bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sampling Theorem and Aliasing in Biomedical Signal Processing
Authors: Mintchev Martin 
Published: April 2006

Abstract
Despite digital techniques for data acquisition and processing being widely used in biomedical research for quite some time, inappropriate signal conditioning and digitization are still potential pitfalls threatening both the reliability of the experiments and the proper interpretation of the acquired data. The aim of this chapter is to review: (1) the Sampling (Nyquist) Theorem; (2) the concept of aliasing; (3) the importance of antialiasing low‐pass filtering for eliminating the effect of aliasing and appropriately determining the sampling frequency; (4) the advantages of properly chosen filter cut‐off frequency and slope for determining the minimal required sampling frequency; and (5) the impact of incorrectly selected sampling frequency on the interpretation of biomedical data. In a case study, a model of electrogastrographic (EGG) recording is mixed with a model of electrocardiographic (EKG) artifact in an overall white noise environment. The resulting composite signal is low‐pass filtered and then digitized with a sampling frequency of 1 Hz. The cut‐off frequency of the first‐order low‐pass filter is altered from 0.5 Hz to 0.1 Hz. Amplitude frequency spectra of the digitized recordings are investigated to illustrate the effect of aliasing. An example with a real human electrogastrogram, in which an EKG artifact is present, illustrates the simulation results. When a first‐order antialiasing filter is used, at least a five‐fold difference between the filter cut‐off frequency and the sampling frequency is recommended for compliance with the Sampling Theorem. Increasing the order of the antialiasing filter can reduce the required sampling frequency, but can also make the entire instrumentation system underdamped, thus injecting oscillatory artifacts every time abrupt or sudden changes in the external conditions during the recording occur.
Arterial Blood Pressure Processing
Authors: Di Rienzo Marco , Castiglioni Paolo , Parati Gianfranco 
Published: April 2006

AbstractThis chapter contains descriptions of (1) signal processing techniques for the analysis of data derived from devices providing a discontinuous measure of blood pressure, (2) techniques for the analysis of continuous arterial blood pressure recordings, (3) the main methods for the analysis of blood pressure variability, and (4) techniques for the estimation of the baroreflex function from the analysis of spontaneous fluctuations of blood pressure and heart rate.
Assistive Technology
Authors: Roca-Dorda Joaquín , Elena Del-Campo-Adrián M. , Roca-Gonzalez Joaquín , Saneiro-Silva Mar 
Published: April 2006

AbstractA first throughout history, the relationship between the society and disabled people has noticed a great improvement. Initially, society adopted good‐hearted, charitable, philanthropic, and paternal attitudes toward disability (via the participation of the church, the crown, the wealthy social classes, etc.) followed by the state actions justified by the public or company‐like deeds (war‐crippled and labor handicap people, etc.). Only later did it reached the present position, on a whole aiming at the complete guarantee of the natural rights of everybody as members of a fair, democratic and equal society.Gradually, along this evolution, the implementation of the technological resources (in hand) came to improve the integration results relation for disabled people.Finally, the availability of new and powerful technologies (ICTs, robotics, etc.), simultaneously with a new point of view of the society about diversity and integration, brought together very different technological and assistancial fields of the present multidisciplinary “corpus” integrated in the AT. This article will try to bring this field into view, from both a mainly technological viewpoint (techniques, devices, products, systems) and a sociological viewpoint (historical overview, services, laws, influence on society and users).More specific attention, focused on the computer access, will be developed because of its importance as the main engine of the latest developments.
Capillary Electrophoresis
Authors: Kenndler Ernst 
Published: April 2006

AbstractWith capillary electrophoresis, ionic analytes can be separated in free solution under the influence of an electric field. The capillary or microchannel format offers several advantages over classical electrophoresis, mainly the much lower time of analysis, low sample, chemical and solvent consumption, on‐column detection and quantification, and the possibility for on‐line combination with a mass spectrometer. Supporting media like porous material or gels are not needed. Thus the potential analytes cover the size range from 0.1 nm to several μm and reach from small molecules like drugs to viruses, bacteria, and eukaryotic cells. The high voltage that can be applied due to the capillary dimensions and the composition of the buffer leads, together with the high charge numbers of biomolecules like proteins or polynucleotides, to very high separation efficiencies. The large variability of the working conditions allows for separation of charged and uncharged analytes, for the latter by using hybrid methods combining electrokinetic mass transport and chromatographic separation principles.
Capillary Permeability
Authors: Bassingthwaighte James B. 
Published: April 2006

