bluuebunny/crossref_metadata_2025 huggingface dataset:
Methane Production during Storage of Anaerobically Digested Municipal Organic Waste
Authors: Hansen Trine Lund , Sommer Svend G. , Gabriel S⊘ren , Christensen Thomas H.
Published: April 2006

Anaerobic digestion of source‐separated municipal organic waste is considered feasible in Denmark. The limited hydraulic retention in the biogas reactor (typically 15 d) does not allow full degradation of the organic waste. Storage of anaerobically digested municipal organic waste can therefore be a source of methane (CH4) emission that may contribute significantly to the potential global warming impact from the waste treatment system. This study provides a model for quantifying the CH4 production from stored co‐digested municipal organic waste and estimates the production under typical Danish climatic conditions, thus quantifying the potential global warming impact from storage of the digested municipal organic waste before its use on agricultural land. Laboratory batch tests on CH4 production as well as temperature measurements in eight full‐scale storage tanks provided data for developing a model estimating the CH4 production in storage tanks containing digested municipal organic waste. The temperatures measured in separate storage tanks on farms receiving digested slurry were linearly correlated with air temperature. In storage tanks receiving slurry directly from biogas reactors, significantly higher temperatures were measured due to the high temperatures of the effluent from the reactor. Storage tanks on Danish farms are typically emptied in April and have a constant inflow of digested material. During the warmest months the content of digested material is therefore low, which limits the yearly CH4 production from storage.
Poultry Litter Application to Loblolly Pine Forests
Authors: Friend Alexander L. , Roberts Scott D. , Schoenholtz Stephen H. , Mobley Juanita A. , Gerard Patrick D.
Published: April 2006

Forestland application of poultry manure offers an alternative to the conventional practice of pastureland application. Before such a practice is considered viable, however, it must be demonstrated that the forest ecosystem is capable of absorbing the nutrients contained in poultry manure, especially nitrogen (N) and phosphorus (P). From the forestry perspective, it must also be demonstrated that tree growth is not diminished. We investigated these questions using loblolly pine (Pinus taeda L.) stands growing in central Mississippi in an area of high poultry production. Stockpiled broiler litter was applied to newly thinned, 8‐yr‐old stands at 0, 4.6, and 18.6 dry Mg ha−1, supplying 0, 200, and 800 kg N ha−1 and 0, 92, and 370 kg P ha−1, respectively. Levels of nitrate in soil water, monitored at a 50‐cm depth with porous cup tension lysimeters, exceeded 10 mg N L−1 during the first two years after application in the 18.6 Mg ha−1 rate but only on two occasions in the first year for the lower rate of application. Phosphate was largely absent from lysimeter water in all treatments. Other macronutrients (K, Ca, Mg, S) were elevated in lysimeter water in proportion to litter application rates. Soil extractable nitrate showed similar trends to lysimeter water, with substantial elevation during the first year following application for the 18.6 Mg ha−1 rate. Mehlich III–extractable phosphate peaked in excess of 100 μg P g−1 soil during the third year of the study for the 18.6 Mg ha−1 rate. The 4.6 Mg ha−1 rate did not affect extractable soil P. Tree growth was increased by the poultry litter. Total stem cross‐sectional area, or basal area, was approximately 20% greater after 2 yr for both rates of litter application. Overall, the nutrients supplied by the 4.6 Mg ha−1 rate were contained by the pine forest and resulted in favorable increases in tree growth. The higher rate, by contrast, did pose some risk to water quality through the mobilization of nitrate. These results show that, under the conditions of this study, application of poultry litter at moderate rates of approximately 5 Mg ha−1 to young stands of loblolly pine offers an alternative disposal option with minimal impacts to water quality and potential increases in tree growth.
Comparing Carbon Substrates for Denitrification of Subsurface Drainage Water
Authors: Greenan Colin M. , Moorman Thomas B. , Kaspar Thomas C. , Parkin Timothy B. , Jaynes Dan B.
Published: April 2006

Nitrate in water from tile drained corn (Zea maysL.) and soybean [Glycine max(L.) Merr.] fields in the U.S. Midwest contributes to nitrate contamination of surface waters. Denitrification‐based biofilters are a promising strategy for reducing nitrate concentrations, but these systems require an external carbon supply to sustain denitrification. The ability of four organic materials to serve as carbon substrates for denitrification biofilters was evaluated in this laboratory study. Wood chips, wood chips amended with soybean oil, cornstalks, and cardboard fibers were mixed with subsoil (oxidized till) and incubated anaerobically for 180 d. Periodically,15NO3–N was added to maintain nitrate N concentrations between 10 and 100 mg L−1All of the materials stimulated NO3–N removal and the degree of removal from highest to lowest was: cornstalks, cardboard fibers, wood chips with oil, and wood chips alone. Analysis of15N showed that immobilization and dissimilatory nitrate reduction to ammonium accounted for <4% of NO3–N removal in all treatments, therefore denitrification was the dominant NO3–N removal process. Cardboard fibers, wood chips and oil, and wood chips alone did not support as much denitrification as cornstalks, but their rates of NO3–N removal were steady and would probably continue longer than cornstalks. The addition of soybean oil to wood chips significantly increased denitrification over wood chips alone.
Mineralization of Hormones in Breeder and Broiler Litters at Different Water Potentials and Temperatures
Authors: Hemmings Sarah N. J. , Hartel Peter G.
Published: April 2006

