bluuebunny/crossref_metadata_2025 huggingface dataset:
Plants, People, and Culture in the Prehistoric Central Bahamas: A View from the Three Dog Site, an Early Lucayan Settlement on San Salvador Island, Bahamas
Authors: Berman Mary Jane , Pearsall Deborah M.
Published: April 2006

Paleoethnobotanical remains from the Three Dog site (SS-21), an early Lucayan site located on San Salvador, Bahamas, are presented and compared to data from other prehistoric Caribbean sites. Flotation, in situ, and screen recovery (1/16", 1.58 mm) revealed six taxa of fuelwood and charred Sapotaceae seed fragments. Preliminary SEM analysis of six chert microliths revealed possible evidence of the Caribbean aroid, Xanthosoma sp. (cocoyam, malanga, yautía) or Zamia sp. The presence of Sapotaceae and possibly Xanthosoma sp. or Zamia sp. in the archaeobotanical record can be attributed to a number of alternative explanations. The site"s inhabitants may have transported these plants from their homelands and transplanted them to home gardens. An alternative view is that they exploited or managed wild representatives or created disturbed habitats that encouraged the spread of wild or cultivated forms. The pollen data from two Bahama cores, one from Andros, the other from San Salvador, reflect anthropogenic disturbance during the prehistoric occupational sequence. The increasing frequency of Sapotaceae pollen in the San Salvador sequence is consistent with the occurrence of Sapotaceae at the Three Dog site. Finally, preservation- and recovery-related issues are discussed. The study suggests that multiple means of data recovery must be employed to gain a more representative picture of prehistoric Caribbean plant use and floristic environment.
Determining the Geological Provenance of Obsidian Artifacts from the Maya Region: A Test of the Efficacy of Visual Sourcing
Authors: Braswell Geoffrey E. , Clark John E. , Aoyama Kazuo , McKillop Heather I. , Glascock Michael D.
Published: April 2006

During the last four decades, mesoamerican archaeologists regularly have employed various chemical assay techniques to determine the geological sources of obsidian artifacts. In recent years, the reliability of these analytical procedures has increased and their costs have declined, encouraging the assay of ever larger samples. Nonetheless, several constraints make it unlikely that compositional data will be used routinely to attribute entire collections to their geological sources. This report describes a test of visual sourcing, a technique that for many sites in the Maya region is only slightly less accurate than compositional assay. We also propose sampling strategies that combine visual and compositional sourcing in ways that allow large collections to be accurately sourced at low costs. Finally, we suggest ways to develop the technique for use throughout Latin America.
The Barricade and Abandonment of Chunchucmil: Implications for Northern Maya Warfare
Authors: Dahlin Bruce H.
Published: April 2006

A long low mound of rubble incompletely surrounds part of the central zone at the Classic Period site of Chunchucmil, Yucatan, Mexico. This wall was hastily built from stone robbed from nearby buildings and roadbeds and it clearly served as a defensive barricade. All indications are that the barricade represents a one-time event whereupon the site was attacked, overrun, and abandoned. Re-analysis of other known fortified sites across Yucatan"s northern plains show some fundamental similarities. I suggest that all sites with barricades still standing suffered wars of annihilation rather than wars of conquest and subjugation by the victors. I suggest that the Chunchucmil distribution node was annihilated because its proximity to consumption centers in nuclear Mesoamerica reduced the competitiveness of other Yucatecan coastal trade sites that were located further away along the Gulf Coast maritime trade route.
Craft and Local Power: Embedded Specialization in Tiwanaku Cities
Authors: Janusek John Wayne
Published: April 2006

Proponents of many comparative models of craft specialization explain variability in the organization of production according to the nature of elite interest and economic demand. To this end, many propose a basic dichotomy between independent and attached specialization, whereby valued goods are produced for elites in controlled, nondomestic workshops. I examine new evidence for craft production in the prehispanic Andean polity of Tiwanaku (A. D. 500-1150). I outline expectations for these two forms of specialization and, based on ethnohistorical research in the Tiwanaku region, propose a third form, termed embedded specialization. I appraise primary evidence for the production of ceramic vessels at the site of Tiwanaku and the production of musical instruments at the nearby regional site of Lukurmata. Weighing expectations against evidence, I argue that in Tiwanaku centers many goods were produced by kin-based groups residing in large residential compounds. Skilled production served the overarching political economy and the demands of nonspecialists, but it was neither strictly independent of nor directly attached to elite interests. Craft was rooted in segmentary principles of sociopolitical order, and so was local but not wholly autonomous. On a comparative scale, I suggest that embedded production characterized some states emphasizing corporate strategies of political integration.
An Aztec Palace at Chiconautla, Mexico
Authors: Elson Christina M.
Published: April 2006

