bluuebunny/crossref_metadata_2025 huggingface dataset:
Artificial Kidney, Modeling of Transport Phenomena in
Authors: Eloot Sunny , Verdonck Pascal
Published: April 2006

Patients suffering from renal failure can be treated with a renal replacement therapy. Although a possible transplantation is determined by the availability of kidney donors, peritoneal dialysis is only adequate for patients with sufficient remaining renal function. As a third alternative, hemodialysis therapy can be used in which the patient's blood is purified extracorporeally in a hemodialyzer. To have better insight in this blood purification modality, dialyzer geometry, membrane properties, fluid characteristics, and the basic transport phenomena are described.

Focused on a hollow fiber dialyzer, an overview is given of models and experiments describing blood and dialysate flow on a macroscopic basis. Also, the physical models handling of microscopic phenomena like concentration polarization and mass transport are described.

Finally, in‐house developed CFD (computational fluid dynamics) and experimental models are presented, which aim at optimizing dialyzer geometry by looking more in detail at transport processes and fluid properties inside the dialyzer. First, a macroscopic CFD model to visualize blood and dialysate flow distributions was developed and validated using SPECT (single‐photon emission‐computed tomography) medical imaging. Second, a microscopic numerical model was developed to describe flow and mass transport in a single dialyzer fiber. After model calibration and validation, the impact on solute removal of a variable fiber length and diameter was assessed for small and middle molecules. Also, the model was used to examine the effect of flow maldistribution by implementing the experimental SPECT results.
Microarray Data Analysis
Authors: Moffitt Richard , Wang May
Published: April 2006

Microarray analysis is an emerging field, simultaneously harnessing advances in semiconductor manufacturing, biochemistry, medicine, computation, and algorithms research. Microarrays now provide a platform for an unprecedented genome‐wide view of a biological sample. Microarray analysis makes use of the vast amounts of data that the microarray platform provides. It is through the intelligent combination of mathematical algorithms and clinical validation that microarray analysis provides a real opportunity to realize the goal of targeted personalized medicine. One day, the information from a single microarray might be able to tell a doctor if a patient has cancer, what type of cancer it is, what the prognosis is, and what drug to use to best fight the cancer. The foundation of this story is being built in laboratories across the world today and it starts with sound microarray analysis.

Microarray analysis is a multistep process that converts raw microarray data into biomarkers for clinical use. First, noise must be removed from raw data using preprocessing methods, such as normalization and artifact removal. Clean data can then be used to select important features or to build predictive rules called classifiers. The results of feature selection and classification are lists of biomarkers that are appropriate for classifying the data into groups such as benign or malignant. These biomarkers must then be validated clinically or through knowledge‐based approaches. The results of validation can then be used as feedback in order to select better features or build better classifiers.
Mammography
Authors: Ng Kwan-Hoong , Jamal Noriah
Published: April 2006

Mammography is a radiographic examination that is specially designed for detecting breast pathology. This procedure is performed by exposing low‐energy x‐ray on a compressed breast resulting in an image. Mammography is considered the single most important diagnostic modality in the early detection of breast cancer. Today's dedicated mammographic equipment, specially designed x‐ray screen‐film combinations, coupled with controlled film processing, can detect very low contrast lesions as small as 5 microns, as much as two years before they are palpable. The historical technical development from the early primitive breast imaging to the modern digital imaging is briefly reviewed.

Mammography technology until now was dominated by screen‐film. In screen‐film mammography, the image acquisition, display, archival, and retrieval is accomplished using the same medium, film. By overcoming many of the technical limitations of screen‐film mammography, digital mammography provides images of improved contrast sensitivity and facilitates the accurate detection and diagnosis of breast cancer. Since its introduction in the mid‐1980s, the American College of Radiology (ACR) mammography accreditation program has changed the practice of mammography, with recommendations for minimum standards of practice and quality control that spurred technological advances and ensured quality of service. It has also improved the quality of mammography internationally. The advent of digital mammography is expected to open up several exciting and potentially important applications in breast imaging and management.
Electrical Impedance Tomography Induced Current
Authors: Gençer Nevzat G.
Published: April 2006

The ultimate goal of induced‐current electrical impedance tomography (ICEIT) is to image the electrical impedance distribution within the human body. In ICEIT, time‐varying magnetic fields are applied to induce currents in the body and surface voltage measurements are used to reconstruct impedance distribution. Time‐varying fields are usually generated by sinusoidal current‐carrying wires encircling the conducting body. Given the conductivity distribution, calculating the surface voltages due a given coil configuration is named as the
forward problem
of ICEIT. Reconstructing the unknown impedance distribution from the surface voltage measurements is the
inverse problem
. This article introduces the basic theory and numerical studies related to the forward and inverse problem of ICEIT. Basic properties of a possible data acquisition system are discussed. Images reconstructed using a 16‐electrode, 6‐coil data acquisition system are presented.
Soft Tissue Scaffolds
Authors: Guan Jianjun , Stankus John J. , Wagner William R.
Published: April 2006

