1,721,023 research outputs found
Waste Cooking Oil as Eco-Friendly Rejuvenator for Reclaimed Asphalt Pavement
Full text linkOver 50 MioT of Waste Cooking Oil (WCO) was collected worldwide in 2020 from domestic and industrial activities, constituting a potential hazard for both water and land environments, and requiring appropriate disposal management strategies. In line with the principles of circular economy and eco-design, in this paper an innovative methodology for the valorisation of WCO as a rejuvenating agent for bitumen 50/70 coming from Reclaimed Asphalt Pavement (RAP) is reported. In particular, WCO or hydrolysed WCO (HWCO) was modified by transesterification or amidation reactions to achieve various WCO esters and amides. All samples were characterised by nuclear magnetic resonance, melting, and boiling point. Since rejuvenating agents for RAP Cold Mix Asphalt require a melting point <= 0 degrees C, only WCO esters could further be tested. Efficiency of WCO esters was assessed by means of the Asphaltenes Dispersant Test and the Heithaus Parameter. In particular, bitumen blends containing 25 wt% of WCO modified with 2-phenylethyl alcohol, showed high dispersing capacity in n-heptane even after a week, compared to bitumen alone (1 h). Additionally, the Heithaus Parameter of this bitumen blend was almost three times higher than bitumen alone, further demonstrating beneficial effects deriving from the use of WCO esters as rejuvenating agents
Mechanical and Physical Changes in Bio-Polybutylene-Succinate Induced by UVC Ray Photodegradation
Full text linkBio-polybutylene succinate (PBS) is a biodegradable polymer obtained from renewable feedstock having physical–mechanical properties like traditional low-density polyethylene (LDPE). PBS is employed by many manufacturing sectors, from biomedical to agri-food and cosmetics. Although some studies have already evaluated the resistance of PBS to photodegradation caused by natural outdoor solar exposure (UVA-UVB), a systematic study on the resistance to degradation caused by exposure to UVC rays, which is the subject of this study, has not yet been carried out. PBS was exposed to UVC either neat or filled with 2% carbon black (CB). Mechanical and physical characterization (tensile, hardness, calorimetry, contact angle, morphology, and surface roughness analyses) indicates that the bulk and surface properties of the polymer matrix changes after exposure to UVC radiations, due to a severe degradation. However, the presence of carbon black compensates for the degradation phenomenon. Because UVC rays are used for the sterilization process, necessary in applications such as biomedical, cosmetic, pharmaceutical, food, and other products, a comparison of the protocol used in this paper with the literature’s data has been reported and discussed
Efficient chemo-enzymatic transformation of animal biomass waste for eco-friendly leather production
Full text linkEnzymatically processed animal biomass derived from treated bovine hides (wet blue scraps) is herein used as building block for the synthesis of a novel biopolymer. An enzymatic hydrolysis process allows to produce water-soluble lower molecular weight proteins (Bio-A), which are then reacted with glycerol and maleic anhydride (MA) in order to obtain a new intermediate (Bio-IA). With Bio-IA in hand, co-polymerization in the presence of acrylic acid is then carried out. Hydrolysed biomass, intermediates and the final biopolymer (Bio-Ac) have been characterized by means of NMR, FTIR and GPC analysis. Bio-Ac shows good performance when used as retanning agent to produce leather. Physical and mechanical properties of the leather treated with Bio-Ac have been compared with acrylic resin retanned leather, showing similar performance. The reported protocol represents an environmental-friendly interesting alternative to traditional petrochemical based retanning agents, commonly used by the leather industry
Iminophosphine-palladium(0) complexes as catalysts for the Stille reaction.
