bluuebunny/crossref_metadata_2025 huggingface dataset:
IPTelephony
Authors: Chapman Caesar Matthew , Ghosal Dipak
Published: November 2003

IP telephony networks have emerged as an alternative to the public switched telephone network (PSTN) for providing voice and video transport services. IP telephony systems are designed to transmit packetized voice using the Internet Protocol (IP), allowing providers the ability to bypass the PSTN and offer advanced intelligent network (AIN) services. In this article we present a detailed survey of various issues in IP telephony networks. We discuss how open protocols and architectural entities are designed, as well as how they are used in common deployment scenarios. We outline several issues of packet audio over IP networks and show how the efficient design of IP telephony network elements can significantly improve the received audio quality. IP networks may require advanced resource management and pricing strategies to offer superior quality of service (QoS) under conditions of high demand. We conclude this article with a discussion of security and regulatory issues in IP telephony networks.
Microstrip Patch Arrays
Authors: Waterhouse R. B. , Ghorbani K.
Published: November 2003

In this paper a summary of microstrip patch array technology is presented. A variety of fixed beam linear and planar microstrip patch arrays, including design cases, as well as phased arrays incorporating this form of printed antenna are examined. It is shown that microstrip patches are a very versatile style of antenna and can be readily integrated into a multitude of arrays. The complexity of these arrays depends on the degree of control of the radiation performance that is required. Microstrip patch antennas are a cost effective solution to many wireless communication applications and will continue to be utilized in these systems for many years to come.
Antenna Arrays
Authors: Sahalos John N.
Published: November 2003

An attempt is made to describe antenna arrays. The fundamental theory of the array factor and the appropriate indices are described. Linear arrays with uniform binomial and Chebyshev excitations are presented. Planar, rectangular and circular as well as 3‐D and conformal arrays are outlined. Pattern synthesis for uniform and Chebyshev arrays is explained. Array design procedures by sampling or by root matching of Taylor and Bayliss line sources are analyzed. In the pattern synthesis Fourier transform, Woodward‐Lawson (WL) and orthogonal methods are included. Matrix methods, simplex and gradient methods simulated annealing and genetic algorithms are formalized for the design of antenna arrays systems. Antenna arrays combined with signal processing, known as smart antennas, are also discussed. Mutual coupling of the array elements is presented and array feeds are shown for various antenna arrays. Applications and examples as well as appropriate references are included in most of the above topics.
Digital Audiobroadcasting
Authors: Bauer Rainer
Published: November 2003

These days, the use of digital communication techniques is becoming more and more common. While wireline and mobile personal communication services have already taken the step from analog to digital, audio broadcasting is still at the beginning of the digital age. The first part of this article motivates the need for digital audio broadcasting (DAB) and summarizes the advantages of digital transmission compared to analog techniques. The second part sketches different approaches in digital audio broadcasting, both systems which are already in operation today and systems which are about to be introduced in the near future. Finally Eureka‐147 DAB, which has been adopted by many countries worldwide, is described in more detail as an example for an existing digital audio broadcasting system.
Antenna Modeling Techniques
Authors: Volakis John L. , Eibert Thomas F.
Published: November 2003

Antennas are the basic devices which transition an electronic signal within the wired network to an electromagnetic wave that travels through space for possible reception by a corresponding receiving system. They are consequently essential components of any wireless communication system, and the recent rapid growth in consumer wireless devices also resulted in high demand for new antennas satisfying a variety of specialized electrical performance (gain, bandwidth, radiation patterns, etc.) as well as structural and material requirements (size, shape, etc.). Computational techniques play an increasingly more significant role in the design of antennas for commercial as well as military applications and in this chapter we discuss the most popular frequency domain methods for antenna analysis. The standard integral equation and finite element methods are described along with hybrid techniques which combine finite element, integral and high frequency approaches for efficient analysis of antennas in isolation and in presence of the mounting platforms. Example simulations are also given to demonstrate the capability of recent analysis methods for narrowband(wire and patch) and broadband(spiral) antennas in isolations and on full‐scale aircraft.
Ultrawideband Radio
Authors: Siwiak Kazimierz (Kai) , Huckabee Laura L.
Published: November 2003

Ultra WideBand (UWB) signaling is a modern wireless technique whereby very short baseband signals are transmitted and received without a radio frequency (RF) carrier. This technique re‐uses previously allocated RF bands by spreading the impulse energy thinly in a wide spectrum, thus rendering signals imperceptible in the noise floor of conventional narrow band receivers. There are several methods of generating and radiating UWB signals, including a “low duty cycle UWB” implemented as Time‐Modulated UWB™ (TM‐UWB™), and a high duty cycle “direct sequence phase coded UWB” (DS‐UWB). Unique ways of coding and positioning the impulses, as in Transmitted‐Reference Delay hopped UWB (TRD‐UWB), can result in the efficient raking of the indoor multipath energy. Here, the technological basics and performance of time position coded impulse UWB, the direct sequence coded UWB, and the transmitted reference UWB approaches are explained. Applications of UWB devices are presented and potential uses of UWB are described. Short pulse, low power techniques have enabled practical through‐the‐wall radars, centimeter precision 3‐D positioning, and communications capabilities at the high data rates, all with exceptional spatial capacities.
Digital Phase Modulation and Demodulation
Authors: Xiong Fuqin
Published: November 2003