When poultry litter is landspread, steroidal hormones present in the litter may reach surface waters, where they may have undesirable biological effects. In a laboratory study, we determined the mineralization of [4–14C]‐labeled 17β‐estradiol, estrone, and testosterone in breeder litter at three different water potentials (−56, −24, and −12 MPa) and temperatures (25, 35, and 45°C), and in broiler litter at two different water potentials (−24 and −12 MPa) and temperatures (25 and 35°C). Mineralization was similar in both litters and generally increased with increasing water content and decreasing temperature. After 23 wk at −24 MPa, an average of 27, 11, and <2% of the radiolabeled testosterone applied to breeder litter was mineralized to 14CO2 at 25, 35, and 45°C, respectively. In contrast, mineralization of the radiolabeled estradiol and estrone was <2% after 25 wk at all water potentials, except after 17 wk at 25°C and −12 MPa, where up to 5.9% of the estradiol and 7.8% of the estrone was mineralized. The minimal mineralization suggests that the litters may still be potential sources of hormones to surface and subsurface waters.
Impact of Diet, Moisture, Location, and Storage on Soluble Phosphorus in Broiler Breeder Manure
Authors: Maguire R. O. , Plumstead P. W. , Brake J.
Published: April 2006

Decreasing dietary phosphorus (P) has the potential to reduce P excreted in manure and therefore alleviate the environmental degradations associated with intensive animal farming. We evaluated reducing dietary P for broiler breeders as an aid to reduce manure total and water soluble phosphorus (WSP). Broiler breeders were fed diets high and low in dietary P, with and without phytase, from 22 to 64 wk of age. At the end of the 42‐wk production period, manure was collected from four locations in each two‐thirds slat, one‐third litter breeder pen: the litter scratch area, under the drinker in the slat area, under the feeder in the slat area, and in a clean area of the slat area away from feeder or drinker. After the initial sampling, all manure was removed from pens and representative samples were stored for 6 mo with and without feed mixed in to simulate the effect of spilled feed. Total P was determined on all pen samples, and moisture and WSP determined on the pen and stored samples. The manure collected under the drinker had much greater moisture due to spilled water. This was associated with much greater WSP in this location, showing the importance of good water management. The manure from under the feeder had similar WSP as manure from the clean area, so spilled feed did not significantly affect WSP. Dietary phytase either had no effect or significantly decreased manure WSP. However, addition of dietary phytase to the feed led to slightly elevated manure moisture. Since moisture was correlated with manure WSP this may explain some of the variability in WSP results between studies. Over 6 mo of storage WSP increased and generally followed the same ranking order at 168 d as at 1 d among the dietary treatments (high > high + phytase > low > low + phytase). Combining decreased dietary P and phytase reduced both manure total P and WSP by 42%. As total P and WSP are indicators of the long and short term impacts manure applications can have on P losses from manured soils, diet modification should be seen as environmentally beneficial.
Arteries, Elastic Properties of
Authors: Hayashi Kozaburo
Published: April 2006

The elastic properties of arterial wall are very important because they are closely related to arterial physiology and pathology, especially via effects on blood flow and arterial mass transport. Furthermore, stresses and strains in the arterial wall, which are prerequisite for the understanding of the pathophysiology and mechanics of the cardiovascular system, cannot be analyzed without exact knowledge of the arterial elasticity. First of all, the structure of arterial wall and its basic elastic characteristics are briefly explained. Then, tensile testing,
in vitro
pressure‐diameter tests, and in vivo techniques are dealt with for the measurement of arterial elasticity. Several equations and parameters proposed to mathematically describe biomechanical data obtained from uniaxial tensile and pressure‐diameter tests are introduced together with representative constitutive equations for the complete expression of arterial elasticity. Finally, the article demonstrates several results on the elastic properties of normal and diseased arterial walls, in particular in hypertension and atherosclerosis.
Audiometry
Authors: Borton Thomas E. , Borton Bettie B. , Blumsack Judith T.
Published: April 2006

Audiometry is the measurement of hearing. It entails the use of electronic instrumentation to deliver auditory signals to a listener and is used in the functional assessment, diagnosis, and rehabilitation of hearing impairment. Modern assessment of the auditory system includes measurement of sensitivity to pure tones and speech, evaluation of middle ear function (e.g., with tympanometry and acoustic reflex measurement), auditory evoked potential evaluation, and measurement of otoacoustic emissions. The sound pathways of the ear and psychophysical methods used in audiometry are reviewed in this chapter. Fundamentals and interpretation of pure tone and speech audiometric results are highlighted, and the clinical applications of modern electrophysiologic methods for audiometry are described. Auditory evoked potential, acoustic immittance, and otoacoustic emission measures are discussed.
Biofeedback
Authors: Arena John C. , Devineni Trishul , McGowan Edward J.
Published: April 2006

