1,720,967 research outputs found
Lipophilic and polar interaction forces between acidic drugs and membrane phospholipids encoded in IAM-HPLC indexes: their role in membrane partition and relationships with BBB permeation data.
No full textThe membrane phospholipid affinity data, logkwIAM , for 18 acidic and unionized drugs spanning a wide lipophilicity range were measured by HPLC on two different phospholipid stationary phases, i.e. IAM.PC.MG and IAM.PC.DD2. These data related weakly with both log PN values, the n-octanol/water partition coefficients of the neutral forms, and log D7.4 values, the n-octanol/water partition coefficients of the mixtures of neutral and ionized forms at pH 7.4. The lack of collinearity confirms that, differently from partition in n-octanol/water, partition in phospholipids encodes not only lipophilic/hydrophobic intermolecular recognition forces but also ionic bonds, due to electrostatic interactions between electrically charged species and phospholipids, according to the ???pH-piston hypothesis???. Since, differently from bases, electrostatic interactions between acids and phospholipids take place at the surface of phospholipid layers (choline moieties), and not near their lipophilic core (phosphate moieties), they were parameterized by a new procedure yielding ?????' logkwIAM??? parameters, i.e. the difference between the IAM retention factors observed for the analytes and those of neutral compounds with the same n-octanol partition values displayed by the analytes at pH 7.4. All acidic analytes, but one, and all unionized analytes, but the unionizable ones, showed positive ??'logkwIAM values, indicating that they partition stronger in phospholipids than in n-octanol. Log BB values (capability to pass BBB) weakly related with both lipophilicity and phospholipid affinity values; in contrast they inversely related with ??'logkwIAM values. The relationships between log BB and ??'logkwIAM practically overlapped the previously found log BB/??logkwIAM relationships for bases. The excess of polar interaction component between acidic drugs and phospholipids, mainly electrostatic forces, although enhancing partition in phospholipids, hinders membrane passage, analogously to the behavior previously reported for bases.
The study suggests that IAM-HPLC is an effective technique to perform simple and fast measurements of the intermolecular recognition forces related to membrane partition and permeation. This can contribute to better understand the mechanisms governing both partition of charged species in cell membranes and passage through them, also allowing the possible optimization of the pharmacokinetic properties of the drugs at the early stages of their development
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
Caratterizzazione quali-quantitativa del PM10 nelle aree individuate come critiche nel piano regionale di tutela della qualità dell'area, al fine di comprendere con rigore scientifico la loro origine.
No full textIl particolato atmosferico, i cui effetti negativi sulla salute umana sono ormai ben noti dalla comunità scientifica, è una matrice ambientale di grande complessità e variabilità.
Pertanto, grazie alla collaborazione con l'Agenzia Regionale Protezione Ambientale Campania (ARPAC), è stato analizzato il PM10 nelle sue componenti chimiche (specie ioniche,metalli,IPA e componenti carboniose) ed è stato associato lo stesso a possibili fonti d'origine mediante l'utilizzo di un modello a recettore (PMF)
Level, potential sources of polycyclic aromatic hydrocarbons (PAHs) in particulate matter (PM10) in Naples
No full textIn Naples, particulate matter PM10 associated with polycyclic aromatic hydrocarbons (PAHs) in ambient air were determined in urban background (NA01) and urban traffic (NA02) sites.The principal objective of the study was to determine the concentration and distribution of PAHs in PM10 for identification of their possible sources (through diagnostic ratio - DR and principal component analysis - PCA) and an estimation of the human health risk (from exposure to airborne TEQ). Airborne PM10 samples were collected on quartz filters using a Low Volume Sampler (LVS) for 24 h with seasonal samples (autumn, winter, spring and summer) of about 15 days each between October 2012 and July 2013. The PM10 mass was gravimetrically determined. The PM10 levels, in all seasons, were significantly higher (P < 0.001) in the urban-traffic site (NA02) than in the urban-background site (NA01). The filters were then extracted with dichloromethane using an ultrasonicator (SONICA) to perform a detailed characterization of 12 priority PAHs proposed by the USEPA, by gas chromatography-mass spectrometer (GC-MS) analysis.The concentration of Benzo[a]Pyrene, BaP (EU and National limit value: 1 ng m-3 in PM10), varied from 0.065 ng m-3 during autumn time to 0.872 ng m-3 in spring time (NA01) and from 0.120 ng m-3 during autumn time to 1.48 ng m-3 of winter time (NA02) with four overshoots.In NA02 the trend of σ12 PAHs was comparable to NA01 but were observed higher values than NA01. In fact, the mean concentration of σ12 PAHs, in urban-traffic site was generally 2 times greater than in urban-background site in all the campaigns.PAHs with 5 and 6 ring, many of which are suspected carcinogens or genotoxic agents, (i.e Benzo[a]Pyrene, Indeno[1,2,3-cd]Pyrene, Benzo[b]Fluoranthene, Benzo[k]Fluoranthene and Benzo[g,h,i]Perylene), had a large contribution (~50-55%) of total PAHs concentration in PM10 in two sites and in each of the campaigns.Diagnostic ratio analysis and PCA suggested a substantial contributions from traffic emission with minimal influence from coal combustion and natural gas emissions. In particular diesel vehicular emissions were the major source of PAHs at the studied sites. The use of Toxicity Equivalence Quantity (TEQ) concentration provide a better estimation of carcinogenicity activities; health risk to adults and children associated with PAHs inhalation was assessed by taking into account the lifetime average daily dose and corresponding incremental lifetime cancer risk (ILCR). The ILCR was within the acceptable range (10-6-10-4), indicating a low health risk to residents in these areas
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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