bluuebunny/crossref_metadata_2025_split huggingface dataset:
MOLECULAR-FUNCTIONAL STUDIES OF ADAPTIVE GENETIC VARIATION IN PROKARYOTES AND EUKARYOTES
Authors: Watt Ward B , Dean Antony M 
Published: July 2002

▪ Abstract  Knowledge of both prokaryotic and eukaryotic organisms is essential to the study of molecular evolution. Their common ancestry mandates that their molecular functions share many aspects of adaptation and constraint, yet their differences in size, ploidy, and structural complexity also give rise to divergent evolutionary options. We explore the interplay of adaptation, constraint, and neutrality in their evolution by the use of genetic variants to probe molecular function in context of molecular structure, metabolic organization, and phenotype-environment interactions. Case studies ranging from bacteria to butterflies, flies, and vertebrates emphasize, among other points:a. the importance of moving from initial recording of evolutionary pattern variation to studying the processes underlying the patterns, by experiment, reconstructive inference, or both; b. the complementarity, not conflict, of finding different performance and fitness impacts of natural variants in prokaryotes or eukaryotes, depending on the nature and magnitude of the variants, their locations and roles in pathways, the nature of molecular function affected, and the resulting organismal phenotype-environment interactions leading to selection or its absence; c. the importance of adaptive functional interaction of different kinds of variants, as in gene expression variants versus variants altering polypeptide properties, or interaction of changes in enzymes' active sites with complementary changes elsewhere that adjust catalytic function in different ways, or coadaptation of different steps' properties in pathways; d. the power afforded by combining structural and functional analyses of variants with study of the variants' phenotype-environment interactions to understand how molecular changes affect (or fail to affect) adaptive mechanisms “in the wild.”Comparative study of prokaryotes and eukaryotes in this multifaceted way promises to deliver both new insights into evolution and a host of new and productive questions about it.
TISSUE RENIN-ANGIOTENSIN SYSTEM:A Site of Drug Action?
Authors: Zimmerman and Ben G. , Dunham Earl W. 
Published: July 2002

▪ Abstract  In this review, we present background material that provides partial support for a tissue renin-angiotensin system (RAS). Evidence for the existence of this system relied in part the use of drugs, which has entailed using low doses or concentrations of angiotensin-converting enzyme inhibitors, renin inhibitors, and angiotensin antagonists to block the RAS in vascular beds and in isolated arteries or organs. Other evidence for a tissue RAS has depended upon measurements of the components of the system, i.e. enzymes, substrates, and mRNAs for these proteins. All of these components were first believed to be present in the heart and blood vessels; however, it is now known that renin in the circulating blood derived from the kidney is used for the local synthesis of angiotensins. The main emphasis of the review is on the renal RAS because it is believed that the local RAS is most prominent in this organ. The renal RAS is probably involved in the long- rather than short-term regulation of renal vascular resistance and maintenance of normal blood pressure through the regulation of sodium reabsorption.
Role of Estrogen Receptor Beta in Estrogen Action
Authors: Pettersson Katarina , Gustafsson Jan-Åke 
Published: July 2002

▪ Abstract  There was a time when the classification of sex hormones was simple. Androgens were male and estrogens female. What remains true today is that in young adults androgen levels are higher in males and estrogen levels higher in females. More recently we have learned that estrogens are necessary in males for regulation of male sexual behavior, maintenance of the skeleton and the cardiovascular system, and for normal function of the testis and prostate. The importance of androgen in females was never in doubt, it is after all the precursor of estrogen as the substrate for aromatase, the enzyme that produces estrogen. In addition, the tissue distribution of androgen receptors suggests that androgens themselves are important in the ovary, uterus, breast, and brain.New information promises to clarify some of the complex issues of the physiological roles of estrogen and the contribution of estrogen to the development of neoplastic diseases in humans. The discovery of the second estrogen receptor, the creation of mutant mice defective in both estrogen receptors and in the aromatase gene, the solution of the structures of the ligand-binding domains of estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ), the finding of novel routes through which estrogen receptors can modulate transcription, and the identification of a man with a bi-allelic disruptive mutation of the ERα gene are but some of the milestones. This review focuses on the mechanistic aspects of signal transduction mediated by ERs and on the physiological consequences of deficiency of estrogen or estrogen receptor in the available mouse models.
Capacity Theory as a Model of Cortical Behavior
Authors: Handy Todd C. 
Published: July 2002

