bluuebunny/crossref_metadata_2025 huggingface dataset:
Medium Access Control (MAC) Protocols
Authors: Faragó András , Syrotiuk Violet R.
Published: November 2003

Themedium access control(MAC) protocol serves a vital role in all networks in which communication is based on a broadcast (or multiaccess) channel. The MAC protocol is directly responsible for controlling access to the communication resources, subject to the technological constraints of the hardware. This article provides a taxonomy of MAC protocols, and then reviews some of the most important MAC protocols according to their method of sharing the medium since this best characterizes their operation.
Millimeter‐Wave Antennas
Authors: Chen Zhizhang (David)
Published: November 2003

A comprehensive review of millimeter‐wave antennas for telecommunications is presented. Major advances have been made in the past two decades on the development of lens and horn antennas to optically controlled millimeter‐wave antennas. In particular, a number of new antennas, such as extended hemispherical lens antennas, printed circuit antennas, active integrated antennas as well as photoconducting antennas, have resulted in excellent performance in millimeter‐wave frequencies. An attempt is made to categorize various mm‐wave antennas and to summarize the associated developments. An introduction to the concept of millimeter‐wave frequency band and its application is also presented at the beginning.
Optical Fiber Local Area Networks
Authors: Shadaram Mehdi , Gonzalez‐Lozano Virgilio E.
Published: November 2003

Communication between computers is an essential part of modern living and the telecommunication industry is one of world's fastest growing. There is an increasing demand for higher bandwidth, almost doubling the data rate every year. This has reached a point where a single transmission medium such as twisted pair or coaxial cable is not capable of transmitting the load. Thus, for a reliable and high‐speed data transfer, computers are connected through a network of point‐to‐point communication links. These types of networks usually referred to as local area network or LAN. The main purpose of a LAN is to share resources such as files, printers, programs, databases, etc; among the nodes in the network. The initial designs were intended for communication between computers at short distances; however, the length of the links has grown from a few meters to a few kilometers. If computers are connected via optical fiber links, the LAN is referred to as optical fiber LAN. Since the early 1970s optical fibers have been utilized as transmission media in long and short distance communication links. The capacity of optical fibers has increased from several Mbit/sec per km to about 300 Gbit/sec per km; and could reach thousands of Gbit/sec in the near future. Other properties like small size, lightweight, and immunity to electromagnetic interference noise also provide a crucial advantage for optical fibers over other mediums. Some common types of Optical LANs are FDDI, optical Ethernet at various speeds, Fibre Channel and ATM LAN emulation.
Image Compression
Authors: Mertins Alfred
Published: November 2003

The aim of this article is to give an overview of some of the most important image compression tools and techniques. We start by looking at the theoretical background of data compression and describe source coding as a tradeoff between compression ratio and fidelity. Subsequently we explain the principles of PCM, DPCM, transform coding, vector quantization and entropy coding. Then we present the discrete cosine and wavelet transforms, which are the two most important transforms in image compression. Following a discussion of state‐of‐the‐art embedded wavelet compression methods, we review the JPEG, JPEG‐LS, and JPEG2000 standards for the compression of continuous‐tone images.
Partial‐Response Signals for Communications
Authors: Rizos Apostolos
Published: November 2003

Partial response signaling is a technique where correlation is introduced between successive transmitted symbols in a communications system. The purpose of this correlation is to give favorable spectral properties to the signal, so that it can match the channel characteristics or satisfy bandwidth requirements. The correlation between symbols, which is a form of (controlled) intersymbol interference, requires relatively complex receiver techniques, like MLSE (maximum likelihood sequence estimation), in order to minimize performance losses. The MLSE complexity had initially restricted the range of practically implementable PR systems to simple schemes like duobinary or modified duobinary. However, with the increased computational power that modern electronic circuits offer, these receiver techniques have feasible implementation now and this has led to a wider use of more complex partial response systems, in applications such as magnetic recording and bandwidth‐efficient twisted pair line transmission.
Broadband Wireless Access
Authors: Sari Hikmet
Published: November 2003

Broadband wireless access (BWA) is an access technology that is particularly suited to new operators without an existing infrastructure to serve the end users. It is in direct competition with incumbent telecom operators' digital subscriber lines (DSL) and cable operators' cable modem technology. BWA systems make use of millimeter‐wave radio frequencies above 20 GHz as well as of microwave frequencies between 2 and 11 GHz. BWA systems at millimeter‐wave frequencies are often referred to as Local Multipoint Distribution Service (LMDS) systems. While LMDS systems are designed for line‐of‐sight (LOS) propagation and use small cell sizes, BWA access systems at lower microwave frequencies are designed for non‐LOS propagation and typically use much larger cell sizes. In this article, we present the basic characteristics of both types of BWA networks, describe the technologies used and the current standardization work in this field by the IEEE 802.16 Group in the US and the ETSI in Europe.
High‐Speed Photodetectors for Optical Communications
Authors: Selim Ünlü M. , Dosunmu Olufemi , Emsley Matthew
Published: November 2003