The theory and practice of biofeedback has rapidly matured over the last three decades due in part to advances in the fields of microelectronics, digital computing, and signal processing. There has been concurrent progress in our understanding of complex biological systems, human disease mechanisms, and behavioral principles of learning involved in physiological functions. The medical and scientific instrumentation of biofeedback has proliferated along with the expansion of clinical applications of the technology to numerous disease states. In this article, an attempt is made to clearly define the diffuse area of biofeedback and provide a brief historical overview of its development. A review of the basic learning principles derived from laboratory findings underlying biofeedback and competing theories is made. Described are the major types of medical instrumentation and engineering design specifications of common biofeedback systems. Also covered are the basic physiological parameters captured and processed by these flexible medical devices. The literature documenting the outcomes of widely used biofeedback paradigms in clinical settings are briefly highlight. Finally, some major themes and future directions that the technology and medical application of biofeedback are likely to take us are proposed.
Bioinformatics
Authors: Abbas Ali , Liu Lei
Published: April 2006

The past two decades have witnessed revolutionary changes in biomedical research and biotechnology and an explosive growth of biomedical data. High throughput technologies developed in automated DNA sequencing, functional genomics, proteomics, and metabolomics enable production of such high volume and complex data that the data analysis becomes a big challenge. Consequently, a promising new field, bioinformatics has emerged and is growing rapidly. Combining biological studies with computer science, mathematics, and statistics, bioinformatics develops methods, solutions, and software to discover patterns, generate models, and gain insight knowledge of complex biological systems.
Biomagnetism
Authors: Cheyne Douglas , Verba Jini
Published: April 2006

The science of biomagnetism refers to the measurement of magnetic fields produced by living organisms. These tiny magnetic fields are produced by naturally occurring electric currents resulting from muscle contraction, or signal transmission in the nervous system, or by the magnetization of biological tissue. This article discusses biomagnetic instruments and applications of these instruments as well as future direction of the field.
Biomaterials for Dentistry
Authors: Armstrong Steve
Published: April 2006

Biomaterials are used in the oral cavity either to restore function, comfort, or aesthetics caused by developmental disorders, disease, or trauma. More elective procedures are being requested and performed purely for aesthetic purposes as the incidence of caries has dropped in certain population groups and as patients have become more aware of various restorative or cosmetic options. However, the replacement of diseased tooth structure or missing teeth accounts for the bulk of work in restorative dentistry. The instruments and materials used in the surgical aspects of oral, maxillofacial and periodontal surgery have much in common with medicine. This article will focus on those commonly used materials in the restoration of individual teeth or the replacement of missing teeth.
Biomaterials, Absorbable
Authors: Borden Mark
Published: April 2006

Current techniques in orthopedic surgery use a variety of implants that are specifically designed to aid in the healing of bone, ligaments, and tendons throughout the skeleton. These implants are commonly used to provide temporary mechanical support and stabilization to the site of the injury while the tissue heals. However, once their function is complete, the implants remain and can be a source of long‐term complications. Resorbable implants, on the other hand, are a unique class of devices that have the ability to breakdown into harmless by‐products that are absorbed by the body. Composed of polymers, ceramics, or composites, these versatile materials have different mechanisms of resorption, degradation profiles, and mechanical properties. As a result, they have been used in a variety of clinical applications including fracture repair, sports medicine, and bone grafting. This chapter discusses the requirements and function of resorbable orthopedic devices, and reviews the properties and healing behavior of common resorbable materials.
Biomaterials: Carbon
Authors: More Robert B , Bokros Jack C
Published: April 2006

Inorganic, elemental carbon is one of the oldest, and yet newest, biomaterials. This article discusses the background, properties, biocompatibility, and medical applications for carbon biomaterials.
Biomaterials: Bioceramics
Authors: Jones Julian R. , Hench Larry L.
Published: April 2006

Bioceramics are ceramics that can be used for the reconstruction or regeneration of diseased or damaged tissues, they can be bioinert (e.g., alumina and zirconia), resorbable in the body (e.g., tricalcium phosphate), or bioactive (e.g., bioactive glass, hydroxyapatite), which bond to certain tissues and are used in regenerative medicine. In orthopedics, diseased joints are traditionally replaced by prostheses made of bioinert materials that may last up to 15 years. Advanced metal alloys, special polymers, and bioinert ceramics are the basis of this success. However, as life expectancy of our population increases, patients require >30 years from their devices. For large bone defects and severely diseased or damaged soft tissue such as the lung and the liver, transplantation is used, but donors are never enough. To satisfy this growing need for very long term tissue repair a shift of emphasis on
replacement
of tissues to
regeneration
of tissues is needed. An understanding and use of biological approaches is essential. This article describes current applications of bioceramics as medical devices and discusses development of porous bioceramic and composite scaffolds for tissue engineering. It suggests that bioactive ceramics will be used for future biomedical devices for regenerative medicine due to their potential for guiding tissue regeneration by stimulating cells at the genetic level.
Biomaterials, Corrosion and Wear of
Authors: Narayan Roger J. , Marek Miroslav , Jin Chunming
Published: April 2006

