐flight secondary ion mass spectrometry demonstrated that UV treatment led to chain scission and film crosslinking and, in this way, decreased the amount and/or size of nanoscaled defects originally present in the films. Annealing on the other hand induced a film reorganization in favor of longer, well‐ordered fluorocarbon chains. However, a deformation process that was applied to study the film adhesion properties induced chain scissions with reorganization. Aging tests exhibited an oxidation of the top‐most layer for both the as‐deposited and posttreated samples. Finally, the film stability was improved after UV treatment for both the nondeformed and deformed samples. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

14-3-3 Proteins Participate in Light Signaling through Association with PHYTOCHROME INTERACTING FACTORs

14-3-3 proteins are regulatory proteins found in all eukaryotes and are known to selectively interact with phosphorylated proteins to regulate physiological processes. Through an affinity purification screening, many light-related proteins were recovered as 14-3-3 candidate binding partners. Yeast two-hybrid analysis revealed that the 14-3-3 kappa isoform (14-3-3κ) could bind to PHYTOCHROME INTERACTING FACTOR3 (PIF3) and CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1). Further analysis by in vitro pull-down assay confirmed the interaction between 14-3-3κ and PIF3. Interruption of putative phosphorylation sites on the 14-3-3 binding motifs of PIF3 was not sufficient to inhibit 14-3-3κ from binding or to disturb nuclear localization of PIF3. It was also indicated that 14-3-3κ could bind to other members of the PIF family, such as PIF1 and PIF6, but not to LONG HYPOCOTYL IN FAR-RED1 (HFR1). 14-3-3 mutants, as well as the PIF3 overexpressor, displayed longer hypocotyls, and a pif3 mutant displayed shorter hypocotyls than the wild-type in red light, suggesting that 14-3-3 proteins are positive regulators of photomorphogenesis and function antagonistically with PIF3. Consequently, our results indicate that 14-3-3 proteins bind to PIFs and initiate photomorphogenesis in response to a light signal.     

Multiplexed holographic transmission gratings recorded in holographic polymer-dispersed liquid crystals: static and dynamic studies

The optimization of the experimental parameters of two multiplexed holographic transmission gratings recorded in holographic polymer-dispersed liquid crystals is investigated. Two methods are used to record the holograms: simultaneous and sequential multiplexing. These two processes are optimized to produce two multiplexed Bragg gratings that have the same and the highest possible diffraction efficiencies in the first order. The two methods show similar results when suitable recording parameters are used. The parameters of the recorded gratings (mainly the refractive-index modulation) are retrieved by use of an extension of the rigorous coupled-wave theory to multiplexed gratings. Finally, the response of the holograms to an electric field is studied. We demonstrate few coupling effects between the behavior of both gratings, and we expect a possibility of switching from one grating to the other.     

On invariant configuration of a three-fingered grasp

When grasping an object using three-fingered end-effectors, a certain geometrical entity can be created based on the grasping points and a definition of an auxiliary point. This geometric configuration is referred to as the invariant configuration of the three-fingered grasp. This article exploits the geometric properties of such configuration using screw theory and inner product spaces. The results are shown to present themselves as an elegant and efficient framework in calculating the friction forces between the fingers and the grasped object and/or in defining the instantaneous motion of the finger-tips in accomplishing the desired motion of the grasped object.