Download or read book Surface Modification and Characterization of Cellulose Nanocrystal for Biomedical Applications written by Seyedeh Parinaz Akhlaghi and published by . This book was released on 2014 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: There is an ever-increasing desire to develop novel materials that could control the release of active compounds and increase their stability. Replacing petroleum-based synthetic polymers with sustainable materials has many advantages, such as reducing the dependence on fossil fuels, and diminishing environmental pollution. Recently, cellulose nanocrystal (CNC) obtained by acid hydrolysis of cellulose fibres has gained a lot of interest. The high mechanical strength, large and negatively charged surface area, and the presence of several hydroxyl groups that allow for modification with different functionalities make CNC an excellent candidate for various applications in the biomedical field. This thesis explores (i) the surface modification and characterization of modified CNC and (ii) the biomedical applications of these novel sustainable nanomaterials.
Download or read book Nanocellulose written by Jin Huang and published by John Wiley & Sons. This book was released on 2019-08-05 with total page 514 pages. Available in PDF, EPUB and Kindle. Book excerpt: Comprehensively introduces readers to the production, modifications, and applications of nanocellulose This book gives a thorough introduction to the structure, properties, surface modification, theory, mechanism of composites, and functional materials derived from nanocellulose. It also provides in-depth descriptions of plastics, composites, and functional nanomaterials specifically derived from cellulose nanocrystals, cellulose nanofibrils, and bacterial cellulose. It includes the most recent progress in developing a conceptual framework of nanocellulose, as well as its numerous applications in the design and manufacture of nanocomposites and functional nanomaterials. The book also looks at the relationship between structure and properties. Featuring contributions from many noted experts in the field, Nanocellulose: From Fundamentals to Advanced Materials examines the current status of nanocomposites based on nanocelluloses. It covers surface modification of nanocellulose in the nanocomposites development; reinforcing mechanism of cellulose nanocrystals in nanocomposites; and advanced materials based on self-organization of cellulose nanocrystals. The book studies the role of cellulose nanofibrils in nanocomposites, as well as a potential application based on colloidal properties of cellulose nanocrystals. It also offers strategies to explore biomedical applications of nanocellulose. Provides comprehensive knowledge on the topic of nanocellulose, including the preparation, structure, properties, surface modification and strategy Covers new reports on the application of nanocellulose Summarizes three kinds of nanocellulose (cellulose nanocrystals, cellulose nanofibrils, and bacterial cellulose) and their production, modification, and applications Nanocellulose: From Fundamentals to Advanced Materials is a useful resource for specialist researchers of chemistry, materials, and nanotechnology science, as well as for researchers and students of the subject.
Download or read book Cellulose Nanocrystals written by Vimal Katiyar and published by Walter de Gruyter GmbH & Co KG. This book was released on 2020-10-12 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cellulose nanocrystals are being used more frequently as processing and nanofabrication techniques have advanced considerably. Cellulose Nanocrystals includes topics including Extraction and Fabrication Methodologies, Scale-Up Strategies and Life Cycle Assessment, Surface Modification Strategies, Nanocomposites, and Characterization and Testing Protocols. This book will appeal to physical, chemical and biological scientists as well as engineers.
Download or read book Nanocellulose written by Mainak Mukhopadhyay and published by John Wiley & Sons. This book was released on 2024-03-06 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt: NANOCELLULOSE This book provides the latest up-to-date information on the exciting applications of nanocellulose in human diseases by giving in-depth explanations of their synthesis, characterization, and real-world applications in the biomedical sectors. Nanocellulose is a promising nanomaterial with unique qualities including low cost, durability, non-toxicity, accessibility, etc. Cellulose can be classified into two types: nanocrystals and nanofibrils, depending on the way it is extracted from trees, plants, or other cellulose-containing species. Textiles, cosmetics, and food products are just a few of the commercial uses for nanocellulose. However, it also has strong potential for use in medicine. The book presents the most recent scientific research on nanocellulose as a biopolymer and its potential uses in medicine. The reader will discover: explains the synthesis of bacterial nanocellulose from different bacterial species and their characteristics; details processes and applications of electrospinning and the synthesis of novel nanocellulose-based nanocomposite materials; discusses the various surface functionalization processes of cellulose and their advantages and disadvantages; delves into the application of nanocellulose in tissue engineering and grafting, such as in wound dressing and implants; discusses nanocellulose as a carrier for drug delivery, as well as the synthesis of antibacterial nanocomposites for treating multi-drug-resistant bacteria; explores the role of nanocellulose in the treatment of renal failure, nanocellulose hydrogel for ophthalmic and dental applications. Audience Researchers in areas including environmental biotechnology, bioprocess engineering, renewable energy, chemical engineering, nanotechnology, biotechnology, and microbiology will be interested in this book.