Digital phase modulation is a class of power‐ and bandwidth‐efficient modulations widely used in telecommunications. In this article, the reader will first be introduced to the general concept of digital phase modulation, and the notions of bandwidth and power efficiency. The commonly used class of digital phase modulation schemes, that is,
M
‐ary phase shift keying (MPSK), are described in detail. Their signal waveform expressions, signal constellations, and power spectral densities (PSDs) are presented. The block diagrams of the modulator and the optimal coherent demodulator are presented and explained. The symbol and bit error rate (BER) of the demodulator is derived and symbol error probability graphs are given. Widely used binary PSK (BPSK) and quaternary PSK (QPSK) are treated as special cases of MPSK. Next, differential PSK schemes are introduced, which are particularly useful in wireless fading channels. Their symbol error probability expressions and graphs are presented. At the end, two important phase modulation variations, namely, offset QPSK (OQPSK) and π/4‐DQPSK, and the advanced continuous‐phase modulation (CPM), including multi‐
h
CPM, are briefly introduced.
Adaptive Antenna Arrays
Authors: Kim Kyungjung , Sarkar Tapan K. , Palma Magdalena Salazar
Published: November 2003

Conventional adaptive techniques generally deal with antenna arrays that consist of omni directional isotropic radiating elements uniformly spaced. When the uniformity in the spacing is relaxed one then needs multiple snapshots in estimating the complex amplitude of the signal of interest (SOI) arriving from a known direction in the presence of multipaths, clutter and thermal noise. Usually a statistical methodology is used for the adaptive process which makes it difficult to incorporate the various electromagnetic effects like mutual coupling between the elements, presence of near field scatterers and so on and obtain a real time solution in a dynamic environment where the interference scenario may change from snap shot to snap shot.

The object of this article is to present an adaptive methodology that can not only deal with realistic antenna elements operating in a real environment but can also handle the effects of mutual coupling between the antenna elements. In addition, one can incorporate in this methodology the effects of near field scatterers and use of dissimilar antenna elements in the array. The analysis is carried out by using a dynamic electromagnetic analysis tool. In addition, an array transformation technique is used to mitigate the various complex electromagnetic effects in a non‐uniformity spaced nonplanar array in the presence of the mutual coupling and transform the problem to that of a virtual linear array of uniformly spaced omni directional isotropic point radiators operating in free space. The preprocessed data from the interpolated virtual array is analyzed using a direct data domain least squares approach utilizing a single snapshot of data to estimate the strength of the signal of interest arriving from a known direction in the presence of coherent strong jammers, clutter and thermal noise. In addition, this methodology is quite amenable to real time processing.

Thus this adaptive methodology is split into two parts. First one uses an electromagnetic analysis tool in conjunction with an interpolation algorithm to transform the induced voltages in the real antenna elements due to the presence of mutual coupling and near field scatterers to that of a virtual array containing isotropic omni directional point radiators. Then a direct data domain least square method is applied to the pre processed data to obtain the desired signal strength in the presence of strong interferers, clutter and thermal noise. Numerical results are represented to illustrate the efficiency and accuracy of this method. No attempt has been made to cite the earlier references; the bibliography provides a list where supplemental information may be available.
ALOHA
Protocols
Authors: Metzner John J.
Published: November 2003

ALOHA protocols deal with largely uncoordinated packet transmissions by multiple senders, where the senders all learn of success or collision via a common feedback channel. Slotted ALOHA involves sending fixed‐size packets in random time slots. Unslotted ALOHA involves sending variable‐size packets at any starting time. The article provides a brief analysis of ALOHA efficiency and stability, and explains some modifications to ALOHA that improve these properties. The improvements include collision resolution algorithms, reservation ALOHA, multichannel ALOHA, capture ALOHA, multibase ALOHA, and nonbinary ALOHA. Also discussed is the use of ALOHA with a time constraint and CDMA‐related spread ALOHA.
Wideband
CDMA
in Third‐Generation Cellular Communication Systems
Authors: Mark Jon W. , Zhu Shihua
Published: November 2003

