1,721,048 research outputs found
Dimethyl Isosorbide As a Green Solvent for Sustainable Ultrafiltration and Microfiltration Membrane Preparation
No full textDimethyl isosorbide (DMI)—a well-known biobased high boiling green solvent—was used for the first time in the preparation of poly(vinylidene fluoride)- and poly(ether sulfone)-based membranes. Preliminary thermodynamic (Hansen and Hildebrand solubility parameters, relative energy difference) and kinetic (viscosity) studies on DMI confirmed that this solvent possesses the required physical/chemical properties to be exploited in casting membranes. Membranes were prepared by nonsolvent induced phase separation (NIPS) and a combination of vapor induced phase separation (VIPS)-NIPS techniques varying the exposure time to humidity. This latter approach led to the formation of membranes with a porous architecture avoiding the use of any pore forming additive. The so-prepared membranes were, then, fully characterized in terms of morphology, polymorphism (in case of PVDF), wettability, thickness, porosity, pore size, and water permeability. The membranes revealed different structures and a tunable pore size in the range of ultrafiltration (UF) and microfiltration (MF) that render them ideal for applications in water treatment processes.Dimethyl isosorbide (DMI) - a well-known biobased high boiling green solvent - was used for the first time in the preparation of poly(vinylidene fluoride)- and poly(ether sulfone)-based membranes. Preliminary thermodynamic (Hansen and Hildebrand solubility parameters, relative energy difference) and kinetic (viscosity) studies on DMI confirmed that this solvent possesses the required physical/chemical properties to be exploited in casting membranes. Membranes were prepared by nonsolvent induced phase separation (NIPS) and a combination of vapor induced phase separation (VIPS)-NIPS techniques varying the exposure time to humidity. This latter approach led to the formation of membranes with a porous architecture avoiding the use of any pore forming additive. The so-prepared membranes were, then, fully characterized in terms of morphology, polymorphism (in case of PVDF), wettability, thickness, porosity, pore size, and water permeability. The membranes revealed different structures and a tunable pore size in the range of ultrafiltration (UF) and microfiltration (MF) that render them ideal for applications in water treatment processes
Preparation of polymeric membranes and microcapsules using an ionic liquid as morphology control additive
No full textHydrophilic porous polyethersulfone (PES) membranes and microcapsules were prepared via Non-Solvent Induced Phase Separation (NIPS) with the ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) as structure control agent, added to the conventionally employed PVPK17 pore former. The introduction of [BMIM][PF6] affects the phase inversion mechanism, resulting in different morphologies of the materials. Optimal conditions for the preparation of membranes (ILMs) were: 10-15 wt.% PES, 0-4 wt.% PVPK17, 5-25 wt.% [BMIM][PF6], while slightly different conditions were applied for the preparation of microcapsules (ILMCs): 10% wt.% PES, 0-4% wt.% PVPK17, and 5-15 wt.% [BMIM][PF6]. Thus, the produced porous spongy microcapsules (average diameter â\u88¼800 μm) and flat sheet ionic liquid membranes (ILMs) were characterized by electronic microscopy (SEM), FTIR and Raman spectroscopy and thermal analysis. [BMIM][PF6] concentration is a key factor for controlling the internal membrane morphology. Indeed, higher concentrations of [BMIM][PF6] additive increases the viscosity of casting solution and reduces solvent exchange speed, thereby altering the membrane morphology from a channelled structures (finger-like) to a spongy type
Enzyme-mediated extraction of limonene, linalool and linalyl acetate from bergamot peel oil by pervaporation
Full text linkBergamot peel oil is highly attractive for food and pharmaceutical industries due to its content of valuable essential oil, which is enriched with high-added valuable compounds, such as limonene, linalool and linalyl acetate. Nevertheless, there are some limitations for the separation of such compounds. In this framework, pervaporation (PV) technology was proposed as a tool for the separation of limonene, linalool, and linalyl acetate from bergamot oil by using two different commercial organophilic membranes (PDMS-1070 and POMSPEI). The use of an enzymatic pre-treatment was also investigated in order to enhance the performance of selected membranes. All PV experiments were carried out at different temperatures (ranging from 25-40 °C) in order to analyze the temperature dependence by the Arrhenius relationship. Experimental data indicated that both investigated membranes did not present significant differences in terms of enrichment factor, independently from the enzymatic pre-treatment (at 25 °C). However, the enrichment factors increased significantly at 40°C when enzymes were applied. The experimental results clearly indicate that PV is a viable approach for the recovery of such aroma solutes from bergamot peel oils as it yields good separations under mild operating conditions. The efficiency of the pervaporative process is indeed enhanced if assisted by an enzymatic treatment
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
Book of Abstracts ITM SEMINAR DAY 2021
No full textDialkyl carbonates (DACs) are well-known green solvents and reagents that are extensively investigated as safe alternatives to chlorine reagents. In fact, they can replace alkyl halides and dimethyl sulfate in alkylation and carbonylation reactions as well as phosgene and its derivatives in the alkoxycarbonylation ones [1,2]. In this talk, I will be presenting our latest results in the high yielding scale-up synthesis of non-commercially available or expensive DACs via transcarbonylation reactions of an alcohol with DMC promoted by the nitrogen-based organocatalyst, 1,5,7-
triazabicyclo[4.4.0]dec-5-ene (TBD). Compared to previously published works [3,4], the proposed procedure has been customized for DACs large scale production (up to 100 mL of product obtained). Purification of these compounds has been achieved by fractional distillation and the exceeding reagents have been recovered and recycled. The selected DACs for this study include both symmetrical and unsymmetrical compounds, incorporating several alkyl, alkoxyalkyl, alkylamino
and alkylthio functional groups. Chemical-physical properties of the new DACs have been also evaluated, as well as their water solubility. Furthermore, biodegradability and cytotoxicity tests have been carried out to investigate the effects of the different substituents on the greenness of these potential solvents and reagents. Finally, both commercially available cyclic carbonates (namely ethylene carbonate – EC and propylene carbonate – PC) and selected samples of the newly
synthetized DACs, have been investigated as green solvents for membrane preparation, using nonsolvent induced phase separation (NIPS) and vapor induced inverse phase separation (VIPS) techniques, achieving both porous and plain membranes. Physical-chemical, morphology, mechanical proprieties and the performance in terms of water permeability and rejection of these new membranes have been also evaluated
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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