Microstructure and Mechanical Behavior of Powder Metallurgy Mg98.5Gd1Zn0.5 Alloy

The Mg_98.5Gd₁Zn_0.5 alloy produced by a powder metallurgy route was studied and compared with the same alloy produced by extrusion of ingots. Atomized powders were cold compacted and extruded at 623 K and 673 K (350 °C and 400 °C). The microstructure of extruded materials was characterized by α-Mg grains, and Mg₃Gd and 14H-LPSO particles located at grain boundaries. Grain size decreased from 6.8 μm in the extruded ingot, down to 1.6 μm for powders extruded at 623 K (350 °C). Grain refinement resulted in an increase in mechanical properties at room and high temperatures. Moreover, at high temperatures the PM alloy showed superplasticity at high strain rates, with elongations to failure up to 700 pct.     

Influence of the gas diffusion cathode structure on the performance of an air-breathing proton exchange membrane fuel cell

This study presents a comprehensive analysis regarding the relevance of the cathode electrode structure on the performance of an air-breathing proton exchange membrane fuel cell, for which water management is a critical issue. In the light of the obtained results, general guidelines for designing a high-performance cathode for air-breathing operation are provided. Selecting adequate characteristics for the gas diffusion electrode in the cathode is shown to be crucial for optimizing performance. Sufficiently thin catalytic layers increase impressively Pt utilization by favouring the access of oxygen and protons to the electroactive centres. The properties of the gas diffusion medium for air-breathing cathodes have been also observed to be critical. The study reveals that selection criteria for gas diffusion layers based on high air permeability and good hydrophobicity does not ensure optimal performance. The ability of the GDL macroporous structure to expel water from the cathode is decisive for improving oxygen access to the catalytic layer and obtaining high-performance air-breathing fuel cells.     

Competence Assessment in Higher Education: A Dynamic Approach

Advances in the implementation of the European Higher Education Area have had a great impact on university environment and the process of design, evaluation, and implementation of new curricula. Identifying competence levels among students can help course organizers to improve both academic content and teaching/learning processes. The present study addresses this issue by examining the implementation of an Internet‐based competency assessment tool. We analyze the status and evolution of soft skills among students on the Official Masters program Creating and Managing Innovative Technology‐Based Companies at the University of Barcelona, using a tool known as Tricuspoid, specifically designed for evaluating entrepreneurial competences. The results show that the tool, first, enables students to identify their strong and weak points and to develop personal strategies for improvement; second, provides teachers with additional information about the effects of their input on student competences; and third, supplies useful information for quality management of the Master's programs, because it can detect trends in the training needs of new students and help to enhance content accordingly, and therefore match the design of the academic program to the requirements of labor market. © 2012 Wiley Periodicals, Inc.     

Mechanical properties of new stainless steels based on the system Fe‐30Mn‐5A1‐XCr‐0.5C

New stainless steels based on the system Fe‐30Mn‐5AI‐XCr‐0.5C (Cr mass contents of ≤ 9 %) were developed and evaluated as a replacement of conventional AISI 304 steel. The alloys were produced by induction melting and thermomechanically processed to obtain a fine equiaxed microstructure. A typical thermomechanical processing for AISI 300 austenitic stainless steels was used and included forging at 1200°C, rolling at 850 °C and final recrystallization at 1050 °C. A final fully austenitic microstructure with grains of about 150 μm in size was obtained in all the steels. Tensile tests at temperatures ranging from ‐196 to 400 °C showed similar results for the various alloys tested. In accordance with the values for the elongation to fracture, this temperature range was subdivided into three regions. In the temperature range of ‐196 °C to room temperature, elongation to fracture increases with decreasing temperature. At temperatures ranging from 100 to 300 °C, elongation to fracture increases with testing temperature and serrations on the stress‐strain curve were observed. Finally, higher testing temperatures were accompanied by a decrease in ductility. Examination of the microstructures after deformation led to the conclusion that mechanical twinning was the dominant mechanism of deformation at the tested temperatures.     

SELECTIVE DETERMINATION OF β-GLUCAN OF DIFFERING MOLECULAR SIZE,USING THE CALCOFLUOR-FLUORIMETRIC FLOW-INJECTION-ANALYSIS (FIA) METHOD

When using the calcofluor-fluorimetric flow-injection-analysis (FIA) method to determine β-glucan in wort and beer, the actual range of β-glucan molecular weights effectively complexed by the calcofluor, and consequently the total amount detected, is dependent on the ionic strength of the eluent. In the base eluent of very low ionic strength (20 ppm of calcofluor in aqueous 0.1 M TRIS, pH = 11), only β-glucan molecules of molecular weight greater than approximately 200, 000 daltons are fully complexed by calcofluor, and consequently fully detected. As the molecular weight of β-glucan molecules decreases, β-glucan is only partially complexed by calcofluor, and hence partially detected. By increasing the ionic strength of the base eluent through adding successive amounts of NaCl up to a maximum of 1%, the molecular weight of β-glucan which can be detected by the method decreases down to about 65, 000 daltons, whereas the molecular weights below about 10,000 daltons are not significantly complexed nor detected. Different size ranges of β-glucan have been isolated and characterized by enzymatic degradation of high molecular weight standard β-glucan, followed by classical gel permeation chromatography (GPC), using Sephacryl S-400 HR as stationary phase, pure water as eluent, and dextrans as molecular weight markers.     

