bluuebunny/crossref_metadata_2025 huggingface dataset:
Decision tree reduction
Authors: Cockett J. R. B. , Herrera J. A.
Published: July 2002

The reduction algorithm is a technique for improving a decision tree in the abseence of aproecise cost criterion. The result of applying the algorithm is an irreducible tree that is no less efficient than the original, and may be more efficient. Irreducible trees arise in discrete decision theory as an algebraic form for decision trees. This form has significant computational properties. In fact, every irreducible is optimal with respect to some expected testing cost criterion and is strictly better than any given distinct tree with respect to some criterion.

Many irreducibles are decision equivalent to a given tree; onely some of these are
reductions
of the tree. The reduction algorithm is a particular way of finding one of these. It tends to preserve the overall structure of the tree by reducing the subtrees first.

A bound on the complexity of this algorithm with input tree
t
is
O
(hgt9
t
)
2
). usize(
t
) is the
uniform
size of the tree (the number of leaves less one) and hgt(
t
) is the height of the tree. This means that decision tree reduction has the same worst-case order of complexity as most heuristic methods for building suboptimal trees. While the purpose of using heuristics is often rather different, such comparisons are an indication of the efficiency of the reduction algorithms.
ARCHAEOLOGICAL APPROACHES TO THE ORGANIZATION OF DOMESTIC LABOR: Household Practice and Domestic Relations
Authors: Hendon Julia A.
Published: July 2002

▪ Abstract  The household has emerged as a focus of archaeological inquiry over the past decade. This review summarizes issues raised by economic and feminist anthropologists about the meaning of the terms household and domestic and then considers research on household archaeology, craft specialization, and gender relevant to the study of the organization of domestic labor. It is argued that the common functional definition of the household as an adaptive mechanism reacting to environmental and social conditions underconceptualizes the household and renders its study unlikely to contribute to our understanding of economic and social processes in past societies. Studies of craft specialization and women's economic production that emphasize what members of the domestic group do and how that action is valued are more successful in demonstrating the dynamic interaction between household and society.
The Biological Stress Response and Lifestyle: Catecholamines and Blood Pressure
Authors: James Gary D. , Brown Daniel E.
Published: July 2002

Many measures in human biology that are studied as immutable traits are actually fluctuating physiological functions that adjust body systems to rapid changes in the environment. This overview discusses what has been learned about the response to the stressors inherent in continuously changing microenvironments in modern Western societies of two related physiological functions: the release of catecholamines and blood pressure. The review shows that many factors that are part of or influence lifestyle—including perception and cognitive state, the nature of the social situation, foods, stimulants and exercise—and external conditions such as temperature, continuously alter catecholamine levels and blood pressure. Because lifestyle stress may be an important selective force in human populations, studies of dynamic functions that react to it, such as catecholamine release and blood pressure, may be important in understanding the ongoing dynamics of human evolution.
WHEN ANTHROPOLOGY IS AT HOME: The Different Contexts of a Single Discipline
Authors: Peirano Mariza G. S.
Published: July 2002

▪ Abstract  For a long time anthropology was defined by the exoticism of its subject matter and by the distance, conceived as both cultural and geographic, that separated the researcher from the researched group. This situation has changed. In a few years we may assess the twentieth century as characterized by a long and complex movement, with theoretical and political implications, that replaced the ideal of the radical encounter with alterity with research at home. But “home” will, as always, incorporate many meanings, and anthropology will maintain, in its paradigmatic assumption, a socio-genetic aim toward an appreciation for, and an understanding of, difference. In some cases, difference will be the route to theoretical universalism via comparison; in others, it will surface as a denunciation of exoticism or a denial of its appeal. This review examines different moments and contexts in which an attempt at developing anthropology “at home” became an appropriate quest.
MISSION ARCHAEOLOGY
Authors: Graham Elizabeth
Published: July 2002

▪ Abstract  “Mission archaeology” is a novel conjunction of terms devised to focus attention on an archaeology of mission sites, and thereby on the light that can be shed on the process of the Christianization of the Americas by examining the material culture of missions. Discussion centers on a summary of mission research in the Spanish-occupied territories of North America and Mayan Mesoamerica. I then draw conclusions from these data, and from anthropological and historical analyses of mission encounters, to suggest where mission studies should be headed and the role that archaeology can play in expanding our knowledge of the mission transformation.
The Case for Sound Symbolism
Authors: Nuckolls Janis B.
Published: July 2002