AbstractThe capillary barrier serves to protect cells from noxious materials bound to intravascular proteins and to regulate pressures and volumes of interstitial fluid, while allowing passage of essential substrates from the blood and the removal of metabolites. The permeability of capillaries to a solute depends on the anatomy of the capillary wall and the nature of the solute. The walls consist of monolayers of endothelial cells with characteristics peculiar to the individual organ: Most capillaries have openings between endothelial cells and some have holes through them. Hydrophilic and polar solutes traverse these “pores”, whereas lipid‐soluble solutes can permeate the lipid bilayer or the endothelial cell membranes. For some solutes, special solute‐specific transporter proteins in the cell membrane facilitate transfer across the membrane. For estimating permeability coefficients and determining the mechanism of permeation, tracer experiments done under varied circumstances are generally the most informative. Osmotic transient experiments, performed by changing osmolarity inside the capillary, require relatively complex analysis because there are simultaneous fluxes of both water and solutes.
Complexity, Scaling, and Fractals in Biological Signals
Authors: West Bruce 
Published: April 2006

AbstractA biological signal carries information about the complex biological phenomena being measured and is typically a time series having both a regular and random component. This chapter focuses on dynamic physiologic phenomena, in order to reduce the number of time series discussed to a manageable size. The output of dynamical physiologic systems, such as the cardiac system, the respiratory system and the motor control system, have all been shown to be fractal or multifractal statistical time series. Consequently, the fractal dimension turns out to be a significantly better indicator of health than the more traditional measures, such as heart rate, breathing rate, and stride rate, all average quantities. Fractal physiology, as this field has come to be called, focuses on the complexity of the human body and the characterization of that complexity through fractal measures and the dynamics of such measures. These new measures reveal that the traditional interpretation of disease as the loss of regularity is not adequate and a better interpretation of disease is the loss of variability, or more accurately, the loss of complexity.
Computed Tomography
Authors: Lu Donghui , Bai Er-wei , Wang Ge 
Published: April 2006

AbstractComputed tomography (CT) is a prime example of modern technologies and has found wide applications in medical imaging, industrial nondestructive evaluation, microtomography, and other areas. In this article, we focus on x‐ray CT. First, we review the development of CT, review its physical and mathematical principles, and explain the imaging geometries and systems. Then, we discuss the reconstruction algorithms, presenting both the key ideas and the mathematical details, which reflect the advancement in the field over recent years. Finally, we report future perspectives.
Muscle Fiber Conduction Velocity
Authors: Beck Rebecca 
Published: April 2006

Abstract
The speed with which an action potential (AP), or excitatory impulse, travels along the membrane of a skeletal muscle fiber is known as its conduction velocity (CV). Muscle fiber CV may be estimated from the electromyogram (EMG) and can be used as a sensitive measure of the excitability of the muscle fiber membrane in addition to being related to the type, diameter, rate of activation, temperature, and physiological or pathological state of the muscle fiber. Conduction velocity estimates are frequently used as a fatigue index, with applications in ergonomics, kinesiology, rehabilitation, functional electrical stimulation, and, more recently, as a diagnostic tool. Conduction velocity estimation is discussed in the following pages from its genesis to issues regarding its measurement and potential clinical and diagnostic value.
Confocal Microscopy
Authors: Diaspro Alberto , Federici Federico , Faretta Mario , Usai Cesare 
Published: April 2006

AbstractIn modern times, there is an increasing demand for three‐dimensional (3‐D) optical microscopy. The main reason lies in the fact that optical microscopy is still unique in its ability to allow the complete three‐dimensional examination of biological structures in a hydrated state under experimental conditions that allow the preservation of living or physiological states, also when compared with other high‐resolution techniques. This fact coupled with the advent of fluorescence labeling permits the study of the complex and delicate relationships exist in between structure and function in biological systems. One relevant step, in terms of progress in 3‐D optical microscopy, was the invention of the confocal microscope in its different solutions. Minsky, in 1957, invented a confocal microscope identical with the concept later developed extensively by Egger and Davidovits at Yale, by Sheppard and Wilson at Oxford, and by Brakenhoff et al. in Amsterdam. It was in the mid‐1970s, with the advent of affordable computers and lasers, and the development of digital image processing software, that the first confocal laser scanning microscopes became available in several laboratories and applied to biological and material specimens.
Digital Filters
Authors: Lipping Tarmo 
Published: April 2006

AbstractThe basic ideas behind digital filtering are presented in this chapter. The filtering techniques are divided into linear and nonlinear techniques. The main concepts used in the analysis and design of linear filters are defined and the general design procedure is described. Several classes of nonlinear filtering techniques, likeL‐filters, stack filters, order statistic filters, and hybrid filters, are presented. The basic ideas of these techniques and the possible design criteria are described. The reader is referred to further literature for the design algorithms.
Discrete Fourier Transform
Authors: Itiki Cinthia 
Published: April 2006

