Skip to main content Accessibility help
×
  1. Home
  2. Browse subjects
  3. Life Sciences
  4. Bioengineering
  5. Content listing

Refine search

Refine search

Access:
Content type:
Publication date:
Apply   From and To filters
Subject: Show more
Journals Show more
Publishers: Show more
Societies Show more
Series: Show more
Collections: Show more

Actions for selected content:

Select all | Deselect all
  • View selected items
  • Export citations
  • Download PDF (zip)
  • Save to Kindle
  • Save to Dropbox
  • Save to Google Drive

Save Search

You can save your searches here and later view and run them again in "My saved searches".

Please provide a title, maximum of 40 characters.
Cancel
×

361 results in Bioengineering

Page 7 of 19

Cybernetic Modeling for Bioreaction Engineering
  • Doraiswami Ramkrishna, Hyun-Seob Song
  • Published online:
    29 September 2018
    Print publication:
    18 October 2018
  • Uniquely focusing on dynamic modeling, this volume incorporates metabolic regulation as a survival mechanism for cells, by driving metabolism through optimal investment of its resources for control of enzyme synthesis and activity. Consequently, the models have a proven record of describing various uptake patterns of mixed carbon substrates that have become significant in modern applications of biomass for the production of bioenergy. The models accurately describe dynamic behavior of microbes in nutrient environments with mixtures of complementary substrates, such as carbon and nitrogen. Modeling of large metabolic networks (including prospects for extension to genome scale) is enabled by lumped hybrid cybernetic models with an unparalleled capacity to predict dynamic behavior of knockout strains. This is an invaluable, must-have reference for bio-researchers and practicing engineers.

  • 13 - Solution Strategies for Solid and Fluid Mechanics Problems

  • Cees Oomens, Technische Universiteit Eindhoven, The Netherlands, Marcel Brekelmans, Technische Universiteit Eindhoven, The Netherlands, Sandra Loerakker, Technische Universiteit Eindhoven, The Netherlands, Frank Baaijens, Technische Universiteit Eindhoven, The Netherlands
  • Book:
    Biomechanics
    Published online:
    02 February 2018
    Print publication:
    08 February 2018, pp 270-291

  • Summary

    Introduction

    The goal of the present chapter is to describe a procedure to formally determine solutions for solid mechanics problems, fluid mechanics problems and problems with filtration and diffusion. Mechanical problems in biomechanics can be very diverse, and most problems are so complex that it is impossible to derive analytical solutions and often very complicated to determine numerical solutions. Fortunately, in most cases it is not necessary to describe all phenomena related to the problem in full detail; simplifying assumptions can be made, thus reducing the complexity of the set of equations that have to be solved. The present chapter deals with formulating problems and solution strategies, starting from the most general set of equations and gradually reducing the generality by imposing simplifying assumptions. In Section 13.2 this will be done for solids. Section 13.3 is devoted to the solution of fluid mechanics problems. The last section of this chapter discusses diffusion and filtration.

    Solution Strategies for Deforming Solids

    In this section, it is assumed that the material (or material fraction) to be considered can be modelled as a deforming solid continuum. This implies that it is possible and significant to define a reference configuration or reference state. With respect to the reference state, the displacement field as a function of time supplies a full description of the deformation process to which the continuum is subjected (at least under the restrictions given in previous chapters, such as a constant temperature). After all, for a displacement field that is known as a function of time, it is possible to directly calculate the local deformation history (applying the kinematics: see Chapter 10) and subsequently, the stress state as a function of time (using the constitutive equations: see Chapter 12). The relevant fields, from a mechanical point of view, that are obtained in this way for the continuum have to satisfy the balance equations (see Chapter 11). In addition, the initial conditions have to be fulfilled: at the beginning of the process, the positions of the material points in space have to be prescribed, usually in accordance with the reference configuration, and also the initial velocities of the material points have to be in agreement with the specification of the initial state.

  • 7 - Biological Materials and Continuum Mechanics

  • Cees Oomens, Technische Universiteit Eindhoven, The Netherlands, Marcel Brekelmans, Technische Universiteit Eindhoven, The Netherlands, Sandra Loerakker, Technische Universiteit Eindhoven, The Netherlands, Frank Baaijens, Technische Universiteit Eindhoven, The Netherlands
  • Book:
    Biomechanics
    Published online:
    02 February 2018
    Print publication:
    08 February 2018, pp 133-154

  • Summary

    Introduction

    Up to this point, all treated problems have been in some way one-dimensional. In Chapter 3 we have discussed equilibrium of two- and three-dimensional bodies and in Chapter 4 the fibres were allowed to have some arbitrary orientation in three-dimensional space. But, when deformations were involved, the focus was on fibres and bars, dealing with one-dimensional force–strain relationships. Only one-dimensional equations were solved. In this chapter and the ones that follow, the theory will be extended to the description of three-dimensional bodies, and it is opportune to spend some time looking at the concept of a continuum.

