Biomaterials

A Basic Introduction

Author: Qizhi Chen,George Thouas

Publisher: CRC Press

ISBN: 148222769X

Category: Medical

Page: 736

View: 2454

Explores Biomedical Science from a Unique Perspective Biomaterials: A Basic Introduction is a definitive resource for students entering biomedical or bioengineering disciplines. This text offers a detailed exploration of engineering and materials science, and examines the boundary and relationship between the two. Based on the author’s course lecture notes and many years of research, it presents students with the knowledge needed to select and design biomaterials used in medical devices. Placing special emphasis on metallic, ceramic, polymeric, and composite biomaterials, it explains the difference between materials science and materials engineering, introduces basic concepts and principles, and analyzes the critically important properties of biomaterials. Explains Complex Theories Using Aspects of Daily Life This text provides an appropriate balance between depth and broadness of coverage, and offers an understanding of the most important concepts and principles to students from a wide academic spectrum. It delivers the science of biomaterials in laymen terms, from a material standpoint, as well as a clinical applications point of view. It equips students majoring in materials science/engineering with knowledge on the fundamentals of how biomaterials behave at a biological level, and provides students majoring in medicine with information that is generally unavailable in traditional medical courses. The authors incorporate learning objectives at the beginning of each chapter, as well as chapter highlights, problems, and exercises at the end of each chapter. In addition, they present objectives, suggested activities, and reference material for further reading. Contains an overview of medical science vis-à-vis materials science, describes anatomy, histology, and cell biology Highlights health issues and diseases where biomaterials can easily find medical applications Presents knowledge of the relationship between the biomaterials and the living body Evaluates medical devices and looks into their respective regulations Biomaterials: A Basic Introduction contains an overview of basic biomaterials and concepts, and is written for upper-division students in the US/Canada, and second-level students in universities worldwide.

Biomaterials Science

An Introduction to Materials in Medicine

Author: Buddy D. Ratner,Allan S. Hoffman,Frederick J. Schoen,Jack E. Lemons

Publisher: Academic Press

ISBN: 008087780X

Category: Medical

Page: 1573

View: 7293

The revised edition of this renowned and bestselling title is the most comprehensive single text on all aspects of biomaterials science. It provides a balanced, insightful approach to both the learning of the science and technology of biomaterials and acts as the key reference for practitioners who are involved in the applications of materials in medicine. Over 29,000 copies sold, this is the most comprehensive coverage of principles and applications of all classes of biomaterials: "the only such text that currently covers this area comprehensively" - Materials Today Edited by four of the best-known figures in the biomaterials field today; fully endorsed and supported by the Society for Biomaterials Fully revised and expanded, key new topics include of tissue engineering, drug delivery systems, and new clinical applications, with new teaching and learning material throughout, case studies and a downloadable image bank

Introduction to Biomaterials

Basic Theory with Engineering Applications

Author: J. L. Ong,Mark R. Appleford,Gopinath Mani

Publisher: Cambridge University Press

ISBN: 0521116902

Category: Medical

Page: 419

View: 1753

A succinct introduction to the field of biomaterials engineering, packed with practical insights.

Biomaterials

An Introduction

Author: Joon Park,R. S. Lakes

Publisher: Springer Science & Business Media

ISBN: 0387378804

Category: Technology & Engineering

Page: 562

View: 6773

With sixty years of combined experience, the authors of this extensively revised book have learned to emphasize the fundamental materials science, structure-property relationships, and biological responses as a foundation for a wide array of biomaterials applications. This edition includes a new chapter on tissue engineering and regenerative medicine, approximately 1900 references to additional reading, extensive tutorial materials on new developments in spinal implants and fixation techniques and theory. It also offers systematic coverage of orthopedic implants, and expanded treatment of ceramic materials and implants.

