bluuebunny/crossref_metadata_2025 huggingface dataset:
HEMOGLOBIN METABOLISM IN THE MALARIA PARASITEPLASMODIUM FALCIPARUM
Authors: Francis Susan E. , Sullivan David J. , Goldberg and Daniel E.
Published: July 2002

▪ Abstract  Hemoglobin degradation in intraerythrocytic malaria parasites is a vast process that occurs in an acidic digestive vacuole. Proteases that participate in this catabolic pathway have been defined. Studies of protease biosynthesis have revealed unusual targeting and activation mechanisms. Oxygen radicals and heme are released during proteolysis and must be detoxified by dismutation and polymerization, respectively. The quinoline antimalarials appear to act by preventing sequestration of this toxic heme. Understanding the disposition of hemoglobin has allowed identification of essential processes and metabolic weakpoints that can be exploited to combat this scourge of mankind.
DEVELOPMENT OF HYBRID STRAINS FOR THE MINERALIZATION OF CHLOROAROMATICS BY PATCHWORK ASSEMBLY
Authors: Reineke Walter
Published: July 2002

▪ Abstract  The persistence of chloroaromatic compounds can be caused by various bottlenecks, such as incomplete degradative pathways or inappropriate regulation of these pathways. Patchwork assembly of existing pathways in novel combinations provides a general route for the development of strains degrading chloroaromatics. The recruitment of known complementary enzyme sequences in a suitable host organism by conjugative transfer of genes might generate a functioning hybrid pathway for the mineralization of some chloroaromatics not degraded by the parent organisms. The rational combination uses (a) peripheral, funneling degradation sequences originating from aromatics-degrading strains to fulfill the conversion of the respective analogous chloroaromatic compound to chlorocatechols as the central intermediates; (b) a central chlorocatechol degradation sequence, the so-called modified ortho pathway, which brings about elimination of chlorine substituents; and (c) steps of the 3-oxoadipate pathway to reach the tricarboxylic acid cycle. The genetic organization of these pathway segments has been well characterized. The specificity of enzymes of the xylene, benzene, biphenyl, and chlorocatechol pathways and the specificity of the induction systems for the chlorinated substrates are analyzed in various organisms to illustrate eventual bottlenecks and to provide alternatives that are effective in the conversion of the “new” substrate. Hybrid pathways are investigated in “new” strains degrading chlorinated benzoates, toluenes, benzenes, and biphenyls. Problems occurring after the conjugative DNA transfer and the “natural” solution of these are examined, such as the prevention of misrouting into the meta pathway, to give a functioning hybrid pathway. Some examples clearly indicate that patchwork assembly also happens in nature.
Gain of Function Mutants: Ion Channels and G Protein-Coupled Receptors
Authors: Lester Henry A. , Karschin Andreas
Published: July 2002

Many ion channels and receptors display striking phenotypes for gainof-function mutations but milder phenotypes for null mutations. Gain of molecular function can have several mechanistic bases: selectivity changes, gating changes including constitutive activation and slowed inactivation, elimination of a subunit that enhances inactivation, decreased drug sensitivity, changes in regulation or trafficking of the channel, or induction of apoptosis. Decreased firing frequency can occur via increased function of K+or Cl−channels. Channel mutants also cause gain-of-function syndromes at the cellular and circuit level; of these syndromes, the cardiac long-QT syndromes are explained in a more straightforward way than are the epilepsies. G protein– coupled receptors are also affected by activating mutations.
COULOMB BREAKUP OF NUCLEI—APPLICATIONS TO ASTROPHYSICS
Authors: Baur G. , Rebel H.
Published: July 2002

▪ Abstract  The Coulomb dissociation process, induced by the intense source of quasi-real photons acting as nuclear particles pass through the field of a heavy nucleus, has attracted a great deal of attention. As a specific application, and as a means of access to the time-reversed radiative-capture reactions, which are of astrophysical interest at stellar energies, this process provides several advantages, based on larger cross sections and on the flexibilities of the breakup kinematics. Difficulties in the analysis arise from possible interference by nuclear interactions and final-state effects through multiphoton exchange (postacceleration), which need careful consideration. A number of theoretical and experimental investigations that have been performed, since the introduction of this novel approach have provided interesting new information, resulting in an improved and detailed understanding of the experimental conditions, and of the theoretical basis of the method. The progress in experiment and theory is reviewed, and various cases of actual interest and current applications are discussed.
MEASUREMENT OF THE CKM MATRIX ELEMENT |Vub| AND EXCLUSIVE B → πℓν AND B → ρℓν DECAYS
Authors: Gibbons Lawrence K.
Published: July 2002

▪ Abstract  The magnitude of the CKM matrix element |Vub| plays an important role in testing the unitarity of the CKM matrix. The first measurements of the exclusive b → u quark transitions [Formula: see text] and [Formula: see text], and the subsequent determination of |Vub|, are reviewed here.
The QCD Coupling Constant
Authors: Hinchliffe Ian , Manohar Aneesh
Published: July 2002