▪ Abstract  The proposal that linguistic sounds such as phonemes, features, syllables, or tones can be meaningful, or sound-symbolic, contradicts the principles of arbitrariness and double articulation that are axiomatic to structural linguistics. Nevertheless, a considerable body of research that supports principles of sound symbolism has accumulated. This review discusses the most widely attested forms of sound symbolism and the research programs linked to sound symbolism that have influenced linguists and anthropologists most. Numerous reports of magnitude sound symbolism in the form of experimental studies and comparative surveys have been integrated into a biologically based theory of its motivation. Magnitude sound symbolism also catalyzed a number of experimental studies by psychologists and linguists in search of a universal sound-symbolic substrate underlying all languages. Although the search for a sound-symbolic substrate has been abandoned, the success rates of these studies have never been satisfactorily explained. Sound-symbolic processes have had a definitive impact on morphological analyses of phonesthemes and on historical linguists' understandings of diachronic processes. A typologically widespread form of sound symbolism occurs as a kind of lexical class known as the ideophone, which is conspicuously underdeveloped in standard average European languages, and highly perplexing for linguists and anthropologists. Although it has always been a respectable domain of inquiry in ethnopoetics and interpretive ethnography, the case for sound symbolism has of late been argued with renewed vigor on the part of psychological anthropologists and philosophers who see a paradigm shift under way.
Sociolinguistics and Linguistic Anthropology of US Latinos
Authors: Mendoza-Denton Norma
Published: July 2002

▪ Abstract  Issues in the linguistic study of US Latinos are reviewed, with an emphasis on recent work in sociolinguistics. Predominant models of language contact are evaluated, as are factors contributing to variation. Among these factors are (a) the state of changes in progress; (b) the complexity of historical, socioeconomic, and demographic conditions of US Latinos; (c) the community's degree of contact with other ethnic/linguistic groups; (d) language attitudes toward the matrix and embedded languages; (e) the local evaluation and patterns of use of particular variants; and (f) the possibility of autochthonous innovation within the dialect. Questions of US Latino participation in changes beyond those in their immediate communities are addressed. The need to connect linguistic variation with other aspects of semiotic meaning is emphasized.
The Anthropology of Reform and the Reform of Anthropology: Anthropological Narratives of Recovery and Progress in China
Authors: Harrell Stevan
Published: July 2002

▪ Abstract  Since the beginning of China's Reform and Opening policy in 1978, the anthropological study of China has revived, and anthropology as a discipline has revived in China. Chinese anthropologists have become part of the world community of anthropologists. Anthropology in and about China has described a society occupied both with recovery from the cultural devastation of High Socialism and with progress toward an uncertain modernity. These narratives of recovery and progress can be followed through the anthropological study of communities—rural, urban, and in between—of individuals' lives, including gender and sexuality, family and marriage, childhood and education, consumption and leisure, and of the nation and its constituent ethnic and regional parts.
BORON IN PLANT STRUCTURE AND FUNCTION
Authors: Blevins Dale G. , Lukaszewski Krystyna M.
Published: July 2002

▪ Abstract  New and exciting developments in boron research in the past few years greatly contributed to better understanding of the role of boron in plants. Purification and identification of the first boron-polyol transport molecules resolved much of the controversy about boron phloem mobility. Isolation and characterization of the boron-polysaccharide complex from cell walls provided the first direct evidence for boron crosslinking of pectin polymers. Inhibition and recovery of proton release upon boron withdrawal and restitution in plant culture medium demonstrated boron involvement in membrane processes. Rapid boron-induced changes in membrane function could be attributed to boron-complexing membrane constituents. Boron may affect metabolic pathways by binding apoplastic proteins to cis-hydroxyl groups of cell walls and membranes, and by interfering with manganese-dependent enzymatic reactions. In addition, boron has been implicated in counteracting toxic effects of aluminum on root growth of dicotyledonous plants. Molecular investigations of boron nutrition have been initiated by the discovery of a novel mutant of Arabidopsis thaliana with an altered requirement for boron.
THE SHIKIMATE PATHWAY
Authors: Herrmann Klaus M. , Weaver Lisa M.
Published: July 2002

▪ Abstract  The shikimate pathway links metabolism of carbohydrates to biosynthesis of aromatic compounds. In a sequence of seven metabolic steps, phosphoenolpyruvate and erythrose 4-phosphate are converted to chorismate, the precursor of the aromatic amino acids and many aromatic secondary metabolites. All pathway intermediates can also be considered branch point compounds that may serve as substrates for other metabolic pathways. The shikimate pathway is found only in microorganisms and plants, never in animals. All enzymes of this pathway have been obtained in pure form from prokaryotic and eukaryotic sources and their respective DNAs have been characterized from several organisms. The cDNAs of higher plants encode proteins with amino terminal signal sequences for plastid import, suggesting that plastids are the exclusive locale for chorismate biosynthesis. In microorganisms, the shikimate pathway is regulated by feedback inhibition and by repression of the first enzyme. In higher plants, no physiological feedback inhibitor has been identified, suggesting that pathway regulation may occur exclusively at the genetic level. This difference between microorganisms and plants is reflected in the unusually large variation in the primary structures of the respective first enzymes. Several of the pathway enzymes occur in isoenzymic forms whose expression varies with changing environmental conditions and, within the plant, from organ to organ. The penultimate enzyme of the pathway is the sole target for the herbicide glyphosate. Glyphosate-tolerant transgenic plants are at the core of novel weed control systems for several crop plants.
GRAVITATIONAL MICROLENSING IN THE LOCAL GROUP
Authors: Paczyński Bohdan
Published: July 2002