Many materials suffer degradation with time when exposed to aggressive chemical environments within the human body. In metallic biomaterials, degradation results from electrochemical corrosion. Ceramic and polymeric biomaterials may undergo physical or chemical deterioration processes. In addition, mechanical forces may act to increase damage by wear, abrasion, or environment‐induced cracking processes.
Biomaterials, Polymers
Authors: Zhang Min , James Susan P.
Published: April 2006

Biomaterials are materials of synthetic as well as of natural origin in contact with tissue or biological fluids, including metals, ceramics, polymers, and composites. The main advantages of polymeric biomaterials over ceramics and metals are the variety of composition, properties and available forms (solid, hydrogel, and solution), and ease of fabrication into complex shapes (films, sheets, fibers, powders, etc.) and structures because synthetic polymers are easily tailored to specific applications. As a result, the types of polymerization, the composition and properties of polymers, and polymers used as biomaterials will be discussed.
Biomaterials, Surface Properties of
Authors: McArthur Sally L. , Shard Alexander G.
Published: April 2006

In this article, we intend to provide a broad overview of the basic properties of surfaces, their interactions with biological systems, and how surfaces can be changed to suit particular biomaterial applications. Of particular importance is the requirement for surface characterization. Differences between surface and bulk properties can arise via a number of different processes. However they arise, it is important to ensure that the surface properties of the material are verified before ascribing any biological effect to the material. To complete this article, we provide an outline of the most commonly employed surface characterization techniques and include references to more detailed texts to aid the interested reader.
Biomaterials, Testing and Structural Properties of
Authors: Shi Donglu , Wen Xuejun
Published: April 2006

Previous studies have shown that the porous hydroxyapatite (HA) is bioactive and can be and used as a bone substitute in hard tissue prosthetics. However, the weak mechanical properties of HA are the primary obstacles to its applications. One approach to have a bone substitute with both required mechanical strength and bioactivity would be improve the bioactivity of some strong substrates. To this end, two major deposition methods, suspension method, and thermal deposition method, were employed in this work in which HA was uniformly coated onto the surfaces of highly porous and strong substrate of alumina. In suspension method, finely ground HA powders were mixed in an organic solvent and a binder to form suspension for coatings. In the thermal decomposition method, calcium 2‐ethyl hexanoate and bis(2‐ethyhexyl) phosphite were used as starting materials. Both techniques have proved to be effective in forming an adherent coating of HA onto a porous alumina substrate. The adherent strength of the HA coating is satisfactory for bone replacements. The thermal decomposition method, in comparison to the HA–glass suspension technique, eliminates all glasses (as sintering aids) that are not bioactive. Mechanical properties, interfacial adhesion behaviors, structural properties, and bioactive behaviors are studied using mechanical testing, scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and differential thermal analysis (DTA). The coated HA layer bonds strongly to the substrate through interface diffusion, and the layer is microstructurally and chemically uniform on the surfaces of the interconnected pores in the matrix of the substrate. The mechanical property testing results demonstrate that porous substrates with HA coating are much stronger than porous substrate made of pure HA. The compressive strength of the HA composite reaches 10 MPa, a value 10 times higher than that of porous HA. The
in vitro
bioactivity of HA coating on promoting the calcium phosphate deposition was affected by both structural crystallinity and specific surface area. High temperature sintering inevitably changes the crystallinity of the coated HA, and in turn affects its bioactivity. Well‐crystallized HA that is heat treated at high temperatures has resulted in a reduced bioactivity. The bio reaction rate was found to increase with the surface area of HA. The stability of the well crystallized HA is associated with the high driving force required for the formation of hydroxy‐carbonate apatite (HCA) phase. These results indicate a high potential for structural bone substitutes in the hard tissue prosthetics.
Biomaterials: Tissue Engineering and Scaffolds
Authors: Khang Gilson , Lee Sang Jin , Kim Moon Suk , Lee Hai Bang
Published: April 2006

Tissue engineering offers an alternative to whole organ and tissue transplantation for diseased, failed, or abnormally functioning organs. Tissue engineering requires a triad of components: (1) Harvested and dissociatedcellsfrom the donor tissue; (2)scaffoldsmade of biomaterials on which cells are attached and cultured, then implanted at the desired site in functioning tissue; and (3)growthfactorsthat promote and/or prevent cell adhesion, proliferation, migration, and differentiation by up‐regulating or down‐regulating the synthesis of protein, growth factors, and receptors.