▪ Abstract  This paper presents a summary of the current status of determinations of the strong coupling constant αs. A detailed description of the definition, scale dependence, and inherent theoretical ambiguities is given. The various physical processes that can be used to determine αs are reviewed and attention is given to the uncertainties, both theoretical and experimental.
Human UDP-Glucuronosyltransferases: Metabolism, Expression, and Disease
Authors: Tukey Robert H. , Strassburg Christian P.
Published: July 2002

In vertebrates, the glucuronidation of small lipophilic agents is catalyzed by the endoplasmic reticulum UDP-glucuronosyltransferases (UGTs). This metabolic pathway leads to the formation of water-soluble metabolites originating from normal dietary processes, cellular catabolism, or exposure to drugs and xenobiotics. This classic detoxification process, which led to the discovery nearly 50 years ago of the cosubstrate UDP-glucuronic acid ( 19 ), is now known to be carried out by 15 human UGTs. Characterization of the individual gene products using cDNA expression experiments has led to the identification of over 350 individual compounds that serve as substrates for this superfamily of proteins. This data, coupled with the introduction of sophisticated RNA detection techniques designed to elucidate patterns of gene expression of the UGT superfamily in human liver and extrahepatic tissues of the gastrointestinal tract, has aided in understanding the contribution of glucuronidation toward epithelial first-pass metabolism. In addition, characterization of the UGT1A locus and genetic studies directed at understanding the role of bilirubin glucuronidation and the biochemical basis of the clinical symptoms found in unconjugated hyperbilirubinemia have uncovered the structural gene polymorphisms associated with Crigler-Najjar’s and Gilbert’s syndrome. The role of the UGTs in metabolism and different disease states in humans is the topic of this review.
Use of Biomarkers and Surrogate Endpoints in Drug Development and Regulatory Decision Making: Criteria, Validation, Strategies
Authors: Lesko LJ , Atkinson AJ
Published: July 2002

In the future, biomarkers will play an increasingly important role in all phases of drug development, including regulatory review. However, only a few of these biomarkers will become established well enough to serve in regulatory decision making as surrogate endpoints, thereby substituting for traditional clinical endpoints. Even generally accepted surrogate endpoints are unlikely to capture all the therapeutic benefits and potential adverse effects a drug will have in a diverse patient population. Accordingly, combinations of biomarkers probably will be needed to provide a more complete characterization of the spectrum of pharmacologic response. In the future, pharmacogenomic approaches, including those based on differential expression of gene arrays, will provide panels of relevant biomarkers that can be expected to transform the drug development process.
Ca2+/CaM-Dependent Kinases: From Activation to Function
Authors: Hook Sara S , Means Anthony R
Published: July 2002

Calmodulin (CaM) is an essential protein that serves as a ubiquitous intracellular receptor for Ca2+. The Ca2+/CaM complex initiates a plethora of signaling cascades that culminate in alteration of cellular functions. Among the many Ca2+/CaM-binding proteins to be discovered, the multifunctional protein kinases CaMKI, II, and IV play pivotal roles. Our review focuses on this class of CaM kinases to illustrate the structural and biochemical basis for Ca2+/CaM interaction with and regulation of its target enzymes. Gene transcription has been chosen as the functional endpoint to illustrate the recent advances in Ca2+/CaM-mediated signal transduction mechanisms.
The Pulmonary Collectins and Surfactant Metabolism
Authors: Hawgood Samuel , Poulain Francis R
Published: July 2002

▪ Abstract  Lung surfactant covers and stabilizes a large, delicate surface at the interface between the host and the environment. The surfactant system is placed at risk by a number of environmental challenges such as inflammation, infection, or oxidant stress, and perhaps not surprisingly, it demonstrates adaptive changes in metabolism in response to alterations in the alveolar microenvironment. Recent experiments have shown that certain components of the surfactant system are active participants in the regulation of the alveolar response to a wide variety of environmental challenges. These components are capable not only of maintaining a low interfacial surface tension but also of amplifying or dampening inflammatory responses. These observations suggest that regulatory molecules are capable of both sensing the environment of the alveolus and providing feedback to the cells regulating surfactant synthesis, secretion, alveolar conversion, and clearance. In this review we examine the evidence from in vitro systems and gene-targeted mice that two surfactant-associated collectins (SP-A and SP-D) may serve in these roles and help modify surfactant homeostasis as part of a coordinated host response to environmental challenges.
ROOT SYSTEM REGULATION OF WHOLE PLANT GROWTH
Authors: Aiken R. M. , Smucker A. J. M.
Published: July 2002

▪ Abstract  New evidence confirms earlier postulates that root signals to shoots, including abscisic acid, nitrate flux, and cytokinins, modify whole plant growth processes including leaf expansion, stomatal behavior, and biosynthesis of photosynthetic enzymes. Root signals are thought to reflect soil water, nutrient, and mechanical attributes, as sensed by roots. Meristematic activities in root tips initiate changes in root architecture, modifying the soil volume subject to root uptake, and may provide multiple sensory and signaling capabilities. Knowledge of root signals regulating whole plant growth processes suggests new analytical and experimental tools for integrated analysis of plant phasic development, optimal growth, and ecological fitness.
THEEVOLUTION OFASEXUALFUNGI: Reproduction, Speciation and Classification
Authors: Taylor JW , Jacobson DJ , Fisher MC
Published: July 2002

