Citation, Dr. Stephen C. Cowin, M.A. Biot Medal, 2004
Professor Cowin is currently a City University of New York Distinguished Professor in the Departments of Biomedical and Mechanical Engineering at City College. In 2002-2003 he served as interim chair of the new Department of Biomedical Engineering at City College and as the Director of the New York Center for Biomedical Engineering at the City University of New York. He also serves as an Adjunct Professor of Orthopaedics at the Mt. Sinai School of Medicine in New York City. Before taking up his position at City College in 1988 he was the Alden J. Laborde Professor of Engineering in the Department of Biomedical Engineering at Tulane University. He was also a Professor of Applied Statistics in the Graduate School, and Adjunct Professor in the Department of Orthopaedics of the School of Medicine at Tulane.
Professor Cowin received his BES and MS in Civil Engineering from Johns Hopkins University in 1956 and 1958, respectively, and his Ph.D. in Engineering Mechanics from the Pennsylvania State University in 1962. After one year on the faculty at the Pennsylvania State University, he began a 25-year-long association with Tulane University in 1963. His principal research interest is the mechanics of materials, particularly in determining the influence of microstructure on the gross mechanical behavior of granular, porous, composite, and biological materials.
Professor Cowin is the author of over 200 research papers and editor or co-editor of five books. He is presently or has been a Regional Editor for Forma, an Associate Editor of the Journal of Applied Mechanics and the Journal of Biomechanical Engineering, a member of the Editorial Board of the Journal of Biomechanics, International Journal of Biomechanics and Modeling in Mechanobiology, Annals of Biomedical Engineering, and the Editorial Advisory Board of the Handbook of Bioengineering and the Handbook of Mechanics, Materials, and Structures. He is presently at work on a senior/first graduate year textbook tentatively entitled Tissue Mechanics.
Professor Cowin’s work is highly cited in the scientific literature. Seventeen of his papers are cited for more that 50 times. A few examples are shown in the following:
· His seminal paper with M.A. Goodman on “Continuum theory for granular materials,” which set the theoretical foundation for granular materials, was cited 209 times.
· His work on the mechanics of bones “A continuous wave technique for the measurement of the elastic properties of cortical bone” with R.B. Ashman, W.C. Vanbuskirk, and J.C. Rice, was cited 212 times.
· Other examples include “On the dependence of the elasticity and strength of cancellous bone on apparent density” cited 189 times, and “A model for the excitation of osteocytes by mechanical loading-induced bone fluid shear stresses” cited 176 times.
Professor Cowin was the recipient of the Best Paper Award from the Bioengineering Division of the American Society of Mechanical Engineers in 1992, the recipient of the Melville Medal from the American Society of Mechanical Engineers in 1993, and the recipient of the European Society of Biomechanics Research Award in 1994. In 1999 he received the H. R. Lissner Medal of the American Society of Mechanical Engineers for contributions to biomedical engineering.
Professor Cowin has made major contributions in a number of theoretical and applied mechanics fields, which include mechanics of granular materials, porous materials, polar fluid, bone mechanics, soft tissue mechanics, adaptive elasticity, biomechanics, and biomedical technology. With the background of the Biot Medal, we focus on Professor Cowin’s contributions in applying poromechanics to the mechanics of bones and his leading role in the mechanics of granular materials and materials with voids. As Professor Cowin stated in his authoritative review paper “Bone poroelasticity”:
“The purpose of this paper is to review the application of poroelasticity theory to the study of the mechanical behavior of fluid-saturated living bone tissue. Bone fluid has many functions. It transports nutrients to, and carries waste from, the bone cells (osteocytes) buried in the bony matrix. It is involved in the transport of mineral ions to the bone tissue for storage and retrieval of those mineral ions when they are needed by the body. Recently, bone fluid flow has been suggested to have a role in bone’s mechanosensory system. Bone deformation causes the bone fluid to flow over the bone cell membrane; the shear stress of the flowing fluid is sensed by the cell … A full physiological understanding of this mechanosensory system will likely provide insight into the following three important clinical problems: (a) the long-term stability of bone implants, (b) the physiological mechanism underlying osteoporosis, and (c) bone maintenance in long-duration space flights and long-term bed rest.”
This is indeed a fascinating field.
In the following, we compile quotations from the supporting letters to demonstrate the deep influence of Professor Cowin’s work on the theoretical and applied science of poromechanics.