The results of George Vaillant's 1935 excavation at the Postclassic site of Chiconautla are presented. Vaillant suggested that the structure he excavated. Casas Reales, was the palace of an elite family. My analysis of the architecture and associated artifacts supports his proposition. The Postclassic (A. D. 1150-1520) artifacts from the palace provide evidence that the elites at Casas Reales engaged in household rituals, obsidian working, and cotton-cloth production. This analysis contributes to a better understanding of elite behavior in the Basin of Mexico and enables us to evaluate the degree of fit between archaeological and ethnohistoric data.
Estudios energeticos de la produccion de cal en tiempos teotihuacanos y sus implicaciones
Authors: Barba Luis A. , Frunz José Luis Córdova
Published: April 2006

Aunque se tienen evidencias tempranas del uso de cal en el área Maya, fue a partir del uso de los recubrimientos de cal en Teotihuacan que se generaliza su empleo en el Altiplano central de México. Con el fin de determinar el impacto que la utilización de la cal tuvo en el medio ambiente y en la sociedad que la produjo, se realizaron estimaciones de la superficie total recubierta con aplanados en la ciudad prehispánica y de la cantidad de energía que requiere la roca caliza para transformarse en cal utilizable. Con estos datos se hizo una estimación de la cantidad de madera necesaria para producir esa energía. Los resultados sugieren que aunque fue grande la cantidad de madera requerida, no dejó señales de su explotación en los sedimentos del Valle de Teotihuacan, lo que sugiere que la cal fue procesada de lugares cercanos. Se concluye que durante su evolución, la ciudad de Teotihuacan manejó procesos tecnológicos cada vez más complejos que demandaron mayores cantidades de energía. Dada la cantidad de energía, el desarrollo tecnológico involucrado en su producción y la información que proporciona, la cal merece un sitio más destacado entre los materiales estudiados por la arqueología.
The Ring Villages of Central Brazil: A Challenge for Amazonian Archaeology
Authors: Wüst Irmhild , Barreto Cristiana
Published: April 2006

This article offers a challenge to previous interpretations of the ring villages of Central Brazil. Specifically, these large villages that were occupied by ceramic-making agriculturalists have been characterized as marginal and anomalous developments resulting from late population movements triggered by the European conquest. New data presented here show that the ring villages have a much greater time depth. Their sudden appearance around A. D. 800 is explained as a local response to both regional and external pressures. Information on settlement pattern variables such as village layout and size, differences in cultural inventory, and comparison of archaeological and ethnographic data illustrate sociopolitical and demographic changes through time that have critical implications for Amazonian archaeology.
Getting Closer to the Source: Using Ethnoarchaeology to Find Ancient Pottery Making in the Naco Valley, Honduras
Authors: Connell Samuel V.
Published: April 2006

The problem of finding the locations of ceramic production has limited interpretations of prehispanic Mesoamerican economies. A new method for locating pottery-making is offered that emphasizes ties between the process of clay extraction and the manufacture of ceramic goods at the same clay source. Observations at modern brick and roof tile-making factories (tejeras) in the Naco Valley, Honduras, show that an effective arrangement for intensive production of ceramic goods is to create the finished product at the clay source. The major topographic transformations caused by clay extraction at tejeras, such as borrow pits and escarpments, are also signatures of prehistoric clay removal and, in many cases, can contribute to the identification of ancient pottery-making locations. A potential production locus was identified at the previously unremarkable and peripheral Site 108, where excavations successfully uncovered a prehistoric pottery workshop. By expanding the scope of our research methodologies, in this case actually implementing ethnoarchaeological understandings to the archaeological record, and by gathering more evidence for ancient pottery production, in this case at clay sources in rural areas, we are better positioned to understand the complexities of Mesoamerican economies.
Evaluation of total intravenous anesthesia with propofol or ketamine-medetomidine-propofol combination in horses
Authors: Umar Mohammed A. , Yamashita Kazuto , Kushiro Tokiko , Muir William W.
Published: April 2006

Objective—To compare the anesthetic and cardiorespiratory effects of total IV anesthesia with propofol (P-TIVA) or a ketamine-medetomidine-propofol combination (KMP-TIVA) in horses.