Of these three key components, scaffolds be play a critical role. Scaffolds direct the growthof cells seeded within the porous structure of the scaffold, orof cells migrating from the surrounding tissue, to eventually mimick a natural extracellular matrix. In this section, a review is given of the biomaterials and procedures used in the development of tissue‐engineered scaffolds, including: (1) natural and synthetic, polymeric biomaterials (2) bioceramic scaffolds, (3) cytokine‐released scaffolds, (4) the fabrication and characterization of scaffolds, (5) surface modifications, and (6) scaffold sterilization. However, to approach a more natural three‐dimensional environment necessary for successful organ and tissue transplantation, the combined efforts of researchers from the fields of biology, biochemistry, and material science/engineering will be needed to further develop scaffolds that will support biological signals for tissue growth and reorganization.
Biomechanics of Exercise Fitness
Authors: Ariel Gideon
Published: April 2006

The main purpose of this article is to focus on the biomechanical principles of movement, the scientific bases of training and fitness, and the optimization of human performance at any age. These are not just nonsense concepts added to the quantities of known theories, but are objectively quantifiable procedures that encompass our understandings and can produce precise conclusions. Mathematical principles and gravitational formulations provide the cornerstones for optimizing human performance. Biological, anatomical, physiological, and medical discoveries are always under investigation, challenge, and improvement and these findings will be incorporated into many of the current theories.
Blood Collection and Processing
Authors: Terry Teresa M. , Cox Josephine H.
Published: April 2006

Access to affordable, quality healthcare is considered one of the basic rights of human beings. By ensuring that the benefits of modern medicine are available to all, we can prevent people from dying prematurely, increase productivity, and health of everyone. Blood is one of the most easily accessible sources of body fluids that can provide information on health status and changes induced as a result of drug, vaccine, or other therapeutic interventions. This article describes the general procedures for drawing and processing of blood for screening, analysis, and diagnostic purposes.

The life blood streaming thro’ my heart, Or my more dear immortal part, Is not more fondly dear. John Bunyan, Pilgrim’s Progress.
Blood Gas Measurements
Authors: Elsharydah Ahmad , Cork Randall C.
Published: April 2006

Blood gas measurement‐monitoring is essential to monitor gas exchange in critically ill patients in the intensive care units, and “standard of care” monitoring to deliver general anesthesia. It is a cornerstone in the diagnosis and management of the patient's oxygenation and acid‐base disorders. Moreover, it may indicate the onset or culmination of cardiopulmonary problems, and may help in evaluating the effectiveness of the applied therapy. Numerous studies and reports have shown the significance of utilizing blood gas analyses in preventing serious oxygenation and acid‐base problems. This article gives a summarized explanation of the common methods and instruments used nowadays in blood gas measurements in clinical medicine. This explanation includes a brief history of the development of these methods and instruments, the principles of their operation, a general description of their designs, and some of their clinical uses, hazards, risks, limitations, and finally the direction in the future to improve these instruments or to invent new ones.
Blood Pressure, Automatic Control of
Authors: Yu Yih‐Choung
Published: April 2006

Automatic blood pressure control is a technique that regulates the infusion rates of pharmacological agents automatically to maintain a patient’s mean arterial pressure within a desired level. Patients under blood pressure regulation treatment are usually in cardiac surgery or suffering from postsurgical hypertension or other cardiac diseases with abnormal arterial blood pressure. This treatment is usually performed by experienced personnel in the operation room or intensive care unit, which is very difficult and time consuming. An automatic controller that could deliver drugs based on a patient’s physiologic conditions safely and effectively without human intervention would be beneficial to both patients and medical care personnel.

This article reviews various automatic control schemes that have been developed to regulate mean arterial pressure for patients with postsurgical hypertension using sodium nitroprusside proportional‐derivative‐integral controllers, adaptive controllers, rule‐based controllers, and neural‐network based controllers are common control strategies described in the literature. A brief description of each control scheme is provided, followed by examples of controller designs from the literature. Evaluations of the controller performance in computer simulation, animal studies, or clinical tests on human subjects are discussed.
Blood Rheology
Authors: Tran‐Son‐Tay Roger , Shyy Wei
Published: April 2006

This article provides the fundamental background for understanding blood rheology, and appreciating its contributions to the improvement of our understanding and assessment of diseases. Because blood rheology is a very broad subject, this article focuses mainly on the role of red blood cell deformability in clinical studies. A review is given of the rheological properties of blood, the impact of cell deformability in clinical situations, the assessment of cell deformabilty using cell filtration and cell elongation, and the most common methods used to measure the rheological properties of blood and individual blood cells.
Bone and Teeth, Properties of
Authors: Lakes Roderic , Katz J. Lawrence
Published: April 2006

