0
Your cart

Your cart is empty

Price
  • R50 - R100 (1)
  • R100 - R250 (12)
  • R250 - R500 (85)
  • R500+ (9,040)
  • -
Status
Format
Author / Contributor
Publisher

Books > Science & Mathematics > Chemistry > Physical chemistry

Chemistry of Functional Materials Surfaces and Interfaces - Fundamentals and Applications (Paperback): Andrei Honciuc Chemistry of Functional Materials Surfaces and Interfaces - Fundamentals and Applications (Paperback)
Andrei Honciuc
R4,202 Discovery Miles 42 020 Ships in 12 - 19 working days

Chemistry of Functional Materials Surfaces and Interfaces: Fundamentals and Applications gives a descriptive account of interfacial phenomena step-by-step, from simple to complex, to provide readers with a strong foundation of knowledge in interfacial materials chemistry. Many case studies are provided to give real-world examples of problems and their solutions, allowing readers to make the connection between fundamental understanding and applications. Emerging applications in nanomaterials and nanotechnology are also discussed. Throughout the book, the author explains the common interface and surface equations, models, methods, and applications in the creation of functional materials. The goal of Chemistry of Functional Materials Surfaces and Interfaces is to provide readers with the basic understanding of the common tools of surface and interface chemistry for application in materials science and nanotechnology. This book is suitable for researchers and practitioners in the disciplines of materials science and engineering and surface and interface chemistry.

Annual Reports on NMR Spectroscopy, Volume 102 (Hardcover): Graham A. Webb Annual Reports on NMR Spectroscopy, Volume 102 (Hardcover)
Graham A. Webb
R6,971 R5,832 Discovery Miles 58 320 Save R1,139 (16%) Ships in 12 - 19 working days

Annual Reports on NMR Spectroscopy, Volume 102 has established itself as a premier resource for both specialists and non-specialists who are looking to become familiar with new techniques and applications pertaining to NMR spectroscopy.

Superhydrophobic Surfaces - Fabrications to Practical Applications (Hardcover): Mehdi Khodaei, Xiuyong Chen, Hua Li Superhydrophobic Surfaces - Fabrications to Practical Applications (Hardcover)
Mehdi Khodaei, Xiuyong Chen, Hua Li
R3,315 Discovery Miles 33 150 Ships in 10 - 15 working days
Complexity and Complex Chemo-Electric Systems (Paperback): Stanislaw Sieniutycz Complexity and Complex Chemo-Electric Systems (Paperback)
Stanislaw Sieniutycz
R5,244 Discovery Miles 52 440 Ships in 12 - 19 working days

Complexity and Complex Chemo-Electric Systems presents an analysis and synthesis of chemo-electric systems, providing insights on transports in electrolytes, electrode reactions, electrocatalysis, electrochemical membranes, and various aspects of heterogeneous systems and electrochemical engineering. The book describes the properties of complexity and complex chemo-electric systems as the consequence of formulations, definitions, tools, solutions and results that are often consistent with the best performance of the system. The book handles cybernetics, systems theory and advanced contemporary techniques such as optimal control, neural networks and stochastic optimizations (adaptive random search, genetic algorithms, and simulated annealing). A brief part of the book is devoted to issues such as various definitions of complexity, hierarchical structures, self-organization examples, special references, and historical issues. This resource complements Sieniutycz' recently published book, Complexity and Complex Thermodynamic Systems, with its inclusion of complex chemo-electric systems in which complexities, emergent properties and self-organization play essential roles.

Handbook of Flame Retardants (Hardcover): George Wypych Handbook of Flame Retardants (Hardcover)
George Wypych
R8,871 R6,139 Discovery Miles 61 390 Save R2,732 (31%) Ships in 12 - 19 working days

Handbook of Flame Retardants contains an extensive evaluation of the existing literature, products and patents related to flame retardance. As a perfect complement to The Databook of Flame Retardants, this book explains the roles, selection, mechanisms of action, use in different polymers and products, and health and environmental issues of over 350 different products. Chapters highlight the fundamentals of material burning and the associated stages of heat, flame and smoke, properties and mechanisms, and preventive, delaying and extinguishing attributes of 27 chemical groups of flame retardants. Examples of synergistic and antagonistic actions of various additives are discussed next, along with testing methods. The book concludes with chapters providing guidance on optimal selection of flame retardants for various polymers and information on the toxicity of flame retardants and their effects on the environment.