Abstract for “High‐Speed Photodetectors for Optical Communications”

We discuss the fundamental properties, basic requirements and limitations of photodetectors pertaining to applications in high‐speed optical communications. The requirements for high‐speed photodetectors include high responsivity at the communication wavelengths, compatible size for coupling to optical fibers as well as low cost and reliability. There are fundamental limitations for high‐speed operation and trade‐offs between various performance parameters for photodetectors. We review these limitations, including those due to capacitance charging and the transit‐time of photogenerated carriers, and present examples of state‐of‐the‐art devices. Although there exists a wide range of photodetectors suitable for optical communications, we will focus on a particular subset of photovoltaics called photodiodes. Several different types of photodiodes will be introduced, including the PIN, Schottky, avalanche and metal‐semiconductor‐metal (MSM) photodiode, along with their individual strengths and weaknesses. In addition, detectors such as the resonant cavity enhanced (RCE) and waveguide photodiode, designed to overcome many of the fundamental limitations associated with conventional structures, are also presented.
Land‐Mobile Satellite Communications*
Authors: Schodorf Jeffrey B.
Published: November 2003

Land mobile satellite communications systems are discussed. Topics covered include a brief description of current and future LMSC systems characteristics, an overview of the LMSC propagation channel, error mitigation strategies, multiple access schemes, and network aspects. Most topics are covered in moderate detail with relevant equations and illustrative figures. Major references are also included so that topics of interest can be pursued in more depth by interested readers.
Packet‐Switched Networks
Authors: Stiliadis Dimitrios
Published: November 2003

Packet switching is replacing circuit‐switching as the dominant technology in networking. Communication in packet switched networks is enabled through an exchange of messages. Each message is carried over one or multiple packets, and packets from multiple users are interleaved on the same links. Because of the bursty nature of data communications, packet switching offers several advantages in terms of link utilization and delay behavior. In this article, we outline the fundamental concepts of packet switching, such as statistical multiplexing, forwarding and routing, and layered protocol design. We also show how these concepts apply to the Internet that is the most popular packet switched network.
Iterative Detection Algorithms in Communications
Authors: Chugg Keith M.
Published: November 2003

This article motivates the use of algorithms that exchange and update soft decision information in order to improve the performance or reduce the complexity of digital communication receivers. A general and standard approach to the design of such algorithms is then described based on concepts from decision theory and conventional receiver design. A condition for the optimality of this approach is given and motivation for its effectiveness in the absence of this condition is provided. Specific applications of this general approach are summarized.
Convolutional Codes
Authors: Wesel Richard D.
Published: November 2003

Convolutional codes represent one technique within the general class of channel codes. Channel codes (also called error correction codes) permit reliable communication of an information sequence over a channel that adds noise, introduces bit errors, or otherwise distorts the transmitted signal. This article introduces the fundamental aspects of convolutional codes. A discussion of encoder structure introduces shift register diagrams, state diagrams, equivalent encoders, minimal encoders, and catastrophic encoders. Then, trellis diagrams provide the foundation for a description of both maximum likelihood and finite‐traceback implementations of Viterbi decoding. Viterbi decoding provides one technique for computing free distance, which is a first order metric of encoder performance. Finally, the article presents the generating function method for enumerating error events and shows how it may be used in union bounds on bit error rate that are accurate at high SNR.
Acoustic Echo Cancellation
Authors: Hänsler Eberhard
Published: November 2003

This article explains the problem of acoustical echoes and their cancellation. It focuses on the hands‐free telephone as one of the major applications for echo cancelling devices. Beginning with a short discussion of a system formed by a loudspeaker and a microphone located within the same enclosure, the properties of speech signals and noise are described. The major part of the echo can be cancelled by an adaptive filter connected in parallel to the loudspeaker and the microphone. Residual echoes are suppressed by an additional filter within the outgoing signal path. Algorithms for the adaptation of the echo cancelling filter are described. Because of its robustness and its low computational complexity the NLMS algorithm is primarily applied. Measures to improve the speed of convergence and to avoid divergence in case of double talk or strong local noise are discussed. Echo cancellation for stereophonic systems, cancellation in subbands, and the applications of block processing techniques conclude the article.
Pulse Amplitude Modulation
Authors: Bjerke Bjørn A.
Published: November 2003

Pulse amplitude modulation (PAM) is a modulation method used in digital communication systems to facilitate transmission of digital information. The modulation method is used in baseband as well as carrier‐modulated systems. A PAM modulator maps binary information (bits) into analog waveforms which differ only in amplitude. In this article, we provide a mathematical description of PAM signals. This description is used for investigating their spectral characteristics and is also the foundation for discussing the various elements of PAM receivers. In particular, we consider PAM signal demodulation and detection and give a brief overview of carrier recovery and symbol synchronization.
Wireless Local Loop Standards and Systems
Authors: Hashemi Homayoun
Published: November 2003