An Introduction to Biomaterials, Second Edition

Author: Jeffrey O. Hollinger

Publisher: CRC Press

ISBN: 1439812578

Category: Medical

Page: 644

View: 5496

A practical road map to the key families of biomaterials and their potential applications in clinical therapeutics, Introduction to Biomaterials, Second Edition follows the entire path of development from theory to lab to practical application. It highlights new biocompatibility issues, metrics, and statistics as well as new legislation for intellectual property. Divided into four sections (Biology, Biomechanics, Biomaterials Interactions; Biomaterials Testing, Statistics, Regulatory Considerations, Intellectual Property; Biomaterials Compositions; and Biomaterials Applications), this dramatically revised edition includes both new and revised chapters on cells, tissues, and signaling molecules in wound healing cascades, as well as two revised chapters on standardized materials testing with in vitro and in vivo paradigms consistent with regulatory guidelines. Emphasizing biocompatibility at the biomaterial-host interface, it investigates cell-cell interactions, cell-signaling and the inflammatory and complement cascades, specific interactions of protein-adsorbed materials, and other inherent biological constraints including solid-liquid interfaces, diffusion, and protein types. Unique in its inclusion of the practicalities of biomaterials as an industry, the book also covers the basic principles of statistics, new U.S. FDA information on the biomaterials-biology issues relevant to patent applications, and considerations of intellectual property and patent disclosure. With nine completely new chapters and 24 chapters extensively updated and revised with new accomplishments and contemporary data, this comprehensive introduction discusses 13 important classes of biomaterials, their fundamental and applied research, practical applications, performance properties, synthesis and testing, potential future applications, and commonly matched clinical applications. The authors include extensive references, to create a comprehensive, yet manageable didactic work that is an invaluable desk references and instructional text for undergraduates and working professionals alike.

Introduction to Biomaterials

Author: Donglu Shi

Publisher: 清华大学出版社有限公司

ISBN: 9787302108078

Category: Biomaterials

Page: 253

View: 3764

This book gives a fundmaentally comprehensive introduction to most of the important biomaterials including ceramics, metals, and polymers.

Cereal Straw as a Resource for Sustainable Biomaterials and Biofuels

Chemistry, Extractives, Lignins, Hemicelluloses and Cellulose

Author: RunCang Sun

Publisher: Elsevier

ISBN: 9780080932675

Category: Technology & Engineering

Page: 300

View: 897

Materials from renewable resources are receiving increased attention, as leading industries and manufacturers attempt to replace declining petrochemical-based feedstocks with products derived from natural biomass, such as cereal straws. Cereal straws are expected to play an important role in the shift toward a sustainable economy, and a basic knowledge of the composition and structure of cereal straw is the key to using it wisely. Cereal Straw as a Resource for Sustainable Biomaterials and Biofuels: Chemistry, Extractives, Lignins, Hemicelluloses and Cellulose provides an introduction to straw chemistry. Topics discussed include the structure, ultrastructure, and chemical composition of straw; the structure and isolation of extractives from the straw; the three main components of straw: cellulose, hemicelluloses, and lignins; and chemical modifications of straw for industrial applications. This book will be helpful to scientists interested in the areas of natural resource management, environmental chemistry, plant chemistry, material science, polysaccharide chemistry, and lignin chemistry. It will also be of interest to academic and industrial scientists/researchers interested in novel applications of agricultural residues for industrial and/or recycling technologies. Provides the basics of straw composition and the structure of its cell walls Details the procedures required to fractionate straw components to produce chemical derivatives from straw cellulose, hemicelluloses, and lignins Elucidates new techniques for the production of biodegradable materials for the energy sector, chemical industry, and pulp and paper business

Biomaterials

A Nano Approach

Author: Seeram Ramakrishna,Murugan Ramalingam,T .S. Sampath Kumar,Winston O. Soboyejo

Publisher: CRC Press

ISBN: 1420047825

Category: Technology & Engineering

Page: 372

View: 3857

There are several well-known books on the market that cover biomaterials in a general way, but none provide adequate focus on the future of and potential for actual uses of emerging nanontechnology in this burgeoning field. Biomaterials: A Nano Approach is written from a multi-disciplinary point of view that integrates aspects of materials science and engineering, nanotechnology, bioengineering, and biosciences. The book fills a glaring void in the literature by providing a comprehensive discussion of biomaterials and a scientifically plausible extrapolation of likely scenarios in which nanotechnology could play a significant role. The authors introduce and examine basic concepts, processing methodologies, and techniques involved in the preparation and characterization of nanobiomaterials that are specific to biomedical applications. A Self-Contained Book Illustrating Past, Present, and Future Trends in Biomaterials Spanning from the historical development of biomaterials to cutting-edge advances in the field, the text describes how basic concepts in nanotechnology are applied to the processing of novel nanobiomaterials, including nanostructured metals and alloys. With its illustrative examples and presentation of applications, this text offers a solid framework for understanding present and future trends of biomaterials in human healthcare systems. It is an ideal companion resource for students, researchers, and industrial scientists who specialize in biomaterials and nanobiomaterials.