Chemistry, Manufacture and Applications of Natural Rubber (Paperback, 2nd edition): Shinzo Kohjiya, Yuko Ikeda Chemistry, Manufacture and Applications of Natural Rubber (Paperback, 2nd edition)
Shinzo Kohjiya, Yuko Ikeda
R5,251 Discovery Miles 52 510 Ships in 12 - 19 working days

Chemistry, Manufacture and Applications of Natural Rubber, Second Edition presents the latest advances in the processing, properties and advanced applications of natural rubber (NR), drawing on state-of-the-art research in the field. Chapters cover manufacturing, processing and properties of natural rubber, describing biosynthesis, vulcanization for improved performance, strain-induced crystallization, self-reinforcement, rheology and mechanochemistry for processing, computer simulation of properties, scattering techniques and stabilizing agents. Applications covered include natural rubber, carbon allotropes, eco-friendly soft bio-composites using NR matrices and marine products, the use of NR for high functionality such as shape memory, NR for the tire industry, and natural rubber latex with advanced applications. This is an essential resource for academic researchers, scientists and (post)graduate students in rubber science, polymer science, materials science and engineering, and chemistry. In industry, this book enables professionals, R&D, and producers across the natural rubber, tire, rubber and elastomer industries, as well as across industries looking to use natural rubber products, to understand and utilize natural rubber for cutting-edge applications.

Handbook of Modern Coating Technologies - Applications and Development (Hardcover): Mahmood Aliofkhazraei, Ali Nasar, Mircea... Handbook of Modern Coating Technologies - Applications and Development (Hardcover)
Mahmood Aliofkhazraei, Ali Nasar, Mircea Chipara, Nadhira Bensaada Laidani, Jeff Th.M. DeHosson
R6,178 R4,250 Discovery Miles 42 500 Save R1,928 (31%) Ships in 12 - 19 working days

Handbook of Modern Coating Technologies: Application and Development reviews recent applications and developments of modern coating technologies. The topics in this volume consist of role of antibacterial coatings in the development of biomaterials, insights of technologies for self-healing organic coatings, sensor applications, application of carbon nanotubes-based coating in the field of art conservation, oxide-based self-cleaning and corrosion-protective coatings, protective coatings for wood, applications of optical coatings on spectral selective structures, application of natural antimicrobial coating for controlling foodborne pathogens on meat and fresh produce, efficacy of antimicrobial coating in reducing pathogens on meat, composite membrane: fabrication, characterization, and applications, development of nanostructured HVOF coatings on high strength steel components for turbine blades, nanoscale multilayered composite coating, applications of sol-gel coatings, application of graphene in protective coating industry, application of coatings in outdoor high-voltage installations, defects and doping effects in thin films of transparent and conductive oxides, and functional coatings for lab-on-a-chip systems based on phospholipid polymers.

Biopolymer-Based Metal Nanoparticle Chemistry for Sustainable Applications - Volume 2: Applications (Paperback): Mahmoud... Biopolymer-Based Metal Nanoparticle Chemistry for Sustainable Applications - Volume 2: Applications (Paperback)
Mahmoud Nasrollahzadeh
R4,233 Discovery Miles 42 330 Ships in 12 - 19 working days

Biopolymers are becoming an increasingly important area of research as traditional chemical feedstocks run low and concerns about environmental impacts increase. One area of particular interest is their use for more sustainable development of metal nanoparticles. Biopolymer-Based Metal Nanoparticle Chemistry for Sustainability Applications, Volume 2 reviews key uses of biopolymers and biopolymer-based metal nanoparticles for a range of key sustainability-focused applications. After providing contextual examples of applications across the fields of food science, biomedicine and biochemistry, the book goes on to explore further sustainability-focused applications of Biopolymer-Based Metal Nanoparticles in such important areas as catalysis, environmental science, biosensing, and energy.