The effort to develop soft tissues is one of the most demanding and challenging applications in tissue engineering. Soft tissues such as myocardium, blood vessels, skeletal muscle, adipose tissue, and even cartilage often possess large volumes, have high cell densities, and can be mechanically active. 3‐D scaffolds that match the mechanical properties of the tissue that they are replacing are preferred for soft tissue engineering, because such materials might transmit mechanical forces to the developing tissue duringin vitroorin vivodevelopment. A well‐defined biodegradation rate is ideal so that host tissue can replace the scaffold and that stress can be transferred from the support scaffold to the new tissue over an appropriate time period. The scaffolds not only serve as a structural support, but also can play an important role in facilitating cell adhesion, growth, and vascularization throughout the scaffold both duringin vitrocell culture andin vivotissue regeneration.

Currently used materials meeting these criteria are diverse and include entirely synthetic materials as well as those that are derived from natural sources, and formats that are continuous on a microscale (hydrogels) and those that have defined microporous architectures. Although natural materials have the inherent advantage of bioactivity, they also possess limitations when employed as soft tissue scaffolds that may be overcome with synthetics. Some limitations associated with natural materials include inducement of an immune response that can lead to rapid degradation as well as poor batch‐to‐batch consistencies. Synthetic polymers permit better control over chemical and physical properties leading to tunability in mechanical strength and degradation rate. Surface properties of synthetic materials can also be more easily modified for improved cell attachment or migration. Some disadvantages of synthetic tissue scaffolds consist of potential toxic degradation products and undesired inflammatory responses. In addition, fabrication methods can process materials into scaffolds of desired porosity, morphologies, and anisotropies. The focus of this article will provide a brief overview of the scaffold preparation, properties, and applications of soft tissue scaffolds.
Cartilage Scaffolds
Authors: Park Grace E. , Webster Thomas J.
Published: April 2006

Perhaps due to its complex structure and composition, articular cartilage has been known to be one of the most common sources of pain and suffering in the body. Moreover, few biomaterials exist to treat the numerous problems associate cartilage decomposition and injury. This chapter will first present cartilage structure and properties useful in understanding cartilage problems and why it has been so difficult to repair cartilage damage. Then, this chapter will cover current technologies for articular cartilage repairs, emphasizing natural and synthetic materials. Lastly, this chapter will stress one promising approach for creating the next generation of cartilage scaffolds that involves nanotechnology. In this manner, this chapter will present a comprehensive view of cartilage structure, disease, and associate treatment methods.

Many attempts to design better cartilage replacements are being attempted, from natural to synthetic materials. In the synthetic materials world, it seems that the best advances are being realized when attempting to mimic the unique nano‐ and micro‐structure of cartilage tissue, which includes mimicking the arrangement of collagen in each zone of cartilage tissue. It is through these attempts of manipulating chondrocyte function to regrow cartilage tissue that new materials may be found to heal this traditionally difficult anatomical area.
Batteries for Implantable Biomedical Applications
Authors: Holmes Curtis F. , Owens Boone B.
Published: April 2006

Battery‐powered medical devices have been surgically implanted into the bodies of several million persons during the past one‐third of a century. Implantable devices have been used to treat an increasingly diverse number of conditions including cardiac arrhythmias, chronic pain, epilepsy, hearing loss, obesity, vision loss, and scoliosis. It is estimated that in the year 2004 over 500,000 heart pacemakers were implanted.

A lithium primary battery powers the typical cardiac pacemaker. The reliability and the longevity of the pacemaker are determined by its design and manufacturing parameters, as well as therapy‐related variables. As battery failure results in a cessation of pacemaker output, the selection of the appropriate battery is an important step in the product development. A large number of battery designs have been developed to meet the unique requirements of implantable medical devices, ranging from the very‐low‐rate batteries that can power a pacemaker for many years, to the high‐rate batteries required for cardiac defibrillators.
Sensor Biocompatibility and Biofouling in Real‐Time Monitoring
Authors: Voskerician Gabriela , Anderson James
Published: April 2006

The development of reliable implantable electrochemical sensors for long‐term continuousin vivomonitoring of clinically important analytes remains one of the great challenges of biomedical engineering technology today. Although significant advances in the intravascular and subcutaneous biosensor development have been achieved, the biological response to the implantable biosensors continues to have a limiting impact on the performance and lifetime of such sensors, preventing their long‐term use in real‐time monitoring of critical analytes. Here, we examine the current status of research and development in this area, emphasizing the effect of the inflammatory and wound healing response on sensor biofouling. Also, the biocompatibility aspects of sensor implantation are discussed, as they are part of the inseparable dynamic continuum of biocompatibility and biofouling initiated by the presence of any foreign material/devicein vivo.
MRI Safety
Authors: Woods Terry O.
Published: April 2006