Bone has a variety of functions in the body of which some of the most important are structural in nature: protection of vulnerable body parts, support of the body, and to provide muscle attachments. A knowledge of the mechanical and adaptive properties of bone is useful in the design and use of prostheses that replace a bone or a portion of a bone. Mechanical properties of bone are also of interest in trauma biomechanics and in efforts to prevent injury to the body. As for teeth, they also are replaced by artificial materials which are called upon to perform the mechanical functions of the original tooth. This article contains a survey of known properties of bone and teeth and their components collagen and apatite, with an emphasis on bone and its mechanical properties.
Bone Density Measurement
Authors: Qin Yixian , Mittra Erik
Published: April 2006

Bone degeneration, i.e., osteoporosis, remains a major public health problem through its association with fragility fractures. Bone mineral density (BMD) measurement is a clinical tool to diagnose osteoporosis or low bone density, predict the risk of fracture, and monitor changes in bone density over time. Assessment of BMD has become as essential element in the early evaluation of patients at risk for osteopenia and osteoporosis. The noninvasive measurement of BMD is done with a variety of technologies for many different skeletal sites. Many image modalities and techniques have been developed to improve the quality and the accuracy of the measurement for bone mineral and dense assessment. There are two major densitometry techniques commonly used in assessing bone density, i.e., radiography‐based densitometry and ultrasound‐based assessment. Dual‐energy X‐ray absorptiometry (DXA) and quantitative ultrasound (QUS) are two current acceptable modalities for bone density testing and the assessment tools for predicting fracture risk. Growing awareness of the impact of osteoporosis on the elderly population and the consequent costs of health care, together with development of new treatments to prevent fractures, have led to a rapid increase in the demand for bone densitometry measurements. The historical development, their working principles, strengths, and limitations of these technologies will be discussed in this article.
Brachytherapy, Intravascular
Authors: Mourtada Firas
Published: April 2006

The scope of this article is on the delivery devices for IVB and tools needed to assess the dosimetric properties of such brachytherapy devices. (Dosimetry is a subspecialty of radiation physics that deals with the measurement of the absorbed dose or dose rate resulting from the interaction of ionizing radiation with matter.) Such techniques are useful and can be applied in other future applications that require delivery of ionizing radiation to a target within a few millimeters from a radioactive source.
Skin Substitute for Burns, Bioactive
Authors: Demling Robert H. , DeSanti Leslie
Published: April 2006

The new generation of skin substitutes are developed to be biologically active. The concept behind providing bioactivity is that the wound healing process can be substantially improved as compared with a simple synthetic barrier‐type dressing. It remains to be seen just how much better this new generation of products will impact the burn wound. To date, the new products to be discussed have not displaced the more inert standard burn wound dressings, but rather are used in conjunction and for quite specific indications.

The skin substitutes are initially classified according to whether they are to be used as a temporary wound covering to decrease pain and augment healing or a permanent skin substitute to add to or replace the remaining skin components.

The ideal properties and indications for these products will be better clarified after a discussion of the function of normal skin and the effect of a burn on skin integrity.
Capacitive Microsensors for Biomedical Applications
Authors: Tsoukalas D. , Chatzandroulis S. , Goustouridis D.
Published: April 2006

The use of reliable, high performance miniature sensors in the medical field is of growing importance for patient health monitoring. Batch sensor fabrication, as this has been introduced by Integrated Circuit (IC) manufacturing, is an efficient way to produce silicon sensors with desirable characteristics. Since microsensors combine small size with electrical and mechanical principles of operation they constitute together with microactuators what is usually called Microelectromechanical Systems (MEMS). These components are mainly made from silicon and other related materials to explore existing know‐how and infrastructure of silicon technology. All of the above factors have allowed for fast growth of the microsensor field during the last years. This article focuses on physical microsensors used in the medical field that are based on the capacitive approach.
Cardiac Output, Indicator Dilution Measurement of
Authors: Donovan F. M. , Taylor B. C.
Published: April 2006

Knowledge of cardiac output is important for determining the hemodynamic status of an individual. A direct measurement of cardiac output is difficult, since to obtain a direct measurement would require collecting and measuring all of the blood pumped from the heart. Therefore it is necessary to develop indirect methods for the measurement of this important parameter. The Fick and other indicator dilution methods are two of the invasive procedures that produce good results. The fundamental equations and theory necessary to understand the indicator dilution methods of measuring cardiac output including the steady‐state Fick method, the transient indicator dilution methods with recirculation, and the thermal dilution method are developed and their application is explained.
Cardiopulmonary Resuscitation
Authors: Grayden Edward
Published: April 2006

This article will first review the history of CPR followed by a detailed analysis of the pulmonary and cardiac physiology relevant to the application of these resuscitative functions. An overview of Emergency Cardiac Care (ECC) will be undertaken to enlighten the reader about the organizational process guiding CPR. The actual mechanism of BLS and ACLS will be then addressed with a brief overview of defibrillators. Finally, the salient points of this article will be summarized and future directions of resuscitation will be explored.
Cobalt‐60 Units for Radiotherapy
Authors: Cunningham John R.
Published: April 2006