Design—Randomized experimental trial.

Animals—12 horses.

Procedure—Horses received medetomidine (0.005 mg/kg [0.002 mg/lb], IV). Anesthesia was induced with midazolam (0.04 mg/kg [0.018 mg/lb], IV) and ketamine (2.5 mg/kg [1.14 mg/lb], IV). All horses received a loading dose of propofol (0.5 mg/kg [0.23 mg/lb], IV), and 6 horses underwent P-TIVA (propofol infusion). Six horses underwent KMP-TIVA (ketamine [1 mg/kg/h {0.45 mg/lb/h}] and medetomidine [0.00125 mg/kg/h {0.0006 mg/lb/h}] infusion; the rate of propofol infusion was adjusted to maintain anesthesia). Arterial blood pressure and heart rate were monitored. Qualities of anesthetic induction, transition to TIVA, and maintenance of and recovery from anesthesia were evaluated.

Results—Administration of KMP IV provided satisfactory anesthesia in horses. Compared with the P-TIVA group, the propofol infusion rate was significantly less in horses undergoing KMP-TIVA (0.14 ± 0.02 mg/kg/min [0.064 ± 0.009 mg/lb/min] vs 0.22 ± 0.03 mg/kg/min [0.1 ± 0.014 mg/lb/min]). In the KMP-TIVA and P-TIVA groups, anesthesia time was 115 ± 17 minutes and 112 ± 11 minutes, respectively, and heart rate and arterial blood pressure were maintained within acceptable limits. There was no significant difference in time to standing after cessation of anesthesia between groups. Recovery from KMP-TIVA and P-TIVA was considered good and satisfactory, respectively.

Conclusions and Clinical Relevance—In horses, KMP-TIVA and P-TIVA provided clinically useful anesthesia; the ketamine-medetomidine infusion provided a sparing effect on propofol requirement for maintaining anesthesia.
Sampling Theorem and Aliasing in Biomedical Signal Processing
Authors: Mintchev Martin
Published: April 2006

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

This 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

A 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.
Autocorrelation and Cross‐Correlation Methods
Authors: Kohn André Fabio
Published: April 2006

The autocorrelation of a random signal and the cross‐correlation between two signals have often been employed in biomedical research. This chapter presents the main concepts involved in these two signal processing tools, providing the bases for their correct use and for a correct interpretation of the results they provide. Examples complement the theoretical coverage.
Capillary Electrophoresis
Authors: Kenndler Ernst
Published: April 2006

With 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

The 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

A 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

Computed 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

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

In 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

The 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

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

DNA 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

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

Electrical 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

Passive 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

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

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

Electrophoresis, 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

Claude 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

Recording 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

Extracorporeal 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.
Hidden Markov Models
Authors: Even Jeremie , Abbas Ali
Published: April 2006

A
hidden Markov model (HMM)
is a
system
that evolves over time with
probabilistic Markov dynamics
, and whose states are
hidden
(unobservable). One of the most studied applications of hidden Markov models is the recognition of patterns in spoken language to identify words. This is the main purpose of speech recognition theory. HMM theory has evolved to include many other fields such as biosciences, computer vision, communications, acoustics, and finance. This chapter presents an introduction to hidden Markov models and is organized as follows. The first section introduces the fundamentals of hidden Markov models. The next section discusses three fundamental problems and their applications: 1. The evaluation problem: given a model and a sequence of observations, how do we compute the probability of the sequence (likelihood of the sequence given the model)? 2. The decoding problem (most probable explanation): given a model and a sequence of observations, what is the optimal, in some meaningful sense, sequence of states that produced the observations? 3. The estimation problem: given a sequence of observations, how do we adjust the model parameters to maximize the probability of getting the sequence?