Abstract
Growing evidence suggests that a more complete understanding of cortical function requires developing cognitive models that are predictive of multivariate neural behavior (e.g., Raichle, 2000; Shulman et al., 1997). Towards this end, one approach is to interpret population-specific activity in cortex from the perspective of capacity theories of selective attention (e.g., Handy, Hopfinger, & Mangun, in press). In brief, the model is founded on the ideas that (1) processing capacity is limited and (2) different processes may draw on different capacities (e.g., Boles & Law 1998; Polson & Friedman, 1988; see Kramer & Spinks, 1991). Testable hypotheses are then based on whether manipulations of process-specific load will lead to negative or positive covariation between different function-related clusters of activation in cortex—the predicted pattern depends on whether or not the clusters in question are assumed to share a common processing capacity. Expanding on these ideas, the current article addresses several recent issues that have arisen in the effort to apply capacity theory to the study of cortical function.
Procedural Learning in Broca's Aphasia: Dissociation between the Implicit Acquisition of Spatio-Motor and Phoneme Sequences
Authors: Goschke Thomas , Friederici Angela D. , Kotz Sonja A. , van Kampen Anja 
Published: July 2002

AbstractProcedural learning of spatio-motor and phoneme sequences was investigated in patients with Broca's and Wernick's aphasia and age-matched controls. In Experiment 1, participants performed a standard serial reaction task (SRT) in which they manually responded to a repeating sequence of stimulus locations. Both Broca's and Wernick's aphasics showed intact sequence learning, as indicated by a reliable response time (RT) cost when the repeating sequence was swithched to a random sequence. In Experiment 2, Broca's aphasics and controls performed a new serial search task (SST), which allowed us to investigate the learning of a spatio-motor sequence and a phoneme sequence independently from each other. On each trial, four letters were presented visually, followed by a single auditorily presented letter. Participants had to press one of four response keys to indicate the location of the auditory letter in the visual display. The arrangement of the visual letters was changed from trial to trial such that either the key-presses or the auditory letters followed a repeating pattern, while the other sequence was random. While controls learned both the key-press and the phoneme sequences, Broca's aphasics were selectively impaired in learning the phoneme sequence. This dissociation between learning of spatio-motor and phoneme sequences supports the assumption that partially separable brain systems are involved in proceedural learning of differenct types of sequential structures.
Phonological Processing in Visual Rhyming: A Developmental ERP Study
Authors: Grossi Giordana , Coch Donna , Coffey-Corina Sharon , Holcomb Phillip J. , Neville Helen J. 
Published: July 2002

Abstract
We employed a visual rhyming priming paradigm to characterize the development of brain systems important for phonological processing in reading. We studied 109 right-handed, native English speakers within eight age groups: 7-8, 9-10, 11-12, 13-14, 15-16, 17-18, 19-20, and 21-23. Participants decided whether two written words (prime-target) rhymed (JUICE-MOOSE) or not (CHAIR-MOOSE). In similar studies of adults, two main event-related potential (ERP) effects have been described: a negative slow wave to primes, larger over anterior regions of the left hemisphere and hypothesized to index rehearsal of the primes, and a negative deflection to targets, peaking at 400-450 msec, maximal over right temporal-parietal regions, larger for nonrhyming than rhyming targets, and hypothesized to index phonological matching. In this study, these two ERP effects were observed in all age groups; however, the two effects showed different developmental timecourses. On the one hand, the frontal asymmetry to primes increased with age; moreover, this asymmetry was correlated with reading and spelling scores, even after controlling for age. On the other hand, the distribution and onset of the more posterior rhyming effect (RE) were stable across age groups, suggesting that phonological matching relied on similar neural systems across these ages. Behaviorally, both reaction times and accuracy improved with age. These results suggest that different aspects of phonological processing rely on different neural systems that have different developmental timecourses.
Posterior Corpus Callosum and Interhemispheric Transfer of Somatosensory Information: An fMRI and Neuropsychological Study of a Partially Callosotomized Patient
Authors: Fabri Mara , Polonara Gabriele , Pesce Maria Del , Quattrini Angelo , Salvolini Ugo , Manzoni Tullio 
Published: July 2002

Abstract
Interhemispheric somatosensory transfer was studied by functional magnetic resonance imaging (fMRI) and neuropsychological tests in a patient who underwent resection of the corpus callosum (CC) for drug-resistant epilepsy in two stages. The first resection involved the anterior half of the body of CC and the second, its posterior half and the splenium. For the fMRI study, the hand was stimulated with a rough sponge. The neuropsychological tests included: Tactile Naming Test (TNT), Same-Different Recognition Test (SDRT), and Tactile Finger Localization Test (intra- and intermanual tasks, TFLT). The patient was studied 1 week before and then 6 months and 1 year after the second surgery. Before this operation, unilateral tactile stimulation of either hand activated contralaterally the first (SI) and second (SII) somatosensory areas and the posterior parietal (PP) cortex, and SII and PP cortex ipsilaterally. All three tests were performed without errors. In both postoperative sessions, somatosensory activation was observed in contralateral SI, SII, and PP cortex, but not in ipsilateral SII and PP cortex. Performance was 100% correct in the TNT for the right hand, but below chance for the left; in the other tests, it was below chance except for TFLT in the intramanual task. This case provides the direct demonstration that activation of SII and PP cortex to stimulation of the ipsilateral hand and normal interhemispheric transfer of tactile information require the integrity of the posterior body of the CC.
A Neural Network Model of Lateralization during Letter Identification
Authors: Shevtsova Natalia , Reggia James A. 
Published: July 2002