▪ Abstract  The status of searches for gravitational microlensing events of the stars in our galaxy and in other galaxies of the Local Group, the interpretation of the results, some theory, and prospects for the future are reviewed. The searches have already unveiled ∼ 100 events, at least two of them caused by binaries, and have already proven to be useful for studies of the Galactic structure. The events detected so far are probably attributable to the effects of ordinary stars, and possibly to substellar brown dwarfs; however, a firm conclusion cannot be reached yet because the analysis published to date is based on a total of only 16 events. The current searches, soon to be upgraded, will probably allow determination of the mass function of stars and brown dwarfs in the next few years; these efforts will also provide good statistical information about binary systems, in particular their mass ratios. They may also reveal the nature of dark matter and allow us to detect planets and planetary mass objects.
OBSERVATIONAL SELECTION BIAS AFFECTING THE DETERMINATION OF THE EXTRAGALACTIC DISTANCE SCALE
Authors: Teerikorpi P.
Published: July 2002

▪ Abstract  The influence of Malmquist bias on the studies of extragalactic distances is reviewed, with brief glimpses of the history from Kapteyn to Scott. Special attention is paid to two kinds of biases, for which the names Malmquist biases of the first and second kind are proposed. The essence of these biases and the situations where they occur are discussed.

The bias of the first kind is related to the classical Malmquist bias (involving the “volume effect”), while the bias of the second kind appears when standard candles are observed at different (true) distances, whereby magnitude limit cuts away a part of the luminosity function. In particular, study of the latter bias in distance indicators such as Tully Fisher, available for large fundamental samples of galaxies, allows construction of an unbiased absolute distance scale in the local galaxy universe where approximate kinematic relative distances can be derived. Such investigations, using the method of normalized distances or of the Spaenhauer diagram, support the linearity of the Hubble law and make it possible to derive an unbiased value of the Hubble constant.
VARIABILITY OF ACTIVE GALACTIC NUCLEI
Authors: Ulrich Marie-Helene , Maraschi Laura , Urry C. Megan
Published: July 2002

▪ Abstract  A large collective effort to study the variability of active galactic nuclei (AGN) over the past decade has led to a number of fundamental results on radio-quiet AGN and blazars. In radio-quiet AGN, the ultraviolet (UV) bump in low-luminosity objects is thermal emission from a dense medium, very probably an accretion disk, irradiated by the variable X-ray source. The validity of this model for high-luminosity radio-quiet AGN is unclear because the relevant UV and X-ray observations are lacking. The broad-line gas kinematics appears to be dominated by virialized motions in the gravity field of a black hole, whose mass can be derived from the observed motions. The “accretion disk plus wind” model explains most of the variability (and other) data and appears to be the most appropriate model at present. Future investigations are outlined.

In blazars, rapid variability at the highest energies (gamma-rays) implies that the whole continuum is relativistically boosted along the line of sight. The general correlation found between variations in TeV gamma rays and in X rays for Mrk 421, and between variations in GeV gamma rays and in the IR–optical–UV bands for 3C 279, two prototype objects, supports models in which the same population of relativistic electrons radiates the low-frequency continuum via synchrotron and the high frequency continuum via inverse Compton scattering of soft photons. Identifying the dominant source of soft photons, which is at present unclear, will strongly constrain the jet physics.
ASTRONOMICAL SEARCHES FOR EARTH-LIKE PLANETS AND SIGNS OF LIFE
Authors: Woolf Neville , Angel J. Roger
Published: July 2002

▪ Abstract  If Earth-like planets orbit nearby stars, they could be detectable with specially designed telescopes. Direct observations would be very revealing, particularly low resolution infrared spectra, which could establish habitability on the basis of temperature and atmospheric water. Abundant, primitive life based on organized molecular structure might reveal itself, as on Earth, by an atmospheric composition modified in ways unlikely to be from inorganic processes. The technical challenge is to detect and obtain spectra of an object with Mbol∼ 28 that is very close to a star and some 5 × 109times less luminous. Indirect methods, used to detect Jupiter-mass planets, do not seem to offer an easy intermediate step to finding Earth-like planets. However, the direct detection techniques needed for spectroscopy also offer a viable method for discovery by imaging. Thermal infrared wavelengths, in which a planet emits most energy, are the most favorable. A robust search for planets of ∼100 nearby solar-type stars, with spectroscopic follow-up of Earth-like candidates, could be made with an interferometer ∼75 m in length. In visible light, the Next Generation Space Telescope (NGST) could, with the addition of a high resolution correction instrument, see Earth-like planets around a dozen or so of the nearest stars. Both infrared and optical instruments are possible within the range of current space agency plans.
Sources of Relativistic Jets in the Galaxy
Authors: Mirabel I. F. , Rodríguez L. F.
Published: July 2002