Download or read book Surface Modification of Cellulose Nanocrystal for Advanced Applications written by Zhen Zhang and published by . This book was released on 2017 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cellulose nanocrystals (CNC) are bio-based nanoparticles, which display an array of interesting properties related to their renewability, biocompatibility, high tensile strength and elastic modulus, high aspect ratio, low density, low coefficient of thermal expansion, and liquid crystal behavior. As a result, CNC can be exploited in a wide variety of applications, which include the fields of composites, catalysts, emulsions or colloidosomes. However, the engineering of innovative nanomaterials from CNC generally requires a fine control of their surface properties by chemical modification, to tailor their dispersive, interfacial and self-assembling properties, or to introduce novel functionalities. In this context, the surface functionalization of cellulose nanocrystals by esterification and Surface-Initiated Atom Transfer Radical Polymerization (SI-ATRP) reactions was envisaged, with the objective to develop novel advanced materials. The first chapter describes the state-of-the-art of the field in which the cellulose nanocrystals are presented, with their properties, methods of functionalization and potential applications. A brief overview of the SI-ATRP reaction is also given. In the second chapter, a convenient method is proposed to directly characterize the polymer grafted by SI-ATRP on the CNC surface, without cleaving the polymer from the nanoparticle. The SI-ATRP grafting of polystyrene (PS) at the CNC surface was performed from brominated CNC initiators, in the presence of a sacrificial initiator. With this work, we show that Dynamic light scattering (DLS) is a convenient tool to monitor the polymerization process, while differential scanning calorimetry (DSC) can be used to verify if the polymerization rates of the grafted and free polymers coincide. Finally, we demonstrate that thermogravimetric analysis (TGA) can be used to directly estimate the molecular weight of the PS grafted at the surface of the CNC without cleaving the polymer from the nanoparticle. In the third chapter, both SI-ATRP and Surface-Initiated Activator Re-Generated by Electron Transfer ATRP (SI-ARGET ATRP) were conducted to graft PS and P4VP on the surface of CNC. The SI-ATRP and SI-ARGET ATRP approaches were systematically compared to evaluate the potential benefit of each method. The surface initiating efficiencies (SIE) of the CNC-Br macroinitiators with regards to styrene or P4VP were evaluated by TGA and EA, respectively. The combination of analytical methods such as FT-IR, DLS, DSC, TGA, and EA demontrated that the SI-ARGET ATRP reaction favored the grafting of longer polymer chains with lower grafting densities compared with the classical SI-ATRP method. The impact of catalyst concentration and propagation rate on the differences noted was particularly discussed. In the fourth chapter, pH-responsive P4VP-g-CNC nanohybrids were prepared by SI-ATRP and subsequently used to stabilize gold nanoparticles (Au NPs) and produce recyclable catalysts. The presence of P4VP brushes at the CNC surface led to the growing of Au NPs of lower averaged diameter compared with the diameter of the Au NPs deposited on pristine CNC. The catalytic performance of pristine Au NPs, Au NPs stabilized by CNC (Au@CNC) and Au NPs stabilized by P4VP-g-CNC (Au@P4VP-g-CNC) were then compared, through the measurement of the turnover frequency (TOF) obtained after catalytic reduction of 4-nitrophenol (4NP), used as a model reaction. Compared with pristine Au NPs, the catalytic activity of Au@CNC and Au@P4VP-g-CNC were about 10 and 24 times better, respectively. Moreover, the Au@P4VP-g-CNC material could be conveniently recovered by flocculation at basic pH, and the recycled catalyst remained highly active. In the fifth chapter, Ultraviolet (UV)-responsive poly(cinnamoyloxy ethyl methacrylate) (PCEM) was grafted on CNC using SI-ATRP. The resultant PCEM-grafted