1,720,964 research outputs found
Self-assembling in surfactant aggregates: An alternative way to the realization of fluorescence chemosensors for Cu(II) ions
No full textThe self-assembling of the proper subunits of fluorescence chemosensors within surfactant aggregates in water allows the easy design, realization, and testing of new effective sensing systems. It was shown that a proper ligand and a fluorescent dye, once transferred from bulk water into an inert surfactant aggregate, are kept in such a close proximity that communication between the binding site and the signaling unit effectively occurs, thus avoiding the need for a covalent connection between the sensor's two units. To further simplify the sensing system and get rid of the inert surfactant which somehow implies the dilution of the sensor's active components in the aggregate, we have synthesized a series of lipophilic ligands for Cu(II) based on dipeptides GlyLys and GlyGlu functionalized with n-alkyl chains of different lengths at the N-terminus. These ligands are soluble in water and can form homoaggregates in the absence and in the presence of Cu(II) ions. Lipophilic fluorophores, like 8-anilino-naphthalensulfonic acid or Rhodamine 6G, are effectively bound into the aggregate pseudophase, and the binding of Cu(II) ions to the dipeptide units causes a strong fluorescence quenching. The sensor system is very sensitive to Cu(II) (concentrations in the submicromolar range are detected), is promptly reversible, and no interference is observed due to the presence of many metal ions. The sensitivity of the systems improves by decreasing the ligand concentration and (up to a point) the ligand's cmc
Self-Assembling in Surfactant Aggregates: an Alternative Way to the Realization of Fluorescent Chemosensors for Cu(II) Ions
No full textSimultaneous LC-HRMS determination of 28 benzodiazepines and metabolites in hair
No full textA liquid chromatography-high resolution mass spectrometry (LC-HRMS) method for the simultaneous identification and quantification of 28 benzodiazepines, including 6 metabolites, in 50 mg of hair has been validated. Positive ion electrospray ionization and HRMS determination in full-scan mode were realized on an Orbitrap mass spectrometer at a nominal resolving power of 60,000. In-source collisional experiments were conducted to obtain additional information for a more reliable identification of the investigated drugs. HRMS in full-scan mode allowed the exact determination of molecular masses of all analytes eluting in the HPLC run, so that both the immediate and retrospective screening of results for drugs and their metabolites were available. Sample preparation consisted of an overnight incubation in phosphate buffer pH 8.4 and a subsequent liquid/liquid extraction with methylene chloride/diethyl ether (90:10). Gradient elution was performed on a Luna C18 analytical column and four deuterated analogues were used as internal standards (IS). Validation was performed using both spiked hair samples and hair samples from subjects treated with benzodiazepines. Selectivity was evaluated by analysis of 20 certified blank hair samples. Extraction efficiency and matrix effects were evaluated by analysis of true positive samples. The lowest limits of quantification (LLOQs) ranged from 1 to 10 pg/mg. Linearity was investigated in the range from LLOQ to 1,000 pg/mg, for each compound (R(2) 0.998-0.999). Mean relative errors, calculated at three concentration levels, ranged from 1 to 20% (absolute value). Precision, at concentrations higher than the LLOQs, was always less than 15% expressed as percentage relative standard deviation. After validation, the procedure was applied to real samples collected for clinical and forensic toxicology purposes from subjects who were assumed to have taken benzodiazepines
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
Monitoring haloperidol exposure in body fluids and hair of children by liquid chromatography-high-resolution mass spectrometry.
No full textNeonatal Hair-Analysis by Liquid Chromatography-High-Resolution Mass Spectrometry to Reveal Gestational Exposure to Venlafaxine
Full text linkVenlafaxine (VEN) is a second generation antidepressant drug, belonging to the class of selective serotonine and norepinephrine reuptake inhibitors, widely used in the treatment of depression and anxiety disorders. Though its pharmacological profile is considered safe, treatment with VEN can cause several nervous, gastrointestinal, cardiovascular and genitourinary adverse effects. Therapeutic drug monitoring for VEN could be useful in specific situations, including exposure to the drug during pregnancy. A liquid chromatography-high-resolution mass spectrometry method was developed and validated for the assay of VEN in 2.5-mg hair samples from 2 newborn identical twin sisters. The analyte was extracted by a rapid, simultaneous pulverization and extraction step, allowing analysis when tiny amounts of hair are available, such as in the case of a newborn. Gradient elution on an Atlantis T3 column was performed using nordiazepam-d5 as an internal standard. Positive ion electrospray ionization and high-resolution full scan determination were performed in an Orbitrap mass spectrometer. The method was linear range in the range 0.2-25 ng/mg, and had a quantification limit of 0.2 ng/mg, a relative standard deviation in the range 0.7%-1.4% (intra-assay) and 2.9%-5.9% (interassay), and was accurate (as % relative error) in the range -9% to + 2%, using a hair sample size as low as 2.5 mg. The utilization of high-resolution/high accuracy mass spectrometry in full-scan mode allowed both the quantitative determination of VEN in the hair of the 2 newborns and the straightforward identification of 4 VEN metabolites, namely O-desmethylvenlafaxine, N-desmethylvenlafaxine, N,N-didesmethylvenlafaxine, and N,O-didesmethylvenlafaxine, by means of retrospective screening, thus unequivocally documenting in utero exposure
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
High performance liquid chromatography-high resolution mass spectrometry and micropulverized extraction for the quantification of amphetamines, cocaine, opioids, benzodiazepines, antidepressants and hallucinogens in 2.5 mg hair samples
No full textA high performance liquid chromatography-high resolution mass spectrometry (HPLC-HRMS) method for simultaneous screening and quantification of 28 drugs was developed and validated for 2.5 mg hair samples. Target drugs and their metabolites included amphetamines, cocaine, opioids, benzodiazepines, antidepressants, and hallucinogens. After decontamination, hair samples were extracted with 200 μL of a mixture of water: acetonitrile:1 M trifluoroacetic acid (80:10:10, v/v) using a 5 min simultaneous pulverization/extraction step. The extracts were analysed by HPLC-HRMS in an Orbitrap at a nominal resolution of 60,000, with concomitant in source collisional experiments (in source CID). Gradient elution on an Atlantis T3 column resolved 28 target compounds and 5 internal standards. Total chromatographic run time was 26 min. Calibration was achieved by linear regression analysis utilizing six calibration points; R2 ranged from 0.9964 to 0.9999, the limits of quantification were 0.1 ng/mg for 8 compounds, 0.2 ng/mg for 16 compounds and 0.5 ng/mg for 4 compounds; mean relative errors from -21% to +23% were obtained; relative standard deviation, used to estimate repeatability and intermediate reproducibility at three concentrations, was always less than 20%. Process efficiency and recoveries for all analytes were better than 65 and 73%, respectively, at any concentration. The method was applied to hair samples from forensic investigations that contained a broad assortment of drugs of abuse and pharmaceuticals. The use of concomitant HRMS full scan and CID afforded the possibility of retrospective analysis for discovering untargeted drugs
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