▪ Abstract  Phylogenetic and population genetic methods that compare nucleic acid variation are being used to identify species and populations of pathogenic fungi and determine how they reproduce in nature. These studies show that asexual or sexual reproductive morphology does not necessarily correlate with clonal or recombining reproductive behavior, and that fungi with all types of reproductive morphologies and behaviors can be accommodated by a phylogenetic species concept. Although approximately one fifth of described fungi have been thought to be asexual and clonal, recent studies have shown that they are also recombining. Whether a particular pathogen reproduces clonally or by recombination depends on factors relating to its biology and its distribution in space and time. Knowing the identity of species and populations and their reproductive modes, while taking a broad view of pathogen behavior in space and time, should enhance the ability of pathologists to control pathogens and even predict their behavior.
APOMICTIC, POLYPHAGOUSROOT-KNOTNEMATODES: Exceptionally Successful and Damaging Biotrophic Root Pathogens
Authors: Trudgill David L. , Blok Vivian C.
Published: July 2002

▪ Abstract  Most apomictic root-knot nematodes (RKN; Meloidogyne spp.) have host ranges that encompass the majority of flowering plants, and M. incognita is possibly the world's most damaging crop pathogen. The ancestors, age, and origins of the polyphagous RKN are obscure, but there is increasing evidence that M. incognita, M. javanica, and M. arenaria are closely related, heterogeneous species with a recent, hybrid (reticulate) origin. If so, they must owe much of their current worldwide distributions to spread by agriculture. Host resistance appears to be generally durable in the field, but laboratory studies suggest that apomixis does not prevent evolution in response to selection by a parasitic bacterium (Pasteuria penetrans) and host resistance. Maintaining general fitness may be the evolutionary priority for most populations of polyphagous RKN, and a wide host range, important in the field but not in the laboratory, may be conserved by apomixis. Several factors may help confer a wide host range, including suppression of host resistance, perhaps as a consequence of the strength of the induced susceptible response. Resistance genes effective against RKN appear not to have resulted from coevolution. Rates of juvenile invasion and/or development are low in many wild and some crop plants, with the result that they are both poor hosts and sustain less damage. Overall, it is suggested that greater coordination, particularly of fundamental research, is required.
Economic Determinants of Electoral Outcomes
Authors: Lewis-Beck Michael S. , Stegmaier Mary
Published: July 2002

Economic conditions shape election outcomes in the world's democracies. Good times keep parties in office, bad times cast them out. This proposition is robust, as the voluminous body of research reviewed here demonstrates. The strong findings at the macro level are founded on the economic voter, who holds the government responsible for economic performance, rewarding or punishing it at the ballot box. Although voters do not look exclusively at economic issues, they generally weigh those more heavily than any others, regardless of the democracy they vote in.
HUMAN-COMPUTER INTERACTION: Psychology as a Science of Design
Authors: Carroll John M.
Published: July 2002

▪ Abstract  Human-computer interaction (HCI) study is the region of intersection between psychology and the social sciences, on the one hand, and computer science and technology, on the other. HCI researchers analyze and design specific user interface technologies (e.g. pointing devices). They study and improve the processes of technology development (e.g. task analysis, design rationale). They develop and evaluate new applications of technology (e.g. word processors, digital libraries). Throughout the past two decades, HCI has progressively integrated its scientific concerns with the engineering goal of improving the usability of computer systems and applications, which has resulted in a body of technical knowledge and methodology. HCI continues to provide a challenging test domain for applying and developing psychological and social theory in the context of technology development and use.
COMORBIDITY OF ANXIETY AND UNIPOLAR MOOD DISORDERS
Authors: Mineka Susan , Watson David , Clark Lee Anna
Published: July 2002

▪ Abstract  Research on relationships between anxiety and depression has proceeded at a rapid pace since the 1980s. The similarities and differences between these two conditions, as well as many of the important features of the comorbidity of these disorders, are well understood. The genotypic structure of anxiety and depression is also fairly well documented. Generalized anxiety and major depression share a common genetic diathesis, but the anxiety disorders themselves are genetically hetergeneous. Sophisticated phenotypic models have also emerged, with data converging on an integrative hierarchical model of mood and anxiety disorders in which each individual syndrome contains both a common and a unique component. Finally, considerable progress has been made in understanding cognitive aspects of these disorders. This work has focused on both the cognitive content of anxiety and depression and on the effects that anxiety and depression have on information processing for mood-congruent material.
Social Cognitive Theory: An Agentic Perspective
Authors: Bandura Albert
Published: July 2002