CNC (PCEM-g-CNC) exhibits high UV absorption properties and undergoes crosslinking under UV irradiation. When the PCEM-g-CNC nanohybrids were incorporated in poly(vinyl chloride), transparent composite films with UV-blocking properties were obtained. The comparison of the optical and mechanical properties of the films before and after UV-irradiation allowed it to be demonstrated that the PCEM-g-CNC nanoparticles also acted as thermal and UV-stabilizers for PVC. Meanwhile, the tensile mechanical properties of the PVC film were significantly improved, and further increased after UV-irradiation. In the sixth chapter, a facile method to prepare colloidosomes at room temperature is proposed from w/o inverse Pickering emulsions containing silica precursors and stabilized by cinnamate modified CNC (Cin-CNC). Cin-CNC Pickering surfactants were prepared by acylation with an excess of cinnamoyl chloride. The Cin-CNC surface displayed partial wettability with both toluene and water, which allowed stabilization w/o inverse Pickering emulsions. The Cin-CNC particles around the droplets were subsequently locked by cross-linking TEOS or TBOS silica precursors at the water/toluene interface, leading to an intricate network of polysiloxane within the Cin-CNC shell. In optimized conditions, the Cin-CNC/silica colloidosomes obtained displayed a robust shell and slow releasing capacity with regards to encapsulated molecules such as rhodamine B or fluorescent deoxyribonucleic acid (DNA). In the last chapter, we summarized the general conclusions of the thesis and proposed some recommendations for the future work. The cellulose nanocrystals were modified by esterification and surface initiated Atom Transfer Radical Polymerization. The characterization, mechanism and advanced applications of the functionalized CNC were envisaged. Based on the research and results in this project, we also proposed some recommendations for the future work on the modification of CNC and the other advanced applications.
Download or read book Handbook of Nanocellulose and Cellulose Nanocomposites 2 Volume Set written by Hanieh Kargarzadeh and published by John Wiley & Sons. This book was released on 2017-06-19 with total page 914 pages. Available in PDF, EPUB and Kindle. Book excerpt: An up-to-date and comprehensive overview summarizing recent achievements, the state of the art, and trends in research into nanocellulose and cellulose nanocomposites. Following an introduction, this ready references discusses the characterization as well surface modification of cellulose nanocomposites before going into details of the manufacturing and the self-assembly of such compounds. After a description of various alternatives, including thermoplastic, thermosetting, rubber, and fully green cellulose nanocomposites, the book continues with their mechanic and thermal properties, as well as crystallization and rheology behavior. A summary of spectroscopic and water sorption properties precedes a look at environmental health and safety of these nanocomposites. With its coverage of a wide variety of materials, important characterization tools and resulting applications, this is an essential reference for beginners as well as experienced researchers.
Download or read book Bacterial NanoCellulose written by Miguel Gama and published by CRC Press. This book was released on 2016-04-19 with total page 315 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first book dedicated to the potential applications and unique properties of bacterial cellulose (BC), this seminal work covers the basic science, technology, and economic impact of this bulk chemical as well as the companies and patents that are driving the field. It reviews the biosynthesis and properties of BC, including genetics and characterization; discusses the advancing technology as it relates to product development, bioreactors, and production; and analyzes the economic impact of BC on a diverse range of industry applications, including materials and biomaterials, biological and polymer sciences, and electromechanical engineering.