ITU, the international wireless standards body, has adopted both IMT‐2000 (European) and CDMA‐2000 (North American) as multiple access technologies for 3G air interface. IMT‐2000 is direct‐sequence wideband CDMA, while CDMA‐2000 is multi‐carrier CDMA. Of relevance are the transmission and reception issues in the physical layer and resource management issues in the link layer. This article describes and discusses the IMT‐2000 network architecture and the associated signaling mechanisms as a 3G air interface for service support using wideband DS‐CDMA as multiple access strategy. To combat channel impairments, IMT‐2000 uses a combination of channel coding and spectrum spreading. To circumvent the need for stringent synchronization, IMT‐2000 uses two‐layer spreading: orthogonal codes for channelization in the first layer and non‐orthogonal codes for scrambling in the second layer. For the downlink, every base station in the cellular system uses the same set of Hadamard codes or orthogonal variable spreading factor codes as its channelization codes, while each cell uses a cell‐specific Gold code as its scramble code.
Scalar and Vector Quantization
Authors: Kaukoranta Timo
Published: November 2003

Scalar quantization is a basic technique for analog‐to‐digital signal transformation. It has an extensive theoretical background in addition to the practical usefulness. Vector quantization offers very good possibilities for lossy signal compression. The method has the great advance that its decoding runs extremely fast. Unfortunately, it includes other complexity problems such as the construction of the codebook, the search of the nearest reproduction vector, and the storage of the codebook. This work describes the basic properties of quantization and introduces several vector quantization structures briefly. Most common methods for codebook construction are described also.
Iterative Detection Methods For Multiuser Direct‐SequenceCDMASystems
Authors: Rasmussen Lars K.
Published: November 2003

In this paper, the fundamental principles behind iterative multiuser detection are presented. Such strategies are also known as iterative interference cancellation. Cancellation structures can be constructed in a systematic manner, using an interference cancellation unit. The inter‐connection of such units decides the specific cancellation strategy, whether cancellation is done serially, in parallel or as a combination of the two. The unit itself is characterized by a tentative decision function. In this paper we particularly focus on four different tentative decision functions and provide theoretical background. The considered decision functions are the linear, hard, clipped linear, and hyperbolic tangent functions, respectively. The concept of weighted cancellation is also presented and explained. Selected numerical examples are included to illustrate the characteristic convergence behavior and bit error rate performance.
Geosynchronous Satellite Communications
Authors: Lee Lin‐Nan , Karimullah Khalid
Published: November 2003

In this article, we discuss the development of the geosynchronous satellite concept. We explore frequency bands and orbital slots, satellite antenna beam patterns, transmission techniques, multiple‐access techniques and onboard processing. Also included is a discussion of satellite communications system equipment. We conclude with a section on GEO satellite system link budgets.
Signature Sequences forCDMACommunications
Authors: Ottosson Tony , Ström Erik , Svensson Arne
Published: November 2003

Code‐division multiple accessis a method allowing several users to share a common physical channel. Different users use differentsignature sequencesfor their messages. The signature sequences and the channel determine theinterferencebetween different users in the receiver and the performance of the synchronization method used, and thus the signature sequences represent an important part of the multiple access method. In this article, an overview of code‐division multiple access is presented and properties of signature sequences are discussed. Some common classes of signature sequences are described and their properties are summarized. Some remarks on the difficulty in designing signature sequences are also given at the end.
Spread Spectrum Signals for Digital Communications
Authors: Proakis John G.
Published: November 2003

Spread spectrum signals is a class of signals that were designed primarily for use in digital communication systems to overcome either intentional or unintentional interference. We begin by illustrating the basic elements of a spread spectrum digital communication system. Next, we consider the transmission of a binary information sequence by means of binary PSK. Later, we discuss frequency‐hopped (FH) spread spectrum. Finally, we close with a section on commercial spread spectrum systems.
cdma
2000
Authors: Corazza Giovanni Emanuele , Vanelli‐Coralli Alessandro
Published: November 2003

cdma2000 is the multicarrier wideband code‐division multiple access (CDMA) radio interface included in the International Mobile Telecommunications‐2000 (IMT‐2000) family of standards. The cdma2000 radio interface has been developed within the Third Generation Partnership Project 2 (3GPP2). The multicarrier structure pertains strictly to the forward link baseline configuration, where three adjacent direct‐sequence spread RF carriers are used, while in the reverse link a single direct‐spread RF carrier is adopted. cdma2000 is backward compatible with the TIA/EIA‐IS‐95‐B standard, also known as cdmaOne. The article introduces the role of cdma2000 within IMT‐2000, the 3GPP2 organization, and the general characteristics of the standard. It then describes in detail the air interface protocol architecture, in terms of physical layer, medium access control layer, link access control layer, upper signaling layer, and system procedures. Finally, the key features of the cdma2000, also in comparison with other 3G CDMA air interfaces, are summarized.
Wireless Sensor Networks
Authors: Megerian Seapahn , Potkonjak Miodrag
Published: November 2003