▪ Abstract  The capacity to exercise control over the nature and quality of one's life is the essence of humanness. Human agency is characterized by a number of core features that operate through phenomenal and functional consciousness. These include the temporal extension of agency through intentionality and forethought, self-regulation by self-reactive influence, and self-reflectiveness about one's capabilities, quality of functioning, and the meaning and purpose of one's life pursuits. Personal agency operates within a broad network of sociostructural influences. In these agentic transactions, people are producers as well as products of social systems. Social cognitive theory distinguishes among three modes of agency: direct personal agency, proxy agency that relies on others to act on one's behest to secure desired outcomes, and collective agency exercised through socially coordinative and interdependent effort. Growing transnational embeddedness and interdependence are placing a premium on collective efficacy to exercise control over personal destinies and national life.
On Happiness and Human Potentials: A Review of Research on Hedonic and Eudaimonic Well-Being
Authors: Ryan Richard M. , Deci Edward L.
Published: July 2002

▪ Abstract  Well-being is a complex construct that concerns optimal experience and functioning. Current research on well-being has been derived from two general perspectives: the hedonic approach, which focuses on happiness and defines well-being in terms of pleasure attainment and pain avoidance; and the eudaimonic approach, which focuses on meaning and self-realization and defines well-being in terms of the degree to which a person is fully functioning. These two views have given rise to different research foci and a body of knowledge that is in some areas divergent and in others complementary. New methodological developments concerning multilevel modeling and construct comparisons are also allowing researchers to formulate new questions for the field. This review considers research from both perspectives concerning the nature of well-being, its antecedents, and its stability across time and culture.
Meta-Analysis: Recent Developments in Quantitative Methods for Literature Reviews
Authors: Rosenthal R. , DiMatteo M. R.
Published: July 2002

▪ Abstract  We describe the history and current status of the meta-analytic enterprise. The advantages and historical criticisms of meta-analysis are described, as are the basic steps in a meta-analysis and the role of effect sizes as chief coins of the meta-analytic realm. Advantages of the meta-analytic procedures include seeing the “landscape” of a research domain, keeping statistical significance in perspective, minimizing wasted data, becoming intimate with the data summarized, asking focused research questions, and finding moderator variables. Much of the criticism of meta-analysis has been based on simple misunderstanding of how meta-analyses are actually carried out. Criticisms of meta-analysis that are applicable are equally applicable to traditional, nonquantitative, narrative reviews of the literature. Much of the remainder of the chapter deals with the processes of effect size estimation, the understanding of the heterogeneity of the obtained effect sizes, and the practical and scientific importance of the effect sizes obtained.
Socioeconomic Status and Child Development
Authors: Bradley Robert H. , Corwyn Robert F.
Published: July 2002

▪ Abstract  Socioeconomic status (SES) is one of the most widely studied constructs in the social sciences. Several ways of measuring SES have been proposed, but most include some quantification of family income, parental education, and occupational status. Research shows that SES is associated with a wide array of health, cognitive, and socioemotional outcomes in children, with effects beginning prior to birth and continuing into adulthood. A variety of mechanisms linking SES to child well-being have been proposed, with most involving differences in access to material and social resources or reactions to stress-inducing conditions by both the children themselves and their parents. For children, SES impacts well-being at multiple levels, including both family and neighborhood. Its effects are moderated by children's own characteristics, family characteristics, and external support systems.
Measuring Social Class in US Public Health Research: Concepts, Methodologies, and Guidelines
Authors: Krieger N. , Williams D. R. , Moss N. E.
Published: July 2002

Increasing social inequalities in health in the United States and elsewhere, coupled with growing inequalities in income and wealth, have refocused attention on social class as a key determinant of population health. Routine analysis using conceptually coherent and consistent measures of socioeconomic position in US public health research and surveillance, however, remains rare. This review discusses concepts and methodologies concerning, and guidelines for measuring, social class and other aspects of socioeconomic position (e.g. income, poverty, deprivation, wealth, educattion). These data should be collected at the individual, household, and neighborhood level, to characterize both childhood and adult socioeconomic position; fluctuations in economic resources during these time periods also merit consideration. Guidelines for linking census-based socioeconomic measures and health data are presented, as are recommendations for analyses involving social class, race/ethnicity, and gender. Suggestions for research on socioeconomic measures are provided, to aid monitoring steps toward social equity in health.
Social Capital: Its Origins and Applications in Modern Sociology
Authors: Portes Alejandro
Published: July 2002

This paper reviews the origins and definitions of social capital in the writings of Bourdieu, Loury, and Coleman, among other authors. It distinguishes four sources of social capital and examines their dynamics. Applications of the concept in the sociological literature emphasize its role in social control, in family support, and in benefits mediated by extrafamilial networks. I provide examples of each of these positive functions. Negative consequences of the same processes also deserve attention for a balanced picture of the forces at play. I review four such consequences and illustrate them with relevant examples. Recent writings on social capital have extended the concept from an individual asset to a feature of communities and even nations. The final sections describe this conceptual stretch and examine its limitations. I argue that, as shorthand for the positive consequences of sociability, social capital has a definite place in sociological theory. However, excessive extensions of the concept may jeopardize its heuristic value.
Intermarriage and Homogamy: Causes, Patterns, Trends
Authors: Kalmijn Matthijs
Published: July 2002