Engineering Materials for Biomedical Applications

Author: Teoh Swee Hin

Publisher: World Scientific

ISBN: 9814481645

Category: Medical

Page: 352

View: 5860

The success of any implant or medical device depends very much on the biomaterial used. Synthetic materials (such as metals, polymers and composites) have made significant contributions to many established medical devices. The aim of this book is to provide a basic understanding on the engineering and processing aspects of biomaterials used in medical applications. Of paramount importance is the tripartite relationship between material properties, processing methods and design. As the target audiences cover a wide interdisciplinary field, each chapter is written with a detailed background so that audience of another discipline will be able to understand. For the more knowledgeable reader, a detailed list of references is included. Contents:Introduction to Biomaterials Engineering and Processing — An Overview (S H Teoh)Durability of Metallic Implant Materials (M Sumita & S H Teoh)Corrosion of Metallic Implants (D J Blackwood et al.)Surface Modification of Metallic Biomaterials (T Hanawa)Biorestorative Materials in Dentistry (A U J Yap)Bioceramics: An Introduction (B Ben-Nissan & G Pezzotti)Polymeric Hydrogels (J Li)Bioactive Ceramic-Polymer Composites for Tissue Replacement (M Wang)Composites in Biomedical Applications (Z M Huang & S Ramakrishna)New Methods and Materials in Prosthetics for Rehabilitation of Lower Limb Amputees (P V S Lee)Chitin-Based Biomaterials (E Khor) Readership: Undergraduates and postgraduates (in bioengineering, materials science and engineering, mechanical engineering, dental and orthopaedic departments), engineers, researchers, academics/lecturers and industrialists. Keywords:Biomaterials Engineering and Processing;Durability of Metallic Implants;Surface Modification;Dental Materials;Bioceramics;Polymeric Hydrogels;Composites;Prosthetics;ChitinKey Features:Contains detailed information on the latest biomaterials (such as polymers, metals, ceramics and composites ) used in medical devicesProvides a good understanding into the durability issues such as an in-depth treatment of corrosion and fretting fatigue of metallic implantsIt leads the reader to have a greater appreciation on the need for surface modification so as to enable the medical device to have the appropriate tissue response

Handbook of Biomaterial Properties

Author: William Murphy,Jonathan Black,Garth Hastings

Publisher: Springer

ISBN: 1493933051

Category: Technology & Engineering

Page: 676

View: 8992

This book provides tabular and text data relating to normal and diseased tissue materials and materials used in medical devices. Comprehensive and practical for students, researchers, engineers, and practicing physicians who use implants, this book considers the materials aspects of both implantable materials and natural tissues and fluids. Examples of materials and topics covered include titanium, elastomers, degradable biomaterials, composites, scaffold materials for tissue engineering, dental implants, sterilization effects on material properties, metallic alloys, and much more. Each chapter author considers the intrinsic and interactive properties of biomaterials, as well as their appropriate applications and historical contexts. Now in an updated second edition, this book also contains two new chapters on the cornea and on vocal folds, as well as updated insights, data, and citations for several chapters.

Electronic Materials Science

Author: Eugene A. Irene

Publisher: John Wiley & Sons

ISBN: 9780471711636

Category: Science

Page: 400

View: 438

A thorough introduction to fundamental principles and applications From its beginnings in metallurgy and ceramics, materials science now encompasses such high- tech fields as microelectronics, polymers, biomaterials, and nanotechnology. Electronic Materials Science presents the fundamentals of the subject in a detailed fashion for a multidisciplinary audience. Offering a higher-level treatment than an undergraduate textbook provides, this text benefits students and practitioners not only in electronics and optical materials science, but also in additional cutting-edge fields like polymers and biomaterials. Readers with a basic understanding of physical chemistry or physics will appreciate the text's sophisticated presentation of today's materials science. Instructive derivations of important formulae, usually omitted in an introductory text, are included here. This feature offers a useful glimpse into the foundations of how the discipline understands such topics as defects, phase equilibria, and mechanical properties. Additionally, concepts such as reciprocal space, electron energy band theory, and thermodynamics enter the discussion earlier and in a more robust fashion than in other texts. Electronic Materials Science also features: * An orientation towards industry and academia drawn from the author's experience in both arenas * Information on applications in semiconductors, optoelectronics, photocells, and nanoelectronics * Problem sets and important references throughout * Flexibility for various pedagogical needs Treating the subject with more depth than any other introductory text, Electronic Materials Science prepares graduate and upper-level undergraduate students for advanced topics in the discipline and gives scientists in associated disciplines a clear review of the field and its leading technologies.