In this tutorial presentation basic principles and applications of Wireless Local Loops (WLL) systems are reviewed. WLL Technology is described and major mobile‐radio based and proprietary radio interface standards are explored. Spectrum and capacity issues of WLL based on cellular radio principles are presented, and economic aspects of wired and wireless loops are compared. Broadband applications of WLL are also briefly outlined.
Modeling and Analysis Of Digital Optical Communications Systems
Authors: Shtaif Mark
Published: November 2003

This article reviews the modeling and operation of digital optical communications systems focusing on the description of fundamental physical principles and their mathematical representation. It covers issues related to optical amplification and noise, detection and estimation of error‐rates, propagation in optical fibers in the presence of dispersion and nonlinear effects and includes a brief introduction to polarization related phenomena.
Optical Wireless Laser Communications: Free‐Space Optics
Authors: Killinger Dennis
Published: November 2003

A brief overview of the technical and scientific basis for Free Space Optics Laser Communication for point‐to‐point laser beam telecommunication through the atmosphere is covered in this chapter. Subjects include the historical background of Free Space Optics (FSO), current commercial applications, laser and LED optical sources, atmospheric scatter and attenuation, optical detectors and noise considerations, the FSO Range Equation with examples of several commercial units, atmospheric refractive turbulence effects, telescope design and alignment problems, and eye safety considerations.
JPEG2000Image Coding Standard
Authors: Usevitch B. E.
Published: November 2003

JPEG2000 is a new international image compression standard developed to address some of the shortcomings of the original JPEG standard. JPEG2000 delivers lossy and lossless image compression using the same wavelet based algorithms. A key feature of JPEG2000 is that it produces a very flexible bit stream by only coding the image data once. This bit stream can be rearranged such that sequential decoding gives images of progressively larger size, higher quality, or more colors. All the resultant bit streams maintain a strict embedded property such that truncation of the bit streams gives optimal compressed representations for the given truncated length.
Cochannel Interference in Digital Cellular
TDMA
Networks
Authors: Glisic Savo G. , Pirinen Pekka
Published: November 2003

This Chapter focuses on co‐channel interference in cellular TDMA networks. Both the generation of co‐channel interference and the appropriate interference suppression methods are considered. Contributions of frequency reuse,spatial filtering and time domain interference cancellation on the residual interference are described. Effects of variable propagation parameters (especially lognormal shadowing),cluster sizes and interference parameters to the outage probability are illustrated. Furthermore, the spectrum efficiency examples are shown in the form of the Erlang capacity at variable cluster sizes and quality‐of‐service criteria.
Satellites in
IP
Networks
Authors: Jamalipour Abbas
Published: November 2003

A satellite has been an important element of telecommunications networks for many years, providing long distance telephony and television broadcasting. The involvement of satellites in IP networks is a direct result of new trends in global telecommunications where the Internet traffic will hold a dominant share in the total network traffic and special features of high‐capacity satellite channels to be discussed in this chapter. The large geographical coverage of the satellite footprint and its unique broadcasting capabilities as well as its high‐capacity channels keep the satellite as an irreplaceable part of communications systems, despite the high cost and long development and launching cycle of a satellite system. In this chapter, the role of satellites in future wireless Internet networks will be discussed and relevant research issues will be explored.
Cable Modems
Authors: McMullin Donald G.
Published: November 2003

Examined in this article are the critical requirements for high speed digital modem applications in a Hybrid Fiber Coax (HFC) environment. An overview of the basic elements and modulation formats of the system including the RF (Radio Frequency) tuner, IF (Intermediate Frequency) amplifiers, and frequency allocations for 2‐way transmission on a single cable are presented. A brief introduction to the data protocols and layer architectures of the modern TCP/IP internet stack is given. Requirements for IMD (Inter‐Modulation Distortion) and NF (Noise Figure) in a digital QAM (Quadrature Amplitude Modulation) system are contrasted with the traditional analog NTSC (National Television Standards Committee) format, which the cable systems were initially designed to support. RF, IF and overall system requirements for downstream and upstream data paths are presented including detailed performance requirements for AFEs (Analog Front Ends), ADCs (Analog to Digital Converters) and DACs (Digital to Analog Converters).
Communication Satellite Onboard Processing
Authors: Bernstein Steven
Published: November 2003

The primary purpose of communication satellites is to receive signals from one or more sources and relay them to intended recipients. To accomplish this many communication satellites incorporate one or more “translating repeaters” or “transponders” which simply amplify and frequency‐translate a band of frequencies. However, digital circuit and signal processing technology has progressed to the point that it is feasible and advantageous to implement more powerful processing functions on‐board the satellite. On‐board processing can enable systems to: make more effective use of power and bandwidth; improve multiple access performance; reject interference; and provide richer interconnectivity. On‐board techniques include: beam switching; adaptive antennas; demodulation‐remodulation; access control; and packet switching. This article will discuss each of the techniques and give a number of system application examples.
Sequential Decoding of Convolutional Codes
Authors: Han Yunghsiang S. , Chen Po‐Ning
Published: November 2003