▪ Abstract  Black holes of stellar mass and neutron stars in binary systems are first detected as hard X-ray sources using high-energy space telescopes. Relativistic jets in some of these compact sources are found by means of multiwavelength observations with ground-based telescopes. The X-ray emission probes the inner accretion disk and immediate surroundings of the compact object, whereas the synchrotron emission from the jets is observed in the radio and infrared bands, and in the future could be detected at even shorter wavelengths. Black-hole X-ray binaries with relativistic jets mimic, on a much smaller scale, many of the phenomena seen in quasars and are thus called microquasars. Because of their proximity, their study opens the way for a better understanding of the relativistic jets seen elsewhere in the Universe. From the observation of two-sided moving jets it is inferred that the ejecta in microquasars move with relativistic speeds similar to those believed to be present in quasars. The simultaneous multiwavelength approach to microquasars reveals in short timescales the close connection between instabilities in the accretion disk seen in the X-rays, and the ejection of relativistic clouds of plasma observed as synchrotron emission at longer wavelengths. Besides contributing to a deeper understanding of accretion disks and jets, microquasars may serve in the future to determine the distances of jet sources using constraints from special relativity, and the spin of black holes using general relativity.
The Cosmic Infrared Background: Measurements and Implications
Authors: Hauser Michael G. , Dwek Eli
Published: July 2002

▪ Abstract  The cosmic infrared background records much of the radiant energy released by processes of structure formation that have occurred since the decoupling of matter and radiation following the Big Bang. In the past few years, data from the Cosmic Background Explorer (COBE) mission provided the first measurements of this background, with additional constraints coming from studies of the attenuation of TeV γ-rays. At the same time, there has been rapid progress in resolving a significant fraction of this background with the deep galaxy counts at infrared wavelengths from the Infrared Space Observatory (ISO) instruments and at submillimeter wavelengths from the Submillimeter Common User Bolometer Array (SCUBA) instrument. This article reviews the measurements of the infrared background and sources contributing to it and discusses the implications for past and present cosmic processes.
ENZYMATIC TRANSITION STATES AND TRANSITION STATE ANALOG DESIGN
Authors: Schramm Vern L.
Published: July 2002

All chemical transformations pass through an unstable structure called the transition state, which is poised between the chemical structures of the substrates and products. The transition states for chemical reactions are proposed to have lifetimes near 10−13sec, the time for a single bond vibration. No physical or spectroscopic method is available to directly observe the structure of the transition state for enzymatic reactions. Yet transition state structure is central to understanding catalysis, because enzymes function by lowering activation energy. An accepted view of enzymatic catalysis is tight binding to the unstable transition state structure. Transition state mimics bind tightly to enzymes by capturing a fraction of the binding energy for the transition state species. The identification of numerous transition state inhibitors supports the transition state stabilization hypothesis for enzymatic catalysis. Advances in methods for measuring and interpreting kinetic isotope effects and advances in computational chemistry have provided an experimental route to understand transition state structure. Systematic analysis of intrinsic kinetic isotope effects provides geometric and electronic structure for enzyme-bound transition states. This information has been used to compare transition states for chemical and enzymatic reactions; determine whether enzymatic activators alter transition state structure; design transition state inhibitors; and provide the basis for predicting the affinity of enzymatic inhibitors. Enzymatic transition states provide an understanding of catalysis and permit the design of transition state inhibitors. This article reviews transition state theory for enzymatic reactions. Selected examples of enzymatic transition states are compared to the respective transition state inhibitors.
The 26S Proteasome: A Molecular Machine Designed for Controlled Proteolysis
Authors: Voges D. , Zwickl P. , Baumeister W.
Published: July 2002

▪ Abstract  In eukaryotic cells, most proteins in the cytosol and nucleus are degraded via the ubiquitin-proteasome pathway. The 26S proteasome is a 2.5-MDa molecular machine built from ∼31 different subunits, which catalyzes protein degradation. It contains a barrel-shaped proteolytic core complex (the 20S proteasome), capped at one or both ends by 19S regulatory complexes, which recognize ubiquitinated proteins. The regulatory complexes are also implicated in unfolding and translocation of ubiquitinated targets into the interior of the 20S complex, where they are degraded to oligopeptides. Structure, assembly and enzymatic mechanism of the 20S complex have been elucidated, but the functional organization of the 19S complex is less well understood. Most subunits of the 19S complex have been identified, however, specific functions have been assigned to only a few. A low-resolution structure of the 26S proteasome has been obtained by electron microscopy, but the precise arrangement of subunits in the 19S complex is unclear.
Telemedicine: Emerging e-medicine
Authors: Mun Seong K. , Turner Jeanine W.
Published: July 2002

▪ Abstract  This paper reviews the emergence of telemedicine and its recent expansion and use within the healthcare industry. Through this review, several examples of telemedicine within a variety of applications provide a broad context to discuss the challenges and opportunities facing the emergence of e-medicine. These examples provide snapshots of a teleradiology system used by the military, teleconsultations used in neurosurgery and hemodialysis, and home telemedicine used in diabetes care. Based on the discussion of telemedicine's history and expansion and the examples provided, a framework is offered for understanding the evolution of telemedicine applications through four stages. These stages include: (a) development of basic technological capabilities, (b) development of relevant applications, (c) the integration of technical applications within a complex environment, and (d) transformation of the operating environment. Implications for this framework are discussed.
Biophysical Injury Mechanisms in Electrical Shock Trauma
Authors: Lee Raphael C. , Zhang Dajun , Hannig Jurgen
Published: July 2002