Food, Medical, and Environmental Applications of Polysaccharides (Paperback): Kunal Pal, Indranil Banerjee, Preetam Sarkar,... Food, Medical, and Environmental Applications of Polysaccharides (Paperback)
Kunal Pal, Indranil Banerjee, Preetam Sarkar, Arindam Bit, Doman Kim, …
R5,826 Discovery Miles 58 260 Ships in 12 - 19 working days

Food, Medical, and Environmental Applications of Polysaccharides provides a detailed resource for those interested in the design and preparation of polysaccharides for state-of-the-art applications. The book begins with an introductory section covering sources, chemistry, architectures, bioactivity, and chemical modifications of polysaccharides. Subsequent parts of the book are organized by field, with chapters focusing on specific applications across food, medicine, and the environment. This is an extremely valuable book for researchers, scientists, and advanced students in biopolymers, polymer science, polymer chemistry, biomaterials, materials science, biotechnology, biomedical engineering, cosmetics, medicine, food science, and environmental science. This important class of biopolymer can offer attractive properties and modification potential, enabling its use in groundbreaking areas across food, medical, and environmental fields. The book will be of interest to scientists, R&D professionals, designers, and engineers who utilize polysaccharide-based materials.

Theoretical and Computational Approaches to Predicting Ionic Liquid Properties (Paperback): Aswathy Joseph, Suresh Mathew Theoretical and Computational Approaches to Predicting Ionic Liquid Properties (Paperback)
Aswathy Joseph, Suresh Mathew
R4,618 Discovery Miles 46 180 Ships in 12 - 19 working days

Theoretical and Computational Approaches to Predicting Ionic Liquid Properties highlights new approaches to predicting and understanding ionic liquid behavior and selecting ionic liquids based on theoretical knowledge corroborated by experimental studies. Supported throughout with case studies, the book provides a comparison of the accuracy and efficiency of different theoretical approaches. Sections cover the need for integrating theoretical research with experimental data, conformations, electronic structure and non-covalent interactions, microstructures and template effects, thermodynamics and transport properties, and spectro-chemical characteristics. Catalytic and electrochemical properties are then explored, followed by interfacial properties and solvation dynamics. Structured for ease of use, and combining the research knowledge of a global team of experts in the field, this book is an indispensable tool for those involved with the research, development and application of ionic liquids across a vast range of fields.

Advances in Catalysis, Volume 67 (Hardcover): Chunshan Song Advances in Catalysis, Volume 67 (Hardcover)
Chunshan Song
R6,478 R5,416 Discovery Miles 54 160 Save R1,062 (16%) Ships in 12 - 19 working days

Advances in Catalysis, Volume 67, fills the gap between journal papers and textbooks across the diverse areas of catalysis research. For more than 60 years, this series has dedicated itself to record and present the latest progress in the field of catalysis, providing the scientific community with comprehensive and authoritative reviews. This series is an invaluable and comprehensive resource for chemical engineers and chemists working in the field of catalysis in both academia and industry, with this release focusing on solid acids, surface acidity and heterogeneous acid catalysis.

Handbook on the Physics and Chemistry of Rare Earths, Volume 58 - Including Actinides (Hardcover): Vitalij K Pecharsky,... Handbook on the Physics and Chemistry of Rare Earths, Volume 58 - Including Actinides (Hardcover)
Vitalij K Pecharsky, Jean-Claude G. Bunzli
R10,152 R8,479 Discovery Miles 84 790 Save R1,673 (16%) Ships in 12 - 19 working days

Handbook on the Physics and Chemistry of Rare Earths: Including Actinides, Volume 58, the latest release in this continuous series that covers all aspects of rare earth science, including chemistry, life sciences, materials science and physics, presents interesting chapters on Forensic applications of rare earth materials, and Rare earths, the seventeen-position nob.

Quantum Boundaries of Life, Volume 82 (Hardcover): Roman R. Poznanski, Erkki J. Brandas Quantum Boundaries of Life, Volume 82 (Hardcover)
Roman R. Poznanski, Erkki J. Brandas
R7,096 R5,937 Discovery Miles 59 370 Save R1,159 (16%) Ships in 12 - 19 working days

Quantum Boundaries of Life, Volume 82 in the Advances in Quantum Chemistry series, presents current topics in this rapidly developing field that have emerged at the cross section of mathematics, physics, chemistry and biology. Topics covered include Quantum Considerations of Neural Memory, Functional Neural Electron Transport, Plasmon-polariton mechanism of the saltatory conduction in myelinated axons, Quantum Field Theory Formulation of Brain Dynamics: Nonequilibrium, Multi Field Theory Formulation of Brain Dynamics, Quantum Protein Folding, Classical-Quantum Interplay in Living Neural Tissue Function, Quantum Effects in Life Dynamics, Quantum transport and utilization of free energy in protein a-helices, and much more. The book's message is simple. Mystics prefer to put consciousness in the cosmos to avoid Darwinism. If the seat of consciousness is found to evolve within all animals, then we have a Darwinian understanding not only of the origin of life and species according to natural selection but also concerning consciousness and, in particular, life being quantum Darwinian.

