1,720,975 research outputs found
Natural products with taxol-like anti-tumour activity : synthetic approaches to eleutherobin and dictyostatin
No full textEleutherobin and dictyostatin are antimitotic compounds which exert their cytotoxic activity by a taxol-like mode of action, i.e., hypernucleating tubulin assembly and interfering with the dynamic instability of the cytoskeleton during mitosis. A formal total synthesis
of eleutherobin was accomplished by accessing a key intermediate reported by
Danishefsky and coworkers in their 1998 synthesis of the natural product. The key step of our strategy, used for obtaining the [8.4.0] fused bicyclic ring system, is a ring-closing metathesis (RCM) reaction of a densely functionalized diene under forcing conditions, using Grubbs’ second-generation catalyst. Synthetic approaches to dictyostatin are also described,
and in particular the preparation of the C15–C23 fragment of the macrolide, containing 5 of its 11 stereocenters
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
Dose-response decrease in plasma tryptophan and brain tryptophan and serotonin after tryptophan-free amino acid mixtures in rats
No full textRats fasted 15 hours were treated p.o. with increasing amounts (660 and 1320 mg/kg body weight) of a mixture containing a fixed proportion of seven essential amino acids (L-phenylalanine 13.6%, L-leucine 6.0%, L-isoleucine 12.1%, L-methionine 12.1%, L-lysine 30.3%, L-threonine 10.6%, L-valine 15.2%) and lacking tryptophan. The mixtures produced a dose-response decrease of free (by 34% after the lower dose and by 58% after the higher dose of the mixture) and total (by 10 and 31%) plasma tryptophan and of brain tryptophan (by 38 and 65%), serotonin (by 17 and 41%) and 5-hydroxyindole acetic acid (by 21 and 49%). The mechanisms of these changes are discussed
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
Effectiveness of diclofenac eyedrops in reducing postoperative inflammation and angiographic CME after cataract surgery
No full textEffectiveness of diclofenac eyedrops in reducing inflammation and the incidence of cystoid macular edema after cataract surgery
No full textPURPOSE: To evaluate the effectiveness of diclofenac eyedrops in reducing inflammation and the incidence of angiographic cystoid macular edema (CME) after cataract surgery and intraocular lens (IOL) implantation.
SETTING: Eye Clinic, Institute of Biomedical Sciences, San Paolo Hospital, Milan, Italy.
METHODS: Eighty-eight patients having cataract extraction were enrolled in a randomized clinical trial: 42 were given diclofenac eyedrops and 46, placebo. Postoperative inflammation in both groups was graded for 6 months using a dedicated system.
RESULTS: Eight patients (9%) had evidence of angiographic CME approximately 1 month after surgery: seven of these were in the placebo group (P = .039). This difference was not significant 3 and 6 months postoperatively. The signs of ocular inflammation were greater in the eyes receiving placebo; the difference was particularly evident up to 1 week after surgery. There was no significant difference in visual acuity between the two groups at any follow-up point, but the contrast sensitivity of the eyes that received diclofenac improved significantly at 10.5 cycles per degree 1 month postoperatively.
CONCLUSION: Diclofenac eyedrops effectively reduced ocular inflammation and the occurrence of angiographic CME after cataract surgery
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
- …