After the first MRI scanners were approved by the FDA in 1984, they were rapidly adopted by the clinical community and have become one of the most common imaging tools. The MR environment produces unique safety requirements for implants and other medical devices. The principal MR safety issues are magnetically induced force and torque, RF heating, and image artifact. This article defines MR characteristics that affect safety and outlines the potential hazards produced by medical devices in the MR environment. It also summarizes ASTM International test methods that can be used to evaluate the MR safety of medical devices and describes ongoing efforts in MR standards development.
Neuromuscular Coordination in Gait, EMG Analysis of
Authors: Pedotti Antonio , Frigo Carlo
Published: April 2006

EMG signals are a neurological manifestation of the complex motor control mechanism. The relationship between EMG and its mechanical counterpart has been reviewed. Different ways to extract information from movement analysis are presented, and the role of advanced modeling procedures is discussed. The main concepts of multifactorial movement analysis are exemplified with reference to normal human walking.
Surface Electromyography (EMG) Signal Processing
Authors: Farina Dario
Published: April 2006

An overview of the common methods for processing surface electromyographic (EMG) signals is provided. The extraction of information from the surface EMG is based on the analysis of global properties of the interference signal or on the decomposition of the signal into single‐motor unit activities. Global analysis includes estimation of amplitude, power spectrum, average muscle fiber conduction velocity, and recurrence quantification. Single‐motor unit analysis is based on spatial filtering and spatial sampling. These techniques are reviewed and their limitations outlined. Finally, open issues in surface EMG signal processing are discussed.
Noise in Instrumentation
Authors: Chimeno Mireya Fernández , González Miguel Ángel García , Drechsler Manuel Vargas , Castro Juan José Ramos
Published: April 2006

Noise is an important factor to consider in the design of biomedical instrumentation systems. When calculating the total noise in an instrumentation system, it is necessary to consider the noise contributions of all elements: sensors, electronic systems, noise coming from external sources, etc. In this chapter, after an historical introduction, we define some mathematical properties of random processes useful for noise characterization; the different kinds of noise usually found in physical systems; the noise characteristics of sensors and electronic devices; and illustrate the methodology of analysis of complex systems from the point of view of biomedical applications when considering different noise sources. Finally, we provide an example for the noise analysis of a biomedical system.
Heart Rate Variability (HRV): Nonlinear HRV
Authors: Eyal Shulamit , Akselrod Solange
Published: April 2006

The cardiovascular system is considered to be a nonlinear system. Therefore, an effort exists to study its signals, such as heart rate and blood pressure, by applying nonlinear dynamics tools in addition to the commonly used linear tools. This chapter provides a brief introduction to the nonlinear field in conjunction with the main results obtained in studying heart rate variability. The main nonlinear methods discussed here are phase space portrait, surrogate data test for nonlinearity, and the two most commonly used parameters: the correlation dimension and the largest Lyapunov exponents. In order to complete the view on nonlinear analysis of the cardiovascular system, nonlinearity in blood pressure is presented briefly.
Electroporation
Authors: Miklavčič Damijan , Puc Marko
Published: April 2006

Electroporation is a transient phenomenon that increases permeability of the cell plasma membrane. In the state of high permeability, the plasma membrane allows ions and small and large molecules to be introduced into the cytoplasm, although the cell plasma membrane in its normal state represents a considerable barrier for them. Besides introduction of different substances to the cytoplasm, the permeabilized cell membrane allows cell fusion or insertion of proteins into cell membrane. Efficacy of electroporation and its applications strongly depends on parameters that can be divided into parameters of the electric field (i.e., pulse amplitude, pulse duration, pulse repetition frequency, number of pulses, and pulse shape), and parameters that define the state of cells, their surroundings, and cell geometry (i.e., temperature, osmotic pressure, cell size and shape, etc.). With properly chosen values of the electric field parameters, the process of electroporation is reversible and cells return into their normal physiological state. If these parameters exceed certain values (e.g., amplitude of pulses is too high or duration of pulses is too long), cells are irreversibly permeabilized and lose their viability.
Nanometer‐Scale Probes
Authors: Fletcher Dan
Published: April 2006

Scanning probe microscopes using nanometer‐scale probes enable imaging of materials with spatial resolution on the order of atoms. The most popular scanning probe techniques, including scanning tunneling microscopy (STM), scanning near‐field optical microscopy (SNOM), and atomic force microscopy (AFM), can be used to measure the topographical, electrical, optical, and mechanical properties of materials in environments including vacuum, air, and water. High spatial resolution is achieved by confining interactions between the probe and sample surface to the nanometer‐scale dimensions of the probe itself. As a result of their unique imaging and measurement capabilities, scanning probe microscopes using nanometer‐scale probes have become essential for high‐resolution characterization of biomaterials and biological molecules.
Scaffolds for Cell and Tissue Engineering
Authors: Jones Julian R.
Published: April 2006