Essential Biomaterials Science

Author: David Williams

Publisher: Cambridge University Press

ISBN: 0521899087

Category: Science

Page: 672

View: 2642

This groundbreaking single-authored textbook equips students with everything they need to know to truly understand the hugely topical field of biomaterials science, including essential background on the clinical necessity of biomaterials, relevant concepts in biology and materials science, comprehensive and up-to-date coverage of all existing clinical and experimental biomaterials, and the fundamental principles of biocompatibility. It features extensive case studies interweaved with theory, from a wide range of clinical disciplines, equipping students with a practical understanding of the phenomena and mechanisms of biomaterials performance; a whole chapter dedicated to the biomaterials industry itself, including guidance on regulations, standards and guidelines, litigation, and ethical issues to prepare students for industry; informative glossaries of key terms, engaging end-of-chapter exercises, and up-to-date lists of recommended reading. Drawing on the author's 40 years' experience in biomaterials, this is an indispensible resource for students studying these lifesaving technological advances.

Biological Materials Science

Biological Materials, Bioinspired Materials, and Biomaterials

Author: Marc André Meyers,Po-Yu Chen

Publisher: Cambridge University Press

ISBN: 1107010454

Category: Technology & Engineering

Page: 644

View: 1137

Takes a materials science approach, correlating structure-property relationships with function across a broad range of biological materials.

Bone Repair Biomaterials

Author: J A Planell,S M Best,D Lacroix,A Merolli

Publisher: Elsevier

ISBN: 1845696611

Category: Technology & Engineering

Page: 496

View: 3551

Bone repair is a fundamental part of the rapidly expanding medical care sector and has benefited from many recent technological developments. With an increasing number of technologies available, it is vital that the correct technique is selected for specific clinical procedures. This unique book will provide a comprehensive review of the materials science, engineering principles and recent advances in this important area. The first part of the book reviews the fundamentals of bone repair and regeneration. Chapters in the second part discuss the science and properties of biomaterials used for bone repair such as metals, ceramics, polymers and composites. The final section of the book discusses clinical applications and considerations with chapters on such topics as orthopaedic surgery, tissue engineering, implant retrieval and ethics of bone repair biomaterials. With its distinguished editors and team of international contributors, Bone repair biomaterials is an invaluable reference for researchers and clinicians within the biomedical industry and academia. Provides a comprehensive review of the materials science, engineering principles and recent advances in this important area Reviews the fundamentals of bone repair and regeneration addressing social, economic and clinical challenges Examines the properties of biomaterials used for bone repair with specific chapters assessing metals, ceramics, polymers and composites

Orthopaedic Biomaterials in Research and Practice, Second Edition

Author: Kevin L. Ong,Scott Lovald,Jonathan Black

Publisher: CRC Press

ISBN: 1466503513

Category: Medical

Page: 476

View: 3445

Revised, expanded, and updated, Orthopaedic Biomaterials in Research and Practice, Second Edition introduces materials science and applies it to medical research and treatment. This book incorporates math and engineering, which makes it accessible to trainees and others working in the industry who are lacking primary mathematical and engineering training. What’s New in the Second Edition: In the second edition, the new material includes regeneration, hybrid and replant materials, tissue engineering, electrical stimulation for tissue growth and repair, modeling of material behavior in service, and long-term function of materials in patients. It explores tools for non-destructive and destructive analysis of explanted devices, and provides updates on all material classes including shape memory and degradable alloys, fracture-resistant ceramics, and bioabsorbable polymers. It provides a compendium for implant host response including in-depth discussion of metallosis and hypersensitive response. It also adds new case studies, worked problems, and a complete self-evaluation test with annotated answers. Includes focused, practical study questions after each chapter Presents extensive, detailed figures accompanying example problems and concepts Provides a one-stop reference for understanding all biomaterials that are used in contemporary orthopaedic surgery and beyond Introduces key concepts of relevance in each chapter Orthopaedic Biomaterials in Research and Practice, Second Edition serves as a textbook for orthopaedic residents. It can also serve as a review for the Orthopaedists In-Training Examination (OITE), the Orthopaedic Self-Assessment Examination, or the Orthopaedic Board Examination.