This article surveys many variants of sequential decoding in literature. Rather than introducing them chronologically, this article first presents the Algorithm A, a general sequential search algorithm. The stack algorithm and the Fano algorithm are then described in details. Next, trellis variants of sequential decoding, including the recently proposed maximum‐likelihood sequential decoding algorithm, are discussed. Additionally, decoding complexity and error performance of sequential decoding are investigated, followed by a discussion on the implementation of sequential decoding from various practical aspects. Moreover, classes of convolutional codes that are particularly appropriate for sequential decoding are outlined.
Neural Networks and Applications to Communications
Authors: Manolakos Elias S.
Published: November 2003

Neural Networks are highly interconnected distributed information processing architectures that are built by connecting together many simple processing elements. They come in many different flavors but all share the ability tolearni.e. to adapt their structure to capture the process that generates information in their environment, and utilize the internally formed representation of that process topredict, orgeneralize, when presented with unseen novel patterns. In this article we first introduce the basics of neural networks by describing the structure of commonly used neuron processors, some popular network architectures and learning rules. Then we explain why neural network methods have been utilized so extensively in the field of communications by presenting typical snapshots of their use in a representative subset of communication applications. Our intention is to introduce the interested non‐expert reader to the subject matter and not to present a comprehensive survey of the very large related literature.
Low‐Bit‐Rate Speech Coding
Authors: Ramírez Miguel Arjona , Minami Mario
Published: November 2003

This article is focused on speech coding methods for achieving communication quality speech at bit rates of 4 kbit/s and lower. The speech coding techniques are based on an all‐pole model of the vocal tract which may be implemented in the time domain with appropriately selected excitation functions or else may be fit to a spectral analysis of the speech signal. Three main types of coders are described below. Code‐excited linear prediction (CELP) coders select their excitation from waveform codebooks using analysis‐by‐synthesis closed‐loop techniques, which need to be supplemented by speech classification and open‐loop parametric techniques for keeping up with quality at lower rates. The prototypical sinusoidal coder (SC) has a bank of oscillators for signal synthesis, driven by a model of the magnitude spectrum. However, phase regeneration is important in enhancing speech reconstruction at low rates. Waveform interpolation (WI) coders afford a wider time‐frequency footprint for the representation of the excitation, showing a good potential for achieving toll quality at bit rates below 4 kbit/s.
Product Codes
Authors: Kschischang Frank R.
Published: November 2003

Product codes, introduced by Elias in 1954, combine simple constituent codes into a more powerful one, with a structure that is well‐suited for iterative decoding. This article reviews the construction of product codes, derives some of their basic properties, and briefly describes some iterative decoding methods for these codes.
MEMSforRF/Wireless Applications
Authors: De Los Santos Héctor J.
Published: November 2003

Since the mid‐1990s, the prospect of applying microelectromechanical systems (MEMS) technology in RF/wireless communications systems has received considerable attention. This is due to RF MEMS' potential to provide the high‐performance devices that will enable the sophisticated, yet portable, wireless appliances demanded by consumers. In this chapter we first provide a review of the global connectivity problem, and how it motivates these wireless appliances. Then, we present the fundamentals of RF MEMS fabrication technology, in particular, bulk and surface micromachining, together with a sample of the structures and performance of some of the most important passive devices and circuits, such as inductors, varactors, transmission lines, resonators, switches and phase shifters, it makes possible.
Orthogonal Transmultiplexers: A Time‐Frequency Perspective
Authors: Akansu Ali N. , Sencar Husrev T.
Published: November 2003

We present a time‐frequency interpretation of orthogonal sets used in a transmultiplexer configuration that plays an important role in many single and multiuser communication systems in this article. It's shown that once independently treatedmulticarrier modulationtechniques like FDMA, TDMA and CDMA have their unified theoretical treatment usingorthogonal transformsand filter banks. This treatment helps one to build a multicarrier modulation based communication system using optimally designed orthogonal function set or signatures.
WDMMetropolitan‐Area Optical Networks
Authors: Tomkos Ioannis
Published: November 2003

In this article, the characteristics, requirements and architectures of optical metropolitan area networks are presented. The main features of system offerings proposed for metro networks are also discussed. We outline our considerations about the evolution of metro area networks from SONET rings, to transparent wavelength‐routed WDM rings. We also describe the major transport impairments that limit the performance of transparent WDM metropolitan area networks and we present the characteristics of metro‐optimized optical amplifiers, fibers and optical add/drop multiplexers. Finally, we discuss recent research results that demonstrate that a properly engineered system utilizing application‐optimized components and fiber will enable the buildup of cost‐effective metro‐optimized WDM all‐optical networks.
H
uffman Coding
Authors: Yang En‐hui , He Da‐ke
Published: November 2003