Abstract

Digital signal processing techniques provide parameters and tools to represent discrete‐time signals, both in time domain and frequency domain. One tool is the discrete Fourier transform (DFT), which associates a discrete‐time signal {
x
(
n
)} containing a finite number
N
of samples to a discrete‐frequency representation {
X
(
k
)} containing a finite number
N
of components. DFT is very useful for linear and circular convolution, for spectral and time‐frequency analyses, and for filtering. It is applied to several biomedical signals, such as evoked potentials, electrocardiographic, electroencephalographic, and electromyographic signals, among others.
DNA Sequencing
Authors: Papp Jeanette , Knight Vivian 
Published: April 2006

AbstractDNA sequencing is the process of determining the order of base molecules along a strand of DNA. DNA is an information‐coding molecule, with the information encoded in the sequence of bases. This basic molecular unit has the same essential physical and chemical organization in all living organisms. The base sequence codes for the proteins that living cells require to survive, grow, and reproduce. With few exceptions, every cell in an organism contains the full and unique complement of DNA necessary for each stage of the organism's growth. Thus, a DNA sequence cannot only uniquely identify an individual organism, but can also give insight into the biology of an organism. This makes DNA sequencing a powerful tool in many aspects of biomedical research. DNA sequencing techniques have been employed since the 1970s and have undergone several rapid advances in technology. The Human Genome Project was the impetus behind one growth spurt. The race to complete the human genome sequence drove improvements in instrumentation and informatics. We are currently seeing another sudden leap forward in sequencing technology that is likely to change the field significantly. Sequencing technologies are becoming faster, cheaper, and more accurate, spurred by the National Institute of Health's challenge to achieve the $1,000 human genome in the next decade.
Electrocardiogram (ECG) Mapping
Authors: Fischer Gerald 
Published: April 2006

Abstract

Body surface mapping records the electrocardiogram (ECG) on the entire body (torso) surface using a grid of many leads (more than 30) on the torso surface. Although many studies have demonstrated that mapping provides more information than the standard 12‐lead ECG, it is still only a powerful scientific tool but not in widespread clinical use. The challenge is to retrieve and display diagnostic information such that it can be assessed by the naked eye. This chapter first provides an overview on basic tools and standards for ECG mapping. Here, more careful data preprocessing and better instrumentation is required than for the 12‐lead ECG. Mathematical tools for estimating the number of independent signals are discussed. The classical potential and parameter maps are addressed shortly. Recently, the model‐based back projection of the body surface ECG data onto the cardiac surface (inverse problem, functional imaging) has been successfully validated in
in vitro
models and humans. A short introduction to the basics of functional imaging is provided and two promising approaches are highlighted. Limitations and potential for further improvement are discussed. Thus, the additional information in many leads needs sophisticated methods for displaying the source pattern on the actual cardiac geometry. The sole improvement of instrumentation in terms of more leads without the support of tailored algorithms does not provide any new diagnostic information.
Electrical Impedance Imaging, Injected Current
Authors: Eyüboglu B. Murat 
Published: April 2006

AbstractElectrical impedance imaging (EII) is an imaging modality that is used to produce images of tissue resistivity (or its reciprocal conductivity) distribution within a conductor object. It is also known as electrical impedance tomography (EIT) since the reconstructed images are tomographic. EII images are reconstructed using electrical measurements (voltage or current) made on the surface when current or voltage is applied to the conductor medium to be imaged.In vivoEIT images of different parts of the human body have been produced to monitor various functions and detect abnormalities.
Electric Properties of Tissues
Authors: Miklavčič Damijan , Pavšelj Nataša , Hart Francis X. 
Published: April 2006

AbstractPassive electric properties of biological tissues such as permittivity and conductivity are important in applied problems of electrical stimulation in studying of human electromagnetic fields interactions and development of diagnostic and therapeutic procedures. The current densities and pathways resulting from an applied electrical stimulus are dictated to a large extent by the relative permittivity and specific conductivity of biological tissues; energy absorption also depends on tissue properties. We briefly present some theoretical basis for the current conduction in biologic materials and factors affecting the measurement of tissue dielectric properties that need to be taken into account when designing the measurement procedure. Large discrepancies between the data reported by different researchers are found in the literature, which are caused by factors such as different measuring techniques used, the fact that tissue samples were taken from different species, circumstances under which the measurements were performed, and many others. Electric properties of some biological tissues are summarized and data ranges of values found for relative permittivity and specific conductivity in the literature are given. Finally, we present some applications of bioimpedance measurements.
Electrical Impedance Plethysmography
Authors: Eyüboğlu B. Murat 
Published: April 2006