People have a tendency to marry within their social group or to marry a person who is close to them in status. Although many characteristics play a role in the choice of a spouse, sociologists have most often examined endogamy and homogamy with respect to race/ethnicity, religion, and socioeconomic status. I first give an overview of hypotheses on the causes of endogamy and homogamy. The various hypotheses that have been suggested in the literature can be distinguished as arguments about three more general factors: (a) the preferences of marriage candidates for certain characteristics in a spouse, (b) the interference of “third parties” in the selection process, and (c) the constraints of the marriage market in which candidates are searching for a spouse. Second, I summarize empirical research by answering four questions: (a) To what extent are groups endogamous and how do groups differ in this respect? (b) How has endogamy changed over time? (c) Which factors are related to endogamy? (d) How do various dimensions of partner choice coincide? Third, I discuss strengths and weaknesses of past research. Strengths include the mass of descriptive work that has been done and the development of a multifaceted theoretical perspective which gives sociological theorizing an edge over psychological and economic theories of partner choice. Weaknesses include the lack of standardization of methods in describing patterns and trends and the relatively weak integration of empirical and theoretical work.
Ethnic and Nationalist Violence
Authors: Brubaker Rogers , Laitin David D.
Published: July 2002

Work on ethnic and nationalist violence has emerged from two largely nonintersecting literatures: studies of ethnic conflict and studies of political violence. Only recently have the former begun to attend to the dynamics of violence and the latter to the dynamics of ethnicization. Since the emergent literature on ethnic violence is not structured by clearly defined theoretical oppositions, we organize our review by broad similarities of methodological approach: (a) Inductive work at various levels of aggregation seeks to identify the patterns, mechanisms, and recurrent processes implicated in ethnic violence. (b) Theory-driven work employs models of rational action drawn from international relations theory, game theory, and general rational action theory. (c) Culturalist work highlights the discursive, symbolic, and ritualistic aspects of ethnic violence. We conclude with a plea for the disaggregated analysis of the heterogeneous phenomena we too casually lump together as “ethnic violence.”
Cases and Biographies: An Essay on Routinization and the Nature of Comparison
Authors: Heimer Carol A.
Published: July 2002

▪ Abstract  Routines, protocols, and organization charts focus attention, structure cognition, and shape decision making. Participants in organizations, legal systems, and markets compare cases, deciding which protocol governs the treatment of each case in a stream. But situations vary in the extent to which thought and action are effectively governed by routines and standard operating procedures. In less structured or more chaotic situations, biography is an alternative form of analysis that shapes cognition and helps people make sense of otherwise uninterpretable events. Biography and narrative do their work by constructing the causal unity of objects over time rather than by constructing causation from a comparison across similar cases. Using examples such as critically ill infants, animals, heirlooms, the penalty phase of capital trials, juvenile justice, the lower criminal courts, religious relics, and cloth, the paper compares case and biographical analysis in organizations, legal settings, and markets, asking how these different ways of thinking come about and what follows from them.
Augmentation of Intrapericardial Nitric Oxide Level by a Prolonged-Release Nitric Oxide Donor Reduces Luminal Narrowing After Porcine Coronary Angioplasty
Authors: Baek Sang Hong , Hrabie Joseph A. , Keefer Larry K. , Hou Dongming , Fineberg Naomi , Rhoades Rodney , March Keith L.
Published: July 2002

Background

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Nitric oxide (NO) is a potent vasodilator and antiplatelet agent that suppresses vascular smooth muscle cell proliferation. Hypothesizing that generating NO in the pericardial space would reduce luminal narrowing after coronary angioplasty without affecting systemic hemodynamics, we have determined the effect of a novel NO donor on vascular healing after balloon overstretch.

Methods and Results

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Diazeniumdiolated bovine serum albumin (D-BSA; molecular weight 74 kDa, half-life for NO release 20 days) was radioiodinated and found by intravital γ-imaging to have a longer residence time in pig pericardium than a low-molecular-weight (0.5 kDa) analogue (22 versus 4.6 hours, respectively). Intrapericardial injection of D-BSA immediately before 30% overstretch of normal left anterior descending and left circumflex coronary arteries dose dependently reduced the intimal/medial area ratio by up to 50% relative to controls treated with underivatized albumin when measured 2 weeks after intervention. Positive remodeling was also noted, which increased luminal area relative to control.