The third section presents an application of hidden Markov models in computational biology.
Higher‐Order Statistics
Authors: Hadjileontiadis Leontios J. , Panas Stavros M. , Rekanos Ioannis T.
Published: April 2006

In the past 15 years, we have witnessed an expansion of higher‐order statistics (spectra) (HOS)‐based techniques, which have been applied to a wide range of signal processing and system theory problems. This expansion is a direct result of the advantageous properties of HOS, which make them favorable in problems where nonGaussianity, nonminimum phase, colored noise, or nonlinearities are important and must be accounted for. To this end, HOS have been applied to the design of advanced communications, sonar, radar, speech, biomedical, geophysical, and imaging systems. The purpose of the present study is to review the main aspects of the application of HOS in the biomedical engineering field by presenting biomedical application problems that can directly benefit from the use of HOS, in order to aid the reader in grasping the utility of HOS‐based techniques within the biomedical signal processing framework. Fundamental definitions and properties of HOS are initially presented, pointing out the general reasons that are behind the use of HOS in signal processing (i.e., extraction of information because of deviations from normality, estimation of the phase of parametric signals, and detection and characterization of the properties of nonlinear mechanisms that generate time series). Next, a variety of HOS‐based biomedical applications are described, referring to detection of nonlinearities (e.g., quadratic phase‐coupling), denoising‐signal estimation, system identification, classification, and compression issues, and involving analysis of electroencephalogram, electrocardiogram, surface electromyogram, electroneurogram, bioacoustic signals (lung, heart, bowel sounds), tremor, and tissue signatures. Finally, an extensive list of references in the area is provided as a companion aid to the reader for further exploitation of HOS.
Hilbert Transform
Authors: Saad Ziad
Published: April 2006

The Hilbert Transform of real‐valued time signal function
s
(
t
) is another real‐valued function that differs only in phase from
s
(
t
). The transform leaves the amplitude spectrum of
s
(
t
) unchanged, but changes the positive frequency phase spectrum by
π
/2 and the negative frequency phase spectrum by −
π
/2. For example, the Hilbert Transform of a sine function is a cosine function of equal magnitude. In biomedical applications, the Hilbert Transform is mostly used to describe the instantaneous amplitude and frequency of oscillatory signals such as respiration movements and narrow band signals such as filtered electroencephalograms (EEG). In addition, the Hilbert Transform is used to estimate delay differences between signals.

We present the various properties and parameters derived from the Hilbert Transform with emphasis on their applicability to biomedical signal analysis.
Hippocampus
Authors: Soltanian-Zadeh Hamid , Elisevich Kost
Published: April 2006

The hippocampus (HC), a discrete anatomical landmark of the mesial temporal lobe of the brain, is part of the limbic system of the brain and subserves both learning and memory. Several clinical pathological entities are affected by the HC so that its clinical investigation has been a focus of intense work. Its intrinsic connectivity with its feedforward and feedback circuitry underlies a complex organization that, when disturbed, can give rise to debilitating conditions such as epilepsy. The application of electroencephalographic and imaging methodologies to the study of this structure has provided a means of not only lateralizing the site of pathology but determining the nature of the condition.
Independent Component Analysis
Authors: Boscolo Riccardo
Published: April 2006

The term Independent Component Analysis (ICA) broadly refers to the set of statistical principles as well as to the estimation algorithms derived from them, whose aim is to extract statistically independent components in the data, generally through some filtering procedure that can be linear or non‐linear, act on a batch of data at the time or process the data samples as they become available (adaptive).

The field of Independent Component Analysis can be seen as stemming from the groundwork of several researchers, who in the last decade of the 20th century investigated fundamental statistical problems, such as the relationship between gaussianity and statistical dependence, redundancy reduction principles, and information preserving networks.
Electromyography (EMG) Modeling
Authors: Dimitrova N.A. , Dimitrov G.V.
Published: April 2006