Lightly supervised acquisition of named entities and linguistic patterns for multilingual text mining

Named Entity Recognition and Classification (NERC) is an important component of applications like Opinion Tracking, Information Extraction, or Question Answering. When these applications require to work in several languages, NERC becomes a bottleneck because its development requires language-specific tools and resources like lists of names or annotated corpora. This paper presents a lightly supervised system that acquires lists of names and linguistic patterns from large raw text collections in western languages and starting with only a few seeds per class selected by a human expert. Experiments have been carried out with English and Spanish news collections and with the Spanish Wikipedia. Evaluation of NE classification on standard datasets shows that NE lists achieve high precision and reveals that contextual patterns increase recall significantly. Therefore, it would be helpful for applications where annotated NERC data are not available such as those that have to deal with several western languages or information from different domains.     

Text summarization contribution to semantic question answering: New approaches for finding answers on the web

As the Internet grows, it becomes essential to find efficient tools to deal with all the available information. Question answering (QA) and text summarization (TS) research fields focus on presenting the information requested by users in a more concise way. In this paper, the appropriateness and benefits of using summaries in semantic QA are analyzed. For this purpose, a combined approach where a TS component is integrated into a Web‐based semantic QA system is developed. The main goal of this paper is to determine to what extent TS can help semantic QA approaches, when using summaries instead of search engine snippets as the corpus for answering questions. In particular, three issues are analyzed: (i) the appropriateness of query‐focused (QF) summarization rather than generic summarization for the QA task, (ii) the suitable length comparing short and long summaries, and (iii) the benefits of using TS instead of snippets for finding the answers, tested within two semantic QA approaches (named entities and semantic roles). The results obtained show that QF summarization is better than generic (58% improvement), short summaries are better than long (6.3% improvement), and the use of TS within semantic QA improves the performance for both named‐entity‐based (10%) and, especially, semantic‐role‐based QA (47.5%). © 2011 Wiley Periodicals, Inc.     

Inclusive access to emergency services: an action research project focused on hearing-impaired citizens

Universal Access in the Information Society - In case of emergency, hearing-impaired people are not always able to access emergency services, and hence, they do not have equal access to social...     

Mast Cell and Astrocyte Hemichannels and Their Role in Alzheimer’s Disease,ALS, and Harmful Stress Conditions

Considered relevant during allergy responses, numerous observations have also identified mast cells (MCs) as critical effectors during the progression and modulation of several neuroinflammatory conditions, including Alzheimer’s disease (AD) and amyotrophic lateral sclerosis (ALS). MC granules contain a plethora of constituents, including growth factors, cytokines, chemokines, and mitogen factors. The release of these bioactive substances from MCs occurs through distinct pathways that are initiated by the activation of specific plasma membrane receptors/channels. Here, we focus on hemichannels (HCs) formed by connexins (Cxs) and pannexins (Panxs) proteins, and we described their contribution to MC degranulation in AD, ALS, and harmful stress conditions. Cx/Panx HCs are also expressed by astrocytes and are likely involved in the release of critical toxic amounts of soluble factors—such as glutamate, adenosine triphosphate (ATP), complement component 3 derivate C3a, tumor necrosis factor (TNFα), apoliprotein E (ApoE), and certain miRNAs—known to play a role in the pathogenesis of AD, ALS, and other neurodegenerative disorders. We propose that blocking HCs on MCs and glial cells offers a promising novel strategy for ameliorating the progression of neurodegenerative diseases by reducing the release of cytokines and other pro-inflammatory compounds.     

Effect of the surface chemical groups of activated carbons on their surface adsorptivity to aromatic adsorbates based on π-π interactions

Three activated carbons with different surface chemical groups were used to analyse the influence of these groups on their adsorption capacities towards aromatic-type molecules whose adsorption is based on π-π interactions with surface arene centres. The three activated carbons studied were a low-functionalized carbon (Merck), an oxygen-rich carbon obtained by HNO₃ oxidation of Merck, and a nitrogen-rich carbon also prepared from Merck by mild HNO₃ oxidation followed by treatment with a dicyanodiamide/dimethyl formamide mixture at 300 °C. The nature of the surface chemical groups of the three activated carbons was investigated by both physical and chemical techniques (TPD, XPS, Boehm analysis and pH potentiometric titration). A systematic study of the adsorptions of a series of analogous aromatic adsorbates on the three activated carbons was carried out to study the adsorption mechanisms. In all cases the adsorption mechanism is based on π-π interactions between the aromatic moiety of the adsorbates and the arene centres of the graphite sheets. The differences in the normalized adsorption capacities of the adsorbents for a set of adsorbates indicate that the π-donor or π-withdrawing character of the functional groups have a clear influence on the basicity of the arene centres.