    Consider a certain amount of solid and/or fluid material in a three-dimensional space. Although in reality for neighbouring points in space the (physical) character and behaviour of the residing material may be completely different (because of discontinuities at the microscopic level, which become clearer on reducing the scale of observation), it is common practice that a less detailed description (at a macroscopic level) with a more gradual change of physical properties is used. The discontinuous heterogeneous reality is homogenized and modelled as a continuum. To make this clearer, consider the bone in Fig. 7.1. Although one might conceive the bone at a macroscopic level, as depicted in Fig. 7.1(a), as a massive structure filling all the volume that it occupies in space, it is clear from Fig. 7.1(b) that at a smaller scale the bone is a discrete structure with open spaces in between (although the spaces can be filled with a softer material or a liquid). At an even smaller scale, at the level of one single trabecula, individual cells can be recognized. This phenomenon is typical for biological materials at any scale, whether it is at the organ level, the tissue level or cellular level, or even smaller. At each level, a very complex structure can be observed, and it is not feasible to take into account every detail of this structure. That is why a homogenization of the structure is necessary, and, depending on the objectives of the modelling (which is the question that has to be answered in the context of the selection of the theoretical model), a certain level of homogenization is chosen.

  • 16 - Solution of the Three-Dimensional Convection–Diffusion Equation by Means of the Finite Element Method

  • Cees Oomens, Technische Universiteit Eindhoven, The Netherlands, Marcel Brekelmans, Technische Universiteit Eindhoven, The Netherlands, Sandra Loerakker, Technische Universiteit Eindhoven, The Netherlands, Frank Baaijens, Technische Universiteit Eindhoven, The Netherlands
  • Book:
    Biomechanics
    Published online:
    02 February 2018
    Print publication:
    08 February 2018, pp 342-362

  • Summary

    Introduction

    The two- and three-dimensional convection–diffusion equations play an important role in many applications in biomedical engineering. One typical example is the analysis of the effectiveness of different types of bioreactors for tissue engineering. Tissue engineering is a rapidly evolving interdisciplinary research area aiming at the replacement or restoration of diseased or damaged tissue. In many cases, devices made of artificial materials are only capable of partially restoring the original function of native tissues, and may not last for the full lifetime of a patient. In addition, there is no artificial replacement for a large number of tissues and organs. In tissue engineering, new, autologous tissues are grown. The tissue proliferation and differentiation process is strongly affected by mechanical stimuli and transport of oxygen, minerals, nutrients and growth factors. To optimize bioreactor systems, it is necessary to analyse how these systems behave. The convection–diffusion equation plays an important role in this kind of simulating analysis.

    Figure 16.1 shows two different bioreactor configurations, both of which have been used in the past to tissue engineer articular cartilage. The work was especially focussed on glucose, oxygen and lactate, because these metabolites play a major role in the biosynthesis and survival of chondrocyte. Questions ranged from: ‘Does significant nutrient depletion occur at the high cells concentrations required for chondrogenesis?’ to ‘Do increasing transport limitations due to matrix accumulation significantly affect metabolite distributions?’ Figure 16.2 shows a typical result for the calculated oxygen distributions in the two bioreactor configurations.

    This chapter explains the discretization of the convection-diffusion equation in two or three dimensions. First, the diffusion equation is discussed; thereafter, the convection–diffusion equation is elaborated. The spatial discretization of the weighting function is based on the Galerkin method.

    Diffusion Equation

    Consider a two- or three-dimensional domain with boundary. As in the onedimensional model problem, the boundary is split into a part along which the essential boundary conditions are specified, and a part along which the natural boundary conditions may be specified. The generic form of the diffusion equation is given by

  • Preface to the First Edition

  • Cees Oomens, Technische Universiteit Eindhoven, The Netherlands, Marcel Brekelmans, Technische Universiteit Eindhoven, The Netherlands, Sandra Loerakker, Technische Universiteit Eindhoven, The Netherlands, Frank Baaijens, Technische Universiteit Eindhoven, The Netherlands
  • Book:
    Biomechanics
    Published online:
    02 February 2018
    Print publication:
    08 February 2018, pp xv-xvi

  • Summary

    In September 1997, an educational programme in Biomedical Engineering, unique in the Netherlands, started at the Eindhoven University of Technology, together with the University of Maastricht, as a logical step after almost two decades of research collaboration between both universities. This development culminated in the foundation of the Department of Biomedical Engineering in April 1999 and the creation of a graduate programme (MSc) in Biomedical Engineering in 2000 and Medical Engineering in 2002.

