1,721,182 research outputs found
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
Simultaneous ultra-high performance liquid chromathograpy-electrospray ionization-quadrupole-time of flight mass spectrometry quantification of endogenous anandamide and related N-acylethanolamides in bio-matrices
No full textWe describe and validate a sensitive UHPLC-ESI-QTOF-MS method for the simultaneous quantification of seven endocannabinoids and non-endocannabinoids related N-acylethanolamides: N-arachidonoylethanolamide, N-palmitoylethanolamide, N-stearoylethanolamide, N-oleoylethanolamide, N-linoleoylethanolamide, N-α-linolenoylethanolamide and N-eicosapentaenoylethanolamide in several bio-matrices for the purpose of research and clinical application. We examined effects of different liquid-liquid and solid phase extraction on the recovery of endocannabinoids and N-acylethanolamides. Protein precipitation with cooled acetone and extraction with acetonitrile (1% v/v formic acid) using OASIS HLB cartridge gave better results. Separation was performed on a Waters Acquity UPLC HSST3 column using a 9min elution gradient coupled with high resolution mass spectrometry (QTOF/MS). The high sensitivity of the developed method allow its application on sample with low volumes or low levels of endocannabinoids and N-acylethanolamides and make the method suitable for routine measurement in human bio-matrices, such as plasma, serum (500μL), urine (1mL) and tissues (10-30mg). Its application in clinical research could contribute to unravel pathophysiological roles of these family of lipid mediators and disclose novel diagnostic and prognostic marker
Automated fast procedure for the simultaneous extraction of hair sample performed with an automated workstation
No full textIntroduction: Hair testing has a leading role in toxicology practice and even more in those aspects tightly linked to the assessment of psychoactive drug use and abuse in social life. Aim: The objective of the present study was to develop and validate an automated SPE sample-preparation step, suited for GC/MS confirmation analysis of basic drugs in hair drug control. The method was studied and optimized for quantitative determination and in a second time it was extended to real hair samples. The purpose of method validation was to ensure good reliability, reproducibility and quickness. Methods: Janus Automated Workstation (PerkinElmer) was employed to perform SPE hair extraction, using 96-well plate SPEC MP1 acquired from Varian (Agilent Technologies). After derivatization of dried extracts, screening confirmations were performed using gas chromatography (GC) followed by mass spectrometry (MS). GC/MS data were validated following standard guidelines, but our attention was focused on three headings: samples cross-contamination, "memory effect" and extraction recovery. Results: Validation requests were fully accomplished and we always obtained best results with the automated procedure. For instance, analytes mean recovery was between 70 and 90% and data analysis proved that no contamination between samples occurred. Conclusions: The automated workstation has shown good reliability (cross contamination and "memory effect" were tested and excluded), effectiveness (no false negative was detected), solvent saving (500 μL/sample vs traditionally LLE 4. mL/sample) and quickness (50. min for 96 tests cycle)
Identificazione del butilone in un soggetto poliassuntore di sostanze stupefacenti
No full textNella presentazione viene descritto un caso di suicidio mediante impiccamento di un soggetto maschio di 41 anni, noto assuntore di sostanze stupefacenti, tra le quali cocaina, cristalmet e mefedrone, affetto da depressione ed in terapia con lormetazepam.
Le indagini tossicologiche hanno evidenziato la presenza del catinone sintetico butilone a livello urinario e nella matrice pilifera. Nel sangue è stata rilevata solamente la presenza di benzoilecgonina, mentre nella matrice pilifera, oltre al butilone, sono risultate presenti cocaina, benzoilecgonina, amfetamina,metamfetamina, MDMA, ketamina e citalopram.
La peculiarità del caso è insita nel rilievo del butilone che, non essendo presente nelle librerie computerizzate di spettri di massa, è stato identificato attraverso il raffronto con gli spettri di massa reperiti in letteratura e con l’analisi HPLC-qTOF con la determinazione della massa esatta
Mass quantification of anandamide and related N-acylethanolamides in plasma for clinical investigations
No full textThe endocannabinoid (EC) anandamide and the related N-acylethanolamides (NAEs) are a family of lipid mediators involved in a wide range of biological effects. It is well known that EC plays a role in the regulation of energy homeostasis and lipid and glucose metabolism, in the regulation of the immune system [1] and in various aspects of human reproduction [2]. Furthermore the endocannabinoid system is believed to regulate energy balance and behaviour among which food intake, fear, and anxiety [3]. It became clear that an altered qualitative or quantitative production of these substances might contribute to the outcome of some pathologies demonstrating the need of a sensitive analytical method for the accurate identification and quantification of these molecules in biological fluids of healthy subjects and patients. We describe the set up of a sensitive solid phase extraction and isotope-dilution UPLC-MS/MS method for the simultaneous quantification of seven EC and NAEs in human plasma and serum for the purpose of research and clinical application. We examined effects of different protein precipitation protocols and liquid-liquid extraction and solid phase extraction on the recovery of ECs and NAEs and matrix effects. Protein precipitation with cooled acetone and extraction with acetonitrile (1% formic acid) using OASIS HLB cartridge gave better results. Separation was performed on an Waters Acquity UPLC hsst3 column using a gradient elution coupled with tripe-TOF MS in 9 minutes. Calibration curves range from 0.125 ng/ml to 200 ng/ml for each NAEs. The developed method is suitable for routine measurement of ECs and NAEs analysed in human plasma and serum samples (500 μl) in clinical settings as shown by quality control samples. [1] Nagarkatti P, Pandey R, Rieder SA, Hegde VL, (2009) Future Med Chem 1:1333-1349. [2] Taylor AH, Amoako AA, Bambang K, Karasu T, Gebeh A, Lam PM, Marzcylo TH, Konje JC (2010) Clin Chim Acta 411:921-930. [3] Di Marzo V, Matias I (2005) Nature Neurosci 8:585-589
- …
