1,720,953 research outputs found
Advancing sustainable packaging: The role of nanofibers in bioplastics
No full textIn the last few decades, the packaging industry has become one of the fastest-growing industries worldwide, owing to some changes in standards of living, consumption habits, and global trade expansion. Bio-based materials have emerged as one of the most interesting subjects of research in the packaging industry due to the environmental concerns associated with materials derived from petrochemical sources, such as resource depletion, recycling challenges, and biodegradation which have resulted in the development of eco-friendly materials.
Polymers are widely used in the packaging industries, and synthetic polymers are extensively employed mainly because of their outstanding mechanical properties, effective barriers against oxygen and water, and ease of processability. However, they present significant downsides, such as poor degradability and challenges in recyclability, and as a result, packaging waste constitutes a large portion of post-consumer solid waste, leading to ecological problems. Therefore, extensive research is being conducted to develop biopolymers in the packaging industry. The challenges associated with the global usage of biopolymers include poor mechanical and barrier properties and high production costs. In order to modify the properties of biopolymers, various methods could be employed, such as reinforcing the polymer matrix with nanomaterials, especially nanofibers.
The first goal of this project was to optimize the process of preparing nanofibers derived from hemp. Pre-treatments were applied before the fibers underwent the refining process to reduce the number of steps required for refinement and to investigate their effect on the stability and diameter of the nanofibers produced. This approach not only saves time, energy, and costs but also enhances the overall efficiency of the process, representing a significant step forward for the industry.
In this study, mechanical treatment was applied for the fibrillation of hemp fibers. This method has significant advantages over chemical treatment, particularly in terms of reducing the amount of chemicals used. This aligns with one of the most important goals of this project, promoting a more sustainable and cost-effective approach.
In order to improve the efficiency of the fibrillation process, several pre-treatments were applied. Among them, the pre-treatment involving fiber hydration by immersing the fiber in water for one hour, subjecting it to a strong vacuum for 30 minutes, and processing it in a pressure cooker at high temperature (≈120°C) and pressure (12 psi) for 10 minutes resulted in the smallest fiber size reduction after eight passes. Furthermore, based on the stability test, this sample exhibited the highest stability, remaining stable after seven days.
Another goal of this project was to improve the mechanical and barrier properties of biodegradable nanocomposite films for packaging applications. Polybutylene succinate (PBS) has high flexibility, high elongation at break, good biodegradability, and water resistance. However, due to its low molecular weight, low stiffness, poor oxygen resistance, and high cost, its potential applications are limited. Therefore, one solution could be the addition of hemp nanofibers (HNF) to PBS in order to enhance biodegradation and reduce costs. In this study, nanocomposites of PBS and HNF, with a ratio of 95/5, were first prepared using an extruder and hydraulic press. Their barrier and mechanical properties were then investigated. Then, these properties were compared with the properties of nanocomposites containing PBS/HNF with the addition of beeswax and sodium dodecyl sulfate (SDS) at different ratios.
The moisture content, water absorption capacity, and water solubility tests showed that adding beeswax reduced moisture content, water absorption, and water solubility. These effects became more pronounced with increasing amounts of beeswax. Similarly, introducing SDS as a surfactant resulted in a greater decrease in these properties compared to adding beeswax alone, with further reductions observed as the concentration of SDS increased.
Furthermore, the results of the water vapor permeability (WVP) test revealed that the incorporation of nanofibers resulted in a decrease in the film permeability due to its hydrophilic nature. However, beeswax created a barrier that hindered the movement of water vapor molecules through the film due to its hydrophobic nature. The extent of this decrease depends on the amount and distribution of the beeswax. When SDS was introduced to the film’s formulation, its bridging effect could further reduce the WVP amounts of films, though only at low SDS concentrations. Overall, the interactions between all components (PBS, hemp nanofiber, beeswax, SDS) can influence the final film structure.
Additionally, mechanical tests demonstrated that adding HNF to PBS films increased tensile strength and modulus. However, this led to a decrease in elongation at break. For samples with beeswax in the formulation, the flexibility of the films increased, resulting in an increase in the film's elongation. In terms of tensile strength and tensile modulus, beeswax improved the compatibility between PBS and HNF. This enhancement led to better dispersion of hemp nanofiber within the PBS matrix, resulting in a more uniform composite and improved tensile strength. Meanwhile, the addition of beeswax to the formulation, due to its plasticizing effect, is expected to reduce the tensile modulus. In the final compositions, SDS was added to the film formulation. At low concentrations, SDS behaves as a surfactant, reducing the surface tension between PBS and HNF. This leads to a better dispersion of the nanofibers throughout the PBS matrix, which could reduce stress concentration. Well-dispersed nanofibers create a more uniform stress distribution within the film. This can help prevent premature failure at specific points and allow for more stretching before breaking, potentially increasing elongation. While SDS aids in dispersion at lower concentrations, excess SDS can interact with the surfaces of both PBS and HNF, disrupting the natural interactions (such as hydrogen bonding) between them, which contribute to the overall strength and integrity of the film and their disruption can make the film more susceptible to breaking under stress, potentially leading to decreased elongation. Meanwhile, the initial addition of SDS enhanced the composite's tensile strength mainly because of improved PBS-HNF adhesion and better stress transfer from the polymer matrix to the fibers. The addition of SDS over the optimal concentration resulted in phase separation, which could be regarded as a weak point in the composite, thereby having an adverse effect on the tensile strength. It was observed that by introducing SDS to the formulation tensile modulus also decreased.
Overall, the nanocomposites prepared exhibited promising properties for sustainable packaging applications. Nevertheless, additional research and development are essential to improve and optimize the material properties further for optimal performance
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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