The aim of tissue engineering is to combine the disciplines of engineering and biology to help the body's own regenerative mechanisms to repair diseased or damaged tissue to its original state and function. One strategy is to seed a patient's progenitor cells on a scaffold, which will act as a support and stimulus of tissue growth. The cells will lay down tissue in the shape of the scaffold and this biocomposite can be implanted into a defect with the scaffold dissolving as the tissue regenerates. Scaffold design is one of the important aspects of this strategy and will be discussed in this entry. The entry discusses the criteria for an ideal scaffold and the use of bioinert, bioresorble, and bioactive materials. The use of polymers, ceramics, glasses, and composites as scaffold materials and the processing techniques used to create tissue scaffolds are described and the advantages of using each material and each processing technique are discussed.
Tissue Engineering of Blood Vessels
Authors: Nerem Robert M.
Published: April 2006

A “holy grail” for cardiovascular researchers over the past half century has been the tissue engineering of a small‐diameter blood vessel substitute. There is a need for this substitute because blood vessel substitutes made from synthetic materials do not work in the small diameters required for coronary bypass surgery, and many patients do not have the native vessels normally used in such surgical procedures. Even in the replacement of larger blood vessels where synthetic grafts do work, it is hoped that an enhanced patency might be achieved through tissue engineering, i.e., a more biological approach.
Tissue Engineering of Cardiac Tissues
Authors: Stock Ulrich A. , Schenke-Layland Katja
Published: April 2006

The emerging field of cardiac tissue engineering focuses on the development of heart valves and myocardium. Hence, the following article will give a detailed overview of the biomaterials approaches of these two tissues attempting to compromise what has been accomplished so far and what remains to be achieved.
Tissue‐Engineered Liver
Authors: Berthiaume François , Yarmush Martin L.
Published: April 2006

The severe donor liver shortage, high cost, and complexity of orthotopic liver transplantation have prompted the search for alternative treatment strategies for end‐stage liver disease, which would require less donor material, be cheaper, and be less invasive. Hepatic tissue engineering encompasses several approaches to develop adjunct internal liver support methods, such as hepatocyte transplantation and implantable hepatocyte‐based devices, as well as temporary extracorporeal liver support techniques, such as bioartificial liver assist devices. As hepatocytes are highly sensitive to various environmental parameters, such as culture medium, substrate composition and topology, the presence or absence of contacts with other cells, and physical forces, it is important to first develop a small‐scale liver functional unit that performs stable long‐term liver‐specific functions. This unit forms the basis of larger devices that contain sufficient numbers of cells to have a therapeutic benefit. The major hurdles in the scale‐up of liver cell‐based assist devices is the procurement of a sufficient number of cells, and the engineering of devices that provide good oxygen and nutrient transport to the cells. These remaining challenges must be resolved in order to develop the next generation of implantable and extracorporeal devices for adjunct or temporary liver assist.
Tissue‐Engineered Peripheral Nerve
Authors: Leach Jennie B.
Published: April 2006

Peripheral nerves can be injured by a variety of mechanisms but can regenerate on their own if the injury is not extensive. Nerve grafts, the current standard of surgical care for repairing large nerve gaps, are successful, but they can be associated with several major drawbacks. To overcome these disadvantages, researchers are designing “off‐the‐shelf” nerve guide implants; thus, a multidisciplinary effort is underway to engineer nerve repair through a deeper understanding of the dynamic cell–cell and cell–environment interactions that occur during regeneration. This entry, which focuses on literature published in the last 5 years, first emphasizes new nerve guide designs that have been demonstrated to improve functional regenerationin vivo. The second section reviews studies that have deepened our understanding ofin vitroandin vivoneural regenerative responses via new biomaterials technologies and imaging techniques. These critical advancements in peripheral nerve tissue engineering provide templates for future mechanistic studies and improved strategies to aid functional regenerationin vivo.
Myoelectric Signal Processing
Authors: Morin Evelyn
Published: April 2006

The myoelectric signal or electromyogram (EMG) is recorded during voluntary contraction of skeletal muscle. Surface EMG (sEMG) is detected at the skin surface using electrodes attached to the skin over the muscle of interest. The resultant signal varies randomly about a zero mean value. This signal can be processed to provide information concerning the physiological and the biomechanical state of the muscle. This article covers two major processing paradigms—amplitude estimation and spectral analysis. sEMG amplitude estimation involves estimating the time‐varying standard deviation of the signal. Amplitude estimators from the simple integrated EMG to more complicated estimators, involving prewhitening filters, multiple channels of sEMG, and adaptive smoothing, are covered. Spectral analysis of sEMG is done to characterize the signal in the frequency domain, Fourier analysis of stationary sEMG, recorded during isometric, isotonic contractions, and time‐frequency analysis of nonstationary sEMG recorded during dynamic contractions, are discussed.
Myoelectric Manifestations of Muscle Fatigue
Authors: Merletti R. , Farina D.
Published: April 2006

