1,721,012 research outputs found
Steroids from sponges: occurrence of steroidal Δ4,7-3,6-diketones in the marine sponge Raphidostila incisa
No full textR. incisa contained C27-C29 steroidal 4,7,22-triene-3,6-diones along with major amts. of 5α,8α-epidioxy-Δ6 sterols. The structures of the hitherto undescribed steroidal 4,7-diene-3,6-diketones were proven by the synthesis of 4,7,22-ergostatriene-3,6-dione
Biomonitoring of human exposure to methyl bromide by isotope dilution mass spectrometry of peptide adducts
No full textA procedure for the determination of haemoglobin adducts formed by exposure to methyl bromide was evaluated as a possible method for the measurement of a biological index of exposure to the alkylating agent. The reaction products after in vitro incubation were used to design the chemical syntheses of deuterated peptides corresponding to the tryptic peptides where the modified residues had been identified. These peptides were used as standards for the quantitative evaluation of real samples, The correlation coefficient was r = 0.998 in the range 2.5-20 ppm. The relative standard deviation was about 3%, Blood samples were digested with trypsin and the mixture was analysed by liquid chromatography/electrospray mass spectrometry through selected ion monitoring of the mass signal relative to the modified peptides;, The analysis of blood samples from workers exposed to methyl bromide demonstrated the usefulness of this mass spectrometric-based method fur the monitoring of human exposure to the genotoxic alkylating agent via the synthesis of suitable peptide standards. This procedure is the first alternative method to the wed established monitoring of N-terminal adducts, the latter not being applicable to all alkylating agent
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
MASS-SPECTROMETRIC ANALYSIS OF RAT HEMOGLOBIN BY FAB-OVERLAPPING - PRIMARY STRUCTURE OF THE ALPHA-MAJOR AND OF 4 BETA-CONSTITUTIVE CHAINS
No full text1. The globin chain components of Sprague-Dawley rat hemoglobin were obtained by reverse-phase HPLC which showed the presence of two alpha-chain and four beta-chains. 2. The accurate molecular weight of each globin chain was determined by means of electrospray mass spectrometry. Extensive mass spectrometric analysis on several enzymatic digests by fast atom bombardment mass spectrometry (FAB-overlapping) meant to determine the complete sequence of the alpha-major and of the four beta-globins. 3. The primary structure of the alpha-major globin was found in agreement with literature data (Garrick et al., 1975 Biochem. J. 149, 245-258; Chua el al., 1987). 4. Sequence analysis of the four beta-globin chains showed that amino acid differences are restricted to two protein portions: the region 22-25 and 123-125, the remaining portions of the molecule being unchanged in the four globins. Furthermore, all the amino acid replacements correspond to single point DNA mutations and (with the exception of the substitution Asp 22 --> Asn in the beta(2)-globin) involve uncharged substitutions
Imbrunimento non enzimatico disoluzioni zuccherine. Nota 1 - Isolamento e caratterizzazione di derivati del furano da soluzioni acquose acide
No full textMASS-SPECTROMETRY IN FORENSIC CHEMISTRY .1. PIGMENT IDENTIFICATION BY DIRECT MIXTURE ANALYSIS IN A CASE OF BANK NOTE FALSIFICATION
No full textA rapid mass spectrometry procedure, based on direct mixture analysis using conventional electron ionization in both the low and high resolution modes, was used to match pigments present on a counterfeit $100 United States bank note with pigments contained in two inks suspected of having been used. The results demonstrated that the pigments present on the false bank note and those contained in the inks were the same
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
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