The past 25 years have witnessed widespread applications of Huffman coding. In this article, the theme of Huffman coding is thoroughly discussed. The concepts of uniquely decodable codes and prefix codes are reviewed. The Huffman coding problem is defined. The Huffman coding algorithm, the adaptive Huffman coding algorithm, Golomb codes, and Gallager‐Voorhis codes are described in detail. Their performance is analyzed theoretically. Applications of Huffman coding are also mentioned.
Digital Optical Correlation for Fiberoptic Communication Systems
Authors: McGeehan John E. , Hauer Michelle C. , Willner Alan E.
Published: November 2003

There is increasing interest in performing many key signal processing functions in the optical domain. Optical correlation, or matched filtering, of digital signals is one such key function that is used to compare a given bit pattern with one that is ‘stored’ in an optical correlator. The current and potential applications of digital optical correlators are introduced and the process by which many optical correlators operate is explained in detail. In addition, a number of specific optical correlator designs are presented and explored in greater depth. Significant limitations and implementation challenges as well as potential solutions are also discussed.
Optical Crossconnects
Authors: Fan Li
Published: November 2003

Optical network provides enormous bandwidth for the increasing information traffic. It will relieve potential capacity bottlenecks, reduce hardware complexity and costs, and make it easier for carriers to deploy future developments. Optical crossconnects are one of the key elements to deliver and manage this optical layer for rapid provision, routing and network monitoring. Silicon‐based optical MEMS have shown to be the technology of choice for low cost and scalable optical crossconnects because they allow mass manufacturing of highly accurate miniaturized parts and use materials with excellent mechanical and electrical properties.
Economics
Authors: Reisman Harold
Published: November 2003

Introduction

Discovery

Development and Scale‐Up

Bioactivity and Clinical Issues

Manufacturing

Validation and Regulatory Issues

Regulatory Issues

Payment and Compensation

Bibliography

Additional Reading
Methanotrophs
Authors: McDonald Ian R. , Murrell J. Colin
Published: November 2003

Introduction

Physiology and Biochemistry of Methanotrophs

Genetics of Methanotrophs

Molecular Biology of the Methane Oxidation Pathway

Molecular Ecology of Methanotrophs

Functional Gene Probes for Methanotrophs

Biotechnology

Acknowledgments

Bibliography
Osmotic Stress, Secretion Rate
Authors: Ryu Joon Soo , Lee Gyun Min
Published: November 2003

Introduction

Osmolality

Medium Osmolality

Effect of Osmotic Pressure on Hybridoma Cell Growth and Antibody Production

Enhanced Specific Antibody Secretion Rate of Hybridomas Resulting from Hyperosmotic Pressure Is Cell‐Line Specific

Explanation for Enhancedat Elevated Osmolality

Application of Hyperosmotic Pressure to Antibody Production Processes

Application of Hypo‐osmotic Pressure to Antibody Production Processes

Bibliography
Herbicides, Inhibiting 4‐Hydroxyphenylpyruvate Dioxygenase (HPPD)
Authors: Little J. P. , Pallett Ken E.
Published: November 2003

4‐Hydroxyphenyl pyruvate dioxygenase (HPPD) is a recently identified herbicide target site. There are currently seven known herbicides that inhibit this target; five commercialized: sulcotrione, isoxaflutole, benzofenap, pyrazolynate, and pyrazoxyfen, and two in the process of being commercialized: mesotrione and benzobicyclon. These herbicides can be classed within three families of 4‐benzoyl‐cyclic aryl or heteroaryl compounds: the benzoyl‐isoxazoles, the benzoyl‐cyclohexanediones, and the benzoyl‐hydroxypyrazoles. As enzymes inhibitors, all share or can give rise to a diketone pharmacophore within their structure. All of these herbicides produce characteristic bleaching symptoms in susceptible species due to the consequences of HPPD inhibition. HPPD catalyzes a complex reaction in which the ketoacid of tyrosine, namely, hydroxyphenylpyruvate (HPPA) is oxidized, decarboxylated, and then rearranged to give 2,5‐dihydroxyphenylacetic acid, or homogentisic acid (HGA). HGA is the precursor of plastoquinone and tocopherols, and the former is a cofactor of phytoene desaturase. This enzyme is key in the biosynthesis of carotenoids, inhibition of which leads to the bleaching symptoms due to the reduction of photosynthetic pigment (chlorophylls and carotenoids) and chloroplast development.