Among physiologists, “fatigue” has been defined in different ways. One definition is the “failure to maintain the required or expected force.” This chapter examines muscle fatigue. After the introduction, the next section examines sites of neuromuscular fatigue. Equations that quantify fatigue are given. A later section discusses myoelectric manifestations of muscle fatigue. Finally, the chapter concludes with estimates of EMG variables and fatigue indexes.
Muscle Pain
Authors: Graven-Nielsen Thomas , Arendt-Nielsen Lars
Published: April 2006

Acute and chronic pain originating from deep somatic structures represent a major part of complaints in patients seeking health services. In a large survey, it was found that approximately 50% of the respondents had experienced pain or unpleasantness originating from musculoskeletal structures within two weeks before the interview. Moreover, musculoskeletal pain complaints were the main reason for 10% of all visits to a clinical practice in the United States. Thus, it is generally accepted that pain from deep tissues constitutes a special diagnostic and therapeutic challenge, and insights into the peripheral and central neurobiological mechanisms are necessary to improve diagnosis and management strategies.
Homecare
Authors: Tilford Arthur R.
Published: April 2006

Until now, the “at best” or near “best” homecare environment has been so costly that few, except those with nearly unlimited financial resources, could demand it. Even those with unlimited funds were still at the mercy of the established medical facility when laboratory work was required or extensive surgery was indicated. However, with the dramatic surge of advancements in communications, computer technology, and biomedical products including materials, the homecare environment can reach the level of professionalism found only within the established medical facility or hospital.
Telesurgery
Authors: Sood Sanjay P.
Published: April 2006

Medicine — inherently a forward‐looking domain of high social relevance — banks heavily upon technology for empowering clinicians and patients. Almost all sensational clinical developments are presumably the gifts of synergistic efforts of an extraordinary fusion of clinicians, engineers, and researchers. This synergy has transformed medicine into one of those few domains where technology is exploited to the maximum. Boundaries between medicine and technology are no longer distinct and definite. The role of engineers at the rear end is soaring, and someone has rightly said that the future of medicine is technology. Technologically fertile medical procedures like minimally invasive surgery have revolutionized surgical practices. Very mechanically, robotics has not only walked into medicine but has also secured a commanding position in critical procedures like surgeries. Besides fueling the basic developments, robotic surgery has enhanced precision, performance, and outcome. Continuing this technological march toward clinical excellence, clinicians, engineers, and researchers, in their stride, have been able to surmount an even more exciting technology calledtelesurgery. This novel technology enables surgeons to perform surgical procedures over a distance. Telesurgery is an umbrella term that implies the use of telemedicine in surgery. This extension has virtually ended the tyranny of geography as far as the duo of a surgeon and a patient is concerned. Telesurgery is a conglomerate of other state‐of‐the‐art technologies like virtual reality, haptics, 3‐dimensional simulation techniques, and networking technologies. Concepts like telementoring, teleproctoring, telepresence, and telerobotics fall under its domain. Consistent efforts by associated professionals are helping to get over initial issues and challenges to enable telesurgery to reach a level of application, at large.
Robotic Rehabilitation Therapy
Authors: Krebs Hermano I. , Hogan Neville
Published: April 2006

The demand for rehabilitation services is growing apace with the graying of the population, with the number of senior citizens 65 years of age and older projected to increase by 88% in the coming years. With this increase in the number of senior citizens comes increased incidence of age‐related pathologies including cerebral vascular accident (stroke). This situation creates both a need and an opportunity to deploy technologies such as robotics to assist recovery. In this chapter, the authors focus on the use of robotics to aid recovery after stroke, but the knowledge and know‐how may apply similarly to other diseases and afflictions. The authors focus solely on robots that support and enhance the productivity of clinicians in their efforts to facilitate a disabled individual's recovery. An overview of existing rehabilitation robots for the upper and lower extremity, of technology limitations, of design choices, and of clinical results is presented. The focus of the remainder of the chapter is on clinical results and on the biology of neuro‐recovery. This new class of interactive robotic devices, together with the understanding of its potentials and limitations, are poised to strongly influence how rehabilitation medicine will be practiced in the twenty‐first century.
Orthopedic Bone Cement
Authors: Deb Sanjukta
Published: April 2006

Acrylic bone cement has a distinctive place in the domain of synthetic biomaterials. It is one of the earliest synthetic polymers to be used in the body and is the most widely used materials in the anchoring of prosthesis to bone in a cemented arthroplasty. However, the cement is not without its own drawbacks and has often been related to the failure of a clinical arthroplasty. This article provides an understanding of the chemistry, composition, physical and mechanical properties, risks and failure mechanisms, improvements, and current trends of acrylic bone cements.
Genetic Algorithms
Authors: Najarian Kayvan , Eichelberger Christopher N.
Published: April 2006

