1,720,989 research outputs found
Mechanical properties of 3-glycidoxypropyltrimethoxysilane based hybrid organic-inorganic materials
No full textMechanical properties of 3-glycidoxypropylmethoxysilane based hybrid organic-inorganic materials
No full textAbstract
Hybrid organic-inorganic materials were synthesized from acid catalysed sols of tetraethyl orthosilicate, 3-glycidoxypropyltrimethoxysilane and titanium or zirconium alkoxides. The mechanical properties of these materials were measured in different conditions of preparation. The elastic modulus E was determined by a resonance method and by Knoop microindentation. After a thermal treatment at 125°C for 120 h, E was around 3–5 and 1–2 GPa for the samples synthesized with titanium butoxide or zirconium butoxide, respectively. An increase in E in the samples cured for longer times was observed. Knoop microhardness also increased with the heating time and was larger in samples synthesized from titanium alkoxides than zirconium alkoxides. The two methods gave results in good agreement when applied to samples treated for shorter times. In the other samples Knoop microindentation gave a larger value of E compared to the resonance vibration method. Hardness to elastic modulus ratio, H/E, was evaluated by Knoop microindentation. The elastic recovery at the longest heat treatment time was similar to that of soda-lime glasses. Fracture toughness was measured by three points flexural test, a KIc in the range of 0.4–0.5 MPa m1/2 was evaluated for samples treated during 168 h
Do young know that smoking hurts?,Ma i giovani sanno che il fumo fa male?
No full textE’ noto come il fumo di tabacco sia la principale causa evitabile di morte nel mondo. Nei paesi industrializzati, la prevalenza dei fumatori nella popolazione generale è in costante diminuzione. Se si considerano solamente gli adolescenti, si assiste invece ad un aumento della prevalenza dei fumatori nella fascia di età minore di 15 anni. Tale dato è rilevante, in quanto i giovani sono particolarmente suscettibili alla dipendenza da tabacco; nello specifico, circa l’80% degli individui che cominciano a fumare durante l’adolescenza, manterrà la sua abitudine nell’età adulta e un terzo di essi morirà prematuramente a causa di malattie fumo-correlate. Le motivazioni che spingono i giovani a fumare dipendono da un processo multifattoriale complesso: si intersecano infatti fattori di rischio ambientali, sociodemografici e comportamentali-individuali. La dipendenza da fumo di sigaretta origina da due effetti: il primo è dovuto alla nicotina, il secondo risiede negli aspetti psico-comportamentali del fumare. Mentre le patologie fumo-correlate sono ben note, meno noti sono gli effetti avversi legati al fumo di sigaretta elettronica: esso è associato a neoplasie, riduzione della fertilità, aumento del rischio per obesità, ipertensione, effetti cardiovascolari, ulcera gastrica, problemi comportamentali. Negli ultimi anni, gli Stati Europei hanno intrapreso molte iniziative per limitare l’abitudine tabagica. L’insieme di tali interventi ha diminuito la prevalenza dei fumatori nella popolazione generale; essi invece non hanno dimostrato la stessa efficacia tra i giovanissimi, tra i quali, invece, la prevalenza è in aumento. Tale evidenza è lo specchio di come sia necessario disporre di misure volte a ridurre la diffusione dell’abitudine tabagica fin dall’epoca adolescenzial
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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