An Introduction to Tissue-Biomaterial Interactions

Author: Kay C. Dee,David A. Puleo,Rena Bizios

Publisher: John Wiley & Sons

ISBN: 0471461121

Category: Science

Page: 248

View: 9671

An Introduction to Tissue-Biomaterial Interactions acquaints an undergraduate audience with the fundamental biological processes that influence these sophisticated, cutting-edge procedures. Chapters one through three provide more detail about the molecular-level events that happen at the tissue-implant interface, while chapters four through ten explore selected material, biological, and physiological consequences of these events. The importance of the body’s wound-healing response is emphasized throughout. Specific topics covered include:Structure and properties of biomaterials Proteins Protein-surface interactions Blood-biomaterial interactions Inflammation and infection The immune system Biomaterial responses to implantation Biomaterial surface engineering Intimal hyperplasia and osseointegration as examples of tissue-biomaterial interactions The text also provides extensive coverage of the three pertinent interfaces between the body and the biomaterial, between the body and the living cells, and between the cells and the biomaterial that are critical in the development of tissue-engineered products that incorporate living cells within a biomaterial matrix. Ideal for a one-semester, biomedical engineering course, An Introduction to Tissue-Biomaterial Interactions provides a solid framework for understanding today’s and tomorrow’s implantable biomedical devices.

Protein Physics

A Course of Lectures

Author: Alexei V. Finkelstein,Oleg Ptitsyn

Publisher: Elsevier

ISBN: 0081012365

Category: Science

Page: 528

View: 1656

Protein Physics: A Course of Lectures covers the most general problems of protein structure, folding and function. It describes key experimental facts and introduces concepts and theories, dealing with fibrous, membrane, and water-soluble globular proteins, in both their native and denatured states. The book systematically summarizes and presents the results of several decades of worldwide fundamental research on protein physics, structure, and folding, describing many physical models that help readers make estimates and predictions of physical processes that occur in proteins. New to this revised edition is the inclusion of novel information on amyloid aggregation, natively disordered proteins, protein folding in vivo, protein motors, misfolding, chameleon proteins, advances in protein engineering & design, and advances in the modeling of protein folding. Further, the book provides problems with solutions, many new and updated references, and physical and mathematical appendices. In addition, new figures (including stereo drawings, with a special appendix showing how to use them) are added, making this an ideal resource for graduate and advanced undergraduate students and researchers in academia in the fields of biophysics, physics, biochemistry, biologists, biotechnology, and chemistry. Fully revised and expanded new edition based on the latest research developments in protein physics Written by the world's top expert in the field Deals with fibrous, membrane, and water-soluble globular proteins, in both their native and denatured states Summarizes, in a systematic form, the results of several decades of worldwide fundamental research on protein physics and their structure and folding Examines experimental data on protein structure in the post-genome era