Genetic algorithms are presented in theory, practice, and applications relevant to biomedical engineering.
Microencapsulation
Authors: Prakash Satya , Bhathena Jasmine
Published: April 2006

Over the past two decades, microencapsulation research has made great strides in developing approaches for the controlled release of therapeutic agents, targeted delivery of drugs, bacterial cells, mammalian cells, DNA and other nucleic acids, proteins, and so on to the host. Microencapsulation is a process whereby biologically active materials, such as tissue, cells, or cellular constituents, are enclosed within microscopic, semipermeable polymeric membranes which allows for bidirectional diffusion necessary for the entry of nutrients and oxygen and the exit of therapeutic protein products and cellular metabolic waste materials. In addition, the membrane is protective against larger molecules such as antibodies, white blood cells, or tryptic enzymes. The concept of microencapsulation was officially introduced in the 1960s by T. M. S. Chang, who coined the term “artificial cell” to describe the technology. The field has since broadened with the development of novel microencapsulation devices, improved membrane parameters and more suitable cell lines. Consequently, microencapsulation is currently being tested for the treatment of a wide variety of disorders such as kidney and liver failure, diabetes mellitus, anemia, dwarfism, hemophilia, and central nervous system insufficiencies. Although transplantation remains the primary mechanism in which cellular microcapsules are introduced, oral administration through the gastrointestinal tract has been successfully applied. In discussing microencapsulation technology, a major distinction is in the use of artificial cells that now range from macro‐dimensions, to micron‐dimensions, to nano‐dimensions, and to molecular dimensions. Details of the various microcapsule membranes and microencapsulation methods for encapsulation of live mammalian cells, bacterial cells, drugs and other bioactive molecules are described. Further, the uses of microencapsulation technology in pharmaceutical, biotechnological, biomedical and clinical applications including current challenges and future prospects are illustrated.
Flow in Healthy and Stenosed Arteries
Authors: Tang Dalin
Published: April 2006

Mathematical and computational models for blood flow in normal and diseased arteries include vessel geometry, material properties, governing equations, and proper initial and boundary conditions. Models for stenosis, carotid, coronary, aorta, abdominal aortic aneurysm, pulmonary capillaries, graft, and stent are presented, with controlling factors and research focuses for each model discussed and proper references cited. Recent trends and potential applications for artery modeling are also discussed.
Aortic Stenosis and Systemic Hypertension, Modeling of
Authors: Garcia Damien , Durand Louis-Gilles
Published: April 2006

Aortic stenosis is the most common cardiovascular disease after systemic hypertension and coronary artery disease in developed countries. It induces an obstruction to blood flow from the left ventricle to the aorta resulting in an increase in left ventricular afterload. More than 30% of patients with aortic stenosis have concomitant systemic hypertension. In such patients, the left ventricle faces a double pressure overload (valvular and vascular). A detailed understanding of the respective impacts of aortic stenosis and hypertension on left ventricular function would help to better predict whether aortic valve replacement and/or antihypertensive medical treatment would be beneficial. To better understand how coexisting aortic stenosis and hypertension affect the left ventricular function, we developed a relatively simple mathematical cardiovascular model to simulate the ventricular‐valvular‐vascular hemodynamic interaction(V3model). The present chapter provides a detailed description of the V3model along with numerical findings as well as their clinical implications. Several simulations with the V3model were performed to describe the effect of aortic stenosis on left ventricular stroke work and show the effect of coexistent systemic hypertension. Our simulations demonstrated that mild or moderate aortic stenosis has a small impact on left ventricular stroke work, whereas the latter increases noticeably when aortic stenosis becomes severe. They also showed that even mild hypertension may greatly influence left ventricular stroke work in patients with aortic stenosis. The mathematical V3model thus provides a potentially useful tool to investigate complex cardiovascular interactions that could be of great clinical interest.
Multivariate Biomedical Signal Processing
Authors: Rezek Iead
Published: April 2006

Modeling physiological functions, such as heart rate and respiration, cannot be done singly, as they are interdependent due to the nervous system. Thus, they must be modeled as a set. This paper discusses modeling entire sets of variables. Probability is taken into consideration. The paper introduces the topic, then discussed multivariate linear models. The next section covers multivariate maximum likelihood inference, followed by a section on multivariate Bayesian inference. Examples and extensions are presented next. The paper concludes with an appendix on expanding a linear model with an uninformative prior.
Functional Optical Imaging of Intrinsic Signals in Cerebral Cortex
Authors: Hallum L. E. , Chen S. C. , Cloherty S. L. , Morley J. W. , Suaning G. J. , Lovell N. H.
Published: April 2006