Advances in Catalysis, Volume 66 (Hardcover): Chunshan Song Advances in Catalysis, Volume 66 (Hardcover)
Chunshan Song
R6,490 R5,429 Discovery Miles 54 290 Save R1,061 (16%) Ships in 12 - 19 working days

Advances in Catalysis, Volume 66, fills the gap between journal papers and textbooks across the diverse areas of catalysis research. For more than 60 years, this series has dedicated itself to record and present the latest progress in the field of catalysis, providing the scientific community with comprehensive and authoritative reviews. This series is an invaluable and comprehensive resource for chemical engineers and chemists working in the field of catalysis in both academia and industry.

Biopolymers and Their Industrial Applications - From Plant, Animal, and Marine Sources, to Functional Products (Paperback):... Biopolymers and Their Industrial Applications - From Plant, Animal, and Marine Sources, to Functional Products (Paperback)
Sabu Thomas, Sreeraj Gopi, Augustine Amalraj
R4,855 Discovery Miles 48 550 Ships in 12 - 19 working days

Biopolymers and Their Industrial Applications: From Plant, Animal, and Marine Sources to Functional Products is a detailed guide to the use of biopolymers for advanced applications across a range of key industries. In terms of processing and cost, bio-based polymers are becoming increasingly viable for an ever-broadening range of novel industrial applications. The book begins with an overview of biopolymers, explaining resources, demands, sustainability, life cycle assessment (LCA) modeling and simulation, and classifications. Further in-depth chapters explore the latest techniques and methodologies for isolation and physicochemical characterization, materials selection, and processing for blends and composites. Chapters 6 to 14 each focus on the preparation and applications of biopolymers in a specific industrial area, including food science and nutraceuticals, medicine and pharmaceuticals, textiles, cosmeceutical, packaging, adhesives and automotive, 3D printing, super capacitor and energy storage devices, and environmental applications. The final chapter compares and analyzes biopolymers alongside synthetic polymers, also offering valuable insight into social, economic, and environmental aspects. This is an essential resource for those seeking to understand, research, or utilize biopolymers in industrial applications. This includes researchers, scientists, and advanced students working in biopolymers, polymer science, polymer chemistry, biomaterials, materials science, nanotechnology, composites, and biotechnology. This is a highly valuable book for scientists, R&D professionals, designers, and engineers across multiple industries and disciplines, who are looking to utilize biopolymers for components and products.

Advances in Physical Organic Chemistry, Volume 54 (Hardcover): Ian Williams, Nick Williams Advances in Physical Organic Chemistry, Volume 54 (Hardcover)
Ian Williams, Nick Williams
R6,947 R5,808 Discovery Miles 58 080 Save R1,139 (16%) Ships in 12 - 19 working days

Advances in Physical Organic Chemistry, Volume 54, presents the latest reviews of recent work in physical organic chemistry. The book provides a valuable source of information that is ideal not only for physical organic chemists applying their expertise to both novel and traditional problems, but also for non-specialists across diverse areas who identify a physical organic component in their approach to research. Its hallmark is a quantitative, molecular level understanding of phenomena across a diverse range of disciplines.

Introduction to Quantum Mechanics (Paperback, 2nd edition): S. M. Blinder Introduction to Quantum Mechanics (Paperback, 2nd edition)
S. M. Blinder
R4,243 Discovery Miles 42 430 Ships in 12 - 19 working days

Introduction to Quantum Mechanics, 2nd Edition provides an accessible, fully updated introduction to the principles of quantum mechanics. It outlines the fundamental concepts of quantum theory, discusses how these arose from classic experiments in chemistry and physics, and presents the quantum-mechanical foundations of current scientific developments. Beginning with a solid introduction to the key principles underpinning quantum mechanics in Part 1, the book goes on to expand upon these in Part 2, where fundamental concepts such as molecular structure and chemical bonding are discussed. Finally, Part 3 discusses applications of this quantum theory across some newly developing applications, including chapters on Density Functional Theory, Statistical Thermodynamics and Quantum Computing. Drawing on the extensive experience of its expert author, Introduction to Quantum Mechanics, 2nd Edition is a lucid introduction to the principles of quantum mechanics for anyone new to the field, and a useful refresher on fundamental knowledge and latest developments for those varying degrees of background.