Conclusions

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Perivascular exposure of coronary arteries to NO via intrapericardial D-BSA administration reduced flow-restricting lesion development after angioplasty in pigs without causing significant systemic effects. The data suggest that intrapericardial delivery of NO donors for which NO release rates and pericardial residence times are matched and optimized might be a beneficial adjunct to coronary angioplasty.
Witchcraft Fears and Psychosocial Factors in Disease
Authors: Bever Edward
Published: July 2002

Historians, anthropologists, and psychologists have tended to discount the role of “psychosomatic” disease in witchcraft beliefs because they have misunderstood, and therefore underestimated, the connection between interpersonal relations, psychological well-being, and physical health. Current medical knowledge about the relationship between psychological distress, the physiological stress reaction, and somatic disorders, however, gives grounds for a more positive assessment of the traditional notion that ill will can cause illness and accidents. Disturbed interpersonal relations can cause, or contribute to, an extremely wide range of physical maladies, with or without any accompanying fear of witchcraft or magic. Evidence of this effect can be found in reports from a wide range of cultures. It is a significant element in a systematic sample of witch cases from early modern Württemberg.
The Licensing of Null Arguments in American Sign Language
Authors: Bahan Benjamin , Kegl Judy , Lee Robert G. , MacLaughlin Dawn , Neidle Carol
Published: July 2002

The distribution of null arguments across languages has been accounted for in terms of two distinct strategies: licensing by agreement and licensing by topic. Lillo-Martin (1986, 1991) claims that American Sign Language (ASL) exploits both strategies for licensing null arguments, depending on the morphological characteristics of the verb. Here we show that this is incorrect. Once the nonmanual correlates of agreement features (comparable to the nonmanual expressions of other syntactic features) in ASL are recognized, it becomes apparent that null arguments in this language are systematically licensed by an expression of syntactic agreement.
Mirror Theory: Syntactic Representation in Perfect Syntax
Authors: Brody Michael
Published: July 2002

In the better-developed sciences it is the departures from symmetry rather than the symmetries that are typically taken to be in need of explanation. Mirror theory is an attempt to look at some of the central properties of syntactic representations in this spirit.

The core hypothesis of this theory is that in syntactic representations complementation expresses morphological structure: X is the complement of Y only if Y-X form a morphological unit'a word. A second central assumption is the elimination of phrasal projection: a head X in a syntactic tree should be taken to ambiguously represent both the zero-level head(s) and its (their) associated phrasal node(s).
V. Multi-Level Analysis of Cortical Neuroanatomy in Williams Syndrome
Authors: Galaburda Albert M. , Bellugi Ursula
Published: July 2002

The purpose of a neuroanatomical analysis of Williams Syndrome (WMS) brains is to help bridge the knowledge of the genetics of this disorder with the knowledge on behavior. Here, we outline findings of cortical neuroanatomy at multiple levels. We describe the gross anatomy with respect to brain shape, cortical folding, and asymmetry. This, as with most neuroanatomical information available in the literature on anatomical-functional correlations, links up best to the behavioral profile. Then, we describe the cytoarchitectonic appearance of the cortex. Further, we report on some histometric results. Finally, we present findings of immunocy-tochemistry that attempt to link up to the genomic deletion. The gross anatomical findings consist mainly of a small brain that shows curtailment in the posterior-parietal and occipital regions. There is also subtle dysmorphism of cortical folding. A consistent finding is a short central sulcus that does not become opercularized in the interhemispheric fissure, bringing attention to a possible developmental anomaly affecting the dorsal half of the hemispheres. There is also lack of asymmetry in the planum temporale. The cortical cytoarchitecture is relatively normal, with all sampled areas showing features typical of the region from which they are taken. Measurements in area 17 show increased cell size and decreased cell-packing density, which address the issue of possible abnormal connectivity. Immunostaining shows absence of elastin but normal staining for Lim-1 kinase, both of which are products of genes that are part of the deletion. Finally, one serially sectioned brain shows a fair amount of acquired pathology of microvascular origin related most likely to underlying hypertension and heart disease.
Brain Activation During Reading in Deep Dyslexia: An MEG Study
Authors: Laine Matti , Salmelin Riitta , Helenius Päivi , Marttila Reijo
Published: July 2002

Magnetoencephalographic (MEG) changes in cortical activity were studied in a chronic Finnish-speaking deep dyslexic patient during single-word and sentence reading. It has been hypothesized that in deep dyslexia, written word recognition and its lexical-semantic analysis are subserved by the intact right hemisphere. However, in our patient, as well as in most nonimpaired readers, lexical-semantic processing as measured by sentence-final semantic-incongruency detection was related to the left superior-temporal cortex activation. Activations around this same cortical area could be identified in single-word reading as well. Another factor relevant to deep dyslexic reading, the morphological complexity of the presented words, was also studied. The effect of morphology was observed only during the preparation for oral output. By performing repeated recordings 1 year apart, we were able to document significant variability in both the spontaneous activity and the evoked responses in the lesioned left hemisphere even though at the behavioural level, the patient's performance was stable. The observed variability emphasizes the importance of estimating consistency of brain activity both within and between measurements in brain-damaged individuals.
Electrophysiological Correlates of Conscious Vision: Evidence from Unilateral Extinction
Authors: Marzi Carlo A. , Girelli Massimo , Miniussi Carlo , Smania Nicola , Maravita Angelo
Published: July 2002

