1,720,989 research outputs found
Supercritical fluid extraction of paclitaxel and baccatin III from needles of Taxus cuspidata
No full textPaclitaxel and baccatin III are extracted from the ground needles of the yew tree Taxus cuspidata using supercritical carbon dioxide with and without the addition of several cosolvents, The pressure and temperature ranges tested were from 100 to 300 bar and from 305 to 343 K, respectively, and the cosolvents were ethylacetate, methanol, dichloromethane, and ethylether. To diminish a variety of waxy and nonpolar compounds the ground needles are treated with n-hexane before the extraction. The highest selectivity of paclitaxel and baccatin III in the extracts during the first four hours of SFE was about 0.262 and 0.644 mass %, respectively. Supercritical fluid extraction using carbon dioxide with and without cosolvents was found to be more selective than the conventional organic solvent extraction.This work was supported by the Ministry of Science
and Technology, the Korea Science and Engineering
Foundation, and the University Awards Program of the
Korea Advanced Institute of Science and Technology
Detection of cognitive impairment using a machine-learning algorithm [Corrigendum]
No full textYoun YC, Choi SH, Shin HW, et al. Neuropsychiatr Dis Treat. 2018;14:2939–2945.On page 2944, under Supplementary materials section, the Table S2 was incorrect.Read the original article
SUPERCRITICAL-FLUID EXTRACTION OF TAXOL AND BACCATIN-III FROM NEEDLES OF TAXUS-CUSPIDATA
No full textTaxol and baccatin III were extracted from the ground needles of Taxus cuspidata using supercritical carbon dioxide mixed with 3 wt % ethanol as a cosolvent. The pressure and temperature ranges used to attain supercritical fluid condition are 100 approximately 300 bar and 40 approximately 70-degrees-C, respectively. However, the amount of taxol and baccatin III in the extract obtained at 100 bar was not noticeable, while the major portion of extract was found to be the waxy compounds. The highest selectivity of taxol and baccatin III were about 0.094 and 0.158 wt %, respectively, at 40-degrees-C and 300 bar. At the same pressure and temperature condition, taxol and baccatin III selectivities in the extract obtained from the ground seeds of Taxus cuspidata was about 0.198 and 0.157 wt %, respectively.This work was supported by the Ministry of Science and Technology, the Korea Science and
Engineering Foundation, and University Awards Program of the Korea Advanced Institute of Science and
Technology
Nuclear quadrupole interactions of the Rb-87 nuclear magnetic resonance in a nonlinear optical crystal RbTiOAsO4
No full textThe Rb-87 nuclear magnetic resonance (NMR) in a RbTiOAsO4 single crystal was investigated by employing a Bruker FT NMR spectrometer. Instead of one central line, four central lines were obtained. There were two sets of crystallographically inequivalent Rb+ ions: Rb(1) and Rb(2). Two resonance lines in the Rb(1) nucleus and two resonance lines in the Rb(2) nucleus were caused by magnetically inequivalent sites. The angular dependences led to different values for the quadrupole coupling constant and the asymmetry parameter: e(2)qQ/h = 19.26 +/- 0.03 MHz and eta = 0.59 +/- 0.02 for the Rb(1) ion, and e(2)q Q / h = 23.58 +/- 0.07 MHz and eta = 0.44 +/- 0.05 for the Rb(2) ion. The EFG tensors of Rb(1) and Rb(2) were non-axially symmetric, and the orientations of their principal axes did not coincide. The Rb(1) ions, which are surrounded by nine oxygen atoms, are low in symmetry while the Rb(2) ions, which are surrounded by nine oxygen atoms, show high symmetry
An intramolecular interaction between Src homology 3 domain and guanylate kinase-like domain required for channel clustering by postsynaptic density-95/SAP90
No full textMembers of the postsynaptic density-95 (PSD-95)/SAP90 family of membrane-associated guanylate kinase (MAGUK) proteins function as multimodular scaffolds that organize protein-signaling complexes at neuronal synapses. MAGUK proteins contain PDZ, Src homology 3 (SH3), and guanylate kinase (GK)-like domains, all of which can function as sites for specific protein-protein interactions. We report here a direct protein-protein interaction between the SH3 domain and the GK region in the PSD-95 family of MAGUKs. The SH3 domain of the PSD-95 family appears to have an atypical binding specificity, because the classical SH3 binding (-P-X-X-P-) motif is absent from the GK domain. Although SH3-GK binding can occur in either an intramolecular or intermolecular manner, the intramolecular mode is preferred, possibly because of additional tertiary interactions available when the SH3 and GK domains are adjacent in the same polypeptide. Mutations disrupting the intramolecular SH3-GK interaction do not interfere with PSD-95 association with the K+ channel Kv1.4 or with the GK domain-binding protein GKAP. The same mutations, however, inhibit the clustering of Kv1.4 by PSD-95, suggesting that the intramolecular SH3-GK interaction may modulate the clustering activity of PSD-95.This work was supported by the Brain Science Research Program of Korea Ministry of Science and Technology, Korea Research Foundation Grants 98-019-D00022 and 99-041-D00352, and the Korea Science and Engineering Foundation 1999 grant (E.K.). M.S. is Assistant Investigator of the Howard Hughes Medical Institute
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
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