▪ Abstract  Electrical shock trauma tends to produce a very complex pattern of injury, mainly because of the multiple modes of frequency-dependent tissue-field interactions. Historically, Joule heating was thought to be the only cause of electrical injuries to tissue by commercial-frequency electrical shocks. In the last 15 years, biomedical engineering research has improved the understanding of the underlying biophysical injury mechanisms. Besides thermal burns secondary to Joule heating, permeabilization of cell membranes and direct electroconformational denaturation of macromolecules such as proteins have also been identified as tissue-damage mechanisms. This review summarizes the physics of tissue injury caused by contact with commercial-frequency power lines, as well as exposure to lightning and radio frequency (RF), microwave, and ionizing radiation. In addition, we describe the anatomic patterns of the resultant tissue injury from these modes of electromagnetic exposures.
Wavelets in Temporal and Spatial Processing of Biomedical Images
Authors: Laine Andrew F.
Published: July 2002

▪ Abstract  We review some of the most recent advances in the area of wavelet applications in medical imaging. We first review key concepts in the processing of medical images with wavelet transforms and multiscale analysis, including time-frequency tiling, overcomplete representations, higher dimensional bases, symmetry, boundary effects, translational invariance, orientation selectivity, and best-basis selection. We next describe some applications in magnetic resonance imaging, including activation detection and denoising of functional magnetic resonance imaging and encoding schemes. We then present an overview in the area of ultrasound, including computational anatomy with three-dimensional cardiac ultrasound. Next, wavelets in tomography are reviewed, including their relationship to the radon transform and applications in position emission tomography imaging. Finally, wavelet applications in digital mammography are reviewed, including computer-assisted diagnostic systems that support the detection and classification of small masses and methods of contrast enhancement.
Soft Lithography in Biology and Biochemistry
Authors: Whitesides George M. , Ostuni Emanuele , Takayama Shuichi , Jiang Xingyu , Ingber Donald E.
Published: July 2002

▪ Abstract  Soft lithography, a set of techniques for microfabrication, is based on printing and molding using elastomeric stamps with the patterns of interest in bas-relief. As a technique for fabricating microstructures for biological applications, soft lithography overcomes many of the shortcomings of photolithography. In particular, soft lithography offers the ability to control the molecular structure of surfaces and to pattern the complex molecules relevant to biology, to fabricate channel structures appropriate for microfluidics, and to pattern and manipulate cells. For the relatively large feature sizes used in biology (≥50 μm), production of prototype patterns and structures is convenient, inexpensive, and rapid. Self-assembled monolayers of alkanethiolates on gold are particularly easy to pattern by soft lithography, and they provide exquisite control over surface biochemistry.
SOLVATION: HOW TO OBTAIN MICROSCOPIC ENERGIES FROM PARTITIONING AND SOLVATION EXPERIMENTS
Authors: Chan Hue Sun , Dill Ken A.
Published: July 2002

▪ Abstract  Oil-water partitioning, solubilities, and vapor pressure experiments on small-molecule compounds are often used as models to obtain energies for biomolecular modeling. For example, measured partition coefficients, K, are often inserted into the formula −RTlnK to obtain quantities thought to represent microscopic contact interaction free energies. We review evidence here that this procedure does not always give microscopically meaningful free energies. Some partitioning processes, particularly involving polymeric solvents such as octanol or hexadecane, are governed not only by translational entropies and contact interactions, but also by free energies resulting from changes in the conformations of the polymer chains upon solute insertion. The Flory-Huggins theory is more suitable for these situations than is the classical approach. We discuss the physical bases for both approaches.
DNA Recognition by Cys2His2 Zinc Finger Proteins
Authors: Wolfe Scot A. , Nekludova Lena , Pabo Carl O.
Published: July 2002

▪ Abstract  Cys2His2 zinc fingers are one of the most common DNA-binding motifs found in eukaryotic transcription factors. These proteins typically contain several fingers that make tandem contacts along the DNA. Each finger has a conserved ββα structure, and amino acids on the surface of the α-helix contact bases in the major groove. This simple, modular structure of zinc finger proteins, and the wide variety of DNA sequences they can recognize, make them an attractive framework for attempts to design novel DNA-binding proteins. Several studies have selected fingers with new specificities, and there clearly are recurring patterns in the observed side chain–base interactions. However, the structural details of recognition are intricate enough that there are no general rules (a “recognition code”) that would allow the design of an optimal protein for any desired target site. Construction of multifinger proteins is also complicated by interactions between neighboring fingers and the effect of the intervening linker. This review analyzes DNA recognition by Cys2His2 zinc fingers and summarizes progress in generating proteins with novel specificities from fingers selected by phage display.
Quantitative Chemical Analysis of Single Cells
Authors: Cannon Jr D. M. , Winograd N. , Ewing A. G.
Published: July 2002