To study the electrophysiological correlates of conscious vision, we recorded event-related potentials (ERPs) in a patient with partial unilateral visual extinction as a result of right-hemisphere damage. When, following bilateral presentations, contralesional stimuli were not perceived, there was an absence of the early attention-sensitive P1 (80-120 msec) and N1 (140-180 msec) components of the ERP response. In contrast, following unilateral presentations, or in those bilateral presentations in which contralesional stimuli were perceived (about 60%), these ERP components were present. These results provide novel evidence that extinction involves the stage of early focusing of attention and that the P1 and N1 components of visual ERPs are reliable physiological correlates of conscious vision.
Neglect Between but Not Within Auditory Objects
Authors: Cusack Rhodri , Carlyon Robert P. , Robertson Ian H.
Published: July 2002

Unilateral neglect is frequently characterized by the presence of extinction, which is a lack of awareness to contralesional visual stimuli in the presence of those further towards the ipsilesional side. It has been established that this visual extinction can be reduced if the stimuli are grouped together into a single object. However, attention between and within auditory objects has never before been studied. We demonstrate for the first time that unilateral neglect—hitherto thought primarily to be a disorder of visuospatial processing—involves a specific deficit in allocating attention between auditory objects separated only in time and not in space. Importantly, this deficit is restricted to comparisons between sounds: the patients' ability to make within-sound comparisons is similar to that of controls. These differences cannot be explained in terms of different time spans over which comparisons must be made. The results suggest unilateral neglect is linked to—if not actually determined by—a reduction in attentional capacity in both the visual and auditory domains, and across the dimensions of both space and time. The findings have potential clinical applications.
The Time Course of Visual Processing: From Early Perception to Decision-Making
Authors: VanRullen Rufin , Thorpe Simon J.
Published: July 2002

Experiments investigating the mechanisms involved in visual processing often fail to separate low-level encoding mechanisms from higher-level behaviorally relevant ones. Using an alternating dual-task event-related potential (ERP) experimental paradigm (animals or vehicles categorization) where targets of one task are intermixed among distractors of the other, we show that visual categorization of a natural scene involves different mechanisms with different time courses: a perceptual, task-independent mechanism, followed by a task-related, category-independent process. Although average ERP responses reflect the visual category of the stimulus shortly after visual processing has begun (e.g. 75-80 msec), this difference is not correlated with the subject's behavior until 150 msec poststimulus.
Conjoining Three Auditory Features: An Event-Related Brain Potential Study
Authors: Woods David L. , Alain Claude
Published: July 2002

The mechanisms of auditory feature processing and conjunction were examined with event-related brain potential (ERP) recording in a task in which participants responded to target tones defined by the combination of location, frequency, and duration features amid distractor tones varying randomly along all feature dimensions. Attention effects were isolated as negative difference (Nd) waves by subtracting ERPs to tones with no target features from ERPs to tones with one, two, or three target features. Nd waves were seen to all tones sharing a single feature with the target, including tones sharing only target duration. Nd waves associated with the analysis of frequency and location features began at latencies of 60 msec, whereas Nd-Duration waves began at 120 msec. Nd waves to tones with single target features continued until 400+ msec, suggesting that once begun, the analysis of tone features continued exhaustively to conclusion. Nd-Frequency and Nd-Location waves had distinct scalp distributions, consistent with generation in different auditory cortical areas. Three stages of feature processing were identified: (1) Parallel feature processing (60-140 msec): Nd waves combined linearly, such that Nd-wave amplitudes following tones with two or three target features were equal to the sum of the Nd waves elicited by tones with only one target feature. (2) Conjunction-specific (CS) processing (140-220 msec): Nd amplitudes were enhanced following tones with any pair of attended features. (3) Target-specific (TS) processing (220-300 msec): Nd amplitudes were specifically enhanced to target tones with all three features. These results are consistent with a facilitatory interactive feature analysis (FIFA) model in which feature conjunction is associated with the amplified processing of individual stimulus features. Activation of N-methyl-D-aspartate (NMDA) receptors is proposed to underlie the FIFA process.
Discourse Representation in the Two Cerebral Hemispheres
Authors: Long Debra L. , Baynes Kathleen
Published: July 2002

Readers construct at least two interrelated representations when they comprehend a text: (a) a propositional representation containing the individual ideas that are derived from each sentence and the relations among them and (b) a discourse model, a representation of the context or situation to which the text refers. We used a paradigm called “item priming in recognition” to examine how these representations are stored in the cerebral hemispheres. In Experiment 1, the priming paradigm was used in combination with a lateralized visual field (VF) procedure. We found evidence that readers' representations were structured according to propositional relations, but only in the left hemisphere. Item recognition was facilitated when a concept was preceded by another concept from the same proposition when targets were presented to the left, but not to the right, hemisphere. We found priming in both hemispheres, however, when targets were context-appropriate senses of ambiguous words or topics of passages. In Experiment 2, we replicated the priming effects in three callosotomy patients. We argue that the distinction between a propositional representation and a discourse model is important with respect to how discourse is represented in the brain. The propositional representation appears to reside in the left hemisphere, whereas aspects of the discourse model appear to be represented in both hemispheres.
Learning to Forget: Continual Prediction with LSTM
Authors: Gers Felix A. , Schmidhuber Jürgen , Cummins Fred
Published: July 2002

