1,721,172 research outputs found
Choline-based eutectic mixtures as catalysts for effective synthesis of cyclic carbonates from epoxides and CO2
Full text linkCO2 is a renewable, abundant and cheap C1-feedstock and its conversion to cyclic carbonates starting from
epoxides has been widely explored in the last years. Nevertheless, conducting this reaction under mild and
sustainable conditions is still a challenging task. Herein we present the use of choline-salt based eutectic mixtures
as catalysts for the reaction of CO2 with epoxides to give cyclic carbonates. Choline chloride and choline iodide
have been coupled with various hydrogen bond donors (HBDs), mainly cheap and bio-based carboxylic acids and
polyols, to form two classes of eutectic mixtures. Very good yields were achieved under mild conditions (80 ◦C in
7–22 h) for various terminal epoxides, with both classes of catalysts. While a pressure of 0.4 MPa of CO2 is
required to obtain appreciable conversions using choline chloride-based mixture, atmospheric pressure of CO2
(balloon) has been successfully used with choline iodide-based mixtures. Furthermore, the catalysts could be
recycled without appreciable loss of the catalytic activity. The improved catalytic performance of both cholinebased
eutectic mixtures is attributed to the synergistic activity of the halide, responsible for the opening of the
epoxy-ring, and the HBD that has a role in the stabilization of the alkoxide intermediate
Metodo per separare e recuperare polietilene e alluminio da un materiale poliaccoppiato
No full textL’invenzione fa riferimento ad una nuova tecnologia a base di switchable hydrophilic solvents (SHS) per la separazione e recupero di polietilene a bassa densità (LDPE) e alluminio da imballaggi alimentari (poliaccoppiato). Il nuovo metodo, interamente sostenibile, consente il recupero di entrambi i materiali in elevate quantità (> 99% per l'alluminio e > 80% per il polietilene) e buona qualità (≥ 86% di alluminio non ossidato). L’invenzione appartiene agli approcci chimici per separare LDPE e alluminio da residui sminuzzati di poliaccoppiat
Effects of ionic liquids on membrane fusion and lipid aggregation of egg-PC liposomes
Full text linkIn this study we have explored the effects of different groups of ionic liquids (ILs) on membrane fusion. The ILs used contain different head groups: N-methylimidazolium, 3-methylpyridinium and N-methylpyrrolidinium; short alkyl or ether functionalized side chains (with one or two ethoxy functionalities), paired with chloride anion. These ILs have been compared with 1-dodecyl-3-methylimidazolium bromide as example of a highly lipophilic IL. The effect of ILs on membrane fusion was investigated through pyrene steady state fluorescence probing, using the IE factor and excimer/monomer ratio (IE/IM) as parameters. The ratio between the vibronic bands of pyrene (I1/I3 ratio) has been used to monitor the effect of ILs on the aggregation properties of egg-PC liposomes. The effect of different ILs’ families was evident; the pyridinium ILs induced a greater extent of fusion than pyrrolidinium and imidazolium ILs having the same side chain. Marginal effect could be attributed to different anions. ILs with short alkyl chains were usually more effective than ether functionalized ones. The aggregation behaviors of ILs having dioxygenated chains have been measured in buffer solution
Can integrin agonists have cards to play against cancer? A literature survey of small molecules integrin activators.
Full text linkThe ability of integrins to activate and integrate intracellular communication illustrates the potential of these receptors to serve as functional distribution hubs in a bi-directional signal transfer outside-in and inside-out the cells. A tight regulation of the integrin signalling is paramount for normal physiological functions such as migration, proliferation, and differentiation and a misregulated integrin activity could be associated with several pathological conditions. Because of the important roles of integrins and their ligands in biological development, immune responses, leukocyte traffic, haemostasis, and cancer, their potential as therapeutic tools is now widely recognized. Nowadays extensive efforts have been made to discover and develop small molecule ligands as integrin antagonists whereas less attention has been payed to agonists. In recent years, it has been recognized that integrin agonists could open up novel opportunities for therapeutics, which gain benefits to increase rather than decrease integrin-dependent adhesion and transductional events. For instance, a significant factor in chemo-resistance in melanoma is a loss of integrin-mediated adhesion; in this case, stimulation of integrin signalling by agonists significantly improved the response to chemotherapy. In this review, we overview results about small molecules which revealed an activating action on some integrins, especially those involved in cancer, and to examine from a medicinal chemistry point of view their structure and behavior
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
Surfactants from Itaconic Acid: Physicochemical Properties and Assessment of the Synthetic Strategies
No full textSurfactants are a wide class of compounds used in a broad spectrum of industrial and everyday applications. In this paper, we present the synthesis of a new family of surfactants having C12 and C18 alkyl chains obtained from itaconic acid and fatty amines, molecules industrially obtained from renewable resources. Main physicochemical properties of synthesized surfactants have been measured and their rheological behaviors have been evaluated at the air-water interface using the pendant drop technique. Some of the synthesized surfactants are stimuli responsive compounds, switchable to a polar form in the presence of CO2. The synthetic strategies have been optimized aiming at the sustainability of the process employing a complete set of green metrics and the software EATOS
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
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