Foams - Emerging Technologies (Hardcover): Huijin Xu, Chen Yang, Dengwei Jing Foams - Emerging Technologies (Hardcover)
Huijin Xu, Chen Yang, Dengwei Jing
R3,325 Discovery Miles 33 250 Ships in 10 - 15 working days
Annual Reports on Computational Chemistry, Volume 16 (Hardcover): David A Dixon Annual Reports on Computational Chemistry, Volume 16 (Hardcover)
David A Dixon
R7,024 R5,873 Discovery Miles 58 730 Save R1,151 (16%) Ships in 12 - 19 working days

Annual Reports in Computational Chemistry, Volume 16, provides timely and critical reviews of important topics in computational chemistry. Topics covered in this series include quantum chemistry, molecular mechanics, force fields, chemical education, and applications in academic and industrial settings. Focusing on the most recent literature and advances in the field, each article covers a specific topic of importance to computational chemists.

Annual Reports on NMR Spectroscopy, Volume 101 (Hardcover): Atta-ur Rahman Annual Reports on NMR Spectroscopy, Volume 101 (Hardcover)
Atta-ur Rahman
R6,974 R5,836 Discovery Miles 58 360 Save R1,138 (16%) Ships in 12 - 19 working days

Annual Reports on NMR Spectroscopy, has established itself as a premier resource for both specialists and non-specialists who are looking to become familiar with new techniques and applications pertaining to NMR spectroscopy.

Thermodynamics - Principles Characterizing Physical and Chemical Processes (Paperback, 5th edition): Jurgen M. Honig Thermodynamics - Principles Characterizing Physical and Chemical Processes (Paperback, 5th edition)
Jurgen M. Honig
R4,269 Discovery Miles 42 690 Ships in 12 - 19 working days

Thermodynamics: Principles Characterizing Physical and Chemical Processes, Fifth Edition is an authoritative guide on the physical and chemical processes based on classical thermodynamic principles. Emphasis is placed on fundamental principles, with a combination of theory and practice that demonstrates their applications in a variety of disciplines. Revised and updated to include new material and novel formulations, this edition features a new chapter on algebraic power laws and Fisher information theory, along with detailed updates on irreversible phenomena, Landau theory, self-assembly, Caratheodory's theorem, and the effects of externally applied fields. Drawing on the experience of its expert author, this book is a useful tool for both graduate students, professional chemists, and physicists who wish to acquire a more sophisticated overview of thermodynamics and related subject matter.

Superlubricity (Paperback, 2nd edition): Ali Erdemir, Jean Michel Martin, Jianbin Luo Superlubricity (Paperback, 2nd edition)
Ali Erdemir, Jean Michel Martin, Jianbin Luo
R4,992 Discovery Miles 49 920 Ships in 12 - 19 working days

Superlubricity - the state between sliding systems where friction is reduced to almost immeasurable amounts - holds great potential for improving both the economic and environmental credentials of moving mechanical systems. Research in this field has progressed tremendously in recent years, and there now exist several theoretical models, recognised techniques for computational simulations and interesting experimental evidence of superlubricity in practise. Superlubricity, Second Edition, presents an extensively revised and updated overview of these important developments, providing a comprehensive guide to the physical chemistry underpinning molecular mechanisms of friction and lubrication, current theoretical models used to explore and assess superlubricity, examples of its achievement in experimental systems, and discussion of potential future applications. Drawing on the extensive knowledge of its expert editors and global team of authors from across academia and industry, Superlubricity, Second Edition, is a great resource for all those with a need to understand, model or manipulate surface interactions for improved performance.