Functional optical imaging of intrinsic signals (OIIS) measures very small changes in the absorption and reflectance of light from neural tissue during a physiological event. These small changes, usually less than 2% of the dc‐coupled signal, may be captured by a light‐sensitive device such as a CCD (charge‐coupled device) camera. These small signals are, by way of cerebral metabolism and hemodynamics, an indirect means of measuring neural activity. As a result of the small size of the signals, many aspects of the acquisition system are designed so as to minimize noise and nontrivial image processing is often required to extract the signals from the raw image sequence. The OIIS technique has been central to neuroscience research in the past two decades and is of increasing clinical relevance. It is frequently used to identify functional maps of cortical regions of interest, especially, but not limited to, the visual cortex, auditory cortex, somatosensory cortex, and olfactory bulb. Animal models studied include rats, cats, chinchillas, and monkeys. More recently, OIIS has been used intraoperatively in humans to further the understanding of the diseased brain, such as the brain in seizure. Optical imaging may resolve the spatial details of neural activity to within 50 μm, yet the temporal resolution of neural activity observed via intrinsic signals is limited because of the origin of the intrinsic signals in cerebral metabolism and hemodynamics. OIIS requires the tissue in question to be exposed to the light‐sensitive device. However, with respect to the target tissue, it is less invasive than traditional microelectrode recordings of single‐cell activity or fluorescent dye imaging techniques.
A perceptual discrimination investigation of the own‐race effect and intergroup experience
Authors: Walker Pamela M. , Hewstone Miles
Published: April 2006

Research over the past two decades has demonstrated that individuals are better at the recognition and discrimination of own‐ versus other‐race faces. Recent evidence, however, supports an own‐race effect at the level of perceptual encoding in adults. The current study examines the perceptual basis of the own‐race effect in secondary students from two racially segregated communities (White and South Asian). The contact hypothesis is investigated, as other‐race experience may influence other‐race face perception. Face stimuli were generated by morphing together South Asian and White faces along a linear continuum. In a same/different perceptual discrimination task participants judged whether face stimuli were physically identical to, or different from, the original faces. Results revealed a significant own‐race effect for the White participants only, wherein they were better at discriminating White relative to South Asian faces. Other‐race individuating experience was found to predict the own‐race effect, indicating that other‐race experience influences other‐race face perceptual expertise. Copyright © 2006 John Wiley & Sons, Ltd.
Learning a spatial skill for surgery: how the contributions of abilities change with practice
Authors: Keehner Madeleine , Lippa Yvonne , Montello Daniel R. , Tendick Frank , Hegarty Mary
Published: April 2006

We examined changes in performance as people learned to use an angled laparoscope, a challenging spatial skill that must be mastered by surgeons who perform minimally invasive techniques. In Experiment 1, novices took tests of spatial and general reasoning ability, and then learned to operate an angled laparoscope, simulated in a virtual environment, over 12 learning sessions. Initial performance showed considerable variability among learners, with performance related to general and spatial abilities. As learning progressed, interindividual variability diminished and all learners attained proficiency; the correlation with general ability diminished but the correlation with spatial ability remained significant. In Experiment 2, performance by highly experienced surgeons on the simulation was excellent from the first session, confirming its ecological validity. The findings contribute to theories of skill acquisition. They also have practical implications for the selection of surgeons and for the potential use of virtual environments in surgical training. Copyright © 2006 John Wiley & Sons, Ltd.
The impact of background musical tempo and timbre congruity upon ad content recall and affective response
Authors: Oakes Steve , North Adrian C.
Published: April 2006

This study investigated whether the tempo and timbre of background music influenced responses to radio ads. In Experiment 1 (in addition to a no‐music control condition), slow‐ or fast‐tempo background music was superimposed over the same ad. The slow‐tempo music treatment produced significantly higher levels of ad content recall compared to the fast‐tempo music treatment. Musical presence (slow‐ and fast‐tempo treatments combined vs. no‐music) significantly reduced levels of ad content recall. In Experiment 2, when three versions of digitally produced background music timbres were superimposed over a no‐music version of another ad, results revealed positive main effects of timbre congruity upon recall of ad content and affective responses to the ad. Copyright © 2006 John Wiley & Sons, Ltd.
The effects of aging on remembering intentions: performance on a simulated shopping task
Authors: Farrimond Samantha , Knight Robert G. , Titov Nick
Published: April 2006

Three studies are described in which age differences on a task measuring memory for delayed intentions using naturalistic stimuli were examined. A simulated street scene was constructed from a network of photographs and sounds that participants could move through using a touch screen while completing a series of event‐based shopping errand instructions. The objective of the research was to identify the cognitive processes involved in the task that were vulnerable to the effects of ageing. Memory search but not cue detection was specifically affected in older persons when participants were given fewer trials to learn the instructions. There was no age specific effect on cue detection or memory search in either an unfamiliar street or one with increased levels of irrelevant visual and auditory noise. Cue detection but not memory search was disproportionately affected in older persons after filled interruptions, suggesting that the capacity for self‐initiated reinstatement of working memory is reduced in old age. In general, using a computer‐based simulation of a real‐life task was found to be a practical means of examining the effects on behaviour and cognition of task parameters that are significant in assessing everyday memory abilities. Copyright © 2006 John Wiley & Sons, Ltd.
Learner and information characteristics in the design of powerful learning environments
Authors: Paas Fred , Kester Liesbeth
Published: April 2006

