1,721,167 research outputs found
Ricerche scientifiche in Egitto e Siria: il carteggio fra Francesco Redi e Alessandro Pini (1681-84)
No full textSulla base di un carteggio esistente presso la Biblioteca Laurentiana di Firenze è stato analizzato criticamente il carteggio Redi, frutto dei rapporti epistolari fra Francesco redi e Alessandro Pini. Da esso si deducono interessanti notizie anche a livello di etnodemografia medica su l'Impero Turco nel XVII secolo
Insights into the mechanism(s) of action and therapeutic applications of Esculentin-1a-derived antimicrobial peptides
Full text linkCationic α-helical antimicrobial peptides (AMPs) hold promise for treatment of the raising multi-drug resistant microbial infections, due to their broad spectrum of activity and membrane-perturbing mechanism of action. Compared to conventional antibiotics, these features make them newsworthy molecules that hardly induce microorganisms to acquire resistance to them. Among these pathogens, Pseudomonas aeruginosa is the most clinically relevant Gram-negative bacterium known to cause serious human infections, e.g. pneumoniae, especially in immune-compromised patients, such as cystic fibrosis (CF) sufferers and keratitis, associated to contact lens (CL) wear. This is due to the unique ability of this pathogen to adhere to different types of inert materials or biological tissues, and to grow in a more resistant and dangerous sessile life form, called biofilm. Recently, two Esculentin-1a-derived antimicrobial peptides i.e. Esc(1-21) and its D-amino acids containing Esc(1-21)-1c, [Esc peptides], have been fully characterized for their powerful antipseudomonal activity against both planktonic and biofilm forms. The diastereomer showed a higher bactericidal activity than the all-L isomer against the more dangerous Pseudomonas biofilm phenotype; a lower cytotoxicity and higher biostability. However, when tested in vitro against the free-living form of this pathogen, it displayed a weaker bactericidal effect. Here, to investigate the reason accounting for this discrepancy, mechanistic studies on intact bacterial cells were initially carried out. Then to further understand the effect of packing parameters, i.e. composition, charge, shape and negative intrinsic curvature of membrane phospholipids in the membrane-permeabilizing activity of Esc peptides, leakage assays and circular dichroism spectroscopy analysis were carried out. Our results have suggested that the weaker in vitro antibacterial activity of Esc(1-21)-1c on the planktonic phenotype of the Gram-negative bacterium P. aeruginosa is mainly correlated to a slighter ability in permeabilizing both outer and inner bacterial membranes. Notably, experiments with lipid vesicles have suggested that if electrostatic interactions between negatively-charged membrane phospholipids and positively-charged peptide molecules do play a crucial role in the peptides’ membrane perturbing activity, this latter is hampered by the bilayer structure packing parameters including hydrogen bonding and intrinsic curvature, associated to phosphatidylserine (PE), especially for the diastereomer compared to all-L parent peptide. In parallel, we explored the molecular mechanism underlying the biofilm inhibition activity of Esc peptides when used at dosages below the minimal growth inhibitory concentration (1/8 MIC), by studying the peptides’ effect on the expression of key genes involved in the bacterial virulence and motility, as well as the peptide’ interaction with the bacterial signaling nucleotide ppGpp. Our findings revealed that the two D-amino acids containing Esc(1-21)-1c, confer the peptide the ability to downregulate the expression of biofilm-associated genes, likely as a result of increased peptide stability and prolonged binding to ppGpp compared to the all-L peptide. Furthermore, we reported two different applicative strategies to ameliorate the biological properties of these two AMPs: (i) encapsulation in poly(lactide-co-glycolide) (PLGA) nanoparticles; and (ii) covalent conjugation to soft CLs. In the first case, to enhance the peptides’ bioavailability and to optimize their translocation to the target infectious site, Esc peptides were loaded into PLGA nanoparticles (NPs) engineered with polyvinyl alcohol (PVA). The peptides-loaded NPs were found to be more efficient in diffusing through artificial CF mucus and simulated bacterial extracellular matrix compared to the free peptides. Moreover, they were more efficient in inhibiting P. aeruginosa growth under both in vitro and in vivo conditions at long term. In the second case, Esc peptides were covalently immobilized to hydrogel soft CLs and tested for their ability to reduce bacterial colonization. The antimicrobial CLs were able to cause more than four log reduction in the number of bacterial cells within 20 min and to reduce bacterial adhesion to their surface in 24 hours. Finally, the ability of both peptides to limit the onset of microbial resistance was also evaluated by exposing Pseudomonas strains to multiple cycles of treatment at sub-MIC dosages. Interestingly, in contrast with conventional antibiotics, Esc peptides did not induce resistance in P. aeruginosa cells. Overall, besides providing knowledges on the molecular mode(s) of action the two esculentin-derived AMPs, our data suggest that Esc peptides, particularly Esc(1-21)-1c, have great potential to be developed as novel drugs for treatment and prevention of P. aeruginosa pneumonia and keratitis
Simulation model of a passive decay heat removal system for lead-cooled fast reactors
No full textThe generation IV lead cooled fast reactors are of particular interest for the Italian research: several influential companies (Ansaldo Nucleare, ENEA) are involved in these important European R&D projects. At present, one significant European project in progress is lead cooled European advanced demonstrator reactor (LEADER) which includes, among its goals, the construction of a lead-cooled fast reactor demonstrator, advanced lead fast reactor European demonstrator (ALFRED). The demonstrator has to include technical solutions that simplify the construction phase and assure full safety in operation; according to the latest guidelines, ALFRED final configuration will be characterized by a secondary loop providing bayonet-tube steam generators. The authors have addressed the issue of bayonet-tube steam generators proposing the external boiling bayonet steam generator (EBBSG) system, in which the reaction heat is extracted from the lead by means of coolant under vapor phase. This is possible thanks to an external feed-water boiling, based on the known Loeffler scheme, coupled to the bayonet tube concept. In the present paper, the authors propose a decay heat removal (DHR) system to match the EBBSG scheme. The DHR system is fully passive, exploiting natural circulation phenomena. The performance of the proposed DHR system is investigated through a Matlab-Simulink model. The results are satisfactory since, according to the simulations, the proposed DHR system is able to keep the primary coolant temperature within a safety range for a sufficient time, avoiding the lead freezing or over-heating
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
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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