Modeling is a measure of our understanding of processes and a tool for checking hypotheses and making prognoses. Any attempt to understand and explain electromyographic (EMG) signals, their characteristics, and changes is related to modeling. The authors’ aim is to present the main ideas of EMG modeling in terms understandable to people without special mathematical education. The main physical regularities that rule the formation of electrical potentials in a volume conductor (extracellular medium) are pictorially demonstrated and can be realized ignoring equations. Potentials produced by individual muscle fibers are the basis of EMG signals, which is why a more detailed picture of the physical basis for modeling single‐fiber potentials (SFPs) generated in a homogeneous volume conductor of infinite extent is presented. It is demonstrated why the shape of SFP changes with distance from the active fibers, why amplitude of EMG signal can be an unreliable characteristic, and why detection of EMG by needle and surface electrodes has different sensitivity to prolonged phase of repolarization or to after‐depolarization in intracellular action potential (IAP) and to IAP propagation velocity along the fiber. Description of some equations resulting in fast calculation of the motor unit potentials and interference EMG are presented. The latest papers on mathematical modeling that take into account inhomogeneous and restricted muscle tissue are discussed.
Knowledge Engineering
Authors: Povalej Petra , Mertik Matej , Kokol Peter
Published: April 2006

“What is knowledge?” According to Webster's Dictionary, knowledge is defined as a fact or condition of knowing something with familiarity gained through experience or association. It may be described as a set of models that describe various properties and behaviors within a considered domain. Knowledge can be recorded in an individual brain or stored in organizational processes, products, facilities, systems, and documents. Usually the knowledge about particular domain is captured in a knowledge base, which is the assembly of all of the information and knowledge of a specific field of interest. According to the Online Decision Support Systems Glossary, a knowledge base is defined as a collection of facts, rules, and procedures, which are organized within schemas.

A field within artificial intelligence that develops knowledge‐based systems (KBS) is called knowledge engineering (KE). Such systems are computer systems that deal with complex problems by making use of knowledge. The development of KBS involves identifying a real‐world problem‐solving task, representing the key components of this task in the KBS, and implementing the inference process that produces solutions. Therefore, three key processes are involved in KE. First, there is a process of capturing the knowledge from the domain experts‐knowledge acquisition that is followed by the task of producing a representation of the problem that captures the key features. At the end, there is a task of developing an inference mechanism that describes the interactions involved in deriving solutions. We will present these processes in more detail in the following paragraphs.
Lung Tissue Viscoelasticity
Authors: Suki Béla , Lutchen Kenneth R.
Published: April 2006

The viscoelastic properties of connective tissues play fundamental roles in the functioning of many organs and organisms as well as in the interactions of these macroscopic biosystems with the complex environment they live in. An emerging view exists that the viscoelastic properties of the extracellular matrix of the lung reflect, to a large extent, the underlying complexity of its structure. This chapter summarizes the phenomenological description of lung tissue viscoelasticity and its relation to tissue composition and structure. In particular, it is shown that the constitutive equation and, hence, the stress relaxation of the lung tissue follows a power law functional form. The constituents of the connective tissue mainly determine the proportionality constants, whereas the complex structural organization of the tissue is responsible for the power law and the numerical value of the exponent. It is argued that the power law constitutive equation develops from the complexity of the structure and the interactions among the components. A concise mathematical description of the constitutive equation of the lung tissue can be based on fractional calculus, which is related to the fractal properties of the collagen‐elastin fiber network embedded in the proteoglycan matrix.
Markov Chains
Authors: Even Jeremie , Abbas Ali E.
Published: April 2006

Markov chains represent the evolution of a system with a first‐order probabilistic dependence. They are often used to describe population processes modeling of the evolution of populations analogous to biological populations. Markov chains are named after the Russian mathematician Andrey Alexeyevitch Markov, who established their first results. In this article, the authors provide a detailed introduction to the theory of Markov chains and present several applications and examples for their results.
Medical Devices, Design and Modification of
Authors: Hyman William A.
Published: April 2006

The design of medical devices is generally a complex and demanding process, often with high potential risk to patients if the device does not function as envisioned. The initial challenge is to correctly capture clinical requirements and to manipulate and to translate these requirements into a technically competent and reliable device that can and will be used effectively in the clinical environment. Successful medical device design includes active consideration of the human factors aspects of user needs and an adequate system safety and risk analysis. Instructions for use including installation and service and manufacturing must also be considered throughout the design cycle. Modification of existing designs whether by the original manufacturer or by the device owner, or a third party, requires particular care so that carefully made decisions during the initial design cycle are not undone by a hastily conceived fix or upgrade. The reuse of devices labeled by the manufacturer as single use only is one example of a “modification” that has received considerable attention and FDA scrutiny. The design process is subject to FDA regulation under the Design Controls section of the Quality Systems Regulations. Compliance with these regulations requires broad knowledge of them by everyone on the design team.