Long short-term memory (LSTM; Hochreiter & Schmidhuber, 1997) can solve numerous tasks not solvable by previous learning algorithms for recurrent neural networks (RNNs). We identify a weakness of LSTM networks processing continual input streams that are not a priori segmented into subsequences with explicitly marked ends at which the network's internal state could be reset. Without resets, the state may grow indefinitely and eventually cause the network to break down. Our remedy is a novel, adaptive “forget gate” that enables an LSTM cell to learn to reset itself at appropriate times, thus releasing internal resources. We review illustrative benchmark problems on which standard LSTM outperforms other RNN algorithms. All algorithms (including LSTM) fail to solve continual versions of these problems. LSTM with forget gates, however, easily solves them, and in an elegant way.
Nonlinear Component Analysis as a Kernel Eigenvalue Problem
Authors: Schölkopf Bernhard , Smola Alexander , Müller Klaus-Robert
Published: July 2002

A new method for performing a nonlinear form of principal component analysis is proposed. By the use of integral operator kernel functions, one can efficiently compute principal components in high-dimensional feature spaces, related to input space by some nonlinear map—for instance, the space of all possible five-pixel products in 16 × 16 images. We give the derivation of the method and present experimental results on polynomial feature extraction for pattern recognition.
Properties of Support Vector Machines
Authors: Pontil Massimiliano , Verri Alessandro
Published: July 2002

Support vector machines (SVMs) perform pattern recognition between two point classes by finding a decision surface determined by certain points of the training set, termed support vectors (SV). This surface, which in some feature space of possibly infinite dimension can be regarded as a hyperplane, is obtained from the solution of a problem of quadratic programming that depends on a regularization parameter. In this article, we study some mathematical properties of support vectors and show that the decision surface can be written as the sum of two orthogonal terms, the first depending on only the margin vectors (which are SVs lying on the margin), the second proportional to the regularization parameter. For almost all values of the parameter, this enables us to predict how the decision surface varies for small parameter changes. In the special but important case of feature space of finite dimension m, we also show that there are at most m + 1 margin vectors and observe that m + 1 SVs are usually sufficient to determine the decision surface fully. For relatively small m, this latter result leads to a consistent reduction of the SV number.
Synaptic Delay Learning in Pulse-Coupled Neurons
Authors: Hüning Harald , Glünder Helmut , Palm Günther
Published: July 2002

We present rules for the unsupervised learning of coincidence between excitatory postsynaptic potentials (EPSPs) by the adjustment of post-synaptic delays between the transmitter binding and the opening of ion channels. Starting from a gradient descent scheme, we develop a robust and more biological threshold rule by which EPSPs from different synapses can be gradually pulled into coincidence. The synaptic delay changes are determined from the summed potential—at the site where the coincidence is to be established—and from postulated synaptic learning functions that accompany the individual EPSPs. According to our scheme, templates for the detection of spatiotemporal patterns of synaptic activation can be learned, which is demonstrated by computer simulation. Finally, we discuss possible relations to biological mechanisms.
GTM: The Generative Topographic Mapping
Authors: Bishop Christopher M. , Svensén Markus , Williams Christopher K. I.
Published: July 2002

Latent variable models represent the probability density of data in a space of several dimensions in terms of a smaller number of latent, or hidden, variables. A familiar example is factor analysis, which is based on a linear transformation between the latent space and the data space. In this article, we introduce a form of nonlinear latent variable model called the generative topographic mapping, for which the parameters of the model can be determined using the expectation-maximization algorithm. GTM provides a principled alternative to the widely used self-organizing map (SOM) of Kohonen (1982) and overcomes most of the significant limitations of the SOM. We demonstrate the performance of the GTM algorithm on a toy problem and on simulated data from flow diagnostics for a multiphase oil pipeline.
Independent Component Analysis Using an Extended Infomax Algorithm for Mixed Subgaussian and Supergaussian Sources
Authors: Lee Te-Won , Girolami Mark , Sejnowski Terrence J.
Published: July 2002

An extension of the infomax algorithm of Bell and Sejnowski (1995) is presented that is able blindly to separate mixed signals with sub- and supergaussian source distributions. This was achieved by using a simple type of learning rule first derived by Girolami (1997) by choosing negentropy as a projection pursuit index. Parameterized probability distributions that have sub- and supergaussian regimes were used to derive a general learning rule that preserves the simple architecture proposed by Bell and Sejnowski (1995), is optimized using the natural gradient by Amari (1998), and uses the stability analysis of Cardoso and Laheld (1996) to switch between sub- and supergaussian regimes. We demonstrate that the extended infomax algorithm is able to separate 20 sources with a variety of source distributions easily. Applied to high-dimensional data from electroencephalographic recordings, it is effective at separating artifacts such as eye blinks and line noise from weaker electrical signals that arise from sources in the brain.