    Already at the start of this educational programme, it was decided that a comprehensive course in biomechanics had to be part of the curriculum and that this course had to start right at the beginning of the Bachelor phase. A search for suitable material for this purpose showed that excellent biomechanics textbooks exist. But many of these books are very specialized to certain aspects of biomechanics. The more general textbooks address mechanical or civil engineers or physicists who wish to specialize in biomechanics, so these books include chapters or sections on biology and physiology. Almost all books that were found are at Masters or post-graduate level, requiring basic to sophisticated knowledge of mechanics and mathematics. At a more fundamental level, only books could be found that were written for mechanical and civil engineers.

    We decided to write our own course material for the basic training in mechanics appropriate for our candidate biomedical engineers at Bachelor level, starting with the basic concepts of mechanics and ending with numerical solution procedures, based on the finite element method. The course material assembled in the current book comprises three courses for our biomedical engineering curriculum, distributed over the three years of their Bachelor studies. Chapters 1 to 6 mostly treat the basic concepts of forces, moments and equilibrium in a discrete context in the first year. Chapters 7 to 13 in the second year discuss the basis of continuum mechanics, and Chapters 14 to 18 in the third year are focussed on solving the field equations of mechanics using the finite element method.

  • Preface to the Second Edition

  • Cees Oomens, Technische Universiteit Eindhoven, The Netherlands, Marcel Brekelmans, Technische Universiteit Eindhoven, The Netherlands, Sandra Loerakker, Technische Universiteit Eindhoven, The Netherlands, Frank Baaijens, Technische Universiteit Eindhoven, The Netherlands
  • Book:
    Biomechanics
    Published online:
    02 February 2018
    Print publication:
    08 February 2018, pp xvii-xviii

  • Summary

    Since 2009, when this book was published for the first time, we have been using it in our Biomechanics courses in the educational programme Biomedical Engineering, giving us hands-on experience with the book and the exercises. When we were investigating ideas for a second edition, we found that external reviewers were primarily asking for more examples and exercises, concurring with our own thoughts on the book. Over the years, we have assembled quite a number of examples that were often used to animate the lectures and to illustrate the theory in biomedical applications. At the same time, the number of available exercises increased considerably. Eventually, adding many of these examples and increasing the number of exercises are the most significant changes in the second edition. The major changes in the text are:

  • • Mathematical preliminaries are now concentrated in Chapter 1 and no longer spread over different chapters.

  • • At some points in the original text, explanations were terse and too concise for students. Based on our experiences over the past eight years, we have extended the text at a number of points and, most importantly, added the earlier mentioned new examples. The biggest change is in Chapter 12, including a separate section on material frame indifference of constitutive equations and a more extensive treatment of hyperelastic materials.

    • The objectives of the book did not change. It is still meant to be a basic training in mechanics, appropriate for our candidate biomedical engineers at Bachelor level, starting with the basic concepts of mechanics and ending with numerical solution procedures. This book differs from most books on biomechanics, which are usually aimed at students with already considerable knowledge in continuum mechanics and wishing to enter the field of biomechanics. Consequently, those books pay great attention to biology and physiology. In contrast, we assume that students start at a very basic level in terms of mechanics, but already have substantial physiological and biological background knowledge.

  • 2 - The Concepts of Force and Moment

  • Cees Oomens, Technische Universiteit Eindhoven, The Netherlands, Marcel Brekelmans, Technische Universiteit Eindhoven, The Netherlands, Sandra Loerakker, Technische Universiteit Eindhoven, The Netherlands, Frank Baaijens, Technische Universiteit Eindhoven, The Netherlands
  • Book:
    Biomechanics
    Published online:
    02 February 2018
    Print publication:
    08 February 2018, pp 16-38

  • Summary

    Introduction

    We experience the effects of force in everyday life and have an intuitive notion of force. For example, we exert a force on our body when we lift or push an object, while we continuously (fortunately) feel the effect of gravitational forces, for instance while sitting, walking, etc. All parts of the human body in one way or the other are loaded by forces. Our bones provide rigidity to the body and can sustain high loads. The skin is resistant to force: simply pull on the skin to witness this. The cardiovascular system is continuously loaded dynamically owing to the pulsating blood pressure. The bladder is loaded and stretched when it fills up. The intervertebral discs serve as flexible force-transmitting media that give the spine its flexibility. Beside force, we are using levers all the time in our daily life to increase the ‘force’ that we want to apply to some object, for example by opening doors with the latch, opening a bottle with a bottle-opener. We feel the effect of a lever arm when holding a weight close to our body instead of using a stretched arm. These experiences are the result of the moment that can be exerted by a force. Understanding the impact of force and moment on the human body requires us to formalize the intuitive notion of force and moment. That is the objective of this chapter.