The structure and available physicochemical data, toxicology and ecotoxicology data, of these bleaching herbicides is presented, together with a more detailed review of each compound.
Acetylcholine Receptors
Authors: Jewess Philip J.
Published: November 2003

Acetylcholine receptors are protein receptors present on the post‐synaptic membrane in the cholinergic nervous system. They specifically bind the neurotransmitter acetylcholine. Upon binding, acetylcholine induces a conformational change that stimulates the opening of cation channels in the nerve membrane, either directly (the nicotinic receptor) or indirectly (the muscarinic receptor), thus, propagating the nerve impulse. The nicotinic acetylcholine receptor (nAChR) is the target for the neonicotinoid insecticides exemplified by imidacloprid, nicotine, the microbial natural product spinosad and insecticides such as cartap based on nereistoxin isolated from a marine worm. The nAChR is one representative of a superfamily of ligand‐gated ion‐channel receptors having a common evolutionary origin, other examples of which are the glycine, γ‐amino butyric acid, glutamate, and 5‐hydroxytryptamine receptors. Typically, the nAChR is a transmembrane protein consisting of five subunits of four different types round a central core, which comprises the ion channel through which cations are allowed to pass from one side of the membrane to the other. Two subunits (designated alpha) are responsible for binding acetylcholine. The neonicotinoids act as both agonists in mimicking the action of acetylcholine and antagonists in blocking its action. This disrupts the working of the nervous system and is responsible for the insecticides' toxicity.
Animal Health Products
Authors: Reeves P. T.
Published: November 2003

A vast range of veterinary chemical products are used in the animal health sector. Those that control external parasites (ectoparasites) on domestic animals are known as ectoparasiticides and comprise two major groups—pesticides and systemic insecticides/acaricides. Ectoparasites of companion animals are a major cause of dermatologic problems in animals and act as vectors for various pathogens. Ectoparasites cause production losses in food‐producing animals that incur enormous costs to the livestock industry. The manifestations of ectoparasites on food‐producing animals include anemia; reduced production of meat, milk, and eggs; reduced quality and quantity of fleece; damage to hides (cattle grubs and cockle of sheep pelts from lice infestations); hypersensitivity reactions (to the itchmitePsorergates ovisof sheep); transmission of animal diseases (pinkeye of cattle, encephalitis of horses, anaplasmosis of cattle); and decreased resistance to other diseases. Presently, chemical treatment applied prophylactically, strategically, or tactically remains the main option for ectoparasite control.
Avian Repellants
Authors: Avery Michael L.
Published: November 2003

Although there are numerous potential applications for avian repellants, such compounds are not the answer to every crop damage situation. Understanding the specifics of bird‐crop interaction is essential to successful use of chemical bird repellants. However, even the most successful repellant will not eliminate bird damage. The only way to accomplish this is to employ netting or some other means of exclusion. Repellants are tools or methods that are best viewed as components of integrated management plans, rather than as solutions by themselves.
Capillary Electrophoresis
Authors: Safarpour Hudan , Asiaie Reza
Published: November 2003

Since its first commercial introduction in the late 1980s, capillary electrophoresis has rapidly and continuously grown as an invaluable technique to address and resolve challenging issues. This has placed it on a platform complementary to liquid chromatography. Capillary electrophoresis has been employed in the separation of a broad range of polar as well as charged and neutral analytes at relatively low levels. The driving force behind this tremendous volume of research lies in the sensitivity, robustness, and versatility of capillary electrophoresis techniques. In addition, the ever more stringent regulatory requirements have further catalyzed this movement.
Chitin Biosynthesis Inhibitors
Authors: Jewess P. J.
Published: November 2003

Chitin biosynthesis inhibitors have significant effect on athropods, mollusks, annelid worms, coelenterates, the eggs of nematodes, and certain fungi. Consequently, they are not expected to have much of an effect on mammals, birds, and plants, which has limited their commercial success. Two groups of insecticides that interfere with chitin synthesis have been discovered by random screening. These are the benzolyureas and the thiadiazinone compound buprofezin.
Chemical Properties Estimation
Authors: Boethling Robert S. , Howard Philip H. , Meylan William M.
Published: November 2003

This article addresses the estimation of chemical properties that determine the environmental behavior of agrochemicals and ultimately the exposure of humans and other organisms to these substances. Chemical properties frequently used in environmental assessment include melting temperature, boiling temperature, vapor pressure,n‐octanol/water partition coefficient, water solubility, acid or base dissociation constant, Henry's Law, and bioconcentration/bioaccumulation factor for aquatic organisms. Also, bioaccumulation from air to vegetation and sorption to aerosols are emerging as important determinants of environmental fate.
F
ood
Q
uality
P
rotection
A
ct of 1996
Authors: Bailey Joseph E.
Published: November 2003

No prior legislation has had as profound an effect on pesticide regulation as has the Food Quality Protection Act of 1996 (FQPA). Created as an amendment to both the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) and the Federal Food, Drug and Cosmetic Act, the implementation of FQPA initiated many improvements in the processes of pesticide regulation. For instance, the FQPA has helped ensure that the public is more protected from potential risks from pesticide exposure than was ensured by previous legislation. Risk‐assessment science and methodologies, in particular, have advanced significantly since the passage of the FQPA. Therefore, the public is assured that the food supply of this nation will be safer as a result of the FQPA and that the nation's infants and children are better protected because of this important legislation.
Fungicides, an Overview
Authors: Brent Keith J.
Published: November 2003

This article is an introduction to the large and diverse range of chemicals that are used to control fungal diseases of plants, and which are considered in greater detail in subsequent articles.