This article reviews the history and background of Cobalt and discusses the physics of activation, the specification of source strength, the unit design, and clinical applications.
Cochlear Prostheses
Authors: Spelman Francis A.
Published: April 2006

This article is an update of the article Cochlear Prosthesis in the Ist ed. of this Encyclopedia and discusses candidates for implants, the auditory system and periphery, the history and evaluation of Cochlear implants, the theory of operation, and the costs and benefits of implementation.
Codes and Regulations: Medical Devices
Authors: Waxler Morris , Kaeding Patricia J.
Published: April 2006

The U.S. Food and Drug Administration (FDA) regulates medical devices according to specific definitions, classifications, requirements, codes, and standards. The FDAs authority and framework for medical device regulation are specified in the Federal Food, Drug, and Cosmetic Act. Pursuant to the Act, FDA determines the entities subject to regulation, evaluates whether products and regulated entities are in compliance, and initiates appropriate regulatory and enforcement actions. The FDAs requirements affect each stage of a medical device’s lifecycle. Some FDA requirements apply to particular periods of a medical device’s lifecycle. Others apply more broadly. Design, technical development, preclinical testing, clinical study, market authorization and approval, postmarket assessment, modification, obsolescence, redesign, and labeling requirements are part of this regulatory framework for medical devices.
Resin‐Based Composites
Authors: Cannon Mark
Published: April 2006

Composite dental restorative filling materials are synthetic resins that have had a revolutionary impact on dental practice. No other dental materials have stimulated such rapid change in an inarguably short period of time. The advent of resin‐based composite occurred during the “Golden Age of Dentistry” and mirrored the overall effect that high technology had on society. Virtually everyone has been made aware of “bonding” or “cosmetic dentistry” by the mass media. The success of “bonding” or “cosmetic dentistry” depended on the development of esthetic dental restorative (filling) materials such as resin‐based composites and to the advent of dental adhesives, which allowed for the successful placement of the new esthetic materials.
Computed Tomography
Authors: Dennis Michael J.
Published: April 2006

Computed tomograhy (CT), also know as CAT scanning, is a major diagnostic imaging method utilizing the measurement of thousands of X‐ray transmission measurements through the patient to generate detailed cross‐sectional images. The resultant image is a matrix of CT numbers where each picture element or pixel is a scaled value of the linear attenuation coefficient or X‐ray density of the tissue contained in the corresponding volume element or voxel in the patient. The ability to eliminate over and underlying structures from the X‐ray data allows the ability to discern differences of these CT number values to a fraction of a percent. The technology has continued to improve since its development in the 1970s with faster, higher resolution systems to rapidly produce a large number of two‐dimebnsional (2D) axial images, and the use of processing methods to generate three‐dimensional (3D) presentations of the anatomy.

Material consider in this article include the basic principles of CT: the evolution of different data acquisition geometries for more rapid scanning; the various components of a CT system; reconstruction methods used to determine the cross‐sectional distribution of densities from the transmission measurements; scan techniques including helical, cardiac, and angiographic scanning, display techniques for presenting the 3D data; factors affecting patient dose; factors affecting resolution and image noise; and CT artifacts or errors that can occur in the images.
Contact Lenses
Authors: Ritchey Eric R.
Published: April 2006

Contact lenses are prescription medical devices applied to the anterior surface of the cornea for the temporary correction of refractive error. Contact lenses can be used successfully to correct a number of refractive error conditions, such as myopia, hyperopia, presbyopia, and aphakia. Currently, there are an estimated 38 million contact lens wearers in the United States and 125 million contact lens wearers worldwide, making contact lenses one of the most commonly prescribed medical devices available. The ability to wear contact lenses successfully is dependent on numerous factors, including but not limited to the contact lens design and materials, corneal health and physiology, the lens to epithelium interface, proper use of lens care solutions, patient compliance, professional fitting and follow‐up care. Unacceptable contact lens fits can lead to deleterious results ranging from poor lens comfort to microbial keratitis and permanent loss of visual acuity.
Cryosurgery
Authors: Gage Andrew A.
Published: April 2006

Cryosurgery is a method of therapy that uses freezing temperatures to achieve curative effects on diseased or abnormal tissues. This article reviews the historical background of cryosurgery, the mechanisms of tissue injury due to freezing, and the techniques of application of freezing temperatures to the tissue. The technical description reviews the types of cryogens and cryosurgical apparatus and the methods of monitoring the freezing process. Clinical uses of cryosurgical techniques for diverse organs and tissues, both neoplastic and non‐neoplastic diseases, are described.
Cutaneous Blood Flow, Doppler Measurement of
Authors: Khaodhiar Lalita , Veves Aristidis
Published: April 2006