Abstract
The causes of cerebral lateralization of cognitive and other functions are currently not well understood. To investigate one aspect of function lateralization, a bihemispheric neural network model for a simple visual identification task was developed that has two parallel interacting paths of information processing. The model is based on commonly accepted concepts concerning neural connectivity, activity dynamics, and synaptic plasticity. A combination of both unsupervised (Hebbian) and supervised (Widrow-Hoff) learning rules is used to train the model to identify a small set of letters presented as input stimuli in the left visual hemifield, in the central position, and in the right visual hemifield. Each visual hemifield projects onto the contralateral hemisphere, and the two hemispheres interact via a simulated corpus callosum. The contribution of each individual hemisphere to the process of input stimuli identification was studied for a variety of underlying asymmetries. The results indicate that multiple asymmetries may cause lateralization. Lateralization occurred toward the side having larger size, higher excitability, or higher learning rate parameters. It appeared more intensively with strong inhibitory callosal connections, supporting the hypothesis that the corpus callosum plays a functionally inhibitory role. The model demonstrates clearly the dependence of lateralization on different hemisphere parameters and suggests that computational models can be useful in better understanding the mechanisms underlying emergence of lateralization.
On the Complexity of Computing and Learning with Multiplicative Neural Networks
Authors: Schmitt Michael 
Published: July 2002

In a great variety of neuron models, neural inputs are combined using the summing operation. We introduce the concept of multiplicative neural networks that contain units that multiply their inputs instead of summing them and thus allow inputs to interact nonlinearly. The class of multiplicative neural networks comprises such widely known and well-studied network types as higher-order networks and product unit networks. We investigate the complexity of computing and learning for multiplicative neural networks. In particular, we derive upper and lower bounds on the Vapnik-Chervonenkis (VC) dimension and the pseudo-dimension for various types of networks with multiplicative units. As the most general case, we consider feedforward networks consisting of product and sigmoidal units, showing that their pseudo-dimension is bounded from above by a polynomial with the same order of magnitude as the currently best-known bound for purely sigmoidal networks. Moreover, we show that this bound holds even when the unit type, product or sigmoidal, may be learned. Crucial for these results are calculations of solution set components bounds for new network classes. As to lower bounds, we construct product unit networks of fixed depth with super-linear VC dimension. For sigmoidal networks of higher order, we establish polynomial bounds that, in contrast to previous results, do not involve any restriction of the network order. We further consider various classes of higher-order units, also known as sigma-pi units, that are characterized by connectivity constraints. In terms of these, we derive some asymptotically tight bounds. Multiplication plays an important role in both neural modeling of biological behavior and computing and learning with artificial neural networks. We briefly survey research in biology and in applications where multiplication is considered an essential computational element. The results we present here provide new tools for assessing the impact of multiplication on the computational power and the learning capabilities of neural networks.
Comparison of Approximate Methods for Handling Hyperparameters
Authors: MacKay David J. C. 
Published: July 2002

I examine two approximate methods for computational implementation of Bayesian hierarchical models, that is, models that include unknown hyperparameters such as regularization constants and noise levels. In the evidence framework, the model parameters are integrated over, and the resulting evidence is maximized over the hyperparameters. The optimized hyperparameters are used to define a gaussian approximation to the posterior distribution. In the alternative MAP method, the true posterior probability is found by integrating over the hyperparameters. The true posterior is then maximized over the model parameters, and a gaussian approximation is made. The similarities of the two approaches and their relative merits are discussed, and comparisons are made with the ideal hierarchical Bayesian solution.In moderately ill-posed problems, integration over hyperparameters yields a probability distribution with a skew peak, which causes signifi-cant biases to arise in the MAP method. In contrast, the evidence framework is shown to introduce negligible predictive error under straightforward conditions. General lessons are drawn concerning inference in many dimensions.
The Human Dimensions of Geomorphological Work in Britain
Authors: Douglas Ian , Lawson Nigel 
Published: July 2002