This themed issue aims to present some current directions in cognitive load research. The contributions to this issue represent a compilation of symposia contributions to the 11th European Conference for Research on Learning and Instruction (EARLI), 2005, in Nicosia, Cyprus. These cognitive load symposia were focused on empirical and theoretical perspectives on designing powerful learning environments by aligning learner characteristics, information characteristics, or both with the knowledge structures underlying the cognitive architecture. This article provides an introduction to cognitive load theory and the instructional design consequences of these characteristics, and a short overview of the contributions to this issue. Copyright © 2006 John Wiley & Sons, Ltd.
Impact of reducing intrinsic cognitive load on learning in a mathematical domain
Authors: Ayres Paul
Published: April 2006

This paper examines the effectiveness of instructional strategies that lower cognitive load by reducing task complexity (intrinsic cognitive load). Three groups of 13‐year‐old students were required to learn a mathematical task under different conditions. One group (Isolated) followed a strategy that used part‐tasks where the constituent elements were isolated from each other (element isolation). A second group (Integrated) received whole tasks where all elements were fully integrated, and a third group (Mixed) followed a mixed strategy progressing from part‐tasks to whole‐tasks. Results indicated that the part‐task strategy was effective in lowering cognitive load for all students, but only benefitted learning for students with low prior knowledge. In contrast, students with a higher prior knowledge learned significantly more having studied whole tasks during instruction compared with part‐tasks. The mixed‐mode method proved to be ineffective for both levels of prior knowledge. These results are discussed in terms of cognitive load theory. Copyright © 2006 John Wiley & Sons, Ltd.
Problem format and presentation sequence: effects on learning and mental effort among US high school students
Authors: Olina Zane , Reiser Robert , Huang Xiaoxia , Lim Jung , Park Sanghoon
Published: April 2006

The study involving 209 high school students in an instructional program about comma rules was an attempt to test the concepts of cognitive load theory in a real classroom setting. It investigated the effects of (a) cued versus conventional problems and (b) blocked versus random problem presentation sequence during practice on the performance and perceived mental effort of lower‐ and higher‐achieving students. The researchers anticipated that cued problems would reduce learner extraneous cognitive load while random problem presentation sequence would increase germane cognitive load. The researchers also predicted that expected effects may not hold true for higher‐achieving students. The treatments yielded a near‐significant interaction effect for mental effort ratings indicating that conventional problems may have appeared harder to lower‐achieving students while cued problems may have appeared harder to higher‐achieving students. There were no notable performance differences. Issues related to researching cognitive load theory effects in a real classroom setting are discussed. Copyright © 2006 John Wiley & Sons, Ltd.
Modality and variability as factors in training the elderly
Authors: van Gerven Pascal W. M. , Paas Fred , van Merriënboer Jeroen J. G. , Schmidt Henk G.
Published: April 2006

Cognitive load theory (CLT) predicts that bimodal processing of instructional material decreases the level of extraneous cognitive load, whereas increased training variability increases the level of germane cognitive load. It was hypothesized that a combination of these strategies leads to optimal learning, especially in older adults. Forty young and forty elderly learners were trained to solve complex problems. The results showed that bimodal training leads to lower cognitive load than unimodal training. Furthermore, random presentation of examples (high variability) led to higher performance than blocked presentation (low variability) in both age groups. However, there was no combined effect of modality and variability. Moreover, the elderly did not take disproportionate advantage of the bimodal and random conditions. It was concluded that these training methods bear important potential in the light of lifelong learning. Copyright © 2006 John Wiley & Sons, Ltd.
Cognitive load and the format of instructional aids for coherence formation
Authors: Seufert Tina , Brünken Roland
Published: April 2006

Learning with multiple representations is a highly demanding cognitive process because learners have to build referential connections between externally presented representations in order to construct a coherent mental representation. Several approaches for supporting coherence formation have been examined, which can be assigned to two types of helping strategies: first, learners can be assisted in recognising corresponding elements and structures on a surface feature level (e.g. by hyperlinking). Second, they can be supported on a deep structure level (i.e. by explaining the relations of corresponding structures more or less explicitly). In a 2 × 2 experimental study the effects on learning performance and cognitive load of both types of help were compared. Results show that coherence formation can be efficiently supported by deep structure level help (DLH) especially in combination with surface level help (SLH). Hyperlinks seem to guide learners' attention to relevant connections that are additionally explained by the deep structure help. Copyright © 2006 John Wiley & Sons, Ltd.