1,721,018 research outputs found
Investigation of amorphous and crystalline phosphates in magnesium phosphate ceramics with solid-state 1H and 31P NMR spectroscopy
No full textMagnesium phosphate ceramics are chemically-bonded ceramics for bioengineering and civil engineering applications. Information about the nature of the reaction products, especially the amorphous fraction, and their role in the setting reaction, essential for linking reaction mechanisms to microstructure and performance of ceramics, is lacking. By exploiting 1H and 31P magic-angle spinning nuclear magnetic resonance spectroscopy, in addition to the crystalline reaction product (MKP), two amorphous phases, characterized by two distinct proton and phosphorous environments, have been identified. The results pointed to amorphous hydrated orthophosphate compounds which are the precursors of MKP. They show different 1H spin-lattice relaxation dynamics, and, higher water mobility with respect to MKP. Although these amorphous precursors should not be crypto-structural variants of MKP, they likely host similar structural units. Conversion into MKP is thought to occur through relatively minor rearrangements, as in Ca phosphate hydrates. The new information provided in this work allows us to propose a model for the setting reaction based on an existing theory involving a densification process, analogue to sol-gel processing of ceramics, coherent with results from small angle neutron scattering and mechanisms predicted by reaction kinetics analysis
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
Technical Note: Post-burial alteration of bones: Quantitative characterization with solid-state 1H MAS NMR
No full textThe identification of markers of the modifications occurring in human bones after death and of the sedimentary and post-sedimentary processes affecting their state of preservation, is of interest for several scientific disciplines. A new index, obtained from spectral deconvolution of the 1H MAS NMR spectra of bones, relating the number of organic protons to the amount of hydrogen nuclei in the OH– groups of bioapatite, is proposed as indicator of the state of preservation of the organic fraction. In the osteological material from three different archaeological sites, this index resulted positively correlated with the extent of collagen loss derived from infrared spectroscopy. Its sensitivity to changes in the physical and chemical characteristics of bone allows to identify distinct diagenetic pathways specific to each site and to distinguish different trajectories within the same site
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
Bone diagenesis in the medieval cemetery of Vratislavs’ Palace in Prague
No full textDiagenetic modifications in human bones from the early-medieval cemetery discovered in the garden of Vratislavs’ Palace, in the central Malá Strana district of Prague, have been investigated combining histological analysis and instrumental analysis with X-ray diffraction, infrared, and 31P NMR spectroscopy. A total of 15 ribs samples were collected for the study. One sample belonged to a child, whereas, of the other samples from adults, 7 belonged to males, 5 to females, and for 2 the sex attribution was uncertain. A diagenetic pathway common to most of the studied samples was considered the result of a burial environment characterized by a nearly static water regime, with limited temperature excursions, moderately oxic to suboxic, and with pH fluctuations around the limit of apatite recrystallization window, in agreement with the fine textured clay-rich soil, its low hydraulic conductivity, and the measured soil pH. A second pattern, related to variations in the microenvironment, interested a limited number of samples with poorer histological preservation. This was interpreted as the result of higher pH and a better oxygenated environment, which favoured mineral recrystallization. Further reactivation of deterioration processes probably occurred later in some of the graves perturbed by works conducted in the seventeenth century. This work highlights the complementarity of the information obtained from the adopted techniques in order to gain insights into the post-mortem fate of the human remains and their sedimentary environment. In this respect, the quantification of the amount of phosphorus in the amorphous hydrated layer of apatite provided a unique type of information on the mineral component of bone and its reorganization during diagenesis, revealing that a relevant fraction can survive diagenesis, at variance with what previously supposed
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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