Abstract
Variations of electrical impedance of various parts of human body with physiological activity are well known. Fluctuations in the electrical impedance of human thorax are synchronous with both respiratory activity and also with the cardiac cycle. Electrical impedance plethysmography is used to estimate the volume changes in different parts of the body due to pulsation of blood. Impedance pneumography is used to monitor volume changes in the thorax with ventilation. Impedance cardiography (ICG), a simple and noninvasive method, is used to estimate cardiac output based on the variation of thoracic impedance during the cardiac cycle. Clearly, changes in global impedance of the thorax, with cardiac activity, are produced not only by one source. Ventricular volume changes, blood volume in the great blood vessels, variation of blood flow rate and pulmonary circulation, changes in the geometry of the thorax are all contributors to the global impedance signal. But their relative contributions to the global impedance variation are not fully understood and still subject to continuing research.
Electromagnetic Waves
Authors: Hinrikus Hiie 
Published: April 2006

Abstract
The definition of the electromagnetic waves (EMWs), the main steps in the history of electromagnetism, and EMW bands are discussed in the introduction. Theoretical background includes Maxwell equations and wave equation with its solution for plane waves. The main properties of the wave in perfect and lossy, homogeneous and inhomogeneous, and isotropic and anisotropic media are described. The phenomena of dispersion, reflection, and refraction are explained, and formulas for the wave parameters in different conditions are presented. The conditions for full refraction and reflection as well as the equation for wave propagation trajectory inside a multilayered medium are discussed. The properties of the standing wave are described. The theoretical limit for the spatial resolution is given.
Electrophoresis
Authors: Ohshima Hiroyuki 
Published: April 2006

AbstractElectrophoresis, which is the motion of charged colloidal particles in an electrolyte solution under an applied electric field, provides us with fundamental information on the surface potential and the surface charge density of the particles. Approximate analytic expressions for the electrophoretic mobility of various types of particles including particles with no surface structures and those with surface structures such as biological cells are given.
Entropy
Authors: Abbas Ali E. 
Published: April 2006

AbstractClaude Shannon introduced entropy as a measure of information about a discrete random variable. Shannon's work set the Magna Carta of the information age and the dawn of a new science called information theory. Although information theory started with a discovery of the fundamental laws of data compression and transmission, it has now become a unifying theory with profound intersections with probability, statistics, computer science, management science, economics, bioinformatics, politics, and has numerous applications in many other fields. This article provides a basic introduction to the entropy of a random variable as well as the basic elements of information theory.
Gait Patterns
Authors: Abernethy Bruce , Lu William W. 
Published: April 2006

AbstractRecording and analyzing human gait patterns has long held the interest of biomechanists, bioengineers, kinesiologists, and clinicians and therapists involved in pediatric, geriatric, and rehabilitative medicine. In large part this is because gait is one of the most fundamental and functionally critical of all human movements and the description, explanation, and understanding of gait patterns are as central to basic questions related to movement control and coordination as they are to applied ones related to the clinical identification and correction of abnormalities arising from disease, disuse, or injury. The essential kinematics, kinetics, and underlying neuromuscular contributions to the human walking and running gait patterns are now quite well understood although controversy still remains as to how best to model each of these patterns and as to what drivers trigger the transitions between these modes of coordination at critical speeds of travel or at critical changes in the nature of the terrain or the trajectory of travel. Recent computer models of gait are increasingly capable of accurately accounting for individual differences in gait patterns and these provide promise for aiding clinical assessment of disease onset and progression, surgical decision‐making, and the assessment and enhancement of rehabilitative progress in the future.
Hemodialysis and Hemofiltration
Authors: Conrad Steven A. 
Published: April 2006

AbstractExtracorporeal techniques for fluid management and solute removal are a mainstay in the treatment of acute and chronic renal failure. Hemodialysis is the removal of small solutes from the blood by diffusion across a semipermeable membrane into a countercurrently flowing dialysate solution. Ultrafiltration is the removal fluid across a porous membrane by the application of a hydrostatic pressure. Solutes of small to middle size are removed by convection. The combination of ultrafiltration with replacement of fluid into the bloodstream constitutes hemofiltration. The two techniques are frequently combined as hemodiafiltration. The biophysical principles of convective and diffusive membrane transport are developed in this chapter, and their application to mathematical models is provided. The composition, performance, and biocompatibility of older and newer synthetic membranes are described. Methods for analysis of mass transfer, such as clearance, in hemodiafilters are presented. Mathematical models of urea kinetics using one and two compartmental models and their application to the dialysis prescription are also developed and presented.