Characterization of carbon nanotube 3D-structures infused with low viscosity epoxy resin system

This work presents the use of carbon nanotube (CNT) skeletons and the resin infusion process as a path towards the production of polymer composites with high and well dispersed nanotube content. A general purpose low viscosity epoxy resin was used as matrix in the reported process assessment. Thin CNT papers, called skeletons, were initially produced to obtain CNT networks. The impregnation was made by infiltrating the non-diluted resin through the carbon nanotube structure. The results show the proposed processing approach as one capable of producing well dispersed nanocomposites with high CNT loading (more than 15 wt% CNT by composite weight), which are important for developing high performance structures based on carbon nanotubes with good thermal and electrical conductivity. The absolute mechanical performance was lower than expected, and discussed in light of manufacturing problems detected by microscopy observations under scanning electron microscopy (SEM).     

Thermo-physical properties and TEM analysis of silver based MMCs utilizing metallized multiwall-carbon nanotubes

Metal matrix composites with embedded multiwall-carbon nanotubes (MWNT) are attractive because MWNTs exhibit high intrinsic thermal conductivity. Thus to improve the thermal conductivity of a metal matrix, silver matrix composites with MWNT were prepared by “chemical” mixing, different active elements were introduced enhancing the bonding between inclusions and matrix. The evolution of the thermal conductivity and the coefficient of thermal expansion CTE as a function of the MWNT concentration and the presence of active elements cobalt, molybdenum or nickel in the silver matrix in Ag–X/MWNT composites are presented. A transition from weak to strong matrix/MWNT bonding is observed by adding active elements, the latter leading concomitantly to an increase in thermal conductivity and a decrease in CTE. The thermal conductivity was found to increase by up to 10% for a composition of 0.2 wt.% MWNT and cobalt as active element and a 6% decrease in CTE compared to a pure silver reference.     

Application of visible and near infrared spectroscopy in non-destructive evaluation of cement materials

In the twenty-first century, there has been rapid urbanization in economically emerging countries. Many scientific research studies have proposed methods to monitor the quality of materials used in engineering works. Quality inspections are most often made of structure-related materials such as concrete. All the concrete used in construction work is subjected to a test that breaks the samples to evaluate its final mechanical strength. In this sense, remote sensing can contribute to mapping and monitoring construction materials, allowing investigation and identification of various properties such as mechanical strength and water content in a non-destructive manner. The materials can be inspected directly on site, in a rapid, non-invasive, and inexpensive manner; this is crucial for the ongoing process of construction. The spectral behaviour of four different mechanical strengths of two cement materials based on Portland cement, cement paste, and mortar was observed using a FieldSpec® 3 spectroradiometer. The spectral curves generated by recording the reflected and absorbed electromagnetic radiation of the samples were interpreted based on the theory of vibrational and electronic spectroscopy. The objective of this work is to show a novel technique for assisting in the analysis of solid samples using visible and near infrared spectroscopy. Through this study, a spectral contrast between different samples of the paste and mortar was found. Besides, it was possible to detect the presence and the corresponding proportion of water in the samples. Wavelet analysis enabled records of statistical evidence of spectral contrast, and showed that the depth of water absorption features is inversely proportional to compressive strength in the cement materials under study. This work is innovative, because there are no studies in the literature on the application of this technique as an aid tool for differentiating compressive strengths of Portland-cement-based materials.     

Does knowledge about attention-deficit/hyperactivity disorder impact teachers' reported behaviors and perceptions?

This study surveyed elementary school teachers in Melbourne, Australia to investigate their knowledge about attention-deficit/hyperactivity disorder (ADHD) and its impact on their reported behavior toward and perceptions of children with ADHD. Consistent with previous international findings, teachers demonstrated good overall knowledge about ADHD, with strengths in knowledge of symptoms/diagnosis and weaknesses in knowledge of causes and treatments. To investigate how knowledge impacted reported behaviors and perceptions, teachers also read vignettes of children with ADHD symptoms and rated their reactions to these children. In general, teachers with high, and to some extent average, knowledge about ADHD reported more helpful behaviors (e.g., help-seeking for their students) and perceptions (e.g., perceive the benefit of behavioral and educational treatments). However, teachers with high and average knowledge also predicted that these children would be more disruptive in the classroom, and reported having less confidence in their ability to manage these children. Implications and need for future research are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Zum mechanismus der thermischen abspaltung von chlorwasserstoff aus polyvinylchlorid. 5. Mitt.: Über die verteilung der polyensequenzlängen in thermisch abgebauten technischen polyvinylchloriden und in anwesenheit stabilisierend wirkender substanzen

The rates of dehydrochlorination of commercial poly (vinyl chlorides) and the distribution of the lengths of the resulting polyene sequences may vary widely depending on the origin of the polymer. – In the presence of diphenyllead dichloride the rate of dehydrochlorination is increased, while the resulting discoloration is less intense compared to that of pure poly (vinyl chloride) because of a shift of the polyene sequence lengths distribution. Genuine stabilizers, on the other hand, effect retardation in dehydrochlorination as well as a shift of the sequence lengths distribution towards shorter polyene sequences. The causes for this behavior of admixed stabilizers using lead and cadmium octoate as examples as well as of internally stabilized PVC are discussed.     

Über die hitzestabilisierung von PVC durch blei-, barium- und cadmiumoctoat

The following reactions between carbonic acid salts of bivalent metals as heat-stabilizers and PVC take place during heat-treatment:

• Chemical HCI-bonding by stabilizers (HCI-acceptance);
• esterification of isolated allylic chlorine atoms in the polymer chains, starting from a complex formed by stabilizer molecules and labile chlorine atoms:
• the stabilizer inhibits formation of longer polyene sequences by exchange reactions of the allylic chlorine atoms with the ester groups of the stabilizer.

Reaction (a) prevents an autocatalytic acceleration of the HCI splitting off by HCI. Reaction (b) eliminates ?labile”? chlorine atoms of the polymer which are responsible for the thermal instability of PVC. Reaction (c) prevents the formation of longer polyene sequences, which absorb in the visible range of the spectrum.     

Our university clinics need research--so does our specialty!]

University research has to serve as a substrate for science and technology and should raise a qualified, critical but motivated younger generation of scientists. These need a basic research which is independent and not oriented towards any short-term goals. An open and easy collaboration without any interdependence is necessary between the university and industry. All this requires greater autonomy for the universities. in German-speaking countries, many people distrust progress. However, it is not a matter of 'progress at any price' but of a careful, pertinent analysis of the benefits and risks. Parsimony in science and research is dangerous and shortsighted. To invest in research means to invest in the future.     

Harvesting Wiki Consensus: Using Wikipedia Entries as Vocabulary for Knowledge Management

Vocabularies that provide unique identifiers for conceptual elements of a domain can improve precision and recall in knowledge-management applications. Although creating and maintaining such vocabularies is generally hard, wiki users easily manage to develop comprehensive, informal definitions of terms, each one identified by a URI. Here, the authors show that the URIs of Wikipedia entries are reliable identifiers for conceptual entities. They also demonstrate how Wikipedia entries can be used for annotating Web resources and knowledge assets and give precise estimates of the amount of Wikipedia URIs in terms of the popular Proton ontology's top-level concepts.