Sensor networks consist of a set of sensor nodes, each equipped with one or more sensors, communication subsystems, storage and processing resources, and in some cases actuators. The sensors in a node observe phenomena such as thermal, optic, acoustic, seismic, and acceleration events, while the processing and other components analyze the raw data and formulate answers to specific user requests. Recent advances in technology have paved the way for the design and implementation of new generations of sensor network nodes, packaged in very small and inexpensive form factors with sophisticated computation and wireless communication abilities. Although still at infancy, these new classes of sensor networks, generally referred to as wireless sensor networks (WSN), show great promise and potential with applications ranging in areas that have already been addressed, to domains never before imagined. In this article we provide an overview of this new and exciting field and a brief discussion on the factors pushing the recent flurry of sensor network related research and commercial undertakings. We also provide overview discussions on architectural design characteristics of such networks including physical components, software layers, and higher level services. At each step, we highlight special characteristics of WSNs and discuss why existing approaches and results from wireless communication networks are not necessarily suitable in WSN domains. We conclude by briefly summarizing the state of the art and the future research directions.
Wireless Application Protocol (
WAP
)
Authors: Andreadis Alessandro , Giambene Giovanni
Published: November 2003

The
Wireless Application Protocol
(WAP) is the result of the WAP Forum's efforts for allowing mobile users to access easily the Internet. WAP contains a lightweight protocol stack (based on the Internet one) well suited for the wireless scenario. It also includes an application environment for the development of user applications, allowing the delivery of information services to mobile phones. A review of the protocol stack and system architecture is provided here together with some aspects related to the tools to develop WAP applications.
Multimedia Over Digital Subscriber Lines
Authors: Zheng Haitao , Liu K. J. Ray
Published: November 2003

The purpose of the chapter is to examine multimedia communications systems in the context of joint source channel optimization. The key to the design of high‐performance multimedia communications systems is the ability to perform efficient resource allocation. The characteristics of source traffic raise a wider variety of channel design and configuration issues. The traffic generator should plan source traffic flow wisely to make intelligent use of channel resources. The channel designer should have the ability to adjust transmission design and configuration according to source traffic characteristics. In this chapter, we explore this joint design concept in ADSL by comparing two transmission architectures and their associated resource allocation procedures. The study indicates that the characteristics of both multimedia traffic and ADSL transmission channel can be jointly utilized to provide efficient resource usage.
Bandwidth Reduction Techniques for Video Services
Authors: da Fonseca Nelson L. S.
Published: November 2003

A single videostream requires a considerable amount of bandwidth. Considering a potential population of several million viewing households, the network bandwidth demand would be beyond the present‐day network capacity. Such a demand prevents the deployment of VoD on a large scale. In this paper, techniques for the reduction of the bandwidth demand of video services are presented. The techniques discussed here are: piggybacking, patching, batching, and periodic broadcasting.
Channel Tracking in Wireless Communication Systems
Authors: Bottomley Gregory E. , Arslan Hüseyin
Published: November 2003

Channel estimation is an integral part of standard adaptive receiver designs used in digital wireless communication systems. In this article, commonly used approaches to channel tracking are reviewed, including both filtering and recursive approaches. These approaches are based on approximate models of how the channel response changes with time. Both reference‐assisted (pilot symbols, pilot channel) and data‐directed channel tracking are considered. Applications include second and third generation digital cellular communication systems, which employ time‐division multiple‐access (TDMA) or direct‐sequence code‐division multiple‐access (DS‐CDMA).
Services Via Mobility Portals
Authors: Ralph Daniel , Shephard Chris
Published: November 2003

This paper examines the importance of mobility portal services and the technologies that will be essential in delivering content over next generation network technologies. Finally, proposed developments are discussed which will extend the functionality available at the mobile portal through the improvements in terminal capability and development of protocols for delivery of content over a mobile network.
Optical Transport System Engineering
Authors: Cvijetic Milorad
Published: November 2003

The fundamentals of optical transport system engineering are introduced in this article. Optical transport system engineering is related to the physical layer of an optical network, and takes into account the optical signal propagation length, characteristics of optical elements used (optical fibers, lasers, optical amplifiers, photodiodes, etc.), modulation bit rate, networking impact and transmission requirements. The article involves accounting for different impairments that degrade and compromise the integrity of an optical signal on its way from the source (semiconductor laser) on through photodetection by photodiode, and to the decision point, where it is recovered from corruptive additives (noise, crosstalk, and interference.)
Constrained Coding Techniques for Data Storage
Authors: Coene Wim M. J. , Hollmann Henk D. L.
Published: November 2003

Modulation codes such as runlength‐limited codes have been widely employed in magnetic and optical data storage systems. We review the main techniques involved in the design and use of these codes: the maximal code rate or capacity, graphical presentations of constraints, encoders and decoders, and code construction methods such as the ACH state‐splitting algorithm. We conclude this survey by discussing some recent developments and research trends.
Interference Modeling in Wireless Communications
Authors: Yang Xueshi , Petropulu Athina P.
Published: November 2003