Materials

Introduction and Applications

Author: Witold Brostow,Haley E. Hagg Lobland

Publisher: John Wiley & Sons

ISBN: 0470523794

Category: Science

Page: 480

View: 2855

Presents a fully interdisciplinary approach with a stronger emphasis on polymers and composites than traditional materials books Materials science and engineering is an interdisciplinary field involving the properties of matter and its applications to various areas of science and engineering. Polymer materials are often mixed with inorganic materials to enhance their mechanical, electrical, thermal, and physical properties. Materials: Introduction and Applications addresses a gap in the existing textbooks on materials science. This book focuses on three Units. The first, Foundations, includes basic materials topics from Intermolecular Forces and Thermodynamics and Phase Diagrams to Crystalline and Non-Crystalline Structures. The second Units, Materials, goes into the details of many materials including Metals, Ceramics, Organic Raw Materials, Polymers, Composites, Biomaterials, and Liquid Crystals and Smart Materials. The third and final unit details Behavior and Properties including Rheological, Mechanical, Thermophysical, Color and Optical, Electrical and Dielectric, Magnetic, Surface Behavior and Tribology, Materials, Environment and Sustainability, and Testing of Materials. Materials: Introduction and Applications features: Basic and advanced Materials concepts Interdisciplinary information that is otherwise scattered consolidated into one work Links to everyday life application like electronics, airplanes, and dental materials Certain topics to be discussed in this textbook are more advanced. These will be presented in shaded gray boxes providing a two-level approach. Depending on whether you are a student of Mechanical Engineering, Electrical Engineering, Engineering Technology, MSE, Chemistry, Physics, etc., you can decide for yourself whether a topic presented on a more advanced level is not important for you—or else essential for you given your professional profile Witold Brostow is Regents Professor of Materials Science and Engineering at the University of North Texas. He is President of the International Council on Materials Education and President of the Scientific Committee of the POLYCHAR World Forum on Advanced Material (42 member countries). He has three honorary doctorates and is a Member of the European Academy of Sciences, Member of the National Academy of Sciences of Mexico, Foreign Member of the National Academy of Engineering of Georgia in Tbilisi and Fellow of the Royal Society of Chemistry in London. His publications have been cited more than 7200 times. Haley Lobland is the Associate Director of LAPOM at the University of North Texas. She is a Member of the POLYCHAR Scientific Committeee. She has received awards for her research presented at conferences in: Buzios, Rio de Janeiro, Brazil; NIST, Frederick, Maryland; Rouen, France; and Lviv, Ukraine. She has lectured in a number of countries including Poland and Spain. Her publications include joint ones with colleagues in Egypt, Georgia, Germany, India, Israel, Mexico, Poland, Turkey and United Kingdom.

PEEK Biomaterials Handbook

Author: Steven M. Kurtz

Publisher: William Andrew

ISBN: 143774463X

Category: Technology & Engineering

Page: 298

View: 766

PEEK biomaterials are currently used in thousands of spinal fusion patients around the world every year. Durability, biocompatibility and excellent resistance to aggressive sterilization procedures make PEEK a polymer of choice replacing metal in orthopedic implants, from spinal implants and hip replacements to finger joints and dental implants. This Handbook brings together experts in many different facets related to PEEK clinical performance as well as in the areas of materials science, tribology, and biology to provide a complete reference for specialists in the field of plastics, biomaterials, medical device design and surgical applications. Steven Kurtz, author of the well respected UHMWPE Biomaterials Handbook and Director of the Implant Research Center at Drexel University, has developed a one-stop reference covering the processing and blending of PEEK, its properties and biotribology, and the expanding range of medical implants using PEEK: spinal implants, hip and knee replacement, etc. Full coverage of the properties and applications of PEEK, the leading polymer for spinal implants. PEEK is being used in a wider range of new applications in biomedical engineering, such as hip and knee replacements, and finger joints. These new application areas are explored in detail. Essential reference for plastics enginers, biomedical engineers and orthopedic professionals involved in the use of the PEEK polymer, and medical implants made from PEEK.

Structural Biomaterials

Author: Julian F. V. Vincent

Publisher: Princeton University Press

ISBN: 9780691025131

Category: Science

Page: 244

View: 1222

"This book should go a long way towards filling the communication gap between biology and physics in [the area of biomaterials]. It begins with the basic theory of elasticity and viscoelasticity, describing concepts like stress, strain, compliance, and plasticity in simple mathematical terms. . . . For the non-biologist, these chapters provide a clear account of macromolecular structure and conformation. . . . [Vincent's work] is a delight to read, full of interesting anecdotes and examples from unexpected sources. . . . I can strongly recommend this book, as it shows how biologists could use mechanical properties as well as conventional methods to deduce molecular structure."--Anna Furth, The Times Higher Education Supplement In what is now recognized as a standard introduction to biomaterials, Julian Vincent presents a biologist's analysis of the structural materials of organisms, using molecular biology as a starting point. He explores the chemical structure of both proteins and polysaccharides, illustrating how their composition and bonding determine the mechanical properties of the materials in which they occurincluding pliant composites such as skin, artery, and plant tissue; stiff composites such as insect cuticle and wood; and biological ceramics such as teeth, bone, and eggshell. Here Vincent discusses the possibilities of taking ideas from nature with biomimicry and "intelligent" (or self-designing and sensitive) materials.