“Professor Cowin has done very fundamental and ground breaking work in the area of porous materials. His 1979 paper with Nunziato on porous materials set the foundation for the modern theory of such materials. The theory is derived from principles and concepts of Continuum Thermodynamics and incorporates inertial effects associated with the opening and closing of pores. It has been cited nearly 100 times in the literature. … There are numerous porous materials in daily life of which bones are a prime example. Professor Cowin has been a pioneer in modeling a bone as a porous material and his work in this area has led to significant discoveries that have resulted in the improved diagnosis and treatment of medical problems related to the fracture and the healing of bones.”
“It had long been guessed that the cells of bone (osteocytes), which lie within tiny interconnecting cavities in the hard matrix, might have a signalling function, and indeed some pioneers, like Piekarski, had applied some (necessarily) rather primitive modelling to the problem. However, no one had to try to model in any detail what went on, but Steve decided that the time was ripe for a real attempt. In 1994 he published, with Weinbaum and Zeng a real hard-nosed model of the whole process of shear-induced stimulation of osteocytes, and of the osteocytic processes that lie in the canaliculi [No. 140]. This paper has been hugely influential, for instance it has been cited 167 times so far in Science Citation Index and any book concerned even peripherally with bony adaptation (such as my own ‘Bone: structure and mechanics) has to deal with it. … Steve’s group have published a whole series of papers since, refining the model, dealing with the effect of the biological materials that partially fill up the tiny canaliculi, with whether the effective signals are streaming potentials or direct shear effects on the cell processes and similar matters. He published a review in 1999 [No. 174] which is a clear and rigorous explanation of the field. A recent, 2003, paper in J Biomech [No. 200] is a splendid attempt to deal with the messy interactions of physiological processes and their interactions with poroelastic phenomena. … Workers on bone adaptation now nearly all take the work of Cowin as a starting point for their own investigations.”
“While I was still a graduate student—and before I had met him—my dissertation research was guided by Steve’s seminal contributions to the literature regarding the functional adaptation of bone to mechanical usage. … Even a cursory glance at Steve’s CV shows what a remarkable influence he has had in leading progress in the field of bone mechanics. … Characteristic of Steve’s work has been his knack for developing and adapting rigorous engineering methods to accommodate increasingly accurate physiological knowledge about bone behavior. The incorporation of poroelasticity theory and methods into the study of bone behavior certainly allows for better descriptions of the mechanics of bone as a material. However, the insights from the incorporation of fluid descriptions into continuum models of bone are crucial when considering bone as a living material. The interaction of fluid and solid is the essential mechanism that can account for the mechanosensory properties of living bone, and leading to new theoretical, computational and experimental investigations of bone.”
“Professor Cowin is one of the leading, most successful and influential scientists in the development and application of the mechanics of porous materials such as bone adaptation and remodeling, flowing granular materials and cellular mechano-sensory transduction in bones. His achievements are concerned and his name particularly associated with the mechanics of bone, as one example of a living porous material. Of particular importance is his pioneering work on the general theory of adaptive elastic materials as a model for the physiological process of bone remodeling, which had and still has a tremendous impact in the scientific community… Nowadays Cowin’s theory of adaptive elasticity is frequently applied to serve as a fundamental basis for advanced investigations in the field of bone mechanics, for the proper design of orthopedic prostheses with the goal to improve the outcome of clinical treatments.”
“The pioneering work of Steve Cowin and his former student M. A. Goodman on mechanics of granular materials which appeared in 1972 incorporates the gradient of porosity into a rigorous continuum model and is now considered to be a classic work in the field. This well known theory has since been applied by numerous investigators to a host of problems involving the slow and rapid flow of granular materials. Another pioneering work of Steve and his former student D. M. Hegedus appears in 1976 and is on bone remodeling. This work which spawned a whole domain of research in bone mechanics has grown into new models that incorporated poroelasticity to explain the mechanosensory processes in living tissue.”
“His work ranges through a spectrum of key topics in continuum mechanics, including solid and fluid mechanics and thermomechanics, but he is best known for his work in bone mechanics, granular materials and the elasticity of materials with voids. In each of these areas he has made profound, far-reaching and influential contributions.”
“The scholastic achievement of Professor Cowin is very impressive. His research subjects cover a wide range; from fluids to solids, granular materials to continuum materials, polar materials to materials with voids, from classical elasticity to modern biomechanics. There are not many researchers in mechanics that cover such wide subjects.”
“In mid-career Dr. Cowin introduced the fabric tensor concept to describe cancellous bone and used this idea to describe Wolff’s century-old observation as to the directional orientation of trabecular bone at modeling equilibrium. The theory was later extended to non-equilibrium remodeling and the paper describing it was the recipient of the 1993 ASME Melville Medal, the highest literature award of the society for an original research paper. … By 1990 it was clear that a cellular level biological model was needed to explain the mechanosensory mechanism by which bone senses mechanical load. …In 1995 the authors received the Research Award of the European Society of Biomechanics for the latter contribution. …Some feeling for the tremendous impact that Professor Cowin’s research has had can be gleaned from the fact that his original research papers in porous media mechanics and biomechanics have been cited nearly 4000 times, an achievement that is probably unmatched by any researcher in this field.”