Analytical Pyrolysis of Natural Organic Polymers, Volume 20 (Paperback, 2nd edition): S.C. Moldoveanu Analytical Pyrolysis of Natural Organic Polymers, Volume 20 (Paperback, 2nd edition)
S.C. Moldoveanu
R5,819 Discovery Miles 58 190 Ships in 12 - 19 working days

Analytical Pyrolysis of Natural Organic Polymers, Second Edition, Volume 20 describes the methodology of analytical pyrolysis, the results of pyrolysis for a variety of biopolymers, and several practical applications of analytical pyrolysis on natural organic polymers and their composite materials. The book describes the results of pyrolysis for biopolymers and some chemically modified natural organic polymers. In addition, the many applications of analytical pyrolysis are covered in detail, including topics such as polymer detection used in forensic science, structure elucidation of specific polymers, and identification of small molecules present in polymers (anti-oxidants, plasticizers, etc.).

Chemical Physics and Quantum Chemistry, Volume 81 (Hardcover): Erkki J. Brandas, Kenneth Ruud Chemical Physics and Quantum Chemistry, Volume 81 (Hardcover)
Erkki J. Brandas, Kenneth Ruud
R7,082 R5,924 Discovery Miles 59 240 Save R1,158 (16%) Ships in 12 - 19 working days

Advances in Quantum Chemistry presents surveys of current topics in this rapidly developing field one that has emerged at the cross section of the historically established areas of mathematics, physics, chemistry, and biology. It features detailed reviews written by leading international researchers. In this volume the readers are presented with an exciting combination of themes.

From Kibbutz Fishponds To The Nobel Prize: Taking Molecular Functions Into Cyberspace (Hardcover): Arieh Warshel From Kibbutz Fishponds To The Nobel Prize: Taking Molecular Functions Into Cyberspace (Hardcover)
Arieh Warshel
R1,558 Discovery Miles 15 580 Ships in 10 - 15 working days

What Arieh Warshel and fellow 2013 Nobel laureates Michael Levitt and Martin Karplus achieved - beginning in the late 1960s and early 1970s when computers were still very primitive - was the creation of methods and programs that describe the action of biological molecules by 'multiscale models'. In this book, Warshel describes this fascinating, half-century journey to the apex of science.From Kibbutz Fishponds to The Nobel Prize is as much an autobiography as an advocacy for the emerging field of computational science. We follow Warshel through pivotal moments of his life, from his formative years in war-torn Israel in an idealistic kibbutz that did not encourage academic education; to his time in the army and his move to the Technion where he started in his obsession of understanding the catalytic power of enzymes; to his eventual scientific career which took him to the Weizmann Institute, Harvard University, Medical Research Council, and finally University of Southern California. We read about his unique contributions to the elucidation of the molecular basis of biological functions, which are combined with instructive stories about his persistence in advancing ideas that contradict the current dogma, and the nature of his scientific struggle for recognition, both personal and for the field to which he devoted his life. This is, in so many ways, more than just a memoir: it is a profoundly inspirational tale of one man's odyssey from a kibbutz that did not allow him to go to a university to the pinnacle of the scientific world, highlighting that the correct mixture of persistence, talent and luck can lead to a Nobel Prize.

Free Delivery
Pinterest Twitter Facebook Google+
You may like...
WTF - Capturing Zuma: A Cartoonist's…
Zapiro Paperback R295 R272 Discovery Miles 2 720
A Working Life, Cruel Beyond Belief
Alfred Temba Qabula Paperback R159 Discovery Miles 1 590
The History of the Saracens - Comprising…
Simon Ockley Paperback R715 Discovery Miles 7 150
A Perfumed Scorpion
Idries Shah Hardcover R534 Discovery Miles 5 340
The Ramadan Cookbook - 80 Delicious…
Anisa Karolia Hardcover R585 R530 Discovery Miles 5 300
The Women's Khutbah Book - Contemporary…
Sa'diyya Shaikh, Fatima Seedat Paperback R380 R351 Discovery Miles 3 510
The Land Is Ours - Black Lawyers And The…
Tembeka Ngcukaitobi Paperback  (11)
R400 R369 Discovery Miles 3 690
Islamic Teachings Series: Faith
Muhammad Tahir-ul-Qadri Paperback R252 Discovery Miles 2 520
International Brigade Against Apartheid…
Ronnie Kasrils, Muff Andersson, … Paperback R320 R295 Discovery Miles 2 950
Dear Pastors and Priests - Messages from…
Ayman Alhasan Paperback R774 R690 Discovery Miles 6 900

 

Partners