In wireless communication networks, signal reception is often corrupted by interference from other sources that share the same propagation medium. Knowledge of the statistics of interference is important in achieving optimum signal detection and estimation. We here discuss statistical‐physical models for modeling interference. The interesting feature of these models is that they are non‐Gaussian, and in certain cases are heavy‐tail distributed. The latter property introduces several challenges in the analysis of interference, since heavy‐tail processes lack second‐order statistics. A introduction on heavy‐tail processes is also provided.
Interleavers for Serial and Parallel Concatenated (
TURBO
) Codes
Authors: Duman Tolga M.
Published: November 2003

Along with convolutional codes, interleavers constitute building blocks of serial and parallel concatenated convolutional (turbo) codes. In this paper, we examine properties of interleavers, in particular, we discuss the “interleaver gain”, that is, the effect of the interleaver length on the bit error probability of the turbo code over an additive white Gaussian noise (AWGN) channel. We review several basic interleaver design approaches, and present some of the most promising interleaver design algorithms in detail together with examples. Although there is significant literature on interleaver design for parallel concatenated convolutional codes, there are only a few results available for serial concatenation. Therefore, while important results on serial concatenation are reviewed, most of the article is devoted for parallel concatenation.
Golay Complementary Sequences
Authors: Parker Matthew G. , Paterson Kenneth G. , Tellambura Chintha
Published: November 2003

This chapter gives an up‐to‐date review of Complementary Sequences, first defined by Marcel Golay. The survey discusses correlation and spectral properties of the sequences aswell as describing applications. It also presents fundamental constructions for Complementary Sequences and Complementary Sets. Connections with orthogonal and Hadamard matrices are also elaborated.
Bit‐Interleaved Coded Modulation
Authors: Goeckel Dennis L.
Published: November 2003

Bit‐interleaved coded modulation (BICM), a recently introduced method for protecting against distortion during information transmission, has shown both theoretical and practical promise. In this article, the history of coded modulation is briefly reviewed to motivate the development of BICM. The encoder and various decoding methods of BICM are then discussed in detail, and performance curves are presented for BICM when a noniterative decoder is employed. These performance curves and other recent work demonstrate that BICM is a very appealing method of coded modulation for communication systems, particularly for operation over the communication channels typically encountered in wireless communication systems.
Golay Codes
Authors: Greferath Marcus
Published: November 2003

Golay Codes are well‐known and important codes which play a role both in the theory of algebraic coding and in its applications. This article is devoted to a discussion of the basics regarding these codes. We will touch issues like constructions, decoding and relations to finite geometry and lattices. The presentation finishes with a discussion of the role of Golay codes in ring‐linear coding theory.
Packet‐Rate Adaptive Receivers for Mobile Communications
Authors: Batalama Stella N.
Published: November 2003

In this chapter we consider the problem of designing short‐data‐record (packet‐rate) adaptive receivers for mobile communications. A complete adaptive antenna‐array DS‐CDMA receiver structure is developed and used as an illustration throughout our presentation. Receiver performance is measured in terms of output signal‐to‐interference‐plus‐noise‐ratio and bit‐error‐rate, as well as packet error rate and normalized packet throughput under slotted ALOHA accessing with or without forward error correction.
Communications for Intelligent Transportation Systems
Authors: Andrisano Oreste , Pasolini Gianni , Verdone Roberto , Nakagawa Masao
Published: November 2003

The paper presents an overview of the evolution of research in the field of communications for ITS (Intelligent Transportation Systems). After a brief description of the services aimed at improving safety and efficiency of road transport, a synthetic view of the past and current research activities is presented and the role of communication‐based systems for ITS service provision is discussed. Several examples of dedicated systems currently studied are presented, afterwards the attention is focused on the assessment of existing relevant standards in mobile communications to define and activate new ITS services. As far as dedicated solutions are concerned, the paper shows some results related to radars as well as 60 GHz and infrared communication systems. An example of ITS service provision by means of an already standardized system is given evaluating the feasibility of an Emergence Warning service based on GPRS (General Packet Radio Service); furthermore the performance of road‐to‐vehicle and target‐to‐vehicle communication, based on Bluetooth, is addressed by means of both an analytical and experimental approach.
Polarization Mode Dispersion Mitigation
Authors: Bülow Henning
Published: November 2003

With the increase of the channel bit rate to 10 Gbit/s and beyond, polarization mode dispersion (PMD) might become visible as a degrading property of the transmission link. To enable data transmission via high PMD fibers, various dynamically adapting PMD compensators have been proposed. The impact of PMD on a transmission system is discussed and solutions for compensators are explained which are based on optical processing of the distorted optical field or on electrical processing of the photo diode signal after detection in the receiver.
Signal Quality Monitoring in Optical Networks
Authors: Shake Ippei
Published: November 2003

Several approaches to signal quality monitoring in optical networks are introduced. In the section 2, conventional digital techniques (bit interleaved parity, digital wrapper and others) and relatively new approach (pseudo BER estimation using variable decision circuit) are shown. In the section 3, novel approaches using analog parameters (statistical method using histogram evaluation, optical SNR or other parameters monitor with spectrum measurement and pilot tone technique with sub‐carrier multiplexing) are presented.
Optical Transmitters, Receivers, and Noise
Authors: Winzer Peter J.
Published: November 2003