▪ Abstract  A fundamental perspective can be achieved by targeting single cells for analysis with the goal of deconvoluting complex biological functions. However, single-cell studies have their own difficulties, such as minute volumes and sample amounts. Quantitative chemical analysis of single cells has emerged as a powerful new area in recent years due to several technological advancements. The development of microelectrodes has allowed the measurement of redox-active species as a function of cellular dynamics. This miniaturization trend is also evident in the separation sciences with the application of small column separations to single cells. Desorption ionization methods with mass spectrometric detection have shown single-cell capability owing to numerous technological developments. Finally, fluorescence imaging has also progressed to the point where single-cell dynamics can be probed by native fluorescence utilizing either single or multiple photon excitation. The results of these studies are reviewed with an emphasis on the quantitation of single-cell dynamics.
Pulsed and Parallel-Polarization EPR Characterization of the Photosystem II Oxygen-Evolving Complex
Authors: Britt R. David , Peloquin Jeffrey M. , Campbell Kristy A.
Published: July 2002

▪ Abstract  Photosystem II uses visible light to drive the oxidation of water, resulting in bioactivated electrons and protons, with the production of molecular oxygen as a byproduct. This water-splitting reaction is carried out by a manganese cluster/tyrosine radical ensemble, the oxygen-evolving complex. Although conventional continuous-wave, perpendicular-polarization electron paramagnetic resonance (EPR) spectroscopy has significantly advanced our knowledge of the structure and function of the oxygen-evolving complex, significant additional information can be obtained with the application of additional EPR methodologies. Specifically, parallel-polarization EPR spectroscopy can be used to obtain highly resolved EPR spectra of integer spin Mn species, and pulsed EPR spectroscopy with electron spin echo-based sequences, such as electron spin echo envelope modulation and electron spin echo-electron nuclear double resonance, can be used to measure weak interactions obscured in continuous-wave spectroscopy by inhomogeneous broadening.
ENDOCYTOSIS AND MOLECULAR SORTING
Authors: Mellman Ira
Published: July 2002

▪ Abstract  Endocytosis in eukaryotic cells is characterized by the continuous and regulated formation of prolific numbers of membrane vesicles at the plasma membrane. These vesicles come in several different varieties, ranging from the actin-dependent formation of phagosomes involved in particle uptake, to smaller clathrin-coated vesicles responsible for the internalization of extracellular fluid and receptor-bound ligands. In general, each of these vesicle types results in the delivery of their contents to lysosomes for degradation. The membrane components of endocytic vesicles, on the other hand, are subject to a series of highly complex and iterative molecular sorting events resulting in their targeting to specific destinations. In recent years, much has been learned about the function of the endocytic pathway and the mechanisms responsible for the molecular sorting of proteins and lipids. This review attempts to integrate these new concepts with long-established views of endocytosis to present a more coherent picture of how the endocytic pathway is organized and how the intracellular transport of internalized membrane components is controlled. Of particular importance are emerging concepts concerning the protein-based signals responsible for molecular sorting and the cytosolic complexes responsible for the decoding of these signals.
STRATIGRAPHIC RECORD OF THE EARLY MESOZOIC BREAKUP OF PANGEA IN THE LAURASIA-GONDWANA RIFT SYSTEM
Authors: Olsen Paul E.
Published: July 2002

▪ Abstract  Rift basins of the Central Atlantic Margins (CAM) of North America and Morocco preserve largely continental sequences of sedimentary strata and less important minor basalt flows spanning much of the early Mesozoic. The best known is the Newark basin of New Jersey, New York, and Pennsylvania where an astronomically calibrated magnetic polarity time scale is developed.

Lacustrine cycles of Milankovitch origin are commonly present in CAM basins, with the period changing from 10 ky (paleoequator with coals), to 20 ky (4°–10°N), to perhaps 40 ky northward with evaporites. Cycles of ∼100 ky, 413 ky, and ∼2 my are also important.

Four mostly unconformity-bounded tectonostratigraphic sequences are present. The Anisian TS I is fluvial and eolian. TS II–TS IV (Late Triassic to Early Jurassic) consist of “tripartite” lacustrine sequences caused by extension pulses. The Newark basin accumulation rate history allows comparison with quantitative rift basin models.

The North American plate's slow northward drift resulted in a relative shift of climate, although the rapid humidification during the latest Triassic and Early Jurassic is associated with a sea-level rise. The Triassic-Jurassic mass extinction is of independent origin, plausibly impact related.
THERMOHALINE CIRCULATION: High-Latitude Phenomena and the Difference Between the Pacific and Atlantic
Authors: Weaver A. J. , Bitz C. M. , Fanning A. F. , Holland M. M.
Published: July 2002

▪ Abstract  Deepwater formation, the process whereby surface water is actively converted into deep water through heat and freshwater exchange at the air-sea interface, is known to occur in the North Atlantic but not in the North Pacific. As such, the thermohaline circulation is fundamentally different in these two regions. In this review we provide a description of this circulation and outline a number of reasons as to why deep water is formed in the North Atlantic but not in the North Pacific. Special emphasis is given to the role of interactions with the Arctic Ocean. We extend our analysis to discuss the observational evidence and current theories for decadal-interdecadal climate variability in each region, with particular focus on the role of the ocean. Differences between the North Atlantic and North Pacific are highlighted.
The Role of Plants in Controlling Rates and Products of Weathering: Importance of Biological Pumping
Authors: Lucas Y
Published: July 2002