Download or read book Surface Modifications of Nanocellulose written by Ning Lin and published by Elsevier. This book was released on 2024-06-01 with total page 484 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface Modifications of Nanocellulose: Strategies, Methods, and Applications establishes the basic framework of nanocellulose. This book systemically summarizes the strategy and protocols of surface modifications on nanocellulose and comprehensively analyzes the relationship between surface modifications and their functional applications. It provides a one-stop reference for researchers engaged in biopolymer research with a commitment to the development of highly-valued functional polymers, nanomaterials, and green chemistry. Systemically summarizes the strategy and protocols of surface modifications on nanocellulose Includes a database for the modified species as a reference book for surface modification on nanocellulose Illustrates the relationship between modification and applications of nanocellulose Provides inspiration for the development of potential functional modification in this field
Download or read book Nanocelluloses written by Elena Vismara and published by MDPI. This book was released on 2020-05-12 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanocelluloses: Synthesis, Modification and Applications is a book that provides some recent enhancements of various types of nanocellulose, mainly bacterial nanocellulose, cellulose nanocrystals and nanofibrils, and their nanocomposites. Bioactive bacterial nanocellulose finds applications in biomedical applications, https://doi.org/10.3390/nano9101352. Grafting and cross-linking bacterial nanocellulose modification emerges as a good choice for improving the potential of bacterial nanocellulose in such biomedical applications as topical wound dressings and tissue-engineering scaffolds, https://doi.org/10.3390/nano9121668. On the other hand, bacterial nanocellulose can be used as paper additive for fluorescent paper, https://doi.org/10.3390/nano9091322, and for the reinforcement of paper made from recycled fibers, https://doi.org/10.3390/nano9010058. Nanocellulose membranes are used for up-to-date carbon capture applications, https://doi.org/10.3390/nano9060877. Nanocellulose has been applied as a novel component of membranes designed to address a large spectrum of filtration problems, https://doi.org/10.3390/nano9060867. Poly(vinyl alcohol) (PVA) and cellulose nanocrystals (CNC) in random composite mats prepared using the electrospinning method are widely characterized in a large range of physical chemical aspects, https://doi.org/10.3390/nano9050805. Similarly, physical chemical aspects are emphasized for carboxylated cellulose nanofibrils produced by ammonium persulfate oxidation combined with ultrasonic and mechanical treatment, https://doi.org/10.3390/nano8090640. It is extraordinary how nanocellulose can find application in such different fields. Along the same lines, the contributions in this book come from numerous different countries, confirming the great interest of the scientific community for nanocellulose.
Download or read book Cellulose Nanoparticles written by Vijay Kumar Thakur and published by Royal Society of Chemistry. This book was released on 2021-07-01 with total page 534 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cellulose nanoparticles (CNP) are a class of bio-based nanoscale materials, which are of interest due to their unique structural features and properties such as biocompatibility, biodegradability, and renewability. They are promising candidates for applications including in biomedicine, pharmaceuticals, electronics, barrier films, nanocomposites, membranes, and supercapacitors. New resources, extraction procedures and treatments are currently under development to satisfy increasing demands for cost-effective and sustainable methods of manufacturing new types of cellulose nanoparticle-based materials on an industrial scale. Cellulose Nanoparticles: Chemistry and Fundamentals covers the synthesis, characterization and processing of cellulose nanomaterials. It aims to address the recent progress in the production methodologies for cellulose nanoparticles, covering principal cellulose resources and the main processes used for isolation. Chapters cover the preparation and characterisation of cellulose nanocrystals and nanofibrils. Together with Volume 2, these books form a useful reference work for graduate students and researchers in chemistry, materials science, nanoscience and green nanotechnology.
Download or read book Handbook of Nanocellulose and Cellulose Nanocomposites written by Hanieh Kargarzadeh and published by John Wiley & Sons. This book was released on 2017-03-02 with total page 897 pages. Available in PDF, EPUB and Kindle. Book excerpt: An up-to-date and comprehensive overview summarizing recent achievements, the state of the art, and trends in research into nanocellulose and cellulose nanocomposites. Following an introduction, this ready references discusses the characterization as well surface modification of cellulose nanocomposites before going into details of the manufacturing and the self-assembly of such compounds. After a description of various alternatives, including thermoplastic, thermosetting, rubber, and fully green cellulose nanocomposites, the book continues with their mechanic and thermal properties, as well as crystallization and rheology behavior. A summary of spectroscopic and water sorption properties precedes a look at environmental health and safety of these nanocomposites. With its coverage of a wide variety of materials, important characterization tools and resulting applications, this is an essential reference for beginners as well as experienced researchers.