The history of fungicide discovery and use, from ancient times up to the present, is outlined. There has been an evolutionary trend towards fungicides of higher potency with correspondingly lower application rates. This has been accompanied by achievement of greater specificity of action against target organisms, conferring a greater margin of safety to crops, human health, and environment and often permitting systemic movement within treated plants, but unfortunately bearing a greater risk of development of resistance.

Advances in genetics are likely to increase greatly the range of disease‐resistant crop varieties. Biological control agents may come into use in some situations, and the use of husbandry methods that decrease disease pressures is increasing. Fungicides, however, will remain a major component of crop disease management for decades to come.

There is a vital need for continued discovery and development of new fungicides. This is not only to provide even more effective and safe products but also to delay, avoid, or overcome resistance build‐up by increasing the biochemical diversity of treatment programs and by controlling resistant populations that have already arisen against existing products.

It is equally important to secure the most profitable, durable, and safe performance, through precise application of fungicides in time and space, and through using them within integrated disease management programs that combine the use of a range of chemical and nonchemical countermeasures.
Fungicides, Anilopyrimidines
Authors: Leroux Pierre
Published: November 2003

The anilinopyrimidine fungicides have very similar structures, and they only differ by their substituents in the 4 position of the pyrimidine ring. They are mainly effective against Ascomycetes (e.g.,Alternaria,Botrytis,Monilinia,Venturia); cyprodinil exhibits the widest spectrum of activity. Under field conditions, the anilinopyrimidines have good protective and residual activities against fungal pathogens; some curative effects can also be recorded. Their precise mode of action is not yet known; they can affect the biosynthesis of methionine and prevent fungal secretions of hydrolytic enzymes involved in the infection process of fungi. Their metabolism occurs via the cleavage of the anilino‐pyrimidine linkage and hydroxylation of the alkyl, the pyrimidinyl, or the phenyl moieties.
Fungicides, Inhibitors of Mitochondrial Energy Production
Authors: Orth Ann B. , Kuhn Paul J. , Schmitt Mark R.
Published: November 2003

Inhibitors of mitochondrial energy metabolism and production of adenosine triphosphate (ATP) have been and continue to be highly effective and commercially successfully fungicides. Disruption of this essential cellular function is achieved both by specific interactions with proteins involved in electron transport functions, as well as nonspecific disruption of the mitochondrial membrane's ability to utilize an electrochemical proton gradient to drive ATP synthesis. Given the diversity of respiratory targets susceptible to inhibition that have resulted in both broad‐ and narrow‐spectrum fungicides, it is very likely that additional effective respiration targets that will be identified in the future. Mitochondrial respiration likely will remain a valuable target for identifying new, safe, and effective means to control fungal diseases.
Fungicides, Phenylpyrroles
Authors: Pillonel Ch , Knauf‐beiter G. , Steinemann A.
Published: November 2003

Fenpiclonil and fludioxonil are two phenylpyrrole fungicides related to pyrrolnitrin, a natural antibiotic first isolated fromPseudomonas pyrrocinia. Both fungicides have been reported either as foliar fungicides or as seed treatment as effective for disease management on fruits, vegetables, maize, potato and cereals. They are active on a wide range of fungi belonging to the generaMonilia,Gibberella,Botryotinia,Venturia,Sclerotinia,Fusarium,Tanatephorus, andAlternaria.

The site of biological activity, at the surface of the leaves after foliar application and at the outside surface of the seed after seed treatment, accounts for the strong protective activity of fenpiclonil and fludioxonil. Biochemical studies revealed that the protein kinase PK‐III, potentially involved in the osmoregulation pathway, is the target of phenylpyrrole fungicides. A cascade of events has been postulated which originates in the inhibition of PK‐III and leads to the accumulation of polyols and cell death.
Herbicides, Identification of Biologically Active Materials
Authors: Weimer Monte R. , Clifford Gerwick B.
Published: November 2003

The approaches and tools for herbicide lead generation and optimization are increasingly sophisticated. Inputs to screens derived from traditional chemistry, natural products, or combinatorial chemistry are testedin vivoagainst plants, orin vitroagainst a target enzyme or receptor. In both cases, high throughput capacity is made possible by automated sample handling and data tracking. Specificin vitrotargets may be identified and validated by chemical or genetic means. Increasingly, an inhibitor of a target may be designed with the aid of detailed biochemical and computational tools. If the target compound is active, it will be advanced in successive levels of whole plant testing under conditions that increasingly reflect the actual performance needs of the new herbicide. Detailed studies of uptake, translocation, metabolism in the plant, or partitioning in the soil may be used to understand the barriers to activity delivery and guide the optimization effort. Further, activity on nontarget organisms and persistence in the environment are assessed to ensure the lead optimization program is directed toward discovery of products that are safe to the environment and the end user. Although increasingly sophisticated technical tools provide high quality data to help direct decision making, it is the curiosity and initiative of the discovery scientist that is ultimately responsible for a herbicide product breakthrough.
Macropore and Preferential Flow
Authors: Jarvis Nicholas
Published: November 2003