“Professor Cowin has been the international leader in the important field of bone mechanics for decades; … most importantly, however, he has led the field by insisting on mathematical rigor coupled with biological relevance. At the time when modern biomechanics was truly beginning (early to mid-1970s), Professor Cowin provided important leadership … His place in the history of biomechanics is assured.”
“Although it has been known that the granular material contains distributed void, no rigorous continuum theory taking the porosity into consideration had been known until Cowin’s theory proposed in 1974. Professor Cowin formulated a theory of continua with fractional solids content, which describes the porosity in material, and he succeeded to produce many fruitful results on mechanics of granular flow from his theory.”
“In the 1970-80’s Cowin was the co-developer of the Goodman-Cowin continuum theory of granular flows, and the Mehrabadi-Cowin theory for the initial deformation of granular materials. These works were seminal contributions and continue to be widely cited up to the present day. Cowin has been a prolific author of significant publications treating various aspects of granular materials, microstructural and generalized continua, anisotropic elasticity and poroelasticity and general mechanics of porous materials. His research was not limited to theoretical studies; Cowin also introduced experimental techniques that led to the discovery of phenomena that arise during the deformation of granular materials. Some of his work dealing with stresses in bins and grain elevators integrated these theoretical investigations with the work of practitioners to derive results that were both understandable and useful to design engineers.”
“Professor Stephen Cowin has made outstanding research contributions to poromechanics over four decades. While his initial research contributions were in the granular materials and powder technology, he demonstrated an early interest in biological problems (e.g. using a polar fluid to model blood flow). Like Dr Maurice Biot, inquisitiveness about the natural world has been a hallmark of Stephen's research. Stephen moves between different fields with apparent ease. This variety of research is only possible because of his deep and abiding interest in the behaviour of physical systems.”
“Professor Cowin has made many important contributions to the mechanics of porous and granular materials over a period of more than 30 years, including basic theoretical developments and applications, especially in the field of biomechanics. … Cumulatively, he has the most impressive record of original research and a reputation which stands high internationally.”
“I first learned of Dr. Cowin’s work when I was a graduate student in the late 80’s and early 90’s at Stanford. … When I began to read of the work of Dr. Cowin it was clear that he was motivated by the same kind of fundamental urge. It was also clear that his prior work had established the fundamental principles of continuum mechanics and thermodynamics that a mechanically adaptive tissue must follow. Thus, he formed the foundation upon which my work (which was more applied) was built.”
“The main focus of his research has been on bone mechanics and he has addressed a range of issues pertaining to this fascinating and very complex subject. They included higher-order continuum theories such as Cosserat theory, constitutive modeling of bone including fabric tensors approach, application of poroelastic theory to cellular materials with fluids such as bone, bone remodeling, mechanosensory mechanisms in bone, fluid flow in bone, and other phenomena. One of the seminal contributions of Steven Cowin is in the area of poroelasticity. He extended and developed the theory proposed by Maurice Biot and applied it to biological materials such as bone. He has a number of publications presenting the fundamentals of this theory and its applications, including a very impressive survey article on “Bone Poroelasticity” [J. Biomechanics, 32, 1999].”
“My research is focused on the physical mechanisms involved in the control of tissue growth, healing, and homeostasis, especially bone adaptation influenced by mechanical environment, and how these mechanisms can be utilized in the treatment and prevention of disease and injury. Hard tissues, i.e., bone, have a complex structure and play a significant role in the skeleton. I am attracted into this very interesting research area because of its interesting bi-phase behaviors under mechanical loading, which is analytically defined by Biot’s theory. Dr. Cowin’s work has extended Biot’s poroelasticity into biological microstructures and other materials. He has described mechanical behavior in the combined solid and fluid phases of bone in response to physical loading, such as fluid flow in a unit of bone, e.g., osteon. His work has guided many analytical experimental researches including mine. His fundamental work has been used in several of my bone fluid flow research projects funded by the National Institute of Health, Department of Defense, and the Whitaker Research Foundation. … Dr. Cowin has put remarkable efforts in education. He helped the initiation of Biomedical Engineering Programs at the Tulane University and at the City University of New York, and has been invited for numerous guest lectures. He is very supportable for young scientists in the field.”
2004
