1,720,963 research outputs found
Study and development of green water-based methodologies to process biobased and biodegradable polymers for coatings and electronics applications
No full textRheological response of polylactic acid dispersions in water with xanthan gum
Full text linkIn this work, the rheological behaviour of stable PLA dispersions in water, intended for coating applications, was investigated. The newly prepared dispersions consist of PLA particles with average diameter of 221.9 ± 2.0 nm based on DLS and SEM analyses, at concentrations varying in the 5-22 wt % range. Xanthan gum (XG), a bacterial polysaccharide, was used as a thickening agent to modulate the viscosity of the formulations. The rheological properties of the PLA dispersions with different XG and PLA contents were studied in steady shear, amplitude sweep and frequency sweep experiments. Under steady shear conditions, the viscosity of all the formulations showed a shear-thinning behaviour similar to XG solutions in the whole investigated 1-1000 s-1 range, with values dependent on both PLA particles and XG concentrations.
Amplitude and frequency sweep data revealed a weak-gel behaviour except in the case of the most diluted sample, with moduli dependent on both PLA and XG content. A unified scaling parameter was identified in the volume fraction (Φ) of the PLA particles, calculated by considering the dependence of the continuous phase density on the XG concentration. Accordingly, a mastercurve at different volume fractions was built through the Time-Concentration Superposition (TCS) approach. The mastercurve describes the rheological response of the system over a wider frequency window than the experimentally accessible one, and reveals the presence of a superimposed relaxation process in the high-frequency region
Complementary and Alternative Medicine: Italian Validation of a Questionnaire on Nurses' Personal and Professional Use, Knowledge, and Attitudes
No full textBACKGROUND:
Patients are showing an increasing interest in the use of complementary and alternative medicine (CAM). Most nurses are open to the adoption of CAM into clinical nursing practice, but they may experience a lack of knowledge about the safe and effective use of these therapies. Several studies concerning nurses' knowledge and attitudes toward CAM have been published, but only in one, the authors (Shorofi and Arbon) used a validated questionnaire. In Italy, there are no validated questionnaires to investigate this aspect of nursing practice.
PURPOSE:
To test the psychometric properties of the Italian Shorofi and Arbon questionnaire for use with Italian nurses.
METHODS:
A forward-backward translation method was used to translate the questionnaire from English to Italian. Content validity, face validity and reliability were established.
RESULTS AND CONCLUSIONS:
This study examined the potential usefulness of the Shorofi and Arbon questionnaire for the evaluation of CAM knowledge of Italian speaking nurses, which showed good content validity and good reliability
Glycolysis of semi-interpenetrated polymer network foam based on poly(vinyl chloride) for recovery and reuse of the individual components
No full textRigid semi-Interpenetrated Polymer Network (semi-IPN) foam based on poly(vinyl chloride) (PVC) and crosslinked polyurea/isocyanurate are complex materials that at present are not recyclable. They are used in many fields, including wind blade cores. In this work we studied the depolymerization of the crosslinked portion of the foam under glycolysis conditions for the separation and reuse of the individual components. Reaction products were characterized by FT-IR, NMR, solvent solubility, DSC, elemental analysis, titration of amine and hydroxyl groups and rheology measurements. Triisocyanurates and urea moieties were synthesized and used as model compounds. Glycolysis conditions were optimized to maximize depolymerization while minimizing PVC degradation. The parameters studied were reaction time (8 min to 3 h), temperature (155 to 200 °C), catalyst (potassium acetate or dibutyl tin dilaurate (DBTL)), glycol (ethylene glycol, 1,4 butanediol, diethylene glycol, dipropylene glycol, polyethylene glycol), as well as the effect of PVC thermal stabilizers such as hindered phenols and organo-phosphites. The results showed that the optimal reaction condition for foam glycolysis is 165-175 °C for 20-30 min, using DBTL as catalyst and including thermal stabilizers. No drastic difference was noticed by the kind of glycol used, except for PEG that led to greater PVC degradation. The greatest part of the crosslinked portion (≥90 %) was depolymerized and the result were mainly hydroxyl- and in minor amount amine- terminated oligomers. The recovered PVC (purity roughly 90 %) had a low degree of degradation and a viscosity suitable for its processing as thermoplastic material, i.e. by injection moulding
Asymmetric vinylogous aldol addition of alkylidene oxindoles on trifluoromethyl-α,β-unsaturated ketones
No full textA novel vinylogous aldol addition of alkylidene oxindole with 1-trifluoromethyl-3-alkylidene-propan-2- ones is presented. The reaction, catalyzed by a bifunctional tertiary amine, provides an efficient application of the vinylogous reactivity of oxindoles for the preparation of enantioenriched trifluoromethylated allylic alcohols
Morphology and Mechanical Properties of Poly(vinyl alcohol)/Poly(lactic acid) Blend Films Prepared from Aqueous Dispersions
Full text linkIn this study, the preparation of poly(vinyl alcohol) (PVA)/poly(lactic acid) (PLA) blends of different compositions, 100/0, 75/25, 50/50, 25/75, and 0/100, by mixing water solutions of the former and water dispersions of the latter polymer, is reported. Two distinct dispersions of PLA are prepared using a commercial-grade polyester and two different surfactants, an anionic one and a neutral one. Films of PLA and of the corresponding blends are obtained by simply drying at 60 °C the water dispersions without or with the PVA. The films are characterized by infrared spectroscopy, differential scanning calorimetry (DSC), and scanning electron microscope (SEM) analysis. This evidences an island-like morphology, with the continuous phase consisting of a PVA rich phase at all compositions except 25/75, for which an inverted phase composition, with a continuous phase made mostly of PLA, is instead found. Voids caused by air bubbles trapped in the initial mixture are observed in particular in the formulations with the anionic surfactant. The trapped bubbles result in premature thermal degradation by thermogravimetric analysis (TGA) and mechanical failure during clamping. Films with the neutral stabilizer are tougher than the bare commercial PLA, with Young modulus and elongation at break depending on the combination of the composition and arrangement of blend phases
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
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