This article is designed to open up the field of optical modulation and reception on an introductory level by discussing a selection of optical modulation techniques currently viewed as being most promising. Further, high‐performance optical receiver structures and their noise properties are outlined, both for the fiber channel and for the free‐space channel. Basic receiver design rules as well as important performance trade‐offs are extracted. Frequently used concepts for quantifying receiver performance, such as receiver sensitivity, quantum limit, Q‐factor, and optical signal‐to‐noise ratio (OSNR) are explained.
Crystallization, Bulk, Macromolecules
Authors: de la Rosa Ana Paulina Barba , McPherson Alexander
Published: November 2003

Introduction

The Uniqueness of Macromolecular Crystals

Methods for Growth of Protein Crystals

Methods for Promoting Supersaturation

The Crystallization of Proteins by Variation of pH or Temperature

Bibliography
Lactones, Biocatalytic Synthesis
Authors: Sugai Takeshi , Ohta Hiromichi
Published: November 2003

Introduction

Hydrolysis of Ester Functionality of Corresponding Racemic Lactones

Lactonization of Hydroxy Acids and Their Derivatives

Reduction of Carbonyl Precursors

Oxidation of Diol Precursors

Baeyer–Villiger Type Oxidation of Ketones

Separation of Isomers by the Enzymatic Action on Other Functionalities That Are Appended to the Molecules

Approaches Based on the Biodegradation of Lipids and Aromatics

Preparation of Some Lactones of Special Interest

Conclusions

Acknowledgment

Bibliography
Bioassays: Phytotoxicity to Succeeding Crops
Authors: Pestemer Wilfried
Published: November 2003

Bioassays provide inexpensive and easy‐to‐handle methods for the determination of phytoxic compounds, mainly herbicides, in soil and water. Their advantages are their potential for detecting only phytotoxic isomers, quantifying residues, and determining possible recropping risks within the same bioassay procedure. Their main disadvantage is that mixtures of phytotoxic compounds cannot be separated and that samples with an unknown history usually cannot be analyzed properly. Nevertheless, bioassays may be used for the quantitative determination of residues and give results comparable to physical and chemical methods.
Amidine Insecticide/Acaricides
Authors: Hollingworth Robert
Published: November 2003

The amidines are a small class of insecticide/acaricides that share common structural and biological features and have the same mechanism of action. The group currently consists of the compounds amitraz, chlordimeform, and cymiazole. Under most circumstances, these compounds and their metabolites are biodegraded at a rate that ensures that they do not accumulate in the environment or in living organisms.
Fungicides, Quinoxyfen
Authors: Henry Matthew J.
Published: November 2003

Quinoxyfen is a new fungicide developed by Dow AgroSciences. It is a quinoline‐based fungicide also known by the codes of XDE‐795 or LY211795. Quinoxyfen is specifically active against powdery mildew pathogens of monocots and dicots. The stability of quinoxyfen in the soil has been shown to vary depending on soil type and source.
Herbicides, an Overview
Authors: Plimmer Jack R.
Published: November 2003

Herbicides are important for many reasons. Cultivation of plants for economic or ornamental purposes entails an incessant struggle against losses from pests. Weeds not only reduce yields by competing for sunlight, water, and nutrients, but they also reduce the quality of products and overgrow adjacent areas and bodies of water. Some of them actually produce phytotoxins (allelochemicals) that reduce crop growth. Uncontrolled weed infestations drastically reduce crop yields and decrease crop, turf, timber, and forage quality. The broadest definition of “herbicides” includes all agents that destroy or inhibit plant growth.
Herbicides, Alphabetical Classification
Authors: Plimmer Jack R.
Published: November 2003

Farmers, advisers, and researchers know which herbicides are best suited to combat specific resistant weeds. To support the use of herbicides suitable for resistance management, the enclosed classification of herbicides is proposed. The herbicides are classified alphabetically according to their target sites, modes of action, similarity of induced symptoms or chemical classes.
Herbicides, Imidazolinones
Authors: Shaner Dale
Published: November 2003

The imidazolinone herbicides represent a powerful tool for weed management. There are six different imidazolinone herbicides (imazamethabenz methyl, imazethapyr, imazamox, imazapic, imazapyr, and imazaquin) used in leguminous crops, cereals, forestry, non‐cropland, and on imidazolinone‐resistant maize, rice, canola, sunflower, and wheat. These herbicides share certain attributes such as low toxicity on animals, birds, fishes, and invertebrates, but they differ in their crop selectivity. Crop selectivity depends on the chemical structure of the imidazolinone. In this review, one can easily compare and contrast the different properties of the imidazolinones that affect their selectivity and environmental fate. The toxicological profile of each herbicide is presented as well as the weed spectrum for each compound. In addition, the degradation pathway for each herbicide in the soil and plants is shown.
Herbicides, Pyridine Carboxylate
Authors: Molin William T. , Vaughn Kevin C.
Published: November 2003