▪ Abstract  The recycling of elements by plants and plant-induced biological activity cause the rates and products of weathering to be markedly different from what would result in abiotic processes. Plants directly control water dynamics, weathering, and the chemistry of weathering solutions, which is clearly exhibited in equatorial areas where old weathering mantles are greatly influenced by biological activity. Depending on the dynamics of plant-induced organometallic compounds, this weathering results in either clayey soils, which are in a dynamic equilibrium sustained by the forest's cycling of elements, or sandy soils. In most places (tropical as well temperate areas), the weathering mantle can be regarded as being in a dynamic equilibrium sustained by plants.
Giant Dike Swarms: Earth, Venus, and Mars
Authors: Ernst RE , Grosfils EB , Mège D
Published: July 2002

▪ Abstract  Earth, Venus, and Mars all exhibit populations of giant (radiating, linear, and arcuate) mafic dike swarms hundreds to >2000 km in length. On Earth the dikes are exposed by erosion, while on Venus and Mars their presence is mainly inferred from associated volcanic morphology and surface deformation. The apparent absence of plate tectonics in the geologic record of Venus and Mars means that the observed population of swarms remains geometrically intact, while on Earth plate tectonics has fragmented swarms. About 30 giant radiating swarms have so far been identified on Earth, but with further study the number is expected to rise and may eventually coincide with the hundreds of mantle plume head events now being proposed. On Venus, at least 118 radiating swarms are distributed across the planet, and new high resolution mapping is revealing additional swarms. On Mars, up to 16 giant dike swarms are observed, most associated with the Tharsis region.
RATES OF MOLECULAR EVOLUTION: Phylogenetic Issues and Applications
Authors: Mindell David P. , Thacker Christine E.
Published: July 2002

▪ Abstract  The proper relationship between systematics practice and our understanding of evolution has been long debated. Systematists seek to avoid assumptions about evolutionary process in their methods, yet a growing body of evidence indicates that patterns in rates of evolution can be used to reduce effects of homoplasy. We review variable evolutionary rates for molecular characters in the context of constraints on mutation and fixation. Some constraints, like the genetic code for protein-coding genes, are consistent in the direction of their effects, whereas others, like population size and cladogenesis frequency, are historically variable within and among lineages.

We review methods for assessing rate variability, and we estimate comparative absolute rates of change for five sets of mitochondrial DNAs in 12 vertebrates for application in phylogenetic analyses. Unequal weights for subsets of mitochondrial DNAs improved congruence with the most highly corroborated tree in many but not all cases. The largest data set (12,120 bases) yielded the same tree under all four weighting alternatives. This is consistent with the notion, echoing the law of large numbers, that as data sets increase in size, homoplasy will tend to cancel itself out. Even if this notion has validity, however, evolutionary biology will remain vital in systematics if we want to: match sets of taxa with characters likely to be historically informative (when data sets are not sufficiently large); avoid comparing characters with different histories due to reticulations, horizontal transfer, or lineage sorting; avoid assuming random distribution of homoplasy; be alerted to the possibility of long-branch attraction problems; and understand the cause of the hierarchy of taxa in nature as inheritance of genetic material and descent with modification.
WHEN DOES MORPHOLOGY MATTER?
Authors: Koehl M. A. R.
Published: July 2002

▪ Abstract  The performance of an organism is the crucial link between its phenotype and its ecological success. When does an organism's morphology affect its performance? Quantitative mechanistic analyses of how function depends on biological form have shown that the relationship between morphology and performance can be nonlinear, context-dependent, and sometimes surprising. In some cases, small changes in morphology or simple changes in size can lead to novel functions, while in other cases changes in form can occur without performance consequences. Furthermore, the effect of a specific change in morphology can depend on the size, shape, stiffness, or habitat of an organism. Likewise, a particular change in posture or behavior can produce opposite effects when performed by bodies with different morphologies. These mechanistic studies not only reveal potential misconceptions that can arise from the descriptive statistical analyses often used in ecological and evolutionary research, but they also show how new functions, and novel consequences of changes in morphology, can arise simply as the result of changes in size or habitat. Such organismal-level mechanistic research can be used in concert with other tools to gain insights about issues in ecology (e.g. foraging, competition, disturbance, keystone species, functional groups) and evolution (e.g. adaptation, interpretation of fossils, and origin of novelty).
Toward an Integration of Landscape and Food Web Ecology: The Dynamics of Spatially Subsidized Food Webs
Authors: Polis Gary A. , Anderson Wendy B. , Holt Robert D.
Published: July 2002