SummaryThe transfer of materials from the natural environment to the urban and industrially built environment produces two broad impacts on the landscape: a removal of materials from the earth's surface (a change in geomorphology) and the accumulation of a stock of concrete and other materials elsewhere in cities and industrial zones (a change in urban morphology). Thus, industrial activity transforms natural landscapes and, in doing so, has to be considered to be a geological and geomorphological agent. On the global scale, the deliberate shift of around 57,000 Mt (megatons)/yr of materials through mineral extraction processes exceeds the annual transport of sediment to the oceans by rivers (some 22,000 Mt/yr) by almost a factor of three. On the island of Britain, the total deliberate shift of earth‐surface materials is between 688 and 972 Mt/yr, depending on whether or not the replacement of overburden in opencast coal mining is taken into account. The export of sediment to the oceans by rivers is only 10 Mt/yr whereas the export of materials in solution is about 40 Mt/yr, making the deliberate materials shift nearly 14 times larger than the shift caused by natural processes. Processes examined by industrial ecology, such as direct excavation, urban development, and waste dumping are those most driving changes in the shape of the British landscape today. These transformations pose added costs. Industrial ecology will produce an understanding of the hidden costs associated with these transformations. Such an understanding will help in planning and encouraging the reuse of materials everywhere and in identifying the key areas for intervention to reduce off‐site geomorphological impacts and costs.
Industrial Ecology as a Cultural Phenomenon: On Objectivity as a Normative Position
Authors: Boons Frank , Roome Nigel 
Published: July 2002

SummaryTaking a recent column by Braden Allenby in this journal as a starting point, we argue the need for researchers in the field of industrial ecology to reflect upon its normative aspects. We argue that the field will advance through an explicit discourse on such issues as epistemological positions, the inherent normative nature of using metaphors, and the way in which the field of study relates to the field of practice.In “Culture and Industrial Ecology,” Allenby raises, and begins to address, some critical questions that define the field of industrial ecology. We suggest that his arguments dismiss too lightly issues that are central to this developing field. The purpose of this reply is to open up for further discussion what industrial ecology is, and what it is not.We begin by summarizing Allenby's line of reasoning. We explore his arguments around the notion of objectivity and the questions he raises about the relationship among objective science, normative positions, opinions, and fads. While Allenby makes a strong plea for industrial ecology to maintain objectivity and avoid normative positions, we contend that any positions on what should or should not be included in a field of study carry normative intent. Although science might seek to be objective in its method, scientists are rarely free of such normative positions. These positions need to be explicit and open to debate. Also, Allenby's position implies that industrial ecology as a field of study should be separated from industrial ecology as a field of practice. We argue that the interrelation of these fields provides important advantages.Our main concern is that Allenby's position forestalls discussion on important issues at the heart of the field of study. We examine some key issues around the concept of objectivity and propose an agenda for research on the cultural and ideological aspects of industrial ecology.
Product Environmental Life‐Cycle Assessment Using Input‐Output Techniques
Authors: Joshi Satish 
Published: July 2002

SummaryLife‐cycle assessment (LCA) facilitates a systems view in environmental evaluation of products, materials, and processes. Life‐cycle assessment attempts to quantify environmental burdens over the entire life‐cycle of a product from raw material extraction, manufacturing, and use to ultimate disposal. However, current methods for LCA suffer from problems of subjective boundary definition, inflexibility, high cost, data confidentiality, and aggregation.This paper proposes alternative models to conduct quick, cost effective, and yet comprehensive life‐cycle assessments. The core of the analytical model consists of the 498 sector economic input‐output tables for the U.S. economy augmented with various sector‐level environmental impact vectors. The environmental impacts covered include global warming, acidification, energy use, non‐renewable ores consumption, eutrophication, conventional pollutant emissions and toxic releases to the environment. Alternative models are proposed for environmental assessment of individual products, processes, and life‐cycle stages by selective disaggregation of aggregate input‐output data or by creation of hypothetical new commodity sectors. To demonstrate the method, a case study comparing the life‐cycle environmental performance of steel and plastic automobile fuel tank systems is presented.
Servicizing the Chemical Supply Chain
Authors: Reiskin Edward D. , White Allen L. , Johnson Jill Kauffman , Votta Thomas J. 
Published: July 2002

SummaryServicizing—the transformation from product‐to service‐based enterprise—is a major force in changing how firms manage material input, throughput, and output. Redefinition of the firm as a service provider instead of a product manufacturer means that function, not form, is the source of added value delivered to the customer. To realize the dematerialization benefits of such a transformation requires a fundamental realignment of the supplier‐customer relationship. Instead of the traditional incentives to maximize the volume of physical product sold, servicizing requires a partnership wherein the financial rewards of reduced material consumption are shared between supplier and customer. We illustrate this partnership concept with the example of chemical management services (CMS), an approach that is gaining momentum in the automobile and electronics sector. Compensation and gain‐sharing based on chemical efficiency and chemical use reduction, often tied to fixed price mechanisms, lie at the core of the CMS model. Diffusion of the servicizing model holds much promise for driving dematerialization while reducing the environmental burden of product manufacturers.