1,720,969 research outputs found
Comparison of Ten Metal-Doped LaFeO3 Samples on Photocatalytic Degradation of Antibiotics in Water under Visible Light: Role of Surface Area and Aqueous Phosphate Ions
Full text linkDoping semiconducting oxides, such as LaFeO3 (LF), with metallic elements is a good strategy to improve the performance of photocatalysts. In this study, LF and ten different nanopowders metal-doped at the La or Fe site of LaFeO3 were evaluated in the photocatalytic degradation of ciprofloxacin (CP) and oxytetracycline (OTC). The following metals were used in the doping (mol%) process of LF: Pd 3% and 5%; Cu 10%; Mg 5%, 10%, and 20%; Ga 10%; Y 10% and 20%; and Sr 20%. The doped samples were synthetized using a citrate auto-combustion technique. From the X-ray diffraction (XRD) data, only a single crystalline phase, namely an orthorhombic perovskite structure, was observed except for trace amounts of PdO in the sample with Pd 5%. The specific surface area (SSA) ranged from 9 m(2) g(-1) (Ga 10%) to 20 m(2) g(-1) (Mg 20%). SEM images show that all samples were constituted from agglomerates of particles whose sizes ranged from ca. 20 nm (Mg 20%) to ca. 100 nm (Pd 5%). Dilute aqueous solutions (5 x 10(-6) M) prepared for both CP and OTC were irradiated for 240 min under visible-light and in the presence of H2O2 (10(-2) M). The results indicate a 78% removal of OTC with Cu 10% doped LF in a phosphate buffer (pH = 5.0). The degradation of CP is affected by pH and phosphate ions, with 78% (in unbuffered solution) and 54% (in phosphate buffer, pH = 5.0) removal achieved with Mg 10% doped LF. The reactions follow a pseudo-first order kinetic. Overall, this study is expected to deepen the assessment of photocatalytic activity by using substrates with different absorption capacities on photocatalysts
Rammed Earth stabilised with waste materials: A sustainable and resistant solution
Full text linkEarthen dwellings are part of the vernacular architecture and cultural heritage of many countries in the Mediterranean region, and a renovated interest towards these types of structures is now widespread in the same countries mainly due to sustainability reasons. However, poor resistance to weathering compromises their durability and their popular acceptance. A fascinating option to improve the resistance of earthen structures while preserving their environmental sustainability is to use locally available waste materials as stabilisers. In this paper, the evolution over time of the mechanical resistance of rammed earth stabilised with residues from widespread industrial processes (i.e. fly ash from coal combustion and calcium carbide residue from acetylene production) was investigated. Waste-stabilisation prompted optimal long-term mechanical resistance; on the other hand, laboratory samples exhibited low compressive strengths in the short-term when cured under standard conditions. The addition of a supplementary industrial residue (i.e. gypsum from flue gas desulfurization) was explored to enhance the early-age strength. Results confirmed the short-term strength benefits induced by gypsum addition
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
The system Al2O3 and (Sr,Mg)-doped LaGaO3: phase composition and electrical properties
No full textMixtures of a-Al2O3 and La0.8Sr0.2Ga0.8Mg0.2O3 d, with a-Al2O3 concentrations ranging from 1 to 20 wt.%, were uniaxially and
isostatically pressed and finally sintered at 1500 jC for 4 h. The phase composition and microstructure were investigated by X-ray powder
diffraction and scanning electron microscopy techniques. The electrical properties were studied by complex impedance spectroscopy in a
wide range of temperatures (200–800 jC) in air. In the sintered bodies pure a-Al2O3 was not detected; the partial substitution of Al for Ga
was suggested entailing the formation of the solid solutions of perovskite-type (La0.8Sr0.2)(Ga1 x yAlxMgy)O3 d and La0.8Sr0.2Ga1 xAlx
O3 d. a-Al2O3 added to La0.8Sr0.2Ga0.8Mg0.2O3 d inhibited the grain growth of the majority phase. Under isothermal conditions, the
electrical conductivity decreases with increasing alumina content, while the activation energies increase
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
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