No full textThe cross-coupling of iodobenzene with tributylphenylethynylstannane or tributylvinylstannane is efficiently catalysed by iminophosphine–palladium(0)–olefin complexes of the type [Pd(h2-dmf)(P-N)] (dmf, dimethylfumarate; P-N, 1-(PPh2)-C6H4-2-CvNR (R¼alkyl, aryl)). The catalytic activity depends on the R substituent of the imino group: the highest reaction rates are obtained using arylsubstituted iminophosphines. Equivalent catalytic systems can be obtained using a palladium source such as Pd(OAc)2 or Pd(dba)2(dibenzylideneacetone, dba) in combination with the iminophosphine ligands. In the coupling of iodobenzene with tributylphenylethynylstannane, the highest reaction rates are obtained using an iminophosphine/palladium molar ratio of 2:1, while in the vinylstannane–iodobenzene coupling the best P-N/Pd ratio is 1:1
Mechanistic study of the cross-coupling of alkynyl stannaes with aryl iodides catalyed by η2-(dimethyl fumarate)Palladium(0) complexes with iminophosphine ligands.
No full textThe reactions of [Pd(η2-dmfu)(P–N)] [dmfu = dimethyl fumarate; P–N = 2-(PPh2)C6H4-1-CHNR, R = C6H4OMe-4 (1a), CHMe2 (2a)] and [Pd(η2-dmfu)(P–N)2] with IC6H4CF3-4, ISnBu3 and PhCCSnBu3 have been studied under pseudo-first-order conditions. The oxidative addition of IC6H4CF3-4 yields [PdI(C6H4CF3-4)(P–N)] (1b or 2b). No reaction takes place with PhCCSnBu3 and also with ISnBu3 in the presence of an excess of PhC
CSnBu3. In the presence of fumaronitrile (fn), 1b and 2b undergo transmetalation by PhCCSnBu3 followed by fast reductive elimination to yield [Pd(η2-fn)(P–N)]. The same reaction sequence occurs for the system [PdI(C6H4CF3-4)(P–N)]/P–N (1 : 1 molar ratio) to give [Pd(η2-fn)(P–N)2]. The palladium(0) complexes are active catalysts in the cross-coupling of PhCCSnBu3 with aryl iodides ArI (Ar = C6H4CF3-4, Ph). The catalytic efficiency depends on the complex:
[Pd(η2-dmfu)(P–N)2] > [Pd(η2-dmfu)(P–N)], and on the substituent R: C6H4OMe-4 > CHMe2. The reactivity and
spectroscopic data suggest a catalytic cycle involving initial oxidative addition of ArI to a palladium(0) species,
followed by transmetalation of the product and by fast reductive elimination to regenerate the starting palladium(0) compound. For [Pd(η2-dmfu)(P–N)] as catalyst, the oxidative addition is the rate-determining step, while for [Pd(η2-dmfu)(P–N)2] the oxidative addition and the transmetalation steps occur at comparable rate
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
Synthesis, characterization and catalytic activity of novel ruthenium complexes bearing NNN click based ligands
No full textNovel air stable ruthenium(ii) complexes bearing tridentate ligands bis((1-benzyl-1H-1,2,3-triazol-4-yl)methyl)amine (L1), 1-(1-benzyl-1H-1,2,3-triazol-4-yl)-N-(pyridin-2-ylmethyl)methanamine (L2) or 2-(4-phenyl-1H-1,2,3-triazol-1-yl)-N-(pyridin-2-ylmethyl)ethan-1-amine (L3) were synthesised. The nitrogen based ligands were easily prepared by virtue of click chemistry using cheap and commercially available reagents. The ruthenium complexes were obtained by heating the Ru(PPh3)(3)Cl-2 precursor and the tridentate NNN ligand in toluene under reflux for 2 hours, achieving yields of 82-87%. These complexes were fully characterized by means of NMR, FT-IR and high resolution ESI spectroscopy. The crystal structure of one of the complexes was determined. These complexes showed excellent activity and selectivity in the hydrogenation of ketones and aldehydes. DFT calculations show that complex 3 may react through an outer-sphere catalytic cycle rather than via an inner-sphere mechanism
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
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