Until recently, the prevailing conceptual model of water infiltration into soils was based on the idea that “new” incoming water displaced existing “old” water uniformly, with water moving downward in the soil profile as a broad and well‐defined “wetting front.” Similarly, the prevailing view of agrochemical transport was that leaching took place as a chromatographic process, with the chemical as fully exposed to adsorption sites in undisturbed field soils as it would be both in laboratory batch experiments on water–slurry mixtures, and in column leaching experiments on repacked soils. The idea that water flow and chemical transport normally takes place as a uniform displacement process in soils has now been abandoned, and it has been replaced by an understanding that the heterogeneity of undisturbed soils in the field often leads to markedly nonuniform patterns of water flow and agrochemical displacement.
Pesticide Adjuvants
Authors: Richard J. , Thacker M.
Published: November 2003

Pesticide adjuvants are chemicals that are added to pesticide formulations in order to enhance the effectiveness of the active ingredient. Adjuvants are not intended to be pesticidal. For legislative purposes, the government of the United Kingdom defines adjuvants as “Any substance, other than water, without significant pesticidal properties, which enhances or is intended to enhance, the effectiveness of a pesticide when it is added to the pesticide.” The aim of this review article is to provide the reader with an introduction to pesticide adjuvants.
Pesticide Formulations
Authors: Woods Thomas S.
Published: November 2003

The science of crop protection product formulations has made major advances in recent years. In fact, the old idea that the discipline of formulations is more an art than a science has long been overshadowed by the scientific depth of the underpinning technology. This article will provide a general overview of the great variety of product forms available to the formulation scientist for designing a crop protection product that is acceptable in the world of modern agriculture.
Herbicides, Protoporphyrinogen Oxidase Inhibitors
Authors: Dayan Franck E. , Duke Stephen O.
Published: November 2003

Protox inhibitors account for 11% of the 270 herbicides registered for use in the US. Most of the Protox inhibitors are being marketed for use with soybean. The most recent data from a survey of 11 US states showed that Protox inhibitors were applied to 14% of the 26 million ha. that were planted with soybean. In contrast, 62% of the cultivated area received applications of glyphosate, highlighting the rate of adoption of glyphosate‐resistant soybean technology. A total of 0.6 million kg of Protox inhibitors were applied to soybean fields, accounting for 2% of the total amount of herbicides applied. In contrast, glyphosate accounted for 56% of all the herbicides applied by weight to soybean fields, demonstrating the impact that genetically engineered herbicide‐resistant soybean has on traditional agricultural practices.
Propesticides
Authors: Ujváry István
Published: November 2003

For most pesticides, the chemically intact active ingredient of the marketed formulation is responsible for the biological activity at the molecular level. In some cases, however, the actual substance responsible for the desired effect is a chemically transformed product of the pesticide that was applied in the field. Such transformations are activation processes usually involving enzymes characteristic to the target organism, but the conversion can occur in the environment and by nonenzymatic processes. The expected biological activity is typically observable only in studies with whole organisms or in the field. The increase in selective toxicity for the target and nontarget organisms results from differential uptake, translocation, and metabolism of such pesticide precursors or propesticides. Selectivity, thus, increased safety, of neurotoxic insecticides can be achieved by incorporation of specific sulfur functionalities into the parent compound. Differential phytotoxicity of several classes of herbicides is based on selective oxidative and hydrolytic degradations in various plants. Hydrolysis and reduction are involved in the bioactivation of several profungicides. Bioactivation processes are also important for some organic and inorganic rodenticides. Although in many cases the propesticide nature of a compound was discovered during structure optimization and metabolism studies, there are several examples where incorporation of metabolically labile moieties into an insufficiently selective lead compound was crucial for commercial development.
QSAR
Authors: Plummer Ernest L.
Published: November 2003

The speed, intensity, and duration of the biological response of an organism to a chemical compound is directly related to the structure of the compound. For decades, scientists have attempted to understand exactly what this relationship is so that better compounds can be designed. In 1964, with the publication of two seminal articles outlining a new paradigm call Quantitative Structure‐Activity Relationships or QSAR, pesticide and drug discovery moved from a process driven by observation and analogy to one driven by statistics and quantitative models. In the late twentieth century, high throughput screening and combinatorial chemistry have moved the design process to one of volume and probability. The success of this approach is still dependent on the same principles as those developed in 1964.
Solid Phase Extraction
Authors: Noland Patrick
Published: November 2003

Solid phase extraction is the process whereby target analytes in a solution are separated from a matrix using a fixed bed of a solid material. It is a widely used alternative or adjunct to liquid–liquid extraction. Historically, solid phase extraction is an ancient technology. Sand/charcoal filters for water probably represent some of the first solid phase systems. Most solid phase extraction systems today are adaptations of conventional column chromatography. Therefore, modern solid phase extraction is a powerful selective tool for effective separation.