The pyridinecaboxylates, dithiopyr, and thiazopyr are a new class of mitotic inhibitor herbicides used for the control of grasses and small‐seeded broadleaf weeds in turf, rice, and oranges and grapefruits. Dithiopyr and thiazopyr are the commercial entries from a large patent estate and share the common characteristic of having bis‐pentafluoro alkyl substitutions at the 2′ and 6′ positions on a pyridine ring. The pyridineczrboxylates have high unit activity, low water solubility, and bind tightly to organic matter, properties that are similar to the dinitroaniline herbicides. The pyridinecarboxylates have low mammalian and avian toxicity, and they are rapidly metabolized and eliminated. Discovery and understanding of the enzyme systems responsible for pyridinecarboxylate metabolism has led to the isolation of the genes for these systems. Transformation of plants with these genes has resulted in plants tolerant to pyridinecarboxylates.
PhotosystemIEnergy Diverters
Authors: Vaughn Kevin
Published: November 2003

The photosystem (PS) I diverter herbicides include several of the oldest in the herbicide arsenal, introduced in the mid‐late 1950s by ICI (now Syngenta) and still commercially available. Because of this long‐term use, a sizeable literature exists on their use as herbicides, their biochemical effects on mammals and plants, and the development of herbicide‐resistant weed biotypes. Because of this voluminous literature, this review will cite mainly recent references, referring the reader to previous reviews for further details of the earlier literature.
USDA
‐
ARS
Pesticide Properties Database
Authors: Herner Albert E. , Acock Basil
Published: November 2003

The Agricultural Research Service Pesticide Properties Database (ARS‐PPD) has been developed to provide water quality modelers and managers with a list of the pesticide properties most important for predicting the potential of pesticides to move into ground and surface waters under a range of weather and soil conditions. The ARS‐PPD is a compendium of the chemical and physical properties of about 330 pesticides. The list includes pesticides currently registered with the U.S. Environmental Protection Agency as well as pesticides no longer in use.
Weed Species
Authors: Bryson Charles T.
Published: November 2003

Weeds are a major deterrent to agricultural and forest productivity and adversely effect urban, natural plant communities, and human and livestock health. Usually, the most troublesome weeds in an area originated somewhere else in the world. Weeds possess traits that give them biological, ecological, and reproductive advantages over non‐weedy plants. Of the 8000 or so weeds in the world, about 200 species are responsible for about 95% of the weed problems of food, feed, fiber, and livestock production. These and additional species cost billions of U.S. dollars in forestry and urban areas and threaten species diversity in natural communities worldwide. About 73% of the world's weeds are dicots (broadleaf weeds) and 25% are monocots (grasses, sedges, rushes, and other monocot groups), whereas the remaining 2% are peridiophytes (ferns and fern allies) and gymonsperms (conifers and conifer allies). An overview is provided for weeds, including a general definition, economic losses, spread, identification sources, population shifts, thresholds, competitive index, effects on tillage production systems, and major species of the world in agriculture, forestry, urban areas, and natural communities.
Insecticides, Mode of Action
Authors: Insecticide Resistance Action Committee
Published: November 2003

The following document was prepared by the Insecticide Resistance Action Committee. It was formed in 1984 to provide a coordinated crop protection industry response to the development of resistance in insect and mite pests. “The mission of IRAC is to develop resistance management strategies to enable growers to use crop production products in a way to maintain the efficacy. The organization is implementing comprehensive strategies to confront resistance.”
Aflatoxins and Aflatoxicoses
Authors: Shurtleff Malcolm
Published: November 2003

Aflatoxins are a group of polyketide metabolites produced mainly by stains of the fungus
Aspergillus flavus
and the closely related species
A. parasiticus
. The most biologically active aflatoxin is B1; it is considered the most potent naturally occurring carcinogen known. Aflatoxins have been shown to produce cancer in all species tested; epidemiologic evidence suggests that they are involved in human liver cancer in some parts of the world. Therefore, many nations have set statutory limits on the concentration of aflatoxins in food and feed.
Streptomycin
Authors: Sundin George W.
Published: November 2003

Streptomycin was the second antibiotic to be utilized in clinical medicine, and its class of antibiotics, the aminoglycosides, helped fuel the antibiotic age of modern clinical medicine. Streptomycin is one of many antibiotics with importance as a feed amendment for growth promotion in agricultural animals. Since the early 1950s, streptomycin has been utilized for bacterial plant disease control. The most important use of streptomycin in plant disease control has probably been in the management of fire blight caused by
Erwinia amylovora
.
Disinfection
Authors: Maloy Otis C.
Published: November 2003