    Definition of a Force Vector

    Imagine pulling on a thin wire that is attached to a wall. The pulling force exerted on the point of application is a vector with a physical meaning: it has

  • • a length: the magnitude of the pulling force

  • • an orientation in space: the direction of the wire

  • • a line-of-action, which is the line through the force vector.

    • The graphical representation of a force vector, denoted by, is given in Fig. 2.1. The ‘shaft’ of the arrow indicates the orientation in space of the force vector. The point of application of the force vector is denoted by the point P.

  • About the Cover

  • Cees Oomens, Technische Universiteit Eindhoven, The Netherlands, Marcel Brekelmans, Technische Universiteit Eindhoven, The Netherlands, Sandra Loerakker, Technische Universiteit Eindhoven, The Netherlands, Frank Baaijens, Technische Universiteit Eindhoven, The Netherlands
  • Book:
    Biomechanics
    Published online:
    02 February 2018
    Print publication:
    08 February 2018, pp xiii-xiv

  • Summary

    The cover contains images reflecting biomechanics research topics at the Eindhoven University of Technology. An important aspect of mechanics is experimental work to determine material properties and to validate models. The application field ranges from microscopic structures at the level of cells to larger organs like the heart. The core of biomechanics is constituted by models formulated in terms of partial differential equations and computer models to derive approximate solutions.

  • • Main image: Myogenic precursor cells have the ability to differentiate and fuse to form multinucleated myotubes. This differentiation process can be influenced by means of mechanical as well as biochemical stimuli. To monitor this process of early differentiation, immunohistochemical analyses are performed to provide information concerning morphology and localization of characteristic structural proteins of muscle cells. In the illustration, the sarcomeric proteins actin (red), and myosin (green) are shown. Nuclei are stained blue. Image courtesy of Mrs Marloes Langelaan.

  • • Left top: To study the effect of a mechanical load on the damage evolution of skeletal tissue, an in-vitro model system using tissue engineered muscle was developed. The image shows this muscle construct in a set-up on a confocal microscope. In the device the construct can be mechanically deformed by means of an indentor. Fluorescent identification of both necrotic and apoptotic cells can be established using different staining techniques. Image courtesy of Mrs Debby Gawlitta.

  • • Left middle: A three-dimensional finite element mesh of the human heart ventricles is shown. This mesh is used to solve the equations of motion for the beating heart. The model was used to study the effect of depolarization waves and mechanics in the paced heart. Image courtesy of Mr Roy Kerckhoffs.

  • • Left bottom: The equilibrium equations are derived from Newton's laws and describe (quasi-)static force equilibrium in a three-dimensional continuum. See Eqs. (8.33), (8.34) and (8.35) in the present book.

  • 5 - Fibres: Time-Dependent Behaviour

  • Cees Oomens, Technische Universiteit Eindhoven, The Netherlands, Marcel Brekelmans, Technische Universiteit Eindhoven, The Netherlands, Sandra Loerakker, Technische Universiteit Eindhoven, The Netherlands, Frank Baaijens, Technische Universiteit Eindhoven, The Netherlands
  • Book:
    Biomechanics
    Published online:
    02 February 2018
    Print publication:
    08 February 2018, pp 79-115

  • Summary

    Introduction

    In the previous chapter on fibres, the material behaviour was constantly considered to be elastic, meaning that a unique relation exists between the extensional force and the deformation of the fibre. This implies that the force versus stretch curves for the loading and unloading path are identical. There is no history dependency, and all energy that is stored into the fibre during deformation is regained during the unloading phase. This also implies that the rate of loading or unloading does not affect the force–stretch curves. However, most biological materials do not behave elastically.

    An example of a loading history and a typical response of a biological material is shown in Figs. 5.1(a) and (b). In Fig. 5.1(a), a deformation history is given that might be used in an experiment to mechanically characterize some material specimen. The specimen is rapidly stretched to a certain value, then the deformation is fixed and after a certain time restored to zero. After a short resting period, the stretch is applied again but to a higher value of the stretch. This deformation cycle is repeated several times. In this case the length change is prescribed and the associated force is measured. Figure 5.1(b) shows the result of such a measurement. When the length of the fibre is kept constant, the force decreases with time. This phenomenon is called relaxation. Conversely, if a constant load is applied, the length of the fibre will increase. This is called creep.

    When the material is subjected to cyclic loading, the force versus stretch relation in the loading process is usually somewhat different from that in the unloading process. This is called hysteresis and is demonstrated in Fig. 5.2. The difference in the response paths during loading and unloading implies that energy is dissipated, usually in the form of heat, during the process. Most biological materials show more or less the behaviour given above, which is called visco-elastic behaviour. The present chapter discusses how to describe this behaviour mathematically. Pure viscous behaviour, as can be attributed to an ideal fluid, is considered first.

Page 7 of 19