Download or read book Handbook of Nanocelluloses written by Ahmed Barhoum and published by Springer Nature. This book was released on 2022-07-15 with total page 1081 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Handbook covers the fundamental aspects, experimental setup, synthesis, properties, and characterization of different nanocelluloses. It also explores the technology challenges of nanocelluloses and the emerging applications and the global markets of nanocelluloses-based systems. In particular, this book: · Covers the history of nanocelluloses, types and classifications, fabrication techniques, critical processing parameters, physical and chemical properties, surface functionalization, and other treatments to allow practical applications. · Covers all recent aspects of nanocelluloses technologies, from experimental set-up to industrial applications. · Includes new physical, chemical and biological techniques for nanocelluloses fabrication, in-depth treatment of their surface functionalization, and characterization. · Discusses the unique properties of nanocelluloses that can be obtained by modifying their diameter, morphology, composition and dispersion in other materials. · Discusses the properties and morphology of several kinds of dispersion in polymeric materials, such as micro/nanofiberlated cellulose, cellulose nanofibers, cellulose nanocrystals, amorphous cellulose nanoparticles, and hybrid cellulose nanomaterials. · Presents the different techniques for dispersion, and self-assembly of polymeric materials, critical parameters of synthesis, modelling and simulation, and characterization methods. · Highlights a wide range of emerging applications of nanocelluloses, e.g. drug delivery, tissue engineering, medical implants, medical diagnostics and therapy, biosensors, catalysis, energy harvesting, energy storage, water/waste treatment, papermaking, textiles, construction industry, automotive, aerospace and many more. · Provides an outlook on the opportunities and challenges for the fabrication and manufacturing of nanocelluloses in industry. · Provides an in-depth look at the nature of nanocelluloses in terms of their applicability for industrial uses. · Provides in-depth insight and review on most recent types of nanocelluloses-based systems of unique structures and compositions. · Highlights the challenges and interdisciplinary perspective of nanocelluloses-based systems in science, biology, engineering, medicine, and technology, incorporating both fundamentals and applications. - Demonstrates how cutting-edge developments in nanofibers translate into real-world innovations in a range of industry sectors. This Handbook is a valuable reference for materials scientists, biologists, physicians, chemical, biomedical, manufacturing and mechanical engineers working in R&D industry and academia, who want to learn more about how nanocelluloses-based systems are commercially applied.
Download or read book Cellulose Nanocrystal Nanoparticles Hybrid Nanocomposites written by Denis Rodrigue and published by Woodhead Publishing. This book was released on 2021-08-26 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cellulose Nanocrystal/Nanoparticles Hybrid Nanocomposites: From Preparation to Applications presents a broad survey of the main innovations in the field of functionalized cellulose at the nanoscale and for hybrid nanoparticles-based nanocomposites for industrial application. The book covers the properties and applications of cellulose, including particle extraction, synthesis, functionalization of cellulose at the nanoscale, and hybrid nanoparticles and their processing and characterizations. Readers will find this to be a single and comprehensive reference for future research on polymer-based nanocomposites. Hybrid nanocomposites based on cellulose at the nanoscale, and hybridized with other reinforcement agents represent a key advance in polymer-based materials. Cellulose is considered the most abundant polymer on the planet and an essential renewable resource. There is considerable research interest in the simple extraction and synthesis, nanoscale dimensions, high aspect ratio, mechanical, electrical and thermal properties of cellulose at the nanoscale and its hybridized materials. Nanocomposites and bio-nanocomposites with hybrid reinforcements, for example, are novel materials with enhanced properties due to the integration of cellulose with other nanoparticles, and new methods have been developed to extract cellulose at the nanoscale. The extracted cellulose shows potential applications in nanocomposites, and functionalization techniques are essential to create enhanced nanocomposites, particularly for hybrid nanoparticles. Presents the state-of-the-art in functionalized cellulose at the nanoscale, along with industrial applications of hybrid-nanoparticles-based nanocomposites Details the properties and applications of cellulose at the nanoscale and for hybrid nanocomposites Gives updates on hybrid nanoparticles, including the processing and characterization of nanocomposites Brings together expertise from chemistry, polymer science, engineering and manufacturing
Download or read book Cellulose Nanocomposites written by American Chemical Society. Meeting and published by . This book was released on 2006 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt: Introduction to cellulose nanocomposites; strategies for preparation of cellulose wiskers from microcrystalline cellulose as reinforcement in nanocomposites; self-assembly of cellulose nanocrystals: parabolic focal conic films; cellulose fibrils: isolation, characterization, and capability for technical applications; morphology of cellulose and its nanocomposites; useful insights into cellulose nanocomposites using raman spectroscopy; novel methods for interfacial modification of cellulose - reinforced composites; cellulose nanocrystals for thermoplastic reinforcement: effect of filler surface chemistry on composite properties; the structure and mechanical properties of cellulose nanocomposites prepared by twin screw extrusion; preparation and properties of biopolymer-based nanocomposites films using microcrystalline cellulose; nanocompusites based on cellulose microfibril; cellulose microfibers as reinforcing agents for structural materials; dispersion of soybean stock-based nanofiber in plastic matrix; polysulfone-cellulose nanocomposites; bacterial cellulose and its nanocomposites for biomedical applications.
