1,720,961 research outputs found
Fast and convenient synthesis of α-N-protected amino acid hydrazides
No full textA fast, simple and convenient synthesis of α-N-protected amino acid hydrazides is reported. The procedure involves the reaction between hydrazine monohydrate and the mixed anhydride obtained from an α-N-protected amino acid and ethyl chloroformate. When methylhydrazine was used, the reaction showed a good selectivity, yielding a mixture of 1-acyl-1-methylhydrazine and 1-acyl-2-methylhydrazine in a ratio 87:13. In contrast, when the reaction was carried out with phenylhydrazine, only 1-acyl-2-phenylhydrazine was obtained. No significant difference in reactivity was observed with the different amino acids and N-protection introduced
Bench-scale tests on ultrasound-assisted acidwashing and thermal desorption of mercury from dredging sludge and other solid matrices
No full textA series of ultrasonic assisted acid washing and thermal desorption tests were performed on sludge and other solid matrices with the aim to assay these removal technologies and to determine if the application of low frequency ultrasound was effective to enhance mercury removal. Unpolluted dredging sludge, 820 K calcinated dredging sludge, silica and alumina were characterized, polluted with a known concentration of mercury and treated both by acid washing and thermal desorption with and without low frequency ultrasound application. The acid washing was carried out by a 4% HNO3 acid solution and the thermal desorption was performed in a 370-620 K range. X-ray semi-quantitative analysis of dredging sludge before and after acid washing and granulometric curves of the matrices after the ultrasonic treatment were considered in order to evidence chemical or physical changes during these treatments. Total residual mercury measurements were carried out before and after sonication. Results showed not measurable acid washing extraction from polluted dredging sludge, a little (3%) extraction from 820 K heat-treated sludge and a significant (10-20%) extraction from alumina and silica within 120 min of treatment. The ultrasound application gave generally poor improvement of the mercury removal. On the contrary thermal desorption of mercury was somewhat effective for alumina, silica and heat-treated dredging sludge samples in which mercury removal was 30-40% at 370 K and 90-99% at 570 K. Likewise ultrasound application did not improve desorption. Instead, the thermal treatment of dredging sludge had a negligible amount of mercury desorption at 370 K but it reached 95% at 570 K. The application of ultrasound improved the thermal extraction of 25% in the 470-520 K range of temperature
Walking versus cycling test: Physiological responses in normobaric hypoxia
No full textBACKGROUND: Races that take place in the mountains cover a variety of terrains at several altitudes. Atest for predicting acute mountain sickness has been developed on the basis of a "normal" population but not on the basis of an athlete population. The aim of this study was to compare the Richalet Test to a specific test for athletes. METHODS: Eleven subjects (age: 29.7±8.9 years, VO2peak: 55.7±8.5 mL/kg/min) underwent two incremental tests on a cycle ergometer (CE) and treadmill (TR). Then, they underwent two tests on the CE and TR composed of: 1) five minutes of rest in normoxia; 2) five minutes of rest in hypoxia (fraction of inspired oxygen (11.5%); 3) five minutes of walking or cycling at an intensity of 80% of the respiratory compensation point in hypoxia; and 4) five minutes of rest in normoxia. We compared the following parameters at rest and during exercise: Desaturation, ventilatory and cardiac response. RESULTS: None of the mean values of the investigated parameters differed between the two tests (P>0.05), but some subjects who had out-of-range values on the CEdid not have out-of-range values on the TR(or vice versa). CONCLUSIONS: We showed that there were: 1) no differences in the mean values of the analyzed parameters between the two protocols; and 2) that the responses to the CEand TRprotocols varied across individuals. For individuals who are planning to hike or run at a high altitude they should undergo a walking test. Additionally, when athletes plan to compete at high altitudes, the intensity of the test should be similar to that planned for the race
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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