We focus on the implications of movement, landscape variables, and spatial heterogeneity for food web dynamics. Movements of nutrients, detritus, prey, and consumers among habitats are ubiquitous in diverse biomes and can strongly influence population, consumer-resource, food web, and community dynamics. Nutrient and detrital subsidies usually increase primary and secondary productivity, both directly and indirectly. Prey subsidies, by movement of either prey or predators, usually enhance predator abundance beyond what local resources can support. Top-down effects occur when spatially subsidized consumers affect local resources by suppressing key resources and occasionally by initiating trophic cascades. Effects on community dynamics vary with the relative amount of input, the trophic roles of the mobile and recipient entities, and the local food web structure. Landscape variables such as the perimeter/area ratio of the focal habitat, permeability of habitat boundaries, and relative productivity of trophically connected habitats affect the degree and importance of spatial subsidization.
Origins, Evolution, and Diversification of Zooplankton
Authors: Rigby Susan , Milsom Clare V.
Published: July 2002

▪ Abstract  Fossil plankton are difficult to identify but have formed a major component of most marine ecosystems throughout geological time. The earliest fossil heterotrophs include planktic forms, and subsequent adaptive innovations quickly appeared in the plankton; these include metazoans and animals with hard parts. Movement into the plankton occurred sporadically throughout geological history and seems to have been independent of any biological or environmental forcing mechanism. Subsequent radiations and extinctions in the cohort of plankton closely reflect events in the benthos. The diversity of zooplankton rose quickly during the early Paleozoic era, but low plankton diversity characterized the late Paleozoic. Significant radiations during early Mesozoic times led to an overall increase in diversity through the Phanerozoic eon. As the composition of the zooplankton has changed, so has their effect on biogeochemical cycles.
Applied Evolution
Authors: Bull J. J. , Wichman H. A.
Published: July 2002

▪ Abstract  Evolutionary biology is widely perceived as a discipline with relevance that lies purely in academia. Until recently, that perception was largely true, except for the often neglected role of evolutionary biology in the improvement of agricultural crops and animals. In the past two decades, however, evolutionary biology has assumed a broad relevance extending far outside its original bounds. Phylogenetics, the study of Darwin's theory of “descent with modification,” is now the foundation of disease tracking and of the identification of species in medical, pharmacological, or conservation settings. It further underlies bioinformatics approaches to the analysis of genomes. Darwin's “evolution by natural selection” is being used in many contexts, from the design of biotechnology protocols to create new drugs and industrial enzymes, to the avoidance of resistant pests and microbes, to the development of new computer technologies. These examples present opportunities for education of the public and for nontraditional career paths in evolutionary biology. They also provide new research material for people trained in classical approaches.
Mistletoe—A Keystone Resource in Forests and Woodlands Worldwide
Authors: Watson David M.
Published: July 2002

▪ Abstract  Mistletoes are a diverse group of parasitic plants with a worldwide distribution. The hemiparasitic growth form is critical to understanding their biology, buffering variation in resource availability that constrains the distribution and growth of most plants. This is manifested in many aspects of mistletoe life history, including extended phenologies, abundant and high-quality fruits and nectar, and few chemical or structural defenses. Most mistletoe species rely on animals for both pollination and fruit dispersal, and this leads to a broad range of mistletoe-animal interactions. In this review, I summarize research on mistletoe biology and synthesize results from studies of mistletoe-animal interactions. I consolidate records of mistletoe-vertebrate interactions, incorporating species from 97 vertebrate families recorded as consuming mistletoe and from 50 using mistletoe as nesting sites. There is widespread support for regarding mistletoe as a keystone resource, and all quantitative data are consistent with mistletoe functioning as a determinant of alpha diversity. Manipulative experiments are highlighted as a key priority, and six explicit predictions are provided to guide future experimental research.

The facts which kept me longest scientifically orthodox are those of adaptation—the pollen-masses in Asclepias—the misseltoe, with its pollen carried by insects and seed by Birds—the woodpecker, with its feet and tail, beak and tongue, to climb the tree and secure insects. To talk of climate or Lamarckian habit producing such adaptation to other organic beings is futile. This difficulty, I believe I have surmounted.

     From a letter to Asa Gray by Charles Darwin, 1857.
GLOBAL CHANGE AND HUMAN SUSCEPTIBILITY TO DISEASE
Authors: Daily Gretchen C. , Ehrlich Paul R.
Published: July 2002

▪ Abstract  Although the loss of good health is inherently unpredictable, human behavior at the individual and societal levels profoundly influences the incidence and evolution of disease. In this review, we define the human epidemiological environment and describe key biophysical, economic, sociocultural, and political factors that shape it. The potential impact upon the epidemiological environment of biophysical aspects of global change—changes in the size, mobility, and geographic distribution of the human population; land conversion; agricultural intensification; and climate change—is then examined. Human vulnerability to disease is strongly and deleteriously influenced by many of these ongoing, intensifying alterations. We then examine threats to human defenses against disease, including immune suppression, loss of biodiversity and indigenous knowledge, and the evolution of antibiotic resistance. Effective responses will require greatly enhanced attention by and collaboration among experts in diverse academic disciplines, in the private sector, and in government worldwide.