The necessity for measuring the skin blood flows occurs in many areas of physiology, pharmacology, and clinical medicine. Although the measurement of blood flow in the large blood vessels in the human body has been performed for centuries, the use of techniques to explore microcirculation have just evolved over the past 30 years. Available tests for assessing the skin microcirculation include tissue pH measurement, radioactive isotope clearance, capillary microscopy, plethysmography, transcutaneous oxygen tension, ultrasonic Doppler flowmetry, and laser Doppler flowmetry.
Defibrillators
Authors: Roth Bradley J.
Published: April 2006

A defibrillator is a medical device that delivers an electric shock to a heart that is in ventricular fibrillation. Defibrillators come in two types: external and internal. An Automated External Defibrillator (AED) is designed to deliver a shock through electrodes attached to the body surface. A physician, a paramedic, or even an untrained bystander can use an AED to apply a shock to an unconscious victim. An Implantable Cardioverter Defibrillator (ICD) is surgically implanted into patients who are at risk for ventricular fibrillation. The ICD monitors the electrical activity of the heart and delivers a shock when fibrillation is detected. Both devices operate by charging a capacitor to a high voltage and then discharging it through the heart.
Differential Counts, Automated
Authors: Zelmanovic David , Kunicka Jolanta
Published: April 2006

This article includes a discussion of the cellular properties that are used to automatically analyze white blood cells and describes the techniques used to measure these properties. Examples are provided of the implementation of these techniques on commercial hematology analyzers. Finally, there is a brief discussion of the relative merits of the analysis methods in terms of result accuracy and laboratory efficiency.
Digital Angiography
Authors: Bennett James R.
Published: April 2006

Computer technology has played an essential role in improving anesthesia patient care and reducing healthcare costs. This article provides a synopsis of computer applications in the areas of anesthesia monitoring, anesthesia information systems, computer simulations of human patients, computer anesthesia control, computer‐assisted diagnosis and decisions, and telemedicine in anesthesia.
Echocardiography and Doppler Echocardiography
Authors: Rahko Peter S.
Published: April 2006

Echocardiography is a diagnostic technique that uses ultrasound (high frequency sound) to produce an image of the heart in real time. The comprehensive echocardiographic exam uses multiple imaging formats to evaluate the heart. These include direct imaging of the heart with M‐mode, two‐dimensional, and three‐dimensional formats and direct interrogation of blood flow through cardiac chambers and across valves with pulsed Doppler, continuous wave Doppler, and color flow Doppler.

Echocardiographic transducers may be placed in multiple locations on the chest wall to obtain different views of the heart and also, using specialized devices, inside the esophagus and stomach and inside the heart mounted on special catheters that allow interrogation using a miniaturized transducer.

To achieve usable information the reflected ultrasound signal is intensively processed after it is detected in the transducer. Modern transducers have upward of 256 transmit and receive elements that process the ultrasound signal. The reflected ultrasound signal is manipulated in multiple selective ways to best display the wide range of cardiac anatomy and motion encountered in the exam. Similarly, several different techniques of processing are used to display and quantify Doppler analysis of blood flow.

Data from the echocardiographic exam is used to quantify anatomic size and shape of cardiac chambers, diagnose changes in cardiac structure characteristics of different kinds of cardiac disease, evaluate functional performance of the heart as a pump, characterize normal and abnormal anatomy, motion, and blood flow characteristics of heart valves, and determine the presence of various other abnormalities in and around the heart such as collections of fluid, blood clots, tumors, or areas of calcification.

Echocardiography is a powerful diagnostic tool that safely and noninvasively evaluates the heart.
Electroanalgesia, Systemic
Authors: Limoge Aime , Stanley Ted
Published: April 2006

Electroanalgesia, electroanesthesia, neurostimulation, neuromodulation, and other physical methods of producing analgesia, anesthesia, and/or decreased sensitivity to painful stimuli are old concepts that are beginning to be revitalized in the recent past. For > 40 years, there has been a revival of electrotherapy in the treatment of pain. Analgesia by electrical current is now based on transcutaneous or percutaneous nerve stimulation, deep stimulation, posterior spinal cords stimulation, and transcutaneous cranial electrical stimulation. One reason for this has been the increased awareness of spinal and supraspinal opioid analgesic mechanisms, including the precise pathways, receptors, and neurotransmitters involved in pain perception, recognition, modulation, and blockade. Another reason is the renewed belief that nonpharmacological manipulation of these receptors and transmitters should be possible with electricity since numerous progress have been made in the development of electric current waveforms that result in significant potentiation of the analgesic and hypnotics action of many intravenous and inhaled anesthetics without producing significant side effects. Finally, recent successes of transcutaneous electrical nerve stimulation (TENS) in the treatment of pain and transcutaneous cranial electrical stimulation (TCES) as a supplement during anesthesia to obtain postoperative analgesia by potentiating the anesthetic agents used during the intra‐ and postoperative phases. The popularity of electroacupuncture in a variety of pain and pain related areas have focused the attention of investigators and the public on electricity as a beneficial medical therapy. In this article, some of the most recent developments in nerve and brain stimulatory techniques using electrical stimulation to produce analgesia are addressed.