Download or read book Nanocellulose written by Mainak Mukhopadhyay and published by John Wiley & Sons. This book was released on 2024-02-07 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: NANOCELLULOSE This book provides the latest up-to-date information on the exciting applications of nanocellulose in human diseases by giving in-depth explanations of their synthesis, characterization, and real-world applications in the biomedical sectors. Nanocellulose is a promising nanomaterial with unique qualities including low cost, durability, non-toxicity, accessibility, etc. Cellulose can be classified into two types: nanocrystals and nanofibrils, depending on the way it is extracted from trees, plants, or other cellulose-containing species. Textiles, cosmetics, and food products are just a few of the commercial uses for nanocellulose. However, it also has strong potential for use in medicine. The book presents the most recent scientific research on nanocellulose as a biopolymer and its potential uses in medicine. The reader will discover: explains the synthesis of bacterial nanocellulose from different bacterial species and their characteristics; details processes and applications of electrospinning and the synthesis of novel nanocellulose-based nanocomposite materials; discusses the various surface functionalization processes of cellulose and their advantages and disadvantages; delves into the application of nanocellulose in tissue engineering and grafting, such as in wound dressing and implants; discusses nanocellulose as a carrier for drug delivery, as well as the synthesis of antibacterial nanocomposites for treating multi-drug-resistant bacteria; explores the role of nanocellulose in the treatment of renal failure, nanocellulose hydrogel for ophthalmic and dental applications. Audience Researchers in areas including environmental biotechnology, bioprocess engineering, renewable energy, chemical engineering, nanotechnology, biotechnology, and microbiology will be interested in this book.
Download or read book Cellulose Nanoparticles written by Vijay Kumar Thakur and published by . This book was released on 2021-07-09 with total page 1154 pages. Available in PDF, EPUB and Kindle. Book excerpt: This two-volume set covers Cellulose Nanoparticles: Chemistry and Fundamentals and Cellulose Nanoparticles: Synthesis and Manufacturing. These books form a useful reference work for graduate students and researchers in chemistry, materials science, nanoscience and green nanotechnology.
Download or read book Nanocellulose written by and published by BoD – Books on Demand. This book was released on 2024-05-29 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book introduces the fundamentals of nanocelluloses. Nanocellulose is a cellulosic material with one dimension in the nanometer range and is derived from natural cellulosic materials, animals, and bacterial sources. This book discusses the mechanical, optical, ecofriendly, and thermal properties of nanocelluloses as well as their availability, recyclability, and renewability. It also highlights manufacturing methods and environmentally friendly extraction methods involving enzymatic processes. Moreover, the book explores advancements in nanocellulose preparation and the wide variety of applications of nanocellulose, such as in reinforcement, medical applications, material surface alterations, pest control, and more. Finally, the book examines the various stages of nanocellulose production, ranging from isolation methods to strategies for functionalization. With its thorough examination, this volume serves as a valuable resource for researchers and professionals, equipping them with the knowledge and techniques needed to fully exploit the capabilities of this remarkable material.