Disinfection is generally considered to be the killing or inactivation of disease‐producing microorganisms in animals, seeds, or other plant parts but is sometimes used mistakenly to describe sterilizing surfaces and other inanimate objects. However, since inanimate objects cannot become infected, eliminating pathogens from these surfaces is correctly termed disinfestation. Disinfection can be accomplished by several methods but usually is by the application of chemicals (disinfectants) or heat. Development of antibiotics and systemic fungicides has made available relatively nonphytotoxic disinfectant chemicals. However, overuse of these materials may hasten the emergence of fungicide‐resistant strains of pathogens and eliminate beneficial organisms from plant surfaces.
Biological Control
Authors: Bull Carolee T.
Published: November 2003

Biological control of plant disease has been described for many crops and diseases, but development of these into commercially viable disease control options is rare. Biological control has yet to achieve the consistent levels of control and use that have been obtained by other methods.
Electrophoresis
Authors: Lane Leslie C.
Published: November 2003

Electrophoresis refers to mitigation of charged particles (molecules) in an electric field. It was conceived as a way to separate molecules by surface charge. Today, electrophoresis more often forces molecules through gels separating by size. It is now a versatile family of techniques to determine nucleic acid size, sequence, and structure; to determine protein size and charge; to resolve complex mixtures; and to determine purity. Its speed and simplicity encourage novel applications and creative tinkering.
PCR
Authors: Henson Joan M. , Elliott Monica
Published: November 2003

The polymerase chain reaction (PCR) is a method to amplify DNA exponentially by in vitro DNA synthesis. Amplification usually consists of three steps that are repeated 10 to 50 times in an automated thermal cycler. The first step is thermal denaturation of target DNA to be amplified. The second step is annealing of two oligonucleotide primers to the separated DNA strands. The final step is DNA synthesis by a thermostable DNA polymerase that extends the primers.
Rhizosphere
Authors: Raaijmakers Jos M.
Published: November 2003

The rhizosphere is the narrow zone of soil influences by living roots, as manifested by the leakage and exudation of substances that affect microbial activity. The term rhizosphere was initially introduced in 1904 by Lorentz Hiltner in reference to the soil layer of intense bacterial activity surrounding roots of the Leguminoseae. Later, this definition was extended to include all plant species. The rhizosphere is an environment that the plant helps to create and where microbial activity constitutes a major influential force.
Tillage
Authors: Bhat Ravi G. , Subbarao Krishna V.
Published: November 2003

Tillage is a cultural practice of fragmenting and burying plant residues through plowing or in general, a process of soil inversion using practices such as disking, ripping, plowing, and chiseling to prepare land for new planting. Tillage enhances the degradation of plant materials left in the field after harvest by mixing them with soil and exposes subsoil to the top layer. Probably no cultural practice has a greater impact on the soil environment than tillage.
Genetically Modified Microorganisms (GMM) in Soil Environments
Authors: Van Overbeek Leo , Van Elsas Dick
Published: November 2003

The early 1970s witnessed a major breakthrough in molecular biology with the discovery of restriction enzymes. From that moment on, it has been possible to modify the genetic constitution of all organisms, and a new era in human history started. In the early years of genetic modification, the perspectives of these approaches were tremendous. However, these expectations have been tempered ever since and have even led to an upheaval because of two reasons. In this article, we focus on the requirements for the application of genetically modified microorganism strains in natural, unconstrained environments such as agricultural fields, and discuss approaches for tracking released GMM strains as well as limiting their spread by the construction of so‐called self‐containing mechanisms.
Herbicides: Sulfonylureas
Authors: Plimmer Jack , Gammon Derek
Published: November 2003

The sulfonylurea herbicides were discovered in the 1970s, and sulfometuron was introduced commercially in 1982. They are active at extremely low rates, and 28 active ingredients have been registered worldwide. They inhibit plant cell division by targeting the enzyme ALS or acetolactate synthase, a key enzyme in the biosynthesis of branched chain amino acids. Their mammalian toxicity is very low. A key structural feature is the sulfonylurea moiety linked to a substituted pyrimidine or triazine ring.
Widow and widower remarriage: An analysis in a rural 19th century Costa Rican population and a cross‐cultural discussion
Authors: Madrigal L. , Ware B. , Melendez M.
Published: November 2003

Although the topic of remarriage features saliently in the cultural anthropological literature, it is virtually absent in the biological anthropology journals. This is perplexing, given that remarriage affects the differential reproductive success of males and females in a community, and could well impact a community's population structure. In this paper, we research remarriage practices in a rural 19th century community in Costa Rica. Although we find support for the proposition that males are more likely to remarry than females, we find that widows who remarry are not all young and able to reproduce. Our findings support the cross‐culturally‐generated suggestion that a female's ability not to remarry is tied to her to ability to own property. Remarriage is a topic of interest to biological anthropologists from a cross‐cultural and biocultural perspective. Am J Phys Anthropol, 2003. © 2003 Wiley‐Liss, Inc.